If $R$ is a finite Boolean ring with $1\neq 0$ then prove that $R\cong \mathbb Z_2\times \mathbb Z_2\times \cdots\times \mathbb Z_2$.  How should I proceed? Please give some hints only.

Question: If $R$ is a finite boolean ring, then show $R \cong \mathbb Z_2 \times \mathbb Z_2 \times \cdots\times \mathbb Z_2$.   I know that   $\mathrm{char}(R) =2$  $R$ has $2^k$ elements for some $k$  (this is because, if $p\neq 2$ is a prime with $p\mid|R|$, then there exists a non-zero $x \in R$ s.t. $px=0$ and $p $ is odd $\implies x=0$, contradiction).   Does this suffice to answer my question?


I applied subsurf modifier, saved the file and then quit the blender but when I reopned it I realized that I need to go back but it doesn't undo it and my undo history is empty. Can anyone help me?

I had just finished creating a realistic human head in blender that took me about four hours to make. I then tried to open it in a new file but I accidentally saved over it.  Someone please help, I'm really upset about losing all that time and effort.


I was reading the ATtiny13A datasheet and I can't figure out what's that symbol in the general digital I/O schematic. I've circled it the figure below.

Could someone please tell me what the symbol ringed in red represents?     I know it has ON Switch pointing to it, but the symbol has other lables in different parts of the document.


I'm trying to generate valid sitemap with php. The logic is simple. I forwarded all ^(.+)index_sitemal.xml request to my index_sitemap.php file in .htaccess. PHP script is below:  <?php  header( "content-type: application/xml; charset=UTF-8" );     echo '<?xml version="1.0" encoding="UTF-8"?>'."\n";     echo '<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">'."\n";     $len = 10;   // to take     $min = 50;  // minimum     $max = 100;  // maximum     $range = [];     foreach (range(0, $len - 1) as $i) {         while(in_array($num = mt_rand($min, $max), $range));         $range[] = $num;         echo '<sitemap><loc>http://'.$_SERVER['SERVER_NAME'].'/sitemap/'.$num.'.xml</loc></sitemap>'."\n";     }     echo '</sitemapindex>'; ?>   In browser it displays good.  Link for image - (sorry low reputation)   But while trying to validate the xml I'm getting type error.  Link for image - (sorry low reputation)   Is there any way to display a dynamic sitemap using php?

I have to generate a xml file dynamically at runtime. Please help me in generating the below XML file dynamically using PHP.  <?xml version="1.0" encoding="UTF-8"?> <xml>  <track>      <path>song1.mp3</path>      <title>Track 1 - Track Title</title>  </track>  <track>      <path>song2.mp3</path>      <title>Track 2 - Track Title</title>  </track>  <track>      <path>song3.mp3</path>      <title>Track 3 - Track Title</title>  </track>  <track>      <path>song4.mp3</path>      <title>Track 4 - Track Title</title>  </track>  <track>      <path>song5.mp3</path>      <title>Track 5 - Track Title</title>  </track>  <track>      <path>song6.mp3</path>      <title>Track 6 - Track Title</title>  </track>  <track>      <path>song7.mp3</path>      <title>Track 7 - Track Title</title>  </track>  <track>      <path>song8.mp3</path>      <title>Track 8 - Track Title</title>  </track>


I have some cinnamon orange tea in my kitchen that has been sitting there for 3 years. Would it still be safe to drink?  It is in a container with a lid.

This box of tea has an expiration date which has passed but I would like to know if I can still use it. What do you think?


When I type on the terminal: sudo apt install gnome-tweaks  I get an error: The following packages have unmet dependencies:  gnome-tweaks : Depends: gnome-shell-extension-prefs but it is not going to be installed E: Unable to correct problems, you have held broken packages.  Doing the same for gnome-shell-extension-prefs shows a more detailed error: The following packages have unmet dependencies:  gnome-shell-extension-prefs : Depends: gnome-shell (= 3.36.4-1ubuntu1~20.04.2) but 3.36.6-1ubuntu0.20.04.1~wip1 is to be installed                                Depends: gnome-shell-common (= 3.36.4-1ubuntu1~20.04.2) but 3.36.6-1ubuntu0.20.04.1~wip1 is to be installed                                Recommends: chrome-gnome-shell but it is not going to be installed E: Unable to correct problems, you have held broken packages.  However I have no held packages, apt-mark showhold has empty output. For some reason gnome-shell-extension-prefs depends on WIP dependencies, and something is preventing me from installing them. Do I have to allow dependencies from unstable channels or something like that? What could be the issue here?

After upgrading from 10.04 to 12.04 I am trying to install different packages.  For instance ia32-libs and skype (4.0).  When trying to install these, I am getting the 'Unable to correct problems, you have held broken packages' error message.   Output of commands:  sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   After running this:  sudo dpkg --configure -a foo@foo:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.


I am editing my brother’s paper, and I realized I am unsure about the possessive form of Marine Corps, such as     The best kept secret of the Marine Corps   Is it     the Marine Corps’ best kept secret   or     the Marine Corp’s best kept secret   I am leaning towards the first because the s is part of the word corps.

What is the possessive of a noun ending in ‑s?  Are these both right, or is the second one wrong?   the boys' books the boss' car


$1+x+x^2+x^3+\dotsb+x^n=\frac{1-x^{n+1}}{1-x}$, assuming $x\neq1$ I am having a hard time proving by induction on this one. I am getting stuck on trying to prove for $k+1$ (or some variable that proves that it holds true for the next case). I tried to find the base case by plugging in $2$ and $3$ but I feel like I am missing a fundamental part of the problem required to solve it. Sorry for this if this is not the correct way to post things as its my first time! EDIT: - Wow thanks for the help guys! That was incredibly fast.

So what I am trying to prove is for any real number x and natural number n, prove $$x^n-1=(x-1)(x^{n-1}+x^{n-2}+...+x+1)$$   I think that to prove this I should use induction, however I am a bit stuck with how to implement my induction hypothesis. My base case is when $n=2$ we have on the left side of the equation $x^2-1$ and on the right side: $(x-1)(x+1)$ which when distributed is $x^2-1$. So my base case holds.   Now I assume that $x^n-1=(x-1)(x^{n-1}+x^{n-2}+...+x+1)$ for some $n$. However, this is where I am stuck. Am I trying to show $x^{n+1}-1=(x-1)(x^n + x^{n-1}+x^{n-2}+...+x+1)$? I am still a novice when it comes to these induction proofs. Thanks


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

I am analyzing a file xyz.txt which contains hifen separated records. I want to extract records based on the presence of the strings FADED:100,  AM:FF and GG. Subsequently, I need to write them to a new file, faded100.txt. The source file include more then 40 thousand records, looking like below.   --- --------  --- -- -- -- -- -- -- -- -- -- -- -- -- -- --  --- --- -- --      rtuyss  A/A go go go go go go go go go go go go go go  IRE AP  QQ Z ORDER xxxxxxx1  country: 201  NVDS        TEMPROR   EXTREME  BUS TIME:       TRASS: 12       AIDED: 12        FADED: 100                        U  U  U  u  U  A  U  O  O  O  O  O  O  O                  GG   Y  Y  Y  Y  Y  O  Y  O  O  O  O  O  O  O   POU ATM UNITED #  AM:FF   Y  Y  Y  Y  Y  O  Y  O  O  O  O  O  O  O   POU POU POU POU --- --------  --- -- -- -- -- -- -- -- -- -- -- -- -- -- --  --- --- -- --  rtuyss  A/A go go go go go go go go go go go go go go  IRE AP  QQ Z ORDER xxxxxxx1  country: 201  NVDS        TEMPROR   EXTREME  BUS TIME:       TRASS: 12       AIDED: 12        FADED: 200                        U  U  U  u  U  A  U  O  O  O  O  O  O  O                   ZZ  Y  Y  Y  Y  Y  O  Y  O  O  O  O  O  O  O   POU ATM UNITED #   AM:FF  Y  Y  Y  Y  Y  O  Y  O  O  O  O  O  O  O   POU POU POU POU  --- --------  --- -- -- -- -- -- -- -- -- -- -- -- -- -- --  --- --- -- --  rtuyss  A/A go go go go go go go go go go go go go go  IRE AP  QQ Z ORDER xxxxxxx1  country: 201  NVDS        TEMPROR   EXTREME  BUS TIME:       TRASS: 12       AIDED: 12        FADED: 100                       U  U  U  u  U  A  U  O  O  O  O  O  O  O                   IP Y  Y  Y  Y  Y  O  Y  O  O  O  O  O  O  O   POU ATM UNITED #   AM:FF Y  Y  Y  Y  Y  O  Y  O  O  O  O  O  O  O   POU POU POU POU  --- --------  --- -- -- -- -- -- -- -- -- -- -- -- -- -- --  --- --- -- --


Whenever I post any question I am expressed as "unknown" in preview and something like "user_.. " as display name with my question or any comment. How can I edit my display name?? I have been using my account since recently.

How can I change (or remove / reset ) my name on a site in Stack Exchange network?


I'm brand new at electronics, and brand new at Arduino. I know very little about eighter, so please bear over with me... :-) To top it of, this is my very first post here on Electronics.  I'm working as a frontend developer, and my first Arduino project is about controlling a slot car via a website.  I can turn an LED on and off, remotely from a website, and I have connected the slot car to the Arduino, like I connected the LED, but of course there isn't enough power to get it running very fast. I does run, but sloooow... :-) I used a digital multi meter and saw that there were only 2V in the tracks, compared to 14.8V when plugged in the wall.  With my very limited knowledge of electronics, I was wondering if I could plug the slot car into the normal power socket, and somehow control how much power that goes into the tracks with Arduino.  How do I do that? With a resistor? Or?  Thank you in advance.

I'm attempting to control the speed of two slot cars in a set using Arduino.    Each car is controlled by a controller with a variable resistor that looks like this:    They're wired in parallel to the same 17V DC power supply:    Simplified:    For Arduino control, I experimented with manipulating a single car's speed using a MOSFET. It worked really well. Using a PWM output on the Arduino, I was able to pulse the MOSFET on and off to throttle the current and change the car's speed. The behavior of the MOSFET seemed to be exactly the same as the variable resistor controller; the resistance, voltage, and current fluctuated the same way on various parts of the circuit.  Enter car B. I added a MOSFET to the setup and mimicked the MOSFET wiring for car A, grounding them both to the Arduino ground. The result looks like this:    Here's a sketch:    Close up, MOSFET A:    MOSFET B:    At first, all seemed well. I sent signals to MOSFET A and successfully changed Car A's speed. I stopped Car A and pulsed MOSFET B, and I was able to control Car B's speed just fine.  Then, I turned Car B to a constant speed, and sent a signal to MOSFET A while Car B was still running. Car A started, but Car B's speed immediately dropped as a result of running Car A.  I hooked a multimeter up across the rails of Car B and watched its voltage while it ran on its own. Then, sure enough, when Car A started running alongside it, Car B's voltage dropped dramatically.  I figured this was because of my wiring configuration, so I left the multimeter on Car B, and made one change. I replaced MOSFET A with the original slot car controller:    I started running Car B again using its MOSFET. The multimeter showed a steady voltage, so I began to squeeze Car A's controller (the variable resistor), and Car A's speed increased. This time, however, unlike using a MOSFET to control Car A, the variable resistor did not affect Car B's voltage at all. Car B remained at a steady speed the whole time.  Any idea why this happens? The MOSFET seemed to function the same as the variable resistor (empirically) with a single car, but had totally different behavior with two cars in parallel. Is it because the MOSFET is not really changing resistance to current, but just switching it on and off, so it opens up another path for current to flow fully every time it closes? Is there an Arduino-controllable alternative to a MOSFET that would fluctuate actual resistance like the variable resistor? Digital potentiometer? Servo hooked up to a potentiometer? ;) I'm really curious what the difference is and what causes the major differences in behavior.


