I came upon this reading the python  on the super keyword:  If the second argument is omitted, the super object returned is unbound. If the second argument is an object, isinstance(obj, type) must be true. If the second argument is a type, issubclass(type2, type) must be true (this is useful for classmethods).  Can someone please give me an example of a distinction between passing a Type as a second argument versus passing an Object?   Is the documentation talking about an instance of an object?  Thank you.

In Python, what are metaclasses and what do we use them for?


Today I tried updating Ubuntu 13.04 to Ubuntu 14.04. The installtion went fine so I restarted my computer and it came up with a grub rescue> prompt! I have no idea what to do and I am no Linux pro(In fact I first heard about it a week ago:)). Please help now I can't even access windows right now and I need to get some work done, PLEASE HELP!

I recently repartitioned my HDD and I have damaged GRUB on my system. On boot I get the GRUB rescue prompt and I have to go through the following steps in order to boot normally:  set root=(hd0,msdos6) set prefix=(hd0,msdos6)/boot/grub insmod normal normal   (Those steps were found on another post on here!).  I'm very tired of repeating this on every boot, how do I permanently fix GRUB?


I love proving different things on mathematics, I mean, I love knowing where math theorems, methods and formulas come from. But most math books don't prove or show that kind of things. Do you know any book that could satisfy my wish? Obviously, there are lots of branches of mathematics, but I'm asking you to tell me, for example, "Oh, I know that X book proves all calculus theorems", "I've got a book called X that explains where all geometry formulas come from", etc.   Thank you

There was a time when I avoided math proofs, but now I am starting to enjoy them. I am taking Intro to Linear Algebra and am falling in love with proofs. Are there any introduction to mathematical proofs books that blow the others out of the water?


I recently got over a problem. For short ranges, the properties dialog displays relative timestamps like "2 hours ago". Normally I am fine with that, but at internet shortcuts I cant see the exact date anywhere.    Is there any way to turn this feature off?

Anyone know a way to immediately show the seconds of a file's date modified property in the GUI? So if you create a file, any file in any directory, right-click and choose Properties, the date modified (if it's recent) will say something like "dd/mm/yyy hh:mm, one minute ago" - reminder this is in Windows 7. Windows XP did it normally. Then they changed something.  If you wait a while, eventually you'll see the seconds, I'm not sure how long a while is, but this is incredibly annoying if you want to troubleshoot something that relies on the seconds of timestamps... is there a setting? registry key I can change perhaps?  I'm literally using Chrome, pasting in the path of the directory to be able to see the seconds quickly (as a workaround) but would be nice to be able to use Win7.


I wrote a program that generates prime numbers. Are there better ways of doing so? Additionally, how could I improve my own method. public static void main(String[] args) {         ArrayList<Integer> primeNumbers = new ArrayList<Integer>(primeNumberGenerator(1000));         System.out.println(primeNumbers);          }      public static ArrayList<Integer> primeNumberGenerator(int range){                  ArrayList<Integer> primeNumbers = new ArrayList<Integer>();         int brake = 0;         int index = 0;          for(int i = 2; i < range; i++){             brake = 0;             for(int p = 2; p < range; p++){                 if((i%p) == 0 && i != p && brake == 0){                     brake = 1;                 }             }             if(brake == 0){                 primeNumbers.add(index, i);                 index += 1;             }             brake = 0;         }     return primeNumbers;     }

Which is the fastest algorithm to find out prime numbers using C++? I have used sieve's algorithm but I still want it to be faster!


In a recent(-ish) episode of the Big Bang Theory, the men recruit the women to help out in the lab, and they had to do a lot of soldering.  Throughout the episode the cast pronounced "solder" as "sodder" which I thought was interesting. Is this the pronunciation used in the whole of the US (and Canada)? What happened to the "l"?

I have been listening to a podcast where the host pronounces the word solder as "sodder" or "sod-der", even "saw-der". Same thing happened when the lecturer of one of my EE classes pronounced the word solder. As for me I pronounce the word solder as "sole-der" with a distinct L and a longish O.


How can I sort all my questions by date (by time) in that list that I get to after clicking on my user's name at the top of the screen (right after the envelope icon)?    Update:  I am sorry I forgot to mention that I want my questions to be sorted by the time they were asked, not by the time of their latest responds.   And also, I would want to be able to see the oldest questions at the top of the list (which means that the very first question that I ever asked on "StackOverflow" must be first from top).

The list of questions I asked on my account page is nice, but I keep finding myself clicking on "next" because the newer questions are listed on later pages.  Assuming that it is more likely that a given user would want to check his newer questions for answers, wouldn't it be better if older questions were moved to later pages rather than newer?


So, I just recently installed Ubuntu 12.04 with a windows installer (Wubi) and I want to delete Windows 7 completely leaving Ubuntu alone. Does anyone know how to do that without having to do everything all over again?

I have installed Ubuntu on my D: partition using Wubi. Is there any way in which I can remove my Windows from C: drive and move my existing Ubuntu installation to C: drive and make it a regular install.


I'm a fairly new LaTeX user, so please excuse me if this is a simple newbie question.  I am using the exam package to create, well, an exam. I use both the \choices and \oneparchoices environments and I would like them to be aligned instead of the choices ones being far more indented. This MWE should illustrate my point:  \documentclass{exam}  \begin{document}  \begin{questions}     \question     Question 1     \begin{oneparchoices}        \correctchoice Answer 1        \choice Answer 2        \choice Answer 3    \end{oneparchoices}     \question    Question 2     \begin{choices}     \correctchoice Answer 1     \choice Answer 2     \choice Answer 3    \end{choices}     \end{questions}   \end{document}     I'm sure the more experienced users can solve this easily, but I'm stuck.

I want to create an multiple choices question with this indenting format  1. ########    A. ###    B. ###    C. ### 2. ########    ########    A. ###    B. ###    C. ###   The choices have same indentation as the question text.  But, using the default exam documentclass, I get this format  1. ########      A. ###      B. ###      C. ### 2. ########    ########      A. ###      B. ###      C. ###   Hence, I try to set the \leftmargin to 0pt inside the choices environment to get what I want.  \documentclass{exam} \begin{document} \begin{questions}   \question   How old are you?   \begin{choices}     \setlength{\leftmargin}{0pt}     \choice 14     \choice 17     \choice 19     \choice 20     \choice 23   \end{choices} \end{questions} \end{document}   But, It get nowhere.  So, What is the right way to set indentation of choice in exam documentclass?


I'm seeing this all over my Katz and Lindell book and I don't see where they introduced it.

In a , the setup function is mentioned with the $setup(1^n)$ or $setup(1^l)$. I want to know what is meant here.   Is it multiples of ones or representing something else? Also, why is this used here?


I know that if a post accumulates six offensive (or spam) flags it is auto-deleted.  What happens with comments?  Do enough "rude or offensive" flags on a comment also auto-delete it?  (Spam isn't a flag reason for comments.)  If so, what is the threshold?  If comments can be auto-deleted by flags, do reasons other than rude/offensive trigger it too, or just that one?

Comments can now be upvoted and flagged. How do those features work? Do users get rep for their upvoted comments? Do upvoted comments have any effect on comment sorting? And can users see their own comment upvote number somewhere?  Related:  The  about comments


first of all excuse me for asking this way but I didn't know another way to express what I need. If anyone can edit the question, I would be very pleased.  Often searching for some materials through internet I finish opening some pages (repositories) whose contain all the information that I need but I don't know how to download all those files & folders. It is the possibility to download them one by one, but doing this for a big repository is almost impossible. For example these URL:  or  .  Can anyone help please?

How can I download all pages from a website?  Any platform is fine.


Any advice on how to go about fixing this bracket?  How do I finding out the replacement model/part details for this thing?

I have reversed some that have broken on the bottom to the other side, which is a temporary fix.  These brackets are not flush with the back wood panel but fit over a 1" x 1/2" strip.  Any help with locating these would be awesome.  I need at least 4 sets.  Thanks.


how to write the Apex test class for decimal numbers to words? how to code coverage in class public String getNumberTOWord(Decimal num) {          Decimal junkVal = num;         Decimal junkValPaisa = junkVal - Math.floor(junkVal);         junkVal = Math.floor(junkVal);         System.debug(junkVal);         //Decimal rounded = junKValPaisa.setScale(2);       //  System.debug(rounded);         String obStr = junkVal.toPlainString();         System.debug(obStr);         String[] numReversed = obStr.split('');         System.debug(numReversed);         String[] actnumber = reverse(numReversed);         System.debug(actnumber);         String firstHalf = convertInWords(numReversed, actnumber);         System.debug(firstHalf);                  Integer tmp = Math.round(junkValPaisa * 100);          junkValPaisa = (Decimal)tmp / 100; System.debug('jj :' + junkValPaisa);         system.debug(junkValPaisa);         String paisaStr = junkValPaisa.toPlainString();         System.debug(paisaStr);                 String secondHalf;         System.debug(secondHalf);         System.debug(paisaStr);        if (paisaStr == '0')                      {             secondHalf = '';                      } else if (paisaStr.length() != 4) {             paisaStr = paisaStr + '0';             paisaStr = paisaStr.substring(2);                          String [] numReversedPaisa = paisaStr.split('');             String[] actnumberPaisa = reverse(numReversedPaisa);             secondHalf = convertInWords(numReversedPaisa, actnumberPaisa);             system.debug('paisaStr:'+paisaStr);             system.debug(secondHalf);         }          System.debug('secondHalf :'+secondHalf);          String SumOFHalves = '';            System.debug('SumOFHalves :'+SumOFHalves);         System.debug('secondHalf :'+secondHalf);         if (secondHalf.length() > 3) {             firstHalf = firstHalf.replace('Only', ' And ');             secondHalf = paisaStr.replace('Only', '/100 ');             SumOFHalves = firstHalf + secondHalf;         } else {             firstHalf = firstHalf.replace('Only', '');             SumOFHalves = firstHalf;         }          // IF amount has any value         if (SumOFHalves.length() > 5) {             return SumOFHalves;         } else {             return '';         }     }

This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the  tag.  This canonical question is intended to address several classes of common questions by providing a quick summary and links to comprehensive resources:   How do I start writing my first unit test?  How do I unit test this code?  I need help writing this unit test.   Salesforce Stack Exchange looks for detailed, specific questions that the community can help you with, and can't write tests on your behalf. We feel that working with the resources below can help you get started, and we encourage you to make an attempt to write your test and return to SFSE with your specific questions when you encounter challenges you can't resolve.


all my materials applied to my model is not being rendered out when i go in for the final render. as shown here. PS look closely its not just a black bachground the bottom picture is what is suppposed to be rendered  any help would be appreciated

I've imported an .OBJ file to my scene and it looks good in viewport, but when I try to render with F12 it's completely black.  Clearing custom split normals data (in object data panel) removes black rendering issue, but also completely destroys the shading in viewport and render.  Is there a way to somehow retain the viewport like shading in render?


