$x^3+7=y^2$ find all solutions in natural numbers I tried to check  a residue of the division on $3,4,5,7,9,12,13$ I want to prove that this equation has not solutions because left part gives some residue and right part other. Actually I don't know is it true . And am I on right way of solving this problem? But I proved this for $x^3+7=y^4$ by checking residues when dividing on $13$ If I'm on right way ,can you say division of what I need to check , to get the result? If not tell me please what to do.


Find a general solution to $x^2-2y^2=1$  I found that (3,2) is a solution. Now what should I do? I can not catch what the question really want.  It is about pell's equation. Would you give me a form of general solution?


Idiomatic expression about the insignificance of details

I'm trying to find an idiomatic expression that discards the importance of little details for seeing at the big picture. In Spanish we have a saying that goes something like "Sometimes the trees do not let us see the forest." I was wondering if there is a similar expression that's used in written English.


I have written some code in C by taking the maximum size of char array as 100. It worked well. But when I increase the maximum size of char array to 10000 it gives me segmentation fault(as it has exceeded its limit). Can someone tell me how can I increase the maximum size and store a string of length 10000.   i.e How can I take the "char a[100]" as "char a[10000]" and execute the same code????


remove space for text after figures or tables

The code is as follows      \begin{figure}[h] \centering \includegraphics[width=0.5\linewidth]{figure} \caption{Comparison elements in a row of $A_1$ and $B_1$} \label{fig} \end{figure} The above Figure shows that ...   The above is what I usually do in Latex. But I found the text after an inserted figures always has a space at the front. Like in this case there is a white space before   The above Figure shows that ...   How to remove the white space? One solution I know is to insert "\\" ,after$\end{figure}$.


How to set to int value null? Java Android

which is the best way to set already defined int to null?  private int xy(){     int x = 5;     x = null; //-this is ERROR     return x; }   so i choose this  private int xy(){     Integer x = 5;     x = null; //-this is OK     return (int)x; }   Then i need something like :  if(xy() == null){     // do something }   And my second question can i safely cast Integer to int?  Thanks for any response.


So, when I point a laser at a piece of wire (pointed at a specific angle), a circle of light appears on a wall behind it (see image below). I am trying to see why this happens and if there are any readings on this. Could anyone give some tips on what I should search for or any references?   ()  So this is a problem for a physics tournament, but I haven't tried it myself yet. However I have found a video depicting what I mean.


Why can't I at least upvote and comment on correct and helpful answers without first earning reputation?

I don't mean to be unhelpful, but I don't sit around waiting for new questions to come in so I can hopefully answer them faster and more thoroughly than everyone else on the internet. I've tried this and failed miserably.  However, by simply being able to upvote other correct answers each time I find something that works for me, I feel like I could contribute to the community without committing too much time.   Moreover, by being able to comment on other people's questions, I feel like I could help describe my own experience solving similar problems in ways that can be helpful without having to post my own 95% redundant answer.  Basically, I feel like I'm being punished for NOT asking any questions (see here: ), which I haven't had to do because I've been so successful at finding answers to similar questions on S.O., and therefore I'm stuck with my 1 reputation and no easy way to contribute to the site.  UPDATE - This guy and I have the same problem, so I guess I'm actually hurting the site by posting a duplicate question. Great.


Where to create the desktop configuration file of an app so that it can be locked to launcher?

On GNOME desktop environment, I have added an app to favorites and I can launch the app from that list clicking on the icon of the favorites list.   But when I launch, a similar icon of the app appears side by side. I mean, two icons of the app are showing instead of one. Where should I create a .desktop file so that when I click on the app icon, it launches with no redundant icon?


Which episodes of Fairy Tail are anime-exclusive?

Up to episode 175, I know Fairy Tail has some episodes which are not in the manga.  If I want to watch the series again but not the episodes that are anime-exclusive, which ones should I skip?  This question is inspired by , I just decided to do the same for Fairy Tail


I created a table which I would like to align to a picture (next to each other). I attach you my code and the result of it (as you can see, they are not aligned). I would like, if possible, to split the figure and the table 50-50 (so that both of them have the same width but without exceeding the margins). \documentclass{article} \usepackage[utf8]{inputenc} \usepackage[super]{natbib} \usepackage{comment} \usepackage{graphicx} \usepackage{float} \usepackage{hyperref} \hypersetup{     colorlinks,     citecolor=black,     filecolor=black,     linkcolor=black,     urlcolor=black } \usepackage{amsmath} \usepackage{mathtools} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{caption} \usepackage{adjustbox} \usepackage{lipsum} \usepackage{lscape} \usepackage{multicol} \usepackage{longtable} \usepackage{chngcntr} \counterwithin{figure}{section} \counterwithin{table}{section} \captionsetup[figure]{font=small,labelfont=bf} \captionsetup[table]{font=small,labelfont=bf} \usepackage[justification=centering]{caption} \usepackage{eurosym} \usepackage{mhchem} \usepackage{relsize} \usepackage[table, dvipsnames]{xcolor} \renewcommand*\descriptionlabel[1]{\hspace\leftmargin$#1$} \usepackage{enumitem}   \usepackage{array,ragged2e} \newcolumntype{C}{>{\Centering\hspace{0pt}}p{0.1\textwidth}} \usepackage[output-decimal-marker={,}]{siunitx}  \usepackage{booktabs, makecell, tabularx} \newcolumntype{L}{>{\raggedright\arraybackslash}X} \newcolumntype{M}{p{\dimexpr 0.25\textwidth-2\tabcolsep}} \newcolumntype{P}[1]{>{\centering\arraybackslash}p{#1}}  \usepackage{longtable,array,ragged2e} \newlength\mylen \setlength\mylen{\dimexpr0.25\textwidth-1.5\tabcolsep-0.25\arrayrulewidth\relax} \newcolumntype{Z}{>{\RaggedRight}p{\mylen}}  \usepackage[export]{adjustbox}   % <--- \usepackage{booktabs, tabularx}   \makeatletter \newcommand*{\rom}[1]{\expandafter\@slowromancap\romannumeral #1@} \makeatother \def\changemargin#1#2{\list{}{\rightmargin#2\leftmargin#1}\item[]} \let\endchangemargin=\endlist   \bibliographystyle{abbrvnat} \setcitestyle{authoryear,open={(},close={)}}  \begin{document}   \begin{table}[ht]     \begin{tabularx}{\linewidth}{@{}c X @{}}     \includegraphics[width=0.5 \linewidth,valign=c]{sd5.png}     &            \begin{tabular}{lcc}             \toprule         & Deterministic   & Stochastic \\                     \midrule         Mean                & \euro430,96M  & \euro429,89M   \\         StDev               & \euro6,36M    & \euro5,44M     \\         n                   & 100           & 100        \\         \midrule         Best SP result      & \multicolumn{2}{c}{-\euro 4,40M}  \\         Worst SP result     & \multicolumn{2}{c}{+\euro 2,89M}  \\         Average performance & \multicolumn{2}{c}{-\euro 1,08M}  \\         t-test              & \multicolumn{2}{c}{3,87e-10}\\ \hline \end{tabular}     \end{tabularx} \caption{Analysis of the comparison between the SP and the deterministic model.} \label{tab:my-table} \end{table}


What package and command do I have to insert to write letter V in a handwriting style using Inline Math Mode?  Below is the result I want to obtain:


How to convert an array into an arraylist of string arrays?

I am trying to convert a string array into an arraylist. However, when I use this code to print the list, it returns values like this @3fec1b24. Could anyone help me with this?  ArrayList<String[]> dataList = new ArrayList<>(); dataRow = new String[nc]; dataList.add(dataRow);


Is it possible to interpolate different sprites?

I can interpolate different animations based on position, rotation, and scale.  I want to do the same for different sprites, automatically.  For example, lets say I have a soda can being crushed.  I have 2 sprites:  One is the soda can uncrushed, and one is the soda can fully crushed.  I want to only use those 2 sprites, and have Unity automatically transition from the normal can to the crushes can.  How can I do this without making a bunch of key frames in between?


How to apply windows for each specific column in SQL?

I want to get last event done per each user for each specific unit_of_measure: I have this table: person_id   event_time       event_derscription   unit_of_measure  ----------------------------------------------------------------- 1           20200801120101  "some description"     "unit1" 1           20200801120501  "some description 2"   "unit1" 1           20200801120501  "some description 2"   "unit9" 2           20200801120301  "some description 3"   "unit1" 2           20200801120501  "some description 4"   "unit1"  Expected output is: person_id   event_time       event_derscription   unit_of_measure  ----------------------------------------------------------------- 1           20200801120101  "some description"     "unit1" 2           20200801120301  "some description 2"   "unit1" 1           20200801120501  "some description 2"   "unit9"  What I tried: select *  from      (select           person_id, event_time, event_derscription, unit_of_measure,           rank() over (partition by unit_of_measure order by event_time desc) as RN       from           test.person_events       where           partition_name = 20200801       group by           person_id, event_time, event_description, unit_of_measure)  where      RN = 1;  // I try to use group by person_id to get the result for each person_id but it did not work   The output of my above code is: person_id   event_time       event_derscription   unit_of_measure  ----------------------------------------------------------------- 2           20200801120301  "some description 2"   "unit1" 1           20200801120501  "some description 2"   "unit9"  is there are any mistake I did ?


What does the operator `-gt` in shell scripts mean?

Hi I have this sentence and I want to know what does it means please.  if [[ -z "$1" ]]; then   #  --> this is if the value of the parameter $1 is zero     PASO=1 elif [[ "$1" -gt 1 ]] ; then  # but i don't know what this flags mean? .."-gt"     LOG "[$(date +%T)] Parametros incorrectos"     exit 255 else     PASO=$1 fi   What does -gt mean?


