Role playing is an excellent hobby to train your problem solving skills. You learn to look at situations from different view points (i.e. the characters) and you have various skills and resources at your hands (from dangerous to trivial, from magical to mundane...) which you will often sort through, combine and apply to solve the problem at hand. In our group of RPG veterans this fact leads to a strong prevalence of what I will call MacGyver-ism. Let me explain using an example:  One of the recurring items is the molotov cocktail, or some genre-specific variant. It is highly efficient, trivial to create (pour liquid into bottle) and the ingredients are wide spread and cheap (gazoline/lamp oil, a bottle, some cloth). The process seems to be so simple that even untrained characters of low intelligence should easily be able to do it.  Just as MacGyver will do in his shows, the players will often combine mundane items and/or trivial skills in unforseeable ways to get an advantage, be it combat or plot wise. This can lead to solutions which are:  very unrealistic given the setting (i.e. some medieval character would probably not know how to manufacture a molotov cocktail) overpowered (tips balance of certain encounters/problems, especially low-tech close-combat settings) are hard to forsee/prevent, as the needed ingredients are wide-spred and freely available (I can hardly keep my players from buying lamp oil or bottles)  So far I have not yet found a very compelling reason why my players should not be creating molotov cocktails (or similar improvised devices) all the time, and in settings where such solutions seems to be very unfitting (say, high fantasy). How can I limit or control the prevalence of over-improvisation or MacGyver-ism in players actions? As the first answers and comments heavily focused on the molotov: I am just as well concerned about players being true to their characters knowledge and possibilites as I am about the problem of power balance.  A medievalish soldier just should not possess the knowledge to build improvised firearms, bombs or complicated mechanical contraptions.  I have absolutely no problems with PCs being smart, creative and inventive while solving problems. I have a problem though, when the players are smart/inventive in ways which don't fit the setting or their supposed PC knowledge. As it was suggested that his question is not entirely system agnostic (I somewhat agree), here some systems where I have struggled with this issue: MERP (low magic high fantasy), Call of Cthulhu (Investigative/Horror), DSA (high magic high fantasay)


Python array - changing one value changes multiple slots

Is there any reason why the below happens? In both cases, we defined grid as 3 by 3 array of zeroes, but when we change middle value to 2, three values are changed to 2 whereas in the second case, only one value was changed to 2.      grid=[[0]*3]*3 grid[1][1]=2 print(grid) [[0, 2, 0], [0, 2, 0], [0, 2, 0]]  grid=[[0 for i in range(3)] for i in range(3)]  grid[1][1]=2 print(grid) [[0, 0, 0], [0, 2, 0], [0, 0, 0]]


Using stackoverflow for community product and paying

We're developing an software product that has both a community (free) and a paying version. The paying version has some features the community has not, but it's a fully functional application.  We moved part of our support to stackoverflow (for the community questions), can we also ask customers of the paying application to use stackoverflow (no problem it's public) ?  sorry if this has been asked N times where N it's no more countable ;-)


Formatting number values on Visualforce page

I am wondering if it is possible to dynamically format input numbers in Visualforce components when rendering as HTML. I am able to successfully accomplish this when rendering as output tags doing the following:  <apex:outputText value="{0, number, ###,##0}">     <apex:param value="{!myNumber}"/> </apex:outputText>   Which yields a value of 123,456 provided myNumber is an Integer of 123456. In an ideal world, this would work in inputText as well (and there are ways to accomplish this via javascript), but I am curious if there is anything "out of the box" with Salesforce.  UPDATE: Modified original question after noticing a syntax error.


How to remove all event handler from an Observable collection's CollectionChanged event (not for Control's click event)

I don't want to do -= for each individual event handler added, but looking for a common implementation to remove all event handler added to this collection. I know there is already a Q/A to remove event handlers from Control's event, but don't find the same helpful for a generic Observable collection. Given 'string' Observable collection as an example, it can be of any type  public class ABC  {     public ObservableCollection<string> MyObservableCollection     {          get;         set;     } }


Won Announcer badge even without sharing the link externally

A few hours ago, I won an Announcer (Bronze) badge on . The message under achievements tab said:     You've earned the "Announcer" badge (Share a link to a question later visited by 25 unique IP addresses) for "Does USB-C to HDMI take more processing power than direct USB-C to DisplayPort?".   I am a software developer and I understand how the mechanics behind earning this badge work. (Clicking on the Share button beneath the question gives a personalized URL. Hitting the URL will tell the Stack Exchange backend that the URL was visited along with the IP address information.)  Now as I understand, just clicking the Share button (to generate the customized URL), without actually posting the URL anywhere shouldn't work, right? However, I have observed this on couple occasions that I have earned this badge even without sharing the URL externally.  Does simply generating the URL triggers the visit counter corresponding to my user account, so that any new visit to the post is counted against my account? I don't agree with that. However, I have earned Announcer badge couple times that prove otherwise. I have never posted the link elsewhere (except just once, for the sake of earning the badge).  Could this possibly be a bug in the Stack Exchange backend? If yes, this makes for a potential opportunity of gaming the system, where I simply generate the link for popular/hot questions and earn Bronze badges quickly.


What do I need for extreme macro photography?

I am wanting to venture into some extreme macro photography, specifically insects, such as . After doing some research I have believe that my 1::25 macro lens will be sufficient if I am to use some extension tubes (which I have bought).  I would like to shoot the in the wild, is this possible/likely? Or is this always a catch, then release style of shooting?  Regarding the link I've posted, would this be possible with a 1:25 macro and extension tubes? I have a set of three (21mm, 31mm and 13mm). How would you go about shoot a blue bottle for example? Surely they are going to fly away? Should I use a tripod or will that cause more of a hindrance than a help? Are there any techniques/tricks I could use to get a sharp focus on my subject?


Showing $\sum\limits_{i=1}^n\frac1{\sqrt i}>\sqrt n$ by induction.

I need to prove this inequality by using induction: $(\frac{1}{\sqrt1} + \frac{1}{\sqrt2} + \dots + \frac{1}{\sqrt{n}} > \sqrt{n}$ for $n\geq2$.  $$\sum\limits_{i=1}^n\frac1{\sqrt i}>\sqrt n$$  I easily get by the base case for $n=2$, you get $2 > 1/4$, which is true. Then you make the assumption to be true for $(1/\sqrt1) + (1/\sqrt2) + (1/\sqrt3) +...+ (1/\sqrt n)) > \sqrt n$  And then you have to prove for $(1/\sqrt1) + (1/\sqrt2) + (1/\sqrt3) +...+ (1/\sqrt n ) + (1/\sqrt{n+1}) > \sqrt{n+1} .$  I don't know where to go from here. any help would be appreciated. Thank you.


Help Understanding How Long It Will Take To Heat My Wire

I am trying to find out how many Amperes I will need to reach a certain temperature in a certain time (Milliseconds)  I need a thick wire to slow the melting of the wire. "Nichrome is the wire I'll be using" now in the American Gauge. I want to use 12 as its thick but not too thick and on Wikipedia, when I was checking how many amps I will need to reach a specific temperature using that gauge type it said I will need around 39.03A to reach around 1400F but in what time period will I reach that? Thicker wires are much slower to heat up but smaller wires are very weak.   P S I am very new to the American Wire Gauge so forgive me if I'm wrong.    I need a thicker, more sturdy wire that can put in a high PSI environment and still reach temperatures of 2-4 millisecond. The problems i see is thicker wire don't have as much resistance and a smaller mutil-twisted smaller wire. Is there away i can change that and still reach my desired temp of 1400F?


Yet another LinkedHashSet .equals dilema

I know this has been asked several times and I promise I have read over 100 articles before resorting to posting. Here is my issue:   I have created my own object (WorkoutData). It is made up of several string variables, and integer and a linked list of strings:  public class WorkoutData implements Serializable {     private static final long serialVersionUID = 878893767880469289L;     String workoutLocation;     String bodyPart;     String exercise;     int numOfSets;     LinkedList<LinkedList<String>> datesSetsAndReps; }  In case any duplicates ever get into my datafile I am reading the objects into a LinkedHashSet. My thinking is that this will automatically eliminate any duplicates.   Of course this isn't working, because each object has its own ID and therefore will not be "equal" to another object. To try to get around this I have overridden the equals and hashCode inside my WorkoutData class.  For some reason it is still not working. Here is how I am loading my linkedHashSet:  for (int iterator = 0; iterator < numberOfWorkouts; iterator++)     tempWorkoutDataSet.add((WorkoutData) in.readObject());   Here are my overridden methods in the WorkoutData class:  @Override public boolean equals(Object other) {     if (other == null)     {         return false;     }      if (this.getClass() != other.getClass())     {         return false;     }      if (!this.workoutLocation.equals(((WorkoutData)other).workoutLocation))     {         return false;     }      if (!this.bodyPart.equals(((WorkoutData)other).bodyPart))     {         return false;     }      if (!this.exercise.equals(((WorkoutData)other).exercise))     {         return false;     }      return true; }  public int hashCode() {     return this.workoutLocation.length(); }   The hashset contains duplicates no matter what I try. I think the equals method is correct, but I freely admit I have no idea what the hashCode method is meant to accomplish.    This question is NOT a duplicate of "How do I compare strings in Java?". That question only talks about the == vs .equals issue. My issue has more to do with overriding hashCode.  I think that is where my problem lies. Couple that with the fact that I am still unclear exactly what the hashCode override is meant to accomplish.


What is the difference between an electric field and gravitational field?

Since the electrostatic field and the Newtonian gravitational field share a similar form: proportional to   $$  \frac{1}{r^2} $$  Is there any qualitative difference between motions under the influence of electric field and gravitational field?


While running Function in selenium getting null pointer exception for fluent wait

The color if the button is null     Exception in thread "main" java.lang.NullPointerException   public static void main(String[] args) throws InterruptedException {      WebDriver driver = new FirefoxDriver();     driver.get("http://toolsqa.com/automation-practice-switch-windows/");      FluentWait<WebDriver> wait = new FluentWait<WebDriver>(driver);     wait.pollingEvery(250,  TimeUnit.MILLISECONDS);     wait.withTimeout(2, TimeUnit.SECONDS);      Function<WebDriver, Boolean> function = new Function<WebDriver, Boolean>()             {                 public Boolean apply(WebDriver arg0) {                     WebElement element = arg0.findElement(By.id("colorVar"));                     String color = element.getAttribute("color");                     System.out.println("The color if the button is " + color);                     if(color.equals("red"))                     {                         return true;                     }                     return false;                 }             };      wait.until(function); }


How to include file with extension SVG in LaTeX(Tex.tex)?

