How to make the main content div fill height of screen with css

So I have a webpage with a header, mainbody, and footer. I want the mainbody to fill 100% of the page (fill 100% in between footer and header) My footer is position absolute with bottom: 0. Everytime I try to set the mainbody to 100% height or change position or something it will also overflow the header. If if set the body to position absolute with top: 40 (cause my header is 40px high), it will just go 40px too far down, creating a scroll bar.  I created a simple html file since i cannot actually post the entire page/css from the actual project. With the sample code, even though the maincontent body fills the screen, it goes 40px too far down (cause of the header I assume).    html, body {   margin: 0;   padding: 0; }  header {   height: 40px;   width: 100%;   background-color: blue; }  #maincontent {   background-color: green;   height: 100%;   width: 100%; }  footer {   height: 40px;   width: 100%;   background-color: grey;   position: absolute;   bottom: 0; }      <title>test</title>   <link href="style.css" rel="stylesheet" type="text/css">

            Anyone knows the answer?


Update-manager does not show all updates

Ever since I upgraded to 13.10, the software updater does not show all the available updates. Some will appear and can be installed just fine, but once it claims that all software is up to date, using sudo apt-get upgrade shows that there are still more packages waiting to be updated. I can update them via the command line, but that only solves things temporarily. I'm not sure why some show up and others don't. How can I make Update Manager update all packages?  Update-manager shows this:    But apt-get shows this:   Thanks!


"Open with" configuration gets screwed up unpredictably on El Capitan

I've been having a problem on my El Capitan installation for a few months. At unpredictable times, the system "unlearns" the programs associated with certain file types.  For example, I double click a PDF in Finder, and it tries to open it with Microsoft Word (which of course complains it is unable to open it). To fix, I have to [right-click -> "Open With" -> "Other..." ] a PDF file, go find Preview (which by the way is not even in the "Recommended Applications") and select "Always Open With", and then the problem goes away for some time.  For a while I thought this problem was limited to PDFs, and was somehow a bug caused by Microsoft Office.  However, just now I had the same problem, but the system defaulted to iTerm for opening hyperlinks! So when I clicked on a link inside an email, it caused an empty iTerm to be opened... To fix I had to create a shortcut to a webpage, then [right-click -> "Open With" -> "Other..." ] and select Firefox.  Would be glad for any help to restore sanity, or at least to understand what is going on!


How come people say "I'm friends with sb." rather than "I'm a friend with sb."?  And there are expressions like "He was friends with Jack"...  It's just not grammatical! How can "I" or "he" be "friends"?


DFS: Use Dictionary to store visited states VS. array

I'm counting the probability of staying on an N by N chessboard after K steps, given that the starting position is r, c. Here's my code:  def knightProbability(self, N, K, r, c):     # dfs.     answer = 0     dp = [[[-1] * N]*N] * (K+1)     # dfs with memoization.     self.dic = {}     return self.dfs(N, K, r, c, dp) # Starting at r, c, what's the probability of staying on board after k moves.    def dfs(self, N, k, r, c, dp):     offsets = [(-1, -2), (-1, 2), (-2, -1), (-2, 1), (1, -2), (1, 2), (2, -1), (2, 1)]     answer = 0.0      if k == 0:         return 1.0      '''if dp[k][r][c] >= 0:         return dp[k][r][c]'''     if str(k) + ":" + str(r) + ":" + str(c) in self.dic:         return self.dic[str(k) + ":" + str(r) + ":" + str(c)]      for offset in offsets:         new_r = r + offset[0]         new_c = c + offset[1]         if new_r > -1 and new_r < N and new_c > -1 and new_c < N:             answer += self.dfs(N, k-1, new_r, new_c, dp) * 1.0 / 8 # with k-1 steps, what's the probability?     '''dp[k][r][c] = answer'''     self.dic[str(k) + ":" + str(r) + ":" + str(c)] = answer     return answer   It's a simple dfs. When I use a dictionary to store and retrieve visited states (k, r, c) like I'm doing now, it works. However, if I use a k by N by N array to store and retrive them, I'm not getting the correct answers. Any ideas why? The commented part is the storing/ retrieving from the array parts I'm talking about, which should be doing the same thing as the current code.


Difference in Interest Calculations Using Loan Calculator

Suppose that I have a loan value x and interest rate r.  The simple interest is then x*(1+r).  If I take out a loan compounded annually and paid monthly for 12 months the amount at the end of the year would be the same.  Why is it then that loan calculators give a different value?  For example, if I were to borrow 100 at 10% I would owe 110 in simple interest and so 110/12 each month, yet using an online calculator I get that I owe 5.48 in interest for a total of 105.48.  Why the discrepancy?  EDIT:  Since it's due to differences in principal due, which one is actually the APR of the loan?


Lost power during upgrade, how do I recover?

I was attempting to update my 11.10 install to 12.04beta. During the install step, I accidentally lost power to my laptop (the power cable came unplugged) and it shut down. Whenever I go to boot now, I can select my install via Grub and it loads up to where the sign-in should happen, but I get a display that looks like what you see as soon as you shut down. It looks like it locks after checking for the battery.   Is there anyway, with or without Live media, to restore my machine's install/update to 12.04 but still keep my settings/applications/files?


was trying out this LeetCode question   The output supposed to be [3,2,1,4,5] but I keep on getting [3,2,1,4]. I believe there's problem with my current pointer but couldn't think stop it from referring to head. I'm new to C++ by the way. Any assistance would be greatly appreciated. class Solution { public:     ListNode* reverseKGroup(ListNode* head, int k) {         // head = [1,2,3,4,5]         k = 3;         cout << "RECURSE" << endl;         ListNode* current = head;         ListNode* next = NULL;         ListNode* prev = NULL;         for(int i = 0; i < k; i++){             if(head == NULL){                 return current;             }else{                 next = head->next;                 head->next = prev;                                  prev = head;                 head = next;             }         }                  current->next = reverseKGroup(head, k);         return prev;     } };


Acceptable example of when to use a dynamic_cast?

What would be a genuinely-acceptable example of usage for a derived cast? I have always thought they are only used when implementing "hacks" but if this is not the case, could someone give an acceptable example of when to use one?


In Catan, if you roll a seven and move the robber, do you actually have to rob someone?

Rolling a seven forces you to move the robber from its current position, to another hex. Are you allowed to move the robber to a hex (other than the desert) from which no one is producing resources? Your blockage of production becomes "trivial," and you have no one to rob. Are there times where this might make sense? One might be from a "political" point of view, perhaps if you don't want to disturb the current balance of power? Or might it make sense to block a hex where you don't want someone to build a settlement, rather than actually having one already?


I have 256 colors working just fine in konsole,. I thought I'd give tmux a try because, unlike screen, it seems to support vi mode.  However I find that the colors of my prompt show up and this is most likely because I have a 256 color mode prompt. What do I need to do to get tmux to recognize all 256 colors?


I'm planning on commuting by bicycle to work in hot Montreal, though this question is probably relevant to anyone who bikes to work in a city with temperatures above 20 degrees Celsius (68 degrees Fahrenheit). I have to wear business casual to formal clothes (no jacket, usually).  How do I not sweat?  I'm particularly looking for   Helmet features that prevent sweating Tips on rhythm, speed, pace, etc. that prevent sweating Bags that will make me sweat less (I'm leaning toward nice, office-friendly panniers at the moment but I'm open to other suggestions)   Any other tips would be greatly appreciated.


Is there a function $f: \mathbb{R} \to \mathbb{R}$ such that $\lim\limits_{x\to p}f(x)=\infty$ for every $p \in \mathbb{R}$

I was wondering if there is a function $f: \mathbb{R} \to \mathbb{R}$ such that its limit at every point is infinite.   I guess not, because what would its graph look like, but then again, I don't know how to prove it.


If $0 < a \le b \le c \le d$ and $abcd = 1$ prove that $$a+b^2+c^3+d^4 \ge \frac{1}{a}+\frac{1}{b^2}+\frac{1}{c^3}+\frac{1}{d^4}$$   I first thought of multiplying both sides with $\big(\frac{1}{a}+\frac{1}{b^2}+\frac{1}{c^3}+\frac{1}{d^4}\big)$  Then by applying C-S inequality in the LHS the inequality would be $$16 \ge \Big(\frac{1}{a}+\frac{1}{b^2}+\frac{1}{c^3}+\frac{1}{d^4}\Big)^2$$  But if $(a,b,c,d)=(\frac14,1,1,4)$ the inequality does not hold true.


I'm sorry if this question goes against the meta for posting questions - I attached all the "beware, this is a soft-question" tags I could.  This is a question I've been asking myself now for some time. In most areas, there's a "cut off age" to be good at something. For example, you're not going to make the NHL if you start playing hockey at 20. It just won't happen.  So my question then, how late is too late to start studying math and make a career out of it? By "start studying math" I mean, to really try to understand and comprehend the material (as opposed to just being able to do well in a formal, intuitional environment).   I don't mean this from a "do what you love, its not too late" motivational perspective. I mean this from a purely biological perspective; at approximately what age has your brain's capacity to learn effectively and be influenced by your learning stop? When does the biological clock for learning new math run out?  My reasoning for asking this question is (for those who care): I love math. Really I do. But , having spent the first 21 years of my life in sports/video games/obtaining a degree in a scientific field which I care nothing of/etc, despite all my best attempts at trying to learn math, am I just too late starting to ever actually be good enough at it to make it a career? I've almost completed my second degree (in Math), but find that in many cases, despite how I look at a problem, I lack the intuition to comprehend it. I'm going to single him out (sorry), only as an example, but Qiaochu Yuan is my age.   Note 1: If this question isn't a suitable post, I won't be offended at all if you vote to close - I know this question borders what's acceptable to ask.  Note 2: Thanks to everyone for reading and taking the time for the great responses. Really appreciate it!


Mistakenly, I lost a partition by disk initializing in Win10.  How can I recover it?  The former:   sector size(logical/physical): 512B/4096B partition table: gpt start: 1049kb, end: 4001GB file system: ext4   The latter:   sector size(logical/physical): i don't know it. partition table: gpt  Number  Start (sector)    End (sector)  Size       Code  Name    1              34          262177   128.0 MiB   0C01  Microsoft reserved part    Just the initializing was done.


Identify a short horror story about a cursed man with imps crawling under his skin

I have a recollection of reading this particular horror story as a young teen (circa 1993?), but cannot now find it. It was written in a style reminiscent of Edgar Allan Poe’s. (I have browsed the latter’s tales to no avail, however.) Here follows the story as I remember it. Thanks in advance to anyone who can point me in the right direction.  (The setting might be the 19th century.) A man travels (possibly to India or South America) to meet a friend (probably an archaeologist or explorer) who wrote to ask him to come since he has fallen terribly ill. There, the main character finds his friend uncooperative and secretive. The sick man’s health fluctuates, and his bouts of illness correlate with large lumps appearing on his skin.  One night, the puzzled protagonist decides to spy on his friend, and sees him cutting open one of his cysts with a knife. An imp-like creature emerges from the wound and addresses the feverish man. I do not remember its exact words; they seemed to imply that the infected fellow had a duty to perform should he wish to be rid of this curse. It left me with the general impression that he had to return an artifact or restore something to its earlier condition, but that this task was impossible, dooming him to a (hopefully short) life of torment borne of his own flesh.  I believe the story ends at this point, or maybe shortly afterwards as the onlooking character reels in horror and flees.


