Good night,  I'm using the Elsevier journal template, I need to set up a table like Image 1. I'm a beginner in TeX and I still have not understood how to merge cells into a table. Ideally, the table should be in the format of Image 2. The code I have in the template is:  \begin{table}[h] \centering \begin{tabular}{l l l l l} \hline \textbf{Author} & \textbf{Year} & \textbf{Blockchain} & \textbf{Implementation}\\ \hline {[31]} & 2018 & Ethereum & None \\ {[33]} & 2018 & Ethereum & Simulation \\ {[34]} & 2017 & Ethereum & Simulation \\ {[36]} & 2018 & Ethereum & Complete \\ {[37]} & 2017 & Ethereum & Simulation \\ \hline \end{tabular} \caption{Related Work.} \end{table}   Table from template:     Table I need:    The second image I did in Word, but it must be in the format of the template I'm using.


Why Starfleet ship don't have dedicate boarding party?

I see all the time, important character (i.e: bridge crew), might include the captain and first mate (case of ) are in boarding party. Dead crew result in missing slot at the bridge. Why don't starfleet have a (few) dedicate boarding team consist of marines to do boarding action. It might take only dozen of marines for boarding action that does not take much crew space. Marines are better at fighting, because they spend all the time training fighting, not how to man the station. And their dead don't have much impact on functioning of the ship.


Warning: Unusual traffic from your computer. Why is this happening?

This warning keeps showing up and I have no idea why. My OS is Ubuntu 14.04 LTS.  To continue, please type the characters below: About this page Our systems have detected unusual traffic from your computer network. This page checks to see if it's really you sending the requests, and not a robot. Why did this happen? IP address: XXX.XXX.XXX.XXX Time: 2016-01-20T12:04:04Z URL:   Can someone help me out?


Find all numbers that are their own multiplicative inverse in mod p where p is prime.

Find all numbers that are their own multiplicative inverse in $mod$ $p$ where $p$ is prime.   I recall that when $p$ is prime, all integers from 1 to the modulus minus 1, so all numbers from $1$ to $p-1$, have multiplicative inverses in mod $p$. So, the numbers that are their own multiplicative inverse would be $1$ and $1-p$. Can someone please explain why?


I have a ubuntu 16.04 Server without Internet Connection. It gets updates over a central apt-cacher-ng server. I have copied the ubuntu-esm-infra.list to the central server to /etc/apt-cacher-ng/ and restarted the apt-cacher but our 16.04 ubuntu is still getting the error: Ign:1 https://esm.ubuntu.com/infra/ubuntu xenial-infra-security InRelease Ign:2 https://esm.ubuntu.com/infra/ubuntu xenial-infra-updates InRelease  Fehl:3 https://esm.ubuntu.com/infra/ubuntu xenial-infra-security Release  Received HTTP code 403 from proxy after CONNECT Fehl:4 https://esm.ubuntu.com/infra/ubuntu xenial-infra-updates Release Received HTTP code 403 from proxy after CONNECT  E: Das Depot »https://esm.ubuntu.com/infra/ubuntu xenial-infra-security Release« enthält keine    Release-Datei. N: Eine Aktualisierung von solch einem Depot kann nicht auf eine sichere Art durchgeführt werden, daher ist es standardmäßig deaktiviert. N: Weitere Details zur Erzeugung von Paketdepots sowie zu deren Benutzerkonfiguration finden Sie in der Handbuchseite apt-secure(8).  What can i do to solve the problem? Many thanks in advanced R.


I installed MuseScore on Ubuntu 18.04 using snap from the terminal.  After I installed it I wanted to add it to the dock. Instead of the usual 'Add to Favorites' I get 'Quit' and 'All Windows >'.  What do I need to do to add MuseScore to the Dock?


I want to find the last two digits of $9^{9^9}$ or $9^{81}$. I tried using Euler's theorem but I can't make anything of it. Any hint or a guide? Thanks!


Many IC's I've seen suggest decoupling capacitors across Vdd to Vss - this is sensible.  However some IC's for example the dsPIC33FJ128GP802 has THREE Vss pins and only two Vdd pins (AVdd and Vdd.) So would I put a decoupling capacitor on each Vdd pin, or from each Vdd pin to each Vss pin?


What axiomatizations exist for special relativity?

Einstein 1905 gives the following axiomatization of special relativity (Perrett and Jeffery's translation):   The laws by which the states of physical systems undergo change  are not affected, whether these changes of state be referred to the one or the other of two systems of coordinates in uniform translatory motion. Any ray of light moves in the "stationary" system of coordinates with the determined velocity $c$, whether the ray be emitted by a stationary or by a moving body.   What other axiomatizations are possible?  References  Einstein, "On the electrodynamics of moving bodies," 1905, Annalen der Physik. 17 (1905) 891; English translation by Perrett and Jeffery available at


We know that in the set of nth roots of unity there are exactly $n$ distinct complex numbers: $C_n = \{z \in \mathbb{C} : z^{n} = 1 \}   = \{e^{i2k\pi/n}, \;  k = 0, 1, ...,n-1 \} $ and they lie on the unit circle. Now collect all roots of unity for every $n \in \mathbb{N}$ and consider the set $C =  \{C_n, \;  n \in \mathbb{N}\}$.   Is the set $C$ the unit circle, that is $\{C_n, \;  n \in \mathbb{N}\} = \{z \in \mathbb{C} : |z| = 1 \}$ ?   Obviously $\{C_n, \;  n \in \mathbb{N}\} \subseteq \{z \in \mathbb{C} : |z| = 1 \}$, but I didn't manage to prove the other inclusion (if it is true).


What does an "E" mean in a resistor value? (ie 150E)

I'm trying to build a dc motor controller circuit as described .  But it requires 2 "150E" resistors  From looking online I believe this means 15 ohms but I'm curious as to why, and why I couldn't find anywhere explaining such.


Interpretation of the Granger causality test

I would like to clarify how  can/should be used in practice, and how to interpret the statistical significance given by the test.  Also, I would like to fill this table with things like "we don't know" or if we know something, what do we know (It will for sure not be causality, but maybe something else?).                          X Granger cause Y sig.   X Granger cause Y not  Y Granger cause X sig.                     ...                     ...  Y Granger cause X not                      ...                     ...


Find features that use specific domain in ArcCatalog?

I have a geodb file with a set of domains.  Now, I need to check which are the features with attributes using a specific domain in arccatalog. Is there any way to accomplish that?


Sci Fi book about society sprung from a prison ship coexisting with giant squid predators

I read this book two years ago at a local library and can't remember the name of it. The book is really old, written in the 60s. It has a peach cover with multicolored text.  It's about a man living in a society on an alien planet where a prison ship had crashed and the survivors banded together to form a society. He gets a promotion to a telegraph operator. I think they called it semaphore operator.   There are giant squid predators that are in a relationship with the human population. They let them live in exchange for food and are worshipped by a theocracy. There is one particular big squid who is the King and he wrecks everything the protagonist had including killing his mentor after the protagonist started talking about how they were not beholden to the monsters.


Improving bound on $\sqrt{2 \sqrt{3 \sqrt{4 \ldots}}}$

An old challenge problem I saw asked to prove that  $\sqrt{2 \sqrt{3 \sqrt{4 \ldots}}} < 3$. A simple calculation shows the actual value seems to be around $2.8$, which is pretty close to $3$ but leaves a gap. Can someone find $C < 3$ and prove $\sqrt{2 \sqrt{3 \sqrt{4 \ldots}}} < C$?


Why has Stack Exchange stopped working on the Android app?

Recently I started to post  and  for , see:    and .   After realizing that the iOS app has better features and fewer bugs than the Android app, I  that Stack Exchange has decided to stop working on the Android app. In other words, very slow fixing of bugs, no work on features.  I've seen from About in the Android-app:     It is still evolving and we are committed to making it a little better each day   So, I want know why has Stack Exchange (nearly) stopped working on the , or at least working on it way less than on the ?  Update: Nearly after a year it seems nothing was done. I fear that the Stack Exchange Android App is being discontinued!


What is USB overhead and why does it reduce the theoretical transfer rate so much?

I've been reading a lot about the topic USB/FireWire recently and stumbled upon the fact that, despite USB 2.0 having a rate of 480MBit/s, it often does not reach the actual transfer rate of 60MB/s. Often there is some sort of overhead mentioned, but I really don't understand what it means and there doesn't seem to be any sort of comprehendable explanation for someone who's not really tech-savvy like me.  I've also read that FireWire has this overhead too, but it doesn't seem to be as severe as for USB. Why is that?   EDIT: I guess I'm talking about MBit. Also, so you could say it's because of extra data being sent too, like these overhead bits for error checking, that my data that I want to transfer, for example, is being sent far below the theoretical rate?


Is there a nice solution to get a "presenter mode" for Latex presentations?

I really like the way Keynote and MS Office (and also OpenOffice & similar) support a presentation mode that displays the current slide, the next (and maybe previous) slide, the elapsed and current time, and also any notes attached to the slides on one screen and the presentation itself on the beamer/second screen.  It enables me to give good, professional presentations without having to know everything by heart (I suck at that).  I found a , but I am looking for alternatives, especially OS-independent would be great. Not having to create 3 different PDFs is a boon.  Any hints?


Assuming consistency of ZF, ZF$\setminus ${Power Set axiom} is consistent. But can we prove consistency of ZF$\setminus ${Power Set axiom} without assuming consistency of ZF.


I am looking for a book (a small book or course pdf or videos  ) for study the riemannian geometry  for the beginning i need just  a basic understanding of Riemannian geometry  thank you for any suggestions


After reading  question, I remember wondering about this while watching the movie:  In Spider-Man: Far From Home,     When Spider-Man tries to get a pass from helping fight the Elementals, he brings up names of people who can help instead of him. Fury has an answer for each name, but when Spider-Man suggested Captain Marvel, Fury's response was really strict and he was not willing to even consider hearing about it.   However, in Captain Marvel     I remember them being in good terms. Even somehow friendly.   When was that change of relations?


