Why does Meta Stack Exchange have its own chat server?

Edit:      explains that Stack Overflow has its own server due to sheer volume of traffic. However, it doesn't explain why Meta Stack Exchange has its own server, having only 5 active rooms compared to Stack Exchange's 60 active rooms.  To differentiate my question, I've changed my scope to specifically ask why Meta Stack Exchange has a separate chat server      Original Post  The Stack Exchange network has  for user chat.    (Stack Overflow)  (Meta Stack Exchange)  (Super User, Server Fault, Arqade, Ubuntu, Mathematics, Web Applications, and all other SE sites)   Why do Stack Overflow, Meta Stack Exchange, and Stack Exchange use separate, independent chat servers instead of sharing one subdomain?    Having separate servers means that users can have three separate chat accounts without even realizing. I only recently realized that, in addition to my  and per-site profiles, I also had separate accounts for , , and .  Profiles are fully separate with different profile settings, ignored user lists, favorited rooms, bookmarked conversations, and parent users. Each server has its own unique , , and .  I read a  speculating the servers may have been separated to improve performance. That reasoning could explain why Stack Overflow () is separate from Stack Exchange (). But if performance were the reason, why separate Meta Stack Exchange? As of posting, Meta only has   *Note: This question is not about unique per-site domain URLs. See


Install Ubuntu/Linux on new Kaby Lake processor

I'm buying a new laptop and refuse to use Win 10.  Being disabled, I’m having a hard time getting/searching for an answer to what I hope is a fairly straight forward question:  Can I install Ubuntu or any Linux distribution on the new Intel Kaby Lake processors?  I’m not sure what specific info you’ll need, so I’m including all the major specs: Sager P650HS-G / HM175 chipset / 7820HK processor / 64 GB RAM - Kingston Hyper X CL14 2400MHz / nVidia 1070 w/ G-Sync / Samsung 960 Pro NVMe M.2 for the OS / Duel Samsung 850 EVO SSD in RAID / Bigfoot Wireless-N1535 M.2  Hopefully all this will work with Ubuntu.  If any components listed need something special installed to work, please help direct me to what else I’ll need to do.  Thank you everyone for your help with this question!


What is the maximum number of images allowed per question?  I believe it's five links per question, but unsure about images.  If there's a good way to circumvent, that would be appreciated.    Sometimes it's not possible to grab text.  (for what it's worth, pushing the limit .)


As SE grows, lots of communities grow using it. Why not? So far, so good. As SE grows, lots of people find answers for their problems just being forwarded here by different search engines. Halleluja. As they get more and more solutions here, they want to reciprocate and give answers. Or they want to get help here by asking questions. And then they face moderation, close requests, migrations and alike. Let me introduce you , a user I kept an eye on for a week. He asked a question, thanked for all replies, stayed humble and helpful in his replies. He still could not grasp the differences between stackoverflow.com, programming.stackexchange.com and superuser.com. He could not keep up with our rules and did rage quit. Finally my question after this long prologue: How could we be more welcoming? How could we ease the learning curve? Is there really such a big gap between discussing issues through code (stackoverflow) or concepts and design (programming)? Is it a bigger difference than say the [c#] and the [java] tags? Am I the minority who has to jump between communities back and forth to ask and answer questions? Probably there is no clear answer to this, but I hope I made a difference just by you - my reader - reading this question.


Trying to remember name of an eerie story about a seemingly uninhabited Greek island

I read this in an old anthology years ago. A traveler is staying at a Greek seaside town when he notices a wooded island off the coast. He asks some of the local fishermen if they will give him a ride over to this island but no one will even talk about it. Later a young man with a noticeable scar surreptitously offers to take him across. Once there, the traveller leaves the fisherman to wait on the shore and has a look around. Once in the woods he finds stone sculptures of amazing realism, some very worn,  some newer, all with a look of surprise on their faces. The traveller, really concerned, returns to the boat, where he finds a sculpture of the scarred young man. Just as he realizes whose island this is, he hears someone behind him. Will he turn to look? Anyone remember this one?


Cancelling the downvote lead to +2 not +5

I have a question on voting system of SO. So I have seen a trend among some community members that they prefer to first downvote  the question and then point out the corrections they were hoping to see in the comments section and once it's done and they cancel their downvote.  No problems in that except that as I have read in the Reputation system of SO, it is written that on cancelling the downvote to the  question you will be awarded +2. That means there is a net loss of 3 reputation. Now the thing is, judging the quality of the question is a subjective thing. This could lead to good loss of reputation of OP. I don't think many community members know of this rule.  Today I faced this situation. Though the member didn't intentionally wanted to create me a loss of reputation, but it did. I think a  little hovering message while downvoting can go a long way to prevent this.


Changing Hostname and Serving with Apache

I want to serve my website locally with my hostname. It's gibberish now, but people in my network can reach it. Let's say my hostname is  >hostname ABCabcABC   And, if my local people open a browser and open http://ABCabcABC, they can reach my website.   I want my website to be reached at, let's say, http://aaa  I tried changing my hostname with hostname command. It didn't work.   I tried to make a new VirtualHost file and typed a new 'ServerName` value, but it didn't work either.   How can I fix this?   Thanks in advance.


How to change Drupal module load sorting(weight) order

I need to understand how can we change module weight.   Do we really change that value for custom module. What are the default values? If we change weight value what will be effect on Drupal bootstrap process?


How to fix no sound output from speakers or headphones?

If I plug in speakers or headphones to my PC I get no audio out from either. In my sound setting, the default is set to the speakers and the little icon with the green bars moves up and down with the sound as if it is working.  I have done a clean reinstall of Windows 7 and still have the same problem. Device Manager shows all drivers are good. I've reinstalled them just in case and same issue. I've been using the motherboard CD to install the drivers. I tried to uninstall it and allowed Windows 7 to find the driver automatically and it did but I'm still having the same issue.  What are my options? Or what do you recommended I do?


Finding the symmetry point in a quadratic graph

How do I find the symmetry point for a graph based on a quadratic equation?


We are having a file in Linux which contains one line per record, but problem comes when the line contains some new line characters. In this case, the backslash is appended at the end of line and the record is split into multiple lines. So below is my problem:  "abc def \ xyz pqr"   should be:  "abc def xyz pqr"   I tried sed -I 's/\\\n/ /g' <file_name> which is not working. I also tried the tr command but it replaces only one character, not the string.  Can you please suggest any command to handle this issue.


How to disable captive portal detection? How to remove exclamation mark on Wi-Fi or signal icon in Lollipop?

When connected to the Internet, the system checks if it's in a walled garden, which is simply trying to connect to Google. If it fails, in Android 5, there'll be an exclamation mark on the WiFi icon or signal icon.   In some situations, this is annoying. Say, in China, Google is blocked, the exclamation mark will always be there, which is meaningless.  How can I disable this check, and make the system assume, connected WiFi/mobile data is connected Internet?


Is there a key for AES-128, 256 etc, where cleartext equals ciphertext? (regardless of modes like chaining or ctr-cbc)


How to make a startup command uTorrent server

My issue that after reboot, I must enter this command using SSH PuTTY.    utserver -settingspath /opt/utorrent-server-alpha-v3_3/ -daemon   After this command I can access the uTorrent IP page.  How can I make it start up automatically?


What is the XY problem?  When asking questions, how do I recognize when I'm falling into it?  How do I avoid it?


Prove that sum of uniform distribution (-1,1) is also uniform (-n,n)?

If $d_i \in U(-1,1)$ (uniform distribution between -1 and 1 - not sure what the canonical notation is for this), then it seems intuitive that $\sum_{i=1}^n d_i \in U(-n,n)$ and thus $$P\big(\sum_{i=1}^n d_i > 0\big) = \frac{1}{2}$$.  If this is true, it also seems intuitive that $P\big(\sum_{i=1}^n p_id_i\big) \in U(-n,n)$ where $p_i \in {-1,1}$. That is, we can apply the same ideas to a combination of additions/subtractions, not just a summation.  I'm not classically trained in statistics and don't know if this is a standard theorem or if I am way off base here. Is this true / false? If it is true, is it provable using classical statistical techniques?


Site moderators can't see the history of the FAQ page

The now-retired FAQ page for SE sites still has a publicly visible revision history, e.g.:    for SFF SE  for German SE etc.   Publicly visible, that is, except to moderators of the site in question. For instance, I can't view the SFF post linked above: it gives me an  page. It seems very peculiar to have a post which is visible to nearly every member of the site, or even without being logged in at all, but invisible to those few users  who can normally see more pages than other users.  Presumably (?) this is something to do with the fact that these pages used to be editable only by moderators, and when this permission was changed, somebody went too far and took away visibility as well as editability. Obviously it's an extremely low-priority bug, but also a weird and unusual one.


Prove if the sum is convergent, then the square is convergent

I've seen multiple ways on how to solve it online (and most likely the majority are wrong), but I don't know how to solve this fully so that I could get the full grade during my exam.  The question is as follows:     Prove that if $\sum a_n$ is convergent with $a_n > 0$ for all $n$,   then $\sum a^2_n$ is also convergent.   I understand that the starting point to prove this is that $\lim a_n =0$, but after that I really don't know what I'm supposed to say.


What's the best way to check if a file exists in C?

Is there a better way than simply trying to open the file?  int exists(const char *fname) {     FILE *file;     if ((file = fopen(fname, "r")))     {         fclose(file);         return 1;     }     return 0; }


GPG error: The following signatures couldn't be verified because the public key is not available

Possible Duplicate:          after sudo apt-get update I get this error:  W: GPG error: http://archive.hivemind.me all Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3C962022012520A0


When a creature changes form is its melded equipment still burdensome?

My human PC has been forced to assume magically the form of a typical , and his gear has melded into this new form. Does this melded equipment still have weight? If it does still have weight, should that weight be added to squirrel-me's body weight, or should squirrel-me be considered carrying that gear, probably making it so squirrel-me pretty much can't move?


Is the inversion in “Let’s see ʜᴏᴡ ᴄᴀɴ ᴡᴇ do this” an error for “Let’s see ʜᴏᴡ ᴡᴇ ᴄᴀɴ do this”?

I’m reading about the C++ Boost library, and  drew my attention:     Once the two steps have been successfully completed, the process can   start writing to and reading from the address space to send to and   receive data from other processes. Now, let’s see how can we do this   using Boost.Interprocess.   I assume the sentence in bold should be written as let's see how we can do this.   Has the original sentence been mistakenly written by somehow (like perhaps by a non-native speaker, for example), or was this reversed order intended to emphasize something?


How do i post the content of the div on the middle of the body?

hello i am working in an web applications when i want to  put the grid on the center  my code not work and the grid still on the same place , this is what i tried, i am stuck with it  and i did many way but this  that i want i cant get it any help please ? <!DOCTYPE html>    <title>griad</title>

     The output of my code:  and this is what i want:


Biblatex-apa style is missing a comma in the references. why?

