Evaluate  $$\lim_{n\to\infty} \left[\left(1+\frac{1}{n}\right)\left(1+\frac{2}{n}\right)\left(1+\frac{3}{n}\right)...........\left(1+\frac{n}{n}\right)\right]^\frac{1}{n}$$ I have tried to solve this problem by taking logarithm but it works for finding the limit of functions but not in the case of sequences the answer to the problem is 4/e


Why can't Stack Exchange just log me into other sites automatically?

I have 7 or 8 accounts across the Stack Exchange site. When I bring the StackExchange dropdown menu down, it lists all my accounts for each forum and my reputation for each as well. Why, when I click on some of them, do I have to either "Log In" again, or refresh the page when the notification pops up the top saying Welcome back scrowler, you have been logged in. Please refresh the screen  I don't want to log in again and again, and I don't want to have to refresh the screen (call me impatient).  Request:   click on one of the SE networks in the drop down have the link automatically generate the required authentication cookies required for the site continue   Objective:   prevent the need to log in, or refresh the page after automatic login when clicking on a linked SE account


Could any one tell me how to solve this two?  $1.$ As a ring $\mathbb{Z}[i]/(3-i)\cong\ ?$ $2.$ $L=\mathbb{R}[x]/(x^2-x+1),\ M=\mathbb{R}[x]/(x^2+x+1),\ N=\mathbb{R}[x]/(x^2+2x+1)$. Who is isomorphic to whom as a ring?  I know the definition of $\mathbb{Z}[i]/(3-i)= x(=a+ib)+(3-i)=c+id$ please help.


If the universe is expanding, it would make sense that the spaces between particles are getting bigger. If this is so, then the particles which make up atoms are also affected. Does that imply the spaces between the components of an atom will become large for the subatomic forces to hold? Are atoms getting weaker?


How do you make a function change the variable put into it in javascript?

I have been doing sheet.stopTC(aVal)  and it seems to go fine, however here:  key: "stopTC", value: function stopTC(z) {    if (z == true) {     z = false;     console.log("cache started");   } else {     z = true;     console.log("cache stopped");   }   return z; }  //globals aVal = false   the variable is globally set to false but when it comes back the aVal stays false instead of changing to true`.  Sorry I'm new to programming and can't get my head around it.


Every point of an open ball is a centre for the open ball.

Suppose $X$ is  a nonempty set and $d$ is an ultrametric on $X$ i.e.,$$d(x,y)\le\max\{d(x,z),d(z,y)\}$$ for all $x,y \in X$. Suppose B is an open ball of $(X,d)$. Show that every point of B is a centre for B.  I can't understand the statement I have to prove as how can an open ball have more than one centre . Please Help!!  I found the problem from Searcoid's Book on Metric Space!  Thank You!!


fine the limit : $\lim_{ n \to \infty }\frac{1}{n}\int_{0}^{n}{ \frac{x\ln(1+\frac{x}{n})}{1+x}}=?$

fine the limit :  $$\lim_{ n \to \infty }\frac{1}{n}\int_{0}^{n}{ \frac{x\ln(1+\frac{x}{n})}{1+x}}=?$$  My Try: in the  $$I=\int_{}^{}{ \frac{x\ln(1+\frac{x}{n})}{1+x}}=\left(x+n\right)\ln\left(\left|x+n\right|\right)+\left(\ln\left(n\right)-\ln\left(n-1\right)\right)\ln\left(\left|x+1\right|\right)+\operatorname{Li}_2\left(-\dfrac{x+1}{n-1}\right)+\left(-\ln\left(n\right)-1\right)+c$$  now?


Does the phrase "if that's fine with you" require a question mark?

Say I have the sentence:     I suggest we do an interview at 12 pm, if that's fine with you.   Is this sentence a direct question which requires a question mark, or should I keep it the way it is?


How can I find out what email I used to sign up using the Android app?

EDIT: I tried logging the exact same way, except from Electrical Engineering (the first community I joined), and this time it worked. I though where you tried to log in had no impact on your Stack exchange account, turns out it does. Thanks everyone who answered!  Some time ago I created this very account, using the same phone I am using now. My problem is, I have no idea how I created the account.  I apparently used neither my usual mail address nor my usual Google account. When I log out then back in with this phone, it works using a Google account but I suspect it is my friend's, who logged multiple times on other Google apps on my phone.  This account doesn't have much, and I could easily create another, but I don't like creating multiple accounts just because I lost one. Help?


Proving recursive sequence converges to $\sqrt{2}$

Consider the sequence $x_{n+1} = \frac{1}{2} (x_n + \frac{2}{x_n})$, $x_1 = 2$. Prove that it converges to $\sqrt{2}$.  I want to show that all of $x_n$ is bounded below by $\sqrt{2}$ using induction. However, I can't see how knowing $x_n \geq \sqrt{2}$ helps show that $\frac{1}{2} (x_n + \frac{2}{x_n}) \geq \sqrt{2}$. Namely, it's not clear whether a higher value of $x_n$ produces a lower (or higher) value of $x_{n+1}$.  Edit: I am looking for a solution that does not use AM-GM (which is proven later in the text that I am reading).


Integral domain( not merely $\mathbb{Z}$ ). Prove that $\gcd(ca, cb) = c\gcd(a, b)$

In an integral domain $\gcd$ is only defined up to associate relation. It's defined as follows: $d = \gcd(a,b) \Leftrightarrow d|a, d|b$ and $c|a, c|b$ implies $c|d$.  Or we can say that $(d)$ is minimal among principal ideals containing $(a,b)$. All the same.  But how to prove $\gcd(ca,cb) = c\gcd(a,b)$? I found similar questions, but they were about $\mathbb{Z}$ and not an arbitrary integral domain, I don't think it counts as a duplicate.


Share one User Table with two Drupal Sites

I have a drupal site which has thousands registered users. (I also added fields like age,dob country etc at /admin/config/people/accounts/fields)  I have another site which is hosted at the same hosting with different database.  Is there a way that i can use first site USERS table in the second site ?  (user registration, forget password and login etc will be connected to first site)  Any clue?  thanks


I think that this might be a stupid question, but I never figured this out. I think this might be a stupid question. If I get rid of the that, is it a run on? I see it a lot, so I think that it is right, but I can't figure out what it's called or the exact rules of it since "I think" and "This might be a stupid question" both seem like independent clauses, so why can they go together? I remember also seeing the following sentence in a book too. I want to tell her I would've known. Thank you! This is my first time using Stack Exchange, so please tell me if I did something wrong.


No indexing with `glossaries` and MakeIndex

I'm using the glossaries package to define a list of acronyms, and I cannot get the .idx and .ind files to write themselves. This is my MWE:  %!TEX TS-program = xelatex %!TEX encoding = UTF-8 Unicode \documentclass[12pt,oneside]{book} \usepackage{makeidx} \usepackage[french]{babel} \usepackage{fontspec,xltxtra,xunicode} \usepackage{hyperref} \usepackage[nonumberlist,acronym]{glossaries} \newacronym{np}{\textsc{np}}{nom propre} \makeglossaries \makeindex  \begin{document} \printglossary[title=Abréviations dans les gloses morphosyntaxiques,type=acronym,nopostdot]  Il s'agit d'un \acrshort{np}.  \tableofcontents \end{document}   And here is what I get on the console log when, after compiling to pdf a first time, I run MakeIndex:  This is makeindex, version 2.15 [TeX Live 2016] (kpathsea + Thai support). Scanning input file myDoc.idx...done (0 entries accepted, 0 rejected). Nothing written in myDoc.ind. Transcript written in myDoc.ilg.   That means that when compiling a second time, the glossary won't print. I tried using \makenoidxglossaries and \printnoidxglossary, but this brings another problem (not on this MWE) that I'll address another time.


Hope someone can help me, I am really getting confused. So I am just getting into electronics, and a project i would like to do is to make my own LED strip lighting for a workbench. I understand that a 12V strip needs a constant 12V supply, and if the usage is 0.900A per strip / meter and I want 2 strips, I will need a minimum of 12V 1.8A supply. I also understand that I should increase the supply by 20% so as to not over tax the unit.  So a good supply would be 12V 2.25A. If I have a PSU that provides 12V 5A is this too much or is it safe as the LEDS will only draw what they need? Thanks in advance


I learned that the comma is used before a coordinating conjunction that links two independent clauses but in this sentence, one clause is an incomplete sentence, lacking its (obvious) subject. Is this still acceptable or is an exception to the rule?     The students were highly engaged in the revision process, and commented on   the benefits of giving and receiving feedback through the system.


How do I render the word "Vǫlundarkviða" with bookman and xelatex?

Here's my MWE:   \documentclass{article} \usepackage{fontspec} \usepackage{bookman} \usepackage[T1]{fontenc} % Thought this was unnecessary with XeLaTeX \begin{document} Vǫlundarkviða \end{document}   And here is the result:     As you can see, the second letter is missing. Also, I feel like fontenc should not be there. How do I do this properly?


Why was T'Challa allowed to become Black Panther before the challenge?

T'Challa must fight any challengers to be accepted as King of Wakanda after his father dies. After that, he becomes the Black Panther.  Several scenes in the 2018 movie, Black Panther, show he already has the super-strength and super-speed of the Black Panther before the challenge.  Why was he allowed to accept the plant juice that transforms his body before he became king?  I can accept answers from other Black Panther material besides the movie as long as the source is canon.


JavaScript Array.map(parseInt) causes NaN error

When try something like this in JavaScript ['10','10','10'].map(parseInt)   You will get this is as a result: [ 10, NaN, 2 ]  Why does this happen?


Is this Xbox 360 controller fake? How can I tell?

Just bought it on ebay from a chinese seller with high rating. The item description said it was GENIUNE. But I'm still skeptical. Even thought It works well on my pc the box looks suspicious on the backside. What should I look for to verify the authenticity of this controller?  Please take a look at these photos, and use them as an example if possible.


Is it possible to work offline in Google Chrome (as in Firefox?)

I'd like to access cached copies of web pages even when I can't connect to the Internet in Google Chrome.  To work offline in Firefox, I can click File -> Work Offline. Is there a similar "offline mode" in Chrome?


My experience with building websites is limited, but i have used Google Fonts (GF) for some basic presentation websites before. I was recently given some branding guidelines built by other providers which used GF for everything, including print items, eg. business cards, brochures, etc. And I did just use this identity to build a white paper for this client using GF, which seems to look ok even when printed on paper.  Is GF a technically good alternative to commercial fonts? Any downsides to using GF for non-web work?  Their  doesn't mention anything on this specifically and seems to position these fonts as web assets.     Making the web more beautiful, fast, and open through great typography. We believe the best way to bring personality and performance to websites and products is through great design and technology. Our goal is to make that process simple, by offering an intuitive and robust directory of open source designer web fonts.   Also, since their fonts appear to be Open Source, does this mean its 100% ok to use the fonts for non-web commercial work?


How to append to /etc/hosts file from the termimal?