Wi-Fi is not detected on my fresh Ubuntu 19.10 installation on an  installation. The Settings > Wi-Fi page states "No Wi-Fi Adapter Found". The liveboot from a USB stick that I tried out before the installation had the Wi-Fi working fine.  Which driver do I need to install and how do I install it?  The output of the  on my computer is shown here:   Without Wi-Fi, my computer is without internet connection, so I will need to download installation files with another computer and copy files on a USB stick.  Thanks for any help!

I have a Dell Vostro 5490 with Ubuntu 18.04 installed in dual boot with Windows 10. I currently have no WIFI. I have tried to update and upgrade my packages, and I have also followed  guide, but without success. Except for the things mentioned, my Ubuntu is completely stock, I have not done any other modifications. Please help me out with this issue, any help would be greatly appreciated!  This is the output from the command lspci -knn | grep Net -A3; rfkill list:  00:14.3 Network controller [0280]: Intel Corporation Device [8086:02f0]     Subsystem: Intel Corporation Device [8086:42a4]     Kernel driver in use: iwlwifi     Kernel modules: iwlwifi 0: hci0: Bluetooth     Soft blocked: yes     Hard blocked: no   Here is a paste of the output from the command dmesg | grep iwl:


I had a Xbox One with a GTA V account on it, but now I have a PS4. Can I transfer my Xbox One account over and get it on my PS4?

Is it possible to transfer my character from GTA 5 Online, which I played on XBOX One, to my Playstation 4?


I'm new to shell scripting and I came across these expressions   ${var:-val} and ${var-val}  ${var:+val} and ${var+val}  ${var:=val} and ${var=val}  so how are they evaluated and what are the differences between them

I saw this in the end of an awesome shell script but I can't understand the login here because I think it's being short-handed for a longer command.  spark ${@:-`cat`}   This apears at the end of . Any ideas?  + Marks for some one who extends it into a full segment of code, even if its slower (Better for explanation)


How do I install flash player 11.2.202.442 over 11.2.202.440?  Using Ubuntu 12.04.  This is my wife's computer, and she just told me she can't see any videos using Flash Player. Message says She needs to update...  I'm not sure about the "right" procedure.  I need step by step info (or tutorial), so that I can show her how it's done.

I have had significant problems with watching flash video in 64-bit Ubuntu.  Does anyone know of a good way to get flash running on the platform?


I am an Indian in Germany. I have a type D visa that says 'Deutschland' and its validity is from 1.4.19 to 31.8.19 ( 5 months). I don't have a resident permit, and I am in Germany only for a semester-long student exchange program. I wanted to know if I can travel to other Schengen states in July and August. It's said there is a 90/180 rule with this visa, so I can travel to Schengen states other than Germany upto 90 days in any 180 day period. But, when do my 90 days start; do they start on the day I entered Germany or do they start when I step out of Germany into another Schengen state? Super confused over here and any help will be appreciated, since my travel plans are frozen because of this! Thanks!

I have requested for a French long term (Type D) student visa from a consulate in India. It's a national Type D visa and not a Schengen visa. My question is that can we still go to other Schengen countries on this visa? If not then can we get a Schengen visa from a consulate in France?


I am planning a trip and it is important to me to arrive on time, so I want to calculate how much hours behind schedule can the plane arrive. For example, if I want to be at the destination airport at 12:00, and I take a flight that is supposed to arrive at 11:00, what are the chances that the flight actually arrives after 12:00?  This probably depends on the origin, destination, airplane, etc., so I am looking for statistical data tables. Where can I find such tables?

My flight got canceled yesterday and I am currently waiting for the delayed next flight.   Is there any website that keeps records of airlines being delayed/canceled? I would like to know my chances. I did find some sites through google (flightaware, flightstats), but they focus on us flights only and I am currently in the azores.


Why do we need to repeat the verb "to be" in this kind of statements?:   She is being kind to me.   It is supposed that the second "be" takes a meaning of the verb "behave".

What is the difference in meaning between the following two sentences?  (1) I am completely honest with you right now. (2) I am being completely honest with you right now.


I'm creating a T-shirt using an image licenced under . The main problem I'm facing is how do I attribute the image used? Do I put the attribution on the site I sell the T-shirt on, or do I put it right on the T-shirt?

Edit:   To be extremely succinct: How to credit imagery used on a business card or ballpoint pen?      Inspired by  I started to think:  How do you attribute and give credit, when you use images and resources that are Creative Commons, copyleft; are in the public domain or have variation of "free" licensing?   (Some of the answers to the above questions grazes that question but it is not really the main issue in that question).  How do you attribute - say -:    a background tiled image for web? a background tiled image for print?   (the point here being tiny-weeny images)   an icon set web? an icon set print? To make it more fiddly: tiny images you might use for t-shirts, printed objects such as ballpoint pens, t-shirts, keyrings, letterheads?   For web; there seems to be divided between those who think that in the source code is fine and those who do not. For web you could make a link somewhere discreet that says "credits". This does not really work for print. If you enthusiastically stand on the shoulders of giants, and use what is legally yours to use, your printed leaflet would be bogged down in 6point text attributions.   (Yes, there are differences between countries; I am asking on a general note.)   Edit: I could add GNU licenses, but that is usually pretty straightforward, as it is mainly concerned with software, code, programming snippets, digital programmable objects etc.


I want to take a string: x = 'The following is a string: \'Here is a nice python string\'  and split it, but keep the inner string intact so it returns: ['The', 'following', 'is', 'a', 'string:', '\'Here is a nice python string \'']  This should act the same for {} or [] or (), however, not <>.

I have a string which is like this:  this is "a test"   I'm trying to write something in Python to split it up by space while ignoring spaces within quotes. The result I'm looking for is:  ['this','is','a test']   PS. I know you are going to ask "what happens if there are quotes within the quotes, well, in my application, that will never happen.


By $A$ we denote an arbitrary commutative ring. Suppose that for each $a\in A$ $(a)=(a^2)$ (i.e. $\forall a\in A$ $\exists b$ such that $ba^2=a$).   It is easy to see that this implies that each prime ideal in $A$ is maximal. For example, suppose $\rho$ is a prime ideal, i.e. $A/\rho$ is an integral domain. So, for each $\bar{a}\in A/\rho$ ($\bar{a}\ne \bar{0}$) there exists $\bar{b}\in A/\rho$ such that $\bar{b}\bar{a^2}=\bar{a}$. It follows that $\bar{a}\bar{b}=\bar{1}$ as $A/\rho$ is an integral domain.   Well, I'd like to understand if the converse is true. So, is it true that if each prime ideal is maximal then $\forall a$ $(a)=(a^2)$? I would like to add that I am assuming $R$ is reduced (no nilpotent elements).

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


I got this question from "An Introduction to Analytic Number Theory". I am looking for a just a hint. The question is to prove that, for all $n$ greater than 1, $$\sum_{k=1}^{n}\frac{1}{k}$$ is never an integer. My idea to prove this is to do induction on $n$ and show that each sum is written in lowest for as  $$\frac{a}{n!}$$ for some integer $a$. Starting with $n=2$ as the base case. $\frac{3}{2}=\frac{3}{2!}$ which is in its lowest form and is not an integer. So now for our inductive step. We must show that because  $$\sum_{k=1}^{\infty}\frac{1}{k}=\frac{a}{n!}$$ with $\gcd(a,n!)=1$ the same is true for $n$. First, we will add $\frac{1}{n+1}$ to $\frac{a}{n!}$. We have:  $$\frac{a}{n!}+\frac{1}{n+1}=\frac{a(n+1)+n!}{(n+1)!}.$$ Now, I need to show that  $$\gcd\left( a(n+1)+n!,(n+1)! \right)$$ From here is the part I need a hint for. I think I have to use Bezout's lemma. Can you help?

If $n>1$ is an integer, then $\sum \limits_{k=1}^n \frac1k$ is not an integer.  If you know , then you know there must be a prime $p$ between $n/2$ and $n$, so $\frac 1p$ appears in the sum, but $\frac{1}{2p}$ does not. Aside from $\frac 1p$, every other term $\frac 1k$ has $k$ divisible only by primes smaller than $p$. We can combine all those terms to get $\sum_{k=1}^n\frac 1k = \frac 1p + \frac ab$, where $b$ is not divisible by $p$. If this were an integer, then (multiplying by $b$) $\frac bp +a$ would also be an integer, which it isn't since $b$ isn't divisible by $p$.  Does anybody know an elementary proof of this which doesn't rely on Bertrand's Postulate? For a while, I was convinced I'd seen one, but now I'm starting to suspect whatever argument I saw was wrong.


I think the fonts in the Stack Exchange iOS app are too small, and I want to regulate the length of them. Could you add this function?

Can you add a setting for choosing font size in iPhone mobile app?   It's hard to read questions.


Please see  I often open Chrome and the incognito windows together (Chrome on left and incognito on right). But sometimes due to my fast speed of clicking, the window shifts from right to left. I can't see how I did it. Click and drag did not work. How do I shift back to left and right without closing and reopening the window.

Usually I need much pages to be open at one time. So there is a Windows task panel. When I open multiple Google Chrome windows by Ctrl+N they appear in some order at the Windows task panel. Also in each windows I can create multiple tabs with pages (Ctrl+T).  I would like to create certain order of Google chrome Windows in the task panel. Say first is window with multiple tabs of my email accounts (gmail, yahoo mail etc). Second is window with tabs of google drive pages (different spreadsheets and docs files pages).  But sometime (I don't know why and how) the order changes itsef. Say window with emails tabs goes down... And then to create initial order I need to close all the windows and reopen them.  Could you please help with following: 1. Why order changes? 2. How can I change the order without closing and reopening all the windows? 3. If I create set of startup pages in the Google Chrome settings all of them open in the separate tabs but within one window. May I create a setting to open them in certain order of windows on each startup of Google Chrome?


How should I go about doing occlusion culling with glDrawElements? I am dealing with voxel-like terrain. I want to avoid drawing the faces that are facing another block. I just don't know how to incorporate this with glDrawElements. Should I even use glDrawElements?

