Is there a way to derive the Gauss-Faraday Law in the Covariant formulation of classical electromagnetism from the Lagrangian density?

everywhere I look I can only find derivations of the Gauss–Ampère law $\partial_\alpha F^{\alpha\beta}=\mu_0 J^{\beta}$, and this follows quite simply from the variational method with the Lagrangian Density, but I cannot seem to find any way to derive the Gauss-Faraday law $\partial_\alpha\left(\frac{1}{2}\epsilon^{\alpha\beta\gamma\delta}F_{\gamma\delta}\right)=0$ (equivalently as $\partial_\gamma F_{\alpha\beta} + \partial_\alpha F_{\beta\gamma} + \partial_\beta F_{\gamma\alpha}=0$ "Bianchi identity") also from the Lagrangian Density and Euler-Lagrange Equations. As far as I know the Gauss–Ampère law represents only half of the Maxwell's equations, the other half being represented by the Gauss-Faraday law, does this mean that Faraday's law of induction and Gauss's law for magnetism are not equations of motion of the fields in question?


If $aRb \land bRc$ never occurs, is a relation considered transitive?

Studying relation properties. My definition of a transitive relation is as follows:     A relation is transitive if and only if $\forall a,b,c \in A [aRb \land bRc \implies aRc]$   My question is: if $aRb \land bRc$ never occurs in the first place, is the relation considered transitive?  I ask this because when I read $\forall a,b,c \in A [aRb \land bRc \implies aRc]$ I read it as follows: "when $a$ relates with $b$ and $b$ relates with $c$, $a$ relates to $c$". But since this "when" never happens, there is no condition to evaluate to decide if it is transitive or not.  The same issue occurs with antisymmetry, where $\forall a,b \in A[aRb \land bRa \implies a = b]$ - what if $aRb \land bRa$ never occurs in the first place?  EDIT  I just remembered that $F_0\implies whatever$ is always $V_0$.... I guess this answers my question... kinda.


Finding the limit of $\frac{1}{x}\left(\frac{1}{\arctan x}-\frac{1}{x}\right)$ when $x\to 0$

How to find $$\lim _{x\to 0} \frac{1}{x}\left(\frac{1}{\arctan x}-\frac{1}{x}\right)$$?  I tried doing it by L'Hospital, but I had to do it five times! Is there an easier way around this?


How to define natural numbers in terms of real numbers?

Some problems of theory of real numbers are about proving that some real numbers are irrational. But I find it a bit confusing to prove that some real number cannot be expressed (equal) to the quotient of two intgers, when you are working in the theory of real numbers where term "integer" is not defined. So I think we can easily define "integer" as "difference of two natural numbers", then how can we define naturals ? Will this definition be "strong" enough to prove that there is no natural number between two consecutive natural numbers ? Or maybe there is an easier way to define integers in terms of reals without defining naturals ?


A lot of my songs won't play on my iPhone anymore. They are still listed as being there, they just won't play and a red square and circle are placed by them. I've tried everything and nothing has made the problem go away.  How to make the song playable again?


How do I see if an image with 2px or more exist? Current code:  if( $("#imageID").length < 10) {     //Do something    }


Why it is not possible to measure the drift velocity for electron by timing their travel along a conductor? I know electron is very small and we cannot measure each electron time of collision but than how we measure drift velocity if we can't calculate time?


What is the overview of TSR's Basic editions of D&D?

There are a variety of editions of D&D published by TSR in parallel to AD&D that get collectively called “Basic D&D”, but the overall relationship of the editions to each other — and which are even separate editions — is not really obvious. It's especially not clear to the uninitiated.   What is the basic overview of these editions that would help someone trying to get a clear grip on these oft-overlooked games?


How can I do a Cache Refresh in Google Chrome?

I don't know what exactly it's called, by cache refresh I mean, refresh the page after clearing its cache. I don't want to clear the entire browser cache.  I can't seem to cache refresh my pages. In Firefox, I know it to be Shift+Refresh.  In Chrome, I've tried Ctrl+R, Ctrl+Refresh, Alt+Refresh, Shift+Refresh but none of them work.


How to change the order of windows in grub

GNU GRUB version 2.02 beta2-9ubuntu1.3 Ubuntu Advanced options for Ubuntu Memory test Memory test serial console 115200 Windows 8 (Loader)   Recently I decided to install Ubuntu and Windows 8.1 in different partitions. They both work. The problem is that I want that the windows run with no key before 5 seconds, or put it the first.


How do I change all files (different types including .sh, .py, and other executable files) in a known directory to permission 775 without listing all of the file names?  I mean "all" of them in that directory, no exception.  UPDATED: The command below actually solved the problem for me. Any explanations why "+" instead of a "\"?  find . -type f -name "*.*" -exec chmod 775 {} +


I installed Ubuntu on my Asus G750JS, but the WiFi in not working.  Some info :  $ sudo lshw -class network  *-network                         description: Network controller        product: BCM4352 802.11ac Wireless Network Adapter        vendor: Broadcom Inc. and subsidiaries        physical id: 0        bus info: pci@0000:03:00.0        version: 03        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress bus_master cap_list        configuration: driver=bcma-pci-bridge latency=0        resources: irq:18 memory:eda00000-eda07fff memory:ed800000-ed9fffff   *-network        description: Ethernet interface        product: QCA8171 Gigabit Ethernet        vendor: Qualcomm Atheros        physical id: 0        bus info: pci@0000:04:00.0        logical name: enp4s0        version: 10        serial: 40:16:7e:11:a1:4b        capacity: 1Gbit/s        width: 64 bits        clock: 33MHz        capabilities: pm pciexpress msi msix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation        configuration: autonegotiation=on broadcast=yes driver=alx latency=0 link=no multicast=yes port=twisted pair        resources: irq:19 memory:edb00000-edb3ffff ioport:d000(size=128)   *-network        description: Ethernet interface        physical id: 1        logical name: enp0s20u4        serial: 5e:7d:35:46:96:50        capabilities: ethernet physical        configuration: broadcast=yes driver=rndis_host driverversion=22-Aug-2005 firmware=RNDIS device ip=192.168.42.101 link=yes multicast=yes`   $ lspci -vnn | grep Network      03:00.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM4352 802.11ac Wireless Network Adapter [14e4:43b1] (rev 03)     Subsystem: AzureWave BCM4352 802.11ac Wireless Network Adapter [1a3b:2123]'   I tried:  $ sudo rfkill  ID TYPE      DEVICE      SOFT      HARD  0 bluetooth hci0   unblocked unblocked   This doesn't make any difference:  sudo rfkill unblock all   I also tried:  sudo apt-get purge bcmwl-kernel-source sudo apt update sudo update-pciids sudo apt install firmware-b43-installer sudo reboot sudo apt install bcmwl-kernel-source   This as well:  sudo apt-get install --reinstall git linux-headers-$(uname -r) build-essential dkms`   Nothings works. Does anyone ever had the same problem and found a solution? I spent hours on forums and tried different things, but nothing changes. The WiFi still doesn't work. I obviously tried the FN+F2 button combination.


Blender 2.8 viewport shading - random color: how to assign different color

When in the 3D viewport, you can set your mesh colors to "random". But can you change this randomly assigned color of one certain mesh to something different, in case you -like me - happen to have a much too similar color in another mesh, and unfortunately the two are overlapping?


I'd like to know how the following code is evaluated

int x=10;   int y=5;  printf("%d",(y,x));   So, here's this code. This code prints 10 when run. I'd like to know how it does so. Specifically, what the comma and parenthesis are doing in the printf statement.


why SO shows me posts to review if I am not allowed to review them?

I see    and then I click and see    what's the point of showing me how many articles are available to review if I can't review them? Wouldn't be better if it was shown only when some action could be performed?


Cannot connect Iphone 5 ios7 to ubuntu 12.04   Endless loop of 'Trust this computer' if I trust it. The device 'Samis' is locked. Enter the passcode on the device and click 'Try again'. Unable to mount device with message  DBus error org.freedesktop.DBus.Error.NoReply: Message did not receive a reply (timeout by message bus)    How can I connect my iphone with ubuntu?


How to validate phone number and assign country code to it?

I was just wondering how people are handling phone number validation. What im doing is; a user enters in mobile-phone(071412345) number and based on the first three digits assigns an international code(+4401412345) to it. But I had to declare a regex for each country, and how can i make this cleaner/better?  The suggested link is not really what im looking for


403 Forbidden on files with different names but identical content and permissions

I'm running CentOS 6.3 and Apache 2.2.15.  I'm using the defaults setup for apache.  The files I'm serving are in  /var/www/html   Here are two of them   [root@gisele html]# ls -l *-production-1.0.6.pdf  -r--r--r--. 1 root root 171769 Jan  1 21:12 copy-installation-production-1.0.6.pdf -r--r--r--. 1 root root 171769 Jan  1 20:59 installation-production-1.0.6.pdf   The copy file is a file created by doing   cp installation-production-1.0.6.pdf copy-installation-production-1.0.6.pdf   Through a virtual host mapping I'm accessing these documents.  copy-installation-production-1.0.6.pdf will serve. installation-production-1.0.6.pdf returns a 403 forbidden.  The only difference, is that the original file was copied onto the server from another machine.  Any idea why this original file will not serve but the copy will?