I'm trying to append to the /etc/hosts file from the termimal:  sudo echo -e "127.0.0.1      localhost-myproject" >> /etc/hosts   Even though I'm doing as sudo, it won't let me. I get permission denied:  bash: /etc/hosts: Permission denied   I've looked at a couple other posts and they instruct like this. But I'm getting this error. How can I do this? Thanks


Do I need to restart my world inorder to receive new game content?

Do I have to restart my world in order to get new features added to the game or does my world, before the update, gain the features on it's own?


XeLatex Beamer font not available whereas it is for article

I'm trying to use Avenir Next with my Beamer presentation.   However, for the following MWE it switches back to the default beamer font.  MWE:  \documentclass[10pt]{beamer}  \usepackage{xltxtra} \setmainfont{Avenir Next LT Pro}  \usepackage{lipsum}  \begin{document}  \begin{frame}{Bla} \lipsum[1] \end{frame}  \end{document}   For other slides it sometimes also throws the error:     LaTeX Font Warning: Some font shapes were not available, defaults substituted.   Whereas it does work for a normal article class:  \documentclass{article}  \usepackage{xltxtra} \setmainfont{Avenir Next LT Pro}  \usepackage{lipsum}  \begin{document}  \lipsum[1]  \end{document}   Any thoughts to what could be going on?


How do I manually arrange the items in a folder in 14.04?

Icons can be arranged manually on the desktop, but I can't find any way to do it inside any other kind of folder. This is a big shame, as I used to (in 12.04) manually lay out and change the icons within some special folders. Also, I remember the zoom in level (ctrl +) used to get saved for particular folders, e.g. so icons would display uniformly bigger in a particular folder. Anyone have an idea how to get this functionality back, and why it went away in the first place? Thanks


square matrices A and B have equal rows/colomns and A*B = I matrix does that mean that B*A also = I?

If you have two square matrices with equal rows and columns A and B and AB = the identity matrix does that mean that BA also equals the identity matrix?


Ubuntu 18.04 USB installer fails to start: "Ubiquity not installed"

Trying to install Ubuntu 18.04 on an Asus UX305C.  I Downloaded Ubuntu Desktop ISO on 21/06/2018 about 16:00H  I used Unetbootin from a ThinkPad running 18.04 to install the iso files onto a USB2 SanDisk USB.   I boot the laptop from the USB. I chose Install.   Instead of Installing it takes me to the "try Ubuntu" live session. I click install disk icon nothing happens.   I tried to manually run Ubiquity. It produces a crash report that says Ubiquity is not installed.   I go to that location and the BIN directory is there.  I run it again (with the bug report open) to be sure that it's currently running.   Close bug report, run again. Nothing. Wait a bit, get same bug crash report.   What am I doing wrong?


How to unlock Sweet Tooth in Rocket League?

How do you get Sweeth Tooth's ice cream van (from Twisted Metal) in Rocket League?


How to make Gnome's "Activities" bar always visible?

I just installed Gnome, and when I click on "Activities" a convenient bar shows up from the left, allowing me to switch to other applications. Unfortunately, the bar hides as soon as I choose an application.  How to make this bar always visible?


Best file system for an external hard drive sharing between OS X and Windows

I would like to buy an external hard drive that I'll use on Mac OS X and on Windows, but I don't know the best file system for it (reading and writing on the both system).  I know I can used FAT32 easily, but I have files bigger than 4 GB so I can't use this file system.  So, I think for NTFS or HFS, but I know I can use on the two systems with software, but I don't know the fastest one to transfer files. Also, I don't know if I can use ext3 or ext4.  If someone knows one of the best way to use an external drive on Windows and Mac without used FAT32, please tell me.


How do I transfer data between Ubuntu and CentOS  using LAN cable, in the same network? I tried installing Samba which did not go well in CentOS.


Is the sizeof(some pointer) always equal to four?

For example: sizeof(char*) returns 4.  As does int*, long long*, everything that I've tried.  Are there any exceptions to this?


I am new to this amazing world of 3D modeling. I wanted to know how can I start 3D modeling from scratch? I am very new to this,I googled up and found that blender is a nice software for 3D modeling and its free too, so I decided to work onto this.  I wanna know is there any background required for learning 3D modeling or anyone(having some prior interest) can start up with this.  well I have some programming experience in C, C++, C#, and python, so am I set with that to learn 3D modeling or do i need to gather some more knowledge or experience in any other field.  From where should I start?


How to Enable TLS 1.2 on MS SQL Server 2012 SP1?

im having trouble connecting to MS SQL Server 2012 SP1 with regards to TLS Handshake. as stated by microsoft, SP1 only supports TLSv1 to TLSv1.1, if i'm not mistaken. I have been developing a spring/java application which uses JPA/jdbc to connect to the database but it requires me to use TLSv1.2 minimum. is there a way to enable TLSv1.2 on SQL Server 2012 SP1? or applying the SP2 packages to get the support for TLS 1.2 will not affect or has backward compatibility with old version of connectors.


I've read many times, including here on  that the commonly known explanation of flight is wrong, and that airplanes can fly because the shape of their wings deflects air down. This makes sense, but as far as I can tell it doesn't explain upside down flight or symmetric wings.  The images I've seen show an inclined wing, which forces the air to go downwards. But how can planes fly upside down then?


The micro-USB port of my Xperia Arc with ICS it's broken. How can I enter to ADB by wireless, without connecting the cable? I am not root, and I need to enter to ADB to root my phone. I can connect to my phone from my PC by SSH. Or there's a another way to root it?


Error while importing networkx module in QGIS 2.18.16

I am trying to import networkx module in QGIS 2.18.16 but getting the error message. Any suggestions?  Traceback (most recent call last):   File "<input>", line 1, in <module>   File "C:/PROGRA~1/QGIS2~1.18/apps/qgis/./python\qgis\utils.py", line 607, in _import     mod = _builtin_import(name, globals, locals, fromlist, level)   File "C:\PROGRA~1\QGIS2~1.18\apps\Python27\lib\site-packages\networkx\__init__.py", line 74, in <module>     from networkx import release ImportError: cannot import name release


Resize root partition from home partition space ubuntu 18.04

I want to resize my root partition using Gparted but before doing it I want to make sure I'm doing it correctly. Here is a screenshot of my GParted:    I know this question has been answered before here:  but the answer is too old and I want to know will that work in Ubuntu 18.04 or I have to try other method. And also is it better to mess around with Gparted or Uninstall and reinstall ubuntu


Regression coefficients that flip sign after including other predictors

Imagine   You run a linear regression with four numeric predictors (IV1, ..., IV4) When only IV1 is included as a predictor the standardised beta is +.20 When you also include IV2 to IV4 the sign of the standardised regression coefficient of IV1 flips to -.25 (i.e., it's become negative).   This gives rise to a few questions:   With regards to terminology, do you call this a "suppressor effect"? What strategies would you use to explain and understand this effect? Do you have any examples of such effects in practice and how did you explain and understand these effects?


Is it possible in QGIS print composer to include a numeric scale in an html box?

For work I always have to create a table with my name, project name, date etc. into my map layouts. I also need to include the scale like "1:150000" in that table.   So far I am solving that by including an html table with the html box function of the print composer. Is there a way to automatically include the right scale? So far I only managed to automatically include the date by using a little javascript. Maybe something similar is also possible for the scale?


Java 9 official release: how to install JDK9 directly?

Java 9 was released officially today, so is there a way to install the JDK on Ubuntu (16.04) without having to change version numbers and checksums?  I was trying to use the webupd8 oracle-java9-installer, but each time it failed with the same error message. I followed the recommended solutions posted to these questions, none of them worked for me -          I get the same error message that others have mentioned, even after following the recommended steps.    ...Downloading Oracle Java 9... --2017-09-22 02:51:55--  http://download.java.net/java/jdk9/archive/181/binaries/jdk-9+181_linux-x64_bin.tar.gz Resolving download.java.net (download.java.net)... 216.68.101.35,216.68.101.32  Connecting to download.java.net (download.java.net)|216.68.101.35|:80... connected.  HTTP request sent, awaiting response... 404 Not Found  2017-09-22 02:51:56 ERROR 404: Not Found. download failed Oracle JDK 9 is NOT installed.  dpkg: error processingpackage oracle-java9-installer (--configure):  subprocess installed post-installation script returned error exit status 1 Errors were encountered while processing:  oracle-java9-installer   E: Sub-process/usr/bin/dpkg returned an error code (1)


The limit of the derivative of an increasing and bounded function is always $0$?

Let $\,f : \mathbb{R} \rightarrow \mathbb{R}$ be a infinitely differentiable function that is  increasing and bounded. Then is it true that $\lim_{x\to \infty}f'(x)=0$?


Quasi-components and components coincide for compact Hausdorff spaces

I am attempting to solve exercise 1.10.1 from Topology and Geometry by Bredon:  If $X$ is a compact Hausdorff space then show that its quasicomponents are connected (and hence that its quasi-components coincide with its components).  The definition of the relation used for quasi-components is "$d(p) = d(q)$ for every discrete valued map $d$ on $X$."  He gives the hint: If $C$ is a quasi-component, let $C = \cap C_{\alpha}$ where the $C_\alpha$ are the clopen sets containing $C$. If $C$ is disconnected, then $C = A \cup B, A \cap B = \emptyset, A,B$ closed. Let $f:X \to [0,1]$ be $0$ on $A$ and 1 on $B$. Put $U = f^{-1}([0,\frac{1}{2}))$ and apply the following result: Let $X$ be a compact space and let $\{C_\alpha \mid \alpha \in A\}$ be a collection of closed sets, closed with respect to finite intersections. Let $C = \cap C_\alpha$ and suppose that $C \subset U$ with $U$ open. Then $C_\alpha \subset U$ for some $\alpha$.  I don't understand which collection of closed sets to use. If we use the clopen sets $C_\alpha$, and we have that $C \subset U$ but $U \subset X - B$, so $B = \emptyset$, and we don't need some $C_\alpha \subset U$. Furthermore, how would we show that $C \subset U$, it seems to more or less assumes $B = \emptyset$.


Issue with jquery onclick (not triggering)

I am having a strange issue.  I have created a code snippet where the user can create dynamic input elements and remove them as well  When I click the remove class then it's not triggering the onclick event.  <input type='button' value='Add Button' id='addButton'>

   I have created a jsFiddle


Seeking a short story title that is set in the Egyptian pyramids

This short story is set in one of one the pyramids of Egypt, I think. It may not seem like sci-fi, but I’m pretty sure I read it in a science fiction anthology.  The narrator is part of a tour group off to tour a pyramid. As the group makes its way to the site, the narrator begins to notice fleeting images of strange creatures near the group. For example, he glimpses a baboon-like animal darting about on the face of the pyramid.  Once inside the pyramid, the group goes deeper and deeper into the structure. Slowly it dawns on the narrator that perhaps they are all dead and they are descending into the underworld. He is the only one cognizant of this possibility it seems. Everyone else seems oblivious as they listen to one member of the group read text from a guide book. I think the last line of the story is something to this effect:     We continue to descend.


