text:
AEC From the Ground Up-IFCs in Action31 Jan, 2006 By: AIA ,H. Edward Goldberg
The 3D object exchange format of choice for BIM buildings.
At The Aec/St Convention in Washington, D.C., in December, I noted quite a bit of interest in BIM (building information modeling) and the IFC (Industry Foundation Class) format. BIM software is what the AEC industry is turning to for the creation of building designs, and it appears that the IFC format will be the open downstream transfer format for that information. NIBS (National Institute of Building Standards; www.nibs.org), the group creating the new National BIM Standard, has decided that IFC is the best method for information transfer, and the GSA (General Services Administration) has mandated that, starting in July, the delivery of IFC-transferable BIM data will be required for the preliminary design phase of all of its new fiscal year 2006 projects.
What are IFCs?
The IFC system is a data representation standard and file format used to define architectural and construction-related CAD graphic data as 3D real-world objects. Its main purpose is to provide architects and engineers with the ability to exchange data between CAD tools, cost estimation systems and other construction-related applications. IFC provides a set of definitions for all object element types encountered in the building industry and a text-based structure for storing those definitions in a data file. IFC uses a plain text file, while CAD developers store data in product-specific binary file formats that best suit their own systems. To standardize 3D object data, developers provide Save As IFC and Import IFC commands, which map the IFC object definitions to their CAD system's 3D representations of these objects.
Modern BIM systems are able to create rich internal representations of building components, and the IFC format adds a common language for transferring that information between different BIM applications while maintaining its meaning. This reduces the need to remodel the same building in each different application.
This nonproprietary format has been developed by the IAI (International Alliance for Interoperability; www.iai-na.org/). This global consortium of commercial companies and research organizations was founded in 1995. Its North American chapter is now part of NIBS. According to the IAI, the IFC model is intended to support interoperability across individual, discipline-specific applications used to design, construct and operate buildings by capturing information about all aspects of a building throughout its lifecycle. It was specifically developed as a means to exchange data between model-based applications in the AEC and FM industries.
Spreading support
At this writing, Autodesk's Architectural Desktop and Revit Building, Bentley Architecture, Graphisoft's ArchiCAD and Nemetschek's Allplan have implemented IFC capability. VectorWorks IFC implementation will be available later this year. Now that these BIM applications support IFC export, other software vendors are beginning to develop solutions that use BIM data created during the building design process.
Below is a sampling of applications that can use and manipulate data created in BIM software programs. All transfer their 3D information using the IFC file format schema.
Roamer JS is the hub of the NavisWorks JetStream design review solution. It delivers interactive visualization and smooth real-time walkthrough and review of even the largest and most complex 3D models. It's compatible with most popular 3D design and laser scan file formats, and with the addition of IFC import, can open models quickly for walkthrough and review of geometry and object information. The Clash Detective JS plug-in eliminates manual checking of object clashes. It finds and manages both hard and clearance clashes. Geometry created in different 3D design applications can be reviewed together and automatically checked against each other. Clash test results are stored and merged to create a complete record of all interferences found. Users can set up their own clash test rules and produce detailed reports as HTML documents.
Solibri Model Checker v3
Think of Solibri Model Checker as a spell checker for virtual models (figure 1). The program analyzes building models for integrity, quality and physical security. It checks for potential flaws and weaknesses in the design, highlights clashing components and determines whether the model complies with building codes and the organization's own best practices. It also helps users extract information from the building model for use in downstream applications such as quantity and cost calculation. The latest version of Solibri Model Checker highlights the source of problems by making the rest of the building invisible and illustrates problematic components within the footprint of the wall plan to make them easy to locate. Because this software is user customizable, it can check for code requirements such as egress distance and door size per occupant load in a given space. According to the developer, the GSA will use this software to check the correctness of the BIM data it requires from its architectural consultants.
Figure 1. Solibri Model Checker validates a BIM model for correctness and checks for redundancies.
YIT COVE and Tarmo, Graphisoft Constructor and Estimator
YIT, a Nordic construction and services company, developed two IFC-based programs to work with Graphisoft models. COVE is a tool for model-based information management of the construction process. It uses IFCs to import information from various design and other programs into a single 3D construction model. TARMO cost estimation software is able to integrate the construction schedule to create a 4D model. YIT has used COVE in production since 1999 on more than 200 projects. In 2004 YIT sold rights to develop and market the product to Graphisoft. At the same time, the companies agreed on a strategic partnership for further development of product model technology into commercial software. The commercial tool based on COVE is called Graphisoft Constructor 2005, and the one based on TARMO is Graphisoft Estimator 2005 (figure 2).
Figure 2. Graphisoft s Constructor 2005 and Estimator 2005 use IFC import to reuse building information in a construction model.
Data Design System Building Services Partner
Available primarily in Europe, Data Design System's Building Services Partner is designed to facilitate model-based collaboration with other disciplines using IFC files or an advanced IFC model server environment. The company also developed an IFC file viewer that opens and displays IFC models created by applications such as DDS Building Services Partner. This tool is available for download free at the company Web site.
DDS Partner is an integrated system for planning, production and control of HVAC, piping and electrical system documentation. It's a proficient planning tool not only for the professional consulting engineer, but also installation contractors and ventilation specialists. Facility managers can also gain productivity using the system. DDS HVAC Partner delivers integrated calculations for building heat loss, duct sizing and pressure loss. Its tools handle pipe network sizing, under-floor heating design, and quantity extraction. Electrical Partner's lighting calculations help users develop effective lighting schemes for projects. Those who need a more advanced lighting solution can use Dialux or Relux software directly with Electrical Partner. This product's built-in CAD engine has DXF/DWG support as well as IFC integration.
ideCAD Structural 5
Developed in Turkey for structural designers of tall buildings, ideCAD Structural 5 is integrated analysis, design and detailing software for reinforced concrete constructions. It covers all relevant phases, from dynamic analyses to design of reinforced concrete cross-sections. Reinforcement details are automatically generated. A joint platform on the Web allows collaboration between structural engineers and architects. Users design and plan using real components such as walls, windows, columns, beams and foundations. A 3D user interface displays both 3D building models and their related analysis results for evaluation. This integrated visualization ability supports not only creation of renderings and animations, but also smooth and simple project planning. Static calculation and reinforced-concrete measurements are carried out on the basis of the 3D calculation model. Compatibility with IFC, DXF and DWG enables exchange of data with other CAD programs (figure 3).
Figure 3. IdeCAD is a stand-alone CAD program that uses IFC support to exchange data with other CAD programs.
Just Starting
Today downstream IFC-based applications are still in their infancy. The following site lists software certified by the IAI: www.bauwesen.fh-muenchen.de/iai/ImplementationOverview.htm. The reality as I see it, and as I mentioned in my November 2005 column (http://aec.cadalyst.com/1105aec/), is that the main benefit of BIM software currently comes from increased productivity in creating construction documents. Although the downstream segment of the industry is just getting started, I anticipate a plethora of software that will eventually integrate, collate and extrapolate BIM data in ways that are not even imagined today. These new solutions—receiving and transferring their data through future versions of the IFC format—will surely make the AEC industry more productive and offer new profit streams for professionals using them.
H. Edward Goldberg, AIA, NCARB, is a practicing licensed architect and AEC industry analyst. Ed's full-length book, Autodesk Architectural Desktop 2006: A Comprehensive Tutorial (Prentice Hall; www.prenhall.com) is now available. Contact Ed for online Architectural Desktop training delivered directly to the desktop. Visit www.hegra.org for more information, or e-mail email@example.com.
About the Author: AIA
About the Author: H. Edward Goldberg
For Mold Designers! Cadalyst has an area of our site focused on technologies and resources specific to the mold design professional. Sponsored by Siemens NX. Visit the Equipped Mold Designer here!
For Architects! Cadalyst has an area of our site focused on technologies and resources specific to the building design professional. Sponsored by HP. Visit the Equipped Architect here!


text:
Full Description
Please fill out the 's full description. In this page you could:
- Describe the purpose of the and the learning goals for the tasks within.
- Describe your role in this . What made you interested in this topic? What do you hope to achieve by organizing this ? Are you an expert, enthusiastic or a novice?
- Include any prerequisite knowledge or skills needed to participate in the , the intended start date, estimated pace, commitment, amount of work, and the length of time the participants can expect to work together (a few days, a few weeks, or forever).
- Provided any other information that could be useful for people interested in joining the . In what ways can participants expect to contribute to the creation of tasks and assessing each others\' contributions? What will the final task comprise?

subset: commoncrawl


text:
Ingredients for 6 servings:
View the complete recipe
Escoffier? I thought that Antonin Carême was the world's first celebrity chefs.
One could argue that fact, but since Escoffier stole all Careme's idea and became even more famous, I do with him! ;) I'd consider Careme the first Master Chef.
This looks delicious! And I'm eager to try it, but I'm not sure where to find vanilla bean...can I use vanilla extract instead?
Hmmm, I wonder if coconut or lemon ice cream would work instead of vanilla.
I'm no flavour matching expert but I like the sound of it!
Two words: food porn.
Beautiful dish, beautiful presentation.
Making this just to have another excuse to use the freakishly small wooden spoon that you and Michelle sent with the first sales of SFQ sauce!
(ps: SFQ = best sauce evah!)
Oh, Yum! I could have a few helpings of those.
Peachalious! Can't wait for some of your desserts when you come. Hurry, hurry.
A freakishly small spoon AND a dessert food wish? You are awesomesauce in chef form.
Looks amazing, one question, I live in Costa Rica and raspberries are really difficult to come by, do you think the recipe could work woth strawberries?
Thanks, it looks amazing, one question, raspberries are really hard to get in Costa Rica, do you think it would work with strawberries?
Can I use Sherry vinegar or White Wine vinegar instead of Balsamic? Or better to leave it out altogether?
two words: Delicious.
Chef John, what do you think about adding some almond extract to the poaching liquid along with the vanilla bean?
Could be good, give it a try!
Hello Chef John from London England,
Can i make these with nectarines? Aka shaved peaces with no hairy skin?
My food would be taramasalata with the smoked cods roe. Thanks!
Jenny D


text:
The Town of Vail was overwhelmed last week with the arrival of The Rocky Mountain Coal Mining Institute (www.rmcmi.org). Hundreds of members of this organization chose Vail for their 100th anniversary conference. They arrived from all over the United States and Canada to participate in training and educational seminars.