Make a slide background optional in Beamer

I've got a background in my custom template which I'd like to be able to switch off for certain slides.  Ideally I'd do this with an option to \begin{frame}.  My template is very loosely based on the approach in .  I've seen  and ; what I'm looking for is essentially the reverse of the latter, but cleanly (if I get this template right I won't be the only one using it so I wan't it to be robust).  This ends up being quite a lot of code just for an MWE.  The most relevant bit is probably first, in beaminnerthemecf.sty:  \mode<presentation>  \setbeamertemplate{background}{ \begin{tikzpicture}   \useasboundingbox[inner sep=0] (0,0) rectangle(\paperwidth,\paperheight);   \node[anchor=north,opacity=0.25] (bkg) at (current page.north) {\includegraphics[width=\paperwidth,height=\paperheight]{example-image-a}};   \fill[color=red,anchor=north west] (0,\the\paperheight) rectangle(\the\paperwidth,0.85\paperheight);   \node[anchor= south east, red,align=right] at (0.975\paperwidth,0.025\paperheight){\normalsize\insertauthor\\[0.2em]\normalsize\insertdate};     \ifnum\thepage>1\relax%     \ifx\insertframesubtitle\@empty%       {\node[anchor=north west, white,font=\Large] at (0.025\paperwidth,0.975\paperheight){\insertframetitle};}       \else{%         \node[anchor=north west, white,font=\Large] at (0.025\paperwidth,0.985\paperheight){\insertframetitle};%         \node[anchor=north west, white,font=\large] at (0.025\paperwidth,0.925\paperheight){\insertframesubtitle};%       }%      \fi    \fi   \end{tikzpicture} }  % Title page \defbeamertemplate*{title page}{cf}[1][]{%     \begin{tikzpicture}[overlay, remember picture, shift={(current page.south west)}]         \useasboundingbox (current page.south west) rectangle(\paperwidth,\paperheight);         \node[anchor=center, red,inner sep=0,align=center,text width=0.8\paperwidth] at (0.5\paperwidth,0.5\paperheight){\inserttitle};     \end{tikzpicture} } % Items \setbeamertemplate{items}[square] \setbeamertemplate{sections/subsections in toc}[square] \mode<all>   to test it we can compile dummy.tex:  \documentclass{beamer} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \title{\Large{\textbf{There Is No Largest Prime Number}}} \date[ISPN ’80]{27th International Symposium of Prime Numbers} \author[Euclid]{Euclid of Alexandria \texttt{euclid@alexandria.edu}} \usetheme{cf}  \begin{document}  \begin{frame} \titlepage \end{frame}  \begin{frame} % This is where I'd like to turn off the background image \frametitle{There Is No Largest Prime Number}  \framesubtitle{The proof uses \textit{reductio ad absurdum}.}  This is a test \begin{enumerate} \item Suppose $p$ were the largest prime number.  \item Let $q$ be the product of the first $p$ numbers.  \item Then $q+1$ is not divisible by any of them.  \item But $q + 1$ is greater than $1$, thus divisible by some prime number not in the first $p$ numbers. \end{enumerate} \end{frame}  \end{document}   Also needed are beamerouterthemecf.sty:  \mode<presentation> % Frame title \defbeamertemplate*{frametitle}{cf}[1][]{ } \mode<all>   and beamercolorthemecf.sty:  \mode<presentation> % Settings \setbeamercolor*{title page header}{fg=white} \setbeamercolor*{author}{fg=white} \setbeamercolor*{date}{fg=white} \setbeamercolor*{item}{fg=red} \setbeamercolor*{normal text}{fg=black} \mode<all>


Given $f(z)$ is an analytic complex function, show $f^*(z^*)$ is also analytic

This exercise is from Arfken mathematical methods for physicists): "The function $f(z)=u(x,y)+iv(x,y)$ is analytic. Show that $f^*(z^*)$ is also analytic."  There must be some simple proof (and not related to series), because there is little said about complex analysis in the book before this exercise (The only important thing said is Cauchy-Riemann conditions). Not sure, but I think if $f(z)=u(x,y)+iv(x,y)$ then $f^*(z^*)=u(x,-y)-iv(x,-y)=g(x,y)+ih(x,y)$. Now $g$ and $h$ must satisfy the Cauchy-Reimann conditions and their first partial derivatives with respect to $x$ and $y$ must be continuous. Yet I can't show any of them. Any suggestions for developing this idea?


What is the rule of thumb for mixing doughs?

Without delving too deeply into specialty doughs, but addressing more than just  and , what concerns can I evaluate when calculating the technique for approaching a dough?  For instance, some recipes say not to mix too much, others would imply that beating every bit of air out of the dough is the best thing for it. What I am looking for is a set of criteria, maybe a flowchart, that outlines how to deal with having a well-reasoned technique (as opposed to just following a recipe).  Crumble, cream, or melt the fat first? Paddle or hook? Beat, fold or whisk? Knead once and rest or knead three times and throw? I would assume that to some extent getting air in or out, activating and mixing ingredients, distributing fats more or less evenly, and so forth play a factor in any decision. However, I have no idea what those different things do, or the food science behind them. What general principles would help me understand what each factor does, so that I can have more confidence when staring down the ingredients, whether for some cookies or pizza crusts or muffins?


How to make LuaLaTeX multithreaded when `--shell-escape` is enabled?

I found this thread:    It works great. But when I change to LuaLaTeX there is still just 1 cpu active.  So is there a way to achive this with LuaLaTeX aswell?


Need to brush up on my late-undergrad and early-grad physics and was wondering if anyone can recommend books or lecture notes (hard copy, or on-line) that also have solutions.   Two that I have come across are:  Princeton Problems in Physics with Solutions - Nathan Newbury  University of Chicago Graduate Problems in Physics with Solutions - Jeremiah A. Cronin  Spacetime Physics - Taylor & Wheeler (favorite book on special relativity; has a lot of problems with solutions at the back; a lot of the problems really enforce the material and discuss paradoxes)  If possible, please also provide a reason why you like the books as opposed to just listing them.


How to apply border radius after drawing a rectangle?

Photoshop doesn't support to apply border radius after drawing of rectangle. I found  and tried myself but seems to be not working. Is there any step is missed or is there any other idea to apply border radius after drawing a rectangle?


rename files based on the directory name

for i in L*; do cd $i find . -type f -name 'botrytis_cinerea_T12345.*' -exec rename 's/botrytis_cinerea_T12345/"$i"/g' {} \; done   I get the error  find: missing argument to `-exec' rename: not enough arguments  Usage:  rename [options] expression replacement file...  Options:  -v, --verbose    explain what is being done  -s, --symlink   act on symlink target   -h, --help     display this help and exit  -V, --version  output version information and exit  For more details see rename(1).


How to sync iPhone 4S/iPod (iOS6.1.3) on 13.04

I'd like to sync my music and transfer it to my iPhone in Ubuntu 13.04. Trouble is I've tried using Banshee, Rhythmbox, GTKPod and nothing happens. Banshee goes through the process of viewing/adding tracks and it even "appears" to sync music, but when I check it on my iPhone, there is absolutely no music on the device. Over at the  website, it states  Latest Release: 1.0.7 Development/Unstable Release: 1.1.5 Tested with iPod Touch 1G/2G/3G/4G, iPhone 1G/2G/3G/3GS/4/4S/5, iPad 1/2/3rd Gen and Apple TV running up to firmware 6.1.3 on Linux, Mac OS X and Windows.  So I believe I should be able to sync my device. However Ubuntu's version of libimobiledevice is 1.1.4, so how can I update that package exactly? I don't really want to use an unstable package to get syncing to work, but I've found no other solutions. I have even tried installing iTunes with PlayonLinux and sadly, syncing is not supported with Wine at this time. Any suggestions? Any help would be much appreciated.


Telepathic twins communicate across the stars

The story starts with a space agency on earth looking for and testing twins. It seems that some are gifted in a way that allows them to communicate with each other even if they aren't speaking. The main character and his brother are such gifted twins and they are placed into a space program where one will stay on earth and the other will go into space.  As the story progresses, the brother who stays on earth ages faster then the one who went into space and creepily enough, when the space brother returns he ends up getting married to his great-great-great niece.


Get default colored plots with "no markers" command in pgfplots

I want to plot several curves with a \foreach command in pgfplots. I don't want any markers, and I can't find a way to get colored plots without markers in a \foreach loop. Using no markers gets rid of markers and colors.  \documentclass[12pt]{article} \usepackage{pgfplots} \usepackage{tikz}  \begin{document} \begin{tikzpicture} \begin{axis} \foreach \pas in {1,2,...,10}  { \addplot[mark=none] expression {\pas*\x}; } \end{axis}  \end{tikzpicture} \end{document}


Testing the sum of coefficients in regression analysis in R

Hi StackExchange community, I would like to ask how to perform a statistic test on the sum of coefficients in regression analysis in R, possibly using a Wald test. As per my data, I have the historical price of gold and a dummy variable that represents whether a certain date indicating economic uncertainty or not. The equation is shown below: Stock Return(t) = α + Gold Return(t) + (Gold Return(t) x Dummy(t)) + e or R(t) = α + β1Xi + β2XiXii + e I would like to see whether the sum of β1 + β2 is statistically significant, possibly using t-stat and Walt tests. Thank you very much for your consideration in advance.


"You are going to want to" vs "You will want to"

So I was going to say something the other day like   "After eating this, you are going to want to go there."  I wanted to express that after eating that, the person would end up with a wish about going to some place. It's taken out of context, it could be a restaurant or so here.    Is this a correct/good way of saying this? What gave me some doubts is that it was kind of a messy sentence to say. It has two "go" in it and everything. Is perhaps the formulation "After eating this, you will want to go to there" better? As I understood from the thread below though, "you will want to" is more intended for instructions. So how would this fit here?    Is this thing expressed differently in different regions?    The other day was one of the first day of my life that I spent in an English speaking country, so I realized that I've got to step up my game a few notches :)


I deleted ubuntu and now GRUB doesn't boot into windows anymore

I am aware that if you just delete ubuntu, your pc isn't going to work anymore. I followed this guide on how to repair the MBR but it won't work so now I'm doomed. it said to do:  -bootrec /fixmbr  -boorrec /fixboot  When I boot up I get the "Minimal Bash-Like line editing is supported, For the first word...."   I can't factory reset with a windows DVD because there's no recovery partition (apparently) .  I don't care if I lose any files at all, I just want my pc working again preferably with windows but ubuntu could work to.   Possible extra info: I was on Windows 8.1 and ubuntu 14.04 (I think, possibly 14.10) Grub version 2.02 beta2-9  Please help me, I know I messed up.


crontab -e. Added entries but no /etc/crontab

I did edit /etc/crontab using corntab -e. I have only one entry  After save contab is not created despite the message.  To be honest I have no idea what to do. I simply want to create a simple daily job. Second question. How can I change the editor for crontab -e?


Another example of a non-Hausdorff topological space in which all compact subsets are closed

One example of a non-Hausdorff topological space in which all compact subsets are closed is the co-countable topology on an uncountable set, as demonstrated .   It was claimed (as a now-deleted answer to the above question) that the compact complement topology on $\mathbb{R}$ was another example, but this was proven incorrect .   Can someone provide an additional example of a non-Hausdorff space in whihc all compact subsets are closed?


Every time I import a KML into QGIS the line lengths are wrong. A line that was 191 ft on Google Earth is now 260 feet in QGIS.   How can I solve this problem?


How to draw these (closed contours) diagrams using TikZ or PSTricks?

First, I must say I have no knowledge about PGF/TikZ nor PSTricks, but I would like to draw the following or similar closed contours using one of them or another adequate package. Where can I find the TikZ and the PSTricks manuals? I would appreciate if you could indicate the code to draw one of the diagrams.  ADDED: I've found  TikZ Manual for Version 2.10. It coincides with the package version installed on my computer, as I checked after the help of Benedikt Bauer's comments.  Diagram A     Diagram B


OK something weird happened to me I did the following equality comparison in Nodejs and surprisingly it replied with true.  (2 ** 64) - 1000 === (2 ** 64) // true   Why is that?  > for (let i = 0; i<=20; i++) ... console.log(i, (2 ** 64) - (2 ** i) === (2 ** 64)) 0 true 1 true 2 true 3 true 4 true 5 true 6 true 7 true 8 true 9 true 10 true 11 false 12 false 13 false 14 false 15 false 16 false 17 false 18 false 19 false 20 false


I need information about the following font. From a first look I thought it is commercial, is it? Also what are math fonts that can fit well with it?  I appreciate your suggestions.    EDIT:  I see the following in Document Properties:


Texlive 2013, where to place custom themes?

