What's the result? $1/i=?$, where $i=\sqrt{-1}$

I just had my first math class in the university, and I understood everything pretty well, but I think I have misread this one because I read that the result is $-1$. Thanks for your answers!


Bugged software center catalog - dep paradox

I had not installing any packages recently, but when i launched Software center, I saw a message: "Item cannot be installed or removed..."  /i am translating dumps from foreign language, so it might be not super precise with original/      those solutions didnt work at all. I have some kind of paradox:  sudo apt-get install -f   tells me, that 2 packages will be installed: libdbus-glib-1-2:i386 libnspr4:i386 (and there is need to download 0 B/217 kB of archives) - strange; why it needs i386 deps in x64 arch system anyway?  I choose Y and it dumps:  (Reading database ... 300571 files and directories currently installed.) Unpacking libdbus-glib-1-2:i386 (from .../libdbus-glib-1-2_0.98-1ubuntu1.1_i386.deb) ... dpkg: processing error /var/cache/apt/archives/libdbus-glib-1-2_0.98-1ubuntu1.1_i386.deb (--unpack):  './usr/share/doc/libdbus-glib-1-2/changelog.Debian.gz' is different from the same file on the system Missing report of program apport, becouse MaxReports limit reached Unpacking libnspr4:i386 (from .../libnspr4_4.9.5-0ubuntu0.12.04.1_i386.deb) ... dpkg: processing error /var/cache/apt/archives/libnspr4_4.9.5-0ubuntu0.12.04.1_i386.deb (--unpack):  './usr/share/doc/libnspr4/changelog.Debian.gz' is different from the same file on the system Missing report of program apport, becouse MaxReports limit reached dpkg-deb: error: subprocess paste was killed by signal (Interrupted stream) There were errors while processing:  /var/cache/apt/archives/libdbus-glib-1-2_0.98-1ubuntu1.1_i386.deb  /var/cache/apt/archives/libnspr4_4.9.5-0ubuntu0.12.04.1_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   therefore I've removed /var/cache/ folder just in case;  then tried to install required deps independently:  sudo apt-get install libdbus-glib-1-2:i386   dumped:  You need to use "apt-get -f install", to repair following problems: Following packages has broken dependencies:  libnss3:i386 : Requires: libnspr4:i386 (>= 4.8.6) but it will be not installed E: Broken dependencies. Please try use "apt-get -f install" without packages (or give a solution).   so then I did:  sudo apt-get install libnspr4:i386   and it dumped:  You need to use "apt-get -f install", to repair following problems: Following packages has broken dependencies:  libgconf-2-4:i386 : Requires: libdbus-glib-1-2:i386 (>= 0.78) but it will be not installed E: Broken dependencies. Please try use "apt-get -f install" without packages (or give a solution).   both needs each one to allow install other one? paradox? i am in mess.  ps, if no solutions will be found to this I can copy packages from other working mirror pc /just dont want to clone whole partition/, which folder is used for storing this packages?


Greatest common divisor is divisible by every common divisor

Can anyone give a proof for the following elementary assertion without use of Bézout's theorem which says that The Greatest Common Divisor of two integers is an integer linear combination of them.  "Every common divisor of two integers divides their greatest common divisor."  I should mention that I do not want to use the definition of GCD with prime factorization.


com.termux linked or mounted on SD (Root Available)

So I'm trying to get more space into my termux to download and use I'm trying to mount the folder onto the SD does anyone know how to already or done it? I've seen that it isn't possible but I don't see why wouldn't it be especially with root


How to convert a Decimal to a Double in C#?

I want to use a Track-Bar to change a Form's opacity. This is my code: decimal trans = trackBar1.Value / 5000; this.Opacity = trans;  When I build the application, it gives the following error:  Cannot implicitly convert type decimal to double   I have tried using trans and double, but then the Control doesn't work. This code worked fine in a past VB.NET project.


.NET Attributes: Why does GetCustomAttributes() make a new attribute instance every time?

So I was playing around a little more with attributes in .NET, and realized that every call to Type.GetCustomAttributes() creates a new instance of my attribute. Why is that? I would think that the attribute instance would basically be a singleton-per-MemberInfo, with 1 instance bound to the Type, PropertyInfo, etc...  Here is my test code:  using System;  namespace AttribTest { [AttributeUsage(AttributeTargets.Class)] class MyAttribAttribute : Attribute {     public string Value { get; set; }      public MyAttribAttribute()         : base()     {         Console.WriteLine("Created MyAttrib instance");     } }  [MyAttrib(Value = "SetOnClass")] class MyClass { }  class Program {     static void Main(string[] args)     {         Console.WriteLine("Getting attributes for MyClass.");         object[] a = typeof(MyClass).GetCustomAttributes(false);         ((MyAttribAttribute)a[0]).Value = "a1";          Console.WriteLine("Getting attributes for MyClass.");         a = typeof(MyClass).GetCustomAttributes(false);         Console.WriteLine(((MyAttribAttribute)a[0]).Value);          Console.ReadKey();     } } }   Now if I were to implement attributes, I would expect the output to be:  Created MyAttrib instance Getting attributes for MyClass. Getting attributes for MyClass. a1   Where the "class loader" (sorry, I have more of a Java background, not 100% sure how .net loads its types) would compile MyClass, and create an instance of MyAttribAttribute, and store them together somewhere. (probably the Perm Gen in the heap if this were Java) The 2 calls to GetCustomAttributes() would then just return the same earlier created instance.  But the actual output is:  Getting attributes for MyClass. Created MyAttrib instance Getting attributes for MyClass. Created MyAttrib instance SetOnClass   So... why? It seems like creating a new instance of all these objects for every call is a bit excessive, and not good for performance/memory management.  Is there any way to always get the same instance over and over?  Anyone have any ideas why it was designed this way?  The reason I care at all is because I made a custom attribute that internally holds some validation information, so in the Attribute I basically have a "private bool Validated" that I set to true. The validation stuff takes a while, so I don't want to run it every time. Now the problem is that since it creates a new instance of the attribute each time I get the attributes, Validated is always "false".


How to keep the layer control expanded in leaflet? It gets open when the user hover on it by default

var baseLayers = {   "Streets": streets,   "Grayscale": grayscale,   "Topography": topograph };  var overlays = {   "workplaces": workplaces };  L.control.layers(baseLayers, overlays,myIcon).addTo(map);


How do I rotate the viewport around the local (to the view port) - Z axis?  Basically what you would  get if you were to hit R with the camera selected in camera view.


Right-click on Dell Precision 5520 touchpad, with 18.04, not working

After installing Ubuntu Bionic Beaver, the right-click button of the touchpad stopped working.  Any fixes?  Thanks!


What is the probability that $THTH$ occurs before $HTHH$ in an infinite sequence of coin flips?    The expected number of flips until you first see $THTH$ is $6$, while the expected number until you first see $HTHH$ is $10$. Intuitively, I would guess that the probability that $THTH$ occurs before $HTHH$ is $3/4$. Is there a formal argument to compute this probability?  Probabilistic model: We denote by $(X_{n})_{n \geq 1}$ the random variable of coin flips, taking values in $\{H,T\}^{\mathbb{N}}$. We let $t_{THTH}$ be the first time that $THTH$ occurs in the sequence. We have $$ \mathbb{E}[t_{H}] = \frac{1}{2} \mathbb{E}[t_{H} | X_{1} = H] +  \frac{1}{2} \mathbb{E}[t_{H} | X_{1} = T] = \frac{1}{2}  +  \frac{1}{2} (\mathbb{E}[t_{H}] + 1  ). $$  $$ \mathbb{E}[t_{TH}] = \frac{1}{2} \mathbb{E}[t_{TH} | X_{1} = H] +  \frac{1}{2} \mathbb{E}[t_{TH} | X_{1} = T] $$


There are 2 groups of order 6 (up to isomorphism)

I need to show that there are only 2 groups of order 6 up to isomorphism.  I did prove it, but the proof is quite cumbersome. I wonder if there is a very concise proof.  My proof outline: Suppose $G$ is of order 6 and is not $\mathbb{Z}_6$. Then any element that is not identity must have order 2 or 3.  I went on to show that there must be a element of order 2 and another one of order 3, and the intersection of the cyclic subgroups generated by the two is the identity. Then I'm able to show it is isomorphic to $S_3$.


Keyboard shortcut to switch between applications in Mission Control

Does Apple have keyboard shortcuts to switch between applications in Mission Control? (Instead of hovering over with the cursor)?  e.g., which key combination cal I press to get me from "preview" to "app store?"


Beamer theme, remove navigation bar from one slide

I'm using beamer and the theme Copenhagen. I would like to remove the navigation menu (the list of section mames shown at the top of each slide) from the first (first page) and from the summary slides.  How can I do that?


I know that the equation $$ z^2=-8i $$ has two solutions, namely $z=\pm(2-2i)$. However, $\sqrt{-8i}$ is defined to be $2-2i$. Similar to the real case, $\sqrt{}$ selects the solution such that $\text{Re}(z)\geq 0$.  Why is this a convenient definition for the complex case? Is it merely the natural extension of the definition for the real case? Or is there a deeper reason? What about, for example, $$ z^4=-8i, $$ which has two solutions with positive real parts. What is the criteria here?


How to create a random number with range?

I am trying to create a random phone number with a range. The format being (xxx)-xxx-xxx and the area code not starting with 0,8, or 9 and the next set of three being in a range from 100-742 and then the last set of 4 can be any digit. How would i create the first two parts? Any help would be appreciated. Thanks!  import java.util.*; import java.text.*;  public class PhoneNumber{     public static void main(String[] arg){         Random ranNum = new Random();         //int areaCode = 0;         //int secSet = 0;         //int lastSet = 0;         DecimalFormat areaCode = new DecimalFormat("(000)");         DecimalFormat secSet = new DecimalFormat("-000");         DecimalFormat lastSet = new DecimalFormat("-0000");         //DecimalFormat phoneNumber = new DecimalFormat("(###)-###-####");         int i = 0;         //areaCode = (ranNum.nextInt()); //cant start with 0,8,9         //secSet = (ranNum.nextInt()); // not greater than 742 and less than 100         //lastSet = (ranNum.nextInt(999)) + 1; // can be any digits           i = ranNum.nextInt();         System.out.print(areaCode.format(i));         i = ranNum.nextInt();         System.out.print(secSet.format(i));         i = ranNum.nextInt();         System.out.print(lastSet.format(i));      } }


Java instantiate final object for the second time

This can't be achieved, you cannot instantiate an already instantiated final object:  private void myMethod(){     final Object object = null;      object = new Object(); }   Eclipse gives you an error message:  The final local variable object cannot be assigned. It must be blank and not using a compound assignment  However, if you pass this object to another method:  private void _myMethod(Object object){     object = new Object(); }   This can be achieved!  final form:  private void myMethod(){     final Object object = null;      _myMethod(object); }  private void _myMethod(Object object){     object = new Object(); }   Could anyone explain me this? It is so confusing how Java works.


How should be the course of learning for Particle Physics?

I'm a senior high school student. I want to learn particle physics as a hobby. I did some research about it ,and I learned that I should learn Quantum Field Theory for entering Particle Physics. QFT needs some high degree math. How can be a possible learning path in math/physics for me?


Proof that a matrix is similar to one the following matrices.