\b, \c, \d, \i, \j, \l, \o, \t, \u, and \v etc. are already defined but I never find them useful.  Instead I wish to redefine some of them for my own convenience like \t in replace of \theta, \ in place of \lambda.  Is that possible?


Evaluate $\int _{\frac{\pi}{6} }^ \frac{\pi}{3} \frac{\sin t+\cos t }{\sqrt{\sin 2t}} dt$

I want to evaluate $$\int _{\frac{\pi}{6} }^ \frac{\pi}{3} \frac{\sin t+\cos t }{\sqrt{\sin 2t}} dt$$ I  tried to use the properties of the integral to reduce the integral. But I failed. Also I tried using $\sin C+ \sin D$ and $\sin 2t$ trignometric identities. Nothing worked!!  This question has only one answer    But that answer is not satisfactory for me because When a person  see that integral for the first time , how do he know about that particular trick. Is there any elegant way to solve this problem?


What is the added benefit of conducting a "multivariate multiple regression" over several "multiple regressions"?

SPSS, Stata and SAS can all conduct multivariate multiple regressions (i.e. more than 2 continuous predictors and more than 2 outcomes) as GLM. Consequently, the multivariate tests answers the question "which of the predictors (if any) is significantly related to at least one of the outcomes?".  Because one has to refer to the univariate tables anyway to determine the direction of this effect (while controlling for multiple comparisons), I ask the question what is the added benefit of conducting the multivariate tests in the first place?  Thank you!


Problem: Sidewaysfigure automatically start a new page

Basically, I have a blank page, I inserted the subsection title and underneath I want to add a sideways figure.   \subsection{Findings} \begin{sidewaysfigure} \centering \includegraphics[scale = 0.2]{hi.pdf} \captionof{figure}{picture1}  \label{123} \end{sidewaysfigure}   However, the problem is that I managed to get subsection title printed on one page, but the sideways figure is always on the another page. Is it possible make them appear on the same page ?


I updated my 18.04 to 18.10 and after rebooting it gets stuck on the boot screen. What can I do to fix this? In case it helps, I have an Nvidia card...


Can back home phrase mean back at my place as in,     I couldn't find the book in school. Back home, I found it in my cabinet.


Problem: Find $(2^{a}+1,2^{b}+1),$ where $a$ and $b$ are prime numbers greater than $3$ and $(x,y)$ represents the $\gcd(x,y).$  My Attempt: Observe that $(2^a+1,2^b+1)=(2^{a-b}-1,2^b+1)$ if we assume that $a>b.$ Thus it is obvious that $(2^a+1,2^b+1)=2^{(a,b)}\pm1.$ Since $(a,b)=1$, we have $(2^a+1,2^b+1)=1,3.$ I can't figure out the condition under which $(2^a+1,2^b+1)=3.$ Please help.


I am running Ubuntu in WSL on Windows 10.  jamesk is my windows Active Directory username as well as my default username in WSL. I have set up cron as follows:   Created task in task scheduler (runs on logon as user jamesk, run with highest privileges checked) to do the following two actions:   C:\Windows\System32\wsl.exe sudo /usr/sbin/service rsyslog start C:\Windows\System32\wsl.exe sudo /etc/init.d/cron start  Added following two lines to visudo:   jamesk ALL=NOPASSWD: /etc/init.d/cron start jamesk ALL=NOPASSWD: /usr/sbin/service rsyslog start  Added following five lines to root crontab (my IT folks said I should put cron jobs in the root crontab vice my user crontab):   0 14 * * 3 cd /mnt/c/Users/jamesk/Documents/ubuntu_backups/ && /bin/tar -cvpzf backup-$(date +%F)-pre-update.tar.gz --exclude=/backup-$(date +%F)-pre-update.tar.gz --one-file-system / 3 14 * * 3 /usr/bin/apt-get update -y 6 14 * * 3 /usr/bin/apt-get upgrade -y 9 14 * * 3 /usr/bin/apt-get autoremove -y 12 14 * * 3 cd /mnt/c/Users/jamesk/Documents/ubuntu_backups/ && /bin/tar -cvpzf backup-$(date +%F)-post-update.tar.gz --exclude=/backup-$(date +%F)-post-update.tar.gz --one-file-system /    cron is successfully running; I can see in the log files in /var/log/apt that upgrade is run.  But neither of the backup files are created.  So I looked in /var/log/syslog and saw the following error lines:  CRON[230]: (root) CMD ([231] cd /mnt/c/Users/jamesk/Documents/ubuntu_backups/ && /bin/tar -cvpzf backup-$(date +)  CRON[230]: (CRON) error (grandchild #231 failed with exit status 2)  CRON[230]: (CRON) info (No MTA installed, discarding output)  CRON[230]: (root) END ([231] cd /mnt/c/Users/jamesk/Documents/ubuntu_backups/ && /bin/tar -cvpzf backup-$(date +)  I've searched for tar exit status 2 and found nothing helpful to tell me what the error might be.  I also tried adding %> term.txt to the end of the line to get any terminal output, but it looks like the command is not even being fully run (i.e. term.txt is not created).  I noticed that the command seems to be cut off in the logs, made me think that the space after date might be an issue.  So I tried putting the filename in quotes with no change, also tried escaping the space with a \ but that didn't change anything either.  I've tried running the command manually outside of cron, both as root and as jamesk, and it works fine in both cases (just need sudo at the start of the command when run as jamesk).  I then thought that it might be a permissions issue (i.e. the task to start cron is run as jamesk and the root crontab is being executed).  So I stopped the cron service within WSL, used sudo su to become root, and started the cron service as root, then changed the time of one of the backup lines to make it run immediately.  Got the same error.  So I'm stumped as to why this is not working in cron but works fine if I type the command manually.  Does anybody have ideas?  I appreciate any help in solving this.


Is there a way to make Cycles Render the default in Blender instead of Blender Render? (I hope this hasn't been asked before.)


How to install Oracle 18C XE package on Ubuntu 18.04

I have downloaded Oracle 18C XE the rpm file, but I don't know how to install the database.


Why can't I initialize my fields in my structs?

I am surprised that I can't initialize my fields in structs, why is it like that? Like:  struct MyStruct {     private int a = 90; }   but it's a complie time error. I don't know why it's a problem? Please explain this to me.


Do I get shells, subshells, and orbitals right?

I would like to make sure my (very superficial) understanding of electron shells, subshells, and orbitals is correct. I did look them all up on the Internet, but none of the sources said exactly what I think is going on, so I might be wrong. So, as far as I understand, shell, subshells, and orbitals are not, strictly speaking, actual, physical locations around an atom's nucleus. Shells and subshells are more like abstractions: shell $1$ is the set of all electrons of an atom with principal quantum number $1$, and subshell $s$ is the set of all electrons of an atom with quantum azimuthal number $0$. Orbital $1s$ is not a place either, it's a probability function that tells you how likely you are to find an electron with $n = 1$ and $\ell=0$ in a given point in space. Still, the plot for $1s$ will basically describe a physical location around the nucleus, if you consider all points in space where the probability isn't $0$ as points of that location. (Or nearly zero, as I seem to recall it's never exactly zero.) However, I also read that for $k > l$, electrons with  $n=k$ are more energetic and hence farther away from the nucleus than electrons with $n=l$. So, I guess that there are only certain regions of space around the nucleus where an electron with $n=k$ can be, and that they're generally larger than the regions described by orbitals. So, ultimately, I guess that both shells and orbitals can be seen as locations, although they aren't strictly speaking. I don't know about subshells, because I'm not sure if electrons can only have specific values $\ell$ at a specific distance from the nucleus. Am I making any sense?


Allow sound file uploads in questions and answers?

Should Stack Exchange introduce the ability to upload embedded sounds (maybe via HTML5/Flash, whichever the user has) as part of questions and answers to Stack Exchange?  It could require a certain amount of rep to stop new users from doing it frivolously.  My rationale behind this is the new language & usage sites.  I often find myself thinking that it might be helpful, when discussing a regional dialect or something, for the person answering to just pronounce what they're trying to describe in words.


Is there a way to write with FTP using the Finder

I'm aware of this question , but my question is specifically targetted to anyone who has used Ubuntu, and fully understands how seamless FTP can be.  I'm looking to natively connect to an FTP server and be able to read and write. And open up folders in Atom or Sublime Text and just start editing files on the server.  Here are the options that I am aware of and have already tried, but none of them are as elegant as Ubuntu where you can just open a remote folder and start editing. If anyone knows of something, please let me know?  At the moment transit is the best option.  -   None of the others can edit whole folders in Sublime by importing the folder structure into the sidebar.  -   -   -


I got stuck on this problem. I tried to separate the real and the imaginary part in both sides of the condition and the inequality but got no clue. Can anyone give me some hint? I really appreciate:          Suppose that $z^2 = \sum_{k=1}^{n}{z_k^2}$, here $z, z_k \in \mathbb{C}$. Prove that $|\text{Re} z| \le \sum_{k=1}^{n}{|\text{Re} z_k|}$


Get python program to end by pressing anykey and not enter

How can I get my Python program to end by pressing any key without pressing enter. So if the user types "c", the program should automatically end without pressing enter.  My code so far:  print("Hi everyone! This is just a quick sample code I made") print("Press anykey to end the program.")


Show that $v$ is harmonic and rotation invariant iff $v(z)=A\log |z|+B$ for some constants $A$ and $B$

Let $\Omega$ be a domain in $\mathbb{C}$ and $v$ be a function on $\Omega.$ Suppose that $v(z)$ depends only on $|z|$ and not on arg$z.$ Show that $v$ is harmonic if and only if  $v(z)=A\log |z|+B$ for some constants $A$ and $B$.  Any hint. Thanks in advance!


Can a Canadian volunteer in the US without applying for a work visa? If so, what documents are needed?

I would like to volunteer at the Emerald City comic convention in Seattle.  What documentation do I need to cross the US border? I am Canadian.


Offline Installation: How to install a full TeX distribution in an offline computer?

As I understand it, a snapshot of the MiKTeX/TeXlive is available on .  How do I install a complete (with all packages) TeX distribution on an offline computer (without Internet) ? Is MiKTeX/TeXlive snapshot available on a DVD (for a price)/free or on some "TeX user groups"?  Is the MiKTeX/TeXlive snapshot available for free for download? If so, where can I find it?


This command to rename all files fails: "find: 'rename': No such file or directory"

Trying to replace all file names in a directory with ai to newai.  Execute: find . -exec rename 's/ai/newai/' {} ";" Error: find: ‘rename’: No such file or directory   What could be the problem here, and how can I fix it?


Sometimes I need to login on my Linux Mint 19 PC remotely via ssh. To make this more secure I try to switch to use Public Key authentication (as I already use it on my raspberries).  Basically the authentication works. But only if I logged in via GUI previously. After a fresh start of the system, the ssh server denies the public key authentication.  What could be the issue here?


