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A Survey on State-of-the-Art Drowsiness Detection Techniques	8	--- paper_title: Driver’s Face Detection Using Space-time Restrained Adaboost Method paper_content: Face detection is the first step of vision-based driver fatigue detection method. Traditional face detection methods have problems of high false-detection rates and long detection times. A space-time restrained Adaboost method is presented in this paper that resolves these problems. Firstly, the possible position of a driver’s face in a video frame is measured relative to the previous frame. Secondly, a space-time restriction strategy is designed to restrain the detection window and scale of the Adaboost method to reduce time consumption and false-detection of face detection. Finally, a face knowledge restriction strategy is designed to confirm that the faces detected by this Adaboost method. Experiments compare the methods and confirm that a driver’s face can be detected rapidly and precisely. --- paper_title: Real time drowsiness detection using eye blink monitoring paper_content: According to analysis reports on road accidents of recent years, it's renowned that the main cause of road accidents resulting in deaths, severe injuries and monetary losses, is due to a drowsy or a sleepy driver. Drowsy state may be caused by lack of sleep, medication, drugs or driving continuously for long time period. An increase rate of roadside accidents caused due to drowsiness during driving indicates a need of a system that detects such state of a driver and alerts him prior to the occurrence of any accident. During the recent years, many researchers have shown interest in drowsiness detection. Their approaches basically monitor either physiological or behavioral characteristics related to the driver or the measures related to the vehicle being used. A literature survey summarizing some of the recent techniques proposed in this area is provided. To deal with this problem we propose an eye blink monitoring algorithm that uses eye feature points to determine the open or closed state of the eye and activate an alarm if the driver is drowsy. Detailed experimental findings are also presented to highlight the strengths and weaknesses of our technique. An accuracy of 94% has been recorded for the proposed methodology. --- paper_title: Driver Drowsiness Detection Using Eye-Closeness Detection paper_content: The purpose of this paper was to devise a way to alert drowsy drivers in the act of driving. One of the causes of car accidents comes from drowsiness of the driver. Therefore, this study attempted to address the issue by creating an experiment in order to calculate the level of drowsiness. A requirement for this paper was the utilisation of a Raspberry Pi Camera and Raspberry Pi 3 module, which were able to calculate the level of drowsiness in drivers. The frequency of head tilting and blinking of the eyes was used to determine whether or not a driver felt drowsy. With an evaluation on ten volunteers, the accuracy of face and eye detection was up to 99.59 percent. --- paper_title: Performing systematic literature reviews in software engineering paper_content: Context: Making best use of the growing number of empirical studies in Software Engineering, for making decisions and formulating research questions, requires the ability to construct an objective summary of available research evidence. Adopting a systematic approach to assessing and aggregating the outcomes from a set of empirical studies is also particularly important in Software Engineering, given that such studies may employ very different experimental forms and be undertaken in very different experimental contexts.Objectives: To provide an introduction to the role, form and processes involved in performing Systematic Literature Reviews. After the tutorial, participants should be able to read and use such reviews, and have gained the knowledge needed to conduct systematic reviews of their own.Method: We will use a blend of information presentation (including some experiences of the problems that can arise in the Software Engineering domain), and also of interactive working, using review material prepared in advance. --- paper_title: Subjective sleepiness, simulated driving performance and blink duration: examining individual differences. paper_content: The present study aimed to provide subject-specific estimates of the relation between subjective sleepiness measured with the Karolinska Sleepiness Scale (KSS) and blink duration (BLINKD) and lane drifting calculated as the standard deviation of the lateral position (SDLAT) in a high-fidelity moving base driving simulator. Five male and five female shift workers were recruited to participate in a 2-h drive (08:00-10:00 hours) after a normal night sleep and after working a night shift. Subjective sleepiness was rated on the KSS in 5-min intervals during the drive, electro-occulogram (EOG) was measured continuously to calculate BLINKD, and SDLAT was collected from the simulator. A mixed model anova showed a significant (P Language: en --- paper_title: Performing systematic literature reviews in software engineering paper_content: Context: Making best use of the growing number of empirical studies in Software Engineering, for making decisions and formulating research questions, requires the ability to construct an objective summary of available research evidence. Adopting a systematic approach to assessing and aggregating the outcomes from a set of empirical studies is also particularly important in Software Engineering, given that such studies may employ very different experimental forms and be undertaken in very different experimental contexts.Objectives: To provide an introduction to the role, form and processes involved in performing Systematic Literature Reviews. After the tutorial, participants should be able to read and use such reviews, and have gained the knowledge needed to conduct systematic reviews of their own.Method: We will use a blend of information presentation (including some experiences of the problems that can arise in the Software Engineering domain), and also of interactive working, using review material prepared in advance. --- paper_title: An Evaluation of Emerging Driver Fatigue Detection Measures and Technologies paper_content: Operator fatigue and sleep deprivation have been widely recognized as critical safety issues that cut across all modes in the transportation industry. FMCSA, the trucking industry, highway safety advocates, and transportation researchers have all identified driver fatigue as a high priority commercial vehicle safety issue. Fatigue affects mental alertness, decreasing an individual’s ability to operate a vehicle safely and increasing the risk of human error that could lead to fatalities and injuries. Sleepiness slows reaction time, decreases awareness, and impairs judgment. Fatigue and sleep deprivation impact all transportation operators (airline pilots, truck drivers, and railroad engineers, for example). Adding to the difficulty of understanding the fatigue problem and developing effective countermeasures to address operator fatigue is the fact that the incidence of fatigue is underestimated because it is so hard to quantify and measure. Obtaining reliable data on fatigue-related crashes is challenging because it is difficult to determine the degree to which fatigue plays a role in crashes. Fatigue, however, can be managed, and effectively managing fatigue will result in a significant reduction in related risk and improved safety. This study focuses on recent developments in mathematical models and vehicle-based operator alertness monitoring technologies. The major objective of this paper is to review and discuss many of the activities currently underway to develop unobtrusive, in-vehicle, real-time drowsy driver detection and fatigue-monitoring/alerting systems. --- paper_title: Driver Fatigue Detection Using Mouth and Yawning Analysis paper_content: Summary Driver fatigue is an important factor in large number of accidents. There has been much work done in driver fatigue detection. This paper presents driver fatigue detection based on tracking the mouth and to study on monitoring and recognizing yawning. The authors proposed a method to locate and track driver’s mouth using cascade of classifiers proposed by Viola-Jones for faces. SVM is used to train the mouth and yawning images. During the fatigue detection mouth is detected from face images using cascade of classifiers. Then, SVM is used to classify the mouth and to detect yawning then alert Fatigue. --- paper_title: Driver drowsiness detection using face expression recognition paper_content: An important application of machine vision and image processing could be driver drowsiness detection system due to its high importance. In recent years there have been many research projects reported in the literature in this field. In this paper, unlike conventional drowsiness detection methods, which are based on the eye states alone, we used facial expressions to detect drowsiness. There are many challenges involving drowsiness detection systems. Among the important aspects are: change of intensity due to lighting conditions, the presence of glasses and beard on the face of the person. In this project, we propose and implement a hardware system which is based on infrared light and can be used in resolving these problems. In the proposed method, following the face detection step, the facial components that are more important and considered as the most effective for drowsiness, are extracted and tracked in video sequence frames. The system has been tested and implemented in a real environment. --- paper_title: Video-Based Classification of Driving Behavior Using a Hierarchical Classification System with Multiple Features paper_content: Driver fatigue and inattention have long been recognized as one of the main contributing factors in traffic accidents. Therefore, the development of intelligent driver assistance systems, which provides automatic monitoring of driver's vigilance, is an urgent and challenging task. This paper presents a novel system for video-based driving behavior recognition. The fundamental idea is to monitor driver's hand movements and to use these as predictors for safe/unsafe driving behavior. In comparison to previous work, the proposed method utilizes hierarchical classification and treats driving behavior in terms of a spatio-temporal reference framework as opposed to a static image. The approach was verified using the Southeast University Driving-Posture Dataset, a dataset comprised of video clips covering aspects of driving such as: normal driving, responding to a cell phone call, eating and smoking. After pre-processing for illumination variations and motion sequence segmentation, eight classes of behavior were... --- paper_title: A novel approach for drowsy driver detection using head posture estimation and eyes recognition system based on wavelet network paper_content: Fatigue and drowsiness are a part of everyday life for millions of people. They reduce reaction time, vigilance, alertness and concentration, therefore, the ability of performing attention-based activities (such as driving) is impaired. In this paper, a drowsy driver detection system has been developed, using video processing analyzing eyes blinking concepts for measuring eyes closure duration and head posture estimation to verify the driver vigilance state. There are two contributions in this paper. the first one resides in combining two parameters of drowsiness analysis. The second is the creation of a new method of head posture estimation. --- paper_title: Driver’s Face Detection Using Space-time Restrained Adaboost Method paper_content: Face detection is the first step of vision-based driver fatigue detection method. Traditional face detection methods have problems of high false-detection rates and long detection times. A space-time restrained Adaboost method is presented in this paper that resolves these problems. Firstly, the possible position of a driver’s face in a video frame is measured relative to the previous frame. Secondly, a space-time restriction strategy is designed to restrain the detection window and scale of the Adaboost method to reduce time consumption and false-detection of face detection. Finally, a face knowledge restriction strategy is designed to confirm that the faces detected by this Adaboost method. Experiments compare the methods and confirm that a driver’s face can be detected rapidly and precisely. --- paper_title: An Evaluation of Emerging Driver Fatigue Detection Measures and Technologies paper_content: Operator fatigue and sleep deprivation have been widely recognized as critical safety issues that cut across all modes in the transportation industry. FMCSA, the trucking industry, highway safety advocates, and transportation researchers have all identified driver fatigue as a high priority commercial vehicle safety issue. Fatigue affects mental alertness, decreasing an individual’s ability to operate a vehicle safely and increasing the risk of human error that could lead to fatalities and injuries. Sleepiness slows reaction time, decreases awareness, and impairs judgment. Fatigue and sleep deprivation impact all transportation operators (airline pilots, truck drivers, and railroad engineers, for example). Adding to the difficulty of understanding the fatigue problem and developing effective countermeasures to address operator fatigue is the fact that the incidence of fatigue is underestimated because it is so hard to quantify and measure. Obtaining reliable data on fatigue-related crashes is challenging because it is difficult to determine the degree to which fatigue plays a role in crashes. Fatigue, however, can be managed, and effectively managing fatigue will result in a significant reduction in related risk and improved safety. This study focuses on recent developments in mathematical models and vehicle-based operator alertness monitoring technologies. The major objective of this paper is to review and discuss many of the activities currently underway to develop unobtrusive, in-vehicle, real-time drowsy driver detection and fatigue-monitoring/alerting systems. --- paper_title: Eye tracking system to detect driver drowsiness paper_content: This paper describes an eye tracking system for drowsiness detection of a driver. It is based on application of Viola Jones algorithm and Percentage of Eyelid Closure (PERCLOS). The system alerts the driver if the drowsiness index exceeds a pre-specified level. --- paper_title: Real time drowsiness detection using eye blink monitoring paper_content: According to analysis reports on road accidents of recent years, it's renowned that the main cause of road accidents resulting in deaths, severe injuries and monetary losses, is due to a drowsy or a sleepy driver. Drowsy state may be caused by lack of sleep, medication, drugs or driving continuously for long time period. An increase rate of roadside accidents caused due to drowsiness during driving indicates a need of a system that detects such state of a driver and alerts him prior to the occurrence of any accident. During the recent years, many researchers have shown interest in drowsiness detection. Their approaches basically monitor either physiological or behavioral characteristics related to the driver or the measures related to the vehicle being used. A literature survey summarizing some of the recent techniques proposed in this area is provided. To deal with this problem we propose an eye blink monitoring algorithm that uses eye feature points to determine the open or closed state of the eye and activate an alarm if the driver is drowsy. Detailed experimental findings are also presented to highlight the strengths and weaknesses of our technique. An accuracy of 94% has been recorded for the proposed methodology. --- paper_title: Driver Drowsiness Detection Using Eye-Closeness Detection paper_content: The purpose of this paper was to devise a way to alert drowsy drivers in the act of driving. One of the causes of car accidents comes from drowsiness of the driver. Therefore, this study attempted to address the issue by creating an experiment in order to calculate the level of drowsiness. A requirement for this paper was the utilisation of a Raspberry Pi Camera and Raspberry Pi 3 module, which were able to calculate the level of drowsiness in drivers. The frequency of head tilting and blinking of the eyes was used to determine whether or not a driver felt drowsy. With an evaluation on ten volunteers, the accuracy of face and eye detection was up to 99.59 percent. --- paper_title: Information data flow in AWAKE multi-sensor driver monitoring system paper_content: Hypovigilance detection and warning systems are currently based on stand alone sensor approaches. This paper presents a multisensor system that allows the information fusion of different sources (vehicle, driver and environmental sensing parameters) and contributes to the decrease of false alarms and misses of the hypovigilance detection system. A hybrid scheme- centralized communication and data flow management of integrated stand alone systems- is adopted, which in turn, allows the real time application to monitor the driver and provide imminent and information messages according to his/her state and adapted to the external traffic and environmental scenario. The data flow between all systems, sensors and modules is described to synthesize the functional architecture. The system development is funded by the European so-called AWAKE project. --- paper_title: Subjective sleepiness, simulated driving performance and blink duration: examining individual differences. paper_content: The present study aimed to provide subject-specific estimates of the relation between subjective sleepiness measured with the Karolinska Sleepiness Scale (KSS) and blink duration (BLINKD) and lane drifting calculated as the standard deviation of the lateral position (SDLAT) in a high-fidelity moving base driving simulator. Five male and five female shift workers were recruited to participate in a 2-h drive (08:00-10:00 hours) after a normal night sleep and after working a night shift. Subjective sleepiness was rated on the KSS in 5-min intervals during the drive, electro-occulogram (EOG) was measured continuously to calculate BLINKD, and SDLAT was collected from the simulator. A mixed model anova showed a significant (P Language: en --- paper_title: Driver Drowsiness Detection Based on Time Series Analysis of Steering Wheel Angular Velocity paper_content: A novel driver drowsiness detection method based on time series analysis of the steering wheel angular velocity is proposed in this paper. Firstly, the steering behavior under the fatigue state is analyzed, followed by the determination of the temporal detection window, and then, the data series of the steering wheel angular velocity in the temporal detection window is selected as the detection feature. IF the detection feature satisfies the extent constraint and the variability constraint in the temporal window, a drowsiness state is detected accordingly. At last, experiment tests validate our method has good performance and could be well used in the real world. --- paper_title: Online Detection of Driver Fatigue Using Steering Wheel Angles for Real Driving Conditions paper_content: This paper presents a drowsiness on-line detection system for monitoring driver fatigue level under real driving conditions, based on the data of steering wheel angles (SWA) collected from sensors mounted on the steering lever. The proposed system ﬁrstly extracts approximate entropy (ApEn)featuresfromﬁxedslidingwindowsonreal-timesteeringwheelanglestimeseries. Afterthat, this system linearizes the ApEn features series through an adaptive piecewise linear ﬁtting using a given deviation. Then, the detection system calculates the warping distance between the linear features series of the sample data. Finally, this system uses the warping distance to determine the drowsiness state of the driver according to a designed binary decision classiﬁer. The experimental data were collected from 14.68 h driving under real road conditions, including two fatigue levels: “wake” and “drowsy”. The results show that the proposed system is capable of working online with an average 78.01% accuracy, 29.35% false detections of the “awake” state, and 15.15% false detections of the “drowsy” state. The results also conﬁrm that the proposed method based on SWA signal is valuable for applications in preventing trafﬁc accidents caused by driver fatigue. --- paper_title: Automatic Detection of Driver Fatigue Using Driving Operation Information for Transportation Safety paper_content: Fatigued driving is a major cause of road accidents. For this reason, the method in this paper is based on the steering wheel angles (SWA) and yaw angles (YA) information under real driving conditions to detect drivers' fatigue levels. It analyzes the operation features of SWA and YA under different fatigue statuses, then calculates the approximate entropy (ApEn) features of a short sliding window on time series. Using the nonlinear feature construction theory of dynamic time series, with the fatigue features as input, designs a "2-6-6-3" multi-level back propagation (BP) Neural Networks classifier to realize the fatigue detection. An approximately 15-h experiment is carried out on a real road, and the data retrieved are segmented and labeled with three fatigue levels after expert evaluation, namely "awake", "drowsy" and "very drowsy". The average accuracy of 88.02% in fatigue identification was achieved in the experiment, endorsing the value of the proposed method for engineering applications. --- paper_title: EEG-based Driver Fatigue Detection paper_content: Fatigue is a gradual process leads to a slower reaction time. Fatigue is the major cause of road accidents around the globe. This paper proposes, implements and tests a system to detect fatigue based on Electroencephalogram (EEG) signal. The system produces fatigue index which is relevant to the level of subject's drowsiness. The input to the system is EEG signal which is measured by inexpensive single electrode neuro-signal acquisition device. The system was tested on locally collected dataset for a car simulation driver in different drowsiness levels. The system was able to detect the fatigue level for all subjects in different levels of tiredness. --- paper_title: Detection of Driver Drowsiness Using Wavelet Analysis of Heart Rate Variability and a Support Vector Machine Classifier paper_content: Driving while fatigued is just as dangerous as drunk driving and may result in car accidents. Heart rate variability (HRV) analysis has been studied recently for the detection of driver drowsiness. However, the detection reliability has been lower than anticipated, because the HRV signals of drivers were always regarded as stationary signals. The wavelet transform method is a method for analyzing non-stationary signals. The aim of this study is to classify alert and drowsy driving events using the wavelet transform of HRV signals over short time periods and to compare the classification performance of this method with the conventional method that uses fast Fourier transform (FFT)-based features. Based on the standard shortest duration for FFT-based short-term HRV evaluation, the wavelet decomposition is performed on 2-min HRV samples, as well as 1-min and 3-min samples for reference purposes. A receiver operation curve (ROC) analysis and a support vector machine (SVM) classifier are used for feature selection and classification, respectively. The ROC analysis results show that the wavelet-based method performs better than the FFT-based method regardless of the duration of the HRV sample that is used. Finally, based on the real-time requirements for driver drowsiness detection, the SVM classifier is trained using eighty FFT and wavelet-based features that are extracted from 1-min HRV signals from four subjects. The averaged leave-one-out (LOO) classification performance using wavelet-based feature is 95% accuracy, 95% sensitivity, and 95% specificity. This is better than the FFT-based results that have 68.8% accuracy, 62.5% sensitivity, and 75% specificity. In addition, the proposed hardware platform is inexpensive and easy-to-use. --- paper_title: Detecting Drowsy Driver Using Pulse Sensor paper_content: The driver’s condition, which involves staying focus on the road, is the most important aspect to consider whenever one is driving. To ignore the importance of this could result in severe physical injuries, deaths and economic losses. Again, previous researches were focused mainly on the physical conditions of the driver; eg movement of head and drowsiness. However, this research is focused on the driver’s heart rate by using an infrared heart-rate sensor or pulse sensor. These sensors are non-intrusively measured heart pulse wave from the driver’s heart. By doing experiment, the results show clear pulse wave signal can be obtained by looking at the low to high frequency (LF/HF ratio) which calculate HRV frequency domain of the driver’s heart rate time series. The LF/HF ratio shows decreasing trends as the drivers go from the state of being awake and alert to the state of drowsiness. Therefore, accidents can be avoided if there is an alert system to keep the drivers alert and focused on the road. --- paper_title: Wearable driver drowsiness detection system based on biomedical and motion sensors paper_content: Driver drowsiness detection system had been developed as mobile device application such as Percentage of Eye Closure (PERCLOS) measured by using mobile device camera. Nevertheless, the mobile device has the potential risk of distracting the driver's attention, causing accidents. Thus, a wearable-type drowsiness detection system is proposed to overcome such issue. The proposed system used self-designed wristband consisted of photoplethysmogram sensor and galvanic skin response sensor. The sensors data are sent to the mobile device which served as a main analyzing processing unit. Those data are analyzed along with the motion sensors, which are the mobile device built-in accelerometer and gyroscope sensors. Five features are extracted accordingly based on the received raw sensors data, including heart rate, pulse rate variability, respiratory rate, stress level, and adjustment counter. Those features are further served as computation parameters to a support vector machine to derive the driver drowsiness state. The testing results indicated that the accuracy of the system with SVM model reached up to 98.3%. In addition, driver will be alerted using graphical and vibration alarm generated by the mobile device. In fact, the integration of driver physical behavior and physiological signals is proven to be an outstanding solution to detect driver drowsiness in a safer, more flexible and portable used. --- paper_title: Detecting Driver Drowsiness Using Wireless Wearables paper_content: The National Highway Traffic Safety Administration data show that drowsy driving causes more than 100,000 crashes a year. In order to prevent these devastating accidents, it is necessary to build a reliable driver drowsiness detection system which could alert the driver before a mishap happens. In the literature, the drowsiness of a driver can be measured by vehicle-based, behavior-based, and physiology-based approaches. Comparing with the vehicle-based and behavior-based measurements, the physiological measurement of drowsiness is more accurate. With the latest release of wireless wearable devices such as biosensors that can measure people's physiological data, we aim to explore the possibility of designing a user-friendly and accurate driver drowsiness detection system using wireless wearables. In this paper, we use a wearable biosensor called Bio Harness 3 produced by Zephyr Technology to measure a driver's physiological data. We present our overall design idea of the driver drowsiness detection system and the preliminary experimental results using the biosensor. The detection system will be designed in two phases: The main task of the first phase is to collect a driver's physiological data by the biosensor and analyze the measured data to find the key parameters related to the drowsiness. In the second phase, we will design a drowsiness detection algorithm and develop a mobile app to alert drowsy drivers. The results from this project can lead to the development of real products which can save many lives and avoid many accidents on the road. Furthermore, our results can be widely applied to any situation where people should not fall asleep: from the applications in mission-critical fields to the applications in everyday life. --- paper_title: Driver fatigue detection system paper_content: The research aims to detect the onset of drowsiness in drivers, while the vehicle is in motion. Detection is done by continuously looking out for symptoms of drowsiness, while considering both physiological and physical signs. Physiological factors include core body temperature and pulse rate. Both of these parameters will decrease during the onset of drowsiness. These are monitored by using somatic sensors. Physical cues including yawning, drooping eyelids, closed eyes and increased blink durations. Once the system detects that the driver is drowsy by using a combination of these factors, it alerts the driver across multiple stages depending on the severity of the symptoms. The system also becomes attuned to the driver's unique characteristics over time, thus reducing the margin of false positives. --- paper_title: A Hybrid Approach to Detect Driver Drowsiness Utilizing Physiological Signals to Improve System Performance and Wearability paper_content: Driver drowsiness is a major cause of fatal accidents, injury, and property damage, and has become an area of substantial research attention in recent years. The present study proposes a method to detect drowsiness in drivers which integrates features of electrocardiography (ECG) and electroencephalography (EEG) to improve detection performance. The study measures differences between the alert and drowsy states from physiological data collected from 22 healthy subjects in a driving simulator-based study. A monotonous driving environment is used to induce drowsiness in the participants. Various time and frequency domain feature were extracted from EEG including time domain statistical descriptors, complexity measures and power spectral measures. Features extracted from the ECG signal included heart rate (HR) and heart rate variability (HRV), including low frequency (LF), high frequency (HF) and LF/HF ratio. Furthermore, subjective sleepiness scale is also assessed to study its relationship with drowsiness. We used paired t-tests to select only statistically significant features (p < 0.05), that can differentiate between the alert and drowsy states effectively. Significant features of both modalities (EEG and ECG) are then combined to investigate the improvement in performance using support vector machine (SVM) classifier. The other main contribution of this paper is the study on channel reduction and its impact to the performance of detection. The proposed method demonstrated that combining EEG and ECG has improved the system’s performance in discriminating between alert and drowsy states, instead of using them alone. Our channel reduction analysis revealed that an acceptable level of accuracy (80%) could be achieved by combining just two electrodes (one EEG and one ECG), indicating the feasibility of a system with improved wearability compared with existing systems involving many electrodes. Overall, our results demonstrate that the proposed method can be a viable solution for a practical driver drowsiness system that is both accurate and comfortable to wear. --- paper_title: A new system for driver drowsiness and distraction detection paper_content: Drowsiness especially in long distance journeys is a key factor in traffic accidents. In this paper a new module for automatic driver drowsiness detection based on visual information and Artificial Intelligence is presented. The aim of this system is to locate, track and analyze both the driver's face and eyes to compute a drowsiness index to prevent accidents. Both face and eye detection is performed by Haar-like features and AdaBoost classifiers. In order to achieve better accuracy in face tracking, we propose a new method which is combination of detection and object tracking. Proposed face tracking method, also has capability to self correction. After eye region is found, Local Binary Pattern (LBP) is employed to extract eye characteristics. Using these features, an SVM classifier was trained to perform eye state analysis. To evaluate the effectiveness of proposed method, a drowsy person was pictured, while his EEG signals were taken. In this video we were able to track face by an accuracy of 100% and detecting eye blink by accuracy of 98.4%. Also we can calculate face orientation and tilt using eye position which is valuable knowledge about driver concentration. Finally, we can make a decision about drowsiness and distraction of the driver. Experimental results show high accuracy in each section which makes this system reliable for driver drowsiness detection. ---	Title: A Survey on State-of-the-Art Drowsiness Detection Techniques Section 1: INTRODUCTION Description 1: Introduce the importance of drowsiness detection, its impact on road safety, and the motivation behind the review. Section 2: RESEARCH METHODOLOGY Description 2: Describe the systematic approach used to gather and evaluate research papers on drowsiness detection techniques. Section 3: DROWSINESS DETECTION TECHNIQUES Description 3: Provide a detailed review of various drowsiness detection techniques, categorized by their approach, and discuss their pros and cons. Section 4: A COMPARATIVE STUDY OF DDT Description 4: Conduct a comparative analysis of different drowsiness detection techniques and discuss their advantages and disadvantages. Section 5: HYBRID APPROACHES OF DDT Description 5: Discuss the combination of different drowsiness detection techniques to enhance detection accuracy and reliability. Section 6: CLASSIFICATION METHODS USED FOR DDT Description 6: Detail the various classification methods used in drowsiness detection systems, including their pros and cons, and comparative performance. Section 7: COMPARATIVE STUDY OF CLASSIFICATION METHODS Description 7: Present a comparative study of different classification methods, discussing their error rates and suitability under various conditions. Section 8: CONCLUSION Description 8: Summarize the main findings of the survey, highlighting the most effective drowsiness detection techniques and future research directions.
Survey of Down Link Data Allocation Algorithms in IEEE 802.16 WiMAX	10	--- paper_title: Fundamentals of WiMAX: Understanding Broadband Wireless Networking paper_content: This is the eBook version of the printed book. Praise for Fundamentals of WiMAX "This book is one of the most comprehensive books I have reviewed ... it is a must-read for engineers and students planning to remain current or who plan to pursue a career in telecommunications. I have reviewed other publications on WiMAX and have been disappointed. This book is refreshing in that it is clear that the authors have the in-depth technical knowledge and communications skills to deliver a logically laid out publication that has substance to it." Ron Resnick, President, WiMAX Forum "This is the first book with a great introductory treatment of WiMAX technology. It should be essential reading for all engineers involved in WiMAX. The high-level overview is very useful for those with non-technical background. The introductory sections for OFDM and MIMO technologies are very useful for those with implementation background and some knowledge of communication theory. The chapters covering physical and MAC layers are at the appropriate level of detail. In short, I recommend this book to systems engineers and designers at different layers of the protocol, deployment engineers, and even students who are interested in practical applications of communication theory." Siavash M. Alamouti, Chief Technology Officer, Mobility Group, Intel "This is a very well-written, easy-to-follow, and comprehensive treatment of WiMAX. It should be of great interest." Dr. Reinaldo Valenzuela, Director of Wireless Research, Bell Labs "Fundamentals of WiMAX is a comprehensive guide to WiMAX from both industry and academic viewpoints, which is an unusual accomplishment. I recommend it to anyone who is curious about this exciting new standard." Dr. Teresa Meng, Professor, Stanford University, Founder and Director, Atheros Communications "Andrews, Ghosh, and Muhamed have provided a clear, concise, and well-written text on 802.16e/WiMAX. The book provides both the breadth and depth to make sense of the highly complicated 802.16e standard. I would recommend this book to both development engineers and technical managers who want an understating of WiMAX and insight into 4G modems in general." Paul Struhsaker, VP of Engineering, Chipset platforms, Motorola Mobile Device Business Unit, former vice chair of IEEE 802.16 working group "Fundamentals of WiMAX is written in an easy-to-understand tutorial fashion. The chapter on multiple antenna techniques is a very clear summary of this important technology and nicely organizes the vast number of different proposed techniques into a simple-to-understand framework." Dr. Ender Ayanoglu, Professor, University of California, Irvine, Editor-in-Chief, IEEE Transactions on Communications "Fundamentals of WiMAX is a comprehensive examination of the 802.16/WiMAX standard and discusses how to design, develop, and deploy equipment for this wireless communication standard. It provides both insightful overviews for those wanting to know what WiMAX is about and comprehensive, in-depth chapters on technical details of the standard, including the coding and modulation, signal processing methods, Multiple-Input Multiple-Output (MIMO) channels, medium access control, mobility issues, link-layer performance, and system-level performance." Dr. Mark C. Reed, Principal Researcher, National ICT Australia, Adjunct Associate Professor, Australian National University "This book is an excellent resourc... --- paper_title: eOCSA: An algorithm for burst mapping with strict QoS requirements in IEEE 802.16e Mobile WiMAX networks paper_content: Mobile WiMAX systems based on the IEEE 802.16e standard require all downlink allocations to be mapped to a rectangular region in the two dimensional subcarrier-time map. Many published resource allocation schemes ignore this requirement. It is possible that the allocations when mapped to rectangular regions may exceed the capacity of the downlink frame, and the QoS of some flows may be violated. The rectangle mapping problem is a variation of the bin or strip packing problem, which is known to be NP-complete. In a previous paper, an algorithm called OCSA (One Column Striping with non-increasing Area first mapping) for rectangular mapping was introduced. In this paper, we propose an enhanced version of the algorithm. Similar to OCSA, the enhanced algorithm is also simple and fast to implement; however, eOCSA considers the allocation of an additional resource to ensure the QoS. eOCSA also avoids an enumeration process and so lowers the complexity to O(n2). --- paper_title: Fundamentals of WiMAX: Understanding Broadband Wireless Networking paper_content: This is the eBook version of the printed book. Praise for Fundamentals of WiMAX "This book is one of the most comprehensive books I have reviewed ... it is a must-read for engineers and students planning to remain current or who plan to pursue a career in telecommunications. I have reviewed other publications on WiMAX and have been disappointed. This book is refreshing in that it is clear that the authors have the in-depth technical knowledge and communications skills to deliver a logically laid out publication that has substance to it." Ron Resnick, President, WiMAX Forum "This is the first book with a great introductory treatment of WiMAX technology. It should be essential reading for all engineers involved in WiMAX. The high-level overview is very useful for those with non-technical background. The introductory sections for OFDM and MIMO technologies are very useful for those with implementation background and some knowledge of communication theory. The chapters covering physical and MAC layers are at the appropriate level of detail. In short, I recommend this book to systems engineers and designers at different layers of the protocol, deployment engineers, and even students who are interested in practical applications of communication theory." Siavash M. Alamouti, Chief Technology Officer, Mobility Group, Intel "This is a very well-written, easy-to-follow, and comprehensive treatment of WiMAX. It should be of great interest." Dr. Reinaldo Valenzuela, Director of Wireless Research, Bell Labs "Fundamentals of WiMAX is a comprehensive guide to WiMAX from both industry and academic viewpoints, which is an unusual accomplishment. I recommend it to anyone who is curious about this exciting new standard." Dr. Teresa Meng, Professor, Stanford University, Founder and Director, Atheros Communications "Andrews, Ghosh, and Muhamed have provided a clear, concise, and well-written text on 802.16e/WiMAX. The book provides both the breadth and depth to make sense of the highly complicated 802.16e standard. I would recommend this book to both development engineers and technical managers who want an understating of WiMAX and insight into 4G modems in general." Paul Struhsaker, VP of Engineering, Chipset platforms, Motorola Mobile Device Business Unit, former vice chair of IEEE 802.16 working group "Fundamentals of WiMAX is written in an easy-to-understand tutorial fashion. The chapter on multiple antenna techniques is a very clear summary of this important technology and nicely organizes the vast number of different proposed techniques into a simple-to-understand framework." Dr. Ender Ayanoglu, Professor, University of California, Irvine, Editor-in-Chief, IEEE Transactions on Communications "Fundamentals of WiMAX is a comprehensive examination of the 802.16/WiMAX standard and discusses how to design, develop, and deploy equipment for this wireless communication standard. It provides both insightful overviews for those wanting to know what WiMAX is about and comprehensive, in-depth chapters on technical details of the standard, including the coding and modulation, signal processing methods, Multiple-Input Multiple-Output (MIMO) channels, medium access control, mobility issues, link-layer performance, and system-level performance." Dr. Mark C. Reed, Principal Researcher, National ICT Australia, Adjunct Associate Professor, Australian National University "This book is an excellent resourc... --- paper_title: Fundamentals of WiMAX: Understanding Broadband Wireless Networking paper_content: This is the eBook version of the printed book. Praise for Fundamentals of WiMAX "This book is one of the most comprehensive books I have reviewed ... it is a must-read for engineers and students planning to remain current or who plan to pursue a career in telecommunications. I have reviewed other publications on WiMAX and have been disappointed. This book is refreshing in that it is clear that the authors have the in-depth technical knowledge and communications skills to deliver a logically laid out publication that has substance to it." Ron Resnick, President, WiMAX Forum "This is the first book with a great introductory treatment of WiMAX technology. It should be essential reading for all engineers involved in WiMAX. The high-level overview is very useful for those with non-technical background. The introductory sections for OFDM and MIMO technologies are very useful for those with implementation background and some knowledge of communication theory. The chapters covering physical and MAC layers are at the appropriate level of detail. In short, I recommend this book to systems engineers and designers at different layers of the protocol, deployment engineers, and even students who are interested in practical applications of communication theory." Siavash M. Alamouti, Chief Technology Officer, Mobility Group, Intel "This is a very well-written, easy-to-follow, and comprehensive treatment of WiMAX. It should be of great interest." Dr. Reinaldo Valenzuela, Director of Wireless Research, Bell Labs "Fundamentals of WiMAX is a comprehensive guide to WiMAX from both industry and academic viewpoints, which is an unusual accomplishment. I recommend it to anyone who is curious about this exciting new standard." Dr. Teresa Meng, Professor, Stanford University, Founder and Director, Atheros Communications "Andrews, Ghosh, and Muhamed have provided a clear, concise, and well-written text on 802.16e/WiMAX. The book provides both the breadth and depth to make sense of the highly complicated 802.16e standard. I would recommend this book to both development engineers and technical managers who want an understating of WiMAX and insight into 4G modems in general." Paul Struhsaker, VP of Engineering, Chipset platforms, Motorola Mobile Device Business Unit, former vice chair of IEEE 802.16 working group "Fundamentals of WiMAX is written in an easy-to-understand tutorial fashion. The chapter on multiple antenna techniques is a very clear summary of this important technology and nicely organizes the vast number of different proposed techniques into a simple-to-understand framework." Dr. Ender Ayanoglu, Professor, University of California, Irvine, Editor-in-Chief, IEEE Transactions on Communications "Fundamentals of WiMAX is a comprehensive examination of the 802.16/WiMAX standard and discusses how to design, develop, and deploy equipment for this wireless communication standard. It provides both insightful overviews for those wanting to know what WiMAX is about and comprehensive, in-depth chapters on technical details of the standard, including the coding and modulation, signal processing methods, Multiple-Input Multiple-Output (MIMO) channels, medium access control, mobility issues, link-layer performance, and system-level performance." Dr. Mark C. Reed, Principal Researcher, National ICT Australia, Adjunct Associate Professor, Australian National University "This book is an excellent resourc... --- paper_title: WiMAX Technology and Network Evolution paper_content: Written and edited by experts who have developed WiMAX technology and standards WiMAX, the Worldwide Interoperability for Microwave Access, represents a paradigm shift in telecommunications technology. It offers the promise of cheaper, smaller, and simpler technology compared to existing broadband options such as DSL, cable, fiber, and 3G wireless. WiMAX Technology and Network Evolution is the first publication to present an accurate, complete, and objective description of mobile WiMAX technology. Each chapter was written and edited by experts, all of whom have been directly engaged in and lead the development of WiMAX either through the IEEE 802.16 Working Group or the WiMAX Forum. As a result, the book addresses not only key technical concepts and design principles, but also a wide range of practical issues concerning this new wireless technology, including: Detailed description of WiMAX technology features and capabilities from both radio and network perspectives WiMAX technology evolution in the near and long term Emerging broadband services enabled by the WiMAX networks Regulatory issues affecting WiMAX deployment and global adoption WiMAX accounting, roaming, and network management Each chapter ends with a summary and a list of references to facilitate further research. Wireless engineers, service designers, product managers, telecommunications professionals, network operators, and academics will all gain new insights into the key issues surrounding the development and implementation of mobile WiMAX. Moreover, the book will help them make informed management and business decisions in devising their own WiMAX strategies. --- paper_title: WiMAX Networks: Techno-Economic Vision and Challenges paper_content: Ignited by the mobile phone's huge success at the end of last century, the demand for wireless services is constantly growing. To face this demand, wireless systems have been and are deployed at a large scale. These include mobility-oriented technologies such as GPRS, CDMA or UMTS, and Local Area Network-oriented technologies such as WiFi. WiMAX Networks covers aspects of WiMAX quality of service (QoS), security, mobility, radio resource management, multiple input multiple output antenna, planning, cost/revenue optimization, physical layer, medium access control (MAC) layer, network layer, and so on. --- paper_title: Wimax Technology for Broadband Wireless Access paper_content: WiMAX Broadband Wireless Access Technology, based on the IEEE 802.16 standard, is at the origin of great promises for many different markets covering fixed wireless Internet Access, Backhauling and Mobile cellular networks. WiMAX technology is designed for the transmission of multimedia services (voice, Internet, email, games and others) at high data rates (of the order of Mb/s per user). It is a very powerful but sometimes complicated technique. The WiMAX System is described in thousands of pages of IEEE 802.16 standard and amendments documents and WiMAX Forum documents. WiMAX: Technology for Broadband Wireless Access provides a global picture of WiMAX and a large number of details that makes access to WiMAX documents much easier. All the aspects of WIMAX are covered. Illustrations and clear explanations for all the main procedures of WiMAX are pedagogically presented in a succession of relatively short chapters Topics covered include WiMAX genesis and framework, WiMAX topologies, protocol layers, MAC layer, MAC frames, WiMAX multiple access, the physical layer, QoS Management, Radio Resource Management, Bandwidth allocation, Network Architecture, Mobility and Security Features a glossary of abbreviations and their definitions, and a wealth of explanatory tables and figures Highlights the most recent changes, including the 802.16e amendment of the standard, needed for Mobile WiMAX Includes technical comparisons of WiMAX vs. 802.11 (WiFi) and cellular 3G technologies This technical introduction to WiMAX, explaining the rather complex standards (IEEE 802.16-2004 and 802.16e) is a must read for engineers, decision-makers and students interested in WiMAX, as well as other researchers and scientists from this evolving field. --- paper_title: Burst Construction and Packet Mapping Scheme for OFDMA Downlinks in IEEE 802.16 Systems paper_content: In this paper, we propose a burst construction and packet mapping scheme in the orthogonal frequency-division multiple access (OFDMA) downlinks of IEEE 802.16 systems. In the standard of the systems, there are some restrictions on the usage of downlink radio resources and they are defined in the physical layer (PHY) specification. One of the main restrictions is that a rectangular region, which is called Burst, is defined on a two-dimensional domain of time and frequency, and packets must be allocated within the region. However, how to define the burst and allocate data packets within the burst is left implementation dependent. Therefore, we consider a burst construction and packet mapping scheme that is easy to realize on systems and attains efficient usage of radio resources. By computer simulation, it has been confirmed that the proposed scheme can decrease not only the control data ratio within the rectangles, but also control data that must be transmitted at the head of every frame, which can result in higher throughput. --- paper_title: WiMAX Downlink OFDMA Burst Placement for Optimized Receiver Duty-Cycling paper_content: Mobile wireless broadband access networks are now becoming a reality, thanks to the emerging IEEE 802.16e standard. This kind of network offers different challenges when compared to the fixed ones, as power consumption becomes a major concern. In this standard, a strict organization of the downlink bursts is not guaranteed in the OFDMA frame and this may lead to extra power consumption for the receiver, decreasing the device's lifetime. In the present paper, we introduce an optimization algorithm capable of reducing the activity of each receiver in the system for decoding its addressed bursts, thanks to a better time-frequency organization of the bursts. We first work on fitting bursts within the smallest frame, and show that the minimal number of OFDM symbols is enough in 70 to 80% of the cases, while one extra is needed otherwise. Using a binary tree implementation of an exhaustive burst placement search, we also show that we can gain 20 to 30% in duty-cycling of the receivers by selecting the best configuration, hence gaining the corresponding energy. This holds for receivers decoding either their bursts only or all the bursts from the beginning of the frame up to their own bursts before sleeping, depending on the scenario. The full search is sustainable for up to 8 user bursts per frame. --- paper_title: Two-Dimensional Resource Allocation for OFDMA System paper_content: The resource allocation problem in OFDMA system is how to assign two-dimensional blocks covering time and frequency to multi-users. Resource allocation is crucial to system performance but is not defined in IEEE 802.16 standards. We proved that the problem of resource allocation in IEEE 802.16 standard is NP-complete. To approximately solve the problem in real time, we present a fast heuristic algorithm with O(n2) computational complexity based on topology evaluation. Simulation results show that the allocation result is competitive. --- paper_title: A Cross-Layer Framework for Overhead Reduction, Traffic Scheduling, and Burst Allocation in IEEE 802.16 OFDMA Networks paper_content: IEEE 802.16 orthogonal frequency-division multiple access (OFDMA) downlink subframes have a special 2-D channel-time structure. Allocation resources from such a 2-D structure incur extra control overheads that hurt network performance. Existing solutions try to improve network performance by designing either the scheduler in the medium access control layer or the burst allocator in the physical layer, but the efficiency of overhead reduction is limited. In this paper, we point out the necessity of “codesigning” both the scheduler and the burst allocator to efficiently reduce overheads and improve network performance. Under the partial-usage-of-subcarriers model, we propose a cross-layer framework that covers overhead reduction, real-time and non-real-time traffic scheduling, and burst allocation. The framework includes a two-tier priority-based scheduler and a bucket-based burst allocator, which is more complete and efficient than prior studies. Both the scheduler and the burst allocator are tightly coupled together to solve the problem of arranging resources to data traffic. Given available space and bucket design from the burst allocator, the scheduler can well utilize the frame resource, reduce real-time traffic delays, and maintain fairness. On the other hand, with priority knowledge and resource assignment from the scheduler, the burst allocator can efficiently arrange downlink bursts to satisfy traffic requirements with low complexity. Through analysis, the cross-layer framework is validated to give an upper bound to overheads and achieve high network performance. Extensive simulation results verify that the cross-layer framework significantly increases network throughput, maintains long-term fairness, alleviates real-time traffic delays, and enhances frame utilization. --- paper_title: Optimal WiMAX frame packing for minimum energy consumption paper_content: Minimizing energy consumption is an urgent and challenging problem. As in any communication system, high energy efficiency in WiMAX systems should be maintained by increasing resource efficiency. Thus, WiMAX resources should be properly utilized by optimizing the construction of downlink (DL) bursts. This paper proposes an energy-efficient scheme that maximizes the use of resources at the base station (BS) by reducing the energy wasted caused by sending padding bits instead of useful data. The problem was formulated as nonlinear integer programming model. Due to the complexity of the problem, this paper presents first the formulation of the base model for optimal DL bursts construction problem assuming the packet is represented by one burst. Then, the formulation is expanded to allow the representation of packets by several bursts. The results show an improvement in data packing that maximizes the utilization of frames, and minimizes energy wastage. --- paper_title: A Linear-Complexity Burst Packing Scheme for IEEE 802.16e OFDMA Downlink Frames paper_content: The problem of efficiently shaping downlink data bursts into rectangles and packing them in the OFDMA subframe is not addressed by the IEEE 802.16 standard, and is left as an implementation issue. In this paper, we propose a linear complex- ity bursts packing algorithm to maximize radio resources usage on the OFDMA downlink. Our scheme shapes the bursts into identical width, places them in column direction and maximally fills the columns by shifting the bursts on different columns. By simulation, we show that the scheme can push the radio resource usage over 95%, which is on average 20% improvement compared with the simple 2D fixed-bin strip packing and 8% improvement with the exhaustive search. Moreover, the proposed scheme is also power-efficient, because subscriber stations (SSs) do not need to receive a large aggregated burst created for packing problem complexity reduction. --- paper_title: Greedy scheduling algorithm (GSA) - Design and evaluation of an efficient and flexible WiMAX OFDMA scheduling solution paper_content: WiMAX is one of the most promising technologies to provide broadband wireless access in the near future. In this paper we focus on the study of the combined performance of a WiMAX Base Station MAC downlink scheduler and OFDMA packing algorithm which mainly determine the usage efficiency of the available radio resources. We design and analyze an efficient and flexible solution, greedy scheduling algorithm (GSA), and evaluate its performance as compared to several relevant alternative solutions. Specifically, we analyze performance differences with respect to efficiency, flexibility to provide per subscriber station burst shape preferences, interference mitigation and computational load. Our results show that GSA achieves a performance similar to the one of the competing approaches considered in terms of efficiency, even better in some cases, and significantly outperforms them in flexibility to provide per subscriber station burst shape preferences, interference mitigation and computational load. As a conclusion, the proposed GSA solution is a promising candidate to maximize the utilization of the available WiMAX radio resources at a low computational cost while at the same time being able to fulfill a wide range of requirements based on operators' preferences and/or network environment specifics. --- paper_title: An energy-efficient scheme for WiMAX downlink bursts construction paper_content: One of the challenges in WiMAX networks is to increase resource and power efficiency by optimizing the downlink (DL) burst construction. This paper proposes an energy-efficient scheme that maximizes the use of resources at the base station (BS) while reducing the energy wasted caused by sending padding bits instead of useful data. This paper presents the derivation of the general optimization problem that was formulated as a nonlinear integer programming model. A simple case formulation is used to illustrate the general application. The results show an improvement in data packing that maximizes the utilization of frames, and minimizes energy wastage. --- paper_title: Condensed Downlink MAP Structures for IEEE 802.16e Wireless Metropolitan Area Networks (MANs) paper_content: The new mobile wireless metropolitan area network (WMAN) architecture imposes a demanding performance requirement on the radio resource to provide broadband internet access. The radio resource is partitioned as bursts in time and frequency domains and used by mobile stations (MS) in an exclusive manner. The base station (BS) functionally serves as a resource controller for traffic to and from the MSs associated with it, and thus naturally generates the proper downlink (DL) and uplink (UL) MAPs for active MSs based on service and traffic requirements. However, the DL-MAP construction scheme in IEEE 802.16e OFDMA standard, which was designed for handling irregular traffic pattern of MS, often produces a large DL-MAP, as a certain small amount of data distribution to MSs will render a potential overhead of information elements (IE) in DL-MAP and limit the overall capacity. Moreover, the robustness requirement on MAP broadcasting would further cause severe system overhead. As a solution, we propose two exclusive condensed DL-MAP structures, which only carry partial information of each rectangular burst in order to reduce the size of IE in DL-MAP. For each condensed DL-MAP structure, the algorithms for BS to produce the condensed DL-MAP structure and the scheme for MS to precisely reconstruct the original DL-MAP structure are provided. As confirmed by the analytical results, the proposed condensed DL-MAP can achieve significant DL-MAP size reduction compared with standard DL-MAP structure. --- paper_title: Efficient downlink scheduling with power boosting in mobile IEEE 802.16 networks paper_content: In current mobile broadband wireless access (BWA) technologies, which are based on orthogonal frequency division multiple access (OFDMA), terminals close to cell edge experience poor channel quality, due to severe path-loss and high interference from concurrent transmissions in nearby cells. To mitigate this problem we propose: (a) to partition the set of sub-channels into chunks, which are assigned different power levels; (b) the design of a data scheduling and allocation algorithm positioned in the medium access control (MAC) layer of the base station (BS), exploiting such a partitioning. The framework is analyzed in a multi-cell IEEE 802.16 network by means of system-level packet-based simulations, with detailed MAC and physical layer abstractions in combination with realistic models of the wireless channel and interference. --- paper_title: OBBP: An Efficient Burst Packing Algorithm for IEEE802.16e Systems paper_content: Mobile communications have witnessed a phenomenal increase in the amount of users, services, and applications. Orthogonal Frequency Division Multiple Access (OFDMA) targets to provide broadband connectivity to wide area coverage, in mobile environments, for Next Generation Networks (NGNs), which results in significant design challenges in the MAC (Medium Access Control) layer to provide an efficient resource allocation in a cost-effective manner. This paper proposes a two-dimensional (2D) Burst Packing (BP) algorithm for OFDMA downlink (DL) subframe that can provide the service providers with an efficient, fast, flexible, and high-spectral efficiency method to allocate system resources among the Mobile Stations (MSs). The proposed Orientation-Based Burst Packing (OBBP) algorithm uses the Orientation Factors (OFs) of the bursts as a criteria to achieve the challenging issues in the BP problem. The simulation results show that OBBP algorithm can achieve a high packing efficiency up to 99.2% when the burst size ratio (BSR) is 50%. --- paper_title: Cross-layer design for radio resource allocation based on priority scheduling in OFDMA wireless access network paper_content: The orthogonal frequency-division multiple access (OFDMA) system has the advantages of flexible subcarrier allocation and adaptive modulation with respect to channel conditions. However, transmission overhead is required in each frame to broadcast the arrangement of radio resources to all mobile stations within the coverage of the same base station. This overhead greatly affects the utilization of valuable radio resources. In this paper, a cross layer scheme is proposed to reduce the number of traffic bursts at the downlink of an OFDMA wireless access network so that the overhead of the media access protocol (MAP) field can be minimized. The proposed scheme considers the priorities and the channel conditions of quality of service (QoS) traffic streams to arrange for them to be sent with minimum bursts in a heuristic manner. In addition, the trade-off between the degradation of the modulation level and the reduction of traffic bursts is investigated. Simulation results show that the proposed scheme can effectively reduce the traffic bursts and, therefore, increase resource utilization. --- paper_title: eOCSA: An algorithm for burst mapping with strict QoS requirements in IEEE 802.16e Mobile WiMAX networks paper_content: Mobile WiMAX systems based on the IEEE 802.16e standard require all downlink allocations to be mapped to a rectangular region in the two dimensional subcarrier-time map. Many published resource allocation schemes ignore this requirement. It is possible that the allocations when mapped to rectangular regions may exceed the capacity of the downlink frame, and the QoS of some flows may be violated. The rectangle mapping problem is a variation of the bin or strip packing problem, which is known to be NP-complete. In a previous paper, an algorithm called OCSA (One Column Striping with non-increasing Area first mapping) for rectangular mapping was introduced. In this paper, we propose an enhanced version of the algorithm. Similar to OCSA, the enhanced algorithm is also simple and fast to implement; however, eOCSA considers the allocation of an additional resource to ensure the QoS. eOCSA also avoids an enumeration process and so lowers the complexity to O(n2). --- paper_title: A downlink data region allocation algorithm for IEEE 802.16e OFDMA paper_content: IEEE 802.16e specifies a connection-oriented centralized medium access control (MAC) protocol, based on time division multiple access (TDMA), which adds mobility support to the MAC protocol defined by the IEEE 802.16 standard for fixed broadband wireless access. To this end, orthogonal frequency division multiple access (OFDMA) is specified as the air interface. In OFDMA, the MAC frame extends over two dimensions: time, in units of OFDMA symbols, and frequency, in units of logical sub-channels. The base station (BS) is responsible for allocating data into the MAC frames so as to meet the quality of service (QoS) guarantees of the admitted connections of the mobile stations (MSs). This is done on a frame-by-frame basis by defining the content of map messages, which advertise the position and shape of data regions reserved for transmission to/from MSs. We refer to the latter operation as data region allocation. In this paper, we propose a sample data region allocation algorithm (SDRA), and we evaluate its performance by means of Monte Carlo analysis. The effectiveness of SDRA is assessed in several scenarios, involving mixed voice over IP (VoIP) and best effort MSs, different modulations, and frequency re-use plans. --- paper_title: Two-dimensional downlink burst construction in IEEE 802.16 networks paper_content: Several burst construction algorithms for orthogonal frequency division multiple access were proposed. However, these algorithms did not meet the downlink burst characteristics specified in the IEEE 802.16 standard. This article therefore proposes the best corner-oriented algorithm (BCO). BCO not only complies with downlink burst characteristics, but also considers the three issues to obtain high throughput, as follows: BCO maintains all free slots as a continuous area by constructing each burst in the corner of the available bandwidth area for minimizing external fragmentation; BCO shrinks the burst area to minimize internal fragmentation, if the requested bandwidth has been satisfied; and for exploring the continuous subchannels with good channel quality, BCO ensures that the burst adopts an optimal modulation coding scheme by selecting the excellent corner that can generate the maximal throughput. The simulation results indicate that BCO achieves 2-9 times the throughput achieved by the previous algorithms under a heavy load. --- paper_title: An Efficient Downlink Data Mapping Algorithm for IEEE802.16e OFDMA Systems paper_content: In the IEEE 802.16e OFDMA systems, the data mapping algorithm maps the data to the appropriate rectangular regions in the two-dimensional matrix of time and frequency domain. Each region is described by an Information Element (IE) which is used for signaling and occupies a slot. The IEs as well as vacant slots in the allocated rectangular region result in a substantial amount of overhead. In order to minimize the overhead so as to increase system throughput, the paper proposes a "Mapping with Appropriate Truncation and Sort" (MATS) algorithm. Extensive simulations are conducted in terms of mapping efficiency, mapping cost and system throughput to evaluate the performance of MATS. The results show that compared with Raster, MATS can increase the mapping efficiency by up to 2.4% and reduce the mapping cost by up to 80% and 37% for constant bit rate traffic and variable bit rate traffic, respectively. Moreover, system throughput is increased by more than 3% in the 10 MHz bandwidth network. Consequently, MATS can substantially reduce the overhead and achieve high system throughput. --- paper_title: Piggybacking Scheme of MAP IE for Minimizing MAC Overhead in the IEEE 802.16e OFDMA Systems paper_content: This paper analyzes Media Access Control(MAC) overhead of the IEEE 802.16e systems and shows that it causes to degrade system performance critically. MAP, a control message about resource allocation, is broadcasted with high robustness and uses a great amount of radio resource for it. This paper also proposes an advanced scheme which transmits MAP IE, a component of MAP, piggybacked on data packets, and uses fast feedback to conserve the transmission reliability of the MAP IE. Then, MAP IEs can be transmitted with high data rate, and the amount of radio resource for transmitting MAP IEs becomes extremely small. Numerical analysis and simulation results show that the proposed scheme can significantly improve the MAC overhead. --- paper_title: eOCSA: An algorithm for burst mapping with strict QoS requirements in IEEE 802.16e Mobile WiMAX networks paper_content: Mobile WiMAX systems based on the IEEE 802.16e standard require all downlink allocations to be mapped to a rectangular region in the two dimensional subcarrier-time map. Many published resource allocation schemes ignore this requirement. It is possible that the allocations when mapped to rectangular regions may exceed the capacity of the downlink frame, and the QoS of some flows may be violated. The rectangle mapping problem is a variation of the bin or strip packing problem, which is known to be NP-complete. In a previous paper, an algorithm called OCSA (One Column Striping with non-increasing Area first mapping) for rectangular mapping was introduced. In this paper, we propose an enhanced version of the algorithm. Similar to OCSA, the enhanced algorithm is also simple and fast to implement; however, eOCSA considers the allocation of an additional resource to ensure the QoS. eOCSA also avoids an enumeration process and so lowers the complexity to O(n2). ---	Title: Survey of Down Link Data Allocation Algorithms in IEEE 802.16 WiMAX Section 1: INTRODUCTION Description 1: Provide an overview of WiMAX technology, its advantages, and the challenges associated with resource allocation in WiMAX systems. Introduce the importance of scheduling and data packing algorithms, and highlight the paper's focus on downlink packing algorithms. Section 2: WIMAX OVERVIEW Description 2: Offer a general description of WiMAX as a wireless broadband solution, its standards, and key features. Section 3: PHY layer overview Description 3: Detail the physical layer specifications of WiMAX including the operating bands, OFDMA, modulation schemes, and frame structures. Section 4: MAC layer overview Description 4: Discuss the MAC layer, including its sublayers, functions such as PDU construction, QoS scheduling, call admission control, and bandwidth allocation. Section 5: WIMAX FRAME ALLOCATION Description 5: Explain the frame allocation process in TDD WiMAX, including the use of DL-MAP and UL-MAP messages, and the packing data into downlink and uplink frames. Section 6: DL-Map and its overhead Description 6: Illustrate how WiMAX assigns slots to users in downlink, the structure and impact of DL-MAP on the overall system, and an example scenario to highlight DL-MAP overhead. Section 7: Wastages slots in downlink frame Description 7: Provide a scenario to show how the packing process can lead to wastage slots in the downlink frame and discuss the implications on system performance. Section 8: SURVEY OF DOWNLINK PACKING ALGORITHMS Description 8: Conduct a comprehensive survey of various downlink packing algorithms, discuss their focus and efficiency based on different factors like fragments, power consumption, DL_MAP overhead, and cross-layer design considerations. Section 9: Some considerations and design factors for downlink packing algorithm Description 9: Discuss the considerations and design factors essential for developing an efficient downlink packing algorithm, emphasizing the trade-offs among different performance aspects. Section 10: CONCLUSION Description 10: Summarize the study, reiterate the importance of optimizing trade-offs in downlink data packing algorithms, and point out the need for comprehensive comparative analysis of existing algorithms under varied traffic classes.
Multivariate Statistical Process Control Charts and the Problem of Interpretation : A Short Overview and Some Applications in Industry	5	--- paper_title: RESEARCH ISSUES AND IDEAS IN STATISTICAL PROCESS CONTROL paper_content: An overview is given of current research on control charting methods for process monitoring and improvement. A historical perspective and ideas for future research also are given. Research topics include: variable sample size and sampling interval met.. --- paper_title: Multivariate SPC Methods for Process and Product Monitoring paper_content: Statistical process control methods for monitoring processes with multivariate measurements in both the product quality variable space and the process variable space are considered. Traditional multivariate control charts based on X2 and T2 statistics .. --- paper_title: Generalized contribution plots in multivariate statistical process monitoring paper_content: Abstract This paper discusses contribution plots for both the D -statistic and the Q -statistic in multivariate statistical process control of batch processes. Contributions of process variables to the D -statistic are generalized to any type of latent variable model with or without orthogonality constraints. The calculation of contributions to the Q -statistic is discussed. Control limits for both types of contributions are introduced to show the relative importance of a contribution compared to the contributions of the corresponding process variables in the batches obtained under normal operating conditions. The contributions are introduced for off-line monitoring of batch processes, but can easily be extended to on-line monitoring and to continuous processes, as is shown in this paper. --- paper_title: Comparisons of Multivariate CUSUM Charts paper_content: We consider several distinct approaches for controlling the mean of a multivariate normal process including two new and distinct multivariate CUSUM charts, several multiple univariate CUSUM charts, and a Shewhart x2 control chart. The performances of th.. --- paper_title: A review of multivariate control charts paper_content: A review of the literature on control charts for multivariate quality control (MQC) is given, with a concentration on developments occurring since the mid-1980s. Multivariate cumulative sum (CUSUM) control procedures and a multivariate exponentially weighted moving average (EWMA) control chart are reviewed and recommendations are made regarding their use. Several recent articles that give methods for interpreting an out-of-control signal on a multivariate control chart are analyzed and discussed. Other topics such as the use of principal components and regression adjustment of variables in MQC, as well as frequently used approximations in MQC, are discussed. --- paper_title: Multivariate generalizations of cumulative sum quality-control schemes paper_content: This article presents the design procedures and average run lengths for two mulativariater cumulative sum (CUSUM) quality-control procedures. The first CUSUM procedure reduces each multivariate observation to a scalar and then forms a CUSUM of the scalars. The second CUSUM procedure forms a CUSUM vector directly from the observations. These two procedures are compared with each other and with the multivariate Shewhart chart. Other multivariate quality-control procedures are mentioned. Robustness, the fast initial response feature for CUSUM schemes, and combined Shewhart-CUSUM schemes are discussed. --- paper_title: Multivariate statistical process control—recent results and directions for future research paper_content: The performance of a product often depends on several quality characteristics. These characteristics may have interactions. In answering the question “Is the process in control?”, multivariate statistical process control methods take these interactions into account. In this paper, we review several of these multivariate methods and point out where to fill up gaps in the theory. The review includes multivariate control charts, multivariate CUSUM charts, a multivariate MMA chart, and multivariate process capability indices. The most important open question from a practical point of view is how to detect the variables that caused an out-of-control signal. Theoretically, the statistical properties of the methods should be investigated more profoundly. --- paper_title: Multivariate CUSUM Quality- Control Procedures paper_content: It is a common practice to use, simultaneously, several one-sided or two-sided CUSUM procedures of the type proposed by Page (1954). In this article, this method of control is considered to be a single multivariate CUSUM (MCUSUM) procedure. Methods are given for approximating parameters of the distribution of the minimum of the run lengths of the univariate CUSUM charts. Using a new method of comparing multivariate control charts, it is shown that an MCUSUM procedure is often preferable to Hotelling's TZ procedure for the case in which the quality characteristics are bivariate normal random variables. --- paper_title: Multivariate Statistical Process Control with Industrial Applications paper_content: This applied, self-contained text provides detailed coverage of the practical aspects of multivariate statistical process control (MVSPC) based on the application of Hotelling's T2 statistic. MVSPC is the application of multivariate statistical techniques to improve the quality and productivity of an industrial process. The authors, leading researchers in this area who have developed major software for this type of charting procedure, provide valuable insight into the T2 statistic. Intentionally including only a minimal amount of theory, they lead readers through the construction and monitoring phases of the T2 control statistic using numerous industrial examples taken primarily from the chemical and power industries. These examples are applied to the construction of historical data sets to serve as a point of reference for the control procedure and are also applied to the monitoring phase, where emphasis is placed on signal location and interpretation in terms of the process variables. Specifically devoted to the T2 methodology, Multivariate Statistical Process Control with Industrial Applications is the only book available that concisely and thoroughly presents such topics as how to construct a historical data set; how to check the necessary assumptions used with this procedure; how to chart the T2 statistic; how to interpret its signals; how to use the chart in the presence of autocorrelated data; and how to apply the procedure to batch processes. The book comes with a CD-ROM containing a 90-day demonstration version of the QualStat multivariate SPC software specifically designed for the application of T2 control procedures. The CD-ROM is compatible with Windows 95, Windows 98, Windows Me Millennium Edition, and Windows NT operating systems. --- paper_title: Improving the Performance of the Chi-square Control Chart via Runs Rules paper_content: The most popular multivariate process monitoring and control procedure used in the industry is the chi-square control chart. As with most Shewhart-type control charts, the major disadvantage of the chi-square control chart, is that it only uses the information contained in the most recently inspected sample; as a consequence, it is not very efficient in detecting gradual or small shifts in the process mean vector. During the last decades, the performance improvement of the chi-square control chart has attracted continuous research interest. In this paper we introduce a simple modification of the chi-square control chart which makes use of the notion of runs to improve the sensitivity of the chart in the case of small and moderate process mean vector shifts. --- paper_title: Multivariate Profile Charts for Statistical Process Control paper_content: The multivariate profile (MP) chart is a new control chart for simultaneous display of univariate and multivariate statistics. It is designed to analyze and display extended structures of statistical process control data for various cases of grouping, reference distribution, and use of nominal specifications. For each group of observations, the scaled deviations from reference values are portrayed together as a modified profile plot symbol. The vertical location of the symbol is determined by the multivariate distance of the vector of means from the reference values. The graphical display in the MP chart enjoys improved visual characteristics as compared with previously suggested methods. Moreover, the perceptual tasks required by the use of the MP chart provide higher accuracy in retrieving the quantitative information. This graphical display is used to display other combined univariate and multivariate statistics, such as measures of dispersion, principal components, and cumulative sums --- paper_title: Multivariate SPC Methods for Process and Product Monitoring paper_content: Statistical process control methods for monitoring processes with multivariate measurements in both the product quality variable space and the process variable space are considered. Traditional multivariate control charts based on X2 and T2 statistics .. --- paper_title: Multivariate Quality Control Using Finite Intersection Tests paper_content: Multivariate quality control problems involve the evaluation of a process based on the simultaneous behavior of p variables. Most multivariate quality control procedures evaluate the in-control or out-of-control condition based upon an overall statistic.. --- paper_title: Decomposition of T2 for Multivariate Control Chart Interpretation paper_content: Cumulative sum (CUSUM) control charts have been widely used for monitoring the process mean. Relatively little attention has been given to the use of CUSUM charts for monitoring the process variance. The properties of CUSUM charts based on the logarithm.. --- paper_title: A Practical Approach for Interpreting Multivariate T2 Control Chart Signals paper_content: A persistent problem in multivariate control chart procedures is the interpretation of a signal. Determining which variable or group of variables is contributing to the signal can be a difficult task fo rthe practitioner. However, a procedure for decomp.. --- paper_title: Generalized contribution plots in multivariate statistical process monitoring paper_content: Abstract This paper discusses contribution plots for both the D -statistic and the Q -statistic in multivariate statistical process control of batch processes. Contributions of process variables to the D -statistic are generalized to any type of latent variable model with or without orthogonality constraints. The calculation of contributions to the Q -statistic is discussed. Control limits for both types of contributions are introduced to show the relative importance of a contribution compared to the contributions of the corresponding process variables in the batches obtained under normal operating conditions. The contributions are introduced for off-line monitoring of batch processes, but can easily be extended to on-line monitoring and to continuous processes, as is shown in this paper. --- paper_title: Investigation and characterization of a control scheme for multivariate quality control paper_content: A new scheme for multivariate statistical quality control is investigated and characterized. The control scheme consists of three steps and it will identify any out-of-control samples, select the subset of variables that are out of control, and diagnose the out-of-control variables. A new control variable selection algorithm, the backward selection algorithm, and a new control variable diagnosis method, the hyperplane methods, are proposed. It is shown by simulation that the control scheme is useful in cases where the process variables are correlated and where they are uncorrelated. --- paper_title: Identification and Quantification in Multivariate Quality Control Problems paper_content: Many quality control problems are multivariate in character since the quality of a given product or object consists simultaneously of more than one variable. A good multivariate quality control procedure should possess three important properties, namely, the control of the overall error rate, the easy identification of errant variables, and the easy quantification of any changes in the variable means. In this paper a procedure is suggested based on the construction of exact simultaneous confidence intervals for each of the variable means that meets each of these three goals. Both parametric and nonparametric procedures are considered, and critical point evaluation through tables, numerical integration, and simulation is discussed. Various examples of the implementation of the procedure are given. --- paper_title: IDENTIFYING THE OUT OF CONTROL VARIABLE IN A MULTIVARIATE CONTROL CHART paper_content: The identification of the out of control variable, or variables, after a multivariate control chart signals, is an appealing subject for many researchers in the last years. In this paper we propose a new method for approaching this problem based on principal components analysis. Theoretical control limits are derived and a detailed investigation of the properties and the limitations of the new method is given. A graphical technique which can be applied in some of these limiting situations is also provided. --- paper_title: Improving the Sensitivity of the T2 Statistic in Multivariate Process Control paper_content: The T2 statistic in multivariate process control is a function of the residuals taken from a set of linear regressions of the process variables. These residuals are contained in the conditional T2 terms of the orthogonal decomposition of the statistic... --- paper_title: Monitoring a Multivariate Step Process paper_content: The productivity of an industrial processing unit often depends on equipment that changes over time. These changes may not be consistent, and , in many cases, may appear to occur in stages. Although changes in the process levels within each stage may ap.. --- paper_title: Multivariate Control Charts for Individual Observations paper_content: When p correlated process characteristics are being measured simultaneously, often individual observations are initially collected. The process data are monitored and special causes of variation are identified in order to establish control and to obtain.. --- paper_title: Visualization of multivariate data with radial plots using SAS paper_content: Data visualization tools can provide very powerful information and insight when performing data analysis. In many situations, a set of data can be adequately analyzed through data visualization methods alone. In other situations, data visualization can be used for preliminary data analysis. In this paper, radial plots are developed as a SAS-based data visualization tool that can improve one's ability to monitor, analyze and control a process. Using the program developed in this research, we present two examples of data analysis using radial plots; the first example is based on data from a particle board manufacturing process and the second example is a business process for monitoring the time-varying level of stock return data. --- paper_title: Multivariate Process Monitoring Using the Dynamic Biplot paper_content: Summary ::: ::: In this article, we present a method for monitoring multivariate process data based on the Gabriel biplot. In contrast to existing methods that are based on some form of dimension reduction, we use reduction to two dimensions for displaying the state of the process but all the data for determining whether it is in a state of statistical control. This approach allows us to detect changes in location, variation, and correlational structure accurately yet display a large amount of information concisely. We illustrate the use of the biplot on an example of industrial data and also discuss some of the issues related to a practical implementation of the method. --- paper_title: IDENTIFYING THE OUT OF CONTROL VARIABLE IN A MULTIVARIATE CONTROL CHART paper_content: The identification of the out of control variable, or variables, after a multivariate control chart signals, is an appealing subject for many researchers in the last years. In this paper we propose a new method for approaching this problem based on principal components analysis. Theoretical control limits are derived and a detailed investigation of the properties and the limitations of the new method is given. A graphical technique which can be applied in some of these limiting situations is also provided. ---	Title: Multivariate Statistical Process Control Charts and the Problem of Interpretation: A Short Overview and Some Applications in Industry Section 1: INTRODUCTION Description 1: Introduce the basic concept of Statistical Process Control (SPC), highlight the limitations of univariate SPC in process industries, and provide an overview of multivariate SPC techniques and their historical development. Section 2: CONTROLLING AND MONITORING MULTIVARIATE PROCESSES USING CONTROL CHARTS Description 2: Describe the implementation of multivariate statistical process control using control charts, including detailed explanations of Phase I and Phase II control charting, and discuss different types of multivariate control charts such as Shewhart, CUSUM, and EWMA. Section 3: IDENTIFYING THE OUT-OF-CONTROL VARIABLE Description 3: Present various methods for detecting which specific variables are out of control when an out-of-control signal is identified in a multivariate control chart, including Bonferroni limits, principal component analysis, and contribution plots. Section 4: APPLICATIONS OF MULTIVARIATE SPC TECHNIQUES IN THE INDUSTRIAL ENVIRONMENT Description 4: Discuss real-world applications of multivariate SPC techniques in industry, focusing on a three-variable case study in a chemical process, and describe Phase I and Phase II analysis procedures along with identification methods for out-of-control variables. Section 5: COMMENTS Description 5: Offer concluding remarks and discuss potential areas for further research in the domain of multivariate SPC, such as robust design, nonparametric control charts, and improved methods for interpreting out-of-control signals.
A Review of Closed-Loop Algorithms for Glycemic Control in the Treatment of Type 1 Diabetes	6	--- paper_title: Closing the Loop: The Adicol Experience paper_content: The objective of the project Advanced Insulin Infusion using a Control Loop (ADICOL) was to develop a treatment system that continuously measures and controls the glucose concentration in subjects with type 1 diabetes. The modular concept of the ADICOL's extracorporeal artificial pancreas consisted of a minimally invasive subcutaneous glucose system, a handheld PocketPC computer, and an insulin pump (D-Tron, Disetronic, Burgdorf, Switzerland) delivering subcutaneously insulin lispro. The present paper describes a subset of ADICOL activities focusing on the development of a glucose controller for semi-closed-loop control, an in silico testing environment, clinical testing, and system integration. An incremental approach was adopted to evaluate experimentally a model predictive glucose controller. A feasibility study was followed by efficacy studies of increasing complexity. The ADICOL project demonstrated feasibility of a semi-closed-loop glucose control during fasting and fed conditions with a wearable, m... --- paper_title: The future of open- and closed-loop insulin delivery systems. paper_content: We have analysed several aspects of insulin-dependent diabetes mellitus, including the glucose metabolic system, diabetes complications, and previous and ongoing research aimed at controlling glucose in diabetic patients. An expert review of various models and control algorithms developed for the glucose homeostasis system is presented, along with an analysis of research towards the development of a polymeric insulin infusion system. Recommendations for future directions in creating a true closed-loop glucose control system are presented, including the development of multivariable models and control systems to more accurately describe and control the multi-metabolite, multi-hormonal system, as well as in-vivo assessments of implicit closed-loop control systems. --- paper_title: Hypoglycaemia: The limiting factor in the glycaemic management of Type I and Type II Diabetes* paper_content: Hypoglycaemia is the limiting factor in the glycaemic management of diabetes. Iatrogenic hypoglycaemia is typically the result of the interplay of insulin excess and compromised glucose counterregulation in Type I (insulin-dependent) diabetes mellitus. Insulin concentrations do not decrease and glucagon and epinephrine concentrations do not increase normally as glucose concentrations decrease. The concept of hypoglycaemia-associated autonomic failure (HAAF) in Type I diabetes posits that recent antecedent iatrogenic hypoglycaemia causes both defective glucose counterregulation (by reducing the epinephrine response in the setting of an absent glucagon response) and hypoglycaemia unawareness (by reducing the autonomic and the resulting neurogenic symptom responses). Perhaps the most compelling support for HAAF is the finding that as little as 2 to 3 weeks of scrupulous avoidance of hypoglycaemia reverses hypoglycaemia unawareness and improves the reduced epinephrine component of defective glucose counterregulation in most affected patients. The mediator and mechanism of HAAF are not known but are under active investigation. The glucagon response to hypoglycaemia is also reduced in patients approaching the insulin deficient end of the spectrum of Type II (non-insulin-dependent) diabetes mellitus, and glycaemic thresholds for autonomic (including epinephrine) and symptomatic responses to hypoglycaemia are shifted to lower plasma glucose concentrations after hypoglycaemia in Type II diabetes. Thus, patients with advanced Type II diabetes are also at risk for HAAF. While it is possible to minimise the risk of hypoglycaemia by reducing risks ‐ including a 2 to 3 week period of scrupulous avoidance of hypoglycaemia in patients with hypoglycaemia unawareness ‐ methods that provide glucose-regulated insulin replacement or secretion are needed to eliminate hypoglycaemia and maintain euglycaemia over a lifetime of diabetes. [Diabetologia (2002) 45:937‐948] --- paper_title: Physiologic evaluation of factors controlling glucose tolerance in man: measurement of insulin sensitivity and beta-cell glucose sensitivity from the response to intravenous glucose. paper_content: The quantitative contributions of pancreatic responsiveness and insulin sensitivity to glucose tolerance were measured using the "minimal modeling technique" in 18 lean and obese subjects (88-206% ideal body wt). The individual contributions of insulin secretion and action were measured by interpreting the dynamics of plasma glucose and insulin during the intravenous glucose tolerance test in terms of two mathematical models. One, the insulin kinetics model, yields parameters of first-phase (phi 1) and second-phase (phi 2) responsivity of the beta-cells to glucose. The other glucose kinetics model yields the insulin sensitivity parameters, SI. Lean and obese subjects were subdivided into good (KG greater than 1.5) and lower (KG less than 1.5) glucose tolerance groups. The etiology of lower glucose tolerance was entirely different in lean and obese subjects. Lean, lower tolerance was related to pancreatic insufficiency (phi 2 77% lower than in good tolerance controls [P less than 0.03]), but insulin sensitivity was normal (P greater than 0.5). In contrast, obese lower tolerance was entirely due to insulin resistance (SI diminished 60% [P less than 0.01]); pancreatic responsiveness was not different from lean, good tolerance controls (phi 1: P greater than 0.06; phi 2: P greater than 0.40). Subjects (regardless of weight) could be segregated into good and lower tolerance by the product of second-phase beta-cell responsivity and insulin sensitivity (phi 2 . SI). Thus, these two factors were primarily responsible for overall determination of glucose tolerance. The effect of phi 1 was to modulate the KG value within those groups whose overall tolerance was determined by phi 2 . SI. This phi 1 modulating influence was more pronounced among insulin sensitive (phi 1 vs. KG, r = 0.79) than insulin resistant (obese, low tolerance; phi 1 vs. KG, r = 0.91) subjects. This study demonstrates the feasibility of the minimal model technique to determine the etiology of impaired glucose tolerance. --- paper_title: Reduced beta-cell compensation to the insulin resistance associated with obesity in members of caucasian familial type 2 diabetic kindreds. paper_content: OBJECTIVE: Both obesity and a family history of diabetes reduce insulin sensitivity, but the impact of obesity on insulin secretion among individuals predisposed to diabetes is uncertain. We used a pedigree-based approach to test the hypothesis that beta-cell compensation to the insulin resistance associated with obesity is defective among individuals predisposed to diabetes by virtue of a strong family history of type 2 diabetes before the development of diabetes or glucose intolerance. RESEARCH DESIGN AND METHODS: A total of 126 members of 26 families ascertained for at least a sib pair with type 2 diabetes with onset before age 65 years underwent a tolbutamide-modified frequently sampled intravenous glucose tolerance test (FSIGT). Family members included 26 individuals with impaired glucose tolerance and 100 individuals with normal glucose tolerance (NGT). The acute insulin response to glucose (AIRglucose) was determined and insulin sensitivity (S(I)) estimated by minimal model analysis of FSIGT data. The beta-cell compensation for insulin sensitivity was estimated from the disposition index (DI), calculated as the product of S(I) and AIRglucose. Obesity was measured by BMI. RESULTS: Among all individuals, BMI was a significant predictor of both S(I) and AIRglucose, as expected. However, BMI also significantly predicted DI (P = 0.002) after correcting for age, sex, family membership, and glucose tolerance status. The relationship of BMI and DI was confirmed in 85 individuals with NGT who were aged 30), S(I) decreased progressively and significantly with obesity whereas AIRglucose rose significantly from lean to most obese classes. In contrast to the expectation of complete beta-cell compensation with obesity D1 fell significantly (P = 0.004) among obese family members. This relationship was not observed in control subjects. CONCLUSIONS: Individuals with a genetic predisposition to diabetes show a reduced beta-cell compensatory response to the reduced insulin sensitivity associated with obesity. We propose that this impaired compensation may be one manifestation of the underlying genetic defect in susceptible individuals. This finding helps explain the multiplicative effects of family history and obesity on risk of type 2 diabetes. --- paper_title: Continuous Glucose Monitoring and Intensive Treatment of Type 1 Diabetes paper_content: BACKGROUND ::: The value of continuous glucose monitoring in the management of type 1 diabetes mellitus has not been determined. ::: ::: ::: METHODS ::: In a multicenter clinical trial, we randomly assigned 322 adults and children who were already receiving intensive therapy for type 1 diabetes to a group with continuous glucose monitoring or to a control group performing home monitoring with a blood glucose meter. All the patients were stratified into three groups according to age and had a glycated hemoglobin level of 7.0 to 10.0%. The primary outcome was the change in the glycated hemoglobin level at 26 weeks. ::: ::: ::: RESULTS ::: The changes in glycated hemoglobin levels in the two study groups varied markedly according to age group (P=0.003), with a significant difference among patients 25 years of age or older that favored the continuous-monitoring group (mean difference in change, -0.53%; 95% confidence interval [CI], -0.71 to -0.35; P<0.001). The between-group difference was not significant among those who were 15 to 24 years of age (mean difference, 0.08; 95% CI, -0.17 to 0.33; P=0.52) or among those who were 8 to 14 years of age (mean difference, -0.13; 95% CI, -0.38 to 0.11; P=0.29). Secondary glycated hemoglobin outcomes were better in the continuous-monitoring group than in the control group among the oldest and youngest patients but not among those who were 15 to 24 years of age. The use of continuous glucose monitoring averaged 6.0 or more days per week for 83% of patients 25 years of age or older, 30% of those 15 to 24 years of age, and 50% of those 8 to 14 years of age. The rate of severe hypoglycemia was low and did not differ between the two study groups; however, the trial was not powered to detect such a difference. ::: ::: ::: CONCLUSIONS ::: Continuous glucose monitoring can be associated with improved glycemic control in adults with type 1 diabetes. Further work is needed to identify barriers to effectiveness of continuous monitoring in children and adolescents. (ClinicalTrials.gov number, NCT00406133.) --- paper_title: An overview of pancreatic beta-cell defects in human type 2 diabetes: Implications for treatment paper_content: Type 2 diabetes is the most common form of diabetes in humans. It results from a combination of factors that impair beta-cell function and tissue insulin sensitivity. However, growing evidence is showing that the beta-cell is central to the development and progression of this form of diabetes. Reduced islet and/or insulin-containing cell mass or volume in Type 2 diabetes has been reported by several authors. Furthermore, studies with isolated Type 2 diabetic islets have consistently shown both quantitative and qualitative defects of glucose-stimulated insulin secretion. The impact of genotype in affecting beta-cell function and survival is a very fast growing field or research, and several gene polymorphisms have been associated with this form of diabetes. Among acquired factors, glucotoxicity, lipotoxicity and altered IAPP processing are likely to play an important role. Interestingly, however, pharmacological intervention can improve several defects of Type 2 diabetes islet cells in vitro, suggesting that progression of the disease might not be relentless. --- paper_title: The hot IVGTT two-compartment minimal model: indexes of glucose effectiveness and insulin sensitivity paper_content: A two-compartment minimal model (2CMM) has been proposed [A. Caumo and C. Cobelli. Am. J. Physiol. 264 ( Endocrinol. Metab. 27): E829–E841, 1993] to describe intravenous glucose tolerance test (IVGTT) labeled (hereafter hot) glucose kinetics. This model, at variance with the one-compartment minimal model (1CMM), allows the estimation of a plausible profile of glucose production. The aim of this study is to show that the 2CMM also allows the assessment of insulin sensitivity (![Formula][1] ), glucose effectiveness (![Formula][2] ), and plasma clearance rate (PCR). The 2CMM was identified on stable-isotope IVGTTs performed in normal subjects ( n = 14). Results were (means ± SE) ![Formula][3] = 0.85 ± 0.14 ml ⋅ kg−1 ⋅ min−1, PCR = 2.02 ± 0.14 ml ⋅ kg−1 ⋅ min−1, and ![Formula][4] = 13.83 ± 2.54 × 10−2ml ⋅ kg−1 ⋅ min−1 ⋅ μU−1 ⋅ ml. The 1CMM was also identified; glucose effectiveness and insulin sensitivity indexes were ![Formula][5] V = 1.36 ± 0.08 ml ⋅ kg−1 ⋅ min−1and ![Formula][6] V = 12.98 ± 2.21 × 10−2ml ⋅ kg−1 ⋅ min−1 ⋅ μU−1 ⋅ ml, respectively, where V is the 1CMM glucose distribution volume.![Formula][7] V was lower than PCR and higher than ![Formula][8] and did not correlate with either [ r = 0.45 (NS) and r = 0.50 (NS), respectively], whereas ![Formula][9] V was not different from and was correlated with![Formula][10] ( r = 0.95; P compares well ( r = 0.78; P < 0.001) with PCR normalized by the 2CMM total glucose distribution volume. In conclusion, the 2CMM is a powerful tool to assess glucose metabolism in vivo. ::: ::: [1]: /embed/mml-math-1.gif ::: [2]: /embed/mml-math-2.gif ::: [3]: /embed/mml-math-3.gif ::: [4]: /embed/mml-math-4.gif ::: [5]: /embed/mml-math-5.gif ::: [6]: /embed/mml-math-6.gif ::: [7]: /embed/mml-math-7.gif ::: [8]: /embed/mml-math-8.gif ::: [9]: /embed/mml-math-9.gif ::: [10]: /embed/mml-math-10.gif ::: [11]: /embed/mml-math-11.gif --- paper_title: Coefficients of normal blood glucose regulation. paper_content: A previously formulated glucose-insulin feed-back theory was simplified with appropriate assumptions for the purpose of determining which physiological sensitivity coefficients dominate the mathematical characteristics of the normal insulin and glucose tolerance curves. It was found from experimental data that these physiological coefficients approximate the well-known critical damping criteria of servomechanism theory. Correlations between theoretical and experimental results were made with some particular solutions of the necessary differential equations, obtained with the aid of an electronic analogue computer. Using a distribution volume of 17.5 liters for the 70-kg adult in three different methods of approach, it was found that the average coefficients of the insulin and glucose responses of the liver, pancreas, and peripheral tissues are approximately ⍺ = 0.780 unit/hr/unit, β = 0.208 unit/hr/g, γ = 4.34 g/hr/unit, and δ = 2.92 g/hr/g. ::: ::: Submitted on December 27, 1960 --- paper_title: A Mathematical Model for the Glucose Induced Insulin Release in Man paper_content: Abstract. The dynamics of the insulin response to intravenously administered glucose were studied in man. It was shown that (a) insulin response to prolonged stimulation is biphasic; (b) if the glucose stimulus is repeated with short intervals, inhibition of the second response occurs; (c) if longer time-intervals are used, enhancement of the response is noted at the second stimulation. These findings suggest that when the pancreatic islets are exposed to hyperglycaemia, three, kinetically distinct phenomena are initiated. Glucose induces almost instantaneous initiation of insulin release. Shortly thereafter, the pancreas enters a refractory phase. Thirdly, and at a later stage, a state of potentiation is built up in the islets. The effect of glucose on insulin synthesis is not considered here.–Against this background, and based on an earlier model, a mathematical model for the analysis of the glucose-insulin interplay during glucose infusions was constructed. The model describes the eventual occurrence of glucosuria, changes in the concentration of glucose in its pool, and mimics the effects of regulatory hormones when hypoglycemia appears. Insulin secretion is assumed to be con trolled, in a multiplicative manner, by an immediate glucose function, a hypothetical potentiator that is slowly generated by glucose, and a negative factor with a shorter time-course which corresponds to the refractory phase of the pancreas. A three compartment model is used in the simulation of the metabolism and distribution of insulin after its release. Finally, glucose utilization is described as a multiplicative function, related to the prevailing concentrations of glucose in blood and insulin in the extracellular space.–This model is able to simulate all the experimental situations described in this report, both in normal man and in the diabetic syndrome, in which insulin secretion shows varying degrees of impairment. The results of the simulation of individual experiments are given either as a set of theoretical parameter values, or described as the insulin response of the model to a standard, hypothetical glucose stimulus. The latter alternative is an attractive method for objectively evaluating the insulin response to a standard glucose load in clinical materials. --- paper_title: PID controller tuning for the first-order-plus-dead-time process model via Hermite-Biehler theorem. paper_content: This paper discusses PID stabilization of a first-order-plus-dead-time (FOPDT) process model using the stability framework of the Hermite-Biehler theorem. The FOPDT model approximates many processes in the chemical and petroleum industries. Using a PID controller and first-order Padé approximation for the transport delay, the Hermite-Biehler theorem allows one to analytically study the stability of the closed-loop system. We derive necessary and sufficient conditions for stability and develop an algorithm for selection of stabilizing feedback gains. The results are given in terms of stability bounds that are functions of plant parameters. Sensitivity and disturbance rejection characteristics of the proposed PID controller are studied. The results are compared with established tuning methods such as Ziegler-Nichols, Cohen-Coon, and internal model control. --- paper_title: Modelingβ-Cell Insulin Secretion - Implications for Closed-Loop Glucose Homeostasis paper_content: Glucose sensing and insulin delivery technology can potentially be linked to form a closed-loop insulin delivery system. Ideally, such a system would establish normal physiologic glucose profiles. To this end, a model of β-cell secretion can potentially provide insight into the preferred structure of the insulin delivery algorithm. Two secretion models were evaluated for their ability to describe plasma insulin dynamics during hyperglycemic clamps (humans; n = 7), and for their ability to establish and maintain fasting euglycemia under conditions simulated by the minimal model. The first β-cell model (SD) characterized insulin secretion as a static component that had a delayed response to glucose, and a dynamic component that responded to the rate of increase of glucose. The second model (PID) described the response in terms of a proportional component without delay, an integral component that adjusted basal delivery in proportion to hyper/hypoglycemia, and a derivative component that responded to the rat... --- paper_title: Cascade control strategy for external carbon dosage in predenitrifying process paper_content: We propose a cascade control strategy composed of two Proportional-Integral (PI) controllers to regulate the nitrate concentration in the predenitrifying process by manipulating the external carbon dosage. It controls the nitrate concentrations in the effluent as well as in the final anoxic reactor simultaneously to strictly satisfy the quality of the effluent as well as to remove the effects of disturbances more quickly. The design of two PI controllers in the cascade control loop can be completed with the Ziegler–Nichols (Z–N) tuning rule together with a simple relay feedback identification method. Results from the Benchmark simulation confirm that both good set point tracking and satisfactory disturbance rejection can be guaranteed due to the structural advantages of the proposed cascade control strategy. Also, compared with a previous work, the fluctuation of the nitrate concentration in the effluent has been decreased significantly. --- paper_title: Continuous Glucose Monitoring and Intensive Treatment of Type 1 Diabetes paper_content: BACKGROUND ::: The value of continuous glucose monitoring in the management of type 1 diabetes mellitus has not been determined. ::: ::: ::: METHODS ::: In a multicenter clinical trial, we randomly assigned 322 adults and children who were already receiving intensive therapy for type 1 diabetes to a group with continuous glucose monitoring or to a control group performing home monitoring with a blood glucose meter. All the patients were stratified into three groups according to age and had a glycated hemoglobin level of 7.0 to 10.0%. The primary outcome was the change in the glycated hemoglobin level at 26 weeks. ::: ::: ::: RESULTS ::: The changes in glycated hemoglobin levels in the two study groups varied markedly according to age group (P=0.003), with a significant difference among patients 25 years of age or older that favored the continuous-monitoring group (mean difference in change, -0.53%; 95% confidence interval [CI], -0.71 to -0.35; P<0.001). The between-group difference was not significant among those who were 15 to 24 years of age (mean difference, 0.08; 95% CI, -0.17 to 0.33; P=0.52) or among those who were 8 to 14 years of age (mean difference, -0.13; 95% CI, -0.38 to 0.11; P=0.29). Secondary glycated hemoglobin outcomes were better in the continuous-monitoring group than in the control group among the oldest and youngest patients but not among those who were 15 to 24 years of age. The use of continuous glucose monitoring averaged 6.0 or more days per week for 83% of patients 25 years of age or older, 30% of those 15 to 24 years of age, and 50% of those 8 to 14 years of age. The rate of severe hypoglycemia was low and did not differ between the two study groups; however, the trial was not powered to detect such a difference. ::: ::: ::: CONCLUSIONS ::: Continuous glucose monitoring can be associated with improved glycemic control in adults with type 1 diabetes. Further work is needed to identify barriers to effectiveness of continuous monitoring in children and adolescents. (ClinicalTrials.gov number, NCT00406133.) --- paper_title: Process Control in Municipal Solid Waste Incinerators: Survey and Assessment paper_content: As there is only rare and scattered published information about the process control in industrial incineration facilities for municipal solid waste (MSW), a survey of the literature has been supplemented by a number of waste incineration site visits in Belgium and the Netherlands, in order to make a realistic assessment of the current status of technology in the area. Owing to the commercial character, and therefore, the confidentiality restrictions imposed by plant builders and many of the operators, much of the information collected has either to be presented in a generalized manner, and in any case anonymously. The survey was focused on four major issues: process control strategy, process control systems, monitors used for process control and finally the correlation between the 850°C/2 s rule in the European waste incineration directive and integrated process control. The process control strategies range from reaching good and stable emissions at the stack to stabilizing and maximizing the energy outpu... --- paper_title: Nonlinear model predictive control of glucose concentration in subjects with type 1 diabetes paper_content: A nonlinear model predictive controller has been developed to maintain normoglycemia in subjects with type 1 diabetes during fasting conditions such as during overnight fast. The controller employs a compartment model, which represents the glucoregulatory system and includes submodels representing absorption of subcutaneously administered short-acting insulin Lispro and gut absorption. The controller uses Bayesian parameter estimation to determine time-varying model parameters. Moving target trajectory facilitates slow, controlled normalization of elevated glucose levels and faster normalization of low glucose values. The predictive capabilities of the model have been evaluated using data from 15 clinical experiments in subjects with type 1 diabetes. The experiments employed intravenous glucose sampling (every 15 min) and subcutaneous infusion of insulin Lispro by insulin pump (modified also every 15 min). The model gave glucose predictions with a mean square error proportionally related to the prediction horizon with the value of 0.2 mmol L−1 per 15 min. The assessment of clinical utility of model-based glucose predictions using Clarke error grid analysis gave 95% of values in zone A and the remaining 5% of values in zone B for glucose predictions up to 60 min (n = 1674). In conclusion, adaptive nonlinear model predictive control is promising for the control of glucose concentration during fasting conditions in subjects with type 1 diabetes. --- paper_title: Blood Glucose Control by a Model Predictive Control Algorithm with Variable Sampling Rate Versus a Routine Glucose Management Protocol in Cardiac Surgery Patients: A Randomized Controlled Trial paper_content: Context: Elevated blood glucose levels occur frequently in the critically ill. Tight glucose control by intensive insulin treatment markedly improves clinical outcome. Objective and Design: This is a randomized controlled trial comparing blood glucose control by a laptop-based model predictive control algorithm with a variable sampling rate [enhanced model predictive control (eMPC); version 1.04.03] against a routine glucose management protocol (RMP) during the peri- and postoperative periods. Setting: The study was performed at the Department of Cardiac Surgery, University Hospital. Patients: A total of 60 elective cardiac surgery patients were included in the study. Interventions: Elective cardiac surgery and treatment with continuous insulin infusion (eMPC) or continuous insulin infusion combined with iv insulin boluses (RMP) to maintain euglycemia (target range 4.4–6.1 mmol/liter) were performed. There were 30 patients randomized for eMPC and 30 for RMP treatment. Blood glucose was measured in 1- to 4... --- paper_title: Closing the Loop: The Adicol Experience paper_content: The objective of the project Advanced Insulin Infusion using a Control Loop (ADICOL) was to develop a treatment system that continuously measures and controls the glucose concentration in subjects with type 1 diabetes. The modular concept of the ADICOL's extracorporeal artificial pancreas consisted of a minimally invasive subcutaneous glucose system, a handheld PocketPC computer, and an insulin pump (D-Tron, Disetronic, Burgdorf, Switzerland) delivering subcutaneously insulin lispro. The present paper describes a subset of ADICOL activities focusing on the development of a glucose controller for semi-closed-loop control, an in silico testing environment, clinical testing, and system integration. An incremental approach was adopted to evaluate experimentally a model predictive glucose controller. A feasibility study was followed by efficacy studies of increasing complexity. The ADICOL project demonstrated feasibility of a semi-closed-loop glucose control during fasting and fed conditions with a wearable, m... --- paper_title: Nonlinear model predictive control of glucose concentration in subjects with type 1 diabetes paper_content: A nonlinear model predictive controller has been developed to maintain normoglycemia in subjects with type 1 diabetes during fasting conditions such as during overnight fast. The controller employs a compartment model, which represents the glucoregulatory system and includes submodels representing absorption of subcutaneously administered short-acting insulin Lispro and gut absorption. The controller uses Bayesian parameter estimation to determine time-varying model parameters. Moving target trajectory facilitates slow, controlled normalization of elevated glucose levels and faster normalization of low glucose values. The predictive capabilities of the model have been evaluated using data from 15 clinical experiments in subjects with type 1 diabetes. The experiments employed intravenous glucose sampling (every 15 min) and subcutaneous infusion of insulin Lispro by insulin pump (modified also every 15 min). The model gave glucose predictions with a mean square error proportionally related to the prediction horizon with the value of 0.2 mmol L−1 per 15 min. The assessment of clinical utility of model-based glucose predictions using Clarke error grid analysis gave 95% of values in zone A and the remaining 5% of values in zone B for glucose predictions up to 60 min (n = 1674). In conclusion, adaptive nonlinear model predictive control is promising for the control of glucose concentration during fasting conditions in subjects with type 1 diabetes. --- paper_title: Blood Glucose Control by a Model Predictive Control Algorithm with Variable Sampling Rate Versus a Routine Glucose Management Protocol in Cardiac Surgery Patients: A Randomized Controlled Trial paper_content: Context: Elevated blood glucose levels occur frequently in the critically ill. Tight glucose control by intensive insulin treatment markedly improves clinical outcome. Objective and Design: This is a randomized controlled trial comparing blood glucose control by a laptop-based model predictive control algorithm with a variable sampling rate [enhanced model predictive control (eMPC); version 1.04.03] against a routine glucose management protocol (RMP) during the peri- and postoperative periods. Setting: The study was performed at the Department of Cardiac Surgery, University Hospital. Patients: A total of 60 elective cardiac surgery patients were included in the study. Interventions: Elective cardiac surgery and treatment with continuous insulin infusion (eMPC) or continuous insulin infusion combined with iv insulin boluses (RMP) to maintain euglycemia (target range 4.4–6.1 mmol/liter) were performed. There were 30 patients randomized for eMPC and 30 for RMP treatment. Blood glucose was measured in 1- to 4... --- paper_title: Tight glycaemic control by an automated algorithm with time-variant sampling in medical ICU patients paper_content: OBJECTIVE ::: Tight glycaemic control (TGC) in critically ill patients improves clinical outcome, but is difficult to establish The primary objective of the present study was to compare glucose control in medical ICU patients applying a computer-based enhanced model predictive control algorithm (eMPC) extended to include time-variant sampling against an implemented glucose management protocol. ::: ::: ::: DESIGN ::: Open randomised controlled trial. ::: ::: ::: SETTING ::: Nine-bed medical intensive care unit (ICU) in a tertiary teaching hospital. ::: ::: ::: PATIENTS AND PARTICIPANTS ::: Fifty mechanically ventilated medical ICU patients. ::: ::: ::: INTERVENTIONS ::: Patients were included for a study period of up to 72 h. Patients were randomised to the control group (n = 25), treated by an implemented insulin algorithm, or to the eMPC group (n = 25), using the laptop-based algorithm. Target range for blood glucose (BG) was 4.4-6.1 mM. Efficacy was assessed by mean BG, hyperglycaemic index (HGI) and BG sampling interval. Safety was assessed by the number of hypoglycaemic-episodes < 2.2 mM. Each participating nurse filled-in a questionnaire regarding the usability of the algorithm. ::: ::: ::: MEASUREMENTS AND MAIN RESULTS ::: BG and HGI were significantly lower in the eMPC group [BG 5.9 mM (5.5-6.3), median (IQR); HGI 0.4 mM (0.2-0.9)] than in control patients [BG 7.4 mM (6.9-8.6), p < 0.001; HGI 1.6 mM (1.1-2.4), p < 0.001]. One hypoglycaemic episode was detected in the eMPC group; no such episodes in the control group. Sampling interval was significantly shorter in the eMPC group [eMPC 117[Symbol: see text]min (+/- 34), mean (+/- SD), vs 174 min (+/- 27); p < 0.001]. Thirty-four nurses filled-in the questionnaire. Thirty answered the question of whether the algorithm could be applied in daily routine in the affirmative. ::: ::: ::: CONCLUSIONS ::: The eMPC algorithm was effective in maintaining tight glycaemic control in severely ill medical ICU patients. --- paper_title: Blood Glucose Control by a Model Predictive Control Algorithm with Variable Sampling Rate Versus a Routine Glucose Management Protocol in Cardiac Surgery Patients: A Randomized Controlled Trial paper_content: Context: Elevated blood glucose levels occur frequently in the critically ill. Tight glucose control by intensive insulin treatment markedly improves clinical outcome. Objective and Design: This is a randomized controlled trial comparing blood glucose control by a laptop-based model predictive control algorithm with a variable sampling rate [enhanced model predictive control (eMPC); version 1.04.03] against a routine glucose management protocol (RMP) during the peri- and postoperative periods. Setting: The study was performed at the Department of Cardiac Surgery, University Hospital. Patients: A total of 60 elective cardiac surgery patients were included in the study. Interventions: Elective cardiac surgery and treatment with continuous insulin infusion (eMPC) or continuous insulin infusion combined with iv insulin boluses (RMP) to maintain euglycemia (target range 4.4–6.1 mmol/liter) were performed. There were 30 patients randomized for eMPC and 30 for RMP treatment. Blood glucose was measured in 1- to 4... --- paper_title: Model Predictive Control of Type 1 Diabetes: An in Silico Trial paper_content: BACKGROUND ::: The development of artificial pancreas has received a new impulse from recent technological advancements in subcutaneous continuous glucose monitoring and subcutaneous insulin pump delivery systems. However, the availability of innovative sensors and actuators, although essential, does not guarantee optimal glycemic regulation. Closed-loop control of blood glucose levels still poses technological challenges to the automatic control expert, most notable of which are the inevitable time delays between glucose sensing and insulin actuation. ::: ::: ::: METHODS ::: A new in silico model is exploited for both design and validation of a linear model predictive control (MPC) glucose control system. The starting point is a recently developed meal glucose-insulin model in health, which is modified to describe the metabolic dynamics of a person with type 1 diabetes mellitus. The population distribution of the model parameters originally obtained in healthy 204 patients is modified to describe diabetic patients. Individual models of virtual patients are extracted from this distribution. A discrete-time MPC is designed for all the virtual patients from a unique input-output-linearized approximation of the full model based on the average population values of the parameters. The in silico trial simulates 4 consecutive days, during which the patient receives breakfast, lunch, and dinner each day. ::: ::: ::: RESULTS ::: Provided that the regulator undergoes some individual tuning, satisfactory results are obtained even if the control design relies solely on the average patient model. Only the weight on the glucose concentration error needs to be tuned in a quite straightforward and intuitive way. The ability of the MPC to take advantage of meal announcement information is demonstrated. Imperfect knowledge of the amount of ingested glucose causes only marginal deterioration of performance. In general, MPC results in better regulation than proportional integral derivative, limiting significantly the oscillation of glucose levels. ::: ::: ::: CONCLUSIONS ::: The proposed in silico trial shows the potential of MPC for artificial pancreas design. The main features are a capability to consider meal announcement information, delay compensation, and simplicity of tuning and implementation. --- paper_title: An implantable subcutaneous glucose sensor array in ketosis-prone rats: closed loop glycemic control. paper_content: A closed loop system of diabetes control would minimize hyperglycemia and hypoglycemia. We therefore implanted and tested a subcutaneous amperometric glucose sensor array in alloxan-diabetic rats. Each array employed four sensing units, the outputs of which were processed in real time to yield a unified signal. We utilized a gain-scheduled insulin control algorithm which rapidly reduced insulin delivery as glucose concentration declined. Such a system was generally effective in controlling glycemia and the degree of lag between blood glucose and the sensor signal was usually 3-8 min. After prolonged implantation, this lag was sometimes longer, which led to impairment of sensor accuracy. Using a prospective two-point calibration method, sensor accuracy and closed loop control were good. A revised algorithm yielded better glycemic control than the initial algorithm did. Future research needs to further improve calibration methods and reduce foreign body fibrosis in order to avoid a time-related increase in lag duration. --- paper_title: The Benefit of Subcutaneous Glucagon During Closed-Loop Glycemic Control in Rats With Type 1 Diabetes paper_content: Because of its prolonged action, subcutaneously administered insulin has a potential for overcorrection hypoglycemia during closed-loop glucose control. For this reason, we hypothesized that subcutaneous glucagon, whose action is faster, could lessen the risk for hypoglycemia during closed-loop control. We therefore compared insulin alone versus insulin plus glucagon in diabetic rats in a controlled closed-loop study. Both hormones were delivered by algorithms based on proportional error, derivative error, and the glucose history. Based on this algorithm, glucagon was delivered when glucose was declining and approaching a hypoglycemic level. The delivery of glucagon was largely reciprocal with the delivery of insulin. With the addition of glucagon, there was less hypoglycemia at the glucose nadir, less hyperglycemia later in the study, and lower absolute error values during these periods. We also found that for 7 days after glucagon reconstitution, commercially available glucagon retained its original ability to quickly raise glucose level. We conclude that when subcutaneous insulin delivery is accompanied by subcutaneous glucagon, glycemic control during closed-loop treatment is improved. Since its action is faster than that of insulin, glucagon may prove useful during closed-loop diabetes control. --- paper_title: Pharmacodynamics And Stability of Subcutaneously Infused Glucagon in A Type 1 Diabetic Swine Model In Vivo paper_content: Background: The objective of this study was to determine the in vivo pharmacodynamics of glucagon and to test its glycemic effect over days by assessing its time course of activity and potency in a... --- paper_title: Diminished B cell secretory capacity in patients with noninsulin-dependent diabetes mellitus. paper_content: In order to assess whether patients with noninsulin-dependent diabetes mellitus (NIDDM) possess normal insulin secretory capacity, maximal B cell responsiveness to the potentiating effects of glucose was estimated in eight untreated patients with NIDDM and in eight nondiabetic controls. The acute insulin response to 5 g intravenous arginine was measured at five matched plasma glucose levels that ranged from approximately 100-615 mg/dl. The upper asymptote approached by acute insulin responses (AIRmax) and the plasma glucose concentration at half-maximal responsiveness (PG50) were estimated using nonlinear regression to fit a modification of the Michaelis-Menten equation. In addition, glucagon responses to arginine were measured at these same glucose levels to compare maximal A cell suppression by hyperglycemia in diabetics and controls. Insulin responses to arginine were lower in diabetics than in controls at all matched glucose levels (P less than 0.001 at all levels). In addition, estimated AIRmax was much lower in diabetics than in controls (83 +/- 21 vs. 450 +/- 93 microU/ml, P less than 0.01). In contrast, PG50 was similar in diabetics and controls (234 +/- 28 vs. 197 +/- 20 mg/dl, P equals NS) and insulin responses in both groups approached or attained maxima at a glucose level of approximately 460 mg/dl. Acute glucagon responses to arginine in patients with NIDDM were significantly higher than responses in controls at all glucose levels. In addition, although glucagon responses in control subjects reached a minimum at a glucose level of approximately 460 mg/dl, responses in diabetics declined continuously throughout the glucose range and did not reach a minimum. Thus, A cell sensitivity to changes in glucose level may be diminished in patients with NIDDM. In summary, patients with NIDDM possess markedly decreased maximal insulin responsiveness to the potentiating effects of glucose. Such a defect indicates the presence of a reduced B cell secretory capacity and suggests a marked generalized impairment of B cell function in patients with NIDDM. --- paper_title: Autonomic mechanism and defects in the glucagon response to insulin-induced hypoglycaemia. paper_content: In summary, this article briefly reviews the evidence that three separate autonomic inputs to the islet are capable of stimulating glucagon secretion and that each is activated during IIH. We have reviewed our evidence that these autonomic inputs mediate the glucagon response to IIH, both in non-diabetic animals and humans. Finally, we outline our new preliminary data suggesting an eSIN in an autoimmune animal model of T1DM. We conclude that the glucagon response to IIH is autonomically mediated in non-diabetic animals and humans. We further suggest that at least one of these autonomic inputs, the sympathetic innervation of the islet, is diminished in autoimmune T1DM. These data raise the novel possibility that an autonomic defect contributes to the loss of the glucagon response to IIH in T1DM. --- paper_title: A Novel Insulin Delivery Algorithm in Rats With Type 1 Diabetes: The Fading Memory Proportional-Derivative Method paper_content: An algorithm designed to automatically control insulin delivery was tested in rats with Type 1 diabetes. This nonlinear algorithm included a fading memory component of proportional and derivative errors in order to simulate normal insulin secretion. Error-weighting functions for the proportional and derivative terms were used with a performance index designed for error adaptation. In the first version of the algorithm, the proportional gain was adaptively varied. In the second version, a low rate of basal insulin delivery was adaptively varied. Six 6-h studies with each version were conducted using frequent blood sampling and intravenous insulin delivery. In Version 2 studies, blood glucose levels during the last two hours were well-controlled and significantly lower than in Version 1 (118 +/- 2.0 vs. 130 +/- 2.9 mg/dL). Neither version produced hypoglycemia. Future research using this algorithm needs to focus on automated glucose sensing in combination with insulin delivery. --- paper_title: Fuzzy-Based Controller for Glucose Regulation in Type-1 Diabetic Patients by Subcutaneous Route paper_content: This paper presents an advisory/control algorithm for a type-1 diabetes mellitus (TIDM) patient under an intensive insulin treatment based on a multiple daily injections regimen (MDIR). The advisory/control algorithm incorporates expert knowledge about the treatment of this disease by using Mamdani-type fuzzy logic controllers to regulate the blood glucose level (BGL). The overall control strategy is based on a two-loop feedback strategy to overcome the variability in the glucose-insulin dynamics from patient to patient. An inner-loop provides the amount of both rapid/short and intermediate/long acting insulin (RSAI and ILAI) formulations that are programmed in a three-shots daily basis before meals. The combined preparation is then injected by the patient through a subcutaneous route. Meanwhile, an outer-loop adjusts the maximum amounts of insulin provided to the patient in a time-scale of days. The outer-loop controller aims to work as a supervisor of the inner-loop controller. Extensive closed-loop simulations are illustrated, using a detailed compartmental model of the insulin-glucose dynamics in a TIDM patient with meal intake --- paper_title: Neural network modeling and control of type 1 diabetes mellitus. paper_content: This paper presents a developed and validated dynamic simulation model of type 1 diabetes, that simulates the progression of the disease and the two term controller that is responsible for the insulin released to stabilize the glucose level. The modeling and simulation of type 1 diabetes mellitus is based on an artificial neural network approach. The methodology builds upon an existing rich database on the progression of type 1 diabetes for a group of diabetic patients. The model was found to perform well at estimating the next glucose level over time without control. A neural controller that mimics the pancreas secretion of insulin into the body was also developed. This controller is of the two term type: one stage is responsible for short-term and the other for mid-term insulin delivery. It was found that the controller designed predicts an adequate amount of insulin that should be delivered into the body to obtain a normalization of the elevated glucose level. This helps to achieve the main objective of insulin therapy: to obtain an accurate estimate of the amount of insulin to be delivered in order to compensate for the increase in glucose concentration. --- paper_title: Fuzzy filter for state estimation of a glucoregulatory system. paper_content: A filter based on fuzzy logic for state estimation of a glucoregulatory system is presented. A published non-linear model for the dynamics of glucose and its hormonal control including a single glucose compartment, five insulin compartments and a glucagon compartment was used for simulation. The simulated data were corrupted by an additive white noise with zero mean and a coefficient of variation (CV) of between 2 and 20% and then submitted to the state estimation procedure using a fuzzy filter (FF). The performance of the FF was compared with an extended Kalman filter (EKF) for state estimation. Both the FF and the EKF were evaluated in the following cases: (a) five state variables are measurable; three plasma variables are measurable; only plasma glucose is measurable; (b) for different measurement noise levels (CV of 2-20%); and (c) a mismatch between the glucoregulatory system and the given mathematical model (uncertain or approximate model). In contrast to the FF, in the case of approximate model of the glucose system, the EKF failed to achieve useful state estimation. Moreover, the performance of the FF was independent of the noise level. In conclusion, the FF approach is a viable alternative for state estimation in a noisy environment and with an uncertain mathematical model of the glucoregulatory system. --- paper_title: A robust controller for insulin pumps based on H-infinity theory paper_content: The feedback control of insulin pumps for diabetic patients is discussed. Because the parameters in the mathematical model of the blood glucose dynamics present a considerable amount of uncertainty, the H- infinity framework is well suited for the design of controllers that take into account a nice compromise between robust closed-loop regulation of a constant set point and performance expressed in terms of peak values of the plasma glucose concentration. > ---	Title: A Review of Closed-Loop Algorithms for Glycemic Control in the Treatment of Type 1 Diabetes Section 1: Introduction Description 1: Introduce the significance of insulin in diabetes management, challenges in treating Type 1 diabetes, and the concept of closed-loop glycemic control. Section 2: History of Closed Loop Systems Description 2: Detail the historical development of closed-loop systems, components involved, and significant advancements in glucose sensing and insulin delivery technology. Section 3: Proportional-Integral-Derivative (PID) Algorithms Description 3: Explain the fundamentals and application of PID algorithms in closed-loop glycemic control, including successful implementations and inherent challenges. Section 4: Model Predictive Control Algorithms Description 4: Describe the principles of Model Predictive Control (MPC) algorithms and their application in managing insulin delivery for tight glycemic control. Section 5: Fading Memory Proportional Derivative Algorithm Description 5: Introduce the Fading Memory Proportional Derivative (FMPD) algorithm, its components, and its advantages over traditional PID approaches in diabetes management. Section 6: Other Algorithms Description 6: Review additional closed-loop control algorithms such as H-infinity loops, fuzzy logic systems, and neural networks, with their respective advantages and application in glycemic control.
A Survey on Gas Sensing Technology	15	--- paper_title: Differential Absorption Lidar to Measure Subhourly Variation of Tropospheric Ozone Profiles paper_content: A tropospheric ozone Differential Absorption Lidar system, developed jointly by The University of Alabama in Huntsville and the National Aeronautics and Space Administration, is making regular observations of ozone vertical distributions between 1 and 8 km with two receivers under both daytime and nighttime conditions using lasers at 285 and 291 nm. This paper describes the lidar system and analysis technique with some measurement examples. An iterative aerosol correction procedure reduces the retrieval error arising from differential aerosol backscatter in the lower troposphere. Lidar observations with coincident ozonesonde flights demonstrate that the retrieval accuracy ranges from better than 10% below 4 km to better than 20% below 8 km with 750-m vertical resolution and 10-min temporal integration. --- paper_title: Design and Construction of an Odour Sensor for Various Biomedical Applications paper_content: This project deals with the construction of electronic device that senses odour and its application in Telesurgery. Of the body's five senses, the sense of Smell is the most mysterious. In the past, gas chromatography and mass spectrometry have been used as sensing systems, although these are usually expensive and time consuming. Today, the development of odour sensor helped to analyze odors and hence applied in various Medical applications such as, Telesurgery. The odour sensor is generally made of two main parts: a sensing system and a pattern recognition system. The sensing system of the "Odour Sensor" consists of individual thin-film carbon-black polymer homogeneously mingled throughout a non-conducting polymer. When the composite is exposed to a vapor-phase analyte, the resistance varies, which is unique for each odour. The change in resistance is converted into voltage and hence given to the Computer through a Data Acquisition Card. The analysis of Sensor output is done using MatLAB code called Smellware. The response of the Smellware is given to Artificial Neural Network, that is pattern recognition system and hence odour is determined. The main application of this developed odour sensor is Telesurgery. The odour sensor would identify odours in the remote surgical environment. These identified odours would then be electronically transmitted to another site where an odour generation system would recreate them. This developed "odour sensor" was successfully tested and was submitted as a Project Work. --- paper_title: Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection paper_content: Abstract: Various applications, such as pollution monitoring, toxic-gas detection, noninvasive medical diagnostics and industrial process control, require sensitive and selectivedetection of gas traces with concentrations in the parts in 10 9 (ppb) and sub-ppb range.The recent development of quantum-cascade lasers (QCLs) has given a new aspect toinfrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLsare attractive spectroscopic sources because of their excellent properties in terms of narrowlinewidth, average power and room temperature operation. In combination with these lasersources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity,compact sensor platform, fast time-response and user friendly operation. This paper reportsrecent developments on quantum cascade laser-based photoacoustic spectroscopy for tracegas detection. In particular, different applications of a photoacoustic trace gas sensoremploying a longitudinal resonant cell with a detection limit on the order of hundred ppb ofozone and ammonia are discussed. We also report two QC laser-based photoacousticsensors for the detection of nitric oxide, for environmental pollution monitoring andmedical diagnostics, and hexamethyldisilazane, for applications in semiconductormanufacturing process. --- paper_title: Trace amount formaldehyde gas detection for indoor air quality monitoring paper_content: Formaldehyde is not only a carcinogenic chemical, but also causes sick building syndrome. Very small amounts of formaldehyde, such as those emitted from building materials and furniture, pose great concerns for human health. A Health Canada guideline, proposed in 2005, set the maximum formaldehyde concentration for long term exposure (8-hours averaged) as 40 ppb (50 μg/m3). This is a low concentration that commercially available formaldehyde sensors have great difficulty to detect both accurately and continuously. In this paper, we report a formaldehyde gas detection system which is capable of pre-concentrating formaldehyde gas using absorbent, and subsequently thermally desorbing the concentrated gas for detection by the electrochemical sensor. Initial results show that the system is able to detect formaldehyde gas at the ppb level, thus making it feasible to detect trace amount of formaldehyde in indoor environments. --- paper_title: Response Speed Optimization Of Thermal Gas-flow Sensors For Medical Application paper_content: Gas-flow sensors, for medical applications (respiration monitoring), require a relatively large bandwidth (10-300 Hz). Fast flow changes occur e.g. at the start of inspiration. Thermal gas-flow sensors are very favourable for medical applications. Due to the small size, they have a small influence on the total system (small obstruction in a tube). On the other hand, the response speed of these sensors is not automatically large enough: temperature changes take a relatively long time. Optimization of the response speed is necessary. --- paper_title: A study on NDIR-based CO2 sensor to apply remote air quality monitoring system paper_content: Recently, various CO2 sensors reported in the literature may be classified in two major categories depending on measuring principle of sensors. Fist, the chemical CO2 gas sensors have the principal advantage of a very low energy consumption and small size. On the negative side, It is difficult to apply to a variety of practical fields because they have a short lifetime and as well as low durability. Second, NDIR-based CO2 sensor is commonly used in monitoring indoor air quality due to relatively high accuracy compared with that of a chemical CO2 gas sensor. In this paper, therefore, we evaluate NDIR-based CO2 sensors to verify applicable potentialities of them in a remote air quality monitoring system. In addition, the principle and structure of NDIR CO2 sensor is discussed, and then we analyze the CO2 concentration has been measured in the real platform of subway station for a month. Finally this paper proposes that the accuracy of the measuring values from NDIR CO2 sensor is enough for indoor air quality monitoring applications. --- paper_title: Workflow for High Throughput Screening of Gas Sensing Materials paper_content: The workflow of a high throughput screening setup for the rapid identification of new and improved sensor materials is presented. The polyol method was applied to prepare nanoparticular metal oxides as base materials, which were functionalised by surface doping. Using multi-electrode substrates and high throughput impedance spectroscopy (HT-IS) a wide range of materials could be screened in a short time. Applying HT-IS in search of new selective gas sensing materials a NO2-tolerant NO sensing material with reduced sensitivities towards other test gases was identified based on iridium doped zinc oxide. Analogous behaviour was observed for iridium doped indium oxide. --- paper_title: Overview of automotive sensors paper_content: An up-to-date review paper on automotive sensors is presented. Attention is focused on sensors used in production automotive systems. The primary sensor technologies in use today are reviewed and are classified according to their three major areas of automotive systems application-powertrain, chassis, and body. This subject is extensive. As described in this paper, for use in automotive systems, there are six types of rotational motion sensors, four types of pressure sensors, five types of position sensors, and three types of temperature sensors. Additionally, two types of mass air flow sensors, five types of exhaust gas oxygen sensors, one type of engine knock sensor, four types of linear acceleration sensors, four types of angular-rate sensors, four types of occupant comfort/convenience sensors, two types of near-distance obstacle detection sensors, four types of far-distance obstacle detection sensors, and and ten types of emerging, state-of the-art, sensor technologies are identified. --- paper_title: The Effects of the Location of Au Additives on Combustion-generated SnO2 Nanopowders for CO Gas Sensing paper_content: The current work presents the results of an experimental study of the effects of the location of gold additives on the performance of combustion-generated tin dioxide (SnO(2)) nanopowders in solid state gas sensors. The time response and sensor response to 500 ppm carbon monoxide is reported for a range of gold additive/SnO(2) film architectures including the use of colloidal, sputtered, and combustion-generated Au additives. The opportunities afforded by combustion synthesis to affect the SnO(2)/additive morphology are demonstrated. The best sensor performance in terms of sensor response (S) and time response (τ) was observed when the Au additives were restricted to the outermost layer of the gas-sensing film. Further improvement was observed in the sensor response and time response when the Au additives were dispersed throughout the outermost layer of the film, where S = 11.3 and τ = 51 s, as opposed to Au localized at the surface, where S = 6.1 and τ = 60 s. --- paper_title: Highly sensitive and selective ammonia gas sensor paper_content: We have fabricated and examined an ammonia gas sensor with high sensitivity using thick-film technology. The sensing material of the gas sensor is FeO/sub x/-WO/sub 3/-SnO/sub 2/ oxide semiconductor. The sensor exhibits resistance increase upon exposure to low concentration of ammonia gas. The resistance of the sensor is decreased, on the other hand, for exposure to reducing gases such as ethyl alcohol, methane, propane and carbon monoxide. We have proposed and investigated a novel method for detecting ammonia gas quite selectively by using a sensor array with two sensing elements which contains an ammonia gas sensor and a compensation element. The compensation element is a Pt-doped WO/sub 3/-SnO/sub 2/ gas sensor which shows an opposite direction of resistance change in comparison with the ammonia gas sensor upon exposure to ammonia gas. Excellent selectivity has been achieved using the sensor array with two sensing elements. --- paper_title: Airborne Chemical Sensing with Mobile Robots paper_content: Airborne chemical sensing with mobile robots has been an active research area since the beginning of the 1990s. This article presents a review of research work in this field, including gas distribution mapping, trail guidance, and the different subtasks of gas source localisation. Due to the difficulty of modelling gas distribution in a real world environment with currently available simulation techniques, we focus largely on experimental work and do not consider publications that are purely based on simulations. --- paper_title: Odour measurement using conducting polymer gas sensors and an artificial neural network decision system paper_content: The conventional way of assessing the magnitude of nuisance odours using an olfactometer and a sensory panel is costly. This paper describes experiments that have been conducted into matching the results from trained sensory panellists to those from a conducting polymer-based electronic nose. By taking the data from the electronic nose and applying them to a trained neural network, it has been shown that the data can be manipulated to give rise to results that are within a few percent of those from the sensory panellists. This is the first time that an electronic nose has been calibrated in terms of odour intensity measurements and it points the way forward to more objective measurements of nuisance odours. --- paper_title: Compact Raman lidar for hydrogen gas leak detection paper_content: A compact Raman lidar system for hydrogen gas leak detection was constructed. Laser-induced fluorescence at a distance of 70 m and Raman scattering light from N 2 gas at short range could be detected. --- paper_title: Planar Zeolite Film-Based Potentiometric Gas Sensors Manufactured by a Combined Thick-Film and Electroplating Technique paper_content: Zeolites are promising materials in the field of gas sensors. In this technology-oriented paper, a planar setup for potentiometric hydrocarbon and hydrogen gas sensors using zeolites as ionic sodium conductors is presented, in which the Pt-loaded Na-ZSM-5 zeolite is applied using a thick-film technique between two interdigitated gold electrodes and one of them is selectively covered for the first time by an electroplated chromium oxide film. The influence of the sensor temperature, the type of hydrocarbons, the zeolite film thickness, and the chromium oxide film thickness is investigated. The influence of the zeolite on the sensor response is briefly discussed in the light of studies dealing with zeolites as selectivity-enhancing cover layers. --- paper_title: Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection paper_content: A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. --- paper_title: Measurement of CH4 by differential infrared optical absorption spectroscopy paper_content: To solve the problem that the current use of optical methods used to detect various gases existing in sensors and signal processing was too complicated, detection sensitivity was not high, detection of the type of gases was single. We used optical phase-shifted grating laser window adjust the differential infrared absorption spectrometry and studied Spectrum adjustment and detection signal processing problem. CH4 in cigarette main smoke of different kind brands was measured continuously by differential optical absorption spectroscopy (DOAS). By using RM200 rotating disk smoking machine with 20 smoking flue, 20 kinds of gas were inserted into the rotating disk and ignited every 3s. By use of DOAS technique, the measurement was completed with in 6~7min after the gas was transported into a White cell with 31.5m path length which was connected to the smoking machine. This technique can improve the measuremental temporal resolution compared with traditional method. At the beginning, the press in White cell was 5.2×104 Pa and it increased to 1.03×105Pa while the measurement finished. The result shows the concentration of CH4 in main gas is between 0.89mg/m3 and 1.54mg/m. Pool in the White cell entrance placed wide infrared wavelength LED light source, light source after a large-diameter phase-shifted fiber grating access to White cell, Through the piezoelectric ceramic (PZT) phase-shift controlled Phase-Shifted Fiber Bragg Grating to infra-red LED into a laser modulation of narrowband continuous changes in light, wavelength corresponding to various gases such as CH4 absorption spectrum. White cell output pool signals entered into the photoelectric detector and ADC further, controlled by computer-related demodulation digitally. It can achieve high sensitivity digital lock-in amplifier function and be suitable for high-resolution detection of trace gases. Through simulation studies and practical tests, The results show that the piezoelectric ceramic (PZT) control Phase-Shifted Fiber Bragg Grating spectral scan can effectively suppress the background optical interference, the elimination of Rayleigh scattering and Raman scattering. Phase-Shifted Fiber Bragg Grating modulation and digital lock-in amplifier detection sensitivity of the combination improve three orders of magnitude. The methods solve the problem a wide range of gas detection by one kind of equipment. The device is small size, low cost, easy to carry, can measure a wide range of gas content, and has an important application value for environmental monitoring. If the White pool with underwater ocean can detect trace gases, for rivers and the marine environment and resources to detect environmental monitoring is also of great significance. --- paper_title: Membrane Based Measurement Technology for in situ Monitoring of Gases in Soil paper_content: The representative measurement of gas concentration and fluxes in heterogeneous soils is one of the current challenges when analyzing the interactions of biogeochemical processes in soils and global change. Furthermore, recent research projects on CO(2)-sequestration have an urgent need of CO(2)-monitoring networks. Therefore, a measurement method based on selective permeation of gases through tubular membranes has been developed. Combining the specific permeation rates of gas components for a membrane and Dalton's principle, the gas concentration (or partial pressure) can be determined by the measurement of physical quantities (pressure or volume) only. Due to the comparatively small permeation constants of membranes, the influence of the sensor on its surrounding area can be neglected. The design of the sensor membranes can be adapted to the spatial scale from the bench scale to the field scale. The sensitive area for the measurement can be optimized to obtain representative results. Furthermore, a continuous time-averaged measurement is possible where the time for averaging is simply controlled by the wall-thickness of the membrane used. The measuring method is demonstrated for continuous monitoring of O(2) and CO(2) inside of a sand filled Lysimeter. Using three sensor planes inside the sand pack, which were installed normal to the gas flow direction and a reference measurement system, we demonstrate the accuracy of the gas-detection for different flux-based boundary conditions. --- paper_title: A wireless home safety gas leakage detection system paper_content: A wireless safety device for gas leakage detection is proposed. The device is intended for use in household safety where appliances and heaters that use natural gas and liquid petroleum gas (LPG) may be a source of risk. The system also can be used for other applications in the industry or plants that depend on LPG and natural gas in their operations. The system design consists of two main modules: the detection and transmission module, and the receiving module. The detection and transmitting module detects the change of gas concentration using a special sensing circuit built for this purpose. This module checks if a change in concentration of gas(es) has exceeded a certain pre-determined threshold. If the sensor detects a change in gas concentration, it activates and audiovisual alarm and sends a signal to the receiver module. The receiver module acts as a mobile alarm device to allow the mobility within the house premises. The system was tested using LPG and the alarm was activated as a result of change in concentration. --- paper_title: Catalytic Fiber Bragg Grating Sensor for Hydrogen Leak Detection in Air paper_content: The explosion risk linked to the use of hydrogen as fuel requires low-cost and efficient sensors. We present here a multipoint in-fiber sensor capable of hydrogen leak detection in air as low as 1% concentration with a response time smaller than a few seconds. Our solution makes use of fiber Bragg gratings (FBGs) covered by a catalytic sensitive layer made of a ceramic doped with noble metal which, in turn, induces a temperature elevation around the FBGs in the presence of hydrogen in air. --- paper_title: A wireless, passive carbon nanotube-based gas sensor paper_content: A gas sensor, comprised of a gas-responsive multiwall carbon nanotube (MWNT)-silicon dioxide (SiO/sub 2/) composite layer deposited on a planar inductor-capacitor resonant circuit is presented here for the monitoring of carbon dioxide (CO/sub 2/), oxygen (O/sub 2/), and ammonia (NH/sub 3/). The absorption of different gases in the MWNT-SiO/sub 2/ layer changes the permittivity and conductivity of the material and consequently alters the resonant frequency of the sensor. By tracking the frequency spectrum of the sensor with a loop antenna, humidity, temperature, as well as CO/sub 2/, O/sub 2/ and NH/sub 3/ concentrations can be determined, enabling applications such as remotely monitoring conditions inside opaque, sealed containers. Experimental results show the sensor response to CO/sub 2/ and O/sub 2/ is both linear and reversible. Both irreversible and reversible responses are observed in response to NH/sub 3/, indicating both physisorption and chemisorption of NH/sub 3/ by the carbon nanotubes. A sensor array, comprised of an uncoated, SiO/sub 2/ coated, and MWNT-SiO/sub 2/ coated sensor, enables CO/sub 2/ measurement to be automatically calibrated for operation in a variable humidity and temperature environment. --- paper_title: Development of a protected gas sensor for exhaust automotive applications paper_content: A /spl beta/-alumina-based gas sensor for automotive exhaust application (hydrocarbon, CO, NO/sub 2/ detection in 10-1000 ppm concentration range) has been developed by thick film technology (screen-printing) in the frame of a European project. The sensing device consists of a solid electrolyte (/spl beta/ alumina) and of two metallic electrodes having different catalytic properties, the whole system being in contact with the surrounding atmosphere to be analyzed. The detection principle is based on the chemisorption of oxygen which leads to a capacitance effect at the metal-electrolyte interface, resulting in a measurable difference of potential depending on nature and concentration of pollutants and on the sensor temperature. For application in exhaust pipe, a porous protective layer based on /spl alpha/-alumina for preserving the sensing material and the metal electrodes from contamination and deterioration was screen-printed on the sensing element. For limiting the possible interface interactions between the overlapped layers, a new concept of screen -printable ink was set up based on mixing the oxide powder and its gelly precursor without any inorganic binder addition. The performances of the sensor were tested both on laboratory and engine bench. The sensitivity is relevant for exhaust application, and the long-term stability is improved by the protective layer. --- paper_title: A MEMS-based Benzene Gas Sensor with a Self-heating WO3 Sensing Layer paper_content: In the study, a MEMS-based benzene gas sensor is presented, consisting of a quartz substrate, a thin-film WO3 sensing layer, an integrated Pt micro-heater, and Pt interdigitated electrodes (IDEs). When benzene is present in the atmosphere, oxidation occurs on the heated WO3 sensing layer. This causes a change in the electrical conductivity of the WO3 film, and hence changes the resistance between the IDEs. The benzene concentration is then computed from the change in the measured resistance. A specific orientation of the WO3 layer is obtained by optimizing the sputtering process parameters. It is found that the sensitivity of the gas sensor is optimized at a working temperature of 300 °C. At the optimal working temperature, the experimental results show that the sensor has a high degree of sensitivity (1.0 KΩ ppm−1), a low detection limit (0.2 ppm) and a rapid response time (35 s). --- paper_title: Circuit and Noise Analysis of Odorant Gas Sensors in an E-Nose paper_content: In this paper, the relationship between typical circuit structures of gas sensor circuits and their output noise is analyzed. By using averaged segmenting periodical graph and improved histogram estimation methods, we estimated their noise power spectra and optimal probability distribution functions (pdf). The results were confirmed through experiment studies. --- paper_title: Novel nano-hybrid gas sensor based on n-TiO2 functionalized by phthalocyanines via supersonic beam co-deposition: Performance and application to automotive air quality paper_content: Supersonic beams of TiO2 clusters and metal phthalocyanines have been developed for the synthesis of hybrid for gas-sensing applications. This approach allows high degree of control on the properties of the synthesized materials and on the interface between clusters and organic molecules, so that new functional materials with novel and promising sensing properties are obtained. These materials can be synthesized in different architectures, shape and phases, and are constituted by nanocrystalline clusters of TiO2 functionalized during the growth by the co-deposited molecules. The outcome is a porous nanostructured material characterized by a diffused organic-inorganic interface at the nanoscale. The properties of the codeposited interfaces, where the functionalization of the hybrid material plays a crucial role, can be tailored directly acting on the beam parameters of the cluster (mass size distribution, phase) and of the organic molecules (kinetic energy, deposition rate). --- paper_title: Thermopile sensor array for an electronic nose integrated non-selective NDIR gas detection system paper_content: The fabrication and characterization of a thermopile sensor array is described in this work. The device is intended to be part of a non-dispersive infrared (NDIR) gas detection system integrated in an electronic nose where each sensor is not oriented for the detection of a particular substance. Different designs were considered changing the size of the array (9 or 16 elements) and improving some specific detector performance parameters: responsivity and noise equivalent power (NEP). After device fabrication, the measurements of these parameters show a good agreement with the thermal one-dimensional model used for the design. --- paper_title: A Real-Time De-Noising Algorithm for E-Noses in a Wireless Sensor Network paper_content: A wireless e-nose network system is developed for the special purpose of monitoring odorant gases and accurately estimating odor strength in and around livestock farms. This system is to simultaneously acquire accurate odor strength values remotely at various locations, where each node is an e-nose that includes four metal-oxide semiconductor (MOS) gas sensors. A modified Kalman filtering technique is proposed for collecting raw data and de-noising based on the output noise characteristics of those gas sensors. The measurement noise variance is obtained in real time by data analysis using the proposed slip windows average method. The optimal system noise variance of the filter is obtained by using the experiments data. The Kalman filter theory on how to acquire MOS gas sensors data is discussed. Simulation results demonstrate that the proposed method can adjust the Kalman filter parameters and significantly reduce the noise from the gas sensors. --- paper_title: Quartz Crystal Microbalance Coated with Sol-gel-derived Thin Films as Gas Sensor for NO Detection paper_content: This paper presents the possibilities and properties of Indium tin oxide (ITO)-covered quartz crystal as a NOx toxic gas-sensor. The starting sol-gel solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol (0-20% by weight). The ITO thin films were deposited on the gold electrodes of quartz crystal by spin-coating technique and subsequently followed a standard photolithography to pattern the derived films to ensure all sensors with the same sensing areas. All heat treatment processes were controlled below 500°C in order to avoid the piezoelectric characteristics degradation of quartz crystal (Quartz will lose its piezoelectricity at ~573°C due to the phase change from α to β). The electrical and structural properties of ITO thin films were characterized with Hall analysis system, TG/DTA, XRD, XPS, SEM and etc. The gas sensor had featured with ITO thin films of ~100nm as the receptor to sense the toxic gas NO and quartz crystal with frequency of 10MHz as the transducer to transfer the surface reactions (mass loading, etc) into the frequency shift. A homemade setup had been employed to measure the sensor response under the static mode. The experimental results had indicated that the ITO-coated QCM had a good sensitivity for NO gas, ~12Hz/100ppm within 5mins. These results prove that the ITO-covered quartz crystals are usable as a gas sensor and as an analytical device. --- paper_title: Temperature Gradient Effect on Gas Discrimination Power of a Metal-Oxide Thin-Film Sensor Microarray paper_content: The paper presents results concerning the effect of spatial inhomogeneous operating temperature on the gas discrimination power of a gas-sensor microarray, with the latter based on a thin SnO2 film employed in the KAMINA electronic nose. Three different temperature distributions over the substrate are discussed: a nearly homogeneous one and two temperature gradients, equal to approx. 3.3 °C/mm and 6.7 °C/mm, applied across the sensor elements (segments) of the array. The gas discrimination power of the microarray is judged by using the Mahalanobis distance in the LDA (Linear Discrimination Analysis) coordinate system between the data clusters obtained by the response of the microarray to four target vapors: ethanol, acetone, propanol and ammonia. It is shown that the application of a temperature gradient increases the gas discrimination power of the microarray by up to 35 %. --- paper_title: Development of laser based spectroscopic trace-gas sensors for environmental sensor networks and medical exposure monitors paper_content: We report wavelength modulated TDLAS/QEPAS trace gas sensors with reduced size, efficiency, and cost for use in environmental sensor networks and medical exposure monitors. CO2 measurements with a 2 mum diode laser dissipate <1 W. --- paper_title: Vinegar Classification Based on Feature Extraction and Selection From Tin Oxide Gas Sensor Array Data paper_content: Tin oxide gas sensor array based devices were often cited in publications dealing with food products. However, during the process of using a tin oxide gas sensor array to analysis and identify different gas, the most important and difficult was how to get useful parameters from the sensors and how to optimize the parameters. Which can make the sensor array can identify the gas rapidly and accuracy, and there was not a comfortable method. For this reason we developed a device which satisfied the gas sensor array act with the gas from vinegar. The parameters of the sensor act with gas were picked up after getting the whole acting process data. In order to assure whether the feature parameter was optimum or not, in this paper a new method called “distinguish index”(DI) has been proposed. Thus we can assure the feature parameter was useful in the later pattern recognition process. Principal component analysis (PCA) and artificial neural network (ANN) were used to combine the optimum feature parameters. Good separation among the gases with different vinegar is obtained using principal component analysis. The recognition probability of the ANN is 98 %. The new method can also be applied to other pattern recognition problems. --- paper_title: Flame-Spray-Made Undoped Zinc Oxide Films for Gas Sensing Applications paper_content: Using zinc naphthenate dissolved in xylene as a precursor undoped ZnO nanopowders were synthesized by the flame spray pyrolysis technique. The average diameter and length of ZnO spherical and hexagonal particles were in the range of 5 to 20 nm, while ZnO nanorods were found to be 5–20 nm wide and 20–40 nm long, under 5/5 (precursor/oxygen) flame conditions. The gas sensitivity of the undoped ZnO nanopowders towards 50 ppm of NO2, C2H5OH and SO2 were found to be 33, 7 and 3, respectively. The sensors showed a great selectivity towards NO2 at high working temperature (at 300 °C), while small resistance variations were observed for C2H5OH and SO2, respectively. --- paper_title: Application research of laser gas detection technology in the analysis of sulphur hexafluoride paper_content: The decision of latent fault in SF 6 gas electrical equipment can be made more timely and accurately through online monitoring of content change of HF, one of SF 6 gas decomposition. Tunable diode laser absorption spectroscopic (TDLAS) technology applies the wavelength tunable characteristics of diode lasers to gain the absorption spectroscopy of the selected absorption line of the target gas for the qualitative or quantitative analysis of the target gas. Because of its high sensitivity, high selectivity, short response time and without cross-interference, etc., we can achieve online monitoring and make the detection of HF more direct, accurate and timely through installing the technical equipment in the SF 6 electrical equipment monitoring site location. The analysis shows that the TDLAS technology is an effective and reliable method of SF 6 online monitoring technique. --- paper_title: Gas Sensors Based on Electrospun Nanofibers paper_content: Nanofibers fabricated via electrospinning have specific surface approximately one to two orders of the magnitude larger than flat films, making them excellent candidates for potential applications in sensors. This review is an attempt to give an overview on gas sensors using electrospun nanofibers comprising polyelectrolytes, conducting polymer composites, and semiconductors based on various sensing techniques such as acoustic wave, resistive, photoelectric, and optical techniques. The results of sensing experiments indicate that the nanofiber-based sensors showed much higher sensitivity and quicker responses to target gases, compared with sensors based on flat films. --- paper_title: Cytochrome C Biosensor—A Model for Gas Sensing paper_content: This work is about gas biosensing with a cytochrome c biosensor. Emphasis is put on the analysis of the sensing process and a mathematical model to make predictions about the biosensor response. Reliable predictions about biosensor responses can provide valuable information and facilitate biosensor development, particularly at an early development stage. The sensing process comprises several individual steps, such as phase partition equilibrium, intermediate reactions, mass-transport, and reaction kinetics, which take place in and between the gas and liquid phases. A quantitative description of each step was worked out and finally combined into a mathematical model. The applicability of the model was demonstrated for a particular example of methanethiol gas detection by a cytochrome c biosensor. The model allowed us to predict the optical readout response of the biosensor from tabulated data and data obtained in simple liquid phase experiments. The prediction was experimentally verified with a planar three-electrode electro-optical cytochrome c biosensor in contact with methanethiol gas in a gas tight spectroelectrochemical measurement cell. --- paper_title: The Multi-Chamber Electronic Nose—An Improved Olfaction Sensor for Mobile Robotics paper_content: One of the major disadvantages of the use of Metal Oxide Semiconductor (MOS) technology as a transducer for electronic gas sensing devices (e-noses) is the long recovery period needed after each gas exposure. This severely restricts its usage in applications where the gas concentrations may change rapidly, as in mobile robotic olfaction, where allowing for sensor recovery forces the robot to move at a very low speed, almost incompatible with any practical robot operation. This paper describes the design of a new e-nose which overcomes, to a great extent, such a limitation. The proposed e-nose, called Multi-Chamber Electronic Nose (MCE-nose), comprises several identical sets of MOS sensors accommodated in separate chambers (four in our current prototype), which alternate between sensing and recovery states, providing, as a whole, a device capable of sensing changes in chemical concentrations faster. The utility and performance of the MCE-nose in mobile robotic olfaction is shown through several experiments involving rapid sensing of gas concentration and mobile robot gas mapping. --- paper_title: Gas-sensing properties of catalytically modified WO/sub 3/ with copper and vanadium for NH/sub 3/ detection paper_content: Ammonia gas detection by pure and catalytically modified WO/sub 3/-based gas sensors was analyzed. Sensor response of pure tungsten oxide to NH/sub 3/ was unsatisfactory, probably due to the unselective oxidation of ammonia into NO/sub x/. Copper and vanadium were introduced in different concentrations and the resulting material was annealed at different temperatures in order to improve the sensing properties for NH/sub 3/ detection. The introduction of Cu and V as catalytic additives improved the sensor response to NH/sub 3/. Possible reaction mechanisms of NH/sub 3/ over these materials are discussed. Sensor responses to other gases like NO/sub 2/ or CO and interference of humidity on ammonia detection were also analyzed so as to choose the best sensing element. --- paper_title: Remote Moisture Sensing utilizing Ordinary RFID Tags paper_content: The paper presents a concept where pairs of ordinary RFID tags are exploited for use as remotely read moisture sensors. The pair of tags is incorporated into one label where one of the tags is embedded in a moisture absorbent material and the other is left open. In a humid environment the moisture concentration is higher in the absorbent material than the surrounding environment which causes degradation to the embedded tag's antenna in terms of dielectric losses and change of input impedance. The level of relative humidity or the amount of water in the absorbent material is determined for a passive RFID system by comparing the difference in RFID reader output power required to power up respectively the open and embedded tag. It is similarly shown how the backscattered signal strength of a semi-active RFID system is proportional to the relative humidity and amount of water in the absorbent material. Typical applications include moisture detection in buildings, especially from leaking water pipe connections hidden beyond walls. Presented solution has a cost comparable to ordinary RFID tags, and the passive system also has infinite life time since no internal power supply is needed. The concept is characterized for two commercial RFID systems, one passive operating at 868 MHz and one semi-active operating at 2.45 GHz. --- paper_title: A Nanopore Structured High Performance Toluene Gas Sensor Made by Nanoimprinting Method paper_content: Toluene gas was successfully measured at room temperature using a device microfabricated by a nanoimprinting method. A highly uniform nanoporous thin film was produced with a dense array of titania (TiO2) pores with a diameter of 70~80 nm using this method. This thin film had a Pd/TiO2 nanoporous/SiO2/Si MIS layered structure with Pd-TiO2 as the catalytic sensing layer. The nanoimprinting method was useful in expanding the TiO2 surface area by about 30%, as confirmed using AFM and SEM imaging. The measured toluene concentrations ranged from 50 ppm to 200 ppm. The toluene was easily detected by changing the Pd/TiO2 interface work function, resulting in a change in the I-V characteristics. --- paper_title: Dynamic thermal conductivity sensor for gas detection paper_content: A dynamic thermal conductivity sensor for gas detection based on the transient thermal response of a SiC microplate slightly heated by a screen-printed Pt resistance is described. This sensor is developed for specific applications such as the determination of carbon monoxide content in hydrogen for fuel cell, or that of methane in biogas applications. On the contrary of existing devices, the apparatus developed here does not need any reference cell, it operates in transient mode near room temperature (�T ≈ 5 K in air), so has a very low power requirements (≈5 mW) and keeps the gas near thermal equilibrium which simplifies the mathematical model and eases data processing. In test gases mixtures (N2 + He), absolute and precise measurement of the gas thermal conductivity have been achieved, leading to the exact molar fraction of the gas to detect with a good reproducibility. © 2003 Elsevier B.V. All rights reserved. --- paper_title: On the Electrooxidation and Amperometric Detection of NO Gas at the Pt/Nafion® Electrode paper_content: Abstract : The electrochemical oxidation of nitric oxide (NO) gas at the Pt/Nafion â electrode has been studied at a concentration of 500 ppm. The electrooxidation of NO taking place over a wide potential range can be described by a transcendental equation, from which the half-wave potential of the reaction can be determined. For NO oxidation with appreciable overpotentials but negligible mass-transfer effects, the Tafel kinetics applies. The obtained charge transfer coefficient (a) and the exchange current density (i o ) are 0.77 and 14 mA/cm 2 , respectively. An amperometric NO gas sensor based on the Pt/Nafion â electrode has been fabricated and tested over the NO concentration range from 0 to 500 ppm. The Pt/Nafion â electrode was used as an anode at a fixed potential, preferably 1.15 V (vs. Ag/AgCl/sat. KCl), which assures current limitation by diffusion only. The sensitivity of the electrochemical sensor was found to be 1.86 mA/ppm/cm 2 . The potential interference by other gases, such as nitrogen dioxide (NO --- paper_title: Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring paper_content: Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition. --- paper_title: A thin-film SnO2 sensor system for simultaneous detection of CO and NO2 with neural signal evaluation paper_content: Simultaneous CO and NO 2 measurements are of importance for the ventilation control of automobiles and other applications. For this purpose semiconducting SnO 2 sensors are often used. A well known disadvantage of SnO 2 sensors is the concurrent reaction of the oxidizing NO 2 and the reducing CO on the sensor surface, which causes a near zero sensor signal in the presence of both gases in a certain range of mixtures. A second disadvantage of SnO 2 sensors are the long rise and decay times of the sensor signal. The combination of different SnO 2 sensors, operated at different temperatures and combined with a signal evaluation system based on a specially trained neural forward network (artificial neural net (ANN)) solves this problem. The runtime version of the neural net is a small program, compatible with customary micro controllers. These signal evaluation techniques are applicable to similar problems using sensor arrays or single sensors in a non-stationary operating mode. --- paper_title: Electronic nose: A toxic gas sensor by polyaniline thin film conducting polymer paper_content: This paper presents study of toxic gas sensing property by polyaniline thin film conducting polymer for ammonia gas. In this work, the precipitate of the conducting polymer has been synthesized by chemical method. The conducting polymer film which acts as an active layer of sensor was prepared with the help of the precipitate (of the conducting polymer) by spin-coating technique. The deposited films were characterized by FTIR spectroscopy and four probe method. The study indicates that, the resistance of the film decreases with the increase in concentration of ammonia at the known volume. --- paper_title: Conductive polymer‐carbon black composites‐based sensor arrays for use in an electronic nose paper_content: Polymer‐carbon black composites are a new class of chemical detecting sensors used in electronic noses. These composites are prepared by mixing carbon black and polymer in an appropriate solvent. The mixture is deposited on a substrate between two metal electrodes, whereby the solvent evaporates leaving a composite film. Arrays of these chemiresistors, made from a chemically diverse number of polymers and carbon black, swell reversibly, inducing a resistance change on exposure to chemical vapors. These arrays generate a pattern that is a unique fingerprint for the vapor being detected. With the aid of algorithms these patterns are processed and recognized. These arrays can detect and discriminate between a large number of chemical vapors. --- paper_title: Gas Sensor Based on Photonic Crystal Fibres in the 2ν3 and ν2 + 2ν3 Vibrational Bands of Methane paper_content: Abstract: In this work, methane detection is performed on the 2 ” 3 and ” 2 + 2 ” 3 absorptionbands in the Near-Infrared (NIR) wavelength region using an all-ﬁbre optical sensor. Hollow-core photonic bandgap ﬁbres (HC-PBFs) are employed as gas cells due to their compactness,good integrability in optical systems and feasibility of long interaction lengths with gases.Sensing in the 2 ” 3 band of methane is demonstrated to achieve a detection limit one orderof magnitude better than that of the ” 2 + 2 ” 3 band. Finally, the ﬁlling time of a HC-PBF isdemonstrated to be dependent on the ﬁbre length and geometry.Keywords: gas detectors; methane; ﬁbre optic sensors; photonic crystal ﬁbres; hollow-corephotonic bandgap ﬁbres; absorption spectroscopy1. IntroductionMethane (CH 4 ) is a very common gas, found in many industrial applications where it carries a sig-niﬁcant explosion hazard, and in the environment where it can give rise to strong greenhouse effectcontributing to global warming. It is therefore of great interest to develop methane sensors to accurately --- paper_title: ZnO:Al Thin Film Gas Sensor for Detection of Ethanol Vapor paper_content: The ZnO:Al thin films were prepared by RF magnetron sputtering on Si substrate using Pt as interdigitated electrodes. The structure was characterized by XRD and SEM analyses, and the ethanol vapor gas sensing as well as electrical properties have been investigated and discussed. The gas sensing results show that the sensitivity for detecting 400 ppm ethanol vapor was ~20 at an operating temperature of 250°C. The high sensitivity, fast recovery, and reliability suggest that ZnO:Al thin film prepared by RF magnetron sputtering can be used for ethanol vapor gas sensing. --- paper_title: Application of ultrasonic to a hydrogen sensor paper_content: A fast responce hydrogen sensor using ultrasonic was developed and demonstrated. It uses the difference in sound velocity between hydrogen and the air. Thus, it is possible to measure hydrogen concentration by measuring the sound velocity changing when hydrogen is mixed in the air. The hydrogen sensor using ultrasonic in this study can be very fast in response time which was less than 84 msec. We also have shown that it is possible to detect hydrogen concentration as low as 100 ppm with the distance between ultrasonic probes as small as 20 mm. Temperature variation test was also demonstrated between −10 and 50°C and confirmed that it can match with calculation results. --- paper_title: Real-Time Gas Identification by Analyzing the Transient Response of Capillary-Attached Conductive Gas Sensor paper_content: In this study, the ability of the Capillary-attached conductive gas sensor (CGS) in real-time gas identification was investigated. The structure of the prototype fabricated CGS is presented. Portions were selected from the beginning of the CGS transient response including the first 11 samples to the first 100 samples. Different feature extraction and classification methods were applied on the selected portions. Validation of methods was evaluated to study the ability of an early portion of the CGS transient response in target gas (TG) identification. Experimental results proved that applying extracted features from an early part of the CGS transient response along with a classifier can distinguish short-chain alcohols from each other perfectly. Decreasing time of exposition in the interaction between target gas and sensing element improved the reliability of the sensor. Classification rate was also improved and time of identification was decreased. Moreover, the results indicated the optimum interval of the early transient response of the CGS for selecting portions to achieve the best classification rates. --- paper_title: Thermal and flow analysis of SiC-based gas sensors for automotive applications paper_content: Different block and tube mounting alternatives for SiC-based gas sensors were studied by means of temperature measurements and simulation of heat transfer and gas flow for steady state conditions. The most preferable tube mounting design was determined. Simulation-based guidelines were developed for designing tube-mounted gas sensors in the exhaust pipes of diesel and petrol engines, taking into account thermal constraints and flow conditions. --- paper_title: Bromocresol Green/Mesoporous Silica Adsorbent for Ammonia Gas Sensing via an Optical Sensing Instrument paper_content: A meso-structured Al-MCM-41 material was impregnated with bromocresol green (BG) dye and then incorporated into a UV-Vis DRA spectroscopic instrument for the online detection of ammonia gas. The absorption response of the Al-MCM-41/BG ammonia sensing material was very sensitive at the optical absorption wavelength of 630 nm. A high linear correlation was achieved for ppmv and sub-ppmv levels of ammonia gas. The response time for the quantitative detection of ammonia gas concentrations ranging from 0.25 to 2.0 ppmv was only a few minutes. The lower detection limit achieved was 0.185 ppmv. The color change process was fully reversible during tens of cycling tests. These features together make this mesoporous Al-MCM-41 material very promising for optical sensing applications. --- paper_title: Theory of power laws for semiconductor gas sensors paper_content: It has long been known empirically that the electric resistance of a semiconductor gas sensor under exposure to a target gas (partial pressure P) is proportional to Pn where n is a constant fairly specific to the kind of target gas (power law). This paper aims at providing a theoretical basis to such power laws. It is shown that the laws can be derived by combining a depletion theory of semiconductor, which deals with the distribution of electrons between surface state (surface charge) and bulk, with the dynamics of adsorption and/or reactions of gases on the surface, which is responsible for accumulation or reduction of surface charges. The resulting laws describe well sensor response behavior to oxygen, reducing gases and oxidizing gases. --- paper_title: Trace amount formaldehyde gas detection for indoor air quality monitoring paper_content: Formaldehyde is not only a carcinogenic chemical, but also causes sick building syndrome. Very small amounts of formaldehyde, such as those emitted from building materials and furniture, pose great concerns for human health. A Health Canada guideline, proposed in 2005, set the maximum formaldehyde concentration for long term exposure (8-hours averaged) as 40 ppb (50 μg/m3). This is a low concentration that commercially available formaldehyde sensors have great difficulty to detect both accurately and continuously. In this paper, we report a formaldehyde gas detection system which is capable of pre-concentrating formaldehyde gas using absorbent, and subsequently thermally desorbing the concentrated gas for detection by the electrochemical sensor. Initial results show that the system is able to detect formaldehyde gas at the ppb level, thus making it feasible to detect trace amount of formaldehyde in indoor environments. --- paper_title: MICROMACHINED THIN FILM SNO2 GAS SENSORS IN TEMPERATURE-PULSED OPERATION MODE paper_content: Abstract Gas detection measurements based on a micromachined SnO 2 gas sensor with periodically pulsed heater voltage are presented. Additionally, the field-effect-induced changes in resistivity of the sensitive layer caused by the heater voltage were investigated. The combination of both results leads to an improved design for low power SnO 2 gas sensors. In temperature-pulsed mode, the sensor resistances were measured at constant delays after the pulse edges. The measurements were carried out with the common test gases carbon monoxide and nitric dioxide in synthetic air with 50% humidity. In the cold pulse phase, the CO sensor response is higher and shows only a slow decrease with increasing pulse duration. The sensor sensitivity is related to the pulsed heated mode, on the one hand, and the continuously heated, on the other. The comparison of the measurement results reveals that the temperature-pulsed operation mode (TPOM) caused a significant reduction of power consumption and higher sensitivity. --- paper_title: A CMOS Single-Chip Gas Recognition Circuit for Metal Oxide Gas Sensor Arrays paper_content: This paper presents a CMOS single-chip gas recognition circuit, which encodes sensor array outputs into a unique sequence of spikes with the firing delay mapping the strength of the stimulation across the array. The proposed gas recognition circuit examines the generated spike pattern of relative excitations across the population of sensors and looks for a match within a library of 2-D spatio-temporal spike signatures. Each signature is drift insensitive, concentration invariant and is also a unique characteristic of the target gas. This VLSI friendly approach relies on a simple spatio-temporal code matching instead of existing computationally expensive pattern matching statistical techniques. In addition, it relies on a novel sensor calibration technique that does not require control or prior knowledge of the gas concentration. The proposed gas recognition circuit was implemented in a 0.35 μm CMOS process and characterized using an in-house fabricated 4 × 4 tin oxide gas sensor array. Experimental results show a correct detection rate of 94.9% when the gas sensor array is exposed to propane, ethanol and carbon monoxide. --- paper_title: Gas sensing properties of CNT-SnO2 Nanocomposite Thin Film Prepared by E-beam Evaporation paper_content: This work presents new results on the gas sensing study of CNT-SnO2 nanocomposite thin film prepared by e-beam evaporation process. The SnO2 gas sensing layers have been achieved with varying CNT concentration. Structural and morphological characterization by means of SEM TEM and XRD indicate that CNTs is incorporated in form of small fragments uniformly dispersed within SnO2 crystal and CNT inclusion does not modify surface morphology and slightly alter the crystal structure. Electrical characterizations highlight a very peculiar and interesting behavior for the layer tested. The SnO2 film's conductance decreases by more than two orders of magnitude with 1%CNT concentration. As CNT content increases to 1%, CO, ethanol, and particularly NO2 responses are improved and the working temperature tends to reduce. In addition, 1% CNT-SnO2 exhibit maximized response to NO2 with sensitivity of ~10 at very low NO2 concentration of 250 ppb at 200degC. --- paper_title: Highly sensitive and selective ammonia gas sensor paper_content: We have fabricated and examined an ammonia gas sensor with high sensitivity using thick-film technology. The sensing material of the gas sensor is FeO/sub x/-WO/sub 3/-SnO/sub 2/ oxide semiconductor. The sensor exhibits resistance increase upon exposure to low concentration of ammonia gas. The resistance of the sensor is decreased, on the other hand, for exposure to reducing gases such as ethyl alcohol, methane, propane and carbon monoxide. We have proposed and investigated a novel method for detecting ammonia gas quite selectively by using a sensor array with two sensing elements which contains an ammonia gas sensor and a compensation element. The compensation element is a Pt-doped WO/sub 3/-SnO/sub 2/ gas sensor which shows an opposite direction of resistance change in comparison with the ammonia gas sensor upon exposure to ammonia gas. Excellent selectivity has been achieved using the sensor array with two sensing elements. --- paper_title: Enhancement of MOS gas sensor selectivity by 'on-chip' catalytic filtering paper_content: Abstract A novel approach to enhancing the selectivity of a thick-film metal-oxide-semiconductor gas sensor is presented. The approach complements the efforts of many investigators who have tried to improve metal-oxide-semiconductor gas sensor selectivity by altering the sensing material alone. The discussion and data presented will focus on how 'on-chip' catalytic filtering is employed to build a selective fuel gas sensor without any adverse effects on the sensor's sensitivity or speed of response. Data are also presented showing the sensor's stable response to methane over an extended concentration range for over three years. --- paper_title: Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection paper_content: A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. --- paper_title: A wireless home safety gas leakage detection system paper_content: A wireless safety device for gas leakage detection is proposed. The device is intended for use in household safety where appliances and heaters that use natural gas and liquid petroleum gas (LPG) may be a source of risk. The system also can be used for other applications in the industry or plants that depend on LPG and natural gas in their operations. The system design consists of two main modules: the detection and transmission module, and the receiving module. The detection and transmitting module detects the change of gas concentration using a special sensing circuit built for this purpose. This module checks if a change in concentration of gas(es) has exceeded a certain pre-determined threshold. If the sensor detects a change in gas concentration, it activates and audiovisual alarm and sends a signal to the receiver module. The receiver module acts as a mobile alarm device to allow the mobility within the house premises. The system was tested using LPG and the alarm was activated as a result of change in concentration. --- paper_title: Advances in SAW Gas Sensors Based on the Condensate-Adsorption Effect paper_content: A surface-acoustic-wave (SAW) gas sensor with a low detection limit and fast response for volatile organic compounds (VOCs) based on the condensate-adsorption effect detection is developed. In this sensor a gas chromatography (GC) column acts as the separator element and a dual-resonator oscillator acts as the detector element. Regarding the surface effective permittivity method, the response mechanism analysis, which relates the condensate-adsorption effect, is performed, leading to the sensor performance prediction prior to fabrication. New designs of SAW resonators, which act as feedback of the oscillator, are devised in order to decrease the insertion loss and to achieve single-mode control, resulting in superior frequency stability of the oscillator. Based on the new phase modulation approach, excellent short-term frequency stability (±3 Hz/s) is achieved with the SAW oscillator by using the 500 MHz dual-port resonator as feedback element. In a sensor experiment investigating formaldehyde detection, the implemented SAW gas sensor exhibits an excellent threshold detection limit as low as 0.38 pg. --- paper_title: Thin-film SnO2 sensor arrays controlled by variation of contact potential—a suitable tool for chemometric gas mixture analysis in the TLV range paper_content: The selectivity of SnO 2 thin-film gas sensors can be modulated by changing the contact areas of the contact electrodes. The investigated SnO 2 arrays have been structured with two mask steps only. Gas mixture analysis in the German threshold limit value (TLV) range has been performed with an integrated thin-film sensor array using principal component regression (PCR) analysis. As an example, NO 2 , CO, CH 4 and H 2 O mixtures in air have been analyzed. In this case additional doping materials, catalysts, temperature gradients, etc., to enhance selectivity are not necessary. --- paper_title: Atomic layer deposition of tin dioxide sensing film in microhotplate gas sensors paper_content: We report the use of atomic layer deposition (ALD) to produce the gas-sensitive tin dioxide film in a microhotplate gas sensor. The performance of the device was demonstrated using ethanol, acetone and acrylonitrile as model analytes. Fast response times and low drift rates of the output signal were measured, indicating a structurally stable tin dioxide film and reflecting the capabilities of ALD in gas sensor applications. Fabrication of the microhotplate using tungsten metallization and plasma deposited silicon dioxide dielectrics is also detailed. --- paper_title: Methane and Carbon Monoxide Gas Detection system based on semiconductor sensor paper_content: One of the most important actual problems in the gas detection field is that there are strong demands for gas methane leak detection and CO (carbon monoxide) detection to prevent explosions or CO poisoning accidents. In this sense, the present paper describes technical characteristics, test results, and a concluding application for methane and carbon monoxide based gas detection using a sensor which can detect both CO and methane with a single sensing element. The paper presents the detection method as well as the apparatus functional sketch. --- paper_title: Metal Oxide Gas Sensors: Sensitivity and Influencing Factors paper_content: Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above. --- paper_title: Multi-layered thick-film gas sensor array for selective sensing by catalytic filtering technology paper_content: A C3H8 gas sensor array with high sensitivity and good selectivity by the combination of the catalytic filtering and the gas diffusion control has been achieved. The gas sensor array consists of a couple of catalytic filter layers, one with a Pd and the other with a Pt, a SiO2 insulating layer and two sensing layers on an alumina substrate. The sensor array shows high sensitivity to 500 ppm of C3H8 at temperature above 400°C and good selectivity for the interfering gases such as CO and C2H5OH by using a simple signal processing technique. --- paper_title: Low-power micro gas sensor paper_content: The stable and low-power heating characteristics of a microheater are very important for the micro gas sensor. Membrane-type gas sensors have been fabricated by silicon IC technology. Steady-state thermal analysis by the finite-element method is performed to optimize the thermal properties of the gas sensor. From the analysis, the desirable size of the microheater for low power consumption is determined. The heating properties of fabricated poly-Si and Pt microheaters have been tested. The sensing characteristics of the packaged microsensor are also examined. --- paper_title: Metal oxide nano-crystals for gas sensing paper_content: Abstract This review article is focused on the description of metal oxide single crystalline nanostructures used for gas sensing. Metal oxide nano-wires are crystalline structures with precise chemical composition, surface terminations, and dislocation-defect free. Their nanosized dimension generate properties that can be significantly different from their coarse-grained polycrystalline counterpart. Surface effects appear because of the magnification in the specific surface of nanostructures, leading to an enhancement of the properties related to that, such as catalytic activity or surface adsorption. Properties that are basic phenomenon underlying solid-state gas sensors. Their use as gas-sensing materials should reduce instabilities, suffered from their polycrystalline counterpart, associated with grain coalescence and drift in electrical properties. High degree of crystallinity and atomic sharp terminations make them very promising for better understanding of sensing principles and for development of a new generation of gas sensors. These sensing nano-crystals can be used as resistors, in FET based or optical based gas sensors. The gas experiments presented confirm good sensing properties, the possibility to use dopants and catalyser such in thin film gas sensors and the real integration in low power consumption transducers of single crystalline nanobelts prove the feasibility of large scale manufacturing of well-organized sensor arrays based on different nanostructures. Nevertheless, a greater control in the growth is required for an application in commercial systems, together with a thorough understanding of the growth mechanism that can lead to a control in nano-wires size and size distributions, shape, crystal structure and atomic termination. --- paper_title: The surface and materials science of tin oxide paper_content: Abstract The study of tin oxide is motivated by its applications as a solid state gas sensor material, oxidation catalyst, and transparent conductor. This review describes the physical and chemical properties that make tin oxide a suitable material for these purposes. The emphasis is on surface science studies of single crystal surfaces, but selected studies on powder and polycrystalline films are also incorporated in order to provide connecting points between surface science studies with the broader field of materials science of tin oxide. The key for understanding many aspects of SnO 2 surface properties is the dual valency of Sn. The dual valency facilitates a reversible transformation of the surface composition from stoichiometric surfaces with Sn 4+ surface cations into a reduced surface with Sn 2+ surface cations depending on the oxygen chemical potential of the system. Reduction of the surface modifies the surface electronic structure by formation of Sn 5s derived surface states that lie deep within the band gap and also cause a lowering of the work function. The gas sensing mechanism appears, however, only to be indirectly influenced by the surface composition of SnO 2 . Critical for triggering a gas response are not the lattice oxygen concentration but chemisorbed (or ionosorbed) oxygen and other molecules with a net electric charge. Band bending induced by charged molecules cause the increase or decrease in surface conductivity responsible for the gas response signal. In most applications tin oxide is modified by additives to either increase the charge carrier concentration by donor atoms, or to increase the gas sensitivity or the catalytic activity by metal additives. Some of the basic concepts by which additives modify the gas sensing and catalytic properties of SnO 2 are discussed and the few surface science studies of doped SnO 2 are reviewed. Epitaxial SnO 2 films may facilitate the surface science studies of doped films in the future. To this end film growth on titania, alumina, and Pt(1 1 1) is reviewed. Thin films on alumina also make promising test systems for probing gas sensing behavior. Molecular adsorption and reaction studies on SnO 2 surfaces have been hampered by the challenges of preparing well-characterized surfaces. Nevertheless some experimental and theoretical studies have been performed and are reviewed. Of particular interest in these studies was the influence of the surface composition on its chemical properties. Finally, the variety of recently synthesized tin oxide nanoscopic materials is summarized. --- paper_title: Gas sensors based on anodic tungsten oxide paper_content: Nanostructured porous tungsten oxide materials were synthesized by the means of electrochemical etching (anodization) of tungsten foils in aqueous NaF electrolyte. Formation of the sub-micrometer size mesoporous particles has been achieved by infiltrating the pores with water. The obtained colloidal anodic tungsten oxide dispersions have been used to fabricate resistive WO3 gas sensors by drop casting the sub-micrometer size mesoporous particles between Pt electrodes on Si/SiO2 substrate followed by calcination at 400 °C in air for 2 h. The synthesized WO3 films show slightly nonlinear current–voltage characteristics with strong thermally activated carrier transport behavior measured at temperatures between −20 °C and 280 °C. Gas response measurements carried out in CO, H2, NO and O2 analytes (concentration from 1 to 640 ppm) in air as well as in Ar buffers (O2 only in Ar) exhibited a rapid change of sensor conductance for each gas and showed pronounced response towards H2 and NO in Ar and air, respectively. The response of the sensors was dependent on temperature and yielded highest values between 170 °C and 220 °C. --- paper_title: A thin-film SnO2 sensor system for simultaneous detection of CO and NO2 with neural signal evaluation paper_content: Simultaneous CO and NO 2 measurements are of importance for the ventilation control of automobiles and other applications. For this purpose semiconducting SnO 2 sensors are often used. A well known disadvantage of SnO 2 sensors is the concurrent reaction of the oxidizing NO 2 and the reducing CO on the sensor surface, which causes a near zero sensor signal in the presence of both gases in a certain range of mixtures. A second disadvantage of SnO 2 sensors are the long rise and decay times of the sensor signal. The combination of different SnO 2 sensors, operated at different temperatures and combined with a signal evaluation system based on a specially trained neural forward network (artificial neural net (ANN)) solves this problem. The runtime version of the neural net is a small program, compatible with customary micro controllers. These signal evaluation techniques are applicable to similar problems using sensor arrays or single sensors in a non-stationary operating mode. --- paper_title: Feasibility of wireless gas detection with an FMCW RADAR interrogation of passive RF gas sensor paper_content: The feasibility of the remote measurement of gas detection from an RF gas sensor has been experimentally investigated. It consists of a Frequency-Modulated Continuous-Wave (FMCW) RADAR interrogation of an antenna loaded by the passive sensor. The frequency band of the RADAR [28.8–31GHz] allows the detection of the resonant frequencies of Whispering Gallery Modes that are sensitive to gas concentration. Reported experimental results provide the proof-of-concept of remote measurement of gas concentration fluctuation from RADAR interrogation of this new generation of passive gas sensors. --- paper_title: Detection of hydrogen fluoride using SnO2-based gas sensors : Understanding of the reactional mechanism paper_content: Tin dioxide-based gas sensors are very efficient devices for the detection of hydrogen fluoride in trace levels since amounts lower than 50 ppb can be detected. Considering the working temperatures of tin dioxide-based gas sensors which are included between 25 and 500 ◦C, the best sensitivity was obtained when the sensor's temperature was maintained at 380 ◦C. In order to explain why high sensitivity is obtained for this temperature and then to understand the reactional mechanism between HF molecules and tin dioxide surfaces, X-ray photoelectron spectroscopy investigations were performed on tin dioxide samples treated with HF vapors at temperatures ranging from 200 to 500 ◦C. For this temperature range, the comparison between the electrical response curves and the XPS characterization, led to the consideration of two separate temperature ranges, where the interaction mechanism between HF and SnO2 can be explained. For temperature lower than 380 ◦C, the adsorption of HF induces the formation of surface hydroxyl groups and SnF4 species. In that case, the electrical conductance of the sensitive material gradually increases. Beyond this temperature, water vapors desorb from tin dioxide surfaces and then the electrical conductance is lowered. Finally, for both ranges of temperatures, the interaction mechanism occurring at the gas/detector interface is proposed. --- paper_title: Gas Sensors Based on Conducting Polymers paper_content: The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review. --- paper_title: CMOS single-chip gas detection system comprising capacitive, calorimetric and mass-sensitive microsensors paper_content: A single-chip gas detection system fabricated in industrial CMOS technology combined with post-CMOS micro-machining is presented. The sensors rely on a chemo-sensitive polymer layer, which absorbs predominantly volatile organic compounds (VOCs). A mass-sensitive resonant-beam oscillator, a capacitive sensor incorporated into a second-order /spl Sigma//spl Delta/-modulator, a calorimetric sensor with low-noise signal conditioning circuitry and a temperature sensor are monolithically integrated on a single chip along with all necessary driving and signal conditioning circuitry. The preprocessed sensor signals are converted to the digital domain on chip. An additional integrated controller sets the sensor parameters and transmits the sensor values to an off-chip data recording unit via a standard serial interface. A 6-chip-array has been flip-chip packaged on a ceramic substrate, which forms part of a handheld VOC gas detection unit. Limits of detection (LOD) of 1-5 ppm n-octane, toluene or propan-1-ol have been achieved. --- paper_title: Design of conducting polymer gas sensors : modelling and experiment paper_content: Abstract The use of conducting polymers as active materials in chemical sensors is growing rapidly; for example they have been used in the place of metal oxides to sense gases and vapours, such as NH 3 , NO 2 and alcohols. Here we model a polymer gas sensor in terms of homogeneous diffusion coupled to simple adsorption within a bounded layer. From the model we present analytical expressions of the adsorbate profiles for the diffusion-rate limited, reaction-rate limited and intermediate cases in terms of fundamental dimensionless parameters. The model is then used to calculate the conductance of a typical chemiresistor which consists of a pair of co-planar electrodes below on electropolymerised thin polymer film and on an impermeable substrate. The analytical expression for the electric field is combined with the diffusion reaction equations by assuming an single carrier conduction model. Finally, the theoretical chemiresistor response is calculated in six limiting cases and compared with experimental data on pyrrole-based conducting polymers. In practice the gas-polymer interaction is likely to be much more complex and so we are extending our model to consider in more detail the conduction principles. --- paper_title: Electronic nose: A toxic gas sensor by polyaniline thin film conducting polymer paper_content: This paper presents study of toxic gas sensing property by polyaniline thin film conducting polymer for ammonia gas. In this work, the precipitate of the conducting polymer has been synthesized by chemical method. The conducting polymer film which acts as an active layer of sensor was prepared with the help of the precipitate (of the conducting polymer) by spin-coating technique. The deposited films were characterized by FTIR spectroscopy and four probe method. The study indicates that, the resistance of the film decreases with the increase in concentration of ammonia at the known volume. --- paper_title: Comparative studies on polymer coated SAW and STW resonators for chemical gas sensor applications paper_content: This paper presents and compares experimental data from performance tests on polymer coated 433 MHz surface acoustic wave (SAW) and 1 GHz surface transverse wave (STW) based two-port resonators for chemical gas sensor applications. The acoustic devices were coated with gas sensitive polymer films of different thickness' and viscoelastic properties as parylene C, poly-(2-hydroxyethylmethacrylate) (PHEMA) and poly-(n-butyl-methacrylate) (PBMA). Then they were gas probed using perchloroethylene and water. The SAW versus STW sensor sensitivities, insertion loss, loaded Q and distortion of the frequency and phase responses during gas probing were evaluated and compared. It was found that STW devices, when coated with thin sensitive polymer layers, retain low loss, high Q and low noise and feature substantially higher relative gas sensitivities compared to their SAW counterparts. Coated SAW sensors can stand substantially thicker soft polymer films than STW ones but at the expense of highly degraded electrical and noise performance and moderate increase in relative sensitivity. --- paper_title: CMOS single-chip gas detection system comprising capacitive, calorimetric and mass-sensitive microsensors paper_content: A single-chip gas detection system fabricated in industrial CMOS technology combined with post-CMOS micro-machining is presented. The sensors rely on a chemo-sensitive polymer layer, which absorbs predominantly volatile organic compounds (VOCs). A mass-sensitive resonant-beam oscillator, a capacitive sensor incorporated into a second-order /spl Sigma//spl Delta/-modulator, a calorimetric sensor with low-noise signal conditioning circuitry and a temperature sensor are monolithically integrated on a single chip along with all necessary driving and signal conditioning circuitry. The preprocessed sensor signals are converted to the digital domain on chip. An additional integrated controller sets the sensor parameters and transmits the sensor values to an off-chip data recording unit via a standard serial interface. A 6-chip-array has been flip-chip packaged on a ceramic substrate, which forms part of a handheld VOC gas detection unit. Limits of detection (LOD) of 1-5 ppm n-octane, toluene or propan-1-ol have been achieved. --- paper_title: Study on selectivity enhancement of tin dioxide gas sensor using non-conducting polymer membrane paper_content: A non-conducting polymer membrane can be used as a molecular sieve to enhance the selectivity of a tin dioxide gas sensor. A commercial polymer, polyimide XU218 of the Eiba-Geigy company, is coated on the surface of a tin dioxide gas sensor FIGARO TGS842 which was designed to detect methane. The polymer coated sensor is calibrated in a high accuracy testing system which is controlled by a PC with GPIB and mass flow controllers (MFCs). Three gases, hydrogen, methane, and ammonia, are used to investigate the response of the sensor. It is found that the sensor shows a characteristic change in response to ammonia and an almost negligible change in response to hydrogen and methane. --- paper_title: Conductive polymer‐carbon black composites‐based sensor arrays for use in an electronic nose paper_content: Polymer‐carbon black composites are a new class of chemical detecting sensors used in electronic noses. These composites are prepared by mixing carbon black and polymer in an appropriate solvent. The mixture is deposited on a substrate between two metal electrodes, whereby the solvent evaporates leaving a composite film. Arrays of these chemiresistors, made from a chemically diverse number of polymers and carbon black, swell reversibly, inducing a resistance change on exposure to chemical vapors. These arrays generate a pattern that is a unique fingerprint for the vapor being detected. With the aid of algorithms these patterns are processed and recognized. These arrays can detect and discriminate between a large number of chemical vapors. --- paper_title: Gas sensing properties of CNT-SnO2 Nanocomposite Thin Film Prepared by E-beam Evaporation paper_content: This work presents new results on the gas sensing study of CNT-SnO2 nanocomposite thin film prepared by e-beam evaporation process. The SnO2 gas sensing layers have been achieved with varying CNT concentration. Structural and morphological characterization by means of SEM TEM and XRD indicate that CNTs is incorporated in form of small fragments uniformly dispersed within SnO2 crystal and CNT inclusion does not modify surface morphology and slightly alter the crystal structure. Electrical characterizations highlight a very peculiar and interesting behavior for the layer tested. The SnO2 film's conductance decreases by more than two orders of magnitude with 1%CNT concentration. As CNT content increases to 1%, CO, ethanol, and particularly NO2 responses are improved and the working temperature tends to reduce. In addition, 1% CNT-SnO2 exhibit maximized response to NO2 with sensitivity of ~10 at very low NO2 concentration of 250 ppb at 200degC. --- paper_title: A wireless, passive carbon nanotube-based gas sensor paper_content: A gas sensor, comprised of a gas-responsive multiwall carbon nanotube (MWNT)-silicon dioxide (SiO/sub 2/) composite layer deposited on a planar inductor-capacitor resonant circuit is presented here for the monitoring of carbon dioxide (CO/sub 2/), oxygen (O/sub 2/), and ammonia (NH/sub 3/). The absorption of different gases in the MWNT-SiO/sub 2/ layer changes the permittivity and conductivity of the material and consequently alters the resonant frequency of the sensor. By tracking the frequency spectrum of the sensor with a loop antenna, humidity, temperature, as well as CO/sub 2/, O/sub 2/ and NH/sub 3/ concentrations can be determined, enabling applications such as remotely monitoring conditions inside opaque, sealed containers. Experimental results show the sensor response to CO/sub 2/ and O/sub 2/ is both linear and reversible. Both irreversible and reversible responses are observed in response to NH/sub 3/, indicating both physisorption and chemisorption of NH/sub 3/ by the carbon nanotubes. A sensor array, comprised of an uncoated, SiO/sub 2/ coated, and MWNT-SiO/sub 2/ coated sensor, enables CO/sub 2/ measurement to be automatically calibrated for operation in a variable humidity and temperature environment. --- paper_title: Dynamic Control of Adsorption Sensitivity for Photo-EMF-Based Ammonia Gas Sensors Using a Wireless Network paper_content: This paper proposes an adsorption sensitivity control method that uses a wireless network and illumination light intensity in a photo-electromagnetic field (EMF)-based gas sensor for measurements in real time of a wide range of ammonia concentrations. The minimum measurement error for a range of ammonia concentration from 3 to 800 ppm occurs when the gas concentration magnitude corresponds with the optimal intensity of the illumination light. A simulation with LabView-engineered modules for automatic control of a new intelligent computer system was conducted to improve measurement precision over a wide range of gas concentrations. This gas sensor computer system with wireless network technology could be useful in the chemical industry for automatic detection and measurement of hazardous ammonia gas levels in real time. --- paper_title: Observation of dynamic behavior of PD-generated SF/sub 6/ decompositions using carbon nanotube gas sensor paper_content: The authors had proposed a new detection method for partial discharge (PD) occurring in sulfur hexafluoride (SF/sub 6/) gas using a carbon nanotube (CNT) gas sensor. In the previous study, we had investigated the dependency of gas sensor response on applied voltage and gas sensor position. In this paper, a series of experiments was performed to observe dynamic behavior of decomposition gas using the CNT gas sensor. The gas sensor responses to PD under several SF/sup 6/ gas pressures were measured. It was found that the sensor response normalized by PD power increased almost linearly with the gas pressure. The result is useful to understand the mechanism how the gas pressure influences the generation and diffusion of decomposition gas. Effects of absorbent placed inside the discharge chamber were also investigated. Finally, the gas sensor responses were measured with a time interval after PD was extinguished to check if an offline diagnosis was possible. Although the sensor response decreased with elapsed time after PD was extinguished, it was still possible to detect the residual decomposition gas using the CNT gas sensor. --- paper_title: Detection of individual gas molecules adsorbed on graphene paper_content: The ultimate aim of any detection method is to achieve such a level of sensitivity that individual quanta of a measured entity can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity1, 2, 3, 4. The fundamental reason limiting the resolution of such sensors is fluctuations due to thermal motion of charges and defects5, which lead to intrinsic noise exceeding the sought-after signal from individual molecules, usually by many orders of magnitude. Here, we show that micrometre-size sensors made from graphene are capable of detecting individual events when a gas molecule attaches to or detaches from graphene's surface. The adsorbed molecules change the local carrier concentration in graphene one by one electron, which leads to step-like changes in resistance. The achieved sensitivity is due to the fact that graphene is an exceptionally low-noise material electronically, which makes it a promising candidate not only for chemical detectors but also for other applications where local probes sensitive to external charge, magnetic field or mechanical strain are required. --- paper_title: The effect of sequence length on DNA decorated CNT gas sensors paper_content: This article reports the effect of deoxyribonucleic acid (DNA) sequence length on the sensing characteristics of DNA decorated single-walled carbon nanotube (SWNT) devices. First, SWNTs were assembled on micro electrodes via a versatile, solution based Dielectrophoresis process. Then four single-stranded poly-G oligomers with lengths of 8, 16, 24 and 32 were decorated on SWNTs and the response of SWNT sensors to methanol and IPA vapors were measured. We found that the optimum DNA sequence length for sensing applications was 24. Sequence length of DNA had a dramatic impact on the response of DNA-SWNT sensors. This phenomenon can be explained by the difference in binding affinities of nucleotides on SWNTs and the conformations that DNA forms on SWNTs. These experimental results have significant implications for the interactions between DNA and SWNTs. They can facilitate the development of DNA functionalized SWNT sensors in analytical chemistry, biochemistry and environmental monitoring applications. --- paper_title: Remote Moisture Sensing utilizing Ordinary RFID Tags paper_content: The paper presents a concept where pairs of ordinary RFID tags are exploited for use as remotely read moisture sensors. The pair of tags is incorporated into one label where one of the tags is embedded in a moisture absorbent material and the other is left open. In a humid environment the moisture concentration is higher in the absorbent material than the surrounding environment which causes degradation to the embedded tag's antenna in terms of dielectric losses and change of input impedance. The level of relative humidity or the amount of water in the absorbent material is determined for a passive RFID system by comparing the difference in RFID reader output power required to power up respectively the open and embedded tag. It is similarly shown how the backscattered signal strength of a semi-active RFID system is proportional to the relative humidity and amount of water in the absorbent material. Typical applications include moisture detection in buildings, especially from leaking water pipe connections hidden beyond walls. Presented solution has a cost comparable to ordinary RFID tags, and the passive system also has infinite life time since no internal power supply is needed. The concept is characterized for two commercial RFID systems, one passive operating at 868 MHz and one semi-active operating at 2.45 GHz. --- paper_title: Differential Absorption Lidar to Measure Subhourly Variation of Tropospheric Ozone Profiles paper_content: A tropospheric ozone Differential Absorption Lidar system, developed jointly by The University of Alabama in Huntsville and the National Aeronautics and Space Administration, is making regular observations of ozone vertical distributions between 1 and 8 km with two receivers under both daytime and nighttime conditions using lasers at 285 and 291 nm. This paper describes the lidar system and analysis technique with some measurement examples. An iterative aerosol correction procedure reduces the retrieval error arising from differential aerosol backscatter in the lower troposphere. Lidar observations with coincident ozonesonde flights demonstrate that the retrieval accuracy ranges from better than 10% below 4 km to better than 20% below 8 km with 750-m vertical resolution and 10-min temporal integration. --- paper_title: Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection paper_content: Abstract: Various applications, such as pollution monitoring, toxic-gas detection, noninvasive medical diagnostics and industrial process control, require sensitive and selectivedetection of gas traces with concentrations in the parts in 10 9 (ppb) and sub-ppb range.The recent development of quantum-cascade lasers (QCLs) has given a new aspect toinfrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLsare attractive spectroscopic sources because of their excellent properties in terms of narrowlinewidth, average power and room temperature operation. In combination with these lasersources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity,compact sensor platform, fast time-response and user friendly operation. This paper reportsrecent developments on quantum cascade laser-based photoacoustic spectroscopy for tracegas detection. In particular, different applications of a photoacoustic trace gas sensoremploying a longitudinal resonant cell with a detection limit on the order of hundred ppb ofozone and ammonia are discussed. We also report two QC laser-based photoacousticsensors for the detection of nitric oxide, for environmental pollution monitoring andmedical diagnostics, and hexamethyldisilazane, for applications in semiconductormanufacturing process. --- paper_title: A study on NDIR-based CO2 sensor to apply remote air quality monitoring system paper_content: Recently, various CO2 sensors reported in the literature may be classified in two major categories depending on measuring principle of sensors. Fist, the chemical CO2 gas sensors have the principal advantage of a very low energy consumption and small size. On the negative side, It is difficult to apply to a variety of practical fields because they have a short lifetime and as well as low durability. Second, NDIR-based CO2 sensor is commonly used in monitoring indoor air quality due to relatively high accuracy compared with that of a chemical CO2 gas sensor. In this paper, therefore, we evaluate NDIR-based CO2 sensors to verify applicable potentialities of them in a remote air quality monitoring system. In addition, the principle and structure of NDIR CO2 sensor is discussed, and then we analyze the CO2 concentration has been measured in the real platform of subway station for a month. Finally this paper proposes that the accuracy of the measuring values from NDIR CO2 sensor is enough for indoor air quality monitoring applications. --- paper_title: Detection of gases by correlation spectroscopy paper_content: This paper describes the detection of various common gases by means of Correlation Spectroscopy, employing a Complementary-Source-Modulation (CoSM) approach based on compact light-emitting diode (LED) sources. Theoretical results for the quantitative detection of O in air are presented, with the use of practical low cost LED sources. --- paper_title: Compact Raman lidar for hydrogen gas leak detection paper_content: A compact Raman lidar system for hydrogen gas leak detection was constructed. Laser-induced fluorescence at a distance of 70 m and Raman scattering light from N 2 gas at short range could be detected. --- paper_title: Measurement of CH4 by differential infrared optical absorption spectroscopy paper_content: To solve the problem that the current use of optical methods used to detect various gases existing in sensors and signal processing was too complicated, detection sensitivity was not high, detection of the type of gases was single. We used optical phase-shifted grating laser window adjust the differential infrared absorption spectrometry and studied Spectrum adjustment and detection signal processing problem. CH4 in cigarette main smoke of different kind brands was measured continuously by differential optical absorption spectroscopy (DOAS). By using RM200 rotating disk smoking machine with 20 smoking flue, 20 kinds of gas were inserted into the rotating disk and ignited every 3s. By use of DOAS technique, the measurement was completed with in 6~7min after the gas was transported into a White cell with 31.5m path length which was connected to the smoking machine. This technique can improve the measuremental temporal resolution compared with traditional method. At the beginning, the press in White cell was 5.2×104 Pa and it increased to 1.03×105Pa while the measurement finished. The result shows the concentration of CH4 in main gas is between 0.89mg/m3 and 1.54mg/m. Pool in the White cell entrance placed wide infrared wavelength LED light source, light source after a large-diameter phase-shifted fiber grating access to White cell, Through the piezoelectric ceramic (PZT) phase-shift controlled Phase-Shifted Fiber Bragg Grating to infra-red LED into a laser modulation of narrowband continuous changes in light, wavelength corresponding to various gases such as CH4 absorption spectrum. White cell output pool signals entered into the photoelectric detector and ADC further, controlled by computer-related demodulation digitally. It can achieve high sensitivity digital lock-in amplifier function and be suitable for high-resolution detection of trace gases. Through simulation studies and practical tests, The results show that the piezoelectric ceramic (PZT) control Phase-Shifted Fiber Bragg Grating spectral scan can effectively suppress the background optical interference, the elimination of Rayleigh scattering and Raman scattering. Phase-Shifted Fiber Bragg Grating modulation and digital lock-in amplifier detection sensitivity of the combination improve three orders of magnitude. The methods solve the problem a wide range of gas detection by one kind of equipment. The device is small size, low cost, easy to carry, can measure a wide range of gas content, and has an important application value for environmental monitoring. If the White pool with underwater ocean can detect trace gases, for rivers and the marine environment and resources to detect environmental monitoring is also of great significance. --- paper_title: Tunable erbium-doped fiber ring laser for applications of infrared absorption spectroscopy paper_content: Abstract We fabricate a low noise erbium-doped fiber ring laser that can be continuously tuned over 102 nm by insertion of the fiber Fabry–Perot tunable filter (FFP-TF) in the ring cavity with a novel cavity structure and the optimal gain medium length. As an application of this fiber ring laser, we performed the absorption spectroscopy of acetylene ( 13 C 2 H 2 ) and hydrogen cyanide (H 13 C 14 N) and measure the absorption spectra of more than 50 transition lines of these gases with an excellent signal to noise ratio (SNR). The pressure broadening coefficients of four acetylene transition lines are obtained using this fiber ring laser and an external cavity laser diode. --- paper_title: Investigation of Wavelength Modulation and Wavelength Sweep Techniques in Intracavity Fiber Laser for Gas Detection paper_content: Wavelength modulation technique (WMT) and wavelength sweep technique (WST) are introduced into intracavity fiber laser for both gas concentration sensing and absorption wavelength detection in this paper. The principle of gas sensing and spectral analysis using WMT and WST was studied. Polynomial fit was adopted to model the system nonlinear characteristic, based on which absorption wavelength can be detected. The system optimization and acetylene gas sensing were both realized, and the absolute detected error can be increased less than 75 ppm. The absorption wavelengths of the detected gas were calculated based on the polynomial fitting results of the system nonlinear. The absorption wavelengths of acetylene were detected using this method, with absolute error no more than 0.445 nm. The system has the ability of realizing both concentration sensing and gas-type recognition. --- paper_title: In situ FTIR investigations of reverse water gas shift reaction activity at supercritical conditions paper_content: Abstract In situ Fourier transform infrared spectroscopy was employed to investigate the formation of CO and other adsorbed species on Al 2 O 3 -supported catalysts exposed to a supercritical mixture of CO 2 and H 2 ( P = 138 bar ; T = 342 K ; molar CO 2 / H 2 = 19 ). On just the Al 2 O 3 support, surface carbonates are observed consistent with literature reports with some evidence of surface formates. On Pd / Al 2 O 3 , however, several surface species including carbonates, formates, and CO are unambiguously observed. On Pd / Al 2 O 3 , a peak at 1900 – 1920 cm - 1 corresponds to adsorbed CO. Based on the presence of water peaks at reaction conditions, the reverse water gas shift reaction is the most plausible mechanism for CO formation. The CO peak evolves with time on stream, gradually increasing in intensity from ∼ 20 min to 5 h. This suggests that short-residence time continuous reactors are preferred over batch reactors to minimize the effects of possible catalyst deactivation by CO. Interestingly, the CO peak was not observed on either Ru / Al 2 O 3 or Ni / Al 2 O 3 catalysts suggesting that either of these catalysts may be better suited than Pt- or Pd-based catalysts for hydrogenation in supercritical CO 2 . --- paper_title: Wavelength Sweep of Intracavity Fiber Laser for Low Concentration Gas Detection paper_content: Wavelength sweep technique (WST) is introduced into intracavity fiber laser (ICFL) for low concentration gas detection. The limitation induced by noise can be eliminated using this method, and the performance of the system is improved. The sensitivity of the system is reduced to less than 200 ppm. With WST, the sweeping characteristic of the ICFL can be described according to known gas absorption spectra. --- paper_title: Photonic MEMS for NIR in-situ Gas Detection and Identification paper_content: We report on a novel sensing technique combining photonics and microelectromechanical systems (MEMS) for the detection and monitoring of gas emissions in environmental, medical, and industrial applications. We discuss how MEMS-tunable vertical-cavity surface-emitting lasers (VCSELs) can be exploited for in-situ detection and NIR spectroscopy of several gases, such as O2, N2O, CH4, HF, HCl, etc., with estimated sensitivities between 0.1 and 20 ppm on footprints <<10-3 mm3. The VCSELs can be electrostatically tuned with a continuous wavelength shift up to 20 nm, allowing for unambiguous NIR signature determination. Selective concentration analysis in heterogeneous gas compositions is enabled, thus paving the way to an integrated optical platform for multiplexed gas identification by bandgap and device engineering. We will discuss here, in particular, our efforts on the development of a 760 nm AlGaAs-based tunable VCSEL for O2 detection. --- paper_title: Mobile robots with active IR-optical sensing for remote gas detection and source localization paper_content: While other robots use in-situ measurements for gas leak detection and localization, we propose to apply remote sensing. It is easier and safer to conduct, permits rapid scans and is applicable to leak sources high up. An IR-optical sensor is used, exploiting spectral absorption effects of gases. Tailored leak detection and localization strategies are proposed. A simulation environment with a 3D model of the gas concentration field is used for developing and testing the detection and localization strategies. The system performance is demonstrated in a case study with a chemical plant. --- paper_title: Detection of trace concentrations of helium and argon in gas mixtures by laser-induced breakdown spectroscopy paper_content: We report what we believe to be the first demonstration of the detection of trace quantities of helium and argon in binary and ternary gas mixtures with nitrogen by laser-induced breakdown spectroscopy (LIBS). Although significant quenching of helium transitions due to collisional deactivation of excited species was observed, it was found that losses in analytical sensitivity could be minimized by increasing the laser irradiance and decreasing the pressure at which the analyses were performed. In consequence, limits of detection of parts-per-million and tens of parts-per-million and linear dynamic ranges of several orders of magnitude in analyte concentration were obtained. The results of this study suggest that LIBS may have potential applications in the detection of other noble gases at trace concentrations. --- paper_title: Application research of laser gas detection technology in the analysis of sulphur hexafluoride paper_content: The decision of latent fault in SF 6 gas electrical equipment can be made more timely and accurately through online monitoring of content change of HF, one of SF 6 gas decomposition. Tunable diode laser absorption spectroscopic (TDLAS) technology applies the wavelength tunable characteristics of diode lasers to gain the absorption spectroscopy of the selected absorption line of the target gas for the qualitative or quantitative analysis of the target gas. Because of its high sensitivity, high selectivity, short response time and without cross-interference, etc., we can achieve online monitoring and make the detection of HF more direct, accurate and timely through installing the technical equipment in the SF 6 electrical equipment monitoring site location. The analysis shows that the TDLAS technology is an effective and reliable method of SF 6 online monitoring technique. --- paper_title: Non-selective NDIR array for gas detection paper_content: A micro component for a non-selective NDIR (non dispersive infrared) gas detection system is presented in this work. This device consist of an IR detection module composed of a thermopile and a thin film filter array. The thermopile arrays (up to 4x4) are built on a silicon substrate by bulk micro-machining processes. The whole matrix is built on a thin freestanding silicon oxide/silicon nitride membrane of 2100x2100μm2 defined by anisotropic wet etching. To ensure the existence of hot and cold junctions for each detector we define on the insulating membrane absorbers and ribs, 6μm thick, by heavy boron doping of the silicon underneath. The ribs crisscross the membrane contacting the silicon bulk acting as a heat sink. Absorbers are located in the centre of each individual pseudo-membrane defined by the ribs intersection. Incident radiation heats up the absorber creating a temperature difference that is measured by the thermocouples that are placed between the absorber and the ribs. On a second chip, the elements of the filter array are fabricated in a matching configuration. The filters are built on a silicon substrate alternating thin films of different refraction index acting like a Fabry-Perot structure with 2-8μm silicon oxide cores. The transmitted filter peaks are not tuned for the detection of any specific substance: they configure a non selective general purpose filter array (400-4000 cm-1), making signal processing and pattern recognition techniques necessary. Both dies have been fabricated and characterized and have been successfully attached using flip-chip techniques. The measurements on these devices have been used to build an optical simulation tool that allows the assessment of the whole NDIR system behaviour in operating conditions.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. --- paper_title: Midinfrared sensors meet nanotechnology: Trace gas sensing with quantum cascade lasers inside photonic band-gap hollow waveguides paper_content: An integrated midinfrared sensing system for trace level (ppb) gas analysis combining a quantum cascade laser with an emission frequency of 10.3μm with a frequency matched photonic band-gap hollow core waveguide has been developed, demonstrating the sensing application of photonic band-gap fibers. The photonic band-gap fiber simultaneously acts as a wavelength selective waveguide and miniaturized gas cell. The laser emission wavelength corresponds to the vibrational C–H stretch band of ethyl chloride gas. This sensing system enabled the detection of ethyl chloride at concentration levels of 30ppb (v∕v) with a response time of 8s probing a sample volume of only 1.5mL in a transmission absorption measurement within the photonic band-gap hollow core waveguide, which corresponds to a sensitivity improvement by three orders of magnitude compared to previously reported results obtained with conventional hollow waveguides. --- paper_title: Comparison of infrared sources for a differential photoacoustic gas detection system paper_content: Abstract A prototype of the differential photoacoustic measurement system with an optical cantilever microphone has been developed. The system is based on gas filter correlation method. The proposed system allows real-time measurement of various IR-absorbing gases from the flowing sample or in the open air. Three setups with different kind of infrared sources were carried out to study selectivity and sensitivity of the prototype and applicability of the source types with differential method. The sources were a mechanically chopped blackbody radiator, electrically chopped blackbody radiator and mechanically chopped CO 2 -laser. A detection limit for C 2 H 4 was estimated with all three infrared sources. Cross sensitivity and detection limits of gases CH 4 , C 2 H 4 and CO 2 were measured with the mechanically chopped blackbody radiator. This crossinterference matrix was also modeled using HITRAN database and completed with CO and H 2 O. The measurements indicate that at least ppb-level detection of ethylene using CO 2 -laser, sub-ppm level with mechanically chopped blackbody and ppm-level with electrically modulated blackbody is possible with a proposed differential system. --- paper_title: A CMOS Single-Chip Gas Recognition Circuit for Metal Oxide Gas Sensor Arrays paper_content: This paper presents a CMOS single-chip gas recognition circuit, which encodes sensor array outputs into a unique sequence of spikes with the firing delay mapping the strength of the stimulation across the array. The proposed gas recognition circuit examines the generated spike pattern of relative excitations across the population of sensors and looks for a match within a library of 2-D spatio-temporal spike signatures. Each signature is drift insensitive, concentration invariant and is also a unique characteristic of the target gas. This VLSI friendly approach relies on a simple spatio-temporal code matching instead of existing computationally expensive pattern matching statistical techniques. In addition, it relies on a novel sensor calibration technique that does not require control or prior knowledge of the gas concentration. The proposed gas recognition circuit was implemented in a 0.35 μm CMOS process and characterized using an in-house fabricated 4 × 4 tin oxide gas sensor array. Experimental results show a correct detection rate of 94.9% when the gas sensor array is exposed to propane, ethanol and carbon monoxide. --- paper_title: Catalytic Fiber Bragg Grating Sensor for Hydrogen Leak Detection in Air paper_content: The explosion risk linked to the use of hydrogen as fuel requires low-cost and efficient sensors. We present here a multipoint in-fiber sensor capable of hydrogen leak detection in air as low as 1% concentration with a response time smaller than a few seconds. Our solution makes use of fiber Bragg gratings (FBGs) covered by a catalytic sensitive layer made of a ceramic doped with noble metal which, in turn, induces a temperature elevation around the FBGs in the presence of hydrogen in air. --- paper_title: Olfactory detection of methane, propane, butane and hexane using conventional transmitter norms paper_content: Abstract A Si based four element integrated calorimetric sensor was constructed for olfactory detection of hydrocarbon mixtures up to their lower explosion limit (LEL) concentration. In order to construct a four-wire, inherently explosion-proof transmitter, the power consumption of each sensor was reduced below 50 mW and a sequential read-out scheme was adopted. Olfactory detection is based on the principal component analysis (PCA) and partial least square (PLS) fitting. --- paper_title: An Analytic Model Of Thermal Drift In Piezoresistive Microcantilever Sensors paper_content: A closed-form semiempirical model has been developed to understand the physical origins of thermal drift in piezoresistive microcantilever sensors. The two-component model describes both the effects of temperature-related bending and heat dissipation on the piezoresistance. The temperature-related bending component is based on the Euler–Bernoulli theory of elastic deformation applied to a multilayer cantilever. The heat dissipation component is based on energy conservation per unit time for a piezoresistive cantilever in a Wheatstone bridge circuit, representing a balance between electrical power input and heat dissipation into the environment. Conduction and convection are found to be the primary mechanisms of heat transfer, and the dependence of these effects on the thermal conductivity, temperature, and flow rate of the gaseous environment is described. The thermal boundary layer value that defines the length scale of the heat dissipation phenomenon is treated as an empirical fitting parameter. Using t... --- paper_title: Dynamic thermal conductivity sensor for gas detection paper_content: A dynamic thermal conductivity sensor for gas detection based on the transient thermal response of a SiC microplate slightly heated by a screen-printed Pt resistance is described. This sensor is developed for specific applications such as the determination of carbon monoxide content in hydrogen for fuel cell, or that of methane in biogas applications. On the contrary of existing devices, the apparatus developed here does not need any reference cell, it operates in transient mode near room temperature (�T ≈ 5 K in air), so has a very low power requirements (≈5 mW) and keeps the gas near thermal equilibrium which simplifies the mathematical model and eases data processing. In test gases mixtures (N2 + He), absolute and precise measurement of the gas thermal conductivity have been achieved, leading to the exact molar fraction of the gas to detect with a good reproducibility. © 2003 Elsevier B.V. All rights reserved. --- paper_title: Evaluation of two gas chromatography-olfactometry methods: the detection frequency and perceived intensity method. paper_content: Two gas chromatography-olfactometry methods were evaluated in terms of repeatability, range of sensitivity and discriminating properties. Six volatile flavour compounds at various concentration levels were analysed by a panel of eight assessors using the detection frequency method and the perceived intensity method. The coefficient of variance, averaged over the individual compounds for three replicate samples, was 16% for the detection frequency method and 28% for the intensity method. The average correlation coefficient of the individual compounds with concentration was 0.93 (range 0.88-0.99) for the intensities. They were slightly higher than those for the detection frequencies (0.91, range 0.81-0.97). The detection frequency method was more accurate in terms of repeatability, and the intensity method was more accurate with regard to discrimination between concentration levels. The range of sensitivity was similar for both methods. --- paper_title: Comparison of various detection limit estimates for volatile sulphur compounds by gas chromatography with pulsed flame photometric detection. paper_content: This paper addresses the variations that presently exist regarding the definition, determination, and reporting of detection limits for volatile sulphur compounds by gas chromatography with pulsed flame photometric detection (GC-PFPD). Gas standards containing hydrogen sulphide (H(2)S), carbonyl sulphide (COS), sulphur dioxide (SO(2)), methyl mercaptan (CH(3)SH), dimethyl sulphide (DMS), carbon disulphide (CS(2)), and dimethyl disulphide (DMDS) in concentrations varying from 0.36ppb (v/v) up to 1.5ppm (v/v) in nitrogen were prepared with permeation tubes and introduced in the gas chromatograph using a 0.25-ml gas sampling loop. After measuring the PFPD response versus concentration, the method detection limit (MDL), the Hubaux-Vos detection limit (x(D)), the absolute instrument sensitivity (AIS), and the sulphur detectivity (D(s)) were determined for each sulphur compound. The results show that the MDL determined by the US Environmental Protection Agency procedure consistently underestimates the minimum concentrations of volatile sulphur compounds that can be practically distinguished from the background noise with the PFPD. The Hubaux-Vos detection limits and the AIS values are several times higher than the MDL, and provide more conservative estimates of the lowest concentrations that can be reliably detected. Sulphur detectivities are well correlated with AIS values but only poorly correlated with MDL values. The AIS is recommended as a reliable and cost-effective measure of detection limit for volatile sulphur compounds by GC-PFPD, since the AIS is easier and faster to determine than the MDL and the Hubaux-Vos detection limit. In addition, this study confirmed that the PFPD response is nearly quadratic with respect to concentration for all volatile sulphur compounds. --- paper_title: A prototype acoustic gas sensor based on attenuation paper_content: Acoustic attenuation provides the potential to identify and quantify gases in a mixture. We present results for a prototype attenuation gas sensor for binary gas mixtures. Tests are performed in a pressurized test cell between 0.2 and 32atm to accommodate the main molecular relaxation processes. Attenuation measurements using the 215-kHz sensor and a multiseparation, multifrequency research system both generally match theoretical predictions for mixtures of CO2 and CH4 with 2% air. As the pressure in the test cell increases, the standard deviation of sensor measurements typically decreases as a result of the larger gas acoustic impedance. --- paper_title: Ultrasonic Nondestructive Evaluation Systems: Models and Measurements paper_content: Ultrasonic Nondestructive Evaluation Systems: Models and Measurements provides the latest information and techniques available for ultrasonic nondestructive evaluation (NDE) inspections. Using a systems level approach, this book employs aspects of Fourier analysis, linear system theory, and wave propagation and scattering theory to develop a comprehensive model of an entire ultrasonic measurement system. The book also describes in detail the measurements needed to obtain all the system model parameters. This integrated approach leads to a new model-based engineering technology for designing, using and optimizing ultrasonic nondestructive evaluation inspections. Practicing engineers, teachers, and students alike will learn about the latest developments in NDE technology, including a recently developed pulse-echo method for measuring the sensitivity of an ultrasonic transducer, and the use of Gaussian beam theory in simulating the wave fields generated by ultrasonic transducers. In addition, this unique book incorporates MATLAB examples and exercises which allow readers to conduct simulated inspections and implement the latest modeling technology. Written by recognized experts in NDE research, Ultrasonic Nondestructive Evaluation Systems: Models and Measurements is designed to combine well-developed techniques with the latest advances in technology. --- paper_title: Gas density metering in ultrasonic gas flowmeters using impedance measurements and chemometrics paper_content: Measurements using ultrasonic transducers confirm that the density of the gaseous medium can be predicted from impedance measurements on the same transducers. Tests were performed with the following gases under different pressure: SF6, N2, He, and air. These gases were selected to achieve a large span of densities. Using chemometric techniques can circumvent any possible dual sensitivity of the transducers on temperature and density. Sensitivity analysis of the transducers as a function of density is also performed and compared with experimental results. The densitometer under discussion uses impedance variation as an intermediate variable. Impedance variations can be converted to variations in frequency. Finally, the scenario of ultrasonic mass flowmetering is discussed with plausible models for realising computer integrated mass measurements using ultrasonic transducers in dual mode, viz. Contra-propagating transit time and impedance modes. --- paper_title: Gas concentration detection using ultrasonic based on wireless sensor networks paper_content: In this article, a low power consumption wireless sensor for binary gas mixtures real-time quantitative analysis is presented. This small size wireless gas sensor, which is developed based on an improved time-of-flight (TOF) method, can evaluate target gas in gas mixtures with high resolution. And the wireless sensor network system reduce power consumption using a power control IEEE802.15.4 standard, which can provide an effective mechanism for improving energy efficiency by decreasing the transmitting power directly. In contrast with some other gas analysis techniques, it avoids the problem of the secondary pollution and the short sensor life of using chemic sensor, and the high power consumption problem of traditional TOF methods, makes ultrasonic wireless gas sensor available. Currently, this gas quantitative analysis system consists of several Wireless Ultrasonic Gas Sensor nodes (WUGS) and a master node. The WUGS hardware consists of a microcontroller for obtaining measuring data from the ultrasonic channel, and a Zigbee transceiver for transmitting the data sets to a master sensor node. Furthermore, an environmental monitoring chamber was designed for testing this WUGS using sulfur hexafluoride (SF 6 ) and hydrogen (H 2 ) mixed with air respectively. The resolutions of the tests were within 30µV/V and 500µV/V, respectively. The power cost of the WUGS during the detection period is lower than 90mW. The main advantages of this gas concentration measurement are high accuracy to the gas of which molecular weight is different largely from air, low power consumption and ease of network setup. The sensors have shown good stability for more than three months in a high-voltage substation, for an SF 6 leak alarm system test. --- paper_title: A Sonar-Based Technique for the Ratiometric Determination of Binary Gas Mixtures paper_content: Abstract We have developed an inexpensive sonar-based instrument to provide a routine on-line monitor of the composition and stability of several gas mixtures having application in a Cherenkov Ring Imaging Detector. The instrument is capable of detecting small ( --- paper_title: Application of ultrasonic to a hydrogen sensor paper_content: A fast responce hydrogen sensor using ultrasonic was developed and demonstrated. It uses the difference in sound velocity between hydrogen and the air. Thus, it is possible to measure hydrogen concentration by measuring the sound velocity changing when hydrogen is mixed in the air. The hydrogen sensor using ultrasonic in this study can be very fast in response time which was less than 84 msec. We also have shown that it is possible to detect hydrogen concentration as low as 100 ppm with the distance between ultrasonic probes as small as 20 mm. Temperature variation test was also demonstrated between −10 and 50°C and confirmed that it can match with calculation results. --- paper_title: Whispering gallery dielectric resonator modes for W-band devices paper_content: The utilization of planar millimeter-wavelength whispering gallery dielectric resonator modes for the design of W-band directional filters and power combiners is studied. The device presented combines the output power of several millimeter-wavelength devices in a single step by means of whispering gallery dielectric resonator (DR) modes. At millimeter wavelengths the cylindrical DRs used on their conventional TE, TM, or hybrid modes are impractically small. When used in their whispering gallery modes (WGMs) these cylindrical DRs have dimensions larger than normal for millimeter wavelength. After a description of the WGM phenomena, both electromagnetic and circuit parameters of these resonators are defined when they are coupled with transmission lines. The analysis based on the ring resonator model makes it possible to predict the theoretical responses of any devices. Experimental results obtained for directional filters and for power combiners in W-band are given. > --- paper_title: Hand-Held Miniature Chemical Analysis System (μChemlab) for Detection of Trace Concentrations of Gas Phase Analytes paper_content: A miniature, integrated chemical laboratory (μChemLab) is being developed that utilizes microfabrication to provide faster response, smaller size, lower power operation, and an ability to utilize multiple analysis channels for enhanced versatility and chemical discrimination. Improved sensitivity and selectivity are achieved with three cascaded components: (1) a sample collector/concentrator, (2) a gas chromatographic (GC) separator, and (3) a chemically selective surface acoustic wave (SAW) array detector. Prototypes of all three components have been developed and demonstrated both individually and when integrated on a novel electrical and fluidic printed circuit board. A hand-held autonomous system containing two analysis channels and all supporting electronics and user interfaces is currently being assembled and tested. --- paper_title: Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection paper_content: Abstract: Various applications, such as pollution monitoring, toxic-gas detection, noninvasive medical diagnostics and industrial process control, require sensitive and selectivedetection of gas traces with concentrations in the parts in 10 9 (ppb) and sub-ppb range.The recent development of quantum-cascade lasers (QCLs) has given a new aspect toinfrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLsare attractive spectroscopic sources because of their excellent properties in terms of narrowlinewidth, average power and room temperature operation. In combination with these lasersources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity,compact sensor platform, fast time-response and user friendly operation. This paper reportsrecent developments on quantum cascade laser-based photoacoustic spectroscopy for tracegas detection. In particular, different applications of a photoacoustic trace gas sensoremploying a longitudinal resonant cell with a detection limit on the order of hundred ppb ofozone and ammonia are discussed. We also report two QC laser-based photoacousticsensors for the detection of nitric oxide, for environmental pollution monitoring andmedical diagnostics, and hexamethyldisilazane, for applications in semiconductormanufacturing process. --- paper_title: Trace amount formaldehyde gas detection for indoor air quality monitoring paper_content: Formaldehyde is not only a carcinogenic chemical, but also causes sick building syndrome. Very small amounts of formaldehyde, such as those emitted from building materials and furniture, pose great concerns for human health. A Health Canada guideline, proposed in 2005, set the maximum formaldehyde concentration for long term exposure (8-hours averaged) as 40 ppb (50 μg/m3). This is a low concentration that commercially available formaldehyde sensors have great difficulty to detect both accurately and continuously. In this paper, we report a formaldehyde gas detection system which is capable of pre-concentrating formaldehyde gas using absorbent, and subsequently thermally desorbing the concentrated gas for detection by the electrochemical sensor. Initial results show that the system is able to detect formaldehyde gas at the ppb level, thus making it feasible to detect trace amount of formaldehyde in indoor environments. --- paper_title: Enhanced toxic gas detection using a MEMS preconcentrator coated with the metal organic framework absorber paper_content: Widespread and timely sensing of explosives, toxic chemicals and industrial compounds needs fast, sensitive detection technology that is affordable and portable. Many gas detectors developed for portable applications are based on sensing a change in resistivity or other non-selective material properties, often leading to low sensitivity and selectivity. In this paper, we report a new generation of the UIUC MEMS gas preconcentrator (muGPC) and its integration into a microfluidic M-8 (muM8) detector to demonstrate an enhanced overall detection limit and selectivity in detecting a toxic gas simulant. The integration creates a portable sensor to sniff an analyte of interest at concentration of 10 ppb or below. --- paper_title: Microfabricated preconcentrator-focuser for a microscale gas chromatograph paper_content: The design, fabrication, and testing of a preconcentrator-focuser (PCF), consisting of a thick micromachined Si heater packed with a small quantity of a granular adsorbent material are described. The PCF is developed to capture and concentrate vapors for subsequent focused thermal desorption and analysis in a micro gas chromatograph. The microheater contains an array of high-aspect-ratio, etched-Si heating elements, 520 /spl mu/m (h)/spl times/50 /spl mu/m (w)/spl times/3000 /spl mu/m (l), bounded by an annulus of Si and thermally isolated from the remaining substrate by an air gap. This structure is sandwiched between Pyrex glass plates with inlet/outlet ports that accept capillary tubes for sample flow and is sealed by anodic bonding (bottom) and rapidly annealed glass/metal/Si solder bonding (top). The large microheater surface area allows for high adsorption capacity and efficient, uniform thermal desorption of vapors captured on the adsorbent within the structure. The adsorbent consists of roughly spherical granules, /spl sim/200 /spl mu/m in diameter, of a high-surface-area, graphitized carbon. Key design considerations, fabrication technologies, and results of performance tests are presented with an emphasis on the thermal desorption characteristics of several representative volatile organic compounds as a function of volumetric flow rates and heating rates. Preconcentration factors as high as 5600 and desorbed peak widths as narrow as 0.8 s are achieved from 0.25-L samples of benzene at modest heating rates. The effects of operating variables on sensitivity, chromatographic resolution, and detection limits are assessed. Testing of this PCF with a micromachined separation column and integrated sensor array is discussed briefly. --- paper_title: Methane and Carbon Monoxide Gas Detection system based on semiconductor sensor paper_content: One of the most important actual problems in the gas detection field is that there are strong demands for gas methane leak detection and CO (carbon monoxide) detection to prevent explosions or CO poisoning accidents. In this sense, the present paper describes technical characteristics, test results, and a concluding application for methane and carbon monoxide based gas detection using a sensor which can detect both CO and methane with a single sensing element. The paper presents the detection method as well as the apparatus functional sketch. --- paper_title: Metal Oxide Gas Sensors: Sensitivity and Influencing Factors paper_content: Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above. --- paper_title: Comparison of infrared sources for a differential photoacoustic gas detection system paper_content: Abstract A prototype of the differential photoacoustic measurement system with an optical cantilever microphone has been developed. The system is based on gas filter correlation method. The proposed system allows real-time measurement of various IR-absorbing gases from the flowing sample or in the open air. Three setups with different kind of infrared sources were carried out to study selectivity and sensitivity of the prototype and applicability of the source types with differential method. The sources were a mechanically chopped blackbody radiator, electrically chopped blackbody radiator and mechanically chopped CO 2 -laser. A detection limit for C 2 H 4 was estimated with all three infrared sources. Cross sensitivity and detection limits of gases CH 4 , C 2 H 4 and CO 2 were measured with the mechanically chopped blackbody radiator. This crossinterference matrix was also modeled using HITRAN database and completed with CO and H 2 O. The measurements indicate that at least ppb-level detection of ethylene using CO 2 -laser, sub-ppm level with mechanically chopped blackbody and ppm-level with electrically modulated blackbody is possible with a proposed differential system. --- paper_title: Feasibility of wireless gas detection with an FMCW RADAR interrogation of passive RF gas sensor paper_content: The feasibility of the remote measurement of gas detection from an RF gas sensor has been experimentally investigated. It consists of a Frequency-Modulated Continuous-Wave (FMCW) RADAR interrogation of an antenna loaded by the passive sensor. The frequency band of the RADAR [28.8–31GHz] allows the detection of the resonant frequencies of Whispering Gallery Modes that are sensitive to gas concentration. Reported experimental results provide the proof-of-concept of remote measurement of gas concentration fluctuation from RADAR interrogation of this new generation of passive gas sensors. --- paper_title: Design and Characterization of Micropost-Filled Reactor to Minimize Pressure Drop While Maximizing Surface-Area-to-Volume-Ratio paper_content: Micropost-filled reactors are commonly found in many micro total analysis system applications because of their high surface area for the surrounding volume. Design rules for micropost-filled reactors are presented here to optimize the performance of the micro-preconcentrator, which is a component of a micro gas chromatography system. The dimensionless figure of merit is proposed to be used to minimize the pressure drop while maximizing the surface-area-to-volume-ratio for a given overall channel geometry of the micropost-filled preconcentrator. Two independent models from the literature are used to predict the pressure drop across the micropost-filled channels for low Reynolds number flows. The pressure drop can be expressed solely as a function of a design parameter, β = a/s, a ratio of a radius of each post and a half-spacing between two adjacent posts. Pressure drop measurements are performed to experimentally corroborate the pressure drop model and the optimization using the dimensionless figure of merit. As the number of microposts; for a given β increases in a given channel size, a greater surface-area-to-volume-ratio will occur for a fixed pressure drop. Therefore, increasing the arrays of posts with smaller diameters and spacing will optimize the microreactor for higher surface area for a given flow resistance, at least until Knudsen flow begins to dominate.Copyright © 2006 by ASME --- paper_title: Vertically Aligned ZnO Nanorod Arrays Coated with $\hbox{SnO}_{\bf 2}$/Noble Metal Nanoparticles for Highly Sensitive and Selective Gas Detection paper_content: Mimicking the biological olfactory receptor array that possesses large surface area for molecule capture, vertically aligned ZnO nanowire arrays, used as structural templates, were coated with SnO2/noble metal nanoparticles as active materials for fabrication of 3-D gas sensors. The gas sensors showed room-temperature responses to environmental toxic gases, such as NO2 and H2S, down to ppb level, which can be attributed to the large surface area of their 3D structure and catalytic behaviors of noble metals. A sensor array composed of three sensors with the different noble metals decoration (Pd, Pt, and Au) has shown capability to discriminate five different gases (H2S, NO2, NH3, H2, and CO) when using principal component analysis (PCA) incorporated the response speed as a discrimination factor. This study demonstrates a rational strategy to prepare sensing devices with 3-D structures for selective detection, which can be readily extended to other sensing materials that can be hardly grown as 3-D nanowire arrays. --- paper_title: Evaluation of Multitransducer Arrays for the Determination of Organic Vapor Mixtures paper_content: A study of vapor recognition and quantification by polymer-coated multitransducer (MT) arrays is described. The primary data set consists of experimentally derived sensitivities for 11 organic vapors obtained from 15 microsensors comprising five cantilever, capacitor, and calorimeter devices coated with five different sorptive−polymer films. These are used in Monte Carlo simulations coupled with principal component regression models to assess expected performance. Recognition rates for individual vapors and for vapor mixtures of up to four components are estimated for single-transducer (ST) arrays of up to five sensors and MT arrays of up to 15 sensors. Recognition rates are not significantly improved by including more than five sensors in an MT array for any specific analysis, regardless of difficulty. Optimal MT arrays consistently outperform optimal ST arrays of similar size, and with judiciously selected 5-sensor MT arrays, one-third of all possible ternary vapor mixtures are reliably discriminated fr... --- paper_title: Enhanced gas sensing by individual SnO2 nanowires and nanobelts functionalized with Pd catalyst particles. paper_content: The sensing ability of individual SnO2 nanowires and nanobelts configured as gas sensors was measured before and after functionalization with Pd catalyst particles. In situ deposition of Pd in the same reaction chamber in which the sensing measurements were carried out ensured that the observed modification in behavior was due to the Pd functionalization rather than the variation in properties from one nanowire to another. Changes in the conductance in the early stages of metal deposition (i.e., before metal percolation) indicated that the Pd nanoparticles on the nanowire surface created Schottky barrier-type junctions resulting in the formation of electron depletion regions within the nanowire, constricting the effective conduction channel and reducing the conductance. Pd-functionalized nanostructures exhibited a dramatic improvement in sensitivity toward oxygen and hydrogen due to the enhanced catalytic dissociation of the molecular adsorbate on the Pd nanoparticle surfaces and the subsequent diffusion ... --- paper_title: Detection of gases with arrays of micromachined tin oxide gas sensors paper_content: Abstract A good detection of NO 2 , CO and toluene at low concentrations has been carried out by using a micromachined gas sensor array composed of three devices working at different temperatures. The structure is fabricated using standard microelectronic technologies and tin oxide layers as sensitive material. The total power consumption of the array is in the range of 150 mW and a good uniformity of temperature is achieved, thanks to a silicon plug placed under the active area of each sensor. With this device type, it is possible to discriminate gases in a mixture when each array microsensor is heated at a proper temperature. --- paper_title: A Gradient Microarray Electronic Nose Based on Percolating SnO2 Nanowire Sensing Elements paper_content: Fabrication, characterization, and tests of the practical gradient microarray electronic nose with SnO2 nanowire gas-sensing elements are reported. This novel device has demonstrated an excellent performance as a gas sensor and e-nose system capable of promptly detecting and reliably discriminating between several reducing gases in air at a ppb level of concentration. It has been found that, in addition to the temperature gradient across the nanowire layer, the density and morphological inhomogeneities of nanowire mats define the discriminating power of the electronic nose. --- paper_title: CMOS single-chip gas detection system comprising capacitive, calorimetric and mass-sensitive microsensors paper_content: A single-chip gas detection system fabricated in industrial CMOS technology combined with post-CMOS micro-machining is presented. The sensors rely on a chemo-sensitive polymer layer, which absorbs predominantly volatile organic compounds (VOCs). A mass-sensitive resonant-beam oscillator, a capacitive sensor incorporated into a second-order /spl Sigma//spl Delta/-modulator, a calorimetric sensor with low-noise signal conditioning circuitry and a temperature sensor are monolithically integrated on a single chip along with all necessary driving and signal conditioning circuitry. The preprocessed sensor signals are converted to the digital domain on chip. An additional integrated controller sets the sensor parameters and transmits the sensor values to an off-chip data recording unit via a standard serial interface. A 6-chip-array has been flip-chip packaged on a ceramic substrate, which forms part of a handheld VOC gas detection unit. Limits of detection (LOD) of 1-5 ppm n-octane, toluene or propan-1-ol have been achieved. --- paper_title: Application of electronic nose technology in detection of combustible gas paper_content: Based on the study of the theory and constituent of the electronic nose systems, a set of combined gas sensor array, microcontroller and PC for detection of gas mixture is designed and constructed. Four kinds of gas (hydrogen, methane, acetylene, propane) are tested by the system. The feature parameters are picked up from each curve of the gas sensor's reaction. The experimental samples are analyzed by the method of PCA (principal component analysis) and BPNN (BP neural network). The result shows that the four kinds of gas could not be distinguished well by the method of PCA. While BPNN can solve the problem of sensor cross-sensitivity, and four kinds of gas can be identified qualitatively, the recognition probability of BPNN is more than 90%. --- paper_title: A wireless, passive carbon nanotube-based gas sensor paper_content: A gas sensor, comprised of a gas-responsive multiwall carbon nanotube (MWNT)-silicon dioxide (SiO/sub 2/) composite layer deposited on a planar inductor-capacitor resonant circuit is presented here for the monitoring of carbon dioxide (CO/sub 2/), oxygen (O/sub 2/), and ammonia (NH/sub 3/). The absorption of different gases in the MWNT-SiO/sub 2/ layer changes the permittivity and conductivity of the material and consequently alters the resonant frequency of the sensor. By tracking the frequency spectrum of the sensor with a loop antenna, humidity, temperature, as well as CO/sub 2/, O/sub 2/ and NH/sub 3/ concentrations can be determined, enabling applications such as remotely monitoring conditions inside opaque, sealed containers. Experimental results show the sensor response to CO/sub 2/ and O/sub 2/ is both linear and reversible. Both irreversible and reversible responses are observed in response to NH/sub 3/, indicating both physisorption and chemisorption of NH/sub 3/ by the carbon nanotubes. A sensor array, comprised of an uncoated, SiO/sub 2/ coated, and MWNT-SiO/sub 2/ coated sensor, enables CO/sub 2/ measurement to be automatically calibrated for operation in a variable humidity and temperature environment. --- paper_title: Remote Moisture Sensing utilizing Ordinary RFID Tags paper_content: The paper presents a concept where pairs of ordinary RFID tags are exploited for use as remotely read moisture sensors. The pair of tags is incorporated into one label where one of the tags is embedded in a moisture absorbent material and the other is left open. In a humid environment the moisture concentration is higher in the absorbent material than the surrounding environment which causes degradation to the embedded tag's antenna in terms of dielectric losses and change of input impedance. The level of relative humidity or the amount of water in the absorbent material is determined for a passive RFID system by comparing the difference in RFID reader output power required to power up respectively the open and embedded tag. It is similarly shown how the backscattered signal strength of a semi-active RFID system is proportional to the relative humidity and amount of water in the absorbent material. Typical applications include moisture detection in buildings, especially from leaking water pipe connections hidden beyond walls. Presented solution has a cost comparable to ordinary RFID tags, and the passive system also has infinite life time since no internal power supply is needed. The concept is characterized for two commercial RFID systems, one passive operating at 868 MHz and one semi-active operating at 2.45 GHz. --- paper_title: Detection and discrimination of pure gases and binary mixtures using a dual-modality microcantilever sensor paper_content: A new method for detecting and discriminating pure gases and binary mixtures has been investigated. This approach is based on two distinct physical mechanisms which can be simultaneously employed within a single microcantilever: heat dissipation and resonant damping in the viscous regime. An experimental study of the heat dissipation mechanism indicates that the sensor response is directly correlated to the thermal conductivity of the gaseous analyte. A theoretical data set of resonant damping was generated corresponding to the gas mixtures examined in the thermal response experiments. The combination of the thermal and resonant response data yields more distinct analyte signatures that cannot otherwise be obtained from the detection modes individually. ---	Title: A Survey on Gas Sensing Technology Section 1: Introduction Description 1: This section introduces the growing importance of gas sensing technology, its applications, and the main areas of research and development in the field. Section 2: Classification of Gas Sensing Methods Description 2: This section classifies the various gas sensing technologies based on different principles and properties, providing a foundational overview for further discussion. Section 3: Performance Indicators and Gas Sensor's Stability Description 3: This section discusses the key performance indicators used to evaluate gas sensors, such as sensitivity and selectivity, and explores factors that affect sensor stability. Section 4: Metal Oxide Semiconductor Description 4: This section covers sensors based on metal oxide semiconductors, detailing their operating principles, advantages, challenges, and applications. Section 5: Polymers Description 5: This section describes polymer-based gas sensors, explaining their working principles, advantages, limitations, and usage in detecting specific gases. Section 6: Carbon Nanotubes Description 6: This section explores the utilization of carbon nanotubes (CNTs) in gas sensing, highlighting their properties, performance, and potential applications. Section 7: Moisture Absorbing Material Description 7: This section details how moisture-absorbing materials are used in gas sensing, particularly in RFID-based systems for humidity detection. Section 8: Classification Based on Sensors' Operating Modes Description 8: This section classifies sensors based on their operating modes, such as direct contact and wireless transducers, and discusses their integration. Section 9: Optical Methods Description 9: This section gives an overview of optical methods used in gas sensing, discussing their principles, advantages, and limitations. Section 10: Calorimetric Methods Description 10: This section explains calorimetric methods for gas sensing, including catalytic and thermal conductivity sensors, and discusses their mechanisms and applications. Section 11: Gas Chromatograph Description 11: This section covers gas chromatography as a method for gas sensing, focusing on its analytical capabilities, sensitivity, and selectivity. Section 12: Acoustic Methods Description 12: This section describes gas sensing methods based on acoustic principles, such as speed of sound and attenuation, outlining their operational parameters and applications. Section 13: Components of Wireless Sensor Networks Description 13: This section introduces the components and functionalities of wireless sensor networks used in gas sensing technologies. Section 14: Some Approaches to Improve Sensitivity and Selectivity Description 14: This section discusses various approaches to enhance the sensitivity and selectivity of gas sensors, including modifying sensor materials and employing pre-concentration techniques. Section 15: Conclusions Description 15: This section summarizes the survey findings, compares different gas sensing technologies, discusses the factors affecting performance, and provides insights into future development trends in the field.
