ReCaptcha gets worse and worse. Often I need to solve 12 image puzzles before ReCaptcha acknowledges me as a human.  There are a lot of nice CAPTCHA solutions are out there, most self-hosted (which allows for nice data protection as well). Choose any reasonable one except ReCaptcha.  In the  near future, ReCaptcha will lock out many users anyway, see  In an informal survey, people noticed that there are many different browser combinations, which are just untrusted for Google. They seem to get a lot of ReCaptcha v2 image puzzles (what do you deem acceptable? I think 12 is way too many) and just fail v3.  So please use a different CAPTCHA. Possibly just one with old-style garbled text, which is generated serverside. Hosting your own CAPTCHA isn't too complicated, complies with data retention laws (especially GDPR), and allows setting a reasonable threshold instead of just accepting what Google thinks how many you need to solve today.  Here is the

I, like most SE users, am occasionally presented with a CAPTCHA to prove I'm human for one of any number of reasons. At the time of this writing there are  and  on Meta regarding CAPTCHAs and such questions often appear on the Community Bulletin (one appeared today which is what prompted this request). If I could search by emotion, I'm guessing the majority would be tagged .  On Monday, Google announced that  they have developed can solve reCAPTCHA with a 99.8% success rate. Searching around for  indicating human solve success rate all indicate percentages less than that (for audio CAPTCHAs much less than that). This is no longer a valid method for determining if a user is human.  The  to the highest rated Meta question on CAPTCHAs indicated that the SE staff were "heavily discussing this issue" and "agree that the current state of affairs sucks big-time" back in August 2012. Considering the advancement of a computer's ability to solve CAPTCHAs since then, I think it's about time for an alternative.  I'm not claiming to have a definitive answer but suggestions are, of course, welcome.  And I understand that polishing the meta split is probably priority right now, but can we at least get this on the docket?


This is my object:   As you can see, the right side has a weird protrusion, and where the project meets the mirror, it seems to kind of go up rather than remain flat.

I am currently trying to develop my modeling skills, and following a tutorial found on YouTube. The tutorial teaches how to create an anvil. At 19:10 or so into the video, a subdivision surface modifier is used to create a smooth, soft look.  However, when I do the same, mine looks very sharp and generally bad.  Any ideas why? I will include the blend file below, I appreciate your time and suggestions.    This is his when he subdivides, which is very different from mine when I do the same at the same settings. (I cannot post more pictures because I am new, but if you check the blend file I attached, you should be able to see the difference.   This is what it looks like when I subsurf without the base face.


Questions  are fairly common.  New users sign up, treat Stack Overflow like a forum, and wind up with a suspended account.  They then post here for help, and a moderator ends up writing the same explanation that was written the last time this came up.  Can we do a better job about warning users that their behavior is starting them on the path toward ?  After, say, their first two posts are flagged and deleted can we throw up a red warning banner at the top, linking to a page describing what kinds of posts are acceptable (and unacceptable) here, and warning that they're on the verge of being suspended?    Similar to   and probably a duplicate of

Another "miséricorde":  Consider  (emphasis added):  I think its okay, please dont take any efforts for me. I personally do not feel the system helps ask good questions. I dont know why asking for a software in this case is bad. Basically I needed a command that would give me this data. There is no other way I could have asked the question. I could have changed the question just for the sake of changing. I feel I am better off elsewhere. Thanks for your very very prompt responses. Regards. Bye. – user1744649  We just lost another user due to inadequate guidance on what questions are allowed.  The  by the time they are banned has been proven incorrect. Given that , we need a better way to make sure that users can understand how to ask good questions and what types of questions are allowed. I suggest that we warn newcomers, in a clear but positive tone, when one of their questions has been closed, downvoted (to a score of -2 or lower), or deleted, so that they don't repeat the same mistake.  This is probably best done the next time the user asks a question, and should appear as an "interstitial" page prior to reaching the actual Ask Question form.  The page should not appear to users:  with at least 50 (or perhaps 75 or 100) reputation that have asked a good question since the last downvoted/closed/deleted question that have fixed a bad question and had it reopened/undeleted/upvoted.  The content of the page should be adapted based on the specific problem with the previous question.  I would imagine something similar to the following (example for a question closed as off topic on Super User):  Before you ask another question... One or more of your previous questions have been closed as off topic. The scope of on-topic questions is defined in the , as follows:  What kind of questions can I ask here? Super User is for computer enthusiasts and power users. If you have a question about …  computer hardware, computer software, or personal and home computer networking  and it is not about …  programming and software development, video games or consoles, websites or web services like Facebook, Twitter, and WordPress, electronic devices, media players, cell phones or smart phones, except insofar as they interface with your computer, issues specific to corporate IT support and networks, asking for a shopping or product recommendation,  … then you’re in the right place to ask your question!  Please make sure that the question you are about to ask is on topic as described above. If you need help determining whether your question can be asked on this site, you can ask for advice on  or . You may also want to edit your previous question to address any problems associated with it. To ensure a high standard of content quality and prevent disruption to the community, users who repeatedly post low-quality questions  Continue  The  doesn't address this issue as it is shown only to users with 10 reputation or less (rather than up to 50 and possibly higher) and does not address the specific problem with previous low-quality questions.  The point of this feature request is to provide a easily understood targeted message that actually teaches the user about what happened with the previous question he or she asked.  The EULA is generic and may not have conveyed the intended message clearly if the user still asked a low-quality or off-topic question. For reference,  currently has 143 reputation and the proposed message would probably have been shown after the first closed or deleted question. I know this can be a complex feature to implement, since it needs to be adaptive, but this should help eliminate confusion on what the rules are and minimize the incidence of good-faith users getting post-banned.


While working on a homework assignment, I came across an interesting dilemma that I want to delve more into. The question essentially said to flip the first bit in the key string and then see what S boxes it will effect. Then it says to do the same for decryption.   I went through the process of doing this encryption and then decryption and found that each process is the exact opposite. This makes sense logically but I feel like that is not as... secure? Would the S boxes be the exact same in the decryption phase as in the encryption phase just in reverse? Wouldn't there be a way to sense the pattern here? I know DES is not the most secure system anyway but this seems even more unsecured? I'm just a bit confused on how the math from encryption to decryption works. Clearly it isn't linear but it seems like it?

If DES decryption is the same as encryption done in reverse order, then how can the reversed S-Box convert 4 bits into 6 bits?


I'm looking for information on a German POW based taken to a camp in England during WW2. His name was Karl Weber I believe at some point he was based in Nuneaton. He could speak English and was the 'go between' at the camp. He was a talented artist and sculptor and there is still a sculpture of his in England. He had a very good friendship with my grandmother who was a WAAF nurse. And he drew an amazing portrait of her which I have hanging in my house. I would really like to know what happened to him after the war. I cannot find him on Ancestry or Findmypast.   Does anyone know where else I could look?

Where can I find information on German soldiers from World War I and World War II?   I am curious to find out about my ancestors' role in the wars, i.e. what rank they had, where they where fighting, with whom and anything else.


This probably has a very simple answer of some sort, but I'm not a mathematician. For the hyperoperation sequence: $$G(n,a,b)$$ ...there are obvious defined values for positive integer values of $n$ $$G(1,a,b)=a+b$$ $$G(2,a,b)=a \cdot b$$ $$G(3,a,b)=a^b$$  My question is, how to account for non-integer values of $n$, such as: $$G(2.5,a,b)=???$$

I noticed this  which attempts to find the shades of grey between a linear and log scale where results are between zero and one.  However, I was looking for the more general case where we find the continuum between the operators themselves - add, multiply, and exponentiation or even higher.  The function could be a hyperoperation$(n,x,y)$, where $x$ and $y$ are the numbers to operate on, and $n$ is allowed to be a non-integer number for the type of operator. So $n=1$ would be 'addition', $n=2$ would be multiplication, and $n=3$ would be exponentiation. But one would also have $n=2.5$ to be the shade of grey BETWEEN multiplication and exponentiation, or $n=3.5$ or $4$ for beyond exponentiation and tetration).  I want the formula to work with real numbers, not just integers. Any thoughts?  These related posts may also be of interest:


Prove that solution of the equation $8x^3-4x^2-4x+1= 0$ has roots $\cos\frac{\pi}{7},\cos\frac{3 \pi}{7}\space \text{and}\space \cos\frac{5 \pi}{7}$.    How to even solve it ? I have no idea.   Because cubic have no formula like quadratic equations to obtain the roots and the expression like $\cos\frac{\pi}{7}$ is something that I don't think I can evaluate with my limited knowledge (I'm in highschool) of only $\cos 2x$ or $\cos 3x$ type. Since it has denominator of 7, I thought maybe the seventh root of unity might help me, but since only some of its multiples are used, I don't think so it will be of much use.   How do I solve this problem. Please help.

Prove that $\cos\theta$ is root of equation $8x^3-4x^2-4x+1=0$, given $\theta=\frac{\pi}{7}$.   I put $\cos\theta$ in equation, but couldn't show the left-hand side to be zero.


Is this the correct order in a list of adjectives in a sentence?:  1.Quantity or number  2.Quality or opinion  3.Size  4.Age  5.Shape  6.Color  7.Proper adjective (often nationality, other place of origin, or material)  8.Purpose or qualifier  Example: I have 1 cheap little old white american sleeping mattress.  Is it the same thing if we use adjectival nouns(nouns which occupy the function of an adjective when there are 2 nouns in a row)?. Here are some examples:     a race horse is a horse that runs in races   a horse race is a race for horses   a boat race is a race for boats    a love story is a story about love   a war story is a story about war   a tennis ball is a ball for playing tennis   tennis shoes are shoes for playing tennis    a computer exhibition is an exhibition of computers

She is a well-developed, tall, young woman. She is a tall, young, well-developed woman.   In the sentences, which order of adjectives is correct? I'd like to know the rule for placing various adjectives.


define("WEBMASTER_EMAIL","");
  $from_Email = "garglawfirm@gmail.com";
   //send email to the client...  $subject = "Trademark Registration Request";
 $message = "Hi ".$client_applicantName.",
   Your request for Trademark Registration has been received. We will Proceed it!..  Your Request Id is: ".$lastInserId." and Applicant Type is: ".$client_applicantType." Sent by Garg Law Firm";                  $send = @mail(WEBMASTER_EMAIL, $subject, $message,        "To: ".$client_applicantEmail."\r\n"       ."From: ".$from_Email."\r\n"       ."Return-path: ".$client_applicantEmail."\r\n"       ."MIME-Version: 1.0\r\n"       ."Content-type: text/html; charset=iso-8859-1\r\n");
 if($send){
        echo "";
           }else{
           echo "";
       }

This is a tricky one and I've always relied on techniques, such as permission-based emails (i.e. only sending to people you have permission to send to) and not using blatantly spamish terminology.  Of late, some of the emails I send out programmatically have started being shuffled into people's spam folder automatically and I'm wondering what I can do about it.  This is despite the fact that these particular emails are not ones that humans would mark as spam, specifically, they are emails that contain license keys that people have paid good money for, so I don't think they're going to consider them spam  I figure this is a big topic in which I am essentially an ignorant simpleton.