How do I uninstall  ? I don't remember having installed it and it doesn't even work:   There is no entry under Programs and Features in the Control Panel:    I also checked the my Microsoft Office Professional Plus 2013 installer and under Add/Remove features I could find Word, Excel etc, but no Skype.    So how do I get rid of it? oO


What are the dev-loop services that started on boot?

After booting I ran systemd-analyze blame and here are the results:       21.596s systemd-journal-flush.service      18.658s dev-sda8.device      15.099s dev-loop33.device      15.034s dev-loop19.device      15.012s dev-loop34.device      14.989s dev-loop21.device      14.877s dev-loop15.device      14.866s dev-loop26.device      14.773s dev-loop27.device      14.684s dev-loop30.device      14.677s dev-loop32.device      14.649s dev-loop35.device      14.590s dev-loop25.device      14.267s dev-loop23.device      14.192s dev-loop24.device      14.156s dev-loop29.device      14.133s dev-loop16.device      14.065s dev-loop31.device      14.059s dev-loop28.device      13.821s dev-loop20.device      13.531s dev-loop22.device      13.495s dev-loop14.device      13.364s dev-loop18.device   What are these dev-loopxx.device (xx denotes numbers) services and why are they taking so much time? Are they related to the mounting of snaps? Can I reduce the boot time by disabling them? I'm running Ubuntu 18.04 alongside Windows 10.


I was messing around with a USB camera. I wanted to change the cable because is trimmed but as I was cutting it I saw a small thing (image below). As I was trying to cut the casing and see what it has inside I saw a spark. I tried to connect it with another cable but I don't know if I'm gonna damage the camera or the USB port.    What is it and can I connect the camera without it?


What benefit does the opening and closing of "wings" have for Star Wars fighters?

The X-Wing opens its wings when in combat mode, but what purpose do the two modes have? Usually a fighter will become sleeker for higher speed, and then open itself up to allow better manoeuvring; but in space there is no benefit in terms of aerodynamics.  So what are the benefits in Star Wars to opening up wings?


Connecting 3 monitors to macbook pro 2018 via thunderbolt 3

I looked for 20 minutes for a post similar to mines, and couldn't find one. Which is interesting to me, because I don't understand why people want to use the display to HDMI instead of using thunderbolt USB-c port natively instead. Before I get to this...I shall ask my question.  I plan on buying a MacBook Pro-2018 15 inch for my home-based business. I need to connect 3 monitors to this laptop. I understand the 15 inch MacBook Pro comes with 4 thunderbolts 3 ports. I plan to buy 3 24-27 inch monitors that are 4k display. Also, I understand that the charger for this laptop uses a Thunderbolt 3 port, which leaves me with 3 left. Will connecting 3 monitors that have Thunderbolt 3 ports leave me with performance issues? Will the refresh rate lower?  Finally, why do I see a lot of post with people using old 2.0 display port to HDMI; why they can use Thunderbolt 3 port natively?


Does the speed of light vary in non-inertial frames?

The speed of light is the same in all inertial frames.  Does it change from a non-inertial frame to another? Can it be zero?  If it is not constant in non-inertial frames, is it still bounded from above?


For a given prime $p$ and integer $k$,  $k∈<1, p-1>$ $S(k)$ is defined as a sum of remainders of $k, k^2, k^3, ..., k^{p-1}$ when divided by $p$. Prove that $S(k)=\frac{1}{2}p(p-1)$ is true for an odd number of different k. I managed to prove that $S(p-1)=\frac{1}{2}p(p-1)$ but can't see how to do it further.


Looking for a short story about an insect-like alien captured by humans on its own planet

This poor creature is taken aboard the spaceship and the humans do not know that it is intelligent.  The alien can repeat what it hears, e,g, "pass the sugar".  It is able to escape at night and it communicates messages to its fellow aliens.  It directs that they turn up the heat of the atmosphere (somehow they can do this) so as to force the humans to leave.  The alien protagonist states that it will die w/ the humans or leave with them.


How to find substring inside a string (or how to grep a variable)?

I'm using BASH, and I don't know how to find a substring. It keeps failing, I've got a string (should this be an array?)  Below, LIST is a string list of database names, SOURCE is the reply, one of those databases. The following still doesn't work:  echo "******************************************************************" echo "*                  DB2 Offline Backup Script                     *" echo "******************************************************************" echo "What's the name of of the  database you would like to backup?" echo "It will be named one in this list:" echo "" LIST=`db2 list database directory | grep "Database alias" | awk '{print $4}'` echo $LIST echo "" echo "******************************************************************" echo -n ">>> " read -e SOURCE  if expr match "$LIST" "$SOURCE"; then     echo "match"     exit -1 else     echo "no match" fi exit -1   I've also tried this but doesn't work:  if [ `expr match "$LIST" '$SOURCE'` ]; then


Can we use light slingshotting behind a blackhole as a cosmic mirror to our past?

It seams to me that light from our solar system can slingshot around the back side of a black hole, so that if we focus a telescope beyond the edges of a black hole we could in essence use them as mirrors to ourself and study our own solar system at a time roughly twice the light years away as the black hole. Would it spread and distort the light like a prism as it curves around the black hole because different light frequencies have more energy and therefore different gravitational attraction to the blackhole?   Maybe there is a way to correct for this?


Connecting two relative clauses in one sentence

I would like to write an essay which gives information about the charts but because I am not native English speaker, when I started to write down my essay I came across the similar problems that I do sometimes.  Here my sentence:  Figure 1 and figure 2 show the percentage of people, WHOSE age is between 25-44 and over 65, WHO purchased concert, cinema and theater tickets online over the first three months of 2006 in three countries, WHICH are Australia, the UK, Malaysia.  Here is my questions:  1.How can I give the information of age and of what do people buy in one sentence?  2.Such vital and important information on the figures can be used as indefinite relative clause?


What packages are in Ubuntu but not in Debian?

Ubuntu uses packages from Debian (it is based on Debian).  I wonder what extra packages or package classes are added to Ubuntu?  I expect to see some proprietary software, some extra office software, some build-in adware...  Let's compare with latest stable releases. But it doesn't hurt if you add some important historical notes too...  I am talking only about official upstream package repositories. No need to talk about PPA.  I am not interested in branding or styling or release cycle or support or whatever discussed at  difference. Only about the difference in packages and that link doesn't tell anything related they I haven't mentioned in my question.


Why is list.toArray() an object while converting ArrayList to String[]?

To make it very clear this is not a duplicate of these questions  and  but it is of relevance to them.  Suppose we have a conversion method from ArrayList to String [] as described in answers of the first link I've referred to:   List<String> stockList = new ArrayList<String>(); stockList.add("stock1"); stockList.add("stock2");  String[] stockArr = new String[stockList.size()]; stockArr = stockList.toArray(stockArr);  for(String s : stockArr)    System.out.println(s);    With the print statement my output would look like this:   stock1 stock2   But what if I wanted my output to be in an array format (like [stock1,stock2]) and I excluded the conversion to String, i.e, the for loop towards the end.   If I would print out just the String[] it would give me a garbage value like [Ljava.lang.String;@5636bc0a. This I guess is probably because of problems with the jvm returns toArray as an object.   Why is it this way and what is the work around for this?   I need a String [] that gives me a meaningful value. I need it in this format because I am using this conversion to call a JAX-WS function in my project which accepts only String[] values:   myJaxWSObj.setValue(String[] myArrayOfStrings);   EDIT  Thanks for the answers, but some of you must have misunderstood the question. I want to convert ArrayList to String[] and not to String. So doing any sort of .toString() wouldn't help me much because as I mentioned above I need to call a JAX-WS class which accepts only String[] values. So the problem is not with System.out.println().   Suppose I do a .toString() conversion I would need to convert it back to String[] by doing something like stockArr.split(""). I wanted to know if there is another work around for that.   EDIT 2  This has nothing to do with printing Arrays, it has to do with conversion of List to an Array of Strings.


I used ubuntu in my previous laptop for some years now. I installed it via wubi. Recently I bought a new laptop and I want to do the same thing. Although I used ubuntu almost exclussively, for some reason I DON'T want to make a partition in my new laptop. I only want to install it like I did in my previous one.    So, I installed it in my previous laptop about three or four years ago (it was ubuntu 12.04 back then or maybe an older version). I remember that I dowloaded a small .exe from the ubuntu page (about 2mb if I remember correctly). When I ran it, a window opened and asked me how much space do I want to dedicate to ubuntu, my user name and a password. Now I cannot find it anywhere. I downloaded the 14.04.2 version from here:  and I created a virtual cd with deamon. I found the wubi.exe in that and I executed it, but it says that I should restart my computer. It is not like the previous time that it installed ubuntu inside windows. Should I do it? Is it the same, or it will do a partition? I found an older version of wubi somewhere (for 9.04). If I use that one, will I be able to update later to 14.04 from inside ubuntu? I forgot to mention that my new computer (as my previous one) runs windows7 and not 8 (I know that wubi doesn't work with win8).     Thank you very much!


How to show that the mean is (weakly) consistent

How can I show that the mean is weakly consistent? Is weakly consistent the same as consistent?


I can run faster than _____. (1) him (2) he?

Consider the sentence "I can run faster than 15 miles per hour." Its meaning is clear and to my eyes obviously grammatically correct. Now let me present some variations that have given me trouble for a long time.  I am faster than 15 miles per hour. – To me this is clearly incorrect. Directly comparing me to a speed doesn't seem right. We need to compare my speed to a speed, or me to another person.  I can run faster than him. – Compared to the base sentence, there is a distinct shift in meaning of the comparison. While before I named a speed faster than which I can run, now I am naming a person. It doesn't seem quite right. I realize the parts of speech can change, but my initial objection is that "him" is not a speed.  I can run faster than he. – This seems most correct to me, but still somehow feels objectionable. Is this in fact the correct way to say it? And if so, is it proper as is or need I say "... faster than he can" or even "... faster than he can run?"  I am faster than him. – With "am" instead of "can run" it now seems slightly more correct. But is it?  I am faster than he. – I'm in doubt here. It doesn't seem wrong to me to say, "I am faster than he is" or even "I am faster than he is fast." (Though I suppose that is a given since I could hardly properly compare to some other category as in "I am faster than he is smart.")  My speed is faster than his. – Hmm. This seems more proper as "my speed is greater than his."   So which of these constructions is correct and which is incorrect? Is there a general rule that I can follow? UPDATE The scholarly article  may be of great interest to some readers!  Once we accept that the elided constituent and its antecedent can differ in form, it becomes reasonable to ask how large this difference can be. The answer in Rooth (1992), Fiengo and May (1994), Chung et al. (1995) and subsequent work is that the wiggle room is actually quite small: the elided constituent and its antecedent are allowed to differ only in the realization of inﬂectional morphology. Other than that, both constituents have to be syntactically and lexically isomorphic.