Overview of Spintronic Sensors, Internet of Things, and Smart Living	5	--- paper_title: Sensing as a Service Model for Smart Cities Supported by Internet of Things paper_content: The world population is growing at a rapid pace. Towns and cities are accommodating half of the world's population thereby creating tremendous pressure on every aspect of urban living. Cities are known to have large concentration of resources and facilities. Such environments attract people from rural areas. However, unprecedented attraction has now become an overwhelming issue for city governance and politics. The enormous pressure towards efficient city management has triggered various Smart City initiatives by both government and private sector businesses to invest in ICT to find sustainable solutions to the growing issues. The Internet of Things (IoT) has also gained significant attention over the past decade. IoT envisions to connect billions of sensors to the Internet and expects to use them for efficient and effective resource management in Smart Cities. Today infrastructure, platforms, and software applications are offered as services using cloud technologies. In this paper, we explore the concept of sensing as a service and how it fits with the Internet of Things. Our objective is to investigate the concept of sensing as a service model in technological, economical, and social perspectives and identify the major open challenges and issues. --- paper_title: Towards the trillion sensors market paper_content: Purpose ::: ::: ::: ::: – This article aims to provide an insight into recent deliberations on the possibility of a global sensor market reaching one trillion units per annum within the next decade. ::: ::: ::: ::: ::: Design/methodology/approach ::: ::: ::: ::: – Following an introduction, which includes details of the TSensors Summit, this article discusses existing high volume sensor applications with multi-billion unit growth prospects. It then considers certain new and emerging applications, including the Internet of Things. This is followed by technological considerations and a brief discussion. ::: ::: ::: ::: ::: Findings ::: ::: ::: ::: – The possibility of a global sensor market reaching one trillion units per annum within the next decade is the topic of serious debate. Several applications representing multi-billion levels have been identified and the ongoing TSensors Summit activities seek to identify further high volume, high growth uses and the factors that will stimulate them. While MEMS will play a central role, other, often new sensor technologies will be vital to achieving the trillion unit level. ::: ::: ::: ::: ::: Originality/value ::: ::: ::: ::: – This article provides a timely review of recent deliberations surrounding the feasibility of achieving a global, trillion sensor market. --- paper_title: Challenges in healthcare and welfare intercloud paper_content: In this paper, we introduce healthcare and welfare provisioning intercloud on an example of Aging in Place platform. We relate it to earlier work both in healthcare and intercloud domain. We describe goals and architecture of the platform and demonstrate benefits of applying Cloud Computing solutions to previously identified challenges. Subsequently, we list and analyze challenges that seem to be unique to such setting and identify risk factors. --- paper_title: Wireless sensor networks in intelligent transportation systems paper_content: Wireless sensor networks (WSNs) offer the potential to significantly improve the efficiency of existing transportation systems. Currently, collecting traffic data for traffic planning and management is achieved mostly through wired sensors. The equipment and maintenance cost and time-consuming installations of existing sensing systems prevent large-scale deployment of real-time traffic monitoring and control. Small wireless sensors with integrated sensing, computing, and wireless communication capabilities offer tremendous advantages in low cost and easy installation. In this paper, we first survey existing WSN technologies for intelligent transportation systems (ITSs), including sensor technologies, energy-efficient networking protocols, and applications of sensor networks for parking lot monitoring, traffic monitoring, and traffic control. Then, we present new methods on applying WSNs in traffic modeling and estimation and traffic control, and show their improved performance over existing solutions. Copyright © 2008 John Wiley & Sons, Ltd. --- paper_title: New challenges to power system planning and operation of smart grid development in China paper_content: The future development trend of electric power grid is smart grid, which includes such features as secure and reliable, efficient and economical, clean and green, flexible and compatible, open and interactive, integrated and so on. The concept and characteristics of smart grid are introduced in this paper. On the basis of practical national situation, the development plans of smart grid in china with Chinese characteristics are proposed. Smart grid development in china is bases on information technology, communication technology, computer technology with the high integration with infrastructure of generating, transmission and distribution power system. Besides, smart grid development in china brings forward many new challenge and requirements for power system planning and operation in 9 key technologies as below: 1. Planning and construction of strong ultra high voltage (UHV) power grid 2. Large-scale thermal power, hydropower and nuclear power bases integration of power grid 3. Large-scale renewable energy sources integration of power grid 4. Distributed generation and coordinated development of the grids of various voltage ratings 5. Study on smart grid planning and developing strategy 6. Improve the controllability of the power grid based on power electronics technology. 7. Superconductivity, energy storage and other new technologies widely used in power system 8. Power system security monitoring, fast simulation, intelligent decision-making and comprehensive defense technology 9. The application of emergency and restoration control technology in power system In response to the challenge, this paper presents the main research contents, detailed implementation plan and anticipated goals of above 9 key technologies. Some measures and suggestions for power system planning and operation of smart grid development in China are given in this paper. --- paper_title: Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing paper_content: The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications. --- paper_title: An Internet of Things Framework for Smart Energy in Buildings: Designs, Prototype, and Experiments paper_content: Smart energy in buildings is an important research area of Internet of Things (IoT). As important parts of the smart grids, the energy efficiency of buildings is vital for the environment and global sustainability. Using a LEED-gold-certificated green office building, we built a unique IoT experimental testbed for our energy efficiency and building intelligence research. We first monitor and collect 1-year-long building energy usage data and then systematically evaluate and analyze them. The results show that due to the centralized and static building controls, the actual running of green buildings may not be energy efficient even though they may be “green” by design. Inspired by “energy proportional computing” in modern computers, we propose an IoT framework with smart location-based automated and networked energy control, which uses smartphone platform and cloud-computing technologies to enable multiscale energy proportionality including building-, user-, and organizational-level energy proportionality. We further build a proof-of-concept IoT network and control system prototype and carried out real-world experiments, which demonstrate the effectiveness of the proposed solution. We envision that the broad application of the proposed solution has not only led to significant economic benefits in term of energy saving, improving home/office network intelligence, but also bought in a huge social implication in terms of global sustainability. --- paper_title: Internet of Things for Smart Cities paper_content: The Internet of Things (IoT) shall be able to incorporate transparently and seamlessly a large number of different and heterogeneous end systems, while providing open access to selected subsets of data for the development of a plethora of digital services. Building a general architecture for the IoT is hence a very complex task, mainly because of the extremely large variety of devices, link layer technologies, and services that may be involved in such a system. In this paper, we focus specifically to an urban IoT system that, while still being quite a broad category, are characterized by their specific application domain. Urban IoTs, in fact, are designed to support the Smart City vision, which aims at exploiting the most advanced communication technologies to support added-value services for the administration of the city and for the citizens. This paper hence provides a comprehensive survey of the enabling technologies, protocols, and architecture for an urban IoT. Furthermore, the paper will present and discuss the technical solutions and best-practice guidelines adopted in the Padova Smart City project, a proof-of-concept deployment of an IoT island in the city of Padova, Italy, performed in collaboration with the city municipality. --- paper_title: Internet of Things: A Survey on Enabling Technologies, Protocols, and Applications paper_content: This paper provides an overview of the Internet of Things (IoT) with emphasis on enabling technologies, protocols, and application issues. The IoT is enabled by the latest developments in RFID, smart sensors, communication technologies, and Internet protocols. The basic premise is to have smart sensors collaborate directly without human involvement to deliver a new class of applications. The current revolution in Internet, mobile, and machine-to-machine (M2M) technologies can be seen as the first phase of the IoT. In the coming years, the IoT is expected to bridge diverse technologies to enable new applications by connecting physical objects together in support of intelligent decision making. This paper starts by providing a horizontal overview of the IoT. Then, we give an overview of some technical details that pertain to the IoT enabling technologies, protocols, and applications. Compared to other survey papers in the field, our objective is to provide a more thorough summary of the most relevant protocols and application issues to enable researchers and application developers to get up to speed quickly on how the different protocols fit together to deliver desired functionalities without having to go through RFCs and the standards specifications. We also provide an overview of some of the key IoT challenges presented in the recent literature and provide a summary of related research work. Moreover, we explore the relation between the IoT and other emerging technologies including big data analytics and cloud and fog computing. We also present the need for better horizontal integration among IoT services. Finally, we present detailed service use-cases to illustrate how the different protocols presented in the paper fit together to deliver desired IoT services. --- paper_title: A Study on the Sensitivity of a Spin Valve with Conetic-Based Free Layers paper_content: An exchange-biased spin valve with Conetic-based free layers of Co90Fe10, Co90Fe10/Conetic and Conetic was investigated. The spin valve with the Co90Fe10 free layer showed the highest giant magnetoresistance (GMR) ratio of 4% but showed the lowest normalized sensitivity of 0.02 Oe-1. The GMR ratio of 3% and the normalized sensitivity of 0.07 Oe-1 were obtained for the spin valve with the Co90Fe10/Conetic free layer after annealing. The spin valve having the Conetic free layer showed softer magnetic properties and well-defined smaller anisotropy than the other spin valves. Though the spin valve showed the lowest GMR of 0.4% after annealing, it showed the highest normalized sensitivity of 0.14 Oe-1. Our study shows that further improvement in MR response of spin valves with Conetic-based free layers can make a spin valve sensor promising for detecting extremely low fields. --- paper_title: Nobel Lecture: Origin, development, and future of spintronics paper_content: Electrons have a charge and a spin, but until recently, charges and spins have been considered separately. In conventional electronics, the charges are manipulated by electric fields but the spins are ignored. Other classical technologies, magnetic recording, for example, are using the spin but only through its macroscopic manifestation, the magnetization of a ferromagnet. This picture started to change in 1988 when the discovery Baibich et al., 1988; Binash et al., 1989 of the giant magnetoresistance GMR of the magnetic multilayers opened the way to an efficient control of the motion of the electrons by acting on their spin through the orientation of a magnetization. This rapidly triggered the development of a new field of research and technology, today called spintronics and, like the GMR, exploiting the influence of the spin on the mobility of the electrons in ferromagnetic materials. Actually, the influence of the spin on the mobility of the electrons in ferromagnetic metals, first suggested by Mott 1936 , had been experimentally demonstrated and theoretically described in my Ph.D. thesis almost 20 years before the discovery of 1988. The GMR was the first step on the road of the exploitation of this influence to control an electrical current. Its application to the read heads of hard disks greatly contributed to the fast rise in the density of stored information and led to the extension of the hard disk technology to consumer’s electronics. Then, the development of spintronics revealed many other phenomena related to the control and manipulation of spin currents. Today this field of research is expanding considerably, with very promising new axes like the phenomena of spin transfer, spintronics with semiconductors, molecular spintronics, or single-electron spintronics. --- paper_title: Magnetoresistance of FeCo Nanocontacts With Current-Perpendicular-to-Plane Spin-Valve Structure paper_content: We have achieved a magnetoresistance (MR) ratio of 7%-10% at a resistance area product (RA) of 0.5-1.5 Omegamum2 by ferromagnetic FeCo nanocontacts in Al nano-oxide-layer (NOL) with current-perpendicular-to-plane spin-valve (CPP-SV) structure. Conductive atomic-force-microscopy shows clear current-path regions of a few nanometers in size surrounded by the Al-NOL. The MR dependence on resistance area product (RA) is well explained by the current-confined-path model assuming that the spin-dependent scattering has an FeCo nanocontact origin, different from tunnel magnetoresistance (TMR). Resistance increases with increasing bias voltage, indicating joule heating by high-current density in nanocontacts, in contrast to TMR. The MR origin is mainly interpreted as spin-dependent scattering due to domain wall formed at ferromagnetic nanocontact --- paper_title: MR ratio enhancement by NOL current-confined-path structures in CPP spin valves paper_content: We have compared the magnetoresistance (MR) performance of current-confined-path (CCP) current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) spin valve films with a nano-oxide-layer (NOL), made between natural oxidation (NO) and ion-assisted oxidation (IAO). For the NO, an MR ratio was only 1.5% at an RA of 370 m/spl Omega//spl mu/m/sup 2/, whereas for the IAO, an MR ratio was greatly increased to 5.4% at an RA of 500 m/spl Omega//spl mu/m/sup 2/. Fitted data by the Valet-Fert model showing larger MR enhancement effect by the IAO is explained by the improvement of the metal-purity of the Cu inside the CCP structure. By further improvement of metal-purity of the Cu, a large MR ratio of more than 30% can be expected at a small RA of 300 m/spl Omega//spl mu/m/sup 2/. The CCP-CPP spin valve film is a promising candidate for realizing high-density recording heads for 200 to 400-Gbpsi recording. --- paper_title: Enhancement of giant magnetoresistance by L21 ordering in Co2Fe(Ge0.5Ga0.5) Heusler alloy current-perpendicular-to-plane pseudo spin valves paper_content: We report large magnetoresistance (MR) output in fully epitaxial Co2Fe(Ge0.5Ga0.5)/Ag/Co2Fe(Ge0.5Ga0.5) current-perpendicular-to-plane pseudo spin valves. The resistance-area product change (ΔRA) of 12 mΩμm2 at room temperature (RT), equivalent to MR ratio of 57%, and ΔRA = 33 mΩμm2 at 10 K, equivalent to MR ratio of 183%, were obtained by using L21-ordered Co2Fe(Ge0.5Ga0.5) ferromagnetic electrodes. The bulk spin scattering asymmetry (β) were estimated to be ∼0.83 at RT and ∼0.93 at 10 K for the L21-ordered Co2Fe(Ge0.5Ga0.5) films by the Valet-Fert model, indicating that the L21-ordered Co2FeGe0.5Ga0.5 Heusler alloy is virtually half-metal at 10 K, but its half-metallicity is degraded at RT. --- paper_title: Nobel Lecture: From spin waves to giant magnetoresistance and beyond paper_content: The “Institute for Magnetism” within the department for solid-state physics at the research center in Julich, Germany, which I joined in 1972, was founded in 1971 by Professor W. Zinn. The main research topic was the exploration of the model magnetic semiconductors EuO and EuS with Curie temperatures Tc=60 K and Tc =17 K, respectively. As I had been working with light scattering LS techniques before I came to Julich, I was very much interested in the observation of spin waves in magnetic materials by means of LS. LS can be performed with grating spectrometers, which is called Raman spectroscopy, and alternatively by Brillouin light scattering BLS spectroscopy. In the latter case, a Fabry-Perot FP interferometer is used for the frequency analysis of the scattered light see righthand side of Fig. 1 . The central part consists of two FP mirrors whose distance is scanned during operation. BLS spectroscopy is used when the frequency shift of the scattered light is small below 100 GHz , as expected for spin waves in ferromagnets. In the early 1970s, an interesting instrumental development took place in BLS, namely, the invention of the multipass operation, and later, the combination of two multipass interferometers in tandem. The inventor was Dr. J. A. Sandercock in Zurich. Since we had the opportunity to install a new laboratory, we decided in favor of BLS, initially using a single three-pass instrument as displayed on the righthand side of Fig. 1. With this, we started investigating spin waves in EuO. We indeed were able to find and identify the expected spin waves as shown by the peaks in Fig. 1 marked green . Different intensities on the Stokes S and antiStokes aS side were known from other work to be due to the magneto-optic interaction of light with the spin waves. The peaks marked red remained a puzzle for some time until good luck came to help us. Good luck in this case was a breakdown of the system, a repair and unintentional interchange of the leads when reconnecting the magnet to the power supply. To our surprise S and aS side were now reversed. To understand what this means, one has to know that classically S and aS scattering is related to the propagation direction of the observed mode, which is opposite for the two cases. This can be understood from the corresponding Doppler shift, which is to higher frequencies when the wave travels towards the observer and down when away from him. The position of the observer here would be the same as of the viewer in Fig. 1. The appearance of the red peak in the spectra on only either the S or the aS side can be explained by an unidirectional propagation of the corresponding spin wave along the surface of the sample. It can be reversed by reversing B0 and M. The unidirectional behavior of the wave can be understood on the basis of symmetry. For this, one has to know that axial vectors which appear in nature, such as B and M on the left-hand side of Fig. 1, reverse their sign under time inversion and so does the sense of the propagation of the surface wave as indicated. The upper and lower parts of Fig. 1, on the left-hand side therefore are linked by time inversion symmetry, which is valid without damping. Hence, the unidirectional behavior reflects the symmetry of the underlying system. Finally, the observed wave could be identified as the DamonEshbach DE surface mode known from theory and from microwave experiments. From the magnetic parameters of EuO, one predicts in the present case that the penetration depth of the DE mode will be a few 100 A. Sample thickness d is of the order of mm. Therefore, for the present purpose, EuO is opaque. In this case, the wave traveling on the backside of the sample in the opposite direction to the wave on the front side cannot be seen in this experiment. BLS is then either S or aS but not both at the same time. Due to all of these unique features, the results of Fig. 1 have also been chosen as examples for current research in magnetism in a textbook on “Solid State Physics” Ibach and Luth, 1995, p. 186 . --- paper_title: Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing paper_content: The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications. --- paper_title: Spin Valve Devices With Synthetic-Ferrimagnet Free-Layer Displaying Enhanced Sensitivity for Nanometric Sensors paper_content: Spin valves (SVs) with synthetic-antiferromagnet (SAF) pinned layers and synthetic-ferrimagnet (SF) free-layers deposited by ion beam deposition are optimized for incorporation in nanometric sensors. The results on combined SAF-SF structures indicate a reduced saturation and offset fields when compared with the simple top-pinned or SAF structure. Therefore, SAF-SF SV display sensitivities of ~0.025%/Oe (200 nm sensor), ~0.1%/Oe (500 nm sensor), and ~0.2%/Oe (1 μm sensor), which correspond to an improvement of 2x, 4.5x, and 7x, respectively, when compared with all other SV stacks tested. The results are relevant for geometries where nanometric SVs are incorporated within very narrow gaps of magnetic flux concentrators leading to superior and competitive gains in sensitivity. These geometries have the unique feature of submicrometric spatial resolution, and have high impact on surface scanning applications. --- paper_title: Comparison of the soft magnetic properties of permalloy and conetic thin films paper_content: Abstract The soft magnetic properties of the substrate/[non-buffer or buffer Ta]/[permalloy (Ni 80 Fe 20 ) or conetic (Ni 77 Fe 14 Cu 5 Mo 4 )]/Ta prepared by ion beam sputter deposition are investigated. The value of the surface resistance of the conetic film is twice as high as that of the permalloy film. The value of the coercivity and magnetic susceptibility of the conetic film decreased by 25% and doubled relative to that of the permalloy film. The coercivity, with a value of 0.12 Oe, and the magnetic susceptibility, with a value of 1.2×10 4 for the conetic film, are suitable for soft magnetic biosensor applications. --- paper_title: Fabrication of Fully-Epitaxial Co$_{{{2}}}$MnSi/Ag/Co$_{{{2}}}$MnSi Giant Magnetoresistive Devices by Elevated Temperature Deposition paper_content: (001)-oriented epitaxial Co2MnSi (CMS) films were grown by elevating the substrate temperature during deposition instead of a conventional post-annealing process. The CMS film deposited at 250°C showed a very flat surface morphology, large saturation magnetization, and a highly L21-ordered crystal structure. A CMS/Ag/CMS giant-magnetoresistive device with CMS layers grown at 250°C showed the high magnetoresistance ratio (33%) at room temperature. This ratio was close to that realized in the case of samples fabricated using post-annealing at 500-550°C. The elevated temperature deposition for the Heusler electrodes is a promising method to fabricate a practical magnetic read sensor for next generation hard disc drives without high temperature annealing process over 300°C. --- paper_title: Giant tunneling magnetoresistance up to 330% at room temperature in sputter deposited Co2FeAl/MgO/CoFe magnetic tunnel junctions paper_content: Magnetoresistance ratio up to 330% at room temperature (700% at 10 K) has been obtained in a spin-valve-type magnetic tunnel junction (MTJ) consisting of a full-Heusler alloy Co2FeAl electrode and a MgO tunnel barrier fabricated on a single crystal MgO (001) substrate by sputtering method. The output voltage of the MTJ at one-half of the zero-bias value was found to be as high as 425 mV, which is the largest reported to date in MTJs using Heusler alloy electrodes. The present finding suggests that Co2FeAl may be one of the most promising candidates for future spintronics devices applications. --- paper_title: Improvement of the low-frequency sensitivity of MgO-based magnetic tunnel junctions by annealing paper_content: Magnetic tunnel junctions can serve as ultrasensitive low-frequency magnetic sensors, however, their low-frequency performance is limited by low-frequency noise, i.e., 1/f noise. In this paper, we investigate the 1/f noise in MgO magnetic tunnel junctions (MTJs) with a tunneling magnetoresistance (TMR) of 160%, and examine the influence of annealing and MTJ size. The results show that the annealing process can not only dramatically improve the TMR, but can also strongly decrease the MTJ noise. The effect is discussed in terms of the structure of MgO barriers and tunneling probabilities. Increasing the MTJ area to 6400 μm2 yields a voltage spectral density as low as 11 nV/Hz1/2 at 1000 Hz. The possible reasons for the area dependence are discussed. --- paper_title: Effect of electrode composition on the tunnel magnetoresistance of pseudo-spin-valve magnetic tunnel junction with a MgO tunnel barrier paper_content: The authors investigate the effect of electrode composition on the tunnel magnetoresistance (TMR) ratio of (CoxFe100−x)80B20∕MgO∕(CoxFe100−x)80B20 pseudo-spin-valve magnetic tunnel junctions (MTJs). TMR ratio is found to strongly depend on the composition and thicknesses of CoFeB. High resolution transmission electron microscopy shows that the crystallization process of CoFeB during annealing depends on the composition and the thicknesses of the CoFeB film, resulting in different TMR ratios. A TMR ratio of 500% at room temperature and of 1010% at 5K are observed in a MTJ having 4.3nm and 4-nm-thick (Co25Fe75)80B20 electrodes with a 2.1-nm-thick MgO barrier annealed at 475°C. --- paper_title: Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers paper_content: Magnetically engineered magnetic tunnel junctions (MTJs) show promise as non-volatile storage cells in high-performance solid-state magnetic random access memories (MRAM)1. The performance of these devices is currently limited by the modest (<∼70%) room-temperature tunnelling magnetoresistance (TMR) of technologically relevant MTJs. Much higher TMR values have been theoretically predicted for perfectly ordered (100) oriented single-crystalline Fe/MgO/Fe MTJs. Here we show that sputter-deposited polycrystalline MTJs grown on an amorphous underlayer, but with highly oriented (100) MgO tunnel barriers and CoFe electrodes, exhibit TMR values of up to ∼220% at room temperature and ∼300% at low temperatures. Consistent with these high TMR values, superconducting tunnelling spectroscopy experiments indicate that the tunnelling current has a very high spin polarization of ∼85%, which rivals that previously observed only using half-metallic ferromagnets2. Such high values of spin polarization and TMR in readily manufactureable and highly thermally stable devices (up to 400 °C) will accelerate the development of new families of spintronic devices. --- paper_title: Improved tunnel magnetoresistance of magnetic tunnel junctions with Heusler Co2FeAl0.5Si0.5 electrodes fabricated by molecular beam epitaxy paper_content: The authors have developed a magnetic tunnel junction of Co2FeAl0.5Si0.5 electrodes and a MgO barrier fabricated by molecular beam epitaxy and observed that this device had a tunnel magnetoresistance ratio of 386% at approximately 300 K and 832% at 9 K. The lower Co2FeAl0.5Si0.5 electrode was annealed during and after deposition resulting in a highly ordered structure with small roughness. This highly ordered structure could be obtained by annealing treatment even at low temperatures. Furthermore, a weak temperature dependence of the tunnel magnetoresistance ratio was observed for the developed magnetic tunnel junction. --- paper_title: Influence of growth and annealing conditions on low-frequency magnetic 1/f noise in MgO magnetic tunnel junctions paper_content: Magnetic 1/f noise is compared in magnetic tunnel junctions with electron-beam evaporated and sputtered MgO tunnel barriers in the annealing temperature range 350 - 425 °C. The variation of the magnetic noise parameter (αmag) of the reference layer with annealing temperature mainly reflects the variation of the pinning effect of the exchange-bias layer. A reduction in αmag with bias is associated with the bias dependence of the tunneling magnetoresistance. The related magnetic losses are parameterized by a phase lag e, which is nearly independent of bias especially below 100 mV. The similar changes in magnetic noise with annealing temperature and barrier thickness for two types of MgO magnetic tunnel junctions indicate that the barrier layer quality does not affect the magnetic losses in the reference layer. --- paper_title: Giant magnetic tunneling effect in Fe/Al2O3/Fe junction paper_content: Abstract A giant magnetoresistance ratio of 30% at 4.2 K and 18% at 300 K was observed for the first time in an Fe/Al 2 O 3 /Fe junction. The conductance at room temperature was expressed well by G =96.2 (1 + 0.09 cos θ)(Ω -1 ), where θ is the angle between the magnetizations of two iron electrodes. The dependence of the magnetoresistance ratio, saturated resistance and also the tunneling current on temperature were measured in the range 4.2–300 K. The results support the claim that the giant magnetoresistance is due to the magnetic tunneling of electrons between the electrodes through the thin Al 2 O 3 insulator. --- paper_title: Shot Noise in Magnetic Tunnel Junctions: Evidence for Sequential Tunneling paper_content: We report the experimental observation of sub-Poissonian shot noise in single magnetic tunnel junctions, indicating the importance of tunneling via impurity levels inside the tunnel barrier. For junctions with weak zero-bias anomaly in conductance, the Fano factor (normalized shot noise) depends on the magnetic configuration being enhanced for antiparallel alignment of the ferromagnetic electrodes. We propose a model of sequential tunneling through nonmagnetic and paramagnetic impurity levels inside the tunnel barrier to qualitatively explain the observations. --- paper_title: Breakdown mechanisms in MgO based magnetic tunnel junctions and correlation with low frequency noise paper_content: Magnetic tunnel junctions (MTJs) are very attractive for magnetic random access memories (MRAMs), thanks to their combination of non-volatility, speed, low power and endurance. In particular spin transfer torque (STT) RAMs based on STT writing show a very good downsize scalability. However, an issue is that at each write event, the MTJ is submitted to an important electrical stress due to write voltage of the order of half of the electrical breakdown voltage. Here we present a study of breakdown mechanisms in MgO based MTJ performed under pulsed conditions. We developed a model of charge trapping/detrapping on barrier defects to explain and predict device endurance. We also show that endurance is correlated to low frequency 1/f noise and that such noise measurement could thus be used as a non destructive and predictive tool for the reliability of the devices. --- paper_title: Sub-Poissonian shot noise in CoFeB/MgO/CoFeB-based magnetic tunneling junctions paper_content: We measured the shot noise in the CoFeB/MgO/CoFeB-based magnetic tunneling junctions with a high tunneling magnetoresistance ratio (over 200% at 3 K). Although the Fano factor in the anti-parallel configuration is close to unity, it is observed to be typically 0.91\pm0.01 in the parallel configuration. It indicates the sub-Poissonian process of the electron tunneling in the parallel configuration due to the relevance of the spin-dependent coherent transport in the low bias regime. --- paper_title: 60% magnetoresistance at room temperature in Co–Fe/Al–O/Co–Fe tunnel junctions oxidized with Kr–O2 plasma paper_content: The influence of the mixed inert gas species for plasma oxidization process of a metallic Al layer on the tunnel magnetoresistance (TMR) was investigated for a magnetic tunnel junction (MTJ), Ta 50 A/Cu 200 A/Ta 200 A/Ni–Fe 50 A/Cu 50 A/Mn75Ir25 100 A/Co70Fe30 25 A/Al–O/Co70Fe30 25 A/Ni–Fe 100 A/Cu 200 A/Ta 50 A. Using Kr–O2 plasma, a 58.8% of TMR ratio was obtained at room temperature after annealing the junction at 300 °C, while the achieved TMR ratio of the MTJ fabricated with usual Ar–O2 plasma remained 48.6%. A faster oxidization rate of the Al layer by using Kr–O2 plasma is a possible cause to prevent the over oxidization of the Al layer, which depolarizes the surface of the underlaid ferromagnetic electrode, and to realize a large magnetoresistance. --- paper_title: Dilute ferromagnetic semiconductors: Physics and spintronic structures paper_content: This review compiles results of experimental and theoretical studies on thin films and quantum structures of semiconductors with randomly distributed Mn ions, which exhibit spintronic functionalities associated with collective ferromagnetic spin ordering. Properties of p-type Mn-containing III-V as well as II-VI, V_2-VI_3, IV-VI, I-II-V, and elemental group IV semiconductors are described paying particular attention to the most thoroughly investigated system (Ga,Mn)As that supports the hole-mediated ferromagnetic order up to 190 K for the net concentration of Mn spins below 10%. Multilayer structures showing efficient spin injection and spin-related magnetotransport properties as well as enabling magnetization manipulation by strain, light, electric fields, and spin currents are presented together with their impact on metal spintronics. The challenging interplay between magnetic and electronic properties in topologically trivial and non-trivial systems is described, emphasizing the entangled roles of disorder and correlation at the carrier localization boundary. Finally, the case of dilute magnetic insulators is considered, such as (Ga,Mn)N, where low temperature spin ordering is driven by short-ranged superexchange that is ferromagnetic for certain charge states of magnetic impurities. --- paper_title: Epitaxial Co2Cr0.6Fe0.4Al thin films and magnetic tunnelling junctions paper_content: Epitaxial thin films of the theoretically predicted half metal Co2Cr0.6Fe0.4Al were deposited by dc magnetron sputtering on different substrates and buffer layers. The samples were characterized by x-ray and electron beam diffraction (RHEED) demonstrating the B2 order of the Heusler compound with only a small fraction of disorder on the Co sites. Magnetic tunnelling junctions with Co2Cr0.6Fe0.4Al electrode, AlOx barrier and Co counter electrode were prepared. From the Julliere model a spin polarization of Co2Cr0.6Fe0.4Al of 54% at T = 4 K was deduced. The relation between the annealing temperature of the Heusler electrodes and the magnitude of the tunnelling magnetoresistance effect was investigated and the results are discussed in the framework of morphology and surface order based on in situ scanning tunnelling microscopy (STM) and RHEED investigations. --- paper_title: Experimental investigations of SiO2 based ferrite magnetic tunnel junction paper_content: We report experimental results of ferrite based magnetic tunnel junction. Ferrite junction and spin transport through SiO2 were interesting since they can readily replace the conventional electronics. We fabricated a cobalt ferrite/SiO2/cobalt nickel ferrite based magnetic tunnel junction over a copper coated n-silicon substrate using a RF/DC magnetron sputtering. The tunneling magnetoresistance shows a very good response to applied field and we achieved a TMR of about 16%. Although theoretically it was predicted infinite TMR for half metallic ferromagnetic junction, the deviation was explained on the basis of incoherent scattering along the interfaces. --- paper_title: Tunnel magnetoresistance of 604% at 300K by suppression of Ta diffusion in CoFeB∕MgO∕CoFeB pseudo-spin-valves annealed at high temperature paper_content: The authors observed tunnel magnetoresistance (TMR) ratio of 604% at 300K in Ta∕Co20Fe60B20∕MgO∕Co20Fe60B20∕Ta pseudo-spin-valve magnetic tunnel junction annealed at 525°C. To obtain high TMR ratio, it was found critical to anneal the structure at high temperature above 500°C, while suppressing the Ta diffusion into CoFeB electrodes and in particular to the CoFeB∕MgO interface. X-ray diffraction measurement of MgO on SiO2 or Co20Fe60B20 shows that an improvement of MgO barrier quality, in terms of the degree of the (001) orientation and stress relaxation, takes place at annealing temperatures above 450°C. The highest TMR ratio observed at 5K was 1144%. --- paper_title: 230% room temperature magnetoresistance in CoFeB/MgO/CoFeB magnetic tunnel junctions paper_content: The magnetoresistance ratio of 230% at room temperature is reported. This was achieved in spin-valve type magnetic tunnel junctions using MgO barrier layer and amorphous CoFeB ferromagnetic electrodes fabricated on thermally oxidized Si substrates. The amorphous CoFeB electrodes are of great advantage to the polycrystalline FeCo electrodes in achieving a high homogeneity in small 100 nm-sized MTJs. --- paper_title: Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions paper_content: The tunnel magnetoresistance (TMR) effect in magnetic tunnel junctions (MTJs)1,2 is the key to developing magnetoresistive random-access-memory (MRAM), magnetic sensors and novel programmable logic devices3,4,5. Conventional MTJs with an amorphous aluminium oxide tunnel barrier, which have been extensively studied for device applications, exhibit a magnetoresistance ratio up to 70% at room temperature6. This low magnetoresistance seriously limits the feasibility of spintronics devices. Here, we report a giant MR ratio up to 180% at room temperature in single-crystal Fe/MgO/Fe MTJs. The origin of this enormous TMR effect is coherent spin-polarized tunnelling, where the symmetry of electron wave functions plays an important role. Moreover, we observed that their tunnel magnetoresistance oscillates as a function of tunnel barrier thickness, indicating that coherency of wave functions is conserved across the tunnel barrier. The coherent TMR effect is a key to making spintronic devices with novel quantum-mechanical functions, and to developing gigabit-scale MRAM. --- paper_title: Band overlap via chemical pressure control in double perovskite (Sr2−xCax)FeMoO6 (0 ⩽ x ⩽ 2.0) with TMR effect paper_content: Abstract The chemical pressure control in (Sr 2− x Ca x )FeMoO 6 (0 ⩽ x ⩽ 2.0) with double perovskite structure has been investigated systematically. We have performed first-principles total energy and electronic structure calculations for x = 0 and x = 2.0. The increasing Ca content in (Sr 2− x Ca x )FeMoO 6 samples increases the magnetic moment close to the theoretical value due to reduction of Fe/Mo anti-site disorder. An increasing Ca content results in increasing (Fe 2+ + Mo 6+ )/(Fe 3+ + Mo 5+ ) band overlap rather than bandwidth changes. This is explained from simple ionic size arguments and is supported by X-ray absorption near edge structure (XANES) spectra and band structure calculations. --- paper_title: Dependence of magnetoresistance on temperature and applied voltage in a 82Ni-Fe/Al-Al2O3/Co tunneling junction paper_content: Abstract The dependence of magnetoresistance on temperature T and on the applied voltage V in a 82Ni-Fe/Al-Al 2 O 3 /Co tunneling junction has been studied. The magnetoresistance Δ R / R increased rapidly at T ⩽ 30 K and V ⩽2.5 mV. The result is discussed by taking into account the tunneling conductance due to ferromagnetic tunneling and nonferromagnetic tunneling causing the zero-bias anomaly. --- paper_title: 70% TMR at room temperature for SDT sandwich junctions with CoFeB as free and reference Layers paper_content: Spin dependent tunneling (SDT) wafers were deposited using dc magnetron sputtering. SDT junctions were patterned and connected with one layer of metal lines using photolithography techniques. These junctions have a typical stack structure of Si(100)-Si/sub 3/N/sub 4/-Ru-CoFeB-Al/sub 2/O/sub 3/-CoFeB-Ru-FeCo-CrMnPt with the antiferromagnet CrMnPt layers for pinning at the top. High-resolution transmission electron microscopy (HRTEM) reveals that the CoFeB has an amorphous structure and a smooth interface with the Al/sub 2/O/sub 3/ tunnel barrier. Although it is difficult to pin the amorphous CoFeB directly from the top, the use of a synthetic antiferromagnet (SAF) pinned layer structure allows sufficient rigidity of the reference CoFeB layer. The tunnel junctions were annealed at 250/spl deg/C for 1 h and tested for magneto-transport properties with tunnel magnetoresistive (TMR) values as high as 70.4% at room temperature, which is the highest value ever reported for such a sandwich structure. This TMR value translates to a spin polarization of 51% for CoFeB, which is likely to be higher at lower temperatures. These junctions also have a low coercivity (Hc) and a low parallel coupling field (Hcoupl). The combination of a high TMR, a low Hc, and a low Hcoupl is ideal for magnetic field sensor applications. --- paper_title: Spin-tunnel-junction thermal stability and interface interdiffusion above 300 °C paper_content: Spin tunnel junctions (CoFe/Al2O3/CoFe/MnIr) were fabricated with tunneling magnetoresistance (TMR) of 39%–41% after anneal at 300 °C, decreasing to 4%–6% after anneal at 410 °C. Junction resistance decreases from (0.8–1.6) to (0.5–0.8) M Ω μm2 during anneal. The pinned-layer moment decreases by 44% after anneal at 435 °C, but the free-layer moment does not change. The current–voltage characteristics change significantly and become asymmetric above 300 °C. Rutherford backscattering analysis (RBS) shows that above 300 °C, strong interdiffusion starts at the CoFe/MnIr interface with Mn moving into CoFe, causing the electrode moment to decrease. Mn eventually reaches the Al2O3/CoFe interface contributing to the TMR decrease. RBS analysis of a separate CoFe/Al2O3/CoFe structure shows only minor structural changes at the CoFe/Al2O3 interfaces after anneal at 435 °C, possibly leading to a second mechanism for the loss of interface polarization and TMR. --- paper_title: Spin dependent electron tunneling between ferromagnetic films paper_content: Abstract The hysteresis of tunneling resistance in Gd/GdO x / Fe and Fe / GdO x / Fe junctions in the external magnetic field has been observed. The relative changes of tunneling resistance were of order 2.5–7.7%. The domain structures and magnetization reversal processes in the area of tunneling junctions were investigated by defocused electron microscopy. We found that the ferromagnetic coupling between electrodes of the junction strongly modified the domain structures and magnetization reversal processes in the area of tunnel junction. The hysteresis of tunneling resistance was closely connected with magnetization processes in the junction area. We estimated the polarization of tunneling densities of states for Fe electrodes to be not lower than 17% and the change of barrier height corresponding to the barrier spin filtering effect to be of order 1 meV. --- paper_title: Giant tunneling magnetoresistance up to 410% at room temperature in fully epitaxial Co∕MgO∕Co magnetic tunnel junctions with bcc Co(001) electrodes paper_content: Fully epitaxial Co(001)∕MgO(001)∕Co(001) magnetic tunnel junctions (MTJs) with metastable bcc Co(001) electrodes were fabricated with molecular beam epitaxy. The MTJs exhibited giant magnetoresistance (MR) ratios up to 410% at room temperature, the highest value reported to date. Temperature dependence of the MR ratio was observed to be very small compared with fully epitaxial Fe∕MgO∕Fe and textured CoFeB∕MgO∕CoFeB MTJs. The MR ratio of the Co∕MgO∕Co MTJ showed larger bias voltage dependence than that of the epitaxial Fe∕MgO∕Fe MTJs, which probably reflects the band structures of bcc Co and Fe for the k‖=0 direction. --- paper_title: Fabrication of fully epitaxial Co2MnSi∕MgO∕Co2MnSi magnetic tunnel junctions paper_content: Fully epitaxial magnetic tunnel junctions (MTJs) were fabricated with full-Heusler alloy Co2MnSi thin films as both lower and upper electrodes and with a MgO tunnel barrier. The fabricated MTJs showed clear exchange-biased tunnel magnetoresistance (TMR) characteristics with high TMR ratios of 179% at room temperature (RT) and 683% at 4.2K. In addition, the TMR ratio exhibited oscillations as a function of the MgO tunnel barrier thickness (tMgO) at RT, having a period of 0.28nm, for tMgO ranging from 1.8to3.0nm. --- paper_title: Low frequency noise peak near magnon emission energy in magnetic tunnel junctions paper_content: We report on the low frequency (LF) noise measurements in magnetic tunnel junctions (MTJs) below 4 K and at low bias, where the transport is strongly affected by scattering with magnons emitted by hot tunnelling electrons, as thermal activation of magnons from the environment is suppressed. For both CoFeB/MgO/CoFeB and CoFeB/AlOx/CoFeB MTJs, enhanced LF noise is observed at bias voltage around magnon emission energy, forming a peak in the bias dependence of noise power spectra density, independent of magnetic configurations. The noise peak is much higher and broader for unannealed AlOx-based MTJ, and besides Lorentzian shape noise spectra in the frequency domain, random telegraph noise (RTN) is visible in the time traces. During repeated measurements the noise peak reduces and the RTN becomes difficult to resolve, suggesting defects being annealed. The Lorentzian shape noise spectra can be fitted with bias-dependent activation of RTN, with the attempt frequency in the MHz range, consistent with magnon dyn... --- paper_title: Co2FeAl based magnetic tunnel junctions with BaO and MgO/BaO barriers paper_content: We succeed to integrate BaO as a tunneling barrier into Co2FeAl based magnetic tunnel junctions (MTJs). By means of Auger electron spectroscopy it could be proven that the applied annealing temperatures during BaO deposition and afterwards do not cause any diffusion of Ba neither into the lower Heusler compound lead nor into the upper Fe counter electrode. Nevertheless, a negative tunnel magnetoresistance (TMR) ratio of -10% is found for Co2FeAl (24 nm) / BaO (5 nm) / Fe (7 nm) MTJs, which can be attributed to the preparation procedure and can be explained by the formation of Co- and Fe-oxides at the interfaces between the Heusler and the crystalline BaO barrier by comparing with theory. Although an amorphous structure of the BaO barrier seems to be confirmed by high-resolution transmission electron microscopy (TEM), it cannot entirely be ruled out that this is an artifact of TEM sample preparation due to the sensitivity of BaO to moisture. By replacing the BaO tunneling barrier with an MgO/BaO double lay... --- paper_title: Very low 1/f barrier noise in sputtered MgO magnetic tunnel junctions with high tunneling magnetoresistance paper_content: Low frequency 1/f barrier noise has been investigated in sputtered MgO magnetic tunnel junctions (MTJs) with a tunneling magnetoresistance ratio of up to 330% at room temperature. The lowest normalized noise parameter α of the tunnel barrier reaches 2.5 × 10−12–2.1 × 10−11 μm2, which is comparable to that found in MTJs with the MgO barrier grown by MBE or electron–beam evaporation. This normalized barrier noise is almost bias independent in the voltage range of up to ±1.2 V. The low noise level and high voltage stability may reflect the high quality of the sputtered MgO with a uniform distribution of defects in the MgO layer. --- paper_title: 1/f noise in MgO double-barrier magnetic tunnel junctions paper_content: Low frequency noise has been investigated in MgO double-barrier magnetic tunnel junctions (DMTJs) with tunneling magnetoresistance (TMR) ratios up to 250% at room temperature. The noise shows a 1/f frequency spectrum and the minimum of the noise magnitude parameter is 1.2×10−10 μm2 in the parallel state for DMTJs annealed at 375 °C. The bias dependence of noise and TMR suggests that DMTJs with MgO barriers can be useful for magnetic field sensor applications. --- paper_title: Optimized thickness of superconducting aluminum electrodes for measurement of spin polarization with MgO tunnel barriers paper_content: Superconducting tunneling spectroscopy (STS) is one of the most useful techniques for measuring the tunneling spin polarization of magnetic materials, typically carried out using aluminum electrodes. Recent studies using MgO barriers have shown the extreme sensitivity of the spin polarization to annealing at temperatures up to ∼400°C. Here the authors show that by optimizing the thickness of aluminum superconducting electrodes, STS measurements can be carried out even for such high annealing temperatures. --- paper_title: Linearization and Field Detectivity in Magnetic Tunnel Junction Sensors Connected in Series Incorporating 16 nm-Thick NiFe Free Layers paper_content: In this work, arrays of MgO-based magnetic tunnel junction elements (5×20 μm2) connected in series are studied for sensor applications. Linearization is obtained by combining shape anisotropy with a longitudinal hard bias field set by CoCrPt permanent magnets integrated on the sides of the array. We show that this architecture has the drawback of a large footprint in the chip, but is largely compensated by the weak bias voltage dependence and huge electric robustness, when comparing with individual magnetic tunnel junctions. --- paper_title: MEMS approach for making a low cost, high sensitivity magnetic sensor paper_content: An approach based on electromechanical systems (MEMS) technology will be presented that essentially eliminates the problem of 1/f noise in small magnetic sensors. The sensor based on this approach, the MEMS flux concentrator sensor, should outperform all other high sensitivity vector magnetometers in terms of cost, power consumption, and sensitivity. The method for achieving this improvement is to employ flux concentrators on MEMS structures that are near the magnetic sense element. The motion of the flux concentrators modulates the magnetic field and shifts the operating frequency of the sensor to higher frequencies where 1/f noise is unimportant. The data presented here provides our first evidence that the MEMS flux concentrator improves the signal to noise ratio at low frequencies. --- paper_title: MgO based picotesla field sensors paper_content: MgO magnetic tunnel junctions with RA=150Ωμm2 and tunnel magnetic resistance=100% were patterned into pillars with different geometries with areas up to 2000μm2. Sensors were incorporated in 500nm thick Co94Zr3Nb4 flux guides with different shapes and free layer stabilization was achieved through internal (Co66Cr16Pt18 pads) and external longitudinal bias fields (3.5mT). Sensitivities of 870%∕mT were obtained in the center of the transfer curve. Noise levels of 97pT∕Hz0.5 at 10Hz, 51pT∕Hz0.5 at 30Hz, and 2pT∕Hz0.5 at 500kHz were measured in the linear region of the transfer curve. --- paper_title: Low frequency picotesla field detection using hybrid MgO based tunnel sensors paper_content: Low frequency ultrasensitive magnetic sensors are required for magnetocardiography (1pT at 10Hz) applications. MgO based magnetic tunnel junctions with RA=100–150Ωμm2 and tunnel magnetic resistance=100% were patterned into rectangular pillars with side up to 50μm. Sensors were incorporated in 500nm thick Co94Zr3Nb4 flux guides. Sensor linearization was achieved through internal (Co66Cr16Pt18 pads) and external (3.5mT) longitudinal bias fields resulting in sensitivities of 720%∕mT. Noise levels of 97pT∕Hz0.5 at 10Hz, 51pT∕Hz0.5 at 30Hz, and 2pT∕Hz0.5 at 500kHz were measured in the linear region of the transfer curve. --- paper_title: Magnetic tunnel junction sensors with pTesla sensitivity for biomedical imaging paper_content: Ultrasensitive magnetic field sensors at low frequencies are necessary for several biomedical applications. Suitable devices can be achieved by using large area magnetic tunnel junction sensors combined with permanent magnets to stabilize the magnetic configuration of the free layer and improve linearity. However, further increase in sensitivity and consequently detectivity are achieved by incorporating also soft ferromagnetic flux guides. A detailed study of tunnel junction sensors with variable areas and aspect ratios is presented in this work. In addition, the effect in the sensors transfer curve, namely in their coercivity and sensitivity, as a consequence of the incorporation of permanent magnets and flux guides is also thoroughly discussed. Using sensors with a tunnel magnetoresistance of ~200 %, incorporating both permanent magnets and flux guides sensitivities of 220-260 %/mT were obtained for high aspect ratio sensors, increasing to values larger than ~2000%/mT for large areas and low aspect ratio sensors. Measured noise levels of the final device at 10 Hz yield 3.9×10 -17 V 2 /Hz, leading to an improved lowest detectable field of ~ 94 pT/ Hz 0.5 . --- paper_title: Linearization strategies for high sensitivity magnetoresistive sensors paper_content: Ultrasensitive magnetic field sensors envisaged for applications on biomedical imaging require the detection of low-intensity and low-frequency signals. Therefore linear magnetic sensors with enhanced sensitivity low noise levels and improved field detection at low operating frequencies are necessary. Suitable devices can be designed using magnetoresistive sensors, with room temperature operation, adjustable detected field range, CMOS compatibility and cost-effective production. The advent of spintronics set the path to the technological revolution boosted by the storage industry, in particular by the development of read heads using magnetoresistive devices. New multilayered structures were engineered to yield devices with linear output. We present a detailed study of the key factors influencing MR sensor performance (materials, geometries and layout strategies) with focus on different linearization strategies available. Furthermore strategies to improve sensor detection levels are also addressed with best reported values of ∼40 pT/√Hz at 30 Hz, representing a step forward the low field detection at room temperature. --- paper_title: Magnetic Field Sensors Based on Giant Magnetoresistance (GMR) Technology: Applications in Electrical Current Sensing paper_content: The 2007 Nobel Prize in Physics can be understood as a global recognition to the rapid development of the Giant Magnetoresistance (GMR), from both the physics and engineering points of view. Behind the utilization of GMR structures as read heads for massive storage magnetic hard disks, important applications as solid state magnetic sensors have emerged. Low cost, compatibility with standard CMOS technologies and high sensitivity are common advantages of these sensors. This way, they have been successfully applied in a lot different environments. In this work, we are trying to collect the Spanish contributions to the progress of the research related to the GMR based sensors covering, among other subjects, the applications, the sensor design, the modelling and the electronic interfaces, focusing on electrical current sensing applications. --- paper_title: Iddq testing for CMOS VLSI paper_content: It is little more than 15-years since the idea of Iddq testing was first proposed. Many semiconductor companies now consider Iddq testing as an integral part of the overall testing for all IC's. This paper describes the present status of Iddq testing along with the essential items and necessary data related to Iddq testing. As part of the introduction, a historical background and discussion is given on why this test method has drawn attention. A section on physical defects with in-depth discussion and examples is used to illustrate why a test method outside the voltage environment is required. Data with additional information from case studies is used to explain the effectiveness of Iddq testing. In Section IV, design issues, design styles, Iddq test vector generation and simulation methods are discussed. The concern of whether Iddq testing will remain useful in deep submicron technologies is addressed (Section V). The use of Iddq testing for reliability screening is described (Section VI). The current measurement methods for Iddq testing are given (Section VII) followed by comments on the economics of Iddq testing (Section VIII). In Section IX pointers to some recent research are given and finally, concluding remarks are given in Section X. --- paper_title: Power pin testing: making the test coverage complete paper_content: Most modern ICs have multiple power and ground pins. It becomes necessary that all these pins are indeed connected to the board. In this paper a structural test method is presented for testing the connections of power and ground pins to the board. This on-chip test method is based on supply current detection between a bonding pad and its connection to the IC power distribution network. The method has been implemented and evaluated on a CMOS IC, using IEEE Std. 1149.1 to control and observe the embedded current sensors. --- paper_title: Non-contact electric-coupling-based and magnetic-field-sensing-assisted technique for monitoring voltage of overhead power transmission lines paper_content: Adopting non-contact electric coupling for voltage monitoring avoids electrical connection to high-voltage transmission lines, making installation of the sensing platforms easier and enabling wide-area deployment. However, coupled transformation matrix is difficult to determine in practice as the exact spatial positions of the transmission lines are typically unknown and dynamic. This problem can be overcome by integrating magnetic field sensing with stochastic optimization algorithm. In this technique, magnetic signals emanated from the overhead transmission lines are measured by magnetic sensor arrays to determine the coupling coefficients so that the high voltage of the transmission lines can be deduced from the induced voltage in the copper bars on the ground. This proposed technique can be potentially implemented with low-cost copper induction bars and magnetoresistive (MR) sensors. Thus sectional and wide-area deployment may become possible and Ferranti effect and travelling lightning waves can then be monitored. Its enhanced sensing ability over potential transformers (PTs) can largely improve transient-fault identification and save cost for transmission-network inspection. --- paper_title: Nonintrusive Current Sensor for the Two-Wire Power Cords paper_content: This paper presents a nonintrusive current sensor for the two-wire power cords connected to household and commercial appliances. The sensor uses a gapped magnetic core surrounding the power cord to constrain the distribution of the magnetic field induced by the current. The magnetic fields in four air gaps of the magnetic core are respectively measured by four magnetoresistive (MR) sensors. The current in the power cord and the rotation angle of the power cord around its central axis are calculated together by the output voltages of the four MR sensors. The current sensor encircles the power cord without any alignment process and can detect the current nonintrusively in the two-wire power cords of any type, such as zip-cord or nonmetallic sheathed cable. The experimental results show that the nonlinearity of the sensor is ±1.5% for the current range from 0 to 20 A with the maximum error limited to ±1.8%, this sensor is ideally suited for measuring the end use of electric power in residential and commercial areas. --- paper_title: Design, installation, and field experience with an overhead transmission dynamic line rating system paper_content: Dynamic line rating (DLR) systems for high voltage overhead transmission lines have been installed by three utilities over the past five years. These DLR systems utilize the Power Donut/sup TM/ to measure load and conductor temperature at several locations over the length of the circuit. The effective wind acting on the conductor at each site is determined in real-time by a dynamic heat balance and used to compute the normal, LTE and STE ratings each minute. The lowest ratings of all locations define the circuit's ratings and are sent to SCADA as analog signals. This method is known as the conductor temperature model (CTM) as opposed to the weather model (WM) which calculates ratings using weather data only. These first DLR installations have also measured weather parameters at each ground station location to allow a comparison of the two methods. Data from the latest of these systems is presented and the behavior of the real time ratings are discussed. --- paper_title: A vehicle detection algorithm based on wireless magnetic sensor networks paper_content: At present, the research of parking management system based on Wireless Sensor Networks (WSN) and Anisotropic Magneto Resistive (AMR) sensors have made great progress. However, due to the diversity of the vehicle magnetic signal and the interference caused by the adjacent parking spaces, vehicle detection technique using wireless magnetic sensor networks is still immature. For accurately detecting a parking vehicle in a parking lot, we propose a detection algorithm named Relative Extremum Algorithm (REA). On the parking lot at Shenzhen Institutes of Advanced Technology (SIAT), 82 sensor devices are deployed to evaluate the performance of REA. By running the system for more than half a year, we observe that the vehicle detection accuracy of the REA is above 98.8%. --- paper_title: A Parking Occupancy Detection Algorithm Based on AMR Sensor paper_content: Recently, with the explosive increase of automobiles in cities, parking problems are serious and even worsen in many cities. This paper proposes a new algorithm for parking occupancy detection based on the use of anisotropic magnetoresistive sensors. Parking occupancy detection is abstracted as binary pattern recognition problem. According to the status of the parking space, the recognition result contains two categories: vacant and occupied. The feature extraction method of the parking magnetic signal is proposed. In addition, the classification criteria are derived based on the distance discriminate analysis method. Eighty-two sensor nodes are deployed on the roadside parking spaces. By running the system for six months, we observed that the accuracy rate of the proposed parking occupancy detection algorithm is better than 98%. --- paper_title: Traffic measurement and vehicle classification with a single magnetic sensor paper_content: Wireless magnetic sensor networks offer a very attractive, low-cost alternative to inductive loops for traffic measurement in freeways and at intersections. In addition to vehicle count, occupancy and speed, the sensors yield traffic information (such as vehicle classification) that cannot be obtained from loop data. Because such networks can be deployed in a very short time, they can also be used (and reused) for temporary traffic measurement. This paper reports the detection capabilities of magnetic sensors, based on two field experiments. The first experiment collected a two-hour trace of measurements on Hearst Avenue in Berkeley. The vehicle detection rate is better than 99 percent (100 percent for vehicles other than motorcycles); and estimates of vehicle length and speed appear to be better than 90 percent. Moreover, the measurements also give inter-vehicle spacing or headways, which reveal such interesting phenomena as platoon formation downstream of a traffic signal. Results of the second experiment are preliminary. Sensor data from 37 passing vehicles at the same site are processed and classified into 6 types. Sixty percent of the vehicles are classified correctly, when length is not used as a feature. The classification algorithm can be implemented in real time by the sensor node itself, in contrast to other methods based on high scan-rate inductive loop signals, which require extensive offline computation. We believe that when length is used as a feature, 80-90 percent of vehicles will be correctly classified. --- paper_title: A Cross-Correlation Technique for Vehicle Detections in Wireless Magnetic Sensor Network paper_content: Vehicle detections are an important research field and attract many researchers. Most research efforts have been focused on vehicle parking detection (VPD) in indoor parking lot. For on-street parking, strong noise disturbances affect detection accuracy. To deal with vehicle detections in on-street environment, we propose two vehicle detection algorithms based on a cross-correlation technique in wireless magnetic sensor networks. One is for VPD, and the other one is for vehicle speed estimation (VSE). The proposed VPD algorithm combines the state-machine detection and the cross-correlation detection. In the VSE, speed estimation is based on the calculation of the normalized cross correlation between the signals of two sensors along the road with a certain spacing. Experimental results show that the VPD has an accuracy of 99.65% for arrival and 99.44% for departure, while the VSE has an accuracy of 92%. --- paper_title: The Development of Vehicle Position Estimation Algorithms Based on the Use of AMR Sensors paper_content: This paper focuses on the use of anisotropic magnetoresistive (AMR) sensors for imminent crash detection in cars. The AMR sensors are used to measure the magnetic field from another vehicle in close proximity to estimate relative position and velocity from the measurement. An analytical formulation for the relationship between magnetic field and vehicle position is developed. The challenges in the use of the AMR sensors include their nonlinear behavior, limited range, and magnetic signature levels that vary with each type of car. An adaptive filter based on the iterated extended Kalman filter (IEKF) is developed to automatically tune filter parameters for each encountered car and to reliably estimate relative car position. The utilization of an additional sonar sensor during the initial detection of the encountered vehicle is shown to highly speed up the parameter convergence of the filter. Experimental results are presented from a number of tests with various vehicles to show that the proposed sensor system is viable. --- paper_title: Vehicle detection using a magnetic field sensor paper_content: The measurement of vehicle magnetic moments and the results from use of a fluxgate magnetic sensor to actuate a lighting system from the magnetic fields of passing vehicles is reported. A typical U.S. automobile has a magnetic moment of about 200 A-m2(Ampere-meters2), while for a school bus it is about 2000 A-m2. When the vehicle is modeled as an ideal magnetic dipole with a moment of 200 A-m2, the predicted results from an analysis of the sensor-vehicle geometry agree closely with observations of the system response to automobiles. --- paper_title: VEHICLE DETECTION AND COMPASS APPLICATIONS USING AMR MAGNETIC SENSORS paper_content: This paper presents a review of magnetic sensing and discusses applications for magnetic sensors. Focus is on magnetic sensing in vehicle detection and navigation that is based on magnetic fields. --- paper_title: Portable Roadside Sensors for Vehicle Counting, Classification, and Speed Measurement paper_content: This paper focuses on the development of a portable roadside magnetic sensor system for vehicle counting, classification, and speed measurement. The sensor system consists of wireless anisotropic magnetic devices that do not require to be embedded in the roadway-the devices are placed next to the roadway and measure traffic in the immediately adjacent lane. An algorithm based on a magnetic field model is proposed to make the system robust to the errors created by larger vehicles driving in the nonadjacent lane. These false calls cause an 8% error if uncorrected. The use of the proposed algorithm reduces this error to only 1%. Speed measurement is based on the calculation of the cross correlation between longitudinally spaced sensors. Fast computation of the cross correlation is enabled by using frequency-domain signal processing techniques. An algorithm for automatically correcting for any small misalignment of the sensors is utilized. A high-accuracy differential Global Positioning System is used as a reference to measure vehicle speeds to evaluate the accuracy of the speed measurement from the new sensor system. The results show that the maximum error of the speed estimates is less than 2.5% over the entire range of 5-27 m/s (11-60 mi/h). Vehicle classification is done based on the magnetic length and an estimate of the average vertical magnetic height of the vehicle. Vehicle length is estimated from the product of occupancy and estimated speed. The average vertical magnetic height is estimated using two magnetic sensors that are vertically spaced by 0.25 m. Finally, it is shown that the sensor system can be used to reliably count the number of right turns at an intersection, with an accuracy of 95%. The developed sensor system is compact, portable, wireless, and inexpensive. Data are presented from a large number of vehicles on a regular busy urban road in the Twin Cities, MN, USA. --- paper_title: Vehicle Detection and Classification for Low-Speed Congested Traffic With Anisotropic Magnetoresistive Sensor paper_content: A vehicle detection and classification system has been developed based on a low-cost triaxial anisotropic magnetoresistive sensor. Considering the characteristics of vehicle magnetic detection signals, especially the signals for low-speed congested traffic in large cities, a novel fixed threshold state machine algorithm based on signal variance is proposed to detect vehicles within a single lane and segment the vehicle signals effectively according to the time information of vehicles entering and leaving the sensor monitoring area. In our experiments, five signal features are extracted, including the signal duration, signal energy, average energy of the signal, ratio of positive and negative energy of x-axis signal, and ratio of positive and negative energy of y-axis signal. Furthermore, the detected vehicles are classified into motorcycles, two-box cars, saloon cars, buses, and Sport Utility Vehicle commercial vehicles based on a classification tree model. The experimental results have shown that the detection accuracy of the proposed algorithm can reach up to 99.05% and the average classification accuracy is 93.66%, which verify the effectiveness of our algorithm for low-speed congested traffic. --- paper_title: Wireless magnetic sensors for traffic surveillance paper_content: Sensys Networks' VDS240 vehicle detection system is a wireless sensor network composed of a collection of 3'' by 3'' by 2'' sensor nodes put in the center of a lane and a 6'' by 4'' by 4'' access point (AP) box placed 15' high on the side of the road. A node measures changes in the earth's magnetic field induced by a vehicle, processes the measurements to detect the vehicle, and transfers the processed data via radio to the AP. The AP combines data from the nodes into information for the local controller or the Traffic Management Center (TMC). An AP communicates via radio directly with up to 96 nodes within a range of 150'; a Repeater extends the range to 1000'. This range makes it suitable to deploy VDS240 networks for traffic counts, stop-bar and advance detection, and measurement of queue lengths on ramps and at intersections, as well as parking guidance and enforcement. VDS240 is self-calibrating, IP-addressable and remotely monitored. Data are not lost because unacknowledged data packets are retransmitted. The accuracy of VDS240 for vehicle counts, speed and occupancy is comparable to that of well-tuned loops. Because the nodes report individual vehicle events, the AP also calculates individual vehicle lengths, speeds and inter-vehicle headways--measurements that can be used for new traffic applications. In July 2007, VDS240 systems were deployed in arterials and freeways in several cities and states, and 30 customer trials were underway in the US, Australia, Europe and South Africa. --- paper_title: Experimental study of a vehicle detector with an AMR sensor paper_content: Abstract This paper proposes a vehicle detector with an anisotropic magnetoresistive (AMR) sensor and addresses experimental study carried out to show the detector's characteristics and performance. The detector consists of an AMR sensor and mechanical and electronic apparatuses. Composed of four magnetoresistors, the AMR sensor senses disturbance of the earth's magnetic field caused by a moving vehicle over the sensor itself and then produces an output indicative of the moving vehicle. Experiments have been carried out with three stages. At the first stage, the outputs of the sensor have been analyzed to show the validity of the detector's circuit and the detecting method. At the second stage, the detector has been tested on a local highway in Korea. Through the field tests, the outputs of the detector in response to various kinds of moving vehicles have been collected and analyzed. At the final stage, to verify the performance of the detector, traffic volumes on the highway have been measured with the detector and compared with the exact traffic volumes in a highly congested traffic. --- paper_title: Wireless sensor networks in intelligent transportation systems paper_content: Wireless sensor networks (WSNs) offer the potential to significantly improve the efficiency of existing transportation systems. Currently, collecting traffic data for traffic planning and management is achieved mostly through wired sensors. The equipment and maintenance cost and time-consuming installations of existing sensing systems prevent large-scale deployment of real-time traffic monitoring and control. Small wireless sensors with integrated sensing, computing, and wireless communication capabilities offer tremendous advantages in low cost and easy installation. In this paper, we first survey existing WSN technologies for intelligent transportation systems (ITSs), including sensor technologies, energy-efficient networking protocols, and applications of sensor networks for parking lot monitoring, traffic monitoring, and traffic control. Then, we present new methods on applying WSNs in traffic modeling and estimation and traffic control, and show their improved performance over existing solutions. Copyright © 2008 John Wiley & Sons, Ltd. --- paper_title: A Cross-Correlation Technique for Vehicle Detections in Wireless Magnetic Sensor Network paper_content: Vehicle detections are an important research field and attract many researchers. Most research efforts have been focused on vehicle parking detection (VPD) in indoor parking lot. For on-street parking, strong noise disturbances affect detection accuracy. To deal with vehicle detections in on-street environment, we propose two vehicle detection algorithms based on a cross-correlation technique in wireless magnetic sensor networks. One is for VPD, and the other one is for vehicle speed estimation (VSE). The proposed VPD algorithm combines the state-machine detection and the cross-correlation detection. In the VSE, speed estimation is based on the calculation of the normalized cross correlation between the signals of two sensors along the road with a certain spacing. Experimental results show that the VPD has an accuracy of 99.65% for arrival and 99.44% for departure, while the VSE has an accuracy of 92%. --- paper_title: Automatic vehicle classification using wireless magnetic sensor paper_content: This paper proposes an extension to our previous work on an automatic low-computed vehicle classification using embedded wireless magnetic sensor. A realization of our vehicle classification on embedded wireless magnetic sensor is studied in this work. The implementation allows real-time vehicle classification based on vehicle magnetic length, averaged energy, and Hill-pattern peaks. The system automatically detects vehicles, extracts features, and classifies them. The three features are of low-computation. We classify vehicles into 4 types: motorcycle, car, pickup and van. The classification shows a promising result. It can classify motorcycle with 95% accuracy. The classification rates between 70%-80% are achieved with car, pickup and van due to their similarity in these extracted features. The results obtained are comparable to our implementation using PC in our previous work and demonstrate that the algorithm can be realized on the embedded wireless magnetic sensor. --- paper_title: Portable Roadside Sensors for Vehicle Counting, Classification, and Speed Measurement paper_content: This paper focuses on the development of a portable roadside magnetic sensor system for vehicle counting, classification, and speed measurement. The sensor system consists of wireless anisotropic magnetic devices that do not require to be embedded in the roadway-the devices are placed next to the roadway and measure traffic in the immediately adjacent lane. An algorithm based on a magnetic field model is proposed to make the system robust to the errors created by larger vehicles driving in the nonadjacent lane. These false calls cause an 8% error if uncorrected. The use of the proposed algorithm reduces this error to only 1%. Speed measurement is based on the calculation of the cross correlation between longitudinally spaced sensors. Fast computation of the cross correlation is enabled by using frequency-domain signal processing techniques. An algorithm for automatically correcting for any small misalignment of the sensors is utilized. A high-accuracy differential Global Positioning System is used as a reference to measure vehicle speeds to evaluate the accuracy of the speed measurement from the new sensor system. The results show that the maximum error of the speed estimates is less than 2.5% over the entire range of 5-27 m/s (11-60 mi/h). Vehicle classification is done based on the magnetic length and an estimate of the average vertical magnetic height of the vehicle. Vehicle length is estimated from the product of occupancy and estimated speed. The average vertical magnetic height is estimated using two magnetic sensors that are vertically spaced by 0.25 m. Finally, it is shown that the sensor system can be used to reliably count the number of right turns at an intersection, with an accuracy of 95%. The developed sensor system is compact, portable, wireless, and inexpensive. Data are presented from a large number of vehicles on a regular busy urban road in the Twin Cities, MN, USA. --- paper_title: Vehicle Detection and Classification for Low-Speed Congested Traffic With Anisotropic Magnetoresistive Sensor paper_content: A vehicle detection and classification system has been developed based on a low-cost triaxial anisotropic magnetoresistive sensor. Considering the characteristics of vehicle magnetic detection signals, especially the signals for low-speed congested traffic in large cities, a novel fixed threshold state machine algorithm based on signal variance is proposed to detect vehicles within a single lane and segment the vehicle signals effectively according to the time information of vehicles entering and leaving the sensor monitoring area. In our experiments, five signal features are extracted, including the signal duration, signal energy, average energy of the signal, ratio of positive and negative energy of x-axis signal, and ratio of positive and negative energy of y-axis signal. Furthermore, the detected vehicles are classified into motorcycles, two-box cars, saloon cars, buses, and Sport Utility Vehicle commercial vehicles based on a classification tree model. The experimental results have shown that the detection accuracy of the proposed algorithm can reach up to 99.05% and the average classification accuracy is 93.66%, which verify the effectiveness of our algorithm for low-speed congested traffic. --- paper_title: Magnetoresistive-based biosensors and biochips. paper_content: Over the past five years, magnetoelectronics has emerged as a promising new platform technology for biosensor and biochip development. The techniques are based on the detection of the magnetic fringe field of a magnetically labeled biomolecule interacting with a complementary biomolecule bound to a magnetic-field sensor. Magnetoresistive-based sensors, conventionally used as read heads in hard disk drives, have been used in combination with biologically functionalized magnetic labels to demonstrate the detection of molecular recognition. Real-world bio-applications are now being investigated, enabling tailored device design, based on sensor and label characteristics. This detection platform provides a robust, inexpensive sensing technique with high sensitivity and considerable scope for quantitative signal data, enabling magnetoresistive biochips to meet specific diagnostic needs that are not met by existing technologies. --- paper_title: Detection of 10-nm Superparamagnetic Iron Oxide Nanoparticles Using Exchange-Biased GMR Sensors in Wheatstone Bridge paper_content: We demonstrated the use of exchange-biased giant magnetoresistance (GMR) sensors in Wheatstone bridge for the detection of 10-nm superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs were synthesized via coprecipitation method, exhibiting a superparamagnetic behavior with saturation magnetization of 57 emu/g. The output voltage signal of the Wheatstone bridge exhibits log-linear function of the concentration of SPIONs (from 10 ng/ml to 0.1 mg/ml), making the sensors suitable for use as a SPION concentration detector. Thus the combination of 10 nm SPIONs and the exchange-biased GMR sensors has potential to be used in the bio-detection applications where ultra-small bio-labels are needed. --- paper_title: Matrix-insensitive protein assays push the limits of biosensors in medicine paper_content: Advances in biosensor technologies for in vitro diagnostics have the potential to transform the practice of medicine. Despite considerable work in the biosensor field, there is still no general sensing platform that can be ubiquitously applied to detect the constellation of biomolecules in diverse clinical samples (for example, serum, urine, cell lysates or saliva) with high sensitivity and large linear dynamic range. A major limitation confounding other technologies is signal distortion that occurs in various matrices due to heterogeneity in ionic strength, pH, temperature and autofluorescence. Here we present a magnetic nanosensor technology that is matrix insensitive yet still capable of rapid, multiplex protein detection with resolution down to attomolar concentrations and extensive linear dynamic range. The matrix insensitivity of our platform to various media demonstrates that our magnetic nanosensor technology can be directly applied to a variety of settings such as molecular biology, clinical diagnostics and biodefense. --- paper_title: Magnetic Nanoparticle Sensors paper_content: Many types of biosensors employ magnetic nanoparticles (diameter = 5–300 nm) or magnetic particles (diameter = 300–5,000 nm) which have been surface functionalized to recognize specific molecular targets. Here we cover three types of biosensors that employ different biosensing principles, magnetic materials, and instrumentation. The first type consists of magnetic relaxation switch assay-sensors, which are based on the effects magnetic particles exert on water proton relaxation rates. The second type consists of magnetic particle relaxation sensors, which determine the relaxation of the magnetic moment within the magnetic particle. The third type is magnetoresistive sensors, which detect the presence of magnetic particles on the surface of electronic devices that are sensitive to changes in magnetic fields on their surface. Recent improvements in the design of magnetic nanoparticles (and magnetic particles), together with improvements in instrumentation, suggest that magnetic material-based biosensors may become widely used in the future. --- paper_title: Magnetoresistive-based biosensors and biochips. paper_content: Over the past five years, magnetoelectronics has emerged as a promising new platform technology for biosensor and biochip development. The techniques are based on the detection of the magnetic fringe field of a magnetically labeled biomolecule interacting with a complementary biomolecule bound to a magnetic-field sensor. Magnetoresistive-based sensors, conventionally used as read heads in hard disk drives, have been used in combination with biologically functionalized magnetic labels to demonstrate the detection of molecular recognition. Real-world bio-applications are now being investigated, enabling tailored device design, based on sensor and label characteristics. This detection platform provides a robust, inexpensive sensing technique with high sensitivity and considerable scope for quantitative signal data, enabling magnetoresistive biochips to meet specific diagnostic needs that are not met by existing technologies. --- paper_title: Integration of Magnetoresistive Biochips on a CMOS Circuit paper_content: Since 2006, fully scalable matrix-based magnetoresistive biochips have been proposed. This integration was initially achieved with thin film switching devices and moved to complementary metal-oxide-semiconductor (CMOS) switching devices and electronics. In this paper, a new microfabrication process is proposed to integrate magnetoresistive sensors on a small CMOS chip (4 mm2). This chip includes a current generator, multiplexers, and a diode in series with a spin valve as matrix element. In this configuration, it is shown that the fabricated spin-valves have similar magnetic characteristics when compared to standalone spin valves. This validates the successfulness of the developed microfabrication process. The noise of each matrix element is further characterized and compared to the noise of a standalone spin valve and a portable electronic platform designed to perform biological assays. Although the noise is still higher, the spin valve integrated on the CMOS chip enables an increase in density and compactness of the measuring electronics. --- paper_title: Magnetic Nanoparticles for Magnetoresistance-Based Biodetection paper_content: Magnetic nanoparticles (MNPs) have been studied widely as a powerful diagnostic probe and therapeutic agent for biomedical applications. In recent years, they are also found to be sensitive to magnetoresistive (MR) devices and MNP-MR biochips are predicted to be more affordable, portable and sensitive than the conventional optical detection methods. In this MNP-MR biochip design, MNP probes are required to have high magnetic moment, high susceptibility, and be target-specific. This review summarizes recent advances in chemical syntheses and functionalization of MNPs with controlled magnetic properties for sensitive MR detection and for bio-sensing applications. --- paper_title: Biological applications of magnetic nanoparticles. paper_content: In this review an overview about biological applications of magnetic colloidal nanoparticles will be given, which comprises their synthesis, characterization, and in vitro and in vivo applications. The potential future role of magnetic nanoparticles compared to other functional nanoparticles will be discussed by highlighting the possibility of integration with other nanostructures and with existing biotechnology as well as by pointing out the specific properties of magnetic colloids. Current limitations in the fabrication process and issues related with the outcome of the particles in the body will be also pointed out in order to address the remaining challenges for an extended application of magnetic nanoparticles in medicine. --- paper_title: Detection of Magnetically Labelled Microcarriers for Suspension Based Bioassay Technologies paper_content: Microarrays and suspension-based assay technologies have attracted significant interest over the past decade with applications ranging from medical diagnostics to high throughput molecular biology. The throughput and sensitivity of a microarray will always be limited by the array density and slow reaction kinetics. Suspension (or bead) based technologies offer a conceptually different approach, improving detection by substituting a fixed plane of operation with millions of microcarriers. However, these technologies are currently limited by the number of unique labels that can be generated in order to identify the molecular probes on the surface. We have proposed a novel suspension-based technology that utilizes patterned magnetic films for the purpose of generating a writable label. The microcarriers consist of an SU-8 substrate that can be functionalized with various chemical or biological probes and magnetic elements, which are individually addressable by a magnetic sensor. The magnetization of each element is aligned in one of two stable directions, thereby acting as a magnetic bit. In order to detect the stray field and identify the magnetic labels, we have developed a microfluidic device with an integrated tunneling magnetoresistive (TMR) sensor, sourced from Micro Magnetics Inc. We present the TMR embedding architecture as well as detection results demonstrating the feasibility of magnetic labeling for lab-on-a-chip applications. --- paper_title: Giant magnetoresistive biochip for DNA detection and HPV genotyping. paper_content: A giant magnetoresistive (GMR) biochip based on spin valve sensor array and magnetic nanoparticle labels was developed for inexpensive, sensitive and reliable DNA detection. The DNA targets detected in this experiment were PCR products amplified from Human Papillomavirus (HPV) plasmids. The concentrations of the target DNA after PCR were around 10 nM in most cases, but concentrations of 10 pM were also detectable, which is demonstrated by experiments with synthetic DNA samples. A mild but highly specific surface chemistry was used for probe oligonucleotide immobilization. Double modulation technique was used for signal detection in order to reduce the 1/f noise in the sensor. Twelve assays were performed with an accuracy of approximately 90%. Magnetic signals were consistent with particle coverage data measured with Scanning Electron Microscopy (SEM). More recent research on microfluidics showed the potential of reducing the assay time below one hour. This is the first demonstration of magnetic DNA detection using plasmid-derived samples. This study provides a direct proof that GMR sensors can be used for biomedical applications. --- paper_title: Magnetoresistive performance and comparison of supermagnetic nanoparticles on giant magnetoresistive sensor-based detection system paper_content: Giant magnetoresistive (GMR) biosensors have emerged as powerful tools for ultrasensitive, multiplexed, real-time electrical readout, and rapid biological/chemical detection while combining with magnetic particles. Finding appropriate magnetic nanoparticles (MNPs) and its influences on the detection signal is a vital aspect to the GMR bio-sensing technology. Here, we report a GMR sensor based detection system capable of stable and convenient connection, and real-time measurement. Five different types of MNPs with sizes ranging from 10 to 100 nm were investigated for GMR biosensing. The experiments were accomplished with the aid of DNA hybridization and detection architecture on GMR sensor surface. We found that different MNPs markedly affected the final detection signal, depending on their characteristics of magnetic moment, size, and surface-based binding ability, etc. This work may provide a useful guidance in selecting or preparing MNPs to enhance the sensitivity of GMR biosensors, and eventually lead to a versatile and portable device for molecular diagnostics. --- paper_title: Quantitative detection of DNA labeled with magnetic nanoparticles using arrays of MgO-based magnetic tunnel junction sensors paper_content: We have demonstrated the detection of 2.5μM target DNA labeled with 16nm Fe3O4 nanoparticles (NPs) using arrays of magnetic tunnel junction sensors with (001)-oriented MgO barrier layers. A MTJ sensor bridge was designed to detect the presence of magnetic NPs bonded with target DNA. A raw signal of 72μV was obtained using complementary target DNA, as compared with a nonspecific bonding signal of 25μV from noncomplementary control DNA. Our results indicate that the current system’s detection limit for analyte DNA is better than 100nM. --- paper_title: Advances in Giant Magnetoresistance Biosensors With Magnetic Nanoparticle Tags: Review and Outlook paper_content: We present a review of giant magnetoresistance (GMR) spin valve sensors designed for detection of magnetic nanoparticles as biomolecular labels (nanotags) in magneto-nano biodetection technology. We discuss the intricacy of magneto-nano biosensor design and show that as few as approximately 14 monodisperse 16-nm superparamagnetic nanoparticles can be detected by submicron spin valve sensors at room temperature without resorting to lock-in (narrow band) detection. GMR biosensors and biochips have been successfully applied to the detection of biological events in the form of both protein and DNA assays with great speed, sensitivity, selectivity, and economy. The limit of molecular detection is well below 10 pM in concentration, and the protein or DNA assay time can be under two hours. The technology is highly scalable to deep multiplex detection of biomarkers in a complex disease, and amenable to integration of microfluidics and CMOS electronics for portable applications. On-chip CMOS circuitry makes a sensor density of 0.1-1 million sensors per square centimeter feasible and affordable. The theoretical and experimental results thus far suggest that magneto-nano biochip-based GMR sensor arrays and nanotags hold great promise in biomedicine, particularly for point-of-care molecular diagnostics of cancer, infectious diseases, radiation injury, cardiac diseases, and other diseases. --- paper_title: Internet of Things (IoT): A Vision, Architectural Elements, and Future Directions paper_content: Ubiquitous sensing enabled by Wireless Sensor Network (WSN) technologies cuts across many areas of modern day living. This offers the ability to measure, infer and understand environmental indicators, from delicate ecologies and natural resources to urban environments. The proliferation of these devices in a communicating-actuating network creates the Internet of Things (IoT), wherein sensors and actuators blend seamlessly with the environment around us, and the information is shared across platforms in order to develop a common operating picture (COP). Fueled by the recent adaptation of a variety of enabling wireless technologies such as RFID tags and embedded sensor and actuator nodes, the IoT has stepped out of its infancy and is the next revolutionary technology in transforming the Internet into a fully integrated Future Internet. As we move from www (static pages web) to web2 (social networking web) to web3 (ubiquitous computing web), the need for data-on-demand using sophisticated intuitive queries increases significantly. This paper presents a Cloud centric vision for worldwide implementation of Internet of Things. The key enabling technologies and application domains that are likely to drive IoT research in the near future are discussed. A Cloud implementation using Aneka, which is based on interaction of private and public Clouds is presented. We conclude our IoT vision by expanding on the need for convergence of WSN, the Internet and distributed computing directed at technological research community. --- paper_title: The History of WiMAX: A Complete Survey of the Evolution in Certification and Standardization for IEEE 802.16 and WiMAX paper_content: Most researchers are familiar with the technical features of WiMAX technology but the evolution that WiMAX went through, in terms of standardization and certification, is missing and unknown to most people. Knowledge of this historical process would however aid to understand how WiMAX has become the widespread technology that it is today. Furthermore, it would give insight in the steps to undertake for anyone aiming at introducing a new wireless technology on a worldwide scale. Therefore, this article presents a survey on all relevant activities that took place within three important organizations: the 802.16 Working Group of the IEEE (Institute of Electrical and Electronics Engineers) for technology development and standardization, the WiMAX Forum for product certification and the ITU (International Telecommunication Union) for international recognition. An elaborated and comprehensive overview of all those activities is given, which reveals the importance of the willingness to innovate and to continuously incorporate new ideas in the IEEE standardization process and the importance of the WiMAX Forum certification label granting process to ensure interoperability. We also emphasize the steps that were taken in cooperating with the ITU to improve the international esteem of the technology. Finally, a WiMAX trend analysis is made. We showed how industry interest has fluctuated over time and quantified the evolution in WiMAX product certification and deployments. It is shown that most interest went to the 2.5 GHz and 3.5 GHz frequencies, that most deployments are in geographic regions with a lot of developing countries and that the highest people coverage is achieved in Asia Pacific. This elaborated description of all standardization and certification activities, from the very start up to now, will make the reader comprehend how past and future steps are taken in the development process of new WiMAX features. --- paper_title: Future internet: The Internet of Things paper_content: Nowadays, the main communication form on the Internet is human-human. But it is foreseeable that in a near soon that any object will have a unique way of identification and can be addressed so that every object can be connected. The Internet will become to the Internet of Things. The communicate forms will expand from human-human to human-human, human-thing and thing-thing (also called M2M).This will bring a new ubiquitous computing and communication era and change people's life extremely. Radio Frequency Identification techniques (RFID) and related identification technologies will be the cornerstones of the upcoming Internet of Things (IOT).This paper aims to show a skeleton of the Internet of Things and we try to address some essential issues of the Internet of Things like its architecture and the interoperability, etc. At the beginning we describe an overview of the Internet of Things. Then we give our architecture design proposal of the Internet of Things and then we design a specific the Internet of Things application model which can apply to automatic facilities management in the smart campus. At last, we discuss some open questions about the Internet of Things. --- paper_title: Research on the architecture of Internet of Things paper_content: The Internet of Things is a technological revolution that represents the future of computing and communications. It is not the simple extension of the Internet or the Telecommunications Network. It has the features of both the Internet and the Telecommunications Network, and also has its own distinguishing feature. Through analysing the current accepted three-layer structure of the Internet of things, we suggest that the three-layer structure can't express the whole features and connotation of the Internet of Things. After reanalysing the technical framework of the Internet and the Logical Layered Architecture of the Telecommunication Management Network, we establish new five-layer architecture of the Internet of Things. We believe this architecture is more helpful to understand the essence of the Internet of Things, and we hope it is helpful to develop the Internet of Things. --- paper_title: The Internet of Things: A survey paper_content: This paper addresses the Internet of Things. Main enabling factor of this promising paradigm is the integration of several technologies and communications solutions. Identification and tracking technologies, wired and wireless sensor and actuator networks, enhanced communication protocols (shared with the Next Generation Internet), and distributed intelligence for smart objects are just the most relevant. As one can easily imagine, any serious contribution to the advance of the Internet of Things must necessarily be the result of synergetic activities conducted in different fields of knowledge, such as telecommunications, informatics, electronics and social science. In such a complex scenario, this survey is directed to those who want to approach this complex discipline and contribute to its development. Different visions of this Internet of Things paradigm are reported and enabling technologies reviewed. What emerges is that still major issues shall be faced by the research community. The most relevant among them are addressed in details. --- paper_title: Wireless sensor networks: a survey paper_content: This paper describes the concept of sensor networks which has been made viable by the convergence of micro-electro-mechanical systems technology, wireless communications and digital electronics. First, the sensing tasks and the potential sensor networks applications are explored, and a review of factors influencing the design of sensor networks is provided. Then, the communication architecture for sensor networks is outlined, and the algorithms and protocols developed for each layer in the literature are explored. Open research issues for the realization of sensor networks are also discussed. --- paper_title: Future Internet: The Internet of Things Architecture, Possible Applications and Key Challenges paper_content: The Internet is continuously changing and evolving. The main communication form of present Internet is human-human. The Internet of Things (IoT) can be considered as the future evaluation of the Internet that realizes machine-to-machine (M2M) learning. Thus, IoT provides connectivity for everyone and everything. The IoT embeds some intelligence in Internet-connected objects to communicate, exchange information, take decisions, invoke actions and provide amazing services. This paper addresses the existing development trends, the generic architecture of IoT, its distinguishing features and possible future applications. This paper also forecast the key challenges associated with the development of IoT. The IoT is getting increasing popularity for academia, industry as well as government that has the potential to bring significant personal, professional and economic benefits. --- paper_title: Study and application on the architecture and key technologies for IOT paper_content: IOT refers to the third scientific and economic tide after computer, Internet in the global information industry, having attracted highly attention of governments, enterprises, and academia, and brought a huge new market for the communication industry. At present, global main operators and equipment suppliers begin to provide M2M business and solution. Here mainly introduces the concept of IOT, analyses the structure of IOT: perception layer, network layer, application layer. Sets forth the key technologies of IOT: RFID, network communication, etc. At length, it proposes the future development and reform trend of IOT. --- paper_title: Internet of Things (IoT): A Vision, Architectural Elements, and Future Directions paper_content: Ubiquitous sensing enabled by Wireless Sensor Network (WSN) technologies cuts across many areas of modern day living. This offers the ability to measure, infer and understand environmental indicators, from delicate ecologies and natural resources to urban environments. The proliferation of these devices in a communicating-actuating network creates the Internet of Things (IoT), wherein sensors and actuators blend seamlessly with the environment around us, and the information is shared across platforms in order to develop a common operating picture (COP). Fueled by the recent adaptation of a variety of enabling wireless technologies such as RFID tags and embedded sensor and actuator nodes, the IoT has stepped out of its infancy and is the next revolutionary technology in transforming the Internet into a fully integrated Future Internet. As we move from www (static pages web) to web2 (social networking web) to web3 (ubiquitous computing web), the need for data-on-demand using sophisticated intuitive queries increases significantly. This paper presents a Cloud centric vision for worldwide implementation of Internet of Things. The key enabling technologies and application domains that are likely to drive IoT research in the near future are discussed. A Cloud implementation using Aneka, which is based on interaction of private and public Clouds is presented. We conclude our IoT vision by expanding on the need for convergence of WSN, the Internet and distributed computing directed at technological research community. --- paper_title: The Internet of Things: A survey paper_content: This paper addresses the Internet of Things. Main enabling factor of this promising paradigm is the integration of several technologies and communications solutions. Identification and tracking technologies, wired and wireless sensor and actuator networks, enhanced communication protocols (shared with the Next Generation Internet), and distributed intelligence for smart objects are just the most relevant. As one can easily imagine, any serious contribution to the advance of the Internet of Things must necessarily be the result of synergetic activities conducted in different fields of knowledge, such as telecommunications, informatics, electronics and social science. In such a complex scenario, this survey is directed to those who want to approach this complex discipline and contribute to its development. Different visions of this Internet of Things paradigm are reported and enabling technologies reviewed. What emerges is that still major issues shall be faced by the research community. The most relevant among them are addressed in details. --- paper_title: Perpetual and low-cost power meter for monitoring residential and industrial appliances paper_content: The recent research efforts in smart grids and residential power management are oriented to monitor pervasively the power consumption of appliances in domestic and non-domestic buildings. Knowing the status of a residential grid is fundamental to keep high reliability levels while real time monitoring of electric appliances is important to minimize power waste in buildings and to lower the overall energy cost. Wireless Sensor Networks (WSNs) are a key enabling technology for this application field because they consist of low-power, non-invasive and cost-effective intelligent sensor devices. We present a wireless current sensor node (WCSN) for measuring the current drawn by single appliances. The node can self-sustain its operations by harvesting energy from the monitored current. Two AAA batteries are used only as secondary power supply to guarantee a fast start-up of the system. An active ORing subsystem selects automatically the suitable power source, minimizing power losses typical of the classic diode configuration. The node harvests energy when the power consumed by the device under measurement is in the range 10W÷10kW, which also corresponds to the range of current 50mA÷50A drawn directly from the main. Finally the node features a low-power, 32-bit microcontroller for data processing and a wireless transceiver to send data via the IEEE 802.15.4 standard protocol. --- paper_title: Wireless sensor networks: a survey paper_content: This paper describes the concept of sensor networks which has been made viable by the convergence of micro-electro-mechanical systems technology, wireless communications and digital electronics. First, the sensing tasks and the potential sensor networks applications are explored, and a review of factors influencing the design of sensor networks is provided. Then, the communication architecture for sensor networks is outlined, and the algorithms and protocols developed for each layer in the literature are explored. Open research issues for the realization of sensor networks are also discussed. --- paper_title: Energy conservation in wireless sensor networks: A survey paper_content: In the last years, wireless sensor networks (WSNs) have gained increasing attention from both the research community and actual users. As sensor nodes are generally battery-powered devices, the critical aspects to face concern how to reduce the energy consumption of nodes, so that the network lifetime can be extended to reasonable times. In this paper we first break down the energy consumption for the components of a typical sensor node, and discuss the main directions to energy conservation in WSNs. Then, we present a systematic and comprehensive taxonomy of the energy conservation schemes, which are subsequently discussed in depth. Special attention has been devoted to promising solutions which have not yet obtained a wide attention in the literature, such as techniques for energy efficient data acquisition. Finally we conclude the paper with insights for research directions about energy conservation in WSNs. --- paper_title: A Nonintrusive Power Supply Design for Self-Powered Sensor Networks in the Smart Grid by Scavenging Energy From AC Power Line paper_content: An advanced metering and monitoring system based on autonomous, ubiquitous and maintenance-free wireless sensor networks is of great significance to the smart grid. However, the power supply for sensor nodes (especially those installed on high-voltage side) remains one of the most challenging issues. To date, miniaturized, reliable, low-cost and flexible designs catering the massive application of self-powered sensor nodes in the smart grid are still limited. This paper presents a nonintrusive design of power supply to support the sensor network applied in the smart grid. Using a cantilever-structured magnetoelectric (ME) composite, the energy harvester is able to scavenge energy from the power-frequency (50 Hz) magnetic field distributed around the transmission line. Design considerations for this specific type of scavenger have been discussed, and optimized energy harvester prototypes have been fabricated, which are further tested on a power line platform. Experimental results show that the single-cell and double-cell energy harvesters are capable of producing 0.62 mW and 1.12 mW at 10 A, respectively, while corresponding power outputs are enhanced to 4.11 mW and 9.40 mW at 40 A. The good energy harvesting ability of this particular ME composite indicates its great potential to make a nonintrusive, miniaturized, flexible and cost-effective power supply, which possesses great application prospects in the smart grid. --- paper_title: Routing Techniques in Wireless Sensor Networks: A Survey paper_content: Wireless sensor networks consist of small nodes with sensing, computation, and wireless communications capabilities. Many routing, power management, and data dissemination protocols have been specifically designed for WSNs where energy awareness is an essential design issue. Routing protocols in WSNs might differ depending on the application and network architecture. In this article we present a survey of state-of-the-art routing techniques in WSNs. We first outline the design challenges for routing protocols in WSNs followed by a comprehensive survey of routing techniques. Overall, the routing techniques are classified into three categories based on the underlying network structure: flit, hierarchical, and location-based routing. Furthermore, these protocols can be classified into multipath-based, query-based, negotiation-based, QoS-based, and coherent-based depending on the protocol operation. We study the design trade-offs between energy and communication overhead savings in every routing paradigm. We also highlight the advantages and performance issues of each routing technique. The article concludes with possible future research areas. --- paper_title: Minimum-energy mobile wireless networks revisited paper_content: We propose a protocol that, given a communication network, computes a subnetwork such that, for every pair $(u,v)$ of nodes connected in the original network, there is a minimum-energy path between $u$ and $v$ in the subnetwork (where a minimum-energy path is one that allows messages to be transmitted with a minimum use of energy). The network computed by our protocol is in general a subnetwork of the one computed by the protocol given in [13]. Moreover, our protocol is computationally simpler. We demonstrate the performance improvements obtained by using the subnetwork computed by our protocol through simulation. --- paper_title: Integration of plug-in hybrid electric vehicles into energy and comfort management for smart building paper_content: Abstract The smart building and plug-in hybrid electric vehicle (PHEV) are two promising technologies. The integration of these two emerging technologies holds great promises in improving the power supply reliability and the flexibility of building energy and comfort management. The overall control goal of the smart building is to maximize the customer comfort with minimum power consumption. In this study, multi-agent technology coupled with particle swarm optimization (PSO) is proposed to address the control challenge. The proper aggregation of a number of PHEVs turns out to be able to provide both capacity and energy to make the building more economical and more reliable by impacting the building energy flow. Case studies and simulation results are presented and discussed in the paper. --- paper_title: Multi-port topology for composite energy storage and its control strategy in micro-grid paper_content: Energy storage system (ESS) plays a significant role in micro-grid, but single energy storage can't meet the comprehensive requirements of micro-grid applications. Due to technical and economic reasons, composite energy storage is a better choice nowadays, which can combine all the suitable energy storages together, take the best of their positives to meet customer's demand. So the topology for composite energy storage is very important. Typical topology can be used for composite energy storage is compared, upon which, a novel multi-port port based on DC-link interfacing and magnetic coupling method is proposed for composite energy storage application. The multi-port topology allows different kinds of energy storage and/or micro-sources to get in, where energy can be controlled to flow bi-directionally, in and out of energy storage. And a novel Economical inverter based on three phase four switch topology is introduced for micro-grid interface of composite energy storage, which have features of low cost, easy to control and suitable for energy storage application. A double layer control strategy is designed for composite energy storage, the upper layer is responsible for energy management, and a knowledge based energy management method is utilized to separate different energy storage. In the lower layer, a phase shift PWM method is utilized to control energy flow between different ports. Simulation experiments testified their feasibility --- paper_title: Noncontact Power Meter paper_content: Energy metering is increasingly important in today's power grid. With real-time power meters, utilities can efficiently incorporate renewables and consumers can tailor their demand accordingly. Several high-profile attempts at delivering realtime energy analytics to users, including Google Power Meter and Microsoft Hohm, have essentially failed because of a lack of sufficient richness and access to data at adequate bandwidth for reasonable cost. High performance meters can provide adequate data, but require custom installation at prohibitive expense, e.g., requiring an electrician for installation. This paper presents hardware and signal processing algorithms that enable high bandwidth measurements of voltage, current, harmonics, and power on an aggregate electrical service (such as a residential powerline) for nonintrusive analysis with hardware that requires no special skill or safety considerations for installation. --- paper_title: Photovoltaic and wind energy systems monitoring and building/home energy management using ZigBee devices within a smart grid paper_content: The actual electric grid was developed to offer electricity to the clients from centralized generation, so with large-scale distributed renewable generation there is an urgent need for a more flexible, reliable and smarter grid. The wireless technologies are becoming an important asset in the smart grid, particularly the ZigBee devices. These smart devices are gaining increased acceptance, not only for building and home automation, but also for energy management, efficiency optimization and metering services, being able to operate for long periods of time without maintenance needs. In this context, this paper provides new comprehensive field tests using open source tools with ZigBee technologies for monitoring photovoltaic and wind energy systems, and also for building and home energy management. Our experimental results demonstrate the proficiency of ZigBee devices applied in distributed renewable generation and smart metering systems. --- paper_title: A review on optimized control systems for building energy and comfort management of smart sustainable buildings paper_content: Buildings all around the world consume a significant amount of energy, which is more or less one-third of the total primary energy resources. This has raised concerns over energy supplies, rapid energy resource depletion, rising building service demands, improved comfort life styles along with the increased time spent in buildings; consequently, this has shown a rising energy demand in the near future. However, contemporary buildings’ energy efficiency has been fast tracked solution to cope/limit the rising energy demand of this sector. Building energy efficiency has turned out to be a multi-faceted problem, when provided with the limitation for the satisfaction of the indoor comfort index. However, the comfort level for occupants and their behavior have a significant effect on the energy consumption pattern. It is generally perceived that energy unaware activities can also add one-third to the building’s energy performance. Researchers and investigators have been working with this issue for over a decade; yet it remains a challenge. This review paper presents a comprehensive and significant research conducted on state-of-the-art intelligent control systems for energy and comfort management in smart energy buildings (SEB’s). It also aims at providing a building research community for better understanding and up-to-date knowledge for energy and comfort related trends and future directions. The main table summarizes 121 works closely related to the mentioned issue. Key areas focused on include comfort parameters, control systems, intelligent computational methods, simulation tools, occupants’ behavior and preferences, building types, supply source considerations and countries research interest in this sector. Trends for future developments and existing research in this area have been broadly studied and depicted in a graphical layout. In addition, prospective future advancements and gaps have also been discussed comprehensively. --- paper_title: A novel current sensor for home energy use monitoring paper_content: This paper presents a novel magnetic sensor array based technique for measuring currents in a group of enclosed conductors. It is designed specifically for monitoring the real-time power consumptions of North American homes. The technique consists of three key components: magnetic field sensors deployed in close proximity of the power conductors to be measured; algorithms to compute the conductor currents based on the magnetic fields measured; a simple, integrated sensor calibration and communication scheme. Prototype devices have been developed based on the technique. Extensive lab and field tests have demonstrated that the technique can provide adequate current measurements for residential homes. Combining with the non-intrusive load monitoring methods, the proposed measurement technique represents an attractive platform to create a complete home energy use tracking system. --- paper_title: Demand Side Management: Demand Response, Intelligent Energy Systems, and Smart Loads paper_content: Energy management means to optimize one of the most complex and important technical creations that we know: the energy system. While there is plenty of experience in optimizing energy generation and distribution, it is the demand side that receives increasing attention by research and industry. Demand Side Management (DSM) is a portfolio of measures to improve the energy system at the side of consumption. It ranges from improving energy efficiency by using better materials, over smart energy tariffs with incentives for certain consumption patterns, up to sophisticated real-time control of distributed energy resources. This paper gives an overview and a taxonomy for DSM, analyzes the various types of DSM, and gives an outlook on the latest demonstration projects in this domain. --- paper_title: Getting to green: understanding resource consumption in the home paper_content: Rising global energy demands, increasing costs and limited natural resources mean that householders are more conscious about managing their domestic resource consumption. Yet, the question of what tools Ubicomp researchers can create for residential resource management remains open. To begin to address this omission, we present a qualitative study of 15 households and their current management practices around the water, electricity and natural gas systems in the home. We find that in-the-moment resource consumption is mostly invisible to householders and that they desire more real-time information to help them save money, keep their homes comfortable and be environmentally friendly. Designing for domestic sustainability therefore turns on improving the visibility of resource production and consumption costs as well as supporting both individuals and collectives in behavior change. Domestic sustainability also highlights the caveat of potentially creating a green divide by making resource management available only to those who can afford the technologies to support being green. Finally, we suggest that the Ubicomp community can contribute to the domestic and broader sustainability agenda by incorporating green values in designs and highlight the challenge of collecting data on being green. --- paper_title: Towards a zero-configuration wireless sensor network architecture for smart buildings paper_content: Today's buildings account for a large fraction of our energy consumption. In an effort to economize scarce fossil fuels on earth, sensor networks are a valuable tool to increase the energy efficiency of buildings without severely reducing our quality of life. Within a smart building many sensors and actuators are interconnected to form a control system. Nowadays, the deployment of a building control system is complicated because of different communication standards. In this paper, we present a web services-based approach to integrate resource constrained sensor and actuator nodes into IP-based networks. A key feature of our approach is its capability for automatic service discovery. For this purpose, we implemented an API to access services on sensor nodes following the architectural style of representational state transfer (REST). We implemented a prototype application based on TinyOS 2.1 on a custom sensor node platform with 8 Kbytes of RAM and an IEEE 802.15.4 compliant radio transceiver. --- paper_title: Development of an energy monitoring system for large public buildings paper_content: Abstract Building energy consumption is an important component of the total social energy consumption, especially for large public buildings in China. Building energy conservation is one valid method for increasing energy efficiency. In order to locate the status of energy consumption for large public buildings, such as supermarket, government office buildings, hospital and campus buildings, an Internet-based energy monitoring system was developed. The implementation of this system was introduced in detail, including the principle of selecting monitoring points at the bottom layer, the design of a data collector with storage function avoiding data loss caused by network faults, and the development of database and application software at the top layer. The monitoring platform releases the energy consumption data on the web, so the authorized users can access the data any time and anywhere through Internet. In addition, the data display system is given in form of graph-charts or tables, so users can choose any kind of data they want to see, either instant values uploaded every 5 min or historic data uploaded every hour, day and month. The platform has been used in some large public buildings in Liaoning Province in China over two years, and the results confirm its feasibility and validity. --- paper_title: Intelligent Management Systems for Energy Efficiency in Buildings: A Survey paper_content: In recent years, reduction of energy consumption in buildings has increasingly gained interest among researchers mainly due to practical reasons, such as economic advantages and long-term environmental sustainability. Many solutions have been proposed in the literature to address this important issue from complementary perspectives, which are often hard to capture in a comprehensive manner. This survey article aims at providing a structured and unifying treatment of the existing literature on intelligent energy management systems in buildings, with a distinct focus on available architectures and methodology supporting a vision transcending the well-established smart home vision, in favor of the novel Ambient Intelligence paradigm. Our exposition will cover the main architectural components of such systems, beginning with the basic sensory infrastructure, moving on to the data processing engine where energy-saving strategies may be enacted, to the user interaction interface subsystem, and finally to the actuation infrastructure necessary to transfer the planned modifications to the environment. For each component, we will analyze different solutions, and we will provide qualitative comparisons, also highlighting the impact that a single design choice can have on the rest of the system. --- paper_title: Sensors in Intelligent Buildings paper_content: We've all heard of `sick-building' syndrome and the misery this can inflict in the workplace in terms of poor health and lost production. The notion of the Intelligent Building is the modern civil engineer's Big Idea in tackling these and other such deficiencies. The intelligent building can adapt itself to maintain an optimized environment. This ability relies on sensors as a front-line technology - the subject of this volume. Gassmann and Meixner tackle the subject matter by using five categories of intelligent building technology: energy and HVAC (heating, ventilation and air conditioning), information and transportation, safety and security, maintenance, and facility management. These categories of home and building technology are intended to encompass domestic as well as workplace and public environments, but as the introduction states, the breakthrough into the domestic market is not quite here yet. They have targeted, successfully in this reviewer's opinion, the researcher and designer in the field who has his or her own specific interest in sensor issues. Each section of the book contains a number of articles contributed from predominantly European, particularly German and Swiss, research institutions. They cover subjects as diverse as inflatable buildings and a combination of a sensing chair and sensing floor that allows the exact interaction of a human user with his/her immediate surroundings to be integrated within an information system. A fascinating item on biometric access security systems brings to life the `spy-thriller' world of automatic iris and fingerprint scanners as a means of secure access to key-less buildings. The discussion extends to threats to such systems whereby `replay' attacks, for example presenting a face recognition system with a photograph of an individual, reveal the necessary further steps if the technology is to be considered safe. Inevitably though, it is the massive strides in communications and processing technology that are visible in the contributions to this volume that point to where most of the advances will come. The massive interconnection issue of numerous sensors, the `nervous system' of the building is approached in items covering the complexities of fieldbus systems and the use of `wireless' in-building networks. This well presented volume with good quality illustration ends in an investigation of system technologies for the automated home of the near future. Presence-controlled heating and air-conditioning, telemonitoring of the sick or elderly, gas and fire detection and of course a high data rate communication backbone to link everything: all these could feature in the future household. We shall see. Peter Foote --- paper_title: Current and Voltage Reconstruction From Non-Contact Field Measurements paper_content: Non-contact electromagnetic field sensors can monitor voltage and current in multiple-conductor cables from a distance. Knowledge of the cable and sensor geometry is generally required to determine the transformation that recovers voltages and currents from the sensed electromagnetic fields. This paper presents a new calibration technique that enables the use of non-contact sensors without the prior knowledge of conductor geometry. Calibration of the sensors is accomplished with a reference load or through observation of in situ loads. --- paper_title: An integrated system for buildings’ energy-efficient automation: Application in the tertiary sector paper_content: Although integrated building automation systems have become increasingly popular, an integrated system which includes remote control technology to enable real-time monitoring of the energy consumption by energy end-users, as well as optimization functions is required. To respond to this common interest, the main aim of the paper is to present an integrated system for buildings’ energy-efficient automation. The proposed system is based on a prototype software tool for the simulation and optimization of energy consumption in the building sector, enhancing the interactivity of building automation systems. The system can incorporate energy-efficient automation functions for heating, cooling and/or lighting based on recent guidance and decisions of the National Law, energy efficiency requirements of EN 15232 and ISO 50001 Energy Management Standard among others. The presented system was applied to a supermarket building in Greece and focused on the remote control of active systems. --- paper_title: A WSN-based testbed for energy efficiency in buildings paper_content: Residential and business buildings account for a large fraction of the overall world energy consumption. Despite the high energy costs and the raising awareness about the impact on climate changes, a significant part of energy consumption in buildings is still due to an improper use of electrical appliances. In this paper we propose GreenBuilding, a sensor-based system for automated power management of electrical appliances in a building. We implemented GreenBuilding as a prototype system and deployed it in a real household scenario to perform a prolonged experimental analysis. The obtained results show that GreenBuilding is able to provide significant energy savings by using appropriate energy conservation strategies tailored to specific appliances. --- paper_title: A Novel Approach for Fault Location of Overhead Transmission Line With Noncontact Magnetic-Field Measurement paper_content: Prompt and accurate location of faults in a large-scale transmission system can accelerate system restoration, reduce outage time, and improve system reliability. Traditional approaches are categorized into traveling-wave-based and impedance-based measurement techniques. The traveling-wave-based approach requires detection devices to connect to the high-voltage transmission line, making the solution complex and costly. And the impedance-measurement-based approach is highly dependent on the quality of the signal and affected by fault resistance, ground resistance and non-homogeneity in line configuration. Hence, these approaches may cause a location error that is unacceptable in certain operation cases. In this paper, a novel approach based on noncontact magnetic-field measurement is proposed. With the magnetic field measured along the transmission line by using highly sensitive, broadband, and a low-cost magnetoresistive magnetic sensor, the fault span can be located. The collected data can be further used for identifying the fault type and location within the fault span. The overall system was designed and numerical simulations were performed on typical tower configurations. The simulated results verify the validity of the proposed scheme. --- paper_title: Challenges in reliability, security, efficiency, and resilience of energy infrastructure: Toward smart self-healing electric power grid paper_content: This article deals with the challenges in reliability, security, efficiency, and resilience of energy infrastructure for a smart self-healing electric power grid. The electricity grid faces three looming challenges: its organization, its technical ability to meet 25 year and 50 year electricity needs, and its ability to increase its efficiency without diminishing its reliability and security. These three are not unrelated, as the grid's present organization reflects an earlier time when electrification was developing, objectives and needs were simpler, and today's technology was still over the horizon. Given economic, societal, and quality-of-life issues and the ever-increasing interdependencies among infrastructures, a key challenge before us is whether the electricity infrastructure will evolve to become the primary support for the 21st century's digital society a smart grid with self-healing capabilities or be left behind as an 20th century industrial relic. --- paper_title: Effect of sag on transmission line paper_content: This paper looks into the factors affecting sag in conductors while erecting an overhead line, it is very important that conductors are under safe tension. If the conductors are too much stretched between supports, the stress in the conductor may reach unsafe value and in certain cases the conductors may break due to excessive tension. The conductor sag should be kept to a minimum in order to reduce the conductor material required and to avoid extra pole height for sufficient clearance above ground level. It is also desirable that tension in the conductor should be low to avoid the mechanical failure of conductor and to permit the use of less strong supports. The effects of sag on electrical construction were examined. Also, a look into the solution to effect of sag were examined. The meaning sag was not left out. This write up suggested ways to reduce the effect of sag on overhead line conductors. --- paper_title: Design, installation, and field experience with an overhead transmission dynamic line rating system paper_content: Dynamic line rating (DLR) systems for high voltage overhead transmission lines have been installed by three utilities over the past five years. These DLR systems utilize the Power Donut/sup TM/ to measure load and conductor temperature at several locations over the length of the circuit. The effective wind acting on the conductor at each site is determined in real-time by a dynamic heat balance and used to compute the normal, LTE and STE ratings each minute. The lowest ratings of all locations define the circuit's ratings and are sent to SCADA as analog signals. This method is known as the conductor temperature model (CTM) as opposed to the weather model (WM) which calculates ratings using weather data only. These first DLR installations have also measured weather parameters at each ground station location to allow a comparison of the two methods. Data from the latest of these systems is presented and the behavior of the real time ratings are discussed. --- paper_title: A vehicle detection algorithm based on wireless magnetic sensor networks paper_content: At present, the research of parking management system based on Wireless Sensor Networks (WSN) and Anisotropic Magneto Resistive (AMR) sensors have made great progress. However, due to the diversity of the vehicle magnetic signal and the interference caused by the adjacent parking spaces, vehicle detection technique using wireless magnetic sensor networks is still immature. For accurately detecting a parking vehicle in a parking lot, we propose a detection algorithm named Relative Extremum Algorithm (REA). On the parking lot at Shenzhen Institutes of Advanced Technology (SIAT), 82 sensor devices are deployed to evaluate the performance of REA. By running the system for more than half a year, we observe that the vehicle detection accuracy of the REA is above 98.8%. --- paper_title: Reducing emergency services response time in smart cities: An advanced adaptive and fuzzy approach paper_content: Nowadays, the unprecedented increase in road traffic congestion has led to severe consequences on individuals, economy and environment, especially in urban areas in most of big cities worldwide. The most critical among the above consequences is the delay of emergency vehicles, such as ambulances and police cars, leading to increased deaths on roads and substantial financial losses. To alleviate the impact of this problem, we design an advanced adaptive traffic control system that enables faster emergency services response in smart cities while maintaining a minimal increase in congestion level around the route of the emergency vehicle. This can be achieved with a Traffic Management System (TMS) capable of implementing changes to the road network's control and driving policies following an appropriate and well-tuned adaptation strategy. This latter is determined based on the severity of the emergency situation and current traffic conditions estimated using a fuzzy logic-based scheme. The obtained simulation results, using a set of typical road networks, have demonstrated the effectiveness of our approach in terms of the significant reduction of emergency vehicles' response time and the negligible disruption caused to the non-emergency vehicles travelling on the same road network. --- paper_title: Green Transport System: A Technology Demonstration of Adaptive Road Lighting with Giant Magnetoresistive Sensor Network for Energy Efficiency and Reducing Light Pollution paper_content: To enhance energy efficiency and reduce light pollution of overnight road lighting in suburban traffic, we propose a novel green transport system based on giant magnetoresistive (GMR) sensors. The basic principle is to detect the perturbation to the earth magnetic field by a ferrous vehicle with GMR sensors. This system can switch on the road lighting to full illumination gradually before the motor vehicle arrives and dim it out after the vehicle leaves without the driver noticing. Based on a sparse suburban road in the countryside of Hong Kong, a demonstration model was constructed to illustrate its feasibility. GMR sensors and the associated electrical energy control components including signal processors, relays, and dimmers were integrated into a complete system. The experimental result indicates that the sensing principle is feasible and the whole system can function together coherently to achieve over 90% energy saving. Such system can be scaled up to be implemented in real road conditions. --- paper_title: Train Detection by Magnetic Field Measurement with Giant Magnetoresistive Sensors for High-Speed Railway paper_content: Train detection, as part of the railway signaling system, is important for safe operation of high-speed railway. The recent flourishing development of high-speed railway stimulates the research need of train detection technology to enhance the safety and reliability of train operation. This paper proposes a new technique for train detection through magnetic field measurement by giant magnetoresistive sensors. This technology was studied by the analysis of magnetic field distribution in the high-speed rail system obtained from modeling and simulation. The results verify the feasibility for detection of train presence, number of rolling stocks, speed, and length. It can overcome the limitations of track circuits and provide additional measurement capabilities to the signaling system. This detection system can be built with low cost and minimal maintenance load as well as compacted construction. Therefore, it may serve as a new train detection system to help improve the current systems, enhancing and promoting the safety and reliability of high-speed rail system. --- paper_title: Wireless sensor networks for traffic management and road safety paper_content: Wireless sensor networks (WSN) employ self-powered sensing devices that are mutually interconnected through wireless ad-hoc technologies. This study illustrates the basics of WSN-based traffic monitoring and summarises the possible benefits in Intelligent Transport Systems (ITS) applications for the improvement of quality and safety of mobility. Compared with conventional infrastructure-based monitoring systems, this technology facilitates a denser deployment of sensors along the road, resulting in a higher spatial resolution of traffic parameter sampling. An experimental data analysis reported in this study shows how the high spatial resolution can enhance the reliability of traffic modelling as well as the accuracy of short-term traffic state prediction. The analysis uses the data published by the freeway performance measurement system of the University of California-Berkeley and the California Department of Transportation. A microscopic cellular automata model is used to estimate traffic flow and occupancy over time on a road segment in which a relevant traffic-flow anomaly is detected. The analysis shows that the estimate accuracy improves for increasing number of active sensors, as feasible in the case of WSN-based monitoring systems. --- paper_title: A Communications-Oriented Perspective on Traffic Management Systems for Smart Cities: Challenges and Innovative Approaches paper_content: The growing size of cities and increasing population mobility have determined a rapid increase in the number of vehicles on the roads, which has resulted in many challenges for road traffic management authorities in relation to traffic congestion, accidents, and air pollution. Over the recent years, researchers from both industry and academia have been focusing their efforts on exploiting the advances in sensing, communication, and dynamic adaptive technologies to make the existing road traffic management systems (TMSs) more efficient to cope with the aforementioned issues in future smart cities. However, these efforts are still insufficient to build a reliable and secure TMS that can handle the foreseeable rise of population and vehicles in smart cities. In this survey, we present an up-to-date review of the different technologies used in the different phases involved in a TMS and discuss the potential use of smart cars and social media to enable fast and more accurate traffic congestion detection and mitigation. We also provide a thorough study of the security threats that may jeopardize the efficiency of the TMS and endanger drivers' lives. Furthermore, the most significant and recent European and worldwide projects dealing with traffic congestion issues are briefly discussed to highlight their contribution to the advancement of smart transportation. Finally, we discuss some open challenges and present our own vision to develop robust TMSs for future smart cities. --- paper_title: Wireless sensor networks for healthcare: A survey paper_content: Becoming mature enough to be used for improving the quality of life, wireless sensor network technologies are considered as one of the key research areas in computer science and healthcare application industries. The pervasive healthcare systems provide rich contextual information and alerting mechanisms against odd conditions with continuous monitoring. This minimizes the need for caregivers and helps the chronically ill and elderly to survive an independent life, besides provides quality care for the babies and little children whose both parents have to work. Although having significant benefits, the area has still major challenges which are investigated in this paper. We provide several state of the art examples together with the design considerations like unobtrusiveness, scalability, energy efficiency, security and also provide a comprehensive analysis of the benefits and challenges of these systems. --- paper_title: Cloud-enabled wireless body area networks for pervasive healthcare paper_content: With the support of mobile cloud computing, wireless body area networks can be significantly enhanced for massive deployment of pervasive healthcare applications. However, several technical issues and challenges are associated with the integration of WBANs and MCC. In this article, we study a cloud-enabled WBAN architecture and its applications in pervasive healthcare systems. We highlight the methodologies for transmitting vital sign data to the cloud by using energy-efficient routing, cloud resource allocation, semantic interactions, and data security mechanisms. --- paper_title: nanoLAB: An ultraportable, handheld diagnostic laboratory for global health paper_content: Driven by scientific progress and economic stimulus, medical diagnostics will move to a stage in which straightforward medical diagnoses are independent of physician visits and large centralized laboratories. The future of basic diagnostic medicine will lie in the hands of private individuals. We have taken significant strides towards achieving this goal by developing an autoassembly assay for disease biomarker detection which obviates the need for washing steps and is run on a handheld sensing platform. By coupling magnetic nanotechnology with an array of magnetically responsive nanosensors, we demonstrate a rapid, multiplex immunoassay that eliminates the need for trained technicians to run molecular diagnostic tests. Furthermore, the platform is battery-powered and ultraportable, allowing the assay to be run anywhere in the world by any individual. --- paper_title: Point of Care Diagnostics: Status and Future paper_content: Introduction A Why POC Diagnostics? B Time B Patient Responsibility and Compliance B Cost B Diagnostic Targets C Proteins C Metabolites and Other Small Molecules C Nucleic Acids C Human Cells D Microbes/Pathogens D Drugs and Food Safety D Current Context of POC Assays E POC Glucose Assays E Lateral Flow Assays E Limitations of “Traditional” POC Approaches F Enabling Technologies G Printing and Laminating G Microfluidic Technologies and Approaches: “Unit Operations” for POC Devices G Pumping and Valving H Mixing I Separation I Reagent Storage J Sample Preparation K Surface Chemistry and Device Substrates L Physical Adsorption L Bioaffinity Attachment L Covalent Attachment M Substrate Materials M Detection M Electrochemical Detection N Optical Detection N Magnetic Detection N Label-Free Methods O Enabling Multiplexed Assays O Recent Innovation O Lateral Flow Assay Technologies O Proteins P Antibodies P Protein Expression and Purification Q Nucleic Acids Q Aptamers R Infectious Diseases and Food/Water Safety R Blood Chemistry S Coagulation Markers S Whole Cells S Trends, Unmet Needs, Perspectives T Glucose T Global Health and the Developing World T Personalized Medicine and Home Testing U Technology Trends U Multiplexing V Author Information V Biographies V Acknowledgment W References W --- paper_title: Improving Healthcare Accessibility through Point-of-Care Technologies paper_content: Background: The NIH is committed to improving healthcare quality in the US and has set up initiatives to address problems such as the fragmented nature of healthcare provision. A hypothesis has been developed that testing closer to the point at which care is delivered may reduce fragmentation of care and improve outcomes. Methods: The National Institute of Biomedical Imaging and Bioengineering (NIBIB), the NIH’s National Heart, Lung, and Blood Institute, and the National Science Foundation sponsored a workshop, “Improving Health Care Accessibility through Point-of-Care Technologies,” in April 2006. The workshop assessed the clinical needs and opportunities for point-of-care (POC) technologies in primary care, the home, and emergency medical services and reviewed minimally invasive and noninvasive testing, including imaging, and conventional testing based on sensor and lab-on-a-chip technologies. Emerging needs of informatics and telehealth and healthcare systems engineering were considered in the POC testing context. Additionally, implications of evidence-based decision-making were reviewed, particularly as it related to the challenges in producing reliable evidence, undertaking regulation, implementing evidence responsibly, and integrating evidence into health policy. Results: Many testing procedures were considered to be valuable in the clinical settings discussed. Technological solutions were proposed to meet these needs, as well as the practical requirements around clinical process change and regulation. From these considerations, a series of recommendations was formulated for development of POC technologies based on input from the symposium attendees. Conclusion: NIBIB has developed a funding initiative to establish a Point-of-Care Technologies Research Network that will work to bridge the technology/clinical gap and provide the partnerships necessary for the application of technologies to pressing clinical needs in POC testing. ---	<format> Title: Overview of Spintronic Sensors, Internet of Things, and Smart Living Section 1: Introduction Description 1: Introduce the concept of smart living and the role of IoT and spintronic sensors in achieving it. Section 2: Spintronic sensors Description 2: Explain the basic principles and different types of spintronic sensors, along with their fabrication and sensing capabilities. Section 3: Winning combination: IoT and spintronic sensors Description 3: Provide a brief introduction to the concept and architecture of IoT, and discuss how wireless spintronic sensor networks (WSSNs) can be integrated into the IoT platform. Section 4: IoT and spintronic sensors enabling smart living Description 4: Discuss how WSSN-based solutions can support smart building, smart grid, smart transport, and smart healthcare applications. Section 5: Conclusion and outlook Description 5: Summarize the paper and provide future directions for the development and integration of spintronic sensors and IoT for smart living. </format>
Security Threats and Privacy Issues in Vehicular Ad-Hoc Network (VANET): Survey and Perspective	9	--- paper_title: AN INSIGHT OVERVIEW OF ISSUES AND CHALLENGES IN VEHICULARADHOC NETWORK paper_content: Vehicular Ad hoc Networks is a kind of special wireless ad hoc network, which has the characteristics of high node mobility and fast topology changes. The Vehicular Networks can provide wide variety of services, range from safety-related warning systems to improved navigation mechanisms as well as information and entertainment applications. These additional features make the routing and other services more challenging and cause vulnerability in network services. These problems include network architecture, vanet protocols, routing algorithms, as well as security issues. In this paper, we provide a review for the researches related to Vehicular Ad Hoc Networks and also try to propose solution for related issues and challenges. --- paper_title: Minimization of Denial of services attacks in Vehicular Adhoc networking by applying different constraints paper_content: The security of Vehicular ad hoc networking is of great importance as it involves serious life threats. Thus to provide secure communication amongst Vehicles on road, the conventional security system is not enough. It is necessary to prevent the network resources from wastage and give them protection against malicious nodes so that to ensure the data bandwidth availability to the legitimate nodes of the network. This work is related to provide a non conventional security system by introducing some constraints to minimize the DoS (Denial of services) especially data and bandwidth. The data packets received by a node in the network will pass through a number of tests and if any of the test fails, the node will drop those data packets and will not forward it anymore. Also if a node claims to be the nearest node for forwarding emergency messages then the sender can effectively identify the true or false status of the claim by using these constraints. Consequently the DoS(Denial of Services) attack is --- paper_title: Vehicular Ad Hoc Networks paper_content: Vehicular Ad Hoc Network (VANET) is an emerging new technology integrating Ad Hoc network, cellular technology and wireless LAN (WLAN) to achieve vehicle to vehicle and vehicle to infrastructure communication for intelligent transportation systems (ITS). VANETs are distinguished from other kinds of Ad Hoc networks by node movement characteristics, their hybrid network architectures and new application scenarios. The vehicular network provides wide variety of services, ranging from safety-related warning systems to improved navigation mechanisms as well as information and entertainment applications. Therefore, VANETs pose many unique networking research challenges, and the design of efficient routing protocols that not only forward packets with good end to end delay but also take into consideration the reliability and progress in data packets forwarding. In this paper, we provide a review of VANETs architecture, its characteristics, applications various routing protocols and challenges. --- paper_title: Security Attacks and Solutions in Vehicular Ad Hoc Networks: A Survey paper_content: Vehicular Ad hoc Networks (VANETs) have emerged recently as one of the most attractive topics for researchers and automotive industries due to their tremendous potential to improve traffic safety, efficiency and other added services. However, VANETs are themselves vulnerable against attacks that can directly lead to the corruption of networks and then possibly provoke big losses of time, money, and even lives. This paper presents a survey of VANETs attacks and solutions in carefully considering other similar works as well as updating new attacks and categorizing them into different classes. --- paper_title: An overview of mobile ad hoc networks: applications and challenges paper_content: In the past few years, we have seen a rapid expansion in the field of mobile computing due to the proliferation of inexpensive, widely available wireless devices. However, current devices, applications and protocols are solely focused on cellular or wireless local area networks (WLANs), not taking into account the great potential offered by mobile ad hoc networking. A mobile ad hoc network is an autonomous collection of mobile devices (laptops, smart phones, sensors, etc.) that communicate with each other over wireless links and cooperate in a distributed manner in order to provide the necessary network functionality in the absence of a fixed infrastructure. This type of network, operating as a stand-alone network or with one or multiple points of attachment to cellular networks or the Internet, paves the way for numerous new and exciting applications. Application scenarios include, but are not limited to: emergency and rescue operations, conference or campus settings, car networks, personal networking, etc. ::: This paper provides insight into the potential applications of ad hoc networks and discusses the technological challenges that protocol designers and network developers are faced with. These challenges include routing, service and resource discovery, Internet connectivity, billing and security. --- paper_title: DSRC-Type Communication System for Realizing Telematics Services paper_content: The decisive factor for the popularization of telematics services in the future is the ability to produce advanced services that match the needs of drivers and passengers. The Dedicated Short Range Communications (DSRC)type of wireless communication system, which is being developed for the Intelligent Transport Systems (ITS), is one of the broadband wireless systems contributing to the improvement of driver and passenger needs, such as convenience, entertainment, comfort and safety. In this paper, the possibility of applying this system to telematics services will be explored. Further, a description of the future prospects for ubiquitous networking will be provided, in the knowledge that the existence of information communication equipment mounted vehicles will remain. --- paper_title: Mobile Ad Hoc Networking: Imperatives and Challenges paper_content: A mobile ad hoc network (MANET), sometimes called a mobile mesh network, is a self- configuring network of mobile devices connected by wireless links. The Ad hoc networks are a new wireless networking paradigm for mobile hosts. Unlike traditional mobile wireless networks, ad hoc networks do not rely on any fixed infrastructure. Instead, hosts rely on each other to keep the network connected. It represent complex distributed systems that comprise wireless mobile nodes that can freely and dynamically self-organize into arbitrary and temporary, ''ad-hoc'' network topologies, allowing people and devices to seamlessly internetwork in areas with no pre-existing communication infrastructure. Ad hoc networking concept is not a new one, having been around in various forms for over 20 years. Traditionally, tactical networks have been the only communication networking application that followed the adhoc paradigm. Recently, the introduction of new technologies such as the Bluetooth, IEEE 802.11 and Hyperlan are helping enable eventual commercial MANET deployments outside the military domain. These recent evolutions have been generating a renewed and growing interest in the research and development of MANET.So,we would like to propose the challenges and imperativels that the MANET is facing. --- paper_title: On Data-Centric Trust Establishment in Ephemeral Ad Hoc Networks paper_content: We argue that the traditional notion of trust as a relation among entities, while useful, becomes insufficient for emerging data-centric mobile ad hoc networks. In these systems, setting the data trust level equal to the trust level of the data- providing entity would ignore system salient features, rendering applications ineffective and systems inflexible. This would be even more so if their operation is ephemeral, i.e., characterized by short-lived associations in volatile environments. In this paper, we address this challenge by extending the traditional notion of trust to data-centric trust: trustworthiness attributed to node-reported data per se. We propose a framework for data-centric trust establishment: First, trust in each individual piece of data is computed; then multiple, related but possibly contradictory, data are combined; finally, their validity is inferred by a decision component based on one of several evidence evaluation techniques. We consider and evaluate an instantiation of our framework in vehicular networks as a case study. Our simulation results show that our scheme is highly resilient to attackers and converges stably to the correct decision. --- paper_title: Vehicular Ad-Hoc Networks (VANETs) - An Overview and Challenges paper_content: Vehicu lar ad-hoc networks (VANETs) technology has emerged as an important research area over the last few years. Being ad-hoc in nature, VA NET is a type of networks that is created from the concept of establishing a network of cars for a specific need or situation. VA NETs have now been established as reliable networks that vehicles use for co mmunication purpose on highways or urban environments. Along with the benefits, there arise a large number of challenges in VANET such as provisioning of QoS, h igh connectivity and bandwidth and security to vehicle and individual privacy. This article presents state-of-the-art of VANET and discusses the related issues. Network architecture, signal modeling and propagation mechanis m, mobility modeling, routing protocols and network security are discussed in detail. Main findings of this paper are that an efficient and robust VANET is one wh ich satisfies all design parameters such as QoS, minimu m latency, low BER and high PDR. So me key research areas and challenges in VANET are presented at the end of the paper. --- paper_title: Security Attacks and Solutions in Vehicular Ad Hoc Networks: A Survey paper_content: Vehicular Ad hoc Networks (VANETs) have emerged recently as one of the most attractive topics for researchers and automotive industries due to their tremendous potential to improve traffic safety, efficiency and other added services. However, VANETs are themselves vulnerable against attacks that can directly lead to the corruption of networks and then possibly provoke big losses of time, money, and even lives. This paper presents a survey of VANETs attacks and solutions in carefully considering other similar works as well as updating new attacks and categorizing them into different classes. ---	Title: Security Threats and Privacy Issues in Vehicular Ad-Hoc Network (VANET): Survey and Perspective Section 1: Introduction Description 1: Introduce the concept of Vehicular Ad-Hoc Networks (VANETs) and its significance. Mention the purpose and scope of the paper. Section 2: Overview of Vehicular Ad-Hoc Network (VANET) Description 2: Provide a detailed description of VANET, including its definition, characteristics, and how it functions. Section 3: Security Threats in VANET Description 3: Discuss various security threats faced by VANETs, such as eavesdropping, spoofing, denial-of-service attacks, etc. Section 4: Privacy Issues in VANET Description 4: Explain the privacy concerns associated with VANETs, including potential misuse of data and challenges in maintaining user privacy. Section 5: Impact of Mobility on Security Description 5: Analyze how the mobility of nodes affects the security and reliability of VANETs, and discuss the resulting challenges. Section 6: Fault Detection and Network Management Description 6: Address the issues of fault detection and network management in VANETs, highlighting why they are more complex compared to other networks. Section 7: Solutions and Mitigations Description 7: Outline potential solutions and mitigation strategies to address the security threats and privacy issues in VANETs. Section 8: Future Research Directions Description 8: Suggest areas for future research, identifying gaps in current knowledge and proposing directions for further study. Section 9: Conclusion Description 9: Summarize the key points discussed in the paper and reinforce the importance of addressing security and privacy issues in VANETs.
An Overview on Gripping Force Measurement at the Micro and Nano-Scales Using Two-Fingered Microrobotic Systems	16	--- paper_title: Manipulation at the NanoNewton level: Micrograpsing for mechanical characterization of biomaterials paper_content: This paper presents the use of a monolithic, force-feedback MEMS (microelectomechanical systems) microgripper for characterizing both elastic and viscoelastic properties of highly deformable hydrogel microcapsules (15–25µm) at wet state during micromanipulation. The single-chip microgripper integrates an electrothermal microactuator and two capacitive force sensors, one for contact detection (force resolution: 38.5nN) and the other for gripping force measurements (force resolution: 19.9nN). Through nanoNewton force measurements, closed-loop force control, and visual tracking, the system quantified Young's modulus values and viscoelastic parameters of alginate microcapsules, demonstrating an easy-to-operate, accurate compression testing technique for characterizing soft, micrometer-sized biomaterials. --- paper_title: Autonomous micromanipulation using a new strategy of accurate release by rolling paper_content: This paper presents our work in developing an autonomous micromanipulation system. The originality of our system is that it takes advantage of adhesion to grip micro-objects by using a single fingered gripper. This is in fact a tipless cantilever previously designed for atomic force microscopy applications. We describe vision techniques employed to process images provided by an optical microscope, allowing to position accurately the end-effector for a gripping task. A theoretical study of the direct force measurement device and an experimental validation show how we can improve the measurement of impact and contact forces. Then we explain the strategy used to bring the gripper into contact with the object, based on force control and kinematic redundancy. Finally, a simplified model of the release task is proposed in order to determine conditions that allow to roll the object, and then to place it with precision. --- paper_title: Quadrilateral Modelling and Robust Control of a Nonlinear Piezoelectric Cantilever paper_content: Piezocantilevers are commonly used for the actuation of micromechatronic systems. These systems are generally used to perform micromanipulation tasks which require high positioning accuracy. However, the nonlinearities, i.e., the hysteresis and the creep, of piezoelectric materials and the influence of the environment (vibrations, temperature change, etc.) create difficulties for such a performance to be achieved. Various models have been used to take into account the nonlinearities but they are often complex. In this paper, we study a one degree of freedom piezoelectric cantilever. For that, we propose a simple new model where the hysteresis curve is approximated by a quadrilateral and the creep is considered to be a disturbance. To facilitate the modelling, we first demonstrate that the dynamic hysteresis of the piezocantilever is equivalent to a static hysteresis, i.e., a varying gain, in series with a linear dynamic part. The obtained model is used to synthesize a linear robust controller, making it possible to achieve the performances required in micromanipulation tasks. The experimental results show the relevance of the combination of the developed model and the synthesized robust H infin controller. --- paper_title: Optical tweezers: the next generation paper_content: JOHANNES Kepler is famous for discovering the laws of planetary motion, but he is less well known for writing what may have been the first science-fiction story to involve space travel. During his observations, the German astronomer noticed that tails of comets always point away from the Sun, which suggested that the Sun was exerting a sort of radiant pressure. This led him in 1609 – the year in which he published the first of his laws – to propose sailing from the Earth to the Moon on light itself. Of course, that was and still is the stuff of science fiction, but 400 years later Kepler's initial ideas about moving matter with light are very much a reality. --- paper_title: Force feedback-based microinstrument for measuring tissue properties and pulse in microsurgery paper_content: Miniaturized and "smart" instruments capable of characterizing the mechanical properties of tiny biological tissues are needed for research in biology, physiology and biomechanics, and can find very important clinical applications for diagnostics and minimally invasive surgery (MIS). We are developing a set of robotic microinstruments designed to augment the performance of the surgeon during MIS. These microtools are intended to restore (or even enhance) the finger palpation capabilities that the surgeon exploits to characterize tissue hardness and to measure pulsating vessels in traditional surgery, but that are substantially reduced in MIS. The paper describes the main features and the performance of a prototype miniature robotic instrument consisting of a microfabricated microgripper, instrumented with semiconductor strain-gauges as force sensors. For the (in vitro) experiments reported in the paper, the microgripper is mounted on a workstation and teleoperated. A haptic interface provides force feedback to the operator. We have demonstrated that the system can discriminate tiny skin samples based on their different elastic properties, and feel microvessels based on pulsating fluid flowing through them. --- paper_title: Magnetic separation techniques: their application to medicine paper_content: Whilst separation techniques relying on gravitational forces have become relatively sophisticated in their application to biology the same is not true for magnetic separation procedures. The use of the latter has been limited to the few cells which contain paramagnetic iron. However with the development of several different types of magnetic particles and selective delivery system (e.g. monoclonal antibodies) the use of magnetic separation techniques is growing rapidly. This review describes the different types of particles currently available, the magnetic separation technique applied to the different magnetic compounds and illustrates major uses to which magnetic separation procedures are currently applied in the area of biology and medicine. --- paper_title: Vacuum tool for handling microobjects with a NanoRobot paper_content: One of the basic tasks a robot has to perform is to manipulate objects. For macroscopic applications mechanical grippers usually grasp the workpiece. Because of the different scaling of gravity and adhesion such tools are no more suitable in micro manipulation. A better strategy is to use adhesion forces or vacuum. Therefore, after a brief introduction to adhesion phenomenons this paper focuses on the investigation of a vacuum gripping tool consisting of a glass pipette and a computer controlled vacuum supply. Special emphasis is laid on the optimization of the tool's parameters in order to improve its pick and place capability. The tool has been integrated into the ETHZ NanoRobot and tested on dedicated benchmark test. It was possible to grip 100 /spl mu/m sized diamond crystals and deposit them at arbitrary positions. Also emergency routines that allow to reliably get rid of sticking particles are presented. Finally the new setup of the multi-tool NanoRobot containing both the vacuum pipette and a microfabricated gripper is presented. It enables handling of micro-parts with more flexibility by working hand in hand. --- paper_title: Modeling the trajectory of a microparticle in a dielectrophoresis device paper_content: Micro- and nanoparticles can be trapped by a nonuniform electric field through the effect of the dielectrophoretic principle. Dielectrophoresis (DEP) is used to separate, manipulate, and detect microparticles in several domains, such as in biological or carbon nanotube manipulations. Current methods to simulate the trajectory of microparticles under a DEP force field are based on finite element model (FEM), which requires new simulations when electrode potential is changed, or on analytic equations limited to very simple geometries. In this paper, we propose a hybrid method, between analytic and numeric calculations and able to simulate complex geometries and to easily change the electrode potential along the trajectory. A small number of FEM simulations are used to create a database, which enables online calculation of the object trajectory as a function of electrode potentials. --- paper_title: Overview of Microgrippers and Design of a Micromanipulation Station Based on a MMOC Microgripper paper_content: This paper deals with an overview of recent microgrippers. As the end-effectors of micromanipulation systems, microgrippers are crucial point of such systems for their efficiency and their reliability. The performances of current microgrippers are presented and offer a stroke extending from 50mum to approximately 2 mm and a maximum forces varying from 0.1 mN to 600 mN. Then, micromanipulation system based on a piezoelectric microgripper and a SCARA robot is presented --- paper_title: Resource Letter: LBOT-1: Laser-based optical tweezers. paper_content: This Resource Letter provides a guide to the literature on optical tweezers, also known as laser-based, gradient-force optical traps. Journal articles and books are cited for the following main topics: general papers on optical tweezers, trapping instrument design, optical detection methods, optical trapping theory, mechanical measurements, single molecule studies, and sections on biological motors, cellular measurements and additional applications of optical tweezers. --- paper_title: Improvement of Strain Gauges Microforces Measurement using Kalman Optimal Filtering paper_content: Manipulation of small components and assembly of microsystems require force measurement. In the microworld (the world of very small components), signal/noise ratio is very low due to the weak amplitude of the signals. To be used in feedback control or in a micromanipulation system, a force sensor must allow static and dynamic measurements. In this paper, we present a micro-force measurement system based on the use of strain gauges and a Kalman optimal filter. Using a model of the measurement system and a statistical description of the noise, the optimal filter allows filtering the noise without loss of dynamic measurement. The performances of the measurement system are improved and fast force variations can be measured. --- paper_title: Squeeze film air bearings using piezoelectric bending elements paper_content: Reference LSA-CONF-2000-016 Conference Web Site: http://server.woomeranet.com.au/~movic2000/default.html Record created on 2006-12-07, modified on 2016-08-08 --- paper_title: A micro-particle positioning technique combining an ultrasonic manipulator and a microgripper paper_content: The acoustic radiation force acts on particles suspended in a fluid in which acoustic waves are present. It can be used to establish a force field throughout the fluid volume capable of positioning the particles in predictable locations. Here, a device is developed which positions the particles in a single line by the sequential use of two excitation frequencies which have been identified by a finite element model of the system. The device is designed such that at one end there is an opening which allows the fingers of a microgripper to enter the fluid chamber. Hence the gripper can be used to remove the last particle in the line. The high accuracy of the positioning of the particles prior to gripping means that the microgripper needs just to return to a fixed position in order to remove subsequent particles. Furthermore, the effects of the microgripper fingers entering the fluid volume whilst the ultrasound field is excited are examined. One result being the release of a particle stuck to a gripper finger. It is believed that this combination of techniques allows for considerable scope in the automation of microgripping procedures. --- paper_title: Design, fabrication, and testing of a 3-DOF HARM micromanipulator on (1 1 1) silicon substrate paper_content: In this study, a novel HARM (high aspect ratio micromachining) micromanipulator fabricated on (1 1 1) silicon wafer is reported. The micromanipulator consists of a positioning stage, a robot arm, supporting platforms, conducting wires, and bonding pads. These components are monolithically integrated on a chip through the presented processes. The three-degrees-of-freedom (3-DOF) positioning of the micromanipulator is realized by using the integration of two linear comb actuators and a vertical comb actuator. The robot arm is used to manipulate samples with dimension in the order of several microns to several hundred microns, for instance, optical fibers and biological samples. The robot arm could be a gripper, a needle, a probe, or even a pipette. Since the micromanipulator is made of single crystal silicon, it has superior mechanical properties. A micro gripper has also been successfully designed and fabricated. © 2005 Published by Elsevier B.V. --- paper_title: Development of a tactile low-cost microgripper with integrated force sensor paper_content: This paper describes recent results of the development of a novel tactile force-sensing microgripper based on a flexure hinge fabricated in stainless steel by wired electro discharge machining (EDM). The gripper was equipped with a commercial semiconductor strain-gauge and a piezo stack. The microgripper is an end-effector of a microrobot developed to grasp and manipulate tiny objects. Acquiring force-information with the microgripper is of fundamental importance in order to achieve the dexterity and sensing capabilities required to perform micromanipulation or assembly tasks. --- paper_title: Capillary self-alignment assisted hybrid robotic handling for ultra-thin die stacking paper_content: Ultra-thin dies are difficult to package because of their fragility and flexibility. Current ultra-thin die integration technology for 3D microsystems relies on robotic pick-and-place machines and machine vision, which has rather limited throughput for high-accuracy assembly of fragile ultra-thin dies. In this paper, we report a hybrid assembly strategy that consists of robotic pick-and-place using a vacuum micro-gripper, and droplet self-alignment by capillary force. Ultra-thin dies with breakable links are chosen as part of the assembly strategy. Experimental results show that we can align ultra-thin (10μm) dies with sub-micron accuracy without machine vision. A fully automatic sequence of stacking several of these dies is demonstrated. Up to 12 ultra-thin dies have been stacked. These early results show that die-to-die integration of ultra-thin dies with higher throughput than the current industry robot is possible by applying both robotic handling and droplet self-alignment to ultra-thin die assembly. --- paper_title: A hybrid-type electrostatically driven microgripper with an integrated vacuum tool paper_content: Abstract Reliable and accurate pick and release of microobjects is a long-standing challenge at the microscale manipulation field. This paper presents a new hybrid type of microelectromechanical systems (MEMS) microgripper integrated with an electrostatic mechanism and vacuum technology to achieve a reliable and accurate manipulation of microobjects. The microgripper is fabricated by a surface and bulk micromachining technology. Vacuum pipelines are constructed by bonding technique. The pick and release micromanipulation of microobjects is accomplished by electrostatic driving force caused by comb structure and an auxiliary air pressure force from air pump. A deflection of 25 μm at the tip of the gripper is achieved with the applied voltage of 80 V. The performance of this new hybrid type of microgripper was experimentally demonstrated through the manipulation of 100–200 μm polystyrene balls. Experimental results show that this microgripper can successfully fulfil the pick and release micromanipulation. Theoretical analyses were conducted to have a more comprehensive understanding of the release principle. Based on this paper, the new kind of hybrid microgripper will possibly provide an effective solution to the manipulation of submicrometer-sized objects. --- paper_title: Haptic Teleoperation for 3-D Microassembly of Spherical Objects paper_content: In this paper, teleoperated 3-D microassembly of spherical objects with haptic feedback is presented. A dual-tip gripper controlled through a haptic interface is used to pick-and-place microspheres (diameter: 4-6 μm). The proposed approach to align the gripper with the spheres is based on a user-driven exploration of the object to be manipulated. The haptic feedback is based on amplitude measurements from cantilevers in dynamic mode. That is, the operator perceives the contact while freely exploring the manipulation area. The data recorded during this exploration are processed online and generate a virtual guide to pull the user to the optimum contact point, allowing correct positioning of the dual tips. A preliminary scan is not necessary to compute the haptic feedback, which increases the intuitiveness of our system. For the pick-and-place operation, two haptic feedback schemes are proposed to either provide users with information about microscale interactions occurring during the operation, or to assist them while performing the task. As experimental validation, a two-layer pyramid composed of four microspheres is built in ambient conditions. --- paper_title: Noise characterization in millimeter sized micromanipulation systems paper_content: Abstract Efficient and dexterous manipulation of very small (micrometer and millimeter sized) objects require the use of high precision micromanipulation systems. The accuracy of the positioning is nevertheless limited by the noise due to vibrations of the end effectors making it difficult to achieve precise micrometer and nanometer displacements to grip small objects. The purpose of this paper is to analyze the sources of noise and to take it into account in dynamic models of micromanipulation systems. Environmental noise is studied considering the following sources of noise: ground motion and acoustic noises. Each source of noise is characterized in different environmental conditions and a separate description of their effects is investigated on micromanipulation systems using millimeter sized cantilevers as end effectors. Then, using the finite difference method (FDM), a dynamic model taking into account studied noises is used. Ground motion is described as a disturbance transmitted by the clamping to the tip of the cantilever and acoustic noises as external uniform and orthogonal waves. For model validation, an experimental setup including cantilevers of different lengths is designed and a high resolution laser interferometer is used for vibration measurements. Results show that the model allows a physical interpretation about the sources of noise and vibrations in millimeter sized micromanipulation systems leading to new perspectives for high positioning accuracy in robotics micromanipulation through active noise control. --- paper_title: Manipulation at the NanoNewton level: Micrograpsing for mechanical characterization of biomaterials paper_content: This paper presents the use of a monolithic, force-feedback MEMS (microelectomechanical systems) microgripper for characterizing both elastic and viscoelastic properties of highly deformable hydrogel microcapsules (15–25µm) at wet state during micromanipulation. The single-chip microgripper integrates an electrothermal microactuator and two capacitive force sensors, one for contact detection (force resolution: 38.5nN) and the other for gripping force measurements (force resolution: 19.9nN). Through nanoNewton force measurements, closed-loop force control, and visual tracking, the system quantified Young's modulus values and viscoelastic parameters of alginate microcapsules, demonstrating an easy-to-operate, accurate compression testing technique for characterizing soft, micrometer-sized biomaterials. --- paper_title: Automated nanohandling by microrobots paper_content: The rapid development of nanotechnology has created a need for advanced nanohandling tools and techniques. One active branch of research in this area focuses on the use of microrobots for automated handling of micro- and nanoscale objects. Automated Nanohandling by Microrobots presents work on the development of a versatile microrobot-based nanohandling robot station inside a scanning electron microscope (SEM). The SEM serves as a powerful vision sensor, providing a high resolution and a high depth of focus, allowing different fields of application to be opened up. The pre-conditions for using a SEM are high-precision, user-friendly microrobots which can be integrated into the SEM chamber and equipped with application-specific tools. Automated Nanohandling by Microrobots introduces an actuation principle for such microrobots and presents a new robot design. Different aspects of this research field regarding the hardware and software implementation of the system components, including the sensory feedback for automated nanohandling, are discussed in detail. Extensive applications of the microrobot station for nanohandling, nano-characterization and nanostructuring are provided, together with the experimental results. Based upon the Microrobotics course for students of computer sciences and physics at the University of Oldenburg, Automated Nanohandling by Microrobots provides the practicing engineer and the engineering student with an introduction to the design and applications of robot-based nanohandling devices. Those unfamiliar with the subject will find the text, which is complemented throughout by the extensive use of illustrations, clear and simple to understand. --- paper_title: Microrobotic cell injection paper_content: Advances in microbiology demonstrate the need for manipulating individual biological cells, such as for cell injection which includes pronuclei injection and intracytoplasmic injection. Conventionally, cell injection has been conducted manually. In this paper, we present a microrobotic system capable of performing automatic embryo pronuclei DNA injection autonomously and semi-autonomously through a hybrid visual servoing control scheme. After injection, the DNA injected embryos were transferred into a pseudopregnant foster female mouse to reproduce transgenic mice for cancer studies. Experimental results show that the injection success rate was 100%. The system setup, hybrid control scheme and other important issues in this application, such as automatic focusing, are discussed. --- paper_title: NanoLab: A nanorobotic system for automated pick-and-place handling and characterization of CNTs paper_content: Carbon nanotubes (CNTs) are one of the most promising materials for nanoelectronic applications. Before bringing CNTs into large-scale production, a reliable nanorobotic system for automated handling and characterization as well as prototyping of CNT-based components is essential. This paper presents the NanoLab setup, a nanorobotic system that combines specially developed key components such as electrothermal microgrippers and mobile microrobots inside a scanning electron microscope. The working principle and fabrication of mobile microrobots and electrothermal microgripper as well as their interaction and integration is described. Furthermore, the NanoLab is used to explore novel key strategies such as automated locating of CNTs for pick-and-place handling and methods for electrical characterization of CNTs. The results have been achieved within the framework of a European research project where the scientific knowledge will be transfered into an industrial system that will be commercially available for potential customers. --- paper_title: Improvement of Strain Gauges Microforces Measurement using Kalman Optimal Filtering paper_content: Manipulation of small components and assembly of microsystems require force measurement. In the microworld (the world of very small components), signal/noise ratio is very low due to the weak amplitude of the signals. To be used in feedback control or in a micromanipulation system, a force sensor must allow static and dynamic measurements. In this paper, we present a micro-force measurement system based on the use of strain gauges and a Kalman optimal filter. Using a model of the measurement system and a statistical description of the noise, the optimal filter allows filtering the noise without loss of dynamic measurement. The performances of the measurement system are improved and fast force variations can be measured. --- paper_title: Automated nanohandling by microrobots paper_content: The rapid development of nanotechnology has created a need for advanced nanohandling tools and techniques. One active branch of research in this area focuses on the use of microrobots for automated handling of micro- and nanoscale objects. Automated Nanohandling by Microrobots presents work on the development of a versatile microrobot-based nanohandling robot station inside a scanning electron microscope (SEM). The SEM serves as a powerful vision sensor, providing a high resolution and a high depth of focus, allowing different fields of application to be opened up. The pre-conditions for using a SEM are high-precision, user-friendly microrobots which can be integrated into the SEM chamber and equipped with application-specific tools. Automated Nanohandling by Microrobots introduces an actuation principle for such microrobots and presents a new robot design. Different aspects of this research field regarding the hardware and software implementation of the system components, including the sensory feedback for automated nanohandling, are discussed in detail. Extensive applications of the microrobot station for nanohandling, nano-characterization and nanostructuring are provided, together with the experimental results. Based upon the Microrobotics course for students of computer sciences and physics at the University of Oldenburg, Automated Nanohandling by Microrobots provides the practicing engineer and the engineering student with an introduction to the design and applications of robot-based nanohandling devices. Those unfamiliar with the subject will find the text, which is complemented throughout by the extensive use of illustrations, clear and simple to understand. --- paper_title: Development of a piezoelectric polymer-based sensorized microgripper for microassembly and micromanipulation paper_content: This paper presents the design, fabrication, and calibration of a piezoelectric polymer-based sensorized microgripper. Electro discharge machining technology is employed to fabricate the superelastic alloy-based microgripper. It was experimentally tested to show the improvement of mechanical performance. For integration of force sensor in the microgripper, the sensor design based on the piezoelectric polymer PVDF film and fabrication process are presented. The calibration and performance test of the force sensor-integrated microgripper are experimentally carried out. The force sensor-integrated microgripper is applied to fine alignment tasks of micro opto-electrical components. Experimental results show that it can successfully provide force feedback to the operator through the haptic device and play a main role in preventing damage of assembly parts by adjusting the teaching command. --- paper_title: Manipulation at the NanoNewton level: Micrograpsing for mechanical characterization of biomaterials paper_content: This paper presents the use of a monolithic, force-feedback MEMS (microelectomechanical systems) microgripper for characterizing both elastic and viscoelastic properties of highly deformable hydrogel microcapsules (15–25µm) at wet state during micromanipulation. The single-chip microgripper integrates an electrothermal microactuator and two capacitive force sensors, one for contact detection (force resolution: 38.5nN) and the other for gripping force measurements (force resolution: 19.9nN). Through nanoNewton force measurements, closed-loop force control, and visual tracking, the system quantified Young's modulus values and viscoelastic parameters of alginate microcapsules, demonstrating an easy-to-operate, accurate compression testing technique for characterizing soft, micrometer-sized biomaterials. --- paper_title: Three-dimensional automated micromanipulation using a nanotip gripper with multi-feedback paper_content: In this paper, three-dimensional (3D) automated micromanipulation at the scale of several micrometers using a nanotip gripper with multi-feedback is presented. The gripper is constructed from protrudent tips of two individually actuated atomic force microscope cantilevers; each cantilever is equipped with an optical lever. A manipulation protocol allows these two cantilevers to form a gripper to pick and place micro-objects without adhesive-force obstacles in air. For grasping, amplitude feedback from the dithering cantilever with its normal resonant frequency is used to search a grasping point by laterally scanning the side of the microspheres. Real-time force sensing is available for monitoring the whole pick-and-place process with pick-up, transport and release steps. For trajectory planning, an algorithm based on the shortest path solution is used to obtained 3D micropatterns with high levels of efficiency. In experiments, 20 microspheres with diameters from 3 µm to 4 µm were manipulated and 5 3D micropyramids with two layers were built. Three-dimensional micromanipulation and microassembly at the scale of several microns to the submicron scale could become feasible through the newly developed 3D micromanipulation system with a nanotip gripper. --- paper_title: Vision-based force measurement paper_content: This paper demonstrates a method to visually measure the force distribution applied to a linearly elastic object using the contour data in an image. The force measurement is accomplished by making use of the result from linear elasticity that the displacement field of the contour of a linearly elastic object is sufficient to completely recover the force distribution applied to the object. This result leads naturally to a deformable template matching approach where the template is deformed according to the governing equations of linear elasticity. An energy minimization method is used to match the template to the contour data in the image. This technique of visually measuring forces we refer to as vision-based force measurement (VBFM). VBFM has the potential to increase the robustness and reliability of micromanipulation and biomanipulation tasks where force sensing is essential for success. The effectiveness of VBFM is demonstrated for both a microcantilever beam and a microgripper. A sensor resolution of less than +/-3 nN for the microcantilever and +/-3 mN for the microgripper was achieved using VBFM. Performance optimizations for the energy minimization problem are also discussed that make this algorithm feasible for real-time applications. --- paper_title: Force Sensing and Control in Micromanipulation paper_content: In micromanipulation, the size of the manipulated object is usually much less than 1 mm in a single dimension, in which case gravitational and inertial forces are no longer dominant. This leads to problems (for manipulation through force) that are not evident in the macroworld, and for which the macroworld techniques alone may not be adequate to provide solutions. This paper surveys critical issues and their available solutions related to force control in micromanipulation. It focuses on: 1) techniques for dealing with adhesion forces and 2) methods for force sensing and control --- paper_title: Improvement of Strain Gauges Microforces Measurement using Kalman Optimal Filtering paper_content: Manipulation of small components and assembly of microsystems require force measurement. In the microworld (the world of very small components), signal/noise ratio is very low due to the weak amplitude of the signals. To be used in feedback control or in a micromanipulation system, a force sensor must allow static and dynamic measurements. In this paper, we present a micro-force measurement system based on the use of strain gauges and a Kalman optimal filter. Using a model of the measurement system and a statistical description of the noise, the optimal filter allows filtering the noise without loss of dynamic measurement. The performances of the measurement system are improved and fast force variations can be measured. --- paper_title: PI force control of a microgripper for assembling biomedical microdevices paper_content: Recent work is presented on the control of a microgripper based on flexure joints, fabricated by LIGA and instrumented with force sensors. The force sensors are semiconductor strain gauges which have been integrated in the microgripper and experimentally characterised. The microgripper is the core component of a workstation developed to grasp and manipulate tiny objects, such as components of biomedical microdevices. A proportional integral (PI) force control of the microgripper has been implemented. The results of the tracking experiments prove that this control algorithm can assure performance suitable for the intended applications. --- paper_title: Force feedback-based microinstrument for measuring tissue properties and pulse in microsurgery paper_content: Miniaturized and "smart" instruments capable of characterizing the mechanical properties of tiny biological tissues are needed for research in biology, physiology and biomechanics, and can find very important clinical applications for diagnostics and minimally invasive surgery (MIS). We are developing a set of robotic microinstruments designed to augment the performance of the surgeon during MIS. These microtools are intended to restore (or even enhance) the finger palpation capabilities that the surgeon exploits to characterize tissue hardness and to measure pulsating vessels in traditional surgery, but that are substantially reduced in MIS. The paper describes the main features and the performance of a prototype miniature robotic instrument consisting of a microfabricated microgripper, instrumented with semiconductor strain-gauges as force sensors. For the (in vitro) experiments reported in the paper, the microgripper is mounted on a workstation and teleoperated. A haptic interface provides force feedback to the operator. We have demonstrated that the system can discriminate tiny skin samples based on their different elastic properties, and feel microvessels based on pulsating fluid flowing through them. --- paper_title: Integrated microendeffector for micromanipulation paper_content: Micromanipulation is needed for assembly and maintenance of micromachines and their parts. If the handled objects are miniaturized, interactive forces, such as the van der Waals force, surface tension force, and electrostatic force between microobjects and gripper surface become dominant in the air, and they act as adhesive forces. We cannot neglect such adhesive forces in micromanipulation. Considering the physical phenomena in the microworld, we propose reduction methods for adhesive forces. Surface roughness of the endeffector surface is effective to reduce the van der Waals force. We propose making the micropyramids on the endeffector surface by micromachining techniques. We designed and made a prototype of the microgripper with a microendeffector, the gripping surface of which is formed to have several micropyramids. Experimental results show effectiveness of the micropyramids for reduction of the adhesive force. We also made a semiconductor strain gauge at the end of the microendeffector for grasping force measurement. Both micropyramids and integrated piezoresistive force sensor are fabricated on the microendeffector by the micromachining techniques. Performance of this force sensor is shown. --- paper_title: Towards a force-controlled microgripper for assembling biomedical microdevices paper_content: This paper presents recent results on the development and control of a microgripper based on flexure joints, fabricated by LIGA and instrumented with semiconductor strain-gauge force sensors. The microgripper is the end-effector of a workstation developed to grasp and manipulate tiny objects such as the components of a typical biomedical microdevice. The development of the force control in the microgripper is of fundamental importance in order to achieve the dexterity and sensing capabilities required to perform assembly tasks for biomedical microdevices. As a step towards the definition of the force control strategy, system identification techniques have been used to model the microgripper. Results indicate that a proportional integral (PI) controller could be used to assure, at the same time, closed-loop stability of the system, and a bandwidth suitable for the intended applications. The force control is based on strain-gauge sensors which have been integrated in the microgripper and experimentally characterized. Sensor response in the idling condition and during grasp showed that they can provide useful information for force control of the microgripper. --- paper_title: A flexure-based gripper for small-scale manipulation paper_content: A small-scale flexure-based gripper was designed for manipulation tasks requiring precision position and force control. The gripper is actuated by a piezoelectric ceramic stack actuator and utilizes strain gages to measure both the gripping force and displacement. The position and force bandwidths were designed for ten Hertz and one hundred Hertz, respectively, in order to afford human-based teleoperative transparency. The gripper serves effectively as a one degree-of-freedom investigation of compliant mechanism design for position and force controlled micromanipulation. Data is presented that characterizes the microgripper performance under both pure position and pure force control, followed by a discussion of the attributes and limitations of flexure-based design. --- paper_title: Vision-based force measurement paper_content: This paper demonstrates a method to visually measure the force distribution applied to a linearly elastic object using the contour data in an image. The force measurement is accomplished by making use of the result from linear elasticity that the displacement field of the contour of a linearly elastic object is sufficient to completely recover the force distribution applied to the object. This result leads naturally to a deformable template matching approach where the template is deformed according to the governing equations of linear elasticity. An energy minimization method is used to match the template to the contour data in the image. This technique of visually measuring forces we refer to as vision-based force measurement (VBFM). VBFM has the potential to increase the robustness and reliability of micromanipulation and biomanipulation tasks where force sensing is essential for success. The effectiveness of VBFM is demonstrated for both a microcantilever beam and a microgripper. A sensor resolution of less than +/-3 nN for the microcantilever and +/-3 mN for the microgripper was achieved using VBFM. Performance optimizations for the energy minimization problem are also discussed that make this algorithm feasible for real-time applications. --- paper_title: The effect of material properties and gripping force on micrograsping paper_content: This paper presents our work in developing a force controlled microgripper and micrograsping strategies using optical beam deflection techniques. The optical beam deflection sensor is based on modified atomic force microscopy techniques and is able to resolve forces below a nano-Newton. A variety of gripper fingers made from materials with different conductivity and surface roughness is analyzed theoretically and experimentally using the force sensor. These results provide insight into the mechanics of micromanipulation, and the results are used to develop micrograsping strategies. A design of a microfabricated force controlled microgripper is presented along with initial experimental results in applying various gripping forces to microparts. The results demonstrate the important role gripping force plays in the grasping and releasing of microparts. --- paper_title: Vision-based sensing of forces in elastic objects paper_content: Abstract A minimally intrusive, vision-based, computational force sensor for elastically deformable objects is proposed in this paper. Estimating forces from the visually measured displacements is straightforward in the case of the linear problem of small displacements, but not in the case of the large displacements where geometric non-linearities must be taken into account. From the images of the object taken before and after the deformation, we compute the deformation gradients and logarithmic strains. Using the stress–strain relationships for the material, we compute the Cauchy’s stresses and from this we estimate the locations and magnitudes of the external forces that caused the deformation. A sensitivity analysis is performed to examine the effect of small deviations in the experimentally captured displacements on the estimated external forces. This analysis showed that the small-strain case is more sensitive and prone to numerical errors than the large-strain case. Additionally, a related method that is indirect and iterative is also presented in which we assume that we know the locations of the external forces. Numerical and experimental studies are presented for both micro- and macro-scale objects. The main conclusion of this work is that the vision-based force estimation is viable if the displacements of the deforming object can be captured accurately. --- paper_title: Current integration force and displacement self-sensing method for cantilevered piezoelectric actuators paper_content: This paper presents a new method of self-sensing both of the displacement and the external applied force at the tip of piezoelectric cantilevers. Integrated electric current across piezoelectric actuators is compensated against material nonlinearities (creep, hysteresis) to provide reliable information. We propose to compensate the hysteresis by using the Prandtl-Ishlinskii static approach while an auto regressive and moving average exogenous (ARMAX) model is used to minimize the creep influence. The quasistatic estimation, electronic circuit, and aspects related to long-term charge preservations are described or referenced. As an experiment, we tested the actuator entering in contact with a fixed force sensor. An input signal of 20 V peak-to-peak (10% of maximum range) led to force self-sensing errors inferior to +/-8%. A final discussion about method accuracy and its limitations is made. --- paper_title: Towards a force-controlled microgripper for assembling biomedical microdevices paper_content: This paper presents recent results on the development and control of a microgripper based on flexure joints, fabricated by LIGA and instrumented with semiconductor strain-gauge force sensors. The microgripper is the end-effector of a workstation developed to grasp and manipulate tiny objects such as the components of a typical biomedical microdevice. The development of the force control in the microgripper is of fundamental importance in order to achieve the dexterity and sensing capabilities required to perform assembly tasks for biomedical microdevices. As a step towards the definition of the force control strategy, system identification techniques have been used to model the microgripper. Results indicate that a proportional integral (PI) controller could be used to assure, at the same time, closed-loop stability of the system, and a bandwidth suitable for the intended applications. The force control is based on strain-gauge sensors which have been integrated in the microgripper and experimentally characterized. Sensor response in the idling condition and during grasp showed that they can provide useful information for force control of the microgripper. --- paper_title: Automatic dextrous microhandling based on a 6-DOF microgripper paper_content: The demand for automatic quality inspection of individual micro-components has increased strongly in the micro-optoelectronics industry. In many cases, quality inspection of those micro-components needs dexterous microhandling. However, automatic dexterous handling of microcomponents is a very challenging issue which is barely explored. This paper presents a high-DOF (degrees of freedom) automatic dexterous handling and inspection system for micro-optoelectronic components using a novel 6-DOF piezoelectric microgripper. The control system includes three hierarchical layers: an actuator control layer, a motion planning layer and a mission control layer. Machine vision is applied in automatic manipulation. The performance of the system is demonstrated in a vision-based automatic inspection task for 300 × 300 × 100- μ m-sized optoelectronics components and reached a cycle time of 7.1 ± 0.3 s. --- paper_title: Development of a tactile low-cost microgripper with integrated force sensor paper_content: This paper describes recent results of the development of a novel tactile force-sensing microgripper based on a flexure hinge fabricated in stainless steel by wired electro discharge machining (EDM). The gripper was equipped with a commercial semiconductor strain-gauge and a piezo stack. The microgripper is an end-effector of a microrobot developed to grasp and manipulate tiny objects. Acquiring force-information with the microgripper is of fundamental importance in order to achieve the dexterity and sensing capabilities required to perform micromanipulation or assembly tasks. --- paper_title: Development of a piezoelectric polymer-based sensorized microgripper for microassembly and micromanipulation paper_content: This paper presents the design, fabrication, and calibration of a piezoelectric polymer-based sensorized microgripper. Electro discharge machining technology is employed to fabricate the superelastic alloy-based microgripper. It was experimentally tested to show the improvement of mechanical performance. For integration of force sensor in the microgripper, the sensor design based on the piezoelectric polymer PVDF film and fabrication process are presented. The calibration and performance test of the force sensor-integrated microgripper are experimentally carried out. The force sensor-integrated microgripper is applied to fine alignment tasks of micro opto-electrical components. Experimental results show that it can successfully provide force feedback to the operator through the haptic device and play a main role in preventing damage of assembly parts by adjusting the teaching command. --- paper_title: Manipulation at the NanoNewton level: Micrograpsing for mechanical characterization of biomaterials paper_content: This paper presents the use of a monolithic, force-feedback MEMS (microelectomechanical systems) microgripper for characterizing both elastic and viscoelastic properties of highly deformable hydrogel microcapsules (15–25µm) at wet state during micromanipulation. The single-chip microgripper integrates an electrothermal microactuator and two capacitive force sensors, one for contact detection (force resolution: 38.5nN) and the other for gripping force measurements (force resolution: 19.9nN). Through nanoNewton force measurements, closed-loop force control, and visual tracking, the system quantified Young's modulus values and viscoelastic parameters of alginate microcapsules, demonstrating an easy-to-operate, accurate compression testing technique for characterizing soft, micrometer-sized biomaterials. --- paper_title: Design, simulation and testing of electrostatic SOI MUMPs based microgripper integrated with capacitive contact sensor paper_content: Abstract In this paper a detailed modeling, simulations and testing of a novel electrostatically actuated microgripper integrated with capacitive contact sensor is presented. Microgripper is actuated with lateral comb drive system and transverse comb system is used to sense contact between micro-object and microgripper jaws. The design is optimized in standard SOI-MUMPs micromachining process using L-Edit of MEMS-Pro. Finite element analysis of microgripper is performed in COVENTOR-WARE which shows total displacement of 15.5 μm at the tip of jaws when voltage of 50 Vdc is applied at the actuator. Finite element analysis of sensor part is performed and results are compared with analytical model. Modal analysis is performed to investigate mode shapes and natural frequencies of the microgripper. Microgripper is tested experimentally and total displacement of 17 μm is achieved at the tip of microgripper. The slight difference between finite element analysis and experimental results is due to small variations in the material properties, deposited during the fabrication process. The change in capacitance of capacitive contact sensor is linearly calibrated with the change in the displacement. The sensitivity of contact sensor is 90 fF/μm. The total size of microgripper is 5.03 mm × 6.5 mm. --- paper_title: Monolithically Integrated Two-Axis Microtensile Tester for the Mechanical Characterization of Microscopic Samples paper_content: This paper describes the first monolithically integrated two-axis microtensile tester and its application to the automated stiffness measurement of single epidermal plant cells. The tensile tester consists of a two-axis electrostatic actuator with integrated capacitive position sensors and a two-axis capacitive microforce sensor. It is fabricated using a bulk silicon microfabrication process. The actuation range is +/-16 m along both axes with a position resolution of 20 nm. The force sensor is capable of measuring forces up to +/-60 N with a resolution down to 60 nN. The position-feedback sensors as well as the force sensor are calibrated by direct comparison with reference standards. A complete uncertainty analysis through the entire calibration chain based on the Monte Carlo method is presented. The functionality of the tensile tester is demonstrated by the automated stiffness measurement of the elongated cells in plant hairs (trichomes) as a function of their size. This enables a quantitative understanding and a model-based simulation of plant growth based on actual measurement data. --- paper_title: Design of a Micro-Gripper and an Ultrasonic Manipulator for Handling Micron Sized Objects paper_content: This work reports on a system consisting of a MEMS (microelectromechanical system) gripper and an ultrasonic manipulator. The gripper is electrostatically actuated and includes an integrated force sensor measuring the gripping force. The device is monolithically fabricated using a silicon-on-insulator (SOI) fabrication process. The resolution of the force sensor is in the sub-micronewton range and, therefore, provides feedback of the forces that dominate the micromanipulation processes. A MEMS ultrasonic device is described which aligns small objects such as biological cells prior to manipulation with the gripper. The concept is demonstrated with polymer spheres, glass spheres and Hela cancer cells, thus providing a useful tool in micro-robotics and biological research. --- paper_title: Automatic dextrous microhandling based on a 6-DOF microgripper paper_content: The demand for automatic quality inspection of individual micro-components has increased strongly in the micro-optoelectronics industry. In many cases, quality inspection of those micro-components needs dexterous microhandling. However, automatic dexterous handling of microcomponents is a very challenging issue which is barely explored. This paper presents a high-DOF (degrees of freedom) automatic dexterous handling and inspection system for micro-optoelectronic components using a novel 6-DOF piezoelectric microgripper. The control system includes three hierarchical layers: an actuator control layer, a motion planning layer and a mission control layer. Machine vision is applied in automatic manipulation. The performance of the system is demonstrated in a vision-based automatic inspection task for 300 × 300 × 100- μ m-sized optoelectronics components and reached a cycle time of 7.1 ± 0.3 s. --- paper_title: Development of a tactile low-cost microgripper with integrated force sensor paper_content: This paper describes recent results of the development of a novel tactile force-sensing microgripper based on a flexure hinge fabricated in stainless steel by wired electro discharge machining (EDM). The gripper was equipped with a commercial semiconductor strain-gauge and a piezo stack. The microgripper is an end-effector of a microrobot developed to grasp and manipulate tiny objects. Acquiring force-information with the microgripper is of fundamental importance in order to achieve the dexterity and sensing capabilities required to perform micromanipulation or assembly tasks. --- paper_title: Noise characterization in millimeter sized micromanipulation systems paper_content: Abstract Efficient and dexterous manipulation of very small (micrometer and millimeter sized) objects require the use of high precision micromanipulation systems. The accuracy of the positioning is nevertheless limited by the noise due to vibrations of the end effectors making it difficult to achieve precise micrometer and nanometer displacements to grip small objects. The purpose of this paper is to analyze the sources of noise and to take it into account in dynamic models of micromanipulation systems. Environmental noise is studied considering the following sources of noise: ground motion and acoustic noises. Each source of noise is characterized in different environmental conditions and a separate description of their effects is investigated on micromanipulation systems using millimeter sized cantilevers as end effectors. Then, using the finite difference method (FDM), a dynamic model taking into account studied noises is used. Ground motion is described as a disturbance transmitted by the clamping to the tip of the cantilever and acoustic noises as external uniform and orthogonal waves. For model validation, an experimental setup including cantilevers of different lengths is designed and a high resolution laser interferometer is used for vibration measurements. Results show that the model allows a physical interpretation about the sources of noise and vibrations in millimeter sized micromanipulation systems leading to new perspectives for high positioning accuracy in robotics micromanipulation through active noise control. --- paper_title: Monolithically Integrated Two-Axis Microtensile Tester for the Mechanical Characterization of Microscopic Samples paper_content: This paper describes the first monolithically integrated two-axis microtensile tester and its application to the automated stiffness measurement of single epidermal plant cells. The tensile tester consists of a two-axis electrostatic actuator with integrated capacitive position sensors and a two-axis capacitive microforce sensor. It is fabricated using a bulk silicon microfabrication process. The actuation range is +/-16 m along both axes with a position resolution of 20 nm. The force sensor is capable of measuring forces up to +/-60 N with a resolution down to 60 nN. The position-feedback sensors as well as the force sensor are calibrated by direct comparison with reference standards. A complete uncertainty analysis through the entire calibration chain based on the Monte Carlo method is presented. The functionality of the tensile tester is demonstrated by the automated stiffness measurement of the elongated cells in plant hairs (trichomes) as a function of their size. This enables a quantitative understanding and a model-based simulation of plant growth based on actual measurement data. --- paper_title: The effect of material properties and gripping force on micrograsping paper_content: This paper presents our work in developing a force controlled microgripper and micrograsping strategies using optical beam deflection techniques. The optical beam deflection sensor is based on modified atomic force microscopy techniques and is able to resolve forces below a nano-Newton. A variety of gripper fingers made from materials with different conductivity and surface roughness is analyzed theoretically and experimentally using the force sensor. These results provide insight into the mechanics of micromanipulation, and the results are used to develop micrograsping strategies. A design of a microfabricated force controlled microgripper is presented along with initial experimental results in applying various gripping forces to microparts. The results demonstrate the important role gripping force plays in the grasping and releasing of microparts. --- paper_title: Development of a tactile low-cost microgripper with integrated force sensor paper_content: This paper describes recent results of the development of a novel tactile force-sensing microgripper based on a flexure hinge fabricated in stainless steel by wired electro discharge machining (EDM). The gripper was equipped with a commercial semiconductor strain-gauge and a piezo stack. The microgripper is an end-effector of a microrobot developed to grasp and manipulate tiny objects. Acquiring force-information with the microgripper is of fundamental importance in order to achieve the dexterity and sensing capabilities required to perform micromanipulation or assembly tasks. --- paper_title: Noise characterization in millimeter sized micromanipulation systems paper_content: Abstract Efficient and dexterous manipulation of very small (micrometer and millimeter sized) objects require the use of high precision micromanipulation systems. The accuracy of the positioning is nevertheless limited by the noise due to vibrations of the end effectors making it difficult to achieve precise micrometer and nanometer displacements to grip small objects. The purpose of this paper is to analyze the sources of noise and to take it into account in dynamic models of micromanipulation systems. Environmental noise is studied considering the following sources of noise: ground motion and acoustic noises. Each source of noise is characterized in different environmental conditions and a separate description of their effects is investigated on micromanipulation systems using millimeter sized cantilevers as end effectors. Then, using the finite difference method (FDM), a dynamic model taking into account studied noises is used. Ground motion is described as a disturbance transmitted by the clamping to the tip of the cantilever and acoustic noises as external uniform and orthogonal waves. For model validation, an experimental setup including cantilevers of different lengths is designed and a high resolution laser interferometer is used for vibration measurements. Results show that the model allows a physical interpretation about the sources of noise and vibrations in millimeter sized micromanipulation systems leading to new perspectives for high positioning accuracy in robotics micromanipulation through active noise control. --- paper_title: Modeling the trajectory of a microparticle in a dielectrophoresis device paper_content: Micro- and nanoparticles can be trapped by a nonuniform electric field through the effect of the dielectrophoretic principle. Dielectrophoresis (DEP) is used to separate, manipulate, and detect microparticles in several domains, such as in biological or carbon nanotube manipulations. Current methods to simulate the trajectory of microparticles under a DEP force field are based on finite element model (FEM), which requires new simulations when electrode potential is changed, or on analytic equations limited to very simple geometries. In this paper, we propose a hybrid method, between analytic and numeric calculations and able to simulate complex geometries and to easily change the electrode potential along the trajectory. A small number of FEM simulations are used to create a database, which enables online calculation of the object trajectory as a function of electrode potentials. --- paper_title: Fusing force and vision feedback for micromanipulation paper_content: We present experimental results that investigate the integration of two disparate sensing modalities, force and vision, for sensor-based microassembly. By integrating these sensing modes, we are able to provide feedback in a task-oriented frame of reference over a broad range of motion with an extremely high precision. An optical microscope is used to provide visual feedback down to micron resolutions. We have developed an optical beam deflection sensor to provide nanonewton level force feedback or nanometric level position feedback. The value of integrating these two disparate sensing modalities is demonstrated during controlled micropart impact experiments. Using force feedback alone to control micropart contact transitions, impact forces of over 140 nN were generated before the desired contact force of 2 nN was achieved. When visual servoing is integrated with the force control framework, micropart impact forces of only 9 nN and final contact forces of 2 nN were easily achieved. --- paper_title: The effect of material properties and gripping force on micrograsping paper_content: This paper presents our work in developing a force controlled microgripper and micrograsping strategies using optical beam deflection techniques. The optical beam deflection sensor is based on modified atomic force microscopy techniques and is able to resolve forces below a nano-Newton. A variety of gripper fingers made from materials with different conductivity and surface roughness is analyzed theoretically and experimentally using the force sensor. These results provide insight into the mechanics of micromanipulation, and the results are used to develop micrograsping strategies. A design of a microfabricated force controlled microgripper is presented along with initial experimental results in applying various gripping forces to microparts. The results demonstrate the important role gripping force plays in the grasping and releasing of microparts. --- paper_title: Automatic dextrous microhandling based on a 6-DOF microgripper paper_content: The demand for automatic quality inspection of individual micro-components has increased strongly in the micro-optoelectronics industry. In many cases, quality inspection of those micro-components needs dexterous microhandling. However, automatic dexterous handling of microcomponents is a very challenging issue which is barely explored. This paper presents a high-DOF (degrees of freedom) automatic dexterous handling and inspection system for micro-optoelectronic components using a novel 6-DOF piezoelectric microgripper. The control system includes three hierarchical layers: an actuator control layer, a motion planning layer and a mission control layer. Machine vision is applied in automatic manipulation. The performance of the system is demonstrated in a vision-based automatic inspection task for 300 × 300 × 100- μ m-sized optoelectronics components and reached a cycle time of 7.1 ± 0.3 s. ---	Title: An Overview on Gripping Force Measurement at the Micro and Nano-Scales Using Two-Fingered Microrobotic Systems Section 1: Introduction Description 1: Introduce the topic of microrobotics and the importance of gripping force measurement at micro and nano scales using two-fingered microrobotic systems. Section 2: Force measurement Description 2: Discuss the range of gripping forces required for different applications and the importance of force measurement in microrobotics. Section 3: Piezoresistive force sensors Description 3: Explain the principle, advantages, and limitations of piezoresistive force sensors used in microrobotic applications. Section 4: Piezoelectric force sensors Description 4: Describe the piezoelectric force sensors, their working principle, and their suitability for dynamic force measurements. Section 5: Capacitive force sensors Description 5: Detail the capacitive force sensors, their construction, and the benefits they offer over other types of sensors. Section 6: Optical force sensors Description 6: Cover the use of optical force sensors in microrobotics, including the advantages and challenges associated with these sensors. Section 7: Force measurement by vision Description 7: Discuss the techniques of force measurement by vision, its high-resolution capabilities, and its applications in microrobotic manipulation tasks. Section 8: Discussion about force sensor resolution Description 8: Provide a discussion on the resolutions of different force sensors and the impact of environmental factors on these resolutions. Section 9: Two-fingered micromanipulation systems and force measurement at the micro-scale Description 9: Present a chronological overview of the development and application of two-fingered micromanipulation systems with embedded force sensors. Section 10: From 1992: the extensive use of strain gauges Description 10: Summarize early developments in microrobotics focusing on the use of strain gauges for force measurement in micromanipulation. Section 11: From 2000: Toward the measurement of forces at the nano-Newton scale by the use of external measurement systems Description 11: Explore advancements made in force measurement at the nano-Newton scale through the use of external systems before the development of embedded sensors. Section 12: From 2003: Toward embedded and high resolution force sensors Description 12: Discuss the drive towards embedding high-resolution force sensors within microrobots and the associated challenges. Section 13: From 2006: The use of MEMS-based microgrippers with embedded capacitive force sensors Description 13: Highlight significant advances made with MEMS-based microgrippers and capacitive force sensors for precise force measurement and control. Section 14: Discussion Description 14: Summarize the main characteristics, performance measures, and challenges of gripping force sensors in current microrobotic systems. Section 15: Conclusion Description 15: Recap the developments in gripping force measurement technologies and their applications in microrobotics. Section 16: Future trends Description 16: Outline potential future directions in the field of gripping force measurement at the micro and nano scales.