From Xanathar's:  Slayer's Prey Starting at 3rd level, you can focus your ire on one foe, increasing the harm you inflict on it. As a bonus action, you designate one creature you can see within 60 feet of you as the target of this feature. The first time each turn that you hit that target with a weapon attack, it takes an extra 1d6 damage from the weapon.  It says you that the first time each turn that you hit THAT target you deal 1d6, so, that being said, can you:  Turn 1: Mark a creature with Slayer Prey Turn 2: Hit the creature with Slayer Prey, gaining the 1d6 bonus damage, designate another creature with Slayers Prey and gain the 1d6 bonus damage again?  My thoughts are: You are hiting the secord creature for the first time in this turn, so this should work, right?

In the recent book Xanathar's Guide to Everything, there are some subclasses/archetypes added for Rangers, among them the  (p. 43), which gives some specific helpful features. Hunter's Sense  At 3rd level, you gain the ability to peer at a creature and magically discern how best to hurt it. As an action, choose one creature you can see within 60 feet of you. You immediately learn whether the creature has any damage immunities, resistances, or vulnerabilities and what they are. If the creature is hidden from divination magic, you sense that it has no damage immunities, resistances, or vulnerabilities. You can use this feature a number of times equal to your Wisdom modifier (minimum of once). You regain all expended uses of it when you finish a long rest.  The limitations on use are clearly spelled out. Slayer's Prey  Starting at 3rd level, you can focus your ire on one foe, increasing the harm you inflict on it. As a bonus action, you designate one creature you can see within 60 feet of you as the target of this feature. The first time each turn that you hit that target with a weapon attack, it takes an extra 1d6 damage from the weapon. This benefit lasts until you finish a short or long rest. It ends early if you designate a different creature.  So from this, I would interpret it as it being able to switch from creature to creature at will, but there is no guidance as to what happens if the creature under the mark dies, or if you can carry it (so to speak) from encounter to encounter. Is there a limitation on the use of Slayer's Prey in the wording that I am missing? Or is this a basically a multiple use feature? (i.e., you can designate any creature as a bonus action, with no limitations on uses per day)? The extra d6 seems a little overpowering at lower levels, and somewhat meh at higher levels. FWIW, the GM basically allowed it as multi-use for the session, and was going to also try to find clarification.


I am on my first LaTeX homework using winedt. I have just written my hello world code and saved it properly. Now I am wondering which compiling button is the right one to build a PDF file among the five buttons PDFTeXify, PDFLaTeX, PDFTeX, TeXify and LaTeX buttons. How can I differ them?

I am confused about what TeX and its offspring (LaTeX, pdfTeX/pdfLaTeX, e-TeX, ConTeXt, LuaTeX, etc.) are.  Some, like LaTeX, seem like add ons to TeX (maybe a change to the eyes and mouth, but not stomach). Others, like pdfTeX, seem like changes to the underlying system (i.e., a change to the stomach).  Is there a good reference that explains the differences and the evolution?


Is there currently any way to change the path that a camera is following during an animation? I'd like to be able to snap the camera to a new path at a set frame after it finishes following the first path. Is this possible, or do I have to make a new camera entirely?

I currently use a Track to Constraint to make the camera automatically point to an empty.   In an animation the camera is moved along a bezier curve (follow path).   How could I change the curve and track to constraint at a certain frame to focus on another aspects of the scene?


How can i connect to my desktop version of linux from windows, i need graphic mode ?

I need to access one of my school Linux servers from my home computer that runs Windows. And I need to access graphical desktop (X server) on them remotely, not only shell.  The problem includes 3 Linux servers with different settings. I don't have admin privileges on any of them and cannot change those settings. The 3 servers are called Aisa, Lethe and Aura (somebody loves Greek mythology here). All of them are part of school's local network.  I need to access graphical interface on either Lethe or Aura, any of them would be fine.  Here is what I have found out:   ports for services like VPN are not available on any of the 3 SSH is allowed on Lethe and Aisa, not on Aura. I can still access Aura when I SSH to Aisa or Lethe using Putty and then ssh aura. I have tried  that allows graphical connection from windows to Linux via SSH. I was only able to connect to Aisa this way (why not to Lethe?! Putty works there).   So what can I try to get graphical connection to either Lethe or Aura from my Windows computer? Any suggestions are very much welcome.  edit Here is the code showing how I get disconnected from Aura back to Aisa after running vncserver:  aisa:/home/user>$ ssh aura Last login: Sat Oct 13 00:00:00 2012 from aisa.domain.com aura:/home/user>$ module add vnc aura:/home/user>$ vncserver  New 'aura.domain.com:1 (user)' desktop is aura.domain.com:1  Starting applications specified in /home/user/.vnc/xstartup Log file is /home/user/.vnc/aura.domain.com:1.log  aura:/home/user>$ Connection to aura closed by remote host. Connection to aura closed. aisa:/home/user>$    edit 2 Content of file /home/user/.vnc/aura.domain.com:1.log after executing command vncserver:  aura:/home/user>$ cat /home/user/.vnc/aura.domain.com:1.log /packages/run/vnc-4.1.2/Xvnc: error while loading shared libraries: libstdc++.so.6: cannot open shared object file: No such file or directory /home/user/.vnc/xstartup: line 4: xsetroot: command not found /home/user/.xsession: line 15: xset: command not found vncconfig: unable to open display "aura.domain.com:1" /home/user/.xsession: line 42: xmodmap: command not found Module xv Module modules Module viewers Module WindowMaker-0.80.2 Module mozilla ModuleCmd_Load.c(199):ERROR:105: Unable to locate a modulefile for 'mozilla' stty: standard input: For this device invalid ioctl wmaker: error while loading shared libraries: libtiff.so.3: cannot open shared object file: No such file or directory   Note: I have translated some strings that were displayed in czech (Aura is running czech version of Red Hat)


(It's hard for me to summarize the problem precisely with the title...) The harmonic series $\sum_{i=1}^{\infty}\frac{1}{n}$ is not convergent as we all know. Now I partition the series into 2 series, one consisted of denominators containing digit 9 in decimal form and the other consisted of the rest entries, as follows: $$ \sum{b_n}=\frac{1}{9}+\frac{1}{19}+\frac{1}{29}+\cdots +\frac{1}{90}+\frac{1}{91}+\cdots +\frac{1}{99}+\frac{1}{109}+\frac{1}{119}+\cdots , $$ $$ \sum{c_n}=1+\frac{1}{2}+\cdots +\frac{1}{8}+\frac{1}{10}+\cdots +\frac{1}{88}+\frac{1}{100}+\cdots  $$ I need to prove that $\sum b_n$ is not convergent while $\sum c_n$ is. I've merely got an intuitive idea: As the number of digits of denominator increases, the digit-9-contained denominators appear more frequently and the digit-9-not-contained denominators appear less frequently. To show this, one only need to consider the probability of a digit-9-not-contained denominator of n-digit, approximately $(\frac{9}{10})^n$, which goes to $0$ when $n$ goes to infinity. However, this is only a rough and intuitive idea and I don't know how to prove it in a quantitative and rigid manner. Any help would be aprreciated!

I know that the harmonic series $1 + \frac12 + \frac13 + \frac14 + \cdots$ diverges. I also know that the sum of the inverse of prime numbers $\frac12 + \frac13 + \frac15 + \frac17 + \frac1{11} + \cdots$ diverges too, even if really slowly since it's $O(\log \log n)$.  But I think I read that if we consider the numbers whose decimal representation does not have a certain digit (say, 7) and sum the inverse of these numbers, the sum is finite (usually between 19 and 20, it depends from the missing digit). Does anybody know the result, and some way to prove that the sum is finite?


The question is short and simple.  Say I use i.e. in my formal publication. Which is correct?     ... by the interior landmarks, i.e. elevators and escalators.   Or     ... by the interior landmarks, i.e., elevators and escalators.   What about e.g.? Is it always followed by a ,?

If I remember correctly from English class, then one should put a comma after "i.e.", i.e., the Latin abbreviation for id est.  But lately I've seen the comma after "i.e." dropped in books. So what is the rule or consensus here if any?


After the fight in Dwarvish ruins (Moria), Gandalf the grey fell and:      rose as Gandalf the white.   What is the backstory of white wizards and grey ones?  Is there a order of wizards in this universe? What factors decide that the status of one wizard is to be elevated to a different color e.g. from Grey to white?  I'm new to LOTR universe so this may come across as a basic question.

In the first book of the LoTR, after his fight with the Balrog of Moria, Gandalf the Grey changed to .   My question is, who made the decision to 'promote' him from grey to white? Was it ? Or was it the ? Or was it the ?


How can I raise all open windows of one application?  Raising one window of an application one at a time is very slow in intuitive. Any short cuts?

I have an application using multiple windows. How can I quickly bring all the windows of that application to the foreground?   When I scroll through the applications with the scroll-wheel it only shows one window. When going to the next window, the last window is brought to the background again.  When I click on the application icon, I get a full-screen overview of all the windows. I have to select each window manually and move my mouse across half the screen several times.  My best solution so far is minimizing all windows (Ctrl+Super+D) and then show the windows of my application using the scroll-wheel.  Is there a better solution?


Given two integers $x$ and $y$,  Is $\gcd(x,y)=1$ equivalent to $ p \not \mid x $ for EVERY prime divisor of $y$  the actual question is to find all  integers $k$ such that   $$\gcd(k+8,18)=1$$  thanks.

Let $a,b,n$ be integers such that  $\gcd(a,n)=\gcd(b,n)=1$. How to show that $\gcd(ab,n)=1$?   In other words, how to show that if two integers $a$ and $b$ each have no non-trivial common divisor with and integer $n$, then their product does no have a non-trivial common divisor with $n$ either.     This is a problem that is an exercise in my course.   Intuitively it seems plausible and it is easy to check in specific cases but how to  give an actual proof is not obvious.


I want to rotate a collection of objects (such as, say, two cubes) in blender python but without using bpy.ops.transform.rotate operation. How may I go about doing that? (Clarification: I am not trying to rotate them individually, but rather rotate both of the cubes around one point, just as the bpy.ops.transform.rotate would).