I am required to prove the following statement: Let $A \in \Bbb M_2(\Bbb R)$ . Prove that if $A$ has one eigenvalue λ, then A is similar to $     \begin{bmatrix}     λ & 0  \\     0 & λ  \\     \end{bmatrix}$ or $     \begin{bmatrix}     λ & 1  \\     0 & λ  \\     \end{bmatrix}$ I was able to prove that if the geometric multiplicity of λ is 2 then $A$ is diagonalizable so it is similar to $     \begin{bmatrix}     λ & 0  \\     0 & λ  \\     \end{bmatrix}$. I was trying to find a way to prove that if the geometric multiplicity of λ is 1 then $A$ is similar to     $\begin{bmatrix}     λ & 1  \\     0 & λ  \\     \end{bmatrix}$ but couldn't figure out how. Assistance will be more than welcomed.


How to round off longitude and latitude values

How do you round off these longitude and latitude values to 6 decimals each?  p1 contains the longitude and latitude values and "latValue" and "longValue" contain their respective values separately.  p1 = new LatLng((float) (location.getLatitude()),                     (float) (location.getLongitude()));  float latValue = (float) p1.latitude; float longValue = (float) p1.longitude;


Are all statements about math inherently formal? Can one do math without formal logic?

Are all people who do mathematics applying (whether they know it or not) formal logic?   Does every statement someone may make about math, at its core, a formal statement in mathematical logic? (I'm not asking whether it can be translated into mathematical logic, but whether at its core it already is formal.)      Most of the time, when I hear my professors speaking about mathematics, they use natural language - with some precise terms thrown in. For example, one professor might say,     "All positive real numbers have $2$ square roots."   If we were to write down this statement formally, on the other hand, it might go something like this:     $\forall x(x\in\mathbb R^+ \implies \exists y \exists z(y\in\mathbb R \land z\in\mathbb R \land (y\neq z) \land (y^2 = x) \land (z^2 = x))$.   If I were to ask my professor if they really meant the second statement, they might squint at it for a second, tell me I'm using the exterior product incorrectly, then (after clarification) remark, "Well, I suppose you could write it that way, but you know what I meant." (The dialogue here is fictional, but reflects some of the responses I've gotten from professors when I tried to draw out extremely formal statements from them.)  What this brings me to is the question of, when they said the first statement, were they   expressing in natural language a formal statement in mathematical logic (such as the second statement, for example), or simply stating a truth about the positive real numbers?   I feel like most of my math professors would assert that they were merely stating a truth about the positive real numbers, not trying to express in natural language some convoluted formal statement of mathematical logic. It appears to me that not all of my professors have training in, or even care about, formal logic. This is incomprehensible to me, especially when I read about the foundations of math being entirely based on formal logic.     If mathematics is as its core formal, then how could one do any math without formal logic?   In an  elsewhere on the site, user Yuval Filmus stated that "From the point of view of the acting mathematician, foundations are only needed if they're your specialty."  He goes on to request of the asker, "please don't take this formal stuff too seriously. While entertaining and fruitful, it is only one way to look at math." But my response to this is:     Why? If they're the foundations for everything we do, shouldn't everyone care about them?   I realize this question was rather long-winded, but I hope I successfully expressed some of my confusion and frustration, and I would appreciate any advice in making sense of these topics.


Train fare 4 Euros higher for travel to airport than to its two adjacent stations

Is it legal to have a higher train fare for travel to/from airport when adjacent stops are way cheaper? I frequently travel to an airport that is connected to its serving city by rail service. A one way train fare to/from the airport to/from the city is 5 Euros. It's roughly a 15 minutes train ride. However, travelling on the same identical train that stops at the airport and boarding/alighting from any of the adjacent stops costs 1.10-1.20 Euros. E.g.  1 station before the airport's station to the city: 1.20 Euros Airport's station to the city: 5 Euros 1 station after the airport's station to the city: 1.10 Euros  I find the 5 Euros fare quite good compared to some prices that can be found elsewhere. However, I don't find this to be ethical and was wondering if there might be any justification for the 450% higher rate (e.g. arguing that the airport's station infrastructure is what adds to train fare). If this is indeed Price Discrimination, is it legal?


Human can't digest cellulose.....but the length of small intestine is approximately same in humans and herbivores

My question is why herbivores are able to digest cellulose and why can't we??


What lenses should I use for bird photography

I am looking for lenses to use with my Nikon D5600 that would be good for bird photography. I recently bought it and was wondering what lenses would be good. My budget is up to $400. Thanks in advance


Incorrect wording for "Top Network Users" on Stack Exchange front page

So, I noticed last week that . Well, it turns out that the wording is actually completely incorrect.  noticed that all of the users on the front page are the OPs of the questions listed there. This area is the issue:  It reads  Top Network Users These users asked or provided top answers for the posts on this page  I found that confusing, so I proposed this wording (provided by ):  Top Network Users These users provided the top questions and answers on this page  But, again, the users listed there are the ones who asked the questions; none answered them:  (click for larger image) Since all of the "Top Network Users" are the askers, it should be something like this:  Top Network Users These users asked the questions listed on this page  Either that, or answerers of those questions should be included along with the askers.


In coordinate geometry, points are defined by ordered pairs. However, I have never come across a rigorous definition of what an ordered pairs is, specially given the fact that the same element can occur twice in such a set but not in in sets defined in ZFC.


What is the reason for 'microcytic' anaemia?

I know the causes for microcytic anaemia are Fe deficiency, prolonged inflammation, Thalessemia, Sideroblastic etc. All these logically point to a decrease in Haemoglobin synthesis - either Haeme or globin.  But my doubt is, what exactly causes the microcytosis? Lesser Hb can explain the hypochromicity, but how does it explain the decreased MCV?


Packaging a pre-populated SQLite database with my Android App

I'm a beginner in Android programming, fairly well experienced in Java. I'm using Android Studio with KitKate and Lollipop Emus and HW, developing for Froyo. I want to know what's presently the best accepted and easiest to implement way of including a database with my Android App.  I've looked at ActiveAndroid, but I followed their documentation exactly and found I was far from the only person to struggle with it's implementation - even the best programmers I know told me I was flogging a dead horse.  A very commonly posted link is this:   It's 6 years old, and I'd rather follow today's best practises.  TIA,  TH  [Edit]  I've explained that this question is with regards as to whether the ReignDesign post is still acceptable, and, or, if there are any other better resources or libraries one can use that make this very common task as easy as it should be.


Making a tabular span multiple pages - package interaction prevents longtable as a drop-in replacement

I have a tabular which relies on a number of packages to achieve the desired appearance, specifically:   Scale text to a particular (smaller) size Force column wrapping instead of shrinking text further Increase space between different rows to distinguish between wrapped items Disable right justification and hyphenation for a tidier look   I discovered that the table will end up needing to span multiple pages, but in this situation longtable is not a drop-in replacement for tabular and I am getting confused with the number of packages involved. How can I achieve the desired effect (a tabular spanning multiple pages, with all other visual elements, including the float caption, retained)? As a second question, can what I've written be simplified in some way?  \documentclass{scrartcl} \usepackage{booktabs,array,parskip,adjustbox,enumitem} \usepackage[UKenglish]{babel} \newcolumntype{x}[1]{>{\raggedright}p{#1}} \begin{document}   \begin{table} \begin{hyphenrules}{nohyphenation} \renewcommand{\arraystretch}{1.5} \caption{Example table}\label{tab:example} \centering \begin{adjustbox}{width=1\textwidth} \begin{tabular}{x{.2\columnwidth}@{\hskip 6\tabcolsep}x{.4\columnwidth}@{\hskip 6\tabcolsep}x{.4\columnwidth}} \toprule {\textbf{Column One}} & {\textbf{Column Two}} & {\textbf{Column Three}} \tabularnewline \midrule  ABC & \begin{itemize}[leftmargin=*] \item This is an item in column two. \item This is another item in column two. \end{itemize} & \begin{itemize}[leftmargin=*] \item Here is something in column three:   \begin{itemize}   \item It   \item consists   \item of   \item many   \item different   \item lines   \end{itemize} \end{itemize} \tabularnewline  DEF & \begin{itemize}[leftmargin=*] \item Additional blah blah making for a long sentence spanning multiple lines. \item Another item. \item Continuing the theme of items in column two. \end{itemize} & \begin{itemize}[leftmargin=*] \item Here we also have a rather long item that needs multiple lines to fit. \item Yet another item. \item Blah, blah:   \begin{itemize}   \item It's a very long example of a sub-item in this column, here   \item Yet more   \end{itemize} \end{itemize}  \tabularnewline  GHI & \begin{itemize}[leftmargin=*] \item Another long, long long long long long long long long long long long block of text. \item This particular one is medium-medium medium in lenght. \item This sentence means nothing in particular, it's blah. \end{itemize} & \begin{itemize}[leftmargin=*] \item Blah \end{itemize}  \tabularnewline  JKL & \begin{itemize}[leftmargin=*] \item Blah, blah, blah, blah, blah. \item Putting in fake data gets tedious. \item Reading it is probably more boring still. \end{itemize} & \begin{itemize}[leftmargin=*] \item Blah \end{itemize} \tabularnewline  MNO & \begin{itemize}[leftmargin=*] \item This was also a really long item so I am going to type and type and type until I run out of words. \end{itemize} & \begin{itemize}[leftmargin=*] \item Blah \item Can \item we \item span \item multiple \item pages \item with \item lots \item of \item text? \item Becauase \item this \item really \item needs \item to \item be \item multipage. \end{itemize} \tabularnewline  \bottomrule \end{tabular} \end{adjustbox} \renewcommand{\arraystretch}{1} \end{hyphenrules} \end{table}  \end{document}


Include some kind of "header"-file to VBScript

Our schematics capturing tool (PADS Designer) offers the possibility to "automate" several processteps using VBScripts. For example, you can create a PDF either by opening the relevant GUI (3 clicks), enter some additional inforamtion (3 to 5 clicks and some typing) or by running a script (2 clicks). This script include every information we genearlly entered in the GUI. So I went for the scripting option.   In the meantime, I created a set of scripts, helping my colleagues and me to save time. Just recently I reviewed my code with a more experienced colleague (no vbs-experience, or knowled regarding the schematics tool, though), who suggested, I could unify my function calls and names of variables and so on. For example, most of my scripts need file-system-objects, or objects related to the schematics tool; furthermore there's some functions I repeatedly use. Those functions and objects appear in each script file, regardless wether or not I use them. So, the scripts got longer and longer with each new script.   My scripts are written using Notepad++, as    the schematics tool offers no "integrated" scritping environment, I don't use Visual Studio (or some other tool) and  it worked with little effort regarding setup for me.    Now I wonder, if it's possible to add some kind of "header" file that I can include in each vbs-file. this "header" should contain    functions I use in more than one script,  declaration of global variable and constants.    Can this be done, and how?