Which direction should the title text rotate after collapsing a panel?

I recently built a filter panel similar to .  My panel is different in that it can be collapsed out of the way to free up room for the results (see below)    I felt that the first letter of the title should basically remain in the same place as a user clicks to expand / collapse the panel so I went with option A but another developer thinks option B looks better.  I can't find anything official so I thought I'd ask here.  After collapsing a panel should the title read down, up or not matter either way?


How to find country using IP address in PHP?

I have IP ranges of the country. And I am checking the the user IP address within this ranges if true then he is able to see the site otherwise he wont. I have use following code,  $ip = $_SERVER['REMOTE_ADDR'];    if(ip2long($ip) >= $ipstart && ip2long($ip) <= $ipend){         return true;     }    My question is that if somebody comes from different country suppose ABC with his laptop/notebook to another country suppose XYZ then will above code works? on the same laptop.  How will it be possible for the above scenario for ipv4 and ipv6?  [EDIT]  Which IP address $_SERVER['REMOTE_ADDR'] fetch, will it be the machine IP or the connection IP, so that we can know that he now in this country?  Thanks


How performance is increased on using non-synchronised class as compared to synchronized class?

In  tutorial it is given that StringBuffer is synchronized and StringBuilder is not   Can a class be synchonized ? I know that  synchronized methods are locked for particular thread and non synchronized are not.But how does a performance of the programe is increased with non-syncronized method? Code from    public class Main {     public static void main(String[] args) {         int N = 77777777;         long t;      {         StringBuffer sb = new StringBuffer();         t = System.currentTimeMillis();         for (int i = N; i --> 0 ;) {             sb.append("");         }         System.out.println(System.currentTimeMillis() - t);     }      {         StringBuilder sb = new StringBuilder();         t = System.currentTimeMillis();         for (int i = N; i --> 0 ;) {             sb.append("");         }         System.out.println(System.currentTimeMillis() - t);    }   } }   gives the numbers of 2241 ms for StringBuffer vs 753 ms for StringBuilder.   and accoding to  the extracode is the synchronised keyword in StringBuffer.Does this synchronised keyword cost the extra 1488ms and if so then should we always prefer StringBuilder instead of StringBuffer?  Thanks in advance.


How to make overlay still work inside lstlisting environment?

Problem  I want to explain C# programming language step by step using overlay in beamer.cls. But it does NOT works as shown in the following figure.  How to solve this problem?    Code Snippet  \documentclass[dvipsnames,cmyk]{beamer}  \usepackage{listings}  \begin{document}  \defverbatim[colored]\Lst{% \begin{lstlisting}[language={[Sharp]C}] using System; public delegate void Foo(object o); \uncover<1>{public class Foo} \uncover<2>{\{} \uncover<3>{public static void Main()} \end{lstlisting}}  \begin{frame}{MyListing} \Lst \end{frame}  \end{document}


Fixed-position header and menu on a web page -- is that okay?

A client of mine is insisting on two things for a website I am designing:    That every single link is shown in the header – about 10 links or so with no sub-categories. ie. no drop-downs, rollovers, or sub-navigation.   That the header is always visible and static up the top. The content below it will scroll independently but the header is always up the top.    Now, to me, I don't like the idea of the navigation being always up the top. It means I have to go to lengths to reduce the height so that you can see enough content below it on smaller monitors. I believe that users know to find navigation up the top intuitively and don't need to have the nav forced on them at all times. In the client's eyes – this is "easier" – but in mine, it's treating the audience as stupid and smacks of Web 1.0 principles (namely frames).  So my question is – is it bad UX to have a fixed-position header?


Nontrivial subring with unity different from the whole ring?

Is there an example of a ring $R$ with unity and a nontrivial subring $J$, such that $1_J \ne 1_R$?


What does tracking do in BF4 and what are field upgrades?

When you like level up does some of that score go in the tracking things? How do you get the field upgrade score and what do they do?


Total degree of a product of polynomials

Note: This is not a duplicate of . The accepted answer there gives some answer to my question here, but the question is not a duplicate...   I'm currently brushing up on some algebra with "Abstract Algebra" by Grillet, Second Edition.  We consider, for a unital Ring $R$ and a family of sets $(X_i)_{i\in I}$ the polynomial ring  $$ R[(X_i)_{i\in I}] $$  I don't think the details of this construction are too important here; suffice it to say that we are dealing with the free $R$-algebra over the free commutative monoid of all monomials $$ X^k=\Pi_{i\in I}\, X^{k_i}\,,\; k \in \mathbb{N}^I\,, k_i = 0\, \text{ for almost all } i $$ with multiplication $X^k X^l = X^{k+l}$.  The degree of a polynomial $0 \neq A \in R[(X_i)_{i\in I}]$ with coefficients $a_k$ is defined as $$ \max\left\{\sum_{i \in I} k_i;\, k\in I^\mathbb{N}\,,\, k_i = 0\, \text{ for almost all } i\, \land \, a_k \neq 0\right\} $$  I generally put quite a lot of trust into textbooks as carefully written as this one, but the following statement on page 127 seems wrong to me and I am stuck trying to prove it:     Proposition 6.4. For all $A, B \neq 0$ in $R[(X_i)_{i\in I}]$:   ...   (4)  if $R$ has no zero divisors, then $\deg(\,AB\,) = \deg A + \deg B$   What I have proven is $\deg(\,AB\,) \leq \deg A + \deg B$, which was part (3) of the proposition.  However, part (4) baffles me. I started out expecting this to be easy but got stuck; and now I'm really a little too exhausted because I couldn't let go and kept on thinking about how to prove this. I'm actually wondering if this is actually wrong and was just a copy-paste error from the corresponding page 121 for the univariate case, where we have the exact same statement, safe for there only being one variable. A counterexample is probably not that hard, but I'm really too tired right now, and then I actually already got sidetracked just brushing up on basics required for my bachelor's thesis with this already, in the first place.  Why I feel like this isn't right: For $k \in I^\mathbb{N}$ with finite support, the $k$-th coefficient of $AB$ is  $$ (AB)_k = \sum_{(m,\,n) \in (I^\mathbb{N})^2;\,m + n = k} a_m b_n $$  where the $a_i, b_i$ are the coefficients of $A$, respectively $B$. In the univariate case, the degree formula holds if $R$ has no zero divisors, because the leading coefficient of the product is the product of the leading coefficients. However, in the multivariate case, each coefficient can be a sum of products:  Picking indices $\nu\,,\, \mu$ with $\sum_i \nu_i = \deg A$ and $\sum_i \mu_i = \deg B$, I don't see how $R$ having no zero divisors would lead to the coefficient $$ (AB)_{\nu + \mu} = \sum_{(m,\,n) \in (I^\mathbb{N})^2;\,m + n = \nu + \mu} a_m b_n $$ being nonzero, although it seems obvious that $AB \neq 0$ if we look at the $i$-degree $$ \max\left\{k_i;\, k\in I^\mathbb{N}\,,\, k_j = 0\, \text{ for almost all } j\, \land \, a_k \neq 0\right\} $$ for some $i \in I$ (should I be wrong with this reasoning, please tell me), so that $R[(X_i)_{i\in I}]$ is a domain, if $R$ is.  I also failed to find anything about this on good old Google or here.  So, am I right in assuming this part of the proposition quoted above is wrong?  I'm all out of creative mojo, so if someone could just plug me an easy counterexample, I'd be very, very happy... if the statement is actually true, I'd appreciate some help in proving it.


It does not throw exception ConcurrentModificationException

I have the below code and I would expect it to throw a ConcurrentModificationException, but it runs successfully. Why does this happen?  public void fun(){     List <Integer>lis = new ArrayList<Integer>();     lis.add(1);     lis.add(2);      for(Integer st:lis){         lis.remove(1);         System.out.println(lis.size());     } }  public static void main(String[] args) {     test t = new test();     t.fun(); }


Javascript global variable naming conflicts

A newbie learning javascript :)  This is my html page and the associated js code  <!DOCTYPE html>   <title> A Basic Function </title> <link rel="stylesheet" href="css/c03.css" />
Travelworth

Welcome to our site!
      basic-function.js  var msg="A New Message"; //Line 1 var msg="A Second Message";//Line 2  function updatemessage() {  var e = document.getElementById('message'); e.textContent = msg; }  updatemessage();   Q1:-  This webpage displays the message from the Line2 instead of Line1.  I am guessing this is because the "msg" variable declared in Line 2 is considered the "latest" and the interpreter has proceeded with that.  Is my assumption right ?  Q2:-  If that is the case, then there will be instances where a webpage may utilize multiple js files written by different people.  How the naming conflict will be handled on global variables between these two different js files referenced in the same webpage ?  Can someone explain ?


Is there a good reason to define helper macros second?

As a mathematician, my training is to define my terms before I use them. As a computer programmer, I recognize that there are sometimes good reasons to call a method/function/procedure before its full definition has been given. But all other things being equal, I still prefer to define helper methods before they are used rather than afterwards.  However, in TeX programming, the convention seems to be backwards. A simple example of this is the following, taken from :  \newcommand{\utriangle}{\text{\doutriangle}}  \newcommand{\doutriangle}{%   \linethickness{.1ex}%   \setlength{\unitlength}{.8ex}%   \begin{picture}(1,1)(0,-1)   \polygon(0,1)(1,0)(1,1)   \end{picture}% }   (Note: This is taken out of context; don't try to run it by itself.)  Another example is Donald Knuth's definition of the \loop ... \if ... \repeat construction:  \def\loop#1\repeat{%  \def\body{#1}\iterate} \def\iterate{%  \body \let\next\iterate  \else \let\next\relax\fi \next} \let\repeat=\fi   Although I have not tested this, it looks to my eye as if defining \iterate before \loop would have exactly the same effect. [I honestly have no idea about \let\repeat=\fi, since I know \fi constructions can be rather finicky.]  Is this convention arbitrary, or is there a good reason for it? For instance, are there common situations in which the code will break if the helper macro is defined first?


Exeception on After Insert, Record is read only

I'm writing a trigger for new opportunity products to populate  a field Product_Category__c (on opportunity lineitem) getting the value from Product_Category_new__c (on Product).  This is my trigger:  trigger SetProductCategory on OpportunityLineItem (after insert) {      for (OpportunityLineItem opplineitem: Trigger.new) {                    opplineitem.Product_Category__c =  opplineitem.PricebookEntry.Product2.Product_Category_new__c;     }      }   I get this error message:     execution of AfterInsert caused by: System.FinalException: Record is read-only   I have tried with before insert;in this case there aren't errors but the value Product category it's not saved on Opportunity Line item.  I have found that:  In a after insert trigger is not allowed change field using trigger.new  Please can you suggest a solution for this? i would like to copy the value Product category (Product) on Product Category (Opportunity Product)  after the insert of the new opportunity products.  Thanks in advantage for any advice.  Br


Who's flying the Enterprise when Kirk and his crew are sleeping?