In order to optimize my script, I would need some help to perform a rotation around the cursor (see )  With low-level python, that means, without bpy.ops.* operations.  I have to admit that I didn't find a good overview on how to make rotation with python without bpy.ops. Do I have to perform matrix operations for a simple rotation around an axis Z located at the cursor position?


I seem to have trouble deciding whether or not to use 'a' or 'an' when followed by quantities:     Built (a/an) 120 lb. robot.   and     Built (a/an) 18"x 18"x 18" robot.     In terms of pronunciation, the first case could go like:     Built a one-hundred-and-twenty pound robot.   or, like:     Built an a-hundred-and-twenty pound robot.   Which would it be?

In the following example, is it appropriate to use a or an as the indefinite article, and why?     He ate __ green apple.   I know that in the case of just "apple", it would be "an apple," but I've heard conflicting answers for "green apple," where the noun is separated from the article by an adjective.  Also, which is more appropriate in this case:     He ate  __ enormous Pop-Tart.


Usually as said in most posts, about how tin/lead/tungsten etc. replace copper/iron/silver etc. My worlds continue to have a mix of both (Like Copper, Lead, Tungsten, Gold) and I have no guarantee on what world may have the original hardmode ores. Is there anyway for me to know? Is there any reason the original and new ores keep mixing?

The Terraria 1.2 update introduced  that make generated worlds varied not only in layout, but in availability of various features as well. What is the fastest way to get a world that has the features I need? Is there a program that can help goad Terraria to generate a world that fits my criteria, or perhaps a tool that will let me quickly tell if a generated world has the features I have in mind?


Most of the people seem pretty much content with classical electromagnetic theory .And most of the applications use classical EM theory .However, in such situations I would like to know what was the necessity of Quantum Electrodynamics. Is it an advanced version of classical EMT ? Does it remove any flaws in classical EMT ? Are there any practical applications of QED ?

Imagine you're teaching a first course on quantum mechanics in which your students are well-versed in classical mechanics, but have never seen any quantum before.  How would you motivate the subject and convince your students that in fact classical mechanics cannot explain the real world and that quantum mechanics, given your knowledge of classical mechanics, is the most obvious alternative to try?  If you sit down and think about it, the idea that the state of a system, instead of being specified by the finitely many particles' position and momentum, is now described by an element of some abstract (rigged) Hilbert space and that the observables correspond to self-adjoint operators on the space of states is not at all obvious.  Why should this be the case, or at least, why might we expect this to be the case?   Then there is the issue of measurement which is even more difficult to motivate.  In the usual formulation of quantum mechanics, we assume that, given a state $|\psi \rangle$ and an observable $A$, the probability of measuring a value between $a$ and $a+da$ is given by $|\langle a|\psi \rangle |^2da$ (and furthermore, if $a$ is not an eigenvalue of $A$, then the probability of measuring a value in this interval is $0$).  How would you convince your students that this had to be the case?  I have thought about this question of motivation for a couple of years now, and so far, the only answers I've come up with are incomplete, not entirely satisfactory, and seem to be much more non-trivial than I feel they should be.  So, what do you guys think?  Can you motivate the usual formulation of quantum mechanics using only classical mechanics and minimal appeal to experimental results?  Note that, at some point, you will have to make reference to experiment.  After all, this is the reason why we needed to develop quantum mechanics.  In principle, we could just say "The Born Rule is true because its experimentally verified.", but I find this particularly unsatisfying.  I think we can do better.  Thus, I would ask that when you do invoke the results of an experiment, you do so to only justify fundamental truths, by which I mean something that can not itself just be explained in terms of more theory.  You might say that my conjecture is that the Born Rule is not a fundamental truth in this sense, but can instead be explained by more fundamental theory, which itself is justified via experiment.  Edit:  To clarify, I will try to make use of a much simpler example.  In an ideal gas, if you fix the volume, then the temperature is proportional to pressure.  So we may ask "Why?".  You could say "Well, because experiment.", or alternatively you could say "It is a trivial corollary of the ideal gas law.".  If you choose the latter, you can then ask why that is true.  Once again, you can just say "Because experiment." or you could try to prove it using more fundamental physical truths (using the kinetic theory of gases, for example).  The objective, then, is to come up with the most fundamental physical truths, prove everything else we know in terms of those, and then verify the fundamental physical truths via experiment.  And in this particular case, the objective is to do this with quantum mechanics.


I did not understand what is meant by length of intercept? Isn't intercept the point where the line cuts the axis? How can a point have a length? The answer given for length of intercept is $8\sqrt { 2 } $

How to find the coordinates of the points A and B? If one gets that, then distance formula can be used to find the length.


In Unix, when exec  If Real user ID is not same with file owner, and Set user ID bit is on, then, effective user id is changed to file owner's, and saved set user ID too. Because Effective user ID is copied to Saved set user ID when exec.     At this moment, Why saved set userID is needed?   Because of security problem? if it is right, especially what case?

Real UID, effective UID, and some systems even have a "saved UID". What's the purpose of all these, especially the last one?


How would one prove the following:$$\left(1+\frac 1 n\right)^n < \left(1+\frac 1 {n+1}\right)^{n+1}$$  This is taken from the book challenge and thrill of precollege mathematics.

Show that $U_n:=\left(1+\dfrac{1}{n}\right)^n$, $n\in\Bbb N$, defines a monotonically increasing sequence.   I must show that $U_{n+1}-U_n\geq0$, i.e. $$\left(1+\dfrac{1}{n+1}\right)^{n+1}-\left(1+\dfrac{1}{n}\right)^n\geq0.$$  I am trying to go ahead of this step.


for start, let's define a class and instance of the class  class c:     @classmethod     def m(cls, a):         return a + 1 a = c()   those methods are used the same way  >>> c.m(5), a.m(5) 6, 6   and cls in both cases is c  but c.m is a.m is False and c.m == a.m is True  why is the class method called by instance and class not the same and why am I able to call it even by an instance of that class  it would make sense if cls were not the same in both cases  EDIT:  I already knew the difference between is and ==  I was already successfully using is to check if two classes are the same (type(a) is int for example), but I did learn I should use it for is None, so thanks anyway for leading me to that page  My question actually was why are they not the same object  they even have same ID id(a.m) == id(c.m)

My  has failed me.  In Python, are the following two tests for equality equivalent?  n = 5 # Test one. if n == 5:     print 'Yay!'  # Test two. if n is 5:     print 'Yay!'   Does this hold true for objects where you would be comparing instances (a list say)?  Okay, so this kind of answers my question:  L = [] L.append(1) if L == [1]:     print 'Yay!' # Holds true, but...  if L is [1]:     print 'Yay!' # Doesn't.   So == tests value where is tests to see if they are the same object?


So I'm using an IDataReader to hydrate some business objects, but I don't know at runtime exactly what fields will be in the reader.  Any fields that aren't in the reader would be left null on the resulting object.  How do you test if a reader contains a specific field without just wrapping it in a try/catch?

How do I check to see if a column exists in a SqlDataReader object?  In my data access layer, I have create a method that builds the same object for multiple stored procedures calls.  One of the stored procedures has an additional column that is not used by the other stored procedures.  I want to modified the method to accommodate for every scenario.  My application is written in C#.


She also winces and jumps when Harry uses his name.

Multiple times in the early series Hermione and other muggle-borns refer to Voldemort as you-know-who. Why would they be scared of saying the name? They didn't grow up with the fear, and Voldemort seemed to have been gone.


Simple question: I have this title "Past 10 Week Performance", and someone is telling me that it's supposed to be "Past 10 Weeks Performance". Which one is correct? My gut tells me it's the 1st one.

I need to request leave for one day and for more than one day.  What's the correct way of using the word day?  Which is correct for a single day of leave?        1 day's leave   1 day leave      What about more than one day?        2 day's leave   2 days' leave      Please clarify with explanation.


I am a Georgian citizen and living currently in Germany, possessing a German residence permit. Am I allowed to enter Romania for a few days? I know Romania is not in the Schengen area, but there are some confusing rules (for me) about Schengen visa holders. I would be grateful if anyone could give me a simple yes/no answer.

I am a student in Germany and i have a residence permit here for 2 years, which is also a Schengen visa, I suppose. Do I need a separate visa if i wish  to travel to Romania?


My compiler is not showing up any error whereas it does give a run time error can somebody can me whats wrong with the typecasting i did? Code shows error Exception in thread "main" java.lang.ClassCastException: class practice.Animal cannot be cast to class practice.Dog (practice.Animal and practice.Dog are in unnamed module of loader 'app'`)

Upcasting is allowed in Java, however downcasting gives a compile error.   The compile error can be removed by adding a cast but would anyway break at the runtime.   In this case why Java allows downcasting if it cannot be executed at the runtime? Is there any practical use for this concept?   public class demo {   public static void main(String a[]) {       B b = (B) new A(); // compiles with the cast,                           // but runtime exception - java.lang.ClassCastException   } }  class A {   public void draw() {     System.out.println("1");   }    public void draw1() {     System.out.println("2");   } }  class B extends A {   public void draw() {     System.out.println("3");   }   public void draw2() {     System.out.println("4");   } }


I am trying to "su/sudo" command to switch to a regular user. It asks me password and I enter admin password then it says su: Authentication failure. How can I switch to regular user, what is the problem?  walter@walter-VirtualBox:~/testdir$ su Password:  su: Authentication failure walter@walter-VirtualBox:~/testdir$

I am having problems with the su command. I know my password and I am typing it correctly but su indicates authentication failure.  So I checked on the internet and then went into recovery mode and changed my username's password to what I was entering before.  Even now entering the same password on su gives me authentication failure.  Please suggest what am I doing wrong??


when i try to open any partion i find this error   Error mounting /dev/sda5 at /media/mano/upnto: Command-line `mount -t "ntfs" -o "uhelper=udisks2,nodev,nosuid,uid=1000,gid=1000" "/dev/sda5" "/media/mano/upnto"' exited with non-zero exit status 14: The disk contains an unclean file system (0, 0). Metadata kept in Windows cache, refused to mount. Failed to mount '/dev/sda5': Operation not permitted The NTFS partition is in an unsafe state. Please resume and shutdown Windows fully (no hibernation or fast restarting), or mount the volume read-only with the 'ro' mount option.   but  when i try to mount it i get this error   mount: special device /dev/sda5 does not exist

Whenever I boot Ubuntu, I get a message that it cannot mount my windows partition, and I can choose to either wait, skip or manually mount.  When I try to enter my Windows partition through Nautilus I get a message saying that this partition is hibernated and that I need to enter the file system and properly close it, something I have done with no problem so I don't know why this happens.    Here's my partition table, if any more data is needed please let me know.     Device Boot      Start         End      Blocks   Id  System /dev/sda1            2048    20000767     9999360   83  Linux /dev/sda2        20002814   478001151   228999169    5  Extended /dev/sda3   *   478001152   622532607    72265728    7  HPFS/NTFS/exFAT /dev/sda4       622532608   625141759     1304576   82  Linux swap / Solaris /dev/sda5        20002816   478001151   228999168   83  Linux


Once other reason I was tempted to set up this account when I saw my bro was having multiple Christmas Hats to show off...  Aren't there any of those this year?