I have been trying to solve this problems for hours, but there is no solution in sight.  Until a few weeks ago, my biblatex-apa style was working like a charm. Although, after installing the updates and Biber, the reference section became a problem. It should display a journal article by two authors with a comma after the first author, but it doesn't:     Weber, M. & Ruch, W. (2012). The role of character strengths in adolescent romantic relationships: An initial study on partner selection and mates’ life satisfaction. Journal of adolescence, 35(6), 1537–1546. doi:10.1016/j.adolescence.2012.06.002   it should look like this:     Weber, M., & Ruch, W. (2012). The role of character strengths in adolescent romantic relationships: An initial study on partner selection and mates’ life satisfaction. Journal of adolescence, 35(6), 1537–1546. doi:10.1016/j.adolescence.2012.06.002   This is how my document looks like:   \documentclass[12pt, onecolumn]{apa6}   \usepackage[utf8]{inputenc} \usepackage[american]{babel} \usepackage{csquotes} \usepackage[style= apa, backend=biber]{biblatex} \bibliography{testbib} \DeclareLanguageMapping{american}{american-apa}   \begin{document}  Some text \parencite{Weber2012}.  \printbibliography \end{document}   And the BibTeX file:  @article{Weber2012, abstract = {}, author = {Weber, M. and Ruch, W.}, doi = {10.1016/j.adolescence.2012.06.002}, file = {}, issn = {1095-9254}, journal = {Journal of adolescence}, number = {6}, pages = {1537--1546}, pmid = {22749517}, publisher = {Elsevier Ltd}, title = {{The role of character strengths in adolescent romantic relationships: An initial        study on partner selection and mates' life satisfaction.}}, url = {http://www.ncbi.nlm.nih.gov/pubmed/22749517}, volume = {35}, year = {2012} }    I have tried various things so far, but none of it helped: e.g,   \renewcommand*{\finalnamedelim}{ \finalandcomma}   or  \renewcommand\finalandcomma{\addcomma}   Even in the biblatex manual, the reference examples of two authors is without the comma (it works for three or more authors). There should be a comma, according to . Why is that comma not there? And how could I insert that into my references?


Problem Statement     Given finite $X \neq \emptyset$ together with an associative binary operation, if left-cancellation and right-cancellation laws hold, is $X$ a group?   Attempt  We know that for all $x, y, z \in X$, left-cancellation $$xy = xz \implies y = z$$ holds.  Thus, the function $L_{x}:X \to X$ defined by $$L_{x}(w)=xw$$ is injective.  Since $X$ is finite, $L_{x}$ must also be surjective.  This means that there exists an element $e$ of $X$ such that $L_{x}(e)=x$, i.e. $x=xe$.  First, we want to show that $e$ is in fact a two-sided identity for $X$.  So let $v$ be an arbitrary element of $X$, and consider $xv=(xe)v=x(ev)$ (by associativity).  Thus, by left-cancellation, $v=ev$ for all $v$, i.e. $e$ is a left identity.  Now consider $vv=v(ev)=(ve)v$ (again, by associativity).  By right-cancellation, we conclude that $v=ve$, i.e. $e$ is a right identity.  Next, we need to show the existence of inverses.  From before, for every $w \in X$, the function $x \mapsto wx$ is surjective, so there is an element, say $w_R$, such that $w{w_R} = e$.  Similarly, there is an element $w_L$ such that ${w_L}w = e$.  Since $$w_L = {w_L}e = {w_L}(w{w_R}) = ({w_L}w){w_R} = e{w_R} = w_R,$$ we conclude that $w_L = w_R$ is a two-sided inverse for $w$.  Caveat  But wait!  I have not yet established closure of the binary operation!  Additionally, I also need to show that the result in this problem may be false if $X$ is infinite.  Any hints you can provide will be gladly appreciated!  Question     Is my attempt above acceptable for the given problem at hand?  Or would there be a more direct approach?


How to hide a block based on content type?

I have a custom content type where when loaded, I want to HIDE (no show) a regions block. Been looking around trying to find the answer and have come up short. Ideally, I'd want to do it in a preprocess or something, not within a template. Tried accomplishing it with Context, but appears that only allows you to add blocks to regions, not remove them. Fairly new to Drupal, so bare with me.


How do I respond to my professors email about recommendation letter? He is out of the country for sometime and his FIL is ill

I have contacted my professor about recommendation letter for my applications to PhD programmes. He has provided letters for few of my application.   Right now I am applying to few more universities and have contacted him again to provide few more letters in support of my application. He responded by saying that he is in a different country and his father-in-law is ill. He said he would provide the letters once again when he is back in the country. How should I respond to his email? I feel bad about constantly bothering him about letters of recommendation.


Function Olympiad Problem: Define $f(n)$ such that $f(n)$ is a positive integer, $f(n+1)$ $>$ $f(n)$ and $f(f(n))$ $=$ $3n$. The value of $f(10)$ is?

If you know me at all, or have read my profile, or have seen any of my previous questions, you might know that I am very interested in Olympiad maths and have come across many challenging maths problems, although I'm not too strong in the functions department myself. Could you please help me with the following problem? Again, any help and contributions are greatly appreciated.  For each positive integer $n$, define $f(n)$ such that $f(n)$ is a positive integer, $f(n+1)$ $>$ $f(n)$ and $f(f(n))$ $=$ $3n$. The value of $f(10)$ is?  This was a multiple choice question, and the possible answers were (A)12, (B)15, (C)19, (D)21, (E)30  Okay, so far I know that this function must be injective because it is strictly increasing, because $f(n+1) > f(n)$. I don't think that we can know yet if this function is surjective or not.  This shouldn't be too much of a hassle for most experienced mathematicians (like the users of this site) but for me it makes little sense. And I try, I really do! Just now I searched what injective and surjective means, and I finally understand that much, so... yea. Improvement.  Anyway, any help or contributions will be greatly appreciated. Thank you! :)


How can I verify a Google authentication API access token?

How can I verify a Google authentication access token?  I need to somehow query Google and ask: Is [given access token] valid for the [example@example.com] Google account?  Short version: It's clear how an access token supplied through the  can be used to then request data from a range of Google services. It is not clear how to check if a given access token is valid for a given Google account. I'd like to know how.  Long version: I'm developing an API that uses token-based authentication. A token will be returned upon provision of a valid username+password or upon provision of a third-party token from any one of N verifiable services.  One of the third-party services will be Google, allowing a user to authenticate against my service using their Google account. This will later be extended to include Yahoo accounts, trusted OpenID providers and so on.  Schematic example of Google-based access:    The 'API' entity is under my full control. The 'public interface' entity is any web- or desktop-based app. Some public interfaces are under my control, others will not be and others still I may never even know about.  Therefore I cannot trust the token supplied to the API in step 3. This will be supplied along with the corresponding Google account email address.  I need to somehow query Google and ask: Is this access token valid for example@example.com?  In this case, example@example.com is the Google account unique identifier - the email address someone uses to log in to their Google account. This cannot be assumed to be a Gmail address - someone can have a Google account without having a Gmail account.  The Google documentation clearly states how, with an access token, data can be retrieved from a number of Google services. Nothing seems to state how you can check if a given access token is valid in the first place.  Update The token is valid for N Google services. I can't try a token against a Google service as means of verifying it as I won't know which subset of all Google's services a given user actually uses.  Furthermore, I'll never be using the Google authentication access token to access any Google services, merely as a means of verifying a supposed Google user actually is who they say they are. If there is another way of doing this I'm happy to try.


What future consequences are possible from a Standard Visitor visa refusal?

Well, I was supposed to visit UK on 20th-22nd July this year to participate in a competition / conference as an undergraduate student from Bangladesh. I submitted my application on 18th June but it was refused:     As Evidence of your circumstances you have submitted bank name statement in your father's name... for account number ***** shows a balance of ***BDT (around 2,500USD) after a deposit of ***BDT (around 1,600USD). There is no evidence of the source of these funds. You have provided electricity bills but no evidence of your father's employment or income. I am not satisfied that the documents you have provided evidence your circumstances and this lends me to doubt that you are seeking entry only for the purpose and duration stated. I am not satisfied that you are genuine visitor and will leave the the United Kingdom at the end of your visit.   I should've probably added another document stating my father's occupation and that he will bear my costs. However, it is general knowledge in my country that a father will very likely bear the cost of his children. Probably not so in the UK. Incidentally, I have searched the term Visa refused for source of funds from a private window and the first page of Google results are all related to UK visas.  What pains me most is that this letter was signed on 23rd July even though I submitted my application a month earlier. Which means that for the whole time they didn't process my application. They could have called/contacted me if they needed any further documents. However they didn't which, I think, means they tend to reject applications more than they accept and do not care much about the applicants.  However, I will not reapply for a visa as the event in which I was due to participate is already over.  I was wondering what the future consequences of this refusal might be. I have previously visited India for a conference and stayed for 11 days.  Now that I have this smirch in my passport will it affect my future visits to other countries?    There were six of us. We all submitted similar documents according to my knowledge. However, only one received a visa, probably because he had visited Russia and USA. Two of us were refused and the other three are still waiting for their decisions.


Where does the Pauli Repulsive Force come from that counteracts the attraction between atoms and ions?

I'm learning about such things as ionic and covalent bonds, and the reason given for the ionic bonds is electrostatic attraction. However, if that were true, then the two ions would accelerate toward each other and shortly collide with each other. There must be a force opposite the electrostatic force that is repelling the ions, with exactly the same magnitude so as to cancel out the electrostatic force. (Edit: I'm actually referring to the ionic bond between cations and anions in this first paragraph, like sodium and chloride ions. Below is what I found by researching this topic, dealing mainly with covalent/molecular bonding.)  The following quote is from The Mechanical Universe:     For example, the potential energy of a pair of Hydrogen atoms has a   position of stable equilibrium. The potential energies of interaction   between atoms are due to the electrical forces between them, causing   attraction when they're far apart. At smaller distances, they resist   being squeezed together. The result is an equilibrium position where   attraction and repulsion are in perfect balance. At that position,   they bind in a Hydrogen molecule.   I understand that on a larger (planetary) scale, there is a centrifugal potential that is inversely proportional to the distance $r$ that adds up with the gravitational potential to create this graph:    I'm looking for an analogue to this on the molecular scale. I've recently found out about the , which gives this equation and curve:$$V_{LJ}=\epsilon \left[ \left(\frac{r_m}{r}\right)^{12} - 2\left(\frac{r_m}{r}\right)^6 \right]$$    In the wikipedia article, it says     ...the repulsive term describes Pauli repulsion at short ranges due to overlapping electron orbitals    Later on it is noted that     The repulsive term has no theoretical justification.   So then this is my question: What is the nature of the "Pauli repulsive force"?  If it's possible, I would appreciate an answer with cited sources.   Edit: After some more research, I've found that attraction between two hydrogen atoms (which are both neutral) comes from . Collectively, the attraction and repulsive forces at the molecular scale are dubbed the . The wiki on Van der Waals forces mentions A repulsive component resulting from the Pauli exclusion principle that prevents the collapse of molecules. I would like to learn more about how the Pauli exclusion principle manifests itself as a repulsive force between any two atoms/ions.