Of course the Antlers, a hotel and conference center that is always afraid of missing out on the fun, volunteered to host "emergency disaster training" for 2 days. This involved real life, re-enactments of rescue operations involving different scenarios around our property and common areas.
The pictures really don't illustrate how life-like these situations were. Some guests actually thought there were live rescues occurring as they passed through the staging areas. What made it believable were the "victims" that were not afraid to scream as though they were in pain and the rescue teams shouting out instructions as they assured the "victims" that help was on its way.
As the second day of mock rescues were winding down, I was approached by a guest who had these comments. "My kids really were fascinated by all of this and I had no idea what went on behind the scenes. These people really are professionals." His young son looked up at me and said "Mister, do you have a coal mine here?"
"No we don't, but there are some not too far away in the mountains" was my reply.
He looked back at his dad and said " too bad because I sure would feel safe if something happened in your mine."


text:
BOJ's new price forecasts Friday to be credibility test
The Bank of Japan is set on Friday to project that it will meet its 2 percent inflation target in two years, a forecast analysts say may be too optimistic and could put the bank's credibility on the line.
The central bank, charged with overturning years of dogged deflation, is not expected to come up with any fresh policy initiatives after new Governor Haruhiko Kuroda stunned markets on April 4 by promising to inject about $1.4 trillion into the economy to hit the inflation target in roughly two years.
Instead, the focus will be on the BOJ's economic forecasts to be released in its twice-yearly outlook report and how they compare with private-sector economists, many of whom argue that 2 percent inflation in two years is unrealistic.
"These new BOJ figures will be more a vow of determination rather than credible forecasts," said Yoshiki Shinke, chief economist at Dai-ichi Life Research Institute in Tokyo.
"It would take a drastic change of corporate behavior for inflation to hit 2 percent in Japan. Companies would really have to believe that prices and sales will start to rise, enough to make them lift wages and spending. That will probably take much longer than two years," he said.
Kuroda has vowed to do what ever it takes to achieve the price target in two years, putting the central bank's reputation on the line to restore an inflation level that has rarely been hit since the early 1990s.
The forecasts in the report are based on the median expectations of the BOJ's nine board members, including Kuroda.
The BOJ is likely to raise its forecast for the fiscal year to March 2015 to show the core consumer price index (CPI) rising about 1.5 percent, sources familiar with its thinking said. That is higher than its current forecast for a 0.9 percent increase and excludes the impact of an expected sales tax increase in 2014.
It is also likely to add an extra year of projections to show that by the fiscal year ending March 2016, core CPI, which excludes fresh food prices, will hit the central bank's 2 percent inflation target, the sources said.
Economist Shinke is among the majority of private-sector economists who expect core CPI to rise only around 0.5 percent in the year to March 2015, excluding the effect of the expected sales tax hike, and around 1 percent in fiscal 2015/16.
Most analysts polled by Reuters after the BOJ's policy meeting on April 4 said the central bank will not be able to achieve its inflation target within two years.
(Editing by Neil Fullick)


text:
In 2013, city officials in Melbourne, Australia, assigned ID numbers and email addresses to each of the city's more than 70,000 trees. Designers of the city's Urban Forest Strategy program intended for residents to use the addresses to report issues like disease or dangerous branches. However, residents did more than that: they began writing thousands of messages directly to the trees.
They have written heartfelt notes to individual trees to express their love and admiration, to share their memories and to express their gratitude for protection from the sun and carbon dioxide. Sometimes they ask the trees for their views on current events, or write simply to say hello or apologize for their dog's choice of a urinal.
Occasionally, officials respond to emails on behalf of the trees. One day soon, however, Melbourne's trees – fitted with an array of sensors and connected to low-cost wireless communications – could truly speak for themselves, sharing a wealth of data: temperature, humidity, noise levels, carbon dioxide concentrations, glucose levels and motion readings. Such data can be used to preserve and protect the health of urban forests, which play a vital role in improving air and water quality, reducing stormwater runoff, lowering urban ground temperatures, reducing energy use and mitigating greenhouse gas emissions.
Such is the power of the Internet of Things (IoT), a wave of innovation in which billions of everyday objects – not just trees, but trash cans, lampposts, parking spots, traffic signals, roadways, hospital equipment, appliances, manufacturing lines, crops in the field and much, much more – are being equipped with sensors, processors and communication devices to share valuable data across the Internet and, in some cases, to act on it.
At its most basic level, the IoT offers an affordable means to understand and manage real-world things from a distance while giving some things – a thermostat, for example – the data and capabilities they need to manage themselves. As the people of Melbourne have shown, however, once the things in the IoT are connected and given a voice, they become more than just "things." They become part of a living experience shaped by interactions among people, places and objects, among product, nature and life. They become contributors to what beckons just beyond the IoT: the Internet of Experiences.
While participants in the IoT tend to focus on "things" – the individual smart devices connected to a network – the Internet of Experiences aims higher, concentrating on what becomes possible when smart devices piggyback off one another's capabilities to create experiences: innovative services that simplify and enhance daily life in ways never possible before. Enabling a tree, for example, to report, "I'm being attacked by caterpillars," which prompts a computer to dispatch a drone equipped to treat the situation. Or a highway to report, "I've reached my carrying capacity," which prompts the rerouting of automobiles onto alternate routes.
Such capabilities, however, only become possible when the maker of one device imagines, anticipates and virtually simulates how it can leverage the capabilities of devices made by others to improve the user's experience. The trick, experience experts say, is to put the user at the center of the solution's reason for being, which is the essence of the Experience Economy.
"We have moved from a purely transaction-based, commodities economy to one based on goods, then services, and now experiences – meaningful experiences in a purpose-based economy," said Albert Boswijk, a co-author of Economy of Experiences and founder and managing director of the European Centre for the Experience and Transformation Economy. "The digitization of products and services is happening so fast that it's difficult for us as human beings to make sense of it all. But, rest assured, this digital transformation will change the impact and depth of personal experience."
Against this backdrop, Boswijk said, the IoT is a means to an end. "The Internet of Things enables the digitalization of experiences, and everything that can be digitalized can be personalized. This is key, as every experience is by definition personal."
While giants such as Amazon and Netflix have benefited from the personalization that digitization enables – recommendations of other books or movies a customer might like based on past selections, for example – the sensor-laden world of the IoT greatly expands the behavioral and contextual data available to shape and deliver personalized experiences. By enabling their devices to share data with other devices on the network (with the user's permission, of course), and to evolve as the user's needs and wants change, organizations that aspire to the Internet of Experiences greatly enrich the value they can deliver.
Consider, for example, personal health and well-being devices like the Smart Body Analyzer from Withings (Issy-les-Moulineaux, France). It can detect a user's weight, fat mass, body mass index and heart rate, capture room temperature and display air quality, including carbon dioxide levels. Significantly, it can share this data not only with the user and their Withings smartphone app, but with other apps that the user may turn to for weight loss management, fitness tracking, food logging or fertility and pregnancy tracking. The result is the ability to deliver individualized monitoring, goals, tips and coaching to help users reach their personal objectives.
Put those capabilities together with a smart refrigerator, however, and the weight-loss management app could remind the late-night snacker (with a message displayed on the refrigerator door when he grasps the handle) that he has reached his calorie limit for the day. Pair both with a smart exercise bike and he could receive a text message proposing an apple for 15 minutes of pedaling.
Noted experience author and lecturer Joe Pine, who coined the term "the Experience Economy" with his co-author, James Gilmore, sees in this personalization the potential for the Internet of Experiences to bring consumers closer to a Market of One.
"The key aspect of your customer, the one who pays you and whom you've placed at the center of everything you do, is the word 'one,'" Pine said. "It's the individual customer you need to engage. It's not a market. It's not a segment. It's not a niche. It's an individual, living breathing customer."
In an economy of endless choice, he adds, "it's the individual relationship you have with that individual customer that is the only lasting competitive advantage you're going to have."
Companies that design for the Internet of Experiences also think not only about what their device can deliver today, but how it can evolve. In the Internet of Experiences, conventional physical products are mere "delivery vehicles," or conduits, for ever-evolving experiences. This transformation is already evident as, increasingly, new or upgraded products arrive in consumers' homes virtually, in the form of ongoing software updates to devices they already own.
When DJI, a drone-maker headquartered in Shenzhen, China, decided to make its drones easier and safer to fly, hoping to attract more novice users, it didn't design and release a new product; it issued a software update that added new flight modes to existing drones. It even transformed the built-in 1920 x 1080 pixel camera on one model into a 2704 x 1520 pixel camera via a software update alone.
Withings took a software update path, too, transforming its Pulse pedometer into a new product, Pulse Ox, which improves on the original product by capturing blood oxygen levels, providing automatic wake-up detection, and working not only in English but in five other languages as well. Likewise, home-automation company Nest (Palo Alto, California) used software-only updates in its third-generation Nest Learning thermostat to give customers the option to set the device to display either temperature or an analog or digital clock. Thanks to software integration, these updated Nest thermostats can now send alerts or shut off the heating system if a Nest Protect smoke alarm detects smoke or carbon monoxide.
Arguably, however, no company has mastered the art of product and experience transformation through software updates more than Tesla Motors. When Tesla (Palo Alto, California) decided to add a "crawl" feature, allowing drivers to ease into slow cruise control in heavy traffic, it issued an over-the-air software release that added the feature at once to the entire fleet of existing Tesla cars.
Previous enhancements delivered via software update include automatic emergency braking, forward- and side-collision warnings and avoidance, traffic-based navigation, commute advice, range assurance to reduce the risk of being out of range of a charging device, and a remote-start capability via smartphone.
With its next major software update, Tesla plans to add "Autosteer," essentially transforming the Model S sedan from a smart car into a self-driving car, including a valet "Autopark" feature that lets customers summon their cars from their parking spots via smartphone.
As the company states on its blog, "Model S actually improves while you sleep. When you wake up, added functionality, enhanced performance and improved user experience make you feel like you are driving a new car. We want to improve cars in ways most people didn't imagine possible."
Tesla's approach demonstrates that, done well, the Internet of Experiences should make once-complex offerings and activities technologically simple, easy and convenient. Behind the scenes, however, blending products, services, software, content, technology, cloud and data into an experience within the multidirectional hyper-connected world of the Internet of Experiences remains a complex undertaking.