Last year's Winter Bash looked like a success from my point of view. Any info on what we are getting for Christmas this year ?


it can be demonstrated by elementary means that the curves $y=\cos x$ and $y=x$ meet exactly once, at a value $x=\alpha$ satisfying: $$\cos \alpha = \alpha$$ it is also evident (empirically) that simple reiterated pressing of the cosine button on a calculator produces a sequence that seems to converge at a steady, modest pace, from any initial real value to $0.73908\dots$.   however for some time I have fiddled about ineffectually attempting to prove this convergence. this is interesting from a psychological point of view -  because I believed the problem was just beyond my reach, I failed to spot a fairly simple proof-idea, which requires no more than high-school calculus and trigonometry.   or at least that is my present thought! the following proof-idea seems OK, though i haven't dotted every i and crossed every t, and since I know myself to be error-prone, I would appreciate it if someone more experienced could check the argument, and remedy any deficiencies - or at worst detect some fundamental flaw I haven't noticed.  I am uncertain how to finish off, and also about how to properly manage the role of $\delta$ - in fact the convergence, though not rapid, seems very robust with regard to initial values.  thank you   firstly, since we know the number $\alpha$ exists, this simplifies the demonstration. it suffices to show that:  $$\exists \delta,\lambda \in (0,1) .  \forall x \in \mathbb{R}.|x-\alpha| \lt \delta \rightarrow  |\cos x - \alpha| \lt \lambda |x-\alpha|$$  set $\beta=\sin \alpha = \sqrt{1-\alpha^2}$ and let $x=\alpha +\epsilon$. then: $$ |x-\alpha| = |\epsilon| $$ and $$\cos x = \cos \alpha \cos \epsilon - \sin \alpha \sin \epsilon = \alpha (1+O(\epsilon^2)) - \beta(\epsilon + O(\epsilon^3)) $$so: $$ |\cos x - \alpha| = \beta |\epsilon|+O(\epsilon^2)= (\beta +O(\epsilon))|\epsilon| $$ giving $$ |\cos x - \alpha| = (\beta +O(\epsilon))|x-\alpha| $$

In Radian mode, continually pressing the $\cos$ function of a number causes the result to converge to $x=0.739085133$, a fixed point of $\cos(x)$. Repeating this behavior with the $\sin$ function causes the result to converge to $x=0$, a fixed point of $\sin(x)$.   What happens if this is done using the tan function? It seems that $x=0$ is a repelling fixed point with no convergence in this case.  What would be the best way to explain these results mathematically?


When I attempt to start Ubuntu 14.04 in a VM I get this error (I have not started it before):  VT-x/AMD-V hardware acceleration is not available on this machine   What can I do?

So I am trying to run Ubuntu in a virtualbox but on installing 12.10 from the .iso I was greeted by a warning telling me that audio wouldn't work then I pressed next and this popped up:  Failed to open a session for the virtual machine Tux 3 VT-x features locked or unavailable in MSR (VERR_VMX_MSR_LOCKED_OR_DISABLED) Details  Result Code:  E_FAIL (0x80004005) Component:  Console Interface:  IConsole {db7ab4ca-2a3f-4183-9243-c1208da92392}   And then it doesn't work.  I assigned 4GB of my 8GB to Ubuntu, 100 dynamically allocated GB of space, and 12MB of graphics memory. I'm running an Asus p8z77 V LX mobo with an Intel i5 3550 processor.   Downloaded 12.04.2 on my PC and tried again. Still getting the same message.


How can I create a CanDestroy tag in such a way that only Cracked Stone Bricks can be destroyed. Im on Bedrock 1.16 for ps4. The code is this: /give @p stone_pickaxe 1 0 {"Minecraft:can_destroy":["blocks":["98:2"]}} Either the answer or the item id (the thing needed) for cracked stone bricks would help. Thanks in advance Edit: People have been suggesting  The question there asks how to add nbt data such as lore or enchantments. This is different from what I'm asking. Im asking how to make a pickaxe that can only destroy a certain block which has data value. The reason the data value is important is because in bedrock stonebrick has 4 options: 0 - normal, 1 - mossy, 2 - cracked and 3 - Chisled. I'm asking how to add a data value of 2 to the block id  in the CanDestroy tag TLDR: How to add data value to blocks inside a CanDestroy Tag.

This question was recently split into different questions for each workaround. See   meta posts for more information.   Can you use NBT tags in commands? I’ve tried commands that normally work in Java Edition like: give @s minecraft:planks 30 1 {display:{Lore:["Wooden planks"]}} give @s stone_pickaxe{Unbreakable:1b} give @s item_frame{EntityTag:{Invisible:1b}} summon villager ~ ~ ~ {Offers:{Recipes:[{buy:{id:"emerald",Count:5b},sell:{id:"diamond_sword"}}]}} summon tnt ~ ~ ~ {Fuse:20s}


Is linux free from almost all security vulnerabilities when compared with windows? If there are so, can i install any patches to fix them? Thanks in advance.

Is it possible for my Linux box to become infected with a malware?  I haven't heard of it happening to anyone I know, and I've heard quite a few times that it isn't possible. Is that true?  If so, what's up with Linux Anti-Virus (security) software?


I need to prove that the Lindenbaum-Tarski algebra is dense in the sense that: if     $ [\phi] \leqslant [\psi] $ then there is an $\chi $ such that  $ [\phi] \leqslant [\chi] $ and $[\chi] \leqslant [\psi]  $ I know this is only true if there are infinite  sentential letters. I started by writting that If $ \psi= p_0p_1..p_n \space \space  \psi=q_0q_1...q_m$   then $ \chi= \psi \land q $  for some propositional variable q  that does not appear  $ \psi $ satisfies that $ [\chi ] \leqslant [\psi]  $ that is, by definition,  $  \chi \models \psi $. But i still have to proof that  $  [\phi] \leqslant [\chi] $ I guess it has something to do with the initial  hypotesis   $ [\phi] \leqslant [\psi] $  but i can not find out how.

Suppose we define the following relationship of ordering between propositions in PROP: $$ \phi < \psi := (\models \phi \rightarrow \psi \land \lnot(\models \psi \rightarrow \phi) ) $$ Show that if exists $\phi$ and $\psi$ such that: $$ \phi < \psi $$ Then there is a $\sigma$ such that: $$ \phi < \sigma < \psi $$ I have tried to use valuation to find what $\sigma$ could possibly be, so for all valuations v:  If $v(\phi)=0$ and $v(\psi)=0$ then, since $\models \sigma \rightarrow \psi$, $v(\sigma)=0$  If $v(\phi)=1$ and $v(\psi)=1$ then, since $\models \phi \rightarrow \sigma$, $v(\sigma)=1$  It is impossible that $v(\phi)=1$ and $v(\psi)=0$ since $\models \phi \rightarrow \psi$  If $v(\phi)=1$ and $v(\psi)=0$ then $v(\sigma)$ could be either 0 or 1, and it would satisfy the tautologies, but if:  $v(\sigma)=0$, then the valuation of $\sigma$ would be equal to valuation of $\psi$ for all valuations and thus $\models \psi \rightarrow \sigma$, which is a contraditcion; $v(\sigma)=1$, then the valuation of $\sigma$ would be equal to valuation of $\phi$ for all valuations and thus $\models \sigma \rightarrow \phi$, which is a contraditcion.


I've created a function where all drop downs on the page with the class ".dropdown" do something when changed. However adding subsequent dropdowns dynamically do not trigger the event. How can I make the dynamic dropdowns trigger the change event?  $(".dropdown").change(function () {     //Do Something });

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


In Return of the Jedi, Luke and Leia steal an Imperial Speeder Bike to chase and stop some Imperial Scout Troopers. Almost immediately, Luke thinks to jam their comlinks and tells Leia to do so.  Why does the Imperial Speeder Bike have a one-flip switch capable of jamming their own comlinks?     LUKE   (pointing to the controls)   Quick! Jam their comlink. Center switch!

During the speeder bike chase in Return of the Jedi, Luke Skywaker instructs Leia to jam the communications of the Imperial Scout Troopers they are chasing/being chased by.   The jammer seems to be activated by a simple switch, which strikes as odd. Is communications jamming such a common function of a speeder bike such that it needs a prominent, easy to reach control?   The explanation I've come up with is that the Empire enforces control by preventing the general populace from spreading information quickly. Comms jammers are routinely installed in all Imperial vehicles and equipment, much like cameras and RFID technology come in a lot of electronic devices in our world.  So, does communication jamming technology appear a lot in Star Wars – both movies and extended universe? Does the theory hold up?


So I have a problem of   $$a_n = \left(1 + \frac{2}{n}\right)^n$$  I need to determine whether it is diverging or converging and find the limit if it is converging I found an answer on symbol lab of $e^2$ but I do not know how they got that type of answer

I was wondering if it is possible to get a link to a rigorous proof that  $$\displaystyle \lim_{n\to\infty} \left(1+\frac {x}{n}\right)^n=\exp x$$


Reading the libsodium  I see that is uses a key length of 32 bytes (256 bit) for private/public key encryption.  For RSA private/public key encryption a key length of 2048 (or 4095) bit is suggested. Why is the key length in libsodium so much shorter? Is the used algorithm so much more "efficient"? Or is there something I am missing?

I understand how ECC is based on the discrete log problem and RSA on integer factorization. I've read several references that show how a solution to either of these problems can typically be adapted to solve the other - for example,  claims:      The asymptotic running time of the best discrete logarithm algorithm   is approximately the same as that of the best general-purpose   factoring algorithm. Therefore, it requires about as much effort to   solve the discrete logarithm problem modulo a 512-bit prime as it does   to factor a 512-bit RSA modulus.   Now, I suspect that this isn't true, but I'd like to get a feel for why it isn't true.  For instance, as I understand it, the generalized number field sieve can be applied both to solve integer factorization and to solve discrete log. Why is it that it gives such an extreme speed up in integer factorization compared to brute-force, and less so in improving discrete log?  If the asymptotic running times for both applications are approximately the same, then I'm completely confused. I suspect that I'm comparing the wrong parameters, but how is it that ECC key-sizes can be so much smaller that in RSA?


What is the limit of sequence $a(n)$= $\left(\frac{1.3.5....(2n-1)}{2.4.6....(2n)}\right)$.  I calculate $\lim \left(\frac{a(n+1)}{a(n)}\right)$ which comes 1.So I am confirm that limit of $a(n)$$\ne$$0$.But what is actual limit?

