Friend of mine, got upvoted for one of his nice answer and got downvoted for same answer by someone without any reason. Even reason for downvote is also not mentioned in comment.  It is assumed that low quality answer or answer with lots of mistakes can get downvoted without reasons, but this was really good answer.  Is there any way to get this down-vote reviewed by moderator as this is real bad experience to have down vote on good answer without proper/silly reason.  Reference is   Note: I think if down-voting is not reviewed because it is personal opinion then it will play big role in case of bounty award question. Please explain.  Update:  Another example is .  Why downvoting should be reviewed if applied for review?  Newcomers coming across the community sometimes get offended due to getting down-votes with no explanation or with no valid reason. Community sometimes trust person by their experience of rewards got (reputations & badges) only.   To grow community with active users, it can be possible to provide such a thing under revision of higher privileged users. Also we can define some rules so that we can reduce 'downvote reviews' less in numbers. (e.g. downvote review can be applied once per week if no comments on downvote present). Of course, there is lot of things that can be build on this, like we had designed review audit (one of smart mechanism).

I've posted a question or an answer, and I have received one or more downvotes. I am not really sure why I was down voted, or I think I know why, but I disagree.  Why did this happen, and what should I do about it?


Now Nvidia with Optimus and glfrx and Bumblebee works fine here.  I want to stay with kernel 3.5.0.22 and not being automatically updated again.  How do I switch off automatic kernel updates?

I am running Ubuntu 12.04.1 LTS i686 on VirtulBox. Every time I check the updates, there's a new Linux kernel. If I install the new kernel, I have to install the Virtulbox Guest Additions again and reboot the server. I don't want to do this every week. I know I can manually uncheck the kernel packages from update manager, but is there a way to skip the kernel update automatically? I found an answer here, but it's for Ubuntu 10. Thanks.


I searched for 15 minutes and to me the syntax still isn't clear... would this:  */5 8,9,10,11,12,13,14,15,16,17,18,19,20 * * *     run the job every 5 minutes from 8(8am) to 20 (8pm)?

This is a  about using cron & crontab.   You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is not answered below then the answers will help you gather information that will help the community help you. This information should be edited into your original question.  The answer for 'Why is my crontab not working, and how can I troubleshoot it?' can be seen below.  This addresses the cron system with the crontab highlighted.


I'm setting this up as a new question because I changed my installation and I thought that might be relevant: previously I was using Wubi, but I felt like that was causing a lot of performance issues (the whole thing ran really slow), so I partitioned my drive and installed Ubuntu 12.04 natively, and it seems to run much faster.  But I still can't get my wireless to work.  I know this question has been addressed elsewhere, and I have honestly tried almost every solution suggested, but it still doesn't work.    My jockey.log says:       2013-09-08 14:50:10,100 WARNING: /sys/module/wl/drivers does not exist, cannot rebind wl driver     2013-09-08 14:50:10,188 DEBUG: BroadcomWLHandler enabled(): kmod disabled, bcm43xx: blacklisted, b43: blacklisted, b43legacy: blacklisted   For further information on my driver, when i run:  lspcci -nn -d 14e4:   I  get:  0c:00.0 Network controller [0280]: Broadcom Corporation CMB4312 802.11b/g LP-PHY [14e4:4315] (rev 01)   Any help would be very much appreciated.

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


I have a $100 US bill that is torn. Can I use the half with the serial numbers to get my money back from a bank?  I tried to use a vending machine and accidentally put in a 100 dollar bill. It tore it in half. I have a half with the serial numbers. Can I get the money back from the bank or the establishment?

The vending machine swallowed half of my $5 bill, and the other half remained in my hand. Can I get my $5 back, or is it all lost forever?


How to interpret white noise test from Stata? Have a white noise means that a variable does not have autocorrelation.  Can I say here that all of my variables has a white noise (does not have autocorrelation)? How can I see it?   wntestq a   Portmanteau test for white noise  ---------------------------------------   Portmanteau (Q) statistic =    28.0682   Prob > chi2(40)           =     0.9221    wntestq b   Portmanteau test for white noise  ---------------------------------------   Portmanteau (Q) statistic =   162.3201   Prob > chi2(40)           =     0.0000    wntestq  c   Portmanteau test for white noise  ---------------------------------------   Portmanteau (Q) statistic =   162.6615   Prob > chi2(40)           =     0.0000    wntestq  d   Portmanteau test for white noise  ---------------------------------------   Portmanteau (Q) statistic =   192.8795   Prob > chi2(40)           =     0.0000    wntestq  e   Portmanteau test for white noise  ---------------------------------------   Portmanteau (Q) statistic =   182.2451   Prob > chi2(40)           =     0.0000    wntestq  f   Portmanteau test for white noise  ---------------------------------------   Portmanteau (Q) statistic =   126.0059   Prob > chi2(40)           =     0.0000

After taking a statistics course and then trying to help fellow students, I noticed one subject that inspires much head-desk banging is interpreting the results of statistical hypothesis tests.  It seems that students easily learn how to perform the calculations required by a given test but get hung up on interpreting the results.  Many computerized tools report test results in terms of "p values" or "t values".  How would you explain the following points to college students taking their first course in statistics:   What does a "p-value" mean in relation to the hypothesis being tested?  Are there cases when one should be looking for a high p-value or a low p-value? What is the relationship between a p-value and a t-value?


Let $a,b,c$ be integers, prove that if $\gcd(a,b) =1$ then $\gcd(ab,c) = \gcd(a,c)\times\gcd(b,c)$  I don't know what to do after I got the combinations of $ab$ and $c$.

How can I prove that if $\gcd(a, b) = 1$, then $\gcd(ab, c) = \gcd(a, c) \times \gcd(b, c)$?  By eea there exists $ax+by=1$ from $\gcd(a,b)=1$ so a and be are co-primes there also exists $dk=a$ and $dj= b$ where $d=\gcd(a,b)=1$ this is all the information I have gathered from the question but I dont know how to approach and solve it. Can anyone help explain to me how to arrive at the answer? Thanks!


I have an ASUS Q500A 64bit notebook with oem installed Windows 8. I am preparing to install Ubuntu 13.04 to dual boot.  Any basic install advice would be nice, will Win8 secure boot, uefi, interfere and how can I get around it.

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


Imagine I have 30 students in a class. In this class, I wish to give 2 apples per student. Consequently, the total number of apples I give out are: $$ \frac{2\text{apples}}{\text{student}}\times30\text{students}=60 $$ apples. We can write this as: $$ 2\times30=2\left(\underbrace{1+1+1+1...1}_{\text{30 times}}\right)=\underbrace{2+2...+2}_{\text{30 times}} $$ My question is as follows (I have asked a similar question, but have not received a satisfactory response in the past): who is the ``first'' 2 in the $2+2..+2$ assigned to? Is there an ordering implict in this sum? Or does this operation speak nothing of the order, except that each student was counted exactly once?

Consider any integer, suppose a number 3. We can break any such integer down into a sequence of 1's. So, we can write: $$ 3\equiv1+1+1 $$ 3 represents what we get when we add 1 to 1 to another 1. Conceptually, what I am getting confused with, is the fact that notionally, at least according to this definition, there is one unit at the beginning, to which we add another, and yet a third. There seems to be a sequence here, which would imply there being an order. Am I missing something obvious?


I was able to install Ubuntu on a mini pc and to configure everything I needed, I lost a lot of time configuring stuff and recompiling part of the kernel following different tutorials on internet. I have also customized unity, now I don't want to loose the same time next time.  Is there a way to create a distribution from what is now in my HDD and be sure that if I install this distro next time on the same machine,or another,  starting from scratch, everything will be exactly how it is now?  (I don't want to create a disk image.)

I installed Ubuntu 14.04.1 on one of my laptops and now I want distribute that exact installation to a few of my friends. I tried making an iso with Gparted on a live session but it makes a 500 GB file (I've only used around 8 GB) .   Thanks in Advance !


I have an Sea-gate 500gb hard disc that is completely dead, i mean when i connect hard disc to my system it is not getting detected.   But i had so much of important data in it, i need those data now. Are there any way to get them back or get it repaired?  Are there any possibilities to recover the data from that dead hard disc from any special hardware???  How can i solve this???

What steps can I take to try to recover lost or inaccessible data from any storage device?  Answers:   This applies to any computer storage device, e.g. internal/external hard drives, USB sticks, flash memory. The most important thing is to STOP using it, any type of I/O can ruin your chances of a recovery.     We have separate questions covering common problems with USB flash drives in greater detail:


Reviving a four year old unanswered question:   This time providing the output pdf files:       Not only font thickness, but microtypography is also different. You'd be able to notice if you open both documents in "maximized" mode, and switch back and forth between the pdfs very quickly (e.g., with Alt-Tab or something similar, I'm using i3wm so it's very easy for me). As an example, in the second word 'ipsum', 'u' is closer to 's' in latex, but closer to 'm' in pdflatex.  How to fix this, i.e., have consistent look of the document?  Since I like the thicker text but use pdflatex for my work, how to reproduce the thicker text in pdflatex?  EDIT 1: So I noticed the thickness is not visible in google pdf viewer, but it's visible in both evince, and zathura pdf viewers. I haven't tested adobe acrobat though.

Why is my document pdf generated by pdflatex looks different from the one generated by latex+dvips+ps2pdf ? From the code below, i have tow different papers switch to the tow cited commands above :  \documentclass[10pt,a4paper]{article} \usepackage[utf8]{inputenc} \usepackage[francais]{babel} \usepackage[T1]{fontenc} \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{graphicx} \usepackage{lipsum} \author{M ROUAN SERIK} \title{Article with \LaTeXe} \fontfamily{cmr} \begin{document} \maketitle \section{Titled section} \lipsum \end{document}   Here's my pdffonts for the tow pdfs : Pdflatex:    name                   type     encoding  emb sub uni object ID   ------------------------------- ---------------- --- --- --- ---------   AMTRHA+SFRM1728        Type 1    Custom   yes yes no       4  0   DPTCLU+SFRM1200        Type 1    Custom   yes yes no       5  0   JVZRKA+CMMI12          Type 1    Builtin  yes yes no       6  0   UEWNID+SFBX1440        Type 1    Custom   yes yes no       7  0   FOVERL+SFRM1000        Type 1    Custom   yes yes no       8  0     latex+dvips+ps2pdf      name                                 type              encoding         emb sub uni object ID   ------------------------------------ ----------------- ---------------- --- --- --- ---------   WVMUEH+SFRM1000                      Type 1C           WinAnsi          yes yes no        16  0   ZHRBNN+SFBX1440                      Type 1C           WinAnsi          yes yes no      14  0   IMJWCD+CMMI12                        Type 1C           Custom           yes yes no      12  0   MDMSVR+SFRM1200                      Type 1C           WinAnsi          yes yes no      10  0   TWHNMT+SFRM1728                      Type 1C           WinAnsi          yes yes no       8  0


If $f$ is a real-valued uniformly continuous function on $A$, then for every Cauchy sequence $(x_n)$ in $A$, $(f(x_n))$ is a real Cauchy sequence.   But why do we need the uniform continuity of $f$ for this?  If $f$ is continuous on $A$ then for any point $c$ in $A$, and any Cauchy sequence $(x_n)$ converging to $c$, $(f(x_n))$ converges to $f(c)$, thus making it a Cauchy sequence.