I`m trying to include a parallax Effect into one of my cutsom page templates. The js function is returning the following error in the firebug console:  TypeError: $ is not a function  The error is on the first line wich is:  var parallaxElements = $('.parallax'),  Any help would be appreciated. Here the full code:      var parallaxElements = $('.parallax'),         parallaxQuantity = parallaxElements.length;      $(window).on('scroll', function () {      window.requestAnimationFrame(function () {      for (var i = 0; i < parallaxQuantity; i++) {         var currentElement =  parallaxElements.eq(i);         var scrolled = $(window).scrollTop();          currentElement.css({         'transform': 'translate3d(0,' + scrolled * -0.3 + 'px, 0)'         });      } });  });

I know that jQuery is loaded, because I can switch out the $ for 'jQuery' and everything behaves as expected, but this will be a messy script if I can't fix this  This script:  jQuery(document).ready(function(){     $("ul.vimeo_desc_feed li a").click(function(){         alert($(this).attr('href'));         return false;     }) });   Produces the error $ is not a function  This script:  jQuery(document).ready(function(){     jQuery("ul.vimeo_desc_feed li a").click(function(){         alert(jQuery(this).attr('href'));         return false;     }) });   works fine.


So when you do @User, it does notify the user, but I'd appreciate it if it became a link to their profile automatically, which can also be turned off as you type it. i.e. when you do the @ symbol, someones name comes up in a box. Next to that name we could have a "do not link" if they don't wanna link the profile.  Sort of like facebook.  Edit: i'd say this is partially duplicate.  The people in that question believe that this won't work. I suggest, in the suggestion box that comes up when you type @, there can be a list of the usernames. e.g. when you do @RegisteredUser, there are a bunch of Registered User names so just list them with profile pictures so the user can select which one. All of this is in the box where normally the site would suggest the name you're about to tag.

When you respond to someone in a comment you use @PersonsName. Is there anyway it could be linked like this @


If $\triangle$ is the area of triangle with side lengths $a,b,c$, then show that $\triangle \le\dfrac{1}{4}\cdot\sqrt{(a+b+c)abc}$. Also show that equality occurs in the above inequality when $a=b=c$  My attempt is as follows:-  $$\triangle=\sqrt{s(s-a)(s-b)(s-c)}$$  $$\triangle=\dfrac{1}{4}\sqrt{(a+b+c)(b+c-a)(a+c-b)(a+b-c)}$$  $$b+c-a>0,a+c-b>0,a+b-c>0$$  So we can apply $A.M\ge G.M$  $$\dfrac{b+c-a+a+c-b+a+b-c}{3}\ge\left((b+c-a)(a+c-b)(a+b-c)\right)^\frac{1}{3}$$ $$\dfrac{a+b+c}{3}\ge\left((b+c-a)(a+c-b)(a+b-c)\right)^\frac{1}{3}\tag{1}$$  As $a>0,b>0,c>0$, we can also say  $$\dfrac{a+b+c}{3}\ge(abc)^\frac{1}{3}\tag{2}$$  But we can't say from this that $(abc)^\frac{1}{3}\ge\left((b+c-a)(a+c-b)(a+b-c)\right)^\frac{1}{3}$  So I tried $G.M\ge H.M$ for $a,b,c$  $$(abc)^\frac{1}{3}\ge\dfrac{3abc}{ab+bc+ca}$$ $$\dfrac{ab+bc+ca}{3}\ge(abc)^\frac{2}{3}\tag{3}$$  Seems like it didn't produce anything useful, so  I tried $G.M\ge H.M$ for $b+c-a,a+c-b,a+b-c$  $$\left((b+c-a)(a+c-b)(a+b-c)\right)^\frac{1}{3}\ge\dfrac{3(b+c-a)(a+c-b)(a+b-c)}{((b+c-a)(a+c-b)+(a+c-b)(a+b-c)+(b+c-a)(a+b-c))}$$  $$\left((b+c-a)(a+c-b)(a+b-c)\right)^\frac{1}{3}\ge\dfrac{3(b+c-a)(a+c-b)(a+b-c)}{2ab+2bc+2ca-a^2-b^2-c^2}\tag{4}$$  But again it didn't produce anything useful, so I tried something else.  Applying $A.M\ge G.M$ for $a+b+c,a+b-c,b+c-a,a+c-b$  $$\dfrac{2(a+b+c)}{4}\ge\left((a+b+c)(b+c-a)(a+c-b)(a+b-c)\right)^\frac{1}{4}$$ $$\dfrac{a+b+c}{2}\ge\left((a+b+c)(b+c-a)(a+c-b)(a+b-c)\right)^\frac{1}{4}$$  Squaring both sides  $$\dfrac{(a+b+c)^2}{4}\ge\left((a+b+c)(b+c-a)(a+c-b)(a+b-c)\right)^\frac{1}{2}$$  By cachy's inequality:-  $$(1^2+1^2+1^2)(a^2+b^2+c^2)\ge(a+b+c)^2$$ $$3(a^2+b^2+c^2)\ge(a+b+c)^2$$ $$\dfrac{3(a^2+b^2+c^2)}{4}\ge\dfrac{(a+b+c)^2}{4}\tag{5}$$  Hence  $$\dfrac{3(a^2+b^2+c^2)}{4}\ge\left((a+b+c)(b+c-a)(a+c-b)(a+b-c)\right)^\frac{1}{2}\tag{6}$$  Dividing by $4$  $$\dfrac{3(a^2+b^2+c^2)}{16}\ge\triangle$$  So I tried all these approaches, but unfortunately didn't arrive at the required result. What can we do here? Please help me in this.

If $\triangle$ be the area of $\triangle ABC$ with side lengths $a,b,c$. Then show that $\displaystyle \triangle\leq \frac{1}{4}\sqrt{(a+b+c)\cdot abc}$   and also show that equality hold if $a=b=c$.  $\bf{My\; Try}::$ Here we have to prove $4\triangle\leq \sqrt{(a+b+c)\cdot abc}$  Using the formula $$\triangle = \sqrt{s(s-a)(s-b)(s-c)},$$ where $$2s=(a+b+c)$$  So $$4\triangle = \sqrt{2s(2s-2a)(2s-2b)(2s-2c)}=\sqrt{(a+b+c)\cdot(b+c-a)\cdot(c+a-b)\cdot(a+b-c)}$$  Now using $\bf{A.M\geq G.M}$ for $(b+c-a)\;,(c+a-b)\;,(a+b-c)>0$  $$\displaystyle \frac{(b+c-a)+(c+a-b)+(a+b-c)}{3}\geq \sqrt[3]{(b+c-a)\cdot(c+a-b)\cdot(a+b-c)}$$  So we get $\displaystyle (a+b+c)\geq 3\sqrt[3]{(b+c-a)\cdot(c+a-b)\cdot(a+b-c)}$  But I did not understand how can I prove above inequality  help Required  Thanks


I use  app on my iPhone as 2-Factor-Authentication agent. I have added tokes for numerous Web applications that I routinely log into via various devices.  Now, I wish to reset my iPhone and set it up again as a new device. How do I easily restore the tokens for the various services that are currently added in Google Authenticator?  I never backup my iPhone on iCloud/iTunes. Hence, I am not looking to backup and restore from a backup.  I found  tutorial which guides with migrating tokes onto the app running on a separate phone. I just have a single iPhone, which I am looking to reset and re-install the authenticator app onto.

Just got a new iPhone 7, but when it restored it lost all my Google Authenticator two factor auth codes. I still have them all in my old phone, how can I port them to my new iPhone 7?  This is quite frustrating.


How to interpret this? What does the ARIMA(0,0,0)(0,1,0)[12] means in laymans term?

I would appreciate if someone could help me write the mathematical equation for the seasonal ARIMA (2,1,0) x (0,2,2) period 12. I'm a little confused with how to go about this. I would prefer an equation involving $Y_t , e_t, θ$ and $Θ$.


Have a look at . User is asking for clarification for why he didn't earn that badge. That user edited (re-tagged)  which was inactive for more than 6 months. But he didn't earn the badge. Does tag edit count for Excavator badge?  If no, we need to mention it on . If yes, Why didn't that user earn that badge? (.)

I know tag-edits do not count towards the 500 edits required for the Copy Editor badge. Do they count to the 100 for the Archaeologist badge? It seems they should because you are making a 6-month-inactive post active again.


On my Xenial test system, I've got already gdm3 installed. Now I'd like to install the lightdm package as well. When I do so, it asks which default display manager should be used:  I need to avoid this question (going to install those packages with Chef). How do I do that? With debconf-get-selections, I found: $ debconf-get-selections | grep lightdm # Choices: gdm3, lightdm lightdm shared/default-x-display-manager    select  gdm3 lightdm lightdm/daemon_name string  /usr/sbin/lightdm  Based on that, I created a file with an answer and gave it to debconf-set-selections: $ cat /tmp/lightdm lightdm shared/default-x-display-manager select lightdm  $ sudo debconf-set-selections -v /tmp/lightdm info: Trying to set 'shared/default-x-display-manager' [select] to 'lightdm' info: Loading answer for 'shared/default-x-display-manager'  But when I now run apt install lightdm, it still asks this question. Why is it still asking that question and how can I avoid that?

I'm trying to build an Ansible Playbook to deploy some Ubuntu 12.04 servers on Linode, but my problem seems to be an Ubuntu one. When I run different combinations of apt-get or aptitude I always get the following dialog that I have to respond to.     I'd like this to be answered from the command line so that it doesn't interrupt the automatic deployment. Any ideas?  My current commands are below. Note that I'm trying to set DEBIAN_FRONTEND:  #!/bin/bash  echo 'DEBIAN_FRONTEND="noninteractive"' >> /etc/profile echo 'DEBIAN_FRONTEND="noninteractive"' >> ~/.profile  source /etc/profile source ~/.profile  # This next line is the one that pops up the dialog sudo aptitude -y install iptables-persistent  # Need this to fix an issue with the package post-install (this works fine.) sudo sed \     -i 's/\(modprobe -q ip6\?table_filter\)/\1 || true/g' \     /var/lib/dpkg/info/iptables-persistent.postinst; \ sudo aptitude install iptables-persistent