No Wifi on HP Stream Mini - complete NOOB

I just installed Ubuntu 20.04 onto a HP Stream Mini desktop and am unable to get wifi to work.  I've researched and find a lot of references to issues with Broadcom drivers but nothing that seems to work.  Read through this thread () but the suggested solutions didn't work.  The device appears:   lsspci -knn | grep Net -A2  04:00.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM43142 802.11b/g/n [14e4:4365] (rev 01)     Subsystem: Hewlett-Packard Company BCM43142 802.11b/g/n [103c:804a]     Kernel modules: bcma, wl   But nothing in the network settings except the wired connection. It's probably something pretty stupid but I can't find it.


Book flight with virtual credit card. Airline requires me to present the physical card prior to checking

I booked a flight for myself using my virtual credit card. It is a totally legit VISA card to my name from a bank in the departure country. However, it is totally virtual.  Now, after the payment, there is a message from the airline (Laos airlines) that says that I must present the physical credit card in order to check-in. However, I do not have any physical credit card, as it is a virtual one.  I contacted the bank and they said they are sorry and they cannot provide any document to the airline proving that I am the owner of the card.  The airline said they are sorry, if I will not present the card at the counter I cannot check-in. They also refused to reimburse me the flight so that I could buy it with another card (physical).  Do you have any ideas on how to go ahead?


If I aimed two identical lasers at a screen, what would the interference pattern look like?

If I aimed two identical lasers at a distant screen, what would the interference pattern look like? Could this be modelled as a wavefront passing through two slits, i.e. the double slit experiment?  I want to simulate the interference of two identical laser beams and be able to vary the laser separation, distance to screen, wavelength etc and model the corresponding change in interference pattern.


How to take in the elements of a list of unknown length as parameters for function? Python

I would like to be able to take a list of unknown length in for function parameters like this: With a list lis = [1, 2, 3, ...] and a function def func(a, b, c, ...): ... the elements of the list go into the function as individual parameters, func(1, 2, 3, ...) *not func([1, 2, 3, ...]) Is this possible?


Is there away to render update the objects that move while the back drop will be in scene? I have a huge scene setup it takes 3 to 4 mins per frame to render on the 1920 x 1080, I have learned many things to reduce render time while keeping good quality but in scene where camera doesn't move, only the character or car etc. I would like to render only updating the movement rather than doing whole picture but keeping the background in the render. When I have a good video editing software I know I can croma key characters etc. But would be nice to able to skip that process if possible.


Computing Galois Group of $\mathbb{Q}(\sqrt{2},\sqrt{3}):\mathbb{Q}$

Galois Group of $\mathbb{Q}(\sqrt{2},\sqrt{3}):\mathbb{Q}$ is cumbersome to computing. Is easy to find the all four possible candidates but is cumberstone to show that they are automorphisms:  For multiplication is too long showing that  $f((a+b\sqrt{2}+c\sqrt{3}+d\sqrt{6})(a'+b'\sqrt{2}+c'\sqrt{3}+d'\sqrt{6}))=f(a+b\sqrt{2}+c\sqrt{3}+d\sqrt{6})f(a'+b'\sqrt{2}+c'\sqrt{3}+d'\sqrt{6})$  For some non trivial candidate since the left hand side expands in $16$ terms. What about $\mathbb{Q}(\sqrt{2},\sqrt{3},\sqrt{5}):\mathbb{Q}$? there are $7$ non trivial candidates and multiplication expands in $64$ terms!   How to do it in a tricker form?  Edit(Let me be more precise in my question):   I know that if $f\in\Gamma(\mathbb{Q}(\sqrt{2},\sqrt{3}):\mathbb{Q})$, then $f(\sqrt{2})=\pm\sqrt{2}$, $f(\sqrt{3})=\pm\sqrt{3}$ so there are $4$ candidates for $\mathbb{Q}$-Automorphisms. Candidates are given by:  $f_1(a+b\sqrt{2}+c\sqrt{3}+d\sqrt{6})=a+b\sqrt{2}+c\sqrt{3}+d\sqrt{6}$  $f_2(a+b\sqrt{2}+c\sqrt{3}+d\sqrt{6})=a-b\sqrt{2}+c\sqrt{3}-d\sqrt{6}$  $f_3(a+b\sqrt{2}+c\sqrt{3}+d\sqrt{6})=a+b\sqrt{2}-c\sqrt{3}-d\sqrt{6}$  $f_4(a+b\sqrt{2}+c\sqrt{3}+d\sqrt{6})=a-b\sqrt{2}-c\sqrt{3}+d\sqrt{6}$  But I need to check that they are $\mathbb{Q}$-Automorphisms in $\mathbb Q(\sqrt{2},\sqrt{3})$. All candidates $f_i$ fixes $\mathbb{Q}$ and is obvious that all preserves sums, $f_1$ obviously preserves product also since is the identity, but is cumberstone to show that $f_i(xy)=f_i(x)_if(y)$ to conclude $f_i\in\Gamma(\mathbb{Q}(\sqrt{2},\sqrt{3}):\mathbb{Q})$.


My mother has forgotten her screen lock password. is a four digit number. how can I reset phone so she can use it again?  Please assist!


I would like to disable  Shift+Command+Q keyboard shortcut for Log Out.   I am using Karabiner at the moment, but I only managed to disable it completely using the following xml:  <?xml version="1.0"?> <root>     <item>         <name>Disable COMMAND SHIFT Q for Logout</name>         <identifier>disable_CMD_SHIFT_Q_private</identifier>         <autogen>__KeyToKey__ KeyCode::Q, VK_SHIFT | VK_COMMAND | ModifierFlag::NONE, KeyCode::VK_NONE</autogen>     </item> </root>   but I would like to have the keyboard combination available in emacs (in ESS for debugging).  Is there some way that I can effectively unmap the keyboard combination?


Algebraic process to find numbers so that $xy=45$ and $x+y=18$

Can someone help me with the following question?  The sum of two numbers is $18$ and their product is $45$. Find the numbers.  I know that the answer is $15$ and $3$. But how do I find that answer algebraically? It tried doing it as $x+y=18$ and $xy=45$ and then $x= 18-y$ and I substituted in $xy=45$. I got it as $(18-y)y =45$, and I don't know what to do next.


How did the usage of the word "pretty" become synonymous with the word "really"?

When and how did Americans come to accept and widely interchange the word "pretty" for "really"?  (ex. "It was a pretty big tornado".  "She had a pretty bad headache".)


Swap separation for multiple distributions

I have 3 Linux distributions on my machine (Ubuntu, Arch and Fedora). I allocated half the RAM size (3GB) as swap for each of them. (I have realized that having 3 distributions is not of much use to me, but I still have them.)   The problem is now the 3 distributions mount all the 3 swap partitions while loading, and treat swap as a single 9GB partition.   Now when I hibernate my system, obviously no distribution ever wakes up from hibernation.   Is there any way to overcome this?


What to do with my answers that appear duplicate?

This is partly in reference to   Sometimes when posting answer on Stackoveflow I find my self posting same answer as someone else at almost exactly same time. Previously when I would notice that '1 New Answer' appeared I would check the answer first and than discard my answer if i found it to be duplicate. If that answer was different from mine I would finish writing my answer.     My own solution: After reading responses to this question and answers on some of the links that were submitted I have decided to follow advice from @kate-gregory to finish writing my answer without paying attention to new answer that might pop up. Once I post my answer if I find it to be very similar I try to improve or reword it to be a better answer.   PS. Therefore I'm no longer asking for a reason to stop me from answering.


My first post.  Successfully migrated from win 7 to ubuntu 12.04.1 on my samsung netbook. working smoothly.  But I had installed 32 bit version.  Is there any advantage of going in for 64 bit?  What are the risks. Ram Prasad


Enable WP to accept standard jQuery code embeding between the  tags

I don't know what is the reason that WP is not accepting the standard embedding technique from jquery website (  ):  <!doctype html>       <meta charset="utf-8" />     <title>Demo</title>       jQuery               And allowing you only to wp_register_script your scripts in the functions.php or in the header.  I want be able to embed the jQuery the way it is supposed to be and where I want in my template files.  So, the question is how can I enable the standard embeding recognition of jquery code in WP?    If that's not possible, is there a plugin for that or what files do I need to hack in WP core, if that's not possible to solve by some hook?


What happens when identical overlapping effects have their end-condition met?

The  () added the "Combining Game Effects" section which states (emphasis mine):  Different game features can affect a target at the same time. But when two or more game features have the same name, only the effects of one of them—the most potent one—apply while the durations of the effects overlap. [...]  The Essentials Kit has a further clarification on these rules in its "Effects with the Same Name Don't Stack" section (page 3, emphasis mine):  [...] But when two or more effects have the same proper name, only one of them applies while the durations of the effects overlap (a duration is a time span of 1 round or more). [...]  I'm unsure whether the further clarification will change my following examples but we do know for sure that with overlapping identical effects, one instance will be what I'd call "active" (will have effects) and the other will be what I'd call "inactive" (won't have effects). That all squared away, I think my question will make more sense with examples:  The  Fire Form trait:  [...] The first time it enters a creature's space on a turn, that creature takes 5 (1d10) fire damage and catches fire; until someone takes an action to douse the fire, the creature takes 5 (1d10) fire damage at the start of each of its turns.  If a creature is under the effects of multiple instances of Fire Form, and somebody uses their action to douse the fire, are both instances removed or only one?  The  spell:  [...] If the target willingly moves before then, it immediately takes 1d8 thunder damage, and the spell ends. [...]  If a creature is under the effects of multiple instances of booming blade, and they move, are both instances removed or only one?  The  spell:  [...] At the end of each of its turns, the target can make another Wisdom saving throw. On a success, the spell ends on the target. [...]  If a creature is under the effects of multiple instances of hold monster, and they succeed on a save, are both instances removed or only one?   Can an "inactive" effect end when its end-condition is met (letting them end simultaneously), or do these sorts of things always end one at a time? Or perhaps the answer is something in-between?  There is also the following related question:    Both answers there supports that if you are grappled by multiple creatures and you make a check to remove a grapple, you only remove one of the grapples. It's not perfectly analogous situation but it is somewhat similar.


I have to model a 15-puzzle game board in Ruby. As a representation, I chose to use a multidimensional array (as a classic 2x2 matrix) with rows and columns.  My question is: is it better to subclass Array, in order to store all the relevant informations inside self or is it better to create a new class, and internally use an instance variable to keep track of the multidim array?  The API is meant to be the same in both cases, my question is about the implementation.


I am wondering why/how Stack Overflow is so fast.     "Stack Overflow is a programming Q & A site that's free. ... And fast. Very, very fast."   -


My team wants to move news section of our website to subdomain ex "news.website.com" does it affect SEO? Can anyone tell me pro and cons of this thing?


I have some questions regarding secondary citations (in an computer-science research paper that should be published in a journal). I know that they should be avoided when possible, but it is not always that easy. More specifically, my situation is this:  Article A says:     The average value of ... in ... is ... [B]. [C]’s study says that in ... the value is ...   This statement is exactly what i need for my paper. If I read [B] and [C], I see that [A] cited them correctly and if I would have found these two other articles myself, I would have written the same.  Now how to cite this in a correct way?      [B] and [C] say (cited in [A]) ...   and do a “bad” secondary quote;    [B] and [C] say ...   and neglect the investigation done by [A] and peform citation plagiarism;    [A] says ...   and neglect that the data was the achievement of [B] and [C].    [A] says based on the findings of [B] and [C] ...   and do a secondary quote again.