Is there a way to include svg figures directly into LaTeX? I have only mySVG.svg file and myTex.tex file. The big question is how to include this svg into my file with extension tex. I tried all examples in this forum, but without any results for me.   Important! I have only .svg and .tex file, not .pdf_tex or my svg in pdf format. Is it possible to generate them with latex syntaxis.   Maybe i need something like this (BUT THIS NOT WORKING FOR ME)   \newcommand{\includesvg}[1]{%  \executeiffilenewer{MYSVG.svg}{MYSVG.pdf}%  {inkscape -z -D --file=MYSVG.svg %  --export-pdf=MYSVG.pdf --export-latex}%   and if this code generate PDF inside in \begin{document}  \begin{figure} \centering   \executeiffilenewer{MYSVG.svg}{MYSVG.pdf}{inkscape -z -D --file=MYSVG.svg --export-pdf=MYSVG.pdf}   \includegraphics[width=\columnwidth]{MYSVG.pdf}   \caption{FIRST SVG}   \label{fig:normal}  \end{figure}


Why do we notate the greatest common divisor of $a$ and $b$ as $(a,b)$?

In my textbook on elementary number theory from a class last year, as well as elsewhere through my academic experience and even posts here, I often see the greatest common divisor notated as $(a,b)$ (where this represents the greatest common divisor of $a,b$).  My question is, why is such an unusual notation used? I say it's unusual (if not a bit absurd), for a couple of reasons:   It is unintuitive. It does not grant the reader an immediate knowledge of what it means. In particular, I can easily see it being misinterpreted as an ordered pair of points, and not as a function (which it basically is and I touch on in a second) or representing a single value. Good notation would be immediately understood, no? One should not struggle with parsing through the context or meaning. A clearer notation is often used, and just three letters away. You could certainly think of $(a,b)$ as an ordered pair, if we consider it a function. I often see the alternate $gcd(a,b)$: a function, which takes in two inputs ($a$ and $b$), and outputs their greatest common divisor (or factor, if you prefer). Merely adding the three letters makes the notation clearer by clarifying it is  a function, and using a relatively well-accepted acronym. (Or, at least, I often hear it abbreviated "g.c.d." in school.)   I've mulled this over for a while and I can't think of much without borrowing inspiration from other "unusual" notations. For example:   Common understanding in context: consider the $\log(x)$ function. Depending on context, without a base stated as seen here, it can be presumed to mean whatever is most "appropriate." It could be base $e$ (common in mathematics), base $10$ (common in engineering), or base $2$ (common in computer science). The ambiguity is essentially resolved by context in other words - personally, not a fan of that (I like the explicit stating of bases for full clarity), but if such a motivation holds elsewhere, it might stand to reason that $(a,b)$ could just be taken as a shorthand and "understood" in the context of number theory to simply be the greatest common divisor. That it is in fact used despite $gcd(a,b)$ being clearer and somewhat common also does seem to suggest this playing a role. Perhaps it just started that way and it kept being used. For example,  (based on a ) regarding how logarithms, roots, and exponentiation can be unintuitive from a notation perspective, and proposes an alternative, easier to understand notation. I haven't been in middle school in nearly a decade, but guessing from discussions online, that obviously hasn't really picked up too much. In that sense, perhaps it's like that for $(a,b)$: like we still notate exponentiation, etc., the same way today despite how counterintuitive it is (at least for students), perhaps it just "stuck" and proliferated?   I wasn't able to easily find any reason why online, and it bugs me a bit, so I ask:     Why do we so unintuitively notate the greatest common divisor of two numbers $a,b$ as $(a,b)$?   I of course recognize that this is somewhat moot in light of how easily it's made clear - as established above, all I have to do is append the front of the parenthetical by $gcd$ or $gcf$ to make it way better. And of course, people do that. But I'm more curious in where this ambiguous former notation arose and, in light of a better notation, why it is still used today.


Consider  a  variant  of  DSA  in  which  the message space is $\mathbb Z_q$ and the hash function is replaced by the identity function.  (So the second component of the signature is now $s := k^{−1} \cdot ( m + xr ) \mod q $). Show that this variant is not secure.  How would one go about this problem?


Odds ratio MLE calculation: unconditional vs conditional?

I am running an odds ratio calculation for site methylation amongst cases and controls.   In this situation is it preferable to use a conditional or unconditional MLE? I am asking because R uses a conditional estimator while scipy uses an unconditional estimator. See .  As a result, I am getting differences in the p-values calculated. I found an article from 1984 which suggests that conditional MLE is far superior. If this is the case, why does scipy API suggest that using unconditional MLE is much more common?   It was also asked  by gotgenes. But no answer was provided so far.   odds_extractor <- function(cpg_id,disease,control){         # Make a temporary data frame to hold just one cpg site frequency table         temp <- cpg_list[[cpg_id]][c(disease, control),]         # Get all of the a,b,c,d values         a <- as.numeric(temp[1,1])         b <- as.numeric(temp[1,2])         c <- as.numeric(temp[2,1])         d <- as.numeric(temp[2,2])         # Perform the odds ratio calculation         oddsratio(a+rts,b+rts,c+rts,d+rts)  } ... writting[i,4] <- odds_extractor(names(cpg_list)[i],disease,control)$estimate


Compare dates in javascript which use 'D MMM YY - HH.MM.SS' formatting

I'm a little bit new to javascript (but not scripting in general). Does anyone know a good way to compare dates which use this formatting? Need it for 'google script' if statements.  if ('14 Jul 16 - 16.34.06' > '5 May 17 - 08.24.27'); {  ;do this }  ;another example if ('7 Oct 16 - 09.19.55' < '28 Nov 16 - 02.06.12') {  ;do this }   Should I use moment.js perhaps? Seems a bit big.  Thanks for the help!


How do you sort du -sh /dir/* by size? I read one site that said use | sort -n but that's obviously not right. Here's an example that is wrong.  [~]# du -sh /var/* | sort -n 0       /var/mail 1.2M    /var/www 1.8M    /var/tmp 1.9G    /var/named 2.9M    /var/run 4.1G    /var/log 8.0K    /var/account 8.0K    /var/crash 8.0K    /var/cvs 8.0K    /var/games 8.0K    /var/local 8.0K    /var/nis 8.0K    /var/opt 8.0K    /var/preserve 8.0K    /var/racoon 12K     /var/aquota.user 12K     /var/portsentry 16K     /var/ftp 16K     /var/quota.user 20K     /var/yp 24K     /var/db 28K     /var/empty 32K     /var/lock 84K     /var/profiles 224M    /var/netenberg 235M    /var/cpanel 245M    /var/cache 620M    /var/lib 748K    /var/spool


I'm dynamically trying to create a div which has a content and delete button whenever this 'createaction' button is clicked.  I have an onclick function whenever the delete button is clicked. but my code here does not work, and I think it is because the delete button id is the same.  In what way can i make these buttons unique from each other?  $("#createAction").click(function() {   var targetDate = $("#targetDate").val();   var newAction = "

                         <button type='button' id='delete'> delete</button>
                      Target Date:" + targetDate + "
";   $("#actionPlanInfo").append(newAction);    $("#targetDate").val('');    $("#delete").on("click", function() {     var confirmation = confirm('Are you sure you want to delete this action plan/s?');     if (confirmation == true) {       $(this).parent().parent().remove();     }   }); });


Conferences as publication venues – black and white or is there a grey or third way?

There are two ways of treating conferences that are commonly mentioned on this site:   Conferences are publication venues for papers (or similar). Submissions will be subjected to a serious peer review, are citable as evidence, and are a relevant achievement. Submitting the same material to two different conferences or a journal and a conference would be considered self-plagiarism.  This applies to computer science and engineering (or at least some subfields thereof) – for details, see:  Conferences are not publication venues. The material presented there is typically also published in journals, books, and similar – but this process is not tied to the conference; it may occur before the conference, later, or even not at all. Submissions are only subjected to minimal review¹, are not citable as evidence, and not considered a big achievement. Participating in conferences is still considered important though. It is common that authors present the same material at different conferences.  This applies to the majority of fields.  ¹ to weed out utter crap or to decide what should be a talk and what a poster   In light of , I am interested whether the above two cases are the only two. To me, it would not be surprising if this actually is the case, as the two categories have a self-preserving mechanisms. For example, for a conference belonging to the first category, weakening the criteria for submission would usually be a bad move. On the other hand, I am very well aware that I do not know every field’s customs. Hence, I am asking: Are there conferences that hold a status not described by the two categories above? Please answer only if you can name and describe such a conference – if this question remains unanswered, this would be an acceptable and meaningful outcome.  Note that this is only about what is submitted directly to the conference for the purpose of being presented there. Whether articles corresponding to the presented material will be collected for a book, special issue of a journal, or other form of proceedings – be it with separate peer review or not – is irrelevant for the purposes of this question.


How to I append an element to a 2D array in Python? ("representing a hash table of arrays")

So I am trying to make a hash function that put an element k into a 2D array based on it's mod. For this example the size of the outer array is 4. So to start out the hash table I want it to be a 2D array that has the size of the outer array to be 4. Then there will be 4 empty arrays inside the outer array. Like so...  n = 4 A = [[]]* n   Which is [ [], [], [], [] ] So when I use the hash function like this hash(A, 2) it should output this [ [], [], [2], [] ] based on this code below...  def hash(A, k):     idx = k % 4      for i in range(len(A)):         for j in range(len(A[i])):             if i == idx:                 print(A[i][j])                 A[i][j] = A[i][j].append(k)   So the problem is that it outputs this [ [], [], [], [] ] and not this [ [], [], [2], [] ].   I have tried...  def hash(A, k):     idx = k % 4     A[idx].append(k)   but this only outputs [[2], [2], [2], [2]] which is not what I want.   How do I make my hash function give me this output [ [], [], [2], [] ]?  (P.S. I know it's a lot better to simply just make an array of linked lists. I am doing this for a better understanding of hash table if they were implemented with arrays and to get a better understanding of 2D arrays.)


how i install code block in my Ubuntu.when i search in my Ubuntu Application center code block it's shows various applications.i want to install c or c++ editor then tell me which is correct for me.


We're a web design company that have created several websites for clients, all of which have a back link to our own website. I was just wondering the best strategy for this:   Should the keywords be in the title, alt and link text? E.g Keyword? Should we make the keyword the same on all the client web sites? Should we incorporate our company name as the link text?   Are there any other general things I should follow?  UPDATE: Currently we have "designed & built by ". Are we better off having something like ""?


How to send an email to a well-known professor for a possible PhD student position?

I am applying for graduate physics and I was wondering to work with a well-known professor in Caltech. He is a pioneer in the field that I am interested in. I have a kinda outstanding background, however, I am not sure if the professor is looking for exotic genius students who have completed their master at 18 or something! In this sense, I am very ordinary. How should I send an email to the professor and finally understand if I have any chance to do my PhD under his supervision or not?  P.S. I just want to know how one should contact a professor to make themselves sure that whether the professor is willing to accept them as a graduate student. I do not ask please decide on behalf of me.


How can I get a VirtualKey enum from a string? For example trying to get the enum for the letter "w" from the string "w".


Invariance of lagrangian with $\frac{d}{dt}(f(q,t))$

I know that if we have a lagrangian such that  $$ L'=L+\frac{d}{dt}(f(q,t))$$ then the equation of motion will be the same for $L$ or $L'$.  But I would like to know if there is a proof of the opposite, ie :  If $L$ and $L'$ describe the same motion, then $$ L'=L+\frac{d}{dt}(f(q,t))$$  I don't know how to prove it?