I'm writing a derivation in an upper level physics class and I use derivatives extensively. I'm using the commath package \od{}{} command and they are being sized differently in different places. Also, most of them are too small for my liking.  I previously used physymb before it was deprecated and that didn't have this problem.  Here is part of the code:  \documentclass{article}   \usepackage{nopageno}     \usepackage{amsmath}     \usepackage{commath}     \usepackage{geometry}     \geometry{margin=.75in} \newcommand{\half}{\frac{1}{2}} \title{\vspace{-1cm}Coulomb Scattering from a Fixed Point Charge, aka, Rutherford Scattering} \date{} \author{} \begin{document}     \maketitle     Skipping irrelevant things... From this we can get the equations of motion:  \begin{align} \od{~}{t}\left(\pd{\mathcal{L}}{\dot{r}}\right)&=\pd{\mathcal{L}}{r} & \longrightarrow & &\od{~}{t}&\left(m\dot{r}\right)=mr\dot{\phi}^2+\frac{C}{r^2}\\ \od{~}{t}\left(\pd{\mathcal{L}}{\dot{\phi}}\right)&=\pd{\mathcal{L}}{\phi}   & \longrightarrow & &\od{~}{t}&\left(mr^2\dot{\phi}\right)=0  \end{align} where $C = \frac{Z_1Z_2e^2}{4\pi\epsilon_o}$.  The term $mr^2\dot{\phi}$ is simply the instantaneous angular momentum, and we see from Equation (2) that this is constant: \[mr^2\dot{\phi}=L = mv_ob .\] This yields\[\dot{\phi}=\frac{L}{mr^2}\text{ or }\frac{v_ob}{r^2}.\]  Using this in Equation (1) we can write \begin{equation} \od{~}{t}\left(m\dot{r}\right)=mr\frac{v_o^2b^2}{r^4}+\frac{C}{r^2} \end{equation} At this point, a substitution of variable is appropriate for $r$, so we let $r=\dfrac{1}{u}$. We will see after a bit of work that this helps quite a bit.  First we calculate $\dot{r}=\dfrac{-1}{u^2}\dot{u}$. Then we make use of the chain rule to change from time derivatives to $\phi$ derivatives: \begin{align*} \od{u}{t}&=\od{u}{\phi}\od{\phi}{t}\\ \dot{u}&=\od{u}{\phi}\dot{\phi}\\ \dot{u}&=\od{u}{\phi}v_o b u^2 \end{align*} This gives us $\dot{r}=-v_ob\od{u}{\phi}$.  Using the same chain rule for the time derivative on the left side of Equation (3) we get \[m\od{~}{\phi}\left(-v_ob\od{u}{\phi}\right)\left(v_o b u^2\right)=mv_o^2b^2u^3+Cu^2\] \[-mv_o^2b^2u^2\od[2]{u}{\phi}= mv_o^2b^2u^3+Cu^2\] \[\od[2]{u}{\phi}=-u-\frac{C}{2Eb^2}\] where $E$ is the initial energy given above.       Skipping more irrelevant stuff....      \end{document}   When I compile in pdfLaTeX2e Equations 1 and 2 have small derivatives. Equation 3 does not.  In the last three equations in the last align* environment there is a mixture of big and small.  I prefer the big.  I have tried different fonts (default, tgschola, fouriernc) and also tried the document amsart. No changes in the derivatives. I am using TeXLive on Windows 7.  Please explain why there is a mixture of sizes and how I can easily force the derivative sizes to match the ordinary text.

The commath package use the TeX command \ifinner to select between inline math mode and display math mode. Because of this, it fail to work properly with some display math environments.  In the breqn package, we find:     The test \ifinner is unreliable for distinguishing whether we are in a displayed formula or an inline formula: (...) So we provide a more reliable test. But it might have been provided already by the amsmath package.   The more reliable test should be \if@display but only replace \ifinner with  \if@display in commath.sty not work. Any suggestion?


I am running a new install of Ubuntu 18.10 on Wayland. I recently installed the Polo file manager and it has made itself the default file manager. However I prefer Nautilus to be the default when I plug in a USB-Stick.   How can I make Nautilus the default application for my USB-sticks again?

A while back, I set my default file manager to Nemo. I like it a lot, but it constantly crashes. I remember editing a text file to set it as default, but I forgot which file it was. How do I switch back to the Nautilus file manager?


Is it possible to insert a list of States in Salesforce with the Metadata API?  How? Thank you very much.  Additional Question (02-June-2021@12:11CEST): I have retrieved the XML file containing the list of States/Countries (it is now stored in C:...\TEST1\force-app\main\default*settings*\ The file name is Address.settings-meta.xml I have copied/past this file into another sub-directory where I keep a copy of the code of the "Destination Org called DEV1: ...\DEV1\force-app\main\default*settings*\ I was expecting to be able to deploy the XML file with Visual Studio Code + SFDX CLI but, the deployment is not successful: I get an error without details. Then, I try to deploy the same xml file with Workbench. The deployment is apparently successful BUT when I go to that Org to verify if the States have been deployed... I observe they a have NOT been deployed. Any input that might help me? Thank you.

I'm having problems understanding how to deploy Address.settings with the Metadata API.  As in:  how do I structure the package.xml?    I have this as Address.settings (shortened for brevity)  <?xml version="1.0" encoding="UTF-8"?> <AddressSettings xmlns="http://soap.sforce.com/2006/04/metadata">     <countriesAndStates>         <countries>             <active>true</active>             <integrationValue>Andorra</integrationValue>             <isoCode>AD</isoCode>             <label>Andorra</label>             <orgDefault>false</orgDefault>             <standard>true</standard>             <visible>true</visible>         </countries>         ....         </countriesAndStates>         </AddressSettings>   And this is the package.xml:   <?xml version="1.0" encoding="UTF-8"?> <Package xmlns="http://soap.sforce.com/2006/04/metadata">     <types>         <members>Address</members>         <name>Settings</name>     </types>     <version>42.0</version> </Package>   After zipping this up and deploying through the Metadata API in Workbench I get this error:  The object 'Address' of type Settings was included in the manifest file package.xml but the associated settings metadata is missing from the 'settings' folder   Can you see what is wrong with the package.xml in this case?


I have the usual problem of non-numeric way of citation of Biblatex. Prior to compilation I deleted auxiliary files. When I copied code into Overleaf it compiled correctly. As my IDE I'm using TexStudio. What else could go wrong?  \documentclass{report}   \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage{lmodern} \usepackage[ngerman,english]{babel} %\usepackage[style=numeric-comp]{biblatex} %the same problem with that line \usepackage[backend=biber,style=numeric,sortcites,sorting=nty,backref,natbib,hyperref]{biblatex}  \addbibresource{ref.bib} \begin{document} First citation:  \cite{avron2003topological}  Second citation:   \cite{ozawa2019topological}  Third citation:  \cite{latexcompanion}  \printbibliography[title=References]  \end{document}   EDIT: Additionally I get error:  This is BibTeX, Version 0.99d (MiKTeX 2.9.7140 64-bit) The top-level auxiliary file: document.aux I found no \citation commands---while reading file document.aux I found no \bibdata command---while reading file document.aux I found no \bibstyle command---while reading file document.aux

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


Ive only been introduced to Blender yesterday and have been trawling through the tutorials and loving it, definitely a new fan, albeit still taking very small steps.  I exported a VRML from a GIS application (ArcScene).  I have done little to the scene in Blender, apart from adding some material effects to the ground layer.  What I can't understand is why my final render has a lot of noise in it.  Can someone give me some pointers on how to get a better quality render?  Is it something to do with the render settings or have I missed something on the import/configuration of the scene?

I know that this question is a bit old or maybe overdone, but I'm running the latest edition of Blender and when I use the Cycles engine I get really fuzzy results and I can't find a simple, non-compromising solution to the quality.  I don't know exactly what I'm doing wrong here, but I'm sure others share my frustration.  Leaving everything in default settings, I started a new project and switched to the Cycles render.  I duplicated the cube and set colors for two Diffuse BSDF shaders, then went ahead and made walls and a floor all sharing the same diffuse shader.  I made two windows to emit blue light.  The screenshot has gaps between the walls because of the setup:  I'm aware that it's considered very incomplete and many have come to terms with some amount of noise, but is this normal?  Furthermore, with default settings or not, I can't change the amount of noise produced.  Supposedly, using "progressively refine" in the rendering tab should make it refine itself indefinitely, however Cycles only counts to 10 refines and then stops, creating a render which is a pixel-perfect match of the ordinary rendering method when it's completed.  I understand that there are tricks that can be used to reduce noise, but at the cost of extra processing time and usually small quality conflicts, like blurring.  My question essentially boils down to is this Cycles' current limit?


Context:   Assume I wanted to use RSA as the basis for a hash function or DRBG. Also assume that my construct would be insecure if someone were to have the private key. Is there any way generate the a usable public key to be used such that it is provably just as hard for me to generate the private key as it would be for anyone to do so?  I'm willing to take for granted:   the existence of a suitable source of nothing-up-my-sleeve numbers the availability of significant computational resources.     The best idea I've come up with would depend on the ability to prove a lower bound the the size of the smallest factor in a number (e.g.: an $N$-bit number where all factors are at least of size $N*0.49$-bits) with significantly less work than it takes to actually factor it. (That and the ability to find such numbers.)

It is possible to find an efficient algorithm for constructing a provably hard to factor number $N$, together with a witness that shows that it is indeed hard to factor. EDIT, since it was not clear: I also want to be sure that even the person that constructed the number cannot factor it.  Of course, a random large enough integer is going to be hard to factor with high probability, but we might be unlucky.  There are also multi-party protocols for shared generation of RSA moduli (such as ), but I would like a non interactive technique.  Motivation: This was suggested by Poncho's answer to


I have a database with an calender table that can be filled. Except date, title etc. You can also enter a brief description.  The description is of type: longtext  and Collation: latin1_swedisch_ci  When people use the form on the website (using text with ë, ä, ü etc) it all gets put into the database without a problem.  But when I try to get the data out of the DB to edit or to show, it doesnt show up. This is because of the special chars.  My website uses charset=iso-8859-1.  I tried to convert the column and the webpage to UTF-8 but nothing works. The Data either doesn't show, or breaks where the special is supposed to be.  Anyone has an idea how I can solve this??

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


Prove that for every positive integer $n$, $38^n+31$ is a composite number. for example $38+31=69$ is composite. $38^2+31=1475$ is also composite. I have tried modulo but it didn't work.

I search the least n such that   $$38^n+31$$   is prime.   I checked the $n$ upto $3000$ and found none, so the least prime of that form must have more than $4000$ digits. I am content with a probable prime, it need not be a proven prime.


Following this tutorial     and trying to use the command  echo 'prefix=/usr/local' > node/etc/npmrc   however I get a permission denied error, even when using sudo.  Any ideas?

I've been given sudo access on one of our development RedHat linux boxes, and I seem to find myself quite often needing to redirect output to a location I don't normally have write access to.  The trouble is, this contrived example doesn't work:  sudo ls -hal /root/ > /root/test.out   I just receive the response:  -bash: /root/test.out: Permission denied   How can I get this to work?


