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What are 'return' pins? On a VGA connector, there are numerous 'ground' pins. Three of these are Red return, Green return and Blue return; But why does each color component have its own ground pin? I would like to visit Iran as a tourist but I'd also like to visit the USA some time after. I know the relations between the two countries are bad.   Is it likely that I'm not allowed to enter the USA after having been to Iran?   If it matters, I've never been to either of those countries. I'm a Swiss citizen, an atheist from a Christian background. How to access Winter 13's Push Major functionality We are ISV Partners and all of our packaging orgs have been upgraded to Winter 13. One of the features of Winter 13 was supposed to allow us to push major release versions to subscriber orgs. I would have expected it to be in the previously existing "Push Upgrade" section of our packaging orgs, but that still only allows pushing patch versions.  If it didn't make the final Winter 13 release, I would have expected Salesforce to take it off the release page. Is this something we have to ask to be enabled? If $d(x,y)$ is a metric, then $\frac{d(x,y)}{1 + d(x,y)}$ is also a metric This started to happen immediately after I had rebooted the first time after doing a system upgrade. It first starts with a dialogue that says "System program problem detected". Then when I try to hit 'report problem' not much happens. I am led through a dialogue that always ends up the problem cannot be solved.  I am aware this is not a lot of information, however I'm not sure which information I need to publish and how should I obtain it to debug this problem.  Here's a screenshot! Set of left cosets is a group Let $N$ be a normal subgroup of $G$. Let $G/N = \{gN : g \in G \}$. Show that the $(G/N, \circ, 1_{G/N})$ is a group, where:  $\circ : G/N \times G/N \rightarrow G/N$ is defined by $(gN \circ hN) = ghN$ and $1_{G/N} = 1*N$.  Thanks for your help. Is there a way to determine which features / variables of the dataset are the most important / dominant within a k-means cluster solution? How can I copy coverart from flac to opus with ffmpeg I am trying to convert some flac files which all have coverart embedded to opus with ffmpeg. All but the coverart gets copied over just fine, but I find myself unable to move the cover over as well. Tried all sorts of -mapmetadata stuff I could find so far, but no luck, the result is always missing the coverart.  While the original .flac reports to have a video stream with the coverart  Duration: 00:02:53.51, start: 0.000000, bitrate: 910 kb/s    Stream #0:0: Audio: flac, 44100 Hz, stereo, s16    Stream #0:1: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 500x500 [SAR 1:1 DAR 1:1], 90k tbr, 90k tbn, 90k tbc   the created opus files does not have any graphics:  size=    2815kB time=00:02:53.51 bitrate= 132.9kbits/s speed= 104x video:0kB audio:2793kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.811556%   I tried -vcodec copy, -mapmetadata 0, -mapmetadata 0:s:0 so far, with no luck. Doesnt seem to have anything todo with opus, as I have the same problem converting to aac.  So is there a way to get the cover out of the flac file and move it over to the new file in on go using ffmpeg, or do I have to extract it first and then glue it back again later to the new file with extra commands? Can I uninstall and reinstall Ubuntu Software Center? Combine rows / concatenate rows I accidentally moved all folders from root to a subfolder. (/bin, /etc, /home, /lib, /usr... all moved) The only ones that were not moved, since they were in use, are  /bak, /boot, /dev, /proc, /sys.  Now, any command that I try to execute will simply not happen. I constantly get "No such file or directory".  I am connected through ssh and through ftp, but I cannot move files through ftp, as direct SU login is disabled. I also have access to the actual server if I need to do something directly from there.  I'm assuming I would need to edit a configuration file in order to tell it where to find the /bin folder and that would help me get access again, but I don't know which file that would be or how to do it (since I can't even run chmod to change permissions).  Is there any way out of this other than re-installing?  I am working on an old version of CentOS.  I'm extremely new to the world of Linux, hence this action and the question... The Software Center in Ubuntu 16.04 (Gnome Software) shows only part of the packages available. While e.g. apt list qtcreator correctly lists the corresponding package a search in Software Center finds nothing.  Is there something misconfigured? I upgraded from 15.10. Until now I have used the old Ubuntu Software Center which worked fine. Keyboard shortcut to switch between applications in Mission Control Does Apple have keyboard shortcuts to switch between applications in Mission Control? (Instead of hovering over with the cursor)?  e.g., which key combination cal I press to get me from "preview" to "app store?" Zooming to selection in arcpy.mapping and only seeing selected features? I selected data by using select layer by attribute, then I need to only select these selection and zoom in to the selection.  my code is this, it can zoom in base on the scale I set, but I see other adjacent polygon that has other Code_No, why?  Layer = arcpy.mapping.ListLayers(mxd, "lyr", df)        arcpy.SelectLayerByAttribute_management(lyr, "NEW_SELECTION", "Code_NO = '%s'"%mycodeNo)            df.extent = lyrLayer1.getSelectedExtent() df.scale *= 2 How can I make a bootable, unattended USB restore disk? I have a load of 14.04 kiosk systems, halfway across the country. These are horrible little integrated devices. I need to upgrade them all to 16.04 to support a new software stack. do-release-upgrade works half the time. The other half it destroys the install. In addition, the CPUs are really slow and  network connections at some sites are also pretty shoddy. So even when it works, upgrading takes a long time.  So new plan. I can make a fully-installed system image for each kiosk in Virtualbox, or LXC, or whatever. I need a way to get these images unpacked onto the systems.  The main problem here is there are very few technical people available at the other end. And I don't want to fly 200 miles to do this myself. I need something that is almost completely automated and doesn't require a keyboard.  I'm imagining a scenario where:   I make a system image for each kiosk I make a bootable USB drive for each kiosk and copy on the kiosk image. I label each and post them. At the other end, a staff member with physical access to the USB ports just plugs in the right drive and reboots. The bootable element of this then writes and expands the disk image.   It's that "bootable element" that I'm looking for. I was expecting that something like this might already exist (for bulk reimaging installations) but it's possible I'm in new territory. Anything that gets my images installed without manual interference (past plugging it in) gets points.  As far as I know, options like Clonezilla require somebody with a keyboard to tell it what to do. I need something that doesn't require a keyboard, just gets on and does it. Graphing the amount of time a function takes The most efficient way to implement an integer based power function pow(int, int) What is the most efficient way given to raise an integer to the power of another integer in C?  // 2^3 pow(2,3) == 8  // 5^5 pow(5,5) == 3125 Let $R$ be a commutative ring and $I_1, \dots, I_n$ pairwise comaximal ideals in $R$, i.e., $I_i + I_j = R$ for $i \neq j$. Why are the ideals $I_1^{n_1}, ... , I_r^{n_r}$ (for any $n_1,...,n_r \in\mathbb N$) also comaximal? How can I correct this code to get an answer? If a variable is declared as static in a function's scope it is only initialized once and retains its value between function calls. What exactly is its lifetime? When do its constructor and destructor get called?  void foo()  {      static string plonk = "When will I die?"; }