I am trying to install the lib32asound2 (dpkg -i lib32asound2_1.0.25-4ubuntu4_amd64.deb ) package on Ubuntu 13.1 but instead I get this message:  (Reading database ... 224124 files and directories currently installed.) Preparing to replace lib32asound2 1.0.25-4ubuntu4 (using lib32asound2_1.0.25-4ubuntu4_amd64.deb) ... Unpacking replacement lib32asound2 ... dpkg: dependency problems prevent configuration of lib32asound2:  lib32asound2 depends on libasound2 (= 1.0.25-4ubuntu4); however:   Version of libasound2:amd64 on system is 1.0.27.2-1ubuntu6.  dpkg: error processing lib32asound2 (--install):  dependency problems - leaving unconfigured Errors were encountered while processing:  lib32asound2   Could anyone help me out, please?


Given the following class class sq():     def __init__(self,func,x):         self.func = func         self.x = x      def square(self):         return self.func(self.x)**2      y = lambda x,p: x + p p_ls =  range(1,11) x = 0  objects = [sq(lambda x: y(x,pi),x) for pi in p_ls] squares = [sq(lambda x: y(x,pi),x).square() for pi in p_ls] #[1, 4, 9, 16, 25, 36, 49, 64, 81, 100] squares1 = [obj.square() for obj in objects] #[100, 100, 100, 100, 100, 100, 100, 100, 100, 100]  i can't understand why squares are not equal to squares1. Its seems like all objects in objects list are using p = p_ls[-1]. Is there a way to "store" func each time the class is called ?


What is the variance of the sample variance? In other words I am looking for $\mathrm{Var}(S^2)$.  I have started by expanding out $\mathrm{Var}(S^2)$ into $E(S^4) - [E(S^2)]^2$  I know that $[E(S^2)]^2$ is $\sigma$ to the power of 4. And that is as far as I got.


Drawing an arrays data structure linked with arrows using Tikz

I would like to implement the following image representation of two arrays with arrows using TikZ.    Please provide some hints to go in the right direction.


Where is the Ubuntu file system root directory in Windows Subsystem for Linux and vice versa?

I have installed Ubuntu subsystem on Windows 10 (after enabling feature in settings), but where is the Ubuntu file system root directory located in the drive?


How can Zeno's dichotomy paradox be disproved using mathematics?

A brief description of the paradox taken from :     Suppose Sam wants to catch a stationary bus. Before he can get there, he must get halfway there. Before he can get halfway there, he must get a quarter of the way there. Before traveling a quarter, he must travel one-eighth; before an eighth, one-sixteenth; and so on.      This description requires one to complete an infinite number of tasks, which Zeno maintains is an impossibility. This sequence also presents a second problem in that it contains no first distance to run, for any possible (finite) first distance could be divided in half, and hence would not be first after all. Hence, the trip cannot even begin.      The paradoxical conclusion then would be that travel over any finite   distance can neither be completed nor begun, and so all motion must be   an illusion.   How can this be disproved using math, as obviously we can all move a walk from one place to another?


Can someone explain the grammar of this sentence to me?

Can someone please explain this “would have” + verb construction in this sentence?     “Why did you wait outside? I would’ve text you when I got here”   I’m a little confused. Shouldn’t it be “I would’ve texted”?  Also, why is it “got here” not “get here”?


Interaction in the linear schrödinger equation

Recently I have done some simulations with a linear system that behaves similarly to the wave equation. Now I have a bit of trouble understanding when interaction is possible in linear theories, especially in the context of quantum mechanics. If we, for instance, consider a linear theory like the maxwell equations we have no interaction between two light waves (as far as I recount). I have read the general answer , however I still do not get how one would formulate the interaction between e.g. two electrons described by a wave function. If we take the time dependent Schrödinger Equation: $$i \hbar \frac{\partial}{\partial t} | \psi \rangle = \hat{H} | \psi \rangle $$ How would the Hamiltonian be formulated to incorporate interaction and still be linear? The often seen expression $$\hat{H} = \hat{T} + \hat{V}$$ where $$\hat{V} = \frac{e^2}{4 \pi \epsilon_{0}} \frac{1}{\left| \vec{r}_{1} - \vec{r}_{2} \right|} $$ does not make so much sense to me here, because I do not understand how $\vec{r}_1 , \vec{r}_2$ would be defined at different times in the time dependent Schrödinger equation without involving the wave function itself in a non linear fashion.


How can I reach the UI to configure the autostart applications in Ubuntu 11.10? Please don't tell me, I have to do it using the terminal or creating a starter on my own and please don't tell me, it is gone!


How to get long enumerate list in \longtabu across the page like MS word can easily do?

The following is the problematic example:  \documentclass[12pt]{article} \usepackage{longtable} \usepackage{tabu} \usepackage{array} \usepackage{lipsum}  \begin{document} {\setlength{\tabulinesep}{3pt}   \begin{longtabu}to \textwidth { | m{2cm} | X[c] | }         \hline         Item & item \\         \hline         Item &          \begin{enumerate}             \item \lipsum[1]             \item \lipsum[2]             \item \lipsum[3]             \item \lipsum[4]         \end{enumerate}\\         \hline \end{longtabu} \end{document}   It generates two pages     There are two problems:   The enumerate list is split with first row, leaving the first row in the first page lonely. The enumerate list is directly running out of the second page. How to solve this in longtabu?   Can't latex just achieve the effect of MS word? In MS word, you just keep typing with list like, and they automatically across the page like this


Clicking "I'm done" without any action on an accepted answer fails the audit

I was recently presented with  of an accepted answer that looked fine to me. Without any action on my side, the "I'm done" button was available. I assumed this was due to the answer being accepted (I haven't encountered this situation before) and I considered it worth clicking.     Fail.   So there are basically two bugs here:   the "I'm done" button shouldn't have been available since I didn't do anything Since I didn't downvote, flag or comment, the audit shouldn't have failed


If $f$ is integrable, how to show that $\sum_{n=1}^\infty 2^n\lambda(\{\lvert f\rvert\ge 2^n\})<\infty$

I want to show the following converse of an (apparently) common integration theory exercise. Suppose $f:[0,1]\rightarrow\mathbb R$ is integrable, then $$\sum_{n=1}^\infty 2^n\lambda(\{\lvert f\rvert\ge 2^n\})<\infty.$$ Since series convergence is annoying to prove, I thought the best way to tackle this problem would be by assuming that the series doesn't converge, then showing that $f$ can't be integrable. However, I couldn't get much from the series not converging, as the terms of the series might well go to $0$ even if the series doesn't converge. Is there something I'm missing to make this approach work? Or is a direct proof easier somehow?


I have big with tags(parsed xml)  How to remove from string this elements:      <Error>                  <Text></Text>         <Severity></Severity>     </Error>   just   xml = xml.replaceAll("<Error>.*</Error>", "")   not works, error still in string..


How to fix EFI boot "Software Update is Required for this disk" when trying to boot linux?

I created a bootable linux USB following . When I startup the machine holding Option an EFI Boot drive shows up. When I select it, it goes to Apple Logo Loading > Then Light Grey Screen > Apple Logo Loading Again > Then the messages below show up:    With internet, I can update whatever this is, it takes 4 minutes, then the machine reboots to normal Macintosh HD. When I boot back again it keeps asking for an update. I updated 4 times and it stills shows up.  Without internet, the message below shows up:   When I click "Startup Disk" the EFI boot does not show up and all I can select is my Macintosh HD.   (this image is from a forum, my Macbook is up-to-date, MacOS Catalina 10.15.4)  Googling up I found this could happen because of T2 chip securities, I disabled all of it's securities in recovery mode. The problem persists. What may be causing this issue? How can I fix it?


If two matrices $A$ and $B$ commute, then $e^{A+B} = e^A e^B$ by rearrangement of the $A$'s and $B$'s in the sum. But would the converse be true?   So far I've tried to find a counterexample by considering the cases where $A$ and $B$ are 2x2 real upper triangular matrices, but those don't work.   Any hint is appreciated, thanks.


In several places on this site the sum $\displaystyle\sum_{n=1}^{\infty}\dfrac{\sin(n)}{n}$ has been discussed as a generalized alternating series, which therefore converges. I am curious about the sum $\displaystyle\sum_{n=1}^{\infty}\dfrac{|\sin(n)|}{n}$, which I am sure does not converge.  Here is my "proof".  Steps 2 and 3 clearly needs some clarification.  Step 1) Define $A\subset\mathbb{R}$ by $A:=[\pi/4,3\pi/4]\cup[5\pi/4,7\pi/4]\cup\ldots$.  For any $x\in A$, $|\sin(x)|\geq\sqrt{2}/2$.  Step 2) Since $\pi$ is irrational, roughly half the integers are in $A$.  That is, if we define $\#_A(n)$ to be the cardinality of $\{1,\ldots,n\}\cap A$, $\displaystyle\lim_{n\to\infty}\dfrac{\#_A(n)}{n}=\dfrac{1}{2}$.  Step 3) Therefore $\displaystyle\sum_{n=1}^{\infty}\dfrac{|\sin(n)|}{n}>\sum_{n>0,n\in A}\dfrac{|\sin(n)|}{n}>\sum_{n>0,n\in A}\dfrac{\sqrt{2}/2}{n}\approx\dfrac{1}{2}\sum_{i=1}^n\dfrac{\sqrt{2}/2}{n}$.  Step 4) Since the last sum in Step 3 diverges, the sum $\displaystyle\sum_{n=1}^{\infty}\dfrac{|\sin(n)|}{n}$ diverges.  I beleive this is more or less intuitively right, but I do not really know the theory to make rigorous Steps 2 and 3.


Having issue retrieving data from firebase databse

I'm having issue retrieving data from firebase.im trying to get the  information related to this node "0506326662" and the sub-node "Location". I also created class named UserInformation that will hold the data as an object but for some reason i'm getting an error and i have no clue where it comes from and why.   databaseReference.child("Users").child(numbeT).                 child("Location").addValueEventListener(new ValueEventListener() {             @Override             public void onDataChange(@NonNull DataSnapshot dataSnapshot) {                  for(DataSnapshot ds:dataSnapshot.getChildren())                 {                      uInfo=new UserInformation();                      uInfo.setLastOnline(ds.child(numbeT).getValue(UserInformation.class).getLastOnline());                     uInfo.setLag(ds.child(numbeT).getValue(UserInformation.class).getLag());                     uInfo.setLat(ds.child(numbeT).getValue(UserInformation.class).getLat());                  }     ERROR LogCat(firebase)  2019-03-23 17:58:52.187 4657-4657/com.alrubaye.mytracker E/AndroidRuntime: FATAL EXCEPTION: main     Process: com.alrubaye.mytracker, PID: 4657     java.lang.NullPointerException: Attempt to invoke virtual method 'java.text.SimpleDateFormat com.alrubaye.mytracker.UserInformation.getLastOnline()' on a null object reference         at com.alrubaye.mytracker.MyServie$1.onDataChange(MyServie.java:79)         at com.google.firebase.database.core.ValueEventRegistration.fireEvent(com.google.firebase:firebase-database@@16.1.0:75)         at com.google.firebase.database.core.view.DataEvent.fire(com.google.firebase:firebase-database@@16.1.0:63)         at com.google.firebase.database.core.view.EventRaiser$1.run(com.google.firebase:firebase-database@@16.1.0:55)         at android.os.Handler.handleCallback(Handler.java:873)         at android.os.Handler.dispatchMessage(Handler.java:99)         at android.os.Looper.loop(Looper.java:193)         at android.app.ActivityThread.main(ActivityThread.java:6669)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)   UserInformation class:  package com.alrubaye.mytracker;  import java.text.SimpleDateFormat;  public class UserInformation {     private SimpleDateFormat lastOnline;     private String lag;     private String lat;      public UserInformation() {      }      public SimpleDateFormat getLastOnline() {         return lastOnline;     }      public void setLastOnline(SimpleDateFormat lastOnline) {         this.lastOnline = lastOnline;     }      public String getLag() {         return lag;     }      public void setLag(String lag) {         this.lag = lag;     }      public String getLat() {         return lat;     }      public void setLat(String lat) {         this.lat = lat;     } }


There are plenty of recipes regarding how to cook fish, and other foods, in olive oil.  This puzzles me because olive oil has a very low smoking point. So I'll burn it if I cook fish at 350 degrees. If I set the temp to 200 degrees, the fish will cook for ages and will basically boil in it's own juices.  So how do seasoned cooks deal with this? How do you cook in olive oil?