In $\mathbb R$, all Cauchy sequences are convergent and all convergent sequences are Cauchy. So, why isn't continuity enough to preserve Cauchy sequences?  A function is continuous iff it preserves convergent sequences.  A sequence is convergent iff it is Cauchy.  So, why doesn't it follow that continuous functions preserve Cauchy sequences?


It works (not as I wanted, the loop breaks if there is any 'x' present in the text like 'asdx') if I set condition as c=='x' but not if I put it as s=="x" (so loop breaks only if I type a single x only)  public static void main(String[] args) throws IOException {     InputStreamReader i = new InputStreamReader(System.in);     String z = "";     boolean bool=true;     while (bool==true) {         int x = i.read();         char c = (char) x;         String s = Character.toString(c);         z += s;         if (s=="x") {             bool=false;         }     }     out.println(z); }

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


I'm new here, and I'm learning how to use LATEX. Please, I have a small problem in that the equation number appears an a new line. That is, it is not on the same line as the equation.  \begin{equation} f(l) = a_i*(l-x_i)+y_i     \hspace{1cm}     x_i\leq l\geq x_n \end{equation}

I'm pretty new to LaTeX, completely new actually, and there is one thing I can't quite understand.  I get the error "Display math should end with $$" when writing an equation like this:  \begin{equation}  $R_{2}$=$\frac{U_{R_2}}{I_2}$=$\frac{2,95\, \mathrm{V}$}{$0,03*10^{-3}\, \mathrm{A}$} = 7,10\,\mathrm{k}\Omega \,.  \label{eq:Bsp_OhmsLaw}\end{equation}   I tried a lot of things, I also skimmed these forums. Nothing seemed to help :-(  Thanks in advance!


I want to make content verticle align center with fixing the height. I've tried below css but did not worked. i dont want to use absolute postion method to use and cant change the markup.  row-fluid{display: table;}  .span7{     display: table-cell;     vertical-align: middle; }   HTML:

Pan India search

Search properties by City, Locality or Builder.

   CSS:  .carou-title {     color: #f68500;     font-family: "open-sans",Arial,Helvetica,sans-serif;     font-size: 54px;     font-weight: 300;     line-height: 70px; } .span7{   border:red solid 1px; float:left;   } .span5{ flaot:right;} .carou-sub-title {     color: #2e2e2e;     font-family: "open-sans",Arial,Helvetica,sans-serif;     font-size: 26px;     font-weight: 100;     line-height: 34px;     margin-bottom: 0; }  .row-fluid{ border:black solid 1px; width:800px; margin:0 auto; overflow: hidden;}   ex.

I want to center a div vertically with CSS. I don't want tables or JavaScript, but only pure CSS. I found some solutions, but all of them are missing Internet Explorer 6 support.
Div to be aligned vertically
   How can I center a div vertically in all major browsers, including Internet Explorer 6?


When is it academically correct to use "&" ? In university standard writing can you every use & instead of the word "and"?

Are there rules of usage when using the ampersand "&" instead of "and"?  Are they completely interchangeable?   The ampersand seems more casual, but I'm not sure.


I would like to cite this article from the web:   This is what I have in the body:   \indent The proportion of students cheating in schools vary from country to country. Grimes and Rezek found that the proportion of students involved in cheating is higher in six transtional economies, Belarus, Croatia, Kyrgyzstan, Lithuania, Russia and Ukraine, than in the United States. \cite{grimesrezek} \\   My bibliography section:  \section*{REFERENCES} \bibliographystyle{dcu} \bibliography{eor}  @article{grimesrezek,     author  = "Paul Grimes", "Jon Rezek"     title   = "The Determinants of Cheating by High School Economics Students: A Comparative Study of Academic Dishonesty in the Transitional Economies",     year    = "2005",     journal = "International Review of Economics Education",     volume  = "4",     issue  = "2",     pages   = "23--45" }   This is my preamble:  \documentclass[11pt,reqno]{amsart}  % Packages \usepackage{graphicx} \usepackage{amssymb,amsthm} \usepackage{natbib} \bibpunct{(}{)}{;}{;}{,}{,} \usepackage{xr-hyper} \usepackage[   colorlinks=true,   citecolor=blue,   urlcolor=blue,   linkcolor=blue ]{hyperref} \usepackage{bm} \usepackage{fullpage} \usepackage{ amssymb } \usepackage{caption}  \captionsetup{labelfont=normalfont,               labelsep=colon} \usepackage{mathabx} \makeatletter \def\subsection{\@startsection{subsection}{1}%   \z@{.5\linespacing\@plus.7\linespacing}{-.5em}%   {\normalfont\itshape}} \def\@sect#1#2#3#4#5#6[#7]#8{%   \edef\@toclevel{\ifnum#2=\@m 0\else\number#2\fi}%   \ifnum #2>\c@secnumdepth \let\@secnumber\@empty   \else \@xp\let\@xp\@secnumber\csname the#1\endcsname\fi   \@tempskipa #5\relax   \ifnum #2>\c@secnumdepth     \let\@svsec\@empty   \else     \refstepcounter{#1}%     \edef\@secnumpunct{%       \ifdim\@tempskipa>\z@ % not a run-in section heading         \@ifnotempty{#8}{.\@nx\enspace}%       \else         \@ifempty{#8}{.}{.\@nx\enspace}%       \fi     }%     \@ifempty{#8}{%       \ifnum #2=\tw@ \def\@secnumfont{\bfseries}\fi}{}%     \protected@edef\@svsec{%       \ifnum#2<\@m         \@ifundefined{#1name}{}{%           \ignorespaces\csname #1name\endcsname\space         }%       \fi       \@seccntformat{#1}%     }%   \fi   \ifdim \@tempskipa>\z@ % then this is not a run-in section heading     \begingroup #6\relax     \@hangfrom{\hskip #3\relax\@svsec}{\interlinepenalty\@M #8\par}%     \endgroup     \ifnum#2>\@m \else \@tocwrite{#1}{#8}\fi   \else   \def\@svsechd{#6\hskip #3\@svsec     \@ifnotempty{#8}{\ignorespaces#8\unskip        %\@addpunct.        }%     \ifnum#2>\@m \else \@tocwrite{#1}{#8}\fi   }%   \fi   \global\@nobreaktrue   \@xsect{#5}} \makeatother  \pagestyle{plain}  \setlength{\parskip}{\baselineskip} \setlength{\parindent}{12pt}  \setcounter{secnumdepth}{2}  \allowdisplaybreaks[4]  % Commenting/debugging \let\IG\iffalse \let\ENDIG\fi  %% Shortcuts \newcommand{\td}[2]{\dfrac{d #1}{d #2}} \newcommand{\std}[2]{\dfrac{d^2 #1}{d {#2}^2}} \newcommand{\ctd}[3]{\dfrac{d^2 #1}{d #2 d #3}}  \newcommand{\pd}[2]{\dfrac{\partial #1}{\partial #2}} \newcommand{\spd}[2]{\dfrac{\partial^2 #1}{\partial {#2}^2}} \newcommand{\cpd}[3]{\dfrac{\partial^2 #1}{\partial #2 \partial #3}}  \newcommand{\pdi}[2]{\partial #1/\partial #2}  \newcommand{\LR}{\Leftrightarrow} \newcommand{\Lg}{\mathcal{L}} \newcommand{\half}{\tfrac{1}{2}} \newcommand{\eqp}{\phantom{=}} \newcommand{\eqs}{\buildrel s \over =} \newcommand{\me}{\mathrm{e}}   pdf output:

I have searched the tutorials but have not been successful in understand them. The tutorials always mensionam concepts that I do not know. I would like to understand the basics of BibTeX.  By basics I mean:   How do I install BiBTeX? How to build a file in bib? For this question assume that I already have the bibtex format each reference provided by databases like MathSciNet. See observation 1 below. What I write commands in the file format. Tex to call call the format file bib? How to exploit the format of the bibliography that comes out in PDF? The commands are made in the preamble of the file. Arquifo bib or format. Tex? What must be the BiBTeX with biblatex? Is there any tutorial (in pdf or video) that teaches step by step how to operate BiBTeX?   Observation 1 I already have the bibtex format each reference provided by databases like MathSciNet:   @article {MR2373353,  AUTHOR = {Avila, Artur and Lyubich, Mikhail},  TITLE = {Hausdorff dimension and conformal measures of {F}eigenbaum {J}ulia sets},  JOURNAL = {J. Amer. Math. Soc.},  FJOURNAL = {Journal of the American Mathematical Society},  VOLUME = {21},  YEAR = {2008}, NUMBER = {2},  PAGES = {305--363},  ISSN = {0894-0347},  MRCLASS = {37F35 (37F10 37F25)},  MRNUMBER = {2373353 (2009i:37112)},  MRREVIEWER = {Feliks Przytycki},  DOI = {10.1090/S0894-0347-07-00583-8},  URL = {http://dx.doi.org/10.1090/S0894-0347-07-00583-8}, }


Currently I have opened port 80 and 443 for 192.168.2.40 (My Apache Server) and when I am not in my network, my external IP (68.237.174.32) correctly resolves to the Apache server.   I have a Linksys EA2700 router.  When in my network, I can only use the internal IP address to reach it (192.168.2.40). If I attempt to go to 68.237.174.32 while on my wifi network, I am given a blank page.  What changes do I need to make so that the external IP works while I am in my network?  I want 68.237.174.32 to resolve to 192.168.2.40 while I am within my network.  Note: NAT is enabled.  Thank you!

Even though I have seen and read quite a few similar Q's I was still unable to understand what is required for me to be able to do this.  I have an internal network. One of the machines is a web server. The router is configured for NAT redirecting a specific port to to that machine.  A public domain name is configured using dynamic DNS to point to my external address.  So incoming communication hits the router from its WAN interface and gets pointed to the internal server on the right port.  But if I try to use my public domain name from another machine within my network if fails to be redirected to the server.    In a way I would like that the same NAT rules would apply not only to incoming traffic but to outgoing (sort-of) traffic and have it sent back to the right server.  Assuming this helps, my router (D-Link DSL-2760U) does support static routing, but I am not sure how to configure it. It has the following parameters:   IP Version DstIP/PrefixLength Gateway Interface Metric


I never got the blueprint for a hyper drive parts and now I am stuck in my first star system. I have tried deleting local game content (with and without steam cloud sync) and going into the programs and deleting everything related to NMS. Please help.

Is there a way to start over?  No spoilers here, but after a certain point in the game I wish I had done something different, so I'd like to perhaps start over and make some different decisions based on my current game play experience.