What are the compiled costs of each Formula function

Each  has a compiled cost that contributes towards the  compiled character formula limit.  What are the current compiled costs associated with each formula function?


portal users cannot own partner accounts

I am having an issue while updating an existing community contact/account:  Contact has 'created by' and 'Owner' set to  Salesforce Standard User. And then from that Contact I created a community user. Now with REST API I am trying to update that Contact's 'owner' field to Community user I see following error: Portal users cannot own partner accounts


Find all real numbers $x$ for which $\frac{8^x+27^x}{12^x+18^x}=\frac76$

Find all real numbers $x$ for which $$\frac{8^x+27^x}{12^x+18^x}=\frac76$$  I have tried to fiddle with it as follows:   $$2^{3x} \cdot 6 +3^{3x} \cdot 6=12^x \cdot 7+18^x \cdot 7$$ $$ 3 \cdot 2^{3x+1}+ 2 \cdot 3^{3x+1}=7 \cdot 6^x(2^x+3^x)$$ Dividing both sides by $6$ gives us $$2^{3x}+3^{3x}=7 \cdot 6^{x-1}(2^x+3^x)$$  Is this helpful? If so, how should I proceed form here? If not any hints would be greatly appreciated.


If $V_0$ is the subspace of matrices of the form $C=AB-BA$ for some $A,B$ in a vector space $V$ then $V_0=\{A\in V|\operatorname{Trace} (A)=0\}$

If $V_0$ is the subspace consisting of matrices of the form $C=AB-BA$ for some $A,B$ in a vector space $V$ then $V_0=\{A\in V|\operatorname{Trace}(A)=0\}$.  The problem above is one of the past qualifying exam problems. I can prove that  $V_0\subset\{A\in V|\operatorname{Trace}(A)=0\}$ but I do not know what to do with converse.  Thank you in advance.


So, here is a table:  \begin{table}[h] \begin{tabular}{llllllll} \rowcolor[HTML]{EFEFEF}  \textbf{foo}            & \textbf{bar}           & \textbf{foobar}        & \textbf{fsj}           & \textbf{jifd}          & \textbf{jifd}          & \textbf{jif}                                                          & \textbf{ifi}                                                          \\ \hline \multicolumn{1}{|l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{\cellcolor[HTML]{FFCCC9}{\color[HTML]{3166FF} 1}} & \multicolumn{1}{l|}{\cellcolor[HTML]{FFCCC9}{\color[HTML]{3166FF} 1}} \\ \hline \multicolumn{1}{|l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{0}                                                & \multicolumn{1}{l|}{1}                                                \\ \hline \multicolumn{1}{|l|}{1} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{\cellcolor[HTML]{FFCCC9}{\color[HTML]{3166FF} 1}} & \multicolumn{1}{l|}{\cellcolor[HTML]{FFCCC9}{\color[HTML]{3166FF} 1}} \\ \hline \multicolumn{1}{|l|}{1} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{\cellcolor[HTML]{FFCCC9}{\color[HTML]{3166FF} 1}} & \multicolumn{1}{l|}{\cellcolor[HTML]{FFCCC9}{\color[HTML]{3166FF} 1}} \\ \hline \multicolumn{1}{|l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{\cellcolor[HTML]{FFCCC9}{\color[HTML]{3166FF} 1}} & \multicolumn{1}{l|}{\cellcolor[HTML]{FFCCC9}{\color[HTML]{3166FF} 1}} \\ \hline \multicolumn{1}{|l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{0}                                                & \multicolumn{1}{l|}{0}                                                \\ \hline \multicolumn{1}{|l|}{0} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{0}                                                & \multicolumn{1}{l|}{1}                                                \\ \hline \multicolumn{1}{|l|}{0} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{1} & \multicolumn{1}{l|}{0} & \multicolumn{1}{l|}{0}                                                & \multicolumn{1}{l|}{0}                                                \\ \hline \end{tabular} \end{table}   Now I am trying to change the \textbf{foo} (name of first column) to \neg B  But I get the following error: ! Missing $ inserted.                   $ l.55 }


Serialization Interface is empty in JDK Source. What is the use of implementing it

It was marked duplicate and i am expanding my question.  My question is how JDK internally serializing objects.  How ObjectxxxStreams class serializing when the class implements that interface.?  I was looking into the serialization topic and deeply dived into the JDK Source code.    This was the source code of serialization Interface in JDK.  package java.io; public interface Serializable { }   There is nothing in this interface.  What is the use of implementing this interface.  I know that, to serialize a object we should implement this.  I know what serialization is and how to work with that.  But how serialization happens internally using ObjectInputStream and ObjectOutputStream.  These classes are how related to serialization. Alternatively let us keep that those two classes are doing their duty.  All my question is why we need to implement this empty interface to serialize and deserialize objects and how it works internally?  Please explain in detail about this.


Do we have a better approximation of $c$ than 299792458 m/s?

All sites give this value as "exact" value. I mean, what's after the comma? 299792458,000 m/s?


I have the following content in wsgi.py file:  import os import sys  from channels.asgi import get_channel_layer from django.core.wsgi import get_wsgi_application  sys.path.append('/home/project') sys.path.append('/home/project/Project_Web_Main')  os.environ.setdefault("DJANGO_SETTINGS_MODULE", "Project_Web_Main.settings")  application = get_wsgi_application() channel_layer = get_channel_layer()   but I have the following error when importing: from channels.asgi import get_channel_layer  ImportError: No module named channels.asgi


Subtract two dates using Shell Scripting

How can I subtract two dates in epoch format using Shell Scripting. I want the output in Months, Days, Hours format. Also It should work even for more than 12 months ( as I came across few which were resetting to 0 months if more than 12)


I am using Ubuntu 14.04 LTS along side Windows 7. I am trying to log into Ubuntu, but can't pass boot screen, doesn't matter how long I wait.    The problem started when I installed a series of software and tried to restart the system. The software were requirements of a course and are listed under title Software available through apt-get and Software available through easy_install in the following link:


Transforming a square to regular triangle

I am trying to find the mapping for a square [(0,0),(1,0),(0,1),(1,1)] to a right angled triangle [(0,0),(1,0),(0,1)] then to a arbitary triangle in 2d. The issue I am having is a) finding the mapping from the square to right angled triangle; b) the process in applying the mapping. I know the process for the right angled triangle to the arbitary one: $ (x,y)^T = \begin{bmatrix} x_1-x_0 & x_2-x_0\\ y_1-y_0 & y_2-y_0 \end{bmatrix} (\hat{x},\hat{y})^T+(x_0,y_0)^T$, where $\hat{}$ signifies the right angled triangle. However, I am unsure what the original mapping is, i.e. the equation of the change. For the square I am struggling to think of a mapping and then have no idea how to apply it. My first attempt was to take the mapping, $ (\hat{x},\hat{y})^T = (\eta_1(1-\eta_2),\ \eta_2)^T $. Then find the Jacobian, $ J = \begin{bmatrix} 1-\eta_2 & \eta_1 \\ 0 & 1 \end{bmatrix} $. Which gives the transformation, $ (\hat{x},\hat{y})^T = \begin{bmatrix} 1-\eta_2 & \eta_1 \\ 0 & 1 \end{bmatrix}(\eta_1,\eta_2)^T $ , I think. The reason I look to do this is for numerical quadratures. I am not sure if the above is correct so any advice would be great - even if it is a good book on mappings!


I need a feature for saving draft posts in my account in some sites like Math.SE. I use different computers and sometimes have several questions to be asked once I find a computer with internet access. At least I don't forget them if I can save them in my account instead of discarding them before 20min obstacle or similar rules.


Use Super+ to switch workspaces in Ubuntu 16.04

I would like to set up Ubuntu to switch between workspaces when pressing Super+Number (ie: Super+1 goes to workspace 1, etc etc)  I have the correct shortcuts set in the Keyboard settings, but instead of switching workspaces it opens up the app from the drawer on the left. For the life of me I cannot figure out how to disable the default Super+Number shortcut in 16.04.  There's been multiple post and links I've found regarding much older installs of Ubuntu (12.XX~ish), they recommend modifying compizconfig, but I don't know if that's still relevant to 16.04.  Additionally, I found another question regarding 17.10:   However, the suggestion there to try gsettings set org.gnome.shell.extensions.dash-to-dock hot-keys false returns No such schema 'org.gnome.shell.extensions.dash-to-dock'  Any help that anyone can offer would be a huge help!


How does temperature differ from mean kinetic energy?

If I understand it correctly, temperature is the measure of the average kinetic energy of a substance. Why is it then that $T\neq \bar E_{k}$ or something similar? Why is the kelvin a base unit and temperature a base quantity in The International System of Units (SI)?


tl;dr ... found a script that uses ${1+"$@"} to forward command line arguments to another script. What exactly does this do? When do you use it instead of $@ and "$@"?  There's a simple shell script called runhaskell that is distributed with ghc on Ubuntu 15.10 (and perhaps others). I am trying to figure out how to replace it with something that's aware of cabal sandboxes. The shell script looks like this. It appears to have some variables that aren't used and an unnecessary shebang-like comment (from an earlier version of the script?)  #!/bin/bash exedir="/usr/lib/ghc/bin" exeprog="runghc" executablename="$exedir/$exeprog" datadir="/usr/share" bindir="/usr/bin" topdir="/usr/lib/ghc" #!/bin/sh  exec "$executablename" -f "$bindir/ghc" ${1+"$@"}   I'm having trouble understanding the last line. /usr/lib/ghc/bin/runghc is a native executable that runhaskell evidently delegates to, and one of the arguments it passes in is the location of the compiler. Okay, no problem.  What does ${1+"$@"} do and when should you use it? My best guess is that 1 is just a test that always succeeds and that this construction is just being used just to pass in the arguments verbatim. I remember POSIX requires that $@ and "$@" behave somewhat differently from what you'd expect, but I don't remember the exact details.


Does anybody know how Machinarium handles save states?  I put about a half hour into it the other day, clicked 'Save,' and then quit.  Loaded it up today to continue and lo and behold, my save game was nowhere to be found.  One caveat is that I don't have internet access currently...is it possible that it syncs save states with the Steam cloud?


"Two and two makes four" vs. "two and two make four"

Two and two makes four.   Two and two make four.      Which is grammatical? Please provide your reasoning.