I want to render a cube-mesh (a.k.a. Minecraft-style) world. If I render each existing cube it will eat up FPS pretty quickly. How can I optimize it? I understand that the point is to not render invisible meshes (faces?) but my problem is to find out what is invisible and what isn't.


The title of the movie is John Dies at the End, but for some reason this doesn't happen. He dies for a short while in the middle, and then comes back, but this makes the title inaccurate, especially since the whole movie is based on the premise that the drug they take allows them to be all- knowing. So what's the deal here?

The 2012 adaptation of David Wong's "John Dies at the End" ends without John dying at the end at all. While the core of the film espouses the belief that time is not linear, the word "end" suggests there is a beginning and an end to things.  Why is the movie called John Dies at the End?


I have a few guest machines on VMware. Up until now I was keeping my time sync with ntpd inside guests. Now our VMware admins decided to setup VM hosts to keep time, so VMs don't have to. I disabled ntpd in guests, so far so good.   The problem is that I don't completely trust VMware host's timekeeping and would like to monitor time offset in guests with respect to public time sources.  How can I do that?

I am searching for a command-line that allows me to check the system time deviance to a NTP server specified on the command-line. I don't want to change/adapt the system time - only displays the deviance.  Nice would be an text-mode display as it is used by the windows tool w32tm.exe:  14:09:06 d:+00.0331970s o:+00.0046684s [                           *                           ] 14:09:08 d:+00.0331985s o:+00.0050307s [                           *                           ] 14:09:10 d:+00.0331980s o:+00.0050342s [                           *                           ] 14:09:12 d:+00.0341736s o:+00.0041995s [                           *                           ] 14:09:14 d:+00.0341737s o:+00.0048171s [                           *                           ] 14:09:16 d:+00.0331742s o:+00.0043771s [                           *                           ] 14:09:18 d:+00.0341740s o:+00.0045760s [                           *                           ]   What program should I use?


I have two laptops (asus and HP), in the ASUS all the tools work correctly the problem is in the HP.  On my HP Laptop 14-cm0xxx laptop, I have problems starting Wi-Fi and Bluetooth.  I don't think it's a hardware problem, since everything worked correctly with the Windows operating system before switching to Ubuntu 18.04. I have tried several solutions on the network but without any positive results, I tried to solve the problem by installing ubuntu 19.10 and the same problem follows.  Here are some information about the components of my system:   description: Notebook  Product: HP Laptop 14-cm0xxx (3PX47LA # ABM)  Manufacturer: HP  version: Chassis Version  Series: 5CG82547RX  width: 64 bits   * -network    description: Ethernet interface    Product: RTL8111 / 8168/8411 PCI Express Gigabit Ethernet Controller    Manufacturer: Realtek Semiconductor Co., Ltd.    I attach images with the problems          lspci -knn | grep Net -A3; rfkill list   Result  Network controller [0280]: Realtek Semiconductor Co., Ltd. Device [10ec:d723] Subsystem: Hewlett-Packard Company Device [103c:8319] Kernel modules: rtl8723de 05:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc.  [AMD/ATI] Raven Ridge [Radeon Vega Series / Radeon Vega Mobile Series] [1002:15dd] (rev c5)

The wireless drivers for the RTL8723DE appeared for downloading and the module is now usable for Wi-Fi.   See   But the bluetooth part of it is yet not supported on Ubuntu. How this can be fixed?  lsusb shows  Bus 001 Device 003: ID 0bda:b009 Realtek Semiconductor Corp.    And usb-devices | awk '/0bda/' RS=  T:  Bus=01 Lev=02 Prnt=02 Port=03 Cnt=01 Dev#=  3 Spd=12  MxCh= 0 D:  Ver= 1.10 Cls=e0(wlcon) Sub=01 Prot=01 MxPS=64 #Cfgs=  1 P:  Vendor=0bda ProdID=b009 Rev=02.00 S:  Manufacturer=Realtek S:  Product=802.11n WLAN Adapter S:  SerialNumber=00e04c000001 C:  #Ifs= 2 Cfg#= 1 Atr=e0 MxPwr=500mA I:  If#= 0 Alt= 0 #EPs= 3 Cls=e0(wlcon) Sub=01 Prot=01 Driver=btusb I:  If#= 1 Alt= 0 #EPs= 2 Cls=e0(wlcon) Sub=01 Prot=01 Driver=btusb


I am a new user of Linux migrating from Windows. I do not know much about Ubuntu. I've installed Ubuntu 14.04 version. At start, Software Center was working, but now Software Center is not working. It is showing this error:     Failed to download repository information. Check your internet network   Please tell me the solution of this problem, and also give me some useful tips % tricks about linux.

When I run software updater it says that it failed to download repository information and to check Internet connectivity.  I have Internet connectivity.  How do I fix this?  editing to add content of sources,list:  sorry I can't figure out how to paste in the content of sources.list without making a huge mess.  Some of it previews as really large bold print.  I tried to follow the block quoting and code rules but it is a huge mess anyway.


I'm currently working on a project on Blender and I'm still trying to familiarise myself with the interface so I'm quite a beginner at the moment. I was working on a figure and then I'm not quite sure what I clicked on it took me to a different interface other than the initial one where you edit the figures and stuff.  This is what I'm getting when I open my saved project    Thank you!

I accidentally opened too many menus (or windows) and I want to reset them to default.  It is really annoying, and effecting my animation.  Thanks


I'm am study some classical logic and I am having trouble with argument validity. I learned to think of validity as determined by the definition "If the premises are true, then the conclusion must be true". Keeping the truth table of conditionals in the back of my mind has served fairly well in my exercises of evaluating arguments. However, I came across this example on the internet, "All cats are mammals, All tigers are mammals, Therefore all tigers are cats". The site says that this argument has true premises and a true conclusion yet it is invalid. Thinking of the conditional definition would't this be a true implying a true, which means the argument is valid? I appreciate any clarification.

My text book gives the definition of validity as "An argument is valid IFF if the premises are true, then the conclusion must be true". Using a conditional elimination on the RHS of the IFF yields "An argument is valid IFF the premises are false or the conclusion is true".   Yet, this seems strange to me. Am I doing something incorrect with my manipulation or is this definition actually true? Surely the criteria for a valid argument goes beyond a false set of premises or a true conclusion.


Issue: Apparently I got a temporary review ban. It seems like I should have recommended an answer for deletion instead of saying that it looked good. I would like to read again the answer I had misjudged to understand where my decision failed. However it seems like I cannot access the now deleted answer.  Feature request: when temporarily banning someone from reviewing, give access to the content that have been misjudged so that the user can learn from it.    My ban:    My inability to learn from it as I cannot access the deleted answer:

So moderators just got . Often, these bans are due to specific very bad reviews, like approving spam or non-answers. It will be common for us to give links to these bad reviews in the ban message that the reviewers will be presented with.  However, many of these reviewers lack the necessary reputation to see deleted posts. If we're banning someone from review for approving spam or non-answers, almost all of the time those posts will be deleted. If we give them links to the reviews they performed, they won't see the now-deleted posts that they approved, and won't have a chance to learn what they did wrong.  As examples of this, I had to actually take a screenshot to show the reviewers  and  the posts that triggered their ban, because they could no longer see them.  I propose that reviewers of any reputation level be able to see posts that they reviewed, even ones that were later deleted, if they are presented with a link to their review. They already saw the post once, so there's no harm in showing it to them again, and reviewers are going to need to see why they made a bad call on a particular review.


Does anyone have a nice geometric example of function in $H^1(U)$ which is not continuous, where $U \subset R^2$ and has a smooth boundary. I want something that is easy to remember.

Hy everybody got a quick question. I know that all function F in a Sobolev Space has a continuous representative called U such as U=F almost everywhere.  Lets take for example: The Sobolev space on ]-1,1[    the function F(x)=0 on x<0 and F(x)=1 x>0  we can't find a continuous representative because it would be on a larger interval let say ]-eps ,eps[ so not in a Sobolev space the function F(x)=x on x<0 and x>0 and F(0)=1 where we could find the representative U=x   My question is: if F isn't continuous is it sure that it isn't an element of a Sobolev Space? It was given was given as a necessary condition in my course.  Thanks for the help.


I have a true/false question:  Every n × n-matrix A with real entries has at least one real eigenvalue.   I am thinking that this is true but I would like to hear other opinions.  Thanks

I was trying to show that orthogonal matrices have eigenvalues $1$ or $-1$.  Let $u$ be an eigenvector of $A$ (orthogonal) corresponding to eigenvalue $\lambda$. Since orthogonal matrices preserve length, $ \|Au\|=|\lambda|\cdot\|u\|=\|u\|$. Since $\|u\|\ne0$, $|\lambda|=1$.  Now I am stuck to show that lambda is only a real number. Can any one help with this?


The code below doesnt throw any warnings while i compile   #include <iostream>   void GetHMACCode(unsigned char* buffer,long bufferLength,unsigned char** pResult,unsigned int &nResultLen){}   unsigned char *pCRCBufferptr ;   main() {  unsigned char *pHMAC  = NULL;  int ncrcDataLength;  unsigned int nHMACLen = 0;  GetHMACCode(pCRCBufferptr,ncrcDataLength,&pHMAC,nHMACLen);   }   But When i add an extra argument in the function (not in the function call), I get the below warning  myFile.cpp: In function ‘int main()’: myFile.cpp:11: warning: deprecated conversion from string constant to ‘char*’   Added extra arguement in the function    #include <iostream>   void GetHMACCode(unsigned char* buffer,long bufferLength,unsigned char** pResult,unsigned int &nResultLen,char *extra_arg = "11111111111111111111"){}   unsigned char *pCRCBufferptr ;   main() {  unsigned char *pHMAC  = NULL;  int ncrcDataLength;  unsigned int nHMACLen = 0;  GetHMACCode(pCRCBufferptr,ncrcDataLength,&pHMAC,nHMACLen);   }   I am confused why this warnign is being thrown   Thanks Tejas

So I'm working on an exceedingly large codebase, and recently upgraded to gcc 4.3, which now triggers this warning:     warning: deprecated conversion from string constant to ‘char*’   Obviously, the correct way to fix this is to find every declaration like  char *s = "constant string";   or function call like:  void foo(char *s); foo("constant string");   and make them const char pointers.  However, that would mean touching 564 files, minimum, which is not a task I wish to perform at this point in time.  The problem right now is that I'm running with -werror, so I need some way to stifle these warnings.  How can I do that?


The output which I get while installing ClipGrab using ppa is :-  Reading package lists... Done W: The repository 'http://ppa.launchpad.net/clipgrab-team/ppa/ubuntu yakkety Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. E: Failed to fetch http://ppa.launchpad.net/clipgrab-team/ppa/ubuntu/dists/yakkety/main/binary-amd64/Packages  404  Not Found E: Some index files failed to download. They have been ignored, or old ones used instead. jaggu@jaggu-Lenovo-G50-80:~$ sudo apt-get install clipgrab Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  clipgrab : Depends: libavcodec-extra-53 (>= 4:0.8.6) but it is not installable E: Unable to correct problems, you have held broken packages. jaggu@jaggu-Lenovo-G50-80:~$    How do I solve this problem and install ClipGrab ?