So I have installed TeXlive 2013 following the steps  I was previously using my custom theme called beamerthemeEinstein.sty that I placed at     /usr/share/texmf/tex/latex/beamer/base/themes/theme then I run     sudo texhash and it worked amazingly.  Now with TeXlive 2013 my custom theme is not recognized, I get  ! LaTeX Error: File `beamerthemeEinstein.sty' not found.    Where should I place   it now? Anyone knows where to place custom themes using the 2013 version? Many thanks!


How to set, permanently, my own directory instead of /home/bin in $PATH in ubuntu?

This might be a repeated question, but I couldn't relate to any previous answer. I basically want to run my shell-script from anywhere in ubuntu 16.04 (whether I'm inside the directory where the shell-script is placed or not).  I know the first method which is to place the shell-script inside the /home/user/bin directory (that is already set in the $PATH), change the shell-script permission mode and, finally, reset the bash by re-starting the terminal. This way everything worked fine.   But, since I want to learn how to set the environment myself, instead of using /home/user/bin I would like to use my own created directory.  So, I placed my shell-script inside a newly created /home/workspace/myproject/bin directory and, of course, I changed its mode. Then run the following command:  echo $PATH   Then, amended the $PATH variable as follow:  PATH="/echo/command/result:/home/workspace/myproject/bin"   Then, set the environment:  source /etc/environment && export PATH   But it doesn't work !  UPDATE   I know I could also do it through editing the ~/.profile file. But my aim is to do it directly from the terminal without having to open and edit a file. And you can see why, using only two commands in a row, immediately after finishing writing the shell-script, is much faster, right ?   To be clear: I want to know why resetting of the /etc/environment didn't work?


I wanted to upgrade from Ubuntu 16.04 to 17.04.  I created a bootable usb stick in Ubuntu 16.04 using Startup Disk Creator selecting the downloaded 17.04 iso.  I'm using a Kingston 8GB usb stick.  I can select the stick in the BIOS and boot menu, but the system keeps starting up as usual via the main start up disk. Ignoring the usb stick.  I'm reading similar posts about the matter, but I don't find a suitable answer.


How to get aleph and beth symbols in similar font?

If aleph, beth, gimel, and daleth are needed in their mathematical meanings (identifiers for cardinality), how can we get them in the same font or at least reasonably similar in style. The following simple approach makes aleph different from the rest in style:  \documentclass{article} \usepackage{amssymb} \begin{document} \[ \aleph \beth \gimel \daleth \] \end{document}   The aleph is smaller and has thinner strokes:    Apparently the reason is that amssymb does not have aleph. What might be the simplest fix?


How can I format a var_dump's output for use as a variable?

I have a function that spits out an array using print_r and would like to capture the information inside a variable to input it into a function for a specific use case. I've simplified the output to make it easier to understand.  [fruit] => 'banana' [color] => 'yellow' [sizes] => array('small', 'medium')   I would like it formatted as so:  $var = 'fruit' => 'banana', 'color' => 'yellow', 'sizes' => array('small', 'medium');   This way I can copy and paste the output of the first and assign it to a new default variable.


Using this regex /var userId = (\d+)/, I can find the id of the user. Except it returns "var userId = 117051" instead of just 117051. I looked around in regexr but I'm not very good with regex. Is there a way to only get the id?


Prove that there exists a unique linear map that extends the map from a basis

My professor has stated the following lemma:  Let $U$ and $V$ be two vector spaces and $B$ a basis for $U$. If $f:B\rightarrow V$ is a map, then there exists a unique linear map $A: U \rightarrow V$ such that $A(x)=f(x)\ \forall\ x\in B$  How can I prove this lemma? (This is not a homework problem.)


I recently changed to a newer phone and currently using my old android phone as a sort of "ipod". However, it always shows the message that there is no sim card. I know this is just an annoyance but is there anyway to disable it? I am rooted running a custom sense 4 rom on ICS. Is there anything I could flash to remove this message? Or disable the cellular radio completely?   Screenshot (click for larger variant)


Euler's equation for rigid body rotation applied to inertia frame, with body frame both rotated and translated with respect to the world frame

The Euler equation is usually expressed in a local body frame: $$ τ_b=I_b \dot{\vec \omega}_b + \vec \omega_b \times I_b \vec \omega_b  $$ Where the subscript $b$ indicates that the respective term is expressed in the body frame $b$. Assuming the body frame is both rotating and translating (over time) with respect to the inertia frame, how can we express the Euler equations in the inertial (fixed) frame? Related to the previous question, in such a case, how would the Inertia tensor expressed in the inertial frame ($I_I$) be related to the constant one expressed in the body frame ($I_b$)?  discusses a related question, however, it seems that the answer only treats the case where the body frame is rotating with respect to the inertial frame. If possible please include references to detailed discussions on the topic and how the result is derived.


Is there a null set that is not a Borel set?

In my module notes, if $A$ is a Borel and $m(A)=0$, then it is not necessarily true that any subset $B$ of $A$ (with $m(B=0)$) is Borel.  So I am wondering if there is a null set that is not a Borel set?


Is it proper to omit periods after honorifics (Mr, Mrs, Dr)?

I've been reading the Economist lately and they apparently don't punctuate honorifics like "Mr.", "Mrs.", e.g.     The popular rejection of Mr Mubarak offers the Middle East’s best chance for reform in decades.   I believe it's a British magazine, but is such a use proper or common in American English?


Java String Array, count number of spaces " "

I am requesting a string from the user. After the user enters their strings a prompt asks if they want to see strings with no, one or more spaces in their strings, then displays the strings. I am running into issues with counting the spaces in the string. The code provided only counts 1 if there is more than one space in the string. Whole code: import java.util.*; import java.util.Scanner;  public class CountSpacesInStrings {  public static void main(String[] args)  {          Scanner s = new Scanner(System.in);     String[] array = new String[20];     System.out.println("Please enter anything..., or type QUIT to quit.");          for (int i = 0; i < array.length; i++) {         array[i] = s.nextLine();         boolean result = Arrays.stream(array).anyMatch("QUIT"::equals);        if(result)         {            break;        }     }     String str = null;     int len = -1;               System.out.println("Would you like to display strings with No Spaces, One Space or More? Type No, One, More to see the results: ");     String answer = s.nextLine();     if(answer.equals("No")){                  for (int i = 0; i < array.length;i++) {             int count = 0;             if (array[i] != null) {                 if (array[i].charAt(i) != ' ') {                     count++;                     System.out.println(count);                 }             }         }                           }         else if(answer.equals("One"))         {             for (int i = 0; i < array.length;i++) {                 int count = 0;                 if (array[i] != null) {                     if (array[i].charAt(i) != ' ') {                         count++;                         System.out.println(count);                     }                                              //System.out.print(array[i] + " ");                    }              }         }         else             System.out.println("No values to show");      System.out.println(); }     } The section I'm looking at is:         if(answer.equals("No")){                  for (int i = 0; i < array.length;i++) {             int count = 0;             if (array[i] != null) {                 if (array[i].charAt(i) != ' ') {                     count++;                     System.out.println(count);                 }             }         }


How does one correctly punctuate a sentence that declares that one has a question?

Possible Duplicate:              My son, who is in fourth grade, wrote the following sentence in response to a story he'd read: "Another question I had was why were people swimming with dolphins." His teacher gave him no credit for this sentence.  She contended that the sentence must conclude with a question mark.  I believe that the sentence represents a declaration and not a question, and that the concluding period is appropriate and correct.  Would someone kindly help?


Physics history -- the Ultraviolet Catastrophe

I will ask my question in a way that's all handwaving and no math, and I will welcome handwaving answers. I'm interested in visualizing the concepts. We had an idea about the atom as a massive nucleus with positive charge, surrounded by lightweight negative charges. But we knew that opposite charges attract. So why didn't the electrons fall into the nucleus? We had a model for that. Masses attract, and the earth doesn't fall into the sun because it's in orbit. Maybe the electrons were in orbit around the nucleus. But accelerated charges always radiate. Accelerated electrons would radiate away their energy. They would fall into lower and lower orbits until they fell into the nucleus. So that model failed. At that point there were various alternatives available. We could figure that charges don't always attract, and look for a reason that the attraction didn't happen in this specific case. We could figure that accelerated charges don't always radiate, and look for a reason that these particular charges don't radiate. We could postulate a hidden repulsive force, a sixth force, that balances away the charge attraction in this particular case. Why not? We did that for the strong force and the weak force. Why not one more? Or we could use the following reasoning: Since accelerated electrons always radiate, electrons must be mostly stationary. They continually absorb random radiation from elsewhere and radiate it away again. So they jostle around, but they don't have any consistent velocity and they give as good as they get. They are mostly stuck in place near specific areas, and we can statistically estimate where those areas are. It takes a set quantum of energy to get from one of those areas to another (or the energy is lost as radiation to go the other direction.) Those are the only places electrons can be close to a nucleus, so they can't fall in. Free electrons don't have to emit quantized radiation. Electrons in a radio tower can emit any frequency the tower operator chooses. But electrons in an atom do. What is it about an atom that keeps the electrons from falling into the nucleus? Why are they stuck in quantized orbitals? Opposite charges attract, that's the biggest fundamental force, what is the opposing force that keeps it from happening this particular time?


A manifold $M$ is said to admit a field of tangent $k$-planes if its tangent bundle admits a subbundle of dimension $k$. How do I see that $\mathbb{RP}^4$ and $\mathbb{RP}^6$ do not admit fields of tangent $2$-planes?


Why does "echo a b c d e | echo" display no result?

I piped one echo command into the other   🌐 echo a b c d e f g h i | echo   🌐 echo $? 0   Contrary to my intuition, there was no output, however there was also no error returned. I expected, that echo a b c d | echo  is only an unnecessary redundant alternative to echo a b c d . But it is not the case, Why were the arguments lost on their way through the pipe?


Use case for extendable-output functions (XOF) such as SHAKE128/SHAKE256

defines 2 functions, SHAKE128 and SHAKE256, as extendable-output functions (XOFs) that can have variable output length. But in Appendix A.2 marks:     it is possible to use an XOF as a hash function by   selecting a fixed output length. However, XOFs have the potential for generating related   outputs—a property that designers of security applications/protocols/systems may not expect of   hash functions   Later it describes a theoretical use case (and explicitly discourage such uses):     For example, a naïve (and non-approved) way   for two parties to agree to derive a 112-bit Triple DES key from a message designated as keymaterial would be to compute SHAKE128(keymaterial, keylength), where keylength is 112.   However, if an attacker is able to induce one of the parties to use a different value for keylength, say 168 bits, but the same value for keymaterial   So what is the use case for these functions? Is there any reasonable use case where these functions should be used instead of standard (fixed-size output functions) SHA-3 functions?


Is Purity monotonically decreasing with increasing Von Neumann entropy?

I want to know whether Purity is monotonically decreasing for increasing Von Neumann entropy or not. In other words, I want to know whether the following proposition holds or not, \begin{align} S(\rho_1)<S(\rho_2)~~~~\Longleftrightarrow ~~~~ \text{Tr}\rho_1^2>\text{Tr}\rho_2^2, \end{align} where $S(\rho)=-\text{Tr}\rho\log \rho$ is the Von Neumann entropy.