Why is $\underbrace {i^{i^{i^{.^{.^{.^{i}}}}}}}_{n \ times}$ converging?

Introduction:  Recently I found out that $i^i \approx 0.20788$ has no imaginary part. I got interested and then wanted to know whether there are other $n$ for which $\underbrace {i^{i^{i^{.^{.^{.^{i}}}}}}}_{n \ times}$ has no inaginary part.  So I wrote  (I'm a beginner at python, could be very bad code :) which plots what I call the $i-Tower\ up\ to\ n = 100$. It looks like this:   Question:  Let's use this convention: ${}^ni = \underbrace{i^{i^{i^{.^{.^{.^{i}}}}}}}_{n \ times}$.   Why is the sequence ${}^ni\ |\ n \in \mathbb{N}$ converging?   ${}^{20}i \approx 0.48770 + 0.41217i$   ${}^{60}i \approx 0.437584 + 0.360535i$   ${}^{100}i \approx 0.43829+ 0.36059i$  What I already noticed is that the angle between the lines you can draw from ${}^ni$ over ${}^{n+1}i$ to ${}^{n+2}i$ is $<90°$.   Is that angle equal for all $n$? Is there a way to give the exact value of $x = {}^ni \ $with$\ {n \rightarrow \infty}$? What is the connection between $i$ and $x$. Is $x$ a special complex number that is maybe already known or comes up in other places?


How to get first N elements of a list in C#?

I would like to use Linq to query a bus schedule in my project, so that at any time I can get the next 5 bus arrival times. How can I limit my query to the first 5 results?  More generally, how can I take a slice of a list in C#? (In Python I would use mylist[:5] to get the first 5 elements.)


What happened to each of The Original Forty?

J. K. Rowling had released ( and then ) the original draft for the names of the students in Harry's year.  Not counting the ones crossed out, these are the original forty names:   Abbott, Hannah Bones, Susan Boot, Trevor Brocklehurst, Mandy Brown, Lavender Bulstrode, Millicent Corner, Michael Cornfoot, Stephen Crabbe, Vincent Davis, Tracey Entwhistle, Kevin Finch-Fletchley, Justin Finnigan, Seamus Goldstein, Anthony Goyle, Gregory Granger, Hermione Greengrass, Queenie Hopkins, Wayne Jones, Megan Li, Sue Longbottom, Neville MacDougal, Isobel Macmillan, Ernest Malfoy, Draco Malone, Roger Moon, Lily Nott, Theodore Parkinson, Pansy Patel, Madhari Patel, Mati Perks, Sally-Anne Potter, Harry Rivers, Oliver Roper, Sophie Runcorn Smith, Sally Thomas, Gary Turpin, Lisa Weasley, Ronald Zabini, Blaise   Which ones ended up becoming characters? What were their final names? Which ones have yet to be appear?


Victim of Community (Machine) Moderator?

Are my suggested edits wrong?     Here are the links of my suggested edits.             These are the list of edits that I have suggested and got the rejection from no human being but a community (machine) moderator.  Please suggest me some way so that my edits are not rejected again.     I would always love to suggest some edits, so there is no reason for me to stop suggesting some correct edits, isn't it?


proof with multiplicative inverses mod n

I am trying to write a proof for-  show that if [b] and [c] are both multiplicative inverses of [a] in Zn, then b congruent c (mod n)   I don't know a lot about multiplicative inverse proofs and any help will be appreciated.


Will inactive accounts be deleted? If so, what happens to questions and answers made by those accounts? What are the criteria for deletion?


Definite integration question $\int_0^{\frac{\pi}{2}} \frac{dx}{3+2\sin x+\cos x}$

Question -  $$\int_0^{\frac{\pi}{2}} \frac{dx}{3+2\sin x+\cos x}$$  I have tried this question and also tried to find online on google. But I only found questions that involves only 2 terms. So i dont have any other way except to ask it here.  Please help me.


Unable to install new apps after upgrading to 20.04

I am not experienced in terminal operations in Ubuntu. Whenever I try to add a repository I get a message: E : Malformed entry 52 in list file etc/apt/sources.list  Please suggest a solution.


For my project in machine learning, I want to draw in LaTex a Graph with a common vertex Like this example: How can I do it, please?


I understand that at the equator, you will have maximum centripetal force acting on you, whereas if you're standing directly on the pole you will have none. But because centripetal is a resultant force, why isn't the value of $g$ GREATER on the equator because you'd need a greater force to 'pull' you inwards to force you to travel in circular motion?


On average what is the likelihood that a research fellow will eventually become a lecturer or an assistant professor?

I was trying to determine the probability that someone who is currently a research fellow will become a lecturer or assistant professor within the next five years and I was wondering if someone could approximate it here. I suppose that it is dependent on many factors but is it possible to calculate a rough estimation without additional details or with stated assumptions?


APT Can't add repositories! Ubuntu 16.04 minimal

I built a Ubuntu minimal installation (32-bit) to a VirtualBox Machine. Everything worked without a hitch, and the first things I installed were xorg and lxqt, including dependencies. It booted up fine, and I thought it was working well, until I tried to add a new repository in the terminal.  Here's the command:  sudo add-apt-repository ppa:nilarimogard/webupd8   Once I hit enter, I am immediately met with this error:  sudo: add-apt-repository: command not found   I've also tried this command:  sudo add-apt-repository ppa:kdenlive/kdenlive-stable   with the same result. Running sudo apt-get install firefox installs Firefox with no problems; it's adding new repositories that causes the issue. Aside from installing a few programs via synaptic, I have done nothing to the system. I have not un-installed anything. Does anyone know what is going wrong?


Prove that if $gcd(a, b)=d$ then $gcd(a^2, b^2 )=d^2$

how can i prove that?  Prove that if $gcd(a, b)=d$, then $gcd(a^2, b^2 )=d^2$


Can I apply for US visa while I am a visitor in Canada?

I am an Indian passport holder and currently visiting Canada. I have a 10 year multiple entry visit visa for Canada and I want to apply for a US visit visa.   Can I apply for a US visa in Canada while I am a visitor in Canada?


Is there a physical reason for level repulsion and avoided crossings?

Suppose we have a Hamiltonian that depends on various real parameters.  When tuning the values of these parameters, the energy eigenvalues will often avoid crossing each other.  Why?  Is there a physically intuitive justification for  and ?  It would be nice to see a general argument.


How resilient is Ubuntu to repeated "power-off" shutdowns?

My company is considering the use of Ubuntu as an OS for use on a hardware device.     It would be installed on compact flash drive - apparently this is not standard flash drive but a specific type of memory that is supposed to "cope" with immediate power shutdown (I am not sure how this is achieved but they are supposedly a "high end" card).    The units that would be run using Ubuntu are the type of units that will not be gracefully shutdown - the power cable would be removed and that is that.     Can anybody give me some advice on the potential problems that can occur? Is Ubuntu a good system that can deal with this kind of power outage and reboot successfully on next startup?     I realise that nothing is unbreakable, but is it a commonly used OS for an embedded setup? Is it asking for trouble to use Ubuntu in this kind of environment?


For my homework I am asked to do the following:  Solve $au_x+bu_y=f(x,y)$, where $f(x,y)$ is a given function. If $a\neq 0$ write the solution in the form $$u(x,y)=(a^2+b^2)^{-\frac{1}{2}}\int_{L}fds +g(bx-ay)$$ where the integral is a line integral and $L$ is the characteristic line segment from the $y$-axis to the point $(x,y)$ and $g$ is an arbitrary function of one variable. A hint to use the coordinata method (change of coordinates) is given.  For the $g(bx-ay)$ part we have $g_x(bx-ay)=bg'$ and $g_y=-ag'$ so this satisfies $ag_x+bg_y=0$ and therefore is the homogeneous solution. For the rest I realized that $au_x+bu_y$ is the directional derivative of $u$ along the characteristic line $c=bx-ay$ and therefore integrating along this line to solve seems reasonable. However I am unclear about the particulars. If anyone could help me out I would be very thankful. Also, isn't it important that besides specifying $a\neq 0$ we also have $b\neq 0$?


Why don't electrons crash into the nuclei they "orbit"?

I'm having trouble understanding the simple "planetary" model of the atom that I'm being taught in my basic chemistry course.   In particular,    I can't see how a negatively charged electron can stay in "orbit" around a positively charged nucleus. Even if the electron actually orbits the nucleus, wouldn't that orbit eventually decay?  I can't reconcile the rapidly moving electrons required by the planetary model with the way atoms are described as forming bonds. If electrons are zooming around in orbits, how do they suddenly "stop" to form bonds.     I understand that certain aspects of quantum mechanics  to address these problems, and that there are  of atoms. My question here is whether the planetary model itself addresses these concerns in some way (that I'm missing) and whether I'm right to be uncomfortable with it.


flex-grow doesnt work, what did I do wrong?

I'm new to frontend web coding and I wanted to make a mockup website to speed up my learning process. I wanted to make the sign-in part align in the middle of the page, i found some tutorial using flex-grow so it would scale with size, but this is what I got instead:    What did I do wrong?  (I only posted snippets of code I think would matter not to complicate things)    .sign-in {   display: flex;   justify-content: space-between;   align-items: center;   flex-grow: 1;   **<THE PART WHERE THE PROBLEM ARISES>** }  .sign-in-text {   display: flex;   align-items: left;   flex-direction: column;   font-size: 3.5em;   font-weight: bold;   margin: 0;   padding: 0; }  .not-sign-in-text {   font-size: 2rem;   padding: 0;   margin: 0; }  .miss-you {   font-size: 1.5rem;   font-weight: 500; }  .sign-in-form {   display: flex;   align-items: left;   flex-direction: column; } <!DOCTYPE html>      <meta charset="UTF-8">   <meta name="viewport" content="width=device-width, initial-scale=1.0">   <link href="style.css" rel="stylesheet" />   <link href="index.css" rel="stylesheet" />   <title>ELOHSSA</title>

         sign in.                                          We missed you already :(
         <form class="sign-in-form">
            Username:            <input type="text">

            Password:           <input type="password">

           <button type="submit" class="button">                                         Sign in.                                     </button>
       </form>
          Thanks for helping!


Google search console error: "Your Sitemap or Sitemap index file doesn't properly declare the namespace" when using HTTPS namespace URL

We migrated our site from HTTP to HTTPS. Then we verified our property in search console and submit the new sitemap with HTTPS URLs.   After submission it has the error "Your Sitemap or Sitemap index file doesn't properly declare the namespace."    This appears to be because we used https://www.sitemaps.org/schemas/sitemap/0.9 instead of http://www.sitemaps.org/schemas/sitemap/0.9. Is this really important to use the HTTP version of that URL in sitemap?   That URL is redirected to HTTPS and google is also supporting HTTPS.


