How to convert the matrix completion problem to the standard SDP form?

Given the matrix completion problem defined below.  \begin{equation} \begin{array}{ll} \text{minimize }{X \in \mathbb{R}^{m \times n}} & \sum_{(i,j) \in \Omega} ( X_{ij} - Z_{ij} )^2 + \lambda \text{trace}(\sqrt[]{X^TX}) , \end{array} \end{equation} where, $Z$ is the observed matrix, $X$ is a low rank matrix that we want to find, $\Omega$ stores the row and column indices of the observed set. with tuning parameter $\lambda > 0$.  However it is a SDP problem and could be formulated as, \begin{equation*} \begin{array}{ll} \text{minimize }{x \in \mathbb{R}^p} & c^T x \\ \text{subject to } & x_1 A_1 + \cdots + x_p A_p \preceq B, \end{array} \end{equation*} for some fixed $c, B, A_i, \; i=1,\ldots,p$.  As the matrix completion problem utilizes the trace norm, F.Y.I, there are two ways of formulating the trace norm through optimization, \begin{equation} \begin{array}{ll} \max_{Y \in \mathbb{R}^{m \times n}} & \text{trace}(X^T Y) \\ \text{subject to} &  \left[ \begin{array}{cc} I_m & Y \\ Y^T & I_n \end{array} \right] \succeq 0, \end{array} \label{eq:aa:primal} \end{equation} and its alternative dual, \begin{equation} \begin{array}{ll} \min_{\substack{W_{1} \in \mathbb{S}^{m}, \\ W_{2} \in \mathbb{S}^{n}}} & \text{trace}(W_{1}) + \text{trace}(W_{2}) \\ \text{subject to} &  \left[ \begin{array}{cc} W_{1} & (1/2) X \\ (1/2) X^T & W_{2} \end{array} \right] \succeq 0, \end{array} \label{eq:aa:dual} \end{equation}  What I have achieved so far,  \begin{align*} \min_{X \in \mathbb{R}^{m \times n}} \|P_\Omega(X-Z)\|_F^2 + \lambda \| X \|_{\text{tr}} \\ = \text{trace}(\left(P_\Omega(X-Z)\right)^TP_\Omega(X-Z)) + \lambda \| X \|_{\text{tr}}\\ = \|\left(P_\Omega(X-Z)\right)^TP_\Omega(X-Z)\|_{tr} + \lambda \| X \|_{\text{tr}} \end{align*}  $$\| X \|_{\text{tr}} = \text{trace}(\sqrt[]{X^TX})$$


Why is this injection from $\mathbb{N^N}$ to $\mathbb{N}$ wrong?

I was looking to generate an injection from $\mathbb{N^N}$ to $\mathbb{R}$, and this is what i created: $$ \begin{align*} g: \mathbb{N^N} \hookrightarrow \mathbb{R}  \\ f \mapsto p_1^{f(0)}p_2^{f(1)}p_3^{f(2)} \dots \end{align*} $$ Where $p_i$ is the $i$th prime number. It looks like it creates an injection due to the fundamental theorem of arithmetic, but as it maps to only natural numbers, I can't see why its wrong, because clearly $|\mathbb{N^N|} > |\mathbb{N}|$?


Science Fiction story about humans escaping earth's destruction

I remember this story being told to me about this alien race that observed this planet and its intelligent life. They find out that the planet will soon die due to the sun or something and want to send a rescue mission to save the people.  Turns out the people have already figured this out and saved themselves. The plot twist is that this planet is actually earth and the civilisation is the human race.   I’ve been trying to find what this story is but I haven’t found anything. Does anyone have an idea? I believe it isn’t an incredibly long story. Nor is it pessimistic — it’s actually a very optimistic story of the human race.


I have Kali-64bit installed in Virtual Box, and I'm simply trying to set the MATE environment as my default for when I reboot/shutdown and log in afterwards.  I've tried  update-alternatives --config x-session-manager   and choosing mate-session (be it auto/manual mode) but I still get signed into the default GNOME environment.  Yet when I run update-alternatives command again, MATE is still selected and hasn't reverted back to GNOME.    This should be such a minute command that I've ran on two other Kali installations and it worked flawlessly, yet on my Vbox installations, the update-alternatives just wouldn't stick.


How do you prove a triangle with the hypotenuse of length 5 and other sides with lengths 3 and 4 is a right triangle?

I can see that it obviously will be satisfied by the pythagorean theorem, that is:  $$3^2+4^2=5^2$$  But I am sure this isn't the way to prove the statement since you are making the assumption that it is a right triangle. I know I also can't use any of the trig functions like sin, cos, tan. Then given the sides of the triangle, can I prove this to be a right triangle?


Replace identical lines with just one line at end in Notepad++

Can I replace identical lines with just one line at the end in Notepad++? E.g. from:  1st January 2013 //some text1 1st January 2013 //some text2 1st January 2013 //some text3 1st January 2013   to:  //some text1 //some text2 //some text3 1st January 2013   Also is it possible, if I have all dates from 1 to 30 or 31, to replace them individually at their last appearance?


I only have 700 MB CD.  Tried to save to USB but still asks to burn image CD and I don't have CD big enough.  Can I bypass burn image CD? how? if not how big does CD have to be? disc burner only has DVD drive option so I cant select USB as option even when USB in computer.  Computer has all necessary hardware called for by ubuntu.


I watched videos on youtube regarding general relativity which say that "imagine a ball kept on a trampoline bends it." But for this explanation, we are using earth's gravity to explain gravity and bend in space time. So how does mass in space bends spacetime as no(negligible) gravity acting on it.


Check if a URL is valid in PHP allowing wildcards

I need to check if a string is a valid URL, allowing wildcards in the name. For example, I've URLs sanitized as follows (lowercased, removed the path like example.com/path, added http:// or https://):  http://example.com  http://www.example.com  http://*.example.com   These URLs are VALID. Instead, I would mark as invalid URLs like:  http://example.*.com  http://example  http://*.it (and obviously any not-valid URL, so remove invalid characters etc.)   Anyone can help? I've tried many regex, but no one works..  My pattern should be something like: [http://].[*|a-z|www].[a-z].[tld] (allowing also fourth-level domains!)  Thanks in advance!


Basically, when a dweller becomes pregnant, I can usually send them back to their work stations from the Residence room. For some reason, that doesn't apply to all of them, since sometimes they get stuck in said Residence room, i.e. I'm not able to select them and drag them to a different room as the green silhouette (that appears when you drag dwellers around) disappears as soon as I drag it (but is still there if I just hold my finger over said pregnant dweller). What gives?


Showing the bibliographic entry in a popup when you hover over the citation key

I thought it would be useful to have bibliographic entries displayed as a tooltip so readers are not interrupted by following hyperlinks or trying to find the Bibliography, so I created the following command:  \newcommand\annocite[1]{\pdfmarkupcomment[markup=Underline,subject=Citation]    {\parencite{#1}}{\fullcite{#1}}}   Unfortunately this does not work. Instead of showing the bibliographic entry in the popup, it merely displays the citation key; i.e., the \fullcite command seems to have no effect. I believe the problem is related to argument expansion. Here is a MWE:  \documentclass{article} \usepackage{biblatex,pdfcomment,filecontents} \bibliography{\jobname}  \newcommand\annocite[1]{\pdfmarkupcomment[markup=Underline,subject=Citation]     {\parencite{#1}}{\fullcite{#1}}}  \begin{filecontents}{\jobname.bib} @article{Bli74,   author = {Blinder, Alan S.},   year = {1974},   title = {The economics of brushing teeth},   journaltitle = {Journal of Political Economy},   volume = {82},   number = {4},   pages = {887--891}, } \end{filecontents}  \begin{document} Hover over this citation: \annocite{Bli74}  The tooltip should contain the following text: \fullcite{Bli74}  \end{document}   Can anyone think of a solution, or better, a way to redefine biblatex' citation commands (e.g., \parencite, \cite) to do this automatically?


Reason for Subject-Verb Inversion: Only in cases where A is B, shall the Company do X

Possible Duplicate:             In the following, why does subject-verb inversion occur? Is it necessary? And what is this type of inversion called?   Colleague’s original:     Only in cases where A is B, the Company shall do X.   I changed to the following:     Only in cases where A is B shall the Company do X.    Searching Google for “shall the Company” gives examples such as:     In no event shall the Company ...   Under no circumstances shall the Company ...    And these all seem quite natural.   “In no event” and “under no circumstances” seem to be prepositional phrases, yet I would say simply, with no inversion:     In the fridge, you will find some beer.    Is the S-V inversion maybe some sort of archaic style that remains in legal or maybe religious texts? Perhaps a remaining German-style syntax?


I can edit a question and have it change, but if I approve an edit from another, this is not enough to make the change happen

I don't need further approvers for my edits on Stack Overflow, but if I approve another person's edit (which is often the edit I wanted to make), the edit needs to wait for more approvers.  Can it be changed so that if someone who can make edits without further approvers, approves an edit, it doesn't need further approvers ether?    It appears that in the interest of better quality reviews, you have to at least notionally improve the edit as an extra step. Is there a way this could be more obvious as I might not be the only one who didn't know this?


Bourbaki's construction of the monoid of fractions of a commutative monoid $E$ and the concept of "identification"

Let $E$ be a commutative monoid with identity $e$, $S\subseteq E$, and let $S'$ be the submonoid of E generated by $S$.   For every invertible element $x$ of E, $x^{*}$ denotes the inverse of $x$.   Let $R(x,y)$ denote the following relation:  $$\text{there exist }a,b\in E\text{ and }p,q,s\in S'\text{ such that }x=(a,p), y=(b,q)\text{ and }aqs=bps;$$  this is an equivalence relation on the product monoid $E\ \times\ S'$, compatible with its law. Denote the quotient monoid $E\times S'/R$ by $E_{S}$.   For $a\in E$ and $p\in S'$, let $a/p$ denote the equivalence class of $(a,p)$ modulo R. Then, mapping  $$\varepsilon: E\longrightarrow E_{S},\ a\mapsto a/e,$$  is a homomorphism.  For every $a\in E$ and $p\in S'$, we have $a/p=(a/e)(e/p)$: i.e., $a/p=\varepsilon(a)\varepsilon(p)^{*}.$   Therefore, $\varepsilon(E) \cup\varepsilon(S)^{*}$ generates $E_{S}$, where $\varepsilon(S)^{*}$ denotes the set of invertible elements of $\varepsilon(S)$.  This construction is taken from Bourbaki's Algebra. Now Bourbaki goes on to say:   Question: Can someone please explain what is going on in this screenshot? (I understand why $\varepsilon$ is injective.) In particular, I don't understand how one can "identify" $E_S$ with the submonoid of $\Phi$ generated by $E\cup S^*$? This whole business of "identification" is unclear to me: I don't understand what I am exactly able to do logically and formally whenever I am to told to "identify" two objects.  Any help will be appreaciated. Thank you.