A survey of methods for time series change point detection	14	--- paper_title: Contrast and change mining paper_content: Because the world with its markets, innovations, and customers is changing faster than ever before, the key to survival for businesses is the ability to detect, assess, and respond to changing conditions timely and intelligently. Understanding changes and reacting to or acting upon them therefore become a strategic issue not only for companies but also in many other domains. The corresponding need for knowledge has been answered by data mining research by proposing a multitude of methods for analyzing different aspects of change. This article provides an overview of recent works on methods for change analysis, thereby focusing on contrast mining and change mining, the two emerging subfields of contemporary data mining research. © 2011 John Wiley & Sons, Inc. WIREs Data Mining Knowl Discov 2011 1 215–230 DOI: 10.1002/widm.27 --- paper_title: Boosting Classifiers for Drifting Concepts paper_content: In many real-world classification tasks, data arrives over time and the target concept to be learned from the data stream may change over time. Boosting methods are well-suited for learning from data streams, but do not address this concept drift problem. This paper proposes a boosting-like method to train a classifier ensemble from data streams that naturally adapts to concept drift. Moreover, it allows to quantify the drift in terms of its base learners. Similar as in regular boosting, examples are re-weighted to induce a diverse ensemble of base models. In order to handle drift, the proposed method continuously re-weights the ensemble members based on their performance on the most recent examples only. The proposed strategy adapts quickly to different kinds of concept drift. The algorithm is empirically shown to outperform learning algorithms that ignore concept drift. It performs no worse than advanced adaptive time window and example selection strategies that store all the data and are thus not suited for mining massive streams. The proposed algorithm has low computational costs. --- paper_title: Inertial hidden markov models: modeling change in multivariate time series paper_content: Faced with the problem of characterizing systematic changes in multivariate time series in an unsupervised manner, we derive and test two methods of regularizing hidden Markov models for this task. Regularization on state transitions provides smooth transitioning among states, such that the sequences are split into broad, contiguous segments. Our methods are compared with a recent hierarchical Dirichlet process hidden Markov model (HDP-HMM) and a baseline standard hidden Markov model, of which the former suffers from poor performance on moderate-dimensional data and sensitivity to parameter settings, while the latter suffers from rapid state transitioning, over-segmentation and poor performance on a segmentation task involving human activity accelerometer data from the UCI Repository. The regularized methods developed here are able to perfectly characterize change of behavior in the human activity data for roughly half of the real-data test cases, with accuracy of 94% and low variation of information. In contrast to the HDP-HMM, our methods provide simple, drop-in replacements for standard hidden Markov model update rules, allowing standard expectation maximization (EM) algorithms to be used for learning. --- paper_title: Unsupervised change analysis using supervised learning paper_content: We propose a formulation of a new problem, which we call change analysis, and a novel method for solving the problem. In contrast to the existing methods of change (or outlier) detection, the goal of change analysis goes beyond detecting whether or not any changes exist. Its ultimate goal is to find the explanation of the changes.While change analysis falls in the category of unsupervised learning in nature, we propose a novel approach based on supervised learning to achieve the goal. The key idea is to use a supervised classifier for interpreting the changes. A classifier should be able to discriminate between the two data sets if they actually come from two different data sources. In other words, we use a hypothetical label to train the supervised learner, and exploit the learner for interpreting the change. Experimental results using real data show the proposed approach is promising in change analysis as well as concept drift analysis. --- paper_title: Adaptive Change Detection in Heart Rate Trend Monitoring in Anesthetized Children paper_content: The proposed algorithm is designed to detect changes in the heart rate trend signal which fits the dynamic linear model description. Based on this model, the interpatient and intraoperative variations are handled by estimating the noise covariances via an adaptive Kalman filter. An exponentially weighted moving average predictor switches between two different forgetting coefficients to allow the historical data to have a varying influence in prediction. The cumulative sum testing of the residuals identifies the change points online. The algorithm was tested on a substantial volume of real clinical data. Comparison of the proposed algorithm with Trigg's approach revealed that the algorithm performs more favorably with a shorter delay. The receiver operating characteristic curve analysis indicates that the algorithm outperformed the change detection by clinicians in real time --- paper_title: Automatic change detection in multimodal serial MRI: application to multiple sclerosis lesion evolution paper_content: The automatic analysis of subtle changes between MRI scans is an important tool for assessing disease evolution over time. Manual labeling of evolutions in 3D data sets is tedious and error prone. Automatic change detection, however, remains a challenging image processing problem. A variety of MRI artifacts introduce a wide range of unrepresentative changes between images, making standard change detection methods unreliable. In this study we describe an automatic image processing system that addresses these issues. Registration errors and undesired anatomical deformations are compensated using a versatile multiresolution deformable image matching method that preserves significant changes at a given scale. A nonlinear intensity normalization method is associated with statistical hypothesis test methods to provide reliable change detection. Multimodal data is optionally exploited to reduce the false detection rate. The performance of the system was evaluated on a large database of 3D multimodal, MR images of patients suffering from relapsing remitting multiple sclerosis (MS). The method was assessed using receiver operating characteristics (ROC) analysis, and validated in a protocol involving two neurologists. The automatic system outperforms the human expert, detecting many lesion evolutions that are missed by the expert, including small, subtle changes. --- paper_title: Online Bayesian change point detection algorithms for segmentation of epileptic activity paper_content: Epilepsy is a dynamic disease in which the brain transitions between different states. In this paper, we focus on the problem of identifying the time points, referred to as change points, where the transitions between these different states happen. A Bayesian change point detection algorithm that does not require the knowledge of the total number of states or the parameters of the probability distribution modeling the activity of epileptic brain in each of these states is developed in this paper. This algorithm works in online mode making it amenable for real-time monitoring. To reduce the quadratic complexity of this algorithm, an approximate algorithm with linear complexity in the number of data points is also developed. Finally, we use these algorithms on ECoG recordings of an epileptic patient to locate the change points and determine segments corresponding to different brain states. --- paper_title: Change-Point Detection of Climate Time Series by Nonparametric Method paper_content: In one of the data mining techniques, change-point detection is of importance in evaluating time series measured in real world. For decades this technique has been developed as a nonlinear dynam- ics. We apply the method for detecting the change points, Singular Spectrum Transformation (SST), to the climate time series. To know where the struc- tures of climate data sets change can reveal a climate background. In this paper we discuss the structures of precipitation data in Kenya and Wrangel Island (Arctic land) by using the SST. --- paper_title: Comparison of techniques for detection of discontinuities in temperature series paper_content: Several techniques for the detection of discontinuities in temperature series are evaluated. Eight homogenization techniques were compared using simulated datasets reproducing a vast range of possible situations. The simulated data represent homogeneous series and series having one or more steps. Although the majority of the techniques considered in this study perform very well, two methods seem to work slightly better than the others: the standard normal homogeneity test without trend, and the multiple linear regression technique. Both methods are distinctive because of their sensitivity concerning homogeneous series and their ability to detect one or several steps properly within an inhomogeneous series. Copyright © 2003 Environment Canada. Published by John Wiley & Sons, Ltd. --- paper_title: Audio segmentation for speech recognition using segment features paper_content: Audio segmentation is an essential preprocessing step in several audio processing applications with a significant impact e.g. on speech recognition performance. We introduce a novel framework which combines the advantages of different well known segmentation methods. An automatically estimated log-linear segment model is used to determine the segmentation of an audio stream in a holistic way by a maximum a posteriori decoding strategy, instead of classifying change points locally. A comparison to other segmentation techniques in terms of speech recognition performance is presented, showing a promising segmentation quality of our approach. --- paper_title: Bayesian on-line spectral change point detection: a soft computing approach for on-line ASR paper_content: Current automatic speech recognition (ASR) works in off-line mode and needs prior knowledge of the stationary or quasi-stationary test conditions for expected word recognition accuracy. These requirements limit the application of ASR for real-world applications where test conditions are highly non-stationary and are not known a priori. This paper presents an innovative frame dynamic rapid adaptation and noise compensation technique for tracking highly non-stationary noises and its application for on-line ASR. The proposed algorithm is based on a soft computing model using Bayesian on-line inference for spectral change point detection (BOSCPD) in unknown non-stationary noises. BOSCPD is tested with the MCRA noise tracking technique for on-line rapid environmental change learning in different non-stationary noise scenarios. The test results show that the proposed BOSCPD technique reduces the delay in spectral change point detection significantly compared to the baseline MCRA and its derivatives. The proposed BOSCPD soft computing model is tested for joint additive and channel distortions compensation (JAC)-based on-line ASR in unknown test conditions using non-stationary noisy speech samples from the Aurora 2 speech database. The simulation results for the on-line AR show significant improvement in recognition accuracy compared to the baseline Aurora 2 distributed speech recognition (DSR) in batch-mode. --- paper_title: Image change detection algorithms: a systematic survey paper_content: Detecting regions of change in multiple images of the same scene taken at different times is of widespread interest due to a large number of applications in diverse disciplines, including remote sensing, surveillance, medical diagnosis and treatment, civil infrastructure, and underwater sensing. This paper presents a systematic survey of the common processing steps and core decision rules in modern change detection algorithms, including significance and hypothesis testing, predictive models, the shading model, and background modeling. We also discuss important preprocessing methods, approaches to enforcing the consistency of the change mask, and principles for evaluating and comparing the performance of change detection algorithms. It is hoped that our classification of algorithms into a relatively small number of categories will provide useful guidance to the algorithm designer. --- paper_title: Scalable Time Series Change Detection for Biomass Monitoring Using Gaussian Process. paper_content: Biomass monitoring, specifically, detecting changes in the biomass or vegetation of a geographical region, is vital for studying the carbon cycle of the system and has significant implications in the context of understanding climate change and its impacts. Recently, several time series change detection methods have been proposed to identify land cover changes in temporal profiles (time series) of vegetation collected using remote sensing instruments. In this paper, we adapt Gaussian process regression to detect changes in such time series in an online fashion. While Gaussian process (GP) has been widely used as a kernel based learning method for regression and classification, their applicability to massive spatio-temporal data sets, such as remote sensing data, has been limited owing to the high computational costs involved. In our previous work we proposed an efficient Toeplitz matrix based solution for scalable GP parameter estimation. In this paper we apply these solutions to a GP based change detection algorithm. The proposed change detection algorithm requires a memory footprint which is linear in the length of the input time series and runs in time which is quadratic to the length of the input time series. Experimental results show that both serial and parallel implementations of our proposed method achieve significant speedups over the serial implementation. Finally, we demonstrate the effectiveness of the proposed change detection method in identifying changes in Normalized Difference Vegetation Index (NDVI) data. Increasing availability of high resolution remote sensing data has encouraged researchers to extract knowledge from these massive spatio-temporal data sets in order to solve different problems pertain- ing to our ecosystem. Land use land cover (LULC) monitoring, specifically identifying changes in land cover, is one such problem that has significant applications in detecting deforestation, crop ro- tation, urbanization, forest fires, and other such phenomenon. The knowledge about the land cover changes can then be used by policy makers to take important decisions regarding urban planning, natural resource management, water source management, etc. In this paper we focus on the problem of identifying changes in the biomass or vegetation in a geographical region. Biomass is defined as the mass of living biological organisms in a unit area. In the context of this study, we restrict our monitoring to plant (specifically crop) biomass over large geographic regions. In recent years biomass monitoring is increasingly becoming important, as biomass is a great source of renewable energy. Moreover, biomass monitoring is also important from the changing climate perspective, as changes in climate are reflected in the change in biomass, and vice versa. The knowledge about biomass changes over time across a geographical region can be used estimate quantitative biophysical parameters which can be incorporated into global climate models. The launch of NASA's Terra satellite in December of 1999, with the Moderate Resolution Imag- ing Spectroradiometer (MODIS) instrument aboard, introduced a new opportunity for terrestrial remote sensing. MODIS data sets represent a new and improved capability for terrestrial satel- lite remote sensing aimed at meeting the needs of global change research. With thirty-six spectral bands, seven designed for use in terrestrial application, MODIS provides daily coverage, of moderate spatial resolution, of most areas on the earth. Land cover products are available in 250m, 500m, or 1000m resolutions (17). MODIS land products are generally available within weeks or even days --- paper_title: Graph-Based Change-Point Detection paper_content: We consider the testing and estimation of change-points -- locations where the distribution abruptly changes -- in a data sequence. A new approach, based on scan statistics utilizing graphs representing the similarity between observations, is proposed. The graph-based approach is non-parametric, and can be applied to any data set as long as an informative similarity measure on the sample space can be defined. Accurate analytic approximations to the significance of graph-based scan statistics for both the single change-point and the changed interval alternatives are provided. Simulations reveal that the new approach has better power than existing approaches when the dimension of the data is moderate to high. The new approach is illustrated on two applications: The determination of authorship of a classic novel, and the detection of change in a network over time. --- paper_title: Multiple-change-point detection for high dimensional time series via sparsified binary segmentation paper_content: Time series segmentation, which is also known as multiple-change-point detection, is a well-established problem. However, few solutions have been designed specifically for high dimensional situations. Our interest is in segmenting the second-order structure of a high dimensional time series. In a generic step of a binary segmentation algorithm for multivariate time series, one natural solution is to combine cumulative sum statistics obtained from local periodograms and cross-periodograms of the components of the input time series. However, the standard 'maximum' and 'average' methods for doing so often fail in high dimensions when, for example, the change points are sparse across the panel or the cumulative sum statistics are spuriously large. We propose the sparsified binary segmentation algorithm which aggregates the cumulative sum statistics by adding only those that pass a certain threshold. This 'sparsifying' step reduces the influence of irrelevant noisy contributions, which is particularly beneficial in high dimensions. To show the consistency of sparsified binary segmentation, we introduce the multivariate locally stationary wavelet model for time series, which is a separate contribution of this work. --- paper_title: Gaussian process for nonstationary time series prediction paper_content: In this paper, the problem of time series prediction is studied. A Bayesian procedure based on Gaussian process models using a nonstationary covariance function is proposed. Experiments proved the approach effectiveness with an excellent prediction and a good tracking. The conceptual simplicity, and good performance of Gaussian process models should make them very attractive for a wide range of problems. --- paper_title: Estimation and comparison of multiple change-point models paper_content: This paper provides a new Bayesian approach for models with multiple change points. The centerpiece of the approach is a formulation of the change-point model in terms of a latent discrete state variable that indicates the regime from which a particular observation has been drawn. This state variable is specified to evolve according to a discrete-time discrete-state Markov process with the transition probabilities constrained so that the state variable can either stay at the current value or jump to the next higher value. This parameterization exactly reproduces the change point model. The model is estimated by Markov chain Monte Carlo methods using an approach that is based on Chib (1996). This methodology is quite valuable since it allows for the fitting of more complex change point models than was possible before. Methods for the computation of Bayes factors are also developed. All the techniques are illustrated using simulated and real data sets. --- paper_title: Bayesian on-line spectral change point detection: a soft computing approach for on-line ASR paper_content: Current automatic speech recognition (ASR) works in off-line mode and needs prior knowledge of the stationary or quasi-stationary test conditions for expected word recognition accuracy. These requirements limit the application of ASR for real-world applications where test conditions are highly non-stationary and are not known a priori. This paper presents an innovative frame dynamic rapid adaptation and noise compensation technique for tracking highly non-stationary noises and its application for on-line ASR. The proposed algorithm is based on a soft computing model using Bayesian on-line inference for spectral change point detection (BOSCPD) in unknown non-stationary noises. BOSCPD is tested with the MCRA noise tracking technique for on-line rapid environmental change learning in different non-stationary noise scenarios. The test results show that the proposed BOSCPD technique reduces the delay in spectral change point detection significantly compared to the baseline MCRA and its derivatives. The proposed BOSCPD soft computing model is tested for joint additive and channel distortions compensation (JAC)-based on-line ASR in unknown test conditions using non-stationary noisy speech samples from the Aurora 2 speech database. The simulation results for the on-line AR show significant improvement in recognition accuracy compared to the baseline Aurora 2 distributed speech recognition (DSR) in batch-mode. --- paper_title: Long-term temperature trends and variability on Spitsbergen: the extended Svalbard Airport temperature series, 1898–2012 paper_content: One of the few long instrumental records available for the Arctic is the Svalbard Airport composite series that hitherto began in 1911, with observations made on Spitsbergen, the largest island in the Svalbard Archipelago. This record has now been extended to 1898 with the inclusion of observations made by hunting and scientific expeditions. Temperature has been observed almost continuously in Svalbard since 1898, although at different sites. It has therefore been possible to create one composite series for Svalbard Airport covering the period 1898–2012, and this valuable new record is presented here. The series reveals large temperature variability on Spitsbergen, with the early 20th century warming as one striking feature: an abrupt change from the cold 1910s to the local maxima of the 1930s and 1950s. With the inclusion of the new data it is possible to show that the 1910s were colder than the years at the start of the series. From the 1960s, temperatures have increased, so the present temperature level is significantly higher than at any earlier period in the instrumental history. For the entire period, and for all seasons, there are positive, statistically significant trends. Regarding the annual mean, the total trend is 2.6°C/century, whereas the largest trend is in spring, at 3.9°C/century. In Europe, it is the Svalbard Archipelago that has experienced the greatest temperature increase during the latest three decades. The composite series may be downloaded from the home page of the Norwegian Meteorological Institute and should be used with reference to the present article. Keywords: Arctic; homogenization; Spitsbergen; Svalbard; temperature records; temperature trends. (Published: 22 January 2014) To access the supplementary material for this article, please see Supplementary files in the column to the right (under Article Tools). Citation: Polar Research 2014, 33 , 21349, http://dx.doi.org/10.3402/polar.v33.21349 --- paper_title: Time Series Analysis and Its Applications paper_content: Characteristics of time series.- Time series regression and exploratory data analysis.- ARIMA models.- Spectral analysis and filtering.- Additional time domain topics.- State-space models.- Statistical methods in the frequency domain. --- paper_title: Semi-supervised time series classification paper_content: The problem of time series classification has attracted great interest in the last decade. However current research assumes the existence of large amounts of labeled training data. In reality, such data may be very difficult or expensive to obtain. For example, it may require the time and expertise of cardiologists, space launch technicians, or other domain specialists. As in many other domains, there are often copious amounts of unlabeled data available. For example, the PhysioBank archive contains gigabytes of ECG data. In this work we propose a semi-supervised technique for building time series classifiers. While such algorithms are well known in text domains, we will show that special considerations must be made to make them both efficient and effective for the time series domain. We evaluate our work with a comprehensive set of experiments on diverse data sources including electrocardiograms, handwritten documents, and video datasets. The experimental results demonstrate that our approach requires only a handful of labeled examples to construct accurate classifiers. --- paper_title: Clustering of time-series subsequences is meaningless: implications for previous and future research paper_content: Time series data is perhaps the most frequently encountered type of data examined by the data mining community. Clustering is perhaps the most frequently used data mining algorithm, being useful in it's own right as an exploratory technique, and also as a subroutine in more complex data mining algorithms such as rule discovery, indexing, summarization, anomaly detection, and classification. Given these two facts, it is hardly surprising that time series clustering has attracted much attention. The data to be clustered can be in one of two formats: many individual time series, or a single time series, from which individual time series are extracted with a sliding window. Given the recent explosion of interest in streaming data and online algorithms, the latter case has received much attention. We make an amazing claim. Clustering of streaming time series is completely meaningless. More concretely, clusters extracted from streaming time series are forced to obey a certain constraint that is pathologically unlikely to be satisfied by any dataset, and because of this, the clusters extracted by any clustering algorithm are essentially random. While this constraint can be intuitively demonstrated with a simple illustration and is simple to prove, it has never appeared in the literature. We can justify calling our claim surprising, since it invalidates the contribution of dozens of previously published papers. We will justify our claim with a theorem, illustrative examples, and a comprehensive set of experiments on reimplementations of previous work. --- paper_title: Change-Point Detection in Time-Series Data by Relative Density-Ratio Estimation paper_content: The objective of change-point detection is to discover abrupt property changes lying behind time-series data. In this paper, we present a novel statistical change-point detection algorithm that is based on non-parametric divergence estimation between two retrospective segments. Our method uses the relative Pearson divergence as a divergence measure, and it is accurately and efficiently estimated by a method of direct density-ratio estimation. Through experiments on real-world human-activity sensing, speech, and Twitter datasets, we demonstrate the usefulness of the proposed method. --- paper_title: Graph-Based Change-Point Detection paper_content: We consider the testing and estimation of change-points -- locations where the distribution abruptly changes -- in a data sequence. A new approach, based on scan statistics utilizing graphs representing the similarity between observations, is proposed. The graph-based approach is non-parametric, and can be applied to any data set as long as an informative similarity measure on the sample space can be defined. Accurate analytic approximations to the significance of graph-based scan statistics for both the single change-point and the changed interval alternatives are provided. Simulations reveal that the new approach has better power than existing approaches when the dimension of the data is moderate to high. The new approach is illustrated on two applications: The determination of authorship of a classic novel, and the detection of change in a network over time. --- paper_title: A regularized kernel-based approach to unsupervised audio segmentation paper_content: We introduce a regularized kernel-based rule for unsupervised change detection based on a simpler version of the recently proposed kernel Fisher discriminant ratio. Compared to other kernel-based change detectors found in the literature, the proposed test statistic is easier to compute and has a known asymptotic distribution which can effectively be used to set the false alarm rate a priori. This technique is applied for segmenting tracks from TV shows, both for segmentation into semantically homogeneous sections (applause, movie, music, etc.) and for speaker diarization within the speech sections. On these tasks, the proposed approach outperforms other kernel-based tests and is competitive with a standard HMM-based supervised alternative. --- paper_title: A novel changepoint detection algorithm paper_content: We propose an algorithm for simultaneously detecting and locating changepoints in a time series, and a framework for predicting the distribution of the next point in the series. The kernel of the algorithm is a system of equations that computes, for each index i, the probability that the last (most recent) change point occurred at i. We evaluate this algorithm by applying it to the change point detection problem and comparing it to the generalized likelihood ratio (GLR) algorithm. We find that our algorithm is as good as GLR, or better, over a wide range of scenarios, and that the advantage increases as the signal-to-noise ratio decreases. --- paper_title: Graph-Based Change-Point Detection paper_content: We consider the testing and estimation of change-points -- locations where the distribution abruptly changes -- in a data sequence. A new approach, based on scan statistics utilizing graphs representing the similarity between observations, is proposed. The graph-based approach is non-parametric, and can be applied to any data set as long as an informative similarity measure on the sample space can be defined. Accurate analytic approximations to the significance of graph-based scan statistics for both the single change-point and the changed interval alternatives are provided. Simulations reveal that the new approach has better power than existing approaches when the dimension of the data is moderate to high. The new approach is illustrated on two applications: The determination of authorship of a classic novel, and the detection of change in a network over time. --- paper_title: Optimal Composition of Real-Time Systems paper_content: Abstract Real-time systems are designed for environments in which the utility of actions is strongly time-dependent. Recent work by Dean, Horvitz and others has shown that anytime algorithms are a useful tool for real-time system design, since they allow computation time to be traded for decision quality. In order to construct complex systems, however, we need to be a ble to compose larger systems from smaller, reusable anytime modules. This paper addresses two basic problems associated with composition: how to ensure the interruptibility of the composed system; and how to allocate computation time optimally among the components. The first problem is solved by a simple and general construction that incurs only a small, constant penalty. The second is solved by an off-line compilation process. We show that the general compilation problem is NP-complete. However, efficient local compilation techniques, working on a single program structure at a time, yield glo bally optimal allocations for a large class of programs. We illustrate these results with two simple applications. --- paper_title: Polishing the Right Apple: Anytime Classification Also Benefits Data Streams with Constant Arrival Times paper_content: Classification of items taken from data streams requires algorithms that operate in time sensitive and computationally constrained environments. Often, the available time for classification is not known a priori and may change as a consequence of external circumstances. Many traditional algorithms are unable to provide satisfactory performance while supporting the highly variable response times that exemplify such applications. In such contexts, anytime algorithms, which are amenable to trading time for accuracy, have been found to be exceptionally useful and constitute an area of increasing research activity. Previous techniques for improving anytime classification have generally been concerned with optimizing the probability of correctly classifying individual objects. However, as we shall see, serially optimizing the probability of correctly classifying individual objects K times, generally gives inferior results to batch optimizing the probability of correctly classifying K objects. In this work, we show that this simple observation can be exploited to improve overall classification performance by using an anytime framework to allocate resources among a set of objects buffered from a fast arriving stream. Our ideas are independent of object arrival behavior, and, perhaps unintuitively, even in data streams with constant arrival rates our technique exhibits a marked improvement in performance. The utility of our approach is demonstrated with extensive experimental evaluations conducted on a wide range of diverse datasets. --- paper_title: Scalable machine learning for massive datasets: Fast summation algorithms paper_content: Huge data sets containing millions of training examples with a large number of attributes are relatively easy to gather. However one of the bottlenecks for successful inference is the computational complexity of machine learning algorithms. Most state-of-the-art nonparametric machine learning algorithms have a computational complexity of either O (N2) or O (N3), where N is the number of training examples. This has seriously restricted the use of massive data sets. The bottleneck computational primitive at the heart of various algorithms is the multiplication of a structured matrix with a vector, which we refer to as matrix-vector product (MVP) primitive. The goal of my thesis is to speedup up some of these MVP primitives by fast approximate algorithms that scale as O (N) and also provide high accuracy guarantees . I use ideas from computational physics, scientific computing, and computational geometry to design these algorithms. The proposed algorithms have been applied to speedup kernel density estimation, optimal bandwidth estimation, projection pursuit, Gaussian process regression, implicit surface fitting, and ranking. --- paper_title: An Algorithm Based on Singular Spectrum Analysis for Change-Point Detection paper_content: This paper is devoted to application of the singular-spectrum analysis to sequential detection of changes in time series. An algorithm of change-point detection in time series, based on sequential application of the singular-spectrum analysis is developed and studied. The algorithm is applied to different data sets and extensively studied numerically. For specific models, several numerical approximations to the error probabilities and the power function of the algorithm are obtained. Numerical comparisons with other methods are given. --- paper_title: Learning transportation mode from raw gps data for geographic applications on the web paper_content: Geographic information has spawned many novel Web applications where global positioning system (GPS) plays important roles in bridging the applications and end users. Learning knowledge from users' raw GPS data can provide rich context information for both geographic and mobile applications. However, so far, raw GPS data are still used directly without much understanding. In this paper, an approach based on supervised learning is proposed to automatically infer transportation mode from raw GPS data. The transportation mode, such as walking, driving, etc., implied in a user's GPS data can provide us valuable knowledge to understand the user. It also enables context-aware computing based on user's present transportation mode and design of an innovative user interface for Web users. Our approach consists of three parts: a change point-based segmentation method, an inference model and a post-processing algorithm based on conditional probability. The change point-based segmentation method was compared with two baselines including uniform duration based and uniform length based methods. Meanwhile, four different inference models including Decision Tree, Bayesian Net, Support Vector Machine (SVM) and Conditional Random Field (CRF) are studied in the experiments. We evaluated the approach using the GPS data collected by 45 users over six months period. As a result, beyond other two segmentation methods, the change point based method achieved a higher degree of accuracy in predicting transportation modes and detecting transitions between them. Decision Tree outperformed other inference models over the change point based segmentation method. --- paper_title: Time Series Epenthesis: Clustering Time Series Streams Requires Ignoring Some Data paper_content: Given the pervasiveness of time series data in all human endeavors, and the ubiquity of clustering as a data mining application, it is somewhat surprising that the problem of time series clustering from a single stream remains largely unsolved. Most work on time series clustering considers the clustering of individual time series, e.g., gene expression profiles, individual heartbeats or individual gait cycles. The few attempts at clustering time series streams have been shown to be objectively incorrect in some cases, and in other cases shown to work only on the most contrived datasets by carefully adjusting a large set of parameters. In this work, we make two fundamental contributions. First, we show that the problem definition for time series clustering from streams currently used is inherently flawed, and a new definition is necessary. Second, we show that the Minimum Description Length (MDL) framework offers an efficient, effective and essentially parameter-free method for time series clustering. We show that our method produces objectively correct results on a wide variety of datasets from medicine, zoology and industrial process analyses. --- paper_title: Using mobile phones to determine transportation modes paper_content: As mobile phones advance in functionality and capability, they are being used for more than just communication. Increasingly, these devices are being employed as instruments for introspection into habits and situations of individuals and communities. Many of the applications enabled by this new use of mobile phones rely on contextual information. The focus of this work is on one dimension of context, the transportation mode of an individual when outside. We create a convenient (no specific position and orientation setting) classification system that uses a mobile phone with a built-in GPS receiver and an accelerometer. The transportation modes identified include whether an individual is stationary, walking, running, biking, or in motorized transport. The overall classification system consists of a decision tree followed by a first-order discrete Hidden Markov Model and achieves an accuracy level of 93.6p when tested on a dataset obtained from sixteen individuals. --- paper_title: Graph-Based Change-Point Detection paper_content: We consider the testing and estimation of change-points -- locations where the distribution abruptly changes -- in a data sequence. A new approach, based on scan statistics utilizing graphs representing the similarity between observations, is proposed. The graph-based approach is non-parametric, and can be applied to any data set as long as an informative similarity measure on the sample space can be defined. Accurate analytic approximations to the significance of graph-based scan statistics for both the single change-point and the changed interval alternatives are provided. Simulations reveal that the new approach has better power than existing approaches when the dimension of the data is moderate to high. The new approach is illustrated on two applications: The determination of authorship of a classic novel, and the detection of change in a network over time. --- paper_title: Semi-supervised time series classification paper_content: The problem of time series classification has attracted great interest in the last decade. However current research assumes the existence of large amounts of labeled training data. In reality, such data may be very difficult or expensive to obtain. For example, it may require the time and expertise of cardiologists, space launch technicians, or other domain specialists. As in many other domains, there are often copious amounts of unlabeled data available. For example, the PhysioBank archive contains gigabytes of ECG data. In this work we propose a semi-supervised technique for building time series classifiers. While such algorithms are well known in text domains, we will show that special considerations must be made to make them both efficient and effective for the time series domain. We evaluate our work with a comprehensive set of experiments on diverse data sources including electrocardiograms, handwritten documents, and video datasets. The experimental results demonstrate that our approach requires only a handful of labeled examples to construct accurate classifiers. --- paper_title: An online kernel change detection algorithm paper_content: A number of abrupt change detection methods have been proposed in the past, among which are efficient model-based techniques such as the Generalized Likelihood Ratio (GLR) test. We consider the case where no accurate nor tractable model can be found, using a model-free approach, called Kernel change detection (KCD). KCD compares two sets of descriptors extracted online from the signal at each time instant: The immediate past set and the immediate future set. Based on the soft margin single-class Support Vector Machine (SVM), we build a dissimilarity measure in feature space between those sets, without estimating densities as an intermediary step. This dissimilarity measure is shown to be asymptotically equivalent to the Fisher ratio in the Gaussian case. Implementation issues are addressed; in particular, the dissimilarity measure can be computed online in input space. Simulation results on both synthetic signals and real music signals show the efficiency of KCD. --- paper_title: Understanding mobility based on GPS data paper_content: Both recognizing human behavior and understanding a user's mobility from sensor data are critical issues in ubiquitous computing systems. As a kind of user behavior, the transportation modes, such as walking, driving, etc., that a user takes, can enrich the user's mobility with informative knowledge and provide pervasive computing systems with more context information. In this paper, we propose an approach based on supervised learning to infer people's motion modes from their GPS logs. The contribution of this work lies in the following two aspects. On one hand, we identify a set of sophisticated features, which are more robust to traffic condition than those other researchers ever used. On the other hand, we propose a graph-based post-processing algorithm to further improve the inference performance. This algorithm considers both the commonsense constraint of real world and typical user behavior based on location in a probabilistic manner. Using the GPS logs collected by 65 people over a period of 10 months, we evaluated our approach via a set of experiments. As a result, based on the change point-based segmentation method and Decision Tree-based inference model, the new features brought an eight percent improvement in inference accuracy over previous result, and the graph-based post-processing achieve a further four percent enhancement. --- paper_title: Comprehensive Context Recognizer Based on Multimodal Sensors in a Smartphone paper_content: Recent developments in smartphones have increased the processing capabilities and equipped these devices with a number of built-in multimodal sensors, including accelerometers, gyroscopes, GPS interfaces, Wi-Fi access, and proximity sensors. Despite the fact that numerous studies have investigated the development of user-context aware applications using smartphones, these applications are currently only able to recognize simple contexts using a single type of sensor. Therefore, in this work, we introduce a comprehensive approach for context aware applications that utilizes the multimodal sensors in smartphones. The proposed system is not only able to recognize different kinds of contexts with high accuracy, but it is also able to optimize the power consumption since power-hungry sensors can be activated or deactivated at appropriate times. Additionally, the system is able to recognize activities wherever the smartphone is on a human's body, even when the user is using the phone to make a phone call, manipulate applications, play games, or listen to music. Furthermore, we also present a novel feature selection algorithm for the accelerometer classification module. The proposed feature selection algorithm helps select good features and eliminates bad features, thereby improving the overall accuracy of the accelerometer classifier. Experimental results show that the proposed system can classify eight activities with an accuracy of 92.43%. --- paper_title: Unsupervised change analysis using supervised learning paper_content: We propose a formulation of a new problem, which we call change analysis, and a novel method for solving the problem. In contrast to the existing methods of change (or outlier) detection, the goal of change analysis goes beyond detecting whether or not any changes exist. Its ultimate goal is to find the explanation of the changes.While change analysis falls in the category of unsupervised learning in nature, we propose a novel approach based on supervised learning to achieve the goal. The key idea is to use a supervised classifier for interpreting the changes. A classifier should be able to discriminate between the two data sets if they actually come from two different data sources. In other words, we use a hypothetical label to train the supervised learner, and exploit the learner for interpreting the change. Experimental results using real data show the proposed approach is promising in change analysis as well as concept drift analysis. --- paper_title: Learning transportation mode from raw gps data for geographic applications on the web paper_content: Geographic information has spawned many novel Web applications where global positioning system (GPS) plays important roles in bridging the applications and end users. Learning knowledge from users' raw GPS data can provide rich context information for both geographic and mobile applications. However, so far, raw GPS data are still used directly without much understanding. In this paper, an approach based on supervised learning is proposed to automatically infer transportation mode from raw GPS data. The transportation mode, such as walking, driving, etc., implied in a user's GPS data can provide us valuable knowledge to understand the user. It also enables context-aware computing based on user's present transportation mode and design of an innovative user interface for Web users. Our approach consists of three parts: a change point-based segmentation method, an inference model and a post-processing algorithm based on conditional probability. The change point-based segmentation method was compared with two baselines including uniform duration based and uniform length based methods. Meanwhile, four different inference models including Decision Tree, Bayesian Net, Support Vector Machine (SVM) and Conditional Random Field (CRF) are studied in the experiments. We evaluated the approach using the GPS data collected by 45 users over six months period. As a result, beyond other two segmentation methods, the change point based method achieved a higher degree of accuracy in predicting transportation modes and detecting transitions between them. Decision Tree outperformed other inference models over the change point based segmentation method. --- paper_title: Using mobile phones to determine transportation modes paper_content: As mobile phones advance in functionality and capability, they are being used for more than just communication. Increasingly, these devices are being employed as instruments for introspection into habits and situations of individuals and communities. Many of the applications enabled by this new use of mobile phones rely on contextual information. The focus of this work is on one dimension of context, the transportation mode of an individual when outside. We create a convenient (no specific position and orientation setting) classification system that uses a mobile phone with a built-in GPS receiver and an accelerometer. The transportation modes identified include whether an individual is stationary, walking, running, biking, or in motorized transport. The overall classification system consists of a decision tree followed by a first-order discrete Hidden Markov Model and achieves an accuracy level of 93.6p when tested on a dataset obtained from sixteen individuals. --- paper_title: Change Detection in Streaming Multivariate Data Using Likelihood Detectors paper_content: Change detection in streaming data relies on a fast estimation of the probability that the data in two consecutive windows come from different distributions. Choosing the criterion is one of the multitude of questions that need to be addressed when designing a change detection procedure. This paper gives a log-likelihood justification for two well-known criteria for detecting change in streaming multidimensional data: Kullback-Leibler (K-L) distance and Hotelling's T-square test for equal means (H). We propose a semiparametric log-likelihood criterion (SPLL) for change detection. Compared to the existing log-likelihood change detectors, SPLL trades some theoretical rigor for computation simplicity. We examine SPLL together with K-L and H on detecting induced change on 30 real data sets. The criteria were compared using the area under the respective Receiver Operating Characteristic (ROC) curve (AUC). SPLL was found to be on the par with H and better than K-L for the nonnormalized data, and better than both on the normalized data. --- paper_title: Change-Point Detection in Time-Series Data by Relative Density-Ratio Estimation paper_content: The objective of change-point detection is to discover abrupt property changes lying behind time-series data. In this paper, we present a novel statistical change-point detection algorithm that is based on non-parametric divergence estimation between two retrospective segments. Our method uses the relative Pearson divergence as a divergence measure, and it is accurately and efficiently estimated by a method of direct density-ratio estimation. Through experiments on real-world human-activity sensing, speech, and Twitter datasets, we demonstrate the usefulness of the proposed method. --- paper_title: Cusum techniques for timeslot sequences with applications to network surveillance paper_content: We develop two cusum change-point detection algorithms for data network monitoring applications where numerous and various performance and reliability metrics are available to aid with the early identification of realized or impending failures. We confront three significant challenges with our cusum algorithms: (1) the need for nonparametric techniques so that a wide variety of metrics can be included in the monitoring process, (2) the need to handle time varying distributions for the metrics that reflect natural cycles in work load and traffic patterns, and (3) the need to be computationally efficient with the massive amounts of data that are available for processing. The only critical assumption we make when developing the algorithms is that suitably transformed observations within a defined timeslot structure are independent and identically distributed under normal operating conditions. To facilitate practical implementations of the algorithms, we present asymptotically valid thresholds. Our research was motivated by a real-world application and we use that context to guide the design of a simulation study that examines the sensitivity of the cusum algorithms. --- paper_title: Multiple-change-point detection for high dimensional time series via sparsified binary segmentation paper_content: Time series segmentation, which is also known as multiple-change-point detection, is a well-established problem. However, few solutions have been designed specifically for high dimensional situations. Our interest is in segmenting the second-order structure of a high dimensional time series. In a generic step of a binary segmentation algorithm for multivariate time series, one natural solution is to combine cumulative sum statistics obtained from local periodograms and cross-periodograms of the components of the input time series. However, the standard 'maximum' and 'average' methods for doing so often fail in high dimensions when, for example, the change points are sparse across the panel or the cumulative sum statistics are spuriously large. We propose the sparsified binary segmentation algorithm which aggregates the cumulative sum statistics by adding only those that pass a certain threshold. This 'sparsifying' step reduces the influence of irrelevant noisy contributions, which is particularly beneficial in high dimensions. To show the consistency of sparsified binary segmentation, we introduce the multivariate locally stationary wavelet model for time series, which is a separate contribution of this work. --- paper_title: A unifying framework for detecting outliers and change points from non-stationary time series data paper_content: We are concerned with the issues of outlier detection and change point detection from a data stream. In the area of data mining, there have been increased interest in these issues since the former is related to fraud detection, rare event discovery, etc., while the latter is related to event/trend by change detection, activity monitoring, etc. Specifically, it is important to consider the situation where the data source is non-stationary, since the nature of data source may change over time in real applications. Although in most previous work outlier detection and change point detection have not been related explicitly, this paper presents a unifying framework for dealing with both of them on the basis of the theory of on-line learning of non-stationary time series. In this framework a probabilistic model of the data source is incrementally learned using an on-line discounting learning algorithm, which can track the changing data source adaptively by forgetting the effect of past data gradually. Then the score for any given data is calculated to measure its deviation from the learned model, with a higher score indicating a high possibility of being an outlier. Further change points in a data stream are detected by applying this scoring method into a time series of moving averaged losses for prediction using the learned model. Specifically we develop an efficient algorithms for on-line discounting learning of auto-regression models from time series data, and demonstrate the validity of our framework through simulation and experimental applications to stock market data analysis. --- paper_title: Break detection in the covariance structure of multivariate time series models paper_content: In this paper, we introduce an asymptotic test procedure to assess the stability of volatilities and cross-volatilites of linear and nonlinear multivariate time series models. The test is very flexible as it can be applied, for example, to many of the multivariate GARCH models established in the literature, and also works well in the case of high dimensionality of the underlying data. Since it is nonparametric, the procedure avoids the difficulties associated with parametric model selection, model fitting and parameter estimation. We provide the theoretical foundation for the test and demonstrate its applicability via a simulation study and an analysis of financial data. Extensions to multiple changes and the case of infinite fourth moments are also discussed. --- paper_title: Change-Point Detection with Feature Selection in High-Dimensional Time-Series Data paper_content: Change-point detection is the problem of finding abrupt changes in time-series, and it is attracting a lot of attention in the artificial intelligence and data mining communities. In this paper, we present a supervised learning based change-point detection approach in which we use the separability of past and future data at time t (they are labeled as +1 and -1) as plausibility of change-points. Based on this framework, we propose a detection measure called the additive Hilbert-Schmidt Independence Criterion (aHSIC), which is defined as the weighted sum of the HSIC scores between features and its corresponding binary labels. Here, the HSIC is a kernel-based independence measure. A novel aspect of the aHSIC score is that it can incorporate feature selection during its detection measure estimation. More specifically, we first select features that are responsible for an abrupt change by using a supervised approach, and then compute the aHSIC score by employing the selected features. Thus, compared with traditional detection measures, our approach tends to be robust as regards noise features, and so the aHSIC is suitable for a use with high-dimensional time-series change-point detection problems. We demonstrate that the proposed change-point detection method is promising through extensive experiments on synthetic data sets and a real-world human activity data set. --- paper_title: PCA Feature Extraction for Change Detection in Multidimensional Unlabeled Data paper_content: When classifiers are deployed in real-world applications, it is assumed that the distribution of the incoming data matches the distribution of the data used to train the classifier. This assumption is often incorrect, which necessitates some form of change detection or adaptive classification. While there has been a lot of work on change detection based on the classification error monitored over the course of the operation of the classifier, finding changes in multidimensional unlabeled data is still a challenge. Here, we propose to apply principal component analysis (PCA) for feature extraction prior to the change detection. Supported by a theoretical example, we argue that the components with the lowest variance should be retained as the extracted features because they are more likely to be affected by a change. We chose a recently proposed semiparametric log-likelihood change detection criterion that is sensitive to changes in both mean and variance of the multidimensional distribution. An experiment with 35 datasets and an illustration with a simple video segmentation demonstrate the advantage of using extracted features compared to raw data. Further analysis shows that feature extraction through PCA is beneficial, specifically for data with multiple balanced classes. --- paper_title: Change Detection in Multivariate Datastreams: Likelihood and Detectability Loss paper_content: We address the problem of detecting changes in multivariate datastreams, and we investigate the intrinsic difficulty that change-detection methods have to face when the data dimension scales. In particular, we consider a general approach where changes are detected by comparing the distribution of the log-likelihood of the datastream over different time windows. Despite the fact that this approach constitutes the frame of several change-detection methods, its effectiveness when data dimension scales has never been investigated, which is indeed the goal of our paper. We show that the magnitude of the change can be naturally measured by the symmetric Kullback-Leibler divergence between the pre- and post-change distributions, and that the detectability of a change of a given magnitude worsens when the data dimension increases. This problem, which we refer to as \emph{detectability loss}, is due to the linear relationship between the variance of the log-likelihood and the data dimension. We analytically derive the detectability loss on Gaussian-distributed datastreams, and empirically demonstrate that this problem holds also on real-world datasets and that can be harmful even at low data-dimensions (say, 10). --- paper_title: Change-Point Detection in Time-Series Data Based on Subspace Identification paper_content: In this paper, we propose series of algorithms for detecting change points in time-series data based on subspace identification, meaning a geometric approach for estimating linear state-space models behind time-series data. Our algorithms are derived from the principle that the subspace spanned by the columns of an observability matrix and the one spanned by the subsequences of time-series data are approximately equivalent. In this paper, we derive a batch-type algorithm applicable to ordinary time-series data, i.e. consisting of only output series, and then introduce the online version of the algorithm and the extension to be available with input-output time-series data. We illustrate the effectiveness of our algorithms with comparative experiments using some artificial and real datasets. --- paper_title: Change-Point Detection in Time-Series Data by Relative Density-Ratio Estimation paper_content: The objective of change-point detection is to discover abrupt property changes lying behind time-series data. In this paper, we present a novel statistical change-point detection algorithm that is based on non-parametric divergence estimation between two retrospective segments. Our method uses the relative Pearson divergence as a divergence measure, and it is accurately and efficiently estimated by a method of direct density-ratio estimation. Through experiments on real-world human-activity sensing, speech, and Twitter datasets, we demonstrate the usefulness of the proposed method. --- paper_title: Change-Point Detection of Climate Time Series by Nonparametric Method paper_content: In one of the data mining techniques, change-point detection is of importance in evaluating time series measured in real world. For decades this technique has been developed as a nonlinear dynam- ics. We apply the method for detecting the change points, Singular Spectrum Transformation (SST), to the climate time series. To know where the struc- tures of climate data sets change can reveal a climate background. In this paper we discuss the structures of precipitation data in Kenya and Wrangel Island (Arctic land) by using the SST. --- paper_title: An Algorithm Based on Singular Spectrum Analysis for Change-Point Detection paper_content: This paper is devoted to application of the singular-spectrum analysis to sequential detection of changes in time series. An algorithm of change-point detection in time series, based on sequential application of the singular-spectrum analysis is developed and studied. The algorithm is applied to different data sets and extensively studied numerically. For specific models, several numerical approximations to the error probabilities and the power function of the algorithm are obtained. Numerical comparisons with other methods are given. --- paper_title: Scalable Time Series Change Detection for Biomass Monitoring Using Gaussian Process. paper_content: Biomass monitoring, specifically, detecting changes in the biomass or vegetation of a geographical region, is vital for studying the carbon cycle of the system and has significant implications in the context of understanding climate change and its impacts. Recently, several time series change detection methods have been proposed to identify land cover changes in temporal profiles (time series) of vegetation collected using remote sensing instruments. In this paper, we adapt Gaussian process regression to detect changes in such time series in an online fashion. While Gaussian process (GP) has been widely used as a kernel based learning method for regression and classification, their applicability to massive spatio-temporal data sets, such as remote sensing data, has been limited owing to the high computational costs involved. In our previous work we proposed an efficient Toeplitz matrix based solution for scalable GP parameter estimation. In this paper we apply these solutions to a GP based change detection algorithm. The proposed change detection algorithm requires a memory footprint which is linear in the length of the input time series and runs in time which is quadratic to the length of the input time series. Experimental results show that both serial and parallel implementations of our proposed method achieve significant speedups over the serial implementation. Finally, we demonstrate the effectiveness of the proposed change detection method in identifying changes in Normalized Difference Vegetation Index (NDVI) data. Increasing availability of high resolution remote sensing data has encouraged researchers to extract knowledge from these massive spatio-temporal data sets in order to solve different problems pertain- ing to our ecosystem. Land use land cover (LULC) monitoring, specifically identifying changes in land cover, is one such problem that has significant applications in detecting deforestation, crop ro- tation, urbanization, forest fires, and other such phenomenon. The knowledge about the land cover changes can then be used by policy makers to take important decisions regarding urban planning, natural resource management, water source management, etc. In this paper we focus on the problem of identifying changes in the biomass or vegetation in a geographical region. Biomass is defined as the mass of living biological organisms in a unit area. In the context of this study, we restrict our monitoring to plant (specifically crop) biomass over large geographic regions. In recent years biomass monitoring is increasingly becoming important, as biomass is a great source of renewable energy. Moreover, biomass monitoring is also important from the changing climate perspective, as changes in climate are reflected in the change in biomass, and vice versa. The knowledge about biomass changes over time across a geographical region can be used estimate quantitative biophysical parameters which can be incorporated into global climate models. The launch of NASA's Terra satellite in December of 1999, with the Moderate Resolution Imag- ing Spectroradiometer (MODIS) instrument aboard, introduced a new opportunity for terrestrial remote sensing. MODIS data sets represent a new and improved capability for terrestrial satel- lite remote sensing aimed at meeting the needs of global change research. With thirty-six spectral bands, seven designed for use in terrestrial application, MODIS provides daily coverage, of moderate spatial resolution, of most areas on the earth. Land cover products are available in 250m, 500m, or 1000m resolutions (17). MODIS land products are generally available within weeks or even days --- paper_title: Change-point detection for recursive Bayesian geoacoustic inversions paper_content: In order to carry out geoacoustic inversion in low signal-to-noise ratio (SNR) conditions, extended duration observations coupled with source and/or receiver motion may be necessary. As a result, change in the underlying model parameters due to time or space is anticipated. In this paper, an inversion method is proposed for cases when the model parameters change abruptly or slowly. A model parameter change-point detection method is developed to detect the change in the model parameters using the importance samples and corresponding weights that already are available from the recursive Bayesian inversion. If the model parameter change abruptly, a change-point will be detected and the inversion will restart with the pulse measurement after the changepoint. If the model parameters change gradually, the inversion (based on constant model parameters) may proceed until the accumulated model parameter mismatch is significant and triggers the detection of a change-point. These change-point detections form the heu... --- paper_title: A Bayesian Analysis for Change Point Problems paper_content: A sequence of observations undergoes sudden changes at unknown times. We model the process by supposing that there is an underlying sequence of parameters partitioned into contiguous blocks of equal parameter values; the beginning of each block is said to be a change point. Observations are then assumed to be independent in different blocks given the sequence of parameters. In a Bayesian analysis it is necessary to give probability distributions to both the change points and the parameters. We use product partition models (Barry and Hartigan 1992), which assume that the probability of any partition is proportional to a product of prior cohesions, one for each block in the partition, and that given the blocks the parameters in different blocks have independent prior distributions. Given the observations a new product partition model holds, with posterior cohesions for the blocks and new independent block posterior distributions for parameters. The product model thus provides a convenient machinery for allo... --- paper_title: Gaussian process for nonstationary time series prediction paper_content: In this paper, the problem of time series prediction is studied. A Bayesian procedure based on Gaussian process models using a nonstationary covariance function is proposed. Experiments proved the approach effectiveness with an excellent prediction and a good tracking. The conceptual simplicity, and good performance of Gaussian process models should make them very attractive for a wide range of problems. --- paper_title: Gaussian Process Change Point Models paper_content: We combine Bayesian online change point detection with Gaussian processes to create a nonparametric time series model which can handle change points. The model can be used to locate change points in an online manner; and, unlike other Bayesian online change point detection algorithms, is applicable when temporal correlations in a regime are expected. We show three variations on how to apply Gaussian processes in the change point context, each with their own advantages. We present methods to reduce the computational burden of these models and demonstrate it on several real world data sets. --- paper_title: Bayesian online changepoint detection to improve transparency in human-machine interaction systems paper_content: This paper discusses a way to improve transparency in human-machine interaction systems when no force sensors are available for both the human and the machine. In most cases, position-error based control with fixed proportional-derivative (PD) controllers provides poor transparency. We resolve this issue by utilizing a gain switching method, switching them to be high or low values in response to estimated force changes at the slave environment. Since the slave-environment forces change abruptly in real time, it is difficult to set the precise value of the threshold for these gain switching decisions. Moreover, the threshold value has to be observed and tuned in advance to utilize the gain switching approach. Thus, we adopt Bayesian online changepoint detection to detect the abrupt slave environment change. This changepoint detection is based on the Bayes' theorem which is typically used in probability and statistics applications to generate the posterior distribution of unknown parameters given both data and prior distribution. We then show experimental results which demonstrate the Bayesian online changepoint detection has the ability to discriminate both free motion and hard contact. Additionally, we incorporate the online changepoint detection in our proposed gain switching controller and show the superiority of our proposed controller via experiment. --- paper_title: Estimation and comparison of multiple change-point models paper_content: This paper provides a new Bayesian approach for models with multiple change points. The centerpiece of the approach is a formulation of the change-point model in terms of a latent discrete state variable that indicates the regime from which a particular observation has been drawn. This state variable is specified to evolve according to a discrete-time discrete-state Markov process with the transition probabilities constrained so that the state variable can either stay at the current value or jump to the next higher value. This parameterization exactly reproduces the change point model. The model is estimated by Markov chain Monte Carlo methods using an approach that is based on Chib (1996). This methodology is quite valuable since it allows for the fitting of more complex change point models than was possible before. Methods for the computation of Bayes factors are also developed. All the techniques are illustrated using simulated and real data sets. --- paper_title: Online Bayesian change point detection algorithms for segmentation of epileptic activity paper_content: Epilepsy is a dynamic disease in which the brain transitions between different states. In this paper, we focus on the problem of identifying the time points, referred to as change points, where the transitions between these different states happen. A Bayesian change point detection algorithm that does not require the knowledge of the total number of states or the parameters of the probability distribution modeling the activity of epileptic brain in each of these states is developed in this paper. This algorithm works in online mode making it amenable for real-time monitoring. To reduce the quadratic complexity of this algorithm, an approximate algorithm with linear complexity in the number of data points is also developed. Finally, we use these algorithms on ECoG recordings of an epileptic patient to locate the change points and determine segments corresponding to different brain states. --- paper_title: Graph-Based Change-Point Detection paper_content: We consider the testing and estimation of change-points -- locations where the distribution abruptly changes -- in a data sequence. A new approach, based on scan statistics utilizing graphs representing the similarity between observations, is proposed. The graph-based approach is non-parametric, and can be applied to any data set as long as an informative similarity measure on the sample space can be defined. Accurate analytic approximations to the significance of graph-based scan statistics for both the single change-point and the changed interval alternatives are provided. Simulations reveal that the new approach has better power than existing approaches when the dimension of the data is moderate to high. The new approach is illustrated on two applications: The determination of authorship of a classic novel, and the detection of change in a network over time. --- paper_title: A regularized kernel-based approach to unsupervised audio segmentation paper_content: We introduce a regularized kernel-based rule for unsupervised change detection based on a simpler version of the recently proposed kernel Fisher discriminant ratio. Compared to other kernel-based change detectors found in the literature, the proposed test statistic is easier to compute and has a known asymptotic distribution which can effectively be used to set the false alarm rate a priori. This technique is applied for segmenting tracks from TV shows, both for segmentation into semantically homogeneous sections (applause, movie, music, etc.) and for speaker diarization within the speech sections. On these tasks, the proposed approach outperforms other kernel-based tests and is competitive with a standard HMM-based supervised alternative. --- paper_title: Kernel change-point analysis paper_content: We introduce a kernel-based method for change-point analysis within a sequence of temporal observations. Change-point analysis of an unlabelled sample of observations consists in, first, testing whether a change in the distribution occurs within the sample, and second, if a change occurs, estimating the change-point instant after which the distribution of the observations switches from one distribution to another different distribution. We propose a test statistic based upon the maximum kernel Fisher discriminant ratio as a measure of homogeneity between segments. We derive its limiting distribution under the null hypothesis (no change occurs), and establish the consistency under the alternative hypothesis (a change occurs). This allows to build a statistical hypothesis testing procedure for testing the presence of a change-point, with a prescribed false-alarm probability and detection probability tending to one in the large-sample setting. If a change actually occurs, the test statistic also yields an estimator of the change-point location. Promising experimental results in temporal segmentation of mental tasks from BCI data and pop song indexation are presented. --- paper_title: Graph-Based Change-Point Detection paper_content: We consider the testing and estimation of change-points -- locations where the distribution abruptly changes -- in a data sequence. A new approach, based on scan statistics utilizing graphs representing the similarity between observations, is proposed. The graph-based approach is non-parametric, and can be applied to any data set as long as an informative similarity measure on the sample space can be defined. Accurate analytic approximations to the significance of graph-based scan statistics for both the single change-point and the changed interval alternatives are provided. Simulations reveal that the new approach has better power than existing approaches when the dimension of the data is moderate to high. The new approach is illustrated on two applications: The determination of authorship of a classic novel, and the detection of change in a network over time. --- paper_title: Complex network from pseudoperiodic time series: topology versus dynamics. paper_content: We construct complex networks from pseudoperiodic time series, with each cycle represented by a single node in the network. We investigate the statistical properties of these networks for various time series and find that time series with different dynamics exhibit distinct topological structures. Specifically, noisy periodic signals correspond to random networks, and chaotic time series generate networks that exhibit small world and scale free features. We show that this distinction in topological structure results from the hierarchy of unstable periodic orbits embedded in the chaotic attractor. Standard measures of structure in complex networks can therefore be applied to distinguish different dynamic regimes in time series. Application to human electrocardiograms shows that such statistical properties are able to differentiate between the sinus rhythm cardiograms of healthy volunteers and those of coronary care patients. --- paper_title: An exact distribution-free test comparing two multivariate distributions based on adjacency paper_content: A new test is proposed comparing two multivariate distributions by using distances between observations. Unlike earlier tests using interpoint distances, the new test statistic has a known exact distribution and is exactly distribution free. The interpoint distances are used to construct an optimal non-bipartite matching, i.e. a matching of the observations into disjoint pairs to minimize the total distance within pairs. The cross-match statistic is the number of pairs containing one observation from the first distribution and one from the second. Distributions that are very different will exhibit few cross-matches. When comparing two discrete distributions with finite support, the test is consistent against all alternatives. The test is applied to a study of brain activation measured by functional magnetic resonance imaging during two linguistic tasks, comparing brains that are impaired by arteriovenous abnormalities with normal controls. A second exact distribution-free test is also discussed: it ranks the pairs and sums the ranks of the cross-matched pairs. Copyright 2005 Royal Statistical Society. --- paper_title: From time series to complex networks: the visibility graph paper_content: In this work we present a simple and fast computational method, the visibility algorithm, that converts a time series into a graph. The constructed graph inherits several properties of the series in its structure. Thereby, periodic series convert into regular graphs, and random series do so into random graphs. Moreover, fractal series convert into scale-free networks, enhancing the fact that power law degree distributions are related to fractality, something highly discussed recently. Some remarkable examples and analytical tools are outlined in order to test the method's reliability. Many different measures, recently developed in the complex network theory, could by means of this new approach characterize time series from a new point of view. --- paper_title: An online algorithm for segmenting time series paper_content: In recent years, there has been an explosion of interest in mining time-series databases. As with most computer science problems, representation of the data is the key to efficient and effective solutions. One of the most commonly used representations is piecewise linear approximation. This representation has been used by various researchers to support clustering, classification, indexing and association rule mining of time-series data. A variety of algorithms have been proposed to obtain this representation, with several algorithms having been independently rediscovered several times. In this paper, we undertake the first extensive review and empirical comparison of all proposed techniques. We show that all these algorithms have fatal flaws from a data-mining perspective. We introduce a novel algorithm that we empirically show to be superior to all others in the literature. --- paper_title: Time Series Epenthesis: Clustering Time Series Streams Requires Ignoring Some Data paper_content: Given the pervasiveness of time series data in all human endeavors, and the ubiquity of clustering as a data mining application, it is somewhat surprising that the problem of time series clustering from a single stream remains largely unsolved. Most work on time series clustering considers the clustering of individual time series, e.g., gene expression profiles, individual heartbeats or individual gait cycles. The few attempts at clustering time series streams have been shown to be objectively incorrect in some cases, and in other cases shown to work only on the most contrived datasets by carefully adjusting a large set of parameters. In this work, we make two fundamental contributions. First, we show that the problem definition for time series clustering from streams currently used is inherently flawed, and a new definition is necessary. Second, we show that the Minimum Description Length (MDL) framework offers an efficient, effective and essentially parameter-free method for time series clustering. We show that our method produces objectively correct results on a wide variety of datasets from medicine, zoology and industrial process analyses. --- paper_title: Clustering Time Series Using Unsupervised-Shapelets paper_content: Time series clustering has become an increasingly important research topic over the past decade. Most existing methods for time series clustering rely on distances calculated from the entire raw data using the Euclidean distance or Dynamic Time Warping distance as the distance measure. However, the presence of significant noise, dropouts, or extraneous data can greatly limit the accuracy of clustering in this domain. Moreover, for most real world problems, we cannot expect objects from the same class to be equal in length. As a consequence, most work on time series clustering only considers the clustering of individual time series "behaviors," e.g., individual heart beats or individual gait cycles, and contrives the time series in some way to make them all equal in length. However, contriving the data in such a way is often a harder problem than the clustering itself. In this work, we show that by using only some local patterns and deliberately ignoring the rest of the data, we can mitigate the above problems and cluster time series of different lengths, i.e., cluster one heartbeat with multiple heartbeats. To achieve this we exploit and extend a recently introduced concept in time series data mining called shapelets. Unlike existing work, our work demonstrates for the first time the unintuitive fact that shapelets can be learned from unlabeled time series. We show, with extensive empirical evaluation in diverse domains, that our method is more accurate than existing methods. Moreover, in addition to accurate clustering results, we show that our work also has the potential to give insights into the domains to which it is applied. --- paper_title: Automated Change Detection and Reactive Clustering in Multivariate Streaming Data paper_content: Many automated systems need the capability of automatic change detection without the given detection threshold. This paper presents an automated change detection algorithm in streaming multivariate data. Two overlapping windows are used to quantify the changes. While a window is used as the reference window from which the clustering is created, the other called the current window captures the newly incoming data points. A newly incoming data point can be considered a change point if it is not a member of any cluster. As our clustering-based change detector does not require detection threshold, it is an automated detector. Based on this change detector, we propose a reactive clustering algorithm for streaming data. Our empirical results show that, our clustering-based change detector works well with multivariate streaming data. The detection accuracy depends on the number of clusters in the reference window, the window width. --- paper_title: A Bayesian Approach to Concept Drift paper_content: To cope with concept drift, we placed a probability distribution over the location of the most-recent drift point. We used Bayesian model comparison to update this distribution from the predictions of models trained on blocks of consecutive observations and pruned potential drift points with low probability. We compare our approach to a non-probabilistic method for drift and a probabilistic method for change-point detection. In our experiments, our approach generally yielded improved accuracy and/or speed over these other methods. --- paper_title: Concept Drift Detection Through Resampling paper_content: Detecting changes in data-streams is an important part of enhancing learning quality in dynamic environments. We devise a procedure for detecting concept drifts in data-streams that relies on analyzing the empirical loss of learning algorithms. Our method is based on obtaining statistics from the loss distribution by reusing the data multiple times via resampling. We present theoretical guarantees for the proposed procedure based on the stability of the underlying learning algorithms. Experimental results show that the method has high recall and precision, and performs well in the presence of noise. ---	Title: A Survey of Methods for Time Series Change Point Detection Section 1: Introduction Description 1: Introduce the significance of time series analysis and change point detection in various fields and provide motivating examples. Section 2: Background Description 2: Clarify the basic concepts related to change point detection, including definitions and problem formulation. Section 3: Criteria Description 3: Discuss the practical challenges in applying change point detection, such as online detection, scalability, algorithm constraints, and performance evaluation. Section 4: Review Description 4: Provide an overview of the main categories of change point detection algorithms, including both supervised and unsupervised methods. Section 5: Supervised Methods Description 5: Detail various supervised learning approaches used in change point detection, such as binary and multi-class classifiers. Section 6: Unsupervised Methods Description 6: Explore different unsupervised learning techniques applied to time series change point detection. Section 7: Likelihood Ratio Methods Description 7: Discuss methods that utilize likelihood ratios to compare probability distributions and identify change points. Section 8: Subspace Model Methods Description 8: Present approaches based on subspace modeling for analyzing changes in time series sequences. Section 9: Probabilistic Methods Description 9: Outline probabilistic techniques like Bayesian methods for change point detection. Section 10: Kernel-Based Methods Description 10: Describe kernel-based methods which employ test statistics to assess the homogeneity of data. Section 11: Graph-Based Methods Description 11: Introduce graph-based frameworks that apply two-sample tests on equivalent graphs to detect change points. Section 12: Clustering Methods Description 12: Explain clustering approaches that use techniques like sliding window and minimum description length for change point detection. Section 13: Discussion and Comparison Description 13: Compare and contrast the surveyed methods based on key criteria to help practitioners choose the most appropriate algorithm. Section 14: Conclusions and Challenges for Future Work Description 14: Summarize the state of change point detection research, identify challenges, and suggest directions for future research.
A survey of dual-feasible and superadditive functions	23	--- paper_title: A cutting-plane approach for the two-dimensional orthogonal non-guillotine cutting problem paper_content: Abstract The two-dimensional orthogonal non-guillotine cutting problem (NGCP) appears in many industries (like wood and steel industries) and consists in cutting a rectangular master surface into a number of rectangular pieces, each with a given size and value. The pieces must be cut with their edges always parallel or orthogonal to the edges of the master surface ( orthogonal cuts ). The objective is to maximize the total value of the pieces cut. In this paper, we propose a two-level approach for solving the NGCP, where, at the first level, we select the subset of pieces to be packed into the master surface without specifying the layout, while at a second level we check only if a feasible packing layout exists. This approach has been already proposed by Fekete and Schepers [S.P. Fekete, J. Schepers, A new exact algorithm for general orthogonal d -dimensional knapsack problems, ESA 97, Springer Lecture Notes in Computer Science 1284 (1997) 144–156; S.P. Fekete, J. Schepers, On more-dimensional packing III: Exact algorithms, Tech. Rep. 97.290, Universitat zu Koln, Germany, 2000; S.P. Fekete, J. Schepers, J.C. van der Veen, An exact algorithm for higher-dimensional orthogonal packing, Tech. Rep. Under revision on Operations Research, Braunschweig University of Technology, Germany, 2004] and Caprara and Monaci [A. Caprara, M. Monaci, On the two-dimensional knapsack problem, Operations Research Letters 32 (2004) 2–14]. We propose improved reduction tests for the NGCP and a cutting-plane approach to be used in the first level of the tree search to compute effective upper bounds. Computational tests on problems derived from the literature show the effectiveness of the proposed approach, that is able to reduce the number of nodes generated at the first level of the tree search and the number of times the existence of a feasible packing layout is tested. --- paper_title: New reduction procedures and lower bounds for the two-dimensional bin packing problem with fixed orientation paper_content: The two-dimensional bin-packing problem (2BP) consists of minimizing the number of identical rectangles used to pack a set of smaller rectangles. In this paper, we propose new lower bounds for 2BP in the discrete case. They are based on the total area of the items after application of dual feasible functions (DFF). We also propose the new concept of data-dependent dual feasible functions (DDFF), which can also be applied to a 2BP instance. We propose two families of Discrete DFF and DDFF and show that they lead to bounds which strictly dominate those obtained previously. We also introduce two new reduction procedures and report computational experiments on our lower bounds. Our bounds improve on the previous best results and close 22 additional instances of a well-known established benchmark derived from literature. --- paper_title: Integer and Combinatorial Optimization paper_content: FOUNDATIONS. The Scope of Integer and Combinatorial Optimization. Linear Programming. Graphs and Networks. Polyhedral Theory. Computational Complexity. Polynomial-Time Algorithms for Linear Programming. Integer Lattices. GENERAL INTEGER PROGRAMMING. The Theory of Valid Inequalities. Strong Valid Inequalities and Facets for Structured Integer Programs. Duality and Relaxation. General Algorithms. Special-Purpose Algorithms. Applications of Special- Purpose Algorithms. COMBINATORIAL OPTIMIZATION. Integral Polyhedra. Matching. Matroid and Submodular Function Optimization. References. Indexes. --- paper_title: A branch-and-price-and-cut algorithm for the pattern minimization problem paper_content: In cutting stock problems, after an optimal (minimal stock usage) cutting plan has been devised, one might want to further reduce the operational costs by minimizing the number of setups. A setup operation occurs each time a different cutting pattern begins to be produced. The related optimization problem is known as the Pattern Minimization Problem, and it is particularly hard to solve exactly. In this paper, we present different techniques to strengthen a formulation proposed in the literature. Dual feasible functions are used for the first time to derive valid inequalities from different constraints of the model, and from linear combinations of constraints. A new arc flow formulation is also proposed. This formulation is used to define the branching scheme of our branch-and-price-and-cut algorithm, and it allows the generation of even stronger cuts by combining the branching constraints with other constraints of the model. The computational experiments conducted on instances from the literature show that our algorithm finds optimal integer solutions faster than other approaches. A set of computational results on random instances is also reported. --- paper_title: Bin packing with items uniformly distributed over intervals [a,b] paper_content: We consider the problem of packing n items which are drawn uniformly from intervals of the form [a,b], where 0 ≪ a ≪ b ≪ 1. For a fairly large class of a and b, we determine a lower bound on the asymptotic expected number of bins used in an optimum packing. The method of proof is related to the dual of the linear programming problem corresponding to the bin packing problem. We demonstrate that these bounds are tight by providing simple packing strategies which achieve them. --- paper_title: A General Framework for Bounds for Higher-Dimensional Orthogonal Packing Problems paper_content: Higher-dimensional orthogonal packing problems have a wide range of practical applications, including packing, cutting, and scheduling. In the context of a branch-and-bound framework for solving these packing problems to optimality, it is of crucial importance to have good and easy bounds for an optimal solution. Previous efforts have produced a number of special classes of such bounds. Unfortunately, some of these bounds are somewhat complicated and hard to generalize. We present a new approach for obtaining classes of lower bounds for higher-dimensional packing problems; our bounds improve and simplify several well-known bounds from previous literature. In addition, our approach provides an easy framework for proving correctness of new bounds. --- paper_title: Computing redundant resources for the resource constrained project scheduling problem paper_content: Several efficient lower bounds and time-bound adjustment methods for the resource constrained project scheduling problem (RCPSP) have recently been proposed. Some of them are based on redundant resources. In this paper we define redundant functions which are very useful for computing redundant resources. We also describe an algorithm for computing all maximal redundant functions. Once all these redundant functions have been determined, we have to identify those that are useful for bounding. Surprisingly, their number is reasonable even for large resource capacities, so a representative subset of them can be tabulated to be used efficiently. Computational results on classical RCPSP instances confirm their usefulness. --- paper_title: A Subadditive Approach to Solve Linear Integer Programs paper_content: A method is presented for solving pure integer programs by a subadditive method. This work extends to the integer linear problem a method for solving the group problem. It uses some elements of both enumeration and cutting plane theory in a unified setting. The method generates a subadditive function and solves the original integer linear program. --- paper_title: An improved typology of cutting and packing problems paper_content: The number of publications in the area of Cutting and Packing (C&P) has increased considerably over the last two decades. The typology of C&P problems introduced by Dyckhoff [Dyckhoff, H., 1990. A typology of cutting and packing problems. European Journal of Operational Research 44, 145–159] initially provided an excellent instrument for the organisation and categorisation of existing and new literature. However, over the years also some deficiencies of this typology became evident, which created problems in dealing with recent developments and prevented it from being accepted more generally. In this paper, the authors present an improved typology, which is partially based on Dyckhoff’s original ideas, but introduces new categorisation criteria, which define problem categories different from those of Dyckhoff. Furthermore, a new, consistent system of names is suggested for these problem categories. Finally, the practicability of the new scheme is demonstrated by using it as a basis for a categorisation of the C&P literature from the years between 1995 and 2004. � 2006 Elsevier B.V. All rights reserved. --- paper_title: New classes of fast lower bounds for bin packing problems paper_content: The bin packing problem is one of the classical NP-hard optimization problems. In this paper, we present a simple generic approach for obtaining new fast lower bounds, based on dual feasible functions. Worst-case analysis as well as computational results show that one of our classes clearly outperforms the previous best economical lower bound for the bin packing problem by Martello and Toth, which can be understood as a special case. In particular, we prove an asymptotic worst-case performance of 3/4 for a bound that can be computed in linear time for items sorted by size. In addition, our approach provides a general framework for establishing new bounds. --- paper_title: Computing redundant resources for the resource constrained project scheduling problem paper_content: Several efficient lower bounds and time-bound adjustment methods for the resource constrained project scheduling problem (RCPSP) have recently been proposed. Some of them are based on redundant resources. In this paper we define redundant functions which are very useful for computing redundant resources. We also describe an algorithm for computing all maximal redundant functions. Once all these redundant functions have been determined, we have to identify those that are useful for bounding. Surprisingly, their number is reasonable even for large resource capacities, so a representative subset of them can be tabulated to be used efficiently. Computational results on classical RCPSP instances confirm their usefulness. --- paper_title: A Linear Programming Approach to the Cutting Stock Problem---Part II paper_content: In this paper, the methods for stock cutting outlined in an earlier paper in this Journal [Opns Res 9, 849--859 1961] are extended and adapted to the specific full-scale paper trim problem. The paper describes a new and faster knapsack method, experiments, and formulation changes. The experiments include ones used to evaluate speed-up devices and to explore a connection with integer programming. Other experiments give waste as a function of stock length, examine the effect of multiple stock lengths on waste, and the effect of a cutting knife limitation. The formulation changes discussed are i limitation on the number of cutting knives available, n balancing of multiple machine usage when orders are being filled from more than one machine, and m introduction of a rational objective function when customers' orders are not for fixed amounts, but rather for a range of amounts. The methods developed are also applicable to a variety of cutting problems outside of the paper industry. --- paper_title: A new LP-based lower bound for the cumulative scheduling problem paper_content: Abstract This paper deals with the computation of lower bounds for Cumulative Scheduling Problems. Based on a new linear programming formulation, these lower bounds take into account how resource requirements can be satisfied simultaneously for a given resource capacity. One of the main interests of this paper is that the solutions of the LP can be tabulated, for a given value of resource capacity. Thus, even if it is based on a linear programming formulation, the computation of the bounds is low time consuming as confirmed by our computational results on the Resource Constrained Project Scheduling Problem. --- paper_title: A Linear Programming Approach to the Cutting-Stock Problem paper_content: The cutting-stock problem is the problem of filling an order at minimum cost for specified numbers of lengths of material to be cut from given stock lengths of given cost. When expressed as an integer programming problem the large number of variables involved generally makes computation infeasible. This same difficulty persists when only an approximate solution is being sought by linear programming. In this paper, a technique is described for overcoming the difficulty in the linear programming formulation of the problem. The technique enables one to compute always with a matrix which has no more columns than it has rows. --- paper_title: Computing redundant resources for the resource constrained project scheduling problem paper_content: Several efficient lower bounds and time-bound adjustment methods for the resource constrained project scheduling problem (RCPSP) have recently been proposed. Some of them are based on redundant resources. In this paper we define redundant functions which are very useful for computing redundant resources. We also describe an algorithm for computing all maximal redundant functions. Once all these redundant functions have been determined, we have to identify those that are useful for bounding. Surprisingly, their number is reasonable even for large resource capacities, so a representative subset of them can be tabulated to be used efficiently. Computational results on classical RCPSP instances confirm their usefulness. --- paper_title: Computing redundant resources for the resource constrained project scheduling problem paper_content: Several efficient lower bounds and time-bound adjustment methods for the resource constrained project scheduling problem (RCPSP) have recently been proposed. Some of them are based on redundant resources. In this paper we define redundant functions which are very useful for computing redundant resources. We also describe an algorithm for computing all maximal redundant functions. Once all these redundant functions have been determined, we have to identify those that are useful for bounding. Surprisingly, their number is reasonable even for large resource capacities, so a representative subset of them can be tabulated to be used efficiently. Computational results on classical RCPSP instances confirm their usefulness. --- paper_title: A cutting-plane approach for the two-dimensional orthogonal non-guillotine cutting problem paper_content: Abstract The two-dimensional orthogonal non-guillotine cutting problem (NGCP) appears in many industries (like wood and steel industries) and consists in cutting a rectangular master surface into a number of rectangular pieces, each with a given size and value. The pieces must be cut with their edges always parallel or orthogonal to the edges of the master surface ( orthogonal cuts ). The objective is to maximize the total value of the pieces cut. In this paper, we propose a two-level approach for solving the NGCP, where, at the first level, we select the subset of pieces to be packed into the master surface without specifying the layout, while at a second level we check only if a feasible packing layout exists. This approach has been already proposed by Fekete and Schepers [S.P. Fekete, J. Schepers, A new exact algorithm for general orthogonal d -dimensional knapsack problems, ESA 97, Springer Lecture Notes in Computer Science 1284 (1997) 144–156; S.P. Fekete, J. Schepers, On more-dimensional packing III: Exact algorithms, Tech. Rep. 97.290, Universitat zu Koln, Germany, 2000; S.P. Fekete, J. Schepers, J.C. van der Veen, An exact algorithm for higher-dimensional orthogonal packing, Tech. Rep. Under revision on Operations Research, Braunschweig University of Technology, Germany, 2004] and Caprara and Monaci [A. Caprara, M. Monaci, On the two-dimensional knapsack problem, Operations Research Letters 32 (2004) 2–14]. We propose improved reduction tests for the NGCP and a cutting-plane approach to be used in the first level of the tree search to compute effective upper bounds. Computational tests on problems derived from the literature show the effectiveness of the proposed approach, that is able to reduce the number of nodes generated at the first level of the tree search and the number of times the existence of a feasible packing layout is tested. --- paper_title: Integer and Combinatorial Optimization paper_content: FOUNDATIONS. The Scope of Integer and Combinatorial Optimization. Linear Programming. Graphs and Networks. Polyhedral Theory. Computational Complexity. Polynomial-Time Algorithms for Linear Programming. Integer Lattices. GENERAL INTEGER PROGRAMMING. The Theory of Valid Inequalities. Strong Valid Inequalities and Facets for Structured Integer Programs. Duality and Relaxation. General Algorithms. Special-Purpose Algorithms. Applications of Special- Purpose Algorithms. COMBINATORIAL OPTIMIZATION. Integral Polyhedra. Matching. Matroid and Submodular Function Optimization. References. Indexes. --- paper_title: Exact Algorithm for Minimising the Number of Setups in the One-Dimensional Cutting Stock Problem paper_content: The cutting stock problem is that of finding a cutting of stock material to meet demands for small pieces of prescribed dimensions while minimising the amount of waste. Because changing over from one cutting pattern to another involves significant setups, an auxiliary problem is to minimise the number of different patterns that are used. The pattern minimisation problem is significantly more complex, but it is of great practical importance. In this paper, we propose an integer programming formulation for the problem that involves an exponential number of binary variables and associated columns, each of which corresponds to selecting a fixed number of copies of a specific cutting pattern. The integer program is solved using a column generation approach where the subproblem is a nonlinear integer program that can be decomposed into multiple bounded integer knapsack problems. At each node of the branch-and-bound tree, the linear programming relaxation of our formulation is made tighter by adding super-additive inequalities. Branching rules are presented that yield a balanced tree. Incumbent solutions are obtained using a rounding heuristic. The resulting branch-and-price-and-cut procedure is used to produce optimal or approximately optimal solutions for a set of real-life problems. --- paper_title: A branch-and-price-and-cut algorithm for the pattern minimization problem paper_content: In cutting stock problems, after an optimal (minimal stock usage) cutting plan has been devised, one might want to further reduce the operational costs by minimizing the number of setups. A setup operation occurs each time a different cutting pattern begins to be produced. The related optimization problem is known as the Pattern Minimization Problem, and it is particularly hard to solve exactly. In this paper, we present different techniques to strengthen a formulation proposed in the literature. Dual feasible functions are used for the first time to derive valid inequalities from different constraints of the model, and from linear combinations of constraints. A new arc flow formulation is also proposed. This formulation is used to define the branching scheme of our branch-and-price-and-cut algorithm, and it allows the generation of even stronger cuts by combining the branching constraints with other constraints of the model. The computational experiments conducted on instances from the literature show that our algorithm finds optimal integer solutions faster than other approaches. A set of computational results on random instances is also reported. --- paper_title: Integer and Combinatorial Optimization paper_content: FOUNDATIONS. The Scope of Integer and Combinatorial Optimization. Linear Programming. Graphs and Networks. Polyhedral Theory. Computational Complexity. Polynomial-Time Algorithms for Linear Programming. Integer Lattices. GENERAL INTEGER PROGRAMMING. The Theory of Valid Inequalities. Strong Valid Inequalities and Facets for Structured Integer Programs. Duality and Relaxation. General Algorithms. Special-Purpose Algorithms. Applications of Special- Purpose Algorithms. COMBINATORIAL OPTIMIZATION. Integral Polyhedra. Matching. Matroid and Submodular Function Optimization. References. Indexes. --- paper_title: New classes of fast lower bounds for bin packing problems paper_content: The bin packing problem is one of the classical NP-hard optimization problems. In this paper, we present a simple generic approach for obtaining new fast lower bounds, based on dual feasible functions. Worst-case analysis as well as computational results show that one of our classes clearly outperforms the previous best economical lower bound for the bin packing problem by Martello and Toth, which can be understood as a special case. In particular, we prove an asymptotic worst-case performance of 3/4 for a bound that can be computed in linear time for items sorted by size. In addition, our approach provides a general framework for establishing new bounds. --- paper_title: New reduction procedures and lower bounds for the two-dimensional bin packing problem with fixed orientation paper_content: The two-dimensional bin-packing problem (2BP) consists of minimizing the number of identical rectangles used to pack a set of smaller rectangles. In this paper, we propose new lower bounds for 2BP in the discrete case. They are based on the total area of the items after application of dual feasible functions (DFF). We also propose the new concept of data-dependent dual feasible functions (DDFF), which can also be applied to a 2BP instance. We propose two families of Discrete DFF and DDFF and show that they lead to bounds which strictly dominate those obtained previously. We also introduce two new reduction procedures and report computational experiments on our lower bounds. Our bounds improve on the previous best results and close 22 additional instances of a well-known established benchmark derived from literature. --- paper_title: Computing redundant resources for the resource constrained project scheduling problem paper_content: Several efficient lower bounds and time-bound adjustment methods for the resource constrained project scheduling problem (RCPSP) have recently been proposed. Some of them are based on redundant resources. In this paper we define redundant functions which are very useful for computing redundant resources. We also describe an algorithm for computing all maximal redundant functions. Once all these redundant functions have been determined, we have to identify those that are useful for bounding. Surprisingly, their number is reasonable even for large resource capacities, so a representative subset of them can be tabulated to be used efficiently. Computational results on classical RCPSP instances confirm their usefulness. --- paper_title: Exact Algorithm for Minimising the Number of Setups in the One-Dimensional Cutting Stock Problem paper_content: The cutting stock problem is that of finding a cutting of stock material to meet demands for small pieces of prescribed dimensions while minimising the amount of waste. Because changing over from one cutting pattern to another involves significant setups, an auxiliary problem is to minimise the number of different patterns that are used. The pattern minimisation problem is significantly more complex, but it is of great practical importance. In this paper, we propose an integer programming formulation for the problem that involves an exponential number of binary variables and associated columns, each of which corresponds to selecting a fixed number of copies of a specific cutting pattern. The integer program is solved using a column generation approach where the subproblem is a nonlinear integer program that can be decomposed into multiple bounded integer knapsack problems. At each node of the branch-and-bound tree, the linear programming relaxation of our formulation is made tighter by adding super-additive inequalities. Branching rules are presented that yield a balanced tree. Incumbent solutions are obtained using a rounding heuristic. The resulting branch-and-price-and-cut procedure is used to produce optimal or approximately optimal solutions for a set of real-life problems. --- paper_title: Valid inequalities based on simple mixed-integer sets paper_content: In this paper we use facets of simple mixed-integer sets with three variables to derive a parametric family of valid inequalities for general mixed-integer sets. We call these inequalities two-step MIR inequalities as they can be derived by applying the simple mixed-integer rounding (MIR) principle of Wolsey (1998) twice. The two-step MIR inequalities define facets of the master cyclic group polyhedron of Gomory (1969). In addition, they dominate the strong fractional cuts of Letchford and Lodi (2002). --- paper_title: New classes of fast lower bounds for bin packing problems paper_content: The bin packing problem is one of the classical NP-hard optimization problems. In this paper, we present a simple generic approach for obtaining new fast lower bounds, based on dual feasible functions. Worst-case analysis as well as computational results show that one of our classes clearly outperforms the previous best economical lower bound for the bin packing problem by Martello and Toth, which can be understood as a special case. In particular, we prove an asymptotic worst-case performance of 3/4 for a bound that can be computed in linear time for items sorted by size. In addition, our approach provides a general framework for establishing new bounds. --- paper_title: Strengthening Chvatal-Gomory Cuts and Gomory fractional cuts paper_content: Chvatal-Gomory and Gomory fractional cuts are well-known cutting planes for pure integer programming problems. Various methods for strengthening them are known, for example based on subadditive functions or disjunctive techniques. We present a new and surprisingly simple strengthening procedure, discuss its properties, and present some computational results. --- paper_title: A Subadditive Approach to Solve Linear Integer Programs paper_content: A method is presented for solving pure integer programs by a subadditive method. This work extends to the integer linear problem a method for solving the group problem. It uses some elements of both enumeration and cutting plane theory in a unified setting. The method generates a subadditive function and solves the original integer linear program. --- paper_title: Strengthening Chvatal-Gomory Cuts and Gomory fractional cuts paper_content: Chvatal-Gomory and Gomory fractional cuts are well-known cutting planes for pure integer programming problems. Various methods for strengthening them are known, for example based on subadditive functions or disjunctive techniques. We present a new and surprisingly simple strengthening procedure, discuss its properties, and present some computational results. --- paper_title: Exact Algorithm for Minimising the Number of Setups in the One-Dimensional Cutting Stock Problem paper_content: The cutting stock problem is that of finding a cutting of stock material to meet demands for small pieces of prescribed dimensions while minimising the amount of waste. Because changing over from one cutting pattern to another involves significant setups, an auxiliary problem is to minimise the number of different patterns that are used. The pattern minimisation problem is significantly more complex, but it is of great practical importance. In this paper, we propose an integer programming formulation for the problem that involves an exponential number of binary variables and associated columns, each of which corresponds to selecting a fixed number of copies of a specific cutting pattern. The integer program is solved using a column generation approach where the subproblem is a nonlinear integer program that can be decomposed into multiple bounded integer knapsack problems. At each node of the branch-and-bound tree, the linear programming relaxation of our formulation is made tighter by adding super-additive inequalities. Branching rules are presented that yield a balanced tree. Incumbent solutions are obtained using a rounding heuristic. The resulting branch-and-price-and-cut procedure is used to produce optimal or approximately optimal solutions for a set of real-life problems. --- paper_title: New reduction procedures and lower bounds for the two-dimensional bin packing problem with fixed orientation paper_content: The two-dimensional bin-packing problem (2BP) consists of minimizing the number of identical rectangles used to pack a set of smaller rectangles. In this paper, we propose new lower bounds for 2BP in the discrete case. They are based on the total area of the items after application of dual feasible functions (DFF). We also propose the new concept of data-dependent dual feasible functions (DDFF), which can also be applied to a 2BP instance. We propose two families of Discrete DFF and DDFF and show that they lead to bounds which strictly dominate those obtained previously. We also introduce two new reduction procedures and report computational experiments on our lower bounds. Our bounds improve on the previous best results and close 22 additional instances of a well-known established benchmark derived from literature. --- paper_title: A branch-and-price-and-cut algorithm for the pattern minimization problem paper_content: In cutting stock problems, after an optimal (minimal stock usage) cutting plan has been devised, one might want to further reduce the operational costs by minimizing the number of setups. A setup operation occurs each time a different cutting pattern begins to be produced. The related optimization problem is known as the Pattern Minimization Problem, and it is particularly hard to solve exactly. In this paper, we present different techniques to strengthen a formulation proposed in the literature. Dual feasible functions are used for the first time to derive valid inequalities from different constraints of the model, and from linear combinations of constraints. A new arc flow formulation is also proposed. This formulation is used to define the branching scheme of our branch-and-price-and-cut algorithm, and it allows the generation of even stronger cuts by combining the branching constraints with other constraints of the model. The computational experiments conducted on instances from the literature show that our algorithm finds optimal integer solutions faster than other approaches. A set of computational results on random instances is also reported. --- paper_title: Bin packing with items uniformly distributed over intervals [a,b] paper_content: We consider the problem of packing n items which are drawn uniformly from intervals of the form [a,b], where 0 ≪ a ≪ b ≪ 1. For a fairly large class of a and b, we determine a lower bound on the asymptotic expected number of bins used in an optimum packing. The method of proof is related to the dual of the linear programming problem corresponding to the bin packing problem. We demonstrate that these bounds are tight by providing simple packing strategies which achieve them. --- paper_title: The Two-Dimensional Finite Bin Packing Problem. Part II: New lower and upper bounds paper_content: This paper is the second of a two part series and describes new lower and upper bounds for a more general version of the Two-Dimensional Finite Bin Packing Problem (2BP) than the one considered in Part I (see Boschetti and Mingozzi 2002). With each item is associated an input parameter specifying if it has a fixed orientation or it can be rotated by \(90^{\circ}\). This problem contains as special cases the oriented and non-oriented 2BP. The new lower bound is based on the one described in Part I for the oriented 2BP. The computational results on the test problems derived from the literature show the effectiveness of the new proposed lower and upper bounds. --- paper_title: New classes of fast lower bounds for bin packing problems paper_content: The bin packing problem is one of the classical NP-hard optimization problems. In this paper, we present a simple generic approach for obtaining new fast lower bounds, based on dual feasible functions. Worst-case analysis as well as computational results show that one of our classes clearly outperforms the previous best economical lower bound for the bin packing problem by Martello and Toth, which can be understood as a special case. In particular, we prove an asymptotic worst-case performance of 3/4 for a bound that can be computed in linear time for items sorted by size. In addition, our approach provides a general framework for establishing new bounds. --- paper_title: The Two-Dimensional Finite Bin Packing Problem. Part II: New lower and upper bounds paper_content: This paper is the second of a two part series and describes new lower and upper bounds for a more general version of the Two-Dimensional Finite Bin Packing Problem (2BP) than the one considered in Part I (see Boschetti and Mingozzi 2002). With each item is associated an input parameter specifying if it has a fixed orientation or it can be rotated by \(90^{\circ}\). This problem contains as special cases the oriented and non-oriented 2BP. The new lower bound is based on the one described in Part I for the oriented 2BP. The computational results on the test problems derived from the literature show the effectiveness of the new proposed lower and upper bounds. --- paper_title: New lower bounds for the three-dimensional finite bin packing problem paper_content: The three-dimensional finite bin packing problem (3BP) consists of determining the minimum number of large identical three-dimensional rectangular boxes, bins, that are required for allocating without overlapping a given set of three-dimensional rectangular items. The items are allocated into a bin with their edges always parallel or orthogonal to the bin edges. The problem is strongly NP-hard and finds many practical applications. We propose new lower bounds for the problem where the items have a fixed orientation and then we extend these bounds to the more general problem where for each item the subset of rotations by 90° allowed is specified. The proposed lower bounds have been evaluated on different test problems derived from the literature. Computational results show the effectiveness of the new lower bounds. --- paper_title: New reduction procedures and lower bounds for the two-dimensional bin packing problem with fixed orientation paper_content: The two-dimensional bin-packing problem (2BP) consists of minimizing the number of identical rectangles used to pack a set of smaller rectangles. In this paper, we propose new lower bounds for 2BP in the discrete case. They are based on the total area of the items after application of dual feasible functions (DFF). We also propose the new concept of data-dependent dual feasible functions (DDFF), which can also be applied to a 2BP instance. We propose two families of Discrete DFF and DDFF and show that they lead to bounds which strictly dominate those obtained previously. We also introduce two new reduction procedures and report computational experiments on our lower bounds. Our bounds improve on the previous best results and close 22 additional instances of a well-known established benchmark derived from literature. --- paper_title: Exact Algorithm for Minimising the Number of Setups in the One-Dimensional Cutting Stock Problem paper_content: The cutting stock problem is that of finding a cutting of stock material to meet demands for small pieces of prescribed dimensions while minimising the amount of waste. Because changing over from one cutting pattern to another involves significant setups, an auxiliary problem is to minimise the number of different patterns that are used. The pattern minimisation problem is significantly more complex, but it is of great practical importance. In this paper, we propose an integer programming formulation for the problem that involves an exponential number of binary variables and associated columns, each of which corresponds to selecting a fixed number of copies of a specific cutting pattern. The integer program is solved using a column generation approach where the subproblem is a nonlinear integer program that can be decomposed into multiple bounded integer knapsack problems. At each node of the branch-and-bound tree, the linear programming relaxation of our formulation is made tighter by adding super-additive inequalities. Branching rules are presented that yield a balanced tree. Incumbent solutions are obtained using a rounding heuristic. The resulting branch-and-price-and-cut procedure is used to produce optimal or approximately optimal solutions for a set of real-life problems. --- paper_title: A branch-and-price-and-cut algorithm for the pattern minimization problem paper_content: In cutting stock problems, after an optimal (minimal stock usage) cutting plan has been devised, one might want to further reduce the operational costs by minimizing the number of setups. A setup operation occurs each time a different cutting pattern begins to be produced. The related optimization problem is known as the Pattern Minimization Problem, and it is particularly hard to solve exactly. In this paper, we present different techniques to strengthen a formulation proposed in the literature. Dual feasible functions are used for the first time to derive valid inequalities from different constraints of the model, and from linear combinations of constraints. A new arc flow formulation is also proposed. This formulation is used to define the branching scheme of our branch-and-price-and-cut algorithm, and it allows the generation of even stronger cuts by combining the branching constraints with other constraints of the model. The computational experiments conducted on instances from the literature show that our algorithm finds optimal integer solutions faster than other approaches. A set of computational results on random instances is also reported. --- paper_title: Integer and Combinatorial Optimization paper_content: FOUNDATIONS. The Scope of Integer and Combinatorial Optimization. Linear Programming. Graphs and Networks. Polyhedral Theory. Computational Complexity. Polynomial-Time Algorithms for Linear Programming. Integer Lattices. GENERAL INTEGER PROGRAMMING. The Theory of Valid Inequalities. Strong Valid Inequalities and Facets for Structured Integer Programs. Duality and Relaxation. General Algorithms. Special-Purpose Algorithms. Applications of Special- Purpose Algorithms. COMBINATORIAL OPTIMIZATION. Integral Polyhedra. Matching. Matroid and Submodular Function Optimization. References. Indexes. --- paper_title: A Subadditive Approach to Solve Linear Integer Programs paper_content: A method is presented for solving pure integer programs by a subadditive method. This work extends to the integer linear problem a method for solving the group problem. It uses some elements of both enumeration and cutting plane theory in a unified setting. The method generates a subadditive function and solves the original integer linear program. --- paper_title: Strengthening Chvatal-Gomory Cuts and Gomory fractional cuts paper_content: Chvatal-Gomory and Gomory fractional cuts are well-known cutting planes for pure integer programming problems. Various methods for strengthening them are known, for example based on subadditive functions or disjunctive techniques. We present a new and surprisingly simple strengthening procedure, discuss its properties, and present some computational results. --- paper_title: Strengthening Chvatal-Gomory Cuts and Gomory fractional cuts paper_content: Chvatal-Gomory and Gomory fractional cuts are well-known cutting planes for pure integer programming problems. Various methods for strengthening them are known, for example based on subadditive functions or disjunctive techniques. We present a new and surprisingly simple strengthening procedure, discuss its properties, and present some computational results. --- paper_title: Strengthening Chvatal-Gomory Cuts and Gomory fractional cuts paper_content: Chvatal-Gomory and Gomory fractional cuts are well-known cutting planes for pure integer programming problems. Various methods for strengthening them are known, for example based on subadditive functions or disjunctive techniques. We present a new and surprisingly simple strengthening procedure, discuss its properties, and present some computational results. --- paper_title: Valid inequalities based on simple mixed-integer sets paper_content: In this paper we use facets of simple mixed-integer sets with three variables to derive a parametric family of valid inequalities for general mixed-integer sets. We call these inequalities two-step MIR inequalities as they can be derived by applying the simple mixed-integer rounding (MIR) principle of Wolsey (1998) twice. The two-step MIR inequalities define facets of the master cyclic group polyhedron of Gomory (1969). In addition, they dominate the strong fractional cuts of Letchford and Lodi (2002). --- paper_title: Valid inequalities based on simple mixed-integer sets paper_content: In this paper we use facets of simple mixed-integer sets with three variables to derive a parametric family of valid inequalities for general mixed-integer sets. We call these inequalities two-step MIR inequalities as they can be derived by applying the simple mixed-integer rounding (MIR) principle of Wolsey (1998) twice. The two-step MIR inequalities define facets of the master cyclic group polyhedron of Gomory (1969). In addition, they dominate the strong fractional cuts of Letchford and Lodi (2002). --- paper_title: New reduction procedures and lower bounds for the two-dimensional bin packing problem with fixed orientation paper_content: The two-dimensional bin-packing problem (2BP) consists of minimizing the number of identical rectangles used to pack a set of smaller rectangles. In this paper, we propose new lower bounds for 2BP in the discrete case. They are based on the total area of the items after application of dual feasible functions (DFF). We also propose the new concept of data-dependent dual feasible functions (DDFF), which can also be applied to a 2BP instance. We propose two families of Discrete DFF and DDFF and show that they lead to bounds which strictly dominate those obtained previously. We also introduce two new reduction procedures and report computational experiments on our lower bounds. Our bounds improve on the previous best results and close 22 additional instances of a well-known established benchmark derived from literature. --- paper_title: Strengthening Chvatal-Gomory Cuts and Gomory fractional cuts paper_content: Chvatal-Gomory and Gomory fractional cuts are well-known cutting planes for pure integer programming problems. Various methods for strengthening them are known, for example based on subadditive functions or disjunctive techniques. We present a new and surprisingly simple strengthening procedure, discuss its properties, and present some computational results. --- paper_title: Exact Algorithm for Minimising the Number of Setups in the One-Dimensional Cutting Stock Problem paper_content: The cutting stock problem is that of finding a cutting of stock material to meet demands for small pieces of prescribed dimensions while minimising the amount of waste. Because changing over from one cutting pattern to another involves significant setups, an auxiliary problem is to minimise the number of different patterns that are used. The pattern minimisation problem is significantly more complex, but it is of great practical importance. In this paper, we propose an integer programming formulation for the problem that involves an exponential number of binary variables and associated columns, each of which corresponds to selecting a fixed number of copies of a specific cutting pattern. The integer program is solved using a column generation approach where the subproblem is a nonlinear integer program that can be decomposed into multiple bounded integer knapsack problems. At each node of the branch-and-bound tree, the linear programming relaxation of our formulation is made tighter by adding super-additive inequalities. Branching rules are presented that yield a balanced tree. Incumbent solutions are obtained using a rounding heuristic. The resulting branch-and-price-and-cut procedure is used to produce optimal or approximately optimal solutions for a set of real-life problems. --- paper_title: The Two-Dimensional Finite Bin Packing Problem. Part II: New lower and upper bounds paper_content: This paper is the second of a two part series and describes new lower and upper bounds for a more general version of the Two-Dimensional Finite Bin Packing Problem (2BP) than the one considered in Part I (see Boschetti and Mingozzi 2002). With each item is associated an input parameter specifying if it has a fixed orientation or it can be rotated by \(90^{\circ}\). This problem contains as special cases the oriented and non-oriented 2BP. The new lower bound is based on the one described in Part I for the oriented 2BP. The computational results on the test problems derived from the literature show the effectiveness of the new proposed lower and upper bounds. --- paper_title: Valid inequalities based on simple mixed-integer sets paper_content: In this paper we use facets of simple mixed-integer sets with three variables to derive a parametric family of valid inequalities for general mixed-integer sets. We call these inequalities two-step MIR inequalities as they can be derived by applying the simple mixed-integer rounding (MIR) principle of Wolsey (1998) twice. The two-step MIR inequalities define facets of the master cyclic group polyhedron of Gomory (1969). In addition, they dominate the strong fractional cuts of Letchford and Lodi (2002). --- paper_title: A Subadditive Approach to Solve Linear Integer Programs paper_content: A method is presented for solving pure integer programs by a subadditive method. This work extends to the integer linear problem a method for solving the group problem. It uses some elements of both enumeration and cutting plane theory in a unified setting. The method generates a subadditive function and solves the original integer linear program. --- paper_title: New classes of fast lower bounds for bin packing problems paper_content: The bin packing problem is one of the classical NP-hard optimization problems. In this paper, we present a simple generic approach for obtaining new fast lower bounds, based on dual feasible functions. Worst-case analysis as well as computational results show that one of our classes clearly outperforms the previous best economical lower bound for the bin packing problem by Martello and Toth, which can be understood as a special case. In particular, we prove an asymptotic worst-case performance of 3/4 for a bound that can be computed in linear time for items sorted by size. In addition, our approach provides a general framework for establishing new bounds. --- paper_title: A Linear Programming Approach to the Cutting-Stock Problem paper_content: The cutting-stock problem is the problem of filling an order at minimum cost for specified numbers of lengths of material to be cut from given stock lengths of given cost. When expressed as an integer programming problem the large number of variables involved generally makes computation infeasible. This same difficulty persists when only an approximate solution is being sought by linear programming. In this paper, a technique is described for overcoming the difficulty in the linear programming formulation of the problem. The technique enables one to compute always with a matrix which has no more columns than it has rows. --- paper_title: New classes of fast lower bounds for bin packing problems paper_content: The bin packing problem is one of the classical NP-hard optimization problems. In this paper, we present a simple generic approach for obtaining new fast lower bounds, based on dual feasible functions. Worst-case analysis as well as computational results show that one of our classes clearly outperforms the previous best economical lower bound for the bin packing problem by Martello and Toth, which can be understood as a special case. In particular, we prove an asymptotic worst-case performance of 3/4 for a bound that can be computed in linear time for items sorted by size. In addition, our approach provides a general framework for establishing new bounds. --- paper_title: New reduction procedures and lower bounds for the two-dimensional bin packing problem with fixed orientation paper_content: The two-dimensional bin-packing problem (2BP) consists of minimizing the number of identical rectangles used to pack a set of smaller rectangles. In this paper, we propose new lower bounds for 2BP in the discrete case. They are based on the total area of the items after application of dual feasible functions (DFF). We also propose the new concept of data-dependent dual feasible functions (DDFF), which can also be applied to a 2BP instance. We propose two families of Discrete DFF and DDFF and show that they lead to bounds which strictly dominate those obtained previously. We also introduce two new reduction procedures and report computational experiments on our lower bounds. Our bounds improve on the previous best results and close 22 additional instances of a well-known established benchmark derived from literature. --- paper_title: Exact Algorithm for Minimising the Number of Setups in the One-Dimensional Cutting Stock Problem paper_content: The cutting stock problem is that of finding a cutting of stock material to meet demands for small pieces of prescribed dimensions while minimising the amount of waste. Because changing over from one cutting pattern to another involves significant setups, an auxiliary problem is to minimise the number of different patterns that are used. The pattern minimisation problem is significantly more complex, but it is of great practical importance. In this paper, we propose an integer programming formulation for the problem that involves an exponential number of binary variables and associated columns, each of which corresponds to selecting a fixed number of copies of a specific cutting pattern. The integer program is solved using a column generation approach where the subproblem is a nonlinear integer program that can be decomposed into multiple bounded integer knapsack problems. At each node of the branch-and-bound tree, the linear programming relaxation of our formulation is made tighter by adding super-additive inequalities. Branching rules are presented that yield a balanced tree. Incumbent solutions are obtained using a rounding heuristic. The resulting branch-and-price-and-cut procedure is used to produce optimal or approximately optimal solutions for a set of real-life problems. --- paper_title: A new LP-based lower bound for the cumulative scheduling problem paper_content: Abstract This paper deals with the computation of lower bounds for Cumulative Scheduling Problems. Based on a new linear programming formulation, these lower bounds take into account how resource requirements can be satisfied simultaneously for a given resource capacity. One of the main interests of this paper is that the solutions of the LP can be tabulated, for a given value of resource capacity. Thus, even if it is based on a linear programming formulation, the computation of the bounds is low time consuming as confirmed by our computational results on the Resource Constrained Project Scheduling Problem. --- paper_title: A branch-and-price-and-cut algorithm for the pattern minimization problem paper_content: In cutting stock problems, after an optimal (minimal stock usage) cutting plan has been devised, one might want to further reduce the operational costs by minimizing the number of setups. A setup operation occurs each time a different cutting pattern begins to be produced. The related optimization problem is known as the Pattern Minimization Problem, and it is particularly hard to solve exactly. In this paper, we present different techniques to strengthen a formulation proposed in the literature. Dual feasible functions are used for the first time to derive valid inequalities from different constraints of the model, and from linear combinations of constraints. A new arc flow formulation is also proposed. This formulation is used to define the branching scheme of our branch-and-price-and-cut algorithm, and it allows the generation of even stronger cuts by combining the branching constraints with other constraints of the model. The computational experiments conducted on instances from the literature show that our algorithm finds optimal integer solutions faster than other approaches. A set of computational results on random instances is also reported. --- paper_title: Computing redundant resources for the resource constrained project scheduling problem paper_content: Several efficient lower bounds and time-bound adjustment methods for the resource constrained project scheduling problem (RCPSP) have recently been proposed. Some of them are based on redundant resources. In this paper we define redundant functions which are very useful for computing redundant resources. We also describe an algorithm for computing all maximal redundant functions. Once all these redundant functions have been determined, we have to identify those that are useful for bounding. Surprisingly, their number is reasonable even for large resource capacities, so a representative subset of them can be tabulated to be used efficiently. Computational results on classical RCPSP instances confirm their usefulness. --- paper_title: CUTGEN1: a problem generator for the standard one-dimensional cutting stock problem paper_content: In this paper a problem generator for the Standard One-dimensional Cutting Stock Problem (1D-CSP) is developed. The problem is defined and its parameters are identified. Then it is shown what features have been included in the program in order to allow for the generation of easily reproducible random problem instances. Finally, by applying the generator a set of benchmark problems is identified. ---	Title: A Survey of Dual-Feasible and Superadditive Functions Section 1: Introduction Description 1: This section introduces the concept of dual-feasible functions, their applications, and the objective of the survey. Section 2: DFF and superadditive functions Description 2: This section provides definitions and properties of dual-feasible and superadditive functions and explains their relationships. Section 3: Dual-feasible functions Description 3: This section elaborates on the concept of dual-feasible functions and presents alternative definitions and properties. Section 4: Superadditive functions and maximal DFF Description 4: This section discusses the role of superadditive nondecreasing functions, introduces the notion of maximal DFF, and defines their properties. Section 5: DFF and valid inequalities Description 5: This section highlights the use of dual-feasible functions in generating valid inequalities for integer programs. Section 6: Frameworks for creating valid DFF Description 6: This section presents frameworks for obtaining complex superadditive functions by combining simpler ones. Section 7: Compositions and linear combinations Description 7: This section explains how to combine dual-feasible functions using linear combinations and compositions. Section 8: Finding a corresponding dominant function by symmetry Description 8: This section demonstrates the process of creating a maximal dual-feasible function from a non-maximal one by utilizing symmetry. Section 9: Improving a function by studying its limiting behavior Description 9: This section describes a method for obtaining a maximal DFF from a non-maximal superadditive function by analyzing its limiting behavior. Section 10: Using two different functions for x and r_x Description 10: This section illustrates the approach of using two different DFFs for integer and fractional parts of values. Section 11: Using the ceiling function Description 11: This section discusses how to derive superadditive functions by leveraging the ceiling function. Section 12: Comparative analysis of dual-feasible functions Description 12: This section surveys various dual-feasible functions proposed in the literature, providing explicit definitions and determining their maximality. Section 13: Fekete and Schepers Description 13: This section examines the dual-feasible functions proposed by Fekete and Schepers and their properties. Section 14: Boschetti and Mingozzi Description 14: This section details the functions introduced by Boschetti and Mingozzi, highlighting their applications and effectiveness. Section 15: Carlier et al. Description 15: This section describes the contributions of Carlier et al. to dual-feasible functions and their improvements. Section 16: Vanderbeck Description 16: This section explores the dual-feasible functions used by Vanderbeck and their impact on pattern minimization problems. Section 17: Burdett and Johnson Description 17: This section outlines the function for rational values proposed by Burdett and Johnson and its application in deriving valid inequalities. Section 18: Letchford and Lodi Description 18: This section explains the dual-feasible function proposed by Letchford and Lodi to strengthen Chvátal-Gomory and Gomory fractional cuts. Section 19: Dash and Günlük Description 19: This section introduces a maximal dual-feasible function derived by Dash and Günlük from their extended mixed-integer rounding inequalities. Section 20: Summary Description 20: This section summarizes key findings, dominance relations, maximality properties, and applications of dual-feasible functions discussed in the survey. Section 21: Bin-packing instances Description 21: This section compares different dual-feasible functions for various bin-packing problem instances and evaluates their lower-bounding effectiveness. Section 22: Composing functions Description 22: This section analyzes the performance improvements obtained by composing different dual-feasible functions. Section 23: Strengthening the column generation model for the PMP with DFF Description 23: This section evaluates the effectiveness of dual-feasible functions in strengthening valid inequalities for the pattern minimization problem.
Continuous Opinion Dynamics under Bounded Confidence: A Survey	7	--- paper_title: A Discrete Nonlinear and Non-Autonomous Model of Consensus Formation paper_content: Consensus formation among n experts is modeled as a positive discrete dynamical system in n dimensions. The well–known linear but non–autonomous model is extended to a nonlinear one admitting also various kinds of averaging beside the weighted arithmetic mean. For this model a sufficient condition for reaching a consensus is presented. As a special case consensus formation under bounded confidence is analyzed. --- paper_title: Modelling collective opinion formation by means of active Brownian particles paper_content: The concept of active Brownian particles is used to model a collective opinion formation process. It is assumed that individuals in community create a two-component communication field that influences the change of opinions of other persons and/or can induce their migration. The communication field is described by a reaction-diffusion equation, the opinion change of the individuals is given by a master equation, while the migration is described by a set of Langevin equations, coupled by the communication field. In the mean-field limit holding for fast communication we derive a critical population size, above which the community separates into a majority and a minority with opposite opinions. The existence of external support (e.g. from mass media) changes the ratio between minority and majority, until above a critical external support the supported subpopulation exists always as a majority. Spatial effects lead to two critical "social" temperatures, between which the community exists in a metastable state, thus fluctuations below a certain critical wave number may result in a spatial opinion separation. The range of metastability is particularly determined by a parameter characterizing the individual response to the communication field. In our discussion, we draw analogies to phase transitions in physical systems. PACS. 05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion - 05.65.+b Self- organized systems - 87.23.Ge Dynamics of social systems --- paper_title: A stabilization theorem for dynamics of continuous opinions paper_content: A stabilization theorem for processes of opinion dynamics is presented. The theorem is applicable to a wide class of models of continuous opinion dynamics based on averaging (like the models of Hegselmann-Krause and Weisbuch-Deffuant). The analysis detects self-confidence as a driving force of stabilization. --- paper_title: Communication regimes in opinion dynamics: Changing the number of communicating agents paper_content: This article contributes in four ways to the research on time-discrete continuous opinion dynamics with compromising agents. First, communication regimes are introduced as an elementary concept of opinion dynamic models. Second, we develop a model that covers two major models of continuous opinion dynamics, i.e. the basic model of Deffuant and Weisbuch as well as the model of Krause and Hegselmann. To combine these models, which handle different numbers of communicating agents, we convert the convergence parameter of Deffuant and Weisbuch into a parameter called self-support. Third, we present simulation results that shed light on how the number of communicating agents but also how the self-support affect opinion dynamics. The fourth contribution is a theoretically driven criterion when to stop a simulation and how to extrapolate to infinite many steps. --- paper_title: How can extremism prevail? A study based on the relative agreement interaction model paper_content: Abstract: We model opinion dynamics in populations of agents with continuous opinion and uncertainty. The opinions and uncertainties are modified by random pair interactions. We propose a new model of interactions, called relative agreement model, which is a variant of the previously discussed bounded confidence. In this model, uncertainty as well as opinion can be modified by interactions. We introduce extremist agents by attributing a much lower uncertainty (and thus higher persuasion) to a small proportion of agents at the extremes of the opinion distribution. We study the evolution of the opinion distribution submitted to the relative agreement model. Depending upon the choice of parameters, the extremists can have a very local influence or attract the whole population. We propose a qualitative analysis of the convergence process based on a local field notion. The genericity of the observed results is tested on several variants of the bounded confidence model. --- paper_title: Consensus Strikes Back in the Hegselmann-Krause Model of Continuous Opinion Dynamics Under Bounded Confidence paper_content: The agent-based bounded confidence model of opinion dynamics of Hegselmann and Krause (2002) is reformulated as an interactive Markov chain. This abstracts from individual agents to a population model which gives a good view on the underlying attractive states of continuous opinion dynamics. We mutually analyse the agent-based model and the interactive Markov chain with a focus on the number of agents and onesided dynamics. Finally, we compute animated bifurcation diagrams that give an overview about the dynamical behavior. They show an interesting phenomenon when we lower the bound of confidence: After the first bifurcation from consensus to polarisation consensus strikes back for a while. --- paper_title: Continuous Opinion Dynamics: Insights through Interactive Markov Chains paper_content: We reformulate the agent-based opinion dynamics models of Weisbuch-Deffuant and Hegselmann-Krause as interactive Markov chains. So we switch the scope from a finite number of n agents to a finite number of n opinion classes. Thus, we will look at an infinite population distributed to opinion classes instead of agents with real number opinions. The interactive Markov chains show similar dynamical behavior as the agent-based models: stabilization and clustering. Our framework leads to a discrete bifurcation diagram for each model which gives a good view on the driving forces and the attractive states of the system. The analysis shows that the emergence of minor clusters in the Weisbuch-Deffuant model and of meta-stable states with very slow convergence to consensus in the Hegselmann Krause model are intrinsic to the dynamical behavior. --- paper_title: Better Being Third Than Second In A Search For A Majority Opinion paper_content: Monte Carlo simulations of a Sznajd model show that if a near-consensus is formed out of four initially equally widespread opinions, the one which at intermediate times is second in the number of adherents usually loses out against the third-placed opinion. --- paper_title: Consensus Strikes Back in the Hegselmann-Krause Model of Continuous Opinion Dynamics Under Bounded Confidence paper_content: The agent-based bounded confidence model of opinion dynamics of Hegselmann and Krause (2002) is reformulated as an interactive Markov chain. This abstracts from individual agents to a population model which gives a good view on the underlying attractive states of continuous opinion dynamics. We mutually analyse the agent-based model and the interactive Markov chain with a focus on the number of agents and onesided dynamics. Finally, we compute animated bifurcation diagrams that give an overview about the dynamical behavior. They show an interesting phenomenon when we lower the bound of confidence: After the first bifurcation from consensus to polarisation consensus strikes back for a while. --- paper_title: Continuous Opinion Dynamics: Insights through Interactive Markov Chains paper_content: We reformulate the agent-based opinion dynamics models of Weisbuch-Deffuant and Hegselmann-Krause as interactive Markov chains. So we switch the scope from a finite number of n agents to a finite number of n opinion classes. Thus, we will look at an infinite population distributed to opinion classes instead of agents with real number opinions. The interactive Markov chains show similar dynamical behavior as the agent-based models: stabilization and clustering. Our framework leads to a discrete bifurcation diagram for each model which gives a good view on the driving forces and the attractive states of the system. The analysis shows that the emergence of minor clusters in the Weisbuch-Deffuant model and of meta-stable states with very slow convergence to consensus in the Hegselmann Krause model are intrinsic to the dynamical behavior. --- paper_title: Dynamics of structured attitudes and opinions paper_content: Opinion dynamic models frequently assume an opinion to be a onedimensional concept and only sometimes vectors of opinions are considered. Contrary, psychological attitude theory considers an attitude to be a multidimensional concept, where each dimension is composed of beliefs and evaluative components. In this article we extend classic basic models of opinion dynamics such that they can capture this multidimensionality. We present models where individuals talk about difierent issues, e.g. evaluations or beliefs about the relation between objects and attributes. We present reinterpretations the results of previous simulations and we present results of simulations of new dynamics. Those new dynamics are based on a hierarchical approach to bounded confldence. --- paper_title: Consensus Strikes Back in the Hegselmann-Krause Model of Continuous Opinion Dynamics Under Bounded Confidence paper_content: The agent-based bounded confidence model of opinion dynamics of Hegselmann and Krause (2002) is reformulated as an interactive Markov chain. This abstracts from individual agents to a population model which gives a good view on the underlying attractive states of continuous opinion dynamics. We mutually analyse the agent-based model and the interactive Markov chain with a focus on the number of agents and onesided dynamics. Finally, we compute animated bifurcation diagrams that give an overview about the dynamical behavior. They show an interesting phenomenon when we lower the bound of confidence: After the first bifurcation from consensus to polarisation consensus strikes back for a while. --- paper_title: Compromise and Synchronization in Opinion Dynamics paper_content: Abstract.We discuss two models of opinion dynamics. We first present a brief review of ::: the Hegselmann and Krause (HK) compromise model in two dimensions, ::: showing that it is possible to simulate the dynamics ::: in the limit of an infinite number of agents by solving numerically a rate equation for ::: a continuum distribution of opinions. Then, we discuss the Opinion Changing Rate (OCR) model, ::: which allows to study under which conditions a group of agents with a ::: different natural tendency (rate) to change opinion can find the ::: agreement. In the context of the this model, consensus is viewed as a synchronization ::: process. --- paper_title: Modelling Group Opinion Shift to Extreme : the Smooth Bounded Confidence Model paper_content: We consider the phenomenon of opinion shift to the extreme reported in the social psychology literature. We argue that a good candidate to model this phenomenon can be a new variant of the bounded confidence (BC) model, the smooth BC model which we propose in this paper. This model considers individuals with a continuous opinion and an uncertainty. Individuals interact by random pairs, and attract each other's opinion proportionally to a Gaussian function of the distance between their opinions. We first show that this model presents a shift to the extreme when we introduce extremists (very convinced individuals with extreme opinions) in the population, even if there is the same number of extremists located at each extreme. This behaviour is similar to the one already identified with other versions of BC model. Then we propose a modification of the smooth BC model to account for the social psychology data and theories related to this phenomenon. The modification is based on the hypothesis of perspective taking (empathy) in the context of consensus seeking. --- paper_title: MONTE CARLO SIMULATION OF DEFFUANT OPINION DYNAMICS WITH QUALITY DIFFERENCES paper_content: In this work, the consequences of different opinion qualities in the Deffuant model were examined. If these qualities are randomly distributed, no different behavior was observed. In contrast to that, systematically assigned qualities had strong effects to the final opinion distribution. There was a high probability that the strongest opinion was one with a high quality. Furthermore, under the same conditions, this major opinion was much stronger than in the models without systematic differences. Finally, a society with systematic quality differences needed more tolerance to form a complete consensus than one without or with unsystematic ones. --- paper_title: Truth and Cognitive Division of Labour First Steps towards a Computer Aided Social Epistemology paper_content: The paper analyzes the chances for the truth to be found and broadly accepted under conditions of cognitive division of labour combined with a social exchange process. Cognitive division of labour means, that only some individuals are active truth seekers, possibly with different capacities. The social exchange process consists in an exchange of opinions between all individuals, whether truth seekers or not. We de- velop a model which is investigated by both, mathematical tools and computer simulations. As an analytical result the Funnel theorem states that under rather weak conditions on the social process a consensus on the truth will be reached if all individuals posses an arbitrarily small inclination for truth seeking. The Leading the pack theorem states that under certain conditions even a single truth seeker may lead all individuals to the truth. Systematic simulations analyze how close and how fast groups can get to the truth depending on the frequency of truth seekers, their capacities as truth seekers, the position of the truth (more to the extreme or more in the centre of an opinion space), and the willingness to take into account the opinions of others when exchanging and updating opinions. A tricky movie visualizes simulations results in a parameter space of higher dimensions. --- paper_title: Minorities in a Model for Opinion Formation paper_content: We study a model for social influence in which the agents' opinion is a continuous variable [G. Weisbuch et al., Complexity \textbf{7}, 2, 55 (2002)]. The convergent opinion adjustment process takes place as a result of random binary encounters whenever the difference between agents' opinions is below a given threshold. The inhomogeneity in the dynamics gives rise to a complex steady state structure, which is also highly dependent on the threshold and on the convergence parameter of the model. --- paper_title: A pr 2 00 4 The role of network topology on extremism propagation with the Relative Agreement opinion dynamics paper_content: In Deffuant et al. (J. Artif. Soc. Soc. Simulation 5 (2002) 4), we proposed a simple model of opinion dynamics, which we used to simulate the influence of extremists in a population. Simulations were run without any specific interaction structure and varying the simulation parameters, we observed different attractors such as predominance of centrism or of extremism. We even observed in certain conditions, that the whole population drifts to one extreme of the opinion, even if initially there are an equal number of extremists at each extreme of the opinion axis. In the present paper, we study the influence of the social networks on the presence of such a dynamical behavior. In particular, we use small-world networks with variable connectivity and randomness of the connections. We find that the drift to a single extreme appears only beyond a critical level of connectivity, which decreases when the randomness increases. --- paper_title: Communication regimes in opinion dynamics: Changing the number of communicating agents paper_content: This article contributes in four ways to the research on time-discrete continuous opinion dynamics with compromising agents. First, communication regimes are introduced as an elementary concept of opinion dynamic models. Second, we develop a model that covers two major models of continuous opinion dynamics, i.e. the basic model of Deffuant and Weisbuch as well as the model of Krause and Hegselmann. To combine these models, which handle different numbers of communicating agents, we convert the convergence parameter of Deffuant and Weisbuch into a parameter called self-support. Third, we present simulation results that shed light on how the number of communicating agents but also how the self-support affect opinion dynamics. The fourth contribution is a theoretically driven criterion when to stop a simulation and how to extrapolate to infinite many steps. --- paper_title: Attitude Dynamics With Limited Verbalisation Capabilities paper_content: This article offers a new perspective for research on opinion dynamics. It demonstrates the importance of the distinction of opinion and attitude, which originally has been discussed in literature on consumer behaviour. As opinions are verbalised attitudes not only biases in interpretation and adoption processes have to be considered but also verbalisation biases should be addressed. Such biases can be caused by language deficits or social norms. The model presented in this article captures the basic features of common opinion dynamic models and additionally biases in the verbalisation process. Further, it gives a first analysis of this model and shows that precision as bias in the verbalisation process can influence the dynamics significantly. Presenting and applying the concept of area of influential attitudes the impact of each parameter (selective attitude, selective interpretation, and precision) is analysed independently. Some preliminary results for combined effects are presented. --- paper_title: How can extremism prevail? A study based on the relative agreement interaction model paper_content: Abstract: We model opinion dynamics in populations of agents with continuous opinion and uncertainty. The opinions and uncertainties are modified by random pair interactions. We propose a new model of interactions, called relative agreement model, which is a variant of the previously discussed bounded confidence. In this model, uncertainty as well as opinion can be modified by interactions. We introduce extremist agents by attributing a much lower uncertainty (and thus higher persuasion) to a small proportion of agents at the extremes of the opinion distribution. We study the evolution of the opinion distribution submitted to the relative agreement model. Depending upon the choice of parameters, the extremists can have a very local influence or attract the whole population. We propose a qualitative analysis of the convergence process based on a local field notion. The genericity of the observed results is tested on several variants of the bounded confidence model. --- paper_title: Opinion Dynamics Driven by Various Ways of Averaging paper_content: The paper treats opinion dynamics under bounded confidence when agents employ, beside an arithmetic mean, means like a geometric mean, a power mean or a random mean in aggregating opinions. The different kinds of collective dynamics resulting from these various ways of averaging are studied and compared by simulations. Particular attention is given to the random mean which is a new concept introduced in this paper. All those concrete means are just particular cases of a partial abstract mean, which also is a new concept. This comprehensive concept of averaging opinions is investigated also analytically and it is shown in particular, that the dynamics driven by it always stabilizes in a certain pattern of opinions. ---	Title: Continuous Opinion Dynamics under Bounded Confidence: A Survey Section 1: Introduction Description 1: Write an introductory overview discussing the emergence of opinion dynamics, the nature of continuous opinion dynamics, and relevant models and their historical contexts. Section 2: The models Description 2: Describe the two main models of continuous opinion dynamics (Deffuant-Weisbuch and Hegselmann-Krause) in both their agent-based and density-based formulations, including definitions and key processes. Section 3: The Deffuant-Weisbuch model Description 3: Provide a detailed explanation of the Deffuant-Weisbuch (DW) model, including its agent-based and density-based versions, mathematical formulations, and behavior under different conditions. Section 4: The Hegselmann-Krause model Description 4: Offer a thorough description of the Hegselmann-Krause (HK) model, outlining its agent-based and density-based versions, mathematical formulations, and unique characteristics. Section 5: Bifurcation Diagrams Description 5: Present and explain the bifurcation diagrams for both homogeneous density-based models, highlighting the location and transitions of clusters concerning the bound of confidence. Section 6: Extensions Description 6: Review various extensions to the basic continuous opinion dynamics models, including multidimensional opinions, heterogeneous bounds of confidence, social networks, different communication regimes, and other miscellaneous factors. Section 7: Conclusions and open problems Description 7: Summarize the key findings, highlight the importance of these models, and discuss the remaining open problems and future research directions in the field of continuous opinion dynamics.
Systematic Literature Review (SLR) of Resource Scheduling and Security in Cloud Computing	14	--- paper_title: SCHEDULING IN CLOUD COMPUTING paper_content: Cloud computing is an emerging technology. It process huge amount of data so scheduling mechanism works as a vital role in the cloud computing. Thus my protocol is designed to minimize the switching time, improve the resource utilization and also improve the server performance and throughput. This method or protocol is based on scheduling the jobs in the cloud and to solve the drawbacks in the existing protocols. Here we assign the priority to the job which gives better performance to the computer and try my best to minimize the waiting time and switching time. Best effort has been made to manage the scheduling of jobs for solving drawbacks of existing protocols and also improvise the efficiency and throughput of the server. --- paper_title: A heuristic resource scheduling scheme in time-constrained networks paper_content: Abstract Sensor device is emerging as a promising enabler for the development of new solutions in a plethora of Internet of Things (IoT) applications. With the explosion of connected devices, it is essential for conversion gateway between the Internet and sensor nodes to support end-to-end (e2e) interoperability because the current Internet Protocol (IT) does not support end-to-end delay in IEEE 802.15.4e. As part of IoT, we propose a scheduling scheme of multiple channels and multiple timeslots to minimize the e2e delay in multi-hop environments. The proposed greedy heuristic approach is compared with the meta-heuristics in terms of the given end-to-end delay bound. Although the meta-heuristics is more accurate in finding a global optimum or sub-optimal values than the greedy heuristic approach, this advantage comes at the expense of high complexity. The simulation results show that the proposed scheme reduces the complexity by obtaining suboptimal solutions that satisfy the e2e delay requirement. --- paper_title: Above the Clouds: A Berkeley View of Cloud Computing paper_content: Cloud Computing, the long-held dream of computing as a utility, has the potential to transform a large part of the IT industry, making software even more attractive as a service and shaping the way IT hardware is designed and purchased. Developers with innovative ideas for new Internet services no longer require the large capital outlays in hardware to deploy their service or the human expense to operate it. They need not be concerned about overprovisioning for a service whose popularity does not meet their predictions, thus wasting costly resources, or underprovisioning for one that becomes wildly popular, thus missing potential customers and revenue. Moreover, companies with large batch-oriented tasks can get results as quickly as their programs can scale, since using 1000 servers for one hour costs no more than using one server for 1000 hours. This elasticity of resources, without paying a premium for large scale, is unprecedented in the history of IT. Cloud Computing refers to both the applications delivered as services over the Internet and the hardware and systems software in the datacenters that provide those services. The services themselves have long been referred to as Software as a Service (SaaS). The datacenter hardware and software is what we will call a Cloud. When a Cloud is made available in a pay-as-you-go manner to the general public, we call it a Public Cloud; the service being sold is Utility Computing. We use the term Private Cloud to refer to internal datacenters of a business or other organization, not made available to the general public. Thus, Cloud Computing is the sum of SaaS and Utility Computing, but does not include Private Clouds. People can be users or providers of SaaS, or users or providers of Utility Computing. We focus on SaaS Providers (Cloud Users) and Cloud Providers, which have received less attention than SaaS Users. From a hardware point of view, three aspects are new in Cloud Computing. --- paper_title: Workflow scheduling in cloud: a survey paper_content: To program in distributed computing environments such as grids and clouds, workflow is adopted as an attractive paradigm for its powerful ability in expressing a wide range of applications, including scientific computing, multi-tier Web, and big data processing applications. With the development of cloud technology and extensive deployment of cloud platform, the problem of workflow scheduling in cloud becomes an important research topic. The challenges of the problem lie in: NP-hard nature of task-resource mapping; diverse QoS requirements; on-demand resource provisioning; performance fluctuation and failure handling; hybrid resource scheduling; data storage and transmission optimization. Consequently, a number of studies, focusing on different aspects, emerged in the literature. In this paper, we firstly conduct taxonomy and comparative review on workflow scheduling algorithms. Then, we make a comprehensive survey of workflow scheduling in cloud environment in a problem---solution manner. Based on the analysis, we also highlight some research directions for future investigation. --- paper_title: A decentralized self-adaptation mechanism for service-based applications in the cloud paper_content: Cloud computing, with its promise of (almost) unlimited computation, storage, and bandwidth, is increasingly becoming the infrastructure of choice for many organizations. As cloud offerings mature, service-based applications need to dynamically recompose themselves to self-adapt to changing QoS requirements. In this paper, we present a decentralized mechanism for such self-adaptation, using market-based heuristics. We use a continuous double-auction to allow applications to decide which services to choose, among the many on offer. We view an application as a multi-agent system and the cloud as a marketplace where many such applications self-adapt. We show through a simulation study that our mechanism is effective for the individual application as well as from the collective perspective of all applications adapting at the same time. --- paper_title: Scaling in Cloud Computing paper_content: The cloud computing is a resource and offers computer assets with services instead of a deliverable product which allows storage and shar- ing of the files of multiple types like audio, video, software's, data files and many more. The data is shared over internet cloud storage and can be accessed for free and also at an affordable price. The effective way of sharing the information and technology by collaboration the real world to availed the competitive advantages. This paper makes a brief description about the cloud computing and its scaling techniques the main explanation is on vertical scaling and horizontal scaling with examples. --- paper_title: A survey on security issues in service delivery models of cloud computing paper_content: Cloud computing is a way to increase the capacity or add capabilities dynamically without investing in new infrastructure, training new personnel, or licensing new software. It extends Information Technology's (IT) existing capabilities. In the last few years, cloud computing has grown from being a promising business concept to one of the fast growing segments of the IT industry. But as more and more information on individuals and companies are placed in the cloud, concerns are beginning to grow about just how safe an environment it is. Despite of all the hype surrounding the cloud, enterprise customers are still reluctant to deploy their business in the cloud. Security is one of the major issues which reduces the growth of cloud computing and complications with data privacy and data protection continue to plague the market. The advent of an advanced model should not negotiate with the required functionalities and capabilities present in the current model. A new model targeting at improving features of an existing model must not risk or threaten other important features of the current model. The architecture of cloud poses such a threat to the security of the existing technologies when deployed in a cloud environment. Cloud service users need to be vigilant in understanding the risks of data breaches in this new environment. In this paper, a survey of the different security risks that pose a threat to the cloud is presented. This paper is a survey more specific to the different security issues that has emanated due to the nature of the service delivery models of a cloud computing system. --- paper_title: The management of security in Cloud computing paper_content: Cloud computing has elevated IT to newer limits by offering the market environment data storage and capacity with flexible scalable computing processing power to match elastic demand and supply, whilst reducing capital expenditure. However the opportunity cost of the successful implementation of Cloud computing is to effectively manage the security in the cloud applications. Security consciousness and concerns arise as soon as one begins to run applications beyond the designated firewall and move closer towards the public domain. The purpose of the paper is to provide an overall security perspective of Cloud computing with the aim to highlight the security concerns that should be properly addressed and managed to realize the full potential of Cloud computing. Gartner's list on cloud security issues, as well the findings from the International Data Corporation enterprise panel survey based on cloud threats, will be discussed in this paper. --- paper_title: The Performance Evaluation of Proactive Fault Tolerant Scheme over Cloud using CloudSim Simulator paper_content: The main issues in a cloud based environment are security, process fail rate and performance. Fault tolerance plays a key role in ensuring high serviceability and reliability in cloud. Nowadays, demands for high fault tolerance, high serviceability and high reliability are becoming unprecedentedly strong, building a high fault tolerance, high serviceability and high reliability cloud is a critical, challenging, and urgently required task. A lot of research is currently underway to analyze how clouds can provide fault tolerance for an application. When numbers of processes are too many and any virtual machine is overloaded then the processes are failed causing lot of rework and annoyance for the users. The major cause of the failure of the processes at the virtual machine level are overloading of virtual machines, extra resource requirements of the existing processes etc. This paper introduces dynamic load balancing techniques for cloud environment in which RAM/Broker (resource awareness module) proactively decides whether the process can be applied on an existing virtual machine or it should be assigned to a different virtual machine created a fresh or any other existing virtual machine. So, in this way it can tackle the occurrence of fault. This paper also proposed a mechanism which proactively decides the load on virtual machines and according to the requirement either creates a new virtual machine or uses an existing virtual machine for the assigning the process. Once a process completes it will update the virtual machine status on the broker service so that other processes can be assigned to it. --- paper_title: Above the Clouds: A Berkeley View of Cloud Computing paper_content: Cloud Computing, the long-held dream of computing as a utility, has the potential to transform a large part of the IT industry, making software even more attractive as a service and shaping the way IT hardware is designed and purchased. Developers with innovative ideas for new Internet services no longer require the large capital outlays in hardware to deploy their service or the human expense to operate it. They need not be concerned about overprovisioning for a service whose popularity does not meet their predictions, thus wasting costly resources, or underprovisioning for one that becomes wildly popular, thus missing potential customers and revenue. Moreover, companies with large batch-oriented tasks can get results as quickly as their programs can scale, since using 1000 servers for one hour costs no more than using one server for 1000 hours. This elasticity of resources, without paying a premium for large scale, is unprecedented in the history of IT. Cloud Computing refers to both the applications delivered as services over the Internet and the hardware and systems software in the datacenters that provide those services. The services themselves have long been referred to as Software as a Service (SaaS). The datacenter hardware and software is what we will call a Cloud. When a Cloud is made available in a pay-as-you-go manner to the general public, we call it a Public Cloud; the service being sold is Utility Computing. We use the term Private Cloud to refer to internal datacenters of a business or other organization, not made available to the general public. Thus, Cloud Computing is the sum of SaaS and Utility Computing, but does not include Private Clouds. People can be users or providers of SaaS, or users or providers of Utility Computing. We focus on SaaS Providers (Cloud Users) and Cloud Providers, which have received less attention than SaaS Users. From a hardware point of view, three aspects are new in Cloud Computing. --- paper_title: Service Level Agreement in Cloud Computing paper_content: Cloud computing that provides cheap and pay-as-you-go computing resources is rapidly gaining momentum as an alternative to traditional IT Infrastructure. As more and more consumers delegate their tasks to cloud providers, Service Level Agreements(SLA) between consumers and providers emerge as a key aspect. Due to the dynamic nature of the cloud, continuous monitoring on Quality of Service (QoS) attributes is necessary to enforce SLAs. Also numerous other factors such as trust (on the cloud provider) come into consideration, particularly for enterprise customers that may outsource its critical data. This complex nature of the cloud landscape warrants a sophisticated means of managing SLAs. This paper proposes a mechanism for managing SLAs in a cloud computing environment using the Web Service Level Agreement(WSLA) framework, developed for SLA monitoring and SLA enforcement in a Service Oriented Architecture (SOA). We use the third party support feature of WSLA to delegate monitoring and enforcement tasks to other entities in order to solve the trust issues. We also present a real world use case to validate our proposal. --- paper_title: A Categorisation of Cloud Computing Business Models paper_content: This paper reviews current cloud computing business models and presents proposals on how organisations can achieve sustainability by adopting appropriate models. We classify cloud computing business models into eight types: (1) Service Provider and Service Orientation; (2) Support and Services Contracts; (3) In- House Private Clouds; (4) All-In-One Enterprise Cloud; (5) One-Stop Resources and Services; (6) Government funding; (7) Venture Capitals; and (8) Entertainment and Social Networking. Using the Jericho Forum’s ‘Cloud Cube Model’ (CCM), the paper presents a summary of the eight business models. We discuss how the CCM fits into each business model, and then based on this discuss each business model’s strengths and weaknesses. We hope adopting an appropriate cloud computing business model will help organisations investing in this technology to stand firm in the economic downturn. --- paper_title: Systematic Reviews in the Social Sciences : A Practical Guide paper_content: Such diverse thinkers as Lao-Tze, Confucius, and U.S. Defense Secretary Donald Rumsfeld have all pointed out that we need to be able to tell the difference between real and assumed knowledge. The systematic review is a scientific tool that can help with this difficult task. It can help, for example, with appraising, summarising, and communicating the results and implications of otherwise unmanageable quantities of data. This is important because quite often there are so many studies, and their results are often so conflicting, that no policymaker or practitioner could possibly carry out this task themselves.Systematic review methods have been widely used in health care, and are becoming increasingly common in the social sciences (fostered, for example, by the work of the Campbell Collaboration). ::: ::: This book outlines the rationale and methods of systematic reviews, giving worked examples from social science and other fields. It requires no previous knowledge, but takes the reader through the process stage by stage. It draws on examples from such diverse fields as psychology, criminology, education, transport, social welfare, public health, and housing and urban policy, among others.The book includes detailed sections on assessing the quality of both quantitative, and qualitative research; searching for evidence in the social sciences;meta-analytic and other methods of evidence synthesis; publication bias; heterogeneity; and approaches to dissemination. --- paper_title: Cloud Computing and Grid Computing 360-Degree Compared paper_content: Cloud Computing has become another buzzword after Web 2.0. However, there are dozens of different definitions for Cloud Computing and there seems to be no consensus on what a Cloud is. On the other hand, Cloud Computing is not a completely new concept; it has intricate connection to the relatively new but thirteen-year established Grid Computing paradigm, and other relevant technologies such as utility computing, cluster computing, and distributed systems in general. This paper strives to compare and contrast Cloud Computing with Grid Computing from various angles and give insights into the essential characteristics of both. --- paper_title: Scaling in Cloud Computing paper_content: The cloud computing is a resource and offers computer assets with services instead of a deliverable product which allows storage and shar- ing of the files of multiple types like audio, video, software's, data files and many more. The data is shared over internet cloud storage and can be accessed for free and also at an affordable price. The effective way of sharing the information and technology by collaboration the real world to availed the competitive advantages. This paper makes a brief description about the cloud computing and its scaling techniques the main explanation is on vertical scaling and horizontal scaling with examples. --- paper_title: The management of security in Cloud computing paper_content: Cloud computing has elevated IT to newer limits by offering the market environment data storage and capacity with flexible scalable computing processing power to match elastic demand and supply, whilst reducing capital expenditure. However the opportunity cost of the successful implementation of Cloud computing is to effectively manage the security in the cloud applications. Security consciousness and concerns arise as soon as one begins to run applications beyond the designated firewall and move closer towards the public domain. The purpose of the paper is to provide an overall security perspective of Cloud computing with the aim to highlight the security concerns that should be properly addressed and managed to realize the full potential of Cloud computing. Gartner's list on cloud security issues, as well the findings from the International Data Corporation enterprise panel survey based on cloud threats, will be discussed in this paper. --- paper_title: SCHEDULING IN CLOUD COMPUTING paper_content: Cloud computing is an emerging technology. It process huge amount of data so scheduling mechanism works as a vital role in the cloud computing. Thus my protocol is designed to minimize the switching time, improve the resource utilization and also improve the server performance and throughput. This method or protocol is based on scheduling the jobs in the cloud and to solve the drawbacks in the existing protocols. Here we assign the priority to the job which gives better performance to the computer and try my best to minimize the waiting time and switching time. Best effort has been made to manage the scheduling of jobs for solving drawbacks of existing protocols and also improvise the efficiency and throughput of the server. --- paper_title: Utility functions in autonomic systems paper_content: Utility functions provide a natural and advantageous framework for achieving self-optimization in distributed autonomic computing systems. We present a distributed architecture, implemented in a realistic prototype data center, that demonstrates how utility functions can enable a collection of autonomic elements to continually optimize the use of computational resources in a dynamic, heterogeneous environment. Broadly, the architecture is a two-level structure of independent autonomic elements that supports flexibility, modularity, and self-management. Individual autonomic elements manage application resource usage to optimize local service-level utility functions, and a global arbiter allocates resources among application environments based on resource-level utility functions obtained from the managers of the applications. We present empirical data that demonstrate the effectiveness of our utility function scheme in handling realistic, fluctuating Web-based transactional workloads running on a Linux cluster. --- paper_title: DepSky: Dependable and Secure Storage in a Cloud-of-Clouds paper_content: The increasing popularity of cloud storage services has lead companies that handle critical data to think about using these services for their storage needs. Medical record databases, large biomedical datasets, historical information about power systems and financial data are some examples of critical data that could be moved to the cloud. However, the reliability and security of data stored in the cloud still remain major concerns. In this work we present DepSky, a system that improves the availability, integrity, and confidentiality of information stored in the cloud through the encryption, encoding, and replication of the data on diverse clouds that form a cloud-of-clouds. We deployed our system using four commercial clouds and used PlanetLab to run clients accessing the service from different countries. We observed that our protocols improved the perceived availability, and in most cases, the access latency, when compared with cloud providers individually. Moreover, the monetary costs of using DepSky in this scenario is at most twice the cost of using a single cloud, which is optimal and seems to be a reasonable cost, given the benefits. --- paper_title: A Categorisation of Cloud Computing Business Models paper_content: This paper reviews current cloud computing business models and presents proposals on how organisations can achieve sustainability by adopting appropriate models. We classify cloud computing business models into eight types: (1) Service Provider and Service Orientation; (2) Support and Services Contracts; (3) In- House Private Clouds; (4) All-In-One Enterprise Cloud; (5) One-Stop Resources and Services; (6) Government funding; (7) Venture Capitals; and (8) Entertainment and Social Networking. Using the Jericho Forum’s ‘Cloud Cube Model’ (CCM), the paper presents a summary of the eight business models. We discuss how the CCM fits into each business model, and then based on this discuss each business model’s strengths and weaknesses. We hope adopting an appropriate cloud computing business model will help organisations investing in this technology to stand firm in the economic downturn. --- paper_title: Logging Solutions to Mitigate Risks Associated with Threats in Infrastructure as a Service Cloud paper_content: Cloud computing offers computational resources such as processing, networking, and storage to customers. However, the cloud also brings with it security concerns which affect both cloud consumers and providers. The Cloud Security Alliance (CSA) define the security concerns as the seven main threats. This paper investigates how threat number one (malicious activities performed in consumers' virtual machines/VMs) can affect the security of both consumers and providers. It proposes logging solutions to mitigate risks associated with this threat. We systematically design and implement a prototype of the proposed logging solutions in an IaaS to record the history of customer VM's files. The proposed system can be modified in order to record VMs' process behaviour log files. These log files can assist in identifying malicious activities (spamming) performed in the VMs as an example of how the proposed solutions benefits the provider side. The proposed system can record the log files while having a smaller trusted computing base compared to previous work. Thus, the logging solutions in this paper can assist in mitigating risks associated with the CSA threats to benefit consumers and providers. --- paper_title: Pricing Cloud Compute Commodities: A Novel Financial Economic Model paper_content: In this study, we design, develop, and simulate a cloud resources pricing model that satisfies two important constraints: the dynamic ability of the model to provide a high satisfaction guarantee measured as Quality of Service (QoS) - from users perspectives, profitability constraints - from the cloud service providers perspectives We employ financial option theory and treat the cloud resources as underlying assets to capture the realistic value of the cloud compute commodities (C3). We then price the cloud resources using our model. We discuss the results for four different metrics that we introduce to guarantee the quality of service and price as follows: (a) Moore's law based depreciation of asset values, (b) new technology based volatility measures in capturing price changes, (c) a new financial option pricing based model combining the above two concepts, and (d) the effect of age of resources and depreciation of cloud resource on QoS. We show that the cloud parameters can be mapped to financial economic model and we discuss the results of cloud compute commodity pricing for various parameters, such as the age of the resource, quality of service, and contract period. --- paper_title: Dynamic Resource Allocation in Computing Clouds Using Distributed Multiple Criteria Decision Analysis paper_content: In computing clouds, it is desirable to avoid wasting resources as a result of under-utilization and to avoid lengthy response times as a result of over-utilization. In this paper, we propose a new approach for dynamic autonomous resource management in computing clouds. The main contribution of this work is two-fold. First, we adopt a distributed architecture where resource management is decomposed into independent tasks, each of which is performed by Autonomous Node Agents that are tightly coupled with the physical machines in a data center. Second, the Autonomous Node Agents carry out configurations in parallel through Multiple Criteria Decision Analysis using the PROMETHEE method. Simulation results show that the proposed approach is promising in terms of scalability, feasibility and flexibility. --- paper_title: Adaptive Management of Virtualized Resources in Cloud Computing Using Feedback Control paper_content: Cloud computing as newly emergent computing environment offers dynamic flexible infrastructures and QoS guaranteed services in pay-as-you-go manner to the public. System virtualization technology which renders flexible and scalable system services is the base of the cloud computing. How to provide a self-managing and autonomic infrastructure for cloud computing through virtualization becomes an important challenge. In this paper, using feedback control theory, we present VM-based architecture for adaptive management of virtualized resources in cloud computing and model an adaptive controller that dynamically adjusts multiple virtualized resources utilization to achieve application Service Level Objective (SLO) in cloud computing. Compared with Xen, KVM is chosen as a virtual machine monitor (VMM) to implement the architecture. Evaluation of the proposed controller model showed that the model could allocate resources reasonably in response to the dynamically changing resource requirements of different applications which execute on different VMs in the virtual resource pool to achieve applications SLOs. --- paper_title: SPORC: Group Collaboration using Untrusted Cloud Resources paper_content: Cloud-based services are an attractive deployment model for user-facing applications like word processing and calendaring. Unlike desktop applications, cloud services allow multiple users to edit shared state concurrently and in real-time, while being scalable, highly available, and globally accessible. Unfortunately, these benefits come at the cost of fully trusting cloud providers with potentially sensitive and important data. ::: ::: To overcome this strict tradeoff, we present SPORC, a generic framework for building a wide variety of collaborative applications with untrusted servers. In SPORC, a server observes only encrypted data and cannot deviate from correct execution without being detected. SPORC allows concurrent, low-latency editing of shared state, permits disconnected operation, and supports dynamic access control even in the presence of concurrency. We demonstrate SPORC's flexibility through two prototype applications: a causally-consistent key-value store and a browser-based collaborative text editor. ::: ::: Conceptually, SPORC illustrates the complementary benefits of operational transformation (OT) and fork* consistency. The former allows SPORC clients to execute concurrent operations without locking and to resolve any resulting conflicts automatically. The latter prevents a misbehaving server from equivocating about the order of operations unless it is willing to fork clients into disjoint sets. Notably, unlike previous systems, SPORC can automatically recover from such malicious forks by leveraging OT's conflict resolution mechanism. --- paper_title: Venus: verification for untrusted cloud storage paper_content: This paper presents Venus, a service for securing user interaction with untrusted cloud storage. Specifically, Venus guarantees integrity and consistency for applications accessing a key-based object store service, without requiring trusted components or changes to the storage provider. Venus completes all operations optimistically, guaranteeing data integrity. It then verifies operation consistency and notifies the application. Whenever either integrity or consistency is violated, Venus alerts the application. We implemented Venus and evaluated it with Amazon S3 commodity storage service. The evaluation shows that it adds no noticeable overhead to storage operations. --- paper_title: Static and dynamic server allocation in systems with on/off sources paper_content: A system consisting of a number of servers, where demands of different types arrive in bursts (modelled by interrupted Poisson processes), is examined in the steady state. The problem is to decide how many servers to allocate to each job type, so as to minimize a cost function expressed in terms of average queue sizes. First, an exact analysis is provided for an isolated IPP/M/n queue. The results are used to compute the optimal static server allocation policy. The latter is then compared to four heuristic policies which employ dynamic switching of servers from one queue to another (such switches take time and hence incur costs). --- paper_title: Depot: Cloud Storage with Minimal Trust paper_content: The paper describes the design, implementation, and evaluation of Depot, a cloud storage system that minimizes trust assumptions. Depot tolerates buggy or malicious behavior by any number of clients or servers, yet it provides safety and liveness guarantees to correct clients. Depot provides these guarantees using a two-layer architecture. First, Depot ensures that the updates observed by correct nodes are consistently ordered under Fork-Join-Causal consistency (FJC). FJC is a slight weakening of causal consistency that can be both safe and live despite faulty nodes. Second, Depot implements protocols that use this consistent ordering of updates to provide other desirable consistency, staleness, durability, and recovery properties. Our evaluation suggests that the costs of these guarantees are modest and that Depot can tolerate faults and maintain good availability, latency, overhead, and staleness even when significant faults occur. --- paper_title: HAIL: a high-availability and integrity layer for cloud storage paper_content: We introduce HAIL (High-Availability and Integrity Layer), a distributed cryptographic system that allows a set of servers to prove to a client that a stored file is intact and retrievable. HAIL strengthens, formally unifies, and streamlines distinct approaches from the cryptographic and distributed-systems communities. Proofs in HAIL are efficiently computable by servers and highly compact---typically tens or hundreds of bytes, irrespective of file size. HAIL cryptographically verifies and reactively reallocates file shares. It is robust against an active, mobile adversary, i.e., one that may progressively corrupt the full set of servers. We propose a strong, formal adversarial model for HAIL, and rigorous analysis and parameter choices. We show how HAIL improves on the security and efficiency of existing tools, like Proofs of Retrievability (PORs) deployed on individual servers. We also report on a prototype implementation. --- paper_title: A new model to ensure security in cloud computing services paper_content: In the commercial world, various computing needs are provided as a service. Service providers meet these computing needs in different ways, for example, by maintaining software or purchasing expensive hardware. Security is one of the most critical aspects in a cloud computing environment due to the sensitivity and importance of information stored in the cloud. The risk of malicious insiders in the cloud and the failure of cloud services have received a great deal of attention by companies. This paper focuses on issues related to data security and privacy in cloud computing and proposes a new model, called Multi-Cloud Databases (MCDB). The purpose of the proposed new model is to address security and privacy risks in the cloud computing environment. Three security issues will be examined in our proposed model: data integrity, data intrusion, and service availability. --- paper_title: Data Storage Security Model for Cloud Computing paper_content: Data security is one of the biggest concerns in adopting Cloud computing. In Cloud environment, users remotely store their data and relieve themselves from the hassle of local storage and maintenance. However, in this process, they lose control over their data. Existing approaches do not take all the facets into consideration viz. dynamic nature of Cloud, computation & communication overhead etc. In this paper, we propose a Data Storage Security Model to achieve storage correctness incorporating Cloud’s dynamic nature while maintaining low computation and communication cost. --- paper_title: Deployment models: Towards eliminating security concerns from cloud computing paper_content: Cloud computing has become a popular choice as an alternative to investing new IT systems. When making decisions on adopting cloud computing related solutions, security has always been a major concern. This article summarizes security concerns in cloud computing and proposes five service deployment models to ease these concerns. The proposed models provide different security related features to address different requirements and scenarios and can serve as reference models for deployment. --- paper_title: BlueSky: A Cloud-Backed File System for the Enterprise paper_content: We present BlueSky, a network file system backed by cloud storage. BlueSky stores data persistently in a cloud storage provider such as Amazon S3 or Windows Azure, allowing users to take advantage of the reliability and large storage capacity of cloud providers and avoid the need for dedicated server hardware. Clients access the storage through a proxy running on-site, which caches data to provide lower-latency responses and additional opportunities for optimization. We describe some of the optimizations which are necessary to achieve good performance and low cost, including a log-structured design and a secure in-cloud log cleaner. BlueSky supports multiple protocols--both NFS and CIFS--and is portable to different providers. ---	Title: Systematic Literature Review (SLR) of Resource Scheduling and Security in Cloud Computing Section 1: INTRODUCTION Description 1: Introduce the importance of scheduling in cloud computing, the associated security issues, and the objectives of this paper. Outline the organization of the paper. Section 2: BACKGROUND Description 2: Provide a general view of cloud computing, cloud architecture, features, obstacles, research method, and research questions. Section 3: Cloud Definition Description 3: Discuss the various definitions of cloud computing, the Service Level Agreement (SLA), and the concerns of Quality of Service (QoS). Section 4: Research Method Description 4: Explain the Systematic Literature Review (SLR) method, its stages, and its necessity for this research, including identifying gaps and classifications. Section 5: Research Questions Description 5: List the specific research questions that guide this study. Section 6: Scope Description 6: Define the scope of the research using the PICOC model. Section 7: SEARCH STRATEGY Description 7: Discuss the choice of the search period, search strings, electronic resources, and manual search methods. Section 8: Study Selection Criteria and Procedures Description 8: Describe the inclusion/exclusion criteria and the procedures for performing the selection of studies. Section 9: QUALITY ASSESSMENT Description 9: Outline the decision-making process about the quality of existing work and the quality assessment questionnaires. Section 10: DATA EXTRACTION Description 10: Detail the proposed questions for data extraction from each paper, including the types of models, security issues, and outcomes. Section 11: SYNTHESIS Description 11: Explain the process for synthesizing data from the studies, including the synthesis strategy and threats to validity. Section 12: LIMITATIONS Description 12: Discuss the limitations anticipated in this research. Section 13: DISCUSSION Description 13: Discuss the findings from the SLR, including recent related approaches, models, and the proposed solution. Section 14: CONCLUSION Description 14: Summarize the paper’s findings and the importance of SLR in cloud computing scheduling and security.
Congestion Control Techniques in WSNs: A Review	15	--- paper_title: A Light-Weight Opportunistic Forwarding Protocol with Optimized Preamble Length for Low-Duty-Cycle Wireless Sensor Networks paper_content: In wireless sensor networks, sensed information is expected to be reliably and timely delivered to a sink in an ad-hoc way. However, it is challenging to achieve this goal because of the highly dynamic topology induced from asynchronous duty cycles and temporally and spatially varying link quality among nodes. Currently some opportunistic forwarding protocols have been proposed to address the challenge. However, they involve complicated mechanisms to determine the best forwarder at each hop, which incurs heavy overheads for the resource-constrained nodes. In this paper, we propose a light-weight opportunistic forwarding (LWOF) scheme. Different from other recently proposed opportunistic forwarding schemes, LWOF employs neither historical network information nor a contention process to select a forwarder prior to data transmissions. It confines forwarding candidates to an optimized area, and takes advantage of the preamble in low-power-listening (LPL) MAC protocols and dual-channel communication to forward a packet to a unique downstream node towards the sink with a high probability, without making a forwarding decision prior to data transmission. Under LWOF, we optimize LPL MAC protocol to have a shortened preamble (LWMAC), based on a theoretical analysis on the relationship among preamble length, delivery probability at each hop, node density and sleep duration. Simulation results show that LWOF, along with LWMAC, can achieve relatively good performance in terms of delivery reliability and latency, as a receiver-based opportunistic forwarding protocol, while reducing energy consumption per packet by at least twice. --- paper_title: Secure Data Aggregation In Wireless Sensor Networks paper_content: Wireless sensor networks (WSNs) usually consists of a large number of sensors which have limited capability in terms of communication, computation and memory [1] (Akyildiz et al. IEEE Commun. Mag. 40 (8), 102–114, 2002), [2] (Yick et al. Comput. Networks, 52 (12), 2292–2330, 2008). These sensors are deployed in a remote and unsurveillant field and they autonomously form before they engage in a predefined sensing task. WSNs renders possible solutions to many problems in both civilian and military applications, including temperature monitoring, wildfire detection, animal tracking, and battlefield surveillance. Therefore, it is challenging to come up with efficient ways to collect desired data, given the sensors only have simple hardware and software resources. For instance, most of the sensors only have a short lifetime due to the non-rechargeable battery which is a bottleneck for designing WSNs protocols. --- paper_title: A Congestion-Aware Routing Algorithms Based on Traffic Priority in Wireless Sensor Networks paper_content: Wireless sensor network allow the network manager to measure the observed events in a short radio range and give them an appropriate response. In many applications of wireless sensor network, due to the high volume of traffic, probability of congestion and packet loss increases. Congestion in sensor networks has a direct effect on energy efficiency and quality of service applications. Congestion may cause a buffer overflow, longer queuing time and higher packet loss. Packet loss not only reduces the reliability and quality of service application but also wastes energy. In this paper, a scheme for controlling congestion in wireless sensor network is proposed. The aim of the proposed method is to reduce congestion by considering the priority of data. In the proposed algorithm, according to the data priority, the packets will be classified. According to type of packet, traffic is redirected to control congestion in the network. Finally, the proposed algorithm is simulated and the result shows that the proposed algorithm improves the number of packet loss, energy consumption and average buffer size rather than the similar algorithm. --- paper_title: Hop‐by‐Hop Congestion Avoidance in wireless sensor networks based on genetic support vector machine paper_content: Abstract Congestion in wireless sensor networks causes packet loss, throughput reduction and low energy efficiency. To address this challenge, a transmission rate control method is presented in this article. The strategy calculates buffer occupancy ratio and estimates the congestion degree of the downstream node. Then, it sends this information to the current node. The current node adjusts the transmission rate to tackle the problem of congestion, improving the network throughput by using multi-classification obtained via Support Vector Machines (SVMs). SVM parameters are tuned, using genetic algorithm. Simulations showed that in most cases, the results of the SVM network match the actual data in training and testing phases. Also, simulation results demonstrated that the proposed method not only decreases energy consumption, packet loss and end to end delay in networks, but it also significantly improves throughput and network lifetime under different traffic conditions, especially in heavy traffic areas. --- paper_title: Quality of Information for Wireless Body Area Networks paper_content: The Wireless Body Area Networks (WBANs) are a specific group of Wireless Sensor Networks (WSNs) that are used to establish patient monitoring systems which facilitate remote sensing of patients over a long period of time. In this type of system, there is possibility that the information accessible to the health expert at the end point may divert from the original information generated. In some cases, these variations may cause an expert to make a diverse decision from what would have been made specified to the original data. The proposed work contributes toward overcoming this foremost difficulty by defining a quality of information (QoI) metric that helps to preserve the required information. In this paper, we analytically model the QoI as reliability of data generation and reliability of data transfer in WBAN. --- paper_title: Data Aggregation in Wireless Sensor Networks: Previous Research, Current Status and Future Directions paper_content: Wireless sensor networks (WSNs) consist of large number of small sized sensor nodes, whose main task is to sense the desired phenomena in a particular region of interest. These networks have large number of applications such as habitat monitoring, disaster management, security and military etc. Sensor nodes are very small in size and have limited processing capability as these nodes have very low battery power. WSNs are also prone to failure, due to low battery power constraint. Data aggregation is an energy efficient technique in WSNs. Due to high node density in sensor networks same data is sensed by many nodes, which results in redundancy. This redundancy can be eliminated by using data aggregation approach while routing packets from source nodes to base station. Researchers still face trouble to select an efficient and appropriate data aggregation technique from the existing literature of WSNs. This research work depicts a broad methodical literature analysis of data aggregation in the area of WSNs in specific. In this survey, standard methodical literature analysis technique is used based on a complete collection of 123 research papers out of large collection of 932 research papers published in 20 foremost workshops, symposiums, conferences and 17 prominent journals. The current status of data aggregation in WSNs is distributed into various categories. Methodical analysis of data aggregation in WSNs is presented which includes techniques, tools, methodology and challenges in data aggregation. The literature covered fifteen types of data aggregation techniques in WSNs. Detailed analysis of this research work will help researchers to find the important characteristics of data aggregation techniques and will also help to select the most suitable technique for data aggregation. Research issues and future research directions have also been suggested in this research literature. --- paper_title: A Survey on Reliability Protocols in Wireless Sensor Networks paper_content: Wireless Sensor Network (WSN) applications have become more and more attractive with the miniaturization of circuits and the large variety of sensors. The different application domains, especially critical fields of WSN use, make the reliability of data acquisition and communication a hot research field that must be tackled efficiently. Indeed, the quality of largely used, cheap-cost wireless sensors and their scarce energy supply support these reliability challenges that lead to data loss or corruption. For solving this problem, the conception of a reliability mechanism that detects these shortcomings and recovers to them becomes necessary. In this article, we present a survey on existing reliability protocols conceived especially for WSNs due to their special features. The deep classification and discussion in this study allow for understanding the pros and cons of state-of-the-art works in order to enhance the existing schemes and fill the gaps. We have classified the works according to the required level of reliability, the manner to identify the origins of the lack of reliability, and the control to recover this lack of reliability. Across the discussion along this study, we deduce that the cross-layer design between MAC, routing, and transport layers presents a good concept to efficiently overcome the different reliability holes. --- paper_title: A Survey on Reliability Protocols in Wireless Sensor Networks paper_content: Wireless Sensor Network (WSN) applications have become more and more attractive with the miniaturization of circuits and the large variety of sensors. The different application domains, especially critical fields of WSN use, make the reliability of data acquisition and communication a hot research field that must be tackled efficiently. Indeed, the quality of largely used, cheap-cost wireless sensors and their scarce energy supply support these reliability challenges that lead to data loss or corruption. For solving this problem, the conception of a reliability mechanism that detects these shortcomings and recovers to them becomes necessary. In this article, we present a survey on existing reliability protocols conceived especially for WSNs due to their special features. The deep classification and discussion in this study allow for understanding the pros and cons of state-of-the-art works in order to enhance the existing schemes and fill the gaps. We have classified the works according to the required level of reliability, the manner to identify the origins of the lack of reliability, and the control to recover this lack of reliability. Across the discussion along this study, we deduce that the cross-layer design between MAC, routing, and transport layers presents a good concept to efficiently overcome the different reliability holes. --- paper_title: Quality of Information for Wireless Body Area Networks paper_content: The Wireless Body Area Networks (WBANs) are a specific group of Wireless Sensor Networks (WSNs) that are used to establish patient monitoring systems which facilitate remote sensing of patients over a long period of time. In this type of system, there is possibility that the information accessible to the health expert at the end point may divert from the original information generated. In some cases, these variations may cause an expert to make a diverse decision from what would have been made specified to the original data. The proposed work contributes toward overcoming this foremost difficulty by defining a quality of information (QoI) metric that helps to preserve the required information. In this paper, we analytically model the QoI as reliability of data generation and reliability of data transfer in WBAN. --- paper_title: A Survey on Reliability Protocols in Wireless Sensor Networks paper_content: Wireless Sensor Network (WSN) applications have become more and more attractive with the miniaturization of circuits and the large variety of sensors. The different application domains, especially critical fields of WSN use, make the reliability of data acquisition and communication a hot research field that must be tackled efficiently. Indeed, the quality of largely used, cheap-cost wireless sensors and their scarce energy supply support these reliability challenges that lead to data loss or corruption. For solving this problem, the conception of a reliability mechanism that detects these shortcomings and recovers to them becomes necessary. In this article, we present a survey on existing reliability protocols conceived especially for WSNs due to their special features. The deep classification and discussion in this study allow for understanding the pros and cons of state-of-the-art works in order to enhance the existing schemes and fill the gaps. We have classified the works according to the required level of reliability, the manner to identify the origins of the lack of reliability, and the control to recover this lack of reliability. Across the discussion along this study, we deduce that the cross-layer design between MAC, routing, and transport layers presents a good concept to efficiently overcome the different reliability holes. --- paper_title: A Light-Weight Opportunistic Forwarding Protocol with Optimized Preamble Length for Low-Duty-Cycle Wireless Sensor Networks paper_content: In wireless sensor networks, sensed information is expected to be reliably and timely delivered to a sink in an ad-hoc way. However, it is challenging to achieve this goal because of the highly dynamic topology induced from asynchronous duty cycles and temporally and spatially varying link quality among nodes. Currently some opportunistic forwarding protocols have been proposed to address the challenge. However, they involve complicated mechanisms to determine the best forwarder at each hop, which incurs heavy overheads for the resource-constrained nodes. In this paper, we propose a light-weight opportunistic forwarding (LWOF) scheme. Different from other recently proposed opportunistic forwarding schemes, LWOF employs neither historical network information nor a contention process to select a forwarder prior to data transmissions. It confines forwarding candidates to an optimized area, and takes advantage of the preamble in low-power-listening (LPL) MAC protocols and dual-channel communication to forward a packet to a unique downstream node towards the sink with a high probability, without making a forwarding decision prior to data transmission. Under LWOF, we optimize LPL MAC protocol to have a shortened preamble (LWMAC), based on a theoretical analysis on the relationship among preamble length, delivery probability at each hop, node density and sleep duration. Simulation results show that LWOF, along with LWMAC, can achieve relatively good performance in terms of delivery reliability and latency, as a receiver-based opportunistic forwarding protocol, while reducing energy consumption per packet by at least twice. --- paper_title: A Survey on Reliability Protocols in Wireless Sensor Networks paper_content: Wireless Sensor Network (WSN) applications have become more and more attractive with the miniaturization of circuits and the large variety of sensors. The different application domains, especially critical fields of WSN use, make the reliability of data acquisition and communication a hot research field that must be tackled efficiently. Indeed, the quality of largely used, cheap-cost wireless sensors and their scarce energy supply support these reliability challenges that lead to data loss or corruption. For solving this problem, the conception of a reliability mechanism that detects these shortcomings and recovers to them becomes necessary. In this article, we present a survey on existing reliability protocols conceived especially for WSNs due to their special features. The deep classification and discussion in this study allow for understanding the pros and cons of state-of-the-art works in order to enhance the existing schemes and fill the gaps. We have classified the works according to the required level of reliability, the manner to identify the origins of the lack of reliability, and the control to recover this lack of reliability. Across the discussion along this study, we deduce that the cross-layer design between MAC, routing, and transport layers presents a good concept to efficiently overcome the different reliability holes. --- paper_title: RCRT: rate-controlled reliable transport for wireless sensor networks paper_content: Emerging high-rate applications (imaging, structural monitoring, acoustic localization) will need to transport large volumes of data concurrently from several sensors. These applications are also loss-intolerant. A key requirement for such applications, then, is a protocol that reliably transport sensor data from many sources to one or more sinks without incurring congestion collapse. In this paper, we discuss RCRT, a rate-controlled reliable transport protocol suitable for constrained sensor nodes. RCRT uses end-to-end explicit loss recovery, but places all the congestion detection and rate adaptation functionality in the sinks. This has two important advantages: efficiency and flexibility. Because sinks make rate allocation decisions, they are able to achieve greater efficiency since they have a more comprehensive view of network behavior. For the same reason, it is possible to alter the rate allocation decisions (for example, from one that ensures that all nodes get the same rate, to one that ensures that nodes get rates in proportion to their demands), without modifying sensor code at all. We evaluate RCRT extensively on a 40-node wireless sensor network testbed and show that RCRT achieves more than twice the rate achieved by a recently proposed interference-aware distributed rate-control protocol, IFRC [23]. --- paper_title: Traffic-- -Aware Dynamic Routing to Alleviate Aware Dynamic Routing to Alleviate Aware Dynamic Routing to Alleviate Aware Dynamic Routing to Alleviate Congestion in paper_content: Congestion is one of the problems encountered in Wireless Sensor Networks (WSNs). Many algorithms came into existence. They all focused on the solution by reducing the number of packets to be sent by the sender node. This solution is not ideal as it cause decrease in overall throughput in the WSN. This paper focuses on a dynamic aware routing algorithm which is aware of network traffic and probability of congestion. This solves problem of congestion in WSNs through optimal use of idle nodes in the network. Though congestion areas, the algorithm sends less packets while it sends more packets through many paths that contains idle nodes or the nodes that have less load. The proposed algorithm can overcome obstacles created by congestion and provide best throughput performance in WSNs. --- paper_title: Congestion Avoidance Based on Lightweight Buffer Management in Sensor Networks paper_content: A wireless sensor network is constrained by computation capability, memory space, communication bandwidth, and above all, energy supply. When a critical event triggers a surge of data generated by the sensors, congestion may occur as data packets converge toward a sink. Congestion causes energy waste, throughput reduction, and information loss. However, the important problem of congestion avoidance in sensor networks is largely open. This paper proposes a congestion-avoidance scheme based on lightweight buffer management. We describe simple yet effective approaches that prevent data packets from overflowing the buffer space of the intermediate sensors. These approaches automatically adapt the sensors' forwarding rates to nearly optimal without causing congestion. We discuss how to implement buffer-based congestion avoidance with different MAC protocols. In particular, for CSMA with implicit ACK, our 1/k-buffer solution prevents hidden terminals from causing congestion. We demonstrate how to maintain near-optimal throughput with a small buffer at each sensor and how to achieve congestion-free load balancing when there are multiple routing paths toward multiple sinks --- paper_title: Explicit and precise rate control for wireless sensor networks paper_content: The state of the art congestion control algorithms for wireless sensor networks respond to coarse-grained feedback regarding available capacity in the network with an additive increase multiplicative decrease mechanism to set source rates. Providing precise feedback is challenging in wireless networks because link capacities vary with traffic on interfering links. We address this challenge by applying a receiver capacity model that associates capacities with nodes instead of links, and use it to develop and implement the first explicit and precise distributed rate-based congestion control protocol for wireless sensor networks --- the wireless rate control protocol (WRCP). Apart from congestion control, WRCP has been designed to achieve lexicographic max-min fairness. Through extensive experimental evaluation on the USC Tutornet wireless sensor network testbed, we show that WRCP offers substantial improvements over the state of the art in flow completion times as well as in end-to-end packet delays. ---	Title: Congestion Control Techniques in WSNs: A Review Section 1: INTRODUCTION Description 1: This section provides a detailed background on wireless sensor networks (WSNs), the significance of congestion control, and the phases involved in congestion control. Section 2: LITERATURE REVIEW Description 2: This section discusses various congestion control algorithms for WSNs, their types, and their operational procedures. Section 3: RCRT Description 3: This section describes the RCRT (Rate-Controlled Reliable Transport) protocol and its mechanism for resolving congestion. Section 4: I2MR Description 4: This section covers the I2MR (Interference and Interdependency Mitigated Routing) protocol, how it controls congestion, and its limitations. Section 5: TADR Description 5: This section elaborates on the TADR (Traffic-Aware Dynamic Routing) protocol, including its congestion control mechanism and drawbacks. Section 6: Buffer-Based Congestion Avoidance Scheme Description 6: This section outlines the buffer-based congestion avoidance scheme and its effectiveness in load balancing and buffer access. Section 7: DAIPaS Description 7: This section explains the DAIPaS (Dynamic Alternative Interference-aware Path Selection) protocol and its strategy for congestion control. Section 8: Fusion Description 8: This section describes the Fusion method for congestion control, including its reliance on queue length and hop-by-hop flow control. Section 9: WRCP (Wireless Rate Control Protocol) Description 9: This section details the WRCP protocol and its use of a receiver capacity model for fast convergence and fair rate allocation. Section 10: TRCCIT (Tunable Reliability with Congestion Control for Information Transport) Description 10: This section discusses the TRCCIT protocol, its hybrid acknowledgment approach, and multipath forwarding for congestion control. Section 11: DPCC (Decentralized Predictive Congestion Control) Description 11: This section focuses on the DPCC protocol, including its adaptive flow and back-off interval selection approaches. Section 12: GMCAR (Grid-based Multipath with Congestion Avoidance Routing) Description 12: This section introduces the GMCAR protocol, its grid-based methodology, and its effectiveness in reducing delay and increasing network output. Section 13: TASA (Traffic Aware Scheduling Algorithm) Description 13: This section elaborates on the TASA protocol, its scheduling approach, and its use of graph theory methods for traffic management. Section 14: OTF (On-the-Fly Scheduling) Description 14: This section describes the OTF scheduling approach, including its slot-based interference prevention and traffic load adaptation. Section 15: PERFORMANCE COMPARISON Description 15: This section presents a performance comparison of the discussed congestion control schemes, highlighting their operational strategies, strengths, and weaknesses.
Learning and the Unknown: Surveying Steps toward Open World Recognition	5	--- paper_title: Zero-Shot Learning—A Comprehensive Evaluation of the Good, the Bad and the Ugly paper_content: Due to the importance of zero-shot learning, i.e. classifying images where there is a lack of labeled training data, the number of proposed approaches has recently increased steadily. We argue that it is time to take a step back and to analyze the status quo of the area. The purpose of this paper is three-fold. First, given the fact that there is no agreed upon zero-shot learning benchmark, we first define a new benchmark by unifying both the evaluation protocols and data splits of publicly available datasets used for this task. This is an important contribution as published results are often not comparable and sometimes even flawed due to, e.g. pre-training on zero-shot test classes. Moreover, we propose a new zero-shot learning dataset, the Animals with Attributes 2 (AWA2) dataset which we make publicly available both in terms of image features and the images themselves. Second, we compare and analyze a significant number of the state-of-the-art methods in depth, both in the classic zero-shot setting but also in the more realistic generalized zero-shot setting. Finally, we discuss in detail the limitations of the current status of the area which can be taken as a basis for advancing it. --- paper_title: Incremental Open Set Intrusion Recognition Using Extreme Value Machine paper_content: Typically, most network intrusion detection systems use supervised learning techniques to identify network anomalies. A problem exists when identifying the unknowns and automatically updating a classifier with new query classes. This is defined as an open set incremental learning problem and we propose to extend a recently introduced method, the Extreme Value Machine (EVM) to address the issue of identifying new classes during query time. The EVM is derived from the statistical extreme value theory and is the first classifier that can perform kernel-free, nonlinear, variable bandwidth outlier detection combined with incremental learning. In this paper, we utilize the EVM for intrusion detection and measure the open set recognition performance of identifying known and unknown classes. Additionally, we evaluate the performance on the KDDCUP’99 dataset and compare the results with the state-ofthe- art Weibull-SVM (W-SVM). Our findings demonstrate that the EVM mirrors the performance of the W-SVM classifier, while it supports incremental learning. --- paper_title: Open Set Fingerprint Spoof Detection Across Novel Fabrication Materials paper_content: A fingerprint spoof detector is a pattern classifier that is used to distinguish a live finger from a fake (spoof) one in the context of an automated fingerprint recognition system. Most spoof detectors are learning-based and rely on a set of training images. Consequently, the performance of any such spoof detector significantly degrades when encountering spoofs fabricated using novel materials not found in the training set. In real-world applications, the problem of fingerprint spoof detection must be treated as an open set recognition problem where incomplete knowledge of the fabrication materials used to generate spoofs is present at training time, and novel materials may be encountered during system deployment. To mitigate the security risk posed by novel spoofs, this paper introduces: 1) the use of the Weibull-calibrated SVM (W-SVM), which is relatively robust for open set recognition, as a novel-material detector and a spoof detector and 2) a scheme for the automatic adaptation of the W-SVM-based spoof detector to new spoof materials that leverages interoperability across classifiers. Experiments conducted on new partitions of the LivDet 2011 database designed for open set evaluation suggest: 1) a 97% increase in the error rate of the existing spoof detectors when tested using new spoof materials and 2) up to 44% improvement in spoof detection performance across spoof materials when the proposed adaptive approach is used. --- paper_title: On optimum recognition error and reject tradeoff paper_content: The performance of a pattern recognition system is characterized by its error and reject tradeoff. This paper describes an optimum rejection rule and presents a general relation between the error and reject probabilities and some simple properties of the tradeoff in the optimum recognition system. The error rate can be directly evaluated from the reject function. Some practical implications of the results are discussed. Examples in normal distributions and uniform distributions are given. --- paper_title: On the feasibility of classification-based product package authentication paper_content: Depending on the product category the authenticity of a consumer good concerns economic, social and/or environmental issues. Counterfeited drugs are a threat to patient safety and cause significant economic losses. Different from physical-marking based approaches this work investigates authentication of drugs based on intrinsic texture features of the packaging material. Therefore, it is assumed that the packaging material of a certain drug shows constant but discriminative textural features which enable authentication, i.e. to prove if the packaging material is genuine or not. This objective requires considering a binary classification problem with an open set of negative classes, i.e. unknown and unseen counterfeits. In order to investigate the feasibility a novel drug packaging texture databases was acquired. The experimental evaluation of two basic requirements in texture classification serves as an evidence on the basic feasibility. --- paper_title: Novelty detection: a review - part 1: statistical approaches paper_content: Novelty detection is the identification of new or unknown data or signal that a machine learning system is not aware of during training. Novelty detection is one of the fundamental requirements of a good classification or identification system since sometimes the test data contains information about objects that were not known at the time of training the model. In this paper we provide state-of-the-art review in the area of novelty detection based on statistical approaches. The second part paper details novelty detection using neural networks. As discussed, there are a multitude of applications where novelty detection is extremely important including signal processing, computer vision, pattern recognition, data mining, and robotics. --- paper_title: Finding the Unknown: Novelty Detection with Extreme Value Signatures of Deep Neural Activations paper_content: Achieving or even surpassing human-level accuracy became recently possible in a variety of application scenarios due to the rise of convolutional neural networks (CNNs) trained from large datasets. However, solving supervised visual recognition tasks by discriminating among known categories is only one side of the coin. In contrast to this, novelty detection is still an unsolved task where instances of yet unknown categories need to be identified. Therefore, we propose to leverage the powerful discriminative nature of CNNs to novelty detection tasks by investigating class-specific activation patterns. More precisely, we assume that a semantic category can be described by its extreme value signature, that specifies which dimensions of deep neural activations have largest values. By following this intuition, we show that already a small number of high-valued dimensions allows to separate known from unknown categories. Our approach is simple, intuitive, and can be easily put on top of CNNs trained for vanilla classification tasks. We empirically validate the benefits of our approach in terms of accuracy and speed by comparing it against established methods in a variety of novelty detection tasks derived from ImageNet. Finally, we show that visualizing extreme value signatures allows to inspect class-specific patterns learned during training which may ultimately help to better understand CNN models. --- paper_title: Data-Fusion Techniques for Open-Set Recognition Problems paper_content: Most pattern classification techniques are focused on solving closed-set problems in which a classifier is trained with samples of all classes that may appear during the testing phase. In many situations, however, samples of unknown classes, i.e., whose classes did not have any example during the training stage, need to be properly handled during testing. This specific setup is referred to in the literature as open-set recognition. Open-set problems are harder as they might be ill-sampled, not sampled at all, or even undefined. Differently from existing literature, here we aim at solving open-set recognition problems combining different classifiers and features while, at the same time, taking care of unknown classes. Researchers have greatly benefited from combining different methods in order to achieve more robust and reliable classifiers in daring recognition conditions, but those solutions have often focused on closed-set setups. In this paper, we propose the integration of a newly designed open-set graph-based optimum-path forest (OSOPF) classifier with genetic programming (GP) and majority voting fusion techniques. While OSOPF takes care of learning decision boundaries more resilient to unknown classes and outliers, GP combines different problem features to discover appropriate similarity functions and allows a more robust classification through early fusion. Finally, the majority-voting approach combines different classification evidence from different classifier outcomes and features through late-fusion techniques. Performed experiments show the proposed data-fusion approaches yield effective results for open-set recognition problems, significantly outperforming existing counterparts in the literature and paving the way for investigations in this field. --- paper_title: Towards Open World Recognition paper_content: With the of advent rich classification models and high computational power visual recognition systems have found many operational applications. Recognition in the real world poses multiple challenges that are not apparent in controlled lab environments. The datasets are dynamic and novel categories must be continuously detected and then added. At prediction time, a trained system has to deal with myriad unseen categories. Operational systems require minimal downtime, even to learn. To handle these operational issues, we present the problem of Open World Recognition and formally define it. We prove that thresholding sums of monotonically decreasing functions of distances in linearly transformed feature space can balance “open space risk” and empirical risk. Our theory extends existing algorithms for open world recognition. We present a protocol for evaluation of open world recognition systems. We present the Nearest Non-Outlier (NNO) algorithm that evolves model efficiently, adding object categories incrementally while detecting outliers and managing open space risk. We perform experiments on the ImageNet dataset with 1.2M+ images to validate the effectiveness of our method on large scale visual recognition tasks. NNO consistently yields superior results on open world recognition. --- paper_title: Using Visual Rhythms for Detecting Video-Based Facial Spoof Attacks paper_content: Spoofing attacks or impersonation can be easily accomplished in a facial biometric system wherein users without access privileges attempt to authenticate themselves as valid users, in which an impostor needs only a photograph or a video with facial information of a legitimate user. Even with recent advances in biometrics, information forensics and security, vulnerability of facial biometric systems against spoofing attacks is still an open problem. Even though several methods have been proposed for photo-based spoofing attack detection, attacks performed with videos have been vastly overlooked, which hinders the use of the facial biometric systems in modern applications. In this paper, we present an algorithm for video-based spoofing attack detection through the analysis of global information which is invariant to content, since we discard video contents and analyze content-independent noise signatures present in the video related to the unique acquisition processes. Our approach takes advantage of noise signatures generated by the recaptured video to distinguish between fake and valid access videos. For that, we use the Fourier spectrum followed by the computation of video visual rhythms and the extraction of different characterization methods. For evaluation, we consider the novel unicamp video-attack database, which comprises 17 076 videos composed of real access and spoofing attack videos. In addition, we evaluate the proposed method using the replay-attack database, which contains photo-based and video-based face spoofing attacks. --- paper_title: A bounded neural network for open set recognition paper_content: Open set recognition is, more than an interesting research subject, a component of various machine learning applications which is sometimes neglected: it is not unusual the existence of learning systems developed on the top of closed-set assumptions, ignoring the error risk involved in a prediction. This risk is strictly related to the location in feature space where the prediction has to be made, compared to the location of the training data: the more distant the training observations are, less is known, higher is the risk. Proper handling of this risk can be necessary in various situation where classification and its variants are employed. This paper presents an approach to open set recognition based on an elaborate distance-like computation provided by a weightless neural network model. The results obtained in the proposed test scenarios are quite interesting, placing the proposed method among the current best ones. --- paper_title: Connecting the dots: Toward accountable machine-learning printer attribution methods paper_content: Abstract Digital forensics is rapidly evolving as a direct consequence of the adoption of machine-learning methods allied with ever-growing amounts of data. Despite the fact that these methods yield more consistent and accurate results, they may face adoption hindrances in practice if their produced results are absent in a human-interpretable form. In this paper, we exemplify how human-interpretable (a.k.a., accountable) extensions can enhance existing algorithms to aid human experts, by introducing a new method for the source printer attribution problem. We leverage the recently proposed Convolutional Texture Gradient Filter (CTGF) algorithm’s ability to capture local printing imperfections to introduce a new method that maps and highlights important attribution features directly onto the investigated printed document. Supported by Random Forest classifiers, we isolate and rank features that are pivotal for differentiating a printer from others, and back-project those features onto the investigated document, giving analysts further evidence about the attribution process. --- paper_title: Novelty detection and multi-class classification in power distribution voltage waveforms paper_content: Accurate classification of events in waveforms from electrical distribution networks.Novelty detection: dynamic identification of new classes of events.SVDD using negative examples and maximal margin separation: better generalization.Experiments using real data: significant improvements in classification accuracy.Direct application as part of tools to assist mitigation processes in power utilities. The automatic analysis of electrical waveforms is a recurring subject in the power system sector worldwide. In this sense, the idea of this paper is to present an original approach for automatic classification of voltage waveforms in electrical distribution networks. It includes both the classification of the waveforms in multiple known classes, and the detection of new waveforms (novelties) that are not available during the training stage. The classification method, based on the Support Vector Data Description (SVDD), has a suitable formulation for this task, because it is capable of fitting a model on a relatively small set of examples, which may also include negative examples (patterns from other known classes or even novelties), with maximal margin separation. The results obtained on both simulated and real world data demonstrate the ability of the method to identify novelties and to classify known examples correctly. The method finds application in the mitigation process of emergencies normally performed by power utilities' maintenance and protection engineers, which requires fast and accurate event cause identification. --- paper_title: Learning Person-Specific Representations From Faces in the Wild paper_content: Humans are natural face recognition experts, far out-performing current automated face recognition algorithms, especially in naturalistic, “in the wild” settings. However, a striking feature of human face recognition is that we are dramatically better at recognizing highly familiar faces, presumably because we can leverage large amounts of past experience with the appearance of an individual to aid future recognition. Meanwhile, the analogous situation in automated face recognition, where a large number of training examples of an individual are available, has been largely underexplored, in spite of the increasing relevance of this setting in the age of social media. Inspired by these observations, we propose to explicitly learn enhanced face representations on a per-individual basis, and we present two methods enabling this approach. By learning and operating within person-specific representations, we are able to significantly outperform the previous state-of-the-art on PubFig83, a challenging benchmark for familiar face recognition in the wild, using a novel method for learning representations in deep visual hierarchies. We suggest that such person-specific representations aid recognition by introducing an intermediate form of regularization to the problem. --- paper_title: Open set intrusion recognition for fine-grained attack categorization paper_content: Confidently distinguishing a malicious intrusion over a network is an important challenge. Most intrusion detection system evaluations have been performed in a closed set protocol in which only classes seen during training are considered during classification. Thus far, there has been no realistic application in which novel types of behaviors unseen at training - unknown classes as it were - must be recognized for manual categorization. This paper comparatively evaluates malware classification using both closed set and open set protocols for intrusion recognition on the KDDCUP'99 dataset. In contrast to much of the previous work, we employ a fine-grained recognition protocol, in which the dataset is loosely open set - i.e., recognizing individual intrusion types - e.g., “sendmail”, “snmp_guess”, …, etc., rather than more general attack categories (e.g., “DoS”,“Probe”,“R2L”,“U2R”,“Normal”). We also employ two different classifier types - Gaussian RBF kernel SVMs, which are not theoretically guaranteed to bound open space risk, and W-SVMs, which are theoretically guaranteed to bound open space risk. We find that the W-SVM offers superior performance under the open set regime, particularly as the cost of misclassifying unknown classes at query time (i.e., classes not present in the training set) increases. Results of performance tradeoff with respect to cost of unknown as well as discussion of the ramifications of these findings in an operational setting are presented. --- paper_title: Convolutional Neural Network approaches to granite tiles classification paper_content: Abstract The quality control process in stone industry is a challenging problem to deal with nowadays. Due to the similar visual appearance of different rocks with the same mineralogical content, economical losses can happen in industry if clients cannot recognize properly the rocks delivered as the ones initially purchased. In this paper, we go toward the automation of rock-quality assessment in different image resolutions by proposing the first data-driven technique applied to granite tiles classification. Our approach understands intrinsic patterns in small image patches through the use of Convolutional Neural Networks tailored for this problem. Experiments comparing the proposed approach to texture descriptors in a well-known dataset show the effectiveness of the proposed method and its suitability for applications in some uncontrolled conditions, such as classifying granite tiles under different image resolutions. --- paper_title: iCaRL: Incremental Classifier and Representation Learning paper_content: A major open problem on the road to artificial intelligence is the development of incrementally learning systems that learn about more and more concepts over time from a stream of data. In this work, we introduce a new training strategy, iCaRL, that allows learning in such a class-incremental way: only the training data for a small number of classes has to be present at the same time and new classes can be added progressively. iCaRL learns strong classifiers and a data representation simultaneously. This distinguishes it from earlier works that were fundamentally limited to fixed data representations and therefore incompatible with deep learning architectures. We show by experiments on CIFAR-100 and ImageNet ILSVRC 2012 data that iCaRL can learn many classes incrementally over a long period of time where other strategies quickly fail. --- paper_title: Place categorization and semantic mapping on a mobile robot paper_content: In this paper we focus on the challenging problem of place categorization and semantic mapping on a robot without environment-specific training. Motivated by their ongoing success in various visual recognition tasks, we build our system upon a state-of-the-art convolutional network. We overcome its closed-set limitations by complementing the network with a series of one-vs-all classifiers that can learn to recognize new semantic classes online. Prior domain knowledge is incorporated by embedding the classification system into a Bayesian filter framework that also ensures temporal coherence. We evaluate the classification accuracy of the system on a robot that maps a variety of places on our campus in real-time. We show how semantic information can boost robotic object detection performance and how the semantic map can be used to modulate the robot's behaviour during navigation tasks. The system is made available to the community as a ROS module. --- paper_title: Classification Under Streaming Emerging New Classes: A Solution Using Completely-Random Trees paper_content: This paper investigates an important problem in stream mining, i.e., classification under streaming emerging new classes or SENC . The SENC problem can be decomposed into three subproblems: detecting emerging new classes, classifying known classes, and updating models to integrate each new class as part of known classes. The common approach is to treat it as a classification problem and solve it using either a supervised learner or a semi-supervised learner. We propose an alternative approach by using unsupervised learning as the basis to solve this problem. The proposed method employs completely-random trees which have been shown to work well in unsupervised learning and supervised learning independently in the literature. The completely-random trees are used as a single common core to solve all three subproblems: unsupervised learning, supervised learning, and model update on data streams. We show that the proposed unsupervised-learning-focused method often achieves significantly better outcomes than existing classification-focused methods. --- paper_title: Probability Models for Open Set Recognition paper_content: Real-world tasks in computer vision often touch upon open set recognition: multi-class recognition with incomplete knowledge of the world and many unknown inputs. Recent work on this problem has proposed a model incorporating an open space risk term to account for the space beyond the reasonable support of known classes. This paper extends the general idea of open space risk limiting classification to accommodate non-linear classifiers in a multi-class setting. We introduce a new open set recognition model called compact abating probability (CAP), where the probability of class membership decreases in value (abates) as points move from known data toward open space. We show that CAP models improve open set recognition for multiple algorithms. Leveraging the CAP formulation, we go on to describe the novel Weibull-calibrated SVM (W-SVM) algorithm, which combines the useful properties of statistical extreme value theory for score calibration with one-class and binary support vector machines. Our experiments show that the W-SVM is significantly better for open set object detection and OCR problems when compared to the state-of-the-art for the same tasks. --- paper_title: Modular ensembles for one-class classification based on density analysis paper_content: One-Class Classification (OCC) is an important machine learning task. It studies a special classification problem that training samples from only one class, named target class, are available or reliable. Recently, various OCC algorithms have been proposed, however many of them do not adequately deal with multi-modality, multi-density, the noise and arbitrarily shaped distributions of the target class. In this paper, we propose a novel Density Based Modular Ensemble One-class Classifier (DBM-EOC) algorithm which is motivated by density analysis, divide-and-conquer method and ensemble learning. DBM-EOC first performs density analysis on training samples to obtain a minimal spanning tree using density characteristics of the target class. On this basis, DBM-EOC automatically identifies clusters, multi-density distributions and the noise in training samples using extreme value analysis. Then target samples are categorized into several groups called Local Dense Subset (LDS). Samples in each LDS are close to each other and their local densities are similar. A simple base OCC model e.g. the Gaussian estimator is built for each LDS afterwards. Finally all the base classifiers are modularly aggregated to construct the DBM-EOC model. We experimentally evaluate DBM-EOC with 6 state-of-art OCC algorithms on 5 synthetic datasets, 18 UCI benchmark datasets and the MNIST dataset. The results show that DBM-EOC outperforms other competitors in majority cases especially when the datasets are multi-modality, multi-density or noisy. We propose a modular ensemble OCC algorithm DBM-EOC based on density analysis.We analyze peculiarities of the target class which are crucial for OCC.DBM-EOC obtains a tree structure of the target class considering density.DBM-EOC can automatically detect clusters and remove noise samples.DBM-EOC solves OCC problems with the divide-and-conquer method. --- paper_title: Challenges in detecting UAS with radar paper_content: The recent proliferation of drones has contributed to the emergence of new threats in security applications. Because of their great agility and small size, UAS can be used for numerous missions and are very challenging to detect. Radar technology with its all-weather capability can play an important role in detecting UAS-based threats and in protecting critical assets. However, to be successful, radars have to quickly scan large volumes with great sensitivity, eliminate nuisance alarms from birds and discriminate UAS from ground targets. Radar parameters, antenna scan techniques and target classification requirements for UAS detection are analyzed. A radar implementation is discussed and preliminary results presented. Overall, an X-band radar with electronic scanning capability can contribute to a reliable and affordable solution for detecting UAS-based threats. --- paper_title: Local Novelty Detection in Multi-class Recognition Problems paper_content: In this paper, we propose using local learning for multiclass novelty detection, a framework that we call local novelty detection. Estimating the novelty of a new sample is an extremely challenging task due to the large variability of known object categories. The features used to judge on the novelty are often very specific for the object in the image and therefore we argue that individual novelty models for each test sample are important. Similar to human experts, it seems intuitive to first look for the most related images thus filtering out unrelated data. Afterwards, the system focuses on discovering similarities and differences to those images only. Therefore, we claim that it is beneficial to solely consider training images most similar to a test sample when deciding about its novelty. Following the principle of local learning, for each test sample a local novelty detection model is learned and evaluated. Our local novelty score turns out to be a valuable indicator for deciding whether the sample belongs to a known category from the training set or to a new, unseen one. With our local novelty detection approach, we achieve state-of-the-art performance in multi-class novelty detection on two popular visual object recognition datasets, Caltech-256 and Image Net. We further show that our framework: (i) can be successfully applied to unknown face detection using the Labeled-Faces-in-the-Wild dataset and (ii) outperforms recent work on attribute-based unfamiliar class detection in fine-grained recognition of bird species on the challenging CUB-200-2011 dataset. --- paper_title: Audio Event Recognition in the Smart Home paper_content: After giving a brief overview of the relevance and value of deploying automatic audio event recognition (AER) in the smart home market, this chapter reviews three aspects of the productization of AER which are important to consider when developing pathways to impact between fundamental research and “real-world” applicative outlets. In the first section, it is shown that applications introduce a variety of practical constraints which elicit new research topics in the field: clarifying the definition of sound events, thus suggesting interest for the explicit modeling of temporal patterns and interruption; running and evaluating AER in 24/7 sound detection setups, which suggests to recast the problem as open-set recognition; and running AER applications on consumer devices with limited audio quality and computational power, thus triggering interest for scalability and robustness. The second section explores the definition of user experience for AER. After reporting field observations about the ways in which system errors affect user experience, it is proposed to introduce opinion scoring into AER evaluation methodology. Then, the link between standard AER performance metrics and subjective user experience metrics is being explored, and attention is being drawn to the fact that F-score metrics actually mash up the objective evaluation of acoustic discrimination with the subjective choice of an application-dependent operation point. Solutions to the separation of discrimination and calibration in system evaluation are introduced, thus allowing the more explicit separation of acoustic modeling optimization from that of application-dependent user experience. Finally, the last section analyses the ethical and legal issues involved in deploying AER systems which are “listening” at all times into the users’ private space. A review of the key notions underpinning European data and privacy protection laws, questioning if and when these apply to audio data, suggests a set of guidelines which summarize into empowering users to consent by fully informing them about the use of their data, as well as taking reasonable information security measures to protect users’ personal data. --- paper_title: Authorship Attribution for Social Media Forensics paper_content: The veil of anonymity provided by smartphones with pre-paid SIM cards, public Wi-Fi hotspots, and distributed networks like Tor has drastically complicated the task of identifying users of social media during forensic investigations. In some cases, the text of a single posted message will be the only clue to an author’s identity. How can we accurately predict who that author might be when the message may never exceed 140 characters on a service like Twitter? For the past 50 years, linguists, computer scientists, and scholars of the humanities have been jointly developing automated methods to identify authors based on the style of their writing. All authors possess peculiarities of habit that influence the form and content of their written works. These characteristics can often be quantified and measured using machine learning algorithms. In this paper, we provide a comprehensive review of the methods of authorship attribution that can be applied to the problem of social media forensics. Furthermore, we examine emerging supervised learning-based methods that are effective for small sample sizes, and provide step-by-step explanations for several scalable approaches as instructional case studies for newcomers to the field. We argue that there is a significant need in forensics for new authorship attribution algorithms that can exploit context, can process multi-modal data, and are tolerant to incomplete knowledge of the space of all possible authors at training time. --- paper_title: An Empirical Study and Analysis of Generalized Zero-Shot Learning for Object Recognition in the Wild paper_content: We investigate the problem of generalized zero-shot learning (GZSL). GZSL relaxes the unrealistic assumption in conventional zero-shot learning (ZSL) that test data belong only to unseen novel classes. In GZSL, test data might also come from seen classes and the labeling space is the union of both types of classes. We show empirically that a straightforward application of classifiers provided by existing ZSL approaches does not perform well in the setting of GZSL. Motivated by this, we propose a surprisingly simple but effective method to adapt ZSL approaches for GZSL. The main idea is to introduce a calibration factor to calibrate the classifiers for both seen and unseen classes so as to balance two conflicting forces: recognizing data from seen classes and those from unseen ones. We develop a new performance metric called the Area Under Seen-Unseen accuracy Curve to characterize this trade-off. We demonstrate the utility of this metric by analyzing existing ZSL approaches applied to the generalized setting. Extensive empirical studies reveal strengths and weaknesses of those approaches on three well-studied benchmark datasets, including the large-scale ImageNet with more than 20,000 unseen categories. We complement our comparative studies in learning methods by further establishing an upper bound on the performance limit of GZSL. In particular, our idea is to use class-representative visual features as the idealized semantic embeddings. We show that there is a large gap between the performance of existing approaches and the performance limit, suggesting that improving the quality of class semantic embeddings is vital to improving ZSL. --- paper_title: Open Set Domain Adaptation paper_content: When the training and the test data belong to different domains, the accuracy of an object classifier is significantly reduced. Therefore, several algorithms have been proposed in the last years to diminish the so called domain shift between datasets. However, all available evaluation protocols for domain adaptation describe a closed set recognition task, where both domains, namely source and target, contain exactly the same object classes. In this work, we also explore the field of domain adaptation in open sets, which is a more realistic scenario where only a few categories of interest are shared between source and target data. Therefore, we propose a method that fits in both closed and open set scenarios. The approach learns a mapping from the source to the target domain by jointly solving an assignment problem that labels those target instances that potentially belong to the categories of interest present in the source dataset. A thorough evaluation shows that our approach outperforms the state-of-the-art. --- paper_title: Zero-Shot Learning — The Good, the Bad and the Ugly paper_content: Due to the importance of zero-shot learning, the number of proposed approaches has increased steadily recently. We argue that it is time to take a step back and to analyze the status quo of the area. The purpose of this paper is three-fold. First, given the fact that there is no agreed upon zero-shot learning benchmark, we first define a new benchmark by unifying both the evaluation protocols and data splits. This is an important contribution as published results are often not comparable and sometimes even flawed due to, e.g. pre-training on zero-shot test classes. Second, we compare and analyze a significant number of the state-of-the-art methods in depth, both in the classic zero-shot setting but also in the more realistic generalized zero-shot setting. Finally, we discuss limitations of the current status of the area which can be taken as a basis for advancing it. --- paper_title: Overcoming the challenge for text classification in the open world paper_content: Classification is often referred to as the task of discriminating one class from others in a given set of classes. Traditionally, classifiers work well assuming that a priori knowledge of all classes are given. Unfortunately, a presenting of unknown class during testing can lead to poor performance of even state-of-the-art classifiers due to observed classes being incorrectly identified to other classes. Recent proposed open world recognition framework provides a promising venue for tackling this challenge. While the majority of works in this relative new field is in computer vision, the rare work in Natural Language Processing shows its instability in its performance and is not based on the open world recognition framework. To tackle this problem, we represent our Nearest Centroid Class (NCC) which is incremental learning and able to detect unknown class during testing. Our model yields promising results in a document classification on text classification domains among current state-of-the-art models. --- paper_title: Towards Open-Set Identity Preserving Face Synthesis paper_content: We propose a framework based on Generative Adversarial Networks to disentangle the identity and attributes of faces, such that we can conveniently recombine different identities and attributes for identity preserving face synthesis in open domains. Previous identity preserving face synthesis processes are largely confined to synthesizing faces with known identities that are already in the training dataset. To synthesize a face with identity outside the training dataset, our framework requires one input image of that subject to produce an identity vector, and any other input face image to extract an attribute vector capturing, e.g., pose, emotion, illumination, and even the background. We then recombine the identity vector and the attribute vector to synthesize a new face of the subject with the extracted attribute. Our proposed framework does not need to annotate the attributes of faces in any way. It is trained with an asymmetric loss function to better preserve the identity and stabilize the training process. It can also effectively leverage large amounts of unlabeled training face images to further improve the fidelity of the synthesized faces for subjects that are not presented in the labeled training face dataset. Our experiments demonstrate the efficacy of the proposed framework. We also present its usage in a much broader set of applications including face frontalization, face attribute morphing, and face adversarial example detection. --- paper_title: Open Set Learning with Counterfactual Images paper_content: In open set recognition, a classifier must label instances of known classes while detecting instances of unknown classes not encountered during training. To detect unknown classes while still generalizing to new instances of existing classes, we introduce a dataset augmentation technique that we call counterfactual image generation. Our approach, based on generative adversarial networks, generates examples that are close to training set examples yet do not belong to any training category. By augmenting training with examples generated by this optimization, we can reformulate open set recognition as classification with one additional class, which includes the set of novel and unknown examples. Our approach outperforms existing open set recognition algorithms on a selection of image classification tasks. --- paper_title: RO-SVM: Support Vector Machine with Reject Option for Image Categorization paper_content: When applying Multiple Instance Learning (MIL) for image categorization, an image is treated as a bag containing a number of instances, each representing a region inside the image. The categorization of this image is determined by the labels of these instances, which are not specified in the training data-set. Hence, these instance labels are needed to be estimated together with the classifier. To improve classification reliability, we propose in this paper a new Support Vector Machine approach by incorporating a reject option, named RO-SVM to determine the instance labels, and the rejection region during the training phase simultaneously. Our approach can also be easily extended to solve multi-class classification problems. Experimental results demonstrate that higher categorization accuracy can be achieved with our RO-SVM method, comparing to approaches that do not exclude uninformative image patches. Our method is able to produce results comparable even with few training samples. --- paper_title: Extreme Value Analysis for Mobile Active User Authentication paper_content: In this paper, we propose to improve the performance of mobile Active Authentication (AA) systems in the low false alarm region using the statistical Extreme Value Theory (EVT). The problem is studied under a Bayesian framework where extremal observations that contribute to mis-verification are given more prominence. We prop~e modeling !he.tail. of the match distribution using a Generalized Pareto Distrfbution (GPD) in order to make better inferences about the extremal observations. A method based on the mean excess function is introduced for parameter estimation of the GPD. Effectiveness of the proposed framework is demonstrated using publicly available unconstrained mobile active authentication datasets. It is shown that the proposed EVT-based method can significantly enhance the performance of traditional AA systems in the low false alarm rate region. --- paper_title: A Survey of Stealth Malware Attacks, Mitigation Measures, and Steps Toward Autonomous Open World Solutions paper_content: As our professional, social, and financial existences become increasingly digitized and as our government, healthcare, and military infrastructures rely more on computer technologies, they present larger and more lucrative targets for malware. Stealth malware in particular poses an increased threat because it is specifically designed to evade detection mechanisms, spreading dormant, in the wild for extended periods of time, gathering sensitive information or positioning itself for a high-impact zero-day attack. Policing the growing attack surface requires the development of efficient anti-malware solutions with improved generalization to detect novel types of malware and resolve these occurrences with as little burden on human experts as possible. In this paper, we survey malicious stealth technologies as well as existing solutions for detecting and categorizing these countermeasures autonomously. While machine learning offers promising potential for increasingly autonomous solutions with improved generalization to new malware types, both at the network level and at the host level, our findings suggest that several flawed assumptions inherent to most recognition algorithms prevent a direct mapping between the stealth malware recognition problem and a machine learning solution. The most notable of these flawed assumptions is the closed world assumption: that no sample belonging to a class outside of a static training set will appear at query time. We present a formalized adaptive open world framework for stealth malware recognition and relate it mathematically to research from other machine learning domains. --- paper_title: Open set recognition for automatic target classification with rejection paper_content: Training sets for supervised classification tasks are usually limited in scope and only contain examples of a few classes. In practice, classes that were not seen in training are given labels that are always incorrect. Open set recognition (OSR) algorithms address this issue by providing classifiers with a rejection option for unknown samples. In this work, we introduce a new OSR algorithm and compare its performance to other current approaches for open set image classification. --- paper_title: Open set source camera attribution and device linking paper_content: Camera attribution approaches in digital image forensics have most often been evaluated in a closed set context, whereby all devices are known during training and testing time. However, in a real investigation, we must assume that innocuous images from unknown devices will be recovered, which we would like to remove from the pool of evidence. In pattern recognition, this corresponds to what is known as the open set recognition problem. This article introduces new algorithms for open set modes of image source attribution (identifying whether or not an image was captured by a specific digital camera) and device linking (identifying whether or not a pair of images was acquired from the same digital camera without the need for physical access to the device). Both algorithms rely on a new multi-region feature generation strategy, which serves as a projection space for the class of interest and emphasizes its properties, and on decision boundary carving, a novel method that models the decision space of a trained SVM classifier by taking advantage of a few known cameras to adjust the decision boundaries to decrease false matches from unknown classes. Experiments including thousands of unconstrained images collected from the web show a significant advantage for our approaches over the most competitive prior work. --- paper_title: Open set recognition of aircraft in aerial imagery using synthetic template models paper_content: Fast, accurate and robust automatic target recognition (ATR) in optical aerial imagery can provide game-changing ::: advantages to military commanders and personnel. ATR algorithms must reject non-targets with a high degree of ::: confidence in a world with an infinite number of possible input images. Furthermore, they must learn to recognize new ::: targets without requiring massive data collections. Whereas most machine learning algorithms classify data in a closed set ::: manner by mapping inputs to a fixed set of training classes, open set recognizers incorporate constraints that allow for ::: inputs to be labelled as unknown. We have adapted two template-based open set recognizers to use computer generated ::: synthetic images of military aircraft as training data, to provide a baseline for military-grade ATR: (1) a frequentist ::: approach based on probabilistic fusion of extracted image features, and (2) an open set extension to the one-class support ::: vector machine (SVM). These algorithms both use histograms of oriented gradients (HOG) as features as well as artificial ::: augmentation of both real and synthetic image chips to take advantage of minimal training data. Our results show that ::: open set recognizers trained with synthetic data and tested with real data can successfully discriminate real target inputs ::: from non-targets. However, there is still a requirement for some knowledge of the real target in order to calibrate the ::: relationship between synthetic template and target score distributions. We conclude by proposing algorithm modifications ::: that may improve the ability of synthetic data to represent real data. --- paper_title: Analyzing the Roles of Descriptions and Actions in Open Systems paper_content: This paper analyzes relationships between the roles of descriptions and actions in large scale, open ended, geographically distributed, concurrent systems. Rather than attempt to deal with the complexities and ambiguities of currently implemented descriptive languages, we concentrate our analysis on what can be expressed in the underlying frameworks such as the lambda calculus and first order logic. By this means we conclude that descriptions and actions complement one another; neither being sufficient unto itself. This paper provides a basis to begin the analysis of the very subtle relationships that hold between descriptions and actions in Open Systems. --- paper_title: Metric learning for large scale image classification: generalizing to new classes at near-zero cost paper_content: We are interested in large-scale image classification and especially in the setting where images corresponding to new or existing classes are continuously added to the training set. Our goal is to devise classifiers which can incorporate such images and classes on-the-fly at (near) zero cost. We cast this problem into one of learning a metric which is shared across all classes and explore k-nearest neighbor (k-NN) and nearest class mean (NCM) classifiers. We learn metrics on the ImageNet 2010 challenge data set, which contains more than 1.2M training images of 1K classes. Surprisingly, the NCM classifier compares favorably to the more flexible k-NN classifier, and has comparable performance to linear SVMs. We also study the generalization performance, among others by using the learned metric on the ImageNet-10K dataset, and we obtain competitive performance. Finally, we explore zero-shot classification, and show how the zero-shot model can be combined very effectively with small training datasets. --- paper_title: Domain Adaptation for Visual Recognition paper_content: Domain adaptation is an active, emerging research area that attemptsto address the changes in data distribution across training and testingdatasets. With the availability of a multitude of image acquisition sensors,variations due to illumination, and viewpoint among others, computervision applications present a very natural test bed for evaluatingdomain adaptation methods. In this monograph, we provide a comprehensiveoverview of domain adaptation solutions for visual recognitionproblems. By starting with the problem description and illustrations,we discuss three adaptation scenarios namely, i unsupervised adaptationwhere the "source domain" training data is partially labeledand the "target domain" test data is unlabeled, ii semi-supervisedadaptation where the target domain also has partial labels, and iiimulti-domain heterogeneous adaptation which studies the previous twosettings with the source and/or target having more than one domain,and accounts for cases where the features used to represent the datain each domain are different. For all these topics we discuss existingadaptation techniques in the literature, which are motivated by theprinciples of max-margin discriminative learning, manifold learning,sparse coding, as well as low-rank representations. These techniqueshave shown improved performance on a variety of applications suchas object recognition, face recognition, activity analysis, concept classification,and person detection. We then conclude by analyzing thechallenges posed by the realm of "big visual data", in terms of thegeneralization ability of adaptation algorithms to unconstrained dataacquisition as well as issues related to their computational tractability,and draw parallels with the efforts from vision community on imagetransformation models, and invariant descriptors so as to facilitate improvedunderstanding of vision problems under uncertainty. --- paper_title: Support Vector Machines with Embedded Reject Option paper_content: In this paper, the problem of implementing the reject option in support vector machines (SVMs) is addressed. We started by observing that methods proposed so far simply apply a reject threshold to the outputs of a trained SVM. We then showed that, under the framework of the structural risk minimisation principle, the rejection region must be determined during the training phase of a classifier. By applying this concept, and by following Vapnik's approach, we developed a maximum margin classifier with reject option. This led us to a SVM whose rejection region is determined during the training phase, that is, a SVM with embedded reject option. To implement such a SVM, we devised a novel formulation of the SVM training problem and developed a specific algorithm to solve it. Preliminary results on a character recognition problem show the advantages of the proposed SVM in terms of the achievable error-reject trade-off. --- paper_title: Steps Toward Robust Artificial Intelligence paper_content: Recent advances in artificial intelligence are encouraging governments and corporations to deploy AI in high-stakes settings including driving cars autonomously, managing the power grid, trading on stock exchanges, and controlling autonomous weapons systems. Such applications require AI methods to be robust to both the known unknowns (those uncertain aspects of the world about which the computer can reason explicitly) and the unknown unknowns (those aspects of the world that are not captured by the system’s models). This article discusses recent progress in AI and then describes eight ideas related to robustness that are being pursued within the AI research community. While these ideas are a start, we need to devote more attention to the challenges of dealing with the known and unknown unknowns. These issues are fascinating, because they touch on the fundamental question of how finite systems can survive and thrive in a complex and dangerous world --- paper_title: Attribute-Based Classification for Zero-Shot Visual Object Categorization paper_content: We study the problem of object recognition for categories for which we have no training examples, a task also called zero--data or zero-shot learning. This situation has hardly been studied in computer vision research, even though it occurs frequently; the world contains tens of thousands of different object classes, and image collections have been formed and suitably annotated for only a few of them. To tackle the problem, we introduce attribute-based classification: Objects are identified based on a high-level description that is phrased in terms of semantic attributes, such as the object's color or shape. Because the identification of each such property transcends the specific learning task at hand, the attribute classifiers can be prelearned independently, for example, from existing image data sets unrelated to the current task. Afterward, new classes can be detected based on their attribute representation, without the need for a new training phase. In this paper, we also introduce a new data set, Animals with Attributes, of over 30,000 images of 50 animal classes, annotated with 85 semantic attributes. Extensive experiments on this and two more data sets show that attribute-based classification indeed is able to categorize images without access to any training images of the target classes. --- paper_title: Lifelong Machine Learning paper_content: Abstract NOTE ⁃ A New Edition of This Title is Available: Lifelong Machine Learning, Second Edition Lifelong Machine Learning (or Lifelong Learning) is an advanced machine learning paradigm that le... --- paper_title: Unbounded cache model for online language modeling with open vocabulary paper_content: Recently, continuous cache models were proposed as extensions to recurrent neural network language models, to adapt their predictions to local changes in the data distribution. These models only capture the local context, of up to a few thousands tokens. In this paper, we propose an extension of continuous cache models, which can scale to larger contexts. In particular, we use a large scale non-parametric memory component that stores all the hidden activations seen in the past. We leverage recent advances in approximate nearest neighbor search and quantization algorithms to store millions of representations while searching them efficiently. We conduct extensive experiments showing that our approach significantly improves the perplexity of pre-trained language models on new distributions, and can scale efficiently to much larger contexts than previously proposed local cache models. --- paper_title: Multi-class Fukunaga Koontz discriminant analysis for enhanced face recognition paper_content: Linear subspace learning methods such as Fisher's Linear Discriminant Analysis (LDA), Unsupervised Discriminant Projection (UDP), and Locality Preserving Projections (LPP) have been widely used in face recognition applications as a tool to capture low dimensional discriminant information. However, when these methods are applied in the context of face recognition, they often encounter the small-sample-size problem. In order to overcome this problem, a separate Principal Component Analysis (PCA) step is usually adopted to reduce the dimensionality of the data. However, such a step may discard dimensions that contain important discriminative information that can aid classification performance. In this work, we propose a new idea which we named Multi-class Fukunaga Koontz Discriminant Analysis (FKDA) by incorporating the Fukunaga Koontz Transform within the optimization for maximizing class separation criteria in LDA, UDP, and LPP. In contrast to traditional LDA, UDP, and LPP, our approach can work with very high dimensional data as input, without requiring a separate dimensionality reduction step to make the scatter matrices full rank. In addition, the FKDA formulation seeks optimal projection direction vectors that are orthogonal which the existing methods cannot guarantee, and it has the capability of finding the exact solutions to the "trace ratio" objective in discriminant analysis problems while traditional methods can only deal with a relaxed and inexact "ratio trace" objective. We have shown using six face database, in the context of large scale unconstrained face recognition, face recognition with occlusions, and illumination invariant face recognition, under "closed set", "semi-open set", and "open set" recognition scenarios, that our proposed FKDA significantly outperforms traditional linear discriminant subspace learning methods as well as five other competing algorithms. HighlightsSolve small-sample-size problem in LDA, UDP, LPP using FKT formulation.Can work with high dimensional data without inverting any scatter matrices.Finds optimal projection direction vectors that are orthogonal.Finds exact solutions to the objective in the form of trace ratio.Improvement in unconstrained face recognition scenarios. --- paper_title: The open-set problem in acoustic scene classification paper_content: Acoustic scene classification (ASC) has attracted growing research interest in recent years. Whereas the previous work has investigated closed-set classification scenarios, the predominant ASC application is open-set in nature. The contributions of the paper are (i) the first investigation of ASC in an open-set scenario, (ii) the formulation of open-set ASC as a detection problem, (iii) a classifier tailored to the open-set scenario and (iv) a new assessment protocol and metric. Experiments show that, despite the challenge of open-set ASC, reliable performance is achieved with the support vector data description classifier for varying levels of openness. --- paper_title: Towards Open World Recognition paper_content: With the of advent rich classification models and high computational power visual recognition systems have found many operational applications. Recognition in the real world poses multiple challenges that are not apparent in controlled lab environments. The datasets are dynamic and novel categories must be continuously detected and then added. At prediction time, a trained system has to deal with myriad unseen categories. Operational systems require minimal downtime, even to learn. To handle these operational issues, we present the problem of Open World Recognition and formally define it. We prove that thresholding sums of monotonically decreasing functions of distances in linearly transformed feature space can balance “open space risk” and empirical risk. Our theory extends existing algorithms for open world recognition. We present a protocol for evaluation of open world recognition systems. We present the Nearest Non-Outlier (NNO) algorithm that evolves model efficiently, adding object categories incrementally while detecting outliers and managing open space risk. We perform experiments on the ImageNet dataset with 1.2M+ images to validate the effectiveness of our method on large scale visual recognition tasks. NNO consistently yields superior results on open world recognition. --- paper_title: The Extreme Value Machine paper_content: It is often desirable to be able to recognize when inputs to a recognition function learned in a supervised manner correspond to classes unseen at training time. With this ability, new class labels could be assigned to these inputs by a human operator, allowing them to be incorporated into the recognition function—ideally under an efficient incremental update mechanism. While good algorithms that assume inputs from a fixed set of classes exist, e.g. , artificial neural networks and kernel machines, it is not immediately obvious how to extend them to perform incremental learning in the presence of unknown query classes. Existing algorithms take little to no distributional information into account when learning recognition functions and lack a strong theoretical foundation. We address this gap by formulating a novel, theoretically sound classifier—the Extreme Value Machine (EVM). The EVM has a well-grounded interpretation derived from statistical Extreme Value Theory (EVT), and is the first classifier to be able to perform nonlinear kernel-free variable bandwidth incremental learning. Compared to other classifiers in the same deep network derived feature space, the EVM is accurate and efficient on an established benchmark partition of the ImageNet dataset. --- paper_title: Specialized Support Vector Machines for Open-set Recognition paper_content: Often, when dealing with real-world recognition problems, we do not need, and often cannot have, knowledge of the entire set of possible classes that might appear during operational testing. In such cases, we need to think of robust classification methods able to deal with the"unknown"and properly reject samples belonging to classes never seen during training. Notwithstanding, almost all existing classifiers to date were mostly developed for the closed-set scenario, i.e., the classification setup in which it is assumed that all test samples belong to one of the classes with which the classifier was trained. In the open-set scenario, however, a test sample can belong to none of the known classes and the classifier must properly reject it by classifying it as unknown. In this work, we extend upon the well-known Support Vector Machines (SVM) classifier and introduce the Specialized Support Vector Machines (SSVM), which is suitable for recognition in open-set setups. SSVM balances the empirical risk and the risk of the unknown and ensures that the region of the feature space in which a test sample would be classified as known (one of the known classes) is always bounded, ensuring a finite risk of the unknown. In this work, we also highlight the properties of the SVM classifier related to the open-set scenario, and provide necessary and sufficient conditions for an RBF SVM to have bounded open-space risk. --- paper_title: Incremental and Distributed Learning with Support Vector Machines paper_content: Due to the increase in the amount of data gathered every day in the real world problems (e.g., bioinformatics), there is a need for inductive learning algorithms that can incrementally process large amounts of data that is being accumulated over time in physically distributed, autonomous data repositories. In the incremental setting, the learner gradually refines a hypothesis (or a set of hypotheses) as new data become available. Because of the large volume of data involved, it may not be practical to store and access the entire dataset during learning. Thus, the learner does not have access to data that has been encountered at a previous time. Learning in the distributed setting can be defined in a similar fashion. An incremental or distributed learning algorithm is said to be exact if it gives the same results as those obtained by batch learning (i.e., when the entire dataset is accessible to the learning algorithm during learning). We explore exact distributed and incremental learning algorithms that are variants and extensions of the support vector machine (SVM) family of learning algorithms. For the sake of simplicity, suppose that we have two data sets and , and we want to learn from them in an incremental setting using SVM. A naive approach (Syed, Liu & Sung, 1999) works as follows: 1. Apply the SVM algorithm to and generate a set of support vectors --- paper_title: On optimum recognition error and reject tradeoff paper_content: The performance of a pattern recognition system is characterized by its error and reject tradeoff. This paper describes an optimum rejection rule and presents a general relation between the error and reject probabilities and some simple properties of the tradeoff in the optimum recognition system. The error rate can be directly evaluated from the reject function. Some practical implications of the results are discussed. Examples in normal distributions and uniform distributions are given. --- paper_title: Finding the Unknown: Novelty Detection with Extreme Value Signatures of Deep Neural Activations paper_content: Achieving or even surpassing human-level accuracy became recently possible in a variety of application scenarios due to the rise of convolutional neural networks (CNNs) trained from large datasets. However, solving supervised visual recognition tasks by discriminating among known categories is only one side of the coin. In contrast to this, novelty detection is still an unsolved task where instances of yet unknown categories need to be identified. Therefore, we propose to leverage the powerful discriminative nature of CNNs to novelty detection tasks by investigating class-specific activation patterns. More precisely, we assume that a semantic category can be described by its extreme value signature, that specifies which dimensions of deep neural activations have largest values. By following this intuition, we show that already a small number of high-valued dimensions allows to separate known from unknown categories. Our approach is simple, intuitive, and can be easily put on top of CNNs trained for vanilla classification tasks. We empirically validate the benefits of our approach in terms of accuracy and speed by comparing it against established methods in a variety of novelty detection tasks derived from ImageNet. Finally, we show that visualizing extreme value signatures allows to inspect class-specific patterns learned during training which may ultimately help to better understand CNN models. --- paper_title: Growing a multi-class classifier with a reject option paper_content: In many classification problems objects should be rejected when the confidence in their classification is too low. An example is a face recognition problem where the faces of a selected group of people have to be classified, but where all other faces and non-faces should be rejected. These problems are typically solved by estimating the class densities and assigning an object to the class with the highest posterior probability. The total probability density is thresholded to detect the outliers. Unfortunately, this procedure does not easily allow for class-dependent thresholds, or for class models that are not based on probability densities but on distances. In this paper we propose a new heuristic to combine any type of one-class models for solving the multi-class classification problem with outlier rejection. It normalizes the average model output per class, instead of the more common non-linear transformation of the distances. It creates the possibility to adjust the rejection threshold per class, and also to combine class models that are not (all) based on probability densities and to add class models without affecting the boundaries of existing models. Experiments show that for several classification problems using class-specific models significantly improves the performance. --- paper_title: Open set face recognition using transduction paper_content: This paper motivates and describes a novel realization of transductive inference that can address the open set face recognition task. Open set operates under the assumption that not all the test probes have mates in the gallery. It either detects the presence of some biometric signature within the gallery and finds its identity or rejects it, i.e., it provides for the "none of the above" answer. The main contribution of the paper is open set TCM-kNN (transduction confidence machine-k nearest neighbors), which is suitable for multiclass authentication operational scenarios that have to include a rejection option for classes never enrolled in the gallery. Open set TCM-kNN, driven by the relation between transduction and Kolmogorov complexity, provides a local estimation of the likelihood ratio needed for detection tasks. We provide extensive experimental data to show the feasibility, robustness, and comparative advantages of open set TCM-kNN on open set identification and watch list (surveillance) tasks using challenging FERET data. Last, we analyze the error structure driven by the fact that most of the errors in identification are due to a relatively small number of face patterns. Open set TCM-kNN is shown to be suitable for PSEI (pattern specific error inhomogeneities) error analysis in order to identify difficult to recognize faces. PSEI analysis improves biometric performance by removing a small number of those difficult to recognize faces responsible for much of the original error in performance and/or by using data fusion. --- paper_title: Novelty detection and multi-class classification in power distribution voltage waveforms paper_content: Accurate classification of events in waveforms from electrical distribution networks.Novelty detection: dynamic identification of new classes of events.SVDD using negative examples and maximal margin separation: better generalization.Experiments using real data: significant improvements in classification accuracy.Direct application as part of tools to assist mitigation processes in power utilities. The automatic analysis of electrical waveforms is a recurring subject in the power system sector worldwide. In this sense, the idea of this paper is to present an original approach for automatic classification of voltage waveforms in electrical distribution networks. It includes both the classification of the waveforms in multiple known classes, and the detection of new waveforms (novelties) that are not available during the training stage. The classification method, based on the Support Vector Data Description (SVDD), has a suitable formulation for this task, because it is capable of fitting a model on a relatively small set of examples, which may also include negative examples (patterns from other known classes or even novelties), with maximal margin separation. The results obtained on both simulated and real world data demonstrate the ability of the method to identify novelties and to classify known examples correctly. The method finds application in the mitigation process of emergencies normally performed by power utilities' maintenance and protection engineers, which requires fast and accurate event cause identification. --- paper_title: An optimum character recognition system using decision functions paper_content: The character recognition problem, usually resulting from characters being corrupted by printing deterioration and/or inherent noise of the devices, is considered from the viewpoint of statistical decision theory. The optimization consists of minimizing the expected risk for a weight function which is preassigned to measure the consequences of system decisions As an alternative minimization of the error rate for a given rejection rate is used as the critenon. The optimum recogition is thus obtained. The optimum system consists of a conditional-probability densisities computer; character channels, one for each character; a rejection channel; and a comparison network. Its precise structure and and ultimate performance depend essentially upon the signals and noise structure. Explicit examples for an additive Gaussian noise and a ``cosine'' noise are presented. Finally, an error-free recognition system and a possible criterion to measure the character style and deteriortation are presented. --- paper_title: Modular ensembles for one-class classification based on density analysis paper_content: One-Class Classification (OCC) is an important machine learning task. It studies a special classification problem that training samples from only one class, named target class, are available or reliable. Recently, various OCC algorithms have been proposed, however many of them do not adequately deal with multi-modality, multi-density, the noise and arbitrarily shaped distributions of the target class. In this paper, we propose a novel Density Based Modular Ensemble One-class Classifier (DBM-EOC) algorithm which is motivated by density analysis, divide-and-conquer method and ensemble learning. DBM-EOC first performs density analysis on training samples to obtain a minimal spanning tree using density characteristics of the target class. On this basis, DBM-EOC automatically identifies clusters, multi-density distributions and the noise in training samples using extreme value analysis. Then target samples are categorized into several groups called Local Dense Subset (LDS). Samples in each LDS are close to each other and their local densities are similar. A simple base OCC model e.g. the Gaussian estimator is built for each LDS afterwards. Finally all the base classifiers are modularly aggregated to construct the DBM-EOC model. We experimentally evaluate DBM-EOC with 6 state-of-art OCC algorithms on 5 synthetic datasets, 18 UCI benchmark datasets and the MNIST dataset. The results show that DBM-EOC outperforms other competitors in majority cases especially when the datasets are multi-modality, multi-density or noisy. We propose a modular ensemble OCC algorithm DBM-EOC based on density analysis.We analyze peculiarities of the target class which are crucial for OCC.DBM-EOC obtains a tree structure of the target class considering density.DBM-EOC can automatically detect clusters and remove noise samples.DBM-EOC solves OCC problems with the divide-and-conquer method. --- paper_title: Local Novelty Detection in Multi-class Recognition Problems paper_content: In this paper, we propose using local learning for multiclass novelty detection, a framework that we call local novelty detection. Estimating the novelty of a new sample is an extremely challenging task due to the large variability of known object categories. The features used to judge on the novelty are often very specific for the object in the image and therefore we argue that individual novelty models for each test sample are important. Similar to human experts, it seems intuitive to first look for the most related images thus filtering out unrelated data. Afterwards, the system focuses on discovering similarities and differences to those images only. Therefore, we claim that it is beneficial to solely consider training images most similar to a test sample when deciding about its novelty. Following the principle of local learning, for each test sample a local novelty detection model is learned and evaluated. Our local novelty score turns out to be a valuable indicator for deciding whether the sample belongs to a known category from the training set or to a new, unseen one. With our local novelty detection approach, we achieve state-of-the-art performance in multi-class novelty detection on two popular visual object recognition datasets, Caltech-256 and Image Net. We further show that our framework: (i) can be successfully applied to unknown face detection using the Labeled-Faces-in-the-Wild dataset and (ii) outperforms recent work on attribute-based unfamiliar class detection in fine-grained recognition of bird species on the challenging CUB-200-2011 dataset. --- paper_title: Support vector machines with a reject option paper_content: This paper studies $\ell_1$ regularization with high-dimensional features for support vector machines with a built-in reject option (meaning that the decision of classifying an observation can be withheld at a cost lower than that of misclassification). The procedure can be conveniently implemented as a linear program and computed using standard software. We prove that the minimizer of the penalized population risk favors sparse solutions and show that the behavior of the empirical risk minimizer mimics that of the population risk minimizer. We also introduce a notion of classification complexity and prove that our minimizers adapt to the unknown complexity. Using a novel oracle inequality for the excess risk, we identify situations where fast rates of convergence occur. --- paper_title: RO-SVM: Support Vector Machine with Reject Option for Image Categorization paper_content: When applying Multiple Instance Learning (MIL) for image categorization, an image is treated as a bag containing a number of instances, each representing a region inside the image. The categorization of this image is determined by the labels of these instances, which are not specified in the training data-set. Hence, these instance labels are needed to be estimated together with the classifier. To improve classification reliability, we propose in this paper a new Support Vector Machine approach by incorporating a reject option, named RO-SVM to determine the instance labels, and the rejection region during the training phase simultaneously. Our approach can also be easily extended to solve multi-class classification problems. Experimental results demonstrate that higher categorization accuracy can be achieved with our RO-SVM method, comparing to approaches that do not exclude uninformative image patches. Our method is able to produce results comparable even with few training samples. --- paper_title: Support Vector Machines with Embedded Reject Option paper_content: In this paper, the problem of implementing the reject option in support vector machines (SVMs) is addressed. We started by observing that methods proposed so far simply apply a reject threshold to the outputs of a trained SVM. We then showed that, under the framework of the structural risk minimisation principle, the rejection region must be determined during the training phase of a classifier. By applying this concept, and by following Vapnik's approach, we developed a maximum margin classifier with reject option. This led us to a SVM whose rejection region is determined during the training phase, that is, a SVM with embedded reject option. To implement such a SVM, we devised a novel formulation of the SVM training problem and developed a specific algorithm to solve it. Preliminary results on a character recognition problem show the advantages of the proposed SVM in terms of the achievable error-reject trade-off. --- paper_title: Assumed density filtering methods for learning Bayesian neural networks paper_content: Buoyed by the success of deep multilayer neural networks, there is renewed interest in scalable learning of Bayesian neural networks. Here, we study algorithms that utilize recent advances in Bayesian inference to efficiently learn distributions over network weights. In particular, we focus on recently proposed assumed density filtering based methods for learning Bayesian neural networks – Expectation and Probabilistic backpropagation. Apart from scaling to large datasets, these techniques seamlessly deal with non-differentiable activation functions and provide parameter (learning rate, momentum) free learning. In this paper, we first rigorously compare the two algorithms and in the process develop several extensions, including a version of EBP for continuous regression problems and a PBP variant for binary classification. Next, we extend both algorithms to deal with multiclass classification and count regression problems. On a variety of diverse real world benchmarks, we find our extensions to be effective, achieving results competitive with the state-of-the-art. --- paper_title: Reducing Network Agnostophobia paper_content: Agnostophobia, the fear of the unknown, can be experienced by deep learning engineers while applying their networks to real-world applications. Unfortunately, network behavior is not well defined for inputs far from a networks training set. In an uncontrolled environment, networks face many instances that are not of interest to them and have to be rejected in order to avoid a false positive. This problem has previously been tackled by researchers by either a) thresholding softmax, which by construction cannot return "none of the known classes", or b) using an additional background or garbage class. In this paper, we show that both of these approaches help, but are generally insufficient when previously unseen classes are encountered. We also introduce a new evaluation metric that focuses on comparing the performance of multiple approaches in scenarios where such unseen classes or unknowns are encountered. Our major contributions are simple yet effective Entropic Open-Set and Objectosphere losses that train networks using negative samples from some classes. These novel losses are designed to maximize entropy for unknown inputs while increasing separation in deep feature space by modifying magnitudes of known and unknown samples. Experiments on networks trained to classify classes from MNIST and CIFAR-10 show that our novel loss functions are significantly better at dealing with unknown inputs from datasets such as Devanagari, NotMNIST, CIFAR-100, and SVHN. --- paper_title: SSD: Single Shot MultiBox Detector paper_content: We present a method for detecting objects in images using a single deep neural network. Our approach, named SSD, discretizes the output space of bounding boxes into a set of default boxes over different aspect ratios and scales per feature map location. At prediction time, the network generates scores for the presence of each object category in each default box and produces adjustments to the box to better match the object shape. Additionally, the network combines predictions from multiple feature maps with different resolutions to naturally handle objects of various sizes. SSD is simple relative to methods that require object proposals because it completely eliminates proposal generation and subsequent pixel or feature resampling stages and encapsulates all computation in a single network. This makes SSD easy to train and straightforward to integrate into systems that require a detection component. Experimental results on the PASCAL VOC, COCO, and ILSVRC datasets confirm that SSD has competitive accuracy to methods that utilize an additional object proposal step and is much faster, while providing a unified framework for both training and inference. For \(300 \times 300\) input, SSD achieves 74.3 % mAP on VOC2007 test at 59 FPS on a Nvidia Titan X and for \(512 \times 512\) input, SSD achieves 76.9 % mAP, outperforming a comparable state of the art Faster R-CNN model. Compared to other single stage methods, SSD has much better accuracy even with a smaller input image size. Code is available at https://github.com/weiliu89/caffe/tree/ssd. --- paper_title: The Extreme Value Machine paper_content: It is often desirable to be able to recognize when inputs to a recognition function learned in a supervised manner correspond to classes unseen at training time. With this ability, new class labels could be assigned to these inputs by a human operator, allowing them to be incorporated into the recognition function—ideally under an efficient incremental update mechanism. While good algorithms that assume inputs from a fixed set of classes exist, e.g. , artificial neural networks and kernel machines, it is not immediately obvious how to extend them to perform incremental learning in the presence of unknown query classes. Existing algorithms take little to no distributional information into account when learning recognition functions and lack a strong theoretical foundation. We address this gap by formulating a novel, theoretically sound classifier—the Extreme Value Machine (EVM). The EVM has a well-grounded interpretation derived from statistical Extreme Value Theory (EVT), and is the first classifier to be able to perform nonlinear kernel-free variable bandwidth incremental learning. Compared to other classifiers in the same deep network derived feature space, the EVM is accurate and efficient on an established benchmark partition of the ImageNet dataset. --- paper_title: Adversarial Robustness: Softmax versus Openmax paper_content: Deep neural networks (DNNs) provide state-of-the-art results on various tasks and are widely used in real world applications. However, it was discovered that machine learning models, including the best performing DNNs, suffer from a fundamental problem: they can unexpectedly and confidently misclassify examples formed by slightly perturbing otherwise correctly recognized inputs. Various approaches have been developed for efficiently generating these so-called adversarial examples, but those mostly rely on ascending the gradient of loss. In this paper, we introduce the novel logits optimized targeting system (LOTS) to directly manipulate deep features captured at the penultimate layer. Using LOTS, we analyze and compare the adversarial robustness of DNNs using the traditional Softmax layer with Openmax, which was designed to provide open set recognition by defining classes derived from deep representations, and is claimed to be more robust to adversarial perturbations. We demonstrate that Openmax provides less vulnerable systems than Softmax to traditional attacks, however, we show that it can be equally susceptible to more sophisticated adversarial generation techniques that directly work on deep representations. --- paper_title: Towards Reaching Human Performance in Pedestrian Detection paper_content: Encouraged by the recent progress in pedestrian detection, we investigate the gap between current state-of-the-art methods and the “perfect single frame detector”. We enable our analysis by creating a human baseline for pedestrian detection (over the Caltech pedestrian dataset). After manually clustering the frequent errors of a top detector, we characterise both localisation and background-versus-foreground errors. To address localisation errors we study the impact of training annotation noise on the detector performance, and show that we can improve results even with a small portion of sanitised training data. To address background/foreground discrimination, we study convnets for pedestrian detection, and discuss which factors affect their performance. Other than our in-depth analysis, we report top performance on the Caltech pedestrian dataset, and provide a new sanitised set of training and test annotations. --- paper_title: Faster R-CNN: Towards Real-Time Object Detection with Region Proposal Networks paper_content: State-of-the-art object detection networks depend on region proposal algorithms to hypothesize object locations. Advances like SPPnet [1] and Fast R-CNN [2] have reduced the running time of these detection networks, exposing region proposal computation as a bottleneck. In this work, we introduce a Region Proposal Network (RPN) that shares full-image convolutional features with the detection network, thus enabling nearly cost-free region proposals. An RPN is a fully convolutional network that simultaneously predicts object bounds and objectness scores at each position. The RPN is trained end-to-end to generate high-quality region proposals, which are used by Fast R-CNN for detection. We further merge RPN and Fast R-CNN into a single network by sharing their convolutional features—using the recently popular terminology of neural networks with ’attention’ mechanisms, the RPN component tells the unified network where to look. For the very deep VGG-16 model [3] , our detection system has a frame rate of 5 fps ( including all steps ) on a GPU, while achieving state-of-the-art object detection accuracy on PASCAL VOC 2007, 2012, and MS COCO datasets with only 300 proposals per image. In ILSVRC and COCO 2015 competitions, Faster R-CNN and RPN are the foundations of the 1st-place winning entries in several tracks. Code has been made publicly available. --- paper_title: Figure of Merit Training for Detection and Spotting paper_content: Spotting tasks require detection of target patterns from a background of richly varied non-target inputs. The performance measure of interest for these tasks, called the figure of merit (FOM), is the detection rate for target patterns when the false alarm rate is in an acceptable range. A new approach to training spotters is presented which computes the FOM gradient for each input pattern and then directly maximizes the FOM using backpropagation. This eliminates the need for thresholds during training. It also uses network resources to model Bayesian a posteriori probability functions accurately only for patterns which have a significant effect on the detection accuracy over the false alarm rate of interest. FOM training increased detection accuracy by 5 percentage points for a hybrid radial basis function (RBF) - hidden Markov model (HMM) wordspotter on the credit-card speech corpus. --- paper_title: Intriguing properties of neural networks paper_content: Deep neural networks are highly expressive models that have recently achieved state of the art performance on speech and visual recognition tasks. While their expressiveness is the reason they succeed, it also causes them to learn uninterpretable solutions that could have counter-intuitive properties. In this paper we report two such properties. ::: First, we find that there is no distinction between individual high level units and random linear combinations of high level units, according to various methods of unit analysis. It suggests that it is the space, rather than the individual units, that contains of the semantic information in the high layers of neural networks. ::: Second, we find that deep neural networks learn input-output mappings that are fairly discontinuous to a significant extend. We can cause the network to misclassify an image by applying a certain imperceptible perturbation, which is found by maximizing the network's prediction error. In addition, the specific nature of these perturbations is not a random artifact of learning: the same perturbation can cause a different network, that was trained on a different subset of the dataset, to misclassify the same input. --- paper_title: The Pascal Visual Object Classes (VOC) Challenge paper_content: The Pascal Visual Object Classes (VOC) challenge is a benchmark in visual object category recognition and detection, providing the vision and machine learning communities with a standard dataset of images and annotation, and standard evaluation procedures. Organised annually from 2005 to present, the challenge and its associated dataset has become accepted as the benchmark for object detection.This paper describes the dataset and evaluation procedure. We review the state-of-the-art in evaluated methods for both classification and detection, analyse whether the methods are statistically different, what they are learning from the images (e.g. the object or its context), and what the methods find easy or confuse. The paper concludes with lessons learnt in the three year history of the challenge, and proposes directions for future improvement and extension. --- paper_title: Microsoft COCO: Common Objects in Context paper_content: We present a new dataset with the goal of advancing the state-of-the-art in object recognition by placing the question of object recognition in the context of the broader question of scene understanding. This is achieved by gathering images of complex everyday scenes containing common objects in their natural context. Objects are labeled using per-instance segmentations to aid in precise object localization. Our dataset contains photos of 91 objects types that would be easily recognizable by a 4 year old. With a total of 2.5 million labeled instances in 328k images, the creation of our dataset drew upon extensive crowd worker involvement via novel user interfaces for category detection, instance spotting and instance segmentation. We present a detailed statistical analysis of the dataset in comparison to PASCAL, ImageNet, and SUN. Finally, we provide baseline performance analysis for bounding box and segmentation detection results using a Deformable Parts Model. --- paper_title: Deep neural networks are easily fooled: High confidence predictions for unrecognizable images paper_content: Deep neural networks (DNNs) have recently been achieving state-of-the-art performance on a variety of pattern-recognition tasks, most notably visual classification problems. Given that DNNs are now able to classify objects in images with near-human-level performance, questions naturally arise as to what differences remain between computer and human vision. A recent study [30] revealed that changing an image (e.g. of a lion) in a way imperceptible to humans can cause a DNN to label the image as something else entirely (e.g. mislabeling a lion a library). Here we show a related result: it is easy to produce images that are completely unrecognizable to humans, but that state-of-the-art DNNs believe to be recognizable objects with 99.99% confidence (e.g. labeling with certainty that white noise static is a lion). Specifically, we take convolutional neural networks trained to perform well on either the ImageNet or MNIST datasets and then find images with evolutionary algorithms or gradient ascent that DNNs label with high confidence as belonging to each dataset class. It is possible to produce images totally unrecognizable to human eyes that DNNs believe with near certainty are familiar objects, which we call “fooling images” (more generally, fooling examples). Our results shed light on interesting differences between human vision and current DNNs, and raise questions about the generality of DNN computer vision. --- paper_title: Confidence Prediction for Lexicon-Free OCR paper_content: Having a reliable accuracy score is crucial for real world applications of OCR, since such systems are judged by the number of false readings. Lexicon-based OCR systems, which deal with what is essentially a multi-class classification problem, often employ methods explicitly taking into account the lexicon, in order to improve accuracy. However, in lexicon-free scenarios, filtering errors requires an explicit confidence calculation. In this work we show two explicit confidence measurement techniques, and show that they are able to achieve a significant reduction in misreads on both standard benchmarks and a proprietary dataset. --- paper_title: Fast R-CNN paper_content: This paper proposes a Fast Region-based Convolutional Network method (Fast R-CNN) for object detection. Fast R-CNN builds on previous work to efficiently classify object proposals using deep convolutional networks. Compared to previous work, Fast R-CNN employs several innovations to improve training and testing speed while also increasing detection accuracy. Fast R-CNN trains the very deep VGG16 network 9x faster than R-CNN, is 213x faster at test-time, and achieves a higher mAP on PASCAL VOC 2012. Compared to SPPnet, Fast R-CNN trains VGG16 3x faster, tests 10x faster, and is more accurate. Fast R-CNN is implemented in Python and C++ (using Caffe) and is available under the open-source MIT License at https://github.com/rbgirshick/fast-rcnn. --- paper_title: Simple and Scalable Predictive Uncertainty Estimation using Deep Ensembles paper_content: Deep neural networks (NNs) are powerful black box predictors that have recently achieved impressive performance on a wide spectrum of tasks. Quantifying predictive uncertainty in NNs is a challenging and yet unsolved problem. Bayesian NNs, which learn a distribution over weights, are currently the state-of-the-art for estimating predictive uncertainty; however these require significant modifications to the training procedure and are computationally expensive compared to standard (non-Bayesian) NNs. We propose an alternative to Bayesian NNs that is simple to implement, readily parallelizable, requires very little hyperparameter tuning, and yields high quality predictive uncertainty estimates. Through a series of experiments on classification and regression benchmarks, we demonstrate that our method produces well-calibrated uncertainty estimates which are as good or better than approximate Bayesian NNs. To assess robustness to dataset shift, we evaluate the predictive uncertainty on test examples from known and unknown distributions, and show that our method is able to express higher uncertainty on out-of-distribution examples. We demonstrate the scalability of our method by evaluating predictive uncertainty estimates on ImageNet. --- paper_title: Towards Open Set Deep Networks paper_content: Deep networks have produced significant gains for various visual recognition problems, leading to high impact academic and commercial applications. Recent work in deep networks highlighted that it is easy to generate images that humans would never classify as a particular object class, yet networks classify such images high confidence as that given class - deep network are easily fooled with images humans do not consider meaningful. The closed set nature of deep networks forces them to choose from one of the known classes leading to such artifacts. Recognition in the real world is open set, i.e. the recognition system should reject unknown/unseen classes at test time. We present a methodology to adapt deep networks for open set recognition, by introducing a new model layer, OpenMax, which estimates the probability of an input being from an unknown class. A key element of estimating the unknown probability is adapting Meta-Recognition concepts to the activation patterns in the penultimate layer of the network. OpenMax allows rejection of "fooling" and unrelated open set images presented to the system; OpenMax greatly reduces the number of obvious errors made by a deep network. We prove that the OpenMax concept provides bounded open space risk, thereby formally providing an open set recognition solution. We evaluate the resulting open set deep networks using pre-trained networks from the Caffe Model-zoo on ImageNet 2012 validation data, and thousands of fooling and open set images. The proposed OpenMax model significantly outperforms open set recognition accuracy of basic deep networks as well as deep networks with thresholding of SoftMax probabilities. --- paper_title: A Discriminative Feature Learning Approach for Deep Face Recognition paper_content: Convolutional neural networks (CNNs) have been widely used in computer vision community, significantly improving the state-of-the-art. In most of the available CNNs, the softmax loss function is used as the supervision signal to train the deep model. In order to enhance the discriminative power of the deeply learned features, this paper proposes a new supervision signal, called center loss, for face recognition task. Specifically, the center loss simultaneously learns a center for deep features of each class and penalizes the distances between the deep features and their corresponding class centers. More importantly, we prove that the proposed center loss function is trainable and easy to optimize in the CNNs. With the joint supervision of softmax loss and center loss, we can train a robust CNNs to obtain the deep features with the two key learning objectives, inter-class dispension and intra-class compactness as much as possible, which are very essential to face recognition. It is encouraging to see that our CNNs (with such joint supervision) achieve the state-of-the-art accuracy on several important face recognition benchmarks, Labeled Faces in the Wild (LFW), YouTube Faces (YTF), and MegaFace Challenge. Especially, our new approach achieves the best results on MegaFace (the largest public domain face benchmark) under the protocol of small training set (contains under 500000 images and under 20000 persons), significantly improving the previous results and setting new state-of-the-art for both face recognition and face verification tasks. --- paper_title: Dropout as a Bayesian Approximation: Representing Model Uncertainty in Deep Learning paper_content: Deep learning tools have gained tremendous attention in applied machine learning. However such tools for regression and classification do not capture model uncertainty. In comparison, Bayesian models offer a mathematically grounded framework to reason about model uncertainty, but usually come with a prohibitive computational cost. In this paper we develop a new theoretical framework casting dropout training in deep neural networks (NNs) as approximate Bayesian inference in deep Gaussian processes. A direct result of this theory gives us tools to model uncertainty with dropout NNs -- extracting information from existing models that has been thrown away so far. This mitigates the problem of representing uncertainty in deep learning without sacrificing either computational complexity or test accuracy. We perform an extensive study of the properties of dropout's uncertainty. Various network architectures and non-linearities are assessed on tasks of regression and classification, using MNIST as an example. We show a considerable improvement in predictive log-likelihood and RMSE compared to existing state-of-the-art methods, and finish by using dropout's uncertainty in deep reinforcement learning. ---	Title: Learning and the Unknown: Surveying Steps toward Open World Recognition Section 1: Introduction Description 1: Introduce the concept of open world recognition and its importance in current machine learning research. Section 2: Formalizing Open Set Recognition Description 2: Discuss the formalization of open set recognition, including the definition, mathematical models, and key properties. Section 3: Approaches that sometimes solve OSR Description 3: Analyze various approaches and discuss why some algorithms may partially address OSR while others fall short. Section 4: Open Set Deep Networks Description 4: Examine the challenges and current solutions related to open set recognition in deep learning frameworks. Section 5: Conclusion Description 5: Summarize the key points, the progress made, and emphasize the ongoing challenges and future directions in the field of open world recognition.
