This problem actually appeared out of the blue. I've nearly exhausted every option I can find here, but it barely helped.   Here is my situation:   I tried ccsm to enable Ubuntu unity plugin, but every options are unchecked and it seems every time I configure and exit, it revert back to "everything unchecked". My guest account seems working normally. Reinstalling ubuntu-desktop and unity also didn't help.  After trying export DISPLAY=:0  sudo dconf reset -f /org/compiz/ setsid unity    Unity launcher and the panel flashed for a split of a second and then disappeared again
When I login, nothing happens.   I am presented with my desktop wallpaper.    No Dash, no Launcher, nothing.
Some faces of a model don't respond to UV Mapping I can't seem to get these particular faces to take the UV Mapping. I selected the entire object, entered edit mode, hit U>Unwrap.   The rest of the mesh takes the uv wrapping, but not those faces for some reason.    It looks normal in solid mode.     Does anyone know what could be causing this? Sigma algebra and algebra difference I need to find algorithm that can calculate centroid A (aka gravity center, geometric center, center of mass) from the figure where circles T1,T2,T3,T4,T5,..,Tn intersect AND length of line R from centroid to farthest corner of mentioned figure   Following information is given:   T1   Latitude    =   56.999883   Longitude   =   24.144473   Radius  =   943 T2   Latitude    =   57.005352   Longitude   =   24.151168   Radius  =   857 T3   Latitude    =   57.005352   Longitude   =   24.163356   Radius  =   714 T4   Latitude    =   56.999042   Longitude   =   24.168506   Radius  =   714 T5   Latitude    =   56.994226   Longitude   =   24.15709    Radius  =   771   Result should look like this:  A Latitude = XX.XXXXXXX    Longitude = XX.XXXXXXX  Radius = XX    As you probably already figured out, I am working on software that can find device location by closest Wifi Access Points or Mobile Base stations, as number of access points or base stations might change, I need an algorithm that can adapt to uncertain amount of points.  There are some similar questions  and , but none of them exactly answers to my question. Finding $\tan t$ if $t=\sum\tan^{-1}(1/2t^2)$ I am solving this problem. If $$\sum\limits_{i=1}^{\infty} \tan^{-1}\biggl(\frac{1}{2i^{2}}\biggr)= t$$ then find the value of $\tan{t}$.   My solution is like the following: I can rewrite: \begin{align*} \tan^{-1}\biggl(\frac{1}{2i^{2}}\biggr) &amp; = \tan^{-1}\biggl[\frac{(2i+1) - (2i-1)}{1+(2i+1)\cdot (2i-1)}\biggr] \\\ &amp;= \tan^{-1}(2i+1) - \tan^{-1}(2i-1) \end{align*}  and when I take the summation the only term which remains is $-\tan^{-1}(1)$, from which I get the value of $\tan{t}$ as $-1$. But the answer appears to be $1$. Can anyone help me on this. I installed the ubuntu 12.04 server edition for my server pc . i had installed lamp server. i need to change the var/www location to my secondary hard disk location. i was configured so many time to at gedit /etc/apache2/sites-available/default here is my code  &lt;VirtualHost *:80&gt;     ServerAdmin webmaster@localhost      #DocumentRoot /var/www     DocumentRoot /media/myserver/     &lt;Directory /&gt;         Options FollowSymLinks         AllowOverride None     &lt;/Directory&gt;     #&lt;Directory /var/www/&gt;         &lt;Directory /media/myserver/&gt;         Options Indexes FollowSymLinks MultiViews         AllowOverride None         Order allow,deny         allow from all     &lt;/Directory&gt;      ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/     &lt;Directory "/usr/lib/cgi-bin"&gt;         AllowOverride None         Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch         Order allow,deny         Allow from all     &lt;/Directory&gt;      ErrorLog ${APACHE_LOG_DIR}/error.log      # Possible values include: debug, info, notice, warn, error, crit,     # alert, emerg.     LogLevel warn      CustomLog ${APACHE_LOG_DIR}/access.log combined      Alias /doc/ "/usr/share/doc/"     &lt;Directory "/usr/share/doc/"&gt;         Options Indexes MultiViews FollowSymLinks         AllowOverride None         Order deny,allow         Deny from all         Allow from 127.0.0.0/255.0.0.0 ::1/128     &lt;/Directory&gt;  &lt;/VirtualHost&gt;   and also used  sudo chown -R var/www /media/myserver/   and  chmod -R 755 /media/myserver/   still i was not able to connect my /media/myserver and my browser show the following message  Forbidden  You don't have permission to access / on this server.   