After upgrading from 10.04 to 12.04 I am trying to install different packages.  For instance ia32-libs and skype (4.0).  When trying to install these, I am getting the 'Unable to correct problems, you have held broken packages' error message.   Output of commands:  sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   After running this:  sudo dpkg --configure -a foo@foo:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.


Let $p$ be a prime number. If -1 is a square in $\mathbf F_p$, it means that there exists an element of order 4. So $p-1$ is divisible by 4 and therefore $p \equiv 1$ (mod 4). I wonder the converse is also true. Does $p \equiv 1$ (mod 4) mean the existence of an element whose square is $-1$ in $\mathbf F_p$?

I came across this problem and I believe Lagrange's theorem is the key to its solution.  The question is:     Let $p$ be an odd prime. Prove that there is some integer $x$ such that $x^2 \equiv −1 \pmod p$ if and only if $p \equiv 1 \pmod 4$.   I appreciate any help.  Thanks.


I have a few div elements, I want to hide overflow characters when div resizing like this   to this  how to do this every time i resize page.  Can i do it from CSS?

Let's say I have a string "I like big butts and I cannot lie" and I cut it with overflow:hidden, so it displays something like this:     I like big butts and I cann   cutting off the text. Is it possible to display this like this:     I like big butts and I cann...   using CSS?


The following formula appears in the :    How do I express this format, in which minimize is in line with the J(...) expression, and directly above the Thetas?  I tried looking for a similar example in the  book, but did not notice anything similar.

As far as I understand, whatever can be done using DeclareMathOperator can also be achieved using newcommand, but not the other way around. If this is the case, what are the circumstances where DeclareMathOperator is the better choice? When should I take solely newcommand?  I found a question regarding , and I wonder what other aspects should be taken into consideration when it comes to choosing which method to use when defining math operators.


main is not a keyword in java.  How does the JVM know to execute the main method as the starting point of any program?

So far I've been using public void run() {} methods to execute my code in Java. When/why might one want to use main() or init() instead of run()?


I'm self-studying from Apostol, Calculus, Volume I and am having trouble with the following exercise (Section 10.16, #15, p. 402):  Let $\{a_n\}$ and $\{b_n\}$ be two sequences with $a_n > 0$ and $b_n > 0$ for all $n \geq N$, and let $c_n = b_n - \frac{b_{n+1} a_{n+1}}{a_n}$.  Prove that: (a) If there is a positive constant $r$ such that $c_n \geq r > 0$ for all $n \geq N$, then $\sum a_n$ converges.  [Hint: Show that $\sum_{k=N}^n a_k \leq \frac{a_N b_N}{r}$.] (b)If $c_n \leq 0$ for $n \geq N$ and if $\sum 1/b_n$ diverges, then $\sum a_n$ diverges. [Hint: show that $\sum a_n$ dominates $\sum 1/b_n$.]  For part (a) I cannot seem to figure out how to arrive at the hint, nor how to use it. I looked at a simple test case of $b_n = 1$, so we arrive at $$ c_n = 1 - \frac{a_{n+1}}{a_n} \geq r > 0 \qquad \forall \; n \geq N$$ Hence, we have $\lim_{n \to \infty} \frac{a_{n+1}}{a_n} < 1 - r$, and hence $ < 1$.  Therefore, $\sum a_n$ converges. So, from the simple case we see a bit of what's going on.  My inclination is then to do a proof by contradiction… Suppose the limit is $\geq 1$ and get a contradiction (which should result since $b_n$ will need to go to $0$, contradicting the positivity of $b_n - b_{n+1} \frac{a_{n+1}}{a_n}$.  Obviously, this doesn't make any use of the hint, though, so maybe is the wrong idea.  I do think this contradiction will work, but it seems Apostol envisioned a more direct approach that I do not see.

I want to prove the following:  Let $\{ a_n \}$ and $\{ b_n \}$ be two sequences with $a_n>0$ and $b_n>0$ for all $n \geq N$, and let $$c_n = b_n - \frac{a_{n+1}b_{n+1}}{a_n}$$  Then   If there exists $r>0$ such that $0<r\leq c_n \text{ ; } \forall n\geq N$ then $\displaystyle\sum a_n$ converges. If $c_n\leq0$ for $n\geq N$ and if $\displaystyle\sum \dfrac{1}{b_n}$ diverges, then so does $\displaystyle\sum a_n$.   So far I know how to use and prove Cauchy's, D'Alambert's and the integral criterion, so I'd like a hint on either using those or a new idea. The book suggests that for $1$, I show that  $$\sum\limits_{k = N}^n {{a_k} \leq  \frac{{{a_N}{b_N}}}{r}} $$  and for $2$, to prove that $\displaystyle\sum a_n$ dominates $\displaystyle\sum \dfrac{1}{b_n}$  I'd like to prove this with previous theory on series convergence (Cauchy's and/or D'Alambert's preferrably, comparison test) since it is what precedes the problem, and would appreaciate great HINTS rather than answers.   I can't seem to understand the inequalities. I mean, Cauchy's and D'Alambert's criteria reveal that the proof relies on the fact that a geometric series of with ratio $|r| < 1$ converges, but I can't understand the motivation in this proof.    Summing up the work.  For 1:  $$\eqalign{   & {b_N} = {c_N} + \frac{{{a_{N + 1}}}}{{{a_N}}}{b_{N + 1}}  \cr    & {b_N} = {c_N} + \frac{{{a_{N + 1}}}}{{{a_N}}}{c_{N + 1}} + \frac{{{a_{N + 2}}}}{{{a_N}}}{b_{N + 2}}  \cr    & {b_N} = {c_N} + \frac{{{a_{N + 1}}}}{{{a_N}}}{c_{N + 1}} + \frac{{{a_{N + 2}}}}{{{a_N}}}{c_{N + 2}} + \frac{{{a_{N + 3}}}}{{{a_N}}}{b_{N + 3}} \cr} $$  Induction over $n$ we get  $${b_N} = {c_N} + \frac{{{a_{N + 1}}}}{{{a_N}}}{c_{N + 1}} + \frac{{{a_{N + 2}}}}{{{a_N}}}{c_{N + 2}} +  \cdots  + \frac{{{a_{N + n}}}}{{{a_N}}}{c_{N + n}} + \frac{{{a_{N + n + 1}}}}{{{a_N}}}{b_{N + n + 1}}$$  So  $$\eqalign{   & {b_N} \geqslant r\left( {1 + \frac{{{a_{N + 1}}}}{{{a_N}}} + \frac{{{a_{N + 2}}}}{{{a_N}}} +  \cdots  + \frac{{{a_{N + n}}}}{{{a_N}}}} \right) + \frac{{{a_{N + n + 1}}}}{{{a_N}}}{b_{N + n + 1}}  \cr    & {b_N} > r\left( {1 + \frac{{{a_{N + 1}}}}{{{a_N}}} + \frac{{{a_{N + 2}}}}{{{a_N}}} +  \cdots  + \frac{{{a_{N + n}}}}{{{a_N}}}} \right)  \cr    & \frac{{{a_N}{b_N}}}{r} > {a_N} + {a_{N + 1}} + {a_{N + 2}} +  \cdots  + {a_{N + n}} = \sum\limits_{k = N}^n {{a_k}}  \cr} $$  As desired.


Everyday I see the annoying popup message in the upper right corner saying:  A new version of DivX is available Update Now / What's New   I'm closing it using X button, but it's appearing again after some short time (every ~10-15 minutes), so it's very annoying. It's basically forcing me the upgrade which I don't want to do currently. Either I don't want to uninstall it (however it's the last resort). Is there any way to disable that kind of popup? Or ignore it for the next few weeks?

The DivX player has installed a junk notification on my Mac saying:     A new version of DivX is available.   as shown below:    This stupid notification bumps up every hour or so, and there is no way to turn it off (there's no disable option when I click on it's icon). I don't want and don't need their software. I can't see the player in my Notification panel.    Question: How to prevent DivX from spamming me with notifications?


Why do I have to use .ToString() for this code to work: confirmedAcceptance = int.Parse(dr["confirmedAcceptance"].ToString());    This creates error: confirmedAcceptance = int.Parse(dr["confirmedAcceptance"]);

What is the main difference between int.Parse() and Convert.ToInt32()? Which one is to be preferred


I installed 18.04 after 14.04. The default grub entry was 18.04 and 14.04 was displayed below. After a 14.04 update, things changed.  Instead of booting into 18.04 advanced options and choose the first kernel before last and then remove the last linux image and headers, reboot again in ubuntu 18.04 and make an update to the last kernel.... I tried to delete the unused linux image and headers hoping that will do the job. It didn't.  I tried 'sudo update-grub' in ubuntu 18.04 and then reboot, but no change. (I use 18.04 ubuntu-mate and 14.04 ubuntu).  Is there a way to put 18.04 as default, besides waiting for a new kernel update in 18.04?

Can you guys please help me use Grub Customizer to set an older version of the kernel 4.4.0 of Ubuntu 16.04 LTS as default when booting? I'm not using a dual boot system, and I have installed 4.4.8 kernel to help me solve the suspend problem, but it's draining my battery.  What do I have to do, I wouldn't want to f*** things up.


I tried \texttt{@(x)x.^2} or directly @(x)x.^2 but texmaker gives Missing $ inserted. I gues it is because x.^2 which is assumed to be math syntax. Can you help?

I need to output the below text but since \ is a special character, I cannot:  [RegularExpression(@"\d+")]   Also sometimes I need use dollar sign $ as well but it seems to be a special char, too.  What is the way to escape those in LaTeX?  UPDATE:  I used \verb as suggested but I am unable to run commands inside it. Also, in the output the font and the opacity of the text is different than the default one:  \verb|[RegularExpression(\newline @"\d+")]|


Let $M$ be a smooth manifold. Given affine connection $\nabla:\Gamma(TM)\times\Gamma(TM)\to\Gamma(TM)$, I want to check that curvature tensor field $R(X,Y)Z=\nabla_X\nabla_YZ-\nabla_Y\nabla_XZ-\nabla_{[X,Y]}Z$ is $Z$  $C^\infty(M)$ linear.   So I want to check $R(X,Y)fZ=fR(X,Y)Z$. I can surely check this in local coordinates.   Q: Is there any trick I can use to simplify my checking?