I am currently using the very arbitrary TES1-4902 to cool water (small amounts) using a 5V 2.4A USB Battery Pack (2 Peltiers TES1-4902, 2 5V 2.4 A USB Battery Packs = 5V 4.8A)    Recently, it has come to my attention that a different Peltier setup may be able to increase my efficiency, thus giving me more "bang for my buck".    The current situation that I am in is that I need to achieve the maximum cooling power to cool small amounts of water as quick as possible; however, I need to reduce power consumption so that instead of buying two 5v 2.4A USB battery packs I can buy 1, 3.4 A USB battery pack to support my project and thus reduce my price.   I know that the more power you put into a peltier, the cooler it gets, so less power is counter-intuitive: so I will split my question into two parts:   1) Is there a more efficient Peltier (where the rated IMAX/VMAX/DT is more efficient than what I have) that runs on a 5V 2.4A batterry, that takes into account more power is needed to start the Peltier than to run it continuously?    How about a 5v 4.8A  battery?   2) Using a 3.4 AMP, 5V USB Battery pack, is there any way I can achieve a similar cooling effect than what I currently have (TES1-4902, 5V 4.8A (2 of them)? by using a more efficient peltier?    Thank you so much, while someone answers me I am learning how to read data sheets more efficiently; however, so many of you are much more knowledgeable than me I thought it may be useful to ask you guys who have been so helpful in the past.   Thanks!!!

I am trying to achieve the strongest cooling effect using a TEC Peltier element.    Currently, my set up is two small, 20mm x 20mm peltier TES1-4902 run with a 5V 2.4A USB Battery Pack per peltier.   I need a way to reduce my costs while keeping the same cooling power.   Right now, it is expensive for me to run this set up due to the fact I need two batteries, and I am also looking to improve my efficiency while cutting out an entire battery and/or Peltier. The reason I have two separate battery packs is that I can not find a cheap, small, and thin battery pack that will output 4.8 Amps: however, putting two battery packs in a series may help eliminate one peltier.     So, I have a few branching question that center around a theme:  1) Would a larger Peltier allow for a stronger cooling effect as a result of a larger surface area, say like a 50MM x 50MM peltier, despite the fact (presumably) that it may be more difficult to cool one single peltier than 2 smaller, seperate ones?   2) Is there a Peltier size that would allow me to reduce my power consumption while maintaining a similar cooling effect?   3) Is there a way that I can output 5V 4.8A that is not in two separate USB battery packs that is small and relatively cheap, as battery price:output ability for small scale consumer is quite high and USB battery packs have been the cheapest source of sustainable power for me.    My problem stems from the fact that I am trying to pump as much power and achieve as much cooling power as possible without having to have, say, two battery packs and make the project too expensive. I need a way to reduce my costs while keeping the same cooling power.


Is it possible to draw a diagram of this image, which is very simple:

Recently I have learned how to draw simple stuff with TikZ. I really like it. Now I wonder if it is possible to draw with TikZ on a image. Instead of pasting a image in Illustrator and adding some vectors to point something in the picture I would like to do it using TikZ. Is it possible?   For example, on a picture of a computer (PNG,etc) I would like to draw some arrows and labels saying "Keyboard", "Monitor", etc.


I have a quite a interesting problem regarding table primary key when inserting new rows to Postgres DB using Hasura. In a short summary this is what happened: There was old backend for the app that I am currently developing which used MySql database and my task was to move all of data to new Hasura/Postgress DB, so i wrote scripts that move that data and it went fine. Script inserted all of the users data including their primary keys because of user relationship with other tables. Problem occurred when i tried to insert new users with Hasura mutation:  Uniqueness violation. duplicate key value violates unique constraint "users_pkey"  What I assume happened is: My PK on users is not default type integer/auto-increment , it is:  id - integer, primary key, unique, default: nextval('users_id_seq'::regclass)  and when i try to insert new row it tries to assign it latest PK that Hasura remembers it inserted and user with that PK is already imported from MySql DB. Is there some way to edit my table PK so it is integer/auto-increment or someone has some creative solution. Thanks in advance!

I ran into the problem that my primary key sequence is not in sync with my table rows.   That is, when I insert a new row I get a duplicate key error because the sequence implied in the serial datatype returns a number that already exists.  It seems to be caused by import/restores not maintaining the sequence properly.


Do VAR and VEC require no unit-roots? I have three variables where two are difference-stationary (unit roots) and one is trend-stationary (no unit root). The three of them are cointegrated.   Questions:   1) Can I conduct VEC in the presence of unit-roots? 2) If yes, should I difference my variables to make them stationary? 3) Should I be conducting the Johansen test on differenced variables?

I have 4 time series. One of them is stationary and rest of them are not. I need to find relation between them. I will use AIC to decide lag length.   Should I use VAR or VECM to find relation between them?  Will VAR or VECM give me relation in terms of equation which can be used for forecasting?  Do I need to perform Johansen's test of cointegration?  What good would it do?


Jen’s dog broke her six inch long pencil off at a random point on the pencil. Find the density function and the expected value of the ratio of the shorter piece and the longer piece.  $X$ is longer piece and $Y$ is smaller  $U \sim U(0,6)$  Define $X = \text{max}\{U, 6-U\}$  so that  $$X = \begin{cases} 6-U,  & 0 < U < 3 \\ U, & 3 \leq U < 6 \end{cases} $$  It follows that  $$X = \frac{6 + |2U - 6|}{2}$$   Similarly  $$Y = \frac{6 - |6-2U|}{2}$$   Let $Z=Y/X$  $$F_Z(z) = P (Z \leq z)$$  $$=P\left(\frac{6 + |2U - 6|}{6 - |6-2U|} \leq z \right)$$  I don't know what to do next

A uniform random number X divides [0, 1] into two segments. Let R be the ratio of the smaller versus the larger segment. How do I compute the density of R?


I have a file containing a list of users and information, each line is a separate user written like so:   alfred,butler,male,70,7:15.    I want to grab the names only from the list so I can create a user for them.   Once I have the names I can simply use a for loop and echo useradd with each of the usernames then simply copy and paste the text. How do I approach grabbing the characters before the first comma?

Is it possible to import users by using CSV file? or something like a LDAP connection to import all users?


My laptop configuration: Windows 7 - 32 bit - Intel Pentium 2.1 Ghz Dual Core - 2 GB RAM - 320GB HDD (for software development and also for practice).

For a given hardware configuration, how do I find out if Ubuntu will run on it? What considerations should I take into account when choosing an Ubuntu version and  such as:    with a lighter desktop than the usual Gnome and Unity  with the even lighter LXDE desktop   Obviously Ubuntu does not run on some processor architectures. So how do I go about choosing the right version and derivate. How can I find out the minmal system requirements?


I would like to download both Ubuntu and GIMP to install on a computer with no internet connectivity. I presume simply downloading Ubuntu and burning an ISO disk will take care of the former.   However, GIMP directs me to , and the emailed download link from there takes me back to : I cannot find anything on that page that would permit me to download GIMP for Ubuntu.    Walton

I have a friend who has got a computer that is not connected to the Internet. Is there any way to install software offline easily?


This might be a bit of a weird question and usually easily solvable, but company restrictions prevent me from doing this the easy way, so please bear with me.  In my office work-space I've been assigned a mouse to work with. This mouse unfortunately is slightly defective. Defective enough to be highly annoying but not defective enough to pass for a replacement. The main problem is:  Sometimes when I single-click, the mouse sends 2 clicks in a row, resulting in a double-click  This is highly annoying, for example it has caused me to close 2 windows instead of just the one I want multiple times. And as a programmer, when I want to place the cursor at a specific point in my code I accidentally select the whole line and start overwriting what I made before.  Of course I've consulted  for this. Step 1:     Verify your clicking method: Make sure that you are performing a true single physical click. A single-click occurs when you press and release a mouse button one time.   Well... Microsoft doesn't take my complaint very serious it seems. The article basically ends with me having to turn the mouse off and on again.  So I tried messing with the double-click speed settings in windows. But the only thing it really changes is the maximum delay between clicks for it to register a double-click. This doesn't solve my problem at all because the speed at witch these inputs are send are close to a few millisecond. And I still want to actually double-click when I want to.  I can only see 2 options that would fix my dilemma (and I prefer the latter):   Physically break the mouse - If my mouse literally doesn't work anymore, I can get a replacement, hopefully by the end of this day, probably by the end of the week. Find a way to force a time delay between clicks to register as a double-click - the problem is caused by inputs that are being send a few milliseconds in a row. A human is pretty much physically restricted to having a clicking delay of about 100 milliseconds, if I can somehow filter out these false positives by enforcing a - let's say - 50 millisecond delay required before I can click again for a double click, that would solve my problem. In theory.

This is the second mouse dying on me because of a poor switch ! Under most operating systems there is a option to set the max time interval in which two mouse clicks are processed as on double click.  Logically there has to be a way to set a minimum double click time interval!  I surely could replace the broken switch but there are costs for the new switch, time and basic soldering needed for that. Obviously this should be the last possible step to take.  Firstly I want to try to let the computer handle the broken mouse. I am searching a fix for windows and especially for linux (ubuntu) systems.  E: as Matt Eckert mentioned the problem is that the mouse switch is gotten loose and is producing two signals with just one key press. I've never mentioned that I want to set up anything within th mouse. Sorry for the misunderstanding, I thought that this problem occurs very often so that everyone understands the problem with the give information.  Under Windows there is only the option to set the maximum time interval in in which a double click is recognized. I need to set up the minimum time interval. In other word a double click should only be recognized if the time difference between two mouse clicks is at least for example half of a millisecond.


Take a look at this document:  \documentclass[twoside]{article}  % For blind text \usepackage[english]{babel} \usepackage{blindtext}  % To make sections begin on new page \usepackage{titlesec} % Command for new sections beginning on new page \newcommand{\sectionbreak}{\clearpage}  % Headers \usepackage{fancyhdr} \pagestyle{fancy} \fancyhf{} % Header on top right on odd pages \fancyhead[OR]{{\textsc{\leftmark}}\quad\quad\thepage} % Reader on top left on even pages \fancyhead[EL]{\thepage\quad\quad{\textsc{\leftmark}}} \renewcommand{\sectionmark}[1]{\markboth{#1}{}}  % Otherwise colors won't work! \usepackage[usenames,dvipsnames,svgnames,table]{xcolor}  \begin{document}  \section{Section 1} \blindtext[2]  \section{Section 2} \blindtext[2]  \section{Section 3} \blindtext[2]  \section{Section 4} \blindtext[2]  \end{document}   Nice, no? But how boooorrrriiing. No color, no nothing. This hasn't had Carliste's magic touch yet. But fortunately, LaTeX supports color, and I'll use them!  Now, there are some ways to change the  according to the section number. However, I want to do something similar, but different: I want to change the color of the header according to the section number, with my own custom colors. Oh, this changes everything.  So, what did I try? I using a nested ifthenelse statement to get the wanted result. I also tried pulling my hair out and browsing answers for hours. But back to the ifthenelse statement – I really don't get why this doesn't work:  \documentclass[twoside]{article}  % For blind text \usepackage[english]{babel} \usepackage{blindtext,ifthen}  % To make sections begin on new page \usepackage{titlesec} % Command for new sections beginning on new page \newcommand{\sectionbreak}{\clearpage}  % Headers \usepackage{fancyhdr} \pagestyle{fancy} \fancyhf{} % yum yum yum \ifthenelse{\equal{\thesection}{1}}{\fancyhead[OR]{\textcolor{red}{{\textsc{\leftmark}}\quad\quad\thepage}}}{\fancyhead[OR]{\textcolor{blue}{{\textsc{\leftmark}}\quad\quad\thepage}}} % Reader on top left on even pages \fancyhead[EL]{\thepage\quad\quad{\textsc{\leftmark}}} \renewcommand{\sectionmark}[1]{\markboth{#1}{}}  % Otherwise colors won't work! \usepackage[usenames,dvipsnames,svgnames,table]{xcolor}  \begin{document}  \section{Section 1} \blindtext[2]  \section{Section 2} \blindtext[2]  \section{Section 3} \blindtext[2]  \section{Section 4} \blindtext[2]  \end{document}   This technically should make the first page header red and the second page header blue, but I think the engine has short-term memory loss (or maybe I'm not using it correctly – this is more likely the correct answer, but I don't want to admit it) but it's all blue, as if it doesn't heed or notice my meticulously crafted ifthenelse statement, which would have been much, much more intricate had it responded to me the first time (i.e. with the example above).   Now I need some help, which preferably doesn't involve the use of xcolor's color series (I mean, it's almost what I want, but unfortunately you're only able to choose the first and last color manually – every other color in between is a user-defined gradation between the first and the last one. Unfortunately this gradation has a mathematical basis and can't be manipulated into using just any random color which satisfies human want (as far as I can tell, anyway).  Also, maybe sometime in the future I would like to expand this to subsections, but I think I'll be able to figure out that bit by myself if I get a proper header with this question :) thanks :)