Intuitive example of this quantifier implication property - First Order Logic

This question is mainly about building intuition. A lot of the logic rules on First Order Logic make a lot of intuitive sense, like $\lnot\lnot P\equiv P $. Some less, but with an example, everything becomes clear, like $\lnot P \land \left( P \lor Q \right) \Rightarrow Q$. It might seem convoluted first, but with an example, its truth value becomes intuitively clear: "If I say that I have a dog or a cat, and I don't have a dog, then yeah, of course I have a cat". In the case of the quantifiers ($\forall $ and $\exists$), most of the properties fall on the former, and (at least for me) are quite self evident, like $\forall x \left[ P(a) \rightarrow Q(x) \right] \equiv P(a) \rightarrow \forall x \left[ Q(x) \right]$, but two in specific are not very intuitive without an example. Given a universe $U \neq \emptyset$: $$[1]: \forall x \left[P(x) \Rightarrow Q(a) \right] \equiv \exists x \left[ P(x) \right] \Rightarrow Q(a) $$ $$[2]: \exists x \left[P(x) \Rightarrow Q(a) \right] \equiv \forall x \left[ P(x) \right] \Rightarrow Q(a) $$ After an example, formula [1] becomes quite clear: "Saying 'For any person, if they are on Mars then Mars is populated' is the same as 'If there is a person on mars, then mars is populated' ". My problem really comes with [2]. I tried thinking of an example or some logic for it, but the best I could come up with was (in reverse order): "Saying 'If all people are in a hotel, then the hotel is full' is the same as 'there's one person which decides if the hotel is full or not (the last one)' ". I don't think that's right though, because one: That example is a biconditional, not an implication. And second: that example doesn't imply $\exists x \left[P(x) \rightarrow Q(a) \right]$, but actually $\exists ! x \left[P(x) \rightarrow Q(a) \right]$. So my question is: What is an example that can make that concept more intuitively clear? Edit: Though previously marked as a duplicate of , both the question and answer only talk about one side of the equivalence, being: $\exists x \left[P(x) \Rightarrow Q(a) \right] \Rightarrow (\forall x \left[ Q(x) \right] \Rightarrow P(a)) $, but the answer doesn't touch the $ U \neq \emptyset \land (\forall x \left[ Q(x) \right] \Rightarrow P(a) )\Rightarrow \exists x \left[P(x) \Rightarrow Q(a) \right] $ side of things (corrected with $U \neq \emptyset$ and $\Rightarrow$ as pointed out by tkf), so my doubt still remains.


Novel from the late '80s - early '90s. Can't remember much about it - didn't finish it. About a humanoid (Alien? Time traveler? Can't remember) who visits Earth in the Middle Ages & gets involved with two people. One of them is a Norman knight who tries to take advantage of the traveler's advanced technology to defeat his enemies.


Cannot boot without USB stick after successful install

I installed Ubuntu yesterday via a bootable USB drive, created with unetbootin. Everything went very well, but now the computer does not boot unless the USB drive is plugged in. If it's not, then when the computer boots, the boot sequence screen just appears and if I select the hard drive, it will just reboot and go back to this boot sequence screen, until I plug in the USB drive.  Any ideas? Thanks a lot for your help!  UPDATE: Having some valuable data on the machine, I would prefer a solution that doesn't involve reinstalling, but from the first replies, I guess this may be what I have to do eventually. Thanks!  GM  ==  EDIT: output of sudo fdisk -l below  Disk /dev/sda: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x000742dc     Device Boot      Start         End      Blocks   Id  System /dev/sda1            2048  1449474047   724736000   83  Linux /dev/sda2      1449476094  1465147391     7835649    5  Extended Partition 2 does not start on physical sector boundary. /dev/sda5      1449476096  1465147391     7835648   82  Linux swap / Solaris  Disk /dev/sdb: 4009 MB, 4009754624 bytes 255 heads, 63 sectors/track, 487 cylinders, total 7831552 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xc3072e18     Device Boot      Start         End      Blocks   Id  System         /dev/sdb1   *        8064     7831551     3911744    b  W95 FAT32   ==  EDIT2 bootinfo output:


Is it possible to edit my own comments?  I've been able to edit a comment, I think, but I went back to a comment posted earlier and don't see a way to edit it now, but rather only delete it.


Applications in Play Store cannot be downloaded

I have moved to Australia from India. My Google Play Store doesn't allow me to download Australian applications. It tells me that the application is not available in my country, but I am in Australia, so why am I not allowed to download? The application I'm trying to download is free of cost. Please help.


What determines the order of review queues in the new drop-down?

Before the recent changes to the top bar, I'm pretty sure that review queues were always listed in descending order of items pending.  Now we have a drop-down preview on the review icon (thanks!), and I can't figure out what determines the order.  It's not number of items pending (either ascending or descending).  It's not a fixed order of queues.  And it's not necessarily the same order as on the review page when you click through to it.  Examples follow.  This is not a duplicate of .  The SO and network top bars aren't the same, and neither of the explanations on that question, including one from Shog9, is consistent with what I am seeing now.  If Shog's explanation is correct then Close and Reopen should be first on Writers (they're not) and not first on Mi Yodeya (they are).  I don't have enough reputation on SO to check whether what that question reports is still true there.      This is what I currently see on Writers, where I am a moderator.  The sizes of the queues, in order, are: 0, 0, 2, 0, 3, 1.    But it's not a fixed order of queues either.  This is what I see on Mi Yodeya, where I am also a moderator.    And it doesn't match the order on the reviews page:    The reviews page is in descending order, as usual.  I haven't looked at enough cases with the new topbar to know if that's consistent, but I'll assume it is.      This is from Meta.SE, where I am not a moderator, so it's not somehow connected to moderator status.


Let $K$ be a field, which is a finitely generated $\mathbb{Z}$-algebra. Show that $K$ has characteristic $> 0$. I have this hint but I am not quit sure that I understand it; if $\operatorname{char}(K) = 0$, then $\mathbb{Z} \subset K$, then $\Bbb Q \subset K$, and $K$ is a finitely generated $\Bbb Q$-algebra. Use Zariski's Lemma to show that $K$ is a finitely generated $\Bbb Q$-module, and then Artin-Tate Lemma to get a contradiction


Wifi adapter rtl8821ce not working on 20.04

I upgraded my hp laptop from 19.10 to 20.04. (new installation).   Now I cannot activate the rtl8821ce WiFi module.   For 19.10. there was a hint in ask ubuntu   sudo dpkg -i rtl8821ce-dkms_5.2.5.2.1.30816.20190425-0ubuntu1_all.deb   which worked well, but it doesn't work with 20.04.


Find $(a^2+b^2),$ where $(a+b)=\dfrac{a}{b}+\dfrac{b}{a}$

The question is the same .Find $a^2+b^2$. I think we have to find $a$ and $b$ firstly. Given that $a$ and $b$ are integers.


Difference between "Should" vs "ought to"

It's essential that the documents (should)/(ought to) be destroyed immediately.   Which one is more suitable one as I know "ought to" and "should" are synonyms.


So, I decided to build an underwater glass dome to try and recreate Atlantis. It worked fine, but only one problem: It's filled with water! How do I remove all of it?


Ubuntu 16.04.3 update GPG error (public key not available)

I'm using Ubuntu 16.04.3 LTS. I've been using it for over a year, updating every couple of months with no problems. Today I updated and I got these strange public key errors. I have no idea what this means nor where to start.  Here are the errors:  Err:9 http://dl.google.com/linux/chrome/deb stable Release.gpg                  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6494C6D6997C215E Fetched 308 kB in 1s (159 kB/s)                                                 Reading package lists... Done W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error:      http://dl.google.com/linux/chrome/deb stable Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6494C6D6997C215E W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/Release.gpg  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6494C6D6997C215E W: Some index files failed to download. They have been ignored, or old ones used instead.   I already tried researching on-line but have found the explanations to be extremely confusing. Please help me understand:  1) What these errors mean.  2) How to fix them.


I now and then see :     first hit after typing "difference between stub and mock " into google: martinfowler.com/articles/mocksArentStubs.html Can you explain why I am googling for you?   imho all programming questions should be welcome, even if they are very easy to find by googling. To be the #1 one place, SO should contain answers for ALL programming questions. Or am I wrong?


How to store arbitrary data for some HTML tags

I'm making a page which has some interaction provided by javascript. Just as an example: links which send an AJAX request to get the content of articles and then display that data in a div. Obviously in this example, I need each link to store an extra bit of information: the id of the article. The way I've been handling it in case was to put that information in the href link this:     I then use jQuery to find the a.article elements and attach the appropriate event handler. (don't get too hung up on the usability or semantics here, it's just an example)  Anyway, this method works, but it  a bit, and isn't extensible at all (what happens if the click function has more than one parameter? what if some of those parameters are optional?)  The immediately obvious answer was to use attributes on the element. I mean, that's what they're for, right? (Kind of).     In  I asked if this method was valid, and it turns out that short of defining my own DTD (I don't), then no, it's not valid or reliable. A common response was to put the data into the class attribute (though that might have been because of my poorly-chosen example), but to me, this smells even more. Yes it's technically valid, but it's not a great solution.  Another method I'd used in the past was to actually generate some JS and insert it into the page in a


I'm looking for a proof and/or a hint for this. I just got finished for $n=2$, but got stuck proving it for general $n$, apparently some background knowledge is required that's not present in the book.


How can I remove YUMI (multiboot usb creator) software?

I downloaded the .deb version of  YUMI (multiboot usb creator) from the  and I wanted to make a bootable usb for Windows 98 to run on Virtualbox, but anyway the software asked for my sudo password inside the software itself and I felt it was a fishing scam, so I wanted to remove it.   But when I go to the Ubuntu Software Center it says "reinstall", there is no remove option. And I wasn't able to remove it from the terminal using apt-get --purge remove yumi_0.0.1-1_all.deb  I am running Xubuntu 14.04.  Any idea?


USB boot problem in HP Pavilion G6 (32-bit)

I have a HP pavilion g6 series (32-bit) system. I was using Ubuntu 16.04 LTS and everything was working fine until I downloaded BleachBit and used the app incorrectly. It somehow damaged my Ubuntu badly.  I downloaded an ISO image of 32-bit Xubuntu. I have a 64GB sandisk USB, I copied the ISO image to the USB drive but I have another file on the USB device. I tried to boot my laptop with this USB but nothing appears; my system keeps on starting normally.  I want to install this new iso image but I can't. Is there a way to install it without USB or CD?


Can anyone help me with this?     If 738 consecutive integers are added together, where the 178th number in the sequence is 4,256,815, what is the remainder when this sum is divided by 6?