Creating Windows EXE from Java(FX) through Eclipse

I can't create Windows software through Eclipse. Using "Run" does run the app as it should, but I would like to start it without Eclipse, preferably as an independent Windows app, using a mere double-click. Although  suggests several approaches, they all require additional knowledge that I do not posses.  I have tried using Launch4J but it also requires additional knowledge. I am astounded that it is so difficult to create a simple Windows-Java-app.  EDIT I am using this pom.xml:  <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">  <modelVersion>4.0.0</modelVersion> <groupId>foo</groupId> <artifactId>bar</artifactId> <version>1.0.0</version> <name>baz</name> <description></description>  <dependencies> </dependencies>  <build>     <plugins>         <plugin>             <groupId>com.zenjava</groupId>             <artifactId>javafx-maven-plugin</artifactId>             <version>8.8.3</version>             <configuration>                 <mainClass>application.Main</mainClass>                 <updateExistingJar>true</updateExistingJar>                 <skipCopyingDependencies>true</skipCopyingDependencies>                 <useLibFolderContentForManifestClasspath>true</useLibFolderContentForManifestClasspath>             </configuration>             <executions>                 <execution>                     <phase>package</phase>                     <goals>                         <goal>build-jar</goal>                     </goals>                 </execution>             </executions>         </plugin>         <plugin>             <groupId>org.apache.maven.plugins</groupId>             <artifactId>maven-compiler-plugin</artifactId>             <version>3.5.1</version>             <configuration>                 <source>1.8</source>                 <target>1.8</target>             </configuration>         </plugin>     </plugins> </build> </project>   But Eclipse gives this error message:  Failed to execute goal com.zenjava:javafx-maven-plugin:8.8.3:build-jar   the goal being  clean compile package -e   Maven is installed, trying to run it with minimal appendancies.


Clickable URL gets segmented by the new line?

In my reference, I have a clickable link. It is cut into two lines automatically.  Problem comes when I click it. When I click it, the part in the 2nd line is not included. I am directed to the non-sense http://www  How can I fix it?


How to make labels visible after using Clip to Current Data Driven Extent?

I would like to use the Clip to current Data Driven Page extent feature, however, it covers up the labels that are already present, leaving visible features unlabelled. Does anyone know how to force ArcMap to draw the labels within the visible portion?


If $\sum_{n=1}^{\infty} a_n$ is absolutely convergent, then $\sum_{n=1}^{\infty} (a_n)^2$ is convergent

Let $\sum_{n=1}^{\infty} a_n$ be a series in R. Prove that if $\sum_{n=1}^{\infty} a_n$ is absolutely convergent, then $\sum_{n=1}^{\infty} (a_n)^2$ is convergent.


Integral of type $\displaystyle \int\frac{1}{\sqrt[4]{x^4+1}}dx$

How can I solve integral of types  (1) $\displaystyle \int\dfrac{1}{\sqrt[4]{x^4+1}}dx$  (2) $\displaystyle \int\dfrac{1}{\sqrt[4]{x^4-1}}dx$


Help! Let $f(x,y)$ given by $f(x,y)=ax^2+by^2+cxy+dx+ey+l$ in $R^2$. If $(x_0, y_0)$ is a local maximum point of $f$, show that $(x_0, y_0)$ is an global maximum point.  The suggestion to consider the function $g$ given by $g (t)=f(x_0+ht,y_0+kt)$ and verify that its graph is a parabola. Even with the suggestion, I could not do it.  Excuse, my English is not very good!


Is there any convenience in name date-time related columns? created and delivered, … or createdTS, deliveredTS or createdAt, deliveredAt or…


How long is the longest running anime series?

I know that the Pokemon anime has over 800 episodes, and One Piece has 600+ episodes, but I've heard that they are not in the top 10 of anime with the most number of episodes.  So what anime is longest?


document.write loading scripts dynamically

I am trying to load script dynamically. This is my code:  document.write('<script type="text/javascript">window.jQuery || document.write(\"<script src=\'http://code.jquery.com/jquery-1.10.2.min.js\'></script>\")</script>');   This is inside B.js which is loaded as script on A.html. But I get error. The end script tag inside double quotes is treated as if it's nested script tag and breaking the code.  Any ideas how to fix this?


Why divide by $n-2$ for residual standard errors

I was just watching a lecture on statistics and someone was calculating something called the residual standard error. It looked a lot like finding the average of the square of the residuals, the residuals being the difference between the prediction of your model and the actual values. So for a linear fit, the prediction is $\hat{y}(x_i)=mx_i+b$ and the actual value is $y_i$. So the residual is $r_i = (y_i - \hat{y}(x_i))$. The residual standard error is $\frac{1}{n-2}\sum_i r_i^2$. I don't understand why dividing by $n-2$ is necessary?   Update: I have a better idea. If there are only two data points, then the residuals would all be zero. So you could not estimate the error with only two points. But this still does not explain why dividing by $n-2$ is a good idea. It only explains why the formula is undefined for $n=2$.


Monopoly: Can I Buy Properties Right Before I Go To Jail?

I rolled doubles three times in a row, and I landed on Illinois Avenue on my last roll. I want to buy it, but since it's my third double I'm going to jail. I want to buy it right now at the regular market price instead of at an auction because the other players have a ton of money and may bid very high for Illinois Avenue.   Can I buy it now? Thanks!


Positioning two forest trees side by side as numbered gb4e subexamples

I am adjusting  to position two syntax trees side by side, as numbered subexamples.   The problem I am having is too much whitespace between the second-level label ("a.") and the tree, particularly the first one. This space only appears if I add the tabularx environment from the solution, I do not have that issue with the forest and the gb4e packages on their own and in combination. I seem to have enough space on the page for both tree examples to fit nicely; is there a way I could do that with these packages? As it is, the positioning is weird.  MWE:  \documentclass[11pt]{article} \usepackage{fontspec} \usepackage[margin=1truein]{geometry}  % The below is a standard package setup for syntax trees. \usepackage{forest} \useforestlibrary{linguistics} \forestapplylibrarydefaults{linguistics}  % This package is for numbered linguistic examples. \usepackage{gb4e}  % The following three packages allow me to position trees side by side and as numbered examples. \usepackage{tabularx} \usepackage{array} \usepackage{environ}  % The following code is later used to to position trees side by side and as numbered examples. \newcolumntype{T}{>{\refstepcounter{tabenum}}X} \newcounter{tabenum}[xnumi] \renewcommand{\thetabenum}{\thexnumi\alph{tabenum}} \newcommand*{\tabex}{\relax\alph{tabenum}.\quad} \NewEnviron{multiexe}{%     \setlength{\extrarowheight}{1ex}     \begin{tabularx}{\linewidth}[t]{@{}TTT@{}}        \BODY     \end{tabularx} }  \begin{document}  \begin{exe} \ex  \begin{multiexe}  \tabex  \begin{forest} [S[NP[D\\A][N\\cat]][VP[VP\\slept][PP[P\\on][NP[D\\the][N\\mat]]]]] \end{forest}  \label{tree1} & \tabex  \begin{forest} [S[NP[D\\A][N\\cat]][VP\\slept]] \end{forest}  \label{tree2}  \end{multiexe} \end{exe}   \end{document}


Normally, we can search a keyword in a list of pdf files using the following command:  for file in *pdf; do  pdftotext "$file" - | grep keyword done   Now, from the search result, If I want to find the title name along with the authors/writers of the file manually, without using pdfinfo command, what will I have to do?


Could someone help me on how to fix this bad encoding?  The right output would be Église (this is what I have in the DB), however I'm getting Ã‰glise in the html output.  After running mb_detect_encoding(), I get "UTF-8". I've tried utf8_decode() without success, so I'm kind of lost and would need some guidance. Thanks all!


I'm an opengl programmer, and I would like to use opengl 4.0; problem is that I cannot install any proprietary drivers, and when I type : glxinfo | grep "OpenGL version" in the terminal, it outputs me :  OpenGL version string: 3.0 Mesa 10.5.2 OpenGL shading language version string: 1.30 OpenGL context flags: (none)   Can anyone tell me how I could update mesa to 4.x+ ?   EDit :   lspci -k | grep -EA2 'VGA|3D' 00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)     Subsystem: Hewlett-Packard Company Device 1972     Kernel driver in use: i915


Prove $\int_{0}^{x}f+\int_{0}^{f(x)}f^{-1}=xf(x)\qquad\text{for all $x\geq0$}$

Suppose that the function $f:[0,\infty)\rightarrow\mathbb{R}$ is continuous and strictly increasing and that $f:(0,\infty)\rightarrow\mathbb{R}$ is differentiable. Moreover, assume $f(0)=0$. Consider the formula $$\int_{0}^{x}f+\int_{0}^{f(x)}f^{-1}=xf(x)\qquad\text{for all $x\geq0$}$$ Prove this formula.     Attempt: Consider that $g(x)=\int_{0}^{x}f+\int_{0}^{f(x)}f^{-1}-xf(x)$ which is continuous on $\mathbb{R}$. Then differentiate $g(x)$, we have $g'(x)=f(x)+xf'(x)-f(x)-xf'(x)=0$. Thus for all $x$, $$g(x)-g(0)=0\Longrightarrow\int_{0}^{x}f+\int_{0}^{f(x)}f^{-1}-xf(x)=0$$    I am not sure my the equality valid not or not. If not, can someone give me a suggestion to modify the proof. Thanks.


Is the "protophobic fifth force" observed in nuclear decays a new fundamental force?

There is a recent paper in , also on the  that claims the discovery of a fifth force, mediated by a 17 MeV boson, which explains an anomaly in nuclear decays.  Is this a real effect? Could the claimed particle be some sort of composite particle such as a pion?


Schengen business visa extension in Spain

I'm travelling to Spain for business purpose and my visa is valid for just 14 days. Now I have another very urgent business to attend to in the Netherlands. Can I extend my stay for another 10 days to complete my business meeting in the Netherlands?  Can I get an extension in Spain, prior to entering the Netherlands? I haven't left for Spain yet and currently staying in my residence country (India).


How to check whether systemd is unmounting my device? (and why?)

This is a followup to .  I figured out something is unmounting my device right after I mount it.  This device is being used by a database (Vertica), which is down and not using the directory while I'm running the mount command.  I'm trying to figure out:   Is systemd the one which unmounts the device? How can I debug why is that happening? How do I fix it?   Here's an example of what is happening:  [root@mymachine systemd]# mount -t ext4 /dev/xvdx /vols/data5; ls -la /vols/data5; sleep 5; ls -la /vols/data5 total 36 drwxr-xr-x   5 dbadmin verticadba  4096 Jul 23  2017 . drwxr-xr-x   9 root    root          96 Jul 16 18:52 .. drwxrwx--- 503 dbadmin verticadba 12288 Jul 23 13:51 somedb drwx------   2 root    root       16384 Nov 30  2016 lost+found drwxrwxrwx   2 dbadmin verticadba  4096 Jun 20 08:32 tmp total 0 drwxr-xr-x 2 root root  6 Jun  8  2017 . drwxr-xr-x 9 root root 96 Jul 16 18:52 .. [root@mymachine ~]#    fstab:  # # /etc/fstab # Created by anaconda on Mon May  1 18:59:01 2017 # # Accessible filesystems, by reference, are maintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # UUID=29342a0b-e20f-4676-9ecf-dfdf02ef6683 /                       xfs     defaults        0 0 /dev/xvdb swap swap defaults,nofail 0 0 /dev/xvdy /vols/data ext4 defaults 0 0 /dev/xvdx /vols/data5 ext4 defaults 0 0   Some more logs as per 's suggestion:  Aug 01 16:55:19 mymachine kernel: EXT4-fs (xvdx): mounted filesystem with ordered data mode. Opts: (null) Aug 01 16:55:19 mymachine systemd[1]: Unit vols-data5.mount is bound to inactive unit dev-xvdl.device. Stopping, too. Aug 01 16:55:19 mymachine systemd[1]: Unmounting /vols/data5... Aug 01 16:55:19 mymachine umount[353194]: umount: /vols/data5: target is busy. Aug 01 16:55:19 mymachine umount[353194]: (In some cases useful info about processes that use Aug 01 16:55:19 mymachine umount[353194]: the device is found by lsof(8) or fuser(1)) Aug 01 16:55:19 mymachine systemd[1]: vols-data5.mount mount process exited, code=exited status=32 Aug 01 16:55:19 mymachine systemd[1]: Failed unmounting /vols/data5.