$ wget https://raw.github.com/mseknibilel/OpenStack-Grizzly-Install-Guide/master/KeystoneScripts/keystone_basic.sh  --2014-03-05 12:55:27--  https://raw.github.com/mseknibilel/OpenStack-Grizzly-Install-Guide/master/KeystoneScripts/keystone_basic.sh Resolving proxy4.xxxxx.com (proxy4.xxxxx.com)... 10.201.51.54   Connecting to proxy4.xxxxx.com (proxy4.xxxxx.com)|10.201.51.54|:8080... connected. Proxy tunneling failed: Proxy Authentication RequiredUnable to establish SSL connection.  Could someone let me know, where and in which file I need to set proxy password and user to get wget working?.


How do I load external images into Excel?

I have a table with a column of links (URLs) to images. I want to load the linked images into the next cell over.   For example:  A1 contains    http://example.com/image.jpg   I want to load the image in B1.   How can I do it?


Which Ubuntu for Eee 901 - to run from SD card?

I would like to use linux on our company laptop Asus Eee 901 - specs:  CPU Intel Atom 1.66 GHz,  RAM 1 GB DDR2 Display 8.9 inch, 1024x600 pixels  As I am not allowed to modify the OS and MBR I want to boot from SD slot and use some SDHC card (can buy something like Class 10 for better performance).  I need some user friendly distro with GUI. In first approach the laptop will serve as portable device for sorting and backup photos (to external usb HDD) and videos on holiday and occasional web access.  So I need some usable image viewer, file manager and current web browser - capable to run on the screen only 600 pixels high... And running a little bit more quickly than the Windows :-)  What would you recommend? Lubuntu?  thanks


Are holograms in midair physically possible?

Is it possible for holograms, as in 3D projections of light in midair, to exist?   Consider this image. If a projector, placed in the same position as the gray circle in the first image, were to project some sort of light into the air, would it be able to form a three-dimensional image such as this bowl?


Validity of LTL formulas in a given transition system

Say I have the following transition system:    I've understood how I can tell if □a and ⟡b are valid (□a is invalid because a is not true is S2 and ⟡b is valid there is a state (i.e. S1) in which b is true. Please correct me if I'm wrong). But how do I reason the validity of the following formulas:  □(a -> b)  □⟡(a ^ b)  ?


Drupal Views Exposed Filter ( Creating seperate filters for parent , child & grandchild )

How can one achieve following in exposed fliters  FILTER ONE (PARENT) FILTER TWO ( CHILD ) FILTER THREE ( GRAND CHILD )..  I dont want SHS or HS,   Please guide.


Which usage is correct for the word Rebel?

Which is the correct version, Rebels Outpost or Rebel Outpost? Doesn't the "s" signify that its multiple rebels? And rebel meaning "To rebel"? Rebel could also be used as plural couldn't it, in third person context? Used in a sentence. Become part of the Rebels Outpost team or Become part of the Rebel Outpost team.


Proving that a Hölder space is a Banach space

I am trying to show that the Hölder space $C^{k,\gamma}(\bar{U})$ is a Banach space. To do this, I successfully proved that the mapping $\| \quad \| : C^{k,\gamma}(\bar{U}) \to [0,\infty)$ is a norm, by proving its properties.   But how do I show that the sequence $\{u_k\}_{k=1}^\infty \subset C^{k,\gamma}(\bar{U})$ converges to $u \in C^{k,\gamma}(\bar{U})$, that is, how do I show that $$\lim_{k \to \infty}\|u_k-u\|=0,$$ which would mean the normed linear space is complete, and hence a Banach space?  Here are the following taken from PDE Evans, 2nd edition, page 255:     Definition. The Hölder space $$C^{k,\gamma}(\bar{U})$$ consists of all functions $u \in C^k(\bar{U})$ for which the norm $$\|u\|_{C^{k,y}(\bar{U})}:= \sum_{|\alpha|\le k} \|D^\alpha u \|_{C(\bar{U})}+\sum_{|\alpha|=k} [D^\alpha u]_{C^{0,\gamma}(\bar{U})}$$ is finite.   Also from page 254,     Definitions. (i) If $u : U \to \mathbb{R}$ is bounded and continuous, we write $$\|u\|_{C(\bar{U})}:=\sup_{x\in U}|u(x)|.$$      (ii) The $\gamma$th-Hölder seminorm of $u : U \to \mathbb{R}$ is $$[u]_{C^{0,\gamma}(\bar{U})}:=\sup_{\substack{x,y\in U \\ x \neq y}} \left\{\frac{|u(x)-u(y)|}{|x-y|^\gamma} \right\},$$ and the $\gamma$th-Hölder norm is $$\|u\|_{C^{0,\gamma}(\bar{U})}:=\|u\|_{C(\bar{U})}+[u]_{C^{0,\gamma}(\bar{U})}.$$   This is all I got so far: \begin{align} \|u_k-u\|_{C^{k,\gamma}(\bar{U})}&=\sum_{|\alpha|\le k} \|D^\alpha u \|_{C(\bar{U})}+\sum_{|\alpha|=k} [D^\alpha u]_{C^{0,\gamma}(\bar{U})} \\ &= \sum_{|\alpha|\le k} \sup_{x\in U} |u_k(x)-u(x)|+ \sum_{|\alpha|=k} \sup_{\substack{x,y\in U \\ x \neq y}} \left\{\frac{|[u_k(x)-u(x)]-[u_k(y)-u(y)]|}{|x-y|^\gamma} \right\}. \end{align} Now, where can I go from here, to show that $\lim_{k \to \infty}\|u_k-u\|_{C^{k,\gamma}(\bar{U})}=0$? The sequence is Cauchy, and I have to use that fact somehow.


Clear Developer Console Test Run Results

Being familiar with the Developer console.. Can Any one tell me how to clear the test run results area in the developer console  This is the section that I want to clear...


How can I show activeness in a Committed Proposal in Area 51 with a new account?

I found an interesting Proposal, and I'd like to answer on the questions or vote the answers.  However, I have only one reputation, and I need at least five rep points to make an answer.  Is creating new questions the only way to gain enough reputation points to be able to start answering? Do I need to push the "Commit!"-button before I can do anything on a given Proposal?  (I waded through the Area 51 FAQ, but I didn't catch anything on my eye which would have answered my question)


How to remove a specific package from dependency list of another package?

Since I'm using Qt5 I want to uninstall all the qt4 libs. I tried it with the following command  sudo apt-get remove libqt4-*   which attempts to remove all the qt4 libs but in addition it wants to remove texlive and vlc which I don't want to be uninstalled.  Is there a way to keep those two packages? I found apt-mark hold but then they wouldn't be updated, too, so that doesn't suit for me.


load command from history but don't execute yet, so I can modify it

In bash, I know how to   history |grep foo   which will give me a list of numbered commands from history containing foo. If I want to run one of those commands with a different argument, I can copy paste using the mouse. I don't want to repeat an exact command. I want to load it at the prompt and change something, then execute it. Is there a way to do so? Up arrow doesn't always work for me.


Title in Google does not match  of document

One of my project's title tag doesn't appear to be getting crawled by Google properly. The title tag of the home page reads:  <title>Grande Prairie Jobs | Job Board for Grande Prairie, Alberta and Area</title>   Google, on the other hand, indexes the title as gpjobs.ca.    Is there something I'm doing wrong here? Any insight would be really helpful.   One thing, the first  of the document is gpjobs. Could this be causing the  incorrect title? I guess I just don't understand why Google would index it with the <h1> rather than the <title>.  Edit: To clarify for whoever marked this question as a duplicate of , my site actually had a landing page where Google indexed it correctly. After launching the site and submitting a sitemap, Google has indexed the title as above. What I'm trying to establish and correct, is why the site has an indexed title of the first h1 on the page and not the title. I expected the title to be picked up.


How to prove any strictly upper triangular matrices are nilpotent?

i don't know about the Cayley-Hamilton, soooo how can i prove this?


Need expert help with tricky redirect problem

I actually posted about this years ago, never got anywhere. Did more research, did testing, got something I thought worked and mostly did, but it seems to get bogged down in infinite loops under certain circumstances. I am at my wit's end. Anyone who can help me resolve this, you are my hero for life. :)  The Problem  I run a photo gallery and I changed my website structure a few years ago.   The Old Site  The old structure, an album had a form like this:  http://desktopscenes.com/Name Of Album (Year)/default.html   Individual photo slides were like this:  http://desktopscenes.com/Name Of Album (Year)/slides/Name Of Slide.html   And the actual slide was:  http://desktopscenes.com/Name Of Album (Year)/slides/Name Of Slide.jpg   The New Site  An album is like this:  http://desktopscenes.com/Name_Of_Album_-_Year/index.htm   A photo slide like this:  http://desktopscenes.com/Name_Of_Album_-_Year/slides/Name_Of_Slide.htm   And the photo:   http://desktopscenes.com/Name_Of_Album_-_Year/slides/Name_Of_Slide.jpg   So What I Need to Happen Is:   Change all spaces to underscores. Change the year references from " (Year)" to "_-_Year". Change "html" to "htm". Not break anything else. :)   My Attempt  You'd think this would be fairly simple. And in fact I actually got this to work -- most of the time. The problem is that occasionally something sends a request and sends it into an infinite loop.  Here's my code.  RewriteEngine On Rewritecond %{HTTP_HOST} ^(desktopscenes.com|www.desktopscenes.com)$ [nc] RewriteRule ^(.*)\s(.*)$ $1_$2 [N,NE] RewriteRule ^(.*)\((.*)$ $1-_$2 [N,NE] RewriteRule ^(.*)\)(.*)html$ http://desktopscenes.com/$1$2htm [NE,R=301,L] RewriteRule ^(.*)\)(.*)jpg$ http://desktopscenes.com/$1$2jpg [NE,R=301,L]   A Clue - Revised!  If 'proper' requests come in as they should, this works fine. I think the problem is if a request comes in that is incorrect. In particular, sometimes I get a request like this on the old site:  http://desktopscenes.com/Name Of Album (Year)/Name Of Slide.jpg   Notice the "slides" folder is missing. I am pretty sure this request created an infinite loop.  ETA: Looking through my logs I am now seeing this is much more common than I thought. I would love a way, if possible, to add the "slides/" folder back in if a request for a .jpg comes in without "slides/" in the URI.  In Closing  Thank you for listening and attempting to help me with this. It has literally been bothering me for years!  Addendum  I have also been changing apostrophes in the original names to dashes. But these are infrequent so they are less important.  Revised Code  This is what I have now  RewriteEngine On Rewritecond %{HTTP_HOST} ^(desktopscenes.com|www.desktopscenes.com)$ [nc] RewriteRule ^(Test.*)\s(.*)$ $1_$2 [N,NE] RewriteRule ^(Test.*)\((.*)$ $1-_$2 [N,NE] RewriteRule ^(Test.*)\)(.*)/slides/(.*)html$ http://desktopscenes.com/$1$2/slides/$3htm [NE,R=301,L] RewriteRule ^(Test.*)\)(.*)/slides/(.*)jpg$ http://desktopscenes.com/$1$2/slides/$3jpg [NE,R=301,L]   This handles the case where I have album (year)/subalbum/slides.html or whatnot.  The "Test" is in there so I can test this on a dummy structure without blowing up the rest of the site.  I am still not sure how to handle requests of the form:      Of Album (Year)/Name Of Slide.jpb  That is no "slides". I am not sure what the regex is to NOT find a particular string, I guess I could look that up.  Another Update - Adding back "/slides/"  I don't need to search for "no slides". Since the ones that match "slides" have the "L" suffix they should stop processing once found. (Correct?)  So I was able to add this:  RewriteRule ^(Test.*)\)([^/]*)/(.*)jpg$ http://desktopscenes.com/$1$2/slides/$3jpg [NE,R=301,L]   Which actually adds the "/slides" back in if not present on a JPG request, which is great!  When I tried to do the same for HTML however:  RewriteRule ^(Test.*)\)([^/]*)/(.*)html$ http://desktopscenes.com/$1$2/slides/$3htm [NE,R=301,L]   It doesn't work. Any idea why?