What are the benefits for viewers of subtitling over dubbing -or- dubbing over subtitling foreign TV and film?  I've noticed some media will opt for subtitles, while others will opt to dub.   There must be benefits and drawbacks to both, for example:   Reading vs. Listening:  Reading might be harder to put oneself in the scene, where as listening could make you feel a part of the "show".   Are there any studies or any data as to benefits and drawbacks of subtitling vs. dubbing?


What happened with the menu that comes if I hover over my username in the top-bar? It was one of the most used feature on Stackoverflow since I've used it regularly to get a quick overview over my recent activities or reputation changes.  Is it possible to get it back somehow?


Tag Gold Badges have reset the awarded date to yesterday

I got notifications yesterday that I had earned gold tag badges on scifi stack exchange which was odd because I earned those badges years ago and was actually the first person to have those. Notification:  Badge 1:  Badge 2:  Here's  I closed as duplicate about a year ago with my gold tag badge privileges.


Remove duplicates from ArrayList in Java

I currently have some array lists and am trying to transfer some elements into a different array.   Here's what I have so far:  //create array separate from user input to remove duplicates  ArrayList<String> idsWithoutDuplicates  = new ArrayList<String>(); for (int i = 0; i < missionIds.size(); i++){     if (idsWithoutDuplicates.contains(missionIds.get(i))== false)         idsWithoutDuplicates.add(missionIds.get(i));  }  //search for mission numbers within array of array  for (int k = 0; k < idsWithoutDuplicates.size(); k++ ){     int idSize=0;     for (int employeeName = 0; employeeName <ids.size(); employeeName++){         for (int employeeId = 0; employeeId <ids.get(employeeName).size(); employeeId++){             /* when id is located, use the employee array to locate the other missions to               * which they belong */             if (ids.get(employeeName).get(employeeId).equals(idsWithoutDuplicates.get(k))){                 for (employeeId = 0; employeeId < ids.get(employeeName).size(); employeeId++){                     ArrayList<String> count  = new ArrayList<String>(); // ---> separate array for each employees total missions                     if (ids.get(employeeName).get(employeeId).equals(idsWithoutDuplicates.get(k)) == false &&                          count.contains(ids.get(employeeName).get(employeeId))== false){                         count.add(ids.get(employeeName).get(employeeId));                           idSize += count.size();                           for (int i= 0; i < count.size(); i++){                             System.out.print(count.get(i));                         }                     }                 }             }         }     }     System.out.println(idsWithoutDuplicates.get(k) + "\t    " + idSize);  }   The last if statement is trying to eliminate any duplicates with the contains condition, but this doesn't seem to work. I've tried converting 'count' to a set but this didn't work either.


A tag I've created now shows as created by the Community ♦ user; why?

A while back I've created a new tag [xsd-1.1] (). It now shows to have been created by the "Community" user; why is this?


Why is b=`git branch` different from just git branch

I don't understand the behavior of Bash in this case: If I type git branch, I get a list of branches. BUT if I try to put it into a variable, say, b=`git branch`; echo $b, I get an output as if I made ls; git branch. The content of a directory is listed together with the branches. Could someone please explain this behavior?


The mystery of the tagged answer - and more

It is (currently)   to tag answers. Yet, if I query , then  does have a tag, namely javascript. I'm at a loss: how did that happen?†  SELECT Id, Tag FROM Posts, PostsTags  WHERE Posts.PostTypeId = 2 AND Posts.Id = PostsTags.PostId   Edit: The are also five answers (, , ,  and ) with a view count of 1 instead of 0:  SELECT Id, ViewCount FROM Posts WHERE PostTypeId = 2 AND ViewCount <> 0   These results also hold through at least January 10.      †: PostTypeId = 2 means that the post is an answer, not a question (PostTypeId = 1).


Can't modify objects after creation in object mode

I don't know what I pressed, but this happened before.   I can't undo or redo in object mode but it still works in edit mode. When I move an object to another layer I need to press an "OK" button. Can't use the lower half of the left toolbar in object mode, it is grayed out.   Here are a couple pictures:      What is causing this strange behavior?


With k-fold cross-validation, do you average all $k$ models to build the final model?

When performing k-fold cross validation, I understand that you obtain the accuracy metrics by pointing all the folds except one at that one fold and make predictions, and then repeat this process $k$ times.  You can then run accuracy metrics on all of your instances (precision, recall, % classified correctly), which ought to be the same as if you calculated them each time and then averaged the result (correct me if I'm wrong).  The end result you want is a final model.  Do you average the models obtained to make your set of $k$ predictions to end up with the model that has the accuracy metrics obtained by the above method?


Bug or feature parsing with map function an array from string to integer on Javascript

I want it to parse to integers a String's array that had the id's from a selected html element, so I use this code:  var x = ["1", "2","3","4","5"]; var y = x.map(parseInt);   I was expecting:  [1,2,3,4,5]   But instead I get:  [1,NaN,NaN,NaN,NaN]   If I change it to this other ways it works as expected:  var z = x.map(function(item){return parseInt(item)}); var q = x.map(Number);   You can see it the same behavior on safari, chrome and firefox live here:   So my question is: Is this a bug or a feature?


Reference and biography indentation issue

I have added a reference in my latex template. The problem is shown in a picture below    If you see the last reference, it goes a bit leftwards. I have found that it appears only for the last reference, whichever, reference comes last. I think it is a possible template issue.  here is MWE  \documentclass{fcs} \usepackage{bm}  \volumn{ } \doi{ } \articletype{REVIEW~ARTICLE} \copynote{{\copyright} Higher Education Press and Springer-Verlag Berlin Heidelberg 2012} \ratime{Received month dd, yyyy; accepted month dd, yyyy} \email{$\times\times\times\times@\times\times\times.\times\times\times$} \title{$\bm{Frontiers~ of~ Computer~ Science}$\\[2mm] Instruction for authors} \author{Firstname LASTNAME \xff $^{1,2}$} \address{{1\quad Higher Education Press, Beijing 100029, China}\\ {2\quad Acadcmic Journal Division, Beijing 100029, China}}  \markboth{Front. Comput. Sci.}{Firstname LASTNAME: please insert running head here}  \begin{document} \maketitle \setcounter{page}{1} \setlength{\baselineskip}{14pt}  \begin{abstract} A short abstract of up to 300 words written in one paragraph, clearly indicating the object and scope of the paper as well as the results achieved, should appear on the first page. It should be written using the abstract environment. \end{abstract}  \Keywords{Up to 8 words separated by commas.}  \section{Introduction}  \noindent Frontiers of Computer Science is an international peer-reviewed academic journal sponsored by the Ministry of Education of China. The journal is jointly published by Higher Education Press of China and Springer on a bimonthly basis in English. Online versions are available through both http://www.springerlink.com/content/11704 and http://journal.hep.com.cn/fcs.  In-text citations must agree with the references in either numbering or names and year. The references should be presented completely and without mistakes, and should be the original publication. We use the citation-sequence system, that is to number the citations according to sequence of their first appearance. Journal names should be spelled out in full. Examples are given in     \cite{KargerD,Mastroianni,SchlessingerD,ZhugeH}.  \Acknowledgements{The ``Acknowledgement section'' is the general term for the list of contributions etc}  \begin{thebibliography}{99} \bibitem{Mastroianni} Verta O. Mastroianni C, Talia D. A super-peer model for resource discovery services in large-scale grids. Future Generation Computer Systems, 2005, 21(8): 1235--1248  \bibitem{ZhugeH} Zhuge H. The Knowledge Grid. Singapore: World Scientific Publishing   Co., 2004  \bibitem{SchlessingerD} Schlessinger D. Schaechter M. Bacterial toxins. In: Schaechter M, Medoff G, Eisenstein BI, eds. Mechanisms of microbial disease. 2nd ed. Baltimore: Williams and Wilkins, 1993, 162--175  \bibitem{KargerD} Karger D. Ruhl M. Simple efficient load balancing algorithms for peer-to-peer systems. In: Proceedings of Sixteenth Annual ACM Symposium on Parallelism in Algorithm and Architectures. 2004, 36--40 \end{thebibliography}  %% \Biography{#1}{#2} %% #1 is the file name of photo, %% #2 is author's biography \Biography{fcs-2}{Please provide each author's biography here with no more than 120 words. The photo can be informal. Our journal prefers to exhibit an encouraging atmosphere. Please use a one that best suits our journal.}    \end{document}   It also appears in following cases 1) if no biography 2) even if the bbibliograhy is added in this way \bibliographystyle{unsrt}     \bibliography{oo} What I understand after lot of R & D is that perhaps its a templates issue. Any way to solve it.  Here is the screenshot  Whatever the end line is, either a biography or a reference, this problem appears.  The FCS latex template could be downloaded at following URL:


Sum the series $\frac{3}{1⋅2⋅4}+\frac{4}{2⋅3⋅5}+ \frac{5}{3⋅4⋅6}+...\text{(upto n terms)}$

$\frac{3}{1⋅2⋅4}+\frac{4}{2⋅3⋅5}+ \frac{5}{3⋅4⋅6}+...\text{(upto n terms)}$  The general term seems to be $$T_r= \frac{r+2}{r(r+1)(r+3)}.$$  I see no way to telescope this because the factors of the denominator of the general term are not in arithmetic progression.  Do I have to use something else? Or am I missing some easy manipulation?


Google Script Fails to Return Boolean Value

I want to create a simple function that returns a boolean value when the word "website" appears in a specific cell. When I run the debugger, matches returns undefined.   function myFunction() {   var url = ss.getRange(8,1).getValue().toString();    var matches = url.includes("website");   return matches;  }   Why doesn't my function return a boolean value?


Resetting my transforms but I can't do an even bevel

I'm having some basic problems with bevels. Or rather with resetting the scale of my object.  To recreate my problem.    Create  abox scale it in x:10, and z 0.1 ctrl+A choose apply scale to deltas select long edge on the mesh and ctrl+b to bevel. Bevel is not even.   What am I doing wrong?


I feel like I know the answer to this, but how do you feel about justified type when it comes to common ux principles.  My gut tells me not to use it, but I'd like a better reason than that. I'm finding some issues with dyslexia and users who suffer from it could have a lot of issues reading the type.


