What Is The Fastest We Have Seen Wally West Travel?
Can the Flash run faster than light?
Find the infinite sum $\sum_{k=1}^{\infty}\sqrt k - 2\sqrt {k + 1} + \sqrt {k + 2} $ I am facing a problem, where I have to find the partial sum of a sequence/sum and with that, the infinite sum of the sequence.  $\sum_{k=1}^{\infty}\sqrt k - 2\sqrt {k + 1} + \sqrt {k + 2} $   The problem here is that I don't know how to proceed. I would be thankful if someone would steer me in the right direction. I'm trying to install bang and olufsen drivers, or HP hd audio driver, as only 2 of the 4 speakers work and the 2 amps don't work in ubuntu  lspci -v | grep -i audio 00:03.0 Audio device: Intel Corporation Broadwell-U Audio Controller (rev 09)     Subsystem: Hewlett-Packard Company Broadwell-U Audio Controller 00:1b.0 Audio device: Intel Corporation Wildcat Point-LP High Definition Audio Controller (rev 03)     Subsystem: Hewlett-Packard Company Wildcat Point-LP High Definition Audio Controller   The volume is terrible. Is there any way to fix this?  The speakers work perfectly on the pre-installed Windows 8. Why does an atom remain uncharged after emission of an alpha particle? When an alpha particle is emitted, two protons and two neutrons leave the nucleus but the electrons remain the same in number. Why does the atom remain uncharged although it appears it should have a net charge of $-2e$? This is from page 3 of  ().  Copying the relevant segment:     Stirling’s approximation tells us $\sqrt{2\pi n} (n/e)^n \leq n! \leq e^{1/12n} \sqrt{2\pi n} (n/e)^n$. In particular we can use this to say that   $$ {n \choose k} \leq \left(\frac{en}{ k}\right)^k$$   I tried the tactic of combining bounds from $n!$, $k!$ and $(n-k)!$ and it didn't work. How does this bound follow from stirling's approximation? Why is it important to apply transformation to an objects data? A relative of mine has received a multiple-entry UK visa for 2 years. Is there a particular limit on how many months in total per year she can stay in UK? The way I understand the current rule is that such visitors can enter UK as many times as they want as long as they do not stay for longer than 6 months per single visit. However, does this mean that if she stayed with us for 5 months and went back home for 1-2 months, she could come and stay for another 5 months? I heard that it is advisable to spend only 180 day per calendar year in UK and not more, but I could not find that rule in any official UK Home Office documents. Thanks in advance for any info about this. I have a question about XTP_CHECKPOINT.  I'm using SQL Server 2014. I have a database that is in SIMPLE recovery model mode. It is also being replicated.  There are no open transactions. I've run DBCC OPENTRAN and it returns:     "No active open transactions."   But I keep getting this message whenever I try to create or drop a table or delete data: (I've replaced my actual database name with the word database_name)     "The transaction log for database 'database_name' is full due to 'XTP_CHECKPOINT'"     Does anyone know why this might be happening, and, more importantly, how can I make it stop?  And yes, the database really is in SIMPLE recovery model mode. i.e. The transaction log should truncate automatically.  Incidentally, another database that I have in full recovery mode did the same thing, started returning the same error:     The transaction log for database 'database_name' is full due to 'XTP_CHECKPOINT'   I tried to change the log growth settings to unlimited growth, but it wouldn't let me, returning the same error.  I can reproduce the problem without any XTP stuff at all, except for just the filegroup. Here's how: How to create a color of the same brightness and saturation? Let's consider three colors: Red, Green and Blue. For blue I created a specific shade, something like #F2F5F7. If you see this color, it has a certain level of shade, brightness and saturation value of blue.  I want to create the same equivalent color but for Green and Red, how to get that? What's the best way to communicate between view controllers? Being new to objective-c, cocoa, and iPhone dev in general, I have a strong desire to get the most out of the language and the frameworks.  One of the resources I'm using is Stanford's CS193P class notes that they have left on the web.  It includes lecture notes, assignments and sample code, and since the course was given by Apple dev's, I definitely consider it to be "from the horse's mouth".  Class Website:   Lecture 08 is related to an assignment to build a UINavigationController based app that has multiple UIViewControllers pushed onto the UINavigationController stack.  That's how the UINavigationController works.  That's logical.  However, there are some stern warnings in the slide about communicating between your UIViewControllers.  I'm going to quote from this serious of slides:   Page 16/51:     How Not To Share Data         Global Variables or singletons         This includes your application delegate      Direct dependencies make your code less reusable         And more difficult to debug &amp; test         Ok.  I'm down with that.  