I have been trying all the day to understand the Riemann Surface of the $\sqrt z$. I Can not understand . Can anyone help me to understand how this picture is Riemann Surface of $\sqrt z$. The other questioner did not ask this question. He already could visualize my question's answer. So I request you not to try to block this question. This is the only source from where I get help.   Please read that question.    Explanation in simple words will be highly appreciated.

I'm looking at the Riemann surface of $f(z) = z^{1/2}$ so the set $\{(z,w) \in \mathbb{C}^2 : w^2 = z \}$. I understand that the point of the riemann surface is to understand this multi-valued function.  Now I visualise this as taking two copies of the complex plane both with a slit in them (negative real axis say) and then I put them on top of each other, flip the top one and then sort of join them up along the slit and that's fine and I can see that that will form some surface where the local coordinates are given by projection onto the z or w axis. But here I am just dealing with the domain of the function $f(z)$.  My difficulty is when I think of the analogous situation with say $\{(x,y) \in \mathbb{R}^2 : y^2 = x\}$ this "surface" is just a line and I can see how given a point on this "line" we have an associated pair $(x,y)$. Now when I look at the Riemann surface described above all I see is the domain of the function $f(z)$ I can't see how each point of the surface is in anyway related to a pair $(z,w)$.  I realise this is quite a vague question and I am struggling to put my frustration with this concept into words - I hope this makes sense! I've now added a (terrible) diagram which may help to illustrate my issue:    Thanks


For a project I have been contracted to work on a collaborating Chinese programmer has provided some software to simplify some tasks.  I am unaware whether this software package contains malware or not.  I would like to run this software and still protect my computer.    While I am not a Ubuntu noob I am newish to the OS.  I understand that under Windows I run the risk of infecting my entire computer.    I am wondering what would be the best practice to protect my computer, private information, and data. Can I create a new user account and install the software with that account?  Will that only protect the information on my primary login but not the computer as a whole?  Note - the software involves running from ./softwarename.sh.  The software is provided as a complete package and I do not have to download it (or anything) from the internet.  I do not have to install any packages, third-party libraries etc.  All I need to do is run a remote license manager (rlm) via a shell script and start the software from a shell script.

I want to run small untrusted programs, but restrict them from accessing any files outside of their folder, network access, and everything else that they don't really need. What is the simplest way to achieve this?


I just became a Canadian citizen and will travel with Canadian passport to USA. Does ESTA need to be updated with this information?

This is about entering the USA. I have   Hungarian citizenship with a 10 year B1/B2 visa in my passport I got before Hungary became part of the VWP. Real soon now, I will become a Canadian citizen (my oath is on April 5th) and will get a passport.   Since I, as a person, have a visa, am I obliged to enter into the USA with that? Or can I just forget it and use my Canadian passport? I know I could do whatever I want if I didn't have a visa but with that in the picture I am unsure.  describes a number of situations but not mine.


for root, dirs, files in os.walk(rawsource):     print("root is {}".format(root))     try:         os.system("cd {}".format(root))         print("root in the try: was {}".format(root))         print("pwd is {}".format(os.system("pwd")))  I am not sure why: os.system("cd {}".format(root)) is failing. Meaning, it doesnt appear to properly be changing directory cd to the value of root, but instead appears to be staying at /Users/user/Project But, print("root in the try: was {}".format(root)) is properly outputting the proper directory within the loop. This is the output: pwd is 0 root is /Users/user/Project/src/main/gateway root in the try: was /Users/user/Project/src/main/gateway /Users/user/Project  Why might this be happening?

How do you call an external command (as if I'd typed it at the Unix shell or Windows command prompt) from within a Python script?


I'm currently trying to create a program that generates random numbers between 1 and 45 with no duplicates. My program works when I run it without the else statement whenever a duplicate comes up it inputs the number 0, when I use the else statement the function breaks. I want to display random numbers between 1 and 45 however the variable size must dictate the size of the array. For example random integers between 1 and 45 with an array size of 35.  using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;  namespace RandomArray { public class RandomArrayNoDuplicates {     static void Main(string[] args)     {         int size = 45;         int[] noDuplicateArray = new int[size];         noDuplicateArray = InitializeArrayWithNoDuplicates(size);         DisplayArray(noDuplicateArray);         ExitProgram();      } //end Main     static Random rng = new Random();      /// <summary>     /// Creates an array with each element a unique integer     /// between 1 and 45 inclusively.     /// </summary>     /// <param name="size"> length of the returned array < 45     /// </param>     /// <returns>an array of length "size" and each element is     /// a unique integer between 1 and 45 inclusive </returns>     ///     static void ExitProgram()     {         Console.Write("\n\nPress any key to exit program: ");         Console.ReadKey();     }//end ExitProgram      public static int[] InitializeArrayWithNoDuplicates(int size)     {     int number;     int[] noDuplicates = new int[size];          for (int i = 0; i < size; i++)         {             number = rng.Next(1, size);             if (!noDuplicates.Contains(number))                 noDuplicates[i] = number;            // else            //     i--;         }         return noDuplicates;      }     static void DisplayArray(int[] noDuplicates)     {     foreach (int element in noDuplicates)         {             Console.Write("\t" + element + "\n");         }     } } }   The issue lies in this bit of code:  public static int[] InitializeArrayWithNoDuplicates(int size)     {     int number;     int[] noDuplicates = new int[size];          for (int i = 0; i < size; i++)         {             number = rng.Next(1, size);             if (!noDuplicates.Contains(number))                 noDuplicates[i] = number;            // else            //     i--;         }         return noDuplicates;   but I'm unsure how to fix it. I would prefer to use the random.next function rather than using enumberable approach. Thanks

What is the best way to randomize the order of a generic list in C#? I've got a finite set of 75 numbers in a list I would like to assign a random order to, in order to draw them for a lottery type application.


Can someone tell me how to detect if "specialword" appears in an array? Example:  categories: [     "specialword"     "word1"     "word2" ]

What is the most concise and efficient way to find out if a JavaScript array contains a value? This is the only way I know to do it: function contains(a, obj) {     for (var i = 0; i < a.length; i++) {         if (a[i] === obj) {             return true;         }     }     return false; }  Is there a better and more concise way to accomplish this?


I'm looking for some script (program) which would help in editing LaTeX code. Usually I have a mess in my .tex code, so it would be good if the script could align tabulars and so on. It would also be nice, if it allows editing code (for example replace every $$ with \begin{equation}...\end{equation} and vice versa).  Is there any program which is doing such a thing? It can be program, or a plugin of texstudio or a bash (python) script as well. However I don` want to change my editor (if it is of course possible).

I'm looking for a LaTeX code sniffer and/or code beautifier, because I'm creating a CI server for my LaTeX books and I wanted a few things. :D


I have installed Ubuntu 17.04 on my spare SSD and everything went smoothly but when starting up, it takes forever to get to the Login Screen.  I saw  and I too have the encryption enabled but I don't understand the answer in it. I checked the links provided but I don't think there's a solution in them.

I reinstalled Ubuntu 17.04 Desktop 64-bit UEFI on my Laptop on a harddisk.  Laptop: Intel Core i5-5200U, Intel HD Graphics 5500, 16 GB Ram.  Booting takes ~120 seconds (from pressing the powerswitch to loginscreen, with Ubuntu 16.04.2 on a ssd it takes less than 20 seconds).    $ systemd-analyze blame           5.187s dev-sdb2.device           4.268s ModemManager.service           3.138s accounts-daemon.service           2.852s fwupd.service           2.688s grub-common.service           2.421s irqbalance.service           2.367s apport.service           2.360s gpu-manager.service           2.269s NetworkManager.service           1.641s thermald.service           1.632s polkit.service           1.567s rsyslog.service           1.336s keyboard-setup.service           1.241s lightdm.service           1.240s plymouth-quit-wait.service           1.231s speech-dispatcher.service           1.172s udisks2.service           1.159s apparmor.service           1.019s alsa-restore.service            976ms repowerd.service            957ms upower.service            900ms bluetooth.service            821ms systemd-resolved.service            792ms dev-hugepages.mount            792ms dev-mqueue.mount            789ms avahi-daemon.service            755ms sys-kernel-debug.mount            689ms systemd-cryptsetup@cryptswap1.service            663ms systemd-modules-load.service            638ms rtkit-daemon.service            599ms systemd-backlight@backlight:intel_backlight.service            540ms systemd-rfkill.service            511ms systemd-udevd.service            505ms systemd-fsck@dev-disk-by\x2duuid-F685\x2d7079.service            456ms systemd-machine-id-commit.service            455ms openvpn.service            444ms systemd-timesyncd.service            386ms systemd-user-sessions.service            326ms systemd-journald.service            321ms kmod-static-nodes.service            273ms systemd-logind.service            243ms colord.service            239ms systemd-udev-trigger.service            227ms wpa_supplicant.service            199ms networking.service            192ms console-setup.service            191ms systemd-tmpfiles-setup-dev.service            188ms pppd-dns.service            184ms systemd-hostnamed.service            171ms user@1000.service            170ms systemd-localed.service            165ms setvtrgb.service            162ms systemd-tmpfiles-setup.service            131ms dns-clean.service            101ms systemd-journal-flush.service             92ms resolvconf.service             91ms sys-fs-fuse-connections.mount             82ms systemd-sysctl.service             79ms systemd-remount-fs.service             70ms systemd-random-seed.service             51ms ufw.service             44ms systemd-update-utmp.service             42ms boot-efi.mount             37ms snapd.socket             14ms plymouth-start.service             11ms plymouth-read-write.service              6ms snapd.autoimport.service              4ms ureadahead-stop.service              4ms dev-mapper-cryptswap1.swap              3ms systemd-update-utmp-runlevel.service              1ms swapfile.swap     Any ideas?


Regarding road costs in Civ5,  :     Based on experience, it appears that   you only have to pay 1G for each hex   of roads that are inside your   cultural borders. That means that you   don't have to pay to maintain a long   road to a city-state if it goes   through neutral land   Is this correct? Do I only pay for roads that are inside my borders?  (I think this factor is pretty important when settling a new city further off to get a luxury resource, isn't it?)

Playing civilization 5 the game explicitly says roads cost gold to maintain. This is of course a  in the answer to .  However, looking at the income report I do not see a "road maintenance" entry, and comparing with the number of roads I have it really feels that they do not cost 1 gold per tile, which is what I assumed from the game description. Further, I'm pretty sure building a single road tile does not affect my income.  So, do roads really cost gold to maintain, and if they do - how does it work? Is it really 1 gold per road tile, regardless of where that tile is?