Difference in putting method in Constructor or Outside it in a Class (Gives same Result)

The following 2 snippets give same result. I wondered what is the real diffence in these 2 approaches and when should one be used instead of another way. Can someone help me out understanding the difference?    Case 1:   class Person{   constructor(name){     this.name = name;   }    printData(){     console.log(this.name);   } }   Case 2 :   class Person{   constructor(name){     this.name = name;     this.printData = function(){       console.log(this.name);     }   } }


when i try to remove element there is an error, i have uploaded the error in the image section. any help to fix? of any other way to get the code fixed and working smoothly and it it works while deleting the middle element not the first or second duplication issue ,fixed using iterator. hatsooff to stack overflow . all good  import java.util.*;  public class EarthquakeList { private ArrayList<EarthquakeNode> records;  public EarthquakeList() {    records = new ArrayList<EarthquakeNode>();  }  public boolean isempty() {       return true; }   public void add(String EarthquakeLo,String EarthquakeDt, double EarthquakeSgth, int EarthquakeDu) {    EarthquakeNode en = new EarthquakeNode(EarthquakeLo, EarthquakeDt, EarthquakeSgth, EarthquakeDu);    records.add(en); }   public boolean remove(String EarthquakeLo,String EarthquakeDt) {    boolean flag= false;    for(EarthquakeNode earthquake: records)    {        if(earthquake.getLocation().equalsIgnoreCase(EarthquakeLo))        {            if(earthquake.getDate().equals(EarthquakeDt))            {                records.remove(earthquake);                flag=true;             }        }    }    return flag;  }    public EarthquakeNode search(String EarthquakeLo,String EarthquakeDt) {    EarthquakeNode node= null;    for(EarthquakeNode earthquake: records)    {        if(earthquake.getLocation().equalsIgnoreCase(EarthquakeLo))        {            if(earthquake.getDate().equals(EarthquakeDt))            {                 node=earthquake;            }        }    }    return node; }   public boolean clear() {     int count=records.size();    for(EarthquakeNode earthquake: records)    {        count=count-1;        records.remove(earthquake);       }    if(count==0)    {    System.out.println("already empty");    return false;}     else     System.out.println("every thing is removed");    return true; }   public boolean isempty(String EarthquakeLo,String EarthquakeDt) {    boolean flag= false;    for(EarthquakeNode earthquake: records)    {        if(earthquake.getLocation().equalsIgnoreCase(EarthquakeLo))        {            if(earthquake.getDate().equals(EarthquakeDt))            {                flag=true;            }        }    }    return flag; }   public void print() {    for(EarthquakeNode earthquake: records)    {        System.out.println( earthquake.getLocation() +" - "               + earthquake.getDate()+ " - "                + earthquake.getStrength() + " on rector scale"+                "-" + earthquake.getDuration() + "mins");    }  }   }


ajax sent html input file content jquery

I have a form with a file input.  <input id="frm-documentForm-documentForm-files" class="required_1" type="file" data-nette-rules="[{"op":":filled","msg":"FILE\/S are mandatory!"}]" required="" multiple="" name="files[]">   And jquery code  $('#frm-documentForm-documentForm-files').change(function() {         $.ajax({             url: "?do=getProperties",             type: 'POST',             data: this,             processData: false,             contentType: "multipart/form-data",             success: function(data) {                 alert("success");             }         });   And when I dump post or files, both are empty. (array())  What do I need to do to fix it?  Thanks for you help.


Why does join syntax with stacked on clauses work?

I have three versions of the same select query ():  CREATE TABLE MainTable(ID INT) CREATE TABLE SubTable(ID INT, Type CHAR(2)) CREATE TABLE SubTableType(Type CHAR(2))  INSERT MainTable VALUES (1), (2) INSERT SubTable VALUES (1, 'AB'), (2, 'AB'), (3, 'CD') INSERT SubTableType VALUES ('AB')  SELECT  * FROM    MainTable P JOIN    SubTable L ON  P.ID = L.ID JOIN    SubTableType LT ON  L.Type = LT.Type  SELECT  * FROM    MainTable P JOIN    SubTable L JOIN    SubTableType LT ON  L.Type = LT.Type ON  P.ID = L.ID  SELECT  * FROM    MainTable P JOIN    SubTable L JOIN    SubTableType LT ON  P.ID = L.ID ON  L.Type = LT.Type   The first two select statements work and produce the same result. The third reports the error,      The multi-part identifier "P.ID" could not be bound.    appears to claim that the first two queries are semantically equivalent, though they may perform differently. My question is rather about the syntax. I've always written joins according to the first pattern, and I didn't even realize that the second pattern was permissible. Clearly it is, but then why isn't the third pattern also acceptable? The  doesn't seem to touch on this, so I'm trying to find documentation that spells out what is and isn't permissible.


Create 3 correlated variables with pre-specified correlations

I start with a vector of random numbers sampled from a normal distribution:  R<-rnorm(100, mean=0, sd=30)   I would now like to create 3 variables that are correlated with each other with a pre-specified correlation. In addition I would like to have these three variables correlated with R with a pre-specified correlation.  For example A, B, C would have correlation 0.7 with each other, and A, B, C would have correlation 0.6 with R.  I.e. I am looking for the following covariance matrix:      R   A   B   C R   1  .6  .6  .6 A  .6   1  .7  .7 B  .6  .7   1  .7 C  .6  .7  .7   1   How can this be done in R?


The question: Let $f(x) = e^{-x}\sin(x)$. Calculate $f^{(2001)}(0)$. Note that in the question, $f^{(n)}(x)$. means the $n$-th derivative of $f$. I calculated the first six derivatives on zero and got: $f^{(0)}(0) = 0$. $f^{(1)}(0) = 1$. $f^{(2)}(0) = -2$. $f^{(3)}(0) = 2$. $f^{(4)}(0) = 0$. $f^{(5)}(0) = -4$. $f^{(6)}(0) = 8$. So, the pattern isn't pretty clear. Also, I thought that if $n$ is even, then: $f^{(n)}(x) = -e^{-x}\cos(x) - f(x) + f^{(1)}(x) - f^{(2)}(x) + ... + f^{(n-3)}(x) - f^{(n-2)}(x) - f^{(n-1)}(x)$. and $f^{(n - 1)}(x) = e^{-x}\cos(x) + f(x) - f^{(1)}(x) + f^{(2)}(x) + ... + f^{(n-4)}(x) - f^{(n-3)}(x) - f^{(n-2)}(x)$. So by substituting $f^{(n - 1)}(x)$ in the first equation, we get: $f^{(n)}(x) = -2(e^{-x}\cos(x) + f(x) - f^{(1)}(x) + f^{(2)}(x) + ... + f^{(n-4)}(x) - f^{(n-3)}(x))$ I tried to the same thing with $n$ being odd and tried to perform an induction to get a formula for the value of $f^{(n)}(x)$ but couldn't find a way to do so. Any ideas?


What a pronoun should one use: "you" or "yours"?

This document sets out the rights and responsibilities of [you || yours], the Company, and the concerned third parties.   If "the Client's rights" can be rephrased to "the rights of Client", then, I suppose, "your rights" can be rephrased to "the rights of you", but "the rights of yours" sounds greater.  So, is either variant appropriate and which should one better use?


Creating a Circuit with Resistors Given the Total Resistance

How can I create a circuit with a total resistance of 144.7 ohm which is composed of 10-ohm resistors? How many parallel and/or series resistors should it contain?  I've tried solving this but the nearest total resistance to 144.7 ohm that I get is 144 ohm exactly. Actually, this isn't for real-life usage rather just a circuit analysis problem. Please help.


Finite bit strings that do not contain '$00$'

I am studying for an exam and I am having trouble with this practice question:  In this question, we consider finite bit strings that do not contain $00$. Examples of such bitstrings are $0101010101$ and $11110111$. For any integer $n\geq 2$, let $B_n$ be the number of bitstrings of length $n$ that do not contain $00$.   Determine $B_2$ and $B_3$. Prove that $B_n = B_{n-1} + B_{n-2}$ for each $n\geq 4$. For each $n\geq 2$, express $B_n$ in terms of a Fibonacci number.   Any help is greatly appreciated


I am stuck with the following problem: (GATE-Question)  Let $f:\mathbb C\rightarrow \mathbb C$ be an arbitrary analytic function satisfying $f(0)=0$ and $f(1)=2.$ Then, which of the following items is correct?       (a) there exists a sequence $\{z_{n}\}$ such that $|z_{n}|> n$ and $|f(z_{n})|> n$,   (b) there exists a sequence $\{z_{n}\}$ such that $|z_{n}|>n$ and $|f(z_{n})|< n$,   (c) there exists a bounded sequence $\{z_{n}\}$ such that  $|f(z_{n})|> n$,   (d) there exists a sequence $\{z_{n}\}$ such that $z_{n} \rightarrow 0$ and $f(z_{n})\rightarrow 2.$   I do not know how to progress with the problem or what property to use. Please help. Thanks in advance for your time.


How can I uninstall MongoDB and reinstall the latest version?

I need to uninstall mongodb completely from my system (Ubuntu 11.10) and install version 2.0.5.  Currently, when I run:  mongo db   I get the following error:     MongoDB shell version: 2.0.1   connecting to: db   Wed Jun  6 13:05:03 Error: couldn't connect to server 127.0.0.1 shell/mongo.js:84   exception: connect failed


What is the difference between in the meaning of  these two sentences:         I will remember to post the letter.   I will remember posting the letter.      How can we know where to use gerund or infinitive? Are there any specific verbs that can be used particularly for gerund and infinitive separately?


NullPointerException while checking element of array

I have class: public class Board {    private Object[][] fields;     public Board(int x, int y) {        Object[][] fields = new Object[x][y];    }     void IsFree(int x, int y) {        if (fields[x][y] == null)            System.out.println("Free");        else System.out.println("Not free");  } }  I got NullPointerException when I compare element of array with null. I want to check if this is "empty".


Let $x(t)$ and $a$ be in unit meters, and $t$ unit time. If we look at the indefinite integral $$ \int\frac{\frac{dx}{dt}}{x(t) + a} dx $$ then we note that the units of the above expression are $\frac{meters}{seconds}$. If we evaluate the integral, we get $$ \frac{dx}{dt}\log(a + x(t)) $$ But the log has units meters in its argument, which, as I understand, transcendental functions' arguments should be dimensionless. Changing the indefinite integral into a definite one does not necessarily fix this, because, as I understand $$ \int_{x=x_0}^{x=x_1}\frac{\frac{dx}{dt}}{x(t) + a} dx =  \frac{dx}{dt}\log(a + x(t))|^{x=x_1}_{x=x_0} = \frac{dx}{dt}(x=x_1)\log(a+x_1) - \frac{dx}{dt}(x=x_0)\log(a+x_0) $$  so what gives?


Two definitions of locally compact space

I have seen two definitions of locally compact topological space   A topological space $(X,\mathcal{F})$ is said to be locally compact if for every $x\in X$, there exists a compact set that contains an open neighborhood of $x$. A topological space $(X,\mathcal{F})$ is said to be locally compact if for every $x\in X$, there exists an open neighborhood of $x$ whose closure is compact.   Are these two definitions equivalent? It's clear that the second implies the first, but I don't see why the first implies the second. Suppose that $U $ is an open neighborhood of $x$ with $x\in U\subset K$, here $K$ is a compact set. Since compact sets may not be closed in a non-Hasudorff topological space, the closure of $U$ may not be contained $K$, so we can't say the closure of $U$ is compact.


AMD 64 OS installation in Intel processer

I'm using Sony laptop with intel i3 (64bit) processor, i'm facing problem while installing amd-64 bit os, please help me to resolve this issue.   amd-64 bit os will support Intel (64bit) processor ? I have Desktop with AMD athlon (64 bit) processor , if i install in this amd-64 bit OS is working , if i install same os in my laptop intel processor i'm not able to install.   please help me.


