I need to create a network flow model for building (if possible) the new organizing schema for the following problem: At the Computer Science Department at the beginning of the first semester there are p freshmen (study) groups: group i contains n(i) students, for all i = 1, p. For the second semester the Department wants to reorganize these groups in such a way that: ->the new organizing schema has r groups; ->the new group j contains m(j) students, for any j = 1, r; ->any new group cannot contain more than c students which were classmates in a same old group from the former organizing schema (c ∈ NN∗ \ {1}). - My idea would be to use a network that contains a bipartite graph but don't know how to organise students and grups inside it and how to describe this bipartition.

The problem I'm attempting to solve is formulated like this:  A department consists of n groups such as for each group i in $\overline{1,n}$ contains $p_i$ members.  A change in the organization is wanted so that:  the new organizing schema contains q groups of members each group in $\overline{1,q}$ will contain $k_i$ members the new groups may not contain more than c members which were part of the same old group (c $\geq$ 2 , c $\in \mathbb{N}$)  How to find a model based on a flow network to build this new organizing schema?  I've tried building a network flow graph but I had trouble in representing the member groups and the restriction that no more than c members which were part of an old group can be present in a new group. Thank you for reading the question, any hint or solution is greatly appreciated.


My son asked me to make a Pokemon trainer club account so he can play Pokemon go, when the game fist launched.But I count because the servers were always down. so i was able to log in with my google account and been playing ever since. Just a few days ago i was able to make an account with Pokemon trainer club but i have to start all over again. Is there any way to sync my two accounts so i can continue at the level I'm at?

I am  with the Google login for Pokemon Go. Is there any way, be it contacting support or through Trainer Club, to either link my Google account to a new Trainer Club account or transfer my account to a Trainer Club account?  It seems like a better idea to have a Trainer Club account, so if there are Google login problems it won't matter.  Does anyone know if something like this is possible?


How safe is it if I run the suggested command line. Is there a bug?  The following packages were automatically installed and are no longer required:    linux-headers-4.15.0-32 linux-headers-4.15.0-32-generic   linux-headers-4.15.0-33 linux-headers-4.15.0-33-generic   linux-headers-4.15.0-34 linux-headers-4.15.0-34-generic   linux-image-4.15.0-32-generic linux-image-4.15.0-33-generic   linux-image-4.15.0-34-generic linux-modules-4.15.0-32-generic   linux-modules-4.15.0-33-generic linux-modules-4.15.0-34-generic   linux-modules-extra-4.15.0-32-generic linux-modules-extra-4.15.0-33-generic   linux-modules-extra-4.15.0-34-generic  Use 'sudo apt autoremove' to remove them.

I started using Ubuntu and like it so far. I got my first system at a point where problems would really hurt. Normally I do the apt-get upgrade stuff quite brain-off but this here made me feel a bit uncertain. The following packages were automatically installed and are no longer required:   linux-headers-4.15.0-29 linux-headers-4.15.0-29-generic linux-image-4.15.0-29-generic linux-modules-4.15.0-29-generic linux-modules-extra-4.15.0-29-generic Use 'sudo apt autoremove' to remove them.  I believe that newer version of this modules are installed and used already and that this old ones can be removed. But that is just me theory. When running autoremove it says that 335 MB will be freed. Is this safe or not? Update: I went for the autoremove with purge (even if I have enough space) I just seem to be greedily. It then popped up a purple screen asking me: A new version of /boot/grub/menu.lst is available, but the version installed currently has been locally modified. What would you like to do about menu.lst?  install the package maintainer's version keep the local version currently installed show the differences between the versions show a side-by-side difference between the versions show a 3-way difference between available versions do a 3-way merge between available versions (experimental) List item start a new shell to examine the situation  if I choose option 2: keep the local version, will it keep revert back to 4.15.0-29? what should I do. I'm sure this is just a small thing but I dont want this system to have short or longterm issues. Update: I compared both versions: one was the grub list and the other was some tmp list. one was version 29 and the other had version 34. I pressed: keep the local version currently installed twice and rebootet. $ uname -r 4.15.0-34-generic  hope that grub list is okay and its not the tmp list. Nevertheless I wanted to thank all you guys for the amount of very detailed answers. I felt a bit bad for all the time you spent answering me the initial question. But this seems to stand up for a decent community.


Let $(X, \cal M, \mu)$ be a measure space with $\mu(X)<\infty$. Why  \begin{align} \lim_{p\to\infty}\|f\|_p=\|f\|_\infty \end{align} for all $f\in L_\infty$?

Could someone help me prove that given a finite measure space $(X, \mathcal{M}, \sigma)$ and a measurable function $f:X\to\mathbb{R}$ in $L^\infty$ and some $L^q$, $\displaystyle\lim_{p\to\infty}\|f\|_p=\|f\|_\infty$?    I don't know where to start.


"Our mutual friend" or "our common friend" - which is more suitable ? Why is that so ?

When I was a student of EFL, I was taught the word "mutual" implies a reciprocal relationship where X does to Y what Y does to X.  If John admires Peter as much as Peter admires John, we can say their admiration is mutual.  That said, can I say that Charles and I have a mutual friend ?


I'm working on creating a small graph in tikz. However, I'm a bit lazy and don't want to create the actual curve in tikz, but I do want the axes and some text to be done in LateX because it looks much nicer. So I'm basically including a graphic and then doing  the tikz picture "on top". However, when I use the following code  \documentclass{article} \usepackage{tikz} \begin{document} \begin{tikzpicture} \includegraphics[scale=.5]{fig12.PNG}; \draw [->] (0,0) -- (8,0); \draw [->] (0,0) -- (0,4); \end{tikzpicture} \end{document}   I get     Which isn't quite what I'm looking for =)  When I include the the graphic at the end of the tikz picture, it sits on top of the axes and stuff, and I'd still need to put points and text on top of it. How can I properly position this image?

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


I have looked into multiple questions about this already, but none of the answers seems to work on my problem. I am using biblatex for referencing. When citing in text, i would like to have : (Author et. al. 2010). For now it is working for all my references, but for 2 or 3 articles.   Here is my code   \documentclass[12pt,a4paper,oneside]{book} \usepackage[backend=biber,style=authoryear,maxbibnames=20,maxcitenames=1]{biblatex}  \addbibresource{mybibliography.bib}  \printbibliography   and mybibliography.bib  @article{pinxten2017risk,   title={At-risk at the gate: prediction of study success of first-year science and engineering students in an open-admission university in Flanders—any incremental validity of study strategies?},   author={Pinxten, Maarten and Van Soom, Carolien and Peeters, Christine and De Laet, Tinne and Langie, Greet},   journal={European Journal of Psychology of Education},   pages={1--22},   year={2017},   publisher={Springer} }   I want to get :  \parencite{pinxten2017risk}      (Pinxten et al. 2017)   but instead i get:   \parencite{pinxten2017risk}      (Pinxten, Van Soom, et al. 2017)   How can i fix this?

In the header of my document I set the maximal author names to 2:  \usepackage[style=authoryear-icomp, maxbibnames=9, maxcitenames=2, backend=biber]{biblatex}   Now, when I cite texts with two authors, LaTeX gives me the following:     (Author_A/ Author_B 2012: 232)   When I have three authors or more, LaTeX makes it:     (Author_A/ Author_B et al. 2012: 232)   But I want LaTeX to just name the first author if there are more than two authors ... like this:     (Author_A et al. 2012: 232)   Any tips on how to achieve this ?


I'm looking for a short story that's a dialogue between a researcher and an AI. The AI is told it's a person waking up in a dark room, and slowly comes to realize it's actually just a machine with no physical body.   The setting would be the lab they're in. I vaguely remember some plot twist where the one you think is the researcher is actually the AI, but I really don't remember.   I read the story online ~2 years ago, but I don't know the publish date. I don't know the name of the AI. The researcher was male. I don't think it was a well-known author.

I had read a story / article about artificial intelligence, I think it was last year (2012) but I'm not sure when it was published. It was on an online blog for an institute I believe. I am telling the story in quotes, just to demarcate where the story begins and ends.  In the story, a scientist is trying to build a perfect AI system which can respond to human interaction perfectly. Apparently the only way this is possible is to make the computer believe that it is human. He creates what he believes is the solution, and asks a friend to volunteer for a test, and the friend agrees. For the test the friend is supposed to step into a tank full of a liquid. As soon as he enters the tank, he is told, he will lose all his sensations - no vision, no hearing etc. After entering the tank, he talks to the computer and responds, and isn't able to recognise that he is in fact talking to a computer. After some time (days? Don't remember) has passed, he begins to worry - why is he still trapped in the tank? At this point the scientist tells him that he is in fact the computer he has made, the memory that he has of the human life till the time he enters the tank has been implanted in the machine, so he thinks he is human. He is not in a tank, he is a computer, and that is why he can't see or feel anything. The story ends here.  It is told from the perspective of the computer itself, but since it is an article in a science blog / forum for a technical college, it feels like you're reading an actual experiment when you start reading. It was a rather nice surprise ending to the story in my opinion. I just can not seem to be able to locate the article / story anywhere. Can somebody who might have read this help me? Even just pointing me in the direction of the site it is hosted on would be great.


Why is the output "false2", when the condition at the if block is 1 which is true ?     #include<stdio.h> int main(){ int x=0; if (x++) printf("true1"); else if (x==1) printf("false2"); return 0;}

In C, what is the difference between using ++i and i++, and which should be used in the incrementation block of a for loop?


I have a C# console application that I am running with its output type set to "Windows Application" to prevent the console from being seen during normal use. However, I would like the option to alternatively run the program as a console application at will, in case the user wanted to troubleshoot and view the console's output.  Is it possible to pass a command-line argument to the executable to either run the application in "Console" mode or "Windows Application" mode depending on the user's desire? If not, is there any other way to change on the fly if an application will show the console or not?