For an affine connection $\nabla$, prove the curvature R  $R(X,Y,Z,\alpha)=\alpha(\nabla_X \nabla_Y Z - \nabla_Y \nabla_X Z -\nabla_{[X,Y]}Z)$  with $X,Y,Z$ vector fields and $\alpha$ a co-vector, is a tensor.  So I realise the aim is probably to show that each of the three terms in the expression for $R$ are tensors themselves as then the result will obviously follow. However, I'm not too sure how to show each of these terms are tensors. Do I need to expand out each covariant derivate to get a bunch of connection coefficients and then see some cancellations? Still though, I'm not too sure what I'll want to see after all of this so that I can say "…therefore $R$ is a tensor".  Also, very much related to the question, I'm a bit confused with the difference between  $\nabla_Y Z$ $\space \space $ and $\space \space $  $\nabla_{\mu}\omega$.  The second one I know as the covariant derivative of a 1-form, but what is meant by the covariant derivate of a vector $\textit{field}$? As in, what's the difference between the $\nabla_Y$ and $\nabla_{\mu}$?  Edit: In answering this last question, I have realised that $\nabla_YZ=Y^{\mu}\nabla_{\mu}Z^{\nu}$ and $\nabla_{\mu}\omega=\nabla_{\mu}\omega_{\nu}$.


Suppose you have a ball that is covered in magnets, in which the North Pole of every magnet faces outward. Is this a monopole? Or at least "functions" as a monopole? And what will happen if you placed the ball over a floor tiled in magnets with the North Pole of every one facing up?  Also, I recently saw another poster's question on what would happen if you positioned a ball plated in magnets North Pole outward inside a hollow ball that was plated on the inside North Pole facing inward. One answer-er said if you built the sphere perfectly, then the forces would cancel out, and the ball would drop to the floor. The answer for me seems kinda counter intuitive, as if the ball was dropping toward the floor, the bottom-hemisphere's magnetic field would have greater potency while the upper hemisphere's would fade away. Wouldn't it just levitate at least? Of course not in the center, as it is affected by gravity, but wouldn't it still levitate contrary to one of the physical laws I heard of? Thanks guys, I'm kinda confused.

If I was to take a bunch of magnets and arrange them in a sphere (And keep them there with glue or plastic or something) so that the north pole faces the outside of the sphere and the south pole faces the inside, would the magnet have the same pole no matter what way I turn it or would the magnet be neutralized or something.  I'm envisioning a sphere made of magnets so that no matter what way I turn it it is always the same pole and that a bunch of these repelling each other would be really cool, is this possible?  In effect would this create a monopole magnet?


How to I achieve a GUI restart in ubuntu 18.04 using Gnome on the standard X Windows Server.  Seems like the  doesn't apply anymore.

How can I restart X Window Server from the command line?  I'd really like to be able to restart my GUI without having to do a full system reboot.


I'm writing a book in a language that has lengthy words yet poor support/scope for hyphenation. My current book is far from justified. I would like to manually mark places within words where LaTeX could introduce a space if necessary (break a single long word into two words) instead of optional hyphens.  I believe \allowbreak should work but I can't get it to work in normal body text. Is there an alternative to allowbreak? Should I enclose my entire book text within a \texttt (which I think is necessary for allowbreak but not completely sure)?  Basically I want to know if there is something like \abc which can be introduced into something like verylongword\abcmorewords resulting in either verylongwordmorewords or verylongword morewords.

I have a sentence that contains a number of long dataset names. I would like to allow LaTeX to break these names at certain positions that I would like to specify somehow just like I can use \- to allow a word break with hyphenation. But: I would like LaTeX not to insert a dash (which could be mistaken as belonging to the dataset name). How can I do this?   (Something similar is realized in the url package so I guess I could just read that code :) I would not like to use the url package here to be able to make a syntactical (and typographic) difference between urls and datset names.)


public static Dictionary<string, User> userList = new Dictionary<string, User>();   That's how "userList" gets declared in another class. BTW the name of that class is "User" the same as the type, which could cause the problem but i am not sure. I have no idea how to make this work honestly.  Here's the full script:  Some things in the script dont make sense yet because i copied some stuff from another script.  But basically i am trying to check if a nickName already exists in a static dictionary, and if so notify the user and don't do anything else.

I've seen a few different ways to iterate over a dictionary in C#.  Is there a standard way?


brownguy@brownguy:~$ sudo apt-get -f install Reading package lists... Error! N: Ignoring file 'some-ppa.list.save.2' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension E: Type 'brownguy@brownguy:~$' is not known on line 1 in source list /etc/apt/sources.list.d/libdvdcss.list E: The list of sources could not be read. N: Ignoring file 'some-ppa.list.save.2' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension N: Ignoring file 'some-ppa.list.save.2' in directory '/etc/apt/sources.list.d/' as it has an invalid filename extension E: The package lists or status file could not be parsed or opened.

Every once in a while I see users having issues to update due to errors like this:  E:Type 'ain' is not known on line 1 in source list /etc/apt/sources.list.d/some-ppa.list'   with varying types/line numbers/source list files (often after removing a PPA).  How can such an error be fixed?


I want to replace a text which contains "?" character using regex.   var test = "{=countAreas?area=123}";  I want to replace it with:  "{=countAreas?area=123}X"  I tried below code but "?" character creates an issue since it's a part of regex's identifiers:  test.replace(new RegExp(arrMatch[i], 'g'), "" + arrMatch[i] + "X");

I would like to create a String.replaceAll() method in JavaScript and I'm thinking that using a regex would be most terse way to do it.  However, I can't figure out how to pass a variable in to a regex.  I can do this already which will replace all the instances of "B" with "A".  "ABABAB".replace(/B/g, "A");   But I want to do something like this:  String.prototype.replaceAll = function(replaceThis, withThis) {     this.replace(/replaceThis/g, withThis); };   But obviously this will only replace the text "replaceThis"...so how do I pass this variable in to my regex string?


I have more than one AC power source and I want to detect which one of them is ON which one is OFF using a Microcontroller. So my question here is what is the cheapest and smallest in size method to detect whether an AC power line is there or not?   From 100~240 VAC to 3.3V Steady DC

I have the following power supply configuration: AC MAINS -> UPS -> 24V POWER SUPPLY -> 5V VOLTAGE REGULATOR -> PCB (microcontroller). What's the best solution to detect the power outage on the mains with the microcontroller? I also need to detect the zero-crossing so that I can control the speed of an AC motor.


when I press 'N' I'm supposed to find a 'shadeless' option under shading, but I cant seem to make it appear. I've tried hard to find a solution but there doesn't seem to be one.   Here's how it's supposed to look like      and here's how mine looks like     Thank you in advance.

I'm trying to display models that have shading drawn or baked directly on the textures, but I can't figure out how to disable Blender's default scene lighting. If there are no lights in the scene, everything is black, but I want to see the textured objects fully bright. How do I disable the lighting?  NOTE: Just before posting this, I found the "Shadeless" material property, which does more or less what I want. However, is there a way to globally toggle the default lighting?


There is a fundamental aspect of the way permissions work in linux directories I think I have not understood.  I have this folder I was trying to access from my local apache server :  sudo chmod 777 /home/ut/programmes/Programmation/p5-linux/ sudo -u www-data ls /home/ut/programmes/Programmation/p5-linux/ ls: cannot read directory '/home/ut/programmes/Programmation/p5-linux/': Permission denied    Why is it not working ? even though the permission is 777 ?  Moreover, by doing :   sudo chown ut:www-data /home/ut sudo chmod 710 /home/ut   without changing anything to the permission in /home/ut/programmes/Programmation/p5-linux/, now this is what I get :  sudo -u www-data ls /home/ut/programmes/Programmation/p5-linux/ icudtl.dat  libffmpegsumo.so  locales  nw.pak  p5  p5.png  Projets   the only thing I did was to change the group of a parent dictory. why does it work now ?

I have a personal folder /a/b on the server with permission 700. I don't want others to list the contents in /a/b. The owner of /a is root.  Now I need to open the full authorities of directory /a/b/c to all users.  I changed the permission of /a/b/c to 777 but it is still inaccessible for others.


Most of the examples of fundamental groups have been "discrete" in nature. I'm wondering if there is an example which is not like that. A possible preliminary question could be if there is a space whose fundamental group is the rationals.  Edit: This has been marked as a duplicate; it is with respect to my subquestion about rationals however the linked answer does not say anything about topological spaces whose fundamental groups are the real numbers.

Which path connected space has fundamental group isomorphic to the group of rationals? More generally, is every group the fundamental group of a space?


Whenever I try to run sudo apt-get -f install I get this error. Here is all of the output of sudo apt-get -f install:  Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following extra packages will be installed:   codeblocks-contrib codeblocks-dev gamin libcodeblocks0 libgamin0   libwxsmithlib-dev Recommended packages:   valgrind The following packages will be REMOVED:   codeblocks-headers The following NEW packages will be installed:   gamin libgamin0 libwxsmithlib-dev The following packages will be upgraded:   codeblocks-contrib codeblocks-dev libcodeblocks0 3 upgraded, 3 newly installed, 1 to remove and 20 not upgraded. 5 not fully installed or removed. Need to get 0 B/5,309 kB of archives. After this operation, 1,163 kB of additional disk space will be used. Do you want to continue? [Y/n] Y (Reading database ... 174515 files and directories currently installed.) Preparing to unpack .../codeblocks-dev_13.12-3_amd64.deb ... Unpacking codeblocks-dev (13.12-3) over (13.12-1) ... dpkg: error processing archive /var/cache/apt/archives/codeblocks-dev_13.12-3_amd64.deb (--unpack):  trying to overwrite '/usr/include/codeblocks/externaldepsdlg.h', which is also in package codeblocks-headers 13.12-1 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Errors were encountered while processing:  /var/cache/apt/archives/codeblocks-dev_13.12-3_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   Does anyone think they can help me solve this problem?

For example:  $ sudo apt-get install curl Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: bsh : Depends: libjline-java but it is not going to be installed groovy : Depends: libjline-java but it is not going to be installed rhino : Depends: libjline-java but it is not going to be installed E: Unmet dependencies.   Try 'apt-get -f install' with no packages (or specify a solution).   I get the same or similar errors when I attempt to install clojure1.3, leiningen, and several other packages.   When I try the suggestion made in the error message, this is what happens:  $ sudo apt-get -f install  Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following packages were automatically installed and are no longer required:   diffstat linux-headers-3.2.0-26-generic linux-headers-3.2.0-26 dh-apparmor dkms html2text libmail-sendmail-perl libsys-hostname-long-perl Use 'apt-get autoremove' to remove them. The following extra packages will be installed:   libjline-java Suggested packages:   libjline-java-doc The following NEW packages will be installed:   libjline-java 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. 23 not fully installed or removed. Need to get 0 B/72.0 kB of archives. After this operation, 129 kB of additional disk space will be used. Do you want to continue [Y/n]? Y (Reading database ... 226243 files and directories currently installed.) Unpacking libjline-java (from .../libjline-java_1.0-1_all.deb) ... dpkg: error processing /var/cache/apt/archives/libjline-java_1.0-1_all.deb (--unpack):  trying to overwrite '/usr/share/java/jline.jar', which is also in package scala 2.9.2-400 Errors were encountered while processing:  /var/cache/apt/archives/libjline-java_1.0-1_all.deb E: Sub-process /usr/bin/dpkg returned an error code (1)  $ sudo apt-get upgrade Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies:  bsh : Depends: libjline-java but it is not installed  groovy : Depends: libjline-java but it is not installed  rhino : Depends: libjline-java but it is not installed E: Unmet dependencies. Try using -f.