Add (replace) hyperlink to pictures in a Picture Library Slideshow Web Part

On our team site we have added a web part that is a "Picture Library Slideshow" web part. Currently clicking on the images that scroll in the slideshow directs the browser to just the image's URL. I would like to modify that to point to any other URL of my choice.   I have tried forcing a modification of the javascript that is generated by the slideshow webpart using my own script on the page. Looking at the source, the Picture Library uses a var that actually sets the links, it's called "linkArray":  var pictureArray = ['http://intranet/HomePicture/_w/image1.jpg','http://intranet/HomePicture/_w/image2.jpg']; var linkArray = ['http://intranet/HomePicture/image1.jpg','http://intranet/HomePicture/image2.jpg']; var titleArray = ['','']; var descriptionArray = ['','']; var heightArray = [268,268]; var widthArray = [383,383];   Using my own script I tried to clear out the array and insert my own links into it, but for some reason the links only update (i.e. my script's function runs) after the first image changes. Even if I manually change the first image's href tag, the script still thinks the "first" image is the second one that the slideshow scrolls to. Is there a way to force the function to overwrite the existing javascript immediately on page load?


Alice and Bob play the following game with an $n \times n$ matrix, where $n$ is odd. Alice fills in one of the entries of the matrix with a real number, then Bob, then Alice and so forth until the entire matrix is filled. At the end, the determinant of the matrix is taken. If it is nonzero, Alice wins; if it is zero, Bob wins. Determine who wins playing perfect strategy each time.    When $n$ is even it's easy to see why Bob wins every time. and for $n$ equal to $3$ I have brute-forced it. Bob wins. But for $n = 5$ and above I can't see who will win on perfect strategy each time. Any clever approaches to solving this problem?


Itemized list side by side with a figure

I am trying to create a slide: on the left is an itemized list, on the right is a figure. It seems I can use tabular in beamer, however, the following code doesn't work - it complains about extra \frame. I also tried fragile option, but no avail. Can someone help?   \RequirePackage[demo]{graphicx} \documentclass{beamer} \begin{document}  \begin{frame} \begin{tabular}{ll}      \begin{itemize}         \item test 1         \item test 2     \end{itemize}      & \includegraphics{demo}  \end{tabular} \end{frame}  \end{document}


I did a factory reset on my Toshiba laptop. I didn't realize it would wipe out all my existing files. Is there any way to recover the files that were on there before I reset it?


How make a frame of cloth simulation into a permanent object?

I'm using the cloth modifier on a plane, and I was wondering if it is possible to take away the animation, with the default of that object being what it is in a frame of that animation.    I want the cloth to look like that in the beginning of the animation (or without an animation at all, really), where it looks like this:


Issues with the templates, when I use a wstring and a wchar_t

I've written a function that turns a string into a vector. Now I want to make a template of the types, because I also want to use wstrings and wchar_t. Because they are in a csv file. Here are my files ... main.cpp #include <iostream> #include <fstream> #include "trans.h" #include "vector_to_string.cpp"  using namespace std;  int main() {     wifstream tstream("translation.csv");     wstring s;      while (getline(tstream, s)){         vector<wstring> vec = vector_from_string(s, ',');         wstring ws = vec[0];         Trans<wstring> t(ws);         wcout << t.translate(Spanish) << endl;      } }  vector_to_string.cpp template <class T, typename U> std::vector<T> vector_from_string(T to_vec, U delimit) {     int pos = 0, len = 0;     std::vector<T> vec;     for (int i = 0; i < to_vec.length(); i++) {         U c = to_vec.at(i);         if (c == delimit) {             vec.push_back(to_vec.substr(pos, len));             len = 0;             pos = i + 1;         } else if (i == to_vec.length() - 1) {             int end = to_vec.length() - pos;             vec.push_back(to_vec.substr(pos, end));         } else {             len++;         }     }     return vec; }  translation.csv # English , French, German, Spanish a,une,ein,UNE aa,aa,aa,Automóvil club británico aaa,aaa,aaa,aaa aaron,aaron,aaron,Aaron ab,un B,ab,Un B abandoned,abandonné,verlassen,abandonné abc,abc,ABC,a B C aberdeen,aberdeen,aberdeen,Aberdeen abilities,capacités,Fähigkeiten,capacités ability,aptitude,Fähigkeit,aptitud able,capable,imstande,capaz aboriginal,Aborigène,Ureinwohner,aborigène abortion,Avortement,Abtreibung,avortement about,à propos,Über,Al respecto above,au dessus de,über,au dessus de abraham,abraham,abraham,Abrahán abroad,à l'étranger,im Ausland,en el Extranjero abs,abdos,Abs,abdos ...  The problem is in vector_to_string () but I can't find the problem, and I get this syntax error ... undefined reference to `std::vector<std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, std::allocator<std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> > > > demonic::vector_from_string<std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, wchar_t>(std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >, wchar_t)'  What is the problem and how can I best solve it?


login issues after xubuntu 15.10 upgrade

not so recently had my laptop ask for ubuntu to do an upgrade. now when I try to open it it goes through a xubuntu screen then back to what looks like a dos prompt asking for login and then password. I don't remember it asking for any info during the upgrade and i never used a login before but now i've been locked out of my pc for months. I've tried everything i can think of! somebody help this idiot get my pc back. And no this is not a dup of the one whose unity isnt working because this has nothing to do with unity. I cant even get to unity because the computer gets stuck at login. One person suggested that whatever I set it as when I first loaded ubuntu years ago is what it is. Great! except I have no idea what that would be and I have tried every possible combination of login and password combos I can think of. Since I've been doing this for 3 or 4 months Ive tried A LOT of combos. And on top of that when I type the password it appears to enter no character, data, on and on. So I dont even know if it is even working there.


will booting Ubuntu in my samsung np550p5c-s06in brick it?

i bought this laptop in july,2013... and it was manufactured in march... i wanted to dual boot it with ubuntu (using wubi) and windows 8.1(running now). can it harm my computer? if yes then is there any way to prevent it?


I am getting out of memory error,how to resolve?what is mean by Permgen space area? What is causing it?  What is solution for it?  java.lang.OutOfMemoryError: PermGen space     java.lang.ClassLoader.defineClass1(Native Method)     java.lang.ClassLoader.defineClassCond(Unknown Source)     java.lang.ClassLoader.defineClass(Unknown Source)     java.security.SecureClassLoader.defineClass(Unknown Source)     org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1814)     org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:872)     org.jboss.web.tomcat.service.WebAppClassLoader.findClass(WebAppClassLoader.java:75)     org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1325)     org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1204)     com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:289)     java.sql.DriverManager.getConnection(Unknown Source)     java.sql.DriverManager.getConnection(Unknown Source)


Apt-get fails on 16.04 or 18.04 installing mongodb

When I attempt to install mongodb using the instructions on https://docs.mongodb.com/getting-started/shell/tutorial/install-mongodb-on-ubuntu/ on 16.04 I get the following result on the install step:  jonathan@poseidon:~$ sudo apt-get install mongodb-org Reading package lists... Done Building dependency tree        Reading state information... Done Package mongodb-org is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'mongodb-org' has no installation candidate   I checked the HTTP traffic with Wireshark and found that the only traffic was a HTTP GET for the list and a HTTP 304 response which suggests that the problem lies in my local configuration files. My sources.list.d file contains the following entry:  mongodb-org-3.4.list   What do I need to do to continue to troubleshoot this problem?  EDIT: I tried to do this again on a new install of 16.04 under VirtualBox. I retrieved the key, created the list file, and did sudo apt update with the following results:  jonathan@Ubuntu-16:~$ sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 0C49F3730359A14518585931BC711F9BA15703C6 [sudo] password for jonathan:  Executing: /tmp/tmp.uWYpRUWfjK/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com:80 --recv 0C49F3730359A14518585931BC711F9BA15703C6 gpg: requesting key A15703C6 from hkp server keyserver.ubuntu.com gpg: key A15703C6: public key "MongoDB 3.4 Release Signing Key <packaging@mongodb.com>" imported gpg: Total number processed: 1 gpg:               imported: 1  (RSA: 1) jonathan@Ubuntu-16:~$ echo "deb http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.2 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-3.4.list deb http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.2 multiverse jonathan@Ubuntu-16:~$ sudo apt update Ign:1 http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.2 InRelease Get:2 http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.2 Release [3 462 B] Hit:3 http://mx.archive.ubuntu.com/ubuntu xenial InRelease                Get:4 http://security.ubuntu.com/ubuntu xenial-security InRelease [94.5 kB]                    Get:5 http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.2 Release.gpg [801 B]                       Get:6 http://mx.archive.ubuntu.com/ubuntu xenial-updates InRelease [95.7 kB]            Ign:5 http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.2 Release.gpg                        Get:7 http://mx.archive.ubuntu.com/ubuntu xenial-backports InRelease [92.2 kB]                     Reading package lists... Done       W: GPG error: http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.2 Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D68FA50FEA312927 E: The repository 'http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.2 Release' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. jonathan@Ubuntu-16:~$    As you can see, the key retrieved was for Mongodb 3.4, not Mongodb 3.2 and this explains the GPG failure in apt update. Any one know where to get the correct key?


Anyone seen this one yet? Vote too old to be changed, unless post is edited My vote was only a few hours old. Then I realized the answer was wrong. Updated my question and went to remove the vote. Even after updating question I still have the issue. Small issue, but frustrating.  See also:


Given a matrix A such that $a_{ij} = \frac{1}{i + j - 1}$, prove that A is invertible and that $A^{-1}$ has all integer entries.

Essentially just the title. This is supposed to be the introductory Upper Division Linear Algebra class so we haven't covered the determinant yet. I'm mentioning this because I am aware of the theorem that states that the conclusion would follow if the determinant was either 1 or -1. We haven't proven that in class yet so we can't use it. Anyway, if any of you have any ideas or hints, I would greatly appreciate it.   Thank you!   EDIT: Actually, that theorem does not apply in the way I stated. Either way, it cannot be used to solve this problem as it wasn't covered in class.   EDIT 2: This question is different than the other question asking why the elements of the inverse of the Hilbert Matrix are integers because my solution cannot include much outside of row reduction (elementary matrices), the definition of matrix multiplication, and the basic properties of matrix inverses.


Does the Higgs boson give mass to ALL other particles?

The  gave mass to other particles via spontaneous symmetry breaking; does this mean it gives mass to all particles that have mass - such as neutrinos, quarks or weak bosons and strong bosons (gluons)?  In the articles I've seen its not clear what the criteria is for the Higgs Field to couple to particles to give mass; Anna v's answer suggest that electo-weak vertexes are required; but the linked article suggests it also couples to quarks.


Does Burning Hands really require touching thumbs?

The D&D 5E spell Burning Hands has verbal and somatic components, and is described like this:     As you hold your hands with thumbs touching and fingers spread, a thin sheet of flames shoots forth from your outstretched fingertips. [...]   The rule for somatic components, however, is that If a spell require a somatic component, the caster must have free use of at least one hand to perform these gestures.  So, what happens if a character has one hand free but the other is restricted so it can't be reached? What if one hand is occupied and fingers can't be spread like this? To a greater extreme, is this spell unavailable to a character who has only one arm?   Or, from a technical angle: is the description here a specific rule for this spell which overrides the general rule for somatic components, or is it just flavor text intended to give a visual for one possible way to cast the spell?


How to write to terminal device stdin of running process from a different terminal without any prior preparation?