I'm trying to make a document with multiple "themes." This involves changing the color of the headers, section names, and headers based on what the current section is. The colors I want to use are custom colors.  Now, I know how to make this the same for the whole document, but I was trying to find a way that would automatically change it automatically depending on the current section value. I thought that it would be really easy with the ifthen package, as it seemed to be made for this (I could see if the section was equal to a value). However, it did not go as expected. I have a MWE below. Here I changed only the subsection name for clarity. I tried to make the subsections of Section One red and the subsections of Section Two blue. However, it seems like everything is blue. I did something similar for the header, but didn't go anywhere. Could anyone kindly point me in the right direction with this?  \documentclass[twoside]{article}  % For blind text \usepackage[english]{babel} \usepackage{blindtext}  % Here begins my attempt \usepackage{ifthen} \usepackage{titlesec} % Coloring the section names (didn't mess with this, but I am using this as the basis of coloring the section and subsection names) \titleformat{\section}{\LARGE\normalfont\center\color{blue}}{\thesection}{1em}{} % My attempted ifthenelse statement. I put the if, then, and else arguments on different lines for clarity \ifthenelse {\equal{\thesection}{Section One}} {\titleformat{\subsection}{\Large\normalfont\color{red}}{\thesubsection}{1em}{}} {\titleformat{\subsection}{\Large\normalfont\color{blue}}{\thesubsection}{1em}{}} % Sections begin on new page \newcommand{\sectionbreak}{\clearpage}  % For headers \usepackage{fancyhdr} \pagestyle{fancy} \fancyhf{} \fancyhead[OR]{{\textsc{\leftmark}}\quad\quad\thepage} \fancyhead[EL]{\thepage\quad\quad{\textsc{\leftmark}}} \renewcommand{\sectionmark}[1]{\markboth{#1}{}}  % For colors \usepackage[usenames,dvipsnames,svgnames,table]{xcolor}  \begin{document}  \section{Section One}  \subsection{Subsection One} \blindtext[5]  \subsection{Subsection Two} \blindtext[5]  \section{Section Two}  \subsection{Subsection One} \blindtext[5]  \subsection{Subsection Two} \blindtext[5]  \end{document}


Iam using STM32F401 microcontroller to drivie mosfets for bidirectional current control for safe charging and discharging operation of a Battery pack.  My microcontroller maximum PWM output to drive mosfets are 3.3v . i would like to amplify 3.3v to 10v to drive the mosfets with low Rds for power consumption.  So when i search in internet i came up with two results to amplify 3.3v to 10v . one is NPN transistor common emitter configuration. another is DC-DC boost converter.  I would like to know which is the best method to amplify 3.3 v to 10 v to drive Mosfets.  My Circuit:   In the above circuit i have used NPN transistor just for an understanding and completion of the circuit.  but I would like to know which method is best and efficient to use DC-DC boost converter or NPN Transistor

I have basic knowledge about NPN transistors and I know how they work: for current gain based on the small input current in the base we are able to drive large amount of current in between collector and emitter.   In my circuit I need to amplify 3.3V of my stm32 micro controller input to 10 V output to drive a Mosfet switch.  I want to give 10V input to the gate of the MOSFET to get very low Rds. I am using STM32 micro controller for controlling. Its maximum output voltage is 3.3V but I need 10V so I planned to use an NPN transistor in common emitter configuration so that I can amplify 3.3V to 10V and then I can give that to the gate of the MOSFET.  I understood that the amount of voltage we give in input to the base we will get as large voltage between collector and emitter based on the resistors. I also understood the voltage gain based on Rc and RE for example if Rc = 1k and Re = 100 ohm the gain is 10. But I cant understand how to choose a resistor and how much current should I use how much current to amplify to amplify the voltage, and how much voltage to give to get 10V as output. How this entire thing works based on voltage amplification based on my circuit.    I have searched on google but I can't 100% understand it.


Almost every time when I'm shutting down or rebooting the system I get the following message before the system actually shuts down:  A stop job is running for Session 1 of user xy   It waits for 1:30min and then continues with the shutdown. I'm using Debian stretch with Gnome 3. This message does not appear in the syslog.  Any ideas?

The following message appears almost every time I shutdown my computer:  A stop job is running for Session c2 of user ... (1min 30s)   It waits for 1min30s then continues the shutdown process. I follow  and get the  (I can't paste directly the log here because it's very long). Unfortunately, I don't understand the log by myself. Could anyone help me to find out what makes my system doesn't shutdown properly?  I run Arch Linux with kernel 4.4.5-1-ARCH, my systemd version is 229-3.  Addition 1: I observe that every time I logout, and then shutdown my computer from the login screen, it doesn't get the message A stop job is running.... I tried to logout before shutdown for many times, so I think it doesn't occur by chance. Hope that information could help.  Addition 2: It is always session c2 that causes shutdown hanging. So as @n.st suggest, I looked at  again and stored loginctl session-status c2 instead of dmesg, but then there is nothing on the shutdown-log.txt. I replaced loginctl session-status c2 by systemd-cgls and got the following log:  Control group /: -.slice └─init.scope   ├─   1 /usr/lib/systemd/systemd-shutdown reboot --log-level 6 --log-target ...   ├─1069 /usr/lib/systemd/systemd-shutdown reboot --log-level 6 --log-target ...   ├─1071 /bin/sh /usr/lib/systemd/system-shutdown/debug.sh reboot   └─1074 systemd-cgls   Any ideas?  Note: After I updated to kernel 4.6.4-1-ARCH and systemd 230-7, the error no longer happened.


I am currently working on a paper and using overleaf online editor to write it. Problem is, that I am not able to put and between name of two authors and it is limited to those cases where the paper that I'm citing has only two authors and works for other cases. Here is a sample  bibtex:  @article{nikora2004water,   title={Water-worked gravel surfaces: High-order structure functions at the particle scale},   author={Nikora, Vladimir, and Walsh, Jeremy},   journal={Water Resources Research},   volume={40},   number={12},   year={2004},   publisher={Wiley Online Library} }   I have tried following variations:  author={Nikora, Vladimir, and Walsh, Jeremy}, author={Nikora, Vladimir and, Walsh, Jeremy}, author={Nikora, Vladimir and Walsh, Jeremy}, author={Nikora, Vladimir and Walsh, Jeremy},   and none of them work. Here is the sample output of what happens:     My desired output is to see V. Nikora and J. Walsh and I am not able to get there. I have to mentioned that I've tried using \usepackage{natbib} which did not fix anything as well.

How to correctly display and to separate among the BibLaTeX's author's names?  Code:  @book{atl1,     label     = {SELLS},     author    = {Cristopher TAVARES, Kirk FERTITTA, Brent RECTOR, Chris SELLS},     title     = {ATL Internals},     subtitle  = {Working with ATL 8},     edition   = {2},     publisher = {Addison-Wesley Professional},     date      = {2006-07-15},     pages     = {888}     }   Output:    In this case I'm trying to display this as Cristopher TAVARES, Kirk FERTITTA, Brent RECTOR and Chris SELLS before ATL Internals....  How do I to deal with this, please?  Thanks a lot!


I have a 1.8TB Production database in my test environment on a 2TB drive. Currently there is only 1 .MDF and 1 .LDF (on a separate drive).  The Database has had some major cleanup of unused indexes, Archived tables, and de-fragmented.  The actual data size being used is now only 300GB (after an SP_Spaceused) of the 1.8TB container.    I have tried multiple DBCC Shrinkfiles (larger and smaller Target sizes varying from 100MB to 2GB) without success.  The job never fails, but after 22 hours of running (at multiple attempts of sizes) I stopped the job.  No errors, Database is in simple recovery mode, drives are not full, nothing in windows or SQL error logs.  I've also tried the Truncate option that finishes successfully, but no space is released.  Why do I want to shrink you might ask?  I want to migrate from 1.mdf to (1.mdf + 3.ndf) data files for improved performance (on a RAID 10 set of Drives).  I don't have enough disk space on my 2TB drive now to do it all on the same RAID Set.    My thoughts were, shrinkfile (truncate) or Shrinkfile Target in smaller increments.  The truncate completes successfully and SQL thought the minimum size would be around 300GB.  Unfortunately, the DB only shrunk to 1.2TB initially and I believe there is more unused space that could be freed.  Its like there is some kind of Ghost record or row that cannot be moved in order to reclaim that unused space.  I did run Integrity Checks with physical, indexes and data purity which reported no errors.  I can shrink other databases on the same server without any troubles...just this one that is giving me trouble.  Has anyone Run into this?