Performance evaluation of component-based software systems: A survey	5	--- paper_title: Nieuwenhuis Performance comparison of middleware threading strategies paper_content: The spectacular growth of E-business applications on the Internet has boosted the development of middleware technology. Middleware is software that manages interactions between applications distributed across a heterogeneous computing environment. In the competitive E-business market the ability to deliver a high and predictable performance of E-business applications is crucial to avoid customer churn, and thus loss of revenue. This raises the need for service providers to be able to predict and control performance. The performance of middleware-based applications depends strongly on the choice of the so-called threading strategy, describing how the middleware layer handles competing method invocation requests. The goal of this paper is to provide an understanding of the impact of threading strategies on the performance of middlewarebased applications. To this end, we (1) develop new quantitative models for the performance of middleware under different threading strategies, (2) perform extensive test lab experiments to compare the performance under different threading strategies, and (3) explain the experimental results by relating them to the quantitative models. As such, this paper provides new and fundamental insight in the impact of threading strategies on the performance of E-business applications. --- paper_title: The Future of Software Performance Engineering paper_content: Performance is a pervasive quality of software systems; everything affects it, from the software itself to all underlying layers, such as operating system, middleware, hardware, communication networks, etc. Software Performance Engineering encompasses efforts to describe and improve performance, with two distinct approaches: an early-cycle predictive model-based approach, and a late-cycle measurement-based approach. Current progress and future trends within these two approaches are described, with a tendency (and a need) for them to converge, in order to cover the entire development cycle. --- paper_title: Making the Business Case for Software Performance Engineering paper_content: Shrinking budgets and increased fiscal accountability mean that management needs a sound financial justification before committing funds to software process improvements such as Software Performance Engineering (SPE). Preparing a business case for SPE can demonstrate that the commitment is financially worthwhile and win support for an SPE initiative. This paper presents an introduction to the use of business case analysis to justify investing in SPE to reduce costs due to performance failures. A case study illustrates how to perform a financial analysis and calculate a projected return on investment. --- paper_title: Process algebra for performance evaluation paper_content: This paper surveys the theoretical developments in the field of stochastic process algebras, process algebras where action occurrences may be subject to a delay that is determined by a random variable. A huge class of resource-sharing systems - like large-scale computers, client-server architectures, networks - can accurately be described using such stochastic specification formalisms. The main emphasis of this paper is the treatment of operational semantics, notions of equivalence, and (sound and complete) axiomatisations of these equivalences for different types of Markovian process algebras, where delays are governed by exponential distributions. Starting from a simple actionless algebra for describing time-homogeneous continuous-time Markov chains, we consider the integration of actions and random delays both as a single entity (like in known Markovian process algebras like TIPP, PEPA and EMPA) and as separate entities (like in the timed process algebras timed CSP and TCCS). In total we consider four related calculi and investigate their relationship to existing Markovian process algebras. We also briefly indicate how one can profit from the separation of time and actions when incorporating more general, non-Markovian distributions. --- paper_title: Model-based performance prediction in software development: a survey paper_content: Over the last decade, a lot of research has been directed toward integrating performance analysis into the software development process. Traditional software development methods focus on software correctness, introducing performance issues later in the development process. This approach does not take into account the fact that performance problems may require considerable changes in design, for example, at the software architecture level, or even worse at the requirement analysis level. Several approaches were proposed in order to address early software performance analysis. Although some of them have been successfully applied, we are still far from seeing performance analysis integrated into ordinary software development. In this paper, we present a comprehensive review of recent research in the field of model-based performance prediction at software development time in order to assess the maturity of the field and point out promising research directions. --- paper_title: Component Software: Beyond Object-Oriented Programming paper_content: From the Publisher: ::: Component Software: Beyond Object-Oriented Programming explains the technical foundations of this evolving technology and its importance in the software market place. It provides in-depth discussion of both the technical and the business issues to be considered, then moves on to suggest approaches for implementing component-oriented software production and the organizational requirements for success. The author draws on his own experience to offer tried-and-tested solutions to common problems and novel approaches to potential pitfalls. Anyone responsible for developing software strategy, evaluating new technologies, buying or building software will find Clemens Szyperski's objective and market-aware perspective of this new area invaluable. --- paper_title: SAAM: a method for analyzing the properties of software architectures paper_content: While software architecture has become an increasingly important research topic in recent years, insufficient attention has been paid to methods for evaluation of these architectures. Evaluating architectures is difficult for two main reasons. First, there is no common language used to describe different architectures. Second, there is no clear way of understanding an architecture with respect to an organization's life cycle concerns -software quality concerns such as maintainability portability, modularity, reusability, and so forth. We address these shortcomings by describing three perspectives by which we can understand the description of a software architecture and then proposing a five-step method for analyzing software architectures called SAAM (Software Architecture Analysis Method). We illustrate the method by analyzing three separate user interface architectures with respect to the quality of modifiability. > --- paper_title: Stochastic Petri Nets An Introduction To The Theory paper_content: Thank you very much for reading stochastic petri nets an introduction to the theory. Maybe you have knowledge that, people have look hundreds times for their favorite novels like this stochastic petri nets an introduction to the theory, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some malicious bugs inside their computer. --- paper_title: ATAM: Method for Architecture Evaluation paper_content: Abstract : If a software architecture is a key business asset for an organization, then architectural analysis must also be a key practice for that organization. Why? Because architectures are complex and involve many design tradeoffs. Without undertaking a formal analysis process, the organization cannot ensure that the architectural decisions made-particularly those which affect the achievement of quality attribute such as performance, availability, security, and modifiability-are advisable ones that appropriately mitigate risks. In this report, some of the technical and organizational foundations for performing architectural analysis are discussed, the Architecture Tradeoff Analysis Method (ATAM), is presented. The ATAM is a technique for analyzing software architectures that has been developed and refined in practice over the past three years. --- paper_title: Performance Modeling and Evaluation of Distributed Component-Based Systems Using Queueing Petri Nets paper_content: Performance models are used increasingly throughout the phases of the software engineering lifecycle of distributed component-based systems. However, as systems grow in size and complexity, building models that accurately capture the different aspects of their behavior becomes a more and more challenging task. In this paper, we present a novel case study of a realistic distributed component-based system, showing how queueing Petri net models can be exploited as a powerful performance prediction tool in the software engineering process. A detailed system model is built in a step-by-step fashion, validated, and then used to evaluate the system performance and scalability. Along with the case study, a practical performance modeling methodology is presented which helps to construct models that accurately reflect the system performance and scalability characteristics. Taking advantage of the modeling power and expressiveness of queueing Petri nets, our approach makes it possible to model the system at a higher degree of accuracy, providing a number of important benefits --- paper_title: Performance prediction of component-based systems : A survey from an engineering perspective paper_content: Performance predictions of component assemblies and the ability of obtaining system-level performance properties from these predictions are a cru- cial success factor when building trustworthy component-based systems. In order to achieve this goal, a collection of methods and tools to capture and analyze the performance of software systems has been developed. These methods and tools aim at helping software engineers by providing them with the capability to understand design trade-offs, optimize their design by identifying performance inhibitors, or predict a systems performance within a specified deployment envi- ronment. In this paper, we analyze the applicability of various performance pre- diction methods for the development of component-based systems and contrast their inherent strengths and weaknesses in different engineering problem scenar- ios. In so doing, we establish a basis to select an appropriate prediction method and to provide recommendations for future research activities, which could sig- nificantly improve the performance prediction of component-based systems. --- paper_title: Model-Driven Software Development: Technology, Engineering, Management paper_content: Part I: Introduction. 1. Introduction. 2. MDSD - Basic Ideas and Terminology. 3. Case Study: A Typical Web Application. 4. Concept Formation. 5. Classification. Part II: Domain Architectures. 6. Metamodeling. 7. MDSD-Capable Target Architectures. 8. Building Domain Architectures. 9. Code Generation Techniques. 10. Model Transformation Techniques. 11. MDSD Tools: Roles, Architecture, Selection Criteria, and Pointers. 12. The MDA Standard. Part III: Processes and Engineering. 13. MDSD Process Building Blocks and Best Practices. 14. Testing. 15. Versioning. 16. Case Study: Embedded Component Infrastructures. 17. Case Study: An Enterprise System. Part IV: Management. 18. Decision Support. 1.9 Organizational Aspects. 20. Adoption Strategies for MDSD. References. Index. --- paper_title: Software component models paper_content: Component-based Development (CBD) is an important emerging topic in Software Engineering, promising long sought after benefits like increased reuse and reduced time-to-market (and hence software production cost). However, there are at present many obstacles to overcome before CBD can succeed. For one thing, CBD success is predicated on a standardised market place for software components, which does not yet exist. In fact currently CBD even lacks a universally accepted terminology. Existing component models adopt different component definitions and composition operators. Therefore much research remains to be done. We believe that the starting point for this endeavour should be a thorough study of current component models, identifying their key characteristics and comparing their strengths and weaknesses. A desirable side-effect would be clarifying and unifying the CBD terminology. In this tutorial, we present a clear and concise exposition of all the current major software component models, including a taxonomy. The purpose is to distill and present knowledge of current software component models, as well as to present an analysis of their properties with respect to commonly accepted criteria for CBD. The taxonomy also provides a starting point for a unified terminology. --- paper_title: Component Software: Beyond Object-Oriented Programming paper_content: From the Publisher: ::: Component Software: Beyond Object-Oriented Programming explains the technical foundations of this evolving technology and its importance in the software market place. It provides in-depth discussion of both the technical and the business issues to be considered, then moves on to suggest approaches for implementing component-oriented software production and the organizational requirements for success. The author draws on his own experience to offer tried-and-tested solutions to common problems and novel approaches to potential pitfalls. Anyone responsible for developing software strategy, evaluating new technologies, buying or building software will find Clemens Szyperski's objective and market-aware perspective of this new area invaluable. --- paper_title: Performance Solutions A Practical Guide To Creating Responsive Scalable Software paper_content: Thank you for downloading performance solutions a practical guide to creating responsive scalable software. As you may know, people have search numerous times for their favorite books like this performance solutions a practical guide to creating responsive scalable software, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some malicious bugs inside their laptop. --- paper_title: Model-based performance prediction in software development: a survey paper_content: Over the last decade, a lot of research has been directed toward integrating performance analysis into the software development process. Traditional software development methods focus on software correctness, introducing performance issues later in the development process. This approach does not take into account the fact that performance problems may require considerable changes in design, for example, at the software architecture level, or even worse at the requirement analysis level. Several approaches were proposed in order to address early software performance analysis. Although some of them have been successfully applied, we are still far from seeing performance analysis integrated into ordinary software development. In this paper, we present a comprehensive review of recent research in the field of model-based performance prediction at software development time in order to assess the maturity of the field and point out promising research directions. --- paper_title: Component Software: Beyond Object-Oriented Programming paper_content: From the Publisher: ::: Component Software: Beyond Object-Oriented Programming explains the technical foundations of this evolving technology and its importance in the software market place. It provides in-depth discussion of both the technical and the business issues to be considered, then moves on to suggest approaches for implementing component-oriented software production and the organizational requirements for success. The author draws on his own experience to offer tried-and-tested solutions to common problems and novel approaches to potential pitfalls. Anyone responsible for developing software strategy, evaluating new technologies, buying or building software will find Clemens Szyperski's objective and market-aware perspective of this new area invaluable. --- paper_title: Towards Automatic Construction of Reusable Prediction Models for Component-Based Performance Engineering paper_content: Performance predictions for software architectures can reveal performance bottlenecks and quantitatively support design decisions for different architectural alternatives. As software architects aim at reusing existing software components, their performance properties should be included into performance predictions without the need for manual modelling. However, most prediction approaches do not include automated support for modelling implemented components. Therefore, we propose a new reverse engineering approach, which generates Palladio performance models from Java code. In this paper, we focus on the static analysis of Java code, which we have implemented as an Eclipse plugin called Java2PCM. We evaluated our approach on a larger component-based software architecture, and show that a similar prediction accuracy can be achieved with generated models compared to completely manually specified ones. --- paper_title: UML-Based Performance Modeling Framework for Component-Based Distributed Systems paper_content: We describe a performance modeling framework that can be used in the development and maintenance of component-based distributed systems, such as those based on the CORBA, EJB, and COM+ platforms. The purpose of the framework is to produce predictive performance models that can be used for obtaining performance related information on the target system at all stages of its life cycle. The framework defines a UML-based notation for describing performance models, and a set of special techniques for modeling component-based distributed systems. In addition, we present a transformation for converting the resulting models into a format that can be solved approximately for a number of relevant performance metrics. --- paper_title: Model-based performance prediction in software development: a survey paper_content: Over the last decade, a lot of research has been directed toward integrating performance analysis into the software development process. Traditional software development methods focus on software correctness, introducing performance issues later in the development process. This approach does not take into account the fact that performance problems may require considerable changes in design, for example, at the software architecture level, or even worse at the requirement analysis level. Several approaches were proposed in order to address early software performance analysis. Although some of them have been successfully applied, we are still far from seeing performance analysis integrated into ordinary software development. In this paper, we present a comprehensive review of recent research in the field of model-based performance prediction at software development time in order to assess the maturity of the field and point out promising research directions. --- paper_title: Efficient Performance Models in Component-Based Software Engineering paper_content: Performance evaluation of Component-Based software systems should be performed as early as possible during the software development life cycle. Unfortunately, a detailed quantitative analysis is often not possible during such stages, as only the system outline is available, with very little quantitative knowledge. In this paper we propose an approach based on Queueing Network analysis for performance evaluation of component-based software systems at the software architectural level. Our approach provides performance bounds which can be efficiently computed. Starting from annotated UML diagrams we compute bounds on the system throughput and response time without explicitly deriving or solving the underlying multichain and multiclass Queueing Network model. We illustrate with an example how the technique can be applied to answer many performance-related questions which may arise during the software design phase. --- paper_title: CB-SPE Tool: Putting component-based performance engineering into practice paper_content: A crucial issue in the design of Component-Based (CB) applications is the ability to early guarantee that the system under development will satisfy its Quality of Service requirements. In particular, we need rigorous and easy-to-use techniques for predicting and analyzing the performance of the assembly based on the properties of the constituent components. To this purpose, we propose the CB-SPE framework: a compositional methodology for CB Software Performance Engineering (SPE) and its supporting tool. CB-SPE is based on, and adapts to a CB paradigm, the concepts and steps of the well-known SPE technology, using for input modeling the standard RT-UML PA profile. The methodology is compositional: it is first applied by the component developer at the component layer, achieving a parametric performance evaluation of the components in isolation; then, at the application layer, the system assembler is provided with a step-wise procedure for predicting the performance of the assembled components on the actual platform. We have developed the CB-SPE tool reusing as much as possible existing free tools. In this paper we present the realized framework, together with a simple application example. --- paper_title: Performance modeling from software components paper_content: When software products are assembled from pre-defined components, performance prediction should be based on the components also. This supports rapid model-building, using previously calibrated sub-models or "performance components", in sync with the construction of the product. The specification of a performance component must be tied closely to the software component specification, but it also includes performance related parameters (describing workload characteristics and demands), and it abstracts the behaviour of the component in various ways (for reasons related to practical factors in performance analysis). A useful set of abstractions and parameters are already defined for layered performance modeling. This work extends them to accommodate software components, using a new XML-based language called Component-Based Modeling Language (CBML). With CBML, compatible components can be inserted into slots provided in a hierarchical component specification based on the UML component model. --- paper_title: Model-Based performance prediction with the palladio component model paper_content: One aim of component-based software engineering (CBSE) is to enable the prediction of extra-functional properties, such as performance and reliability, utilising a well-defined composition theory. Nowadays, such theories and their accompanying prediction methods are still in a maturation stage. Several factors influencing extra-functional properties need additional research to be understood. A special problem in CBSE stems from its specific development process: Software components should be specified and implemented independent from their later context to enable reuse. Thus, extra-functional properties of components need to be specified in a parametric way to take different influence factors like the hardware platform or the usage profile into account. In our approach, we use the Palladio Component Model (PCM) to specify component-based software architectures in a parametric way. This model offers direct support of the CBSE development process by dividing the model creation among the developer roles. In this paper, we present our model and a simulation tool based on it, which is capable of making performance predictions. Within a case study, we show that the resulting prediction accuracy can be sufficient to support the evaluation of architectural design decisions. --- paper_title: Performance modeling and prediction of enterprise JavaBeans with layered queuing network templates paper_content: Component technologies, such as Enterprise Java Beans (EJB) and .NET, are used in enterprise servers with requirements for high performance and scalability. This work considers performance prediction from the design of an EJB system, based on the modular structure of an application server and the application components. It uses layered queueing models, which are naturally structured around the software components. This paper describes a framework for constructing such models, based on layered queue templates for EJBs, and for their inclusion in the server. The resulting model is calibrated and validated by comparison with an actual system. --- paper_title: Packaging Predictable Assembly paper_content: Significant economic and technical benefits accrue from the use of pre-existing and commercially available software components to develop new systems. However, challenges remain that, if not adequately addressed, will slow the adoption of software component technology. Chief among these are a lack of consumer trust in the quality of components, and a lack of trust in the quality of assemblies of components without extensive and expensive testing. This paper describes prediction-enabled component technology (PECT). A PECT results from integrating component technology with analysis models. An analysis model permits analysis and prediction of assembly-level properties prior to component composition, and, perhaps, prior to component acquisition. Analysis models also identify required component properties and their certifiable descriptions. Component technology supports and enforces the assumptions underlying analysis models; it also provides the medium for deploying PECT instances and PECT-compliant software components. This paper describes the structure of PECT. It discusses the means of establishing the predictive powers of a PECT so that consumers may obtain measurably bounded trust in both components and design-time predictions based on the use of these components. We demonstrate these ideas in a simple but illustrative model problem: predicting average endto-end latency of a 'soft' real time application built from off-the-shelf software components. --- paper_title: Predicting the Behavior of a Highly Configurable Component Based Real-Time System paper_content: Software components and the technology supporting component based software engineering contribute greatly to the rapid development and configuration of systems for a variety of application domains. Such domains go beyond desktop office applications and information systems supporting e-commerce, but include systems having real-time performance requirements and critical functionality. Discussed in this paper are the results from an experiment that demonstrates the ability to predict deadline satisfaction of threads in a real-time system where the functionality performed is based on the configuration of the assembled software components. Presented is the method used to abstract the large, legacy code base of the system software and the application software components in the system; the model of those abstractions based on available architecture documentation and empirically-based, runtime observations; and the analysis of the predictions which yielded objective confidence in the observations and model created which formed the underlying basis for the predictions. --- paper_title: From design to analysis models: a kernel language for performance and reliability analysis of component-based systems paper_content: To facilitate the use of non-functional analysis results in the selection and assembly of components for component-based systems, automatic prediction tools should be devised, to predict some overall quality attribute of the application without requiring extensive knowledge of analysis methodologies to the application designer. To achieve this goal, a key idea is to define a model transformation that takes as input some "design-oriented" model of the component assembly and produces as a result an "analysis-oriented" model that lends itself to the application of some analysis methodology. However, to actually devise such a transformation, we must face both the heterogeneous design level notations for component-based systems, and the variety of non-functional attributes and related analysis methodologies we could be interested in. In this perspective, we define a kernel language whose aim is to capture the relevant information for the analysis of non-functional attributes of component-based systems, with a focus on performance and reliability. Using this kernel language as a bridge between design-oriented and analysis-oriented notations we reduce the burden of defining a variety of direct transformations from the former to the latter to the less complex problem of defining transformations to/from the kernel language. The proposed kernel language is defined within the MOF (Meta-Object Facility) framework, to allow the exploitation of MOF-based model transformation facilities. --- paper_title: Model-driven performance analysis paper_content: Model-Driven Engineering (MDE) is an approach to develop software systems by creating models and applying automated transformations to them to ultimately generate the implementation for a target platform. Although the main focus of MDE is on the generation of code, it is also necessary to support the analysis of the designs with respect to quality attributes such as performance. To complement the model-to-implementation path of MDE approaches, an MDE tool infrastructure should provide what we call model-driven analysis. This paper describes an approach to model-driven analysis based on reasoning frameworks. In particular, it describes a performance reasoning framework that can transform a design into a model suitable for analysis of real-time performance properties with different evaluation procedures including rate monotonic analysis and simulation. The concepts presented in this paper have been implemented in the PACC Starter Kit, a development environment that supports code generation and analysis from the same models. --- paper_title: Performance prediction for black-box components using reengineered parametric behaviour models paper_content: In component-based software engineering, the response time of an entire application is often predicted from the execution durations of individual component services. However, these execution durations are specific for an execution platform (i.e. its resources such as CPU) and for a usage profile. Reusing an existing component on different execution platforms up to now required repeated measurements of the concerned components for each relevant combination of execution platform and usage profile, leading to high effort. This paper presents a novel integrated approach that overcomes these limitations by reconstructing behaviour models with platform-independent resource demands of bytecode components. The reconstructed models are parameterised over input parameter values. Using platform-specific results of bytecode benchmarking, our approach is able to translate the platform-independent resource demands into predictions for execution durations on a certain platform. We validate our approach by predicting the performance of a file sharing application. --- paper_title: TESTEJB - A measurement framework for EJBs paper_content: Specification of Quality of Service (QoS) for components can only be done in relation to the QoS the components themselves are given by imported components. Developers as well as users need support in order to derive valid data for specification respectively for checking whether a selected component complies with its specification. In this paper we introduce the architecture of a measurement framework for EJBs giving such support and discuss in detail the measurement of the well understood property of response time. --- paper_title: Snapshot of CCL : A Language for Predictable Assembly paper_content: Abstract : Construction and composition language (CCL) plays several roles in our approach to achieving automated predictable assembly. CCL is used to produce specifications that contain structural, behavioral, and analysis-specific information about component technologies, as well as components and assemblies in such technologies. These specifications are translated to one or more reasoning frameworks that analyze and predict the runtime properties of assemblies. CCL processors can also be used to automate many of the constructive activities of component-based development through various forms of program generation. Using a common specification for prediction and construction improves confidence that analysis models match implementations. This report presents a snapshot of CCL by examining a small example CCL specification. --- paper_title: The COMQUAD component model: enabling dynamic selection of implementations by weaving non-functional aspects paper_content: The reliability of non-functional contracts is crucial for many software applications. This added to the increasing attention this issue lately received in software engineering. Another development in software engineering is toward component-based systems. The interaction of both, non-functional aspects and components, is a relatively new research area, which the COMQUAD project is focusing on.Our component model, presented in this paper, enables the specification and runtime support of non-functional aspects in component-based systems. At the same time, a clear separation of non-functional properties and functionally motivated issues is provided. We achieve this by extending the concepts of the existing component-based systems Enterprise JavaBeans (EJB) and CORBA Components (CCM). Non-functional aspects are described orthogonally to the application structure using descriptors, and are woven into the running application by the component container acting as a contract manager. The container implicitly instantiates component specifications and connects them according to the current requests. The selection of actual implementations depends on the particular client's non-functional requirements. This technique also enables adaptation based on the specific quantitative capabilities of the running system.In this paper we give a detailed description of the COMQUAD component model and the appropriate container support. We also provide a simple case study of a multimedia application for better understanding. --- paper_title: Predicting real-time properties of component assemblies: a scenario-simulation approach paper_content: This work addresses the problem of predicting timing properties of multitasking component assemblies during the design phase. For real-time applications, it is of vital importance to guarantee that the timing requirements of an assembly are met. We propose a simulation-based approach for predicting the real-time behaviour of an assembly based on models of its constituent components. Our approach extends the scenario-based method in [J. Muskens et al. (2004)] by offering a system model that is tailored to the domain of real-time applications. Contributions of This work include the possibility to handle the following features: mutual exclusion, combinations of aperiodic and periodic tasks and synchronization constraints. The analytical approach we used in previous work cannot handle these features. Therefore, we introduce the simulation-based approach. Our simulator provides data about dynamic resource consumption and real-time properties like response time, blocking time and number of missed deadlines per task. We have validated our approach using a video-decoder application. --- paper_title: Exploring performance trade-offs of a JPEG decoder using the deepcompass framework paper_content: Designing embedded systems for multiprocessor platforms requires early prediction and balancing of multiple system quality attributes. We present a design space exploration framework for component-based software systems that allows an architect to get insight into a space of possible design alternatives with further evaluation and comparison of these alternatives. The framework provides (a) tool-guided design of multiple alternatives of software and hardware architectures, (b) early design-time predictions of performance properties and identification of bottlenecks for each architectural alternative, and (c) evaluation of each alternative with respect to multi-objective trade-offs. The performance prediction technique employs modeling of individual components and composition of the models into a system model representing the system behaviour and resource usage. We illustrate the framework by a case study of a JPEG decoder application. For this system, we consider architectural alternatives, show their specification, and explore their trade-offs with respect to task latencies, resource utilization and system cost. --- paper_title: The Method of Layers paper_content: Distributed applications are being developed that contain one or more layers of software servers. Software processes within such systems suffer contention delays both for shared hardware and at the software servers. The responsiveness of these systems is affected by the software design, the threading level and number of instances of software processes, and the allocation of processes to processors. The Method of Layers (MOL) is proposed to provide performance estimates for such systems. The MOL uses the mean value analysis (MVA) linearizer algorithm as a subprogram to assist in predicting model performance measures. > --- paper_title: Performance and scalability of EJB applications paper_content: We investigate the combined effect of application implementation method, container design, and efficiency of communication layers on the performance scalability of J2EE application servers by detailed measurement and profiling of an auction site server.We have implemented five versions of the auction site. The first version uses stateless session beans, making only minimal use of the services provided by the Enterprise JavaBeans (EJB) container. Two versions use entity beans, one with container-managed persistence and the other with bean-managed persistence. The fourth version applies the session fasade pattern, using session beans as a fasade to access entity beans. The last version uses EJB 2.0 local interfaces with the session fasade pattern. We evaluate these different implementations on two popular open-source EJB containers with orthogonal designs. JBoss uses dynamic proxies to generate the container classes at run time, making an extensive use of reflection. JOnAS pre-compiles classes during deployment, minimizing the use of reflection at run time. We also evaluate the communication optimizations provided by each of these EJB containers.The most important factor in determining performance is the application implementation method. EJB applications with session beans perform as well as a Java servlets-only implementation and an order-of-magnitude better than most of the implementations based on entity beans. The fine-granularity access exposed by the entity beans limits scalability. Use of session fasade beans improves performance for entity beans, but only if local communication is very efficient or EJB 2.0 local interfaces are used. Otherwise, session fasade beans degrade performance.For the implementation using session beans, communication cost forms the major component of the execution time on the EJB server. The design of the container has little effect on performance. With entity beans, the design of the container becomes important. In particular, the cost of reflection affects performance. For implementations using session fasade beans, local communication cost is critically important. EJB 2.0 local interfaces improve the performance by avoiding the communication layers for local communications. --- paper_title: Revel8or: Model Driven Capacity Planning Tool Suite paper_content: Designing complex multi-tier applications that must meet strict performance requirements is a challenging software engineering problem. Ideally, the application architect could derive accurate performance predictions early in the project life-cycle, leveraging initial application design-level models and a description of the target software and hardware platforms. To this end, we have developed a capacity planning tool suite for component-based applications, called Revel8tor. The tool adheres to the model driven development paradigm and supports benchmarking and performance prediction for J2EE, .Net and Web services platforms. The suite is composed of three different tools: MDAPerf, MDABench and DSLBench. MDAPerf allows annotation of design diagrams and derives performance analysis models. MDABench allows a customized benchmark application to be modeled in the UML 2.0 Testing Profile and automatically generates a deployable application, with measurement automatically conducted. DSLBench allows the same benchmark modeling and generation to be conducted using a simple performance engineering Domain Specific Language (DSL) in Microsoft Visual Studio. DSLBench integrates with Visual Studio and reuses its load testing infrastructure. Together, the tool suite can assist capacity planning across platforms in an automated fashion. --- paper_title: Design-level performance prediction of component-based applications paper_content: Server-side component technologies such as Enterprise JavaBeans (EJBs), .NET, and CORBA are commonly used in enterprise applications that have requirements for high performance and scalability. When designing such applications, architects must select suitable component technology platform and application architecture to provide the required performance. This is challenging as no methods or tools exist to predict application performance without building a significant prototype version for subsequent benchmarking. In this paper, we present an approach to predict the performance of component-based server-side applications during the design phase of software development. The approach constructs a quantitative performance model for a proposed application. The model requires inputs from an application-independent performance profile of the underlying component technology platform, and a design description of the application. The results from the model allow the architect to make early decisions between alternative application architectures in terms of their performance and scalability. We demonstrate the method using an EJB application and validate predictions from the model by implementing two different application architectures and measuring their performance on two different implementations of the EJB platform. --- paper_title: Mean-Value Analysis of Closed Multichain Queuing Networks paper_content: It is shown that mean queue sizes, mean waiting times, and throughputs in closed multiple-chain queuing networks which have product-form solution can be computed recursively without computing product terms and normalization constants. The resulting computational procedures have improved properties (avoidance of numerical problems and, in some cases, fewer operations) compared to previous algorithms. Furthermore, the new algorithms have a physically meaningful interpretation which provides the basis for heuristic extensions that allow the approximate solution of networks with a very large number of closed chains, and which is shown to be asymptotically valid for large chain populations. --- paper_title: Early performance testing of distributed software applications paper_content: Performance characteristics, such as response time, through put and scalability, are key quality attributes of distributed applications. Current practice, however, rarely applies systematic techniques to evaluate performance characteristics. We argue that evaluation of performance is particularly crucial in early development stages, when important architectural choices are made. At first glance, this contradicts the use of testing techniques, which are usually applied towards the end of a project. In this paper, we assume that many distributed systems are built with middleware technologies, such as the Java 2 Enterprise Edition (J2EE) or the Common Object Request Broker Architecture (CORBA). These provide services and facilities whose implementations are available when architectures are defined. We also note that it is the middleware functionality, such as transaction and persistence services, remote communication primitives and threading policy primitives, that dominate distributed system performance Drawing on these observations, this paper presents a novel approach to performance testing of distributed applications. We propose to derive application-specific test cases from architecture designs so that performance of a distributed application can be tested using the middleware software at early stages of a development process. We report empirical results that support the viability of the approach. --- paper_title: Performance prediction of component-based applications paper_content: One of the major problems in building large-scale enterprise systems is anticipating the performance of the eventual solution before it has been built. The fundamental software engineering problem becomes more difficult when the systems are built on component technology. This paper investigates the feasibility of providing a practical solution to this problem. An empirical approach is proposed to determine the performance characteristics of component-based applications by benchmarking and profiling. Based on observation, a model is constructed to act as a performance predictor for a class of applications based on the specific component technology. The performance model derived from empirical measures is necessary to make the problem tractable and the results relevant. A case study applies the performance model to an application prototype implemented by two component infrastructures: CORBA and J2EE. --- paper_title: Theory of software reliability based on components paper_content: We present a foundational theory of software system reliability based on components. The theory describes how component developers can design and test their components to produce measurements that are later used by system designers to calculate composite system reliability — without implementation and test of the system being designed. The theory describes how to make component measurements that are independent of operational profiles, and how to incorporate the overall system-level operational profile into the system reliability calculations. In principle, the theory resolves the central problem of assessing a component, which is: a component developer cannot know how the component will be used and so cannot certify it for an arbitrary use; but if the component buyer must certify each component before using it, component-based development loses much of its appeal. This dilemma is resolved if the component developer does the certification and provides the results in such a way that the component buyer can factor in the usage information later, without repeating the certification. Our theory addresses the basic technical problems inherent in certifying components to be released for later use in an arbitrary system. Most component research has been directed at functional specification of software components; our theory addresses the other, equally important, side of the coin: component quality. --- paper_title: Performance specification of software components paper_content: Component-based software engineering is concerned with predictability in both functional and performance behavior, though most formal techniques have typically focused their attention on the former. Reasoning about the (functional or performance) behavior of a component-based system must be compositional in order to be scalable. Compositional performance reasoning demands that components include performance specifications, in addition to descriptions of functional behavior. Unfortunately, as explained in this paper, classical techniques and notations for performance analysis are either unsuitable or unnatural to capture performance behaviors of generic software components. They fail to work in the presence of parameterization and layering. The paper introduces elements of a compositional approach to performance analysis using a detailed example. It explains that performance specification problems are so basic that there are unresolved research issues to be tackled even for the simplest reusable components. These issues must be tackled by any practical proposal for sound performance reasoning. Only then will software developers be able to engineer new systems by choosing and assembling components that best fit their performance (time and space) requirements. --- paper_title: Tools and experiments supporting a testing-based theory of component composition paper_content: Development of software using off-the-shelf components seems to offer a chance for improving product quality and developer productivity. This article reviews a foundational testing-based theory of component composition, describes tools that implement the theory, and presents experiments with functional and nonfunctional component/system properties that validate the theory and illuminate issues in component composition. The context for this work is an ideal form of Component-Based Software Development (CBSD) supported by tools. Component developers describe their components by measuring approximations to functional and nonfunctional behavior on a finite collection of subdomains. Systems designers describe an application-system structure by the component connections that form it. From measured component descriptions and a system structure, a CAD tool synthesizes the system properties, predicting how the system will behave. The system is not built, nor are any test executions performed. Neither the component sources nor executables are needed by systems designers. From CAD calculations a designer can learn (approximately) anything that could be learned by testing an actual system implementation. The CAD tool is often more efficient than it would be to assemble and execute an actual system. Using tools that support an ideal separation between component- and system development, experiments were conducted to investigate two related questions: (1) To what extent can unit (that is, component) testing replace system testingq (2) What properties of software and subdomains influence the quality of subdomain testingq --- paper_title: Software component composition: a subdomain-based testing-theory foundation paper_content: Composition of software elements into assemblies (systems) is a fundamental aspect of software development. It is an important strength of formal mathematical specification that the descriptions of elements can be precisely composed into the descriptions of assemblies. Testing, on the other hand, is usually thought to be ‘non-compositional.’ Testing provides information about any executable software element, but testing descriptions have not been combined to describe assemblies of elements. The underlying reason for the compositional deficiency of testing is that tests are samples. When two elements are composed, the input samples (test points) for the first lead to an output sample, but it does not match the input test points of the second, following element. The current interest in software components and component-based software development (CBSD) provides an ideal context for investigating elements and assemblies. In CBSD, the elements (components) are analysed without knowledge of the system(s) to be later assembled. A fundamental testing theory of component composition must use measured component properties (test results) to predict system properties. This paper proposes a testing-based theory of software component composition based on subdomains. It shows how to combine subdomain tests of components into testing predictions for arbitrarily complex assemblies formed by sequence, conditional, and iteration constructions. The basic construction of the theory applies to functional behaviour, but the theory can also predict the system's non-functional properties from component subdomain tests. Compared with the alternative of actually building and testing a system, theoretical predictions are computationally more efficient. The theory can also be described as an exercise in modelling. Components are replaced by abstractions derived from testing them, and these models are manipulated to model system behaviour. This article replaces a previously published version. DOI: 10.1002/stvr.368. Copyright © 2007 John Wiley & Sons, Ltd. --- paper_title: Automating the performance management of component-based enterprise systems through the use of redundancy paper_content: Component technologies are increasingly being used for building enterprise systems, as they can address complex functionality and flexibility problems and reduce development and maintenance costs. Nonetheless, current component technologies provide little support for predicting and controlling the emerging performance of software systems that are assembled from distinct components.This paper presents a framework for automating the performance management of complex, component-based systems. The adopted approach is based on the alternate usage of multiple component variants with equivalent functional characteristics, each one optimized for a different running environment. A fully-automated framework prototype for J2EE is presented, along with results from managing a sample enterprise application on JBoss. A mechanism that uses monitoring data to learn and automatically improve the framework's management behaviour is proposed. The framework imposes no extra requirements on component providers, or on the component technologies. --- paper_title: A framework for performance monitoring, modelling and prediction of component oriented distributed systems paper_content: We present a framework that can be used to identify performance issues in component-oriented distributed systems. The framework consists of a monitoring module, a modelling module and a prediction module, that are interrelated. The monitoring block extracts real-time performance data from a live or under development system. The modelling block generates UML models of the system showing where the performance problems are located and drives the monitoring process. The performance prediction block simulates different system-loads on the generated models and pinpoints possible performance issues. The technological focus is currently on Enterprise Java Beans systems. --- paper_title: Performance Solutions A Practical Guide To Creating Responsive Scalable Software paper_content: Thank you for downloading performance solutions a practical guide to creating responsive scalable software. As you may know, people have search numerous times for their favorite books like this performance solutions a practical guide to creating responsive scalable software, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some malicious bugs inside their laptop. --- paper_title: TESTEJB - A measurement framework for EJBs paper_content: Specification of Quality of Service (QoS) for components can only be done in relation to the QoS the components themselves are given by imported components. Developers as well as users need support in order to derive valid data for specification respectively for checking whether a selected component complies with its specification. In this paper we introduce the architecture of a measurement framework for EJBs giving such support and discuss in detail the measurement of the well understood property of response time. --- paper_title: Detecting Performance Antipatterns in Component Based Enterprise Systems paper_content: We introduce an approach for automatic detection of performance antipatterns. The approach is based on a number of advanced monitoring and analysis techniques. The advanced analysis is used to identify relationships and patterns in the monitored data. This information is subsequently used to reconstruct a design model of the underlying system, which is loaded into a rule engine in order to identify predefined antipatterns. We give results of applying this approach to identify a number of antipatterns in two JEE applications. Finally, this work also categorises JEE antipatterns into categories based on the data needed to detect them. --- paper_title: Performance prediction for black-box components using reengineered parametric behaviour models paper_content: In component-based software engineering, the response time of an entire application is often predicted from the execution durations of individual component services. However, these execution durations are specific for an execution platform (i.e. its resources such as CPU) and for a usage profile. Reusing an existing component on different execution platforms up to now required repeated measurements of the concerned components for each relevant combination of execution platform and usage profile, leading to high effort. This paper presents a novel integrated approach that overcomes these limitations by reconstructing behaviour models with platform-independent resource demands of bytecode components. The reconstructed models are parameterised over input parameter values. Using platform-specific results of bytecode benchmarking, our approach is able to translate the platform-independent resource demands into predictions for execution durations on a certain platform. We validate our approach by predicting the performance of a file sharing application. --- paper_title: A model transformation approach for the early performance and reliability analysis of component-based systems paper_content: The adoption of a “high level” perspective in the design of a component-based application, without considering the specific features of some underlying supporting platform, has the advantage of focusingon the relevant architectural aspects and reasoning about them in a platform independent way, omitting unnecessary details that could even not be known at the earliest development stages.On the other hand, many of the details that are typically neglected in this high-level perspective must necessarily be taken into account to obtain a meaningful evaluation of different architectural choices in terms of extra-functional quality attributes, like performance or reliability. Toward the reconciliation of these two contrasting needs, we propose a model-based approach whose goal is to support the derivation of sufficiently detailed prediction models from high level models of component-based systems, focusing on the prediction of performance and reliability. We exploit for this purpose a refinement mechanism based on the use of model transformation techniques. --- paper_title: Automatic inclusion of middleware performance attributes into architectural UML software models paper_content: Distributed systems often use a form of communication middleware to cope with different forms of heterogeneity, including geographical spreading of the components, different programming languages and platform architectures, etc. The middleware, of course, impact the architecture and the performance of the system. This paper presents a model transformation framework to automatically include the architectural impact and the overhead incurred by using a middleware layer between several system components. Using this framework, architects can model the system in a middleware-independent fashion. Accurate, middleware-aware models can then be obtained automatically using a middleware model repository. The actual transformation algorithm is presented in more detail. The resulting models can be used to obtain performance models of the system. From those performance models, early indications of the system performance can be extracted. --- paper_title: Performance prediction for component compositions paper_content: A stepwise approach is proposed to predict the performance of component compositions. The approach considers the major factors influencing the performance of component compositions in sequence: component operations, activities, and composition of activities. During each step, various models - analytical, statistical, simulation - can be constructed to specify the contribution of each relevant factor to the performance of the composition. The architects can flexibly choose which model they use at each step in order to trade prediction accuracy against prediction effort. The approach is illustrated with an example about the performance prediction for an Automobile Navigation System. --- paper_title: Component Composition with Parametric Contracts paper_content: We discuss compositionality in terms of (a) component interoperability and contractual use of components, (b) component adaptation and (c) prediction of properties of composite components. In particular, we present parametric component contracts as a framework treating the above mentioned facets of compositionality in a unified way. Parametric contracts compute component interfaces in dependency of context properties, such as available external services or the profile how the component will be used by its clients. Under well-specified conditions, parametric contracts yield interfaces offering interoperability to the component context (as they are component-specifically generated). Therefore, parametric contracts can be considered as adaptation mechanism, adapting a components providesor requires-interface depending on connected components. If non-functional properties are specified in a component provides interface, parametric contracts compute these nonfunctional properties in dependency of the environment. --- paper_title: Software component models paper_content: Component-based Development (CBD) is an important emerging topic in Software Engineering, promising long sought after benefits like increased reuse and reduced time-to-market (and hence software production cost). However, there are at present many obstacles to overcome before CBD can succeed. For one thing, CBD success is predicated on a standardised market place for software components, which does not yet exist. In fact currently CBD even lacks a universally accepted terminology. Existing component models adopt different component definitions and composition operators. Therefore much research remains to be done. We believe that the starting point for this endeavour should be a thorough study of current component models, identifying their key characteristics and comparing their strengths and weaknesses. A desirable side-effect would be clarifying and unifying the CBD terminology. In this tutorial, we present a clear and concise exposition of all the current major software component models, including a taxonomy. The purpose is to distill and present knowledge of current software component models, as well as to present an analysis of their properties with respect to commonly accepted criteria for CBD. The taxonomy also provides a starting point for a unified terminology. --- paper_title: How far are we from the definition of a common software performance ontology? paper_content: The recent approaches to software performance modeling and validation share the idea of annotating software models with information related to performance (e.g. operational profile) and transforming the annotated model into a performance model (e.g. a Stochastic Petri Net). Up to date, no standard has been defined to represent the information related to performance in software artifacts, although clear advantages in tool interoperability and model transformations would stem from it. This paper is aimed at questioning whether a software performance ontology (i.e. a standard set of concepts and relations) is achievable or not. We consider three meta-models defined for software performance, that are the Schedulability, Performance and Time profile of UML, the Core Scenario Model and the Software Performance Engineering meta-model. We devise two approaches to the creation of an ontology: (i) bottom-up, that extracts common knowledge from the meta-models, (ii) top-down, that is driven from a set of requirements. --- paper_title: An empirical investigation of the effort of creating reusable models for performance prediction paper_content: Model-based performance prediction methods aim at evaluating the expected response time, throughput, and resource utilisation of a software system at design time, before implementation. Existing performance prediction methods use monolithic, throw-away prediction models or component-based, reusable prediction models. While it is intuitively clear that the development of reusable models requires more effort, the actual higher amount of effort has not been quantified or analysed systematically yet. To study the effort, we conducted a controlled experiment with 19 computer science students who predicted the performance of two example systems applying an established, monolithic method (Software Performance Engineering) as well as our own component-based method (Palladio). The results show that the effort of model creation with Palladio is approximately 1.25 times higher than with SPE in our experimental setting, with the resulting models having comparable prediction accuracy. Therefore, in some cases, the creation of reusable prediction models can already be justified, if they are reused at least once. --- paper_title: Predicting the Behavior of a Highly Configurable Component Based Real-Time System paper_content: Software components and the technology supporting component based software engineering contribute greatly to the rapid development and configuration of systems for a variety of application domains. Such domains go beyond desktop office applications and information systems supporting e-commerce, but include systems having real-time performance requirements and critical functionality. Discussed in this paper are the results from an experiment that demonstrates the ability to predict deadline satisfaction of threads in a real-time system where the functionality performed is based on the configuration of the assembled software components. Presented is the method used to abstract the large, legacy code base of the system software and the application software components in the system; the model of those abstractions based on available architecture documentation and empirically-based, runtime observations; and the analysis of the predictions which yielded objective confidence in the observations and model created which formed the underlying basis for the predictions. --- paper_title: Rule-based automatic software performance diagnosis and improvement paper_content: There are many advantages to analyzing performance at the design level, rather than waiting until system testing. However the necessary expertise in making and interpreting performance models may not be available, and the time for the analysis may be prohibitive. This work addresses both these difficulties through automation. Starting from an annotated specification in UML, it is possible to automatically derive a performance model. This work goes further to automate the performance analysis, and to explore design changes using diagnostic and design-change rules. The rules generate improved performance models which can be transformed back to an improved design. They untangle the effects of the system configuration (such as the allocation of processors) from limitations of the design, and they recommend both configuration and design improvements. This paper describes a prototype called Performance Booster (PB), which incorporates several rules, and demonstrates its feasibility by applying PB to the design of several case studies (tutorial and industrial). It also addresses how the changes at the level of a performance model should be implemented in the software. --- paper_title: Performance Solutions A Practical Guide To Creating Responsive Scalable Software paper_content: Thank you for downloading performance solutions a practical guide to creating responsive scalable software. As you may know, people have search numerous times for their favorite books like this performance solutions a practical guide to creating responsive scalable software, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some malicious bugs inside their laptop. --- paper_title: Exploring performance trade-offs of a JPEG decoder using the deepcompass framework paper_content: Designing embedded systems for multiprocessor platforms requires early prediction and balancing of multiple system quality attributes. We present a design space exploration framework for component-based software systems that allows an architect to get insight into a space of possible design alternatives with further evaluation and comparison of these alternatives. The framework provides (a) tool-guided design of multiple alternatives of software and hardware architectures, (b) early design-time predictions of performance properties and identification of bottlenecks for each architectural alternative, and (c) evaluation of each alternative with respect to multi-objective trade-offs. The performance prediction technique employs modeling of individual components and composition of the models into a system model representing the system behaviour and resource usage. We illustrate the framework by a case study of a JPEG decoder application. For this system, we consider architectural alternatives, show their specification, and explore their trade-offs with respect to task latencies, resource utilization and system cost. --- paper_title: Performance prediction for black-box components using reengineered parametric behaviour models paper_content: In component-based software engineering, the response time of an entire application is often predicted from the execution durations of individual component services. However, these execution durations are specific for an execution platform (i.e. its resources such as CPU) and for a usage profile. Reusing an existing component on different execution platforms up to now required repeated measurements of the concerned components for each relevant combination of execution platform and usage profile, leading to high effort. This paper presents a novel integrated approach that overcomes these limitations by reconstructing behaviour models with platform-independent resource demands of bytecode components. The reconstructed models are parameterised over input parameter values. Using platform-specific results of bytecode benchmarking, our approach is able to translate the platform-independent resource demands into predictions for execution durations on a certain platform. We validate our approach by predicting the performance of a file sharing application. --- paper_title: Performance prediction of component-based applications paper_content: One of the major problems in building large-scale enterprise systems is anticipating the performance of the eventual solution before it has been built. The fundamental software engineering problem becomes more difficult when the systems are built on component technology. This paper investigates the feasibility of providing a practical solution to this problem. An empirical approach is proposed to determine the performance characteristics of component-based applications by benchmarking and profiling. Based on observation, a model is constructed to act as a performance predictor for a class of applications based on the specific component technology. The performance model derived from empirical measures is necessary to make the problem tractable and the results relevant. A case study applies the performance model to an application prototype implemented by two component infrastructures: CORBA and J2EE. --- paper_title: Predicting the performance of component-based software architectures with different usage profiles paper_content: Performance predictions aim at increasing the quality of software architectures during design time. To enable such predictions, specifications of the performance properties of individual components within the architecture are required. However, the response times of a component might depend on its configuration in a specific setting and the data send to or retrieved from it. Many existing prediction approaches for component-based systems neglect these influences. This paper introduces extensions to a performance specification language for components, the Palladio Component Model, to model these influences. The model enables to predict response times of different architectural alternatives. A case study on a component-based architecture for a web portal validates the approach and shows that it is capable of supporting a design decision in this scenario. --- paper_title: Modelling of input-parameter dependency for performance predictions of component-based embedded systems paper_content: The guaranty of meeting the timing constraints during the design phase of real-time component-based embedded software has not been realized. To satisfy real-time requirements, we need to understand behaviour and resource usage of a system over time. In this paper, we address both aspects in detail by observing the influence of input data on the system behaviour and performance. We extend an existing scenario simulation approach that features the modelling of input parameter dependencies and simulating the execution of the models. The approach enables specification of the dependencies in the component models, as well as initialisation of the parameters in the application scenario model. This gives a component-based application designer an explorative possibility of going through all possible execution scenarios with different parameter initialisations, and finding the worst-case scenarios where the predicted performance does not satisfy the requirements. The identification of these scenarios is important because it avoids system redesign at the later stage. In addition, the conditional behaviour and resource usage modelling with respect to the input data provide more accurate prediction. --- paper_title: An empirical investigation of the effort of creating reusable models for performance prediction paper_content: Model-based performance prediction methods aim at evaluating the expected response time, throughput, and resource utilisation of a software system at design time, before implementation. Existing performance prediction methods use monolithic, throw-away prediction models or component-based, reusable prediction models. While it is intuitively clear that the development of reusable models requires more effort, the actual higher amount of effort has not been quantified or analysed systematically yet. To study the effort, we conducted a controlled experiment with 19 computer science students who predicted the performance of two example systems applying an established, monolithic method (Software Performance Engineering) as well as our own component-based method (Palladio). The results show that the effort of model creation with Palladio is approximately 1.25 times higher than with SPE in our experimental setting, with the resulting models having comparable prediction accuracy. Therefore, in some cases, the creation of reusable prediction models can already be justified, if they are reused at least once. --- paper_title: Software performance in the real world: personal lessons from the performance trauma team paper_content: In the nine years that we have been involved in software performance engineering (SPE) and performance testing engagements we have learned several things. Across numerous eCommerce applications and an enterprise CRM product suite, our knowledge base about the field of Software Performance Engineering is constantly evolving. The focus of this paper is what we have learned in the areas of SPE project management, performance testing, defining the scope of SPE projects, ITIL, post production performance support, and exploration of the boundaries of applied SPE. Is it really just about performance. --- paper_title: The Future of Software Performance Engineering paper_content: Performance is a pervasive quality of software systems; everything affects it, from the software itself to all underlying layers, such as operating system, middleware, hardware, communication networks, etc. Software Performance Engineering encompasses efforts to describe and improve performance, with two distinct approaches: an early-cycle predictive model-based approach, and a late-cycle measurement-based approach. Current progress and future trends within these two approaches are described, with a tendency (and a need) for them to converge, in order to cover the entire development cycle. --- paper_title: Performance Model Estimation and Tracking Using Optimal Filters paper_content: To update a performance model, its parameter values must be updated, and in some applications (such as autonomic systems) tracked continuously over time. Direct measurement of many parameters during system operation requires instrumentation which is impractical. Kalman filter estimators can track such parameters using other data such as response times and utilizations, which are readily observable. This paper adapts Kalman filter estimators for performance model parameters, evaluates the approximations which must be made, and develops a systematic approach to setting up an estimator. The estimator converges under easily verified conditions. Different queueing-based models are considered here, and the extension for state-based models (such as stochastic Petri nets) is straightforward. --- paper_title: Predicting the Behavior of a Highly Configurable Component Based Real-Time System paper_content: Software components and the technology supporting component based software engineering contribute greatly to the rapid development and configuration of systems for a variety of application domains. Such domains go beyond desktop office applications and information systems supporting e-commerce, but include systems having real-time performance requirements and critical functionality. Discussed in this paper are the results from an experiment that demonstrates the ability to predict deadline satisfaction of threads in a real-time system where the functionality performed is based on the configuration of the assembled software components. Presented is the method used to abstract the large, legacy code base of the system software and the application software components in the system; the model of those abstractions based on available architecture documentation and empirically-based, runtime observations; and the analysis of the predictions which yielded objective confidence in the observations and model created which formed the underlying basis for the predictions. --- paper_title: Next generation data centers: trends and implications paper_content: In this talk we will discuss next generation data centers and the important impact they will have upon enterprise applications. Specifically, we will discuss the technical and economical trends motivating the move towards large scale distributed data centers consisting of tens of thousands of servers and hundreds of petabytes of storage. We will explain the roles and advantages of virtual machines and other virtualization technologies in these environments and also explore how they exacerbate the complexity of management and achieving predictable application behavior.To better illustrate issues emerging in such environments we will describe early experiments we conducted with a 1000-processor utility rendering service created for DreamWorks Animation that was used to render the films Shrek II and Madagascar. We will discuss the lessons learned from this experience.Next, we consider the trend towards service oriented architectures for enterprise application platforms. Service orientation provides for more flexible and agile information technology systems but further increases the complexity of management and behavior. We will explore the implications of composing services dynamically using an SOA approach.These trends for enterprise application platforms and the trends towards next generation data centers have helped to drive our current research agenda. Our goal is to enable the flexibility and agility offered by these new technologies while enabling cost effective management, predictable behavior and improved quality of service. We will give an overview of our research on model driven design for enterprise application infrastructure, automated deployment, and operations of distributed application services executing in a virtualized, shared resource pool within these next generation data centers.Finally, we will summarize the implications, challenges, and opportunities posed by these trends on academic and industrial research. In particular, we consider the impact on software performance and software performance engineering and pose important unanswered questions. --- paper_title: Rule-based automatic software performance diagnosis and improvement paper_content: There are many advantages to analyzing performance at the design level, rather than waiting until system testing. However the necessary expertise in making and interpreting performance models may not be available, and the time for the analysis may be prohibitive. This work addresses both these difficulties through automation. Starting from an annotated specification in UML, it is possible to automatically derive a performance model. This work goes further to automate the performance analysis, and to explore design changes using diagnostic and design-change rules. The rules generate improved performance models which can be transformed back to an improved design. They untangle the effects of the system configuration (such as the allocation of processors) from limitations of the design, and they recommend both configuration and design improvements. This paper describes a prototype called Performance Booster (PB), which incorporates several rules, and demonstrates its feasibility by applying PB to the design of several case studies (tutorial and industrial). It also addresses how the changes at the level of a performance model should be implemented in the software. --- paper_title: Performance Solutions A Practical Guide To Creating Responsive Scalable Software paper_content: Thank you for downloading performance solutions a practical guide to creating responsive scalable software. As you may know, people have search numerous times for their favorite books like this performance solutions a practical guide to creating responsive scalable software, but end up in infectious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some malicious bugs inside their laptop. --- paper_title: A framework for automated generation of architectural feedback from software performance analysis paper_content: A rather complex task in the performance analysis of software architectures has always been the interpretation of the analysis results and the generation of feedback that may help developers to improve their architecture with alternative "better performing" solutions. This is due, on one side, to the fact that performance analysis results may be rather complex to interpret (e.g., they are often collections of different indices) and, on the other side, to the problem of coupling the "right" architectural alternatives to results, that are the alternatives that allow to improve the performance by resolving critical issues in the architecture. In this paper we propose a framework to interpret the performance analysis results and to propose alternatives to developers that improve their architectural designs. The interpretation of results is based on the ability to automatically recognize performance anti-patterns in the software architecture. The whole process of result interpretation and generation of architectural alternatives is supported by a tool based on the Layered Queueing Network notation. --- paper_title: Experimentation in software engineering: an introduction paper_content: The purpose of Experimentation in Software Engineering: An Introduction is to introduce students, teachers, researchers, and practitioners to experimentation and experimental evaluation with a focus on software engineering. The objective is, in particular, to provide guidelines for performing experiments evaluating methods, techniques and tools in software engineering. The introduction is provided through a process perspective. The focus is on the steps that we go through to perform experiments and quasi-experiments. The process also includes other types of empirical studies. The motivation for the book emerged from the need for support we experienced when turning our software engineering research more experimental. Several books are available which either treat the subject in very general terms or focus on some specific part of experimentation; most focus on the statistical methods in experimentation. These are important, but there were few books elaborating on experimentation from a process perspective, none addressing experimentation in software engineering in particular. The scope of Experimentation in Software Engineering: An Introduction is primarily experiments in software engineering as a means for evaluating methods, techniques and tools. The book provides some information regarding empirical studies in general, including both case studies and surveys. The intention is to provide a brief understanding of these strategies and in particular to relate them to experimentation. Experimentation in Software Engineering: An Introduction is suitable for use as a textbook or a secondary text for graduate courses, and for researchers and practitioners interested in an empirical approach to software engineering. (Less) --- paper_title: Performance prediction for black-box components using reengineered parametric behaviour models paper_content: In component-based software engineering, the response time of an entire application is often predicted from the execution durations of individual component services. However, these execution durations are specific for an execution platform (i.e. its resources such as CPU) and for a usage profile. Reusing an existing component on different execution platforms up to now required repeated measurements of the concerned components for each relevant combination of execution platform and usage profile, leading to high effort. This paper presents a novel integrated approach that overcomes these limitations by reconstructing behaviour models with platform-independent resource demands of bytecode components. The reconstructed models are parameterised over input parameter values. Using platform-specific results of bytecode benchmarking, our approach is able to translate the platform-independent resource demands into predictions for execution durations on a certain platform. We validate our approach by predicting the performance of a file sharing application. --- paper_title: TESTEJB - A measurement framework for EJBs paper_content: Specification of Quality of Service (QoS) for components can only be done in relation to the QoS the components themselves are given by imported components. Developers as well as users need support in order to derive valid data for specification respectively for checking whether a selected component complies with its specification. In this paper we introduce the architecture of a measurement framework for EJBs giving such support and discuss in detail the measurement of the well understood property of response time. --- paper_title: Automatic inclusion of middleware performance attributes into architectural UML software models paper_content: Distributed systems often use a form of communication middleware to cope with different forms of heterogeneity, including geographical spreading of the components, different programming languages and platform architectures, etc. The middleware, of course, impact the architecture and the performance of the system. This paper presents a model transformation framework to automatically include the architectural impact and the overhead incurred by using a middleware layer between several system components. Using this framework, architects can model the system in a middleware-independent fashion. Accurate, middleware-aware models can then be obtained automatically using a middleware model repository. The actual transformation algorithm is presented in more detail. The resulting models can be used to obtain performance models of the system. From those performance models, early indications of the system performance can be extracted. --- paper_title: Detecting Performance Antipatterns in Component Based Enterprise Systems paper_content: We introduce an approach for automatic detection of performance antipatterns. The approach is based on a number of advanced monitoring and analysis techniques. The advanced analysis is used to identify relationships and patterns in the monitored data. This information is subsequently used to reconstruct a design model of the underlying system, which is loaded into a rule engine in order to identify predefined antipatterns. We give results of applying this approach to identify a number of antipatterns in two JEE applications. Finally, this work also categorises JEE antipatterns into categories based on the data needed to detect them. --- paper_title: Architecture-Based Software Reliability Analysis: Overview and Limitations paper_content: With the growing size and complexity of software applications, research in the area of architecture-based software reliability analysis has gained prominence. The purpose of this paper is to provide an overview of the existing research in this area, critically examine its limitations, and suggest ways to address the identified limitations --- paper_title: A model-driven approach to performability analysis of dynamically reconfigurable component-based systems paper_content: Dynamic reconfiguration techniques appear promising to build component-based (C-B) systems for application domains that have strong adaptability requirements, like the mobile and the service-oriented computing domains. However, introducing dynamic reconfiguration features into a C-B application makes even more challenging the design and verification of functional and non functional requirements. Our goal is to support the model-based analysis of the effectiveness of reconfigurable C-B applications, with a focus on the assessment of the non-functional performance and reliability attributes. As a first step towards this end, we address the issue of selecting suitable analysis models for reconfigurable systems, suggesting to this end the use of joint performance and reliability (performability) models. Furthermore, we propose a model-driven approach to automatically transform a design model into an analysis model. For this purpose, we build on the existence of intermediate languages that have been proposed to facilitate this transformation and we extend one of them, to capture the core features (from a performance/reliability viewpoint) of a dynamically reconfigurable C-B system. Finally, we illustrate by a simple application example the main steps of the proposed approach. --- paper_title: Hybrid performance modeling approach for network intensive distributed software paper_content: When designing and evaluating software architectures and network facilities for hosting demanding distributed applications, taking performance considerations into account is essential. A key factor in assessing the performance of such a distributed system is the network latency and its relation to the application behaviour. In this respect, it is important to include the performance impact of the network into the performance models used during the entire design cycle of the system.A framework is proposed that allows to model both the software and the network components separately and extracts a single set of performance estimates for the entire system. This has the advantage of allowing the network and software aspects to be modeled separately using the modeling languages and tools most suited to those system aspects. A case study is presented to illustrate the use of the framework and its usefulness in predicting system performance. --- paper_title: Modelling of input-parameter dependency for performance predictions of component-based embedded systems paper_content: The guaranty of meeting the timing constraints during the design phase of real-time component-based embedded software has not been realized. To satisfy real-time requirements, we need to understand behaviour and resource usage of a system over time. In this paper, we address both aspects in detail by observing the influence of input data on the system behaviour and performance. We extend an existing scenario simulation approach that features the modelling of input parameter dependencies and simulating the execution of the models. The approach enables specification of the dependencies in the component models, as well as initialisation of the parameters in the application scenario model. This gives a component-based application designer an explorative possibility of going through all possible execution scenarios with different parameter initialisations, and finding the worst-case scenarios where the predicted performance does not satisfy the requirements. The identification of these scenarios is important because it avoids system redesign at the later stage. In addition, the conditional behaviour and resource usage modelling with respect to the input data provide more accurate prediction. ---	Title: Performance evaluation of component-based software systems: A survey Section 1: Introduction Description 1: This section provides an overview of the paper, discussing the goal of classifying performance prediction and measurement approaches for component-based software systems proposed over the last ten years. Section 2: Software Component Performance Description 2: This section introduces the key terms and concepts needed to understand the challenges of performance evaluation methods for component-based systems. Section 3: Performance Evaluation Methods Description 3: This section summarizes the main approaches to performance evaluation for component-based software systems, including prediction approaches based on UML and proprietary meta-models, middleware-focused methods, and formal specification methods. Section 4: Critical Reflection Description 4: This section offers a critical analysis of the surveyed approaches, discussing their benefits and drawbacks, and details the factors impacting component performance and their descriptions. Section 5: Future Directions Description 5: This section outlines possible future research directions in the field of performance evaluation of component-based systems, including model expressiveness, support for runtime and dynamic architectures, and domain-specific methods. Section 6: Conclusions Description 6: This section concludes the survey, summarizing the current state of the field and the importance of developing mixed approaches that incorporate both measurements and modelings to handle the complexity of component-based systems.
A Survey of the Path Partition Conjecture	9	--- paper_title: On a cycle partition problem paper_content: Let G be any graph and let c(G) denote the circumference of G. We conjecture that for every pair c"1,c"2 of positive integers satisfying c"1+c"2=c(G), the vertex set of G admits a partition into two sets V"1 and V"2, such that V"i induces a graph of circumference at most c"i, i=1,2. We establish various results in support of the conjecture; e.g. it is observed that planar graphs, claw-free graphs, certain important classes of perfect graphs, and graphs without too many intersecting long cycles, satisfy the conjecture. This work is inspired by a well-known, long-standing, analogous conjecture involving paths. --- paper_title: Uniquely (m, k)τ-colourable graphs and k − τ-saturated graphs paper_content: Abstract For a graph G , the path number τ ( G ) is defined as the order of a longest path in G . An ( m , k ) τ -colouring of a graph H is a partition of the vertex set of H into m subsets such that each subset induces a subgraph of H for which τ is at most k . The k − τ -chromatic number χ k τ ( H ) is the least m for which H has an ( m , k ) τ -colouring. A graph H is uniquely ( m , k ) τ -colourable if χ k τ ( H ) = m and there is only one partition of the vertex set of H which is an ( m , k ) τ -colouring of H . A graph G is called k − τ -saturated if τ ( G ) ⩽ k and τ ( G + e ) ⩾ k + 1 for all e ϵ E ( G ). For k = 1, the graphs obtained by taking the join of k − τ -saturated graphs (which are empty graphs in this case) are known to be uniquely colourable graphs. In this paper we construct uniquely ( m , k ) τ -colourable graphs (for all positive integers m and k ) using k − τ -saturated graphs in a similar fashion. As a corollary we characterise those p for which there exists a uniquely ( m , k ) τ -colourable graph of order p . --- paper_title: P_{m}-saturated graphs with minimum size paper_content: By \(P_m\) we denote a path of order \(m\). A graph \(G\) is said to be \(P_m\)-saturated if \(G\) has no subgraph isomorphic to \(P_m\) and adding any new edge to \(G\) creates a \(P_m\) in \(G\). In 1986 L. Kaszonyi and Zs. Tuza considered the following problem: for given \(m\) and \(n\) find the minimum size \(sat(n;P_m)\) of \(P_m\)-saturated graph and characterize the graphs of \(Sat(n;P_m)\) - the set of \(P_m\)-saturated graphs of minimum size. They have solved this problem for \(n\geq a_m\) where \(a_m=\begin{cases}3\cdot 2^{k-1}-2 &\quad\text{ if }\quad m=2k,\, k\gt 2\\ 2^{k+1}-2 &\quad\text{ if }\quad m=2k+1,\, k\geq 2\end{cases}\). We define \(b_m=\begin{cases}3\cdot 2^{k-2} &\quad\text{ if }\quad m=2k,\, k\geq 3\\ 3\cdot 2^{k-1}-1 &\quad\text{ if }\quad m=2k+1,\, k\geq 3\end{cases}\) and give \(sat(n;P_m)\) and \(Sat(n;P_m)\) for \(m\geq 6\) and \(b_m\leq n\leq a_m\). --- paper_title: A note on a cycle partition problem paper_content: Abstract Let G be any graph, and let c ( G ) denote the circumference of G . If, for every pair c 1 , c 2 of positive integers satisfying c 1 + c 2 = c ( G ) , the vertex set of G admits a partition into two sets V 1 and V 2 such that V i induces a graph of circumference at most c i , i = 1 , 2 , then G is said to be c -partitionable. In [M.H. Nielsen, On a cycle partition problem, Discrete Math. 308 (2008) 6339–6347], it is conjectured that every graph is c -partitionable. In this paper, we verify this conjecture for a graph with a longest cycle that is a dominating cycle. Moreover, we prove that G is c -partitionable if c ( G ) ≥ \| V ( G ) \| − 3 . --- paper_title: Saturated graphs with minimal number of edges paper_content: Let F = {F1,…} be a given class of forbidden graphs. A graph G is called F-saturated if no Fi ∈ F is a subgraph of G but the addition of an arbitrary new edge gives a forbidden subgraph. In this paper the minimal number of edges in F-saturated graphs is examined. General estimations are given and the structure of minimal graphs is described for some special forbidden graphs (stars, paths, m pairwise disjoint edges). --- paper_title: On a tree-partition problem paper_content: Abstract If T = ( V , E ) is a tree then – T denotes the additive hereditary property consisting of all graphs that does not contain T as a subgraph. For an arbitrary vertex v of T we deal with a partition of T into two trees T 1 , T 2 , so that V ( T 1 ) ∩ V ( T 2 ) = { v } , V ( T 1 ) ∪ ( T 2 ) = V ( T ) , E ( T 1 ) ∩ E ( T 2 ) = ∅ , E ( T 1 ) ∪ E ( T 2 ) = E ( T ) , T [ V ( T 1 ) \ { v } ] ⊆ E ( T 1 ) and T [ V ( T 2 ) \ { v } ] ⊆ E ( T 2 ) . We call such a partition a T v − p a r t i t i o n of T . We study the following em: Given a graph G belonging to –T . Is it true that for any T v -partition T 1 , T 2 of T there exists a partition { V 1 , V 2 } of the vertices of G such that G [ V 1 ] ∈ − T 1 and G [ V 2 ] ∈ − T 2 ? This problem provides a natural generalization of Δ-partition problem studied by L. Lovasz ([L. Lovasz, On decomposition of graphs. Studia Sci. Math. Hungar. 1 (1966) 237–238]) and Path Partition Conjecture formulated by P. Mihok ([P. Mihok, Problem 4, in: M. Borowiecki, Z. Skupien (Eds.), Graphs, Hypergraphs and Matroids, Zielona Gora, 1985, p. 86]). We present some partial results and a contribution to the Path Kernel Conjecture that was formulated with connection to Path Partition Conjecture. --- paper_title: A note on the Path Kernel Conjecture paper_content: Let @t(G) denote the number of vertices in a longest path in a graph G=(V,E). A subset K of V is called a P"n-kernel of G if @t(G[K])@?n-1 and every vertex [email protected][email protected]?K is adjacent to an end-vertex of a path of order n-1 in G[K]. It is known that every graph has a P"n-kernel for every positive integer [email protected]?9. R. Aldred and C. Thomassen in [R.E.L. Aldred, C. Thomassen, Graphs with not all possible path-kernels, Discrete Math. 285 (2004) 297-300] proved that there exists a graph which contains no P"3"6"4-kernel. In this paper, we generalise this result. We construct a graph with no P"1"5"5-kernel and for each integer l>=0 we provide a construction of a graph G containing no P"@t"("G")"-"l-kernel. --- paper_title: Graphs with not all possible path-kernels paper_content: Abstract The Path Partition Conjecture states that the vertices of a graph G with longest path of length c may be partitioned into two parts X and Y such that the longest path in the subgraph of G induced by X has length at most a and the longest path in the subgraph of G induced by Y has length at most b , where a + b = c . Moreover, for each pair a , b such that a + b = c there is a partition with this property. A stronger conjecture by Broere, Hajnal and Mihok, raised as a problem by Mihok in 1985, states the following: For every graph G and each integer k , c ⩾ k ⩾2 there is a partition of V ( G ) into two parts (K, K ) such that the subgraph G [ K ] of G induced by K has no path on more than k −1 vertices and each vertex in K is adjacent to an endvertex of a path on k −1 vertices in G [ K ]. In this paper we provide a counterexample to this conjecture. --- paper_title: Graph coloring problems paper_content: Planar Graphs. Graphs on Higher Surfaces. Degrees. Critical Graphs. The Conjectures of Hadwiger and Hajos. Sparse Graphs. Perfect Graphs. Geometric and Combinatorial Graphs. Algorithms. Constructions. Edge Colorings. Orientations and Flows. Chromatic Polynomials. Hypergraphs. Infinite Chromatic Graphs. Miscellaneous Problems. Indexes. --- paper_title: A survey of hereditary properties of graphs paper_content: In this paper we survey results and open problems on the structure of additive and hereditary properties of graphs. The important role of vertex partition problems, in particular the existence of uniquely partitionable graphs and reducible properties of graphs in this structure, is emphasized. Many related topics, including questions on the complexity of related problems, are investigated. --- paper_title: Cycles in k-traceable oriented graphs paper_content: A digraph of order at least k is termed k-traceable if each of its subdigraphs of order k is traceable. It turns out that several properties of tournaments-i.e., the 2-traceable oriented graphs-extend to k-traceable oriented graphs for small values of k. For instance, the authors together with O. Oellermann have recently shown that for k=2,3,4,5,6, all k-traceable oriented graphs are traceable. Moon [J.W. Moon, On subtournaments of a tournament, Canad. Math. Bull. 9(3) (1966) 297-301] observed that every nontrivial strong tournament T is vertex-pancyclic-i.e., through each vertex there is a cycle of every length from 3 up to the order of T. The present paper reports results pertaining to various cycle properties of strong k-traceable oriented graphs and explores the extent to which pancyclicity is retained by strong k-traceable oriented graphs. For each k>=2 there are infinitely many k-traceable oriented graphs-e.g. tournaments. However, we establish an upper bound (linear in k) on the order of k-traceable oriented graphs having a strong component with girth greater than 3. As an application of our findings, we show that the Path Partition Conjecture holds for 1-deficient oriented graphs having a strong component with girth at least 6. (A digraph is 1-deficient if its order is exactly one more than the order of its longest paths.) --- paper_title: A note on path kernels and partitions paper_content: The detour order of a graph G, denoted by @t(G), is the order of a longest path in G. A subset S of V(G) is called a P"n-kernel of G if @t(G[S])@?n-1 and every vertex v@?V(G)-S is adjacent to an end-vertex of a path of order n-1 in G[S]. A partition of the vertex set of G into two sets, A and B, such that @t(G[A])@?a and @t(G[B])@?b is called an (a,b)-partition of G. In this paper we show that any graph with girth g has a P"n"+"1-kernel for every n<3g2-1. Furthermore, if @t(G)=a+b, 1@?a@?b, and G has girth greater than 23(a+1), then G has an (a,b)-partition. --- paper_title: Longest path partitions in generalizations of tournaments paper_content: We consider the so-called Path Partition Conjecture for digraphs which states that for every digraph, D, and every choice of positive integers, @l"1,@l"2, such that @l"1+@l"2 equals the order of a longest directed path in D, there exists a partition of D into two digraphs, D"1 and D"2, such that the order of a longest path in D"i is at most @l"i, for i=1,2. We prove that certain classes of digraphs, which are generalizations of tournaments, satisfy the Path Partition Conjecture and that some of the classes even satisfy the conjecture with equality. --- paper_title: Stable set meeting every longest path paper_content: Laborde, Payan and Xuong conjectured that every digraph has a stable set meeting every longest path. We prove that this conjecture holds for digraphs with stability number at most 2. --- paper_title: A Traceability Conjecture for Oriented Graphs paper_content: A (di)graph $G$ of order $n$ is $k$-traceable (for some $k$, $1\leq k\leq n$) if every induced sub(di)graph of $G$ of order $k$ is traceable. It follows from Dirac's degree condition for hamiltonicity that for $k\geq2$ every $k$-traceable graph of order at least $2k-1$ is hamiltonian. The same is true for strong oriented graphs when $k=2,3,4,$ but not when $k\geq5$. However, we conjecture that for $k\geq2$ every $k$-traceable oriented graph of order at least $2k-1$ is traceable. The truth of this conjecture would imply the truth of an important special case of the Path Partition Conjecture for Oriented Graphs. In this paper we show the conjecture is true for $k \leq 5$ and for certain classes of graphs. In addition we show that every strong $k$-traceable oriented graph of order at least $6k-20$ is traceable. We also characterize those graphs for which all walkable orientations are $k$-traceable. --- paper_title: Progress on the Traceability Conjecture for Oriented Graphs paper_content: A digraph is k -traceable if each of its induced subdigraphs of order k is traceable. The Traceability Conjecture is that for k ≥ 2 every k -traceable oriented graph of order at least 2k-1 is traceable. The conjecture has been proved for k ≤ 5 . We prove that it also holds for k=6 . --- paper_title: Combinatorics and graph theory paper_content: Graph Theory: Introductory Concepts.- Trees.- Planarity.- Colorings.- Matchings.- Ramsey Theory.- References Combinatorics: Three Basic Problems.- Binomial Coefficients.- The Principle of Inclusion and Exclusion.- Generating Functions.- Polya's Theory of Counting.- More Numbers.- Stable Marriage.- References Infinite Combinatorics and Graph Theory: Pigeons and Trees.- Ramsey Revisited.- ZFC.- The Return of der Koenig.- Ordinals, Cardinals, and Many Pigeons.- Incompleteness and Coardinals.- Weakly Compact Cardinals.- Finite Combinatorics with Infinite Consequences.- Points of Departure.- References. --- paper_title: The Path Partition Conjecture is true for some generalizations of tournaments paper_content: Abstract The Path Partition Conjecture for digraphs states that for every digraph D , and every choice of positive integers λ 1 , λ 2 such that λ 1 + λ 2 equals the order of a longest directed path in D , there exists a partition of D in two subdigraphs D 1 , D 2 such that the order of the longest path in D i is at most λ i for i = 1 , 2 . We present sufficient conditions for a digraph to satisfy the Path Partition Conjecture. Using these results, we prove that strong path mergeable, arc-locally semicomplete, strong 3-quasi-transitive, strong arc-locally in-semicomplete and strong arc-locally out-semicomplete digraphs satisfy the Path Partition Conjecture. Some previous results are generalized. --- paper_title: Traceability of k-traceable oriented graphs paper_content: A digraph of order at least k is k-traceable if each of its subdigraphs of order k is traceable. We note that 2-traceable oriented graphs are tournaments and for k>=3, k-traceable oriented graphs can be regarded as generalized tournaments. We show that for [email protected][email protected]?6 every k-traceable oriented graph is traceable, thus extending the well-known fact that every tournament is traceable. This result does not extend to k=7. In fact, for every k>=7, except possibly for k=8 or 10, there exist k-traceable oriented graphs that are nontraceable. However, we show that for every k>=2 there exists a smallest integer t(k) such that every k-traceable oriented graph of order at least t(k) is traceable. --- paper_title: Digraphs -- Theory, Algorithms and Applications paper_content: The theory of directed graphs has developed enormously over recent decades, yet this book (first published in 2000) remains the only book to cover more than a small fraction of the results. New research in the field has made a second edition a necessity. Substantially revised, reorganised and updated, the book now comprises eighteen chapters, carefully arranged in a straightforward and logical manner, with many new results and open problems. As well as covering the theoretical aspects of the subject, with detailed proofs of many important results, the authors present a number of algorithms, and whole chapters are devoted to topics such as branchings, feedback arc and vertex sets, connectivity augmentations, sparse subdigraphs with prescribed connectivity, and also packing, covering and decompositions of digraphs. Throughout the book, there is a strong focus on applications which include quantum mechanics, bioinformatics, embedded computing, and the travelling salesman problem. Detailed indices and topic-oriented chapters ease navigation, and more than 650 exercises, 170 figures and 150 open problems are included to help immerse the reader in all aspects of the subject. Digraphs is an essential, comprehensive reference for undergraduate and graduate students, and researchers in mathematics, operations research and computer science. It will also prove invaluable to specialists in related areas, such as meteorology, physics and computational biology. --- paper_title: The Path Partition Conjecture is true for claw-free graphs paper_content: The detour order of a graph G, denoted by @t(G), is the order of a longest path in G. The Path Partition Conjecture (PPC) is the following: If G is any graph and (a,b) any pair of positive integers such that @t(G)=a+b, then the vertex set of G has a partition (A,B) such that @t()=)= --- paper_title: A survey of hereditary properties of graphs paper_content: In this paper we survey results and open problems on the structure of additive and hereditary properties of graphs. The important role of vertex partition problems, in particular the existence of uniquely partitionable graphs and reducible properties of graphs in this structure, is emphasized. Many related topics, including questions on the complexity of related problems, are investigated. --- paper_title: A note on path kernels and partitions paper_content: The detour order of a graph G, denoted by @t(G), is the order of a longest path in G. A subset S of V(G) is called a P"n-kernel of G if @t(G[S])@?n-1 and every vertex v@?V(G)-S is adjacent to an end-vertex of a path of order n-1 in G[S]. A partition of the vertex set of G into two sets, A and B, such that @t(G[A])@?a and @t(G[B])@?b is called an (a,b)-partition of G. In this paper we show that any graph with girth g has a P"n"+"1-kernel for every n<3g2-1. Furthermore, if @t(G)=a+b, 1@?a@?b, and G has girth greater than 23(a+1), then G has an (a,b)-partition. --- paper_title: A note on path kernels and partitions paper_content: The detour order of a graph G, denoted by @t(G), is the order of a longest path in G. A subset S of V(G) is called a P"n-kernel of G if @t(G[S])@?n-1 and every vertex v@?V(G)-S is adjacent to an end-vertex of a path of order n-1 in G[S]. A partition of the vertex set of G into two sets, A and B, such that @t(G[A])@?a and @t(G[B])@?b is called an (a,b)-partition of G. In this paper we show that any graph with girth g has a P"n"+"1-kernel for every n<3g2-1. Furthermore, if @t(G)=a+b, 1@?a@?b, and G has girth greater than 23(a+1), then G has an (a,b)-partition. --- paper_title: The Path Partition Conjecture is true for claw-free graphs paper_content: The detour order of a graph G, denoted by @t(G), is the order of a longest path in G. The Path Partition Conjecture (PPC) is the following: If G is any graph and (a,b) any pair of positive integers such that @t(G)=a+b, then the vertex set of G has a partition (A,B) such that @t()=)= --- paper_title: On a Closure Concept in Claw-Free Graphs paper_content: IfGis a claw-free graph, then there is a graphcl(G) such that (i)Gis a spanning subgraph ofcl(G), (ii)cl(G) is a line graph of a triangle-free graph, and (iii)the length of a longest cycle inGand incl(G) is the same. A sufficient condition for hamiltonicity in claw-free graphs, the equivalence of some conjectures on hamiltonicity in 2-tough graphs and the hamiltonicity of 7-connected claw-free graphs are obtained as corollaries. --- paper_title: Closure and stable Hamiltonian properties in claw-free graphs paper_content: In the class of k-connected claw-free graphs, we study the stability of some Hamiltonian properties under a closure operation introduced by the third author. We prove that (i) the properties of pancyclicity, vertex pancyclicity and cycle extendability are not stable for any k (i.e., for any of these properties there is an infinite family of graphs Gk of arbitrarily high connectivity k such that the closure of Gk has the property while the graph Gk does not); (ii) traceability is a stable property even for k = 1; (iii) homogeneous traceability is not stable for k = 2 (although it is stable for k = 7). The article is concluded with several open questions concerning stability of homogeneous traceability and Hamiltonian connectedness. © 2000 John Wiley & Sons, Inc. J Graph Theory 34: 30–41, 2000 --- paper_title: The Path Partition Conjecture is true for claw-free graphs paper_content: The detour order of a graph G, denoted by @t(G), is the order of a longest path in G. The Path Partition Conjecture (PPC) is the following: If G is any graph and (a,b) any pair of positive integers such that @t(G)=a+b, then the vertex set of G has a partition (A,B) such that @t()=)= --- paper_title: Cycles in k-traceable oriented graphs paper_content: A digraph of order at least k is termed k-traceable if each of its subdigraphs of order k is traceable. It turns out that several properties of tournaments-i.e., the 2-traceable oriented graphs-extend to k-traceable oriented graphs for small values of k. For instance, the authors together with O. Oellermann have recently shown that for k=2,3,4,5,6, all k-traceable oriented graphs are traceable. Moon [J.W. Moon, On subtournaments of a tournament, Canad. Math. Bull. 9(3) (1966) 297-301] observed that every nontrivial strong tournament T is vertex-pancyclic-i.e., through each vertex there is a cycle of every length from 3 up to the order of T. The present paper reports results pertaining to various cycle properties of strong k-traceable oriented graphs and explores the extent to which pancyclicity is retained by strong k-traceable oriented graphs. For each k>=2 there are infinitely many k-traceable oriented graphs-e.g. tournaments. However, we establish an upper bound (linear in k) on the order of k-traceable oriented graphs having a strong component with girth greater than 3. As an application of our findings, we show that the Path Partition Conjecture holds for 1-deficient oriented graphs having a strong component with girth at least 6. (A digraph is 1-deficient if its order is exactly one more than the order of its longest paths.) --- paper_title: Longest path partitions in generalizations of tournaments paper_content: We consider the so-called Path Partition Conjecture for digraphs which states that for every digraph, D, and every choice of positive integers, @l"1,@l"2, such that @l"1+@l"2 equals the order of a longest directed path in D, there exists a partition of D into two digraphs, D"1 and D"2, such that the order of a longest path in D"i is at most @l"i, for i=1,2. We prove that certain classes of digraphs, which are generalizations of tournaments, satisfy the Path Partition Conjecture and that some of the classes even satisfy the conjecture with equality. --- paper_title: Stable set meeting every longest path paper_content: Laborde, Payan and Xuong conjectured that every digraph has a stable set meeting every longest path. We prove that this conjecture holds for digraphs with stability number at most 2. --- paper_title: A Traceability Conjecture for Oriented Graphs paper_content: A (di)graph $G$ of order $n$ is $k$-traceable (for some $k$, $1\leq k\leq n$) if every induced sub(di)graph of $G$ of order $k$ is traceable. It follows from Dirac's degree condition for hamiltonicity that for $k\geq2$ every $k$-traceable graph of order at least $2k-1$ is hamiltonian. The same is true for strong oriented graphs when $k=2,3,4,$ but not when $k\geq5$. However, we conjecture that for $k\geq2$ every $k$-traceable oriented graph of order at least $2k-1$ is traceable. The truth of this conjecture would imply the truth of an important special case of the Path Partition Conjecture for Oriented Graphs. In this paper we show the conjecture is true for $k \leq 5$ and for certain classes of graphs. In addition we show that every strong $k$-traceable oriented graph of order at least $6k-20$ is traceable. We also characterize those graphs for which all walkable orientations are $k$-traceable. --- paper_title: Progress on the Traceability Conjecture for Oriented Graphs paper_content: A digraph is k -traceable if each of its induced subdigraphs of order k is traceable. The Traceability Conjecture is that for k ≥ 2 every k -traceable oriented graph of order at least 2k-1 is traceable. The conjecture has been proved for k ≤ 5 . We prove that it also holds for k=6 . --- paper_title: The Path Partition Conjecture is true for some generalizations of tournaments paper_content: Abstract The Path Partition Conjecture for digraphs states that for every digraph D , and every choice of positive integers λ 1 , λ 2 such that λ 1 + λ 2 equals the order of a longest directed path in D , there exists a partition of D in two subdigraphs D 1 , D 2 such that the order of the longest path in D i is at most λ i for i = 1 , 2 . We present sufficient conditions for a digraph to satisfy the Path Partition Conjecture. Using these results, we prove that strong path mergeable, arc-locally semicomplete, strong 3-quasi-transitive, strong arc-locally in-semicomplete and strong arc-locally out-semicomplete digraphs satisfy the Path Partition Conjecture. Some previous results are generalized. --- paper_title: Traceability of k-traceable oriented graphs paper_content: A digraph of order at least k is k-traceable if each of its subdigraphs of order k is traceable. We note that 2-traceable oriented graphs are tournaments and for k>=3, k-traceable oriented graphs can be regarded as generalized tournaments. We show that for [email protected][email protected]?6 every k-traceable oriented graph is traceable, thus extending the well-known fact that every tournament is traceable. This result does not extend to k=7. In fact, for every k>=7, except possibly for k=8 or 10, there exist k-traceable oriented graphs that are nontraceable. However, we show that for every k>=2 there exists a smallest integer t(k) such that every k-traceable oriented graph of order at least t(k) is traceable. ---	Title: A Survey of the Path Partition Conjecture Section 1: Introduction Description 1: Introduce the Path Partition Conjecture (PPC), its significance, history, and main objectives of the survey. Section 2: The PPC and the Lattice of Additive Hereditary Properties Description 2: Define key notations and terminologies used in the study, and discuss the relevance of additive hereditary properties to the PPC. Section 3: W_p-maximal Sets and P_p+2-kernels Description 3: Explore the concept of W_p-maximal sets and P_p+2-kernels, including related conjectures and theorems. Section 4: The PPC and Cycle Structure Description 4: Present the relationship between cycle structures in graphs and the PPC, including important results and corollaries. Section 5: The PPC Restricted to Special Classes of Graphs Description 5: Discuss the PPC’s validity for special classes of graphs such as claw-free graphs and planar graphs, including theorems and significant results. Section 6: The PPC for t-deficient Graphs Description 6: Investigate the PPC’s implications for t-deficient graphs, providing key theorems and asymptotic results. Section 7: Generalized Chromatic Numbers Description 7: Examine the connection between the PPC and generalized chromatic numbers, as well as related conjectures and bounds. Section 8: Directed and Oriented Analogues of the PPC Description 8: Briefly discuss the directed and oriented versions of the PPC and their challenges and results achieved thus far. Section 9: Conclusion Description 9: Summarize the main findings of the survey, the current state of the PPC, and potential directions for future research.
Image Registration: A Review of Elastic Registration Methods Applied to Medical Imaging	6	--- paper_title: Image Registration using Fractional Fourier Transform paper_content: This image registration (IR) is a fundamental task in many image processing applications such as medical diagnosis, satellite imaging, super-resolution image reconstruction etc. Fourier transform based methods have also been in use for IR purposes for both the shifted and rotated images using the phase correlation method (Brown, 1992). As fractional Fourier transform (FRFT) is a generalization of the conventional Fourier transform, it is natural to extend its use in IR applications. In this paper, the authors propose the use of the FRFT in IR problems involving either linear shifts or pure rotations in the given images to be registered. Simulation results of the proposed techniques are also presented --- paper_title: Intra-subject Elastic Registration of 3D Ultrasound Images paper_content: Abstract 3D registration of ultrasound images is an important and fast-growing research area with various medical applications, such as image-guided radiotherapy and surgery. However, this registration process remains extremely challenging due to the deformation of soft tissue and the existence of speckles in these images. This paper presents a technique for intra-subject, intra-modality elastic registration of 3D ultrasound images. Using the general concept of attribute vectors, we define the corresponding voxels in the fixed and moving images. Our method does not require presegmentation and does not employ any numerical optimization procedure. As the computational requirements are minimal, the method has potential use in real-time applications. The technique is implemented and tested on 3D ultrasound images of human liver, captured by a 3D ultrasound transducer. The results show that the method is sufficiently accurate and robust even in cases where artifacts such as shadows exist in the ultrasound data. --- paper_title: Nonrigid registration using free-form deformations: application to breast MR images paper_content: In this paper the authors present a new approach for the nonrigid registration of contrast-enhanced breast MRI. A hierarchical transformation model of the motion of the breast has been developed. The global motion of the breast is modeled by an affine transformation while the local breast motion is described by a free-form deformation (FFD) based on B-splines. Normalized mutual information is used as a voxel-based similarity measure which is insensitive to intensity changes as a result of the contrast enhancement. Registration is achieved by minimizing a cost function, which represents a combination of the cost associated with the smoothness of the transformation and the cost associated with the image similarity. The algorithm has been applied to the fully automated registration of three-dimensional (3-D) breast MRI in volunteers and patients. In particular, the authors have compared the results of the proposed nonrigid registration algorithm to those obtained using rigid and affine registration techniques. The results clearly indicate that the nonrigid registration algorithm is much better able to recover the motion and deformation of the breast than rigid or affine registration algorithms. --- paper_title: Segmentation of ultrasound images by using wavelet transform paper_content: This paper presents a new feature extraction method for the segmentation of ultrasound images. Wavelet transform is proposed for determination of the textures in the ultrasound images. Elements of the feature vectors are formed by the wavelet coefficients at several decomposition level. In this study, incremental self-organized neural network (INeN) is proposed as the classifier. The classification performance is increased by using the wavelet transform and the INeN together. --- paper_title: A review of cardiac image registration methods paper_content: In this paper, the current status of cardiac image registration methods is reviewed. The combination of information from multiple cardiac image modalities, such as magnetic resonance imaging, computed tomography, positron emission tomography, single-photon emission computed tomography, and ultrasound, is of increasing interest in the medical community for physiologic understanding and diagnostic purposes. Registration of cardiac images is a more complex problem than brain image registration because the heart is a nonrigid moving organ inside a moving body. Moreover, as compared to the registration of brain images, the heart exhibits much fewer accurate anatomical landmarks. In a clinical context, physicians often mentally integrate image information from different modalities. Automatic registration, based on computer programs, might, however, offer better accuracy and repeatability and save time. --- paper_title: Robust registration for computer-integrated orthopedic surgery: Laboratory validation and clinical experience paper_content: Abstract In order to provide navigational guidance during computer-integrated orthopedic surgery, the anatomy of the patient must first be registered to a medical image or model. A common registration approach is to digitize points from the surface of a bone and then find the rigid transformation that best matches the points to the model by constrained optimization. Many optimization criteria, including a least-squares objective function, perform poorly if the data include spurious data points (outliers). This paper describes a statistically robust, surface-based registration algorithm that we have developed for orthopedic surgery. To find an initial estimate, the user digitizes points from predefined regions of bone that are large enough to reliably locate even in the absence of anatomic landmarks. Outliers are automatically detected and managed by integrating a statistically robust M -estimator with the iterative-closest-point algorithm. Our in vitro validation method simulated the registration process by drawing registration data points from several sets of densely digitized surface points. The method has been used clinically in computer-integrated surgery for high tibial osteotomy, distal radius osteotomy, and excision of osteoid osteoma. --- paper_title: A fast image registration technique for motion artifact reduction in DSA paper_content: In digital subtraction angiography (DSA), patient motion is the primary cause of image quality degradation. The motion correction algorithms developed so far were not sufficiently fast so as to be suitable for integration in a clinical setting. In this paper we describe a new image registration technique for motion artifact reduction in DSA which is fully automatic, effective, and computationally very efficient. Using an image content driven control point selection mechanism and modern graphics hardware for image warping, the algorithm requires less than one second per DSA image (on average). Preliminary experiments on cerebral DSA images illustrate the applicability of the technique. --- paper_title: Image-processing technique for suppressing ribs in chest radiographs by means of massive training artificial neural network (MTANN) paper_content: When lung nodules overlap with ribs or clavicles in chest radiographs, it can be difficult for radiologists as well as computer-aided diagnostic (CAD) schemes to detect these nodules. In this paper, we developed an image-processing technique for suppressing the contrast of ribs and clavicles in chest radiographs by means of a multiresolution massive training artificial neural network (MTANN). An MTANN is a highly nonlinear filter that can be trained by use of input chest radiographs and the corresponding "teaching" images. We employed "bone" images obtained by use of a dual-energy subtraction technique as the teaching images. For effective suppression of ribs having various spatial frequencies, we developed a multiresolution MTANN consisting of multiresolution decomposition/composition techniques and three MTANNs for three different-resolution images. After training with input chest radiographs and the corresponding dual-energy bone images, the multiresolution MTANN was able to provide "bone-image-like" images which were similar to the teaching bone images. By subtracting the bone-image-like images from the corresponding chest radiographs, we were able to produce "soft-tissue-image-like" images where ribs and clavicles were substantially suppressed. We used a validation test database consisting of 118 chest radiographs with pulmonary nodules and an independent test database consisting of 136 digitized screen-film chest radiographs with 136 solitary pulmonary nodules collected from 14 medical institutions in this study. When our technique was applied to nontraining chest radiographs, ribs and clavicles in the chest radiographs were suppressed substantially, while the visibility of nodules and lung vessels was maintained. Thus, our image-processing technique for rib suppression by means of a multiresolution MTANN would be potentially useful for radiologists as well as for CAD schemes in detection of lung nodules on chest radiographs. --- paper_title: A Survey of Medical Image Registration paper_content: The purpose of this paper is to present a survey of recent (published in 1993 or later) publications concerning medical image registration techniques. These publications will be classified according to a model based on nine salient criteria, the main dichotomy of which is extrinsic versus intrinsic methods. The statistics of the classification show definite trends in the evolving registration techniques, which will be discussed. At this moment, the bulk of interesting intrinsic methods is based on either segmented points or surfaces, or on techniques endeavouring to use the full information content of the images involved. --- paper_title: Fast parametric elastic image registration paper_content: We present an algorithm for fast elastic multidimensional intensity-based image registration with a parametric model of the deformation. It is fully automatic in its default mode of operation. In the case of hard real-world problems, it is capable of accepting expert hints in the form of soft landmark constraints. Much fewer landmarks are needed and the results are far superior compared to pure landmark registration. Particular attention has been paid to the factors influencing the speed of this algorithm. The B-spline deformation model is shown to be computationally more efficient than other alternatives. The algorithm has been successfully used for several two-dimensional (2-D) and three-dimensional (3-D) registration tasks in the medical domain, involving MRI, SPECT, CT, and ultrasound image modalities. We also present experiments in a controlled environment, permitting an exact evaluation of the registration accuracy. Test deformations are generated automatically using a random hierarchical fractional wavelet-based generator. --- paper_title: A hierarchical approach to elastic registration based on mutual information paper_content: Abstract A hierarchical approach to elastic registration based on mutual information, in which the images are progressively subdivided, locally registered, and elastically interpolated, is presented. To improve the registration, a combination of prior and floating information on the joint probability is proposed. It is shown that such a combination increases the registration speed at the coarser levels in hierarchy, enables a registration of finer details, and provides additional guidance to the optimisation process. Besides, a threefold local registration consistency test and correction of shading were employed to increase the overall registration performance. The proposed hierarchical method for elastic registration was tested on an experimental database of 2D images of histochemically differently stained serial cross-sections of human skeletal muscle. The obtained results show that 95% of the images could be successfully registered. The inclusion of prior information is an important break through that may enable routine use of the mutual information cost function in a variety of 2D and 3D image registration algorithms in the future. --- paper_title: Elastic Medical Image Registration Based on Image Intensity paper_content: A two-step elastic medical image registration approach is proposed, which is based on the image intensity. In the first step, the global affine medical image registration is used to establish one-to-one mapping between the two images to be registered. After this first step, the images are registered up to small local elastic deformation. Then the mapped images are used as inputs in the second step, during which, the study image is modeled as elastic sheet by being divided into several subimages. Moving the individual subimage in the reference image, the local displacement vectors are found and the global elastic transformation is achieved by assimilating all of the local transformation into a continuous transformation. This algorithm has been tested on both simulated and tomographic images. --- paper_title: 3D Registration of Ultrasound Images Based on Morphology Skeleton paper_content: In order to eliminate displacement and elastic deformation between images of adjacent frames in course of 3D ultrasonic image reconstruction, elastic registration based on morphology skeleton was adopted in this paper. Feature points of connected skeleton are extracted automatically by accounting topical curvature extreme points several times. Initial registration is processed according to barycenter of skeleton. Whereafter, elastic registration based on radial basis function are processed according to feature points of skeleton. Result of example demonstrate that according to traditional rigid registration, elastic registration based on skeleton feature retain natural difference in shape for organ's different part, and eliminate slight elastic deformation between frames caused by image obtained process simultaneously. This algorithm has a high practical value for image registration in course of 3D ultrasound image reconstruction --- paper_title: Automatic hybrid registration for 2-dimensional CT abdominal images paper_content: Registration of abdominal images plays an important role in clinical practice, however, because of the complex deformations of organ structure and volume, abdominal image registration remains a challenge. In this paper, a hybrid registration approach is proposed, which consists of two procedures: intensity-based registration procedure and landmark-based registration procedure. In intensity-based registration, in order to speed up registration convergence and to improve registration computation efficiency, a wavelet-based hierarchical method is proposed, in which the global displacements are corrected using mutual information algorithm. In the landmark-based registration, firstly, the landmark points are selected automatically; and then, the local non-linear deformations are corrected using the elastically thin-plate splines. By combining the advantages of intensity-based registration method and that of landmark-based method, the proposed approach can register the images accurately and efficiently. The registration performance of the proposed algorithm is validated by experiments on clinical computed tomography (CT) abdominal images. --- paper_title: Medical image registration paper_content: Radiological images are increasingly being used in healthcare and medical research. There is, consequently, widespread interest in accurately relating information in the different images for diagnosis, treatment and basic science. This article reviews registration techniques used to solve this problem, and describes the wide variety of applications to which these techniques are applied. Applications of image registration include combining images of the same subject from different modalities, aligning temporal sequences of images to compensate for motion of the subject between scans, image guidance during interventions and aligning images from multiple subjects in cohort studies. Current registration algorithms can, in many cases, automatically register images that are related by a rigid body transformation (i.e. where tissue deformation can be ignored). There has also been substantial progress in non-rigid registration algorithms that can compensate for tissue deformation, or align images from different subjects. Nevertheless many registration problems remain unsolved, and this is likely to continue to be an active field of research in the future. --- paper_title: Evaluation of hierarchical elastic medical image registration method paper_content: The paper investigates the hierarchical approach to elastic medical image registration based on mutual information (MI) (Likar, B. and Pernus, F., Image and Vision Computing, vol.19, p.33-44, 2001), in which images are progressively subdivided, locally registered, and elastically interpolated using a thin-plate spline. The technique has been shown to be efficient and robust with small local transformations. However, problems do exist with this technique. First, MI is a statistical property of the two images, so the reduction in the number of samples due to the partitioning of the images into smaller sub-images reduces the statistical quality of the joint intensity histogram. Also, the partitioning scheme may lose some important information, such as edges, which lie exactly on the partition. The statistical problem of MI is resolved by resampling and combining with global MI. An overlapping scheme is implemented in which the image is subdivided into sub-images which overlap their neighbours. This helps to overcome the edge problems. Experiments show that these two methods can improve the registration results to some limited extent (PSNR) and the visual result is much better, especially for the overlapping window scheme. --- paper_title: Image registration using hierarchical B-splines paper_content: Hierarchical B-splines have been widely used for shape modeling since their discovery by Forsey and Bartels. We present an application of this concept, in the form of free-form deformation, to image registration by matching two images at increasing levels of detail. Results using MRI brain data are presented that demonstrate high degrees of matching while unnecessary distortions are avoided. We compare our results with the nonlinear ICP (iterative closest point) algorithm (used for landmark-based registration) and optical flow (used for intensity-based registration). --- paper_title: Image Registration using Fractional Fourier Transform paper_content: This image registration (IR) is a fundamental task in many image processing applications such as medical diagnosis, satellite imaging, super-resolution image reconstruction etc. Fourier transform based methods have also been in use for IR purposes for both the shifted and rotated images using the phase correlation method (Brown, 1992). As fractional Fourier transform (FRFT) is a generalization of the conventional Fourier transform, it is natural to extend its use in IR applications. In this paper, the authors propose the use of the FRFT in IR problems involving either linear shifts or pure rotations in the given images to be registered. Simulation results of the proposed techniques are also presented --- paper_title: Automatic hybrid registration for 2-dimensional CT abdominal images paper_content: Registration of abdominal images plays an important role in clinical practice, however, because of the complex deformations of organ structure and volume, abdominal image registration remains a challenge. In this paper, a hybrid registration approach is proposed, which consists of two procedures: intensity-based registration procedure and landmark-based registration procedure. In intensity-based registration, in order to speed up registration convergence and to improve registration computation efficiency, a wavelet-based hierarchical method is proposed, in which the global displacements are corrected using mutual information algorithm. In the landmark-based registration, firstly, the landmark points are selected automatically; and then, the local non-linear deformations are corrected using the elastically thin-plate splines. By combining the advantages of intensity-based registration method and that of landmark-based method, the proposed approach can register the images accurately and efficiently. The registration performance of the proposed algorithm is validated by experiments on clinical computed tomography (CT) abdominal images. --- paper_title: Elastic registration of 2D abdominal CT images using hybrid feature point selection for liver lesions paper_content: Abdominal CT images have distinct intensity distribution. This feature is used to correct local deformations in the image. Reference and study images are decomposed using wavelet decomposition. Global deformations are first corrected applying rigid registration by use of maximization of Mutual Information as the similarity measure at each level of registration hierarchy. Initially registered image and reference image are further elastically registered using landmark based elastic registration. Here landmarks or feature points are obtained by first intensity thresholding the images followed by boundary selection to obtain lesion boundaries and finally obtaining the centroid and convex hull points of lesions within the images. Convex hull points that lie on the boundary of lesions coupled with centroids of lesions are helpful in precisely identifying the lesions. An advantage of this is that lesions are enhanced to allow for deformations to be precisely determined. This is useful in improving diagnostic accuracy. The performance of algorithm is tested on a real case study of abdominal CT images with liver abscess. Considerable improvement in correlation coefficient and Signal to Noise ratio of the two images is observed. ---	Title: Image Registration: A Review of Elastic Registration Methods Applied to Medical Imaging Section 1: INTRODUCTION Description 1: Provide an overview of image registration, its objectives, and applications in various fields including medical imaging. Section 2: Image registration in medical imaging Description 2: Explore the historical growth, significance, and different applications of image registration in the field of medical imaging. Section 3: Rigid and Elastic registration Description 3: Discuss the differences between rigid and elastic registration, and their specific applications within medical imaging. Section 4: ELASTIC REGISTRATION APPLIED TO MEDICAL IMAGING Description 4: Examine various methods and approaches used for elastic registration in medical imaging, including specific cases and studies. Section 5: METHODOLOGY USED Description 5: Detail the methodology adopted for hybrid image registration, highlighting key processes such as initial registration, segmentation, and elastic registration. Section 6: EXPERIMENTAL RESULTS Description 6: Present the results obtained from the experimental implementation of the discussed methodologies.
Survey on Routing Protocols for Under Water Sensor Networks	9	--- paper_title: Silent Positioning in Underwater Acoustic Sensor Networks paper_content: In this paper, we present a silent positioning scheme termed UPS for underwater acoustic sensor networks. UPS relies on the time difference of arrivals locally measured at a sensor to detect range differences from the sensor to four anchor nodes. These range differences are averaged over multiple beacon intervals before they are combined to estimate the 3-D sensor location through trilateration. UPS requires no time synchronization and provides location privacy at underwater vehicles/sensors whose locations need to be determined. To study the performance of UPS, we model the underwater acoustic channel as a modified ultrawideband Saleh-Valenzuela model: The arrival of each path cluster and the paths within each cluster follow double Poisson distributions, and the multipath channel gain follows a Rician distribution. Based on this channel model, we perform both theoretical analysis and simulation study on the position error of UPS under acoustic fading channels. The obtained results indicate that UPS is an effective scheme for underwater vehicle/sensor self-positioning. --- paper_title: DFR: Directional flooding-based routing protocol for underwater sensor networks paper_content: Unlike terrestrial sensor networks, underwater sensor networks (UWSNs) have different characteristics such as a long propagation delay, a narrow bandwidth and high packet loss. Hence, existing path setup-based routing protocols proposed for terrestrial sensor networks are not applicable in the underwater environment. For example, they take much time when establishing a path between source and destination nodes due to the long propagation delay. In addition, the path establishment requires much overhead of control messages. Moreover, the dynamic and high packet loss degrades reliability, which invokes more retransmissions. Even though exiting routing protocols such as VBF were proposed to improve the reliability, they did not take into account the link quality. That is, there is no guarantee that packets reach the sink safely especially when a link is error-prone. In this paper, we therefore propose a directional flooding-based routing protocol, called DFR. Basically, DFR relies on a packet flooding technique to increase the reliability. However, the number of nodes which flood a packet is controlled in order to prevent a packet from flooding over the whole network and the nodes to forward the packet are decided according to the link quality. In addition, DFR also addresses a well-known void problem by allowing at least one node to participate in forwarding a packet. Our simulation study using ns-2 proves that DFR is more suitable for UWSNs especially when links are prone to packet loss. --- paper_title: Improving the Robustness of Location-Based Routing for Underwater Sensor Networks paper_content: This paper investigates a fundamental networking problem in underwater sensor networks: robust and energy-efficient routing. We present an adaptive location-based routing protocol, called hop-by-hop vector-based forwarding (HH-VBF). It uses the notion of a "routing vector" (a vector from the source to the sink) acting as the axis of the "routing pipe", similar to the vector based forward (VBF) routing in the work of P. Xie, J.-H. Cui and L. Lao (VBF: Vector-Based Forwarding Protocol for Underwater Sensor Networks. Technical report, UCONN CSE Technical Report: UbiNet-TR05-03 (BECAT/CSE-TR-05-6), Feb. 2005). Unlike the original VBF approach, however, HH-VBF suggests the use of a routing vector for each individual forwarder in the network, instead of a single network-wide source-to-sink routing vector. By the creation of the hop-by-hop vectors, HH-VBF can overcome two major problems in VBF: (1) too small data delivery ratio for sparse networks; (2) too sensitive to "routing pipe" radius threshold. We conduct simulations to evaluate HH-VBF, and the results show that HH-VBF yields much better performance than VBF in sparse networks. In addition, HH-VBF is less sensitive to the routing pipe radius threshold. Furthermore, we also analyze the behavior of HH-VBF and show that assuming proper redundancy and feedback techniques, HH-VBF can facilitate the avoidance of any "void" areas in the network. --- paper_title: REBAR: A Reliable and Energy Balanced Routing Algorithm for UWSNs paper_content: In this paper, we propose a reliable and energy-efficient routing algorithm for underwater wireless sensor networks (UWSNs). We first use a sphere energy depletion model to analyze the energy consumption of nodes in UWSNs. We then extend the model by considering the node mobility in UWSNs. Our analysis is in accordance with the common view that although water flows might cause the underwater environment more dynamic, this instability can actually improve energy-efficiency. However, the nodes closer to the sink still tend to die early, causing network partition around the sink. Accordingly, we propose a Reliable and Energy BAlanced Routing algorithm (REBAR). We explore the tradeoff between packet delivery ratio and energy efficiency. We design an adaptive scheme for setting data propagation range in order to balance the energy consumption throughout the network. Multi-path routing is used to provide redundancy. We further extend REBAR to deal with possible routing voids in the network which could be common in UWSNs. Simulation results show that our protocol outperforms existing VBF-based approaches in terms of reliability and network lifetime. --- paper_title: Sector-Based Routing with Destination Location Prediction for Underwater Mobile Networks paper_content: Unlike in terrestrial sensor networks where the locations of destination nodes are often assumed to be fixed and accurately known, such assumptions are usually not valid in underwater sensor networks where the destination nodes tend to be mobile inherently, either due to their self-propelling capability, or due to random motion caused by ocean currents. As a result, many existing location-based routing protocols do not work well in underwater environments. We propose a location-based routing protocol that is designed for mobile underwater acoustic sensor networks, called "Sector-based Routing with Destination Location Prediction (SBR-DLP)". While the SBR-DLP also assumes that a node knows its own location like many other location-based routing protocols, it predicts the location of the destination node, and therefore, relaxes the need for precise knowledge of the destination's location. Through simulations, the SBR-DLP is shown to enhance the packet delivery ratio significantly when all nodes are mobile. ---	Title: Survey on Routing Protocols for Under Water Sensor Networks Section 1: Introduction Description 1: Introduce underwater sensor networks (UWSNs), mention differences compared to terrestrial sensor networks, including energy consumption, node cost, deployment, power requirements, and mediums of communication. Discuss the challenges of routing in UWSNs and why specialized protocols are needed. Section 2: Vector Based Forwarding (VBF) Description 2: Describe the VBF protocol, which handles packet losses and node failures through redundant and interleaved paths, and emphasize its scalability and energy-saving characteristics. Section 3: Hop by Hop Vector Based Forwarding (HH-VBF) Description 3: Explain the HH-VBF protocol, focusing on its use of virtual pipes for per-hop forwarding, and the computations made by nodes to forward packets based on their location. Section 4: Focused Beam Routing (FBR) Description 4: Detail the FBR protocol, highlighting its prevention of unnecessary broadcast flooding, suitability for both static and mobile nodes, and location-awareness requirements for source and destination nodes. Section 5: Reliable and Energy Balanced Routing Algorithm (REBAR) Description 5: Cover the REBAR protocol, a location-based method that uses geographic information for data transfer, defines nodes by unique IDs, and utilizes specific assumptions about node locations and data transfer rates. Section 6: Sector-based Routing with Destination Location Prediction (SBR-DLP) Description 6: Describe the SBR-DLP protocol, which avoids data packet flooding by predicting and utilizing destination mobility information, and selecting the next hop using candidate nodes within a communication circle. Section 7: Direction Flooding Based Routing (DFR) Description 7: Discuss the DFR protocol, which enhances reliability through packet flooding, and requires nodes to know their location, one-hop neighbor locations, and the final destination. Section 8: Location Aware Source Routing (LASR) Description 8: Explain the LASR protocol, which uses link quality metrics and location awareness to handle high latency of acoustic channels, and includes all relevant network information in the protocol header. Section 9: Conclusion Description 9: Summarize the surveyed UWSN routing protocols and their comparative aspects, emphasizing energy efficiency and dynamic network handling abilities. Point out which protocols are best suited for specific applications based on the comparisons.
A Succinct Overview of Virtual Reality Technology Use in Alzheimer’s Disease	12	--- paper_title: Virtual Immersion for Post-Stroke Hand Rehabilitation Therapy paper_content: Stroke is the leading cause of serious, long-term disability in the United States. Impairment of upper extremity function is a common outcome following stroke, often to the detriment of lifestyle and employment opportunities. While the upper extremity is a natural target for therapy, treatment may be hampered by limitations in baseline capability as lack of success may discourage arm and hand use. We developeda virtual reality (VR) system in order to encourage repetitive task practice. This system combined an assistive glove with a novel VR environment. A set of exercises for this system was developed to encourage specific movements. Six stroke survivors with chronic upper extremity hemiparesis volunteered to participate in a pilot study in which they completed 18 one-hour training sessions with the VR system. Performance with the system was recorded across the 18 training sessions. Clinical evaluations of motor control were conducted at three time points: prior to initiation of training, following the end of training, and 1 month later. Subjects displayed significant improvement on performance of the virtual tasks over the course of the training, although for the clinical outcome measures only lateral pinch showed significant improvement. Future expansion to multi-user virtual environments may extend the benefits of this system for stroke survivors with hemiparesis by furthering engagement in the rehabilitation exercises. --- paper_title: Effects of Virtual Reality Simulator Training Method and Observational Learning on Surgical Performance paper_content: Background ::: Virtual reality (VR) simulators and Web-based instructional videos are valuable supplemental training resources in surgical programs, but it is unclear how to optimally integrate them into minimally invasive surgical training. --- paper_title: Nu!RehaVR: virtual reality in neuro tele-rehabilitation of patients with traumatic brain injury and stroke paper_content: The availability of virtual environments on the Web is fostering new applications of virtual reality in several fields, including some therapeutical applications. We present an application of virtual reality applied to the tele-rehabilitation of patients with traumatic brain injury and stroke. Our system, based on X3D and Ajax3D technologies, enhances the possibility of making tele-rehabilitation exercises aimed at the recovery of the neurological disease. The system, called Nu!RehaVR, has been designed to integrate the activity carried out on a tele-rehabilitation system, Nu!Reha (Nu!Reha is a trademark of Pragma Engineering srl. See http://www.nureha.eu) desk, with the activities performed in the virtual worlds, through some rehabilitation exercises in contexts incompatible with the patients’ impairments (not able to move or forced in static positions because of therapies, etc.). The architecture of Nu!RehaVR and the environments associated to two exercises, “Utilising an elevator to reach a given floor” and “Crossing a road using a traffic light”, are illustrated. These exercises can be considered as prototypes of a series of tele-rehabilitation exercises which help to stimulate the patients performing actions in relatively dangerous scenarios. The system is designed to allow the remote monitoring and assessment of the patient’s activities by the medical staff at the hospital using the communication facilities of the tele-rehabilitation system. --- paper_title: Virtual Reality Therapy for Adults Post-Stroke: A Systematic Review and Meta-Analysis Exploring Virtual Environments and Commercial Games in Therapy paper_content: BACKGROUND ::: The objective of this analysis was to systematically review the evidence for virtual reality (VR) therapy in an adult post-stroke population in both custom built virtual environments (VE) and commercially available gaming systems (CG). ::: ::: ::: METHODS ::: MEDLINE, CINAHL, EMBASE, ERIC, PSYCInfo, DARE, PEDro, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews were systematically searched from the earliest available date until April 4, 2013. Controlled trials that compared VR to conventional therapy were included. Population criteria included adults (>18) post-stroke, excluding children, cerebral palsy, and other neurological disorders. Included studies were reported in English. Quality of studies was assessed with the Physiotherapy Evidence Database Scale (PEDro). ::: ::: ::: RESULTS ::: Twenty-six studies met the inclusion criteria. For body function outcomes, there was a significant benefit of VR therapy compared to conventional therapy controls, G = 0.48, 95% CI = [0.27, 0.70], and no significant difference between VE and CG interventions (P = 0.38). For activity outcomes, there was a significant benefit of VR therapy, G = 0.58, 95% CI = [0.32, 0.85], and no significant difference between VE and CG interventions (P = 0.66). For participation outcomes, the overall effect size was G = 0.56, 95% CI = [0.02, 1.10]. All participation outcomes came from VE studies. ::: ::: ::: DISCUSSION ::: VR rehabilitation moderately improves outcomes compared to conventional therapy in adults post-stroke. Current CG interventions have been too few and too small to assess potential benefits of CG. Future research in this area should aim to clearly define conventional therapy, report on participation measures, consider motivational components of therapy, and investigate commercially available systems in larger RCTs. ::: ::: ::: TRIAL REGISTRATION ::: Prospero CRD42013004338. --- paper_title: A meta-analysis of the training effectiveness of virtual reality surgical simulators paper_content: The increasing use of virtual reality (VR) simulators in surgical training makes it imperative that definitive studies be performed to assess their training effectiveness. Indeed, in this paper we report the meta-analysis of the efficacy of virtual reality simulators in: 1) the transference of skills from the simulator training environment to the operating room, and 2) their ability to discriminate between the experience levels of their users. The task completion time and the error score were the two study outcomes collated and analyzed in this meta-analysis. Sixteen studies were identified from a computer-based literature search (1996-2004). The meta-analysis of the random effects model (because of the heterogeneity of the data) revealed that training on virtual reality simulators did lessen the time taken to complete a given surgical task as well as clearly differentiate between the experienced and the novice trainees. Meta-analytic studies such as the one reported here would be very helpful in the planning and setting up of surgical training programs and for the establishment of reference `learning curves' for a specific simulator and surgical task. If any such programs already exist, they can then indicate the improvements to be made in the simulator used, such as providing for more variety in their case scenarios based on the state and/or rate of learning of the trainee --- paper_title: Modulation of cortical activity in 2D versus 3D virtual reality environments: An EEG study paper_content: Abstract There is a growing empirical evidence that virtual reality (VR) is valuable for education, training, entertaining and medical rehabilitation due to its capacity to represent real-life events and situations. However, the neural mechanisms underlying behavioral confounds in VR environments are still poorly understood. In two experiments, we examined the effect of fully immersive 3D stereoscopic presentations and less immersive 2D VR environments on brain functions and behavioral outcomes. In Experiment 1 we examined behavioral and neural underpinnings of spatial navigation tasks using electroencephalography (EEG). In Experiment 2, we examined EEG correlates of postural stability and balance. Our major findings showed that fully immersive 3D VR induced a higher subjective sense of presence along with enhanced success rate of spatial navigation compared to 2D. In Experiment 1 power of frontal midline EEG (FM-theta) was significantly higher during the encoding phase of route presentation in the 3D VR. In Experiment 2, the 3D VR resulted in greater postural instability and modulation of EEG patterns as a function of 3D versus 2D environments. The findings support the inference that the fully immersive 3D enriched-environment requires allocation of more brain and sensory resources for cognitive/motor control during both tasks than 2D presentations. This is further evidence that 3D VR tasks using EEG may be a promising approach for performance enhancement and potential applications in clinical/rehabilitation settings. --- paper_title: Egocentric and allocentric memory as assessed by virtual reality in individuals with amnestic mild cognitive impairment paper_content: Abstract Present evidence suggests that medial temporal cortices subserve allocentric representation and memory, whereas egocentric representation and memory also depends on parietal association cortices and the striatum. Virtual reality environments have a major advantage for the assessment of spatial navigation and memory formation, as computer-simulated first-person environments can simulate navigation in a large-scale space. Twenty-nine patients with amnestic MCI (aMCI) were compared with 29 healthy matched controls on two virtual reality tasks affording to learn a virtual park (allocentric memory) and a virtual maze (egocentric memory). Participants further received a neuropsychological investigation and MRI volumetry at the time of the assessment. Results indicate that aMCI patients had significantly reduced size of the hippocampus bilaterally and the right-sided precuneus and inferior parietal cortex. aMCI patients were severely impaired learning the virtual park and the virtual maze. Smaller volumes of the right-sided precuneus were related to worse performance on the virtual maze. Participants with striatal lacunar lesions committed more errors than participants without such lesions on the virtual maze but not on the virtual park. aMCI patients later converting to dementia (n = 15) had significantly smaller hippocampal size when compared with non-converters (n = 14). However, both groups did not differ on virtual reality task performance. Our study clearly demonstrates the feasibility of virtual reality technology to study spatial memory deficits of persons with aMCI. Future studies should try to design spatial virtual reality tasks being specific enough to predict conversion from MCI to dementia and conversion from normal to MCI. --- paper_title: Health and safety implications of virtual reality : A review of empirical evidence paper_content: For the last 10 years a number of papers have been written that discuss human factors issues associated with virtual reality (VR). The nature of these papers has gradually evolved from speculation and anecdotal report to empirical research. Despite developments in VR technology, some participants still experience health and safety problems associated with VR use-termed VR-induced symptoms and effects (VRISE). The key concern from the literature is VR-induced sickness, experienced by a large proportion of VR participants, but for the majority these effects are mild and subside quickly. This paper makes a number of recommendations regarding the future direction of research into health and safety implications of VR, including the need to take into account the way in which VR is being used when conducting empirical research: first, to ensure that studies consider both effects and their consequences; second, to ensure that empirical trials reflect the actual likely context of VR use; third, to consider interactions between effects; and finally, to consider ways in which effects can be managed. --- paper_title: Virtual Reality Rehabilitation from Social Cognitive and Motor Learning Theoretical Perspectives in Stroke Population paper_content: Objectives. To identify the virtual reality (VR) interventions used for the lower extremity rehabilitation in stroke population and to explain their underlying training mechanisms using Social Cognitive (SCT) and Motor Learning (MLT) theoretical frameworks. Methods. Medline, Embase, Cinahl, and Cochrane databases were searched up to July 11, 2013. Randomized controlled trials that included a VR intervention for lower extremity rehabilitation in stroke population were included. The Physiotherapy Evidence Database (PEDro) scale was used to assess the quality of the included studies. The underlying training mechanisms involved in each VR intervention were explained according to the principles of SCT (vicarious learning, performance accomplishment, and verbal persuasion) and MLT (focus of attention, order and predictability of practice, augmented feedback, and feedback fading). Results. Eleven studies were included. PEDro scores varied from 3 to 7/10. All studies but one showed significant improvement in outcomes in favour of the VR group (P < 0.05). Ten VR interventions followed the principle of performance accomplishment. All the eleven VR interventions directed subject's attention externally, whereas nine provided training in an unpredictable and variable fashion. Conclusions. The results of this review suggest that VR applications used for lower extremity rehabilitation in stroke population predominantly mediate learning through providing a task-oriented and graduated learning under a variable and unpredictable practice. --- paper_title: Virtual reality induced symptoms and effects (VRISE) : Comparison of head mounted display (HMD), desktop and projection display systems paper_content: Abstract Virtual reality (VR) systems are used in a variety of applications within industry, education, public and domestic settings. Research assessing reported symptoms and side effects of using VR systems indicates that these factors combine to influence user experiences of virtual reality induced symptoms and effects (VRISE). Three experiments were conducted to assess prevalence and severity of sickness symptoms experienced in each of four VR display conditions; head mounted display (HMD), desktop, projection screen and reality theatre, with controlled examination of two additional aspects of viewing (active vs. passive viewing and light vs. dark conditions). Results indicate 60–70% participants experience an increase in symptoms pre–post exposure for HMD, projection screen and reality theatre viewing and found higher reported symptoms in HMD compared with desktop viewing (nausea symptoms) and in HMD compared with reality theatre viewing (nausea, oculomotor and disorientation symptoms). No effect of lighting condition was found. Higher levels of symptoms were reported in passive viewing compared to active control over movement in the VE. However, the most notable finding was that of high inter- and intra-participant variability. As this supports other findings of individual susceptibility to VRISE, recommendations are offered concerning design and use of VR systems in order to minimise VRISE. --- paper_title: Virtual Reality as Assessment Tool in Psychology paper_content: Virtual environments (VEs), offering a new human-computer interaction paradigm, have attracted much attention in clinical psychology, especially in the treatment of phobias. However, a possible new application of VR in psychology is as assessment tool: VEs can be considered as an highly sophisticated form of adaptive testing. This chapter describes the context of current psychological assessment and underlines possible advantages of a VR based assessment tool. The chapter also details the characteristics of BIVRS, Body Image Virtual Reality Scale, an assessment tool designed to assess cognitive and affective components of body image. It consists of a non-immersive 3D graphical interface through which the patient is able to choose between 9 figures of different size which vary in size from underweight to overweight. The software was developed in two architectures, the first (A) running on a single user desktop computer equipped with a standard virtual reality development software and the second (B) splitted into a server (B1) accessible via Internet and actually running the same virtual ambient as in (A) and a VRML client (B2) so that anyone can access the application. --- paper_title: Mild cognitive impairment and deficits in instrumental activities of daily living: a systematic review paper_content: IntroductionThere is a growing body of evidence that subtle deficits in instrumental activities of daily living (IADL) may be present in mild cognitive impairment (MCI). However, it is not clear if there are IADL domains that are consistently affected across patients with MCI. In this systematic review, therefore, we aimed to summarize research results regarding the performance of MCI patients in specific IADL (sub)domains compared with persons who are cognitively normal and/or patients with dementia.MethodsThe databases PsycINFO, PubMed and Web of Science were searched for relevant literature in December 2013. Publications from 1999 onward were considered for inclusion. Altogether, 497 articles were retrieved. Reference lists of selected articles were searched for potentially relevant articles. After screening the abstracts of these 497 articles, 37 articles were included in this review.ResultsIn 35 studies, IADL deficits (such as problems with medication intake, telephone use, keeping appointments, finding things at home and using everyday technology) were documented in patients with MCI. Financial capacity in patients with MCI was affected in the majority of studies. Effect sizes for group differences between patients with MCI and healthy controls were predominantly moderate to large. Performance-based instruments showed slight advantages (in terms of effect sizes) in detecting group differences in IADL functioning between patients with MCI, patients with Alzheimer’s disease and healthy controls.ConclusionIADL requiring higher neuropsychological functioning seem to be most severely affected in patients with MCI. A reliable identification of such deficits is necessary, as patients with MCI with IADL deficits seem to have a higher risk of converting to dementia than patients with MCI without IADL deficits. The use of assessment tools specifically designed and validated for patients with MCI is therefore strongly recommended. Furthermore, the development of performance-based assessment instruments should be intensified, as they allow a valid and reliable assessment of subtle IADL deficits in MCI, even if a proxy is not available. Another important point to consider when designing new scales is the inclusion of technology-associated IADL. Novel instruments for clinical practice should be time-efficient and easy to administer. --- paper_title: Virtual reality exposure therapy for the treatment of anxiety disorders: An evaluation of research quality paper_content: Abstract Randomized controlled trials (RCTs) support the effectiveness of virtual reality exposure therapy (VRET) for anxiety disorders; however, the overall quality of the VRET RCT literature base has yet to be evaluated. This study reviewed 27 VRET RCTs and the degree of adherence to 8 RCT research design criteria derived from existing standards. Adherence to the study quality criteria was generally low as the articles met an average 2.85 criteria (SD = 1.56). None of the studies met more than six quality criteria. Study quality did not predict effect size; however, a reduction in effect size magnitude was observed for studies with larger sample sizes when comparing VRET to non-active control groups. VRET may be an effective method of treatment but caution should be exercised in interpreting the existing body of literature supporting VRET relative to existing standards of care. The need for well-designed VRET research is discussed. --- paper_title: Virtual reality in mental health : a review of the literature. paper_content: BACKGROUND ::: Several virtual reality (VR) applications for the understanding, assessment and treatment of mental health problems have been developed in the last 10 years. The purpose of this review is to outline the current state of virtual reality research in the treatment of mental health problems. ::: ::: ::: METHODS ::: PubMed and PsycINFO were searched for all articles containing the words "virtual reality". In addition a manual search of the references contained in the papers resulting from this search was conducted and relevant periodicals were searched. Studies reporting the results of treatment utilizing VR in the mental health field and involving at least one patient were identified. ::: ::: ::: RESULTS ::: More than 50 studies using VR were identified, the majority of which were case studies. Seventeen employed a between groups design: 4 involved patients with fear of flying; 3 involved patients with fear of heights; 3 involved patients with social phobia/public speaking anxiety; 2 involved people with spider phobia; 2 involved patients with agoraphobia; 2 involved patients with body image disturbance and 1 involved obese patients. There are both advantages in terms of delivery and disadvantages in terms of side effects to using VR. Although virtual reality based therapy appears to be superior to no treatment the effectiveness of VR therapy over traditional therapeutic approaches is not supported by the research currently available. ::: ::: ::: CONCLUSIONS ::: There is a lack of good quality research on the effectiveness of VR therapy. Before clinicians will be able to make effective use of this emerging technology greater emphasis must be placed on controlled trials with clinically identified populations. --- paper_title: Using Virtual Reality for Cognitive Training of the Elderly paper_content: There is a pressing demand for improving the quality and efficacy of health care and social support services needed by the world’s growing elderly population, especially by those affected by mild cognitive impairment (MCI) and Alzheimer’s disease (AD)-type early-stage dementia. Meeting that demand can significantly benefit from the deployment of innovative, computer-based applications capable of addressing specific needs, particularly in the area of cognitive impairment mitigation and rehabilitation. In that context, we present here our perspective viewpoint on the use of virtual reality (VR) tools for cognitive rehabilitation training, intended to assist medical personnel, health care workers, and other caregivers in improving the quality of daily life activities of people with MCI and AD. We discuss some effective design criteria and developmental strategies and suggest some possibly useful protocols and procedures. The particular innovative supportive advantages offered by the immersive interactive cha... --- paper_title: How do people with persecutory delusions evaluate threat in a controlled social environment? A qualitative study using virtual reality. paper_content: 20 participants with persecutory delusions and 20 controls entereda virtual underground train containing neutral characters. Under these circumstances, peoplewith persecutory delusions reported similar levels of paranoia as non-clinical participants.The transcripts of a post-virtual reality interview of the ﬁrst 10 participants in each groupwere analysed. --- paper_title: Virtual reality in neuroscience research and therapy paper_content: The compatibility of virtual reality systems with brain imaging techniques and their use for animal research have aided the widespread adoption of virtual reality environments in both experimental and therapeutic domains. Here the authors review advances in virtual reality technology and its applications. --- paper_title: Virtual Reality in Psychotherapy: Review paper_content: Virtual reality (VR) has recently emerged as a potentially effective way to provide general and specialty health care services, and appears poised to enter mainstream psychotherapy delivery. Because VR could be part of the future of clinical psychology, it is critical to all psychotherapists that it be defined broadly. To ensure appropriate development of VR applications, clinicians must have a clear understanding of the opportunities and challenges it will provide in professional practice. This review outlines the current state of clinical research relevant to the development of virtual environments for use in psychotherapy. In particular, the paper focuses its analysis on both actual applications of VR in clinical psychology and how different clinical perspectives can use this approach to improve the process of therapeutic change. --- paper_title: Perspective taking abilities in amnestic mild cognitive impairment and Alzheimer's disease paper_content: Abstract Perspective taking is the ability to imagine what a scene looks like from a different viewpoint, which has been reported to be impaired in Alzheimer's disease (AD). This study compared overhead and first-person view perspective taking abilities in patients with mild cognitive impairment (MCI) and AD. A newly developed Arena Perspective Taking Task (APTT), using an environment of a circular arena, was used to compare 23 AD patients and 38 amnestic MCI patients with 18 healthy controls. The results were contrasted with a published perspective taking test (Standardized Road-Map Test of Direction Sense, RMTDS). The AD group was impaired in both overhead and first-person view APTT versions, but the impairment in the overhead view version applied specifically to women. Patients with aMCI were impaired in the first-person view but not in the overhead view version. Substantial sexual differences were found in the overhead but not in the first-person view APTT version. The RMTDS resembled both APTT versions: patients with aMCI were impaired in this test and also women in both patient groups were less accurate than men. Using the receiver operating characteristic analysis, the highest predictive power for MCI and AD patients diagnosis versus controls was observed for their success rate in the first-person view version. The results suggest distinction between overhead and first-person view perspective taking in the impairment of aMCI patients and the sex differences. The first-person view perspective taking is a potentially important candidate psychological marker for AD. --- paper_title: Vection and visually induced motion sickness: how are they related? paper_content: The occurrence of visually induced motion sickness has been frequently linked to the sensation of illusory self-motion (so-called vection), however, the precise nature of this relationship is still not fully understood. To date, it is still a matter of debate whether or not vection is a necessary prerequisite for visually induced motion sickness (VIMS). That is, can there be visually induced motion sickness without any sensation of self-motion? In this paper, we will describe the possible nature of this relationship, review the literature that may speak to this relationship (including theoretical accounts of vection and VIMS), and offer suggestions with respect to operationally defining and reporting these phenomena in future. --- paper_title: Virtual Reality and Serious Games in Healthcare paper_content: This chapter discusses the applications and solutions of emerging Virtual Reality (VR) and video games technologies in the healthcare sector, e.g. physical therapy for motor rehabilitation, exposure therapy for psychological phobias, and pain relief. Section 2 reviews state-of-the-art interactive devices used in current VR systems and high-end games such as sensor-based and camera-based tracking devices, data gloves, and haptic force feedback devices. Section 3 investigates recent advances and key concepts in games technology, including dynamic simulation, flow theory, adaptive games, and their possible implementation in serious games for healthcare. Various serious games are described in this section: some were designed and developed for specific healthcare purposes, e.g. BreakAway (2009)’s Free Dive, HopeLab (2006)’s Re-Mission, and Ma et al. (2007)’s VR game series, others were utilising off-the-shelf games such as Nintendo Wii sports for physiotherapy. A couple of experiments of using VR systems and games for stroke rehabilitation are highlighted in section 4 as examples to showcase the benefits and impacts of these technologies to conventional clinic practice. Finally, section 5 points some future directions of applying emerging games technologies in healthcare, such as augmented reality, Wii-mote motion control system, and even full body motion capture and controller free games technology demonstrated recently on E3 2009 which have great potentials to treat motor disorders, combat obesity, and other healthcare applications. --- paper_title: Moving from Virtual Reality Exposure-Based Therapy to Augmented Reality Exposure-Based Therapy: A Review paper_content: This paper reviews the move from virtual reality exposure-based therapy (VRET) to augmented reality exposure-based therapy (ARET). Unlike virtual reality (VR), which entails a complete virtual environment (VE), augmented reality (AR) limits itself to producing certain virtual elements to then merge them into the view of the physical world. Although the general public may only have become aware of AR in the last few years, AR type applications have been around since beginning of the 20th century. Since, then, technological developments have enabled an ever increasing level of seamless integration of virtual and physical elements into one view. Like VR, AR allows the exposure to stimuli which, due to various reasons, may not be suitable for real-life scenarios. As such, AR has proven itself to be a medium through which individuals suffering from specific phobia can be exposed “safely” to the object(s) of their fear, without the costs associated with programming complete virtual environments. Thus, ARET can offer an efficacious alternative to some less advantageous exposure-based therapies. Above and beyond presenting what has been accomplished in ARET, this paper also raises some ARET related issues, and proposes potential avenues to be followed. These include the definition of an AR related term, the type of measures to be used to qualify the user’s experience in an augmented reality environment (ARE), the development of alternative geospatial referencing systems, as well as the potential use of ARET to treat social phobia. Overall, it may be said that the use of ARET, although promising, is still in its infancy but that, given a continued cooperation between clinical and technical teams, ARET has the potential of going well beyond the treatment of small animal phobia. --- paper_title: Controlling Social Stress in Virtual Reality Environments paper_content: Virtual reality exposure therapy has been proposed as a viable alternative in the treatment of anxiety disorders, including social anxiety disorder. Therapists could benefit from extensive control of anxiety eliciting stimuli during virtual exposure. Two stimuli controls are studied in this study: the social dialogue situation, and the dialogue feedback responses (negative or positive) between a human and a virtual character. In the first study, 16 participants were exposed in three virtual reality scenarios: a neutral virtual world, blind date scenario, and job interview scenario. Results showed a significant difference between the three virtual scenarios in the level of self-reported anxiety and heart rate. In the second study, 24 participants were exposed to a job interview scenario in a virtual environment where the ratio between negative and positive dialogue feedback responses of a virtual character was systematically varied on-the-fly. Results yielded that within a dialogue the more positive dialogue feedback resulted in less self-reported anxiety, lower heart rate, and longer answers, while more negative dialogue feedback of the virtual character resulted in the opposite. The correlations between on the one hand the dialogue stressor ratio and on the other hand the means of SUD score, heart rate and audio length in the eight dialogue conditions showed a strong relationship: r(6)?=?0.91, p?=?0.002; r(6)?=?0.76, p?=?0.028 and r(6)?=?-0.94, p?=?0.001 respectively. Furthermore, more anticipatory anxiety reported before exposure was found to coincide with more self-reported anxiety, and shorter answers during the virtual exposure. These results demonstrate that social dialogues in a virtual environment can be effectively manipulated for therapeutic purposes. --- paper_title: How we experience immersive virtual environments: the concept of presence and its measurement * paper_content: This paper reviews the concept of presence in immersive virtual environments, the sense of being there signalled by people acting and responding realistically to virtual situations and events. We argue that presence is a unique phenomenon that must be distinguished from the degree of engagement, involvement in the portrayed environment. We argue that there are three necessary conditions for presence: the (a) consistent low latency sensorimotor loop between sensory data and proprioception; (b) statistical plausibility: images must be statistically plausible in relation to the probability distribution of images over natural scenes. A constraint on this plausibility is the level of immersion; (c) behaviour-response correlations: Presence may be enhanced and maintained over time by appropriate correlations between the state and behaviour of participants and responses within the environment, correlations that show appropriate responses to the activity of the participants. We conclude with a discussion of methods for assessing whether presence occurs, and in particular recommend the approach of comparison with ground truth and give some examples of this. --- paper_title: Sense of Presence and Metacognition Enhancement in Virtual Reality Exposure Therapy in the Treatment of Social Phobias and the Fear of Flying paper_content: The aim of this research effort is to identify feeling-of-presence and metacognitive amplifiers over existing well-established VRET treatment methods. Patient real time projection in virtual environments during stimuli exposure and electroencephalographyi¾?EEG report sharing are among the techniques, which have been used to achieve the desired result. Initialized from theoretical inferences, is moving towards a proof-of-concept prototype, which has been developed as a realization of the proposed method. The evaluation of the prototype made possible with an expert team of 28 therapists testing the fear of public speaking and fear of flying case studies. --- paper_title: A Dual-Modal Virtual Reality Kitchen for (Re)Learning of Everyday Cooking Activities in Alzheimer's Disease paper_content: Everyday action impairment is one of the diagnostic criteria of Alzheimer's disease and is associated with many serious consequences, including loss of functional autonomy and independence. It has been shown that the (re)learning of everyday activities is possible in Alzheimer's disease by using error reduction teaching approaches in naturalistic clinical settings. The purpose of this study is to develop a dual-modal virtual reality platform for training in everyday cooking activities in Alzheimer's disease and to establish its value as a training tool for everyday activities in these patients. Two everyday tasks and two error reduction learning methods were implemented within a virtual kitchen. Two patients with Alzheimer's disease and two healthy elderly controls were tested. All subjects were trained in two learning sessions on two comparable cooking tasks. Within each group (i.e., patients and controls), the order of the training methods was counterbalanced. Repeated measure analysis before and after learning was performed. A questionnaire of presence and a verbal interview were used to obtain information about the subjective responses of the participants to the VR experience. The results in terms of errors, omissions, and perseverations (i.e., repetitive behaviors) indicate that the patients performed worse than the controls before learning, but that they reached a level of performance similar to that of the controls after a short learning session, regardless of the learning method employed. This finding provides preliminary support for the value of the dual-modal virtual reality platform for training in everyday cooking activities in Alzheimer's disease. However, further work is needed before it is ready for clinical application. --- paper_title: Evaluation of a virtual reality‐based memory training programme for Hong Kong Chinese older adults with questionable dementia: a pilot study paper_content: Background ::: ::: Older adults with questionable dementia are at risk of progressing to dementia, and early intervention is considered important. The present study investigated the effectiveness of a virtual reality (VR)-based memory training for older adults with questionable dementia. ::: ::: ::: ::: Methods ::: ::: A pre-test and post-test design was adopted. Twenty and 24 older adults with questionable dementia were randomly assigned to a VR-based and a therapist-led memory training group, respectively. Primary outcome measures included the Multifactorial Memory Questionnaire and Fuld Object Memory Evaluation. ::: ::: ::: ::: Results ::: ::: Both groups demonstrated positive training effects, with the VR group showing greater improvement in objective memory performance and the non-VR group showing better subjective memory subtest results in the Multifactorial Memory Questionnaire. ::: ::: ::: ::: Conclusion ::: ::: The use of VR seems to be acceptable for older adults with questionable dementia. Further study on the effect of educational background and memory training modality (visual, auditory) is warranted. Copyright © 2011 John Wiley & Sons, Ltd. --- paper_title: Virtual reality in mental health : a review of the literature. paper_content: BACKGROUND ::: Several virtual reality (VR) applications for the understanding, assessment and treatment of mental health problems have been developed in the last 10 years. The purpose of this review is to outline the current state of virtual reality research in the treatment of mental health problems. ::: ::: ::: METHODS ::: PubMed and PsycINFO were searched for all articles containing the words "virtual reality". In addition a manual search of the references contained in the papers resulting from this search was conducted and relevant periodicals were searched. Studies reporting the results of treatment utilizing VR in the mental health field and involving at least one patient were identified. ::: ::: ::: RESULTS ::: More than 50 studies using VR were identified, the majority of which were case studies. Seventeen employed a between groups design: 4 involved patients with fear of flying; 3 involved patients with fear of heights; 3 involved patients with social phobia/public speaking anxiety; 2 involved people with spider phobia; 2 involved patients with agoraphobia; 2 involved patients with body image disturbance and 1 involved obese patients. There are both advantages in terms of delivery and disadvantages in terms of side effects to using VR. Although virtual reality based therapy appears to be superior to no treatment the effectiveness of VR therapy over traditional therapeutic approaches is not supported by the research currently available. ::: ::: ::: CONCLUSIONS ::: There is a lack of good quality research on the effectiveness of VR therapy. Before clinicians will be able to make effective use of this emerging technology greater emphasis must be placed on controlled trials with clinically identified populations. --- paper_title: Virtual reality and neuropsychology: upgrading the current tools. paper_content: Background: Virtual reality (VR) is an evolving technology that has been applied in various aspects of medicine, including the treatment of phobia disorders, pain distraction interventions, surgical training, and medical education. These applications have served to demonstrate the various assets offered through the use of VR. Objective: To provide a background and rationale for the application of VR to neuropsychological assessment. Methods: A brief introduction to VR technology and a review of current ongoing neuropsychological research that integrates the use of this technology. Conclusions: VR offers numerous assets that may enhance current neuropsychological assessment protocols and address many of the --- paper_title: Non-Pharmacological Intervention for Memory Decline paper_content: Non-pharmacological intervention of memory difficulties in healthy older adults, as well as those with brain damage and neurodegenerative disorders, has gained much attention in recent years. The two main reasons that explain this growing interest in memory rehabilitation are the limited efficacy of current drug therapies and the plasticity of the human central nervous and the discovery that during aging, the connections in the brain are not fixed but retain the capacity to change with learning. Moreover, several studies have reported enhanced cognitive performance in patients with neurological disease, following non-invasive brain stimulation [i.e., repetitive transcranial magnetic stimulation and transcranial direct current stimulation to specific cortical areas]. The present review provides an overview of memory rehabilitation in individuals with mild cognitive impairment and in patients with Alzheimer’s disease with particular regard to cognitive rehabilitation interventions focused on memory and non-invasive brain stimulation. Reviewed data suggest that in patients with memory deficits, memory intervention therapy could lead to performance improvements in memory, nevertheless further studies need to be conducted in order to establish the real value of this approach. --- paper_title: NeuroVR 2--a free virtual reality platform for the assessment and treatment in behavioral health care. paper_content: At MMVR 2007 we presented NeuroVR (http://www.neurovr.org) a free virtual reality platform based on open-source software. The software allows non-expert users to adapt the content of 14 pre-designed virtual environments to the specific needs of the clinical or experimental setting. Following the feedbacks of the 2000 users who downloaded the first versions (1 and 1.5), we developed a new version--NeuroVR 2 (http://www.neurovr2.org)--that improves the possibility for the therapist to enhance the patient's feeling of familiarity and intimacy with the virtual scene, by using external sounds, photos or videos. More, when running a simulation, the system offers a set of standard features that contribute to increase the realism of the simulated scene. These include collision detection to control movements in the environment, realistic walk-style motion, advanced lighting techniques for enhanced image quality, and streaming of video textures using alpha channel for transparency. --- paper_title: VREAD: A Virtual Simulation to Investigate Cognitive Function in the Elderly paper_content: Recent studies have shown that people with mild cognitive impairment (MCI) may convert to Alzheimer's disease (AD) over time although not all MCI cases progress to dementia. The diagnosis of MCI is important to allow prompt treatment and disease management before the neurons degenerate to a stage beyond repair. Hence, the ability to obtain a method of identifying MCI is of great importance. VREAD is a quick, easy and friendly tool that was developed with an aim to investigate cognitive functioning in a group of healthy elderly and those with MCI. It focuses on the task of following a route, since Topographical Disorientation (TD) is common in AD. The results shows that this novel simulation was able to predict with about 90% overall accuracy using weighting function proposed to discriminate between MCI and healthy elderly. --- paper_title: Video game training enhances cognitive control in older adults paper_content: Cognitive control is defined by a set of neural processes that allow us to interact with our complex environment in a goal-directed manner. Humans regularly challenge these control processes when attempting to simultaneously accomplish multiple goals (multitasking), generating interference as the result of fundamental information processing limitations. It is clear that multitasking behaviour has become ubiquitous in today's technologically dense world, and substantial evidence has accrued regarding multitasking difficulties and cognitive control deficits in our ageing population. Here we show that multitasking performance, as assessed with a custom-designed three-dimensional video game (NeuroRacer), exhibits a linear age-related decline from 20 to 79 years of age. By playing an adaptive version of NeuroRacer in multitasking training mode, older adults (60 to 85 years old) reduced multitasking costs compared to both an active control group and a no-contact control group, attaining levels beyond those achieved by untrained 20-year-old participants, with gains persisting for 6 months. Furthermore, age-related deficits in neural signatures of cognitive control, as measured with electroencephalography, were remediated by multitasking training (enhanced midline frontal theta power and frontal-posterior theta coherence). Critically, this training resulted in performance benefits that extended to untrained cognitive control abilities (enhanced sustained attention and working memory), with an increase in midline frontal theta power predicting the training-induced boost in sustained attention and preservation of multitasking improvement 6 months later. These findings highlight the robust plasticity of the prefrontal cognitive control system in the ageing brain, and provide the first evidence, to our knowledge, of how a custom-designed video game can be used to assess cognitive abilities across the lifespan, evaluate underlying neural mechanisms, and serve as a powerful tool for cognitive enhancement. --- paper_title: Detecting Everyday Action Deficits in Alzheimer’s Disease Using a Nonimmersive Virtual Reality Kitchen paper_content: Alzheimer’s disease (AD) causes impairments affecting instrumental activities of daily living (IADL). Transdisciplinary research in neuropsychology and virtual reality has fostered the development of ecologically valid virtual tools for the assessment of IADL, using simulations of real life activities. Few studies have examined the benefits of this approach in AD patients. Our aim was to examine the utility of a non-immersive virtual coffee task (NI-VCT) for assessment of IADL in these patients. We focus on the assessment results obtained from a group of 24 AD patients on a task designed to assess their ability to prepare a virtual cup of coffee, using a virtual coffee machine. We compared performance on the virtual task to an identical daily living task involving the actual preparation of a cup of coffee, as well as to global cognitive, executive, and caregiver-reported IADL functioning. Relative to 32 comparable, healthy elderly (HE) controls, AD patients performed worse than HE controls on all tasks. Correlation analyses revealed that NI-VCT measures were related to all other neuropsychological measures. Moreover, regression analyses demonstrated that performance on the NI-VCT predicted actual task performance and caregiver-reported IADL functioning. Our results provide initial support for the utility of our virtual kitchen for assessment of IADL in AD patients. ( JINS , 2014, 20 , 1–10) --- paper_title: Egocentric and allocentric memory as assessed by virtual reality in individuals with amnestic mild cognitive impairment paper_content: Abstract Present evidence suggests that medial temporal cortices subserve allocentric representation and memory, whereas egocentric representation and memory also depends on parietal association cortices and the striatum. Virtual reality environments have a major advantage for the assessment of spatial navigation and memory formation, as computer-simulated first-person environments can simulate navigation in a large-scale space. Twenty-nine patients with amnestic MCI (aMCI) were compared with 29 healthy matched controls on two virtual reality tasks affording to learn a virtual park (allocentric memory) and a virtual maze (egocentric memory). Participants further received a neuropsychological investigation and MRI volumetry at the time of the assessment. Results indicate that aMCI patients had significantly reduced size of the hippocampus bilaterally and the right-sided precuneus and inferior parietal cortex. aMCI patients were severely impaired learning the virtual park and the virtual maze. Smaller volumes of the right-sided precuneus were related to worse performance on the virtual maze. Participants with striatal lacunar lesions committed more errors than participants without such lesions on the virtual maze but not on the virtual park. aMCI patients later converting to dementia (n = 15) had significantly smaller hippocampal size when compared with non-converters (n = 14). However, both groups did not differ on virtual reality task performance. Our study clearly demonstrates the feasibility of virtual reality technology to study spatial memory deficits of persons with aMCI. Future studies should try to design spatial virtual reality tasks being specific enough to predict conversion from MCI to dementia and conversion from normal to MCI. --- paper_title: Interactive computer-training as a therapeutic tool in Alzheimer’s disease paper_content: Abstract The current study sought to evaluate a novel kind of interactive computer-based cognitive training (ICT) in Alzheimer’s disease (AD). AD patients (N = 9), age- and gender-matched patients with a major depressive episode (N = 9), and healthy control subjects (N = 10) were trained to use an ICT program that relates to activities of daily living (ADL). Digital photographs of a shopping route were implemented in a close-to-reality simulation on a computer touch-screen. The task was to find a predefined shopping route, to buy three items, and to answer correctly 10 multiple-choice questions addressing knowledge related to the virtual tasks. Training performance was rated using the number of mistakes (wrong way), time needed for the tasks, number of correct multiple-choice answers, and of repeat of instruction. Compared to normal controls and depressed patients, AD patients performed significantly worse with regard to all variables. Within a 4-week training period including 12 sessions, however, substantial training gains were observed, including a significant reduction of mistakes. Training effects were sustained until follow-up 3 weeks later. The performance of the depressed patients and the normal controls improved as well, with no difference between the two groups. Self-reported effects revealed that the training was well perceived. Thus, the task performance of AD patients improved substantially and subjects appeared to have liked this approach to ICT. New interactive media, therefore, may yield interesting opportunities for rehabilitation and (psycho)therapeutic interventions. --- paper_title: Mild cognitive impairment and deficits in instrumental activities of daily living: a systematic review paper_content: IntroductionThere is a growing body of evidence that subtle deficits in instrumental activities of daily living (IADL) may be present in mild cognitive impairment (MCI). However, it is not clear if there are IADL domains that are consistently affected across patients with MCI. In this systematic review, therefore, we aimed to summarize research results regarding the performance of MCI patients in specific IADL (sub)domains compared with persons who are cognitively normal and/or patients with dementia.MethodsThe databases PsycINFO, PubMed and Web of Science were searched for relevant literature in December 2013. Publications from 1999 onward were considered for inclusion. Altogether, 497 articles were retrieved. Reference lists of selected articles were searched for potentially relevant articles. After screening the abstracts of these 497 articles, 37 articles were included in this review.ResultsIn 35 studies, IADL deficits (such as problems with medication intake, telephone use, keeping appointments, finding things at home and using everyday technology) were documented in patients with MCI. Financial capacity in patients with MCI was affected in the majority of studies. Effect sizes for group differences between patients with MCI and healthy controls were predominantly moderate to large. Performance-based instruments showed slight advantages (in terms of effect sizes) in detecting group differences in IADL functioning between patients with MCI, patients with Alzheimer’s disease and healthy controls.ConclusionIADL requiring higher neuropsychological functioning seem to be most severely affected in patients with MCI. A reliable identification of such deficits is necessary, as patients with MCI with IADL deficits seem to have a higher risk of converting to dementia than patients with MCI without IADL deficits. The use of assessment tools specifically designed and validated for patients with MCI is therefore strongly recommended. Furthermore, the development of performance-based assessment instruments should be intensified, as they allow a valid and reliable assessment of subtle IADL deficits in MCI, even if a proxy is not available. Another important point to consider when designing new scales is the inclusion of technology-associated IADL. Novel instruments for clinical practice should be time-efficient and easy to administer. --- paper_title: Allothetic orientation and sequential ordering of places is impaired in early stages of Alzheimer's disease: corresponding results in real space tests and computer tests paper_content: Spatial disorientation and learning problems belong to the integral symptoms of Alzheimer's disease (AD). A circular arena for human subjects (2.9 m diameter, 3 m high) was equipped with a computerized tracking system, similar to that used in animals. We studied navigation in 11 subjects diagnosed with early stages of Alzheimer's disease (AD), 27 subjects with subjective problems with memory or concentration, and 10 controls. The task was to locate one or several unmarked goals using the arena geometry, starting position and/or cues on the arena wall. Navigation in a real version and a computer map view version of the tests yielded similar results. The AD group was severely impaired relative to controls in navigation to one hidden goal in eight rotated positions. The impairment was largest when only the cues on the wall could be used for orientation. Also, the AD group recalled worse than controls the order of six sequentially presented locations, though they recalled similarly to controls the positions of the locations. The group with subjective problems was not impaired in any of the tests. Our results document the spatial navigation and non-verbal episodic memory impairment in the AD. Similar results in real and map view computer tests support the use of computer tests in diagnosis of cognitive disturbances. --- paper_title: Age and dementia related differences in spatial navigation within an immersive virtual environment. paper_content: Immersive virtual reality (VR) is an innovative tool that can allow study of human spatial navigation in a realistic but controlled environment. The purpose of this study was to examine age- and Alzheinrer's disease-related differences in route learning and memory using VR. The spatial memory task took place in a VR environment set up on a Computer Workstation. Participants were immersed by putting video unit goggles over their eyes using a Head Mounted. Participants were shown a path within a virtual city, and then had to navigate it as quickly and accurately as possible. They were granted four learning trials on this path. An interference path was then presented before asking participants to re-navigate the first route at short and long delays. Finally, participants were tested for recognition of the city's buildings and objects. Young adults were consistently quicker and more accurate in their path navigation than older participants whilst those patients with Alzheimer's Disease made more mistakes on the recognition task in particular, being more likely to mistakenly affirm having seen an element in the city when it was in fact a foil. Our study would suggest that spatial navigation is susceptible to the effects of aging and Alzheimer's Disease. The potential applications ofVR to the study of spatial navigation is seemingly important in that it may help place the science of neuropsychology on firmer scientific grounds in terms of its validity to real world function and dysfunction. --- paper_title: An innovative virtual reality system for mild cognitive impairment: Diagnosis and evaluation paper_content: In advanced countries throughout the world, the population of Alzheimer's Disease(AD) patients has been gradually increasing with the aging of the society. As a result, it has become an important research topic how to diagnose AD early and give necessary treatment and training to AD patients, especially those with mild cognitive impairment(MCI), whose executive functions such as response inhibition, cognitive flexibility, attention switching and planning may display evident disorder and impairment. Unlike traditional paper tests and subjective assessments by the patient's relatives, this study adopts virtual reality(VR) technology to develop a novel diagnosis & assessment system, which uses head mounted display(HMD), game technology and sensors to generate an interactive and panoramic scenario—a virtual convenience store—for assessment of executive functions and memory. A variety of tasks of multi-layered difficulty-level hierarchy, such as memorizing a shopping list, looking for certain goods, and checking out, has been designed for customized and adaptive assessment, training, and treatment of MD. In the meantime, the study also records test-takers' performance data (including path and central-vision movement) in the process of all tasks for the development of a novel diagnosis & assessment method. Moreover, test-takers' technology acceptance is measured for assessing the elderly's subjective perception of new technology and discussing the topic of human-machine interaction. In the study, tests on 2 healthy adults have been completed, the system's functionality has been preliminarily verified, and test-takers' subjective perception of the system has been investigated. --- paper_title: Effects of Enactment in Episodic Memory: A Pilot Virtual Reality Study with Young and Elderly Adults paper_content: None of the previous studies on aging have tested the influence of action with respect to the degree of interaction with the environment (active or passive navigation) and the source of itinerary choice (self or externally imposed), on episodic memory encoding. The aim of this pilot study was to explore the influence of these factors on feature binding (the association between what, where and when) in episodic memory and on the subjective sense of remembering. Navigation in a virtual city was performed by 64 young and 64 older adults in one of four modes of exploration: (1) passive condition where participants were immersed as passengers of a virtual car (no interaction, no itinerary control), (2) itinerary control (the subject chose the itinerary, but did not drive the car), (3) low or (4) high navigation control (the subject just moved the car on rails or drove the car with a steering wheel and a gas pedal on a fixed itinerary, respectively). The task was to memorize as many events encountered in the virtual environment as possible along with their factual (what), spatial (where), and temporal (when) details, and then to perform immediate and delayed memory tests. An age-related decline was evidenced for immediate and delayed feature binding. Compared to passive and high navigation conditions, and regardless of age groups, feature binding was enhanced by low navigation and itinerary control conditions. The subjective sense of remembering was boosted by the itinerary control in older adults. Memory performance following high navigation was specifically linked to variability in executive functions. The present findings suggest that the decision of the itinerary is beneficial to boost episodic memory in aging, although it does not eliminate age-related deficits. Active navigation can also enhance episodic memory when it is not too demanding for subjects' cognitive resources. --- paper_title: Can a novel computerized cognitive screening test provide additional information for early detection of Alzheimer's disease? paper_content: Abstract Background Virtual reality testing of everyday activities is a novel type of computerized assessment that measures cognitive, executive, and motor performance as a screening tool for early dementia. This study used a virtual reality day-out task (VR-DOT) environment to evaluate its predictive value in patients with mild cognitive impairment (MCI). Methods One hundred thirty-four patients with MCI were selected and compared with 75 healthy control subjects. Participants received an initial assessment that included VR-DOT, a neuropsychological evaluation, magnetic resonance imaging (MRI) scan, and event-related potentials (ERPs). After 12 months, participants were assessed again with MRI, ERP, VR-DOT, and neuropsychological tests. Results At the end of the study, we differentiated two subgroups of patients with MCI according to their clinical evolution from baseline to follow-up: 56 MCI progressors and 78 MCI nonprogressors. VR-DOT performance profiles correlated strongly with existing predictive biomarkers, especially the ERP and MRI biomarkers of cortical thickness. Conclusions Compared with ERP, MRI, or neuropsychological tests alone, the VR-DOT could provide additional predictive information in a low-cost, computerized, and noninvasive way. --- paper_title: How different spatial representations interact in virtual environments: the role of mental frame syncing paper_content: 뀀ഀȠ 뀀ഀȠ Silvia SerinoGiuseppe Riva 뀀ഀȠ 뀀ഀȠ 뀀ഀȠ 뀀ഀȠ 뀀ഀȠ 뀀ഀȠ 뀀ഀȠ Abstract This experiment is aimed at understanding how egocentric experiences, allocentric viewpoint-dependent representations, and allocentric viewpoint-independent representations interact when encoding and retrieving a spatial environment. Although several cognitive theories have highlighted the interaction between reference frames, it is less clear about the role of a real-time presentation of allocentric viewpoint-dependent representation on the spatial organization of information. Sixty participants were asked to navigate in two virtual cities to memorize the position of one hidden object. Half of the participants had the possibility to visualize the virtual city with an inter- active aerial view. Then, they were required to find the position of the object in three different experimental con- ditions (''retrieval with an interactive aerial view'' vs. ''retrieval on a map'' vs. ''retrieval without an interactive aerial view''). Results revealed that participants were sig- nificantly more precise in retrieving the position of the object when immersed in an egocentric experience with the interactive aerial view. The retrieval of spatial information is facilitated by the presence of the interactive aerial view of the city, since it provides a real-time allocentric view- point-dependent representation. More participants with high preference for using cardinal points tend to be more accurate when they were asked to retrieve the position of the object on the map. As suggested by the mental frame syncing hypothesis, the presence of an allocentric 뀀ഀȠ 뀀ഀȠ 뀀ഀȠoduction --- paper_title: Spatial navigation impairment is proportional to right hippocampal volume paper_content: Cognitive deficits in older adults attributable to Alzheimer's disease (AD) pathology are featured early on by hippocampal impairment. Among these individuals, deterioration in spatial navigation, manifested by poor hippocampus-dependent allocentric navigation, may occur well before the clinical onset of dementia. Our aim was to determine whether allocentric spatial navigation impairment would be proportional to right hippocampal volume loss irrespective of general brain atrophy. We also contrasted the respective spatial navigation scores of the real-space human Morris water maze with its corresponding 2D computer version. We included 42 cognitively impaired patients with either amnestic mild cognitive impairment (n = 23) or mild and moderate AD (n = 19), and 14 cognitively intact older controls. All participants underwent 1.5T MRI brain scanning with subsequent automatic measurement of the total brain and hippocampal (right and left) volumes. Allocentric spatial navigation was tested in the real-space version of the human Morris water maze and in its corresponding computer version. Participants used two navigational cues to locate an invisible goal independent of the start position. We found that smaller right hippocampal volume was associated with poorer navigation performance in both the real-space (β = −0.62, P 0.59) subjects. The respective real-space and virtual scores strongly correlated with each other. Our findings indicate that the right hippocampus plays a critical role in allocentric navigation, particularly when cognitive impairment is present. --- paper_title: BrightArm™ therapy for patients with advanced dementia: A feasibility study paper_content: Virtual reality use in cognitive rehabilitation of advanced dementia has been sparse. Three residents of a Dementia Ward participated in a feasibility study of the BrightArm™ system. They played custom games targeting several cognitive domains including short-term and working memory. Clinician observation revealed a positive effect on emotive state, with technology well accepted by all participants. --- paper_title: Spatial navigation deficit in amnestic mild cognitive impairment paper_content: Patients with Alzheimer's disease (AD) frequently have difficulties with spatial orientation in their day-to-day life. Although AD is typically preceded by amnestic mild cognitive impairment (MCI), spatial navigation has not yet been studied in MCI. Sixty-five patients were divided into five groups: probable AD (n = 21); MCI, further classified as amnestic MCI single domain (n = 11); amnestic MCI multiple domain (n = 18), or nonamnestic MCI (n = 7), and subjective memory complaints (n = 8). These patients, together with a group of healthy control subjects (n = 26), were tested by using a four-subtests task that required them to locate an invisible goal inside a circular arena. Each subtest began with an overhead view of the arena showed on a computer monitor. This was followed by a real navigation inside of the actual space, an enclosed arena 2.9 m in diameter. Depending on the subtest, the subjects could use the starting position and/or cues on the wall for navigation. The subtests thus were focused on allocentric and egocentric navigation. The AD group and amnestic MCI multiple-domain group were impaired in all subtests. The amnestic MCI single-domain group was impaired significantly in subtests focused on allocentric orientation and at the beginning of the real space egocentric subtest, suggesting impaired memory for allocentric and real space configurations. Our results suggest that spatial navigation impairment occurs early in the development of AD and can be used for monitoring of the disease progression or for evaluation of presymptomiatic AD. --- paper_title: Temporal Order Memory Assessed during Spatiotemporal Navigation As a Behavioral Cognitive Marker for Differential Alzheimer's Disease Diagnosis paper_content: Episodic memory impairment is a hallmark for early diagnosis of Alzheimer9s disease. Most actual tests used to diagnose Alzheimer9s disease do not assess the spatiotemporal properties of episodic memory and lead to false-positive or -negative diagnosis. We used a newly developed, nonverbal navigation test for Human, based on the objective experimental testing of a spatiotemporal experience, to differentially Alzheimer9s disease at the mild stage ( N = 16 patients) from frontotemporal lobar degeneration ( N = 11 patients) and normal aging ( N = 24 subjects). Comparing navigation parameters and standard neuropsychological tests, temporal order memory appeared to have the highest predictive power for mild Alzheimer9s disease diagnosis versus frontotemporal lobar degeneration and normal aging. This test was also nonredundant with classical neuropsychological tests. As a conclusion, our results suggest that temporal order memory tested in a spatial navigation task may provide a selective behavioral marker of Alzheimer9s disease. --- paper_title: Impaired Allocentric Spatial Memory Underlying Topographical Disorientation paper_content: The cognitive processes supporting spatial navigation are considered in the context of a patient (CF) with possible very early Alzheimer's disease who presents with topographical disorientation. Her verbal memory and her recognition memory for unknown buildings, landmarks and outdoor scenes was intact, although she showed an impairment in face processing. By contrast, her navigational ability, quantitatively assessed within a small virtual reality (VR) town, was significantly impaired. Interestingly, she showed a selective impairment in a VR object-location memory test whenever her viewpoint was shifted between presentation and test, but not when tested from the same viewpoint. We suggest that a specific impairment in locating objects relative to the environment rather than relative to the perceived viewpoint (i.e. allocentric rather than egocentric spatial memory) underlies her topographical disorientation. We discuss the likely neural bases of this deficit in the light of related studies in humans and animals, focusing on the hippocampus and related areas. The specificity of our test indicates a new way of assessing topographical disorientation, with possible application to the assessment of progressive dementias such as Alzheimer's disease. --- paper_title: Spatial memory impairments in amnestic mild cognitive impairment in a virtual radial arm maze paper_content: Author contributions ::: ::: Dr Jun-Young Lee conceived the study, acquired, and interpreted the data. Ms Sooyeon Kho and Ms Hye Bin Yoo analyzed the data and edited the article. Ms Soowon Park made major revisions to the Introduction section. Dr Jung-Seok Choi and Jun Soo Kwon acquired the patients and their clinical reports. The corresponding authors Dr Kyung Ryeol Cha and Dr Hee-Yeon Jung designed the research and the experiments. All authors made substantial contributions to conception and design of the paper, acquisition of data, or analysis and interpretation of data, and drafted the article or revised it for critically important content. ::: ::: ::: ::: Disclosure ::: ::: The authors report no conflict of interest in this work. No competing financial interests exist. --- paper_title: Involving Persons with Dementia in the Evaluation of Outdoor Environments paper_content: ABSTRACT Using virtual reality (VR), we examined the barriers to and facilitators of functioning outdoors in persons with dementia (PwD) and investigated the generalizability of findings in VR to the real world. An existing town center was modeled in VR. PwD took part in both real-world and VR walks. Based on the results, the model was redesigned and then tested again. Performance on the walks improved, and potentially beneficial adaptations to outdoor environments were identified, but limitations of VR as a representation of the real world were also identified. We conclude that VR models, together with a rigorous behavioral testing method, can be a useful tool for the evaluation of outdoor environments and for identifying improvements for PwD. --- paper_title: Detecting navigational deficits in cognitive aging and Alzheimer disease using virtual reality paper_content: Background:Older adults get lost, in many cases because of recognized or incipient Alzheimer disease (AD). In either case, getting lost can be a threat to individual and public safety, as well as to personal autonomy and quality of life. Here we compare our previously described real-world navigation test with a virtual reality (VR) version simulating the same navigational environment. Methods:Quantifying real-world navigational performance is difficult and time-consuming. VR testing is a promising alternative, but it has not been compared with closely corresponding real-world testing in aging and AD. We have studied navigation using both real-world and virtual environments in the same subjects: young normal controls (YNCs, n = 35), older normal controls (ONCs, n = 26), patients with mild cognitive impairment (MCI, n = 12), and patients with early AD (EAD, n = 14). Results:We found close correlations between real-world and virtual navigational deficits that increased across groups from YNC to ONC, to MCI, and to EAD. Analyses of subtest performance showed similar profiles of impairment in real-world and virtual testing in all four subject groups. The ONC, MCI, and EAD subjects all showed greatest difficulty in self-orientation and scene localization tests. MCI and EAD patients also showed impaired verbal recall about both test environments. Conclusions:Virtual environment testing provides a valid assessment of navigational skills. Aging and Alzheimer disease (AD) share the same patterns of difficulty in associating visual scenes and locations, which is complicated in AD by the accompanying loss of verbally mediated navigational capacities. We conclude that virtual navigation testing reveals deficits in aging and AD that are associated with potentially grave risks to our patients and the community. GLOSSARYAD = Alzheimer disease; EAD = early Alzheimer disease; MCI = mild cognitive impairment; MMSE = Mini-Mental State Examination; ONC = older normal control; std. wt. = standardized weight; THSD = Tukey honestly significant difference; VR = virtual reality; YNC = young normal control. --- paper_title: Controlling Memory Impairment in Elderly Adults Using Virtual Reality Memory Training: A Randomized Controlled Pilot Study paper_content: Background. Memory decline is a prevalent aspect of aging but may also be the first sign of cognitive pathology. Virtual reality (VR) using immersion and interaction may provide new approaches to the treatment of memory deficits in elderly individuals. Objective. The authors implemented a VR training intervention to try to lessen cognitive decline and improve memory functions. Methods. The authors randomly assigned 36 elderly residents of a rest care facility (median age 80 years) who were impaired on the Verbal Story Recall Test either to the experimental group (EG) or the control group (CG). The EG underwent 6 months of VR memory training (VRMT) that involved auditory stimulation and VR experiences in path finding. The initial training phase lasted 3 months (3 auditory and 3 VR sessions every 2 weeks), and there was a booster training phase during the following 3 months (1 auditory and 1 VR session per week). The CG underwent equivalent face-to-face training sessions using music therapy. Both groups par... --- paper_title: Autobiographical Memory Deficits in Alzheimer's Disease paper_content: Autobiographical memory comprises memories of one's own past that are characterized by a sense of subjective time and autonoetic awareness. Although autobiographical memory deficits are among the major complaints of patients with dementia, they have rarely been systematically assessed in mild cognitive impairment and Alzheimer's disease. We therefore investigated semantic and episodic aspects of autobiographical memory for remote and recent life periods in a sample of 239 nursing home residents (165 in different stages of Alzheimer's disease, 33 with mild cognitive impairment, and 41 cognitively unimpaired) with respect to potential confounders. Episodic autobiographical memories, especially the richness of details, were impaired early in the course of Alzheimer's disease or even in the preclinical phase, while semantic memories were spared until moderate stages, indicating a dissociation between both memory systems. The examination of autobiographic memory loss can facilitate the clinical diagnosis of Alzheimer's disease. --- paper_title: Augmented reality annotations to assist persons with Alzheimers and their caregivers paper_content: Persons with Alzheimer's disease (AD) and their caregivers implement diverse strategies to cope with memory loss. A common strategy involves placing tags on drawers or removing cabinet doors to make their contents visible. This study describes the Ambient aNnotation System (ANS), aimed at assisting people suffering from AD and their caregivers with this task. The system has two main modules: The tagging subsystem allows caregivers to create and manage ambient annotations in order to assist people with memory problems. The second subsystem allows people with AD to use a mobile phone to recognize tags in the environment and to receive relevant information in the form of audio, text, or images. The identification of these tags is performed in real time by uploading images from the mobile phone to a server, which uses the SURF algorithm for object recognition. We describe the design and implementation of the system as well as results of the evaluation of its performance and efficiency. ANS can process query images approximately every 2 s and is able to locate users in their homes with a precision of 0.93. A usability study conducted with six subjects determined that audio notifications are more effective than vibrating notifications to alert the user about tags in the environment. --- paper_title: Is it possible to use highly realistic virtual reality in the elderly? A feasibility study with image-based rendering paper_content: Background: Virtual reality (VR) opens up a vast number of possibilities in many domains of therapy. The primary objective of the present study was to evaluate the acceptability for elderly subjects of a VR experience using the image-based rendering virtual environment (IBVE) approach and secondly to test the hypothesis that visual cues using VR may enhance the generation of autobiographical memories. ::: Methods: Eighteen healthy volunteers (mean age 68.2 years) presenting memory complaints with a Mini-Mental State Examination score higher than 27 and no history of neuropsychiatric disease were included. Participants were asked to perform an autobiographical fluency task in four conditions. The first condition was a baseline grey screen, the second was a photograph of a well-known location in the participant’s home city (FamPhoto), and the last two conditions displayed VR, ie, a familiar image-based virtual environment (FamIBVE) consisting of an image-based representation of a known landmark square in the center of the city of experimentation (Nice) and an unknown image-based virtual environment (UnknoIBVE), which was captured in a public housing neighborhood containing unrecognizable building fronts. After each of the four experimental conditions, participants filled in self-report questionnaires to assess the task acceptability (levels of emotion, motivation, security, fatigue, and familiarity). CyberSickness and Presence questionnaires were also assessed after the two VR conditions. Autobiographical memory was assessed using a verbal fluency task and quality of the recollection was assessed using the “remember/know” procedure. ::: Results: All subjects completed the experiment. Sense of security and fatigue were not significantly different between the conditions with and without VR. The FamPhoto condition yielded a higher emotion score than the other conditions (P,0.05). The CyberSickness questionnaire showed that participants did not experience sickness during the experiment across the VR conditions. VR stimulates autobiographical memory, as demonstrated by the increased total number of responses on the autobiographical fluency task and the increased number of conscious recollections of memories for familiar versus unknown scenes (P,0.01). ::: Conclusion: The study indicates that VR using the FamIBVE system is well tolerated by the elderly. VR can also stimulate recollections of autobiographical memory and convey familiarity of a given scene, which is an essential requirement for use of VR during reminiscence therapy. --- paper_title: A Pilot Evaluation of a Therapeutic Game Applied to Small Animal Phobia Treatment paper_content: This study presents Catch Me game, a therapeutic game for teaching patients how to confront to their feared animals during spider and cockroach phobia treatment, and evaluates whether inclusion of gaming elements into therapeutic protocol does have an added value for the treatment. The Catch Me game was designed in order to help patients learn about their feared animals and to learn how to apply adapted confrontation strategies and techniques with the lowest possible anxiety level. In this study, Catch Me game was evaluated in terms of knowledge acquisition, anxiety level, self-efficacy belief acquisition, and appeal to both participants and therapists. Data collection consisted of quantitative measures on a sample of 14 non-clinical population. The results showed that the game significantly improved knowledge and self-efficacy belief regarding the feared animal, and significantly decreased the anxiety level of participants. Moreover, both participants and the therapists were highly satisfied with the game. --- paper_title: GenVirtual: An Augmented Reality Musical Game for Cognitive and Motor Rehabilitation paper_content: Electronic games have been used to stimulate cognitive functions such as attention, concentration and memory. This paper presents GenVirtual, which is an augmented reality musical game and is proposed to help people with learning disabilities. The intention is to help the patient in the following skills: creativity, attention, memory (storage and retrieval), planning, concentration, ready-response, hearing and visual perception, and motor coordination. The therapist has flexibility to place the musical and visual elements, allowing him to create different scenarios to each patient. GenVirtual uses Augmented Reality technology to allow people with physical disorders to interact with the game. Patients with no fingers can also play this game. GenVirtual was evaluated by a music therapist who considered it as a facilitating and motivating game to the learning process and that it has the potential to improve the life of the people with special needs. --- paper_title: Mixing Realities? An Application of Augmented Reality for the Treatment of Cockroach Phobia paper_content: Augmented reality (AR) refers to the introduction of virtual elements in the real world. That is, the person is seeing an image composed of a visualization of the real world, and a series of virtual elements that, at that same moment, are super-imposed on the real world. The most important aspect of AR is that the virtual elements supply to the person relevant and useful information that is not contained in the real world. AR has notable potential, and has already been used in diverse fields, such as medicine, the army, coaching, engineering, design, and robotics. Until now, AR has never been used in the scope of psychological treatment. Nevertheless, AR presents various advantages. Just like in the classical systems of virtual reality, it is possible to have total control over the virtual elements that are super-imposed on the real world, and how one interacts with those elements. AR could involve additional advantages; on one side it could be less expensive since it also uses the real world (this does not need to be modeled), and it could facilitate the feeling of presence (the sensation of being there), and reality judgment (the fact of judging the experience as real) of the person since the environment he or she is in, and what he or she is seeing is, in fact the "reality." In this paper, we present the data of the first case study in which AR has been used for the treatment of a specific phobia, cockroaches phobia. It addresses a system of AR that permits exposure to virtual cockroaches super-imposed on the real world. In order to carry out the exposure, the guidelines of Ost with respect to "one-session treatment" were followed. The results are promising. The participant demonstrated notable fear and avoidance in the behavioral avoidance test before the treatment, and not only was an important decrease in the scores of fear and avoidance observed after the treatment, but also the participant was capable of approaching, interacting, and killing live cockroaches immediately following the treatment. The results are maintained in a follow-up conducted 1 month after the termination of the treatment. --- paper_title: Augmented reality cube game for cognitive training: an interaction study. paper_content: There is the potential that cognitive activity may delay cognitive decline in people with mild cognitive impairment. Games provide both cognitive challenge and motivation for repeated use, a prerequisite for long lasting effect. Recent advances in technology introduce several new interaction methods, potentially leading to more efficient, personalized cognitive gaming experiences. In this paper, we present an Augmented Reality (AR) cognitive training game, utilizing cubes as input tools, and we test the cube interaction with a pilot study. The results of the study revealed the marker occlusion problem, and that novice AR users can adjust to the developed AR environment after a small number of sessions. --- paper_title: Moving from Virtual Reality Exposure-Based Therapy to Augmented Reality Exposure-Based Therapy: A Review paper_content: This paper reviews the move from virtual reality exposure-based therapy (VRET) to augmented reality exposure-based therapy (ARET). Unlike virtual reality (VR), which entails a complete virtual environment (VE), augmented reality (AR) limits itself to producing certain virtual elements to then merge them into the view of the physical world. Although the general public may only have become aware of AR in the last few years, AR type applications have been around since beginning of the 20th century. Since, then, technological developments have enabled an ever increasing level of seamless integration of virtual and physical elements into one view. Like VR, AR allows the exposure to stimuli which, due to various reasons, may not be suitable for real-life scenarios. As such, AR has proven itself to be a medium through which individuals suffering from specific phobia can be exposed “safely” to the object(s) of their fear, without the costs associated with programming complete virtual environments. Thus, ARET can offer an efficacious alternative to some less advantageous exposure-based therapies. Above and beyond presenting what has been accomplished in ARET, this paper also raises some ARET related issues, and proposes potential avenues to be followed. These include the definition of an AR related term, the type of measures to be used to qualify the user’s experience in an augmented reality environment (ARE), the development of alternative geospatial referencing systems, as well as the potential use of ARET to treat social phobia. Overall, it may be said that the use of ARET, although promising, is still in its infancy but that, given a continued cooperation between clinical and technical teams, ARET has the potential of going well beyond the treatment of small animal phobia. --- paper_title: ON THE CONVERGENCE OF AFFECTIVE AND PERSUASIVE TECHNOLOGIES IN COMPUTER-MEDIATED HEALTH-CARE SYSTEMS paper_content: This paper offers a portrayal of how affective computing and persuasive technologies can converge into an effective tool for interfacing biomedical engineering with behavioral sciences and medicine. We describe the characteristics, features, applications, present state of the art, perspectives, and trends of both streams of research. In particular, these streams are analyzed in light of the potential contribution of their convergence for improving computer-mediated health-care systems, by facilitating the modification of patients' attitudes and behaviors, such as engagement and compliance. We propose a framework for future research in this emerging area, highlighting how key constructs and intervening variables should be considered. Some specific implications and challenges posed by the convergence of these two technologies in health care, such as paradigm change, multimodality, patients' attitude improvement, and cost reduction, are also briefly addressed and discussed. --- paper_title: Using Virtual Reality for Cognitive Training of the Elderly paper_content: There is a pressing demand for improving the quality and efficacy of health care and social support services needed by the world’s growing elderly population, especially by those affected by mild cognitive impairment (MCI) and Alzheimer’s disease (AD)-type early-stage dementia. Meeting that demand can significantly benefit from the deployment of innovative, computer-based applications capable of addressing specific needs, particularly in the area of cognitive impairment mitigation and rehabilitation. In that context, we present here our perspective viewpoint on the use of virtual reality (VR) tools for cognitive rehabilitation training, intended to assist medical personnel, health care workers, and other caregivers in improving the quality of daily life activities of people with MCI and AD. We discuss some effective design criteria and developmental strategies and suggest some possibly useful protocols and procedures. The particular innovative supportive advantages offered by the immersive interactive cha... --- paper_title: Remote measurement of cognitive stress via heart rate variability paper_content: Remote detection of cognitive load has many powerful applications, such as measuring stress in the workplace. Cognitive tasks have an impact on breathing and heart rate variability (HRV). We show that changes in physiological parameters during cognitive stress can be captured remotely (at a distance of 3m) using a digital camera. A study (n=10) was conducted with participants at rest and under cognitive stress. A novel five band digital camera was used to capture videos of the face of the participant. Significantly higher normalized low frequency HRV components and breathing rates were measured in the stress condition when compared to the rest condition. Heart rates were not significantly different between the two conditions. We built a person-independent classifier to predict cognitive stress based on the remotely detected physiological parameters (heart rate, breathing rate and heart rate variability). The accuracy of the model was 85% (35% greater than chance). ---	Title: A Succinct Overview of Virtual Reality Technology Use in Alzheimer’s Disease Section 1: Introduction Description 1: Provide an introduction to the topic, detailing the significance of VR technology in the context of Alzheimer’s disease (AD). Section 2: Current Applications of VR in Psychotherapy Description 2: Discuss the general application areas of VR in psychotherapy and list examples relevant to Alzheimer’s disease. Section 3: VR Technologies and Devices Description 3: Describe the types of VR technologies and devices used, including their levels of immersion and interaction. Section 4: Importance of Immersion and Presence Description 4: Explain the role of immersion and presence in VR applications, and how these factors affect the effectiveness of VR-based interventions for AD patients. Section 5: Health and Safety Considerations Description 5: Address the health and safety implications of using VR, particularly focusing on issues like cyber-sickness and VR-induced symptoms. Section 6: Literature Review Methodology Description 6: Outline the methodology followed for the literature review, including information on literature search, selection criteria, and categorization. Section 7: Categorization of VR Applications Used in AD Description 7: Present a detailed classification of VR systems based on their intended purpose, impairment focus, methodology, and type of interaction. Section 8: Intended Purpose of VR Applications Description 8: Discuss the primary goals of VR applications in the context of Alzheimer’s disease – assessment, diagnosis, cognitive training, and caregivers’ training. Section 9: Focal Aspects in VR Research for AD Description 9: Identify the specific cognitive impairment features considered most relevant for VR diagnostic and training purposes in AD research. Section 10: Interaction Techniques in VR Description 10: Describe the different techniques for user interaction in VR systems, including tasks, activities, and games, and their relevance to AD applications. Section 11: Emerging Augmented Reality Applications Description 11: Highlight the emerging use of augmented reality (AR) in addition to VR for cognitive training and rehabilitation of AD patients. Section 12: Conclusion Description 12: Summarize the key findings of the review, emphasize the need for more immersive and effective VR applications, and suggest future directions for research and development in this field.