How can someone have 101 reputation on multiple SE sites?

I came across this account and noticed that it has got a reputation of exactly 101 points on more than 20 Stack Exchange platforms even without posting any question or answer (see image below). At first I thought it's due to the first days of SE when there hasn't been such strict reputation gaining rules as today. But then I saw that this is even true for accounts that have been created only half a year ago.        So, am I missing something here like "Take this online introduction tour and gain 101 points"? I'm asking because for me it takes quite a long time to gain enough repution to become a productive member (voting, commenting, editing,..) on SE. Especially when joining a new platform.    DISCLAIMER: I don't demand anything I'm just wondering. ;)


What can i do to update the android version of my android device if there is no available update available for my device?

my device is ondo vi10. it is a android tablet i bought from a IT Fair. The current android version is 4.0.3. What are some ways i can update it?


I am trying to write a tutorial for simple QGIS functions. I would like to include a set of buttons, each with an explanation of what its function is. Can anyone tell me where I could find the buttons as an image, or would I need to print screen and cut up (digitally) each toolbar?


Can someone please give me feedback on my attempted proof that Zorn's Lemma implies the Axiom of Choice? I have a very good idea how to do it, but need help with some small details.   This is my proof so far... major gaps missing, please help!  Let $X$ be a nonempty set. Let $S = \{f : f \text{ is a choice function on } A \subset \mathcal{P}_{0}{X}\}$. Explain why $S$ nonempty. Declare $f_{1} \leq f_{2}$ if $Dom(f_{1}) \subset Dom(f_{2})$ (Why is this a partial ordering?). Let $T$ be a chain in $S$. Let $F$ be the union on the functions in $T$. (Why is $F$ also a choice function?) Therefore, by Zorn's Lemma, there exists a maximal function $m$. (Why is $m$ a choice function on every $A \subset PX$). Suppose not, then there exists an $A \subset \mathcal{P}_{0}{X}$ such that $m$ is not defined on $A$ (Don't know how to finish this!!) Therefore, $f \in S$ and $m < f$, contradicting $m$ being maximal. Thus, $m$ is a choice function for the entire set $\mathcal{P}{X}$.


I am trying to use CSS selector :before to put image before text. This is my snippet  But it seems the alignments is a bit off. Text is not vertically aligned with the image.    .resource {   color: #007f00;     display: inline;     margin-top: 20px;  } .resource:before {  content: '';     width: 26px;     height: 20px;     display: inline-block;     margin-right:5px;     background-size: contain;     background-repeat: no-repeat;     margin-top: 19px;     background-image:url("https://www.w3schools.com/bootstrap/cinqueterre.jpg");  }
Presentation
     I have added margin-top in :before but it didn't work. Any help would be appreciated.


unity error: An object refrence is required for non-static field, method, or property "Enemy.points"

using System.Collections; using System.Collections.Generic; using UnityEngine;  public class Enemy : MonoBehaviour {     public Animator Wall;     public AudioSource hurtSound;     public Animator animator;     public int maxHealth = 100;     int currentHealth;     public int points = 0;     public GameObject camera;     void Start()     {         currentHealth = maxHealth;     }           public void TakeDamage(int damage)     {         currentHealth -= damage;         animator.SetTrigger("hurt");         hurtSound.PlayOneShot(hurtSound.clip);         if(currentHealth <= 0)         {             Die();         }     }      void Die(){         Wall.Play("goDown");         animator.SetBool("isDead", true);         GetComponent<Collider2D>().enabled = false;         this.enabled = false;         points += 1;         Debug.Log(points);              }       } using System.Collections; using System.Collections.Generic; using UnityEngine;  public class door : MonoBehaviour {          void Update(){         if(Enemy.points == 3){             print("yeee");         }     }  }  i want to refrence the points int to a diferent script but i cant because of this error An object refrence is required for non-static field, method, or property Enemy.points. here is the points int public int points = 0;  here is where i am tring to refrence it void Update(){         if(Enemy.points == 3){             print("yeee");         }     }  but it doesnt work help


I installed Ubuntu and now I want to get rid of it because I hardly use it. I deleted the Ubuntu partitions, but that also broke Grub. I reinstalled Ubuntu and then repaired Grub, but I still want to get rid of Ubuntu. I don't have a CD burner, so I cant create a Windows rescue disk. I want to know if I can delete Ubuntu partitions and reinstall Grub via live USB to still be able to boot into Windows 7.


How to pass the password to su/sudo/ssh without overriding the TTY?

I'm writing a C Shell program that will be doing su or sudo or ssh. They all want their passwords in console input (the TTY) rather than stdin or the command line.  Does anybody know a solution?  Setting up password-less sudo is not an option.   could be an option, but it's not present on my stripped-down system.


Unable to install Ubuntu 14.04 LTS on packard bell imedia S2185 with win 8 previously instlled

I was following the guide at:    I changed the BIOS to show the boot menu and selected the 14.04 installation USB drive.  Next, when prompted, I selected, "Try Ubuntu without installing"  This brings me to a screen displaying:   BusyBox v1.21.1 etc. finishing in a mount failure  failed: No such device  Can not mount /dev/loop0 (/cdrom/casper/filesystem.squashfs) on //filesystem.squashfs  Any ideas why Ubuntu will not run?


Setting compression method when exporting composer from QGIS to PDF

I see that export of the composer to PDF in QGIS uses JPEG compression by deafult (my estimate maybe 75-80%, which is not good enough for my maps). Where can I change this? Can I set somewhere lossless compression/compaction (e.g. LZW)?


Does an Indian citizen need a transit visa in Australia?

Indian passport holder. Do I need transit visa in Sydney?


How to fix an iPhone stuck on "Connect to iTunes" screen after iOS8 update?

My iPhone 5S is stuck on the "Connect to iTunes" screen after trying to install the iOS 8 update. I can't connect to iTunes because I have a Google Chromebook.  I don't know what to do. I'm dyslexic and I have Asperger's. I need the iPhone to communicate with people because I have speech problems.


Why do I see an "Hiding Questions" message for non-existent tags?

When trying to view the  tag on Gaming.SE I see this message:    This tag apparently doesn't exist, nor have I ignored it.  When I try to view the tag page for a tag I have ignored, I don't see this message:    Why is this message appearing?


Possible Duplicate:          I have edited a few posts today and the edits got accepted. But, I did not gain any reputation.   What could be the reason?


Please name this 70's/80's (foreign) dystopian totalitarian sci-fi movie

Saw this in the late eighties. Boy escapes the grasp of an all female command and having been misled to believe a holocaust type scenario joins with a girl.  They work their way through a series of rooms. The final scene, I remember, involves the boy slicing the wall with a knife to reveal sunlight and sand (beach or desert).  It was a false lie in a totalitarian underground cult. I believe it was subtitled thus foreign.


Unmangling the result of std::type_info::name

I'm currently working on some logging code that supposed to - among other things - print information about the calling function. This should be relatively easy, standard C++ has a type_info class. This contains the name of the typeid'd class/function/etc. but it's mangled. It's not very useful. I.e. typeid(std::vector<int>).name() returns St6vectorIiSaIiEE.  Is there a way to produce something useful from this? Like std::vector<int> for the above example. If it only works for non-template classes, that's fine too.  The solution should work for gcc, but it would be better if I could port it. It's for logging so it's not so important that it can't be turned off, but it should be helpful for debugging.


I am quite confused what's the difference between =, $ and # before the Request.QueryString?  <a href='MyPage.aspx?Variable=<%= Request.QueryString["Variable"] %>'>Go to this page


new here. I have an old E-machine which as Windows Vista on it and I want to erase the Windows Vista, and install Ubuntu on it instead, but I am not sure where to start. Can I first install Ubuntu, and THEN erase Windows Vista, or is there a more sure method? I appreciate your help.


Is there any gold standard for modeling irregularly spaced time series?

In field of economics (I think) we have  ARIMA and GARCH for regularly spaced time series and Poisson, Hawkes for modeling point processes, so how about attempts for modeling irregularly (unevenly) spaced time series - are there (at least) any common practices?  (If you have some knowledge in this topic you can also expand the corresponding .)  Edition (about missing values and irregular spaced time series) :  Answer to @Lucas Reis comment. If gaps between measurements or realizations variable are spaced due to (for example) Poisson process there is no much room for this kind of regularization, but it exists simple procedure : t(i) is the i-th time index of variable x (i-th time of realization x), then define gaps between times of measurements as g(i)=t(i)-t(i-1), then we discretize g(i) using constant c, dg(i)=floor(g(i)/c and create new time series with number of blank values between old observations from original time series i and i+1 equal to dg(i), but the problem is that this procedure can easily produce time series with number of missing data much larger then number of observations, so the reasonable estimation of missing observations' values could be impossible and too large c delete "time structure/time dependence etc." of analysed problem (extreme case is given by taking c>=max(floor(g(i)/c)) which simply collapse irregularly spaced time series into regularly spaced  Edition2 (just for fun): Image accounting for missing values in irregularly spaced time series or even case of point process.


How can I find out what caused my reputation loss?

I'm new to this site. Although I  had made my account almost 6 months ago,  I've started using stackexchange only very recently (about 10-15 days). I'm active particularly on stackexchange mathematics. The reason why I'm writing this is I want to know in what ways can a person lose reputation on any stackexchange website? I had a reputation of 717 on stackexchange mathematics but the moment I refreshed the page I lost about 20 points and my reputation came down to 697. No-one has downvoted any of my posts. I do not have any problem with losing reputation but I should like to know where I lost 20 points without any reason?


So I bought some Atlantic salmon 2 days ago and put it in the freezer soon as we got it from the grocery.   Anyways last night I put it in the fridge to thaw out for today, well today's plan's got moved around and I didn't have a chance to cook it.....so I put it back in the freezer.  Is this safe? (if I decide to dethaw it again for the fridge)?