I assume Kirk (and his crew) have got to get some rest after a long day of investigating new planets and hassling other ships in space, so who is flying the Enterprise when Kirk and his crew are asleep?  Not concerned with what the crew does on duty, but rather what someone else does when Kirk's crew is off duty.


Interpreting the value of standard errors

After computing the standard error of regression, my answer is 3.55 what does the value mean


What IDEs ("GUIs/editors") do others use for Python coding?


skype: error while loading shared libraries: libXv.so.1: cannot open shared object file: No such file or directory

I am using Ubuntu 14.04 and have tried the suggestions in the following post:  and still get the same error


I have all tables and database encoded with utf8_general_ci and all data in database are ok. When I select data with PHP (PDO) and print in CLI (and when I save these data into db) texts contains question marks:  Raw, zagra? te? rol? wiceprezydenta   Why ? What's wrong ? I tried SET NAMES solution but don't work. Part of my code:  <?php setlocale(LC_ALL, 'pl_PL'); ini_set('default_charset','utf-8'); mb_internal_encoding("UTF-8"); putenv('LANG=pl_PL.UTF-8'); $db = new PDO('mysql:host=localhost;dbname=nameofdb;charset=utf-8','root','******', array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8")); // body...


How to double-click in PDF document to go to source code?

When creating a document, I usually build a DVI document because the YAP viewer has a nice feature which allows me to double-click on a word in the DVI document which then causes the source-code window to appear with the cursor on the word (or line) in the source code corresponding to the word in the DVI document where I clicked.  My understanding is that this feature is not available with PDF documents?  Is this correct or can I set up a PDF viewer to cross-reference the source code when I click a word in the PDF document?


how can I iterate the elements of an array and show a message when it's in the middle in javascript?

I am a newbie trying to understand the basics of Javascript with some basic exercises but I can't do this one. Any idea of how should I write it instead?  var array5 = [1,2,3,4,5];  for (var i=0; i<array5.length; i++) { console.log(array5[i]);   if (array5===[2]) {   alert("we are in the middle of loop");} }   PD: by the way, it has to be using the for loop and conditional if.  Thanks!


Script to add balise [img][/img] on each line of text linux?

I just got a script who upload image file on to a web hoster; at the end I got a file with all the links (one link per line) and I would like to add [img] at the beginning of each link and [/img] at the end.


This is recent behavior, but I couldn't figure out since exactly when this is happening:  % !TEX encoding = UTF-8 Unicode % !TEX TS-program = pdflatexmk \documentclass{beamer}  \usepackage{filecontents}  \begin{filecontents}{foo.bib} @misc{Fallick2004a, author = {Fallick, Bruce and Fleischman, Charles A.}, title = {{Employer-to-Employer Flows in the U.S. Labor Market: The Complete Picture of Gross Worker Flows}}, url = {http://www.federalreserve.gov/econresdata/researchdata/feds200434.html}, year = {2004} } \end{filecontents}  \usepackage[     backend=biber,     style=authoryear-comp,     natbib=true ]{biblatex} \bibliography{foo} \begin{document}  \begin{frame} \citet{Fallick2004a} \end{frame} \end{document}   Output:  Fallick and Fleischman, (2004)   This happens for all sorts of references, but only textcite and citet, not citep. I tried re-installing   sudo apt-get install texlive-full   to no avail.


Proving $\frac{\tan x+\sec x-1}{\tan x-\sec x+1}=\frac{1+\sin x}{\cos x}$

How do I myself start off this question:     Show that: $$\frac{\tan x+\sec x-1}{\tan x-\sec x+1}=\frac{1+\sin  x}{\cos x}$$   I have tried to express the LHS in terms of $\sin x$ and $\cos x$,  simplified the resulting expression, squared numerator and denominator  and simplified again, by this time I was lost in the forest…


Light Capture of Full-Frame Lens on Crop Body

Given two lenses: a full-frame lens and a crop lens, both at focal lengths necessary to capture the same frame on their respective systems and at the same f/stop. The physical size of the aperture opening (entrance pupil) has to be larger on the full-frame lens in order to deliver light across the entire larger sensor. When mounting that full-frame lens on a crop body, does that larger aperture opening have any effect on the light captured by the crop sensor?  For example, between a 36mm f/2.8 full-frame lens and a 24mm f/2.8 aps-c lens both mounted on the same aps-c body shooting the same scene at the same f/stop and ISO, does the full-frame lens allow capturing at a faster shutter speed? Or is all the extra light wasted because it falls outside the area covered by the crop sensor and both lenses will perform exactly the same?


Showing that $\lim_{n \rightarrow \infty}\frac{1^k+2^k+...+n^k}{n^{k+1}}=\frac{1}{k+1}$ using integral

How can I show (using upper-, lower-, Riemann-sums) that  $$\lim_{n \rightarrow \infty}\frac{1^k+2^k+...+n^k}{n^{k+1}}=\frac{1}{k+1}$$  with $k, n \in \mathbb{N}$?  The hint I received is that $\frac{x^{k+1}}{k+1}$ is a antiderivative of $x^k$ and $\int_a^bf(x)\mathrm{d}x=F(b)-F(a)$.


Is it possible that $A \approx B$ but $A/B \not \approx (e)$?

If we have two isomorphic groups $A$ and $B$, where $B\subset A$, is it possible that $A/B \not \approx (e)$? Obviously, $A$ and $B$ are infinite.


Is there a way to disable changing the background in GNOME?

I am setting up Ubuntu 12.04 with Gnome3 for a computer lab.  I don't want the users to be able to change the background of the computer.  Is there a way to prevent this? Or to revert the background back when the computer reboots?


A loop to select all active layers in a project

I am trying to export all active layers in a QGIS project to a specified folder, below is what I get atm  Outputdir='C:/Users/DN/Downloads/Test/'   layer = iface.activeLayer()  QgsVectorFileWriter.writeAsVectorFormat( layer, Outputdir + layer.name() + ".shp", "utf-8", layer.crs(), "ESRI Shapefile", 1)   It only works when I click on the layer that I want to export, I am wondering if it's possible to write a loop to loop through all active layers in the project and export them.


On a 2-d grid how many different move paths can be made that begin at $(0,0)$ and end at $(x,y)$ with $x\gt 0$,$y\gt 0$. Restriction : left,down and diagonally moves aren't allowed .


math conditionals using (if - else - fi) command

I saw these command when i searching sth. I wonder if we can increase numbers if conditions.  it's like if{0} = a, if{1}=b, if{2}=c, if{3}=d etc.  \newcommand{mycommand}[1]{ \if{#1 != 0} Some text, because it's nonzero \else Some other text, because it's zero \fi }  \mycommand{0} \mycommand{1}


Let $p\geq 5$ be a prime. Show that $\sum_{k=0}^{\frac {p-1}{2}} {\binom p k}3^k \equiv 2^p-1 \pmod {p^2}$

Let $p\geq 5$ be a prime. Show that  $$\sum_{k=0}^{\frac {p-1}{2}} {\binom p k}3^k \equiv 2^p-1 \pmod {p^2}$$  I couldn't prove that $p^2$ divides it.    My solution that $\text {mod } p$ works:  Since each term except ${\binom p 0} 3^0$ is divisible by $p$, we are left to show that $1+pk \equiv 2^p-1 \pmod p$. By Fermat's Little Theorem, $p\mid 2^p-2$, so the rest follows clearly.


What are the ways to make a dual power supply from a single voltage source?

I have a function generator IC  from EXAR. It's application circuits uses dual power supply +/-9 volts. How can I make such a 9-0-9 dual supply from a single voltage source like a battery or an adapter?


Indefinite Integration of real valued function

Why  $\int e^{-x^2} dx$ cannot be expressed in a closed form? Definite integration of this function is possible however I could not understand why indefinite Integration is not possible.


Generics in C#, using type of a variable as parameter

I have a generic method   bool DoesEntityExist<T>(Guid guid, ITransaction transaction) where T : IGloballyIdentifiable;   How do I use the method in the following way:  Type t = entity.GetType(); DoesEntityExist<t>(entityGuid, transaction);   I keep receiving the foollowing compile error:     The type or namespace name 't' could   not be found (are you missing a using   directive or an assembly reference?)   DoesEntityExist<MyType>(entityGuid, transaction);   works perfectly but I do not want to use an if directive to call the method with a separate type name every time.


I have newest Latitude 5490 with 8th gen i7 and 16gb of RAM.  The screen of my laptop is little bit yellowish in comparison to my previous laptop (Latitude 5480). I have updated all the drivers and tried all the conventional methods available on YouTube like :  -- setting different RGB in color management I have tried selecting sRGB2.1 profile. -- changing color setting in Intel Graphic control like contrast , hue options. -- turning on off , night mode.   but none worked , can anyone help me please its urgent.


"We are American" or "We are Americans"? The singular vs. the plural form?

Which expression is more idiomatic or correct:        We are American  We are Americans   Should I use American in the singular or in the plural form? And why?


Getting error using JMeter behind a proxy

I am new to JMeter and trying to run a test from behind a corporate proxy. I read on the same from apache site and followed the same process so as to run the test. However, i am still  unable to record a test from behind the proxy.      This message always appears after pressing on 'Start' recording:     After that, I have changed apache port to 8000 as in below and made it different      This time after pressing on start was this message


A family having 4 children has 3 girl children. What is the probability that their 4th child is a son?

This is similar to the .  So there are five cases, the gender of the children written according to their age,   GGGG GGGB GGBG GBGG BGGG   So the probability should be $\frac{4}{5}$. But the given answer is $\frac{3}{4}$.  Am I missing something?