Canonical seems to have deleted flash player. Where can i download (from terminal or browser and install myself with sudo) for Ubuntu 14.04 LTS  i uninstalled as some live sport site was not wwortking, then tried :   sudo apt-get install adobe-flashplugin   Error I got :     upgraded, 2 newly installed, 0 to remove and 413 not upgraded. Need   to get 8,958 kB of archives. After this operation, 31.1 MB of   additional disk space will be used. Do you want to continue? [Y/n] y   Err  trusty/partner adobe-flashplugin   i386 1:20170411.1-0ubuntu0.14.04.1   404  Not Found [IP: 91.189.92.150   80] Err  trusty/partner   adobe-flash-properties-gtk i386 1:20170411.1-0ubuntu0.14.04.1   404    Not Found [IP: 91.189.92.150 80] E: Failed to fetch      404  Not Found [IP: 91.189.92.150 80]      E: Failed to fetch      404  Not Found [IP: 91.189.92.150 80]      E: Unable to fetch some archives, maybe run apt-get update or try with   --fix-missing? t@t5:~$

I am using ubuntu 13.10 on evaluation board and my internet is not working. Also i need to install softwares and apt-get install is also not working.  Terminal says :  E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?  source :


Here is the picture of my problem. I cannot boot my laptop and cannot log on to the ubuntu screen. I have serious problems as I have copied the wrong info on the data recovery through Test disk.  What actually happened:  1) Used testdisk and backed up 2 files. 1 file was not imoportant. Now the hard drive space is now completely full. I tried so many sources on Askubuntu and google but still no help.  2) Keep showing black screen with "_" flashing - The link that I uploaded is here.  Please help, cannot sleep until its done. Very important files including family and work is here.  Now my screen keeps blinking:  Thanks

My memory is completely full when I tried following the data recovery and copied the wrong file using command line tool Test Disk. As it was taking so long to copy, I turned it off and I realized I copied the wrong file. Now my laptop memory is now full and lead me to more problems.  I have had similar problems to :       Now my screen keeps blinking:   Can anybody help? Many thanks. Wish you all the best.


I am currently hosting in a data center and paying a very large monthly bill.  We are moving to a new office and I have been toying with the idea of installing a leased line and self hosting.  Public facing bandwidth use currently at:  4 x web servers each peak at 4mbps 1 x web server peak at 25mbps  Total peak output: 41mbps  Why type of leased line would I need considering we want to double usage?  I am currently being quoted in UK Pounds:  100mb over 100mb @ £600/month  Would this be enough bandwidth?

This is a  about  Related:      I have a question regarding capacity planning. Can the Server Fault community please help with the following:   What kind of server do I need to handle some number of users? How many users can a server with some specifications handle? Will some server configuration be fast enough for my use case? I'm building a social networking site: what kind of hardware do I need? How much bandwidth do I need for some project? How much bandwidth will some number of users use in some application?


For what p is the condition number of a given matrix $A$, using the p norm on matrices, minimal?  The condition number on $A$ is given as:  $$K(A,p) = \|A\|_p \times \|A^{-1}\|_p$$  I tried simplifying this further but got nowhere, I feel like I'm missing something. Any help would be appreciated!

I'm solving questions from am exam that I failed miserably, so I would love it if someone can take a look at my proof and make sure I'm not making any gross mistakes.  Question  Let $A$ a symmetric matrix. Which $\rho$-norm minimizes $A$'s condition number: $\kappa(A,\rho)$?  Edit  Well, my solution was clearly wrong. I would love any suggestion or direction for solution you might have.  Thanks! :)


Is there an intuitive explanation for why the complex numbers $(\mathbb{C}$) are algebraically closed, but $\mathbb{R}$ isn't?

I find it curious that Complex Numbers give enough flexibility to be algebraically closed, where the reals, rational numbers do not.  For the reals it is easy to see that they cannot be used to solve equations like $x^2 + 1 =0$.  Geometrically, one can look at the number line as see that any $x$ squared yields a positive number which when added to one cannot get you back to zero.  In the complex case, however, we are working with the plane.  In this case exponents stretch and rotate any given $x$.  It is easy to therefore see in the particular circumstance that if $x=i$ that $x^2$ rotates it to $-1$ which when added to one yields the desired result (i.e. $0$).  So because the Complex Numbers are algebraically closed, I conclude that any polynomial equation with complex coefficients my be solved by choosing one or more $x$'s in the plane and rotating them and stretching them such that they will combine using the given coefficients to produce the RHS.    Question: Why is it that we do not need a larger space than the plane to solve Complex polynomial equations?  I have tried to find a sufficient answer through Google, but was not able.  I also searched M.SE and could not find a sufficient answer.  I am not a mathematician, so I am looking for an intuitive answer if possible.


I want to connect my Dell (Windows 7) to my Acer (Windows Vista) and use them as dual monitors. The screen on my Dell is broken and I can't read anything on it. I tried to hook it up to my television and that didn't work. I found out that I need a VGA to HDMI adapter.  Is it possible to connect my two laptops even though they have different operating systems? Do I need any specific cables? I have three cables but I'm not sure if I can use them. One has two ends that seem like you can use them for the phones or something. Any help is appreciated.

Is it possible to make my laptop's screen act as a second monitor for my desktop computer?


I saw a video In which the girl says I think I can smell the spiritual  As far as I know articles can not be used with adjectives . No?

In this video the girl says I think I can smell the spiritual  As far as I know articles can not be used with adjectives . No?


I'm trying to achieve my dream in drawing useless bullshit. But after learning jQuery in 10 minutes, I ran into the problem that the delay function does not work as it should.      So, I have 500 black small divs with class "luls". The idea is that when you hover over them with a mouse, they light up in a random color, and after a certain time they take back the black color. BUT they NOT.    Take a .  $(document).ready(function() {     $( ".luls" ).each(function(index) {         $(this).mouseenter(function() {             // It's just a random color function, do not focus on it.                            var hue = 'rgb(' + (Math.floor((256-199)*Math.random()) + 200) + ',' + (Math.floor((256-199)*Math.random()) + 200) + ',' + (Math.floor((256-199)*Math.random()) + 200) + ')';             $(this).css("background-color", hue);         });         setTimeout(function() {             $(this).css('background-color', 'black');         }, 1000);     }); });   I tried to use delay() and setTimeout, even mouseover, but it does not work. Need your help.

I have a method that uses the  function and makes a call to another method. On initial load method 2 works fine. However, after the timeout, I get an error that says method2 is undefined. What am I doing wrong here?  ex:  test.prototype.method = function() {     //method2 returns image based on the id passed     this.method2('useSomeElement').src = "http://www.some.url";     timeDelay = window.setTimeout(this.method, 5000); };  test.prototype.method2 = function(name) {     for (var i = 0; i < document.images.length; i++) {         if (document.images[i].id.indexOf(name) > 1) {             return document.images[i];         }     } };


I need help to answer the folowing problem:     Let $F$ be a field, $n\ge 1$ and $G=F^n\bigoplus F^n\bigoplus Mat(n,F).$ That is an element of $G$ has the form $(v,w,X)$ where $v$ and $w$ are n-by-1 vectors and $X$ is $n$-by$-n$ matrix, all with entires in $F$.      Define an operator on $G$ by:      $$(v_1,w_1,X_1)(v_2,w_2,X_2)=(v_1+v_2,w_1+w_2,X_1+X_2+v_1w_2^t)$$      Show that $G'=\left\{(0,0,X), X\in Mat(n,F)\right\}$. Where $G'$ is the derived group of $G$ i.e $G′=\left\{[a,b],a,b∈G\right\}$   I poved the following inclusion:  we need to compute the commutator $[(v_1, w_1, X_1), (v_2, w_2, X_2)]$. Before jumping into the computation it's clearer to first write out the inverses.  We have:  $(v_1, w_1, X_1)^{-1}      = (-v_1, -w_1, -X_1 + v_1 w_1^t)$   and  $(v_2, w_2, X_2)^{-1}      = (-v_2, -w_2, - X_2 + v_2 w_2^t)$  Then  $[(v_1, w_1, X_1), (v_2, w_2, X_2)]$   $= (v_1, w_1, X_1)(v_2, w_2, X_2) (v_1, w_1, X_1)^{-1} (v_2, w_2, X_2)^{-1}$  $= (v_1, w_1, X_1)(v_2, w_2, X_2)(-v_1, -w_1,  - X_1 + v_1 w_1^t) (-v_2, -w_2, - X_2 + v_2 w_2^t)$  The $v$'s and $w$'s all cancel out nicely in the first two coordinates. The third coordinate is some $n \times n$ matrix.  We have just proved that the set of commutators is a subset of the set of all elements of the form $(0, 0, X)$.   So we have shown that   $G'\subset \{(0,0,X)\}$. Please help me to prove the other inclusion. Thanks in advance.


I'm still learning the new 2.8 layout. I screwed up my interface somehow and I can't scroll in / out.   I try doing load startup file, but it resets me back to the default cube.  How can I reset the interface while keeping the model I've been working on ?

Is there a way to open files without changing the UI layout?  Sometimes in older files the layout will be in the old 2.4x style, which can be annoying.  One way would seem to be appending everything in, but that gets tedious with having to do it over again and again for objects, materials, textures, etc.


Someone may have already asked this question, but I was not able to find it.     Prove that   $$\sum_{k = 1}^n k! \cdot k = (n + 1)! - 1$$   I tried to use the method that is generally applied to geometric series, i.e. writing $S_n - \phi(\cdot)S_n = \dots$ in such a way that almost all terms cancel out. The problem is that in this case it does not work because there is nothing constant in the series' terms.

Use induction to prove that    $\displaystyle\sum_{r=1}^n r\cdot r! =(n+1)! -1$   I first showed that the formula holds true for $n=1$.  Then I put n as $k$ and got an expression for the sum in terms of $k$.  I then found the sum till the $(k+1)$th term by adding the $(k+1)$th term to both sides of the equation and compared it to the sum expression I get by plugging $k+1$ into the sum expression given in the question - they don't match.


Let $f$ be analytic in $\mathbb D$ and continuous in $\overline {\mathbb D}$ . Let $A$ $=$ {$ e^{i \theta}| |\theta - \pi |< \epsilon$} , for $\epsilon > 0$ small enough such that $f|_{A} = 0$ . Show that $f$ is identically equal to $0$ on $\mathbb D$.

Suppose I have a function $f$ that is analytic on the unit disk $D = \{ z \in \mathbb{C} : |z| < 1 \}$ that is also continuous up to $\bar{D}$. If $f$ is identically zero on some segment of of the boundary (e.g. $\{ e^{it}, 0 \leq t \leq \pi/2 \}$ ), is it then true that $f$ is identically zero on the entire boundary?   I know that analytic functions that are zero at an accumulation point inside the domain of analyticity are identically zero throughout the entire domain, but I don't know what (if anything) can be said if something similar occurs on the boundary of the domain.