Currently I drilled into the JSE source code for fun. From some tutorials I found a principle two equals objects (i.e. as to object a and b a.equals(b) returns true) must have the same hashcode, on the other hand, two objects with the same hashcode are not necessarily equals. According to the HashTable source code of Java API (), e.g. refer to line 254, we can almost derive equals => same hashcode, but I still can not fully understand why two objects with the same hashcode are not necessarily equals. Anyone can give more reasoning on this? Thanks in advance    Note! This question is more interested in why two objects with the same hash code are not necessarily equals

What issues / pitfalls must be considered when overriding equals and hashCode?


The roots of this polynomial are $(-1)\zeta^n$. Where $\zeta$ is the 5th root of unity.  So the splitting field should just be $\mathbb{Q}(\zeta)$.  This has galois group $\mathbb{Z}/4$ since it's just a cyclotomic extension.  Is this correct?  Source:

I need help to find the Galois Group of $x^5 +1$. I know that it has a 5-cycle and a 4 cycle and is not a subgroup of $A_5$. Thanks!


Given real numbers $a$ and $b$ satisfying $a \leq b$, define:  $$\langle a,b\rangle (x) = \mathrm{min}(b,\mathrm{max}(a,x)) = \mathrm{max}(a,\mathrm{min}(b,x))$$  (These numbers are equal because $a \leq b$. See  for some relevant abstract generalities.)  So basically, the function $$\langle a,b\rangle : \mathbb{R} \rightarrow \mathbb{R}$$ has the effect of "truncating" a real number so as to lie in the interval $[a,b]$.  This function shows up implicitly in one of my applied math homework assignments. We're modelling the amount of fluid in a reservoir; due to rainfall or evaporation, the volume changes, but it always remains between $0$ and $V_\mathrm{max}$, and hence the function $\langle 0,V_\mathrm{max}\rangle$ implicitly shows up in our numerical model.  I'll bet the function $\langle a,b\rangle$ shows up all over applied math, so:     Question. Does this function have an accepted name or notation?

I was surprised to find the clamp function absent from  and . Is this mainly a concept particular to computer programming? Is it known by another name in mathematics? I'll be editing the Wikipedia shortly to include a reference to this function but I want to make sure I'm not omitting some synonymous terms I'm currently unaware of.  $$   \operatorname{clamp}(x) = \max( a , \min( x , b ) ) \in [a,b] $$


I saw that I received the 'Custodian' badge for reviewing suggested edits, but my rep doesn't allow me to review suggested edits.    I don't remember the action that lead to the attribution of this badge, but I never got to review a suggested edit.

I just got awarded the third "Custodian" badge on StackOverflow. Given my current reputation (< 800) I have access to two review queues only. So where did the third badge come from?   When taking a deeper look into my badge history, I got awarded one Custodian badge for reviewing late answers and one for reviewing first posts. The third badge I got was for reviewing an edit made to one of my answers.  Is this the purpose of the Custodian badge - or should it just be awarded for reviews of changes made to other people's posts for >2k users?


I am testing a method in a class. Which is calling a method of abstract class.  Eg:  class abstract Abstract {   public ReturnObject abstractMethod(SomeObject value) {     // do something     return returnObject;   } }  class Concreate extends Abstract {    public ReturnObject concreteMethod(SomeObject value) {    //do something    returnObject = abstractMethod(value);    return returnObject;    }  }  My UT is   class ConcreateTest {   @InjectMocks   private Concreate conctrete;    @Mock   private Concreate conctrete2;    @Test   public void test_method() {      when(conctrete2.abstractMethod(value)).thenReturn(returnObject);      conctrete.concreteMethod(value);   }  }   This way it is returning me NullPointerException.

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


I have Windows 10 and Ubuntu 16.04 on my system. Windows 10 runs on SSD and Ubuntu runs on HDD.   Originally I created a 200 GB partition for Ubuntu. Now I want to format Ubuntu and install from scratch but I have important files on my HDD as well.   How can I just format that 200 GB Ubuntu partition and reinstall Ubuntu 16.04?

I was experiencing problems with Ubuntu Desktop like missing and broken system packages, missing Unity package and other problems. So I decided that the best solution (without touching Windows files) is just to reinstall Ubuntu.  I looked everywhere and found the way but got confused as some say that I supposed to choose "Erase Ubuntu and reinstall", others say that I supposed to choose "Something else" and just select it manually while installation. I thought the first option would be better and just safer as I don’t want any of Windows files to be touched but it says that it has a bug that erases all other partitions...   Current Ubuntu version: 17.04 desktop 32bit will be replaced with 16.04.0 desktop 32bit (as 32bit 17.04 version is no longer available)   What’s the safer option to choose? And if the second one is, how to make sure it’s Ubuntu partition?


A quick google returns the answer on the parity of zero:  Zero is an even number. In other words, its parity—the quality of an integer being even or odd—is even. The simplest way to prove that zero is even is to check that it fits the definition of "even": it is an integer multiple of 2, specifically 0 × 2.  So I know I've answered my own question but I still wanted to ask whether in some respects zero is the only number that is neither even nor odd?

Some books say that even numbers start from $2$ but if you consider the number line concept, I think zero($0$) should be even because it is in between $-1$ and $+1$ (i.e in between two odd numbers). What is the real answer?


As shown in image, I have checked algorithm.cwl, and I am sure I have \usepackage{algorithm} in my source, but the command related to this package cannot auto-completed. Who can tell me why, thank you.

I included the chemfig package to draw chemical stuff in LaTex. But the commands aren't recognized by TeXstudio. I even added the package to the autocompletion list in the settings to get recognized in every document but that doesn't help either.  The commands are red like following:     The file compiles as it should, so everything works except the recognition of the chemfig commands.


Edit: a follow-up question: .  My developer committed a huge mistake and we cannot find our Mongo database anywhere in the server.  He logged into the server, and saved the following shell under ~/crontab/mongod_back.sh:    #!/bin/sh DUMP=mongodump OUT_DIR=/data/backup/mongod/tmp  // 备份文件临时目录 TAR_DIR=/data/backup/mongod      // 备份文件正式目录 DATE=`date +%Y_%m_%d_%H_%M_%S`   // 备份文件将以备份对间保存 DB_USER=Guitang                  // 数库操作员 DB_PASS=qq■■■■■■■■■■■■■■■■■■■■■  // 数掘库操作员密码 DAYS=14                          // 保留最新14天的份 TARBAK="mongod_bak_$DATE.tar.gz" // 备份文件命名格式 cd $OUT_DIR                      // 创建文件夹 rm -rf $OUT_DIR/*                // 清空临时目录 mkdir -p $OUT_DIR/$DATE          // 创建本次备份文件夹 $DUMP -d wecard -u $DB_USER -p $DB_PASS -o $OUT_DIR/$DATE  // 执行备份命令 tar -zcvf $TAR_DIR/$TAR_BAK $OUT_DIR/$DATE       // 将份文件打包放入正式 find $TAR_DIR/ -mtime +$DAYS -delete             // 除14天前的旧备   And then he ran it and it outputted permission denied messages, so he pressed Ctrl+C. The server shut down automatically. He tried to restart it but got a grub error:    He contacted AliCloud, the engineer connected the disk to another working server so that he could check the disk. Looks like some folders are gone, including /data/ where the mongodb is!   We don't understand how the script could destroy the disk including /data/; And of course, is it possible to get the /data/ back?   PS: He did not take snapshot of the disk before.   PS2: As people mention "backups" a lot, we have lots of important users and data coming these 2 days, the purpose of this action was to backup them (for the first time), then they turned out to be entirely deleted.

Please note: The answers and comments to this  question contains content from another, similar question that has received a lot of attention from outside media but turned out to be hoax question in some kind of viral marketing scheme. As we don't allow ServerFault to be abused in such a way, the original question has been deleted and the answers merged with this question.      Here's a an entertaining tragedy. This morning I was doing a bit of maintenance on my production server, when I mistakenly executed the following command:  sudo rm -rf --no-preserve-root /mnt/hetznerbackup /  I didn't spot the last space before / and a few seconds later, when warnings was flooding my command line, I realised that I had just hit the self-destruct button. Here's a bit of what burned into my eyes:  rm: cannot remove `/mnt/hetznerbackup': Is a directory rm: cannot remove `/sys/fs/ecryptfs/version': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/inode_readahead_blks': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/mb_max_to_scan': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/delayed_allocation_blocks': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/max_writeback_mb_bump': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/mb_stream_req': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/mb_min_to_scan': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/mb_stats': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/trigger_fs_error': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/session_write_kbytes': Operation not permitted rm: cannot remove `/sys/fs/ext4/md2/lifetime_write_kbytes': Operation not permitted # and so on..   I stopped the task and was relieved when I discovered that the production service was still running. Sadly, the server no longer accept my public key or password for any user via SSH.  How would you move forward from here? I'll swim an ocean of barbed wire to get that SSH-access back.  The server is running Ubuntu-12.04 and hosted at Hetzner.


I'm using the ZSH bash   I found and followed the directions here to symlink Sublime Text 3 to subl      The first task is to make a symlink to subl. Assuming you've placed   Sublime Text in the Applications folder, and that you have a ~/bin   directory in your path, you can run:  ln -s "/Applications/Sublime Text.app/Contents/SharedSupport/bin/subl" ~/bin/subl    First I had an error, not bin folder in my user directory, so I went ahead and created an empty one, then the command worked.  However I got this error: zsh: command not found: subl  I also added the export path into my .zshrc file export EDITOR='subl -w'  And I still get that error :(

I’m using Mac OS X Yosemite and I want to be able to open Sublime Text 2 from the terminal with a command like this:  sublime .   I’ve typed this into terminal   ln -s "/Applications/Sublime Text 2.app/Contents/SharedSupport/bin/subl" ~/bin/sublime   And also this variant:  ln -s "/Applications/Sublime Text.app/Contents/SharedSupport/bin/subl" /usr/local/bin/sublime   In the terminal, if I type in:  echo $PATH   I get:  /usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin   I’ve tried editing my .bash_profile, right now it’s blank  After all this, I try sublime . and get the following error:     -bash: sublime: command not found   I’m completely new to Mac OS X, and terminal configuration, and am really struggling to figure out why I can't get it to work so any help would be appreciated.


Now that I have what want all the basics and running ok I would like to learn the best way to backup os and data before i attempt my first compile of a basic c++ program then learning python is next unless someone tells me something I sould learn before that.

This question exists because it has historical significance, but it is not considered a good, on-topic question for this site, so please do not use it as evidence that you can ask similar questions here.  While you are encouraged to help maintain its answers, please understand that "big list" questions are not generally allowed on Ask Ubuntu and will be closed per the .   Backup is incredibly important. Obviously there's no best backup tool, but a comparison of the options would be very interesting.   Graphical Interface? Command line? Incremental backups? Automatic backups? Install method: In standard repositories? PPA?


I would like to disable the Workspace app with the command below but cannot seem to find the right package name. Does anyone know the package name? adb shell pm disable-user --user 0 <package_name>

I am using Android 4.0.3 and I can no longer find package name for some app. If I recall, I used to go to Applications and has been able to see it there.   So, how can I see full package name of some app? Like, the app's name is "Test" and I need to see its package com.test.mytest.


