Is cross-posting allowed on multiple sites if they use a different language?
Is it OK to crosspost Stack Overflow questions, now that the Portuguese SO is open?
How can I get a copy of a Canadian visa refusal letter? I have applied for a Canadian Temporary Resident Visa (TRV); a previous paper application was refused in 2016. I have lost the copy of my refusal letter and want to submit it when I apply for my new visa. How how can I get the a copy of the 2016 refusal letter from Embassy? How do I remember which units counter which in StarCraft 2? How can I pin a program to the Windows 7 Taskbar, with parameters? How to convert light activated switch Possible Beamer bug: Frame number has different color than date in infolines footer Need help to understand Maximum Likelihood Estimation for multivariate normal distribution? In maximum likelihood estimation for the parameter, mean $\mu$ of multivariate normal distribution, I end up with the following result:  $\mu_{MLE} = \dfrac{1}{n}\sum_{i=1}^n x_i$  The way I understand the above equation is the following way below, but I am wondering if the above equation means the following equation:  $\mu_{MLE} = \begin{bmatrix}\mu_1\\\mu_2\\\vdots\\\mu_n\end{bmatrix} = \begin{bmatrix}\dfrac{1}{n}\sum_{i=1}^n x_1\\\dfrac{1}{n}\sum_{i=1}^n x_2\\\vdots\\\dfrac{1}{n}\sum_{i=1}^n x_i\end{bmatrix} = \begin{bmatrix}E(X_1)\\E(X_2)\\\vdots\\E(X_n)\end{bmatrix} = \begin{bmatrix}\bar{X_1} \\ \bar{X_2} \\ \vdots \\ \bar{X_n}\end{bmatrix}$   And also Maximum Likelhood Estimation for $\Sigma$, I have ended up with the following equation:  $\Sigma_{MLE} = \dfrac{1}{n}\sum_{i=1}^n(x_i-\mu)(x_i-\mu)^T = \begin{bmatrix}Var(\sigma_{11}) &amp; Cov(\sigma_{12}) &amp; \dots &amp; Cov(\sigma_{1n}) \\ Cov(\sigma_{21}) &amp; Var(\sigma_{22}) &amp; \dots &amp; Cov(\sigma_{2n}) \\ {}&amp; \vdots&amp;  \\ Cov(\sigma_{n1}) &amp; Cov(\sigma_{n2}) &amp; \dots &amp; Var(\sigma_{nn})  \end{bmatrix}$  Somehow, I got the equation following some algebraic steps, but I can't see how this part, $\dfrac{1}{n}\sum_{i=1}^n(x_i-\mu)(x_i-\mu)^T$, works and produces the covariance matrix. Hope to hear some explanations. Does the force of kinetic friction increase with the relative speed of the objects involved? If not, why not? Does the force of kinetic friction increase with the relative speed of the objects involved?    I have heard and read that the answer is no.  This is counter intuitive, and is a big part of why the "Airplane on a Treadmill" question is so interesting.  What phenomena are at work with kinetic friction, and why does it not increase with relative speed? As discussed here:  offering actual money as a bounty sets the wrong incentives. However I would suggest giving users the ability to pay with money for offering a bounty regardless of their reputation. The bounty would still count as reputation for the receiving user but would not be discounted from the paying user's reputation. Problem with pstricks and htlatex/tex4ht Consider the following MWE:  \documentclass{article} \usepackage{pst-all}  \begin{document}   \begin{pspicture}(0,-3)(12,5)       \psline[linewidth=2pt]{-&gt;}(1.5,0)(0,0)   \end{pspicture} \end{document}   This compiles fine with latex (not with pdflatex) but when run with htlatex it leads to the ghostscript error:  System call: dvips -E -q -Ppdf -f q.idv -pp 2 &gt; zzq.ps System return: 0 System call: gs -sDEVICE=pngalpha -sOutputFile=q0x.png -r110x110 -dEPSCrop -dBackgroundColor=16#ffffff -dTextAlphaBits=2 -dGraphicsAlphaBits=2 -q -dbatch -dNOPAUSE zzq.ps -c quit Error: /configurationerror in --setpagedevice-- Additional information: [/PageSize [0 0]] Operand stack:    --nostringval--   (%%BoundingBox: 72 72 72 72)   --dict:1/2(ro)(G)--   --nostringval--   --nostringval--   (%%BoundingBox: 72 72 72 72)   1   72   72   false   --dict:1/1(L)-- Execution stack:    %interp_exit   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   --nostringval--   --nostringval--   false   1   %stopped_push   1951   1   3   %oparray_pop   1950   1   3   %oparray_pop   --nostringval--   1934   1   3   %oparray_pop   1820   1   3   %oparray_pop   --nostringval--   %errorexec_pop   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   %ztokenexec_continue   (scanner state)   --nostringval--   --nostringval--   --nostringval--   --nostringval--   --nostringval--   --nostringval--   1913   10   3   %oparray_pop   --nostringval--   --nostringval--   --dict:1/10(L)--   --nostringval--   15   %dict_continue Dictionary stack:    --dict:1190/1684(ro)(G)--   --dict:0/20(G)--   --dict:82/200(L)-- Current allocation mode is local Last OS error: Invalid argument Current file position is 169 GPL Ghostscript 9.16: Unrecoverable error, exit code 1 --- Warning --- System return: 256 Entering q.css Entering q.tmp   This code used to work fine. From other examples I suspect that the problem has something to do with dvips having trouble determining the bounding box for the image (compare with  -- although the solution given here, of using separate files for each image, is not a viable solution for me), but I have not been able to work out what the problem is.  