Let $f:\mathbb{R}\rightarrow \mathbb{R}$ be a continuous function such that $f(\mathbb{R}$) is countable. Show that $f$ is constant.  Some ideas: proving the contrapositive. To suppose that $f$ is not constant and to use the intermediate value theorem to prove that $f(\mathbb{R})$ is not countable.  Any help?

Let $f\colon[0,1] \to \mathbb{R}$ be a continuous function  such that any irrational number is mapped to a rational number. Then $f$ must be a constant.  Well, the context isn't that much, I was reading some interesting function constructions on Hardy's book. Then raised this question.   As the solution suggest it is an elementary exercise. But definitely interesting.


I'm studying the effect of 3 independent variables on one dependent variable, the correlation result indicated that all of the independent variables show a positive relationship with the dependent variable but after I ran the multiple regression analysis, the beta coefficient for one of the independent variables was negative, can anyone explain why ? can such negative value be justified ?

I have a dataset where there is a high degree of multicollinearity, with all variables correlating positively with each other and the dependent variable. However, on some of the models I run I get a couple of significant negative coefficients. Basically there are two coefficients that depending on what variables I include in the model, I can manipulate their signs.  My understanding is that if the variance-covariance matrix only contain positive values, then all coefficients should also be positive. Is this correct?


I want to create such a query using REST that returns me items created in the month of February. To do so I searched for the functions we can implement to the REST query and I have found month() function available with the reference:       I built the query siteCollection/_api/web/lists/getbytitle('Pages')/items?$select=Created&$filter=month(Created) eq '02'  But it gives me an error The query is not valid   I did not find any example of using the month() function while building the REST query.   Can anyone please help me to do so?

I would like to filter a datetime field but I only want to filter MONTH  var requestUri = "xxxx/getByTitle('Contact')/items?$select=CellPhone,mdate,ddate&$filter= Birthday ge '" + today + "'";   The query is working fine and I also tried month(birthday) as it was in the odata specifications but didn't work.  How can I get the month from the Birthday Datetime field.I can get it from my today variable.


Hi I have forgotten my BIOS Supervisor password. Hence I am not able to get into the BIOS Setting. How to reset the BIOS password as I am unable to install UBUNTU. I use Lenovo G580. Regards Radhakanta

When I'm trying to boot my PC from the Xubuntu minimal CD, it fails. It just goes straight to the other operating system, windows vista.  I don't have admin access is that occurring the problem? My computer is really old. It is the 32 bit.  How to solve this problem?


Recently I learned Singleton pattern. And had to realize one. For example:  public class Singleton {     private static Singleton instance;      private InnerObject innerObject; //all functionality is here      private Singleton() {         innerObject = new InnerObject();     }      public static Singleton getInstance() {         if (instance == null) {             synchronized (Singleton.class) {                 if (instance == null) {                     instance = new Singleton();                 }             }         }         return instance;     }      public InnerObjectResult getResult() {         return innerObject.getResult(); //delegate method call     } }   But earlier I would realize this one like this:  public class Singleton {     private static InnerObject innerObject;      static {         innerObject = new InnerObject();     }      public static InnerObjectResult getResult() {         return innerObject.getResult();     } }   Thus the result is the same: innerObject initialized once, but the code is cleaner and I don't have to worry about multithreading. I know that pattern doesn't rest on specific languages and probably you can't do something like this elsewhere, but I'm interested in this particular situation. Thank you very much!

What real (i.e. practical) difference exists between a static class and a singleton pattern?  Both can be invoked without instantiation, both provide only one "Instance" and neither of them is thread-safe. Is there any other difference?


Scenario 1: x=c(1,2,3,4) y=c(2,2,2,2)   Scenario 2: x=c(3,3,3,3) y=c(2,2,2,2)   Scenario 3: x=c(3,3,3,3) y=c(3,3,3,3)   In R, when I used "cor(method="kendall")": [1] NA Warning message: In cor(x, y, method = "kendall") : the standard deviation is zero  Note: all values are ordinal. From my point of view, at least for Scenario 3, the "corr coef" should be 1 as the two sets of values perfectly match.

I am trying to get the correlation between 2 variables, given a set of data. Once in a while, in the given data set,When one of the variables has a constant value, since the standard deviation of that variable is zero, I get an NA value for the correlation. (In R). I would like to assign a value for the correlation in these scenarios explicitly or try to get some value through alternate means, so that I am able to compare this point with other times I compute the correlation. How do I go about it? (1) Should I add some noise to that variable and compute the correlation again. Would that be a meaningful thing to do?


W: GPG error: http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04 ./ Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2F7F0DA5FD5B64B9 W: The repository 'http://download.opensuse.org/repositories/home:/strycore/xUbuntu_16.04 ./ Release' is not signed. 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.   I am trying to get rid of the above error message seemingly related to release key and opensuse url.  What would be the proper solution?

I added some extra repositories with the Software Sources program. But when I reload the package database, I get an error like the following:     W: GPG error:  trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8BAF9A6F   I know I can fix it using apt-key in a terminal, according to the official Ubuntu documentation. But I would have liked to do it graphically. Is there a way to do this without using a terminal?


I am stuck with proving antisymmetry under the natural numbers. Prove "For each x,y E N, if x <= y and y <= x, then x=y. I am not really sure where to start with this proof.  Im assuming I will need to prove it directly. And I am only able to use defintion of addition, multiplication, and order in the natural numbers. Any tips for this proof would be so greatly appreciated.  Thanks!

I'm having trouble deriving the following fact from the basic properties of $+_{\mathbb{N}}$ and the definition:  Definition. $\forall n, m \in \mathbb{N}: (n \geq m) \leftrightarrow (\exists a \in \mathbb{N}): n = m + a$. Fact. $\forall a, b \in \mathbb{N}: (a \geq b ~\land~ b \geq a) \rightarrow a = b$.  I've tried several different strategies, but none works. I think the fact that 0 isn't the successor of any natural number is the key both in the base case and the inductive step, but I keep going in circles trying to make use of that (and other basic facts about addition on $\mathbb{N}$). I would show you my notes, but there is really nothing of substance in them. I've made almost no progress since yesterday.


I am using the UWP skype app.  I know there are more questions like this, but I think the skype app has changed lately and they are no longer relevant.   I'm dying to prevent skype from running in the background because I'm fighting for memory space, every bit counts.   Skype version 8.37.0.98  Application version 14.37.98.0  Windows 10  No other relevant settings that I can find besides this one:   As you can see after a restart it is still here as suspended:   And it is not in startup:    I don't know what else to do to stop this app.   Thanks!

How to stop Skype from starting automatically when booting Windows 10?  I can't find such an option, either in the Skype app settings or in the Task Manager > Startup tab.


I need assistance creating a query for two tables.    The first table books already has an author (the author's name) and illustrator (illustrator) in the author and illustrator column.  The second table people also has the name of the author in the name column. The third table books_people has the two columns book_id and author_id and a third column called occupation   This is more of a conversion from having the authors directly in the books table to having a separate table creating a relation between two tables (one-to-many) ( table: books_authors ). I would also need help making the column of that relation submit the occupation.  Books Table:   +----+--------------+----------------+-----------------+ | id |    title     |     author     |     artist      | +----+--------------+----------------+-----------------+ |  1 | Tower of God | SIU            | SIU             | |  2 | Zippy Ziggy  | KIM Eun-jung   | HWANG Seung-man | |  4 | Beelzebub    | Tamura Ryuuhei | Tamura Ryuuhei  | +----+--------------+----------------+-----------------+   People Table:   +-------+-----------------+ |  id   |      name       | +-------+-----------------+ |    32 | SIU             | |  4053 | KIM Eun-jung    | |  4055 | HWANG Seung-man | | 28490 | Tamura Ryuuhei  | +-------+-----------------+   Books_People Table   +----------+-----------+----------------+ | comic_id | person_id |   occupation   | +----------+-----------+----------------+   Expected result:   +----------+-----------+----------------+ | comic_id | person_id |   occupation   | +----------+-----------+----------------+ |        1 |        32 | author, artist | |        2 |      4053 | author         | |        2 |      4055 | artist         | |        4 |     28490 | author, artist | +----------+-----------+----------------+   What im trying to do here is "create" the rows after the relations have been made.

Using MySQL, I can do something like:  SELECT hobbies FROM peoples_hobbies WHERE person_id = 5;   My Output:  shopping fishing coding   but instead I just want 1 row, 1 col:  Expected Output:  shopping, fishing, coding   The reason is that I'm selecting multiple values from multiple tables, and after all the joins I've got a lot more rows than I'd like.  I've looked for a function on  and it doesn't look like the CONCAT or CONCAT_WS functions accept result sets.  So does anyone here know how to do this?


Here is my attempt :  If order of $A$ is $2$, then $$A=         \begin{pmatrix}         2 & 2  \\         2 & 5  \\         \end{pmatrix}  \Rightarrow \det A=6.$$ Also the eigenvalues in this case are $1,6$.  If order $A$ is $3$, then $$A=         \begin{pmatrix}         2 & 2 & 3 \\         2 & 5 & 6 \\         3 & 6 & 10 \\         \end{pmatrix} \Rightarrow \det A=15$$ Also the eigenvalues in these case are $1,1,15.$  If order of $A$ is $4$, then $$         \begin{pmatrix}         2 & 2 & 3 & 4 \\         2 & 5 & 6 & 8\\         3 & 6 & 10 & 12\\         4 & 8 & 12 & 17\\ \end{pmatrix} \Rightarrow \det A=-21.$$ I found that $1$ is an eigenvalue here by directly putting $\lambda=1$ in the characteristic determinant. But $-21$ is not the eigenvalue.  I couldn't use information about eigenvalues so I looked at the pattern of determinants :  $6,15,-21,...?$ Observed that they are $3\times 2,3 \times 5,-3 \times 7$. From this pattern it might be possible that next term is $-3 \times 11$ since $2,5,7$ are primes and next is $11$. Also the negative sign can be in the pattern $+,+,-,-,+,+,-,-,+,+...$ As it seems to me I will have to calculate order $5$ too to get some more concrete idea with respect to this way. But isn't there some elegant method?  I see that every such order $n$ matrix is "engraved to upper-left inside" order $n+1$ such matrix and every $A$ is symmetric. Thanks.  PS : I wrongly calculated $\det A_{4 \times 4}=-21$. It should be $31$.