Is there a way to show the console in a Windows application?  I want to do something like this:  static class Program {     [STAThread]     static void Main(string[] args) {         bool consoleMode = Boolean.Parse(args[0]);          if (consoleMode) {             Console.WriteLine("consolemode started");             // ...         } else {             Application.EnableVisualStyles();             Application.SetCompatibleTextRenderingDefault(false);             Application.Run(new Form1());         }     } }


i wrote the code:  List<Task> tt = new List<Task>(); for (int i = 0; i < 5; i++) {     tt.Add(     new Task((o) =>     {         Thread.Sleep(Convert.ToInt32(o)*1000);         Console.WriteLine("end of {0}!", Convert.ToInt32(o));     },i)); }  tt.ForEach(t => t.Start()); Task.WaitAll(tt.ToArray());   and it show me in console: end of 1!   (interval 1 sec)  end of 2!   (interval 1 sec)  end of 3!   (interval 1 sec)  end of 4!   (interval 1 sec)  end of 5!   (interval 1 sec)  but if i get this code:  List<Task> tt = new List<Task>(); for (int i = 0; i < 5; i++) {     tt.Add(     new Task( () =>     {         Thread.Sleep(i*1000);         Console.Write("end! ");     })); }  tt.ForEach(t => t.Start()); Task.WaitAll(tt.ToArray());   then i have this answer: (interval 5 seconds and all in one moment): end! end! end! end! end!  Could you explain me this phenomenon?  I think that:  This is due to the fact that the variable "i" is continuously incremented and thread has access to the variables? In this case, each thread will remember the last value "i" so each thread will wait for 5 seconds and just send a message?  It's good reason?

I met an interesting issue about C#. I have code like below.  List<Func<int>> actions = new List<Func<int>>();  int variable = 0; while (variable < 5) {     actions.Add(() => variable * 2);     ++ variable; }  foreach (var act in actions) {     Console.WriteLine(act.Invoke()); }   I expect it to output 0, 2, 4, 6, 8. However, it actually outputs five 10s.  It seems that it is due to all actions referring to one captured variable. As a result, when they get invoked, they all have same output.  Is there a way to work round this limit to have each action instance have its own captured variable?


I got this problem when I tried to apply material for my sculpt, it just didn't apply, it was just gray, in rendered/material preview mode (see photos). I don't know what the problem is but now it isn't working on normal objects too. I'am using latest Blender version and I have Radeon RX570 graphic card. I never had this problem before. I tried sending sculpt to a friend if he can colour it, and it worked for him.

I don't know why but now, when i go in material preview or rendered (in solid mode it works fine), my object is entirely gray, or invisible idk, because it has the same color of the background. I've been working for days on this project without having this issue, it suddenly showed up. I tried opening other old projects and suddenly they all do the same so i guess it is some blender program setting that applies for all the projects, but idk how it happened cuz i didn't change anything :/, anyone got any tips?


Hi there I'm trying to make a lottery, generating 6 random numbers adding them to an array and then getting a users numbers and adding them to an array. This is what I've tried so far.  Heres my lottery class,  class Lottery {     Random rand = new Random();     // generating lottery numbers     int cpnum;     int[] allCpNumbers = new int[100];      // bets placed     int betsPlaced; }   Here's my for loop to generate the random numbers and add them into my array  // printing lottery numbers for(int i = 0; i <= 6; i++) {     lottery.cpnum = rand.nextInt(50) + 1;     lottery.allCpNumbers[i] = lottery.cpnum; }   When printing the random numbers it gives me this   System.out.println(lottery.allCpNumbers);   Output:  [I@1b6d3586  I want it to be a set of 6 random numbers arranged like 3,13,10,43,12 etc.

In Java, arrays don't override toString(), so if you try to print one directly, you get the className + '@' + the hex of the  of the array, as defined by Object.toString():  int[] intArray = new int[] {1, 2, 3, 4, 5}; System.out.println(intArray);     // prints something like '[I@3343c8b3'   But usually, we'd actually want something more like [1, 2, 3, 4, 5]. What's the simplest way of doing that? Here are some example inputs and outputs:  // Array of primitives: int[] intArray = new int[] {1, 2, 3, 4, 5}; //output: [1, 2, 3, 4, 5]  // Array of object references: String[] strArray = new String[] {"John", "Mary", "Bob"}; //output: [John, Mary, Bob]


Let $f:X\to Y$ and $g:Y\to X$ be maps such that $fg=id_Y$ and $gf=Id_X$, then $f$ is bijective.   I already proved that $f$ is injective. Let $x,x'\in X$ and $f(x)=f(x')$. Then we have $g(f(x))=g(f(x'))$ and therefore $x=x'$. Hence $f(x)=f(x') \iff x=x'$ and $f$ is injective.  How do I prove that $f$ is surjective?   Let $y\in Y$. Choose $x=\cdots$. Then ... Therefore $f(x)=y$.  Can someone help me?

Say $f:X\rightarrow Y$ and $g:Y\rightarrow X$ are functions where $g\circ f:X\rightarrow X$ is the identity. Which of $f$ and $g$ is onto, and which is one-to-one?


This could be true since the both have infinite range and other common properties. They both have fields.

Recently, I  was pondering over the thought that is most of the elementary particles have intrinsic magnetism, then can gravity be just a weaker form of electromagnetic attraction? But decided the idea was silly.    But I then googled it and found  article. Is this idea really compatible with other theories as the article mentions? Is there any chance of this proposition being true?


1.His latest two books are excellent. 2.His two latest books are excellent. Could you show me the difference between these in meaning? Thanks

a. His two previous books  b. His previous two books   .............   His 2 latest previous books His 2 previous latest books His previous latest 2 books His latest previous 2 books His previous 2 latest books His latest 2 previous books  I am wondering what is the difference could be between these in meaning?  Which one do you use? which one you don't use?  I think just especially native speakers or learned ones in English can provide the most proper answer.  Thanks


I recently submitted a Puppet patch which would have enabled the EPEL repository on a number of our CentOS 7 systems (I need this in order to install Python 3).  One of the sysadmins rejected the patch, claiming that EPEL is not safe, and can conflict with the base repository packages. I was told that EPEL can make determining "which package will be available on which node somewhat unpredictable."  I am a software developer now, but I was a full-time sysadmin from 1995 to 2013. I have never heard about this kind of conflict before, and asking a few friends about it, none of them have either.  So my question is: can EPEL conflict with the stock/base CentOS 7 repositories? Is there any documentation out there of this happening? I didn't find anything when searching online, except a couple of statements indicating exactly the opposite.

Are there any downsides in enabling epel repository on a server machine or is it something every sysadmin does?


Reading code from packages/whatever, I often find commands like \@M, \p@, \z@, \m@ne, \@ne, \tw@ etc. What is the point in using those instead of the (IMHO more understandable) 10000, pt, -1, 1, 2 etc?

For example, in plain.tex and in hyrules.tex (package hyplain) we find such code:  \chardef\active=13 \catcode`\~=\active     \chardef\myh@us@catcode=\the\catcode`\_ ... \catcode`\_=\myh@us@catcode   Are there any other ways to store a number and why this way is preferable to others?


I am studying a function where I found the some hash properties.  Hash functions:   Given a code c is computationally infeasible to find m such that h(m) = c Given m is computationally infeasible to find n != m such that h(m) = h(n) It is computationally infeasible to find any pair (m, n) such that h(m) = h(n)   Actually every point is clear to me. But I wondering what is the difference between point 2 and point 3? Can anyone give me any clue? Thanks.

Are there any cryptographic hash functions for which there is a known pre-image attack, or a known second pre-image attack, but not both?  The attack doesn't have to be practical - just anything that beats the security claim of the hash function.  Intuitively, 2nd pre-image attacks would be easier to find than pre-image attacks, but I'm not aware of any examples or that either property implies the other.  I believe there are no known pre-image attacks on the common crop of hash functions in use today, so I'm interested in historic, obsolete and proposed-but-not-adopted hash functions, but  constructed specifically to demonstrate the possibility of such attacks.


What happens if you forgot your email and you can't activate your account. Is there some way you can retrieve your email for that account? Any info will help.

I started my app today and it said that I needed to verify my email. But I don't know the email I chose. I logged on every email in but there was never a verify email. Is there a way to know your email on Pokemon Go?


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


"Spot it!" is a fun card game, played with 55 cards, each having eight symbols. There are more than 50 symbols in all. There is always one, and only one, matching symbol between any two cards, and this is the feature on which all the games playable with these cards are based. Some mathematical aspects of the game are discussed  before.    Here's my question: How are these cards designed?! Put in a more mathematical way, is there an algorithm (not a brute-froce on!) to find all subsets of size $k$ of a set of size $n$, so that each two subsets have exactly one element in common?  Thanks.  Upadte: It seems that my question has been answered .

I just purchased the game . As per , the structure of the game is as follows:     Game has 55 round playing cards. Each card has eight randomly placed symbols. There are a total of 50 different symbols through the deck. The most fascinating feature of this game is any two cards selected will always have ONE (and only one) matching symbol to be found on both cards.   Is there a formula you can use to create a derivative of this game with different numbers of symbols displayed on each card.  Assuming the following variables:   S = total number of symbols C = total number of cards N = number of symbols per card   Can you mathematically demonstrate the minimum number of cards (C) and symbols (S) you need based on the number of symbols per card (N)?


I know this is a very simple question-reading and parsing an xml file and has tons of solutions here already.Could you kindly assist me before shutting down this question?I'm new to C# and Xamarin as well,and have tried tons of solutions already but the result is always the same- nothing gets printed out to the console.Regardless of my implementation.The values are always null.Could you kindly check my code out,i have no idea why i'm not getting any data.  public List<SamplePoint> ReadFromFile()     {         pointList = new List<SamplePoint> ();               xmldoc = new XmlDocument ();             xmldoc.Load (fileLocation); //this is read from the sdcard of the device  XmlNodeList nodeList = xmldoc.DocumentElement.SelectNodes ("/SamplePoints/SamplePoint");          foreach(XmlNode node in nodeList){               endDate = node.SelectSingleNode ("EndDate").InnerText;              startDate = node.SelectSingleNode ("startDate").InnerText;   return pointsList;         }

I've got an XML document with a default namespace. I'm using a XPathNavigator to select a set of nodes using Xpath as follows:     XmlElement myXML = ...;   XPathNavigator navigator = myXML.CreateNavigator(); XPathNodeIterator result = navigator.Select("/outerelement/innerelement");   I am not getting any results back: I'm assuming this is because I am not specifying the namespace. How can I include the namespace in my select?


On  on tex.SE (and on many, many other posts on several sites) I once again noticed that pictures uploaded are always made full page width.  This is often way too much for the image. For example in the linked question, I uploaded a math-formatted equation. That would fill the whole width and become enormous. So I have to append white-space on either side of it and upload it like that.  Is there no way to set image sizes? At least to set the sizes to the original image sizes - I would understand issues with users setting their own dimensions, but at the very least the picture should not be shown in larger dimensions that what it is uploaded in.

Is it possible to resize an image in an answer? For example,  has  that should have the image in the answer, but it's too big.  Is there a way to handle resizing?


Is there any way to disable autostart apps at boot time? I need to disable some of them (not all) like Facebook, etc to get quicker boot time. I'm asking how to do this on Android 9.0.