Math Olympiad (Number Theory) solution verification

Let $n,p > 1$ be positive integers and $p$ be prime. Given that $n \mid p−1$ and $p \mid n^3 −1$, prove that $4p − 3$ is a perfect square.  Iran 2005 My solution; $n \mid p−1 \implies kn + 1 = p\tag{1}$ $p \mid  n^3 −1 \implies p \mid n^2 + n + 1$ (as $ p \ge n + 1 > n-1.$) Putting (1) in the above equation implies; $$ nk + 1 \mid n^2 + n + 1 +\ [+(k-1)n - (k-1)n] \\\implies nk + 1 \mid n + 1 - k \\\implies |n + 1 - k| \ge nk + 1$$ Case 1 : $ n + 1 - k > 0$ Then, $n \ge n(k+1)$ which is not possible. Case 2: $ n + 1 - k < 0$ Then, $ k \ge n(k+1) + 2$ which is also not possible, Hence $ n + 1 - k = 0$ Putting this into (1) $\implies p=n^2 + n + 1 \implies 4p-3 = (2n+1)^2$ I read through my solution and everything seems to check out, but I have never done the splitting into two cases thing before so I am just suspicious about that. Could you please tell me if my proof is correct and checks out, Thanks!


Any difference between Hardware RAID and Software RAID?

I'm building a new server (Small Business Server 2008), but I can't get the built-in RAID controller (AMD SB700) to work and have basically given up on it ever working with Server 2008. Fine.  But my question is... is there any real difference between Hardware (such as ) and Software (Window's built in Drive Mirroring) for RAID 1?  Assuming the drives are identical models, etc., it seems that there would be a negligible difference, just based on my guessing/wishfull thinking.


Need to convert Photoshop layers to InDesign layers

I'm using Photoshop CS6 to make a label and I need to convert all layers to InDesign CS4. I've never done this...is it possible?


Good Afternoon all,  I am trying to typeset a symbol that I have been using to represent the integral of a regulated function. This symbol is the standard integral symbol, with the letter "R" superimposed on it.  I have tried using \mathllap, \mathclap and \mathrlap (as suggested ), however none of these have managed to give the desired effect. When I tried doing it without the limits of integration, it got close to working, however then I was unable to have the limits to the right hand side of the symbol:  \mathop{\mathrlap{\int}R}_a^b f   Any help would be greatly appreciated, thank you in advance!  Minimal Example:  \documentclass{article}  \usepackage{amsmath,mathtools}  \begin{document}  Take the regulated function $f$, we want to compare the Riemann integral, $\int_a^b f$ to the regulated integral $\mathop{\mathrlap{\int}R}_a^b f$ by taking sequences of step functions.  We will prove that $$ \mathop{\mathrlap{\int}R}_a^b f = \int_a^b f $$  \end{document}


How do you derive Fleming's left hand rule?

How do you derive ? What is the theoretical explanation for the directions of the magnetic field, current and the force on the current for being oriented in that way relative to one another?


Sample size for logistic regression with categorical independent variables

Trying to find a sample size for logistic regression I found a rule of thumb in   I cite:  Sample size considerations. Sample size calculation for logistic regression is a complex problem, but based on the work of Peduzzi et al. (1996) the following guideline for a minimum number of cases to include in your study can be suggested. Let p be the smallest of the proportions of negative or positive cases in the population and k the number of covariates (the number of independent variables), then the minimum number of cases to include is: N = 10 k / p If the resulting number is less than 100 you should increase it to 100 as suggested by Long (1997).  From:     I understand there are extra complexities like statistical power, stability and orthogonality of the variables.  But anyways, my question is if the fact that I have categorical variables would affect the sample needed. I ask this because for every level of a categorical variable you have one parameter.  More precisely, do I have to count every level of categorical variables as different variables to calculate sample size?


How do I use what's returned by a python function if it return more than one value?

So I have this code:  def validate_username(username):     find_username = cursor.execute("SELECT username FROM user WHERE username = ?", (username, ))     if find_username.fetchone() is not None:         username_is_valid = False         invalid_reason = 'Username already exists'     elif len(username) > 255:         username_is_valid = False         invalid_reason = 'Invalid format'     elif not match(r"[^@]+@[^@]+\.[^@]+", username):         username_is_valid = False         invalid_reason = 'Username must be an email address'     else:         username_is_valid = True         invalid_reason = None     return username_is_valid, invalid_reason   So obviously, it will return one of those:  (False, 'Username already exists') (False, 'Invalid format') (False, 'Username must be an email address') (True, None)   Now what I want to do is to pass those two arguments into variables so that they can be reused, printed, etc. but for some reason I can't really find how to do it online; I'm assuming because I don't word my question properly. Maybe someone here can provide some guidance?  Basically the goal here is to run the function with the username, then if the username is invalid, print why it's invalid and if it's valid, then proceed further.


Accented characters in mathematical mode

As you can see I am writing solutions for some high school students. I wanted to write speed "velocità" with the accent on the a using $\mathrm{velocità}$ instead of the classic $\text{...}$ or $\textup{...}$. Why the a accented in Italian language is omitted when I use the mathematical mode? Is there a way to accent a letter in mathematical mode using \mathrm? \documentclass{article} \usepackage[utf8]{inputenc}  \usepackage{amsmath,amssymb} \usepackage{parskip}  \begin{document} Una sintetica risoluzione di alcuni esercizi assegnati. Se un computer esegue delle operazioni o dei calcoli al secondo vuol dire che esegue con una certa velocità le istruzioni assegnate. Quindi indico con $n_c$ (una sorta di velocità) i calcoli al secondo e ricordando la formula della velocità scalare media fornita a lezione e alle scuole medie \[\text{velocità}=\frac{\mathrm{spazio}}{\mathrm{tempo}}\] Se adattiamo la formula appena scritta avremo: \[t=\mathrm{tempo}=\frac{1\, \text{calcolo}}{n_c}=\frac{1}{6.7\times\text{calcoli}/\text{sec} }\approx 15\,\text{ns}\]  $\mathrm{velocità}$ \end{document}


Question:  Show that $n^2 + 3n + 5$ is not divisible by $121$, where $n$ is an integer.


I have Datetimes formated as "16 Apr 2020 02:07 PM CST" and I need to compare it to another datetime just like that to know which date came first.  What I tried to do until now was:  var firstDate = "16 Apr 2020 02:07 PM CST"; var secondDate = "23 Apr 2020 06:07 AM CST";  var diff = Math.abs(firstDate - secondDate);    That or I tried to check if one was greater than the other and got similar results.


test class for a method that returns collection of records

I have a class the returns the set of records based on lastmodified date. So how to write a test class and test the results of that class ..  In a test class, If I instantiate a class and call the method then it covers me 100%. But when I try to verify the results it doesn't  return me any records   public with sharing class UnclaimCases {     public list<case> caseami {get;set;}     public string strhours = Label.DateFilter; // custom label stores values in hours      public integer hours = integer.valueof(strhours);     Datetime currenttime = system.now();     datetime  acttime  = currenttime.addhours(-hours);     public final static Id custid = Schema.SObjectType.case.getRecordTypeInfosByName().get('Support').getRecordTypeId();         public UnclaimCases()     {       caseami = [Select CaseNumber,Priority,Response_Due_Date__c,Response_time_elapsed__c from case where RecordTypeID =:custid AND (Status = 'Unclaimed' OR Status ='Escalated' ) AND Product_Type__c = 'A' AND Owner.Name = 'T Queue' AND LastModifiedDate >: acttime  AND LastModifiedDate < : currenttime  ORDER BY Priority  LIMIT 10000 ];     }      public pagereference inc()      {          Datetime currenttimeami = system.now();          datetime  acttimeami  = currenttime.addhours(-hours);          caseami = [Select CaseNumber,Priority,Response_Due_Date__c,Response_time_elapsed__c from case where RecordTypeID =:custid AND (Status = 'Unclaimed' OR Status ='Escalated' ) AND Product_Type__c = 'A' AND Owner.Name = 'T Queue' AND LastModifiedDate >: acttimeami  AND LastModifiedDate <: currenttimeami ORDER BY Priority LIMIT 10000 ];          system.debug('caseami' + caseami );          system.debug(' current datetime value ' + currenttimeami );          system.debug(' act datetime value ' + acttimeami );         return null;     }   }   #Test class   @isTest public class TestUnclaimCases  {      @isTest static void Unclamethod()         {              Id queueId =[select Id from Group where Name = 'T Queue' and Type = 'Queue'].Id;              Id custid = Schema.SObjectType.case.getRecordTypeInfosByName().get('Support').getRecordTypeId();               case c1 = new case(RecordTypeId = custid, Status = 'Unclaimed', Product_Type__c = 'A',Priority = 'SEV 1' , ownerid=queueId);               insert c1;     datetime delay1 = datetime.now.addhours(-2);           Test.setcreateddate(c1,delay1);             case c2 = new case(RecordTypeId = custid, Status = 'Rep On Site', Product_Type__c = 'A',Priority = 'SEV 2' , ownerid=queueId);            insert c2;   datetime delay2 = datetime.now.addhours(-2);           Test.setcreateddate(c2,delay2);             case c3 = new case(RecordTypeId = custid, Status = 'Escalated', Product_Type__c = 'A',Priority = 'SEV 2' );             insert c3;           datetime delay3 = datetime.now.addhours(-2);           Test.setcreateddate(c3,delay3);              UnclaimCases uc = new UnclaimCases();             uc.inc();             //list<case> fuc.caseami;             system.assertEquals(2,uc.caseami.size());           }     }


Student loans can be forgiven after ten years of being a teacher ().  If there is no chance for a new teacher to pay off the loan in ten years, is there any benefit to pay anything other than the minimum (income-based) payment for ten years?


How can I use AppleScript to reshow the last OS X notification (in the notification banner)?

After the notification disappears, I want to be able to make it appear again through AppleScript.


Can a youtube video be embedded in an HTML Email

Hey everyone. This is my first post here, I wasn't sure if it should go on stack overflow or here, but this seemed like the best option.  The question is pretty straightforward. Can I embed a youtube video in an HTML email? I did a quick test and it didn't work. Would it be dependent on the mail client?   Let me know if anyone has a solution to this. Thanks.


My computer is a lenovo and I have windows 8.1 installed and was wondering if there is a way to boot my PC with Ubuntu without a disc or flash drive.  I just want to try it out since I don't like the way my PC runs with 8.1. If I like the way Ubuntu runs and looks I would like to Install it without a disc or Flash drive. Let me know if this is possible.  Thanks,


Rotate an entity to look at the same place as the player

I try to make a tagged Armor Stand look at the same place as the player, but I can't find a way to do it.  For example, if the player looks in the direction of the (x, y, y) block, the Armor Stand should look at the (x, y, z) block.   For now I wrote the following command, but it only rotates the Armor Stand in the same direction as the player, it doesn't make it look at the same place:  /execute as @e[tag=my_armor_stand] at @s rotated as @p run teleport @s ~ ~ ~ ~ ~  If this should take more than one command, it is also okay.


Number of matrices satisfying a given property

Let $A$ be a $2\times 2$ matrix with complex entries.How to find the number of $2\times 2$ matrices $A$ satisfying the equation $A^3=A$ ?


I am following this tutorial -  (note at the 3:12 mark in the video is where the step I need help is)  I need to put a logo onto a trophy I made in Blender. I am following all the way to the point where in the tutorial he says to switch the mapping to UV. But I dont see a "mapping" window like his. I have Image Mapping, but no plain Mapping window. I really need help to get this done. I am on a deadline for a championship football game film. I got the trophy all set, I only need to get it textured and get this logo on there and I can finish.