Can someone tell me why this code is not hiding elements dynamically added to the html document:  $("p , h1 , h2").mousedown(function(){     $(this).hide(); });   This selection works only with the existing element in the html page, but doesn't work with what I add with after method on the fly. It seems that any new p element or h1 element that get added in the fly doesn't get any recognition from this selector.

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


Because I watched this when I was so young, I might have meld two shows into one.   these people have white jewels in the center of their fore heads to activate their powers, they place their index & middle fingers on their temples. I think they would glow as well I also remember a white, teenage girl with long brown hair as one of the main leads

There was this cool tv show I used to watch as a kid (in the 1990's I think). It was about a world where water was extremely rare and people used to fight over it, however there was this person who had this large 3D polyhedron shaped device (big enough to fit a few people in it) that could synthesise water.  Now, this device was either a time travel device or could just make water (not sure but I remember some time travel aspect as they could either remember the world the way it was where water was plentiful or could travel back to it on occasion).  Anyway, would love to know if this rings any bells?????  It was on in the UK (but maybe the US too, not sure).


Let $x,y,z>0$ and satisfying $3xy+yz+2zx=6$  Find Maximum of this expression: $P=\frac{1}{x^2+1}+\frac{4}{y^2+4}+\frac{3z}{9+z^2}$

Demand $z=x+y$ and $x^2/4 + y^2/5 + z^2/25 = 1$. What is the maximum value of $f(x,y,z) = x^2+y^2+z^2$?   I've been attempting this with Lagrange multipliers in a few different ways. However, the resulting system of equations with two lagrangians has so many variables that it becomes very complicated. Can someone show how this is to be done manually?  I also attempted turning it into two unknowns by replacing $z$ with $x+y$. However, this also led nowhere.


I just read  but I am still not quite sure about the reasoning for the choices. In particular, I'd like to understand exactly what is meant by "content" and "non-content/other" images and why I should use img when I am adding content images to my site and background-image when adding non content images.   Here is my understanding of "content" and "non-content" image:  Content images are those images that are dynamically generated. For example, images of users that are displayed on their profile page and images that are uploaded to a photo gallery, a blog, etc.  Non-content images are those non-dynamic images that are part of the site design. They're "baked in" if you will. E.g. logos, image links, image buttons, etc.  If my definitions are correct - and please tell me if they're not - then it seems to me the reasoning for using each would be as follows (although this isn't exactly apparent in the article linked to, hence my follow up question):   Non content images tend to not change as much as content images. I.e. logos, button images, links with images, etc. tend to stay the same. They're only changed if the site owner decides to redesign the site.  Content images, on the other hand, tend to change frequently. New images are uploaded often, users change their profile images and photo galleries, etc.    So because of the dynamic nature of content images, they need an img tag that can dynamically be modified by whatever tech stack the site is driven by. The not so frequently changing images don't need image tags. They can be loaded from the site design assets directly in the css file for performance and easy maintainability.   Is that about right or am I missing something?

In what situations is it more appropriate to use an HTML IMG tag to display an image, as opposed to a CSS background-image, and vice-versa?  Factors may include accessibility, browser support, dynamic content, or any kind of technical limits or usability principles.


Let $\{a_n\}_{n \geq0}$ and $\{b_n\}_{n \geq0}$ be two real sequences and suppose that $\lim_{n \to \infty} b_n=b \geq 0$ exist. Show that $$\limsup_{n \to \infty}a_nb_n= \limsup_{n \to \infty}a_n \cdot \lim_{n \to \infty}b_n$$  I am stacked on this problem. Could anyone give me a hint?

I´m not sure how to start with this proof, how can I do it? $$ \limsup ( a_n b_n ) \leqslant \limsup a_n \limsup b_n  $$ I also have to prove, if $ \lim a_n $ exists then: $$ \limsup ( a_n b_n  ) = \limsup a_n \limsup b_n  $$ Help please, it´s not a homework I want to learn.


[* MWE ADDED AT BOTTOM *]  I need help understanding the error I am getting on the line with only }. They are marked below...While it doesn't affect anything when I compile it,  I would like to fix it, because any changes I make cause it to not be able to compile. LaTeX Error: Something's wrong--perhaps a missing \item. Any help would be great.   \documentclass[landscape, 12pt]{report}  \usepackage{ocgx} \usepackage{tikz} \usepackage{array}  \newcommand{\myarrow}{\raisebox{1ex}{\tikz \draw[->, line width=1.25mm] (0,0)--++(1,0);}}  \newcommand{\ocgItem}[2]{% \colorbox{% \ifcase#1 \or red\or green\fi }{\huge Item 1}% } \begin{document} \begin{minipage}[t]{5cm} \switchocg{ocg1}{% \fcolorbox{black}{white}{%     \bfseries\Large%     \resizebox{5cm}{!}{\begin{tabular}{c c c c c c c c c c c c c c}   \\ \\ \\   {\Huge Project 1} \\  \\ \\ \\ \end{tabular}}}}\\%     \begin{ocg}{OCG 1}{ocg1}{0}              \colorbox{white}{%                 \parbox{10cm}{%                     \colorbox{green}{\begin{center} \begin{tabular}{m{4.18cm}}    Step 1 \end{tabular} \end{center} }\\%                     \colorbox{red}{\normalsize \color{white}{\begin{center} \begin{tabular}{m{4.3cm}}    Step 2 \end{tabular} \end{center} }\\%                     }%                  } %ERROR ON THIS LINE     \end{ocg} \end{minipage}% \end{document}   [EDIT]  MWE below  \documentclass{article}  \usepackage{xcolor}  \begin{document}     \colorbox{red}{%  \begin{center} \begin{tabular}{c}    Step 2 \end{tabular} \end{center} } %ERROR ON THIS LINE \end{document}

I wanto to center a text in a colorbox which is scaled horicontal over the complete site.    How is this possible?  \documentclass[ ]{scrreprt}  \usepackage[ ]{scrpage2}  \usepackage[ngerman]{babel}                 %% Deutsches Sprachpaket \usepackage[utf8]{inputenc}                 %% Eingabezeichensatz UTF-8 \usepackage[T1]{fontenc}                    %% Kodierung für Umlaute \usepackage[ngerman]{translator}            %% Für Abkürzungsverzeichnis benötigt \usepackage{lmodern}                        %% Moderne Version von Computer Modern \usepackage{setspace}                       %% Zeileabstand anpassen \usepackage{xcolor}                         %% Definieren von Farben  \begin{document}  \chapter{} \definecolor{lightgray}{gray}{0.5} \newcommand \colbox [1]{\par\noindent\colorbox{gray}{\begin{minipage}{\textwidth}{ {#1}} \hfill \end{minipage}}}  \colbox{TEXT}  \end{document}   Moreover I want to avoid the overfull hbox.


I don't know the difference between how we make a car and how do we make a car.   I searched on the internet; there are examples for both but I do not understand in which cases they would each be used.

This question is inspired by comments on . The original poster wrote:     How to correct this error?   And comments say that it's an incorrect question. Better is     How do I correct this error?   I am not a native English speaker, so the fact that both versions sound natural to me is quite irrelevant. But I would like to ask anyway whether the first version is really bad.  I have seen a lot of questions starting with How to, so if you say that the first version is incorrect, could you please summarize when it is OK to use How to and when it is preferable to say How do I.


I am using TeXstudio to edit Latex and create pdf files. The text is not smooth in the pdf files created by TeXstudio in my computer. When I zoom in, it will be   But if I use my friend's computer to generate the pdf files, it will be like below when I zoom in to see    Both computers have Windows 7 as OS, same Version of TeXstudio. What settings should I change to make the text smooth?  Edited:  I created two pdf files from same .tex files by TeXstudio in my and my friend's computers. The files can be downloaded in below link

I have the following LaTeX-document:  \documentclass[a4paper,11pt]{article} \usepackage[utf8x]{inputenc} \usepackage[ngerman]{babel}  \usepackage[T1]{fontenc}  \title{Sample} \author{Litb}  \begin{document}  \maketitle  \begin{abstract}  This is a report about my praxis phase at the company foo bar which I enjoyed. \end{abstract}  \end{document}   Much to my frustration, compiling with pdflatex creates a document with Bitmap-fonts. The reader's font-list shows that it uses Type3 fonts.  If I remove the fontenc loading, then I get a PDF using vector-fonts, but I heard that I should keep it, for having native German Umlauts working.  Does anyone know how I can get vector fonts with T1, and why it keeps using bitmap fonts if I have that package-load line in it?


So we have square matrices $A$ and $B$. Now suppose $A^2$ and $B^2$ are similar, does it follow that $A$ and $B$ are similar? I don't think so, but I'm having trouble showing is not.  My attempt: If $A$ is similar to $B$, and $A$ is similar to $C$, then $B$ is also similar to C. More importantly, $A$ is similar to the diagonal matrix of its eigenvalues, then $B$ must also be. So $A$ and $B$ have the same eigen values. But then I realised that this question doesn't even make the assumption that $A$ and $B$ are invertible, so they may or may not have those eigen values.  Can someone give me some hints to this question? If this is a proof by counterexample, is there at least some way to narrow the possible contradictions down by some theorem?

I know that the converse is true; that is, if A and B are similar matrices, then $A^2$ and $B^2$ are similar . However, I'm not sure about the reverse.


Evaluate: $$\int_{0}^{1} \frac{\ln^k x}{x+1}$$   It looks like the only way to start this is to use that $$\frac{1}{x+1}= \sum_{n = 0}^{\infty} (-1)^n x^n $$ Then we have to evaluate $$\int_{0}^{1} {\ln^k x}\sum_{n = 0}^{\infty} (-1)^n x^n = \int_{0}^{1} \sum_{n = 0}^{\infty} (-1)^n x^n{\ln^k x}=\sum_{n = 0}^{\infty} \int_{0}^{1}(-1)^n x^n \ln^kx$$  For $k = 1$, it comes to be $\frac{\pi^2}{12}$ For $k = 3$, it comes to be $\frac{7\pi^4}{720}$ So, there is $\zeta(k+1)$ involved. EDIT: After trying for different values of  $k$ it seems like the integral evaluates to be $(1 - \frac{1}{2^k}) \zeta(k+1)$ Any help would be appreciated.

I would like to show the following identity:     $$\boxed{ I :=  \int_0^1 \dfrac{(\ln(x))^5}{1+x} \mathrm{d}x = -\dfrac{31\pi^6}{252} }$$     Here is what I tried. The change of variables $u=1/x$ yields $$I= \int_1^{\infty} \dfrac{(\ln(x))^5}{1+1/u} \dfrac{1}{u^2} \mathrm{d}u = \int_1^{\infty} \dfrac{(\ln(x))^5}{u^2+u} \mathrm{d}u$$ Then $z=u-1$ gives $$I = \int_{0}^{\infty} \dfrac{(\ln(z+1))^5}{z^2+3z+2} \mathrm{d}z $$ with $z^2+3z+2=(z+1)(z+2)$. I wanted to use contour integration like , but I was not sure how to proceed in this case. Anyway, the computations of the residues (of which "well-chosen" function? Maybe something like ?) seem to be difficult.  I believe that we can generalize to $\frac{(\ln(x))^n}{1+x}$, or maybe even more (e.g. $\frac{(\ln(x))^n}{ax^2+bx+c}$). Related computations are: , , , .  Thank you for your detailed help.