This question aims to create an ""  of numerous questions that ask about determinants of specific matrices (I may have missed a few):              The general question of this type is  Let $A$ be a square matrix of rank$~1$, let $I$ the identity matrix of the same size, and $\lambda$ a scalar. What is the determinant of $A+\lambda I$?  A clearly very closely related question is  What is the characteristic polynomial of a matrix $A$ of rank$~1$?


I've got a problem that has me stumped.  I want to get the blue div in the top right of the following snippet to align to the bottom right and still have the text wrap around it to the left.  I am able to edit the HTML but I am unable to nest anything inside the
 tag as this is dynamically inserted.    .container{   width: 500px;   border: 1px solid red;   overflow: auto;   position: relative; } .lower-right{   width: 150px;   height: 60px;   background-color: blue;   float: right; }

Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It       has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop       publishing software like Aldus PageMaker including versions of Lorem Ipsum.

     It seems like it should be simple but I just can't work it out.

Every time I try to do something seemingly-simple in CSS, it doesn't work.  I have a content div that contains a 460x160 image. All I want to do is position the image at the bottom-right corner and wrap my text around it.
          text text text text text text ...
   So I want it to look like:  ------------------ | text text text | | text text text | | text text -----| | text text |    | ------------------   Doing it with a top-left or top-right image is cake:  #contents img { float:right; }  ------------------ | text text |    | | text text -----| | text text text | | text text text | ------------------   Now how do I push that to the bottom? The best I've come up with so far are:  #contents img { float:right; margin-top: 90%} // really needs to be 100%-160px  ------------------ | text text      | | text text      | | text text -----| | text text |    | ------------------   In this case the text does not print in the margin, so there is white space above the image.  #contents { position:relative; } #contents img { position:absolute; right:0; bottom:0; }  -or-  // move the img tag under the text in the html and: #contents img { float:right; margin-top:-160; }  ------------------ | text text text | | text text text | | text text -----| | text text | te | ------------------   In this case the text prints over or under the image.  So... how can I accomplish this?


Let's for any cardinal $\alpha$ define $S_\alpha$ as the group of all permutations of a set of cardinality $\alpha$.  Is there some sort of classification of normal subgroups of $S_\alpha$?  For $\alpha < \aleph_0$ it is well known: they are $E$, $A_\alpha$ and itself (and also $C_2 \times C_2$ in the special case when $\alpha = 4$)  However, what is for $\alpha \geq \aleph_0$?   Here we have the following subgroups, that are obviously normal:  1)For any cardinal $\beta$, such that $\aleph_0 \leq \beta \leq \alpha$, we have the subgroup $S_\alpha^{\leq \beta}$ of all permutations with the cardinality of their support $\beta$ or less.  2)For any cardinal $\beta$, such that $\aleph_0 \leq \beta \leq \alpha$, we have the subgroup $S_\alpha^{< \beta}$ of all permutations with the cardinality of their support strictly less than $\beta$.  3)The subgroup $A_\alpha$ of all permutations, that are equal to a product of even number of transpositions  4)The trivial subgroup  My question is: is there anything else? And if there is, then what?

I recently took a course on group theory, which mentioned that the following proposition is equivalent to the continuum hypothesis: "The infinite symmetric group (i.e. the group of permutations on the set $\mathbb{N}$) has exactly 4 normal subgroups." Does anyone have any references or explanation for this?


I have read email attachment and if archive file then find out how many files are there into archive file. and any exe using programmatically without store any temporary location. I have find out getting attachment content as string or byte. from this string I need to get all files with its content and filename how this possible. thanks in advance

How can I list the contents of a zipped folder in C#? For example how to know how many items are contained within a zipped folder, and what is their name?


I have an hp pavilion g6 laptop that have ubuntu as operating system , and I had no other OS on it. but now I need to install win7 with ubuntu. and I cant do it. can anybody help me with this

I have Ubuntu on my laptop. Now I want install Windows 7 in a dual-boot. How can I do this? I can't lose my Ubuntu files, and I'm afraid that I might break . Go  for UEFI only!


Let $U$ be bounded, with $C^1$ boundary. Show that a "typical" function $u\in L^p(U)$ does not have a trace on $\partial U$. More precisely, prove that does not exist a bounded linear operator $$T:L^p(U) \to L^p( \partial U)$$ such that $Tu=u|_{\partial U}$ whenever $u \in C(\overline U) \cap L^p(U)$.  I have seen other questions about this problem. However, the hint I was given is first that the open set is a unit ball.  But I have no idea about how to do it, Can anyone give me some further hint or answer? Thanks!

This question is from PDE by Evans, 1st edition, Chapter 5, Problem 14. It has been posted  previously, however, I cannot quite put all the information together from the responses there. Hopefully you can help me now. The problem is as follows:     Let $U$ be bounded with a $C^1$ boundary. Show that a ''typical''   function $u \in L^p(U) \ (1 \leq p < \infty)$ does not have a trace on   $\partial U$. More precisely, prove there does not exist a bounded   linear operator      \begin{equation} T:L^p(U) \to L^p(\partial U) \end{equation}      such that $Tu = \left. u \right|_{\partial U}$ whenever $u \in C(\overline{U}) \cap L^p(U)$.   So what we're trying to find is a bounded sequence of functions that go to infinity at the boundary, correct? Because then $Tu = \left. u \right|_{\partial U}$ is undefined.  I like the idea of using the $\mathrm{dist}(x, \partial U)$ function to do this. I was thinking about defining the function  \begin{equation} u(x) = \frac{1}{\mathrm{dist}(x,\partial U)}, \end{equation}  which must be in $L^p(U)$ since $U$ is bounded (hence integral of $\varepsilon$ over $U$ is finite, right?). But this function is not continuous at the boundary, and so $u \notin C(\overline{U})$. Can this be modified somehow?  Another option is to use that the boundary is $C^1$. So for each $x^0 \in \partial U$ there exists an $r > 0$ and a $C^1$ function $\gamma : \mathbb{R}^{n-1} \to \mathbb{R}$ such that $U \cap B(x^0,r) = \{ x \in B(x^0,r) \ | \ x_n > \gamma(x_1,\ldots, x_n) \}$. So around every point on the boundary we can find a ball where the n'th coordinate is greater than the $C^1$ function $\gamma$. How can we use this?


So I have this which is supposed to be side by side in the middle before the media query hits and then when it hits it should stack on top of each other. I have no idea why it's behaving th way it is.  I tried making it centered when ti's at its full width but it doesnt want to center and when I make the browser less than 400px they stack weirdly, they do stack on top but not centered.    .wrapper {      margin-top: 15%;     border : 2px solid #000;      overflow:hidden;   }      .wrapper div {      min-height: 300px;      padding: 10px;   }   #one {     background-color: orange;     float:left;      display: inline;     margin-left: 30%;     height: 400px;     width:250px;     border-right:2px solid #000;   }   #two {      background-color: orange;     float:left;      margin-right:30px;     height: 400px;     width:250px;     border-right:2px solid #000;   }      @media screen and (max-width: 400px) {      #one {        float: none;       margin-right:0;       bottom: 10%;       border:0;      }      #two {          float: none;         margin-right:0;         bottom: 10%;         border:0;         }   }

one

two

How can I horizontally center a
 within another
 using CSS?

Foo foo


The model I'm using is subdivided and mirrored. Here are some pics of the problem, both the solid form and the edit mode.

was following a tutorial where I stumbled into this weird line in my mirrored mesh (sorry for the feet lol)      You can also download the blender file


I am thinking to use ArcPy to select by attribute, after that I want to display the selected features attribute in a table on the map, how can I make it?

I am using ArcGIS 10.1 and I have a non-spatial table and some layers in a Data Frame.   When I switch to Layout View I want to be able to show the map in a data frame element and the table in another element (something that one could do with "Add Table To Layout" from Table Options, but I want to do this in one step without having to go to Table Options).   Is there a way to do this using ArcPy?   I couldn't find any function in the ArcPy library that would create a new Layout Element ... and then I also don't know how to add the contents of the table to the Layout Element.


My Warlock just got a ring with the Artificer Infusion "Spell-Refueling Ring", this infusion states:  While wearing this ring, the creature can recover one expended spell slot as an action. The recovered slot can be of 3rd level or lower. Once used, the ring can't be used again until the next dawn.  However, I am a Warlock which means that at 7th level, I literally do not have any 3rd level or lower spell slots. Does the ring thus become useless at this point and I should just give it to another party member?

In the recently released preview of the Wild Magic Barbarian that will be in Tasha's Cauldron of Everything (), I noticed the 6th level feature 'Bolstering Magic'. This feature has two applications. One acts as a Bless-type option, the second one reads:  Roll a d3. The creature [you're touching] regains one expended spell slot, the level of which equals the number rolled or lower (the creature’s choice). Once a creature receives this benefit, that creature can’t receive it again until after a long rest.  Suppose this effect is used on a Warlock of level 7 or above, and for the sake of argument suppose we rolled a 3 on the d3. All of their spell slots are of spell level 4. What happens?  Nothing, the Warlock doesn't have the right type of spell slot to regain The Warlock has (expended) spell slots of Level 4 and higher, and now has a level 3 spell slot Something else happens, namely ...


We have blob variable which have random strings, size of the blob file is 4MB It's a variable and we want to split/chunk it to 400KB Is it possible to split the variable directly instead of saving to file and then chunk it  Thanks, Srini.

I have a list of arbitrary length, and I need to split it up into equal size chunks and operate on it. There are some obvious ways to do this, like keeping a counter and two lists, and when the second list fills up, add it to the first list and empty the second list for the next round of data, but this is potentially extremely expensive.  I was wondering if anyone had a good solution to this for lists of any length, e.g. using generators.  I was looking for something useful in itertools but I couldn't find anything obviously useful. Might've missed it, though.  Related question:


I am trying to decide if I want to tile my shower myself. Can I tile in sections on different days? Say if I can only get a few walls done and have to stop, is that ok? I have built an L shaped shower with a bench seat in the short leg. I am pretty confident I can do a good job but it may take me longer than it would a more experienced tile setter. I don't want to compromise the integrity of the shower. Thanks in advance.

I am tiling my bathroom floor and don't soon have a full day to dedicate to the job. Is it ok to lay down a few tiles each day and come back to the job when I have time? I would only lay mortar for the tiles I have time to lay each day.    My concern is that the mortar wouldn't properly "join" to the previously laid sections of tile and cause an inferior result, but I'm not really basing this concern on any facts. That is what I'm hoping to learn with this question.