How is an experimental particle physicist evaluated?

As an undergraduate student majoring in physics, I intend to apply for a Ph.D. in experimental particle physics. I have known that working as physicists in this field is kind of different, as they are always affiliated to a collaboration (like CMS in LHC) and may appear as authors in loads of related papers, resulting in high citations. Therefore it seems traditional evaluations of a researcher (focusing on the citations or h-index) do not work when assessing an excellent and famous experimental particle physicist.  Thus I am asking:   How are particle researchers assessed in reality, in the case when a Ph.D. applier is searching for and comparing professors in the similar field, or when a researcher is going to find a position as an assistant professor? Does the specific role of a scientist in the collaboration (say, the group leader) matter in this evaluation procedure? How does university ranking play into this? What are the probable differences between professors in particle physics who work at a higher-ranked institution (ranked by physics major) and those who work at a lower-ranked one – given that they are both affiliated to some big collaboration. This question comes to me since it seems one cannot distinguish a famous particle physicist by the conventional method which is performed by university ranking.


How to snap 2D cursor to vertex in UV editor?

I'm in the UV Editor and I've UV-projected my object there. Now I want to move the 2D cursor to snap to any vertex of that object. How to do it properly? I tried to turn on snap and set snap to vertex, but when I drag the 2D cursor, it won't snap at all. Snap to increment (grid) is working fine, but snap to vertex is not working . Any idea ?


$G$ is a finite abelian group. $|G| = p^n$ where $p$ is a prime. Show that $G$ has a subgroup of order $p^r, r \leq n$ without Sylow Theorems.

I know that for $G$ to have a subgroup of order $p^r$ it must have an element of order $p^r$.  My approach to this problem was to use the Fundamental Theorem of finite abelian groups. i.e there are, up to isomorphism, only the following abelian groups of order $p^n$:  $\mathbb Z_{p^{a_1}} \times \mathbb Z_{p^{a_2}} \times \mathbb Z_{p^{a_3}} \times ... \times \mathbb Z_{p^{a_k}}$, where $a_i \in \mathbb N$ and $a_1 + a_2 + a_3 + ... + a_k = n$  Then I was going to show that each group of this form has an element of order $p^r$.  I started off by using Cauchy's theorem to show that each group of the form $\mathbb Z_{p^{m}}$ where $m \in \mathbb N, m \ne 0$ has an element of order $p$.   However, I am stuck now an do not know how to show that each group of the form $\mathbb Z_{p^{a_1}} \times \mathbb Z_{p^{a_2}} \times \mathbb Z_{p^{a_3}} \times ... \times \mathbb Z_{p^{a_k}}$  has an element of order $p^r$, where r is every integer less than $n$.  Does anyone know how to prove this without using Sylow theorems?


I’ve used my machine twice.  I went to try to put a different attachment on it and the pin won’t move.


How can I change the default program installation directory in Windows 7?

Windows 7 is installed on my C drive, which is quite small.  I am very tired of instructing new programs to put their files on my larger D drive during installation; I would like to change the default drive.   says that you can use a registry hack, but I am giving Microsoft the benefit of the doubt and naively assuming that a configuration option exists somewhere.  It's 2010... do I really have to hack my registry to make a simple tweak like this?  Also, there's a  that explains how to move the "Users" directory and create a symlink, which could also work.  However, at the moment I have some apps in C:\Program Files, some apps in C:\Program Files (x86), and some apps in the corresponding folders on D:\, so it would be a hassle.  Also, my small OS boot drive is a 10k RPM WD Raptor, and I feel like that probably gives a speed boost to apps installed on it that need to read & write to their directories a bunch.  I wonder if it actually matters.


Convert AutoCAd file (.dwg) to shapefile

I have a CAD file to convert into shapefile. Unfortunately, I don't have access to AutoCAD, MapInfo or ArcGIS atm. All I have access to is QGIS.  I'll need to convert this CAD file to shapefile to be used in a specialised software which can use/edit shapefile.  I tried couple of online tools without any success. Any help? BTW the size of the CAD file is less than 2MB.


How are new things added to the replicator?

In any series of Star Trek using this technology, how are new items--food-related or not--added to the replicator database for future replication? Couldn't find anything on  or the .  Is there an official procedure involving some sort of program where you name and describe what it is before adding a sample? Or is it more of a "here ya go" type of insertion? Can you only give a partial list of ingredients and tell the machine it needs certain extra things to be complete (give it beef, then specify it also needs a bun, lettuce, tomato, and Miracle Whip)?  If there are differences in procedure between generations, I'd like to know those as well.  Don't care about canonicity.


Showing meta questions in the same manner as linked and related questions

In the right column there are linked and related questions. I'm suggesting to add a third section: "Meta".  If a question on the main site is linked to by a question on meta, that meta question should show up in the meta section of the question on the main site.  We could also have this meta section on meta, since meta also is meta meta.


Given $|z|<1$ prove $\lim_{n \to \infty} z^n=0$.

Given $|z|<1$ with $z \in \mathbb{C}$ prove $\lim_{n \to \infty} z^n=0$.  My attempt given $\epsilon >0$ we wish to show that there exists $\delta >0$ such that $n> \delta$ means $|z^n-0| < \epsilon$.  For $n \in \mathbb{N}$. We have $|z^n|=|z|^n$. We wish $|z|^n < \epsilon$. This means,  $$n \ln |z| < \ln \epsilon$$  But because $\ln |z|<\ln 1=0$ dividing both sides by $\ln |z|$ gives:  $n> \frac{\ln \epsilon}{\ln |z|}$  So that's what we choose for $\delta$.   My question is is how can we get away from the assumption that $n \in \mathbb{N}$. Or is this correct even with the assumption?


An answer to previous  on link rots indicated that they are best fixed by user edits. Such edits are limited to a minimum of 6 characters, which is sometimes not the case with link rots. So how should they be fixed?


In an algebra course I am computing homology groups of chain complexes and for this I need to calculate the kernel of the map $$\mathbf{Z}/n\mathbf{Z} \to \mathbf{Z}/n\mathbf{Z},\quad x+n\mathbf{Z}\mapsto dx+n\mathbf{Z}$$ My guess is that the kernel is exactly $$\frac{n}{\gcd(n,d)}\mathbf{Z}/n\mathbf{Z}. $$ However I am not quite sure and since I need to proceed with the calculations a Yes or No would be appreciated:)


Space between text and upper line in mdframed

I am using the following code:  \documentclass[11pt,a4paper,twoside]{book} \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage[english]{babel}  \usepackage{mdframed} \theoremstyle{definition} \newmdtheoremenv[linewidth=1.1pt]{Definition}{Definition}[chapter]  \begin{document}  \begin{Definition} (blah blah)\newline Text... \end{Definition}  \end{document}   which produces    Is it possible to reduce the space between the first line of text and the upper black line?  Thank you in advance!


Determining if 1,814cM match from AncestryDNA is Half Sibling?

My son recently had a match come up as close family the match is male and 1814cm.    His only living grandfather is already in our tree at 1857cm.  All other grandparents are deceased and have never participated in Ancestry DNA.    When I review the shared matched between my son and the matched male they have matches consistent with my ex-husbands family.  However none of my ex husbands brothers (his uncles) have done DNA testing.   My son has no grandchildren.    Is it possible that 1814cm could be the child of one of my ex husbands brothers children or am I looking at the possibility that there is a half sibling to my son?


How do you describe your mathematical research in layman's terms?

"You do research in mathematics!  Can you explain your research to me?"   If you're a research mathematician, and you have any contact with people outside of the mathematics community, I'm sure you've been asked this question many times.  For years now, I've struggled to find a satisfying answer.  I think an ideal answer to this question should:   be accessible to someone who hasn't studied math since high school build intrigue and wonder honestly, albeit vaguely reflect your research only require a few sentences   (Of course, these guidelines will change depending on the audience and venue.  For example, speaking with an engineer over a meal allows more time and technical language than would speaking with a stranger on a bus.)  I study the representation theory of algebraic groups and Lie algebras over fields of positive characteristic, so I usually say something along the following lines:     I work with two algebraic objects that are closely related called algebraic groups and Lie algebras.  These objects can act on spaces (like three-dimensional space) by transforming them in a nice way, and I study these actions.  One aspect of my work that is especially challenging is that I use number systems in which a chosen prime number is equal to zero.   Honestly, based on my guidelines above, I think this response is poor, but with so much to communicate in such limited terms with such limited time, the task seems nearly impossible.  Using my guidelines, how would you describe your own field of research? Or, if my guidelines are too strict, how would you deal with this question?


Function of second grep in `ps | grep -v | grep`

ps aux  | grep firefox   Lists all processes having the string "firefox"  ps aux  | grep -v firefox   Lists all the processes without the string "firefox"  ps aux  | grep -v grep | grep firefox ?  What does this second grep does ? grep itself is a command then why we are grepping another grep ?


Suppose we create very large spherical body by using gamma rays generator and they will concentrate on a single point at the centre of sphere.We will place this spherical body thousands of kms above the sun so that it can draw energy from sun.Can the centre of the sphere create a Mini Black hole by the energy from the concentration of gamma rays?  [Just applying my 14 yrs old brain..if im wrong then please correct me...]


Difference between general linear model and generalized linear model

Is there a big difference between general linear model and generalized linear model? I am quite confused a bit with the two.


fsck error on boot: /dev/sda6: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY

I dual boot Ubuntu and Windows 7. I was browsing on FireFox in Ubuntu and all of a sudden I get some error message, so I rebooted.  Now when I try to boot into Ubuntu I get this message:  fsck from util-linux 2.26.2 /dev/sda6 contains a file system with errors, check forced. /dev/sda6: Inodes that were part of a corrupted orphan linked list found.  /dev/sda6: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.         (i.e., without -a or -p options) fsck exited with status code 4 The root filesystem on /dev/sda6 requires a manual fsck  Busybox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built in shell (ash) Enter 'help' for a list of built-in commands.  (initramfs) _   How can I fix this?


Why isn't .profile sourced when opening a terminal?

Just installed Ubuntu 14.04.1 LTS.  According to .profile,  # ~/.profile: executed by the command interpreter for login shells.  # This file is not read by bash, if ~/.bash_profile or ~/.bash_login exists.   There is no ~/.bash_profile or ~/.bash_login.  It does not seem to source .profile when opening a terminal.   Why doesn't it source .profile when opening a terminal? Why is .profile there if it is not sourced? How do I know/control what is sourced when a new terminal is opened? When a new terminal is opened, does it do a "login"? Where is a good place to add $HOME/bin to my path? .bashrc? Will that cause a problem because .profile has the same code?


how to convert 0 to 5 V signal into 4 to 20mA current transmitter

i want to make a voltage to current converter which is also known as current transmitter. i want to  convert 0 to 5v into a 4 to 20mA current loop which can be received by a powered load. i want to make the circuit using op-amp. please someone help me by suggesting some tested circuit. thanks in advance           – Schematic created using


I am using Ubuntu 13.10 host. Inside it I installed VirtualBox with Kali Linux. The Wireless for Kali is not working. What could be causing this issue?