I have a question,I'd like to send data using method post using ajax call,so I do like that:          jQuery.noConflict();          jQuery(document).ready(function () {         $("input#submit").click(function(){             $.ajax({                 type: "POST",                 url: "ajax?uid="+<?php echo   $sf_user->getGuardUser()->getId() ?>+"fid="+<?php echo $user->getId() ?>+"fn="+<?php echo $user->getfirstName() ?> +"ln="+<?php echo $user->getlastName() ?>, //                  data: $('form.contact').serialize(),                 success: function(msg){                     $("#thanks").html(msg)                     $("#form-content").modal('hide');                    },                 error: function(){                     alert("Something is wrong!");                 }             });         });     }); </script>   But It seems not working for me, i get this strange error :   ReferenceError: Jean is not defined url: "ajax?uid="+1+"fid="+13+"fn="+Jean +"ln="+paul, //   Very strange because when I remove fn and ln and I keep just the number value it works very well?

What is the easiest way to encode a PHP string for output to a JavaScript variable?  I have a PHP string which includes quotes and newlines.  I need the contents of this string to be put into a JavaScript variable.  Normally, I would just construct my JavaScript in a PHP file, à la:  <script>   var myvar = "<?php echo $myVarValue;?>"; </script>   However, this doesn't work when $myVarValue contains quotes or newlines.


I have two independent Poisson distributed random variables: $\xi$ with parameter $\lambda$ and $\eta$ with parameter $\mu$. I need to show that $${{(\xi - \lambda) - (\eta - \mu)}\over{\sqrt{\xi + \eta}}} \rightarrow N(0,1)\:as\:\lambda,\mu\:\rightarrow\infty $$ where $N(0,1)$ is standard normal distribution. I've tried to do it using the fact that Poisson distribution with parameter $\lambda$ can be approximated by Normal when $\lambda$ is large enough, but i am confused with calculatng the ratio of random variables.Will be very glad for any hints.

Let $X_n$ , $Y_m$ be independent Poisson variables with means $n$, $m$.  $$\frac {X_n -Y_m -(n-m)}{\sqrt{X_n+Y_m}}$$  Find the limiting distribution as $n,m \to \infty$  I know that $\frac{X_n-n}{\sqrt{n}} \to N(0,1)$ but don't know what the next step would be.


I've got custom content-type with several groups and fields. I wanted to change default display of that content-type. I created the node--my_content_type.tpl.php file, and copied the node.tpl.php file into it. Mostly, I want to change display of fields of that content-type, but in that file I've got only a line.   print render($content);   So, I don't have the opportunity to chance display of fields. I want to have field1 on the left and field2 on the right, not one after another as its default.  Could someone help me, please?

I've got custom content-type with several groups and fields.   I want to change default display of that content-type. In which file can I find appropriate code?


i installed ubuntu from a usb instead of running alongside windows i made it the main os... i now have a laptop with ubuntu on it and i really want windows back on the pc  *ive tired sticking the windows recovery disc in nothing   ive tried booting from recov disc nothing .. is there anyway i could earse everything and start from scratch   my computer is "hp pavilion p6536f-b pc bundle"

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


I am implementing a bit of security in a system that was originally built without encryption on a specific piece of data. The plan was to encrypt this piece of data and include it as part of the response in a web service. But this data is plainly available in the front end so the user could easily see the plain value and its encrypted value. How hard is it to derive the key and iv? I think it would be too easy to be comfortable with. Am I right? Is there any security worth doing if they can always see the plain value?

I have a file, which was encrypted with AES-128 in ECB mode. I know the format of the original file and know that all files in this format have the same headers. So, I have an encrypted block and the original block.  Can I get the encryption key, using this information?


I need to get all Assets X with X.ParentId != NULL, and the X.Parent.AccountId != X.AccountId.  SELECT AccountId,Id,ParentId,Parent.AccountId,RecordTypeId,RootAssetId FROM Asset WHERE ParentId != NULL AND Parent.AccountId != AccountId AND RecordType.DeveloperName='RecTypeABC' limit 10   The SOQL above fails with a MALFORMED_QUERY error.  Any idea how to do this?  Thanks

I think I may be hitting some sort of SOQL limitation in the WHERE clause. I am trying to return fields from two parent objects, after comparing two date fields on both Objects.  The goal is to have a list of contacts with associated opportunity fields where the opportunity date field is equal to some contact field.     NOTE: We have a custom junction between Opportunity and Contact named "Opportunity_Contact__c" due to the limits on the standard OCR sObj.   Specifically:  SELECT NAME, Con_Custom_Date__c,   (SELECT Opportunity__r.Name FROM Opportunity_Contacts__r     WHERE Contact__r.Con_Custom_Date__c = Opportunity__r.Opp_Custom_Date__c) FROM Contact   This returns a parsing error. However, if I try switching the query to something like:  SELECT NAME, Con_Custom_Date__c,   (SELECT Opportunity__r.Name FROM Opportunity_Contacts__r     WHERE Contact__r.Con_Custom_Date__c = TODAY and Opportunity__r.Opp_Custom_Date__c = TODAY) FROM Contact   This works. So the date fields are working and I am able to use them in the WHERE clause. However, when I compare one field directly to the other, I get a parsing error..  Why would   WHERE Contact__r.Con_Custom_Date__c = TODAY and Opportunity__r.Opp_Custom_Date__c = TODAY   work while   WHERE Contact__r.Con_Custom_Date__c = Opportunity__r.Opp_Custom_Date__c   triggers a parsing error?  Thanks!


I have installed QGIS 2.14.1,  I am looking for the OpenLayers Plugin which I could not find under Install Plugins, as well as Web menu.

I have been trying to teach myself QGIS by using this forum and others to help. Most of my questions can be answered by downloading plugins that are available through 3rd party repositories but for some reason I am not able to connect with these. Anyone have any ideas why this is the case?


Find a closed formula for $\sum_{n=1}^\infty nx^{n-1}$  I am trying to use the derivative of generalized binomial theorem, $\frac{d}{dx}[(x+1)^r=\sum_{n=0}^\infty \binom{r}{n}x^n] =r(x+1)^{r-1}=\sum_{n=1}^\infty \binom{r}{n}nx^{n-1}$  However, I am not sure how to "get rid" of the binomial term.

How can you evaluate $\sum_{n=1}^\infty nx^{n-1} = \frac{1}{(1-x)^2}$ without relying on the fact that it's the derivative of $\sum_{n=1}^\infty x^n = \frac{1}{1-x} $?


My 2 year and 10 month old started to poo into the potty 3 months ago, he would have a bowel movement once a day since then, but it only lasted for 4 days. He now wants his diaper all the time, and he just "dislikes", "refuses", or "hates" when I try to sit him down on the potty. When I asked/said, "let's poop", he hates it!  I started to put just underwear on him yesterday, and of course, he has many accidents, he even poops in the underwear! Should I still put underwear on him? or sit him on the potty frequently? Or should I just still continue with the diapers?

I spent three days this weekend (took a day off work) potty training my 2.5 year old daughter. She has been showing signs of being ready for a while - telling me when she wets her diaper, talking about the potty etc.   I used a more relaxed version of the Nathan Azrin method, basically practicing with a doll first, and then giving her an m&m for "dry checks" (she checks to see if she's dry), and 2 m&ms and a "prize" from a prize box everytime she went in the potty. I didn't train for naptime or bedtime, and used a pullup for sleeping for now.   The first two days went really well, and she only had one accident the second day. She even pooped in the potty the first day. The second day, she seemed to be doing well with the pee, but was holding her poo in, and eventually ended up pooping in the bath in the evening of the second day :(  The third day, she was just unhappy and seemed to be regressing, not wanting to sit on the potty and holding her pee in. She didn't have any accidents the third day, but was holding her pee (she seems to have great bladder control!) and would go to pee only if i insisted she try sitting on the potty. She didn't poop at all the third day, and was way constipated by the evening. We gave her prune juice, which helped her poo in her diaper while in her bed the morning of the fourth day (which is today).   I'm trying not to be negative, or frustrated, but she just seems to be scared of the potty now, and I'm not sure what I did wrong, or what I can be doing to fix this problem. Help!


I'm on a shared sever without sudo.  I'm using a program running off mono that crashes frequently on a Debian server.  What's the best way to have the process auto-restart?

I have a process which is executed by init.d script on the background. Eg:  case "$1" in      start)        /bin/myprocess &     stop)        killall myprocess     restart)        killall myprocess        /bin/myprocess & esac   In certain conditions, myprocess can fail and return. Is there any (standard) way how to detect its fail and restart in automatically?


Suppose $1 \leq p<\infty$, given $f \in L^p (\mathbb{R})$, define $f_n (x)=n^{1/p} f(nx)$ for n=1,2,3... Prove $f_n$ converges weakly to zero in $L^p$.  Now I can just know the that $ \|f_n\|_p$=$ \|f\|_p$, but cannot prove for any function $g \in L_q$, where $q$ is the conjugate of $p$, the integral converges to zero.  i.e. how to show $\int f_ng$ converges to zero. I'm thinking maybe I can use step functions or continuous functions since they are dense in Lp, so we can approximate, but not sure.

Let $f\in L^p(\mathbb{R}^d)$, with $1<p<\infty$. Is it true that    $$\lambda^{\frac{d}{p}}f(\lambda x ) \rightharpoonup 0\quad \text{ weakly in }L^p\text{ as }\lambda\to+\infty?$$   One has the easy case for $f\in L^{p-\epsilon}\cap L^p$. This condition allows the use of Hölder's inequality as follows (here $\frac{1}{p}+\frac{1}{p'}=1$ and $\phi$ is a continuous function with compact support):  $$\begin{split}\left\lvert \int_{\mathbb{R}^d} \lambda^{\frac{d}{p}} f(\lambda x)\phi(x)\, dx\right\rvert& \le \lambda^{\frac{d}{p}}\lVert f(\lambda x)\rVert_{L^{p-\epsilon}}\lVert \phi\rVert_{L^{(p-\epsilon)'}} \\  &= \lambda ^{\frac{d}{p}- \frac{d}{p-\epsilon} } \lVert f\rVert_{L^{p-\epsilon}}\lVert\phi\rVert_{L^{(p-\epsilon)'}}\to 0. \end{split} $$ But what happens if that condition is removed? I carried out an explicit check on the standard example of a function $f$ that belongs to $L^2(\mathbb{R})$ and does not belong to $L^{2-\epsilon}(\mathbb{R})$ for any $\epsilon > 0$, namely  $$f(x)=\begin{cases} 0 , & x<2 \\ \frac{1}{\sqrt{x}\log x}, & x \ge 2\end{cases}.$$ Taking $\phi=\chi_{[a, b]}$ with $2<a<b$ one has  $$\left \lvert \int_{\mathbb{R}} \lambda^{\frac{1}{2}}f(\lambda x)\phi(x)\, dx \right\rvert  = \dfrac{  \int_{\lambda a }^{\lambda b} \frac{dy}{\sqrt{y}\log(y)} } {\lambda^{\frac{1}{2}}}, $$ and an application of l'Hôpital's rule shows that the right hand side tends to $0$ as $\lambda \to \infty$. This implies weak convergence to $0$ by a standard density argument.   This seems to point towards an affirmative answer to the question in the gray box.


