Audio decoder (mp3) is not present
How do I install the ubuntu-restricted-extras package?
A key doubt about the resultant of two polynomials and their common zero locus I've got a situation where I have a 240V 30A dryer line, and I want to power something else from the same circuit, but NEVER at the same time as the dryer. I'm looking for a switch to use, like a DPDT ON-ON break-before-make switch. There are tons of DPDT switches I've found, and most seem to be ON-OFF. Hardly any show their wiring diagrams, so if they don't give more details, I don't know if they'll work. Note: the second circuit will not use more than 15A, maybe just 12A.  I'm hoping someone can recommend specific switches that will do what I want. Manufacturer and exact part# is what I'm looking for.   Personally, I don't care if it's a knife switch, something that looks like a standard light switch, two buttons, has relays, I don't care. The breaker box is full, it's a long and difficult wire run, and I do not need a separate circuit because I'll NEVER need to run both devices at once.  I could resort to just using one plug and unplugging one then plugging the other one in, but I don't see the point of constantly exposing live wires (the plugs) where something could inadvertently fall on them or water could be sprayed, instead of keeping things all sealed in the wall with a safe, simple switch between two plugs. Why don't digital cameras shoot video at full sensor resolution, or do continuous drive at video framerates? How do you get a Media Type (MIME type) from a file using Java?  So far I've tried JMimeMagic &amp; Mime-Util. The first gave me memory exceptions, the second doesn't close its streams properly. How would you probe the file to determine its actual type (not merely based on the extension)? Why does "unisex" mean both sexes? There are some places where men and women are segregated — for example public toilets and public swimming pool changing areas.  By this I mean, for example, that there are "Men's toilets" and "Ladies' toilets".  However, in some more cosmopolitan swimming baths, and other places, there are such things as unisex changing areas, or unisex toilets.  From my understanding uni- implies one, as in universe, unilateral or unicycle.  However when it comes to unisex, this means both sexes, so applies to two things.  How does uni- mean one in unisex? Does it mean one? Why wasn't Restricted Section of the library better protected? Can we get an alternative to the "That solved my problem!" button that doesn't make the presumption that it solved my problem? I.e. "Yes, that's the problem I have."  In some cases, SE (et. al.) answer something, but the answer really doesn't solve it, it was a "cop-out" -- a "we know there's a problem, but there's currently no fix or workaround". Can we get a button that indicates that "Yes, I acknowledge I have that same problem, and I may have even tried those solutions, but it's not solved by any means." button or something?  I get the purpose of it - make it more friendly and easier to remove duplicates, but I refuse to say "That solved my problem!" if I still have a problem (mostly on principle). I'd rather have a "Ah yes, that's my issue! But, it seems like there's no actual solution there."  As an example: Name of short sci-fi story involving a musician who is punished for listening to Bach I read a short story a long time ago and I can neither remember the title nor the author.  The main character is a musician.  He is sequestered and allowed to play all day on some kind of a fantastic instrument; however, he has been barred from listening to any music for fear that it will stifle with his innate creativity.  Someone secretes him some Bach, he listens to it, and is then caught and cast out.  He gets a series of jobs and is inevitably punished for breaking some music-related taboo.  Any ideas? Torsion elements of a group aren't necessarily a subgroup In a question from an exam in an undergraduate group theory course, we were asked to prove or disprove that the set of all Torsion elements of a group is necessarily a subgroup.  I knew that the set of Torsion elements is closed under the inverse operation, but was later told that it is not closed under multiplication, therefore disproving the claim. However, I couldn't find any examples of a group $G$ and two elements $a,b$ such that both $a$ and $b$ have a finite order, but $ab$ doesn't. I know that for this to happen $G$ must be an infinite and non-Abelian group, but still couldn't find a valid example.   What are some examples of groups/elements fulfilling the aforementioned property? Do's and Don't's of Undergraduate Research I was fortunate enough to get a position as a researcher for the Mayo Clinic's SURF Program this year. My PI's lab focus is on the the immune system's role in CNS axonal and neuronal injury, specifically through the lens of how innate and adaptive immune effectors interact w/ infected neurons.  