A Survey on Recent Advances of Computer Vision Algorithms for Egocentric Video	8	--- paper_title: MILES: Multiple-Instance Learning via Embedded Instance Selection paper_content: Multiple-instance problems arise from the situations where training class labels are attached to sets of samples (named bags), instead of individual samples within each bag (called instances). Most previous multiple-instance learning (MIL) algorithms are developed based on the assumption that a bag is positive if and only if at least one of its instances is positive. Although the assumption works well in a drug activity prediction problem, it is rather restrictive for other applications, especially those in the computer vision area. We propose a learning method, MILES (multiple-instance learning via embedded instance selection), which converts the multiple-instance learning problem to a standard supervised learning problem that does not impose the assumption relating instance labels to bag labels. MILES maps each bag into a feature space defined by the instances in the training bags via an instance similarity measure. This feature mapping often provides a large number of redundant or irrelevant features. Hence, 1-norm SVM is applied to select important features as well as construct classifiers simultaneously. We have performed extensive experiments. In comparison with other methods, MILES demonstrates competitive classification accuracy, high computation efficiency, and robustness to labeling uncertainty --- paper_title: Egocentric recognition of handled objects: Benchmark and analysis paper_content: Recognizing objects being manipulated in hands can provide essential information about a person's activities and have far-reaching impacts on the application of vision in everyday life. The egocentric viewpoint from a wearable camera has unique advantages in recognizing handled objects, such as having a close view and seeing objects in their natural positions. We collect a comprehensive dataset and analyze the feasibilities and challenges of the egocentric recognition of handled objects. We use a lapel-worn camera and record uncompressed video streams as human subjects manipulate objects in daily activities. We use 42 day-to-day objects that vary in size, shape, color and textureness. 10 video sequences are shot for each object under different illuminations and backgrounds. We use this dataset and a SIFT-based recognition system to analyze and quantitatively characterize the main challenges in egocentric object recognition, such as motion blur and hand occlusion, along with its unique constraints, such as hand color, location prior and temporal consistency. SIFT-based recognition has an average recognition rate of 12%, and reaches 20% through enforcing temporal consistency. We use simulations to estimate the upper bound for SIFT-based recognition at 64%, the loss of accuracy due to background clutter at 20%, and that of hand occlusion at 13%. Our quantitative evaluations show that the egocentric recognition of handled objects is a challenging but feasible problem with many unique characteristics and many opportunities for future research. --- paper_title: Figure-ground segmentation improves handled object recognition in egocentric video paper_content: Identifying handled objects, i.e. objects being manipulated by a user, is essential for recognizing the person's activities. An egocentric camera as worn on the body enjoys many advantages such as having a natural first-person view and not needing to instrument the environment. It is also a challenging setting, where background clutter is known to be a major source of problems and is difficult to handle with the camera constantly and arbitrarily moving. In this work we develop a bottom-up motion-based approach to robustly segment out foreground objects in egocentric video and show that it greatly improves object recognition accuracy. Our key insight is that egocentric video of object manipulation is a special domain and many domain-specific cues can readily help. We compute dense optical flow and fit it into multiple affine layers. We then use a max-margin classifier to combine motion with empirical knowledge of object location and background movement as well as temporal cues of support region and color appearance. We evaluate our segmentation algorithm on the large Intel Egocentric Object Recognition dataset with 42 objects and 100K frames. We show that, when combined with temporal integration, figure-ground segmentation improves the accuracy of a SIFT-based recognition system from 33% to 60%, and that of a latent-HOG system from 64% to 86%. --- paper_title: A discriminatively trained, multiscale, deformable part model paper_content: This paper describes a discriminatively trained, multiscale, deformable part model for object detection. Our system achieves a two-fold improvement in average precision over the best performance in the 2006 PASCAL person detection challenge. It also outperforms the best results in the 2007 challenge in ten out of twenty categories. The system relies heavily on deformable parts. While deformable part models have become quite popular, their value had not been demonstrated on difficult benchmarks such as the PASCAL challenge. Our system also relies heavily on new methods for discriminative training. We combine a margin-sensitive approach for data mining hard negative examples with a formalism we call latent SVM. A latent SVM, like a hidden CRF, leads to a non-convex training problem. However, a latent SVM is semi-convex and the training problem becomes convex once latent information is specified for the positive examples. We believe that our training methods will eventually make possible the effective use of more latent information such as hierarchical (grammar) models and models involving latent three dimensional pose. --- paper_title: High Accuracy Optical Flow Estimation Based on a Theory for Warping paper_content: We study an energy functional for computing optical flow that combines three assumptions: a brightness constancy assumption, a gradient constancy assumption, and a discontinuity-preserving spatio-temporal smoothness constraint. In order to allow for large displacements, linearisations in the two data terms are strictly avoided. We present a consistent numerical scheme based on two nested fixed point iterations. By proving that this scheme implements a coarse-to-fine warping strategy, we give a theoretical foundation for warping which has been used on a mainly experimental basis so far. Our evaluation demonstrates that the novel method gives significantly smaller angular errors than previous techniques for optical flow estimation. We show that it is fairly insensitive to parameter variations, and we demonstrate its excellent robustness under noise. --- paper_title: Learning to recognize objects in egocentric activities paper_content: This paper addresses the problem of learning object models from egocentric video of household activities, using extremely weak supervision. For each activity sequence, we know only the names of the objects which are present within it, and have no other knowledge regarding the appearance or location of objects. The key to our approach is a robust, unsupervised bottom up segmentation method, which exploits the structure of the egocentric domain to partition each frame into hand, object, and background categories. By using Multiple Instance Learning to match object instances across sequences, we discover and localize object occurrences. Object representations are refined through transduction and object-level classifiers are trained. We demonstrate encouraging results in detecting novel object instances using models produced by weakly-supervised learning. --- paper_title: Modeling the Shape of the Scene: A Holistic Representation of the Spatial Envelope paper_content: In this paper, we propose a computational model of the recognition of real world scenes that bypasses the segmentation and the processing of individual objects or regions. The procedure is based on a very low dimensional representation of the scene, that we term the Spatial Envelope. We propose a set of perceptual dimensions (naturalness, openness, roughness, expansion, ruggedness) that represent the dominant spatial structure of a scene. Then, we show that these dimensions may be reliably estimated using spectral and coarsely localized information. The model generates a multidimensional space in which scenes sharing membership in semantic categories (e.g., streets, highways, coasts) are projected closed together. The performance of the spatial envelope model shows that specific information about object shape or identity is not a requirement for scene categorization and that modeling a holistic representation of the scene informs about its probable semantic category. --- paper_title: Temporal segmentation and activity classification from first-person sensing paper_content: Temporal segmentation of human motion into actions is central to the understanding and building of computational models of human motion and activity recognition. Several issues contribute to the challenge of temporal segmentation and classification of human motion. These include the large variability in the temporal scale and periodicity of human actions, the complexity of representing articulated motion, and the exponential nature of all possible movement combinations. We provide initial results from investigating two distinct problems -classification of the overall task being performed, and the more difficult problem of classifying individual frames over time into specific actions. We explore first-person sensing through a wearable camera and inertial measurement units (IMUs) for temporally segmenting human motion into actions and performing activity classification in the context of cooking and recipe preparation in a natural environment. We present baseline results for supervised and unsupervised temporal segmentation, and recipe recognition in the CMU-multimodal activity database (CMU-MMAC). --- paper_title: Object Detection with Discriminatively Trained Part-Based Models paper_content: We describe an object detection system based on mixtures of multiscale deformable part models. Our system is able to represent highly variable object classes and achieves state-of-the-art results in the PASCAL object detection challenges. While deformable part models have become quite popular, their value had not been demonstrated on difficult benchmarks such as the PASCAL data sets. Our system relies on new methods for discriminative training with partially labeled data. We combine a margin-sensitive approach for data-mining hard negative examples with a formalism we call latent SVM. A latent SVM is a reformulation of MI--SVM in terms of latent variables. A latent SVM is semiconvex, and the training problem becomes convex once latent information is specified for the positive examples. This leads to an iterative training algorithm that alternates between fixing latent values for positive examples and optimizing the latent SVM objective function. --- paper_title: Learning to Recognize Daily Actions using Gaze paper_content: We present a probabilistic generative model for simultaneously recognizing daily actions and predicting gaze locations in videos recorded from an egocentric camera. We focus on activities requiring eye-hand coordination and model the spatio-temporal relationship between the gaze point, the scene objects, and the action label. Our model captures the fact that the distribution of both visual features and object occurrences in the vicinity of the gaze point is correlated with the verb-object pair describing the action. It explicitly incorporates known properties of gaze behavior from the psychology literature, such as the temporal delay between fixation and manipulation events. We present an inference method that can predict the best sequence of gaze locations and the associated action label from an input sequence of images. We demonstrate improvements in action recognition rates and gaze prediction accuracy relative to state-of-the-art methods, on two new datasets that contain egocentric videos of daily activities and gaze. --- paper_title: Detecting activities of daily living in first-person camera views paper_content: We present a novel dataset and novel algorithms for the problem of detecting activities of daily living (ADL) in firstperson camera views. We have collected a dataset of 1 million frames of dozens of people performing unscripted, everyday activities. The dataset is annotated with activities, object tracks, hand positions, and interaction events. ADLs differ from typical actions in that they can involve long-scale temporal structure (making tea can take a few minutes) and complex object interactions (a fridge looks different when its door is open). We develop novel representations including (1) temporal pyramids, which generalize the well-known spatial pyramid to approximate temporal correspondence when scoring a model and (2) composite object models that exploit the fact that objects look different when being interacted with. We perform an extensive empirical evaluation and demonstrate that our novel representations produce a two-fold improvement over traditional approaches. Our analysis suggests that real-world ADL recognition is “all about the objects,” and in particular, “all about the objects being interacted with.” --- paper_title: Understanding egocentric activities paper_content: We present a method to analyze daily activities, such as meal preparation, using video from an egocentric camera. Our method performs inference about activities, actions, hands, and objects. Daily activities are a challenging domain for activity recognition which are well-suited to an egocentric approach. In contrast to previous activity recognition methods, our approach does not require pre-trained detectors for objects and hands. Instead we demonstrate the ability to learn a hierarchical model of an activity by exploiting the consistent appearance of objects, hands, and actions that results from the egocentric context. We show that joint modeling of activities, actions, and objects leads to superior performance in comparison to the case where they are considered independently. We introduce a novel representation of actions based on object-hand interactions and experimentally demonstrate the superior performance of our representation in comparison to standard activity representations such as bag of words. --- paper_title: Maximum likelihood estimation via the ECM algorithm : a general framework paper_content: Two major reasons for the popularity of the EM algorithm are that its maximum step involves only complete-data maximum likelihood estimation, which is often computationally simple, and that its convergence is stable, with each iteration increasing the likelihood. When the associated complete-data maximum likelihood estimation itself is complicated, EM is less attractive because the M-step is computationally unattractive. In many cases, however, complete-data maximum likelihood estimation is relatively simple when conditional on some function of the parameters being estimated --- paper_title: Learning to recognize objects in egocentric activities paper_content: This paper addresses the problem of learning object models from egocentric video of household activities, using extremely weak supervision. For each activity sequence, we know only the names of the objects which are present within it, and have no other knowledge regarding the appearance or location of objects. The key to our approach is a robust, unsupervised bottom up segmentation method, which exploits the structure of the egocentric domain to partition each frame into hand, object, and background categories. By using Multiple Instance Learning to match object instances across sequences, we discover and localize object occurrences. Object representations are refined through transduction and object-level classifiers are trained. We demonstrate encouraging results in detecting novel object instances using models produced by weakly-supervised learning. --- paper_title: In what ways do eye movements contribute to everyday activities? paper_content: Two recent studies have investigated the relations of eye and hand movements in extended food preparation tasks, and here the results are compared. The tasks could be divided into a series of actions performed on objects. The eyes usually reached the next object in the sequence before any sign of manipulative action, indicating that eye movements are planned into the motor pattern and lead each action. The eyes usually fixated the same object throughout the action upon it, although they often moved on to the next object in the sequence before completion of the preceding action. The specific roles of individual fixations could be identified as locating (establishing the locations of objects for future use), directing (establishing target direction prior to contact), guiding (supervising the relative movements of two or three objects) and checking (establishing whether some particular condition is met, prior to the termination of an action). It is argued that, at the beginning of each action, the oculomotor system is supplied with the identity of the required object, information about its location, and instructions about the nature of the monitoring required during the action. The eye movements during this kind of task are nearly all to task-relevant objects, and thus their control is seen as primarily ‘top-down’, and influenced very little by the ‘intrinsic salience’ of objects. © 2001 Elsevier Science Ltd. All rights reserved. --- paper_title: Understanding egocentric activities paper_content: We present a method to analyze daily activities, such as meal preparation, using video from an egocentric camera. Our method performs inference about activities, actions, hands, and objects. Daily activities are a challenging domain for activity recognition which are well-suited to an egocentric approach. In contrast to previous activity recognition methods, our approach does not require pre-trained detectors for objects and hands. Instead we demonstrate the ability to learn a hierarchical model of an activity by exploiting the consistent appearance of objects, hands, and actions that results from the egocentric context. We show that joint modeling of activities, actions, and objects leads to superior performance in comparison to the case where they are considered independently. We introduce a novel representation of actions based on object-hand interactions and experimentally demonstrate the superior performance of our representation in comparison to standard activity representations such as bag of words. --- paper_title: Modeling Actions through State Changes paper_content: In this paper we present a model of action based on the change in the state of the environment. Many actions involve similar dynamics and hand-object relationships, but differ in their purpose and meaning. The key to differentiating these actions is the ability to identify how they change the state of objects and materials in the environment. We propose a weakly supervised method for learning the object and material states that are necessary for recognizing daily actions. Once these state detectors are learned, we can apply them to input videos and pool their outputs to detect actions. We further demonstrate that our method can be used to segment discrete actions from a continuous video of an activity. Our results outperform state-of-the-art action recognition and activity segmentation results. --- paper_title: Learning to recognize objects in egocentric activities paper_content: This paper addresses the problem of learning object models from egocentric video of household activities, using extremely weak supervision. For each activity sequence, we know only the names of the objects which are present within it, and have no other knowledge regarding the appearance or location of objects. The key to our approach is a robust, unsupervised bottom up segmentation method, which exploits the structure of the egocentric domain to partition each frame into hand, object, and background categories. By using Multiple Instance Learning to match object instances across sequences, we discover and localize object occurrences. Object representations are refined through transduction and object-level classifiers are trained. We demonstrate encouraging results in detecting novel object instances using models produced by weakly-supervised learning. --- paper_title: Fast Bayesian Inference in Dirichlet Process Mixture Models paper_content: There has been increasing interest in applying Bayesian nonparametric methods in large samples and high dimensions. As Markov chain Monte Carlo (MCMC) algorithms are often infeasible, there is a pressing need for much faster algorithms. This article proposes a fast approach for inference in Dirichlet process mixture (DPM) models. Viewing the partitioning of subjects into clusters as a model selection problem, we propose a sequential greedy search algorithm for selecting the partition. Then, when conjugate priors are chosen, the resulting posterior conditionally on the selected partition is available in closed form. This approach allows testing of parametric models versus nonparametric alternatives based on Bayes factors. We evaluate the approach using simulation studies and compare it with four other fast nonparametric methods in the literature. We apply the proposed approach to three datasets including one from a large epidemiologic study. Matlab codes for the simulation and data analyses using the propo... --- paper_title: Fast unsupervised ego-action learning for first-person sports videos paper_content: Portable high-quality sports cameras (e.g. head or helmet mounted) built for recording dynamic first-person video footage are becoming a common item among many sports enthusiasts. We address the novel task of discovering first-person action categories (which we call ego-actions) which can be useful for such tasks as video indexing and retrieval. In order to learn ego-action categories, we investigate the use of motion-based histograms and unsupervised learning algorithms to quickly cluster video content. Our approach assumes a completely unsupervised scenario, where labeled training videos are not available, videos are not pre-segmented and the number of ego-action categories are unknown. In our proposed framework we show that a stacked Dirichlet process mixture model can be used to automatically learn a motion histogram codebook and the set of ego-action categories. We quantitatively evaluate our approach on both in-house and public YouTube videos and demonstrate robust ego-action categorization across several sports genres. Comparative analysis shows that our approach outperforms other state-of-the-art topic models with respect to both classification accuracy and computational speed. Preliminary results indicate that on average, the categorical content of a 10 minute video sequence can be indexed in under 5 seconds. --- paper_title: First-Person Activity Recognition: What Are They Doing to Me? paper_content: This paper discusses the problem of recognizing interaction-level human activities from a first-person viewpoint. The goal is to enable an observer (e.g., a robot or a wearable camera) to understand 'what activity others are performing to it' from continuous video inputs. These include friendly interactions such as 'a person hugging the observer' as well as hostile interactions like 'punching the observer' or 'throwing objects to the observer', whose videos involve a large amount of camera ego-motion caused by physical interactions. The paper investigates multi-channel kernels to integrate global and local motion information, and presents a new activity learning/recognition methodology that explicitly considers temporal structures displayed in first-person activity videos. In our experiments, we not only show classification results with segmented videos, but also confirm that our new approach is able to detect activities from continuous videos reliably. --- paper_title: SenseCam: A Retrospective Memory Aid paper_content: This paper presents a novel ubiquitous computing device, the SenseCam, a sensor augmented wearable stills camera. SenseCam is designed to capture a digital record of the wearer's day, by recording a series of images and capturing a log of sensor data. We believe that reviewing this information will help the wearer recollect aspects of earlier experiences that have subsequently been forgotten, and thereby form a powerful retrospective memory aid. In this paper we review existing work on memory aids and conclude that there is scope for an improved device. We then report on the design of SenseCam in some detail for the first time. We explain the details of a first in-depth user study of this device, a 12-month clinical trial with a patient suffering from amnesia. The results of this initial evaluation are extremely promising; periodic review of images of events recorded by SenseCam results in significant recall of those events by the patient, which was previously impossible. We end the paper with a discussion of future work, including the application of SenseCam to a wider audience, such as those with neurodegenerative conditions such as Alzheimer's disease. --- paper_title: Rapid object detection using a boosted cascade of simple features paper_content: This paper describes a machine learning approach for visual object detection which is capable of processing images extremely rapidly and achieving high detection rates. This work is distinguished by three key contributions. The first is the introduction of a new image representation called the "integral image" which allows the features used by our detector to be computed very quickly. The second is a learning algorithm, based on AdaBoost, which selects a small number of critical visual features from a larger set and yields extremely efficient classifiers. The third contribution is a method for combining increasingly more complex classifiers in a "cascade" which allows background regions of the image to be quickly discarded while spending more computation on promising object-like regions. The cascade can be viewed as an object specific focus-of-attention mechanism which unlike previous approaches provides statistical guarantees that discarded regions are unlikely to contain the object of interest. In the domain of face detection the system yields detection rates comparable to the best previous systems. Used in real-time applications, the detector runs at 15 frames per second without resorting to image differencing or skin color detection. --- paper_title: Constrained parametric min-cuts for automatic object segmentation paper_content: We present a novel framework for generating and ranking plausible objects hypotheses in an image using bottom-up processes and mid-level cues. The object hypotheses are represented as figure-ground segmentations, and are extracted automatically, without prior knowledge about properties of individual object classes, by solving a sequence of constrained parametric min-cut problems (CPMC) on a regular image grid. We then learn to rank the object hypotheses by training a continuous model to predict how plausible the segments are, given their mid-level region properties. We show that this algorithm significantly outperforms the state of the art for low-level segmentation in the VOC09 segmentation dataset. It achieves the same average best segmentation covering as the best performing technique to date [2], 0.61 when using just the top 7 ranked segments, instead of the full hierarchy in [2]. Our method achieves 0.78 average best covering using 154 segments. In a companion paper [18], we also show that the algorithm achieves state-of-the art results when used in a segmentation-based recognition pipeline. --- paper_title: The blur effect: perception and estimation with a new no-reference perceptual blur metric paper_content: To achieve the best image quality, noise and artifacts are generally removed at the cost of a loss of details generating the blur effect. To control and quantify the emergence of the blur effect, blur metrics have already been proposed in the literature. By associating the blur effect with the edge spreading, these metrics are sensitive not only to the threshold choice to classify the edge, but also to the presence of noise which can mislead the edge detection. Based on the observation that we have difficulties to perceive differences between a blurred image and the same reblurred image, we propose a new approach which is not based on transient characteristics but on the discrimination between different levels of blur perceptible on the same picture. Using subjective tests and psychophysics functions, we validate our blur perception theory for a set of pictures which are naturally unsharp or more or less blurred through one or two-dimensional low-pass filters. Those tests show the robustness and the ability of the metric to evaluate not only the blur introduced by a restoration processing but also focal blur or motion blur. Requiring no reference and a low cost implementation, this new perceptual blur metric is applicable in a large domain from a simple metric to a means to fine-tune artifacts corrections. --- paper_title: Detecting activities of daily living in first-person camera views paper_content: We present a novel dataset and novel algorithms for the problem of detecting activities of daily living (ADL) in firstperson camera views. We have collected a dataset of 1 million frames of dozens of people performing unscripted, everyday activities. The dataset is annotated with activities, object tracks, hand positions, and interaction events. ADLs differ from typical actions in that they can involve long-scale temporal structure (making tea can take a few minutes) and complex object interactions (a fridge looks different when its door is open). We develop novel representations including (1) temporal pyramids, which generalize the well-known spatial pyramid to approximate temporal correspondence when scoring a model and (2) composite object models that exploit the fact that objects look different when being interacted with. We perform an extensive empirical evaluation and demonstrate that our novel representations produce a two-fold improvement over traditional approaches. Our analysis suggests that real-world ADL recognition is “all about the objects,” and in particular, “all about the objects being interacted with.” --- paper_title: Investigating keyframe selection methods in the novel domain of passively captured visual lifelogs paper_content: The SenseCam is a passive capture wearable camera and when worn continuously it takes an average of 1,900 images per day. It can be used to create a personal lifelog or visual recording of a wearer's life which can be helpful as an aid to human memory. For such a large amount of visual information to be useful, it needs to be structured into "events", which can be achieved through automatic segmentation. An important component of this structuring process is the selection of keyframes to represent individual events. This work investigates a variety of techniques for the selection of a single representative keyframe image from each event, in order to provide the user with an instant visual summary of that event. In our experiments we use a large test set of 2,232 lifelog events collected by 5 users over a time period of one month each. We propose a novel keyframe selection technique which seeks to select the image with the highest "quality" as the keyframe. The inclusion of "quality" approaches in keyframe selection is demonstrated to be useful owing to the high variability in image visual quality within passively captured image collections. --- paper_title: What is an object? paper_content: We present a generic objectness measure, quantifying how likely it is for an image window to contain an object of any class. We explicitly train it to distinguish objects with a well-defined boundary in space, such as cows and telephones, from amorphous background elements, such as grass and road. The measure combines in a Bayesian framework several image cues measuring characteristics of objects, such as appearing different from their surroundings and having a closed boundary. This includes an innovative cue measuring the closed boundary characteristic. In experiments on the challenging PASCAL VOC 07 dataset, we show this new cue to outperform a state-of-the-art saliency measure [17], and the combined measure to perform better than any cue alone. Finally, we show how to sample windows from an image according to their objectness distribution and give an algorithm to employ them as location priors for modern class-specific object detectors. In experiments on PASCAL VOC 07 we show this greatly reduces the number of windows evaluated by class-specific object detectors. --- paper_title: Story-Driven Summarization for Egocentric Video paper_content: We present a video summarization approach that discovers the story of an egocentric video. Given a long input video, our method selects a short chain of video sub shots depicting the essential events. Inspired by work in text analysis that links news articles over time, we define a random-walk based metric of influence between sub shots that reflects how visual objects contribute to the progression of events. Using this influence metric, we define an objective for the optimal k-subs hot summary. Whereas traditional methods optimize a summary's diversity or representative ness, ours explicitly accounts for how one sub-event "leads to" another-which, critically, captures event connectivity beyond simple object co-occurrence. As a result, our summaries provide a better sense of story. We apply our approach to over 12 hours of daily activity video taken from 23 unique camera wearers, and systematically evaluate its quality compared to multiple baselines with 34 human subjects. --- paper_title: Connecting the dots between news articles paper_content: The process of extracting useful knowledge from large datasets has become one of the most pressing problems in today's society. The problem spans entire sectors, from scientists to intelligence analysts and web users, all of whom are constantly struggling to keep up with the larger and larger amounts of content published every day. With this much data, it is often easy to miss the big picture. ::: ::: In this paper, we investigate methods for automatically connecting the dots - providing a structured, easy way to navigate within a new topic and discover hidden connections. We focus on the news domain: given two news articles, our system automatically finds a coherent chain linking them together. For example, it can recover the chain of events leading from the decline of home prices (2007) to the health-care debate (2009). ::: ::: We formalize the characteristics of a good chain and provide efficient algorithms to connect two fixed endpoints. We incorporate user feedback into our framework, allowing the stories to be refined and personalized. Finally, we evaluate our algorithm over real news data. Our user studies demonstrate the algorithm's effectiveness in helping users understanding the news. --- paper_title: Discovering important people and objects for egocentric video summarization paper_content: We present a video summarization approach for egocentric or “wearable” camera data. Given hours of video, the proposed method produces a compact storyboard summary of the camera wearer's day. In contrast to traditional keyframe selection techniques, the resulting summary focuses on the most important objects and people with which the camera wearer interacts. To accomplish this, we develop region cues indicative of high-level saliency in egocentric video — such as the nearness to hands, gaze, and frequency of occurrence — and learn a regressor to predict the relative importance of any new region based on these cues. Using these predictions and a simple form of temporal event detection, our method selects frames for the storyboard that reflect the key object-driven happenings. Critically, the approach is neither camera-wearer-specific nor object-specific; that means the learned importance metric need not be trained for a given user or context, and it can predict the importance of objects and people that have never been seen previously. Our results with 17 hours of egocentric data show the method's promise relative to existing techniques for saliency and summarization. --- paper_title: SenseCam: A Retrospective Memory Aid paper_content: This paper presents a novel ubiquitous computing device, the SenseCam, a sensor augmented wearable stills camera. SenseCam is designed to capture a digital record of the wearer's day, by recording a series of images and capturing a log of sensor data. We believe that reviewing this information will help the wearer recollect aspects of earlier experiences that have subsequently been forgotten, and thereby form a powerful retrospective memory aid. In this paper we review existing work on memory aids and conclude that there is scope for an improved device. We then report on the design of SenseCam in some detail for the first time. We explain the details of a first in-depth user study of this device, a 12-month clinical trial with a patient suffering from amnesia. The results of this initial evaluation are extremely promising; periodic review of images of events recorded by SenseCam results in significant recall of those events by the patient, which was previously impossible. We end the paper with a discussion of future work, including the application of SenseCam to a wider audience, such as those with neurodegenerative conditions such as Alzheimer's disease. --- paper_title: Aggregating local descriptors into a compact image representation paper_content: We address the problem of image search on a very large scale, where three constraints have to be considered jointly: the accuracy of the search, its efficiency, and the memory usage of the representation. We first propose a simple yet efficient way of aggregating local image descriptors into a vector of limited dimension, which can be viewed as a simplification of the Fisher kernel representation. We then show how to jointly optimize the dimension reduction and the indexing algorithm, so that it best preserves the quality of vector comparison. The evaluation shows that our approach significantly outperforms the state of the art: the search accuracy is comparable to the bag-of-features approach for an image representation that fits in 20 bytes. Searching a 10 million image dataset takes about 50ms. --- paper_title: Novelty detection from an ego-centric perspective paper_content: This paper demonstrates a system for the automatic extraction of novelty in images captured from a small video camera attached to a subject's chest, replicating his visual perspective, while performing activities which are repeated daily. Novelty is detected when a (sub)sequence cannot be registered to previously stored sequences captured while performing the same daily activity. Sequence registration is performed by measuring appearance and geometric similarity of individual frames and exploiting the invariant temporal order of the activity. Experimental results demonstrate that this is a robust way to detect novelties induced by variations in the wearer's ego-motion such as stopping and talking to a person. This is an essentially new and generic way of automatically extracting information of interest to the camera wearer and can be used as input to a system for life logging or memory support. --- paper_title: Social interactions: A first-person perspective paper_content: This paper presents a method for the detection and recognition of social interactions in a day-long first-person video of u social event, like a trip to an amusement park. The location and orientation of faces are estimated and used to compute the line of sight for each face. The context provided by all the faces in a frame is used to convert the lines of sight into locations in space to which individuals attend. Further, individuals are assigned roles based on their patterns of attention. The rotes and locations of individuals are analyzed over time to detect and recognize the types of social interactions. In addition to patterns of face locations and attention, the head movements of the first-person can provide additional useful cues as to their attentional focus. We demonstrate encouraging results on detection and recognition of social interactions in first-person videos captured from multiple days of experience in amusement parks. --- paper_title: Egocentric recognition of handled objects: Benchmark and analysis paper_content: Recognizing objects being manipulated in hands can provide essential information about a person's activities and have far-reaching impacts on the application of vision in everyday life. The egocentric viewpoint from a wearable camera has unique advantages in recognizing handled objects, such as having a close view and seeing objects in their natural positions. We collect a comprehensive dataset and analyze the feasibilities and challenges of the egocentric recognition of handled objects. We use a lapel-worn camera and record uncompressed video streams as human subjects manipulate objects in daily activities. We use 42 day-to-day objects that vary in size, shape, color and textureness. 10 video sequences are shot for each object under different illuminations and backgrounds. We use this dataset and a SIFT-based recognition system to analyze and quantitatively characterize the main challenges in egocentric object recognition, such as motion blur and hand occlusion, along with its unique constraints, such as hand color, location prior and temporal consistency. SIFT-based recognition has an average recognition rate of 12%, and reaches 20% through enforcing temporal consistency. We use simulations to estimate the upper bound for SIFT-based recognition at 64%, the loss of accuracy due to background clutter at 20%, and that of hand occlusion at 13%. Our quantitative evaluations show that the egocentric recognition of handled objects is a challenging but feasible problem with many unique characteristics and many opportunities for future research. --- paper_title: Hidden conditional random fields for phone classification paper_content: In this paper, we show the novel application of hidden conditional random fields (HCRFs) – conditional random fields with hidden state sequences – for modeling speech. Hidden state sequences are critical for modeling the non-stationarity of speech signals. We show that HCRFs can easily be trained using the simple direct optimization technique of stochastic gradient descent. We present the results on the TIMIT phone classification task and show that HCRFs outperforms comparable ML and CML/MMI trained HMMs. In fact, HCRF results on this task are the best single classifier results known to us. We note that the HCRF framework is easily extensible to recognition since it is a state and label sequence modeling technique. We also note that HCRFs have the ability to handle complex features without any change in training procedure. --- paper_title: Detecting activities of daily living in first-person camera views paper_content: We present a novel dataset and novel algorithms for the problem of detecting activities of daily living (ADL) in firstperson camera views. We have collected a dataset of 1 million frames of dozens of people performing unscripted, everyday activities. The dataset is annotated with activities, object tracks, hand positions, and interaction events. ADLs differ from typical actions in that they can involve long-scale temporal structure (making tea can take a few minutes) and complex object interactions (a fridge looks different when its door is open). We develop novel representations including (1) temporal pyramids, which generalize the well-known spatial pyramid to approximate temporal correspondence when scoring a model and (2) composite object models that exploit the fact that objects look different when being interacted with. We perform an extensive empirical evaluation and demonstrate that our novel representations produce a two-fold improvement over traditional approaches. Our analysis suggests that real-world ADL recognition is “all about the objects,” and in particular, “all about the objects being interacted with.” --- paper_title: Learning to recognize objects in egocentric activities paper_content: This paper addresses the problem of learning object models from egocentric video of household activities, using extremely weak supervision. For each activity sequence, we know only the names of the objects which are present within it, and have no other knowledge regarding the appearance or location of objects. The key to our approach is a robust, unsupervised bottom up segmentation method, which exploits the structure of the egocentric domain to partition each frame into hand, object, and background categories. By using Multiple Instance Learning to match object instances across sequences, we discover and localize object occurrences. Object representations are refined through transduction and object-level classifiers are trained. We demonstrate encouraging results in detecting novel object instances using models produced by weakly-supervised learning. --- paper_title: Story-Driven Summarization for Egocentric Video paper_content: We present a video summarization approach that discovers the story of an egocentric video. Given a long input video, our method selects a short chain of video sub shots depicting the essential events. Inspired by work in text analysis that links news articles over time, we define a random-walk based metric of influence between sub shots that reflects how visual objects contribute to the progression of events. Using this influence metric, we define an objective for the optimal k-subs hot summary. Whereas traditional methods optimize a summary's diversity or representative ness, ours explicitly accounts for how one sub-event "leads to" another-which, critically, captures event connectivity beyond simple object co-occurrence. As a result, our summaries provide a better sense of story. We apply our approach to over 12 hours of daily activity video taken from 23 unique camera wearers, and systematically evaluate its quality compared to multiple baselines with 34 human subjects. --- paper_title: Fast unsupervised ego-action learning for first-person sports videos paper_content: Portable high-quality sports cameras (e.g. head or helmet mounted) built for recording dynamic first-person video footage are becoming a common item among many sports enthusiasts. We address the novel task of discovering first-person action categories (which we call ego-actions) which can be useful for such tasks as video indexing and retrieval. In order to learn ego-action categories, we investigate the use of motion-based histograms and unsupervised learning algorithms to quickly cluster video content. Our approach assumes a completely unsupervised scenario, where labeled training videos are not available, videos are not pre-segmented and the number of ego-action categories are unknown. In our proposed framework we show that a stacked Dirichlet process mixture model can be used to automatically learn a motion histogram codebook and the set of ego-action categories. We quantitatively evaluate our approach on both in-house and public YouTube videos and demonstrate robust ego-action categorization across several sports genres. Comparative analysis shows that our approach outperforms other state-of-the-art topic models with respect to both classification accuracy and computational speed. Preliminary results indicate that on average, the categorical content of a 10 minute video sequence can be indexed in under 5 seconds. --- paper_title: Egocentric recognition of handled objects: Benchmark and analysis paper_content: Recognizing objects being manipulated in hands can provide essential information about a person's activities and have far-reaching impacts on the application of vision in everyday life. The egocentric viewpoint from a wearable camera has unique advantages in recognizing handled objects, such as having a close view and seeing objects in their natural positions. We collect a comprehensive dataset and analyze the feasibilities and challenges of the egocentric recognition of handled objects. We use a lapel-worn camera and record uncompressed video streams as human subjects manipulate objects in daily activities. We use 42 day-to-day objects that vary in size, shape, color and textureness. 10 video sequences are shot for each object under different illuminations and backgrounds. We use this dataset and a SIFT-based recognition system to analyze and quantitatively characterize the main challenges in egocentric object recognition, such as motion blur and hand occlusion, along with its unique constraints, such as hand color, location prior and temporal consistency. SIFT-based recognition has an average recognition rate of 12%, and reaches 20% through enforcing temporal consistency. We use simulations to estimate the upper bound for SIFT-based recognition at 64%, the loss of accuracy due to background clutter at 20%, and that of hand occlusion at 13%. Our quantitative evaluations show that the egocentric recognition of handled objects is a challenging but feasible problem with many unique characteristics and many opportunities for future research. --- paper_title: Figure-ground segmentation improves handled object recognition in egocentric video paper_content: Identifying handled objects, i.e. objects being manipulated by a user, is essential for recognizing the person's activities. An egocentric camera as worn on the body enjoys many advantages such as having a natural first-person view and not needing to instrument the environment. It is also a challenging setting, where background clutter is known to be a major source of problems and is difficult to handle with the camera constantly and arbitrarily moving. In this work we develop a bottom-up motion-based approach to robustly segment out foreground objects in egocentric video and show that it greatly improves object recognition accuracy. Our key insight is that egocentric video of object manipulation is a special domain and many domain-specific cues can readily help. We compute dense optical flow and fit it into multiple affine layers. We then use a max-margin classifier to combine motion with empirical knowledge of object location and background movement as well as temporal cues of support region and color appearance. We evaluate our segmentation algorithm on the large Intel Egocentric Object Recognition dataset with 42 objects and 100K frames. We show that, when combined with temporal integration, figure-ground segmentation improves the accuracy of a SIFT-based recognition system from 33% to 60%, and that of a latent-HOG system from 64% to 86%. --- paper_title: Learning to Recognize Daily Actions using Gaze paper_content: We present a probabilistic generative model for simultaneously recognizing daily actions and predicting gaze locations in videos recorded from an egocentric camera. We focus on activities requiring eye-hand coordination and model the spatio-temporal relationship between the gaze point, the scene objects, and the action label. Our model captures the fact that the distribution of both visual features and object occurrences in the vicinity of the gaze point is correlated with the verb-object pair describing the action. It explicitly incorporates known properties of gaze behavior from the psychology literature, such as the temporal delay between fixation and manipulation events. We present an inference method that can predict the best sequence of gaze locations and the associated action label from an input sequence of images. We demonstrate improvements in action recognition rates and gaze prediction accuracy relative to state-of-the-art methods, on two new datasets that contain egocentric videos of daily activities and gaze. --- paper_title: Detecting activities of daily living in first-person camera views paper_content: We present a novel dataset and novel algorithms for the problem of detecting activities of daily living (ADL) in firstperson camera views. We have collected a dataset of 1 million frames of dozens of people performing unscripted, everyday activities. The dataset is annotated with activities, object tracks, hand positions, and interaction events. ADLs differ from typical actions in that they can involve long-scale temporal structure (making tea can take a few minutes) and complex object interactions (a fridge looks different when its door is open). We develop novel representations including (1) temporal pyramids, which generalize the well-known spatial pyramid to approximate temporal correspondence when scoring a model and (2) composite object models that exploit the fact that objects look different when being interacted with. We perform an extensive empirical evaluation and demonstrate that our novel representations produce a two-fold improvement over traditional approaches. Our analysis suggests that real-world ADL recognition is “all about the objects,” and in particular, “all about the objects being interacted with.” --- paper_title: Investigating keyframe selection methods in the novel domain of passively captured visual lifelogs paper_content: The SenseCam is a passive capture wearable camera and when worn continuously it takes an average of 1,900 images per day. It can be used to create a personal lifelog or visual recording of a wearer's life which can be helpful as an aid to human memory. For such a large amount of visual information to be useful, it needs to be structured into "events", which can be achieved through automatic segmentation. An important component of this structuring process is the selection of keyframes to represent individual events. This work investigates a variety of techniques for the selection of a single representative keyframe image from each event, in order to provide the user with an instant visual summary of that event. In our experiments we use a large test set of 2,232 lifelog events collected by 5 users over a time period of one month each. We propose a novel keyframe selection technique which seeks to select the image with the highest "quality" as the keyframe. The inclusion of "quality" approaches in keyframe selection is demonstrated to be useful owing to the high variability in image visual quality within passively captured image collections. --- paper_title: Understanding egocentric activities paper_content: We present a method to analyze daily activities, such as meal preparation, using video from an egocentric camera. Our method performs inference about activities, actions, hands, and objects. Daily activities are a challenging domain for activity recognition which are well-suited to an egocentric approach. In contrast to previous activity recognition methods, our approach does not require pre-trained detectors for objects and hands. Instead we demonstrate the ability to learn a hierarchical model of an activity by exploiting the consistent appearance of objects, hands, and actions that results from the egocentric context. We show that joint modeling of activities, actions, and objects leads to superior performance in comparison to the case where they are considered independently. We introduce a novel representation of actions based on object-hand interactions and experimentally demonstrate the superior performance of our representation in comparison to standard activity representations such as bag of words. --- paper_title: Modeling Actions through State Changes paper_content: In this paper we present a model of action based on the change in the state of the environment. Many actions involve similar dynamics and hand-object relationships, but differ in their purpose and meaning. The key to differentiating these actions is the ability to identify how they change the state of objects and materials in the environment. We propose a weakly supervised method for learning the object and material states that are necessary for recognizing daily actions. Once these state detectors are learned, we can apply them to input videos and pool their outputs to detect actions. We further demonstrate that our method can be used to segment discrete actions from a continuous video of an activity. Our results outperform state-of-the-art action recognition and activity segmentation results. --- paper_title: Learning to recognize objects in egocentric activities paper_content: This paper addresses the problem of learning object models from egocentric video of household activities, using extremely weak supervision. For each activity sequence, we know only the names of the objects which are present within it, and have no other knowledge regarding the appearance or location of objects. The key to our approach is a robust, unsupervised bottom up segmentation method, which exploits the structure of the egocentric domain to partition each frame into hand, object, and background categories. By using Multiple Instance Learning to match object instances across sequences, we discover and localize object occurrences. Object representations are refined through transduction and object-level classifiers are trained. We demonstrate encouraging results in detecting novel object instances using models produced by weakly-supervised learning. --- paper_title: First-Person Activity Recognition: What Are They Doing to Me? paper_content: This paper discusses the problem of recognizing interaction-level human activities from a first-person viewpoint. The goal is to enable an observer (e.g., a robot or a wearable camera) to understand 'what activity others are performing to it' from continuous video inputs. These include friendly interactions such as 'a person hugging the observer' as well as hostile interactions like 'punching the observer' or 'throwing objects to the observer', whose videos involve a large amount of camera ego-motion caused by physical interactions. The paper investigates multi-channel kernels to integrate global and local motion information, and presents a new activity learning/recognition methodology that explicitly considers temporal structures displayed in first-person activity videos. In our experiments, we not only show classification results with segmented videos, but also confirm that our new approach is able to detect activities from continuous videos reliably. --- paper_title: Story-Driven Summarization for Egocentric Video paper_content: We present a video summarization approach that discovers the story of an egocentric video. Given a long input video, our method selects a short chain of video sub shots depicting the essential events. Inspired by work in text analysis that links news articles over time, we define a random-walk based metric of influence between sub shots that reflects how visual objects contribute to the progression of events. Using this influence metric, we define an objective for the optimal k-subs hot summary. Whereas traditional methods optimize a summary's diversity or representative ness, ours explicitly accounts for how one sub-event "leads to" another-which, critically, captures event connectivity beyond simple object co-occurrence. As a result, our summaries provide a better sense of story. We apply our approach to over 12 hours of daily activity video taken from 23 unique camera wearers, and systematically evaluate its quality compared to multiple baselines with 34 human subjects. --- paper_title: Discovering important people and objects for egocentric video summarization paper_content: We present a video summarization approach for egocentric or “wearable” camera data. Given hours of video, the proposed method produces a compact storyboard summary of the camera wearer's day. In contrast to traditional keyframe selection techniques, the resulting summary focuses on the most important objects and people with which the camera wearer interacts. To accomplish this, we develop region cues indicative of high-level saliency in egocentric video — such as the nearness to hands, gaze, and frequency of occurrence — and learn a regressor to predict the relative importance of any new region based on these cues. Using these predictions and a simple form of temporal event detection, our method selects frames for the storyboard that reflect the key object-driven happenings. Critically, the approach is neither camera-wearer-specific nor object-specific; that means the learned importance metric need not be trained for a given user or context, and it can predict the importance of objects and people that have never been seen previously. Our results with 17 hours of egocentric data show the method's promise relative to existing techniques for saliency and summarization. --- paper_title: Egocentric recognition of handled objects: Benchmark and analysis paper_content: Recognizing objects being manipulated in hands can provide essential information about a person's activities and have far-reaching impacts on the application of vision in everyday life. The egocentric viewpoint from a wearable camera has unique advantages in recognizing handled objects, such as having a close view and seeing objects in their natural positions. We collect a comprehensive dataset and analyze the feasibilities and challenges of the egocentric recognition of handled objects. We use a lapel-worn camera and record uncompressed video streams as human subjects manipulate objects in daily activities. We use 42 day-to-day objects that vary in size, shape, color and textureness. 10 video sequences are shot for each object under different illuminations and backgrounds. We use this dataset and a SIFT-based recognition system to analyze and quantitatively characterize the main challenges in egocentric object recognition, such as motion blur and hand occlusion, along with its unique constraints, such as hand color, location prior and temporal consistency. SIFT-based recognition has an average recognition rate of 12%, and reaches 20% through enforcing temporal consistency. We use simulations to estimate the upper bound for SIFT-based recognition at 64%, the loss of accuracy due to background clutter at 20%, and that of hand occlusion at 13%. Our quantitative evaluations show that the egocentric recognition of handled objects is a challenging but feasible problem with many unique characteristics and many opportunities for future research. --- paper_title: Temporal segmentation and activity classification from first-person sensing paper_content: Temporal segmentation of human motion into actions is central to the understanding and building of computational models of human motion and activity recognition. Several issues contribute to the challenge of temporal segmentation and classification of human motion. These include the large variability in the temporal scale and periodicity of human actions, the complexity of representing articulated motion, and the exponential nature of all possible movement combinations. We provide initial results from investigating two distinct problems -classification of the overall task being performed, and the more difficult problem of classifying individual frames over time into specific actions. We explore first-person sensing through a wearable camera and inertial measurement units (IMUs) for temporally segmenting human motion into actions and performing activity classification in the context of cooking and recipe preparation in a natural environment. We present baseline results for supervised and unsupervised temporal segmentation, and recipe recognition in the CMU-multimodal activity database (CMU-MMAC). --- paper_title: Investigating keyframe selection methods in the novel domain of passively captured visual lifelogs paper_content: The SenseCam is a passive capture wearable camera and when worn continuously it takes an average of 1,900 images per day. It can be used to create a personal lifelog or visual recording of a wearer's life which can be helpful as an aid to human memory. For such a large amount of visual information to be useful, it needs to be structured into "events", which can be achieved through automatic segmentation. An important component of this structuring process is the selection of keyframes to represent individual events. This work investigates a variety of techniques for the selection of a single representative keyframe image from each event, in order to provide the user with an instant visual summary of that event. In our experiments we use a large test set of 2,232 lifelog events collected by 5 users over a time period of one month each. We propose a novel keyframe selection technique which seeks to select the image with the highest "quality" as the keyframe. The inclusion of "quality" approaches in keyframe selection is demonstrated to be useful owing to the high variability in image visual quality within passively captured image collections. ---	Title: A Survey on Recent Advances of Computer Vision Algorithms for Egocentric Video Section 1: Introduction Description 1: Provide an overview of the significance and challenges of egocentric video in computer vision, including the practical applications and benefits of wearable cameras. Section 2: Recent Work Description 2: Summarize recent advancements in the field of egocentric video, categorized into object recognition, activity and action detection, and life logging video. Section 3: Object Recognition Description 3: Discuss various approaches and challenges in recognizing objects from egocentric videos, including the analysis, datasets used, and results obtained by different researchers. Section 4: Activity and Action Detection Description 4: Explore methods and evaluations concerning the detection and classification of activities and actions in egocentric video, distinguishing between simple actions and complex activities. Section 5: Life Logging Video Description 5: Delve into techniques for summarizing life logging video data, focusing on keyframe selection, novelty detection, and social interaction recognition. Section 6: Datasets Description 6: Provide a comprehensive overview of publicly available datasets relevant to egocentric video, detailing the types of data and annotations included. Section 7: Summary and Comparison Description 7: Summarize key points from prior sections, comparing methodologies and findings, emphasizing major trends and common techniques in the domain. Section 8: Conclusion Description 8: Conclude with a reflection on the progress and current state of research in egocentric video, noting emerging patterns and potential future directions.
Episturmian words: a survey	29	--- paper_title: Sequences With Grouped Factors paper_content: A connector for making electrical connection to a flexible conductor cable is disclosed which includes a block member having a first surface and a plurality of resilient electrical contact members projecting from the block member. Each of the contact members includes a portion substantially parallel to the first surface of the block member which terminates in a free end, with the parallel portions of the contact members and the first surface of the block member defining a space for receiving a flexible conductor cable to which electrical contact is to be made. The connector further includes a cover member having an inner surface. The cover member and block member are affixed together in such a manner that the inner surface of the cover member depresses the contact members in the direction of the first surface of the block member, whereby the free ends of the contact members exert a spring force against any flexible conductor cable inserted in the defined cable receiving space to make electrical contact with the flexible conductor cable and to hold the flexible conductor cable securely in the electrical connector. --- paper_title: Palindromic factors of billiard words paper_content: We study palindromic factors of billiard words, in any dimension. There are differences between the two-dimensional case, and higher dimension. Arbitrary long palindrome factors exist in any dimension, but arbitrary long palindromic prefixes exist in general only in dimension 2. --- paper_title: Fraenkel's conjecture for six sequences paper_content: Abstract A striking conjecture of Fraenkel asserts that every decomposition of Z >0 into m ⩾3 sets {⌊α i n+β i ⌋} n∈ Z >0 with α i and β i real, α i >1 and α i 's distinct for i =1,…, m satisfies {α 1 ,…,α m }= 2 m −1 2 k : 0⩽k . Fraenkel's conjecture was proved by Morikawa if m =3 and, under some condition, if m =4. Proofs in terms of balanced sequences have been given for m =3 by the author and for m =4 by Altman, Gaujal and Hordijk. In the present paper we use the latter approach to establish Fraenkel's conjecture for m =5 and for m =6. --- paper_title: Coding rotations on intervals paper_content: We show that the coding of rotation by $\alpha$ on $m$ intervals with rationally independent lengths can be recoded over $m$ Sturmian words of angle $\alpha.$ ::: More precisely, for a given $m$ an universal automaton is constructed such that the edge indexed by the vector of values of the $i$th letter on each Sturmian word gives the value of the $i$th letter of the coding of rotation. --- paper_title: A generalization of Sturmian sequences; combinatorial structure and transcendence paper_content: We investigate a class of minimal sequences on a finite alphabet Ak = {1,2,...,k} having (k - 1)n + 1 distinct subwords of length n. These sequences, originally defined by P. Arnoux and G. Rauzy, are a natural generalization of binary Sturmian sequences. We describe two simple combinatorial algorithms for constructing characteristic Arnoux-Rauzy sequences (one of which is new even in the Sturmian case). Arnoux-Rauzy sequences arising from fixed points of primitive morphisms are characterized by an underlying periodic structure. We show that every Arnoux-Rauzy sequence contains arbitrarily large subwords of the form V^2+e and, in the Sturmian case, arbitrarily large subwords of the form V^3+e. Finally, we prove that an irrational number whose base b-digit expansion is an Arnoux-Rauzy sequence is transcendental. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Three distance theorems and combinatorics on words paper_content: The aim of this paper is to investigate the connection between some generalizations of the three distance theorem and combinatorics on words for sequences defined as codings of irrational rotations on the unit circle. We also give some new results concerning the frequencies of factors for such sequences. --- paper_title: Automatic Sequences: Theory, Applications, Generalizations paper_content: Preface 1. Stringology 2. Number theory and algebra 3. Numeration systems 4. Finite automata and other models of computation 5. Automatic sequences 6. Uniform morphisms and automatic sequences 7. Morphic sequences 8. Frequency of letters 9. Characteristic words 10. Subwords 11. Cobham's theorem 12. Formal power series 13. Automatic real numbers 14. Multidimensional automatic sequences 15. Automaticity 16. k-regular sequences 17. Physics Appendix. Hints, references and solutions for selected exercises Bibliography Index. --- paper_title: Balances for fixed points of primitive substitutions paper_content: An infinite word defined over a finite alphabet A is balanced if for any pair (ω,ω') of factors of the same length and for any letter a in the alphabet \|\|ω\|a - \|ω'\|a\| ≤ 1, where \|ω\|a denotes the number of occurrences of the letter a in the word ω. In this paper, we generalize this notion and introduce a measure of balance for an infinite sequence. In the case of fixed points of primitive substitutions, we show that the asymptotic behaviour of this measure is in part ruled by the spectrum of the incidence matrix associated with the substitution. Connections with frequencies of letters and other balance properties are also discussed. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: Transcendence of Sturmian or morphic continued fractions paper_content: Abstract We prove, using a theorem of W. Schmidt, that if the sequence of partial quotients of the continued fraction expansion of a positive irrational real number takes only two values, and begins with arbitrary long blocks which are “almost squares,” then this number is either quadratic or transcendental. This result applies in particular to real numbers whose partial quotients form a Sturmian (or quasi-Sturmian) sequence, or are given by the sequence (1+(⌊ nα ⌋ mod 2)) n ⩾0 , or are a “repetitive” fixed point of a binary morphism satisfying some technical conditions. --- paper_title: Generalized balances in Sturmian words paper_content: One of the numerous characterizations of Sturmian words is based on the notion of balance. An infinite word X on the {0, 1} alphabet is balanced if, given two factors of X, w and w', having the same length, the difference between the number of 0's in w (denoted by \|w\|0) and the number of 0's in w' is at most 1, i.e. \|\|w\|0 - \|w'\|0\| ≤ 1. It is well known that an aperiodic word is Sturmian if and only if it is balanced.In this paper, the balance notion is generalized by considering the number of occurrences of a word u in w (denoted by \|w\|u,) and w'. The following is obtained. Theorem. Let x be a Sturmian word. Let u, w and w' be three factors of x. Then, \|w\| = \|w'\| ⇒ \|\|w\|u - \|w'\|u\| ≤ \|u\|.Another balance property, called equilibrium, is also given. This notion permits us to give a new characterization of Sturmian words. The main techniques used in the proofs are word graphs and return words. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: Characterizations of finite and infinite episturmian words via lexicographic orderings paper_content: In this talk, I will present some new results arising from collaborative work with Jacques Justin (France) and Giuseppe Pirillo (Italy). This work, which extends previous results on extremal properties of infinite Sturmian and episturmian words, is purely combinatorial in nature. Specifically, we characterize by lexicographic order all finite Sturmian and episturmian words, i.e., all (finite) factors of such infinite words. Consequently, we obtain a characterization of infinite episturmian words in a wide sense (episturmian and episkew infinite words). That is, we characterize the set of all infinite words whose factors are (finite) episturmian. Similarly, we characterize by lexicographic order all balanced infinite words over a 2-letter alphabet; in other words, all Sturmian and skew infinite words, the factors of which are (finite) Sturmian. --- paper_title: EPISTURMIAN WORDS: SHIFTS, MORPHISMS AND NUMERATION SYSTEMS paper_content: Episturmian words, which include the Arnoux-Rauzy sequences, are infinite words on a finite alphabet generalizing the Sturmian words and sharing many of their same properties. This was studied in previous papers. Here we gain a deeper insight into these properties. This leads in particular to consider numerations systems similar to the Ostrowski ones and to give a matrix formula for computing the number of representations of an integer in such a system. We also obtain a complete answer to the question: if an episturmian word is morphic, which shifts of it, if any, also are morphic ? --- paper_title: Sturmian words: structure, combinatorics, and their arithmetics paper_content: Abstract We prove some new results concerning the structure, the combinatorics and the arithmetics of the set PER of all the words w having two periods p and q, p ⩽ q , which are coprimes and such that ¦w¦= p + q− 2 . A basic theorem relating PER with the set of finite standard Sturmian words was proved in de Luca and Mignosi (1994). The main result of this paper is the following simple inductive definition of PER : the empty word belongs to PER , If w is an already constructed word of PER , then also ( aw ) (−) and ( bw ) (−) belong to PER , where (−) denotes the operator of palindrome left-closure, i.e. it associates to each word u the smallest palindrome word u (−) having u as a suffix. We show that, by this result, one can construct in a simple way all finite and infinite standard Sturmian words. We prove also that, up to the automorphism which interchanges the letter a with the letter b, any element of PER can be codified by the irreducible fraction p q . This allows us to construct for any n ⩾0 a natural bijection, that we call Farey correspondence, of the set of the Farey series of order n + 1 and the set of special elements of length n of the set St of all finite Sturmian words. Finally, we introduce the concepts of Farey tree and Farey monoid. This latter is obtained by defining a suitable product operation on the developments in continued fractions of the set of all irreducible fractions p q . --- paper_title: Episturmian morphisms and a Galois theorem on continued fractions paper_content: We associate with a word w on a finite alphabet A an episturmian (or Arnoux-Rauzy) morphism and a palindrome. We study their relations with the similar ones for the reversal of w . Then when \|A\|=2 we deduce, using the Sturmian words that are the fixed points of the two morphisms, a proof of a Galois theorem on purely periodic continued fractions whose periods are the reversal of each other. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: Characterizations of finite and infinite episturmian words via lexicographic orderings paper_content: In this talk, I will present some new results arising from collaborative work with Jacques Justin (France) and Giuseppe Pirillo (Italy). This work, which extends previous results on extremal properties of infinite Sturmian and episturmian words, is purely combinatorial in nature. Specifically, we characterize by lexicographic order all finite Sturmian and episturmian words, i.e., all (finite) factors of such infinite words. Consequently, we obtain a characterization of infinite episturmian words in a wide sense (episturmian and episkew infinite words). That is, we characterize the set of all infinite words whose factors are (finite) episturmian. Similarly, we characterize by lexicographic order all balanced infinite words over a 2-letter alphabet; in other words, all Sturmian and skew infinite words, the factors of which are (finite) Sturmian. --- paper_title: Quasiperiodic and Lyndon episturmian words paper_content: Recently the second two authors characterized quasiperiodic Sturmian words, proving that a Sturmian word is non-quasiperiodic if and only if, it is an infinite Lyndon word. Here we extend this study to episturmian words (a natural generalization of Sturmian words) by describing all the quasiperiods of an episturmian word, which yields a characterization of quasiperiodic episturmian words in terms of their directive words. Even further, we establish a complete characterization of all episturmian words that are Lyndon words. Our main results show that, unlike the Sturmian case, there is a much wider class of episturmian words that are non-quasiperiodic, besides those that are infinite Lyndon words. Our key tools are morphisms and directive words, in particular normalized directive words, which we introduced in an earlier paper. Also of importance is the use of return words to characterize quasiperiodic episturmian words, since such a method could be useful in other contexts. --- paper_title: A local balance property of episturmian words paper_content: We prove that episturmian words and Arnoux-Rauzy sequences can be characterized using a local balance property. We also give a new characterization of epistandard words. --- paper_title: On Sturmian and episturmian words, and related topics paper_content: Combinatorics on words plays a fundamental role in various fields of mathematics, not to mention its relevance in theoretical computer science and physics. Most renowned among its branches is the theory of infinite binary sequences called Sturmian words, which are fascinating in many respects, having been studied from combinatorial, algebraic, and geometric points of view. The most well-known example of a Sturmian word is the ubiquitous Fibonacci word, the importance of which lies in combinatorial pattern matching and the theory of words. Properties of the Fibonacci word and, more generally, Sturmian words have been extensively studied, not only because of their significance in discrete mathematics, but also due to their practical applications in computer imagery (digital straightness), theoretical physics (quasicrystal modelling) and molecular biology. --- paper_title: Powers in a class of A-strict standard episturmian words paper_content: This paper concerns a specific class of strict standard episturmian words whose directive words resemble those of characteristic Sturmian words. In particular, we explicitly determine all integer powers occurring in such infinite words, extending recent results of Damanik and Lenz [D. Damanik, D. Lenz, Powers in Sturmian sequences, European J. Combin. 24 (2003) 377-390, doi:10.1016/S0195-6698(03)00026-X], who studied powers in Sturmian words. The key tools in our analysis are canonical decompositions and a generalization of singular words, which were originally defined for the ubiquitous Fibonacci word. Our main results are demonstrated via some examples, including the k-bonacci word, a generalization of the Fibonacci word to a k-letter alphabet (k>=2). --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: Some properties of the Tribonacci sequence paper_content: In this paper, we consider the factor properties of the Tribonacci sequence. We define the singular words, and then give the singular factorization and the Lyndon factorization. As applications, we study the powers of the factors and the overlap of the factors. We also calculate the free index of the sequence. --- paper_title: Conjugacy and episturmian morphisms paper_content: Episturmian morphisms generalize Sturmian morphisms. Here, we study some intrinsic properties of these morphisms: invertibility, presentation, cancellativity, unitarity, characterization by conjugacy. Most of them are generalizations of known properties of Sturmian morphisms. But we present also some results on episturmian morphisms that have not already been stated in the particular case of Sturmian morphisms: characterization of the episturmian morphisms that preserve palindromes, new algorithms to compute conjugates.We also study the conjugation of morphisms in the general case and show that the monoid of invertible morphisms on an alphabet containing at least three letters is not finitely generated. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: A connection between palindromic and factor complexity using return words paper_content: In this paper we prove that for any infinite word W whose set of factors is closed under reversal, the following conditions are equivalent: (I) all complete returns to palindromes are palindromes; (II) P(n) + P(n+1) = C(n+1) - C(n) + 2 for all n, where P (resp. C) denotes the palindromic complexity (resp. factor complexity) function of W, which counts the number of distinct palindromic factors (resp. factors) of each length in W. --- paper_title: EPISTURMIAN WORDS: SHIFTS, MORPHISMS AND NUMERATION SYSTEMS paper_content: Episturmian words, which include the Arnoux-Rauzy sequences, are infinite words on a finite alphabet generalizing the Sturmian words and sharing many of their same properties. This was studied in previous papers. Here we gain a deeper insight into these properties. This leads in particular to consider numerations systems similar to the Ostrowski ones and to give a matrix formula for computing the number of representations of an integer in such a system. We also obtain a complete answer to the question: if an episturmian word is morphic, which shifts of it, if any, also are morphic ? --- paper_title: A generalization of Sturmian sequences; combinatorial structure and transcendence paper_content: We investigate a class of minimal sequences on a finite alphabet Ak = {1,2,...,k} having (k - 1)n + 1 distinct subwords of length n. These sequences, originally defined by P. Arnoux and G. Rauzy, are a natural generalization of binary Sturmian sequences. We describe two simple combinatorial algorithms for constructing characteristic Arnoux-Rauzy sequences (one of which is new even in the Sturmian case). Arnoux-Rauzy sequences arising from fixed points of primitive morphisms are characterized by an underlying periodic structure. We show that every Arnoux-Rauzy sequence contains arbitrarily large subwords of the form V^2+e and, in the Sturmian case, arbitrarily large subwords of the form V^3+e. Finally, we prove that an irrational number whose base b-digit expansion is an Arnoux-Rauzy sequence is transcendental. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: On a characteristic property of ARNOUX–RAUZY sequences paper_content: Here we give a characterization of Arnoux-Rauzy sequences by the way of the lexicographic orderings of their alphabet. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: A characterization of Sturmian morphisms paper_content: A morphism is called Sturmian if it preserves all Sturmian (infinite) words. It is weakly Sturmian if it preserves at least one Sturmian word. We prove that a morphism is Sturmian if and only if it keeps the word ba2ba2baba2bab balanced. As a consequence, weakly Sturmian morphisms are Sturmian. An application to infinite words associated to irrational numbers is given. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: On Sturmian and episturmian words, and related topics paper_content: Combinatorics on words plays a fundamental role in various fields of mathematics, not to mention its relevance in theoretical computer science and physics. Most renowned among its branches is the theory of infinite binary sequences called Sturmian words, which are fascinating in many respects, having been studied from combinatorial, algebraic, and geometric points of view. The most well-known example of a Sturmian word is the ubiquitous Fibonacci word, the importance of which lies in combinatorial pattern matching and the theory of words. Properties of the Fibonacci word and, more generally, Sturmian words have been extensively studied, not only because of their significance in discrete mathematics, but also due to their practical applications in computer imagery (digital straightness), theoretical physics (quasicrystal modelling) and molecular biology. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Some remarks on invertible substitutions on three letter alphabet paper_content: By introducing the notion of “prime substitution” it is shown that the set of invertible substitutions over an alphabet of more than three letters is not finitely generated. Some examples are given. --- paper_title: On Morphisms Preserving Infinite Lyndon Words paper_content: In a previous paper, we characterized free monoid morphisms preserving finite Lyndon words. In particular, we proved that such a morphism preserves the order on finite words. Here we study morphisms preserving infinite Lyndon words and morphisms preserving the order on infinite words. We characterize them and show relations with morphisms preserving Lyndon words or the order on finite words. We also briefly study morphisms preserving border-free words and those preserving the radix order. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: Conjugacy and episturmian morphisms paper_content: Episturmian morphisms generalize Sturmian morphisms. Here, we study some intrinsic properties of these morphisms: invertibility, presentation, cancellativity, unitarity, characterization by conjugacy. Most of them are generalizations of known properties of Sturmian morphisms. But we present also some results on episturmian morphisms that have not already been stated in the particular case of Sturmian morphisms: characterization of the episturmian morphisms that preserve palindromes, new algorithms to compute conjugates.We also study the conjugation of morphisms in the general case and show that the monoid of invertible morphisms on an alphabet containing at least three letters is not finitely generated. --- paper_title: Complexity of sequences and dynamical systems paper_content: Abstract This is a survey of recent results on the notion of symbolic complexity, which counts the number of factors of an infinite sequence, particularly in view of its relations with dynamical systems. --- paper_title: A local balance property of episturmian words paper_content: We prove that episturmian words and Arnoux-Rauzy sequences can be characterized using a local balance property. We also give a new characterization of epistandard words. --- paper_title: Conjugacy of morphisms and Lyndon decomposition of standard Sturmian words paper_content: Using the notions of conjugacy of morphisms and of morphisms preserving Lyndon words, we answer a question of G. Melancon. We characterize cases where the sequence of Lyndon words in the Lyndon factorization of a standard Sturmian word is morphic. In each possible case, the corresponding morphism is given. --- paper_title: A generalization of Sturmian sequences; combinatorial structure and transcendence paper_content: We investigate a class of minimal sequences on a finite alphabet Ak = {1,2,...,k} having (k - 1)n + 1 distinct subwords of length n. These sequences, originally defined by P. Arnoux and G. Rauzy, are a natural generalization of binary Sturmian sequences. We describe two simple combinatorial algorithms for constructing characteristic Arnoux-Rauzy sequences (one of which is new even in the Sturmian case). Arnoux-Rauzy sequences arising from fixed points of primitive morphisms are characterized by an underlying periodic structure. We show that every Arnoux-Rauzy sequence contains arbitrarily large subwords of the form V^2+e and, in the Sturmian case, arbitrarily large subwords of the form V^3+e. Finally, we prove that an irrational number whose base b-digit expansion is an Arnoux-Rauzy sequence is transcendental. --- paper_title: Initial powers of Sturmian sequences paper_content: In this paper we investigate powers of prefixes of Sturmian sequences. We give an explicit formula for ice(ω), the initial critical exponent of a Sturmian sequence ω, defined as the supremum of all real numbers p > 0 for which there exist arbitrary long prefixes of ω of the form up, in terms of its S-adic representation. This formula is based on Ostrowski's numeration system. Furthermore we characterize those irrational slopes α of which there exists a Sturmian sequence ω beginning in only finitely many powers of 2 + e, that is for which ice(ω) = 2. In the process we recover the known results for the index (or critical exponent) of a Sturmian sequence. We also focus on the Fibonacci Sturmian shift and prove that the set of Sturmian sequences with ice strictly smaller than its everywhere value has Hausdorff dimension 1. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Balances for fixed points of primitive substitutions paper_content: An infinite word defined over a finite alphabet A is balanced if for any pair (ω,ω') of factors of the same length and for any letter a in the alphabet \|\|ω\|a - \|ω'\|a\| ≤ 1, where \|ω\|a denotes the number of occurrences of the letter a in the word ω. In this paper, we generalize this notion and introduce a measure of balance for an infinite sequence. In the case of fixed points of primitive substitutions, we show that the asymptotic behaviour of this measure is in part ruled by the spectrum of the incidence matrix associated with the substitution. Connections with frequencies of letters and other balance properties are also discussed. --- paper_title: Quasiperiodic Sturmian words and morphisms paper_content: We characterize all quasiperiodic Sturmian words: a Sturmian word is not quasiperiodic if and only if it is a Lyndon word. Moreover, we study links between Sturmian morphisms and quasiperiodicity. --- paper_title: A characterization of fine words over a finite alphabet paper_content: To any infinite word w over a finite alphabet A we can associate two infinite words min(w) and max(w) such that any prefix of min(w) (resp. max(w)) is the lexicographically smallest (resp. greatest) amongst the factors of w of the same length. We say that an infinite word w over A is"fine"if there exists an infinite word u such that, for any lexicographic order, min(w) = au where a = min(A). In this paper, we characterize fine words; specifically, we prove that an infinite word w is fine if and only if w is either a"strict episturmian word"or a strict"skew episturmian word''. This characterization generalizes a recent result of G. Pirillo, who proved that a fine word over a 2-letter alphabet is either an (aperiodic) Sturmian word, or an ultimately periodic (but not periodic) infinite word, all of whose factors are (finite) Sturmian. --- paper_title: EPISTURMIAN WORDS: SHIFTS, MORPHISMS AND NUMERATION SYSTEMS paper_content: Episturmian words, which include the Arnoux-Rauzy sequences, are infinite words on a finite alphabet generalizing the Sturmian words and sharing many of their same properties. This was studied in previous papers. Here we gain a deeper insight into these properties. This leads in particular to consider numerations systems similar to the Ostrowski ones and to give a matrix formula for computing the number of representations of an integer in such a system. We also obtain a complete answer to the question: if an episturmian word is morphic, which shifts of it, if any, also are morphic ? --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Balances for fixed points of primitive substitutions paper_content: An infinite word defined over a finite alphabet A is balanced if for any pair (ω,ω') of factors of the same length and for any letter a in the alphabet \|\|ω\|a - \|ω'\|a\| ≤ 1, where \|ω\|a denotes the number of occurrences of the letter a in the word ω. In this paper, we generalize this notion and introduce a measure of balance for an infinite sequence. In the case of fixed points of primitive substitutions, we show that the asymptotic behaviour of this measure is in part ruled by the spectrum of the incidence matrix associated with the substitution. Connections with frequencies of letters and other balance properties are also discussed. --- paper_title: Conjugacy and episturmian morphisms paper_content: Episturmian morphisms generalize Sturmian morphisms. Here, we study some intrinsic properties of these morphisms: invertibility, presentation, cancellativity, unitarity, characterization by conjugacy. Most of them are generalizations of known properties of Sturmian morphisms. But we present also some results on episturmian morphisms that have not already been stated in the particular case of Sturmian morphisms: characterization of the episturmian morphisms that preserve palindromes, new algorithms to compute conjugates.We also study the conjugation of morphisms in the general case and show that the monoid of invertible morphisms on an alphabet containing at least three letters is not finitely generated. --- paper_title: EPISTURMIAN WORDS: SHIFTS, MORPHISMS AND NUMERATION SYSTEMS paper_content: Episturmian words, which include the Arnoux-Rauzy sequences, are infinite words on a finite alphabet generalizing the Sturmian words and sharing many of their same properties. This was studied in previous papers. Here we gain a deeper insight into these properties. This leads in particular to consider numerations systems similar to the Ostrowski ones and to give a matrix formula for computing the number of representations of an integer in such a system. We also obtain a complete answer to the question: if an episturmian word is morphic, which shifts of it, if any, also are morphic ? --- paper_title: Directive words of episturmian words: equivalences and normalization paper_content: Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturmian word can be infinitely decomposed over the set of pure episturmian morphisms. Thus, an episturmian word can be defined by one of its morphic decompositions or, equivalently, by a certain directive word. Here we characterize pairs of words directing the same episturmian word. We also propose a way to uniquely define any episturmian word through a normalization of its directive words. As a consequence of these results, we characterize episturmian words having a unique directive word. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: EPISTURMIAN WORDS: SHIFTS, MORPHISMS AND NUMERATION SYSTEMS paper_content: Episturmian words, which include the Arnoux-Rauzy sequences, are infinite words on a finite alphabet generalizing the Sturmian words and sharing many of their same properties. This was studied in previous papers. Here we gain a deeper insight into these properties. This leads in particular to consider numerations systems similar to the Ostrowski ones and to give a matrix formula for computing the number of representations of an integer in such a system. We also obtain a complete answer to the question: if an episturmian word is morphic, which shifts of it, if any, also are morphic ? --- paper_title: Directive words of episturmian words: equivalences and normalization paper_content: Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturmian word can be infinitely decomposed over the set of pure episturmian morphisms. Thus, an episturmian word can be defined by one of its morphic decompositions or, equivalently, by a certain directive word. Here we characterize pairs of words directing the same episturmian word. We also propose a way to uniquely define any episturmian word through a normalization of its directive words. As a consequence of these results, we characterize episturmian words having a unique directive word. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Conjugacy and episturmian morphisms paper_content: Episturmian morphisms generalize Sturmian morphisms. Here, we study some intrinsic properties of these morphisms: invertibility, presentation, cancellativity, unitarity, characterization by conjugacy. Most of them are generalizations of known properties of Sturmian morphisms. But we present also some results on episturmian morphisms that have not already been stated in the particular case of Sturmian morphisms: characterization of the episturmian morphisms that preserve palindromes, new algorithms to compute conjugates.We also study the conjugation of morphisms in the general case and show that the monoid of invertible morphisms on an alphabet containing at least three letters is not finitely generated. --- paper_title: EPISTURMIAN WORDS: SHIFTS, MORPHISMS AND NUMERATION SYSTEMS paper_content: Episturmian words, which include the Arnoux-Rauzy sequences, are infinite words on a finite alphabet generalizing the Sturmian words and sharing many of their same properties. This was studied in previous papers. Here we gain a deeper insight into these properties. This leads in particular to consider numerations systems similar to the Ostrowski ones and to give a matrix formula for computing the number of representations of an integer in such a system. We also obtain a complete answer to the question: if an episturmian word is morphic, which shifts of it, if any, also are morphic ? --- paper_title: Quasiperiodic and Lyndon episturmian words paper_content: Recently the second two authors characterized quasiperiodic Sturmian words, proving that a Sturmian word is non-quasiperiodic if and only if, it is an infinite Lyndon word. Here we extend this study to episturmian words (a natural generalization of Sturmian words) by describing all the quasiperiods of an episturmian word, which yields a characterization of quasiperiodic episturmian words in terms of their directive words. Even further, we establish a complete characterization of all episturmian words that are Lyndon words. Our main results show that, unlike the Sturmian case, there is a much wider class of episturmian words that are non-quasiperiodic, besides those that are infinite Lyndon words. Our key tools are morphisms and directive words, in particular normalized directive words, which we introduced in an earlier paper. Also of importance is the use of return words to characterize quasiperiodic episturmian words, since such a method could be useful in other contexts. --- paper_title: Directive words of episturmian words: equivalences and normalization paper_content: Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturmian word can be infinitely decomposed over the set of pure episturmian morphisms. Thus, an episturmian word can be defined by one of its morphic decompositions or, equivalently, by a certain directive word. Here we characterize pairs of words directing the same episturmian word. We also propose a way to uniquely define any episturmian word through a normalization of its directive words. As a consequence of these results, we characterize episturmian words having a unique directive word. --- paper_title: Inequalities characterizing standard Sturmian and episturmian words paper_content: Considering the smallest and the greatest factors with respect to the lexicographic order we associate to each infinite word r two other infinite words min(r) and max(r). In this paper we prove that the inequalities as ≤ min(s) ≤ max(s) ≤ bs characterize standard Sturmian words (proper ones and periodic ones) and that the condition "for any x ∈ A and lexicographic order < satisfying x = min(A) one has xs ≤ min(s)" characterizes standard episturmian words. --- paper_title: Characterisations of Balanced Words via Orderings paper_content: Three new characterisations of balanced words are presented. Each of these characterisations is based on the ordering of a shift orbit, either lexicographically or with respect to the norm \|ċ\|1 (which counts the number of occurrences of the symbol 1). --- paper_title: Initial powers of Sturmian sequences paper_content: In this paper we investigate powers of prefixes of Sturmian sequences. We give an explicit formula for ice(ω), the initial critical exponent of a Sturmian sequence ω, defined as the supremum of all real numbers p > 0 for which there exist arbitrary long prefixes of ω of the form up, in terms of its S-adic representation. This formula is based on Ostrowski's numeration system. Furthermore we characterize those irrational slopes α of which there exists a Sturmian sequence ω beginning in only finitely many powers of 2 + e, that is for which ice(ω) = 2. In the process we recover the known results for the index (or critical exponent) of a Sturmian sequence. We also focus on the Fibonacci Sturmian shift and prove that the set of Sturmian sequences with ice strictly smaller than its everywhere value has Hausdorff dimension 1. --- paper_title: A characterization of fine words over a finite alphabet paper_content: To any infinite word w over a finite alphabet A we can associate two infinite words min(w) and max(w) such that any prefix of min(w) (resp. max(w)) is the lexicographically smallest (resp. greatest) amongst the factors of w of the same length. We say that an infinite word w over A is"fine"if there exists an infinite word u such that, for any lexicographic order, min(w) = au where a = min(A). In this paper, we characterize fine words; specifically, we prove that an infinite word w is fine if and only if w is either a"strict episturmian word"or a strict"skew episturmian word''. This characterization generalizes a recent result of G. Pirillo, who proved that a fine word over a 2-letter alphabet is either an (aperiodic) Sturmian word, or an ultimately periodic (but not periodic) infinite word, all of whose factors are (finite) Sturmian. --- paper_title: Palindromic Richness paper_content: In this paper, we study combinatorial and structural properties of a new class of finite and infinite words that are 'rich' in palindromes in the utmost sense. A characteristic property of so-called"rich words"is that all complete returns to any palindromic factor are themselves palindromes. These words encompass the well-known episturmian words, originally introduced by the second author together with X. Droubay and G. Pirillo in 2001. Other examples of rich words have appeared in many different contexts. Here we present the first unified approach to the study of this intriguing family of words. Amongst our main results, we give an explicit description of the periodic rich infinite words and show that the recurrent balanced rich infinite words coincide with the balanced episturmian words. We also consider two wider classes of infinite words, namely"weakly rich words"and almost rich words (both strictly contain all rich words, but neither one is contained in the other). In particular, we classify all recurrent balanced weakly rich words. As a consequence, we show that any such word on at least three letters is necessarily episturmian; hence weakly rich words obey Fraenkel's conjecture. Likewise, we prove that a certain class of almost rich words obeys Fraenkel's conjecture by showing that the recurrent balanced ones are episturmian or contain at least two distinct letters with the same frequency. Lastly, we study the action of morphisms on (almost) rich words with particular interest in morphisms that preserve (almost) richness. Such morphisms belong to the class of"P-morphisms"that was introduced by A. Hof, O. Knill, and B. Simon in 1995. --- paper_title: On a characteristic property of ARNOUX–RAUZY sequences paper_content: Here we give a characterization of Arnoux-Rauzy sequences by the way of the lexicographic orderings of their alphabet. --- paper_title: Morse and Hedlund’s Skew Sturmian Words Revisited paper_content: For any infinite word r over A = {a, b} we associate two infinite words min(r), max(r) such that any prefix of min(r) (max(r), respectively) is the lexicographically smallest (greatest, respectively) among the factors of r of the same length. We prove that (min(r); max(r)) = (as, bs) for some infinite word s if and only if r is a proper Sturmian word or an ultimately periodic word of a particular form. This result is based on a lemma concerning sequences of infinite words. --- paper_title: Characterizations of finite and infinite episturmian words via lexicographic orderings paper_content: In this talk, I will present some new results arising from collaborative work with Jacques Justin (France) and Giuseppe Pirillo (Italy). This work, which extends previous results on extremal properties of infinite Sturmian and episturmian words, is purely combinatorial in nature. Specifically, we characterize by lexicographic order all finite Sturmian and episturmian words, i.e., all (finite) factors of such infinite words. Consequently, we obtain a characterization of infinite episturmian words in a wide sense (episturmian and episkew infinite words). That is, we characterize the set of all infinite words whose factors are (finite) episturmian. Similarly, we characterize by lexicographic order all balanced infinite words over a 2-letter alphabet; in other words, all Sturmian and skew infinite words, the factors of which are (finite) Sturmian. --- paper_title: A characterization of Sturmian morphisms paper_content: A morphism is called Sturmian if it preserves all Sturmian (infinite) words. It is weakly Sturmian if it preserves at least one Sturmian word. We prove that a morphism is Sturmian if and only if it keeps the word ba2ba2baba2bab balanced. As a consequence, weakly Sturmian morphisms are Sturmian. An application to infinite words associated to irrational numbers is given. --- paper_title: EPISTURMIAN WORDS: SHIFTS, MORPHISMS AND NUMERATION SYSTEMS paper_content: Episturmian words, which include the Arnoux-Rauzy sequences, are infinite words on a finite alphabet generalizing the Sturmian words and sharing many of their same properties. This was studied in previous papers. Here we gain a deeper insight into these properties. This leads in particular to consider numerations systems similar to the Ostrowski ones and to give a matrix formula for computing the number of representations of an integer in such a system. We also obtain a complete answer to the question: if an episturmian word is morphic, which shifts of it, if any, also are morphic ? --- paper_title: On substitution invariant Sturmian words: An application of Rauzy fractals paper_content: Sturmian words are infinite words that have exactly n + 1 factors of length n for every positive integer n. A Sturmian word s�,� is also defined as a coding over a two-letter alphabet of the orbit of the pointunder the action of the irrational rotation R� : x 7! x + � (mod 1). Yasutomi characterized in (34) all the pairs (�,�) such that the Sturmian word s�,� is a fixed point of some non-trivial substitution. By investigating the Rauzy frac- tals associated with invertible substitutions, we give an alternative geometric proof of Yasutomi's characterization. --- paper_title: A remark on morphic sturmian words paper_content: This Note deals with binary Sturmian words that are morphic, i.e. generated by iterating a morphism. Among these, characteristic words are a well-known subclass. We prove that for every characteristic morphic word x, the four words ax, bx, abx and bax are morphic --- paper_title: A little more about morphic Sturmian words paper_content: Among Sturmian words, some of them are morphic, i.e. fixed point of a non-identical morphism on words. Berstel and Seebold (1993) have shown that if a characteristic Sturmian word is morphic, then it can be extended by the left with one or two letters in such a way that it remains morphic and Sturmian. Yasutomi (1997) has proved that these were the sole possible additions and that, if we cut the first letters of such a word, it didn't remain morphic. In this paper, we give an elementary and combinatorial proof of this result. --- paper_title: EPISTURMIAN WORDS: SHIFTS, MORPHISMS AND NUMERATION SYSTEMS paper_content: Episturmian words, which include the Arnoux-Rauzy sequences, are infinite words on a finite alphabet generalizing the Sturmian words and sharing many of their same properties. This was studied in previous papers. Here we gain a deeper insight into these properties. This leads in particular to consider numerations systems similar to the Ostrowski ones and to give a matrix formula for computing the number of representations of an integer in such a system. We also obtain a complete answer to the question: if an episturmian word is morphic, which shifts of it, if any, also are morphic ? --- paper_title: A generalization of Sturmian sequences; combinatorial structure and transcendence paper_content: We investigate a class of minimal sequences on a finite alphabet Ak = {1,2,...,k} having (k - 1)n + 1 distinct subwords of length n. These sequences, originally defined by P. Arnoux and G. Rauzy, are a natural generalization of binary Sturmian sequences. We describe two simple combinatorial algorithms for constructing characteristic Arnoux-Rauzy sequences (one of which is new even in the Sturmian case). Arnoux-Rauzy sequences arising from fixed points of primitive morphisms are characterized by an underlying periodic structure. We show that every Arnoux-Rauzy sequence contains arbitrarily large subwords of the form V^2+e and, in the Sturmian case, arbitrarily large subwords of the form V^3+e. Finally, we prove that an irrational number whose base b-digit expansion is an Arnoux-Rauzy sequence is transcendental. --- paper_title: Pisot substitutions and Rauzy fractals paper_content: We prove that the dynamical system generated by a primitive unimodular substitution of the Pisot type ond letters satisfying a combinatorial condition which is easy to check, is measurably isomorphic to a domain exchange in R d 1 , and is a nite extension of a translation on the torus T d 1 .I n the course of the proof, we introduce some potentially useful notions: the linear maps associated to a substitution and their dual maps, and the -structure for a dynamical system with respect to a pair of partitions. --- paper_title: COMBINATORIAL PROPERTIES OF ARNOUX–RAUZY SUBSHIFTS AND APPLICATIONS TO SCHRÖDINGER OPERATORS paper_content: We consider Arnoux–Rauzy subshifts X and study various combinatorial questions: When is X linearly recurrent? What is the maximal power occurring in X? What is the number of palindromes of a given length occurring in X? We present applications of our combinatorial results to the spectral theory of discrete one-dimensional Schrodinger operators with potentials given by Arnoux–Rauzy sequences. --- paper_title: RECENT RESULTS ON EXTENSIONS OF STURMIAN WORDS paper_content: Sturmian words are infinite words over a two-letter alphabet that admit a great number of equivalent definitions. Most of them have been given in the past ten years. Among several extensions of Sturmian words to larger alphabets, the Arnoux–Rauzy words appear to share many of the properties of Sturmian words. In this survey, combinatorial properties of these two families are considered and compared. --- paper_title: STRUCTURE OF THREE INTERVAL EXCHANGE TRANSFORMATIONS I : AN ARITHMETIC STUDY paper_content: Dans cet article nous decrivons une generalisation a la dimension 2 de l'algorithme d'Euclide, qui provient de la dynamique des echanges de 3 intervalles. Nous examinons diverses proprietes diophantiennes de cet algorithme, en particulier la, qualite de l'approximation simultanee. Nous montrons qu'il verifie un theoreme de type Lagrange : l'algorithme est finalement periodique si et seulement si les parametres sont dans la meme extension quadratique de Q. --- paper_title: Fine and Wilf's theorem for three periods and a generalization of Sturmian words paper_content: We extend the theorem of Fine and Wilf to words having three periods. We then define the set 3-PER of words of maximal length for which such result does not apply. We prove that the set 3-PER and the sequences of complexity 2n + 1, introduced by Arnoux and Rauzy to generalize Sturmian words, have the same set of factors. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: Characterizations of finite and infinite episturmian words via lexicographic orderings paper_content: In this talk, I will present some new results arising from collaborative work with Jacques Justin (France) and Giuseppe Pirillo (Italy). This work, which extends previous results on extremal properties of infinite Sturmian and episturmian words, is purely combinatorial in nature. Specifically, we characterize by lexicographic order all finite Sturmian and episturmian words, i.e., all (finite) factors of such infinite words. Consequently, we obtain a characterization of infinite episturmian words in a wide sense (episturmian and episkew infinite words). That is, we characterize the set of all infinite words whose factors are (finite) episturmian. Similarly, we characterize by lexicographic order all balanced infinite words over a 2-letter alphabet; in other words, all Sturmian and skew infinite words, the factors of which are (finite) Sturmian. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Palindromes and Sturmian words paper_content: Abstract An infinite word x over the alphabet A is Sturmian if and only if g x ( n ) = n + 1 for any integer n , where g x ( n ) is the number of distinct words of length n occurring in x . A palindrome is a word that can be read indistinctly from left to right or from right to left. We prove that x is Sturmian if and only if h x ( n ) = 1 + ( n mod 2) for any integer n , where h x ( n ) is the number of palindromes of length n occurring in x . An infinite word x over the alphabet A is generated by a morphism f if there exists a letter c ϵ A such that lim n →∞ f n ( c ) = x . We prove the existence of a morphism that generates the palindromes of any infinite Sturmian word generated by a morphism. --- paper_title: Palindromes and Sturmian words paper_content: Abstract An infinite word x over the alphabet A is Sturmian if and only if g x ( n ) = n + 1 for any integer n , where g x ( n ) is the number of distinct words of length n occurring in x . A palindrome is a word that can be read indistinctly from left to right or from right to left. We prove that x is Sturmian if and only if h x ( n ) = 1 + ( n mod 2) for any integer n , where h x ( n ) is the number of palindromes of length n occurring in x . An infinite word x over the alphabet A is generated by a morphism f if there exists a letter c ϵ A such that lim n →∞ f n ( c ) = x . We prove the existence of a morphism that generates the palindromes of any infinite Sturmian word generated by a morphism. --- paper_title: Frequencies of factors in Arnoux-Rauzy sequences paper_content: V. Berthe showed that the frequencies of factors in a Sturmian word of slope α, as well as the number of factors with a given frequency, can be expressed in terms of the continued fraction expansion of α. In this paper we describe a multi-dimensional continued fraction process associated with a class of sequences of (block) complexity kn+1 originally introduced by P. Arnoux and G. Rauzy. This vectorial division algorithm yields simultaneous rational approximations of the frequencies of the letters. We extend Berthe’s result to factors of Arnoux-Rauzy sequences by expressing both the frequencies and the number of factors with a given frequency, in terms of the ‘convergents’ obtained from the generalized continued fraction expansion of the frequencies of the letters. --- paper_title: Episturmian morphisms and a Galois theorem on continued fractions paper_content: We associate with a word w on a finite alphabet A an episturmian (or Arnoux-Rauzy) morphism and a palindrome. We study their relations with the similar ones for the reversal of w . Then when \|A\|=2 we deduce, using the Sturmian words that are the fixed points of the two morphisms, a proof of a Galois theorem on purely periodic continued fractions whose periods are the reversal of each other. --- paper_title: A generalization of Sturmian sequences; combinatorial structure and transcendence paper_content: We investigate a class of minimal sequences on a finite alphabet Ak = {1,2,...,k} having (k - 1)n + 1 distinct subwords of length n. These sequences, originally defined by P. Arnoux and G. Rauzy, are a natural generalization of binary Sturmian sequences. We describe two simple combinatorial algorithms for constructing characteristic Arnoux-Rauzy sequences (one of which is new even in the Sturmian case). Arnoux-Rauzy sequences arising from fixed points of primitive morphisms are characterized by an underlying periodic structure. We show that every Arnoux-Rauzy sequence contains arbitrarily large subwords of the form V^2+e and, in the Sturmian case, arbitrarily large subwords of the form V^3+e. Finally, we prove that an irrational number whose base b-digit expansion is an Arnoux-Rauzy sequence is transcendental. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: EPISTURMIAN WORDS: SHIFTS, MORPHISMS AND NUMERATION SYSTEMS paper_content: Episturmian words, which include the Arnoux-Rauzy sequences, are infinite words on a finite alphabet generalizing the Sturmian words and sharing many of their same properties. This was studied in previous papers. Here we gain a deeper insight into these properties. This leads in particular to consider numerations systems similar to the Ostrowski ones and to give a matrix formula for computing the number of representations of an integer in such a system. We also obtain a complete answer to the question: if an episturmian word is morphic, which shifts of it, if any, also are morphic ? --- paper_title: Palindromic Prefixes and Episturmian Words paper_content: Let $w$ be an infinite word on an alphabet $A$. We denote by $(n_i)_{i \geq 1}$ the increasing sequence (assumed to be infinite) of all lengths of palindrome prefixes of $w$. In this text, we give an explicit construction of all words $w$ such that $n_{i+1} \leq 2 n_i + 1$ for any $i$, and study these words. Special examples include characteristic Sturmian words, and more generally standard episturmian words. As an application, we study the values taken by the quantity $\limsup n_{i+1}/n_i$, and prove that it is minimal (among all non-periodic words) for the Fibonacci word. --- paper_title: Palindromic Richness paper_content: In this paper, we study combinatorial and structural properties of a new class of finite and infinite words that are 'rich' in palindromes in the utmost sense. A characteristic property of so-called"rich words"is that all complete returns to any palindromic factor are themselves palindromes. These words encompass the well-known episturmian words, originally introduced by the second author together with X. Droubay and G. Pirillo in 2001. Other examples of rich words have appeared in many different contexts. Here we present the first unified approach to the study of this intriguing family of words. Amongst our main results, we give an explicit description of the periodic rich infinite words and show that the recurrent balanced rich infinite words coincide with the balanced episturmian words. We also consider two wider classes of infinite words, namely"weakly rich words"and almost rich words (both strictly contain all rich words, but neither one is contained in the other). In particular, we classify all recurrent balanced weakly rich words. As a consequence, we show that any such word on at least three letters is necessarily episturmian; hence weakly rich words obey Fraenkel's conjecture. Likewise, we prove that a certain class of almost rich words obeys Fraenkel's conjecture by showing that the recurrent balanced ones are episturmian or contain at least two distinct letters with the same frequency. Lastly, we study the action of morphisms on (almost) rich words with particular interest in morphisms that preserve (almost) richness. Such morphisms belong to the class of"P-morphisms"that was introduced by A. Hof, O. Knill, and B. Simon in 1995. --- paper_title: Episturmian words and some constructions of de Luca and Rauzy paper_content: Abstract In this paper we study infinite episturmian words which are a natural generalization of Sturmian words to an arbitrary alphabet. A characteristic property is: they are closed under reversal and have at most one right special factor of each length. They are first obtained by a construction due to de LUCA which utilizes the palindrome closure. They can also be obtained by the way of extended RAUZY rules. --- paper_title: Palindromic complexity of infinite words associated with simple Parry numbers paper_content: We study the palindromic complexity of infinite words $u_\beta$, the fixed points of the substitution over a binary alphabet, $\phi(0)=0^a1$, $\phi(1)=0^b1$, with $a-1\geq b\geq 1$, which are canonically associated with quadratic non-simple Parry numbers $\beta$. --- paper_title: Transcendence measures for continued fractions involving repetitive or symmetric patterns paper_content: There is a long tradition in constructing explicit classes of transcendental continued fractions and especially transcendental continued fractions with bounded partial quotients. By means of the Schmidt Subspace Theorem, existing results were recently substantially improved by the authors in a series of papers, providing new classes of transcendental continued fractions. It is the purpose of the present work to show how the Quantitative Subspace Theorem yields transcendence measures for (most of) these numbers. --- paper_title: A connection between palindromic and factor complexity using return words paper_content: In this paper we prove that for any infinite word W whose set of factors is closed under reversal, the following conditions are equivalent: (I) all complete returns to palindromes are palindromes; (II) P(n) + P(n+1) = C(n+1) - C(n) + 2 for all n, where P (resp. C) denotes the palindromic complexity (resp. factor complexity) function of W, which counts the number of distinct palindromic factors (resp. factors) of each length in W. --- paper_title: Powers in a class of A-strict standard episturmian words paper_content: This paper concerns a specific class of strict standard episturmian words whose directive words resemble those of characteristic Sturmian words. In particular, we explicitly determine all integer powers occurring in such infinite words, extending recent results of Damanik and Lenz [D. Damanik, D. Lenz, Powers in Sturmian sequences, European J. Combin. 24 (2003) 377-390, doi:10.1016/S0195-6698(03)00026-X], who studied powers in Sturmian words. The key tools in our analysis are canonical decompositions and a generalization of singular words, which were originally defined for the ubiquitous Fibonacci word. Our main results are demonstrated via some examples, including the k-bonacci word, a generalization of the Fibonacci word to a k-letter alphabet (k>=2). --- paper_title: A generalization of Sturmian sequences; combinatorial structure and transcendence paper_content: We investigate a class of minimal sequences on a finite alphabet Ak = {1,2,...,k} having (k - 1)n + 1 distinct subwords of length n. These sequences, originally defined by P. Arnoux and G. Rauzy, are a natural generalization of binary Sturmian sequences. We describe two simple combinatorial algorithms for constructing characteristic Arnoux-Rauzy sequences (one of which is new even in the Sturmian case). Arnoux-Rauzy sequences arising from fixed points of primitive morphisms are characterized by an underlying periodic structure. We show that every Arnoux-Rauzy sequence contains arbitrarily large subwords of the form V^2+e and, in the Sturmian case, arbitrarily large subwords of the form V^3+e. Finally, we prove that an irrational number whose base b-digit expansion is an Arnoux-Rauzy sequence is transcendental. --- paper_title: Initial powers of Sturmian sequences paper_content: In this paper we investigate powers of prefixes of Sturmian sequences. We give an explicit formula for ice(ω), the initial critical exponent of a Sturmian sequence ω, defined as the supremum of all real numbers p > 0 for which there exist arbitrary long prefixes of ω of the form up, in terms of its S-adic representation. This formula is based on Ostrowski's numeration system. Furthermore we characterize those irrational slopes α of which there exists a Sturmian sequence ω beginning in only finitely many powers of 2 + e, that is for which ice(ω) = 2. In the process we recover the known results for the index (or critical exponent) of a Sturmian sequence. We also focus on the Fibonacci Sturmian shift and prove that the set of Sturmian sequences with ice strictly smaller than its everywhere value has Hausdorff dimension 1. --- paper_title: Sturmian words and words with a critical exponent paper_content: Let S be a standard Sturmian word that is a fixed point of a non-trivial homomorphism. Associated to the infinite word S is a unique irrational number β with 0 0 it contains a fractional power with exponent greater than Ω−e; here Ω is a constant that depends on β. The constant Ω is given explicitly. Using these results we are able to give a short proof of Mignosi's theorem and give an exact evaluation of the maximal power that can occur in a standard Sturmian word. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Transcendence of Numbers with a Low Complexity Expansion paper_content: Abstract A sequence is Sturmian if it has complexity n + l −1, that is, n + l −1 factors of length n for every n ; we show that real numbers whose expansion in some base k ⩾ l is Sturmian are transcendental, and give explicit expressions for these numbers. We then generalize the transcendence property to other sequences of low complexity, particularly the Arnoux–Rauzy sequences. --- paper_title: Some properties of the Tribonacci sequence paper_content: In this paper, we consider the factor properties of the Tribonacci sequence. We define the singular words, and then give the singular factorization and the Lyndon factorization. As applications, we study the powers of the factors and the overlap of the factors. We also calculate the free index of the sequence. --- paper_title: Fractional powers in Sturmian words paper_content: Abstract Given an infinite Sturmian word s , we calculate the function L(m) which gives the length of the longest factor of s having period m . The expression of L(m) makes use of the continued fraction of the irrational α associated with s . --- paper_title: Transcendence of Sturmian or morphic continued fractions paper_content: Abstract We prove, using a theorem of W. Schmidt, that if the sequence of partial quotients of the continued fraction expansion of a positive irrational real number takes only two values, and begins with arbitrary long blocks which are “almost squares,” then this number is either quadratic or transcendental. This result applies in particular to real numbers whose partial quotients form a Sturmian (or quasi-Sturmian) sequence, or are given by the sequence (1+(⌊ nα ⌋ mod 2)) n ⩾0 , or are a “repetitive” fixed point of a binary morphism satisfying some technical conditions. --- paper_title: On the Index of Sturmian Words paper_content: An infinite word x has finite index if the exponents of the powers of primitive words that are factors of x are bounded. F. Mignosi has proved that a Sturmian word has finite index if and only if the coefficients of the continued fraction development of its slope are bounded. Mignosi’s proof relies on a delicate analysis of the approximation of the slope by rational numbers. We give here a proof based on combinatorial properties of words, and give some additional relations between the exponents and the slope. --- paper_title: Frequencies of factors in Arnoux-Rauzy sequences paper_content: V. Berthe showed that the frequencies of factors in a Sturmian word of slope α, as well as the number of factors with a given frequency, can be expressed in terms of the continued fraction expansion of α. In this paper we describe a multi-dimensional continued fraction process associated with a class of sequences of (block) complexity kn+1 originally introduced by P. Arnoux and G. Rauzy. This vectorial division algorithm yields simultaneous rational approximations of the frequencies of the letters. We extend Berthe’s result to factors of Arnoux-Rauzy sequences by expressing both the frequencies and the number of factors with a given frequency, in terms of the ‘convergents’ obtained from the generalized continued fraction expansion of the frequencies of the letters. --- paper_title: A generalization of Sturmian sequences; combinatorial structure and transcendence paper_content: We investigate a class of minimal sequences on a finite alphabet Ak = {1,2,...,k} having (k - 1)n + 1 distinct subwords of length n. These sequences, originally defined by P. Arnoux and G. Rauzy, are a natural generalization of binary Sturmian sequences. We describe two simple combinatorial algorithms for constructing characteristic Arnoux-Rauzy sequences (one of which is new even in the Sturmian case). Arnoux-Rauzy sequences arising from fixed points of primitive morphisms are characterized by an underlying periodic structure. We show that every Arnoux-Rauzy sequence contains arbitrarily large subwords of the form V^2+e and, in the Sturmian case, arbitrarily large subwords of the form V^3+e. Finally, we prove that an irrational number whose base b-digit expansion is an Arnoux-Rauzy sequence is transcendental. --- paper_title: Episturmian words and episturmian morphisms paper_content: Infinite episturmian words are a generalization of Sturmian words which includes the Arnoux-Rauzy sequences. We continue their study and that of episturmian morphisms, begun previously, in relation with the action of the shift operator. Palindromic and periodic factors of these words are described. We consider, in particular, the case where these words are generated by morphisms and introduce then a notion of intercept generalizing that of Sturmian words. Finally, we prove that the frequencies of the factors in a strong sense do exist for all episturmian words. --- paper_title: Descendants of Primitive Substitutions paper_content: Let s = (A, τ) be a primitive substitution. To each decomposition of the form τ (h) = uhv we associate a primitive substitution D [(h,u)] (s) defined on the set of return words to h . The substitution D [(h,u)] (s) is called a descendant of s and its associated dynamical system is the induced system (X h , T h ) on the cylinder determined by h . We show that \( {\cal D}(s) \) , the set of all descendants of s , is finite for each primitive substitution s . We consider this to be a symbolic counterpart to a theorem of Boshernitzan and Carroll which states that an interval exchange transformation defined over a quadratic field has only finitely many descendants. If s fixes a nonperiodic sequence, then \( {\cal D}(s) \) contains a recognizable substitution. Under certain conditions the set \( \Omega (s) = \bigcap_{s^\prime \in {\cal D}(s)}{\cal D}(s^\prime ) \) is nonempty. --- paper_title: A characterization of Sturmian morphisms paper_content: A morphism is called Sturmian if it preserves all Sturmian (infinite) words. It is weakly Sturmian if it preserves at least one Sturmian word. We prove that a morphism is Sturmian if and only if it keeps the word ba2ba2baba2bab balanced. As a consequence, weakly Sturmian morphisms are Sturmian. An application to infinite words associated to irrational numbers is given. --- paper_title: Substitution dynamical systems : Algebraic characterization of eigenvalues paper_content: We give a necessary and sufficient condition allowing to compute explicitly the eigenvalues of the dynamical system associated to any --- paper_title: A remark on morphic sturmian words paper_content: This Note deals with binary Sturmian words that are morphic, i.e. generated by iterating a morphism. Among these, characteristic words are a well-known subclass. We prove that for every characteristic morphic word x, the four words ax, bx, abx and bax are morphic --- paper_title: Morse and Hedlund’s Skew Sturmian Words Revisited paper_content: For any infinite word r over A = {a, b} we associate two infinite words min(r), max(r) such that any prefix of min(r) (max(r), respectively) is the lexicographically smallest (greatest, respectively) among the factors of r of the same length. We prove that (min(r); max(r)) = (as, bs) for some infinite word s if and only if r is a proper Sturmian word or an ultimately periodic word of a particular form. This result is based on a lemma concerning sequences of infinite words. --- paper_title: On complementary triples of Sturmian bisequences paper_content: Abstract A Sturmian bisequence S is a subset of ℤ such that the numbers of elements of S in any two intervals of equal lengths differ by at most 1. A complementary triple of bisequences is a set of three bisequences such that every integer belongs to exactly one bisequence. In the paper a question of Loeve is answered by giving a characterization of all complementary triples of Sturmian bisequences. --- paper_title: STRUCTURE OF THREE INTERVAL EXCHANGE TRANSFORMATIONS I : AN ARITHMETIC STUDY paper_content: Dans cet article nous decrivons une generalisation a la dimension 2 de l'algorithme d'Euclide, qui provient de la dynamique des echanges de 3 intervalles. Nous examinons diverses proprietes diophantiennes de cet algorithme, en particulier la, qualite de l'approximation simultanee. Nous montrons qu'il verifie un theoreme de type Lagrange : l'algorithme est finalement periodique si et seulement si les parametres sont dans la meme extension quadratique de Q. --- paper_title: Characterizations of finite and infinite episturmian words via lexicographic orderings paper_content: In this talk, I will present some new results arising from collaborative work with Jacques Justin (France) and Giuseppe Pirillo (Italy). This work, which extends previous results on extremal properties of infinite Sturmian and episturmian words, is purely combinatorial in nature. Specifically, we characterize by lexicographic order all finite Sturmian and episturmian words, i.e., all (finite) factors of such infinite words. Consequently, we obtain a characterization of infinite episturmian words in a wide sense (episturmian and episkew infinite words). That is, we characterize the set of all infinite words whose factors are (finite) episturmian. Similarly, we characterize by lexicographic order all balanced infinite words over a 2-letter alphabet; in other words, all Sturmian and skew infinite words, the factors of which are (finite) Sturmian. --- paper_title: Characterizations of finite and infinite episturmian words via lexicographic orderings paper_content: In this talk, I will present some new results arising from collaborative work with Jacques Justin (France) and Giuseppe Pirillo (Italy). This work, which extends previous results on extremal properties of infinite Sturmian and episturmian words, is purely combinatorial in nature. Specifically, we characterize by lexicographic order all finite Sturmian and episturmian words, i.e., all (finite) factors of such infinite words. Consequently, we obtain a characterization of infinite episturmian words in a wide sense (episturmian and episkew infinite words). That is, we characterize the set of all infinite words whose factors are (finite) episturmian. Similarly, we characterize by lexicographic order all balanced infinite words over a 2-letter alphabet; in other words, all Sturmian and skew infinite words, the factors of which are (finite) Sturmian. --- paper_title: Quasiperiodic and Lyndon episturmian words paper_content: Recently the second two authors characterized quasiperiodic Sturmian words, proving that a Sturmian word is non-quasiperiodic if and only if, it is an infinite Lyndon word. Here we extend this study to episturmian words (a natural generalization of Sturmian words) by describing all the quasiperiods of an episturmian word, which yields a characterization of quasiperiodic episturmian words in terms of their directive words. Even further, we establish a complete characterization of all episturmian words that are Lyndon words. Our main results show that, unlike the Sturmian case, there is a much wider class of episturmian words that are non-quasiperiodic, besides those that are infinite Lyndon words. Our key tools are morphisms and directive words, in particular normalized directive words, which we introduced in an earlier paper. Also of importance is the use of return words to characterize quasiperiodic episturmian words, since such a method could be useful in other contexts. --- paper_title: Extremal properties of (epi)Sturmian sequences and distribution modulo 1 paper_content: Starting from a study of Y. Bugeaud and A. Dubickas (2005) on a question in distribution of real numbers modulo 1 via combinatorics on words, we survey some combinatorial properties of (epi)Sturmian sequences and distribution modulo 1 in connection to their work. In particular we focus on extremal properties of (epi)Sturmian sequences, some of which have been rediscovered several times. --- paper_title: Symbolic dynamics and rotation numbers paper_content: In the space of binary sequences, minimal sets, that is: sets invariant under the shift operation, that have no invariant proper subsets, are investigated. In applications, such as a piecewise linear circle map and the Smale horseshoe in a mapping of the annulus, each of these sets is invariant under the mapping. These sets can be assigned a unique rotation number equal to the average of the number of ones in the sequences. --- paper_title: Symbolic dynamics of order-preserving orbits paper_content: Abstract The maps we consider are roughly those that can be obtained by truncating non-invertible maps to weakly monotonic maps (they have a flat piece). The binary sequences that correspond to order-preserving orbits are shown to satisfy a minimax principle (which was already known for order-preserving orbits with rational rotation number). The converse is also proven: all minimax orbits are order-preserving with respect to some rotation number. For certain families of such circle maps one can solve exactly for the parameter values for which the map has a specified rotation number rho. For rho rational we obtain the endpoints of the resonance intervals recursively. These parameter values can be organized in a natural way as the nodes of a Farey tree. We give some applications of the ideas discussed. --- paper_title: Conjugacy of morphisms and Lyndon decomposition of standard Sturmian words paper_content: Using the notions of conjugacy of morphisms and of morphisms preserving Lyndon words, we answer a question of G. Melancon. We characterize cases where the sequence of Lyndon words in the Lyndon factorization of a standard Sturmian word is morphic. In each possible case, the corresponding morphism is given. --- paper_title: Inequalities characterizing standard Sturmian and episturmian words paper_content: Considering the smallest and the greatest factors with respect to the lexicographic order we associate to each infinite word r two other infinite words min(r) and max(r). In this paper we prove that the inequalities as ≤ min(s) ≤ max(s) ≤ bs characterize standard Sturmian words (proper ones and periodic ones) and that the condition "for any x ∈ A and lexicographic order < satisfying x = min(A) one has xs ≤ min(s)" characterizes standard episturmian words. --- paper_title: Quasiperiodic Sturmian words and morphisms paper_content: We characterize all quasiperiodic Sturmian words: a Sturmian word is not quasiperiodic if and only if it is a Lyndon word. Moreover, we study links between Sturmian morphisms and quasiperiodicity. --- paper_title: On a characteristic property of ARNOUX–RAUZY sequences paper_content: Here we give a characterization of Arnoux-Rauzy sequences by the way of the lexicographic orderings of their alphabet. --- paper_title: Characterizations of finite and infinite episturmian words via lexicographic orderings paper_content: In this talk, I will present some new results arising from collaborative work with Jacques Justin (France) and Giuseppe Pirillo (Italy). This work, which extends previous results on extremal properties of infinite Sturmian and episturmian words, is purely combinatorial in nature. Specifically, we characterize by lexicographic order all finite Sturmian and episturmian words, i.e., all (finite) factors of such infinite words. Consequently, we obtain a characterization of infinite episturmian words in a wide sense (episturmian and episkew infinite words). That is, we characterize the set of all infinite words whose factors are (finite) episturmian. Similarly, we characterize by lexicographic order all balanced infinite words over a 2-letter alphabet; in other words, all Sturmian and skew infinite words, the factors of which are (finite) Sturmian. --- paper_title: A local balance property of episturmian words paper_content: We prove that episturmian words and Arnoux-Rauzy sequences can be characterized using a local balance property. We also give a new characterization of epistandard words. --- paper_title: A generalization of Sturmian sequences; combinatorial structure and transcendence paper_content: We investigate a class of minimal sequences on a finite alphabet Ak = {1,2,...,k} having (k - 1)n + 1 distinct subwords of length n. These sequences, originally defined by P. Arnoux and G. Rauzy, are a natural generalization of binary Sturmian sequences. We describe two simple combinatorial algorithms for constructing characteristic Arnoux-Rauzy sequences (one of which is new even in the Sturmian case). Arnoux-Rauzy sequences arising from fixed points of primitive morphisms are characterized by an underlying periodic structure. We show that every Arnoux-Rauzy sequence contains arbitrarily large subwords of the form V^2+e and, in the Sturmian case, arbitrarily large subwords of the form V^3+e. Finally, we prove that an irrational number whose base b-digit expansion is an Arnoux-Rauzy sequence is transcendental. --- paper_title: Complementing and exactly covering sequences paper_content: Abstract The following is proved (in a slightly more general setting): Let α1, …, αm be positive real, γ1, …, γm real, and suppose that the system [nαi + γi], i = 1, …, m, n = 1, 2, …, contains every positive integer exactly once (= a complementing system). Then α i α j is an integer for some i ≠ j in each of the following cases: (i) m = 3 and m = 4; (ii) m = 5 if all αi but one are integers; (iii) m ⩾ 5, two of the αi are integers, at least one of them prime; (iv) m ⩾ 5 and αn ⩽ 2n for n = 1, 2, …, m − 4. For proving (iv), a method of reduction is developed which, given a complementing system of m sequences, leads under certain conditions to a derived complementing system of m − 1 sequences. --- paper_title: Fraenkel's conjecture for six sequences paper_content: Abstract A striking conjecture of Fraenkel asserts that every decomposition of Z >0 into m ⩾3 sets {⌊α i n+β i ⌋} n∈ Z >0 with α i and β i real, α i >1 and α i 's distinct for i =1,…, m satisfies {α 1 ,…,α m }= 2 m −1 2 k : 0⩽k . Fraenkel's conjecture was proved by Morikawa if m =3 and, under some condition, if m =4. Proofs in terms of balanced sequences have been given for m =3 by the author and for m =4 by Altman, Gaujal and Hordijk. In the present paper we use the latter approach to establish Fraenkel's conjecture for m =5 and for m =6. --- paper_title: A Characterization of Balanced Episturmian Sequences paper_content: It is well known that Sturmian sequences are the aperiodic sequences that are balanced over a 2-letter alphabet. They are also characterized by their complexity: they have exactly $(n+1)$ factors of length $n$. One possible generalization of Sturmian sequences is the set of infinite sequences over a $k$-letter alphabet, $k \geq 3$, which are closed under reversal and have at most one right special factor for each length. This is the set of episturmian sequences. These are not necessarily balanced over a $k$-letter alphabet, nor are they necessarily aperiodic. In this paper, we characterize balanced episturmian sequences, periodic or not, and prove Fraenkel's conjecture for the class of episturmian sequences. This conjecture was first introduced in number theory and has remained unsolved for more than 30 years. It states that for a fixed $k> 2$, there is only one way to cover $\Z$ by $k$ Beatty sequences. The problem can be translated to combinatorics on words: for a $k$-letter alphabet, there exists only one balanced sequence up to letter permutation that has different letter frequencies. --- paper_title: Quasiperiodic and Lyndon episturmian words paper_content: Recently the second two authors characterized quasiperiodic Sturmian words, proving that a Sturmian word is non-quasiperiodic if and only if, it is an infinite Lyndon word. Here we extend this study to episturmian words (a natural generalization of Sturmian words) by describing all the quasiperiods of an episturmian word, which yields a characterization of quasiperiodic episturmian words in terms of their directive words. Even further, we establish a complete characterization of all episturmian words that are Lyndon words. Our main results show that, unlike the Sturmian case, there is a much wider class of episturmian words that are non-quasiperiodic, besides those that are infinite Lyndon words. Our key tools are morphisms and directive words, in particular normalized directive words, which we introduced in an earlier paper. Also of importance is the use of return words to characterize quasiperiodic episturmian words, since such a method could be useful in other contexts. --- paper_title: On stabilizers of infinite words paper_content: The stabilizer of an infinite word w over a finite alphabet @S is the monoid of morphisms over @S that fix w. In this paper we study various problems related to stabilizers and their generators. We show that over a binary alphabet, there exist stabilizers with at least n generators for all n. Over a ternary alphabet, the monoid of morphisms generating a given infinite word by iteration can be infinitely generated, even when the word is generated by iterating an invertible primitive morphism. Stabilizers of strict epistandard words are cyclic when non-trivial, while stabilizers of ultimately strict epistandard words are always non-trivial. For this latter family of words, we give a characterization of stabilizer elements. --- paper_title: Efficient detection of quasiperiodicities in strings paper_content: A string z is quasiperiodic if there is a second string w ≠ z such that the occurrences of w in z cover z entirely, i.e., every position of z falls within some occurrence of w in z. It is shown here that all maximal quasiperiodic substrings of a string x of n symbols can be detected in time O(n log2 n). --- paper_title: Quasiperiodic infinite words : multi-scale case and dynamical properties paper_content: An infinite word x is said to be quasiperiodic if there exists a finite word q such that x is covered by occurrences of q (such a q is called a quasiperiod of x). Using the notion of derivation, we show that this definition is not sufficient to imply any symmetry in an infinite word. Therefore we introduce multi-scale quasiperiodic words, i.e. quasiperiodic words that admit an infinite number of quasiperiods. Such words are uniformly recurrent, this allows us to study the subshift they generate. We prove that multi-scale quasiperiodic subshifts are uniquely ergodic and have zero topological entropy as well as zero Kolmogorov complexity. Sturmian subshifts are shown to be multi-scale quasiperiodic. --- paper_title: On different generalizations of episturmian words paper_content: In this paper we study some classes of infinite words generalizing episturmian words, and analyse the relations occurring among such classes. In each case, the reversal operator R is replaced by an arbitrary involutory antimorphism @q of the free monoid A^. In particular, we define the class of @q-words with seed, whose ''standard'' elements (@q-standard words with seed) are constructed by an iterative @q-palindrome closure process, starting from a finite word u"0 called the seed. When the seed is empty, one obtains @q-words; episturmian words are exactly the R-words. One of the main theorems of the paper characterizes @q-words with seed as infinite words closed under @q and having at most one left special factor of each length n>=N (where N is some nonnegative integer depending on the word). When N=0 we call such words @q-episturmian. Further results on the structure of @q-episturmian words are proved. In particular, some relationships between @q-words (with or without seed) and @q-episturmian words are shown. --- paper_title: Quasiperiodic Sturmian words and morphisms paper_content: We characterize all quasiperiodic Sturmian words: a Sturmian word is not quasiperiodic if and only if it is a Lyndon word. Moreover, we study links between Sturmian morphisms and quasiperiodicity. --- paper_title: On some problems related to palindrome closure paper_content: In this paper, we solve some open problems related to (pseudo)palindrome closure operators and to the infinite words generated by their iteration, that is, standard episturmian and pseudostandard words. We show that if ϑ is an involutory antimorphism of A , then the right and left ϑ -palindromic closures of any factor of a ϑ -standard word are also factors of some ϑ -standard word. We also introduce the class of pseudostandard words with “seed”, obtained by iterated pseudopalindrome closure starting from a nonempty word. We show that pseudostandard words with seed are morphic images of standard episturmian words. Moreover, we prove that for any given pseudostandard word s with seed, all sufficiently long left special factors of s are prefixes of it. --- paper_title: String Pattern Matching for a Deluge Survival Kit paper_content: String Pattern Matching concerns itself with algorithmic and combinatorial issues related to matching and searching on linearly arranged sequences of symbols, arguably the simplest possible discrete structures. As unprecedented volumes of sequence data are amassed, disseminated and shared at an increasing pace, effective access to, and manipulation of such data depend crucially on the efficiency with which strings are structured, compressed, transmitted, stored, searched and retrieved. This paper samples from this perspective, and with the authors' own bias, a rich arsenal of ideas and techniques developed in more than three decades of history. ---	Title: Episturmian Words: A Survey Section 1: From Sturmian to episturmian Description 1: This section introduces the concept of Sturmian words and their fascinating properties, leading to the natural extension to episturmian words. Section 2: Notation & terminology Description 2: This section provides definitions, notations, and terminologies related to episturmian words, essential for understanding the subsequent sections. Section 3: Definitions & basic properties Description 3: This section offers the foundational definitions and basic properties of episturmian words, including their characteristic attributes and generalizations. Section 4: Equivalence classes Description 4: This section explores the classification of infinite words into equivalence classes based on their factor sets, particularly focusing on episturmian words. Section 5: Bi-infinite episturmian words Description 5: This section extends the concept of episturmian words to bi-infinite words and discusses their recurrence properties and related formulations. Section 6: Strict episturmian words Description 6: This section defines strict episturmian words and discusses their properties in terms of their alphabets and special factors. Section 7: Episturmian morphisms Description 7: This section introduces episturmian morphisms, their significance, and how they generalize Sturmian morphisms to larger alphabets. Section 8: Generators & monoids Description 8: This section details the generators and monoids of episturmian morphisms, demonstrating various inclusions and decompositions. Section 9: Relation with episturmian words Description 9: This section characterizes episturmian words using their decompositions over pure episturmian morphisms and directive words. Section 10: Spins, shifts, and directive words Description 10: This section examines the concepts of spins, shifts, and directive words, illustrating how these notions impact the structure of episturmian words. Section 11: Notation for pure episturmian morphisms Description 11: This section introduces a notation system for pure episturmian morphisms and discusses their operational principles. Section 12: Shifts Description 12: This section explores the impact of shifts on episturmian morphisms and how they relate to conjugate morphisms. Section 13: Block-equivalence & directive words Description 13: This section discusses block-equivalence for spinned words and their influence on representing episturmian words. Section 14: Periodic and purely morphic episturmian words Description 14: This section describes periodic and purely morphic episturmian words in terms of their directive words and morphic structures. Section 15: Arnoux-Rauzy sequences Description 15: This section briefly discusses Arnoux-Rauzy sequences and their combinatorial properties, elucidating their relation to episturmian words. Section 16: Finite Arnoux-Rauzy words Description 16: This section considers finite episturmian words and their enumeration and characterization with respect to their periodic properties. Section 17: Some properties of factors Description 17: This section summarizes various properties of factors of episturmian words including factor complexity, palindromes, and more. Section 18: Factor complexity Description 18: This section provides detailed insights into the complexity of factors in episturmian words. Section 19: Palindromic factors Description 19: This section discusses the palindromic factors in episturmian words and their implications. Section 20: Iterated palindromic closure Description 20: This section elaborates on the process and significance of iterated palindromic closure in the context of episturmian words. Section 21: Palindromic richness Description 21: This section defines and explores the concept of palindromic richness within episturmian words. Section 22: Fractional powers & critical exponent Description 22: This section investigates the occurrence of fractional powers in episturmian words and the concepts of the critical exponent. Section 23: Frequencies Description 23: This section discusses the frequency of factors within episturmian words, providing formulas and examples. Section 24: Return words Description 24: This section introduces the notion of return words and their significance in the study of episturmian words. Section 25: Episkew words Description 25: This section defines episkew words and discusses their equivalence to episturmian words and their properties. Section 26: Extremal properties Description 26: This section explores the extremal properties of episturmian words with respect to lexicographic order. Section 27: Imbalance Description 27: This section discusses the balance properties of episturmian words and how they relate to episturmian sequences. Section 28: Fraenkel's conjecture Description 28: This section addresses Fraenkel's conjecture in the context of balanced episturmian words and recurrent sequences. Section 29: Concluding remarks Description 29: This section concludes the survey by mentioning recent research works and open questions involving episturmian words.
From “hand-written ” to computationally implemented HPSG theories 1 Overview	11	--- paper_title: A Web-Based Instructional Platform For Contraint-Based Grammar Formalisms And Parsing paper_content: We propose the creation of a web-based training framework comprising a set of topics that revolve around the use of feature structures as the core data structure in linguistic theory, its formal foundations, and its use in syntactic processing. --- paper_title: Verb-initial Constructions in Modern Hebrew paper_content: V erb -In itial C on stru ction s in M odern H ebrew by Nurit Melnik B.Sc. (The Hebrew University of Jerusalem) 1993 M.A. (University of California, Berkeley) 1999 A dissertation subm itted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Linguistics in the GRADUATE DIVISION of the UNIVERSITY OF CALIFORNIA, BERKELEY Committee in charge: Professor Andreas Kathol, Chair Professor Paul Kay Professor Johanna Nichols Fall 2002 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. --- paper_title: In search of epistemic primitives in the english resource grammar paper_content: This paper seeks to improve HPSG engineering through the design of more terse, readable and intuitive type signatures. It argues against the exclusive use of IS-A networks and, with reference to the English Resource Grammar, demonstrates that a collection of higher-order datatypes are already acutely in demand in contemporary HPSG design. Some default specification conventions to assist in maximizing the utility of higher-order type constructors are also discussed. --- paper_title: On expressing lexical generalizations in HPSG paper_content: This paper investigates the status of the lexicon and the possibilities for expressing lexical generalizations in the paradigm of Head-Driven Phrase Structure Grammar (HPSG). We illustrate that the architecture readily supports the use of implicational principles to express generalizations over a class of word objects. A second kind of lexical generalizations expressing relations between classes of words is often expressed in terms of lexical rules. We show how lexical rules can be integrated into the formal setup for HPSG developed by King (1989, 1994), investigate a lexical rule specification language allowing the linguist to only specify those properties which are supposed to differ between the related classes, and define how this lexical rule specification language is interpreted. We thereby provide a formalization of lexical rules as used in HPSG. --- paper_title: A Computational Treatment Of Lexical Rules In HPSG As Covariation In Lexical Entries paper_content: This paper proposes a new computational treatment of lexical rules as used in the HPSG framework. A complier is described which translates a set of lexical rules and their interaction into a definite clause encoding, which is called by the base lexical entries in the lexicon. This way, the disjunctive possibilities arising from lexical rule application are encoded as systematic covariation in the specification of lexical entries. The compiler ensures the automatic transfer of properties not changed by a lexical rule. Program transformation techniques are used to advance the encoding. The final output of the compiler constitutes an efficient computational counterpart of the linguistic generalizations captured by lexical rules and allows on-the-fly application of lexical rules. --- paper_title: Head-driven Phrase Structure Grammar paper_content: This book presents the most complete exposition of the theory of head-driven phrase structure grammar (HPSG), introduced in the authors' "Information-Based Syntax and Semantics." HPSG provides an integration of key ideas from the various disciplines of cognitive science, drawing on results from diverse approaches to syntactic theory, situation semantics, data type theory, and knowledge representation. The result is a conception of grammar as a set of declarative and order-independent constraints, a conception well suited to modelling human language processing. This self-contained volume demonstrates the applicability of the HPSG approach to a wide range of empirical problems, including a number which have occupied center-stage within syntactic theory for well over twenty years: the control of "understood" subjects, long-distance dependencies conventionally treated in terms of "wh"-movement, and syntactic constraints on the relationship between various kinds of pronouns and their antecedents. The authors make clear how their approach compares with and improves upon approaches undertaken in other frameworks, including in particular the government-binding theory of Noam Chomsky. --- paper_title: An Open Source Grammar Development Environment and Broad-coverage English Grammar Using HPSG paper_content: The LinGO (Linguistic Grammars Online) project’s English Resource Grammar and the LKB grammar development environment are language resources which are freely available for download for any purpose, including commercial use (see http://lingo.stanford.edu). Executable programs and source code are both included. In this paper, we give an outline of the LinGO English grammar and LKB system, and discuss the ways in which they are currently being used. The grammar and processing system can be used independently or combined to give a central component which can be exploited in a variety of ways. Our intention in writing this paper is to encourage more people to use the technology, which supports collaborative development on many levels. --- paper_title: The Grammar Matrix: An Open-Source Starter-Kit For The Rapid Development Of Cross-Linguistically Consistent Broad-Coverage Precision Grammars paper_content: The grammar matrix is an open-source starter-kit for the development of broad-coverage HPSGs. By using a type hierarchy to represent cross-linguistic generalizations and providing compatibility with other open-source tools for grammar engineering, evaluation, parsing and generation, it facilitates not only quick start-up but also rapid growth towards the wide coverage necessary for robust natural language processing and the precision parses and semantic representations necessary for natural language understanding. ---	Title: From “hand-written” to computationally implemented HPSG theories 1 Overview Section 1: Overview Description 1: Brief introduction about the potential of HPSG for computational implementation and the main focus of the paper. Section 2: Type Definition Description 2: Discuss the approach to defining types in TRALE and LKB, including the organization of type hierarchies and the glb condition. Section 3: Principles Description 3: Explain how HPSG principles are defined in LKB and TRALE, including their application and the differences in approach. Section 4: Lexical Rules Description 4: Overview of the implementation of lexical rules in LKB and TRALE, with emphasis on the "carrying over” of information from input to output. Section 5: Exhaustive Typing and Subtype Covering Description 5: Discuss the concept of exhaustive typing and subtype covering in TRALE and LKB, and their implications for HPSG implementation. Section 6: Definite Relations Description 6: Describe how LKB and TRALE handle definite relations, such as APPEND, and the integration of a programming language into TRALE. Section 7: Non-binary Grammar Rules Description 7: Explain the implementation of non-binary grammar rules in LKB and TRALE, focusing on handling rules with varying numbers of daughters. Section 8: Semantic Representation Description 8: Compare the modules for processing semantic representations (MRS in LKB and Lexical Resource Semantics in TRALE). Section 9: Evaluating Competence and Performance Description 9: Discuss the tools and methods provided by LKB and TRALE for evaluating grammar competence and performance. Section 10: User-Interface Issues and Features Description 10: Compare the user-interface features of LKB and TRALE, including hierarchies display, feature structures, syntactic trees, and command interactions. Section 11: Conclusion Description 11: Summarize the comparison between LKB and TRALE regarding faithfulness to "hand-written" HPSG and the accessibility of the implementation platforms for linguists.
A Review of Selective Forwarding Attacks in Wireless Sensor Networks	3	--- paper_title: Lightweight defense scheme against selective forwarding attacks in wireless sensor networks paper_content: In data-centric wireless sensor networks, the malicious nodes may selectively drop some crucial data packets, which seriously destroy the network's data collection and decrease the availability of sensor services. In this paper, we present a lightweight defense scheme against selective forwarding attacks. According to characteristics of easy positioning the nodes around transmission paths in a structured topology made of hexagonal mesh, the nodes around transmission path are used to monitor packet transmission of its neighbor nodes, judge the attackers' location and resend the packets dropped by the attackers. The method is effective in detecting selective forwarding attacks to ensure reliable packet delivery. Analysis and simulation results show that the proposed scheme consumes less energy and storage. --- paper_title: Directed diffusion: a scalable and robust communication paradigm for sensor networks paper_content: Advances in processor, memory and radio technology will enable small and cheap nodes capable of sensing, communication and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed diffusion paradigm for such coordination. Directed diffusion is datacentric in that all communication is for named data. All nodes in a directed diffusion-based network are application-aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network. We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network. --- paper_title: A Novel Cooperation Mechanism to Enforce Security in Wireless Sensor Networks paper_content: In wireless sensor networks, how to detect the malicious nodes and prevent them from attacking the normal nodes has become one of the most important issues. This paper introduces a new mechanism in which the sensor nodes collaborate with each other to resist denial of service (DoS) attack and protect the being attacked nodes. A reputation-based incentive model for cooperation is also proposed. Simulation results show that the proposed scheme has low false alarm rate and can increase the chance of success in stopping the malicious nodes from attacking the normal nodes in wireless sensor networks. --- paper_title: Research about security mechanism in wireless sensor network paper_content: WSN has been widely used in many prospects, and more and more researchers at home and abroad are paying attention to this hot field. However, due to the deployment of environmental requirements and their conditions, most of the mechanisms used in traditional wireless networks are difficult to directly apply to wireless sensor networks. So, it is very eager to design a special wireless sensor network. This paper introduces wireless sensor network routing protocols and describes the security routing of wireless sensor network. Moreover, this paper has done deep research on SPIN. Finally, through the analysis of NS2 simulation, we prove that SPIN protocol is valuable in security performance evaluation and confidentiality. --- paper_title: GPSR: greedy perimeter stateless routing for wireless networks paper_content: We present Greedy Perimeter Stateless Routing (GPSR), a novel routing protocol for wireless datagram networks that uses the positions of routers and a packet's destination to make packet forwarding decisions. GPSR makes greedy forwarding decisions using only information about a router's immediate neighbors in the network topology. When a packet reaches a region where greedy forwarding is impossible, the algorithm recovers by routing around the perimeter of the region. By keeping state only about the local topology, GPSR scales better in per-router state than shortest-path and ad-hoc routing protocols as the number of network destinations increases. Under mobility's frequent topology changes, GPSR can use local topology information to find correct new routes quickly. We describe the GPSR protocol, and use extensive simulation of mobile wireless networks to compare its performance with that of Dynamic Source Routing. Our simulations demonstrate GPSR's scalability on densely deployed wireless networks. --- paper_title: Denial of Service in Sensor Networks paper_content: Sensor networks hold the promise of facilitating large-scale, real-time data processing in complex environments, helping to protect and monitor military, environmental, safety-critical, or domestic infrastructures and resources, Denial-of-service attacks against such networks, however, may permit real world damage to public health and safety. Without proper security mechanisms, networks will be confined to limited, controlled environments, negating much of the promise they hold. The limited ability of individual sensor nodes to thwart failure or attack makes ensuring network availability more difficult. To identify denial-of-service vulnerabilities, the authors analyzed two effective sensor network protocols that did not initially consider security. These examples demonstrate that consideration of security at design time is the best way to ensure successful network deployment. --- paper_title: Priority and Random Selection for Dynamic Window Secured Implicit Geographic Routing in Wireless Sensor Network paper_content: Problem statement: Sensor nodes are easily exposed to many attacks since it were deployed in unattended adversarial environment with no global addressing and used for critical applications such as battlefield surveillance and emergency response. While the sensor also needs to act as a router to relay a message to a required recipient, then this increased the vulnerabilities to a network layer. However, existing security mechanisms are not permissible to be fitted directly into any sensor network due to constraints on energy and computational capabilities of sensor node itself that require on the modification on the protocols that associated with the sensor node itself in order to provide the security. Approach: In this study, a Dynamic Window Secured Implicit Geographic Forwarding (DWIGF) routing protocol was presented which based on an approach of lazy binding technique and dynamic time on collection window and inherits a geographical routing techniques. Results: The DWIGF was intelligent to minimize a Clear To Send (CTS) rushing attack and robust against black hole and selective forwarding attacks with high packet delivery ratios because of selection of a failed node and an attacker was minimized respectively. Moreover, few routing attacks were eliminated since the routing technique used was classified as geographic routing. Conclusion: This novel routing protocol was promising a secured routing without inserting any existing security mechanism inside. --- paper_title: Lightweight defense scheme against selective forwarding attacks in wireless sensor networks paper_content: In data-centric wireless sensor networks, the malicious nodes may selectively drop some crucial data packets, which seriously destroy the network's data collection and decrease the availability of sensor services. In this paper, we present a lightweight defense scheme against selective forwarding attacks. According to characteristics of easy positioning the nodes around transmission paths in a structured topology made of hexagonal mesh, the nodes around transmission path are used to monitor packet transmission of its neighbor nodes, judge the attackers' location and resend the packets dropped by the attackers. The method is effective in detecting selective forwarding attacks to ensure reliable packet delivery. Analysis and simulation results show that the proposed scheme consumes less energy and storage. --- paper_title: Achieving Network Level Privacy in Wireless Sensor Networks paper_content: Full network level privacy has often been categorized into four sub-categories: Identity, Route, Location and Data privacy. Achieving full network level privacy is a critical and challenging problem due to the constraints imposed by the sensor nodes (e.g., energy, memory and computation power), sensor networks (e.g., mobility and topology) and QoS issues (e.g., packet reach-ability and timeliness). In this paper, we proposed two new identity, route and location privacy algorithms and data privacy mechanism that addresses this problem. The proposed solutions provide additional trustworthiness and reliability at modest cost of memory and energy. Also, we proved that our proposed solutions provide protection against various privacy disclosure attacks, such as eavesdropping and hop-by-hop trace back attacks. Achieving Network Level Privacy in Wireless Sensor Networks --- paper_title: A sequential mesh test based selective forwarding attack detection scheme in wireless sensor networks paper_content: It is very difficult to distinguish between selective forwarding attacks and normal packet drops in wireless sensor networks. In order to detect selective forwarding attack effectively, we propose the sequential mesh test based detection scheme in this paper. The cluster head node detects the packet drop nodes based on the sequential mesh test method after receiving the packet drop reports. This scheme extracts a small quantity of samples to run the test, instead of regulating the total times of test in advance. It decides whether continue the test or not based on the test result until it obtains the final conclusion. We show through experiments that our scheme can provide a higher detection accurate rate and a lower false alarm rate than the existing detection scheme. Meanwhile, it requires less communication and computation power and shorter detection time to detect the selective forwarding attack nodes. --- paper_title: Detection of Selective Forwarding Attacks in Heterogeneous Sensor Networks paper_content: Security is crucial for wireless sensor networks deployed in the military and other hostile environments. Due to the limited transmission range, a sensor node may need multiple hops of transmissions to deliver a packet to the base station. An attacker can launch the selective forwarding attack and drop a portion of packets for which it needs to relay while forward the rest. Selective forwarding attack is hard to detect, since packet drops in sensor networks may be caused by unreliable wireless communications or node failures. In this paper, first we describe an efficient scheme for reporting packet drops, then we present an effective scheme for detecting the selective forwarding attack in a heterogeneous sensor network. The scheme utilizes powerful high-end sensors and is based on the sequential probability ratio test. Our extensive simulations show that the proposed scheme achieves high detection ratio and very low false alarm rate. ---	Title: A Review of Selective Forwarding Attacks in Wireless Sensor Networks Section 1: INTRODUCTION Description 1: This section introduces Wireless Sensor Networks (WSNs), highlighting their structure, communication methods, and security vulnerabilities, particularly focusing on selective forwarding attacks. Section 2: SELECTIVE FORWARDING ATTACK Description 2: This section describes the selective forwarding attack in detail, explaining how malicious nodes drop or selectively forward packets to compromise the network. Section 3: RECENT PROPOSED DETECTION TECHNIQUES OF SELECTIVE FORWARDING ATTACKS Description 3: This section reviews various detection techniques proposed in recent years for identifying and mitigating selective forwarding attacks in WSNs. Section 4: CONCLUSIONS Description 4: This section summarizes the importance of detecting selective forwarding attacks and reviews the recent techniques discussed in the paper, potentially guiding future research directions.
A Review of Redeye Detection and Removal in Digital Images Through Patents	8	--- paper_title: Human Face Detection in Visual Scenes paper_content: We present a neural network-based face detection system. A retinally connected neural network examines small windows of an image, and decides whether each window contains a face. The system arbitrates between multiple networks to improve performance over a single network. We use a bootstrap algorithm for training, which adds false detections into the training set as training progresses. This eliminates the difficult task of manually selecting non-face training examples, which must be chosen to span the entire space of non-face images. Comparisons with another state-of-the-art face detection system are presented; our system has better performance in terms of detection and false-positive rates. --- paper_title: Automatic Red-Eye Removal based on Sclera and Skin Tone Detection paper_content: It is well-known that taking portrait photographs with a built in camera may create a red-eye effect. This effect is caused by the light entering the subject’s eye through the pupil and reflecting from the retina back to the sensor. These red eyes are probably one of the most important types of artifacts in portrait pictures. Many different techniques exist for removing these artifacts digitally after image capture. In most of the existing software tools, the user has to select the zone in which the red eye is located. The aim of our method is to automatically detect and correct the red eyes. Our algorithm detects the eye itself by finding the appropriate colors and shapes without input from the user. We use the basic knowledge that an eye is haracterized by its shape and the white color of the sclera. Combining this intuitive approach with the detection of “skin” around the eye, we obtain a higher success rate than most of the tools we tested. Moreover, our algorithm works for any type of skin tone. The main goal of this algorithm is to accurately remove red eyes from a picture, while avoiding false positives completely, which is the biggest problem of camera integrated algorithms or distributed software tools. At the same time, we want to keep the false negative rate as low as possible. We implemented this algorithm in a web-based application to allow people to correct their images online. --- paper_title: Red Eye Removal using Digital Color Image Processing paper_content: The current paper provides methods to correct the artifact known as “red eye” by means of digital color image processing. This artifact is typically formed in amateur photographs taken with a built-in camera flash. To correct red eye artifacts, an image mask is computed by calculating a colorimetric distance between a prototypical reference “red eye” color and each pixel of the image containing the red eye. Various image processing algorithms such as thresholding, blob analysis, and morphological filtering, are applied to the mask, in order to eliminate noise, reduce errors, and facilitate a more natural looking result. The mask serves to identify pixels in the color image needing correction, and further serves to identify the amount of correction needed. Pixels identified as having red-eye artifacts are modified to a substantially monochrome color, while the bright specular reflection of the eye is preserved. --- paper_title: An efficient automatic redeye detection and correction algorithm paper_content: A fully automatic redeye detection and correction algorithm is presented to address the redeye artifacts in digital photos. The algorithm contains a redeye detection part and a correction part. The detection part is modeled as a feature based object detection problem. Adaboost is used to simultaneously select features and train the classifier. A new feature set is designed to address the orientation-dependency problem associated with the Haar-like features commonly used for object detection design. For each detected redeye, a correction algorithm is applied to do adaptive desaturation and darkening over the redeye region. --- paper_title: Red eye detection with machine learning paper_content: Red-eye is a problem in photography that occurs when a photograph is taken with a flash, and the bright flash light is reflected from the blood vessels in the eye, giving the eye an unnatural red hue. Most red-eye reduction systems need the user to outline the red eyes by hand, but this approach doesn't scale up. Instead, we propose an automatic red-eye detection system. The system contains a red-eye detector that finds red eye-like candidate image patches; a state of the art face detector used to eliminate most false positives (image regions that look but red eyes but are not); and a red-eye outline detector. All three detectors are automatically learned from data, using Boosting. Our system can be combined with a red-eye reduction module to yield a fully automatic red eye corrector. --- paper_title: Probabilistic Automatic Red Eye Detection and Correction paper_content: In this paper we propose a new probabilistic approach to red eye detection and correction. It is based on stepwise refinement of a pixel-wise red eye probability map. Red eye detection starts with a fast non red eye region rejection step. A classification step then adjusts the probabilities attributed to the detected red eye candidates. The correction step finally applies a soft red eye correction based on the resulting probability map. The proposed approach is fast and allows achieving an excellent correction of strong red eyes while producing a still significant correction of weaker red eyes. --- paper_title: Automatic red-eye detection and correction paper_content: "Red-eye" is a phenomenon that causes the eyes of flash photography subjects to appear unnaturally reddish in color. Though commercial solutions exist for red-eye correction, all of them require some measure of user intervention. A method is presented to automatically detect and correct redeye in digital images. First, faces are detected with a cascade of multi-scale classifiers. The red-eye pixels are then located with several refining masks computed over the facial region. The masks are created by thresholding per-pixel metrics, designed to detect red-eye artifacts. Once the redeye pixels have been found, the redness is attenuated with a tapered color desaturation. A detector implemented with this system corrected 95% of the red-eye artifacts in 200 tested images. --- paper_title: Robust real-time object detection paper_content: This paper describes a visual object detection framework that is capable of processing images extremely rapidly while achieving high detection rates. There are three key contributions. The first is the introduction of a new image representation called the “Integral Image” which allows the features used by our detector to be computed very quickly. The second is a learning algorithm, based on AdaBoost, which selects a small number of critical visual features and yields extremely efficient classifiers [4]. The third contribution is a method for combining classifiers in a “cascade” which allows background regions of the image to be quickly discarded while spending more computation on promising object-like regions. A set of experiments in the domain of face detection are presented. The system yields face detection performance comparable to the best previous systems [16, 11, 14, 10, 1]. Implemented on a conventional desktop, face detection proceeds at 15 frames per second. Author email: fPaul.Viola,[email protected] c Compaq Computer Corporation, 2001 This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of the Cambridge Research Laboratory of Compaq Computer Corporation in Cambridge, Massachusetts; an acknowledgment of the authors and individual contributors to the work; and all applicable portions of the copyright notice. Copying, reproducing, or republishing for any other purpose shall require a license with payment of fee to the Cambridge Research Laboratory. All rights reserved. CRL Technical reports are available on the CRL’s web page at http://crl.research.compaq.com. Compaq Computer Corporation Cambridge Research Laboratory One Cambridge Center Cambridge, Massachusetts 02142 USA --- paper_title: A Brief Introduction to Boosting paper_content: Boosting is a general method for improving the accuracy of any given learning algorithm. This short paper introduces the boosting algorithm AdaBoost, and explains the underlying theory of boosting, including an explanation of why boosting often does not suffer from overfitting. Some examples of recent applications of boosting are also described. --- paper_title: Automatic red-eyes detection based on AAM paper_content: Red-eye is a phenomenon that the pupils of people appear unnaturally red when an image is captured using photoflash lamp. There are some algorithms existing for red-eyes detection, but all of them have less accuracy and cannot detect single red-eye. In this paper, a novel approach is proposed to automatically detect red eyes in photos, which is based on active appearance models, and a practicable automatic correction method is presented The goal of the algorithm is to detect all the red-eyes in photos without any human intervention. Finally, experimental results demonstrate the high accuracy and efficiency of the method. --- paper_title: Towards automatic redeye effect removal paper_content: The redeye effect is typically formed in amateur photographs taken with a built-in camera flash. Analysis of the available techniques and products indicates that their efficiency in correcting this artifact is limited and their performance is inconsistent. In this work we propose a user friendly solution, which could be used to restore amateur photographs. In the proposed method the redeye effect is detected using a skin detection module and eye colors are restored using morphological image processing. The new method is computationally efficient, robust to parameter settings and versatile, as it can work in conjunction with a number of skin detection methods. --- paper_title: Digital red eye removal paper_content: The current paper provides methods to correct the artifact known as red eye by means of digital color image processing. This artifact is typically formed in amateur photographs taken with a built-in camera flash. To correct red eye artifacts, an image mask is computed by calculating a colorimetric distance between a prototypical reference red eye color and each pixel of the image containing the red eye. Various image processing algorithms such as thresholding, blob analysis, and morphological filtering, are applied to the mask, in order to eliminate noise, reduce errors, and facilitate a more natural looking result. The mask serves to identify pixels in the color image needing correction, and further serves to identify the amount of correction needed. Pixels identified as having red eye artifacts are modified to a substantially monochrome color, while the bright specular reflection of the eye is preserved. --- paper_title: A fully automatic redeye detection and correction algorithm paper_content: A fully automatic redeye detection and correction algorithm was developed at Eastman Kodak Company Research Laboratories. The algorithm is highly sophisticated so that it is able to distinguish most redeye pairs from scene content. It is also highly optimized for execution speed and memory usage enabling it to be included in a variety of products. Detected redeyes are corrected so that the red color is removed, but the eye maintains a natural look. --- paper_title: Automatic redeye removal for smart enhancement of photos of unknown origin paper_content: The paper describes a modular procedure for automatic correction of redeye artifact in images of unknown origin, maintaining the natural appearance of the eye. First, a smart color balancing procedure is applied. This phase not only facilitates the subsequent steps of processing, but also improves the overall appearance of the output image. Combining the results of a color-based face detector and of a face detector based on a multi-resolution neural network the most likely facial regions are identified. Redeye is searched for only within these regions, seeking areas with high “redness” satisfying some geometric constraints. A novel redeye removal algorithm is then applied automatically to the red eyes identified, and opportunely smoothed to avoid unnatural transitions between the corrected and original parts. Experimental results on a set of over 450 images are reported. --- paper_title: Safe Red-Eye Correction Plug-in Using Adaptive Methods paper_content: An important issue with red-eye correction is that it might result in image degradation. This can be due to the detection of false positives or, even in the case of correct detection, to an inadequate correction technique. Three correction methods are proposed and compared according to their image degradation risk and their expected perceptual quality improvement. Based on those analyses an adaptive system is designed which selects the correction strategy dependent on those measures and the detection confidence. Finally, both qualitative (visual preferences) and quantitative (pixel counts on manual segmented images) evaluation results are shown. --- paper_title: Automatic Red-Eye Removal based on Sclera and Skin Tone Detection paper_content: It is well-known that taking portrait photographs with a built in camera may create a red-eye effect. This effect is caused by the light entering the subject’s eye through the pupil and reflecting from the retina back to the sensor. These red eyes are probably one of the most important types of artifacts in portrait pictures. Many different techniques exist for removing these artifacts digitally after image capture. In most of the existing software tools, the user has to select the zone in which the red eye is located. The aim of our method is to automatically detect and correct the red eyes. Our algorithm detects the eye itself by finding the appropriate colors and shapes without input from the user. We use the basic knowledge that an eye is haracterized by its shape and the white color of the sclera. Combining this intuitive approach with the detection of “skin” around the eye, we obtain a higher success rate than most of the tools we tested. Moreover, our algorithm works for any type of skin tone. The main goal of this algorithm is to accurately remove red eyes from a picture, while avoiding false positives completely, which is the biggest problem of camera integrated algorithms or distributed software tools. At the same time, we want to keep the false negative rate as low as possible. We implemented this algorithm in a web-based application to allow people to correct their images online. --- paper_title: Red eye detection with machine learning paper_content: Red-eye is a problem in photography that occurs when a photograph is taken with a flash, and the bright flash light is reflected from the blood vessels in the eye, giving the eye an unnatural red hue. Most red-eye reduction systems need the user to outline the red eyes by hand, but this approach doesn't scale up. Instead, we propose an automatic red-eye detection system. The system contains a red-eye detector that finds red eye-like candidate image patches; a state of the art face detector used to eliminate most false positives (image regions that look but red eyes but are not); and a red-eye outline detector. All three detectors are automatically learned from data, using Boosting. Our system can be combined with a red-eye reduction module to yield a fully automatic red eye corrector. --- paper_title: Automatic red-eye detection and correction paper_content: "Red-eye" is a phenomenon that causes the eyes of flash photography subjects to appear unnaturally reddish in color. Though commercial solutions exist for red-eye correction, all of them require some measure of user intervention. A method is presented to automatically detect and correct redeye in digital images. First, faces are detected with a cascade of multi-scale classifiers. The red-eye pixels are then located with several refining masks computed over the facial region. The masks are created by thresholding per-pixel metrics, designed to detect red-eye artifacts. Once the redeye pixels have been found, the redness is attenuated with a tapered color desaturation. A detector implemented with this system corrected 95% of the red-eye artifacts in 200 tested images. --- paper_title: Robust real-time object detection paper_content: This paper describes a visual object detection framework that is capable of processing images extremely rapidly while achieving high detection rates. There are three key contributions. The first is the introduction of a new image representation called the “Integral Image” which allows the features used by our detector to be computed very quickly. The second is a learning algorithm, based on AdaBoost, which selects a small number of critical visual features and yields extremely efficient classifiers [4]. The third contribution is a method for combining classifiers in a “cascade” which allows background regions of the image to be quickly discarded while spending more computation on promising object-like regions. A set of experiments in the domain of face detection are presented. The system yields face detection performance comparable to the best previous systems [16, 11, 14, 10, 1]. Implemented on a conventional desktop, face detection proceeds at 15 frames per second. Author email: fPaul.Viola,[email protected] c Compaq Computer Corporation, 2001 This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of the Cambridge Research Laboratory of Compaq Computer Corporation in Cambridge, Massachusetts; an acknowledgment of the authors and individual contributors to the work; and all applicable portions of the copyright notice. Copying, reproducing, or republishing for any other purpose shall require a license with payment of fee to the Cambridge Research Laboratory. All rights reserved. CRL Technical reports are available on the CRL’s web page at http://crl.research.compaq.com. Compaq Computer Corporation Cambridge Research Laboratory One Cambridge Center Cambridge, Massachusetts 02142 USA --- paper_title: Automatic red-eyes detection based on AAM paper_content: Red-eye is a phenomenon that the pupils of people appear unnaturally red when an image is captured using photoflash lamp. There are some algorithms existing for red-eyes detection, but all of them have less accuracy and cannot detect single red-eye. In this paper, a novel approach is proposed to automatically detect red eyes in photos, which is based on active appearance models, and a practicable automatic correction method is presented The goal of the algorithm is to detect all the red-eyes in photos without any human intervention. Finally, experimental results demonstrate the high accuracy and efficiency of the method. --- paper_title: A fully automatic redeye detection and correction algorithm paper_content: A fully automatic redeye detection and correction algorithm was developed at Eastman Kodak Company Research Laboratories. The algorithm is highly sophisticated so that it is able to distinguish most redeye pairs from scene content. It is also highly optimized for execution speed and memory usage enabling it to be included in a variety of products. Detected redeyes are corrected so that the red color is removed, but the eye maintains a natural look. --- paper_title: Automatic redeye removal for smart enhancement of photos of unknown origin paper_content: The paper describes a modular procedure for automatic correction of redeye artifact in images of unknown origin, maintaining the natural appearance of the eye. First, a smart color balancing procedure is applied. This phase not only facilitates the subsequent steps of processing, but also improves the overall appearance of the output image. Combining the results of a color-based face detector and of a face detector based on a multi-resolution neural network the most likely facial regions are identified. Redeye is searched for only within these regions, seeking areas with high “redness” satisfying some geometric constraints. A novel redeye removal algorithm is then applied automatically to the red eyes identified, and opportunely smoothed to avoid unnatural transitions between the corrected and original parts. Experimental results on a set of over 450 images are reported. --- paper_title: Automated red-eye detection and correction in digital photographs paper_content: Caused by light reflected off the subject's retina, red-eye is a troublesome problem in consumer photography. Although most of the cameras have the red-eye reduction mode, the result reality is that no on-camera system is completely effective. In this paper, we propose a fully automatic approach to detecting and correcting red-eyes in digital images. In order to detect red-eyes in a picture, a heuristic yet efficient algorithm is first adopted to detect a group of candidate red regions and then an eye classifier is utilized to confirm whether each candidate region is a human eye. Thereafter, for each detected redeye, we can correct it by the correction algorithm. In case that a red-eye cannot be detected automatically, another algorithm is also provided to detect red-eyes manually with the user's interaction by clicking on an eye. Experimental results on about 300 images with various red-eye appearances demonstrate that the proposed solution is robust and effective. --- paper_title: Automatic red-eye detection and correction paper_content: "Red-eye" is a phenomenon that causes the eyes of flash photography subjects to appear unnaturally reddish in color. Though commercial solutions exist for red-eye correction, all of them require some measure of user intervention. A method is presented to automatically detect and correct redeye in digital images. First, faces are detected with a cascade of multi-scale classifiers. The red-eye pixels are then located with several refining masks computed over the facial region. The masks are created by thresholding per-pixel metrics, designed to detect red-eye artifacts. Once the redeye pixels have been found, the redness is attenuated with a tapered color desaturation. A detector implemented with this system corrected 95% of the red-eye artifacts in 200 tested images. --- paper_title: Towards automatic redeye effect removal paper_content: The redeye effect is typically formed in amateur photographs taken with a built-in camera flash. Analysis of the available techniques and products indicates that their efficiency in correcting this artifact is limited and their performance is inconsistent. In this work we propose a user friendly solution, which could be used to restore amateur photographs. In the proposed method the redeye effect is detected using a skin detection module and eye colors are restored using morphological image processing. The new method is computationally efficient, robust to parameter settings and versatile, as it can work in conjunction with a number of skin detection methods. --- paper_title: Towards automatic redeye effect removal paper_content: The redeye effect is typically formed in amateur photographs taken with a built-in camera flash. Analysis of the available techniques and products indicates that their efficiency in correcting this artifact is limited and their performance is inconsistent. In this work we propose a user friendly solution, which could be used to restore amateur photographs. In the proposed method the redeye effect is detected using a skin detection module and eye colors are restored using morphological image processing. The new method is computationally efficient, robust to parameter settings and versatile, as it can work in conjunction with a number of skin detection methods. --- paper_title: Automatic redeye removal for smart enhancement of photos of unknown origin paper_content: The paper describes a modular procedure for automatic correction of redeye artifact in images of unknown origin, maintaining the natural appearance of the eye. First, a smart color balancing procedure is applied. This phase not only facilitates the subsequent steps of processing, but also improves the overall appearance of the output image. Combining the results of a color-based face detector and of a face detector based on a multi-resolution neural network the most likely facial regions are identified. Redeye is searched for only within these regions, seeking areas with high “redness” satisfying some geometric constraints. A novel redeye removal algorithm is then applied automatically to the red eyes identified, and opportunely smoothed to avoid unnatural transitions between the corrected and original parts. Experimental results on a set of over 450 images are reported. --- paper_title: Automatic Red-Eye Removal based on Sclera and Skin Tone Detection paper_content: It is well-known that taking portrait photographs with a built in camera may create a red-eye effect. This effect is caused by the light entering the subject’s eye through the pupil and reflecting from the retina back to the sensor. These red eyes are probably one of the most important types of artifacts in portrait pictures. Many different techniques exist for removing these artifacts digitally after image capture. In most of the existing software tools, the user has to select the zone in which the red eye is located. The aim of our method is to automatically detect and correct the red eyes. Our algorithm detects the eye itself by finding the appropriate colors and shapes without input from the user. We use the basic knowledge that an eye is haracterized by its shape and the white color of the sclera. Combining this intuitive approach with the detection of “skin” around the eye, we obtain a higher success rate than most of the tools we tested. Moreover, our algorithm works for any type of skin tone. The main goal of this algorithm is to accurately remove red eyes from a picture, while avoiding false positives completely, which is the biggest problem of camera integrated algorithms or distributed software tools. At the same time, we want to keep the false negative rate as low as possible. We implemented this algorithm in a web-based application to allow people to correct their images online. --- paper_title: Automatic red-eye detection and correction paper_content: "Red-eye" is a phenomenon that causes the eyes of flash photography subjects to appear unnaturally reddish in color. Though commercial solutions exist for red-eye correction, all of them require some measure of user intervention. A method is presented to automatically detect and correct redeye in digital images. First, faces are detected with a cascade of multi-scale classifiers. The red-eye pixels are then located with several refining masks computed over the facial region. The masks are created by thresholding per-pixel metrics, designed to detect red-eye artifacts. Once the redeye pixels have been found, the redness is attenuated with a tapered color desaturation. A detector implemented with this system corrected 95% of the red-eye artifacts in 200 tested images. --- paper_title: A Brief Introduction to Boosting paper_content: Boosting is a general method for improving the accuracy of any given learning algorithm. This short paper introduces the boosting algorithm AdaBoost, and explains the underlying theory of boosting, including an explanation of why boosting often does not suffer from overfitting. Some examples of recent applications of boosting are also described. --- paper_title: A fully automatic redeye detection and correction algorithm paper_content: A fully automatic redeye detection and correction algorithm was developed at Eastman Kodak Company Research Laboratories. The algorithm is highly sophisticated so that it is able to distinguish most redeye pairs from scene content. It is also highly optimized for execution speed and memory usage enabling it to be included in a variety of products. Detected redeyes are corrected so that the red color is removed, but the eye maintains a natural look. --- paper_title: Safe Red-Eye Correction Plug-in Using Adaptive Methods paper_content: An important issue with red-eye correction is that it might result in image degradation. This can be due to the detection of false positives or, even in the case of correct detection, to an inadequate correction technique. Three correction methods are proposed and compared according to their image degradation risk and their expected perceptual quality improvement. Based on those analyses an adaptive system is designed which selects the correction strategy dependent on those measures and the detection confidence. Finally, both qualitative (visual preferences) and quantitative (pixel counts on manual segmented images) evaluation results are shown. --- paper_title: Automated red-eye detection and correction in digital photographs paper_content: Caused by light reflected off the subject's retina, red-eye is a troublesome problem in consumer photography. Although most of the cameras have the red-eye reduction mode, the result reality is that no on-camera system is completely effective. In this paper, we propose a fully automatic approach to detecting and correcting red-eyes in digital images. In order to detect red-eyes in a picture, a heuristic yet efficient algorithm is first adopted to detect a group of candidate red regions and then an eye classifier is utilized to confirm whether each candidate region is a human eye. Thereafter, for each detected redeye, we can correct it by the correction algorithm. In case that a red-eye cannot be detected automatically, another algorithm is also provided to detect red-eyes manually with the user's interaction by clicking on an eye. Experimental results on about 300 images with various red-eye appearances demonstrate that the proposed solution is robust and effective. --- paper_title: Automatic red-eye detection and correction paper_content: "Red-eye" is a phenomenon that causes the eyes of flash photography subjects to appear unnaturally reddish in color. Though commercial solutions exist for red-eye correction, all of them require some measure of user intervention. A method is presented to automatically detect and correct redeye in digital images. First, faces are detected with a cascade of multi-scale classifiers. The red-eye pixels are then located with several refining masks computed over the facial region. The masks are created by thresholding per-pixel metrics, designed to detect red-eye artifacts. Once the redeye pixels have been found, the redness is attenuated with a tapered color desaturation. A detector implemented with this system corrected 95% of the red-eye artifacts in 200 tested images. --- paper_title: Towards automatic redeye effect removal paper_content: The redeye effect is typically formed in amateur photographs taken with a built-in camera flash. Analysis of the available techniques and products indicates that their efficiency in correcting this artifact is limited and their performance is inconsistent. In this work we propose a user friendly solution, which could be used to restore amateur photographs. In the proposed method the redeye effect is detected using a skin detection module and eye colors are restored using morphological image processing. The new method is computationally efficient, robust to parameter settings and versatile, as it can work in conjunction with a number of skin detection methods. --- paper_title: Automatic redeye removal for smart enhancement of photos of unknown origin paper_content: The paper describes a modular procedure for automatic correction of redeye artifact in images of unknown origin, maintaining the natural appearance of the eye. First, a smart color balancing procedure is applied. This phase not only facilitates the subsequent steps of processing, but also improves the overall appearance of the output image. Combining the results of a color-based face detector and of a face detector based on a multi-resolution neural network the most likely facial regions are identified. Redeye is searched for only within these regions, seeking areas with high “redness” satisfying some geometric constraints. A novel redeye removal algorithm is then applied automatically to the red eyes identified, and opportunely smoothed to avoid unnatural transitions between the corrected and original parts. Experimental results on a set of over 450 images are reported. --- paper_title: Safe Red-Eye Correction Plug-in Using Adaptive Methods paper_content: An important issue with red-eye correction is that it might result in image degradation. This can be due to the detection of false positives or, even in the case of correct detection, to an inadequate correction technique. Three correction methods are proposed and compared according to their image degradation risk and their expected perceptual quality improvement. Based on those analyses an adaptive system is designed which selects the correction strategy dependent on those measures and the detection confidence. Finally, both qualitative (visual preferences) and quantitative (pixel counts on manual segmented images) evaluation results are shown. ---	Title: A Review of Redeye Detection and Removal in Digital Images Through Patents Section 1: INTRODUCTION Description 1: Provide an introduction to the issue of redeye in photography, discussing its causes, frequency, and impact. Mention the importance of digital solutions for redeye removal and give an overview of the paper's structure. Section 2: CHRONOLOGICAL REVIEW Description 2: Present a timeline and review of patents related to redeye detection and removal. Discuss contributions and methods from major companies and highlight key developments in the technology. Section 3: REDEYE DETECTION Description 3: Describe the various strategies for detecting redeye in images. Differentiate between methods that reduce the search space and those that scan the entire image. Provide examples and explanations of each approach. Section 4: RED EYE DETECTION MODULES Description 4: Detail the components and processes involved in redeye detection modules, including color space conversion, segmentation, and pixel classification. Explain the importance of redness maps and different methodologies adopted to identify redeye pixels. Section 5: REDEYE VALIDATION PROCESSES Description 5: Outline the techniques used to validate detected redeye regions. Discuss criteria such as geometric constraints, the presence of sclera and glint, and skin tone analysis. Explain the steps taken to confirm candidate redeye areas. Section 6: REDEYE CORRECTION Description 6: Discuss the techniques and considerations for correcting redeye once detected. Explain different strategies for color correction, maintaining natural appearance, and avoiding abrupt variations. Include examples of various correction methods and their effectiveness. Section 7: EVALUATION OF THE REDEYE DETECTION AND CORRECTION PROCESSES Description 7: Describe how to evaluate the performance of redeye detection and correction processes. Include criteria and metrics used for assessment, and discuss common errors and their impacts on image quality. Section 8: CURRENT & FUTURE DEVELOPMENTS Description 8: Summarize the advancements in the redeye detection and removal field. Highlight areas needing further research and development, and discuss potential new challenges like peteye color correction. Suggest the creation of a reference dataset for consistent evaluation.
A Review of Medical Image Watermarking Requirements for Teleradiology	11	--- paper_title: Strict integrity control of biomedical images paper_content: The control of the integrity and authentication of medical images is becoming ever more important within the Medical Information Systems (MIS). The intra- and interhospital exchange of images, such as in the PACS (Picture Archiving and Communication Systems), and the ease of copying, manipulation and distribution of images have brought forth the security aspects. In this paper we focus on the role of watermarking for MIS security and address the problem of integrity control of medical images. We discuss alternative schemes to extract verification signatures and compare their tamper detection performance. --- paper_title: Authentication and Data Hiding Using a Hybrid ROI-Based Watermarking Scheme for DICOM Images paper_content: Authenticating medical images using watermarking techniques has become a very popular area of research, and some works in this area have been reported worldwide recently. Besides authentication, many data-hiding techniques have been proposed to conceal patient’s data into medical images aiming to reduce the cost needed to store data and the time needed to transmit data when required. In this paper, we present a new hybrid watermarking scheme for DICOM images. In our scheme, two well-known techniques are combined to gain the advantages of both and fulfill the requirements of authentication and data hiding. The scheme divides the images into two parts, the region of interest (ROI) and the region of non-interest (RONI). Patient’s data are embedded into ROI using a reversible technique based on difference expansion, while tamper detection and recovery data are embedded into RONI using a robust technique based on discrete wavelet transform. The experimental results show the ability of hiding patient’s data with a very good visual quality, while ROI, the most important area for diagnosis, is retrieved exactly at the receiver side. The scheme also shows some robustness against certain levels of salt and pepper and cropping noise. --- paper_title: Medical image security in a HIPAA mandated PACS environment. paper_content: Medical image security is an important issue when digital images and their pertinent patient information are transmitted across public networks. Mandates for ensuring health data security have been issued by the federal government such as Health Insurance Portability and Accountability Act (HIPAA), where healthcare institutions are obliged to take appropriate measures to ensure that patient information is only provided to people who have a professional need. Guidelines, such as digital imaging and communication in medicine (DICOM) standards that deal with security issues, continue to be published by organizing bodies in healthcare. However, there are many differences in implementation especially for an integrated system like picture archiving and communication system (PACS), and the infrastructure to deploy these security standards is often lacking. Over the past 6 years, members in the Image Processing and Informatics Laboratory, Childrens Hospital, Los Angeles/University of Southern California, have actively researched image security issues related to PACS and teleradiology. The paper summarizes our previous work and presents an approach to further research on the digital envelope (DE) concept that provides image integrity and security assurance in addition to conventional network security protection. The DE, including the digital signature (DS) of the image as well as encrypted patient information from the DICOM image header, can be embedded in the background area of the image as an invisible permanent watermark. The paper outlines the systematic development, evaluation and deployment of the DE method in a PACS environment. We have also proposed a dedicated PACS security server that will act as an image authority to check and certify the image origin and integrity upon request by a user, and meanwhile act also as a secure DICOM gateway to the outside connections and a PACS operation monitor for HIPAA supporting information. --- paper_title: Digital watermarking of medical image using ROI information paper_content: Recently, the medical image has been digitized by the development of computer science and digitization of the medical devices. There are needs for database service of the medical image and long term storage because of the construction of PACS (Picture Archiving and Communication System) following DICOM (Digital Imaging Communications in Medicine) standards, telemedicine, and et al. Furthermore, authentication and copyright protection are required to protect the illegal distortion and reproduction of the medical information data. In this paper, we propose digital watermarking technique for medical image that prevents illegal forgery that can be caused after transmitting medical image data remotely. A wrong diagnosis may be occurred if the watermark is embedded into the whole area of image. Therefore, we embed the watermark into some area of medical image, except the decision area that makes a diagnosis so called region of interest (ROI) area in our paper, to increase invisibility. The watermark is the value of bit-plane in wavelet transform of the decision area for certification method of integrity verification. The experimental results show that the watermark embedded by the proposed algorithm can survive successfully in image processing operations such as JPEG lossy compression. --- paper_title: Lossless ROI Medical Image Watermarking Technique with Enhanced Security and High Payload Embedding paper_content: In this article, a new fragile, blind, high payload capacity, ROI (Region of Interest) preserving Medical image watermarking (MIW) technique in the spatial domain for gray scale medical images is proposed. We present a watermarking scheme that combines lossless data compression and encryption technique in application to medical images. The effectiveness of the proposed scheme, proven through experiments on various medical images through various image quality measure matrices such as PSNR, MSE and MSSIM enables us to argue that, the method will help to maintain Electronic Patient Report(EPR)/DICOM data privacy and medical image integrity. --- paper_title: Security Protection of DICOM Medical Images Using Dual-Layer Reversible Watermarking with Tamper Detection Capability paper_content: Teleradiology applications and universal availability of patient records using web-based technology are rapidly gaining importance. Consequently, digital medical image security has become an important issue when images and their pertinent patient information are transmitted across public networks, such as the Internet. Health mandates such as the Health Insurance Portability and Accountability Act require healthcare providers to adhere to security measures in order to protect sensitive patient information. This paper presents a fully reversible, dual-layer watermarking scheme with tamper detection capability for medical images. The scheme utilizes concepts of public-key cryptography and reversible data-hiding technique. The scheme was tested using medical images in DICOM format. The results show that the scheme is able to ensure image authenticity and integrity, and to locate tampered regions in the images. --- paper_title: Potential impact of HITECH security regulations on medical imaging paper_content: Title XIII of Division A and Title IV of Division B of the American Recovery and Reinvestment Act (ARRA) of 2009 [1] include a provision commonly referred to as the “Health Information Technology for Economic and Clinical Health Act” or “HITECH Act” that is intended to promote the electronic exchange of health information to improve the quality of health care. Subtitle D of the HITECH Act includes key amendments to strengthen the privacy and security regulations issued under the Health Insurance Portability and Accountability Act (HIPAA). The HITECH act also states that “the National Coordinator” must consult with the National Institute of Standards and Technology (NIST) in determining what standards are to be applied and enforced for compliance with HIPAA. This has led to speculation that NIST will recommend that the government impose the Federal Information Security Management Act (FISMA) [2], which was created by NIST for application within the federal government, as requirements to the public Electronic Health Records (EHR) community in the USA. In this paper we will describe potential impacts of FISMA on medical image sharing strategies such as teleradiology and outline how a strict application of FISMA or FISMA-based regulations could have significant negative impacts on information sharing between care providers. --- paper_title: Digital Watermarking and Steganography paper_content: Digital audio, video, images, and documents are flying through cyberspace to their respective owners. Unfortunately, along the way, individuals may choose to intervene and take this content for themselves. Digital watermarking and steganography technology greatly reduces the instances of this by limiting or eliminating the ability of third parties to decipher the content that he has taken. The many techiniques of digital watermarking (embedding a code) and steganography (hiding information) continue to evolve as applications that necessitate them do the same. The authors of this second edition provide an update on the framework for applying these techniques that they provided researchers and professionals in the first well-received edition. Steganography and steganalysis (the art of detecting hidden information) have been added to a robust treatment of digital watermarking, as many in each field research and deal with the other. New material includes watermarking with side information, QIM, and dirty-paper codes. The revision and inclusion of new material by these influential authors has created a must-own book for anyone in this profession. ::: ::: This new edition now contains essential information on steganalysis and steganography ::: New concepts and new applications including QIM introduced ::: Digital watermark embedding is given a complete update with new processes and applications --- paper_title: Relevance of watermarking in medical imaging paper_content: Because of the importance of the security issues in the management of medical information, we suggest the use of watermarking techniques to complete the existing measures for protecting medical images. We discuss the necessary requirements for such a system to be accepted by medical staff and its complementary role with respect with existing security systems. We present different scenarios, one devoted to the authentication and tracing of the images, the second to the integrity control of the patient's record. --- paper_title: Reversible medical image watermarking for tamper detection and recovery paper_content: This research paper discussed the usage of watermarking in medical images to ensure the authenticity and integrity of the image and reviewed some watermarking schemes that had been developed. A design of a reversible tamper detection and recovery watermarking scheme was then proposed. The watermarking scheme uses a 640x480x8 bits ultrasound grayscale image as a sample. The concept of ROI (Region Of Interest) and RONI (Region Of Non Interest) were applied. Watermark embedded can be used to detect tampering and recovery of the image can be done. The watermark is also reversible. --- paper_title: Privacy and security in teleradiology paper_content: Teleradiology is probably the most successful eHealth service available today. Its business model is based on the remote transmission of radiological images (e.g. X-ray and CT-images) over electronic networks, and on the interpretation of the transmitted images for diagnostic purpose. Two basic service models are commonly used teleradiology today. The most common approach is based on the message paradigm (off-line model), but more developed teleradiology systems are based on the interactive use of PACS/RIS systems. Modern teleradiology is also more and more cross-organisational or even cross-border service between service providers having different jurisdictions and security policies. This paper defines the requirements needed to make different teleradiology models trusted. Those requirements include a common security policy that covers all partners and entities, common security and privacy protection principles and requirements, controlled contracts between partners, and the use of security controls and tools that supporting the common security policy. The security and privacy protection of any teleradiology system must be planned in advance, and the necessary security and privacy enhancing tools should be selected (e.g. strong authentication, data encryption, non-repudiation services and audit-logs) based on the risk analysis and requirements set by the legislation. In any case the teleradiology system should fulfil ethical and regulatory requirements. Certification of the whole teleradiology service system including security and privacy is also proposed. In the future, teleradiology services will be an integrated part of pervasive eHealth. Security requirements for this environment including dynamic and context aware security services are also discussed in this paper. --- paper_title: Watermarking of chest CT scan medical images for content authentication paper_content: Medical image is usually comprised of region of interest (ROI) and region of non interest (RONI). ROI is the region that contains the important information from diagnosis point of view so it must be stored without any distortion. We have proposed a digital watermarking technique which avoids the distortion of image in ROI by embedding the watermark information in RONI. The watermark is comprised of patient information, hospital logo and message authentication code, computed using hash function. Earlier BCH encryption of watermark is performed to ensure inaccessibility of embedded data to the adversaries. --- paper_title: Proposal for DICOM Multiframe Medical Image Integrity and Authenticity paper_content: This paper presents a novel algorithm to successfully achieve viable integrity and authenticity addition and verification of n-frame DICOM medical images using cryptographic mechanisms. The aim of this work is the enhancement of DICOM security measures, especially for multiframe images. Current approaches have limitations that should be properly addressed for improved security. The algorithm proposed in this work uses data encryption to provide integrity and authenticity, along with digital signature. Relevant header data and digital signature are used as inputs to cipher the image. Therefore, one can only retrieve the original data if and only if the images and the inputs are correct. The encryption process itself is a cascading scheme, where a frame is ciphered with data related to the previous frames, generating also additional data on image integrity and authenticity. Decryption is similar to encryption, featuring also the standard security verification of the image. The implementation was done in JAVA, and a performance evaluation was carried out comparing the speed of the algorithm with other existing approaches. The evaluation showed a good performance of the algorithm, which is an encouraging result to use it in a real environment. --- paper_title: A hierarchical digital watermarking method for image tamper detection and recovery paper_content: In this paper, we present an efficient and effective digital watermarking method for image tamper detection and recovery. Our method is efficient as it only uses simple operations such as parity check and comparison between average intensities. It is effective because the detection is based on a hierarchical structure so that the accuracy of tamper localization can be ensured. That is, if a tampered block is not detected in level-1 inspection, it will be detected in level-2 or level-3 inspection with a probability of nearly 1. Our method is also very storage effective, as it only requires a secret key and a public chaotic mixing algorithm to recover a tampered image. The experimental results demonstrate that the precision of tamper detection and localization is 99.6% and 100% after level-2 and level-3 inspection, respectively. The tamper recovery rate is better than 93% for a less than half tampered image. As compared with the method in Celik et al. [IEEE Trans. Image Process. 11(6) (2002) 585], our method is not only as simple and as effective in tamper detection and localization, it also provides with the capability of tamper recovery by trading off the quality of the watermarked images about 5dB. --- paper_title: Hybrid watermarking of medical images for ROI authentication and recovery paper_content: Medical image data require strict security, confidentiality and integrity. To achieve these stringent requirements, we propose a hybrid watermarking method which embeds a robust watermark in the region of non-interest (RONI) for achieving security and confidentiality, while integrity control is achieved by inserting a fragile watermark into the region of the interest (ROI). First the information to be modified in ROI is separated and is inserted into RONI, which later is used in recovery of the original ROI. Secondly, to avoid the underflow and overflow, a location map is generated for embedding the watermark block-wise by leaving the suspected blocks. This avoids the preprocessing step of histogram modification. The image visual quality, as well as tamper localization, is evaluated. We use weighted peak signal to noise ratio for measuring image quality of watermarked images. Experimental results show that the proposed method outperforms the existing hybrid watermarking techniques. --- paper_title: Four-scanning attack on hierarchical digital watermarking method for image tamper detection and recovery paper_content: In a recent paper presented by Lin et al., a block-based hierarchical watermarking algorithm for digital images is proposed. It adopts parity check and the intensity-relation check to conduct the experiment of image tamper detection. Their experimental results indicate that the precision of tamper detection and localization is 99.6% and 100% after level-2 and level-3 inspections, respectively. The proposed attacks demonstrate that this watermarking algorithm is fundamentally flawed in that the attacker can tamper a watermarked image easily without being detected. In this paper, a four-scanning attack aimed to Lin et al.'s watermarking method is presented to create tampered images. Furthermore, in case they use encryption to protect their 3-tuple-watermark, we proposed a blind attack to tamper watermarked images without being detected. Experimental results are given to support and enhance our conclusions, and demonstrate that our attacks are successful in tampering watermarked images. --- paper_title: Digital watermarking of medical image using ROI information paper_content: Recently, the medical image has been digitized by the development of computer science and digitization of the medical devices. There are needs for database service of the medical image and long term storage because of the construction of PACS (Picture Archiving and Communication System) following DICOM (Digital Imaging Communications in Medicine) standards, telemedicine, and et al. Furthermore, authentication and copyright protection are required to protect the illegal distortion and reproduction of the medical information data. In this paper, we propose digital watermarking technique for medical image that prevents illegal forgery that can be caused after transmitting medical image data remotely. A wrong diagnosis may be occurred if the watermark is embedded into the whole area of image. Therefore, we embed the watermark into some area of medical image, except the decision area that makes a diagnosis so called region of interest (ROI) area in our paper, to increase invisibility. The watermark is the value of bit-plane in wavelet transform of the decision area for certification method of integrity verification. The experimental results show that the watermark embedded by the proposed algorithm can survive successfully in image processing operations such as JPEG lossy compression. --- paper_title: Security for the digital information age of medicine: Issues, applications, and implementation paper_content: Privacy and integrity of medical records is expected by patients. This privacy and integrity is often mandated by regulations. Traditionally, the security of medical records has been based on physical lock and key. As the storage of patient record information shifts from paper to digital, new security concerns arise. Digital cryptographic methods provide solutions to many of these new concerns. In this article we give an overview of new security concerns, new legislation mandating secure medical records and solutions providing security. --- paper_title: Potential impact of HITECH security regulations on medical imaging paper_content: Title XIII of Division A and Title IV of Division B of the American Recovery and Reinvestment Act (ARRA) of 2009 [1] include a provision commonly referred to as the “Health Information Technology for Economic and Clinical Health Act” or “HITECH Act” that is intended to promote the electronic exchange of health information to improve the quality of health care. Subtitle D of the HITECH Act includes key amendments to strengthen the privacy and security regulations issued under the Health Insurance Portability and Accountability Act (HIPAA). The HITECH act also states that “the National Coordinator” must consult with the National Institute of Standards and Technology (NIST) in determining what standards are to be applied and enforced for compliance with HIPAA. This has led to speculation that NIST will recommend that the government impose the Federal Information Security Management Act (FISMA) [2], which was created by NIST for application within the federal government, as requirements to the public Electronic Health Records (EHR) community in the USA. In this paper we will describe potential impacts of FISMA on medical image sharing strategies such as teleradiology and outline how a strict application of FISMA or FISMA-based regulations could have significant negative impacts on information sharing between care providers. --- paper_title: Relevance of watermarking in medical imaging paper_content: Because of the importance of the security issues in the management of medical information, we suggest the use of watermarking techniques to complete the existing measures for protecting medical images. We discuss the necessary requirements for such a system to be accepted by medical staff and its complementary role with respect with existing security systems. We present different scenarios, one devoted to the authentication and tracing of the images, the second to the integrity control of the patient's record. --- paper_title: Privacy and security in teleradiology paper_content: Teleradiology is probably the most successful eHealth service available today. Its business model is based on the remote transmission of radiological images (e.g. X-ray and CT-images) over electronic networks, and on the interpretation of the transmitted images for diagnostic purpose. Two basic service models are commonly used teleradiology today. The most common approach is based on the message paradigm (off-line model), but more developed teleradiology systems are based on the interactive use of PACS/RIS systems. Modern teleradiology is also more and more cross-organisational or even cross-border service between service providers having different jurisdictions and security policies. This paper defines the requirements needed to make different teleradiology models trusted. Those requirements include a common security policy that covers all partners and entities, common security and privacy protection principles and requirements, controlled contracts between partners, and the use of security controls and tools that supporting the common security policy. The security and privacy protection of any teleradiology system must be planned in advance, and the necessary security and privacy enhancing tools should be selected (e.g. strong authentication, data encryption, non-repudiation services and audit-logs) based on the risk analysis and requirements set by the legislation. In any case the teleradiology system should fulfil ethical and regulatory requirements. Certification of the whole teleradiology service system including security and privacy is also proposed. In the future, teleradiology services will be an integrated part of pervasive eHealth. Security requirements for this environment including dynamic and context aware security services are also discussed in this paper. --- paper_title: How to deal with security issues in teleradiology paper_content: Abstract The use of teleradiological systems for medical image communication is increasing significantly. Digital images can be transferred over public telephone (e.g. ISDN) lines to colleagues for interpretation and/or consultation. Thus, a new quality is being introduced into the process of radiological diagnostics. However, technical implementation of such systems is accompanied by little consideration of legal, i.e. data protection and security, issues. In this paper we describe a concept for data protection in teleradiology which unites aspects of privacy and security as well as user aspects. After highlighting the legal situation in Germany we describe the methodology used for deriving the security profile for teleradiology in Germany. As a result the set of security measures which have to be employed with a teleradiology system is listed. A detailed description follows of how the software requirements are implemented in the teleradiology software MEDICUS. --- paper_title: Strict integrity control of biomedical images paper_content: The control of the integrity and authentication of medical images is becoming ever more important within the Medical Information Systems (MIS). The intra- and interhospital exchange of images, such as in the PACS (Picture Archiving and Communication Systems), and the ease of copying, manipulation and distribution of images have brought forth the security aspects. In this paper we focus on the role of watermarking for MIS security and address the problem of integrity control of medical images. We discuss alternative schemes to extract verification signatures and compare their tamper detection performance. --- paper_title: Secure method for sectional image archiving and transmission paper_content: Purpose: Data security becomes an important issue in telemedicine when medical information is transmitted over wide area network. Generally, security is characterized in terms of privacy, authenticity and integrity of digital data. We present a method here which can meet the requirements of privacy, authenticity, and integrity for archiving and transmitting of sectional image such as CT, MR. Methods: The method is described as follows: firstly, image segmentation was done and some patient information was read from image DICOM header. Second, a digital signature for the segmented image was produced using the image sender's private key. Afterwards, the digital signature and patient information were concatenated and embedded into the background area of the image. Finally, the whole image was encrypted to form a digital envelope using the receiver's public key. Results: (1) The image can only be decrypted and read by authorized user who own the private key of the receiving site. (2) The authenticity and integrity can be tested by signature verification. Conclusions: The preliminary results demonstrate that the method we presented here is an effective method for secure archiving and transmitting for sectional medical images. --- paper_title: Fundamentals of Network Security paper_content: Basic Security Concepts - Why is Computer and Network Security Important. Background and History. The Security Trinity. Information Security. Risk Assessment. Security Models. Basic Terminology. More Basic Terminology. Threats, Vulnerabilities and Attacks - Protocols. The OSI Reference Model. TCP/IP Protocol Suite. Useful Web Sites. Search Engines. Mailing Lists. Encryption, Digital Signatures and Certification - Cryptography. Stream Ciphers. Breaking Ciphers. Block Ciphers. Encryption. Public Key Cryptosystems. Message Integrity. Authentication. Digital Signatures. Competing Standards. Digital Certificates. Limitations of Digital Certificates. Certificate Authorities. Public Key Infrastructure. The Future. The Limitations of Encryption. Kerberos - How Kerberos Works. Kerberos- Limitations. Encryption on the WWW - The World Wide Web. Secure Sockets Layer (HTTPS). Secure HTTP (SHTTP). Microsoft's Internet Explorer. Viewing Digital Certificates with Internet Explorer. Viewing the Encryption Strength of IE5. Viewing Certification Authorities with IE5. Netscape Navigator. Viewing Digital Certificates with Navigator. Authenticode Certificates. E-Mail - E-Mail Issues. E-Mail Issues. Secure E-Mail Protocols. Web-Based E-Mail Services. Security of Stored Messages. Identity: Spoofing and Hiding. E-Mail as a weapon. E-Mail Policies. E-Mail Privacy. Auto-Responses. Operating System Security -- Passwords. Password Attacks. Onetime Passwords. Access Control. Data Redundancy. General Recommendations. Modems. Useful Tools. LAN Security - LAN Guidelines. Controlling End-User Access. Concurrent Logins. Available Disk Space. Restrictions to Location or Workstation. Time/Day Restrictions. Access to Directories and Trustee Rights. File Attributes. Other Privileges. Single Sign-On. Policy-Based Network Management. Honeypot Systems. Network Segmentation. Static IP Addresses vs. DHCP. Media and Protocols - Network Media. Plenum Cabling and Risers. WANs. Redundancy and Alternative Connections. Routers and SNMP - Router Issues. SNMP. Virtual Private Networks - Encryption on the Network. Node-to-Node Encryption. End-to-End Encryption. Where to Encrypt. Virtual Private Networks. PPTP. L2TP. IPSec. SOCKS. Firewalls - Firewalls Pros and Cons. Types of Firewalls. Packet Filters vs. Proxies. Firewall Configurations. Restricting Users' Access to the Internet. Firewall Products. Personal Firewalls. Biometrics - Identification and Authentication. Biometric Identification and Authentication. Biometric Identification Reliability. Backup Authentication. Environmental Conditions. User Acceptance. Security of the Biometric System. Interoperability. Costs vs. Savings. Policies and Procedures - Policies vs. Procedures. Information Security Policy Objectives. Developing Security Policies. Policy and Procedure Manuals. Policy Awareness & Education. Policy Enforcement. Policy Format. Security Policy Suggestions. Information Protection Team. Crisis Management Planning. Sources for Information Policies. Auditing and Intrusion Detection - What is an Audit. Operational Security Audits. System Security Auditing. Activity and Usage Auditing. Audit Mistakes. Deficiencies of Traditional Audit Techniques. Intrusion Detection. Intrusion Detection Systems. Host-Based Intrusion Detection Systems. Network-Based Intrusion Detection Systems. Knowledge-Based Intrusion Detection Systems. Statistical-Based Intrusion Detection Systems. Defense In-Depth Approach . Future Directions. Crisis Management Planning - Crisis Management. Disaster Recovery Planning. Computer Security Incident Response Plan. Browser Security - Cookie Files. Cache Files. Autocomplete. --- paper_title: Medical image security in a HIPAA mandated PACS environment. paper_content: Medical image security is an important issue when digital images and their pertinent patient information are transmitted across public networks. Mandates for ensuring health data security have been issued by the federal government such as Health Insurance Portability and Accountability Act (HIPAA), where healthcare institutions are obliged to take appropriate measures to ensure that patient information is only provided to people who have a professional need. Guidelines, such as digital imaging and communication in medicine (DICOM) standards that deal with security issues, continue to be published by organizing bodies in healthcare. However, there are many differences in implementation especially for an integrated system like picture archiving and communication system (PACS), and the infrastructure to deploy these security standards is often lacking. Over the past 6 years, members in the Image Processing and Informatics Laboratory, Childrens Hospital, Los Angeles/University of Southern California, have actively researched image security issues related to PACS and teleradiology. The paper summarizes our previous work and presents an approach to further research on the digital envelope (DE) concept that provides image integrity and security assurance in addition to conventional network security protection. The DE, including the digital signature (DS) of the image as well as encrypted patient information from the DICOM image header, can be embedded in the background area of the image as an invisible permanent watermark. The paper outlines the systematic development, evaluation and deployment of the DE method in a PACS environment. We have also proposed a dedicated PACS security server that will act as an image authority to check and certify the image origin and integrity upon request by a user, and meanwhile act also as a secure DICOM gateway to the outside connections and a PACS operation monitor for HIPAA supporting information. --- paper_title: Medical Image Authentication Using DPT Watermarking: A Preliminary Attempt paper_content: Secure authentication of digital medical image content provides great value to the e-Health community and medical insurance industries. Fragile Watermarking has been proposed to provide the mechanism to authenticate digital medical image securely. Transform Domain based Watermarking are typically slower than spatial domain watermarking owing to the overhead in calculation of coefficients. In this paper, we propose a new Discrete Pascal Transform based watermarking technique. Preliminary experiment result shows authentication capability. Possible improvements on the proposed scheme are also presented before conclusions. --- paper_title: Digital Watermarking and Steganography paper_content: Digital audio, video, images, and documents are flying through cyberspace to their respective owners. Unfortunately, along the way, individuals may choose to intervene and take this content for themselves. Digital watermarking and steganography technology greatly reduces the instances of this by limiting or eliminating the ability of third parties to decipher the content that he has taken. The many techiniques of digital watermarking (embedding a code) and steganography (hiding information) continue to evolve as applications that necessitate them do the same. The authors of this second edition provide an update on the framework for applying these techniques that they provided researchers and professionals in the first well-received edition. Steganography and steganalysis (the art of detecting hidden information) have been added to a robust treatment of digital watermarking, as many in each field research and deal with the other. New material includes watermarking with side information, QIM, and dirty-paper codes. The revision and inclusion of new material by these influential authors has created a must-own book for anyone in this profession. ::: ::: This new edition now contains essential information on steganalysis and steganography ::: New concepts and new applications including QIM introduced ::: Digital watermark embedding is given a complete update with new processes and applications --- paper_title: Relevance of watermarking in medical imaging paper_content: Because of the importance of the security issues in the management of medical information, we suggest the use of watermarking techniques to complete the existing measures for protecting medical images. We discuss the necessary requirements for such a system to be accepted by medical staff and its complementary role with respect with existing security systems. We present different scenarios, one devoted to the authentication and tracing of the images, the second to the integrity control of the patient's record. --- paper_title: Watermarking of chest CT scan medical images for content authentication paper_content: Medical image is usually comprised of region of interest (ROI) and region of non interest (RONI). ROI is the region that contains the important information from diagnosis point of view so it must be stored without any distortion. We have proposed a digital watermarking technique which avoids the distortion of image in ROI by embedding the watermark information in RONI. The watermark is comprised of patient information, hospital logo and message authentication code, computed using hash function. Earlier BCH encryption of watermark is performed to ensure inaccessibility of embedded data to the adversaries. --- paper_title: Conception and limits of robust perceptual hashing: towards side information assisted hash functions paper_content: In this paper, we consider some basic concepts behind the design of existing robust perceptual hashing techniques for content identification. We show the limits of robust hashing from the communication perspectives as well as propose an approach that is able to overcome these shortcomings in certain setups. The consideration is based on both achievable rate and probability of error. We use the fact that most robust hashing algorithms are based on dimensionality reduction using random projections and quantization. Therefore, we demonstrate the corresponding achievable rate and probability of error based on random projections and compare with the results for the direct domain. The effect of dimensionality reduction is studied and the corresponding approximations are provided based on the Johnson-Lindenstrauss lemma. Side-information assisted robust perceptual hashing is proposed as a solution to the above shortcomings. --- paper_title: Experiment of Tamper Detection and Recovery Watermarking in PACS paper_content: Medical images such as x-rays, ultrasounds and MRI (Magnetic Resonance Imaging) plays an important role in helping the physicians to diagnose a disease or body conditions. These images can be tampered with existing image processing tools that is easily available. The usage of security measures such as watermarking can protect the integrity of the images. Numerous watermarking schemes with basic security functions and even tampered image recovery are available. But there is no research on the experimentation of watermarking in the operational environment that involves PACS (Picture Archiving and Communication Systems). This paper will focus on the experiment of selected watermarking scheme running in as imulated operation environment. The watermarked images will be tested to know its effectiveness by comparing its recovery rates. --- paper_title: JPEG 2000 and Digital Watermarking Technique Using in Medical Image paper_content: The Picture Archiving and Communication System(PACS) was introduced for computerization of the medical system and telediagnosis between the hospital. It is becoming possible to create, store, and transmit medical images via PACS. There has been a growing interest in protecting medical images with an enormous amount of information. To improve transmission speed among the hospitals, the medical image should be compression JPEG 2000 by high compression ratio. This paper proposes an algorithm that utilizes both JPEG 2000 and robust watermarking for protection and compression of the medical image. With the proposed algorithm, it takes considerably less time to do JPEG 2000 and watermarking than when they are done separately. Based on the experiment results, it takes 0.72 second for the proposed algorithm and 1.11 second when they are done separately. We confirmed that the proposed algorithm was faster than when they are done separately. --- paper_title: Reversible medical image watermarking for tamper detection and recovery paper_content: This research paper discussed the usage of watermarking in medical images to ensure the authenticity and integrity of the image and reviewed some watermarking schemes that had been developed. A design of a reversible tamper detection and recovery watermarking scheme was then proposed. The watermarking scheme uses a 640x480x8 bits ultrasound grayscale image as a sample. The concept of ROI (Region Of Interest) and RONI (Region Of Non Interest) were applied. Watermark embedded can be used to detect tampering and recovery of the image can be done. The watermark is also reversible. --- paper_title: Security models of digital watermarking paper_content: Digital watermarking, traditionally modeled as communication with side information, is generally considered to have important potential applications in various scenarios such as digital rights managements. However, the current literature mainly focuses on robustness, capacity and imperceptibility. There lacks systematic formal approach in tackling secure issues of watermarking. One one hand, the threat models in many previous works are not sufficiently established, which result in somewhat superficial or even flawed security analysis. On the other hand, there lacks a rigorous model for watermarking in general that allows useful analysis in practice. There has been some efforts in clearing the threat models and formulate rigorous watermarking models. However, there are also many other cases where security issues are lightly or incorrectly treated. In this paper, we survey various security notions and models in previous work, and discuss possible future research directions. --- paper_title: Non-repudiation oblivious watermarking schema for secure digital video distribution paper_content: This paper presents a mechanism and algorithm for creating undeniable watermarks. It assumes a system where a content owner or provider uses outside agents to distribute its content. Content watermarked by distribution agents using this system will be undeniably recognizable by the content provider as originating with that distribution agent. That is to say that given N distribution agents, the content provider will be able to tell which distribution agent watermarked the content. The system does not allow any distribution agent to watermark content that would appear to have been watermarked by another agent and it does also not allow the content provider to watermark content that would appear to have been watermarked by a particular distribution agent. This allows the content provider to place a high degree of trust in the identification of the distribution agent and trace "leak" locations of pirated copies of videos. --- paper_title: Tamper Detection and Recovery for Medical Images Using Near-lossless Information Hiding Technique paper_content: Digital medical images are very easy to be modified for illegal purposes. For example, microcalcification in mammography is an important diagnostic clue, and it can be wiped off intentionally for insurance purposes or added intentionally into a normal mammography. In this paper, we proposed two methods to tamper detection and recovery for a medical image. A 1024 × 1024 x-ray mammogram was chosen to test the ability of tamper detection and recovery. At first, a medical image is divided into several blocks. For each block, an adaptive robust digital watermarking method combined with the modulo operation is used to hide both the authentication message and the recovery information. In the first method, each block is embedded with the authentication message and the recovery information of other blocks. Because the recovered block is too small and excessively compressed, the concept of region of interest (ROI) is introduced into the second method. If there are no tampered blocks, the original image can be obtained with only the stego image. When the ROI, such as microcalcification in mammography, is tampered with, an approximate image will be obtained from other blocks. From the experimental results, the proposed near-lossless method is proven to effectively detect a tampered medical image and recover the original ROI image. In this study, an adaptive robust digital watermarking method combined with the operation of modulo 256 was chosen to achieve information hiding and image authentication. With the proposal method, any random changes on the stego image will be detected in high probability. --- paper_title: The integration of medical images with the electronic patient record and their web-based distribution paper_content: Abstract Medical images are currently created digitally and stored in the radiology department’s picture archiving and communication system. Reports are usually stored in the electronic patient record of other information systems, such as the radiology information system (RIS) and the hospital information system (HIS). But high-quality services can only be provided if electronic patient record data is integrated with digital images in picture archiving and communication systems. Clinicians should be able to access both systems’ data in an integrated and consistent way as part of their regular working environment, whether HIS or RIS. Also, this system should allow for teleconferencing with other users, eg, for consultation with a specialist in the radiology department. This article describes a web-based solution that integrates the digital images of picture archiving and communication systems with electronic patient record/HIS/RIS data and has built-in teleconferencing functionality. This integration has been successfully tested using three different commercial RIS and HIS products. --- paper_title: Applications of data hiding in digital images paper_content: Summary form only given, as follows. The author introduces data hiding in digital imagery as a new and powerful technology with applications including robust digital watermarking of images for copyright protection, image fingerprinting and authentication, tamper detection in digital imagery, covert (invisible) communication using images, access control, copy control in DVDs, embedding subtitles and audio tracks in video signals, etc. Data hiding is a highly multidisciplinary field that combines image and signal processing with cryptography, communication theory, coding theory, signal compression, and the theory of visual perception. --- paper_title: A data-hiding technique with authentication, integration, and confidentiality for electronic patient records paper_content: A data-hiding technique called the "bipolar multiple-number base" was developed to provide capabilities of authentication, integration, and confidentiality for an electronic patient record (EPR) transmitted among hospitals through the Internet. The proposed technique is capable of hiding those EPR related data such as diagnostic reports, electrocardiogram, and digital signatures from doctors or a hospital into a mark image. The mark image could be the mark of a hospital used to identify the origin of an EPR. Those digital signatures from doctors and a hospital could be applied for the EPR authentication. Thus, different types of medical data can be integrated into the same mark image. The confidentiality is ultimately achieved by decrypting the EPR related data and digital signatures with an exact copy of the original mark image. The experimental results validate the integrity and the invisibility of the hidden EPR related data. This newly developed technique allows all of the hidden data to be separated and restored perfectly by authorized users. --- paper_title: Survey of Medical Image Watermarking Algorithms paper_content: Watermarking in medical images is a new area of research and some works in this area have been reported world wide recently. Most of the works are on the tamper detection of the images and embedding of the Electronics Patient Record (EPR) data in the medical images. Watermarked medical images can be used for transmission, storage or telediagnosis. Tamper detection watermarks are useful to locate the regions in the image where some manipulations have been made. EPR data hiding in images improves the confidentiality of the patient data, saves memory storage space and reduce the bandwidth requirement for transmission of images. This paper discusses various aspects of medical image watermarking and makes a review of various watermarking algorithms originally proposed for medical images. --- paper_title: Lossless ROI Medical Image Watermarking Technique with Enhanced Security and High Payload Embedding paper_content: In this article, a new fragile, blind, high payload capacity, ROI (Region of Interest) preserving Medical image watermarking (MIW) technique in the spatial domain for gray scale medical images is proposed. We present a watermarking scheme that combines lossless data compression and encryption technique in application to medical images. The effectiveness of the proposed scheme, proven through experiments on various medical images through various image quality measure matrices such as PSNR, MSE and MSSIM enables us to argue that, the method will help to maintain Electronic Patient Report(EPR)/DICOM data privacy and medical image integrity. --- paper_title: Relevance of watermarking in medical imaging paper_content: Because of the importance of the security issues in the management of medical information, we suggest the use of watermarking techniques to complete the existing measures for protecting medical images. We discuss the necessary requirements for such a system to be accepted by medical staff and its complementary role with respect with existing security systems. We present different scenarios, one devoted to the authentication and tracing of the images, the second to the integrity control of the patient's record. --- paper_title: The Use of Digital Watermarking for Intelligence Multimedia Document Distribution paper_content: Digital watermarking is a promising technology to embed information as unperceivable signals in digital contents. Various watermarking techniques have been proposed to protect copyrights of multimedia digital contents over Internet trading so that ownership of the contents can be determined in subsequent copyrights disputes. However, their applications in preventing unauthorized distribution of intelligence document have not been studied. In this paper, we propose a watermark-based document distribution protocol, which complements conventional cryptography-based access control schemes, to address the problem of tracing unauthorized distribution of sensitive intelligence documents. The reinforcement of document distribution policies requires a concrete support of non-repudiation in the distribution process. The distribution protocol is adapted from our previous work on the watermarking infrastructure for enterprise document management. It makes use of intelligence user certificates to embed the identity of the users into the intelligence documents to whom are distributed. In particular, keeping the identity secrecy between document providers and users (but yet traceable upon disputes) is a key contribution of this protocol in order to support for intelligence applications. We also outline an implementation of the distribution protocol and watermarking scheme employed. --- paper_title: Watermarking of chest CT scan medical images for content authentication paper_content: Medical image is usually comprised of region of interest (ROI) and region of non interest (RONI). ROI is the region that contains the important information from diagnosis point of view so it must be stored without any distortion. We have proposed a digital watermarking technique which avoids the distortion of image in ROI by embedding the watermark information in RONI. The watermark is comprised of patient information, hospital logo and message authentication code, computed using hash function. Earlier BCH encryption of watermark is performed to ensure inaccessibility of embedded data to the adversaries. --- paper_title: Medical image security and EPR hiding using Shamir's secret sharing scheme paper_content: Medical applications such as telediagnosis require information exchange over insecure networks. Therefore, protection of the integrity and confidentiality of the medical images is an important issue. Another issue is to store electronic patient record (EPR) in the medical image by steganographic or watermarking techniques. Studies reported in the literature deal with some of these issues but not all of them are satisfied in a single method. A medical image is distributed among a number of clinicians in telediagnosis and each one of them has all the information about the patient's medical condition. However, disclosing all the information about an important patient's medical condition to each of the clinicians is a security issue. This paper proposes a (k, n) secret sharing scheme which shares medical images among a health team of n clinicians such that at least k of them must gather to reveal the medical image to diagnose. Shamir's secret sharing scheme is used to address all of these security issues in one method. The proposed method can store longer EPR strings along with better authenticity and confidentiality properties while satisfying all the requirements as shown in the results. --- paper_title: Effective Management of Medical Information Through A Novel Blind Watermarking Technique paper_content: Medical Data Management (MDM) domain consists of various issues of medical information like authentication, security, privacy, retrieval and storage etc. Medical Image Watermarking (MIW) techniques have recently emerged as a leading technology to solve the problems associated with MDM. This paper proposes a blind, Contourlet Transform (CNT) based MIW scheme, robust to high JPEG and JPEG2000 compression and simultaneously capable of addressing a range of MDM issues like medical information security, content authentication, safe archiving and controlled access retrieval etc. It also provides a way for effective data communication along with automated medical personnel teaching. The original medical image is first decomposed by CNT. The Low pass subband is used to embed the watermark in such a way that enables the proposed method to extract the embedded watermark in a blind manner. Inverse CNT is then applied to get the watermarked image. Extensive experiments were carried out and the performance of the proposed scheme is evaluated through both subjective and quantitative measures. The experimental results and comparisons, confirm the effectiveness and efficiency of the proposed technique in the MDM paradigm. --- paper_title: High capacity, reversible data hiding in medical images paper_content: In this paper we introduce a highly efficient reversible data hiding technique. It is based on dividing the image into tiles and shifting the histograms of each image tile between its minimum and maximum frequency. Data are then inserted at the pixel level with the largest frequency to maximize data hiding capacity. It exploits the special properties of medical images, where the histogram of their non-overlapping image tiles mostly peak around some gray values and the rest of the spectrum is mainly empty. The zeros (or minima) and peaks (maxima) of the histograms of the image tiles are then relocated to embed the data. The grey values of some pixels are therefore modified. High capacity, high fidelity, reversibility and multiple data insertions are the key requirements of data hiding in medical images. We show how histograms of image tiles of medical images can be exploited to achieve these requirements. Compared with data hiding method in the whole image, our scheme can result in 30%–200% capacity improvement with still better image quality, depending on the medical image content. --- paper_title: Image-Based Electronic Patient Records for Secured Collaborative Medical Applications paper_content: We developed a Web-based system to interactively display image-based electronic patient records (EPR) for secured intranet and Internet collaborative medical applications. The system consists of four major components: EPR DICOM gateway (EPR-GW), image-based EPR repository server (EPR-Server), Web server and EPR DICOM viewer (EPR-Viewer). In the EPR-GW and EPR-Viewer, the security modules of digital signature and authentication are integrated to perform the security processing on the EPR data with integrity and authenticity. The privacy of EPR in data communication and exchanging is provided by SSL/TLS-based secure communication. This presentation gave a new approach to create and manage image-based EPR from actual patient records, and also presented a way to use Web technology and DICOM standard to build an open architecture for collaborative medical applications --- paper_title: Reversible data hiding based on block median preservation paper_content: This paper proposes a reversible data hiding scheme for gray level images. It exploits the high correlation among image block pixels to produce a difference histogram. Secret data is embedded based on a multi-level histogram shifting mechanism with reference to the integer median of each block. The image blocks are divided into four categories due to four corresponding embedding strategies, aiming at preserving the medians during data embedding. In decoder, the median pixels are retrieved first followed by the hidden data extraction, and the host image can be accurately recovered via an inverse histogram shifting mechanism after removing the secret data from the marked image. Experimental results validate the effectiveness of our scheme and demonstrate that it outperforms several previous methods in terms of capacity and marked image's quality. --- paper_title: A local Tchebichef moments-based robust image watermarking paper_content: Protection against geometric distortions and common image processing operations with blind detection becomes a much challenging task in image watermarking. To achieve this, in this paper we propose a content-based watermarking scheme that combines the invariant feature extraction with watermark embedding by using Tchebichef moments. Harris-Laplace detector is first adopted to extract feature points, and then non-overlapped disks centered at feature points are generated. These disks are invariant to scaling and translation distortions. For each disk, orientation alignment is then performed to achieve rotation invariant. Finally, the watermark is embedded in magnitudes of Tchebichef moments of each disk via dither modulation to realize the robustness to common image processing operations and the blind detection. Thorough simulation results obtained by using the standard benchmark, Stirmark, demonstrate that the proposed method is robust against various geometric distortions as well as common image processing operations and outperforms representative image watermarking schemes. --- paper_title: Tamper Detection and Recovery for Medical Images Using Near-lossless Information Hiding Technique paper_content: Digital medical images are very easy to be modified for illegal purposes. For example, microcalcification in mammography is an important diagnostic clue, and it can be wiped off intentionally for insurance purposes or added intentionally into a normal mammography. In this paper, we proposed two methods to tamper detection and recovery for a medical image. A 1024 × 1024 x-ray mammogram was chosen to test the ability of tamper detection and recovery. At first, a medical image is divided into several blocks. For each block, an adaptive robust digital watermarking method combined with the modulo operation is used to hide both the authentication message and the recovery information. In the first method, each block is embedded with the authentication message and the recovery information of other blocks. Because the recovered block is too small and excessively compressed, the concept of region of interest (ROI) is introduced into the second method. If there are no tampered blocks, the original image can be obtained with only the stego image. When the ROI, such as microcalcification in mammography, is tampered with, an approximate image will be obtained from other blocks. From the experimental results, the proposed near-lossless method is proven to effectively detect a tampered medical image and recover the original ROI image. In this study, an adaptive robust digital watermarking method combined with the operation of modulo 256 was chosen to achieve information hiding and image authentication. With the proposal method, any random changes on the stego image will be detected in high probability. --- paper_title: Counterfeiting attacks on oblivious block-wise independent invisible watermarking schemes. paper_content: In this paper, we describe a class of attacks on certain block-based oblivious watermarking schemes. We show that oblivious watermarking techniques that embed information into a host image in a block-wise independent fashion are vulnerable to a counterfeiting attack. Specifically, given a watermarked image, one can forge the watermark it contains into another image without knowing the secret key used for watermark insertion and in some cases even without explicitly knowing the watermark. We demonstrate successful implementations of this attack on a few watermarking techniques that have been proposed in the literature. We also describe a possible solution to this problem of block-wise independence that makes our attack computationally intractable. --- paper_title: Spatial Domain- High Capacity Data Hiding in ROI Images paper_content: Digital watermarking, one of the data hiding techniques has become an emerging area of research due to the wide spread use of Internet and intranets. Though the watermark is used for authentication purpose, its methodology has been adapted for hiding data in many applications namely electronic patient record (EPR) data hiding in medical images. Medical images are usually large sized images and stored without loss of redundancy. Recent researches have proven that appropriate level of JPEG (joint picture expert group) compression may be used on these image types without loss of diagnostic content. This has provided an opportunity for more rapid image transmission. This work focuses on the estimation of the data hiding capacity of region of interest (ROI) medical images and optimizing the JPEG survival level that allow acceptable JPEG compression for conventional spatial domain watermarking techniques namely LSB technique, additive technique and spread spectrum technique --- paper_title: Developing a Digital Image Watermarking Model paper_content: This paper presents a key based generic model for digital image watermarking. The model aims at addressing an identified gap in the literature by providing a basis for assessing different watermarking requirements in various digital image applications. We start with a formulation of a basic watermarking system, and define system inputs and outputs. We then proceed to incorporate the use of keys in the design of various system components. Using the model, we also define a few fundamental design and evaluation parameters. To demonstrate the significance of the proposed model, we provide an example of how it can be applied to formally define common attacks. --- paper_title: Models of Watermarking paper_content: Publisher Summary ::: This chapter provides the conceptual models of watermarking. These models serve as ways of thinking about actual watermarking systems. They fall into two broad groups: models based on a view of watermarking as a method of communication and models based on geometric views of watermarking algorithms. It describes three models of watermarking systems based on the traditional model of a communications channel. These differ in how the cover Work is incorporated into the system. In the basic model, the cover Work is considered noise added during transmission of the watermark signal and in models of watermarking as communications with side information at the transmitter, the cover Work is still considered noise, but the watermark encoding process is provided with its value as side information. In models of watermarking as multiplexing, the cover Work and the watermark are considered two messages multiplexed together for reception by two different “receivers”: a human and a watermark detector, respectively. Part of a watermarking system can be viewed as an extraction process that projects or distorts media space into a marking space. The rest can then be viewed as a simpler watermarking system that operates in marking space rather than in media space. Many watermarking systems fall into the class of correlation-based systems, in which the detector uses some form of correlation as a detection metric. This is true even of many systems not explicitly described as using correlation-based detection. --- paper_title: The integration of medical images with the electronic patient record and their web-based distribution paper_content: Abstract Medical images are currently created digitally and stored in the radiology department’s picture archiving and communication system. Reports are usually stored in the electronic patient record of other information systems, such as the radiology information system (RIS) and the hospital information system (HIS). But high-quality services can only be provided if electronic patient record data is integrated with digital images in picture archiving and communication systems. Clinicians should be able to access both systems’ data in an integrated and consistent way as part of their regular working environment, whether HIS or RIS. Also, this system should allow for teleconferencing with other users, eg, for consultation with a specialist in the radiology department. This article describes a web-based solution that integrates the digital images of picture archiving and communication systems with electronic patient record/HIS/RIS data and has built-in teleconferencing functionality. This integration has been successfully tested using three different commercial RIS and HIS products. --- paper_title: Robust DWT-SVD domain image watermarking: embedding data in all frequencies paper_content: Protection of digital multimedia content has become an increasingly important issue for content owners and service providers. As watermarking is identified as a major technology to achieve copyright protection, the relevant literature includes several distinct approaches for embedding data into a multimedia element (primarily images, audio, and video). Because of its growing popularity, the Discrete Wavelet Transform (DWT) is commonly used in recent watermarking schemes. In a DWT-based scheme, the DWT coefficients are modified with the data that represents the watermark. In this paper, we present a hybrid scheme based on DWT and Singular Value Decomposition (SVD). After decomposing the cover image into four bands, we apply the SVD to each band, and embed the same watermark data by modifying the singular values. Modification in all frequencies allows the development of a watermarking scheme that is robust to a wide range of attacks. --- paper_title: Tamper detection with self-correction hybrid spatial-DCT domains image authentication technique paper_content: The development of effective image authentication techniques is of remarkably growing interest. Some recently developed fragile, semi-fragile/robust or hybrid-watermarking algorithms not only verify the authenticity of the watermarked image but also provide self reconstruction capabilities. However, several algorithms have been reported as vulnerable to various attacks, especially blind pattern matching attacks, with insufficient security. We propose a new blind dual-domain self-embedding watermarking scheme with more secure embedding processes of the image's blocks fragile signatures and robust approximations and more reliable local alterations detection with auto-correction capabilities, surviving normal image content preserving operations. Hence it prevents falsification, the real threat to authentication. --- paper_title: A data-hiding technique with authentication, integration, and confidentiality for electronic patient records paper_content: A data-hiding technique called the "bipolar multiple-number base" was developed to provide capabilities of authentication, integration, and confidentiality for an electronic patient record (EPR) transmitted among hospitals through the Internet. The proposed technique is capable of hiding those EPR related data such as diagnostic reports, electrocardiogram, and digital signatures from doctors or a hospital into a mark image. The mark image could be the mark of a hospital used to identify the origin of an EPR. Those digital signatures from doctors and a hospital could be applied for the EPR authentication. Thus, different types of medical data can be integrated into the same mark image. The confidentiality is ultimately achieved by decrypting the EPR related data and digital signatures with an exact copy of the original mark image. The experimental results validate the integrity and the invisibility of the hidden EPR related data. This newly developed technique allows all of the hidden data to be separated and restored perfectly by authorized users. --- paper_title: Lossless ROI Medical Image Watermarking Technique with Enhanced Security and High Payload Embedding paper_content: In this article, a new fragile, blind, high payload capacity, ROI (Region of Interest) preserving Medical image watermarking (MIW) technique in the spatial domain for gray scale medical images is proposed. We present a watermarking scheme that combines lossless data compression and encryption technique in application to medical images. The effectiveness of the proposed scheme, proven through experiments on various medical images through various image quality measure matrices such as PSNR, MSE and MSSIM enables us to argue that, the method will help to maintain Electronic Patient Report(EPR)/DICOM data privacy and medical image integrity. --- paper_title: Security Protection of DICOM Medical Images Using Dual-Layer Reversible Watermarking with Tamper Detection Capability paper_content: Teleradiology applications and universal availability of patient records using web-based technology are rapidly gaining importance. Consequently, digital medical image security has become an important issue when images and their pertinent patient information are transmitted across public networks, such as the Internet. Health mandates such as the Health Insurance Portability and Accountability Act require healthcare providers to adhere to security measures in order to protect sensitive patient information. This paper presents a fully reversible, dual-layer watermarking scheme with tamper detection capability for medical images. The scheme utilizes concepts of public-key cryptography and reversible data-hiding technique. The scheme was tested using medical images in DICOM format. The results show that the scheme is able to ensure image authenticity and integrity, and to locate tampered regions in the images. --- paper_title: Robust and high-quality time-domain audio watermarking based on low-frequency amplitude modification paper_content: This work proposes a method of embedding digital watermarks into audio signals in the time domain. The proposed algorithm exploits differential average-of-absolute-amplitude relations within each group of audio samples to represent one-bit information. The principle of low-frequency amplitude modification is employed to scale amplitudes in a group manner (unlike the sample-by-sample manner as used in pseudonoise or spread-spectrum techniques) in selected sections of samples so that the time-domain waveform envelope can be almost preserved. Besides, when the frequency-domain characteristics of the watermark signal are controlled by applying absolute hearing thresholds in the psychoacoustic model, the distortion associated with watermarking is hardly perceivable by human ears. The watermark can be blindly extracted without knowledge of the original signal. Subjective and objective tests reveal that the proposed watermarking scheme maintains high audio quality and is simultaneously highly robust to pirate attacks, including MP3 compression, low-pass filtering, amplitude scaling, time scaling, digital-to-analog/analog-to-digital reacquisition, cropping, sampling rate change, and bit resolution transformation. Security of embedded watermarks is enhanced by adopting unequal section lengths determined by a secret key. --- paper_title: Robust Image Watermarking Based on Multiband Wavelets and Empirical Mode Decomposition paper_content: In this paper, we propose a blind image watermarking algorithm based on the multiband wavelet transformation and the empirical mode decomposition. Unlike the watermark algorithms based on the traditional two-band wavelet transform, where the watermark bits are embedded directly on the wavelet coefficients, in the proposed scheme, we embed the watermark bits in the mean trend of some middle-frequency subimages in the wavelet domain. We further select appropriate dilation factor and filters in the multiband wavelet transform to achieve better performance in terms of perceptually invisibility and the robustness of the watermark. The experimental results show that the proposed blind watermarking scheme is robust against JPEG compression, Gaussian noise, salt and pepper noise, median filtering, and Con-vFilter attacks. The comparison analysis demonstrate that our scheme has better performance than the watermarking schemes reported recently. --- paper_title: Robust watermarking and compression for medical images based on genetic algorithms paper_content: A ROI (region of interest) of a medical image is an area including important information and must be stored without any distortion. In order to achieve optimal compression as well as satisfactory visualization of medical images, we compress the ROI by lossless compression, and the rest by lossy compression. Furthermore, security is an important issue in web-based medical information system. Watermarking skill is often used for protecting medical images. In this paper, we present a robust technique embedding the watermark of signature information or textual data around the ROI of a medical image based on genetic algorithms. A fragile watermark is adopted to detect any unauthorized modification. The embedding of watermark in the frequency domain is more difficult to be pirated than in spatial domain. --- paper_title: Digital Watermarking and Steganography paper_content: Digital audio, video, images, and documents are flying through cyberspace to their respective owners. Unfortunately, along the way, individuals may choose to intervene and take this content for themselves. Digital watermarking and steganography technology greatly reduces the instances of this by limiting or eliminating the ability of third parties to decipher the content that he has taken. The many techiniques of digital watermarking (embedding a code) and steganography (hiding information) continue to evolve as applications that necessitate them do the same. The authors of this second edition provide an update on the framework for applying these techniques that they provided researchers and professionals in the first well-received edition. Steganography and steganalysis (the art of detecting hidden information) have been added to a robust treatment of digital watermarking, as many in each field research and deal with the other. New material includes watermarking with side information, QIM, and dirty-paper codes. The revision and inclusion of new material by these influential authors has created a must-own book for anyone in this profession. ::: ::: This new edition now contains essential information on steganalysis and steganography ::: New concepts and new applications including QIM introduced ::: *Digital watermark embedding is given a complete update with new processes and applications --- paper_title: Secret and public key image watermarking schemes for image authentication and ownership verification paper_content: We describe a watermarking scheme for ownership verification and authentication. Depending on the desire of the user, the watermark can be either visible or invisible. The scheme can detect any modification made to the image and indicate the specific locations that have been modified. If the correct key is specified in the watermark extraction procedure, then an output image is returned showing a proper watermark, indicating the image is authentic and has not been changed since the insertion of the watermark. Any modification would be reflected in a corresponding error in the watermark. If the key is incorrect, or if the image was not watermarked, or if the watermarked image is cropped, the watermark extraction algorithm will return an image that resembles random noise. Since it requires a user key during both the insertion and the extraction procedures, it is not possible for an unauthorized user to insert a new watermark or alter the existing watermark so that the resulting image will pass the test. We present secret key and public key versions of the technique. --- paper_title: BLIND DETECTION OF MALICIOUS ALTERATIONS ON STILL IMAGES USING ROBUST WATERMARKS paper_content: Digital image manipulation software is now readily available on personal computers. It is therefore very simple to tamper with any image and make it available to others. Insuring digital image integrity becomes a major issue. In this paper, we propose an original method to protect image authenticity using an invisible and robust watermark. Our scheme is independent of the signer, however the latter must have a high capacity and be able to extract the watermark in full blind detection mode. Our approach is based on the extraction of features from the image. These features are chosen so as to be unaffected by non malicious alterations such as lossy compression. They are embedded in the image using an iterative process so that watermarked image features and information contained in the watermark coincide perfectly. The authenticity is verified by comparing the features of the tested image, with those of the original image recovered from the watermark. (6 pages) --- paper_title: Robust Image Watermarking in the Spatial Domain paper_content: The rapid evolution of digital image manipulation and transmission techniques has created a pressing need for the protection of the intellectual property rights on images. A copyright protection method that is based on hiding an ‘invisible’ signal, known as digital watermark, in the image is presented in this paper. Watermark casting is performed in the spatial domain by slightly modifying the intensity of randomly selected image pixels. Watermark detection does not require the existence of the original image and is carried out by comparing the mean intensity value of the marked pixels against that of the pixels not marked. Statistical hypothesis testing is used for this purpose. Pixel modifications can be done in such a way that the watermark is resistant to JPEG compression and lowpass filtering. This is achieved by minimizing the energy content of the watermark signal at higher frequencies while taking into account properties of the human visual system. A variation that generates image dependent watermarks as well as a method to handle geometrical distortions are presented. An extension to color images is also pursued. Experiments on real images verify the effectiveness of the proposed techniques. --- paper_title: A robust watermarking scheme using self-reference image paper_content: In this paper, a robust watermark scheme for copyright protection is proposed. By modifying the original image in transform domain and embedding a watermark in the difference values between the original image and its reference image, the proposed scheme overcomes the weak robustness problem of embedding a watermark in the spatial domain. Besides, the watermark extraction does not require the original image so it is more practical in real application. The experimental results show that the proposed scheme provides not only good image quality, but is also robust against various attacks, such as JPEG lossy compression, filtering and noise addition. --- paper_title: A Region-Based Lossless Watermarking Scheme for Enhancing Security of Medical Data paper_content: This paper presents a lossless watermarking scheme in the sense that the original image can be exactly recovered from the watermarked one, with the purpose of verifying the integrity and authenticity of medical images. In addition, the scheme has the capability of not introducing any embedding-induced distortion in the region of interest (ROI) of a medical image. Difference expansion of adjacent pixel values is employed to embed several bits. A region of embedding, which is represented by a polygon, is chosen intentionally to prevent introducing embedding distortion in the ROI. Only the vertex information of a polygon is transmitted to the decoder for reconstructing the embedding region, which improves the embedding capacity considerably. The digital signature of the whole image is embedded for verifying the integrity of the image. An identifier presented in electronic patient record (EPR) is embedded for verifying the authenticity by simultaneously processing the watermarked image and the EPR. Combining with fingerprint system, patient’s fingerprint information is embedded into several image slices and then extracted for verifying the authenticity. --- paper_title: Watermarking of chest CT scan medical images for content authentication paper_content: Medical image is usually comprised of region of interest (ROI) and region of non interest (RONI). ROI is the region that contains the important information from diagnosis point of view so it must be stored without any distortion. We have proposed a digital watermarking technique which avoids the distortion of image in ROI by embedding the watermark information in RONI. The watermark is comprised of patient information, hospital logo and message authentication code, computed using hash function. Earlier BCH encryption of watermark is performed to ensure inaccessibility of embedded data to the adversaries. --- paper_title: Medical image security and EPR hiding using Shamir's secret sharing scheme paper_content: Medical applications such as telediagnosis require information exchange over insecure networks. Therefore, protection of the integrity and confidentiality of the medical images is an important issue. Another issue is to store electronic patient record (EPR) in the medical image by steganographic or watermarking techniques. Studies reported in the literature deal with some of these issues but not all of them are satisfied in a single method. A medical image is distributed among a number of clinicians in telediagnosis and each one of them has all the information about the patient's medical condition. However, disclosing all the information about an important patient's medical condition to each of the clinicians is a security issue. This paper proposes a (k, n) secret sharing scheme which shares medical images among a health team of n clinicians such that at least k of them must gather to reveal the medical image to diagnose. Shamir's secret sharing scheme is used to address all of these security issues in one method. The proposed method can store longer EPR strings along with better authenticity and confidentiality properties while satisfying all the requirements as shown in the results. --- paper_title: Medical Image Watermarking with Tamper Detection and Recovery paper_content: This paper discussed security of medical images and reviewed some work done regarding them. A fragile watermarking scheme was then proposed that could detect tamper and subsequently recover the image. Our scheme required a secret key and a public chaotic mixing algorithm to embed and recover a tampered image. The scheme was also resilient to VQ attack. The purposes were to verify the integrity and authenticity of medical images. We used 800x600x8 bits ultrasound (US) greyscale images in our experiment. We tested our algorithm for up to 50% tampered block and obtained 100% recovery for spread-tampered block. I. INTRODUCTION Security of medical images, derived from strict ethics and legislative rules, gives rights to the patient and duties to the health professionals. This imposes three mandatory characteristics: confidentiality, reliability and availability: • Confidentiality means that only the entitled persons have access to the images; • Reliability which has two aspects; Integrity: the image has not been modified by non-authorized person, and authentication: a proof that the image belongs indeed to the correct patient and is issued from the correct source; --- paper_title: On the robustness and security of digital image watermarking paper_content: In most of the digital image watermarking schemes, it becomes a common practice to address security in terms of robustness, which is basically a norm in cryptography. Such consideration in developing and evaluation of a watermarking scheme may severely affect the performance and render the scheme ultimately unusable. This paper provides an explicit theoretical analysis towards watermarking security and robustness in figuring out the exact problem status from the literature. With the necessary hypotheses and analyses from technical perspective, we demonstrate the fundamental realization of the problem. Finally, some necessary recommendations are made for complete assessment of watermarking security and robustness. --- paper_title: An additive and lossless watermarking method based on invariant image approximation and Haar wavelet transform paper_content: In this article, we propose a new additive lossless watermarking scheme which identifies parts of the image that can be reversibly watermarked and conducts message embedding in the conventional Haar wavelet transform coefficients. Our approach makes use of an approximation of the image signal that is invariant to the watermark addition for classifying the image in order to avoid over/underflows. The method has been tested on different sets of medical images and some usual natural test images as Lena. Experimental result analysis conducted with respect to several aspects including data hiding capacity and image quality preservation, shows that our method is one of the most competitive existing lossless watermarking schemes in terms of high capacity and low distortion. --- paper_title: Practical analysis of watermarking capacity paper_content: Digital watermarking embedding is a hot research field of image processing. Digital watermarking is only possible because our vision system is not perfect. A number of applications have emerged such as copyright notification, time stamp and automated monitoring. There have been ingenious works on watermarking capacity, which all assume the attack distortion are Gaussian additive distribution. We argue that these results are beautiful but not practical. It is hard to classify different attacking methods into a uniform format (especially as Gaussian distribution). In the other hand, the capacity of a given image's information is an interesting and important topic. Instead of conventional analysis based on non-precise assumption of attack distortion, this paper concentrates on the problem of how much information that image can carry without much visibility distortion. Our work is based on wavelet transform and mean-squared error since we believe they are representative measure for most work. Comparing with the former work on the watermarking capacity, this paper pays more attention to the influence on capacity of widely used technique such as spread spectrum. In the last part of this paper, we discuss future trends of new watermarking algorithm and their influence on capacity. --- paper_title: Robust Image Watermarking Based on Multiscale Gradient Direction Quantization paper_content: We propose a robust quantization-based image watermarking scheme, called the gradient direction watermarking (GDWM), based on the uniform quantization of the direction of gradient vectors. In GDWM, the watermark bits are embedded by quantizing the angles of significant gradient vectors at multiple wavelet scales. The proposed scheme has the following advantages: 1) increased invisibility of the embedded watermark because the watermark is embedded in significant gradient vectors, 2) robustness to amplitude scaling attacks because the watermark is embedded in the angles of the gradient vectors, and 3) increased watermarking capacity as the scheme uses multiple-scale embedding. The gradient vector at a pixel is expressed in terms of the discrete wavelet transform (DWT) coefficients. To quantize the gradient direction, the DWT coefficients are modified based on the derived relationship between the changes in the coefficients and the change in the gradient direction. Experimental results show that the proposed GDWM outperforms other watermarking methods and is robust to a wide range of attacks, e.g., Gaussian filtering, amplitude scaling, median filtering, sharpening, JPEG compression, Gaussian noise, salt & pepper noise, and scaling. --- paper_title: High capacity data hiding schemes for medical images based on difference expansion paper_content: Since the difference expansion (DE) technique was proposed, many researchers tried to, improve its performance in terms of hiding capacity and visual quality. In this paper, a new scheme, based on DE is proposed in order to increase the hiding capacity for medical images. One of the characteristics of medical images, among the other types of images, is the large smooth regions. Taking advantage of this characteristic, our scheme divides the image into two regions; smooth region and non-smooth region. For the smooth region, a high embedding capacity scheme is applied, while the original DE method is applied to the non-smooth region. Sixteen DICOM images of different modalities were used for testing the proposed schemes. The results showed that the proposed scheme has higher hiding capacity compared to the original schemes. --- paper_title: Dual watermark for image tamper detection and recovery paper_content: An effective dual watermark scheme for image tamper detection and recovery is proposed in this paper. In our algorithm, each block in the image contains watermark of other two blocks. That is to say, there are two copies of watermark for each non-overlapping block in the image. Therefore, we maintain two copies of watermark of the whole image and provide second chance for block recovery in case one copy is destroyed. A secret key, which is transmitted along with the watermarked image, and a public chaotic mixing algorithm are used to extract the watermark for tamper recovery. By using our algorithm, a 90% tampered image can be recovered to a dim yet still recognizable condition (PSNR ~20dB). Experimental results demonstrate that our algorithm is superior to the compared techniques, especially when the tampered area is large. --- paper_title: A robust content-based digital image watermarking scheme paper_content: This paper presents a content-based digital image-watermarking scheme, which is robust against a variety of common image-processing attacks and geometric distortions. The image content is represented by important feature points obtained by our image-texture-based adaptive Harris corner detector. These important feature points are geometrically significant and therefore are capable of determining the possible geometric attacks with the aid of the Delaunay-tessellation-based triangle matching method. The watermark is encoded by both the error correcting codes and the spread spectrum technique to improve the detection accuracy and ensure a large measure of security against unintentional or intentional attacks. An image-content-based adaptive embedding scheme is applied in discrete Fourier transform (DFT) domain of each perceptually high textured subimage to ensure better visual quality and more robustness. The watermark detection decision is based on the number of matched bits between the recovered and embedded watermarks in embedding subimages. The experimental results demonstrate the robustness of the proposed method against any combination of the geometric distortions and various common image-processing operations such as JPEG compression, filtering, enhancement, and quantization. Our proposed system also yields a better performance as compared with some peer systems in the literature. --- paper_title: Multiple watermark embedding scheme in wavelet-spatial domains based on ROI of medical images paper_content: Watermarking in medical images is a new area of research. It has the potential of being a value-added tool for medical confidentiality protection, patient-related information hiding, and information retrieval. Medical image watermarking requires extreme care when embedding additional data within the medical images because the additional information must not affect the image quality as this may cause misdiagnosis. In this paper we present a scheme that depends on the extraction of the ROI (region of interest) and its use as a watermark to be embedded twice; first as a robust watermark in the RONI (region of non interest) in the wavelet domain and again as a fragile watermark in the ROI in the spatial domain. Moreover multiple watermarks such as the physician's digital signature and EPR (Electronics Patient Record) are embedded in the RONI in wavelet domain depending on a private key. We compare this scheme by another one that we presented before to show the robustness of new scheme. In our work we use MRI brain images with a brain tumor as the ROI. The experimental results showed that the watermarked image is robust to JPEG compression, ROI removal, and addition of an additional tumor to the image and some geometrical attacks; lowpass and median filtering and some types of noise as; Gaussian, Poisson, Salt and Pepper and finally Speckle. --- paper_title: Authentication and Data Hiding Using a Hybrid ROI-Based Watermarking Scheme for DICOM Images paper_content: Authenticating medical images using watermarking techniques has become a very popular area of research, and some works in this area have been reported worldwide recently. Besides authentication, many data-hiding techniques have been proposed to conceal patient’s data into medical images aiming to reduce the cost needed to store data and the time needed to transmit data when required. In this paper, we present a new hybrid watermarking scheme for DICOM images. In our scheme, two well-known techniques are combined to gain the advantages of both and fulfill the requirements of authentication and data hiding. The scheme divides the images into two parts, the region of interest (ROI) and the region of non-interest (RONI). Patient’s data are embedded into ROI using a reversible technique based on difference expansion, while tamper detection and recovery data are embedded into RONI using a robust technique based on discrete wavelet transform. The experimental results show the ability of hiding patient’s data with a very good visual quality, while ROI, the most important area for diagnosis, is retrieved exactly at the receiver side. The scheme also shows some robustness against certain levels of salt and pepper and cropping noise. --- paper_title: Multiple watermarking of medical images for content authentication and recovery paper_content: Medical Image data require strict security, confidentiality and integrity when transmitted from one hospital to another hospital. This can be achieved by adopting the procedures which can guarantee the image quality as well as secrecy of patient data to unauthorized users. To achieve these requirements we have proposed a multiple watermarking method. The scheme embeds robust watermark in region of non interest (RONI) for achieving security and confidentiality. While integrity control is achieved by inserting fragile watermark in region of interest ROI. Since ROI in the medical image is important from diagnosis point of view so it must be preserved. In order to avoid the distortion caused in ROI due to watermark insertion process, original ROI data is first separated and embedded outside the ROI. This will help in recovery of original ROI at the receiving end in contrast to the techniques reported in the literature which do not guarantee the integrity of the ROI after watermarking process. The image visual quality as well as tamper localization has been evaluated. We have used weighted peak signal to noise ratio (WPSNR) for measuring image quality after watermarking. --- paper_title: A Low Distorsion and Reversible Watermark: Application to Angiographic Images of the Retina paper_content: Medical image security can be enhanced using watermarking, which allows embedding the protection information as a digital signature, by modifying the pixel gray levels of the image. In this paper we propose a reversible watermarking scheme which guarantees that once the embedded message is read, alterations introduced during the insertion process can be removed from the image. Thereafter, original pixel gray levels of the image are restored. The proposed approach relies on estimation of image signal that is invariant to the insertion process, and permits to introduce a very slight watermark within the image. In fact, the insertion process adds or subtracts at least one gray level to the pixels of the original image. Depending on the image to be watermarked, in our case angiographic images of the retina, it is expected that such image alteration will not have any impact on the diagnosis quality, and consequently that the watermark can be kept within the image while this one is interpreted --- paper_title: Medical Image Integrity Control Combining Digital Signature and Lossless Watermarking paper_content: Enforcing protection of medical content becomes a major issue of computer security. Since medical contents are more and more widely distributed, it is necessary to develop security mechanism to guarantee their confidentiality, integrity and traceability in an autonomous way. In this context, watermarking has been recently proposed as a complementary mechanism for medical data protection. In this paper, we focus on the verification of medical image integrity through the combination of digital signatures with such a technology, and especially with Reversible Watermarking (RW). RW schemes have been proposed for images of sensitive content for which any modification may affect their interpretation. Whence, we compare several recent RW schemes and discuss their potential use in the framework of an integrity control process in application to different sets of medical images issued from three distinct modalities: Magnetic Resonance Images, Positron Emission Tomography and Ultrasound Imaging. Experimental results with respect to two aspects including data hiding capacity and image quality preservation, show different limitations which depend on the watermark approach but also on image modality specificities. --- paper_title: Lossless ROI Medical Image Watermarking Technique with Enhanced Security and High Payload Embedding paper_content: In this article, a new fragile, blind, high payload capacity, ROI (Region of Interest) preserving Medical image watermarking (MIW) technique in the spatial domain for gray scale medical images is proposed. We present a watermarking scheme that combines lossless data compression and encryption technique in application to medical images. The effectiveness of the proposed scheme, proven through experiments on various medical images through various image quality measure matrices such as PSNR, MSE and MSSIM enables us to argue that, the method will help to maintain Electronic Patient Report(EPR)/DICOM data privacy and medical image integrity. --- paper_title: A novel blind watermarking of ECG signals on medical images using EZW algorithm. paper_content: In this paper, we present a novel blind water- marking method with secret key by embedding ECG signals in medical images. The embedding is done when the original image is compressed using the embedded zero-tree wavelet (EZW) algorithm. The extraction process is performed at the decompression time of the watermarked image. Our algorithm has been tested on several CT and MRI images and the peak signal to noise ratio (PSNR) between the original and watermarked image is greater than 35 dB for watermarking of 512 to 8192 bytes of the mark signal. The proposed method is able to utilize about 15% of the host image to embed the mark signal. This marking percentage has improved previous works while preserving the image details. transmission overheads as well as helping for computer aided diagnostics system. In this paper we present a new watermarking method combined with the EZW-based wavelet coder. The principle is to replace significant wavelet coefficients of ECG signals by the corresponding significant wavelet coefficients belong- ing to the host image which is much bigger in size than the mark signal. This paper presents a brief introduction to watermarking and the EZW coder that acts as a platform for our watermarking algorithm. --- paper_title: Multiple embedding using robust watermarks for wireless medical images paper_content: Within the expanding paradigm of medical imaging and wireless communications there is increasing demand for transmitting diagnostic medical imagery over error-prone wireless communication channels such as those encountered in cellular phone technology. Medical images must be compressed with minimal file size to minimize transmission time and robustly coded to withstand these wireless environments. It has been reinforced through extensive research that the most crucial regions of medical images must not be degraded and compressed by a lossless or near lossless algorithm. This type of area is called the Region of Interest (ROI). Conversely, the Region of Backgrounds (ROB) may be compressed with some loss of information to achieve a higher compression level. This type of hybrid coding scheme is most useful for wireless communication where the 'bit-budget' is devoted to the ROI. This paper also develops a way for this system to operate externally to the Joint Picture Experts Group (JPEG) still image compression standard without the use of hybrid coding. A multiple watermarking technique is developed to verify the integrity of the ROI after transmission and in the situation where there may be incidental degradation that is hard to perceive or unexpected levels of compression that may degrade ROI content beyond an acceptable level. The most useful contribution in this work is assurance of ROI image content integrity after image files are subject to incidental degradation in these environments. This is made possible with extraction of DCT signature coefficients from the ROI and embedding multiply in the ROB. Strong focus is placed on the robustness to JPEG compression and the mobile channel as well as minimizing the image file size while maintaining its integrity with the use of semi-fragile, robust watermarking. --- paper_title: Watermarking Image Authentication in Hospital Information System paper_content: With the broad application of electronic management of medical records, the integrality and reality authentication of medical image in hospital information system have been in front us. In order to solute these problems, a novel watermarking image authentication based on DSA is presented. In this paper, we introduce digital signature arithmetic (DSA), and analyze the advantage and shortage of DSA. Then, considering the specialty of medical image, it brings forward integrating reversible digital watermarking with digital signature to form an authentication system. Finally, the system is designed and implemented by using the c# language. The experiment results show that the medical image is difficult to tamper. It effectively solves the problem of complete integrity and reality authentication of medical image. --- paper_title: JPEG 2000 and Digital Watermarking Technique Using in Medical Image paper_content: The Picture Archiving and Communication System(PACS) was introduced for computerization of the medical system and telediagnosis between the hospital. It is becoming possible to create, store, and transmit medical images via PACS. There has been a growing interest in protecting medical images with an enormous amount of information. To improve transmission speed among the hospitals, the medical image should be compression JPEG 2000 by high compression ratio. This paper proposes an algorithm that utilizes both JPEG 2000 and robust watermarking for protection and compression of the medical image. With the proposed algorithm, it takes considerably less time to do JPEG 2000 and watermarking than when they are done separately. Based on the experiment results, it takes 0.72 second for the proposed algorithm and 1.11 second when they are done separately. We confirmed that the proposed algorithm was faster than when they are done separately. --- paper_title: A Region-Based Lossless Watermarking Scheme for Enhancing Security of Medical Data paper_content: This paper presents a lossless watermarking scheme in the sense that the original image can be exactly recovered from the watermarked one, with the purpose of verifying the integrity and authenticity of medical images. In addition, the scheme has the capability of not introducing any embedding-induced distortion in the region of interest (ROI) of a medical image. Difference expansion of adjacent pixel values is employed to embed several bits. A region of embedding, which is represented by a polygon, is chosen intentionally to prevent introducing embedding distortion in the ROI. Only the vertex information of a polygon is transmitted to the decoder for reconstructing the embedding region, which improves the embedding capacity considerably. The digital signature of the whole image is embedded for verifying the integrity of the image. An identifier presented in electronic patient record (EPR) is embedded for verifying the authenticity by simultaneously processing the watermarked image and the EPR. Combining with fingerprint system, patient’s fingerprint information is embedded into several image slices and then extracted for verifying the authenticity. --- paper_title: A Medical Image Authentication System Based on Reversible Digital Watermarking paper_content: This paper discusses the security problem of integrality and reality authentication in medical image, and introduces digital signature technology based on RSA public cryptosystem in brief. It analyzes the merit and insufficiency of digital signature technology. Considering the specialty of medical image, it brings forward integrating reversible digital watermarking with digital signature to form an authentication system. Then, the scheme of the system is carried through. Finally, the system is designed and implemented by using the c# software. The experiment results show that the proposed system has good imperceptibility. It effectively solves the problem of complete integrity and reality authentication of medical image. --- paper_title: Watermarking of chest CT scan medical images for content authentication paper_content: Medical image is usually comprised of region of interest (ROI) and region of non interest (RONI). ROI is the region that contains the important information from diagnosis point of view so it must be stored without any distortion. We have proposed a digital watermarking technique which avoids the distortion of image in ROI by embedding the watermark information in RONI. The watermark is comprised of patient information, hospital logo and message authentication code, computed using hash function. Earlier BCH encryption of watermark is performed to ensure inaccessibility of embedded data to the adversaries. --- paper_title: Lossless watermarking scheme for enhancing security of medical data in PACS paper_content: We propose a lossless watermarking scheme, in a sense that the original image can be exactly recovered from the watermarked one, with the purpose of verifying the integrity and authenticity of medical images in PACS. Our embedding method includes imposing invertible modulations that induce low distortion level, as well as losslessly compressing the status of the original image and carrying such information in the watermarked image. Digital signature of the whole image is embedded for verifying the integrity of the image. An identifier also presented in electronic patient record (EPR) is embedded for verifying the authenticity by simultaneously processing of the watermarked image and the EPR. Combining with fingerprint system, patient’s fingerprint information is further embedded into several image slices and then extracted for verifying the authenticity. No visual quality degradation is detected in the watermarked image. --- paper_title: Clinical Assessment of Watermarked Medical Images 1 paper_content: Problem statement: Digital watermarking provides security to medical images. Watermarking in Region Of Interest (ROI) however distorts medical images but it is known that the resulting loss of fidelity is visually imperceptible. Approach: Clinical assessment will objectively evaluate the distortion on medical images to see whether or not medical diagnosis is altered. We used 75 medical images consisting of x-rays, ultrasound and CT scans. Digital watermarking was inserted in ROI and ROI/Region Of Non Interest (RONI) in all of them. Three assessors were randomly assigned 225 images, each receiving 75, a mixture of watermarked and non watermarked images. Results: Chi square test was used and p<0.05 was considered significant. There was no significant difference between original images and those watermarked in ROI or ROI/RONI. There was no comment on image quality in all the images assessed. Conclusion/Recommendations: Digital watermarking does not alter medical diagnosis when assessed by clinical radiologists. The quality of the watermarked images was also unchanged. --- paper_title: Hybrid watermarking of medical images for ROI authentication and recovery paper_content: Medical image data require strict security, confidentiality and integrity. To achieve these stringent requirements, we propose a hybrid watermarking method which embeds a robust watermark in the region of non-interest (RONI) for achieving security and confidentiality, while integrity control is achieved by inserting a fragile watermark into the region of the interest (ROI). First the information to be modified in ROI is separated and is inserted into RONI, which later is used in recovery of the original ROI. Secondly, to avoid the underflow and overflow, a location map is generated for embedding the watermark block-wise by leaving the suspected blocks. This avoids the preprocessing step of histogram modification. The image visual quality, as well as tamper localization, is evaluated. We use weighted peak signal to noise ratio for measuring image quality of watermarked images. Experimental results show that the proposed method outperforms the existing hybrid watermarking techniques. --- paper_title: Combination Independent Content Feature with Watermarking Annotation for Medical Image Retrieval paper_content: The number of medical images produced in cardiology and radiology department etc. is rising strongly. New challenges arise in efficient medical data management issues, such as information retrieval and security. A novel method of combining watermarking annotation with independent content feature (ICF) for medical image retrieval is proposed. ICF is extracted by independent component analysis (ICA) to represent medical images, and the digital watermark carrying patient' information text is imperceptibly embedded. Experimental results show that the scheme employs locally salient information from medical image, and it has good retrieval performance, and watermarking algorithm used in the scheme has robustness property to the JPEG compression. --- paper_title: Data hiding in binary image for authentication and annotation paper_content: This paper proposes a new method to embed data in binary images, including scanned text, figures, and signatures. The method manipulates "flippable" pixels to enforce specific block-based relationship in order to embed a significant amount of data without causing noticeable artifacts. Shuffling is applied before embedding to equalize the uneven embedding capacity from region to region. The hidden data can be extracted without using the original image, and can also be accurately extracted after high quality printing and scanning with the help of a few registration marks. The proposed data embedding method can be used to detect unauthorized use of a digitized signature, and annotate or authenticate binary documents. The paper also presents analysis and discussions on robustness and security issues. --- paper_title: Tamper Detection and Recovery for Medical Images Using Near-lossless Information Hiding Technique paper_content: Digital medical images are very easy to be modified for illegal purposes. For example, microcalcification in mammography is an important diagnostic clue, and it can be wiped off intentionally for insurance purposes or added intentionally into a normal mammography. In this paper, we proposed two methods to tamper detection and recovery for a medical image. A 1024 × 1024 x-ray mammogram was chosen to test the ability of tamper detection and recovery. At first, a medical image is divided into several blocks. For each block, an adaptive robust digital watermarking method combined with the modulo operation is used to hide both the authentication message and the recovery information. In the first method, each block is embedded with the authentication message and the recovery information of other blocks. Because the recovered block is too small and excessively compressed, the concept of region of interest (ROI) is introduced into the second method. If there are no tampered blocks, the original image can be obtained with only the stego image. When the ROI, such as microcalcification in mammography, is tampered with, an approximate image will be obtained from other blocks. From the experimental results, the proposed near-lossless method is proven to effectively detect a tampered medical image and recover the original ROI image. In this study, an adaptive robust digital watermarking method combined with the operation of modulo 256 was chosen to achieve information hiding and image authentication. With the proposal method, any random changes on the stego image will be detected in high probability. --- paper_title: Data security in medical information system paper_content: The database systems use the mechanisms of granting and revoking privileges and of authorization control to ensure the security of data. However, some users such as administrators or persons in charge of security have access to comprehensive content of database including patient's information that are of intimate nature and must be discreet. To enhance the security and avoid illegal access of such users, we propose in this article a mechanism using the content-based watermarking technique. Patient's information are encrypted and inserted in an image associated to it. This image, with faculties of object-relational and object-oriented databases, is directly integrated into the database. To check the integrity of the image we use the edge map and invariant moments. --- paper_title: Multiple block based authentication watermarking for distribution of medical images paper_content: To provide an effective authentication method for distribution of medical images, we propose a new fragile watermarking method utilizing segmentation information of medical image contents. For medical image modalities like CT, MRI and PET, tissue structures contain a significant amount of clinical information. Hence, it is important to provide an authenticity check of the segmented blocks. The proposed method is based on cryptographically secure fragile watermarking but eliminates the problem of the block-wise independency of existing methods. The vector quantization (VQ) counterfeiting attack is a known vulnerability due to the block-wise independency of existing methods. In our approach, multiple signatures from two different types of blocks are used to defy such attacks. More secure distribution of medical images can be achieved by embedding the watermark. --- paper_title: Detection and Restoration of a Tampered Medical Image paper_content: This paper presents a recoverable image tamper proofing technique using the symmetric key cryptosystem and vector quantization for detecting and restoring of a tampered medical image. Our scheme applies the one-way hashing function and the symmetric key cryptosystem to the host image to generate the verification data. To recover the tampered places, the host image is compressed by vector quantization to generate the recovery data. Once an intruder has modified the host image, our scheme can detect and recover the tampered places according to the embedded verification data and the recovery data. Besides, the proposed scheme can withstand the counterfeit attack. --- paper_title: Tamper detection with self-correction hybrid spatial-DCT domains image authentication technique paper_content: The development of effective image authentication techniques is of remarkably growing interest. Some recently developed fragile, semi-fragile/robust or hybrid-watermarking algorithms not only verify the authenticity of the watermarked image but also provide self reconstruction capabilities. However, several algorithms have been reported as vulnerable to various attacks, especially blind pattern matching attacks, with insufficient security. We propose a new blind dual-domain self-embedding watermarking scheme with more secure embedding processes of the image's blocks fragile signatures and robust approximations and more reliable local alterations detection with auto-correction capabilities, surviving normal image content preserving operations. Hence it prevents falsification, the real threat to authentication. --- paper_title: Multiple watermarking of medical images for content authentication and recovery paper_content: Medical Image data require strict security, confidentiality and integrity when transmitted from one hospital to another hospital. This can be achieved by adopting the procedures which can guarantee the image quality as well as secrecy of patient data to unauthorized users. To achieve these requirements we have proposed a multiple watermarking method. The scheme embeds robust watermark in region of non interest (RONI) for achieving security and confidentiality. While integrity control is achieved by inserting fragile watermark in region of interest ROI. Since ROI in the medical image is important from diagnosis point of view so it must be preserved. In order to avoid the distortion caused in ROI due to watermark insertion process, original ROI data is first separated and embedded outside the ROI. This will help in recovery of original ROI at the receiving end in contrast to the techniques reported in the literature which do not guarantee the integrity of the ROI after watermarking process. The image visual quality as well as tamper localization has been evaluated. We have used weighted peak signal to noise ratio (WPSNR) for measuring image quality after watermarking. --- paper_title: Medical Image Authentication Using DPT Watermarking: A Preliminary Attempt paper_content: Secure authentication of digital medical image content provides great value to the e-Health community and medical insurance industries. Fragile Watermarking has been proposed to provide the mechanism to authenticate digital medical image securely. Transform Domain based Watermarking are typically slower than spatial domain watermarking owing to the overhead in calculation of coefficients. In this paper, we propose a new Discrete Pascal Transform based watermarking technique. Preliminary experiment result shows authentication capability. Possible improvements on the proposed scheme are also presented before conclusions. --- paper_title: Digital watermarking of medical image using ROI information paper_content: Recently, the medical image has been digitized by the development of computer science and digitization of the medical devices. There are needs for database service of the medical image and long term storage because of the construction of PACS (Picture Archiving and Communication System) following DICOM (Digital Imaging Communications in Medicine) standards, telemedicine, and et al. Furthermore, authentication and copyright protection are required to protect the illegal distortion and reproduction of the medical information data. In this paper, we propose digital watermarking technique for medical image that prevents illegal forgery that can be caused after transmitting medical image data remotely. A wrong diagnosis may be occurred if the watermark is embedded into the whole area of image. Therefore, we embed the watermark into some area of medical image, except the decision area that makes a diagnosis so called region of interest (ROI) area in our paper, to increase invisibility. The watermark is the value of bit-plane in wavelet transform of the decision area for certification method of integrity verification. The experimental results show that the watermark embedded by the proposed algorithm can survive successfully in image processing operations such as JPEG lossy compression. --- paper_title: A novel watermarking technique for medical image authentication paper_content: Medical images are stored in PACS (picture archiving and communication systems) that are accessed over the intranet by radiologists for diagnosis. These days the trend is shifting towards a Web based interface for accessing PACS (image) data. This calls for thorough security measures in the information system of the hospital to ensure integrity of medical image data that is being transferred over the public network. The paper analyses various watermarking techniques with a perspective of applying them to medical images stored on the PACS. It discusses the applicability of invertible watermarking technique for ensuring integrity of medical images. Any modification to the watermarked DICOM (digital imaging and communications in medicine) image can be detected with high reliability using invertible fragile watermarking system. A unique content based digital signature can be generated from the image data (pixel data) which would be embedded inside the image in an imperceptible way without increasing the data size that need to be transferred. This signature can be extracted at the radiologist viewer work stations and used for the authentication while the modified pixel data is restored back to original if the image is found to be authentic. This kind of distortion free (erasable) embedding procedure would ensure image retrieval without any modification to pixel data after the authentication process that caters to the unique need of medical images for diagnosis --- paper_title: Survey of Medical Image Watermarking Algorithms paper_content: Watermarking in medical images is a new area of research and some works in this area have been reported world wide recently. Most of the works are on the tamper detection of the images and embedding of the Electronics Patient Record (EPR) data in the medical images. Watermarked medical images can be used for transmission, storage or telediagnosis. Tamper detection watermarks are useful to locate the regions in the image where some manipulations have been made. EPR data hiding in images improves the confidentiality of the patient data, saves memory storage space and reduce the bandwidth requirement for transmission of images. This paper discusses various aspects of medical image watermarking and makes a review of various watermarking algorithms originally proposed for medical images. --- paper_title: Security Protection of DICOM Medical Images Using Dual-Layer Reversible Watermarking with Tamper Detection Capability paper_content: Teleradiology applications and universal availability of patient records using web-based technology are rapidly gaining importance. Consequently, digital medical image security has become an important issue when images and their pertinent patient information are transmitted across public networks, such as the Internet. Health mandates such as the Health Insurance Portability and Accountability Act require healthcare providers to adhere to security measures in order to protect sensitive patient information. This paper presents a fully reversible, dual-layer watermarking scheme with tamper detection capability for medical images. The scheme utilizes concepts of public-key cryptography and reversible data-hiding technique. The scheme was tested using medical images in DICOM format. The results show that the scheme is able to ensure image authenticity and integrity, and to locate tampered regions in the images. --- paper_title: Reversible medical image watermarking for tamper detection and recovery paper_content: This research paper discussed the usage of watermarking in medical images to ensure the authenticity and integrity of the image and reviewed some watermarking schemes that had been developed. A design of a reversible tamper detection and recovery watermarking scheme was then proposed. The watermarking scheme uses a 640x480x8 bits ultrasound grayscale image as a sample. The concept of ROI (Region Of Interest) and RONI (Region Of Non Interest) were applied. Watermark embedded can be used to detect tampering and recovery of the image can be done. The watermark is also reversible. --- paper_title: Watermarking of chest CT scan medical images for content authentication paper_content: Medical image is usually comprised of region of interest (ROI) and region of non interest (RONI). ROI is the region that contains the important information from diagnosis point of view so it must be stored without any distortion. We have proposed a digital watermarking technique which avoids the distortion of image in ROI by embedding the watermark information in RONI. The watermark is comprised of patient information, hospital logo and message authentication code, computed using hash function. Earlier BCH encryption of watermark is performed to ensure inaccessibility of embedded data to the adversaries. --- paper_title: Medical image integrity control seeking into the detail of the tampering paper_content: In this paper, we propose a system which aims at verifying integrity of medical images. It not only detects and localizes alterations, but also seeks into the details of the image modification to understand what occurred. For that latter purpose, we developed an image signature which allows our system to approximate modifications by a simple model, a door function of similar dimensions. This signature is partly based on a linear combination of the DCT coefficients of pixel blocks. Protection data is attached to the image by watermarking. Whence, image integrity verification is conducted by comparing this embedded data to the recomputed one from the observed image. Experimental results with malicious image modification illustrate the overall performances of our system. --- paper_title: Authentication of digital medical images with digital signature technology. paper_content: PURPOSE: To determine whether digital signature technology (DST) can authenticate digital medical images to the same level of authenticity required for interbank electronic transfer of funds. MATERIALS AND METHODS: Message digests were computed for two magnetic resonance images that differed only by the value of a single bit. RSA (Rivest, Shamir, and Adleman) public key cryptography was used to encrypt each message digest to form a digital signature for each image, a process analogous to the established use of RSA DST for electronic funds transfer. The process was then reversed to authenticate the original image from its digital signature. RESULTS: Although the images differed by less than 0.000095%, their message digests differed at 94% of their characters. The digital signature of the original image proved that it was authentic and that the altered image was not authentic. CONCLUSION: RSA DST can establish the authenticity of images to at least the level of confidence required for interbank electronic t... --- paper_title: Medical image security and EPR hiding using Shamir's secret sharing scheme paper_content: Medical applications such as telediagnosis require information exchange over insecure networks. Therefore, protection of the integrity and confidentiality of the medical images is an important issue. Another issue is to store electronic patient record (EPR) in the medical image by steganographic or watermarking techniques. Studies reported in the literature deal with some of these issues but not all of them are satisfied in a single method. A medical image is distributed among a number of clinicians in telediagnosis and each one of them has all the information about the patient's medical condition. However, disclosing all the information about an important patient's medical condition to each of the clinicians is a security issue. This paper proposes a (k, n) secret sharing scheme which shares medical images among a health team of n clinicians such that at least k of them must gather to reveal the medical image to diagnose. Shamir's secret sharing scheme is used to address all of these security issues in one method. The proposed method can store longer EPR strings along with better authenticity and confidentiality properties while satisfying all the requirements as shown in the results. --- paper_title: A Semi-Reversible Watermark for Medical Image Authentication paper_content: This paper addresses the secure storage and transmission of medical informatics in rapidly growing applications such as teleradiology and telesurgery. In particular, we propose a frequency domain digital watermarking technique that can be used to authenticate medical images in a distributed diagnosis and home healthcare environment. The most significant result of our method is the semi-reversibility property that undoes most of the degradation attributable to the watermarking process --- paper_title: Text Fusion Watermarking in Medical Image with Semi-reversible for Secure Transfer and Authentication paper_content: Nowadays, the transmission of digitized medical information has become very convenient due to the generality of Internet. Internet has created the biggest benefit to achieve the transmission of patient information efficiently. However, it is easier that the hackers can grab or duplicate the digitized information on the Internet. This will cause the following problems of medical security and copyright protection. In order to fulfil the security and convenience issues of the patients following goals like the prevention of medical fault, the real-time detection of abnormal event, the support of clinical decision and developing of medical service based on patient has to be achieved. For this purpose this paper proposes the technique called binary embedding technique. It uses the binary information of the text embedded with semi reversible properties in the image are called binary embedding. This technique prevents the distortion of embedded information in the original image due to addition of noise. The concept of semi reversible property is used retains the original information, image quality before and after the process of watermarking is presented as a statistical analysis --- paper_title: Authentication and protection for medical image paper_content: This paper proposes a method to authenticate and protect medical images, especially in the region of interest (ROI). The ROI of a medical image is an important area during diagnosis and must not be distorted during transmission and storage in the hospital information system. The rest of the ROI is used for embedding a watermark that contains the patients data and authentication information, and the authentication information is generated from the ROI by analyzing wavelet coefficients with singular value decomposition (SVD), before embedding the watermark into the discrete wavelet transform (DWT) sub-band. It is important that the ratio of ROI and non-ROI areas is consistent between different systems and doctors, and this ratio is analyzed in this paper. The ROI of watermarked medical image is fragile to any distortion, and patients data and authentication information can be easily extracted from non-ROI. The effectiveness of the new approach is demonstrated empirically. --- paper_title: A Novel Technique for EPR Hiding in Medical Images for Telemedicine paper_content: Medical image data hiding has strict constrains such as high imperceptibility, high capacity and high robustness. Achieving these three requirements simultaneously is difficult. Though some works are reported in the literature on data hiding, watermarking and steganography which are suitable for telemedicine applications, none performs better in all aspects. Electronic Patient Report (EPR) data hiding for telemedicine demands a blind and reversible method. This paper proposes a novel approach to blind reversible data hiding based on integer wavelet transform. Experimental results shows that this scheme outperforms the prior arts in terms of zero BER (Bit Error Rate), higher PSNR (Peak Signal to Noise Ratio), and large EPR data embedding capacity with WPSNR (Weighted Peak Signal to Noise Ratio) around 53 dB, compared with the existing reversible data hiding schemes. --- paper_title: Lossless Watermarking in JPEG2000 for EPR Data Hiding paper_content: With the advances in telemedicine, watermarking for Electronic Patient Record(EPR) data hiding has gained profound importance. Most of the techniques proposed for EPR data hiding are not com- pression tolerant. In this paper we propose a new lossless scheme wherein the watermark- ing is done during the JPEG2000 compression process so that both the watermark and the cover image can be recovered as such at the receiving side. The recovered image is the same as that of the decompressed image when no watermarking has been done. Keywords- JPEG2000, EPR, watermark- ing, bit-plane --- paper_title: Hybrid watermarking of medical images for ROI authentication and recovery paper_content: Medical image data require strict security, confidentiality and integrity. To achieve these stringent requirements, we propose a hybrid watermarking method which embeds a robust watermark in the region of non-interest (RONI) for achieving security and confidentiality, while integrity control is achieved by inserting a fragile watermark into the region of the interest (ROI). First the information to be modified in ROI is separated and is inserted into RONI, which later is used in recovery of the original ROI. Secondly, to avoid the underflow and overflow, a location map is generated for embedding the watermark block-wise by leaving the suspected blocks. This avoids the preprocessing step of histogram modification. The image visual quality, as well as tamper localization, is evaluated. We use weighted peak signal to noise ratio for measuring image quality of watermarked images. Experimental results show that the proposed method outperforms the existing hybrid watermarking techniques. --- paper_title: Medical image tamper approximation based on an image moment signature paper_content: In this paper we propose a medical image integrity verification system that not only allows detecting and localizing one alteration, but also provides an approximation of this latter. For that purpose, we suggest the embedding of an image signature or digest derived from Geometric moments of image pixel blocks. Image integrity verification is then conducted by comparing this embedded signature to the recomputed one. This signature helps to approximate modifications by determining the parameters of the nearest generalized 2D Gaussian. Experimental results with local image modification illustrate the overall performances of our method. --- paper_title: Conception and limits of robust perceptual hashing: towards side information assisted hash functions paper_content: In this paper, we consider some basic concepts behind the design of existing robust perceptual hashing techniques for content identification. We show the limits of robust hashing from the communication perspectives as well as propose an approach that is able to overcome these shortcomings in certain setups. The consideration is based on both achievable rate and probability of error. We use the fact that most robust hashing algorithms are based on dimensionality reduction using random projections and quantization. Therefore, we demonstrate the corresponding achievable rate and probability of error based on random projections and compare with the results for the direct domain. The effect of dimensionality reduction is studied and the corresponding approximations are provided based on the Johnson-Lindenstrauss lemma. Side-information assisted robust perceptual hashing is proposed as a solution to the above shortcomings. --- paper_title: Protecting the Exchange of Medical Images in Healthcare Process Integration with Web Services paper_content: There is now an increasing demand for sharing images and image data for process integration among healthcare institutions. Web services technology has recently been widely proposed and gradually adopted as a platform for supporting integrations. The Health Insurance Portability and Accountability Act (HIPAA) imposes rules as national standards to protect individuals' health information in the U.S., highlighting security and privacy protection requirements. There are so far no holistic solutions to tackle the various protection issues in this area, especially in inter-institutional healthcare progress integration. We propose the exchange of medical images through a medical image exchange platform (MIEP), especially replacing ad-hoc and manual exchange practices. We show how contemporary technologies of Web services and watermarking can help archive images with layered implementation architecture. Through dedicated Web services technologies with watermarking mechanism, not only can the development, deployment, and maintenance of software be streamlined, the privacy protection in medical image exchanges as required by disparate processes can also be much facilitated --- paper_title: Watermarking Is Not Cryptography paper_content: A number of analogies to cryptographic concepts have been made about watermarking. In this paper, we argue that these analogies are misleading or incorrect, and highlight several analogies to support our argument. We believe that the fundamental role of watermarking is the reliable embedding and detection of information and should therefore be considered a form of communications. We note that the fields of communications and cryptography are quite distinct and while communications systems often combine technologies from the two fields, a layered architecture is applied that requires no knowledge of the layers above. We discuss how this layered approach can be applied to watermarking applications. ---	Title: A Review of Medical Image Watermarking Requirements for Teleradiology Section 1: Introduction Description 1: Introduce the background and significance of medical image watermarking in teleradiology, discussing the evolution from film-based to digital imaging and the security and privacy issues involved. Section 2: Security and Privacy Standards Description 2: Discuss the prevailing national and international standards and legislative rules for the security and privacy of medical information, such as ISO27799, HIPAA, and DICOM. Section 3: Medical Information Security Requirements Description 3: Outline the security requirements for medical information in teleradiology, focusing on confidentiality, integrity, and availability. Discuss the different models of teleradiology and their security domains. Section 4: Expected Threats and Conventional Security Measures Description 4: Identify potential security threats to medical images and the conventional measures (firewalls, VPNs, encryption, etc.) currently used to protect them. Section 5: Limitations of the Existing Security Measures Description 5: Highlight the limitations of existing conventional security measures in adequately safeguarding medical images and information. Section 6: Digital Watermarking in Teleradiology Description 6: Introduce the concept of digital watermarking, its components, and its potential benefits for enhancing security in teleradiology systems. Section 7: Advantages of Digital Watermarking Description 7: Explore the various advantages of digital watermarking for medical image applications, including enhanced security, privacy, avoidance of data detachment, and memory and bandwidth savings. Section 8: Choice of Design and Evaluation Parameters Description 8: Discuss the critical design and evaluation parameters for developing and validating digital watermarking schemes specifically for medical images. Section 9: Digital Watermarking Versus Other Security Measures/Tools Description 9: Compare digital watermarking with other security measures and tools, emphasizing their relative strengths and weaknesses. Section 10: Objectives and Applications of Watermarking for Medical Images Description 10: Examine different objectives and specific applications of digital watermarking in medical imaging, such as origin/content authentication, EPR annotation, and tamper detection and recovery. Section 11: Discussion and Conclusions Description 11: Summarize the key findings of the study, discuss the implications for teleradiology, and suggest future research directions for improving security through digital watermarking.