I upgraded my ubuntu to 12.04 through software center and it did not go well. The problem is I'm using this machine after a long time that I don't remember the previous version no (definitely greater than 10.0)  Machine: Asus A8ESeries  The font colors changed to white, it did not detect ext hard drives. I did an upgrade from terminal and now I get the following problems:   The text font color on all windows changed to white The track pad did not work (Which I fixed using this thread ) Network menu not showing wireless option itself. My output for "dmesg | grep iwl" and rfkill list all are blank External hard disk not detecting. I need to back up my files before upgrading again. unity one launcher not working.  no menus at the top right corner and many more failures.    I really need to back up my files which is the most important task. Also get my wireless working. Please kindly help.  Regards, psun

First, I hope that this is not a duplicate, because I found my question quite strange and unique, and I don't have any idea with it.  These days I heard of the new Ubuntu release, version 13.10 and I am quite excited. I have been stuck in 12.04 for such a long time and it's time for a good upgrade. So...I ran update-manager -d and tried to go up to 12.10. (I decided to go up one by one) It took a very long time to download all the required kernel and packages...and soon installing...and some questions asking me if I want to replace the old config files. I did some tweaking with that system before (changing startup applications, TMPFS, zram-enabler, etc) and I thought that it will cause a real crash if I keep these config files. So, I replaced all of them but it goes too slow and it's time I've to go to school. I asked my grandfather if he could help me to click all the 'Replace' buttons for me and shut down the computer after the upgrade finished.  When I was back from school, he told me that he accidentally clicked 'Keep' for the last popup box, and my computer can't function now. The grub menu is still there (made it appear by using the SHIFT key trick), and the splash screen is still visible, and I hope that the login screen is still there, or at least the tty so that I can still do a rescue, but nothing worked. CTRL+ALT+F1 does nothing, and I am sure that the monitor is still functioning.  So what can I do now?


Classify groups that are generated by two elements $x$ and $y$ of order 2.  Could someone help me please ?

Prove a finite group generated by two involutions is dihedral   Is my following argument correct?  Let $G=\langle x,y\rangle$ be a group generated by involutions $x,y$. Let $n=\mathrm{ord}(xy)$ to get a presentation $G=\langle x,y\mid x^2=y^2=(xy)^n=1\rangle $ so G is dihedral of order $2n$ ?  Further note: I realise now my argument is not sufficient as it remains to show $G$ has no other relations.  I just found an idea from a reference which claims "...So $G$ must have a presentation of the form $G=\langle x,y\mid x^2=y^2=(xy)^m=1\rangle $, then one has to show $m=n$..." in which I do not understand why $G$ has exactly a presentation of such form (the presentation inovlves $m$)? That reference also showed $|\langle x,y\rangle |=2n$ which directly led to the conclusion: $m=n$


My friends ask me to build him a web server with 12.04 64-bit server edition in his 1GB RAM server.  Is it recommended or safe? Because I heard 64-bit system need at least 2GB RAM.

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


How can I assign value of $x1+$x2 to bc by piping? here in my code $bc holds no value.  echo -n 'value x1 : ' read x1 echo -n 'value x2 : ' read x2 echo $x1+$x2 | bc echo $bc

I want to assign the result of an expression (i.e., the output from a command) to a variable and then manipulate it – for example, concatenate it with a string, then echo it.  Here's what I've got: #!/bin/bash cd ~/Desktop; thefile= ls -t -U | grep -m 1 "Screen Shot"; echo "Most recent screenshot is: "$thefile;  But that outputs: Screen Shot 2011-07-03 at 1.55.43 PM.png Most recent screenshot is:   So, it looks like that isn't getting assigned to $thefile, and is being printed as it's executed. What am I missing?


I found a couple examples with that word:     The song feels apropos to a midnight jaunt      Clothes that are apropos to the occasion   I'm interested in can we use that following the verb of action. For instance, if I want to express something like the following:  My frined come to my house and bring some candies with him. Could I say It's apropos that you bought the candies, I just have made a tea.

Which is more correct:     Apropos of your earlier comment, I decided to....   or      Apropos your earlier comment, I decided to...   Actually, apropos is so fancy a word, even I, a word maven if I do say so myself, am not entirely sure when to use it.  If I may add to my preposition question, are there any constructions where it would be appropriate to use something like with regard to and not apropos?


For a project at school we need to program a game in JavaFx, we're almost ready with the game but I get a strange error when I use the intersects command (see attachment 1) . In the second and third attachment are the constructors which I use in those line where the error is  . and the last attachment is the ouput window with the error lines .  I already have read the section on this site over NullPointerException but I cant find the fault.  Main code:  if (kogelView.getBoundsInParent().intersects(enemyView1.getBoundsInParent()))             {                    enemyDoodModel1.setXDodeEnemy(enemyModel1.getX());                   enemyDoodView1.UpdateEnemyDood(enemyDoodModel1);                    enemyDoodModel2.setXDodeEnemy(enemyModel2.getX());                   enemyDoodView2.UpdateEnemyDood(enemyDoodModel2);              } }   constructor_1:  public void setXDodeEnemy(int xPos)     {         this.xDood = xPos;      }   constructor_2:  public int getX()     {         return this.xEnemy;      }

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


I have a problem with the automatic punctuation while using \footcite:   I use references whith titles ending with a dot (e.g. 'Die Reichstuerkenhilfe in der Zeit Karls V.'). The dot is part of the title and has to be part of the citation. When I cite several titles, the titles are separated by semicolons (;), and when I add some information after a cited title, this is separated from the title by a comma (,). My problem is: When I cite a title with a dot in the end, the semicolon or comma is automaticly supressed.    How can I make biblatex showing both, the dot, which ist part of the cited title, and the semicolon or comma, which indicate the end of the title? There has to be a mechanism which prohibits several punctuation signs without space in between.  This is the biblatex part of my document's head:  \usepackage[backend=biber,                     style=authortitle-dw,                     namefont=smallcaps,                     idembib=false,                     idemtracker=false,                     ibidtracker=false,                     edbyidem=false,                     edsuper=true,                     sortlocale=de_DE,                     url=false,                      doi=true,                     eprint=false]                     {biblatex}   \renewcommand*{\labelnamepunct}{\addcomma\space }  \renewcommand*{\nametitledelim}{\addcomma\space }  \renewcommand*{\newunitpunct}{\addcomma\space }

I would like to consistently have a comma between the journal and volume number for article references using biblatex with biber as the backend. Unfortunately, the punctuation between the journal and volume is not consistent. Journals whose last word is abbreviated have no comma between the journal and the volume, and the word "Vol." is capitalized. Journals whose last word is not abbreviated have a comma and the word "vol." is not capitalized. I can fix the capitalization by un-commenting the commented lines in the below MWE, but the comma problem is quite perplexing. Apologies if this fix is in an answer somewhere, but I cannot find it (or at least, I don't know what to search for!).  Current output: [1] First Author. “Blah Blah 2”. In: Am. J. Phys. Vol. 72, no. 3 (Mar. 2004), pp. 367–375. [2] Second Author. “Blah blah”. In: Energy Fuel, vol. 27, no. 12 (Dec. 2013), pp. 7778–7789.  Expected output: [1] First Author. “Blah Blah 2”. In: Am. J. Phys., vol. 72, no. 3 (Mar. 2004), pp. 367–375. [2] Second Author. “Blah blah”. In: Energy Fuel, vol. 27, no. 12 (Dec. 2013), pp. 7778–7789.  MWE:  \documentclass{article} \usepackage{filecontents} \usepackage[     backend=biber,     citestyle=numeric-comp, ]{biblatex} \addbibresource{\jobname} % \DefineBibliographyStrings{english}{%     % volume = {\lowercase{v}ol\adddot}, % avoid capitalization after dots. % } \DeclareFieldFormat[article]{volume}{\bibstring{volume}\addspace #1} \DeclareFieldFormat[article]{number}{\bibstring{number}\addspace #1} \renewbibmacro*{volume+number+eid}{%   \printfield{volume}%   \setunit{\addcomma\space}%<---- was \setunit*{\adddot}%   \printfield{number}%   \setunit{\addcomma\space}%   \printfield{eid}} \renewbibmacro*{journal+issuetitle}{%   \usebibmacro{journal}%   \setunit*{\addcomma\addspace}%<---- was \setunit*{\addspace}%   \iffieldundef{series}     {}     {\newunit      \printfield{series}%      \setunit{\addspace}}%   \usebibmacro{volume+number+eid}%   \setunit{\addspace}%   \usebibmacro{issue+date}%   \setunit{\addcolon\space}%   \usebibmacro{issue}%   \newunit}  \begin{filecontents*}{\jobname.bib} @article{York2004, author = {Author, First}, journal = {Am. J. Phys.}, month = mar, number = {3}, pages = {367--375}, title = {{Blah Blah 2}}, volume = {72}, year = {2004} } @article{Baumgardner2013a, author = {Author, Second}, journal = {Energy Fuel}, month = dec, number = {12}, pages = {7778--7789}, title = {{Blah blah}}, volume = {27}, year = {2013} } \end{filecontents*}  \begin{document} \nocite{*} \printbibliography \end{document}


I have a problem undestanding the correspondance of my data to my principal components in PCA. I have a dataset of 50 columns and 20 samples. I use the mapcaplot to apply the PCA algorithm and come up with my plot. However I am unable to understand the meaning of the axes (PC1 and PC2) and therefore understand the linear combination of each of my variables. I also ran the pca algorithm and come up with the coeff matrix, the latent and scores. Still I cannot understand it. Could anyone point me to the right direction please?

In today's pattern recognition class my professor talked about PCA, eigenvectors and eigenvalues.   I understood the mathematics of it. If I'm asked to find eigenvalues etc. I'll do it correctly like a machine. But I didn't understand it. I didn't get the purpose of it. I didn't get the feel of it.        I strongly believe in the following quote:     You do not really understand something unless you can explain it to your grandmother. -- Albert Einstein   Well, I can't explain these concepts to a layman or grandma.   Why PCA, eigenvectors & eigenvalues? What was the need for these concepts? How would you explain these to a layman?


Problem  Find all pairs of $a$ and $b$ such that $ab = a+b, \: \: a,b \in \mathbb{Z}$ is true.  If I divide both sides by $ab$ I get $$1 = \frac{1}{b}+\frac{1}{a} $$ From this equation I can only find one pair that makes this equation true, and that is $a=b=2$. Is this really the only pair of integers? And is this enough of a "proof" or do I need something more, whatever that may be?