I have recently installed Ubuntu 14.04 alongside with Windows 7 which was previously installed. After log-in into Ubuntu, it freezes totally (no keyboard nor mouse interaction). This happens all the time and it gets faster when I try to install a new app. Any help?


How can i see when a file was created. I have looked at man page   ls -lc is for last modification of file status  ls -lu for  access time  ls -l  not exactly indicated which time, last changed?  I tried these, but they don't give me time the file was created.


How to find a symmetric matrix $B$ where $x^T Ax = x^T Bx.$

Find a symmetric matrix $B$ such that for every $3\times 1$ matrix $x$.   $$x^T Ax = x^T Bx\ .$$  Let $$A = \begin{pmatrix}2& 1& -1\\3& 0& 1\\-2& 5& 3\end{pmatrix}$$


How do I reset all of my view panels without having to do the click and drag method?

I would like to find a different solution to closing these windows without having to do the click and drag.


How do I determine the size of an object in Python?

I want to know how to get size of objects like a string, integer, etc. in Python.  Related question:   I am using an XML file which contains size fields that specify the size of value. I must parse this XML and do my coding. When I want to change the value of a particular field, I will check the size field of that value. Here I want to compare whether the new value that I'm gong to enter is of the same size as in XML. I need to check the size of new value. In case of a string I can say its the length. But in case of int, float, etc. I am confused.


Biblatex is not working for me suddenly. I suddenly get the following log file :   Unsuccessful stat on filename containing newline at /var/folders/48/mcfj3ms5211f4zc_b6l9680r0000gn/T/par-6a61736f6e6b6861646b61/cache-6bef3f811cde577dd70e44f9f5046ebc66712c46/inc/lib/XML/LibXML/Simple.pm line 223. data source <?xml version="1.0" encoding="UTF-8"?> <bcf:controlfile version="2.7" xmlns:bcf="https://sourceforge.net/projects/biblatex">   <!-- BIBER OPTIONS -->   <bcf:options component="biber" type="global">     <bcf:option type="singlevalued">       <bcf:key>output_encoding</bcf:key>       <bcf:value>utf8</bcf:value>     </bcf:option>     <bcf:option type="singlevalued">       <bcf:key>input_encoding</bcf:key>       <bcf:value>utf8</bcf:value>     </bcf:option>     <bcf:option type="singlevalued">  .....       <bcf:field>addendum</bcf:field>       <bcf:field>afterword</bcf:field>       <bcf:field>annotator</bcf:field>       <bcf:field>com not found in . INFO - This is Biber 2.1 INFO - Logfile is 'main.blg' INFO - Reading 'main.bcf'   and in the compiling of my text there is an error that can only fixed by recompiling the biblatex. How can i fix it?


In which English accents do they put an h before every word that starts with wh?  . Notice his pronunciation of whisky.


Uninstalled and Installed latest verion of nodejs but when i check version its still the old one

I did as per the solution given in    But when I check nodejs --version  I get v8.10.0  And when I install using this command sudo n latest I get installed : v13.8.0 (with npm 6.13.6)  I have the same version problems with node and npm too, the latest verion installed is not reflected.   whereis nodejs I am getting this output: nodejs: /usr/bin/nodejs /usr/lib/nodejs /usr/share/man/man1/nodejs.1.gz   I tried uninstalling nodejs and installing again the same thing happens. Is this a problem with ubuntu?


Understanding the Formalism of wave function collapse

For example, a perfect measurement ($\hat A=\hat x$) on position:   $$\hat x\psi=x_0\psi$$  The eigenvalue $x_0$ is the result of measurement. The eigenfunction $\psi$ is the wavefunction after measurement. Here solve for the eigenfunction one could get $\psi=\delta(x-x_0)$, so we say that the wavefunction has collapsed to the Dirac Delta?  I am not sure if my understand is flawless.  In a non-ideal measurement, one can only get measurement results as a density distribution. In this case, how does the wavefunction collapse?


Alphanumeric symbols in the data/app directory?

Why are the names of the applications replaced with alphanumeric characters in the data/app directory? I am seeing this when accessing the directory through an adb shell.


Update problem on terminal and Software Center on Ubuntu 16.04

sudo apt-get update and sudo apt-get upgrade gives me this result  E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?  When I check Software Center it shows me 23 new updates available, but when I try to make update it never finish and all the time there is information about 23 new updates.


$\int_{\mathbb R} |f(x)| dx < \infty \implies \int^{\infty}_{n} |f(x)| dx \to 0$ as $n \to \infty$?

Suppose that $\int_{\mathbb R} |f(x)| dx < \infty$.     Can we say that $\int^{\infty}_{n} |f(x)| dx \to 0$ as $n \to \infty$ If yes, how to justify?


I was reading 's excellent answer to  regarding the use of WP_query(), query_posts() and pre_get_posts.  He says "pre_get_posts is a filter, for altering any query. It is most often used to alter only the 'main query'."  It is possible to use pre_get_posts to filter only a specific secondary query created with WP_Query? eg.  $my_secondary_loop = new WP_Query(...); if( $my_secondary_loop->have_posts() ):     while( $my_secondary_loop->have_posts() ): $my_secondary_loop->the_post();        //The secondary loop     endwhile; endif; wp_reset_postdata();   Any help much appreciated.


In a previous question about the English of the KJV a  was helpfully supplied and I read the following      The vocative case is used when directly addressing a person with a noun identifying the person instead of with the second person pronoun “you.”  An example is in Matthew 6:9 which says, “Our Father, which art in heaven.”  Today we are less inclined to say “Our Father, who ARE in heaven.”  It seems more natural to say “Our Father, who IS in heaven.”  The peculiarity of the KJV is based on the faithful translation of the vocative case.  This is not an archaism but a faithful translation of the Greek which has the vocative case.   Like many things, I learned the words as a child and have accepted them all my life without intelligently understanding them.  I am still struggling to understand why the verb is plural and where 'art' comes from.


I don't want to retain my WinXP so I downloaded 'Kubunu 14.04'. However, I can't find it at all, even in my BIOS. Should I download it again?


Often dragging the top of a window ends up expanding it

very often when I drag the top of windows such as a browser window to move it to another location, Ubuntu expands the window instead. This happens regardless I use an external mouse or a trackpad. Is there a way to solve this problem?


Extent of file is different in same coordinate system

I have one TIFF file and one shapefile in the same coordinate system, but it's not overlapping. When I see the extent of both files both are in meters but they are very different.


i am trying to calculate these formulas:   -and-  (p-side: x < -xp , n-side: x > xn) But i wonder, how can i find pn0 and np0 Thanks in advance.


I am reading paper on . I am trying to understand the following statement:     I would like to ask how the Ball doesnot contain the minimum of f? I would appreciate if this could be graphically shown something like following taken from Bayesian Optimization and Data Science


Validation Rule: User only can edit the status field during the edition. No other field should be edit

This is not a duplicated question, but a new one. I created a formula where the user can or should only edit the status field when the status is equal to "Under approval". However, when I change the status to approve or rejected, I can edit the record name and payment name during the edition. How can I prevent user to modify the payment name and account name (lookup) during the record edition? The user should only change the status, not the other fields. The system should not allow the user to save the record, because only the status field can be edit. This is my current formula:   AND(ISPICKVAL( PRIORVALUE( Status__c ), "Under Approval"),AND( NOT(ISPICKVAL(Status__c, "Unpaid")), NOT(ISPICKVAL(Status__c,"Paid"))),  NOT(ISPICKVAL(Status__c, "Approved")),  NOT(ISPICKVAL(Status__c, "Rejected")))   Thanks for helping me!


How does a chip interpret different opcodes?

I have learnt in school about opcodes and how it works with the ALU to add numbers and such, now is my question how the computer is able to understand this, because it is codes and the computer needs something to translate that to actually doing that, in't it? (correct me if I'm wrong plz) I also want to, when I understand that, make my own processor so I can learn the computer bottom-up and become a good computer engineer.


How to enable IMAP php extension on aws EC2 instance

I've tried every way to install imap php extension but I couldn't do it. I am using amazon web service EC2 instance and it has CentOS. while yum search *-imap.* I found a package from cyrus-imap.* but it's not working. I've installed it but it seems to be not the package I want. I have tried many things but there are no package with php-imap on cent os. My application badly needs php-imap extension. My php config # php -v  PHP 7.2.31 (cli) (built: Jul  2 2020 23:17:00) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies  Can anyone help? Thanks in advance.


How to create tally marks / hash marks with LaTeX

Hi  I want to add a column in my table like the given image. How to produce this type of difficult symbol in latex?


So for a particular hotel on expedia.com I can "pay online now" $374 or I can "pay later" $374 (approx). The following screenshot better captures what I mean:    My question is...  why is pay later an approximation whereas pay online now isn't? If I pay later would I essentially be paying at the same rate I'd be paying at if I tried to book the hotel same day (which would be quite expensive, I'd imagine)?


How to automatically crop white space from multiple images?

I have recently scanned a bunch of old photo prints to digital for a slide show but all of them have a bunch of white space around them like this:                                         /\                                       ||                              Unwanted White space   I know how to remove the space manually in GIMP but I was wondering if there is some kind of automatic tool to do it for me because I have way too many to do by hand.


Since I was told my post is a re-post, which it is not, let me re-explain:  I have a div 'box'. In this 'box', there is a 'contentbox' div. In that 'contentbox' there is, by default, a form and a button 'button1'.  When 'button1' is clicked, a new form 'questions' and a new button 'button2' is loaded into 'contentbox'.  'button2' will not click and load more html.   When trying to follow the link that I was apparently "reposting" I changed my JQuery to...  $("#button2").on('click', "#contentholder, loadQuestions());   I want my dynamically loaded button to be able to dynamically create other dynamic content. That way, all processes can occur within my 'contentbox'.  If you still believe I need to go back and look at that post, please be more specific on what I am actually doing wrong. It takes a long time to create these posts, and to simply tell me "repost" does not get me anywhere.   Thank you  JFiddle Demo(With html):           $(document).ready(function () {         $("#button1").click(loadUserNameTable);         $("#button2").click(loadQuestions);         $("#button3").click(loadPasswordChange);         $("button4").click(submit);     });      function loadUserNameTable() {         $("#contentholder").load("nametable.html");     }     function loadQuestions() {         $("#contentholder").load("questions.html");     }     function loadPasswordChanger() {                     $("#contentholder").load("passwordchange.html");     }


I have a capped and maxed stat vault. All dwellers are level 50 and maxed at 10 for all stats across the board. My current objective is getting everyone to a solid 100% happiness. But this isn't working for me. Many dwellers are at the 76% to 96% and not going any higher. Dwellers are in the right rooms according to the green corners and the quest credits. They are also in correct maxed +4 gear for that stat associated with the room. Any ideas or suggestions?  Thanks!


