For example, when administering lethal injections, there are usually two buttons (each on its own harmless) that both need to be pressed by a person before it is administered.  Is there a name for such a system? I'm talking about a system that requires two people to interact to trigger the event, not a system that absolves one of them of guilt.
I am trying to think of what the name of the word/phrase is for when: An important task (not a difficult one, but a mission critical one) is at hand and instead of one person being assigned to it, a group takes on the responsibility to mitigate any consequences happening to one person in case something goes wrong and also to prevent a mistake or malicious intent occurring from one persons doing. (NOT because the task is big and needs to be divided in a group.) E.g.   Two different people needing to turn a key each in a device simultaneously to launch a missile.  Group of people tallying up votes for an election in case one of them were bridged to rig the outcome.
Label callouts in QGIS Has anyone been using callout labelling with QGIS, either trunk or stable?   Used for clustered points. That means the point stays where it is, the label maybe moved if required and a leader (plain or pointed) shows the linkage between the label and the point.   How could I do it (you know what I mean, no coding....)? For all square matrices $A$ and $B$ of the same size, it is true that $(A+B)^2 = A^2 + 2AB + B^2$? The below statement is a true/false exercise.  Statement: For all square matrices A and B of the same size, it is true that $(A + B)2 = A^2 + 2AB + B^2$.  My thought process: Since it is not a proof, I figure I can show by example and come to a valid conclusion based on such example.  My work:  Come up with a square matrix A and B let both be a 2 by 2 matrix(rows and cols must be same).  Matrix $A$:  $A = \begin{array}{ccc} 3 &amp; 5 \\ 4 &amp; 6 \\ \end{array} $  Matrix $B$:  $B =  \begin{array}{ccc} 5 &amp; 8 \\ 9 &amp; 4 \\ \end{array} $  $A + B =  \begin{array}{ccc} 8 &amp; 13 \\ 13 &amp; 10 \\ \end{array}$  $(A + B)^2 =  \begin{array}{ccc} 233 &amp; 234 \\ 234 &amp; 264 \\ \end{array}$  $A^2 =  \begin{array}{ccc} 29 &amp; 45 \\ 36 &amp; 56 \\ \end{array}$  $(AB) =  \begin{array}{ccc} 60 &amp; 44 \\ 74 &amp; 56 \\ \end{array}$  $2(AB) =  \begin{array}{ccc} 120 &amp; 88 \\ 234 &amp; 112 \\ \end{array}$  $B^2 =  \begin{array}{ccc} 97 &amp; 72 \\ 81 &amp; 88 \\ \end{array}$  $A^2 + 2AB + B^2 =  \begin{array}{ccc} 246 &amp; 205 \\ 265 &amp; 256 \\ \end{array}$  Based my above work, the answer is false.   Is there another way to approach the problem? It seems like a lot of work needed to be done for a true/false question which raised my suspicion about whether there is a better way to look at the problem. EXR Transparency Border with bloom and glare was solved by saving to EXR, however when loading that EXR into the VSE over a background a dark border appears around the transparent text that cuts through the glare and bloom. I'm using Blender 2.92.0. EEVEE with bloom Render layers -&gt; Glare -&gt; Composite (with &quot;UseAlpha&quot; checked) Because of past conflicts, I don't believe my advisor will write me a good LOR for postdoc positions. What should I do? Make ubuntu usb bootable on windows Possible Duplicate:             I know there are a lot of tools to create a bootable usb for ubuntu with windows.  But I'm sure, that there was a possibility in the ubuntu installation directory. I used it some time ago, but I can't find it anymore :(  I think it was a .exe, or a .bat, any case a cmd window has opened, some things were executing and the usb was bootable. And it was in the ubuntu directory!  Is there still the possibility to do that? Does that file exist? I unfortunately can't remember. Why I can't edit "Your Communities" list in stackexchange.com and Area 51? I can edit &quot;YOUR COMMUNITIES&quot; in the upper left drop-down menu from any of my communities: (e.g. )    But in  portal there's no &quot;edit&quot; link:    Why is that and how can I edit the list in  portal? What is the equivalent of Windows System Properties or Device Manager? I am new to Ubuntu. In Windows, if I want to know my system properties/configuration, I can see it by going to Control Panel and clicking on the System icon. I can also get a detailed list of the hardware detected/installed by going to the Device Manager.  What are the equivalents of these features in Ubuntu, where a user can see his or her system properties and hardware configuration, like RAM, CPU/processor, hard disk capacity, etc.?    Example of Windows System Properties: How do "pet" Walkers help ward off other Walkers? In both the comics and the show, Michonne first appears with two walkers that she essentially keeps as pets.    The comics sort of half-explain this - as per :     She notices walkers don't attack one another and hacks off the arms and lower jaws of Mike and Terry. She chains them up by their necks to use them as escorts for an escape that was successful.   In , we see that even if they still sort of smell like Walkers, the Walkers can smell/detect the living and will attack.  In ,      We see Andrea effectively making a new "pet" so that she can use to deter the Walkers that she comes across on her trip to the prison. Along the trip, she is shown to come within close range of Walkers, but they give her space when she points the "pets" in the right direction.   