Verbose logging was accidentally left on for one of our database ballooning our database MDF file from roughly 90GB to 192GB.  We've disabled verbose logging, truncated the logging table but now we want to shrink the MDF file to reclaim disk space as the drive the MDF file is on is only around 200GB. I don't have the luxury of increasing its size. Our disk space monitoring tool is alerting me that drive space is less than 8% over and over and over.  Given this is the first instance this has ever happened, we don't expect to ever need that extra 102GB of disk space again. We'd like to reclaim it.   I've tried to use the GUI to shrink the database and the files but it doesn't actually change in size. I've also tried using DBCC SHRINKFILE and DBCC ShrinkDatabase with NoTruncate and TruncateOnly. No matter what I do the file doesn't seem to budge.  One potential issue is that somehow the database initial size is 188GB. Deleting and re-creating the database isn't a very practical option for us so how can I shrink the MDF file and reclaim our disk space?  Running dbcc shrinkfile('My_Data'), I get the following results:  DBID: 5  Field: 1 CurrentSize:24030464 MinimumSize: 128 UsedPages: 17770472 EstimatedPages: 17770472   The database MDF file is still the same size (192,243,712 KB).  The table has a clustered index:  Name:TRACES ObjectID: 394588594 Type: Clustered Index/b-tree   The query:  SELECT     name,     size/128.0 - CAST(FILEPROPERTY(name, 'SpaceUsed') AS int)/128.0 AS AvailableSpaceInMB FROM sys.database_files   ...for the database I am trying to shrink, returns:  Name: My_Data AvailableSpaceInMB: 48693.375000 Name: My_Log  AvailableSpaceInMB: 67028.437500   I've also tried shrinking in small chunks using a PowerShell script that shrinks in 20MB increments. That also doesn't change the size of the MDF file.  I've tried dbcc shrinkfile(My_Data) without any other options from SQL Management Studio. It runs for a long time, finishes, and the MDF file is still the same size. Specifying a target size, it runs for a good 30-40 minutes (finishes) and nothing changes file size wise.  I ran this: DBCC SHRINKFILE (N'My_Data' , 139045) and get the following results:  DbId: 5 Field: 1 CurrentSize: 24030464 MinimumSize: 128 UsedPages: 17808744 EstimatedPages: 17808744


Is it possible to use an application page, residing in the _layouts folder, as the default Welcome page of SharePoint?  According to the  property, only Site Pages can be used as the welcome page. A hack around would be to create a dummy ghostable Site Page, that basically redirects to the application page that I want to display as the welcome page. However, I wanted to avoid this, as I don't really need a Site Page for this particular scenario.

So basically when someone goes to:   http://mysite.com   I would like to show an Application Page that I have created, without the giant URL.  Example of the giant URL :  http://mysite.com/_layouts/ap/myAppPage.aspx   Is there any way for me to do this?


If I search in the internet, I find "hypothesis" is a singular word as I see "is" after it. But I found the following line in the book "Naked Statistics: Stripping the Dread from the Data" by Charles Wheelan (in CHAPTER 9) -  if the null hypothesis were true and this were really a bus full of Changing Lives passengers;  Why "were" is used after "hypothesis"? Should not it be "hypothesis was true"?

Which of these sentences is correct, and why?   "What if the Moon was a Disco ball?" or  "What if the Moon were a Disco ball?"


I am working on a class that inherits from OutputFormatter.  In my WriteResponseBodyAsync method I take in a OutputFormatterWriteContext context and need to call a method that takes an IEnumerable<T> objects as a parameter.  I'm using a third party library that has a method like this -   public SerializedData Serialize<T>(IEnumerable<T> someObject){...}   My WriteResponseBodyAsync method is like this -   public override Task WriteResponseBodyAsync(OutputFormatterWriteContext context)  {      // need to make a call like the below,      // but of course, this won't compile because context.Object is not an IEnumerable<T>.      var serializedData = ThirdParyLibrary.Serialize(context.Object);       return Task.FromResult(serializedData);  }   I don't know how to go from the context.Object the IEnumberable<T> objects. I have tried a few variations of context.Object.GetType() and GetGenericTypeDefinition() and MakeGenericType(..) but none of these help.   Is there way to do something like -   var myType = context.Object.GetType().GetGenericArguments()[0]; //this gets the type inside the enumerable I want to return. IEnumerable<myType> typedObjects = (IEnumerable<myType>) context.Object;

What's the best way to call a generic method when the type parameter isn't known at compile time, but instead is obtained dynamically at runtime?  Consider the following sample code - inside the Example() method, what's the most concise way to invoke GenericMethod<T>() using the Type stored in the myType variable?  public class Sample {     public void Example(string typeName)     {         Type myType = FindType(typeName);          // What goes here to call GenericMethod<T>()?         GenericMethod<myType>(); // This doesn't work          // What changes to call StaticMethod<T>()?         Sample.StaticMethod<myType>(); // This also doesn't work     }      public void GenericMethod<T>()     {         // ...     }      public static void StaticMethod<T>()     {         //...     } }


As you can see in the screenshot, there's a huge gap between sites in the Your Sites list in the app.  Steps to reproduce:   Swipe right from the left edge on the initial screen. Tap the EDIT button. Look at the list.   I'm on a Samsung Galaxy S7 running the Stack Exchange app (version 1.0.89) on Android 7.0 (though this issue has been around for a while; I just forgot to report it :/). I don't own any other devices to test it on. The issue occurs every time I look at the list.

There is some unwanted extra spaces in between each site in the Your Sites section.  Steps to reproduce:   Touch the Nav Icon in the left top corner Touch the EDIT link in YOUR SITES Scroll the screen; there is unwanted spaces in between the each site   For reference I recorded the same:    Configurations:   App Version: 1.0.85 Device Manufacturer: Motorola Device Model: XT1033 OS Version: 5.1 (2)


as you can guess I'm a non-native english. When I write an scientific paper, my major trouble is the language and I'm worried about the review of my english. There are any website or community, where I can post my full paper or part of it, and receive a peer review for my english? Thanks a lot.

As a non-native speaker of English, it can often be hard to spot some of the errors that a native speaker would find. For a long time, I've been thinking about getting a native speaker to help me with proof-reading my texts (articles, theses, application, etc), but I don't quite know where to look. What are some good ways to get proofreading for your texts?  For example, are there any websites on the Internet where one can exchange proofreading services between different languages? (Say, if you help me proofread my text in language x, I'll help you with yours in language y.)


which is correct: a) she didn't mind a mild storm when the rest of her family were present  b) she didn't mind a mild storm when the rest of her family was present

I hope you can enlighten me. I get varying answers in Google and I need to find out which is the correct grammatical structure for these sentences.     The rest of the staff is/are on leave at the moment.      The rest of my family is/are arriving late.


In the question  Anthony's  notes that:      Families like the Malfoys were more than willing to serve Lord Voldemort, whose father was a Muggle (not even a Muggle-born wizard).   In the books was there ever any indication that the Malfoys, or any of Voldemort's most loyal followers, were aware of his half-blood status?  I believe Voldemort went to great lengths to hide that information from others. I'm not even sure Snape was aware, though Dumbledore, Harry, Hermione, and Ron knew through their hunting of the Horcruxes.

Canon seems to conflict a bit on whether Voldemort's Death Eaters knew that Voldemort was a half-blood. In Half-Blood Prince, Tom Riddle refers negatively to his parentage and it reads as if his fellow Slytherins found it amusing in a derisive way, even though Salazar Slytherin was the ancestor of Tom Riddle (HBP - chapter 23 - Horcruxes). In Order of the Phoenix, during the fight in the Department of Mysteries, Harry taunts Bellatrix Lestrange and Lucius Malfoy with the fact that Voldemort is a half-blood, which seems to enrage Bellatrix in particular (OOTP - chapter 35 - Beyond the Veil).   Did the Death Eaters actually know Voldemort was a half-blood?  I would prefer a canon-based answer. JKR and Pottermore are fine.


I'm working on something that requires some very simple arithmetic, but some of the results that come up are just mind-boggling.  For example, paste the following in Chrome / Firefox / Opera DevTools console:  (211.8 - 0.5) + 0.8   The result should be 212.1.... but I keep getting 212.10000000000002  Although I can work around it using toFixed() or Math.ceil() etc. I would like to know what causes things like that to happen.  I may have passed it off as a JSVM bug on a particular JS runtime, but it happens on multiple JS engines.  Any JS / JSVM gurus care to enlighten me?

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


Hi everyone here is my question;  So, let $a$ and $b$ be positive integers. Prove that $(a,b)|[a,b]$. Here what I have so far;  $(a,b)=d$  $[a,b]=m$ so I need an equation of the form $m=d()$. I just need some hints on how to proceed.  Thank you so much in advance.

Show that the following conditions are equivalent:  i) There exist positive integers $a, b$ such that $\gcd(a,b)=d$ and $\operatorname{lcm}(a,b)=m$.  ii) $d\mid m$


I'm creating a simple program in which the user tries to guess whether a "flipped coin" is heads or tails. I've written two variables:   var coin = ["heads", "tails"];  var random = coin[Math.floor(Math.random()*coin.length)];   A function called "runGame" was created to determine if the user input was equal to the random index:   function runGame() {   var input = document.getElementById('choose').value;    if (input === random) {     youWin();   }   else {     youLose();   }   createReset();   console.log(random); }   The createReset function is called (which basically generates a reset button)  and if clicked that calls another function called resetGame:    function resetGame() {   //generate new random index    //enable 'click to flip' button   button.disabled = false;   //paragraph tag resets to default   para.innerHTML = "";   para.classList.remove("class-win");   para.classList.remove("class-lose");   //delete 'click to reset' button   document.body.removeChild(resetButton);   //clear input   Everything works but I've yet to figure out to have the "random" variable generate a new index. (i.e the first time, random = "heads", after reset, random = tails). Basically, how would I approach this? I've tried reinserting var random = coin[Math.floor(Math.random()*coin.length)]; inside this function which DOES choose a new random index (verified through printing it out in console) but input ALWAYS equals the initial index, regardless of what the new index is.   Here is the entire code:
Heads or Tails?
  Enter "heads" or "tails":
 <input type="text" id="choose" value="">

 <button type="button" name="button">Click to Flip!</button>

     var coin = ["heads", "tails"]; var random = coin[Math.floor(Math.random()*coin.length)];  var para = document.querySelector("#result"); var button = document.querySelector("button");  //create reset button var resetButton = document.createElement("button"); var text = document.createTextNode("Click to Reset") //*****************  button.addEventListener('click', runGame); resetButton.addEventListener('click', resetGame);  function runGame() {   var input = document.getElementById('choose').value;    if (input === random) {     youWin();   }   else {     youLose();   }   createReset();   console.log(random); }  function resetGame() {   //generate new random index   var random = coin[Math.floor(Math.random()*coin.length)];   console.log("NEW INDEX: " + random);   //enable 'click to flip' button   button.disabled = false;   //paragraph tag resets to default   para.innerHTML = "";   para.classList.remove("class-win");   para.classList.remove("class-lose");   //delete 'click to reset' button   document.body.removeChild(resetButton);   //clear input  }  //functions within runGame  function youWin() {   para.innerHTML = "You Win!";   para.classList.add("class-win"); }  function youLose() {   para.innerHTML = "Wrong! The answer is " + random;   para.classList.add("class-lose"); }  function createReset() {   resetButton.appendChild(text);   document.body.appendChild(resetButton);   button.disabled = true; }     P.S. I also have trouble figuring out how to clear the input text value. "Input" is a variable defined in a function and I can't access that variable in the reset function.

What is the scope of variables in javascript? Do they have the same scope inside as opposed to outside a function? Or does it even matter? Also, where are the variables stored if they are defined globally?