Consider, for example, Nest's smart thermostat. A Nest "learning" thermostat creates an experience by sensing and then automatically adapting to a homeowner's daily rhythms and personal preferences to make their home safe and comfortable – no programming required. Under the hood, the thermostat is a complex system of sensors, software, processors, circuit boards, communication devices, energy sources, frames, wiring and display monitors. Each of these elements is produced by engineers working in different disciplines, yet they all need to work in sync with one another and with quality technicians, sales and marketing professionals to produce the behavior – the experience – that will delight the customer.
The average 2014 revenue gain reported by the top 8% of IoT market leaders, with nearly a 16% average for all other companies investing in IoT, according to Tata Consultancy Services.
The device itself is complex, but it doesn't operate in a vacuum. To deliver maximum value, such thermostats are being integrated into larger smart home control systems – which may or may not be produced by Nest. Therefore, it must operate not only as a stand-alone system made up of complex subsystems but be capable of operating within a much larger "system of systems," from a smart home system to a smart local electrical grid system, to a smart regional, national or continental electrical grid system.
"An important fact to remember about the IoT is that things talk to other things," Pine said. "One day, I'll turn off my alarm clock when I wake up and it'll signal the house to warm up downstairs and tell my coffee maker to get my coffee on, and maybe my coffee pot will tell my car to heat up because it's a cold day here in Minnesota. Customers will be able to design an entire environment for their ideal living experience. Companies need to think about how their experience integrates into such larger, holistic experiences."
Strategies for addressing such dependencies and complexities are the domain of systems engineering, a collaborative, interdisciplinary approach to designing, realizing and managing complex systems that interact to produce behavior no individual element of the system can (see "Mind-Boggling Complexity"). "The Internet of Things is all about the ubiquity of being connected," said John Blyler, an adjunct assistant professor of systems engineering at Portland State University, editorial director of "IOT Embedded Systems," and co-author of the forthcoming book Systems Engineering Management with Benjamin Blanchard, emeritus professor of Industrial and Systems Engineering at Virginia Polytechnic Institute and State University. "Connectivity is going to cross disciplines. Having everything connected means a lot of our silos are going to have to come down. Proper systems engineering dictates that diverse teams are going to have to come together to make a company's IoT strategy work."
The challenge becomes even bigger when these complex systems become part of the largest system of systems ever created: an ultra-large-scale system (ULSS) known as the IoT, which will incorporate devices from hundreds of thousands of makers, all with differing – even conflicting – objectives and approaches.
"Current engineering practice is ahead of the science," observes Hillary Sillitto, a fellow of the International Council on Systems Engineering (INCOSE) and author of Architecting Systems: Concepts, Principles and Practice. "We are building systems we do not know how to characterize or analyze, and whose behavior we cannot fully predict."
As organizations work through the complex business of mastering and making complexity disappear – a critical element of a positive experience – what is most important, Pine believes, is to "keep the customer at the center of their thinking, and to remember they are not producing things for an Internet of Things, but creating living, evolving experiences within an Internet of Experiences."
Back in Melbourne, Green Leaf Elm, Tree ID 1022165 and citizen "F" are building a relationship that honors this distinction. Once upon a time, "F" might have simply walked by Tree 1022165. But now, Tree 1022165 and "F" are connected. As "F" writes, "we don't have a lot in common, you being a tree and such. But I'm glad we're in this together."
For more information:


text:
The US Supreme Court Thinks Racism Is Dead. What Planet Do They Live On?
In 1999 apartheid's last leader, FW de Klerk, explained to me his motivation for writing an autobiography. "I wanted people to look at our history in its proper time frame. The same mistakes that we made were still being made in the United States and the ex-colonies. Then we carried them on for around 20 years longer. It was a time when we thought it would go away."
De Klerk talked a lot of nonsense that morning, comparing South African apartheid to the EU and insisting it was him, not Nelson Mandela, who ushered in non-racial democracy.
But on the subject of "history's time frame" he was on point. For most of the last century, apartheid was not the exception of one nation but the rule for much of the world that described itself as "civilised". On 1 February 1960 17-year-old Franklin McCain and three black friends went to the whites-only counter at Woolworths in Greensboro, North Carolina, and took a seat. "The day I sat at that counter I had the most tremendous feeling of elation and celebration," he says.
Two days later, the British prime minister Harold Macmillan addressed the South African parliament in Cape Town with an ominous warning. "The wind of change is blowing through this continent," he said. "Whether we like it or not, this growth of national consciousness is a political fact." They didn't like it. But it happened anyway.
In the three years between Macmillan's speech and King's "I have a dream speech", Togo, Mali, Senegal, Zaire, Somalia, Benin, Niger, Burkina Faso, Ivory Coast, Chad, Central African Republic, Democratic Republic of Congo, Gabon, Nigeria, Mauritania, Sierra Leone, Tanganyika and Jamaica all became independent.
Non-racial democracy is a relatively new idea to the west; racism is not. The notion that the people should govern may have been around since ancient Greece, but throughout that time the issue of who counts as people has been continually contested and episodically reassessed.
Last week the US supreme court reassessed the nation's history of voter exclusion and decided the contest was over. The court gutted a key element of the 1965 voting rights act, which demanded that areas with a history of racial discrimination at the polls get prior authorisation before changing their election or voting laws. "There is an old disease, and that disease is cured," argued Bert Rein, when opposing the act before the court earlier this year. "That problem is solved." Justice Roberts agreed, arguing that the provisions were based on "40-year-old" facts.
It's difficult to imagine a less propitious week for that argument. No sooner had the court pronounced racism dead than its skeleton emerged from cupboards galore and started doing the can-can on primetime.
The day before the ruling, the trial of George Zimmerman opened in Florida. Zimmerman, who is Latino, shot dead an unarmed black teenager, Trayvon Martin, claiming he looked "suspicious". He was neither charged nor arrested for several weeks, and then only after nationwide protests. Zimmerman, who had never met Martin, referred to the boy as a "punk" and complained to the police dispatcher: "They always get away." Zimmerman weighs 250lbs and had a 9mm handgun; Martin, 17, weighed 140lbs and had a packet of Skittles and a can of iced tea. Zimmerman claims he was acting in self-defence. "He shot him for the worst of all reasons," said state prosecutor John Guy in his opening statement. "Because he wanted to.''
The day after the ruling, celebrity chef Paula Deen went on the Today show and wept over accusations of racial and sexual harassment that are destroying her empire. In a lawsuit a former employee accuses Deen, among other things, of demanding a "true southern plantation-style wedding" for her brother Earl "Bubba" Heirs in 2007. "Well, what I would really like is a bunch of little niggers to wear long-sleeve white shirts, black shorts and black bow ties," she allegedly said. "You know in the Shirley Temple days, they used to tap dance around."
Since neither Deen nor Zimmerman have been convicted of anything, it should be emphasised that for now they are both innocent. Nonetheless, the allegations and the debates they have provoked provide salient illustrations of the supreme court's folly. I will concentrate on just two.
First, facts that are 40 years old are still facts, and 40 years is not a long period of time when dealing with a centuries-old problem. Apartheid, whether in the US or elsewhere, is a recent phenomenon. Its direct beneficiaries and victims are still alive. Roughly one in five Americans were born after the voting rights act was passed. Deen, who was raised in the deep south, was married that year.
On the rare occasions when my six-year-old son asks questions about the civil rights era, I can point him to his grandparents, who lived through it into adulthood. Nor are its defenders part of some bygone age. Even as the lofty eulogies are prepared for an ailing Nelson Mandela we should not forget that former US vice-president Dick Cheney branded him the leader of a terrorist group in 1986 and the year before his release David Cameron went on a sanctions-busting trip paid for by pro-apartheid lobbyists.
Second, segregation has a legacy – not least because it was so recent. Quashing racist laws does not eliminate racism, only its explicit and codified enforcement. The past has consequences that directly impact the present. History does not just stop because a memory is inconvenient.
The gap between black and white unemployment in the US is roughly the same as it was in 1963; the gap in median income is the same as it was in 1975. Zimmerman did not invent his impressions of Martin out of thin air. They emerge from centuries of demonisation and dehumanisation in which black men, by their very existence, are understood as a threat.
In 2005 Gordon Brown trumpeted the values of "tolerance, liberty and civic duty" exported by the British empire; last month the government settled with thousands of Kenyans tortured under colonial rule.
The speed at which some people seek to flee the past seems to have a direct relationship to their desire to distort it and to live in denial about the present. Power has many parents, but the brutality required to acquire it is an orphan.


text:
Services on Demand
Related links
- Cited by Google
- Similars in Google
Journal of the South African Institution of Civil Engineering
On-line version ISSN 2309-8775
Print version ISSN 1021-2019
J. S. Afr. Inst. Civ. Eng. vol.54 n.1 Midrand Apr. 2012
Weak interlayers in flexible and semi-flexible road pavements: Part 1
F Netterberg; M de Beer
Weak layers, interlayers, laminations and/or interfaces in the upper structural layers of road pavements are specifically prohibited in most road-building specifications. However, such layers are extremely common and often lead to premature pavement distress. In Part 1 of this two-part set of papers, it is shown that from experience with heavy vehicle simulator (HVS) and dynamic cone penetrometer (DCP) testing, the presence of such layers and/or conditions at any depth in the structural layers of a flexible or semi-flexible pavement is far more deleterious than is commonly appreciated. In Part 2 the effects of these weak layers are further modelled and discussed using various examples based an HVS testing and mechanistic pavement analyses. In particular, a weak upper base course of a cemented pavement under a thin bituminous surfacing may lead to severe surfacing (and upper base) failure within a matter of weeks to months after opening to traffic, not excluding failure even during construction. In this paper (Part 1), the causes of weak layers, interlayers, laminations and/or interfaces, together with simple methods for their detection during construction and analyses of their effects on the structural capacity of flexible and semi-rigid (cemented) road pavements, are briefly discussed.
Key words: weak layers, interlayers, detection, pavement, stabilised
Premature distress in the form of rippling, arcuate (curved) slippage cracking or shoving of the surfacing and shallow base failures of pavements with bituminous surfacings is not rare in southern Africa. The authors know of over 100 such cases that have occurred over the last 50 years and have investigated a number of them. Such distress is usually due to the presence of a weak interlayer between the bituminous surfacing and the base course. Weak interlayers are in fact quite common in spite of current precautions specified to prevent them. Pumping of fines through cracks from a weak interlayer (or laminated interface) between a concrete, asphalt or cemented base and the subbase (De Beer 1985) is another well-known form of distress. Photo 1 shows pumping from a cracked cemented base layer, and Photo 2 shows some fatigue cracking and pumping from a recently constructed road. Examples of delamination (possibly due to construction) are shown in Photos 3, 4, 5 and 6.