How to clone a copy of all remote branches on local with git

I encounter an issue with some of my projetc. I started them on my older computer that doesn't work now. But, I have my projetcs on a gitlab repository. However, when I cloned them on my new computer, I just have master branch on my local, I think it's normal. So my question is : how can I have the local copy of the content of remote branches on my local please ? I really don't enjoy to 'checkout' on remote/example branch ... :/ I hope I was clear in my words Sorry for my English, I'm french. Have a nice day


How to get variables from another file in python

For example I have a variable config in config.py. I want to use the variable config in main.py. And the config.py must be pass to main.py through command line. like follows:  python ./main.py ./config.py   I know in lua I can use dofile function. How can I do this in Python  Fixed by


What would keep a hypothetical fusion reactor from "igniting the atmosphere"?

So in the early days of Nuclear fission, there was a concern about the resulting energy igniting the atmosphere in a ball of fire and world-wide death which is awesome terrifying awesomely terrifying. This of course did not happen, and I'm led to believe that these concerns ran along the same vein as concerns raised about the LHC creating a black-hole that would consume the earth (read; sensationalist media fueled, the scientific community at large had no reason to believe this would actually happen).  To my understanding, fusion reactions generate orders of magnitude more energy than fission reactions. It's fairly obvious that hydrogen fusion is self-sustaining in the right environment (see exhibit A - The Sun), and elements up to iron release energy when fusing, so that includes most of our atmosphere. What reason is there to believe that successful achieving fusion in the confines of our atmosphere would not, y'know, set it on fire?


What defines a "description" of a probability distribution?

Say you take a dice and you roll it twice so that you have a pair (X,Y) where X represents the first roll, Y represents the second.   When you have a distribution like max(X,Y), what type of distribution is that? It's not uniform, obviously, because the outcomes of max(X,Y) are clearly more favorable towards the higher numbers. I'm being asked to "describe" the distribution. I know that we can look at each distinct outcome, like:  max(1,1) = 1  max(1,2) = 2  max(1,3) = 3  max(1,4) = 4  max(1,5) = 5  max(1,6) = 6  max(2,1) = 2  max(2,2) = 2  max(2,3) = 3  max(2,4) = 4  max(2,5) = 5  max(2,6) = 6  max(3,1) = 3  max(3,2) = 3  max(3,3) = 3  max(3,4) = 4  max(3,5) = 5  max(3,6) = 6  max(4,1) = 4  max(4,2) = 4  max(4,3) = 4  max(4,4) = 4  max(4,5) = 5  max(4,6) = 6  max(5,1) = 5  max(5,2) = 5  max(5,3) = 5  max(5,4) = 5  max(5,5) = 5  max(5,6) = 6  max(6,1) = 6  max(6,2) = 6  max(6,3) = 6  max(6,4) = 6  max(6,5) = 6  max(6,6) = 6  But is that the most effective way to look at a distribution like this? Is there a faster and more concise way to describe this distribution other than saying the probability of each outcome?  i.e.,  P(max = 1) = 1/36  P(max = 2) = 3/36 = 1/12  P(max = 3) = 5/36  P(max = 4) = 7/36  P(max = 5) = 9/36 = 1/4  P(max = 6) = 11/36  So, obviously, I understand how to LOOK at a discrete distribution and see what the probabilities are, but not until I look at each possible outcome. But what does it mean to "describe" a distribution? This isn't uniform or any sort of discrete distribution we're taught. Can someone provide clarity?


Interaction of Invoke Duplicity and Misty Step

Can you teleport farther away with misty step if you have a double from Invoke Duplicity? The Channel Divinity feature says:     you can cast spells as though you were in the illusion's space, but   you must use your own senses. (PHB 63)   If you were where your duplicate is, you could step to a space 30ft from its position. So if it is 60ft from you, you could teleport to a space 90ft from your actual position. But the spell says that:     you teleport up to 30 feet (PHB 260)   This would put a hard limit on the distance you can travel.  Which rule takes precedence here?


Orthonormality: from finite ($\delta_{ij}$) to infinite ($\delta(x-y)$) dimensional vector spaces

I've been reading  on QM, but I'm unsatisfied with the section on "Generalization to Infinite Dimensions".  Given a finite dimensional vector space with a basis $\{x_i\}$, I understand that the basis is orthonormal if $\langle x_i|x_j\rangle = \delta_{ij}$ (where $\delta_{ij}$ is the Kronecker delta).  Extending this to continuous infinite dimensions, an example "basis" vector (whatever this really means in this case) may look like $|x\rangle$ where $x$ can be any real number in some interval. Apparently the basis vectors $|x\rangle$ and $|y\rangle$ are orthonormal if $\langle x|y\rangle = \delta(x-y)$, where $\delta(x-y)$ is the Dirac delta.  I would be convinced of this generalization if I could show the following:   Define an inner product in the finite dimensional case with a basis satisfying the first orthonormality condition. Let the number of dimensions somehow go from finite to a continuous infinity. Show that in this limit basis still satisfies the second orthonormality condition.   Can the above be done, or is there a fundamental misconception I have here? Do you have any recommended reading? (preferably not an Analysis textbook)


Good book on quantum field theory to start learning as an undergraduate?

I am looking for a book to study QFT in my vacations. I have all the standard maths on an undergraduate physics program level plus a little of group theory.  I found very good reviews from Quantum Field Theory for the Gifted Amateur, although there are a few harsh criticism. I was thinking to buy this book, but found to better to have some advice of more experienced physicists in the subject, given that books are really expensive from where I live. So, is it worth as a first book? Are there better alternatives?


How to start mysql in xampp which is showing error?

I have installed xampp in my laptop. But when i am starting mysql, its showing 3306 error port number used by another application. How can I rectify this eroor ?


Loop-Quantum Gravity versus String Theory

Basically asking what were the motives behind each theory. What was it that led physicists toward these ideas?


graphicx: New Option to be Able to Handle Missing Files (No Error)

I would like to have a new option in the \includegraphicscommand. The idea ist that there is no error when the file does not exist - maybe just a friendly warning.   Ideally, the file extension is not needed (to be flexible in the future) but if it's needed that's also ok (at the moment it's not necessary).  \documentclass[a4paper,11pt]{article}  \usepackage{graphicx}  \begin{document}  \includegraphics[myDoNotComplainIfFileIsMissing]{MyFileThatMayOrMayNotExist.ext}  \end{document}   Possible duplicates


How often does Ubuntu 19.04 and later sync time?

In a default Ubuntu 19.04 - how often is computer time synchronized with time servers?    Once every hour?  Once every day?  Something else entirely?


I am working on a chat application where user have to fill the form before he/she begins the chat. Validation of each form field happens once user enters the value in respective form field. One of the form field is phone number and for which I wrote a regular expression as following. var phoneRegex = RegExp(/^[\+]?[(]?[0-9]{3}[)]?[-\s\.]?[0-9]{3}[-\s\.]?[0-9]{4,10}$/im);  Regex should return 'true' for following phone numbers  +11234567890 - 10 digits with area code 1234567890 - 10 digits 233445678912 - 12 digits 2334456789122222 - 16 digits  My chat application works for first 3 numbers but doesn't work for 16 digit phone number. I am not a huge fan of regex and have limited understanding of it hence I want to to know if my regex has any fault? And if yes then how can I fix it?


Disable Root Password Login... but can I SUDO with a GUI SFTP program?

I fully understand why .  That makes sense.  I can log in as username, then sudo back to root functions just fine from the terminal.    What I'm unable to do is utilize a graphic type of secure file transfer protocol (SFTP) tool (e.g. filezilla) to get access to key directories.  Is there a way to keep the root login disabled and use SFTP, or am I stuck using a terminal $ ssh login with wget or curl for all of my file transfer needs?    The problem is that I can only use wget or curl for content loaded on a server somewhere.  I can't directly upload content from my laptop/desktop development machine to the server.  Yes, I am aware that git style transfers are an other possibility.  I would need a private git repo somewhere to make that work.    Is there a way to set a sudo access for the SFTP tool, without using a root login?  Is there an alternative method to send new content to a online server via remote access, without compromising security?    Same thing goes for downloading / reading systems content.  I know I can do a lot of things via terminal and su - or sudo, but I have to say, reading a systems log file that is 10 megs long is just out of the question with vim or nano.


how can i declare variable in shell and use with condition instruction

I have a first script for exemple :   test1.sh $1='world' var1="hello world" echo $var1   So, i want a script shell, which execute test1.sh according to condition :   for exemple :   if  [ $1= world ];    #execute test1.sh   i don't know how to rely the two shells, if you have any suggestions i ll be thankfull !


du results on filesystem inconsistent with df

What explains the discrepancy in usage (82 GB vs 13 GB) that I see below?   Using df:  $ df -h / Filesystem            Size  Used Avail Use% Mounted on /dev/sda2              96G   82G  9.9G  90% /  Using du:  $ sudo du -cshx / 13G     / 13G     total


I would like to show that if $G = \langle a \rangle$ with order $n$, then $\text{Aut}(G) \cong U(n)$.    I know that $\text{Aut}(G)$ is the group of bijections $\phi:G \rightarrow G$ under composition, but I don't know where to start.   Any help would be much appreciated.


I want to Dual Boot Windows 10 and Kali Linux. That is not a problem, but I don't want to turn off my PC to get into Kali Linux. I want that if I'm on Windows 10, Kali Linux is in the second desktop. Is this possible?


Zorn's Lemma and Theorem of Ring Theory.

$\bf{Theorem.}$ Let $R$ be a commutative ring with identity. If $I$ is a proper ideal of $R$, then $I$ is contained in a maximal ideal.   and     $\bf{Zorn's\;Lemma.}$ Suppose a partially ordered set $P$ has the property that every chain in $P$ has an upper bound in $P$. Then the set $P$ contains at least one maximal element.   I have never seen a demonstration of this theorem without the use of the Zorn's Lemma. I know that Zorn's Lemma is a much more general than rings and I don't see a reason for the theorem to imply the Zorn's Lemma, but it makes me wonder if there can be any kind of equivalence between these two things.


Does the link with trivial knot group trivial?

I know that if a the knot group of a classical knot is isomorphic to the infinite cyclic group, then the knot is unknotted. How about the link, is this result also valid for links. In other words, if the knot group of a link is $\mathbb{Z}^n$, then does this imply that the link is unknotted, where n is the number of components?


How to make sure my computer clock is right and fix it if it is not?