There seem to be plenty of similar questions, for example:    However the answer given is to prepare the program beforehand by making its stdin a pipe.  There's also:    Which is answered by commanding a terminal multiplexer under which the program in question is running. That means it also needs prior preparation.  This question is about how to do this without having done any preparation beforehand.  At first I thought it might be as simple as:  echo foo > /proc/$p/fd/0   but that just writes to the terminal. So then I tried:  echo foo > /proc/$terminal_emulator/fd/$ptmx_fd   but that also fails because it just opens up a new terminal device slave for echo.  I already have an answer using gdb (sigh) which I'll be posting below, but I wonder if anyone knows of a simpler and better alternative.


Two distinct users on Windows at the same time

Can two distinct users legally and ToS-compliantly use the same Windows 10 machine simultaneously (i.e. both being logged in)? If it helps, allow for remote connections.  An ideal answer would be supported by documentation in case the answer is "No".


If yt is pure random walk the variance Var(yt-yt-k) will (increase, decrease or remains constant) as lag k increases?


why the ending symbol dx is also changed into a function of d theta and then multiplied by the integral after substitution?

This is a question about trig substitution used in integrals. Because it is difficult to solve an integral when there is radical in it, we use a trig function of theta to substitute x from the original integral. The only thing I don't understand is why the ending symbol dx, which indicates that we are integrating the function with respect to the "x" variable, is also changed into a function of d theta and then multiplied by the integral after substitution. I think after substitution, we can just rewrite dx into d theta.


Given $A^2$ where A is matrix, how find A?

Problem is simple.  Given $$A^2=\begin{bmatrix}13 & 9 &-9 \\ 0 & 4 & 0 \\ 12 & 12 & -8 \end{bmatrix}$$ How find $A$?  I think a method using eigenvalues and I find them. But I can't find an actual $A$. Is it right to use eigenvalues?


Why is the object, and not the memory address of the object, the first argument in this example c++ snippet?

I have a pretty basic c++ question (coming from a Python background).   I'm working through an example from the 'tour basics' book by Bjarne Stroustrup. Its basically this:   #include <iostream>  using namespace std;  struct Vector {     int sz;         // number of elements in vector     double* elem;   // pointer to elements in vector };  void vector_init(Vector& v, int s) {     v.elem = new double[s];     // allocate an array of s doubles     v.sz = s; }  int main() {      Vector v;     vector_init(v, 10);     return 0; };    What is causing me confusion is that the function vector_init takes a memory address of a vector for its first argument, but when its being used in the main, we are passing the vector v itself, not its memory address (which I assume would be &v rather than v).   This is working code and it compiles, but why do you not need to give the memory address as an argument here?


$\lim_{n\to \infty }\cos (\pi\sqrt{n^{2}-n})$ - second battle

Followed my  ,  I still don't understand why the answers that were given are right.  By simply intuition and using the continuity of cosine, we get that we need to compute  $\lim_{n\to \infty}\cos (\pi n\sqrt{1-\frac{1}{n}})$ and because of that, as I see that, there are two clear limits: 1 and -1, and therefore the limit does not exist  Can someone please explain me why am I wrong? two answers that claimed that the limit is 0 got 25 votes together, so I must be mistaken, But still the answers are not satisfying me.  By the way, Wolfarmalpha  it does not have a limit.  Thank you.


Why are there links to answers in the related questions list?

On two three of the four newest Meta questions, there are posts in the "related" section without a title:    I was curious to see what that was, and the link was a link to an answer. Clicking the link took me to the answer, and the score in the link was the score of the answer, not of the question (in the example above, the answer had score 8 and the question had score 3).  What's also strange is that although it was a link to an answer, it had a question URL (in the example above ).  I saw this happen just recently on several questions on both Meta Stack Exchange and Super User, and I have never seen this happen before. I'm quite sure this is a bug.


Converse of Lagrange Theorem for p-groups.

I need clarification on my understanding of Sylow Theorems.   Can I say that a finite p-group will have a subgroup for each prime power? If the above is valid, can I say then that p-groups satisfy the converse of Lagrange Theorem?   I'm not sure of that statement. Can someone show me a counterexample of it if not? Thanks


Taylor series remainder term to yield $\ln4$ with error terms less than $2^{-10}$

I need to derive the taylor series for $\ln(1+x)$ about $1$ then create an inequality that gives the number of terms that must be taken to yield $\ln4$ with error terms less that $2^{-10}$. I got the taylor series to be $$f(x) = ln(2) + \sum_{n=1}^{\infty} \frac{(-1)^{n+1}(x-1)^n}{n \cdot 2^n}$$ I was wondering if someone could help me with the the error term, I think the answer is suppose to be $n > 2^{10}-1$ but I cant seem to figure out how to get there. thanks


Prove that even $n$ can be partitioned to $\frac n2$ edges

I have to show that the edges of a complete graph on $n$ vertices for even $n$ can be partitioned into $\frac n2$ edge disjoint spanning trees.   I know that a complete graph has $\frac{n(n-1)}{2}$ edges. And for reference, a spanning tree is a tree on all $n$ vertices, so it has $n-1$ edges. But I don't know how to show my statement.


No option in 'flag -> close -> off-topic -> belongs elsewhere' for migrate to stats.SE

On Stack Overflow there a many questions pertaining to statistical software such as .  Most of these questions are programming questions and undoubtedly belong on SO.  However, some questions are really about the underlying statistical ideas, and not about how to use R per se.  They belong on stats.SE (i.e., ).  However, when I flag such questions, CV is not listed with the other SE sites as an option.  Can we add CV to that list?


How can Inheritance be modelled using C?

Is it possible to model inheritance using C? How? Sample code will help.  Edit: I am looking to inherit both data and methods. Containership alone will not help. Substitutability - using any derived class object where a base class object works - is what I need.


How do I create a new tag in the mobile iOS/ Android app? This operation is currently not supported.  When I tap the tags section, a search window opens; when I type something not existing and press Done, the tag section remains blank.  Please add such option to the apps. It is specially important in case of newly launched sites.


multiplying lists function, did not understand the output.python

I have encountered this function:      def square_it(var):     return [var *2] *2  zoo = (square_it([1])) zoo[1][0] +=1 print(zoo)   I dont understand why the output is: [[2, 1],[2,1]] and not [[1, 1], [2, 1]] can someone please explain this? Thanks.


I have a pattern and a string as an input, I'm looking to find that pattern N times in the input but if doesn't work.   I tried with following pattern:      private static Pattern test = Pattern.compile("(<tag>)(.*)(</tag>)");     private static String input = "<tag>hello</tag>blablabla<tag>world</tag>";      public static void main(String[] args) {         MyClass myClass = new MyClass();         System.out.println(myClass.change(input));     }      public static String change(String text) {     StringBuilder s = new StringBuilder();      try {         Matcher m = test.matcher(text);         int pos = 0;         while (m.find()) {             s.append(text, pos, m.start());             pos = m.end();             s.append("&&" + m.group(2) + "&&");         }         s.append(text, pos, text.length());      } catch (Exception e) {         System.out.println("Exception " + e);     }     return s.toString(); }   this is what I'm getting:      &&hello</tag>blablabla<tag>world&&   and this is the result what I want:      &&hello&&blablabla&&world&&   Any idea? Thanks


Test for divergence of $\int_{0}^{\infty} \frac{\sin^2(x)}{x}dx$ without evaluating the integral

I would like to prove that $$\int_{0}^{\infty} \frac{\sin^2(x)}{x}dx$$ diverges without actually evaluating the integral. Is there a convergence test from calculus or real analysis that can show that this integral diverges?  Thanks.  Edit: Someone pointed out that this is a possible duplicate. However, the question put forth as a possible duplicate asks about $\sin(x^2)$, not about $\sin^2(x)$.


Let $n\in\Bbb Z$. Prove that $n$ is a multiple of both $5$ and $9$ if and only if it is a multiple of $45$.

I came across this problem while studying for a midterm and I'm having a tough time proving the first implication:     Let $n\in\Bbb Z$. Prove that $n$ is a multiple of both $5$ and $9$ if and only if it is a multiple of $45.$   I know that:  If n is a multiple of $45, n = 45a,$ where $a \in\Bbb Z.$ Then, $n = 5(9a) = 5b$, where $b = 9a$. Thus, $n$ is a multiple of $5$.   Likewise, $n = 45a = 9(5a) = 9c$, where $c = 5a$. Thus, n is also a multiple of $9$.  Where I have trouble is proving that if $5$ and $9$ divide $n$, $45$ also divides $n.$  $n = 5a$ and $n = 9b$, where $a,b \in\Bbb Z.$  I'm pretty lost as to what my next step here should be. Anyone have a hint to point me in the right direction?


Record Access Issue on After Insert Trigger

A Community User is trying to create a record in a Custom Object, this trigger autofills the account lookup and the account owner is made this custom object owner as well.   Object Level Permission, Account - Public Read Only & Custom Object - Public Read/Write  Without this trigger I am able to create records for that Custom Object but if I try to create a record with this trigger Active - I get an error as      "Error: Invalid Data.  Review all error messages below to correct your   data. Apex trigger AutofillFields caused an unexpected exception,   contact your administrator: AutofillFields: execution of AfterInsert   caused by: System.FinalException: Record is read-only:   Trigger.AutofillFields: line 12, column 1"   trigger AutofillFields on MyCustomObject__c (After Insert,After Update) {      List<User> lstUser = [Select Id, ContactID, Contact.AccountID, Contact.Account.OwnerID, Profile.Name FROM User                              WHERE Profile.Name LIKE 'Customer Community Name'];      for(User iusr : lstUser){         For(MyCustomObject__c irow : Trigger.new){             IF(UserInfo.getUserId().contains(iusr.ID)){                  irow.Account__c = iusr.Contact.AccountID;                 irow.OwnerID = iusr.Contact.Account.OwnerID;                             }         }     } }


If a person depends upon you, what are you for him?

Are you his dependency, dependendee or something else? What is this type of opposite word called?  I believe it is not called antonym, as that would be independent.


Is there software I can load on my web servers to know how much of my traffic is going to china?

I have 15 VMs on Google Cloud and would like to know which one is causing my egress data to china.  How can I tell which one is doing the all that traffic? It has probably been hacked and would like to fix it.


Finding out the remainder of $\frac{11^\text{10}-1}{100}$ using modulus

If $11^\text{10}-1$ is divided by $100$, then solve for '$x$' of the below term $$11^\text{10}-1 = x \pmod{100}$$   Whatever I tried:  $11^\text{2} \equiv 21 \pmod{100}$.....(1)  $(11^\text{2})^\text{2} \equiv (21)^\text{2} \pmod{100}$  $11^\text{4} \equiv 441 \pmod{100}$  $11^\text{4} \equiv 41 \pmod{100}$  $(11^\text{4})^\text{2} \equiv (41)^\text{2} \pmod{100}$  $11^\text{8} \equiv 1681 \pmod{100}$  $11^\text{8} \equiv 81 \pmod{100}$  $11^\text{8} × 11^\text{2} \equiv (81×21) \pmod{100}$ ......{from (1)}  $11^\text{10} \equiv 1701 \pmod{100} \implies 11^\text{10} \equiv 1 \pmod{100}$  Hence, $11^\text{10} -1 \equiv (1-1) \pmod{100} \implies 11^\text{10} - 1 \equiv 0 \pmod{100}$ and thus we get the value of $x$ and it is $x = 0$ and $11^\text{10}-1$ is divisible by $100$.  But this approach take a long time for any competitive exam or any math contest without using calculator. Any easier process on how to determine the remainder of the above problem quickly? That will be very much helpful for me. Thanks in advance.