The aim of this paper (Part 1) is to show by means of case histories, HVS and DCP testing that the presence of weak layers, interlayers, laminations and/or interfaces at any depth in the structural layers (but especially the upper base) of a flexible or semi-flexible pavement are far more deleterious than is generally assumed or appreciated. In Part 2 of this two-part set of papers (De Beer et al 2012 - see page 43 of this edition) this effect is further discussed and demonstrated in more detail using the well-known mechanistic analysis applicable to the structural design of road pavements.
For the purposes of these papers, a weak layer or interlayer is regarded as any layer that is weaker than was assumed in the design and that has a practical measurable thickness, t, of > 1 mm. Such layers are often referred to as "laminations", "biscuits" or, less often, "false layers" (Bergh 1979) or "pie crusts" (Gray 1979) (see Photos 5, 6, 7, 8, 9, 10 and 11).
In addition, a weak interface, on the other hand, is a condition of minimum friction road - possible weak interlayer directly under the surfacing seal (slip) between two layers, or parts of a layer, normally in the upper 75 mm or so in the cemented base, and has no virtual thickness, i.e. t ~ 0 mm. Such weak layers, interlayers, laminations and/or interfaces are illustrated in the afore-mentioned photos.
In terms of consistency, such interlayers may be loose, i.e. with no unconfined com-pressive strength (UCS), and at a relatively lower density, be relatively weak, i.e. with a reduced UCS, or relatively soft (moist and/or plastic) (see Photos 10, 11, 12, 13 and 15).
In practical terms of soil structure, they may be intact (structureless), sheared or laminated. The term "laminations" or, colloquially, "biscuits", is often applied to all of these forms, in spite of the former meaning thinly layered (i.e. geologically up to 10 mm) and the latter implying a relatively hard but brittle material. However, a smooth or striated flat surface (i.e. interface as defined above with thickness t < 1 mm) is usually found immediately below most forms of weak interlayers. Therefore, smooth, flat, inclined or curved surfaces representing interfaces between compacted layers or shear planes within layers are also regarded as forms of undesirable weak interlayers. The detection and laboratory/field testing of interlayers and interlayer shear transfer between layers (including asphalt layers) are, among others, discussed by Oba and Partl (2000), Diakhate et al (2006), and Canestrari et al (2005). The term "chemically stabilised" is used here to mean a material modified or cemented with cement or lime as envisaged in Technical Recommendations for Highways (TRH) 13 (NITRR 1986a).
Regarding carbonation in terms of road structure, a weak layer may or may not be directly related to the existence of a lamination or a weak interface, as it could develop during construction or because of physicochemical breakdown (Netterberg 1991, 1994), or it could be due to a traffic-associated crushing failure as discussed above. However, carbonation of road layers (or parts thereof) should be seen in the context of the layer's use within a road pavement. A strongly cemented layer might show signs of carbonation, but the strength of the carbonated material is still adequate for its use and purpose in the pavement. This could be described as "non-deleterious" carbonation (or simply carbonation), whereas when carbonation causes the properties of the material to deteriorate to the extent that the layer cannot fulfil its intended function, this is known as "deleterious" carbonation, in the context of this set of papers.
Although it has generally been appreciated for many years (e.g. Bergh 1979) that the upper base must be relatively strong and intact, it is not generally appreciated just how critical this is, especially in the case of a pavement with a cemented base under a surface treatment or thin asphalt surfacing. Experience has shown that such pavements constructed in the last 20 to 30 years do not distress so much by cracking as by rippling and shoving of the thin surfacing associated with a weak interlayer, usually some 3 to 20 mm thick, between the base and the surfacing.
The following section demonstrates the importance of a strong upper base layer, and is based largely on the original work by De Beer (1989a, 1989b, 1990) and De Beer et al (1989).
Heavy Vehicle Simulator (HVS)-DCP correlation
Testing of such pavements under the HVS and correlation of the results with special DCP testing of the same pavements resulted in the prediction model given in Equation 1 (De Beer 1989b, 1990; De Beer et al 1989):
RL = Linear rate of deformation (rutting) in mm/million equivalent standard axles (MESA) (See note on MESA after Equation 2)
DNS0 = Average penetration rate in upper 50 mm of pavement, including surfacing in mm/blow (penetration depth measured after every blow)
DSN200 = Total number of blows in upper 200 mm of pavement, including the surfacing (DCP penetration depth measured after every blow) Probability of regression = 50%, R2 = 76%, n = 29.
As the rate of deformation on lightly cemented pavements appears to be linear (De Beer 1989a, 1990), Equation 1 can be rewritten as:
CAPt20 = Structural capacity in terms of MESA to an assumed additional rut depth of (20 - R) mm, measured from an existing rut depth (R) in mm.
Note that MESA = Million Equivalent repetitions of a Standard 80 kN (8 200 kg) Axle with four tyres at 520 kPa tyre pressure.
In this paper the research based on the DCP and HVS testing was done in such a way that the relative damage coefficients for permanent deformation (d) could be determined. These values ranged between 1,2 and 1,8 for the pavements investigated in the relatively dry state, and were used to convert actual HVS tyre loading to equivalent loading repetitions on which Equations 1 and 2 are based. The usual value of d ~ 4 was therefore not used in this study. (For the original work see Chapter 4 in De Beer 1990.)
This model is the same as that used in the CSIR computer software (CSIR 2007) for the analysis and classification of DCP survey data on lightly cemented (C3 and C4 materials) pavements as defined in TRH 4 (COLTO 1996). As stated, the above model (Equation 2) was derived using actual HVS loading repetitions of a given wheel load, converted to MESA or Equivalent Standard Axle Load (ESAL) or E80 units. However, a convenient nomogram to an additional rut depth of [20 - R] mm (modified from the original Figure 13 in De Beer et al 1989) is provided in Figure 1. This shows the approximate structural capacity (CAPt20) in MESA for an additional rut depth of 20 mm, hence the term [20 - R] = 20 mm, with R = 0 mm.
The empirical model given in Equation 2 applies strictly to pavements incorporating C3 or C4 cemented bases, i.e. UCS between 0,5 and 3 MPa (NITRR 1986a, 1986b), with the following DCP characteristics: DSN800: 200 to 750 blows, B > 0 and A < 3 000 (see De Beer 1989b, 1990), a 20 mm maximum terminal rut depth, DN50: 0,5 to 4 mm/blow, and an equivalent structural capacity of up to 20 MESA. However, note that relatively higher values of DN50 (up to 9,5 mm/blow) are also shown in Figure 1, illustrating relatively low associated MESAs. Figure 1 also supplies the DSN50 (total number of blows to penetrate upper 50 mm) associated with DN50 on the vertical axis. It is, however, cleai that even under conditions of relatively high DCP penetration rates in the top 50 mm (if the above model is extrapolated beyond DN50 of 4,0 mm/blow), relatively low structural capacities (MESA) are indeed indicated, which carry some engineering value. For this reason Figure 1 is extrapolated beyond DN50 = 4,0 mm/blow.
Based on field observations by the authors and applying the methodology given above (HVS and DCP), the effect of a weak upper base layer was investigated. The results of this analysis are summarised in Table 1.
Three important observations are apparent from this analysis (Table 1):
Firstly, for the upper 200 mm of the pavement with an average strength of UCS = 1,5 MPa, a reduction in strength of only 300 kPa in the upper 50 mm to 1,2 MPa will roughly halve the structural capacity from 5,2 to 2,7 MESA. A reduction to 1,0 MPa will reduce the capacity to about 2 MESA, while a strength of 0,7 MPa (~ equivalent to a California Bearing Ratio - CBR - of about 80%) will reduce the capacity to about 0,3 MESA. Reductions of strength of this order are not readily apparent to inexperiencedpersonnel and this pavement would probably be surfaced. Although Figure 1 should be regarded as only approximate, in situ DCP-derived UCS strengths as low as 0,3 to 0,5 MPa have been measured in the upper 50 to 75 mm in un-distressed areas of pavements which suffered premature distress within weeks to months of opening to traffic. These former predictions are, therefore, considered reasonable. Although it is probably true that the DCP disturbs the upper base and that the true strengths are therefore higher, the method was based on DCP penetration rates correlated with actual pavement behaviour under the HVS rather than actual UCS values only. Any disturbance has therefore been taken into account. The extremely deleterious nature of a weak upper pavement is well shown by the sample calculations using Equation 2, presented in Table 1.
The second important observation is that it is better for the cemented layer to be "uniformly weaker" throughout than to have the same degree of weakness only in the upper base (~ top 50 mm). For example, the model in Equation 2 predicts that a pavement with an average strength of 1,5 MPa in the upper 200 mm and weak 1,3 MPa upper base of 50 mm would have a capacity of about 2,7 MESA, whereas a pavement with the same 1,2 MPa strength throughout the upper 200 mm would have a capacity of about 3,3 MESA. Similarly, a 200 mm-thick 0,7 MPa pavement (equivalent to a CBR of about 80%) would have a structural capacity of about 0,5 MESA - a plausible number, i.e. twice that of a 1,5 MPa pavement with a 50 mm weak upper layer of 0,7 MPa (Table 1).
A third important observation is that if the strength of the weak upper layer is kept constant, increasing the average strength of the cemented layer decreases rather than increases the capacity. For example, for a 1,2 MPa weak layer, increasing the average strength of the upper 200 mm from 1,5 to 2,0 MPa decreases the structural capacity from 2,7 to 1,9 MESA. This is most probably due to some "strength balancing" in the top 200 mm of the pavement.
Although any limitations of the model have been ignored in the simplistic analysis presented in Table 1, the results should be at least semi-quantitatively valid and serve to illustrate the critical importance of avoiding a weak interlayer between the base and surfacing layers.
Relatively weak layer on strong sublayer
The failure mode assumed in this analysis is that of weakening and/or crushing of the weak layer on a relatively stronger sublayer (see Photos 5, 6, 10 and 11). The apparent anomaly in Figure 1, whereby increasing the strength of the under (sub) layer decreases the structural capacity, can be explained in terms of the structural pavement strength balance. In other words, it is easier to crack a nut by placing it on a harder surface.