Some rules have been given , but I am seeking for a particular clarification.  According to the cited answer, R wouldn't be pronounced in WHERE and ARE (because the final E is unvoiced, so the words are as if ending with R)  But what about the sentence WHERE ARE YOU GOING ? The first R(E) is followed by the vowel A, and the second R(E) is followed by the vowel sound U.  My precise question is: which of the two R's, if any, would be pronounced ?

For example, we have  - car  /kɑː(r)/ - or  /ɔː(r)/  I thought the brackets means you delete it - i.e. non rhotic - but now I see the phonetic spelling of words like "hard" which don't include the r at all /ˈhɑːd/


I came across this integral $$\mathcal{J} = \int_{0}^{1} \frac{\mathrm{d}x}{\sqrt{3x^4+2x^2+3}}$$ According to W|A it equals $\frac{1}{2}$. However, I cannot find a way to crack it. It smells like a Beta integral , but I do not see any obvious subs. One could start by setting $u=x^2$ but there is no clear path after that. A promising way might be the following \begin{align*} \int_{0}^{1} \frac{\mathrm{d}x}{\sqrt{3x^4+2x^2+3}} &= \int_{0}^{1} \frac{\mathrm{d}x}{\sqrt{\left ( 3x^2 +2 \right ) x^2 +3}}\\   &=\int_{0}^{1}\frac{\mathrm{d}x}{\sqrt{3\left ( x^2+ \frac{1}{3}   \right )^2 + \frac{8}{3}}} \\   &= \cdots \end{align*} A clever trigonometric sub might clear things but I don't see something. On the other hand , I don't the theory of elliptic integrals is needed here nor complex analysis ( would be interesting to see a solution using contours, though ) So, any ideas how to evaluate it? P.S: Are there techniques available for these type of problems?

I'm trying to integrate the function $\frac{1}{\sqrt{ax^2+bx+c}}$ for $a<0$ and $b,c>0$.   From a list of integrals of irrational functions from Wikipedia I know the result should contain arcsin or arcos, but I don't understand how to get there.  I've tried Euler's substitution and trigonometric substitution but I always stumble over the fact that $a$ is negative.  Can please someone help me?


I've got this diagram created with Tikz a year before:  \documentclass[paper=letter,headings=big,bibliography=totoc,DIV=9]{scrbook} \KOMAoptions{headsepline=true,fontsize=10pt,draft=false} \usepackage{typearea} \usepackage[spanish.mexico]{babel} \usepackage[utf8]{inputenc} \usepackage[LGR,T1]{fontenc} \usepackage{tikz} \usetikzlibrary{arrows} \usetikzlibrary{calc} \usetikzlibrary{through} \usetikzlibrary{backgrounds} \usetikzlibrary{fit} \usetikzlibrary{fadings}  \begin{document}  \begin{figure}[!h] \begin{center} \begin{tikzpicture} % Trazado de las placas paralelas Placas: \coordinate (P1) at (0,0); \coordinate (P2) at (8.5,0); \coordinate (P3) at (0,1.2); \coordinate (P4) at (8.5,1.2); \coordinate (P5) at (0,-0.1); \coordinate (P6) at (8.5,-0.1); \fill[blue!20!white] (P1) -- (P3) -- (P4) -- (P2) -- cycle; \draw (P1) -- (P2); \draw (P3) -- (P4); \fill[gray!80!white] (P1) -- (P5) -- (P6) -- (P2) -- cycle; % Dimensión de la distancia t entre placas Texto:     \node[draw=none,fill=blue!20!white] (t) at (1,0.5) {$\epsilon$};         \draw[<->] (1.2,0) -- (1.2,1.2);   % line with error Texto: \node[draw=none,fill=blue!20!white] (t2) at (2,0.5) {$fluido$}; Texto: \node[draw=none,fill=white,above] (t3) at (1,1.2) {placa móvil}; Texto: \node[draw=none,fill=white,below] (t2) at (1,-0.1) {placa fija}; % Volumen de control y deformación \node[below] (a) at (3.3,0) {$a$}; \node[below] (b) at (4.8,0) {$b$}; \node[above] (c) at (4.8,1.2) {$c$}; \node[above] (d) at (3.3,1.2) {$d$}; \node[above] (c1) at (5.3,1.2) {$c'$}; \node[above] (d1) at (3.8,1.2) {$d'$}; \draw (a) -- (d) (b) -- (c); \draw[dashed] (a) -- (d1) (b) -- (c1); % Perfil de velocidades \coordinate (u1) at (5.8,0); \coordinate (u2) at (5.8,1.2); \coordinate (u3) at (6.8,1.2); \draw (u1) -- (u2)  (u1) -- (u3); % Vector U \coordinate (u4) at (5.8,1.4); \coordinate (u5) at (6.8,1.4); \draw[->] (u4) -- (u5); % Line with error Texto: \node[draw=none,fill=white,above] (U) at (6.3,1.4) {$U$}; % coordenadas \coordinate (u6) at (5.8,1); \coordinate (u7) at (6.6,1); \coordinate (y1) at (6.6,0); \draw[->] (u6) -- (u7) % Line with error (y1) -- (u7); % Line with error Texto: \node[draw=none,fill=blue!20!white] (u8) at (6.2,1) {$u$}; Texto: \node[draw=none,fill=blue!20!white] (y2) at (6.6,0.5) {$y$}; % ejes \coordinate (x1) at (8.6,0); \node (x2) at (9.1,0) {$x$}; \coordinate(y3) at (3.3,1.7); \node (y4) at (3.3,2.5) {$y$}; \draw[->] (x1) -- (x2); % Line with error \draw[->] (y3) -- (y4); % Line with error % Flecha F \coordinate (F1) at (7.7,1.4); \coordinate (F2) at (8.5,1.4); \draw[thick,->] (F1) -- (F2); % Line with error Texto: \node[draw=none,fill=white,above] (U) at (8.1,1.4) {$F$}; \end{tikzpicture} \end{center} \caption[Deformación a cortante constante.]{Deformación resultante de la aplicación de una fuerza cortante constante.} \label{fig:placas} \end{figure} \end{document}   But when I compile the lines commented as % Line with error shows the lines wrong, I don't understand why, before I compiled well this figure. The error I've got is:  Missing \endcsname inserted. \draw[thick,->]

I'm trying the next code:  \documentclass[pdftex,spanish]{article} \usepackage{babel} \usepackage{tikz}  \begin{document}  Simple arrow:   \begin{tikzpicture}     \draw[->] (-1.5,0) -- (1.5,0); \end{tikzpicture}  \end{document}   but it doesn't work. It throws the errors:    ! Argument of \language@active@arg> has an extra }. ! Paragraph ended before \language@active@arg> was complete.<to be read again>\par \draw[->]   What can I do if it works right without the babel package?


I'm a EU-Moroccan national, and I'd have to travel in Algeria in the future, but as far as Algeria is concerned, it requires a visa for almost every country in the world except its bordering countries' nationals (Morocco and Tunisia) and a few other countries. Can I simply use Moroccan passport for entry and exit in Algeria instead of applying for a visa? Many Arabs told me that I might be blocked because at their say "Arab governments don't accept this switching of passport or tricks" or "they might ask a visa for EU" which is weird because they're supposed to record and see the flux of people pertaining their country. Thought?

I am a citizen of two different countries, and have two passports.  How should I use my passports when traveling?


i am new to designing and i have a huge problem. I can easily generate ideas of layout how they should look but my biggest problem is that i can't or is very hard for me to get suitable colours and their combination. How can i improve my colour feeling and to get rid off this problem?

I'm a web developer, started to become a web designer. However, I think my understanding of colors is not practical yet. There are tools out there that can give you color harmonies, and more stuff, like , but they don't give you the start point. I mean, how should I know that for this web site, I'd better use green and for that website, choose red. How should I know that?  I think color selection is more like an art, instead of being a science, and I'm like "you should become an color artist, in order to become a web designer".  How can I improve my color selection skill?


Can I do OpenCL programming with these hardware specs?  CPU: Intel(R) Core(TM) i5 CPU M480 @ 2.67GHz   Graphics: ATI Mobility Radeon HD 6370   RAM: 4GB  OS: Windows 7 Service Pack 1

Does my machine support ? I found  where the list contains the required hardware requirements. Please find the below screenshots of few of my machine. Does any one of the below support OpenCL?  Screenshot from machine 1:    Screenshot from machine 2:    Screenshot from machine 3:    Does any of my three machines support OpenCL? Or do all the three support OpenCL? I am trying to run a basic OpenCL face-detection program and am failing. I have posted Stack Overflow question  regarding the same.  After running , the "1st machine" is of type GPU 1: Intel HD Graphics 2000. Does it support OpenCL?


I have a bare bones script that has 2 lines:  import bpy  bpy.ops.mesh.rip()   I've made sure I am in EDIT mode and have edges selected in edge mode. It fails with  RuntimeError: Operator bpy.ops.mesh.rip.poll() failed, context is incorrect   But I've fulfilled all of the context rules in the docs. Anybody?

I keep on getting context errors in the Blender Python API.  I don't understand the issue of the context in the API, how do I know which is the correct context?   Thanks!


Let $R$ be a commutative ring, $A$ an ideal of $R$, and $R/A$ an integral domain. Then, as I can see in my book, $(a+A)(b+A)=ab+A=A$. But how does this multiplication exactly go? If $(a+A)(b+A)=ab + aA + Ab + A$ then where does the sum of the terms $aA+Ab$ go?  Also, why does $(a+A)(b+A)=A$ imply that $(a+A)=A$ or $(b+A)=A$?  Thank you for your clarifications.

Say $R$ is a commutative ring and $I\in R$ is an ideal. Let us consider the quotient $R/I$. It is created by taking every element $a\in R$, and adding all the elements of $I$ to it. The elements of $R/I$ are of the form $a+I$ and $b+I$, $\forall a,b\in R$.   Now $$(a+I).(b+I)=(a+i_{1}).(b+i_{2}),\forall (i_{1},i_{2})\in I \times I$$  $$(a+i_{1}).(b+i_{2})=ab+a.i_{2}+b.i_{1}+i_{1}i_{2}=ab+I$$  We know that $a.i_{2}+b.i_{1}+i_{1}i_{2}\in I$.   If $(a+I).(b+I)=ab+I$, then taking suitable $(i_{1},i_{2})\in I\times I$, we should be able to prove $(a+i_{1}).(b+i_{2})=ab+i_{3},\forall i_{3}\in I$. However, can every element in $I$ be generated by taking suitable $i_{1},i_{2}\in I$? And if not, is that the reason why $(a+I).(b+I)$ has to be defined as equal to $ab+I$ in violation of the distributive property of ring elements? This has confused me for a long time.   EDIT: I figured addition does not have to be defined as such because $(a+i_{1})+(b+i_{2})=a+b+i_{1}+i_{2}$, where $i_{1}+i_{2}\in I$. In fact, every element $i\in I$ can be constructed by taking $i_{1}=0$ and $i_{2}=i$. Hence, $(a+I) + (b+I)=a+b+I$ naturally. This is the logic I followed to determine that $(a+I).(b+I)$ doesn't quite work as nicey. I'm not sure if this logic is flawed or not as I haven't had the opportunity to ask anybody.   Thanks for your help in advance!