Why would the Walkers not just attempt to go around the "pets"? What about them creates an effective protective barrier? I really like the new sidebar. With the new top bar eliminating the &quot;Hot Questions&quot; area there, I think this is the perfect place for it. One-click access to time-wasting questions about topics I may or may not have an interest in. Seriously, it's a procrastinator's dream come true. The only suggestion I can add is to extend it. I assume the &quot;hot&quot; algorithm can spit out more than 12 questions, and since we now have a huge amount of room for it(without being restricted to a weird drop-down scrollbox), why not show more? If there's something else planned for that spot, disregard. At a minimum, the title could link to the , as ShaWizDowArd suggested in comments. I've been using SE for a couple years now, and I've never seen that page, so it would add visibility there.    Update: They added a link! Just noticed this, I'm pretty sure it wasn't there yesterday. When you click it, it loads 12 more. At the moment, the link disappears once clicked, so you can see a total of 24 here now. Not a link to the full list, but better: The  lists various combinatorial objects that are described by them. I posit that there might be bijections between these various combinatorial objects. For some of them (like Dyck paths, correctly matched parentheses and paths from the bottom left to top right of a $2n \times 2n$ grid) they are quite obvious.   I was then trying to find a bijection between the number of Dyck words and the number of ways of associating $n$ applications of a binary operator to $n+1$ items (third one on the list). I attempted to do this for a simple case ($n=3$ which is the example provided in the Wikipedia article). However, couldn't find one after multiple hours. Is it reasonable to expect such a bijection will exist? If so, how do we go about finding it?    EDIT: In addition to the very nice answer by @Marc, the following page also helped me see the bijection:   "Let $P$ be the Dyck path and $f(P)$ be the binary tree. If you go up in the Dyck path, create a left child. Otherwise, go up one vertex until creating a new right child is possible and create one."    Here is one of my attempts:   Number of Dyck words with length $2 \times 3$ is $\frac{6 \choose 3}{4} = 5$. They are:  hhhttt; hhthtt; hhttht; hthhtt; hththt  And the number of applications of a binary operator among $3+1=4$ factors is:  ((ab)c)d;     (a(bc))d;     (ab)(cd);     a((bc)d);     a(b(cd))  Both combinatorial objects have been arranged in a way that there is some kind of ordering between them. For the Dyck words for example, if h equals +1 and t equals -1, then the order is lexicographical from the left to the right of the cumulative score along the sequence.   Now, the first and last characters of the Dyck words are always h and t respectively. So, we can ignore them. We are left with:  hhtt; htht; htth; thht; thth  I tried to start from the left of the sequence abcd and if I see 'h', merge the character with the one to its right. This approach didn't produce a valid mapping from the third Dyck word to the third binary operator precedence order. long long implementation in 32 bit machine As per c99 standard, size of long long should be minimum 64 bits. How is this implemented in a 32 bit machine (eg. addition or multiplication of 2 long longs). Also, What is the equivalent of long long in C++. $\{a_n\}$ be a sequence such that $ a_{n+1}^2-2a_na_{n+1}-a_n=0$, then $\sum_1^{\infty}\frac{a_n}{3^n}$ lies in... Let $\{a_n\}$ be a sequence of positive real numbers such that   $a_1 =1,\ \  a_{n+1}^2-2a_na_{n+1}-a_n=0, \ \ \forall n\geq 1$.   Then the sum of the series $\sum_1^{\infty}\frac{a_n}{3^n}$ lies in...  (A) $(1,2]$, (B) $(2,3]$, (C) $(3,4]$, (D)$(4,5]$.   Solution attempt:   Firstly, we figure out what $\frac{a_{n+1}}{a_n}$ is going to look like. We get, from the recursive formula, $\frac{a_{n+1}}{a_n}=1+\sqrt{1+\frac{1}{a_n^2}}$ (remembering the fact that $a_n&gt;0$, the other root is rejected).   We know that, if $\lim_{n \to \infty}\frac{a_{n+1}}{a_n}&gt;1$, then $\lim a_n \to \infty$.   Further, $(a_{n+1}-a_n)= \sqrt{a_n(a_n+1)}&gt;0$. (Again, the other root is rejected due to the same reason).   Hence, $(a_n)$ increases monotonically.   Therefore, the largest value of $\frac{a_{n+1}}{a_n}$ is approximately $1+\sqrt{1+\frac{1}{1}} \approx 2.15$  Now, the sum can be approximated as $\displaystyle\frac{\frac{1}{3}}{1-\frac{2.15}{3}} \approx 1.3$ (In actuality, $\mathbb{sum}&lt; 1.3$).  So, option $(A)$ is the correct answer.   Is the procedure correct?   I have been noticing a handful of this type of questions (based on approximations) lately, and the goal is to find out where the sum / the limit of the sequence might lie.   Is there any "definitive" approach that exploits the recursive formula and gives us the value, or does the approach varies from problem to problem? Could you please help me computing    $\Big\lfloor\underbrace{\sqrt{2017+\sqrt{2017+...+\sqrt{2017}}}}_\text{2017 roots}\Big\rfloor$? Do superheroes/villains like Quicksilver or Flash with super speed get tired due to running? I am including pages using Ajax but I also need to include their respective javascript files, which requires removing the previous javascript files from memory at the same time.  