I know there are other ways I can do this, but I'm a little curious about this anyway.   Basically, I have a breadboard that's mounted on a typical base that has the typical three posts I can hook power to. I want to operate one pair of power rails at 12V and one pair at 5V. And I have one 12V AC adapter and one 5V AC adapter But remember, I have 3 posts on this thing, red, green, black.  My thought is, I can hook the red up to 12V+ and the green up to 5V+ and put both grounds from these power supplies on the same black post?  Then I can wire jumpers from the posts to the rails. Is this kosher? Or does each AC adapter need to use its own ground? Do the grounds need to be isolated, or is ground, ground even if you're using different voltages?  It isn't lost on me I could do this a million other ways, but sharing a ground could be handy, but I haven't seen it done anywhere. Not sure if that's a sign or if I just haven't looked in the right place.  Thanks for any help!
As I'm relatively new to the electronics world, I was wondering if you can connect multiple  ground terminals (corresponding to several different voltage outputs) to the same ground. Or do they each need their own?  In my case I have 5 lines, one 12V, one 3.3V, two 5V and one variable from a 12V in using a  voltage regulator that already has its own ground. So I'm guessing that each would need its own ground, but it is never bad to ask.
Why 220V and 110V? Why did the industry choose these seemingly unintuitive values of 110V and 220V for the mains AC? Is there a physical reason why they aren't simply 100V and 200V? Handle either a list or single integer as an argument I have the need to synchronize the data in certain Salesforce tables (user, account, opportunity, lead, task, contact, etc.) to a local database. For reasons that I won't go into here, I can't use the streaming API. I want to kick off a local process every X minutes that will:   Go through each of the tables on my list Insert any new records Update any existing records that were updated Delete any records locally that were deleted on the server (either deleted directly or indirectly (e.g. through a foreign key relationship, like when an account is deleted its associated tasks are deleted as well).   Can you please offer advice on what API's might be good to use here, and whether one stands out more than the others? Are there any specific design recommendations that might be useful for achieving this goal? Or is there really no practical difference between what REST vs SOAP can do?  It comes down to what is the easiest to maintain/implement? Is there some other route that might be beneficial to use (example: bulk data load to start out followed by outbound messaging tied to all of the objects in question to get updates/inserts/deletes)?   I am using C#/.net. Does String theory say that spacetime is not fundamental but should be considered an emergent phenomenon? Does String theory say that spacetime is not fundamental but should be considered an emergent phenomenon?  If so, can quantum mechanics describe the universe at high energies where there is no spacetime?  Schrodinger equation assumes the presence of time dimension. So how can such equations be valid at extremely high energy?  And is it meaningful to do physics if there is no time dimension?  Would the concepts of Hilbert space, wavefunction collapse etc be useful in that case? .NET create scheduled task on server fails with E_ACCESSDENIED I have an ASP.NET website (in C#) that takes in user data and then attempts to create a windows scheduled task.  Of course, this works great on the DEV machine, but fails to run on the server.  I'm trying to figure out what permission(s) are required on the ASPNET user (or anonymous web user) to create tasks.  The error is:  Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))  Stacktrace:      at MyScheduler.NewWorkItem(String TaskName, Guid&amp; rclsid, Guid&amp; riid, Object&amp; obj)      at MyScheduler.CreateTask(String name)   I've done some searching, and the suggested resolution is to use the web.config 'impersonate' flag to force the application to run as a user with sufficient permissions, as opposed to the ASPNET account which may not have those permissions.  Example:  &lt;system.web&gt;     &lt;identity impersonate="true" /&gt; &lt;/system.web&gt;    Unfortunately, this does not seem to resolve the issue.  From the documentation I read, this should run as the anonymous web user, but it seems that user does not have enough permissions.  I altered the setting to specify a specific domain user that happens to be an administrator on the machine.  Example:  &lt;system.web&gt;     &lt;identity impersonate="true" userName="WindowsDomain\YourUserName" password="YourPassword" /&gt; &lt;/system.web&gt;    Doing this allowed the application to successfully create the Windows Scheduled Task.  So, obviously, with the correct set of Windows 2003 permissions I can get the app to perform as it does in the development environment.  However, I'm not about to place the network or machine administrator account's user credentials in plain text on a Web.config file.  Does anybody happen to know what permissions exactly need to be set in order to get the ASPNET account to behave as desired?  EDIT:  The Win32 API is being used to create scheduled tasks. We are currently working on a windows based application where users capture data. Some data is captured in a table where other data is captured in text blocks. Im currently faced with the dilemma of how to align contents specifically decimal values.  Editable cells in a grid are indicated with a pencil icon which disappears once in edit mode. You will notice that the table consists of various field types, decimals and text. So what should I do and why?  A> right align all cell content  B> left align all cell content  C> right align only decimal values in cells  D> Whatever else you can suggest I am a British national living in Spain and my passport is either lost or stolen. I noticed this two days ago when I was intending to take a trip to Salzburg. As it happens, I managed to travel using my UK Driver's Licence. I think a severe mistake was made, as was pointed out to me in Austria, but as they were Schengen Countries, apparently all that is needed is a proof of identity, not a 'travel document'.  