Possible Duplicate:          I've installed some applications that I mostly like, except for the fact that they all decided they were too important not to auto-start.  None of them give me any option within the application to disable the auto-start "feature."  Can I stop these applications from auto-starting?  And if so, how?  Note: My phone is not rooted, so I'm especially interested in solutions that do not require a rooted device, but all answers are welcome, even if they require rooting the device, since I may do this eventually.  Also note: I'd prefer not to fiddle around with clumsy auto-kill features in task-killer programs, as I've found them to be incredibly unreliable on my phone (Motorola Milestone/Droid).


When we see such a big and difficult to calculate number, we want to use Fermat's little theorem (especially when we see prime number as divider) But how do we approach situation when we have number in power of number in power? And what if we had something like "find remainder of $13^{5^{53}}$ from division by 48". It is already not a prime number, what would we have to change in our solution?

I've just started a cryptography course, so i am not experienced at all how to calculate such big numbers. Clearly, i can't use a calculator, because the number is too big, so i have to calculate it by hand.   Since $101$ is a prime number, i think i should use here Fermat's little theorem. Found some example and tried to solve it this way, but i am totally not sure, if it is correct and if my approach must be this one.   Calculate $5^{3^{1000}}\bmod 101$.  First of all i think i should calculate $3^{1000}\bmod 101$. From Fermat's little theorem i get to $3^{100}\equiv 1\bmod 101$.   Thus $1000=x100+0$ and $x=10$.   $3^{1000}\equiv 3^{999^{10}}  = 1 ^{10} \equiv 102\bmod 101 $  Later i have to calculate $5^{102}\bmod 101$.  Again by Fermat $5^{100}\equiv 1\bmod 101$.  $$102=100\cdot 1 +2$$  Here i am not sure how to move on... I think that my solution is wrong, but i'd love to see your suggeststions and remarks how to solve the problem.  Thank you very much in advance!


Calculate the number $o(\mathbb{R})$ of open subsets of the real line.  I know that the answer is $\mathfrak{c}$ but I don't know how my lecturer got this.  I am doing an introductory topology course, so I know a few topological concepts. Such as that the set of all open intervals forms a base for the real numbers. Is this somehow relevant in showing that  $o(\mathbb{R}) = \mathfrak{c}$?

Let $\mathcal{T}$ be the family of all open sets in $\mathbb{R}$. Show that $| \mathcal{T}|=2^{\aleph_0}$  $\textbf{My Attempt:}$   I know that $\forall A \in \mathcal{T}$. $A$ is the countable union of open intervals with rational end points.   I want to use the Cantor-Bernstein Theorem. That is I need to find injective functions $f$ and $g$ such that $f: 2^{\aleph_0} \to \mathcal{T}$ and $g: \mathcal{T} \to 2^{\aleph_0}$.  I know each $A \in \mathcal{T}$ is of the form $A = \bigcup_{x \in A} (r_x,s_x)$ where $r_x,s_x \in \mathbb{Q}$. How can I use this fact to find the injective function $f$ and $g$?


Is there any good 'Speech to Text' application available for Ubuntu?  I have tried to find something in Software Center but I failed.

Are there any programs that will let me dictate (speech-to-text) to any program? Or at least to a text editor and text fields in Firefox.  I’m not interested in anything that uses an online service, it has to be on-device. It may be a commercial product.


Let X = [11.17, 9.52, 10.69, 9.84, 10.84, 9.88, 10.28, 12.23, 8.49, 10.79] be a normally distributed data with mean = 10.37 and standard deviation = 1.02. How to determine the corresponding value to +1.02 and -1.02 standard deviations, which covers 69% area of the probability distribution.

I have a variable with mean value of 18.85 and standard deviation of 1.45.   I want to define the area that is covered by 1.45 standard deviations left and 1.45 standard deviations on the right side of the mean using these statistics.   How do I do that?


Here they give a classic decomposition but I'm not sure if there's a quick method to arrive at the right hand side from the left, or if I should just memorize this decmomposition.  Thanks

I found this amazingly beautiful identity . How to prove that $A^3+B^3+C^3 - 3ABC = (A+B+C)(A+B\omega+C\omega^2)(A+B\omega^2+C\omega)$ without directly multiplying the factors? (I've already verified it that way). Moreover, how could someone possibly find such a factorization using complex numbers? Is it possible to find such a factorization because $A^3+B^3+C^3 - 3ABC$ is a symmetric polynomial in $A,B,C$?


When I install a graphical distro for personal purpose I usually separate /boot and /home.  When I install a server I stick to /boot and / only, and depending on the project I may consider some other on demand, as I have mentioned  with /var/log and /var/lib/docker.  Based on the premise I am talking about a Linux server it seems there is a tendency of recklessly separating every root directory into partitions I don't get why.    that there is multiple best-practices documents (e.g, CIS Benchmark) that mandate separating /var, /home, /usr, etc, into different file systems.  During my research I have read  which gives good reasons for separating partitions but doesn't seem to be overdone for every directory.  This  and  mention the per directory partitioning, but does not give any reason, just do that for security sake, blindly trusting them!  The fact you could configure different flags on mounting as nodev, nosuid or even noexec doesn't seem such crucial to me as if the user is not sudoer simple denying write access would be enough, and if it is sudoer these flags would not prevent any damage.  The fact you could backup them separated doesn't pay the burden. and the fact you could clear them separated you could simple remove the directory.  The fact you could have badblocks on some of them doesn't make me feel any relieved, such as the badblocks are given by sector, the files would be damaged with or without partitions.  The only fact I can think could be a little good would be if the partitions are on separeted disks and one of them failed to be loaded or had the partition table sector damaged, but depending on the case you wouldn't be able to boot the system anyway, with or without several spread partitions.  Thinking about this last possibility, in order to recover the disk wouldn't make any difference to have one or several partition, you can run testdisk or ddrescue the image in any case will result the same.  I am wondering what are those so called best-practices' reasons for having several partition separation without taking into account which suit the project?

We will be running CentOS 7 on our new server. We have 6 x 300GB drives in raid6 internal to the server. (Storage is largely external in the form of a 40TB raid box.) The internal volume comes to about 1.3TB if formatted as a single volume. Our sysadmin thinks it is a really bad idea to install the OS on one big 1.3TB partition.  I am a biologist. We constantly install new software to run and test, most of which lands in /usr/local. However, because we have about 12 non-computer savvy biologists using the system, we also collect a lot cruft in /home as well. Our last server had a 200GB partition for /, and after 2.5 years it was 90% full. I don't want that to happen again, but I also don't want to go against expert advice!  How can we best use the 1.3TB available to make sure that space is available when and where it's needed but not create a maintenance nightmare for the sysadmin??


Im having trouble believing this T/F Question: if $\mathrm A^2=I$ then $\mathrm A = \pm \mathrm I$  The answer is False but why?  If the matrix is $\mathrm A = \mathrm I,$ say   \begin{bmatrix}1& 0\\      0 & 1 \end{bmatrix}  then $\mathrm A^2$ is also that. And if $\mathrm A = -\mathrm I,$ then it is   \begin{bmatrix}-1 & 0\\                    0 &-1  \end{bmatrix}  and that squared is also the same? Where am i going wrong?

So I'm studying linear algebra and one of the self-study exercises has a set of true or false questions. One of the questions is this:     If $A^2 = I$ (Identity Matrix), then $A = \pm I$ ?   I'm pretty sure it is true but the answer says it's false. How can this be false (maybe it's a typography error in the book)?


Cmd "md ...\" create this folder on my disk.I can't delete it...

I have a folder on my desktop which is named ".." (which itself contains subfolders with an empty name). The folder can't be deleted the usual ways, even not when using the CLI. Does anyone know how I can remove this folder on Windows Vista 64-bit?  Renaming does not work, either (obviously).  This is what "dir /x" echoes:  09.10.2009  15:04    <DIR>                       . 09.10.2009  15:04    <DIR>                       .. 08.03.2007  11:18    <DIR>                       cgi-bin                0 Datei(en),              0 Bytes                3 Verzeichnis(se), 45.866.037.248 Bytes frei


Recently I have purchased a Nikon D3400 having two lenses. They are;   AF-P DX NIKKOR 18-55 mm f/3.5 - 5.6G VR and AF-P DX NIKKOR 70-300 mm f/4.5 - 6.3G ED VR   I would like to purchase a Hood and UV filter for each. I have tried Axcess 67mm YC Clear View UV-HD Lens UV Filter and Axcess 52mm YC Clear View UV-HD Lens UV Filter, but they are not correctly fitting into lens. One (52mm) is smaller and the other (67mm) is larger. Somebody kindly tell me the UV filter and Hood size for both lenses?  Thanks in advance.  EDIT  Inside the cap, its written 55mm (1st lens) and 58mm (2nd lens)

I was looking to get a circular polarizing filter and an UV filter for my Canon 550D, 18-135mm lens. When I checked online I found these filters came in different sizes, like 62mm, 67mm, 72mm, 77mm. How do I know which is right?  Also, will there be any degradation of photo quality if I put both these filters on the lens?


Is there a specific reason I need the self in this model's method? I'm accessing it from another controller.    def self.search(query)     if query       find(:all, conditions: ['lower(first_name) LIKE ? OR lower(last_name) LIKE ?', "%#{query.downcase}%", "%#{query.downcase}%"])     else       find(:all)     end   end

I've been coding in Ruby for sometime now, but I don't understand when to use:  def self.METHOD_NAME end   or just:  def METHOD_NAME end   In any Rails model. Is "self" a modifier like private in Java? When should I use it and when not?. Thanks a ton.


*I need to practice the piano 'a lot' before the concert.*   Using 'a lot' vs 'much' sounds better, but how do I explain this since 'a lot' and 'much' can be used for uncountable items. Is it incorrect to use 'much' or is it just more common to use 'a lot'?

I found the below in  web-site:     We use much in questions and negative clauses to talk about degrees of something.      We don’t use much in affirmative clauses.   Also, it the same web-site, I found the following:     She runs much faster than he does.    also I noticed that some web-sites use much with affirmative clauses:     May we all be having this much fun and getting this much exercise when we're his age!    Is it Okey to use much in affirmative clauses? If yes, when can we use it? and what is the rules?  Update:  Here is another example on how often the word "much" is used  in informal style:     After much consideration I will NOT be performing at the Inauguration with my improv group Capitol Hill-arious


I'm pretty stuck with this problem. I hope you can help me. Let $R=\mathbb{Z}[i] .$ Consider $n \in \mathbb{Z} \backslash\{0\}$ and the ideal $I=R n$ in $R$. Show that $a+b i \in I$ if and only if $n \mid a$ and $n \mid b .$ Show that $R / I$ is a finite ring.  I have already shown the first part, that n|a and n|b iff $a+b i \in I$. But how do I show that the ring is finite? I know that $R$ is a PID and thus that I is a principal ideal. So, $I=\{n(a+i b) \mid a, b \in \mathbb{Z}, \quad n \in \mathbb{N} /\{0\}\}$ must be generated by some element $z\in R$ ; $I=\langle z \rangle$. I think I'm supposed to use these results and that n|a and b. But I just can't seem to make any connections and where to go from here.