Differents argument types on the same function

I have a decimal to octal conversion function, and would like to call it with either an int or an unsigned int depending on some options. My first thought was to copy/paste the code and just change the parameter's type ... is there a better way ?


What are the homology groups $H_k(\mathbb{R}\setminus \{0\})$?

Is there an easy way to calculate the homology groups $$H_k(\mathbb{R}\setminus \{0\}), k\geq 0$$ I was able to calculate $H_k(\mathbb{R}^m\setminus \{0\}), m > 1$ because we have a homeomorphism onto the sphere $S^{m-1}$ whose homology groups I know, but we do not have $\mathbb{R}\setminus \{0\} \cong S^0 = \{-1,1\}$ so for $m=1$ this approach fails. Of course, $H_0(\mathbb{R}\setminus \{0\}) \cong \mathbb{Z} \oplus \mathbb{Z}$ since there are two path components.


jquery on change does not work on cloned element

I do have a button to clone a input field. This input field should trigger a value in a second field after the own value was changed.  But the problem is it does only work on the first one and not on the cloned one.  $(".products:last #automenge").on("change", function() {});   It does work to change the value of the last like:  $(".products:last #autopreisges").val(gesamptpreis);   But the change function seem to not work like that.  Now working snippet !   var products = $(".products").clone();  $('#clone-search').click(function() {   var clonedRow = products.clone().insertAfter(".products:last").find(":input").val(this.value).end();  });  $(".products:last .clautomenge").on("change", function() {   alert("wow"); }); <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>  <div class="products">   <input class="clautomenge" type="text" value="1" name="Menge[]" placeholder="Menge" required /> </div>  <button id="clone-search" class="formstylebutton" type="button">     add one </button>     A fiddle:


Given two coprime integers, find multiples of them that differ by 1

I'll describe the problem with an example.  Find integers $n$ and $m$ such that $n\cdot13 + m\cdot101 = 1$. This is the same as solving the equation $n\cdot13 \equiv 1 \pmod {101}$  I'm revising for a maths exam in a few days and it seems like a lot of the questions and examples rely on an ability to solve this type of problem. I can't seem to find a method in my notes, the solutions just get plucked out of thin air! What is a neat way of doing it on pen and paper with a calculator?


This started as me trying to find the right dropbox version for my system, but now i'm mostly just generally curious and confused because i can't find a clear answer on this.


Hi I am trying to loop through an arraylist but get an error message. So my very specific question is, where am I doing something wrong?  Error message:     Exception in thread "main" java.util.ConcurrentModificationException     at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)     at java.util.ArrayList$Itr.next(ArrayList.java:851)     at main.numberOfNeighbours(main.java:130)     at main.calculateNextGen(main.java:95)     at main.main(main.java:30)   Code:  public static int numberOfNeighbours(boolean[][] arena, int x, int y){     //Calculates a given cells number of neighbours.      int height = arena[0].length;     int width = arena.length;      ArrayList<int[]> cors = new ArrayList<int[]>();     for(int i = -1; i < 2; i++){         for(int e = -1; e < 2; e++){             int[] xy = {x+i, y+e};             cors.add(xy);         }     }  //This is where I get the error     for(int[] xy : cors){         //Exclude cors that are out of range or the cell itself.         if(xy[0] == -1 || xy[1] == -1 || xy[0] == width || xy[0] == height || (xy[0] == x && xy[1] == y)){             int index = cors.indexOf(xy);             cors.remove(index);         }     }      int neighbours = 0;     for(int[] xy : cors){         if(arena[xy[0]][xy[1]]){             neighbours++;         }     }      return neighbours; }   I have been googling but can't find a solution. I think my main problem is that I don't understand the error message so any help explaining that would be great.


I am currently writing a manuscript using \documentclass{book}.  I would like to devote one of the chapters in the manuscript to a proof of an earlier result.  I have named the Chapter:  \chapter{Proof of Theorem \ref{Theorem1}}   and the actual chapter itself (including the chapter name in the table of contents and the chapter title) looks fine.  I have include an image below.    However, in the even numbered pages of the chapter at the top right-hand side of the page is an all-capitalized version of the chapter title, and the reference there does not seem to go through:     I have compiled the code multiple times, so I am sure it is not a compiling error.  Is there any way I can keep the Theorem reference in the title and have it properly show up at the top of the even pages of the chapter?


Elongation in bar with unequal applied forces

How is elongation in a uniform rod with unequal forces acting on opposite sides calculated? If applied forces are equal and opposite, the elongation is defined by the formula ($\delta = \frac{FL}{AE}$).  How does the solution change for the case when forces are unequal (as shown)?


Main page still shows the name of last poster even after he deletes his post

For example, in this question  there was another answer posted by Alex Poole after my answer. Afterwards, he deleted his answer since it was sort of duplicate.   However, the main page still shows his name along with the topic title, here   I understand that a deleted post is not actually permanently deleted, but stays unseen by other members, and only the poster can see it.   But the name shown beside the topic title in the main page is somewhat misleading. In the example shown, the entire thread doesn't show that posters name or contribution, but the main page is showing up. It is not going to hamper anything, I just had an observation.


To be clear here, My question arises from studying Electromagnetic induction and polarisation and photoelectric effect. From here I've gained the knowledge that creation of a photon involves:  Electromagnetic Induction - The fact that a time varying spatial magnetic field which creates a closed loop electric field [Super Confusing as to why universe does that] Polarisation - In the books, they show that light is oscillating electric field vectors and magnetic field vectors Photoelectric Effect - Creation of light has something to do with an electron returning to a lower energy state, not saying that it's the only way.  So how does light get produced? I'm seeking in-depth explanation.  Some Context The question arose when I was talking to my friend about a hypothesis of mine where I was saying that If I released a photon from , say a torch. I could, under some known error margin, say at what instant the photon was created but according to what I've heard multiple times, time stops at light speed. So, any photon at 'c' would basically never had experienced any time. So, from the perspective of the photon, its birth can't be defined. We seem to reach a paradox here, if I observe a time at which the photon was created but the photon has no notion of time, it has no notion of a beginning or an end. Then, I tried to expand the concept of the hypothesis to say that maybe in a similar sense, the universe doesn't hold a concept of beginning or an end. As we experience it's perspective, we can't determine its birth time using our maths which has been cultivate throughout this universe, and we also know that maths do break down when we try to solve equations for the t=0 time of Big Bang. NOTE: This talk was just to have fun, I just like physics and like to talk about the universe, however, I understand that I might have just annoyed someone by ignoring a dozen of laws and theorems that I'm yet to find out about. APOLOGIZES!  I'm expecting a somewhat dumbed down explaination, now don't get too carried away by that. I'm a high school student but I do love a bit of technical mumbo jumbo but I'm just asking to keep in mind that I'm in high school. Example: Say we have an equation: x3+x2-x+44=0 Instead of saying the degree of equation is 3 maybe say the highest power in the equation is 3.


If SE site foo.com exists, could foo.stackexchange.com redirect to it?

I wanted some feedback on Windows 10 upgrades (basically, whether a free upgrade from 7 to 10 is desirable), so I went to superuser.stackexchange.com, which doesn't exist... so I went to what I should have typed in the first place, superuser.com.  For sites that have a URL of /[-\w]+.com/, would it be possible to redirect all foo.stackexchange.com sites to foo.com?


how do I average the lowest 3 of the final 6 numbers in a row of 22? Some cells may be blank

How do I automatically average the lowest 3 of the last 6 numbers in a row of 22 that adds one number per week?  Obviously I need at least 7 numbers to begin using this formula.  Also, some cells in some rows may be blank.


I want to display running clock inside terminal.  I have already gone through  answer but this method only works in zsh terminal. But I want to display in bash.  Is there any other way to display it in bash terminal?


I want to consider a commutative ring $R$ (we can restrict to, say, $k[x,y,z]$ if needed) with an ideal $I$ and a maximal ideal $m$.  Now, I think $I/mI$ is actually a $R/m$-vector space.  I'm wondering if there's a slick way to prove this?  I can define a scalar action  $$R/m \times I/mI \longrightarrow I/mI$$ $$(\bar{h},\bar{f}) \mapsto \overline{hf}$$  where the overbar denotes the respective projection to the quotient.  You can then prove that this is well-defined.  So you can define this scalar multiplication and show that it obeys the vector space axioms, but I'm hoping there's maybe a better way.    Also, if $R$ is Noetherian, we can write a finite list of generators for the ideal $I=(f_{1}, \ldots, f_{k})$.  Is it then necessarily true that $(\bar{f}_{1}, \ldots, \bar{f}_{k})$ is a basis of the vector space $I/mI$?  I suppose I should also check, are all my hypothesis correct here?  I know something like this is true, but maybe I need to be assuming more structure or something.  Thanks!


I've been running Ubuntu (Unity) on a chromebook for a couple of years. I had to reformat the device and now I'm trying to reinstall from a backup. I've downloaded  and copied my backup called trusty_backup.tar.gz to the downloads directory. Whenever I run the reinstall script to install the chroot from the backup I get the error trusty_backup.tar.gz not found.  This is the command I am using: sudo sh ~/Downloads/crouton -f trusty_backup.tar.gz  What have I got wrong? Thanks.


I'm trying to style my table very simply:   table{      border: 1px;      cellpadding: 3px;      cellspacing: 0px; }  td{      text-align:center; }   The td styling works (so I know it's finding the CSS file correctly), but the table styling doesn't. I can add the table styling directly to the table tag and that works (so the arguments are correct), so I'm not sure what I'm doing wrong.


Using Joint Distributions and conditional probabilities

This exercise is particularly confusing me because I do not understand the distribution of 'X-Y' or how to calculate the probabilities


No suspend option in UI on Bionic Beaver

There is no suspend option in desktop 18.04. The only way I found is to go to Settings > power options and to set it to suspend when pressing the start button.  It works but I need to log in every time and it's painfully slow to open up.


In the Matrix Reloaded, Bane aka Smith begins his day as a real man for the first time, cutting himself.  He does this quite often as we come to be aware of in Revolutions, and my question is why exactly did Smith do this?   Was it because he was feeling pain for the first time and overwhelmed at actually being a real human?