I have recently noticed that the time on my computer isn't the same as on the others in my household, and I'm not sure if it's just them, or whether my machine has actually got the wrong time...  So I was wondering if there is some way through Terminal of synchronizing my computer clock with the Ubuntu servers or something? Or at least being able to check that I have the right time for my time zone?  I am running Ubuntu GNOME 15.10 with GNOME 3.18.


What is $|v|$ for complex measure $|v|$?

In Real analysis from Folland, we define $|v|$ when $v << u$ for some positive measure $u$, $dv = f du$ for some $f$ in $L^1$, $d|v| = |f|du$. But in page 99, folland's book, the proof of thm 3.22 says that "IT IS EASILY VERIFIED THAT $d|v| = d|p| + |f|dm"$. Hmm... I can't find definition of $d|v|$ when $dv = dp + fdm$. What is this?


Terminology: Difference between Lemma, Theorem, Definition, Hypothesis, Postulate and a Proposition

Based on observation after reading few books and papers, I think that   Lemma : Lemma contains some information that is commonly used to support a theorem. So, a Lemma introduces a Theorem and comes before that Theorem. The information contained in the Lemma is generally used in the proof of the Theorem.   Q1: What is a Proposition ?   Q2: What is the difference between Proposition and Theorem ? A Proposition can also be proved, in the same way as a Theorem is proven.  Hypothesis :  A hypothesis is like a statement for a guess, and we need to prove that analytically or experimentally.   Q3: What is the difference between Theorem and Hypothesis, for example Null hypothesis in statistics? In general, if a  Theorem is always proven to be true then it no longer becomes a Hypothesis? Am I correct?   Q4: What is the difference between Postulate and Theorem?  Q5 : What is the difference between a proposition and a definition?  Looking for easy to remember answers. Thank you for help.


I've always transcribed "pink" and "ring" with the vowel /I/ (lax) vs. the tense /i/, and my students have never argued with me about it, but suddenly I've been getting a good number of students arguing for the /i/.  They seem to have a vowel somewhere in between perhaps--sometimes it sounds like straight /i/.      Just wondering if you've heard about this happening in certain parts of the country or if this has always been a sort of variant.  Most of my student are from the midwest (Michigan)


I'm using Ubuntu 18.04. How can I add shortcuts to my desktop like in Windows? I'd like to make a shortcut for e.g. the Spotify application (so not a native ubuntu app), and I want to make shortcuts for folders.


How do I get my passport back from the IRS?

The IRS has had my passport for 120 days, and I haven't gotten it back. When I call them, they ask me to wait. I have to go somewhere soon and my visa status needs to be changed too. What should I do? Will they give me letter saying they have lost it so that I can apply for the new one?   I have asked them about this several times and every time they reply saying "I'm sorry ma'am but we can not do anything in this matter" and when I ask them to give me the location or phone number of the IRS office in Austin, they say "We cannot do that."


My one year old son doesn't want to eat. What happened to my son?

When my son was under 11 months old, he ate a lot, but I don't know what changed when he reached 1 year old. It seems like he doesn't like to eat. When we give our son food, sometimes he tries to taste or eat it a little, but then refuses to eat it. I heard from a neighbor that the he may be bored with the food, so we served him different food, but he still doesn't seem to be interested. We also tried to change the way we gave the food to our son, but that didn't solve the problem either. One thing that keeps me a little more calm is that lately he more often asks to be breastfed. Maybe this is caused by his eating less solid food.  I've heard that this phase is pretty normal for all children. What has actually happened to our son in this phase? What makes him not want to eat the food we give him? He has asked for food, but then doesn't eat it. Is it enough that we focus on giving him more in breastfeeding? Because when he doesn't eat as much solid food, he asks for breastfeeding more often.


Did Starkiller base have a hyperdrive? If so, what class?

It has been mentioned that the first Death Star had a class 4 Hyperdrive and a class 20 backup, so it could move from system to system (so it could destroy targets.) As the weapons system of the First Order's Starkiller base is partly based off of the Death Star weapons system, does Starkiller base have a hyperdrive to move?


How to make this start every time I start the computer?

I'm using a backlit keyboard and need to enter this every I start the computer.   #!/bin/bash if [ -f /tmp/keyboard_light ]; then xset -led 3 && rm /tmp/keyboard_light else xset led 3 && touch /tmp/keyboard_light fi   How do I make it to start every time I start my computer?


How to limit number of users who can connect to a hotspot.Talking about an Android tethering hotspot.I do not want more than one device to connect.


Are {/bin, /lib, /sbin} symlinks into /usr in Ubuntu?

I do not have access to an Ubuntu system or chroot. I was hoping if someone could tell me if the  is accurate in saying:     For Quantal, merged /usr should be supported. On new systems installer should create {/bin, /lib, /sbin} symlinks into /usr.


t-test or z-test: assume normality or s≈σ?

Let's say I have a large sample ($n>30$) with mean $\bar{X}$ and standard deviation $S$. I can calculate only: $T=\frac{\bar{X}-\mu}{S/\sqrt{n}}$.  If I want to use t-test for a hypothesis, then I have to assume normality of the population. If I want to use z-test for a hypothesis, then I have to assume that $\boldsymbol{s\approx\sigma}$.  What is the less important assumption? What test should I do? Should I do t-test, z-test or doesn't matter?


I do this command:  $ locate config.yml | while read i; do sed -i '/(swipe)|(pinch)/s/[0-9].*/1/' $i; done   output:  sed: couldn't open temporary file /home/user/.config/fusuma/sedHhlVCW: Permission denied sed: couldn't open temporary file /home/var/lib/gems/2.5.0/gems/fusuma-0.11.1/lib/fusuma/sed41YvwW: Permission denied sed: couldn't open temporary file /var/lib/gems/2.5.0/gems/fusuma-1.10.0/lib/fusuma/sedFSNXeV: Permission denied   So I did with sudo (run as sudo sudo su -> #, but then not all files were change, and as I see from the error above, the files are temporary and with changed name (postfix of all them consist of command and random chars), does this pipe? If so why? How can I persist filenames over pipe?  $ uname -a Linux user 4.19.0-9-amd64 #1 SMP Debian 4.19.118-2 (2020-04-29) x86_64 GNU/Linux  $ type sed sed is aliased to `sed -E'


Ora-39000 bad dump file specification when exporting dump file using expdp

I am trying to perform a windows scheduler job  which will create back up of my database daily once. So for this reason I have created batch file SYSTEM_BACKUP.bat which contains data:  @echo off setlocal EnableDelayedExpansion expdp SYSTEM/SYSTEM@XE PARFILE=export_dump.par   The export_dump.par file contains information:  DIRECTORY=cron_jobs DUMPFILE=SYSTEM_!date:~10,4!!date:~6,2!.!date:~4,2!.dmp LOGFILE=SYSTEM.log SCHEMAS=B1,B2 CONTENT=ALL   When i trying to run the SYSTEM_BACKUP.bat I am getting error as     ORA-39001:invalid argument value,   ORA-39000 bad dump file specification,   ORA-39087:directory name ratormonitor_!date is invalid.    I am trying to create dump file with current datetimestamp attached to the file so the dump file name should look like this SYSTEM_2015.02.03.37.029062831 but getting an error.


What do you call non-standard spellings used by companies that are similar to real English words?

There are many brand names that are misspellings of real English words. Instead of calling them misspellings I would like a more positive term for this type of name.


Variance of sum of random number of random variables (Cambridge University Worksheet)

In the vein of , I'm now at a roadblock on question 3 of this sheet:    (note: it's not my intention to ask every question I get stuck on here, merely the ones which have interesting general results; it just so happens that the two I've struggled with so far fit this criteria)  It goes as follows:  Let $N$ be a non-negative integer-valued random variable with mean $\mu_1$ and variance $\sigma_1^2$, and let $X_1, X_2, ...$ be random variables, each with mean $\mu_2$ and variance $\sigma_2^2$; furthermore, assume that $N, X_1, X_2,  . . .$ are independent. Without using generating functions, calculate the mean and variance of the random variable $S_N = X_1 + ... + X_N$ (when $N=0$ interpret $S_N$ as $0$).  I have the answer to calculating the mean, which I'll write up as an answer for future reference. Here's where I've got to with the variance bit:  $\mathbb{E}(S_N^2) = 0.P(N=0) + \sum_{r=1}^\infty\mathbb{E}((\sum_{i=1}^rX_i)^2).P(N=r)$  For $r=1$, we have the inner expectation as: $\mathbb{E}(X_1^2)$ which is equal to $\sigma_2^2+\mu_2^2$.  For $r > 1$, we have the inner expectation equal to: $r(\sigma_2^2 + 2\mu_2^2)$  So $\mathbb{E}(S_N^2) = (\sigma_2^2+\mu_2^2)P(N=1) + (\sigma_2^2 + 2\mu_2^2)\sum_{r=2}^\infty rP(N=r)$  which is almost in the form where I can use the same trick as in calculating the mean, but not quite.  Any help is much appreciated.


System slow and apps not working on Lineage OS 14.1

Recently I updated my Samsung Galaxy S Duos 2 (GTS7582) from CM 13.1 to Lineage OS 14.1 using the unofficial build I found . It ran smoothly at the beginning and I took to it immediately. However, after installing some apps, I'm experiencing serious speed issues on my phone. Newly installed apps don't even open; if they do, they just stop working and quit. I observed that Lineage is using the same amount of RAM that CM used to use... so I'm guessing the problem is with the ROM I used and not my phone. If anyone knows of a way to speed up my phone, please advise me. If not, can you suggest another ROM that is lighter and more stable. My key requirement is that it should support extending main memory to the SD card, so that the SD card can be used as main memory. This was my primary reason for upgrading to Lineage in the first place, because my phone doesn't have much in the way of internal storage. It should also, ideally, look as good as Lineage.   Thanks :D


I am quite new to latex and I would like to ask you for help with my bibliography.  I am using XelateX on TeXworks in Texmaker. I am writing my thesis based on a template for my university. It is said I need to use biber. The preamble says this:     % Bibliography (references)     \usepackage[backend=biber,                 style=numeric,                 %backref=true,                 abbreviate=true,                 dateabbrev=false,                 alldates=long]{biblatex}   I have downloaded it but can't figure how to compile my file with biber. And I am getting the following message in my Texworks:   I did apply the steps from the previous topic: but it did not resolve my problem. The warnings I get are the same and I get no bibliography.  What should I do to make it work?  I appreciate your help.  Cheers KK  Edit 1: I compiled my .tex file with XeLateX, then Biber and get the following information: Process started  INFO - This is Biber 2.1 INFO - Logfile is 'Thesis.blg' INFO - Reading 'Thesis.bcf' INFO - Found 1 citekeys in bib section 0 INFO - Processing section 0 INFO - Looking for bibtex format file 'bibliography/Bibliography.bib' for section 0 INFO - Decoding LaTeX character macros into UTF-8 INFO - Found BibTeX data source 'bibliography/Bibliography.bib' WARN - Entry ASPS does not parse correctly ERROR - BibTeX subsystem: C:\Users\uqkkepa\AppData\Local\Temp\lU5ArF2aqU\Bibliography.bib_5208.utf8, line 1, syntax error: found "2011", expected "," INFO - WARNINGS: 1 INFO - ERRORS: 1  Process exited with error(s)


Where to post a "canonical answer" when it's not in response to a specific question?