I accidently typed the command sudo chmod -R 0444 /

I accidentally typed the command sudo chmod -R 0444 / now my system won't boot and when I click recovery mode, I get end kernal panic Attempted to kill init exit code=0x00000100.


I want to know about the relationship between focal length and aperture

I have Nikon D7000 and I know the basic relation of shutter speed, aperture, and iso.  All I want to know is focal length and aperture relation.  As I zoom in the camera the f/stop increases (e.g. it starts 3.5 and then to 5.6)  Some one told me that having large aperture gives more blurry background.  (ie: f3.5 will give me more blur than f5.6, if I am not wrong)  However, when I zoom my lens to 140mm minimum f value available becomes 5.6 and it gives me more blurry background than f3.5 at 18mm  Why is this?


Sectioning bibliography by type of referred item

My promoteur has a very unusual requirement: the bibliography needs to be sorted first by specific type of referred item, next by author and by year of publication.   I managed to get this custom sorting done by using makebst and manually editing the .bst, but now there is even greater problem for me: the bibliography itself must be sectioned, so it should look something like this:    Sources  Aahn, A. 2008, whatever dude  Aahn, A. 2009, whatever dude, really  Dictionaries  Encyclopeadia of everythinga, 1999  Wikipaedia, 2000-today  Articles  Aahn, B. and Boss, C., 1889 This issue is not to our concern, good man  Other Materia  Bactera, E.C., 1987, How we totally not-wiped the whole earth.    Can this be done automagically with bibtex? Or do I have to edit the generated file manually?


What is the default username and password for Ubuntu 12.04 via Startup Disk Creator?

I just installed ubuntu-12.04-desktop-i386.iso to my 1GB flash drive via Startup Disk Creator on Ubuntu 12.04. Then, I tried to boot it on my system.  The problem is that it was asking me for username and password.  I tried "ubuntu" with blank password but it didn't work.  The problem has never happened when I installed the same iso file via  on Windows.  Note: There's no option to make passwords in Startup Disk Creator.


How does Druid spell preparation & casting work?

I just want to make sure I have ALL of this correct.  Let's I'm a moon druid at level 3.     My druid has: 2 cantrips, 4 level 1 spell slots, and 2 level 2 spell slots.    Assuming a Wisdom of 16, I can prepare wisdom mod (+3) + level (3) per "instance" (before doing a long rest) which means that I can prepare 6 different spells.  I can choose any combination of 6 spells from the level 1 and 2 list since I only have level 1 and 2 spell slots.    I can cast the same spell as many times as I want (like I can cast goodberry (a lvl 1 spell) technically 6 times (4 level 1 spell slots, and 2 level 2 spell slots). The level 2 slots will increase the damage of course.   I could only cast spike growth (a level 2 spell) 2 times, because I cannot cast it as a level 1 spell.    I could do a long rest and re-prepare 6 more spells and my spell slots would all be refreshed.    Is this correct? Am missing something?


I see a weird language in Windows's Notepad when I open a image in with it

While just playing around with Windows’ features, I did the following:  Right clicked on an image. Clicked on "Open with…" Chose Notepad  And the following appeared:  I did this with many programs and documents, and for all of them, this weird language appeared. And in fact, for all programs and documents which are not Notepad docs, this language appears. What is this? Is it just random or there is something in it? Is there a name of this language and if it is a sort of programming language, can a human understand this? I am almost sure that this isn't coded by the Microsoft programmers.


How to keep footer at the bottom until content filled with body height?

I would like to keep the footer at the bottom of the browser, until the content filled up with body height. let it the content box empty.  what is the correct approach to do this?  here is my try:     SCSS:  .wrapper.container-fluid{     padding:0;     margin: 0;     border:2px dashed red;     display: flex;     flex-direction:column;     height: 100%;     max-height:inherit;      header{         border: 1px  solid blue;     }      div.content{         border:1px solid gray;         display: flex;         flex-direction:row;         height: 100%;          .leftnavi{             border:1px solid gray;             width: 20%;             background:lightgray;         }          .rightContent{             border: 1px solid red;             max-width: 100%;             width: 100%;             background:lightgreen;         }      }      footer{         border: 1px solid green;     } }   html:

Header title goes here

         Header navi goes here

             I am left navi

Lorem ipsum dolor sit amet, consectetur adipisicing elit. Voluptatem quod labore distinctio nulla delectus, recusandae officiis at. Earum accusamus ea, sed dignissimos. Voluptatem, exercitationem! Dignissimos porro labore vel velit beatae.

      Footer goes here


What is a distro-agnostic way determine the OS install date?

I am on a CrunchBang machine and trying to write a script that needs to have the OS install date as a reference.  I searched and found this command:  ls -lct /etc | tail -1 | awk '{print $6, $7, $8}'   It prints  Mar 31 21:24   I did not understand the tail -1 part, but was able figure out that $6 $7 $8 are the 6th 7th 8th occurrences of the last line that the command is referencing.  However, I realized that the year cannot be included as the year was not displayed in the ls -ltc command.  Some people suggested finding the date /etc was created and some checking the /var/log/syslog etc. I thought these might be a little specific to the distro.  What is your recommendation for a truly distro-agnostic way to find the OS install date?


How to fetch data from database as utf-8 CodeIgniter

What is this type of encode: Káº¿t ná»‘i nÃ´ng nghiá»‡p Viá»‡t  It should be "Kết nối nông nghiệp Việt" but the view can't render utf-8, i don't know why. Please take a look at the picture below.  Database config:     ORM::configure(array(     'connection_string' => 'mysql:host='.$db_hostname.';dbname='.$db_name.'',     'username' => ''.$db_username.'',     'password' => ''.$db_password.'' ));     //ORM::configure('driver_options', array(PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8')); #i tried uncomment this line but it's still not working     //ORM::configure('error_mode', PDO::ERRMODE_WARNING);     //ORM::configure('return_result_sets', true);     //ORM::configure('logging', true);


I've tried searching for people with similar questions, but haven't found anything.  I have two dates in JavaScript, both set to the same value... Equality Testing fails on ==, but >= and <= evaluate true.  Below is the code I have in play:  var startDate = new Date( 2011, 7, 30, 0, 0, 0, 0 );  var dt = new Date( 2011, 7, 30, 0, 0, 0, 0 );  if( startDate == dt )     document.write('They Equal
');  if( startDate > dt )     document.write('Start Date is > dt
');  if( startDate >= dt )     document.write('Start Date is >= dt
');  if( startDate < dt )     document.write('Start Date is < dt
');  if( startDate <= dt )     document.write('Start Date is <= dt
');  if( dt == startDate )     document.write('They Equal
');  if( dt > startDate )     document.write('dt > startDate
');  if( dt >= startDate )     document.write('dt >= Start Date
');  if( dt < startDate )     document.write('dt < Start Date
');  if( dt <= startDate )     document.write('dt <= Start Date
');    document.write( dt ); document.write( '
'); document.write( startDate );   Has anyone encountered anything like this, or am I doing something fundamentally wrong?  I tested this is Internet Explorer (9), Firefox 5+, and Chrome.  Update:  So two people posted great answers to my problem, and I thank both of you: xdazz and DaveRandom. I had read an earlier post on stackoverflow.com on a similar question and a guy said that date objects could be compared like any others, and any other example I found always did a < or > type of compare, never a full equality so I wasn't able to make the connection as to why I was doing it wrong.  Thanks to you two, and the others that posted similar answers.


What's more than a girlfriend but less than a wife?

Let's say I am in a committed relationship with a woman, but we are not married; talking about her as "my girlfriend" seems a bit silly, as it conveys the idea of something juvenile, and 1) our relationship is serious and stable and 2) while she's not old, she is definitely not a "girl" anymore.  However, we are not married, thus "my wife" would be an exaggeration; "my woman" could do, but I don't really like it, as it seems to imply an idea of possession rather than companionship. There also are "companion" and "partner", but they don't necessarily mean a romantic relationship. And, of course, "lover" seems more appropriate for a sex affair than a stable relation.  What is the right word to use here?  Also, the inverse variant (being in a committed relationship with a man who is not your husband, and calling him your "boyfriend" doesn't seem right).


How would I go a about making volume light beams?  I have have tried  various tutorials, but they must be for a older version. as applying them does seemingly nothing.  A link to a functioning tutorial would be greatly appreciated as well.  I don't have a picture or .blend to show, as my problem with atmospheric lighting does not pertain to any specific scene.


Hard Disk makes "Click, click, click ..." noise on system start. Won't boot

Computer was humming away happily.  It had downloaded a kernel update eariler in the week and been asking for a reboot since.  This morning I relented.  When the computer powered back up it made a loud repeated clicking noise which I tracked down to my hard drive by opening the cover.  Since then I can't boot the computer - it keeps failing out to netboot (which goes nowhere).  Based on a quick google I think the disk is history.  Does anyone know of a way to recover the disk?  I realise I'm probably SOL but it's worth asking.   Edit  Thanks for the answers.  All very interesting and informative.  Nothing on the drive is worth the cost of a professional recovery service and my backups cover the important bits anyway.  I was just hopeful that I might be able to avoid the nuissance of a rebuild on a new disk.


Cannot create a new file in the file manager on 17.10

I have a problem since the update of Ubuntu 17.10  I cannot create a new file from the GUI. I have to create the files from the console.      Any idea?


Re-number a list when a new entry is inserted

I have a text file of numbered entries:  1. foo 2. bar 100% 3. kittens 4. eat cake 5. unicorns 6. rainbows   and so on up to some large number. Then after an empty line, a new block starts from 1.  I insert a new entry, replacing, say, 4. and I need to renumber all the subsequent entries in the block:  1. foo 2. bar 100% 3. kittens 4. sunshine < 5. eat cake 6. unicorns 7. rainbows


Find the determinant of $A + I$, where $A$ is a real matrix such that $AA^{\top}=I$ and $\det A<0$.

Given a real valued matrix $A$ that satisfies $AA^{\top} = I$ and $\det(A)<0$, calculate $\det(A + I)$.  My start : Since $A$ satisfies  $AA^{\top} = I$, $A$ is a unitary matrix. The determinant of a unitary matrix with real entries is either $+1$ or $-1$. Since we know that $\det(A)<0$, it follows that $\det(A)=-1$.


I'm a little bit confused about the nature of symmetrical reference frames and how they relate to time dilation. To clarify my question, I've written a scenario.  Bob stands on a platform as a train moving at some high velocity goes by. He observes that while his own watch measures 10 seconds elapsed, the train's clock measures 15 seconds elapsed. The train stops, its clock 5 seconds ahead of Bob's.  However, since from the train's point of view, Bob was moving at the same velocity, the passengers measure his watch to have measured 15 seconds while their clock measures 10. When the train stops, Bob's watch is ahead of the train's clock by 5 seconds.  How are these reconciled?