Use induction to prove the following: $1! + 2! + .... + n! \le (n + 1)!$


Should I cite a book that I read to prepare for a talk but did not directly use it?

I have used a few books and articles to prepare for a talk, but I only used some of them directly in my slides. The slides also include parts that are made based my knowledge (background knowledge plus what I learned from reading those sources) but are not new information and could be found in those sources.   Should I cite all of those sources in my references slide? If yes, do I need to reference each piece of material on the slide, or just citing the sources at the end would be enough if I didn't use them directly?  NOTE My question is not a duplication  because that question is asking about referencing for presentation in general, but my question is not about referencing the sources I used directly, but those I read to build up my knowledge for the presentation but did not use directly.


What is the difference between kosher dill pickles and Polish dill pickles?

What is the difference in taste between kosher dill pickles and polish dill pickles? Do they have any visual distinctions that would make it possible to differentiate between them on sight?


I'm stuck in Creative and God mode and lost in the Nether. How can I get out?

I was playing on a multiplayer server with the owner and had been given OP privileges.  I had turned on Creative mode and activated the 'God' command, but before the owner left, he de-opped me. Now I can not get out of Creative or God mode.   So I've tried:    Killing myself & falling into the void  Going to the middle of the nether with coordinates.  Making a portal but I can not light up the portal (Multiplayer server rules).    None of which worked.  Finally I wait for another player to come online, but the player is also not an op so I cannot teleport to him.   Please help me! The only thing I can do is to wait for the Owner of the server!


Linux for work, virtualized Windows for games?

Hello, as a freelance developer I recently found myself severely bound by the memory limit of 32-bit operating systems, and I need to upgrade to a 64-bit system in order to continue working effectively. (To explain: I have to use multiple virtual machines on a daily basis. Right now I have to turn them on/off frequently as I test solutions, and still my main OS is very slow and swapping heavily.)  I planned to migrate from Windows to GNU/Linux for a very long time, and I'd like to use this opportunity to make the switch now. I will still need to keep Windows around (for games, and as a general fall-back scenario), and since I do not want to dual-boot, I would rather like to run it as a virtualized client OS.  What I would like to achieve:   Primary OS - GNU/Linux (64b)   daily work, web browsing, etc several virtualized client OS' via VirtualBox (for testing applications)   Secondary OS - Windows XP (32b) or Windows 7 (64b)   legacy applications (until I find suitable GNU/Linux alternatives) DRM-ed stuff which works problematically under GNU/Linux (e.g. Blu-ray) games which don't have a native Linux client    Notes:   my hardware supports  to assist the virtualization effort I'm not against a bare metal hypervisor (Xen?) nor against using the primary OS as the host (KVM?), as long as it's possible to make it work (sort of) reliably the secondary OS (Windows) must be able to fully use the graphics/audio hardware (3D video games, i.e. OpenGL/OpenAL, DirectX, etc)   I was already looking into several solutions myself, but I did not manage to find reasonable results (mostly on the bit about games). As I don't have any practical experience with this, I would like to kindly ask you guys for your help before I start the migration effort (and hit a road block).  Which solution would you recommend please? (Is the above possible at all?)   Thank you for your help, M.


What permissions should I give to CA Bundle file?

Hi I setup an ssl certificate using godaddy and read the following article: . I am trying to protect an aws ubuntu gitlab instance that uses nginx as a server.  My /etc/ssl/private/ has the following files:  .csr generated on server .key generated on server .crt generated by godaddy .crt BUNDLE generated by godaddy   I have given them the following permissions respectively:  root:root 644 root:ssl-cert 640 root:root 644 root:root 644   Is this correct?  It has been mentioned that this question is the same as  and my only reason that it is distinct is because it is for nginx NOT apache.


Ubuntu 20.04 on DualBoot fail 90% of tries - Initramfs unpacking failed: Decoding failed

I just installed Ubuntun 20.04 on a Dell Latitude 7400 on DualBoot. I had to remove the RST as mentioned on this post :  It works but now I need to test 5 or more times to boot. After the grub screen, most of the time i have a black screen. Sometimes I have this error : Initramfs unpacking failed: Decoding failed And then it starts.  here is a file called initramfs.conf cat /etc/initramfs-tools/initramfs.conf MODULES=most  BUSYBOX=auto  COMPCACHE_SIZE=""  COMPRESS=lz4   DEVICE=  NFSROOT=auto RUNSIZE=10%


Best type of bike lock (materials, style, etc.)

I recently lost the keys to my lock and had to borrow a bolt cutter to free my bike. It was a bit of an eye opener to realise a) just how easy it was for the bolt cutters to cut through my D Lock (<10 seconds), and b) that nobody on a busy town shopping street batted an eyelid at me doing so.  When choosing a new lock, what should I look for in terms of build material or design that would make it harder to cut through (using relatively small/discrete bolt cutters)?


How to detect multicollinearity in a logistic regression where all the independent variables are categorical and binary?

I'm doing a multivariate logistic regression where all my independent variables are categorical and binary. I have transformed all my categorical variables into dummies in order to have  reference groups and interpret my odds-ratios. However, I would like to check if there are eventually  multicollinearity issues.   I plan to calculate Spearman correlation between my independent variables and calculate VIF too. Nevertheless, I have several questions: Is Vif appropriate in this case? Do I have to calculate VIF and Spearman correlation on my categorical variables or their associated dummies?   I have tested other ways to detect multicollinearity (I check if the coefficients vary a lot if I increase my sample size or drop or add variables) and I'm pretty sure there is not a collinearity issue but I would like to have a "quantitative" proof.


What does this residuals versus fitted plot mean about my model?

I have a model that attempts to predict a nation's quality of life index by it's moral indifference to contraception and moral rejection of gambling. Initially the model contained several predictors, but I eliminated most using backwards elimination via AIC. Here is a summary of the model (generated using R):  > summary(fit1)  Call: lm(formula = Quality.of.life.index ~ Morally.unacceptable.ga +      Not.a.moral.issue.co, data = qli_and_moral_ind)  Residuals:     Min      1Q  Median      3Q     Max  -89.670 -25.443  -4.732  36.129  64.441   Coefficients:                         Estimate Std. Error t value Pr(>|t|)     (Intercept)             143.1410    32.7499   4.371  0.00019 *** Morally.unacceptable.ga  -1.7690     0.3603  -4.910 4.71e-05 *** Not.a.moral.issue.co      1.4471     0.7925   1.826  0.07981 .   --- Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1  Residual standard error: 40.39 on 25 degrees of freedom Multiple R-squared:  0.6079,    Adjusted R-squared:  0.5765  F-statistic: 19.38 on 2 and 25 DF,  p-value: 8.266e-06   There are two plots of the model that I can't interpret:    According to the web, the residuals plot above may indicate predictable error, ie that I'm missing some variable in my model. Is that assessment correct? If so, what should I consider adding to the model? It kind of looks like the $y = x^3 - x$ graph - maybe add a cubed term?


Python all values in array get replaced every time a value is added

I am extracting  values from a file and want to put them into an array, However every time a value gets added it replaces all the other values. What is going on?  My code:  allofMS = MS.readlines() line_scanwidth = allofMS[9] Tab_pos = line_scanwidth.find('\t')+1 scanwidth = line_scanwidth[Tab_pos:-4] scanwidth_i = int(scanwidth) MS_array=[ [0] * (scanwidth_i+1) ] * 100000  MS_array[0][0] = "Date"  for x in range(1,scanwidth_i+1):     MS_array[0][x] = x-1  curscan = 1 for x in range(1,num_lines-1):     curline = allofMS[x]     if curline[0:10] == "Start Time": #find start time         Tab_pos = curline.find('\t')+1         scan_date = curline[Tab_pos:]         MS_array[curscan][0] = scan_date         curscan = curscan +1         print(curscan)         print(MS_array[curscan][0])         print(MS_array[5][0])   It returns:  2  4.21.2020 11:52:53.409   4.21.2020 11:52:53.409   3  4.21.2020 11:52:53.409   4.21.2020 11:52:53.409   4  4.21.2020 11:52:58.517   4.21.2020 11:52:58.517   and so on  Thanks for your help.


Why halve the objective function for Lasso?

The objective function of Lasso is often presented by: $ f(\boldsymbol{b}) = \color{red}{\frac{1}{2}} (\boldsymbol{y} - \boldsymbol{Xb})^T (\boldsymbol{y} - \boldsymbol{Xb}) + \lambda ||\boldsymbol{b}||_1$  I understand that scaling the residual sum of squares by half doesn't affect the LASSO estimate. But why to write it like this? In "The Elements of Statistical Learning" (p. 93) , it's explained that scaling was done out of "convenience" without any further explanation.


Can I desaturate incoming light using a filter or series of filters mounted to the lens?

I've got a very difficult shot coming up. I'm photographing moonlight on a country meadow. I do not want to do post work. I need to do everything real time (for reasons too long to get into, there is more going on in the shot that will just complicate the question.)  My only option is to use filters during my shot, to capture the way we perceive moonlight. The camera picks up moonlight as white light. Our eyes, however, perceive it as very desaturated with a slight hint of blue. I've got a blue filter, but the shot just comes out far too blue. I need to desaturate the light coming in to the camera (almost black and white.) Is there any possible way to use lens filters to desaturate light?  I can't shoot in b&w as I'm not only exposing the moonlight, but also a girl with a glowing balloon in the scene. It's all got to be done in one exposure.   Is there any way I can desaturate the light with use of a filter or series of filters?  Thanks a heap guys.  More info: thanks so much everybody, you all are right, but here's why and what I need. I'm having the girl and the balloons to be illuminated with lights and the balloons are going to be different colors and glowing. So she is going to be in full glory color, but she's going to be sitting in dim moonlight. To get the moonlight look, I can desaturate in camera settings and use a filter. But when its time to take the cap off the lens (shutter still open after capturing moonlight) and exposing the girl and balloons, the camera is going to capture her and the balloons in those same desaturated settings. My camera will not change settings in mid exposure, and although I think it can combine two exposures, this is a messier way of getting where I'm trying to go. And post is just about impossible. To capture full color in the image, and then darken and blue and desaturate the rest of the scenery is extremely imperfect.