Surface weakening and even surface disintegration of compacted pavement layers - especially those chemically stabilised - during construction is not new and has been recorded from a number of countries in southern Africa and elsewhere. (e.g. Netterberg et al 1987, 1989; Netterberg 1991, 1994). However, it is not widely known and is poorly understood. Known or suspected causes of, contributory factors towards or mechanisms causing a loose or weak layer at the top of a completed pavement layer include the following (mostly after Netterberg 1991, 1994):
■ Very poor-quality gravel or soil: may shear during compaction
■ Organic matter, including penetrating primer, weed killer, sugars: may retard set and/or prevent hardening
■ Aggregate strength: may break down during compaction, especially near the top of a layer
■ Aggregate durability: some aggregates disintegrate spontaneously
■ Stabiliser type and quality ("fit for pur-pose"): suitability for the soil, soundness, age, rate of setting and hardening, slow slaking of quicklime, generation of gas by carbide lime (SANS 824-2006)
■ Conversion of metastable calcium alu-minate hydrates formed during chemical stabilisation of materials containing free or exchangeable aluminium (some laterites and tropical soils) (Sherwood 1993)
■ Excessive or delayed mixing of chemically stabilised material
■ Insufficient mixing ("brief-mix set"): a type of false set (Netterberg, in preparation)
■ Aeration during mixing: another type of false set (Netterberg, in preparation)
■ Poor vertical mixing through layer thickness
■ Vibrating roller set at too high an amplitude
■ Reversing or stopping vibrating roller while it is vibrating
■ Delayed compaction: breaking down of upper part of layer due to compacting partially set, chemically stabilised or partially dried material
■ Inadequate compaction
■ Overcompaction: breaking up of already compacted, semi-hardened material, and production of new faces uncoated by cement or bitumen
■ Grading across to fill slacks instead of cutting to level (see Photos 5 and 12)
■ Incomplete removal of fines to expose good mosaic after slushing and before sealing
■ Spreading of fines on the base to improve the surface finish
■ Slushing or washing out of stabiliser: prohibited on a chemically stabilised layer, but might occur if emulsion-treated finishing methods (light slush, surface enrichment) or over-watering during finishing or curing are used
■ Primer type and quality: penetrating primers applied too soon, hindering cementation (NITRR 1986a, 1986c)
■ Frost damage (has occurred in the eastern Free State and in Lesotho)
■ Bacterial attack: deterioration of bitumen, generation of gas
■ Soluble salt crystallisation and/or hydra-tion (previously common in southern Africa)
■ Acid attack on chemically stabilised material: acidic material, acid rain (personal communication with Johnson (1989) by main author)
■ Sulphate attack on chemically stabilised material
■ Detrimental carbonation of chemically stabilised material (common in southern Africa) from top and bottom of cemented layer (Sampson et al 1987; Netterberg 1991) (see e.g. Photos 7, 8, 10 and 15 with associated failures
■ Drying out of chemically stabilised material (incomplete hydration of cement): even one drying cycle can halve the UCS - probably a common cause (De Wet & Taute 1985)
■ Wetting and drying cycles during curing of a chemically stabilised layer or due to rain: probably a common cause
■ Positive pore water or pore gas (usually water vapour) pressure developed in very hot weather
■ Positive air pressure developed due to a sudden drop in barometric pressure
■ Positive air pressure developed due to capillarity (air breakage, slaking)
■ Thermal buckling
■ Roots
■ Material variability (variable optimum moisture content (OMC), variable UCSs)
■ Emulsion quality and variability ("fit for purpose"): breaking too soon in plant or road, possibly even when within the specification
■ Variability in cement content (even within the specification)
■ Shearing by recycler and vibrator tyres, tamping roller and vibrator drum
■ Faster setting and/or hardening of the cement used than that calculated in the design
■ False setting of cement induced by high temperature
■ Reluctance of water to mix with the material: (hydrophobic material)
■ Difficulty in compacting 300 mm in a single lift while recycling (Netterberg, in preparation)
■ Use of a tamping or grid roller too high up in the base layer: disturbance and footprint compaction planes too deep to skim off - see Photo 14 (Netterberg, in preparation)
■ Very high ambient temperatures: water vapour or cutter blistering (entrapment of volatiles), accelerated carbonation, flash setting of cement (possibly aggravated by hot undiluted emulsion), accelerated setting and hardening causing compaction problems and poorer ultimate strength, lower pH of cement, accelerated breaking of emulsion, drying out during compac-tion, softening of emulsion "primer", increased pore sizes due to expansion, conversion of reaction products (Netterberg, in preparation)
■ Almost sole reliance on a recycler for mixing of the materials, water, cement and emulsion in one pass only
■ Absorption of water and bitumen by the aggregate: premature breaking of an emulsion and incorrect OMCs
■ Smectite in the gravel: premature coagulation or retardation of an emulsion
■ Amorphous silica in the gravel: delayed expansion and weakening or decomposition of the cement (Botha et al 2005), later considered by Paige-Green (2009) to be extremely unlikely
■ Initial consumption of lime (ICL) or initial consumption of cement (ICC) of material not satisfied
■ Sodium carbonate in the gravel acting as an accelerator to a cement and/or as a retarder to an emulsion
■ Variation in proportions of old road, borrow material and sand during recycling
■ Problem of laboratory acceptance control by UCS testing of a material stabilised with a mixture of both cement and emul-sion: uncertainty of best curing method
■ Use of laboratory mixes for UCS testing instead of road samples
■ Necessity to consider the optimum total fluid content (OTFC), not just the OMC, for compaction of bitumen-stabilised materials
■ Possible interaction between stabilisers: higher cement contents might accelerate the breaking of an emulsion, while higher emulsion contents might hinder hardening of the cement
■ Incompatibly charged dust particles along the base course-seal interface (McNally 1998) - hypothesis now apparently withdrawn (personal communication with McNally 1999 by main author)
■ Detrimental carbonation of chemically stabilised layer from below or from sides after construction
■ Punching (embedment) of chippings during surfacing or by traffic into a cemented base
■ Traffic (crushing of an already weak layer and/or sliding on smooth compaction planes): the actual cause of the failures, aggravated by overloading and especially high actual tyre-road contact stresses
■ Pick-ups of the seal by tyres
The causes, prevention of and remedial measures for all such weakening cannot be discussed in detail here - for some of them see Grant & Netterberg (1984), Kleyn & Buckle (1989) and Netterberg (1991, 1994). However, many are obvious and covered by the standard precautions and specifications (COLTO 1998 Section 8). Some have not been previously identified and will be discussed elsewhere (Netterberg, in preparation) and some are speculative and unproven. The most common causes are believed to be the filling of slacks during the cutting of final levels, overcompaction of a weak aggregate or partially hardened cemented material, salt crystallisation, surface carbonation of a chemically stabilised layer, surface drying out and/or cycles of wetting and drying of a chemically stabilised layer, water vapour pres-sures, the former use of a tar primer on an unhardened chemically stabilised material, and construction during very hot weather, especially with cementitious stabilisers. Some materials perform well in laboratory tests, but have a tendency to form a soft surface or soft base in the field (Bergh 1979).
The use of single-pass mixing is no longer recommended in Australia. At least two passes are recommended, especially for depths exceeding 250 mm (Aust Stab 2000). Weak interlayers probably cause the most problems with chemically stabilised bases, although unstabilised and even G1 crushed stone bases (G1 material as defined in COLTO 1998) are not immune (e.g. Netterberg et al 1989, Wyatt & Thomson 1994). From published (e.g. Paige-Green 1984, 1991, 2009; De Wet & Taute 1985; Bagonza et al 1987) and unpublished results, cement and lime-stabilised materials lose, on average, about half their strength either on carbonation - even after seven years of ideal laboratory curing (Paige-Green 1991) or even after one drying cycle (which may also induce partial carbonation). Some materials may even disintegrate. Weakening due to detrimental carbonation, drying out and/or wet-dry cycles is probably the most common cause of surface weakening of chemically stabilised layers.
The current general use of nuclear methods for compaction control and the practice of sampling only before compaction mean that holes are dug in most modern pavements only when failures are investigated or when the pavements are patched. These modern methods have deprived the engineer of an invaluable method of quality control for the detection of a variety of defects, as well as for the best measurement of layer thickness.
It is also clear that specifications and engineering judgement have failed to prevent the large number of cases of premature distress known. It is therefore considered that additional means are required. These could include:
■ Visual inspection of trial holes for lami-nations, compaction planes and, after spraying with phenolphthalein solution (Netterberg 1984), for adequacy of mixing and depth of stabilisation, including filling of slacks with untreated material or deteriorated windrow material.
■ Testing for carbonation by spraying of phenolphthalein solution and diluted hydrochloric acid (Netterberg 1984; Paige-Green et al 1990) on the surface of completed chemically stabilised layers. (Note that in chemical soil stabilisation, carbonation almost invariably weakens the stabilised material.)
■ Visual inspection of the surface of completed layers aided by simple test methods, such as:
■ Tapping or dragging a hammer or pick handle across the layer and listening to the tone of the sound produced.
■ Dragging a simple 2 m length of chain across the layer (see Photo 4).
■ An electromechanical sounding device or, even better, a simple chain drag as specified in ASTM D 4580-03 (2009b).
■ Possibly a rapid vehicle-mounted infrared method as used on bridge decks (ASTM D 4788-03 2009a) for longer lengths of road.
■ More frequent measurement of the density at various depths, such as from 0 to 50 mm, 50 to 100 mm and 100 to 150 mm, instead of just the usual 150 mm. In this connection it is important to note that sand has to be calibrated for a particular depth of the hole (NITRR 1986b). A nuclear gauge does not determine moisture content to the depth of the density probe when the direct transmission method is used, but only to a single depth which may be as much as 200 mm (or more) by the flush backscatter method (NITRR 1986a). Gravimetric moisture content measurements may therefore be necessary for each depth. The calculation method for measuring the density of different layers by taking depth probe readings at different depths is only approximate.
■ If a chemically stabilised layer has been badly cured - even allowed to dry partially only once - the upper layer has probably been weakened.
Because the standard tests for grading, plasticity and strength are all carried out in the laboratory on a sample from the full thickness of the layer, they are insensitive to the presence of a thin layer of deleterious material even when taken after compaction. Even gradings carried out on samples taken from the full thickness of distressed areas do not necessarily indicate the presence of an interlayer of fines between the base and surfacing (Sampson et al 1985).
