Now, I understand the motivation for quantum gravity. I honestly want to work on a theory myself. However, gravity, according to General Relativity, is not a fundamental force of nature. To me, it's just a natural tendency, or an inertial tendency. (I call them this because of the equivalence between inertial mass and gravitational mass and inertia.) Inertia is one of these tendencies, the tendency to resist induced motion. Gravitation is just the natural tendency to follow a geodesic. Not a force. One could argue that It takes only a mass moving through space for inertia to take place, it takes two bodies for gravity to occur. However, this induced motion must have been caused by something else. Just as with the curvature of spacetime. Quantizing gravity is like quantizing inertia. I am aware that there is no "inertial radiation"; however the gravitational radiation needn't be quantized.  It's just ripples in spacetime. If spacetime were quantized, then I am assuming that it'd be a field, with a value for every point in spacetime. With a QFT, we could determine EVERYTHING- every moment time, every point in space- where a particle is, where it's not. This would not only violate the Heisenberg uncertainty principle, but it would be the reason for non-renormalizability of gravity. Infinite solutions that can't be neglected.  On the flip side, one could argue about the high energy situations such as the Planck epoch, where gravity may need extreme modification. Plus, gravity is a field, so it should be quantized. However, as stated by the renormalization issue, this probably wouldn't be true.  We have a theory for the quantum realm and the three fundamental forces of nature, and we have a theory for the two "great inertial tendencies"- inertia and gravitation.   The Question: Given the info provided above, do we really NEED a quantum gravitational theory, (save for the high energy scenarios)  P.s. What is wrong with putting QFT in curved spacetime? (which I am aware is one of the main needs of the theory, but we don't truly need a graviton, after all, all the fields in the standard model have the natural tendency to follow a geodesic, so this tendency should be added in anyways!)

What I am interested to see are specific examples/reasons why gravity should be quantized. Something more than "well, everything else is, so why not gravity too". For example, isn't it possible that a quantum field theory on curved space-time would be the way treat QFT and gravity in questions where the effects of neither can be ignored?


As a teenager, I read a set of Scifi novels about mutants and humans that rode horses in and around Richmond, VA. I remember that they fought using swords and such. I also seem to remember some reference to a Sea of Grass.  Anyone remember the author/name of the series?

My memory of this is sketchy and I hope I don't jumble it too much. I read two or three books (possibly more exist) in a series in the late 1990s.   The whole thing was mainly SF with a dose of fantasy.  The main character is a man who is immortal. He doesn't age and can recover from even the most horrific wounds.  I'm not sure if there where other immortals (I seem to recall a woman and another man). As far as I can recall, immortals were infertile and couldn't have children.   He lives among a tribe of nomadic people who roam the prairies of post-apocalyptic North America on horseback (society like Native American prairie tribes).  Among their tribes (there is more than one) also live huge (lion-sized?) cats who are telepathic and have near-human level intelligence.   The immortal man is a leader among the nomads and, I seem to recall, he is instrumental in getting the tribes together in a larger alliance and gradually moving them East to the coast.    On the east coast, some cities remain (Pittsburgh I clearly recall) who have a medieval feudal society with a militia and knight-based military. (I clearly remember that military ranks among them had Greek-derived names, which was quite strange.)  There was also a small group of people who had retained pre-apocalypse technology (radios, trucks, helicopters, firearms), possibly survivors or descendants of the military or of some scientists. These people were antagonistic to the immortal and try to kill or capture him. The immortal had some narrow escapes. They mainly work in secret and avoid letting their presence be known among the tribes.


What is the policy on copy-pasting content from other sources for tag wikis?  The tag wiki for  was  a few minutes ago, but the content is just copied from the  announcing the technology.  At first I thought that the edit should be rejected as plagiarism, but the user did insert a link to the blog. Is a link sufficient for attribution? Even if it is, do we really want to just copy-paste content from product pages for our wikis? Especially content which is, in my opinion, a bit too ""?