Per , I've been working for about 2 weeks on trying to get Ajax uploading of files to work in Rails 3 using Paperclip to manage attachments. I finally found a solution that works really well, and is much better than any of the tips I got in several questions that I asked. In the spirit of sharing the final answer to all the questions I was asking I wanted to type up a "canonical answer" that would really explain how I finally got this working, with hopes that it will help many others. There are dozens of questions on this topic, many of which have been answered already. It seems silly to "ask it again" just so I can post my own answer to my own question... So, what I'm wondering is, if you've come up with a really good solution to a commonly asked question, what's the best way to share it with the SO community?


Hide choose file button of input[type='file'] without hiding file choosen name with simple css

If you're trying to remove the default Choose File Button without Removing the Filename label here is the simple CSS solution.


Can I use a charger with the following values:  Input 100-240V 1.5A Output 19V 2.40A  To replace   Input 100-240V 1.6A Output 19V 3.42A


I posted  question on Stack Overflow, and noticed the following behavior. The following quote does somehow cut the rest of the sentence:     'DoSomeList' cannot be used as type parameter 'TImplementation' in the generic type or method 'ServiceCollectionServiceExtensions.AddTransient(IServiceCollection)'. There is no implicit reference conversion from 'DoSomeList' to 'IDo>'.   'IDo>' should be IDo<System.Collections.Generic.List<SomeType>>. Check it out in the edit view.


I would like to clarify the differences between by value and by reference.  I drew a picture     So, for passing by value,  a copy of an identical object is created with a different reference, and the local variable is assigned the new reference, so to point to the new copy  How to understand the words: " If the function modifies that value, the modifications appear also within the scope of the calling function for both passing by value and by reference "  Thanks!


How do I properly clean up Excel interop objects?

I'm using the Excel interop in C# (ApplicationClass) and have placed the following code in my finally clause:  while (System.Runtime.InteropServices.Marshal.ReleaseComObject(excelSheet) != 0) { } excelSheet = null; GC.Collect(); GC.WaitForPendingFinalizers();   Although this kind of works, the Excel.exe process is still in the background even after I close Excel. It is only released once my application is manually closed.  What am I doing wrong, or is there an alternative to ensure interop objects are properly disposed of?


How do I check my promotional credit with Amazon?

I'm trying to figure out how much promotional credit I have before I make a purchase (stupid 1-click for digital purchases).  I do not want to check my gift card balance. I want to know how much promotional credit I have.  For example: As of writing this question, Amazon gives $1 MP3 credit with the purchase of any CD album. I've purchased a few of those, but I don't know how many MP3 credits I have. Where can I check that?  I know I've seen a page in the past with it on it, but I can't find that page now.


Is there a way to print this once every minute? I'm not to sure and I'd rather not search it up to get me confused

Im not sure how to print this statement every minute, or a certain time limit. I wanted to search about it online but I thought people on SO were more relevant.  I have no idea in what to do lol  import time while True:      print("This prints once a minute.")      time.sleep   I want it to print every second or minute


How to check if my visualforce publisher action is running on Salesforce1 or on the web

I want to know if there is a way to detect if my Visualforce page which implements a custom publisher action, is running inside Salesforce1 or inside a desktop browser.  I need this since when I run my visualforce on Salesforce1 it is framed automatically by a "Cancel" and "Submit" button, however when running on the desktop I get none of these buttons so I need to add a specific button to actually save the data.


Showing a relation between binomial and negative binomial analytically

If $X$ is binomial random variable $B(n,p)$ and Y is negative binomial $(r,p)$, How can I show that $F_X(r-1) = 1- F_Y(n-r)$.   While it is possible to show that using the definition of binomial and negative binomial, I am more interested in showing that directly using their p.m.fs.


Do paths in Adobe Photoshop have to be closed?

I am working to convert a png to a vector graphic.  I am outlining the image using the pen tool.  Photoshop insists that the pen tool produce closed loops in order for me to use the "Stroke path..." tool.  Why is this?


Java Error - Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

I am still pretty new to Java. I got a sample at class, to create a simple user interface and a button that should change text upon click.   The GUI opens fine, but once I click on the button, I get a NullPointerException error.   This is my code:   import javax.swing.*; import java.awt.BorderLayout; import java.awt.event.*;  public class GUISimple1 implements ActionListener { JButton button;  public static void main (String[] args) {     GUISimple1 gui = new GUISimple1();     gui.empezar(); }  public void empezar() {      JFrame frame = new JFrame();     JButton button = new JButton ("Click");       button.addActionListener(this);      frame.getContentPane() .add(BorderLayout.NORTH, button);     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);     frame.setSize(300,300);     frame.setVisible(true); }         public void actionPerformed(ActionEvent event) {         button.setText("Me han dado un click!"); } }   And this is the error, I receive when I run the application:   Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at GUISimple1.actionPerformed(GUISimple1.java:27) at     javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402) at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252) at java.awt.Component.processMouseEvent(Component.java:6533) at javax.swing.JComponent.processMouseEvent(JComponent.java:3315) at java.awt.Component.processEvent(Component.java:6298) at java.awt.Container.processEvent(Container.java:2236) at java.awt.Component.dispatchEventImpl(Component.java:4889) at java.awt.Container.dispatchEventImpl(Container.java:2294) at java.awt.Component.dispatchEvent(Component.java:4711) at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888) at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525) at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466) at java.awt.Container.dispatchEventImpl(Container.java:2280) at java.awt.Window.dispatchEventImpl(Window.java:2746) at java.awt.Component.dispatchEvent(Component.java:4711) at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758) at java.awt.EventQueue.access$500(EventQueue.java:97) at java.awt.EventQueue$3.run(EventQueue.java:709) at java.awt.EventQueue$3.run(EventQueue.java:703) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86) at java.awt.EventQueue$4.run(EventQueue.java:731) at java.awt.EventQueue$4.run(EventQueue.java:729) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76) at java.awt.EventQueue.dispatchEvent(EventQueue.java:728) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93) at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)   Any help would be appreciated.   Cheers and thanks in advance.


Is there a continuous function such that $\int_0^{\infty} f(x)dx$ converges, yet $\lim_{x\rightarrow \infty}f(x) \ne 0$?  I know there are such functions, but I just can't think of any example.


Guidelines for adding 's after name of company ending in s

How about adding 's to the name of a company that ends in s for a possessive?  Is it the same guideline (go by how it would be pronounced)?  Thanks.


I am trying to integrate Google Admob into my project, but in running into an issue.    I will go over my project first.    My project is structure on 2 main Java files and around 7 .xml files.   The .xml files are shapes, the .xml files are neither linear or relative layout.  In my main Java file I draw those .xml file shapes to the screen.  So I do not depend on a .xml layout for my project.    EXAMPLE OF SHAPE .XML FILE   <?xml version="1.0" encoding="utf-8"?>  <shape xmlns:android="http://schemes.android.com/apk/res/android" >  <solid android:color="#000" /> <corners android:bottomLeftRadius="15dp" android:bottomRightRadius="15dp" android:topLeftRaidus="17dp" android:topRightRadius="17dp" /> </shape>   So I am trying to add Google ads into my project, so I will need to add the Google ad .xml code.  But I'm not for sure where.   When I put my ad .xml code in one of the shapes .xml code I get and error that says "You can not put this here".     So I thought a little bit and realized I still have my .xml layout file that was created when I created my project.  So I add my ad .xml code there and had no error.   So next I added my Java code in my mainactivity.java,  into the oncreate, and I had no error.    I have 2 Java files, one is my mainactivity.java and the other one is my MV.java.  My MV.java is where I draw all my .xml shapes to the screen.    My Java code looks like this:  protect void onCreate(bundle savedInstanceState) { super.onCreate(savedInstanceState); view = new MV(this);  Adview adView = (AdView) this.findViewById(R.id.adView); AdRequest adRequest = new AdRequest.builder().build(); adView.loadAd(adRequest);  }   I do not get any error with my Java code.  So I thought I could run my application and have my ad.  But when I run my app I get this error.   Attempt to invoke virtual method 'void com.google.android.gms.ads.Adview.loadAd(com.google.android.gms.ads.Adrequest)' on a null object reference    I also did add the Google ad code in my build.gradle and androidmanifest.xml.  how can I get ads to work?


Matrix-vector multiplication with random vector

This question is similar to , but is generalized for rectangular matrices. Suppose we have matrix $\bf{S} \in \mathbb{R}^{m \times n} $ and vector $\bf{y} \in \mathbb{R}^{n}$. $\textbf{y}$ is sampled from a multivariate normal distribution with $\Sigma = \sigma^2 I$, where $\mu$ and $\sigma$ is known: $$ \textbf{y} \sim \mathcal{N}(\mu, \sigma^2 I) $$ $\textbf{S}$ is a fixed, known matrix What is the variance of the product of $\textbf{Sy}$? What I have tried so far (attempted working off of ): \begin{align*} \mathrm{Var}(\textbf{Sy}) &= \mathbb{E}[(\textbf{Sy})^2]-\mathbb{E}[(\textbf{Sy})]^2\\ &= \mathbb{E}[(\textbf{Sy})^T\textbf{Sy}]-\mathbb{E}[\textbf{Sy}]^T\mathbb{E}[\textbf{Sy}]\\ &= \mathbb{E}[\textbf{y}^T\textbf{S}^T\textbf{Sy}] - \mathbb{E}[\textbf{y}^T\textbf{S}^T]\mathbb{E}[\textbf{Sy}] \end{align*} From here, it seems I would like to remove $\textbf{S}$ from the expected value, but I am not sure how to proceed.


What are your remedies for baby acid reflux?

My 9-month baby suffers from moderate acid reflux since she was 3-month old. Our doctor put her on prescription, but we also tried the usual solutions like keeping her propped during sleep (I use a wooden board under the mattress) or avoiding acid foods. All this has helped, but she still sometimes wakes up at night crying.  Is there something else you have found to be useful? At what age, in your experience, reflux mostly disappears?


Meaning of the word "any" in "ineligible for any exemption"

An important legal result hinges on the meaning of the word "any" in this sentence:  "If the effect of the domiciliary requirement under subparagraph (A) is to render the debtor ineligible for any exemption, the debtor may elect to exempt property that is specified under subsection (d)."  My opposition argues that because the debtor is still eligible for some exemptions, he cannot elect to exempt property that is specified under subsection (d). I argue that the effect of the domiciliary requirement rendered my client ineligible for some exemptions, therefore I can elect to exempt property that is specified under subsection (d). It seems like it should be a simple issue, but it has now confused judges all the way up to the 9th Circuit Court of Appeals In other words, one party argues that this sentence means: As long as the debtor is eligible for at least one exemption, the [result occurs]. The other party argues that this sentence means: If the debtor is ineligible for at least one exemption, the [result occurs]. Which is correct, and why?


Im trying to center a (pumpkinvector.jpg) image inside a .div using this classic trick:  .pumpkin{ position: relative; top:50%; left:50%; transform: translate(-50%,-50%); }   It seems to work fine on the very bottom div where background is red. However,  that was just a test, it is not were I need the image to center.  I need to center pumpkinvector.jpg image up top in "grid2" div that inside "grid 6 october" div. October div has additional code and inner class to give background image and make it resize proportionally in height and width %. Using the same centering code above, the pumpkinvector.jpg now flows to the next line and starts to position outside of the .october div. Can someone why this is?  Please bear with me here. I thought the addition of images helps you visualize my problem so I uploaded to my own site instead of js.fiddle. Here is the link:   Please view source to view code. Thanks.  This question is different because it asks how to center div in the context that its parent div has complex markup that makes any traditional centering off and throws in on a new line below parent div.