C++: how to get fprintf results as a std::string w/o sprintf

I am working with an open-source UNIX tool that is implemented in C++, and I need to change some code to get it to do what I want. I would like to make the smallest possible change in hopes of getting my patch accepted upstream. Solutions that are implementable in standard C++ and do not create more external dependencies are preferred.  Here is my problem. I have a C++ class -- let's call it "A" -- that currently uses fprintf() to print its heavily formatted data structures to a file pointer. In its print function, it also recursively calls the identically defined print functions of several member classes ("B" is an example). There is another class C that has a member std::string "foo" that needs to be set to the print() results of an instance of A. Think of it as a to_str() member function for A.  In pseudocode:  class A { public:   ...    void print(FILE* f);   B b;    ...   };  ...  void A::print(FILE *f) {   std::string s = "stuff";   fprintf(f, "some %s", s);   b.print(f); }  class C {   ...   std::string foo;   bool set_foo(std::str);   ... }  ...  A a = new A(); C c = new C();  ...  // wish i knew how to write A's to_str() c.set_foo(a.to_str());   I should mention that C is fairly stable, but A and B (and the rest of A's dependents) are in a state of flux, so the less code changes necessary the better. The current print(FILE* F) interface also needs to be preserved. I have considered several approaches to implementing A::to_str(), each with advantages and disadvantages:   Change the calls to fprintf() to sprintf()   I wouldn't have to rewrite any format strings print() could be reimplemented as: fprint(f, this.to_str()); But I would need to manually allocate char[]s, merge a lot of c strings , and finally convert the character array to a std::string  Try to catch the results of a.print() in a string stream   I would have to convert all of the format strings to << output format. There are hundreds of fprintf()s to convert :-{ print() would have to be rewritten because there is no standard way that I know of to create an output stream from a UNIX file handle (though ).  Use Boost's string    More external dependencies. Yuck. Format's syntax is different enough from printf() to be annoying:    printf(format_str, args) -> cout << boost::format(format_str) % arg1 % arg2 % etc Use Qt's    A different external dependency.    So, have I exhausted all possible options? If so, which do you think is my best bet? If not, what have I overlooked?  Thanks.


Example of a function such that $\varphi\left(\frac{x+y}{2}\right)\leq \frac{\varphi(x)+\varphi(y)}{2}$ but $\varphi$ is not convex

Rudin's Real and Complex Analysis Chapter 3 Exercise 4 is:  Assume that $\varphi$ is a continuous real function on $(a,b)$ s.t. $$\varphi\left(\frac{x+y}{2}\right)\leq \frac{\varphi(x)+\varphi(y)}{2}$$ for all $x,y\in(a,b)$. Prove that $\varphi$ is convex.   The conclusion does not follow if continuity is omitted from the hypotheses.  My question is, is there some way to explicitly construct a counterexample such that  $\varphi\left(\frac{x+y}{2}\right)\leq \frac{\varphi(x)+\varphi(y)}{2}$ for all $x,y\in(a,b)$, but $\varphi$ is not convex?


imagemagick - print 2 pdf pages on one A4 sheet

For university, i like to print out my professors scripts. They usually use beamer- or powerpoint presentations throughout the lectures.  My goal is to have two presentation sheets on one A4 page.  With Adobe Acrobat, this seems to be not so big of a deal but since i switched to Linux completely, i would like to find a solution that works fine without having to use acroread, pdfstudio or another closed source program.  I tried printing with evince, okular and several other applications (which all feature multi-page-printing-options), but the results were often not rotated incorrectly or where scaled much too small. Not having a print-preview doesn't make things easier.  So my newest idea would be to create a new .pdf with imagemagick and have two sheets on one page, one above the other so that i can print it out as big as possible.  Imagemagick should be capable of doing that, but i don't know the right commands!  If there's anyone knowing other/better solutions to the problem, you're of course welcome to share!


Is it better to save bitmaps to Sqlite Databse or Files handling its paths in Database ? - Android

Is Converting bitmaps to byte[] and saving it to Database better performance and management or saving the bitmaps to Files and handling the paths in the Database ?  By better I mean as performance and management.  I have started a new application and i want to know if anybody has faced such a problem, and which solution is preferable for Android apps ?  Note: I am using Greendao as ORM.


I just suggested to regard the  tag as a synonym for the  tag (on WordPress Development SE), because in practice these terms are interchangable. Now I need 4 votes to support it (or 2 downvotes to kill it).  I thought somewhere in the interface (for instance under 'reviews') there would be a prompt that this vote is open. I can't find anything. Am I overlooking something? Or am I supposed to draw attention to it myself by telling everyone that the vote is ?


Convergence to function that is not measurable

Suppose ($X,\cal M, \mu$) is not complete. Show that there is a sequence {$f_n$} of measurable functions on $X$ that converges pointwise a.e. on $X$ to a function $f$ that is not measurable.


While studying, I came upon the problem "Two corridors of widths $a$ and $b$ intersect at right angle. What is the length of the longest pipe that can be carried across the two corridors, touching the corner of the wall where the corridors meet?"  The explanation is not detailed, but the answer is shown as  $(a^{2/3} + b^{2/3})^{3/2}$. I have attempted the problem using trigonometry and derivatives, but got stuck early in. Could someone help with this problem?


Does the big bang violate the conservation of energy?

It is a fact that a thing is existing now because it had already been created. So why don't we take this to account to redefine law of conservation of energy.


why is the definition of the determinant so weird?

I learned linear algebra from books of Friedberg, Gilbert & Strang, Anton etc. by myself. I dare say, that I learned all that stuff eagerly.  Studying by myself, I could not intuitively understand the definition of the determinant (its even – odd manner). I could only memorize the definition, and then use it (or try to use it) to solve some related readers' homework problems or other exercises.  As you know, the purpose of a determinant is literally to determine whether a given system of equations has a unique solution or not.  In other words, the "determinant" will determine whether the row vectors (and equivalently, column vectors) of a given square matrix are independent or not.  If those are mutually independent, then they can geometrically represent an $n$-dimensional quantity (for example, area in 2 dimensions or volume in 3D). If not, some of them are dependent, so they cannot form the $n$-dimensional quantity, and correspondingly the determinant is zero.  A multiple of any row can be added to another, this kind of row elementary operation does not change the determinant value. The picture below illustrates an intuitive understanding of that, too.    Writing the sides of the parallelogram as rows or columns of a square matrix, this transformation transforms it to another with the same value of the determinant.  It can be transformed to Gauss–Jordan form, in this case, each of the row / column vectors are orthogonal because their inner products are all zero. (I tried this with the Gram–Schmidt process; however, intuitively, the result is surely the same.)  Those vectors are orthogonal so it is very clear that just multiplication of the diagonal terms should give directly the aforementioned $n$-dimensional quantity, so that's the determinant in such case.  I understand the determinant in this manner, and it makes sense intuitively.  However the textbook definition mentioned above (defined in the "even–odd" manner) looks very weird to me.  What is the motivation of that definition? And can it be generally derived from my intuition about the $n$-dimensional quantities? I succeeded in doing so for the $2\times2$ and $3\times3$ cases, but I cannot see any generalized relation.  It seems to me that the definition of the determinant comes down magically, without enough logic.  I was wondering if you could help me.  Thank you in advance.


I recently had this problem upgrading Google Chrome in 18.04. I noticed my version had was stuck at 70.x, even though the most stable version was 77.x. I tried re-adding the PPA a bunch of times, but that just caused more errors, because it was now "configured multiple times." This obscured the one crucial error I missed, whenever I ran sudo apt-get update:  E: Repository 'http://dl.google.com/linux/chrome/deb stable Release' changed its 'Origin' value from 'Google, Inc.' to 'Google LLC' N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.


When writing the quotient with respect to, say, a group action, the notation is X/G, and in latex, this compiles to look almost the same as X/G. The problems come when writing the quotient w.r.t. a left action, in which case it is G\X. I thought for the longest time that the author(s) were writing some kind of set difference and that either I or them had confused things.  Ideally I would like X to be slightly elevated above the slash, and G to be slightly lowered below, but keeping the distances in check (nothing like X  /  G just for the sake of elevating/lowering).  Does anyone know of any good tricks or methods to achieve this? Thanks in advance.


Compute the unit digit of ${{43}^{43}}^{43}$

I am trying to find the unit digit of ${{43}^{43}}^{43}$. Normally I would try to break up the exponent to make it easier though 43 is prime so I can't do that. So instead I first considered $43^{43}$ and tried finding a pattern for the unit digits by looking at the first few values:  $43^0=1$  $43^1=43$  $43^2=1849$  $43^3=79507$  $43^4=3418801$  $43^5=147008443$  ...  I then noticed that they repeated every 4 values with a unit digit pattern of {1, 3, 9, 7}.  This is where I am stuck, for a few reasons:   I know I need to prove that this unit digit pattern continues but I'm not quite sure how to do this. I know the unit digit is 1, 3, 7 or 9, but how do I know which one it is? After finding the unit digit of $43^{43}$, how do I then use this to find the unit digit of ${{43}^{43}}^{43}$? Lets say $x$ is the unit digit of $43^{43}$ so would I then need to find the unit digit of $43^x$?   Can someone help me with where I am confused, let me know if the proccess I wrote is incorrect, or explain an easier approach to this problem?


Add keys to table (with picture and code)

As you see in the red part of the picture, I would like to add keys to explain what the brackets stand for. I just added this with paint, but is there a way to do this in tex? Also, are there nicer semantics for explaining such keys, e.g. using a : or spelling brackets as brackets?    \begin{table}[!ht]  \centering \setlength{\tabcolsep}{3pt}     \begin{tabular}{ | l | c c |}   \hline  & Column1 & Column2 \\ \hline     X   & A (B)     & F                 \\          y           & C     & F [D]     \\ \hline         \end{tabular}             \caption{Some table}         \label{tab:table} \end{table}


I have heard that temperature in space is very cold or near to -200 degree celsius in the side opposite to sun.How is this possible?If there are no or negligible amount of molecules in space,how can the term temperature be defined.I have been taught that temperature is just the vibration of molecules.If there are no molecules in space,is it plausible to say that space is neither hot nor cold,when you are exposed to space you feel neither hot nor cold?Please help me in simplest language.


I'm hoping to get an expert opinion on the summation: $$\sum_{n=1}^{\infty} (-x)^n$$ I've attempted to find a closed-form of this expression as follows. $$\sum_{n=1}^{\infty} (-x)^n=S_n$$ $$S_n=-x+x^2+-x^3+x^4...$$ $$-xS_n=x^2+-x^3+x^4+-x^5...$$ $$S_n(1+x)=-x$$ $$S_n=\sum_{n=1}^{\infty} (-x)^n=\frac{-x}{x+1}$$ I'm curious whether there is a more rigorous way to derive this (involving more complex maths), or maybe to contradict my answer.  Another interesting thing is that the series $$\sum_{n=1}^{\infty} (x)^n=\frac{x}{1-x}$$ and when you plot both on a  both they seem like rotations on one another ... but I don't know what do you guys think. Your input will be greatly appreciated.


Length of tube used in barometer is less than 76cm

In barometer the height of mercury in the inverted tube above the open surface level will be 76cm, if mercury is used. Now what if we take a tube filled with mercury but of length less than 76cm and invert it into the tub? (Experiment being done at the sea level)


Splitting a layer containing multiple polygons into multiple layers each containing one polygon

So firstly, I used the buffer tool in Qgis3 to create (twenty) polygons with a certain width from (twenty) points. This lead to the situation below, where o1 and o2 are two original points and 1 and 2 are the resulting polygons. Now, I want points (like A in the picture below) from another point layer to have an attribute stating in which polygon they are. However, in overlapping situations I would like to see both polygon id's to be added, which does not happen when using the 'add polygon attribute to point' (which only adds one polygon id).     To resolve this, I need to have a different layer for each polygon, so I can use dummy variables. How do I create a different layer for each polygon? I have heard of the Split Polygon plug-in in Qgis2, but I am working in Qgis3. To clarify, I would like for both polygons to be kept intact, as I've seen others wanting the overlapping section belonging to only one of the polygons.