Does the std::stack in the C++ STL expose any iterators of the underlying container or should I use that container directly?


Show that $ a，b，c, \sqrt{a}+ \sqrt{b}+\sqrt{c} \in\mathbb Q  \implies  \sqrt{a},\sqrt{b},\sqrt{c} \in\mathbb Q $

Assume that $a，b，c, \sqrt{a}+ \sqrt{b}+\sqrt{c} \in\mathbb Q$ are rational，prove $\sqrt{a},\sqrt{b},\sqrt{c}  \in\mathbb Q$,are rational.  I know that can be proved, would like to know that there is no easier way    $\sqrt a + \sqrt b + \sqrt c = p \in \mathbb Q$, $\sqrt a + \sqrt b  = p- \sqrt c$, $a+b+2\sqrt a \sqrt b = p^2+c-2p\sqrt c$, $2\sqrt a\sqrt b=p^2+c-a-b-2p\sqrt c$, $4ab=(p^2+c-a-b)+4p^2c-4p(p^2+c-a-b)\sqrt c$, $\sqrt c=\frac{(p^2+c-a-b)+4p^c-4ab}{4p(p^2+c-a-b)}\in\mathbb Q$.


Assuming that $f''(a)$ exists, show that: $f''(a)=\lim_{h\to 0}\frac{f(a+h)-2f(a)+f(a-h)}{h^2}$

Assuming that $f''(a)$ exists, show that:   $$f''(a)=\lim_{h\to 0}\frac{f(a+h)-2f(a)+f(a-h)}{h^2}$$   I got the first derivative by using the limit rule $(f(a+h)-f(a))/h$. But when taking the second derivative, I thought of doing the same thing on $f(a)$ of the equation, but I couldn't reach this answer.


zustand when does selector depends on scope?

zutand doc mentioned that you can use selector if a selector doesn't depend on the scope and provide the example below  I didn't understand the doesn't depend on scope part. Could someone provide some examples of when the state depends on the scope so that the selector should not be used? Thanks!


How do i get rid of the grease pencil marks in blender? I put a couple marks on my mesh by mistake and i want to get rid of em all. I already tried using erase and it doesn't work.


I would like to install chef via apt non-interactively, but by default, apt installation brings up this prompt:    Is there a way to skip this step during installation or pass a value to apt install? I'm only using chef-solo, so don't actually need the server component, so simply press return on this prompt.


An exercise in Gathmann's lecture notes about Projective spaces

Exercise 3.5.1 in Gathmann's lecture notes:     Let $L_1$ and $L_2$ be two disjoint lines in $\mathbb{P}^3$, and let $P\in \mathbb{P}^3 \setminus (L_1 \cup L_2)$ be a   point. Show that there is a unique line L meeting $L_1$, $L_2$, and $P$ (i. e. such that $P \in L$ and $L \cap L_i \neq \emptyset$ for $i=1,2$.   And is it true that a line in $\mathbb{P}^3$ is given by a system of two homegeneous linear equations?


How do we use linear regression in which response variable is related to the regressors in a nonlinear fashion?

"This is called a multiple linear regression model because more than one regressor is involved. The adjective linear is employed to indicate that the model is linear in the parameters β 0 , β 1 , . . . , β k , not because y is a linear function of the x ’ s. We shall see subsequently that many models in which y is related to the x ’ s in a nonlinear fashion can still be treated as linear regression models as long as the equation is linear in the β ’ s.” This is a quote from a text book. What I’m trying to understand is the last part, what does “ the equation is linear in the $\beta$’s” mean? In the same vein, how do we check if the equation is linear in the $\beta$’s? Thank you!


Regarding Goldstein's claim that $\mathbf{F} = \dot{\mathbf{p}}$

From Goldstein:     ... The mechanics of the particle is contained in Newton's second law of motion, which states that there exist frames of reference in which the motion of the particle is described by the differential equation $$\mathbf{F} = \frac{d\mathbf{p}}{dt} \equiv \dot{\mathbf{p}},$$ or $$\mathbf{F} = \frac{d}{dt}\left(m\mathbf{v}\right).$$ In most instances, the mass of the particle is constant and [the last equation] reduces to $$\mathbf{F} = m\frac{d\mathbf{v}}{dt} = m\mathbf{a}\textrm{...}$$   What Goldstein is saying troubles me for it implies that $\mathbf{F} = \dot{\mathbf{p}}$ works for a particle of time-varying mass and that contradicts Ján Lalinský's answer to this question: .  What's going on here?  Edit: Some people think that a particle that loses mass that isn't going anywhere--it simply disappears---isn't a useful fiction to solve problems. Consider a ball that is emitting mass isotropically whilst being pushed by some force. In analyzing the motion of this ball there is no need to consider the fact that material is indeed being emitted, all that is needed is the fact that the ball is losing mass. Here we can just use $\mathbf{F} = m\mathbf{a}$ instead of $\mathbf{F} = \dot{\mathbf{p}}$, no?


How to avoid the "http:" part in hyperref's \url?

is it possible to use the \url command from the hyperref package with "shorthand" URLs, e.g.  \url{ipython.org}   instead of   \url{http://ipython.org} ?   It seems that the former would only link to local files on my computer, instead of retrieving the web address. (I suppose I could be using \href, but \url is shorter and I'd like to keep its formatting features.)  Edit in response to karlkoeller's answer:   Sorry for not being sufficiently precise. I don't mind typing the 'http' part so much, but I'd rather not see it printed.   egreg's answer does what I want to do - many thanks!


Intuitive explanation of Euler's formula $e^{it}=\cos(t)+i\sin(t)$

I'm trying to understand  $$e^{it}=\cos(t)+i\sin(t)$$ This comes from the definitions  $$\cos(t)=\frac12(e^{it}+e^{-it}) \quad\text{and}\quad \sin(t)=\frac1{2i}(e^{it}-e^{-it})$$  and those are consistent with the power series definitions of $\cos$ and $\sin$, which are their Taylor series  $$\sum_{k=0}^{\infty}{\frac{(-1)^k z^{2k}}{(2k)!}} \quad\text{and}\quad \sum_{k=0}^{\infty}{\frac {(-1)^k z^{2k+1}} {(2k+1)!}}$$  respectively.     I see all those things. They make sense and are consistent with each other, but I can't believe that $e$ and cosine and sine are so related coincidentally.


Will a user be notified when I @mention a user while editing a comment?

For example, if I forget to tag/mention a user in my comment under a Stack Overflow question or answer and I edit the comment to add the tag, will the tagged user then also be notified?


Does Microsoft Office 2010 have version control?  In other words, does it automatically save old versions of files?


How to activate the Gedit terminal plugin?

I have the following packages installed:   gedit gedit-common gedit-plugins   In Ubuntu 12.04 with these packages installed all that was needed was to activate the terminal plugin and the press Ctrl+F9 to show the bottom panel. This isn't the case with Ubuntu 13.10 (Gedit 3.8.3) and I can't figure out how to do it.


Samsung Apps for Galaxy S4 with CyanogenMod

I am going to change the official stock Android on my Samsung Galaxy S4 to the latest version of CyanogenMod. But after reading some forum threads about how beautiful and useful it is, I have a question regarding Samsung Apps:  Is there any Samsung Apps available or is it possible to install them somehow?  The problem is that I do not really want to lose my camera functionality (double camera photo and automatic color correction), hover function, S Memo, Samsung Apps, S Planner and so on.  What you may suggest me? I really liked that CM functionality, but I also need almost all of the Samsung default tools, like S Memo (the most useful for me).


Difference between conference paper and journal paper

Many times I heard about papers published in conference. But still I am not able to find the major difference between papers published in a conference and those published in a journal. What is the difference?


How to prove that all eigenstate $|0\rangle,|1 \rangle,...| n\rangle $ are non-degenerate?

How to prove that all eigenstate $|0\rangle,|1 \rangle,...| n\rangle $ are non-degenerate where  $a^{\dagger}a|n \rangle =n|n \rangle $


Putting the edit box and the markdown box side by side

I was recently editing a rather long answer on Worldbuilding.SE (but this applies everywhere), and I was trying to see what my formatting looked like and if it was working correctly. However, because of the long answer, the top of the markdown box was in the way and I had to scroll down to see what I had been typing. This gets annoying when I have to do it a lot.  My feature request is to have an option to put these boxes side-by-side so that we can see both what we are typing and what that looks like when rendered with Markdown.  NOTE: For users who do not want the UI changed/think it won't work:   This is how it looks on my computer. There is a lot of margin space to use up for this if some layout changes are acceptable. Also, I think it would be a better idea (than my original feature request) to add an option to do this instead of just putting the boxes side by side, especially because there is not as much margin space on smaller monitors to use. After reading comments, I can see many mixed opinions about whether it would work.


Is there a string.prototype.matchAll ES5 safe alternative?

Just found out that matchAll is not supported by many browser versions.  Is there an ES5 safe alternative for the string.prototype.matchAll method?  const regexp = /(?:\[(.*?)\]\((.*?)\))|([^[]+)/g; const matchedElements = Array.from(value.matchAll(regexp));


Identify for $f(\infty)+f(-\infty)$ in quantum field theory

In Matthew Schwartz's textbook, Quantum Field Theory and the Standard Model, equation 14.68 on page 266 says the following:  $$f(\infty)+f(-\infty)=\lim_{\varepsilon\rightarrow0^+}\varepsilon\int_{-\infty}^{\infty}dtf(t)e^{-\varepsilon|t|}.\tag{14.68}$$  The only constraint stipulated in the text is that $f(\tau)$ must be a smooth function. Can anyone help me to prove this expression? When I try to evaluate the right side by bringing the limit and the $\varepsilon$ inside the integral, I find that the right side is equal to zero. I've tried using Dirac delta function identities to prove this, but I've had no luck.


int Mystery(int N) {   int Sum = 0;   for (int i = 0; i < N; i++)     for (int j = 0; j < i * i; j++)       for (int k = 0; k < j; k++)         Sum++;   return Sum; }   I am learning about complexity, but don't know about this, anyone has any ideas?