I would like to wrap "2cf24dba5fb0a30e26e83b2ac59e29e1b161e5c1fa7425e73043362938b9824" into the frame of lstlisting.  \documentclass[conference]{IEEEtran}  \usepackage{xcolor} \usepackage{amsmath} \usepackage{lmodern} \usepackage{cite} \usepackage{amsmath,amssymb,amsfonts} \usepackage{algorithmic} \usepackage{graphicx} \usepackage{textcomp} \usepackage{listings} \lstset{    basicstyle=\footnotesize,           breakatwhitespace=false,            breaklines=true,                    captionpos=b,                       frame=single,   extendedchars=true,                language=Python,                    numbers=left,       numberstyle=\tiny,                  numbersep=5pt,                     showspaces=false,                   showstringspaces=false,             showtabs=false,                     stepnumber=1,                      tabsize=2,                          title=\lstname,                      belowskip=-1em,   aboveskip=1em,   belowcaptionskip=0em,   columns=fullflexible,   linewidth=8.7cm,   postbreak=\raisebox{0ex}[0ex][0ex]{\ensuremath{\color{black}\hookrightarrow\space}},   literate={,}{,}1   } \def\BibTeX{{\rm B\kern-.05em{\sc i\kern-.025em b}\kern-.08em     T\kern-.1667em\lower.7ex\hbox{E}\kern-.125emX}}  \begin{document} \begin{lstlisting} block = {     'previous_hash': "2cf24dba5fb0a30e26e83b2ac59e29e1b161e5c1fa7425e73043362938b9824" } \end{lstlisting} \end{document}


How To Get Notified When Hard Drives Fail In Dell PowerEdge Servers

I have a Dell PowerEdge R415 and R515 and wondering how I can be alerted remotely when a hard drive fails in either server? Both are running RAID, so I need to be notified, so I can swap out the drive. Both servers only have the basic Baseboard Management Controller. Is this possible with a third party tool/software?


I am trying to print a progress bar in shell as follows  #!/bin/bash  sleep $1 & PID=$! printf "[" counter=1 while kill -0 $PID 2> /dev/null; do      percent_done=$(echo "${counter}*100/${1}" | bc -l )     printf  "▓%.0f" $percent_done     sleep 1     counter=$counter+1 done     printf "] done!"   and i call it as  myScript.sh 10  so the script will invoke a sleep of 1 sec for 10 seconds. On each iteration of the loop, i want to print   ▓<the percentage of the loop completed>  for instance i expect  ▓10▓20▓30▓40▓50▓60 and so on. but i get  ▓10▓11▓12▓13▓14▓15 instead  what am i doing wrong? am i not updating the counter properly? also, if i do   percent_done=$(echo "${counter}/${1}" | bc -l )  then i get  ▓0.1000000000000▓1.100000000000000000▓2.10000000000000000000▓3.10000000000000000000▓ and so on.   Since I dont want the long floating point value, i added the *100 in the expression.  What am i doing wrong?


Re-entering Israel as a tourist after student visa expires?

My husband and I are British nationals living in Israel with student and spouse visas. Our visas expire on 3rd December 2014, and we have been unable to get an appointment to renew them before January 2015.  We want to go home for Christmas to UK  and return to Israel in January, at which time our resident visas will have expired.  Are we likely to be able to re-enter Israel on the normal 90 day tourist visa exemption, and then renew our other visas or is that going to cause problems with us coming back into Israel?


How to hide Content Editor WebPart which has InfoPath form link in it based on condition

I am using SharePoint 2010 and my scenario is I have created an InfoPath form and form link is being set up in Content Editor WebPart to directly open to submit a form for the first time. Everything working fine, now I am in need to hide the link once a form is submitted on the page.   Can any one suggest me how to approach on this or if anyone has snippets that would resolve my problem.  Thanks in advance.


How to read high voltages on microcontroller?

I want to read high voltages, like ~50V, using a microcontroller. I plan to put this as an input into the microcontroller's A/D line. But of course, you shouldn't have voltage that high on the input of a microcontroller or it'll fry.   How might I read high voltages? The main thing is that I need to step down the voltage before reading it. What do I need to consider when stepping down this voltage?  Thanks in advance!  Edit: I noticed in the PIC18 datasheet that it says "The maximum recommended impedance for analog sources is 2.5 kOhms." How does this affect how I step down the voltage, be it with resistive dividers, etc.?


Paralleling power supplies for higher current

I am looking at using two Cincon ( and ) power supplies in parallel to achieve a higher current output. Is this possible? If so, can I just hook them up in parallel, or is there some specific way of doing this to prevent one from "fighting" the other?  Both power supplies are rated for 24V with 1% ripple and noise, +/- 1% voltage accuracy, +/- .5% line regulation, and +/- 1% load regulation.  Ideally, this would be possible since they would both be the same voltage. But, due to tolerances in manufacturing, there is no guarantee that they would be identical voltage outputs.  I wasn't sure if I should also hook up a capacitor in parallel with them to help stabilize the output voltage.


I am on SharePoint 2013 and do not have access to Designer, as a preface.  I am trying to create a list view that filters items by whether or not they were added in the last hour.  I had done this earlier, only with items that were added in the current week, by creating two columns, 'Week Start' and 'Week End', and filtering by Created falling between those two.  Simple enough.  However, filtering list views does not allow for complex functions, nor does the [Today] function recognize time, causing an issue.  Is there any workaround for this?  Thanks.


Why should I regularly run 'apt-get update' and similar commands?

I am completely new to Ubuntu. A friend recommended me to frequently run the following commands:  sudo apt-get upgrade sudo apt-get update sudo apt-get autoremove sudo apt-get autoclean   He said that this will somehow keep my system clean and updated. I do not know what exactly these commands do. Is it really useful to run them regularly?


How to prevent Windows 10 from restarting the computer after installing updates

This questions has been answered previously, e.g. , but all the answers I've seen require using a dropdown in Settings> Update & Security> Advanced Options.  On my version of Windows 10 Pro, there is no such dropdown:    How can I prevent automatic restarts?


Why is finding the roots of a polynomial equation so important? What is to gain?

I have just started a pre calculus class, and our first lessons have been reviews on polynomial equation, quadratics and finding roots or solutions to equations. The topic is fairly simple but I just have to know why is it so important to find an X value of a function that results in it y value to become zero? Why do mathematicians go to such great lengths like creating a quadratic formula? There must be some reason and my lessons have failed to tell why.


Images in user profile fills width in the iOS app

Images in posts and user profile seem to fill screen's width when displaying in the iOS app:           (The gray highlight is not part of the image, this screenshot was taken by click and holding on the image)   This is what it looks like on the web:        This snowflake, , displays weirdly in the iOS app as seen above.


Identification of physical network interface in linux

I'm new to linux and I have server with four network cards. I have to identify which physical network interface is assigned to the names eth0, eth1, eth2 and eth3. I have to disconnect cable from eth2 and do not know which network card it is.  Thanks


Im struggling with how to do things.  My goal is that when in on my jumphost type ssh router1, then it will ssh to the router, and at the same time run an expect script to fill in my password from a password file (which ofcource is readonly to me) preferably it should send it encrypter so that it cant be picked up by anyone.  I have managet to get an expect script to work, but i dont want to have a gazillion expect scripts in my folder (for the amount of routers we have).  Im thinking it could be done using alias commands? I already have alias commands setup so that if i type router1 it will automatically ssh to that particular router.  (i got a message that this was a duplicate, but i have been unsucessfull in finding the duplicate question, so I am gonna try to explain further: Lets say that we, in my company have 100 routers. for now i have made alias'es so when i type router1 in my prompt, it will do ssh router1. I want to try to extend that functionality and shave off a few precious ms of time, by filling in the password automatically.  So in other words im looking for a way to combine alias with an expect script (and possibly a bash script if needed) and i am shockingly bad at any scripting  Hope someone can help :)


Normalizing the final weights vector in the upper bound on the Perceptron's convergence

The convergence of the "simple"  says that:  $$k\leqslant \left ( \frac{R\left \| \bar{\theta} \right \|}{\gamma } \right )^{2}$$  where $k$ is the number of iterations (in which the weights are updated), $R$ is the maximum distance of a sample from the origin, $\bar{\theta}$ is the final weights vector, and  $\gamma$ is the smallest distance from $\bar{\theta}$ to a sample (= the margin of hyperplane).  Many books implicitly say that  $\left \| \bar{\theta} \right \|$ is equal to 1. But why do they normalize it ?


"Slow" scrolling on image causes image to open

When you hold your finger down on a post in the iOS mobile app, then move your finger, the page scrolls, no matter how long it is until you start moving your finger - this is fine.  When viewing posts with images in, you can tap on the image to open it up full screen for zooming etc - still fine.  When you hold your finger down on an image and begin moving it fairly soon, the page scrolls - also still fine.  When you hold your finger down on an image, but pause because you were just finishing reading a sentence, then begin scrolling, the image gets the "active" overlay and when you finish scrolling and release your finger, it opens up full screen - rather annoying and breaks the flow of reading the post.  I think the act of beginning the scroll action should cancel the "I want to open this image for full viewing" action.  iOS App, Version 1.4.0  Update: I just realised that links exhibit the expected behaviour too - holding down then pulling a link to scroll won't navigate to the link upon releasing your finger - it is just the images.    As mentioned in the comments, using the website in Safari on iOS displays the expected behaviour - holding your finger on an image makes it gain the "active" overlay, but as soon as you start scrolling it loses that overlay, and doesn't open when you release your finger.


Is there a way to prevent those pesky .DS_Store files from being ever created?

Is there a way (eg. a binary hack into Finder) to stop it from creating .DS-Stores on LOCAL Volumes?   I am using Leopard, therefore these don't work:    (requires Lion)  (requires Snow Leopard)   Also,  slows down my computer.


Converting point sets to polygon boundaries?

I'm trying to convert sets of points to their respective polygon boundaries.  I think this is something like a Voronoi diagram or Convex Hull, but not quite.  I'm sure there's a technical term for it, but I'm a beginner to GIS.  It's probably best illustrated with the following image:    So, given 4 sets of points (each set in its own colour), what are the four polygons surrounding each respective set of points such that the spacing between polygons maximizes the margins and all the polygons meet together?  Here's a simplified example with 3 points:   A,43.656943,-79.393928,blue B,43.66663,-79.402682,green C,43.656447,-79.408004,green   You'll have to view the following graphic for it to make sense:   Essentially, each point has a colour and you expand a buffer of a certain distance out from it to start.  The hard part is when there's a collision with other points (their boundaries) and where to compute that boundary. The result is a set of polygons (one for each colour/set).


settings_fields() doesn't work for other roles except admin

In my custom plugin, I want other user roles can also save the plugin settings. And I use settings_fields('custom_options') function to save settings.  When I am logged in as an editor or any other role, on clicking the button I am redirected to the while screen page with a message Sorry, you are not allowed to manage these options.  Please, can anyone help me with this?  Thanks in advance!