RSA encryption/decryption process is not working correctly

I'm trying to apply the RSA cryptosystem to encrypt a byte M=72, using predefined modulus n, public key exponent e and private key d.  (n, e, d, p, q) = (4802, 5, 59, 43, 8)  In order to accomplish that, I used the following code on Python console:  C=(M**e)%n M=(C**d)%n print M    the first instruction encrypts the byte as C: using the RSA encryption mathematical expression (** stands for exponentional, and % for modulus in Python programming language) the second decrypts C to get M back: using the RSA decryption mathematical expression.   However, the output shows:     2816   which means that M was incorrectly computed as '2816', although I'm pretty sure that all the values of n, e, d, p and q respect the RSA public key algorithm specification.  Does anyone have any idea?


What is the purpose of using * in kivy Vectors

xx = goal_x - self.car.x     yy = goal_y - self.car.y     **orientation = Vector(*self.car.velocity).angle((xx, yy)) / 180.**     last_signal = [self.car.signal1, self.car.signal2, self.car.signal3, orientation, -orientation]     action = brain.update(last_reward, last_signal)  I am a beginner to programming I want to know that why there is a asterik(*) before the self.car.velocity section in the vector field.


I'm encountering a strange behaviour of Google.  Pages in my site has the form :  .. <title>Title of Article - mysite</title> </head> <body>  <img alt='mysite logo'> ..   So I expect this page to show as "Title of Article - mysite" in the clickable link of google SERP.  However, it is displayed as "Title of Article - mysite - mysite logo".  Why the heck is it fetching part of body as the title?  How can I prevent this from happening ?  Thanks !


Repeat text box below table at every page

How can I repeat a text box below a table in every page?   More specifically, if the table breaks, I have to repeat the same text box below the table at every page and not only in the last page.   I cannot use footer for this implementation because in case the table is only few rows I want to display the text box immediately after the table and not at the bottom of the page.  A sample doc has been .


Proving $S^3$ and $\mathbb{R}^3$ are not homeomorphic

Prove $S^3$ and $\mathbb{R}^3$ are not homeomorphic.   I've encountered this question on a PhD exam in topology. This is at a level where we are expected to understand cohomology already, so there are already a lot of obvious one line proofs I could give (e.g. they don't have the same homology groups). But this appears among the "give a detailed answer" questions, as opposed to the more computational questions in the latter half. (The heading says to show all work and support all statements to the best of my ability.)  So, I am confused about the level of detail I would have to include here. Is there an obvious choice for how to prove this directly without relying on any one liners that assume higher level stuff?  I realize this question is a little opinion based, but maybe the answer will be unambiguous to those with more experience in topology. How would you answer this question?


how can i convert a .jar to ubuntu-freindly code?

i am trying to figure out how to convert a .jar minecraft file into Ubuntu-friendly. the problem is, that Ubuntu does not recognize java.


Understanding the formula for the Confidence Interval of the difference between two sample proportions

I'm having trouble making sense out of the formula $$(\hat{p}_1-\hat{p}_2) \pm 1.96 \sqrt{\frac{\hat{p}_1 (1-\hat{p}_1)}{n_1} + \frac{\hat{p}_2 (1-\hat{p}_2)}{n_2}}$$  Is the idea that the sampling distribution of the difference between proportions of group $1$ and proportions of group $2$ of sample size $n$ is normally distributed regardless of population distribution shape, the same way it is true of the sampling distribution of the sample means, for example?  And in this case, what does that mean exactly? Say we have a sample size of $10$; are we talking about every possible combination of differences between every possible combination of samples of size $10$ for both groups and saying that that "function" is approximately normally distributed? What does it mean to subtract one sampling distribution from another?   And then, where does the square root come from? Is it just the SE of the distribution resulting from subtracting the sampling distribution of sample proportions of group 2 from the sampling distribution of group 1?


iPod 5 stuck on voice over and is locked

My iPod 5 is stuck on voice over, but it's also on lock screen. I do not know how to unlock it and get to settings to turn it off.


newenvironment not taking input arguments

This should be a simple thing, but everywhere I've looked says what I have should work I think. After doing this for a few hours I'm calling it and asking for someone to point out the stupid mistake.  Here's my code:  \newenvironment{questions}[1]{ \stepcounter{QuestionGroup} } { \ifthenelse{\isempty{#1}}     {     0     }     {     #1     }{} }   When I try to compile this, it gives me the "Illegal parameter number in definition of \endquestions." And moreover it works just fine if I change all the #1 to some filler content, so it's not registering that the [1] should be an optional argument input.  So... what gives?


How can I play YouTube in the background without using Safari?

Is there an easy way to keep playing YouTube videos in the background, even if I switch to a different app?  I'm not interested in using . I want something super easy to use.


Does Thranduil play any role in the War of the Ring?

plays a big role in the events of The Hobbit, but he seems absent from the LOTR.  Does he play any part at all in the War of the Ring?  I've never read the books so I don't know if anything regarding Thranduil was left out of the movies.


Array value not assigned to variable value

I'm very confused because in a for loop I'm printing an array value. However, after exiting a loop the output doesn't match what I'm printing. What's going on?  Code:  import numpy as np from itertools import product  def boxBlur(image):          m = len( image ) - 1         n = len( image[1] ) - 1          out = [ [0]* ( n - 1 ) ] * ( m - 1 )          for i,j in product( range(1,m) , range(1,n) ):                 vals = np.array(image[i-1:i+2]).transpose()[j-1:j+2].flatten()                  I = i - 1                 J = j - 1                  out[I][J] = int( sum(vals) / 9 )                  print( "M[" + str(I) + "," + str(J) + "] = " + str(out[I][J]) )           print(out)         return out  image = [[7,4,0,1],           [5,6,2,2],           [6,10,7,8],           [1,4,2,0]]  boxBlur(image)      M[0,0] = 5     M[0,1] = 4     M[1,0] = 4     M[1,1] = 4     [[4, 4], [4, 4]]


Is it safe to finish undercooked poached chicken on a skillet?

So here is a round-up: 1.Bought chicken breast today, it was fresh.  Decided to poach it in multicooker, set timer for 30 minutes.  Checking on the pot 25 mins in, realized that something gone awry with the appliance and it turned off somewhere along the way. The pot was warm (but not really hot), the breast was cooked on the surface, raw in the middle.  Chopped it up into pieces and decided to quickly pan fry it and sautee in some tomato sauce afterward.   My question is: I have read about food danger zones and how those can promote bacterial and toxin growth even if meat appears to be fully cooked without any signs of spoilage. Perhaps I am being paranoid (as it had spent only 25 mins in its quasi-cooked state, and it never fully cooled down), but I just wanted to run it through you guys and make sure it is completely safe to eat it.


"Points in Polygon" command (vector-analysis tools) doesn't appear in QGIS 2.16

I can't find the "Points in Polygon" command under the vector-analysis tools. It is missing from the pull down menu.  Any ideas why?  I just loaded QGIS for the first time on my new PC.


Which is correct: "between me and Larry" or "between Larry and I"?

Which is correct?   I agree with the plan worked up between me and Larry. I agree with the plan worked up between Larry and I.


Should "Thanks for your edit!" message include a link to the review page?

Currently when a user submits a suggested edit, this message appears at the top of the edited post:     Thanks for your edit!      This edit will be visible only to you until it is peer reviewed.   I suggest the words peer reviewed provide a hyperlink to the corresponding review page, where the user can see the diff, and eventually who is approving or rejecting their suggested edit.  Currently, a user that doesn't have access to the "Review" section can only see this by accessing their user profile and looking up their suggested edit in their "Activity" history... which is somewhat asking a lot to new StackExchange users.  This feature should be implemented on all SE sites, as it would contribute to make common site features more easily discoverable to newcomers.


Hi I'm having trouble understanding why the quaternionic group cannot be written as a semi-direct product in a non-trivial way. Is there a proof of why this is the case?


When I went to Turkey, I was warned that my beard would make police think I was a member of a group that is "not popular" with the authorities.  So I removed it.  I was glad I did, because in Amsterdam, they spent about three minutes comparing my face to the photo (the photo was taken before I let the beard grow, so it was actually a good match IMHO).  But two years later, the beard is back on the face but still not in the passport.  I brush it out, but it still tends to look like the clowns on Duck Dynasty.  Is that likely to cause a problem entering U.K. or Spain?  I do have driver licenses (Oklahoma and international) that show the beard.  I'd reference a related question but I can't figure out how to do that in the IOS app.  Someone has done it for me in the comments.  The behavior he described is how the guy in Amsterdam behaved when I DID look like my picture.  That's why I wonder if I should shave.  It's the British Border Force and the Spanish people that I will have to deal with next week.


I'm new to Linux and was wondering if it had any limit. Windows has limit 32bit-4GB, 64bit-128GB or so. Does the 32bit version of Ubuntu have a limit?


How to enter accented letters into mysql database with php?

Tried searching for this question but I think I don't know the jargon. I am entering my site content into a mysql database using php, but all of my accented letters or apostrophes (spanish) get transformed into some crazy encoding. Ex:  ' becomes â€  á becomes Ã¡   and etc. First off I don't know what this means or is, but when displaying them on my site, they definitely do not revert back, nor would I expect them too because if I manually enter in UTF-8 letters they totally work on my site.   Is there a way to fix this without re-entering all of my text? I have a feeling I can extract them using php, decode them and then insert them back in but I do not know the functions that do this. The best solution, and if anyone knows how that would be amazing, would be to just do it within sql. By the way the columns say collation utf8_general_ci.   For some further information, I am not doing anything to the text that gets entered into the database (I know that is bad but I suck at this stuff!) Also I am not doing anything when it is being queried. My functions insert pure text and extract pure text to each page. In this way I can write html into my forms and it appears as html on the page and therefore the browser interprets it correctly. I also have a feeling this is really sloppy but like I said... Thanks for all the help!  -- Edit --  So thanks to people who pointed me to the other questions. However, the way I fixed it was not in that answer, it just gave me the write keywords to start a new search. For anyone who has this problem, the way I fixed it was using the function utf8_decode(). I'm not sure this is a great fix, but at least it is working for now and speed was my biggest priority. I am certain the core problem is in how I am entering the data into the database.


Listing Joined tables in MXD using Python?

I've a question about arcpy List* modules.   I have a quite large amount of data on ArcSDE Server.   Earlier I made a list of the feature classes, and tables in the mxd-s placed there using da.Walk and ListFeatureClasses/ListTableViews.   Now I'd like to list the joined tables too, but I've no further idea how to do it.   Actually is it possible to get these relations?


How many points does the perspective in the viewport use and is it changeable?

I know blender can display both orthographic and perspective projection. But, when we look at a cube in blender's viewport, I'm unable to distinguish by eye, if the projection in the viewport is a one-point, a two-point or a three-point perspective. What does blender use, and is this something changeable?