How can I show   $\lim_{n \to \infty} a_n = 0$  $a_n = {1.3.5 ... (2n-1)\over 2.4.6...(2n)}$  I have shown that $a_n$ is monotonically decreasing. I thought to shown sequence is bounded from below then it automatically would converge and hence my question will be solve. But I'm unable to show its boundedness... Or there maybe another method to prove this. Thanks


I'm travelling to San Francisco (SFO) with family this May. My first flight is with JAL to Narita. After a 12hr layover, the next flight is from Haneda to San Francisco. Similar routing on the way back a few weeks later (SFO-HND / NRT - ? ). Do I need a visa for Japan and if yes, what kind?

I'm arriving from New Delhi, India (Indian passport) with JAL at Narita on 11th July at 07:30 and departing for San Francisco with JAL at 00:05 on 12th July from Haneda. Do I need a transit visa as I'll be switching airports and spending a few hours at JAL City Haneda Airport Hotel?  Previously I had connecting flights from Narita to San Francisco and obtained shore passes to relax at Narita Nikko Hotel. Now I'm travelling with my elderly Mom and do not want complications at Narita immigration or later in the day while going from Narita Airport to Haneda airport. Please advise.


If my issue date of visa is 2nd Feb and valid until 1st April. So if I enter Dubai on 15th March, will my 30 days period start from 15th March and will be valid until 14th April?  Or do I have to exit Dubai 1st of April?

Today I was informed by VFS that my tourist visa for UAE got approved. I'm travelling to UAE on 16th December 2014 and returning on 7th Jan 2015. But when I checked the "valid until" date on the visa it states 30 December 2014.    Does this date mean I should return before December 30th? Should I get it corrected from VFS?


I record with Nikon D3500 always on my PC Desktop and I want it to be ON for 7-8 hours. But the battery life is too short. How can I connect to a power or something to keep ON all the time ?

My wife has a Nikon D3100 that I've been using to film, but the battery typically won't last through long shoots.  I've gathered from searching around that I can't charge the camera with USB, but I wondered if there's ANY way to do that. It seems at least possible that an adapter could exist that would fill in for the battery and plug into the wall, but I haven't been able to find such a thing.  Is there such a product or technique? It would be nice to not buy a second battery, I'm really hoping for a "set it and forget it" solution.


What is the best way to reduce the space generated just before the second item?  \documentclass{article} \begin{document} \begin{enumerate}   \item Item 1   \item \begin{equation}\label{eq:1} x=1 \end{equation}   \item Look at \eqref{eq:1} \end{enumerate} \end{document}   So that the item number is on the same line as the equation. I know I can use inline math ($x=1$) but then I cannot reference the equation in the last item.  EDIT: Made a minimal example

Hi I wish to number equations  with a list environment   \begin{itemize} \item Lol \begin{equation} y_t=h_t(\hat{x}_{t|t-1}) \end{equation} \end{itemize}   I want  y_t=h_t(\hat{x}_{t|t-1}) in the same line of Lol... Can you help me to find out a way?


Being on Ubuntu Server I am trying to write an automation script.  Here is what I have:  #!/bin/bash  while [ "$1" != "" ]; do     case $1 in         -p | --port )           shift                                 PORT=$1                                 ;;         -d | --domain )         shift                                 DOMAIN+=("$1")                                 ;;         -l | --location )       shift                                 PATH=$1                                 ;;         * )                     exit 1     esac     shift done  echo "Parsing finished. List of domain is: " for val in "${DOMAIN[@]}"; do     echo " - $val" done  echo "Generating -d domain list..." for val in "${DOMAIN[@]}"; do     domains="$domains -d $val" done  echo "-d list is: $domains"  echo "Port is: $PORT."  echo "Location to save is: $PATH"  certbot certonly --standalone --standalone-supported-challenges http-01 --http-01-port $PORT $domains --cert-path $PATH   When ran with just two parameters, it works correctly. When I specify the third parameter -l or --location, it gives:  cert-ggm.sh: line 35: certbot: command not found   I tried to rename the -l parameter to capital P, got the same result. The test echoes return correct value parse. What's the deal with the location parameter casting certbot command uncallable? Thank you in advance.

I've installed a version of Ubuntu Server and although I'm fairly still fresh with Ubuntu, I'm trying to create a bash file to run a program in the background. More importantly, I'm trying to get a file nameto display correct and create it before I start running the program (I like my debug stuff).  However, here is my bash script:    #!/bin/bash  PATH="/var/log/servers/Game/"  FILENAME="startup"  EXT=".log"  DATE=$(date +%d-%m-%Y)  NEWFILE=${PATH}${FILENAME}_${DATE}${EXT}   I have verified that the file does exist in the PATH directory. However, the issue is with the date command. When I run the script bash -x game.sh this is what is displays.   + PATH=/var/log/servers/Game/  + FILENAME=startup  + EXT=.log  ++ date +%d-%m-%Y  game.sh: line 5: date: command not found  + DATE=  + NEWFILE=/var/log/servers/Game/startup_.log  + echo /var/log/servers/Game/startup_.log   I don't understand why it would say the command doesn't work, when I can go to the main console and run date and get a valid response.  Any help is greatly appreciated!


Windows 7 asks me that question every time I go to do anything with a file I downloaded from the net. Is there a way to disable that annoying popup for all files, new and old, for all times, no exceptions? I have been clicking on that accursed box for decades, and I have never once clicked no. I do not want to see that popup again, ever. Not for files I just downloaded, not for files I downloaded long ago.  Near duplicate:   Edit ... The following has useful info:   Edit 2 ... After pouring over the links above, and links they point to, I have discovered how to stop the rot.  Watch this space.

I would like to disable the "Open File Security Warning" that says "Do you want to run this file?" whenever I double click on an .exe I download. I have Windows 7 Home Premium, so I don't have the group policies editor. I have tried setting a registry value: HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Associations, value DefaultFileTypeRisk to 6152, but this did no good. This is the only entry under Associations, incidentally, and it was empty before I added this.  Is there a way to disable this message on my system (other than unblocking each .exe file)?


Is it possible to have a IV that is not correlated significantly with the DV but then in the multiple regression analysis this IV explain a significantly % of the unique variance of this DV?  If so, how can we explain it?

I have what is probably a simple question, but it is baffling me right now, so I am hoping you can help me out.  I have a least squares regression model, with one independent variable and one dependent variable. The relationship is not significant. Now I add a second independent variable. Now the relationship between the first independent variable and the dependent variable becomes significant.  How does this work? This is probably demonstrating some issue with my understanding, but to me, but I do not see how adding this second independent variable can make the first significant.


here is my code in jquery, and i want to get the data in tech-support-bullet-chart2  $.ajax({     type:"POST",     url:"includes/bullet-chart.php",     data:{         daterange:ym     } }).done(function(e){     var tech_support = JSON.parse(e);     //console.log(tech_support);     for(i=0;i<t_s.length;i++){     //console.log("support:"+tsn + ", complete:" + tsc + " ,Pending:"+ tsp +", isExist:"+isExist);     $("#div-charts").append('
'+     ''+     '
'+t_s[i]+'()

'+     '
'+         '

' +         '
' +         '

');     }   here is my function in geting the data-sname  $(".tech-support-bullet-chart2").click(function(){ var name = $(this).data("sname"); alert(name);})   and my problem is.. my second code does not working.. please help me on this..   thank you in advance!

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I just bought the brand-new Canon 80D from Amazon, along with new memory card 64GB. When I took the first few pictures, I see that the file names start from "IMG_9545.jpg", "IMG_9546.jpg" and so on ...  I suppose that if the brand-new camera with new memory card, then the pictures should start from "IMG_0001.jpg". I also formatted my card.  Does that mean my Camera already used? Or is it the normal way how file names should be?

Most utilities that I found to check the actuations count haven't been updated in a long time. I also read that the actuations count isn't included in the EXIF data anymore.  So what is the best/easiest way to check the actuations count on a Canon EOS 80D? I have Lightroom and Photoshop available, but I'm willing to install another (free) utility if necessary. I use Windows, Linux is optionally available. Thank you!


I installed nmon on Ubuntu 16.04 as below.  At the time of installation, I can see the file nmon_14g+debian-1build1_amd64.deb downloading, unpacking and installing. After the installation nmon is working fine.   But when I tried to see the downloaded file at the location  /var/cache/apt/archives/ it is not there. I tried to search on the entire system with root id, but I am not able see the file nmon_14g+debian-1build1_amd64.deb.  I tried updatedb and locate *.deb as root but I can't find it!  Can anyone help me figure out where this file has actually gone?  $ nmon The program 'nmon' is currently not installed.  You can install it by typing: sudo apt install nmon   $ sudo apt install nmon [sudo] password for thom:  Reading package lists... Done Building dependency tree        Reading state information... Done The following NEW packages will be installed:   nmon 0 upgraded, 1 newly installed, 0 to remove and 333 not upgraded. Need to get 45.9 kB of archives. After this operation, 173 kB of additional disk space will be used. Get:1 http://in.archive.ubuntu.com/ubuntu xenial/universe amd64 nmon amd64 14g+debian-1build1 [45.9 kB] Fetched 45.9 kB in 6s (6,897 B/s)                                               Selecting previously unselected package nmon. (Reading database ... 180965 files and directories currently installed.) Preparing to unpack .../nmon_14g+debian-1build1_amd64.deb ... Unpacking nmon (14g+debian-1build1) ... Processing triggers for man-db (2.7.5-1) ... Setting up nmon (14g+debian-1build1) ...

I know that packages installed with apt-get are stored in /var/cache/apt/archives.  I just installed mariadb server in Ubuntu 16.04 with following command:  sudo apt install mariadb-server   When I tried to find packages in /var/cache/apt/archives, there are no packages. Where are they stored if it's not in this directory?


While I know this is an extremely well known result, I was trying to derive the expression for $ \langle{x}|{p}\rangle$, as done in Sakurai. It is basically a two line equation, so our starting point is $$\langle x'|p|p' \rangle= -i \hbar \frac{\partial}{\partial x'}\langle x'|p' \rangle. $$ which then leads to $$ p'\langle x'|p' \rangle=-i \hbar \frac{\partial}{\partial x'}\langle x'|p' \rangle. $$ Now, the solution of this differential equation is given to be, $$ \langle x'|p' \rangle=N \text{exp}\Big(\frac {i p' x'}{\hbar}\Big).$$ While it's easy for me to understand the exponential bit of the solution on the RHS, as far as I remember the normalisation constant $N$ should be allowed to be a function of the momentum $p$, because the differential equation is basically of the form $$\frac{\partial f(x,p)}{\partial x}= c(p) f(x,p). $$ Did I get the math wrong or is there another reason for why $N$ is taken as a constant independent of $p$ and $x$?