How to show  that $\mathbb{Z}[i]/I$ is a finite field whenever $I$ is a prime ideal? Is it possible to find the cardinality of $\mathbb{Z}[i]/I$ as well?  I know how to show that it is an integral domain, because that follows very quickly.


What did they have for lunch?   or      What did they had for lunch?

In regard to this , my question is similar but that answer is not clear. I want to know why we use base form of verb, e.g. 'go' to form the past tense instead of past form such as 'went'?     Question: Did you go to a bank?  (Why we use 'go' here, rather than 'went'?)   Answer: I went to a bank.   Am I confusing verb forms with tenses? Please note that I'm not a native speaker so some clarification or reference on this would be helpful.


I am trying to animate Minecraft with a rig, but every time I press I, or G, it comes up with the error message. no suitable context info for active keying set  Why, and how do I fix this so I can animate?

I have an armature associated with a mesh. In Pose Mode I have oriented the armature the way I want, so I press A to select the entire armature and then I press I to insert keyframes.  I've done this successfully on simple models while following tutorials, but back in my real model I'm getting the following error and I don't understand what context is being looked for.     No suitable context info for active keying set   What constitutes a "context" in Pose mode?  What should I be looking for in my model structure that is leading to such an error?


I need to create a custom Lightning component and inside of it I need to output record details page and related lists. There are standard components in App Builder for this: "Record Details" and "Related List - Single" but I can't find a way on how to add it to my component. How can I do this?

I have a form that needs to let the user select 3 out of 5 products, something similar to Order > Add Product (Modal). I was wondering if there was a way to bring that piece into my component (markup) and add some sort of filter that only shows the products I want to show.  What I found so far:  <lightning:listView objectApiName="Products2" listName="productsView" showActionBar="true" enableInlineEdit="true" showRowLevelActions="true"/>   But Product2 is not supported for that component.  also these from browser inspector:  forceMultiAddUsingLVM forceListViewManager   These are data-aura-class attributes when rendered.  I'm looking for directions here. Thanks in advance.


function user_form_edit_form_alter(&$form,&$form_state,&$form_id) {       if ($form_id=="user_register_form") {            $form['profile_user_profile']['field_user_group']['und']['#ajax'] = array(                                                                          'event' => 'change',                                                                         'wrapper' => 'edit-profile-user-profile-field-user-type-und',                                                                         'callback' => 'get_user_type',                                                                         'method' => 'replace',                                                                         'effect' => 'fade'                                                                          );            $form['#submit'][] = 'user_form_edit_form_alter_submit';    }  }    function get_user_type(&$form, &$form_state) {        $selected_user_group = $form_state['values']['profile_user_profile']['field_user_group']['und'][0]['tid'];    //  return '<pre>' . print_r($form, 1) . '</pre>';         // 14= USB , 15= Primary Contractor , 16 = Subcontractor       $output = "";      $output .= '<select class="form-select required" name="profile_user_profile[field_user_type][und]" id="edit-profile-user-profile-field-user-type-und">';      //  if USB then Director, USB Staff, USB Project Manager, Subcontractor          if ($selected_user_group == 15) {                  $output .= '<option value="8">PC Staff</option>';                 $output .= '<option value="9">PC Project Manager</option>';                 $output .= '<option value="10">SC</option>';           }          else if ($selected_user_group == 16) {                  $output .= '<option value="10">SC</option>';           }          else {             $output .= '<option value="5">Board Member</option>';             $output .= '<option value="6">USB Staff</option>';             $output .= '<option value="7">USB Project Manager</option>';           }       $output .= '</select>';      return $output;   }     //  Submit Handler Function    function  user_form_edit_form_alter_submit($form, &$form_state) {          if (isset($form_state['values']['profile_user_profile']['field_user_type']['und'][0]['value'])) {              $user_type_name = $form_state['values']['profile_user_profile']['field_user_type']['und'][0]['value'];                 $user_roles = db_query("SELECT name, rid FROM role where name='%s'",$user_type_name);                   $LastCreatedUsername = $form_state['values']['name'];                 $fetch_uid_arr = db_select('users', 'u')                     ->fields('u', array('uid'))                     ->condition('name', $LastCreatedUsername, '=')                     ->execute()                     ->fetchAssoc();                  $uid = $fetch_uid_arr['uid'];                 $rid = $user_roles['rid'];                 $nid = db_insert('users_roles')                      ->fields(array('uid' => $uid,'rid' => $rid,))                     ->execute();         }   }   ?>enter code here

I have written code like below and all works fine, but while submitting the form I get the error below. I am trying to filter the second dropdown based on the first drop down selection.     An illegal choice has been detected. Please contact the site administrator.   How do I overcome that error?       function dynamic_location_dropdown_form_alter(&$form, $form_state, $form_id) {   if($form_id == 'product_node_form') {    $location_options = array();    if(isset($form['field_destination']['und']['#default_value'][0])) {     $destination = $form['field_destination']['und']['#default_value'][0];   }   else {     $destination = 0;   }    $location_options = dynamic_location_dropdown_locations($destination);    $form['field_destination']['und']['#ajax'] = array(     'event' => 'change',     'wrapper' => 'squadron-wrapper',     'callback' => 'dynamic_location_dropdown_ajax_callback',     'method' => 'replace',   );   $form['field_product_location']['#validated'] = true;   $form['field_product_location']['und']['#prefix'] = '
';   $form['field_product_location']['und']['#suffix'] = '
';   $form['field_product_location']['und']['#options'] = $location_options;   } }  function dynamic_location_dropdown_ajax_callback($form, $form_state) {   $country_id = $form['field_destination']['und']['#value'];   $form['field_product_location']['#validated'] = true;   $form['field_product_location']['und']['#options'] =  dynamic_location_dropdown_locations($country_id);    return $form['field_product_location']; }  function dynamic_location_dropdown_locations($destination_id) {   $nodes = array();   $nodes[''] = '- None -';   if($destination_id != '') {     $select = db_query("       SELECT node.title AS node_title, node.nid AS nid, node.created AS node_created       FROM {node} node       LEFT JOIN {field_data_field_location_country} field_data_field_location_country        ON node.nid = field_data_field_location_country.entity_id        AND (field_data_field_location_country.entity_type = 'node'        AND field_data_field_location_country.deleted = '0')       WHERE (( (node.status = '1')        AND (node.type IN  ('location'))        AND (field_data_field_location_country.field_location_country_nid = $destination_id)))       ORDER BY node_title ASC     ");     $nodes[''] = '- None -';     foreach ($select as $node) {       $nodes[$node->nid] = $node->node_title;     }   }    return $nodes; }


How to prove that:  $$\lim_{n\to\infty} \frac{1^n+2^n+\cdots+n^n}{n^n} = \frac{e}{e-1}$$  Any help is appreciated.

I can show that the following limit exists but I am having difficulties to find it. It is $$\lim_{n\to \infty} \sum_{k=1}^n \frac{k^n}{n^n}$$ Can someone please help me?


If the child processes of the parent which is terminated are adopted by the init process, then how does the system decide if the child process is a daemon process or a zombie process (which must be killed)? And suppose we know there are a lot of zombie processes that one process has created how do we kill all these since killing the parent won't kill them all.

As I understand it, a zombie process has died but still exists as a placeholder in the process table until its parent (or init if the zombie is itself an orphan) checks its exit status.  And my understanding of orphan processes is they are processes that are still alive and running but whose parent has died.  Since a zombie is already dead, its children would be considered orphans, wouldn't they?  Would they be affected be reaping the zombie?  Specifically, would init adopt them as its children only once the zombie was reaped, or would they be adopted as soon as the parent became a zombie?


Assume we have $n$ observations and $p$ explanatory variables we want to model. To apply ridge regression, we choose a constraint parameter $\lambda \geq 0$ and estimate the coefficients $\beta_i$ which minimise: \begin{equation} \sum^{n}_{i=1} \left( y_i - \beta_o - \sum_{j=1}^p\beta_jx_{ij} \right) + \lambda \sum_{j=1}^p \beta_j^2 \end{equation} where $y_i$ are the observations and $x_{ij}$ are the variables. I am reading an Introduction to Statistical Learning, which says:  When λ = 0, the penalty term has no effect, and ridge regression will produce the least squares estimates  and (of ridge regression):  if p > n, then the least squares estimates do not even have a unique solution, whereas ridge regression can still perform well  My questions are the following:  Am I correct in saying that ridge regression (and lasso) fail when $p > n$ and $\lambda = 0$, due to being equivalent to least squares?  If so, is there a solution for all $\lambda > 0$ when $p > n$, particularly when $\lambda$ is very close to zero?  If there is a solution for all $\lambda > 0$ when $p>n$, is there some reason to be wary of applying shrinkage methods like this due to the closeness of the optimisation problem to least squares?

I have understood how ridge regression shrinks coefficients towards zero geometrically. Moreover I know how to prove that in the special "Orthonormal Case," but I am confused how that works in the general case via "Spectral decomposition."


I wanted to test out the following code I had seen in an exam:  void fct(char *s, const char *t) {     while(*s++ = *t++); }   It is supposed to do the same as strcpy(), but when I ran it, it resulted in a segmentation fault at the first time the while-condition was evaluated. There was nothing apparent why it would segfault and others couldn't find the reason either.  I've compiled it with gcc 8.3.0 and gcc 7.3.0 both with the same results. I've also tried to debug with gdb which didn't bring any clarification either.  This is my testing code:  void fct(char *s, const char *t) {     while(*s++ = *t++); }  int main(int argc, char *argv[]) {     fct("hello", "world");     return 0; }   compiled with gcc -Wall -o test test.c. The same happened when the strings were in variables:  int main(int argc, char *argv[]) {     char *a = "hello";     char *b = "world";     fct(a, b);     return 0; }   int main(int argc, char *argv[]) {     char *a = malloc(sizeof(char)*6);     char *b = malloc(sizeof(char)*6);     a = "hello";     b = "world";     fct(a, b);     return 0; }

The following code receives seg fault on line 2:  char *str = "string"; str[0] = 'z';  // could be also written as *str = 'z' printf("%s\n", str);   While this works perfectly well:  char str[] = "string"; str[0] = 'z'; printf("%s\n", str);   Tested with MSVC and GCC.


is shocking.  This is a lack of basic literacy.  Obviously MathJax is needed in chat.