How do I draw an annulus (doughnut) using GDI+?

I have been trying to draw an  (ring with thickness) with a transparent hole and a gradient rim in C# with very little success. Does anyone have any suggestions on how to do this?  here's a nice   Here's the Final result - thanks to BlueMonkMN   Rectangle GetSquareRec(double radius, int x, int y)     {         double r = radius;         double side = Math.Sqrt(Math.Pow(r, 2) / 2);         Rectangle rec = new Rectangle(x - ((int)side), y - ((int)side), (int)(side * 2) + x, (int)(side * 2) + y);          return rec;     }     void Form1_Paint(object sender, PaintEventArgs e)     {           Graphics gTarget = e.Graphics;         gTarget.SmoothingMode = SmoothingMode.AntiAlias;           GraphicsPath pTemp = new GraphicsPath();          Rectangle r = GetSquareRec(200, 225, 225);         pTemp.AddEllipse(r);         pTemp.AddEllipse(GetSquareRec(50, 225, 225));          Color[] colors = new Color[5];         colors[0] = Color.FromArgb(192, 192, 192);         colors[1] = Color.FromArgb(105, 0, 0);         colors[2] = Color.FromArgb(169, 169, 169);         colors[3] = Color.FromArgb(0, 0, 0);         colors[4] = Color.FromArgb(0, 0, 0);          float[] positions = new float[5];         positions[0] = 0f;         positions[1] = 0.1f;         positions[2] = 0.35f;         positions[3] = 0.5f;         positions[4] = 1f;          ColorBlend Cb = new ColorBlend();         Cb.Colors = colors;         Cb.Positions = positions;          PathGradientBrush pgb = new PathGradientBrush(pTemp);         pgb.InterpolationColors = Cb;         pgb.CenterPoint = new PointF(r.X + (r.Width / 2), r.Y + (r.Height / 2));         gTarget.FillPath(pgb, pTemp);      }


Suppose $a \in \mathbb{C}$, $|a| < 1$, and $f(z) = \dfrac{z - a}{1 - \overline{a}z}$. How to prove dependence of $|f(z)|$ on $|z|$?

Let $a \in \mathbb{C}$, $|a| < 1$. Also let $f(z) = \dfrac{z - a}{1 - \overline{a}z}$.  I am asked to prove that $|f(z)| < 1$ if $|z| < 1$ and that $|f(z)| = 1$ if $|z| = 1$.  What is a good way to proceed on this problem?


Gravatar links on "Filtered Questions" page are not HTTPS

Gravatar links on the "Top Network Askers" sidebar of the  page are not HTTPS links. Gravatar links elsewhere on the site seem to use HTTPS links.


Chapterbib gives 'citation undefined' and all [?]

This is my first time posting. I have been struggling to include reference lists after each chapter included in my main .tex file. Though the .bbl file includes all the references, all the citations appear as [?] and no reference list is produced. I have run pdflatex, bibtex, pdflatex, pdflatex. I have tried using one .bib file and creating separate ones for each chapter. I know the .bib file is fine, because I initially had all the writing in the main file, but hadn't put in all the chapters and it compiled fine. When I added the second chapter I realized I needed to use \include{chap} to get separate lists.  Here is an example of my main file:  \documentclass[12pt]{report}  \usepackage[top=1in, bottom=1.25in, left=1.25in, right=1.25in]{geometry} \usepackage{titlesec}  \titleformat{\chapter}{\singlespacing\normalfont\LARGE\bfseries}{\thechapter.}{16pt}{\LARGE} \titleformat{\section}{\singlespacing\normalfont\Large\bfseries}{\thesection}{12pt}{\Large} \titleformat{\subsection}{\singlespacing\bfseries}{\thesubsection}{12pt}{\Large} \titleformat{\subsubsection}{\singlespacing\bfseries}{\thesubsubsection}{12pt}{} \titlespacing*{\chapter}{0pt}{-19pt}{0pt}  \usepackage[round]{natbib} \usepackage{chapterbib}  \usepackage{setspace} \usepackage{url} \usepackage{textcomp} \usepackage{amsmath}  \begin{document} \tableofcontents  \include{chap1} \include{chap2}  \end{document}   Here is an example of a chapter (the others are similar):  \chapter{Surface Energy Balance} \label{else} \doublespacing  Text \citet{Paterson10}.  \singlespacing \bibliographystyle{plainnat} \bibliography{bib1}   And the .bib entry:  @book{Paterson10,     Author = {K. M. Cuffey and W. S. B. Paterson},     Date-Added = {2015-06-01 15:34:50 +0000},     Date-Modified = {2015-06-01 15:35:53 +0000},     Publisher = {Academic Press},     Title = {Physics of {G}laciers},     Year = {2010}}


At first, I try to draw a cylinder which is much different from what I want....  \documentclass{standalone} \usepackage{pgfplots} \pgfplotsset{compat=1.4} \usepackage{tikz-3dplot} \tdplotsetmaincoords{60}{-30} \tdplotsetrotatedcoords{0}{90}{90}% \begin{document} \begin{tikzpicture}   [tdplot_rotated_coords,     scale=3,     mdc/.style={fill=blue, color=blue,draw=none, opacity=.4,line join=round},     length/.style={<->,thick,line cap=round}]   \def\d{1}   \def\r{\d*.45}      % Cylinder    \foreach \t in {0,12,...,348}     \draw[mdc] ({cos(\t   )*\r+\d/2},  0, {sin(\t   )*\r+\d/2}) % side vertice of cylinder             -- ({cos(\t+12)*\r+\d/2},  0, {sin(\t+12)*\r+\d/2})             -- ({cos(\t+12)*\r+\d/2}, \d, {sin(\t+12)*\r+\d/2})             -- ({cos(\t   )*\r+\d/2}, \d, {sin(\t   )*\r+\d/2})             -- cycle; \end{tikzpicture} \end{document}     I am curious to know that it is possible to draw shell figures with TikZ (like bellow pictures), but the above code and figures below are far different from what I want....


The jobs specified in /etc/crontab are running at the wong time, why?

I'm trying to get cron.daily to run just after midnight with the line below     2   0  * * * * ... (the rest is the standard verbiage)   However it is run at  07:36   and claims to be run by anacron (I don't necessarily believe that) What is the scoop,  Oh yeah, my system is in the PST8PDT timexome.


How to proof that RandomSearch is better than GridSearch with mathematics?

I read this link  in which it is discussed why 60 parameters randomly chosen are enough.  But I do not fully understand the formula used   $$1−(1−0.05)n>0.95$$  $$n⩾60$$  I have read the paper of Bergstra and Bengio; but I have not found anything about that formula. Also, I was wondering if RandomSearch is only good for Neural Networks; as I am using RandomForest, XGBoost and SVM.  Thank you


I just updated my ubuntu server 14.04 LTS to 16.04 LTS via apt-get do-release-upgrade.  There haven't been any error messages but after the reboot, no login prompt appears. Just a black screen, sometimes with a blinking cursor on the top left.  Nevertheless login via ssh and LAN still works perfectly.  Any ideas what could have happened and how I could solve it?


error in installing ffmpeg in Ubuntu 14.04

I have downloaded guvcview in Ubuntu 14.04 then I tried to install ffmpeg but it shows error: E: Package 'ffmpeg' has no installation candidate.


I have two Drupal 7 sites running a very similar structure (views, content types, etc) but with a different theme and a few other changes.  I need to have all the nodes of specific content types that are created in site A to be copied to site B. If it is possible, it should work automatically or by running a script. For example, the sync would run as a scheduled cron job.  I do not need both sites to run in the same database, they must have their own separate database, just the same nodes for specific content types.  I've been investigating, and I see that I can use Node Export, Feeds and even a drush command (ne-export/ne-import). I'm not sure yet about how to put all the pieces together. Has anyone done this already?


Measure Lithium ion battery voltage (thus remaining capacity)

What I am working with: I am running my self-made Arduino board (in the sense that I use the Arduino bootloader and code editor) at 3.3V, and powered from a Lithium ion battery, which is USB-charged by a corresponding Microchip charger IC.  What I am trying to achieve: I want to measure battery capacity once every minute or so. I have an LCD attached, so the idea is that the overall setup lets me know how the battery is doing at a given moment. The datasheet of the battery has a voltage versus discharge-level curve, and so by measuring the voltage of the battery, I can estimate the remaining capacity (very roughly but enough for me!).  What I did:   (EDIT: Resistor values updated and P-MOSFET switch added based on @stevenvh and @Jonny's suggestions).  I connected a voltage divider from the battery V_plus, with the larger "portion" going to an analog-read-pin (i.e., ADC) on the Arduino/Atmega chip. The divider is 33 KOhm-to-10 KOhm, thus allowing measurement up to 4.1 Volts maximum of the Li-ion battery from my 3.3V level microcontroller. Also, using one of the I/O pins connected to an n-channel MOSFET, I can switch the current through the divider only when I need the measurement. Here is a rough schematic (updated for a 2nd time based on suggestions of @stevenvh and @Nick):     My question:   How is my current setup? My only constraints are: (1) I would like to make a rough measurement of the battery capacity based on the voltage reading, as described above. (2) I would like to prevent the voltage divider from interfering with my charging IC's reading of battery presence (in my original setup, the divider sometimes caused the IC to misread presence even when the battery was absent).


I am using shp2pgsql in a bash script to import shapefiles into postgres. I can successfully do this for shapefiles with hundreds of records however shapefiles with tens of thousands of records (in this case ~40,000) hangs so I have to use the postGIS shapefile importer in pgAdmin (which works ~30-45 seconds to complete).   I realize it's a substantial jump in magnitude regarding the number of records. Is it possible if I wait long enough it will succeed?  what are the runtime/data limits for shp2pgsql?


How can I install Windows 7 on Ubuntu? (Dual-Boot)

I tried to follow this guide:  (scroll half way down), but I didn't understand anything from that page..  I need something for beginners, please..  Thanks in advance :)


Let $S$ be a nonempty set. Prove that the power set $P(S)$ whose elements are all subsets of $S$, forms ring under the following operations:  \begin{align*} a + b &= (a \cup b) \setminus (a \cap b)\\ a \cdot b &= a \cap b \end{align*}  For proving it's an abelian group first, I've gotten that the identity is $\emptyset$.   \begin{align*}       a + \emptyset           &= (a \cup \emptyset) \setminus (a \cap \emptyset)\\           &= a \setminus \emptyset\\           &= a      \end{align*}  Each element is it's own inverse.   \begin{align*}       a + a         &= (a \cup a) \setminus (a \cap a)\\         &= a \setminus a\\         &= \emptyset      \end{align*}  It's certainly commutative. \begin{align*}       a + b           &= (a \cup b) \setminus (a \cap b)\\          &= (b \cup a) \setminus (b \cap a)\\         &= b + a      \end{align*}  But I can't get associative. That is, $(a + b) + c = a + (b + c)$. Anyone want to aid?  The properties for multiplication aren't too bad either. The only one that is throwingme a curve ball is the left/right distribution. That is,   $a(b + c) = ab + ac$ and $(a + b)c = ac + bc$.  While  and has answers to most parts in proving that it is a ring, it does not explain or show the associativity portion for addition in detail. That is $(a + b) + c = a + (b + c)$ is left very vague.