RSS based Vertical Handoff algorithms for Heterogeneous wireless networks - A Review	7	--- paper_title: Performance evaluation framework for vertical handoff algorithms in heterogeneous networks paper_content: The next generation (4G) wireless network is envisioned as a convergence of different wireless access technologies providing the user with the best anywhere anytime connection and improving the system resource utilization. The integration of wireless local area network (WLAN) hotspots and the third generation (3G) cellular network has recently received much attention. While the 3G-network can provide global coverage with a low data-rate service, the WLAN can provide a high data-rate service within the hotspots. Although increasing the underlay network utilization is expected to increase the user available bandwidth, it may violate the quality-of-service (QoS) requirements of active real-time applications. Hence, achieving seamless handoff between different wireless technologies, known as vertical handoff (VHO), is a major challenge for 4G-system implementation. Several factors, such as application QoS requirements and handoff delay, should be considered to realize an application transparent handoff. We present a novel framework to evaluate the impact of VHO algorithm design on system resource utilization and user perceived QoS. We used this framework to compare the performance of two different VHO algorithms. The results show a very good match between simulation and analytical results. In addition, it clarifies the tradeoff between achieving high resource utilization and satisfying user QoS expectations. --- paper_title: A Traveling Distance Prediction Based Method to Minimize Unnecessary Handovers from Cellular Networks to WLANs paper_content: We propose a handover decision method based on the prediction of traveling distance within an IEEE 802.11 wireless local area network (WLAN) cell. The method uses two thresholds which are calculated by the mobile terminal (MT) as it enters the WLAN cell. The predicted traveling distance is compared against these thresholds to make a handover decision in order to minimize the probability of handover failures or unnecessary handovers from a cellular network to a WLAN. Our analysis shows that the proposed method successfully keeps the number of failed or unnecessary handovers low. ---	Title: RSS based Vertical Handoff algorithms for Heterogeneous wireless networks - A Review Section 1: INTRODUCTION Description 1: This section introduces the concept of vertical handoff in heterogeneous wireless networks, emphasizing the significance of RSS based algorithms and the challenges associated with vertical handoff decisions. Section 2: RSS BASED VHD ALGORITHMS Description 2: This section details the basics of RSS based VHD (Vertical Handoff) algorithms and introduces three specific algorithms explored in this paper. Section 3: ALIVE-HO (adaptive lifetime based vertical handoff) Description 3: This section elaborates on the ALIVE-HO algorithm, its operational methodology, and the scenarios in which it is applied, including its advantages and limitations. Section 4: Algorithm on Adaptive RSS Threshold Description 4: This section discusses the algorithm proposed by Mohanty and Akyildiz, focusing on how it adapts the RSS threshold dynamically to reduce handoff failures and unnecessary handovers between WLAN and 3G networks. Section 5: A Traveling Distance Prediction Based Method Description 5: This section explains the traveling distance prediction-based method developed by Yan et al., which aims to minimize unnecessary handovers by considering the expected time a mobile terminal will spend within a WLAN cell. Section 6: CONCLUSION Description 6: This section provides a summary of the comparative analysis of the three RSS based vertical handoff algorithms, highlighting their respective strengths and weaknesses. Section 7: FUTURE DIRECTIONS Description 7: This section suggests potential future improvements to the discussed algorithms, including periodic sampling of RSS and refining estimations to enhance performance.
Network Layer Mobility: an Architecture and Survey	19	--- paper_title: Mobile Users: To Update or not to Update? paper_content: Tracking strategies for mobile users in wireless networks are studied. In order to save the cost of using the wireless links mobile users should not update their location whenever they cross boundaries of adjacent cells. This paper focuses on three natural strategies in which the mobile users make the decisions when and where to update: the time-based strategy, the number of movements-based strategy, and the distance-based strategy. We consider both memoryless movement patterns and movements with Markovian memory along a topology of cells arranged as a ring. We analyze the performance of each one of the three strategies under such movements, and show the performance differences between the strategies. ---	Title: Network Layer Mobility: an Architecture and Survey Section 1: Introduction Description 1: Introduce the problem of network layer mobility, discuss the limitations of current Internet protocols, and outline the scope and approach of the paper. Section 2: Internet Naming and Addressing Description 2: Discuss the fundamentals of Internet architecture, focusing on the importance of unique network addresses for hosts and the hierarchical structure of addressing. Section 3: Internet Addressing Description 3: Provide details on IP addressing, discussing the significance of the network-id and host-id components, and the necessity of hierarchical addressing for scalable routing. Section 4: Naming Description 4: Explore the concept of host names as user-defined aliases, their translation to IP addresses via DNS, and the challenges posed by mobility. Section 5: Mobility Problem: Directory Service View Description 5: Analyze the impact of host mobility on static name-to-address bindings and the limitations of the DNS in a mobile environment. Section 6: Mobility Problem: Internet View Description 6: Explain how mobility disrupts IP addressing and routing, with a focus on why current Internet architectures fail to support mobile hosts without breaking active TCP connections. Section 7: Network Layer Solution Architecture Description 7: Describe a proposed network layer architecture that enables the integration of mobile end-systems within the Internet, along with key concepts like Mobile Host, Home Address, and Home Network. Section 8: Two Tier Addressing Description 8: Introduce and elaborate on the concept of two-tier addressing to resolve issues associated with dual-use of internet addresses. Section 9: Architecture Components Description 9: Detail the key components of the proposed architecture, including Forwarding Agent (FA), Location Directory (LD), and Address Translation Agent (ATA). Section 10: Location Update Protocol Description 10: Discuss the protocol required to keep the LD and its cached entries up-to-date and consistent to ensure reliable mobile host accessibility. Section 11: Packet Forwarding Operation Description 11: Illustrate the operation of packet forwarding with the inclusion of ATA and FA, detailing the address translation process and transport layer transparency. Section 12: Address Translation Mechanisms Description 12: Describe the methods of address translation, focusing on encapsulation and loose source routing (LSR). Section 13: Mapping to candidate Mobile IP proposals Description 13: Present various Mobile IP proposals and show how they can be mapped to the proposed network architecture, highlighting their unique design choices and mechanisms. Section 14: Columbia Scheme Description 14: Analyze the Columbia Scheme focused on campus environments and its design choices for addressing and forwarding mobility. Section 15: Sony Scheme Description 15: Review Sony's approach to mobile networking, including its unique address mapping tables and update mechanisms. Section 16: LSR Scheme Description 16: Examine the Loose Source Routing (LSR) Scheme and its use of IP routing options to support mobile hosts. Section 17: Mobile IP working-group Proposal Description 17: Discuss the proposal by the IETF Mobile IP working group, focusing on its near-term deployability and design considerations for location updates and address translation. Section 18: IPv6 Mobility Proposal Description 18: Summarize the proposal for mobility support in IPv6, highlighting its enhancements over IPv4 and the elimination of Foreign Agents. Section 19: Summary Description 19: Summarize the key points of the paper, discussing the proposed network layer architecture and how various Mobile IP proposals align with this architecture.
Network Big Data: A Literature Survey on Stream Data Mining	11	--- paper_title: Network Big Data:Present and Future paper_content: Network big data refer to the massive data generated by interaction and fusion of the ternary human-machine-thing universe in the Cyberspace and available on the Internet.The increase of their scale and complexity exceeds that of the capacity of hardware characterized by the Moore law,which brings grand challenges to the architecture and the processing and computing capacity of the contemporary IT systems,meanwhile presents unprecedented opportunities on deeply mining and taking full advantage of the big value of network big data.Therefore,it is pressing to investigate the disciplinary issues and discover the common laws of network big data,and further study the fundamental theory and basic approach to qualitatively or quantitatively dealing with network big data.This paper analyzes the challenges caused by the complexity,uncertainty and emergence of network big data,and summarizes major issues and research status of the awareness,representation,storage,management,mining,and social computing of network big data,as well as network data platforms and applications.It also looks ahead to the development trends of big data science,new modes and paradigm of data computing,new IT infrastructures,and data security and privacy,etc. --- paper_title: O(ε)-Approximation to physical world by sensor networks paper_content: To observe the complicate physical world by a WSN, the sensors in the WSN senses and samples the data from the physical world. Currently, most of the existing work use equi-frequency sampling methods (EFS) or EFS based sampling methods for data acquisition in sensor networks. However, the accuracies of EFS and EFS based sampling methods cannot be guaranteed in practice since the physical world usually varies continuously, and these methods does not support reconstructing of the monitored physical world. To overcome the shortages of EFS and EFS based sampling methods, this paper focuses on designing physical-world-aware data acquisition algorithms to support O(ϵ)-approximation to the physical world for any ϵ ≥ 0. Two physical-world-aware data acquisition algorithms based on Hermit and Spline interpolation are proposed in the paper. Both algorithms can adjust the sensing frequency automatically based on the changing trend of the physical world and given c. The thorough analysis on the performance of the algorithms are also provided, including the accuracies, the smooth of the outputted curves, the error bounds for computing first and second derivatives, the number of the sampling times and complexities of the algorithms. It is proven that the error bounds of the algorithms are O(ϵ) and the complexities of the algorithms are O(1/ϵ1/4). Based on the new data acquisition algorithms, an algorithm for reconstructing physical world is also proposed and analyzed. The theoretical analysis and experimental results show that all the proposed algorithms have high performance in items of accuracy and energy consumption. --- paper_title: Enabling fast prediction for ensemble models on data streams paper_content: Ensemble learning has become a common tool for data stream classification, being able to handle large volumes of stream data and concept drifting. Previous studies focus on building accurate prediction models from stream data. However, a linear scan of a large number of base classifiers in the ensemble during prediction incurs significant costs in response time, preventing ensemble learning from being practical for many real world time-critical data stream applications, such as Web traffic stream monitoring, spam detection, and intrusion detection. In these applications, data streams usually arrive at a speed of GB/second, and it is necessary to classify each stream record in a timely manner. To address this problem, we propose a novel Ensemble-tree (E-tree for short) indexing structure to organize all base classifiers in an ensemble for fast prediction. On one hand, E-trees treat ensembles as spatial databases and employ an R-tree like height-balanced structure to reduce the expected prediction time from linear to sub-linear complexity. On the other hand, E-trees can automatically update themselves by continuously integrating new classifiers and discarding outdated ones, well adapting to new trends and patterns underneath data streams. Experiments on both synthetic and real-world data streams demonstrate the performance of our approach. --- paper_title: Long-Term Incremental Web-Supervised Learning of Visual Concepts via Random Savannas paper_content: The idea of using image and video data available in the World-Wide Web (WWW) as training data for classifier construction has received some attention in the past few years. In this paper, we present a novel incremental and scalable web-supervised learning system that continuously learns appearance models for image categories with heterogeneous appearances and improves these models periodically. Simply specifying the name of the concept that has to be learned initializes the proposed system, and there is no further supervision afterwards. Textual and visual information on web sites are used to filter out irrelevant and misleading training images. To obtain a robust, flexible, and updatable way of learning, a novel learning framework is presented that relies on clustering in order to identify visual subclasses before using an ensemble of random forests, called random savanna, for subclass learning. Experimental results demonstrate that the proposed web-supervised learning approach outperforms a support vector machine (SVM), while at the same time being simply parallelizable in the training and testing phases. --- paper_title: Dynamic classifier ensemble model for customer classification with imbalanced class distribution paper_content: Customer classification is widely used in customer relationship management including churn prediction, credit scoring, cross-selling and so on. In customer classification, an important yet challenging problem is the imbalance of data distribution. In this paper, we combine ensemble learning with cost-sensitive learning, and propose a dynamic classifier ensemble method for imbalanced data (DCEID). For each test customer, it can adaptively select out the more appropriate one from the two kinds of dynamic ensemble approach: dynamic classifier selection (DCS) and dynamic ensemble selection (DES). Meanwhile, new cost-sensitive selection criteria for DCS and DES are constructed respectively to improve the classification ability for imbalanced data. We apply this method to a credit scoring dataset in UCI and a real churn prediction dataset from a telecommunication company. The experimental results show that the classification performance of DCEID is not only better than some static ensemble methods such as weighted random forests and improved balanced random forests, but also better than the existing DCS and DES strategies. --- paper_title: Classification and Novel Class Detection in Concept-Drifting Data Streams under Time Constraints paper_content: Most existing data stream classification techniques ignore one important aspect of stream data: arrival of a novel class. We address this issue and propose a data stream classification technique that integrates a novel class detection mechanism into traditional classifiers, enabling automatic detection of novel classes before the true labels of the novel class instances arrive. Novel class detection problem becomes more challenging in the presence of concept-drift, when the underlying data distributions evolve in streams. In order to determine whether an instance belongs to a novel class, the classification model sometimes needs to wait for more test instances to discover similarities among those instances. A maximum allowable wait time Tc is imposed as a time constraint to classify a test instance. Furthermore, most existing stream classification approaches assume that the true label of a data point can be accessed immediately after the data point is classified. In reality, a time delay Tl is involved in obtaining the true label of a data point since manual labeling is time consuming. We show how to make fast and correct classification decisions under these constraints and apply them to real benchmark data. Comparison with state-of-the-art stream classification techniques prove the superiority of our approach. --- paper_title: An incremental learning vector quantization algorithm for pattern classification paper_content: Prototype classifiers have been studied for many years. However, few methods can realize incremental learning. On the other hand, most prototype classifiers need users to predetermine the number of prototypes; an improper prototype number might undermine the classification performance. To deal with these issues, in the paper we propose an online supervised algorithm named Incremental Learning Vector Quantization (ILVQ) for classification tasks. The proposed method has three contributions. (1) By designing an insertion policy, ILVQ incrementally learns new prototypes, including both between-class incremental learning and within-class incremental learning. (2) By employing an adaptive threshold scheme, ILVQ automatically learns the number of prototypes needed for each class dynamically according to the distribution of training data. Therefore, unlike most current prototype classifiers, ILVQ needs no prior knowledge of the number of prototypes or their initial value. (3) A technique for removing useless prototypes is used to eliminate noise interrupted into the input data. Results of experiments show that the proposed ILVQ can accommodate the incremental data environment and provide good recognition performance and storage efficiency. --- paper_title: A Semi-supervised Ensemble Approach for Mining Data Streams paper_content: There are many challenges in mining data streams, such as infinite length, evolving nature and lack of labeled instances. Accordingly, a semi-supervised ensemble approach for mining data streams is presented in this paper. Data streams are divided into data chunks to deal with the infinite length. An ensemble classification model E is trained with existing labeled data chunks and decision boundary is constructed using E for detecting novel classes. New labeled data chunks are used to update E while unlabeled ones are used to construct unsupervised models. Classes are predicted by a semi-supervised model Ex which is consist of E and unsupervised models in a maximization consensus manner, so better performance can be achieved by using the constraints from unsupervised models with limited labeled instances. Experiments with different datasets demonstrate that our method outperforms conventional methods in mining data streams. --- paper_title: Exponentially Weighted Moving Average Charts for Detecting Concept Drift paper_content: Classifying streaming data requires the development of methods which are computationally efficient and able to cope with changes in the underlying distribution of the stream, a phenomenon known in the literature as concept drift. We propose a new method for detecting concept drift which uses an Exponentially Weighted Moving Average (EWMA) chart to monitor the misclassification rate of an streaming classifier. Our approach is modular and can hence be run in parallel with any underlying classifier to provide an additional layer of concept drift detection. Moreover our method is computationally efficient with overhead O(1) and works in a fully online manner with no need to store data points in memory. Unlike many existing approaches to concept drift detection, our method allows the rate of false positive detections to be controlled and kept constant over time. --- paper_title: Mining time-changing data streams paper_content: Most statistical and machine-learning algorithms assume that the data is a random sample drawn from a stationary distribution. Unfortunately, most of the large databases available for mining today violate this assumption. They were gathered over months or years, and the underlying processes generating them changed during this time, sometimes radically. Although a number of algorithms have been proposed for learning time-changing concepts, they generally do not scale well to very large databases. In this paper we propose an efficient algorithm for mining decision trees from continuously-changing data streams, based on the ultra-fast VFDT decision tree learner. This algorithm, called CVFDT, stays current while making the most of old data by growing an alternative subtree whenever an old one becomes questionable, and replacing the old with the new when the new becomes more accurate. CVFDT learns a model which is similar in accuracy to the one that would be learned by reapplying VFDT to a moving window of examples every time a new example arrives, but with O(1) complexity per example, as opposed to O(w), where w is the size of the window. Experiments on a set of large time-changing data streams demonstrate the utility of this approach. --- paper_title: Density Based Distribute Data Stream Clustering Algorithm paper_content: To solve the problem of distributed data streams clustering, the algorithm DB-DDSC (Density-Based Distribute Data Stream Clustering) was proposed. The algorithm consisted of two stages. First presented the concept of circular-point based on the representative points and designed the iterative algorithm to find the density-connected circular-points, then generated the local model at the remote site. Second designed the algorithm to generate global clusters by combining the local models at coordinator site. The DB-DDSC algorithm can find the the clusters of different shapes under the distributed data stream environment, avoid frequently sending data by using the test-update algorithm, and reduce the data transmission. The experiments show that the DB-DDSC algorithm is feasible and scale expandable. --- paper_title: Online clustering of parallel data streams paper_content: In recent years, the management and processing of so-called data streams has become a topic of active research in several fields of computer science such as, e.g., distributed systems, database systems, and data mining. A data stream can roughly be thought of as a transient, continuously increasing sequence of time-stamped data. In this paper, we consider the problem of clustering parallel streams of real-valued data, that is to say, continuously evolving time series. In other words, we are interested in grouping data streams the evolution over time of which is similar in a specific sense. In order to maintain an up-to-date clustering structure, it is necessary to analyze the incoming data in an online manner, tolerating not more than a constant time delay. For this purpose, we develop an efficient online version of the classical K-means clustering algorithm. Our method's efficiency is mainly due to a scalable online transformation of the original data which allows for a fast computation of approximate distances between streams. --- paper_title: Wavelet Synopsis Based Clustering of Parallel Data Streams paper_content: In many real-life applications, such as stock markets, network monitoring, and sensor networks, data are modeled as dynamic evolving time series which is continuous and unbounded in nature, and many such data streams concur usually. Clustering is useful in analyzing such paralleled data streams. This paper is interested in grouping these evolving data streams. For this purpose, a synopsis is maintained dynamically for each data stream. The construction of the synopsis is based on Discrete Wavelet Transform and utilizes the amnesic feature of data stream. By using the synopsis, a fast computation of approximate distances between streams and the cluster center can be implemented, and an efficient online version of the classical K-means clustering algorithm is developed. Experiments have proved the effectiveness of the proposed method. --- paper_title: A Framework for Clustering Uncertain Data Streams paper_content: In recent years, uncertain data management applications have grown in importance because of the large number of hardware applications which measure data approximately. For example, sensors are typically expected to have considerable noise in their readings because of inaccuracies in data retrieval, transmission, and power failures. In many cases, the estimated error of the underlying data stream is available. This information is very useful for the mining process, since it can be used in order to improve the quality of the underlying results. In this paper we will propose a method for clustering uncertain data streams. We use a very general model of the uncertainty in which we assume that only a few statistical measures of the uncertainty are available. We will show that the use of even modest uncertainty information during the mining process is sufficient to greatly improve the quality of the underlying results. We show that our approach is more effective than a purely deterministic method such as the CluStream approach. We will test the approach on a variety of real and synthetic data sets and illustrate the advantages of the method in terms of effectiveness and efficiency. --- paper_title: Moment: maintaining closed frequent itemsets over a stream sliding window paper_content: This paper considers the problem of mining closed frequent itemsets over a sliding window using limited memory space. We design a synopsis data structure to monitor transactions in the sliding window so that we can output the current closed frequent itemsets at any time. Due to time and memory constraints, the synopsis data structure cannot monitor all possible itemsets. However, monitoring only frequent itemsets make it impossible to detect new itemsets when they become frequent. In this paper, we introduce a compact data structure, the closed enumeration tree (CET), to maintain a dynamically selected set of item-sets over a sliding-window. The selected itemsets consist of a boundary between closed frequent itemsets and the rest of the itemsets. Concept drifts in a data stream are reflected by boundary movements in the CET. In other words, a status change of any itemset (e.g., from non-frequent to frequent) must occur through the boundary. Because the boundary is relatively stable, the cost of mining closed frequent item-sets over a sliding window is dramatically reduced to that of mining transactions that can possibly cause boundary movements in the CET. Our experiments show that our algorithm performs much better than previous approaches. --- paper_title: Verifying and Mining Frequent Patterns from Large Windows over Data Streams paper_content: Mining frequent itemsets from data streams has proved to be very difficult because of computational complexity and the need for real-time response. In this paper, we introduce a novel verification algorithm which we then use to improve the performance of monitoring and mining tasks for association rules. Thus, we propose a frequent itemset mining method for sliding windows, which is faster than the state-of-the-art methods - in fact, its running time that is nearly constant with respect to the window size entails the mining of much larger windows than it was possible before. The performance of other frequent itemset mining methods (including those on static data) can be improved likewise, by replacing their counting methods (e.g., those using hash trees) by our verification algorithm. --- paper_title: Mining frequent itemsets in distributed and dynamic databases paper_content: Traditional methods for frequent itemset mining typically assume that data is centralized and static. Such methods impose excessive communication overhead when data is distributed, and they waste computational resources when data is dynamic. We present what we believe to be the first unified approach that overcomes these assumptions. Our approach makes use of parallel and incremental techniques to generate frequent itemsets in the presence of data updates without examining the entire database, and imposes minimal communication overhead when mining distributed databases. Further, our approach is able to generate both local and global frequent itemsets. This ability permits our approach to identify high-contrast frequent itemsets, which allows one to examine how the data is skewed over different sites. --- paper_title: UDS-FIM: An Efficient Algorithm of Frequent Itemsets Mining over Uncertain Transaction Data Streams paper_content: In this paper, we study the problem of finding frequent itemsets from uncertain data streams. To the best of our knowledge, the existing algorithms cannot compress transaction itemsets to a tree as compact as the classical FP-Tree, thus they need much time and memory space to process the tree. To address this issue, we propose an algorithm UDS-FIM and a tree structure UDS-Tree. Firstly, UDS-FIM maintains probability values of each transactions to an array; secondly, compresses each transaction to a UDS-Tree in the same manner as an FP-Tree (so it is as compact as an FP-Tree) and maintains index of probability values of each transaction in the array to the corresponding tail-nodes; lastly, it mines frequent itemsets from the UDS-Tree without additional scan of transactions. The experimental results show that UDS-FIM has achieved a good performance under different experimental conditions in terms of runtime and memory consumption. --- paper_title: Frequent Items Query Algorithm for Uncertain Sensing Data paper_content: With advances in technology,large amounts of streaming data can be generated continuously by sensors.Due to the inherited limitation of sensors,these continuous sensing data can be uncertain.This calls for stream mining of uncertain sensing data.Frequent items query is valuable in wireless sensor networks(WSNs) and it can be widely used in environmental monitoring,association rules mining,and so on.A basic algorithm which continuously maintains sliding window frequent items over WSNs is proposed.However the basic algorithm needs to maintain all items in the window.Due to this,an improved algorithm is further proposed by optimizing in two aspects:(1) the pruning rules by predicting the upper bound of items probability is developed,which can reduce the candidate set and improve the query efficiency;(2) the large amount of the same items in different window can be compressed by cp-list structure in order to minimize the memory utilization.Finally,experimental results and detailed analysis demonstrate that the high efficiency and low memory cost of the proposed algorithms in WSNs. --- paper_title: O(ε)-Approximation to physical world by sensor networks paper_content: To observe the complicate physical world by a WSN, the sensors in the WSN senses and samples the data from the physical world. Currently, most of the existing work use equi-frequency sampling methods (EFS) or EFS based sampling methods for data acquisition in sensor networks. However, the accuracies of EFS and EFS based sampling methods cannot be guaranteed in practice since the physical world usually varies continuously, and these methods does not support reconstructing of the monitored physical world. To overcome the shortages of EFS and EFS based sampling methods, this paper focuses on designing physical-world-aware data acquisition algorithms to support O(ϵ)-approximation to the physical world for any ϵ ≥ 0. Two physical-world-aware data acquisition algorithms based on Hermit and Spline interpolation are proposed in the paper. Both algorithms can adjust the sensing frequency automatically based on the changing trend of the physical world and given c. The thorough analysis on the performance of the algorithms are also provided, including the accuracies, the smooth of the outputted curves, the error bounds for computing first and second derivatives, the number of the sampling times and complexities of the algorithms. It is proven that the error bounds of the algorithms are O(ϵ) and the complexities of the algorithms are O(1/ϵ1/4). Based on the new data acquisition algorithms, an algorithm for reconstructing physical world is also proposed and analyzed. The theoretical analysis and experimental results show that all the proposed algorithms have high performance in items of accuracy and energy consumption. --- paper_title: A Compression Algorithm for Multi-streams Based on GEP paper_content: This paper applied the Methods which based on GEP in compress multi-streams. The contributions of this paper include: 1) giving an introduction to data function finding based on GEP(DFF-GEP), defining the main conception of Multi-Streams, and revealing the map relation in it; 2) putting forward the Compression Algorithm for Multi-Streams according to map relation lied in data between data streams; and 3)providing an experience with the real data and find that (3.1) the compression ratio of the new methods is 120?150 times as the traditional wavelets method, and 35?70 times as the wavelets and coincidence method; (3.2) the relative error of the new method is about 3?, yet maximum relative error is 0.01 by using the traditional relative error standard, the precision is improved from 7% to 15% as compared with the traditional method. --- paper_title: Continuous privacy preserving publishing of data streams paper_content: Recently, privacy preserving data publishing has received a lot of attention in both research and applications. Most of the previous studies, however, focus on static data sets. In this paper, we study an emerging problem of continuous privacy preserving publishing of data streams which cannot be solved by any straightforward extensions of the existing privacy preserving publishing methods on static data. To tackle the problem, we develop a novel approach which considers both the distribution of the data entries to be published and the statistical distribution of the data stream. An extensive performance study using both real data sets and synthetic data sets verifies the effectiveness and the efficiency of our methods. --- paper_title: Fast Clustering-Based Anonymization Algorithm for Data Streams paper_content: In order to prevent the disclosure of sensitive information and protect users’ privacy,the generalization and suppression of technology is often used to anonymize the quasi-identifiers of the data before its sharing.Data streams are inherently infinite and highly dynamic which are very different from static datasets,so that the anonymization of data streams needs to be capable of solving more complicated problems.The methods for anonymizing static datasets cannot be applied to data streams directly.In this paper,an anonymization approach for data streams is proposed with the analysis of the published anonymization methods for data streams.This approach scans the data only once to recognize and reuse the clusters that satisfy the anonymization requirements for speeding up the anonymization process.Experimental results on the real dataset show that the proposed method can reduce the information loss that is caused by generalization and suppression and also satisfies the anonymization requirements and has low time and space complexity. --- paper_title: Mining Method for Data Quality Detection Rules paper_content: Data quality rules are key to the database quality detection. To discover data quality rules from relational databases automatically and detect the error or abnormal data based on them,the form and evaluation measures of data quality rules are studied,and criterions of computing data quality rules are presented based on data item groups and the confidence threshold. The algorithms of mining minimal data quality rules and the main idea of detecting data errors using data quality rules are also given. The new form of data quality rules makes use of confidence mechanism of association rules and the expression of conditional functional dependencies to describe functional dependencies, conditional functional dependencies and association rules in the same format. It can be concluded that this kind of data quality rules has the properties of conciseness,objectivity,completeness and accuracy of detecting the error or abnormal data. Compared with other related research work,the proposed algorithms have lower temporal complexity,and the discovered quality rules improve the detecting rate. The effectiveness and correctness of the proposed methods are proved by the experiments. ---	Title: Network Big Data: A Literature Survey on Stream Data Mining Section 1: INTRODUCTION Description 1: Provide an introduction to the development of information technology, the significance of big data, and the importance and context of stream data mining in today's landscape. Section 2: Characteristics of Stream Data Mining Description 2: Discuss the unique characteristics of stream data mining in the environment of big data, such as usability, instantaneity, diversity of mode, multi-source heterogeneity, and high cognition. Section 3: Challenges and Research Issues of Stream Data Mining Description 3: Identify and elaborate on the key challenges and research issues faced in stream data mining under the big data setting. Section 4: Research on the Pattern of Stream Data Mining Description 4: Examine the patterns of stream data mining and propose new computational models to handle massive and high-dimensional data sets efficiently. Section 5: Relative Issues of Stream Data Mining Description 5: Explore various issues in stream data mining, such as efficient one-time stream data analysis, privacy mining, and mining in resource-constrained environments. Section 6: RESEARCH PROGRESS IN BIG DATA-ORIENTED STREAM DATA MINING Description 6: Provide the current state of research progress in big data-oriented stream data mining in several sub-fields, including classification, clustering, and frequent item mining. Section 7: Stream Data Mining Based on Classification Description 7: Detail methods of stream data classification, including integrated learning, incremental learning, and concept drift detection. Section 8: Clustering Stream Data Mining Description 8: Discuss various clustering methods and algorithms applied to stream data, addressing issues such as high-dimensional space and distributed computing environments. Section 9: Stream Data Mining Based on Frequent Items Description 9: Cover techniques for mining frequent items from stream data, such as transaction amount-based methods, time-related methods, and approximate methods. Section 10: Other Mining Methods and Mining Quality Analysis Description 10: Review additional stream data mining methods, such as data compression, privacy mining, and quality analysis, and how they contribute to improving the efficiency and effectiveness of stream data mining. Section 11: CONCLUSION Description 11: Summarize the main points of the paper, discuss the infancy of big data-oriented stream data mining, and suggest directions for future research.
Physical mechanism and modeling of heat generation and transfer in magnetic fluid hyperthermia through Néelian and Brownian relaxation: a review	16	--- paper_title: Induction of apoptotic cell DNA fragmentation in human cells after treatment with hyperthermia. paper_content: The biological significance of apoptosis is becoming increasingly clear. Its relevance in tumor response to treatment as well as recent evidence for its important function as a regulating mechanism in tumorigenesis has also been demonstrated. One of the most prominent biological features of apoptosis is nucleosomal DNA fragmentation. In this communication, we present a study of DNA fragmentation in Raji cells which have been subjected to hyperthermia treatment to induce apoptosis. We found that the induction and onset of fragmentation is swift, and consistent with previous reports that fragmentation must be a rapid event. --- paper_title: The effects of 41°C hyperthermia on the DNA repair protein, MRE11, correlate with radiosensitization in four human tumor cell lines paper_content: Purpose: The goal of this study was to determine if reduced availability of the DNA repair protein, MRE11, for the repair of damaged DNA is a basis for thermal radiosensitization induced by moderate hyperthermia. To test this hypothesis, we measured the total amount of MRE11 DNA repair protein and its heat-induced alterations in four human tumor cell lines requiring different heating times at 41°C to induce measurable radiosensitization.Materials and methods: Human colon adenocarcinoma cell lines (NSY42129, HT29 and HCT15) and HeLa cells were used as the test system. Cells were irradiated immediately after completion of hyperthermia. MRE11 levels in whole cell extract, nuclear extract and cytoplasmic extracts were measured by Western blotting. The nuclear and cytoplasmic extracts were separated by TX100 solubility. The subcellular localization of MRE11 was determined by immunofluorescence staining.Results: The results show that for the human tumor cell lines studied, the larger the endogenous amount of MR... --- paper_title: Thermal Therapy, Part III: Ablation Techniques paper_content: Ablative treatments are gaining increasing attention as an alternative to standard surgical therapies, especially for patients with contraindication or those who refuse open surgery. Thermal ablation is used in clinical applications mainly for treating heart arrhythmias, benign prostate hyperplasia, and nonoperable liver tumors; there is also increasing application to other organ sites, including the kidney, lung, and brain. Potential benefi ts of thermal ablation include reduced morbidity and mortality in comparison with standard surgical resection and the ability to treat nonsurgical patients. The purpose of this review is to outline and discuss the engineering principles and biological responses by which thermal ablation techniques can provide elevation of temperature in organs within the human body. Because of the individual problems associated with each type of treatment, a wide range of ablation techniques have evolved including cryoablation as well as ultrasound, radiofrequency (RF), microwave, and laser ablation. Aspects of each ablation technique, including mechanisms of action, equipment required, selection of eligible patients, treatment techniques, and patient outcomes are presented, along with a discussion of limitations of the techniques and future research directions. --- paper_title: Magnetic nanoparticle hyperthermia enhances radiation therapy: A study in mouse models of human prostate cancer paper_content: AbstractPurpose: We aimed to characterise magnetic nanoparticle hyperthermia (mNPH) with radiation therapy (RT) for prostate cancer.Methods: Human prostate cancer subcutaneous tumours, PC3 and LAPC-4, were grown in nude male mice. When tumours measured 150 mm3 magnetic iron oxide nanoparticles (MIONPs) were injected into tumours to a target dose of 5.5 mg Fe/cm3 tumour, and treated 24 h later by exposure to alternating magnetic field (AMF). Mice were randomly assigned to one of four cohorts to characterise (1) intratumour MIONP distribution, (2) effects of variable thermal dose mNPH (fixed AMF peak amplitude 24 kA/m at 160 ± 5 kHz) with/without RT (5 Gy), (3) effects of RT (RT5: 5 Gy; RT8: 8 Gy), and (4) fixed thermal dose mNPH (43 °C for 20 min) with/without RT (5 Gy). MIONP concentration and distribution were assessed following sacrifice and tissue harvest using inductively coupled plasma mass spectrometry (ICP-MS) and Prussian blue staining, respectively. Tumour growth was monitored and compared among ... --- paper_title: Microcalorimetric study of the metabolism of U-937 cells undergoing apoptosis induced by the combined treatment of hyperthermia and chemotherapy paper_content: Hyperthermia is a useful adjunct in cancer therapy, as it can increase the effectiveness and decrease the toxicity of currently available cancer treatments such as chemotherapy and radiation. In this study we determined the power-time curves of U-937 cell line treated by the combination of hyperthermia and Carmofur by using an LKB 2277 Bioactivity Monitor. The maximal thermal power and the heat production were used to evaluate the antitumor effect. Our results show that the combined treatment of hyperthermia and Carmofur had a synergistic antitumor effect, which is consistent with the apoptosis ratio obtained by TUNEL assay. The results also indicate that the metabolic activity of apoptotic cells is lower than that of normal cells. Thus microcalorimetry is a powerful tool in fields of hyperthermia. --- paper_title: Efficacy and safety of intratumoral thermotherapy using magnetic iron-oxide nanoparticles combined with external beam radiotherapy on patients with recurrent glioblastoma multiforme paper_content: Therapy options at the time of recurrence of glioblastoma multiforme are often limited. We investigated whether treatment with a new intratumoral thermotherapy procedure using magnetic nanoparticles improves survival outcome. In a single-arm study in two centers, 66 patients (59 with recurrent glioblastoma) received neuronavigationally controlled intratumoral instillation of an aqueous dispersion of iron-oxide (magnetite) nanoparticles and subsequent heating of the particles in an alternating magnetic field. Treatment was combined with fractionated stereotactic radiotherapy. A median dose of 30 Gy using a fractionation of 5 × 2 Gy/week was applied. The primary study endpoint was overall survival following diagnosis of first tumor recurrence (OS-2), while the secondary endpoint was overall survival after primary tumor diagnosis (OS-1). Survival times were calculated using the Kaplan–Meier method. Analyses were by intention to treat. The median overall survival from diagnosis of the first tumor recurrence among the 59 patients with recurrent glioblastoma was 13.4 months (95% CI: 10.6–16.2 months). Median OS-1 was 23.2 months while the median time interval between primary diagnosis and first tumor recurrence was 8.0 months. Only tumor volume at study entry was significantly correlated with ensuing survival (P < 0.01). No other variables predicting longer survival could be determined. The side effects of the new therapeutic approach were moderate, and no serious complications were observed. Thermotherapy using magnetic nanoparticles in conjunction with a reduced radiation dose is safe and effective and leads to longer OS-2 compared to conventional therapies in the treatment of recurrent glioblastoma. --- paper_title: Magnetic properties and antitumor effect of nanocomplexes of iron oxide and doxorubicin paper_content: Abstract We present a technology and magneto-mechanical milling chamber for the magneto-mechano-chemical synthesis (MMCS) of magneto-sensitive complex nanoparticles (MNC) comprising nanoparticles Fe 3 O 4 and anticancer drug doxorubicin (DOXO). Magnetic properties of MNC were studied with vibrating magnetometer and electron paramagnetic resonance. Under the influence of mechano-chemical and MMCS, the complex show a hysteresis curve, which is typical for soft ferromagnetic materials. We also demonstrate that Lewis lung carcinoma had a hysteresis loop typical for a weak soft ferromagnet in contrast to surrounding tissues, which were diamagnetic. Combined action of constant magnetic field and radio frequency moderate inductive hyperthermia (RFH) below 40°C and MNC was found to induce greater antitumor and antimetastatic effects as compared to conventional DOXO. Radiospectroscopy shows minimal activity of FeS-protein electron transport chain of mitochondria, and an increase in the content of non-heme iron complexes with nitric oxide in the tumor tissues under the influence of RFH and MNC. From the Clinical Editor This study reports on the top-down synthesis of magneto-sensitive complex nanoparticles comprised of Fe 3 O 4 nanoparticles and doxorubicin. Authors also found that Lewis lung carcinoma had a hysteresis loop typical for a weak soft ferromagnet in contrast to surrounding tissues, which were diamagnetic. Combined action of constant magnetic field and radio frequency induced moderate hyperthermia induced both antitumor and antimetastatic effects greater than conventional DOX alone. --- paper_title: Potential for therapy of drugs and hyperthermia. paper_content: The interaction of hyperthermia (41--45 degrees C) and chemotherapeutic agents frequently results in increased cytotoxicity over that predicted for an additive effect, although to date only a very limited number of drugs have been examined for such a possible interaction. At 42 degrees C, the upper limit of temperature useful for whole-body hyperthermia, the most promising agents of those examined to date appear to be the nitrosoureas and cis-platinum. Insufficient data exist for cyclophosphamide, whose long plasma half-life makes it an attractive candidate. Localized heating seems optimum at higher temperatures (43--45 degrees C). At these temperatures, not only those drugs effective at 42 degrees C but particularly bleomycin and possibly amphotericin B become candidates. No data exist in the literature on possible "thermic sensitizers," i.e., drugs which are noncytotoxic at 37 degrees C but which become effective at elevated temperatures. Two special cases are Adriamycin and actinomycin D. These drugs may be contraindicated for clinical use, since not only synergism but also protection by hyperthermia have been demonstrated, depending upon the time-sequence relationships of the heat and drug treatments. --- paper_title: Arrhenius analysis of heat survival curves from normal and thermotolerant CHO cells. paper_content: The temperature compatible with biphasic hyperthermia-survival curves in Chinese hamster ovary cells was increased from 42.5 to 44°C by acute heat conditioning (10 min, 45°C). An Arrhenius analysis... --- paper_title: Circulatory responses of malignant tumors during hyperthermia paper_content: Abstract The use of hyperthermia (elevation of regional body temperature to 41.5°–45°) as an adjuvant to clinical radiation therapy is becoming accepted in clinical practice at this time. It is, therefore, imperative to define the physiological responses of tumors to this modality. In this article, the effect of hyperthermia on the physiological responses of human and murine tumors are evaluated employing pH, oxygen, and flow ultramicroelectrodes. It is determined that hyperthermia causes a rise in tissue oxygen tension ( T p O 2 ) and blood flow at temperatures up to 41°, with a decrease at higher temperatures. Tumor tissue pH is low (6.8) and decreases during hyperthermia by as much as one unit of pH. The evidence linking these observations and the importance of blood flow modifications are discussed. --- paper_title: Interaction of Heat and Drugs In Vitro and In Vivo paper_content: The intention of this chapter is to review existing experimental data on combinations of cytotoxic drugs and hyperthermia. The focus will be on those drugs which are the most likely candidates for potentiation by hyperthermia, and attention will be drawn to findings which may form a basis for the design of clinical studies. --- paper_title: Hyperthermia Induces Apoptosis in Thymocytes paper_content: Mild hyperthermia (43{degree}C for 1 h) induces extensive double-stranded DNA fragmentation and, at a later time, cell death in murine thymocytes. The cleavage of DNA into oligonucleosome-sized fragments resembles that observed in examples of apoptosis including radiation-induced death of thymocytes. Following hyperthermia, incubation at 37{degree}C is necessary to detect DNA fragmentation, although protein and RNA synthesis do not seem to be required. Two protein synthesis inhibitors, cycloheximide and emetine, and two RNA synthesis inhibitors, actinomycin D and 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, do not inhibit DNA fragmentation or cell death in heated thymocytes at concentrations which significantly block these effects in irradiated thymocytes. We have used this difference in sensitivity to show that the DNA fragmentation induced in thymocytes which are irradiated and then heated seems to be caused only by the heating and not by the irradiation. --- paper_title: The cellular and molecular basis of hyperthermia paper_content: Abstract In oncology, the term ‘hyperthermia’ refers to the treatment of malignant diseases by administering heat in various ways. Hyperthermia is usually applied as an adjunct to an already established treatment modality (especially radiotherapy and chemotherapy), where tumor temperatures in the range of 40–43 °C are aspired. In several clinical phase-III trials, an improvement of both local control and survival rates have been demonstrated by adding local/regional hyperthermia to radiotherapy in patients with locally advanced or recurrent superficial and pelvic tumors. In addition, interstitial hyperthermia, hyperthermic chemoperfusion, and whole-body hyperthermia (WBH) are under clinical investigation, and some positive comparative trials have already been completed. In parallel to clinical research, several aspects of heat action have been examined in numerous pre-clinical studies since the 1970s. However, an unequivocal identification of the mechanisms leading to favorable clinical results of hyperthermia have not yet been identified for various reasons. This manuscript deals with discussions concerning the direct cytotoxic effect of heat, heat-induced alterations of the tumor microenvironment, synergism of heat in conjunction with radiation and drugs, as well as, the presumed cellular effects of hyperthermia including the expression of heat-shock proteins (HSP), induction and regulation of apoptosis, signal transduction, and modulation of drug resistance by hyperthermia. --- paper_title: Radiation therapy and hyperthermia improve the oxygenation of human soft tissue sarcomas. paper_content: The adverse prognostic impact of tumor hypoxia has been demonstrated in human malignancy. We report the effects of radiotherapy and hyperthermia (HT) on soft tissue sarcoma oxygenation and the relationship between treatment-induced changes in oxygenation and clinical treatment outcome. Patients receiving preoperative radiotherapy and HT underwent tumor oxygenation measurement pretreatment after the start of radiation/pre-HT and one day after the first HT treatment. The magnitude of improvement in tumor oxygenation after the first HT fraction relative to pretreatment baseline was positively correlated with the amount of necrosis seen in the resection specimen. Patients with <90% resection specimen necrosis experienced longer disease-free survival than those with > or = 90% necrosis. Increasing levels of tumor hypoxia were also correlated with diminished metabolic status as measured by P-31 magnetic resonance spectroscopy. --- paper_title: The relationship between heating time and temperature: its relevance to clinical hyperthermia. paper_content: It is well known that for a given level of damage to either cells in vitro or tissues in situ the relationship between temperature and time of application undergoes a transition in the range 42-43 degrees C and that above this temperature a change of 1 degree C is equivalent to a change in heating time by a factor of two. The present study has concentrated on establishing the relationship between time and temperature over a wide range. The investigation is in two parts, i.e. a review of the literature and an experimental study in which the endpoint used was necrosis in the tail of the baby rat. The aim is to provide information which might help solve a major clinical problem, namely the lack of a satisfactory means of relating treatments given with different temperatures for different lengths of time. The difficulty arises because there is no satisfactory definition of heat dose, in this context. The results confirm the relationship given above for temperatures above the transition. However, below the transition a change of 1 degree C is equivalent to a change in heating time by a factor of six. It is suggested that these relationships provide a means of monitoring a treatment in which the temperature does not remain constant and may vary within a heated volume. The method may also be used to compare treatments from different centres. An indication of the considerable uncertainties of the procedure is given.(ABSTRACT TRUNCATED AT 250 WORDS) --- paper_title: Cellular responses to hyperthermia (40–46°C): Cell killing and molecular events paper_content: The goal of this review is to provide a brief introduction to the effects of hyperthermia on cellular structures and physiology. The review focuses on the effects of hyperthermia thought to contribute to the enhancement of cancer therapy namely the mechanisms of cell killing and the sensitization of cells to ionizing radiation or chemotherapeutic agents. Specifically the review addresses four topics: hyperthermia induced cell killing, mathematical models of cell killing, mechanisms of thermal effects in the hyperthermia temperature range and effects on proteins that contribute to resistance to other stresses, i.e., DNA damage. Hyperthermia has significant effects on proteins including unfolding, exposing hydrophobic groups, and aggregation with proteins not directly altered by hyperthermia. Protein aggregation has effects throughout the cell but has a significant impact within the nucleus. Changes in the associations of nuclear proteins particularly those involved in DNA replication cause the stalling of ... --- paper_title: Hyperthermia adds to chemotherapy. paper_content: The hallmarks of hyperthermia and its pleotropic effects are in favour of its combined use with chemotherapy. Preclinical research reveals that for heat killing and synergistic effects the thermal dose is most critical. Thermal enhancement of drug cytotoxicity is accompanied by cellular death and necrosis without increasing its oncogenic potential. The induction of genetically defined stress responses can deliver danger signals to activate the host's immune system. The positive results of randomised trials have definitely established hyperthermia in combination with chemotherapy as a novel clinical modality for the treatment of cancer. Hyperthermia targets the action of chemotherapy within the heated tumour region without affecting systemic toxicity. In specific clinical settings regional hyperthermia (RHT) or hyperthermic perfusion has proved its value and deserve a greater focus and investigation in other malignancies. In Europe, more specialised centres should be created and maintained as network of excellence for hyperthermia in the field of oncology. --- paper_title: Thermal Therapy, Part 2: Hyperthermia Techniques paper_content: Hyperthermia, the procedure of raising the temperature of a part of or the whole body above normal for a defined period of time, is applied alone or as an adjunctive with various established cancer treatment modalities such as radiotherapy and chemotherapy. Clinical hyperthermia falls into three broad categories, namely, (1) localized hyperthermia, (2) regional hyperthermia, and (3) whole-body hyperthermia (WBH). Because of the various problems associated with each type of treatment, different heating techniques have evolved. In this article, background information on the biological rationale and current status of technologies concerning heating equipment for the application of hyperthermia to human cancer treatment are provided. The results of combinations of other modalities such as radiotherapy or chemotherapy with hyperthermia as a new treatment strategy are summarized. The article concludes with a discussion of challenges and opportunities for the future. --- paper_title: Intracranial Thermotherapy using Magnetic Nanoparticles Combined with External Beam Radiotherapy: Results of a Feasibility Study on Patients with Glioblastoma Multiforme paper_content: We aimed to evaluate the feasibility and tolerability of the newly developed thermotherapy using magnetic nanoparticles on recurrent glioblastoma multiforme. Fourteen patients received 3-dimensional image guided intratumoral injection of aminosilane coated iron oxide nanoparticles. The patients were then exposed to an alternating magnetic field to induce particle heating. The amount of fluid and the spatial distribution of the depots were planned in advance by means of a specially developed treatment planning software following magnetic resonance imaging (MRI). The actually achieved magnetic fluid distribution was measured by computed tomography (CT), which after matching to pre-operative MRI data enables the calculation of the expected heat distribution within the tumor in dependence of the magnetic field strength. Patients received 4–10 (median: 6) thermotherapy treatments following instillation of 0.1–0.7 ml (median: 0.2) of magnetic fluid per ml tumor volume and single fractions (2 Gy) of a radiotherapy series of 16–70 Gy (median: 30). Thermotherapy using magnetic nanoparticles was tolerated well by all patients with minor or no side effects. Median maximum intratumoral temperatures of 44.6°C (42.4–49.5°C) were measured and signs of local tumor control were observed. In conclusion, deep cranial thermotherapy using magnetic nanoparticles can be safely applied on glioblastoma multiforme patients. --- paper_title: Synergistic cell-killing effect of a combination of hyperthermia and heavy ion beam irradiation: in expectation of a breakthrough in the treatment of refractory cancers (review). paper_content: We studied the sensitivity against heavy ion beam and hyperthermia on radioresistant procaryote, Deinococcus radiodurans, for the purpose of cancer therapy. First, we examined the decrease of the survival rate and molecular weight of DNA purified from this cell by acid heat treatment. These decreases were recognized by heating at 55 degrees C below pH 5.0. Then, we assumed that the decrease in survival of D. radiodurans in vivo and damage to its DNA in vitro by acid heating were due to the release of purine rings from the phosphodiester backbone of DNA molecules, i.e., depurination. Second, we investigated the relation between LET (linear energy transfer) and RBE (relative biological effectiveness) on D. radiodurans dry and wet cells using AVF cyclotron at the TIARA facility of JAERI-Takasaki, Japan. These cells were irradiated with carbon (12C5+) ion beam at LET of about 100 keV/microm, neon (20Ne8+) ion beam at LET of about 300 keV/microm and oxygen (16O6+) ion beam at LET of about 400 keV/microm. The peak in the figure of the relation between LET and RBE value was found to increase according to the increase of LET value from 100 keV/microm. Third, we conducted combination treatment with 4.8 kGy of alpha-particles, i.e., boron 10 neutron captured beam induced by Kyoto University Research Nuclear Reactor operated at 5 MW, and hyperthermia at 52 degrees C, which caused the synergistic killing effect on D. radiodurans wet cells. However, being dissimilar to the case of gamma-irradiation, the interval incubation at 30 degrees C in the medium between both treatments could inhibit the recovery of survival. --- paper_title: Thermal Therapy, Part 1: An Introduction to Thermal Therapy paper_content: Thermal therapy is widely known and electromagnetic (EM) energy, ultrasonic waves, and other thermal-conduction-based devices have been used as heating sources. In particular, advances in EM technology have paved the way for promising trends in thermotherapeutical applications such as oncology, physiotherapy, urology, cardiology, ophthalmology, and in other areas of medicine as well. This series of articles is generally written for oncologists, cancer researchers, medical students, biomedical researchers, clinicians, and others who have an interest in this topic. This article reviews key processes and developments in thermal therapy with emphasis on two techniques, namely, hyperthermia [including long-term low-temperature hyperthermia (40-41 degrees C for 6-72 hr), moderate-temperature hyperthermia (42-45 degrees C for 15-60 min), and thermal ablation, or high-temperature hyperthermia (> 50 degrees C for > 4-6 min)]. The article will also provide an overview of a wide range of possible mechanisms and biological effects of heat. This information will be discussed in light of what is known about the degree of temperature rise that is expected from various sources of energy. The review concludes with an evaluation of human exposure risk to EM energy or the corresponding heat, trends in equipment development, and future research directions. --- paper_title: In Vitro Thermochemotherapy of Human Colon Cancer Cells with cis-Dichlorodiammineplatinum(II) and Mitomycin C paper_content: The thermosensitivity of human colon adenocarcinoma (LoVo) cells was investigated as a function of temperature and duration of heating in exponentially growing cultures. At 39-43°, time-dependent survival followed a simple exponential function. D o values decreased progressively with a rise in temperature, from D o at 40° = 38 hr to D o at 42° = 17 hr to D o at 43° = 1.5 hr, thus indicating relative thermoresistance of LoVo cells compared to Chinese hamster ovary cells. Dose-dependent 1-hr survival of LoVo cells treated with cis -dichlorodiammineplatinum(II) and mitomycin C was effectively modified when treatment was conducted under hyperthermic conditions. For both agents and cultures in exponential and stationary growth phases, hyperthermia abolished the initial shoulder portion and steepened the subsequent exponential part of the survival curves for dose-modifying factors at the 10% survival level of 1.5 to 2.0 at 41° and 2.6 to 2.8 at 42°. This significant enhancement of drug-induced cell kill by moderate hyperthermia suggests that thermochemotherapy with mitomycin C and cis -dichlorodiammineplatinum(II) should be tested clinically with both regional and total-body hyperthermia. --- paper_title: Inhibition of repair of radiation-induced damage by mild temperature hyperthermia, referring to the effect on quiescent cell populations paper_content: PurposeWe evaluated the usefulness of mild temperature hyperthermia (MTH) as an inhibitor of the repair of radiation-induced damage in terms of the responses of the total [= proliferating (P) + quiescent (Q)] and Q cell populations in solid tumors in vivo.Materials and methodsSCC VII tumor-bearing mice received a continuous administration of 5-bromo-2′-deoxyuridine (BrdU) to label all P cells. They then underwent high-dose-rate (HDR) γ-ray irradiation immediately followed by MTH or administration of caffeine or wortmannin; alternatively, they underwent reduced-dose rate γ-ray irradiation simultaneously with MTH or administration of caffeine or wortmannin. Nine hours after the start of irradiation, the tumor cells were isolated and incubated with a cytokinesis blocker, and the micronucleus (MN) frequency in cells without BrdU labeling (= Q cells) was determined using immunofluorescence staining for BrdU. The MN frequency in the total tumor cell population was determined using tumors that were not pretreated with BrdU.ResultsIn both the total and Q-cell populations, especially the latter, MTH efficiently suppressed the reduction in sensitivity caused by leaving an interval between HDR irradiation and the assay and decreasing the irradiation dose rate, as well as the combination with wortmannin administration.ConclusionFrom the viewpoint of solid tumor control as a whole, including intratumor Q-cell control, MTH is useful for suppressing the repair of both potentially lethal and sublethal damage. --- paper_title: Effect of hyperthermia on malignant cellsin vivo: A review and a hypothesis paper_content: The relevant literature is reviewed in an attempt to clarify the mechanism of heat-dependent tumor cell destruction in vivo. Malignant cells in vivo appear to be selectively destroyed by hyperthermia in the range of 41-43 degrees C. Heat evidently affects nuclear function, expressed by an inhibited RNA, DNA and protein synthesis and characteristic arrest or delay of cells in certain locations of the cell cycle. However, as these effects appear to be reversible and are observed in normal cells as well as malignant cells, they probably do not explain the hyperthermic induced selective in vivo destruction of malignant cells. Heat-induced cytoplasmic damage appears to be of more importance. Increased lysosomal activation is observed, and is further intensified by a relatively increased anaerobic glycolysis which develops selectively in tumor cells. A hypothesis is proposed and discussed which explains the marked and selective in vivo tumor cell destruction as a consequence of the enhancing effect on the cytoplasmic damage of certain environmental factors (e.g. increased acidity, hypoxia and insufficient nutrition. --- paper_title: Modification of tirapazamine-induced cytotoxicity in combination with mild hyperthermia and/or nicotinamide: reference to effect on quiescent tumour cells. paper_content: C3H/He and Balb/c mice bearing SCC VII or EMT6/KU tumours received continuous administration of 5-bromo-2'-deoxyuridine (BrdU) for 5 days to label all proliferating (P) cells. The tumours were locally heated at 40 degrees C for 60 min and/or the tumour-bearing mice received intraperitoneal injection of nicotinamide, and then tirapazamine (TPZ) was injected intraperitoneally. Sixty minutes after TPZ injection, the tumours were excised, minced and trypsinized. The tumour cell suspensions were incubated with cytochalasin-B (a cytokinesis-blocker), and the micronucleus (MN) frequency in cells without BrdU labelling (quiescent (Q) cells) was determined using immunofluorescence staining for BrdU. The MN frequency in total (P+Q) tumour cells was determined from the tumours that were not pretreated with BrdU. The cytotoxicity of TPZ was evaluated in terms of the frequency of induced micronuclei in binuclear tumour cells (= MN frequency). In both tumour systems, the MN frequencies of Q cells were greater than those of total tumour cell populations. Mild heat treatment elevated the MN frequency in total and Q cells in both tumour systems, but the effect was more marked in Q cells. In total cells, mild heat treatment increased the MN frequency in EMT6/KU tumour cells more markedly than in SCC VII tumour cells. In contrast, in both tumour systems, nicotinamide decreased the MN frequency in both cell populations, with a greater influence on the total cells. The combination of TPZ and mild heat treatment may be useful for sensitizing tumour cells in vivo, including Q cells. --- paper_title: Cell death induced in a murine mastocytoma by 42-47 degrees C heating in vitro: evidence that the form of death changes from apoptosis to necrosis above a critical heat load. paper_content: The pathogenesis of heat-induced cell death is controversial. Categorizing the death occurring after various heat loads as either apoptosis or necrosis might help to elucidate this problem, since it has been shown that these two processes differ in their mode of initiation as well as in their morphological and biochemical features. Log-phase cultures of mastocytoma P-815 x 2.1 were heated at temperatures ranging from 42 to 47 degrees C for 30 min. After 42 degrees C heating a slight increase in apoptosis was observed morphologically. However, after heating at 43, 43.5 and 44 degrees C, there was marked enhancement of apoptosis, and electrophoresis of DNA showed characteristic internucleosomal cleavage. With heating at 45 degrees C both apoptosis and necrosis were enhanced, whereas at 46 and 47 degrees C only necrosis was produced. DNA extracted from the 46 and 47 degrees C cultures showed virtually no degradation, which contrasts with the random DNA breakdown observed in necrosis produced by other types of injury; lysosomal enzymes released during heat-induced necrosis may be inactivated at the higher temperatures. It is suggested that apoptosis following heating may be triggered either by a limited increase in cytosolic calcium levels resulting from mild membrane changes or by DNA damage. Necrosis, on the other hand, is likely to be a consequence of severe membrane disruption. --- paper_title: Implication of Blood Flow in Hyperthermic Treatment of Tumors paper_content: Tumor blood flow varies significantly depending on the type, age, and size of tumors. Furthermore, the distribution of blood perfusion in tumors is quite heterogeneous. Blood flow in tumors may or may not be greater than that in the surrounding normal tissues at normothermic conditions. When heated at 41-430C, tumor blood flow either remains unchanged or increases slightly, usually by a factor of less than 2. The newly formed tumor vessels appear to be so vulnerable to heat that the blood flow decreases at 42-43' C in most of the animal tumors studied so far. By contrast, the blood flow in normal tissues, e. g., skin and muscle, increases by a factor of 3-20 upon heating at 42-450C. Consequently, the heat dissipation by blood flow becomes greater in normal tissues than in tumors during heating, and thereby a greater temperature rise in tumors may occur, resulting in greater damage in tumor relative to normal tissues. The intrinsically acidic intratumor environment becomes further acidic upon heating and accentuates the thermal damage on the tumor cells. Blood perfusion appears to be implicated in such a heat-induced increase in the intratumor acidity. --- paper_title: Thermotherapy using magnetic nanoparticles combined with external radiation in an orthotopic rat model of prostate cancer paper_content: BACKGROUND ::: We evaluated the effects of thermotherapy using magnetic nanoparticles, also referred to as magnetic fluid hyperthermia (MFH), combined with external radiation, in the Dunning model of prostate cancer. ::: ::: ::: METHODS ::: Orthotopic tumors were induced in 96 male Copenhagen rats. Animals were randomly allocated to eight groups, including controls and groups for dose-finding studies of external radiation. Treatment groups received two serial thermotherapy treatments following a single intratumoral injection of magnetic fluid or thermotherapy followed by external radiation (10 Gy). On day 20, after tumor induction, tumor weights in the treatment and control groups were compared and iron measurements in selected organs were carried out. ::: ::: ::: RESULTS ::: Mean maximal and minimal intratumoral temperatures obtained were 58.7 degrees C (centrally) and 42.7 degrees C (peripherally) during the first thermotherapy and 55.4 degrees C and 42.3 degrees C, respectively, during the second of two treatment sessions. Combined thermotherapy and radiation with 20 Gy was significantly more effective than radiation with 20 Gy alone and reduced tumor growth by 87.5-89.2% versus controls. Mean iron content in the prostates on day 20 was 87.5% of the injected dose of ferrites, whereas only 2.5% was found in the liver. ::: ::: ::: CONCLUSIONS ::: An additive effect was demonstrated for the combined treatment at a radiation dose of 20 Gy, which was equally effective in inhibiting tumor growth as radiation alone with 60 Gy. Serial heat treatments were possible without repeated injection of magnetic fluid. The optimal treatment schedules of this combination regarding temperatures, radiation dose, and fractionation need to be defined in further experimental studies. --- paper_title: Cellular effects of hyperthermia: relevance to the minimum dose for thermal damage. paper_content: The specific mechanism of cell killing by hyperthermia is unknown, but the high activation energy of cell killing and other responses to hyperthermia suggest that protein denaturation is the rate-limiting step. Protein denaturation can be directly monitored by differential scanning calorimetry and in general there is a good correlation between protein denaturation and cellular response. Approximately 5% denaturation is necessary for detectable killing. Protein denaturation leads to the aggregation of both denatured and native protein with multiple effects on cellular function. --- paper_title: Differential response of normal and tumor microcirculation to hyperthermia. paper_content: RBC velocity and vessel lumen diameter were measured in individual microvessels in normal (mature granulation) and neoplastic (VX2 carcinoma) tissues grown in a transparent rabbit ear chamber. Blood flow rates were determined before, during, and after local hyperthermia treatments at 40-52 degrees for 1 hr. Blood flow in normal tissue increased dramatically with temperature, but stasis occurred at higher temperatures and/or longer durations of heating. In tumors, blood flow rate did not increase as much, and stasis occurred at lower levels of hyperthermia. Both the magnitude and the time of maximum flow appeared to be bimodal functions of temperature. That is, both of these parameters increased with temperature up to a certain critical temperature, and then decreased at higher temperatures. This critical temperature was approximately 45.7 degrees in normal tissue and 43.0 degrees in tumors. Normal tissue required temperatures greater than 47 degrees to bring about vascular stasis in less than 1 hr, while stasis occurred in tumors in the same time frame at temperatures greater than 41 degrees. Normal tissue could increase its maximum flow capacity up to 6 times its preheating value, while neoplastic tissue could only double its maximum flow capacity. This differential flow response in individual microvessels was used to develop a theoretical framework relating various mechanisms of blood flow modifications due to hyperthermia. --- paper_title: Arrhenius relationships from the molecule and cell to the clinic. paper_content: There are great differences in heat sensitivity between different cell types and tissues. However, for an isoeffefct induced in a specific cell type or tissue by heating for different durations at different temperatures varying from 43-44 degrees C up to about 57 degrees C, the duration of heating must be increased by a factor of about 2 (R value) when the temperature is decreased by 1 degrees C. This same time-temperature relationship has been observed for heat inactivation of proteins, and changing only one amino acid out of 253 can shift the temperature for a given amount of protein denaturation from 46 degrees C to either 43 or 49 degrees C. For cytotoxic temperatures < 43-44 degrees C, R for mammalian cells and tissues is about 4-6. Many factors change the absolute heat sensitivity of mammalian cells by about 1 degrees C, but these factors have little effect on Rs, although the transition in R at 43-44 degrees C may be eliminated or shifted by about 1 degrees C. R for heat radiosensitization are similar to those above for heat cytotoxicity, but Rs for heat chemosensitization are much smaller (usually about 1.1-1.2). In practically all of the clinical trials that have been conducted, heat and radiation have been separated by 30-60 min, for which the primary effect should be heat cytotoxicity and not heat radiosensitization. Data are presented showing the clinical application of the thermal isoeffect dose (TID) concept in which different heating protocols for different times at different temperatures are converted into equiv min at 43 degrees C (EM43). For several heat treatments in the clinic, the TIDs for each treatment can be added to give a cumulative equiv min at 43 degrees C, viz., CEM43. This TID concept was applied by Oleson et al. in a retrospective analysis of clinical data, with the intent of using this approach prospectively to guide future clinical studies. Considerations of laboratory data and the large variations in temperature distributions observed in human tumours indicate that thermal tolerance, which has been observed for mammalian cells for both heat killing and heat radiosensitization, probably is not very important in the clinic.(ABSTRACT TRUNCATED AT 400 WORDS) --- paper_title: Hyperthermic radiosensitization: mode of action and clinical relevance. paper_content: PURPOSE ::: To provide an update on the recent knowledge about the molecular mechanisms of thermal radiosensitization and its possible relevance to thermoradiotherapy. ::: ::: ::: SUMMARY ::: Hyperthermia is probably the most potent cellular radiosensitizer known to date. Heat interacts with radiation and potentiates the cellular action of radiation by interfering with the cells' capability to deal with radiation-induced DNA damage. For ionizing irradiation, heat inhibits the repair of all types of DNA damage. Genetic and biochemical data suggest that the main pathways for DNA double-strand break (DSB) rejoining, non-homologous end-joining and homologous recombination, are not the likely primary targets for heat-induced radiosensitization. Rather, heat is suggested to affect primarily the religation step of base excision repair. Subsequently additional DSB arise during the DNA repair process in irradiated and heated cells and these additional DSB are all repaired with slow kinetics, the repair of which is highly error prone. Both mis- and non-rejoined DSB lead to an elevated number of lethal chromosome aberrations, finally causing additional cell killing. Heat-induced inhibition of DNA repair is considered not to result from altered signalling or enzyme inactivation but rather from alterations in higher-order chromatin structure. Although, the detailed mechanisms are not yet known, a substantial body of indirect and correlative data suggests that heat-induced protein aggregation at the level of attachment of looped DNA to the nuclear matrix impairs the accessibility of the damaged DNA for the repair machinery or impairs the processivity of the repair machinery itself. ::: ::: ::: CONCLUSION ::: Since recent phase III clinical trials have shown significant benefit of adding hyperthermia to radiotherapy regimens for a number of malignancies, it will become more important again to determine the molecular effects underlying this success. Such information could eventually also improve treatment quality in terms of patient selection, improved sequencing of the heat and radiation treatments, the number of heat treatments, and multimodality treatments (i.e. thermochemoradiotherapy). --- paper_title: THERMAL DOSE DETERMINATION IN CANCER THERAPY paper_content: Abstract With the rapid development of clinical hyperthermia for the treatment of cancer either alone or in conjunction with other modalities, a means of measuring a thermal dose in terms which are clinically relevant to the biological effect is needed. A comparison of published data empirically suggests a basic relationship that may be used to calculate a “thermal dose.” From a knowledge of the temperature during treatment as a function of time combined with a mathematical description of the time-temperature relationship, an estimate of the actual treatment calculated as an exposure time at some reference temperature can be determined. This could be of great benefit in providing a real-time accumulated dose during actual patient treatment. For the purpose of this study, a reference temperature of 43°C has been arbitrarily chosen to convert all thermal exposures to “equivalent-minutes” at this temperature. This dose calculation can be compared to an integrated calculation of the “degree-minutes” to determine its prognostic ability. The time-temperature relationship upon which this equivalent dose calculation is based does not predict, nor does it require, that different tissues have the same sensitivity to heat. A computer program written in FORTRAN is included for performing calculations of both equivalent-minutes (t 43 ) and degree-minutes (t dm43 ). Means are provided to alter the reference temperature, the Arrhenius “break” temperature and the time-temperature relationship both above and below the “break” temperature. In addition, the effect of factors such as step-down heating, thermotolerance, and physiological conditions on thermal dose calculations are discussed. The equations and methods described in this report are not intended to represent the only approach for thermal dose estimation; instead, they are intended to provide a simple but effective means for such calculations for clinical use and to stimulate efforts to evaluate data in terms of therapeutically useful thermal units. --- paper_title: Investigations on the possibility of a thermic tumour therapy—I.: Short-wave treatment of a transplanted isologous mouse mammary carcinoma☆☆☆ paper_content: The existing literature on studies of the inhibitory effect of moderate heat doses on malignant tumours is briefly reviewed. ::: ::: An experimental technique of heat treatment of mouse tumours in vivo under accurate control of the intratumoural temperature is described. ::: ::: In experiments with an isologous transplantable mouse mammary carcinoma, controlled application of a moderate heat dose led, in many cases, to a permanent cure of the transplanted tumour without causing any damage to the surrounding normal tissue. ::: ::: The necessary heat doses in the temperature range of 41·5 to 43·5°C are worked out revealing a definite relationship between temperature and exposure time. ::: ::: The heat treatment induces distinct histological changes in the tumour cells, whereas it does not cause any damage to the stromal and vascular cells in the tumour, or to the surrounding normal tissue. ::: ::: Immediately after the heat application, definite changes were revealed in the mitochondria and lysosomes of the tumour cells. These changes increased in intensity with the size of the heat dose and become more pronounced within a few hours or days. Within the first few hours, changes in the nuclei of the tumour cells and in chromosomal and nucleolar chromatin developed, with some variation in the individual cells. 24 hr after the application of a curative dose, all tumour cells showed severe injury. After smaller doses the reaction to the heat was less intense, with variations in the individual cells, and several tumour cells did not show any signs of lethal injury. ::: ::: Autolytic disintegration of the heat-damaged tumour cells occurs very rapidly. The connective tissue of the stroma increases markedly in volume, and a scar forms. ::: ::: The histological examination did not reveal all details of the process, but in the light of biochemical observations, it is reasonable to assume that the direct effect of heat is due to an elective activation of the acid hydrolases localized in the lysosomes of the tumour cells. --- paper_title: Re-setting the biologic rationale for thermal therapy paper_content: This review takes a retrospective look at how hyperthermia biology, as defined from studies emerging from the late 1970s and into the 1980s, mis-directed the clinical field of hyperthermia, by placing too much emphasis on the necessity of killing cells with hyperthermia in order to define success. The requirement that cell killing be achieved led to sub-optimal hyperthermia fractionation goals for combinations with radiotherapy, inappropriate sequencing between radiation and hyperthermia and goals for hyperthermia equipment performance that were neither achievable nor necessary. The review then considers the importance of the biologic effects of hyperthermia that occur in the temperature range that lies between that necessary to kill substantial proportions of cells and normothermia (e.g. 39–42°C for 1 h). The effects that occur in this temperature range are compelling including—inhibition of radiation-induced damage repair, changes in perfusion, re-oxygenation, effects on macromolecular and nanoparticle ... --- paper_title: Physiological mechanisms underlying heat-induced radiosensitization paper_content: The objective of this review is to evaluate hyperthermia related changes in tumor physiologic parameters and their relevance for tumor radiosensitization with particular emphases on tumor oxygenation. Elevation of temperature above the physiological level causes changes in blood flow, vascular permeability, metabolism, and tumor oxygenation. These changes in addition to the cellular effects such as direct cytotoxicity, inhibition of potentially lethal damage and sublethal damage repair, have an important influence on the efficacy of radiotherpay. There is now clear evidence that in a variety of rodent and canine, as well as human tumors, the changes in tumor oxygenation status caused by hyperthermia are temperature dependent and this relationship may greatly influence the response of tumors to thermo-radiotherapy. The improvement of tumor oxygenation after mild hyperthermia, which often lasts for as long as 24–48 h after heating, may increase the likelihood of a positive response of tumors to radiation th... --- paper_title: Local hyperthermia combined with radiotherapy and-/or chemotherapy: recent advances and promises for the future. paper_content: Hyperthermia, one of the oldest forms of cancer treatment involves selective heating of tumor tissues to temperatures ranging between 39 and 45°C. Recent developments based on the thermoradiobiological rationale of hyperthermia indicate it to be a potent radio- and chemosensitizer. This has been further corroborated through positive clinical outcomes in various tumor sites using thermoradiotherapy or thermoradiochemotherapy approaches. Moreover, being devoid of any additional significant toxicity, hyperthermia has been safely used with low or moderate doses of reirradiation for retreatment of previously treated and recurrent tumors, resulting in significant tumor regression. Recent in vitro and in vivo studies also indicate a unique immunomodulating prospect of hyperthermia, especially when combined with radiotherapy. In addition, the technological advances over the last decade both in hardware and software have led to potent and even safer loco-regional hyperthermia treatment delivery, thermal treatment planning, thermal dose monitoring through noninvasive thermometry and online adaptive temperature modulation. The review summarizes the outcomes from various clinical studies (both randomized and nonrandomized) where hyperthermia is used as a thermal sensitizer of radiotherapy and-/or chemotherapy in various solid tumors and presents an overview of the progresses in loco-regional hyperthermia. These recent developments, supported by positive clinical outcomes should merit hyperthermia to be incorporated in the therapeutic armamentarium as a safe and an effective addendum to the existing oncological treatment modalities. --- paper_title: Thermal dose and time—temperature factors for biological responses to heat shock paper_content: The application of hyperthermia in human cancer therapy, especially by radiotherapists who are accustomed to prescribing ionizing radiation treatments in physical dose units, has stimulated workers in this area to consider the possibility and utility of defining a unit of ‘thermal dose’. Previous thermal dose definitions have, primarily, been based on biological isoeffect response relationships, which attempt to relate exposure times that elicit a given biological response at one temperature to exposure times at another temperature that elicit the same biological response. This ‘equivalent time’ method is shown to have certain limitations. For both 42.4 and 45°C hyperthermia, these relationships accurately describe cell survival responses only when the heating rate is rapid (< 0.5°C min−1 from ambient to hyperthermic temperature). Further, the form of these isoeffect relationships appears to be temperature range and cell/tissue-type dependent, and it is suggested that these relationships be referred to as... --- paper_title: Differential thermal sensitivity of tumour and normal tissue microvascular response during hyperthermia paper_content: The goal of this study was to investigate the heat sensitivity of the microcirculation in normal C3H murine leg muscle and a variety of transplanted tumour lines (KHT, SCC-VII, RIF-1, C3H mouse mammary carcinoma, two human mammary carcinomas MDA-468 and S5). Clearance rate of a radioactive tracer monitored following an intra-tissue injection was used as a measurement of microvascular integrity during heat treatment. Clearance rate in all tumours studied was significantly lower after 1 h of heating at 44°C than the initial pretreatment clearance rate. Response of normal muscle differed from that of tumours in that the clearance rate after 1 h of heating at 44°C was similar to the initial clearance rate. Vasculature in the KHT fibrosarcoma was more sensitive to heat treatment than that in other tumours. In response to a heat treatment at 43, 44, 45, and 46°C the same level of microvascular damage occurred in half the time in KHT fibrosarcoma than in normal muscle. Furthermore, vascular damage in both muscle... --- paper_title: Modification of Cell Lethality at Elevated Temperatures The pH Effect paper_content: The lethal response of Chinese hamster ovary cells to hyperthermia was determined at selected extracellular pH. Decreasing pH from 7.6 to 6.7 increased the lethal response of cells over the temperature range of 41 to 44°C. Cell viability was not effected over this pH range at 37°C. The pH sensitizing affect was most prominent at temperatures which were marginally lethal at normal pH (7.4). Four hours of exposure to 42°C decreased survival to 10% at pH 7.4 and 0.01% at pH 6.7. Enhanced cell killing was observed when the cells were exposed to reduced pH and elevated temperatures simultaneously. Prolonging the time of pH exposure before and after hyperthermia did not influence survival. High-density culturing increased the sensitivity of cells to hyperthermia. This affect was due to metabolic acidification of the medium and could be reversed by adjusting the pH. --- paper_title: EGFR-targeted magnetic nanoparticle heaters kill cancer cells without a perceptible temperature rise. paper_content: It is currently believed that magnetic nanoparticle heaters (MNHs) can kill cancer cells only when the temperature is raised above 43 °C due to energy dissipation in an alternating magnetic field. On the other hand, simple heat conduction arguments indicate that in small tumors or single cells the relative rates of energy dissipation and heat conduction result in a negligible temperature rise, thus limiting the potential of MNHs in treating small tumors and metastatic cancer. Here we demonstrate that internalized MNHs conjugated to epidermal growth factor (EGF) and which target the epidermal growth factor receptor (EGFR) do result in a significant (up to 99.9%) reduction in cell viability and clonogenic survival in a thermal heat dose dependent manner, without the need for a perceptible temperature rise. The effect appears to be cell type specific and indicates that magnetic nanoparticles in alternating magnetic fields may effectively kill cancer cells under conditions previously considered as not possible. --- paper_title: Thermotherapy of Prostate Cancer Using Magnetic Nanoparticles: Feasibility, Imaging, and Three-Dimensional Temperature Distribution paper_content: Abstract Objectives To investigate the feasibility of thermotherapy using biocompatible superparamagnetic nanoparticles in patients with locally recurrent prostate cancer and to evaluate an imaging-based approach for noninvasive calculations of the three-dimensional temperature distribution. Methods Ten patients with locally recurrent prostate cancer following primary therapy with curative intent were entered into a prospective phase 1 trial. The magnetic fluid was injected transperineally into the prostates according to a preplan. Patients received six thermal therapies of 60-min duration at weekly intervals using an alternating magnetic field applicator. A method of three-dimensional thermal analysis based on computed tomography (CT) of the prostates was developed and correlated with invasive and intraluminal temperature measurements. The sensitivity of nanoparticle detection by means of CT was investigated in phantoms. Results The median detection rate of iron oxide nanoparticles in tissue specimens using CT was 89.5% (range: 70–98%). Maximum temperatures up to 55°C were achieved in the prostates. Median temperatures in 20%, 50%, and 90% of the prostates were 41.1°C (range: 40.0–47.4°C), 40.8°C (range: 39.5–45.4°C), and 40.1°C (range: 38.8–43.4°C), respectively. Median urethral and rectal temperatures were 40.5°C (range: 38.4–43.6°C) and 39.8°C (range: 38.2–43.4°C). The median thermal dose was 7.8 (range: 3.5–136.4) cumulative equivalent minutes at 43°C in 90% of the prostates. Conclusion The heating technique using magnetic nanoparticles was feasible. Hyperthermic to thermoablative temperatures were achieved in the prostates at 25% of the available magnetic field strength, indicating a significant potential for higher temperatures. A noninvasive thermometry method specific for this approach could be developed, which may be used for thermal dosimetry in future studies. --- paper_title: Normal tissue and solid tumor effects of hyperthermia in animal models and clinical trials. paper_content: Localized hyperthermia therapy by high-energy radio-frequency waves was evaluated in malignant and adjacent normal tissue of 30 patients with 10 types of cancer. Hyperthermia was delivered to superficial and deep visceral cancers in awake patients who had refractory disease. Histological and clinical responses were recorded serially. Toxicity tests in dogs, sheep, and pigs showed that progressive necrosis of normal and cancer tissue occurred at temperatures above 45 degrees C (113 degrees F). However, as normal tissues approached this temperature, intrinsic heat dissipation occurred (possibly due to augmented blood flow) so that temperatures below 45 degrees C could be maintained, whereas most solid tumors did not have this adaptive capacity and could be heated to 50 degrees C (122 degrees F) with virtually no injury to normal organs, s.c. tissue, or skin. To date, 69 treatments have been administered to 36 tumors in the 30 patients. Selective heating was observed in both primary and metastatic tumors located in surface tissues and internal organs. Response appeared to be related to tumor size in that differential heating was possible more often in the larger lesions. In tumors successfully heated, moderate to marked necrosis occurred. Radio-frequency hyperthermia appears to be a safe and potentially useful form of therapy for selected cancer patients. While other cancer treatments are more effective for small tumors, hyperthermia may be uniquely beneficial against larger lesions. --- paper_title: Nearly complete regression of tumors via collective behavior of magnetic nanoparticles in hyperthermia paper_content: One potential cancer treatment selectively deposits heat to the tumor through activation of magnetic nanoparticles inside the tumor. This can damage or kill the cancer cells without harming the surrounding healthy tissue. The properties assumed to be most important for this heat generation (saturation magnetization, amplitude and frequency of external magnetic field) originate from theoretical models that assume non-interacting nanoparticles. Although these factors certainly contribute, the fundamental assumption of 'no interaction' is flawed and consequently fails to anticipate their interactions with biological systems and the resulting heat deposition. Experimental evidence demonstrates that for interacting magnetite nanoparticles, determined by their spacing and anisotropy, the resulting collective behavior in the kilohertz frequency regime generates significant heat, leading to nearly complete regression of aggressive mammary tumors in mice. --- paper_title: Medical application of functionalized magnetic nanoparticles. paper_content: Since magnetic particles have unique features, the development of a variety of medical applications has been possible. The most unique feature of magnetic particles is their reaction to a magnetic force, and this feature has been utilized in applications such as drug targeting and bioseparation including cell sorting. Recently, magnetic nanoparticles have attracted attention because of their potential as contrast agents for magnetic resonance imaging (MRI) and heating mediators for cancer therapy (hyperthermia). Magnetite cationic liposomes (MCLs), one of the groups of cationic magnetic particles, can be used as carriers to introduce magnetite nanoparticles into target cells since their positively charged surface interacts with the negatively charged cell surface; furthermore, they find applications to hyperthermic treatments. Magnetite nanoparticles conjugated with antibodies (antibody-conjugated magnetoliposomes, AMLs) are also applied to hyperthermia and have enabled tumor-specific contrast enhancement in MRI via systemic administration. Since magnetic nanoparticles are attracted to a high magnetic flux density, it is possible to manipulate cells labeled with magnetic nanoparticles using magnets; this feature has been applied in tissue engineering. Magnetic force and MCLs were used to construct multilayered cell structures and a heterotypic layered 3D coculture system. Thus, the applications of these functionalized magnetic nanoparticles with their unique features will further improve medical techniques. --- paper_title: Tumor irradiation with intense ultrasound paper_content: Tumors implanted in the hamster flank have been irradiated in vivo with intense focused ultrasound at a spatial peak intensity of 907 W/cm2. A matrix of points was irradiated under c.w. conditions through the central plane of the tumor and perpendicular to the longitudinal axis of the sound field. A center spacing of 4 mm between matrix points and a time-on period of 2.5 sec at each point produced no cures. A spacing distance of 2 mm with 7 sec time-on period at each point increased mean survival time in non-cured animals and produced a cure rate of 29.4%. Combining the second regime of ultrasound treatment with administration of a chemotherapeutic agent (BCNU) 24 hr after irradiation did not increase mean survival time in the non-cured animals compared to the BCNU non-irradiated shams; however, the cure rate increased to 40%. Secondary tumors which were not seen in any ultrasound shams or controls were observed in all other regimes including BCNU non-irradiated shams. The incidence of secondary tumors was inversely related to the cure rate. --- paper_title: Clinical hyperthermia of prostate cancer using magnetic nanoparticles: presentation of a new interstitial technique. paper_content: The aim of this pilot study was to evaluate whether the technique of magnetic fluid hyperthermia can be used for minimally invasive treatment of prostate cancer. This paper presents the first clinical application of interstitial hyperthermia using magnetic nanoparticles in locally recurrent prostate cancer. Treatment planning was carried out using computerized tomography (CT) of the prostate. Based on the individual anatomy of the prostate and the estimated specific absorption rate (SAR) of magnetic fluids in prostatic tissue, the number and position of magnetic fluid depots required for sufficient heat deposition was calculated while rectum and urethra were spared. Nanoparticle suspensions were injected transperineally into the prostate under transrectal ultrasound and flouroscopy guidance. Treatments were delivered in the first magnetic field applicator for use in humans, using an alternating current magnetic field with a frequency of 100 kHz and variable field strength (0-18 kA m(-1)). Invasive thermometry of the prostate was carried out in the first and last of six weekly hyperthermia sessions of 60 min duration. CT-scans of the prostate were repeated following the first and last hyperthermia treatment to document magnetic nanoparticle distribution and the position of the thermometry probes in the prostate. Nanoparticles were retained in the prostate during the treatment interval of 6 weeks. Using appropriate software (AMIRA), a non-invasive estimation of temperature values in the prostate, based on intra-tumoural distribution of magnetic nanoparticles, can be performed and correlated with invasively measured intra-prostatic temperatures. Using a specially designed cooling device, treatment was well tolerated without anaesthesia. In the first patient treated, maximum and minimum intra-prostatic temperatures measured at a field strength of 4.0-5.0 kA m(-1) were 48.5 degrees C and 40.0 degrees C during the 1st treatment and 42.5 degrees C and 39.4 degrees C during the 6th treatment, respectively. These first clinical experiences prompted us to initiate a phase I study to evaluate feasibility, toxicity and quality of life during hyperthermia using magnetic nanoparticles in patients with biopsy-proven local recurrence of prostate cancer following radiotherapy with curative intent. To the authors' knowledge, this is the first report on clinical application of interstitial hyperthermia using magnetic nanoparticles in the treatment of human cancer. --- paper_title: Progress in applications of magnetic nanoparticles in biomedicine paper_content: A progress report is presented on a selection of scientific, technological and commercial advances in the biomedical applications of magnetic nanoparticles since 2003. Particular attention is paid to (i) magnetic actuation for in vitro non-viral transfection and tissue engineering and in vivo drug delivery and gene therapy, (ii) recent clinical results for magnetic hyperthermia treatments of brain and prostate cancer via direct injection, and continuing efforts to develop new agents suitable for targeted hyperthermia following intravenous injection and (iii) developments in medical sensing technologies involving a new generation of magnetic resonance imaging contrast agents, and the invention of magnetic particle imaging as a new modality. Ongoing prospects are also discussed. --- paper_title: High intensity focused ultrasound for the treatment of rat tumours paper_content: Discrete implanted liver tumours in the rat have been exposed to arrays of 1.7 MHz ultrasound lesions. Focal peak intensities in the range 1.4-3.5 kWcm-2 were used for an exposure time of 10 s. It has been demonstrated that where the whole tumour volume was exposed to the focused ultrasound beam, no evidence of tumour growth could be detected histologically. Where the ultrasonic lesion array was not contiguous, regrowth occurred. Preliminary histological studies confirmed this finding. --- paper_title: Magnetic nanoparticle design for medical diagnosis and therapy paper_content: Magnetic nanoparticles have attracted attention because of their current and potential usefulness as contrast agents for magnetic resonance imaging (MRI) or colloidal mediators for cancer magnetic hyperthermia. This review examines these in vivo applications through an understanding of the involved problems and the current and future possibilities for resolving them. A special emphasis is made on magnetic nanoparticle requirements from a physical viewpoint (e.g. relaxivity for MRI and specific absorption rate for hyperthermia), the factors affecting their biodistribution (e.g. size, surface hydrophobic/hydrophilic balance, etc.) and the solutions envisaged for enhancing their half-life in the blood compartment and targeting tumour cells. --- paper_title: Magnetic fluid hyperthermia (MFH)reduces prostate cancer growth in the orthotopic Dunning R3327 rat model paper_content: BACKGROUND ::: ::: Magnetic fluid hyperthermia (MFH) is a new technique for interstitial hyperthermia or thermoablation based on AC magnetic field-induced excitation of biocompatible superparamagnetic nanoparticles. Preliminary studies in the Dunning tumor model of prostate cancer have demonstrated the feasibility of MFH in vivo. To confirm these results and evaluate the potential of MFH as a minimally invasive treatment of prostate cancer we carried out a systematic analysis of the effects of MFH in the orthotopic Dunning R3327 tumor model of the rat. ::: ::: ::: ::: METHODS ::: ::: Orthotopic tumors were induced by implantation of MatLyLu-cells into the prostates of 48 male Copenhagen rats. Animals were randomly allocated to 4 groups of 12 rats each, including controls. Treatment animals received two MFH treatments following a single intratumoral injection of a magnetic fluid. Treatments were carried out on days 10 and 12 after tumor induction using an AC magnetic field applicator system operating at a frequency of 100 kHz and a variable field strength (0–18 kA/m). On day 20, animals were sacrificed and tumor weights in the treatment and control groups were compared. In addition, tumor growth curves were generated and histological examinations and iron measurements in selected organs were carried out. ::: ::: ::: ::: RESULTS ::: ::: Maximum intratumoral temperatures of over 70°C could be obtained with MFH at an AC magnetic field strength of 18 kA/m. At a constant field strength of 12.6 kA/m, mean maximal and minimal intratumoral temperatures recorded were 54.8°C (centrally) and 41.2°C (peripherally). MFH led to an inhibition of tumor growth of 44%–51% over controls. Mean iron content in the prostates of treated and untreated (injection of magnetic fluids but no AC magnetic field exposure) animals was 82.5%, whereas only 5.3% of the injected dose was found in the liver, 1.0% in the lung, and 0.5% in the spleen. ::: ::: ::: ::: CONCLUSIONS ::: ::: MFH led to a significant growth inhibition in this orthotopic model of the aggressive MatLyLu tumor variant. Intratumoral deposition of magnetic fluids was found to be stable, allowing for serial MFH treatments without repeated injection. The optimal treatment schedules and temperatures for MFH need to be defined in further studies. © 2005 Wiley-Liss, Inc. --- paper_title: Magnetic fluid hyperthermia inhibits the growth of breast carcinoma and downregulates vascular endothelial growth factor expression paper_content: The application of magnetic fluid hyperthermia (MFH) with nanoparticles has been shown to inhibit tumor growth in several animal models. However, the feasibility of using MFH in vivo to treat breast cancer is uncertain, and the mechanism is unclear. In the present study, it was observed that the intratumoral administration of MFH induced hyperthermia significantly in rats with Walker-265 breast carcinomas. The hyperthermia treatment with magnetic nanoparticles inhibited tumor growth in vivo and promoted the survival of the tumor-bearing rats. Furthermore, it was found that MFH treatment downregulated the protein expression of vascular endothelial growth factor (VEGF) in the tumor tissue, as observed by immunohistochemistry. MFH treatment also decreased the gene expression of VEGF and its receptors, VEGF receptor 1 and 2, and inhibited angiogenesis in the tumor tissues. Taken together, these results indicate that the application of MFH with nanoparticles is feasible for the treatment of breast carcinoma. The MFH-induced downregulation of angiogenesis may also contribute to the induction of an anti-tumor effect. --- paper_title: Status of hyperthermia in the treatment of advanced liver cancer. paper_content: The vast majority of patients with malignant liver tumors have inoperable disease. These patients must rely on chemotherapy, radiotherapy, and various locoregional treatments. Although these treatments have demonstrated encouraging response rates, symptom palliation and occasional down staging of tumors, their impact on survival is minor. As a result there has been renewed interest in hyperthermia as a treatment option. This study reviews the current modalities of hyperthermia in terms of clinical results, side effects, limitations, and therapeutic standing. --- paper_title: Theoretical predictions for spatially-focused heating of magnetic nanoparticles guided by magnetic particle imaging field gradients paper_content: Magnetic nanoparticles in alternating magnetic fields (AMFs) transfer some of the field's energy to their surroundings in the form of heat, a property that has attracted significant attention for use in cancer treatment through hyperthermia and in developing magnetic drug carriers that can be actuated to release their cargo externally using magnetic fields. To date, most work in this field has focused on the use of AMFs that actuate heat release by nanoparticles over large regions, without the ability to select specific nanoparticle-loaded regions for heating while leaving other nanoparticle-loaded regions unaffected. In parallel, magnetic particle imaging (MPI) has emerged as a promising approach to image the distribution of magnetic nanoparticle tracers in vivo, with sub-millimeter spatial resolution. The underlying principle in MPI is the application of a selection magnetic field gradient, which defines a small region of low bias field, superimposed with an AMF (of lower frequency and amplitude than those normally used to actuate heating by the nanoparticles) to obtain a signal which is proportional to the concentration of particles in the region of low bias field. Here we extend previous models for estimating the energy dissipation rates of magnetic nanoparticles in uniform AMFs to provide theoretical predictions of how the selection magnetic field gradient used in MPI can be used to selectively actuate heating by magnetic nanoparticles in the low bias field region of the selection magnetic field gradient. Theoretical predictions are given for the spatial decay in energy dissipation rate under magnetic field gradients representative of those that can be achieved with current MPI technology. These results underscore the potential of combining MPI and higher amplitude/frequency actuation AMFs to achieve selective magnetic fluid hyperthermia (MFH) guided by MPI. --- paper_title: Selective inductive heating of lymph nodes. paper_content: Selective Inductive Heating of Lymph Nodes R. GILCHRIST;RICHARD MEDAL;WILLIAM SHOREY;RUSSELL HANSELMAN;JOHN PARROTT;C. TAYLOR; Annals of Surgery --- paper_title: Use of magnetic nanoparticle heating in the treatment of breast cancer. paper_content: Magnetic nanoparticles are promising tools for the minimal invasive elimination of small tumours in the breast using magnetically-induced heating. The approach complies with the increasing demand for breast conserving therapies and has the advantage of offering a selective and refined tuning of the degree of energy deposition allowing an adequate temperature control at the target. The biophysical basis of the approach, the magnetic and structural properties of magnetic nanoparticles are reviewed. Results with model targets and in vivo experiments in laboratory animals are reported. --- paper_title: High Therapeutic Efficiency of Magnetic Hyperthermia in Xenograft Models Achieved with Moderate Temperature Dosages in the Tumor Area paper_content: Purpose ::: Tumor cells can be effectively inactivated by heating mediated by magnetic nanoparticles. However, optimized nanomaterials to supply thermal stress inside the tumor remain to be identified. The present study investigates the therapeutic effects of magnetic hyperthermia induced by superparamagnetic iron oxide nanoparticles on breast (MDA-MB-231) and pancreatic cancer (BxPC-3) xenografts in mice in vivo. --- paper_title: Radiofrequency Ablation of Malignant Liver Tumors paper_content: Background: Radiofrequency ablation (RFA) is being used to treat primary and metastatic liver tumors. The indications, treatment planning, and limitations of hepatic RFA must be defined and refined by surgeons treating hepatic malignancies. Methods: A review of the experience using RFA to treat unresectable primary and secondary hepatic malignancies at the University of Texas M. D. Anderson Cancer Center in Houston, Texas, and the G. Pascale National Cancer Institute in Naples, Italy, is provided. Patient selection, treatment approach, local recurrence rates, and overall cancer recurrence rates following RFA are described. The current literature on RFA of hepatic malignancies is reviewed. Results: RFA of hepatic tumors can be performed percutaneously, laparoscopically, or during an open surgical procedure. Incomplete treatment manifest as local recurrence is more common with a percutaneous approach. The morbidity and mortality rates associated with hepatic RFA are low. Local recurrence rates are low if meticulous treatment planning is performed. RFA can be combined safely with partial hepatic resection of large lesions. The long-term survival rates following RFA of primary and metastatic liver tumors have not yet been established. Conclusions: RFA of hepatic malignancies is a safe and promising technique to produce coagulative necrosis of unresectable hepatic malignancies. Experience with this treatment modality is not yet mature enough to establish long-term outcomes. --- paper_title: Magnetic fluid hyperthermia: focus on superparamagnetic iron oxide nanoparticles. paper_content: Abstract Due to their unique magnetic properties, excellent biocompatibility as well as multi-purpose biomedical potential (e.g., applications in cancer therapy and general drug delivery), superparamagnetic iron oxide nanoparticles (SPIONs) are attracting increasing attention in both pharmaceutical and industrial communities. The precise control of the physiochemical properties of these magnetic systems is crucial for hyperthermia applications, as the induced heat is highly dependent on these properties. In this review, the limitations and recent advances in the development of superparamagnetic iron oxide nanoparticles for hyperthermia are presented. --- paper_title: Magnetic Particle Imaging Tracers: State-of-the-Art and Future Directions paper_content: Magnetic particle imaging (MPI) is an emerging imaging modality with promising applications in diagnostic imaging and guided therapy. The image quality in MPI is strongly dependent on the nature of its iron oxide nanoparticle-based tracers. The selection of potential MPI tracers is currently limited, and the underlying physics of tracer response is not yet fully understood. An in-depth understanding of the magnetic relaxation processes that govern MPI tracers, gained through concerted theoretical and experimental work, is crucial to the development of optimized MPI tracers. Although tailored tracers will lead to improvements in image quality, tailored relaxation may also be exploited for biomedical applications or more flexible image contrast, as in the recent demonstration of color MPI. --- paper_title: Morbidity and quality of life during thermotherapy using magnetic nanoparticles in locally recurrent prostate cancer: Results of a prospective phase I trial paper_content: Purpose: To investigate the treatment-related morbidity and quality of life (QoL) during thermotherapy using superparamagnetic nanoparticles in patients with locally recurrent prostate cancer.Materials and Methods: Ten patients with biopsy-proven locally recurrent prostate cancer following primary therapy with curative intent and no detectable metastases were entered on a prospective phase I trial. Endpoints were feasibility, toxicity and QoL. Following intraprostatic injection of a nanoparticle dispersion, six thermal therapy sessions of 60 min duration were delivered at weekly intervals using an alternating magnetic field. National Cancer Institute (NCI) common toxicity criteria (CTC) and the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 and QLQ-PR25 questionnaires were used to evaluate toxicity and QoL, respectively. In addition, prostate specific antigen (PSA) measurements were carried out.Results: Maximum temperatures up to 55°C were achieved in the prostates at 25–30% of... --- paper_title: Nanoparticle-mediated thermal therapy: Evolving strategies for prostate cancer therapy paper_content: Purpose: Recent advances in nanotechnology have resulted in the manufacture of a plethora of nanoparticles of different sizes, shapes, core physicochemical properties and surface modifications that are being investigated for potential medical applications, particularly for the treatment of cancer. This review focuses on the therapeutic use of customised gold nanoparticles, magnetic nanoparticles and carbon nanotubes that efficiently generate heat upon electromagnetic (light and magnetic fields) stimulation after direct injection into tumours or preferential accumulation in tumours following systemic administration. This review will also focus on the evolving strategies to improve the therapeutic index of prostate cancer treatment using nanoparticle-mediated hyperthermia.Conclusions: Nanoparticle-mediated thermal therapy is a new and minimally invasive tool in the armamentarium for the treatment of cancers. Unique challenges posed by this form of hyperthermia include the non-target biodistribution of nanop... --- paper_title: Physical limits of hyperthermia using magnetite fine particles paper_content: Structural and magnetic properties of fine particles of magnetite are investigated with respect to the application for hyperthermia. Magnetic hysteresis losses are measured in dependence on the field amplitude for selected commercial powders and are discussed in terms of grain size and structure of the particles. For ferromagnetic powders as well as for ferrofluids, results of heating experiments within organic gels in a magnetic high frequency field are reported. The heating effect depends strongly on the magnetic properties of the magnetite particles which may vary appreciably for different samples in dependence on the particle size and microstructure. In particular, the transition from ferromagnetic to superparamagnetic behavior causes changes of the loss mechanism, and accordingly, of the heating effect. The maximum attainable heating effect is discussed in terms of common theoretical models. Rise of temperature at the surface of a small heated sample as well as in its immediate neighborhood in the surrounding medium is measured in dependence on time and is compared with solutions of the corresponding heat conductivity problem. Conclusions with respect to clinical applications are given. --- paper_title: Heating magnetic fluid with alternating magnetic field paper_content: This study develops analytical relationships and computations of power dissipation in magnetic fluid (ferrofluid) subjected to alternating magnetic field. The dissipation results from the orientational relaxation of particles having thermal fluctuations in a viscous medium. --- paper_title: Accuracy of available methods for quantifying the heat power generation of nanoparticles for magnetic hyperthermia. paper_content: In magnetic hyperthermia, characterising the specific functionality of magnetic nanoparticle arrangements is essential to plan the therapies by simulating maximum achievable temperatures. This functionality, i.e. the heat power released upon application of an alternating magnetic field, is quantified by means of the specific absorption rate (SAR), also referred to as specific loss power (SLP). Many research groups are currently involved in the SAR/SLP determination of newly synthesised materials by several methods, either magnetic or calorimetric, some of which are affected by important and unquantifiable uncertainties that may turn measurements into rough estimates. This paper reviews all these methods, discussing in particular sources of uncertainties, as well as their possible minimisation. In general, magnetic methods, although accurate, do not operate in the conditions of magnetic hyperthermia. Calorimetric methods do, but the easiest to implement, the initial-slope method in isoperibol conditions, derives inaccuracies coming from the lack of matching between thermal models, experimental set-ups and measuring conditions, while the most accurate, the pulse-heating method in adiabatic conditions, requires more complex set-ups. --- paper_title: Inductive heating of ferrimagnetic particles and magnetic fluids: Physical evaluation of their potential for hyperthermia paper_content: The potential of colloidal subdomain ferrite particle suspensions (SDP) ('magnetic fluids'), exposed to an alternating magnetic field, is evaluated for hyperthermia. Power absorption measurements of different magnetic fluids are presented in comparison to multidomain ferrite particles (MDP). Variations with frequency as well as magnetic field strength have been investigated. The experimental results clearly indicate a definite superiority of even non-optimized magnetic fluids over MDP ferrites regarding their specific absorption rate (SAR). Based on the work of Shliomis et al. (1990) and Hanson (1991), a solid-state physical model is applied to explain the specific properties of magnetic fluids with respect to a possible use in hyperthermia. The experimentally determined SAR data on magnetic fluids are used to estimate the heating capabilities of a magnetic induction heating technique assuming typical human dimensions and tissue parameters. It is considered that for a moderate concentration of 5 mg ferrite per gram tumour (i.e. 0.5% w/w) and clinically acceptable magnetic fields, intratumoral power absorption is comparable to RF heating with local applicators and superior to regional RF heating (by comparison with clinical SAR measurements from regional and local hyperthermia treatments). Owing to the high particle density per volume, inductive heating by magnetic fluids can improve temperature distributions in critical regions. Furthermore, localized application of magnetic fluids in a tumour might be easier and less traumatic than interstitial implantation techniques. --- paper_title: Heating ability of magnetite nanobeads with various sizes for magnetic hyperthermia at 120kHz, a noninvasive frequency paper_content: We synthesized four kinds of magnetite particles having average sizes of 7, 18, 40, and 80nm and investigated their heating ability when they were dispersed in an agar gel and exposed to an ac magnetic field at 120kHz, a noninvasive frequency for anticancer hyperthermia. The particles 18nm in average diameter gave the highest heating ability, though they exhibited narrow hysteresis loops as compared to the particles having average diameters of 40 and 80nm. This indicates that hysteresis loss does not contribute much to the heat rise by the 120kHz ac field, and Neel relaxation is dominantly contributing to the heat rise by the 18nm sized particles. A calculation based on Neel relaxation loss gave a plausible explanation. --- paper_title: Physics of heat generation using magnetic nanoparticles for hyperthermia. paper_content: Magnetic nanoparticle hyperthermia and thermal ablation have been actively studied experimentally and theoretically. In this review, we provide a summary of the literature describing the properties of nanometer-scale magnetic materials suspended in biocompatible fluids and their interactions with external magnetic fields. Summarised are the properties and mechanisms understood to be responsible for magnetic heating, and the models developed to understand the behaviour of single-domain magnets exposed to alternating magnetic fields. Linear response theory and its assumptions have provided a useful beginning point; however, its limitations are apparent when nanoparticle heating is measured over a wide range of magnetic fields. Well-developed models (e.g. for magnetisation reversal mechanisms and pseudo-single domain formation) available from other fields of research are explored. Some of the methods described include effects of moment relaxation, anisotropy, nanoparticle and moment rotation mechanisms, interactions and collective behaviour, which have been experimentally identified to be important. Here, we will discuss the implicit assumptions underlying these analytical models and their relevance to experiments. Numerical simulations will be discussed as an alternative to these simple analytical models, including their applicability to experimental data. Finally, guidelines for the design of optimal magnetic nanoparticles will be presented. --- paper_title: Magnetic Nanoparticles for Cancer Therapy paper_content: Today, technologies based on magnetic nanoparticles (MNPs) are routinely applied to biological systems with diagnostic or therapeutic purposes. The paradigmatic example is the magnetic resonance imaging (MRI), a technique that uses the magnetic moments of MNPs as a disturbance of the proton resonance to obtain images. Similarly, magnetic fluid hyperthermia (MFH) uses MNPs as heat generators to induce localized cell death. The physical basis of these techniques relies on the interaction with external magnetic fields, and therefore the magnetic moment of the particles has to be maximized for these applications. Targeted drug-delivery based on 'smart' nanoparticles is the next step towards more efficient oncologic therapies, by delivering a minimal dose of drug only to the vicinity of the target. Current improvements in this fields relay on a) particle functionalization with specific ligands for targeting cell membrane recep- tors and b) loading MNPs onto cells (e.g., dendritic cells, T-cells, macrophages) having an active role in tumor grow. Here we review the current state of research on applications of magnetic carriers for cancer therapy, discussing the advances and drawbacks of both passive and targeted delivery of MNPs. The most promising strategies for targeted delivery of MNPs are analyzed, evaluating the expected im- pact on clinical MRI and MFH protocols. --- paper_title: Impact of magnetic field parameters and iron oxide nanoparticle properties on heat generation for use in magnetic hyperthermia. paper_content: Abstract Heating of nanoparticles (NPs) using an AC magnetic field depends on several factors, and optimization of these parameters can improve the efficiency of heat generation for effective cancer therapy while administering a low NP treatment dose. This study investigated magnetic field strength and frequency, NP size, NP concentration, and solution viscosity as important parameters that impact the heating efficiency of iron oxide NPs with magnetite (Fe 3 O 4 ) and maghemite (γ-Fe 2 O 3 ) crystal structures. Heating efficiencies were determined for each experimental setting, with specific absorption rates (SARs) ranging from 3.7 to 325.9 W/g Fe. Magnetic heating was conducted on iron oxide NPs synthesized in our laboratories (with average core sizes of 8, 11, 13, and 18 nm), as well as commercially-available iron oxides (with average core sizes of 8, 9, and 16 nm). The experimental magnetic coil system made it possible to isolate the effect of magnetic field parameters and independently study the effect on heat generation. The highest SAR values were found for the 18 nm synthesized particles and the maghemite nanopowder. Magnetic field strengths were applied in the range of 15.1–47.7 kA/m, with field frequencies ranging from 123 to 430 kHz. The best heating was observed for the highest field strengths and frequencies tested, with results following trends predicted by the Rosensweig equation. An increase in solution viscosity led to lower heating rates in nanoparticle solutions, which can have significant implications for the application of magnetic fluid hyperthermia in vivo . --- paper_title: Simple models for dynamic hysteresis loop calculations of magnetic single-domain nanoparticles: Application to magnetic hyperthermia optimization paper_content: To optimize the heating properties of magnetic nanoparticles (MNPs) in magnetic hyperthermia applications, it is necessary to calculate the area of their hysteresis loops in an alternating magnetic field. The separation between “relaxation losses” and “hysteresis losses” presented in several articles is artificial and criticized here. The three types of theories suitable for describing hysteresis loops of MNPs are presented and compared to numerical simulations: equilibrium functions, Stoner–Wohlfarth model based theories (SWMBTs), and a linear response theory (LRT) using the Neel–Brown relaxation time. The configuration where the easy axis of the MNPs is aligned with respect to the magnetic field and the configuration of a random orientation of the easy axis are both studied. Suitable formulas to calculate the hysteresis areas of major cycles are deduced from SWMBTs and from numerical simulations; the domain of validity of the analytical formula is explicitly studied. In the case of minor cycles, the hys... --- paper_title: Magnetic particle hyperthermia?a promising tumour therapy? paper_content: We present a critical review of the state of the art of magnetic particle hyperthermia (MPH) as a minimal invasive tumour therapy. Magnetic principles of heating mechanisms are discussed with respect to the optimum choice of nanoparticle properties. In particular, the relation between superparamagnetic and ferrimagnetic single domain nanoparticles is clarified in order to choose the appropriate particle size distribution and the role of particle mobility for the relaxation path is discussed. Knowledge of the effect of particle properties for achieving high specific heating power provides necessary guidelines for development of nanoparticles tailored for tumour therapy. Nanoscale heat transfer processes are discussed with respect to the achievable temperature increase in cancer cells. The need to realize a well-controlled temperature distribution in tumour tissue represents the most serious problem of MPH, at present. Visionary concepts of particle administration, in particular by means of antibody targeting, are far from clinical practice, yet. On the basis of current knowledge of treating cancer by thermal damaging, this article elucidates possibilities, prospects, and challenges for establishment of MPH as a standard medical procedure. --- paper_title: Magnetic particle hyperthermia : nanoparticle magnetism and materials development for cancer therapy paper_content: Loss processes in magnetic nanoparticles are discussed with respect to optimization of the specific loss power (SLP) for application in tumour hyperthermia. Several types of magnetic iron oxide nanoparticles representative for different preparation methods (wet chemical precipitation, grinding, bacterial synthesis, magnetic size fractionation) are the subject of a comparative study of structural and magnetic properties. Since the specific loss power useful for hyperthermia is restricted by serious limitations of the alternating field amplitude and frequency, the effects of the latter are investigated experimentally in detail. The dependence of the SLP on the mean particle size is studied over a broad size range from superparamagnetic up to multidomain particles, and guidelines for achieving large SLP under the constraints valid for the field parameters are derived. Particles with the mean size of 18 nm having a narrow size distribution proved particularly useful. In particular, very high heating power may be delivered by bacterial magnetosomes, the best sample of which showed nearly 1 kW g −1 at 410 kHz and 10 kA m −1 . This value may even be exceeded by metallic magnetic particles, as indicated by measurements on cobalt particles. --- paper_title: Maghemite nanoparticles with very high AC-losses for application in RF-magnetic hyperthermia paper_content: Maghemite nanoparticles covalently coated with polyethylene glycol are investigated with respect to different loss processes in magnetic AC-fields. Transmission electron microscopy reveals a narrow size distribution which may be well approximated by a normal distribution (mean diameter 15.3 nm and distribution width 4.9 nm). Aqueous ferrofluids were characterised by DC-magnetometry, by measuring susceptibility spectra for a frequency range 20 Hz to 1 MHz and by calorimetric measurements of specific loss power (SLP) at 330 and 410 kHz for field amplitudes up to 11.7 kA/m. Extremely high values of SLP in the order of 600 W/g result for 400 kHz and 11 kA/m. In addition to liquid ferrofluids measurements were performed with suspensions in gel in order to elucidate the role of Brownian relaxation. The measured susceptibility spectra may be well reproduced by a model using a superposition of Neel and Brown loss processes under consideration of the observed narrow normal size distribution. In this way the observed very high specific heating power may be well understood. Results are discussed with respect to further optimisation of SLP for medical as well as technical RF-heating applications. --- paper_title: Evaluation of iron-cobalt/ferrite core-shell nanoparticles for cancer thermotherapy paper_content: Magnetic nanoparticles (MNPs) offer promise for local hyperthermia or thermoablative cancer therapy. Magnetic hyperthermia uses MNPs to heat cancerous regions in an rf field. Metallic MNPs have larger magnetic moments than iron oxides, allowing similar heating at lower concentrations. By tuning the magnetic anisotropy in alloys, the heating rate at a particular particle size can be optimized. Fe–Co core-shell MNPs have protective CoFe2O4 shell which prevents oxidation. The oxide coating also aids in functionalization and improves biocompatibility of the MNPs. We predict the specific loss power (SLP) for FeCo (SLP ∼450W∕g) at biocompatible fields to be significantly larger in comparision to oxide materials. The anisotropy of Fe-Co MNPs may be tuned by composition and/or shape variation to achieve the maximum SLP at a desired particle size. --- paper_title: The effects of magnetic nanoparticle properties on magnetic fluid hyperthermia paper_content: Magnetic fluid hyperthermia (MFH) is a noninvasive treatment that destroys cancer cells by heating a ferrofluid-impregnated malignant tissue with an ac magnetic field while causing minimal damage to the surrounding healthy tissue. The strength of the magnetic field must be sufficient to induce hyperthermia but it is also limited by the human ability to safely withstand it. The ferrofluid material used for hyperthermia should be one that is readily produced and is nontoxic while providing sufficient heating. We examine six materials that have been considered as candidates for MFH use. Examining the heating produced by nanoparticles of these materials, barium-ferrite and cobalt-ferrite are unable to produce sufficient MFH heating, that from iron-cobalt occurs at a far too rapid rate to be safe, while fcc iron-platinum, magnetite, and maghemite are all capable of producing stable controlled heating. We simulate the heating of ferrofluid-loaded tumors containing nanoparticles of the latter three materials to ... --- paper_title: Theoretical assessment of FePt nanoparticles as heating elements for magnetic hyperthermia paper_content: FePt magnetic nanoparticles (MNPs) are expected to be a high-performance nanoheater for magnetic hyperthermia because of their high Curie temperature, high saturation magnetization, and high chemical stability. Here, we present a theoretical performance assessment of chemically disordered fcc-phase FePt MNPs. We calculate heat generation and heat transfer in the tissue when an MNP-loaded tumor is placed on an external alternating magnetic field. For comparison, we estimate the performances of magnetite, maghemite, FeCo, and L10-phase FePt MNPs. We find that an fcc FePt MNP has a superior ability in magnetic hyperthermia --- paper_title: Nanomedicine: Magnetic Nanoparticles and their Biomedical Applications paper_content: During this past decade, science and engineering have seen a rapid increase in interest for nanoscale materials with dimensions less than 100 nm, which lie in the intermediate state between atoms and bulk (solid) materials. Their attributes are significantly altered relative to the corresponding bulk materials as they exhibit size dependent behavior such as quantum size effects (depending on bulk Bohr radius), optical absorption and emission, coulomb staircase behavior (electrical transport), superparamagnetism and various unique properties. They are active components of ferrofluids, recording tape, flexible disk recording media along with potential future applications in spintronics: a new paradigm of electronics utilizing intrinsic charge and spin of electrons for ultra-high-density data storage and quantum computing. They are used in a gamut of biomedical applications: bioseparation of biological entities, therapeutic drugs and gene delivery, radiofrequency-induced destruction of cells and tumors (hyperthermia), and contrast-enhancement agents for magnetic resonance imaging (MRI). The magnetic nanoparticles have optimizable, controllable sizes enabling their comparison to cells (10-100 μm), viruses (20-250 nm), proteins (3-50 nm), and genes (10-100 nm). Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) provide necessary characterization methods that enable accurate structural and functional analysis of interaction of the biofunctional particles with the target bioentities. The goal of the present discussion is to provide a broad review of magnetic nanoparticle research with a special focus on the synthesis, functionalization and medical applications of these particles, which have been carried out during the past decade, and to examine several prospective directions. --- paper_title: The heating effect of magnetic fluids in an alternating magnetic field paper_content: The heating mechanism and influencing factors of magnetite particles in a 63 kHz alternating magnetic field and 7 kA/m were studied. The results from in vivo heating experiments suggest that magnetite particles can generate enough energy to heat tumor tissue and perform effective hyperthermia. A novel model for predicting power losses has been proposed. --- paper_title: Water-Soluble Iron Oxide Nanocubes with High Values of Specific Absorption Rate for Cancer Cell Hyperthermia Treatment paper_content: Iron oxide nanocrystals (IONCs) are appealing heat mediator nanoprobes in magnetic-mediated hyperthermia for cancer treatment. Here, specific absorption rate (SAR) values are reported for cube-shaped water-soluble IONCs prepared by a one-pot synthesis approach in a size range between 13 and 40 nm. The SAR values were determined as a function of frequency and magnetic field applied, also spanning technical conditions which are considered biomedically safe for patients. Among the different sizes tested, IONCs with an average diameter of 19 ± 3 nm had significant SAR values in clinical conditions and reached SAR values up to 2452 W/gFe at 520 kHz and 29 kAm–1, which is one of the highest values so far reported for IONCs. In vitro trials carried out on KB cancer cells treated with IONCs of 19 nm have shown efficient hyperthermia performance, with cell mortality of about 50% recorded when an equilibrium temperature of 43 °C was reached after 1 h of treatment. --- paper_title: Enhancing cancer therapeutics using size-optimized magnetic fluid hyperthermia paper_content: Magnetic fluid hyperthermia (MFH) employs heat dissipation from magnetic nanoparticles to elicit a therapeutic outcome in tumor sites, which results in either cell death (>42 °C) or damage (<42 °C) depending on the localized rise in temperature. We investigated the therapeutic effect of MFH in immortalized T lymphocyte (Jurkat) cells using monodisperse magnetite (Fe3O4) nanoparticles (MNPs) synthesized in organic solvents and subsequently transferred to aqueous phase using a biocompatible amphiphilic polymer. Monodisperse MNPs, ∼16 nm diameter, show maximum heating efficiency, or specific loss power (watts/g Fe3O4) in a 373 kHz alternating magnetic field. Our in vitro results, for 15 min of heating, show that only 40% of cells survive for a relatively low dose (490 μg Fe/ml) of these size-optimized MNPs, compared to 80% and 90% survival fraction for 12 and 13 nm MNPs at 600 μg Fe/ml. The significant decrease in cell viability due to MNP-induced hyperthermia from only size-optimized nanoparticles demonstrates the central idea of tailoring size for a specific frequency in order to intrinsically improve the therapeutic potency of MFH by optimizing both dose and time of application. --- paper_title: Simulation and experimental studies on magnetic hyperthermia with use of superparamagnetic iron oxide nanoparticles. paper_content: Our purpose of this study was to present simulation and experimental studies on magnetic hyperthermia (MH) with use of an alternating magnetic field (AMF) and superparamagnetic iron oxide nanoparticles (Resovist®). In the simulation studies, the energy dissipation (P) and temperature rise rate (∆T/∆t) were computed under various conditions by use of the probability density function of the particle size distribution based on a log-normal distribution. P and ∆T/∆t and their dependence on the frequency of the AMF (f) largely depended on the particle size of Resovist®. P and ∆T/∆t reached maximum at a diameter of ~24 nm, and were proportional to the amplitude of the AMF (H (0)) raised to a power of ~2.0. In the experimental studies, we made a device for generating an AMF, and measured the temperature rise under various concentrations of Resovist®, H (0), and f. The temperature rise at 10 min after the start of heating was linearly proportional to the concentration of Resovist®, and proportional to H (0) raised to a power of ~2.4, which was slightly greater than that expected from the simulation studies. There was a tendency for the temperature rise to saturate with increasing f. In conclusion, this study will be useful for investigating the feasibility of MH with Resovist® and optimizing the parameters for it. --- paper_title: The heating effect of magnetic fluids in an alternating magnetic field paper_content: The heating mechanism and influencing factors of magnetite particles in a 63 kHz alternating magnetic field and 7 kA/m were studied. The results from in vivo heating experiments suggest that magnetite particles can generate enough energy to heat tumor tissue and perform effective hyperthermia. A novel model for predicting power losses has been proposed. --- paper_title: Size dependence of specific power absorption of Fe3O4 particles in AC magnetic field paper_content: Abstract The specific absorption rate (SAR) values of aqueous suspensions of magnetite particles with different diameters varying from 7.5 to 416 nm were investigated by measuring the time-dependent temperature curves in an external alternating magnetic field (80 kHz, 32.5 kA/m). Results indicate that the SAR values of magnetite particles are strongly size dependent. For magnetite particles larger than 46 nm, the SAR values increase as the particle size decreases where hysteresis loss is the main contribution mechanism. For magnetite particles of 7.5 and 13 nm which are superparamagnetic, hysteresis loss decreases to zero and, instead, relaxation losses (Neel loss and Brownian rotation loss) dominate, but Brown and Neel relaxation losses of the two samples are all relatively small in the applied frequency of 80 kHz. --- paper_title: Simple models for dynamic hysteresis loop calculations of magnetic single-domain nanoparticles: Application to magnetic hyperthermia optimization paper_content: To optimize the heating properties of magnetic nanoparticles (MNPs) in magnetic hyperthermia applications, it is necessary to calculate the area of their hysteresis loops in an alternating magnetic field. The separation between “relaxation losses” and “hysteresis losses” presented in several articles is artificial and criticized here. The three types of theories suitable for describing hysteresis loops of MNPs are presented and compared to numerical simulations: equilibrium functions, Stoner–Wohlfarth model based theories (SWMBTs), and a linear response theory (LRT) using the Neel–Brown relaxation time. The configuration where the easy axis of the MNPs is aligned with respect to the magnetic field and the configuration of a random orientation of the easy axis are both studied. Suitable formulas to calculate the hysteresis areas of major cycles are deduced from SWMBTs and from numerical simulations; the domain of validity of the analytical formula is explicitly studied. In the case of minor cycles, the hys... --- paper_title: Evaluation of iron-cobalt/ferrite core-shell nanoparticles for cancer thermotherapy paper_content: Magnetic nanoparticles (MNPs) offer promise for local hyperthermia or thermoablative cancer therapy. Magnetic hyperthermia uses MNPs to heat cancerous regions in an rf field. Metallic MNPs have larger magnetic moments than iron oxides, allowing similar heating at lower concentrations. By tuning the magnetic anisotropy in alloys, the heating rate at a particular particle size can be optimized. Fe–Co core-shell MNPs have protective CoFe2O4 shell which prevents oxidation. The oxide coating also aids in functionalization and improves biocompatibility of the MNPs. We predict the specific loss power (SLP) for FeCo (SLP ∼450W∕g) at biocompatible fields to be significantly larger in comparision to oxide materials. The anisotropy of Fe-Co MNPs may be tuned by composition and/or shape variation to achieve the maximum SLP at a desired particle size. --- paper_title: Simple models for dynamic hysteresis loop calculations of magnetic single-domain nanoparticles: Application to magnetic hyperthermia optimization paper_content: To optimize the heating properties of magnetic nanoparticles (MNPs) in magnetic hyperthermia applications, it is necessary to calculate the area of their hysteresis loops in an alternating magnetic field. The separation between “relaxation losses” and “hysteresis losses” presented in several articles is artificial and criticized here. The three types of theories suitable for describing hysteresis loops of MNPs are presented and compared to numerical simulations: equilibrium functions, Stoner–Wohlfarth model based theories (SWMBTs), and a linear response theory (LRT) using the Neel–Brown relaxation time. The configuration where the easy axis of the MNPs is aligned with respect to the magnetic field and the configuration of a random orientation of the easy axis are both studied. Suitable formulas to calculate the hysteresis areas of major cycles are deduced from SWMBTs and from numerical simulations; the domain of validity of the analytical formula is explicitly studied. In the case of minor cycles, the hys... --- paper_title: Magnetic Properties of Magnetic Nanoparticles for Efficient Hyperthermia paper_content: Localized magnetic hyperthermia using magnetic nanoparticles (MNPs) under the application of small magnetic fields is a promising tool for treating small or deep-seated tumors. For this method to be applicable, the amount of MNPs used should be minimized. Hence, it is essential to enhance the power dissipation or heating efficiency of MNPs. Several factors influence the heating efficiency of MNPs, such as the amplitude and frequency of the applied magnetic field and the structural and magnetic properties of MNPs. We discuss some of the physics principles for effective heating of MNPs focusing on the role of surface anisotropy, interface exchange anisotropy and dipolar interactions. Basic magnetic properties of MNPs such as their superparamagnetic behavior, are briefly reviewed. The influence of temperature on anisotropy and magnetization of MNPs is discussed. Recent development in self-regulated hyperthermia is briefly discussed. Some physical and practical limitations of using MNPs in magnetic hyperthermia are also briefly discussed. --- paper_title: Spin pinning at ferrite‐organic interfaces paper_content: We have previously reported a drastic moment decrease in NiFe2O4 fine particles (∠100A dia.) coated with an organic surfactant such as oleic acid. Removal of the organic coating restored the moment of the particles. Continued investigation has demonstrated that the apparent moment decrease is due to strong pinning of the spins of those ferrite cations that are bonded to the organic molecules. The evidence for this model includes: (1) UNcoated NiFe2O4 particles, prepared in an otherwise identical fashion and with the same size distribution showed no decrease in moment. This observation eliminates the possibility that defects or abnormal surface morphology are responsible for the decreased moment. (2) Low temperature Mossbauer measurements in zero field of coated and uncoated particles showed identical spectra associated with ordered fine particle NiFe2O4. (3) Mossbauer data taken on coated particles in a field of 68.6 kOe applied along the direction of γ‐ray emission showed only a small decrease of the Pm=... --- paper_title: Magnetic hyperthermia efficiency in the cellular environment for different nanoparticle designs. paper_content: Abstract Magnetic hyperthermia mediated by magnetic nanomaterials is one promising antitumoral nanotherapy, particularly for its ability to remotely destroy deep tumors. More and more new nanomaterials are being developed for this purpose, with improved heat-generating properties in solution. However, although the ultimate target of these treatments is the tumor cell, the heating efficiency, and the underlying mechanisms, are rarely studied in the cellular environment. Here we attempt to fill this gap by making systematic measurements of both hyperthermia and magnetism in controlled cell environments, using a wide range of nanomaterials. In particular, we report a systematic fall in the heating efficiency for nanomaterials associated with tumour cells. Real-time measurements showed that this loss of heat-generating power occurred very rapidly, within a matter of minutes. The fall in heating correlated with the magnetic characterization of the samples, demonstrating a complete inhibition of the Brownian relaxation in cellular conditions. --- paper_title: Simulating physiological conditions to evaluate nanoparticles for magnetic fluid hyperthermia (MFH) therapy applications paper_content: Abstract Magnetite nanoparticles with high self-heating capacity and low toxicity characteristics are a promising candidate for cancer hyperthermia treatment. In order to achieve minimum dosage to a patient, magnetic nanoparticles with high heating capacity are needed. In addition, the influence of physiological factors on the heat capacity of a material should be investigated in order to determine the feasibility. In this study, magnetite nanoparticles coated with lauric acid were prepared by co-precipitation of Fe3+:Fe2+ in a ratio of 2:1, 5:3, 3:2, and 4:3, and the pH was controlled using NaOH. Structural and magnetization characterization by means of X-ray diffractometry (XRD) and a superconducting quantum interference device (SQUID) revealed that the main species was Fe3O4 and further showed that most of the nanoparticles exhibited superparamagnetic properties. All of the magnetic nanoparticles showed a specific absorption rate (SAR) increase that was linear with the magnetic field strength and frequency of the alternating magnetic field. Among all, the magnetic nanoparticles prepared in a 3:2 ratio showed the highest SAR. To further test the influence of physiological factors on the 3:2 ratio magnetic nanoparticles, we simulated the environment with protein (bovine serum albumin, BSA), blood sugar (dextrose), electrolytes (commercial norm-saline) and viscosity (glycerol) to examine the heating capacity under these conditions. Our results showed that the SAR value was unaffected by the protein and blood sugar environments. On the other hand, the SAR value was significantly reduced in the electrolyte environment, due to precipitation and aggregation with sodium ions. For the simulated viscous environment with glycerol, the result showed that the SAR values reduced with increasing glycerol concentration. We have further tested the heating capacity contribution from the Neel mechanism by trapping the magnetic nanoparticles in a solid form of polydimethylsiloxane (PDMS) to eliminate the heating pathway due to a Brownian motion. We measured the heating capability and determined that 47% of the total heat generated by the magnetic nanoparticles was from the Neel mechanism contribution. For evaluating magnetic nanoparticles, this method provides a fast and low cost method for determining qualitative and quantitative information measurement for the effect of physiological interference and could greatly reduce the cost and time by in vitro or animal test. --- paper_title: In vitro characterization of movement, heating and visualization of magnetic nanoparticles for biomedical applications paper_content: Magnetic nanoparticles can be used for a variety of biomedical applications. They can be used in the targeted delivery of therapeutic agents in vivo, in the hyperthermic treatment of cancers, in magnetic resonance (MR) imaging as contrast agents and in the biomagnetic separations of biomolecules. In this study, a characterization of the movement and heating of three different types of magnetic nanoparticles in physiological systems in vitro is made in a known external magnetic field and alternating field respectively. Infra-red (IR) imaging and MR imaging were used to visualize these nanoparticles in vitro. A strong dependence on the size and the suspending medium is observed on the movement and heating of these nanoparticles. First, two of the particles (mean diameter d = 10 nm, uncoated Fe3O4 and d = 2.8 µm, polystyrene coated Fe3O4+γ-Fe2O3) did not move while only a dextran coated nanoparticle (d = 50 nm, γ-Fe2O3) moved in type 1 collagen used as an in vitro model system. It is also observed that the time taken by a collection of these nanoparticles to move even a smaller distance (5 mm) in collagen (~100 min) is almost ten times higher when compared to the time taken to move twice the distance (10 mm) in glycerol (~10 min) under the same external field. Second, the amount of temperature rise increases with the concentration of nanoparticles regardless of the microenvironments in the heating studies. However, the amount of heating in collagen (maximum change in temperature ΔTmax~9 °C at 1.9 mg Fe ml−1 and 19 °C at 3.7 mg Fe ml−1) is significantly less than that in water (ΔTmax~15 °C at 1.9 mg Fe ml−1 and 33 °C at 3.7 mg Fe ml−1) and glycerol (ΔTmax~13.5 °C at 1.9 mg Fe ml−1 and 30 °C at 3.7 mg Fe ml−1). Further, IR imaging provides at least a ten times improvement in the range of imaging magnetic nanoparticles, whereby a concentration of (0–4 mg Fe ml−1) could bevisualized as compared to (0–0.4 mg Fe ml−1) by MR imaging. Based on these in vitro studies, important issues and parameters that require further understanding and characterization of these nanoparticles in vivo are discussed. --- paper_title: Magnetic nanoparticles for interstitial thermotherapy - : feasibility, tolerance and achieved temperatures paper_content: Background: The concept of magnetic fluid hyperthermia is clinically evaluated after development of the whole body magnetic field applicator MFH® 300F and the magnetofluid MFL 082AS. This new system for localized thermotherapy is suitable either for hyperthermia or thermoablation. The magnetic fluid, composed of iron oxide nanoparticles dispersed in water, must be distributed in the tumour and is subsequently heated by exposing to an alternating magnetic field in the applicator. We performed a feasibility study with 22 patients suffering from heavily pretreated recurrences of different tumour entities, where hyperthermia in conjunction with irradiation and/or chemotherapy was an option. The potential to estimate (by post-implantation analyses) and to achieve (by improving the technique) a satisfactory temperature distribution was evaluated in dependency on the implantation technique.Material and methods: Three implantation methods were established: Infiltration under CT fluoroscopy (group A), TRUS (transr... --- paper_title: Water-Soluble Iron Oxide Nanocubes with High Values of Specific Absorption Rate for Cancer Cell Hyperthermia Treatment paper_content: Iron oxide nanocrystals (IONCs) are appealing heat mediator nanoprobes in magnetic-mediated hyperthermia for cancer treatment. Here, specific absorption rate (SAR) values are reported for cube-shaped water-soluble IONCs prepared by a one-pot synthesis approach in a size range between 13 and 40 nm. The SAR values were determined as a function of frequency and magnetic field applied, also spanning technical conditions which are considered biomedically safe for patients. Among the different sizes tested, IONCs with an average diameter of 19 ± 3 nm had significant SAR values in clinical conditions and reached SAR values up to 2452 W/gFe at 520 kHz and 29 kAm–1, which is one of the highest values so far reported for IONCs. In vitro trials carried out on KB cancer cells treated with IONCs of 19 nm have shown efficient hyperthermia performance, with cell mortality of about 50% recorded when an equilibrium temperature of 43 °C was reached after 1 h of treatment. --- paper_title: Design Maps for the Hyperthermic Treatment of Tumors with Superparamagnetic Nanoparticles paper_content: A plethora of magnetic nanoparticles has been developed and investigated under different alternating magnetic fields (AMF) for the hyperthermic treatment of malignant tissues. Yet, clinical applications of magnetic hyperthermia are sporadic, mostly due to the low energy conversion efficiency of the metallic nanoparticles and the high tissue concentrations required. Here, we study the hyperthermic performance of commercially available formulations of superparamagnetic iron oxide nanoparticles (SPIOs), with core diameter of 5, 7 and 14 nm, in terms of absolute temperature increase ΔT and specific absorption rate (SAR). These nanoparticles are operated under a broad range of AMF conditions, with frequency f varying between 0.2 and 30 MHz; field strength H ranging from 4 to 10 kA m(-1); and concentration cMNP varying from 0.02 to 3.5 mg ml(-1). At high frequency field (∼30 MHz), non specific heating dominates and ΔT correlates with the electrical conductivity of the medium. At low frequency field (<1 MHz), non specific heating is negligible and the relaxation of the SPIO within the AMF is the sole energy source. We show that the ΔT of the medium grows linearly with cMNP , whereas the SARMNP of the magnetic nanoparticles is independent of cMNP and varies linearly with f and H(2) . Using a computational model for heat transport in a biological tissue, the minimum requirements for local hyperthermia (Ttissue >42°C) and thermal ablation (Ttissue >50°C) are derived in terms of cMNP , operating AMF conditions and blood perfusion. The resulting maps can be used to rationally design hyperthermic treatments and identifying the proper route of administration - systemic versus intratumor injection - depending on the magnetic and biodistribution properties of the nanoparticles. --- paper_title: Numerical FEM Models for the Planning of Magnetic Induction Hyperthermia Treatments With Nanoparticles paper_content: A numerical FEM model of a magnetic fluid hyperthermia (MFH) treatment on an hepatocellular carcinoma (HCC) metastasis has been simulated. Starting from actual CT images of the patient, a 3-D geometry of the anatomical district has been reconstructed and a coupled electromagnetic and thermal transient analysis has been performed, in order to predict the temperature distribution during the treatment. The in vivo effect of blood perfusion has also been implemented through the Pennes's model. Various simulations have been carried out, based on different particle sizes and concentrations, as well as different exciting field intensities. --- paper_title: Water-Soluble Iron Oxide Nanocubes with High Values of Specific Absorption Rate for Cancer Cell Hyperthermia Treatment paper_content: Iron oxide nanocrystals (IONCs) are appealing heat mediator nanoprobes in magnetic-mediated hyperthermia for cancer treatment. Here, specific absorption rate (SAR) values are reported for cube-shaped water-soluble IONCs prepared by a one-pot synthesis approach in a size range between 13 and 40 nm. The SAR values were determined as a function of frequency and magnetic field applied, also spanning technical conditions which are considered biomedically safe for patients. Among the different sizes tested, IONCs with an average diameter of 19 ± 3 nm had significant SAR values in clinical conditions and reached SAR values up to 2452 W/gFe at 520 kHz and 29 kAm–1, which is one of the highest values so far reported for IONCs. In vitro trials carried out on KB cancer cells treated with IONCs of 19 nm have shown efficient hyperthermia performance, with cell mortality of about 50% recorded when an equilibrium temperature of 43 °C was reached after 1 h of treatment. --- paper_title: Design Maps for the Hyperthermic Treatment of Tumors with Superparamagnetic Nanoparticles paper_content: A plethora of magnetic nanoparticles has been developed and investigated under different alternating magnetic fields (AMF) for the hyperthermic treatment of malignant tissues. Yet, clinical applications of magnetic hyperthermia are sporadic, mostly due to the low energy conversion efficiency of the metallic nanoparticles and the high tissue concentrations required. Here, we study the hyperthermic performance of commercially available formulations of superparamagnetic iron oxide nanoparticles (SPIOs), with core diameter of 5, 7 and 14 nm, in terms of absolute temperature increase ΔT and specific absorption rate (SAR). These nanoparticles are operated under a broad range of AMF conditions, with frequency f varying between 0.2 and 30 MHz; field strength H ranging from 4 to 10 kA m(-1); and concentration cMNP varying from 0.02 to 3.5 mg ml(-1). At high frequency field (∼30 MHz), non specific heating dominates and ΔT correlates with the electrical conductivity of the medium. At low frequency field (<1 MHz), non specific heating is negligible and the relaxation of the SPIO within the AMF is the sole energy source. We show that the ΔT of the medium grows linearly with cMNP , whereas the SARMNP of the magnetic nanoparticles is independent of cMNP and varies linearly with f and H(2) . Using a computational model for heat transport in a biological tissue, the minimum requirements for local hyperthermia (Ttissue >42°C) and thermal ablation (Ttissue >50°C) are derived in terms of cMNP , operating AMF conditions and blood perfusion. The resulting maps can be used to rationally design hyperthermic treatments and identifying the proper route of administration - systemic versus intratumor injection - depending on the magnetic and biodistribution properties of the nanoparticles. --- paper_title: Usable Frequencies in Hyperthermia with Thermal Seeds paper_content: Temperature distributions are computed for tissue models assumed to be heated by constant power seeds, and from that, the heating power which the implants have to produce to achieve clinically acceptable temperatures in the tumor are obtained. Calculations of the heat produced by thermal seeds exposed to an electromagnetic induction field showed it to be strongly dependent on the permeability of the material, on the field frequency, on the seed diameter, and on the orientation of the implants with respect to the field. It is recommended that, other parameters permitting, the implants be oriented parallel to the induction field and that the field frequency be approximately 200 kHz or lower. Under these conditions, implants with diameters as small as 0.25 mm produce sufflcient heat for any clinical application without undue heating by eddy currents flowing within the patient. The use of frequencies above the recommended range puts certain restrictions on the implant geometry and on the magnetic properties of their material. Needles oriented perpendicular to the field produce enough heat to reach therapeutic temperatures only within a narrow range of parameters. --- paper_title: Numerical assessment of a criterion for the optimal choice of the operative conditions in magnetic nanoparticle hyperthermia on a realistic model of the human head. paper_content: PURPOSE ::: This paper presents a numerical study aiming at assessing the effectiveness of a recently proposed optimisation criterion for determining the optimal operative conditions in magnetic nanoparticle hyperthermia applied to the clinically relevant case of brain tumours. ::: ::: ::: MATERIALS AND METHODS ::: The study is carried out using the Zubal numerical phantom, and performing electromagnetic-thermal co-simulations. The Pennes model is used for thermal balance; the dissipation models for the magnetic nanoparticles are those available in the literature. The results concerning the optimal therapeutic concentration of nanoparticles, obtained through the analysis, are validated using experimental data on the specific absorption rate of iron oxide nanoparticles, available in the literature. ::: ::: ::: RESULTS ::: The numerical estimates obtained by applying the criterion to the treatment of brain tumours shows that the acceptable values for the product between the magnetic field amplitude and frequency may be two to four times larger than the safety threshold of 4.85 × 10(8)A/m/s usually considered. This would allow the reduction of the dosage of nanoparticles required for an effective treatment. In particular, depending on the tumour depth, concentrations of nanoparticles smaller than 10 mg/mL of tumour may be sufficient for heating tumours smaller than 10 mm above 42 °C. Moreover, the study of the clinical scalability shows that, whatever the tumour position, lesions larger than 15 mm may be successfully treated with concentrations lower than 10 mg/mL. The criterion also allows the prediction of the temperature rise in healthy tissue, thus assuring safe treatment. ::: ::: ::: CONCLUSIONS ::: The criterion can represent a helpful tool for planning and optimising an effective hyperthermia treatment. --- paper_title: Magnetic nanoparticles for interstitial thermotherapy - : feasibility, tolerance and achieved temperatures paper_content: Background: The concept of magnetic fluid hyperthermia is clinically evaluated after development of the whole body magnetic field applicator MFH® 300F and the magnetofluid MFL 082AS. This new system for localized thermotherapy is suitable either for hyperthermia or thermoablation. The magnetic fluid, composed of iron oxide nanoparticles dispersed in water, must be distributed in the tumour and is subsequently heated by exposing to an alternating magnetic field in the applicator. We performed a feasibility study with 22 patients suffering from heavily pretreated recurrences of different tumour entities, where hyperthermia in conjunction with irradiation and/or chemotherapy was an option. The potential to estimate (by post-implantation analyses) and to achieve (by improving the technique) a satisfactory temperature distribution was evaluated in dependency on the implantation technique.Material and methods: Three implantation methods were established: Infiltration under CT fluoroscopy (group A), TRUS (transr... --- paper_title: Design Maps for the Hyperthermic Treatment of Tumors with Superparamagnetic Nanoparticles paper_content: A plethora of magnetic nanoparticles has been developed and investigated under different alternating magnetic fields (AMF) for the hyperthermic treatment of malignant tissues. Yet, clinical applications of magnetic hyperthermia are sporadic, mostly due to the low energy conversion efficiency of the metallic nanoparticles and the high tissue concentrations required. Here, we study the hyperthermic performance of commercially available formulations of superparamagnetic iron oxide nanoparticles (SPIOs), with core diameter of 5, 7 and 14 nm, in terms of absolute temperature increase ΔT and specific absorption rate (SAR). These nanoparticles are operated under a broad range of AMF conditions, with frequency f varying between 0.2 and 30 MHz; field strength H ranging from 4 to 10 kA m(-1); and concentration cMNP varying from 0.02 to 3.5 mg ml(-1). At high frequency field (∼30 MHz), non specific heating dominates and ΔT correlates with the electrical conductivity of the medium. At low frequency field (<1 MHz), non specific heating is negligible and the relaxation of the SPIO within the AMF is the sole energy source. We show that the ΔT of the medium grows linearly with cMNP , whereas the SARMNP of the magnetic nanoparticles is independent of cMNP and varies linearly with f and H(2) . Using a computational model for heat transport in a biological tissue, the minimum requirements for local hyperthermia (Ttissue >42°C) and thermal ablation (Ttissue >50°C) are derived in terms of cMNP , operating AMF conditions and blood perfusion. The resulting maps can be used to rationally design hyperthermic treatments and identifying the proper route of administration - systemic versus intratumor injection - depending on the magnetic and biodistribution properties of the nanoparticles. --- paper_title: Magnetic nanoparticle hyperthermia cancer treatment efficacy dependence on cellular and tissue level particle concentration and particle heating properties paper_content: The use of nanotechnology for the treatment of cancer affords the possibility of highly specific tumor targeting and improved treatment efficacy. Iron oxide magnetic nanoparticles (IONPs) have demonstrated success as an ablative mono-therapy and targetable adjuvant therapy. However, the relative therapeutic value of intracellular vs. extracellular IONPs remains unclear. Our research demonstrates that both extracellular and intracellular IONPs generate cytotoxicity when excited by an alternating magnetic field (AMF). While killing individual cells via intracellular IONP heating is an attractive goal, theoretical models and experimental results suggest that this may not be possible due to limitations of cell volume, applied AMF, IONP concentration and specific absorption rate (SAR). The goal of this study was to examine the importance of tumor size (cell number) with respect to IONP concentration. Mouse mammary adenocarcinoma cells were incubated with IONPs, washed, spun into different pellet sizes (0.1, 0.5 and 2 million cells) and exposed to AMF. The level of heating and associated cytotoxicity depended primarily on the number of IONPs /amount Fe per cell pellet volume and the relative volume of the cell pellet. Specifically, larger cell pellets achieved greater relative cytotoxicity due to greater iron amounts, close association and subsequently higher temperatures. --- paper_title: Study of the Optimum Dose of Ferromagnetic Nanoparticles Suitable for Cancer Therapy Using MFH paper_content: At present, a successful realization of the magnetic fluid hyperthermia (MFH) therapy is conditioned by some unsolved problems. One of these problems is the choice of the correct particle concentration in order to achieve a defined temperature increase in the tumor tissue. A computer-based model was created using COMSOL: Multiphysics in order to simulate the heat dissipation within the tissue for typical configurations of the tumor position in relation to neighboring blood vessels as well as particle distribution within the tumor. The temperature achieved on the tumor border was investigated taking into account physiological parameters of different types of tissues. Using the correct nanoparticle dosage and considering their specific loss power, it is possible to estimate the efficiency of this therapeutic method. If the tumor shape and position are known by suitable medical imaging techniques (e.g., MRI, CT), simulations like this one could provide data in order to achieve the optimum dose and particle distribution in the tumor. --- paper_title: In vitro characterization of movement, heating and visualization of magnetic nanoparticles for biomedical applications paper_content: Magnetic nanoparticles can be used for a variety of biomedical applications. They can be used in the targeted delivery of therapeutic agents in vivo, in the hyperthermic treatment of cancers, in magnetic resonance (MR) imaging as contrast agents and in the biomagnetic separations of biomolecules. In this study, a characterization of the movement and heating of three different types of magnetic nanoparticles in physiological systems in vitro is made in a known external magnetic field and alternating field respectively. Infra-red (IR) imaging and MR imaging were used to visualize these nanoparticles in vitro. A strong dependence on the size and the suspending medium is observed on the movement and heating of these nanoparticles. First, two of the particles (mean diameter d = 10 nm, uncoated Fe3O4 and d = 2.8 µm, polystyrene coated Fe3O4+γ-Fe2O3) did not move while only a dextran coated nanoparticle (d = 50 nm, γ-Fe2O3) moved in type 1 collagen used as an in vitro model system. It is also observed that the time taken by a collection of these nanoparticles to move even a smaller distance (5 mm) in collagen (~100 min) is almost ten times higher when compared to the time taken to move twice the distance (10 mm) in glycerol (~10 min) under the same external field. Second, the amount of temperature rise increases with the concentration of nanoparticles regardless of the microenvironments in the heating studies. However, the amount of heating in collagen (maximum change in temperature ΔTmax~9 °C at 1.9 mg Fe ml−1 and 19 °C at 3.7 mg Fe ml−1) is significantly less than that in water (ΔTmax~15 °C at 1.9 mg Fe ml−1 and 33 °C at 3.7 mg Fe ml−1) and glycerol (ΔTmax~13.5 °C at 1.9 mg Fe ml−1 and 30 °C at 3.7 mg Fe ml−1). Further, IR imaging provides at least a ten times improvement in the range of imaging magnetic nanoparticles, whereby a concentration of (0–4 mg Fe ml−1) could bevisualized as compared to (0–0.4 mg Fe ml−1) by MR imaging. Based on these in vitro studies, important issues and parameters that require further understanding and characterization of these nanoparticles in vivo are discussed. --- paper_title: Heating magnetic fluid with alternating magnetic field paper_content: This study develops analytical relationships and computations of power dissipation in magnetic fluid (ferrofluid) subjected to alternating magnetic field. The dissipation results from the orientational relaxation of particles having thermal fluctuations in a viscous medium. --- paper_title: Size-dependant heating rates of iron oxide nanoparticles for magnetic fluid hyperthermia. paper_content: Using the thermal decomposition of organometallics method we have synthesized high-quality, iron oxide nanoparticles of tailorable size up to ~15nm and transferred them to a water phase by coating with a biocompatible polymer. The magnetic behavior of these particles was measured and fit to a log-normal distribution using the Chantrell method and their polydispersity was confirmed to be very narrow. By performing calorimetry measurements with these monodisperse particles we have unambiguously demonstrated, for the first time, that at a given frequency, heating rates of superparamagnetic particles are dependent on particle size, in agreement with earlier theoretical predictions. --- paper_title: Monodispersed magnetite nanoparticles optimized for magnetic fluid hyperthermia: Implications in biological systems paper_content: Magnetite (Fe3O4) nanoparticles (MNPs) are suitable materials for Magnetic Fluid Hyperthermia (MFH), provided their size is carefully tailored to the applied alternating magnetic field (AMF) frequency. Since aqueous synthesis routes produce polydisperse MNPs that are not tailored for any specific AMF frequency, we have developed a comprehensive protocol for synthesizing highly monodispersed MNPs in organic solvents, specifically tailored for our field conditions (f = 376 kHz, H0 = 13.4 kA/m) and subsequently transferred them to water using a biocompatible amphiphilic polymer. These MNPs (σavg. = 0.175) show truly size-dependent heating rates, indicated by a sharp peak in the specific loss power (SLP, W/g Fe3O4) for 16 nm (diameter) particles. For broader size distributions (σavg. = 0.266), we observe a 30% drop in overall SLP. Furthermore, heating measurements in biological medium [Dulbecco’s modified Eagle medium (DMEM) + 10% fetal bovine serum] show a significant drop for SLP (∼30% reduction in 16 nm MN... --- paper_title: Simple models for dynamic hysteresis loop calculations of magnetic single-domain nanoparticles: Application to magnetic hyperthermia optimization paper_content: To optimize the heating properties of magnetic nanoparticles (MNPs) in magnetic hyperthermia applications, it is necessary to calculate the area of their hysteresis loops in an alternating magnetic field. The separation between “relaxation losses” and “hysteresis losses” presented in several articles is artificial and criticized here. The three types of theories suitable for describing hysteresis loops of MNPs are presented and compared to numerical simulations: equilibrium functions, Stoner–Wohlfarth model based theories (SWMBTs), and a linear response theory (LRT) using the Neel–Brown relaxation time. The configuration where the easy axis of the MNPs is aligned with respect to the magnetic field and the configuration of a random orientation of the easy axis are both studied. Suitable formulas to calculate the hysteresis areas of major cycles are deduced from SWMBTs and from numerical simulations; the domain of validity of the analytical formula is explicitly studied. In the case of minor cycles, the hys... --- paper_title: The role of blood flow in hyperthermia. paper_content: Abstract In hyperthermia blood flowing through a tissue modifies the temperature distribution produced by the heating technique. The effects of blood flow on temperature distribution during uniform heating of tissues have been calculated using a simple mathematical model, normally employed in the measurement of blood flow by radioisotopes. Blood flow increases the heating time required to produce a certain temperature; it sets a maximum temperature which can be attained by a particular heat input and it produces a pronounced difference in temperature of tissues, with different flows, within the heated volume. --- paper_title: The Energy Conservation Equation for Living Tissue paper_content: The widely used bio-heat transfer equation is examined regarding its term describing the thermal effects of blood perfusion. It is demonstrated, both by physical arguments and numerical results, that the description of thermal convection by blood is inconsistent in this equation, and that results are in error by the same order of magnitude as the convective energy transport itself. --- paper_title: Thermal injury kinetics in electrical trauma. paper_content: The distribution of electrical current and the resultant Joule heating in tissues of the human upper extremity for a worst-case hand-to-hand high-voltage electrical shock was modelled by solving the Bioheat equation using the finite element method. The model of the upper extremity included skin, fat, skeletal muscle, and bone. The parameter sets for these tissues included specific thermal and electrical properties and their respective tissue blood flow rates. The extent of heat mediated cellular injury was estimated by using a damage rate equation based on a single energy barrier chemical reaction model. No cellular injury was assumed to occur for temperatures less than 42 degrees C. This model was solved for the duration of Joule heating required to produce membrane damage in cells, termed the lethal time (of contact) for injury. LT's were determined for contact voltages ranging from 5 to 20 kV. For a 10,000 volt electrical shock LT's for skeletal muscle are predicted to be: 0.5 second in the distal forearm, 1.1 second in the mid-forearm, 1.2 second in the proximal elbow, and 2.0 seconds in the mid-arm. This analysis of the electrical shock provides useful insight into the mechanisms of resultant tissue damage and provides important performance guidelines for the development of safety devices. --- paper_title: Magnetic Fluid Hyperthermia Modeling Based on Phantom Measurements and Realistic Breast Model paper_content: Magnetic fluid hyperthermia (MFH) is a minimally invasive procedure that destroys cancer cells. It is based on a superparamagnetic heat phenomenon and consists in feeding a ferrofluid into a tumor, and then applying an external electromagnetic field, which leads to apoptosis. The strength of the magnetic field, optimal dose of the ferrofluid, the volume of the tumor and the safety standards have to be taken into consideration when MFH treatment is planned. In this study, we have presented the novel complementary investigation based both on the experiments and numerical methodology connected with female breast cancer. We have conducted experiments on simplified female breast phantoms with numerical analysis and then we transferred the results on an anatomically-like breast model. --- paper_title: A New Simplified Bioheat Equation for the Effect of Blood Flow on Local Average Tissue Temperature paper_content: A new simplified three-dimensional bioheat equation is derived to describe the effect of blood flow on blood-tissue heat transfer. In two recent theoretical and experimental studies [1, 2] the authors have demonstrated that the so-called isotropic blood perfusion term in the existing bioheat equation is negligible because of the microvascular organization, and that the primary mechanism for blood-tissue energy exchange is incomplete countercurrent exchange in the thermally significant microvessels. The new theory to describe this basic mechanism shows that the vascularization of tissue causes it to behave as an anisotropic heat transfer medium. A remarkably simple expression is derived for the tensor conductivity of the tissue as a function of the local vascular geometry and flow velocity in the thermally significant countercurrent vessels. It is also shown that directed as opposed to isotropic blood perfusion between the countercurrent vessels can have a significant influence on heat transfer in regions where the countercurrent vessels are under 70-micron diameter. The new bioheat equation also describes this mechanism. --- paper_title: Theory and experiment for the effect of vascular microstructure on surface tissue heat transfer--Part I: Anatomical foundation and model conceptualization. paper_content: A new theoretical model supported by ultrastructural studies and high-spatial resolution temperature measurements is presented for surface tissue heat transfer in a two-part study. In this first paper, vascular casts of the rabbit thigh prepared by the tissue clearance method were serially sectioned parallel to the skin surface to determine the detailed variation of the vascular geometry as a function of tissue depth. Simple quantitative models of the basic vascular structures observed were then analyzed in terms of their characteristic thermal relaxation lengths and a new three-layer conceptual model proposed for surface tissue heat transfer. Fine wire temperature measurements with an 80-micron average diameter thermocouple junction and spatial increments of 20 micrometers between measurement sites have shown for the first time the detailed temperature fluctuations in the microvasculature and have confirmed the fundamental assumptions of the proposed three-layer model for the deep tissue, skeletal muscle and cutaneous layers. --- paper_title: Theory and experiment for the effect of vascular microstructure on surface tissue heat transfer--Part II: Model formulation and solution. paper_content: In this paper the conceptual three-layer representation of surface tissue heat transfer proposed in Weinbaum, Jiji and Lemons [1], is developed into a detailed quantitative model. This model takes into consideration the variation of the number density, size and flow velocity of the countercurrent arterio-venous vessels as a function of depth from the skin surface, the directionality of blood perfusion in the transverse vessel layer and the superficial shunting of blood to the cutaneous layer. A closed form analytic solution for the boundary value problem coupling the three layers is obtained. This solution is in terms of numerically evaluated integrals describing the detailed vascular geometry, a capillary bleed-off distribution function and parameters describing the shunting of blood to the cutaneous layer. Representative heat transfer results for typical physiological conditions are presented. --- paper_title: Recent developments in modeling heat transfer in blood perfused tissues paper_content: Successful hyperthermia treatment of tumors requires understanding the attendant thermal processes in both diseased and healthy tissue. Accordingly, it is essential for developers and users of hyperthermia equipment to predict, measure and interpret correctly the tissue thermal and vascular response to heating. Modeling of heat transfer in living tissues is a means towards this end. Due to the complex morphology of living tissues, such modeling is a difficult task and some simplifying assumptions are needed. Some investigators have recently argued that Pennes' interpretation of the vascular contribution to heat transfer in perfused tissues fails to account for the actual thermal equilibration process between the flowing blood and the surrounding tissue and proposed new models, presumably based on a more realistic anatomy of the perfused tissue. The present review compares and contrasts several of the new bio-heat transfer models, emphasizing the problematics of their experimental validation, in the absence of measuring equipment capable of reliable evaluation of tissue properties and their variations that occur in the spatial scale of blood vessels with diameters less than about 0.2 mm. For the most part, the new models still lack sound experimental grounding, and in view of their inherent complexity, the best practical approach for modeling bio-heat transfer during hyperthermia may still be the Pennes model, providing its use is based on some insights gained from the studies described here. In such cases, these models should yield a more realistic description of tissue locations and/or thermal conditions for which the Pennes model might not apply. > --- paper_title: Is intracellular hyperthermia superior to extracellular hyperthermia in the thermal sense? paper_content: More than 20 years ago, it was hypothesized that intracellular hyperthermia is superior to extracellular hyperthermia. It was further hypothesized that even a single biological cell containing magnetic nanoparticles can be treated for hyperthermia by an AC magnetic field, independent of its surrounding cells. Since experimental investigation of the thermal effects of intracellular hyperthermia is not feasible, these hypotheses have been studied theoretically. The current report shows that nano-scale heating effects are negligible. This study further shows that intracellular heat generation is sufficient to create the necessary conditions for hyperthermia only in a large group of cells loaded with nanoparticles, having an overall diameter of at least 1mm. It is argued in this report that there is no reason to believe that intracellular hyperthermia is superior to extracellular hyperthermia in the thermal sense. --- paper_title: Modeling of temperature profile during magnetic thermotherapy for cancer treatment paper_content: Magnetic nanoparticles (MNPs) used as heat sources for cancer thermotherapy have received much recent attention. While the mechanism for power dissipation in MNPs in a rf field is well understood, a challenge in moving to clinical trials is an inadequate understanding of the power dissipation in MNP-impregnated systems and the discrepancy between the predicted and observed heating rates in the same. Here we use the Rosensweig [J. Magn. Magn. Mater. 252, 370 (2002)] model for heat generation in a single MNP, considering immediate heating of the MNPs, and the double spherical-shell heat transfer equations developed by Andra et al. [J. Magn. Magn. Mater. 194, 197 (1999)] to model the heat distribution in and around a ferrofluid sample or a tumor impregnated with MNPs. We model the heat generated at the edge of a 2.15 cm spherical sample of FeCo/(Fe,Co)3O4 agglomerates containing 95 vol % MNPs with mean radius of 9 nm, dispersed at 1.5–1.6 vol % in bisphenol F. We match the model against experimental data for... --- paper_title: Transient solution to the bioheat equation and optimization for magnetic fluid hyperthermia treatment paper_content: Two finite concentric spherical regions were considered as the tissue model for magnetic fluid hyperthermia treatment. The inner sphere represents the diseased tissue containing magnetic particles that generate heat when an alternating magnetic field is applied. The outer sphere represents the healthy tissue. Blood perfusion effects are included in both the regions. Analytical and numerical solutions of the one-dimensional bioheat transfer equation were obtained with constant and spatially varying heat generation in the inner sphere. The numerical solution was found to be in good agreement with the analytical solution. In an ideal hyperthermia treatment, all the diseased tissues should be selectively heated without affecting any healthy tissue. The present work optimized the magnetic particle concentration in an attempt to achieve the ideal hyperthermia conditions. It was found that, for a fixed amount of magnetic particles, optimizing the magnetic particle distribution in the diseased tissue can signific... --- paper_title: Temperature distribution as function of time around a small spherical heat source of local magnetic hyperthermia paper_content: A spherical region containing magnetic particles embedded in extended muscle tissue is taken as model of small breast carcinomas. Using analytically derived equations the spatial temperature distribution is calculated as function of the time for exposing to an alternating magnetic field. In vitro measurements with muscle tissue yielded such an agreement with the calculations that treatment of small tumors in slightly vascularized tissues on the base of mathematical predictions seems now to be more promising than in the past. --- paper_title: Magnetic Fluid Hyperthermia Modeling Based on Phantom Measurements and Realistic Breast Model paper_content: Magnetic fluid hyperthermia (MFH) is a minimally invasive procedure that destroys cancer cells. It is based on a superparamagnetic heat phenomenon and consists in feeding a ferrofluid into a tumor, and then applying an external electromagnetic field, which leads to apoptosis. The strength of the magnetic field, optimal dose of the ferrofluid, the volume of the tumor and the safety standards have to be taken into consideration when MFH treatment is planned. In this study, we have presented the novel complementary investigation based both on the experiments and numerical methodology connected with female breast cancer. We have conducted experiments on simplified female breast phantoms with numerical analysis and then we transferred the results on an anatomically-like breast model. --- paper_title: Errors between two- and three-dimensional thermal model predictions of hyperthermia treatments. paper_content: A simulation program to study the three-dimensional temperature distributions produced by hyperthermia in anatomically realistic inhomogenous tissue models has been developed using the bioheat transfer equation. The anatomical data for the inhomogeneous tissues of the human body are entered on a digitizing tablet from serial computed tomography (CT) scans. Power deposition patterns from various heating modalities must be calculated independently. The program has been used to comparatively evaluate two- and three-dimensional simulations in a series of parametric calculations based on a simple inhomogeneous tissue model for uniform power deposition. The conclusions are that two-dimensional simulations always lead to significant errors at the ends of tumors (up to tens of degrees). However, they can give valid results for the central region of large tumors, but only with tumor blood perfusions greater than approximately 1 kg/m3/s. These conclusions from the geometrically simple model are substantiated by the results obtained using the full three-dimensional model for actual patient anatomical simulations. In summary, three-dimensional simulations will be necessary for accurate patient treatment planning. The effect of the thermal conductivity, used in the models, on the temperature field has also been studied. The results show that using any thermal conductivity value in the range of 0.4 to 0.6 W/m/degrees C sufficiently characterizes most soft tissues, especially in the presence of high blood perfusion. However, bone (thermal conductivity of 1.16 W/m/degrees C) and fat (thermal conductivity of 0.2 W/m/degrees C) do not fit this generalization and significant errors result if soft tissue values are used. --- paper_title: Study of the Optimum Injection Sites for a Multiple Metastases Region in Cancer Therapy by Using MFH paper_content: Metastases represent the final stage in cancer progression. Their early diagnosis and appropriate treatment are very important in order to maintain a high survival prognostic. The interest in MFH (magnetic fluid hyperthermia) and cancer therapy has noticeably increased in the last years. There are still numerous problems that need to be solved before a clinical model may be tested. The goal of this paper is to both quantify the optimum dose of magnetic material and optimize injection sites in order to achieve a therapeutic temperature of 42degC that may induce apoptosis in tumor cells. A successful realization of this therapy implies a heating zone of at least 2 mm around the tumor. finite element method (FEM) simulations of spherical metastases in liver and breast tissues near a blood vessel were performed using COMSOL multiphysics (heat transfer module) in order to simulate the temperature field produced by ferromagnetic nanoparticles within the tumor and healthy tissues. A systematical variation of tumor diameter and particle dosage was performed for every physical parameter for the tumor tissues mentioned above (e.g., tissue density, tumor/tissue perfusion rate) in order to understand the interdependence of these parameters and their effects on hyperthermia therapy. --- paper_title: Modeling of temperature profile during magnetic thermotherapy for cancer treatment paper_content: Magnetic nanoparticles (MNPs) used as heat sources for cancer thermotherapy have received much recent attention. While the mechanism for power dissipation in MNPs in a rf field is well understood, a challenge in moving to clinical trials is an inadequate understanding of the power dissipation in MNP-impregnated systems and the discrepancy between the predicted and observed heating rates in the same. Here we use the Rosensweig [J. Magn. Magn. Mater. 252, 370 (2002)] model for heat generation in a single MNP, considering immediate heating of the MNPs, and the double spherical-shell heat transfer equations developed by Andra et al. [J. Magn. Magn. Mater. 194, 197 (1999)] to model the heat distribution in and around a ferrofluid sample or a tumor impregnated with MNPs. We model the heat generated at the edge of a 2.15 cm spherical sample of FeCo/(Fe,Co)3O4 agglomerates containing 95 vol % MNPs with mean radius of 9 nm, dispersed at 1.5–1.6 vol % in bisphenol F. We match the model against experimental data for... --- paper_title: Transient solution to the bioheat equation and optimization for magnetic fluid hyperthermia treatment paper_content: Two finite concentric spherical regions were considered as the tissue model for magnetic fluid hyperthermia treatment. The inner sphere represents the diseased tissue containing magnetic particles that generate heat when an alternating magnetic field is applied. The outer sphere represents the healthy tissue. Blood perfusion effects are included in both the regions. Analytical and numerical solutions of the one-dimensional bioheat transfer equation were obtained with constant and spatially varying heat generation in the inner sphere. The numerical solution was found to be in good agreement with the analytical solution. In an ideal hyperthermia treatment, all the diseased tissues should be selectively heated without affecting any healthy tissue. The present work optimized the magnetic particle concentration in an attempt to achieve the ideal hyperthermia conditions. It was found that, for a fixed amount of magnetic particles, optimizing the magnetic particle distribution in the diseased tissue can signific... --- paper_title: Ferromagnetic Nanoparticles Dose Based on Tumor Size in Magnetic Fluid Hyperthermia Cancer Therapy paper_content: The interest in magnetic fluid hyperthermia (MFH) and cancer therapy has noticeably increased in the last years. At present, a successful realization of this interdisciplinary research is hampered by some unsolved problems. One of these problems this paper intended to clarify is how to find an estimate of the appropriate dosage of magnetic nanoparticles that injected into the tumor would help achieve an optimum temperature of 42degC, thus resulting in an increase of the susceptibility for apoptosis in tumor cells. We created a computational model in COMSOL: Multiphysics in order to analyze the heat dissipation within the tumor tissue. By considering various types of tissues with their respective physical and physiological properties (breast, liver, and skin tissues) and also by taking into account the amount of heat generated through the Brownian rotation and the Neel relaxation, it has been studied the tumor border temperature achieved for various concentrations of magnetic nanoparticles in their superparamagnetic behavior. Distinct simulations of a spherical tumor located in a cubical region of a volume of 1.2-3.5 cm3 within the tissue were designed. We performed a systematical variation of tumor diameter and particle dosage for every physical parameter of above mentioned tumor tissues (e.g., tissue density, tumor/tissue perfusion rate). By this systematization we intended to understand the interdependence of these parameters and their effects on hyperthermia therapy. --- paper_title: 3D numerical simulations on GPUs of hyperthermia with nanoparticles by a nonlinear bioheat model paper_content: This paper deals with the numerical modeling of hyperthermia treatments by magnetic nanoparticles considering a 3D nonlinear Pennes' bioheat transfer model with a temperature-dependent blood perfusion in order to yield more accurate results. The tissue is modeled by considering skin, fat and muscle layers in addition to the tumor. The FDM in a heterogeneous medium is employed and the resulting system of nonlinear equations in the time domain is solved by a predictor-multicorrector algorithm. Since the execution of the three-dimensional model requires a large amount of time, CUDA is used to speedup it. Experimental results showed that the parallelization with CUDA was very effective in improving performance, yielding gains up to 242 times when compared to the sequential execution time. --- paper_title: Temperature distribution as function of time around a small spherical heat source of local magnetic hyperthermia paper_content: A spherical region containing magnetic particles embedded in extended muscle tissue is taken as model of small breast carcinomas. Using analytically derived equations the spatial temperature distribution is calculated as function of the time for exposing to an alternating magnetic field. In vitro measurements with muscle tissue yielded such an agreement with the calculations that treatment of small tumors in slightly vascularized tissues on the base of mathematical predictions seems now to be more promising than in the past. --- paper_title: Numerical simulation of effect of vessel bifurcation on heat transfer in the magnetic fluid hyperthermia paper_content: Abstract This research aimed to analyze the mass and heat transfer mechanisms in magnetic fluid hyperthermia (MFH) treatment, revealing the effect of blood flow in a blood vessel bifurcation on the accurate spatial control of the thermal dose. A three-dimensional multiphysical model was developed to obtain the blood flow velocity distribution, concentration distribution of magnetic fluid, and temperature distribution of the treated tumor tissues. The calculated results demonstrate that the structure, size, and position of a bifurcation vessel greatly affect the selection of injection parameters for MFH treatment. The injection parameters considered in this study are the concentration of magnetic fluid, injection volume, arrangement of injections within the targeted tissues, and distance between the injection site and bifurcation. Diffuse injection patterns, large volumes, and low concentrations generally decrease the temperature differences within the tissues. To achieve uniform heating, high injection density and high-concentration magnetic fluids may be applied to the area near the vessel in order to reduce the cooling effect of blood flow. However, a more diffuse injection pattern is advantageous if the distance between the injection site and blood vessel is relatively short for the purpose of eliminating the heating effect of magnetic fluids. --- paper_title: FEM numerical model study of heating in magnetic nanoparticles paper_content: Electromagnetic heating of nanoparticles is complicated by the extremely short thermal relaxation time constants and difficulty of coupling sufficient power into the particles to achieve desired temperatures. Magnetic field heating by the hysteresis loop mechanism at frequencies between about 100 and 300 kHz has proven to be an effective mechanism in magnetic nanoparticles. Experiments at 2.45 GHz show that Fe3O4 magnetite nanoparticle dispersions in the range of 1012 to 1013 NP/mL also heat substantially at this frequency. An FEM numerical model study was undertaken to estimate the order of magnitude of volume power density, Qgen (W m-3) required to achieve significant heating in evenly dispersed and aggregated clusters of nanoparticles. The FEM models were computed using Comsol Multiphysics; consequently the models were confined to continuum formulations and did not include film nano-dimension heat transfer effects at the nanoparticle surface. As an example, the models indicate that for a single 36 nm diameter particle at an equivalent dispersion of 1013 NP/mL located within one control volume (1.0 × 10-19 m3) of a capillary vessel a power density in the neighborhood of 1017 (W m-3) is required to achieve a steady state particle temperature of 52 °C - the total power coupled to the particle is 2.44 μW. As a uniformly distributed particle cluster moves farther from the capillary the required power density decreases markedly. Finally, the tendency for particles in vivo to cluster together at separation distances much less than those of the uniform distribution further reduces the required power density. --- paper_title: Modelling mass and heat transfer in nano-based cancer hyperthermia paper_content: We derive a sophisticated mathematical model for coupled heat and mass transport in the tumour microenvironment and we apply it to study nanoparticle delivery and hyperthermic treatment of cancer. The model has the unique ability of combining the following features: (i) realistic vasculature; (ii) coupled capillary and interstitial flow; (iii) coupled capillary and interstitial mass transfer applied to nanoparticles; and (iv) coupled capillary and interstitial heat transfer, which are the fundamental mechanisms governing nano-based hyperthermic treatment. This is an improvement with respect to previous modelling approaches, where the effect of blood perfusion on heat transfer is modelled in a spatially averaged form. We analyse the time evolution and the spatial distribution of particles and temperature in a tumour mass treated with superparamagnetic nanoparticles excited by an alternating magnetic field. By means of numerical experiments, we synthesize scaling laws that illustrate how nano-based hyperthermia depends on tumour size and vascularity. In particular, we identify two distinct mechanisms that regulate the distribution of particle and temperature, which are characterized by perfusion and diffusion, respectively. --- paper_title: Errors in temperature measurement by thermocouple probes during ultrasound induced hyperthermia paper_content: A major problem in the use of localised hyperthermia for treatment of malignant tumours is to obtain an accurate measurement of the temperature in the tissue being treated. Thermocouple probes have generally been employed for measuring temperature elevation during ultrasound irradiation. However, when small objects such as thermocouples are in an ultrasound field in a medium such as tissue, viscous forces acting between the object and the tissue will cause an additional local rise in temperature (Fry & Fry, 1954a, b; Dunn, 1962; Hynynen et al, 1982). This will produce an error in any measurement of tissue temperature with invasive probes. The magnitude of the temperature elevation resulting from shear viscosity has been measured for 50 μm thermocouples in tumour tissue. --- paper_title: A methodology for determining optimal thermal damage in magnetic nanoparticle hyperthermia cancer treatment paper_content: SUMMARY ::: ::: Hyperthermia treatment of tumors uses localized heating to damage cancer cells and can also be utilized to increase the efficacy of other treatment methods such as chemotherapy. Magnetic nanoparticle hyperthermia is one of the least invasive techniques of delivering heat. It is based on injecting magnetic nanoparticles into the tumor and subjecting them to an alternating magnetic field. The technique is aimed at damaging the tumor without affecting the surrounding healthy tissue. In this preliminary study, we consider a simplified model (two concentric spheres that represent the tumor and its surrounding tissues) that employs a numerical solution of the Pennes bioheat equation. The model assumes a Gaussian distribution for the spatial variation of the applied thermal energy and an exponential decay function for the time variation. The objective of the study is to optimize the parameters that control the spatial and the time variation of the thermal energy. The optimization process is performed by formulating a fitness function that rewards damage in the region representing the tumor but penalizes damage in the surrounding tissues. Because of the flatness of this fitness function near the optimum, a genetic algorithm is used as the optimization method for its robust non-gradient-based approach. The overall aim of this work is to propose a methodology that can be used for hyperthermia treatment in a clinical scenario. Copyright © 2011 John Wiley & Sons, Ltd. --- paper_title: Magnetic Resonance Thermometry During Hyperthermia for Human High-Grade Sarcoma paper_content: Purpose: To determine the feasibility of measuring temperature noninvasively with magnetic resonance imaging during hyperthermia treatment of human tumors. ::: ::: Methods: The proton chemical shift detected using phase-difference magnetic resonance imaging (MRI) was used to measure temperature in phantoms and human tumors during treatment with hyperthermia. Four adult patients having high-grade primary sarcoma tumors of the lower leg received 5 hyperthermia treatments in the MR scanner using an MRI-compatible radiofrequency heating applicator. Prior to each treatment, an average of 3 fiberoptic temperature probes were invasively placed into the tumor (or phantom). Hyperthermia was applied concurrent with MR thermometry. Following completion of the treatment, regions of interest (ROI) were defined on MR phase images at each temperature probe location, in bone marrow, and in gel standards placed outside the heated region. The median phase difference (compared to pretreatment baseline images) was calculated for each ROI. This phase difference was corrected for phase drift observed in standards and bone marrow. The observed phase difference, with and without corrections, was correlated with the fiberoptic temperature measurements. ::: ::: Results: The phase difference observed with MRI was found to correlate with temperature. Phantom measurements demonstrated a linear regression coefficient of 4.70° phase difference per ° Celsius, with an R2 = 0.998. After human images with artifact were excluded, the linear regression demonstrated a correlation coefficient of 5.5° phase difference per ° Celsius, with an R2 = 0.84. In both phantom and human treatments, temperature measured via corrected phase difference closely tracked measurements obtained with fiberoptic probes during the hyperthermia treatments. ::: ::: Conclusions: Proton chemical shift imaging with current MRI and hyperthermia technology can be used to monitor and control temperature during treatment of large tumors in the distal lower extremity. --- paper_title: The practical use of thermocouples for temperature measurement in clinical hyperthermia paper_content: The use of thermocouples as invasive thermometers in clinical hyperthermia is comprehensively and critically reviewed. The ability to construct thermocouple probes as small-bore, multiple junction assemblies is a major reason for their popularity and full constructional details are given. The potential sources of measurement error when using thermocouples both in temperature gradients and in electromagnetic or ultrasonic heating fields are discussed. Emphasis is placed upon simple practical solutions to these problems and a combination of good measurement practice and electrical filtering can reduce errors to an insignificant level. Techniques are suggested for the assessment of thermocouple performance during clinical measurement. With careful use, thermocouples can be reliable and convenient thermometers. --- paper_title: Transient solution to the bioheat equation and optimization for magnetic fluid hyperthermia treatment paper_content: Two finite concentric spherical regions were considered as the tissue model for magnetic fluid hyperthermia treatment. The inner sphere represents the diseased tissue containing magnetic particles that generate heat when an alternating magnetic field is applied. The outer sphere represents the healthy tissue. Blood perfusion effects are included in both the regions. Analytical and numerical solutions of the one-dimensional bioheat transfer equation were obtained with constant and spatially varying heat generation in the inner sphere. The numerical solution was found to be in good agreement with the analytical solution. In an ideal hyperthermia treatment, all the diseased tissues should be selectively heated without affecting any healthy tissue. The present work optimized the magnetic particle concentration in an attempt to achieve the ideal hyperthermia conditions. It was found that, for a fixed amount of magnetic particles, optimizing the magnetic particle distribution in the diseased tissue can signific... --- paper_title: Enhancement in treatment planning for magnetic nanoparticle hyperthermia: optimization of the heat absorption pattern. paper_content: In clinical applications of magnetic nanoparticle hyperthermia for cancer treatment it is very important to ensure a maximum damage to the tumor while protecting the normal tissue. The resultant heating pattern by the nanoparticle distribution in tumor is closely related to the injection parameters. In this study we develop an optimization algorithm to inversely determine the optimum heating patterns induced by multiple nanoparticle injections in tumor models with irregular geometries. The injection site locations, thermal properties of tumor and tissue, and local blood perfusion rates are used as inputs to the algorithm to determine the optimum parameters of the heat sources for all nanoparticle injection sites. The design objective is to elevate the temperature of at least 90% of the tumor above 43 degrees C, and to ensure only less than 10% of the normal tissue is heated to temperatures of 43 degrees C or higher. The efficiency, flexibility and capability of this approach have been demonstrated in a case study of two tumors with simple or complicated geometry. An extensive experimental database should be developed in the future to relate the optimized heating pattern parameters found in this study to their appropriate nanoparticle concentration, injection amount, and injection rate. We believe that the optimization algorithm developed in this study can be used as a guideline for physicians to design an optimal treatment plan in magnetic nanoparticle hyperthermia. ---	Title: Physical Mechanism and Modeling of Heat Generation and Transfer in Magnetic Fluid Hyperthermia through Néelian and Brownian Relaxation: A Review Section 1: Introduction Description 1: Provide background on the current cancer treatments, the concept of thermotherapy, types of hyperthermia, and the rationale behind using hyperthermia as a cancer therapy method. Section 2: Magnetic Fluid Hyperthermia Description 2: Explain the concept of Magnetic Fluid Hyperthermia (MFH), its advantages over other hyperthermia methods, and its applications in clinical trials. Section 3: Heat Generation Model Based on Néelian and Brownian Relaxation Description 3: Detail the mechanisms of heat generation in magnetic nanoparticles via Néelian and Brownian relaxation, including mathematical formulations and the factors influencing these processes. Section 4: Type of Material Description 4: Discuss different types of magnetic nanoparticles used in MFH, their properties, and their suitability for clinical applications. Section 5: Particle Size Description 5: Describe the influence of particle size on the heating efficiency and treatment outcome of MFH. Section 6: Anisotropy Description 6: Discuss the role of magnetic anisotropy in MFH and its influence on the heating properties of nanoparticles. Section 7: Viscosity Description 7: Explain the impact of the medium's viscosity on the heat generation in MFH. Section 8: Magnetic Field Strength Description 8: Detail the relationship between magnetic field strength and heat generation in MFH. Section 9: Magnetic Field Frequency Description 9: Describe the effect of magnetic field frequency on the specific absorption rate (SAR) and the safety considerations for clinical applications. Section 10: Concentration Description 10: Discuss the effect of nanoparticles concentration on the heat generation and treatment outcomes in MFH. Section 11: Polydispersity Description 11: Explain the impact of particle size distribution (polydispersity) on the heat generation efficiency in MFH. Section 12: Bioheat Transfer Model for Heat Distribution Description 12: Provide an overview of various bioheat transfer models used to describe heat distribution in biological tissues during MFH. Section 13: Analytical Modeling Description 13: Summarize the development and application of analytical models to predict temperature distribution during MFH. Section 14: Numerical Modeling Description 14: Describe the use of numerical methods, such as FEM and FDM, to simulate heat transfer phenomena in MFH. Section 15: Optimization Model Description 15: Discuss optimization techniques to maximize therapeutic effects and minimize side effects in MFH. Section 16: Conclusion Description 16: Conclude the review by summarizing the potential of MFH as a cancer treatment and the need for further studies to improve simulation accuracy and treatment effectiveness.
A Survey on Intrusion Detection System for Wireless Network	9	--- paper_title: Using Internal Sensors For Computer Intrusion Detection paper_content: This dissertation introduces the concept of using internal sensors to perform intrusion detection in computer systems. It shows its practical feasibility and discusses its characteristics and related design and implementation issues. ::: We introduce a classification of data collection mechanisms for intrusion detection systems. At a conceptual level, these mechanisms are classified as direct and indirect monitoring. At a practical level, direct monitoring can be implemented using external or internal sensors. Internal sensors provide advantages with respect to reliability, completeness, timeliness and volume of data, in addition to efficiency and resistance against attacks. ::: We introduce an architecture called ESP as a framework for building intrusion detection systems based on internal sensors. We describe in detail a prototype implementation based on the ESP architecture and introduce the concept of embedded detectors as a mechanism for localized data reduction. ::: We show that it is possible to build both specific (specialized for a certain intrusion) and generic (able to detect different types of intrusions) detectors. Furthermore, we provide information about the types of data and places of implementation that are most effective in detecting different types of attacks. ::: Finally, performance testing of the ESP implementation shows the impact that embedded detectors can have on a computer system. Detection testing shows that embedded detectors have the capability of detecting a significant percentage of new attacks. --- paper_title: An overview of wireless intrusion prevention systems paper_content: With the fast development of wireless network, the problems on wireless security have become more and more prominence. And technologies of firewall and intrusion detection cannot solve these problems satisfactorily. However, wireless intrusion prevention systems which can prevent attacks for WLAN excellently have become the research hotspot. In this paper, we firstly indicate the developing history of WIPS, and then summarize the related work on WIPS in academic and engineering application area respectively. Based on these work, we propose a common wireless intrusion prevention framework (CWIPF), and describe some key technologies used in this framework. Finally, we propose some research issues should be focused on in the future. ---	Title: A Survey on Intrusion Detection System for Wireless Network Section 1: INTRODUCTION Description 1: Write about the rapid evolution of wireless networks, their susceptibility to various attacks, the importance of intrusion detection systems (IDS) in securing these networks, and the challenges associated with implementing IDS in wireless environments. Section 2: Types of Wireless network for Intrusion Detection Description 2: Introduce the basics of intrusion detection in wireless networks, defining intrusion and attacks, motivation for intrusion detection, and challenges in developing effective intrusion detection schemes. Section 3: Types of attacks in Wireless network Description 3: Describe various types of attacks faced by wireless networks, including probing & network discovery, surveillance, DOS (Denial of Services) attacks, impersonation, and man-in-the-middle and rogue AP attacks. Section 4: Intrusion Detection System Description 4: Explain what an Intrusion Detection System (IDS) is, how it works, different types of IDS (anomaly detection, misuse detection), and the methods used for intrusion detection. Section 5: Requirements of IDS in Wireless Network Description 5: Discuss the key requirements for an effective IDS in a wireless network, including minimal system resource usage, fault-tolerance, ability to resist subversion, and accuracy in detecting intrusions. Section 6: Wireless Intrusion Prevention System Description 6: Describe the concept of Wireless Intrusion Prevention System (WIPS), its purpose, and how it extends the capabilities of IDS by not only detecting but also preventing wireless intrusions. Section 7: RESEARCH SCOPE Description 7: Provide an overview of the research scope, including the history and development of WIPS, current methodologies, a proposed common framework for wireless intrusion prevention, and future research directions. Section 8: FUTURE WORK Description 8: Suggest potential areas for future research based on the current findings, emphasizing the application and comparison of new algorithms in real-time environments. Section 9: CONCLUSION Description 9: Summarize the findings of the survey, restating the importance of intrusion detection and prevention in wireless networks, and the methods used to address these issues.