It would be really nice to be able to use MathJaX (math formulas) in chat.  Not specially for formulae, but for things like $V_{CC}$ in electronics chat would be very useful.


#!/bin/bash while read server <&3; do   #read server names into the while loop      if [[ ! $server =~ [^[:space:]] ]] ; then  #empty line exception     continue  fi    echo "Connecting to - $server" #ssh "$server"  #SSH login     while read updatedfile <&3 && read oldfile <&4; do              echo Comparing $updatedfile with $oldfile         if diff "$updatedfile" "$oldfile" >/dev/null ; then             echo The files compared are the same. No changes were made.         else             echo The files compared are different.             # copy the new file and put it in the right location             # make a back up of the old file and put in right location (time stamp)             # rm the old file (not the back up)             #cp -f -v $newfile                  mv $oldfile /home/u0146121/backupfiles/$oldfile_$(date +%F-%T)          fi       done 3</home/u0146121/test/newfiles.txt 4</home/u0146121/test/oldfiles.txt done 3</home/u0146121/test/servers.txt   This is my whole script  mv $oldfile /home/u0146121/backupfiles/$_$(date +%F)   This moves the file correctly but it removes the actualy file name and just adds the date. I want to keep the original file name and add the current date to the file name.

I want to be able to move $oldfile to my backup folder and add the date to the file name. So I tried this...  mv $oldfile /home/u0146121/backupfiles/$oldfile_$(date +%F-%T)   This just gives me this output filename. (no orignal filename)  2013-07-11-10:22:25  Then I realized the potential problem for the above method. I have a while read loop that reads through a text file of path names for other files I wanted to compare. So for example, $oldfile is actually =    $ cat oldfiles.txt  /home/u0146121/OldLogFiles/file2.txt   So... I want to be able to move the file2.txt and just keep the file2.txt name and add the date to it as well.


I have no idea how to solve this question. I'm trying to show that given $p(x) = a_0 + a_1 x + .. + a_n x^{n}$ and further assuming that $a_n \neq 0$ and n is odd, there exists x such that p(x)=0.  I'm guessing that Rolle's theorem might come into play somewhere, since I know that by Rolle's theorem if $f:[a,b] \rightarrow \mathbb{R}$ is continuous on [a,b] and differentiable on (a,b) and f(a) = f(b) then $\exists c \in (ab)$ s.t f'(c)=0. Other than this hunch, I have no idea where to begin solving this.  Help would be much appreciated!

I want to prove that every real polynomial of odd degree has at least one real root, using  the intermediate value theorem.  Let $P(x) = x^{2n+1} + a_n x^{2n} + . . . + a_0$ for each $a_i \in \mathbb{R}$ and $n \in \mathbb{N}$.  By the fundamental theorem of algebra I know that $P(x)$ has exactly $2n+1$ complex roots, so  $P(x) = (x+r_1)(x+r_2) . . . (x+r_{2n+1})$ for each $r_i \in \mathbb{C}$  I do not know how to complete this but I do know that, at some point, I probably have to show that each root with imaginary part non zero has to come in conjugate pairs, and since $2n+1$ is odd there is at least $1$ root that is imaginary part $0$ and thus real.


The question :  asks for a reverse firewall used to monitor, preventing or permitting network access, at the process level, with a GUI. There is two such applications namely  and  but they are no more  maintained.   My question is the following : How can we combine existing tools and libraries to build a similar application under linux with a GUI or a text based interface?

I'm looking for a reverse firewall, something like  for Linux, but my google-fu is failing me. Does something like this exist on Linux?


I have line in script which is working, but not working from command line.  echo "User ALL = NOPASSWD: ALL, !/bin/su" | sudo tee -a /etc/sudoers    [user@localhost ~]$ echo "test ALL = NOPASSWD: ALL, !/bin/su" | sudo tee -a /etc/sudoers bash: !/bin/su": event not found [user@localhost ~]$   Edit: I am trying to add a sudo user with no permission to su command and sudo user have password less access to root using sudo -i. I was just checking each command in that script, to see how they work in command line.  I found a workaround for this in command line, that I have to use "'!'"/bin/su. So can someone help to explain why this didn't work in command line?

I tried to create a script by echo'ing the contents into a file, instead of opening it with a editor  echo -e "#!/bin/bash \n /usr/bin/command args"  > .scripts/command   The output:     bash: !/bin/bash: event not found   I've isolated this strange behavior to the .  $ echo ! !    $ echo "!" bash: !: event not found  $ echo \#! #!  $ echo \#!/bin/bash bash: !/bin/bash: event not found    Why is bang causing this?   What are these "events" that bash refers to?     How do I get past this problem and print "#!/bin/bash" to the screen or my file?


If I choose an orthographic view by using the numpad and then try to orbit the geometry by clicking the middle mouse button Blender goes from orthographic to perspective. Why is that the default now? Wouldn't it be more logical if instead of that Blender kept the orthographic mode? In other words: Why Auto Perspective is turned on by default?

I work mostly in ortho mode but after I switch to side, top, left, right or bottom view, and then move around the view changes to perspective. How can I ensure that it always stays in ortho view?


I was spammed by this today:     “Hi? Greeting,   I have read your profile some minutes ago ? english.stackexchange.com     & I think you are a nice person? I'd like to get to know you better.for a chance to discuss an important issue? & we can share great experiences together, I'm sorry if i am embarrassing you i don,t mean so i think you are a nice person & there is something important i want to share with you, Therefore we request you to kindly contact us to E-mail address (  Vivianaisatou@gmx.com  ) not in this site because i am a new in this community and i don't visit this site often,      I am very curious to know more about you,please e-mail me i await your response. Best regards,   I do write my email at my profile, which help other users communicate with me.  Is there any way the community / SE management can help eliminate data mining the users' details by spammers, while still letting us put our emails in public?

I've noticed that emails are not protected in the user description. For example  entered his email and when viewing the source code of the page it is plain text that malicious bots could harvest and exploit to spam. It would be nice if email addresses were automatically encoded to prevent this.


Problem: Let $R=\mathbb{Q}[x,y]$ and consider the ideal   $$I=\{f\in R:f(0,0)=f(1,1)=0\}.$$ Prove that $I=\langle x-y,y-x^2\rangle.$   Since $x-y$ and $y-x^2$ belong to $I$ we have $\langle x-y,y-x^2\rangle\subset I.$ To show the other relation I don't know even how to start.

Let $ Y = \{ (1,1),(0,0\} \subset \mathbb A_k^2$. Find the $ \mathbb I(Y)$.   As if $f(x,y) \in \mathbb I(Y)$ then as $f(0,0)=0$ hence constant term of $f$ is zero and as $f(1,1)=0$ therefore sum of the coefficients of $f(x,y)$ is zero. But how can we describe this set properly?


I have recently upgraded from 16.04 to 18.04 desktop.  In 16.04 I was able to add to the right-click behaviour of icons in the launcher - eg have a simple icon in the launcher bar, right click to show a list of all libreoffice programs and choose the one I wanted. Also I added programs such as FreeFileSync, Disk, gParted to the right-click list on the nautilus icon.  Is it possible to do this within the GNOME environment?  If not then is there an alternative?  I've already looked at Docky, not sure that it does all I need it to...

Is there anyway to add icons groups to the favorites bar aka Ubuntu dock (something like drawers or unity-launcher-folders) in Ubuntu 18.04 ?


I have two Guassian distribution curves, as shown here and I am attempting to color the areas under the curves as well as the intersection between them, like here:    I assumed fillbetween would be the appropriate tool here, but that produced some strange results. Below is the code  \begin{tikzpicture}     \begin{axis}[     axis lines=left,     domain=0:10,      samples=100,     ymin=0,     xtick=\empty,     ytick=\empty,     enlargelimits=false,      clip=false,     ]      \addplot [thick, orange, name path=cat] {gauss(x, 3, 1)} node[pos=0.3, above]{cat};     \addplot [thick, purple!70!black, name path=puma] {gauss(x, 5, 0.5)} node[pos=0.5, above right] {puma};      \path[name path=axis] (axis cs:0,0) -- (axis cs:10,0);      \addplot[         thick,         color=orange,         fill=yellow,         fill opacity=0.25     ]     fill between[         of=cat and axis     ];      \addplot[         thick,         color=purple!70!black,         fill=purple!70!black,         fill opacity=0.25     ]     fill between[         of=puma and axis     ];      \addplot[         thick,         color=white,         fill=blue,         fill opacity=0.25     ]     fill between[         of=cat and puma     ];     \end{axis} \end{tikzpicture}   which produces this:    Every other answer I've found either miraculously makes fillbetween work or avoids it entirely (usually in ways that seem more complicated than is necessary for a simple task such as this).   Can anyone explain to me what is missing to make fillbetween achieve the desired results or recommend a clean alternative? Thanks in advance.


From what I understand after reading :   The purpose of robots.txt file is to disallow crawling of some URLs, but those can still be indexed (and appear in search results) if they are linked from crawlable pages To prevent a page from being indexed I need to make it crawlable and add the noindex meta tag in its head   So, why would I setup a robots.txt file if, in the end, it has no impact on whether pages appear in search results or not?

If I don't want to set any special behavior, is it OK if I don't bother to have a robots.txt file?  Or can the lack of one be harmful?


Why do radioactive isotopes have a half-life? I know that they decay in order to become stable but why would it take out enough subatomic particles to be half? Or am I approaching this question the wrong way: the remaining radioactive substance is going to be half in x amount of time and the other half will be stable atoms.

Carbon-14 has a half-life of 5,730 years.  That means that after 5,730 years, half of that sample decays.  After another 5,730 years, a quarter of the original sample decays (and the cycle goes on and on, and one could use virtually any radioactive isotope).  Why is this so?  Logically, shouldn't it take 2,865 years for the quarter to decay, rather than 5,730?


I want to prove that for $a\gt 0$ and $h\in \mathbb{R}$ the  $$\lim_{h \rightarrow 0} \frac{a^h-1}{h}$$ exists. There is no point of definition for a since it is just a real number greater $0$. Since this problem is set in the context of school and the students do not know the $\log$ function, I just wanted to use the properties of the natural exponential function.   I wanted to use a sequence that converges against $0$ and is monotone and bounded. But I'm not sure whether this might work.  The reason to consider this limit in the first place is to determine the derivative of the exponential function $x \mapsto a^x$.  However, I am not currently interested in computing this limit or derivative—I just want to show that the limit exists.