Let $$\langle x'|p'\rangle = N \exp(\frac{ip'x'}{\hbar})$$ be the overlap between position and momentum space, where $N$ is a normalization constant to be determined.  We can then compute $N$ by  $$ \langle x'|x''\rangle = \int \mathrm{d}p'\langle x'|p'\rangle \langle p'|x''\rangle\\ \rightarrow \delta(x'-x'')=|N|^2 \int \mathrm{d}p'\exp(\frac{ip'(x'-x'')}{\hbar}) \\ =2\pi\hbar |N|^2 \delta(x'-x'') $$  see Sakurai - "Modern Quantum Mechanics" 2nd, Pearson, p. 54.  How was the factor $2\pi\hbar$ obtained? The intermediate step should look something like this: $$ \rightarrow  \delta(x'-x'')=|N|^2 \int \mathrm{d}p'\exp(\frac{ip'(x'-x'')}{\hbar}) \\ =|N|^2 \int \mathrm{d}p'\delta(x'-x'') $$  But all I can think of is that one can say $\int \mathrm{d}p'=\hbar k$ where $k$ is the wavenumber.   What am I missing?


Okay, I made it through a page and a half of questions on this sub-domain that came up under the search "subjective", so I'm sorry if this has already been discussed to death. Please close this as duplicate with a pointer to the best question already asked, as I'm sure if this is a duplicate, it's not the only one.    So, I asked a subjective question a while back because I stopped being able to see the line between subjective and objective when questions like "should I learn more about xyz" and  "what is your favorite tool for thisorthat" and "favorite tricks for nameyourlanguage" kept coming up. And I got shut down right away. I'm not bitter. I was. But I'm not now. But it is a bit of a drag   a) seeing obviously subjective/personal questions get upvoted with hundreds of responses  b) seeing obviously subjective questions that are fun or intriguing get shut down after 10 minutes.  or  c) seeing obviously corny/boring/begging-to-get-shut-down questions in the way of real questions.  I know that the last one is everyone's least favorite and I'd like to think that the subjective rule was created for just those questions. But since subjective duh is a matter of taste, my (c) may be your (b) or (a) and so forth.  And having seen how much discussion has already gone down about this, I'm wondering if maybe we ought to accept that we're not just experts (or those in need of one, or both), but nerds who want to talk shop.  To further this discussion, I'd like to pose a question, a point, and a concept:  question: What are the stats on subjective questions? And by that I mean, are they more likely to be asked be someone with a higher reputation or someone with little or no reputation?  I ask because there is a difference between having a place for us all to wax poetically on our favorite CS joke, and having a problem with vandals storming the gates and asking silly questions about whether HTML is stupid or just really dumb. (I'm not sure that made sense at all. I'll try that again...)  Are subjective questions typically asked by folks as one of their first 10 questions?  a point: I have never understood how community wiki works, how to tell if a question is of that category, how to see only those questions or filter them out, etc. And from what I can tell from previous  discussion here, it has a few flaws to be worked out either way. Wouldn't a community.stackoverflow alleviate most of the problems (or at least give us a stern finger to point people?).  a concept: I think it would be silly to award points and reputation based on subjective questions, as they don't have a right answer. But the idea of trying to do such reminds me of one of my favorite British shows entitled QI.  Celebrities must answer questions that are impossibly hard and trivial and rather then simply getting points for knowing the answer, they are rewarded points for being Quite Interesting. Now, I imagine that would be near to impossible to judge as a group (rabble/angry mob/etc) but at the very least, it could be an encouraging model for such a SO site and would at the very least justify the idea of points for "right answers".  So, having thrown all of that out there, I'm dying to know, is such a SO site already in the works?

Sometimes you just want to let out some steam, and troll about some technology or software. You are not looking for any answers, but for users with similar experiences and interesting stories. So why not create a separate discussion site (trolling.stackoverflow.com?), where you could ask questions like "why do you hate technology X" or "What are the stupidest bugs you encountered in X"?


I'm storing some state information in the URL fragment (hash, whatever you call it).  When I change the window.location.hash in Chrome, and Safari the page doesn't reload - this is the behavior I want.  When I change window.location.hash in Firefox, I get a page reload.  How do I prevent this?  Note: My reason for storing state in the URL is so that userA can send the url to userB and userB will be able so see the same page (loaded by AJAX).    Resolution: For what it's worth, in Firefox (only?) the page will reload if you completely remove the hash including the "#" character.  I ended up just making sure not to delete the entire hash.

How would I have a  action that may have some effects on the current page but would also change the URL in the browser so if the user hits reload or bookmark, then the new URL is used?    It would also be nice if the back button would reload the original URL.  I am trying to record JavaScript state in the URL.


I'm importing the planet data file. After see the Node processing taking about a hour at 2800.0 k/s to finish I think all job will be fast but now Way is still working after 28 hours at 0.5 k/s and done just 31.583k of 402.887k ! ().  The top command shows it taking 15% of RAM and 5% of CPU.  My import command was  $osm2pgsql --number-processes 6 --flat-nodes ./osm_flat_nodes.db --disable-parallel-indexing --latlong --verbose --create --hstore --slim --cache 4000 --database osm --username postgres --host 127.0.0.1 --style ./default.style ./planet-latest.osm.pbf  My machine: CentOS / 32GB RAM / 600GB HDD / 8 Cores  Is this normal?

I'm currently importing the planet-latest.osm.pbf file I downloaded from  some time last week. I'm importing it using the following command:   nohup osm2pgsql -l -U gis -c -v -r pbf --unlogged --drop -s data/planet-latest.osm.pbf &   My problem is that the ways are importing very slowly and based on current speed (0.04k/s) and the  it will take 86 days to import them all. By contrast the nodes imported at 151.3k/s. Even if I waited 86 days for the ways to import (I won't) I would then need to import the relations and sit through all the post-processing.  I recently imported another planet file in .osm format using the same command line arguments and, although it ultimately failed due to  it was moving along at a much faster speed.  From what I can see in the docs I've done everything I can to improve the import speed.  Can anyone tell me why the .pbf format import is moving so much slower over ways than the .osm format?  I'm using PostGIS 9.4 and osm2pgsql 0.88.1. Disks are on a fast SAN, the machine has a single Intel Xeon @ CPU 2.67GHz and 4GB memory. OS is Ubuntu 14.04 Server.


I successfully created a shapefile from OpenStreetMap with the OpenStreetMap tool in QGIS 2.2. When I try to create a polyline layer, it says that there are 8000 values in the db file for the property highway, but after the import I have only 6000 in the attribute list.  The problem is that I don't have all streets available for a given city and because of that I am unable to draw parcels where the streets are their borders. Is that problem normal or am I missing something?

In QGIS 1.8 I used the openstreetmap plugin to request data from the server, or open a .osm XML file, which produced 3 layers (polygons, polylines and points) in QGIS.  This was great (give or take the 64bit bug which highly affects the freshly mapped area I work on), but how do I do that in QGIS 2.x?   I can't find any updated documentation about it.  In the vector menu, I've tried importing from osm servers, I get a .osm file, but then I'm stuck. There's a menu option for loading an XML file, but it produces a spatialite db, which apparently only has non-geometry tables when I try to add it as a spatialite layer. If I open the attribute table, I can see node ids, ways and so on, but I can't figure out how to actually make use of them.  I've also tried adding a vector layer from a .osm XML file. I get a gpsbabel window that shows nothing, then finally an invalid data source message in QGIS.


As far as I know, the relativistic momentum of a particle is given by the equation: $$p=\frac{m_0v}{\sqrt{1-\frac{v^2}{c^2}}}$$ where $m_0$ is the mass of the particle and $v$ is the velocity of the particle.  But why does the number $\sqrt{1-\frac{v^2}{c^2}}$  appear? How can I derive it from the special theory of relativity?  I have not enrolled in University yet, and I couldn't find the proof for the equation above anywhere online.   But if I found the proof for the equation of time dilation $t=\frac{t_0}{\sqrt{1-\frac{v^2}{c^2}}}$ (which I did), can I prove the relativistic momentum equation above?  (Sorry for my English. If the question has been asked anywhere else, or if this question is inappropriate, please let me know. Any answers or comments will be appreciated)

Motivating the non-relativistic momentum $$\mathbf{p} = m\mathbf{v}$$ is quite easy: it is meant to represent the quantity of motion of the particle, and since the mass is one measure of quantity of matter it should be proportional to mass (how much thing is moving) and should be proportional to velocity (how fast and to where it is moving). Now, in Special Relativity the momentum changes. The new quantity of motion becomes $$\mathbf{p} = \dfrac{m\mathbf{v}}{\sqrt{1-\dfrac{v^2}{c^2}}}$$ Or, using $\gamma$ the Lorentz factor $$\mathbf{p} = \gamma(v) m\mathbf{v}$$ where I write $\gamma(v)$ to indicate that the velocity is that of the particle relative to the frame in which the movement is being observed. The need for this new momentum is because the old one fails to be conserved and because using the old one in Newton's second law leads to a law which is not invariant under Lorentz transformations. So the need for a new momentum is perfectly well motivated. What I would like to know is how can one motivate that the correct choice for $\mathbf{p}$ is the $\gamma(v)m\mathbf{v}$. There are some arguments using the mass: considering a colision, requiring momentum to be conserved, transform the velocity and then find how mass should transform. Although this work, it doesn't seem natural, and it is derived in one particular example. On my book there's even something that Einstein wote saying that he didn't think it was a good idea to try transforming the mass from $m$ to $M = \gamma(v)m$, that it was better to simply keep $\gamma$ on the new momentum without trying to combine it with the mass. So I would like to know: without resorting to arguments based on transformation of the mass, how can one motivate the new form of momentum that works for special relativity?


I am trying to figure out how to go about having a user log into a Ubuntu machine, use it to their heart's content, and when they log off delete all of the user data from that account. All of the stuff I have found thus far is about deleting an account instead of just the data. Any help would be a Godsend. Thanks

Is there any way you could revive Guest Sessions in a future LTS distro?  Guest sessions are good security - they give me just enough power to do what I need to do on a daily basis without risking my system. In short, Guest sessions save me from myself.  I had upgraded from 16.04 to 18.04, gotten a problem I couldn't fix and was all to happy to wipe and rebuild my hard drive and return to 16.04.  I can't be the only one who feels this way.


I am Using SQL Server 2008. i have a Table of "Course", having one column with name of "Courses" . I insert "Courses" in table "Course" and get a string For example "Math English Physics".  How do I split a string so I can access each course? How can I split the string by a space and access the item at index 1 which should return "English"?