So I have this table, which I just used an online tool to create, but I want the columns to wrap. So, I just change \begin{tabular} to \begin{tabularx} and then the last column vertical line is about 1cm from the table... How can I fix that gap? \begin{tabularx}{\textwidth}{|X|X|X|X|} \hline Name:                                      & Donald Trump                              & Student ID:                                         & 99999999                                     \\ \hline \multicolumn{2}{|p{0.5\textwidth}|}{Feedback focus:}                                                 & \multicolumn{2}{p{0.5\textwidth}|}{asoidjfaopsidjfp oiajdfpo iasjdfp oiasjdfpo ij}                                \\ \hline \multicolumn{2}{|p{0.5\textwidth}|}{askdljf ;laksjdf;l aksjdf;lkajsd;:}                          & \multicolumn{2}{l|}{as;ldifja;lsdkfja;lsdkfja; slkfj; aldkjf ;aslkdj ;alk}                         \\ \hline \hline \multicolumn{4}{|p{\textwidth}|}{as;ldkf;lkj: aklsduhf asldkj f;alskdjf ;alskdjf ;alskdf }                                                                  \\ \hline Fully Met                                  & Met                                      & Partially Met                                       & Not Met                                      \\ \hline Comments:                                  & \multicolumn{3}{l|}{}                                                                                \\ \hline \multicolumn{4}{|p{\textwidth}|}{asldkjf;alksdj f;laksjdf:as;dlk ja;lsdk fjas;ldkfj a;slkdfj ;lakasdlk;jkdj }                                                                               \\ \hline Fully Met                                  & Met                                      & Partially Met                                       & Not Met                                      \\ \hline Comments:                                  & \multicolumn{3}{l|}{}                                                                                \\ \hline \multicolumn{4}{|p{\textwidth}|}{a;lsdkjf; lakj;l3: alkjdsf l;aksjdf;l kasjd;lf kjasd;l fkjas;ldkfjas;ldkf jas;ldkf ja;sldkfj asldkfj alksjferopijp34qjp asdf} \\ \hline Fully Met                                  & Met                                      & Partially Met                                       & Not Met                                      \\ \hline Comments:                                  & \multicolumn{3}{l|}{}                                                                                \\ \hline \multicolumn{4}{|p{\textwidth}|}{as;ldkfjal;kej ;l4: alskdjf ;lasdkjf ;alskdjf ;laskd}                                                                                \\ \hline Fully Met                                  & Met                                      & Partially Met                                       & Not Met                                      \\ \hline Comments:                                  & \multicolumn{3}{l|}{}                                                                                \\ \hline \multicolumn{4}{|p{\textwidth}|}{asl;dkjf;lk4j: asl;dkjfaslkdjf eirkajp (asl;dkfj a) aslkdjf l}                                                                                \\ \hline Fully Met                                  & Met                                      & Partially Met                                       & Not Met                                      \\ \hline Comments:                                  & \multicolumn{3}{l|}{}                                                                                \\ \hline \end{tabularx}  Gives:


Why is the following query slow?  select count(*)   from [dbo].[mt_dispatch_link]     , [dbo].[_mt_dispatch] [_mt_dispatch]  where   (mt_dispatch_link.contract_id_1 = _mt_dispatch.contract_id       and mt_dispatch_link.dispatch_id_1 = _mt_dispatch.dispatch_id)     or   (mt_dispatch_link.contract_id_2 = _mt_dispatch.contract_id       and mt_dispatch_link.dispatch_id_2 = _mt_dispatch.dispatch_id)     It takes over 10 minutes, and then I tend to stop it at that point. My question is more about how to make sense of the query plan.  Looking at the query plan I can see that the bottom clustered index scan is returning about 250000 records, but the cost is 0% and it is being put into a temporary table.  The top index scan is about 25000 records.  But the cost of 95% comes from the nested join. What conclusions should I draw from this?  The above query plan shows two index scans, does that mean it is doing 25000 + 250000 index scans, or does it mean that it is doing 25000 * 250000 index scans?  If I change the query to this (adding FORCESEEK):  select count(*)   from [dbo].[mt_dispatch_link]     , [dbo].[_mt_dispatch] [_mt_dispatch]       WITH (FORCESEEK)  where   (mt_dispatch_link.contract_id_1 = _mt_dispatch.contract_id       and mt_dispatch_link.dispatch_id_1 = _mt_dispatch.dispatch_id)     or   (mt_dispatch_link.contract_id_2 = _mt_dispatch.contract_id       and mt_dispatch_link.dispatch_id_2 = _mt_dispatch.dispatch_id)   I end up with a much better plan and the query runs instantly:    I ran update statistics on both tables. Didn't fix it unfortunately. The table design is not very good, so I think SQL Server doesn't really understand and is thus coming up with a poor query plan. Some more info about the table design at .  Why is the query optimiser not coming up with the optimum plan?


For convex cyclic hexagon $ABCDEF$, show $AC\cdot BD \cdot CE \cdot DF \cdot EA\cdot FB \geq 27\cdot AB\cdot BC\cdot CD \cdot DE\cdot EF\cdot FA$

Given a convex hexagon $ABCDEF$ inscribed in the circle, prove that   $$AC\cdot BD \cdot CE \cdot DF \cdot EA\cdot FB \;\geq\; 27\cdot AB\cdot BC\cdot CD \cdot DE\cdot EF\cdot FA$$   ("$AC$" means the length of the segment with endpoints $A$ and $C$.)  What I did until now: bashing complex and making problem even harder!


What is the best way to prevent logo distortion and poor quality when allowing users of an app to upload their own logo?

I'm not a fan of allowing any outside logos into an app but it is a Client requirement. The requirement is that a user can upload their logo and it will replace the app logo in a space that is 120px - 160px width. There are several problems to try to prevent when allowing the user to upload a logo:   poor quality image that is pixelated when uploaded wrong size image that will be distorted when displayed unvectored text in logo font images ( which can't be prevented ) wrong aspect ratio logos   I'd like to know what the best parameters to set for an uploaded logo.  We can do a check with the code for the px width and height. But the code can not check if the text has been vectorized.  Any insights would be nice in this problem. Thanks in advance.


I own a pair of usb powered speakers, and I am having trouble finding how to set the usb speakers as the default output. I found the setting where you can switch the outputs but no where to asssign a default. I took screenshot here:


Is it possible to find the following limit without applying L'Hopital's Rule, but only with some transformations? $$\lim_{x\to0}\frac{1-cos(x)}{x^2}$$


How to connect JDBC to MySQL with other IP

When I try with 127.0.0.1 or localhost, there are no errors. but when I try to use a 192.168.xxx IP, a NullPointerException occurs. static Connection conn = null;  public static void main(String[] args) {     final String USERNAME = "root";     final String PASSWORD = "password";//DBMS     final String URL = "jdbc:mysql://192.168.1.2:3306/sqldb";     try {         Class.forName("com.mysql.jdbc.Driver");         conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);         System.out.println("sucess");     } catch (Exception e) {         System.out.println("fail");         try {             conn.close();         } catch (SQLException e1) {         }     } }  When I start, I get  What can I do?


I would like to know how I do so that the text that is next to the image is aligned vertically in the middle, so that it is more orderly next to the image that appears next to it. Starting the snippet, you can see what I say by clicking to see in full screen    <link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">

Title

Lorem Ipsum is simply dummy text of the printing and                                  typesetting industry. Lorem Ipsum has been the industry's standard dummy                                 text ever since the 1500s, when an unknown printer took a galley of type                                  and scrambled it to make a type specimen book. It has survived not only five                                 centuries, but also the leap into electronic typesetting, remaining essentially                                 unchanged.


Stack Exchange profile shows zero count before posting any posts on the respective site

The Stack Exchange network profile page showing zero questions and zero answers for all accounts.  After posting this question, it shows the questions count for Meta Stack Overflow.  Now the issue is clear, I'd posted a question just now on Sports.SE beta site and then I can see the questions count for Sports.SE in my . We should fix it.


What does "Your submission will be handled by Receiving Editor" mean?

I submitted a paper to a journal and after 20 days I got an email which states  Your submission entitled "X" will be handled by Receiving Editor.  What does this mean?


Wilson's Theorem textbook proof question

I'm trying to understand this proof from Stein's Elementary Number Theory, and I understand the pairing of inverses but not the other direction. I have two questions:  $1).$ When the proof says, $l$ a prime divisor of $p$, and so $l<p$ and $l \mid (p-1)!$, is this because $l \mid p \Rightarrow l \mid p!=p*(p-1)!$ and so $l \mid (p-1)!$ (by Euclid)?  $2.)$ Why is it that $p \mid ((p-1)!+1)$?


Proving that any common multiple of two numbers is a multiple of their least common multiple

I'm trying to prove that if there are to numbers $n,m$ (natural numbers), and their smallest common multiple is $k$, so that $k = n·i$ and $k = m·j$ for some $i,j$ natural numbers, any common multiple $q$ of $n,m$ is a multiple of $k$, so that there exists a $g$ so that $q=k·g$.  Logically it seems correct, but I can't seem to prove it... Any help?


Find $n$ satisfying the equation $[\log_21]+[\log_22]+[\log_23]+\dots[\log_2n]=1538 $

If $[\cdot]$ denotes greatest integer function, then what is the value of natural number $n$ satisfying the equation $$[\log_21]+[\log_22]+[\log_23]+\dots[\log_2n]=1538 ?$$   My try:  Note that  $$0+1\times2+2\times2^2+3\times2^3+4\times2^4+5\times2^5+6\times2^6+7\times2^7=1538$$  But the answer is $$n=\sum_{i=0}^72^i=255.$$  How is it derived?


Is it appropriate to call a British person a "Brit"?

Specifically, is it appropriate for a non-British person to call a British person a "Brit"? Whenever I see it from an American source it always feels too familiar or too informal, or both. But I can't tell if that's something real or just my own peculiar hang-up.  How formal is the word "Brit," and how do people from Great Britain feel about others using the word? What about "Brit" as an adjective (e.g., )?


What is the probability that a matrix over $GF(2)$ fails to have full row-rank?