For magic items that give the user an ability boost (Str, Dex , etc), why is the first day (24 hours) benefit counts as "temporary"?  Example: Belt of Physical Perfection: This belt has a large platinum buckle and grants the wearer an enhancement bonus to all physical ability scores (Strength, Dexterity, and Constitution) of +2, +4, or +6. Treat this as a temporary ability bonus for the first 24 hours the belt is worn.  Is the ability boost permanent after a day?  I mean common sense should say that without the belt the user loses the ability boost. So wouldn't it be just as easy to say "so long as the user is has X /holding/wearing/using they get a temporary boosts until X is taken away, dispelled, broken, stolen... etc"?

What is implied by a "temporary ability bonus"?  I've noticed this wording on all of the stat boosting items in the core book.     Treat this as a temporary ability bonus for the first 24 hours the headband is worn.   From:   What is different about the effects of the item on the first twenty four hours, and why does this caveat matter?


if(!/^https?:\/\//.test(val) && foo == 'bar') {     val = 'http://' + val; }   As you can see, the // causes the highlighter to switch to comment mode which is incorrect.

I noticed that sometimes my code gets highlighted in different colors when rendered.   What is syntax highlighting? How does it work? Why isn't my code being highlighted correctly? How do I report a bug or request a new language? How do I use syntax highlighting? What languages are currently available on Stack Exchange?


For example, I kind of expect that in $\mathbb{Z}_{6}$  $\overline{2}$ is prime but I don't know how to prove it (considering the fact that I can test all the different products, but I want a more theorical proof), because I want to show that $\left(\overline{2}\right)$ is a prime ideal. Thanks in advance!

I'm tring to determine the prime elements in the ring $\mathbb{Z}/n\mathbb{Z}$.


The sentence in question:      Every list item that is marked with an * is optional.   The word "asterisks" isn't spelled out, so I'm not sure if "an" or "a" is the correct word to put before it.

I got a question when reading this text:     The name of the decorator should be prepended with an @ symbol.   Should we write "a @ symbol" or "an @ symbol"? As "@" is in fact "at", I would think "an" should be used to avoid the coexistence of two vowels one after the other.  More generally, what is the general rule to know if we have to write "a" or "an" before other symbols like "€", etc.? Is it based on how the symbol is read?


The problem is that I have a Macbook that keeps telling me another computer is using it's IP address. I normally don't have a problem with this as I'd either restart the computer, or router and it would obtain a new IP address.   However, every single IP address the computer is assigned is apparently taken by another computer. I can manually enter an IP and it is then immediately giving a warning about being taken by another computer. I have even left it on automatic DHCP, told the router to assign the computer an IP when DHCP is renewed. And when the computer renews, it says it's being used by another computer.  On the router there is Two other computers (labeled by names) and two android phones (also labeled by names). So I can tell which device is the only Mac on the network. None of the other devices's IPs match the Mac's. And the router states that the Mac's IP has been given the exact IP the Mac says is taken.  I'm not sure what is going on here. But I cannot figure out what the problem is.  So far I have restarted the router and Mac three times and tried to assign over 16 different unique IPs. The router still states the computer is connected and assigned a unique IP while the Mac says it's been assigned an IP that is used by another computer.  If there is anyone that can help with this issue, it would be very appreciative.

Our internet router often stops working at home, but for the the second time only I have got a pop-up error saying:     "another device is using your ip address".   We have an iPhone and a Macbook but as far as a remember this problem occurred for a brief time when we were without an iPhone. In any case, I had a look at  which suggests the problem is a cause of the iPhone and Macbook trying to use the same address.   I changed the IP address via System Preferences > Network > TCP/IP > configure IPv4 Using DHCP with manual address to 11.11.11.11. I then switched back to Using DHCP and clicked 'Renew DHCP Lease'.   When I checked the IP address again it changed to 192.168.1.11. It works now but I wonder if this is a permanent fix or will this problem keep occurring?  Update: The problem persists, but his time without the error message which would leads me to believe that there another problem in addition to the "Another device is using your ip address" problem.


I've been getting some different opinions on this question, and wondered if anyone has a well-motivated response. Basically, if I have a part of a website that's called "My something" or "Your something", I feel that it sets a very different conversational tone of the UI.  "My", would mean that I'm the one saying it, meaning in a way I'm taking ownership of the UI as a user. If the menu item is called "Your", then it's the website presenting this area to me, meaning it contains my things, but it's the website that owns it.  I'm personally leaning more towards using "Your", since at least in the beginning of the user using this website the user will not feel at home in the system, making things like "My" feel a bit off. On the other hand, it seems like "Your" is less of a standard approach, so maybe this matter has already been decided and I just haven't found any good resources on it

Some user interfaces feature titles such as:   My documents My photos My previous orders   While others opt for:   Your documents Your photos Your previous orders   Are their any guidelines addressing which is more suitable to pick in different situations? Is one more preferable than the other?


I'm adding a 40A breaker to the existing panel in my condo to charge an EV (Electric vehicle). I called the city and they said that as long as I have space for the breaker that would be ok. I do have the space but I have to move a 15A breaker to the other side of the panel (Panel is challenger SL12(8-16)CGN) where the connection tab is is the opposite side. Then get the 40A and a 15A breaker. These old breakers are very expensive, $25 for the 15A and $50 for the 40A, maybe because they have the connection in the corners and not the center. The place was built in 1986 (Southern California). I can buy newer breakers and a new panel for about $100 (Square D homeline panel and breakers).   Would I need to use AFCI breaker (new NEC code) if I change the panel? That would change the price too much to do it.   Thanks

This question is about whether "circuits" can be grandfathered if the breaker or panel is changed but the circuit is otherwise not disturbed.   Code is NEC 2017.  My existing main panel has plenty of ampacity but few spaces, and thus, is totally full.  I have several potential paths for an upgrade.    One involves fitting a subpanel and moving 4 circuits (2 double-stuff breakers) there, and adding circuits there.    The other involves outright replacing the main with a very fine 60 space main panel.  No more space problems!  But what happens with AFCI and GFCI requirements? If this were a new house,  nearly all my circuits would require it, but I am grandfathered.  Will the  "new main" scenario void the grandfathering and require that nearly all circuits be upgraded to that protection?   Or can I just move over my old breakers and call it good?


I've purchased S6 and when unlock the there is a phone screen on by default instead of home screen. How to set the default screen to "home" after unlocking device ?  Related :   Update : I used default lock screen and swiping to right to unlock caused issue

I just updated my Nexus 4 to Lollipop. Now, every time I unlock my phone, the Phone app opens. Surely this is a bug and not a feature. It doesn't matter if I received a notification; and I'm not clicking the phone icon at the bottom - I slide to unlock, draw my secret pattern and am instantly taken to the phone app.  Does anyone know what's going on here?


I'm working with 6 LEDs in series, which are rated at:   3V Typical / 3.2V Maximum 20mA.   My power supply is:   19V 3A Maximum   According to my calculations:   I'd need a 50 ohm resistor at 3V I'd be in the negative at 3.2V.   Because my target resistance with the LEDs alone would be below the maximum LED voltage specification, do I need any sort of resistor at all?  Is this the appropriate use case for a 0 ohm resistor?  I plugged in the array last night for around 20 seconds or so, and the wiring seemed to get rather hot which is a bit worrisome... The LEDs however, didn't appear to be brighter than when connecting one at the appropriate resistance.

For blue LEDs with a forward voltage of 3.3 V and supply voltage of 3.3 V, is a series resistor still needed to limit current?  Ohm's Law in this case says 0 Ω, but is this correct in practice?  Perhaps just a small value like 1 or 10 Ω just to be safe?


According to this answer :     I understand the logic, except following sentense:  [ note: because of sufficiency, we have reduced the problem of showing uncorrelatedness with every estimator of 0 to only have to show it for estimators that depend only on T ]  What about the other statistics that is unbiased estimator of zero but not depend on T?  Is there something that i missed about "because of sufficiency" ?

The definition of a sufficient statistic is: Let $X_1,...,X_n$ be a random sample from a distribution indexed by a parameter $\theta$. Let $T$ be a statistic. Suppose that, for every $\theta$ and every possible value $t$ of $T$, the conditional joint distribution of $X_1,...,X_n$ given that $T=t$ depends only on $t$ but not on $\theta$. Then, $T$ is a sufficient statistic for parameter $\theta$.   I feel like I know several pieces of the puzzle (like the factorization theorem) to understanding sufficient statistics but do not have the overall theory down.   My main questions are:  1) Why do they say that $T$ is a sufficient statistic for parameter $\theta$? If $\theta$ were the population mean of a normal distribution, say $\mu$, does it mean that anytime we want to find the probability of, say, $X_1,...,X_n$ occurring in a certain way, that we don't need the value of the mean of the population?  2) In real-life, why do we want to use a sufficient statistic? Is seems that just calculating the statistic shouldn't be that much work (such as the sum of X's) so why do we need it?   Thanks!


When writing large ordinal numbers, does one use commas? Is it 1,234th or 1234th?

Is it necessary to use comma in a big number? For example, if anyone writes one million four hundred thousand and two as 1400002 instead of 1,400,002 on answer sheet of listening section of IELTS test, will it be considered incorrect?  Thanks in advance.


On Ubuntu 14.04, in bash under gnome terminal, Why are files especially directories colored  in different ways?    The green colors hide the text to me (How about to you?). Is it done by terminal or bash? Is it a design  for some purpose?  Can we change the color that hide the text?

There are two directories shown by 'ls'.  Normally directories anywhere are blue on black background.  But the first one is blue on green and impossible to read.  Why is this?  How to make it blue on black, or at least something light on something dark?  This is on Ubuntu 12.04, using bash in Gnome Terminal.  In Konsole, the blue is slightly darker, and possible to read, though could be way better.


I've already asked  about this subject, but now I think I'm almost getting to the point.  I have to split roads in ramps to calculate LS factor (RUSLE - soil erosion)  These are the steps that I'm trying to do:   Create a DEM using Topo to Raster Convert the roads (polyline features) to 3D features using Interpolate shape (ArcGIS 10.1) Split line at vertices.   but now the problem begins...  There are too many vertices in each polyline.  Is there a way to "clean" these vertices leaving only the ones where the slope abruptly changes (from going up to going down) or maybe create points at the Z min and Z max?

I have over sampled polygons that I need to simplify, without changing the shape. basically, I want to reduce the number of vertices, by eliminating the ones that are useless and have the polygons represented with the significant vertices only. I used to do that with ET GeoWizards Plug-in, but I don't have a license anymore. My table has 500.000 features, water polygons.   Any ideas?