Find all solutions to $$xy=x+y$$ Initially the given condition was $x,y\in \Bbb{Z}$.    $$$$In this case, I just guessed that the solutions were $(0,0)$ and $(2,2)$. As far as I can see, these are the only 2 integral solutions possible. However, i'm quite surprised as usually a Diophantine Equation has infinite solutions. Could somebody please show me how to actually $solve$ this equation instead of just guessing the values? Is there any way to $show$ that there are just 2 sets of solutions?  $$$$Secondly, what if $x,y\in \Bbb{R}$? In that case how could the equation be solved? $$$$For both these conditions on the values of $x,y$, is there any way to use Coordinate Geometry to achieve an answer? $$$$ Many thanks in anticipation!  Edit: I forgot to mention that I know the solution using factoring. I was hoping to find a solution using Coordinate Geometry. I was told by a friend that the non integral solutions lie on 2 unique lines, and am hence particularly interested in a geometrical solution.


Let $H_1 , H_2 , ... , H_k $ be subgroups of $G$ and $x_1,x_2,... ,x_k$ be elements of $G$ such that $G=\cup_{i=1}^k x_iH_i$ , then how do we prove that some subgroup $H_i$ has finite index in $G$ ?

This question appears in my textbook's exercises, who can help me prove it?     If a group $G$ is the set-theoretic union of finitely-many cosets, $$G=x_1S_1\cup\cdots\cup x_nS_n$$ prove that at least one of the subgroups $S_i$ has finite index in $G$.   I think that the intersection of these cosets is either empty or a coset of the intersection of all the $S_i$. I want to start from this point to prove it. So I suppose none of these $S_i$ has finite index, but I don't know how to continue?


I heard an opinion that linear algebra has ceased to develop 100 years ago because there's nothing else to "discover" in this branch of mathematics, and no scientific activity other than teaching occurs in this field.  Is this true?

In , it was discussed how LA is a foundation to other branches of mathematics, be they pure or applied. One answer argued that linear problems are fully understood, and hence a natural target to reduce pretty much anything to.   Now, it's evident enough that such a linearisation, if possible, tends to make hard things easier. Find a Hilbert space hidden in your domain, obtain an orthonormal basis, and bam, any point/state can be described as a mere sequence of numbers, any mapping boils down to a matrix; we have some good theorems for existence of inverses / eigenvectors/exponential objects / etc..  So, LA sure is convenient.  OTOH, it seems unlikely that any nontrivial mathematical system could ever be said to be thoroughly understood. Can't we always find new questions within any such framework that haven't been answered yet? I'm not firm enough with Gödel's incompleteness theorems to judge whether they are relevant here. The first incompleteness theorem says that discrete disciplines like number theory can't be both complete and consistent. Surely this is all the more true for e.g. topology.  Is LA for some reason exempt from such arguments, or does it for some other reason deserve to be called the best understood branch of mathematics?


I have posted a  and I liked all the comments and specially both answers that were given to my question.  Both answers were very good, I just chose the one I did on the grounds of the links provided were more to my liking but I appreciated both of them answers and both are correct too, basically there were no legions stationed in London, but a fort was there.  I wanted to show my gratitude to the people who wrote those answers, other than upvoting those answers, is there anything would be proper(according to the rules of the site) to do?

Quite often a number of users will give similar answers to one of my questions. Sometimes someone will give an answer that is interesting, but does not really help with my question.  In all cases, I feel a need to thank the people who answered my question. It isn't always appropriate for me to upvote every answer, and I can only accept one answer. Giving a "thanks" comment on every answer appears to be frowned upon.  So, what's the etiquette?


I am trying to solve this question but am not able to understand how to approach it: What is the polar of an ellipsoid described by the equation:  {$(z_1, . . . , z_d) ∈ R^d: a_1z_1^2 + · · · + a_dz_d^{2} ≤ 1$}, where $a_1, . . . , a_d$ are positive.  I know what generally polar of a set means. Moreover, I am following Algebraic And geometric ideas in the theory of discrete optimization to understand more about the polar of a subset. This link gives a beautiful explanation of how to find polar of various set   I'm trying to approach it the way you solve for a disc but I am still unable to do it. Any help is appreciated Thank you.

The polar of a convex body $C$ is defined as:  For a convex body $C$, its polar $C^*$ is given by $$C^* = \{x\in\mathbb{R}^n: \langle x,c\rangle \le 1, \forall c\in C\}$$  If I start with an orthonormal basis $(e_i)_1^n$, positive constants $(\alpha_j)_1^n > 0$ and the ellipsoid $$\varepsilon = \left\{x\in\mathbb{R}^n: \sum\limits_{j=1}^n \frac{\langle x,e_j\rangle^2}{\alpha_j^2} \leq 1  \right\}$$ how do I show that its polar ellipsoid is $$\varepsilon^* = S_1 = \left\{y\in\mathbb{R}^n: \sum_{j=1}^n \alpha_j^2 \langle y,e_j\rangle^2 \le 1\right\}$$ Using the definition, I saw that $$\varepsilon^* = S_2 = \{z\in\mathbb{R}^n: \langle z,x\rangle \le 1, \text{for all }x\in \varepsilon\}$$ Also, $\langle z,x\rangle = \sum_i\langle z,e_i\rangle\langle x,e_i\rangle$ I used Cauchy Schwartz to do one side of the proof, i.e. $S_1\subseteq S_2$: $$\left(\sum_i\langle y,e_i\rangle\langle x,e_i\rangle\right)^2 \leq \left(\sum_i\alpha_i^2 \langle y,e_i\rangle^2\right)\left(\sum_i \frac{\langle x,e_i\rangle^2}{\alpha_i^2}\right) \le 1 \implies \langle y,x\rangle \le 1$$ I need help with the other direction, i.e. $S_2\subseteq S_1$. Which other inequality might help?


Is it unusual for a 15 months old to fill her mouth with food? She does this fairly often, especially with food she likes, then she realizes her mouth is too full and spits.  We tell her to chew and to take a piece at a time, or to bite off chunks, but it doesn't work every time.  I don't know if this is relevant, but she has always been a fast eater, she was breastfed and it took her about 10 minutes for a full meal

My 20-month-old daughter, given the opportunity, will stuff her cheeks full of food she likes (especially cheese, raisins, or green beans) to the point where it's difficult for her to chew or swallow.  When this happens, she'll work on the food for a little while and then remove it by hand and give it to me (at least she doesn't throw it or drop it.  :-) )  She definitely likes the food; given one or two pieces at a time, she will devour them without stuffing them in her cheeks.  Obviously, I can control the amount I give her at a time, but this is probably not a long-term solution.  How can I encourage her to only take a little bit at a time?


So we have the regular $\delta$-$\epsilon$ definition of continuity as:   (1) For all $\epsilon>0$, there exists a $\delta>0$ such that, if $|x-a|<\delta$, then $|f(x)-f(a)|<\epsilon$.  My question is why is the following definition incorrect?  (2) There exists a $\delta>0$ such that, if $|x-a|<\delta$, then $|f(x)-f(a)|<\epsilon$ for all $\epsilon>0$.  The obvious response is that $\forall x$ $\exists y$ $\neq$ $\exists y$ $\forall x$ (or rather, they are not always equal), but look harder at the grammar: is that necessarily what is going on?  Let us define $p:=$ "There exists a $\delta>0$ such that, if $|x-a|<\delta$, then $|f(x)-f(a)|<\epsilon$"  So we now have the statement:  "$p$ is true for all $\epsilon>0$"  Isn't that sentence identical to the English sentence: "for all $\epsilon>0$, $p$ is true"?  In which case you would have (1):  For all $\epsilon>0$, there exists a $\delta>0$ such that, if $|x-a|<\delta$, then $|f(x)-f(a)|<\epsilon$.  The counterargument that $\forall x$ $\exists y$ $\neq$ $\exists y$ $\forall x$ makes sense if you look at it immediately from a logical view, but because of the way English sentences work (and their vagueness, in a case like this), the "for all $\epsilon>0$" clause can be placed anywhere without changing the meaning of the statement in English.  To illustrate better what I'm talking about, let us imagine that we write our definition as follows:  There exists a $\delta>0$ such that, if $|x-a|<\delta$, then $|f(x)-f(a)|<\epsilon$ (for all $\epsilon>0$).  Or, maybe:  There exists a $\delta>0$ such that, if $|x-a|<\delta$, then $|f(x)-f(a)|<\epsilon$ (N.B. we're talking about all $\epsilon>0$ here!).  Aren't these parentheticals sort of "overlying" the whole statement? Is the fault in my reasoning that $\epsilon$ is being "bound" to an if-then statement before it has been defined? Or am I just blatantly incorrect and this is a case of $\forall x$ $\exists y$ $\neq$ $\exists y$ $\forall x$.  The essential point of all of this is that, if you have the statement: $$ \forall A \exists B : {B \subseteq A} $$ Then in English, this is equivalent to saying, both "For all A, there exists a B such that if B then A", and, "There exists a B such that if B then A, for all A".

I have a set of real numbers $x_1, x_2, \ldots, x_n$ and two functions $f:\mathbb{R} \rightarrow \mathbb{R}$ and $g:\mathbb{R} \rightarrow \mathbb{R}$.  What are the differences between the following statements?   $\forall v \in \{1, \ldots, n\} ~f(x_v) = 0 \vee g(x_v) = 0$ $f(x_v) = 0 \vee g(x_v) = 0 ~\forall v \in \{1, \ldots, n\} ~$


There are many questions on stackoverflow regarding an error printing "Array to string conversion" but none seem to help me.  I'm trying to execute a sql select statement with php. Here is a bit of what im dealing with:  public static function getNumCGS(){     require 'includes/vars.php';     $paramArray = array(":table" => "campground_data");     $query = Utilities::dbSelect("SELECT count(*) FROM :table","campgrounddata", $paramArray);     $r = $query->fetch();     return $r["count(*)"]; }   In Utilities.php:  public static function dbSelect($selectStmt, $dbName, $params){     require_once "config/config.php";     $dbh = Config::connect($dbName);     $query = $dbh->prepare($selectStmt);     $query->setFetchMode(PDO::FETCH_ASSOC);     $query->execute($params) or die("DB Error: " . $query->errorInfo());     return $query; }   In Config.php:  public static function connect($dbname){     $dbserver = "localhost";     $dbuser = "sys";//just a local server     $dbpass = "test1";//just a local server     try {         $dbh = new PDO("mysql:host=$dbserver;dbname=$dbname", $dbuser, $dbpass, NULL);         return $dbh;     }     catch (PDOException $e) {         printf("ERROR: %s", $e->getMessage());         exit();     } }   If I call getNumCGS() It tells me that I have an Array to string conversion problem at the line that executes the query in the dbSelect function.    I've been following an example from a text book, not sure what the deal is. The example I'm seeing passes in an array into the execute call.

Why can't I pass the table name to a prepared PDO statement?  $stmt = $dbh->prepare('SELECT * FROM :table WHERE 1'); if ($stmt->execute(array(':table' => 'users'))) {     var_dump($stmt->fetchAll()); }   Is there another safe way to insert a table name into a SQL query? With safe, I mean that I don't want to do  $sql = "SELECT * FROM $table WHERE 1"


Let there be a function $f:R→R$. Let $A$ & $B$  be two subsets of $R$. From my experience, I know that $f(A∩B)⊆f(A)∩f(B)$.  I don't know how to prove it. Also, are there certain conditions that the function $f$ or the sets $A$ & $B$ should follow for the above condition to be true?