I've been wracking my brain trying to remember a word for a try-hard, pleb artist! It starts with a "d", if I remember correctly, and I'm sorry if the details aren't enough and such. You know, even the definition of this supposed "d" word I can't remember, I'm also quite hazy with. Though I think the general gist of it is mildly derogatory but in a "stating the facts" kinda way. An artist that can't be great or masquerading to be great or something... Starts with a "d" I think... Oof! Any suggestions? Answers?

I've come across this word before. It's not "hypocrite". But the definition of the word was very specific. Basically it's an adjective, it's something you call a person who's really into art; like for example movies and film making.   He keeps talking about it, loves Stanley Kubrick or Jean Luc Godard. He studies the craft and technique, and he criticizes his colleagues' films. He thinks his taste is superior, and that if he given a chance, he would shake the industry. But in reality, he doesn't practice it. He's all talk, but no walk.   What do you call that person? (It also applies to other art forms like music. - "Our local musician sucks. He just does covers of John Mayer and Jason Mraz songs. That's why our music industry doesn't progress because of people like him. I listen to David Bowie and The Beatles, if I knew how to play a guitar, I would totally rock it out". ... )


Let $W$ be a subspace of the finite-dimensional vector space $V$. Show that there is a subspace $U$ of $V$ such that $V \cong U \oplus W$  I understand that by saying $V$ is finite-dimensional means that both $U$ and $W$ are finite-dimensional as well.   I also understand that it is asking to prove that there is a $U \subset V$ such that $V$ is isomorphic to the direct sum of its subspaces $U$ and $W$. To be isomorphic it must be both injective and surjective.  I guess I'm getting confused on how to actually prove the isomorphism given the information. Is this the same as proving $V = U \oplus W$ or does the $\cong$ make a difference? How does one go about proving this?

I want to see if my proof is true or I thought very trivially?    If $H$ is a subspace of a finite dimensional vector space $V$, show there is a subspace $K$ such that $H\cap K=0$ and $H+K=V$    So far I have tried :    $H\subseteq V$ is a subspace $\Rightarrow\,\exists\;K=(V-H)\subseteq V$ $K$ is a subspace because it's the sum of two subspace $V$ and $(-H)$ Now we should prove that $H\cap K=0$ We assume $H\cap K\neq0\Rightarrow\exists\,\vec u\neq0\,,\,\vec u\in H\cap K$ $\vec u\in H\cap K\Rightarrow \begin{cases}\vec u\in H\\\vec u\in K\,\Rightarrow\vec u\in V-H\Rightarrow\vec u\in V,\,\vec u\notin H\end{cases}$ That's a contradiction so our hypothesis was wrong and $\vec u=0$


I want to learn how to use crontab. I see there are two manual pages:   crontab(1)  crontab(5)   Why are there 2 manual pages? What are the differences between them? Do I need to study both in order to use crontab, or is one authoritative?

So, for example, when I type man ls I see LS(1). But if I type man apachectl I see APACHECTL(8) and if I type man cd I end up with cd(n).  I'm wondering what the significance of the numbers in the parentheses are, if they have any.


is there any way to backup as ISO of my current Ubuntu OS with all installed data like SUPER OS. Or, anyway to make like live ISO from my installed Ubuntu with apps, that i will installed it later with installed data,apps etc in my PC or someone else.  If there any solution please reply. Thanks

I would like to customize Ubuntu live CD by installing some additional packages. I have followed   but it doesn't seems to work. Can anyone provide clear instructions?   Note: I do not prefer Remastersys, manual way will be appreciated.  Customization  Packages that I want to install:   Thunderbird    Samba    SSH       Changes that I need:   Remove Games menu from the Application menu Firefox shortcut on Desktop Radiance as the default Theme Different default Ubuntu Wallpaper   Configuration file changes   I want the panel to be placed at the bottom I want to paste my Samba configuration file instead of default Samba configuration I have few Firefox shortcuts and folders I would like to show that in Desktop Also it will be nice if you say me how to change the icon sets   Recent Updates   I have customized Ubuntu 10.10 with Firefox shortcuts and few folders on desktops. Everything went smooth. But the installer gets crashes after choosing the timezone. How do i fix this issue? Also setting wallpaper affects the login screen. The wallpaper which i set is displayed on the login screen also. I just want the default one for the login screen.


I have a simple string variable and I want to save the value when starting application, the application is a standalone and I don't want to use registery. I tried to put the string as settings but it saved in a app.config file.  can I save a variable in the self application?

What I want to achieve is very simple: I have a Windows Forms (.NET 3.5) application that uses a path for reading information. This path can be modified by the user, by using the options form I provide.  Now, I want to save the path value to a file for later use. This would be one of the many settings saved to this file. This file would sit directly in the application folder.  I understand three options are available:   ConfigurationSettings file (appname.exe.config) Registry Custom XML file   I read that the .NET configuration file is not foreseen for saving values back to it. As for the registry, I would like to get as far away from it as possible.  Does this mean that I should use a custom XML file to save configuration settings?  If so, I would like to see code example of that (C#).  I have seen other discussions on this subject, but it is still not clear to me.


I have a class in a namespace that I've used extensively throughout my solution. As the number of classes in this namespace has grown I realize that it would've been a better design decision to place this class (and a few others) into a sub-namespace. Is there any easy way to do this in Visual Studio(C#)?   I'm thinking something like the Class->Refactor->Rename feature.  Perhaps an extension?

I'm doing some architectural cleanup that involves moving a bunch of classes into different projects and/or namespaces. Currently I'm moving the files by hand, building, and then manually adding using Foo statements as needed to resolve compilation errors. Anyone know of a smarter way of doing this? (We're a CodeRush and Refactor! shop, but I'd be interested to hear if Resharper has support for this)


Since deleted posts are visible to 10k users why isn't the button called hide or the post really deleted?  What is the reason that 10k users can still see them? Isn't the purpose of deleting something to actually delete it?

When you reach 10k rep, you get to see other users deleted answers. I just think it's dishonest as a system to call a feature "delete," but show that to totally random strangers in the backroom. Due to the nature of the rep, given enough time, all of the regular users would eventually reach 10k rep, no matter how insensitive or jerk they are.  There's usually a good reason why people hit "delete" to their own work. They regret writing something totally bullshit or maybe they spoke too much about their own work that they shouldn't have.  First of all, is there really a practical reason why 10k rep user should view self-deleted answers? Does the benefit really outweigh the creepiness? (Imagine if total strangers could see your deleted messages in Gmail?)  What suggestions could we make to change it? Borrowing from the email metaphor, I think it makes sense for users to "empty trash" so the items gets seriously deleted. Imho, however the deletion is implemented is not important. It could be a soft delete, SQL Delete, or physical destruction of metal plates as long as the user or the 10k rep user no longer sees the deleted item.  What are the workarounds, if we can't change the behavior?  The least we could do is stop calling it "delete" if it's actually not a "delete." Call it "hide from public" or "actually not delete" or something.  Related user voice:        Edit: Recovery of a deleted-but-good answer is a practical benefit for the community, but I see that as creepy dangerous feature. IMHO, each user should have the rights to take back his or her perfectly good answer, and that the protecting privacy outweighs the benefit or creepiness.   I understand that it's all possible to find things out from Google cache or wherever, but why promote this as default behavior? As 10k rep user, I see others deleted answers by default. @codinghorror wrote:     But like any version control system, deletions are illusory.   Anything and everything that's implemented by human is more or less illusory including phone system and the medical records. Should the government start tapping into phone lines and scanning for words? Remember, this is a question of should had we given the opportunity to design a system.


Just as the title say, consider the integral: $$I=\int_0^{+\infty} \frac{\sin^2 x}{x^2} \,\mathrm{d} x=\frac{1}{2}\int_{-\infty}^{+\infty} \frac{\sin^2 x}{x^2} \,\mathrm{d} x,$$ how to apply the residue theorem to get the answer?

I am looking for a short proof that $$\int_0^\infty \left(\frac{\sin x}{x}\right)^2 \mathrm dx=\frac{\pi}{2}.$$ What do you think?  It is kind of amazing that $$\int_0^\infty \frac{\sin x}{x} \mathrm dx$$ is also $\frac{\pi}{2}.$ Many proofs of this latter one are already in this .


I am starting to learn about the complex exponential form of waves and SHM and was wondering what the significance of the imaginary part is. I know this question has been asked many times in different ways, but I think my question here will be slightly different.  From what I have seen, we use the complex representation because of its convenience as many calculations are simplified (like integration, differentiation, wave superposition and enveloping etc) but we have to extract the real part to get the physical reporesentation. The complex part is useful for this also because it consists of the real and imaginary part which are orthogogonal and so when we apply linear operators such as derivatives we can take the real part before or after applying these. This is not so for non[linear operators, such as getting the power/energy/intensity of a wvae which all depend on the square of the amplitude; the real part must be taken before squaring.  I also know that there is some significance of the imaginary part in quantum mechanics as probabilities are found by multiplying the wavefunction with its complex conjugate, which does not give the same result as just squaring the real part.  So it seems to me that the complex representation can just encode extra information in a convenient way. From what I have read I have not seen there being any extra phsyical interpretation of the imaginary part. I was wondering if someone could clarify or add to this? Parhaps I am also missing something- some physical phenomena where the complex nature of waves becomes apparent and physical results cannot be explained simply from a real representation of waves (whether in quantum mechanics or not)?

I've read that plane wave equations can be represented in various forms, like sine or cosine curves, etc. What is the part of the imaginary unit $i$ when plane waves are represented in the form $$f(x) = Ae^{i (kx - \omega t)},$$ using complex exponentials?


Rear wheel is moving from side to side anyone have any ideas what might be the problem thanks

My rear bike wheel is wobbling back and forth when I ride. Nothing that I have done has worked and I was told that it was gonna cost $100 or more to fix. what do I do to fix it properly?


I'm currently searching for the name of a series (or a short movie perhaps?) that I have seen some time ago.   I remember the video shows a woman living her daily life in a smart home. Some time after she's undergoing some kind of surgery. They extract some kind of device which stores an AI that was placed inside that woman's head.  The AI believes it is the person it just got extracted from. From that moment on the AI lives in some kind of white vast room and has to control the smart home for her former self.  After she refuses, the salesman for this smart home control system just lets her sit inside this white empty room for a long time. Soon her mind is broken and she does as she has been told.

This is a modern movie and rich people can buy this egg with a personal assistant. It's an actual person in it (or a person's mind). I believe it can even operate a toaster.  I believe later in the movie, a person (or their mind) can be transferred to such an egg. As a punishment, they increase the speed of time inside that egg to make the person inside the egg bored to death, so to speak.