How can I unload the currently-loaded javascript files (as well as their code in memory) so that I can load the new page's files? They will more than likely conflict, so having multiple independent files' javascript files loaded. supervisor field on the page of the title with Beamer I am editing a presentation of a research project, I am wondering if there is a field for "supervisor" on the page of the title, for instance \supervisor(which actually does not work)... If not, where do people conventionally add it? I really like the , where certain questions from the Stack Exchange Network are presented, along with a hotness rating that is described as &quot;arbitrary&quot; in its tooltip. Such questions also appear randomly on the sidebar on sites across the network, under the heading &quot;Hot Network Questions&quot;. How do these arbitrary hotness points work, and how are they used to select questions to appear in those lists? Why won't my taskbar display on my secondary monitor? On my secondary monitor (currently using Windows 10), my taskbar will barely show up. I've tried adjusting the resolution to lower ones (it recommends 1920x1080) and it doesn't do much. Is there a way to adjust the taskbar so I can see it?  That is about what I see. I could make it bigger via Snipping Tool and see my entire desktop on the picture but not normally. Add UI elements to UIScrollView? Upon the risk of being down voted as no MWE is present, but at the moment just trying to get some pointers. I updated my MiKTeX installation to the newest available version at the moment (MiKTeX-pdfTeX 4.1 (MiKTeX 20.12)) and now I get an error while building my documentation: Appendix D. (../html/examples/group/latex/refman_doc.tex (../html/examples/group/latex//gro up__group1.tex) [243] ! I can't write on file `../html/examples/group/latex//group__group2.aux'. \@include ...mmediate \openout \@partaux &quot;#1.aux&quot;                                                   \immediate \write \@partau... l.3 \include{group__group2}  Please type another output file name ! Emergency stop. \@include ...mmediate \openout \@partaux &quot;#1.aux&quot;                                                   \immediate \write \@partau... l.3 \include{group__group2}  *** (job aborted, file error in nonstop mode)  some small background:  Started normally with pdflatex doxygen_manual.tex in here is the statement: \subinputfrom{../html/examples/group/latex/}{refman_doc} and in this file again: \include{group__group2} as far as I know the disk is not full and the protections of the files and directories are OK as well  It looks like that now an attempt is made to write to the directory ../html/examples/group/latex/ whilst in the past the file was written to the current directory. I already tried -shell-escape and -enable-write18 (as well as --shell-escape and --enable-write18) but to no avail.  Any known changes in respect to writing the aux file? Any hints  edit I asked another question () with the details and MWE but that was closed with the reason that it was a duplicate of this one ... So I'm adding the information now here: In the question  asked about the problems I encountered due to an update of my MiKTeX distribution, but didn't take the time (at that moment) to create a MWE, so it didn't attract much response. I have the directory structure:  main  manual.tex   group  group__group2.tex refman_doc.tex    manual.tex \documentclass{book} \usepackage{import} \usepackage{hyperref}  \begin{document} \subinputfrom{../group}{refman_doc} \end{document}  group__group2.tex \hypertarget{group__group2}{}{The Second Group}  refman_doc.tex {Module Documentation} \include{group__group2}  When running in the directory main the command pdflatex manual.tex I get the error: ... (../group/../group/refman_doc.tex [1{C:/Users/User/AppData/Local/MiKTeX/2.9/pdf tex/config/pdftex.map}] ! I can't write on file `../group//group__group2.aux'. \@include ...mmediate \openout \@partaux &quot;#1.aux&quot;                                                   \immediate \write \@partau... l.2 \include{group__group2}  Please type another output file name:  but in a non interactive mode (the usual way to run. i.e. with \batchmode) one doesn't get an opportunity to specify the file and the generation crashes. As written in the original question adding options like -shell-escape and / or -enable-write18 didn't help.  Is there a solution for this problem?  edit 2 I did some further test. I replaced the \subinputfrom with an \input statement, although this worked for the limited example above it didn't work for my larger codebase as here (again just a limited view) we have in the refman_doc.tex {Module Documentation} \input{group__group1} \include{group__group2}  with the contents of group_group1.tex similar to group__group2.tex and the file is also parallel to group__group2.tex. This results in the error: (manual.out) (manual.out) (../group/refman_doc.tex  ! LaTeX Error: File `group__group1.tex' not found.  Type X to quit or &lt;RETURN&gt; to proceed, or enter new name. (Default extension: tex)  Enter file name: ! Emergency stop. &lt;read *&gt;  l.2 \input{group__group1}  !  ==&gt; Fatal error occurred, no output PDF file produced!