This question relates to , which is ultimately concerned with .  I do my best to relay the relevant information here.  Within the linked paper, the authors seem to work under the assumption that if we select a random $288 \times 216$ matrix $M$ with entries in $GF(2)$ (the field with two elements), then there is a very high probability that $M$ has full column rank, and that a randomly selected $84 \times 216$ submatrix will have full column rank.  With that in mind, my question is the following:     If a random $m \times n$ matrix $M$ over $GF(2)$ is selected (i.i.d. uniformly random $\{0,1\}$ entries), then what is the probability that $M$ will have maximal rank in the case where         $m = 288, n =216$   $m = 84, n = 216$      I am aware that there is a nice formula for this probability in the case where $M$ is square, but I'm not sure where to find (or how to derive off the top of my head) the corresponding probability for rectangular matrices.    Any help is appreciated.


Why are there dark shadows on model in edit view?

I am trying to follow a tutorial to make a spaceship, but my model has dark shadows on it that the tutorial I am following does not have. These shadows are annoyingly dark and mask the black vertices and edges that I'm trying to work with.   Is there a setting to turn this off?


Macbook Air hard drive - nearly full warning

I went to upload some photos and videos onto my macbook air and was told there was not enough free space, so removed some things onto an external hard drive and emptied my trash. I now have over 30 gb free but I still get the warning saying my hard drive is nearly full. How can I fix this?


I have a non-visual component which manages other visual controls.    I need to have a reference to the form that the component is operating on, but i don't know how to get it.  I am unsure of adding a constructor with the parent specified as control, as i want the component to work by just being dropped into the designer.  The other thought i had was to have a Property of parent as a control, with the default value as 'Me'  any suggestions would be great  Edit:  To clarify, this is a component, not a control, see here :


In the film Memento Leonard's main tattoo reads     JOHN G. RAPED AND MURDERED MY WIFE   That means it was the second attacker who raped his wife. If this was true the postmortem report would've shown that the DNA of the samples found on her body did not match with the first attacker. Even if she survived the attack forensic investigation when she was undergoing treatment would've revealed this.  This should have made the cops search for the second attacker. Why didn't this happen?  If we assume this second guy was smart enough to remove all evidences off Mrs. Leonard's body then how did Leonard know that his wife was raped? Because when Leonard wakes up in the middle of the night and shoots the first attacker he only sees a masked man strangling his wife.


Should I pay for importing my iPhone in the UK?

Until now when arriving from EU to the UK I was walking green corridors and life was good. Now gov.uk website says this ():  You can bring in other goods worth up to £390 (or up to £270 if you arrive by private plane or boat). If you go over your allowance you pay tax and duty on the total value of the goods, not just the value above the allowance. You may have to pay customs duty if you exceed your allowances. You may also have to pay import VAT.  Does that mean that now I should go in the red corridor and declare my iPhone 12 and my Apple Watch Series 6? And pay every time I move through the border? Or keep receipt?


In java if using call by reference i can make changes in value why can't i set it to null

class TestClass { public static void main(String... args) {     Bean b=new Bean();     b.setA(10);     b.setB(20);      changeValue(b);      System.out.println("A "+b.getA());     System.out.println("B "+b.getB());  }   static void changeValue(Bean b) {     b.setA(30);     b.setB(40);     b=null; }}   Hi all, I read few questions on stackoverflow about whether java is call by value or not and then I thought of giving it a try. If using reference i can make changes in the value ...why can't i set it to null? Thanks in advance.


How do I remove an incomplete or broken snap installation of nextcloud on a Raspberry Pi?

First the caveat: I understand that this question involves Mate and a Raspberry Pi so if you consider it outside the realm of this forum just ignore it.  But on the chance that it may be helpful or typical of something involving snaps or that platform, here goes.  I decided to try and install the nextcloud snap. It threw a ton of errors and seemed to freeze in the middle of the process (for over an hour). I killed it and just decided to try and remove it. The install looked like....      $ sudo snap install nextcloud 2016-06-24T08:48:29-04:00 ERROR cannot setup apparmor for snap "nextcloud": cannot load apparmor profile "snap.nextcloud.apache": cannot load apparmor profile: exit status 1 apparmor_parser output: Cache read/write disabled: interface file missing. (Kernel needs AppArmor 2.4 compatibility patch.) Warning: unable to find a suitable fs in /proc/mounts, is it mounted? Use --subdomainfs to override.  2016-06-24T08:53:29-04:00 ERROR cannot setup apparmor for snap "nextcloud": cannot load apparmor profile "snap.nextcloud.apache": cannot load apparmor profile: exit status 1 apparmor_parser output: Cache read/write disabled: interface file missing. (Kernel needs AppArmor 2.4 compatibility patch.) Warning: unable to find a suitable fs in /proc/mounts, is it mounted? Use --subdomainfs to override.  [|] Setup snap "nextcloud" security profiles   When I try snap remove nextcloud I get         error: cannot remove "nextcloud": snap "nextcloud" has changes in progress   What I would primarily like to do is properly remove the snap and recover the space from the partition it created. If partition is the correct term??      $ lsblk NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT loop0         7:0    0  46.6M  0 loop /snap/ubuntu-core/120 loop1         7:1    0 113.9M  0 loop /snap/nextcloud/12 mmcblk0     179:0    0  14.9G  0 disk ├─mmcblk0p1 179:1    0    64M  0 part /boot └─mmcblk0p2 179:2    0  14.8G  0 part /   I tried         snap abort nextcloud       and got         error: cannot find change with id "nextcloud"       I should also note that it doesn't show up as installed as I get only the following     $ snap list   Name         Version               Rev  Developer  Notes   ubuntu-core  16.04+20160531.12-01  120  canonical  -       Though it does show up in....         $ snap interfaces   :network             nextcloud   :network-bind        nextcloud   I tried  $ snap changes ID   Status  Spawn                 Ready  Summary 1    Doing   2016-06-24T12:39:20Z  -      Install "nextcloud" snap  $ sudo snap abort 1  $ snap changes ID   Status  Spawn                 Ready  Summary 1    Abort   2016-06-24T12:39:20Z  -      Install "nextcloud" snap   But the partition is still there.  ** Update, I ran the entire process again for debugging purposes and just let it sit after the "snap abort 1" command.  At some point something seems to have completed in the background because lsblk shows nothing and the snap interfaces query shows nothing.


Is it possible to automatically set numbers=none for single-line lstlisting environments?

I apologise if the answer to my question can be found in the listings documentation and I missed it.  Essentially I would like line numbers to be set only if the number of lines is greater than one.


I'm looking for good book recommendations for preparing for the International Physics Olympiad. As stated on the , the topics covered are about the same as those in the first year or two of a physics degree:        Mechanics: kinematics, dynamics, celestial mechanics, hydrodynamics   Electromagnetism: Maxwell's equations, circuits, matter in EM fields   Waves: damped/driven harmonic oscillators, waves, interference and diffraction, geometrical optics   Modern: special relativity, matter waves, particle and nuclear physics   Thermodynamics: laws of thermodynamics, heat engines, phase transitions      However, there's less of an emphasis on complicated calculations, and more of an emphasis on problem solving and insight. For example, multivariable calculus is almost never used; instead many questions can be elegantly solved by symmetry. I'm looking for textbooks or problem books to bring me to this level, starting from the level of high school physics.


Does the Banach-Tarski paradox contradict our understanding of nature?

Since the  makes a statement about domains defined in terms of real numbers, it would appear to invalidate statements about nature that we derived by applying real analysis. My reasoning is this:  If you can "duplicate" an abstract 3-dimensional ball defined, in the usual way, using the domain of real numbers, then clearly the domain of real numbers must be unsuited to describing physical objects (for instance The Earth), because duplicating them would double their mass (and thereby energy). But we use real numbers to reason about nature and derive new laws (or basic results) all the time in physics.  In the same way as we could integrate over the earth's volume to determine its mass from its density (for instance), we could apply the Banach-Tarski theorem to show that we could generate as many earths as we liked, right?  Does this mean that the mathematical foundation of physics is flawed? (I hope this question is not too provocative!)


When to use extend thread instead of implementing runnable

I have searched quite a bit on a reason to use extend thread instead of runnable and have found very little. Anyone have a good reason for someone who is just learning Java.


In a MCMC implementation of hierarchical models, with normal random effects and a Wishart prior for their covariance matrix, Gibbs sampling is typically used.  However, if we change the distribution of the random effects (e.g., to Student's-t or another one), the conjugacy is lost. In this case, what would be a suitable (i.e., easily tunable) proposal distribution for the covariance matrix of the random effects in a Metropolis-Hastings algorithm, and what should be the target acceptance rate, again 0.234?  Thanks in advance for any pointers.


I applied logistic regression to my data on SAS and here are the ROC curve and classification table.    I am comfortable with the figures in the classification table, but not exactly sure what the roc curve and the area under it show. Any explanation would be greatly appreciated.


hi, why the model looks weird. no double face or normal flip?  I include the blender file


How to punctuate a question within a thought

In a third-person narrative, I want to punctuate the following sentence:     Wasn't art supposed to impact the reader in an emotional way, she wondered.   How would that line be punctuated? I know I could use italics, but my question is, should it be,     Wasn't art supposed to impact its audience in an emotional way? she wondered.    or what? nothing seems entirely right to me. I know I could just change the whole thing—"She wondered whether or not art was ... yada yada ..."; but she is thinking this in response to someone and it's almost a rhetorical question, so I'd like it to remain the way I have it, but be punctuated properly—if that's possible. Grr.


What is the resolution rate that I can expect from Bind resolver (or alternative)?

I would like to create a DNS resolver using Bind9 so all my organization's DNS queries go to this resolver (DNS queries for external domains. The resolver should not be authoritative for the organization's domain). I will restrict the incoming requests from the outside. I tried to search for information about the the load that such resolver can handle:  What is the rate of DNS queries that Bind9 can serve? How many queries per second? Probably, it is also a function of the machine and the bandwidth (assumed to be high), so response that is a function of the machine settings is good as well. Are there any other better alternatives?  Thanks!


Story about a newly discovered planet that turns out to be a machine world with another world inside it

I read this story a long time ago, in the 1980s as a child.  It was science fiction from the 1970s or earlier, it had a 1960s "feel" to the writing.  A short paperback novel?  I don't remember a cover or any author's name.   Exploration ship from Earth finds a nearly idyllic world - lots of beaches and water, compatible plants, etc. When the exploration team lands, they unknowingly activate a sentient robot mind that is the real world.  There are underground caverns and robotic arms hiding among the bushes and trees of the world. The robot-world is camouflage for the robot mind running everything.  It is actually a "caretaker" type robot mind, protecting an even greater robot-mind or its creators below in deeper caverns, or a shellworld around another world. The robotic mind tries to understand the "robots" that came to its world, including taking one or two "explorers" that wander away from the main group, transporting them down to the caverns, "disassembling" them, then being unable to "reassemble" and "activate" them, so it puts the pieces and liquids into a large glass jar and leaves it on the surface for the other "explorers" to find (and possibly reactivate?  Obviously killing a human being and taking them apart will not let them be put back together again!). At some point the robotic mind is so afraid of being found out, it seriously considers awakening its secret, much bigger robot brain below in the lower caverns or inner world.  There is something that will go wrong if the inner world is ever awakened. The technology of the explorers is more 20th Century than 21st Century.  The robotic caretaker does not use "quantum" terminology, so it comes across as being somewhat barely 21st Century technology as well.   I do not know how the novel ended, with or without awakening the "inner" robot mind or people.  Any ideas on whose stand-alone novel this is?