How to troubleshoot marketing e-mail inbox rate / deliverability?

After previously using managed ESP's, we've recently switched over to our own server (CentOS 6) that's set up to send bulk e-mails with 12 IPs/SPF/DKIM. Campaigns are processed and sent via Interspire, but I've been testing with a desktop application also.  Starting from fresh reputation was new for us, but we've been sending out 10/15k a day for the first week (in line with a lot of stuff about reputation building online). What's troubling me is that we're suffering from extremely low open-rates (1% - 3%, compared to 20% - 25% on the same lists with the same content from a managed ESP).  I noticed that 2 of the IP's didn't have a correct rDNS setup, so that is being fixed by devs now, but surely that can't wholly account for the terrible rates I'm seeing?  Mail-Tester.com is showing e-mails sent as 10/10 (everything correctly configured). SenderScore.org is showing all IPs as > 90 sender score (apart from the 2 with incorrect rDNS, which are showing as in the 60s)  From this afternoon, mail I send (multiple attempts) isn't even landing in Hotmail's inbox. It lands in Yahoo fine, but where it goes (inbox or spam) is random, presumably due to the couple of bad IP setups.  My questions are: 1. Where am I going wrong? 2. How can I better troubleshoot the issue? 3. Is there a better method for building up and maintaining inbox rates to major email providers?  Apologies if this is in the wrong area, I took a look around and couldn't see a better fit for it.


Bathroom photons from the edge at the universe

I was looking through my bathroom window this night and I was wondering if any of the photons my retina is hit with are from 13 (40) billion light years away ?!  I was looking through it a few seconds, was that too less of a time?  Do I need a Hubble for this?


While reading a textbook on Physics, I came across this :     Mass is a universal constant. It does not depend upon the position of the body on the Universe but it changes with speed of the body.   It's just two contrasting statements with no further explanation. Maybe the author left it to our curiosity but I can't even find out how mass changes with time. Thanks P.S : This is not a homework question.


Why did R.A.B even use the fake locket at all?

Sirius's brother Regulus took Kreacher to the cave, drank the potion, and swapped the real locket for a fake one.  Inside the fake one was a note telling whoever happened to find the locket--most likely Voldemort--his initials and exactly what he'd done. Voldemort is pretty smart, he would probably figure out everything, kill Kreacher, and take the locket back.  So why did Regulus even bother making a fake locket?  And once he had, why did he put the note in the locket?  It just seems stupid to me.


Why does Naruto use his mother's family name?

Is there any logical and canonical reason to why Naruto used his mother's family name, Uzumaki, instead of his father's family name?


GPIO on base of transistor not scaling linearly

This is really a followup to  to provide an updated schematic and photograph at the request of a commenter on that question.  I'm not sure if there is a better way to provide such an update to a question but here it is anyway...  I have the following circuit:         – Schematic created using   When I measure the voltage across R2 I don't see the 18V being supplied into the collector of transistor scaling linearly with the value of the PWM GPIO of the NodeMCU.  It ranges from 9.35V with the GPIO at 0 (i.e. off) and 17.14V with the GPIO at 1023 (on "full").  With a GPIO value of 512 it reads 13.16V.  I tried my best a photograph of my set up:    About the only thing that is not clear in the photo I think is that the resistor "above" the transistor is between the GPIO with an orange wire and connects to the base (middle pin) of the transistor.


What kind of harm ends the duration of the Incite Greed spell?

The  spell's duration can be ended by my companions doing anything harmful to the afflicted targets. What is considered harmful for the purpose of the spell's duration?     until the spell ends, or until you or your companions do anything   harmful to it.   In many places, the harm is defined when introduced as a term (see for examples: PHB 109; PHB 118; PHB 259). The harm here seems to be undefined, did I miss the definition here or on another page of the book?


Reinstall software-center in Ubuntu 16.04

I wanted to remove and reinstall the software-center package.  I removed it, but now I can't reinstall.  I tried these commands without success:  sudo apt-get update sudo apt-get install software-center   How can I reinstall software-center?    When I performed the install command this is what I got:  $ sudo apt-get install software-center Reading package lists... Done Building dependency tree        Reading state information... Done Package software-center is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'software-center' has no installation candidate


I am adding a div with some children dynamically. When the user clicks on a .delete-marker div I want to call a function. But for some reason it is not calling anything, and I don't seem to see any errors in the console.  for (var i = 0; i < array.length; i++) {     $("input[name='commit']").before("
<input type='text' class='marker-input' name='num[" + i +  "]' id='num[" + i + "]' value=" + array[i]+ " readonly>
x

"); }  $('.delete-marker').on('click', function() {     alert(); });


I installed Ubuntu yesterday, so I'm trying to get used to it.  I'm really close to my router, but my wifi signal gets too low. Sometimes I'm in Facebook or Youtube and the signal is high, almost full, but it is usually in one or two bars, and sometimes none.  I can use Internet normally, I can watch videos and stuff, but the problem is when I try to update something or Ubuntu is downloading stuff, the downloads get stuck or get cancelled telling me that I should check my connection.  How can I fix this? I should be getting a really good signal, I'm really close to my router, my phone has full signal, and a notebook with Windows 7 has full signal here too.  Sorry my bad English and I hope you can help me.  $ lsusb Bus 009 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 002: ID 0bda:8179 Realtek Semiconductor Corp.  Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 006 Device 002: ID 0458:003a KYE Systems Corp. (Mouse Systems) NetScroll+ Mini Traveler / Genius NetScroll 120 Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub


What is the main difference between a vector space and a field?

In my opinion both are almost same. However there should be some differenes like any two elements can be multiplied in a field but it is not allowed in vector space as only scalar multiplication is allowed where scalars are from the field.  Could anyone give me atleast one counter- example where field and vector space are both same. Every field is a vector space but not every vectorspace is a field. I need an example for which a vector space is also a field.  Thanks in advance. (I'm not from mathematical background.)


I'm writing a book using the amsbook class, and I've included a page for acknowledgements using \chapter*{}, thinking it wouldn't show up in the ToC.  However, it does (and for some reason it's supposed to do so, according to the amsbook manual); so the question is, how do I get rid of it from the ToC?


If I wanted to advertise for a freelancer to do a GIS job, where would be a good place? I've advertised on  (which we use frequently), but it doesn't even have a GIS category. Am I allowed to do it here?


Javascript: Is there a way to use a variable in a RegEx expression for what is being searched for?

I used the slice() method to test to see if the contents of a variable was in a main string.  I was trying to use a regex. But, I could not figure out how to put the variable inside the regex.  Here is what I did:      function verifySubstrs(mainStr, head, body, tail) {      // Verify if the 1st string starts with the 2nd string,      var headLength = head.length;      if(mainStr.slice(0, headLength) !== head){         return "Incomplete.";     }   Here is what I wanted to do instead.  I wanted to use the variable "head" where I have the text "head".  function verifySubstrs(mainStr, head, body, tail) {  // Verify if the 1st string starts with the 2nd string,  var TF = /^head/.test(mainStr);  if(TF === false){     return "Incomplete."; }   If I could use a variable in what is being searched for, I could use the same technique for finding the body inside the mainStr and the tail at the end. I am looking for the technique and not just the solution to this particular project.


How to call C++ functions of a class from a Python

I tried with the link: , but I am not able to do the same, here I have problem of declaring extern "C".so please suggest suppose I have the function called 'function.cpp' and I have to call this function in the python code. function.cpp is:  int max(int num1, int num2)   {   // local variable declaration   int result;    if (num1 > num2)     result = num1;   else     result = num2;    return result;   }   Then how i can call this function in python, as I am new for c++. I heard about the 'cython' but I have no idea about it.


Originally posted at  - can we get a "Flag Profile" option to purge the inevitable 's and 's of the StackExchange community?


Determine if $\sum_{n=1}^\infty \frac{n+4^n}{n+6^n}$ converges

I am trying to determine if the sum $\sum_{n=1}^\infty \frac{n+4^n}{n+6^n}$ is convergent or divergent.   In attempting to solve this problem I began by seeing if I could do the divergence test - in this case it is not helpful. The terms $4^n,6^n$ look like geometric series type terms but the $n$ in the numerator and denominator are troublesome. I first tried factoring $n$ out of the expression:  $$\sum_{n=1}^\infty \frac{n+4^n}{n+6^n} = \sum_{n=1}^\infty \frac{1+\frac{4^n}{n}}{1+\frac{6^n}{n}}$$  Next I tried comparing to the series $$\sum_{n=1}^\infty \frac{\frac{4^n}{n}}{\frac{6^n}{n}} = \sum_{n=1}^\infty \frac{{4^n}}{{6^n}} = \sum_{n=1}^\infty{\left(\frac{2}{3}\right)}^n$$  This is a convergent geometric series as $r = \frac{2}{3}\lt1$  now I reason that the series $\sum_{n=1}^\infty \frac{1+\frac{4^n}{n}}{1+\frac{6^n}{n}}$ is neither smaller not greater than the series $\sum_{n=1}^\infty{(\frac{2}{3})}^n$ Am I able to conclude anything in this case by a direct comparison test or can I only conclude that the first series is convergent if the second is greater than the first?  Thanks


Prove that $\lfloor\lfloor x/2 \rfloor / 2 \rfloor = \lfloor x/4 \rfloor$

In class, we briefly covered what "floor" and "ceiling" mean.  Very simple concepts.  They were on one slide, and then we never heard about them again.  But now the following homework problem has popped up:  $$\lfloor\lfloor x/2 \rfloor / 2 \rfloor = \lfloor x/4 \rfloor$$  Usually when I post a problem (especially from homework), I like to demonstrate that I'm not just asking for the answer by showing what I've done, what I know so far, and so on... but in this case, I have absolutely no idea where to even begin.  I will say that my first approach was to create a chart and try various values for "x" in order to see if there's a pattern and to make sure there was no easy counter-example to prove it false.  That was all fine and well, but ultimately I couldn't figure out what to do with the results.  Googling for this is quite difficult, as everyone uses slightly different notation and therefore one search doesn't encompass all the actual results.  The only clue that I've seen so far that kind of sort of makes sense, was when some guy said that "x" should be replaced with "4n + k", since the right-hand side of the equation is divided by 4, so that k is any remainder 0 through 3.  How should one approach this problem?  What kind of manipulations can you do to floors?  What can you assume?  etc. etc. ...