Using a literal string in SELECT statement

Is there an equivalent SOQL syntax to write following SQL?  SELECT Id, 'Northwind Category' AS Note FROM categories


Selecting more then one column when groupBy is present (db_select) - Drupal 8 added 'ONLY_FULL_GROUP_BY'

In my custom Drupal 8 plug-in I perform such query:  $select = db_select('my_table', 'e'); $select->addField('e', 'field1');  $select->condition('field3', 'NULL', '!='); $select->condition('field4', array(11, 12, 31, 32, 33), 'IN');  $select->groupBy("e.field1"); $select->orderBy("e.field1"); $select->orderBy("e.field5"); $entries = $select->execute()->fetchAll(\PDO::FETCH_ASSOC);    And it works fine. It returns me all records grouped by field1 that meets the condition, orderered. But it returns only field1 column.  I wanted to get more columns, so I have added another $select->addField('e', 'field2'); just after first one:  $select = db_select('my_table', 'e'); $select->addField('e', 'field1'); $select->addField('e', 'field2');  $select->condition('field3', 'NULL', '!='); $select->condition('field4', array(11, 12, 31, 32, 33), 'IN');  $select->groupBy("e.field1"); $select->orderBy("e.field1"); $select->orderBy("e.field5"); $entries = $select->execute()->fetchAll(\PDO::FETCH_ASSOC);    This time I get error:     Drupal\Core\Database\DatabaseExceptionWrapper: SQLSTATE[42000]: Syntax error or access violation: 1055 Użyto 'my_database.e.field2' bez umieszczenia w group by:   Which means "my_database.e.field2 has been used without putting in into group by". But I don't want to group by every column I select.  Unfortunatelly Drupal 8 added ONLY_FULL_GROUP_BY :( Then, how can I use groupBy and select more then one column at the same time?


The limit of the alternating series $x - x^2 + x^4 - x^8 + {x^{16}}-\dotsb$ as $x \to 1$

I want to calculate the limit of this sum :  $$\lim\limits_{x \to 1} {\left(x - x^2 + x^4 - x^8 + {x^{16}}-\dotsb\right)}$$  My efforts to solve the problem are described in the .


How Google reacts on display:none for CSS media query?

According to Google Webmaster guideline "Hidden text" is not acceptable. Which means I do have a dov containing some good amount of title or paragraph with link or images if I make it display:none in my CSS, it is against Google crawl policy (thats how it seems).  My question is if I use it within media queries how Google will react? I mean   @media handheld, only screen and (max-width: 767px) {     body {     }     .mobile-friendly{ display:none;} }   for fluid website development we often have to hide certain contents to make the site mobile friendly. Rather than making css for each browser we now code css within same file and define browser behaviour using media queries.  So is google take any action against it?  --Additional Piont/Question Thanks @John Conde; You are right. Google still is not taking much action against Hidden text. But still pro SEO suggest not to use it. In Example using logo within tag on wordpress and text-indenting them to -9999px ... there are more of the tricks involved.  As I am trying to play safe; this is annoying me a lot.    You see they clearly mention CSS display properties. They didn't explain about these media query exception! As I am trying to be over sure and as Google didn't mentioned anything about it I'm still confused on this question. Any Advice?    Thanks for the edits by editors. I'm new here sorry for any inconvenience.  Why you may require to hide few contents? The blog I'm desiring is responsive. I want to let my visitors know about it's mobile friendly design. I have placed few mobile icons for better user experience and usability assurance. But I want them visible only on desktop browser not on mobile. Because if they are already browsing from mobile they don't needed to be notify. Infact I can rather tell them this site can be used as web apps while they are on mobile.


A mathematically mature introduction to Turing Machines and Computability [reference-request]

In the computer science course for mathematicians held at my university Turing Machines have been presented very briefly. So much so that I didn't quite get why they are relevant to mathematics. I did understand what a Turing Machine is, but I feel that the presentation given was (for schedule reasons) quite naive and simplified. So I would like to ask if you can point out a good reference for a mathematically mature introduction to turing machines and computability.


Observation effect in double slit experiment

I have watched some of the lectures given by Brian Greene and Lawrence Krauss about the observation conundrum encountered during the double slit experiment. Can anybody answer me this question?  Is there a difference in results between    case 1: observation by a sentient creature (e.g. human or cat), or  case 2: the unmonitored recording of events (to be looked at later).   It seems to me that if there is a difference, then it is clearly the presence of something conscious/sentient that is making that difference, not just the recording of the events.  It seems also to me that in either case, since electrons are everywhere, and observation of their behaviour makes a difference, there is a serious consequence - scientific method falls victim to this ambiguity in behaviour for the simple reason that it involves observation, so this must undoubtedly affect the physical rules.  Perhaps I should surmise that we are entering an era of understanding where our sentience has to be considered part of the physical reality, and though this is an old idea, most of our top physicists are still saying they are long way from getting a handle on this fact. So:    when they decide that sentience is part of the universe, does that mean "intelligent design" is again on the agenda?   So, can anyone answer, is it case 1 or case 2 above?


I'm working on the following contest math problem:     Define an evil number to be any positive integer that contains the   digit $9$. Show that      $$ \sum_{x} \frac{1}{x} < 80 $$      where the sum is over all non-evil positive integers $x$.   I'm very confused on where to begin. Initially, I tried to consider this sum as part of the sum of $1/x$ over all positive integers, namely by noting that  $$ \sum_{n=1}^{\infty} \frac{1}{n} = \sum_{x} \frac{1}{x} + \sum_{y} \frac{1}{y} $$  where the first summation on the right side is the same as in the problem statement and the second is the sum over all evil numbers. However, I can't seem to find a way to use this since the sum of the left diverges.  Could anyone lend a helping hand?


Cannot understand for loop with two variables

When I use two variables in a for loop with different conditions two conditions like I have used below i<3,j<2 the for loop is always executing till the second condition fails.  #include<iostream> #include<conio.h> using namespace std ; int main() { int i,j ; for(i=0,j=0;i<3,j<2;i++,j++) {     cout<<"hello" ; } getch() ; return 0 ; }    In that code, hello is printed 2 times. Why?  If I use i<3,j<10, "Hello" is printed 10 times. I can't understand why the first condition is being neglected. Is it compiler dependent or something else?  Every thing works normal if I replace with conditions like || (OR) or &&(AND).An other thing is that I cannot initialize i and j in the for loop itself, it is showing me an error, but works fine when I declare variables in C style or one variable outside the for loop, why is it so?  Compiler I have used is Orwell Dev C++. Thanks in advance.


Can we observe a star collapse into a black hole?

Let's say that I happen by a star that has just burned out and is collasping into a black hole. I seat at infinity to watch it as a Schwarzschild observer. Will I ever see the black hole collapse into a black hole in finite time? Or will only become a black hole in the limit? Does a singlarity form in finite time or infinite time?


Hei, guys!  I'm having some trouble with the next problem:  Let $A$ and $B$ be subgroups of $G$. Show that $\sim$ is an equivalence relation when it is defined as follows: $g\sim g'\Leftrightarrow g' = agb$ for some $a$ from $A$, $b$ from $B$.  Should I prove this is valid for any a and b? It says for some elements a and b. But I might as well take the unit element.   Could you give me a clue on how to solve it?  Cheers!


I tried an in-memory Linux distro and I was shocked by how fast it was.  Is there is a way to always cache in memory some (user specified) software like the file explorer so that you can benefit of that speed without having to preload the whole system in the memory (unfeasible if it's your main desktop because there would be not enough memory)


"John Smith and all of us at ABC Corp ARE proud to support..." or "John Smith and all of us at ABC Corp IS proud to support..."


I've downloaded the latest version of Python from their website, but I'm not exactly sure as to how to install from the tar.xz. I've extracted it to the downloads folder, but it leaves me with a folder with more folders inside. What do I do?


Using completing the square method we can derive a formula $ax^2+bx+c=0$ for the quadratic equation to $$x={-b\pm \sqrt{b^2-4ac}\over 2a}$$  I am sure I haven't sees it in any book talking about deriving the cubic equation $ax^3+bx^2+cx+d=0$ using the method of completing the square or the cube.  So how did they derive the cubic formula to solve the cubic equation?


This is my first time in this website. I'm a student in master 2 ans I'm following a course about elliptic curves. And I'm didn't really understand how to calculer the order of a function at a point P for a curve C. (see the picture for the example)    My questions are : 1) How to see Y and X like functions on K(C) ? 2) How to calculate ord(Y) on (0,0)  Thanks a lot for the help !


Looking for a smarter way to do something I'm doing already.  I have a string: "firstbit.secondbit.thirdbit.fourthbit.fifthbit.sixthbit"  The content between the periods changes, but the delimited position in the string is important.  This string will sometimes contain 3 parts only: "firstbit.secondbit.thirdbit"  I need to assign each part to a different variable. So, I'm currently using this uglyness:  #!/bin/sh var="firstbit.secondbit.thirdbit.fourthbit.fifthbit.sixthbit"  first="$(echo $var | cut -d'.' -f1 )" second="$(echo $var | cut -d'.' -f2 )" third="$(echo $var | cut -d'.' -f3 )" fourth="$(echo $var | cut -d'.' -f4 )" fifth="$(echo $var | cut -d'.' -f5 )" sixth="$(echo $var | cut -d'.' -f6 )"   What I'm hoping for is something more like:  echo "$var" | (magic command to assign values to variables here) first second third fourth fifth sixth   So that later on I can:  echo "[$first]"   [firstbit]  echo "[$third]"   [thirdbit]  and so on.  Arrays are no good as I prefer named variables for this system. Can't help but think that there's probably something in awk that can do this but I'm not intimately familiar with it.  Any thoughts?


What's the meaning of the raised finger in "Avengers: Endgame"?

Prior to Iron Man's      final moments,   he sees Strange raise his index finger. I presume this is some kind of message, but I didn't understand the meaning. It seems Stark immediately knows what to do - i.e.      steal the Stones using his nano-tech.


if $E = [0,1] \bigcap \mathbb{Q} $, what is $E^\complement$  with respect to $[0,1]$ and its outer measure $m^\ast(E^\complement)$?  The outer measure is defined thus:  $m^\ast(E^\complement):= \inf_P m(P)$  where $P$ ranges over the set of multi-intervals containing $E$: $E \subseteq P$


When is the official date a degree is obtained?

I've read that there is a difference between the date that a higher degree committee approves a student for graduation and the actual date of graduation. The first being the date that a student becomes a graduand and the second being the date that a student becomes a graduate. These two dates could be far apart. My question is which of these two dates should be shown next to a degree on a CV or resume? Obviously I would like it to be the first, but that would lead to a discrepancy between the date on the resume and the date on the certificate. Someone suggested I could show both the completion and graduation date on my CV.


I have Ubuntu 19.10 (GNU/Linux 5.3.0-1030-raspi2 aarch64). ubuntu@ubuntu:~$ do-release-upgrade Checking for a new Ubuntu release Your Ubuntu release is not supported anymore. For upgrade information, please visit: http://www.ubuntu.com/releaseendoflife  Please install all available updates for your release before upgrading.  But as it tries to do an update: ubuntu@ubuntu:~$ sudo apt update ... E: The repository 'http://ports.ubuntu.com/ubuntu-ports eoan Release' no longer has a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://ports.ubuntu.com/ubuntu-ports eoan-updates Release' no longer has a Release file. ...  I can't install any package either. What is the way to upgrade?