Moving users folder on Windows Vista/7 to another partition

When I format the computer and reinstall Windows, my first step is move the My Documents folder to another partition. In Windows XP it wasn't enough because the desktop folder and another user folders was in the primary partition.  Now in Windows Vista and 7 we can use junctions/symlinks to "move" the folder to another partition and Windows and another programs will think that the data is in the primary partition.  What the fastest and secure steps to move the Users folder to another partition and to create the hardlinks correctly?


Which versions of C++ redistributables can I remove?

I have a number of Microsoft Visual C++ 2005 and 2008 Redistributable and I would like to know which ones are safe to remove, because there are actually more than 10 installed on my computers.   Microsoft Visual C++ 2005 ATL Update kb973923 - x64 8.0.50727.4053 Microsoft Visual C++ 2005 Redistributable Microsoft Visual C++ 2005 (x64) Microsoft Visual C++ 2008 ATL Update kb973924 - x64 9.0.30729.4148 Microsoft Visual C++ 2008 Redistributable - x64 9.0.30729.17 Microsoft Visual C++ 2008 Redistributable - x86 9.0.30729.17 Microsoft Visual C++ 2008 Redistributable - x86 9.0.30729.4148 Microsoft Visual C++ 2008 Redistributable - x86 9.0.30729.4974 Microsoft Visual C++ 2010 x64 Runtime - 10.0.30319   It could be that these versions are all different, but a confirmation of that is fine for me as well. Thanks in advance.  PS. I'm using an x64 machine one windows 7.


Why is the first nested iteration faster than subsequent ones?

Test application:  public class Main {      private static long a = 0;      public static void main(String[] args) {         for (int i = 0; i < 5; i++) {             long start = System.currentTimeMillis();             for (long j = 0; j < 5000000000L; j++) a++;             System.out.println(System.currentTimeMillis() - start);         }          System.out.println("\na = " + a);     } }   The output:  2600 3739 3735 3734 3742   I noticed that the first nested iteration is considerably faster than subsequent ones whenever I run the program.  Why is it so?   Java version:  java version "1.8.0_74" Java(TM) SE Runtime Environment (build 1.8.0_74-b02) Java HotSpot(TM) 64-Bit Server VM (build 25.74-b02, mixed mode)   EDIT  If I copy-paste the outer loop right below the first one:  public class Main {      private static long a = 0;      public static void main(String[] args) {         for (int i = 0; i < 5; i++) {             long start = System.currentTimeMillis();             for (long j = 0; j < 5000000000L; j++) a++;             System.out.println(System.currentTimeMillis() - start);         }          System.out.println("----");          for (int i = 0; i < 5; i++) {             long start = System.currentTimeMillis();             for (long j = 0; j < 5000000000L; j++) a++;             System.out.println(System.currentTimeMillis() - start);         }          System.out.println("\na = " + a);     } }   then again the first iteration is the fastest in both outer loops:  2587 3736 3736 3734 3732 ---- 2560 3737 3734 3735 3740   Even in the first example, I would expect the first iteration to be slower, because of warm-up time (initialization, JIT optimizations, etc), as described in the answers for  which @Mureinik kindly pointed to, but it is the opposite.  EDIT 2  When I increase the limit for j variable by adding another zero to it (ten times), the difference is more than 10 seconds:  25747 38637 37767 38104 38690 ---- 27951 38780 39035 37962 37931   It seems to be a constant ratio of about 2.6/3.7.


How to add a large equation in Latex (problem with \right] \left[)

I want to add this equation to my letter, but it doesn't fit the page: $$ I_{GRV3}=\int_{\Sigma_{i}}\left[4 \pi S_{i}^{i}-v^{\mid i} v_{\mid i}+\frac{1}{4} h^{i j}\left(\Delta_{i m}^{l} \Delta_{j l}^{m}-\Delta_{i m}^{l} \Delta_{i j}^{m}\right)+  \frac{3}{4}\left(K_{i j} K^{i j}-K^{2}\right)-\frac{K}{N} N^{i} \nu_{i i}\right] \sqrt{h} \mathrm{d}^{3} x=0 $$  The problem is that I tried to use an array method to separate them, but I get an error cause I'm separating the \right] from the \left[.


Good texts to learn real analysis by myself

I want to know good books I can  use to learn real analysis by myself. I only have the upcoming Christmas holidays were I get 2-3 weeks off. Any suggestions?


Fast switch input source via CapsLock button in Ubuntu 17.10

I updated my Ubuntu version to 17.10 and I want to configure switching to next input source via CapsLock button. I tried to set CaspLock in keyboard setting, but I cant because nothing happening.  I did actions explained here  and it works, but now when I switching input source I see a pop-up (like as pop-up that shows switching application windows) and must wait a few seconds until it disappears.  How I can resolve my problem?


Ubuntu MATE 16.04 LTS. Nettop HP260G2 with Intel 4405U CPU and DDR4 memory. Sometimes Wi-Fi comes unstable and turns off until reboot.  Installing rtlwifi_new by these instructions  changes nothing.  Boot log contains a list of messages like these:  [   45.297286] pcieport 0000:00:1c.3:    [ 0] Receiver Error         [   45.297292] pcieport 0000:00:1c.3: AER: Corrected error received: id=00e3 [   45.297658] pcieport 0000:00:1c.3: can't find device of ID00e3 [   45.297661] pcieport 0000:00:1c.3: AER: Corrected error received: id=00e3 [   45.297668] pcieport 0000:00:1c.3: PCIe Bus Error: severity=Corrected, type=Physical Layer, id=00e3(Receiver ID) [   45.297671] pcieport 0000:00:1c.3:   device [8086:9d13] error status/mask=00000001/00002000 [   45.297673] pcieport 0000:00:1c.3:    [ 0] Receiver Error         [   45.297678] pcieport 0000:00:1c.3: AER: Corrected error received: id=00e3 [   45.298027] pcieport 0000:00:1c.3: can't find device of ID00e3 [   45.302343] pcieport 0000:00:1c.3: AER: Corrected error received: id=00e3 [   45.302355] pcieport 0000:00:1c.3: PCIe Bus Error: severity=Corrected, type=Physical Layer, id=00e3(Receiver ID) [   45.302359] pcieport 0000:00:1c.3:   device [8086:9d13] error status/mask=00000001/00002000 [   45.302362] pcieport 0000:00:1c.3:    [ 0] Receiver Error         [   45.302368] pcieport 0000:00:1c.3: AER: Corrected error received: id=00e3 [   45.302718] pcieport 0000:00:1c.3: can't find device of ID00e3 [   45.302972] pcieport 0000:00:1c.3: AER: Corrected error received: id=00e3 [   45.302981] pcieport 0000:00:1c.3: PCIe Bus Error: severity=Corrected, type=Physical Layer, id=00e3(Receiver ID) [   45.302984] pcieport 0000:00:1c.3:   device [8086:9d13] error status/mask=00000001/00002000 [   45.302987] pcieport 0000:00:1c.3:    [ 0] Receiver Error         [   45.302993] pcieport 0000:00:1c.3: AER: Corrected error received: id=00e3 [   45.303341] pcieport 0000:00:1c.3: can't find device of ID00e3 [   45.307352] pcieport 0000:00:1c.3: AER: Multiple Corrected error received: id=00e3   Tried to install rtlwifi-new-dkms_0.10_all.deb driver following instructions from here:   Wifi is now working with new driver - Bluetooth symbol is hide. But boot still logging the same errors.  What's wrong here? Thanks everybody for help.


osx server, windows client, running emacs opens it on server not client

I've installed emacsformacosx on my OSX box.  I'd like to shove my macmini in a data center and run it headless.  I've gotten x-windows working.  If I run xeyes, it displays on my Windows 7 client.  Emacs works from the command line on the osx box.  However, if I start up emacs from the windows client, it pops it up on the server instead of the client.  What am I doing wrong?


Do experience points in 5e continue to stack or do they get expended and leave carry over points towards the next level?

I run two campaigns and decided to run them differently based on the PC desires.  In the combat-heavy war-torn campaign I expend all points except those over the leveling up threshold to make it longer and tougher thereby giving the players more combat.  The narrative heavy campaign I have been maintaining the accumulation of all XP so as to make it more fun because they wanted to find items and combat isn't such a high priority.  Both groups have decided they want to join forces and create a single campaign but I can't until I can make them close to equals so I wondered which version is the correct ruling.


Getting Exported bands must have compatible data types; found inconsistent types: Float64 and Float32 using Google Earth Engine

I'm trying to export sentinel-1 bands with this code in Google Earth Engine but I have recently this error. I didn't have this problem in the past. So here is the code.  The code:  var start = new Date("02/05/2015"); var end = new Date("03/05/2015");    var s1 = ee.ImageCollection('COPERNICUS/S1_GRD')       .filterDate(start, end)       //.filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VV'))       // Filter to get images collected in interferometric wide swath mode.       //.filter(ee.Filter.eq('instrumentMode', 'IW'))       .filterBounds(geometry);  var count = s1.size().getInfo();  for (var i = 0; i < count ; i++) {   var img = ee.Image(s1.toList(1, i).get(0));   var geom = img.geometry().getInfo();   Export.image(img, img.get('system:index').getInfo(), {     'scale': 20,     'crs': 'EPSG:4326',     'region': geometry.toGeoJSONString() }); } s1 = s1.toUint16();  Export.table(s1,'Sentinel1_csv');  print(Chart.image.seriesByRegion(s1, geometry, ee.Reducer.mean(),'VH') .setOptions({title: 'VH mean value over time on R3'}));


Today I came across this      If a particular user is suspected, one can make 100% sure of this by   deleting downvoted answers, observing appropriate reputation changes in a   few minutes and undeleting.   Is this type of activity condoned? No one wants to be downvoted, but I thought it was supposed to be anonymous?


I have a CentOS7 installed in a virtual machine. By default, the file system of it was XFS both of the "/" and "/boot". Now I want it to change the file system of the "/boot" to ext3. The reason why I want to change it is I have here a backup server that requires an ext3 file system for it to be able to back up the Linux server. Can I change the XFS to ext3?


Why does comparing strings with the same value with == return false?

In the following code a string is created in pool and then it is concat creating there additional string object. The final is "2cfalse" and is referred by a. Then in line 7, because of Strings' non-repeating nature, I think it does not create separate literal as "2cfalse" so the == operator must return true .. Why its not returning true..  class demo {     public static void main(String aaa[]) {         String a = "";         a += 2;         a += 'c';         a += false;         if (a == "2cfalse")             System.out.println(1);         if (a.equals("2cfalse"))             System.out.println(2);     } }


How do you convert a byte array to a hexadecimal string, and vice versa?

How can you convert a byte array to a hexadecimal string, and vice versa?


I know of krename but I'm wondering if there's a similar app that uses gtk/gnome libraries.    I also know of Thunar but I don't really want a file manager. I just want a bulk renamer.  Are there any applications that provide a GUI just for bulk renaming tasks?


Trigger javascript keyboard events with code?

I'm wondering if it's possible to fake keydown and keyup events in javascript with for example a button? So when a button is clicked (or in my case tapped) it sends keycode 32 or whatever to the browser?