There was a spurious edit to the  tag that I declined, but also noticed that the original  wiki was copy/pasted verbatim from the .  This is a  project, but the website itself doesnt' appear to be (based on the  page).  In this case, is this considered an appropriate use of information (since it is after all a open-source project, and the text from the main page of the website undoubtedly is not only an excellent description but is useful for the curl group as well)?  Or is this something that isn't technically appropriate and should be rewritten (not by me, as I have no clue what it should say).


Problem:  click event is working for button Click Me but click event is not working for label Click Me.  Below is the code  HTML  <button type="button" id="clickMe" class="btn">Click Me</button> <div class="preview">  </div>   JQuery  $('#clickMe').click(function() {     var lab = "<label class=\"click\">Click Me </label>";     $('.preview').append(lab); });  $('.click').click(function() {     alert("You clicked on text"); });

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I am trying the following script for listing the archived files in my current directory.  #!bin/sh for file in *.{zip,jar} do echo $file done   which gives the output:  *.{zip,jar}   Why isn't shell expanding the braces?

I have the following simple script:  #!/bin/bash echo "Bash version ${BASH_VERSION}..." for i in {1..99..2} do         echo $i done   Output in case I run with sh file.sh:  Bash version ... {1..99..2}   Output in case I run with bash file.sh:  Bash version 4.2.25(1)-release... 1 3 5 . . . 99   I have two queries:   If I have written a shabang line specifying shell, shouldn't it run with bash whether I use sh file.sh or bash file.sh? I understand that $BASH_VERSION is not recognized by sh but what is the problem with for loop? Why isn't printing the numbers?


So i have a scene where i have 2 objects with a simple Principled BSDF shaders and it's lit with an HDRI. I tried to look at it in the render view, but for some reason it is entirely gray. Here's how the viewport looks:  And here is how a render of the scene looks:  However, i have no problems in eevee, as you can see here:  Eevee render:  I have no idea what could be causing this. I also have some other objects in another collection, but the collection is disabled for render, so it probably isn't the problem.

Does anybody know why my Viewport Shading has gone all grey. I must have pressed something because it was all fine a minute ago.. thanks


I am using \mathbf{} for include bold symbols in my equation. It works fine with all symbols with the exception of \iota. I tried to use equation environment and to exclude subindex. The following is my writing:  \begin{align}     \mathbf{Y}=\rho \mathbf{WY}+\alpha \mathbf{\iota}_{N}+\mathbf{X\beta}+\mathbf{WX\theta}+\mathbf{u},\label{eqgeneral1}\\      \mathbf{u}=\lambda\mathbf{Wu}+\mathbf{\varepsilon}  \label{eqgeneral2} \end{align}   I obtain this:    I want this:    ¿How can I solve this?

To make Latin-letter variables bold I can use e.g. \mathbf{a}, but while putting Greek letters or symbols such as \nabla inside \mathbf doesn't cause any errors or warnings, it also doesn't do anything else.  What is the best way to make bold math symbols, in particular Greek letters and \nabla?


In Python, why are some built-in functions called using brackets with the method name before the object, e.g.  print("foobar") bool("foobar") ...   While others are built-in method attributes, called with a dot behind the object, e.g.  "foobar".capitalize()   Specifically I'm interested to learn if there is a general principle behind this instead of just common practice and memorization. In cases where you can't quite remember whether it was capitalize("foobar") or "foobar".capitalize(), how do you know?

example:  a_list = [1, 2, 3] a_list.len() # doesn't work len(a_list) # works   Python being (very) object oriented, I don't understand why the 'len' function isn't inherited by the object.  Plus I keep trying the wrong solution since it appears as the logical one to me


I'm attempting to have a planet (with a known mass and radius) orbit it's sun (also with a known mass and radius). It doesn't have to be 100% realistic, but it should be possible that the sun have more than one planet orbit it at a time.  What equations should I use to accomplish this?