Using SQL Server, how do I split a string so I can access item x?  Take a string "Hello John Smith". How can I split the string by space and access the item at index 1 which should return "John"?


If an algorithm executes a statement,  it is n/2 times, then how come O is equal to O(n). Because the video explains that it is because of the degree of a polynomial. Please explain.  for(int i =0;i<n;i=i+2){ sout(n) ---- This statemet can be print n/2 times }  f(n) = n/2  then O(n)

I'd prefer as little formal definition as possible and simple mathematics.


I know that my question sounds impossible, but I would go deeper into it.  I have three Internet connections:   ADSL from Provider 1; ADSL from Provider 2; LTE from Provider 3 (USB WiFi Box).   I need to direct all three connections into a router and serve my hosts with a single WiFi connection. They only see a line called Office_WiFi, but they hiddenly connect alternately to the three Internet connection (so three different public IPs).  My need is to balance the load of the line and manage band for every hosts. Ex: Host 1 needs to upload a large file, my network automatically gives him priority and sets him on ADSL from provider 1 instead of LTE from Provider 3 (USB WiFi Box).  Is there a way to do this?  Someone told me to start using pfSense. Could pfSense help me in this challenge?  Thank you all!  Ps: the problem is having three WANs and a single LAN.

I have two internet connections from two different ISPs and I need to balance the traffic originating to and from my network between the two ISPs. I am using Debian GNU/Linux.  My set-up is like this -  eth0 (192.168.0.0/24) -- Local network  eth1 (192.168.1.0/24) -- ISP #1  eth2 (192.168.2.0/24) -- ISP #2  My local network is connected to this server via eth0 and the box is the DHCP server cum Gateway for all the machines in the LAN.  The server needs to do load-balancing between the two ISPs and also needs to do NAT-ing.  I have followed the routing instructions on  but I still need instructions to do the NAT-ing properly.  Any help will be appreciated.   PS - I know about pFsense but I need to use Linux.


I edited  and noticed my reputation change from 1466 to 1470 (i.e +4). I went to check my reputation changes and found:        Note: My reputation later went down from 1470 to 1468, so it appears the system realized it made a mistake and corrected my reputation, but hasn't gotten rid of the second revision or the history event.  My  still shows 1 suggested edit with 2 revisions.

When I visit the reputation tab of my profile, I see a lot of stuff. I can make out some of it, but not all.   What do all the event types mean? Why do some events show an odd reputation gain or not show any reputation change at all? Why are some events sometimes highlighted in yellow? My reputation suddenly dropped, but I don't see anything. What happened? Why do some events disappear from my reputation history?


As I am beginner I don't have any idea about how to find limits, I want to find the limit as $n\rightarrow \infty$ of  $$\lim_{n\to\infty}n\cdot \sin(2\pi e(n!)) $$  please help.

I tried and got this   $$e=\sum_{k=0}^\infty\frac{1}{k!}=\lim_{n\to\infty}\sum_{k=0}^n\frac{1}{k!}$$ $$n!\sum_{k=0}^n\frac{1}{k!}=\frac{n!}{0!}+\frac{n!}{1!}+\cdots+\frac{n!}{n!}=m$$ where $m$ is an integer. $$\lim_{n\to\infty}n\sin(2\pi en!)=\lim_{n\to\infty}n\sin\left(2\pi n!\sum_{k=0}^n\frac{1}{k!}\right)=\lim_{n\to\infty}n\sin(2\pi m)=\lim_{n\to\infty}n\cdot0=0$$  Is it correct?


I've just installed Sick-Beard on my server. Starting the service via SSH works just fine, as I issue the command  sudo service sickbeard start   However, I can't get the service to start on boot. There are some things I'm quite sure are incorrect, but I don't know what the correct settings should be.  sudo nano /etc/default/sickbeard   currently shows  SB_USER=root SB_PROFILE=/opt/sickbeard/pid   and as for ownership and permissions,  ls -l /opt   shows  drwxrwxrwx 10 root   root   4096 Sep 28 19:24 sickbeard   Now, I'm pretty sure I should not be using root everywhere, and instead I've created a user 'sickbeard', but this does not work either, probably since this user doesn't have the right permissions. (What these should be, I don't know.)  Furthermore, I've followed  with respect to /etc/init.d/sickbeard  Now, basically, if I issue the first command above (sudo service sickbeard start|stop) it works just fine, but without sudo I get  diana@SERVER:~$ service sickbeard start Starting SickBeard start-stop-daemon: unable to set gid to 0 (Operation not permitted)   I'm out of my depth here, have searched back and forth but can't get the service to start without the sudo command which, in my mind, is preventing it from starting on reboot. But I might be wrong, it might be something else entirely, I just don't know what...  Any help is most welcome.

I seem to have some problems with automating some services at startup. I've had this problem before, but I couldn't find out the exact reason what caused this.  I've added both services to startup with:   $ sudo update-rc.d sickbeard defaults   Then:  $ sudo service sickbeard status  * sickbeard is not running  $ sudo service sabnzbdplus status  * SABnzbd+ binary newsgrabber: not running  $ service --status-all   [ + ]  acpid  [ - ]  rsync  [ + ]  rsyslog  [ - ]  sabnzbdplus  [ + ]  saned  [ ? ]  sendsigs  [ - ]  sickbeard   (list is truncated) Screenshot from jobs-admin:   As you can see the app is not starting at boot... What might be causing this?


When I swipe my home screen from bottom to top, I see below screen :  However I want to customise this screen like I want to remove the volume icon from this screen. Is there any way to achieve this. Thanks for any pointer.

iOS 11 provides the ability to customise the lower toggle controls in Control Center (show/hide and rearrange) from Settings → Control Center.  Is it possible to customise the other controls at the top of Control Center, showing/hiding or rearranging toggles and controls?


Prove that $‖·‖_1$ is indeed a norm on $\Bbb{R}^n$.  You are allowed to assume the triangle inequality for the absolute value function, that is,$|a+b|≤|a|+|b|$ .  I know that vector norm $1$ is the sum of all elements in the vector but I am not how to start this proof. And what does this have anything to do with triangle inequality?

I am just curious how you would simply prove that a 1-norm is a norm. Step-by-step would be very helpful. Proofs are not my strong point. Thank you!


I tried to convert it to a form like $ \displaystyle \sum_{r=0}^n\frac{r(-1^r)}{n^{({}^{n-1}C_{r-1})}}   $ And then write the series backwards and add the two, but this doesn't seem to help. Any hints would be appreciated.

Find a closed form expression for $$\sum_{r=0}^n \dfrac{(-1)^r}{\dbinom{n}{r}}$$ where $n$ is an even positive integer.  I tried using binomial identities, but since the binomial coefficient is in the denominator, I can't do much. Also, I'm seeking a non-calculus, elementary solution, if possible. Thanks.


How to find element of order $q^2-1$ in $\text{GL}_2(\mathbb{F}_q)$? I am hoping to find field $\mathbb F_{q^2}$ as subalgebra of $2\times 2$ matrices over field $\mathbb F_q$ where $q$ is power of prime number. I was trying with element $\pmatrix {n&1 \\ 1&0}$ but it works only for $q=2,3,4,8,16$.   It is suggested that this is duplicate of question    But I don't know how to find $\mathbb F_{q^2}$ in $M_2(\mathbb F_q)$.  Here is test in GAP for above matrix - $n$ is generator of the field multiplicative group.  gap> List([2,3,4,5,7,8,9,11,13,16,17,19,23,25,27,29,31,32,37,41], >         k->Order([[Z(k),1],[1,0]]*Z(k)^0)); [ 3, 8, 5, 12, 16, 9, 20, 24, 28, 17, 16, 40, 22, 52, 56, 20, 64, 31, 76, 40 ]   To give my motivation - I want to prove that algebra  $M_2(\mathbb F_q)$ can be represented as ${a+bj}$ for $a,b$ belonging to $\mathbb F_{q^2}$ and multiplication given by Cayley-Dickson $$(a+bj)(c+dj)=ac+\bar db + (da+b\bar c)j,$$  where $j$ is matrix satisfying $\bar j=-j$.

For fixed prime power $q$ show that the general linear group $GL_n(\mathbb F_q)$ of invertible matrices with entries in the finite field $\mathbb F_q$ has an element of order $q^n-1$.   I tried to show this question with showing diagonal matrix but i can't find element directly  competible with order i think i am on wrong way please give me clue ?


I'm using rel='alternate' like this:     http://example.com/_spanish/index.htm'   hreflang='es'   Is it acceptable to leave out the HTTP protocol and use  link rel='alternate' href='//example.com/_spanish/index.htm' hreflang='es'  Thank you

Can I use:  <link rel="alternate" hreflang="en" href="?l=en" />   to link pages with different languages for SEO (recommended for )? Can that URL be relative as in the example above, or does it have to be full (start with http://example.com)?


In Volleyball one player wears a different color shirt in the team while others wear the same color.  What is the reason for it?

Why does one player on a volleyball team have a different color jersey than the rest of the teammates? I notice that this player only plays on the back row and never plays in the front row, and that this player is often shorter than the players that play in the front row.


I wanted to know how to decide between using 2D vs 3D models for games. What are the advantages/disadvantages of using 3D models versus 2D sprites in 2D games?

How much "harder" is 3D than 2D in terms of:   Amount/complexity of the code Level of math skills required Time involved in making art assets   Original title: How hard is 3D game development versus 2D?


This is just a question out of curiosity, but I would like to know how can you install ubuntu on hundreds/thousands of machines at the same time?  Say I have 100 computer that come with no OS how can I install Ubuntu on them? Shall I proceed with the installation manually on each of them? If not what are the technologies and tools one should know?

I need a CD or USB stick, that will install Ubuntu on a completely headless machine. Stick CD in and restart, no keyboard or screen should be involved.  There are a few obstacles:   The language selection menu when you first boot the CD. The fact that the CD menu waits. The installer's asking questions during installation.


what i want to do is make a function that will get a list as an input and a number and will delete the node of that list that equals to that particular number. So if i have a linked list lets say:  struct num // list 1 {         char *val;         struct num *next; };   and i have added 4 items to that list, i want to be able to delete the third item and get back the new list with now 3 items. Everything i have tried till now though wont work, i think because i am not linking the remaining items correctly after i delete one of them.  Since you insist here is what i have till now   struct num1 *temp;     temp = head;  struct num1* deletend(int del){     for ( int i = 0; i < listSize; i++)     {                if (i == del){                 free(temp);             }             temp = temp->next;     }     return temp; }

Is it possible to delete a middle node in the single linked list when the only information available we have is the pointer to the node to be deleted and not the pointer to the previous node?After deletion the previous node should point to the node next to deleted node.