What is causing this passed by reference behaviour in Javascript?

Within Javascript I am having the next funtion 'myFunction'.      Note: I created the following code just for explaining my question.   var arrayReference = [1, 2];  function myFunction() {     var array = getArray();      array.forEach(function (elem) {         remove(elem.attr('id'));     }); }  function getArray() {     return arrayReference; }  function remove(elem) {      $.each(arrayReference, function (index, el) {           if (el == element) {                arrayReference.splice(index, 1);           }      }); }   I would think that var array is just passed by value which will not be affected by a change in arrayReference. Yet it seems to be passed by reference. When the forEach method is called using the fetched array, it executes the remove method just for the first element of the array.   So to be clear: the remove functionality is only executed once in my case. Can this have anything to do with passing by reference? I have no idea what can cause this otherwise.   Good to know: When I comment out this remove function, the foreach is executed twice.


Hi i cannot download anything from the software center nor can i get my updates to install, i get this error

Reading package lists... Error! E: Write error - write (9: Bad file descriptor) E: The package lists or status file could not be parsed or opened. david@david-Inspiron-N5110:~$


Python3 subprocess call not working  import subprocess  subprocess.call("sudo nautilus")


Are all the phrases below correct and if they are , what are the differences? Car's window / car window / the window of  car


Firefox: Is it possible to detach a tab from a window with the keyboard?

I am referencing the action you can make by dragging a tab out of the top bar, which creates a new window wherein to put the dragged tab.


When I try to run something like sudo apt-get install rdesktop, I get this:  Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies:  linux-image-generic-lts-trusty : Depends: linux-image-3.13.0-55-generic but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   When I then trying running sudo apt-get -f install, I get this:  Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following extra packages will be installed:   linux-image-3.13.0-58-generic linux-image-generic-lts-trusty Suggested packages:   fdutils linux-lts-trusty-doc-3.13.0 linux-lts-trusty-source-3.13.0   linux-lts-trusty-tools linux-headers-3.13.0-58-generic The following NEW packages will be installed:   linux-image-3.13.0-58-generic The following packages will be upgraded:   linux-image-generic-lts-trusty 1 upgraded, 1 newly installed, 0 to remove and 83 not upgraded. 2 not fully installed or removed. Need to get 0 B/52.5 MB of archives. After this operation, 198 MB of additional disk space will be used. Do you want to continue [Y/n]? y (Reading database ... 353075 files and directories currently installed.) Unpacking linux-image-3.13.0-58-generic (from .../linux-image-3.13.0-58-generic_3.13.0-58.97~precise1_amd64.deb) ... Done. dpkg: error processing /var/cache/apt/archives/linux-image-3.13.0-58-generic_3.13.0-58.97~precise1_amd64.deb (--unpack):  failed in write on buffer copy for backend dpkg-deb during `./boot/vmlinuz-3.13.0-58-generic': No space left on device No apport report written because the error message indicates a disk full error                                                                               dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.13.0-58-generic /boot/vmlinuz-3.13.0-58-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.13.0-58-generic /boot/vmlinuz-3.13.0-58-generic Errors were encountered while processing:  /var/cache/apt/archives/linux-image-3.13.0-58-generic_3.13.0-58.97~precise1_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   Can anyone help me to understand what's going on here? I have read some related questions but am a bit confused.


I've tried just about everything there is to try and I still can't seem to get my Wi-Fi card working.   I've got a Dell Vostro 14 5490 laptop.   It appears that I don't have a working driver for my card or something along those lines. The Wi-Fi menu in the setting GUI says "No Wi-Fi Adapter Found".  Though, I know there is one and it functions perfectly because I have Windows installed in dual-boot and it works fine on it. I have verified there is no switch on the laptop and the setting is on in the BIOS.  Also, I found  to some drivers for intel wireless cards for linux. I wasn't sure which, if any of these would work for my card. I've just installed the iwlwifi-9000-pu-b0-jf-b0-34.618819.0.tgz and the iwlwifi-9260-th-b0-jf-b0-34.618819.0.tgz drivers. (I'm also not certain if my process in installing these was correct either; all I did was downloaded them and move them to /lib/firmware/ and then unzipped them there. Leaving the zip files and everything in the directory) I did not have any luck in doing this - I even tried restarting the computer.  $ lspci -nn | grep -i network Network Controller [0280]: Intel Corporation Device [8086:02f0]     $ uname -r 5.0.0-31-generic     $ iwconfig enp2s0    no wireless extensions. lo    no wireless extionsions     $ sudo lshw -C network *-network     description: Network controller     product: Intel Corporation     vendor: Intel Corporation     physical id: 14.3     version: 00     width: 64 bits     clock: 33MHz     capabilities: pm msi pciexpress msix bus_master cap_list     configuration: driver=iwlwifi latency=0     resources: irq:16 memory:cc22a0000-c22a3fff     $ dmesg | grep -i firm [    0.204901] ACPI: [Firmware Bug]: BIOS _OSI(Linux) query ignored [    1.233739] [drm] Finished loading DMC firmware i915/kbl_dmc_ver1_04.bin (v1.4) [    1.364414] [Firmware Bug]: ACPI(PXSX) defines _DOD but not _DOS [   20.643192] iwlwifi 0000:00:14.3: loaded firmware version 43.95eb4e97.0 op_mode iwlmvm [   21.051100] Bluetooth: hci0: Firmware revision 0.0 build 26 week 21 2019 [   26.210254] iwlwifi 0000:00:14.3: Failed to load firmware chunk!     $ sudo dpkg -s linux-firmware | grep Ver Version: 1.178.3   After running the linux-firmware update as per the answer below by chili555, I ran the following and got the following output:  $ dmesg | grep iwl   Since the output was so huge, I put it into this pastebin:   Also, during the linux-firmware update, I got a couple informational prints that said:  I: The initramfs will attempt to resume from /dev/dm-2 I: (/dev/mapper/ubuntu--vg-swap_1) I: Set the RESUME variable to override this.   After running the second set of commands in the answer below by chili555, I received the following output:  $ dmesg | grep iwl   Again, due to the output being so massive, I've included it in this pastebin:   The wifi functionality now appears to be working properly subsequent to running the commands in chili555's answer.


Today I uploaded my site to the server, and I get errors like the following:     Unable to generate the derived image located at public://styles/sponsor_image/public/TerraThermaSponsorLogo.png.   Image styles cannot generate images. I have tried to set permissions on styles/* folders with chmod -R 775 styles/, and even tried chmod -R 777 styles/. The folder's owner is OK. I don't get what can be wrong.  The directory associated with public:// is sites/default/files, and it is OK.


How do I register a .NET assembly to the GAC and register it for COM in WIX? (Regasm)

I am making a custom tool (code generator) for VS2008.  I have the wix installer putting in all the registry entries for the visual studio, but what it is not doing is the equivalent of regasm mytool.dll  It is getting into the GAC by virtue of the  Assembly=".net" attribute of the File element. But I am not even entirely sure that getting into the GAC matters.  I think it would work with a regasm /codebase mytool.dll  Thanks


How to determine Windows 10 version when it is not running?

I have upgraded my Windows 8 to Windows 10 recently. After that, I bought a SSD drive for my notebook and removed the regular HDD drive from it and installed a fresh copy of Windows 10 (Home edition). The HDD was put in a external USB case, so I can access my old files and old Windows installation partition as well.  The problem is now I'm having some issues to activate my fresh installation of Windows. I'm not really sure that I should've installed Windows 10 Home or another version.  How can I determine which Windows version is in the old HDD, given that all files are still accessible, but the system itself is not running?  I could just swap the SSD and the HDD again and boot the old system, but it'll be better to find a "software" way of doing that.  addresses what I'm looking for, but for Windows XP. The proposed file doesn't exists in my old installation.


I want my footer to be always on the bottom of the page, even when the content is very short. I have checked this one  but does not work.  My HTML:

     My CSS:   #footer {     height: 320px;    position: absolute;    width: 100%;    bottom: 0;  }   With this one, when I have a short content is ok, but when I have a long one the footer goes in the middle of the page and stuck there. Does anyone have an idea ? Thanks in advance


Any Idea how I generate random Char values in Java? I'm creating a random password generator

I'm creating a random password generator in java and need some help with how I can generate random char values in the program. Any ideas? I'm using a menu system as a way to show different types of passwords to generate like lowercase, uppercase, etc.   Any advice would help.   Thanks!


I've always been told that most electronic devices such as WiFi/phones/laptops and such emit a non-ionizing radiation which is completely fine as it does not damage human DNA. I've been googling and i see people arguing about it but there seems to be no evidence to back up the fact that it's not damaging. I'm just curious is what I'm saying correct? or can it damage the human body as i see people mention it can lead to pretty serious health problems.


I'm struggling to grasp the concept of bias in the context of linear regression analysis.    What is the mathematical definition of bias? What exactly is biased and why/how? Illustrative example?


Ideal value for  when used for a JS event?

I've got a link I want to appear on my page,   add another   But it doesn't look like a link unless I add an href attribute. I'm going to be using jquery to add a .click() event to it, so it doesn't really need anything else.  What's the best value to href to? #? javascript:void(0)? My concern is if someone clicks it before the .click() event gets added or something. # will scroll them to the top of the page, void(0) looks kinda nasty and isn't informative if they look at the address bar...


List of amino acid frequency of different foods?

I'm trying to write a little application calculating the biological value of protein content of different meals using the amino acid frequency of different foods.   The idea is that the user can choose amount and type of different ingredients and finally obtains the biological value index for the meal.  For this calculation I'd need a list of amino acid frequencies of the different foods.  Any idea how I could obtain this?  My first idea was to just use the DNA of the different plants to extrapolate the proteins synthesized and then obtain the amino acid frequency from there but I know that genome and proteome is not correlating.  Any ideas / thoughts?