Want pursue phd in Machine Learning but having a networking background

My situation is similar to but not same as - Please skip to edit 2 below if you want to know the problem in short. Details Talking of my career so far,    I completed undergraduate in CS(computer-science) with WSN (wireless-sensor-networks) as thesis topic (Networks) Joined an MNC(multi-national-company) in Android GPS team and stayed for a year (More Networks! ) Completed masters in CS with Social Network Analysis as main thesis. At this point I got interested in ML (machine-learning), NLP(natural-language-processing) and during my entire program I took related courses. Joined another MNC 11 months back, in their router OS QOS (quality-of-service) team (Networks again! )   I now want to apply for a PhD in ML / NLP from colleges like Carnegie Melon or N NUS, Singapore. But I find I don't have enough recommendation/ work experience in the same field. What should I do - Personal projects in these areas? Personal publication? Working with a startup in these fields ? Kindof desparate now to prepare and apply for some program within the next year.   I know its difficult to suggest something that will definitely work in my case but still wanted some advice from the community.  Edit:- Expanding on the acronyms as suggested in comments. Sorry for the long background but I wanted others to understand my situation by stating "some" of my backgound.  Edit 2 : - Editing this again to highlight my problem in short. I want to pursue phd in fields(ML, NLP) in which I have somewhat less experience. My GPA is not extraordinary for an international student and have only single recommendation in the same. I do have a publication but not related to these areas. Any suggestions for getting my CV to be accepted by any faculty in ivory colleges?


How to disable automatic suspend warning

I'm using ubuntu 13.10 as htpc. To save some power, i have set it to suspend after 30minutes of inactivity. Before entering suspended state, a popup appears to warn me that computer is about to get put to sleep. This is a little annoyance since it appears when i resume the pc later.   How can i disable this notification for good?


Fantasy novel where guy fights with a cloak on his back

There was a novel I read back in the 90s (I’m pretty sure) about a guy who fought using a weighted cloak or cape. There’s very little I remember about it beyond that. He didn’t take the cloak off in the cloak-and-dagger style, but rather used it kind of like a whip from his back and shoulders. Anyone ever heard of it?


Proving continuity in case of unifrom convergence

I got stuck a little bit and I could use some help. Thanks in advance for your time!     Let $f_n$ be a sequence of continuous functions and $f_n$ uniformly converges to $f$.   Prove that f is also a continuous function.


What kind of math would I use to calculate the difference between two degrees on a circle? Say, 38 and 272 degrees?  When I just subtract one position from another sometimes it's more than 180 or sometimes I cross over 0/360.  I need keywords that can help me learn more about it.  Ultimately I want to create an excel formula but I don't know what it is called. Thanks


I removed gnome and gconf2 unknowingly and I am unable to login into Ubuntu.Please help me.


Asking for help in problem 4 of section 2.5 of David Burton book

I am self studying Elementary number theory from David Burton Book. While trying exercises of Section 2.5 , I am unable to think about this problem      If a and b are relatively prime positive integers, prove that Diophantine equation ax-by =c has infinitely many solutions in the positive integers.    Can someone please help in how to solve this problem!!


I want to introduce ssh authentication and I have configured the ssh_config file and disabled passwordauthentication. Now, im trying to access the machine using ssh but the access is denied! Is there any way to access the machine now using password?


Windows 10: Assign a unique icon to file types associated with the same program

On Windows 7 it's relatively easy to assign a unique icon to various file types associated with the same program. How can I achieve that on Windows 10? Thank you.


Why do you have to bond the neutral and the ground wire in the main panel?  Not in separat ？I don't know how that works


Hi. I installed LTSpice in my macbook pro late 2011 with this specs:  OS: Mac OS high Sierra 10.13.6 Graphic: Intel HD Graphic 3000 512MB RAM: 16 GB  somehow I got a bug when i moved a component or wire which showing a shadow of footprints along the moving trajectory. (shown in image)  has anyone encountered the same problem? I've tried to searched the answer but didn't find the same case anywhere. Anyone got an idea?  Thanks for helping. I know this is not 100% EE, let me know if I should post this in stack.


I want to upload file and save it on a server with jquery ajax. I've tried it but it didn't work. It doesn't want to process it. This is what I do:  html code  <form action="" method="post" enctype="multipart/form-data">         <input type="file" name="submit_file" id="submit_file" required >         <input type="text" name="submit_message" id="submit_message">            </form>     validation and ajax       proc_intro.php file  <?php     $submit_file = $_REQUEST[submit_file];     $submit_message = $_REQUEST[submit_message];     $allowed_filetypes = array('.jpg','.gif','.bmp','.png');    $max_filesize = 524288;    $upload_path = './images/';    $filename = $_FILES[$submit_file]['name'];     $ext = substr($filename, strpos($filename,'.'), strlen($filename)-1);      if(!in_array($ext,$allowed_filetypes))       die('The file you attempted to upload is not allowed.');   if(filesize($_FILES['submit_file']['tmp_name']) > $max_filesize)       die('The file you attempted to upload is too large.');   if(!is_writable($upload_path))       die('You cannot upload to the specified directory, please CHMOD it to 777.');  if(move_uploaded_file($_FILES['submit_file']['tmp_name'],$upload_path . $filename))    {        echo '{"result":"success"}';    }else    {         echo '{"result":"fail"}';    } ?>   What can I do to get the file to be uploaded correctly using ajax? Do you have any idea? Thank you in advance.


I have a schengen visa for single entrance. My itinerary shows that My first entry country will be Italy.  At the same time, on my visa there is no country restriction written.   My plans have changed a little after issuing visa and I will travel to my destination through Barcelona with connection of 4 hrs. So technically it turns out that my first entry will be to Spain.   I would like to know if this will cause any issues? Is it ok or not?


I want to output a file's contents while they change, for example if I have the file foobar and I do:  magic_command foobar  The current terminal should display the file's contents and wait until, I don't know, I press ^C.  Then if from another terminal I do:  echo asdf >> foobar  The first terminal should display the newly added line in addition to the original file contents (of course, given that I didn't press ^C).


Can I untap an attacking creature and avoid exchanging combat damage?

Can I untap an opponent's attacking creature with 's ability, and avoid the combat damage that I would be dealt by that creature in the combat phase?


I  have recently bought a Honeywell rth9580 programmable WiFi thermostat. Unfortunately I have old electric heating/cooling system probably from 70's. The system is based on two relays (I guess heating and cooling).  Since transformer doesn't have 3rd wire (C?) by default I would like to make one by connecting extra wire to transformer chassis. Having terminal C I would like to connect wire G  to terminal C and jump terminal G with Y. I measured the voltage between transformer chassis and Rh wire: idle 34VAC,  calling for heating/cooling 24VAC. Here are my questions: 1) Is this setup will work?  2) Is it safe to connect thermostat since voltage on idle is a bit higher than it supposed to?  3) Am I right to assume that transformer won't overheat because thermostat will try to drain to many amps?


Show: $\int f\, d\mu=\int\limits_0^{\infty}\mu(\left\{x\in X: f(x)>t\right\})\, dt$

Let $f\colon X\to\overline{\mathbb{R}}_{\geq 0}$ be a measurable function. Show that     $$ \int f\, d\mu=\int\limits_0^{\infty}\mu(\left\{x\in X: f(x)>t\right\})\, dt. $$     (The right integral is to be read as an Lebesgue-integral.)      Hello, my idea is to approximate $f$ by the functions $$ f_n:=2^{-n}\sum\limits_{k=1}^{\infty}\chi_{\left\{x\in X: f(x)> k/2^n\right\}}. $$  With this approximation by simple functions I got $$ \int\limits_X f\, d\mu=\lim\limits_{n\to\infty}\int\limits_X f_n\, d\mu=\lim\limits_{n\to\infty}\sum\limits_{k=1}^{\infty}\frac{k}{2^n}\cdot\mu\left(\left\{x\in X: f_n(x)=k/2^n\right\}\right)\\=\lim\limits_{n\to\infty}\sum\limits_{k=1}^{\infty}\frac{k}{2^n}\cdot\mu\left(\left\{x\in X:f(x)>k/2^n\right\}\right) $$  This is the point where I do not come along anymore... is that right to this point and if yes: How can I continue in order to get the desired right side?  With regards


For every analytic function $f$ on $G$ (simply connected,open) s.t $f(z) \neq 0, \forall z \in G$, then $\exists$ g analytic in $G$ s.t $g^2 = f$

I have to show that for every analytic function $f$ on $G \subseteq \mathbb{C}$ (Simply connected open set) such that $f(z) \neq 0, \forall z \in G$, then $\exists$ a function g analytic in $G$ such that $g^2 = f$.   Also, I need to give an example of an open set $G$ which is not simply connected and an analytic function $f$ on $G$ with $f(z) \neq 0, \forall z \in G$ such that $f \neq g^2$ for every analytic function $g \in G$.  I do not see how to approach this problem. If I get the first part, maybe the example will be easier.


My MS Access Application uses SQL Database as backend. The permission to SQL database is granted with Windows Authentication mode to a specific user group. Most of users in the group can get access to SQL database but there are some users reported to fail for login in the database. The error message: Connection failed SQLstate: '28000' SQL Server Error: 18456 Login failed for user Domain\UserID  I spent sometime searching for the solution but I could not find one with the same problem. Could anyone give me an advice on this? Many thanks.


Ostensibly, verb conjugation is plural vs singular: "The apple is big." vs "The apples are big." But that doesn't match up with the centuries-old . "They is nice." vs "They are nice." I believe only the latter is correct, not only for plural they but even for singular they. Are there any other exceptions to the singular vs plural verb conjugation? Or is singular they a unique exception to English verb conjugation among all subjects? Is plural vs singular still the way that grammarists explain English verb conjugation?


Renaming Folders using xdg-users-dirs does not work

I'm attempting to rename my special folders. As per my understanding, there are two ways to specify this.   Local, ~/.config/user-dirs.dirs Global, /etc/xdg/user-dirs.defaults   I've changed both locations to my desired configuration. But everytime I do xdg-user-dirs-update, it removes all my settings and rewrites it to point to $HOME.  Why is this happening? I can't see anything in the documentation I'm missing.  Would it hurt me just to disable the feature and make my own folders?


Horizontally, I'm trying to glue left and right cells by "-" without any white space between them. So I tired to create a middle cell between them with content "-", but it has margin among three cells, so I wondered how do I get rid of the white space (padding and margin) between the middle cell and other cells?   HTML

         Left	         -	         Right

         cell	         -	         cell

         cell	         -	         cell

   And the CSS:  #test, th, td {     border: 1px solid black;     margin: 0px; } .mid {     border: none;     padding: 0px;     margin: 0px; }


I have the fps issues, when I did play in the last patch it did work fine, but this patch seems to ruin everything! I did play on high graphics and had shadows and anything at high, now I play on low graphics did turn shadows off but still got the problem, I normally have 60 fps when i play but 4-6 times in a game it drops down to 5-6 fps then it last in 2-3 mins and it goes up again to 60 fps.  How to solve this problem?


How to prove geometrically the limit $\lim_{x \to 0}\frac{1-\cos{x}}{x}$ using squeeze theorem

Here, I ask how to geometrically prove the limit  \begin{equation}\lim_{x \to 0}\frac{1-\cos{x}}{x}\end{equation}  using squeeze theorem. I see so many proofs for the other important limit \begin{equation}\lim_{x \to 0} \frac{\sin{x}}{x}\end{equation} But it seems that no one discussed the first one yet.