I'm working on an Ogre3D + Bullet project that involves planets in a solar system. For all intents and purposes, I'm looking to give each planet it's own gravity sphere.  So far, all I've found are ways to change the "general" gravity Vector3 for the entire scene, but that's it.  While I'd hope to add air friction and other physics later on, for now I just want "prioritized" gravity, like in .  You'll note that the floor in the video has gravity, but when he jumps near the sphere, he is attracted to it sphere instead. That's exactly what I'm going for.  The video is very low quality and doesn't explain how any of it is working, besides the fact that it uses Ogre3D and Bullet.   The planets themselves are on pre-generated paths around the Sun - I'm not looking to apply "real" physics to the solar system itself; just for the planets themselves and eventually "generated gravity" for ships in space.


I got stuck in trying to find a solution to the 3.7 exercise of the Katz-Lindell book. The exercise also assumes the existence of a pseudorandom function. The problem is that a multiple messages encryption scheme has to be non-deterministic in order to be indistinguishable. So how is it possible for such encryption scheme to be CPA vulnerable, if it's non-deterministic as we are considering a multiple messages scenario and a pseudorandom function involved in the Encryption-Decryption process?

In order to be indistinguishable with respect to multiple messages, wouldn't the scheme need to be nondeterministic? How would this then possibly be vulnerable to an adaptive CPA?


I am looking for some basic intuition for  $$\lim_{x \to 0}\frac{\sin x}{x}$$ If we look at it as $f(x)=\sin x\cdot\frac{1}{x}$ so as ${x \to 0}$ $\sin x \to 1$ and $\frac{1}{x} \to \infty $ so it is $0 \cdot \infty$ so why is it equals 1?

How can one prove the statement $$\lim_{x\to 0}\frac{\sin x}x=1$$ without using the Taylor series of $\sin$, $\cos$ and $\tan$? Best would be a geometrical solution.  This is homework. In my math class, we are about to prove that $\sin$ is continuous. We found out, that proving the above statement is enough for proving the continuity of $\sin$, but I can't find out how. Any help is appreciated.


Has anyone had any luck playing portal 2 offline co-op on Mac? My controls are messed up for controller 2 (xbox controllers) and it seems like it's not only my problem. Any tips on how to get it working?

Is there a way to play Portal 2 co-op on a single PC or Mac?  If so, do we need two keyboards, or two mice, or what?  Do we need to buy two copies of the game?  Note: The wireless XBox 360 controller does not work standalone out of the box on either an iMac or Windows 7 PC.  It needs a receiver as well.  I thought it would be Bluetooth, but no.


ZbMATH sent an article for post-publication review. As of a little more than a month ago, I worked at the same department in the same university as one of the authors. We have not cooperated on a paper, but have otherwise interacted.  Should I decline to review the paper due to this conflict of interest (as I would do with a peer review for e.g. a journal article), or do zbMATH reviews have more lax standards for conflicts of interest? The reviews are post-publication, and for a review database and not a journal, and furthermore they are not anonymous, so they are quite different from journal peer reviews.  The review guidelines of zbMATH did not mention conflicts of interest.

If I were asked to review a paper, under what circumstances would I be expected to decline out of a conflict of interest? Could I review a paper for someone...   I have collaborated with N years ago? Who I am currently collaborating with, but we have not yet published a paper together? Who is currently or was once in the same institution as I?


How.  Is it grammatically correct to phrase a question starting with "How to"?  We see "How To" videos that explain how to do something, but is the question form valid English?  Example:  How to add two numbers?  vs  Do you know how to add two numbers?

I see questions formed like "How to do this?" every day.  They are so frequent that I wonder if there is a name for grammatical errors of this kind.