Standard deflection surveys are not appropriate for the detection of a weak base (Grant & Netterberg 1984) or a weak upper layer of a cemented base, as a low (maximum surface) deflection may be maintained by the rest of the layer (Kennedy & Lister 1978). However, the radius of curvature, which is largely affected only by the upper 0,4 m of the pavement (Grant & Walker 1972), will generally be lower (Grant & Netterberg 1984) and has been used by the main author with more success. In the case of falling weight deflectometer (FWD) surveys, the use of the base layer index (BLI) (Horak 2008) might also prove successful.
Such techniques have, of course, been used for many years, but should probably be a requirement, not an option. Once a weak layer at any depth has been detected, its strength can be measured by means of the DCP if it is not too thin (say t > 10 mm) and its effect on structural capacity then assessed mechanistically or, if in the upper cemented base, by means of the CSIR WinDCP computer program (CSIR 2007), or manually by means of Figure 1 or Equation 1. When dealing with thin layers it is advisable to take DCP measurements after every blow close to such layers rather than after the usual five blows. How well the DCP evaluates hard biscuits separated by smooth planes is not known.
Other possible methods for the determination of the strength of thin layers include the rapid compaction control device (RCCD) (De Beer et al 1993), a Clegg hammer (Clegg 1983; ASTM D 5874-02 2008) and other types of portable falling weight testers (Hildebrand 2003). In the case of the Clegg hammer, it may be necessary to consider also readings after one or two blows in preference to just the standard four blows. The bond strength between cemented layers can probably be measured on cores by using ASTM C 1245-06 (2007), or as was reported by Canestrari et al (2005).
Importance of correct zero point measuring with the DCP
The importance of taking the correct zero point (the top of the vertical shoulder of the DCP level with the top of the surfacing, which is not removed, as in TMH 6 (NITRR 1984)) and also the "softness" of the surfacing into account can be illustrated by means of a sensitivity analysis. An investigation of a new road with a rich seal on a C3 base, which had suffered premature distress due to a weak upper base, is presented in Table 2. This table shows that, in the redefined case, taking the zero at the point of inflection, i.e. effectively removing the generally new, hot, soft surfacing from the DCP analysis, resulted in an overall increase in the apparent structural capacity, in many cases a substantial increase. This was originally shown by Netterberg (in preparation).
In Part 2 of this set of papers (De Beer et al 2012 - see page 43 of this edition), the so-called traffic-associated "crushing failure" of lightly cemented layers is also discussed, which demonstrates the effect of tyre contact stresses on these pavement layers.
Most weak layers, interlayers, laminations and/or interfaces can be prevented by good construction practices. For example, the South African standard specifications for road and bridge works (COLTO 1998) include a number of specific precautions clearly designed to prevent such interlayers:
■ The minimum thickness of compacted pavement layers shall be 100 mm (para 3207 (b) (iii)) except in restricted areas where it may be as thin as 75 mm (para 32707 (b)(ii)).
■ The underlying layer shall be free of loose material before a layer of plant-mixed, paver-laid material is placed upon it (para 3703).
■ Mixing in of a chemical (para 3503 (d)) and, presumably also intended, a bituminous (para 3505 (b)) stabiliser shall be carried out over the full depth to be stabilised.
■ Compaction of pavement layers shall be carried out so as to ensure that specified densities are obtained without damaging the lower layers (para 3207 (b)(i)).
■ During compaction, the crust of a chemically stabilised layer shall be lightly harrowed or scarified before final rolling, if required by the engineer, in order to prevent the formation of laminations near the surface of the layer (para 3503(f)).
■ The specified density of a crushed stone base shall be obtained throughout the entire layer, except when only water-rolled and, when so required by the engi-neer, shall be tested at various prescribed depths (para 3604(b)).
■ In restricted areas the required densities of pavement layers shall be obtained throughout the thickness of the layer (para 3208 (b)(ii)).
■ A completed crushed stone base layer shall be free from surface laminations after compaction (para 3604 (b)) and after slushing (para 3604(c)(i)).
■ All excess fines shall be removed from the surface of a gravel (para 3403 (b)(i)) or crushed stone (para 3604 (c)(i)(ii)) base.
■ Curing of a chemically stabilised layer for at least seven days is carefully specified and it is stated that drying out or wet-dry cycles may be cause for rejection if the layer is damaged thereby (para 3503(h)).
■ No priming shall be carried out on a base which is visibly wet or which is at a moisture content in excess of 50% of the OMC (para 4104).
■ Before priming, the base shall be broomed and cleaned of all loose material (para 4105).
■ Asphalt shall not be placed if free water is present on the working surface or if the moisture content of the underlying layer, in the opinion of the engineer, is too high, or if the moisture content of the upper 50 mm of the base exceeds 50% of the OMC (para 4205(b)).
■ Before applying a tack coat or asphalt, the surface shall be broomed and cleaned of all loose or deleterious material (para 4205(c)(ii)).
■ Before applying a seal, the moisture content of the upper 50 mm of base shall be less than 50% of the OMC (para 4304(b)) and shall be cleaned of all dust, dirt, dung, oil, etc (para 4304 (d)(i)).
■ No asphalt overlay (para 4205 (b)) or reseal (para 4304(b)) shall be placed immediately after a rainy spell on an existing cracked or highly permeable surfacing resulting in the trapping of moisture.
In addition to the specific precautions listed above, the aggregate strength and durability requirements for G1 - G3 crushed stone (para 3602(a)) and G4 - G6 gravel materials (para 3402(a)), and also the soluble salt requirement for both crushed stone (para 3601(b)) and gravel (para 3402(c)) are also intended in part to prevent the formation of weak interlayers due to aggregate degradation and salt damage respectively.
However, in spite of all these precautions and earlier versions of many of them dating back many years, cases of premature distress due to weak interlayers continue to occur. This may be due to insufficient appreciation of just how deleterious such interlayers really are, difficulty in complying with some of the precautions and requirements, and/or inadequate supervision. In addition, so many cases are known where the interlayers must have been built-in as such that it must be concluded that they were simply not noticed. Currently, reliance is placed solely on the supervisory staff to detect such layers by whatever means are at their disposal, and no specific tests are specified or in general use. It is clear that reliance solely on visual inspection has proved inadequate in many cases.
Suggested improvements to the above specifications include the following:
■ Underlying layers should always be free of loose material.
■ Holes should be dug in compacted layers to check for laminations, and/or weak interlayers, adequacy of mixing and, by spraying with phenolphthalein solution (Netterberg 1984), for an even distribution of stabiliser throughout the layer, from top to bottom (i.e. ~ ph > 10).
■ The engineer should have the power to test the density, grading and plasticity at any depth in all pavement layers.
■ A tar primer should not be applied to a chemically stabilised layer sooner than about seven days after compaction, nor, indeed, any highly penetrating primer until the layer has been cured by other means (NITRR 1986b: 50).
■ A fluid cutback primer such as MC-30 should not be permitted as a curing membrane as it is ineffective at preventing both moisture loss (Bofinger et al 1978 in TRL & ODA 1993) and carbona-tion (Netterberg et al 1987) for more than a few days. Even a prime such as MC-30 can weaken a cemented material (HRB 1949; Netterberg 1994) possibly due to hindrance of the cement hydration over the depth of penetration (RRL 1952). The surface moisture content should be such as to prevent penetration (HRB 1949). However, this may cause water vapour blistering in hot weather (Netterberg 1994).
■ Additional precautions may be required when utilising marginal or substandard materials (Netterberg et al 1989).
■ Embedment seldom occurs on a crushed stone base. Embedment due to a false layer on a base can be prevented by either carrying out the final compaction with a diluted emulsion or ripping up the top 20 mm after compaction and treating it with diluted emulsion (Bergh 1979). In both cases the prime is omitted.
The experience of the authors, HVS testing and careful DCP testing have shown that the presence of weak layers, interlayers, laminations and/or interfaces is far more deleterious to structural road pavement performance than is commonly assumed. In particular, a thin interlayer of weaker material between a cemented base course and a thin surfacing can lead to extensive distress within weeks or months of opening to traffic. Such distress can usually be predicted by means of careful inspection, as well as by careful DCP testing. The creation of such weak layers, interlayers and/or laminations must therefore be prevented at all costs, even at the expense of other aspects such as surface finish. The causes of weak layers, interlayers, laminations and/or interfaces are many and some may have more than one cause, but most can be prevented simply by application of known good construction practices. However, such conditions are not always prevented by the application of the standard precautions. Engineering judgement and stricter application of visual inspection, supplemented by simple field tests, are therefore required.
This paper is published with the approval of the Executive Director of the CSIR Built Environment Unit.