How do I add a calendar properly in Visual Studio

I want to add a calendar to my Default.aspx. How is this done? My first try was:  <asp:Content ContentPlaceHolderID="PlaceHolderPageTitleInTitleArea" runat="server" EnableViewState="False">  <WebPartPages:WebPartZone runat="server" FrameType="Default" ID="full" Title="loc:full" WebPartVerbRenderMode="TitleBar">     <WebPartPages:XsltListViewWebPart runat="server"         ListUrl="Lists/Calendar"         IsIncluded="True"         JsLink="clientTemplate.js"         NoDefaultStyle="TRUE"         PageType="PAGE_NORMALVIEW"         Default="False"         ViewContentTypeId="0x">     </WebPartPages:XsltListViewWebPart> </WebPartPages:WebPartZone>     However this way causes my calendar to come out a jumbled mess. How can I properly add a calendar to my Default.aspx? Thank you!


Display entire chunk of data A---B if complex filters matches

Possibly stated as duplicate..thanks for accepting   ORDER ALPHA  Facility: 201  ZZZ        COUNTRY Wrong Trace:       Kotak: NA       Soak: NA        NOUN: XP                    O  O  O  O  O  O  O  O  O  O  O  O  O  O                   O  O  O  O  O  O  O  O  O  O  O  O  O  O   LAM AMO ORDER #   P/P R  O  L  H  S  C  N  D  K  M  D  D  C  N   LAM uii ii oo --- --------  --- -- -- -- -- -- -- -- -- -- -- -- -- -- --  --- --- -- --      BZ90rty   K/K AA AA AA NA XP AP NA NA NA NA NA NA AP AP  OOL XP  IP N a      ZX     A/A WD WD WD NA WD WD NA NA NA NA NA NA WD WD  OOL WD  IP Y ORDER BURY  Facility: 201  ZZZ        COUNTRY Wrong Trace:       Kotak: NA       Soak: NA        NOUN: XP                    O  O  O  O  O  O  O  O  O  O  O  O  O  O                   O  O  O  O  O  O  O  O  O  O  O  O  O  O   LAM AMO ORDER #   P/P R  O  L  H  S  C  N  D  K  M  D  D  C  N   LAM uii ii oo --- --------  --- -- -- -- -- -- -- -- -- -- -- -- -- -- --  --- --- -- --      BZ903901  A/A AA AA AA NA XP AP NA NA NA NA NA NA AP AP  OOL XP  IP N a      ZX     A/A WD WD WD NA WD WD NA NA NA NA NA NA WD WD  OOL WD  IP Y  ORDER ALUIO  Facility: 201  ZZZ        COUNTRY Wrong Trace:       Kotak: NA       PAT: NA        NOUN: AP                    O  O  O  O  O  O  O  O  O  O  O  O  O  O                   O  O  O  O  O  O  O  O  O  O  O  O  O  O   LAM AMO ORDER #   P/P R  O  L  H  S  C  N  D  K  M  D  D  C  N   LAM uii ii oo --- --------  --- -- -- -- -- -- -- -- -- -- -- -- -- -- --  --- --- -- --      BZ903901  U/U AA AA AA NA XP AP NA NA NA NA NA NA AP AP  OOL XP  IP N a      ZX     Y/Y WD WD WD NA WD WD NA NA NA NA NA NA WD WD  OOL WD  IP Y ORDER AL123  ...cont....   Display or delete or redirect entire ORDER to ORDER last line data before new order starts, if these filters satisfies, condition 1:IF NOUN  :XP and A/A above A/A is present delete that order or parse to another file. Condition 2:IF NOUN  :AP and Y/Y above U/U is there  delete that order or parse to another file.Deleted Output looks like    ORDER ALPHA Facility: 201  ZZZ        COUNTRY Wrong Trace:       Kotak: NA       Soak: NA        NOUN: XP                    O  O  O  O  O  O  O  O  O  O  O  O  O  O                   O  O  O  O  O  O  O  O  O  O  O  O  O  O   LAM AMO ORDER #   P/P R  O  L  H  S  C  N  D  K  M  D  D  C  N   LAM uii ii oo --- --------  --- -- -- -- -- -- -- -- -- -- -- -- -- -- --  --- --- -- --      BZ90rty   K/K AA AA AA NA XP AP NA NA NA NA NA NA AP AP  OOL XP  IP N a      ZX     A/A WD WD WD NA WD WD NA NA NA NA NA NA WD WD  OOL WD  IP Y   Like this many conditions are there i will add conditions on my own but these are some conditions i posted..... NOTE:Rows are dynamic and ORDER **** (***)may be any letter,but ORDER is constant.


I'm trying to use a DC-DC converter to charge a mobile phone.  This is the converter....  The converter is relatively low power, (5w) and can supply a maximum of 1amp. Testing with both a USB voltmeter and a multimeter indicates that the device is correctly wired and producing 5v.  However, when I plug in my iPhone (or tablet or any other mobile device) there's no sign of any actually charging taking place. (I would normally expect to see a little lightening strike zig-zag symbol appear on the battery)  Is this because there is a minimum current requirement to power the mobile device? Is the device likely to be not charging at all? or is it probably charging ok, but at a very slow rate?  I know that if I were charging a lead-acid battery at a very low current then the battery would still charge, albeit very slowly.  If there is a minimum current requirement for my mobile device, what's it likely to be? I know I can buy higher current 5v supplies, but would prefer to know exactly what I need before hand rather than just buying DC-DC converters on a trial and error basis.  UPDATE - I have left the 'data +' and 'data -' unconnected, and simply connected ground to ground, and Vcc to 5v. My understanding (perhaps wrong) is that a USB device should be able to charge itself with this configuration. It's only if attempting to fast-charge a device 'data +' and 'data -' need to be connected to anything.


All regular* distributions of $\mathcal{D}'(\mathbb{R}^n)$ can be characterised as $L^1_{loc}(\mathbb{R}^n)$. Is there a similar characterisation of the regular distributions of $\mathcal{S}'(\mathbb{R}^n)$?    I often found, that all allgebraically bounded $f \in L^1_{loc}(\mathbb{R}^n)$, i.e. $\exists C>0, N>0:\ |f(t)|\le C(1+|t|)^N$, give regular tempered distributions, but for example this does not contain $\chi_{[-1,1]} \frac{1}{\sqrt{|t|}}\in L^1(\mathbb{R}^n)$, which should also be a regular tempered distribution? On the other hand, it should be "smaller" than $L^1_{loc}(\mathbb{R}^n)$ as $e^t$ won't give a regular tempered distribution.    (*) A tempered distribution $T\in \mathcal{S}'(\mathbb{R}^n)$ is called regular in this context, if it can be represented by an (ordinary) function $f\in L^1_{loc}(\mathbb{R}^n)$, i.e. $$\exists f\in L^1_{loc}(\mathbb{R}^n):\quad T(\phi)=\int_{\mathbb{R}} f \phi\ dx \ \qquad\forall \phi \in \mathcal{S}(\mathbb{R}^n)$$


How to disable the notebook Touch Pad when a wireless USB mouse is connected

I have a Logitech MX Anywhere wireless USB mouse which works very well with Ubuntu.  However, I would like to disable the touch pad when this mouse is connected.  I keep hitting the touch pad with my wrist or thumb and cause the mouse to move to another part of the screen.  I am constantly fixing typos.  I've had this problem since I installed Ubuntu 9.10.  I'm not sure if it is because the biometrics is part of the touchpad, the way the device is built into the system, or the BIOS which does not let me disable it.


Finding equivalence classes of an equivalence relation defined on a powerset, defined by XSY if and only if |X| ≡ |Y| (mod 2)

Let S be the equivalence relation defined on $P$({1, 2, 3, 4}) defined by XSY if and only if |X| ≡ |Y| (mod 2). Write down the equivalence classes of S.   So the absolute value of any set in $P$({1, 2, 3, 4}) will be any of 0, 1, 2, 3, 4  Aka |X| and |Y| can only equal 0, 1, 2, 3, or 4.  For |X| and |Y| to be congruent (mod 2), |X| - |Y| must be divisible by 2.  So would the equivalence classes just be every 5 different sets, each containing subsets with the same absolute value? As in one set for absolute value 0, one set for absolute value 1, etc. all the way to 4?  I'm confused by what equivalence classes actually are, or what the answer to this would even look like. Thanks for any help.


Is there any command line to show tree view directory?

Many tutorials depict tree-view directory to show how they organize their files. Is there any command line to show such view?  Is ls capable to do this?


I'm trying to get an Ubuntu laptop functional for a visually impaired friend. Her impairment is such that a screen magnifier would solve the issue.  I've tried out Kmag (as its the only hit when searching the software center for "magnifier"), but it seems odd the Ubuntu lacks a default.  So I'm assuming I'm missing something obvious.


A Group $G$ is soluble $\iff G^{(k)}=\{e\}$ for some $k$

I am trying to understand the proof of the following proposition:     A finite group $G$ is soluble $\iff G^{(k)}=\{e\}$ for some $k$, where $G^{(0)}=G$, $G^{(i+1)}=[G^i G^i]$ is the derived series.   Proof: Since $G$ is finite there is some $i$ such that $G^{(i)}=G^{(i+1)}$, and clearly $G^{(i)}=G^{(k)}\ \forall k\ge i$. So $\{e\}$ appears in the derived series $\iff G^{(i)}=\{e\}$.  Suppose that $G^{(i)}\ne\{e\}$ and let $G^{(i)}=H_0>H_1>...>H_k=\{e\}$ be a composition series for $G^{(i)}$. Since $\color{red}{G^{(i+1)}\nleq H_1}$ and since $G^{(i+1)}$ is the derived subgroup of $G^{(i)}$, it follows that $H_0/H_1$ is non-abelian. So $G^{(i)}$ is not soluble and hence $G$ is not soluble (since any subgroup of a finite soluble group must be soluble).  Now suppose that $G^{(i)}=\{e\}$. We know that if $X$ is a finite group and $N\lhd X$, then $X$ has a composition series which includes $N$.  $\color{red}{\text{Using this fact repeatedly we get a composition}}$ $\color{red}{\text{series for } G \text{ which includes } G^{(j)} \text{ for all } j\le i}$. It is clear that the composition factors are abelian since $G^{(j)}/G^{(j+1)}$ is abelian for all $j$. So $G$ is soluble. $\quad\quad\square$  I highlighted the parts which I didn't understand. Would somebody be so kind and explain the details. :/


Why is my page scrolling to the top when click on a field and the keyboard appears?

I have the following problem on iOS devices. When I click on an input field and the keyboard appears my page scrolled to the beginning/top. The problem occurs only on iOS devices and it occurs after I have scrolled down bit on the page.   P.S. the page is i.e. the account edit\new page but it is overridden with a custom one. On the original page everything works fine.