I am working on a random quote machine and am trying to add a button that tweets the quote displayed on the screen. I can get it to work for basic quotes using encodeURI() but some of my quotes have special characters like brackets, colons, and semi-colons.  I've tried escape(), encodeURI(), and encodeURIComponent(), but none of these work with these characters. Here is what I have for the twitter button (content is the variable that contains the quote I want to tweet). How can I tweet quotes with these special characters?  $("#twitter-share").click(function(){   window.open('https://twitter.com/intent/tweet?text="' + encodeURI(content) + '"', '_blank');

When encoding a query string to be sent to a web server - when do you use escape() and when do you use encodeURI() or encodeURIComponent():  Use escape:  escape("% +&=");   OR  use encodeURI() / encodeURIComponent()  encodeURI("http://www.google.com?var1=value1&var2=value2");  encodeURIComponent("var1=value1&var2=value2");


Does anyone know of a way to simplify   $$ \sum_{n = 1}^{\infty} \left(\frac{1}{2}\right)^{3n} $$  to a number?

Why does the following hold:  \begin{equation*} \displaystyle \sum\limits_{n=0}^{\infty} 0.7^n=\frac{1}{1-0.7} = 10/3\quad ? \end{equation*}  Can we generalize the above to      $\displaystyle \sum_{n=0}^{\infty} x^n = \frac{1}{1-x}$ ?   Are there some values of $x$ for which the above formula is invalid?  What about if we take only a finite number of terms? Is there a simpler formula?     $\displaystyle \sum_{n=0}^{N} x^n$   Is there a name for such a sequence?    This is being repurposed in an effort to cut down on duplicates, see here: Coping with  duplicate questions.  and here: .


I have several UDFs defined and they work as expected, but intellisense, wherever they are used, underlines them in red and says "Cannot find either column dbo or the user defined function or aggregate." The functions work, they are simply not being recognized by intellisense. Any way of making intellisense recognize them?

I've notice an issue - it feels like a bug but I suspect a 'feature' - in SSMS in SQL Server 2008.  I have various tabs open, for example an alter table script in one table and a SProc that queries that table in another tab, and when I execute my Alter Table script the changes are not reflected in Intellisense in the other tab.  I can create new queries and the changes are still not reflected in Intellisense. If I open a new SSMS instance, the changes are reflected, until I make further changes, of course.  However, if you over-rule Intellisense and push ahead with your modified tables and code, everything compiles without a grumble (as expected).  Is this a bug? A feature? Is there a setting somewhere that alters this behaviour? I checked in the options but couldn't see anything


#include <stdio.h>      int main()     {         int x = 0;          if (x++)             printf("true\n");         else if (x == 1)             printf("false\n");         return 0;     }   Output:  false   Why is the output false?  x++ is post increment; this means that the value of x is used then it is incremented. If it is so, then x=0 should be used and the answer should be true.

Possible Duplicate:          Here is a test case:   void foo(int i, int j) {    printf("%d %d", i, j); } ... test = 0; foo(test++, test);   I would expect to get a "0 1" output, but I get "0 0"  What gives??


So I was using the online editor Writelatex and inserting images there is pretty straightforward. However, it's quite slow so I began to use MacTex.  I'm using the \usepackage{graphicx} but I guess the nucleus of my problem is that I don't know how to create the folderpath on mac. My two images are on my desktop. Here is what I've tried:  \graphicspath{{/Users/david villarreal/Desktop}}   and when I have to insert the two images I say  \includegraphics[width=\columnwidth]{B.png} \includegraphics[width=\columnwidth]{A.png}   Can somebody tell me what it is I'm doing wrong?  When I ask the program to tell me what error I have it highlights the following:   Thanks.

I want to import graphics into my main input file using the macro \includegraphics. It does not work if the filename contains spaces.   also discusses this subject, but there is no solution there.  My compilation routine is latex->dvips->ps2pdf (because of PSTricks).


Could someone tell me where I might find information on deriving the standard error used in confidence and prediction intervals of y at a given value of x on a regression line. I can't find anything on the internet. Thanks for any help.

I want to calculate standard error of y-intercept or constant term in the multiple regression equation $Y = b_0 + b_1X_1 + b_2X_2$  I found the formula for standard error estimation of co-efficient $b_1$ and $b_2$ as given in the link    But I am not getting any formula for estimating the standard error of b0. Could anyone help me out? Regards Koushik


I write a document without writing myself the Contents. I just put the command:  \tableofcontents   and what I write after the command:  \begin document   is automatically added in the Contents. However , when I have a subsubsection the Latex doesn't include it in the Contents. It is like it doesn't recognize it.  For example I have this file:  \documentclass[12pt, fleqn]{report}  \usepackage[utf8]{inputenc}  \usepackage[english,greek]{babel}   \usepackage{graphicx}   \graphicspath{{images/}}   \usepackage{amsmath}   \usepackage{caption}   \usepackage{ragged2e}  \usepackage{graphicx}  \usepackage{afterpage}  \usepackage{fancyhdr}  \usepackage{lipsum}  \usepackage{mathptmx}  \usepackage{anyfontsize}  \usepackage{t1enc}   \usepackage{titlesec}   \setcounter{secnumdepth}{3}  \chapter{A} \section{B} \subsection{C} \subsubsection{D}   Everything until \subsection{C} is included. After I write in the document the\subsubsection{D} , then it doesn't appear in the Table of Contents. Any idea why this is happening?  Thank you.

I am trying to make a subsubsection in a report document. It does this successfully, however it removes the subsection from the contents section of the document.  Is there anyway to rectify this?  I tried using, for example,  \addcontentsline{toc}{subsubsection}{Photoelectric Effect}  but this does not work. Nothing shows up.


I am asked to deduce, in the following order, 3 facts about $G = Gal(f(t) = t^6+3)$ over the rationals:   $G$ is order 6 The elements have orders $1,2,3$  $G \cong S_3$   I have figured these out but in the wrong order so I wanted to write down a different train of thought that I am less sure of to see if there is anything wrong with it.   By Eisenstein $f(t)$ is irreducible, and is thus the minimal polynomial of a root $\beta$ of $f$ over $\mathbb Q$, so if $L$ is the splitting field of $f$ over $\mathbb Q$ then as the degree of $f$ is $6$, then the degree of the extension $\mathbb Q\leq L$ is also $6$. Letting $\xi$ be a primitive $6$-th root of unity, then we see that over $\mathbb Q(\xi) = \mathbb Q(i\sqrt 3), \; f$ factorises as $f(t) = (t^3 + i\sqrt 3)(t^3 - i\sqrt 3)$ . This means that all permutations $\sigma \in Gal(L/\mathbb Q(\xi))$ permute the roots of each cubic factor amongst themselves. i.e. $\sigma$ is a $3$-cycle, and there are three of them. Also we note that complex conjugation preserves $\mathbb Q$ in $L$, so $G$ contains an order $2$ permutation. The identity is order $1$. I am not quite sure how to conclude that there is no element of order $6$, but with that we have that the elements are of orders $1,2,3$ Finally, we notice that composing complex conjugation with one of the $3$-cycles gives us the inverse of the original $3$-cycle. This gives a dihedral relation and hence $G$ is the dihedral group of order $6$, i.e. $G \cong S_3$   I would like to clarify why it is exactly that we can conclude that there is no element of order $6$ in $G$. I can feel that it is a very simple thing that I have overlooked, but I can't figure out what it is and would appreciate a little help or a hint. Additionally I would really appreciate it if anyone could let me know if there's anything flawed with my logic here at all. Thank you.

I have seen the the thread   related to the computation of the Galois group of the same polynomial. However, my question is not about the computation itself but about the group presentation of the Galois group. I will explain.  I have determined that the polynomial $x^6 +3 \in \Bbb{Q}[x]$ has Galois group of order 6. The splitting field is $\Bbb{Q}(a)$, where $a$ is a root of $x^6 + 3$. One can take  $a = \sqrt[6]{3}\zeta$ where $\zeta = e^{2\pi i/6} = e^{\pi i/6}$.  Now I have determined the rest of the roots to be:  $$\begin{array}{ccccc} \alpha_1 &=&  a &&& \alpha_4 = -\alpha_1  \\ \alpha_2 &=& \frac{a^4 + a}{2}= \zeta a &&&  \alpha_5 = -\alpha_2 \\ \alpha_3 &=& \frac{a^4 - a}{2} = \zeta^2 a &&& \alpha_6 = - \alpha_3 \end{array}. $$  I have also computed some automorphisms of the Galois group, for example the automorphism $\tau : \alpha_1 \mapsto \alpha_4$ that has order 2, $\sigma : \alpha_1 \mapsto \alpha_2$ that has order 2 and  $\rho : \alpha_1 \mapsto \alpha_3$ that has order 3. The presence of two automorphisms of order 2 tells me that the Galois group is isomorphic to $S_3$  However the problem now is if I want to identify my $\tau,\sigma$ and $\rho$ as cycles in $S_6$, I get the cycles $(14)$, $(12)$ and $(132)$. I don't think these cycles lie in the copy of $S_3$ inside of $S_6$; what am I misunderstanding here?  Thanks.     Edit: I made a mistake in the calculations. We actually need $\alpha_1 = a = \sqrt[3]{3}\zeta$ where $\zeta = e^{\pi i/6}$. I did not take a primitive 6-th root of unity earlier. Now if I write $a = \sqrt[6]{3}e^{\pi i/6}$, then $a^3 = \sqrt{3}i$ and so $\frac{1 + a^3}{2} = \frac{1 + \sqrt{3}i}{2} = \zeta^2$. So indeed with the redefined $\zeta$ and $a$, the equations now are   $$\begin{array}{ccccc} \alpha_1 &=&  a &&& \alpha_4 = -\alpha_1  \\ \alpha_2 &=& \frac{a^4 + a}{2}= \zeta^2 a &&&  \alpha_5 = -\alpha_2 \\ \alpha_3 &=& \frac{a^4 - a}{2} = \zeta^4 a &&& \alpha_6 = - \alpha_3. \end{array} $$  After all this mess, I have got the automorphisms $\sigma = (12)(45)(36)$ and $\gamma = (135)(246)$. We check that $\sigma\gamma = \gamma^2\sigma$. $\sigma\gamma = (12)(36)(45)(135)(246) = (16)(25)(34)$.   $\gamma^2\sigma = (153)(264)(12)(36)(45) = (16)(25)(34)$ so indeed $\sigma\gamma = \gamma^2\sigma$. Hence the Galois group has elements  $$\{1,\gamma,\gamma^2,\sigma,\sigma\gamma, \sigma\gamma^2\} = \{1, (135)(246),(153)(264),(12)(45)(36),(14)(23)(56),(16)(34)(25)\}.$$


What is the mathematical term for an operation that is self reversing?  For example:   Multiplying by -1 1/x   In general:  f(f(x)) = x

I can think of several examples of functions such that twice application of the function is equivalent to no application of it.   Additive inverse Multiplicative inverse Fourier transform Complex conjugation Any group built up from $\mathbb{Z}_2$, applying (one of) the $\mathbb{Z}_2$ parts' operation.   "Idempotent" came to mind, but that's wrong. It means $f(f(x)) = f(x)$, not $f(f(x))=x$.  What is the word for this "flip-flop" property?