This is what I learned :  $x = 0.\bar3$ (I)  $10x=3.\bar3$ (II)  (II)-(I) :   $9x = 3  => x = 1/3.$ And It's OK.  But now, I think this similar calculation gives me wrong answer:  $x = 0.\bar9$  (I)  $10x=9.\bar9$ (II)  (II)-(I) :   $9x = 9  => x = 1$  Why does: $0.\bar9 = 1 $  ?

I'm told by smart people that $$0.999999999\ldots=1$$ and I believe them, but is there a proof that explains why this is?


I just can't solve this problem in spite of doing a whole book on logs and inequalities     Where $[\dotsc]$ denotes the greatest integer function, what is the value of the natural number $n$ satisfying the equation   $$   [\log_21]+[\log_22]+[\log_23]+\dotsb+[\log_2n] = 1538  $$   A. 255 B. 256 C. 254 D. 313  The answer is A.  Please give an easy solution as I am a high school student. And I do fully understand the meaning of the question but I can't solve it.  Since stack exchange forces me to provide an attempt here it goes- I wrote the equation as $log_2n!=1538$  after this I feel n! should be $2^{1538}  $  and now i am confused...   I hope you got your attempt for the people who put the question on hold.  nice you pointed out chris.. yeah the question is same but the person who posted it has accepted the answer to it not me!....the answer maybe sufficient to understand for him.. but it may not be for me...  PS-whats the point of giving a fake attempt and not speaking the truth?!!

If $[\cdot]$ denotes greatest integer function, then what is the value of natural number $n$ satisfying the equation $$[\log_21]+[\log_22]+[\log_23]+\dots[\log_2n]=1538 ?$$   My try:  Note that  $$0+1\times2+2\times2^2+3\times2^3+4\times2^4+5\times2^5+6\times2^6+7\times2^7=1538$$  But the answer is $$n=\sum_{i=0}^72^i=255.$$  How is it derived?


I'm pretty sure metal loses more of its structure as it heats up and magnetic properties in a material are caused by a particular combination of atomic arrangement and orbital levels so...how does the difference in rotation of Earth's liquid inner and outer core generate any kind of magnetic field? Why wouldn't Earth's magnetic field be even stronger if those two layers were completely stationary and solid?

I am a student of class 9. When I was going through magnetism and read that an earth is a magnet I got some doubts. My question is: is earth really a magnet? Doesn anyone have any proof that earth is a magnet? Is there a magnetic core at the center of the earth? Has anyone reached the core of the earth?


When I'm drawing f(x)=1/x or similar functions, pgfplots draws asymptotes. Do I have to draw the function in two pieces with different domains, or am I missing something?    \documentclass[a4paper]{article} \usepackage{tkz-euclide} \usepackage{pgfplots} \usetkzobj{all}  \begin{document} \begin{center} \begin{tikzpicture} \begin{axis}%     [         grid=major,           x=5mm,         y=5mm,         xtick={-10,-9,...,10},            xmin=-10,         xmax=10,         xlabel={\tiny $x$},         axis x line=middle,         ytick={-10,-9,...,10},         tick label style={font=\tiny},         ymin=-10,         ymax=10,         ylabel={\scriptsize $f(x)$},         axis y line=middle,         no markers,         samples=100,         domain=-10:10,     ]     \addplot[thick] (x,{1/x});     \addplot[dashed] (x,{1/(x-2)}); \end{axis}  \end{tikzpicture} \end{center} \end{document}

I want to plot the function $\frac{3 x}{1 + x}$ with pgfplots. Using  \begin{tikzpicture}     \begin{axis}[axis x line=none, axis y line=none, no markers]         \addplot {3 * x / (1 + x)};     \end{axis} \end{tikzpicture}   I get this:   This is obviously wrong. The same function plotted in Grapher.app:


Over the last few days I shared some things that I learned at work on the SE network in Q&A-style. To me, that seemed better than having the knowledge lost forever in various "internal reports", or worse, labbook entries. When I told my colleagues about it, they seemed intrigued and wanted to try it out as well. We work at a publicly funded research institute, so sharing our knowledge here under a CC-SA license seems like a good "fit" to the overall effort.  Since we have similar interests, we will probably end up voting and working on the same sections and even questions on SE. When we are at work, we will also share the same IP-address.   Before inviting more colleagues, I am wondering about two things:    Should I worry that I will be accused of creating an army of sockpuppets? Due to the overlap in interests and IP-address, this could (and probbly should!) come up. At what point is a subgroup of people that know each other "gaming the system"? It is not unlikely that we will be discussing an issue together until one of us figures it out and shares the solution Q&A style. The 3-4 people that were involved in the discussion then have a  to upvote. Is this considered ethical?

Almost every time a colleague of mine asks a question, we have discussed this problem beforehand. Also, we sometimes meta-discuss the question for stackoverflow (why did I get the "this might be subjective" warning, is this understandable enough, etc). This is less so with answers, but I could believe for some groups this works the same. For now I'll stick to questions, but you could s/question/answer if you like. The resulting question is almost always  Interesting for me, and a problem I don't know the answer to. I probably would favorite it According to me a valid and good question (as we talked about it beforehand) I would probably want to upvote it.  Now I believe to read that "ring voting" is a thing, and I tried to find some questions about this, but didn't find many. I did find and read this blogpost from 2008:  . It reads to me that upvoting 'fraud' is more commonplace then downvoting and it might seem anomalous that I would upvote almost all questions from one user. If all colleagues would do this to their team, you'd get some mediocre questions getting a lot of votes, and some users getting a lot of attention, points etc from that. If you would -as seems to be done -, sort the amount of upvotes for my colleague, you'd get me being 'anomalous' in front of the crowd. On the other hand, as explained above, I do want to upvote almost all stuff some of my colleagues put on here for (I believe) the right reasons: they are questions I consider good and interesting. It's just that I know of all their questions (as they tell me about them), which obviously isn't the case for a random user. So what is the deal?  When is upvoting content from one user frowned upon? Would my usecase be in danger of being a (what I consider 'false') positive for the fraud-detection? (and would you agree with that or not) How to prevent this false positive (if you agree with me it is one, otherwise this is a moot question) -> As noted in the comments: I'm not looking for tricks, so an answer could be "don't vote for your colleagues". I agree that there should be no to 'tricks' around that could be used for real fraud of course


I started by creating a new file, then manually moving it, and then modifying it. It's both a new and removed file, according to Git. Is there a way to make Git handle it like a file transfer?

I've moved a file manually and then I've modified it. According to Git, it is a new file and a removed file. Is there any way to force Git into treating it as a file move?


I was doing a bit of math when I came across logarithmic series. I have no idea from where they come from. They seem so unrelated, that I have no intuition behind them at all. So, can anyone prove that $\displaystyle\sum_{n=1}^{\infty}\frac{(-1)^{n+1}x^{n}}{n}=\ln(1+x)$   $\forall -1<x\leq1$ or atleast point me in the right direction?

Compute the taylor series of $\ln(1+x)$  I've first computed derivatives (up to  the 4th) of ln(1+x)  $f^{'}(x)$ = $\frac{1}{1+x}$  $f^{''}(x) = \frac{-1}{(1+x)^2}$ $f^{'''}(x) = \frac{2}{(1+x)^3}$ $f^{''''}(x) = \frac{-6}{(1+x)^4}$ Therefore the series: $\ln(1+x) = f(a) + \frac{1}{1+a}\frac{x-a}{1!} - \frac{1}{(1+a)^2}\frac{(x-a)^2}{2!} +  \frac{2}{(1+a)^3}\frac{(x-a)^3}{3!} -  \frac{6}{(1+a)^4}\frac{(x-a)^4}{4!} + ...$  But this doesn't seem to be correct. Can anyone please explain why this doesn't work?  The supposed correct answer is:  As $\ln(1+x) = \int (\frac{1}{1+x})dx$ $\ln(1+x) = \Sigma_{k=0}^{\infty} \int (-x)^k dx$


I have a fiddle here:  - but probably someone can advise just by looking below.  <button type="button" id="allocate">Calc</button>   $('#allocate').click(function () {      val1 = 25.00;      val2 = 16.37;      val3 = val1-val2;      alert(val3);  });   25 - 16.37 = 8.63 - however, the alert for val3 = 8.62999999999  Why is it not accurate?  Thank you,  Mark

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


I need to design an onscreen keyboard for a touch device and wondering if there are any standards to follow especially pertaining to key sizes?

There was a not so recent blog post about the ideal button size of touch screen control sizes (sorry there is no link, the website is now a spam trap) that was based on the  form the MIT touch lab that gives some measures of the size and sensitivity of the finger. If found that averages for finger pads are between 10–14mm and fingertips are 8–10mm. This would make 10mm x 10mm a good minimum touch target size.  As the author of the blog pointed out, this ideal contact size is much larger than the suggested size for Windows and Apple devices that is in their design guides. I am wondering why there is such a difference, and whether it makes more sense to increase the size of controls on touch screen applications, or if this is not really a usability issue at all? Also, it seems that many mobile websites and apps seem to completely ignore these principles. I am sure the screen size poses a limitation to how big the interface controls can be, so is this simply a trade-off between being able to fit in as much information versus how easy it is to interact with the control? It feels as if the stylus is not something that is in much use. A similar question has been raised on the minimum/smallest size that you can get away with, but I would consider this to be a different question to what the optimum size should be, because the smallest size accommodates the minimum usability requirement, whereas the optimum size caters for the best usability requirement. Archived link of the blog (original domain shows spam)  And here is another reference it to (just to show that it is not the problem with the link but the website () UPDATE #1: another new reference that has a very precise figure of a minimum of 44 x 44 points, not sure how it is derived exactly but interesting (). Read Section 2. Provide Large Clickable Elementss. UPDATE #2: another reference, this time from  citing touch target size to 9 mm square or greater (48x48 pixels on a 135 PPI display at a 1.0x scaling plateau). They also suggest avoid using touch targets that are less than 7 mm square. UPDATE #3: something from the  that I referenced recently citing 44 x 44 points. UPDATE #4: NN/g has published an article on  and the information/conclusion remains unchanged. UPDATE #5 A really nice write-up on the need to enhance the  of common UI elements, citing the  that the "minimum target size for touch or mouse should be 44×44 pixel" (2.5.5 - Target Size - Level AAA).


Why isn't force $F=m\vec v$ instead of $F=m\vec a$? If I'm standing in a wind that's blowing at a steady 100 mph, would that not impart a force on me?