I have asked  on Retrocomputing; it got answers there, but was later closed and commenters suggested it would be a better fit for Computer Science.  Because my Retrocomputing question already got answers, I couldn't delete it before reposting it on Computer Science.  So, I went to Computer Science and posted a similar question there which is per my humble opinion .  But, after doing so, my old question from Retrocomputing was reopened and migrated to Computer Science, so two questions that are the same exist there.   which per my humble opinion, needs to be merged somehow --- comments and answers from the old should be migrated to the new, I think.  My question  A mod migrated my old question to another SE site where I have already asked a new better question - how to merge these?  I already contacted the mods of Computer Science explaining the problem and asking to merge the questions, but the flag was declined.  Please help in explaining what I should further do in this case.

Questions can be merged into other questions.   What is a merged question? When should questions be merged? Who can merge questions? How do I request it? What happens to merged posts? Anything else I should know about merged questions?


Question: Let $V$ be an inner product space finitely generated over $\Bbb C$ and let $\alpha$ be an endomorphism of $V$ satisfying $\alpha \alpha^* = \alpha^2$. Show that $\alpha$ is selfadjoint.  **Edited after more thought:  I know that in order to be selfadjoint $\alpha^*=\alpha$. Becuase this inner product space is over $\Bbb C$ does it change the proof?   Or, can I show selfadjoint for $\Bbb R$ and then state the proposition that for an inner product space over $\Bbb C$ and an End$(V)$, If $\langle{\alpha(v), v}\rangle \in \Bbb R$ for all $v \in V$, then $\alpha$ is selfadjoint.

Let $V$ be an inner product space, finitely generated over $\mathbb{C}$, $T\in \operatorname{End}(V)$ that satisfies $TT^*=T^2$, show that $T$ is self-adjoint.    I know that $TT^*$ is positive so has positive square-root, thus the square root is positive definite. But I don't feel like this is a proof. Can anyone prove it without considering square root?


I want to draw the following figure without pstricks:    What I have is the following code:  \documentclass{minimal}     \usepackage{forest}  \usepackage[external]{adjustbox}   \newcommand{\menge}[1]{% \mbox{% $% \left\{% \ignorespaces#1% \right\}% $% %\\[-1.5mm] }% }   \forestset{ tag/.style={for tree={parent anchor=south, child anchor=north,align=center,base=top}}, % a style that creates an arrow pointing to the substitution node from a tree top node encoded as daughter  substitution/.style={edge={<-,dashed},l+=\baselineskip}}  \begin{document}  \menge{ \adjustbox{valign=c}{% \begin{forest} tag [S         [NP$_1^1\downarrow$]         [S,name=s1]] \end{forest} } \hspace{1cm} \adjustbox{valign=c}{% \begin{forest} tag [S,name=s2         [NP$_1^1$                 [e]]         [VP                 [NP$_1^2\downarrow$]                 [S*]                 [V$_1$                         [versprach]]]] %\draw(s1.south)--(s2.north); \end{forest} } }  \end{document}   I think connecting two nodes would be the logically correct way to do this, but the scope of the node naming ends with the forest environment, doesn't it. Is there another way to do this?

I want to connect two forest trees with an arrow, in a similar way it is discussed  for plain tikz trees. However, it seems to be impossible to add options to the forest environment in a similar fashion. Simply referencing the nodes will only place the arrow to the right of the right tree. (To avoid confusions: I don't speak about the $\Rightarrow_G$ in the first forest environment, but the bended one, that should connect two specific nodes.)  \documentclass{beamer} \usepackage{tikz} \newcommand{\false}{\mathbf{f}} \usetikzlibrary{calc, positioning} \usetikzlibrary{arrows} \usepackage{forest} \setbeamercovered{transparent} \begin{document}  \begin{frame}{}    % Tree 1 \begin{forest}     [$\sigma$, calign=last         [$a$]         [{\langle \sigma, \{1,2\},\false \rangle}%                  , math content, calign=first, baseline, draw=blue, ellipse,  name = replaceNode             [$\sigma_*$]             [$a$]         ]     ]   \node at (current bounding box.east)         [anchor=west]         {$\Rightarrow_G$}; \end{forest} % % Tree 2 \begin{forest}     [$\sigma$, calign=last         [$a$]         [$\sigma$, calign=last             [$b$]             [{\langle \sigma, \{1,2\},\false \rangle}%                  , math content, calign=first, baseline, name = t1                 [$\sigma$, calign=first                     [$\sigma_*$]                     [$a$]                 ]                 [$b$]             ]         ]     ] \end{forest} % % This arrow should connect two nodes of both trees. \begin{tikzpicture} \draw[->, black, dashed, bend angle=45, bend left] (replaceNode) to (t1); \end{tikzpicture}   \end{frame}  \end{document}   There seems to be the workaround of putting both trees in the same forest environment with a phantom parent node. However, I would appreciate an overlay solution for better modularity of my graphics, especially if more than two trees are involved.


Two particles of same mass in a 2D frame collide with known initial (i) velocities. I would like to know the final (f) velocities of them after the collision.  As in any other collision, momentum is conserved after the collision. Writing in components:  $$ v_{x,1}^{i} +  v_{x,2}^{i} = v_{x,1}^{f} +  v_{x,2}^{f} $$ $$ v_{y,1}^{i} +  v_{y,2}^{i} = v_{y,1}^{f} +  v_{y,2}^{f} $$  The total energy (not the mechanical) is also conserved. K accounts for the thermal energy. $$ v_{x,1}^{2,i} +  v_{y,1}^{2,i} +  v_{x,2}^{2,i} +  v_{y,2}^{2,i}= v_{x,1}^{2,f} +  v_{y,1}^{2,f} +  v_{x,2}^{2,f} +  v_{y,2}^{2,f} + 2 \cdot K/m $$  I obtain with this 3 equations for 4 unknown quantities, the x and y components of the velocities of particle 1 and particle 2.  How could this be solved?. What information should I add? I can only think of modelling the collision with a potential of some kind.

I am trying to calculate the final velocities of two equal mass 2-dimensional circles after an elastic collision. I have tried to figure it out using formulas I know from high school physics, but nothing seems to work. My known variables are:   initial x and y velocities for each circle x and y distances between the centres of the circles at the time of the collision   The variables I would like to solve for are:   final x and y velocities for each circle   Here are diagrams showing all the variables:


I came to a situation, where while I was suggesting an edit, the OP already improved it (better than my version). As this was only 1-2 minutes after the question was posed, OP's edit isn't even listed in the edit history. Am I able to retract my own edit, as it makes no longer sence, and would just look like an degradation? Should I just write a short comment, explaining the issue?

I asked a question on SO:  and got an answer that, while good, I thought could be improved with a minor edit:   After a little while, a comment on the answer showed me that I was wrong to have edited the answer.  How do I undo it?


I have downloaded JDK 7u71 with NetBeans 8.0.2 from . I want to know how to install jdk-7u71-nb-8_0_2-linux-i586.sh on ubuntu. Please help.

Whenever I open a .sh file, it opens it in gedit instead of the terminal. I can't find any option similar to Right Click → Open With → Other Application... → Terminal.  How do I open this file in the terminal?


It says it all in the title. Anything I try (using /teleport, using /execute) teleports the player relative the command block. I just want the player to teleport to y=46 when I power a command block. Thank you for your help.

In 1.12, I had a command block to summon in minecarts on a single point. I then had another command to spread the minecarts out in a radius of 20 blocks, and a following chain command block to teleport them to the y level 64, because the spreadplayers command teleports entities to the highest solid block. The chained command was simply:  tp @e[type=minecart,r=30] ~ 64 ~   In 1.13, this now teleports all the minecarts to point point. I tried  execute at @e[type=minecart,distance=..30] as @e[type=minecart,distance=..30] run tp @s ~ 64 ~   but this does not work, it has the same effect (Teleporting them all on top of eachother). I also replaced @s with @e[type=minecart,distance=..30] to no avail.  Any solutions here?


I use my phone like I do the computer.  Shopping online with a credit card etc.  Surfing unknown sites... Does my phone require an anti-virus application to protect the internal drive of my phone? Can it be damaged by a virus like on a computer?  OS: Android 4.1.1 Phone: Samsung Galaxy S3

I use Linux for half a decade now, so I am not used to dealing with viruses anymore. To my surprise, I saw some discussion about antiviruses in Android. I haven't installed any yet, but this bugs me: are they really necessary? Are there (or were) any known viruses in the market? Doesn't Google runs an antivirus before allowing an app to the market?  I haven't had no problem in one year of Android, but my cellphone has a lot of important information, and I wouldn't like to be surprised with some virus cleaning my phone, or making international calls while I sleep, or whatsoever. Should I install an antivirus?


I write and illustrate children's books. I scan my illustrations to jpeg and then create the book in InDesign.  The proof always looks great but the printed book illustrations are awful. I have tried calibrating my screen, and calling the printer as well as InDesign.  ID converts RGB to CMYK thus causing the problem.  Can anyone help with this issue? Specific settings would be helpful! Thanks

Basically, I've designed a booklet on Photoshop CC. It's an informational booklet so it's quite vibrant with lots of colours and pictures in it.   I've finished it and exported all the files into PDF format. Upon doing this, the PDF's are much "duller" for use of a better word. Now I'm not a designer and the whole thing was a learning process but now I'm reading about CMYK and RGB colour models and conversions etc. I designed the whole thing RGB (because CMYK looked duller obviously. The PDF's aren't disastrous, red is still red, black is still black but it's nowhere near as visually appealing anymore.   Is this just because of the monitor and the models each program uses or when I send my brochure to be printed, am I doomed for a much duller booklet? There's obviously a way around it otherwise all print would be dull.


$$\gcd(f,nk)=\gcd(f,n)·\gcd(f,k)$$   when $(n,k)=1$ by the fundamental theorem of arithmetic.   I tried many times to prove this equation, but I did not get it.

How can I prove that if $\gcd(a, b) = 1$, then $\gcd(ab, c) = \gcd(a, c) \times \gcd(b, c)$?  By eea there exists $ax+by=1$ from $\gcd(a,b)=1$ so a and be are co-primes there also exists $dk=a$ and $dj= b$ where $d=\gcd(a,b)=1$ this is all the information I have gathered from the question but I dont know how to approach and solve it. Can anyone help explain to me how to arrive at the answer? Thanks!