Is there an English word meaning "the use of uncommon words"?

Is there an English word meaning "the use of uncommon words" or similar?


Is it possible to mount a VirtualBox drive image (.vdi) so the contents can be viewed in Nautilus etc.?  I have a windows 2000 .vdi which won't boot ("inaccessible boot device") after upgrading from VirtualBox 2.x to 3.1.6. I believe the IDE drive details have changed and that all I need to do is access the internal drive image and edit the Windows boot.ini to point to the new location.


Is saying "He was well thought of" ending a sentence with a preposition?

If not, is there any other way to say this? (I'm looking for synonyms, not rewordings such as "Others thought well of him.")


My laptop is Lenovo T400, and my OS is Ubuntu 10.10. I change the brightness of my screen by pressing the FN key and one of the two keys for increasing/decreasing brightness.  The brightness I feel comfortable is between two consecutive levels that are offered. So I wonder if it is possible to fine-tune the screen's brightness?


While I'm somewhat interested in job ads in SO, I can't remember seeing one that was related to my interests.  I'm aware that in my main interest topics Dart, Dart Angular,and Flutter there aren't many job offers yet, but almost all ads I get shown are about Java and React, topics I'm not involved in any way. There are also very popular areas like Angular (TS) where I'm very active (#1 top user) but not even here I get related ads.  Is there anything I can do do get more relevant ads or none at all if there are no relevant ads.  A way to dismiss ads I'm not interested in would be great. When I get the same ads I'm not the least bit interested in shown for weeks, the job ads become so useless distraction that the only useful thing to do is to block them.  I can't imagine this being the intention of the SO team.  I also updated my jobs profile a few times with no noticable effect.


Possible to add more than one object via Boolean modifiers?

The following script adds a boolean modifier to the active object. This works great for one cutting and one target object.  Imagine you have one cube and 4 spheres and you would like to end up with the cube having 4 boolean modifiers and each modifier uses one of the four spheres.  Would it be possible via python to collect / sort all the non-active objects and one by one add a modifier to the cube and then add a sphere?      target_obj = context.object     cutter_obj = bpy.data.objects['Sphere']      bool_mod = target_obj.modifiers.new('cutter', 'BOOLEAN')     bool_mod.operation = 'DIFFERENCE'      bool_mod.object = cutter_obj


Could I make money off of the negative oil price?

I saw the price of oil did something at about 1 PM Eastern time that is really bizarre: it went negative. This means that you get paid to take oil off the field. But, the oil price is negative now, and I think it could go lower. So, I would like to make money. Is there a way to flare oil offsite without safety risks? Could we drive nonstop on the highway just to burn gasoline in order to get paid at the gas station? Just curious on if it is feasible to make good money from this.


Why am I getting so many "yearling" badges today?

Here is a screenshot showing this:    Originally I thought it was due to the  today, but on most if not all of these sites, I had 200 rep or more both before and after the recalculation.  Is everybody getting this effect in their notifications?


Unable to install any app after updating ubuntu 14.04

I have ubuntu 14.04 in my laptop Dell inspiron 5558.It showed for updating and i clicked for update. During updating it showed some error. Now it is neither updating any more nor installing any apps. The error message on my laptop is:  error:BrokenCount>0   Please tell me what to do so that i can install any app like before.


How to get speckled shading in Photoshop?

I am trying to achieve, for lack of a better term, a speckled shading in Photoshop. I'm not getting the right effect using noise (even with a gaussian blur) or setting the layer to dissolve.   Here are a couple of good examples of what I'm referring to (they are not exactly the same, but they seem to employ a similar style):       (less so the top edge, more so everything else)  I'd appreciate any help (and, if I'm referring to this technique incorrectly, please let me know)!


my pc (dell inspiron 15) on which ubuntu is installed frequently freezes, here is the logs before the last freeze in attachments. I hope you will see what is the problem because I have no idea.


In Mail's conversation view, by default, quoted text is hidden and can be shown by clicking "See More from XXX" in the bottom of each message. After clicking that, how can quoted text be hidden again?


Interpreting of difference between R lm() with intercept and without it?

I have applied the lm() to a data set. The independent variables are categorical.  First, I use lm() with intercept and I got the next results:  > model <- lm(y ~ factor(x)) > summary(model)  Call: lm(formula = y ~ factor(x))  Residuals:     Min      1Q  Median      3Q     Max  -5.3085 -1.8132 -0.4136  1.4323 11.2480   Coefficients:               Estimate Std. Error t value Pr(>|t|)     (Intercept)     9.3085     0.4064  22.907   <2e-16 *** factor(x)0.75   0.1435     0.6896   0.208    0.836     factor(x)1.5    0.9062     0.6272   1.445    0.151     factor(x)3      0.9040     0.6989   1.293    0.198     --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1   Residual standard error: 2.786 on 126 degrees of freedom Multiple R-squared: 0.0238, Adjusted R-squared: 0.0005601  F-statistic: 1.024 on 3 and 126 DF,  p-value: 0.3844    In the second model I don't use intercept:  > model.1 <- lm(y ~ factor(x) - 1) > summary(model.1)  Call: lm(formula = y ~ factor(x) - 1)  Residuals:     Min      1Q  Median      3Q     Max  -5.3085 -1.8132 -0.4136  1.4323 11.2480   Coefficients:               Estimate Std. Error t value Pr(>|t|)     factor(x)0.25   9.3085     0.4064   22.91   <2e-16 *** factor(x)0.75   9.4520     0.5572   16.96   <2e-16 *** factor(x)1.5   10.2147     0.4778   21.38   <2e-16 *** factor(x)3     10.2125     0.5687   17.96   <2e-16 *** --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1   Residual standard error: 2.786 on 126 degrees of freedom Multiple R-squared: 0.9267, Adjusted R-squared: 0.9243  F-statistic:   398 on 4 and 126 DF,  p-value: < 2.2e-16    If I don't understand the difference between the R-squared value of them? Could I accept the second one as a fit model?  Would somebody help me to understand this problem?


I downloaded a Ubuntu16 ISO file directly from the Ubuntu site, but when I set the virtual disk to install, it just does not run, just open the virtual disk and shows the folders on the boot cd. What do I perform the installation?


Is irrational times rational always irrational?

Is an irrational number times a rational number always irrational?  If the rational number is zero, then the result will be rational. So can we conclude that in general, we can't decide, and it depends on the rational number?


Tiebreakers to decide league position in football (soccer)?

In the English Premier League, the league standing is decided using total points scored over the season, then goal difference, then goals scored - in that order.   What happens if two (or more) teams are tied in all three stats? Are teams then ranked on the results between them? What other methods exist to rank teams (other than the one I mentioned and points averages, like they use in Argentina)?


How is 'rm -rf /' able to delete all files in the system?

I can't get my head around rm -rf / : after the kernel and /bin is deleted, how does rm maintain a run time stack, and communicate with the file system & hardware till it completes deletion? Is rm statically linked with all needed binaries and load the whole file system directory tree into memory when the command initiates?


Something like:  0.1 0.23 0.999   How to pronounce them correctly in English?


What gear should I have to survive the Pumpkin moon (Terraria)

I have fought the pumpkin moon and died like 3 times and made it to wave 7 or 6 whenever the pumpking first appears. I have full turtle armor and my primary melee weapon is a demon sickle. I also have the possessed hatchet, magnet sphere, and sniper rifle. I also have other gear like the Uzi. What should I replace, what should I take out, and what should I add? Thanks!


How to delete selected text in nano editor?

How do I delete selected text in the nano editor?  I came across this issue while needing to delete the virtual host file and replace its content completely by other content. But the problem is that I can't select and delete the entire text at once. And if I delete it character by character, it won't be a computer thing.


Why was Boba Fett considered the greatest bounty-hunter in the galaxy?

In the Star Wars Holiday Special, Darth Vader says this to Boba Fett:     I see why they call you the best bounty hunter in the galaxy.   This seems to be the general attitude of most characters towards Fett. It's also common to hear fans describe him as the greatest bounty-hunter in the Star Wars galaxy.  However, in the actual films, he doesn't do all that much. He helps capture Luke and Han, which was impressive, but not really enough to justify being called the best bounty-hunter in the galaxy.  What exactly has he done in the expanded universes to deserve this title?  I'm not asking for arguments as to why he is or isn't deserving, what I want is a list of his greatest and most impressive canon bounty-hunting accomplishments.  I know he was a powerful fighter who did many impressive things. However, if it isn't bounty-hunting related, it doesn't answer the question.


Should users be allowed to remove the "Possible Duplicate" links on closed questions?

I've noticed the following happen a few times:   A user posts a question. The question is closed as a duplicate and the usual "Possible Duplicate" links are added at the top. The user promptly removes the duplicate links, even though the question is still closed as a duplicate. (excessive use of list items =P)   Now, I could understand this behavior if there was some dispute about whether or not the question was a duplicate, and the OP were to remove the links and post reasons why they disagree with the closing. However, I've noticed this happening without any attempt to defend the question (such as ).  In my opinion, no one should be allowed to remove the "Possible Duplicate" links as long as the question is still closed as a duplicate. The links should remain for the benefit of the community, so they can navigate to the duplicate questions and either post answers there or read them over and judge if the closing was actually fair. Once/if the question is reopened the links could be edited out if one so chooses.  I guess this is part discussion, part feature request:  Could the "Possible Duplicate" links remain un-editable for as long as the question is still closed?


Inverse of a particular matrix: $A = D + aJ$, all entries of $J$ are equal to $1$

Let $$A = D + aJ$$ where $D = \mbox{diag}(d_1,\ldots,d_{n})$ and $J$ is $n\times n$ matrix of all ones. Is it possible to find $A^{-1}$ analytically?


There are many places suggest not to mix British and American spelling in IELTS test, such as the articles on  and nativespeakeronline (No link here. I don't have enough reputation to post more than 2 links). When I search on forums, the most common idea is people in North America prefer -ize and people in other places prefer -ise. However, an article on  says:     the Oxford University Press insists that words such as computerize, capitalize, capsize, organize, organization, privatize, publicize, realize should take the -ize ending     And for some words in this list like "organization", people on forums say most British still prefer "organisation". In this case, if I stick to using British spelling on IELTS test, should I use -ise or -ize for the words in this list?


Tiling problem: 100 by 100 grid and 1 by 8 pieces

Why can't I tile a $100 \times 100$ table with $1$ by $8$ pieces?  If we look at the number of tiles, $100^2$ is divisible by $8$. So this does not contradict existence of such tiling.  The  of coloring the squares by black and white color does not help here either, since the $1\times8$ domino has the same number of white and black squares and so does the whole board.


I'm interested in livestreaming Brood War until I get StarCraft II. Kind of a kickoff event. It would be super helpful to get StarCraft into a window. I've tried a few things, but they all seem to not work, most likely because of how old BW is.  Suggestions?