Taking as our definition of exponentiation repeated multiplication (extended to real exponents by continuity), can we show that the limit   $$\lim_{h\to 0}\dfrac{a^h-1}{h}$$  exists, without l'Hôpital, $e$, or even natural logarithm? Sure, l'Hôpital will work, but that's circular if we're developing calculus of transcendentals from first principles. There is  to this question already by user Neal, but he uses the exponential function with base $e$ (it's been answered many times: see also , , and ).   But using the special properties of $e$ strikes me as circular too; not literally logically circular, in the sense that we are invoking results we're trying to prove, since there are definitions of $e^x$ which make it trivial to verify the derivative. But perhaps pedagogically circular for a complete novice, the special properties of $e$ appear unmotivated because they cannot be justified without reference to the very derivative we are trying to compute (or else a detour through logarithms, but let's not).  Can we find nice squeeze theorem bounds like Neal has, but for the function $a^x$ instead of $e^x$, with the additional handicap that we can't just write $a^x=e^{x\log a}$? I thought to substitute a series expansion for $\log a$, but didn't come up with any bounds that were nicely polynomial in both $x$ and $a$.  I wonder whether the geometric proof of $\lim (\sin x)/x$ (see for example, robjohn's answer ) could be adapted.  Obviously without a reference to natural logarithm, we cannot compute the value of the limit. But I just want to show it exists (via squeeze theorem or monotone convergence). Once we know this limit exists, we can show it behaves like a logarithm, whence there is a unique base for which the limit is 1, which we call $e$. The rest of the development of calculus of exponentials and logs follows easily. This seems like the approach that would appear the most accessible yet motivated to a novice calculus student.   An analogous limit to $\lim\dfrac{a^h-1}{h}$ for understanding to differentiating exponential functions, are the limits $\lim\limits_{n\to\infty} (1+\frac{1}{n})^n$ and $\lim\limits_{n\to\infty} (1+\frac{1}{n})^{n+1}$ for differentiating the logarithm, if you prefer to start with that as your primitive concept. Both limits are shown to exist using  (see WimC's answer  for the first limit, and see David Mitra's answer  for the second limit). I tried without success to use Bernoulli's inequality to show my sequence was monotone. This limit can also be analyzed using  as seen in user94270's answer to . So that inequality may help here.  I would also accept an explanation of why the limit cannot be computed without transcendental techniques, or an opinion why this is not a pedagogically sound approach to introducing the calculus of exponentials and logarithms.  Edit:  has a nice solution by Paramanand Singh to a closely related problem.


Consider the two entries on the following theoretical form,  Name        _______________  or  Name:       _______________  Which is more correct?

When you have a form with fields and captions for these fields, should you do it like that:  Field1: [                       ] Field2: [                       ]   or like that:  Field1  [                       ] Field2  [                       ]   I saw both used in popular application. Microsoft generally uses colons (My computer properties -> Computer Name tab is one example). Opera browser doesn't use colons as separators on forms (example: Preferences form).  I personally don't have a strong opinion on which one is better. But I'm working on this "1000s of winforms" app where I suspect we have forms with and without colons so I would really like to set a standard and go one way or another on all forms because the inconsistency is far worse than any of the options.


Random random = new Random(); int x = scanner.nextInt(bound:20)+1;  (bound:20) is not working to generate a random number from 1 to 20. what is the mistake I have done in this code?

How do I generate a random int value in a specific range? I have tried the following, but those do not work: Attempt 1: randomNum = minimum + (int)(Math.random() * maximum);  Bug: randomNum can be bigger than maximum. Attempt 2: Random rn = new Random(); int n = maximum - minimum + 1; int i = rn.nextInt() % n; randomNum =  minimum + i;  Bug: randomNum can be smaller than minimum.


I have a XeLaTeX document in which it is easy to underfill some vboxes. This is ok for me, as long as the extra space is left at the bottom of the page (by default it is distributed between the boxes in the page). How can I instruct XeLaTeX to do that?

I have a problem. I have several large equations within the text. And when LaTeX does not manage to put the equation on the same page and moves it to the next one, he spreads the paragraphs of the text in the first page. How could I prevent this? I know about \pagebreak and \newpage, but I do not want to force the \newpage, as the text may move (if I add something later or so on) and the pagebreaks may not be valid. I would like to make LaTeX not to spread the paragraphs over a page automatically. Is it possible?  I tried to make an example:  \documentclass[a4paper,12pt,twoside]{book} \usepackage{amsmath} \begin{document}  LaLaLa\\\  LaLaLa\\\  LaLaLa\\\  LaLaLa\\\  \begin{eqnarray} 123&+&123 \\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ \end{eqnarray}  LaLaLa\\\  LaLaLa\\\  \begin{eqnarray} 123&+&123 \\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ 123&+&123 \nonumber\\\ \end{eqnarray}  \end{document}


Consider the following problem:  $$\frac{\text{d}^2y}{\text{d}t^2} + y + \epsilon\ y^3 = 0\ \ \ \ \text{for}\ \  t \geq 0, y(0) = A, y'(0)=0$$  Compute an approximate solution by substitution method:  $y(\tau) = y_0(\tau) + \epsilon\ y_1(\tau) + \epsilon^2y_2(\tau) + \ldots$   $\tau = w(\epsilon)t = (1+\epsilon w_1 + \epsilon^2 w_2 + \ldots)t$  $\text{up to the order}\  \epsilon^2$;  I have hard time using such substitution / perturbation method to approximate the exact solution. Any help?

The question is to find an approximate solution, up to the order of epsilon of following problem.  $$y'' + y+\epsilon y^3 = 0$$ $$y(0) = a$$ $$y'(0) = 0$$  I tried to solve the given problem using perturbation theory.  $$y(t) = y_0(t) + \epsilon y_1(t) + \epsilon^2 y_2(t) + \cdots$$ $$t = w(\epsilon)t = (1 + \epsilon w_1 + \epsilon^2 w_2 + \cdots )t$$  However, i failed to find an appropriate approximate solution... help me!!


I have been trying to create a closet in Blender 2.8 and giving materials to the frame, the doors and the handles, but whenever I try to assign a material for example to certain doors, the whole object got selected. My first idea was to use "Mark Seam" to use it as "boundary" of the different materials, but it didn't work, then I used key P to make separations in the object, but it - although separates the object by selection - still didn't work, it keeps using the whole obejct. Can anyone please help me? Thank you.

How do you add more than one material to a mesh?   I have tried adding two materials to the object, and then assigning one of the materials to a vertex-group, but I could not find a place to assign it.  I am making a striped bouncy ball that I want to deform, so adding a different material by separating the mesh into different objects would not be ideal.


If I wanted to write, there exists an integer $n$ then in symbols this would be written as $$\exists n\in\mathbb{Z}.$$ If I wanted to write, there exists only one integer $n$ then in symbols would be written as $$\exists!n\in\mathbb{Z}.$$ Sometimes this could be mistaken as there exists $!n$ but if so that would be written as $$\exists(!n)\ \lor \ \exists\{!n\}.$$ But what if I wanted to write there exists infinitely many integers $n$. I can’t write $$\exists \text{ infinite } n \in\mathbb{Z}$$ or perhaps $$\exists\text{ inf }n\in\mathbb{Z}$$ can I? If not, is there some mathematical notation to denote this? I thought of something like $$\operatorname*{\text{Exi}}\limits_{n\to\infty}\tag{inspired by $\lim_{n\to\infty}n$}n\in\mathbb{Z}$$ but before I make something up, I want to know for sure if there does not exist a notation of this sort yet. This question came to me after looking at .   Thank you in advance.

We all know that ∃ means “there exists” and ∃! means “there exists exactly one”. Is there a similar notation for existence of an infinite number of examples?


It seems that in Drupal code anything that is neither hook nor Plugin nor Controller nor any other thing with a standard functionality should be a Service. For sure, services make sense when we want to give other modules the possibility to change the functionality that we are writing. But I can think of a lot of scenarios where it is absolutely sufficient to have a normal class. When we just want to create an instance, call a method, nothing else. How can I decide if a class is sufficient, or if a service makes sense? Edit This is not opinion based. There must be a clear and objective reason why we use services in Drupal, and I want to know this reason.

I had this question in mind along all the last week: When I should create a service or an utility function?  In the Drupal Core we have both Services and Utility functions, but I can't find the distinction between them (when I need to create a service or when I need to create an utility function).  I will take as example the  module where I have the  class.  <?php  namespace Drupal\modules_weight\Utility;  class InternalFunctions {    public static function prepareDelta($weight) {     $delta = 100;      $weight = (int) $weight;      if ($weight > $delta) {       return $weight;     }      if ($weight < -100) {       return $weight * -1;     }      return $delta;   }     public static function modulesList($force = FALSE) {     $modules = [];     $installed_modules = system_get_info('module');      $config_factory = \Drupal::service('config.factory');      if ($force) {       $show_system_modules = TRUE;     }     else { modules.       $show_system_modules = $config_factory->get('modules_weight.settings')->get('show_system_modules');     }      $modules_weight = $config_factory->get('core.extension')->get('module');      foreach ($installed_modules as $filename => $module_info) {       if (!isset($module_info['hidden']) && ($show_system_modules || $module_info['package'] != 'Core')) {         $modules[$filename]['name'] = $module_info['name'];         $modules[$filename]['description'] = $module_info['description'];         $modules[$filename]['weight'] = $modules_weight[$filename];         $modules[$filename]['package'] = $module_info['package'];       }     }     uasort($modules, ['Drupal\Component\Utility\SortArray', 'sortByWeightElement']);      return $modules;   }  }   In this class I have two static functions but they are both utility functions or prepareDelta() is an utility function and modulesList() should be in another class and have a service?  The only difference that I found at this time is that inside the namespace Drupal\Component\Utility (where you will see a lot of utility fucntions) none of them use inside a service and usually a service use another services inside (I don't have review all the services to validate this).  So, when I should create a service or an utility function?


How would I go about forgetting my lock-screen password? What can I do to get back in? This is about the iPhone 4, 4S and 5. More of a How-To question, someone I know forgot their password.

I forgot my passcode to my phone because my friend changed it. I'm not locking it, so I can still use my phone. The computer my phone is backed up on is down right now. Is there any way I can go to the apple store and have them unlock my phone? Or any way to take my passcode off besides resetting it on my computer. That option is not possible right now.  Thanks.


what is the order  of group GL2(R), where all the entries of the group are integers mod p, where p is prime.