From a very general point of view, when you have a dataset $X$ and want to predict a label $y$, what is the purpose of beginning with a PCA (principal component analysis) first, and then doing the prediction itself (with logistic regression, or random forest or whatever) from both intuitive and theoretical reason? In which case can this improve the quality of prediction?

Suppose I am running a regression $Y \sim X$. Why by selecting top $k$ principle components of $X$, does the model retain its predictive power on $Y$?   I understand that from dimensionality-reduction/feature-selection point of view, if $v_1, v_2, ... v_k$ are the eigenvectors of covariance matrix of $X$ with top $k$ eigenvalues, then $Xv_1, Xv_2 ... Xv_k$ are top $k$ principal components with maximum variances. We can thereby reduce the number of features to $k$ and retain most of the predictive power, as I understand it.   But why do top $k$ components retain the predictive power on $Y$?   If we talk about a general OLS $Y \sim Z$, there is no reason to suggest that if feature $Z_i$ has maximum variance, then $Z_i$ has the most predictive power on $Y$.   Update after seeing comments: I guess I have seen tons of examples of using PCA for dimensionality reduction. I have been assuming that means the dimensions we are left with have the most predictive power. Otherwise what's the point of dimensionality reduction?


I have to write a maintenance script that iterates over our IPs testing their connectivity to certain services such as nc -sip# mailin-01.mx.aol.com 25.  It has a flag -w ... but it's not what I think it is. That is, I only want this program to run for at max 3 seconds and the places we are connecting to are always up (unless major network problems that the script shouldn't worry about --- not its particular job and would be noticed before the script is run).  I just need it to connect and see if we are getting an error message. This is required before we assign an IP to a user for their web page (this is an alternative to CPanel stuff -- we want our own).

I want know how I can run a command for a specified time say, one minute and if it doesn't complete execution then I should be able to stop it.


I am writing an ad and would like to write: "Our team of economists are at your service and available by phone or email.  They will be happy to respond...".  I know that grammatically speaking, 'team' is the subject of the sentence and, being singular, would dictate that 'it' is "at your service".  BUT, it just feels better reading this and it evokes a picture of a bunch of economists doing what they do rather than a single unit".  Is what I'm doing OK?  Should I be arrested by the grammar police?

I'd say Microsoft have a way of bending the rules and I know that McLaren have won the championship. While this sounds strange, I believe it is correct English (sorry, I'm not native).   But when it's a small company, would you still use it this way? Is a company always plural, or are small companies singular? I.e., would you say Bakery Johnson makes fine bread or Bakery Johnson make fine bread? Is it My book seller, Woody's, have moved or is it has moved?


We have a dedicated SQL Server machine for a SAAS application with about 200+ databases, the server has E5-2620 with 64 GB RAM. Now we want to move all the databases to Azure, so we're looking into the options: we can either go with a Virtual Machine like (DS13 v2) which can support all these databases, or we can use Azure SQL Elastic Pools like Standard with 400 eDTUs.  My question is: in the long run, and from a management and scalability point of view, which option is better? And also will the Standard Elastic Pool with 400 eDTU's provide the same performance as the virtual machine?  One of the major concerns for us is the performance of the SQL databases in Azure, as this is one of the reason to move the whole application to the Azure so that in the future as the no of users grow we can easily upgrade our instances to cater the increased load.

We have a dedicated SQL Server Machine for a SAAS application with about 200+ databases, the server has E5-2620 with 64 GB RAM, Now we want to move all the databases to the Azure, so for looking into the options we can either go with a Virtual Machine like (DS13 v2) which can support all these DBs or can use the Azure SQL Elastic Pools like Standard with 400 eDTUs.  My Question is that in the Long Run and from management and scalability point of view which option is better, and also will the Standard Elastic Pool with 400 eDTU's can provide the same performance as the Virtual Machine?  One of the major concerns for us is the performance of the SQL DBs in Azure, as this is one of the reason to move the whole application to the Azure so that in the future as the no of users grow we can easily upgrade our instances to cater the increased load.


phrase use to I want to know is there any phrase use to in english if yes then how to use it

Which is the correct sentence, if there is a correct one?     I use to be a hitman.        I used to be a hitman.   I've read the second sentence recently in a book, but I was sure it should be I use to be a hitman.


I have a screen instance running and i want to get output of that instance current 'screen' without getting in to the session. Will something like that be possible? (The instance in running a program that produces output every few seconds)

I just want to have a quick overview of my detached GNU screen sessions. Is it possible to dump the current content to stdout ? Something like  screen --print SESSION_NAME > file.txt


I understand that a function $f$ from a set $X$ to a set $Y$ is surjective, if, for every element $y$ in the codomain $Y$ of $f$, there is at least one element $x$ in the domain $X$ of $f$ such that $f(x) = y$.   Is $x^2- \lfloor x \rfloor^2$ surjective for all real numbers greater than or equal to $0$? I know that it is from graphing it, however, I'm not sure how to formally prove it.

The function's domain and codomain are nonnegative real numbers. I've given this countless attempts and I'm out of ideas on how to prove this. What is proving to be tricky to me is writing $x$ in terms of $y$ due to the floor function.


It's my understanding that a z-score can only be calculated and accurately used for data sets that are normally distributed.  Since "perfect" normal distribution almost never occurs in real-world data (where "perfect" normal distribution is defined as 1. The mean, median, and mode all equal the same number, 2. the distribution is perfectly symmetrical between all standard deviations on both sides of the mean, and 3. the distribution is asymptotic), how "close" can the distribution be to perfectly normal for the z-score to still be a valid statistical measure?  If the answer is it has to be a perfectly normal distribution, then my question is why is the z-score so important since it would seldom be a valid measure on real-world data?


public class Bar {   private Foo m_foo;   private int getNumbers(){    m_foo=new Foo();    return 5;  }    public void test1(){    m_foo.print(getNumbers());  } }  public class Foo {   public void print(int x){    System.out.println(x);  } }  public class Main {   public static void main(String args[]){   new Bar().test1();  } }   The NullPointerException occurs in test1()call, but I can't understand the reason behind. Isn't the m_foo supposed to be instantiated in the getNumbers() which should get evaluated first?

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


(How) Can I define font size in math environment universally to effect equation, align or displaymath(\[...\]) etc, but not the inline math? Current, I am doing as:  \documentclass{beamer} \begin{document} Normal text \begin{align} F&=ma\\ E&=mc^2 \end{align}\scriptsize Script text \begin{align} F&=ma\\ E&=mc^2 \end{align} \normalsize \end{document}   to put the equations in scriptsize, which is working.  But, can I (I have my custom theme file) add this in theme file so that the change in fontsize is inbuilt?

The first image is what I have at the moment, the second image is what I would like to get. As you can see, in the second image the formula font size is a little bit bigger than in the first image. I would like to make all the formulas font size a little bit bigger. I tried using, as suggested , \DeclareMathSizes{14}{15}{7}{7} (note that in beamer I am using 14pt as font size) but it did not produce any effect.  \documentclass[14pt,handout,t]{beamer} \usepackage{lmodern} \usepackage[english,italian]{babel} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \geometry{paperwidth=297mm,paperheight=210mm} \usefonttheme{professionalfonts}  \renewcommand{\sfdefault}{phv} %change font \DeclareMathSizes{14}{15}{7}{7}  \begin{document} \begin{frame} complesso: $\alpha=\alpha_{r}+i\alpha_{i}$ \end{frame}  \end{document}


I am hoping someone can give me a bit of advice on how to achieve something.  I am currently working on a model for one of the old MK .. British tanks. In the picture below you can see i have a lot of the basic elements, and am looking to attach the squarish object to the tracks at regular intervals.  I know i can snap objects together, in this case to the face of the mesh making up the track, and can duplicate the object and repeat that process to make the spacing the same. But i am not sure how i can achieve snapping all of the duplicate objects to the track as the track of course goes around the entire tank as opposed to being just a straight line.  Obviously i am a self taught amateur, so i am sorry if this seems like a stupid question, or if i am simply doing this is a difficult or stupid way. I make 3D models for my own love of doing so, and so am not exactly the most knowledgeable.  Any help or pointers would be very much appreciated.

I want to outline a curve in the form of text with a mesh (UV-sphere, cube etc.). How can I do that while saving mesh geometry without using the Curve modifier?


I want to use footcite. The problem is, that in the footcite it self it doesn't use the informations from the .bib file.  From my file:  \documentclass[12pt,a4paper]{article}  \usepackage[utf8]{inputenc} \usepackage[german]{babel} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{makeidx} \usepackage{graphicx} \usepackage{lmodern} \usepackage{tocbasic} \usepackage{biblatex} \usepackage[left=4cm,right=2cm,top=2cm,bottom=2cm]{geometry}  \bibliography{Master}  \author{xx}  \begin{document}  \include{./Titelseite}  \tableofcontents  \include{./Kap_1} %\include{./Kap_2} %\include{./Kap_3} %\include{./Kap_4}  \printbibliography  \end{document}   Master.bib:  @book{A01,   author = {Author, A.},   year = {2001},   title = {Alpha}, }   Kap_01:  \section{Intro} Blabla.\footcite{A01}   The output I get is a footcite^1 but in the bottom of the page there stands no informations about the book but rather just A01 and nothing else. Also using styles like style=mla  style=authordate does not change anything.  Also it doesn't print the bibliography. Why?  Any idea what I'm doing wrong?

Running the minimal example  \documentclass{article} \usepackage{filecontents} \begin{filecontents*}{\jobname.bib} @ARTICLE{example,   author  = {Other, Anthony Norman},   title   = {Some things I did},   year    = {2014},   journal = {J.~Irrep. Res.},   volume  = {1},   number  = {1},   pages   = {1-10} } \end{filecontents*} \usepackage[backend=biber]{biblatex} \addbibresource{\jobname.bib} \begin{document} Hello\cite{example}. \printbibliography \end{document}   I get the warning There were undefined references.  I have read  and know that I need to run:   LaTeX Biber LaTeX   However, my editor is only set up to run BibTeX. How do I go about setting up my editor/IDE to be able to run Biber, and how do I run the LaTeX/Biber/LaTeX cycle?  Answers (sorted alphabetically by editor name)                    Answer guidelines   Each answer should be for one editor. If the editor is cross-platform, if possible give a single answer with notes covering the minor platform variations. Please edit the question to include new answers in the 'link list' Each answer should be 'stand alone', i.e. don't say 'It's almost the same as editor Y but ...' for the editor part Instructions for 'build tools' such as arara or latexmk are welcome but should explain how to set up the editor in question as not all editors allow simple addition of arbitrary tools