$f(S \cap T) \subseteq f(S) \cap f(T)$  $x$ lies in ($S \cap T$), which means the domain has fewer elements than the domain of $S$ and $T$, since $x$ must be in $S$ and $T$. All $f(x)$ values of $x$, which resides in ($S \cap T$) is also a member of $f(S) \cap f(T)$, because $f(S)$ encompasses all $x$ in $S$ even those in ($S \cap T$) and the same can be said about $f(T)$.  Can you give me the solution?


import javax.swing.ImageIcon; import javax.swing.JOptionPane;   public class Example {      public static void main(String[] args) {          String name;          name = JOptionPane.showInputDialog(null, "ENTER TEST BELOW:"," ",3 );          if (name == "TEST") {              JOptionPane.showMessageDialog(null, "Welcome " + name + ", It works "," ",  1, new ImageIcon("Pictures/Example.jpg"));          }          else {              JOptionPane.showMessageDialog(null,"Welcome " + name + ", It doesn't work."," ",  1, new ImageIcon("Pictures/Example.jpg"));          }     }  }

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


I'm a little shaky while writing this one. I answered this question:    I think with a valid answer to push the OP - who is a beginner - into the right direction. The answer received a negative vote. OK, happens.  A minute later I received a negative vote for no reason on another answer. Then suddenly it's getting upvotes again. Then more downvotes on other answers appear - also on old ones. Still while I'm writing here on meta. :-/  What's going on here? Is someone on a downvoting spree? I was so happy coming near the 10k and now this. It seems that lately everything it's getting a little rough here. Even if you give little hints and try to help somebody. I'm just really sad at this moment. Maybe somebody with enough reputation can take a look at it? I may simply remove all my downvoted answers.  As a note: I'm thinking since nearly 30 minutes to press "Post your question" or not. If the answer to this is "You have to live with it", please simply leave a comment and I will remove this question later.

I just noticed that I lost a bunch of points from my reputation score, and I used the "reputation" tab on my user profile page to try and track down the cause.  During my investigation, I noticed there was an unusual event of type "reversal". In the normal place of a question title, it says "voting corrected".     What does this mean, and what caused it?  Did I do something wrong? Why did I lose all of that reputation? Is the system punishing me for leaving too many good answers?  Is there any way to earn it back?


Stack Overflow should have a column named User Tagged that would show questions only from your Favorite Tags.   For example, say, I am interested in answering only questions related to PHP, C++ and HTML.   I should be able to access a page that has only questions related to these favorite tags of mine. So that way I won't have to go through questions of other languages I don't know.  What do you people think?

Why don't we have a Tab that shows only questions for our favorite tags, showing recent first?  I keep having to scroll down the page to find the questions I'm interested in.  It'd be like the Unanswered Questions -> My Tags tab, but for all questions with my favorite tags.


in trying to understand the Wu-Experiment I wonder why the $B$-Field is an axial vector. I know that $\vec{B} = \vec{\nabla} \times \vec{A}$. Under Parity transformation I'd expect $\vec{A} \rightarrow -\vec{A}$, however I don't know whether $\vec{\nabla} \rightarrow -\vec{\nabla}$.

I got the difference between polar vectors and axial vectors (pseudovectors).   An example of pseudovector is $\mathbf{B}$. But why exactly the magnetic field is a pseudovector and its components parallel to an coordinate axis do no change signs if I reverse that axis?


I have found some ID3 tag editor in the web but unfortunately they are no longer available in 13.04 repository. Can anyone give me some recommendation for an ID3 Tag editor program? I need features like being able to tag lots of files at once and to read/write embedded (not linked) album art cover to/from Mp3 files.

I need to tag my MP3 library, and have tried kid3 (which was manual tagging), when I used Kubuntu 9.10 (I now use Ubuntu Meerkat) Here are the features I am hoping for:   A good and clean UI. Tagging should be automatic, like Winamp's autotag feature, which rocks, btw! It should also embed the cover-art in the mp3, not copy a jpeg file in the folder, because now-a-days all players support displaying cover art. But acceptable if not possible. Rename the files as per some regular expression like %TrackNo - %Artist - %Title.  Should be accurate, and more importantly smart. I want to start tagging at night, and hopefully my collection should be done by the morning, w/o it being stuck at a user prompt at 1%.   If one app cant do all, I am willing to use 3, wouldn't mind exposure to a few more apps ;)  I have used picard or someting, and I didnt like it quite a lot. But wouldn't mind using it, if there is no other alternative.   Thanks for your time!


I recieved an email saying that Windows XP's support is ending.  I have a computer with Windows XP and I want to know what are the risks on this computer that  (linked in the email) doesn't talk about.  I am aware they push for a Windows update or a computer change but this computer works well and I am not planning on changing it now or updating to Windows 7/8.  I use this computer for basic web search and mainly Word, Excel...  What should I do to protect my computer from "security threat" and what is this "security threat" exacly?    UPDATE   and  pointed out The email I am talking about most probaly is fake and not sent by Microsoft.  I am still in the unknown about what should I do to keep my computer as safe as possible

Support of Windows XP . There is a lot of fuss and fear around this and many  on what you should do but I haven't found a clear explanation: What does the end of support actually mean?   There won't be any new updates. This is the only thing which is clear. Will we be able to get the old updates?  weakly suggests that yes, but I haven't found any more confirmation of that. Will we be able to install Windows XP on new machines? There was some procedure of confirming the key over the network (registering windows), so will this work as before? Are there any other direct changes for users of Windows XP?     Note: I am not asking on security consequences of the above, and have my own opinion on updates of this product, so please be so kind and skip the big warnings and disclaimers how it's impossible to use XP without updates. There have been a lot of scaring people and no actual explanation of what actually is going on - this question is meant to fill in the gap.


I read that $ 0 < \cos(\theta) < \dfrac{\sin(\theta)}{\theta} < \dfrac{1}{\cos(\theta)}$ for $\theta \in (0,\dfrac{\pi}{2})$. I am confused about the middle part. I don't find it intutive (even from the graph). Please explain me why this is so.

How do I get:  $$\cos{\theta} \lt \frac{\sin{\theta}}{\theta} \lt 1$$


How to change the property of a file in python  I have an mp3 file which has properties like Title, Contributing Artists, Album. How can I access these properties using python and change them

How can I retrieve mp3 metadata in Python?


I am having a lot of trouble putting this text blocks inside the image, I would like to put the text where the black arrow is, how could I do it, I would appreciate some help, thanks.   .bloco {   padding-top: 10%; }  .title {   font-family: 'Sans', sans-serif !important;   font-size: 50px !important;   font-weight: 900 !important; }  .container-fluid {   width: 30% !important; }

404

Estás Perdido?

Esta página não existe
       <button class="btn-entrar container-fluid" onclick="window.location.href='{{ url()->previous() }}'">Voltar</button>

I want to overlay one image with another using CSS. An example of this is the first image (the background if you like) will be a thumbnail link of a product, with the link opening a lightbox / popup showing a larger version of the image.   On top of this linked image I would like an image of a magnifying glass, to show people that the image can be clicked to enlarge it (apparently this isn't obvious without the magnifying glass).


I am trying  to find the inverse Laplace transform of the Gaussian function  $$ G(s)=e^{-cs^2}$$   $L^{-1}\left\{G(s)\right\}= ?$ Where $c> 0$.

Can someone write in details how i can derive the Laplace transform of the Inverse Gaussian distribution? I think i am missing something during the calculation of the interval which gives the Laplace transform $L(s)=E(e^{-sX})$, so can anyone help by providing the exact calculations?


I'm surprised the answer to this isn't obvious after a google searches and articles read. But I tried to upgrade my Ubuntu v18.04 to v20.04 today. First I tried the instruction here:  I got a ~"No new release found message". On that, their suggestion is: The first and recommended approach is to simply wait. Direct upgrades from Ubuntu 18.04 LTS to Ubuntu 20.04 Focal Fossa LTS will most likely be unavailable until late July 2020.  Then I tried here:  Got this message in my (bash) console: "Checking for a new Ubuntu release There is no development version of an LTS available."  That confused me because I thought April 23 was the day. Then I saw this on google: Open the “Software & Updates” Setting in System Settings. Select the 3rd Tab called “Updates“. Set the “Notify me of a new Ubuntu version” drop down menu to “For long-term support versions” if you are using 18.04 LTS; set it to “For any new version” if you are using 19.10. Apr 28, 2020  Okay, since that is exactly what is set in my “Software & Updates” settings, can I just sit tight until late July? Will I get prompted when v20.04 is available by these commands?

I understand that the first point release of Ubuntu 18.04, namely 18.04.1 is now available and that my system should now offer it as an update.  My current OS version is 16.04.5 LTS. In System Settings/Software and Updates I have set 'Notify me of a new Ubuntu version' to 'For long term support versions'. I have tried both the main server and the server for United Kingdom, neither offers an update when Software Updater is clicked or via the Ubuntu Software icon.  Can anyone please tell me why I don't get the option of updating to 18.04?  Edit:  I don't remember the details exactly, but I think that my last LTS point release update was offered automatically a lot sooner after the published release date than where we are now with 18.04.1.  Edit 10th August  It appears that there has been some problem with the update process and that it should be fixed next week, see:    Edit 14th August 18.04.1 LTS now available from UK server,


I wanted to ask a question similar to , but it is from 2012 and does not have any answers or comments or anything.  So what's the suitable action in this case according to SE community? Asking it again?

I asked a question almost as soon as I got my account. I got a few decent answers, but none of them helped solve my problem. The question has long since become buried by newer questions, and there's still no accepted answer. Unfortunately, because there are quite a few answers with votes, to a casual observer it probably looks like the question was answered and I just neglected to mark an answer as accepted, and the system does not consider it "unanswered".  Or, I asked a question that was a bit more difficult to answer. After waiting for some time, I received no answers, little or no comments, and only a few views. The question does show up in the "unanswered" list, but no one has answered my question.  In either case, what's the protocol for me to try to get this question answered?  I see several options:   Post the question a second time, possibly linking to the original, to get attention for the original question. This is encouraged on sites like Reddit.  However, it's probably not appropriate here, since we're encouraged to check for duplicates and not submit a question that's already been asked by someone else, so this probably falls under that heading. Wait for some kind of wiki-like talk page to be implemented, then post a plea on the talk page for input and hope that activity on the talk page bumps up the question. Edit the question, but do nothing further on the Stack Exchange site. If I edit my post to say that I haven't accepted any of the current answers but am looking for more, then the question might get answered eventually by people browsing through old questions to find something they can answer. Post the question on other sites, but link to my original question on Stack Exchange. People will either answer here, or they'll answer on the other site and I can post the accepted answer here myself.  This might be considered spamming, so it might be better to do this without the link.      For more information, see the "" page in the .