Let $\mathbb{F}_3$ be the field with three elements. Let $n\geq 1$. How many elements do the following groups have?   $\text{GL}_n(\mathbb{F}_3)$ $\text{SL}_n(\mathbb{F}_3)$   Here GL is the , the group of invertible n×n matrices, and SL is the , the group of n×n matrices with determinant 1.


This is my fire base data structure:   I am retrieving the data from database using the following method  private DatabaseReference mFirebaseDatabase=FirebaseDatabase.getInstance().getReference();;     private FirebaseDatabase mFirebaseInstance;  mFirebaseDatabase.child("users").child(userId).child(time).addValueEventListener(new ValueEventListener() {             @Override             public void onDataChange(DataSnapshot dataSnapshot) {                 String value = dataSnapshot.getValue(String.class);                 Log.d("Tag", "Value is: " + value);                 System.out.println("Values is :::::::::::::::::::::::::::::::::::: "+value);               }              @Override             public void onCancelled(DatabaseError databaseError) {                 // Failed to read value                 Log.w("Tag", "Failed to read value.", databaseError.toException());               }         });   i am getting the below error   Caused by: java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()   please help  userID part, this is where i create a new entry to store data to the table   private void createUser(String name, String time, String lat, String lon) {         // In real apps this userId should be fetched         // by implementing firebase auth         if (TextUtils.isEmpty(userId)) {             userId = mFirebaseDatabase.push().getKey();             System.out.println("Userid is ------------------------------> "+userId);         }          User user = new User(name, time,lat,lon);          mFirebaseDatabase.child(userId).setValue(user);          addUserChangeListener();     }      /**      * User data change listener      */     private void addUserChangeListener() {         // User data change listener         mFirebaseDatabase.child(userId).addValueEventListener(new ValueEventListener() {             @Override             public void onDataChange(DataSnapshot dataSnapshot) {                 User user = dataSnapshot.getValue(User.class);                  // Check for null                 if (user == null) {                     Log.e(TAG, "User data is null!");                     return;                 }                  Log.e(TAG, "User data is changed!" + user.name + ", " + user.time);                 System.out.println("User data is changed!" + user.name + ", " + user.time);               }              @Override             public void onCancelled(DatabaseError error) {                 // Failed to read value                 Log.e(TAG, "Failed to read user", error.toException());             }         });     }   The above code is used for userId generation,userId is dynamically created every time when a insert function is called

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I have three classes. Class Vehicle, class Truck and class Car. Class Truck and class Car extend from class Vehicle. class Vehicle has three fields:  protected String model; protected int year; protected int price;   Class Truck has one field:  private String color;    and the method:  public String getColor(){     return color;    }   Class Car has one field:  private boolean rusty;   I have an array called vehicles(which stores 30 objects) to store Truck objects as well as Car objects.  I have another class called VehicleDealer in which I have created the array and different methods including:   int VEHICLE_COUNTER= 0;  public void addTruck(String m, int y, int p,String c){     Vehicle truck1 = new Truck( m, y, p, c);     vehicles[VEHICLE_COUNTER] = truck1;      VEHICLE_COUNTER = VEHICLE_COUNTER + 1; }  public void addCar(String m, int y, int p,boolean r){     Vehicle car1 = new Car( m, y, p, r);     vehicles[VEHICLE_COUNTER] = car1;      VEHICLE_COUNTER = VEHICLE_COUNTER + 1; }   public String printAllVehiclesOfColor(String c){      String s = "";     for (int i=0; i < VEHICLE_COUNTER; i++) {          String x = vehicles[i].getColor();        if(x == c){            s += vehicles[i].printThis(i) + "\n"; }          }         return s; }    I have a main class which looks like this:  public class TestDealer{ public static void main(String[] args){      VehicleDealer dealer = new VehicleDealer();  dealer.addTruck("Ford", 2012, 55000, "Green"); dealer.addTruck("Ford", 2001, 23050, "Black"); dealer.addCar("BMW", 2010, 17000, false);  System.out.println(dealer.printAllVehiclesOfColor("Green"));      } }   In this line of code I get an error which says that cannot find symbol for getColor().  for (int i=0; i < VEHICLE_COUNTER; i++) {          String x = vehicles[i].getColor();<---------------        if(x == c){            s += vehicles[i].printThis(i) + "\n"; }          }   So I put the getColor() method in class Vehicle and then tried to compile the code but it did not work as I have not declared a color field in class Car. My question requires me to declare the color field in class Truck only.  What is wrong with my code? I am new to Java. Any help is appreciated. Thank you!!

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


My parents have a 15" Late 2013 MacBook Pro. They would like to upgrade to Big Sur, which is still compatible with that Mac. On the internet, I've read several stories about 2013 MBP's that were unusable after updating. Some articles only named the 13 inch version, others talk about the 2013 MBP in general. I can imagine that this has (almost) only happened to 13 inch versions, because they generally come with less power than the 15 inch version. We'll of course backup it, but we want to prevent everything that brings along extra work. Are there any cases of 15 inch MBP 2013 being bricked after updating to Big Sur, or has that only happened to 13 inch versions? Many thanks in advance!

I want to install Big Sur on my MacBook Air 2014, but I’m concerned about reports that the installation of Big Sur did brick some older MacBook Pro. I couldn’t find any information regarding my MacBook Air 2014. Is it safe to install Big Sur on a MacBook Air 2014?


i need to explore different folders and i try to prevent errors instead to do a try/catch on each folder . I had an error on the 'C:\Windows\InfusedApps' folder when trying to list files. UnauthorizedAccessException:'System.UnauthorizedAccessException: Access to the path 'C:\Windows\InfusedApps' is denied. i would to know if there were a way to test, i tried different things but without success. By example DirectoryInfo has just the "directory" flag like a normal directory. I tried to use ` DirectorySecurity test = FileSystemAclExtensions.GetAccessControl ( new DirectoryInfo(parent.Path) ` But i don't see how use it to detect a difference. Thanks.

I am trying to display a list of all files found in the selected directory (and optionally any subdirectories). The problem I am having is that when the GetFiles() method comes across a folder that it cannot access, it throws an exception and the process stops.  How do I ignore this exception (and ignore the protected folder/file) and continue adding accessible files to the list?  try {     if (cbSubFolders.Checked == false)     {         string[] files = Directory.GetFiles(folderBrowserDialog1.SelectedPath);         foreach (string fileName in files)             ProcessFile(fileName);     }     else     {         string[] files = Directory.GetFiles(folderBrowserDialog1.SelectedPath, "*.*", SearchOption.AllDirectories);         foreach (string fileName in files)             ProcessFile(fileName);     }     lblNumberOfFilesDisplay.Enabled = true; } catch (UnauthorizedAccessException) { } finally {}


I have a string containing a hierarchy of items separated by a '/' character.   E.g.  Class\Order\Family\Genus\Species  I need to split out this string such that each value is its own column as well as displaying the original full string  E.g.  Mammalia\Carnivora\Felidae\Panthera\Panthera tigris   Mammalia\Carnivora\Felidae\Panthera\Panthera leo   Mammalia\Carnivora\Felidae\Panthera\Panthera pardus     becomes  Classification Class Order Family  Genus Species   -------------- ----- ----- ------  ----- ------- Mammalia\Carnivora\Felidae\Panthera\tigris Mammalia  Carnivora Felidae Pathera tigris   Mammalia\Carnivora\Felidae\Panthera\leo Mammalia  Carnivora Felidae Pathera leo   Mammalia\Carnivora\Felidae\Panthera\pardus  Mammalia  Carnivora Felidae Pathera pardus     Finally, not all string will have 5 values so the script will need to enter NULL for values that don't exist  E.g.  Mammalia\Carnivora\Felidae     becomes  Classification Class Order Family  Genus Species   Mammalia\Carnivora\Felidae Mammalia  Carnivora Felidae NULL NULL

Using SQL Server, how do I split a string so I can access item x?  Take a string "Hello John Smith". How can I split the string by space and access the item at index 1 which should return "John"?


The "history" dropdown has quit working, as have "File", "Edit", and the rest at the top of the firefox toolbar.  How do I get these restarted?

... and if so, how to fix / re-enable support? Or would this be fixed by subsequent point releases of Firefox?


I wanted to create a new comment environment with special format of comments to a text. Here is the MWE:  \documentclass[french, 11pt, a4paper, titlepage]{report} \usepackage[T1]{fontenc} \usepackage[utf8x]{inputenc} \usepackage{fontawesome}  \newenvironment{commentaire}[1] { \paragraph{\faCommentsO} } { ~(#1) }  \begin{document}     text above     \begin{commentaire}{author}         comment     \end{commentaire}     text bellow \end{document}   Got those two errors   Illegal parameter number in definition of \endcommentaire line 12 You can't use 'macro parameter character #' in horizontal mode. line 18   I don't understand, especially because my new environment seems to feature  Thank you !

Environments are allowed to have arguments, but reference to those arguments can only appear in the opening code of the environment, and not the closing code.  What is the reason for this, and are there preferred ways around it?  e.g.  \newenvironment{foo}[1]% {some code #1} % allowed {some code #1} % not allowed


I want to hide some information in specific folder. This information is generated from one program and apart from this program nobody can access it. Actually, even if the user is root, he also should not access it.  Access permission is not enough for me. Root also should not delete this folder. Is there any structure for it ?  I also want to do not modify Kernel modules for this operation. I hope there is straightforward path for this job.

My question would be a little bit silly, but who knows because linux is a very rich and sophisticated OS.  Is there a way that a normal user in ubuntu can hide some files from root ?  I know that the root has all privileges ans rights. But, if a simple user can keep files from root that would be awesome and very useful for me.


Every time card:   Period Event Scene   Is to be marked with a Black (/filled) or White (/unfilled) circle, to indicate if the events described with in are Light or Dark, in nature/theme. Periods and Events are marked when created, scenes are marked at the end of them being played out.  For example, the Event of "The Rebels attack, and destroy the Capital", could be a Light event, if they are the good rebels, freeing the people from the dark empire. Or it could be a dark event if they are ruining the peaceful kingdom.  I understand how to decide on the Tone (Light/Dark), but not on what effect these have in game.  I see that they clarify the descriptions on the cards a bit. But do they have a mechanical effect?  I have read through the "How to Play" section in full, but not the appendix on "How/Why Microscope works". I've only flicked through that.  Is there some mechanic i missed, like:   "Within a Dark Period, No more than 50% of the Events at any given time can be Light?" Or "At the end of play count up how many Light/Dark events you have. This is interesting to track as time goes by to learn more about the your preferred playstyle"

I was teaching a game of Microscope today and I kept seeing references to light and dark. While expressing the tone of periods, events, and scenes is good, I remember from the playtest that a parent element's lightness or darkness somehow contributed to its children's tones.   In Microscope, how are the markers of Light and Dark used?