'this' argument to member function has type 'const', but my function is not actually 'const'

I have a C++ std::map that I'm using to store information about connected components. Here's the segment of code from my BaseStation class, it's very basic  //Constructor BaseStation(string name, int x, int y){     id = name;     xpos = x;     ypos = y; }  //Accessors string getName(){     return id; }   In my main code, I have a map declared as   map<BaseStation, vector<string> > connection_map;  The connection_map is updated in a while loop as follows, and then for my own debugging purposes I want to dump the contents of the map. I append a BaseStation object to the map (as the key) and as the value we have the list of links to the BaseStation object:  connection_map[BaseStation(station_name, x, y)] = list_of_links;  list_of_links.clear();  for(auto ptr = connection_map.begin(); ptr != connection_map.end(); ++ptr){     cout << ptr->first.getName() << " has the following list: ";     vector<string> list = ptr->second;     for(int i = 0; i < list.size(); i++){         cout << list[i] << " ";     }     cout << endl; }   This is the error I get in my main when I try to compile my code via clang++:  server.cpp:66:11: error: 'this' argument to member function 'getName' has type   'const BaseStation', but function is not marked const             cout << ptr->first.getName() << " has the following list: ";   and in VSCode, the tooltip highlight at the cout (cout << ptr->first.getName()) is the following:  the object has type qualifiers that are not compatible with the member  function "BaseStation::getName" -- object type is: const BaseStation   I don't understand what's going on, as the getName() function is most definitely not constant, and nowhere do I declare my BaseStation object as const either. If someone could help me out that would be great. Thanks!


"Your vote has been recorded and it affects this post’s ranking " - Stack Overflow's new message about downvoting a question

Thanks for your vote! Your vote has been recorded and it affects this post’s ranking. Since this post’s score is below -1, your vote will not be displayed.   Please consider adding a comment if you think this post can be improved.     when I am trying to put a downvote on a Question Stack Overflow. can some one please explain this new rules? I have seen this message from last two days.


Cartesian product matrix of a set of linear integer arrays in python

I have a set of linear arrays:  [0, 2, 4] [3, 7, 13, 16, 18] [1, 11, 12, 17] [5, 6, 14, 15]   I want to do the equivalent of a SQL cross join of all of these sets onto each other, so that I can create a matrix whose rows would be something like:  [0, 3, 1, 5] (0th entry in each array) [0, 3, 1, 6] (0th 0th 0th 1st) [0, 3, 1, 14] (0th 0th 0th 2nd) [0, 3, 1, 15] (0th 0th 0th 3rd) [0, 3, 2, 5] (0th 0th 1st 0th) ... [4 18 17 15] (last entry in each array)   The brute force way I can think of is nested for-loops which seems hugely inefficient.  Is there a simple way to do this in python? I'm still learning zip and map and list comprehension and thought maybe there's some way using those, but I've been staring at this for a while and could use a nudge.  Thanks for any help!


Is the Canon Rebel T3/ EOS 1100D compatible with Nikon Lenses?

Is the Canon T3 compatible with the Sigma 18-200mm F3.5-6.3 DC OS for Nikon? I'm looking around craigslist looking for a compatible lens.


How do we refer to a question and all of its answers and comments collectively?  What is the normal word to use for this? I associate thread more with forums, not with SE. But is it used? What's the normally understood term on SE?  I also asked a  asking about Q&A sites in general (not just SE convention), and going deeper into language aspects.  Here, I'm asking: What's the common way to say it on SE?


How to shrink a whole chapter to not leave orphans?

A chapter has a full-page image at the end, and its last paragraph overflows two lines to a new page. How to make the last line stays in the bottom of a page so that there's no almost blank page before the image? Shrinking just a page is fine, but I think shrinking the whole chapter will leave no trace.  Let's say the two orphan lines are in page 2, and the image is in page 3, and I want the orphan lines is in page 1, and only the image is in page 2. Putting \pagebreak or \clubpenalty=10000 on the last line doesn't work. There's no paragraph with short last line to use \looseness=-1. Using \enlargethispage{2\baselineskip} the orphan lines and the image are both in page 2. The image then overflows the bottom margin of page 2.


How to set Monday as the first day of the week in GNOME Calendar applet?

What is the recommended way to change the first day of the week to Monday (instead of Sunday, as in the screenshot below)?     I couldn't find anything related in Clock Preferences, nor in System -> Preferences, or System -> Administration.  This probably has something to do with tweaking locales, so here's (possibly relevant) output from locale:  LANG=en_US.utf8 LC_CTYPE="en_US.utf8" LC_NUMERIC="en_US.utf8" LC_TIME="en_US.utf8" ... LC_ALL=   NB: I want to keep English as the UI language both in GNOME and on command line. Dates are currently displayed like this (e.g. ls -l): 2010-10-06 15:32, and I also want to keep that as it is.


What is the word or term used to describe doing an activity or work with a high level of concentration and intention, trying your best?

It would be similar to trying to be extremely careful or precise.   In French it would be "application", For example: "Qui est fait avec application".   Example usage:      John worked with ________. or ...it was done with _______.


Hey guys i have a question i did a house model and i have a plenty of good materials with normal map, multiply shaders is there anyway i can join this all together to make a bake in order for me to export it to an OBJ?


If $X_1,...,X_n$ are iid, what is the mean of the following variable:?  $ \sum (X_i - \bar{X})^2$  I know the answer is $\sigma^2(n-1)$, but how is this calculated in general? If I expand, I get the variables squared, and that turns quite ugly. What's the trick here?


Story Identification: gender changing weather manipulation artist

I'm looking for a story - probably 90s or earlier and about 40 pages long.  A man is a "weather composer" who creates controlled tornados & storms as a kind of performance art.  The world he's living in allows copying & saving brain states, to be restored if an accident befalls the creator (who would lose all memories since their last backup).  One day he wakes up to hear that his earlier self had been killed, with no trace left of the body.  It turns out that his earlier self actually survived - and he eventually meets the original version of himself, who has changed gender to female.  In the end of the story, just as his illicit relationship to his original body is about to be found out, the AI controlling law enforcement & helping him with his compositions arranges a malfunctioning police vehicle long enough for him to make it to the airport & escape to more open-minded regions on pluto.


A combinatorial proof of the identity $\sum\limits_{k=0}^n\binom{2k}{k}\binom{2(n-k)}{n-k}=4^n$

I have to prove that $$\sum_{k=0}^n\binom{2k}{k}\binom{2(n-k)}{n-k}=4^n$$ The questions also asks for an algebraic proof and I used induction for that algebraic proof. For a combinatorial proof I have no idea on how to proceed on it . The first thing I thought of using a set and considering $k$ subsets of it but that idea does not work here. I just want a hint and I would prefer not giving out the full answer.


What does P>0.05; 0.025 < P ≤ 0.05 ; Yes, 0.01 < P ≤ 0.025 and, P ≤ 0.01 mean ? hypothesis testing p-values

I'm learning for my exam which is tomorrow and in the practice exam there are a lot of questions where you can choose between those p-values, but what do they mean?   an example question  A test is standardized in a way that μ = 100. The population variance is unknown. In a sample of 31 persons we find x = 103 and s = 6.28. The research question is whether the sample is drawn from a population with a mean score greater than 100. Can the H0 be rejected with ↵ = 0.05? a. No,P>0.05 b. Yes, 0.025 < P  0.05  c. Yes, 0.01 < P ≤ 0.025  d. Yes, P ≤ 0.01  i just don't understand for what they all stand. how can i interpret them?


How to proof if these graphs are isomorphic or no?

First graph was given by its adjacency matrix, While the second one was given by its edges coordinates, as the theory says graphs are isomorphic by the number of their nodes (one of the signs), as can be seen both have the same number of  the nodes, but my professor wants me to find 1-to-1 correspondence between these two graphs, how can it be done?


How would one evaluate $\int\frac{x\sin(x)}{x^2+1}$ over the real line?

Another exam problem I'm looking at is to evaluate the following integral. $$ \int_{-\infty}^{\infty} \frac{x\hspace{-0.04 in}\cdot\hspace{-0.04 in}\sin(x)}{x^{\hspace{.02 in}2}+1} dx $$ This is a complex analysis exam, so the solution probably involves contours. $\:$ Since the integrand is an even function, one could potentially simplify by changing one endpoint to $0$. However, I have no idea how to make a contour work since the absolute value of the integrand grows exponentially away from the real axis. What does one need to do to evaluate that integral?


I'm having problems with a NullPointerException.  I was doing the debugging and the element is not null, I have the problem in the first IF and I can not see what the problem is. I thought that happened when the state of the element was null, but I tried to fix it and it did not work  // Update: The problem is when I Check the status  for (Items item : master.getItems()) { try {     if (item.getCompany_status().equals("active") || item.getCompany_status().equals("open")) {  if (item.getAddress_snippet() == null) {     cont2++;     Company c = new Company(item.getTitle(), "");                                 arrayCompany.add(c); }else {     cont2++;     Company c = new Company(item.getTitle(), item.getAddress_snippet());                                      arrayCompany.add(c); } } catch (Exception e) {      e.printStackTrace(); } } }


Where did the "Memories transferred through DNA" idea used in Assassin's Creed come from?

In the Assassin's Creed series, one of the major plot devices involves using a machine to explore the memories of the main character's ancestors. The theory behind it is that your DNA stores all the memories of your ancestors within it, and by tapping into them with the Animus machine, you can experience them again. Dr. Warren Vidic, one of the scientists who developed the Animus, explains that it is like an animal's instinctual ability to know where to migrate to, or how to hunt food, without being taught. The knowledge, through the memories of their ancestors, is stored in their DNA.  Is this concept original to Assassin's Creed, or has it appeared previously in a scifi/fantasy work? What is the history of the idea?


Masters application with bad 1st year transcript

When I started the course I had a very negative attitude and did not participate or even bother trying to pass. I am not proud to say that I failed multiple subjects in my first year of degree.  In my second year I came to realize that this is the opportunity I have been given and actually started working really hard on pushing my CGPA up. I have successful done so bringing it up to 3.25 out of 4.0 from a low of 1.9. Once I started actually trying I found that I do have a passion and would love to pursue a master.  I am worried that I stand no chance because of that first year record. My question is do I stand a chance to get in a masters program and what do you think would help strengthen my application.


Construct matrix of ones and zeros based on sequences

We are given ($a_1,a_2,....,a_m$) and ($b_1, b_2,....,b_n$) sequences with non-negative integers.   Decide whether it's possible and if it is construct a matrix $\Re^{m x n}$ of ones("1") and zeros("0") where the number of ones("1") in row $i$ is $\forall i $ : $a_i$ and in column $j$ is $\forall j$ : $b_j$   Any hint is greatly appreciated.