Please tell anyone how to mount myserver at my var/www, thanks advance Why don't Stack Exchange sites use a rich text editor? Why does the Stack Exchange network of sites use Markdown instead of some other rich text editor like FCKEditor or TinyMCE? Force MacBook to drain the battery while connected to charger I leave my MacBook Pro on my desk nearly all the time, connected to the charger with the lid closed, connected to an external display.  I've heard this is bad for the battery health, and everyone in my office have to replace swollen batteries every couple of years. I want to regularly discharge the battery, per , but I don't want to physically unplug it because that temporarily turns off the external monitor, and then I have to reconnect the monitor.  So I am looking for a software method of disabling the power input, to force the laptop to discharge its battery to 20% and then re-enable the power input. Determine whether $(x_n)$ converges if $x_1= a , x_{n+1} = x_n+\frac{1}{x_n}$ for $n \in \mathbb{N}$ Today I upgraded from Ubuntu 12.04 to Ubuntu 13.10. I am not able to watch any videos in Amazon Prime Instant Video. I am getting this message:   An error occurred and your player could not be updated.   This is likely because your Flash Player or Browser needs to be updated. This update is required to play back this video. I am using an old laptop and doing heavy processing that needs high CPU usage for a long time (~30mins - 2hours). When the process puts heavy load on CPU for a long time, CPU overheats and computer shuts down. I don't want to use a cooler/stand because I am carrying this laptop around and working outside home.  Is there a way/application that I can limit CPU usage of a process in Windows?  Note: Setting the priority of the process from task manager does not work.  Note 2: Fans are clean. What's the preferred method of writing AJAX-enabled plugins? I need rules to drop some malicious Apache connections STM32 send from UART3 and receive on UART2 I thought to create a simple test to send and receive a buffer via UART. I succeeded in sending bytes from my PC to the nucleo bord and receiving them in blocking and non-blocking mode. But for some reason I can't succeed to send data from UART3 and receive the bytes on UART2.  I have a nucleo-f103rb and have the following pins setup:   UART2: tx=PA2;rx=PA3 UART3: tx=PB10;rx=PB11   And then the following code:    while (1)   {     /* USER CODE END WHILE */     /* USER CODE BEGIN 3 */     if (HAL_UART_Transmit(&amp;huart3, send, 2, 1000) == HAL_OK)     {         if (HAL_UART_Receive(&amp;huart2, receive, 2, 1000) == HAL_OK)         {             HAL_GPIO_TogglePin(GPIOA, LD2_Pin);         }     }   }   All the boiler plate is generated using cube mx. So the UART 2 and 3 are all default, same for the button pins.    I connected the transmit pin of uart3 to the receiving pin of uart2 I connected the receive pin of uart3 to the transmitting pin of uart2 (while not used in this trivial example though)   What am I missing here?  Update  As comments and answers suggested, I shouldn't be using the blocking mode approach. So I rewrote it slightly to rely more on interrupts.  I attached a callback to the nucleo blue button  void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin) {     if (GPIO_Pin == B1_Pin)     {         HAL_UART_Transmit_IT(&amp;huart3, (uint8_t *)send, 2);     } }   And I added a callback for receiving stuff over uart  void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart) {   /* Prevent unused argument(s) compilation warning */   UNUSED(huart);    /* NOTE : This function should not be modified, when the callback is needed,             the HAL_UART_RxCpltCallback can be implemented in the user file    */       // Toggle the pin to see some proof that I received something      HAL_GPIO_TogglePin(LD2_GPIO_Port, LD2_Pin);       // Resubscribe uart2      HAL_UART_Receive_IT(&amp;huart2, (uint8_t *)receive, 2); }   In the main function I call the interrupt so that the callback is active.  