I had Linux and Windows 10 on my device and then I deleted the Linux via the disk management of the windows 10. But I messed up that part and now when I open my laptop, it takes me directly to the grub rescue and I cannot even access my bios. In the grub rescue, I have tried the ls, set boot and insmod normal commands and none of them worked. It gives me errors and there is literary nothing I can do on grub rescue.  I am really lost what should I do?

I have absolutely no experience with Linux, and I desperately need to get my computer back up and running again with Windows.  How do I remove Ubuntu and reinstall Windows?    Editor's note: many of the answers are about removing Ubuntu from dual-boot but keeping Windows (which is a bit complicated), while other answers are about removing Ubuntu from single-boot (which is easy: basically just format the disk while installing Windows). The question as written is ambiguous between dual-boot or single-boot.


Is there a way to prove the following without having to use the axiom of choice or its countable version?  Let $X$ be an infinite set and $T$ be a topology on $X$. If $T$ contains every infinite subset of $X$, then $T$ is the discrete topology.

Prove or find counterexamples.  Let $X$ be an infinite set and $T$ be a topology on $X$. If $T$ contains every infinite subset of $X$, then $T$ is the discrete topology.


I recently noticed that the date/time disappared from my desktop. Until now I could see them both in the top-right corner of my system and clicking on it would show up the calender, but now it disappeared altogether

Date and time is showing in the login screen (unity-greeter) but not when I login to my session.  When I go to date and time settings the panel is all grey :    Any idea how to recover from this ?


This has been driving me crazy. I know I read this book/books (possibly a trilogy) around the same time as reading Sabriel etc and the Windsinger trilogy. I don't remember a lot but I think it was about an immortal man (Sure that his name started with A) who had bright blue or purple hair (I remember a line about how hair constantly changes colour but only a few people live long enough to see it go past grey). I think he recruits young people and sends them places to do missions (can't remember if its time travel or different universes etc) It ends with one of the girls falling in love with the immortal man and deciding to stay with him. I know that this isn't a lot to go on but if anybody knows what this is, I will be very thankful. Oh and I think one of the books was called Key to the Door or something similar?

I'm trying to remember a book series I read in the mid-2000s. I've tried to remember as much as possible, some of the details might be incorrect. The book series is for young adults/teens and I think the author was Australian.  In the series, some people are born with superpowers and are recruited into the forces of the Babylonian god of Order (good guys), or the Babylonian god of Chaos (bad guys). The forces of Chaos typically travel back in time to alter an event (and thus make the present more chaotic), and the forces of Order have to travel back as well, identify the Chaos agents and stop them from changing history.  The two main characters were a boy (I think his superpowers include telekenisis) and girl at the same high school, in a town with a name similar to Angel Falls or Victoria Springs. Later on in the series a second boy is introduced who also attends the same school, but he is fighting for the bad guys. At the beginning of the first book the story centres on the boy and his mentor, a ~200 year old guy with purple eyes/hair (his superpower is not ageing). He operates from an ancient base underneath a large mountain.  Plot points include the main characters discovering their powers and learning how to use them, getting ingratieted into the order group and delving into the mountain in some sort of trial/ritual.  Can you identify this story?


On MacOS, the default bash on the OS is 3.2.  If I run help trap it says that if the signal_spec is DEBUG, that the command is run after each command, but the bash manpage says it is run before each command.  The actual behavior of this bash agrees with the manpage (i.e. before the command).  I downloaded the source of 4.4.18(1) and built it.  Both the manpage and help trap say that the trap is executed before each command.  However, even then, the text of each of those pieces of documentation are slightly different.  So my naive assumption that the help builtin reads/parses the manpage is clearly incorrect.  So where does help get its info that it relays to the user?

help  displays information about builtin commands. What is the source of help? Does it maintain a database for builtin commands, or does it read some files of each builtin commands (similar to the manpage of each utilities)?  Sometimes I find its information seems to expand that by --help  $ cd --help bash: cd: --: invalid option cd: usage: cd [-L|[-P [-e]]] [dir]  $ help cd cd: cd [-L|[-P [-e]]] [dir]     Change the shell working directory.      Change the current directory to DIR.  The default DIR is the value of the     HOME shell variable.      The variable CDPATH defines the search path for the directory containing     DIR.  Alternative directory names in CDPATH are separated by a colon (:).     A null directory name is the same as the current directory.  If DIR begins     with a slash (/), then CDPATH is not used.      If the directory is not found, and the shell option `cdable_vars' is set,     the word is assumed to be  a variable name.  If that variable has a value,     its value is used for DIR.      Options:         -L  force symbolic links to be followed         -P  use the physical directory structure without following symbolic         links         -e  if the -P option is supplied, and the current working directory         cannot be determined successfully, exit with a non-zero status      The default is to follow symbolic links, as if `-L' were specified.      Exit Status:     Returns 0 if the directory is changed, and if $PWD is set successfully when     -P is used; non-zero otherwise.   I thought help extract the help part of the executable, but for a  python script , it isn't  $ help ./pdf-merge.py bash: help: no help topics match `./pdf-merge.py'.  Try `help help' or `man -k ./pdf-merge.py' or `info ./pdf-merge.py'.  $ ./pdf-merge.py --help usage: pdf-merge.py [-h] [-v] [--ask] [--output OUTPUT] [--title TITLE]                     [--author AUTHOR] [--keyword KEYWORD] [--pdftk PDFTK]                     [--gs GS] [--pdfmarks PDFMARKS] [--unicode]                     PDF [PDF ...]  Merge PDFs preserving bookmarks. Thanks to Larry Cai for suggesting that Unicode be supported and for discussion about the `--pdfmarks` option.  positional arguments:   PDF                  an input PDF to merge  optional arguments:   -h, --help           show this help message and exit   -v, --version        show program's version number and exit   --ask                pause for manual pdfmark tweaking   --output OUTPUT      name of the output PDF   --title TITLE        title of output PDF   --author AUTHOR      author of output PDF   --keyword KEYWORD    keywords for the output PDF   --pdftk PDFTK        path to the pdftk executable   --gs GS              path to the gs (Ghostscript) executable   --pdfmarks PDFMARKS  path to pdfmarks file. If not given, a temporary file                        is used. If given and the file is missing, execution                        will stop after the file is created (before the                        Ghostscript run). If given and the file exists, no                        attempt will be make to use pdftk to generate the mark                        file (I assume your input file is what you want).   --unicode            instead of merging PDFs, convert PDF-formatted unicode                        strings. For example `--unicode '<FEFF03B103B203B3>'                        \u03b1\u03b2\u03b3`


I want the index of the search results when they are being clicked and I have used the following code:-  $('#results').append('

'+dis[searchResult[i]]+'

'); var g = document.getElementById("select"); for (var j = 0; j<g.dis.length; j++) {     g.addEventListener('click',function(index){     console.log(index);     });      }   But that gives the following error:-  search83.js:27 Uncaught TypeError: Cannot read property 'length' of undefined     at HTMLInputElement.<anonymous> (search83.js:27)     at HTMLInputElement.dispatch (jquery.min.js:2)     at HTMLInputElement.v.handle (jquery.min.js:2)

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I recently asked this question about usage of a . although it's pretty must answered, I had a non-fighting situation in mind and ended up with several fighting situations answers.  So here I reiterate my question for a non-fighting situation : Can we get some kind of leverage from already touching or being in proximity of an eventual target?  Take this situation: You are a caster and you are in a parlay with a foe. Discussion goes pretty well and you keep talking and moving around while arguing as peacefully as possible. You get to a point where both you and your foe are now close to each other. You put your hand on his shoulder (or shake his hand) and your foe confesses an abominable betrayal. At that moment, you decide this parlay was useless and prefer to see your foe suffer rather than become your ally.  Since you are already touching you target, can you get any kind of advantage from the fact that you are already making a contact that would allow you to inflict the spell's effect on the target?

I came to think about some situations where it would be almost impossible to miss a melee spell attack (target is grappling you or vice versa, target is holding you or is close to you, your character already has it's hand on the target, etc.). How do you manage those situations?    Do you give an advantage to the caster? Does the spell automatically succeed? Or you just don't ask yourself the question and just play along with the base rules?


Let $p$ be a prime number which is not equal to 2. Prove that if there exists an integer $a$ such that $a^2 \equiv -1 \text{(mod p) }$ then $p \equiv 1 \text{(mod 4)}$.   My attempt: let $p$ be a prime number not equal to 2. Suppose $p \not \equiv 1 \text{(mod 4)}$. Since $p \not= 2$, p must be odd, therefore $p \equiv 3 \text{(mod 4)}$  We have that $a^2 \equiv -1 \text{(mod p) }$ so $p| a^2 + 1 \implies  a^2 + 1 = pm$ for some integer $n$.   $a^2 \equiv 0 \text{(mod 4)} \text{ or } a^2 \equiv 1 \text{(mod 4)} \implies a^2 + 1 \equiv 1 \text{(mod 4)} \text{ or } a^2 + 1 \equiv 2 \text{(mod 4)}$. This means that  $a^2 + 1 \equiv pm \equiv 3m \equiv 1 \text{(mod 4)}$ or  $a^2 + 1 \equiv pn \equiv 3n \equiv 2 \text{(mod 4)}$  But I am not able to reach any contradiction. What am I missing here?

I came across this problem and I believe Lagrange's theorem is the key to its solution.  The question is:     Let $p$ be an odd prime. Prove that there is some integer $x$ such that $x^2 \equiv −1 \pmod p$ if and only if $p \equiv 1 \pmod 4$.   I appreciate any help.  Thanks.


This may sound silly, but I keep hearing people saying "thuh" instead of "thee" for "the" in front of adjectives or nouns starting with a vowel or a diphthong. Like, "thuh' old people, "thuh" other side. I speak the Queen's English (but am not a native speaker). I first noticed this watching the well-known English journalist and historian Andrew Marr on the BBC talking like this. He did this so frequently, almost consistently, that it started bothering me. I don't mind if people start talking like this, I just want to know if this is a new trend. I wrote to the Beeb about this, and they recited basic grammar rules about the pronunciation of "the" in reply, as if I was retarded. Whether you're British English or American, can you help me out? Do you yourself sometimes - or frequently - say "thuh" other side, "thuh" old stuff? (Please don't send me grammar rules. I am a retired English teacher.)

Possible Duplicate:          I have recently seen this image:    Should "a" have been used instead of "an" in the "...an $100,000 apartment" part?