Does anyone have any ideas? Computing sums of divisors in $O(\sqrt n)$ time? I have a sequence: $1,3,5,8,10,14,16,20,23,27,\dots$  I know that the recursive relation is:  $$p[i] := p[i-1] + \text{number of factors of $i$}, \quad \text{with $p[1]=1$.}$$  How do I solve this recursive relation in $O(n^{0.5})$ time? I have to write a program for it, and $n$ can be as large as $10^9$. So, some appropriate precomputation and prestorage is allowed, provided that they comply (memory and time wise) with the range of $n$. How to determine the amount of experience needed for leveling up Related questions under this topic might include:   How should I base how much experience points it takes to get to the next level? What factors are involved in this? How do I keep the player not entertained long enough till he levels up? How can I vary the way the player gets experience points? Galactic Rotation Speeds - Ehrenfest Paradox, Gravitational time dilation, Dark Matter - all of the above? How do you rename root? Not that it's a very good idea to change it, but for fun. According to  post, there are still some problems even after changing entries in /etc/passwd, /etc/shadow, and /etc/sudoers. Any suggestions? apt-get update fails to fetch files, “Temporary failure resolving …” error Err http://archive.canonical.com natty InRelease     Err http://security.ubuntu.com oneiric-security InRelease                Err http://extras.ubuntu.com natty InRelease                             Err http://security.ubuntu.com oneiric-security Release.gpg   Temporary failure resolving ‘security.ubuntu.com’ Err http://archive.canonical.com natty Release.gpg   Temporary failure resolving ‘archive.canonical.com’ Err http://extras.ubuntu.com natty Release.gpg   Temporary failure resolving ‘extras.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric InRelease Err http://gb.archive.ubuntu.com oneiric-updates InRelease Err http://gb.archive.ubuntu.com natty-backports InRelease Err http://gb.archive.ubuntu.com oneiric Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com oneiric-updates Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’ Err http://gb.archive.ubuntu.com natty-backports Release.gpg   Temporary failure resolving ‘gb.archive.ubuntu.com’  Reading package lists... Done W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/InRelease       W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/InRelease   W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/InRelease   W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/InRelease   W: Failed to fetch http://archive.canonical.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘archive.canonical.com’ W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/oneiric-security/Release.gpg  Temporary failure resolving ‘security.ubuntu.com’ W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/Release.gpg  Temporary failure resolving ‘extras.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/oneiric-updates/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Failed to fetch http://gb.archive.ubuntu.com/ubuntu/dists/natty-backports/Release.gpg  Temporary failure resolving ‘gb.archive.ubuntu.com’ W: Some index files failed to download. They have been ignored, or old ones used instead.   This is what I'm seeing when I try to run sudo apt-get update. I did an update on my instance yesterday and am now experiencing this. How can I make something that looks like this?  --------   Text   ---------  where the horizontal rules extend to the margin on either side? I just want to know if it's possible to get Cain and abel installed in ubuntu, it would really help my work instead of dual booting back to my windows 7 just to use it. THanks! something like wye-delta and delta-wye connection.  we can originally know wye-delta connection is step-down transformer and second side voltage phase is being to -30 degree. And also delta-wye connection is step-up transformer and second side voltage phase is being to +30 degree.  But the other side, we also can make wye-delta connection is step-up transformer if it get turn ratio like 1:2. So in this case maybe will be become +30 degree in second side voltage.   apply this principle in scott connection, how can work it?   case1) turn ration 1:2 - step up second side voltage's angle +90 degree?  case2) turn ration 2:1 - step down second side voltage's angle -90 degree?  if you have any information or homepage link, can you leave it for me?  thank you so much. Key uses weak digest algorithm I'am getting this kind of message while updating my ubuntu 16.04 LTS:  W: http://dl.google.com/linux/chrome/deb/dists/stable/Release.gpg: Signature by key 4CCA1EAF950CEE4AB83976DCA040830F7FAC5991 uses weak digest algorithm (SHA1) W: http://dl.google.com/linux/chrome/deb/dists/stable/Release.gpg: Signature by key 3B068FB4789ABE4AEFA3BB491397BC53640DB551 uses weak digest algorithm (SHA1)   Can anyone help me? When is the image of a linear operator (between Banach spaces) closed? Let $T: X \longrightarrow Y$ be a continuous linear map between two Banach spaces.  When is $\operatorname{Ran}(T)$ a closed subspace?  What theorems are there?   Thanks :) "Results found containing ___" too close to header