How can I specify the data value of an item in a /testfor command?

I have used the /testfor command a lot but I ran into a problem I thought you could help with.  This is my command:  /testfor @p[r=3] {Inventory:[{id:"minecraft:log",Count:64b}]}   In this command I want it to test for log number 2, which is birch wood, but the thing is I don't know how to insert that.  I want it so it detects if the player has a 64 stack of birch wood.


Stinky air when I turn on the bathroom faucet...what is causing it?

The sink is pretty close to the toilet...about 2 feet away. I've noticed that often times when I turn on the faucet (either hot or cold), I smell a sewer kind of smell.  What could be causing it?  I thought traps were suppose to prevent this exact thing.


Is it possible to merge two YouTube channels?

I heard that it is now possible to merge two YouTube channels, using Google+ or something like that. If that's true then:   How would I do it? Will both accounts become only one? Will the views and the subscribers be merged, too?


Calling a method unspecified at built-time

Note:  already exists, albeit being for C#.  Let's suppose my code looks like the following:  class SomeClass:      def __init__(self):          pass      def do(self):         print("a")  class SomeOtherClass:      def __init__(self):          pass      def do(self):         print("b")  class B:      def __init__(self):          self.SomeClass = SomeClass()            self.SomeOtherClass = SomeOtherClass()  def __main__():     myclass = B()     desired_class = str(input("The method of which class do you want to execute? "))     myclass.desired_class.do()    I will not know at built-time what method of SomeClass will be called. If-then-else is also not very neat if you have 200 methods and no just 2 to choose from.  How is this done most efficiently in python?  Note: The method will always be an existing method of SomeClass.


Filter out some WiFi networks from list of all available WiFi networks

Is it possible to filter out some WiFi networks from list of all available WiFi networks when I drop down the WiFi list from the menu bar in macOS?  My condo complex has a lot of networks and it clutters the list. I only ever need 3 -- my home  WiFi, my work WiFi, my iPhone WiFi.


Unable to mount USB device after creating "gpt" label with `parted`

I am following the instructions to , but after the completing the step to , I am no longer able to mount the USB.  I first formatted my USB device using the Disks utility tool, with format FAT32.  Then, I unmounted my device:   sudo umount /dev/sdb   and then I used this command:  sudo parted /dev/sdb mklabel gpt   Once the command completed, I got a message about how I might need to update /etc/fstab, but I can't figure out what to put in that file.  I have tried to mount my device where I previously found it (/media/$USER/) but I get this error message when I attempt to do so:  mount: /media/$USER: wrong fs type, bad option, bad superblock on /dev/sdb, missing codepage or helper program, or other error.   I need to be able to mount the device again so that I can copy the .iso using p7zip.  Here is output from a parted --list command:  Model: SanDisk Cruzer Glide (scsi) Disk /dev/sdb: 8004MB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags:


I´m trying to model a race track using a bezier curve, but, when I add modifiers -> array -> curve I get this :    What should I check for to get the mesh following the curve correctly ? Thankyou


Relativistic time dilation on Mars compared to Earth?

What is the time dilation in Mars, compared to earth? Can we accurately calculate it? What information is needed to do these calculations?


Why there's a whirl when you drain the bathtub?

At first I thought it's because of Coriolis, but then someone told me that at the bathtub scale that's not the predominant force in this phenomenon.


"Within", "in", "during", or "over" ? I will call him ---------- the next break

Consider you are in a meeting. The meeting is going to continue for the next several hours. Therefore, some breaks have been devised in order to let people refresh themselves.  Now consider a brief conversation between two guys sitting near each others:     A: Did you notify C that you would be here until 9:00 ?      B: I will call him ........... the next break.   Which one of the prepositions listed below is the best choice?   within during in over     My interpretation:  Using , I can easily rule out "over" and "within" although I have no idea why they are wrong.  Now, the question is what is the difference between "in" and "during" in that context?


How to format a very long set description?

How can I format the following very long set description? Ideally, it should split into two lines.  The general structure of the set description is:  \{f(x) :| x \in S |: P(x)\}  This is a non-standard set notation, which means: the set obtained by running through all the x's in the set S, choosing only those x's that satisfy the predicate P, and then applying the function f to the selected x's and collecting the results into a set.  Additionally, the left part of the set below is of the form a \mapsto b (b being the cases structure). This is simply syntactic sugar for the ordered pair (a,b)  \documentclass{article} \usepackage{amsmath} \begin{document} $$ \left\{\ddot{\mathbf{A}}_{d(\Omega;\dot{E})}(T.d)[i] \mapsto f_{d(\Omega;\dot{E})}^T(l,u)[i]\ :\!|\ i \in [1..T.d.n]\ |\!:\ F_{d(\Omega;\dot{E})}^T[i-1] \leq u \wedge F_{d(\Omega;\dot{E})}^T[i] \geq l\right\} $$ \end{document}   Here the typeset result is seen in context. It extends into the right margin almost all the way to the right edge of the page.      I've tried using \split and \multlined as per egreg's suggestion in a comment below.  SPLIT  \begin{split} \left\{\ddot{\mathbf{A}}_{d(\Omega;\dot{E})}(T.d)[i] \mapsto f_{d(\Omega;\dot{E})}^T(l,u)[i]\ &:\!|\ i \in [1..T.d.n]\\ &|\!:\ F_{d(\Omega;\dot{E})}^T[i-1] \leq u \wedge F_{d(\Omega;\dot{E})}^T[i] \geq l\right\} \end{split}   It produces the following error message:  Extra }, or forgotten \right.   MULTLINED  \begin{multlined}[t] \left\{\ddot{\mathbf{A}}_{d(\Omega;\dot{E})}(T.d)[i] \mapsto f_{d(\Omega;\dot{E})}^T(l,u)[i]\ :\!|\ i \in [1..T.d.n]\\ |\!:\ F_{d(\Omega;\dot{E})}^T[i-1] \leq u \wedge F_{d(\Omega;\dot{E})}^T[i] \geq l\right\} \end{multlined}   It produces the following error message:   Missing \right. inserted.


How to fsck root file system before boot or on reboot

Today I went through my desktop stations running Linux Mint 17.3 Cinnamon and did a file system check of root partitions with Ext4 file systems as follows:  # fsck.ext4 -fn /dev/sdb2   The problem is that on all of the computers I see something similar to this one:  e2fsck 1.42.9 (4-Feb-2014) Warning!  /dev/sdb2 is mounted. Warning: skipping journal recovery because doing a read-only filesystem check. Pass 1: Checking inodes, blocks, and sizes Deleted inode 524292 has zero dtime.  Fix? no  Inodes that were part of a corrupted orphan linked list found.  Fix? no  Inode 524293 was part of the orphaned inode list.  IGNORED. Inode 524294 was part of the orphaned inode list.  IGNORED. Inode 524299 was part of the orphaned inode list.  IGNORED. Inode 524300 was part of the orphaned inode list.  IGNORED. Inode 524301 was part of the orphaned inode list.  IGNORED. Inode 524302 was part of the orphaned inode list.  IGNORED. Inode 524310 was part of the orphaned inode list.  IGNORED. Inode 524321 was part of the orphaned inode list.  IGNORED. Inode 524322 was part of the orphaned inode list.  IGNORED. Inode 524325 was part of the orphaned inode list.  IGNORED. Inode 2492565 was part of the orphaned inode list.  IGNORED. Inode 2622677 was part of the orphaned inode list.  IGNORED. Inode 2622678 was part of the orphaned inode list.  IGNORED. Inode 2883748 was part of the orphaned inode list.  IGNORED. Inode 2884069 was part of the orphaned inode list.  IGNORED. Inode 2885175 was part of the orphaned inode list.  IGNORED. Pass 2: Checking directory structure Entry 'Default_keyring.keyring' in /home/vlastimil/.local/share/keyrings (2495478) has deleted/unused inode 2498649.  Clear? no  Pass 3: Checking directory connectivity Pass 4: Checking reference counts Unattached inode 2491790 Connect to /lost+found? no  Pass 5: Checking group summary information Block bitmap differences:  -(34281--34303) -11650577 -(11650579--11650580) -11650591 -(11650594--11650595) -(13270059--13270073) -(13272582--13272583) -(20542474--20542475) +(26022912--26023347) -(26029568--26030003) Fix? no  Free blocks count wrong (14476802, counted=14476694). Fix? no  Inode bitmap differences:  -(524292--524294) -(524299--524302) -524310 -(524321--524322) -524325 +2491790 -2492565 -2498649 -(2622677--2622678) -2883748 -2884069 -2885175 Fix? no  Free inodes count wrong (7371936, counted=7371916). Fix? no   /dev/sdb2: ********** WARNING: Filesystem still has errors **********  /dev/sdb2: 443232/7815168 files (0.1% non-contiguous), 16757502/31234304 blocks   What I have tried:  # touch /forcefsck   This results in a 2-3 seconds lasting check on startup. Obviously not repairing anything.  That is most probably because my root file system is somehow clean.  # fsck.ext4 -n /dev/sdb2  e2fsck 1.42.9 (4-Feb-2014) Warning!  /dev/sdb2 is mounted. Warning: skipping journal recovery because doing a read-only filesystem check. /dev/sdb2: clean, 443232/7815168 files, 16757502/31234304 blocks   As I can't find almost anything for file system check on boot other than sudo touch /forcefsck, I tried these steps:   echo u > /proc/sysrq-trigger umount /dev/sdb2 fsck -fy /dev/sdb2   This did show up that it had it repaired, to make sure I ran the fsck again without errors. BUT, they are back once I reboot. I am confused right now. Please don't instruct like "create a flash drive and boot from it and ...". I want a solution on reboot or before reboot without booting from some flash drives. Thank you.


Possible ways to crack simple hand ciphers?

We had a quiz in class today where we had to break the ciphertext with the key given, but not the algorithm. Suffice to say that I wasn't able to decrypt it within the allotted time of 12 mins and will probably get a 0% score on the quiz.  So, I was just wondering if there are some kind of standard techniques that are followed when decrypting a simple substitution ciphertext.


Checking if the table has rows results in Null Pointer Exception in SQLiite Android

I want to check if the table has rows and if it contains, then I want to delete it. Below is my code for checking if table has rows in it.       boolean empty = true;     Cursor cursor = db.rawQuery("SELECT count(*) FROM TABLE_NAME",null);     cursor.moveToFirst();     if (cursor.getInt(0) > 0)     {         empty = false;     }     else     {         empty= true;     }     return  empty;    I even tried checking with below code,      boolean empty = true;     Cursor cur = db.rawQuery("SELECT COUNT(*) FROM TABLE_NAME", null);     if (cur != null && cur.moveToFirst()) {         empty = (cur.getInt (0) == 0);     }     cur.close();      return empty;       Both of the above code, throws NullPointerException in line  ("SELECT COUNT(*) FROM TABLE_NAME", null);  Any help would be great !! Thanks


Idiomatic meaning or allusion of "twirl a mustache"

“I have a mustache but I have  not started to twirl it yet” What is the implication of having a mustache, but not yet twirling it?