Convergence of $\sum_{n=2}^{\infty} \frac{1}{n^{p} \ln(n)^{2}}$ for $p>0$

I am attempting to test the convergence for the following series for a final review: $$\sum_{n=2}^{\infty} \frac{1}{n^{p} \ln(n)^{2}}, p>0$$ My classmates and I have tested the convergence for when $p=1$ and $p>1$; the series converges in both cases (Comparison Test). However, we are having problems for when $0<p<1$. Was wondering if we could get some hints for this third case.


What is the difference between "AS" and "IS" in an Oracle stored procedure?

I see Oracle procedures sometimes written with "AS", and sometimes with "IS" keyword.   CREATE OR REPLACE Procedure TESTUSER.KILLINSTANCE (INSTANCEID integer) **AS** ...   vs.  CREATE OR REPLACE Procedure TESTUSER.KILLINSTANCE (INSTANCEID integer) **IS** ...   Is there any difference between the two?   Edit: Apparently, there is no functional difference between the two, but some people follow a convention to use "AS" when the SP is part of a package and "IS" when it is not. Or the other way 'round. Meh.


I remember watching this movie on TV when I was a kid. It must be around 1997-98, but I'm not sure. Of course, the movie itself must be older.  It was about a strange, otherworldly tower-like structure suddenly appearing on a desert-like place (probably somewhere around Middle-East, again not sure). It had healing powers around its surrounding area. One of the main characters had a cancer (lung cancer maybe) and when he came around this structure he was gradually healed.  I remember a specific line in the movie that goes: (Wording might not be the same.) "This thing might be what we call The God for thousands of years."  Once it was discovered, there was a military occupation around and they were arguing about whether or not to destroy while main characters were trying to save it. At some point, they were going inside the structure.  I could not find the movie. Maybe I misremember some things. Anyone have an idea?


So I wrote the following code in C#.   class Test {     int a;     System.IO.StreamReader reader;      public Test()     {         a = 5;         reader = new System.IO.StreamReader(String.Empty);     } }   And the constructor of the class in IL looks like this  .method public hidebysig specialname rtspecialname          instance void  .ctor() cil managed {   // Code size       33 (0x21)   .maxstack  8   IL_0000:  ldarg.0   IL_0001:  call       instance void [mscorlib]System.Object::.ctor()   IL_0006:  nop   IL_0007:  nop   IL_0008:  ldarg.0   IL_0009:  ldc.i4.5   IL_000a:  stfld      int32 Test2.Test::a   IL_000f:  ldarg.0   IL_0010:  ldsfld     string [mscorlib]System.String::Empty   IL_0015:  newobj     instance void [mscorlib]System.IO.StreamReader::.ctor(string)   IL_001a:  stfld      class [mscorlib]System.IO.StreamReader Test2.Test::reader   IL_001f:  nop   IL_0020:  ret } // end of method Test::.ctor   There are 3 nop commands. (Which as I know stands for no operation). What is the need of those commands. I mean what would be the difference if there was no command at all instead of nop


I would like to know the name (code) of fonts in (La)TeX. Let me explain myself:  When I want to import a symbol from a different font, I type something like  \DeclareFontFamily{U} {cmsy}{}   Here cmsy is the (La)TeX encoding, (La)TeX name, (La)TeX code or whatever you want for the family Computer Modern (which is set by default in LaTeX).  If I want to import a symbol from the mathabxpackage (in this case subsetsymbol) I can write  \DeclareFontFamily{U}{matha}{\hyphenchar\font45}   Now the code is matha.  My question is:          Suppose I want to import a single character from Century Modern TT font. What code has it in (La)TeX? Which is the equivalent for cmsy and matha in any other font?


Is there a difference between an Array and a List in Apex?

In the  book on pg 130, they mention that an Array's length is fixed when you initialize it and that multidimensional arrays are not supported. I just tried using the .add function on an array and it worked so I'm sure what they are talking about, but I couldn't make an array of arrays (which could have just been because I didn't have the right syntax). Ignoring syntax errors, there seems to be some sort of difference and thus maybe an (even if just slight) advantage to using one over the other?


What's the effect of adding 'return false' to a click event listener?

Many times I've seen links like these in HTML pages:  Click here !   What's the effect of the return false in there?  Also, I don't usually see that in buttons.  Is this specified anywhere? In some spec in w3.org?


I've declared a 50 bounty for a  asked by me, later (after 48 hours) I found out the answer and the problem was due to a typo. There are no answers for my question even now.  So, can I cancel the bounty? What to do?


I have some questions about .  Should I ask them on , or ? They both have questions about Unity3D.  Where should I ask what kinds of questions? For example (just guessing): Conceptual questions on stackoverflow, and specific questions on game dev?  Edit: I found .


Does casting Contingency via Wish remove the requirement to carry a statuette?

When used to cast another spell, Wish states:     You don't need to meet any requirements in that spell, including costly Components.   (PHB 288) Contingency states:     ...contingency ends on you if its material component is ever not on your person.   (PHB 227) Does this mean that, when cast via Wish, you are always considered to have the statuette on you?


Where should I put my input files that should be accessible from anywhere?

I'm using MiKTeX and TeXnicCenter to compile my projects. Is there a folder where I can store all your input files which I want to include in another document, so I don't have to put all the files in the specific folder where my current document is located?


Signing up during answer post can cause (partial) loss of answer

I just typed out an answer to a site on the SE network I did not use before (). After completing, I clicked on 'sign in' > 'sign in with google' to leverage my network account that has google login capability. As soon as I finished the login+account creation, I was shown my post, and to my horror only the first 2 lines remained (out of 15 or so). In a moment of clarity I went back 5x to the previous page and found my full text but otherwise this would have been a pretty sad entry to the new site. I am using an up to date version of chrome on a mac, but (though I don't sign up for a new site every day) I think I had this at least once before, perhaps a year ago. So suspect there is either a missing autosave when clicking the button that leaves the page, or an issue that not necessarily the latest version is displayed.


Why do some Stack Exchange sites have their own domain names?

I've found a strange thing: some Stack Exchange sites have their own domain names instead of https://[site name].stackexchange.com. The websites which have their own domain names are:          Are there any parameters for allocating specific URLs to Stack Exchange sites?


while loop, does not check the condition

String quit="N";         int i=0;         ArrayList<String> course = new ArrayList<String> ();         Scanner scan = new Scanner(System.in);         while (quit!="y")         {             System.out.println("Enter the Course code or y to exit:");             quit=scan.next();             System.out.println(quit);         };         System.out.println("out");   }   Im trying to quit the loop if the input is "y", but however the while loop continues execution over and over even after the input is "y", please help.


Crass as it may be I have to find a suitable alternative to "circle jerk" which describes a situation in which everyone agrees about some subject but still love getting worked up about it and feed off each other's passion.  I have heard of "echo chamber" but it doesn't work for me.


I am using Texmaker to create a document with pdflatex. When I add an image to it (no spaces in the path), it takes an approperiate amount of space, it shows a black border, however no image shows up. I get no message implicating a missing file.  In preamble:  \usepackage{graphicx} \usepackage{amsthm} \usepackage[utf8]{inputenc} \usepackage{polski} \usepackage[polish]{babel} \usepackage[nottoc]{tocbibind} \usepackage[a4paper,width=150mm,top=25mm,bottom=25mm]{geometry} \usepackage{authoraftertitle} \usepackage{enumitem} \usepackage{fixme} \usepackage{url}  \graphicspath{ {img/} }   Adding graphics:  \includegraphics[width=1\linewidth]{email-invitation}   Result:    What may I be doing wrong?  Update:  Here is a minimal working example:  \documentclass[draft]{report} \usepackage{graphicx} \begin{document} \includegraphics{test} \end{document}   Seems plain simple...


Well we know about quadratic equations, but quad means four, but quadratic equations have two roots. So why is it so?


a car weighs 100kg and has Velocity 0. it accelerates and its speed become 10m/s. its kinetic energy would be 100*10*10/2=5000j.  from another view car is at rest and the world accelerates and has now 10m/s speed.  as energy must be constant it should be:5000=10*10/2*(world mass except car) world mass except car=100kg?  am i using conservation of energy in wrong way, or i cant have that point of view?


Why is $\cos(36°) = \frac{\phi}{2}$ where $\phi$ is the golden ratio?

A recent question had a comment which intrigued me, so I went to Wolfram Alpha and put in $\cos(36°)$ and it was half the golden ratio?  Why is $\cos(36^\circ) = \frac{\phi}{2}$? Is there a nice geometric proof? I have never heard this before and it's quite fascinating. Is it a coincidence?  Is there something special about the angle $\frac{\pi}{5}$?


Windows 8.1 dont have hyper-v - cant use Windows Phone Emulator

Lately i wanted to get into Windows Phone 8 development and i installed Visual Studio 2013 + Windows Phone SDK 8 + Visual Studio 2013 Latest update. My system parameters are: - 8gb ram - Windows 8.1 64bit system - Intel i5 The moment i try to run a Windows Phone project a dialog appears and it says: Title - " Cant start the windows phone emulator" Subtitle - "The Windows Phone Emulator requires Hyper-V.Your PC is missing the following pre-requisites required to run Hyper-V: -Windows 8 Professional(64 bit)"  After i saw that i checked for how to upgrade Normal Windows 8.1 to Windows 8.1 Professional. With no luck i tried to find out more about to install Hyper-V with the BIOS configuration with no luck as well.  Usually i develop on Android with Eclipse(with the Emulator) so i can't understand the reason why a emulator of Windows Phone can't run on my system.  P.S I don't have Hyper-V feature to be turned on/off in the windows feature list.  Thanks heads up for each answer! :)


How to insert a space after a substitution of a variable or a command?

I am trying to learn how to define commands (\newcommand) and variables (\def) in LaTeX.  When I try:  \def \new {$new$}   or  \newcommand{\new}{$new$}   and substitute it in the text:  \documentclass{article}  %\def \new {$new$}            %\newcommand{\new}{$new$}  \begin{document} lala \new lala \end{document}   The substituted text sticks to the following text as shown here:    no matter how many spaces I put after the command.   What causes this behavior and how can I change it?


I am studying in the imperative sentence and I wonder what "No parking" is short for.I also want to get more comprehensive material of the imperative sentence.


What is the best way to store user settings for a .NET application?

I have a .NET 2.0 Windows Forms application. Where is the best place the store user settings (considering Windows guidelines)?  Some people pointed to Application.LocalUserAppDataPath. However, that creates a folder structure like:     C:\Documents and Settings\user_name\Local Settings\Application   Data\company_name\product_name\product_version\   If I release version 1 of my application and store an XML file there, then release version 2, that would change to a different folder, right? I'd prefer to have a single folder, per user, to store settings, regardless of the application version.


Make grey background while using HDRI for renders

I just want to ask if anyone knows how to make background grey while using HDRI so it would be the same as in Substanse painter "Environment Opacity slider" or basically the same as in Material Preview Mode in Blender? Is it possible to make it without options that listed below?:  Not a transparent background and then add grey background picture in photoshop;  Not a heavily blurred background (I found this option here but it still has colors);  Without adding a grey plane at the back while rendering   Just pure grey