Only seems to be for the "Top Users" page of a tag.  Confirmed for multiple sites and tags.


Find parameters $\alpha$ and $\beta$ of a beta distribution, if I have one quantile and the mean

Suppose I'm given the mean and one quantile (e.g. the 95% quantile) of a random variable $x$, and I want to find the parameters $\alpha$ and $\beta$ of a Beta distribution that has the same mean and quantile. Is there an efficient way to do it in R?


Why does every countable limit ordinal have cofinality $\omega$?

According to Wikipedia, if $\alpha$ is a countable limit ordinal, then $\mathrm{cf}(\alpha)=\omega$. It is intuitively clear to me that it should be so. Certainly the cofinality of such an ordinal must be $\geq\omega$. We can now look at what the ordinal ends with. If it has a single $\omega$ at the end, then that is a cofinal subset and we are done. It may, however, not end in $\omega$. It could, for example, end in $\omega$ $\omega$s or $\omega^2$. Then we can pick one element of each $\omega$ constituting the $\omega^2$, and the set of these elements is cofinal in $\alpha$, and its type is $\omega.$ If $\alpha$ ends in $\omega^3$, we can take one element of each $\omega^2$ constituting the $\omega^2$, and get a cofinal subset of type $\omega.$  It seems to me that this reasoning should work. It should probably be done inductively. How should I do it?


I've changed the meta description tag in many of my site pages. Should I select Fetch as Google->Fetch->Add to Index->URL and all linked pages in GWT?  Will Google recrawl the whole site faster than it'd normally?  This option can be used maximum of 10 times in a month. Can there be any side affects when doing this way in case only a few of site pages have changed?


I configured evince to be my default application to open pdf files (using Open with... and clicking on always opening pdf files with this application), but when I type gnome-open foo.pdf instead of evince, I have Nautilus that opens up in the correct folder highlighting the file of my choice.   This is especially disturbing since I am using the LaTeX plugin for gedit, and when I try and compile a tex file to pdf, instead of opening up a new window with my compiled pdf file, I just have nautilus pop-up. I know I can edit the scripts of my gedit LaTeX plugin to call on evince (or acroread) with the pdf I want opened, but this is a workaround and not the solution I am looking for.


I'm trying to install  and this is happening all the time:  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:  woeusb : Depends: libwxgtk3.0-0v5 (>= 3.0.4+dfsg) but it is not installable E: Unable to correct problems, you have held broken packages. dimitri@dimitri-OptiPlex-780:~$    I don't know what to do


How to open java .class files in VS Code or notepad?

I want to open a Java code in VS code. The .java file was Ok but I couldn't open the .class file and I saw some unreadable things in the file. I know the problem is about encoding. VS code can not encode the class file. Is there any solution for that?


I need neat templates for books which aren't about maths or any other science - just your everyday HarryPotter-ish book you read to get your mind off all the bad things happening during the day.  So it needs a decent simple front page (not really obligatory, those can be found everywhere), and neat interesting headings.


Where does the time you spend on Stack Overflow come from?  My number 1: My projects take a couple of minutes to compile and run, so that gives me the time to help people or find some answers (or to learn something by browsing interesting questions).  Some other answers I can imagine (which don't apply to me):   Getting paid by the hour and you just charge your client. Favorite spare time activity. Being a n00b to programming, you don't have a choice but to visit (Stack Overflow is the best).


Dual booting Windows 7 and Ubuntu 13.10. Windows 7 isn't showing up

I have Windows 7 loaded onto my computer. I have never used Ubuntu before and decided to do a dual boot. I installed it as a dual boot and I had the installer create the partition (I did not create it myself). When I booted it up, it shows Ubuntu 13.10 and Windows 7. I could access both, but Ubuntu's display was too big for my screen. I found a page that said to enter: 'sudo apt-get update' and 'sudo apt-get dist-upgrade.' I did both and restarted. I got the black screen whenever I loaded Ubuntu, but I could still access Windows 7. I then put the install disk back in and said to reinstall Ubuntu with all settings staying the same. Now when I boot I get to the menu, and all Ubuntu options are there, but Windows 7 is not. I looked on the hard drive and Windows 7 is still there. I need help keeping the Ubuntu settings as is, and brining Windows 7 back to the boot menu. Thank you!


How do you launch an exe from a specific directory in C#?

I'm trying to set my application to launch DF.exe. If I double click the exe (running it normally), it launches fine, however if I try to do so from the launcher I'm creating, it can't find the files necessary for it to run, leading me to believe that it's finding the exe and running it using the wrong directory. This is what my code looks like: string DFPath = "0.47.04\\DF.exe"; System.Diagnostics.Process.Start(@DFPath);


Why was hyperspace collision not weaponized before the events of The Last Jedi?

Considering the damage that the rebel Star Cruiser dealt to Snoke's ship when jumping to hyperspace, why is this seemingly the first and only time we've seen this? Why are there not say missiles with the means to jump to hyperspace?  I really hope there's a canonical answer for this, as it makes the movie feel like a fan film rather than actual canon.


Prove $3^{2n+1} + 2^{n+2}$ is divisible by $7$ for all $n\ge0$

Expanding the equation out gives  $(3^{2n}\times3)+(2^n\times2^2) \equiv 0\pmod{7}$   Is this correct? I'm a little hazy on my index laws.  Not sure if this is what I need to do? Am I on the right track?


Paired t-test for repeated measurements, but with 2 missing samples.

I am doing a gene expression analysis on blood samples collected from the same 8 goats. My sampling points are before LPS-treatment (0h), and 1h, 2h, 5h and 24h after treatment. I want to compare the mean expression of each post-treatment to the before-treatment values. Due to problems in RNA-extraction, one sample is missing at 1h and one sample is missing at 2h. Is it possible to do a paired t-test with unequal sample size? E.g n=8 at 0h and n=7 at 1h/2h?   I'm using log2 transformed data for the statistical analysis. (We are have decided not to correct for multiple comparisons, but we use a fold-change limit instead)


How can I run dotnet on ubuntu without using sudo?

I've been trying to update the permissions so that I can run a command (specificially dotnet restore). I'm not sure if this issue is specific to running dotnet, or if it is more generic.  I can run the command using sudo dotnet restore, however I want to be able to run this command without sudo.  This is because I want to execute these commands via a CI tool (Jenkins), and I don't want that tool to have access to root commands. . The Jenkins user is unable to run dotnet restore (because of the errors below) or sudo dotnet restore (because it doesn't have root access).  When I run without sudo, I have the following errors from dotnet restore:  /usr/share/dotnet/sdk/2.1.104/NuGet.targets(104,5): error : Access to the path '/{file_path_to_project.csproj}/obj' is denied.  [{file_path_to_project.csproj}] /usr/share/dotnet/sdk/2.1.104/NuGet.targets(104,5): error :   Permission denied [{file_path_to_project.csproj}]   I've been trying to update the read and write permissions for my user on the /usr/share/dotnet/sdk/2.1.104/NuGet.targets file, and the {file_path_to_project.csproj} directory, but so far I still get the same errors.  Does it have something to do with the /obj directory? – When I run ls the obj file is not shown.  How can I update the permissions so that I can access these files without running sudo?  I created a /etc/sudoers.d/dotnet file to see if it would enable dotnet to be run without needing to call sudo.  I added the following contents:  {myusername} {myhostname} = (root) NOPASSWD: /usr/bin/dotnet. However, this still required me to run sudo before dotnet restore to get the correct output.


Show that $\left(\frac{n^{\frac{3}{2}}}{2^n}\right)_{n\geq 0}$ is a null sequence. A null sequence is a sequence tending to $0$.   We need to find a $N\in \mathbb{N}$ for every $\varepsilon >0$, such that $n\geq N:|a_n-0|<\varepsilon$.  Usually, I first try to simplify the argument, but that does not work, since we have $n$ as the exponent and as a base. Secondly, I'll try to achieve an inequality like $n>...$. Tis sadly doesn't work out aswell. This expression is way to hard to simplify.  Is there another method, an easier way to solve this problem?


I rendered a file and it is saved under a tmp file, but I can not find it on my computer. Is there any way to change the file location or another way to find it?


Prove that the square of a prime of form $4k+1$ is the sum of two squares

Suppose that $p$ is a prime of the form $4k + 1$. I'm trying to prove that there exist nonzero integers $a$ and $b$ such that $p^2 = a^2 + b^2$. I begin by noting that $p$ itself can be written as the sum of two squares, since it does not have any prime factors of the form $4k+3$ (this is a theorem from my discrete math textbook: a positive integer $n$ can be represented as the sum of two squares if and only if every prime divisor of $n$ of the form $4k+3$ appears in the canonical representation of $n$ with an even exponent). We thus have $p=u^2+v^2$, and $p^2 = u^4+2u^2v^2+v^4$. I now need to prove that the right-hand side is the sum of two squares, but I'm lost. Obviously, it can be written as the sum of four squares, but that's not what I'm trying to show. Any hint or nudge in the right direction would be appreciated.


Screen annotation software to draw on any app in OSX

I want to draw on any app pdfs, videos, code. It would be helpful to aid in demonstration in a class setting for me. Do you know if any such app exists that does not require an external pen i.e. using mouse or trackpad to draw.


Can You Redeem a PSN Code for a Game You Already "Own" through PS Plus?

If you get a "freebie" game via Playstation Plus and later decide that you want to own the game independently of your subscription, can you enter a code for a game (say from Amazon) while your PS Plus subscription is still active? What if your subscription lapses, can you then buy/redeem a code for a game?


Suppose that $D$ is any number ring (i.e. $D=\mathbb Q(\alpha), \alpha \in \mathbb C$). Let $I$ be any ideal of $D$. Show that $N(I)=|D/I|$ belongs to $I$.  How to start? is there a specific fact will be helpful here


Randomness in pi and other irrational numbers

This is a post I read about pi while looking for stuff about tau -which is two times as much as pi.    This makes me wonder, why does only pi contain such randomness? Don't other non-repeating and non-terminating numbers (like $sqrt(2)$) also have the same quality? Is this just a silly post that is only being biased towards pi, or is this random behavior only inherent to pi?


Python's “//” operator wrongly treated as a comment (part 2)

SO's Google code prettify on python wrongly handles // (floor division) as a C-style comment, , even when the question is tagged .   Here is a more recent example from :  a[:len(a)//3*3]


Only when is the green light on vehicles may cross the train track.  Only when the green light is on vehicles may cross the train track.  which of these is grammatically correct to use, as I have learnt the word only at the beginning of the sentence followed by auxiliary verb(inversion), but it sounds a bit odd to me.


Is there any point in closing resources if the JVM is shutting down

Is there any point in closing resources such as sockets, files, and database connections if the JVM is going to shut down immediately afterwards? The OS isn't going to somehow keep sockets and database connections open, is it?  (I've written a simple TCP server-client application like the one in the , but because I'm targeting Java 6 I can't use try-with-resources like the tutorial does. Also, not all APIs implement AutoCloseable.)