ASTM International 2007. ASTM C 1245-06: Standard test method for determining bond strength between hardened roller compacted concrete and other hardened cementitious mixtures (point load test). Annual Book of ASTM Standards, Vol 4, 04.02, pp 668-672. [ Links ]
ASTM International 2008. ASTM D 5874-02: Standard test method for determination of the impact value (IV) of a soil. Annual Book of ASTM Standards, Vol 4, 04.08, pp 1706-1714. [ Links ]
ASTM International 2009a. ASTM D 4788-03:Standard test method for detecting delaminations in bridge decks using infrared thermography. Annual Book of ASTM Standards, Vol 4, 04.03, pp 490-492. [ Links ]
ASTM International 2009b. ASTM D 4580-03: Standard practice for measuring delaminations in concrete bridge decks by sounding. Annual Book of ASTM Standards, Vol 4, 04.03, pp 464-467. [ Links ]
Aust Stab (Australian Stabilization Industry Association) 2000. Aust Stab News, 6.1: 4. [ Links ]
Bagonza, S, Peete, J M, Newill, D & Freer-Newish, R 1987. Carbonation of stabilized soil cement and soil-lime mixtures. Proceedings, Seminar H, PTRC Transport and Planning Summer Annual Meeting, Bath, UK, pp 29-48. [ Links ]
Bergh, A O 1979. Discussion. Proceedings, 3rd Conference on Asphalt Pavements for Southern Africa, Durban, Vol 2, Paper 40, pp 155-157. [ Links ]
Botha, P, Semmelink, C J & Raubenheimer, J 2005. The real cause of detrimental carbonation in stabilized layers and possible solutions. Proceedings, Conference on the Treatment and Recycling of Materials for Transport Infrastructure (TREMTI), Paris, October, Communication C012. [ Links ]
Canestrari, F, Ferrotti, G, Partl, M N & Santagata, E 2005. Advanced testing and characterization of interlayer shear resistance. Transportation Research Record, 1929: 68-78. [ Links ]
Clegg, B 1983. Design-compatible control of basecourse construction. Australian Road Research, 13(2): 112-122. [ Links ]
COLTO (Committee of Land Transport Officials) 1996. Structural design of flexiblepavements for interurban and rural roads. Draft TRH 4: 1996, Pretoria: Department of Transport. [ Links ]
COLTO (Committee of Land Transport Officials) 1998. South African standard specifications for road and bridge works, 1998, Midrand: SAICE. [ Links ]
CSIR 2007. WinDCP Software, Version 5.1.10002. Available at: http://asphalt.csir.co.za/DCP/index.htm (last accessed on 11 April 2012). [ Links ]
De Beer M, Maina J W & Netterberg, F 2012. Mechanistic modelling of weak interlayers in flexible and semi-flexible road pavements - Part 2. Journal of the South African Institution of Civil Engineering, 54(1) (this issue). [ Links ]
De Beer, M 1985. Behaviour of cementitious subbase layers in bitumen base road structures. MEng thesis, University of Pretoria, Pretoria. [ Links ]
De Beer, M 1989a. Compression failure of lightly cementitious materials. Research Report DPVT 36, Pretoria: CSIR Division of Roads and Transport Technology. [ Links ]
De Beer, M 1989b. Dynamic Cone Penetrometer (DCP)-aided evaluation of the behaviour of pavements with lightly cementitious layers. Research Report DPVT 37, Pretoria: CSIR Division of Roads and Transport Technology. [ Links ]
De Beer, M 1990. Aspects of the design and behaviour of road structures incorporating lightly cementitious layers. PhD thesis, University of Pretoria, Pretoria. [ Links ]
De Beer, M, Kalombo, D K & Horak, E 1993. Rapid compaction control for trench reinstatements and pavement layers. Proceedings, 13th Annual Transportation Convention (ATC '93), Pretoria, 28 June - 1 July. [ Links ]
De Beer, M, Kleyn, E G & Savage, P F 1989. Advances in pavement evaluation and overlay design with the aid of the Dynamic Cone Penetrometer (DCP). Proceedings, 2nd International Symposium on Pavement Evaluation Overlay Design, Rio de Janeiro, 44 pp. [ Links ]
De Wet, L F & Taute, A 1985. Durability of stabilized materials. Proceedings, Annual Transportation Convention (ATC), Paper FB, Pretoria, pp 1-15. [ Links ]
Diakhate, M, Phelipot, A, Millien, A & Petit, C 2006. Shear fatigue behaviour of tack coats in pavements. Road Materials and Pavement Design, an International Journal, 7(2): 201-222. [ Links ]
Grant, M C & Netterberg, F 1984. Determining the cause of distress in pavements with thin bituminous surfacings. Proceedings, 4th Conference on Asphalt Pavements for Southern Africa, Cape Town, pp 655-665. [ Links ]
Grant, M C & Walker, R N 1972. The development of overlay design procedures based on the application of elastic theory. Proceedings, 3rd International Conference on Structural Design of Asphalt Pavements, London, Session V11, pp 1155-1165. [ Links ]
Gray, J W 1979. Discussion. Proceedings, 3rd Conference on Asphalt Pavements for Southern Africa, Durban, Vol 2, p 155. [ Links ]
Hildebrand, G 2003. Comparison of various types of bearing capacity equipment. Nordic Road and Transport, 3: 12-14. [ Links ]
Horak, E 2008. Benchmarking the structural condition of flexible pavements with deflection bowl parameters. Journal of the South African Institution of Civil Engineering, 50(2): 2-9. [ Links ]
HRB (Highway Research Board) 1949. Prevention of moisture loss from bituminous materials. HRB Research Report No 8 - P, Washington, DC: Highway Research Board. [ Links ]
Johnson, D 1989. Jeffares & Green, Consulting Engineers, South Africa, Personal Communication to F Netterberg. [ Links ]
Kennedy, C K & Lister, N W 1978. Prediction of pavementperformance and the design of overlays. Report 833, Transport and Road Research Laboratory (TRRL), Crowthorne, UK. [ Links ]
Kleyn, E G & Buckle, L J 1989. Why prime? Proceedings, 5th Conference on Asphalt Pavements for Southern Africa, Mbabane, Session IX, pp 11-13. [ Links ]
Kleyn, E G 1975. Die gebruik van die dinamiese kegel-peilstaaf (DKP). Report 2/74, Transvaal Roads Department (TRD), Pretoria: TRD (in Afrikaans). [ Links ]
Kleyn, E G 2012. TPA Graph 82.03. Personal communication. [ Links ]
McNally, G H 1998. Soil and Rock Construction Materials. London: Spon. [ Links ]
McNally, G H 1999. Douglas Partners, Consulting Engineers, Australia, Personal Communication to F Netterberg. [ Links ]
Netterberg, F (in preparation). The Trans-Caprivi Highway: A lesson in hot weather stabilisation. [ Links ]
Netterberg, F 1984. Rapid field test for carbonation of lime or cement treated materials. NITRR Research Report RS/2/84, Pretoria: CSIR, National Institute for Transport and Road Research. [ Links ]
Netterberg, F 1991. Durability of lime and cement stabilization. In: Concrete in Pavement Engineering. Halfway House, South Africa: Portland Cement Institute. [ Links ]
Netterberg, F 1994. Surface disintegration of primed pavement layers and blistering of bituminous surfac-ings. Research Report RR 90/275, Pretoria: South African Department of Transport (DoT). [ Links ]
Netterberg, F, Paige-Green, P, Mehring K & Von Solms, C L 1987. Prevention of surface carbonation of lime and cement stabilized pavement layers by more appropriate curing techniques. Proceedings, Annual Transportation Convention (ATC), Pretoria, Paper 4A/X. [ Links ]
Netterberg, F, Van der Vyver, I C & Marais, C P 1989. Some problems experienced during the construction of a substandard base course for a very low volume surfaced road. Proceedings, 5th Conference on Asphalt Pavements for South Africa, Mbabane, Session 1X, pp 28-31. [ Links ]
NITRR (National Institute for Transport and Road Research) 1984. Special methods for testing roads. Draft TMH 6, Pretoria: CSIR, NITRR. [ Links ]
NITRR (National Institute for Transport and Road Research) 1986a. Cementitious stabilizers in road construction. Draft TRH 13, Pretoria: CSIR, NITRR. [ Links ]
NITRR (National Institute for Transport and Road Research) 1986b. Standard methods of testing road construction materials. TMH 1, 2nd ed., Pretoria: CSIR, NITRR. [ Links ]
NITRR (National Institute for Transport and Road Research) 1986c. Prime coats and bituminous curing membranes. TRH 1, Pretoria: CSIR, NITRR. [ Links ]
Oba, K & Partl, M N 2000. Non-destructive IR-thermography for distress detection in asphalt pavements and bridge deck surfacings. Road Materials and Pavement Design, an International Journal, 1(4): 407-418. [ Links ]
Paige-Green, P 1984. A laboratory investigation into the influence of carbonation on the strength of lime-stabilized materials. Proceedings, 8th Regional Conference for Africa on Soil Mechanics and Foundation Engineering, Harare, Vol 1, pp 403-406. [ Links ]
Paige-Green, P 1991. The long-term durability of lime-treated soils. Proceedings, 10th Regional Conference for Africa on Soil Mechanics and Foundation Engineering, Maseru, Vol 1, pp 193-196. [ Links ]
Paige-Green, P 2009. A reassessment of problems affecting stabilized layers in roads in South Africa. Proceedings, 3rd International Symposium on the Treatment and Recycling of Materials for Transport Infrastructure (TREMTI), Antigua, Guatemala, 18-20 November. [ Links ]
Paige-Green, P, Netterberg, F & Sampson, L R 1990. The carbonation of chemically stabilised road construction materials: guide to its identification and treatment. Research Report DPVT 123, Pretoria: CSIR Division of Roads and Transport Technology. [ Links ]
RRL (Road Research Laboratory) 1952. Soil mechanics for road engineers. London: HMSO. [ Links ]
Sampson, L R, Emery, S J & Rose, D 1985. Investigation into premature pavement distress at four sites in the Cape Province. Proceedings, Annual Transportation Convention (ATC), Pretoria, Paper FB. [ Links ]
Sampson, L R, Netterberg, F & Poolman, S F 1987. A full-scale road experiment to evaluate the efficacy of bituminous membranes for the prevention of in-service carbonation of lime and cement stabilized pavement layers. Proceedings, Annual Transportation Convention (ATC), Paper 4A/IX. [ Links ]
SANS 824-2006. South African National Standard: Lime for soil stabilization, ed. 2.1. Pretoria: South African Bureau of Standards. [ Links ]
Sherwood P T 1993. Soil stabilization with cement and lime. State of the Art Review, Transport Research Laboratory (TRL), London: HMSO, 153 p. [ Links ]
TRL & ODA (Transport Research Laboratory and Overseas Development Administration) 1993. A guide to the structural design of bitumen-surfaced roads in tropical and sub-tropical countries, 4th ed. Overseas Road Note 31, Overseas Centre, TRL, Crowthorne, UK. [ Links ]
Wyatt, P J & Thomson, A 1994. Premature failures of thin asphalt wearing courses constructed on highly compacted crushed stone bases. Proceedings, 6th Conference on Asphalt Pavements for Southern Africa, Cape Town, Vol 2, Session VI, pp 156-167. [ Links ]
Contact details:
79 Charles Jackson Street
Weavind Park
Pretoria 0184 South Africa
E: firstname.lastname@example.com
Contact details:
CSIR Built Environment
Pretoria 0001 South Africa
E: email@example.com
DR FRANK NETTERBERG is an independent researcher and specialist consultant on pavement materials and geotechnics. He graduated from the University of Cape fi)wn with a BSc in geology in 1960 and a BSc Hons in 1963 and a PhD in 1970 in Engineering geology from the University of the Witwatersrand, and is a Chartered Engineer and Geologist, a registered Professional Scientist, a Fellow of ICE and SAIEG, and a Member of SAICE and AEG. He has been employed by mining companies, consulting engineers, the CSIR and the University of the Witwatersrand. His research and consulting interests include marginal and unusual materials, pedocretes, soluble salt damage, stabilisation, and active clay roadbeds on which he has published many papers and for which he has received a number of awards.