while (HAL_UART_Receive_IT(&amp;huart2, receive, 2) != HAL_OK);  __NOP(); while (1) { }   Again, when debugging through I do end up in the button released callback, but the callback on the uart receive isn't triggered. When I send stuff from the PC, it does. So it seems that sending stuff via uart3 isn't working. So I guess that must be the wiring.     But I really can't see what I am missing here, the pins are clearly defined in the pinout here: .  I hope the photo is clear enough, but this is how I connected them. Why is there a temperature gradient on Earth? I was thinking about why the poles are colder and I came out with three possible explanations.  1. The atmosphere blocks light beams coming to poles    The Sun is seen only slightly over the horizon at the poles, so the light beams have longer way to the poles. If only this case were true, then the total difference between the poles and the equator would be the same as the energy that was absorbed by the atmosphere.  2. Sun is only slightly over the horizon at the poles.    Poles are often in shadow of the parts of the Earth which are closer to the equator.  3. Poles are farther from the Sun    The longer is the way to Sun the lower is the chance to catch a light from the Sun.  Please, correct me wherever I'm wrong. I'd like to know   Which of these three is most correct?  How significant are the described effects of the other explanations? What resolution should a large format artwork for print be? For wall-sized graphics and large banners (e.g. 3m × 5m), what is an acceptable PPI for print? As I understand it 300 ppi is the typical for 'small' artworks (esp. for clean text resolution). However, for small artworks, the audience usually engages at a much closer distance. Therefore, in the interests of keeping a bitmap file down to a reasonable size, can you get away with a much-reduced PPI for a large format/banner print? Algorithm for determining random events I'm struggling with coming up with an elegant solution to generating random events in the game that I'm working on.  Say there are 4 classes of events that can happen, with varying events in those classes that may occur.  So something along the lines of   main_events = {"common event", "not so common event", "somewhat rare event", "rare event"} sub_events[0] = {"common event 1", "common event 2",..} ...   I have a somewhat kludgey solution in place that first just has a random number generated between 0 and 100, and if the number falls within a given range then a main event will be triggered.  Then I'll do another random roll to see which sub event occurs.  Is there a better solution than something along these lines?  Like I mention, it doesn't feel very elegant, and I'd like to make it easily expandable for the addition of future events. I'm writing a custom module for Drupal 8. It defines a field storage configuration object, in a file called modules/mymod/config/install/field.storage.bloom_stem.bs_twitter_ac.yml.  The problem is that this is not removed when I uninstall the module; it is apparently left behind because, when I re-install the module, I get a crash.   drush -y pm-uninstall mymod drush cr drush -y en mymod      exception 'Drupal\Core\Config\PreExistingConfigException' with message 'Configuration objects (field.storage.bloom_stem.bs_twitter_ac) provided by mymod already exist in active configuration'   So it seems I need to some how manually remove this configuration object. Do I need to provide some more code that deletes it when the module is uninstalled? How can I understand and prove the "sum and difference formulas" in trigonometry? The "" formulas often come in handy, but it's not immediately obvious that they would be true.  \begin{align} \sin(\alpha \pm \beta) &amp;= \sin \alpha \cos \beta \pm \cos \alpha \sin \beta \\ \cos(\alpha \pm \beta) &amp;= \cos \alpha \cos \beta \mp \sin \alpha \sin \beta \end{align}  So what I want to know is,    How can I prove that these formulas are correct? More importantly, how can I understand these formulas intuitively?   Ideally, I'm looking for answers that make no reference to Calculus, or to , although such answers are still encouraged, for completeness. How to use an optimization solver to get t-stats and p-values for the estimates? System freezes completely with Intel Bay Trail