I know that in order to derive $f(x) = x^x,$ you have to take the log of both sides first and then derive it to get $f'(x) = x^x(ln(x)+1).$ I know that if you take the derivative directly using the chain rule, you get the wrong answer. Why is this? I assume it has something to do with the fact that the definition of the derivative has $h\rightarrow 0$ and we would potentially have $(x+h)^{x+h} \rightarrow 0^0$ somehow (which is indeterminate form), but I'm not immediately seeing this.  EDIT: So as has been pointed out, this question has been answered elsewhere. Additionally, I did not provide enough information. Specifically: how am I applying the chain rule to get the wrong answer? (And I suppose 'What wrong answer am I getting?')  As it turns out, I couldn't decide which function is the "outside" function and which function is the "inside" function. Initially, I did the power rule first to get $$f'(x) = x\cdot x^{x-1} \cdot (x^x\cdot \ln(x))= x^{2x}ln(x),$$ which we've seen is wrong.

When deriving $x^x$, why can't you choose $u$ to be $x$, and find $\dfrac{d(x^u)}{du} \dfrac{du}{dx} = x^x$? Or you could go the other way and find $\dfrac{d(u^x)}{du}\dfrac{du}{dx}$, giving $\ln(x)\cdot{x^x}$? Both methods seem to be equally wrong.


I have a round cube 100x150x100mm with radius 2mm (standard mesh shape). I want to make one edge more rounded than the rest - with radius 10mm. How can I do this?

Is there a way (addon or similiar) to bevel vertices individually. The Bevel modifier clamps all vertices the same, I would like it to clamp each vertex individually.  This is the behaviour I would like to have.    This is the current behaviour. (The position of the edge loop on the left change the bevel on the right edge.) How can I avoid that?      Trying to word it better: How do I avoid dense geometry limiting the amount of bevel on all parts of the model?  I would try other non-destructive methods except the bevel modifier as well.


What is the average delay between the time that all of the conditions for the badge have been met and the user actually receiving the badge?

Do badges get calculated in real time, or do they get calculated by an external service? How long does it take for a badge to be awarded, once its requirements are met?  Does Stack Overflow use any external services to do things, like maintenance, e-mailing or badge calculation?


I am trying to make a complete backup of an HDD partition to /dev/sdd (100gb), but I want to only take the contained data (50gb).  I can't access the internal data in the HDD for putting zeros with dd because Linux will not recognize it. Neither can I see the partition (but I know that only one partition exists).  The objective is: to take data (50gb) without free space and take  the tables and partition "form" because I want to clone it onto other HDD with a limit of 70GB, then it should be recognized by Xbox console  About my question: I've search in multiple forums but always uses the classic methods for cloning and surely I need advanced options for solved it  Add about CLONEZILLA: The clonezilla not works for me, because he can't recognized partitions of my hdd (maybe reason why is a xbox360 partition), therefore only can clone all partition..  How could I do it?  Thank you

How to clone a harddisk to a smaller sized one.   Clonezilla is great but it doesn't support such functionality. Also dd and PartImage don't support this demand. rsync will not copy the MBR since an MBR is not a file.   I need to clone a HDD not to take a backup, so rsync is not an acceptable answer.  Any suggestions?


I had three partitions before installing ubuntu on my system now i only see one what happened to my other partitions and the data they held. If its possible i would like to view that data.

I have a Toshiba satellite A-200 laptop with a Vista OS on it with 4 NTFS partitions  (C:) Vista  (D:) Entertainment  (E:) Work  (F:) Sources   and I wanted to start using Ubuntu instead. So I tried it first from the live CD and everything was OK and all the partitions were shown and working and so I decided to install Ubuntu to replace Vista on the (C:) drive. After I did that I can no longer find my folders and files on the (D:), (E:), (F:) partitions and the only file system that is shown is one 198 GB although my HDD is 320 GB.  I can't access the lost data on the remaining 120 GB which I hope is still there and not totally lost  I am now working from the live CD but I am unable to install testdisk. Can I recover the Vista partitions by the product recovery CD to get my laptop back to the factory settings? Can I recover the NTFS partitions using a recovery program for Windows or will that make the problem worse?   I need these data badly as I don't have a backup for them.


One of the things that makes him great is he brings it every night.   I'm pretty sure it should be that make him in the plural, because one of the things is referring to a lot of things and a lot of things should take a plural verb. But I always hear native speakers in America say it in the singular, so with an s.  Another example:     This is one of the responsibilities that comes with greatness and he understands that.   Native speakers always use the verb in the singular (here, comes) even though [I believe] it is grammatically incorrect to use the singular form of the verb there.

In the construction "one of the [plural noun] who ...", should the verb agree with "one" or "[plural noun]"?   For example, which of the two following sentences is grammatically correct? Or are both acceptable?        She was one of the several children who was sold at the auction    She was one of the several children who were sold at the auction.


What would be the neccessary prerequisites to run a map/tile-server (serving raster tiles) using an exported vector source and tm2z-styleset?   Has anyone set up a working environment for that?  Is  a possible package for such a case?

As presented in a  Mapbox Studio allows to create Mapbox vector tiles and export them as a .mbtiles file.  The  library can be used to dynamically style and render Mapbox vector tiles on client (browser) side.  The missing part: How can I self-host Mapbox vector tiles (.mbtiles) so that I can consume them with mapbox-gl.js?  I know that Mapbox Studio can upload the vector tiles to the Mapbox server and let it host the tiles. But that's no option for me, I want to host the vector tiles on my own server.    The TileStream approach below turned out to be a dead end. See my answer for a working solution with Tilelive.    I tried  which can serve image tiles out of .mbtiles files:  My webpage uses mapbox-gl v0.4.0:  <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.4.0/mapbox-gl.css' rel='stylesheet' /> <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.4.0/mapbox-gl.js'></script>   and it creates a mapboxgl.Map in a JavaScript script:    var map = new mapboxgl.Map({     container: 'map',     center: [46.8104, 8.2452],     zoom: 9,     style: 'c.json'   });   The c.json style file configures the vector tile source:  {   "version": 6,   "sprite": "https://www.mapbox.com/mapbox-gl-styles/sprites/bright",   "glyphs": "mapbox://fontstack/{fontstack}/{range}.pbf",   "constants": {     "@land": "#808080",     "@earth": "#805040",     "@water": "#a0c8f0",     "@road": "#000000"   },   "sources": {     "osm_roads": {       "type": "vector",       "url": "tile.json"     }   },   "layers": [{     "id": "background",     "type": "background",     "paint": {       "background-color": "@land"     }   }, {     "id": "roads",     "type": "line",     "source": "osm_roads",     "source-layer": "roads",     "paint": {       "line-color": "@road"     }   }] }   ... with the following TileJSON specification in tile.json:  {   "tilejson": "2.1.0",   "tiles": [     "http://localhost:8888/v2/osm_roads/{z}/{x}/{y}.png"   ],   "minzoom": 0,   "maxzoom": 12 }   ... which points to my TileStream server running at localhost:8888. TileStream has been started with:  node index.js start --tiles="..\tiles"   ... where the ..\tiles folder contains my osm_roads.mbtiles file.  With this setup, I can open my webpage but only see the background layer. In the browser network trace I can see that tiles are indeed loaded when I zoom in, but the browser JavaScript error console contains several errors of the form  Error: Invalid UTF-8 codepoint: 160      in mapbox-gl.js:7   Since vector tiles are not .png images but rather ProtoBuf files, the tiles URL http://localhost:8888/v2/osm_roads/{z}/{x}/{y}.pbf would actually make more sense, but that doesn't work.  Any ideas?


Is there a way, out of the box Salesforce functionality, Lightning Experience, to send somehow an e-mail with an attachment (word or pdf) and merged fields? More specifically, my requirement is:  I am at case record and has relationship with a custom Objcet (Subscription) I need from case record (i have already selected the lookup record from Subscription entity) to send an e-mail with an attached document with filled in the Subscription Number (custom field on subscription) and account's data (name, VAT number etc).  Any suggestions?

How can I render a VisualForce Page as PDF and have a button on the page that saves this PDF as an attachment to a record?  I want to have a button on my object detail page, 'Generate PDF' which will open a VisualForce Page for preview. On the Preview page I need a button to Save or Save and Email this PDF.  Edit - I use the professional edition + API enabled, so I cannot write a controller but maybe replace that with ajax toolkit?   Is that doable?


Suppose I have a class and constructor called TestClass.  public class TestClass {     Foo foo;      public TestClass(Foo foo) {         this.foo = foo;      } }   Here, the constructor accepts an object which is an instance of class Foo. Suppose my static void main(String[] args) does the following, completely separate from any TestClass;   (1) Instantiate foo (2) Pass instance foo to TestClass constructor (3) Change the internal state of foo   After step (3), will the foo within my instance of TestClass also have its state changed?

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


Let $\{X_n\}_{n=1}^\infty$ be a sequence of iid random variables over a probability space $(\Omega,\mathcal{F},\mathrm P)$. Prove that $$\mathrm P\left(\lim_{n\to\infty} X_n \text{ exists}\right)=1$$ iff the distribution $\mu$ of $X_1$ is degenerate, i.e., $\mu(A)\in\{0,1\}$ for all  $A\in\mathcal{B}(\mathbb R)$, the usual Borel-measurable set.    What I have done:  I'm acquainted with the Kolmogorov's Zero-One law, then if $A\in\mathcal{T}$, then $P(A)\in\{0,1\}$. Where $\mathcal{T}$ is the $\sigma-$tail generated by the iid random variable sequence $X_n$. In this case $\sigma(X_1)=\mathcal{T}$.  I proved that $\{\lim X_n\quad\mathrm{exists}\}\in\sigma(X_1)$, therefore $\mathrm{P}(\{\lim X_n\quad\mathrm{exists}\})\in\{0,1\}$.   My intuition is if I prove that $\mathrm{P}(\{\lim X_n=c\})=1$ (for some $c\in\overline{\mathbb{R}}$), then it follows directly that $\mu$ is degenerate. I found in Shiryaev's Probability (second edition) that if $Y$ is  $\mathcal{T}$-measurable, then $\mathrm{P}(\{Y=k\})$ is precisely 1 (for some $k\in\overline{\mathbb{R}}$), but I don't know how to prove the previous claim, but I know that $\lim X_n$ is $\mathcal{T}$-measurable.

I am trying to prove the following.  If $\{ X_n \}$ are iid random variables and not constant, then $R:=P\{ \omega \mid  X_n(\omega)\text{ converges} \}=0$  Using independence I know that by Kolmogorov's 0-1 law, that if $R$ is not $0$ then $R=1$.  So I think the way to do this proof is by contradiction.  So I am trying to show $R=1$ implies the $X_n$ are constant using their identical distribution but sadly it is not working.  Help would  be appreciated.  Thanks!


I am puzzled how to create in LaTeX the following table    I have spent much searching internet and books about latex but I cannot find something relevant. My problem is how to include the first row which is centered and has two columns as you see and also the last row.  Thank you very much.