Ubuntu 20.04: Grub Menu Not Visible after Update from 19.10

I am currently running Ubuntu 20.04 after updating from Ubuntu 19.10. After updating and restarting the computer, the screen is blank but I am still able to select the options from the menu so I know it is there. I have tried reinstalling grub2 and changing the grub theme but the problem still persists. Any other possible solution that would make the grub menu visible again?


When writing a proof, why do we want to assume a different but equivalent condition given in the proposition?

In the proof for the inductive step, we start by assuming $k \ge 10$. But along the way, the author mentions $k \ge 1$ and $k \ge 7$ to justify the inequality.  Why do we bother to do this instead of just sticking with $k \ge 10$?


I have scoured around, reading posts on Cross Validated () and also looking at references including Dobson and McCullagh and Nelder, e.g.  so I am aware that this topic is well trodden. Nevertheless, I am trying to articulate and formalize my understanding of GLM and while several posts have helped me with that, I am conscious of gaps and the possibility of an unsound foundation of my understanding.   In simple linear regression we have some set of observations $(x_i, y_i)$ pairs and treat $y_i$ as a realization of a random variable, $Y_i$, distributed as $Y_i \sim N(\mu_i, \sigma^2)$. The means ($\mu_i$) depend on the predictor but the variance is constant. We model $\mu_i = \beta_0 + (\beta_1 \times x_i)$ (or matrix equivalent ) which I believe is the same as saying $Y_i = \mu_i + \epsilon_i$ with $\epsilon_i \sim N(0,\sigma^2)$. I am not sure but I think a correct way to state $\mu$ is $\mu_i = E[Y_i|X=x]$. Can someone confirm that?  Anyway, we might transform the response to achieve linearity (maybe taking logs) and in that case we are modelling $log(Y_i) = \alpha_0 + (\alpha_1 \times x_i) + \epsilon_i$ where $\epsilon_i$ now is assumed to have a log normal distribution.   We generalize by decomposing the model into:   A structural component ($\beta_0 + (\beta_1 \times x_i)$) A link g(.) A response distribution (or random component) (member of the exponential family - Guassian, bin,gamma etc)   Let's say that the observations are assumed to come from a distribution in the exponential family and to keep things simple assume that it is the Gaussian distribution. Again, the expected value comes out as $E[Y_i|X=x] = \mu_i$, but does so from the first derivative of the b(theta) term in the exponential family form () (pg 29). In the case where we assume a binomial distribution, the expected value comes out at np but it still comes from the first derivative of the b(theta) term when the distribution is expressed in the exponential family form. Note, I don't fully appreciate or understand the derivation of the mean or variance at this stage, perhaps someone could provide a layman's explanation?  Instead of modelling the mean as was done for simple linear regression, we now model a transformation of the mean so instead of saying $\mu_i = \beta_0 + (\beta_1 \times x_i)$ we are saying $g(\mu_i) = \eta_i = \beta_0 + (\beta_1 \times x_i)$ where g is some link function (invertible and differentiable). I think this is a key (yet still somewhat confusing to me) distinction between SLR and GLM. In SLR we transform the response ($y_i$) and model that, in GLM we transform the expected value ($\mu_i$ in the case of the Gaussian example) and model that. Another way of saying it is that in the SLR case we model $E[g(Y_i|X=x)] = \beta_0 + (\beta_1 \times x_i)$ but in the GLM world we are modelling $\eta_i = g[E(Y_i|X=x)] = \beta_0 + (\beta_1 \times x_i)$.   My question is around verifying my understanding and statement of the essence of the foundations of GLM and the differences between GLM and the traditional linear model. Thanks.


How can I boot to linux command line from GRUB?

I botched a gnome install on my virtual box and now when it boots it just hangs up at a black screen.  I wante to get back into a command line and uninstall/reinstall gnome...


How to Calculate the time of Charging and Discharging of battery?

How do I calculate the approximated time for the Charging and Discharging of the battery? Is there any equation available for the purpose? If yes, then please provide me.


Made this custom taxonomy that'll control layout on single posts, basically I want to add two options, Layout 1 and Layout 2.  // Register Custom Taxonomy function custom_taxonomy() {      $labels = array(         'name'                       => _x( 'Layout', 'Taxonomy General Name', 'text_domain' ),         'singular_name'              => _x( 'Layout', 'Taxonomy Singular Name', 'text_domain' ),         'menu_name'                  => __( 'Taxonomy', 'text_domain' ),         'all_items'                  => __( 'All Items', 'text_domain' ),         'parent_item'                => __( 'Parent Item', 'text_domain' ),         'parent_item_colon'          => __( 'Parent Item:', 'text_domain' ),         'new_item_name'              => __( 'New Item Name', 'text_domain' ),         'add_new_item'               => __( 'Add New Item', 'text_domain' ),         'edit_item'                  => __( 'Edit Item', 'text_domain' ),         'update_item'                => __( 'Update Item', 'text_domain' ),         'separate_items_with_commas' => __( 'Separate items with commas', 'text_domain' ),         'search_items'               => __( 'Search Items', 'text_domain' ),         'add_or_remove_items'        => __( 'Add or remove items', 'text_domain' ),         'choose_from_most_used'      => __( 'Choose from the most used items', 'text_domain' ),         'not_found'                  => __( 'Not Found', 'text_domain' ),     );     $capabilities = array(         'manage_terms' => 'foobar',         'edit_terms'   => 'foobar',         'delete_terms' => 'foobar',         'assign_terms' => 'foobar'      );     $args = array(         'labels'                     => $labels,         'hierarchical'               => true,         'public'                     => true,         'show_ui'                    => true,         'show_admin_column'          => false,         'show_in_nav_menus'          => false,         'show_tagcloud'              => false,         'capabilities'               => $capabilities,     );     register_taxonomy( 'Layout', array( 'post' ), $args );  }  // Hook into the 'init' action add_action( 'init', 'custom_taxonomy', 0 );   Capabilities are set to invalid values to stop terms from being edited, but I can't get wp_insert_term working.  Adding two terms to my custom taxonomy can't be so hard, right?  Using this to insert a term doesn't work, although if I changed my custom taxonomy name to 'category', ie WP default it works just fine. What gives?  function example_insert_category() {     $parent_term = term_exists( 'layout' ); // array is returned if taxonomy is given $parent_term_id = $parent_term['term_id']; // get numeric term id     wp_insert_term(         'Example Category',         'layout',         array(           'description' => 'This is an example category created with wp_insert_term.',           'slug'        => 'example-category'         )     ); } add_action( 'after_setup_theme', 'example_insert_category' );


I have an image with two points, aligned something like this:  |----------------| |                | |    .           | |                | |          .     | |                | |----------------|   I have both X, Y coordinates for both points and I need to rotate the image X degrees so it looks like this instead:  |----------------| |                | |                | |    .     .     | |                | |                | |----------------|   Basically so they align next to eachother, what's the math for this? (A code example in C# would be even better but not required)


Since few days: Trouble with mhchem using \listoftables or \listoffigures

I'm having trouble with the mhchem package. When I have a figure with a separate TOC entry that involves a \ce{} environment, I get error messages saying that the control sequence \aaaa is not defined. Few days ago another one have had the same problems, solved by reinstalling MiKTeX, but this does not work for me. At home, with an older version of the packages the MWE works, but in the new version it does not. Here's my MWE:  \documentclass{scrreprt} \usepackage[T1]{fontenc}             \usepackage[version=3]{mhchem}   \begin{document} \tableofcontents \listoffigures \listoftables \begin{figure}[htbp] \centering test \caption[\ce{SiO2}]{\ce{SiO2}}     \label{fig:test} \end{figure} \end{document}   Thanks for any help! The same Version of the document was running without any problems a few days ago!


Find current display screen dimensions where my WPF application is running

I am able to find all the screens dimensions using below code but how can I find which screen my application is about to run? public partial class MainWindow : Window {     public MainWindow()     {        int length = System.Windows.Forms.Screen.AllScreens.Length;     } }


I've always thought that the absolute maximum ratings on a part are the limits that thou shalt not violate.  Period.  End of story.  However, another engineer is making the case that it's okay to exceed the absolute max rating for the input voltage on a microcontroller I/O pin.  Specifically, he wants to apply 5v, current limited to 30uA, to a micro with an absolute max voltage of 3.8v (Vdd + 0.3V <= 3.9V).  The argument being the clamp diodes will take care of the excess voltage.  I couldn't find anything in the datasheet about the I/O hardware on the micro.  When is it okay to exceed the absolute maximum rating on a part?


I have polje[i]=rand()%30+1; for random between 1-30, but how can I make it so it's between 10 and 30?


Why do pdf/image exports fail with OpenLayers Bing layers?

When I try to export a print composition it generates a 0kb file. Is not possible to open this file.  It happened the same with export as image option.  The print composition model is coming from a .qpt file created with QGIS 1.8.  The problem is not in the print composition created with QGIS 1.8. I have the same problem starting with a new composition. The print works regularly if I hide the two maps in the print composition. I can print all the elements that are not maps.  The maps are coming from OpenLayers plugin/bing  What shoud I check to solve it?


I have a UI application in which I consume a WCF service like this  public MainWindow() {     ....     mServiceClient = new ServiceClient("EndPointTCP"); }   Should I create the client as a member of class and close the client along with exit of my application or Should I create a new client whenever its required in a method and close there itself.


There was a sword and shield by the lion. There were a sword and a shield by the lion. Which of the two is correct? Both sound awkward.


I want to create my own Ubuntu distribution. I used cubic or a while, but i am not familiarized with it. I want to create my Ubuntu distribution in another way. For example create a restore point or a backup, or a sfs file of installed Ubuntu on my computer, and boot it on grub or any other bootloader. If not, by using Ubuntu Server or Ubuntu Minimal. Is it possible? Thanks!


I would like to create some tables (including users table and products table) inside MySql Database with those index for each tables:   Private Index (uses int), for relational table purpose only Public Index (uses 32 chars filled with UUID), will be stored at URL and visible to users   The question is should I use public index only or keep those configuration? Please for the advice, thank you!


Reset admin password in Cent OS 7 from grub

I just recently installed cent os 7 and I forgot the admin user password so now I couldnt log in and locked out.  I entered the grub boot menu and tried to change the password using password command but didnt work out.  Am I completely locked out? How to reset the admin password from grub?


What is the importance of torque direction?

I understand the right-hand rule and direction of the force on an arm, but what exactly is this 'direction' that results from the cross product of the vectors $T = r \times F$? On paper, what is this torque 'direction' that comes in or out of a page? What does the torque 'direction' do on a door that is being opened?


Should I use vector logo in SVG format in website? To make responsive logo in responsive website. Need suggestions, which format will be best?