I don't think my wolves would eat an ocelot but I've had one before and it disappeared. There was nowhere for it to leave my house and it was tame.


How to find a suitable association of color with data value in a visualization?

I'm working on a software project that involves creating a visualizer for flood simulations. As part of this project, I've created a water gradient that shows water depth at particular points. To set what values will represent what colors, I go through the data and get the minimum and maximum values that occur and evenly distribute the colors according to that scale.  However, there are often times points in these simulations that have significantly deeper water at them than anywhere else in the simulation. This causes most of the points on the map to have very similar colors and this is not very informative and makes the areas where the water is deeper very hard to see.  My goal is to dedicate a larger range of colors to depths that occur more frequently. For example, if depths go from 0 to 12 but most depths are between 1 and 2, I want more color variation to occur within that range than does between say 11 and 12 or 4 and 5. It seems I need to use standard deviation or something involving normal distribution to do this, but I'm a bit fuzzy on how these things work and how I can use them to accomplish my goal.  Any help that can be provided will be appreciated. Thank you.


If an anti-matter singularity and a normal matter singularity, of equal masses, collided would we (outside the event horizon) see an explosion?


Share reputation between Stack Exchange sites

Possible Duplicate:             I came from Stack Overflow where I participate more frequently, but now I had an issue that I found would be better to be posted on Server Fault, because configuring LDAP isn't a programming topic. It’s my first posting there, which results in enormous restrictions:    I cannot post my answer I had to remove the links   This is caused by the reputation restrictions. They are justified for users which are new to the system, but as more and more Stack Exchange sites arise to separate topics, I think if you have once understood the idea of Stack Exchange, you don’t have to be educated on each site again.  So I would like to propose a sharing of the reputation across all Stack Exchange sites.


When I add a loop cut I get this cross hatching effect. If I add one to the other side as well, then the whole object gets that effect. I've tried changing the shading from flat to smooth, and back. I've recalculated normals, I've removed doubles(0). It doesn't seem to affect the render at least, but i'm not sure if it'll affect anything else like the materials. Or is it just a random glitch that wont do anything else. I've restarted my blender and it didn't take it away either, so I'm lost.


Combinatorics: How to choose k objects from limited number of choices?

Suppose we want to choose a certain number of objects, k, from a variety of choices, all limited. I'm confused about how to set up this problem. I'm pretty sure it's stars and bars, but I don't know how to incorporate the limited amount aspect of the problem.  For example, to explain what I mean, suppose we want a dozen doughnuts, and we're choosing from five chocolate doughnuts, three sprinkled doughnuts, six glazed doughnuts, and one vanilla doughnut. How many ways are there to choose one dozen doughnuts?


I have a common typescript class with some functions.  When I do  this.selected = Object.assign({} as AssignedTestType, newTestType);  the selected instance does not own that functions which are in the type AssignedTestType.  How can I make a 'deep' copy with object.assign? or any alternative method?


Determinants of Matrices det(4A) equals?

Suppose A is a 4 x 4 matrix such that $\det(A) = 1/64$. What will $\det(4A^{-1})^T$ be equal to?  Here's my thinking, $\det(A^T) = \det(A)$ I has no effect on the determinant. And $\det(A^{-1}) = 1/\det(A)$ so $\det(4A^{-1}) = \det(4\times64)$ = can't be 256?  I don't understand, Please help me! THANKS!


Is there a way to detach matplotlib plots so that the computation can continue?

After these instructions in the Python interpreter one gets a window with a plot:  from matplotlib.pyplot import * plot([1,2,3]) show() # other code   Unfortunately, I don't know how to continue to interactively explore the figure created by show() while the program does further calculations.  Is it possible at all? Sometimes calculations are long and it would help if they would proceed during examination of intermediate results.


How to quickly use jquery post to post files?

I have this form and when upload it say undefined index 'banner'. I was able to get other input forms but the "file" is not working, I want something as simple as that javascript code.  <form id="" enctype="multipart/form-data" method="post" action="#" class="courses_create_form"> <input name="banner" type="file" class="form-control" id="banner"> <input name="banner" type="submit" class="form-control" value="upload">  </form>   Here is the jquery script handling it...  <script>      $(document).on('submit', '.courses_create_form', function(e) {     e.preventDefault();      var banner = $("#banner").val();       $.post("uploads/process.php",         {              banner:banner,             today: 'now'          },             function(response,status,Err){             if(status=='error'){ // error             }else if(status=='success'){                 $(".notify").html(response);             }         }); });  </script>       Here is the process.php   <? // process.php echo $_FILES['banner']['name']; ?>


I have an old MacBook Pro (mid-2010) and I am currently running Mountain Lion. Due to lack of any type of support (I cannot install most new versions of applications), I think about installing a newer version, but I don't want the most recent as it will slow my computer down too much. Ideally I would like to upgrade to Mavericks.  I saw a similar topic, which unfortunately doesn't answer my question (as I have never installed my desired version with my Apple ID):    Is there any way I can do this?


Why is the work done by friction zero when body is rolling? Does it mean no energy is dissipated by friction.


I have a shell script:  #!/bin/bash for name in /home/imp/imp/msgs/$1.PK1; do     mv "$name" "${name%.PK1}.BRD" 2>/dev/null >/dev/null done for name in /home/imp/imp/msgs/$1.PK2; do     mv "$name" "${name%.PK2}.MIX" 2>/dev/null >/dev/null done   It works, but only on pre-existing files. What happens, is that more *.PK1 and *.PK2 are created after the initial scan. I'd like this script to "loop" and rename the files that are created afterwards. Is this possible?  UPDATE:  This is what I have now:  #!/bin/bash  while [ ! -z "$(ls *.PK1 *.PK2 2>/dev/null)" ]; do  for name in /home/imp/imp/msgs/$1.PK1; do     mv "$name" "${name%.PK1}.BRD" 2>/dev/null >/dev/null done for name in /home/imp/imp/msgs/$1.PK2; do     mv "$name" "${name%.PK2}.MIX" 2>/dev/null >/dev/null done sleep 1; done   Is that correct?  Thanks.


Should there be two apostrophes to denote possession?

In this sentence, should there be two apostrophes to denote discrete possession, or should there be an apostrophe just after the second subject to denote joint possession?  He said he didn't know anything about John and Jenna's deaths.  Or should it be this:  He said he didn't know anything about the deaths of John and Jenna.


I'm currently using Google Chrome and I run into a problem searching:  Whenever I type something like "Google Chrome" into the address bar, I mean to say, "Search for Google Chrome". However, Chrome by default thinks I'm asking it to Google just the word Chrome.  Any way to disable this, just for the word Google?


Night portrait with noiseless in focus background

We know to take a noiseless night landscape/cityscape, we need use a tripod and set a low ISO. For example in a scene I use ISO 100, aperture f/8.0 and exposure time 30 seconds, I get a night cityscape bright enough and very clean.  My question is, in the same scene described above, if I want to take a portrait and have the same image quality for the background cityscape, how to achieve this ? I can use flash, tripod. Don't forget when focus on the person's face and want have a background in focus, I need use aperture f/8.0 or smaller.  I know slow sync flash, but it will set something like shutter 5 seconds and ISO 800, so the background is not as good as the photo taken with ISO100 and the people maybe blurred a little.  Or some ways in post processing ?


What is the difference between Newtonian and Lagrangian mechanics in a nutshell?

What is Lagrangian mechanics, and what's the difference compared to Newtonian mechanics? I'm a mathematician/computer scientist, not a physicist, so I'm kind of looking for something like the explanation of the Lagrangian formulation of mechanics you'd give to someone who just finished a semester of college physics.  Things I'm hoping to have explained to me:   What's the overall difference in layman's terms? From what I've read so far, it sounds like Newtonian mechanics takes a more local "cause-and-effect"/"apply a force, get a reaction" view, while Lagrangian mechanics takes a more global "minimize this quantity" view. Or, to put it more axiomatically, Newtonian mechanics starts with Newton's three laws of motion, while Lagrangian mechanics starts with the Principle of Least Action. How do the approaches differ mathematically/when you're trying to solve a problem? Kind of similar to above, I'm guessing that Newtonian solutions start with drawing a bunch of force vectors, while Lagrangian solutions start with defining some function (calculating the Lagrangian...?) you want to minimize, but I really have no idea. What are the pros/cons of each approach? What questions are more naturally solved in each? For example, I believe Fermat's Principle of Least Time is something that's very naturally explained in Lagrangian mechanics ("minimize the time it takes to get between these two points"), but more difficult to explain in Newtonian mechanics since it requires knowing your endpoint.


I am  modeling wood properties variation of several individual within the same tree species using multilevel lme().  I specified a first model as :   full <- lme(id ~ dist2 + I(dist2^2)                  ,data=dataGr                  ,random=list(ind=pdDiag(~ dist2 + I(dist2^2)),                               radius=pdDiag(~ dist2 + I(dist2^2)))                  ,control=ctrl, meth='ML')   with 'radius' nested within 'ind'.   As 'id' is a longitudinal variable  according to 'dist2' within 'radius' within 'ind', I want to add an AR(1) autocorrelation error term.  So, I wrote a second model by updating the first one with  :   fullc <-   update(full,  correlation=corARMA(p=1,q=0, form = ~ 1 | ind/radius))   Is it a good way to include autocorrelation error structure in my model?  This specification is also possible and gives slightly different results :    fullc <-   update(full,  correlation=corARMA(p=1,q=0, form = ~ dist2 | ind/radius))   But I don't clearly understand the difference between both specifications. Could you help me ?   Thank you.  Romain.


This is  my code, but my picture is on the left!!! Can anyone share a better code? thanks a lot  \begin{figure}[H] \centering \includegraphics[width=25cm,height=25cm,keepaspectratio]{1.eps} \caption{Aerial view}\label{fig:1} \end{figure}


If a commutative ring is semiprime and its prime ideals are maximal then it is von Neumann regular (absolutely flat).  The converse, although not immediately apparent, can be proven quite easily. But I've been stuck on this one for awhile.  I found that Bourbaki has a question in his treatise on commutative algebra, namely: if all points in Spec(A) are closed (ie. prime ideals are maximal) then A/R (where R is the nilradical) is von Neumann regular (absolutely flat). If this can be proven, the above statement follows immediately since the nilradical of a semiprime ring 0?  Ideas?   Ps: this is my first time posting a question so apologies for any formatting issues.


Proving that every group of order $4$ is isomorphic to $\Bbb Z_4$ or $\Bbb Z^*_8$

I want to prove at any group of order $4$ is isomorphic to either $\Bbb Z_4$ or $\Bbb Z^*_8$. I know that these two groups are not isomorphic to each other because they have different order, but I cannot go further to prove at any group of order 4 should be isomorphic to either of them. Help would be greatly appreciated.  Thanks!


Is $2^{|\mathbb{N}|} = |\mathbb{R}|$? If so, how?  I was reading the Wiki page on the , and it says "Moreover, $\mathbb{R}$ has the same number of elements as the power set of $\mathbb{N}$", but I don't see how this is true?  I feel like it has something to do with binary, but I'm not too sure how it works? Do I have to show a map of all reals can be done in binary? I'm just very confused, and any advice would be appreciated!