I've been researching for a while now and I can't seem to find any way to make radio or transmission waves in blender.  I'm looking for an effect sort of like this, but coming from a point in the animation. I am using Cycles and I am trying to create an internet of things animation, but it is very hard to portray what is happening without waves.  I have already tried to use a particle system, but was unable to achieve this effect. Maybe something like  would work but I'm not sure how to do it without the plane still being there. I also don't have after effects so that isn't really an option for me.  Any help of ways to make waves or to portray them would be greatly appreciated! Thanks!


Desktop doesn't remember brightness settings after a reboot

Every time I reboot my machine the brightness goes back to 100% in Gnome. I wish it would keep the last setting. Is there anyway?


How to install everything on sources.list?

I made a really stupid autoremove mistake. I was uninstalling libssl1.0.0 and it somehow said that pretty much every package I had was now not needed. I didn't really read carefully and I uninstalled a LOT of packages. I saw things like wget and node being uninstalled.  My question is, how do you install everything from sources.list, and would it be plausible to install everything from sources.list to recover from this accident?


Can I travel to the US on a F1 visa to attend a funeral?

I have a valid F1 visa and I want to travel to the US for 2 weeks. My intent is not to study but to visit my best friend who recently lost her boyfriend and to attend his funeral. I read that it takes up to 72 hours to get the application for an ESTA accepted and I need to travel before the 72 hours. So my question is can I travel on the F1 visa that expires in a year (I graduated from the USA last summer) or do I need the ESTA? Do I apply for the ESTA even though it may not be approved in time? I am from the UK.


I am using Ubuntu 16.04lts, I am trying to get rid of a couple of folders.  I have tried what I thought to be the correct method, but they seem to fail.  $ ls -la total 32 drwxrwxr-x 6 rod rod 4096 Aug 20 21:24 . drwxrwxr-x 3 rod rod 4096 Aug 19 15:32 .. drwxrwxr-x 3 rod rod 4096 Aug 20 21:24 BurnWorld.Com -rw-rw-r-- 1 rod rod  423 Aug 20 18:48 ClickCharts Diagram Flowchart Software.desktop -rw-rw-r-- 1 rod rod  395 Aug 21 12:16 DreamPlan Home Design Software.desktop drwxrwxr-x 2 rod rod 4096 Aug 20 18:48 Graphics Related Programs drwxrwxr-x 2 rod rod 4096 Aug 20 18:48 NCH Software Suite drwxrwxr-x 2 rod rod 4096 Aug 19 15:32 Pretty Good Solitaire $ cd /Pretty Good Solitaire bash: cd: /Pretty: No such file or directory $ cd /Pretty_Good_Solitaire bash: cd: /Pretty_Good_Solitaire: No such file or directory $ cd Pretty_Good_Solitaire bash: cd: Pretty_Good_Solitaire: No such file or directory   I am trying to install wine for goodsol and everything fails so I thought I'd get rid of all traces of it, and also Wine which is needed to run it.  Then start afresh and try again.  As you see, it will not go away.


What happens when a foreclosed home sells for more than remaining debt

All questions I've read so far have focused on what happens when the home sells for less than the remaining debt. What happens if someone defaults on their mortgage while the home is worth more than the remaining debt ?  Also will the usual costs associated with selling a home have to be paid as well (like closing costs, realtors, title insurance, etc.) ?


I am first time use timeit function, I am trying to find the time of builtin function sum()  >>> s=[1,2,3] >>> t=timeit.Timer("sum(s)") >>> t.timeit(5)   But it gives error     File "", line 6, in inner      NameError: name 's' is not defined   But it works  >>> s [1, 2, 3] >>> sum(s) 6


Prove that the following ring is commutative

Let $(R, +, ·)$ be a ring and $x^2-x ∈ Z(R)$ for any $x ∈ R$. Prove that the ring is commutative. Here is my attempt: $x^2-x ∈ Z(R)$ then for any $y ∈ R$: $$(x^2-x)y=y(x^2-x)$$ $$x^2y-xy=yx^2-yx$$ $$x^2y-xy=x^2y-yx$$ (Pretty sure I can't change those elements like that, but I can't think of anything else) $$-xy=-yx$$ $$xy=yx$$ which means the ring is commutative. What is the correct way to solve this?


Whilst reading I came across the strange claim that multiplicative inverses exist for only prime values of $n$ in $Z_n$. I am a little puzzled as contrary to that, I know that additive inverses exist for all values of $n$. What would be an approachable proof of the above result?  Thanks in advance.


Manual "Possible duplicate of" comments are wrongly removed when question is closed

When closing a question as duplicate the "Possible duplicate of" comment is automagically added to the question. However when adding such a comment manually: "possible duplicate of random text" that comment is also removed. To me it doesn't make sense that questions which to not point to a SO / SE question or even comments without any links in it are also removed when the question is closed as a dupe. I just found this out by close voting a question as a dupe of another question, but I also added a manual comment which linked to a user profile (because it contains lots of relevant information for OP and possible future reasons): possible duplicate of this [user](http://stackoverflow.com/users/727208/teresko?tab=answers&sort=votes)'s list.  By the looks of it the script simply checks whether the comment starts with "possible duplicate of" and if it matches it will be removed. The  team also did a quick test with a very simple example which also got thrown away: possible duplicate of testing........  I understand that this issue is minor and there might as well be a technical reason for this (i.e. not having to keep track of automatic vs manual comments), but this behavior is kinda odd to me. I can think of two solutions for this:  keep track of manually vs automagically added dupe comments (again you SO people might have a good reason to not want this). Improve the "dupe comment matcher ™" to at least check whether the comment is in the correct format for "auto dupe comments ™" with a proper link to a question page.


Where can I link to an external tutorial?

I would like to help newbies on a Stack Exchange site, by posting a link to a tutorial.  Can I do such a thing, and if so where can I put the link? Can I start a discussion for this, or something similar?


Strugging to render my fire animation with Alpha/Transparency correctly

i've made a little fire animation using the particle system that i'm happy with, but i'm really struggling to output it correctly as a 4second .Mov with alpha/transparency enabled so i can import it into another NLE.  I'm making sure that i'm using a codec with RGBA enabled (I've tried them all now) in a Quicktime container.   Whatever I do, the fire looks fine...but the background stays black/non-transparent.  I then discovered the film/transparent checkbox in the render tab. This fixes the transparency, but now all the Orange colour/glow has gone from the fire, & i'm left with something that looks like grey smoke (see screen grab)  I'm new to Blender, but if someone could talk me through what I need to check/uncheck to make this render correctly, I'd very much appreciate it.  Thanks


How can I add/subtract/multiply/divide properties in the Game Engine?

I am creating a Random Math Engine using the BGE and I am wondering how I can do mathematical operations between two properties. Example: "Property 1 + Property 2" and then it would output the answer in text when you hit "A". But I don't know how to add/subtract/multiply/divide properties together.


I am new to C#. I am not a good programmer but I have worked on some projects which were in Delphi7. In Delphi there is one option; compile the class files to create .dcu. Those .dcu can be used without having the actual code with any other project in Delphi and after build .dcu files need not no given to end user.  Now my actual Question,  Is there any way where I can create some compiled file from my C# class and use that compiled unit with some other project in C# ?  I already tried to create dll and use. Nice Idea, but I don't want to give any other file than Configuration File and Executable file. Since, I created dll that needs to give with application.  I also tried to create a setup of application which build executable, configuration file and dll together. while executing, it extract itself in %temp% folder and executes from there only. So, In this case I am not able to set the configuration file's values.  Again the same question,  Is there any way where I can create some compiled file from my C# class and use that compiled unit with some other project in C# ?    Please suggest the solution  Thanks


Inside the core of a star thermonuclear fusion reaction fuses hydrogen atom into helium releasing massive heat/light and energy.When a black hole eats up enough stars and gases it devours itself by releasing leftover gases and radiation {nothing but energy} called Quasar.  In both the cases there's massive amount of energy involved.I keep hearing the word "Pure Energy" instead of just "Energy". What is pure energy? How is it different from just energy?


Let $X$ be an infinite cofinite space and let $A \subset X$ be infinite. Then $\overline A = X$  I am having a tough time in trying to understand this. Why is every infinite set in an infinite cofinite space dense ?


How to "stick" an object to another such that it follows during animation

I am trying to animate a swimming robot. It looks like this I can easily calculate the centers of the spheres during one swimming strokes and set the keyframes accordingly. Now, is there a way to "stick" the jacks to its two corresponding spheres such that it deforms during the animation? The idea is that the spheres always stay connected. In reality, the arms would elongate and retract. More precisely, the spheres move along the axis defined by the jack around some initial length, while the whole structure translates and rotates.


Right angle triangle with integral vertices

There is right angled triangle with known lengths for each side. Is there a known method to check if all the vertices will be integers if that triangle is placed anywhere on the plane? (or) what is the condition for that?


How to make a permanent alias in oh-my-zsh?

In my .zshrc I tried to make a few aliases .I looked into a lot of places, but I couldn't find out a way that worked. I used this code below:    # Set personal aliases, overriding those provided by oh-my-zsh libs,  # plugins, and themes. Aliases can be placed here, though oh-my-zsh  # users are encouraged to define aliases within the ZSH_CUSTOM folder.  # For a full list of active aliases, run alias. # # Example aliases alias zshconfig="mate ~/.zshrc" alias ohmyzsh="mate ~/.oh-my-zsh" alias n= "nano"   alias m= "mkdir" alias w= "cd ~/Documents/UoMWorkspace/Semester2"   alias j= "cd ~/Documents/UoMWorkspace/Semester2/COMP17412"   Then I wrote a command source ~/.zshrc. Still it didn't resolve the issue. I get error messages like zsh: command not found: j  Could anyone help me with any suggestions and let me know what am I doing wrong?


Where one can ask survey kind of questions about Stack Exchange/ Stack Overflow?

I have few questions regarding the behaviour of users on Stack Exchange which I want to know about from the users of Stack Exchange. Is there any proper platform to ask such questions where I can get sufficient response? Can meta sites serve this purpose?


I am trying to install httpie:  » sudo apt update Hit:1 http://archive.ubuntu.com/ubuntu bionic InRelease Hit:2 http://archive.ubuntu.com/ubuntu bionic-security InRelease Hit:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease Reading package lists... Done                      Building dependency tree        Reading state information... Done All packages are up to date.  » sudo apt install httpie Reading package lists... Done Building dependency tree        Reading state information... Done Package httpie is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'httpie' has no installation candidate   But the package is   This happens for other packages also:  E: Unable to locate package git-annex E: Package 'httpie' has no installation candidate E: Unable to locate package jshon E: Unable to locate package python-pip E: Unable to locate package tree   But they exist too:          What is going on?  This is my sources.list:  » cat /etc/apt/sources.list deb http://archive.ubuntu.com/ubuntu bionic main deb http://archive.ubuntu.com/ubuntu bionic-security main deb http://archive.ubuntu.com/ubuntu bionic-updates main   And this is my system:  » lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description:    Ubuntu 18.04.1 LTS Release:        18.04 Codename:       bionic   EDIT  This is an ubuntu server system, no gui.