I have this table, but wanted to format the first row. I like to match the two columns of first row, and last two columns of the same first row. Any suggestion on how to do that?  \begin{table}[!h]  \caption{Comparison of percentages.} \begin{tabular}{lclclclclc} \hline \hline  Mode &  Var  &  Cum\\ \hline {}       & EF   & CHF    & EF2   & CHF2\\ 1   &  17.5 & 19.1   & 17.5  & 19.1\\ 2   &  11.8 & 12.7   & 29.3  &  31.9\\ 3   &  6.6  &  5.6         & 35.9    &  37.4\\ \hline \end{tabular} \end{table}


In minecraft, I created a command block that kills any player within 100 blocks of it.  How can I shut it down if I don't know the coordinates?

I've placed a command block making it day all the time. I want to turn it off, but I've lost it. What's the quickest way to find it?


I usually see many questions asking personal points of view about some subjects on stackoverflow. I already did some, because sometimes is really important see the point of view of others developers, mainly the more experienced ones and also see in which direction the market is going.  However, the most of these questions are closed by the administrators, in some cases I think it's fair enough, but in others we lose precious informations and good discussions. I know there are others Q&A sites more suitable for this.  However, I was wondering about a new kind of category of questions. In several cases the possibility to create polls for some kind of questions would be enough, mainly these ones with personal points of view.  So, What do you think about polls in some questions? Maybe just for some users  with X reputations achieved. Would be useful for Q&A purposes?

Stuff like polls, recommendations based on subjective constraints, puzzles, webcomics etc. do not belong on the serious main SE sites, where professionals should be considered at work and having just a few spare minutes ("code's compiling") to answer questions, so they should not be distracted by such things. However, I'd also like to have a home for these things still using the SE engine. For the reason I mentioned before, this needs to be a separate place though. Let's call it four.[sitename-here].com.


Where $s_r$ = sum of product of tangents of angles $A_1,A_2...A_n$ taken $r$ at a time.I am expected to prove by induction. How do we use induction in a situation like this?

$$\tan(\theta_1+\theta_2+\cdots+\theta_n)=\frac{S_1-S_3+S_5+\cdots}{1-S_2+S_4+\cdots}$$  where  $S_i$ denotes the sum of product of tangent of angles taken $i$ at a time.     For example,$$\tan(\theta_1+\theta_2)=\frac{S_1}{1-S_2}=\frac{\tan\theta_1+\tan\theta_2} {1-\tan\theta_1\tan\theta_2}$$   (This formula is given  in my textbook with no derivation or background)  How to derive this?


Im selling serial numbers the customers and they get in trouble to copy manually the text while mostly they are mobile users , i want to add the copy button to the serial number generated from database to data table so the customer can copy it with click on button only This is my code: <?php defined( 'ABSPATH' ) || exit(); ?> <?php global $serial_numbers; ?> <?php echo sprintf( '
%s
', esc_html( $heading ) ); ?>

         <?php echo sprintf( '%s
', html_entity_decode( $product_column ) ); ?>         <?php echo sprintf( '%s
', html_entity_decode( $content_column ) ); ?>

     <?php foreach ( $serial_numbers as $serial_number ): ?>
                              <?php                 $product_column_content = html_entity_decode( $product_column_content );                 $product_column_content = str_replace( '{product_url}', esc_url( get_permalink( $serial_number->product_id ) ), $product_column_content );                 $product_column_content = str_replace( '{product_title}', get_the_title( $serial_number->product_id ), $product_column_content );                 echo $product_column_content;                 ?>             	                               <?php                 $serial_column_content = str_replace( '{serial_number}', \PluginEver\SerialNumbers\Helper::decrypt( $serial_number->serial_key ), html_entity_decode( $serial_column_content ) );                 $serial_column_content = str_replace( '{activation_email}', $order->get_billing_email(), $serial_column_content );                 $serial_column_content = str_replace( '{expired_at}', \PluginEver\SerialNumbers\Helper::get_expiration_date( $serial_number ), $serial_column_content );                 $serial_column_content = str_replace( '{activation_limit}', \PluginEver\SerialNumbers\Helper::get_activation_limit( $serial_number ), $serial_column_content );                 echo $serial_column_content;                 ?>
     <?php endforeach; ?>

What is the best way to copy text to the clipboard (multi-browser)? I have tried: function copyToClipboard(text) {     if (window.clipboardData) { // Internet Explorer         window.clipboardData.setData("Text", text);     } else {         unsafeWindow.netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");         const clipboardHelper = Components.classes["@mozilla.org/widget/clipboardhelper;1"].getService(Components.interfaces.nsIClipboardHelper);         clipboardHelper.copyString(text);     } }  But in Internet Explorer it gives a syntax error. In Firefox, it says unsafeWindow is not defined. A nice trick without using :


I'm writing a small console program that calculates your age and I will add some other things later, but the problem is that this code does not calculates the age properly, it just substracts actualYear - birthYear, but if you did not had your birthday yet it displays a wrong age, how can I make this sum all the days and months that i have? I tried a lot of things and didn't work :(  Is there any way to do this using an if statement?  using System; using System.Collections.Generic; using System.Text;  namespace para_joel {     public class Person     {         public string name;         public string surname;          public int birthDay;         public int birthMonth;         public int birthYear;          public int Age()         {             int actualYear = DateTime.Now.Year;             int actualMonth = DateTime.Now.Month;             int actualDay = DateTime.Now.Day;              return actualYear - birthYear;         }     } }

Given a DateTime representing a person's birthday, how do I calculate their age in years?


I have found answers to this but they don't work. I want to invite my friends to like my band page.  If I am on the band page and try to Build an audience, it only gives me options to do this via email. If I am on my personal page I see no option for Build an audience.   I am obviously the administrator to my own page I assume.  What am I missing?

One of my friends on Facebook did a mass invite that I am interested doing myself. I got a message in my notification section which linked his page. I could click on that link and directly "like" the page. The text in my notification's list read, "[Name of friend] has invited you to like his new page [name of page with a link]."  I would like to do this for my own business's page. I have hit "Share" which makes the site show up on my profile, but people are liking my share, which doesn't give me the result I want. I would like people to be invited to like my site directly so they can get status updates and see our pictures and promotions. I'm fairly certain that these friends are interested in such a thing, they just aren't Facebook savvy enough to know how to do that. I'm hoping the notification to directly like the page will help them understand and streamline the process so the friends who want to connect with my business can "like" the site and I can leave my other friends alone.


This post is linked to . The post has many answers, but none are satisfactory. So I am reposting it, since the original post became dormant. When does the top block start to slide assuming sufficient friction between the two and zero friction between the bottom block and the ground?

Consider two blocks, one on top of the other on a frictionless table, with masses $m_1$ and $m_2$ respectively. There is appreciable friction between the blocks, with coefficients $\mu_s$ and $\mu_k$ for static and kinetic respectively. I'm considering the fairly routine problem of determining the maximum horizontal force $F$ (say, to the right) that can be applied to the top block so that the two blocks accelerate together.  The problem is not hard to solve symbolically. If the two blocks move together, their accelerations are the same, and the top block doesn't move with respect to the bottom block, so only static friction is in play. In a standard coordinate system (with $x$ oriented to the right), the sum of horizontal forces for the top block is  $$F-F_{sf}=m_1a$$  and for the bottom block  $$F_{sf}=m_2a$$  where $F_{sf}$ is the force of static friction. Solving for $a$ in these two expressions, and then equating them, gives  $$F=\frac{(m_1+m_2)F_{sf}}{m_2}$$  The maximum such force will therefore be achieved when $F_{sf}$ is maxed out at $\mu_s m_1g$, so  $$F_{max}=\frac{m_1}{m_2}\mu_s(m_1+m_2)g$$  I understand this solution, but conceptually I don't have a response to the following nagging question: $F_{max}$ is clearly larger than the max static friction force $\mu_sm_1g$ (because $\frac{m_1+m_2}{m_2}>1$), so why doesn't the application of a force of magnitude $F_{max}$ to the top block cause kinetic friction to take over? This line of reasoning would suggest that applying a force $F$ of magnitude greater than $\mu_sm_1g$ would cause the top block to start moving with respect to the bottom block (in which case the blocks no longer accelerate together, as in the above solution). I'm at a loss, conceptually, to say what's wrong here. I suspect it has something to do with being careful about reference frames, but a clear explanation would be much appreciated.


Silver badge for good question is defined as "Question score of 25 or more" and I think bronze for nice question is 10 points or more.  I have asked quite a few questions by now many over 10 points and I just had once that got 25 points (i.e. 5 upvotes) but I just noticed that I did not receive any badges for either nice or good questions (and probably same for answers though I have not looked into that yet). Not that I am a "badge collector", but its nice to get the bonus if you have "achieved" it.  Why do I not get these badges? what am I missing here? - I had a look on Meta-SO but didn't see anything obvious like my question.  Here is an example of one question that has 5 votes: . Ok in this instance it was marked as "duplicate" (even though I searched before asking it, you don't always find what you are looking for), but it still matches the 25-point criteria...

I gave an answer and got a score of more than 40 but still have not got silver badge called "Good Answer". Will it take time to get it? I have read somewhere that some jobs are run after certain interval but I have still not received the badge.   Here is the screenshot where you can see that I got 65 points.


Is the following series converging $\sum_{n=2}\dfrac{1}{(\ln n)^{\ln n}}$  I am not able to compare this with anything, can some show the way

Could I have a hint for testing the convergence of the following series please?  $$\sum_{n=2}^\infty\frac{1}{(\ln n)^{\ln n}}$$  Edit  The integral test does not work because $\int_1^n\frac{1}{(\ln x)^{\ln x}}dx$ has not an elementary primitive.  Thank You.


I have 2 identical lists a = [a1,a2,a3] b = [a1,a2,a3] What is a most effective way to iterate over these 2 list simultaneously while i am interesting only in combination of different elements from both lists despite order, i.e a1a2 and a1a3. Combinations a1a1, a2a2, a3a3, a2a1, a3a1 i am interesting to skip, but interesting keep iterators values avaliable.  Want to re phrase questions: interesting in possible combinations of 2 elements from list a = [a1,a2,a3]

I have a list with 15 numbers in, and I need to write some code that produces all 32,768 combinations of those numbers.   I've found  (by Googling) that apparently does what I'm looking for, but I found the code fairly opaque and am wary of using it. Plus I have a feeling there must be a more elegant solution.  The only thing that occurs to me would be to just loop through the decimal integers 1–32768 and convert those to binary, and use the binary representation as a filter to pick out the appropriate numbers.   Does anyone know of a better way? Using map(), maybe?