Don't blindly toss all your methods that will be used for communicating between the viewcontroller into your app delegate and reference the viewcontroller instances in the app delegate methods.  Fair 'nuff.  A bit further on, we get this slide telling us what we should do.  Page 18/51:     Best Practices for Data Flow         Figure out exactly what needs to be communicated   Define input parameters for your view controller   For communicating back up the hierarchy, use loose coupling         Define a generic interface for observers (like delegation)         This slide is then followed by what appears to be a place holder slide where the lecturer then apparently demonstrates the best practices using an example with the UIImagePickerController.  I wish the videos were available! :(  Ok, so... I'm afraid my objc-fu is not so strong.  I'm also a bit confused by the final line in the above quote.  I've been doing my fair share of googling about this and I found what appears to be a decent article talking about the various methods of Observing/Notification techniques:   Method #5 even indicates delegates as an method!  Except.... objects can only set one delegate at a time.  So when I have multiple viewcontroller communication, what am I to do?  Ok, that's the set up gang.  I know I can easily do my communication methods in the app delegate by reference's the multiple viewcontroller instances in my appdelegate but I want to do this sort of thing the right way.  Please help me "do the right thing" by answering the following questions:   When I am trying to push a new viewcontroller on the UINavigationController stack, who should be doing this push.  Which class/file in my code is the correct place? When I want to affect some piece of data (value of an iVar) in one of my UIViewControllers when I am in a different UIViewController, what is the "right" way to do this? Give that we can only have one delegate set at a time in an object, what would the implementation look like for when the lecturer says "Define a generic interface for observers (like delegation)".  A pseudocode example would be awfully helpful here if possible. An $n \times n$ matrix $M$ of integers has the property that $M_{ab} = M_{xy}$ iff $a+b=x+y$. How many distinct elements are there in $M$? Can regular expressions be used to match nested patterns? Is it possible to write a regular expression that matches a nested pattern that occurs an unknown number of times? For example, can a regular expression match an opening and closing brace when there are an unknown number of open/close braces nested within the outer braces?  For example:  public MyMethod() {   if (test)   {     // More { }   }    // More { } } // End   Should match:  {   if (test)   {     // More { }   }    // More { } } Why should we care about groups at all? If a spell is cast on a moveable creature/object and lasts longer than a round, and the creature/object moves, does the spell move with it? Is there any point of using "return !0" in javascript? How to iterate through the name of files in a folder Assume I have many TeX files. For the sake of simplicity, also asssume they are in a single folder or directory.  I want to input all files from within my main LaTeX document. Actually I can create a list of those files using C# in advance.  To enrich my view about LaTeX or TeX, could you tell me whether or not this job can be done only by using pure TeX or LaTeX? How do I access my Windows partition? I have Ubuntu 12.04 installed on my HP G62-453 TU Laptop. I cannot access the contents of my hard disk partition E. What can I do when getting “This question body does not meet our quality standards”? While trying to ask a question, I got the error message     This question body does not meet our quality standards. Please make sure that it completely describes your problem - including what you have already tried - and is written using proper grammar.    Why am I getting this message? What can I do to get the system to accept my question? Can you be more specific? What are good resources on how to ask high-quality questions?      For more information, see  in the . How to display Toast in Android? Macrons appear really wide on all characters, but especially so on the i. Is it possible to make them less wide?  \documentclass{article} \begin{document} Tac\=e, M\=arc\=o, \=unus, f\=\i li\=\i? \end{document} My question might appear the same as the question , but actually I did read all the answers and none of them helped me with the details I need.  I am new to cryptography and my problem is with two time pad attacks on OTP. The problem I had in my course was that I have 10 ciphertexts encrypted with the same key $K$. I am then given another ciphertext that I should decrypt.  I know that XOR-ing two ciphers gives me the XOR of their original messages.  My question is what is the correct thing to do after that?  I tried to take 3 ciphertexts $C_1, C_2$ and $C_3$.  Then get $S_1 = C_1 \oplus C_2  \oplus $' ', also get $S_2 = C_1 \oplus C_3 \oplus$ ' '.  After that I compared all corresponding characters in $S_1$ and $S_2$,  and if $S_1[i] = S_2[i]$ then I calculate $S_1[i] \oplus C_2[i]$ to get $K[i]$.  I tried this on paper before coding and it worked, but I might be missing something.  Is this the right approach? Why does it work?