I am looking for a term which clearly defines somebody as a non-geek, without being derogatory. The best example I have seen is muggle, but it needs context to be understood, as in "You don't meet many muggles at a comic convention", or "even my muggle friends like my autologlyph fractal decal". But while "muggle" makes it clear that he is a part of the "majority which is different", it is often hard to guess who the minority is.   There are also more specific words, but they are mostly so derogatory that I would consider them rude even in a joke, like luser or n00b. I definitely don't want to use them in a normal conversation.   A search in antonym dictionaries didn't bring up anything. Is there really no such word?


Complex integration of $\int_{-\infty}^\infty \frac{dx}{(x^2+1)^2(x^2+16)}$. I see that the poles are at $i,-i,4i,-4i$ and only $i,4i$ are in the upper half plane. Then $\int_{-\infty}^\infty \frac{dx}{(x^2+1)^2(x^2+16)}= 2\pi i[ Res(f(x),i)+Res(f(x),4i)]$.  $Res(f(x),4i)=\frac{1}{(x^2+1)^2} |_{4i} = 1/225$ since 4i is of order 1.  $Res(f(x),4i)=\frac{d}{dx}[\frac{1}{x^2+16}]|_i=\frac{-2x}{(x^2+16)^2}|_i=-2i/225$ since i is a pole of order 2.  This gives that the integral is $2\pi i(\frac{1}{225}+\frac{2i}{225})$ but the answer isn't right. It should be $\frac{3\pi}{100}$ according to wolfram.


Does $\inf(A+B)=\inf(A)+\inf(B)$ really hold?

I am  sure that it holds for ordered sets but in the case of unordered set such as $$A={(1,2,3)}, B={(5,1,4)}$$ it does not hold. As $A+B$ will be ${(6,3,7)}$.    $\inf(A+B)=3$ $$\inf(A)+\inf(B)=1+1=2$$


We had this problem in exam  class  yesterday on Combinatoric  and it was supposed to be the new year gift from our teacher. The exercise was entitled A Gift Problem for the Year 2018      Problem:      The numbers  $1,\frac{1}{2},\frac{1}{3},\frac{1}{4},\cdots,\frac{1}{2018} $ are written on the blackboards. John chooses any two numbers say $x$ and $y$ erases them and writes the number $x+y+xy$.   He continues to do so until there is only one number left on the board.   What are the possible value of the final number?   I understood the problem as follows for instance if John take $x=1$ and $y=\frac{1}{2}$ then $x+y+xy =2$ and the new list becomes $$2,\frac{1}{3},\frac{1}{4},\cdots,\frac{1}{2018} $$   continuing like this and so on.....  Please bear with me  that I do not want to propose my solution since I fell like it was wrong and I don't want to fail the exam before the result get out. but by the way I found, $2017$, $2018$ and $2019$ but I am still suspicious.   You may help is you have an idea.


In how many ways can n men and n women sit in n seats serially, so that no 3 women sit consecutively

I tried a lot, but couldn't find a way.  One thing which I found interesting is that  for n = 7, the maximum women can be  W W M W W M W = 5. Hope this might help someone to give an answer.


For me, the modal/dialog window is positioned semi outside the screen. When resizing the window or opening the developer tools, the issue fixes itself. When resizing it back or closing the developer tools, the issue often reoccurs, but not always.  I'm using Linux with Firefox 55 for a bunch of add-ons that can still not be implemented in more recent versions. Not sure if anything changed in CSS vertical/horizontal alignment since then; positioning an element should be pretty compatible so I figured I'd report it and see if others can reproduce.


How can I exclude a light from being rendered but keep it's effects?

Well, its a bit more than that.   I created my scene, lets say a living room and did add a plane. I did choose Emission as material for the plane. So it is my only light source for that scene. It makes nice light. Of course the plane shows up in the final render.   But I just want to use the light it creates but don´t want to see the plane it self in the final render in the scene.  Can that be done?  Thanks a lot armin


Is there a difference between these two ways of writing a constructor function?

I would like to know if there is any particular difference between these ways of writing a constructor: let Bird = function(name, color) {   this.name = name;   this.color = color;   this.numLegs = 2; }  function Bird() {   this.name = "Albert";   this.color  = "blue";   this.numLegs = 2; }


I'm very interested in macrophotography and I'd like to take photos to the human eye. I have the Canon EOS 80D body and I'm also considering buying the  Canon EF 100mm f/2.8L IS USM Macro Lens. I'd like to take images as the one I have linked below. So, my question is whether I could achieve such results with this gear? Is 1:1 magnification enough for this? (Or do i need greater than life size) and what other considerations should I consider for macro photography?


Creating a virtual machine of an old laptop

I'd like to create a virtual machine of an old laptop and then get rid of the old laptop.  How does licensing of Microsoft xp operating system work?  The operating system was pre-installed on the laptop from the manufacturer.  Can I license with the sticker on the laptop?


What are the current travel restrictions on individuals entering the United States from regions affected by Covid-19?

This community wiki explains the current restrictions by the United States of America on the entry of individuals who may pose a risk of transmission of the SARS-Cov2, the virus which causes the Covid-19 disease.


Is a T-test appropriate for comparing two monthly data sets of mean values where one set is a subset of the other?

I have two sets of monthly Consumer Price Index (CPI) values for the period January 2014 through April 2017. One set is the national monthly CPI for Canada and the second is the provincial monthly CPI for Alberta (a province of Canada).   The CPI values for both Canada and Alberta represent a mean value calculated during the period by randomly sampling values within the geographic region in question. Alberta is part of Canada so there is necessarily some Alberta data being used to contribute to the Canadian CPI mean.  It is clear enough from the data that some months Alberta CPI is higher than the national value and some months it is lower but I want to be able to determine if the overall difference during the study period is statistically significant.   My current approach is to use a T-test and compare the two sets of data to see if there is a significant difference between their means. My concerns are:   A) is there an issue with this approach because the data is temporal? i.e. does the time series nature of the data preclude the use of a T-test?  B) is there an issue with independence given the fact that the Alberta data is a subset of the national data?   C) is there an issue with using a T-test to treat the monthly CPIs as point data given that they themselves are means? I don't have access to the raw data that was used to calculate the monthly CPIs and I am concerned with the validity of taking the mean of mean data to perform the statistical test.  Finally, if a T-test is out as an option, is there another statistical test that is appropriate?


'! Undefined control sequence' and '! Package inputenc error' while typesetting equations

I'm writing complicated equations in LaTeX and I'm getting error messages: for the first two equations I get:  ! Undefined control sequence.  and the third one I get:   ! Package inputenc Error: Unicode char − (U+2212) (inputenc) not set up for use with LaTeX. See the inputenc package documentation for explanation. Type H for immediate help.  Can any one help? These are my equations:  \begin{document} $\sigma \textsupsub{2}{j}(x)\equiv \sum_{j\prime=1}{M}{W \textsupsub{2}     {ij\prime (X)a_{j\prime}(X)}, j,=1,...,M $ %(8b)  $$T= min_j\in [1,M]\Bigg{ \frac {\epsilon a_0(X)}{\mu_j(X)|},\frac  {\in a_0(X)}^2{(\xi\textsupsub{2}{j}(x)})$$   Pr ${X_n=j\mid X_{n-1}=i, X_{n−2}=k,...,X_0=m}=Pr{X_n=j \mid X_(n-1)=i}$ \end{document}   it's supposed to produce:


Why does a zip file appear larger than the source file especially when it is text?

I have a text file that is 19 bytes in size and having compressed the file using zip and 7zip, it appears to be larger. I had a read of the question on  as well as  but considering the file is not already compressed I would have expected further compression. Attached is a screenshot.    EDIT0  I took the example further by creating a file that contained random data as follows dd if=/dev/urandom of=sample.log bs=1G count=1 and attempted to compress the file using both zip and 7zip however there were no compression gains. Why is that?


Handling browser level authentication using Selenium

I am automating an application which contains browser level authentication.  When I open the application, the browser performs basic authentication, i.e. it prompts for a username and password.  How can I handle this scenario using Selenium?


Do I need transit visa for my direct flight that stops in the UK?

Do I need transit visa for the UK for my direct flight (AI 172 from Newark to Ahmedabad)? It has a brief 2-hour break in London, but no plane change is involved.   I am not sure whether I need to exit the plane or not at London; if I do, would I need to go through the immigration process, or will they just check the boarding pass and passport?  The visa stamped on my passport is expired but I have valid  extension and traveling to India to appear for my interview to get my visa stamped during this trip.  I am an Indian passport holder residing in the US on an H1B visa.


Can we estimate the loss of entropy when applying a N-bit hash function to and N-bit random input?

that a cryptographic hash function " is not designed as a bijective mapping from N bit input to N bit output".  So if I feed an N-bit cryptographic hash function with N bits of random input, there's a loss of entropy between the input and output of the hash function.  Considering the md5 hash function, is there a way to estimate that loss of entropy? And is this loss cumulative so I could say, if I apply the hash function enough times, I end up with a 50% loss of entropy?


Let $a,b,c$ be integers such that $\gcd(a,6)=3=\gcd(b,6)$. Show that $\gcd(a+b,6)=6$. Attempt: Let $d = \gcd(a+b,6)$. Then, by definition, $d \mid (a+b)$ and $d \mid 6$. It means that $d=1,2,3$ or $6$. On the other hand, we have $3\mid a$ and $3 \mid b$. Write $a = 3m$ and $b=3n$ for some integers $m$ and $n$. Then, $a+b=3m+3n=3(m+n)$ and so $3 \mid (a+b)$. But, $d \mid (a+b)$. Now, $a+b = dp$ for some integer $p$. Thus, we have $3 \mid dp$ which means $3 \mid d$ or $3 \mid p$. If $3 \mid d$, then $d=3k$ for some integer $k$. Hence, $d$ is either $3$ or $6$. But, how to get $d=6$?


Workaround for Offset 2000 limit on SOQL Query

Problem  I'm trying to make a standard query pagination. I'm using SOAP API.   The logic is classic:  LIMIT recordsByPage OFFSET (recordsByPage*pageNumber)+1,   It works fine, however, I'm facing the 2000 limit of OFFSET:      The maximum offset is 2,000 rows. Requesting an offset greater than   2,000 will result in a NUMBER_OUTSIDE_VALID_RANGE error.   I advice of SF to solve this limit is to create a QueryLocator and use the queryMore.   We have more than 100k records, and the recordsByPage ~50. If I need to go record #50000, It will take 1000 queryMore.  Instead of that, if I use the max (2000) batch size in the queryLocator then I will require 25 queryMore.   From my view this approach is inefficient.   Question  What is the most efficient (performance + less api calls) way to make a query pagination ?


I need a clarification on the semantics of Python.   Is it true that when Python encounters a statement of the form   x = some_term   a new object is being created, as specified by the process of evaluation of the term some_term?  Now suppose that the following lines have been encountered by Python:  x = the_term   y = the_term   Where the_term is some fixed term (assume that it does not contain any references to functions generating "random objects"). As I see this the behaviour of Python should be the following: first a new object O1 is created and associated with the name x. Then a second new object O2 is created and associated with the name y. Both names x and y are now in suitable namespace. Objects O1 and O2 are distinct objects, the are occupying different places in memory, and the got the same values. Hence the test   x == y    should return True, and test  x is y   should return False.  So tell me please why do I observe the following:  x=5  y=5   now x==y returns (of course) True, and x is y returns True.  But if we put:  x=99999999999999999999  y=99999999999999999999   now x==y returns (of course) True, and x is y returns False.  Could you tell me what is happening? What is the "real" semantics of Python (since the one I have described is clearly wrong, as these examples show)?