Although I do research under a professor at my college and I volunteered for a state university lab during the previous summer, this is my first REU/SURF opportunity, and I REALLY want to make a good impression. Here are my questions:  What are the do's and don't's in terms of being a skilled and efficient researcher?  Since I am still an undergrad, I know that I will be a less useful asset to the lab than a grad student or post-doc, but what can I do as an undergrad to not burden my colleagues and PI?  Thank you all for your help! Wishing you all the very best! Automatically resize uploaded images Possible Duplicate:             Could large images of more then 640 pixels wide automatically be resized to reduce loading time and band width use? Not that I have a prehistoric internet connection here, but sometimes pages seem to need unnecessary time to load fully.  I just resized the image  from 179 kb down to 32 kb using a 15% compression rate. I think that is already worth it, although there have been much bigger downsizes in the past.  This feature then propably should/could be combined with , and uploading an image then would result in the following post addition:  [![enter image description here][2]][1]  [1]: http://i.stack.imgur.com/ZSBxw.gif "View &lt;image title&gt; full sized" [2]: http://i.stack.imgur.com/VXmBA.jpg "&lt;Image title&gt;"   Update:  I now understand from  that images áre resized already, but that post authors have to do some changes themselves. Could it then be automated to add the already resized image (that with the l suffix):  [![enter image description here][2]][1]  [1]: http://i.stack.imgur.com/ZSBxw.gif "View &lt;image title&gt; full sized" [2]: http://i.stack.imgur.com/ZSBxwl.jpg "&lt;Image title&gt;" Why can I modify a read-only file? Short Question:  Why can we manipulate a read-only file in Vim using : + w + q + ! even without being an administrator?  Long Question:  I have a text file (myFile.txt) which is read-only for everyone:  navid@navid-ThinkPad-T530:~/ubuntuTest$ ls -l myFile.txt  -r--r--r-- 1 navid navid 26 Aug 22 21:21 myFile.txt   I can open it with Vim without having admin privileges:  navid@navid-ThinkPad-T530:~/ubuntuTest$ vi myFile.txt    I modify it and press: Esc + : + w + q + Enter and I see this error message:  E45: 'readonly' option is set (add ! to override)   So far, everything makes sense.  But when I press: Esc + : + w + q + ! + Enter, Vim saves the changes.  I'm using Ubuntu 16.04 and VIM 7.4. setting up subdomain on ubuntu server How Does The Debugging Option -g Change the Binary Executable? When writing C/C++ code, in order to debug the binary executable the debug option must be enabled on the compiler/linker.  In the case of GCC, the option is -g.  When the debug option is enabled, how does the affect the binary executable?  What additional data is stored in the file that allows the debugger function as it does? How can I make Ubuntu 18.04 / 18.10 desktop use Unity (be like Ubuntu 14.04)? I recently installed Ubuntu 18.04 and I'm not keen on the desktop environment. I want the desktop env. I used to have in Ubuntu 14.04. How can I get it?  I've attempted to use , but when I try to install the Unity's 7.2.5 version using the command:  apt install unity=7.2.5   it gives me   E: Version '7.2.5' for 'unity' was not found   For sure I need to add a PPA for this, but which one!? Compiling the following code and got the error of type illegal.  int main() {     // Compilation error - switch expression of type illegal     switch(std::string("raj"))     {     case"sda":     } }   You cannot use string in either switch or case. Why? Is there any solution that works nicely to support logic similar to switch on strings? If $(a,b)=1$ then prove $(a+b, ab)=1$. Let $a$ and $b$ be two integers such that $\left(a,b\right) = 1$. Prove that $\left(a+b, ab\right) = 1$.   $(a,b)=1$ means $a$ and $b$ have no prime factors in common  $ab$ is simply the product of factors of $a$ and factors of $b$.  Let's say $k\mid a+b$ where $k$ is some factor of $a$.  Then $ka=a+b$ and $ka-a=b$ and $a(k-l)=b$.  So $a(k-l)=b, \  a\mid a(k-1)$ [$a$ divides the left hand side] therefore $a\mid b$ [the right hand side].  But $(a,b)=1$ so $a$ cannot divide $b$.  We have a similar argument for $b$.  So $a+b$ is not divisible by any factors of $ab$.  Therefore, $(a+b, ab)=1$.  Would this be correct? Am I missing anything? How can I automatically log out the guest account after a period of inactivity? As part of a kiosk system, I have set up a Guest account on a Mac OS X Snow Leopard computer. This account is cleared every time someone logs off the computer. However, plenty of people don't. Is there any way that I can automatically log out this guest account after a period of inactivity?  I tried using the security preferences pane, but that just causes the confirm logout dialog to show up.  I have hacked around the /System/Library/User Templates/ folder, so I can set the screensaver, desktop background, &amp;c. If something like ScriptSaver can solve my problem, I will gladly use it. Ubuntu 14.04 slow wireless connection Segmentation fault on large array sizes