My question, therefore, is this. I have business trips over the next three weeks taking me from Spain to Germany, Czech Republic, Austria, and Italy, then back to Germany, and then to the UK. If I obtain an Emergency Passport from the Consulate here in Barcelona, would this be valid as an identity document within Schengen, before I eventually 'cash it in', so to speak, as a travel document when I make my trip from Germany to the UK?  I am hoping so, as I don't fancy my chances of getting back to the UK in time to secure an appointment for a fast-track passport. I am going to call the consulate tomorrow, but would appreciate any advice or prior experience. Is soaking beans 24 hours unrefrigerated safe? Robocall claiming to be IRS saying they are about to sue - Is it legit? We got a recorded call with a message claiming to be from the IRS.  It said they were giving final notice and preparing to file a lawsuit against us.  In our case, the message went to voicemail so the end was cut off, but it seemed like a scam all the way. (We don't have any pending problems with the IRS as far as we know.)  The question was whether this is a known scam? I want to create a math problem-solution sheet. The coefficients a, b, c must be assigned on the fly at random so the generated pdf will show a numeric quadratic equation rather than a symbolic quadratic equation. Note a must not be zero.  \documentclass{article} \begin{document} \section{Problem} Let \(x_1\) and \(x_2\) be the roots of \(a x^2 +bx +c=0\). Find  \(x_1x_2\).  \section{Solution} \[ x_1x_2=\frac{c}{a} \] \end{document}   Please kindly make the solution get automatically simplified. For example: \frac{c}{a}=3 when a=2 and c=6.    Actually the real case is more complex than this one. Not only the equations must be generated at random, but also the associated graphic plots that I write in PSTricks.     I chose Paulo's answer because using Maxima as the computation engine is very very great idea. Other answers are also good and creative, especially Altermundus'. So, I'm using a script I've made to convert videos to the webm format. A certain program calls the script, sending %f which is the full, absolute file name of the video, like this:  converter.sh %f   where %f has two possible extensions, .avi or .mpg.  # /bin/bash ffmpeg -i $1 `dirname $1``basename $1 avi`webm &amp;&amp; rm $1   It currently works perfectly when $1 contains a .avi file, because basename removes the .avi extension. When $1 ends with .mpg instead, the result is .mpgwebm.  How can I modify that script to be able to receive those two possible different formats?    Resuming: If $1 is /somedir/video.avi, the script should do:  ffmpeg -i /somedir/video.avi /somedir/video.webm   And if $1 is /somedir/video.mpg, the script should do:  ffmpeg -i /somedir/video.mpg /somedir/video.webm   I know this might be fool for some people, but I'm kind of new with the bash. How to determine $\int x^2 e^{-x^2}\mathrm dx$? Are there recommendations or pitfalls for playing an archer cleric? In my 4E game, a player is going to try an elven cleric with a longbow (and a mace, just in case). She chose mostly ranged powers. Are there any caveats to playing such a character, or any builds that I could recommend for her? What are the advantages/disadvantages of the new encryption feature in ubuntu 13.10 I'm in the middle of installing 13.10 and the Ubuntu page I was following on how to install from a USB stick says nothing about these two choices (on the Installation type screen):     1) Encrypt the new Ubuntu installation for security (you will choose a security key in the next step).      2) Use LVM with the new Ubuntu installation (this will set up Logical Volume Management. It allows taking snapshots and easier partition resizing)   I'm a writer using the computer for mostly writing ebooks but I also do all the things most people do: buy stuff online, online banking etc. I want my information to be safe but I don't want to overburden my system with security stuff either. And I've read a lot of the similarly themed questions here on the forum but they've all been about stuff more technical than I'm concerned about.   Can somebody please just tell me in real layman's terms about the implications of these two choices? Thank you. Im having trouble with the second part of this question,  Let $H$ be a normal subgroup of $G$ with $|G:H| = n$,  i) Prove $g^n \in H$ $\forall g \in G$ (which i have done)  ii) Give an example to show that this all false when $H$ is not normal in $G$.(which I am having trouble with showing)  Any suggestions? How to deal with downvotes without any explanation How do I determine the size of an object in Python? I want to know how to get size of objects like a string, integer, etc. in Python.  Related question:   I am using an XML file which contains size fields that specify the size of value. I must parse this XML and do my coding. When I want to change the value of a particular field, I will check the size field of that value. Here I want to compare whether the new value that I'm gong to enter is of the same size as in XML. I need to check the size of new value. In case of a string I can say its the length. But in case of int, float, etc. I am confused. Where can I find a standalone installer for Windows 7 Service Pack 1? Is there a way to do concurrent editing? Is there a MediaWiki-like method for supporting concurrent editing of text bodies in Drupal 7?  If no feature currently exists, what are some decent PHP diff libraries that could be wrapped up by a Drupal module that could do the job? I was reasonably certain I've seen this before, but I was wondering how to solve the Diophantine equation  $$a^2+b^2=c^2+d^2$$  I tried a web search and found nothing on this one.  I'm trying to avoid another library trip to a less than local library (maybe I should have taken better notes on that chapter...).  I'm not quite sure how to handle this one.  The only thing I can figure out with this equation, if I remember correctly, is that the sum on either side may only contain prime factors of 2 or odd primes congruent to 1 mod 4.  And if I don't want a and b equal to c and d, the sum can't be prime as I believe a prime congruent to 1 mod 4 can be represented as the sum of 2 squares in exactly one way.  But that doesn't give me any insight into actually solving this problem.