A Survey on Homomorphic Encryption Schemes: Theory and Implementation	9	--- paper_title: Replication is not needed: single database, computationally-private information retrieval paper_content: We establish the following, quite unexpected, result: replication of data for the computational private information retrieval problem is not necessary. More specifically, based on the quadratic residuosity assumption, we present a single database, computationally private information retrieval scheme with O(n/sup /spl epsiv//) communication complexity for any /spl epsiv/>0. --- paper_title: An Intermediate Greek-English Lexicon: Founded Upon the Seventh Edition of Liddell and Scott's Greek-English Lexicon paper_content: This abridgement of the world's most authoritative dictionary of ancient Greek is based on the 1883 revision. It includes some discussion of word usage, citing examples and characteristic phrases. Generally speaking, only words used by late writers and scientific terms have been omitted from the full lexicon. From Homer downwards, to the close of Attic Greek, care has been taken to include all words, as well as those used by Aristotle, Plutarch in his Lives, Polybius, Strabo, Lucian, and the writers of the New Testament. --- paper_title: A new public key cryptosystem based on higher residues paper_content: This paper describes a new public-key cryptosystem based on the hardness of computing higher residues modulo a composite RSA integer. We introduce two versions of our scheme, one deterministic and the other probabilistic. The deterministic version is practically oriented: encryption amounts to a single exponentiation w.r.t. a modulus with at least 768 bits and a 160-bit exponent. Decryption can be suitably opti- mized so as to become less demanding than a couple RSA decryptions. Although slower than RSA, the new scheme is still reasonably compet- itive and has several specific applications. The probabilistic version ex- hibits an homomorphic encryption scheme whose expansion rate is much better than previously proposed such systems. Furthermore, it has se- mantic security, relative to the hardness of computing higher residues for suitable moduli. --- paper_title: Evaluating branching programs on encrypted data paper_content: We present a public-key encryption scheme with the following properties. Given a branching program P and an encryption c′ of an input x, it is possible to efficiently compute a succinct ciphertext c′ from which P(x) can be efficiently decoded using the secret key. The size of c′ depends polynomially on the size of x and the length of P, but does not further depend on the size of P. As interesting special cases, one can efficiently evaluate finite automata, decision trees, and OBDDs on encrypted data, where the size of the resulting ciphertext c′ does not depend on the size of the object being evaluated. These are the first general representation models for which such a feasibility result is shown. Our main construction generalizes the approach of Kushilevitz and Ostrovsky (FOCS 1997) for constructing single-server Private Information Retrieval protocols. ::: ::: We also show how to strengthen the above so that c′ does not contain additional information about P (other than P(x) for some x) even if the public key and the ciphertext c are maliciously formed. This yields a two-message secure protocol for evaluating a length-bounded branching program P held by a server on an input x held by a client. A distinctive feature of this protocol is that it hides the size of the server's input P from the client. In particular, the client's work is independent of the size of P. --- paper_title: Probabilistic encryption & how to play mental poker keeping secret all partial information paper_content: This paper proposes an Encryption Scheme that possess the following property : An adversary, who knows the encryption algorithm and is given the cyphertext, cannot obtain any information about the clear-text. ::: Any implementation of a Public Key Cryptosystem, as proposed by Diffie and Hellman in [8], should possess this property. ::: Our Encryption Scheme follows the ideas in the number theoretic implementations of a Public Key Cryptosystem due to Rivest, Shamir and Adleman [13], and Rabin [12]. --- paper_title: Fundamentals of Abstract Algebra paper_content: Sets, relations and integers introduction to groups permution groups subgroups and normal subgroups homomorphisms and isomorphisms of groups sylow theorem solvable and nilpotent groups finitely generated abelian groups introduction to rings subrings, ideals and homomorphisms extensions of rings direct sum of rings polynomial rings eculidean rings unique factorization domains maximal, prime and primary ideals noetherian and artinian rings modules and vector spaces matrix rings field extensions algebraic extensions multiplicity of roots finite fields Galois theory and applications normal extensions geometric constructions binary codes Groebner bases answers and hints to selected exercises. --- paper_title: A Generalisation, a Simplification and some Applications of Paillier’s Probabilistic Public-Key System paper_content: We propose a generalisation of Paillier's probabilistic public key system, in which the expansion factor is reduced and which allows to adjust the block length of the scheme even after the public key has been fixed, without losing the homomorphic property. We show that the generalisation is as secure as Paillier's original system. We construct a threshold variant of the generalised scheme as well as zero-knowledge protocols to show that a given ciphertext encrypts one of a set of given plaintexts, and protocols to verify multiplicative relations on plaintexts. We then show how these building blocks can be used for applying the scheme to efficient electronic voting. This reduces dramatically the work needed to compute the final result of an election, compared to the previously best known schemes. We show how the basic scheme for a yes/no vote can be easily adapted to casting a vote for up to t out of L candidates. The same basic building blocks can also be adapted to provide receipt-free elections, under appropriate physical assumptions. The scheme for 1 out of L elections can be optimised such that for a certain range of parameter values, a ballot has size only O(log L) bits. --- paper_title: Protocols for secure computations paper_content: Two millionaires wish to know who is richer; however, they do not want to find out inadvertently any additional information about each other’s wealth. How can they carry out such a conversation? This is a special case of the following general problem. Suppose m people wish to compute the value of a function f(x1, x2, x3, . . . , xm), which is an integer-valued function of m integer variables xi of bounded range. Assume initially person Pi knows the value of xi and no other x’s. Is it possible for them to compute the value of f , by communicating among themselves, without unduly giving away any information about the values of their own variables? The millionaires’ problem corresponds to the case when m = 2 and f(x1, x2) = 1 if x1 < x2, and 0 otherwise. In this paper, we will give precise formulation of this general problem and describe three ways of solving it by use of one-way functions (i.e., functions which are easy to evaluate but hard to invert). These results have applications to secret voting, private querying of database, oblivious negotiation, playing mental poker, etc. We will also discuss the complexity question “How many bits need to be exchanged for the computation”, and describe methods to prevent participants from cheating. Finally, we study the question “What cannot be accomplished with one-way functions”. Before describing these results, we would like to put this work in perspective by first considering a unified view of secure computation in the next section. --- paper_title: Public-Key Cryptosystems Based on Composite Degree Residuosity Classes paper_content: This paper investigates a novel computational problem, namely the Composite Residuosity Class Problem, and its applications to public-key cryptography. We propose a new trapdoor mechanism and derive from this technique three encryption schemes : a trapdoor permutation and two homomorphic probabilistic encryption schemes computationally comparable to RSA. Our cryptosystems, based on usual modular arithmetics, are provably secure under appropriate assumptions in the standard model. --- paper_title: A method for obtaining digital signatures and public-key cryptosystems paper_content: An encryption method is presented with the novel property that publicly revealing an encryption key does not thereby reveal the corresponding decryption key. This has two important consequences: (1) Couriers or other secure means are not needed to transmit keys, since a message can be enciphered using an encryption key publicly revealed by the intented recipient. Only he can decipher the message, since only he knows the corresponding decryption key. (2) A message can be “signed” using a privately held decryption key. Anyone can verify this signature using the corresponding publicly revealed encryption key. Signatures cannot be forged, and a signer cannot later deny the validity of his signature. This has obvious applications in “electronic mail” and “electronic funds transfer” systems. A message is encrypted by representing it as a number M, raising M to a publicly specified power e, and then taking the remainder when the result is divided by the publicly specified product, n , of two large secret primer numbers p and q. Decryption is similar; only a different, secret, power d is used, where e * d ≡ 1(mod (p - 1) * (q - 1)). The security of the system rests in part on the difficulty of factoring the published divisor, n . --- paper_title: Evaluating 2-dnf formulas on ciphertexts paper_content: Let ψ be a 2-DNF formula on boolean variables x1,...,xn ∈ {0,1}. We present a homomorphic public key encryption scheme that allows the public evaluation of ψ given an encryption of the variables x1,...,xn. In other words, given the encryption of the bits x1,...,xn, anyone can create the encryption of ψ(x1,...,xn). More generally, we can evaluate quadratic multi-variate polynomials on ciphertexts provided the resulting value falls within a small set. We present a number of applications of the system: ::: ::: In a database of size n, the total communication in the basic step of the Kushilevitz-Ostrovsky PIR protocol is reduced from $\sqrt{n}$ to $\sqrt[3]{n}$. ::: ::: An efficient election system based on homomorphic encryption where voters do not need to include non-interactive zero knowledge proofs that their ballots are valid. The election system is proved secure without random oracles but still efficient. ::: ::: A protocol for universally verifiable computation. --- paper_title: Multi-bit cryptosystems based on lattice problems paper_content: We propose multi-bit versions of several single-bit cryptosystems based on lattice problems, the error-free version of the Ajtai-Dwork cryptosystem by Goldreich, Goldwasser, and Halevi [CRYPTO '97], the Regev cryptosystems [JACM 2004 and STOC 2005], and the Ajtai cryptosystem [STOC 2005]. We develop a universal technique derived from a general structure behind them for constructing their multi-bit versions without increase in the size of ciphertexts. By evaluating the trade-off between the decryption errors and the hardness of underlying lattice problems, it is shown that our multi-bit versions encrypt O(log n)-bit plaintexts into ciphertexts of the same length as the original ones with reasonable sacrifices of the hardness of the underlying lattice problems. Our technique also reveals an algebraic property, named pseudohomomorphism, of the lattice-based cryptosystems. --- paper_title: Verifiable secret-ballot elections paper_content: Privacy in secret-ballot elections has traditionally been attained by using a ballot box or voting booth to disassociate voters from ballots. Although such a system might achieve privacy, there is often little confidence in the accuracy of the announced tally. This thesis describes a practical scheme for conducting secret-ballot elections in which the outcome of an election is verifiable by all participants and even by non-participating observers. All communications are public, yet under a suitable number-theoretic assumption, the privacy of votes remains intact. ::: The tools developed here to conduct such elections have additional independent applications. Cryptographic capsules allow a prover to convince verifiers that either statement A or statement B is true without revealing substantial information as to which. Secret sharing homomorphisms enable computation on shared (secret) data and give a method of distributing shares of a secret such that each shareholder can verify the validity of all shares. --- paper_title: Homomorphic encryption in the cloud paper_content: Since the first notions of fully homomorphic encryption more than 30 years ago, there has been numerous attempts to develop such a system. Finally, in 2009 Craig Gentry succeeded. Homomorphic encryption brings great advantages but it seems that, at least for now, it also brings many practical difficulties. Furthermore, in the last couple of years, several other fully homomorphic systems arose where each has its one advantages and drawbacks. However, with the developments in cloud computing, we need it more than ever to become practical for real-world usages. In this paper we are discussing the strengths and weaknesses of homomorphic encryption and we give a brief description of several promising fully homomorphic encryption systems. Next, we give a special attention to the homomorphic encryption systems for cloud computing. Finally, we discuss some recent developments by IBM and their open-source library for homomorphic encryption. --- paper_title: Survey of Various Homomorphic Encryption algorithms and Schemes paper_content: Homomorphic encryption is the encryption scheme which means the operations on the encrypted data. Homomorphic encryption can be applied in any system by using various public key algorithms. When the data is transferred to the public area, there are many encryption algorithms to secure the operations and the storage of the data. But to process data located on remote server and to preserve privacy, homomorphic encryption is useful that allows the operations on the cipher text, which can provide the same results after calculations as the working directly on the raw data. In this paper, the main focus is on public key cryptographic algorithms based on homomorphic encryption scheme for preserving security. The case study on various principles and properties of homomorphic encryption is given and then various homomorphic algorithms using asymmetric key systems such as RSA, ElGamal, Paillier algorithms as well as various homomorphic encryption schemes such as BrakerskiGentry-Vaikuntanathan (BGV), Enhanced homomorphic Cryptosystem (EHC), Algebra homomorphic encryption scheme based on updated ElGamal (AHEE), Non-interactive exponential homomorphic encryption scheme (NEHE) are investigated. --- paper_title: Computing Blindfolded: New Developments in Fully Homomorphic Encryption paper_content: A fully homomorphic encryption scheme enables computation of arbitrary functions on encrypted data. Fully homomorphic encryption has long been regarded as cryptography's prized "holy grail" - extremely useful yet rather elusive. Starting with the groundbreaking work of Gentry in 2009, the last three years have witnessed numerous constructions of fully homomorphic encryption involving novel mathematical techniques, and a number of exciting applications. We will take the reader through a journey of these developments and provide a glimpse of the exciting research directions that lie ahead. --- paper_title: State Of Art in Homomorphic Encryption Schemes paper_content: The demand for privacy of digital data and of algorithms for handling more complex structures have increased exponentially over the last decade. However, the critical problem arises when there is a requirement for publicly computing with private data or to modify functions or algorithms in such a way that they are still executable while their privacy is ensured. This is where homomorphic cryptosystems can be used since these systems enable computations with encrypted data. A fully homomorphic encryption scheme enables computation of arbitrary functions on encrypted data.. This enables a customer to generate a program that can be executed by a third party, without revealing the underlying algorithm or the processed data. We will take the reader through a journey of these developments and provide a glimpse of the exciting research directions that lie ahead. In this paper, we propose a selection of the most important available solutions, discussing their properties and limitations. --- paper_title: Fully Homomorphic Encryption: Cryptography's holy grail paper_content: For more than 30 years, cryptographers have embarked on a quest to construct an encryption scheme that would enable arbitrary computation on encrypted data. Conceptually simple, yet notoriously difficult to achieve, cryptography's holy grail opens the door to many new capabilities in our cloud-centric, data-driven world. --- paper_title: A Survey of Homomorphic Encryption for Nonspecialists paper_content: Processing encrypted signals requires special properties of the underlying encryption scheme. A possible choice is the use of homomorphic encryption. In this paper, we propose a selection of the most important available solutions, discussing their properties and limitations. --- paper_title: Homomorphic Encryption: Theory&Applications paper_content: The goal of this chapter is to present a survey of homomorphic encryption techniques and their applications. After a detailed discussion on the introduction and motivation of the chapter, we present some basic concepts of cryptography. The fundamental theories of homomorphic encryption are then discussed with suitable examples. The chapter then provides a survey of some of the classical homomorphic encryption schemes existing in the current literature. Various applications and salient properties of homomorphic encryption schemes are then discussed in detail. The chapter then introduces the most important and recent research direction in the filed - fully homomorphic encryption. A significant number of propositions on fully homomorphic encryption is then discussed. Finally, the chapter concludes by outlining some emerging research trends in this exicting field of cryptography. --- paper_title: Recent Advances in Homomorphic Encryption: A Possible Future for Signal Processing in the Encrypted Domain paper_content: Since the introduction of the notion of privacy homomorphism by Rivest et al. in the late 1970s, the design of efficient and secure encryption schemes allowing the performance of general computations in the encrypted domain has been one of the holy grails of the cryptographic community. Despite numerous partial answers, the problem of designing such a powerful primitive has remained open until the theoretical breakthrough of the fully homomorphic encryption (FHE) scheme published by Gentry in the late 2000s. Since then, progress has been fast-paced, and it can now be reasonably said that practical homomorphic encryption-based computing will become a reality in the near future. --- paper_title: Practical homomorphic encryption: A survey paper_content: Cloud computing technology has rapidly evolved over the last decade, offering an alternative way to store and work with large amounts of data. However data security remains an important issue particularly when using a public cloud service provider. The recent area of homomorphic cryptography allows computation on encrypted data, which would allow users to ensure data privacy on the cloud and increase the potential market for cloud computing. A significant amount of research on homomorphic cryptography appeared in the literature over the last few years; yet the performance of existing implementations of encryption schemes remains unsuitable for real time applications. One way this limitation is being addressed is through the use of graphics processing units (GPUs) and field programmable gate arrays (FPGAs) for implementations of homomorphic encryption schemes. This review presents the current state of the art in this promising new area of research and highlights the interesting remaining open problems. --- paper_title: Homomorphic encryption: from private-key to public-key paper_content: We show how to transform any additively homomorphic private-key encryption scheme that is compact, into a public-key encryption scheme. By compact we mean that the length of a homomorphically generated encryption is independent of the number of ciphertexts from which it was created. We do not require anything else on the distribution of homomorphically generated encryptions (in particular, we do not require them to be distributed like real ciphertexts). ::: ::: Our resulting public-key scheme is homomorphic in the following sense. If the private-key scheme is i+1-hop homomorphic with respect to some set of operations then the public-key scheme we construct is i-hop homomorphic with respect to the same set of operations. --- paper_title: A new public key cryptosystem based on higher residues paper_content: This paper describes a new public-key cryptosystem based on the hardness of computing higher residues modulo a composite RSA integer. We introduce two versions of our scheme, one deterministic and the other probabilistic. The deterministic version is practically oriented: encryption amounts to a single exponentiation w.r.t. a modulus with at least 768 bits and a 160-bit exponent. Decryption can be suitably opti- mized so as to become less demanding than a couple RSA decryptions. Although slower than RSA, the new scheme is still reasonably compet- itive and has several specific applications. The probabilistic version ex- hibits an homomorphic encryption scheme whose expansion rate is much better than previously proposed such systems. Furthermore, it has se- mantic security, relative to the hardness of computing higher residues for suitable moduli. --- paper_title: Probabilistic encryption & how to play mental poker keeping secret all partial information paper_content: This paper proposes an Encryption Scheme that possess the following property : An adversary, who knows the encryption algorithm and is given the cyphertext, cannot obtain any information about the clear-text. ::: Any implementation of a Public Key Cryptosystem, as proposed by Diffie and Hellman in [8], should possess this property. ::: Our Encryption Scheme follows the ideas in the number theoretic implementations of a Public Key Cryptosystem due to Rivest, Shamir and Adleman [13], and Rabin [12]. --- paper_title: A Generalisation, a Simplification and some Applications of Paillier’s Probabilistic Public-Key System paper_content: We propose a generalisation of Paillier's probabilistic public key system, in which the expansion factor is reduced and which allows to adjust the block length of the scheme even after the public key has been fixed, without losing the homomorphic property. We show that the generalisation is as secure as Paillier's original system. We construct a threshold variant of the generalised scheme as well as zero-knowledge protocols to show that a given ciphertext encrypts one of a set of given plaintexts, and protocols to verify multiplicative relations on plaintexts. We then show how these building blocks can be used for applying the scheme to efficient electronic voting. This reduces dramatically the work needed to compute the final result of an election, compared to the previously best known schemes. We show how the basic scheme for a yes/no vote can be easily adapted to casting a vote for up to t out of L candidates. The same basic building blocks can also be adapted to provide receipt-free elections, under appropriate physical assumptions. The scheme for 1 out of L elections can be optimised such that for a certain range of parameter values, a ballot has size only O(log L) bits. --- paper_title: New Directions in Cryptography paper_content: Two kinds of contemporary developments in cryptography are examined. Widening applications of teleprocessing have given rise to a need for new types of cryptographic systems, which minimize the need for secure key distribution channels and supply the equivalent of a written signature. This paper suggests ways to solve these currently open problems. It also discusses how the theories of communication and computation are beginning to provide the tools to solve cryptographic problems of long standing. --- paper_title: Public-Key Cryptosystems Based on Composite Degree Residuosity Classes paper_content: This paper investigates a novel computational problem, namely the Composite Residuosity Class Problem, and its applications to public-key cryptography. We propose a new trapdoor mechanism and derive from this technique three encryption schemes : a trapdoor permutation and two homomorphic probabilistic encryption schemes computationally comparable to RSA. Our cryptosystems, based on usual modular arithmetics, are provably secure under appropriate assumptions in the standard model. --- paper_title: A method for obtaining digital signatures and public-key cryptosystems paper_content: An encryption method is presented with the novel property that publicly revealing an encryption key does not thereby reveal the corresponding decryption key. This has two important consequences: (1) Couriers or other secure means are not needed to transmit keys, since a message can be enciphered using an encryption key publicly revealed by the intented recipient. Only he can decipher the message, since only he knows the corresponding decryption key. (2) A message can be “signed” using a privately held decryption key. Anyone can verify this signature using the corresponding publicly revealed encryption key. Signatures cannot be forged, and a signer cannot later deny the validity of his signature. This has obvious applications in “electronic mail” and “electronic funds transfer” systems. A message is encrypted by representing it as a number M, raising M to a publicly specified power e, and then taking the remainder when the result is divided by the publicly specified product, n , of two large secret primer numbers p and q. Decryption is similar; only a different, secret, power d is used, where e * d ≡ 1(mod (p - 1) * (q - 1)). The security of the system rests in part on the difficulty of factoring the published divisor, n . --- paper_title: Multi-bit cryptosystems based on lattice problems paper_content: We propose multi-bit versions of several single-bit cryptosystems based on lattice problems, the error-free version of the Ajtai-Dwork cryptosystem by Goldreich, Goldwasser, and Halevi [CRYPTO '97], the Regev cryptosystems [JACM 2004 and STOC 2005], and the Ajtai cryptosystem [STOC 2005]. We develop a universal technique derived from a general structure behind them for constructing their multi-bit versions without increase in the size of ciphertexts. By evaluating the trade-off between the decryption errors and the hardness of underlying lattice problems, it is shown that our multi-bit versions encrypt O(log n)-bit plaintexts into ciphertexts of the same length as the original ones with reasonable sacrifices of the hardness of the underlying lattice problems. Our technique also reveals an algebraic property, named pseudohomomorphism, of the lattice-based cryptosystems. --- paper_title: Probabilistic encryption & how to play mental poker keeping secret all partial information paper_content: This paper proposes an Encryption Scheme that possess the following property : An adversary, who knows the encryption algorithm and is given the cyphertext, cannot obtain any information about the clear-text. ::: Any implementation of a Public Key Cryptosystem, as proposed by Diffie and Hellman in [8], should possess this property. ::: Our Encryption Scheme follows the ideas in the number theoretic implementations of a Public Key Cryptosystem due to Rivest, Shamir and Adleman [13], and Rabin [12]. --- paper_title: Quadratic Residuosity Problem. paper_content: An airfoil member for a land vehicle in particular for fixing to the roof of a cab of a tractor-trailer rig, in which the airfoil member is provided to reduce drag when positioned substantially horizontally for the case where either there is no trailer unit or the height of the trailer unit is lower than that of the cab of the tractor unit. The airfoil member is also movable between a position in which it acts as an air deflector and a position in which it acts as an airfoil. The airfoil member has a pair of side portions and a central portion having a much thinner cross-section in order to reduce its weight. Its height above the roof of the cab can also be adjusted so that it can be set to the best suited position either as an air deflector or an airfoil in order to reduce drag to a minimum. --- paper_title: CRT-based Fully Homomorphic Encryption over the Integers ⋆ paper_content: In 1978, Rivest, Adleman and Dertouzos introduced the basic concept of privacy homomorphism that allows computation on encrypted data without decryption. It was an interesting work whose idea precedes the recent development of fully homomorphic encryption, although actual example schemes proposed in the paper are all susceptible to simple known-plaintext attacks.In this paper, we revisit one of their proposals, in particular the third scheme which is based on the Chinese Remainder Theorem and is ring homomorphic. It is known that only a single pair of known plaintext/ciphertext is needed to break this scheme. However, by exploiting the standard technique to insert an error to a message before encryption, we can cope with this problem. We present a secure modification of their proposal by showing that the proposed scheme is fully homomorphic and secure against the chosen plaintext attacks under the approximate GCD assumption and the sparse subset sum assumption when the message space is restricted to Z 2 k .Interestingly, the proposed scheme can be regarded as a generalization of the DGHV scheme with larger plaintext space. Our scheme has O ~ ( λ 5 ) ciphertext expansion overhead while the DGHV has O ~ ( λ 8 ) for the security parameter λ . When restricted to the homomorphic encryption scheme with depth of O ( log λ ) , the overhead is reduced to O ~ ( λ ) . Our scheme can be used in applications requiring a large message space Z Q for log Q = O ( λ 4 ) , or SIMD style operations on Z Q k for log Q = O ( λ ) , k = O ( λ 3 ) , with O ~ ( λ 5 ) ciphertext size as in the DGHV. --- paper_title: New Directions in Cryptography paper_content: Two kinds of contemporary developments in cryptography are examined. Widening applications of teleprocessing have given rise to a need for new types of cryptographic systems, which minimize the need for secure key distribution channels and supply the equivalent of a written signature. This paper suggests ways to solve these currently open problems. It also discusses how the theories of communication and computation are beginning to provide the tools to solve cryptographic problems of long standing. --- paper_title: A Generalisation, a Simplification and some Applications of Paillier’s Probabilistic Public-Key System paper_content: We propose a generalisation of Paillier's probabilistic public key system, in which the expansion factor is reduced and which allows to adjust the block length of the scheme even after the public key has been fixed, without losing the homomorphic property. We show that the generalisation is as secure as Paillier's original system. We construct a threshold variant of the generalised scheme as well as zero-knowledge protocols to show that a given ciphertext encrypts one of a set of given plaintexts, and protocols to verify multiplicative relations on plaintexts. We then show how these building blocks can be used for applying the scheme to efficient electronic voting. This reduces dramatically the work needed to compute the final result of an election, compared to the previously best known schemes. We show how the basic scheme for a yes/no vote can be easily adapted to casting a vote for up to t out of L candidates. The same basic building blocks can also be adapted to provide receipt-free elections, under appropriate physical assumptions. The scheme for 1 out of L elections can be optimised such that for a certain range of parameter values, a ballot has size only O(log L) bits. --- paper_title: Public-Key Cryptosystems Based on Composite Degree Residuosity Classes paper_content: This paper investigates a novel computational problem, namely the Composite Residuosity Class Problem, and its applications to public-key cryptography. We propose a new trapdoor mechanism and derive from this technique three encryption schemes : a trapdoor permutation and two homomorphic probabilistic encryption schemes computationally comparable to RSA. Our cryptosystems, based on usual modular arithmetics, are provably secure under appropriate assumptions in the standard model. --- paper_title: Evaluating branching programs on encrypted data paper_content: We present a public-key encryption scheme with the following properties. Given a branching program P and an encryption c′ of an input x, it is possible to efficiently compute a succinct ciphertext c′ from which P(x) can be efficiently decoded using the secret key. The size of c′ depends polynomially on the size of x and the length of P, but does not further depend on the size of P. As interesting special cases, one can efficiently evaluate finite automata, decision trees, and OBDDs on encrypted data, where the size of the resulting ciphertext c′ does not depend on the size of the object being evaluated. These are the first general representation models for which such a feasibility result is shown. Our main construction generalizes the approach of Kushilevitz and Ostrovsky (FOCS 1997) for constructing single-server Private Information Retrieval protocols. ::: ::: We also show how to strengthen the above so that c′ does not contain additional information about P (other than P(x) for some x) even if the public key and the ciphertext c are maliciously formed. This yields a two-message secure protocol for evaluating a length-bounded branching program P held by a server on an input x held by a client. A distinctive feature of this protocol is that it hides the size of the server's input P from the client. In particular, the client's work is independent of the size of P. --- paper_title: Protocols for secure computations paper_content: Two millionaires wish to know who is richer; however, they do not want to find out inadvertently any additional information about each other’s wealth. How can they carry out such a conversation? This is a special case of the following general problem. Suppose m people wish to compute the value of a function f(x1, x2, x3, . . . , xm), which is an integer-valued function of m integer variables xi of bounded range. Assume initially person Pi knows the value of xi and no other x’s. Is it possible for them to compute the value of f , by communicating among themselves, without unduly giving away any information about the values of their own variables? The millionaires’ problem corresponds to the case when m = 2 and f(x1, x2) = 1 if x1 < x2, and 0 otherwise. In this paper, we will give precise formulation of this general problem and describe three ways of solving it by use of one-way functions (i.e., functions which are easy to evaluate but hard to invert). These results have applications to secret voting, private querying of database, oblivious negotiation, playing mental poker, etc. We will also discuss the complexity question “How many bits need to be exchanged for the computation”, and describe methods to prevent participants from cheating. Finally, we study the question “What cannot be accomplished with one-way functions”. Before describing these results, we would like to put this work in perspective by first considering a unified view of secure computation in the next section. --- paper_title: Evaluating 2-dnf formulas on ciphertexts paper_content: Let ψ be a 2-DNF formula on boolean variables x1,...,xn ∈ {0,1}. We present a homomorphic public key encryption scheme that allows the public evaluation of ψ given an encryption of the variables x1,...,xn. In other words, given the encryption of the bits x1,...,xn, anyone can create the encryption of ψ(x1,...,xn). More generally, we can evaluate quadratic multi-variate polynomials on ciphertexts provided the resulting value falls within a small set. We present a number of applications of the system: ::: ::: In a database of size n, the total communication in the basic step of the Kushilevitz-Ostrovsky PIR protocol is reduced from $\sqrt{n}$ to $\sqrt[3]{n}$. ::: ::: An efficient election system based on homomorphic encryption where voters do not need to include non-interactive zero knowledge proofs that their ballots are valid. The election system is proved secure without random oracles but still efficient. ::: ::: A protocol for universally verifiable computation. --- paper_title: Subgroup membership problems and public key cryptosystems paper_content: Public key encryption was first proposed by Diffie and Hellman [16], and widely popularised with the RSA cryptosystem [37]. Over the years, the security goals of public key encryption have been studied [17, 22], as have adversary models [30, 36], and many public key cryptosystems have been proposed and analysed.It turns out that the security of many of those cryptosystems [16, 18, 22, 29, 34, 35] are based on a common class of mathematical problems, called subgroup membership problems. Cramer and Shoup [10] designed a chosen-ciphertextsecure cryptosystem based on a general subgroup membership problem (generalising their previous work [9]), and provided two new instances. Yamamura and Saito [41] defined a general subgroup membership problem, catalogued several known subgroup membership problems, and designed a private information retrieval system based on a subgroup membership problem. Nieto, Boyd and Dawson [31] designed a cryptosystem based on essentially a symmetric subgroup membership problem (see Section 4.4 and Section 6.1).Chapter 2 and 3 contain certain preliminary discussions necessary for the later work. In Chapter 4, we discuss subgroup membership problems, both abstractly and concrete families. For all of the concrete examples, there is a related problem called the splitting problem. We discuss various elementary reductions, both abstract and for concrete families. In cryptographic applications, a third related problem, called the subgroup discrete logarithm problem, is also interesting, and we discuss this in some detail. We also discuss a variant of the subgroup membership problem where there are two subgroups that are simultaneously hard to distinguish. We prove a useful reduction (Theorem 4.11) for this case. The technique used in the proof is reused throughout the thesis.In Chapter 5, we discuss two homomorphic cryptosystems, based on trapdoor splitting problems. This gives us a uniform description of a number of homomorphic cryptosystems, and allows us to apply the theory and results of Chapter 4 to the security of those cryptosystems.Using the technique of Theorem 4.11, we develop a homomorphic cryptosystem that is not based on a trapdoor problem. This gives us a fairly efficient cryptosystem, with potentially useful properties.We also discuss the security of a homomorphic cryptosystem under a nonstandard assumption. While these results are very weak, they are stronger than results obtained in the generic model.In Chapter 6, we develop two key encapsulation methods. The first can be proven secure against passive attacks, using the same technique as in the proof of Theorem 4.11. The second method can be proven secure against active attacks in the random oracle model, but to do this, we need a certain non-standard assumption.Finally, in Chapter 7 we discuss a small extension to the framework developed by Cramer and Shoup [10], again by essentially reusing the technique used to prove Theorem 4.11. This gives us a cryptosystem that is secure against chosen ciphertext attacks, without recourse to the random oracle model or nonstandard assumptions. The cryptosystem is quite practical, and performs quite well compared to other variants of the Cramer-Shoup cryptosystem. --- paper_title: Protocols for secure computations paper_content: Two millionaires wish to know who is richer; however, they do not want to find out inadvertently any additional information about each other’s wealth. How can they carry out such a conversation? This is a special case of the following general problem. Suppose m people wish to compute the value of a function f(x1, x2, x3, . . . , xm), which is an integer-valued function of m integer variables xi of bounded range. Assume initially person Pi knows the value of xi and no other x’s. Is it possible for them to compute the value of f , by communicating among themselves, without unduly giving away any information about the values of their own variables? The millionaires’ problem corresponds to the case when m = 2 and f(x1, x2) = 1 if x1 < x2, and 0 otherwise. In this paper, we will give precise formulation of this general problem and describe three ways of solving it by use of one-way functions (i.e., functions which are easy to evaluate but hard to invert). These results have applications to secret voting, private querying of database, oblivious negotiation, playing mental poker, etc. We will also discuss the complexity question “How many bits need to be exchanged for the computation”, and describe methods to prevent participants from cheating. Finally, we study the question “What cannot be accomplished with one-way functions”. Before describing these results, we would like to put this work in perspective by first considering a unified view of secure computation in the next section. --- paper_title: Evaluating branching programs on encrypted data paper_content: We present a public-key encryption scheme with the following properties. Given a branching program P and an encryption c′ of an input x, it is possible to efficiently compute a succinct ciphertext c′ from which P(x) can be efficiently decoded using the secret key. The size of c′ depends polynomially on the size of x and the length of P, but does not further depend on the size of P. As interesting special cases, one can efficiently evaluate finite automata, decision trees, and OBDDs on encrypted data, where the size of the resulting ciphertext c′ does not depend on the size of the object being evaluated. These are the first general representation models for which such a feasibility result is shown. Our main construction generalizes the approach of Kushilevitz and Ostrovsky (FOCS 1997) for constructing single-server Private Information Retrieval protocols. ::: ::: We also show how to strengthen the above so that c′ does not contain additional information about P (other than P(x) for some x) even if the public key and the ciphertext c are maliciously formed. This yields a two-message secure protocol for evaluating a length-bounded branching program P held by a server on an input x held by a client. A distinctive feature of this protocol is that it hides the size of the server's input P from the client. In particular, the client's work is independent of the size of P. --- paper_title: Homomorphic Public-Key Cryptosystems and Encrypting Boolean Circuits paper_content: In this paper homomorphic cryptosystems are designed for the first time over any finite group. Applying Barrington's construction we produce for any boolean circuit of the logarithmic depth its encrypted simulation of a polynomial size over an appropriate finitely generated group. --- paper_title: Cryptanalysis of Polly Cracker paper_content: An attack on the public key cryptosystem Polly Cracker is described, that reveals the complete secret key /spl sigma/ /spl isin/ F/sub q//sup n/ by means of n (nonadaptively) chosen "fake" ciphertexts. --- paper_title: Cryptanalysis of a homomorphic public-key cryptosystem over a finite group paper_content: The paper cryptanalyses a public-key cryptosystem recently proposed by Grigoriev and Ponomarenko, which encrypts an element from a fixed finite group defined in terms of generators and relations to produce a ciphertext from SL(2, Z). The paper presents a heuristic method for recovering the secret key from the public key, and so this cryptosystem should not be used in practice. --- paper_title: Evaluating 2-dnf formulas on ciphertexts paper_content: Let ψ be a 2-DNF formula on boolean variables x1,...,xn ∈ {0,1}. We present a homomorphic public key encryption scheme that allows the public evaluation of ψ given an encryption of the variables x1,...,xn. In other words, given the encryption of the bits x1,...,xn, anyone can create the encryption of ψ(x1,...,xn). More generally, we can evaluate quadratic multi-variate polynomials on ciphertexts provided the resulting value falls within a small set. We present a number of applications of the system: ::: ::: In a database of size n, the total communication in the basic step of the Kushilevitz-Ostrovsky PIR protocol is reduced from $\sqrt{n}$ to $\sqrt[3]{n}$. ::: ::: An efficient election system based on homomorphic encryption where voters do not need to include non-interactive zero knowledge proofs that their ballots are valid. The election system is proved secure without random oracles but still efficient. ::: ::: A protocol for universally verifiable computation. --- paper_title: Multi-bit cryptosystems based on lattice problems paper_content: We propose multi-bit versions of several single-bit cryptosystems based on lattice problems, the error-free version of the Ajtai-Dwork cryptosystem by Goldreich, Goldwasser, and Halevi [CRYPTO '97], the Regev cryptosystems [JACM 2004 and STOC 2005], and the Ajtai cryptosystem [STOC 2005]. We develop a universal technique derived from a general structure behind them for constructing their multi-bit versions without increase in the size of ciphertexts. By evaluating the trade-off between the decryption errors and the hardness of underlying lattice problems, it is shown that our multi-bit versions encrypt O(log n)-bit plaintexts into ciphertexts of the same length as the original ones with reasonable sacrifices of the hardness of the underlying lattice problems. Our technique also reveals an algebraic property, named pseudohomomorphism, of the lattice-based cryptosystems. --- paper_title: A Decade of Lattice Cryptography. paper_content: Lattice-based cryptography is the use of conjectured hard problems on point lattices in Rn as the foundation for secure cryptographic systems. Attractive features of lattice cryptography include apparent resistance to quantum attacks in contrast with most number-theoretic cryptography, high asymptotic efficiency and parallelism, security under worst-case intractability assumptions, and solutions to long-standing open problems in cryptography. This work surveys most of the major developments in lattice cryptography over the past ten years. The main focus is on the foundational short integer solution SIS and learning with errors LWE problems and their more efficient ring-based variants, their provable hardness assuming the worst-case intractability of standard lattice problems, and their many cryptographic applications. --- paper_title: Lattice-based cryptography paper_content: We describe some of the recent progress on lattice-based cryptography, starting from the seminal work of Ajtai, and ending with some recent constructions of very efficient cryptographic schemes. --- paper_title: NTRU: A Ring-Based Public Key Cryptosystem paper_content: We describe NTRU, a new public key cryptosystem. NTRU features reasonably short, easily created keys, high speed, and low memory requirements. NTRU encryption and decryption use a mixing system suggested by polynomial algebra combined with a clustering principle based on elementary probability theory. The security of the NTRU cryptosystem comes from the interaction of the polynomial mixing system with the independence of reduction modulo two relatively prime integers p and q. --- paper_title: On-the-fly multiparty computation on the cloud via multikey fully homomorphic encryption paper_content: We propose a new notion of secure multiparty computation aided by a computationally-powerful but untrusted "cloud" server. In this notion that we call on-the-fly multiparty computation (MPC), the cloud can non-interactively perform arbitrary, dynamically chosen computations on data belonging to arbitrary sets of users chosen on-the-fly. All user's input data and intermediate results are protected from snooping by the cloud as well as other users. This extends the standard notion of fully homomorphic encryption (FHE), where users can only enlist the cloud's help in evaluating functions on their own encrypted data. In on-the-fly MPC, each user is involved only when initially uploading his (encrypted) data to the cloud, and in a final output decryption phase when outputs are revealed; the complexity of both is independent of the function being computed and the total number of users in the system. When users upload their data, they need not decide in advance which function will be computed, nor who they will compute with; they need only retroactively approve the eventually-chosen functions and on whose data the functions were evaluated. This notion is qualitatively the best possible in minimizing interaction, since the users' interaction in the decryption stage is inevitable: we show that removing it would imply generic program obfuscation and is thus impossible. Our contributions are two-fold:- We show how on-the-fly MPC can be achieved using a new type of encryption scheme that we call multikey FHE, which is capable of operating on inputs encrypted under multiple, unrelated keys. A ciphertext resulting from a multikey evaluation can be jointly decrypted using the secret keys of all the users involved in the computation. - We construct a multikey FHE scheme based on NTRU, a very efficient public-key encryption scheme proposed in the 1990s. It was previously not known how to make NTRU fully homomorphic even for a single party. We view the construction of (multikey) FHE from NTRU encryption as a main contribution of independent interest. Although the transformation to a fully homomorphic system deteriorates the efficiency of NTRU somewhat, we believe that this system is a leading candidate for a practical FHE scheme. --- paper_title: Public-Key Cryptosystems from Lattice Reduction Problems paper_content: We present a new proposal for a trapdoor one-way function, from which we derive public-key encryption and digital signatures. The security of the new construction is based on the conjectured computational difficulty of lattice-reduction problems, providing a possible alternative to existing public-key encryption algorithms and digital signatures such as RSA and DSS. --- paper_title: Revisiting fully homomorphic encryption schemes and their cryptographic primitives paper_content: Lattice-based cryptography plays an important role in modern cryptography. Apart from being a perfect alternative of classic public key cryptosystems, should the quantum computers become available, the lattice-based cryptography also enables many applications that conventional cryptosystems, such as RSA encryption scheme, can not deliver. One of the most significant aspects from this point of view is the fully homomorphic encryption schemes. A fully homomorphic encryption scheme allows one to arbitrarily operate on the encrypted messages, without decrypting it. This notion was raised in 1978, and it becomes a “holy grail” for the cryptographers for 30 years until 2009, Craig Gentry presented a framework to construct a fully homomorphic encryption using ideal lattice. The fully homomorphic encryption schemes, although they may be lacking of efficiency at its current stage, enable many important applications, such as secured cloud searching verifiable outsourced computing. Nevertheless, just like other cryptosystems, and perhaps all other inventions at the initial stage, the fully homomorphic encryption is young, prospective, and hence requires more research. In this thesis, we focus on the security of fully homomorphic encryption schemes. The security of all known fully homomorphic encryption schemes can be reduced to some lattice problems. Therefore, our main tool, not surprisingly, is lattice. Previous work has shown that some of the fully homomorphic encryption schemes can be broken using lattice reduction algorithms. Indeed, there exist several lattice reduction algorithms, such as LLL and L, that run in polynomial time, that can break a homomorphic encryption scheme. However, the running time, even though it is a polynomial algorithm, is still beyond tolerance. Hence, our first step is to optimize those algorithms. In this thesis, we show three different improvements. To sum up, combining those techniques, we are able to accelerate the reduction form O(dβ + dβ) to O(dβ + dβ) when the algorithm is dedicated for those cryptosystems, where d is the dimension of the lattice, and β is the maximum bit-length of the norm of input --- paper_title: Factoring polynomials with rational coefficients paper_content: In this paper we present a polynomial-time algorithm to solve the following problem: given a non-zero polynomial fe Q(X) in one variable with rational coefficients, find the decomposition of f into irreducible factors in Q(X). It is well known that this is equivalent to factoring primitive polynomials feZ(X) into irreducible factors in Z(X). Here we call f~ Z(X) primitive if the greatest common divisor of its coefficients (the content of f) is 1. Our algorithm performs well in practice, cf. (8). Its running time, measured in bit operations, is O(nl2+n9(log(fD3). --- paper_title: Public-Key Cryptosystems from Lattice Reduction Problems paper_content: We present a new proposal for a trapdoor one-way function, from which we derive public-key encryption and digital signatures. The security of the new construction is based on the conjectured computational difficulty of lattice-reduction problems, providing a possible alternative to existing public-key encryption algorithms and digital signatures such as RSA and DSS. --- paper_title: Fully homomorphic encryption with relatively small key and ciphertext sizes paper_content: We present a fully homomorphic encryption scheme which has both relatively small key and ciphertext size. Our construction follows that of Gentry by producing a fully homomorphic scheme from a “somewhat” homomorphic scheme. For the somewhat homomorphic scheme the public and private keys consist of two large integers (one of which is shared by both the public and private key) and the ciphertext consists of one large integer. As such, our scheme has smaller message expansion and key size than Gentry’s original scheme. In addition, our proposal allows efficient fully homomorphic encryption over any field of characteristic two. --- paper_title: Experiments with the Plaintext Space in Gentry’S Somewhat Homomorphic Scheme paper_content: In this paper we propose an interesting improvement of the im- plementation of the original Gentry-Halevi somewhat homomorphic scheme. We suggest to choose a bigger plaintext space, by changing the underlying ideal from $I = (2) to I = (p)$ for some bigger prime $p$. Our analysis show that bigger plaintext space will improve the homomor- phic computation of the somewhat homomorphic scheme while it only slightly increases the complexity of the key generation procedure. The encryption and de- cryption functions have the same complexity. We provide also some experimental computations that support the analysis. --- paper_title: Toward basing fully homomorphic encryption on worst-case hardness paper_content: Gentry proposed a fully homomorphic public key encryption scheme that uses ideal lattices. He based the security of his scheme on the hardness of two problems: an average-case decision problem over ideal lattices, and the sparse (or "low-weight") subset sum problem (SSSP). ::: ::: We provide a key generation algorithm for Gentry's scheme that generates ideal lattices according to a "nice" average-case distribution. Then, we prove a worst-case / average-case connection that bases Gentry's scheme (in part) on the quantum hardness of the shortest independent vector problem (SIVP) over ideal lattices in the worst-case. (We cannot remove the need to assume that the SSSP is hard.) Our worst-case / average-case connection is the first where the average-case lattice is an ideal lattice, which seems to be necessary to support the security of Gentry's scheme. --- paper_title: An improvement of key generation algorithm for Gentry's homomorphic encryption scheme paper_content: One way of improving efficiency of Gentry's fully homomorphic encryption is controlling the number of operations, but our recollection is that any scheme which controls the bound has not proposed. ::: ::: In this paper, we propose a key generation algorithm for Gentry's homomorphic encryption scheme that controls the bound of the circuit depth by using the relation between the circuit depth and the eigenvalues of a basis of a lattice. We present experimental results that show that the proposed algorithm is practical. We discuss security of the basis of the lattices generated by the algorithm for practical use. --- paper_title: Improved key generation for Gentry’s fully homomorphic encryption scheme paper_content: A key problem with the original implementation of the Gentry Fully Homomorphic Encryption scheme was the slow key generation process. Gentry and Halevi provided a fast technique for 2-power cyclotomic fields. We present an extension of the Gentry---Halevi key generation technique for arbitrary cyclotomic fields. Our new method is roughly twice as efficient as the previous best methods. Our estimates are backed up with experimental data. --- paper_title: Faster Fully Homomorphic Encryption paper_content: We describe two improvements to Gentry’s fully homomorphic scheme based on ideal lattices and its analysis: we provide a more aggressive analysis of one of the hardness assumptions (the one related to the Sparse Subset Sum Problem) and we introduce a probabilistic decryption algorithm that can be implemented with an algebraic circuit of low multiplicative degree. Combined together, these improvements lead to a faster fully homomorphic scheme, with a O(λ 3.5) bit complexity per elementary binary add/mult gate, where λ is the security parameter. These improvements also apply to the fully homomorphic schemes of Smart and Vercauteren [PKC’2010] and van Dijk et al. [Eurocrypt’2010]. --- paper_title: (Batch) Fully Homomorphic Encryption over Integers for Non-Binary Message Spaces paper_content: In this paper, we construct a fully homomorphic encryption (FHE) scheme over integers with the message space \(\mathbb {Z}_Q\) for any prime \(Q\). Even for the binary case \(Q=2\), our decryption circuit has a smaller degree than that of the previous scheme; the multiplicative degree is reduced from \(O(\lambda (\log \lambda )^2)\) to \(O(\lambda )\), where \(\lambda \) is the security parameter. We also extend our FHE scheme to a batch FHE scheme. --- paper_title: Fully Homomorphic symmetric scheme without bootstrapping paper_content: Capability of operating over encrypted data makes Fully Homomorphic Encryption(FHE)the Holy Grail for secure data processing applications. Though many applications need only secret keys, FHE has not been achieved properly through symmetric cryptography. Major hurdle is the need to refresh noisy ciphertexts which essentially requires public key and bootstrapping. We introduce a refreshing procedure to make a somewhat homomorphic scheme, fully homomorphic without requiring bootstrapping. Our scheme uses symmetric keys and has performance superior to existing public-key schemes. --- paper_title: Scale-Invariant Fully Homomorphic Encryption over the Integers paper_content: At Crypto 2012, Brakerski constructed a scale-invariant fully homomorphic encryption scheme based on the LWE problem, in which the same modulus is used throughout the evaluation process, instead of a ladder of moduli when doing "modulus switching". In this paper we describe a variant of the van Dijk et al. FHE scheme over the integers with the same scale-invariant property. Our scheme has a single secret modulus whose size is linear in the multiplicative depth of the circuit to be homomorphically evaluated, instead of exponential; we therefore construct a leveled fully homomorphic encryption scheme. This scheme can be transformed into a pure fully homomorphic encryption scheme using bootstrapping, and its security is still based on the Approximate-GCD problem. ::: ::: We also describe an implementation of the homomorphic evaluation of the full AES encryption circuit, and obtain significantly improved performance compared to previous implementations: about 23 seconds resp. 3 minutes per AES block at the 72-bit resp. 80-bit security level on a mid-range workstation. ::: ::: Finally, we prove the equivalence between the error-free decisional Approximate-GCD problem introduced by Cheon et al. Eurocrypt 2013 and the classical computational Approximate-GCD problem. This equivalence allows to get rid of the additional noise in all the integer-based FHE schemes described so far, and therefore to simplify their security proof. --- paper_title: Fully homomorphic encryption without modulus switching from classical GapSVP paper_content: We present a new tensoring technique for LWE-based fully homomorphic encryption. While in all previous works, the ciphertext noise grows quadratically $$B \rightarrow B^2\cdot \text {poly}n$$ with every multiplication before "refreshing", our noise only grows linearly $$B \rightarrow B\cdot \text {poly}n$$. ::: ::: We use this technique to construct a scale-invariant fully homomorphic encryption scheme, whose properties only depend on the ratio between the modulus q and the initial noise level B, and not on their absolute values. ::: ::: Our scheme has a number of advantages over previous candidates: It uses the same modulus throughout the evaluation process no need for "modulus switching", and this modulus can take arbitrary form. In addition, security can be classically reduced from the worst-case hardness of the GapSVP problem with quasi-polynomial approximation factor, whereas previous constructions could only exhibit a quantum reduction from GapSVP. --- paper_title: Efficient Fully Homomorphic Encryption from (Standard) LWE paper_content: We present a fully homomorphic encryption scheme that is based solely on the(standard) learning with errors (LWE) assumption. Applying known results on LWE, the security of our scheme is based on the worst-case hardness of ``short vector problems'' on arbitrary lattices. Our construction improves on previous works in two aspects:\begin{enumerate}\item We show that ``somewhat homomorphic'' encryption can be based on LWE, using a new {\em re-linearization} technique. In contrast, all previous schemes relied on complexity assumptions related to ideals in various rings. \item We deviate from the "squashing paradigm'' used in all previous works. We introduce a new {\em dimension-modulus reduction} technique, which shortens the cipher texts and reduces the decryption complexity of our scheme, {\em without introducing additional assumptions}. \end{enumerate}Our scheme has very short cipher texts and we therefore use it to construct an asymptotically efficient LWE-based single-server private information retrieval (PIR) protocol. The communication complexity of our protocol (in the public-key model) is $k \cdot \polylog(k)+\log \dbs$ bits per single-bit query (here, $k$ is a security parameter). --- paper_title: Lattice-based FHE as secure as PKE paper_content: We show that (leveled) fully homomorphic encryption (FHE) can be based on the hardness of O(n1.5+e)-approximation for lattice problems (such as GapSVP) under quantum reductions for any e 〉 0 (or O(n2+e)-approximation under classical reductions). This matches the best known hardness for "regular" (non-homomorphic) lattice based public-key encryption up to the e factor. A number of previous methods had hit a roadblock at quasipolynomial approximation. (As usual, a circular security assumption can be used to achieve a non-leveled FHE scheme.) Our approach consists of three main ideas: Noise-bounded sequential evaluation of high fan-in operations; Circuit sequentialization using Barrington's Theorem; and finally, successive dimension-modulus reduction. --- paper_title: A Decade of Lattice Cryptography. paper_content: Lattice-based cryptography is the use of conjectured hard problems on point lattices in Rn as the foundation for secure cryptographic systems. Attractive features of lattice cryptography include apparent resistance to quantum attacks in contrast with most number-theoretic cryptography, high asymptotic efficiency and parallelism, security under worst-case intractability assumptions, and solutions to long-standing open problems in cryptography. This work surveys most of the major developments in lattice cryptography over the past ten years. The main focus is on the foundational short integer solution SIS and learning with errors LWE problems and their more efficient ring-based variants, their provable hardness assuming the worst-case intractability of standard lattice problems, and their many cryptographic applications. --- paper_title: On lattices, learning with errors, random linear codes, and cryptography paper_content: Our main result is a reduction from worst-case lattice problems such as SVP and SIVP to a certain learning problem. This learning problem is a natural extension of the 'learning from parity with error' problem to higher moduli. It can also be viewed as the problem of decoding from a random linear code. This, we believe, gives a strong indication that these problems are hard. Our reduction, however, is quantum. Hence, an efficient solution to the learning problem implies a quantum algorithm for SVP and SIVP. A main open question is whether this reduction can be made classical.Using the main result, we obtain a public-key cryptosystem whose hardness is based on the worst-case quantum hardness of SVP and SIVP. Previous lattice-based public-key cryptosystems such as the one by Ajtai and Dwork were only based on unique-SVP, a special case of SVP. The new cryptosystem is much more efficient than previous cryptosystems: the public key is of size O(n2) and encrypting a message increases its size by O(n)(in previous cryptosystems these values are O(n4) and O(n2), respectively). In fact, under the assumption that all parties share a random bit string of length O(n2), the size of the public key can be reduced to O(n). --- paper_title: On ideal lattices and learning with errors over rings paper_content: The “learning with errors” (LWE) problem is to distinguish random linear equations, which have been perturbed by a small amount of noise, from truly uniform ones. The problem has been shown to be as hard as worst-case lattice problems, and in recent years it has served as the foundation for a plethora of cryptographic applications. Unfortunately, these applications are rather inefficient due to an inherent quadratic overhead in the use of LWE. A main open question was whether LWE and its applications could be made truly efficient by exploiting extra algebraic structure, as was done for lattice-based hash functions (and related primitives). ::: ::: We resolve this question in the affirmative by introducing an algebraic variant of LWE called ring-LWE, and proving that it too enjoys very strong hardness guarantees. Specifically, we show that the ring-LWE distribution is pseudorandom, assuming that worst-case problems on ideal lattices are hard for polynomial-time quantum algorithms. Applications include the first truly practical lattice-based public-key cryptosystem with an efficient security reduction; moreover, many of the other applications of LWE can be made much more efficient through the use of ring-LWE. Finally, the algebraic structure of ring-LWE might lead to new cryptographic applications previously not known to be based on LWE. --- paper_title: LWE-Based FHE with Better Parameters paper_content: Fully homomorphic encryption allows a remote server to perform computable functions over the encrypted data without decrypting them first. We propose a public-key fully homomorphic encryption with better parameters from the learning with errors problem. It is a public key variant of Alperin-Sheriff and Peikert's symmetric-key fully homomorphic encryption CRYPTO 2014, a simplified symmetric version of Gentry, Sahai and Waters' CRYPTO 2013, and is based on a minor variant of Regev's public-key encryption scheme STOC 2005 which may be of independent interest. Meanwhile, it can not only homomorphically handle "NAND" circuits, but also conform to the traditional wisdom that circuit evaluation procedure should be a naive combination of homomorphic additions and multiplications. --- paper_title: Optimizations of Brakerski's fully homomorphic encryption scheme paper_content: In this paper, we propose two methods to improve the efficiency of the scheme. Our main optimization is a new method to fulfill the tensor product of vectors, which can significantly reduce the computational overhead in the key switching algorithm, and the basic homomorphic operation is about 40%-50% faster than before by using this method. By truncating the least significant bits from every element of ciphertext vector, another optimization is presented. Using this method, the ciphertext vector can be represented concisely, which can further improve the efficiency. --- paper_title: Multi-identity and Multi-key Leveled FHE from Learning with Errors paper_content: Gentry, Sahai and Waters recently presented the first (leveled) identity-based fully homomorphic (IBFHE) encryption scheme (CRYPTO 2013). Their scheme however only works in the single-identity setting; that is, homomorphic evaluation can only be performed on ciphertexts created with the same identity. In this work, we extend their results to the multi-identity setting and obtain a multi-identity IBFHE scheme that is selectively secure in the random oracle model under the hardness of Learning with Errors (LWE). We also obtain a multi-key fully-homomorphic encryption (FHE) scheme that is secure under LWE in the standard model. This is the first multi-key FHE based on a well-established assumption such as standard LWE. The multi-key FHE of Lopez-Alt, Tromer and Vaikuntanathan (STOC 2012) relied on a non-standard assumption, referred to as the Decisional Small Polynomial Ratio assumption. --- paper_title: Homomorphic Encryption from Learning with Errors: Conceptually-Simpler, Asymptotically-Faster, Attribute-Based paper_content: We describe a comparatively simple fully homomorphic encryption (FHE) scheme based on the learning with errors (LWE) problem. In previous LWE-based FHE schemes, multiplication is a complicated and expensive step involving “relinearization”. In this work, we propose a new technique for building FHE schemes that we call the approximate eigenvector method. In our scheme, for the most part, homomorphic addition and multiplication are just matrix addition and multiplication. This makes our scheme both asymptotically faster and (we believe) easier to understand. --- paper_title: Accelerating NTRU based homomorphic encryption using GPUs paper_content: We introduce a large polynomial arithmetic library optimized for Nvidia GPUs to support fully homomorphic encryption schemes. To realize the large polynomial arithmetic library we convert polynomials with large coefficients using the Chinese Remainder Theorem into many polynomials with small coefficients, and then carry out modular multiplications in the residue space using a custom developed discrete Fourier transform library. We further extend the library to support the homomorphic evaluation operations, i.e. addition, multiplication, and relinearization, in an NTRU based somewhat homomorphic encryption library. Finally, we put the library to use to evaluate homomorphic evaluation of two block ciphers: Prince and AES, which show 2.57 times and 7.6 times speedup, respectively, over an Intel Xeon software implementation. --- paper_title: Fully homomorphic encryption without modulus switching from classical GapSVP paper_content: We present a new tensoring technique for LWE-based fully homomorphic encryption. While in all previous works, the ciphertext noise grows quadratically $$B \rightarrow B^2\cdot \text {poly}n$$ with every multiplication before "refreshing", our noise only grows linearly $$B \rightarrow B\cdot \text {poly}n$$. ::: ::: We use this technique to construct a scale-invariant fully homomorphic encryption scheme, whose properties only depend on the ratio between the modulus q and the initial noise level B, and not on their absolute values. ::: ::: Our scheme has a number of advantages over previous candidates: It uses the same modulus throughout the evaluation process no need for "modulus switching", and this modulus can take arbitrary form. In addition, security can be classically reduced from the worst-case hardness of the GapSVP problem with quasi-polynomial approximation factor, whereas previous constructions could only exhibit a quantum reduction from GapSVP. --- paper_title: Efficient Fully Homomorphic Encryption from (Standard) LWE paper_content: We present a fully homomorphic encryption scheme that is based solely on the(standard) learning with errors (LWE) assumption. Applying known results on LWE, the security of our scheme is based on the worst-case hardness of ``short vector problems'' on arbitrary lattices. Our construction improves on previous works in two aspects:\begin{enumerate}\item We show that ``somewhat homomorphic'' encryption can be based on LWE, using a new {\em re-linearization} technique. In contrast, all previous schemes relied on complexity assumptions related to ideals in various rings. \item We deviate from the "squashing paradigm'' used in all previous works. We introduce a new {\em dimension-modulus reduction} technique, which shortens the cipher texts and reduces the decryption complexity of our scheme, {\em without introducing additional assumptions}. \end{enumerate}Our scheme has very short cipher texts and we therefore use it to construct an asymptotically efficient LWE-based single-server private information retrieval (PIR) protocol. The communication complexity of our protocol (in the public-key model) is $k \cdot \polylog(k)+\log \dbs$ bits per single-bit query (here, $k$ is a security parameter). --- paper_title: Efficient architecture and implementation for NTRUEncrypt system paper_content: NTRU has gained much attention recently because it is relatively efficient for practical implementation among the post-quantum public key cryptosystems. In this paper, an efficient hardware architecture and FPGA implementation of NTRUEncrypt is proposed. The new architecture takes advantage of linear feedback shift register (LFSR) structure for its compact circuitry and high speed. A novel design of the modular arithmetic unit is proposed to reduce the critical path delay. The FPGA implementation results have shown that the proposed design outperforms all the existing works in terms of area-delay product. --- paper_title: Practical Bootstrapping in Quasilinear Time paper_content: Gentry’s “bootstrapping” technique (STOC 2009) constructs a fully homomorphic encryption (FHE) scheme from a “somewhat homomorphic” one that is powerful enough to evaluate its own decryption function. To date, it remains the only known way of obtaining unbounded FHE. Unfortunately, bootstrapping is computationally very expensive, despite the great deal of effort that has been spent on improving its efficiency. The current state of the art, due to Gentry, Halevi, and Smart (PKC 2012), is able to bootstrap “packed” ciphertexts (which encrypt up to a linear number of bits) in time only quasilinear O(λ) = λ · logO(1) λ in the security parameter. While this performance is asymptotically optimal up to logarithmic factors, the practical import is less clear: the procedure composes multiple layers of expensive and complex operations, to the point where it appears very difficult to implement, and its concrete runtime appears worse than those of prior methods (all of which have quadratic or larger asymptotic runtimes). --- paper_title: NTRU: A Ring-Based Public Key Cryptosystem paper_content: We describe NTRU, a new public key cryptosystem. NTRU features reasonably short, easily created keys, high speed, and low memory requirements. NTRU encryption and decryption use a mixing system suggested by polynomial algebra combined with a clustering principle based on elementary probability theory. The security of the NTRU cryptosystem comes from the interaction of the polynomial mixing system with the independence of reduction modulo two relatively prime integers p and q. --- paper_title: On-the-fly multiparty computation on the cloud via multikey fully homomorphic encryption paper_content: We propose a new notion of secure multiparty computation aided by a computationally-powerful but untrusted "cloud" server. In this notion that we call on-the-fly multiparty computation (MPC), the cloud can non-interactively perform arbitrary, dynamically chosen computations on data belonging to arbitrary sets of users chosen on-the-fly. All user's input data and intermediate results are protected from snooping by the cloud as well as other users. This extends the standard notion of fully homomorphic encryption (FHE), where users can only enlist the cloud's help in evaluating functions on their own encrypted data. In on-the-fly MPC, each user is involved only when initially uploading his (encrypted) data to the cloud, and in a final output decryption phase when outputs are revealed; the complexity of both is independent of the function being computed and the total number of users in the system. When users upload their data, they need not decide in advance which function will be computed, nor who they will compute with; they need only retroactively approve the eventually-chosen functions and on whose data the functions were evaluated. This notion is qualitatively the best possible in minimizing interaction, since the users' interaction in the decryption stage is inevitable: we show that removing it would imply generic program obfuscation and is thus impossible. Our contributions are two-fold:- We show how on-the-fly MPC can be achieved using a new type of encryption scheme that we call multikey FHE, which is capable of operating on inputs encrypted under multiple, unrelated keys. A ciphertext resulting from a multikey evaluation can be jointly decrypted using the secret keys of all the users involved in the computation. - We construct a multikey FHE scheme based on NTRU, a very efficient public-key encryption scheme proposed in the 1990s. It was previously not known how to make NTRU fully homomorphic even for a single party. We view the construction of (multikey) FHE from NTRU encryption as a main contribution of independent interest. Although the transformation to a fully homomorphic system deteriorates the efficiency of NTRU somewhat, we believe that this system is a leading candidate for a practical FHE scheme. --- paper_title: Making NTRU as secure as worst-case problems over ideal lattices paper_content: NTRUEncrypt, proposed in 1996 by Hoffstein, Pipher and Silverman, is the fastest known lattice-based encryption scheme. Its moderate key-sizes, excellent asymptotic performance and conjectured resistance to quantum computers could make it a desirable alternative to factorisation and discrete-log based encryption schemes. However, since its introduction, doubts have regularly arisen on its security. In the present work, we show how to modify NTRUEncrypt to make it provably secure in the standard model, under the assumed quantum hardness of standard worst-case lattice problems, restricted to a family of lattices related to some cyclotomic fields. Our main contribution is to show that if the secret key polynomials are selected by rejection from discrete Gaussians, then the public key, which is their ratio, is statistically indistinguishable from uniform over its domain. The security then follows from the already proven hardness of the R-LWE problem. --- paper_title: Improved Security for a Ring-Based Fully Homomorphic Encryption Scheme paper_content: In 1996, Hoffstein, Pipher and Silverman introduced an efficient lattice based encryption scheme dubbed NTRUEncrypt . Unfortunately, this scheme lacks a proof of security. However, in 2011, Stehle and Steinfeld showed how to modify NTRUEncrypt to reduce security to standard problems in ideal lattices. In 2012, Lopez-Alt, Tromer and Vaikuntanathan proposed a fully homomorphic scheme based on this modified system. However, to allow homomorphic operations and prove security, a non-standard assumption is required. In this paper, we show how to remove this non-standard assumption via techniques introduced by Brakerski and construct a new fully homomorphic encryption scheme from the Stehle and Steinfeld version based on standard lattice assumptions and a circular security assumption. The scheme is scale-invariant and therefore avoids modulus switching and the size of ciphertexts is one ring element. Moreover, we present a practical variant of our scheme, which is secure under stronger assumptions, along with parameter recommendations and promising implementation results. Finally, we present an approach for encrypting larger input sizes by extending ciphertexts to several ring elements via the CRT on the message space. --- paper_title: A Subfield Lattice Attack on Overstretched NTRU Assumptions paper_content: The subfield attack exploits the presence of a subfield to solve overstretched versions of the NTRU assumption: norming the public key h down to a subfield may lead to an easier lattice problem and any sufficiently good solution may be lifted to a short vector in the full NTRU-lattice. This approach was originally sketched in a paper of Gentry and Szydlo at Eurocrypt'02 and there also attributed to Jonsson, Nguyen and Stern. However, because it does not apply for small moduli and hence NTRUEncrypt, it seems to have been forgotten. In this work, we resurrect this approach, fill some gaps, analyze and generalize it to any subfields and apply it to more recent schemes. We show that for significantly larger moduli -- a case we call overstretched -- the subfield attack is applicable and asymptotically outperforms other known attacks. ::: ::: This directly affects the asymptotic security of the bootstrappable homomorphic encryption schemes LTV and YASHE which rely on a mildly overstretched NTRU assumption: the subfield lattice attack runs in sub-exponential time $$2^{O\lambda /\log ^{1/3}\lambda }$$ invalidating the security claim of $$2^{\varTheta \lambda }$$ . The effect is more dramatic on GGH-like Multilinear Maps: this attack can run in polynomial time without encodings of zero nor the zero-testing parameter, yet requiring an additional quantum step to recover the secret parameters exactly. ::: ::: We also report on practical experiments. Running LLL in dimension 512 we obtain vectors that would have otherwise required running BKZ with block-size 130 in dimension 8192. Finally, we discuss concrete aspects of this attack, the condition on the modulus q to guarantee full immunity, discuss countermeasures and propose open questions. --- paper_title: Homomorphic Encryption from Learning with Errors: Conceptually-Simpler, Asymptotically-Faster, Attribute-Based paper_content: We describe a comparatively simple fully homomorphic encryption (FHE) scheme based on the learning with errors (LWE) problem. In previous LWE-based FHE schemes, multiplication is a complicated and expensive step involving “relinearization”. In this work, we propose a new technique for building FHE schemes that we call the approximate eigenvector method. In our scheme, for the most part, homomorphic addition and multiplication are just matrix addition and multiplication. This makes our scheme both asymptotically faster and (we believe) easier to understand. --- paper_title: Fully homomorphic encryption with relatively small key and ciphertext sizes paper_content: We present a fully homomorphic encryption scheme which has both relatively small key and ciphertext size. Our construction follows that of Gentry by producing a fully homomorphic scheme from a “somewhat” homomorphic scheme. For the somewhat homomorphic scheme the public and private keys consist of two large integers (one of which is shared by both the public and private key) and the ciphertext consists of one large integer. As such, our scheme has smaller message expansion and key size than Gentry’s original scheme. In addition, our proposal allows efficient fully homomorphic encryption over any field of characteristic two. --- paper_title: Faster Algorithms for Approximate Common Divisors: Breaking Fully-Homomorphic-Encryption Challenges over the Integers paper_content: At EUROCRYPT '10, van Dijk et al. presented simple fully- homomorphic encryption (FHE) schemes based on the hardness of approximate integer common divisors problems, which were introduced in 2001 by Howgrave-Graham. There are two versions for these problems: the partial version (PACD) and the general version (GACD). The seemingly easier problem PACD was recently used by Coron et al. at CRYPTO '11 to build a more efficient variant of the FHE scheme by van Dijk et al.. We present a new PACD algorithm whose running time is essentially the "square root" of that of exhaustive search, which was the best attack in practice. This allows us to experimentally break the FHE challenges proposed by Coron et al. Our PACD algorithm directly gives rise to a new GACD algorithm, which is exponentially faster than exhaustive search. Interestingly, our main technique can also be applied to other settings, such as noisy factoring and attacking low-exponent RSA. --- paper_title: Fully Homomorphic Encryption over the Integers with Shorter Public Keys paper_content: At Eurocrypt 2010 van Dijk et al. described a fully homomorphic encryption scheme over the integers. The main appeal of this scheme (compared to Gentry's) is its conceptual simplicity. This simplicity comes at the expense of a public key size in O(λ10) which is too large for any practical system. In this paper we reduce the public key size to O(λ7) by encrypting with a quadratic form in the public key elements, instead of a linear form. We prove that the scheme remains semantically secure, based on a stronger variant of the approximate-GCD problem, already considered by van Dijk et al. ::: ::: We alsodescribe the first implementation of the resulting fully homomorphic scheme. Borrowing some optimizations from the recent Gentry-Halevi implementation of Gentry's scheme, we obtain roughly the same level of efficiency. This shows that fully homomorphic encryption can be implemented using simple arithmetic operations. --- paper_title: A Comparison of the Homomorphic Encryption Schemes FV and YASHE paper_content: We conduct a theoretical and practical comparison of two Ring-LWE-based, scale-invariant, leveled homomorphic encryption schemes – Fan and Vercauteren’s adaptation of BGV and the YASHE scheme proposed by Bos, Lauter, Loftus and Naehrig. In particular, we explain how to choose parameters to ensure correctness and security against lattice attacks. Our parameter selection improves the approach of van de Pol and Smart to choose parameters for schemes based on the Ring-LWE problem by using the BKZ-2.0 simulation algorithm. --- paper_title: Improved Security for a Ring-Based Fully Homomorphic Encryption Scheme paper_content: In 1996, Hoffstein, Pipher and Silverman introduced an efficient lattice based encryption scheme dubbed NTRUEncrypt . Unfortunately, this scheme lacks a proof of security. However, in 2011, Stehle and Steinfeld showed how to modify NTRUEncrypt to reduce security to standard problems in ideal lattices. In 2012, Lopez-Alt, Tromer and Vaikuntanathan proposed a fully homomorphic scheme based on this modified system. However, to allow homomorphic operations and prove security, a non-standard assumption is required. In this paper, we show how to remove this non-standard assumption via techniques introduced by Brakerski and construct a new fully homomorphic encryption scheme from the Stehle and Steinfeld version based on standard lattice assumptions and a circular security assumption. The scheme is scale-invariant and therefore avoids modulus switching and the size of ciphertexts is one ring element. Moreover, we present a practical variant of our scheme, which is secure under stronger assumptions, along with parameter recommendations and promising implementation results. Finally, we present an approach for encrypting larger input sizes by extending ciphertexts to several ring elements via the CRT on the message space. --- paper_title: Can homomorphic encryption be practical? paper_content: The prospect of outsourcing an increasing amount of data storage and management to cloud services raises many new privacy concerns for individuals and businesses alike. The privacy concerns can be satisfactorily addressed if users encrypt the data they send to the cloud. If the encryption scheme is homomorphic, the cloud can still perform meaningful computations on the data, even though it is encrypted. In fact, we now know a number of constructions of fully homomorphic encryption schemes that allow arbitrary computation on encrypted data. In the last two years, solutions for fully homomorphic encryption have been proposed and improved upon, but it is hard to ignore the elephant in the room, namely efficiency -- can homomorphic encryption ever be efficient enough to be practical? Certainly, it seems that all known fully homomorphic encryption schemes have a long way to go before they can be used in practice. Given this state of affairs, our contribution is two-fold. First, we exhibit a number of real-world applications, in the medical, financial, and the advertising domains, which require only that the encryption scheme is "somewhat" homomorphic. Somewhat homomorphic encryption schemes, which support a limited number of homomorphic operations, can be much faster, and more compact than fully homomorphic encryption schemes. Secondly, we show a proof-of-concept implementation of the recent somewhat homomorphic encryption scheme of Brakerski and Vaikuntanathan, whose security relies on the "ring learning with errors" (Ring LWE) problem. The scheme is very efficient, and has reasonably short ciphertexts. Our unoptimized implementation in magma enjoys comparable efficiency to even optimized pairing-based schemes with the same level of security and homomorphic capacity. We also show a number of application-specific optimizations to the encryption scheme, most notably the ability to convert between different message encodings in a ciphertext. --- paper_title: A Comparison of the Homomorphic Encryption Schemes FV and YASHE paper_content: We conduct a theoretical and practical comparison of two Ring-LWE-based, scale-invariant, leveled homomorphic encryption schemes – Fan and Vercauteren’s adaptation of BGV and the YASHE scheme proposed by Bos, Lauter, Loftus and Naehrig. In particular, we explain how to choose parameters to ensure correctness and security against lattice attacks. Our parameter selection improves the approach of van de Pol and Smart to choose parameters for schemes based on the Ring-LWE problem by using the BKZ-2.0 simulation algorithm. --- paper_title: Ciphers for MPC and FHE paper_content: Designing an efficient cipher was always a delicate balance between linear and non-linear operations. This goes back to the design of DES, and in fact all the way back to the seminal work of Shannon. --- paper_title: On the Homomorphic Computation of Symmetric Cryptographic Primitives paper_content: We present an analysis on the homomorphic computability of different symmetric cryptographic primitives, with the goal of understanding their characteristics with respect to the homomorphic evaluation according to the BGV scheme. Specifically, we start from the framework presented by Gentry, Halevi and Smart for evaluating AES. We provide an improvement of it, then we perform a detailed evaluation on the homomorphic computation of cryptographic algorithms of different families Salsa20 stream cipher, SHA-256 hash function and Keccak sponge function. After the analysis, we report the performance results of the primitives we have implemented using the recently released HElib. In the conclusions we discuss our findings for the different primitives we have analyzed to draw a general conclusion on the homomorphic evaluation of symmetric cryptographic primitives. --- paper_title: Can homomorphic encryption be practical? paper_content: The prospect of outsourcing an increasing amount of data storage and management to cloud services raises many new privacy concerns for individuals and businesses alike. The privacy concerns can be satisfactorily addressed if users encrypt the data they send to the cloud. If the encryption scheme is homomorphic, the cloud can still perform meaningful computations on the data, even though it is encrypted. In fact, we now know a number of constructions of fully homomorphic encryption schemes that allow arbitrary computation on encrypted data. In the last two years, solutions for fully homomorphic encryption have been proposed and improved upon, but it is hard to ignore the elephant in the room, namely efficiency -- can homomorphic encryption ever be efficient enough to be practical? Certainly, it seems that all known fully homomorphic encryption schemes have a long way to go before they can be used in practice. Given this state of affairs, our contribution is two-fold. First, we exhibit a number of real-world applications, in the medical, financial, and the advertising domains, which require only that the encryption scheme is "somewhat" homomorphic. Somewhat homomorphic encryption schemes, which support a limited number of homomorphic operations, can be much faster, and more compact than fully homomorphic encryption schemes. Secondly, we show a proof-of-concept implementation of the recent somewhat homomorphic encryption scheme of Brakerski and Vaikuntanathan, whose security relies on the "ring learning with errors" (Ring LWE) problem. The scheme is very efficient, and has reasonably short ciphertexts. Our unoptimized implementation in magma enjoys comparable efficiency to even optimized pairing-based schemes with the same level of security and homomorphic capacity. We also show a number of application-specific optimizations to the encryption scheme, most notably the ability to convert between different message encodings in a ciphertext. --- paper_title: Scale-Invariant Fully Homomorphic Encryption over the Integers paper_content: At Crypto 2012, Brakerski constructed a scale-invariant fully homomorphic encryption scheme based on the LWE problem, in which the same modulus is used throughout the evaluation process, instead of a ladder of moduli when doing "modulus switching". In this paper we describe a variant of the van Dijk et al. FHE scheme over the integers with the same scale-invariant property. Our scheme has a single secret modulus whose size is linear in the multiplicative depth of the circuit to be homomorphically evaluated, instead of exponential; we therefore construct a leveled fully homomorphic encryption scheme. This scheme can be transformed into a pure fully homomorphic encryption scheme using bootstrapping, and its security is still based on the Approximate-GCD problem. ::: ::: We also describe an implementation of the homomorphic evaluation of the full AES encryption circuit, and obtain significantly improved performance compared to previous implementations: about 23 seconds resp. 3 minutes per AES block at the 72-bit resp. 80-bit security level on a mid-range workstation. ::: ::: Finally, we prove the equivalence between the error-free decisional Approximate-GCD problem introduced by Cheon et al. Eurocrypt 2013 and the classical computational Approximate-GCD problem. This equivalence allows to get rid of the additional noise in all the integer-based FHE schemes described so far, and therefore to simplify their security proof. --- paper_title: Fully homomorphic encryption with relatively small key and ciphertext sizes paper_content: We present a fully homomorphic encryption scheme which has both relatively small key and ciphertext size. Our construction follows that of Gentry by producing a fully homomorphic scheme from a “somewhat” homomorphic scheme. For the somewhat homomorphic scheme the public and private keys consist of two large integers (one of which is shared by both the public and private key) and the ciphertext consists of one large integer. As such, our scheme has smaller message expansion and key size than Gentry’s original scheme. In addition, our proposal allows efficient fully homomorphic encryption over any field of characteristic two. --- paper_title: On Dual Lattice Attacks Against Small-Secret LWE and Parameter Choices in HElib and SEAL paper_content: We present novel variants of the dual-lattice attack against LWE in the presence of an unusually short secret. These variants are informed by recent progress in BKW-style algorithms for solving LWE. Applying them to parameter sets suggested by the homomorphic encryption libraries HElib and SEAL yields revised security estimates. Our techniques scale the exponent of the dual-lattice attack by a factor of \((2\,L)/(2\,L+1)\) when \(\log q = \varTheta {\left( L \log n\right) }\), when the secret has constant hamming weight \(h\) and where \(L\) is the maximum depth of supported circuits. They also allow to half the dimension of the lattice under consideration at a multiplicative cost of \(2^{h}\) operations. Moreover, our techniques yield revised concrete security estimates. For example, both libraries promise 80 bits of security for LWE instances with \(n=1024\) and \(\log _2 q \approx {47}\), while the techniques described in this work lead to estimated costs of 68 bits (SEAL) and 62 bits (HElib). --- paper_title: Efficient Fully Homomorphic Encryption from (Standard) LWE paper_content: We present a fully homomorphic encryption scheme that is based solely on the(standard) learning with errors (LWE) assumption. Applying known results on LWE, the security of our scheme is based on the worst-case hardness of ``short vector problems'' on arbitrary lattices. Our construction improves on previous works in two aspects:\begin{enumerate}\item We show that ``somewhat homomorphic'' encryption can be based on LWE, using a new {\em re-linearization} technique. In contrast, all previous schemes relied on complexity assumptions related to ideals in various rings. \item We deviate from the "squashing paradigm'' used in all previous works. We introduce a new {\em dimension-modulus reduction} technique, which shortens the cipher texts and reduces the decryption complexity of our scheme, {\em without introducing additional assumptions}. \end{enumerate}Our scheme has very short cipher texts and we therefore use it to construct an asymptotically efficient LWE-based single-server private information retrieval (PIR) protocol. The communication complexity of our protocol (in the public-key model) is $k \cdot \polylog(k)+\log \dbs$ bits per single-bit query (here, $k$ is a security parameter). --- paper_title: Algorithms in HElib paper_content: HElib is a software library that implements homomorphic encryption (HE), specifically the Brakerski-Gentry-Vaikuntanathan (BGV) scheme, focusing on effective use of the Smart-Vercauteren ciphertext packing techniques and the Gentry-Halevi-Smart optimizations. The underlying cryptosystem serves as the equivalent of a “hardware platform” for HElib, in that it defines a set of operations that can be applied homomorphically, and specifies their cost. This “platform” is a SIMD environment (somewhat similar to Intel SSE and the like), but with unique cost metrics and parameters. In this report we describe some of the algorithms and optimization techniques that are used in HElib for data movement, linear algebra, and other operations over this “platform.” --- paper_title: Accelerating NTRU based homomorphic encryption using GPUs paper_content: We introduce a large polynomial arithmetic library optimized for Nvidia GPUs to support fully homomorphic encryption schemes. To realize the large polynomial arithmetic library we convert polynomials with large coefficients using the Chinese Remainder Theorem into many polynomials with small coefficients, and then carry out modular multiplications in the residue space using a custom developed discrete Fourier transform library. We further extend the library to support the homomorphic evaluation operations, i.e. addition, multiplication, and relinearization, in an NTRU based somewhat homomorphic encryption library. Finally, we put the library to use to evaluate homomorphic evaluation of two block ciphers: Prince and AES, which show 2.57 times and 7.6 times speedup, respectively, over an Intel Xeon software implementation. --- paper_title: Accelerating SWHE Based PIRs Using GPUs paper_content: In this work we focus on tailoring and optimizing the computational Private Information Retrieval (cPIR) scheme proposed in WAHC 2014 for efficient execution on graphics processing units (GPUs). Exploiting the mass parallelism in GPUs is a commonly used approach in speeding up cPIRs. Our goal is to eliminate the efficiency bottleneck of the Doroz et al. construction which would allow us to take advantage of its excellent bandwidth performance. To this end, we develop custom code to support polynomial ring operations and extend them to realize the evaluation functions in an optimized manner on high end GPUs. Specifically, we develop optimized CUDA code to support large degree/large coefficient polynomial arithmetic operations such as modular multiplication/reduction, and modulus switching. Moreover, we choose same prime numbers for both the CRT domain representation of the polynomials and for the modulus switching implementation of the somewhat homomorphic encryption scheme. This allows us to combine two arithmetic domains, which reduces the number of domain conversions and permits us to perform faster arithmetic. Our implementation achieves 14–34 times speedup for index comparison and 4–18 times speedup for data aggregation compared to a pure CPU software implementation. --- paper_title: High-Speed Fully Homomorphic Encryption Over the Integers paper_content: A fully homomorphic encryption (FHE) scheme is envisioned as a key cryptographic tool in building a secure and reliable cloud computing environment, as it allows arbitrary evaluation of a ciphertext without revealing the plaintext. However, existing FHE implementations remain impractical due to very high time and resource costs. To the authors’ knowledge, this paper presents the first hardware implementation of a full encryption primitive for FHE over the integers using FPGA technology. A large-integer multiplier architecture utilising Integer-FFT multiplication is proposed, and a large-integer Barrett modular reduction module is designed incorporating the proposed multiplier. The encryption primitive used in the integer-based FHE scheme is designed employing the proposed multiplier and modular reduction modules. The designs are verified using the Xilinx Virtex-7 FPGA platform. Experimental results show that a speed improvement factor of up to 44 is achievable for the hardware implementation of the FHE encryption scheme when compared to its corresponding software implementation. Moreover, performance analysis shows further speed improvements of the integer-based FHE encryption primitives may still be possible, for example through further optimisations or by targeting an ASIC platform. --- paper_title: Evaluating the Hardware Performance of a Million-Bit Multiplier paper_content: In this work we present the first full and complete evaluation of a very large multiplication scheme in custom hardware. We designed a novel architecture to realize a million-bit multiplication architecture based on the Schonhage-Strassen Algorithm and the Number Theoretical Transform (NTT). The construction makes use of an innovative cache architecture along with processing elements customized to match the computation and access patterns of the FFT-based recursive multiplication algorithm. When synthesized using a 90nm TSMC library operating at a frequency of 666 MHz, our architecture is able to compute the product of integers in excess of a million bits in 7.74 milliseconds. Estimates show that the performance of our design matches that of previously reported software implementations on a high-end 3 Ghz Intel Xeon processor, while requiring only a tiny fraction of the area. --- paper_title: Accelerating Fully Homomorphic Encryption in Hardware paper_content: We present a custom architecture for realizing the Gentry-Halevi fully homomorphic encryption (FHE) scheme. This contribution presents the first full realization of FHE in hardware. The architecture features an optimized multi-million bit multiplier based on the Schonhage Strassen multiplication algorithm. Moreover, a number of optimizations including spectral techniques as well as a precomputation strategy is used to significantly improve the performance of the overall design. When synthesized using 90 nm technology, the presented architecture achieves to realize the encryption, decryption, and recryption operations in 18.1 msec, 16.1 msec, and 3.1 sec, respectively, and occupies a footprint of less than 30 million gates. --- paper_title: Accelerating Homomorphic Evaluation on Reconfigurable Hardware paper_content: Homomorphic encryption allows computation on encrypted data and makes it possible to securely outsource computational tasks to untrusted environments. However, all proposed schemes are quite inefficient and homomorphic evaluation of ciphertexts usually takes several seconds on high-end CPUs, even for evaluating simple functions. In this work we investigate the potential of FPGAs for speeding up those evaluation operations. We propose an architecture to accelerate schemes based on the ring learning with errors (RLWE) problem and specifically implemented the somewhat homomorphic encryption scheme YASHE, which was proposed by Bos, Lauter, Loftus, and Naehrig in 2013. Due to the large size of ciphertexts and evaluation keys, on-chip storage of all data is not possible and external memory is required. For efficient utilization of the external memory we propose an efficient double-buffered memory access scheme and a polynomial multiplier based on the number theoretic transform (NTT). For the parameter set (\(n=16384,\lceil \log _2 q \rceil ={512}\)) capable of evaluating 9 levels of multiplications, we can perform a homomorphic addition in 0.94 ms and a homomorphic multiplication in 48.67 ms. --- paper_title: Accelerating integer-based fully homomorphic encryption using Comba multiplication paper_content: Fully Homomorphic Encryption (FHE) is a recently developed cryptographic technique which allows computations on encrypted data. There are many interesting applications for this encryption method, especially within cloud computing. However, the computational complexity is such that it is not yet practical for real-time applications. This work proposes optimised hardware architectures of the encryption step of an integerbased FHE scheme with the aim of improving its practicality. A low-area design and a high-speed parallel design are proposed and implemented on a Xilinx Virtex-7 FPGA, targeting the available DSP slices, which offer high-speed multiplication and accumulation. Both use the Comba multiplication scheduling method to manage the large multiplications required with uneven sized multiplicands and to minimise the number of read and write operations to RAM. Results show that speed up factors of 3.6 and 10.4 can be achieved for the encryption step with mediumsized security parameters for the low-area and parallel designs respectively, compared to the benchmark software implementation on an Intel Core2 Duo E8400 platform running at 3 GHz. --- paper_title: Accelerating bootstrapping in FHEW using GPUs paper_content: Recently, the usage of GPU is not limited to the jobs associated with graphics and a wide variety of applications take advantage of the flexibility of GPUs to accelerate the computing performance. Among them, one of the most emerging applications is the fully homomorphic encryption (FHE) scheme, which enables arbitrary computations on encrypted data. Despite much research effort, it cannot be considered as practical due to the enormous amount of computations, especially in the bootstrapping procedure. In this paper, we accelerate the performance of the recently suggested fast bootstrapping method in FHEW scheme using GPUs, as a case study of a FHE scheme. In order to optimize, we explored the reference code and carried out profiling to find out candidates for performance acceleration. Based on the profiling results, combined with more flexible tradeoff method, we optimized the bootstrapping algorithm in FHEW using GPU and CUDA's programming model. The empirical result shows that the bootstrapping of FHEW ciphertext can be done in less than 0.11 second after optimization. --- paper_title: Practical homomorphic encryption: A survey paper_content: Cloud computing technology has rapidly evolved over the last decade, offering an alternative way to store and work with large amounts of data. However data security remains an important issue particularly when using a public cloud service provider. The recent area of homomorphic cryptography allows computation on encrypted data, which would allow users to ensure data privacy on the cloud and increase the potential market for cloud computing. A significant amount of research on homomorphic cryptography appeared in the literature over the last few years; yet the performance of existing implementations of encryption schemes remains unsuitable for real time applications. One way this limitation is being addressed is through the use of graphics processing units (GPUs) and field programmable gate arrays (FPGAs) for implementations of homomorphic encryption schemes. This review presents the current state of the art in this promising new area of research and highlights the interesting remaining open problems. --- paper_title: On CCA-secure somewhat homomorphic encryption paper_content: It is well known that any encryption scheme which supports any form of homomorphic operation cannot be secure against adaptive chosen ciphertext attacks. The question then arises as to what is the most stringent security definition which is achievable by homomorphic encryption schemes. Prior work has shown that various schemes which support a single homomorphic encryption scheme can be shown to be IND-CCA1, i.e. secure against lunchtime attacks. In this paper we extend this analysis to the recent fully homomorphic encryption scheme proposed by Gentry, as refined by Gentry, Halevi, Smart and Vercauteren. We show that the basic Gentry scheme is not IND-CCA1; indeed a trivial lunchtime attack allows one to recover the secret key. We then show that a minor modification to the variant of the somewhat homomorphic encryption scheme of Smart and Vercauteren will allow one to achieve IND-CCA1, indeed PA-1, in the standard model assuming a lattice based knowledge assumption. We also examine the security of the scheme against another security notion, namely security in the presence of ciphertext validity checking oracles; and show why CCA-like notions are important in applications in which multiple parties submit encrypted data to the "cloud" for secure processing. --- paper_title: Notes on Two Fully Homomorphic Encryption Schemes Without Bootstrapping. paper_content: Recently, IACR ePrint archive posted two fully homomorphic encryption schemes without bootstrapping. In this note, we show that these schemes are trivially insecure. Furthermore, we also show that the encryption schemes of Liu and Wang [6] in CCS 2012 and the encryption scheme of Liu, Bertino, and Xun [5] in ASIACCS 2014 are insecure either. --- paper_title: Between a Rock and a Hard Place: Interpolating Between MPC and FHE paper_content: We present a computationally secure MPC protocol for threshold adversaries which is parametrized by a value L. When L = 2 we obtain a classical form of MPC protocol in which interaction is required for multiplications, as L increases interaction is reduced, in that one requires interaction only after computing a higher degree function. When L approaches infinity one obtains the FHE based protocol of Gentry, which requires no interaction. Thus one can trade communication for computation in a simple way. Our protocol is based on an interactive protocol for “bootstrapping” a somewhat homomorphic encryption (SHE) scheme. The key contribution is that our presented protocol is highly communication efficient enabling us to obtain reduced communication when compared to traditional MPC protocols for relatively small values of L. --- paper_title: Outsourcing secure two-party computation as a black box paper_content: Secure multiparty computation SMC offers a technique to preserve functionality and data privacy in mobile applications. Current protocols that make this costly cryptographic construction feasible on mobile devices securely outsource the bulk of the computation to a cloud provider. However, these outsourcing techniques are built on specific secure computation assumptions and tools, and applying new SMC ideas to the outsourced setting requires the protocols to be completely rebuilt and proven secure. In this work, we develop a generic technique for lifting any secure two-party computation protocol into an outsourced two-party SMC protocol. By augmenting the function being evaluated with auxiliary consistency checks and input values, we can create an outsourced protocol with low overhead cost. Our implementation and evaluation show that in the best case our outsourcing additions execute within the confidence intervals of two servers running the same computation and consume approximately the same bandwidth. In addition, the mobile device itself uses minimal bandwidth over a single round of communication. This work demonstrates that efficient outsourcing is possible with any underlying SMC scheme and provides an outsourcing protocol that is efficient and directly applicable to current and future SMC techniques. Copyright © 2016 John Wiley & Sons, Ltd. --- paper_title: Multiparty computation from somewhat homomorphic encryption paper_content: We propose a general multiparty computation protocol secure against an active adversary corrupting up to $$n-1$$ of the n players. The protocol may be used to compute securely arithmetic circuits over any finite field $$\mathbb {F}_{p^k}$$. Our protocol consists of a preprocessing phase that is both independent of the function to be computed and of the inputs, and a much more efficient online phase where the actual computation takes place. The online phase is unconditionally secure and has total computational and communication complexity linear in n, the number of players, where earlier work was quadratic in n. Moreover, the work done by each player is only a small constant factor larger than what one would need to compute the circuit in the clear. We show this is optimal for computation in large fields. In practice, for 3 players, a secure 64-bit multiplication can be done in 0.05 ms. Our preprocessing is based on a somewhat homomorphic cryptosystem. We extend a scheme by Brakerski et al., so that we can perform distributed decryption and handle many values in parallel in one ciphertext. The computational complexity of our preprocessing phase is dominated by the public-key operations, we need $$On^2/s$$ operations per secure multiplication where s is a parameter that increases with the security parameter of the cryptosystem. Earlier work in this model needed $$\varOmega n^2$$ operations. In practice, the preprocessing prepares a secure 64-bit multiplication for 3 players in about 13 ms. --- paper_title: On-the-fly multiparty computation on the cloud via multikey fully homomorphic encryption paper_content: We propose a new notion of secure multiparty computation aided by a computationally-powerful but untrusted "cloud" server. In this notion that we call on-the-fly multiparty computation (MPC), the cloud can non-interactively perform arbitrary, dynamically chosen computations on data belonging to arbitrary sets of users chosen on-the-fly. All user's input data and intermediate results are protected from snooping by the cloud as well as other users. This extends the standard notion of fully homomorphic encryption (FHE), where users can only enlist the cloud's help in evaluating functions on their own encrypted data. In on-the-fly MPC, each user is involved only when initially uploading his (encrypted) data to the cloud, and in a final output decryption phase when outputs are revealed; the complexity of both is independent of the function being computed and the total number of users in the system. When users upload their data, they need not decide in advance which function will be computed, nor who they will compute with; they need only retroactively approve the eventually-chosen functions and on whose data the functions were evaluated. This notion is qualitatively the best possible in minimizing interaction, since the users' interaction in the decryption stage is inevitable: we show that removing it would imply generic program obfuscation and is thus impossible. Our contributions are two-fold:- We show how on-the-fly MPC can be achieved using a new type of encryption scheme that we call multikey FHE, which is capable of operating on inputs encrypted under multiple, unrelated keys. A ciphertext resulting from a multikey evaluation can be jointly decrypted using the secret keys of all the users involved in the computation. - We construct a multikey FHE scheme based on NTRU, a very efficient public-key encryption scheme proposed in the 1990s. It was previously not known how to make NTRU fully homomorphic even for a single party. We view the construction of (multikey) FHE from NTRU encryption as a main contribution of independent interest. Although the transformation to a fully homomorphic system deteriorates the efficiency of NTRU somewhat, we believe that this system is a leading candidate for a practical FHE scheme. --- paper_title: Secure outsourced garbled circuit evaluation for mobile devices paper_content: Garbled circuits provide a powerful tool for jointly evaluating functions while preserving the privacy of each user's inputs. While recent research has made the use of this primitive more practical, such solutions generally assume that participants are symmetrically provisioned with massive computing resources. In reality, most people on the planet only have access to the comparatively sparse computational resources associated with their mobile phones, and those willing and able to pay for access to public cloud computing infrastructure cannot be assured that their data will remain unexposed. We address this problem by creating a new SFE protocol that allows mobile devices to securely outsource the majority of computation required to evaluate a garbled circuit. Our protocol, which builds on the most efficient garbled circuit evaluation techniques, includes a new out-sourced oblivious transfer primitive that requires significantly less bandwidth and computation than standard OT primitives and outsourced input validation techniques that force the cloud to prove that it is executing all protocols correctly. After showing that our extensions are secure in the malicious model, we conduct an extensive performance evaluation for a number of standard SFE test applications as well as a privacy-preserving navigation application designed specifically for the mobile usecase. Our system reduces execution time by 98.92% and bandwidth by 99.95% for the edit distance problem of size 128 compared to non-outsourced evaluation. These results show that even the least capable devices are capable of evaluating some of the largest garbled circuits generated for any platform. --- paper_title: Adaptively Secure Multi-Party Computation from LWE via Equivocal FHE paper_content: Adaptively secure Multi-Party Computation MPC is an essential and fundamental notion in cryptography. In this work, we construct Universally Composable UC MPC protocols that are adaptively secure against all-but-one corruptions based on LWE. Our protocols have a constant number of rounds and communication complexity dependant only on the length of the inputs and outputs it is independent of the circuit size. ::: ::: Such protocols were only known assuming an honest majority. Protocols in the dishonest majority setting, such as the work of Ishai et al. CRYPTO 2008, require communication complexity proportional to the circuit size. In addition, constant-round adaptively secure protocols assuming dishonest majority are known to be impossible in the stand-alone setting with black-box proofs of security in the plain model. Here, we solve the problem in the UC setting using a set-up assumption which was shown necessary in order to achieve dishonest majority. ::: ::: The problem of constructing adaptively secure constant-round MPC protocols against arbitrary corruptions is considered a notorious hard problem. A recent line of works based on indistinguishability obfuscation construct such protocols with near-optimal number of rounds against arbitrary corruptions. However, based on standard assumptions, adaptively secure protocols secure against even just all-but-one corruptions with near-optimal number of rounds are not known. However, in this work we provide a three-round solution based only on LWE and NIZK secure against all-but-one corruptions. ::: ::: In addition, Asharov et al. EUROCRYPT 2012 and more recently Mukherjee and Wichs ePrint 2015 presented constant-round protocols based on LWE which are secure only in the presence of static adversaries. Assuming NIZK and LWE their static protocols run in two rounds where the latter one is only based on a common random string. Assuming adaptively secure UC NIZK, proposed by Groth et al. ACM 2012, and LWE as mentioned above our adaptive protocols run in three rounds. ::: ::: Our protocols are constructed based on a special type of cryptosystem we call equivocal FHE from LWE. We also build adaptively secure UC commitments and UC zero-knowledge proofs of knowledge from LWE. Moreover, in the decryption phase using an AMD code mechanism we avoid the use of ZK and achieve communication complexity that does not scale with the decryption circuit. --- paper_title: A Practical, Secure, and Verifiable Cloud Computing for Mobile Systems paper_content: Cloud computing systems, in which clients rent and share computing resources of third party platforms, have gained widespread use in recent years. Furthermore, cloud computing for mobile systems (i.e., systems in which the clients are mobile devices) have too been receiving considerable attention in technical literature. We propose a new method of delegating computations of resourceconstrained mobile clients, in which multiple servers interact to construct an encrypted program known as garbled circuit. Next, using garbled inputs from a mobile client, another server executes this garbled circuit and returns the resulting garbled outputs. Our system assures privacy of the mobile client’s data, even if the executing server chooses to collude with all but one of the other servers. We adapt the garbled circuit design of Beaver et al. and the secure multiparty computation protocol of Goldreich et al. for the purpose of building a secure cloud computing for mobile systems. Our method incorporates the novel use of the cryptographically secure pseudo random number generator of Blum et al. that enables the mobile client to efficiently retrieve the result of the computation, as well as to verify that the evaluator actually performed the computation. We analyze the server-side and client-side complexity of our system. Using real-world data, we evaluate our system for a privacy preserving search application that locates the nearest bank/ATM from the mobile client. We also measure the time taken to construct and evaluate the garbled circuit for varying number of servers, demonstrating the feasibility of our secure and verifiable cloud computing for mobile systems. c --- paper_title: An Efficient Leveled Identity-Based FHE paper_content: Gentry, Sahai and Waters constructed the first identity-based fully homomorphic encryption schemes from identity-based encryption schemes in CRYPTO 2013. In this work, we focus on improving their IBFHE schemes, using Micciancio and Peikert’s novel and powerful trapdoor in conjunction with Alperin-Sheriff and Peikert’s simple and tight noise analysis technique when performing homomorphic evaluation. --- paper_title: Reuse It Or Lose It: More Efficient Secure Computation Through Reuse of Encrypted Values paper_content: Two-party secure-function evaluation (SFE) has become significantly more feasible, even on resource-constrained devices, because of advances in server-aided computation systems. However, there are still bottlenecks, particularly in the input-validation stage of a computation. Moreover, SFE research has not yet devoted sufficient attention to the important problem of retaining state after a computation has been performed so that expensive processing does not have to be repeated if a similar computation is done again. This paper presents PartialGC, an SFE system that allows the reuse of encrypted values generated during a garbled-circuit computation. We show that using PartialGC can reduce computation time by as much as 96% and bandwidth by as much as 98% in comparison with previous outsourcing schemes for secure computation. We demonstrate the feasibility of our approach with two sets of experiments, one in which the garbled circuit is evaluated on a mobile device and one in which it is evaluated on a server. We also use PartialGC to build a privacy-preserving ``friend-finder'' application for Android. The reuse of previous inputs to allow stateful evaluation represents a new way of looking at SFE and further reduces computational barriers. --- paper_title: Homomorphic Encryption from Learning with Errors: Conceptually-Simpler, Asymptotically-Faster, Attribute-Based paper_content: We describe a comparatively simple fully homomorphic encryption (FHE) scheme based on the learning with errors (LWE) problem. In previous LWE-based FHE schemes, multiplication is a complicated and expensive step involving “relinearization”. In this work, we propose a new technique for building FHE schemes that we call the approximate eigenvector method. In our scheme, for the most part, homomorphic addition and multiplication are just matrix addition and multiplication. This makes our scheme both asymptotically faster and (we believe) easier to understand. ---	Title: A Survey on Homomorphic Encryption Schemes: Theory and Implementation Section 1: INTRODUCTION Description 1: Discusses the origins and basic concept of homomorphic encryption (HE), including its significance, types (PHE, SWHE, FHE), and the main motivation behind this survey. Section 2: RELATED WORK Description 2: Details the existing surveys in the field of HE, comparing them with this work and highlighting the unique contributions of this survey. Section 3: HOMOMORPHIC ENCRYPTION SCHEMES Description 3: Explains the basics of HE theory and presents notable PHE, SWHE, and FHE schemes along with their descriptions, homomorphic properties, and evolution. Section 4: Partially Homomorphic Encryption Schemes Description 4: Focuses on major PHE schemes such as RSA, Goldwasser-Micali, El-Gamal, Benaloh, Paillier, and others, describing their key generation, encryption, decryption algorithms, and homomorphic properties. Section 5: Somewhat Homomorphic Encryption Schemes Description 5: Discusses significant SWHE schemes, including Boneh-Goh-Nissim (BGN), Polly Cracker, Sander-Young-Yung (SYY), and others, focusing on their contributions towards FHE and performance characteristics. Section 6: Fully Homomorphic Encryption Schemes Description 6: Presents various FHE schemes categorized into four main families: Ideal Lattice-based, Integer-based, LWE-based, and NTRU-like schemes. Provides detailed discussions on Gentry's original scheme, subsequent improvements, and recent advancements. Section 7: IMPLEMENTATIONS OF SWHE AND FHE SCHEMES Description 7: Summarizes the implementations of SWHE and FHE schemes after Gentry's work, providing performance evaluations, optimizations, and the impact of various implementation techniques. Section 8: FURTHER RESEARCH DIRECTIONS AND LESSONS LEARNED Description 8: Evaluates the security, speed, and simplicity of current FHE schemes, discussing open problems like circular security, noise-free FHE, multikey FHE, and potential applications such as Functional Encryption (FE) and multiparty computation (MPC). Section 9: CONCLUSION Description 9: Concludes the survey by emphasizing the importance of privacy in the digital age and the potential of HE in preserving the privacy of sensitive data, while summarizing the key findings and future outlook of HE research.
An Overview of Reflection and Its Use in Cooperation	12	--- paper_title: Semantics and implementation of schema evolution in object-oriented databases paper_content: Object-oriented programming is well-suited to such data-intensive application domains as CAD/CAM, AI, and OIS (office information systems) with multimedia documents. At MCC we have built a prototype object-oriented database system, called ORION. It adds persistence and sharability to objects created and manipulated in applications implemented in an object-oriented programming environment. One of the important requirements of these applications is schema evolution, that is, the ability to dynamically make a wide variety of changes to the database schema. In this paper, following a brief review of the object-oriented data model that we support in ORION, we establish a framework for supporting schema evolution, define the semantics of schema evolution, and discuss its implementation. --- paper_title: Models of Expertise in Knowledge Acquisition paper_content: Publisher Summary This chapter presents the models of expertise in knowledge acquisition. The conceptual models, which are developed from interpretation models, consist most often of combinations of models for generic tasks. The conceptual model consists of a diagnostic task, which has as one of its sub tasks a planning task. Project management consists of alternating planning, monitoring, diagnostic, and remedying tasks. The interpretation models provide support for developing the interference and task layers, but far less support exists for domain structures. However, this reflects the state of the art in artificial intelligence (AI), where formalisms are developed for knowledge representation, but there is little insight in what good representations (models) are for objects and actions in a domain. Current research in AI toward models for time, space, substance, and processes may in the near future become valuable for analyzing domains and constructing robust domain knowledge bases. These models or domain theories can be developed into tools that provide initial structures for major domain concepts. The majority of these studies indicate that KCLM as a bridge between data and the design of the KBS is useful. The studies also indicate that KCLM and the interpretation models with KADS are not completely stable and fully developed. --- paper_title: KADS: a modelling approach to knowledge engineering paper_content: Abstract This paper discusses the KADs approach to knowledge engineering. In KADS, the development of a knowledge-based system (KBS) is viewed as a modelling activity. A KBS is not a container filled with knowledge extracted from an expert, but an operational model that exhibits some desired behaviour that can be observed in terms of real-world phenomena. Five basic principles underlying the KADS approach are discussed, namely (i) the introduction of partial models as a means to cope with the complexity of the knowledge engineering process, (ii) the KADS four-layer framework for modelling the required expertise, (iii) the re-usability of generic model components as templates supporting top-down knowledge acquisition, (iv) the process of differentiating simple models into more complex ones and (v) the importance of structure—preserving transformation of models of expertise into design and implementation. The actual activities that a knowledge engineer has to undertake are briefly discussed. We compare the KADS approach to related approaches and discuss experiences and future developments. The approach is illustrated throughout the paper with examples in the domain of troubleshooting audio equipment. --- paper_title: Debugging concurrent systems based on object groups paper_content: This paper presents a debugging method for Concurrent Object-Oriented Systems. Our method is based upon a new notion called Object Groups. An Object Group is a collection of objects which forms a natural unit for performing collective tasks. An Object Group’s Task differs from C. Manning’s nested transaction which is based on the nested request-reply bilateral message passing structures. Each Object Group’s Task permits more general message passing structures. The language constructs which specify and use Object Groups have been introduced into an object-oriented concurrent language ABCL/l. The paper also describes ABCL/l’s debugging tools based on Object Groups. ---	Title: An Overview of Reflection and Its Use in Cooperation Section 1: Introduction Description 1: Introduce the concept of reflection in information systems, its importance, and provide an overview of the research paper's objectives. Section 2: Approaches to Reflection Description 2: Discuss various models and methodologies for reflection in knowledge-based systems and programming languages, including KADS and CLOS. Section 3: KADS: (Knowledge Acquisition and Design System) Description 3: Provide an overview of the KADS methodology, its origins, and its application in developing knowledge-based systems. Section 4: KADS: The Four-layer Model of Expertise Description 4: Explain the four-layer model of expertise in KADS, focusing on domain knowledge, inference knowledge, task knowledge, and strategic knowledge. Section 5: REFLECT: The Meta-level Architecture Description 5: Describe the REFLECT project's approach to enhancing the strategy layer of KADS for reasoning about problem-solving competence. Section 6: CLOS: Common Lisp Object System Description 6: Introduce CLOS and its self-describing facilities, emphasizing its meta-object protocols and extensions for programming reflection. Section 7: Summary Description 7: Summarize the differences between task reflection and programming reflection, and introduce the concept of operational reflection, which integrates both. Section 8: Cooperation through Reflection Description 8: Explain the benefits of reflection in cooperative information systems, particularly in multi-database environments, and introduce the concept of operational reflection. Section 9: Cooperative Aspects of the R-OK Model Description 9: Describe the R-OK (Reflective Object Knowledge) model and its four types of metaobjects for facilitating cooperation among pre-existing information systems. Section 10: Formalisation Description 10: Formalize the reflective aspects of the R-OK model using the Z notation and explain its application in inheritance, location, and action within information systems. Section 11: Reflective Cooperative Processing Activities Description 11: Provide examples of how reflection can be used for cooperative processing, including cooperative instantiation and emergency triggers. Section 12: Self-explanation Description 12: Discuss the principle of self-explanation in reflective systems and its implications for model utility, completeness, and consistency.
Derandomization: a brief overview	16	--- paper_title: Randomized Algorithms paper_content: For many applications, a randomized algorithm is either the simplest or the fastest algorithm available, and sometimes both. This book introduces the basic concepts in the design and analysis of randomized algorithms. The first part of the text presents basic tools such as probability theory and probabilistic analysis that are frequently used in algorithmic applications. Algorithmic examples are also given to illustrate the use of each tool in a concrete setting. In the second part of the book, each chapter focuses on an important area to which randomized algorithms can be applied, providing a comprehensive and representative selection of the algorithms that might be used in each of these areas. Although written primarily as a text for advanced undergraduates and graduate students, this book should also prove invaluable as a reference for professionals and researchers. --- paper_title: How to generate cryptographically strong sequences of pseudo random bits paper_content: We give a set of conditions that allow one to generate 50–50 unpredictable bits.Based on those conditions, we present a general algorithmic scheme for constructing polynomial-time deterministic algorithms that stretch a short secret random input into a long sequence of unpredictable pseudo-random bits.We give an implementation of our scheme and exhibit a pseudo-random bit generator for which any efficient strategy for predicting the next output bit with better than 50–50 chance is easily transformable to an “equally efficient” algorithm for solving the discrete logarithm problem. In particular: if the discrete logarithm problem cannot be solved in probabilistic polynomial time, no probabilistic polynomial-time algorithm can guess the next output bit better than by flipping a coin: if “head” guess “0”, if “tail” guess “1” --- paper_title: On the generation of cryptographically strong pseudo-random sequences paper_content: In this paper we show how to generate from a short random seed S a long sequence of pseudo-random numbers Ri in which the problem of computing one more Ri value given an arbitrarily large subset of the other values is provably equivalent to the cryptanalysis of the associated Rivest-Shamir-Adleman encryption function. --- paper_title: A hard-core predicate for all one-way functions paper_content: A central tool in constructing pseudorandom generators, secure encryption functions, and in other areas are “hard-core” predicates b of functions (permutations) ƒ, discovered in [Blum Micali 82]. Such b ( x ) cannot be efficiently guessed (substantially better than 50-50) given only ƒ( x ). Both b , ƒ are computable in polynomial time. [Yao 82] transforms any one-way function ƒ into a more complicated one, ƒ * , which has a hard-core predicate. The construction applies the original ƒ to many small pieces of the input to ƒ * just to get one “hard-core” bit. The security of this bit may be smaller than any constant positive power of the security of ƒ. In fact, for inputs (to ƒ * ) of practical size, the pieces effected by ƒ are so small that ƒ can be inverted (and the “hard-core” bit computed) by exhaustive search. In this paper we show that every one-way function, padded to the form ƒ( p , x ) = ( p , g ( x )), VV p VV = V x V, has by itself a hard-core predicate of the same (within a polynomial) security. Namely, we prove a conjecture of [Levin 87, sec. 5.6.2] that the scalar product of Boolean vectors p , x is a hard-core of every one-way function ƒ( p , x ) = ( p , g ( x )). The result extends to multiple (up to the logarithm of security) such bits and to any distribution on the x 's for which ƒ is hard to invert. --- paper_title: One-way functions and pseudorandom generators paper_content: One-way are those functions which are easy to compute, but hard to invert on a non-negligible fraction of instances. The existence of such functions with some additional assumptions was shown to be sufficient for generating perfect pseudorandom strings \|Blum, Micali 82\|, \|Yao 82\|, \|Goldreich, Goldwasser, Micali 84\|. Below, among a few other observations, a weaker assumption about one-way functions is suggested, which is not only sufficient, but also necessary for the existence of pseudorandom generators. The main theorem can be understood without reading the sections 3-6. --- paper_title: Hardness vs. randomness paper_content: A simple construction for a pseudorandom bit generator is presented. It stretches a short string of truly random bits into a long string that looks random to any algorithm from a complexity class C (e.g. P, NC, PSPACE, etc.), using an arbitrary function that is hard for C. This generator reveals an equivalence between the problems of proving lower bounds and the problem of generating good pseudorandom sequences. Combining this construction with other arguments, a number of consequences are obtained. > --- paper_title: On yao’s XOR-lemma paper_content: A fundamental lemma of Yao states that computational weakunpredictability of Boolean predicates is amplified when the results of several independent instances are XOR together. We survey two known proofs of Yao's Lemma and present a third alternative proof. The third proof proceeds by first proving that a function constructed by concatenating the values of the original function on several independent instances is much more unpredictable, with respect to specified complexity bounds, than the original function. This statement turns out to be easier to prove than the XOR-Lemma. Using a result of Goldreich and Levin (1989) and some elementary observation, we derive the XOR-Lemma. --- paper_title: Hiding instances in multioracle queries paper_content: Abadi, Feigenbaum, and Kilian have considered instance-hiding schemes [1]. Let f be a function for which no randomized polynomial-time algorithm is known; randomized polynomial-time machine A wants to query an oracle B for f to obtain f(x), without telling B exactly what x is. It is shown in [1] that, if f is an NP-hard function, A cannot query a single oracle B while hiding all but the size of the instance, assuming that the polynomial hierarchy does not collapse. This negative result holds for all oracles B, including those that are non-r.e. --- paper_title: BPP has subexponential time simulations unless EXPTIME has publishable proofs paper_content: It is shown that BPP can be simulated in subexponential time for infinitely many input lengths unless exponential time collapses to the second level of the polynomial-time hierarchy, has polynomial-size circuits, and has publishable proofs (EXPTIME=MA). It is also shown that BPP is contained in subexponential time unless exponential time has publishable proofs for infinitely many input lengths. In addition, it is shown that BPP can be simulated in subexponential time for infinitely many input lengths unless there exist unary languages in MA/P. The proofs are based on the recent characterization of the power of multiprover interactive protocols and on random self-reducibility via low degree polynomials. They exhibit an interplay between Boolean circuit simulation, interactive proofs and classical complexity classes. An important feature of this proof is that it does not relativize.<<ETX>> --- paper_title: Hard-core distributions for somewhat hard problems paper_content: Consider a decision problem that cannot be 1-/spl delta/ approximated by circuits of a given size in the sense that any such circuit fails to give the correct answer on at least a /spl delta/ fraction of instances. We show that for any such problem there is a specific "hard core" set of inputs which is at least a /spl delta/ fraction of all inputs and on which no circuit of a slightly smaller size can get even a small advantage over a random guess. More generally, our argument holds for any non uniform model of computation closed under majorities. We apply this result to get a new proof of the Yao XOR lemma (A.C. Yao, 1982), and to get a related XOR lemma for inputs that are only k wise independent. --- paper_title: Hardness vs. randomness paper_content: A simple construction for a pseudorandom bit generator is presented. It stretches a short string of truly random bits into a long string that looks random to any algorithm from a complexity class C (e.g. P, NC, PSPACE, etc.), using an arbitrary function that is hard for C. This generator reveals an equivalence between the problems of proving lower bounds and the problem of generating good pseudorandom sequences. Combining this construction with other arguments, a number of consequences are obtained. > --- paper_title: Non-Deterministic Exponential Time has Two-Prover Interactive Protocols paper_content: We determine the exact power of two-prover interactive proof systems introduced by Ben-Or, Goldwasser, Kilian, and Wigderson (1988). In this system, two all-powerful noncommunicating provers convince a randomizing polynomial time verifier in polynomial time that the inputx belongs to the languageL. We show that the class of languages having tow-prover interactive proof systems is nondeterministic exponential time.We also show that to prove membership in languages inEXP, the honest provers need the power ofEXP only.The first part of the proof of the main result extends recent techniques of polynomial extrapolation used in the single prover case by Lund, Fortnow, Karloff, Nisan, and Shamir.The second part is averification scheme for multilinearity of a function in several variables held by an oracle and can be viewed as an independent result onprogram verification. Its proof rests on combinatorial techniques employing a simple isoperimetric inequality for certain graphs: --- paper_title: Worst-Case Hardness Suffices for Derandomization: A New Method for Hardness-Randomness Trade-Offs paper_content: Up to know, the known derandomization methods have been derived assuming average-case hardness conditions. In this paper we instead present the first worst-case hardness conditions sufficient to obtain P=BPP. --- paper_title: A new general derandomization method paper_content: We show that quick hitting set generators can replace quick pseudorandom generators to derandomize any probabilistic two-sided error algorithms. Up to now quick hitting set generators have been known as the general and uniform derandomization method for probabilistic one-sided error algorithms, while quick pseudorandom generators as the generators as the general and uniform method to derandomize probabilistic two-sided error algorithms. Our method is based on a deterministic algorithm that, given a Boolean circuit C and given access to a hitting set generator, constructs a discrepancy set for C . The main novelty is that the discrepancy set depends on C , so the new derandomization method is not uniform (i.e., not oblivious ). The algorithm works in time exponential in k(p(n)) where k () is the price of the hitting set generator and p () is a polynomial function in the size of C . We thus prove that if a logarithmic price quick hitting set generator exists then BPP = P. --- paper_title: BPP has subexponential time simulations unless EXPTIME has publishable proofs paper_content: It is shown that BPP can be simulated in subexponential time for infinitely many input lengths unless exponential time collapses to the second level of the polynomial-time hierarchy, has polynomial-size circuits, and has publishable proofs (EXPTIME=MA). It is also shown that BPP is contained in subexponential time unless exponential time has publishable proofs for infinitely many input lengths. In addition, it is shown that BPP can be simulated in subexponential time for infinitely many input lengths unless there exist unary languages in MA/P. The proofs are based on the recent characterization of the power of multiprover interactive protocols and on random self-reducibility via low degree polynomials. They exhibit an interplay between Boolean circuit simulation, interactive proofs and classical complexity classes. An important feature of this proof is that it does not relativize.<<ETX>> --- paper_title: Decoding of Reed Solomon codes beyond the error-correction bound paper_content: We present a randomized algorithm which takes as inputndistinct points {(xi,yi)}i= 1nfromF×F(whereFis a field) and integer parameterstanddand returns a list of all univariate polynomialsfoverFin the variablexof degree at mostdwhich agree with the given set of points in at leasttplaces (i.e.,yi=f(xi) for at leasttvalues ofi), providedt= ?(nd). The running time is bounded by a polynomial inn. This immediately provides a maximum likelihood decoding algorithm for Reed Solomon Codes, which works in a setting with a larger number of errors than any previously known algorithm. To the best of our knowledge, this is the first efficient (i.e., polynomial time bounded) algorithm which provides error recovery capability beyond the error-correction bound of a code for any efficient (i.e., constant or even polynomial rate) code. --- paper_title: Improved low-degree testing and its applications paper_content: NP = PCP(logn, 1) and related results crucially depend upon the close connection between the probability with which a function passes a low degree test and the distance of this function to the nearest degree d polynomial. In this paper we study a test proposed by Rubinfeld and Sudan [30]. The strongest previously known connection for this test states that a function passes the test with probability δ for some δ > 7/8 iff the function has agreement ≈ δ with a polynomial of degree d. We present a new, and surprisingly strong, analysis which shows that the preceding statement is true for arbitrarily small δ, provided the field size is polynomially larger than d/δ. The analysis uses a version of Hilbert irreducibility, a tool of algebraic geometry. As a consequence we obtain an alternate construction for the following proof system: A constant prover 1-round proof system for NP languages in which the verifier uses O(logn) random bits, receives answers of size O(logn) bits, and has an error probability of at most 2− log 1− . Such a proof system, which implies the NP-hardness of approximating Set Cover to within Ω(logn) factors, has already been obtained by Raz and Safra [29]. Raz and Safra obtain their result by giving a strong analysis, in the sense described above, of a new low-degree test that they present. A second consequence of our analysis is a self tester/corrector for any buggy program that (supposedly) computes a polynomial over a finite field. If the program is correct only on δ fraction of inputs where δ = 1/ \|F\| 0.5, then the tester/corrector determines δ and generates O( 1 δ ) values for every input, such that one of them is the correct output. In fact, our results yield something stronger: Given the buggy program, we can construct O( 1 δ ) randomized programs such that one of them is correct on every input, with high probability. Such a strong selfcorrector is a useful tool in complexity theory with some applications known. ∗[email protected]. Supported by an NSF CAREER award, an Alfred P. Sloan Fellowship, and a Packard Fellowship. †[email protected]. Laboratory for Computer Science, MIT, Cambridge, MA 02139. Part of this work was done when this author was at the IBM Thomas J. Watson Research Center. --- paper_title: Pseudorandom generators without the XOR Lemma paper_content: Summary form only given. R. Impagliazzo and A. Wigderson (1997) have recently shown that if there exists a decision problem solvable in time 2/sup O(n)/ and having circuit complexity 2/sup /spl Omega/(n)/ (for all but finitely many n) then P=BPP. This result is a culmination of a series of works showing connections between the existence of hard predicates and the existence of good pseudorandom generators. The construction of Impagliazzo and Wigderson goes through three phases of "hardness amplification" (a multivariate polynomial encoding, a first derandomized XOR Lemma, and a second derandomized XOR Lemma) that are composed with the Nisan-Wigderson (1994) generator. In this paper we present two different approaches to proving the main result of Impagliazzo and Wigderson. In developing each approach, we introduce new techniques and prove new results that could be useful in future improvements and/or applications of hardness-randomness trade-offs. --- paper_title: List decoding: algorithms and applications paper_content: Over the years coding theory and complexity theory have benefited from a number of mutually enriching connections. This article focuses on a new connection that has emerged between the two topics in the recent years. This connection is centered around the notion of “list-decoding” for error-correcting codes. In this survey we describe the list-decoding problem, the algorithms that have been developed, and a diverse collection of applications within complexity theory. --- paper_title: Binary codes with specified minimum distance paper_content: Two n -digit sequences, called "points," of binary digits are said to be at distance d if exactly d corresponding digits are unlike in the two sequences. The construction of sets of points, called codes, in which some specified minimum distance is maintained between pairs of points is of interest in the design of self-checking systems for computing with or transmitting binary digits, the minimum distance being the minimum number of digital errors required to produce an undetected error in the system output. Previous work in the field had established general upper bounds for the number of n -digit points in codes of minimum distance d with certain properties. This paper gives new results in the field in the form of theorems which permit systematic construction of codes for given n, d ; for some n, d , the codes contain the greatest possible numbers of points. --- paper_title: Graph nonisomorphism has subexponential size proofs unless the polynomial-time hierarchy collapses paper_content: We establish hardness versus randomness trade-offs for a broad class of randomized procedures. In particular, we create efficient nondeterministic simulations of bounded round Arthur-Merlin games using a language in exponential time that cannot be decided by polynomial size oracle circuits with access to satisfiability. We show that every language with a bounded round Arthur-Merlin game has subexponential size membership proofs for infinitely many input lengths unless the polynomial-time hierarchy collapses. This provides the first strong evidence that graph nonisomorphism has subexponential size proofs. We set up a general framework for derandomization which encompasses more than the traditional model of randomized computation. For a randomized procedure to fit within this framework, we only require that for any fixed input the complexity of checking whether the procedure succeeds on a given random bit sequence is not too high. We then apply our derandomization technique to four fundamental complexity theoretic constructions: The Valiant-Vazirani random hashing technique which prunes the number of satisfying assignments of a Boolean formula to one, and related procedures like computing satisfying assignments to Boolean formulas non-adaptively given access to an oracle for satisfiability. The algorithm of Bshouty et al. for learning Boolean circuits. Constructing matrices with high rigidity. Constructing polynomial-size universal traversal sequences. We also show that if linear space requires exponential size circuits, then space bounded randomized computations can be simulated deterministically with only a constant factor overhead in space. --- paper_title: BPP has subexponential time simulations unless EXPTIME has publishable proofs paper_content: It is shown that BPP can be simulated in subexponential time for infinitely many input lengths unless exponential time collapses to the second level of the polynomial-time hierarchy, has polynomial-size circuits, and has publishable proofs (EXPTIME=MA). It is also shown that BPP is contained in subexponential time unless exponential time has publishable proofs for infinitely many input lengths. In addition, it is shown that BPP can be simulated in subexponential time for infinitely many input lengths unless there exist unary languages in MA/P. The proofs are based on the recent characterization of the power of multiprover interactive protocols and on random self-reducibility via low degree polynomials. They exhibit an interplay between Boolean circuit simulation, interactive proofs and classical complexity classes. An important feature of this proof is that it does not relativize.<<ETX>> --- paper_title: Trading group theory for randomness paper_content: In a previous paper [BS] we proved, using the elements of the theory of nilpotent groups , that some of the fundamental computational problems in matriz groups belong to NP . These problems were also shown to belong to coNP , assuming an unproven hypothesis concerning finite simple groups . The aim of this paper is to replace most of the (proven and unproven) group theory of [BS] by elementary combinatorial arguments. The result we prove is that relative to a random oracle B , the mentioned matrix group problems belong to ( NP∩coNP ) B . The problems we consider are membership in and order of a matrix group given by a list of generators. These problems can be viewed as multidimensional versions of a close relative of the discrete logarithm problem. Hence NP∩coNP might be the lowest natural complexity class they may fit in. We remark that the results remain valid for black box groups where group operations are performed by an oracle. The tools we introduce seem interesting in their own right. We define a new hierarchy of complexity classes AM ( k ) “just above NP ”, introducing Arthur vs. Merlin games , the bounded-away version of Papdimitriou's Games against Nature . We prove that in spite of their analogy with the polynomial time hierarchy, the finite levels of this hierarchy collapse to AM=AM (2). Using a combinatorial lemma on finite groups [BE], we construct a game by which the nondeterministic player (Merlin) is able to convince the random player (Arthur) about the relation [ G ]= N provided Arthur trusts conclusions based on statistical evidence (such as a Slowly-Strassen type “proof” of primality). One can prove that AM consists precisely of those languages which belong to NP B for almost every oracle B . Our hierarchy has an interesting, still unclarified relation to another hierarchy, obtained by removing the central ingredient from the User vs. Expert games of Goldwasser, Micali and Rackoff. --- paper_title: Near-optimal conversion of hardness into pseudo-randomness paper_content: Various efforts have been made to derandomize probabilistic algorithms using the assumption that there exists a problem in E=dtime(2/sup O(n)/) that requires circuits of size s(n) (for some function s). These results are based on the NW (Nisan & Wigderson, 1997) generator. For the strong lower bound s(n)=2/sup /spl epsi/n/, the optimal derandomization is P=BPP. However, for weaker lower bound functions s(n), these constructions fall short of the natural conjecture for optimal derandomization that bptime(t)/spl sube/ dtime(2?O[s/sup -1/(t)]). The gap is due to an inherent efficiency limitation in NW-style pseudorandom generators. We are able to obtain derandomization in almost optimal time using any lower bound s(n). We do this by using the NW-generator in a more sophisticated way. We view any failure of the generator as a reduction from the given hard function to its restrictions on smaller input sizes. Thus, either the original construction works optimally or one of the restricted functions is as hard as the original. Any such restriction can then be plugged into the NW-generator recursively. This process generates many candidate generators, and at least one is guaranteed to be good. To perform the approximation of the acceptance probability of the given circuit, we run a tournament between the candidate generators which yields an accurate estimate. We explore information theoretic analogs of our new construction. The inherent limitation of the NW-generator makes the extra randomness required by that extractor suboptimal. However, applying our construction, we get an almost optimal disperser. --- paper_title: Simple extractors for all min-entropies and a new pseudorandom generator paper_content: A “randomness extractor” is an algorithm that given a sample from a distribution with sufficiently high min-entropy and a short random seed produces an output that is statistically indistinguishable from uniform. (Min-entropy is a measure of the amount of randomness in a distribution.) We present a simple, self-contained extractor construction that produces good extractors for all min-entropies. Our construction is algebraic and builds on a new polynomial-based approach introduced by Ta-Shma et al. [2001b]. Using our improvements, we obtain, for example, an extractor with output length m = k/(log n)O(1/α) and seed length (1 p α)log n for an arbitrary 0 < α ≤ 1, where n is the input length, and k is the min-entropy of the input distribution.A “pseudorandom generator” is an algorithm that given a short random seed produces a long output that is computationally indistinguishable from uniform. Our technique also gives a new way to construct pseudorandom generators from functions that require large circuits. Our pseudorandom generator construction is not based on the Nisan-Wigderson generator [Nisan and Wigderson 1994], and turns worst-case hardness directly into pseudorandomness. The parameters of our generator match those in Impagliazzo and Wigderson [1997] and Sudan et al. [2001] and in particular are strong enough to obtain a new proof that P = BPP if E requires exponential size circuits.Our construction also gives the following improvements over previous work:---We construct an optimal “hitting set generator” that stretches O(log n) random bits into sΩ(1) pseudorandom bits when given a function on log n bits that requires circuits of size s. This yields a quantitatively optimal hardness versus randomness tradeoff for both RP and BPP and solves an open problem raised in Impagliazzo et al. [1999].---We give the first construction of pseudorandom generators that fool nondeterministic circuits when given a function that requires large nondeterministic circuits. This technique also give a quantitatively optimal hardness versus randomness tradeoff for AM and the first hardness amplification result for nondeterministic circuits. --- paper_title: A new general derandomization method paper_content: We show that quick hitting set generators can replace quick pseudorandom generators to derandomize any probabilistic two-sided error algorithms. Up to now quick hitting set generators have been known as the general and uniform derandomization method for probabilistic one-sided error algorithms, while quick pseudorandom generators as the generators as the general and uniform method to derandomize probabilistic two-sided error algorithms. Our method is based on a deterministic algorithm that, given a Boolean circuit C and given access to a hitting set generator, constructs a discrepancy set for C . The main novelty is that the discrepancy set depends on C , so the new derandomization method is not uniform (i.e., not oblivious ). The algorithm works in time exponential in k(p(n)) where k () is the price of the hitting set generator and p () is a polynomial function in the size of C . We thus prove that if a logarithmic price quick hitting set generator exists then BPP = P. --- paper_title: Another proof that BPP ⊆ PH (and more paper_content: We provide another proof of the Sipser-Lautemann Theorem by which BPP ⊆ MA (⊆ PH). The current proof is based on strong results regarding the amplification of BPP, due to Zuckerman (1996). Given these results, the current proof is even simpler than previous ones. Furthermore, extending the proof leads to two results regarding MA: MA ⊆ ZPPNP (which seems to be new), and that two-sided error MA equals MA. Finally, we survey the known facts regarding the fragment of the polynomial-time hierarchy that contains MA. --- paper_title: NP is as easy as detecting unique solutions paper_content: Abstract For every known NP-complete problem, the number of solutions of its instances varies over a large range, from zero to exponentially many. It is therefore natural to ask if the inherent intractability of NP-complete problem is caused by this wide variation. We give a negative answer to this question using the notion of randomized polynomial time reducibility. We show that the problems of distinguishing between instances of SAT having zero or one solution, or of finding solutions to instances of SAT having a unique solution, are as hard as SAT, under randomized reductions. Several corollaries about the difficulty of specific problems follow. For example, computing the parity of the number of solutions of a SAT formula is shown to be NP-hard, and deciding if a SAT formula has a unique solution is shown to be D p -hard, under randomized reduction. Central to the study of cryptography is the question as to whether there exist NP-problems whose instances have solutions that are unique but are hard to find. Our result can be interpreted as strengthening the belief that such problems exist. --- paper_title: Graph nonisomorphism has subexponential size proofs unless the polynomial-time hierarchy collapses paper_content: We establish hardness versus randomness trade-offs for a broad class of randomized procedures. In particular, we create efficient nondeterministic simulations of bounded round Arthur-Merlin games using a language in exponential time that cannot be decided by polynomial size oracle circuits with access to satisfiability. We show that every language with a bounded round Arthur-Merlin game has subexponential size membership proofs for infinitely many input lengths unless the polynomial-time hierarchy collapses. This provides the first strong evidence that graph nonisomorphism has subexponential size proofs. We set up a general framework for derandomization which encompasses more than the traditional model of randomized computation. For a randomized procedure to fit within this framework, we only require that for any fixed input the complexity of checking whether the procedure succeeds on a given random bit sequence is not too high. We then apply our derandomization technique to four fundamental complexity theoretic constructions: The Valiant-Vazirani random hashing technique which prunes the number of satisfying assignments of a Boolean formula to one, and related procedures like computing satisfying assignments to Boolean formulas non-adaptively given access to an oracle for satisfiability. The algorithm of Bshouty et al. for learning Boolean circuits. Constructing matrices with high rigidity. Constructing polynomial-size universal traversal sequences. We also show that if linear space requires exponential size circuits, then space bounded randomized computations can be simulated deterministically with only a constant factor overhead in space. --- paper_title: Simple extractors for all min-entropies and a new pseudorandom generator paper_content: A “randomness extractor” is an algorithm that given a sample from a distribution with sufficiently high min-entropy and a short random seed produces an output that is statistically indistinguishable from uniform. (Min-entropy is a measure of the amount of randomness in a distribution.) We present a simple, self-contained extractor construction that produces good extractors for all min-entropies. Our construction is algebraic and builds on a new polynomial-based approach introduced by Ta-Shma et al. [2001b]. Using our improvements, we obtain, for example, an extractor with output length m = k/(log n)O(1/α) and seed length (1 p α)log n for an arbitrary 0 < α ≤ 1, where n is the input length, and k is the min-entropy of the input distribution.A “pseudorandom generator” is an algorithm that given a short random seed produces a long output that is computationally indistinguishable from uniform. Our technique also gives a new way to construct pseudorandom generators from functions that require large circuits. Our pseudorandom generator construction is not based on the Nisan-Wigderson generator [Nisan and Wigderson 1994], and turns worst-case hardness directly into pseudorandomness. The parameters of our generator match those in Impagliazzo and Wigderson [1997] and Sudan et al. [2001] and in particular are strong enough to obtain a new proof that P = BPP if E requires exponential size circuits.Our construction also gives the following improvements over previous work:---We construct an optimal “hitting set generator” that stretches O(log n) random bits into sΩ(1) pseudorandom bits when given a function on log n bits that requires circuits of size s. This yields a quantitatively optimal hardness versus randomness tradeoff for both RP and BPP and solves an open problem raised in Impagliazzo et al. [1999].---We give the first construction of pseudorandom generators that fool nondeterministic circuits when given a function that requires large nondeterministic circuits. This technique also give a quantitatively optimal hardness versus randomness tradeoff for AM and the first hardness amplification result for nondeterministic circuits. --- paper_title: Derandomizing Arthur–Merlin Games using Hitting Sets paper_content: We prove that AM (and hence Graph Nonisomorphism) is in NP if for some e > 0, some language in NE ∩ coNE requires nondeterministic circuits of size 2en. This improves results of Arvind and Kobler and of Klivans and van Melkebeek who proved the same conclusion, but under stronger hardness assumptions.The previous results on derandomizing AM were based on pseudorandom generators. In contrast, our approach is based on a strengthening of Andreev, Clementi and Rolim's hitting set approach to derandomization. As a spin-off, we show that this approach is strong enough to give an easy proof of the following implication: for some e > 0, if there is a language in E which requires nondeterministic circuits of size 2en, then P = BPP. This differs from Impagliazzo and Wigderson's theorem "only" by replacing deterministic circuits with nondeterministic ones. --- paper_title: Extractors from Reed-Muller codes paper_content: Finding explicit extractors is an important derandomization goal that has received a lot of attention in the past decade. Previous research has focused on two approaches, one related to hashing and the other to pseudorandom generators. A third view, regarding extractors as good error correcting codes, was noticed before. Yet, researchers had failed to build extractors directly from a good code without using other tools from pseudorandomness. We succeed in constructing an extractor directly from a Reed-Muller code. To do this, we develop a novel proof technique. Furthermore, our construction is the first to achieve a degree close to linear. In contrast, the best previous constructions brought the log of the degree within a constant of optimal, which gives polynomial degree. This improvement is important for certain applications. For example, it follows that approximating the VC dimension to within a factor of N/sup 1-/spl delta// is AM-hard for any positive /spl delta/. --- paper_title: Simple extractors for all min-entropies and a new pseudorandom generator paper_content: A “randomness extractor” is an algorithm that given a sample from a distribution with sufficiently high min-entropy and a short random seed produces an output that is statistically indistinguishable from uniform. (Min-entropy is a measure of the amount of randomness in a distribution.) We present a simple, self-contained extractor construction that produces good extractors for all min-entropies. Our construction is algebraic and builds on a new polynomial-based approach introduced by Ta-Shma et al. [2001b]. Using our improvements, we obtain, for example, an extractor with output length m = k/(log n)O(1/α) and seed length (1 p α)log n for an arbitrary 0 < α ≤ 1, where n is the input length, and k is the min-entropy of the input distribution.A “pseudorandom generator” is an algorithm that given a short random seed produces a long output that is computationally indistinguishable from uniform. Our technique also gives a new way to construct pseudorandom generators from functions that require large circuits. Our pseudorandom generator construction is not based on the Nisan-Wigderson generator [Nisan and Wigderson 1994], and turns worst-case hardness directly into pseudorandomness. The parameters of our generator match those in Impagliazzo and Wigderson [1997] and Sudan et al. [2001] and in particular are strong enough to obtain a new proof that P = BPP if E requires exponential size circuits.Our construction also gives the following improvements over previous work:---We construct an optimal “hitting set generator” that stretches O(log n) random bits into sΩ(1) pseudorandom bits when given a function on log n bits that requires circuits of size s. This yields a quantitatively optimal hardness versus randomness tradeoff for both RP and BPP and solves an open problem raised in Impagliazzo et al. [1999].---We give the first construction of pseudorandom generators that fool nondeterministic circuits when given a function that requires large nondeterministic circuits. This technique also give a quantitatively optimal hardness versus randomness tradeoff for AM and the first hardness amplification result for nondeterministic circuits. --- paper_title: Randomness vs. time: de-randomization under a uniform assumption paper_content: We prove that if BPP/spl ne/EXP, then every problem in BPP can be solved deterministically in subexponential time on almost every input (on every samplable ensemble for infinitely many input sizes). This is the first derandomization result for BPP based on uniform, noncryptographic hardness assumptions. It implies the following gap in the average-instance complexities of problems in BPP: either these complexities are always sub-exponential or they contain arbitrarily large exponential functions. We use a construction of a small "pseudorandom" set of strings from a "hard function" in EXP which is identical to that used in the analogous non-uniform results described previously. However, previous proofs of correctness assume the "hard function" is not in P/poly. They give a non-constructive argument that a circuit distinguishing the pseudo-random strings from truly random strings implies that a similarly-sized circuit exists computing the "hard function". Our main technical contribution is to show that, if the "hard function" has certain properties, then this argument can be made constructive. We then show that, assuming ESP/spl sube/P/poly, there are EXP-complete functions with these properties. --- paper_title: The complexity of computing the permanent paper_content: Abstract It is shown that the permanent function of (0, 1)-matrices is a complete problem for the class of counting problems associated with nondeterministic polynomial time computations. Related counting problems are also considered. The reductions used are characterized by their nontrivial use of arithmetic. --- paper_title: BPP has subexponential time simulations unless EXPTIME has publishable proofs paper_content: It is shown that BPP can be simulated in subexponential time for infinitely many input lengths unless exponential time collapses to the second level of the polynomial-time hierarchy, has polynomial-size circuits, and has publishable proofs (EXPTIME=MA). It is also shown that BPP is contained in subexponential time unless exponential time has publishable proofs for infinitely many input lengths. In addition, it is shown that BPP can be simulated in subexponential time for infinitely many input lengths unless there exist unary languages in MA/P. The proofs are based on the recent characterization of the power of multiprover interactive protocols and on random self-reducibility via low degree polynomials. They exhibit an interplay between Boolean circuit simulation, interactive proofs and classical complexity classes. An important feature of this proof is that it does not relativize.<<ETX>> --- paper_title: PP IS AS HARD AS THE POLYNOMIAL-TIME HIERARCHY* paper_content: In this paper, two interesting complexity classes, PP and $ \oplus {\text{P}}$, are compared with PH, the polynomial-time hierarchy. It is shown that every set in PH is polynomial-time Turing reducible to a set in PP, and PH is included in ${\text{BP}} \cdot \oplus {\text{P}}$. As a consequence of the results, it follows that ${\text{PP}} \subseteq {\text{PH}}$ (or $\oplus {\text{P}} \subseteq {\text{PH}}$) implies a collapse of PH. A stronger result is also shown: every set in PP(PH) is polynomial-time Turing reducible to a set in PP. --- paper_title: Algebraic methods for interactive proof systems paper_content: A new algebraic technique for the construction of interactive proof systems is presented. Our technique is used to prove that every language in the polynomial-time hierarchy has an interactive proof system. This technique played a pivotal role in the recent proofs that IP = PSPACE [28] and that MIP = NEXP [4]. --- paper_title: The complexity of computing the permanent paper_content: Abstract It is shown that the permanent function of (0, 1)-matrices is a complete problem for the class of counting problems associated with nondeterministic polynomial time computations. Related counting problems are also considered. The reductions used are characterized by their nontrivial use of arithmetic. --- paper_title: Pseudorandomness and average-case complexity via uniform reductions paper_content: Impagliazzo and Wigderson (1998) gave the first construction of pseudorandom generators from a uniform complexity assumption on EXP (namely EXP = BPP). Unlike results in the nonuniform setting, their result does not provide a continuous trade-off between worst-case hardness and pseudorandomness, nor does it explicitly establish an average-case hardness result. We obtain an optimal worst-case to average-case connection for EXP: if EXP BPTIME(( )), EXP has problems that are cannot be solved on a fraction 1/2 1/'( ) of the inputs by BPTIME('( )) algorithms, for ' = /sup 1/. We exhibit a PSPACE-complete downward self-reducible and random self-reducible problem. This slightly simplifies and strengthens the proof of Impagliazzo and Wigderson (1998), which used a a P-complete problem with these properties. We argue that the results in Impagliazzo and Wigderson (1998) and in this paper cannot be proved via "black-box" uniform reductions. --- paper_title: PP IS AS HARD AS THE POLYNOMIAL-TIME HIERARCHY* paper_content: In this paper, two interesting complexity classes, PP and $ \oplus {\text{P}}$, are compared with PH, the polynomial-time hierarchy. It is shown that every set in PH is polynomial-time Turing reducible to a set in PP, and PH is included in ${\text{BP}} \cdot \oplus {\text{P}}$. As a consequence of the results, it follows that ${\text{PP}} \subseteq {\text{PH}}$ (or $\oplus {\text{P}} \subseteq {\text{PH}}$) implies a collapse of PH. A stronger result is also shown: every set in PP(PH) is polynomial-time Turing reducible to a set in PP. --- paper_title: Pseudorandom generators without the XOR Lemma paper_content: Summary form only given. R. Impagliazzo and A. Wigderson (1997) have recently shown that if there exists a decision problem solvable in time 2/sup O(n)/ and having circuit complexity 2/sup /spl Omega/(n)/ (for all but finitely many n) then P=BPP. This result is a culmination of a series of works showing connections between the existence of hard predicates and the existence of good pseudorandom generators. The construction of Impagliazzo and Wigderson goes through three phases of "hardness amplification" (a multivariate polynomial encoding, a first derandomized XOR Lemma, and a second derandomized XOR Lemma) that are composed with the Nisan-Wigderson (1994) generator. In this paper we present two different approaches to proving the main result of Impagliazzo and Wigderson. In developing each approach, we introduce new techniques and prove new results that could be useful in future improvements and/or applications of hardness-randomness trade-offs. --- paper_title: Derandomizing Arthur-Merlin Games under Uniform Assumptions paper_content: We study how the nondeterminism versus determinism problem and the time versus space problem are related to the problem of derandomization. In particular, we show two ways of derandomizing the complexity class AM under uniform assumptions, which was only known previously under non-uniform assumptions [13,14]. First, we prove that either AM = NP or it appears to any nondeterministic polynomial time adversary that NP is contained in deterministic subexponential time infinitely often. This implies that to any nondeterministic polynomial time adversary, the graph non-isomorphism problem appears to have subexponential-size proofs infinitely often, the first nontrivial derandomization of this problem without any assumption. Next, we show that either all BPP = P, AM = NP, and PH ⊆ ⊕P hold, or for any t(n) = 2Ω(n), DTIME(t(n)) ⊆ DSPACE(tƐ(n)) infinitely often for any constant Ɛ > 0. Similar tradeoffs also hold for a whole range of parameters. This improves previous results [17,5] and seems to be the first example of an interesting condition that implies three derandomiztion results at once. --- paper_title: Efficiently Approximable Real-Valued Functions paper_content: We define a class, denoted APP, of real-valued functions f : {0, 1}n → [0, 1] such that f can be approximated to within any > 0 by a probabilistic Turing machine running in time poly(n, 1/ ). The class APP can be viewed as a generalization of BPP. We argue that APP is more natural and more important than BPP, and that most results about BPP are better stated as results about APP. We show that APP contains a natural complete problem: computing the acceptance probability of a given Boolean circuit. In contrast, no complete problem is known for BPP. We observe that all known complexity-theoretic assumptions under which BPP can be derandomized also allow APP to be derandomized. On the other hand we construct an oracle under which BPP = P but APP does not collapse to the corresponding deterministic class AP. (However any oracle collapsing APP to AP also collapses BPP to P.) --- paper_title: Comparing notions of full derandomization paper_content: Most of the hypotheses of full derandomization fall into two sets of equivalent statements: those equivalent to the existence of efficient pseudorandom generators and those equivalent to approximating the accepting probability of a circuit. We give the first relativized world where these sets of equivalent statements are not equivalent to each other. --- paper_title: In search of an easy witness: exponential time vs. probabilistic polynomial time paper_content: Restricting the search space (0, l}” to the set of truth tables of “easy” Boolean functions on log 1% variables, as well as using some known hardness-randomness tradeoff., we establish a number of results relating the complexi@ of exponential-time and probabilistic polynomial-time coniplexity classes. In particular; we show that NEXP C P/poly e NEXP = MA; this can be interpreted to say that no derandomization of MA (and, hence, of promise- BPP) is possible unless N EXP contains a hard Boolean function. We also prove several downward closure results for ZPP, RP, BPP, and MA; e.g., we show EXP = BPP EE = BPE, where EE is the double-exponential time class and BPE is the exponential-time analogue of BPP. --- paper_title: Derandomizing Arthur–Merlin Games using Hitting Sets paper_content: We prove that AM (and hence Graph Nonisomorphism) is in NP if for some e > 0, some language in NE ∩ coNE requires nondeterministic circuits of size 2en. This improves results of Arvind and Kobler and of Klivans and van Melkebeek who proved the same conclusion, but under stronger hardness assumptions.The previous results on derandomizing AM were based on pseudorandom generators. In contrast, our approach is based on a strengthening of Andreev, Clementi and Rolim's hitting set approach to derandomization. As a spin-off, we show that this approach is strong enough to give an easy proof of the following implication: for some e > 0, if there is a language in E which requires nondeterministic circuits of size 2en, then P = BPP. This differs from Impagliazzo and Wigderson's theorem "only" by replacing deterministic circuits with nondeterministic ones. --- paper_title: Nonrelativizing separations paper_content: We show that MA/sub EXP/, the exponential time version of the Merlin-Arthur class, does not have polynomial size circuits. This significantly improves the previous known result due to Kannan since we furthermore show that our result does not relativize. This is the first separation result in complexity theory that does not relativize. As a corollary to our separation result we also obtain that PEXP, the exponential time version of PP is nor in P/poly. --- paper_title: Non-Deterministic Exponential Time has Two-Prover Interactive Protocols paper_content: We determine the exact power of two-prover interactive proof systems introduced by Ben-Or, Goldwasser, Kilian, and Wigderson (1988). In this system, two all-powerful noncommunicating provers convince a randomizing polynomial time verifier in polynomial time that the inputx belongs to the languageL. We show that the class of languages having tow-prover interactive proof systems is nondeterministic exponential time.We also show that to prove membership in languages inEXP, the honest provers need the power ofEXP only.The first part of the proof of the main result extends recent techniques of polynomial extrapolation used in the single prover case by Lund, Fortnow, Karloff, Nisan, and Shamir.The second part is averification scheme for multilinearity of a function in several variables held by an oracle and can be viewed as an independent result onprogram verification. Its proof rests on combinatorial techniques employing a simple isoperimetric inequality for certain graphs: --- paper_title: Derandomizing Polynomial Identity Tests Means Proving Circuit Lower Bounds paper_content: We show that derandomizing Polynomial Identity Testing is essentially equivalent to proving arithmetic circuit lower bounds for NEXP. More precisely, we prove that if one can test in polynomial time (or even nondeterministic subexponential time, infinitely often) whether a given arithmetic circuit over integers computes an identically zero polynomial, then either (i) NEXP ⊄ P/poly or (ii) Permanent is not computable by polynomial-size arithmetic circuits. We also prove a (partial) converse: If Permanent requires superpolynomial-size arithmetic circuits, then one can test in subexponential time whether a given arithmetic circuit of polynomially bounded degree computes an identically zero polynomial.Since Polynomial Identity Testing is a coRP problem, we obtain the following corollary: If RP = P (or even coRP ⊆ ∩e > 0 NTIME(2ne), infinitely often), then NEXP is not computable by polynomial-size arithmetic circuits. Thus establishing that RP = coRP or BPP = P would require proving superpolynomial lower bounds for Boolean or arithmetic circuits. We also show that any derandomization of RNC would yield new circuit lower bounds for a language in NEXP.We also prove unconditionally that NEXPRP does not have polynomial-size Boolean or arithmetic circuits. Finally, we show that NEXP ⊄ P/poly if both BPP = P and low-degree testing is in P; here low-degree testing is the problem of checking whether a given Boolean circuit computes a function that is close to some low-degree polynomial over a finite field. --- paper_title: The complexity of computing the permanent paper_content: Abstract It is shown that the permanent function of (0, 1)-matrices is a complete problem for the class of counting problems associated with nondeterministic polynomial time computations. Related counting problems are also considered. The reductions used are characterized by their nontrivial use of arithmetic. --- paper_title: PP IS AS HARD AS THE POLYNOMIAL-TIME HIERARCHY* paper_content: In this paper, two interesting complexity classes, PP and $ \oplus {\text{P}}$, are compared with PH, the polynomial-time hierarchy. It is shown that every set in PH is polynomial-time Turing reducible to a set in PP, and PH is included in ${\text{BP}} \cdot \oplus {\text{P}}$. As a consequence of the results, it follows that ${\text{PP}} \subseteq {\text{PH}}$ (or $\oplus {\text{P}} \subseteq {\text{PH}}$) implies a collapse of PH. A stronger result is also shown: every set in PP(PH) is polynomial-time Turing reducible to a set in PP. --- paper_title: Graph nonisomorphism has subexponential size proofs unless the polynomial-time hierarchy collapses paper_content: We establish hardness versus randomness trade-offs for a broad class of randomized procedures. In particular, we create efficient nondeterministic simulations of bounded round Arthur-Merlin games using a language in exponential time that cannot be decided by polynomial size oracle circuits with access to satisfiability. We show that every language with a bounded round Arthur-Merlin game has subexponential size membership proofs for infinitely many input lengths unless the polynomial-time hierarchy collapses. This provides the first strong evidence that graph nonisomorphism has subexponential size proofs. We set up a general framework for derandomization which encompasses more than the traditional model of randomized computation. For a randomized procedure to fit within this framework, we only require that for any fixed input the complexity of checking whether the procedure succeeds on a given random bit sequence is not too high. We then apply our derandomization technique to four fundamental complexity theoretic constructions: The Valiant-Vazirani random hashing technique which prunes the number of satisfying assignments of a Boolean formula to one, and related procedures like computing satisfying assignments to Boolean formulas non-adaptively given access to an oracle for satisfiability. The algorithm of Bshouty et al. for learning Boolean circuits. Constructing matrices with high rigidity. Constructing polynomial-size universal traversal sequences. We also show that if linear space requires exponential size circuits, then space bounded randomized computations can be simulated deterministically with only a constant factor overhead in space. ---	Title: Derandomization: a brief overview Section 1: History Description 1: Provide a historical context and background on derandomization, including the emergence and significance of randomized algorithms and the belief that BPP may be equal to P. Section 2: Hardness-randomness tradeoffs Description 2: Discuss the core concept of trading computational hardness for randomness and the fundamental results and examples supporting this idea. Section 3: The Nisan-Wigderson generator Description 3: Explain the significance of the NW generator, its construction, and how it improves upon previous results by using hardness assumptions. Section 4: Worst-case hardness-randomness tradeoffs Description 4: Detail the advancements in derandomization achieved through focusing on worst-case hardness and its implications for proving BPP = P. Section 5: Hitting-set generators Description 5: Describe the concept of hitting-set generators, their construction, and their role in achieving derandomization results. Section 6: Recent developments Description 6: Summarize recent advances in derandomization research, including improvements in hardness-randomness tradeoffs and new applications. Section 7: Achieving optimal hardness-randomness tradeoffs Description 7: Discuss what constitutes an optimal hardness-randomness tradeoff and recent results that approach or achieve these optimal tradeoffs. Section 8: Beyond computational complexity Description 8: Explore the implications and applications of hardness-randomness tradeoffs beyond the realm of computational complexity, such as in information theory. Section 9: Back to computational complexity Description 9: Examine how insights from the information-theoretic setting can be used to improve computational complexity results, particularly in constructing extractors. Section 10: Derandomizing BPP Description 10: Provide an in-depth look at the methods and results for derandomizing the class BPP, including both non-uniform and uniform hardness assumptions. Section 11: Derandomizing RP Description 11: Discuss techniques specific to derandomizing the class RP, along with relevant results and their proofs. Section 12: Derandomizing AM Description 12: Detail the challenges and results related to derandomizing the class AM, including significant theorems and their implications. Section 13: Circuit lower bounds from the derandomization of MA Description 13: Investigate the connection between derandomization of MA and circuit lower bounds, including key results and their proofs. Section 14: Circuit lower bounds from the derandomization of BPP Description 14: Explore recent findings that link derandomizing BPP to proving circuit lower bounds for classes like NEXP and the Permanent function. Section 15: Other Results Description 15: Highlight additional results and advancements in derandomization and complexity theory, covering a variety of topics and open questions. Section 16: What Next? Description 16: Discuss open problems and future directions in derandomization research, with a focus on extending current results and addressing unresolved questions.
Open Versus Closed Hearing-Aid Fittings: A Literature Review of Both Fitting Approaches	15	--- paper_title: Occlusion effect of earmolds with different venting systems. paper_content: In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions. --- paper_title: Acoustic Attenuation between the Ears paper_content: In an investigation of the acoustical insulation between the ears, various earphones and obturating devices were used. Bone conduction was shown to be chiefly responsible for the acoustical leakage between the ears. Conditions were determined under which interaural insulation could be increased considerably. Most of the measurements were performed with a compensation method which appears to give more precise results than methods previously used, and which permits phase measurements. --- paper_title: A Multicenter Trial of an Assess-and-Fit Hearing Aid Service Using Open Canal Fittings and Comply Ear Tips paper_content: Large potential benefits have been suggested for an assess-and-fit approach to hearing health care, particularly using open canal fittings. However, the clinical effectiveness has not previously been evaluated, nor has the efficiency of this approach in a National Health Service setting. These two outcomes were measured in a variety of clinical settings in the United Kingdom. Twelve services in England and Wales participated, and 540 people with hearing problems, not previously referred for assessment, were included. Of these, 68% (n = 369) were suitable and had hearing aids fitted to NAL NL1 during the assess-and-fit visit using either open ear tips, or Comply ear tips. The Glasgow Hearing Aid Benefit Profile was used to compare patients fitted with open ear tips with a group of patients from the English Modernization of Hearing Aid Services evaluation, who used custom earmolds. This showed a significant improvement in outcome for those with open ear tips after allowing for age and hearing loss in the analysis. In particular, the benefits of using bilateral open ear tips were significantly larger than bilateral custom ear-molds. This assess-and-fit model showed a mean service efficiency gain of about 5% to 10%. The actual gain will depend on current practice, in particular on the separate appointments used, the numbers of patients failing to attend appointments, and the numbers not accepting a hearing aid solution for their problem. There are potentially further efficiency and quality gains to be made if patients are appropriately triaged before referral. --- paper_title: Preferred signal path delay and high-pass cut-off in open fittings paper_content: AbstractThe combination of delayed sound from a digital hearing aid with direct sound through an open or vented fitting can potentially degrade the sound quality due to audible changes in timbre and/or perception of echo. The present study was designed to test a number of delay and high-pass combinations under worst-case (i.e. most sensitive) conditions. Eighteen normal-hearing and 18 mildly hearing-impaired subjects performed the test in a paired comparison (A/B) task. The subjects were asked to select a preferred setting with respect to sound quality. The test was set in an anechoic chamber using recorded speech, environmental sounds, and own voice. Experimental hearing aids were fitted binaurally with open domes thus providing maximum ventilation. The preference data were processed using a statistical choice model that derives a ratio-scale. The analysis indicated that in these test conditions there was no change in sound quality when varying the delay in the range 5–10 ms and that there was a preferen... --- paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold paper_content: where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects. --- paper_title: Own voice qualities (OVQ) in hearing-aid users: There is more than just occlusion paper_content: AbstractObjective: Hearing-aid users’ problems with their own voice caused by occlusion are well known. Conversely, it remains essentially undocumented whether hearing-aid users expected not to have occlusion-related problems experience own-voice issues. Design: To investigate this topic, a dedicated Own Voice Qualities (OVQ) questionnaire was developed and used in two experiments with stratified samples. Study sample: In the main experiment, the OVQ was administered to 169 hearing-aid users (most of whom were expected not to have occlusion-related problems) and to a control group of 56 normally-hearing people. In the follow-up experiment, the OVQ was used in a cross-over study where 43 hearing-aid users rated own voice for an open fitting and a small-vent earmould fitting. Results: The results from the main experiment show that hearing-aid users (without occlusion) have more problems than the normal-hearing controls on several dimensions of own voice. The magnitude of these differences was found to be ge... --- paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold paper_content: where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects. --- paper_title: The Occlusion Effect in Unilateral versus Bilateral Hearing Aids paper_content: The benefit of bilateral hearing aids is well documented, but many hearing-aid users still wear only one aid. It is plausible that the occlusion effect is part of the reason for some hearing-aid users not wearing both hearing aids. In this study we quantified the subjective occlusion effect by asking ten experienced users of bilateral hearing aids and a reference group of ten normal-hearing individuals to rate the naturalness of their own voice while reading a text sample aloud. The subjective occlusion effect was evaluated in the unilateral versus bilateral condition for a variety of vent designs in earmolds and in a custom hearing aid. The subjective occlusion effect was significantly higher for bilateral hearing aids with all vent designs with the exception of a non-occluding eartip option. The subjective occlusion effect was reduced with the more open vent designs in both the unilateral and bilateral conditions. Assuming that the occlusion effect is a barrier to bilateral hearing aid use, these results indicate that open-hearing-aid fittings can help promote the use of two aids. --- paper_title: Vent configurations on subjective and objective occlusion effect. paper_content: The current study reexamined the effect of vent diameters on objective and subjective occlusion effect (OE) while minimizing two possible sources of variability. Nine hearing-impaired participants with primarily a high-frequency hearing loss were evaluated. Laser shell-making technology was used to make ear inserts of completely-in-the-canal (CIC) hearing aids for the study. This was to minimize any potential slit leakage from the inserts. The vent dimensions were systematically altered during the study. Participants sustained /i/ for 5 sec, and the real-ear occluded response was measured with a custommade program that performed frequency averaging to reduce response variability. Participants also repeated the phrase “Baby Jeannie is teeny tiny” and rated their own voice. The results showed a systematic change in the objective OE and subjective ratings of OE as the vent diameter was modified. Furthermore, a significant correlation was seen between subjective rating and objective occlusion effect. --- paper_title: Relative loudness perception of low and high frequency sounds in the open and occluded ear paper_content: A comparison of published equal loudness contours indicates that different shapes are obtained at a comfortable level when the measurements are done in an occluded ear than when they are done in an open ear, even though all measurements are expressed as dB SPL at the eardrum. This paper presents the result from a loudness balancing test which confirms this observation. Eleven normal-hearing listeners balanced the level of a 500- and a 3000-Hz octave band babble-noise to the level of a 1500-Hz octave band babble-noise. The balancing test was completed in open and occluded ears using a loudspeaker and a hearing aid receiver, respectively. A probe tube microphone was used to measure the actual levels presented near the individual’s eardrum. The results show that an average of 10 dB higher level was selected for the 500-Hz octave band when listening with the occluded ear than when listening with the open ear. A large range of factors is discussed, but no physical explanation for the discrepancy was found. The... --- paper_title: Occlusion effect of earmolds with different venting systems. paper_content: In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions. --- paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold paper_content: where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects. --- paper_title: The Occlusion Effect in Unilateral versus Bilateral Hearing Aids paper_content: The benefit of bilateral hearing aids is well documented, but many hearing-aid users still wear only one aid. It is plausible that the occlusion effect is part of the reason for some hearing-aid users not wearing both hearing aids. In this study we quantified the subjective occlusion effect by asking ten experienced users of bilateral hearing aids and a reference group of ten normal-hearing individuals to rate the naturalness of their own voice while reading a text sample aloud. The subjective occlusion effect was evaluated in the unilateral versus bilateral condition for a variety of vent designs in earmolds and in a custom hearing aid. The subjective occlusion effect was significantly higher for bilateral hearing aids with all vent designs with the exception of a non-occluding eartip option. The subjective occlusion effect was reduced with the more open vent designs in both the unilateral and bilateral conditions. Assuming that the occlusion effect is a barrier to bilateral hearing aid use, these results indicate that open-hearing-aid fittings can help promote the use of two aids. --- paper_title: Vent configurations on subjective and objective occlusion effect. paper_content: The current study reexamined the effect of vent diameters on objective and subjective occlusion effect (OE) while minimizing two possible sources of variability. Nine hearing-impaired participants with primarily a high-frequency hearing loss were evaluated. Laser shell-making technology was used to make ear inserts of completely-in-the-canal (CIC) hearing aids for the study. This was to minimize any potential slit leakage from the inserts. The vent dimensions were systematically altered during the study. Participants sustained /i/ for 5 sec, and the real-ear occluded response was measured with a custommade program that performed frequency averaging to reduce response variability. Participants also repeated the phrase “Baby Jeannie is teeny tiny” and rated their own voice. The results showed a systematic change in the objective OE and subjective ratings of OE as the vent diameter was modified. Furthermore, a significant correlation was seen between subjective rating and objective occlusion effect. --- paper_title: Occlusion effect of earmolds with different venting systems. paper_content: In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions. --- paper_title: The Occlusion Effect in Unilateral versus Bilateral Hearing Aids paper_content: The benefit of bilateral hearing aids is well documented, but many hearing-aid users still wear only one aid. It is plausible that the occlusion effect is part of the reason for some hearing-aid users not wearing both hearing aids. In this study we quantified the subjective occlusion effect by asking ten experienced users of bilateral hearing aids and a reference group of ten normal-hearing individuals to rate the naturalness of their own voice while reading a text sample aloud. The subjective occlusion effect was evaluated in the unilateral versus bilateral condition for a variety of vent designs in earmolds and in a custom hearing aid. The subjective occlusion effect was significantly higher for bilateral hearing aids with all vent designs with the exception of a non-occluding eartip option. The subjective occlusion effect was reduced with the more open vent designs in both the unilateral and bilateral conditions. Assuming that the occlusion effect is a barrier to bilateral hearing aid use, these results indicate that open-hearing-aid fittings can help promote the use of two aids. --- paper_title: Occlusion effect of earmolds with different venting systems. paper_content: In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions. --- paper_title: Hearing aids with external receivers: Can they offer power and cosmetics? paper_content: The design of hearing solutions for people with moderate to severe hearing loss (HL) traditionally encounters the tradeoff between form and function, appearance and performance. That is, patients typically must sacrifice cosmetics and/or ease of use to obtain devices that can provide them with adequate gain and output. Conversely, larger hearing aid (HA) styles may provide sufficient gain, yet reduce patient satisfaction along a number of other variables. In fact, compared with patients with milder losses, persons with moderate to severe sensorineural HL are less satisfied with their hearing aids along a number of dimensions, 1 including: --- paper_title: Effect of low-frequency gain and venting effects on the benefit derived from directionality and noise reduction in hearing aids paper_content: When the frequency range over which vent-transmitted sound dominates amplification increases, the potential benefit from directional microphones and noise reduction decreases. Fitted with clinically appropriate vent sizes, 23 aided listeners with varying low-frequency hearing thresholds evaluated six schemes comprising three levels of gain at 250 Hz (0, 6, and 12 dB) combined with two features (directional microphone and noise reduction) enabled or disabled in the field. The low-frequency gain was 0 dB for vent-dominated sound, while the higher gains were achieved by amplifier-dominated sounds. A majority of listeners preferred 0-dB gain at 250 Hz and the features enabled. While the amount of low-frequency gain had no significant effect on speech recognition in noise or horizontal localization, speech recognition and front/back discrimination were significantly improved when the features were enabled, even when vent-transmitted sound dominated the low frequencies. The clinical implication is that there is... --- paper_title: The Accuracy of Matching Target Insertion Gains With Open-Fit Hearing Aids paper_content: Purpose To assess the accuracy with which target insertion gains were matched for a single type of open-fit hearing aid, both on initial fitting and after adjustment. Method The hearing aids were f... --- paper_title: NAL-NL1 procedure for fitting nonlinear hearing aids: characteristics and comparisons with other procedures. paper_content: A new procedure for fitting nonlinear hearing aids (National Acoustic Laboratories' nonlinear fitting procedure, version 1 [NAL-NL1]) is described . The rationale is to maximize speech intelligibility while constraining loudness to be normal or less. Speech intelligibility is predicted by the Speech Intelligibility Index (SII), which has been modified to account for the reduction in performance associated with increasing degrees of hearing loss, especially at high frequencies . Prescriptions are compared for the NAL-NL1, desired sensation level [input/output], FIG6, and a threshold version of the Independent Hearing Aid Fitting Forum procedures . For an average speech input level, the NAL-NL1 prescriptions are very similar to those of the well-established NAL-Revised, Profound procedure . Compared with the other procedures, NAL-NL1 prescribes less low-frequency gain for flat and upward sloping audiograms . It prescribes less high-frequency gain for steeply sloping high-frequency hearing losses. NAL-NL1 tends to prescribe less compression than the other procedures . All procedures differ considerably from one another for some audiograms . --- paper_title: Own voice qualities (OVQ) in hearing-aid users: There is more than just occlusion paper_content: AbstractObjective: Hearing-aid users’ problems with their own voice caused by occlusion are well known. Conversely, it remains essentially undocumented whether hearing-aid users expected not to have occlusion-related problems experience own-voice issues. Design: To investigate this topic, a dedicated Own Voice Qualities (OVQ) questionnaire was developed and used in two experiments with stratified samples. Study sample: In the main experiment, the OVQ was administered to 169 hearing-aid users (most of whom were expected not to have occlusion-related problems) and to a control group of 56 normally-hearing people. In the follow-up experiment, the OVQ was used in a cross-over study where 43 hearing-aid users rated own voice for an open fitting and a small-vent earmould fitting. Results: The results from the main experiment show that hearing-aid users (without occlusion) have more problems than the normal-hearing controls on several dimensions of own voice. The magnitude of these differences was found to be ge... --- paper_title: The International Outcome Inventory for Hearing Aids (IOI-HA): psychometric properties of the English version. paper_content: The International Outcome Inventory for Hearing Aids (IOI-HA) is a seven-item questionnaire designed to be generally applicable in evaluating the effectiveness of hearing aid treatments. The inventory was developed to facilitate cooperation among researchers and program evaluators in diverse settings. It is brief and general enough to be appended to other outcome measures that might be planned in a particular application, and will provide directly comparable data across otherwise incompatible projects. For this plan to be successful, it is essential to generate psychometrically equivalent translations in the languages in which hearing aid research and treatment assessments are performed. This article reports the psychometric properties of the inventory for the original English version. The items are reasonably internally consistent, providing adequate statistical support for summing the scores to generate a total outcome score. However, for maximum internal consistcncy, it would be desirable to generate t... --- paper_title: The abbreviated profile of hearing aid benefit. paper_content: OBJECTIVE ::: To develop and evaluate a shortened version of the Profile of Hearing Aid Benefit, to be called the Abbreviated Profile of Hearing Aid Benefit, or APHAB. ::: ::: ::: DESIGN ::: The Profile of Hearing Aid Benefit (PHAB) is a 66-item self-assessment, disability-based inventory that can be used to document the outcome of a hearing aid fitting, to compare several fittings, or to evaluate the same fitting over time. Data from 128 completed PHABs were used to select items for the Abbreviated PHAB. All subjects were elderly hearing-impaired who wore conventional analog hearing aids. Statistics of score distributions and psychometric properties of each of the APHAB subscales were determined. Data from 27 similar subjects were used to examine the test-retest properties of the instrument. Finally, equal-percentile profiles were generated for unaided, aided and benefit scores obtained from successful wearers of linear hearing aids. ::: ::: ::: RESULTS ::: The APHAB uses a subset of 24 of the 66 items from the PHAB, scored in four 6-item subscales. Three of the subscales, Ease of Communication, Reverberation, and Background Noise address speech understanding in various everyday environments. The fourth subscale, Aversiveness of Sounds, quantifies negative reactions to environmental sounds. The APHAB typically requires 10 minutes or less to complete, and it produces scores for unaided and aided performance as well as hearing aid benefit. Test-retest correlation coefficients were found to be moderate to high and similar to those reported in the literature for other scales of similar content and length. Critical differences for each subscale taken individually were judged to be fairly large, however, smaller differences between two tests from the same individual can be significant if the three speech communication subscales are considered jointly. ::: ::: ::: CONCLUSIONS ::: The APHAB is a potentially valuable clinical instrument. It can be useful for quantifying the disability associated with a hearing loss and the reduction of disability that is achieved with a hearing aid. --- paper_title: The Occlusion Effect in Unilateral versus Bilateral Hearing Aids paper_content: The benefit of bilateral hearing aids is well documented, but many hearing-aid users still wear only one aid. It is plausible that the occlusion effect is part of the reason for some hearing-aid users not wearing both hearing aids. In this study we quantified the subjective occlusion effect by asking ten experienced users of bilateral hearing aids and a reference group of ten normal-hearing individuals to rate the naturalness of their own voice while reading a text sample aloud. The subjective occlusion effect was evaluated in the unilateral versus bilateral condition for a variety of vent designs in earmolds and in a custom hearing aid. The subjective occlusion effect was significantly higher for bilateral hearing aids with all vent designs with the exception of a non-occluding eartip option. The subjective occlusion effect was reduced with the more open vent designs in both the unilateral and bilateral conditions. Assuming that the occlusion effect is a barrier to bilateral hearing aid use, these results indicate that open-hearing-aid fittings can help promote the use of two aids. --- paper_title: Measuring Satisfaction with Amplification in Daily Life: The SADL Scale paper_content: ObjectiveTo develop a self-report inventory to quantify satisfaction with hearing aids.DesignThe inventory was developed in several stages. To determine the elements that are most important to satisfaction for most people, we conducted structured interviews and then designed a questionnaire. Hearing --- paper_title: Occlusion effect of earmolds with different venting systems. paper_content: In this study the occlusion effect was quantified for five types of earmolds with different venting. Nine normal-hearing listeners and ten experienced hearing aid users were provided with conventional earmolds with 1.6 and 2.4 mm circular venting, shell type earmolds with a novel vent design with equivalent crosssectional vent areas, and nonoccluding soft silicone eartips of a commercial hearing instrument. For all venting systems, the occlusion effect was measured using a probe microphone system and subjectively rated in test and retest sessions. The results for both normal-hearing subjects and hearing aid users showed that the novel vents caused significantly less occlusion than the traditional vents. Occlusion effect associated with the soft silicone eartip was comparable to the nonoccluded ear. Test-retest reproducibility was higher for the subjective occlusion rating than for the objectively measured occlusion. Perceived occlusion revealed a closer relationship to measured occlusion in the ear in which the measured occlusion effect was higher (“high OE” ear) than in the “low OE” ear. As our results suggest that subjective judgment of occlusion is directly related to the acoustic mass of the air column in the vent, the amount of perceived occlusion may be predicted by the vent dimensions. --- paper_title: Effects of earmold type on ability to locate sounds when wearing hearing aids. paper_content: Objective:To determine whether the choice of earmold type can affect aided auditory localization. Hypotheses: 1) for sensorineural hearing losses with good low-frequency hearing (Low group, n = 10), the use of open earmolds could avoid decrements in horizontal plane localization found with closed (o --- paper_title: Effect of low-frequency gain and venting effects on the benefit derived from directionality and noise reduction in hearing aids paper_content: When the frequency range over which vent-transmitted sound dominates amplification increases, the potential benefit from directional microphones and noise reduction decreases. Fitted with clinically appropriate vent sizes, 23 aided listeners with varying low-frequency hearing thresholds evaluated six schemes comprising three levels of gain at 250 Hz (0, 6, and 12 dB) combined with two features (directional microphone and noise reduction) enabled or disabled in the field. The low-frequency gain was 0 dB for vent-dominated sound, while the higher gains were achieved by amplifier-dominated sounds. A majority of listeners preferred 0-dB gain at 250 Hz and the features enabled. While the amount of low-frequency gain had no significant effect on speech recognition in noise or horizontal localization, speech recognition and front/back discrimination were significantly improved when the features were enabled, even when vent-transmitted sound dominated the low frequencies. The clinical implication is that there is... --- paper_title: The national acoustic laboratories (NAL) new procedure for selecting the gain and frequency response of a hearing aid paper_content: ABSTRACT A new procedure is presented for selecting the gain and frequency response of a hearing aid from pure-tone thresholds. This was developed from research which showed that a previous procedure did not meet its aim of amplifying all frequency bands of speech to equal loudness but that frequency responses which did so were considerably more effective. Measurements of 30 sensorineurally hearing-impaired ears (27 subjects), together with data from other studies, were analyzed to determine the best formula for predicting the optimal frequency response, for each individual, from the audiogram. The analysis indicated that a flat audiogram would require a rising frequency response characteristic of about 8 dB/octave up to 1.25 kHz and thereafter a falling characteristic of about 2 dB/octave. Variations in audiogram slope required about one-third as much variation in response slope. Three frequency average (3FA) gain was calculated to equal the 3FA gain of the previous procedure. Forty-four subjects (67 aided ears) fitted by the new procedure were evaluated by paired comparison judgments of the intelligibility and pleasantness of speech. The prescribed frequency response was seldom inferior to, and usually better than, any of several variations having more, or less, low and/or high-frequency amplification. On the average, used gain was approximately equal to prescribed gain. It is concluded that the new formula should prescribe a near optimal frequency response with few exceptions. --- paper_title: Are real-ear measurements (REM) accurate when using the modified pressure with stored equalization (MPSE) method? paper_content: AbstractAudiologists typically verify hearing instrument fitting using real-ear measurements (REM). Recently the modified pressure with stored equalization method (MPSE) has been recommended for use when verifying open non-occluding hearing instruments. The MPSE method does not use a reference microphone to maintain loudspeaker output during real-ear measurements and is therefore susceptible to changes in the signal level at the client's ear which result from movement of the client's head and torso during the verification process. To determine the size of these errors, the real-ear unaided response (REUR) was measured prior to and following the fitting of a non-functioning hearing aid in the contralateral ear. Twenty young adults participated. Identical head positions for the two measurements should yield zero difference measures across all frequencies measured. Loudspeaker-to-client azimuths of 0° and 45° were investigated. Mean difference measures across the frequencies investigated were less than 1dB f... --- paper_title: Real-ear measurement verification for open, non-occluding hearing instruments paper_content: Real-ear measurements using the modified pressure method with concurrent (real-time) equalization can be inaccurate, when amplified sound leaks out of the ear canal and reaches the reference microphone. In such situations the reference microphone will detect an increased sound level and reduce the output of the loudspeaker to maintain the desired level. The risk of having errors due to leaks increases if digital feedback suppression (DFS) is used, thus achieving higher feedback-free gain levels. The following hypotheses were tested: a) using the concurrent equalization method for fitting hearing instruments with DFS may result in underestimated real-ear insertion gain (especially when using open fittings) and b) as the benefit of the DFS system increases, this error also increases. Real-ear measurements were carried out in twenty-one subjects using the modified pressure method with stored equalization as well as with concurrent equalization. The results of the study supports both hypotheses. As a conseque... --- paper_title: Real ear measurement methods for open fit hearing aids: Modified pressure concurrent equalization (MPCE) versus modified pressure stored equalization (MPSE) paper_content: AbstractObjective: The aim of this study was to assess differences between real ear insertion gains (REIG) measured with the modified pressure concurrent equalization (MPCE) and modified pressure stored equalization (MPSE) methods for open fittings in a typical audiology patient population. Design: REIGs were compared for the two methods using a warble tone sweep at 65 dB SPL. The differences between the two methods at 0.25, 0.5, 1, 2, 3, 4 and 6 kHz were recorded. Study sample: Eighty-three ears of a consecutive sample of 48 candidates for open-fit hearing aids were included. Results: The mean difference between MPSE and MPCE REIGs was less than 1 dB at all frequencies. Analysis of variance showed that the main effect of method was not significant, and there was no significant interaction between method and frequency. Conclusions: The results for the MPSE and MPCE methods did not differ significantly for the patients with mild-to-moderate hearing losses tested here, for whom REIGs were generally less tha... --- paper_title: Sentences for Testing Speech Intelligibility in Noise paper_content: A list of ten spoken Swedish sentences was computer edited to obtain new lists with exactly the same content of sound, but with new sentences. A noise was synthesized from the speech material by the computer to produce exactly the same spectrum of speech and noise. The noise was also amplitude modulated by a low frequency noise to make it sound more natural. This material was tested monaurally on 20 normal-hearing subjects. The equality in intelligibility of some of the lists was investigated. Repeated threshold measurements in noise showed a standard deviation of 0.44 dB when the learning effect was outbalanced. Only a small part of the learning effect was due to learning of the word material. Intelligibility curves fitted to the data points in noise and without noise showed maximum steepnesses of 25 and 10%/dB respectively. At constant signal to noise ratio (S/N) the best performance was achieved at a speech level of 53 dB. --- paper_title: Tolerable Hearing Aid Delays. V. Estimation of Limits for Open Canal Fittings paper_content: Objectives: Open canal fittings are a popular alternative to close-fitting earmolds for use with patients whose low-frequency hearing is near normal. Open canal fittings reduce the occlusion effect but also provide little attenuation of external air-borne sounds. The wearer therefore receives a mixture of air-borne sound and amplified but delayed sound through the hearing aid. To explore systematically the effect of the mixing, we simulated with varying degrees of complexity the effects of both a hearing loss and a high-quality hearing aid programmed to compensate for that loss, and used normal-hearing participants to assess the processing. Design: The off-line processing was intended to simulate the percept of listening to the speech of a single (external) talker. The effect of introducing a delay on a subjective measure of speech quality (disturbance rating on a scale from 1 to 7, 7 being maximal disturbance) was assessed using both a constant gain and a gain that varied across frequency. In three experiments we assessed the effects of different amounts of delay, maximum aid gain and rate of change of gain with frequency. The simulated hearing aids were chosen to be appropriate for typical mild to moderate high-frequency losses starting at 1 or 2 kHz. Two of the experiments used simulations of linear hearing aids, whereas the third used fast-acting multichannel wide-dynamic-range compression and a simulation of loudness recruitment. In one experiment, a condition was included in which spectral ripples produced by comb-filtering were partially removed using a digital filter. Results: For linear hearing aids, disturbance increased progressively with increasing delay and with decreasing rate of change of gain; the effect of amount of gain was small when the gain varied across frequency. The effect of reducing spectral ripples was also small. When the simulation of dynamic processes was included (experiment 3), the pattern with delay remained similar, but disturbance increased with increasing gain. It is argued that this is mainly due to disturbance increasing with increasing simulated hearing loss, probably because of the dynamic processing involved in the hearing aid and recruitment simulation. Conclusions: A disturbance rating of 3 may be considered as just acceptable. This rating was reached for delays of about 5 and 6 msec, for simulated hearing losses starting at 2 and 1 kHz, respectively. The perceptual effect of reducing the spectral ripples produced by comb-filtering was small; the effect was greatest when the hearing aid gain was small and when the hearing loss started at a low frequency. --- paper_title: Unaided and aided performance with a directional open-fit hearing aid. paper_content: Differences in performance between unaided and aided performance (omnidirectional and directional) were measured using an open-fit behind-the-ear (BTE) hearing aid. Twenty-six subjects without prior experience with amplification were fitted bilaterally using the manufacturer's recommended procedure. After wearing the hearing aids for one week, the fitting parameters were fine-tuned, based on subjective comments. Four weeks later, differences in performance between unaided and aided (omnidirectional and directional) were assessed by measuring reception thresholds for sentences (RTS in dB), using HINT sentences presented at 0° with R-SpaceTM restaurant noise held constant at 65dBA and presented via eight loudspeakers set 45° apart. In addition, the APHAB was administered to assess subjective impressions of the experimental aid.Results revealed that significant differences in RTS (in dB) were present between directional and omnidirectional performance, as well as directional and unaided performance. Aided om... --- paper_title: Directivity quantification in hearing aids: fitting and measurement effects. paper_content: OBJECTIVE: To evaluate the impact of venting, microphone port orientation, and compression on the electroacoustically measured directivity of directional and omnidirectional behind-the-ear hearing aids. In addition, the average directivity provided across three brands of directional and omnidirectional behind-the-ear hearing aids was compared with that provided by the open ear. DESIGN: Three groups of hearing aids (four instruments in each group) representing three commercial models (a total of 12) were selected for electroacoustic evaluation of directivity. Polar directivity patterns were measured and directivity index was calculated across four different venting configurations, and for five different microphone port angles. All measurements were made for instruments in directional and omnidirectional modes. Single source traditional, and two-source modified front-to-back ratios were also measured with the hearing aids in linear and compression modes. RESULTS: The directivity provided by the open (Knowles Electronics Manikin for Acoustic Research) ear was superior to that of the omnidirectional hearing aids in this study. Although the directivity measured for directional hearing aids was significantly better than that of omnidirectional models, significant variability was measured both within and across the tested models both on average and at specific test frequencies. Both venting and microphone port orientation affected the measured directivity. Although compression reduced the magnitude of traditionally measured front-to-back ratios, no difference from linear amplification was noted using a modified methodology. CONCLUSIONS: The variation in the measured directivity both within and across the directional microphone hearing aid brands suggests that manufacturer's specification of directivity may not provide an accurate index of the actual performance of all individual instruments. The significant impact of venting and microphone port orientation on directivity indicate that these variables must be addressed when fitting directional hearing aids on hearing-impaired listeners. Modified front-to-back ratio results suggest that compression does not affect the directivity of hearing aids, if it is assumed that the signal of interest from one azimuth, and the competing signal from a different azimuth, occur at the same time. --- paper_title: Preferred signal path delay and high-pass cut-off in open fittings paper_content: AbstractThe combination of delayed sound from a digital hearing aid with direct sound through an open or vented fitting can potentially degrade the sound quality due to audible changes in timbre and/or perception of echo. The present study was designed to test a number of delay and high-pass combinations under worst-case (i.e. most sensitive) conditions. Eighteen normal-hearing and 18 mildly hearing-impaired subjects performed the test in a paired comparison (A/B) task. The subjects were asked to select a preferred setting with respect to sound quality. The test was set in an anechoic chamber using recorded speech, environmental sounds, and own voice. Experimental hearing aids were fitted binaurally with open domes thus providing maximum ventilation. The preference data were processed using a statistical choice model that derives a ratio-scale. The analysis indicated that in these test conditions there was no change in sound quality when varying the delay in the range 5–10 ms and that there was a preferen... --- paper_title: Speech recognition in noise using bilateral open-fit hearing aids: The limited benefit of directional microphones and noise reduction paper_content: To investigate speech recognition performance in noise with bilateral open-fi t hearing aids and as reference also with closed earmolds, in omnidirectional mode, directional mode, and directional mode in conjunction with noise reduction. Design: A within-subject design with repeated measures across conditions was used. Speech recognition thresholds in noise were obtained for the different conditions. Study sample: Twenty adults without prior experience with hearing aids. All had symmetric sensorineural mild hearing loss in the lower frequencies and moderate to severe hearing loss in the higher frequencies. Results: Speech recognition performance in noise was not signifi cantly better with an omnidirectional microphone compared to unaided, whereas performance was signifi cantly better with a directional microphone (1.6 dB with open fi tting and 4.4 dB with closed earmold) compared to unaided. With open fi tting, no signifi cant additional advantage was obtained by combining the directional microphone with a noise reduction algorithm, but with closed earmolds a signifi cant additional advantage of 0.8 dB was obtained. Conclusions: The signifi cant, though limited, advantage of directional microphones and the absence of additional signifi cant improvement by a noise reduction algorithm should be considered when fi tting open-fi t hearing aids. --- paper_title: Acoustic Attenuation between the Ears paper_content: In an investigation of the acoustical insulation between the ears, various earphones and obturating devices were used. Bone conduction was shown to be chiefly responsible for the acoustical leakage between the ears. Conditions were determined under which interaural insulation could be increased considerably. Most of the measurements were performed with a compensation method which appears to give more precise results than methods previously used, and which permits phase measurements. --- paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold paper_content: where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects. --- paper_title: Investigation of the Auditory Occlusion Effect with Implications for Hearing Protection and Hearing Aid Design paper_content: Previous research has shown that auditory occlusion effects could inhibit people from using hearing protection devices or hearing aids, which raises safety and usability concerns. The objective of this study was to evaluate occlusion effects as a function of insertion depth (shallow and deep), earplug type (foam earplug and medical balloonbased earplug), and excitation source (bone vibrator and self vocal utterance). Ten participants, six male and four female, completed the experiment. The ANOVA and post hoc tests conducted on the measured occlusion effects revealed main effects of insertion depth and earplug type, as well as an interaction effect between insertion depth and earplug type. The occlusion effect of deeply inserted earplugs was smaller than that of shallowly inserted earplugs by 11.2 dB. At deep insertion, the balloon-based earplugs produced an occlusion effect of 14.9 dB while the foam earplugs produced 5.9 dB. --- paper_title: Active cancellation of occlusion: an electronic vent for hearing aids and hearing protectors. paper_content: The occlusion effect is commonly described as an unnatural and mostly annoying quality of the voice of a person wearing hearing aids or hearing protectors. As a result, it is often reported by hearing aid users as a deterrent to wearing hearing aids. This paper presents an investigation into active occlusion cancellation. Measured transducer responses combined with models of an active feedback scheme are first examined in order to predict the effectiveness of occlusion reduction. The simulations predict 18 dB of occlusion reduction in completely blocked ear canals. Simulations incorporating a 1 mm vent (providing passive occlusion reduction) predict a combined active and passive occlusion reduction of 20 dB. A prototype occlusion canceling system was constructed. Averaged across 12 listeners with normal hearing, it provided 15 dB of occlusion reduction. Ten of the subjects reported a more natural own voice quality and an appreciable increase in comfort with the cancellation active, and 11 out of the 12 preferred the active system over the passive system. --- paper_title: Comparison of Vent Effects between a Solid Earmold and a Hollow Earmold paper_content: where the thickness of the shell was the length of the vent. Vent diameters were 0, 1, 2, and 3 mm. Data Collection and Analysis: The vent effect was evaluated on real-ear aided response, real-ear occluded response during vocalization, subjective occlusion rating, insertion loss, and maximum available gain before feedback. Real-ear measurements were made with the Fonix 6500 probemicrophone real-ear system. Vocalizations from the participants were analyzed with a custom MATLAB program, and statistical analysis was conducted with SPSS software. Results: A systematic vent effect was seen with each earmold type as the nominal vent diameter changed. For the same vent diameter, the vent effect seen with the hollow earmold was greater than that of the solid earmold. Conclusions: Because of the difference in vent length (and thus acoustic mass) between a solid and a hollow earmold, the effect of vent diameter in a hollow earmold is more pronounced than that seen in a solid earmold of the same nominal vent diameter. Thus, a smaller vent diameter will be needed in a hollow earmold than in a solid earmold to achieve similar vent effects. --- paper_title: In the ear hearing device with a valve formed with an electroactive material having a changeable volume and method of operating the hearing device paper_content: For particularly good adaptation to a given hearing situation, an in-the-ear hearing device which has a housing with a channel in the housing that is designed as a through-opening for sound and air between the interior of the ear and the environment outside the ear, the channel is provided with a structural element for changing the size of the through-opening at at least one position. The structural element is a valve formed with electroactive material and the size of the through-opening is adjusted by application of a voltage to the valve. ---	Title: Open Versus Closed Hearing-Aid Fittings: A Literature Review of Both Fitting Approaches Section 1: Introduction Description 1: Provide an overview of hearing loss, the role of hearing aids, and the difference between Behind-The-Ear (BTE) and In-The-Ear (ITE) hearing aids, including preliminary discussions on open and closed fittings. Section 2: The Occlusion Effect Description 2: Describe the physiological basis of the occlusion effect, the structure of the ear canal, and how closed earmolds exacerbate self-produced sound transmission within the ear canal. Section 3: Quantifying the Occlusion Effect Description 3: Differentiate between objective and subjective occlusion effects, and introduce methods used to measure these effects. Section 4: The Objective Occlusion Effect Description 4: Discuss the methodologies for measuring the objective occlusion effect, including real-ear measurements (REM) and frequency responses, and their relevance for open versus closed fittings. Section 5: The Subjective Occlusion Effect Description 5: Explore how individuals perceive their own voice when using different types of hearing aid fittings and how this subjective experience influences satisfaction with the device. Section 6: The Acoustic Mass Description 6: Explain the concept of acoustic mass and its impact on vent design and sound transmission in hearing aids. Section 7: Alternative Vent Types Description 7: Examine specific vent designs and their efficacy in reducing the occlusion effect, particularly focusing on innovative technologies like Flex-Vent TM. Section 8: Open-Fit Hearing Aids Definition of Open-Fit Hearing Aids Description 8: Define open-fit hearing aids, including differences in design and application within the ear canal, and elaborate on manufacturer recommendations. Section 9: Vent Sizes Description 9: Discuss the relationship between vent size and the occlusion effect, and provide guidelines for choosing appropriate vent sizes based on hearing loss levels. Section 10: RIC and RITA Hearing Aids Description 10: Compare Receiver-In-The-Canal (RIC) and Receiver-In-The-Aid (RITA) hearing aids concerning gain before feedback and user preference. Section 11: Fitting of Open-Fit Hearing Aids Description 11: Outline the fitting process for open-fit hearing aids, the software adjustments based on hearing loss, and challenges in achieving optimal gain. Section 12: Advantages of Open-Fit Hearing Aids Description 12: Detail the benefits of open-fit hearing aids, including subjective evaluations, localization, and improvements in daily life experiences. Section 13: Disadvantages of Open-Fit Hearing Aids Description 13: Discuss the limitations of open-fit hearing aids, such as REM accuracy, interaction between direct and amplified sounds, and reduced effectiveness of adaptive features. Section 14: Alternative Approaches Description 14: Introduce alternative methods and innovative designs for reducing occlusion, such as mechanical modifications and active occlusion reduction algorithms. Section 15: Summary and Conclusions Description 15: Provide a summary of the key points discussed in the paper, highlighting the importance of fitting choices, individual needs, and the trade-offs between open and closed hearing-aid fittings.