How to gather more views for a posted question other than putting bounties?

I am new to Stack Exchange and want to know how shall I increase the view of my question which is not getting answered and has gathered small no. of views. I have used bounties in stack overflow in past in order to increase the view count and successfully get the required answer but what if I'm new to some other website of Stack Exchange and do not have enough reputation to put bounties? I know that editing can help and have done it but still, the question remains less viewed. One of my question on  has gathered fewer views and I'm new to that site. I can't offer bounties on it, so Is there any way to tackle with this? EDIT: If the question has answers and none of them are helpful then at least there is a chance that people who answered may soon find the right/helpful or at least look into the depth of question. But, here I'm asking about a scenario where the question hasn't received any answers and fewer views.


Why can a function modify some arguments as perceived by the caller, but not others?

I'm trying to understand Python's approach to variable scope. In this example, why is f() able to alter the value of x, as perceived within main(), but not the value of n?  def f(n, x):     n = 2     x.append(4)     print('In f():', n, x)  def main():     n = 1     x = [0,1,2,3]     print('Before:', n, x)     f(n, x)     print('After: ', n, x)  main()   Output:  Before: 1 [0, 1, 2, 3] In f(): 2 [0, 1, 2, 3, 4] After:  1 [0, 1, 2, 3, 4]


How to link a library with cmake where the library uses thread_local class members

tl;dr Is there a certain way to link libraries to ensure that thread_local variables are properly defined? I have a class along the lines of engine.h class Engine { private:   std::mt19937_64 m_engine;  public:   Engine() = default;   ~Engine() {}    std::mt19937_64& get()   {     return m_engine;   } };  and another class that uses it, threadrandom.h #include "engine.h"  class ThreadRandom { private:   static thread_local Engine m_engine;  public:   ThreadRandom() = default;   ~ThreadRandom() {}    static const float Rnd()   {     std::uniform_real_distribution< float > _engine;     return _uniform( engine() );   } };  I use make to add them into a library with add_library(${PACKAGE} SHARED ${SOURCES})  and then I link it to some tests with target_link_libraries(test ${PACKAGE})  Whenever I try to build this way the thread_local member comes up as undefined. The rest of the compilation works fine if remove the thread_local and keep the engine as simply static (then declaring it in the source file). The same problem occurs with GCC 10 and Clang 12 that I have been testing with. I can also declare a thread_local file in the main executable and have no problem executing it so think the problem occurs with linking the library. Is there a certain way to link libraries to ensure that thread_local variables are properly defined?


Find the minimum value of this rational expression

A question asks, "If x is a postive real number, then find the minimum value of  $[{x + (1/x)}^6  - {x^6 + (1/x)^6} - 2]/ [{x + (1/x)}^3 + {x^3 + (1/x)^3}]$    My try:- I expanded and simplified the numerator and then applied AM - GM and got Numerator $>= 12*sqrt(10) + 18$. Then applying AM-GM on denominator, we get denominator $>= 4*sqrt(6)$.  But I do not know how to combine these two results. How can I proceed?


Why doesn't current decrease in series combination?

I know that the question is quite stupid but I want to get an insight of this case. consider 3 resistors connected in series with a battery, after the current passes through resistor 1 it loses some of its energy, the kinetic energy of the charge carriers will definitely also decrease and so does the drift velocity then why doesn't the current decrease? Its quite confusing.


I want to deploy a war file, to my tomcat manage, and the path is quite long, so I want to enter the path, but whenever I go into open file, I can only select the files manually, by going through the folder. Is there a way to enter the file path, I have attached a picture to show the UI I get  (BTW I'm using 16.04)


Can a nonzero polynomial evaluate to the zero function in a suitable infinite ring of char 0?

I shall assume all rings to be commutative in this question. The impatient can scroll down to the "blockquote" to read the actual question.  Whenever we have a polynomial over a ring, it defines a function from the ring to itself by evaluation. It's reasonable to ask when two different polynomials define the same function.  From the factor theorem it follows that an $n^\text{th}$ degree polynomial over an integral domain has at most $n$ roots. Then it's easy to show this:  Theorem. Let $R$ be an infinite integral domain and let $f \in R[X]$ such that $f(a)=0$ for all $a \in R$, then $f = 0$. Proof. $f$ has infinitely many roots, so it must be the zero polynomial. $\quad\square$  For finite rings a kind of opposite situation occurs:  Theorem. For any finite ring $R$ there are polynomials over $R$ that are different but agree on all elements. Proof. There are only finitely many functions from $R$ to itself, but $R[X]$ is infinite. $\quad\square$  If we make further assumptions it's of course possible to prove more, as Pete L. Clark wrote in this post: []  Then there is the question of infinite rings that are not integral domains. It's relatively easy to come up with examples of a ring $R$ with positive characteristic and a nonzero polynomial that evaluates to the zero function, e.g.: $$ R := \bigoplus_{n=1}^\infty \mathbb{Z}/6\mathbb{Z} \quad\text{and}\quad f(X) := X^3-X.$$  The Question:     This leaves open the case alluded to in this post's title: Is there a commutative ring of characteristic $0$ (hence infinite) such that a nonzero polynomial evaluates to the zero function?


How to search for .zip files instead of all compressed files?

How do you search for a file of a specific type in OS X Yosemite?  I cannot seem to find any instructions on how to do this.   In the Finder search I enter: kind:zip  But it returns all compressed files.  I only want zip files - so this  does not help me much.  All the solutions either use bash, or I cannot find the options they refer to.


What is PrivateFrameworks 'deleted' and why is it using so much CPU?

I noticed a process called deleted using quite a lot of CPU. In the image linked, it shows 10% CPU usage but fluctuates frequently hitting highs of 20% and averaging around 12%. Suspicious that it could be a remnant script from a removed installation, I sampled the process and found that there's a system library called PrivateFrameworks which runs deleted.  What does deleted do? What is PrivateFrameworks responsible for? Is it safe to remove from my Mac?


I have a table called departments which consists of a column called salary. Now I want to have all the details of the highest two salaries in each department. How should we develop a query which yields the required output? Top-N analysis will give it as a whole but not for each department. I want the top two in each department.


Need Regex to validate 11-digit phone number without plus sign

I need a regex to validate phone number without plus (+) sign for example   46123456789,46-123-456-789,46-123-456-789   number should be 11 digit rest of should ignore  i am currently using this Regex /([+]?\d{1,2}[.-\s]?)?(\d{3}[.-]?){2}\d{4}/g  its not correct at all


Difference between void main and int main in C/C++?

Does it matter which way I declare the main function in a C++ (or C) program?


Can someone explain the geometric meaning of the $C^1$ norm on $C^1[X]$, where $X$ is compact.  Thanks in advance.


Why cannot this question with an open bounty be closed?

I have seen a number of questions like:     "Do this work for me please" or without "please"   If such a question doesn't have a bounty, I can downvote it if I want or flag it for closing. But if it has a bounty, then it's protected.  Why?  To be clear, I have nothing against "do-it-for-me" questions in real life, but if it's not allowed on Stack Overflow without a bounty why is it allowed with it?  Update: And you can probably close / put on hold such a question after the bounty time is over..  Examples of such questions that I have flagged:   - was put on hold and deleted by TS   - was put on hold and deleted by TS   - flag was declined   - flag was declined   - flag was declined   - flag was declined   - flag was marked as helpful   - flag was declined   - flag was marked as helpful   - flag was declined   - flag was declined


Let A be a set. Show that $\bigcup_{n\in\mathbb{N}}A^{n}$ is a set

Okay, so, I was reading a book on set theory and I stumbled upon the problem described in the title. The only axioms and axiom schemes that are assumed are the following: Axiom of Existence Axiom of Extensionality Axiom of Comprehension Axiom of Pair Axiom of Union Axiom of Power Set Axiom of Infinity From the theory developed so far I can prove that if A is a set then, for all $n\in\mathbb{N}$, $A^{n}$ (the cartesian product of $n$ copies of $A$) is also a set. I can also prove by induction that, for all $N\in\mathbb{N}$,  $\bigcup_{n=1}^{N}A^{n}$ is also a set. But I can't seem to be able to show that the countable union is a set. Well, I can, but it feels like I'm cheating, so to speak. My idea goes as follows. The book already outlines a proof that $A^{B}$ (the collection of functions from a set $B$ into a set $A$) is a set. I will assume this fact. In particular, we have that $A^{\mathbb{N}}$ is a set. Now we can easily define functions $f_{n}$ from $A^{n}$ into $A^{\mathbb{N}}$ in such a way that $im(f_{i})\cap im(f_{j})=\emptyset$, whenever $i\neq j$. Informally, the idea is taking an element of $A^{n}$ and adding a trail of $n$ at the end. Now, this is where I feel the cheat is. We can "identify" (I choose to use the quotation marks because the book hasn't formally defined this idea, even though I know this kind of trick is used all the time in other areas) $A^{n}$ with its image. So I kind of proved that all of the $A^{n}$ can be realized within $A^{\mathbb{N}}$ (with no overlapping), so their union also can be realized as a subset of $A^{\mathbb{N}}$. This in turn "shows" (with big quotation marks) that the countable union of the $A^{n}$ is a set, as intended. However, I feel that this isn't entirely correct from the point of view of axiomatic set theory, since at no point in the book so far it was shown that if a set $X$ can be realized as a subset $Y$ of another set $Z$, then this implies that $X$ must be a set. No theorems about cardinality have been proven up to this point in the book, either. I feel like the correct way to prove something is a set is either explicitly constructing it from the axioms, or showing that it is a subset of another set, which isn't the same as showing that it can be identified with a subset of another set. This might seem excessively nitpicky, but that's precisely the point. I'm interested in proving this without making any assumptions that don't follow from the axioms listed above. Anyway, I would really appreciate your input. If this argument is correct (and I think it's not), I would really like to know how to justify it. If it's not, how should I go about proving this? I think a hint or two should be enough to get me on the right track.


404 not found errors for PPAs when I run sudo apt update

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