How would you evaluate $$\sum_{n=1}^{\infty}\left(\frac{\sin(n)}{n}\right)^2$$ Wolfram|Alpha says it equals $\;\pi/2-1/2.\;$ If the solution is complicated, ... I can handle complicated.


Can I recover corrupted files from a hard drive?

I have an external hard drive, on which some of the files show up to be corrupt. I have not formatted the drive by accident or anything like that. I just put my data on it, which I wanted to read back later. Some files don't even open, others open with errors, and some are fine. It seems like random pieces of data had been corrupted on my hard drive.  Is there any way to recover those damaged files? I know it's possible to recover files with special software from a hard drive that has been quick formatted, since the data itself is still present that case. But in this case, the data itself is corrupt, so I don't know if it's possible or not...


Ubuntu 14.04 on external hdd as the only hdd

I have a laptop that the internal HDD is dead in. My question is how would I install Ubuntu on a new external HDD and have the laptop boot from it without an internal drive being installed. I've looked at other questions and while some are similar, I havent found anything that exactly matches. I mainly want to use Ubuntu to run Wine so I can play World of Warcraft from a private (legal) server. Thank you in advance.


How come this is Chi-Squared distributed?

Let  $X_1, X_2, ..., X_n$ be normally distributed with mean $\mu$ and variance $\sigma ^2$, then $\frac{(n-1) S^2}{ \sigma^2}$ has a Chi-Square distribution with $n-1$ degrees of freedom.   How come it's chi-square distributed?  Attempt:  $S^2 = \frac{1}{n-1} \sum(X_i-\overline X)^2 = \frac{1}{n-1}(\sum X_i ^2 - (\sum X_i)^2)$.    Here, the first term $\sum X_i^2$ is chi-squared. But you also need to subtract the second term (which is normal distributed with mean $\mu$, and variance $\frac{\sigma^2}{n}$. How does it make it chi-square distributed?


System crashes after January 10, 2018 updates

I faithfully install all of Canonical's system updates.  After installing today's, and rebooting my system to complete installation, the system hung and was unable to complete the update.  While I had no problem recovering by using earlier builds, every attempt to install the latest updates produced the same result.  System diagnostics failed to show any hardware problems or material defects in earlier versions of the OS.  What could be happening?


Calculate the sum $\sum_{k=0}^{\infty} a^{\frac{k(k-1)}{2}}r^k$

How to calculate the sum of this geometric series?  $$\sum_{k=0}^{\infty} a^{\frac{k(k-1)}{2}}r^k, \text{ where}\; 0 \leq a \lt 1 \; \text{and}\;\; r \lt 1$$


I want to simulate the working of this flip flop. How do I do it for every possible combination of jk, ie. when j -> 0, k -> 1, Q = 0, Q_n = 0 when j -> 0, k -> 1, Q = 0, Q_n = 1.   etc, without creating a new frame every time?  \documentclass{beamer} \usepackage[utf8]{inputenc} \usepackage{subfiles} \usepackage{circuitikz} \usepackage{tikz} \usetikzlibrary{arrows,shapes.gates.logic.US,shapes.gates.logic.IEC,calc}  \begin{document} \begin{frame}  \setbeamercovered{dynamic}  \begin{tikzpicture} \path (0,0) rectangle (10,7); % Use this to set the dimensions to approximately the page size     \begin{scope}[shift={({1},{5})}]           \node(J) at (1,0) {$J$};         \node[nand gate US,draw,logic gate inputs = nnn,thick] at ($(J)+(2,0)$) (Nand1){};          \node(K) at ($(J)+(0,-2.5)$) {$K$};         \node[nand gate US, draw, logic gate inputs = nnn,thick] at ($(K)+(2,0)$) (Nand2) {};           \onslide<2>{\node(in1) at ($(J)+(0.5,0.5)$) {\textcolor{red}{\textbf{1}}} ;};         \onslide<3>{\node(in1) at ($(K)+(0.5,0.5)$) {\textcolor{red}{\textbf{0}}} ;};          \node[nand gate US, draw, logic gate inputs = nnn, thick,anchor=input 1] at ($(Nand1)+(3,0)$) (Nand3) {};         \node[nand gate US, draw, logic gate inputs = nnn, thick, anchor = input 3] at ($(Nand2)+(3,0)$) (Nand4) {};          \draw(J) |- (Nand1.input 2);         \draw(K) |- (Nand2.input 2);         \path (J) -- (K) node[midway] (CLK) {$CLK$};          \draw (Nand1.input 3) --++(180:5mm) coordinate (aux) |- (CLK);         \draw (CLK-|aux)|- (Nand2.input 1);          \draw(Nand1.output) |- (Nand3.input 1);         \draw(Nand2.output) |- (Nand4.input 3);          \draw (Nand3.output) -- ([xshift=2cm]Nand3.output);         \draw (Nand4.output) -- ([xshift=2cm]Nand4.output);          \draw (Nand3.output) --++(0:2cm) node[right](Q) {$Q_n$} coordinate[pos=.25] (aux1) coordinate[pos=.5] (aux2);         \draw (Nand4.output) --++(0:2cm) node[right] (QN) {$\overline{Q_n}$} coordinate[pos=.25] (aux3) coordinate[pos=.75] (aux4);          \onslide<2>{\node(out1) at ($(Q)+(0.5,0.5)$) {\textcolor{red}{\textbf{1}}} ;};         \onslide<2>{\node(out2) at ($(QN)+(0.5,0.5)$) {\textcolor{red}{\textbf{1}}} ;};          \draw (Nand2.input 3)--(Nand2.input 3-|aux)--++(-90:5mm)-|(aux2);         \draw (Nand1.input 1)--(Nand1.input 1-|aux)--++(90:5mm)-|(aux4);          \draw(Nand4.input 1) --++(180:5mm) --++(90:3mm) -- ([yshift = -3mm]aux1) --(aux1);         \draw(Nand3.input 3) --++(180:5mm) --++(-90:3mm) -- ([yshift = 3mm]aux3) --(aux3);          \foreach \i in {CLK-|aux,aux1,aux2,aux3,aux4}         \filldraw (\i) circle (1.5pt);     \end{scope}      \end{tikzpicture}    \end{frame} \end{document}


What is the black box around a post when using the comment keyboard shortcut (c)?

So when you use the comment shortcut C, you get the comment box appearing. However, you will get a weird black box.  Here's a picture of before:           And afterwards:           And after reloading, it disappears! This seems weird.  And after looking at the HTML, this seems to be the problem:  <div data-questionid="260187" id="question" class="question keyboard-selected">   After removing the class attribute, the box goes away.


Differences between no child vs no children

a) They have no child. b) They have no children.  Are both a) and b) correct? Though b) seems more common.


Use of parenthesis/curly bracket in split environment: Error for curly bracket on opposite sides of \\

Any help is most appreciated. Thanks!  \documentclass{article} \usepackage{amsmath} \usepackage{mathtool} \begin{document} \begin{align} \begin{split} & v \cdot \left\{ Ax + b \\ & Cx - d \right\} \end{split} \end{align} \end{document}


Creating a keyboard with a microcontroller, do I need an input pin for each key?

I am planning to implement V-USB with an ATMega8 microcontroller. I am interested in implementing an HID device; more specifically, I want to try and make my own simple 26 key keyboard (each corresponding to a letter of the English alphabet).  This may be a stupid question, but do I need an input pin for each key I implement? In other words, will I need to use a microcontroller that has at least 26 I/O pins? Or is there another way to do this?


Two old friends, Jack and Bill, meet after a long time. Jack: Hey, how are you man? Bill: Not bad, got married and I have three kids now. Jack: That’s awesome. How old are they? Bill: The product of their ages is 72 and the sum of their ages is the same as your birth date. Jack: Cool… But I still don’t know. Bill: My eldest kid just started taking piano lessons. Jack: Oh now I get it.  How old are Bill’s kids?  I am not able to figure out how Jack get it when Bill says "My eldest kid just started taking piano lessons"?


How to run a .exe file in command prompt

I don't know much about command prompt, or how it is used, but I want to get a code to access a program of mine and I wants me to open a .exe file with command prompt and input my ID so I can get the password. But whenever I input my ID, it shows the password just briefly and then the command prompt window closes instantly. Is there a way to access the .exe file and put my ID and get my password without the window closing? Thanks in advance!  NOTE:I am running on a windows 10 software.


Chain complexes as functors and chain morphisms as natural transformations

Definition Let $\mathcal{C}$ be any category. A graded object in $\mathcal{C}$ is a sequence $(C_n)_{n\in\mathbb{Z}}$ of objects of $\mathcal{C}$ or, equivalently, a functor $C:\mathbb{Z}\to\mathcal{C}$, where the group of integers is considered as a discrete category. A graded morphism $f:A\to B$ of degree $k$ from a graded object $A$ to a graded object $B$ is a collection $(f_n:A_n\to B_{n+k})_{n\in\mathbb{Z}}$ of morphisms of $\mathcal{C}$. Thai is to say, $f$ is a natural transformation from $A$ to $B\circ s^k$, where $s:\mathbb{Z}\to\mathbb{Z}$ sends $n$ to $n+1$. Of course, a morphism $f:A\to B$ of degree $k$ composes with a morphism $g:B\to C$ of degree $l$ to a morphism $g\circ f:A\to C$ of degree $k+l$. Graded objects in $\mathcal{C}$ and morphisms between them form a category we will denote by $\operatorname{Gr}(\mathcal{C})$.  Definition Now let $\mathcal{C}$ be a pointed category and let $0$ be the constant graded object $(0)_{n\in\mathbb{Z}}$. We shall also write $0$ for any morphism (of whichever degree) that factors through $0$. A chain complex $(C,d)$ in $\mathcal{C}$ is a graded object $C$, together with a morphism $d:C\to C$ of degree $-1$ (its differential) such that $d\circ d=0$. A chain morphism $f:(C,d)\to (C',d')$ is a morphism $f:C\to C'$ of degree $0$ such that $d'\circ f=f\circ d'$. Chain complexes in $\mathcal{C}$ and their chain morphisms form a category we will denote by $\operatorname{Ch}(\mathcal{C})$.  I want to view chain complexes as functors. The only thing I could say was this. Consider $\mathbb{Z}$ as a poset category, where $m\geq n$ means there exists exactly one morphism from $m$ to $n$. Then consider the functor category $\operatorname{Funct}(\mathbb{Z},\mathcal{C})$. Then the category $\operatorname{Ch}(\mathcal{C})$ is the full subcategory of  $\operatorname{Funct}(\mathbb{Z},\mathcal{C})$ with the property that $d_n\circ d_{n+1}=0$ for each $n$.   First question: is it correct what I said in the last few lines?  Other ideas I had, but I couldn't formalize, were: since differentials $d$ of chain complexes are themselves graded morphisms of degree $-1$, maybe I can define a chain complex as a functor on $\mathbb{Z}$ to the category $\operatorname{Gr}(\mathcal{C})$ of graded objects in $\mathcal{C}$. Here the main problem for me was that, if to an integer $n$ I associate a pair $(C,d)$, then I don't know what to associate to each morphism in $\mathbb{Z}$ coming from the order relation $\geq$. Probably this approach is wrong.  Last approach I am trying to formalize was the one consisting in using the arrow category of $\mathcal{C}$ or of $\operatorname{Gr}(\mathcal{C})$, but again I am stuck and don't know how to proceed. For instance, I consider the category $\operatorname{Arr}(\operatorname{Gr(\mathcal{C})})$. An object here is a graded morphism. Then I take the full subcategory of graded endomorphisms of degree $-1$ with the property that any two of them compose to the zero morphisms. Do you have any suggestion or just comments?