How to check if a dice set is correctly weighted?

So let me give you a bit of backstory, I went to a friend's place to play DnD and I decided to put my solar powered dice to charge on top of my friend's standing lamp with the plastic box practically touching the lightbulb. The box , the d10 and the d12 were ruined but the rest seemd in good condition (and even still glowed).  The attached image is of the surviving dice, they seem to be fine on the outside, no bumps or warps apparent. The damaged die I left with my friend as a souvenir.  My concern now is that the remaining dice might have weight issues since they were still really hot when we salvaged them. Is there any reliable way to check if their weight distribution is still fine?


Show that $\sum_{n=1}^{\infty}(n^{3}\sin\left(\frac{1}{n}\right)-n^{2}+\frac{1}{6})$ converges

Let $t\in \mathbb R$. Prove that $\displaystyle{\sum_{n=1}^{\infty}n^{3}\sin\left(\frac{1}{n}\right)-n^{2}+t}$ converges iff $t=\frac{1}{6}$.  While the $(\Rightarrow)$ direction was fairly easy (as $a_n$ should converge to $0$, forcing $t=\frac{1}{6}$), i'm facing some hard time trying to prove the second direction, that is $\displaystyle{\sum_{n=1}^{\infty}(n^{3}\sin\left(\frac{1}{n}\right)-n^{2}+\frac{1}{6})}$ converges. I did notice that $a_n=a_{-n}$ and tried to write this series as a Leibnitz series, but had no luck since the sequence doesn't decrease. I also tried to prove absolute convergence but then again, no luck. Thanks.


A finite sum involving the binomial coefficients and the harmonic numbers

Wikipedia has a proof of the identity $$ H_{n} =\sum_{k=1}^{n} (-1)^{k-1} \binom{n}{k} \frac{1}{k}$$    Curiously, there is also the identity  $$ \frac{1}{n} = \sum_{k=1}^{n} (-1)^{k-1} \binom{n}{k} H_{k} $$  Can the second identity be derived from the first one?


How Stop Refreshing the VF page in SF1 mobile app

Embedded the VF page on a layout and is getting refreshed everytime while touching on it. How can i stop refreshing it. its happening only in SF1 mobile. working fine in Desktop.


Finding the associated matrix of a linear operator

Let $V$ be a complex vector space of dimension $n$ with a scalar product, and let $u$ be an unitary vector in $V$. Let $H_u: V \to V$ be defined as  $$H_u(v) = v - 2 \langle v,u \rangle u$$  for all $v \in V$. I need to find the minimal polynomial and the characteristic polynomial of this linear operator, but the only way I know to find the charactestic polynomial is using the associated matrix of the operator.  I don't know how to find this matrix because I don't know how to deal with the scalar product. Is there some other way to find the characteristic polynomial? If not, how can I find the associated matrix of this linear operator?  Thanks in advance.


Google doesn't seem to update the description or title of my homepage

Before we launched our website, we had set up a "coming soon" page and google picked up the title and description from its contents. So the description in the search results said:     Coming soon! Visit example.org for updates.   It's been a few weeks since we launched our website. We've even created a sitemap and submitted it to Google. In Google Search Console, the pages have been crawled and all the pages are appearing as expected on Google, EXCEPT the homepage which is still not updated! The title and description of the homepage in google search results still says "coming soon.".***  I checked on bing too, but it appears to be fine there.  All other pages seem to be indexed fine on Google. I don't even have any crawl errors in my reports. So what seems to be the problem? I've already waited for 2 weeks.


Create a *.DLL file in run-time and save to a specified location in C#

In my program I need to create a dll file in run-time and need to save it in a specific file location. when i create this dll file in run-time i need to pass a parameter and that parameter will be stored inside dll file and automatically it will copy into specific location. How can i do it with c#. need some guide. thanks.


Can someone please explain to me how I can show the following operator is compact? $$ Af(x)=\int_0^xf(t)dt$$ where $A:L_2[0,1]\rightarrow L_2[0,1]$.  There are two definitions of compactness that I've encountered:  Def1. An operator $L$ is compact if for a bounded sequence $\{ x_n\}$, there exists a convergent subsequence $\{ x_{n_k}\}_k$.  Def2. An operator $L$ is compact if it's continuous and maps a bounded set to a sequentially compact set.  What is the easier/standard method to prove compactness for integral operators?  I also know that "If $L$ is a bounded linear operator on a separable Hilbert space, with orthonormal basis $\{e_n\}$, and $\sum_n\| L e_n\|^2<\infty$, then $L$ is compact. "


How can relativistic effects be the cause of magnetic forces when the normal speeds of carrier charges are so low?

I had read here that magnetism arises from a current because of the special relativistic effect associated with the speed of the moving charges in that current.  However that speed is only on the order of 0.024 cm/s, essentially zero compared to the speed of light, so there cannot be a relativistic effect to consider.  Is special relativity the origin of magnetism?


Is it safe to put a clothes washer outdoors?

I will be short on usable indoor space for a while, but want to be able to wash clothes on site.   Are there any issues with putting a washer (and perhaps, a dryer) outdoors?  Perhaps it needs to be protected from the rain. Would an EZ-UP style canopy be sufficient?


There is a theorem in page 100 of , which says that:     If $\cfrac{dx}{dt} = f(x) = Ax + R_2(x)$, where $A = \cfrac{\partial f}{\partial x}|_{x = 0}$,  $R_2(x) = O(x^2)$, and $\cfrac{dy}{dt} = Ay$, $y(0) = x(0)$, then for any $\vphantom{\cfrac12} T>0$ and for any $\xi > 0$ there exists $\delta > 0$ such that if $|x(0)| < \delta$, then $\vphantom{\cfrac12}|x(t) - y(t)| < \xi \delta$ for all $t$ in the interval $0 < t  < T$.   How can I prove this theorem rigorously?    Cross-posted at math.se .


Given,  $U_t-U_{xx}-2U_x=0$  Using method of separation of variables, find ALL possible solution.  My answer :  $U(x,t)=X(x)T(t)$  $T'(t)/T(t)$=$[X''(x)+2X'(x)]/X(x)$=$\lambda$  From here I'm stuck. Could someone show me some working steps for me to proceed further.


Is there any way to merge two worlds in Minecraft?

Is there any way to merge two worlds? Like take chunks from World A, and put them somewhere in World B?


Pass updated local variable between functions?

I creating functions in my function.php and I have a question regarding passing local variables between functions.  Let say I have the functions below, A and B, and I have the variable $amount.  Now let's say in Function A, $amount changes according to certain conditions.  How do I make sure that the $amount used in Function B, is the updated variable and not just the variable I declared at the beginning.  I thought of using static or globals but I am not sure how this applies to a variable which is dynamic.   function A () {     $amount = 5;      if(isset($_POST['term_id']))     {       if ($_POST['term_id'] == '74' )         $amount = -20;        elseif ($_POST['term_id'] == '75' )         $amount = 500;     }    }    function B () {     echo $amount;   }   Edit:  To toscho, I understand the similarities between the two questions, but my variable is a dynamic variable, whereas the user's variable in the other questions is always constant.


Is it "safe" to ignore perfect random effect correlations in glmer?

I am fitting data from a repeated-meausures design by means of a (generalized) mixed model (lme4) including a fixed effect (2level factor), as well as a random intercept and a random slope for subjects ("keeping it maximal" as recommended by Barr et al. 2013, Journal of Language and Memory).   My random effect correlation is "perfect" , i.e. 1 or -1 (while intercept-/slope variances are close to but not 0), which is apparently indicative of "overparameterization" (Baayen, 2008,Journal of Language and Memory). I see some strange behavior coming along with this: Eg., plotting random effects essentially draws parallel lines, although this doesnt fit the data very well. Also, comparing the full model to a simpler one via PBmodecomp returns an convergence error. I suspect this is all related but may also result from other issues with my data.  .... Thus my question(s): Are results reliable/sound with random effects correlation of 1/-1 ? Can I savely ingore this kind "overfitting" (as it has no further effects) or should I start to remove random effects such as the slope ? Any proposals?


Error when using the commands cd.. and cd. in the terminal

I try to use the commands cd.. and cd. in the terminal to move from my current folder to a previous one, and it shows me a message that the command doesn't exist...   What could the problem be? I'm using Ubuntu 18.04 LTS.


Would I be considered a native English speaker?

I'm currently 16 and I've been wondering if my English is considered as "native" English and the reason why I'm currently questioning this is because I'm currently creating a Curriculum.  I'm a Brit brought up in Spain that has been brought speaking both English and Spanish.  I studied in a Spanish school and have Spanish friends, but I also have British friends, and apart from when I'm speaking with the Spaniards, I think and speak in English.


What fantasy book series has spells cast by two races using dance-like movements, and many worlds?

I am looking for the title of a fantasy series I once started reading at a friend’s house a long time ago, and never got the chance to get the name of the author/series.   It involves the main characters going to multiple worlds; I believe the story opens up on a world ruled by elves and the humans are commoners, slaves, or working class. Also, this world has a series of floating islands that can only be accessed by floating ships, which only the elves have access to.   Another thing I remember is that the series had a unique take on magic, which was done by chanting mysterious words, while using/moving the body in complex movements, almost like a dance. There were two "races" of magic users: one race had mostly-white hair with dark tips, while the other race had mostly-dark hair with white tips.  One of the main characters is one of these races (I can't recall the names of the races, but I know one started with an "A" and the other with a "P"), and I believe (if memory serves right) he is the last of his race, and his name was something like Alfred, Albert, or Alabert. One of his character traits was that he was very clumsy, which made it hard for him to cast spells, but when he did pull one off they were immensely powerful spells.  I also remember there being many worlds that the group of main characters travel to, one being a sort of jungle world with ancient ruins, and a race of huge golems, created by "Alfred's" race long ago by using magic. Another world had huge winged beasts that end up attacking the group of main protagonist, and Alfred ends up casting a very powerful spell, turning himself into a huge dragon, and saving the day.   I know it isn't a lot to go on, but I hope that someone can help me, because I have been searching a long time for this series. I really do want to finish it, I remember it being one of those series that gets you all excited and you can't stop reading. Sorry for the long description. Please, any help is better than none. Thank you all for your time.


I was trying to understand the architecture of transformers especially for the "Positional encoding" part and more precisely on "Why positional embeddings are summed with word embeddings instead of concatenation?" I came across an article saying that:  "Initially, if we pay attention to the figure 2, we will find out that only the first few dimensions of the whole embedding are used to store the information about the positions (Note that the reported embedding dimension is 512 despite our small toy example). And since the embeddings in the Transformer are trained from scratch, the parameters are probably set in a way that the semantic of words does not get stored in the first few dimensions to avoid interfering with the positional encoding."  Here, I have a little problem understanding what it means when it says "the parameters are probably set in a way that the semantics of words does not get stored in the first few dimensions?"  I did not really get it. I would be very grateful if someone could explain this to me or if anyone could recommend an article or any other resource that could help.