What are the prerequisites for studying modern algebraic geometry?

I have studied differential geometry , thought of starting to study algebraic geometry , but it seems completely different from differential geometry . It uses lots of abstract algebraic tools . I wonder how much abstract algebra do I need to learn in order to learn algebraic geometry . Possibly , some reference of algebraic  geometry books will much helpful .  Another thing I see a lot in lecture notes on introductory algebraic geometry is the usage of angle brackets , i suppose they something completely different . What do they mean , anyway ?


I want to draw a bunch of nodes with different styles (a, b, ...) at different points (named 00, 01, ...). I am using the following code:  \foreach \n/\lst in {   a/{00, 14, 20, 34},   b/{01, 11, 23, 33} } {   \foreach \xy in \lst {     \node[\n] at (\xy) {\n};   } }   with the hope that \lst would be assigned a list, and \xy would be assigned elements from this list. However, I get error Package pgf Error: No shape named {01, 11, 23, 33}  is known. How to fix this?


Review reopen post queue suddenly increase

I usually observe other than close votes all review queue has small numbers but today reopen post also have 3 figure number. Is queue was blocked due to some bug?


How can I create a coffee cream effect with Photoshop?

Today I would like to create a coffee cup with the cream floral on it as a text by using Photoshop. It looks like you order a cup of hot cappuccino and the bartender will draw a flower with cream on the surface of coffee but now I want to make it like a text to present a tittle.     I just need to do the cream text effect, no need to draw the whole cup of coffee since i can't use some images. So anyone can tell me how to do this cream effect on Photoshop.  Thanks in advance for any feedback!


CSV list as input parameter in QGIS 3.0 Processing Modeler

I have CSV list with XY coordinates (company and its competitors) which I want to input into simple QGIS Processing model. From this list the model creates and styles two spatial layers.  Everything works well with one exception. I have the input CSV list set up to fixed directory path (see screenshot no. 1). I would like if the model allowed me to select the path to the CSV list when I run the model (see screenshot no. 2).  Does anyone know how to set up a CSV list as an input parameter to QGIS processing model?


Prove that $\mathbb Z^n$ is not isomorphic to $\mathbb Z^m$ for $m\neq n$.   My try:  Let $\mathbb Z^n\cong \mathbb Z^m $. To show that $m=n$.  Case 1: Let $m>n$. Now that $\mathbb Z^m$ has $m$ generators whereas $\mathbb Z^n$ has $n$  generators and an isomorphism takes a generator to generator ; that is the contradiction.  Please correct me if I am wrong.  The case  $m<n$ also follows similarly.


Compare tiny capacitance using comparator

I want to compare the capacitance of two tiny capacitors at around 10^-15 F each. One will change compared to the other by at maximum factor 3. I need to measure the relative difference between them to an accuracy of around 1%. My idea is to connect them in series to form a ”voltage divider” and then connect the middle of them to a comparator which can then compare the voltage between the capacitors to some external reference voltage.  However, I have no experience with comparators or exactly how they work. Would the comparator try to draw a current from the capacitors it was comparing (and thus not work since there’s basically no charge to draw)? What should I look for when buying a comparator for this application?  If this is simply not possible, how else might I accuratley (and cheaply) compare the values of these two capacirors? Note, not looking for some expensive high tech solution here, looking for something which can be done at home by an amature.


How do I really change my login email address?

Fortunately, I can still login with this email address that I have lost access to.  I have been searching around here for a way to update it to the current one I use.  I have found many answers.  But they all give instructions to click on something not displayed or in one case, a page that prompts me to login via another email I no longer have the password for. I need current up to date instructions on how to change my email address or add another email-based login for this same user name that I am posting this with.


How do you reset a USB device from the command line?

Is it possible to reset the connection of a USB device, without physically disconnecting/connecting from the PC?   Specifically, my device is a digital camera. I'm using gphoto2, but lately I get "device read errors", so I'd like to try to do a software-reset of the connection.   From what I can tell, there are no kernel modules being loaded for the camera. The only one that looks related is usbhid.


"Edit waiting" warning did not appear in First Posts Queue

I was reviewing a post in the First Posts Queue when I came across a question I wanted to answer, for reference the question I am talking about is linked this one:    I noticed some easy edits that would make it look nice however when I clicked the edit button nothing happened (as if the edit link was dead).  I opened the question in a normal link and the warning regarding an edit is curently waiting popped up:    I would imagine that in the a review queue if someone tries to edit a question (as they would in a normal question) this warning should also pop up but it did not for me.  Is this a bug?


EDIT: I found the solution for the problem. The float package is necessary to use figures in a multicol environment.  When trying to insert an image into a document, I am unable to use a figure. This following code describes what I am trying to do, but it is not functional.  \documentclass[twoside]{article} \usepackage{graphicx}  \begin{multicols}{2}  \begin{figure}[h]     \includegraphics{image} \end{figure}   On the other hand, not declaring the image as a figure works. The following code is functional, but since the image is not a figure, I cannot properly caption and whatnot:   \documentclass[twoside]{article} \usepackage{graphicx}  \begin{multicols}{2}  \includegraphics{image}   How do I properly insert the image as a graphic, so that I can work with it more?


How do i print a dollar sign within my string in assembly language

title task .model small  .stack 100h  .data  string db "I got 10$ as reward for my hard work",'$' main proc  mov ax,@data mov ds,ax mov ah,9 mov dx,offset string int 21h    mov ah, 4Ch int 21h  main endp end main


What is the good common practice to store shell scripts? (bash, sh, ...)  For now, I have a few bash and sh scripts in my $HOME directory  and I invoke them with  $ bash $HOME/script1.bash arg1, arg2, ...   or  $ sh $HOME/script2.sh arg1, arg2, ...   May I store them in some standard location and invoke them as normal apps like ls, pwd, ...? e.g.  $ script1 arg1, arg2, ... $ script2 arg1, arg2, ...   What is common practice here for advanced linux users?


$P(\limsup A_n)=1 \Leftrightarrow \sum_{n=1}^{\infty} P(A \cap A_n) = \infty\; \forall A, P(A)>0$

Let $\{A_n\}$ be a sequence of independent events. How to prove that $$P(\limsup A_n)=1 \Leftrightarrow \sum_{n=1}^{\infty} P(A \cap A_n) = \infty\; \forall A, P(A)>0?$$   As the $A_n$ are independent I guess I should be using Borel-Cantelli ($\sum_{n=1}^{\infty} P(A_n)=\infty \Rightarrow P(\limsup A_n)=1$) somewhere, but I'm not sure how to get from $P(A \cap A_n)$ to $P(A_n)$.


position of 'only' and the respective change in meaning

What is the difference between the meanings of the two sentences given below?   He plays only as an average player. He only plays as an average player.   I think the second sentence emphasizes more on the fact that he plays as an average player i.e the second sentence is concentrates more on his playing style by comparing it to being average.  This question was asked to me during a verbal test. The question was:  Fill in the blanks:  He _____ as an average player.(only plays, plays only)


What $x$ satisfies $x^2 \equiv x \pmod{n}$ for arbitrary $n \in \mathbb{N}$?

$\textbf{Question}$: Let $n$ be a positive integer. Determine, in terms of $n$, the number of $x$ where $x \in {1,2,\ldots,n}$ for which $x^2 ≡ x \pmod n.$  $\textbf{My solution}$: Let $n=p_1^{a_1}p_2^{a_2}\cdots p_k^{a_k}$. Now for each of the prime power we have two choices :   $p_i^{a_i} \mid x$, $\; $or, $p_i^{a_i} \mid x-1$.   Then Chinese Remainder Theorem would make sure that these $n$ congruences result in one unique $x.$  Hence, our answer is $2^{\omega(n)}$ where $\omega(n)$ denotes the number of distinct prime factors of n.  I wanted to verify my answer and I would also appreciate any kind of remark.


Suppose $\varphi:\mathbb{R}\rightarrow\mathbb{R}$ and for all bounded measurable $f$, $$ \varphi\Big(\int_0^1fd\lambda\Big) \le \int_0^1\varphi(f)d\lambda $$ I'm asked to prove that $\varphi$ is a convex function. I have no idea how to even begin, only idea I've had is to try to suppose that $\varphi''(x)<0$ for some $x\in(0,1)$ but then I haven't got a clue.


if i want to make an item with colored names, unbreakable and enchants higher than maximum 1.16.5

I know that the command for colored items is like this: /give @s diamond_sword{display:{Name:"{\"text\":\"fang\",\"color\":\"black\"}"}}  and for unbreakable enchanted tools, it is this (from what I remember): /give @s emerald{Unbreakable:1,Enchantments:[{id:sharpness,lvl:1000},{id:knockback,lvl:1000}]}  Is there a way I can combine the two?


Let T be a linear transformation from a vector space V over reals into V such that $T-T^2=I$. Show that T is invertible  Solution: I started by multiplying T on both sides and getting   $-T^3=I$


Is it possible to create (render) animated transparent filters?

I would like to know if it is possible to render a transparent animation in Blender to use it as a filter to record video as snapchat does it but with static png filters?


A place for developers to post quick tips/lessons learned and tutorials

I'm a huge fan of StackOverflow.com, but it seems like there should be a related site where developers can post quick tips or lessons learned.  There are many time when I have searched the web and stackoverflow for information on a particular topic or problem I need to solve and have come up empty.  In those time, I have to work at the problem until I solve it.  It would be nice if there was a simple place for me to create a post explaining how to solve the problem without having to post to a forum or start my own blog.  Specifically, it would be a lot like the existing stackoverflow.com, but without the requirement of an initial question.  Instead, developers could post quick tips, lessons learned and tutorials that the community could vote on like they do on stackoverflow.com.    I know posting a question then answering it myself is a possibility on stackoverflow.com. I was just thinking it might be nice to have a companion site related to stackoverflow.com where we as a community could post helpful tutorials for problems we recently had to solve. The site could act as a single blog where all readers could easily be authors, too. It could be a place where we could provide more comprehensive details for solving larger problems than we typically see on stackoverflow.com.   Also, the posts would have to solve a specific problem and not be theory or opinion based.  And we could up/down vote posts like stackoverflow.com.    An example of the kind of post that comes to mind might be something like...  Microsoft releases a new version of OData support via the Web Api.  Searching the web only seems to show the greenfield development path, but many users need to know how to convert their existing web api project to support the new release.  Given that I just went through the process of figuring this out, I'd like to share it with the community.  It's not really the typical short-ish answer you'd see on stackoverflow, and it's not really the size of a typical blog post.  It's something in between.  The kind of thing many companies internally use a tool like Confluence to post these brief tutorials on.


Let $G$ be a graph. Let $k$ be the minimal degree of $G$. Show that $G$ contains a cycle of length $k + 1$.


StackApp site content copied on other public sites

I am using Google Analytics to track the number of visitors coming on my page everyday. Yesterday, I happen to see the referrals and I saw   This is a public website and when I visited it, I saw it has exact contents which I put on   I thought this is not legal but how is it possible that people are copying the content without any kind of attribution.  Is this right ?  How can we prevent people from copying the content on their own website ?