What is wrong with using Kolmogorov's inequality for finding the expectation of the maximum of normal random variables?

I am wondering if someone could help me shed light on why the following bound doesn't work.  Suppose that $X_1, \ldots, X_n \sim N(0,1)$ are independent random variables. I am interested in finding a constant C that satisfies:  $$ E\left[\max_{1\leq i\leq n}|X_i|\right] \leq C \sqrt{log\  n} $$  My Method:  Let $Y = \max_{1\leq i\leq n}|X_i|$  $$ \begin{align} E\left[Y\right] & = \int_{0}^{\infty}P(Y >y)dy \\ &\leq\int_{0}^{\infty}\frac{1}{y^2}\sum_{i=1}^{n}Var(X_i) dy \\ & \leq \int_{0}^{\infty}\frac{n}{y^2}dy \\ \end{align} $$  I used Kolmogorov's inequality in the second step above, but don't know the exact mechanics of why this fails and am unsure why my integral in the end doesn't converge. Is there a specific reason this bounding doesn't work? Am I failing to take into account tail activity? thanks.


Could Yoda defend against a Force choke?

We've seen Yoda deflect Sith lightning, but we haven't seen him defend against a Force choke.  What would happen if Vader or some other powerful Sith lord attempted to apply a Force choke against Yoda?


Why would "to center around" be illogical?

I have seen the discussions of "to center on" vs "to center around", and usually the argument is that "to center X around Y" is illogical. The counter-argument is generally that it is an idiom and therefore does not have to be logical. However, I do not see why this phrase is illogical.  To me, there are clearly to ways that "to center" can be used:   Putting X in the center of Y. Putting the center of X on Y   The first meaning obviously doesn't make sense with "about". You can't center a picture around a page. But in the context of second meaning, I find it is perfectly logical to center X around Y, eg. "to center a circle around a point". "At" and "on" also make sense here, but so does "around".   So why is it necessary to invoke the argument of the idiom? Am I misunderstanding something?  -  Edit: This is not a duplicate of . Most answers there just state it is illogical, not why. The few that do only say that it is illogical since to center X is to put X in the center, which is only the first meaning I mentioned. The answer of user oosterwal comes close but only talks about a set of multiple.  I would like to know why it is illogical to center for example a hullahoop around a candle, i.e. putting the candle in the center of the hullahoop.  Moreover, even the idiomatic use seems logical to me, since for example arguments centered around a main point seem more meant in this second meaning, rather than them being in the center of something.


If i want to use Physics in Unity2D what should be the most efficient way to move the object without interfering physics?    1. Transform.position  2. Rigidbody.Velocity  3. Rigidbody.addForce  4. Transform.translate  5. Rigidbody.movePosition   Seems like there are a lot of ways and each way has a special purpose for when it should be used and when not. I just don't know that.


So the formula for work is$$ \left[\text{work}\right] ~=~ \left[\text{force}\right]  \, \times \, \left[\text{distance}\right] \,. $$  I'm trying to get an understanding of how this represents energy.  If I'm in a vacuum, and I push a block with a force of $1 \, \mathrm{N},$ it will move forwards infinitely. So as long as I wait long enough, the distance will keep increasing. This seems to imply that the longer I wait, the more work (energy) has been applied to the block.  I must be missing something, but I can't really pinpoint what it is.  It only really seems to make sense when I think of the opposite scenario: when slowing down a block that is (initially) going at a constant speed.


Accidentally removed gnome from bionic beaver - ubuntu-desktop doesnt install

Hi guys I accidentally did an autoremove and somehow my gnome desktop was completely wiped out leaving me with just the shell access to my ubuntu 18.04 - I'm trying to reinstall the ubuntu desktop but it doesn't work and keeps giving me an error.  $ sudo apt-get install ubuntu-desktop Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  ubuntu-desktop : Depends: ubuntu-session but it is not going to be installed                   Recommends: gnome-software-plugin-snap but it is not going to be installed                   Recommends: libreoffice-pdfimport but it is not going to be installed                   Recommends: ubuntu-software but it is not going to be installed E: Unable to correct problems, you have held broken packages.   I've tried using taskel - just about anything but it gives the same error. I've managed to install kubuntu-desktop using the same command but whats wrong here. I really would want to get my original desktop back. Please help.


the power set of every well-ordered set is well-ordered implies well ordering

I'm new to set theory and ordinals and such things and currently have a question.  I have a proposition which says that the axiom of choice is equivalent to this: "the power set of every well-ordered set is well-ordered."  It's trivial that the statement is true by well-ordering (which is equivalent to axiom of choice). but I can't find the proof in the opposite way. I also have a proof which I can't understand. It seems that the author tried to prove well-ordering (for any sets) using the mentioned statement. but I can't get it.  Note that I need to prove well-ordering using the mentioned statement not proving the statement with or without AC!  This is the proof:


How to avoid large margins around Matlab plot in PDF

I am preparing image files to be included in a latex document. The image file is generated by printing a Matlab plot.   If I print the plot in eps format, the content of the eps file is fully occupied with the plot;   if I print the plot in pdf format, then there are big margins above and below the plot in the pdf file;   if I use ps2pdf to convert the eps file into a pdf file, the big margins will be added above the plot.   I would like to use pdflatex, so I prefer pdf format of image files. I was wondering how I can save the plot in pdf format without the big margin above and below the plot?


Sometimes I feel difficulty telling the difference between simple past and present perfect.  Given a picture like this:    which one is correct between these two? Or in what sense are they different?  A. He fell off his motorcycle.  B. He has fallen off his motorcycle.


"I wish I could just sit here and lay down beside you forever."  Shouldn’t it be "lie down" instead of "lay down" here?  As we know that the verb following " could" should be of base form. But, here "lay down" is past form of "lie down".   Besides, if we consider "lay down" in present tense it means " laying egg" or "laying something"-  meaning not consistent with the context.   I  want to if the sentence is correct.


Can you use your off-handed weapon for your main attack action?

My friend is 2 weapon fighting a flesh golem. He has one sword that does lightning damage, and one sword that does fire damage. His right hand holds the lightning sword, and his left hand holds the fire sword.  My friend wants to attack with his left hand because lightning heals the golem. However, the DM says that because his left hand is his left hand, he can't use it as his "main" hand, and only attack with it. Is this rules as written/intended?


What software should I use to design infographics?

I am designing an infographic for a charity but I'm unsure whether InDesign would be better than Photoshop even though I have little experience in it. I would be happy to learn though.  What would you use also any tips would be great.


Apache httpd won't stop doing reverse DNS requests for clients' IPs

Obviously my Apache httpd instance is doing reverse DNS (RDNS, give me the hostname for this IP address) lookups for each incoming client connection's IP address. This is bad. Especially since sometimes resolution fails with a missing PTR record - after 28secs.  Diagnostics: I added %D to my "combined" log style and looked at the response times this way: Clearly <1s for all those that are logged with their hostname and 20+s for those that get their IP logged.  This is what I tried:   Turn off the server-status extension. Check that HostnameLookups Off is in the config. Check that mod_access is not given any hostname in an Allow/Deny rule. Check that reverse proxied servers follow the same rules.   What have I missed?


Prove that an expression is divisible by n(n+1)/2

If k is an odd positive integer, prove that for any integer $n≥1$ , $1^k+2^k+3^k+.....+n^k$ is divisible by $\frac {n(n+1)}2$  If k equals to 1, then it is an obvious case. Though the expression is seen to be true for $k=1$ , I could not prove it by induction, as the sum becomes too complex, according to what I did..  So I tried to prove that $1^k+n^k$ is congruent to $ 0(mod (n+1))$. That took me some far, but I could not come to a satisfactory conclusion..   Can anyone please help me with this? I feel there is a smarter approach to this one. Thank you..


Detecting if resistances are parallel or series in complex circuits

I know how to detect when resistors are arranged in parallel or series arrangement and I can also find their equivalent resistance in simple circuits or when resistances are connected in form of triangle but what happens when the arrangement is complex like this :   Which resistors are parallel and which are in series ? How can I find the equivalent resistance in such cases ? Is there rule or method for figuring this out ?


How to easily kill the Google Chrome main process (Windows 7 / Ubuntu Linux)

I like Chrome's feature that lets me restore its pages after it's been closed ungracefully. I use that as a way to save my session (e.g. when just rebooting to install OS updates).  What I've been doing until now:   Open Chrome's Task Manager, look for the Browser process and remember the PID. kill the process with that PID (with kill -9 <pid> in Ubuntu and with the task manager in Windows)   I'm looking for a way to do that in just one click, or as few actions as possible. E.g. with a script that I put on my desktop.  I'm looking for a solution both for Windows 7 and Ubuntu Linux.  Note: I know I could use some session-management Chrome extension instead, but I've tried some of those and they don't work exactly , whereas the method described above works exactly like I want, but is a bit too difficult to use.  Note: On both Linux and Windows all my Chrome processes have the name chrome, so I can't differentiate between tab processes and the browser process by name. I'm saying this because I've seen  to kill the process called google-chrome-stable - I don't have such a process.  Edit: I found  which works very well without the need for an killing any processes. I've voted to close my question as a duplicate.


Catching him with no commander trying to play cards- Risk

It was year 5 and only two colours left on the board (myself and my brother). It was the last turn and his turn to go.   He had finished buying all his moon cards (at this time he had all his commanders except the nuke one). His first move was to play all his nuke cards, forgetting he had lost his commander, this meant he couldn’t win (the cards were his only chance).  I called him out after he tried to play the cards and told him he couldn’t play them if he didn’t have his nuke commander and couldn’t go back to buy it.   Should he have been able to go back and buy his commander which would have resulted in him winning the game, or should we have continued playing allowing him no commander?