I was confused with this equation like why force is equal to $ma$ and not $mv$? Then I read the same question here on stack exchange, it's answers almost made sense but I still can't visualise the situation where a thing is moving at a constant velocity, would it then have no force? But if I think this scenario in my head, it would definitely have force when it hit something. So I wonder if I am mis-associating the terms in the equation?


Among songs from Wee Sing for Baby, there is a song “To Babyland”  The lyrics begin as:      How many miles to Babyland?   Anyone can tell: Up one flight, to the right.   Please to ring the bell”   I am not an English native and I think the lyric is right grammatically because it is written by English native. But I don’t know why “please to ~~” is used. I have learned that “please ring the bell” is right.   And on more question. “up one flight” - here “flight” means “floor”?? (a dictionary says) Is the 2-3rd line sentences mean “ If you go up one floor and go to the right, you will find a door and you should ring the bell on the door.”?? Do I understand well??  Thank you in advance.

I have been around on Twitter for awhile and I regularly find people using "Please to retweet this" or "Please to help me", etc. Is this proper English? I do not think prefixing the infinitive form with a 'to' is necessary here at all.


I have a global variable at the top of my .py file. When I tell my function to do some action on it, the interpreter gives me a statement that suggests that I am talking about a local variable that has been not established.   I'm using Python 3.7.3 and Win 10. The program is supposed to be a Tic Tac Toe game played in console.  Basically, I am lost. The variable is clearly defined, the function is referring to it, yet Python does not see it. I do not know what to do, it's a very simple program and it is not working. I really do not know what to do, from what I have seen on the Net nobody, either in Google or there had a similar problem (that I am aware of, obviously).  # some other variables, all at the top of file, before anything else  turn = 1  # some functions referring to the above variables, all are working  # the function that is "blind"  def changeboard():     if turn % 2 == 1:         t = input (f"Where to put your {p_o_tile}, player one?")          changetile(t, p_o_tile)         turn += 1     else:         t = input(f"Where to put your {p_t_tile}, player two?")          changetile(t, p_t_tile)         turn += 1   The error I get:   Traceback (most recent call last):  ...  File "C:\Users\Szymon Brycki\Desktop\Python Notes\TicTacToe3.py", line 85, in changeboard  if turn % 2 == 1:   UnboundLocalError: local variable 'turn' referenced before assignment  Basically, the function should rotate between players depending on if the turn counter is even or odd. The player who is currently pointed at by the function should tell the game which tile to change into an "x" or "o" Just that. It's really simple and I really cannot guess why it is not working.

How can I create or use a global variable in a function?  If I create a global variable in one function, how can I use that global variable in another function? Do I need to store the global variable in a local variable of the function which needs its access?


I wrote an if statement like:  if word in vocab:     print word   However, I also would like to know the matched word index in vocab.   Is there any way in Python can do this?  I just come up a solution that use vocab.index(word) to get the index, but this way go through the array twice (one in if statement, one call index()). I wonder there should be more efficiency method.  Thanks.

Given a list ["foo", "bar", "baz"] and an item in the list "bar", how do I get its index (1) in Python?


I'm trying to solve the following exercise. Let $a$ and $b$ be relatively prime integers, and $i^{2}=-1 .$ Prove that the natural map $\mathbb{Z} \rightarrow \mathbb{Z}[i] /\langle a+b i\rangle$ induces an isomorphism of $\mathbb{Z} /\left(a^{2}+b^{2}\right) \mathbb{Z}$ with $\mathbb{Z}[i] /\langle a+b i\rangle$. And I'm totally lost. How should I proceed? I have a feeling that I should use the universal property, and take the quotient by the kernel of the natural map. This would induce an isomorphism with the image of the natural map. But I don't know what the kernel would be, and I honestly don't know how to work with rings like $\mathbb{Z}[i] /\langle a+b i\rangle$. Would anyone have a rigorous (and readable!) explanation?

I used this isomorphism today but now I'm having trouble justifying it. The norm function isn't additive so I can't come up with a ring isomorphism to prove the following:     For any $\,a+bi\in\Bbb Z[i],\,\gcd(a,b)=1$, we have a ring isomorphism   $$\Bbb Z[i]/\langle a+bi\rangle\,\cong\Bbb Z/(a^2+b^2)\Bbb Z=:\Bbb Z_{a^2+b^2}.$$   Could someone show me an isomorphism between these rings to prove this?


Some users have suggested  question and answer, but that asks for an exploit, while I am asking for a way to not encounter this in the first place.  Ok, so we all know the infamous words, "too expensive". I think everyone who has played Minecraft knows what these words mean, and for those who don't, I'd advise you to try and not hit those words, because it makes your life harder. So I was looking around the Internet, and I found out that the anvil hits a certain level cap. And I'm trying to enchant my bow, but I don't know how to avoid those words. Is there a certain way to enchant a weapon so it doesn't become "too expensive"? For those players who don't know what "too expensive" means, it's when you hit a certain upgrade cap (I don't really know what it's call, so ima call it upgrade cap) on an anvil. So when you use an anvil, each time you enchant a weapon of your chose, the XP requirement will keep getting higher until you hit the "too expensive mark. Even if you have enough XP, it will still say "too expensive", so enchant you gear WISELY.

Many of the various items have a list of enchantments that would be ideal. For instance, I might want Infinity, Power, Flame, and Punch all on a bow... and at the highest levels. Barring incredible luck, I will never get those with an enchantment table.  I can enchant books until I find those spells, and add them to the bow with an anvil. However, at some point (I haven't yet figured out how many times) it will no longer allow you to add enchantments to an item, saying that it's "too expensive". There is a hidden counter that is incremented every time, and once this goes past a threshold you can never add more magic (though, I've read in places you can continue to repair the item at great cost indefinitely... not clear if that's true or not).  This counter is cumulative, such that if you combine two items' magic into a single item, that won't sidestep the limit.  However, I've only just caught on that one can also combine two books. I can take two Power I books, and make a single Power II book. And I can take two of those, and get it up to Power III, and so on, but also have two spells combined in a book.  If I do this until I get all the magic I need onto a single book (or even just two or three books, supposing the books max out), will I get to the point where the books will no longer combine with the item because it's too expensive? Or are books exempt from the cumulative counter thing? It would suck to spend so much time and effort to get a powerful book and discover that it can't actually be used on anything.  Also, is it true that you can indefinitely repair, as long as you have the repair material and are at level 39? Or is that a misunderstanding of the rules (or maybe just an earlier version of the game and it no longer works like that... I'm on 1.8.9)? Does that only work for those items that can be repaired with diamond/iron, or will it work for fishing rods and bows as well?


It would be nice if I could filter my feed according to the sites I'm interested in. I can select what site to look at. I can select a list of sites to be included in the menu. But the feed continues to send me Qs from all sorts of sites, including many I have no interest in following.

I am a registered user in ,  and several other sites, only because I had to ask 1 or 2 questions. In general, I have no interests in these sites, so I don't want to see them on my Feed. Is it possible to hide them somehow?   For now, I want to see only 4 sites (could be meta or non-meta) on my Feed. Notifications are not an issue, because I normally don't get any notifications from those not-interested-in-sites; I rarely participate there.


The Yoast SEO plugin is great, but it seems to appear in more places then wanted (columns, custom post type pages, etc.). I want to remove this option because as it stands even when I ignore the fields if I save my custom post type I get several fields added to my database.  _yoast_wpseo_google-plus-description _yoast_wpseo_linkdex _yoast_wpseo_opengraph-description _yoast_wpseo_redirect _yoast_wpseo_canonical _yoast_wpseo_sitemap-html-include _yoast_wpseo_sitemap-prio _yoast_wpseo_sitemap-include _yoast_wpseo_meta-robots-adv _yoast_wpseo_meta-robots-nofollow _yoast_wpseo_meta-robots-noindex _yoast_wpseo_metadesc _yoast_wpseo_title   So the goal is to not have them appear on the admin page at all so that they are not entered as values. Thanks in advance for any help with this

Yoasts SEO plugin adds a metabox to the post edit screen. I'm trying to remove this for users who aren't editors or above.  I've tried putting a remove_meta_box call in on admin_init, trying to remove the action on $wpseo_metabox but to no avail.  How do I remove this metabox without requiring user intervention (the user should never know the metabox existed, so clicking on screen options is not an option )


In the movie Logan, they hint at the fact that the X-Men are no more because something happened. While initially Professor-X asks Logan "What did you do?" later he's seen repenting doing something that may have caused the death of the X-Men.   What is it that happened to the X-Men according to the film Logan?  PS: I know how the story goes in the original comic - Old Man Logan. While there they explain what happens exactly, I'm interested in knowing what happened to the X-Men in the film world of Logan.

Throughout the course of Logan, it's obvious that Professor Xavier is having issues controlling his powers, and at the end of the movie, just before      X-24 kills him   he claims to "remember" what he did and expresses regret. We also hear about an incident in Westchester that killed several mutants, that sounds like Xavier may have been involved. Is Xaiver the reason there are no more mutants? Is that why he's sorry, because he knows he killed them all?


I have two global polygon shapefiles in WGS84, and I would like to generate spatial stats on the % area of one shapefile that is overlapping the other. I understand that geometric calculations such as area require a projected coordinate system, but I am wondering if that is necessary in order to calculate % overlap.  I would like to avoid projecting, as these are large datasets. However, in the event that I do have to project, are there recommended projections for running geometric calculations on global data? I've only ever worked with local / regional projections. I am using ArcMap 10.2.

I have two different layers (Layer 1 and Layer 2) both made up of many thousands of polygons. Many of the polygons in Layer 1 overlap to differing degrees with Polygons in Layer 2. I need to calculate how much (percentage) each polygon in Layer 1 overlaps with the polygons in Layer 2.


In the output of less my.pdf,  a string image    not available appears multiple times, for example:  ... Lastly, what remains to ^L image    not available ^L     Implementations and Systems         I would like to grep the string in the pdf file, for example, by pdfgrep. But pdfgrep  -ni "image not available" my.pdf doesn't find anything. What shall I do then?  Related question: Since pdfgrep has similar user interface to grep, how does grep handle a pattern which spans more than one lines?  Thanks.

I find the page numbers of a multiline pattern in a pdf file, by  and     $ pdfgrep -Pn '(?s)image\s+?not\s+?available'  main_text.pdf  49: image    not available 51: image    not available 53: image    not available 54: image    not available 55: image    not available   I would like to extract the page number only,  but because the pattern is multiline, I get  $ pdfgrep -Pn '(?s)image\s+?not\s+?available'  main_text.pdf | awk -F":" '{print $1}' 49    not available 51    not available 53    not available 54    not available 55    not available   instead of  49 51 53 54 55   I wonder how I can extract the page numbers only, regardless if the pattern is multiline? Thanks.


~# sudo apt-get install tor Reading package lists... Done Building dependency tree        Reading state information... Done Package tor is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'tor' has no installation candidate   Can someone please help?

I tried to install Tor on my new version of Ubuntu, but it seems that Tor is not available in the repositories.  How else can I install and use Tor?