I am using windows 8.I wanted to install ubuntu alongside with windows. I can install with windows 7 but not windows 8..Please Guide me


PS: Oops! This is somewhat duplicate. Thanks for those who made interest for this post. I will delete this post in a few hours. Please cite the following link  PS2: Now this post has a one correct answer. Should I delete this post? Let $\zeta_n \in \mathbb{C}$ be a primitive $n^{\textrm{th}}$ root of unity and call $\mathbb{Q}[\zeta_n]$ the $n^{\textrm{th}}$ cyclotomic extension of $\mathbb{Q}$.  Let $m$ and $n$ be positive integers. Describe a simple relation of $m$ and $n$ which is equivalent to $\mathbb{Q}[\zeta_n] = \mathbb{Q}[\zeta_m]$  A student solving exercises on Galois theory made the following argument. Consider $\zeta_{19}$. She could see that $-\zeta_{19}$ is one of primitive $38$th root of unity. So she conclude $\mathbb{Q}[\zeta_{19}] = \mathbb{Q}[\zeta_{38}]$. That was right. But it seems that she thought those two fields are not same. I have told her the fact. However I cannot tell a simple criterion amounts to the above question. Would you please help me?


Which worth it to use first? Load balance or HTTP cache server?

We have a web application that we are about to take live. But I have a fear that the server won't be able to handle all the requests and it won't be as comfortable to the users as a website should be. Currently I'm thinking about using 2 things. One of them is having 2 more additional servers and use them to loadbalance the users between the servers. So it would be 1 Loadbalanced server, 2 webapplication servers and 1 backend (database) server.  The other thing is HTTP cache. Can it be enough if I just get one more server and set it up as a cache server with NginX? Which would you do if you are limited in terms of resources and why? (Maybe how?)


Does rendering on sheepit not render animations done using animation node?

I have this 1000 frames animation where I had the text animated using the animation nodes add-on. However, when I put it on sheepit, the online render farm, none of the text animations showed up. Is there a fix for this?


Manual computation for Fishers exact test for tables larger than 2 x 2

I am wondering how to perform a Fishers exact test on my data which contains two columns and three rows. One of the cells contains zero.               2012    2018 Pass          116     166 Submax         11      45 Fail            9       0   I would like to compare the data between the years 2012 and 2018. Any help would be much appreciated! I only have access to excel but if anyone else can calculate it for me that would be brilliant.


regex match everything between tags with text

I have this code
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\s*##QA##\s*<\/p> works for matichg
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  I would like to match content between both
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Detect charset and convert to utf-8 in Python?

Is there any universal method to detect string charset? I user IPTC tags and have no known encoding. I need to detect it and then change them to utf-8.  Anybody can help?


How can I JSON_decode arrays that has been treated with mysqli_real_escape_string, htmlspecialchars,strip_tags?

Sorry for the long title.  I am kind of paranoid, so I sanitized $_POST that was treated with JSON.stringify(order) via javascript with  $order = mysqli_real_escape_string($db_upload, htmlspecialchars( strip_tags($_POST['order'])));   before inserting into mysql through mysqli prepared statement.  But when I try to json_decode by  foreach(json_decode($row['order'], true) as $id =>$value){     $sumArray[]= array("item" => $id, "value" => $value); }   I get "Invalid argument supplied for foreach() ..."  I know json_decode works when inserted value is   {"Hot water":"1"}   but not when inserted value is  {&quot;Hot water&quot;:&quot;1&quot;}   In this case, how can I json_decode?  Thanks.  edit: I was poor at explaining what I really wanted. As I have mentioned earlier, I already used mysqli prepared statement for inserting the data. I am less worried about sql injection but to advanced xss attacks.  What i really wanted was just how to json_decode  {&quot;Hot water&quot;:&quot;1&quot;}   I decided to go easier method: dropping htmlspecialchars. What I did was   $order = mysqli_real_escape_string($db_upload, strip_tags($_POST['order']));   then,   foreach(json_decode(stripslashes($row['order']), true) as $id =>$value){ $sumArray[]= array("item" => $id, "value" => $value);   }  This worked nicely


Capacitors - аffected by temperature or not?

Are these capacitors аffected by the temperature changing or not?


I have 53 MB of free storage on my internal Storage. But, still, when I am trying to re-install whatsapp messenger, (which is merely of 17.53 MB) after uninstalling it initially, it shows Insufficient Storage Space.  Specifications: Model Number : Micromax A58, Android Version : 4.2.2  What should I do to solve this memory problem?


$g(z)$ analytic implies $\overline{g(\overline{z})}$ analytic?

Let $D = \{x \in \mathbb{C} : \text{Re}(z) > 0\}$, and $g: D \to \mathbb{C}$ an analytic function. Does it follow that$$f(z) = \overline{g(\overline{z})}$$is also analytic?


How to prove $3^{\log_4n} = n^{\log_43}$?

I got this from "4.4 The recursion-tree method for solving recurrences" in book "Introduction to Algorithms"  The recurrence that try to use recursion-tree to solve is: $T(n) = 3T(n/4) + cn^2$


public class Makakiesmarkou {  void swap(int i, int j, int[] arr) {     int t = arr[i];     arr[i] = arr[j];     arr[j] = t; }  public void MySort(int[] T) {     for(int m=0; m<T.length-1; m++)     {         int j=m;         for(int k=m+1; m<T.length-1; k++)         {             if(T[k]<T[j])                 j=k;         }         swap(T[j], T[m], T);     } }  public static void main(String[] args) {      int[] pin= new int[50];     MySort(pin);     System.out.println(Arrays.toString(pin)); }  }   the error when i call MySort in the main class is "non static method MySort[int[]] cannot be referenced from a static context"  what am i doing wrong?


Difference between effect size (partial $R^2$) and coefficients

I am working with spoken language data and use linear models do determine the relationship between different phonological processes in my data.   Background   Measures of the regularity of syllable durations are influenced by how syllable is defined. I used two methods to determine syllable boundaries. Method 1 and 2 give different results for regularity of syllable durations, but the difference between the two methods is not the same for every speaker.  Linear model  I think the frequency of certain phonological processes (vowel elision, insertion of glottal stops and others) might be responisble for these differences. I want to find out if that's true and if yes how much each of these phonological processes contributes to explaining the differences.  Measuring effect size with partial $R^2$/sum of squares  To measure effect size, I could use . The data below is the ANOVA of my model, and from the variance explained by each factor (Sum Sq) I can derive how much of the total variance each factor explains.  Analysis of Variance Table  Response: varcos                           Df Sum Sq Mean Sq F value    Pr(>F)     rel_gs                     1 395.48  395.48 46.9135 7.022e-07 *** rel_all2_gs                1   9.47    9.47  1.1236    0.3006     rel_gs:rel_all_gs          1   1.37    1.37  0.1622    0.6910     rel_gs:rel_all2_gs         1  13.63   13.63  1.6168    0.2168     rel_all_gs:relDur.mean.y   1  15.94   15.94  1.8910    0.1829     rel_all2_gs:relDur.mean.y  1  69.19   69.19  8.2079    0.0090 **  Residuals                 22 185.46    8.43                         Coeffcients  Beta coefficients can also be interpreted as a measure of effect size, as  points out. I was expecting that factors that explain a large part of the variance would also have large coeffcients, and the other way around. But that's not the case. rel_gs:rel_all2_gs has a huge negative coefficient, but explains only a small part of total variance.  Call: lm(formula = varcos ~ rel_gs + rel_all2_gs + rel_all_gs:rel_gs +      rel_all2_gs:rel_gs + relDur.mean.y:rel_all_gs + relDur.mean.y:rel_all2_gs,      data = read.wwb3.diff_syll.perc)  Residuals:     Min      1Q  Median      3Q     Max  -5.7929 -1.5933 -0.5208  1.5569  5.4834   Coefficients:                            Estimate Std. Error t value Pr(>|t|)     (Intercept)                  15.539      2.725   5.702  9.8e-06 *** rel_gs                     -336.020    118.306  -2.840  0.00952 **  rel_all2_gs                 492.997    183.440   2.688  0.01345 *   rel_gs:rel_all_gs          2533.220    810.012   3.127  0.00490 **  rel_gs:rel_all2_gs        -2292.357    716.625  -3.199  0.00414 **  rel_all_gs:relDur.mean.y   -955.239    315.827  -3.025  0.00623 **  rel_all2_gs:relDur.mean.y   691.578    241.394   2.865  0.00900 **    Question  Should I only trust partial $R^2$ for effect size and ignore differences between the coefficients?  P.S.: I asked  some time ago, and it hasn't received much attention and left some issues open. I suppose that might be because the original question wasn't clear enough or was based on toy data. In this question I'm using actual data. If my question could be imporoved in some way I'd be happy to consider any suggestions.


I want to change char* to float without loss

If there's a char* type "37.2", I'd like to change it to float type 37.2, but it's changed to 37.2000008 when I used the atof function. How do I change it to 37.2?


Difference Between Fraunhofer and Fresnel Diffraction

What is the difference between  and ? I mean diffraction is just bending of light waves or waves in general around a point. So how can there be two types of diffractions?  If Diffraction means something else in this context, then please explain the difference between these two types of diffraction.


To meet WCAG AA on desktops, what is the minimum space required between two click targets?

I have already looked at these:        None of these tell us for certain what is the minimum spacing required between two click targets on Desktops while being compliant to WCAG AA. Either I am missing the term that is being used to define this in WCAG Guidelines or this is not defined yet. If this is not defined yet then how much space (in pixels) should I be keeping between two click targets?  Also if possible please guide on the minimum size required for related UI Elements such as Buttons, input boxes, radio and check boxes and Links for being AA Compliant on Desktops.


Why $1/r^2$ and not another power of $r$ in Newton's law of gravitation?

My book introduces the force of gravitation as a non-contact force between two bodies of mass $M_1$ and $M_2$ separated by a distance $r$ . Then it says it is directly proportional to the product of masses $M_1 M_2$ and inversely proportional to $r^2$. Then writes the the force of gravitation as  $$ F = G\dfrac{M_1M_2}{r^2}. $$  But why does it take square of $r$ and not another power? What is the cause of taking $r^2$? Why not another power of $r$?


Limit of $\frac{1^n+2^n+\cdots+(n-1)^n}{n^n}$ as $n$ go into infinity

$$\lim_{n\to\infty}\frac{1^n+2^n+\cdots+(n-1)^n}{n^n}$$  I have found that  the sequence is increasing as $n$ increases. I guess that the answer should be $\frac{1}{1-e}$.