J-invariant and isomorphism of elliptic curves over $\mathbb{Q}$

If two elliptic curves share the same j-invariant then they may not be isomorphic to each other over $\mathbb{Q}$.  Example:     $E_1: y^2 = x^3 + x$      j-inavriat: $1728$      Torsion points: $[(0 : 0 : 1), (0 : 1 : 0)]$      Rank $0$.   $ $     $E_2: y^2 = x^3 + 3 x$      j-inavriat: $1728$      Torsion points: $[(0 : 0 : 1), (0 : 1 : 0)]$      Rank $1$ - generator point $[(1 : 2 : 1)]$   Is there some other invariant or can we define a new type of invariant that if two elliptic curves share the same such invariant then they are isomorphic over $\mathbb{Q}$?  (they can be birationally transformed to each other over $\mathbb{Q}$)


Essential Question: Which Peltier is the most Efficient for reaching coolest temperature, and is the 6V 2A peltier inefficient?  I was looking into more efficient Peltiers for my project and tried to test the amperages of certain Peltiers on a 5V power supply.   Here are the results I have up with:   Using a 5V power supply,    TEC-12704 (12V 4A standard draw) drew 5V 1.4A. Peltier TEC-12705 (12V 5A standard draw) drew 5V 1.36A.    I don't understand how a Peltier rated higher than the previously mentioned runs at a lower power, and furthermore, when converting 12V -> 5V current output using ratios, (12V/5A = 5V/XA, where a 12V 5A Peltier should draw 5V 2.083 Amps? Why is this happening!    Lastly, I tested a 6V 2A Peltier which ran at 5V 2.2 Amps, more amperage at a lower voltage? - so does that mean this is inefficient compared to the last 2 Peltiers?   Currently I am using the 6V 2A Peltier, trying to find a more efficient Peltier and need to figure out: are these weird numbers due to one Peltier being more efficient than the other (critical to my project) or something else?


How do you color code folders in Mavericks?

I used to be able to color code each folder in Finder.   I know I can use tags in Mavericks, but is there a way to restore the ability to actually color code folders?  Thanks.


I have a line shapefile tc_line with 166 segments and a point shapefile tc_point with 8 points, and I loaded them into PostGIS database with DB manager:    and the following were their attribute table:   table tc_line (part)      table tc_point     Because these points are just nearby the line, not right on it, I try to use ST_ClosestPoint first, then use ST_Split to split the line.  @amball, I tested your code in the edited answer and the result showed:  SELECT ST_Split(ln.geom, ST_Collect(newpt_geom)) FROM tc_line AS ln,      (SELECT ST_ClosestPoint(ST_Collect(ln.geom), pt.geom) AS newpt_geom      FROM tc_line AS ln, tc_point AS pt GROUP BY pt.geom) t1 GROUP BY ln.geom;     The result was strange because it had 166 rows just the same as the rows original line had, which means that ST_split didn't work. So I loaded the result as new layer to check it.    But In QGIS I could not see it even I set its CRS, and as I wanted to export it as ESRI shapefile, error message showed up:  Export to vector file failed. Error: creation of layer failed (OGR error:Geometry type of `Geometry Collection' not supported in shapefiles. Type can be overridden with a layer creation option of SHPT=POINT/ARC/POLYGON/MULTIPOINT/POINTZ/ARCZ/POLYGONZ/MULTIPOINTZ. )   So I tried to split the line with 2 stages:   ST_ClosestPoint ST_split   In the first stage I ran the code:      SELECT      tc_point.id as pointid,      St_ClosestPoint(ST_collect(tc_line.geom), tc_point.geom) as closest,     st_astext(St_ClosestPoint(st_collect(tc_line.geom), tc_point.geom)) as text     FROM tc_point, tc_line GROUP BY tc_point.id;   The result were fine: (8 closest points)    and I successfully loaded as new layer tc_proj, and its attribute table:    Then I ran stage 2:  SELECT ST_Split(ln.geom, ST_Collect(tc_proj.geom)) from tc_line as ln, tc_proj GROUP BY ln.geom;   error showed up:  Splitting a Line by a GeometryCollection is unsupported   I am newbie to SQL and SQL open source such as PostGIS. How to work the above task successfully? I am working with PostGIS 2.2.1    Update#1  @amball, I tested your following code,  SELECT ST_Split(ln.geom, newpt_geom) FROM tc_line AS ln,      (SELECT ST_ClosestPoint(ST_Collect(ln.geom), pt.geom) AS newpt_geom       FROM tc_line AS ln, tc_point AS pt      GROUP BY pt.geom) t1 WHERE ST_Intersects(ln.geom, newpt_geom);   and its result,    I don't know why there were 4 rows in the result, and I could see nothing using Create a view, also, Load as new layer outputted nothing. Thus, I still can't determine whether result is correct.


Karate Framework JSON path parsing using regex not working for carriage return

I am working on parsing the name and description value on the basis of the API body but it fails to capture using below code ... it is failing in parsing those description values which is having \r\n in the description text.  $..source..[?(@.name =~ /(.*global.*)/i || @.description =~ /(.*global.*)/i)]   It successfully looking for my search query 'global' and consider below as a matched value 'The information is global and it is embedded in the words'  It fails to capture below because it has \r\n 'global data is nowhere capture.\r\n we should do some other tricks.  Can anyone please help what exact regex should I put which would check 'global' from either Name or Description.


Set $I = \{x \mid x \text{ is a positive integer}\}$ Set $J = \{x \mid 2 < x < 5\}$ Both sets $I$ and $J$ are infinite, I get that. But why is set $I$ denumerable and set $J$ nondenumerable? I just can't get my head around it.


For my website, I am using a static home page page Home (template front-page.php) and for posts- page News (template home.php)  I need to show all the post titles and exceprts on that page News (templ. home.php), but also show the original title and the_content from that page News itself.  This code below while statement shows all the posts, which is good, but the top the_title also shows the title from the first post, not from the News page itself.  How to achieve what I need?  <?php get_header(); ?>      <?php     the_title();           the_content();     ?>  <?php if(have_posts()) while(have_posts()) : the_post(); ?>          <?php         the_title();         ?>          <?php         the_content();         ?>      <?php     endwhile;     ?>    <?php get_footer(); ?>


How can I set up a Dynamic DNS fetching service on Ubuntu Server?

I've created accounts and hostnames within my  account, which is by  far the most commonly used service for my type of server. Can somebody walk me through the configuration process of using ddclient with no-ip, as I'm a command line noob?


Wi-Fi Internal adapter RTL8723BE has weak signal and interference

I use Ubuntu Studio 18.04.2 LTS in a HP Laptop 250 G5 with Intel Pentium CPU N3710, 4 cores, at 1.6 GHZ, and 8 GB RAM.  It is known that there was (or, maybe still is) a Linux bug with the internal WiFi adapter, which is a Hewlett-Packard Company RTL8723BE PCIe Wireless Network Adapter [103c:81c1] (RealTek 802.11 b/g/n Wireless Adapter).  The main issues were:   Bad (weakly) signal gain, and Some kind of "interferences" with the audio and video performance (stuttering).   So I use an external WiFi adapter (USB port).  How can I know if the bug was fixed?  I read the solutions to  I tested it, and they were not effective. The issues are still present!


Placing an identity directly beneath a symbol

How do we we write in latex a phrase directly under another symbol. I want to get the r going to infinity directly beneath the Tilda as shown below . However am unable to do so  I tried using \sim_{\r \rightarrow \infty} but this does not work.


Is std::string size() a O(1) operation?  The implementation of STL I'm using is the one built into VC++


iCloud Photo Library content fills up 16GB phone

My wife has an iPhone with little storage and has iCloud Photo Library enabled on her Mac and iPhone. Recently it's been hitting the limit of the phones storage and breaking other apps.   I would have thought that Photos would be smart enough to keep on thumbnails of the oldest photos, but about 80% of the phone storage is Photos.app and it just keeps downloading more.  What's the best way to handle this? The only options I have come up with are (1) curating photos and videos harder - deleting less good photos etc. (2) disabling iCloud Photo Library completely and only sync certain shared albums.


I am a new programmer, I would like to know how to round to the nearest hundredth. Here is the code import java.util.Scanner;  public class Main {    public static void main(String[] args) {     Scanner in = new Scanner(System.in);      System.out.print("Input first number: ");     double num1 = in.nextDouble();      System.out.print("Input second number: ");     double num2 = in.nextDouble();      System.out.println(num1 + " + " + num2 + " = " + (num1 + num2));      System.out.println(num1 + " - " + num2 + " = " + (num1 - num2));      System.out.println(num1 + " x " + num2 + " = " + (num1 * num2));      System.out.println(num1 + " / " + num2 + " = " + (num1 / num2));   } }  please answer with the code to round to the nearest hundredth. Thank You.


The adverb "quite" has the following meanings :     1: wholly, completely ("not quite   finished")      2: to an extreme : positively "quite   sure" —often used as an intensifier   with a "quite a swell guy" "quite a   beauty"      3: to a considerable extent : rather   ("quite near")   My understanding is that #1 and #2 conflict with #3. For example, when you say "She's quite right", do you mean "She's completely right" or "To a considerable extent, she's right"? Notice that in the latter case you're not saying that she is completely right.  Another example is "I'm quite sure". Does it necessarily mean "I'm completely sure"?   Does the word really have conflicting meanings that can possibly cause ambiguity? Or am I missing something?


Write a script that installs a package file automatically with limited interaction from user

I'm trying to run a package installer from terminal and have it complete with limited interaction from the user. This will need to be ran on any computer.  The bash script I have so far is:  sudo installer -store -pkg "/Users/username/Desktop/test.pkg" -target /   It will not complete and I am getting the following error: installer: Can't load package "/Users/username/Desktop/test.pkg": The requested URL was not found on this server.  Not sure what this error means as I'm a newbie to scripting. Please advise what is needed to fix this.


Initializing variables (int32) inside switch statement

I have a code block that I'm trying to convert from PHP to C++ and the compiler is getting hung up on my switch statements.  I have something along the lines of:  switch(//Some int) {     case 1:     default:         int32 x = 1;         doSomething(x);         break;     case 2:         doSomething(3);         break; }   And this is throwing errors:     error C2360: initialization of 'x' is skipped by 'case' label     I seem to be able to fix this by declaring and initializing the variables outside of the switch statement, but why is this? What's the problem with creating temporary variables in the scope of a switch statement?     Just for further clarification, I am only attempting to use x in that one call to doSomething(x). I don't attempt to use it outside of the switch statement's scope.


how many people have been frozen in carbonite?

in ROTJ leia tells Han he has "hibernation sickness," however in Empire they are unaware if Han would survive the freezing i guess my question is was carbonite freezing common or.?


I assumed that since $a^c \cdot b^c = (ab)^{c}$, then something like $\sqrt{-4} \cdot \sqrt{-9}$ would be $\sqrt{-4 \cdot -9} = \sqrt{36} = \pm 6$ but according to Wolfram Alpha, it's $-6$?


While studying for an Algebra Qualifying Exam I stumbled with an exercise that says   "Describe the ring $\mathbb{Z}[x]/(2x)$".  I've done similar cases, like $\mathbb{Z}[x]/(x)\cong\mathbb{Z}$, $\mathbb{Z}[x]/(2,x)\cong\mathbb{Z}_2$ but in this case I don't have the intuition of what must be the ring.  I think maybe there is no closed form for the ring.  Can someone provide me any hints or ideas? Thanks!


How can I check the integrity of a downloaded Ubuntu CD?

I've just downloaded a CD image of Ubuntu. I know the installer has a check CD option, but how can I check that the image is good before burning it to CD?


How can I make the edge of a mask blurred/feathered like this example in Sketch?


When can we say two networks are different from each other? Is it when they have different subnet masks or when they use different policies? Will it be right to say that a router is needed to connect two 'different' networks?