I'm not a technician and find most Ubuntu instructions are incomprehensible. I bought a printer for the first time in my life today, an HP 1515. I eliminated all Microsoft stuff from my computer last year. The HP installation disc seems incompatible with Ubuntu or with my Toshiba Satellite laptop. When I tried to understand the Ubuntu help page, I was invited to upgrade from Ubuntu 13.04 to 13.10. This in turn requires me to install something. I attempted to install Adobe Flash Player, but I couldn't. This also asks me to install updates to Ubuntu 13.04. This was also impossible to understand or to do.   Is there a simple way to make my printer work? I'd like to stick with free software, but I don't like these complications. I still haven't figured out how to double space, how to put numbers on pages, etc., and may be forced back to Microsoft if Ubuntu doesn't become user friendly for mere writers, not technicians. Thanks to all who offer suggestions.


Assistance on why email is being marked as spam

We are trying to send out a mass email for a client of ours through a third party sender and it is always being sent to the spam folder rather than the inbox. I have below the headers from the email.   Do you have any thoughts on why it might be being filtered as spam? Or how we might be able to fix it?  x-store-info:4r51+eLowCe79NzwdU2kRyU+pBy2R9QCr01wX+2TQb16V+IWYKH89OEXx2kXRCi0YCCbAc2czEzqYF2bH27mAPgHi3rzu7bpgBsHbtZAyLKnNk8fJmBxyu+VguRUNe13q5zZaaanxKw= Authentication-Results: hotmail.com; spf=softfail (sender IP is 64.250.95.18) smtp.mailfrom=almirall@cgdmcanada.com; dkim=none header.d=cgdmcanada.com; x-hmca=fail header.id=almirall@cgdmcanada.com X-SID-PRA: almirall@cgdmcanada.com X-AUTH-Result: FAIL X-SID-Result: FAIL X-Message-Status: n:n X-Message-Delivery: Vj0xLjE7dXM9MDtsPTA7YT0wO0Q9MjtHRD0yO1NDTD00 X-Message-Info: 11chDOWqoTky60iQsYaQEbDMsbZfaHn4uXeEdYJ+hJPs/IZZs8+jCAsGYVfWXZjOH0CIVQtMZgN6eci97N8hFZVMIRvFnbKffwelTwXTo1W1G4O4NpDJy0u1RYUR3/Eg8I879+IgZwjq8NUi6hFsCbgaJ4tlHCzI9/qIYnxslvFwe5kU9IzpYCxXwgvPEsGAo4ciKuRN7XjS74cqqwszN1kev1/vz0rc Received: from mx01.dmtel.ca ([64.250.95.18]) by SNT0-MC1-F52.Snt0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4900);         Thu, 14 Nov 2013 09:10:27 -0800 Received: from E1_NT (199.115.92-98.ip.mltn.standardbroadband.ca [199.115.92.98])         by mx01.dmtel.ca (8.14.4/8.14.4) with ESMTP id rAEHAQiA009774         for <EMAIL ADDRESS REMOVED>; Thu, 14 Nov 2013 12:10:26 -0500 Message-Id: <201311141710.rAEHAQiA009774@mx01.dmtel.ca> From: "Almirall Ltd." <almirall@cgdmcanada.com> Subject: Introducing NEW Tudorza Genuair To: EMAIL ADDRESS REMOVED Content-Type: multipart/related; boundary="wBS=_qJqKiL3XVShQgrlM1RROrtguDYnsT" MIME-Version: 1.0 Date: Thu, 14 Nov 2013 12:11:04 -0500 Return-Path: almirall@cgdmcanada.com X-OriginalArrivalTime: 14 Nov 2013 17:10:27.0926 (UTC) FILETIME=[6A6F8F60:01CEE15C]  This is a multi-part message in MIME format  --wBS=_qJqKiL3XVShQgrlM1RROrtguDYnsT Content-Type: multipart/alternative;         boundary="RxbxbbDQL=_vGDBlBk67MreVItV2mLXC41"  --RxbxbbDQL=_vGDBlBk67MreVItV2mLXC41 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline  Introducing NEW Tudorza Genuair  --RxbxbbDQL=_vGDBlBk67MreVItV2mLXC41 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline  <TITLE>New Page 1</TITLE> <META http-equiv=3DContent-Type content=3D"text/html; charset=3Dwindow= s-1252"> <META content=3DFrontPage.Editor.Document name=3DProgId>

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I am trying to plot a graph using tikz, but I can't seem to be able to highlight the areas between the curves. The result should look something like this:    This is the code I have so far:     \begin{center} \begin{tikzpicture}[scale=0.8]  \draw[->] (0,-0.5) -- (0,4.5) node[anchor=east] {}; \draw[->] (-0.5,0) -- (9,0) node[anchor=north] {}; \draw   (1,-0.2) node[anchor=north] {$a$}         (8,-0.2) node[anchor=north] {$b$}                ; \filldraw[fill=black!10](1,0)--(1,2)--(8,2)--(8,0); \draw [](1,3) parabola bend (2.5,1.5)(4.2,2.4);  \draw [](4.2,2.4) parabola bend (5.5,3)(8,0);  \draw[] (1,0)--(1,3); \end{tikzpicture} \end{center}   The end result I would like to achieve is to have C and D higlighted in orange, while A and B in a dark grey. Don't worry about the axes labels or else, I mostly need help with the shading.  Thanks in advance!!


I'm recording the duration of how long something takes in Java. To do that, I'm running:  long startTime = System.nanoTime(); ... long duration = System.nanoTime() - startTime;   Now, I would like to take the duration and print it out in a format of mm:ss.SSS. How do I do that in Java?


How to get all possible combinations for n arrays with different number of elements?

I have some number of arrays which is unknown at programming time, maybe it is 3 or 4 or 7 ... each array has some elements, i.e,  a={1 2 3 4} b={6 7 5 2 1} c={22 4 6 8 4 8 5 4} d={....} e, f, g, ...   I want to get get all possible combinations by sampling one number from each array for example one case is that I pick up "1" from a, "7" from b, first "8" from c, d[3], e[5],... to make "1,7,8,d[3],e[5],...". It's not possible to use nested for loops because I don't know the number of arrays at compile time. If it was known for example 4 arrays (a,b,c,d) I could use 4 loops:  for (int i = 0; i <= a.Length-1; i++) {    for (int j = 0; i <= b.Length-1; j++)    {       for (int k = 0; i <= c.Length-1; k++)       {          for (int m = 0; i <= d.Length-1; m++)          {             Response[f++] = a[i].toString()+","+b[j].toString()+","+c[k].toString()+","+d[m].toString();          }       }    } }   but for different number of arrays, I don't have any idea.


Why use gradient descent for linear regression, when a closed-form math solution is available?

I am taking the Machine Learning courses online and learnt about Gradient Descent for calculating the optimal values in the hypothesis.  h(x) = B0 + B1X   why we need to use Gradient Descent if we can easily find the values with the below formula? This looks straight forward and easy too. but GD needs multiple iterations to get the value.  B1 = Correlation * (Std. Dev. of y/ Std. Dev. of x)  B0 = Mean(Y) – B1 * Mean(X)   NOTE: Taken as in   I did checked on the below questions and for me it was not clear to understand.      The above answers compares GD vs. using derivatives.


Linking `[foo]` results in []'s being incorrectly escaped

Well, as the title says, I guess:   Start off with [foo]. Use either the keyboard shortcut or editor button to wrap the [foo] in a hyperlink. ... will result in  rather than      This is due to the system blinding/ naively escaping all []'s within the link, without checking whether it is contained with a code block or not.  Weirdly however, the syntax:  (i.e. [[foo]][1]) seems to work regardless, so I'm not sure this escaping of [] is even necessary?  This rendering bug happens both within the preview window, and within the actual post when submitted.


Convert LinkedIn page into showcase page

I see that LinkedIn now offers showcase pages so you don't need to have a company page for a product. My company page is Wine With Spirit and I created a company page for one of our products at Lyfetaste.  Do you know if it's possible to turn that company page into a showcase page?  And if not, would deleting it free the name for me to re-create it as a showcase page?  I don't want to delete it and have it forever stuck.


I get the following output when I use split with regex on a string.  string = "12345678"  string.split(/(..)/)  => ["", "12", "", "34", "", "56", "", "78"]   Why am I getting empty strings from the split method? I realize that using the scan method would give me pairs without the empty strings, but I want to know why split is giving me empty strings.


In CBC mode of encryption, what happen if the IV is changed when it arrives at the receiver end?

What will happen if the Initialiazation Vector (IV), i.e, the initial randomness fed in to the first block arrives mangled at receiver end? How will this affect the decryption? Will the receiver be abl to decrypt all blocks correctly? Or none? Or some?


I want to know, what is the largest prime number? I know prime numbers are whole numbers that cannot be divided by any whole number except 1 and themselves, I also know some primes  like 2, 3, 5, 7, 11... But what is the largest prime number?


Why did R2-D2 not fly in Return of the Jedi?

In :     Artoo butts the golden droid over the edge and steps off himself, tumbling toward the sand.   But in :     ARTOO uses his rocket jets to fly up and into the factory.   Why didn't R2-D2 use his jets in RotJ instead of ending feet up in the sand?  Update: I am looking for an in-universe explanation.


Why downvoting newbies without explanation is allowed?

I am a newbie, I stumbled upon this site yesterday.  In a question I gave a perfectly correct and valid awnser, yet two people downvoted the answer and one downvoted my profile, and no explanation was given.  Why is this allowed? If I did something wrong, I should be told what I did wrong, and if I did not, why the hell they are downvoting me?


Permisson requirement for Song usage in movies

When songs are used in movies, in what circumstances it is required to get permission or is it always required? For example, If a song is played in the background and used as a soundtrack for the movie/TV show, I guess it is definitely required to obtain permission from the owners. But let's say if the song is used indirectly such as playing on radio or playing on TV, is it still required to get permission. Also let's say a character from the movie or TV show is shown singing that song, is it still required to get permission in such cases?


How to pass arguments to function in a bash script?

I'm starting/trying to learn a bit of bash scripting and i'm wondering what is wrong with my method of passing arguments to a function from the terminal (see below) as my method seems similar to many found in internet tutorials.  #!/bin/bash  function addition_example(){     result = $(($1+$2))     echo Addition of the supplied arguments = $result }   I call the script as follows:  source script_name.sh "20" "20"; addition_example    This returns the following:  bash: +: syntax error: operand expected (error token is "+")   I've also tried:  addition_example "$20" "$20"   This returns the following:  bash: result: command not found Addition of the supplied arguments =


Implications of parity violation for molecular biology

In biology, the concept of parity emerges in the context of chiral molecules, where two molecules exist with the same structure but opposite parity. Interestingly, one enantiomer often strongly predominates over the other in natural biological systems (e.g. D-glucose is ubiquitous, L-glucose is rare in nature).  In physics, it has been established that weak interactions violate parity, which (if I understand correctly) implies a physical difference between left- and right-handed systems.  This suggests to me the following questions: Does parity violation in physics affect the physical or chemical properties of chiral molecules? And does this have any implications for our understanding of biological homochirality?