Non-Interactive Differential Privacy: a Survey	10	--- paper_title: Robust De-anonymization of Large Sparse Datasets paper_content: We present a new class of statistical de- anonymization attacks against high-dimensional micro-data, such as individual preferences, recommendations, transaction records and so on. Our techniques are robust to perturbation in the data and tolerate some mistakes in the adversary's background knowledge. We apply our de-anonymization methodology to the Netflix Prize dataset, which contains anonymous movie ratings of 500,000 subscribers of Netflix, the world's largest online movie rental service. We demonstrate that an adversary who knows only a little bit about an individual subscriber can easily identify this subscriber's record in the dataset. Using the Internet Movie Database as the source of background knowledge, we successfully identified the Netflix records of known users, uncovering their apparent political preferences and other potentially sensitive information. --- paper_title: Big data: The next frontier for innovation, competition, and productivity paper_content: The amount of data in our world has been exploding, and analyzing large data sets—so-called big data— will become a key basis of competition, underpinning new waves of productivity growth, innovation, and consumer surplus, according to research by MGI and McKinsey's Business Technology Office. Leaders in every sector will have to grapple with the implications of big data, not just a few data-oriented managers. The increasing volume and detail of information captured by enterprises, the rise of multimedia, social media, and the Internet of Things will fuel exponential growth in data for the foreseeable future. --- paper_title: k-Anonymity: A Model for Protecting Privacy paper_content: Consider a data holder, such as a hospital or a bank, that has a privately held collection of person-specific, field structured data. Suppose the data holder wants to share a version of the data with researchers. How can a data holder release a version of its private data with scientific guarantees that the individuals who are the subjects of the data cannot be re-identified while the data remain practically useful? The solution provided in this paper includes a formal protection model named k-anonymity and a set of accompanying policies for deployment. A release provides k-anonymity protection if the information for each person contained in the release cannot be distinguished from at least k-1 individuals whose information also appears in the release. This paper also examines re-identification attacks that can be realized on releases that adhere to k- anonymity unless accompanying policies are respected. The k-anonymity protection model is important because it forms the basis on which the real-world systems known as Datafly, µ-Argus and k-Similar provide guarantees of privacy protection. --- paper_title: A firm foundation for private data analysis paper_content: In the information realm, loss of privacy is usually associated with failure to control access to information, to control the flow of information, or to control the purposes for which information is employed. Differential privacy arose in a context in which ensuring privacy is a challenge even if all these control problems are solved: privacy-preserving statistical analysis of data. The problem of statistical disclosure control – revealing accurate statistics about a set of respondents while preserving the privacy of individuals – has a venerable history, with an extensive literature spanning statistics, theoretical computer science, security, databases, and cryptography (see, for example, the excellent survey [1], the discussion of related work in [2] and the Journal of Official Statistics 9 (2), dedicated to confidentiality and disclosure control). This long history is a testament the importance of the problem. Statistical databases can be of enormous social value; they are used for apportioning resources, evaluating medical therapies, understanding the spread of disease, improving economic utility, and informing us about ourselves as a species. The data may be obtained in diverse ways. Some data, such as census, tax, and other sorts of official data, are compelled; others are collected opportunistically, for example, from traffic on the internet, transactions on Amazon, and search engine query logs; other data are provided altruistically, by respondents who hope that sharing their information will help others to avoid a specific misfortune, or more generally, to increase the public good. Altruistic data donors are typically promised their individual data will be kept confidential – in short, they are promised “privacy.” Similarly, medical data and legally compelled data, such as census data, tax return data, have legal privacy mandates. In our view, ethics demand that opportunistically obtained data should be treated no differently, especially when there is no reasonable alternative to engaging in the actions that generate the data in question. The problems remain: even if data encryption, key management, access control, and the motives of the data curator --- paper_title: t-Closeness: Privacy Beyond k-Anonymity and l-Diversity paper_content: The k-anonymity privacy requirement for publishing microdata requires that each equivalence class (i.e., a set of records that are indistinguishable from each other with respect to certain "identifying" attributes) contains at least k records. Recently, several authors have recognized that k-anonymity cannot prevent attribute disclosure. The notion of l-diversity has been proposed to address this; l-diversity requires that each equivalence class has at least l well-represented values for each sensitive attribute. In this paper we show that l-diversity has a number of limitations. In particular, it is neither necessary nor sufficient to prevent attribute disclosure. We propose a novel privacy notion called t-closeness, which requires that the distribution of a sensitive attribute in any equivalence class is close to the distribution of the attribute in the overall table (i.e., the distance between the two distributions should be no more than a threshold t). We choose to use the earth mover distance measure for our t-closeness requirement. We discuss the rationale for t-closeness and illustrate its advantages through examples and experiments. --- paper_title: Transparent government, not transparent citizens: a report on privacy and transparency for the Cabinet Office paper_content: 1. Privacy is extremely important to transparency. The political legitimacy of a transparency programme will depend crucially on its ability to retain public confidence. Privacy protection should therefore be embedded in any transparency programme, rather than bolted on as an afterthought. 2. Privacy and transparency are compatible, as long as the former is carefully protected and considered at every stage. 3. Under the current transparency regime, in which public data is specifically understood not to include personal data, most data releases will not raise privacy concerns. However, some will, especially as we move toward a more demand-driven scheme. 4. Discussion about deanonymisation has been driven largely by legal considerations, with a consequent neglect of the input of the technical community. 5. There are no complete legal or technical fixes to the deanonymisation problem. We should continue to anonymise sensitive data, being initially cautious about releasing such data under the Open Government Licence while we continue to take steps to manage and research the risks of deanonymisation. Further investigation to determine the level of risk would be very welcome. 6. There should be a focus on procedures to output an auditable debate trail. Transparency about transparency – metatransparency – is essential for preserving trust and confidence. Fourteen recommendations are made to address these conclusions. --- paper_title: Calibrating Noise to Sensitivity in Private Data Analysis paper_content: We continue a line of research initiated in [10, 11] on privacy-preserving statistical databases. Consider a trusted server that holds a database of sensitive information. Given a query function f mapping databases to reals, the so-called true answer is the result of applying f to the database. To protect privacy, the true answer is perturbed by the addition of random noise generated according to a carefully chosen distribution, and this response, the true answer plus noise, is returned to the user. Previous work focused on the case of noisy sums, in which f = Σ i g(x i ), where x i denotes the ith row of the database and g maps database rows to [0,1]. We extend the study to general functions f, proving that privacy can be preserved by calibrating the standard deviation of the noise according to the sensitivity of the function f. Roughly speaking, this is the amount that any single argument to f can change its output. The new analysis shows that for several particular applications substantially less noise is needed than was previously understood to be the case. The first step is a very clean characterization of privacy in terms of indistinguishability of transcripts. Additionally, we obtain separation results showing the increased value of interactive sanitization mechanisms over non-interactive. --- paper_title: Our Data, Ourselves: Privacy via Distributed Noise Generation paper_content: In this work we provide efficient distributed protocols for generating shares of random noise, secure against malicious participants. The purpose of the noise generation is to create a distributed implementation of the privacy-preserving statistical databases described in recent papers [14,4,13]. In these databases, privacy is obtained by perturbing the true answer to a database query by the addition of a small amount of Gaussian or exponentially distributed random noise. The computational power of even a simple form of these databases, when the query is just of the form Σ i f(d i ), that is, the sum over all rows i in the database of a function f applied to the data in row i, has been demonstrated in [4]. A distributed implementation eliminates the need for a trusted database administrator. The results for noise generation are of independent interest. The generation of Gaussian noise introduces a technique for distributing shares of many unbiased coins with fewer executions of verifiable secret sharing than would be needed using previous approaches (reduced by a factor of n). The generation of exponentially distributed noise uses two shallow circuits: one for generating many arbitrarily but identically biased coins at an amortized cost of two unbiased random bits apiece, independent of the bias, and the other to combine bits of appropriate biases to obtain an exponential distribution. --- paper_title: Privacy: Theory meets Practice on the Map paper_content: In this paper, we propose the first formal privacy analysis of a data anonymization process known as the synthetic data generation, a technique becoming popular in the statistics community. The target application for this work is a mapping program that shows the commuting patterns of the population of the United States. The source data for this application were collected by the U.S. Census Bureau, but due to privacy constraints, they cannot be used directly by the mapping program. Instead, we generate synthetic data that statistically mimic the original data while providing privacy guarantees. We use these synthetic data as a surrogate for the original data. We find that while some existing definitions of privacy are inapplicable to our target application, others are too conservative and render the synthetic data useless since they guard against privacy breaches that are very unlikely. Moreover, the data in our target application is sparse, and none of the existing solutions are tailored to anonymize sparse data. In this paper, we propose solutions to address the above issues. --- paper_title: No free lunch in data privacy paper_content: Differential privacy is a powerful tool for providing privacy-preserving noisy query answers over statistical databases. It guarantees that the distribution of noisy query answers changes very little with the addition or deletion of any tuple. It is frequently accompanied by popularized claims that it provides privacy without any assumptions about the data and that it protects against attackers who know all but one record. In this paper we critically analyze the privacy protections offered by differential privacy. First, we use a no-free-lunch theorem, which defines non-privacy as a game, to argue that it is not possible to provide privacy and utility without making assumptions about how the data are generated. Then we explain where assumptions are needed. We argue that privacy of an individual is preserved when it is possible to limit the inference of an attacker about the participation of the individual in the data generating process. This is different from limiting the inference about the presence of a tuple (for example, Bob's participation in a social network may cause edges to form between pairs of his friends, so that it affects more than just the tuple labeled as "Bob"). The definition of evidence of participation, in turn, depends on how the data are generated -- this is how assumptions enter the picture. We explain these ideas using examples from social network research as well as tabular data for which deterministic statistics have been previously released. In both cases the notion of participation varies, the use of differential privacy can lead to privacy breaches, and differential privacy does not always adequately limit inference about participation. --- paper_title: Calibrating Noise to Sensitivity in Private Data Analysis paper_content: We continue a line of research initiated in [10, 11] on privacy-preserving statistical databases. Consider a trusted server that holds a database of sensitive information. Given a query function f mapping databases to reals, the so-called true answer is the result of applying f to the database. To protect privacy, the true answer is perturbed by the addition of random noise generated according to a carefully chosen distribution, and this response, the true answer plus noise, is returned to the user. Previous work focused on the case of noisy sums, in which f = Σ i g(x i ), where x i denotes the ith row of the database and g maps database rows to [0,1]. We extend the study to general functions f, proving that privacy can be preserved by calibrating the standard deviation of the noise according to the sensitivity of the function f. Roughly speaking, this is the amount that any single argument to f can change its output. The new analysis shows that for several particular applications substantially less noise is needed than was previously understood to be the case. The first step is a very clean characterization of privacy in terms of indistinguishability of transcripts. Additionally, we obtain separation results showing the increased value of interactive sanitization mechanisms over non-interactive. --- paper_title: Our Data, Ourselves: Privacy via Distributed Noise Generation paper_content: In this work we provide efficient distributed protocols for generating shares of random noise, secure against malicious participants. The purpose of the noise generation is to create a distributed implementation of the privacy-preserving statistical databases described in recent papers [14,4,13]. In these databases, privacy is obtained by perturbing the true answer to a database query by the addition of a small amount of Gaussian or exponentially distributed random noise. The computational power of even a simple form of these databases, when the query is just of the form Σ i f(d i ), that is, the sum over all rows i in the database of a function f applied to the data in row i, has been demonstrated in [4]. A distributed implementation eliminates the need for a trusted database administrator. The results for noise generation are of independent interest. The generation of Gaussian noise introduces a technique for distributing shares of many unbiased coins with fewer executions of verifiable secret sharing than would be needed using previous approaches (reduced by a factor of n). The generation of exponentially distributed noise uses two shallow circuits: one for generating many arbitrarily but identically biased coins at an amortized cost of two unbiased random bits apiece, independent of the bias, and the other to combine bits of appropriate biases to obtain an exponential distribution. --- paper_title: Mechanism Design via Differential Privacy paper_content: We study the role that privacy-preserving algorithms, which prevent the leakage of specific information about participants, can play in the design of mechanisms for strategic agents, which must encourage players to honestly report information. Specifically, we show that the recent notion of differential privacv, in addition to its own intrinsic virtue, can ensure that participants have limited effect on the outcome of the mechanism, and as a consequence have limited incentive to lie. More precisely, mechanisms with differential privacy are approximate dominant strategy under arbitrary player utility functions, are automatically resilient to coalitions, and easily allow repeatability. We study several special cases of the unlimited supply auction problem, providing new results for digital goods auctions, attribute auctions, and auctions with arbitrary structural constraints on the prices. As an important prelude to developing a privacy-preserving auction mechanism, we introduce and study a generalization of previous privacy work that accommodates the high sensitivity of the auction setting, where a single participant may dramatically alter the optimal fixed price, and a slight change in the offered price may take the revenue from optimal to zero. --- paper_title: Optimizing linear counting queries under differential privacy paper_content: Differential privacy is a robust privacy standard that has been successfully applied to a range of data analysis tasks. But despite much recent work, optimal strategies for answering a collection of related queries are not known. We propose the matrix mechanism, a new algorithm for answering a workload of predicate counting queries. Given a workload, the mechanism requests answers to a different set of queries, called a query strategy, which are answered using the standard Laplace mechanism. Noisy answers to the workload queries are then derived from the noisy answers to the strategy queries. This two stage process can result in a more complex correlated noise distribution that preserves differential privacy but increases accuracy. We provide a formal analysis of the error of query answers produced by the mechanism and investigate the problem of computing the optimal query strategy in support of a given workload. We show this problem can be formulated as a rank-constrained semidefinite program. Finally, we analyze two seemingly distinct techniques, whose similar behavior is explained by viewing them as instances of the matrix mechanism. --- paper_title: Universally Utility-maximizing Privacy Mechanisms paper_content: A mechanism for releasing information about a statistical database with sensitive data must resolve a trade-off between utility and privacy. Publishing fully accurate information maximizes utility while minimizing privacy, while publishing random noise accomplishes the opposite. Privacy can be rigorously quantified using the framework of differential privacy, which requires that a mechanism's output distribution is nearly the same whether a given database row is included. The goal of this paper is to formulate and provide strong and general utility guarantees, subject to differential privacy. We pursue mechanisms that guarantee near-optimal utility to every potential user, independent of its side information (modeled as a prior distribution over query results) and preferences (modeled via a symmetric and monotone loss function). Our main result is the following: for each fixed count query and differential privacy level, there is a geometric mechanism $M^*$---a discrete variant of the simple and well-studi... --- paper_title: On the geometry of differential privacy paper_content: We consider the noise complexity of differentially private mechanisms in the setting where the user asks d linear queries f:Rn -> R non-adaptively. Here, the database is represented by a vector in R and proximity between databases is measured in the l1-metric. We show that the noise complexity is determined by two geometric parameters associated with the set of queries. We use this connection to give tight upper and lower bounds on the noise complexity for any d ≤ n. We show that for d random linear queries of sensitivity 1, it is necessary and sufficient to add l2-error Θ(min d√d/ε,d√(log (n/d))/ε) to achieve ε-differential privacy. Assuming the truth of a deep conjecture from convex geometry, known as the Hyperplane conjecture, we can extend our results to arbitrary linear queries giving nearly matching upper and lower bounds. ::: Our bound translates to error $O(min d/ε,√(d log(n/d)/ε)) per answer. The best previous upper bound (Laplacian mechanism) gives a bound of O(min (d/ε,√n/ε)) per answer, while the best known lower bound was Ω(√d/ε). ::: In contrast, our lower bound is strong enough to separate the concept of differential privacy from the notion of approximate differential privacy where an upper bound of O(√{d}/ε) can be achieved. --- paper_title: A learning theory approach to non-interactive database privacy paper_content: In this paper we demonstrate that, ignoring computational constraints, it is possible to privately release synthetic databases that are useful for large classes of queries -- much larger in size than the database itself. Specifically, we give a mechanism that privately releases synthetic data for a class of queries over a discrete domain with error that grows as a function of the size of the smallest net approximately representing the answers to that class of queries. We show that this in particular implies a mechanism for counting queries that gives error guarantees that grow only with the VC-dimension of the class of queries, which itself grows only logarithmically with the size of the query class. ::: We also show that it is not possible to privately release even simple classes of queries (such as intervals and their generalizations) over continuous domains. Despite this, we give a privacy-preserving polynomial time algorithm that releases information useful for all halfspace queries, given a slight relaxation of the utility guarantee. This algorithm does not release synthetic data, but instead another data structure capable of representing an answer for each query. We also give an efficient algorithm for releasing synthetic data for the class of interval queries and axis-aligned rectangles of constant dimension. ::: Finally, inspired by learning theory, we introduce a new notion of data privacy, which we call distributional privacy, and show that it is strictly stronger than the prevailing privacy notion, differential privacy. --- paper_title: Publishing Set-Valued Data via Differential Privacy paper_content: Set-valued data provides enormous opportunities for various data mining tasks. In this paper, we study the problem of publishing set-valued data for data mining tasks under the rigorous differential privacy model. All existing data publishing methods for set-valued data are based on partitionbased privacy models, for example k-anonymity, which are vulnerable to privacy attacks based on background knowledge. In contrast, differential privacy provides strong privacy guarantees independent of an adversary’s background knowledge, computational power or subsequent behavior. Existing data publishing approaches for differential privacy, however, are not adequate in terms of both utility and scalability in the context of set-valued data due to its high dimensionality. We demonstrate that set-valued data could be efficiently released under differential privacy with guaranteed utility with the help of context-free taxonomy trees. We propose a probabilistic top-down partitioning algorithm to generate a differentially private release, which scales linearly with the input data size. We also discuss the applicability of our idea to the context of relational data. We prove that our result is (ǫ,δ)-useful for the class of counting queries, the foundation of many data mining tasks. We show that our approach maintains high utility for counting queries and frequent itemset mining and scales to large datasets through extensive experiments on real-life set-valued datasets. --- paper_title: Compressive mechanism: utilizing sparse representation in differential privacy paper_content: Differential privacy provides the first theoretical foundation with provable privacy guarantee against adversaries with arbitrary prior knowledge. The main idea to achieve differential privacy is to inject random noise into statistical query results. Besides correctness, the most important goal in the design of a differentially private mechanism is to reduce the effect of random noise, ensuring that the noisy results can still be useful. This paper proposes the compressive mechanism, a novel solution on the basis of state-of-the-art compression technique, called compressive sensing. Compressive sensing is a decent theoretical tool for compact synopsis construction, using random projections. In this paper, we show that the amount of noise is significantly reduced from O(n) to O(log(n)), when the noise insertion procedure is carried on the synopsis samples instead of the original database. As an extension, we also apply the proposed compressive mechanism to solve the problem of continual release of statistical results. Extensive experiments using real datasets justify our accuracy claims. --- paper_title: Differentially Private Trajectory Data Publication paper_content: With the increasing prevalence of location-aware devices, trajectory data has been generated and collected in various application domains. Trajectory data carries rich in- formation that is useful for many data analysis tasks. Yet, improper publishing and use of trajectory data could jeopardize individual privacy. However, it has been shown that existing privacy-preserving trajectory data publishing methods derived from partition-based privacy models, for example k-anonymity, are unable to provide sufficient privacy protection. In this paper, motivated by the data publishing scenario at the Societe de transport de Montreal (STM), the public transit agency in Montreal area, we study the problem of publishing trajectory data under the rigorous differential privacy model. We propose an efficient data-dependent yet differentially private sanitization algorithm, which is applicable to different types of trajectory data. The efficiency of our approach comes from adaptively narrowing down the output domain by building a noisy prefix tree based on the underlying data. Moreover, as a post-processing step, we make use of the inherent constraints of a prefix tree t o conduct constrained inferences, which lead to better utility. This is the first paper to introduce a practical solution for publi shing large volume of trajectory data under differential privacy. We examine the utility of sanitized data in terms of count queries and frequent sequential pattern mining. Extensive experiments on real-life trajectory data from the STM demonstrate that our approach maintains high utility and is scalable to large trajectory datasets. --- paper_title: Differentially Private Data Release through Multidimensional Partitioning paper_content: Differential privacy is a strong notion for protecting individual privacy in privacy preserving data analysis or publishing. In this paper, we study the problem of differentially private histogram release based on an interactive differential privacy interface. We propose two multidimensional partitioning strategies including a baseline cell-based partitioning and an innovative kd-tree based partitioning. In addition to providing formal proofs for differential privacy and usefulness guarantees for linear distributive queries, we also present a set of experimental results and demonstrate the feasibility and performance of our method. --- paper_title: Differentially Private Spatial Decompositions paper_content: Differential privacy has recently emerged as the de facto standard for private data release. This makes it possible to provide strong theoretical guarantees on the privacy and utility of released data. While it is well-understood how to release data based on counts and simple functions under this guarantee, it remains to provide general purpose techniques to release data that is useful for a variety of queries. In this paper, we focus on spatial data such as locations and more generally any multi-dimensional data that can be indexed by a tree structure. Directly applying existing differential privacy methods to this type of data simply generates noise. We propose instead the class of ``private spatial decompositions'': these adapt standard spatial indexing methods such as quad trees and kd-trees to provide a private description of the data distribution. Equipping such structures with differential privacy requires several steps to ensure that they provide meaningful privacy guarantees. Various basic steps, such as choosing splitting points and describing the distribution of points within a region, must be done privately, and the guarantees of the different building blocks composed to provide an overall guarantee. Consequently, we expose the design space for private spatial decompositions, and analyze some key examples. A major contribution of our work is to provide new techniques for parameter setting and post-processing the output to improve the accuracy of query answers. Our experimental study demonstrates that it is possible to build such decompositions efficiently, and use them to answer a variety of queries privately with high accuracy. --- paper_title: Differentially Private Publication of Sparse Data paper_content: The problem of privately releasing data is to provide a version of a dataset without revealing sensitive information about the individuals who contribute to the data. The model of differential privacy allows such private release while providing strong guarantees on the output. A basic mechanism achieves differential privacy by adding noise to the frequency counts in the contingency tables (or, a subset of the count data cube) derived from the dataset. However, when the dataset is sparse in its underlying space, as is the case for most multi-attribute relations, then the effect of adding noise is to vastly increase the size of the published data: it implicitly creates a huge number of dummy data points to mask the true data, making it almost impossible to work with. ::: We present techniques to overcome this roadblock and allow efficient private release of sparse data, while maintaining the guarantees of differential privacy. Our approach is to release a compact summary of the noisy data. Generating the noisy data and then summarizing it would still be very costly, so we show how to shortcut this step, and instead directly generate the summary from the input data, without materializing the vast intermediate noisy data. We instantiate this outline for a variety of sampling and filtering methods, and show how to use the resulting summary for approximate, private, query answering. Our experimental study shows that this is an effective, practical solution, with comparable and occasionally improved utility over the costly materialization approach. --- paper_title: Differentially private data cubes: optimizing noise sources and consistency paper_content: Data cubes play an essential role in data analysis and decision support. In a data cube, data from a fact table is aggregated on subsets of the table's dimensions, forming a collection of smaller tables called cuboids. When the fact table includes sensitive data such as salary or diagnosis, publishing even a subset of its cuboids may compromise individuals' privacy. In this paper, we address this problem using differential privacy (DP), which provides provable privacy guarantees for individuals by adding noise to query answers. We choose an initial subset of cuboids to compute directly from the fact table, injecting DP noise as usual; and then compute the remaining cuboids from the initial set. Given a fixed privacy guarantee, we show that it is NP-hard to choose the initial set of cuboids so that the maximal noise over all published cuboids is minimized, or so that the number of cuboids with noise below a given threshold (precise cuboids) is maximized. We provide an efficient procedure with running time polynomial in the number of cuboids to select the initial set of cuboids, such that the maximal noise in all published cuboids will be within a factor (ln\|L\| + 1)^2 of the optimal, where \|L\| is the number of cuboids to be published, or the number of precise cuboids will be within a factor (1 - 1/e) of the optimal. We also show how to enforce consistency in the published cuboids while simultaneously improving their utility (reducing error). In an empirical evaluation on real and synthetic data, we report the amounts of error of different publishing algorithms, and show that our approaches outperform baselines significantly. --- paper_title: Differential Privacy via Wavelet Transforms paper_content: Privacy preserving data publishing has attracted considerable research interest in recent years. Among the existing solutions, ∈-differential privacy provides one of the strongest privacy guarantees. Existing data publishing methods that achieve ∈-differential privacy, however, offer little data utility. In particular, if the output dataset is used to answer count queries, the noise in the query answers can be proportional to the number of tuples in the data, which renders the results useless. In this paper, we develop a data publishing technique that ensures ∈-differential privacy while providing accurate answers for range-count queries, i.e., count queries where the predicate on each attribute is a range. The core of our solution is a framework that applies wavelet transforms on the data before adding noise to it. We present instantiations of the proposed framework for both ordinal and nominal data, and we provide a theoretical analysis on their privacy and utility guarantees. In an extensive experimental study on both real and synthetic data, we show the effectiveness and efficiency of our solution. --- paper_title: Fast Private Data Release Algorithms for Sparse Queries paper_content: We revisit the problem of accurately answering large classes of statistical queries while preserving differential privacy. Previous approaches to this problem have either been very general but have not had run-time polynomial in the size of the database, have applied only to very limited classes of queries, or have relaxed the notion of worst-case error guarantees. In this paper we consider the large class of sparse queries, which take non-zero values on only polynomially many universe elements. We give efficient query release algorithms for this class, in both the interactive and the non-interactive setting. Our algorithms also achieve better accuracy bounds than previous general techniques do when applied to sparse queries: our bounds are independent of the universe size. In fact, even the runtime of our interactive mechanism is independent of the universe size, and so can be implemented in the"infinite universe"model in which no finite universe need be specified by the data curator. --- paper_title: Boosting the Accuracy of Differentially Private Histograms Through Consistency paper_content: We show that it is possible to significantly improve the accuracy of a general class of histogram queries while satisfying differential privacy. Our approach carefully chooses a set of queries to evaluate, and then exploits consistency constraints that should hold over the noisy output. In a post-processing phase, we compute the consistent input most likely to have produced the noisy output. The final output is differentially-private and consistent, but in addition, it is often much more accurate. We show, both theoretically and experimentally, that these techniques can be used for estimating the degree sequence of a graph very precisely, and for computing a histogram that can support arbitrary range queries accurately. --- paper_title: Compressive mechanism: utilizing sparse representation in differential privacy paper_content: Differential privacy provides the first theoretical foundation with provable privacy guarantee against adversaries with arbitrary prior knowledge. The main idea to achieve differential privacy is to inject random noise into statistical query results. Besides correctness, the most important goal in the design of a differentially private mechanism is to reduce the effect of random noise, ensuring that the noisy results can still be useful. This paper proposes the compressive mechanism, a novel solution on the basis of state-of-the-art compression technique, called compressive sensing. Compressive sensing is a decent theoretical tool for compact synopsis construction, using random projections. In this paper, we show that the amount of noise is significantly reduced from O(n) to O(log(n)), when the noise insertion procedure is carried on the synopsis samples instead of the original database. As an extension, we also apply the proposed compressive mechanism to solve the problem of continual release of statistical results. Extensive experiments using real datasets justify our accuracy claims. --- paper_title: Differentially Private Data Release through Multidimensional Partitioning paper_content: Differential privacy is a strong notion for protecting individual privacy in privacy preserving data analysis or publishing. In this paper, we study the problem of differentially private histogram release based on an interactive differential privacy interface. We propose two multidimensional partitioning strategies including a baseline cell-based partitioning and an innovative kd-tree based partitioning. In addition to providing formal proofs for differential privacy and usefulness guarantees for linear distributive queries, we also present a set of experimental results and demonstrate the feasibility and performance of our method. --- paper_title: On the complexity of differentially private data release: efficient algorithms and hardness results paper_content: We consider private data analysis in the setting in which a trusted and trustworthy curator, having obtained a large data set containing private information, releases to the public a "sanitization" of the data set that simultaneously protects the privacy of the individual contributors of data and offers utility to the data analyst. The sanitization may be in the form of an arbitrary data structure, accompanied by a computational procedure for determining approximate answers to queries on the original data set, or it may be a "synthetic data set" consisting of data items drawn from the same universe as items in the original data set; queries are carried out as if the synthetic data set were the actual input. In either case the process is non-interactive; once the sanitization has been released the original data and the curator play no further role. For the task of sanitizing with a synthetic dataset output, we map the boundary between computational feasibility and infeasibility with respect to a variety of utility measures. For the (potentially easier) task of sanitizing with unrestricted output format, we show a tight qualitative and quantitative connection between hardness of sanitizing and the existence of traitor tracing schemes. --- paper_title: Optimizing linear counting queries under differential privacy paper_content: Differential privacy is a robust privacy standard that has been successfully applied to a range of data analysis tasks. But despite much recent work, optimal strategies for answering a collection of related queries are not known. We propose the matrix mechanism, a new algorithm for answering a workload of predicate counting queries. Given a workload, the mechanism requests answers to a different set of queries, called a query strategy, which are answered using the standard Laplace mechanism. Noisy answers to the workload queries are then derived from the noisy answers to the strategy queries. This two stage process can result in a more complex correlated noise distribution that preserves differential privacy but increases accuracy. We provide a formal analysis of the error of query answers produced by the mechanism and investigate the problem of computing the optimal query strategy in support of a given workload. We show this problem can be formulated as a rank-constrained semidefinite program. Finally, we analyze two seemingly distinct techniques, whose similar behavior is explained by viewing them as instances of the matrix mechanism. --- paper_title: Differentially Private Publication of Sparse Data paper_content: The problem of privately releasing data is to provide a version of a dataset without revealing sensitive information about the individuals who contribute to the data. The model of differential privacy allows such private release while providing strong guarantees on the output. A basic mechanism achieves differential privacy by adding noise to the frequency counts in the contingency tables (or, a subset of the count data cube) derived from the dataset. However, when the dataset is sparse in its underlying space, as is the case for most multi-attribute relations, then the effect of adding noise is to vastly increase the size of the published data: it implicitly creates a huge number of dummy data points to mask the true data, making it almost impossible to work with. ::: We present techniques to overcome this roadblock and allow efficient private release of sparse data, while maintaining the guarantees of differential privacy. Our approach is to release a compact summary of the noisy data. Generating the noisy data and then summarizing it would still be very costly, so we show how to shortcut this step, and instead directly generate the summary from the input data, without materializing the vast intermediate noisy data. We instantiate this outline for a variety of sampling and filtering methods, and show how to use the resulting summary for approximate, private, query answering. Our experimental study shows that this is an effective, practical solution, with comparable and occasionally improved utility over the costly materialization approach. --- paper_title: Differentially private data cubes: optimizing noise sources and consistency paper_content: Data cubes play an essential role in data analysis and decision support. In a data cube, data from a fact table is aggregated on subsets of the table's dimensions, forming a collection of smaller tables called cuboids. When the fact table includes sensitive data such as salary or diagnosis, publishing even a subset of its cuboids may compromise individuals' privacy. In this paper, we address this problem using differential privacy (DP), which provides provable privacy guarantees for individuals by adding noise to query answers. We choose an initial subset of cuboids to compute directly from the fact table, injecting DP noise as usual; and then compute the remaining cuboids from the initial set. Given a fixed privacy guarantee, we show that it is NP-hard to choose the initial set of cuboids so that the maximal noise over all published cuboids is minimized, or so that the number of cuboids with noise below a given threshold (precise cuboids) is maximized. We provide an efficient procedure with running time polynomial in the number of cuboids to select the initial set of cuboids, such that the maximal noise in all published cuboids will be within a factor (ln\|L\| + 1)^2 of the optimal, where \|L\| is the number of cuboids to be published, or the number of precise cuboids will be within a factor (1 - 1/e) of the optimal. We also show how to enforce consistency in the published cuboids while simultaneously improving their utility (reducing error). In an empirical evaluation on real and synthetic data, we report the amounts of error of different publishing algorithms, and show that our approaches outperform baselines significantly. --- paper_title: Differential Privacy via Wavelet Transforms paper_content: Privacy preserving data publishing has attracted considerable research interest in recent years. Among the existing solutions, ∈-differential privacy provides one of the strongest privacy guarantees. Existing data publishing methods that achieve ∈-differential privacy, however, offer little data utility. In particular, if the output dataset is used to answer count queries, the noise in the query answers can be proportional to the number of tuples in the data, which renders the results useless. In this paper, we develop a data publishing technique that ensures ∈-differential privacy while providing accurate answers for range-count queries, i.e., count queries where the predicate on each attribute is a range. The core of our solution is a framework that applies wavelet transforms on the data before adding noise to it. We present instantiations of the proposed framework for both ordinal and nominal data, and we provide a theoretical analysis on their privacy and utility guarantees. In an extensive experimental study on both real and synthetic data, we show the effectiveness and efficiency of our solution. --- paper_title: Fast Private Data Release Algorithms for Sparse Queries paper_content: We revisit the problem of accurately answering large classes of statistical queries while preserving differential privacy. Previous approaches to this problem have either been very general but have not had run-time polynomial in the size of the database, have applied only to very limited classes of queries, or have relaxed the notion of worst-case error guarantees. In this paper we consider the large class of sparse queries, which take non-zero values on only polynomially many universe elements. We give efficient query release algorithms for this class, in both the interactive and the non-interactive setting. Our algorithms also achieve better accuracy bounds than previous general techniques do when applied to sparse queries: our bounds are independent of the universe size. In fact, even the runtime of our interactive mechanism is independent of the universe size, and so can be implemented in the"infinite universe"model in which no finite universe need be specified by the data curator. --- paper_title: Releasing search queries and clicks privately paper_content: The question of how to publish an anonymized search log was brought to the forefront by a well-intentioned, but privacy-unaware AOL search log release. Since then a series of ad-hoc techniques have been proposed in the literature, though none are known to be provably private. In this paper, we take a major step towards a solution: we show how queries, clicks and their associated perturbed counts can be published in a manner that rigorously preserves privacy. Our algorithm is decidedly simple to state, but non-trivial to analyze. On the opposite side of privacy is the question of whether the data we can safely publish is of any use. Our findings offer a glimmer of hope: we demonstrate that a non-negligible fraction of queries and clicks can indeed be safely published via a collection of experiments on a real search log. In addition, we select an application, keyword generation, and show that the keyword suggestions generated from the perturbed data resemble those generated from the original data. --- paper_title: Publishing Search Logs—A Comparative Study of Privacy Guarantees paper_content: Search engine companies collect the “database of intentions,” the histories of their users' search queries. These search logs are a gold mine for researchers. Search engine companies, however, are wary of publishing search logs in order not to disclose sensitive information. In this paper, we analyze algorithms for publishing frequent keywords, queries, and clicks of a search log. We first show how methods that achieve variants of k-anonymity are vulnerable to active attacks. We then demonstrate that the stronger guarantee ensured by e-differential privacy unfortunately does not provide any utility for this problem. We then propose an algorithm ZEALOUS and show how to set its parameters to achieve (e, δ)-probabilistic privacy. We also contrast our analysis of ZEALOUS with an analysis by Korolova et al. [17] that achieves (e',δ')-indistinguishability. Our paper concludes with a large experimental study using real applications where we compare ZEALOUS and previous work that achieves k-anonymity in search log publishing. Our results show that ZEALOUS yields comparable utility to k-anonymity while at the same time achieving much stronger privacy guarantees. --- paper_title: Differentially Private Publication of Sparse Data paper_content: The problem of privately releasing data is to provide a version of a dataset without revealing sensitive information about the individuals who contribute to the data. The model of differential privacy allows such private release while providing strong guarantees on the output. A basic mechanism achieves differential privacy by adding noise to the frequency counts in the contingency tables (or, a subset of the count data cube) derived from the dataset. However, when the dataset is sparse in its underlying space, as is the case for most multi-attribute relations, then the effect of adding noise is to vastly increase the size of the published data: it implicitly creates a huge number of dummy data points to mask the true data, making it almost impossible to work with. ::: We present techniques to overcome this roadblock and allow efficient private release of sparse data, while maintaining the guarantees of differential privacy. Our approach is to release a compact summary of the noisy data. Generating the noisy data and then summarizing it would still be very costly, so we show how to shortcut this step, and instead directly generate the summary from the input data, without materializing the vast intermediate noisy data. We instantiate this outline for a variety of sampling and filtering methods, and show how to use the resulting summary for approximate, private, query answering. Our experimental study shows that this is an effective, practical solution, with comparable and occasionally improved utility over the costly materialization approach. --- paper_title: Differentially private search log sanitization with optimal output utility paper_content: Web search logs contain extremely sensitive data, as evidenced by the recent AOL incident. However, storing and analyzing search logs can be very useful for many purposes (i.e. investigating human behavior). Thus, an important research question is how to privately sanitize search logs. Several search log anonymization techniques have been proposed with concrete privacy models. However, in all of these solutions, the output utility of the techniques is only evaluated rather than being maximized in any fashion. Indeed, for effective search log anonymization, it is desirable to derive the outputs with optimal utility while meeting the privacy standard. In this paper, we propose utility-maximizing sanitization based on the rigorous privacy standard of differential privacy, in the context of search logs. Specifically, we utilize optimization models to maximize the output utility of the sanitization for different applications, while ensuring that the production process satisfies differential privacy. An added benefit is that our novel randomization strategy maintains the schema integrity in the output search logs. A comprehensive evaluation on real search logs validates the approach and demonstrates its robustness and scalability. --- paper_title: Differentially Private Data Release through Multidimensional Partitioning paper_content: Differential privacy is a strong notion for protecting individual privacy in privacy preserving data analysis or publishing. In this paper, we study the problem of differentially private histogram release based on an interactive differential privacy interface. We propose two multidimensional partitioning strategies including a baseline cell-based partitioning and an innovative kd-tree based partitioning. In addition to providing formal proofs for differential privacy and usefulness guarantees for linear distributive queries, we also present a set of experimental results and demonstrate the feasibility and performance of our method. --- paper_title: Differentially Private Spatial Decompositions paper_content: Differential privacy has recently emerged as the de facto standard for private data release. This makes it possible to provide strong theoretical guarantees on the privacy and utility of released data. While it is well-understood how to release data based on counts and simple functions under this guarantee, it remains to provide general purpose techniques to release data that is useful for a variety of queries. In this paper, we focus on spatial data such as locations and more generally any multi-dimensional data that can be indexed by a tree structure. Directly applying existing differential privacy methods to this type of data simply generates noise. We propose instead the class of ``private spatial decompositions'': these adapt standard spatial indexing methods such as quad trees and kd-trees to provide a private description of the data distribution. Equipping such structures with differential privacy requires several steps to ensure that they provide meaningful privacy guarantees. Various basic steps, such as choosing splitting points and describing the distribution of points within a region, must be done privately, and the guarantees of the different building blocks composed to provide an overall guarantee. Consequently, we expose the design space for private spatial decompositions, and analyze some key examples. A major contribution of our work is to provide new techniques for parameter setting and post-processing the output to improve the accuracy of query answers. Our experimental study demonstrates that it is possible to build such decompositions efficiently, and use them to answer a variety of queries privately with high accuracy. --- paper_title: Private record matching using differential privacy paper_content: Private matching between datasets owned by distinct parties is a challenging problem with several applications. Private matching allows two parties to identify the records that are close to each other according to some distance functions, such that no additional information other than the join result is disclosed to any party. Private matching can be solved securely and accurately using secure multi-party computation (SMC) techniques, but such an approach is prohibitively expensive in practice. Previous work proposed the release of sanitized versions of the sensitive datasets which allows blocking, i.e., filtering out sub-sets of records that cannot be part of the join result. This way, SMC is applied only to a small fraction of record pairs, reducing the matching cost to acceptable levels. The blocking step is essential for the privacy, accuracy and efficiency of matching. However, the state-of-the-art focuses on sanitization based on k-anonymity, which does not provide sufficient privacy. We propose an alternative design centered on differential privacy, a novel paradigm that provides strong privacy guarantees. The realization of the new model presents difficult challenges, such as the evaluation of distance-based matching conditions with the help of only a statistical queries interface. Specialized versions of data indexing structures (e.g., kd-trees) also need to be devised, in order to comply with differential privacy. Experiments conducted on the real-world Census-income dataset show that, although our methods provide strong privacy, their effectiveness in reducing matching cost is not far from that of k-anonymity based counterparts. --- paper_title: Compressive mechanism: utilizing sparse representation in differential privacy paper_content: Differential privacy provides the first theoretical foundation with provable privacy guarantee against adversaries with arbitrary prior knowledge. The main idea to achieve differential privacy is to inject random noise into statistical query results. Besides correctness, the most important goal in the design of a differentially private mechanism is to reduce the effect of random noise, ensuring that the noisy results can still be useful. This paper proposes the compressive mechanism, a novel solution on the basis of state-of-the-art compression technique, called compressive sensing. Compressive sensing is a decent theoretical tool for compact synopsis construction, using random projections. In this paper, we show that the amount of noise is significantly reduced from O(n) to O(log(n)), when the noise insertion procedure is carried on the synopsis samples instead of the original database. As an extension, we also apply the proposed compressive mechanism to solve the problem of continual release of statistical results. Extensive experiments using real datasets justify our accuracy claims. --- paper_title: Fast Private Data Release Algorithms for Sparse Queries paper_content: We revisit the problem of accurately answering large classes of statistical queries while preserving differential privacy. Previous approaches to this problem have either been very general but have not had run-time polynomial in the size of the database, have applied only to very limited classes of queries, or have relaxed the notion of worst-case error guarantees. In this paper we consider the large class of sparse queries, which take non-zero values on only polynomially many universe elements. We give efficient query release algorithms for this class, in both the interactive and the non-interactive setting. Our algorithms also achieve better accuracy bounds than previous general techniques do when applied to sparse queries: our bounds are independent of the universe size. In fact, even the runtime of our interactive mechanism is independent of the universe size, and so can be implemented in the"infinite universe"model in which no finite universe need be specified by the data curator. --- paper_title: Calibrating Noise to Sensitivity in Private Data Analysis paper_content: We continue a line of research initiated in [10, 11] on privacy-preserving statistical databases. Consider a trusted server that holds a database of sensitive information. Given a query function f mapping databases to reals, the so-called true answer is the result of applying f to the database. To protect privacy, the true answer is perturbed by the addition of random noise generated according to a carefully chosen distribution, and this response, the true answer plus noise, is returned to the user. Previous work focused on the case of noisy sums, in which f = Σ i g(x i ), where x i denotes the ith row of the database and g maps database rows to [0,1]. We extend the study to general functions f, proving that privacy can be preserved by calibrating the standard deviation of the noise according to the sensitivity of the function f. Roughly speaking, this is the amount that any single argument to f can change its output. The new analysis shows that for several particular applications substantially less noise is needed than was previously understood to be the case. The first step is a very clean characterization of privacy in terms of indistinguishability of transcripts. Additionally, we obtain separation results showing the increased value of interactive sanitization mechanisms over non-interactive. --- paper_title: Publishing Set-Valued Data via Differential Privacy paper_content: Set-valued data provides enormous opportunities for various data mining tasks. In this paper, we study the problem of publishing set-valued data for data mining tasks under the rigorous differential privacy model. All existing data publishing methods for set-valued data are based on partitionbased privacy models, for example k-anonymity, which are vulnerable to privacy attacks based on background knowledge. In contrast, differential privacy provides strong privacy guarantees independent of an adversary’s background knowledge, computational power or subsequent behavior. Existing data publishing approaches for differential privacy, however, are not adequate in terms of both utility and scalability in the context of set-valued data due to its high dimensionality. We demonstrate that set-valued data could be efficiently released under differential privacy with guaranteed utility with the help of context-free taxonomy trees. We propose a probabilistic top-down partitioning algorithm to generate a differentially private release, which scales linearly with the input data size. We also discuss the applicability of our idea to the context of relational data. We prove that our result is (ǫ,δ)-useful for the class of counting queries, the foundation of many data mining tasks. We show that our approach maintains high utility for counting queries and frequent itemset mining and scales to large datasets through extensive experiments on real-life set-valued datasets. --- paper_title: Boosting the Accuracy of Differentially Private Histograms Through Consistency paper_content: We show that it is possible to significantly improve the accuracy of a general class of histogram queries while satisfying differential privacy. Our approach carefully chooses a set of queries to evaluate, and then exploits consistency constraints that should hold over the noisy output. In a post-processing phase, we compute the consistent input most likely to have produced the noisy output. The final output is differentially-private and consistent, but in addition, it is often much more accurate. We show, both theoretically and experimentally, that these techniques can be used for estimating the degree sequence of a graph very precisely, and for computing a histogram that can support arbitrary range queries accurately. --- paper_title: Differentially Private Trajectory Data Publication paper_content: With the increasing prevalence of location-aware devices, trajectory data has been generated and collected in various application domains. Trajectory data carries rich in- formation that is useful for many data analysis tasks. Yet, improper publishing and use of trajectory data could jeopardize individual privacy. However, it has been shown that existing privacy-preserving trajectory data publishing methods derived from partition-based privacy models, for example k-anonymity, are unable to provide sufficient privacy protection. In this paper, motivated by the data publishing scenario at the Societe de transport de Montreal (STM), the public transit agency in Montreal area, we study the problem of publishing trajectory data under the rigorous differential privacy model. We propose an efficient data-dependent yet differentially private sanitization algorithm, which is applicable to different types of trajectory data. The efficiency of our approach comes from adaptively narrowing down the output domain by building a noisy prefix tree based on the underlying data. Moreover, as a post-processing step, we make use of the inherent constraints of a prefix tree t o conduct constrained inferences, which lead to better utility. This is the first paper to introduce a practical solution for publi shing large volume of trajectory data under differential privacy. We examine the utility of sanitized data in terms of count queries and frequent sequential pattern mining. Extensive experiments on real-life trajectory data from the STM demonstrate that our approach maintains high utility and is scalable to large trajectory datasets. --- paper_title: Publishing Search Logs—A Comparative Study of Privacy Guarantees paper_content: Search engine companies collect the “database of intentions,” the histories of their users' search queries. These search logs are a gold mine for researchers. Search engine companies, however, are wary of publishing search logs in order not to disclose sensitive information. In this paper, we analyze algorithms for publishing frequent keywords, queries, and clicks of a search log. We first show how methods that achieve variants of k-anonymity are vulnerable to active attacks. We then demonstrate that the stronger guarantee ensured by e-differential privacy unfortunately does not provide any utility for this problem. We then propose an algorithm ZEALOUS and show how to set its parameters to achieve (e, δ)-probabilistic privacy. We also contrast our analysis of ZEALOUS with an analysis by Korolova et al. [17] that achieves (e',δ')-indistinguishability. Our paper concludes with a large experimental study using real applications where we compare ZEALOUS and previous work that achieves k-anonymity in search log publishing. Our results show that ZEALOUS yields comparable utility to k-anonymity while at the same time achieving much stronger privacy guarantees. --- paper_title: Differentially Private Data Release through Multidimensional Partitioning paper_content: Differential privacy is a strong notion for protecting individual privacy in privacy preserving data analysis or publishing. In this paper, we study the problem of differentially private histogram release based on an interactive differential privacy interface. We propose two multidimensional partitioning strategies including a baseline cell-based partitioning and an innovative kd-tree based partitioning. In addition to providing formal proofs for differential privacy and usefulness guarantees for linear distributive queries, we also present a set of experimental results and demonstrate the feasibility and performance of our method. --- paper_title: Differentially Private Spatial Decompositions paper_content: Differential privacy has recently emerged as the de facto standard for private data release. This makes it possible to provide strong theoretical guarantees on the privacy and utility of released data. While it is well-understood how to release data based on counts and simple functions under this guarantee, it remains to provide general purpose techniques to release data that is useful for a variety of queries. In this paper, we focus on spatial data such as locations and more generally any multi-dimensional data that can be indexed by a tree structure. Directly applying existing differential privacy methods to this type of data simply generates noise. We propose instead the class of ``private spatial decompositions'': these adapt standard spatial indexing methods such as quad trees and kd-trees to provide a private description of the data distribution. Equipping such structures with differential privacy requires several steps to ensure that they provide meaningful privacy guarantees. Various basic steps, such as choosing splitting points and describing the distribution of points within a region, must be done privately, and the guarantees of the different building blocks composed to provide an overall guarantee. Consequently, we expose the design space for private spatial decompositions, and analyze some key examples. A major contribution of our work is to provide new techniques for parameter setting and post-processing the output to improve the accuracy of query answers. Our experimental study demonstrates that it is possible to build such decompositions efficiently, and use them to answer a variety of queries privately with high accuracy. --- paper_title: Privacy: Theory meets Practice on the Map paper_content: In this paper, we propose the first formal privacy analysis of a data anonymization process known as the synthetic data generation, a technique becoming popular in the statistics community. The target application for this work is a mapping program that shows the commuting patterns of the population of the United States. The source data for this application were collected by the U.S. Census Bureau, but due to privacy constraints, they cannot be used directly by the mapping program. Instead, we generate synthetic data that statistically mimic the original data while providing privacy guarantees. We use these synthetic data as a surrogate for the original data. We find that while some existing definitions of privacy are inapplicable to our target application, others are too conservative and render the synthetic data useless since they guard against privacy breaches that are very unlikely. Moreover, the data in our target application is sparse, and none of the existing solutions are tailored to anonymize sparse data. In this paper, we propose solutions to address the above issues. --- paper_title: Differentially Private Publication of Sparse Data paper_content: The problem of privately releasing data is to provide a version of a dataset without revealing sensitive information about the individuals who contribute to the data. The model of differential privacy allows such private release while providing strong guarantees on the output. A basic mechanism achieves differential privacy by adding noise to the frequency counts in the contingency tables (or, a subset of the count data cube) derived from the dataset. However, when the dataset is sparse in its underlying space, as is the case for most multi-attribute relations, then the effect of adding noise is to vastly increase the size of the published data: it implicitly creates a huge number of dummy data points to mask the true data, making it almost impossible to work with. ::: We present techniques to overcome this roadblock and allow efficient private release of sparse data, while maintaining the guarantees of differential privacy. Our approach is to release a compact summary of the noisy data. Generating the noisy data and then summarizing it would still be very costly, so we show how to shortcut this step, and instead directly generate the summary from the input data, without materializing the vast intermediate noisy data. We instantiate this outline for a variety of sampling and filtering methods, and show how to use the resulting summary for approximate, private, query answering. Our experimental study shows that this is an effective, practical solution, with comparable and occasionally improved utility over the costly materialization approach. --- paper_title: Differential Privacy via Wavelet Transforms paper_content: Privacy preserving data publishing has attracted considerable research interest in recent years. Among the existing solutions, ∈-differential privacy provides one of the strongest privacy guarantees. Existing data publishing methods that achieve ∈-differential privacy, however, offer little data utility. In particular, if the output dataset is used to answer count queries, the noise in the query answers can be proportional to the number of tuples in the data, which renders the results useless. In this paper, we develop a data publishing technique that ensures ∈-differential privacy while providing accurate answers for range-count queries, i.e., count queries where the predicate on each attribute is a range. The core of our solution is a framework that applies wavelet transforms on the data before adding noise to it. We present instantiations of the proposed framework for both ordinal and nominal data, and we provide a theoretical analysis on their privacy and utility guarantees. In an extensive experimental study on both real and synthetic data, we show the effectiveness and efficiency of our solution. --- paper_title: Differentially private search log sanitization with optimal output utility paper_content: Web search logs contain extremely sensitive data, as evidenced by the recent AOL incident. However, storing and analyzing search logs can be very useful for many purposes (i.e. investigating human behavior). Thus, an important research question is how to privately sanitize search logs. Several search log anonymization techniques have been proposed with concrete privacy models. However, in all of these solutions, the output utility of the techniques is only evaluated rather than being maximized in any fashion. Indeed, for effective search log anonymization, it is desirable to derive the outputs with optimal utility while meeting the privacy standard. In this paper, we propose utility-maximizing sanitization based on the rigorous privacy standard of differential privacy, in the context of search logs. Specifically, we utilize optimization models to maximize the output utility of the sanitization for different applications, while ensuring that the production process satisfies differential privacy. An added benefit is that our novel randomization strategy maintains the schema integrity in the output search logs. A comprehensive evaluation on real search logs validates the approach and demonstrates its robustness and scalability. --- paper_title: Private record matching using differential privacy paper_content: Private matching between datasets owned by distinct parties is a challenging problem with several applications. Private matching allows two parties to identify the records that are close to each other according to some distance functions, such that no additional information other than the join result is disclosed to any party. Private matching can be solved securely and accurately using secure multi-party computation (SMC) techniques, but such an approach is prohibitively expensive in practice. Previous work proposed the release of sanitized versions of the sensitive datasets which allows blocking, i.e., filtering out sub-sets of records that cannot be part of the join result. This way, SMC is applied only to a small fraction of record pairs, reducing the matching cost to acceptable levels. The blocking step is essential for the privacy, accuracy and efficiency of matching. However, the state-of-the-art focuses on sanitization based on k-anonymity, which does not provide sufficient privacy. We propose an alternative design centered on differential privacy, a novel paradigm that provides strong privacy guarantees. The realization of the new model presents difficult challenges, such as the evaluation of distance-based matching conditions with the help of only a statistical queries interface. Specialized versions of data indexing structures (e.g., kd-trees) also need to be devised, in order to comply with differential privacy. Experiments conducted on the real-world Census-income dataset show that, although our methods provide strong privacy, their effectiveness in reducing matching cost is not far from that of k-anonymity based counterparts. --- paper_title: Publishing Set-Valued Data via Differential Privacy paper_content: Set-valued data provides enormous opportunities for various data mining tasks. In this paper, we study the problem of publishing set-valued data for data mining tasks under the rigorous differential privacy model. All existing data publishing methods for set-valued data are based on partitionbased privacy models, for example k-anonymity, which are vulnerable to privacy attacks based on background knowledge. In contrast, differential privacy provides strong privacy guarantees independent of an adversary’s background knowledge, computational power or subsequent behavior. Existing data publishing approaches for differential privacy, however, are not adequate in terms of both utility and scalability in the context of set-valued data due to its high dimensionality. We demonstrate that set-valued data could be efficiently released under differential privacy with guaranteed utility with the help of context-free taxonomy trees. We propose a probabilistic top-down partitioning algorithm to generate a differentially private release, which scales linearly with the input data size. We also discuss the applicability of our idea to the context of relational data. We prove that our result is (ǫ,δ)-useful for the class of counting queries, the foundation of many data mining tasks. We show that our approach maintains high utility for counting queries and frequent itemset mining and scales to large datasets through extensive experiments on real-life set-valued datasets. --- paper_title: Compressive mechanism: utilizing sparse representation in differential privacy paper_content: Differential privacy provides the first theoretical foundation with provable privacy guarantee against adversaries with arbitrary prior knowledge. The main idea to achieve differential privacy is to inject random noise into statistical query results. Besides correctness, the most important goal in the design of a differentially private mechanism is to reduce the effect of random noise, ensuring that the noisy results can still be useful. This paper proposes the compressive mechanism, a novel solution on the basis of state-of-the-art compression technique, called compressive sensing. Compressive sensing is a decent theoretical tool for compact synopsis construction, using random projections. In this paper, we show that the amount of noise is significantly reduced from O(n) to O(log(n)), when the noise insertion procedure is carried on the synopsis samples instead of the original database. As an extension, we also apply the proposed compressive mechanism to solve the problem of continual release of statistical results. Extensive experiments using real datasets justify our accuracy claims. --- paper_title: Differentially Private Trajectory Data Publication paper_content: With the increasing prevalence of location-aware devices, trajectory data has been generated and collected in various application domains. Trajectory data carries rich in- formation that is useful for many data analysis tasks. Yet, improper publishing and use of trajectory data could jeopardize individual privacy. However, it has been shown that existing privacy-preserving trajectory data publishing methods derived from partition-based privacy models, for example k-anonymity, are unable to provide sufficient privacy protection. In this paper, motivated by the data publishing scenario at the Societe de transport de Montreal (STM), the public transit agency in Montreal area, we study the problem of publishing trajectory data under the rigorous differential privacy model. We propose an efficient data-dependent yet differentially private sanitization algorithm, which is applicable to different types of trajectory data. The efficiency of our approach comes from adaptively narrowing down the output domain by building a noisy prefix tree based on the underlying data. Moreover, as a post-processing step, we make use of the inherent constraints of a prefix tree t o conduct constrained inferences, which lead to better utility. This is the first paper to introduce a practical solution for publi shing large volume of trajectory data under differential privacy. We examine the utility of sanitized data in terms of count queries and frequent sequential pattern mining. Extensive experiments on real-life trajectory data from the STM demonstrate that our approach maintains high utility and is scalable to large trajectory datasets. --- paper_title: Privacy: Theory meets Practice on the Map paper_content: In this paper, we propose the first formal privacy analysis of a data anonymization process known as the synthetic data generation, a technique becoming popular in the statistics community. The target application for this work is a mapping program that shows the commuting patterns of the population of the United States. The source data for this application were collected by the U.S. Census Bureau, but due to privacy constraints, they cannot be used directly by the mapping program. Instead, we generate synthetic data that statistically mimic the original data while providing privacy guarantees. We use these synthetic data as a surrogate for the original data. We find that while some existing definitions of privacy are inapplicable to our target application, others are too conservative and render the synthetic data useless since they guard against privacy breaches that are very unlikely. Moreover, the data in our target application is sparse, and none of the existing solutions are tailored to anonymize sparse data. In this paper, we propose solutions to address the above issues. --- paper_title: Differentially private search log sanitization with optimal output utility paper_content: Web search logs contain extremely sensitive data, as evidenced by the recent AOL incident. However, storing and analyzing search logs can be very useful for many purposes (i.e. investigating human behavior). Thus, an important research question is how to privately sanitize search logs. Several search log anonymization techniques have been proposed with concrete privacy models. However, in all of these solutions, the output utility of the techniques is only evaluated rather than being maximized in any fashion. Indeed, for effective search log anonymization, it is desirable to derive the outputs with optimal utility while meeting the privacy standard. In this paper, we propose utility-maximizing sanitization based on the rigorous privacy standard of differential privacy, in the context of search logs. Specifically, we utilize optimization models to maximize the output utility of the sanitization for different applications, while ensuring that the production process satisfies differential privacy. An added benefit is that our novel randomization strategy maintains the schema integrity in the output search logs. A comprehensive evaluation on real search logs validates the approach and demonstrates its robustness and scalability. --- paper_title: Publishing Set-Valued Data via Differential Privacy paper_content: Set-valued data provides enormous opportunities for various data mining tasks. In this paper, we study the problem of publishing set-valued data for data mining tasks under the rigorous differential privacy model. All existing data publishing methods for set-valued data are based on partitionbased privacy models, for example k-anonymity, which are vulnerable to privacy attacks based on background knowledge. In contrast, differential privacy provides strong privacy guarantees independent of an adversary’s background knowledge, computational power or subsequent behavior. Existing data publishing approaches for differential privacy, however, are not adequate in terms of both utility and scalability in the context of set-valued data due to its high dimensionality. We demonstrate that set-valued data could be efficiently released under differential privacy with guaranteed utility with the help of context-free taxonomy trees. We propose a probabilistic top-down partitioning algorithm to generate a differentially private release, which scales linearly with the input data size. We also discuss the applicability of our idea to the context of relational data. We prove that our result is (ǫ,δ)-useful for the class of counting queries, the foundation of many data mining tasks. We show that our approach maintains high utility for counting queries and frequent itemset mining and scales to large datasets through extensive experiments on real-life set-valued datasets. --- paper_title: Compressive mechanism: utilizing sparse representation in differential privacy paper_content: Differential privacy provides the first theoretical foundation with provable privacy guarantee against adversaries with arbitrary prior knowledge. The main idea to achieve differential privacy is to inject random noise into statistical query results. Besides correctness, the most important goal in the design of a differentially private mechanism is to reduce the effect of random noise, ensuring that the noisy results can still be useful. This paper proposes the compressive mechanism, a novel solution on the basis of state-of-the-art compression technique, called compressive sensing. Compressive sensing is a decent theoretical tool for compact synopsis construction, using random projections. In this paper, we show that the amount of noise is significantly reduced from O(n) to O(log(n)), when the noise insertion procedure is carried on the synopsis samples instead of the original database. As an extension, we also apply the proposed compressive mechanism to solve the problem of continual release of statistical results. Extensive experiments using real datasets justify our accuracy claims. --- paper_title: Differentially Private Trajectory Data Publication paper_content: With the increasing prevalence of location-aware devices, trajectory data has been generated and collected in various application domains. Trajectory data carries rich in- formation that is useful for many data analysis tasks. Yet, improper publishing and use of trajectory data could jeopardize individual privacy. However, it has been shown that existing privacy-preserving trajectory data publishing methods derived from partition-based privacy models, for example k-anonymity, are unable to provide sufficient privacy protection. In this paper, motivated by the data publishing scenario at the Societe de transport de Montreal (STM), the public transit agency in Montreal area, we study the problem of publishing trajectory data under the rigorous differential privacy model. We propose an efficient data-dependent yet differentially private sanitization algorithm, which is applicable to different types of trajectory data. The efficiency of our approach comes from adaptively narrowing down the output domain by building a noisy prefix tree based on the underlying data. Moreover, as a post-processing step, we make use of the inherent constraints of a prefix tree t o conduct constrained inferences, which lead to better utility. This is the first paper to introduce a practical solution for publi shing large volume of trajectory data under differential privacy. We examine the utility of sanitized data in terms of count queries and frequent sequential pattern mining. Extensive experiments on real-life trajectory data from the STM demonstrate that our approach maintains high utility and is scalable to large trajectory datasets. --- paper_title: Differentially Private Spatial Decompositions paper_content: Differential privacy has recently emerged as the de facto standard for private data release. This makes it possible to provide strong theoretical guarantees on the privacy and utility of released data. While it is well-understood how to release data based on counts and simple functions under this guarantee, it remains to provide general purpose techniques to release data that is useful for a variety of queries. In this paper, we focus on spatial data such as locations and more generally any multi-dimensional data that can be indexed by a tree structure. Directly applying existing differential privacy methods to this type of data simply generates noise. We propose instead the class of ``private spatial decompositions'': these adapt standard spatial indexing methods such as quad trees and kd-trees to provide a private description of the data distribution. Equipping such structures with differential privacy requires several steps to ensure that they provide meaningful privacy guarantees. Various basic steps, such as choosing splitting points and describing the distribution of points within a region, must be done privately, and the guarantees of the different building blocks composed to provide an overall guarantee. Consequently, we expose the design space for private spatial decompositions, and analyze some key examples. A major contribution of our work is to provide new techniques for parameter setting and post-processing the output to improve the accuracy of query answers. Our experimental study demonstrates that it is possible to build such decompositions efficiently, and use them to answer a variety of queries privately with high accuracy. --- paper_title: Differentially Private Publication of Sparse Data paper_content: The problem of privately releasing data is to provide a version of a dataset without revealing sensitive information about the individuals who contribute to the data. The model of differential privacy allows such private release while providing strong guarantees on the output. A basic mechanism achieves differential privacy by adding noise to the frequency counts in the contingency tables (or, a subset of the count data cube) derived from the dataset. However, when the dataset is sparse in its underlying space, as is the case for most multi-attribute relations, then the effect of adding noise is to vastly increase the size of the published data: it implicitly creates a huge number of dummy data points to mask the true data, making it almost impossible to work with. ::: We present techniques to overcome this roadblock and allow efficient private release of sparse data, while maintaining the guarantees of differential privacy. Our approach is to release a compact summary of the noisy data. Generating the noisy data and then summarizing it would still be very costly, so we show how to shortcut this step, and instead directly generate the summary from the input data, without materializing the vast intermediate noisy data. We instantiate this outline for a variety of sampling and filtering methods, and show how to use the resulting summary for approximate, private, query answering. Our experimental study shows that this is an effective, practical solution, with comparable and occasionally improved utility over the costly materialization approach. --- paper_title: Differential Privacy via Wavelet Transforms paper_content: Privacy preserving data publishing has attracted considerable research interest in recent years. Among the existing solutions, ∈-differential privacy provides one of the strongest privacy guarantees. Existing data publishing methods that achieve ∈-differential privacy, however, offer little data utility. In particular, if the output dataset is used to answer count queries, the noise in the query answers can be proportional to the number of tuples in the data, which renders the results useless. In this paper, we develop a data publishing technique that ensures ∈-differential privacy while providing accurate answers for range-count queries, i.e., count queries where the predicate on each attribute is a range. The core of our solution is a framework that applies wavelet transforms on the data before adding noise to it. We present instantiations of the proposed framework for both ordinal and nominal data, and we provide a theoretical analysis on their privacy and utility guarantees. In an extensive experimental study on both real and synthetic data, we show the effectiveness and efficiency of our solution. --- paper_title: Differentially private search log sanitization with optimal output utility paper_content: Web search logs contain extremely sensitive data, as evidenced by the recent AOL incident. However, storing and analyzing search logs can be very useful for many purposes (i.e. investigating human behavior). Thus, an important research question is how to privately sanitize search logs. Several search log anonymization techniques have been proposed with concrete privacy models. However, in all of these solutions, the output utility of the techniques is only evaluated rather than being maximized in any fashion. Indeed, for effective search log anonymization, it is desirable to derive the outputs with optimal utility while meeting the privacy standard. In this paper, we propose utility-maximizing sanitization based on the rigorous privacy standard of differential privacy, in the context of search logs. Specifically, we utilize optimization models to maximize the output utility of the sanitization for different applications, while ensuring that the production process satisfies differential privacy. An added benefit is that our novel randomization strategy maintains the schema integrity in the output search logs. A comprehensive evaluation on real search logs validates the approach and demonstrates its robustness and scalability. --- paper_title: Fast Private Data Release Algorithms for Sparse Queries paper_content: We revisit the problem of accurately answering large classes of statistical queries while preserving differential privacy. Previous approaches to this problem have either been very general but have not had run-time polynomial in the size of the database, have applied only to very limited classes of queries, or have relaxed the notion of worst-case error guarantees. In this paper we consider the large class of sparse queries, which take non-zero values on only polynomially many universe elements. We give efficient query release algorithms for this class, in both the interactive and the non-interactive setting. Our algorithms also achieve better accuracy bounds than previous general techniques do when applied to sparse queries: our bounds are independent of the universe size. In fact, even the runtime of our interactive mechanism is independent of the universe size, and so can be implemented in the"infinite universe"model in which no finite universe need be specified by the data curator. ---	Title: Non-Interactive Differential Privacy: a Survey Section 1: INTRODUCTION Description 1: This section covers the motivation behind the survey and the basic definitions related to differential privacy. Section 2: DIFFERENTIAL PRIVACY Description 2: This section explains the concept of differential privacy, introduces randomized mechanisms, and provides formal definitions along with examples. Section 3: Relaxations Description 3: This section discusses the relaxations of differential privacy and the need for these relaxations to maintain the utility of the data. Section 4: Is differential privacy good enough? Description 4: This section evaluates the effectiveness of differential privacy and addresses some criticisms regarding its applicability. Section 5: Mechanisms Description 5: This section details various mechanisms used to implement differential privacy, including the Laplace mechanism and the Exponential mechanism. Section 6: MEASURING UTILITY Description 6: This section discusses different approaches and metrics to measure the utility of differentially private mechanisms and their effectiveness. Section 7: METHODS Description 7: This section outlines different methods for releasing differentially private data, including histogram construction, sampling and filtering, partitioning, and dimensionality reduction. Section 8: APPLICATIONS Description 8: This section covers real-world applications of differential privacy and highlights successful case studies. Section 9: SYNTHETIC DATABASES Description 9: This section explores the generation and use of synthetic databases to preserve privacy while maintaining data utility. Section 10: CONCLUSIONS Description 10: This section summarizes the findings of the survey, underscoring the importance and applicability of differential privacy in various domains.
A review of High Performance Computing foundations for scientists	7	--- paper_title: Essentials Of Computational Chemistry Theories And Models paper_content: Thank you very much for downloading essentials of computational chemistry theories and models. Maybe you have knowledge that, people have search hundreds times for their chosen books like this essentials of computational chemistry theories and models, but end up in harmful downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they juggled with some malicious bugs inside their laptop. --- paper_title: 369 Tflop-s molecular dynamics simulations on the petaflop hybrid supercomputer ‘Roadrunner’ paper_content: We describe the implementation of a short-range parallel molecular dynamics (MD) code, SPaSM, on the heterogeneous general-purpose Roadrunner supercomputer. Each Roadrunner ‘TriBlade’ compute node consists of two AMD Opteron dual-core microprocessors and four IBM PowerXCell 8i enhanced Cell microprocessors (each consisting of one PPU and eight SPU cores), so that there are four MPI ranks per node, each with one Opteron and one Cell. We will briefly describe the Roadrunner architecture and some of the initial hybrid programming approaches that have been taken, focusing on the SPaSM application as a case study. An initial ‘evolutionary’ port, in which the existing legacy code runs with minor modifications on the Opterons and the Cells are only used to compute interatomic forces, achieves roughly a 2× speedup over the unaccelerated code. On the other hand, our ‘revolutionary’ implementation adopts a Cell-centric view, with data structures optimized for, and living on, the Cells. The Opterons are mainly used to direct inter-rank communication and perform I-O-heavy periodic analysis, visualization, and checkpointing tasks. The performance measured for our initial implementation of a standard Lennard–Jones pair potential benchmark reached a peak of 369 Tflop-s double-precision floating-point performance on the full Roadrunner system (27.7p of peak), nearly 10× faster than the unaccelerated (Opteron-only) version. Copyright © 2009 John Wiley & Sons, Ltd. --- paper_title: Spending Moore's dividend paper_content: Multicore computers shift the burden of software performance from chip designers and processor architects to software developers. --- paper_title: Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices paper_content: We have studied the magnetoresistance of (001)Fe/(001)Cr superlattices prepared by molecularbeam epitaxy. A huge magnetoresistance is found in superlattices with thin Cr layers: For example, with ${t}_{\mathrm{Cr}}=9$ \AA{}, at $T=4.2$ K, the resistivity is lowered by almost a factor of 2 in a magnetic field of 2 T. We ascribe this giant magnetoresistance to spin-dependent transmission of the conduction electrons between Fe layers through Cr layers. --- paper_title: Future hard disk drive systems paper_content: Abstract This paper briefly reviews the evolution of today's hard disk drive with the additional intention of orienting the reader to the overall mechanical and electrical architecture. The modern hard disk drive is a miracle of storage capacity and function together with remarkable economy of design. This paper presents a personal view of future customer requirements and the anticipated design evolution of the components. There are critical decisions and great challenges ahead for the key technologies of heads, media, head–disk interface, mechanics, and electronics. --- paper_title: Utilizing high performance computing for chemistry: parallel computational chemistry. paper_content: Parallel hardware has become readily available to the computational chemistry research community. This perspective will review the current state of parallel computational chemistry software utilizing high-performance parallel computing platforms. Hardware and software trends and their effect on quantum chemistry methodologies, algorithms, and software development will also be discussed. --- paper_title: Scientific data management in the coming decade paper_content: Scientific instruments and computer simulations are creating vast data stores that require new scientific methods to analyze and organize the data. Data volumes are approximately doubling each year. Since these new instruments have extraordinary precision, the data quality is also rapidly improving. Analyzing this data to find the subtle effects missed by previous studies requires algorithms that can simultaneously deal with huge datasets and that can find very subtle effects --- finding both needles in the haystack and finding very small haystacks that were undetected in previous measurements. --- paper_title: Introduction to High Performance Computing for Scientists and Engineers paper_content: Written by high performance computing (HPC) experts, Introduction to High Performance Computing for Scientists and Engineers provides a solid introduction to current mainstream computer architecture, dominant parallel programming models, and useful optimization strategies for scientific HPC. From working in a scientific computing center, the authors gained a unique perspective on the requirements and attitudes of users as well as manufacturers of parallel computers. The text first introduces the architecture of modern cache-based microprocessors and discusses their inherent performance limitations, before describing general optimization strategies for serial code on cache-based architectures. It next covers shared- and distributed-memory parallel computer architectures and the most relevant network topologies. After discussing parallel computing on a theoretical level, the authors show how to avoid or ameliorate typical performance problems connected with OpenMP. They then present cache-coherent nonuniform memory access (ccNUMA) optimization techniques, examine distributed-memory parallel programming with message passing interface (MPI), and explain how to write efficient MPI code. The final chapter focuses on hybrid programming with MPI and OpenMP. Users of high performance computers often have no idea what factors limit time to solution and whether it makes sense to think about optimization at all. This book facilitates an intuitive understanding of performance limitations without relying on heavy computer science knowledge. It also prepares readers for studying more advanced literature. --- paper_title: An optimal multimedia object allocation solution in multi-powermode storage systems paper_content: Given a set of multimedia objects R=lo1, o2, …, okr each of which has a set of multiple versions oi.v=lAi.0, Ai.1, …, Ai.mr, i=1, 2, …, k, there is a problem of distributing these objects in a server system so that user requests for accessing specified multimedia objects can be fulfilled with the minimum energy consumption and without significant degrading of the system performance. This paper considers the allocation problem of multimedia objects in multi-powermode storage systems, where the objects are distributed among multi-powermode storages based on the access pattern to the objects. We design an underlying infrastructure of storage system and propose a dynamic multimedia object allocation policy based on the designed infrastructure, which integrate and prove the optimality of the proposed policy. Copyright © 2010 John Wiley & Sons, Ltd. --- paper_title: Spending Moore's dividend paper_content: Multicore computers shift the burden of software performance from chip designers and processor architects to software developers. --- paper_title: The impact of multicore on math software paper_content: Power consumption and heat dissipation issues are pushing the microprocessors industry towards multicore design patterns. Given the cubic dependence between core frequency and power consumption, multicore technologies leverage the idea that doubling the number of cores and halving the cores frequency gives roughly the same performance reducing the power consumption by a factor of four. With the number of cores on multicore chips expected to reach tens in a few years, efficient implementations of numerical libraries using shared memory programming models is of high interest. The current message passing paradigm used in ScaLAPACK and elsewhere introduces unnecessary memory overhead and memory copy operations, which degrade performance, along with the making it harder to schedule operations that could be done in parallel. Limiting the use of shared memory to fork-join parallelism (perhaps with OpenMP) or to its use within the BLAS does not address all these issues. --- paper_title: Utilizing high performance computing for chemistry: parallel computational chemistry. paper_content: Parallel hardware has become readily available to the computational chemistry research community. This perspective will review the current state of parallel computational chemistry software utilizing high-performance parallel computing platforms. Hardware and software trends and their effect on quantum chemistry methodologies, algorithms, and software development will also be discussed. --- paper_title: The impact of IBM Cell technology on the programming paradigm in the context of computer systems for climate and weather models paper_content: The call for ever-increasing model resolutions and physical processes in climate and weather models demands a continual increase in computing power. The IBM Cell processor's order-of-magnitude peak performance increase over conventional processors makes it very attractive to fulfill this requirement. However, the Cell's characteristics, 256 kB local memory per SPE and the new low-level communication mechanism, make it very challenging to port an application. As a trial, we selected the solar radiation component of the NASA GEOS-5 climate model, which: (1) is representative of column-physics components (half of the total computational time), (2) has an extremely high computational intensity: the ratio of computational load to main memory transfers, and (3) exhibits embarrassingly parallel column computations. In this paper, we converted the baseline code (single-precision Fortran) to C and ported it to an IBM BladeCenter QS20. For performance, we manually SIMDize four independent columns and include several unrolling optimizations. Our results show that when compared with the baseline implementation running on one core of Intel's Xeon Woodcrest, Dempsey, and Itanium2, the Cell is approximately 8.8x, 11.6x, and 12.8x faster, respectively. Our preliminary analysis shows that the Cell can also accelerate the dynamics component (∼25p total computational time). We believe these dramatic performance improvements make the Cell processor very competitive as an accelerator. Copyright © 2009 John Wiley & Sons, Ltd. --- paper_title: octopus: a tool for the application of time-dependent density functional theory paper_content: We report on the background, current status, and current lines of development of the octopus project. This program materializes the main equations of density-functional theory in the ground state, and of time-dependent density-functional theory for dynamical effects. The focus is nowadays placed on the optical (i.e. electronic) linear response properties of nanostructures and biomolecules, and on the non-linear response to high-intensity fields of finite systems, with particular attention to the coupled ionic-electronic motion (i.e. photo-chemical processes). In addition, we are currently extending the code to the treatment of periodic systems (both to one-dimensional chains, two-dimensional slabs, or fully periodic solids), magnetic properties (ground state properties and excitations), and to the field of quantum-mechanical transport or “molecular electronics.” In this communication, we concentrate on the development of the methodology: we review the essential numerical schemes used in the code, and report on the most recent implementations, with special attention to the introduction of adaptive coordinates, to the extension of our real-space technique to tackle periodic systems, and on large-scale parallelization. More information on the code, as well as the code itself, can be found at http://www.tddft.org/programs/octopus/. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) --- paper_title: The Future of Microprocessors paper_content: The performance of microprocessors that power modern computers has continued to increase exponentially over the years for two main reasons. First, the transistors that are the heart of the circuits in all processors and memory chips have simply become faster over time on a course described by Moore’s law,1 and this directly affects the performance of processors built with those transistors. Moreover, actual processor performance has increased faster than Moore’s law would predict,2 because processor designers have been able to harness the increasing numbers of transistors available on modern chips to extract more parallelism from software. This is depicted in figure 1 for Intel’s processors. --- paper_title: Cramming More Components Onto Integrated Circuits paper_content: The future of integrated electronics is the future of electronics itself. The advantages of integration will bring about a proliferation of electronics, pushing this science into many new areas. Integrated circuits will lead to such wonders as home computers—or at least terminals connected to a central computer—automatic controls for automobiles, and personal portable communications equipment. The electronic wristwatch needs only a display to be feasible today. But the biggest potential lies in the production of large systems. In telephone communications, integrated circuits in digital filters will separate channels on multiplex equipment. Integrated circuits will also switch telephone circuits and perform data processing. Computers will be more powerful, and will be organized in completely different ways. For example, memories built of integrated electronics may be distributed throughout the machine instead of being concentrated in a central unit. In addition, the improved reliability made possible by integrated circuits will allow the construction of larger processing units. Machines similar to those in existence today will be built at lower costs and with faster turnaround. --- paper_title: N-body simulation for self-gravitating collisional systems with a new SIMD instruction set extension to the x86 architecture, Advanced Vector eXtensions paper_content: We present a high-performance N-body code for self-gravitating collisional systems accelerated with the aid of a new SIMD instruction set extension of the x86 architecture: Advanced Vector eXtensions (AVX), an enhanced version of the Streaming SIMD Extensions (SSE). With one processor core of Intel Core i7-2600 processor (8 MB cache and 3.40 GHz) based on Sandy Bridge micro-architecture, we implemented a fourth-order Hermite scheme with individual timestep scheme (Makino and Aarseth, 1992), and achieved the performance of 20 giga floating point number operations per second (GFLOPS) for double-precision accuracy, which is two times and five times higher than that of the previously developed code implemented with the SSE instructions (Nitadori et al., 2006b), and that of a code implemented without any explicit use of SIMD instructions with the same processor core, respectively. We have parallelized the code by using so-called NINJA scheme (Nitadori et al., 2006a), and achieved 90 GFLOPS for a system containing more than N = 8192 particles with 8 MPI processes on four cores. We expect to achieve about 10 tera FLOPS (TFLOPS) for a self-gravitating collisional system with N 105 on massively parallel systems with at most 800 cores with Sandy Bridge micro-architecture. This performance will be comparable to that of Graphic Processing Unit (GPU) cluster systems, such as the one with about 200 Tesla C1070 GPUs (Spurzem et al., 2010). This paper offers an alternative to collisional N-body simulations with GRAPEs and GPUs. --- paper_title: octopus: a first-principles tool for excited electron-ion dynamics. paper_content: We present a computer package aimed at the simulation of the electron–ion dynamics of finite systems, both in one and three dimensions, under the influence of time-dependent electromagnetic fields. The electronic degrees of freedom are treated quantum mechanically within the time-dependent Kohn–Sham formalism, while the ions are handled classically. All quantities are expanded in a regular mesh in real space, and the simulations are performed in real time. Although not optimized for that purpose, the program is also able to obtain static properties like ground-state geometries, or static polarizabilities. The method employed proved quite reliable and general, and has been successfully used to calculate linear and non-linear absorption spectra, harmonic spectra, laser induced fragmentation, etc. of a variety of systems, from small clusters to medium sized quantum dots.  2002 Elsevier Science B.V. All rights reserved. --- paper_title: Introduction to High Performance Computing for Scientists and Engineers paper_content: Written by high performance computing (HPC) experts, Introduction to High Performance Computing for Scientists and Engineers provides a solid introduction to current mainstream computer architecture, dominant parallel programming models, and useful optimization strategies for scientific HPC. From working in a scientific computing center, the authors gained a unique perspective on the requirements and attitudes of users as well as manufacturers of parallel computers. The text first introduces the architecture of modern cache-based microprocessors and discusses their inherent performance limitations, before describing general optimization strategies for serial code on cache-based architectures. It next covers shared- and distributed-memory parallel computer architectures and the most relevant network topologies. After discussing parallel computing on a theoretical level, the authors show how to avoid or ameliorate typical performance problems connected with OpenMP. They then present cache-coherent nonuniform memory access (ccNUMA) optimization techniques, examine distributed-memory parallel programming with message passing interface (MPI), and explain how to write efficient MPI code. The final chapter focuses on hybrid programming with MPI and OpenMP. Users of high performance computers often have no idea what factors limit time to solution and whether it makes sense to think about optimization at all. This book facilitates an intuitive understanding of performance limitations without relying on heavy computer science knowledge. It also prepares readers for studying more advanced literature. --- paper_title: 369 Tflop-s molecular dynamics simulations on the petaflop hybrid supercomputer ‘Roadrunner’ paper_content: We describe the implementation of a short-range parallel molecular dynamics (MD) code, SPaSM, on the heterogeneous general-purpose Roadrunner supercomputer. Each Roadrunner ‘TriBlade’ compute node consists of two AMD Opteron dual-core microprocessors and four IBM PowerXCell 8i enhanced Cell microprocessors (each consisting of one PPU and eight SPU cores), so that there are four MPI ranks per node, each with one Opteron and one Cell. We will briefly describe the Roadrunner architecture and some of the initial hybrid programming approaches that have been taken, focusing on the SPaSM application as a case study. An initial ‘evolutionary’ port, in which the existing legacy code runs with minor modifications on the Opterons and the Cells are only used to compute interatomic forces, achieves roughly a 2× speedup over the unaccelerated code. On the other hand, our ‘revolutionary’ implementation adopts a Cell-centric view, with data structures optimized for, and living on, the Cells. The Opterons are mainly used to direct inter-rank communication and perform I-O-heavy periodic analysis, visualization, and checkpointing tasks. The performance measured for our initial implementation of a standard Lennard–Jones pair potential benchmark reached a peak of 369 Tflop-s double-precision floating-point performance on the full Roadrunner system (27.7p of peak), nearly 10× faster than the unaccelerated (Opteron-only) version. Copyright © 2009 John Wiley & Sons, Ltd. --- paper_title: Lattice Boltzmann simulation optimization on leading multicore platforms paper_content: We present an auto-tuning approach to optimize application performance on emerging multicore architectures. The methodology extends the idea of search-based performance optimizations, popular in linear algebra and FFT libraries, to application-specific computational kernels. Our work applies this strategy to a lattice Boltzmann application (LBMHD) that historically has made poor use of scalar microprocessors due to its complex data structures and memory access patterns. We explore one of the broadest sets of multicore architectures in the HPC literature, including the Intel Clovertown, AMD Opteron X2, Sun Niagara!, STI Cell, as well as the single core Intel Itanium.2. Rather than hand-tuning LBMHD for each system, we develop a code generator that allows us identify a highly optimized version for each platform, while amortizing the human programming effort. Results show that our auto- tuned LBMHD application achieves up to a 14times improvement compared with the original code. Additionally, we present detailed analysis of each optimization, which reveal surprising hardware bottlenecks and software challenges for future multicore systems and applications. --- paper_title: Atomistic protein folding simulations on the submillisecond time scale using worldwide distributed computing paper_content: Atomistic simulations of protein folding have the potential to be a great complement to experimental studies, but have been severely limited by the time scales accessible with current computer hardware and algorithms. By employing a worldwide distributed computing network of tens of thousands of PCs and algorithms designed to efficiently utilize this new many-processor, highly heterogeneous, loosely coupled distributed computing paradigm, we have been able to simulate hundreds of microseconds of atomistic molecular dynamics. This has allowed us to directly simulate the folding mechanism and to accurately predict the folding rate of several fast-folding proteins and polymers, including a nonbiological helix, polypeptide alpha-helices, a beta-hairpin, and a three-helix bundle protein from the villin headpiece. Our results demonstrate that one can reach the time scales needed to simulate fast folding using distributed computing, and that potential sets used to describe interatomic interactions are sufficiently accurate to reach the folded state with experimentally validated rates, at least for small proteins. --- paper_title: Utilizing high performance computing for chemistry: parallel computational chemistry. paper_content: Parallel hardware has become readily available to the computational chemistry research community. This perspective will review the current state of parallel computational chemistry software utilizing high-performance parallel computing platforms. Hardware and software trends and their effect on quantum chemistry methodologies, algorithms, and software development will also be discussed. --- paper_title: The Future of Microprocessors paper_content: The performance of microprocessors that power modern computers has continued to increase exponentially over the years for two main reasons. First, the transistors that are the heart of the circuits in all processors and memory chips have simply become faster over time on a course described by Moore’s law,1 and this directly affects the performance of processors built with those transistors. Moreover, actual processor performance has increased faster than Moore’s law would predict,2 because processor designers have been able to harness the increasing numbers of transistors available on modern chips to extract more parallelism from software. This is depicted in figure 1 for Intel’s processors. --- paper_title: Proton Transfer 200 Years after von Grotthuss: Insights from Ab Initio Simulations paper_content: In the last decade, ab initio simulations and especially Car-Parrinello molecular dynamics have significantly conttibuted to the improvement of our undetstanding of both the physical and chemical properties of water, ice, and hydrogen-bonded systems in general. At the heart of this family of in silico techniques lies the crucial idea of computing the -many-body interactions by solving the electronic structure problem 'on the fly" as the simulation proceeds, which circumvents the need for pre-parameterized potential models. In particular, the field of proton transfer in hydrogen-bonded networks greatly benefits from these technical advawes. Here, several systems of seemingly quite different nature and of increasing complexity, such as Grotthuss diffusion in water, excited state proton transfer in solution, phase transitions in ice, and pratonated water networis in the membrane protein bacteriorhodopsin, are discussed in the realms of a unifying viewpoint. --- paper_title: Introduction to High Performance Computing for Scientists and Engineers paper_content: Written by high performance computing (HPC) experts, Introduction to High Performance Computing for Scientists and Engineers provides a solid introduction to current mainstream computer architecture, dominant parallel programming models, and useful optimization strategies for scientific HPC. From working in a scientific computing center, the authors gained a unique perspective on the requirements and attitudes of users as well as manufacturers of parallel computers. The text first introduces the architecture of modern cache-based microprocessors and discusses their inherent performance limitations, before describing general optimization strategies for serial code on cache-based architectures. It next covers shared- and distributed-memory parallel computer architectures and the most relevant network topologies. After discussing parallel computing on a theoretical level, the authors show how to avoid or ameliorate typical performance problems connected with OpenMP. They then present cache-coherent nonuniform memory access (ccNUMA) optimization techniques, examine distributed-memory parallel programming with message passing interface (MPI), and explain how to write efficient MPI code. The final chapter focuses on hybrid programming with MPI and OpenMP. Users of high performance computers often have no idea what factors limit time to solution and whether it makes sense to think about optimization at all. This book facilitates an intuitive understanding of performance limitations without relying on heavy computer science knowledge. It also prepares readers for studying more advanced literature. --- paper_title: 369 Tflop-s molecular dynamics simulations on the petaflop hybrid supercomputer ‘Roadrunner’ paper_content: We describe the implementation of a short-range parallel molecular dynamics (MD) code, SPaSM, on the heterogeneous general-purpose Roadrunner supercomputer. Each Roadrunner ‘TriBlade’ compute node consists of two AMD Opteron dual-core microprocessors and four IBM PowerXCell 8i enhanced Cell microprocessors (each consisting of one PPU and eight SPU cores), so that there are four MPI ranks per node, each with one Opteron and one Cell. We will briefly describe the Roadrunner architecture and some of the initial hybrid programming approaches that have been taken, focusing on the SPaSM application as a case study. An initial ‘evolutionary’ port, in which the existing legacy code runs with minor modifications on the Opterons and the Cells are only used to compute interatomic forces, achieves roughly a 2× speedup over the unaccelerated code. On the other hand, our ‘revolutionary’ implementation adopts a Cell-centric view, with data structures optimized for, and living on, the Cells. The Opterons are mainly used to direct inter-rank communication and perform I-O-heavy periodic analysis, visualization, and checkpointing tasks. The performance measured for our initial implementation of a standard Lennard–Jones pair potential benchmark reached a peak of 369 Tflop-s double-precision floating-point performance on the full Roadrunner system (27.7p of peak), nearly 10× faster than the unaccelerated (Opteron-only) version. Copyright © 2009 John Wiley & Sons, Ltd. --- paper_title: Spending Moore's dividend paper_content: Multicore computers shift the burden of software performance from chip designers and processor architects to software developers. --- paper_title: The Case for Energy-Proportional Computing paper_content: Energy-proportional designs would enable large energy savings in servers, potentially doubling their efficiency in real-life use. Achieving energy proportionality will require significant improvements in the energy usage profile of every system component, particularly the memory and disk subsystems. --- paper_title: The impact of multicore on math software paper_content: Power consumption and heat dissipation issues are pushing the microprocessors industry towards multicore design patterns. Given the cubic dependence between core frequency and power consumption, multicore technologies leverage the idea that doubling the number of cores and halving the cores frequency gives roughly the same performance reducing the power consumption by a factor of four. With the number of cores on multicore chips expected to reach tens in a few years, efficient implementations of numerical libraries using shared memory programming models is of high interest. The current message passing paradigm used in ScaLAPACK and elsewhere introduces unnecessary memory overhead and memory copy operations, which degrade performance, along with the making it harder to schedule operations that could be done in parallel. Limiting the use of shared memory to fork-join parallelism (perhaps with OpenMP) or to its use within the BLAS does not address all these issues. --- paper_title: The impact of IBM Cell technology on the programming paradigm in the context of computer systems for climate and weather models paper_content: The call for ever-increasing model resolutions and physical processes in climate and weather models demands a continual increase in computing power. The IBM Cell processor's order-of-magnitude peak performance increase over conventional processors makes it very attractive to fulfill this requirement. However, the Cell's characteristics, 256 kB local memory per SPE and the new low-level communication mechanism, make it very challenging to port an application. As a trial, we selected the solar radiation component of the NASA GEOS-5 climate model, which: (1) is representative of column-physics components (half of the total computational time), (2) has an extremely high computational intensity: the ratio of computational load to main memory transfers, and (3) exhibits embarrassingly parallel column computations. In this paper, we converted the baseline code (single-precision Fortran) to C and ported it to an IBM BladeCenter QS20. For performance, we manually SIMDize four independent columns and include several unrolling optimizations. Our results show that when compared with the baseline implementation running on one core of Intel's Xeon Woodcrest, Dempsey, and Itanium2, the Cell is approximately 8.8x, 11.6x, and 12.8x faster, respectively. Our preliminary analysis shows that the Cell can also accelerate the dynamics component (∼25p total computational time). We believe these dramatic performance improvements make the Cell processor very competitive as an accelerator. Copyright © 2009 John Wiley & Sons, Ltd. --- paper_title: Millisecond-scale molecular dynamics simulations on Anton paper_content: Anton is a recently completed special-purpose supercomputer designed for molecular dynamics (MD) simulations of biomolecular systems. The machine's specialized hardware dramatically increases the speed of MD calculations, making possible for the first time the simulation of biological molecules at an atomic level of detail for periods on the order of a millisecond---about two orders of magnitude beyond the previous state of the art. Anton is now running simulations on a timescale at which many critically important, but poorly understood phenomena are known to occur, allowing the observation of aspects of protein dynamics that were previously inaccessible to both computational and experimental study. Here, we report Anton's performance when executing actual MD simulations whose accuracy has been validated against both existing MD software and experimental observations. We also discuss the manner in which novel algorithms have been coordinated with Anton's co-designed, application-specific hardware to achieve these results. --- paper_title: The Future of Microprocessors paper_content: The performance of microprocessors that power modern computers has continued to increase exponentially over the years for two main reasons. First, the transistors that are the heart of the circuits in all processors and memory chips have simply become faster over time on a course described by Moore’s law,1 and this directly affects the performance of processors built with those transistors. Moreover, actual processor performance has increased faster than Moore’s law would predict,2 because processor designers have been able to harness the increasing numbers of transistors available on modern chips to extract more parallelism from software. This is depicted in figure 1 for Intel’s processors. --- paper_title: JANUS: an FPGA-based System for High Performance Scientific Computing paper_content: Janus is a modular, massively parallel, and reconfigurable FPGA-based computing system. Each Janus module has one computational core and one host. Janus is tailored to, but not limited to, the needs of a class of hard scientific applications characterized by regular code structure, unconventional data-manipulation requirements, and a few Megabits database. The authors discuss this configurable system's architecture and focus on its use for Monte Carlo simulations of statistical mechanics, as Janus performs impressively on this class of application. --- paper_title: Exploring atomic resolution physiology on a femtosecond to millisecond timescale using molecular dynamics simulations paper_content: Discovering the functional mechanisms of biological systems frequently requires information that challenges the spatial and temporal resolution limits of current experimental techniques. Recent dramatic methodological advances have made all-atom molecular dynamics (MD) simulations an ever more --- paper_title: Introduction to High Performance Computing for Scientists and Engineers paper_content: Written by high performance computing (HPC) experts, Introduction to High Performance Computing for Scientists and Engineers provides a solid introduction to current mainstream computer architecture, dominant parallel programming models, and useful optimization strategies for scientific HPC. From working in a scientific computing center, the authors gained a unique perspective on the requirements and attitudes of users as well as manufacturers of parallel computers. The text first introduces the architecture of modern cache-based microprocessors and discusses their inherent performance limitations, before describing general optimization strategies for serial code on cache-based architectures. It next covers shared- and distributed-memory parallel computer architectures and the most relevant network topologies. After discussing parallel computing on a theoretical level, the authors show how to avoid or ameliorate typical performance problems connected with OpenMP. They then present cache-coherent nonuniform memory access (ccNUMA) optimization techniques, examine distributed-memory parallel programming with message passing interface (MPI), and explain how to write efficient MPI code. The final chapter focuses on hybrid programming with MPI and OpenMP. Users of high performance computers often have no idea what factors limit time to solution and whether it makes sense to think about optimization at all. This book facilitates an intuitive understanding of performance limitations without relying on heavy computer science knowledge. It also prepares readers for studying more advanced literature. --- paper_title: 369 Tflop-s molecular dynamics simulations on the petaflop hybrid supercomputer ‘Roadrunner’ paper_content: We describe the implementation of a short-range parallel molecular dynamics (MD) code, SPaSM, on the heterogeneous general-purpose Roadrunner supercomputer. Each Roadrunner ‘TriBlade’ compute node consists of two AMD Opteron dual-core microprocessors and four IBM PowerXCell 8i enhanced Cell microprocessors (each consisting of one PPU and eight SPU cores), so that there are four MPI ranks per node, each with one Opteron and one Cell. We will briefly describe the Roadrunner architecture and some of the initial hybrid programming approaches that have been taken, focusing on the SPaSM application as a case study. An initial ‘evolutionary’ port, in which the existing legacy code runs with minor modifications on the Opterons and the Cells are only used to compute interatomic forces, achieves roughly a 2× speedup over the unaccelerated code. On the other hand, our ‘revolutionary’ implementation adopts a Cell-centric view, with data structures optimized for, and living on, the Cells. The Opterons are mainly used to direct inter-rank communication and perform I-O-heavy periodic analysis, visualization, and checkpointing tasks. The performance measured for our initial implementation of a standard Lennard–Jones pair potential benchmark reached a peak of 369 Tflop-s double-precision floating-point performance on the full Roadrunner system (27.7p of peak), nearly 10× faster than the unaccelerated (Opteron-only) version. Copyright © 2009 John Wiley & Sons, Ltd. --- paper_title: Extending Amdahl's Law for Energy-Efficient Computing in the Many-Core Era paper_content: An updated take on Amdahl's analytical model uses modern design constraints to analyze many-core design alternatives. The revised models provide computer architects with a better understanding of many-core design types, enabling them to make more informed tradeoffs. --- paper_title: The LINPACK Benchmark : past , present and future paper_content: SUMMARY This paper describes the LINPACK Benchmark and some of its variations commonly used to assess the performance of computer systems. Aside from the LINPACK Benchmark suite, the TOP500 and the HPL codes are presented. The latter is frequently used to obtained results for TOP500 submissions. Information is also given on how to interpret the results of the benchmark and how the results fit into the performance evaluation process. Copyright c � 2003 John Wiley & Sons, Ltd. --- paper_title: Spending Moore's dividend paper_content: Multicore computers shift the burden of software performance from chip designers and processor architects to software developers. --- paper_title: Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices paper_content: We have studied the magnetoresistance of (001)Fe/(001)Cr superlattices prepared by molecularbeam epitaxy. A huge magnetoresistance is found in superlattices with thin Cr layers: For example, with ${t}_{\mathrm{Cr}}=9$ \AA{}, at $T=4.2$ K, the resistivity is lowered by almost a factor of 2 in a magnetic field of 2 T. We ascribe this giant magnetoresistance to spin-dependent transmission of the conduction electrons between Fe layers through Cr layers. --- paper_title: Atomistic protein folding simulations on the submillisecond time scale using worldwide distributed computing paper_content: Atomistic simulations of protein folding have the potential to be a great complement to experimental studies, but have been severely limited by the time scales accessible with current computer hardware and algorithms. By employing a worldwide distributed computing network of tens of thousands of PCs and algorithms designed to efficiently utilize this new many-processor, highly heterogeneous, loosely coupled distributed computing paradigm, we have been able to simulate hundreds of microseconds of atomistic molecular dynamics. This has allowed us to directly simulate the folding mechanism and to accurately predict the folding rate of several fast-folding proteins and polymers, including a nonbiological helix, polypeptide alpha-helices, a beta-hairpin, and a three-helix bundle protein from the villin headpiece. Our results demonstrate that one can reach the time scales needed to simulate fast folding using distributed computing, and that potential sets used to describe interatomic interactions are sufficiently accurate to reach the folded state with experimentally validated rates, at least for small proteins. --- paper_title: Scientific data management in the coming decade paper_content: Scientific instruments and computer simulations are creating vast data stores that require new scientific methods to analyze and organize the data. Data volumes are approximately doubling each year. Since these new instruments have extraordinary precision, the data quality is also rapidly improving. Analyzing this data to find the subtle effects missed by previous studies requires algorithms that can simultaneously deal with huge datasets and that can find very subtle effects --- finding both needles in the haystack and finding very small haystacks that were undetected in previous measurements. --- paper_title: Computer simulation study of the structural stability and materials properties of DNA-intercalated layered double hydroxides. paper_content: The intercalation of DNA into layered double hydroxides (LDHs) has various applications, including drug delivery for gene therapy and origins of life studies. The nanoscale dimensions of the interlayer region make the exact conformation of the intercalated DNA difficult to elucidate experimentally. We use molecular dynamics techniques, performed on high performance supercomputing grids, to carry out large-scale simulations of double stranded, linear and plasmid DNA up to 480 base pairs in length intercalated within a magnesium-aluminum LDH. Currently only limited experimental data have been reported for these systems. Our models are found to be in agreement with experimental observations, according to which hydration is a crucial factor in determining the structural stability of DNA. Phosphate backbone groups are found to align with aluminum lattice positions. At elevated temperatures and pressures, relevant to origins of life studies which maintain that the earliest life forms originated around deep ocean hydrothermal vents, the structural stability of LDH-intercalated DNA is substantially enhanced as compared to DNA in bulk water. We also discuss how the materials properties of the LDH are modified due to DNA intercalation. --- paper_title: Grid Computing: Techniques and Applications paper_content: Designed for senior undergraduate and first-year graduate students, this classroom-tested book shows professors how to teach this subject in a practical way. It encompasses the varied and interconnected aspects of Grid computing, including how to design a system infrastructure and Grid portal. The text covers job submission and scheduling, Grid security, Grid computing services and software tools, graphical user interfaces, workflow editors, and Grid-enabling applications. It also contains programming assignments and multiple-choice questions and answers. The authors Web site offers various instructional resources, including slides and links to software for the programming assignments. --- paper_title: Introduction to High Performance Computing for Scientists and Engineers paper_content: Written by high performance computing (HPC) experts, Introduction to High Performance Computing for Scientists and Engineers provides a solid introduction to current mainstream computer architecture, dominant parallel programming models, and useful optimization strategies for scientific HPC. From working in a scientific computing center, the authors gained a unique perspective on the requirements and attitudes of users as well as manufacturers of parallel computers. The text first introduces the architecture of modern cache-based microprocessors and discusses their inherent performance limitations, before describing general optimization strategies for serial code on cache-based architectures. It next covers shared- and distributed-memory parallel computer architectures and the most relevant network topologies. After discussing parallel computing on a theoretical level, the authors show how to avoid or ameliorate typical performance problems connected with OpenMP. They then present cache-coherent nonuniform memory access (ccNUMA) optimization techniques, examine distributed-memory parallel programming with message passing interface (MPI), and explain how to write efficient MPI code. The final chapter focuses on hybrid programming with MPI and OpenMP. Users of high performance computers often have no idea what factors limit time to solution and whether it makes sense to think about optimization at all. This book facilitates an intuitive understanding of performance limitations without relying on heavy computer science knowledge. It also prepares readers for studying more advanced literature. --- paper_title: 369 Tflop-s molecular dynamics simulations on the petaflop hybrid supercomputer ‘Roadrunner’ paper_content: We describe the implementation of a short-range parallel molecular dynamics (MD) code, SPaSM, on the heterogeneous general-purpose Roadrunner supercomputer. Each Roadrunner ‘TriBlade’ compute node consists of two AMD Opteron dual-core microprocessors and four IBM PowerXCell 8i enhanced Cell microprocessors (each consisting of one PPU and eight SPU cores), so that there are four MPI ranks per node, each with one Opteron and one Cell. We will briefly describe the Roadrunner architecture and some of the initial hybrid programming approaches that have been taken, focusing on the SPaSM application as a case study. An initial ‘evolutionary’ port, in which the existing legacy code runs with minor modifications on the Opterons and the Cells are only used to compute interatomic forces, achieves roughly a 2× speedup over the unaccelerated code. On the other hand, our ‘revolutionary’ implementation adopts a Cell-centric view, with data structures optimized for, and living on, the Cells. The Opterons are mainly used to direct inter-rank communication and perform I-O-heavy periodic analysis, visualization, and checkpointing tasks. The performance measured for our initial implementation of a standard Lennard–Jones pair potential benchmark reached a peak of 369 Tflop-s double-precision floating-point performance on the full Roadrunner system (27.7p of peak), nearly 10× faster than the unaccelerated (Opteron-only) version. Copyright © 2009 John Wiley & Sons, Ltd. --- paper_title: An optimal multimedia object allocation solution in multi-powermode storage systems paper_content: Given a set of multimedia objects R=lo1, o2, …, okr each of which has a set of multiple versions oi.v=lAi.0, Ai.1, …, Ai.mr, i=1, 2, …, k, there is a problem of distributing these objects in a server system so that user requests for accessing specified multimedia objects can be fulfilled with the minimum energy consumption and without significant degrading of the system performance. This paper considers the allocation problem of multimedia objects in multi-powermode storage systems, where the objects are distributed among multi-powermode storages based on the access pattern to the objects. We design an underlying infrastructure of storage system and propose a dynamic multimedia object allocation policy based on the designed infrastructure, which integrate and prove the optimality of the proposed policy. Copyright © 2010 John Wiley & Sons, Ltd. ---	Title: A Review of High Performance Computing Foundations for Scientists Section 1: Introduction Description 1: Introduce the importance and role of scientific computer simulation, and provide an overview of High Performance Computing (HPC) and its application. Section 2: Hardware basics Description 2: Describe the basic components of a computer, including memory, Control Unit, Arithmetic Logic Unit (ALU), and how these components work together. Discuss memory hierarchy in detail. Section 3: Beyond the Von Neumann paradigm Description 3: Explain the limitations of the traditional Von Neumann architecture and discuss modern improvements and alternatives such as integration, clock-rate increase, superscalarity, multicore architecture, multithreading, SIMD instructions, out-of-order execution, and simplified instruction sets. Section 4: Parallel computers Description 4: Discuss the architecture and design of parallel computers, including shared-memory and distributed-memory systems, the importance of network topology, and different types of parallel supercomputers. Section 5: Hybrid and heterogeneous models Description 5: Describe the construction and benefits of hybrid and heterogeneous machines that combine different kinds of processors such as CPUs, GPUs, and special-purpose chips. Include a discussion on the advantages and challenges of these models. Section 6: Distributed computing Description 6: Explain newer forms of high-performance computing like grid computing, volunteer computing, and cloud computing. Discuss how these distributed computing methods work, their benefits and drawbacks. Section 7: Intrinsic limitations to accuracy and efficiency Description 7: Examine the issues related to accuracy and execution time in scientific calculations. Discuss machine precision errors, soft errors, algorithm-specific errors, and the implications of Amdahl's Law and Gustafson's Law on parallel computing.
A Review of Control Algorithms for Autonomous Quadrotors	14	--- paper_title: Attitude Stabilization Control of a Quadrotor UAV by Using Backstepping Approach paper_content: The modeling and attitude stabilization control problems of a four-rotor vertical takeoff and landing unmanned air vehicle (UAV) known as the quadrotor are investigated. The quadrotor’s attitude is represented by the unit quaternion rather than Euler angles to avoid singularity problem. Taking dynamical behavior of motors into consideration and ignoring aerodynamic effect, a nonlinear controller is developed to stabilize the attitude. The control design is accomplished by using backstepping control technique. The proposed control law is based on the compensation for the Coriolis and gyroscope torques. Applying Lyapunov stability analysis proves that the closed-loop attitude system is asymptotic stable. Moreover, the controller can guarantee that all the states of the system are uniformly ultimately bounded in the presence of external disturbance torque. The effectiveness of the proposed control approach is analytically authenticated and also validated via simulation study. --- paper_title: Design and control of quadrotors with application to autonomous flying paper_content: This thesis is about modelling, design and control of Miniature Flying Robots (MFR) with a focus on Vertical Take-Off and Landing (VTOL) systems and specifically, micro quadrotors. It introduces a mathematical model for simulation and control of such systems. It then describes a design methodology for a miniature rotorcraft. The methodology is subsequently applied to design an autonomous quadrotor named OS4. Based on the mathematical model, linear and nonlinear control techniques are used to design and simulate various controllers along this work. The dynamic model and the simulator evolved from a simple set of equations, valid only for hovering, to a complex mathematical model with more realistic aerodynamic coefficients and sensor and actuator models. Two platforms were developed during this thesis. The first one is a quadrotor-like test-bench with off-board data processing and power supply. It was used to safely and easily test control strategies. The second one, OS4, is a highly integrated quadrotor with on-board data processing and power supply. It has all the necessary sensors for autonomous operation. Five different controllers were developed. The first one, based on Lyapunov theory, was applied for attitude control. The second and the third controllers are based on PID and LQ techniques. These were compared for attitude control. The fourth and the fifth approaches use backstepping and sliding-mode concepts. They are applied to control attitude. Finally, backstepping is augmented with integral action and proposed as a single tool to design attitude, altitude and position controllers. This approach is validated through various flight experiments conducted on the OS4. --- paper_title: Artificial intelligent-based feedforward optimized PID wheel slip controller paper_content: Continual improvement of the anti-lock braking system control strategy is the focus of this work. Advances in auto-electronics and sub-systems such as the brake-by-wire technology are the driving forces behind the improvement of the anti-lock braking system. The control strategy has shifted from speed-control to slip-control strategy. In the current slip-control approach, proportional-integral-derivative (PID) controller and its variants: P, PI and PD have been proposed in place of the bang-bang controller mostly used in commercial ABS. Though the PID controller is famous due to its wide applications in industry: irrespective of the nature of the process or system, it might lead to limited performance when applied to the ABS. In order to improve the performance of the PID controller, a neural network inverse model of the plant is used to optimize the reference input slip. The resultant neural network-based PID ABS is then tested in Matlab® /Simulink® simulation environment. The results of the proposed controller, exhibits more accurate slip tracking than the PID-slip controller. --- paper_title: Dynamic analysis and PID control for a quadrotor paper_content: In order to analyze the dynamic characteristics and PID controller performance of a quadrotor, this paper firstly describes the architecture of the quadrotor and analyzes the dynamic model of it. Then, based on the classic scheme of PID control, this paper designs a controller, which aims to regulate the posture (position and orientation) of the 6 d.o.f. quadrotor. Thirdly, the dynamic model is implemented in Matlab/Simulink simulation, and the PID control parameters are obtained according to the simulation results. Finally, a quadrotor with PID controllers is designed and made. In order to do the experiment, a flying experiment for the quadrotor has been done. The results of flying experiment show that the PID controllers robustly stabilize the quadrotor. --- paper_title: Hovering control of a quadrotor paper_content: This paper deals with the hovering control of a quadrotor. First, we derive the quadrotor model using the Euler-Lagrange equation and perform experiment to identify the model parameter. Second, we divide a quadrotor system into two subsystems: the attitude system and the altitude system. For attitude control, we use PID control method, and for the altitude control, we use dynamic surface control (DSC) method. From the Lyapunov stability theory, we prove that all signals of a quadrotor system are uniformly ultimately bounded(UUB). Finally, we present the simulation and experimental results to verify the effectiveness of the proposed control method. --- paper_title: PID vs LQ control techniques applied to an indoor micro quadrotor paper_content: The development of miniature flying robots has become a reachable dream, thanks to the new sensing and actuating technologies. Micro VTOL systems represent a useful class of flying robots because of their strong abilities for small-area monitoring and building exploration. In this paper, we present the results of two model-based control techniques applied to an autonomous four-rotor micro helicopter called quadrotor. A classical approach (PID) assumed a simplified dynamics and a modern technique (LQ) based on a more complete model. Various simulations were performed and several tests on the bench validate the control laws. Finally, we present the results of the first test in flight with the helicopter released. These developments are part of the OS4 project in our lab. --- paper_title: Modeling and control of quadrotor MAV using vision-based measurement paper_content: In this paper we review the mathematics model of quadrotor using Lagrange's equation. We propose a vision-based measurement to stabilize this model. A dual camera method is used for estimating the pose of the quadrotor; positions and attitudes of the quadrotor MAV. One of these cameras is located on-board the quadrotor MAV, and the orther is located on the ground. The control system is developed in Matlab/Simulink. In this paper, we consider a linear controller for our purpose. Linear Quadratic tracking controller with integral action, and Optimal Linear Quadratic Gaussian (LQG) control with integral action are designed for stabilization of the attitude of the quadrotor MAV. Moreover, some measurement noises will be considered in the controller design, too. Finally, this paper will demonstrate how well this control works for a certain flight mission: quadrotor MAV on the ground, and then starting hover, sideway move and keeping the position with a pointing to a certain object fixed in space. --- paper_title: A prototype of an autonomous controller for a quadrotor UAV paper_content: The paper proposes a complete real-time control algorithm for autonomous collision-free operations of the quadrotor UAV. As opposed to fixed wing vehicles the quadrotor is a small agile vehicle which might be more suitable for the variety of specific applications including search and rescue, surveillance and remote inspection. The developed control system incorporates both trajectory planning and path following. Using a differential flatness property the trajectory planning is posed as a constrained optimization problem in the output space (as opposed to the control space), which simplifies the problem. The trajectory and speed profile are parameterized to reduce the problem to a finite dimensional problem. To optimize the speed profile independently of the trajectory a virtual argument is used as opposed to time. A path following portion of the proposed algorithm uses a standard linear multi-variable control technique. The paper presents the results of simulations to demonstrate the suitability of the proposed control algorithm. --- paper_title: Sliding Mode Control of quadrotor paper_content: This paper presents a design method for attitude control of an autonomous quadrotor based sliding Mode Control. We are interested in the dynamic modeling of quadrotor because of it complexity. The dynamic model is used to design a stable and accurate controller to perform the best tracking and attitude results. To stabilize the overall systems, each sliding mode controller is designed based on the Lyapunov stability theory. The advantage of sliding mode control is its not being sensitive to model errors, parametric uncertainties and other disturbances. Lastly, we show that the control law has a good robust and good stability though simulation. --- paper_title: Sliding Mode Control of a Quadrotor Helicopter paper_content: In this paper, we present a new design method for the flight control of an autonomous quadrotor helicopter based on sliding mode control. Due to the under-actuated property of a quadrotor helicopter, the controller can make the helicopter move three positions (x, y, z) and the yaw angle to their desired values and stabilize the pitch and roll angles. A sliding mode control is proposed to stabilize a class of cascaded under-actuated systems. The global stability analysis of the closed-loop system is presented. The advantage of sliding mode control is its insensitivity to the model errors, parametric uncertainties and other disturbances. Simulations show that the control law robustly stabilizes a quadrotor. --- paper_title: Attitude Stabilization Control of a Quadrotor UAV by Using Backstepping Approach paper_content: The modeling and attitude stabilization control problems of a four-rotor vertical takeoff and landing unmanned air vehicle (UAV) known as the quadrotor are investigated. The quadrotor’s attitude is represented by the unit quaternion rather than Euler angles to avoid singularity problem. Taking dynamical behavior of motors into consideration and ignoring aerodynamic effect, a nonlinear controller is developed to stabilize the attitude. The control design is accomplished by using backstepping control technique. The proposed control law is based on the compensation for the Coriolis and gyroscope torques. Applying Lyapunov stability analysis proves that the closed-loop attitude system is asymptotic stable. Moreover, the controller can guarantee that all the states of the system are uniformly ultimately bounded in the presence of external disturbance torque. The effectiveness of the proposed control approach is analytically authenticated and also validated via simulation study. --- paper_title: Adaptive integral backstepping control of a Micro-Quadrotor paper_content: Micro-Quadrotor aerial robots have enormous potential applications in the field of near-area surveillance and exploration in military and commercial applications. However, stabilizing and position control of the robot are difficult tasks because of the nonlinear dynamic behavior and model uncertainties. Backstepping is a widely used control law for under-actuated systems including quadrotor. But general backstepping control algorithm needs accurate model parameters and isn't robust to external disturbances. In this paper, an adaptive integral backstepping control algorithm is proposed to realize robust control of quadrotor. The proposed control algorithm can estimate disturbances online and therefore improve the robustness of the system. Simulation results show that the proposed algorithm performs well against model uncertainties. --- paper_title: Backstepping Control for a Quadrotor Helicopter paper_content: This paper presents a nonlinear dynamic model for a quadrotor helicopter in a form suited for backstepping control design. Due to the under-actuated property of quadrotor helicopter, the controller can set the helicopter track three Cartesian positions (x, y, z) and the yaw angle to their desired values and stabilize the pitch and roll angles. The system has been presented into three interconnected subsystems. The first one representing the under-actuated subsystem, gives the dynamic relation of the horizontal positions (x, y) with the pitch and roll angles. The second fully-actuated subsystem gives the dynamics of the vertical position z and the yaw angle. The last subsystem gives the dynamics of the propeller forces. A backstepping control is presented to stabilize the whole system. The design methodology is based on the Lyapunov stability theory. Various simulations of the model show that the control law stabilizes a quadrotor with good tracking. --- paper_title: Adaptive Control of a Quadrotor with Dynamic Changes in the Center of Gravity paper_content: Abstract In this paper, we address the problem of quadrotor stabilization and trajectory tracking with dynamic changes in the quadrotor's center of gravity. This problem has great practical significance in many UAV applications. However, it has received little attention in literature so far. In this paper, we present an adaptive tracking controller based on output feedback linearization that compensates for dynamical changes in the center of gravity of the quadrotor. Effectiveness and robustness of the proposed adaptive control scheme is verified through simulation results. The proposed controller is an important step towards developing the next generation of agile autonomous aerial vehicles. This control algorithm enables a quadrotor to display agile maneuvers while reconfiguring in real time whenever a change in the center of gravity occurs. --- paper_title: Position trajectory tracking of a quadrotor helicopter based on L1 adaptive control paper_content: We present an adaptive backstepping controller for the position trajectory tracking of a quadrotor. The tracking controller is based on the L1 adaptive control approach and uses a typical nonlinear quadrotor model. We slightly modify the L1 adaptive control design for linear systems to comply with the time-varying nonlinear error dynamics that arise from the backstepping design. Our approach yields a stable adaptive system with verifiable bounds on the tracking error and input signals. The adaptive controller compensates for all model uncertainties and for all bounded disturbances within a particular frequency range, which we specify a priori. The design of this frequency range involves a trade-off between control performance and robustness, which can be managed transparently through the L1 adaptive control design. Simulation results show the powerful properties of the presented control application. --- paper_title: A nonlinear adaptive control approach for quadrotor UAVs paper_content: In this paper, a continuous, time varying adaptive controller is developed for an underactuated quadrotor unmanned aerial vehicle (UAV). The vehicle's dynamic model is subject to uncertainties associated with mass, inertia matrix, and aerodynamic damping coefficients. A Lyapunov based approach is utilized to ensure that position and yaw rotation tracking errors are ultimately driven to a neighborhood about zero that can be made arbitrary small. Simulation results are included to illustrate the performance of the control strategy. --- paper_title: Robust control of quadrotor unmanned air vehicles paper_content: A robust control approach for a quadrotor helicopter is presented. The controller consists of two parts: an attitude controller and a position controller. The attitude controller is designed based on linear control combined with robust compensation. The linear controller is designed for the nominal system to achieve desired nominal performances, while the robust compensator is applied to restrain the effects of uncertainties and external disturbances. The position controller was realized with classical PD method. Experimental results on the Tsinghua Autonomous Quadrotor System (TAQS) which is developed in our laboratory demonstrate the effectiveness of the designed controller. --- paper_title: Robust attitude tracking control of a quadrotor helicopter in the presence of uncertainty paper_content: A robust attitude tracking controller is presented in this paper, which achieves asymptotic tracking of a quadrotor helicopter in the presence of parametric uncertainty and unknown, nonlinear, non-vanishing disturbances, which do not satisfy the linear-in-the-parameters assumption. One of the challenges encountered in the control design is that the control input is premultiplied by a nonlinear, state-varying matrix containing parametric uncertainty. An integral sliding mode control technique is employed to compensate for the nonlinear disturbances, and the input-multiplicative uncertainty is mitigated through innovative algebraic manipulation in the error system development. The proposed robust control law is designed to be practically implementable, requiring no observers, function approximators, or online adaptation laws. Asymptotic trajectory tracking is proven via Lyapunov-based stability analysis, and simulation results are provided to verify the performance of the proposed controller. --- paper_title: Attitude Stabilization Control of a Quadrotor UAV by Using Backstepping Approach paper_content: The modeling and attitude stabilization control problems of a four-rotor vertical takeoff and landing unmanned air vehicle (UAV) known as the quadrotor are investigated. The quadrotor’s attitude is represented by the unit quaternion rather than Euler angles to avoid singularity problem. Taking dynamical behavior of motors into consideration and ignoring aerodynamic effect, a nonlinear controller is developed to stabilize the attitude. The control design is accomplished by using backstepping control technique. The proposed control law is based on the compensation for the Coriolis and gyroscope torques. Applying Lyapunov stability analysis proves that the closed-loop attitude system is asymptotic stable. Moreover, the controller can guarantee that all the states of the system are uniformly ultimately bounded in the presence of external disturbance torque. The effectiveness of the proposed control approach is analytically authenticated and also validated via simulation study. --- paper_title: Robust Optimal Control of Quadrotor UAVs paper_content: This paper provides the design and implementation of an L1-optimal control of a quadrotor unmanned aerial vehicle (UAV). The quadrotor UAV is an underactuated rigid body with four propellers that generate forces along the rotor axes. These four forces are used to achieve asymptotic tracking of four outputs, namely the position of the center of mass of the UAV and the heading. With perfect knowledge of plant parameters and no measurement noise, the magnitudes of the errors are shown to exponentially converge to zero. In the case of parametric uncertainty and measurement noise, the controller yields an exponential decrease of the magnitude of the errors in an L1-optimal sense. In other words, the controller is designed so that it minimizes the L∞-gain of the plant with respect to disturbances. The performance of the controller is evaluated in experiments and compared with that of a related robust nonlinear controller in the literature. The experimental data shows that the proposed controller rejects persistent disturbances, which is quantified by a very small magnitude of the mean error. --- paper_title: Path following controller for a quadrotor helicopter paper_content: A path following controller is presented for a quadrotor helicopter model. The controller relies on input dynamic extension and feedback linearization. The controller allows the designer to specify the speed profile of the quadrotor on the path and its yaw angle as a function of the displacement. --- paper_title: Adaptive Control of a Quadrotor with Dynamic Changes in the Center of Gravity paper_content: Abstract In this paper, we address the problem of quadrotor stabilization and trajectory tracking with dynamic changes in the quadrotor's center of gravity. This problem has great practical significance in many UAV applications. However, it has received little attention in literature so far. In this paper, we present an adaptive tracking controller based on output feedback linearization that compensates for dynamical changes in the center of gravity of the quadrotor. Effectiveness and robustness of the proposed adaptive control scheme is verified through simulation results. The proposed controller is an important step towards developing the next generation of agile autonomous aerial vehicles. This control algorithm enables a quadrotor to display agile maneuvers while reconfiguring in real time whenever a change in the center of gravity occurs. --- paper_title: Adaptive Neural Network for a Quadrotor Unmanned Aerial Vehicle paper_content: A new adaptive neural control scheme for quadrotor helicopter stabilization at the presence of sinusoidal disturbance is proposed in this paper. The adaptive control classical laws such e-modification presents some limitations in particular when persistent oscillations are presenting in the input. These techniques can create a dilemma between weights drifting and tracking errors. To avoid this problem in adaptive Single Hidden Layer neural network scheme, a new solution is proposed in this work. The main idea is based on the use of two SHL in parallel instead of one in the closed loop in order to estimate the unknown nonlinear function in Quadrotor dynamical model. The learning algorithms of the two SHL Networks are obtained using the Lyapunov stability method. The simulation results are given to highlight the performances of the proposed control scheme. --- paper_title: Intelligent fuzzy controller of a quadrotor paper_content: The aim of this work is to describe an intelligent system based on fuzzy logic that is developed to control a quadrotor. A quadrotor is a helicopter with four rotors, that make the vehicle more stable but more complex to model and to control. The quadrotor has been used as a testing platform in the last years for various universities and research centres. A quadrotor has six degrees of freedom, three of them regarding the position: height, horizontal and vertical motions; and the other three are related to the orientation: pitch, roll and yaw. A fuzzy control is designed and implemented to control a simulation model of the quadrotor. The inputs are the desired values of the height, roll, pitch and yaw. The outputs are the power of each of the four rotors that is necessary to reach the specifications. Simulation results prove the efficiency of this intelligent control strategy. --- paper_title: Output Feedback Control of a Quadrotor UAV Using Neural Networks paper_content: In this paper, a new nonlinear controller for a quadrotor unmanned aerial vehicle (UAV) is proposed using neural networks (NNs) and output feedback. The assumption on the availability of UAV dynamics is not always practical, especially in an outdoor environment. Therefore, in this work, an NN is introduced to learn the complete dynamics of the UAV online, including uncertain nonlinear terms like aerodynamic friction and blade flapping. Although a quadrotor UAV is underactuated, a novel NN virtual control input scheme is proposed which allows all six degrees of freedom (DOF) of the UAV to be controlled using only four control inputs. Furthermore, an NN observer is introduced to estimate the translational and angular velocities of the UAV, and an output feedback control law is developed in which only the position and the attitude of the UAV are considered measurable. It is shown using Lyapunov theory that the position, orientation, and velocity tracking errors, the virtual control and observer estimation errors, and the NN weight estimation errors for each NN are all semiglobally uniformly ultimately bounded (SGUUB) in the presence of bounded disturbances and NN functional reconstruction errors while simultaneously relaxing the separation principle. The effectiveness of proposed output feedback control scheme is then demonstrated in the presence of unknown nonlinear dynamics and disturbances, and simulation results are included to demonstrate the theoretical conjecture. --- paper_title: Adaptive Control via Backstepping Technique and Neural Networks of a Quadrotor Helicopter paper_content: Abstract A nonlinear adaptive controller for the quadrotor helicopter is proposed using backstepping technique mixed with neural networks. The backstepping strategy is used to achieve good tracking of desired translation positions and yaw angle while maintaining the stability of pitch and roll angles simultaneously. The knowledge of all physical parameters and the exact model of the quadrotor are not required for the controller, only some properties of the model are needed. In fact, online adaptation of neural networks and some parameters is used to compensate some unmodeled dynamics including aerodynamic effects. Under certain relaxed assumptions, the proposed control scheme can guarantee that all the signals in the closed-loop system are Uniformly Ultimately Bounded (UUB). The design methodology is based on Lyapunov stability. One salient feature of the proposed approach is that the controller can be applied to any type of quadrotor helicopter of different masses and lengths within the same class. The feasibility of the control scheme is demonstrated through simulation results. --- paper_title: Feedback linearization and high order sliding mode observer for a quadrotor UAV paper_content: In this paper, a feedback linearization-based con- troller with a high order sliding mode observer running parallel is applied to a quadrotor unmanned aerial vehicle. The high order sliding mode observer works as an observer and estimator of the effect of the external disturbances such as wind and noise. The whole observer-estimator-control law constitutes an original approach to the vehicle regulation with minimal num- ber of sensors. Performance issues of the controller-observer are illustrated in a simulation study that takes into account parameter uncertainties and external disturbances. I. INTRODUCTION --- paper_title: Backstepping sliding mode controller improved with fuzzy logic: Application to the quadrotor helicopter paper_content: In this paper we present a new design method for the fight control of an autonomous quadrotor helicopter based on fuzzy sliding mode control using backstepping approach. Due to the underactuated property of the quadrotor helicopter, the controller can move three positions (x,y,z) of the helicopter and the yaw angle to their desired values and stabilize the pitch and roll angles. A first-order nonlinear sliding surface is obtained using the backstepping technique, on which the developed sliding mode controller is based. Mathematical development for the stability and convergence of the system is presented. The main purpose is to eliminate the chattering phenomenon. Thus we have used a fuzzy logic control to generate the hitting control signal. The performances of the nonlinear control method are evaluated by simulation and the results demonstrate the effectiveness of the proposed control strategy for the quadrotor helicopter in vertical flights. --- paper_title: Design and construction of a novel quad tilt-wing UAV paper_content: Abstract This paper presents aerodynamic and mechanical design, prototyping and flight control system design of a new unmanned aerial vehicle SUAVI ( S abanci University U nmanned A erial V eh I cle). SUAVI is an electric powered quad tilt-wing UAV that is capable of vertical takeoff and landing (VTOL) like a helicopter and long duration horizontal flight like an airplane. Aerodynamic and mechanical designs are optimized to enhance the operational performance of the aerial vehicle. Both of them have great importance for increasing efficiency, reaching the flight duration goals and achieving the desired tasks. A full dynamical model is derived by utilizing Newton–Euler formulation for the development of the flight control system. The prototype is constructed from carbon composite material. A hierarchical control system is designed where a high level controller (supervisor) is responsible for task decision, monitoring states of the vehicle, generating references for low level controllers, etc. and several low level controllers are responsible for attitude and altitude stabilization. Results of several simulations and real flight tests are provided along with flight data to show performance of the developed UAV. --- paper_title: Modeling and control of a novel tilt — Roll rotor quadrotor UAV paper_content: The use of unmanned aerial vehicles (UAVs) for military, scientific, and civilian sectors are increasing drastically in recent years. The quadrotor platform has been used for many applications and research studies, as well. One of the limiting factors that prevents further implementation of the quadrotor system into applications, is the way quadrotor moves. It needs to tilt along the desired direction of motion. By doing this it can have necessary acceleration towards that direction. But tilting has the undesired effect of moving the onboard cameras' direction of view. This becomes an issue for surveillance and other vision based tasks. This study presents the design and control of a novel quadrotor system. Unlike previous study that uses regular quadrotor, this study proposes an alternative propulsion system formed by tilting rotors. This design eliminates the need of tilting the airframe, and it suggests superior performance with respect to regular quadrotor design. The mathematical model of the tiltable-rotor type quadrotor and designed control algorithms are explained. Various simulations are developed on MATLAB, in which the proposed quadrotor aerial vehicle has been successfully controlled. Comparison of the proposed system to regular quadrotor suggests better performance. ---	Title: A Review of Control Algorithms for Autonomous Quadrotors Section 1: Introduction Description 1: Introduce the significance and applications of quadrotors, and outline the focus and structure of the review. Section 2: Mathematical Model Description 2: Explain the key mathematical equations and models used to describe the dynamics of quadrotors. Section 3: Survey of Control Algorithms Description 3: Provide an overview of the various control algorithms applied to quadrotors, categorizing them into linear and non-linear control schemes. Section 4: Proportional Integral Derivative (PID) Description 4: Discuss the PID control algorithm and its applications, strengths, and limitations in controlling quadrotors. Section 5: Linear Quadratic Regulator/Gaussian-LQR/G Description 5: Examine the LQR and LQG control algorithms, their methodologies, and their effectiveness in quadrotor control. Section 6: Sliding Mode Control (SMC) Description 6: Describe the implementation of sliding mode control, its benefits, and its challenges when applied to quadrotors. Section 7: (Integrator) Backstepping Control Description 7: Analyze the backstepping control algorithm and its integrator variant, focusing on their convergence and disturbance handling capabilities. Section 8: Adaptive Control Algorithms Description 8: Explore adaptive control techniques used for quadrotors, highlighting how they adapt to parameter changes and uncertainties. Section 9: Robust Control Algorithms Description 9: Review robust control strategies designed to handle system uncertainties and disturbances, and discuss their limitations in terms of tracking. Section 10: Optimal Control Algorithms Description 10: Provide insights into optimization-based control methods like LQR and H∞, emphasizing their application to quadrotors and their robustness issues. Section 11: Feedback Linearization Description 11: Explain feedback linearization control methods, their application to quadrotors, and their sensitivity to model inaccuracies. Section 12: Intelligent Control (Fuzzy Logic and Artificial Neural Networks) Description 12: Cover intelligent control approaches such as fuzzy logic and neural networks, discussing their complexity and computational requirements. Section 13: Hybrid Control Algorithms Description 13: Discuss hybrid control schemes that combine multiple control philosophies to overcome individual limitations and enhance overall performance. Section 14: Discussion and Conclusion Description 14: Summarize the findings of the review, discuss the strengths and weaknesses of different control algorithms, and outline future research directions in quadrotor control.
Euler Diagrams 2004 Preliminary Version A Survey of Reasoning Systems Based on Euler Diagrams Abstract	13	--- paper_title: Constraint diagrams: visualizing invariants in object-oriented models paper_content: A new visual notation is proposed for precisely expressing constraints on object-oriented models, as an alternative to mathematical logic notation used in methods such as Syntropy and Catalysis. The notation is potentially intuitive, expressive, integrates well with existing visual notations, and has a clear and unambiguous semantics. It is reminiscent of informal diagrams used by mathematicians for illustrating relations, and borrows much from Venn diagrams. It may be viewed as a generalization of instance diagrams. --- paper_title: The Logical Status of Diagrams paper_content: Acknowledgements 1. Introduction 2. Preliminaries 3. Venn-I 4. Venn-II 5. Venn-II and L0 6. Diagrammatic versus linguistic representation 7. Conclusion Appendix References Index. --- paper_title: SD2: a sound and complete diagrammatic reasoning system paper_content: SD2 is a system of Venn-type diagrams that can be used to reason diagrammatically about sets, their cardinalities and their relationships. They augment the systems of Venn-Peirce diagrams investigated by Shin (1994) to include lower and upper bounds for the cardinalities of the sets represented by regions of diagrams. We summarise their syntax and semantics and introduce inference rules for reasoning with the system. We discuss the soundness of the system and develop a proof strategy for completeness simpler than that adopted by Shin. We expect this strategy to extend to other, richer spider diagram systems and to constraint diagrams, the visual notation that has been used in conjunction with object-oriented modelling notations such as the Unified Modelling Language. --- paper_title: Logic and Visual Information paper_content: From the Publisher: ::: The importance of visual information is clear from its frequent presence in everyday reasoning and communication, and also in computation. This book examines the logical foundations of visual information presented in the form of diagrams, graphs, charts, tables and maps. --- paper_title: Implementing Euler/Venn Reasoning Systems paper_content: This paper proposes an implementation of a Euler/Venn reasoning system using directed acyclic graphs and shows that this implementation is correct with respect to a modified Shin/Hammer mathematical model of Euler/Venn Reasoning. In proving its correctness it will also be shown that the proposed implementation preserves or inherits the soundness and completeness properties of the mathematical model of the Euler/Venn system. --- paper_title: Logic and Visual Information paper_content: From the Publisher: ::: The importance of visual information is clear from its frequent presence in everyday reasoning and communication, and also in computation. This book examines the logical foundations of visual information presented in the form of diagrams, graphs, charts, tables and maps. --- paper_title: The Logical Status of Diagrams paper_content: Acknowledgements 1. Introduction 2. Preliminaries 3. Venn-I 4. Venn-II 5. Venn-II and L0 6. Diagrammatic versus linguistic representation 7. Conclusion Appendix References Index. --- paper_title: The information content of Euler/Venn diagrams paper_content: An ignition system for internal combustion engines. It generates a controlled-duration continuous-wave high-frequency spark, and employs an output transformer in an oscillator which includes a control winding for starting and stopping the oscillator. There is an electronic switch in series with the control winding; and the spark intervals, including duration thereof, are determined by photoelectric engine-timed means that employ a phototransistor. There is a control circuit for the electronic switch, which circuit includes means for minimizing the response time of the phototransistor. --- paper_title: Towards a model theory of Venn diagrams paper_content: In a regenerative type gas turbine application, a mounting apparatus for a recuperator to support the recuperator between the relatively stationary end walls of a gas turbine housing while simultaneously permitting movement of the recuperator in plural directions with respect to the walls caused by thermal expansion. --- paper_title: Modeling Heterogeneous Systems paper_content: Reasoning practices and decision making often require information from many different sources, which can be both sentential and diagrammatic. In such situations, there are many advantages to reasoning with the diagrams themselves, as opposed to re-expressing the information content of the diagram in sentential form and reasoning in an abstract sentential language. Thus for these practices, being able to extract and re-express pieces of information from one kind of representation into another is essential. The main goal of this paper is to propose a general framework for the modeling of heterogeneous reasoning systems and, most importantly, heterogeneous rules of inference in those systems. Unlike some other work in designing heterogeneous systems, our purpose will not be to define just one notion of heterogeneous inference, but rather to provide a framework in which many different kinds of heterogeneous rules of inference can be defined. After proposing this framework, we will then show how it can be applied to a sample heterogeneous system to define a number of different heterogeneous rules of inference. We will also discuss how the framework can be used to define rules of inference similar to the Observe Rule in Barwise and Etchemendy's Hyperproof system. --- paper_title: Using DAG Transformations to Verify Euler/Venn Homogeneous and Euler/Venn FOL Heterogeneous Rules of Inference paper_content: Abstract In this paper we will present a graph-transformation based method for the verification of heterogeneous first order logic (FOL) and Euler/Venn proofs. It has been shown that a special collection of directed acyclic graphs (DAGs) can be used interchangeably with Euler/Venn diagrams in reasoning processes [4]. Thus, proofs which include Euler/Venn diagrams can be thought of as proofs with DAGs where steps involving only Euler/Venn diagrams can be treated as particular DAG transformations. In the work reported here, we will show how the characterization of these manipulations can be used to verify Euler/Venn proofs. Also, a method for verifying the use of heterogeneous Euler/Venn and FOL reasoning rules will be presented that is also based upon DAG transformations. --- paper_title: The Logical Status of Diagrams paper_content: Acknowledgements 1. Introduction 2. Preliminaries 3. Venn-I 4. Venn-II 5. Venn-II and L0 6. Diagrammatic versus linguistic representation 7. Conclusion Appendix References Index. --- paper_title: Logic and Visual Information paper_content: From the Publisher: ::: The importance of visual information is clear from its frequent presence in everyday reasoning and communication, and also in computation. This book examines the logical foundations of visual information presented in the form of diagrams, graphs, charts, tables and maps. --- paper_title: Implementing Euler/Venn Reasoning Systems paper_content: This paper proposes an implementation of a Euler/Venn reasoning system using directed acyclic graphs and shows that this implementation is correct with respect to a modified Shin/Hammer mathematical model of Euler/Venn Reasoning. In proving its correctness it will also be shown that the proposed implementation preserves or inherits the soundness and completeness properties of the mathematical model of the Euler/Venn system. --- paper_title: A case study of the design and implementation of heterogeneous reasoning systems paper_content: In recent years we have witnessed a growing interest in heterogeneous reasoning systems. A heterogeneous reasoning system incorporates representations from a number of different representation systems, in our case a sentential and a diagrammatic system. The advantage of heterogeneous systems is that they allow a reasoner to bridge the gaps among various formalisms and construct threads of proof which cross the boundaries of the systems of representation. In doing this, these heterogeneous systems allow the reasoner to take advantage of each component system’s ability to express information in that component’s area of expertise. The purpose of this paper is twofold: to propose a general theoretical framework, inspired by Barwise and Seligman’s work in Information Theory [Barwise and Seligman, 1997], for the design of heterogeneous reasoning systems and to use this framework as the basis of an implementation of a First Order Logic and Euler/Venn reasoning system. --- paper_title: Reasoning with Extended Venn-Peirce Diagrammatic Systems paper_content: A method for making molten metal for casting directly from cold starting material. Cold starting material is placed in a movable vessel, and a layer of particulate material selected from the group consisting of coke and flux is spread on the top of the starting material in the vessel. One or more flames of hydrocarbon fuel-oxygen mixture are directed to the particulate layer, while translating the vessel along a closed path, so as to heat the particulate to white-hot state and to mix the cold starting material with the particulate thus heated, for melting the starting material. A composition-control agent is added in the material thus melted for producing desired composition of molten metal, while maintaining the flames and the translation. A fluid curtain is formed around the flames to inhibit the flames from directly burning the inner surface of the vessel. --- paper_title: On the Completeness and Expressiveness of Spider Diagram Systems paper_content: Spider diagram systems provide a visual language that extends the popular and intuitive Venn diagrams and Euler circles. Designed to complement object-oriented modelling notations in the specification of large software systems they can be used to reason diagrammatically about sets, their cardinalities and their relationships with other sets. A set of reasoning rules for a spider diagram system is shown to be sound and complete. We discuss the extension of this result to diagrammatically richer notations and also consider their expressiveness. Finally, we show that for a rich enough system we can diagrammatically express the negation of any diagram. --- paper_title: Spider diagrams: A diagrammatic reasoning system paper_content: Spider diagrams combine and extend Venn diagrams and Euler circles to express constraints on sets and their relationships with other sets. These diagrams can be used in conjunction with object-oriented modelling notations such as the Unified Modelling Language. This paper summarises the main syntax and semantics of spider diagrams. It also introduces inference rules for reasoning with spider diagrams and a rule for combining spider diagrams. This system is shown to be sound but not complete. Disjunctive diagrams are considered as one way of enriching the system to allow combination of diagrams so that no semantic information is lost. The relationship of this system of spider diagrams to other similar systems, which are known to be sound and complete, is explored briefly. --- paper_title: Reasoning with spider diagrams paper_content: Spider diagrams combine and extend Venn diagrams and Euler circles to express constraints on sets and their relationships with other sets. These diagrams can usefully be used in conjunction with object-oriented modelling notations such as the Unified Modelling Language (UML). This paper summarises the main syntax and semantics of spider diagrams and introduces four inference rules for reasoning with spider diagrams and a rule governing the equivalence of the Venn and Euler forms of spider diagrams. This paper also details rules for combining two spider diagrams to produce a single diagram which retains as much of their combined semantic information as possible, and discusses disjunctive diagrams as one possible way of enriching the system in order to combine spider diagrams so that no semantic information is lost. --- paper_title: Reasoning with Extended Venn-Peirce Diagrammatic Systems paper_content: A method for making molten metal for casting directly from cold starting material. Cold starting material is placed in a movable vessel, and a layer of particulate material selected from the group consisting of coke and flux is spread on the top of the starting material in the vessel. One or more flames of hydrocarbon fuel-oxygen mixture are directed to the particulate layer, while translating the vessel along a closed path, so as to heat the particulate to white-hot state and to mix the cold starting material with the particulate thus heated, for melting the starting material. A composition-control agent is added in the material thus melted for producing desired composition of molten metal, while maintaining the flames and the translation. A fluid curtain is formed around the flames to inhibit the flames from directly burning the inner surface of the vessel. --- paper_title: On Diagram Tokens and Types paper_content: Rejecting the temptation to make up a list of necessary and sufficient conditions for diagrammatic and sentential systems, we present an important distinction which arises from sentential and diagrammatic features of systems. Importantly, the distinction we will explore in the paper lies at a meta-level. That is, we argue for a major difference in meta-theory between diagrammatic and sentential systems, by showing the necessity of a more fine-grained syntax for a diagrammatic system than for a sentential system. Unlike with sentential systems, a diagrammatic system requires two levels of syntax--token and type. Token-syntax is about particular diagrams instantiated on some physical medium, and type-syntax provides a formal definition with which a concrete representtation of a diagram must comply. While these two levels of syntax are closely related, the domains of type-syntax and token-syntax are distinct from each other. Euler diagrams are chosen as a case study to illustrate the following major points of the paper: (i) What kinds of diagrammatic features (as opposed to sentential features) require two different levels of syntax? (ii) What is the relation between these two levels of syntax? (iii) What is the advantage of having a two-tiered syntax? --- paper_title: Using DAG Transformations to Verify Euler/Venn Homogeneous and Euler/Venn FOL Heterogeneous Rules of Inference paper_content: Abstract In this paper we will present a graph-transformation based method for the verification of heterogeneous first order logic (FOL) and Euler/Venn proofs. It has been shown that a special collection of directed acyclic graphs (DAGs) can be used interchangeably with Euler/Venn diagrams in reasoning processes [4]. Thus, proofs which include Euler/Venn diagrams can be thought of as proofs with DAGs where steps involving only Euler/Venn diagrams can be treated as particular DAG transformations. In the work reported here, we will show how the characterization of these manipulations can be used to verify Euler/Venn proofs. Also, a method for verifying the use of heterogeneous Euler/Venn and FOL reasoning rules will be presented that is also based upon DAG transformations. --- paper_title: Reasoning with Extended Venn-Peirce Diagrammatic Systems paper_content: A method for making molten metal for casting directly from cold starting material. Cold starting material is placed in a movable vessel, and a layer of particulate material selected from the group consisting of coke and flux is spread on the top of the starting material in the vessel. One or more flames of hydrocarbon fuel-oxygen mixture are directed to the particulate layer, while translating the vessel along a closed path, so as to heat the particulate to white-hot state and to mix the cold starting material with the particulate thus heated, for melting the starting material. A composition-control agent is added in the material thus melted for producing desired composition of molten metal, while maintaining the flames and the translation. A fluid curtain is formed around the flames to inhibit the flames from directly burning the inner surface of the vessel. --- paper_title: Reasoning with Extended Venn-Peirce Diagrammatic Systems paper_content: A method for making molten metal for casting directly from cold starting material. Cold starting material is placed in a movable vessel, and a layer of particulate material selected from the group consisting of coke and flux is spread on the top of the starting material in the vessel. One or more flames of hydrocarbon fuel-oxygen mixture are directed to the particulate layer, while translating the vessel along a closed path, so as to heat the particulate to white-hot state and to mix the cold starting material with the particulate thus heated, for melting the starting material. A composition-control agent is added in the material thus melted for producing desired composition of molten metal, while maintaining the flames and the translation. A fluid curtain is formed around the flames to inhibit the flames from directly burning the inner surface of the vessel. --- paper_title: Reasoning with Extended Venn-Peirce Diagrammatic Systems paper_content: A method for making molten metal for casting directly from cold starting material. Cold starting material is placed in a movable vessel, and a layer of particulate material selected from the group consisting of coke and flux is spread on the top of the starting material in the vessel. One or more flames of hydrocarbon fuel-oxygen mixture are directed to the particulate layer, while translating the vessel along a closed path, so as to heat the particulate to white-hot state and to mix the cold starting material with the particulate thus heated, for melting the starting material. A composition-control agent is added in the material thus melted for producing desired composition of molten metal, while maintaining the flames and the translation. A fluid curtain is formed around the flames to inhibit the flames from directly burning the inner surface of the vessel. --- paper_title: What can spider diagrams say paper_content: Spider diagrams are a visual notation for expressing logical statements. In this paper we identify a well known fragment of first order predicate logic, that we call \(\mathcal {ESD}\), equivalent in expressive power to the spider diagram language. The language \(\mathcal {ESD}\) is monadic and includes equality but has no constants or function symbols. To show this equivalence, in one direction, for each diagram we construct a sentence in \(\mathcal {ESD}\) that expresses the same information. For the more challenging converse we show there exists a finite set of models for a sentence S that can be used to classify all the models for S. Using these classifying models we show that there is a diagram expressing the same information as S. --- paper_title: The Expressiveness of Spider Diagrams Augmented with Constants paper_content: Spider diagrams are a visual language for expressing logical statements. Spiders represent the existence of elements and contours denote sets. Several sound and complete spider diagram systems have been developed and it is known that the spider diagram language is equivalent in expressive power to monadic first order logic with equality. However, these sound and complete spider diagram systems do not contain syntactic elements analogous to constants in first order predicate logic. We extend the spider diagram language to include constant spiders which represent specific individuals and give formal semantics for the extended diagram language. We then prove that this extended system is equivalent in expressive power to the language of spider diagrams without constants --- paper_title: Projections in Venn-Euler diagrams paper_content: Venn diagrams and Euler circles have long been used to express constraints on sets and their relationships with other sets. However, these notations can get very cluttered when we consider many closed curves or contours. In order to reduce this clutter, and to focus attention within the diagram appropriately, the notion of a projected contour, or projection, is introduced. Informally, a projected contour is a contour that describes a set of elements limited to a certain context. Through a series of examples, we develop a formal semantics of projections and discuss the issues involved in introducing these. --- paper_title: Towards a formalization of constraint diagrams paper_content: Geared to complement UML and to the specification of large software systems by non-mathematicians, constraint diagrams are a visual language that generalizes the popular and intuitive Venn diagrams and Euler circles, and adds facilities for quantifying over elements and navigating relations. The language design emphasizes scalability and expressiveness while retaining intuitiveness. Spider diagrams form a subset of the notation, leaving out universal quantification and the ability to navigate relations. Spider diagrams have been given a formal definition. This paper extends that definition to encompass the constraint diagram notation. The formalization of constraint diagrams is nontrivial: it exposes subtleties concerned with the implicit ordering of symbols in the visual language, which were not evident before a formal definition of the language was attempted. This has led to an improved design of the language. --- paper_title: Drawing graphs in Euler diagrams paper_content: We describe a method for drawing graph-enhanced Euler diagrams using a three stage method. The first stage is to lay out the underlying Euler diagram using a multicriteria optimizing system. The second stage is to find suitable locations for nodes in the zones of the Euler diagram using a force based method. The third stage is to minimize edge crossings and total edge length by swapping the location of nodes that are in the same zone with a multicriteria hill climbing method. We show a working version of the software that draws spider diagrams. Spider diagrams represent logical expressions by superimposing graphs upon an Euler diagram. This application requires an extra step in the drawing process because the embedded graphs only convey information about the connectedness of nodes and so a spanning tree must be chosen for each maximally connected component. Similar notations to Euler diagrams enhanced with graphs are common in many applications and our method is generalizable to drawing Hypergraphs represented in the subset standard, or to drawing Higraphs where edges are restricted to connecting with only atomic nodes. --- paper_title: Dynamic Euler Diagram Drawing paper_content: In this paper we describe a method to lay out a graph enhanced Euler diagram so that it looks similar to a previously drawn graph enhanced Euler diagram. This task is nontrivial when the underlying structures of the diagrams differ. In particular, if a structural change is made to an existing drawn diagram, our work enables the presentation of the new diagram with minor disruption to the user's mental map. As the new diagram can be generated from an abstract representation, its initial embedding may be very different from that of the original. We have developed comparison measures for Euler diagrams, integrated into a multicriteria optimizer, and applied a force model for associated graphs that attempts to move nodes towards their positions in the original layout. To further enhance the usability of the system, the transition between diagrams can be animated --- paper_title: A reading algorithm for constraint diagrams paper_content: Constraint diagrams are a visual notation designed to complement the Unified Modeling Language in the development of software systems. They generalize Venn diagrams and Euler circles, and include facilities for quantification and navigation of relations. Their design emphasizes scalability and expressiveness while retaining intuitiveness. The formalization of constraint diagrams is non-trivial: previous attempts have exposed subtleties concerned with the ordering of symbols in the visual language. Consequently, some constraint diagrams have more than one intuitive reading. We develop the concept of the dependence graph for a constraint diagram. From the dependence graph, we obtain a set of reading trees. A reading tree provides a partial ordering for some syntactic elements of the diagram. Given a reading tree for a constraint diagram, we present an algorithm that delivers a unique semantic reading. --- paper_title: Towards a default reading for constraint diagrams paper_content: Constraint diagrams are a diagrammatic notation which may be used to express logical constraints. They were designed to complement the Unified Modeling Language in the development of software systems. They generalize Venn diagrams and Euler circles, and include facilities for quantification and navigation of relations. Due to the lack of a linear ordering of symbols inherent in a diagrammatic language which expresses logical statements, some constraint diagrams have more than one intuitive meaning. We generalize, from an example based approach, to suggest a default reading for constraint diagrams. This reading is usually unique, but may require a small number of simple user choices. --- paper_title: Reasoning with Projected Contours paper_content: Projected contours enable Euler diagrams to scale better. They enable the representation of information using less syntax and can therefore increase visual clarity. Here informal reasoning rules are given that allow the transformation of spider diagrams with respect to projected contours. --- paper_title: Reasoning with spider diagrams paper_content: Spider diagrams combine and extend Venn diagrams and Euler circles to express constraints on sets and their relationships with other sets. These diagrams can usefully be used in conjunction with object-oriented modelling notations such as the Unified Modelling Language (UML). This paper summarises the main syntax and semantics of spider diagrams and introduces four inference rules for reasoning with spider diagrams and a rule governing the equivalence of the Venn and Euler forms of spider diagrams. This paper also details rules for combining two spider diagrams to produce a single diagram which retains as much of their combined semantic information as possible, and discusses disjunctive diagrams as one possible way of enriching the system in order to combine spider diagrams so that no semantic information is lost. --- paper_title: Computing Reading Trees for Constraint Diagrams paper_content: Constraint diagrams are a visual notation designed to complement the Unified Modeling Language in the development of software systems. They generalize Venn diagrams and Euler circles, and include facilities for quantification and navigation of relations. Their design emphasizes scalability and expressiveness while retaining intuitiveness. Due to subtleties concerned with the ordering of symbols in this visual language, the formalization of constraint diagrams is non-trivial; some constraint diagrams have more than one intuitive reading. A ‘reading’ algorithm, which associates a unique semantic interpretation to a constraint diagram, with respect to a reading tree, has been developed. A reading tree provides a partial ordering for syntactic elements of the diagram. Reading trees are obtainable from a partially directed graph, called the dependence graph of the diagram. In this paper we describe a ‘tree-construction’ algorithm, which utilizes graph transformations in order to produce all possible reading trees from a dependence graph. This work will aid the production of tools which will allow an advanced user to choose from a range of semantic interpretations of a diagram. --- paper_title: Constraint diagrams: visualizing invariants in object-oriented models paper_content: A new visual notation is proposed for precisely expressing constraints on object-oriented models, as an alternative to mathematical logic notation used in methods such as Syntropy and Catalysis. The notation is potentially intuitive, expressive, integrates well with existing visual notations, and has a clear and unambiguous semantics. It is reminiscent of informal diagrams used by mathematicians for illustrating relations, and borrows much from Venn diagrams. It may be viewed as a generalization of instance diagrams. --- paper_title: Generating Readable Proofs: A Heuristic Approach to Theorem Proving With Spider Diagrams paper_content: An important aim of diagrammatic reasoning is to make it easier for people to create and understand logical arguments. We have worked on spider diagrams, which visually express logical statements. Ideally, automatically generated proofs should be short and easy to understand. An existing proof generator for spider diagrams successfully writes proofs, but they can be long and unwieldy. In this paper, we present a new approach to proof writing in diagrammatic systems, which is guaranteed to find shortest proofs and can be extended to incorporate other readability criteria. We apply the A * algorithm and develop an admissible heuristic function to guide automatic proof construction. We demonstrate the effectiveness of the heuristic used. The work has been implemented as part of a spider diagram reasoning tool. --- paper_title: Layout metrics for Euler diagrams paper_content: We present an aesthetics based method for drawing Euler diagrams. Aesthetic layout metrics have been found to be useful in graph drawing algorithms, which use metrics motivated by aesthetic principles that aid user understanding of diagrams. We have taken a similar approach to Euler diagram drawing, and have defined a set of suitable metrics to be used within a hill climbing multicriteria optimiser to produce "good" drawings. There are added difficulties when drawing Euler diagrams as they are made up of contours whose structural properties of intersection and containment must be preserved under any layout improvements. We describe our Java implementation of a pair of hill climbing variants to find good drawings, a set of metrics that measure aesthetics for good diagram layout, and issues concerning the choice of weightings for a useful combination of the metrics. --- paper_title: Constraint diagrams: A step beyond UML paper_content: The Unified Modeling Language (UML) is a set of notations for modelling object-oriented systems. It has become the de facto standard. Most of its notations are diagrammatic. An exception to this is the Object Constraint Language (OCL) which is essentially a textual, stylised form of first order predicate logic. We describe a notation, constraint diagrams, which were introduced as a visual technique intended to be used in conjunction with the UML for object-oriented modelling. Constraint diagrams provide a diagrammatic notation for expressing constraints (e.g., invariants) that could only be expressed in UML using OCL. --- paper_title: Generating proofs with spider diagrams using heuristics paper_content: We apply the A¤ algorithm to guide a diagrammatic theorem proving tool. The algorithm requires a heuristic function, which provides a metric on the search space. In this paper we present a collection of metrics between two spider diagrams. We combine these metrics to give a heuristic function that provides a lower bound on the length of a shortest proof from one spider diagram to another, using a collection of sound reasoning rules. We compare the effectiveness of our approach with a breadth- first search for proofs. --- paper_title: Generating Euler Diagrams paper_content: This article describes an algorithm for the automated generation of any Euler diagram starting with an abstract description of the diagram. An automated generation mechanism for Euler diagrams forms the foundations of a generation algorithm for notations such as Harel's higraphs, constraint diagrams and some of the UML notation. An algorithm to generate diagrams is an essential component of a diagram tool for users to generate, edit and reason with diagrams.The work makes use of properties of the dual graph of an abstract diagram to identify which abstract diagrams are "drawable" within given wellformedness rules on concrete diagrams. A Java program has been written to implement the algorithm and sample output is included. --- paper_title: A constraint diagram reasoning system paper_content: The Unified Modeling Language (UML) is a collection of notations which are mainly diagrammatic. These notations are used by software engineers in the process of object oriented modelling. The only textual notation in the UML is the Object Constraint Language (OCL). The OCL is used to express logical constraints such as system invariants. Constraint diagrams are designed to provide a diagrammatic alternative to the OCL. Since constraint diagrams are visual they complement existing notations in the UML. Spider diagrams form the basis of constraint diagrams and sound and complete reasoning systems have been developed. Spider diagrams allow subset relations between sets and cardinality constraints on sets to be expressed. In addition to this, constraint diagrams allow universal quantification and relational navigation and hence are vastly more expressive. In this paper we present the first constraint diagram reasoning system. We give syntax and semantics for constraint diagrams we call CD1 diagrams. We identify syntactic criteria that allow us to determine whether a CD1 diagram is satisfiable. We give descriptions of a set of sound and complete reasoning rules for CD1 diagrams. ---	Title: Euler Diagrams 2004 Preliminary Version: A Survey of Reasoning Systems Based on Euler Diagrams Section 1: Introduction Description 1: Introduce Euler diagrams, their semantics, limitations, and the purpose of the survey. Section 2: Reasoning with Euler Diagrams Description 2: Describe Hammer’s Euler diagram reasoning system and its reasoning rules. Section 3: Venn Diagrams Description 3: Outline the features of Venn diagrams and their differences from Euler diagrams. Section 4: Venn-Peirce Diagrams Description 4: Discuss modifications by Peirce to Venn diagrams to increase expressiveness. Section 5: Venn-I Diagrams Description 5: Explain Shin’s Venn-I diagram system and its reasoning rules. Section 6: Venn-II Diagrams Description 6: Describe Shin’s Venn-II diagrams, their rules, and expressive power. Section 7: Euler/Venn Diagrams Description 7: Outline Swoboda and Allwein's Euler/Venn diagram system and its features. Section 8: Spider Diagrams Description 8: Explain the development, features, and reasoning systems of spider diagrams. Section 9: SD1 Diagrams Description 9: Provide details on the SD1 spider diagram system, its syntax, and reasoning rules. Section 10: SD2 Diagrams Description 10: Discuss the SD2 system that extends SD1 with the ability to express upper bounds on cardinalities. Section 11: ESD2 Diagrams Description 11: Outline the ESD2 system that includes Euler-based diagrams and additional syntax. Section 12: Further Spider Diagram Systems Description 12: Explain additional spider diagram systems, including SD3, that further extend the capabilities of SD2. Section 13: Constraint Diagrams Description 13: Describe constraint diagrams, their expressiveness, and their application in software engineering.
Six reasons for rejecting an industrial survey paper	11	--- paper_title: Preliminary Findings from a Survey on the MD State of the Practice paper_content: In the context of an Italian research project, this paper reports on an on-line survey, performed with 155 software professionals, with the aim of investigating about their opinions and experiences in modeling during software development and Model-driven engineering usage. The survey focused also on used modeling languages, processes and tools. A preliminary analysis of the results confirmed that Model-driven engineering, and more in general software modeling, are very relevant phenomena. Approximately 68% of the sample use models during software development. Among then, 44% generate code starting from models and 16% execute them directly. The preferred language for modeling is UML but DSLs are used as well. --- paper_title: Principles of survey research: part 1: turning lemons into lemonade paper_content: Surveys are probably the most commonly-used research method world-wide. Survey work is visible not only because we see many examples of it in software engineering research, but also because we are often asked to participate in surveys in our private capacity, as electors, consumers, or service users. This widespread use of surveys may give us the impression that surveybased research is straightforward, an easy option for researchers to gather important information about products, context, processes, workers and more. In our personal experience with applying and evaluating research methods and their results, we certainly did not expect to encounter major problems with a survey that we planned, to investigate issues associated with technology adoption. This article and subsequent ones in this series describe how wrong we were. We do not want to give the impression that there is any way of turning a bad survey into a good one; if a survey is a lemon, it stays a lemon. However, we believe that learning from our mistakes is the way to make lemonade from lemons. So this series of articles shares with you our lessons learned, in the hope of improving survey research in software engineering. --- paper_title: Stakeholders' Perception of Success: An Empirical Investigation paper_content: Different stakeholders involved in the software development may attribute success to different indicators. Analogously they may support different factors considered the root of successful projects. The study presented in this paper explores how different stakeholders perceive project success and what they deem the effect of specific factors on the project outcome. The study highlighted both commonalities and differences among three main stakeholder classes. A substantial agreement was observed concerning the characteristics that make a project or product successful. As far as the factors that could lead to success are concerned, more bias emerged. --- paper_title: SOA adoption in the Italian industry paper_content: We conducted a personal opinion survey in two rounds – years 2008 and 2011 – with the aim of investigating the level of knowledge and adoption of SOA in the Italian industry. We are also interested in understanding what is the trend of SOA (positive or negative?) and what are the methods, technologies and tools really used in the industry. The main findings of this survey are the following: (1) SOA is a relevant phenomenon in Italy, (2) Web services and RESTFul services are well-known/used and (3) orchestration languages and UDDI are little known and used. These results suggest that in Italy SOA is interpreted in a more simplistic way with respect to the current/real definition (i.e., without the concepts of orchestration/choreography and registry). Currently, the adoption of SOA is medium/low with a stable/positive trend of pervasiveness. --- paper_title: Practical Experiences in the Design and Conduct of Surveys in Empirical Software Engineering paper_content: A survey is an empirical research strategy for the collection of information from heterogeneous sources. In this way, survey results often exhibit a high degree of external validity. It is complementary to other empirical research strategies such as controlled experiments, which usually have their strengths in the high internal validity of the findings. While there is a growing number of (quasi-)controlled experiments reported in the software engineering literature, few results of large scale surveys have been reported there. Hence, there is still a lack of knowledge on how to use surveys in a systematic manner for software engineering empirical research. --- paper_title: Maturity of software modelling and model driven engineering: a survey in the Italian industry paper_content: Background: The main claimed advantage of model driven engineering is the improvement of productivity. However, little information is available about its actual usage during software development and maintenance in the industry. Objective: The main aim of this work is investigating the level of maturity in the usage of software models and model driven engineering in the Italian industry. The perspective is that of software engineering researchers. Method: First, we conducted an exploratory personal opinion survey with 155 Italian software professionals. The data were collected with the help of a web-based on-line questionnaire. Then, we conducted focused interviews with three software professionals to interpret doubtful results. Results: Software modelling is a very relevant phenomenon in the Italian industry. Model driven techniques are used in the industry, even if (i) only for a limited extent, (ii) despite a quite generalized dissatisfaction about available tools and (iii) despite a generally low experience of the IT personnel in such techniques. Limitations: Generalization of results is limited due to the sample size. Moreover, possible self-exclusion from participants not interested in modelling could have biased the results. Conclusion: Results reinforce existing evidence regarding the usage of software modelling and (partially of) model driven engineering in the industry but highlight several aspects of immaturity of the Italian industry. --- paper_title: Software migration projects in Italian industry: Preliminary results from a state of the practice survey paper_content: Software migration is a fundamental and complex task in software maintenance, particularly relevant in recent years given the pervasiveness of Web and of mobile technologies. In the context of an Italian Research Project devoted to the empirical assessment of migration techniques and tools, this paper reports on a survey, performed among 59 Italian Information Technology (IT) companies, with the aim of investigating about their experiences in software migration, their main migration goals, and the pieces of technology adopted. The research project and the survey focused, in particular, on in-house migration projects towards the Web, service oriented architectures and wireless environments. A preliminary analysis of results confirmed that software migration is a very relevant phenomenon. Most migration activities performed in recent years targeted the Web, with a few number of migrations towards mobile and towards service-oriented architectures. Among other things, the survey highlights a limited, and insufficient, usage and availability of tools for supporting migration tasks. --- paper_title: Actual vs. perceived effect of software engineering practices in the Italian industry paper_content: A commonly cited limitation of software engineering research consists in its detachment from the industrial practice. Several studies have analyzed a number of practices and identified their benefits and drawbacks but little is known about their dissemination in the industry. For a set of 18 practices commonly studied in the literature, this paper investigated diffusion, effect on the success, and perceived usefulness in 62 actual industrial projects from 28 Italian IT companies. In particular we proposed a classification of these perceptions and we were able to classify 14 practices. We found statistical evidence that 7 factors have an actual effect (positive for 6 of them, negative for one). Moreover 77% (10 out of 13) of the known good practices (e.g., importance of good project schedule or complete requirements' list) are perceived consistently by the industry. For a few other practices (having a champion's support, using metrics, reducing quality) we noticed a lack of awareness in the industry. Starting from these observations we propose guidelines for industrial practice and suggestions for academic research. --- paper_title: Migration of information systems in the Italian industry: A state of the practice survey paper_content: Context: Software migration-and in particular migration towards the Web and towards distributed architectures-is a challenging and complex activity, and has been particularly relevant in recent years, due to the large number of migration projects the industry had to face off because of the increasing pervasiveness of the Web and of mobile devices. Objective: This paper reports a survey aimed at identifying the state-of-the-practice of the Italian industry for what concerns the previous experiences in software migration projects-specifically concerning information systems-the adopted tools and the emerging needs and problems. Method: The study has been carried out among 59 Italian Information Technology companies, and for each company a representative person had to answer an on-line questionnaire concerning migration experiences, pieces of technology involved in migration projects, adopted tools, and problems occurred during the project. Results: Indicate that migration-especially towards the Web-is highly relevant for Italian IT companies, and that companies tend to increasingly adopt free and open source solutions rather than commercial ones. Results also indicate that the adoption of specific tools for migration is still very limited, either because of the lack of skills and knowledge, or due to the lack of mature and adequate options. Conclusions: Findings from this survey suggest the need for further technology transfer between academia and industry for the purpose of favoring the adoption of software migration techniques and tools. --- paper_title: An exploratory survey on SOA knowledge, adoption and trend in the Italian industry paper_content: The main aim of this work is investigating the level of knowledge and diffusion of SOA (Service Oriented Architecture) in the Italian industry. We are also interested to understand what is the trend of SOA (positive or negative?) and what are the methods, technologies and tools really used in the industry. --- paper_title: Stakeholders' Perception of Success: An Empirical Investigation paper_content: Different stakeholders involved in the software development may attribute success to different indicators. Analogously they may support different factors considered the root of successful projects. The study presented in this paper explores how different stakeholders perceive project success and what they deem the effect of specific factors on the project outcome. The study highlighted both commonalities and differences among three main stakeholder classes. A substantial agreement was observed concerning the characteristics that make a project or product successful. As far as the factors that could lead to success are concerned, more bias emerged. --- paper_title: Software migration projects in Italian industry: Preliminary results from a state of the practice survey paper_content: Software migration is a fundamental and complex task in software maintenance, particularly relevant in recent years given the pervasiveness of Web and of mobile technologies. In the context of an Italian Research Project devoted to the empirical assessment of migration techniques and tools, this paper reports on a survey, performed among 59 Italian Information Technology (IT) companies, with the aim of investigating about their experiences in software migration, their main migration goals, and the pieces of technology adopted. The research project and the survey focused, in particular, on in-house migration projects towards the Web, service oriented architectures and wireless environments. A preliminary analysis of results confirmed that software migration is a very relevant phenomenon. Most migration activities performed in recent years targeted the Web, with a few number of migrations towards mobile and towards service-oriented architectures. Among other things, the survey highlights a limited, and insufficient, usage and availability of tools for supporting migration tasks. --- paper_title: Migration of information systems in the Italian industry: A state of the practice survey paper_content: Context: Software migration-and in particular migration towards the Web and towards distributed architectures-is a challenging and complex activity, and has been particularly relevant in recent years, due to the large number of migration projects the industry had to face off because of the increasing pervasiveness of the Web and of mobile devices. Objective: This paper reports a survey aimed at identifying the state-of-the-practice of the Italian industry for what concerns the previous experiences in software migration projects-specifically concerning information systems-the adopted tools and the emerging needs and problems. Method: The study has been carried out among 59 Italian Information Technology companies, and for each company a representative person had to answer an on-line questionnaire concerning migration experiences, pieces of technology involved in migration projects, adopted tools, and problems occurred during the project. Results: Indicate that migration-especially towards the Web-is highly relevant for Italian IT companies, and that companies tend to increasingly adopt free and open source solutions rather than commercial ones. Results also indicate that the adoption of specific tools for migration is still very limited, either because of the lack of skills and knowledge, or due to the lack of mature and adequate options. Conclusions: Findings from this survey suggest the need for further technology transfer between academia and industry for the purpose of favoring the adoption of software migration techniques and tools. --- paper_title: Preliminary Findings from a Survey on the MD State of the Practice paper_content: In the context of an Italian research project, this paper reports on an on-line survey, performed with 155 software professionals, with the aim of investigating about their opinions and experiences in modeling during software development and Model-driven engineering usage. The survey focused also on used modeling languages, processes and tools. A preliminary analysis of the results confirmed that Model-driven engineering, and more in general software modeling, are very relevant phenomena. Approximately 68% of the sample use models during software development. Among then, 44% generate code starting from models and 16% execute them directly. The preferred language for modeling is UML but DSLs are used as well. --- paper_title: SOA adoption in the Italian industry paper_content: We conducted a personal opinion survey in two rounds – years 2008 and 2011 – with the aim of investigating the level of knowledge and adoption of SOA in the Italian industry. We are also interested in understanding what is the trend of SOA (positive or negative?) and what are the methods, technologies and tools really used in the industry. The main findings of this survey are the following: (1) SOA is a relevant phenomenon in Italy, (2) Web services and RESTFul services are well-known/used and (3) orchestration languages and UDDI are little known and used. These results suggest that in Italy SOA is interpreted in a more simplistic way with respect to the current/real definition (i.e., without the concepts of orchestration/choreography and registry). Currently, the adoption of SOA is medium/low with a stable/positive trend of pervasiveness. --- paper_title: Maturity of software modelling and model driven engineering: a survey in the Italian industry paper_content: Background: The main claimed advantage of model driven engineering is the improvement of productivity. However, little information is available about its actual usage during software development and maintenance in the industry. Objective: The main aim of this work is investigating the level of maturity in the usage of software models and model driven engineering in the Italian industry. The perspective is that of software engineering researchers. Method: First, we conducted an exploratory personal opinion survey with 155 Italian software professionals. The data were collected with the help of a web-based on-line questionnaire. Then, we conducted focused interviews with three software professionals to interpret doubtful results. Results: Software modelling is a very relevant phenomenon in the Italian industry. Model driven techniques are used in the industry, even if (i) only for a limited extent, (ii) despite a quite generalized dissatisfaction about available tools and (iii) despite a generally low experience of the IT personnel in such techniques. Limitations: Generalization of results is limited due to the sample size. Moreover, possible self-exclusion from participants not interested in modelling could have biased the results. Conclusion: Results reinforce existing evidence regarding the usage of software modelling and (partially of) model driven engineering in the industry but highlight several aspects of immaturity of the Italian industry. --- paper_title: Actual vs. perceived effect of software engineering practices in the Italian industry paper_content: A commonly cited limitation of software engineering research consists in its detachment from the industrial practice. Several studies have analyzed a number of practices and identified their benefits and drawbacks but little is known about their dissemination in the industry. For a set of 18 practices commonly studied in the literature, this paper investigated diffusion, effect on the success, and perceived usefulness in 62 actual industrial projects from 28 Italian IT companies. In particular we proposed a classification of these perceptions and we were able to classify 14 practices. We found statistical evidence that 7 factors have an actual effect (positive for 6 of them, negative for one). Moreover 77% (10 out of 13) of the known good practices (e.g., importance of good project schedule or complete requirements' list) are perceived consistently by the industry. For a few other practices (having a champion's support, using metrics, reducing quality) we noticed a lack of awareness in the industry. Starting from these observations we propose guidelines for industrial practice and suggestions for academic research. --- paper_title: An exploratory survey on SOA knowledge, adoption and trend in the Italian industry paper_content: The main aim of this work is investigating the level of knowledge and diffusion of SOA (Service Oriented Architecture) in the Italian industry. We are also interested to understand what is the trend of SOA (positive or negative?) and what are the methods, technologies and tools really used in the industry. --- paper_title: Stakeholders' Perception of Success: An Empirical Investigation paper_content: Different stakeholders involved in the software development may attribute success to different indicators. Analogously they may support different factors considered the root of successful projects. The study presented in this paper explores how different stakeholders perceive project success and what they deem the effect of specific factors on the project outcome. The study highlighted both commonalities and differences among three main stakeholder classes. A substantial agreement was observed concerning the characteristics that make a project or product successful. As far as the factors that could lead to success are concerned, more bias emerged. --- paper_title: Principles of survey research: part 1: turning lemons into lemonade paper_content: Surveys are probably the most commonly-used research method world-wide. Survey work is visible not only because we see many examples of it in software engineering research, but also because we are often asked to participate in surveys in our private capacity, as electors, consumers, or service users. This widespread use of surveys may give us the impression that surveybased research is straightforward, an easy option for researchers to gather important information about products, context, processes, workers and more. In our personal experience with applying and evaluating research methods and their results, we certainly did not expect to encounter major problems with a survey that we planned, to investigate issues associated with technology adoption. This article and subsequent ones in this series describe how wrong we were. We do not want to give the impression that there is any way of turning a bad survey into a good one; if a survey is a lemon, it stays a lemon. However, we believe that learning from our mistakes is the way to make lemonade from lemons. So this series of articles shares with you our lessons learned, in the hope of improving survey research in software engineering. ---	Title: Six Reasons for Rejecting an Industrial Survey Paper Section 1: INTRODUCTION Description 1: Introduce the motivation and background for industrial surveys in software engineering and explain their importance and challenges. Section 2: EXPERIENCE GAINED Description 2: Summarize the authors' experiences and the details of several industrial surveys they have conducted over the past ten years. Section 3: METHOD Description 3: Describe the methodology used to analyze the reviewer comments about the industrial survey papers, including categorizing the comments and analyzing their frequency. Section 4: CRITICISMS Description 4: Present the categorized criticisms received for the survey papers, including their frequency and groundedness, and discuss each criticism in detail. Section 5: No Practical Usefulness Description 5: Discuss the common criticism regarding the lack of practical usefulness of the survey results and provide a rebuttal. Section 6: Sampling Bias Description 6: Describe the issues related to sampling bias, including self-selection bias, sampling frame, and the representativeness of the sample, and suggest possible mitigation strategies. Section 7: Obvious Conclusions Description 7: Address the criticism that survey results are often deemed obvious or non-controversial and provide a counter-argument. Section 8: People's Perceptions Description 8: Explain the limitation of surveys collecting self-reported data and argue for the importance of human perceptions in software engineering. Section 9: Non Respondents Description 9: Discuss the challenges of analyzing non-respondents and the computation of response rates. Section 10: Limited Geographical Scope Description 10: Address the criticism of limited geographical scope in survey studies and discuss its implications on the generalizability of the findings. Section 11: CONCLUSIONS Description 11: Summarize the main findings and argue for a more lenient and understanding approach to evaluating industrial survey papers, emphasizing the importance of such studies despite their limitations.
Approximation Metrics Based on Probabilistic Bisimulations for General State-Space Markov Processes: A Survey	7	--- paper_title: Approximate Analysis of Probabilistic Processes: Logic, Simulation and Games paper_content: We tackle the problem of non robustness of simulation and bisimulation when dealing with probabilistic processes. It is important to ignore tiny deviations in probabilities because these often come from experiments or estimations. A few approaches have been proposed to treat this issue, for example metrics to quantify the non bisimilarity (or closeness) of processes. Relaxing the definition of simulation and bisimulation is another avenue which we follow. We define a new semantics to a known simple logic for probabilistic processes and show that it characterises a notion of epsi-simulation. We also define two-players games that correspond to these notions: the existence of a winning strategy for one of the players determines epsi-(bi)simulation. Of course, for all the notions defined, letting epsi = 0 gives back the usual notions of logical equivalence, simulation and bisimulation. However, in contrast to what happens in fully probabilistic systems when epsi = 0, two-way e-simulation for epsi > 0 is not equal to epsi-bisimulation. Next we give a polynomial time algorithm to compute a naturally derived metric: distance between states s and t is defined as the smallest epsi such that s and t are epsi-equivalent. This is the first polynomial algorithm for a non-discounted metric. Finally we show that most of these notions can be extended to deal with probabilistic systems that allow non-determinism as well. --- paper_title: Weak Bisimulation for Fully Probabilistic Processes paper_content: Bisimulations that abstract from internal computation have proven to be useful for verification of compositionally defined transition systems. In the literature of probabilistic extensions of such transition systems, similar bisimulations are rare. In this paper, we introduce weak and branching bisimulation for fully probabilistic systems, transition systems where nondeterministic branching is replaced by probabilistic branching. In contrast to the nondeterministic case, both relations coincide. We give an algorithm to decide weak (and branching) bisimulation with a time complexity cubic in the number of states of the fully probabilistic system. This meets the worst case complexity for deciding branching bisimulation in the nondeterministic case. In addition, the relation is shown to be a congruence with respect to the operators of PLSCCS, a lazy synchronous probabilistic variant of CCS. We illustrate that due to these properties, weak bisimulation provides all the crucial ingredients for mechanised compositional veri�cation of probabilistic transition systems. --- paper_title: Principles of Model Checking paper_content: Our growing dependence on increasingly complex computer and software systems necessitates the development of formalisms, techniques, and tools for assessing functional properties of these systems. One such technique that has emerged in the last twenty years is model checking, which systematically (and automatically) checks whether a model of a given system satisfies a desired property such as deadlock freedom, invariants, and request-response properties. This automated technique for verification and debugging has developed into a mature and widely used approach with many applications. Principles of Model Checking offers a comprehensive introduction to model checking that is not only a text suitable for classroom use but also a valuable reference for researchers and practitioners in the field. The book begins with the basic principles for modeling concurrent and communicating systems, introduces different classes of properties (including safety and liveness), presents the notion of fairness, and provides automata-based algorithms for these properties. It introduces the temporal logics LTL and CTL, compares them, and covers algorithms for verifying these logics, discussing real-time systems as well as systems subject to random phenomena. Separate chapters treat such efficiency-improving techniques as abstraction and symbolic manipulation. The book includes an extensive set of examples (most of which run through several chapters) and a complete set of basic results accompanied by detailed proofs. Each chapter concludes with a summary, bibliographic notes, and an extensive list of exercises of both practical and theoretical nature. --- paper_title: Approximately Bisimilar Symbolic Models for Incrementally Stable Switched Systems paper_content: Switched systems constitute an important modeling paradigm faithfully describing many engineering systems in which software interacts with the physical world. Despite considerable progress on stability and stabilization of switched systems, the constant evolution of technology demands that we make similar progress with respect to different, and perhaps more complex, objectives. This paper describes one particular approach to address these different objectives based on the construction of approximately equivalent (bisimilar) symbolic models for switched systems. The main contribution of this paper consists in showing that under standard assumptions ensuring incremental stability of a switched system (i.e., existence of a common Lyapunov function, or multiple Lyapunov functions with dwell time), it is possible to construct a finite symbolic model that is approximately bisimilar to the original switched system with a precision that can be chosen a priori. To support the computational merits of the proposed approach, we use symbolic models to synthesize controllers for two examples of switched systems, including the boost dc-dc converter. --- paper_title: Exact and Ordinary Lumpability in Finite Markov Chains paper_content: Exact and ordinary lumpability in finite Markov chains is considered. Both concepts naturally define an aggregation of the Markov chain yielding an aggregated chain that allows the exact determination of several stationary and transient results for the original chain. We show which quantities can be determined without an error from the aggregated process and describe methods to calculate bounds on the remaining results. Furthermore, the concept of lumpability is extended to near --- paper_title: Probabilistic Simulations for Probabilistic Processes paper_content: Several probabilistic simulation relations for probabilistic systems are defined and evaluated according to two criteria: compositionality and preservation of “interesting” properties. Here, the interesting properties of a system are identified with those that are expressible in an untimed version of the Timed Probabilistic concurrent Computation Tree Logic (TPCTL) of Hansson. The definitions are made, and the evaluations carried out, in terms of a general labeled transition system model for concurrent probabilistic computation. The results cover weak simulations, which abstract from internal computation, as well as strong simulations, which do not. --- paper_title: Continuous stochastic logic characterizes bisimulation of continuous-time Markov processes paper_content: In a recent paper Baier et al. [Lecture Notes in Computer Science, Springer-Verlag, 2000, p. 358] analyzed a new way of model-checking formulas of a logic for continuous-time processes—called continuous stochastic logic (henceforth CSL)—against continuous-time Markov chains—henceforth CTMCs. One of the important results of that paper was the proof that if two CTMCs were bisimilar then they would satisfy exactly the same formulas of CSL. This raises the converse question—does satisfaction of the same collection of CSL formulas imply bisimilarity? In other words, given two CTMCs which are known to satisfy exactly the same formulas of CSL does it have to be the case that they are bisimilar? We prove that the answer to the question just raised is “yes”. In fact we prove a significant extension, namely that a subset of CSL suffices even for systems where the state space may be a continuum. Along the way we prove a result to the effect that the set of Zeno paths has measure zero provided that the transition rates are bounded. --- paper_title: O-Minimal Hybrid Systems paper_content: An important approach to decidability questions for verification algorithms of hybrid systems has been the construction of a bisimulation. Bisimulations are finite state quotients whose reachability properties are equivalent to those of the original infinite state hybrid system. In this paper we introduce the notion of o-minimal hybrid systems, which are initialized hybrid systems whose relevant sets and flows are definable in an o-minimal theory. We prove that o-minimal hybrid systems always admit finite bisimulations. We then present specific examples of hybrid systems with complex continuous dynamics for which finite bisimulations exist. --- paper_title: Bisimulation for probabilistic transition systems: a coalgebraic approach paper_content: Abstract The notion of bisimulation as proposed by Larsen and Skou for discrete probabilistic transition systems is shown to coincide with a coalgebraic definition in the sense of Aczel and Mendler in terms of a set functor, which associates to a set its collection of simple probability distributions. This coalgebraic formulation makes it possible to generalize the concepts of discrete probabilistic transition system and probabilistic bisimulation to a continuous setting involving Borel probability measures. A functor ℳ 1 is introduced that yields for a metric space its collection of Borel probability measures. Under reasonable conditions, this functor exactly captures generalized probabilistic bisimilarity. Application of the final coalgebra paradigm to a functor based on ℳ 1 then yields an internally fully abstract semantical domain with respect to probabilistic bisimulation, which is therefore well suited for the interpretation of probabilistic specification and stochastic programming concepts. --- paper_title: Approximately bisimilar symbolic models for nonlinear control systems paper_content: Control systems are usually modeled by differential equations describing how physical phenomena can be influenced by certain control parameters or inputs. Although these models are very powerful when dealing with physical phenomena, they are less suitable to describe software and hardware interfacing the physical world. For this reason there is a growing interest in describing control systems through symbolic models that are abstract descriptions of the continuous dynamics, where each "symbol" corresponds to an "aggregate" of states in the continuous model. Since these symbolic models are of the same nature of the models used in computer science to describe software and hardware, they provide a unified language to study problems of control in which software and hardware interact with the physical world. Furthermore the use of symbolic models enables one to leverage techniques from supervisory control and algorithms from game theory for controller synthesis purposes. In this paper we show that every incrementally globally asymptotically stable nonlinear control system is approximately equivalent (bisimilar) to a symbolic model. The approximation error is a design parameter in the construction of the symbolic model and can be rendered as small as desired. Furthermore if the state space of the control system is bounded the obtained symbolic model is finite. For digital control systems, and under the stronger assumption of incremental input-to-state stability, symbolic models can be constructed through a suitable quantization of the inputs. --- paper_title: Bisimulation for Labelled Markov Processes paper_content: In this paper we introduce a new class of labelled transition systems - Labelled Markov Processes - and define bisimulation for them. Labelled Markov processes are probabilistic labelled transition systems where the state space is not necessarily discrete, it could be the reals, for example. We assume that it is a Polish space (the underlying topological space for a complete separable metric space). The mathematical theory of such systems is completely new from the point of view of the extant literature on probabilistic process algebra; of course, it uses classical ideas from measure theory and Markov process theory. The notion of bisimulation builds on the ideas of Larsen and Skou and of Joyal, Nielsen and Winskel. The main result that we prove is that a notion of bisimulation for Markov processes on Polish spaces, which extends the Larsen-Skou denition for discrete systems, is indeed an equivalence relation. This turns out to be a rather hard mathematical result which, as far as we know, embodies a new result in pure probability theory. This work heavily uses continuous mathematics which is becoming an important part of work on hybrid systems. --- paper_title: HYTECH: A Model Checker for Hybrid Systems paper_content: A hybrid system consists of a collection of digital programs that interact with each other and with an analog environment. Examples of hybrid systems include medical equipment, manufacturing controllers, automotive controllers, and robots. The formal analysis of the mixed digital-analog nature of these systems requires a model that incorporates the discrete behavior of computer programs with the continuous behavior of environment variables, such as temperature and pressure. Hybrid automata capture both types of behavior by combining finite automata with differential inclusions (i.e. differential inequalities). HyTech is a symbolic model checker for linear hybrid automata, an expressive, yet automatically analyzable, subclass of hybrid automata. A key feature of HyTech is its ability to perform parametric analysis, i.e. to determine the values of design parameters for which a linear hybrid automaton satisfies a temporal requirement. --- paper_title: Bisimulation for general stochastic hybrid systems paper_content: In this paper we define a bisimulation concept for some very general models for stochastic hybrid systems (general stochastic hybrid systems). The definition of bisimulation builds on the ideas of Edalat and of Larsen and Skou and of Joyal, Nielsen and Winskel. The main result is that this bisimulation for GSHS is indeed an equivalence relation. The secondary result is that this bisimulation relation for the stochastic hybrid system models used in this paper implies the same kind of bisimulation for their continuous parts and respectively for their jumping structures. --- paper_title: Bisimulation for Communicating Piecewise Deterministic Markov Processes (CPDPs) paper_content: CPDPs (Communicating Piecewise Deterministic Markov Processes) can be used for compositional specification of systems from the class of stochastic hybrid processes formed by PDPs (Piecewise Deterministic Markov Processes). We define CPDPs and the composition of CPDPs, and prove that the class of CPDPs is closed under composition. Then we introduce a notion of bisimulation for PDPs and CPDPs and we prove that bisimilar PDPs as well as bisimilar CPDPs have equal stochastic behavior. Finally, as main result, we prove the congruence property that, for a composite CPDP, substituting components by different but bisimilar components results in a CPDP that is bisimilar to the original composite CPDP (and therefore has equal stochastic behavior). © Springer-Verlag Berlin Heidelberg 2005. --- paper_title: Metrics for Markov Decision Processes with Infinite State Spaces paper_content: We present metrics for measuring state similarity in Markov decision processes (MDPs) with infinitely many states, including MDPs with continuous state spaces. Such metrics provide a stable quantitative analogue of the notion of bisimulation for MDPs, and are suitable for use in MDP approximation. We show that the optimal value function associated with a discounted infinite horizon planning task varies continuously with respect to our metric distances. --- paper_title: Metrics for Finite Markov Decision Processes paper_content: We present metrics for measuring the similarity of states in a finite Markov decision process (MDP). The formulation of our metrics is based on the notion of bisimulation for MDPs, with an aim towards solving discounted infinite horizon reinforcement learning tasks. Such metrics can be used to aggregate states, as well as to better structure other value function approximators (e.g., memory-based or nearest-neighbor approximators). We provide bounds that relate our metric distances to the optimal values of states in the given MDP. --- paper_title: Approximation Metrics for Discrete and Continuous Systems paper_content: Established system relationships for discrete systems, such as language inclusion, simulation, and bisimulation, require system observations to be identical. When interacting with the physical world, modeled by continuous or hybrid systems, exact relationships are restrictive and not robust. In this paper, we develop the first framework of system approximation that applies to both discrete and continuous systems by developing notions of approximate language inclusion, approximate simulation, and approximate bisimulation relations. We define a hierarchy of approximation pseudo-metrics between two systems that quantify the quality of the approximation, and capture the established exact relationships as zero sections. Our approximation framework is compositional for a synchronous composition operator. Algorithms are developed for computing the proposed pseudo-metrics, both exactly and approximately. The exact algorithms require the generalization of the fixed point algorithms for computing simulation and bisimulation relations, or dually, the solution of a static game whose cost is the so-called branching distance between the systems. Approximations for the pseudo-metrics can be obtained by considering Lyapunov-like functions called simulation and bisimulation functions. We illustrate our approximation framework in reducing the complexity of safety verification problems for both deterministic and nondeterministic continuous systems --- paper_title: A theory of timed automata paper_content: Alur, R. and D.L. Dill, A theory of timed automata, Theoretical Computer Science 126 (1994) 183-235. We propose timed (j&e) automata to model the behavior of real-time systems over time. Our definition provides a simple, and yet powerful, way to annotate state-transition graphs with timing constraints using finitely many real-valued clocks. A timed automaton accepts timed words-infinite sequences in which a real-valued time of occurrence is associated with each symbol. We study timed automata from the perspective of formal language theory: we consider closure properties, decision problems, and subclasses. We consider both nondeterministic and deterministic transition structures, and both Biichi and Muller acceptance conditions. We show that nondeterministic timed automata are closed under union and intersection, but not under complementation, whereas deterministic timed Muller automata are closed under all Boolean operations. The main construction of the paper is an (PSPACE) algorithm for checking the emptiness of the language of a (nondeterministic) timed automaton. We also prove that the universality problem and the language inclusion problem are solvable only for the deterministic automata: both problems are undecidable (II i-hard) in the nondeterministic case and PSPACE-complete in the deterministic case. Finally, we discuss the application of this theory to automatic verification of real-time requirements of finite-state systems. --- paper_title: Bisimilar linear systems paper_content: The notion of bisimulation in theoretical computer science is one of the main complexity reduction methods for the analysis and synthesis of labeled transition systems. Bisimulations are special quotients of the state space that preserve many important properties expressible in temporal logics, and, in particular, reachability. In this paper, the framework of bisimilar transition systems is applied to various transition systems that are generated by linear control systems. Given a discrete-time or continuous-time linear system, and a finite observation map, we characterize linear quotient maps that result in quotient transition systems that are bisimilar to the original system. Interestingly, the characterizations for discrete-time systems are more restrictive than for continuous-time systems, due to the existence of an atomic time step. We show that computing the coarsest bisimulation, which results in maximum complexity reduction, corresponds to computing the maximal controlled or reachability invariant subspace inside the kernel of the observations map. These results establish strong connections between complexity reduction concepts in control theory and computer science. --- paper_title: Equivalence notions and model minimization in Markov decision processes paper_content: Many stochastic planning problems can be represented using Markov Decision Processes (MDPs). A difficulty with using these MDP representations is that the common algorithms for solving them run in time polynomial in the size of the state space, where this size is extremely large for most real-world planning problems of interest. Recent AI research has addressed this problem by representing the MDP in a factored form. Factored MDPs, however, are not amenable to traditional solution methods that call for an explicit enumeration of the state space. One familiar way to solve MDP problems with very large state spaces is to form a reduced (or aggregated) MDP with the same properties as the original MDP by combining "equivalent" states. In this paper, we discuss applying this approach to solving factored MDP problems--we avoid enumerating the state space by describing large blocks of "equivalent" states in factored form, with the block descriptions being inferred directly from the original factored representation. The resulting reduced MDP may have exponentially fewer states than the original factored MDP, and can then be solved using traditional methods. The reduced MDP found depends on the notion of equivalence between states used in the aggregation. The notion of equivalence chosen will be fundamental in designing and analyzing algorithms for reducing MDPs. Optimally, these algorithms will be able to find the smallest possible reduced MDP for any given input MDP and notion of equivalence (i.e., find the "minimal model" for the input MDP). Unfortunately, the classic notion of state equivalence from non-deterministic finite state machines generalized to MDPs does not prove useful. We present here a notion of equivalence that is based upon the notion of bisimulation from the literature on concurrent processes. Our generalization of bisimulation to stochastic processes yields a non-trivial notion of state equivalence that guarantees the optimal policy for the reduced model immediately induces a corresponding Optimal policy for the original model. With this notion of state equivalence, we design and analyze an algorithm that minimizes arbitrary factored MDPs and compare this method analytically to previous algorithms for solving factored MDPs. We show that previous approaches implicitly derive equivalence relations that we define here. --- paper_title: Specification and refinement of probabilistic processes paper_content: A formalism for specifying probabilistic transition systems, which constitute a basic semantic model for description and analysis of, e.g. reliability aspects of concurrent and distributed systems, is presented. The formalism itself is based on transition systems. Roughly a specification has the form of a transition system in which transitions are labeled by sets of allowed probabilities. A satisfaction relation between processes and specifications that generalizes probabilistic bisimulation equivalence is defined. It is shown that it is analogous to the extension from processes to modal transition systems given by K. Larsen and B. Thomsen (1988). Another weaker criterion views a specification as defining a set of probabilistic processes; refinement is then simply containment between sets of processes. A complete method for verifying containment between specifications, which extends methods for deciding containment between specifications, which extends methods for deciding containment between finite automata or tree acceptors, is presented. > --- paper_title: Concurrency and Automata on Infinite Sequences paper_content: The paper is concerned with ways in which fair concurrency can be modeled using notations for omega-regular languages - languages containing infinite sequences, whose recognizers a.re modified forms of Buchi or Muller-McNaughton automata. There are characterization of these languages in terms of recursion equation sets which involve both minimal and maximal fix point operators. The class of ω-regular languages is closed under a fair concurrency operator. A general method for proving/deciding equivalences between such languages is obtained, derived from Milner's notion of "simulation". --- paper_title: The metric analogue of weak bisimulation for probabilistic processes paper_content: We observe that equivalence is not a robust concept in the presence of numerical information - such as probabilities-in the model. We develop a metric analogue of weak bisimulation in the spirit of our earlier work on metric analogues for strong bisimulation. We give a fixed point characterization of the metric. This makes available conductive reasoning principles and allows us to prove metric analogues of the usual algebraic laws for process combinators. We also show that quantitative properties of interest are continuous with respect to the metric, which says that if two processes are close in the metric then observable quantitative properties of interest are indeed close. As an important example of this we show that nearby processes have nearby channel capacities - a quantitative measure of their propensity to leak information. --- paper_title: Abstraction in Probabilistic Process AlgebraS paper_content: Process algebras with abstraction have been widely used for the specification and verification of non-probabilistic concurrent systems. The main strategy in these algebras is introducing a constant, denoting an internal action, and a set of fairness rules. Following the same approach, in this paper we propose a fully probabilistic process algebra with abstraction which contains a set of verification rules as counterparts of the fairness rules in standard ACP-like process algebras with abstraction. Having probabilities present and employing the results from Markov chain analysis, these rules are expressible in a very intuitive way. In addition to this algebraic approach, we introduce a new version of probabilistic branching bisimulation for the alternating model of probabilistic systems. Different from other approaches, this bisimulation relation requires the same probability measure only for specific related processes called entries. We claim this definition corresponds better with intuition. Moreover, the fairness rules are sound in the model based on this bisimulation. Finally, we present an algorithm to decide our branching bisimulation with a polynomial-time complexity in the number of the states of the probabilistic graph. --- paper_title: Bisimilar control affine systems paper_content: The notion of bisimulation plays a very important role in theoretical computer science where it provides several notions of equivalence between models of computation. These equivalences are in turn used to simplify analysis and synthesis for these models. In system theory, a similar notion is also of interest in order to develop modular analysis and design tools for purely continuous or hybrid control systems. We introduce two notions of bisimulation for nonlinear systems. We present a differential-algebraic characterization of these notions and show that bisimilar systems of different dimensions are obtained by factoring out certain invariant distributions. Furthermore, we also show that all bisimilar systems of different dimension are of this form. --- paper_title: Comparative Branching-Time Semantics for Markov Chains paper_content: This paper presents various semantics in the branching-time spectrum of discrete-time and continuous-time Markov chains (DTMCs and CTMCs). Strong and weak bisimulation equivalence and simulation preorders are covered and are logically characterized in terms of the temporal logics Probabilistic Computation Tree Logic (PCTL) and Continuous Stochastic Logic (CSL). Apart from presenting various existing branching-time relations in a uniform manner, this paper presents the following new results: (i) strong simulation for CTMCs, (ii) weak simulation for CTMCs and DTMCs, (iii) logical characterizations thereof (including weak bisimulation for DTMCs), (iv) a relation between weak bisimulation and weak simulation equivalence, and (v) various connections between equivalences and pre-orders in the continuous-and discrete-time setting. The results are summarized in a branching-time spectrum for DTMCs and CTMCs elucidating their semantics as well as their relationship. --- paper_title: Metrics for Labelled Markov Processes paper_content: The notion of process equivalence of probabilistic processes is sensitive to the exact probabilities of transitions. Thus, a slight change in the transition probabilities will result in two equivalent processes being deemed no longer equivalent. This instability is due to the quantitative nature of probabilistic processes. In a situation where the process behavior has a quantitative aspect there should be a more robust approach to process equivalence. This paper studies a metric between labelled Markov processes. This metric has the property that processes are at zero distance if and only if they are bisimilar. The metric is inspired by earlier work on logics for characterizing bisimulation and is related, in spirit, to the Hutchinson metric. --- paper_title: On infinite-horizon probabilistic properties and stochastic bisimulation functions paper_content: This work investigates infinite-horizon properties over discrete-time stochastic models with continuous state spaces. The focus is on understanding how the structural features of a model (e.g., the presence of absorbing sets) affect the values of these properties and relate to their uniqueness. Furthermore, we argue that the investigation of these features can lead to approximation bounds for the value of such properties, as well as to improvements on their computation. The article employs the presented results to find a stochastic bisimulation function of two processes. --- paper_title: Approximate abstractions of stochastic systems: A randomized method paper_content: This work introduces a randomized method for the design of an approximate abstraction of a stochastic system and the assessment of its quality. The proposed approach relies on the formulation of the problem as a semi-infinite chance-constrained optimization program and on its solution via randomization. The method has quite general applicability, since it only requires to be able to run multiple executions of the candidate abstract model and of the original system and to compute their distance. Two variants of the notion of distance are considered in view of a possible use of the approximate abstraction for probabilistic safety verification. The approach is tested on a numerical example. --- paper_title: A contractivity approach for probabilistic bisimulations of diffusion processes paper_content: This work is concerned with the problem of characterizing and computing probabilistic bisimulations of diffusion processes. A probabilistic bisimulation relation between two such processes is defined through a bisimulation function, which induces an approximation metric on the expectation of the (squared norm of the) distance between the two processes. We introduce sufficient conditions for the existence of a bisimulation function, based on the use of contractivity analysis for probabilistic systems. Furthermore, we show that the notion of stochastic contractivity is related to a probabilistic version of the concept of incremental stability. This relationship leads to a procedure that constructs a discrete approximation of a diffusion process. The procedure is based on the discretization of space and time. Given a diffusion process, we raise sufficient conditions for the existence of such an approximation, and show that it is probabilistically bisimilar to the original process, up to a certain approximation precision. --- paper_title: Approximate Abstractions of Stochastic Hybrid Systems paper_content: We present a constructive procedure for obtaining a finite approximate abstraction of a discrete-time stochastic hybrid system. The procedure consists of a partition of the state space of the system and depends on a controllable parameter. Given proper continuity assumptions on the model, the approximation errors introduced by the abstraction procedure are explicitly computed and it is shown that they can be tuned through the parameter of the partition. The abstraction is interpreted as a Markov set-Chain. We show that the enforcement of certain ergodic properties on the stochastic hybrid model implies the existence of a finite abstraction with finite error in time over the concrete model, and allows introducing a finite-time algorithm that computes the abstraction. --- paper_title: Approximations of Stochastic Hybrid Systems paper_content: This paper develops a notion of approximation for a class of stochastic hybrid systems that includes, as special cases, both jump linear stochastic systems and linear stochastic hybrid automata. Our approximation framework is based on the recently developed notion of the so-called stochastic simulation functions. These Lyapunov-like functions can be used to rigorously quantify the distance or error between a system and its approximate abstraction. For the class of jump linear stochastic systems and linear stochastic hybrid automata, we show that the computation of stochastic simulation functions can be cast as a tractable linear matrix inequality problem. This enables us to compute the modeling error incurred by abstracting some of the continuous dynamics, or by neglecting the influence of stochastic noise, or even the influence of stochastic discrete jumps. --- paper_title: A numerical approximation scheme for reachability analysis of stochastic hybrid systems with state-dependent switchings paper_content: We describe a methodology for reachability analysis of a certain class of stochastic hybrid systems, whose continuous dynamics is governed by stochastic differential equations and discrete dynamics by state-dependent probabilistic transitions. The main feature of the proposed methodology is that it rests on the weak approximation of the solution to the stochastic differential equation with random mode transitions by a Markov chain. Reachability computations then reduce to propagating the transition probabilities of the approximating Markov chain. An example of applications to system verification is presented. --- paper_title: Approximating labeled Markov processes paper_content: We study approximate reasoning about continuous-state labeled Markov processes. We show how to approximate a labeled Markov process by a family of finite-state labeled Markov chains. We show that the collection of labeled Markov processes carries a Polish space structure with a countable basis given by finite state Markov chains with rational probabilities. The primary technical tools that we develop to reach these results are: a finite-model theorem for the modal logic used to characterize bisimulation; and a categorical equivalence between the category of Markov processes (with simulation morphisms) with the /spl omega/-continuous dcpo Proc, defined as the solution of the recursive domain equation Proc=/spl Pi//sub Labels/ P/sub Prob/(Proc). The correspondence between labeled Markov processes and Proc yields a logic complete for reasoning about simulation for continuous-state processes. --- paper_title: Approximation Metrics for Discrete and Continuous Systems paper_content: Established system relationships for discrete systems, such as language inclusion, simulation, and bisimulation, require system observations to be identical. When interacting with the physical world, modeled by continuous or hybrid systems, exact relationships are restrictive and not robust. In this paper, we develop the first framework of system approximation that applies to both discrete and continuous systems by developing notions of approximate language inclusion, approximate simulation, and approximate bisimulation relations. We define a hierarchy of approximation pseudo-metrics between two systems that quantify the quality of the approximation, and capture the established exact relationships as zero sections. Our approximation framework is compositional for a synchronous composition operator. Algorithms are developed for computing the proposed pseudo-metrics, both exactly and approximately. The exact algorithms require the generalization of the fixed point algorithms for computing simulation and bisimulation relations, or dually, the solution of a static game whose cost is the so-called branching distance between the systems. Approximations for the pseudo-metrics can be obtained by considering Lyapunov-like functions called simulation and bisimulation functions. We illustrate our approximation framework in reducing the complexity of safety verification problems for both deterministic and nondeterministic continuous systems --- paper_title: Approximation and Weak Convergence Methods for Random Processes with Applications to Stochastic Systems Theory paper_content: Control and communications engineers, physicists, and probability theorists, among others, will find this book unique. It contains a detailed development of approximation and limit theorems and methods for random processes and applies them to numerous problems of practical importance. In particular, it develops usable and broad conditions and techniques for showing that a sequence of processes converges to a Markov diffusion or jump process. This is useful when the natural physical model is quite complex, in which case a simpler approximation la diffusion process, for example) is usually made.The book simplifies and extends some important older methods and develops some powerful new ones applicable to a wide variety of limit and approximation problems. The theory of weak convergence of probability measures is introduced along with general and usable methods (for example, perturbed test function, martingale, and direct averaging) for proving tightness and weak convergence.Kushner's study begins with a systematic development of the method. It then treats dynamical system models that have state-dependent noise or nonsmooth dynamics. Perturbed Liapunov function methods are developed for stability studies of nonMarkovian problems and for the study of asymptotic distributions of non-Markovian systems. Three chapters are devoted to applications in control and communication theory (for example, phase-locked loops and adoptive filters). Smallnoise problems and an introduction to the theory of large deviations and applications conclude the book.Harold J. Kushner is Professor of Applied Mathematics and Engineering at Brown University and is one of the leading researchers in the area of stochastic processes concerned with analysis and synthesis in control and communications theory. This book is the sixth in The MIT Press Series in Signal Processing, Optimization, and Control, edited by Alan S. Willsky. --- paper_title: On the Approximation Quality of Markov State Models paper_content: We consider a continuous-time Markov process on a large continuous or discrete state space. The process is assumed to have strong enough ergodicity properties and to exhibit a number of metastable sets. Markov state models (MSMs) are designed to represent the effective dynamics of such a process by a Markov chain that jumps between the metastable sets with the transition rates of the original process. MSMs have been used for a number of applications, including molecular dynamics, for more than a decade. Their approximation quality, however, has not yet been fully understood. In particular, it would be desirable to have a sharp error bound for the difference in propagation of probability densities between the MSM and the original process on long timescales. Here, we provide such a bound for a rather general class of Markov processes ranging from diffusions in energy landscapes to Markov jump processes on large discrete spaces. Furthermore, we discuss how this result provides formal support or shows the limitations of algorithmic strategies that have been found to be useful for the construction of MSMs. Our findings are illustrated by numerical experiments. --- paper_title: Optimal Control of Stochastic Hybrid Systems Based on Locally Consistent Markov Decision Processes paper_content: This paper applies a known approach for approximating controlled stochastic diffusion to hybrid systems. Stochastic hybrid systems are approximated by locally consistent Markov decision processes that preserve local mean and covariance. A randomized switching policy is introduced for approximating the dynamics on the switching boundaries. The validity of the approximation is shown by solving the optimal control problem of minimizing a cost until a target set is reached using dynamic programming. It is shown that using the randomized switching policy, the solution obtained based on the discrete approximation converges to the solution of the original problem --- paper_title: Approximate Model Checking of Stochastic Hybrid Systems paper_content: A method for approximate model checking of stochastic hybrid systems with provable approximation guarantees is proposed. We focus on the probabilistic invariance problem for discrete time stochastic hybrid systems and propose a two-step scheme. The stochastic hybrid system is first approximated by a finite state Markov chain. The approximating chain is then model checked for probabilistic invariance. Under certain regularity conditions on the transition and reset kernels governing the dynamics of the stochastic hybrid system, the invariance probability computed using the approximating Markov chain is shown to converge to the invariance probability of the original stochastic hybrid system, as the grid used in the approximation gets finer. A bound on the convergence rate is also provided. The performance of the two-step approximate model checking procedure is assessed on a case study of a multi-room heating system. --- paper_title: Approximating stochastic biochemical processes with Wasserstein pseudometrics. paper_content: Modelling stochastic processes inside the cell is difficult due to the size and complexity of the processes being investigated. As a result, new approaches are needed to address the problems of model reduction, parameter estimation, model comparison and model invalidation. Here, the authors propose addressing these problems by using Wasserstein pseudometrics to quantify the differences between processes. The method the authors propose is applicable to any bounded continuous-time stochastic process and pseudometrics between processes are defined only in terms of the available outputs. Algorithms for approximating Wasserstein pseudometrics are developed from experimental or simulation data and demonstrate how to optimise parameter values to minimise the pseudometrics. The approach is illustrated with studies of a stochastic toggle switch and of stochastic gene expression in E. coli. --- paper_title: Markov Models and Optimization paper_content: Analysis, probability and stochastic processes piecewise deterministic processes expectations and distributions control theory control by intervention. --- paper_title: Markov Chains and Stochastic Stability paper_content: Meyn & Tweedie is back! The bible on Markov chains in general state spaces has been brought up to date to reflect developments in the field since 1996 - many of them sparked by publication of the first edition. The pursuit of more efficient simulation algorithms for complex Markovian models, or algorithms for computation of optimal policies for controlled Markov models, has opened new directions for research on Markov chains. As a result, new applications have emerged across a wide range of topics including optimisation, statistics, and economics. New commentary and an epilogue by Sean Meyn summarise recent developments and references have been fully updated. This second edition reflects the same discipline and style that marked out the original and helped it to become a classic: proofs are rigorous and concise, the range of applications is broad and knowledgeable, and key ideas are accessible to practitioners with limited mathematical background. --- paper_title: Probabilistic reachability and safety for controlled discrete time stochastic hybrid systems paper_content: In this work, probabilistic reachability over a finite horizon is investigated for a class of discrete time stochastic hybrid systems with control inputs. A suitable embedding of the reachability problem in a stochastic control framework reveals that it is amenable to two complementary interpretations, leading to dual algorithms for reachability computations. In particular, the set of initial conditions providing a certain probabilistic guarantee that the system will keep evolving within a desired 'safe' region of the state space is characterized in terms of a value function, and 'maximally safe' Markov policies are determined via dynamic programming. These results are of interest not only for safety analysis and design, but also for solving those regulation and stabilization problems that can be reinterpreted as safety problems. The temperature regulation problem presented in the paper as a case study is one such case. --- paper_title: Bisimulation for Labelled Markov Processes paper_content: In this paper we introduce a new class of labelled transition systems - Labelled Markov Processes - and define bisimulation for them. Labelled Markov processes are probabilistic labelled transition systems where the state space is not necessarily discrete, it could be the reals, for example. We assume that it is a Polish space (the underlying topological space for a complete separable metric space). The mathematical theory of such systems is completely new from the point of view of the extant literature on probabilistic process algebra; of course, it uses classical ideas from measure theory and Markov process theory. The notion of bisimulation builds on the ideas of Larsen and Skou and of Joyal, Nielsen and Winskel. The main result that we prove is that a notion of bisimulation for Markov processes on Polish spaces, which extends the Larsen-Skou denition for discrete systems, is indeed an equivalence relation. This turns out to be a rather hard mathematical result which, as far as we know, embodies a new result in pure probability theory. This work heavily uses continuous mathematics which is becoming an important part of work on hybrid systems. --- paper_title: Approximating labeled Markov processes paper_content: We study approximate reasoning about continuous-state labeled Markov processes. We show how to approximate a labeled Markov process by a family of finite-state labeled Markov chains. We show that the collection of labeled Markov processes carries a Polish space structure with a countable basis given by finite state Markov chains with rational probabilities. The primary technical tools that we develop to reach these results are: a finite-model theorem for the modal logic used to characterize bisimulation; and a categorical equivalence between the category of Markov processes (with simulation morphisms) with the /spl omega/-continuous dcpo Proc, defined as the solution of the recursive domain equation Proc=/spl Pi//sub Labels/ P/sub Prob/(Proc). The correspondence between labeled Markov processes and Proc yields a logic complete for reasoning about simulation for continuous-state processes. --- paper_title: Metrics for Labelled Markov Processes paper_content: The notion of process equivalence of probabilistic processes is sensitive to the exact probabilities of transitions. Thus, a slight change in the transition probabilities will result in two equivalent processes being deemed no longer equivalent. This instability is due to the quantitative nature of probabilistic processes. In a situation where the process behavior has a quantitative aspect there should be a more robust approach to process equivalence. This paper studies a metric between labelled Markov processes. This metric has the property that processes are at zero distance if and only if they are bisimilar. The metric is inspired by earlier work on logics for characterizing bisimulation and is related, in spirit, to the Hutchinson metric. --- paper_title: Bisimulation for Labelled Markov Processes paper_content: In this paper we introduce a new class of labelled transition systems - Labelled Markov Processes - and define bisimulation for them. Labelled Markov processes are probabilistic labelled transition systems where the state space is not necessarily discrete, it could be the reals, for example. We assume that it is a Polish space (the underlying topological space for a complete separable metric space). The mathematical theory of such systems is completely new from the point of view of the extant literature on probabilistic process algebra; of course, it uses classical ideas from measure theory and Markov process theory. The notion of bisimulation builds on the ideas of Larsen and Skou and of Joyal, Nielsen and Winskel. The main result that we prove is that a notion of bisimulation for Markov processes on Polish spaces, which extends the Larsen-Skou denition for discrete systems, is indeed an equivalence relation. This turns out to be a rather hard mathematical result which, as far as we know, embodies a new result in pure probability theory. This work heavily uses continuous mathematics which is becoming an important part of work on hybrid systems. --- paper_title: Approximating labeled Markov processes paper_content: We study approximate reasoning about continuous-state labeled Markov processes. We show how to approximate a labeled Markov process by a family of finite-state labeled Markov chains. We show that the collection of labeled Markov processes carries a Polish space structure with a countable basis given by finite state Markov chains with rational probabilities. The primary technical tools that we develop to reach these results are: a finite-model theorem for the modal logic used to characterize bisimulation; and a categorical equivalence between the category of Markov processes (with simulation morphisms) with the /spl omega/-continuous dcpo Proc, defined as the solution of the recursive domain equation Proc=/spl Pi//sub Labels/ P/sub Prob/(Proc). The correspondence between labeled Markov processes and Proc yields a logic complete for reasoning about simulation for continuous-state processes. --- paper_title: Metrics for Labelled Markov Processes paper_content: The notion of process equivalence of probabilistic processes is sensitive to the exact probabilities of transitions. Thus, a slight change in the transition probabilities will result in two equivalent processes being deemed no longer equivalent. This instability is due to the quantitative nature of probabilistic processes. In a situation where the process behavior has a quantitative aspect there should be a more robust approach to process equivalence. This paper studies a metric between labelled Markov processes. This metric has the property that processes are at zero distance if and only if they are bisimilar. The metric is inspired by earlier work on logics for characterizing bisimulation and is related, in spirit, to the Hutchinson metric. --- paper_title: Weak Bisimulation for Fully Probabilistic Processes paper_content: Bisimulations that abstract from internal computation have proven to be useful for verification of compositionally defined transition systems. In the literature of probabilistic extensions of such transition systems, similar bisimulations are rare. In this paper, we introduce weak and branching bisimulation for fully probabilistic systems, transition systems where nondeterministic branching is replaced by probabilistic branching. In contrast to the nondeterministic case, both relations coincide. We give an algorithm to decide weak (and branching) bisimulation with a time complexity cubic in the number of states of the fully probabilistic system. This meets the worst case complexity for deciding branching bisimulation in the nondeterministic case. In addition, the relation is shown to be a congruence with respect to the operators of PLSCCS, a lazy synchronous probabilistic variant of CCS. We illustrate that due to these properties, weak bisimulation provides all the crucial ingredients for mechanised compositional veri�cation of probabilistic transition systems. --- paper_title: Bisimulation for probabilistic transition systems: a coalgebraic approach paper_content: Abstract The notion of bisimulation as proposed by Larsen and Skou for discrete probabilistic transition systems is shown to coincide with a coalgebraic definition in the sense of Aczel and Mendler in terms of a set functor, which associates to a set its collection of simple probability distributions. This coalgebraic formulation makes it possible to generalize the concepts of discrete probabilistic transition system and probabilistic bisimulation to a continuous setting involving Borel probability measures. A functor ℳ 1 is introduced that yields for a metric space its collection of Borel probability measures. Under reasonable conditions, this functor exactly captures generalized probabilistic bisimilarity. Application of the final coalgebra paradigm to a functor based on ℳ 1 then yields an internally fully abstract semantical domain with respect to probabilistic bisimulation, which is therefore well suited for the interpretation of probabilistic specification and stochastic programming concepts. --- paper_title: Bisimulation for Labelled Markov Processes paper_content: In this paper we introduce a new class of labelled transition systems - Labelled Markov Processes - and define bisimulation for them. Labelled Markov processes are probabilistic labelled transition systems where the state space is not necessarily discrete, it could be the reals, for example. We assume that it is a Polish space (the underlying topological space for a complete separable metric space). The mathematical theory of such systems is completely new from the point of view of the extant literature on probabilistic process algebra; of course, it uses classical ideas from measure theory and Markov process theory. The notion of bisimulation builds on the ideas of Larsen and Skou and of Joyal, Nielsen and Winskel. The main result that we prove is that a notion of bisimulation for Markov processes on Polish spaces, which extends the Larsen-Skou denition for discrete systems, is indeed an equivalence relation. This turns out to be a rather hard mathematical result which, as far as we know, embodies a new result in pure probability theory. This work heavily uses continuous mathematics which is becoming an important part of work on hybrid systems. --- paper_title: Approximate Model Checking of Stochastic Hybrid Systems paper_content: A method for approximate model checking of stochastic hybrid systems with provable approximation guarantees is proposed. We focus on the probabilistic invariance problem for discrete time stochastic hybrid systems and propose a two-step scheme. The stochastic hybrid system is first approximated by a finite state Markov chain. The approximating chain is then model checked for probabilistic invariance. Under certain regularity conditions on the transition and reset kernels governing the dynamics of the stochastic hybrid system, the invariance probability computed using the approximating Markov chain is shown to converge to the invariance probability of the original stochastic hybrid system, as the grid used in the approximation gets finer. A bound on the convergence rate is also provided. The performance of the two-step approximate model checking procedure is assessed on a case study of a multi-room heating system. --- paper_title: Correctness Issues of Symbolic Bisimulation Computation for Markov Chains ⋆ paper_content: Bisimulation reduction is a classical means to fight the infamous state space explosion problem, which limits the applicability of automated methods for verification like model checking. A signature-based method, originally developed by Blom and Orzan for labeled transition systems and adapted for Markov chains by Derisavi, has proved to be very efficient. It is possible to implement it symbolically using binary decision diagrams such that it is able to handle very large state spaces efficiently. We will show, however, that for Markov chains this algorithm suffers from numerical instabilities, which often result in too large quotient systems. We will present and experimentally evaluate two different approaches to avoid these problems: first the usage of rational arithmetic, and second an approach not only to represent the system structure but also the transition rates symbolically. In addition, this allows us to modify their actual values after the quotient computation. --- paper_title: Metrics for Labelled Markov Processes paper_content: The notion of process equivalence of probabilistic processes is sensitive to the exact probabilities of transitions. Thus, a slight change in the transition probabilities will result in two equivalent processes being deemed no longer equivalent. This instability is due to the quantitative nature of probabilistic processes. In a situation where the process behavior has a quantitative aspect there should be a more robust approach to process equivalence. This paper studies a metric between labelled Markov processes. This metric has the property that processes are at zero distance if and only if they are bisimilar. The metric is inspired by earlier work on logics for characterizing bisimulation and is related, in spirit, to the Hutchinson metric. --- paper_title: Approximate Analysis of Probabilistic Processes: Logic, Simulation and Games paper_content: We tackle the problem of non robustness of simulation and bisimulation when dealing with probabilistic processes. It is important to ignore tiny deviations in probabilities because these often come from experiments or estimations. A few approaches have been proposed to treat this issue, for example metrics to quantify the non bisimilarity (or closeness) of processes. Relaxing the definition of simulation and bisimulation is another avenue which we follow. We define a new semantics to a known simple logic for probabilistic processes and show that it characterises a notion of epsi-simulation. We also define two-players games that correspond to these notions: the existence of a winning strategy for one of the players determines epsi-(bi)simulation. Of course, for all the notions defined, letting epsi = 0 gives back the usual notions of logical equivalence, simulation and bisimulation. However, in contrast to what happens in fully probabilistic systems when epsi = 0, two-way e-simulation for epsi > 0 is not equal to epsi-bisimulation. Next we give a polynomial time algorithm to compute a naturally derived metric: distance between states s and t is defined as the smallest epsi such that s and t are epsi-equivalent. This is the first polynomial algorithm for a non-discounted metric. Finally we show that most of these notions can be extended to deal with probabilistic systems that allow non-determinism as well. --- paper_title: Approximate abstractions of stochastic systems: A randomized method paper_content: This work introduces a randomized method for the design of an approximate abstraction of a stochastic system and the assessment of its quality. The proposed approach relies on the formulation of the problem as a semi-infinite chance-constrained optimization program and on its solution via randomization. The method has quite general applicability, since it only requires to be able to run multiple executions of the candidate abstract model and of the original system and to compute their distance. Two variants of the notion of distance are considered in view of a possible use of the approximate abstraction for probabilistic safety verification. The approach is tested on a numerical example. --- paper_title: Metrics for Labelled Markov Processes paper_content: The notion of process equivalence of probabilistic processes is sensitive to the exact probabilities of transitions. Thus, a slight change in the transition probabilities will result in two equivalent processes being deemed no longer equivalent. This instability is due to the quantitative nature of probabilistic processes. In a situation where the process behavior has a quantitative aspect there should be a more robust approach to process equivalence. This paper studies a metric between labelled Markov processes. This metric has the property that processes are at zero distance if and only if they are bisimilar. The metric is inspired by earlier work on logics for characterizing bisimulation and is related, in spirit, to the Hutchinson metric. --- paper_title: Approximate Analysis of Probabilistic Processes: Logic, Simulation and Games paper_content: We tackle the problem of non robustness of simulation and bisimulation when dealing with probabilistic processes. It is important to ignore tiny deviations in probabilities because these often come from experiments or estimations. A few approaches have been proposed to treat this issue, for example metrics to quantify the non bisimilarity (or closeness) of processes. Relaxing the definition of simulation and bisimulation is another avenue which we follow. We define a new semantics to a known simple logic for probabilistic processes and show that it characterises a notion of epsi-simulation. We also define two-players games that correspond to these notions: the existence of a winning strategy for one of the players determines epsi-(bi)simulation. Of course, for all the notions defined, letting epsi = 0 gives back the usual notions of logical equivalence, simulation and bisimulation. However, in contrast to what happens in fully probabilistic systems when epsi = 0, two-way e-simulation for epsi > 0 is not equal to epsi-bisimulation. Next we give a polynomial time algorithm to compute a naturally derived metric: distance between states s and t is defined as the smallest epsi such that s and t are epsi-equivalent. This is the first polynomial algorithm for a non-discounted metric. Finally we show that most of these notions can be extended to deal with probabilistic systems that allow non-determinism as well. --- paper_title: Metrics for Labelled Markov Processes paper_content: The notion of process equivalence of probabilistic processes is sensitive to the exact probabilities of transitions. Thus, a slight change in the transition probabilities will result in two equivalent processes being deemed no longer equivalent. This instability is due to the quantitative nature of probabilistic processes. In a situation where the process behavior has a quantitative aspect there should be a more robust approach to process equivalence. This paper studies a metric between labelled Markov processes. This metric has the property that processes are at zero distance if and only if they are bisimilar. The metric is inspired by earlier work on logics for characterizing bisimulation and is related, in spirit, to the Hutchinson metric. --- paper_title: Approximate Analysis of Probabilistic Processes: Logic, Simulation and Games paper_content: We tackle the problem of non robustness of simulation and bisimulation when dealing with probabilistic processes. It is important to ignore tiny deviations in probabilities because these often come from experiments or estimations. A few approaches have been proposed to treat this issue, for example metrics to quantify the non bisimilarity (or closeness) of processes. Relaxing the definition of simulation and bisimulation is another avenue which we follow. We define a new semantics to a known simple logic for probabilistic processes and show that it characterises a notion of epsi-simulation. We also define two-players games that correspond to these notions: the existence of a winning strategy for one of the players determines epsi-(bi)simulation. Of course, for all the notions defined, letting epsi = 0 gives back the usual notions of logical equivalence, simulation and bisimulation. However, in contrast to what happens in fully probabilistic systems when epsi = 0, two-way e-simulation for epsi > 0 is not equal to epsi-bisimulation. Next we give a polynomial time algorithm to compute a naturally derived metric: distance between states s and t is defined as the smallest epsi such that s and t are epsi-equivalent. This is the first polynomial algorithm for a non-discounted metric. Finally we show that most of these notions can be extended to deal with probabilistic systems that allow non-determinism as well. --- paper_title: Principles of Model Checking paper_content: Our growing dependence on increasingly complex computer and software systems necessitates the development of formalisms, techniques, and tools for assessing functional properties of these systems. One such technique that has emerged in the last twenty years is model checking, which systematically (and automatically) checks whether a model of a given system satisfies a desired property such as deadlock freedom, invariants, and request-response properties. This automated technique for verification and debugging has developed into a mature and widely used approach with many applications. Principles of Model Checking offers a comprehensive introduction to model checking that is not only a text suitable for classroom use but also a valuable reference for researchers and practitioners in the field. The book begins with the basic principles for modeling concurrent and communicating systems, introduces different classes of properties (including safety and liveness), presents the notion of fairness, and provides automata-based algorithms for these properties. It introduces the temporal logics LTL and CTL, compares them, and covers algorithms for verifying these logics, discussing real-time systems as well as systems subject to random phenomena. Separate chapters treat such efficiency-improving techniques as abstraction and symbolic manipulation. The book includes an extensive set of examples (most of which run through several chapters) and a complete set of basic results accompanied by detailed proofs. Each chapter concludes with a summary, bibliographic notes, and an extensive list of exercises of both practical and theoretical nature. --- paper_title: Labeled Markov processes: stronger and faster approximations paper_content: This paper proposes a measure-theoretic reconstruction of the approximation schemes developed for labeled Markov processes: approximants are seen as quotients with respect to sets of temporal properties expressed in a simple logic. This gives the possibility of customizing approximants with respect to properties of interest and is thus an important step towards using automated techniques intended for finite state systems, e.g. model checking, for continuous state systems. The measure-theoretic apparatus meshes well with an enriched logic, extended with a greatest fix-point, and gives means to define approximants which retain cyclic properties of their target. --- paper_title: Approximate Abstractions of Stochastic Hybrid Systems paper_content: We present a constructive procedure for obtaining a finite approximate abstraction of a discrete-time stochastic hybrid system. The procedure consists of a partition of the state space of the system and depends on a controllable parameter. Given proper continuity assumptions on the model, the approximation errors introduced by the abstraction procedure are explicitly computed and it is shown that they can be tuned through the parameter of the partition. The abstraction is interpreted as a Markov set-Chain. We show that the enforcement of certain ergodic properties on the stochastic hybrid model implies the existence of a finite abstraction with finite error in time over the concrete model, and allows introducing a finite-time algorithm that computes the abstraction. --- paper_title: Metrics for Markov Decision Processes with Infinite State Spaces paper_content: We present metrics for measuring state similarity in Markov decision processes (MDPs) with infinitely many states, including MDPs with continuous state spaces. Such metrics provide a stable quantitative analogue of the notion of bisimulation for MDPs, and are suitable for use in MDP approximation. We show that the optimal value function associated with a discounted infinite horizon planning task varies continuously with respect to our metric distances. --- paper_title: Approximating labeled Markov processes paper_content: We study approximate reasoning about continuous-state labeled Markov processes. We show how to approximate a labeled Markov process by a family of finite-state labeled Markov chains. We show that the collection of labeled Markov processes carries a Polish space structure with a countable basis given by finite state Markov chains with rational probabilities. The primary technical tools that we develop to reach these results are: a finite-model theorem for the modal logic used to characterize bisimulation; and a categorical equivalence between the category of Markov processes (with simulation morphisms) with the /spl omega/-continuous dcpo Proc, defined as the solution of the recursive domain equation Proc=/spl Pi//sub Labels/ P/sub Prob/(Proc). The correspondence between labeled Markov processes and Proc yields a logic complete for reasoning about simulation for continuous-state processes. --- paper_title: Metrics for Labelled Markov Processes paper_content: The notion of process equivalence of probabilistic processes is sensitive to the exact probabilities of transitions. Thus, a slight change in the transition probabilities will result in two equivalent processes being deemed no longer equivalent. This instability is due to the quantitative nature of probabilistic processes. In a situation where the process behavior has a quantitative aspect there should be a more robust approach to process equivalence. This paper studies a metric between labelled Markov processes. This metric has the property that processes are at zero distance if and only if they are bisimilar. The metric is inspired by earlier work on logics for characterizing bisimulation and is related, in spirit, to the Hutchinson metric. --- paper_title: Probabilistic bisimulations of switching and resetting diffusions paper_content: This contribution presents sufficient conditions for the existence of probabilistic bisimulations between two diffusion processes that are additionally endowed with switching and resetting behaviors. A probabilistic bisimulation between two stochastic processes is defined by means of a bisimulation function, which induces an approximation metric over the distance between the two processes. The validity of the proposed sufficient conditions results in the explicit characterization of one such bisimulation function. The conditions depend on contractivity properties of the two stochastic processes. --- paper_title: Approximations of Stochastic Hybrid Systems paper_content: This paper develops a notion of approximation for a class of stochastic hybrid systems that includes, as special cases, both jump linear stochastic systems and linear stochastic hybrid automata. Our approximation framework is based on the recently developed notion of the so-called stochastic simulation functions. These Lyapunov-like functions can be used to rigorously quantify the distance or error between a system and its approximate abstraction. For the class of jump linear stochastic systems and linear stochastic hybrid automata, we show that the computation of stochastic simulation functions can be cast as a tractable linear matrix inequality problem. This enables us to compute the modeling error incurred by abstracting some of the continuous dynamics, or by neglecting the influence of stochastic noise, or even the influence of stochastic discrete jumps. --- paper_title: Approximations of Stochastic Hybrid Systems paper_content: This paper develops a notion of approximation for a class of stochastic hybrid systems that includes, as special cases, both jump linear stochastic systems and linear stochastic hybrid automata. Our approximation framework is based on the recently developed notion of the so-called stochastic simulation functions. These Lyapunov-like functions can be used to rigorously quantify the distance or error between a system and its approximate abstraction. For the class of jump linear stochastic systems and linear stochastic hybrid automata, we show that the computation of stochastic simulation functions can be cast as a tractable linear matrix inequality problem. This enables us to compute the modeling error incurred by abstracting some of the continuous dynamics, or by neglecting the influence of stochastic noise, or even the influence of stochastic discrete jumps. --- paper_title: Approximate Analysis of Probabilistic Processes: Logic, Simulation and Games paper_content: We tackle the problem of non robustness of simulation and bisimulation when dealing with probabilistic processes. It is important to ignore tiny deviations in probabilities because these often come from experiments or estimations. A few approaches have been proposed to treat this issue, for example metrics to quantify the non bisimilarity (or closeness) of processes. Relaxing the definition of simulation and bisimulation is another avenue which we follow. We define a new semantics to a known simple logic for probabilistic processes and show that it characterises a notion of epsi-simulation. We also define two-players games that correspond to these notions: the existence of a winning strategy for one of the players determines epsi-(bi)simulation. Of course, for all the notions defined, letting epsi = 0 gives back the usual notions of logical equivalence, simulation and bisimulation. However, in contrast to what happens in fully probabilistic systems when epsi = 0, two-way e-simulation for epsi > 0 is not equal to epsi-bisimulation. Next we give a polynomial time algorithm to compute a naturally derived metric: distance between states s and t is defined as the smallest epsi such that s and t are epsi-equivalent. This is the first polynomial algorithm for a non-discounted metric. Finally we show that most of these notions can be extended to deal with probabilistic systems that allow non-determinism as well. --- paper_title: Lyapunov-like techniques for stochastic stability paper_content: The purpose of this paper is to give a survey of the results proved in Florchinger (1993) concerning the stabilizability problem for control stochastic nonlinear systems driven by a Wiener process. Sufficient conditions for the existence of stabilizing feedback laws which are smooth, except possibly at the equilibrium point of the system, are provided by means of stochastic Lyapunov-like techniques. The notion of dynamic asymptotic stability in probability of control stochastic differential systems is introduced, and the stabilization by means of dynamic controllers is studied. > --- paper_title: Approximately Bisimilar Symbolic Models for Incrementally Stable Switched Systems paper_content: Switched systems constitute an important modeling paradigm faithfully describing many engineering systems in which software interacts with the physical world. Despite considerable progress on stability and stabilization of switched systems, the constant evolution of technology demands that we make similar progress with respect to different, and perhaps more complex, objectives. This paper describes one particular approach to address these different objectives based on the construction of approximately equivalent (bisimilar) symbolic models for switched systems. The main contribution of this paper consists in showing that under standard assumptions ensuring incremental stability of a switched system (i.e., existence of a common Lyapunov function, or multiple Lyapunov functions with dwell time), it is possible to construct a finite symbolic model that is approximately bisimilar to the original switched system with a precision that can be chosen a priori. To support the computational merits of the proposed approach, we use symbolic models to synthesize controllers for two examples of switched systems, including the boost dc-dc converter. --- paper_title: A contractivity approach for probabilistic bisimulations of diffusion processes paper_content: This work is concerned with the problem of characterizing and computing probabilistic bisimulations of diffusion processes. A probabilistic bisimulation relation between two such processes is defined through a bisimulation function, which induces an approximation metric on the expectation of the (squared norm of the) distance between the two processes. We introduce sufficient conditions for the existence of a bisimulation function, based on the use of contractivity analysis for probabilistic systems. Furthermore, we show that the notion of stochastic contractivity is related to a probabilistic version of the concept of incremental stability. This relationship leads to a procedure that constructs a discrete approximation of a diffusion process. The procedure is based on the discretization of space and time. Given a diffusion process, we raise sufficient conditions for the existence of such an approximation, and show that it is probabilistically bisimilar to the original process, up to a certain approximation precision. --- paper_title: Approximately bisimilar symbolic models for nonlinear control systems paper_content: Control systems are usually modeled by differential equations describing how physical phenomena can be influenced by certain control parameters or inputs. Although these models are very powerful when dealing with physical phenomena, they are less suitable to describe software and hardware interfacing the physical world. For this reason there is a growing interest in describing control systems through symbolic models that are abstract descriptions of the continuous dynamics, where each "symbol" corresponds to an "aggregate" of states in the continuous model. Since these symbolic models are of the same nature of the models used in computer science to describe software and hardware, they provide a unified language to study problems of control in which software and hardware interact with the physical world. Furthermore the use of symbolic models enables one to leverage techniques from supervisory control and algorithms from game theory for controller synthesis purposes. In this paper we show that every incrementally globally asymptotically stable nonlinear control system is approximately equivalent (bisimilar) to a symbolic model. The approximation error is a design parameter in the construction of the symbolic model and can be rendered as small as desired. Furthermore if the state space of the control system is bounded the obtained symbolic model is finite. For digital control systems, and under the stronger assumption of incremental input-to-state stability, symbolic models can be constructed through a suitable quantization of the inputs. --- paper_title: A Contraction Theory Approach to Stochastic Incremental Stability paper_content: We investigate the incremental stability properties of It\^o stochastic dynamical systems. Specifically, we derive a stochastic version of nonlinear contraction theory that provides a bound on the mean square distance between any two trajectories of a stochastically contracting system. This bound can be expressed as a function of the noise intensity and the contraction rate of the noise-free system. We illustrate these results in the contexts of stochastic nonlinear observers design and stochastic synchronization. --- paper_title: Probabilistic bisimulations of switching and resetting diffusions paper_content: This contribution presents sufficient conditions for the existence of probabilistic bisimulations between two diffusion processes that are additionally endowed with switching and resetting behaviors. A probabilistic bisimulation between two stochastic processes is defined by means of a bisimulation function, which induces an approximation metric over the distance between the two processes. The validity of the proposed sufficient conditions results in the explicit characterization of one such bisimulation function. The conditions depend on contractivity properties of the two stochastic processes. --- paper_title: Approximations of Stochastic Hybrid Systems paper_content: This paper develops a notion of approximation for a class of stochastic hybrid systems that includes, as special cases, both jump linear stochastic systems and linear stochastic hybrid automata. Our approximation framework is based on the recently developed notion of the so-called stochastic simulation functions. These Lyapunov-like functions can be used to rigorously quantify the distance or error between a system and its approximate abstraction. For the class of jump linear stochastic systems and linear stochastic hybrid automata, we show that the computation of stochastic simulation functions can be cast as a tractable linear matrix inequality problem. This enables us to compute the modeling error incurred by abstracting some of the continuous dynamics, or by neglecting the influence of stochastic noise, or even the influence of stochastic discrete jumps. --- paper_title: Bisimilar linear systems paper_content: The notion of bisimulation in theoretical computer science is one of the main complexity reduction methods for the analysis and synthesis of labeled transition systems. Bisimulations are special quotients of the state space that preserve many important properties expressible in temporal logics, and, in particular, reachability. In this paper, the framework of bisimilar transition systems is applied to various transition systems that are generated by linear control systems. Given a discrete-time or continuous-time linear system, and a finite observation map, we characterize linear quotient maps that result in quotient transition systems that are bisimilar to the original system. Interestingly, the characterizations for discrete-time systems are more restrictive than for continuous-time systems, due to the existence of an atomic time step. We show that computing the coarsest bisimulation, which results in maximum complexity reduction, corresponds to computing the maximal controlled or reachability invariant subspace inside the kernel of the observations map. These results establish strong connections between complexity reduction concepts in control theory and computer science. --- paper_title: Bisimilar control affine systems paper_content: The notion of bisimulation plays a very important role in theoretical computer science where it provides several notions of equivalence between models of computation. These equivalences are in turn used to simplify analysis and synthesis for these models. In system theory, a similar notion is also of interest in order to develop modular analysis and design tools for purely continuous or hybrid control systems. We introduce two notions of bisimulation for nonlinear systems. We present a differential-algebraic characterization of these notions and show that bisimilar systems of different dimensions are obtained by factoring out certain invariant distributions. Furthermore, we also show that all bisimilar systems of different dimension are of this form. --- paper_title: Adaptive Gridding for Abstraction and Verification of Stochastic Hybrid Systems paper_content: This work is concerned with the generation of finite abstractions of general Stochastic Hybrid Systems, to be employed in the formal verification of probabilistic properties by means of model checkers. The contribution employs an abstraction procedure based on a partitioning of the state space, and puts forward a novel adaptive gridding algorithm that is expected to conform to the underlying dynamics of the model and thus at least to mitigate the curse of dimensionality related to the partitioning procedure. With focus on the study of probabilistic safety over a finite horizon, the proposed adaptive algorithm is first benchmarked against a uniform gridding approach from the literature, and finally tested on a known applicative case study. --- paper_title: On Choosing and Bounding Probability Metrics paper_content: When studying convergence of measures, an important issue is the choice of probability metric. In this review, we provide a summary and some new results concerning bounds among ten important probability metrics/distances that are used by statisticians and probabilists. We focus on these metrics because they are either well-known, commonly used, or admit practical bounding techniques. We summarize these relationships in a handy reference diagram, and also give examples to show how rates of convergence can depend on the metric chosen. --- paper_title: On infinite-horizon probabilistic properties and stochastic bisimulation functions paper_content: This work investigates infinite-horizon properties over discrete-time stochastic models with continuous state spaces. The focus is on understanding how the structural features of a model (e.g., the presence of absorbing sets) affect the values of these properties and relate to their uniqueness. Furthermore, we argue that the investigation of these features can lead to approximation bounds for the value of such properties, as well as to improvements on their computation. The article employs the presented results to find a stochastic bisimulation function of two processes. --- paper_title: Approximate abstractions of stochastic systems: A randomized method paper_content: This work introduces a randomized method for the design of an approximate abstraction of a stochastic system and the assessment of its quality. The proposed approach relies on the formulation of the problem as a semi-infinite chance-constrained optimization program and on its solution via randomization. The method has quite general applicability, since it only requires to be able to run multiple executions of the candidate abstract model and of the original system and to compute their distance. Two variants of the notion of distance are considered in view of a possible use of the approximate abstraction for probabilistic safety verification. The approach is tested on a numerical example. --- paper_title: Approximating labeled Markov processes paper_content: We study approximate reasoning about continuous-state labeled Markov processes. We show how to approximate a labeled Markov process by a family of finite-state labeled Markov chains. We show that the collection of labeled Markov processes carries a Polish space structure with a countable basis given by finite state Markov chains with rational probabilities. The primary technical tools that we develop to reach these results are: a finite-model theorem for the modal logic used to characterize bisimulation; and a categorical equivalence between the category of Markov processes (with simulation morphisms) with the /spl omega/-continuous dcpo Proc, defined as the solution of the recursive domain equation Proc=/spl Pi//sub Labels/ P/sub Prob/(Proc). The correspondence between labeled Markov processes and Proc yields a logic complete for reasoning about simulation for continuous-state processes. --- paper_title: A theory of timed automata paper_content: Alur, R. and D.L. Dill, A theory of timed automata, Theoretical Computer Science 126 (1994) 183-235. We propose timed (j&e) automata to model the behavior of real-time systems over time. Our definition provides a simple, and yet powerful, way to annotate state-transition graphs with timing constraints using finitely many real-valued clocks. A timed automaton accepts timed words-infinite sequences in which a real-valued time of occurrence is associated with each symbol. We study timed automata from the perspective of formal language theory: we consider closure properties, decision problems, and subclasses. We consider both nondeterministic and deterministic transition structures, and both Biichi and Muller acceptance conditions. We show that nondeterministic timed automata are closed under union and intersection, but not under complementation, whereas deterministic timed Muller automata are closed under all Boolean operations. The main construction of the paper is an (PSPACE) algorithm for checking the emptiness of the language of a (nondeterministic) timed automaton. We also prove that the universality problem and the language inclusion problem are solvable only for the deterministic automata: both problems are undecidable (II i-hard) in the nondeterministic case and PSPACE-complete in the deterministic case. Finally, we discuss the application of this theory to automatic verification of real-time requirements of finite-state systems. --- paper_title: Uncertain convex programs: Randomized solutions and confidence levels paper_content: Many engineering problems can be cast as optimization problems subject to convex constraints that are parameterized by an uncertainty or ‘instance’ parameter. Two main approaches are generally available to tackle constrained optimization problems in presence of uncertainty: robust optimization and chance-constrained optimization. Robust optimization is a deterministic paradigm where one seeks a solution which simultaneously satisfies all possible constraint instances. In chance-constrained optimization a probability distribution is instead assumed on the uncertain parameters, and the constraints are enforced up to a pre-specified level of probability. Unfortunately however, both approaches lead to computationally intractable problem formulations. --- paper_title: Approximate Model Checking of Stochastic Hybrid Systems paper_content: A method for approximate model checking of stochastic hybrid systems with provable approximation guarantees is proposed. We focus on the probabilistic invariance problem for discrete time stochastic hybrid systems and propose a two-step scheme. The stochastic hybrid system is first approximated by a finite state Markov chain. The approximating chain is then model checked for probabilistic invariance. Under certain regularity conditions on the transition and reset kernels governing the dynamics of the stochastic hybrid system, the invariance probability computed using the approximating Markov chain is shown to converge to the invariance probability of the original stochastic hybrid system, as the grid used in the approximation gets finer. A bound on the convergence rate is also provided. The performance of the two-step approximate model checking procedure is assessed on a case study of a multi-room heating system. --- paper_title: Probabilistic reachability and safety for controlled discrete time stochastic hybrid systems paper_content: In this work, probabilistic reachability over a finite horizon is investigated for a class of discrete time stochastic hybrid systems with control inputs. A suitable embedding of the reachability problem in a stochastic control framework reveals that it is amenable to two complementary interpretations, leading to dual algorithms for reachability computations. In particular, the set of initial conditions providing a certain probabilistic guarantee that the system will keep evolving within a desired 'safe' region of the state space is characterized in terms of a value function, and 'maximally safe' Markov policies are determined via dynamic programming. These results are of interest not only for safety analysis and design, but also for solving those regulation and stabilization problems that can be reinterpreted as safety problems. The temperature regulation problem presented in the paper as a case study is one such case. --- paper_title: The Scenario Approach for Systems and Control Design paper_content: The ‘scenario approach’ is an innovative technology that has been introduced to solve convex optimization problems with an infinite number of constraints, a class of problems which often occurs when dealing with uncertainty. This technology relies on random sampling of constraints, and provides a powerful means for solving a variety of design problems in systems and control. The objective of this paper is to illustrate the scenario approach at a tutorial level, focusing mainly on algorithmic aspects. Its versatility and virtues will be pointed out through a number of examples in model reduction, robust and optimal control. --- paper_title: Approximating stochastic biochemical processes with Wasserstein pseudometrics. paper_content: Modelling stochastic processes inside the cell is difficult due to the size and complexity of the processes being investigated. As a result, new approaches are needed to address the problems of model reduction, parameter estimation, model comparison and model invalidation. Here, the authors propose addressing these problems by using Wasserstein pseudometrics to quantify the differences between processes. The method the authors propose is applicable to any bounded continuous-time stochastic process and pseudometrics between processes are defined only in terms of the available outputs. Algorithms for approximating Wasserstein pseudometrics are developed from experimental or simulation data and demonstrate how to optimise parameter values to minimise the pseudometrics. The approach is illustrated with studies of a stochastic toggle switch and of stochastic gene expression in E. coli. --- paper_title: On Choosing and Bounding Probability Metrics paper_content: When studying convergence of measures, an important issue is the choice of probability metric. In this review, we provide a summary and some new results concerning bounds among ten important probability metrics/distances that are used by statisticians and probabilists. We focus on these metrics because they are either well-known, commonly used, or admit practical bounding techniques. We summarize these relationships in a handy reference diagram, and also give examples to show how rates of convergence can depend on the metric chosen. --- paper_title: Labeled Markov processes: stronger and faster approximations paper_content: This paper proposes a measure-theoretic reconstruction of the approximation schemes developed for labeled Markov processes: approximants are seen as quotients with respect to sets of temporal properties expressed in a simple logic. This gives the possibility of customizing approximants with respect to properties of interest and is thus an important step towards using automated techniques intended for finite state systems, e.g. model checking, for continuous state systems. The measure-theoretic apparatus meshes well with an enriched logic, extended with a greatest fix-point, and gives means to define approximants which retain cyclic properties of their target. --- paper_title: Approximating labeled Markov processes paper_content: We study approximate reasoning about continuous-state labeled Markov processes. We show how to approximate a labeled Markov process by a family of finite-state labeled Markov chains. We show that the collection of labeled Markov processes carries a Polish space structure with a countable basis given by finite state Markov chains with rational probabilities. The primary technical tools that we develop to reach these results are: a finite-model theorem for the modal logic used to characterize bisimulation; and a categorical equivalence between the category of Markov processes (with simulation morphisms) with the /spl omega/-continuous dcpo Proc, defined as the solution of the recursive domain equation Proc=/spl Pi//sub Labels/ P/sub Prob/(Proc). The correspondence between labeled Markov processes and Proc yields a logic complete for reasoning about simulation for continuous-state processes. ---	Title: Approximation Metrics Based on Probabilistic Bisimulations for General State-Space Markov Processes: A Survey Section 1: Motivations and Objective Description 1: Introduce the motivations for studying approximation metrics based on probabilistic bisimulations, and outline the objectives and structure of the survey. Section 2: Review of Literature Background Description 2: Provide a comprehensive coverage of existing work on simulations, bisimulations, and approximate versions thereof, specifically focusing on probabilistic models. Section 3: Markov Processes over General State Spaces Description 3: Introduce and discuss the models under study, particularly probabilistic processes defined over continuous state spaces. Section 4: Exact and Approximate Probabilistic Bisimulations: Relations, Logics, and Categories Description 4: Present the concept of exact and approximate (strong) probabilistic bisimulation, and provide related characterizations based on algebra, logic, and category theory. Section 5: Approximate Bisimulations via Probabilistic Bisimulation Functions Description 5: Define and characterize the notion of probabilistic bisimulation function, leading to the introduction of approximate metrics between processes' trajectories. Section 6: Characterization of Stochastic Bisimulation Function as solution of a Probabilistic Reachability Problem Description 6: Look at semantic-based computations of distance metrics between comparable probabilistic processes by solving probabilistic reachability problems. Section 7: Discussion and Conclusions Description 7: Discuss the surveyed techniques, highlight their differences, and look forward at future research directions and practical applications.