DR MORRIS DE BEER is a principal researcher at the CSIR (Council for Scientific and Industrial Research) Built Environment Unit, and associate editor of the International Journal for Road Materials and Pavement Design (RMPD). He obtained his BSc (Hons), Masters and PhD degrees in Civil Engineering from the University of Pretoria, where he also acts as guest lecturer. He is registered with the Engineering Council of South Africa as a professional engineer, and is a member of SAICE. He also served on various international technical committees, such as the International Society of Weigh in Motion (ISWIM) and Rilem. His research focus is on structural road pavement behaviour, road design, road materials, and vehicle-tyre-road interaction. He is a member of the Tansport Infrastructure Engineering group at the CSIR Built Environment Unit.
The 27 photos and 12 figures are numbered continuously throughout Part 1 and Part 2 of this two-part set of papers. However, the references and equation numbers are specific to each part.


text:
News Detail Page
2009 AAPT High School Physics Photo Contest
published by AAPT
Mar 30, 2009
The AAPT High School Photo Contest provides an opportunity for students to show their creative and artistic talents along with their understanding of physics. This contest is open to students in grades 9 - 12. Students should register online and mail their printed photos. Entries are limited to 15 per school per year. Instructions and information about the competition are available online. Registration is due May 15, 2009.


text:
In the Mexican city of Tuxtla Gutiérrez in Chiapas state, an interesting experiment is unfolding that could be an early forerunner of a future trend—the use of cell phones as sensors.
Under the city's "Vigilante Taxi Driver" program, cab drivers use GPS-enabled cell phones to send messages and photographs about everything from accidents and potholes to burst water mains, downed streetlights and criminal activity—effectively acting as additional eyes and ears of government to combat high crime rates and run-down infrastructure. The reports go to a control center for routing to the appropriate government agency.
The $1.15 million program has been a resounding success, generating close to 10,000 reports a month from 3,500 drivers and helping recover stolen vehicles, identify counterfeiters, dismantle kidnapping and car-theft gangs and, in some cases, save lives. Little wonder the Chiapas government recently expanded the program to two more cities.
"It's proving to be a great tool for the government and for drivers," says José de Jesús Penagos Nangulari, head of the Logistics Department at the Secretary of Transportation in Tuxtla Gutiérrez. "The government cannot be everywhere at once."
The program won recognition last year by the Intelligent Community Forum, a New York-based smart-city think tank, prompting co-founder Robert Bell to call it "a near-perfect blend of technology and citizen participation."
Citizen-Owned Sensor Networks
The concept of using a simple, ubiquitous technology like cell phones to engage citizens in improving their community is resonating far beyond Chiapas. At least one U.S. city government official has predicted that citizen-owned smartphones will increasingly form the municipal sensor networks of the future. And companies like Intuit are working to reimagine their products to be "mobile first" or "mobile only"—for instance, by considering how they would take advantage of sensors in smartphones.
Meanwhile, researchers are experimenting with putting sensors into cell phones to solve social problems—controlling the spread of diseases, for example, or collecting environmental data on air pollution or radiation—with little or no citizen input required.
Over the next decade, as the Internet of Things ramps up—and its next phase, the Internet of Everything—wireless sensor networks will become an increasingly pervasive form of instrumentation for the gathering and analysis of data of all stripes. But deploying large-scale sensor networks can be cost prohibitive, especially in developing countries. But cell phone networks provide a powerful, ready-made and pervasive wireless infrastructure with massive economies of scale to boot.
"By their sheer numbers, cell phones provide an opportunity to gather geospatial data with much higher granularity and more penetration than previously possible," says RJ Honicky, a former researcher at the University of California, Berkeley and Nokia whose work was a call to action to the industry to consider cell phones as sensing systems.
Problem Solving in the Developing World
Some problems are better suited to mobile sensing than others. For example, cell-phone sensors have great potential for monitoring pollution, which usually concentrates in densely populated areas—where cell phones abound.
"The action is where the people are," says Honicky, now a senior software engineer at Tarana Wireless.
Honicky has already tested a prototype cell phone containing a carbon-monoxide sensor capable of sniffing out the lethal gas and thus saving lives. To help measure air pollution, other researchers at Berkeley have succeeded in miniaturizing a MEMS particulate matter sensor—normally the size of a shoebox—so that it fits inside a cell phone.
Elsewhere, researchers have focused on using cell phones with sensors to create an early-warning system for modeling and predicting the spread of tuberculosis in South Africa, and using cell phones in tandem with water quality sensors to monitor village water supplies.
There's a Sensor for That
The potential applications extend beyond the developing world. Honicky says sensors in cell phones could control temperature in homes and offices; detect emergencies, such as an elderly person's fall or a lack of motion; and "slurp up" data stored in delay-tolerant networks as a person walks past a nearby node, with the cell phone functioning as a data mule.
And as smartphones become even smarter, experts say they will come loaded with even more sensors, such as altimeter sensors that can tell you what floor you're on in a building, and sensors that can detect perspiration to monitor your excitement level and mood, which could become incorporated in video games that will factor in emotion during gameplay.
For now, the cell phone-as-sensor approach is still largely in the idea stage, due in part to issues of size, cost and energy use. Honicky says sensors need to be small enough that they can fit inside increasingly sleek phones without adding bulk, cheap enough that they don't send phone costs soaring, and energy efficient enough that they don't drain a phone's power. All of these challenges will be solved in time, Honicky says.
More problematic, he says, are the massive privacy issues that will come with embedding sensors in smartphones that, arguably, already know and transmit too much personal information.
"You have to earn people's trust," Honicky says. "In the long run, that will require giving control of privacy to the user, and being transparent about how the data is being used."
There may soon be a sensor to help with that, too. Some companies are embarking on a race to develop privacy-protecting sensors and databases.
"It's like an arms race," Honicky says.
Used with the permission of http://thenetwork.cisco.com/. The contents or opinions in this feature are independent and do not necessarily represent the views of Cisco.


text:
Results of the 2009 Economics Network Survey of Lecturers
Executive summary
This is a summary of the report and analysis of the Economics Network Lecturers survey, carried out in April - May 2009. The full report is available as a PDF.
This survey is part of the centre's research programme into teaching and learning in Economics, along with the Student, Alumni and Employers surveys. The main objectives of this survey included clarifying current practices and issues of concern to Economics lecturers and their students, as well as providing the Economics Network and its stakeholders with information about how economics lecturers use our services and what impact it has on their teaching.
This is an observational survey and was conducted online for ease of use and low cost. There were 18 questions, in 3 sections, including free-text commentary.
Profile of respondents
There were 198 respondents from 70 HE institutions across the UK. The results of the survey describe our typical respondent as:
- Male (69.2%)
- First language English (73.7%)
- In the post of Lecturer or Senior Lecturer (56.6%)
- With more then 10 years of experience in teaching in HE (53.0%)
- Having one or more of the administrative roles (82.8%)
Key results
A. About Teaching Economics
When asked about support or advice for their teaching, the majority (79.8%) report receiving advice from colleagues; 47.9% from a central university Education Development/ Support Unit; 41.9% from Economics Network and 9.5% stated that no support was required. Respondents also commented on various sources of advice and support.
When asked about funding received for a teaching/learning project, nearly three quarters of respondents report that they haven't received any. Among those who succeeded in obtaining funding 12.1% received funding from the Economics Network and 15.6% from their university.
Respondents were asked if they had received a teaching award and 15.7% gave positive answer with the awards coming from the Economics network, HE Academy and institutions.
B. Change in teaching practice
Since 2003 in all our lecturers' surveys we have asked respondents if they have changed their teaching practice in the past two years. Two thirds of respondents reporting a change in teaching practice this year. Reasons for change included: Feedback from students (83); Students skills and abilities (76); number of students (62); suggestions from workshops (44); colleagues' suggestions (42).
In their comments lecturers described their reasons for change and their actions. This continuing trend for change of teaching practice due to various reasons increases the demand for services and resources provided by Economics Network.
C. Most important issues in teaching
Respondents were offered a list of current teaching issues and asked to select those which they and their colleagues consider very important (they could select as many issues as they thought relevant in their current teaching). Nearly two thirds of respondents chose Student maths skills and Student motivation as the most important issues, with half of the respondents mentioning Large number of students in lectures and Large tutorial groups. Another issue whose importance increased threefold in the last two years is Specific needs of international students.
As well as commenting on these issues, respondents wrote about the various pressures on their time and differential rewards for success in research and teaching.
D. Support from the Economics Network
Respondents were asked about the Economics Network's services and resources. Nearly half of them (47.5%) replied that they use Economics Network services and resources and positively assessed their value.
We asked lecturers who hadn't used Economics Network resources to comment on their reasons. The majority stressed "time" as a major barrier ("Time is the main constraint") as well as satisfaction with their own teaching.
Those who had used Economics Network resources and services were asked to comment on how it had influenced their teaching and what improvements this made to student learning or educational experience. In their replies many respondents praised the work of the Economics Network and provided suggestions for its future developments.
Among their suggestions were the need to support students, which Economics Network is addressing through the development of two focused websites: Why Study Economics? http://whystudyeconomics.ac.uk to encourage potential students to study economics and Studying Economics http://studyingeconomics.ac.uk to support current students.
Respondents were also asked to share the websites they recommend to their students and their replies will be used to update resources on the Studying Economics site.
Funds permitting, the Economics Network will explore some of the suggested ideas and look to provide the community with further resources and services, as well as highlighting policy issues through the HE Academy.
E. Specialist area networks
At the time of the survey the Economics Network was seeking UK-based academics to contribute teaching resources in their field as part of a HEFCE-funded Open Educational Resources programme. The project, 'Teaching Resources for Undergraduate Economics' (TRUE) covers 14 specialist areas. Respondents were asked if they would be interested in sharing ideas and materials for teaching in these areas. Two thirds of respondents replied positively and their names were passed to the leaders of the specialist groups.
F. Conclusions
Results of the survey demonstrated positive support from the community for the work of the Economics Network. They will also inform centre's strategy and planning of the events, resources, briefings and publications in support of economics lecturers.
- 10103 views