Travel duration from Earth to a star at 9.8 m/s² acceleration

How much time would it take for a traveler (in traveler's perspective) to reach a star at distance $d$, if it accelerates at 9.8 m/s² (for a comfortable travel)?  I understand that $V = V_0 + a\times t$ and such related high-school physics, and I know there is something called Lorentz transformations that I can grab the formulae from the Internet, but I can't really put the numbers together to get what I want, so I would also like to know how to derive the answer to the question from the basic equations.  Also, it is not quite clear to me the role of the $E = mc^2$ in this travel, specifically: in travellers perspective, can it accelerates at 9.8 m/s² indefinitely, using always a constant energy output? In other words, would the ship's engine "feel" the ship heavier, or the mass increase effect would only be observable from another frame of reference?


Related questions in "Ask Question" page is better than the search tool

When I search for similar questions that I am going to ask, I usually can't find anything through the search box on Stack Overflow. But when I enter my question on the "Ask Question" page, the questions suggested through the "Questions with similar titles" box are usually relevant. Do you experience the same thing?


Is LCM of rationals used in higher math?

I read in this school book, an algorithm to find the LCM of rationals. It goes in the following manner. $[\frac{a}{b}, \frac{c}{d}]=\frac{[a,c]}{(b,d)}$.  If you inspect as to why the formula is given so you will realise that this formula gives the smallest positive rational which is an integral multiple of both $\frac{a}{b}$ and $\frac{c}{d}$.  For example, $[\frac{1}{2}, \frac{3}{4}]=\frac{3}{2}$. Where, $\frac{3}{2}=3(\frac{1}{2})=2(\frac{3}{4})$.  Now, what is puzzling me is the idea of LCM. Because I was of the opinion that this is a concept only defined on integer, but here they define it for rational numbers. So, is this a universally accepted formula or was it just something the person who wrote this book put in?  I just realised that someone has already asked a question previously questioning the logic behind this formula. Well, that is not my question. I wish to know whether this formula is actually relevant in higher mathematics.


Netflix not working in Firefox, how to fix?

I just installed 14.04 LTS on my laptop. I tried to go on Netflix but it tells me to install silverlight but that does not work either. What are my options to get Netflix working on my laptop?


Does ubuntu 18.04 LTS support ibus-m17n?

How to install ibus-m17n in Ubuntu 18.04LTS supported desktop?


I want to install Xubuntu with dual boot W8.  So I have downloaded Xubuntu and installed it, but when I want use it, it doesn't detect WIFI, but when I am connected with ethernet it does detect it.  So I have concluded, the driver is missing ?!  How can I install the appropriate driver for my WIFI ?  Thanks for your help.  EDIT :   03:00.0 Network controller [0280]: Qualcomm Atheros AR9485 Wireless Network Adapter [168c:0032] (rev 01)     Subsystem: AzureWave AR9485 Wireless Network Adapter [1a3b:2c97]     Kernel driver in use: ath9k     Kernel modules: ath9k xubuntu@xubuntu:~$    Yeah, but rfkill is strange "Hard blocked"  0: phy0: Wireless LAN     Soft blocked: no     Hard blocked: yes 1: asus-wlan: Wireless LAN     Soft blocked: no     Hard blocked: no 2: asus-bluetooth: Bluetooth     Soft blocked: no     Hard blocked: no 3: hci0: Bluetooth     Soft blocked: no     Hard blocked: no


Find the indexes of several elements in a list

I have an list of integers:   x = [0, 1, 3, 5, 6, 7, 33, 39, 49, 51, 11,        32, 55, 61, 31, 44, 43, 4, 45, 30, 50, 41]   And second list that can only contain elements from x, for example: y = [44, 11, 49]  I need to find the index of each element of y in x.


How does SO get the related questions when I ask question?

When I complete my title of question, the related questions are listed below. I am confused how can SO select the questions, there are no key words or someting like that.


So far I couldn't find anything really, but is it true that curl doesn't really time out at all?   user@host:~# curl http://localhost/testdir/image.jpg   I'm asking because I'm redirecting any request for images in testdir to a separate Apache module which generates those pictures on the fly. It can take up to 15 minutes before the picture is actually ready and delivered to the requesting client.   Will curl always wait (or is it depending on configuration) or is there any sort of timeout?


Regarding uses of $i$ (square root of $-1$)

Are there any uses of 'square root of $-1$' in practical life ; like in Physics ?


VitualBox not detecting my USB devices with a linux host

Since I installed virtualbox 5.0.40 on a mint 18.2 (mate) box I have not been able to connect my usb devices to my virtual machines I have added guest additions and in my usb configurations I select USB3.0 (I tried other settings as well but nothing) but from my virtual machines menu>Devices>USB I get get an empty list.   Would greatly appreciate any suggestions.


Preserve formatting when referencing cells across sheets

Is there a way to show the formatting of the referenced cells from another sheet in Google Sheets?  For example I have a sheet named balance with A1 having a comment and a blue background. When I reference this cell in another sheet within the same document (called rent) - ie =balance! A1 then only the value of the cell shows up - not the comment or the background color.  It would also be useful to know if this can be done with the ImportRange() function so as to have this functionality available when referencing other spreadsheet documents.


What if I give name to a thread but call run() explicitly?

I know that when we call run()  explicitly no new thread is started and the code written inside run() is executed on the main thread. But what if I give a name to a thread and then call run() explicitly as shown in my code?  public class ThreadImpl1 extends Thread{      ThreadImpl1(String name){         super(name);         //start();     }      public void run() {        for(int i=0;i<5;i++)            System.out.println(getName());    }     public static void main(String...s) {       ThreadImpl1 t1=new ThreadImpl1("thread1");       t1.run();       for(int i=0;i<5;i++)            System.out.println(Thread.currentThread().getName());    } }   It gives the following output:  thread1 thread1 thread1 thread1 thread1 main main main main main   Why does the output show its name i.e. thread1? I haven't started the thread yet so it should print "main" all the time.


Freelance for customers outside the US on a B1/B2 visa

I'm a freelancer and I work for customers from Europe (mostly, but no other customer is from US or any related territories). Is it legal for me to work remotely for such customers, during my stay on a B1/B2 visa?  The purpose of the visit would be tourism only, but as I intend to stay for quite a time, I would need to earn some extra money (and prevent my existing business relationships).  I think B visas prohibit working/receiving money from US-based companies only, is that correct?  EDIT: Please note that this is about freelancing - running your own company/self-employment and having business relations with customers rather then working for home company you are permanent employee of.


I wrote this script, but it doesn't work:  #! /bin/bash cront=$(crontab -e) echo 00 23 * * 5 tar -cpzf /var/backup.tar.gz /home/$USER >> $cront   How can I add a cronjob using a script?


can windows virus affect Linux machine through wine?

When we use wine on Linux PC windows Virus can affect folders of wine? I think may be not; But I still Confuse about that. What is accurate answer? Wine is emulator of windows then some question occurred.  1) why windows virus are not affect or affect Linux machine? 2) Is it possible some special viruses are can be able to affect wine? [i.e.Virus can be affect into Wine area. Because Virus also a program. May be possibility it may affect.  Some Key points:- 1)When we install Windows Antivirus in to Wine many (Almost all) antivirus not work properly. Why? 2)Many Programs like Key-logger, worm also not work generally. 3)If we create any program with desire output Delete all .deb .run files. If it work perfectly on wine. Then it can delete hole Linux or partial or not do anything out of wine. Some programs can access Linux Directory out side of Wine.  ex. Google book Down-loader can access Ubuntu desktop. I read link :    But still Confuse here many answers with many views.


How to prove $19\cdot8^n + 17$ is not a prime number?

Prove $19 \cdot8^n + 17$ is not a prime number. (n is a natural number)   How can I prove this statement?


In my ubuntu 14.04, I can not download any program from ubuntu software center - it returns this error message:  Not Found. There isn’t a software package called 'name of the program' in your current software sources.   When I try to install something using ubuntu terminal - it returns this message:  Package fglrx is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'fglrx' has no installation candidate   I tried to change the server and nothing happened.  When I make sudo apt-get upgrade it shows:  The following packages have been kept back: libdbus-1-3:i386 libgl1-mesa-dri:i386 libgl1-mesa-glx:i386 libglapi-mesa:i386 libglib2.0-0:i386 libpango-1.0-0:i386 libpangocairo-1.0-0:i386 libpangoft2-1.0-0:i386 libudev1:i386 libuuid1:i386 0 upgraded, 0 newly installed, 0 to remove and 10 not upgraded."   How do I fix this?


My Epson WF-2540 continuously cycles on and off, it runs a scan check while on. I have no Google cloud services turned on, no firmware updates have been made. Wireless can't be shut off. I have uninstalled it from the PC and re-installed using USB instead of wireless.


What does a ? do in a new Type?[5] assignment?

I have the following piece of code, and I have no idea what the ? means in the construct.  What is it doing?      myObj_Request r = new myObj_Request(); //instantiate intial object r.Channels = new ChannelSequence();    //initial object has another object in channels r.Channels.ChannelType = new ChannelType?[5] { .. } // ok so we have 5 channeltypes...                                                     // but  that ? infront of [5] ?


How to create a centerline from polygon in Arcgis 10

In Network Analyst, I want to create a center line from a road polygon layer of an area for shortest path creation. How do I do this in ArcGIS 10?


How can I send someone a .blend file with cache folder included?

I've been trying to send a person my .blend file with an external cache folder (.bphys format) to render a fire for me, and when he opens it, he can't connect the two. Any solutions?


Calculation & derivation of de-Broglie wavelength

How to calculate the de Broglie wavelength of an $\alpha$ particle that is accelerated through a potential difference of $V$ from rest.


I have placed a plot below another plot in pgfplots. The two plots reside in a separate axisenvironment each, like so:  \documentclass{scrartcl}  \usepackage{pgfplots}  \pgfplotsset{compat=1.12} \begin{document}  \pgfmathdeclarefunction{gauss}{2}{%   \pgfmathparse{1/(#2*sqrt(2*pi))*exp(-((x-#1)^2)/(2*#2^2))}% }  \begin{tikzpicture}[scale = 0.75]   \begin{axis}[axis line style = thick, smooth, no markers,     axis lines = left, axis line style={->}, xmin = 0, xmax = 4, scale     only axis, name = main plot]    \addplot[samples = 200] gnuplot{norm((x-2)/0.75)};   \end{axis}     \begin{axis}[at={(main plot.below south west)}, yshift=-0.3cm,      anchor = north west, axis line style = thick, smooth, no markers,     axis lines = left, axis line style={->}, xmin = 0, xmax = 4, scale     only axis, y = 6cm/3, ymin = 0, ymax = 1.0]    \addplot[samples = 400] {gauss(2, 0.75^2)};   \end{axis}  \end{tikzpicture} \end{document}   What I'd like to do is to draw vertical lines connecting points in the different axisenvironments, like so:    Ideally I would be able to refer to coordinates inside the axis.