How to change Figure/Listing/Table names to anything I want (e.g CodeSnippet)?

Anyone knows how to change the Listing name to Code Snippet?    \documentclass[bsc]{bangorcsthesis} \title{Mirror, mirror on the Web} \author{Loizos Vasileiou} \date{\today} \degreeScheme{BSc Creative Technologies} \supervisor{Prof. Kuncheva L.}  \bibliographySetup[compressed] \addbibresource{references.bib}  \usepackage{soul} \newcommand{\lk}[1]{\textcolor{red}{#1}} \newcommand{\mk}[1]{\textcolor{green}{#1}} \usepackage{listings} \usepackage{color} \definecolor{lightgray}{rgb}{.9,.9,.9} \definecolor{darkgray}{rgb}{.4,.4,.4} \definecolor{purple}{rgb}{0.65, 0.12, 0.82}  \lstdefinelanguage{JavaScript}{   keywords={typeof, new, true, false, catch, function, return, null, catch, switch, var, if, in, while, do, else, case, break},   keywordstyle=\color{blue}\bfseries,   ndkeywords={class, export, boolean, throw, implements, import, this, image, createCapture},   ndkeywordstyle=\color{darkgray}\bfseries,   identifierstyle=\color{black},   sensitive=false,   comment=[l]{//},   morecomment=[s]{/*}{*/},   commentstyle=\color{purple}\ttfamily,   stringstyle=\color{red}\ttfamily,   morestring=[b]',   morestring=[b]" }  \lstset{    language=JavaScript,    backgroundcolor=\color{lightgray},    extendedchars=true,    basicstyle=\footnotesize\ttfamily,    showstringspaces=false,    showspaces=false,    numbers=left,    numberstyle=\footnotesize,    numbersep=9pt,    tabsize=2,    breaklines=true,    showtabs=false,    captionpos=b } \begin{document}  Some text explaining what Listing~\ref{myLabel}.   \begin{lstlisting}[caption=My Javascript Example, label=myLabel] var videoElement = createCapture(VIDEO); \end{lstlisting} \end{document}   Please if you know how to solve this it would be really appreciated. this is my first Latex Project.


How to move window buttons to right in Ubuntu 16.04

I've installed Ubuntu 16.04 on my laptop and I'm using gnome-shell 3.18.4. When I'm trying to move the window buttons to the right by using dconf-edit  I'm unable to move the window buttons to the right. What can I do to move the buttons to the right?


Do you know how I can level up quickly to level 20?its hard for me to level and these quest barely give me xp I want to do dungeons but I'm low level (level 10)


add a second (multiple) owner / user for a folder (website folder)

Im using Plesk 17 and Ubuntu 16, Plesk automatically created an ftp user for my "webspace". I won't give this created user more rights and can't change it easy to my main user withouth messing up everything.  I connect with my main user with a ssh key to the server. I don't allow other users to connect via ssh.  Now if i would connect with bitvise and Dreamweaver i get permission denied, because the owner is the created user by Plesk (dexxxxxx - img).    How i can add a second user withouth changeing the existing groups for this folder ?   I tried to create a group added both users, but like that all other groups get replaced (psacln, root, psaserv -> siteaccess group)  If i replace the user created by plesk the Homepage outputs access denied.  Edit: I tried to add the main user to the same groups like dexxx then i can see the folder but cant write into it. (dexxx can)


I have compiled a list of items that may protect a web form from span.  Which are actually effective?  Please feel free to add additional items.   Store a code as a hidden field and verify it when submitted. Use jQuery to set the method and action fields after page loads. (Also) Use jQuery to encode the action URL Encode the entire webform and use jQuery to decode it after the page loads. Use AJAX instead of the standard submit button action. Use CAPTCHA Place CSS-hidden fields of the form that only bots will find and fill in. Recording time between page load and submission, ignore if less that 1 second. Load the form into the page via AJAX, one second after page loads.


Could not boot from an external hard drive

I burned a live session of Linux Mint 17 Cinnamon to a USB stick. Then I installed LM17C into an external hard drive by using this USB stick. I managed to do it and even successfully started on my computer.  However I have tried to boot it on another computer, yet it did not started and gave the error below:  error: file '/boot/grub/i386-pc/normal.mod' not found. entering rescue mode... grub rescue >   My computer has an Intel processor, but the second PC has AMD. I think this is the problem. I do not know how to solve it, though.


Use model input to amend SQL Query in QGIS Modeler

Is there a way I can use a model input in QGIS modeler to amend the parameters of a SQL query. For example I want a model input (string) to allow me to pick the name of someone I am searching for in a database. In the example below the name is 'Tim'  I know I can change between a 'value', 'pre calculated value', 'model input' and 'algorithm output' but none of these seem to allow me to change a specific parameter within the script.


Why am I still getting a password prompt with ssh with public key authentication?

I'm working from the URL I found here:    My ssh client is Ubuntu 64 bit 11.10 desktop and my server is Centos 6.2 64 bit. I have followed the directions. I still get a password prompt on ssh.  I'm not sure what to do next.


Calculate $\sum_{i=1}^n\sin(\frac{\pi\ i}{2n})$ and $\sum_{i=1}^n\sin(\frac{\pi\ i-\pi}{2n})$

Need to calculate the following:$\sum_{i=1}^n\sin(\frac{\pi\ i}{2n})$, $\sum_{i=1}^n\sin(\frac{\pi\ i-\pi}{2n})$.  I am sorry that this is short, but I don't know how to even begin. I have tried to look for trigonometric identities, but haven't seen something that fits in these cases. I will be glad for some help. Thanks!


I am asking myself the question "Should I do PhD or should I leave academia and go for an industrial career?"  My life-goal is being a professor. And I love to do research.   PhD is surely a bite that not everyone can chew. But I wonder who can chew it?  I never was good at tests and exams. My BSc. GPA was 2.84/4.00 but finished my MSc. with 3.50/4.00  However, currently I am working on a conference paper and I feel like even that is too much for me. It has been nearly 3 months and still, the paper draft is to be improved (not the wording but the content).  I am surely a hard-worker but not always. Sometimes, I let go of my work and absorbed in other stuff (composing, amateur radio etc). If this period is too wide, I have to spend double effort to warm-up and remember where I left.  I don't know how things work in PhD. It usually is 5-6 years. It is the one of two most-challenging milestones in academic career (the other is getting the title Assoc. Prof). Should I completely be a "nerd" and work on my thesis systematically (something I could never make in my entire life) or working periodically but with extra effort is still sufficient?  So, here's my question: If I say "I'm considering to do PhD" and ask your advice, what would you ask me? What kind of skills/characteristics do you look for a potential academician?  I know it is way too late for me to ask this kind of question, as a person who almost finished his master's degree. But better lose the saddle than the horse.


How to install TP link WN822N on Ubuntu?

When I type in lsusb, the device appears as ID 2357:0108  That's right, it's blank at the end. I've updated the usb ids yet its always blank. I have no idea what to install to make this thing work. I'm dual booting on mac osx


When did people start talking about User Experience as a role/domain similar to the way that it's used today?  The earliest reference I can find is the Norman, Miller, Henderson CHI 95 piece on Apple's set up (Donald Norman, Jim Miller, Austin Henderson: What You See, Some of What's in the Future, And How We Go About Doing It: HI at Apple Computer. Proceedings of CHI 1995, Denver, Colorado, USA)  Anything earlier?  [Edit - after @Andrew's nice answer we have 1993 as an earlier date     "I invented the term because I thought Human Interface and usability   were too narrow: I wanted to cover all aspects of the person's   experience with a system, including industrial design, graphics, the   interface, the physical interaction, and the manual." - Don Norman   ]  (I'm writing a talk on communities of practice relating to UX - and want to get my time lines right ;-)


I created a shortcode that is displaying the results as intended, but outside of the div or table cell where I placed the shortcode within my site. Is there a cleaner way to write this that will generate the code in the expected location?   <?php function minisocialvar( $atts ) {   $s = shortcode_atts( array(         'id' => '',         'fb' => '',         'tw' => '',         'ig' => '',         'yt' => '',         'in' => '',         'fk' => '',         'align' => 'left',         'size' => '',     ), $atts ); ?>      <div id="<?php echo $s['id']; ?>" style="text-align: <?php echo $s['align']; ?>;">     <?php if (!empty($s['fb'])) { ?>         <a href="<?php echo $s['fb']; ?>" title="Follow Us On Facebook" target="_blank" class="fb-socialicon">             <span class="fa-stack <?php echo $s['size']; ?>">                                                              <?php } ?>      <?php if (!empty($s['tw'])) { ?>         <a href="<?php echo $s['tw']; ?>" title="Follow Us On Twitter" target="_blank" class="tw-socialicon">             <span class="fa-stack <?php echo $s['size']; ?>">                                                              <?php } ?>      <?php if (!empty($s['ig'])) { ?>          <a href="<?php echo $s['ig']; ?>" title="Follow Us On Instagram" target="_blank" class="ig-socialicon">              <span class="fa-stack <?php echo $s['size']; ?>">                                                                  <?php } ?>      <?php if (!empty($s['yt'])) { ?>          <a href="<?php echo $s['yt']; ?>" title="Watch Us On YouTube" target="_blank" class="yt-socialicon">               <span class="fa-stack <?php echo $s['size']; ?>">                                                                   <?php } ?>       <?php if (!empty($s['in'])) { ?>          <a href="<?php echo $s['in']; ?>" title="Join Us On LinkedIn" target="_blank" class="in-socialicon">             <span class="fa-stack <?php echo $s['size']; ?>">                                                               <?php } ?>      <?php if (!empty($s['fk'])) { ?>          <a href="<?php echo $s['fk']; ?>" title="View Us On Flickr" target="_blank" class="fk-socialicon">             <span class="fa-stack <?php echo $s['size']; ?>">                                                               <?php } ?>
 <?php } ?>  <?php add_shortcode( 'minisocial', 'minisocialvar' );


Need help on how to interpret Gamma Probability density function of gamma(2, 1/10)

The below sample graph was created using R, for an example I came across while reading (on Distribution of time until customer x arrives):  t <- seq(0,1,0.01) ft <- 100*t*exp(-10*t) plot(t,ft,type="l", xlab="T", ylab="f(t)") title(main=expression(paste("Probability density function of ", Gamma(2,frac(1,10)))));   The graph looks like a Percent Point Function, even though it isn't exactly.Am trying to understand on how I interpret it, but am not getting it.  Can someone help on how to read the above plot?  Thanks, -Kamal.


How to make addition symbol inside in a circle?

I need to make + and a dot representing multiplication in a circle. How to do it?