The following code results in SIGSEGV and I cannot understand why is that.  #include <iostream> using namespace std;  struct C {     C(int x) { ptr = new int(x); }     C(C&& c) { ptr = c.ptr; c.ptr = nullptr; }      int* ptr; };  void foo(int* x, C c) {     cout << *x  << endl; }  int main() {     C c(10);     foo(c.ptr, std::move(c));        return 0; }   I would expect the pointer c.ptr to be passed by value to the function foo, however it behaves like its passed by reference.  Now, if I change the ordering of arguments: void foo(C c, int* x), than the problem disappears. The other solution is to create a local copy of c.ptr before calling to x, and than passing that local copy to foo.  I would like to understand why can't i pass c.ptr by value in the sample code above.

Okay, I'm aware that the standard dictates that a C++ implementation may choose in which order arguments of a function are evaluated, but are there any implementations that actually 'take advantage' of this in a scenario where it would actually affect the program?  Classic Example:  int i = 0; foo(i++, i++);   Note: I'm not looking for someone to tell me that the order of evaluation can't be relied on, I'm well aware of that. I'm only interested in whether any compilers actually do evaluate out of a left-to-right order because my guess would be that if they did lots of poorly written code would break (rightly so, but they would still probably complain).


I want to insert some word which is languages of Europe to MySQL. e.g á, ó, Ö,ü.(Sorry, I don't know what language it is. Maybe somebody can help me fix title.)  But it become something can't read.  I try this solution   I find out my PHP version is 5.1.6. So I can't use mysql_set_charset   Mysql charset is utf8_general_ci and version is 5.0.45.  How can I fix this problem?

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


Prove that $\nu(n) \le \nu(2^{n}-1)$  Ok so I have very few ideas for this question. I thought if I could find the prime decomposition of $2^{n}-1$, I could go somewhere with the formula for $\nu$, but I've had little success. Any help would be much appreciated.

Prove that $\tau(2^n-1) \geq \tau(n)$ for all positive integers $n$.  Note that $\tau(2^n-1)=\sum_{d|2^n-1}{1}$. I try to prove by induction.  Base case: When $n=1$, we have $\tau(2-1)=\tau(1)$. Hence, the inequality is true.  Fix an $n$. Assume that the inequality $\tau(2^n-1) \geq \tau(n)$, which is $\sum_{d|2^n-1}{1} \geq \sum_{d|n}{1}$ is true for $n$. Note that $\sum_{d|2^{n+1}-1}{1}=\sum_{d|2^{n}-1}{1}+1 \geq \sum_{d|n}{1}+1=\sum_{d|n+1}{1}$  I don know whether the equality above hold or not. Can anyone guide me?


In a CentOS 7 web server, how do I configure firewalld to block all but a specific list of ip addresses from making successful http or https requests?  I know that I can use httpd.conf to restrict by ip, but how can I get firewalld to restrict by ip? What file? Do I use firewall-cmd? What syntax?  I imagine this involves creating one or more rich rules, which are described in . But I want to make sure that I do this properly. For example, would one rule specify rejecting all http/s requests from anyone?  And then would another rule be required to approve http/s requests for each specific ip?  Would the rule be for the service http/s, or would the rule be for the port 443?  Or some combination? What about logging the rejections and acceptances?

I want to set up CentOS 7 firewall such that, all the incoming requests will be blocked except from the originating IP addresses that I whitelist. And for the Whitelist IP addresses all the ports should be accessible.  I'm able to find few solutions (not sure whether they will work) for iptables but CentOS 7 uses firewalld. I can't find something similar to achieve with firewall-cmd command.  The interfaces are in Public Zone. I have also moved all the services to Public zone already.


My system is:   Dell Latitude 7400 i5-8265U with Windows 10 Pro (1903) VirtualBox 6.0.12 Ubuntu-18.04.3-desktop-amd64 1024MB RAM is assigned to VM (by default).   After clicking on "Try Ubuntu or Install", Ubuntu 18.04.3 crashes, the screen freezes/goes to full black, and nothing else.  What's the solution?

I'm thinking about installing Ubuntu Desktop, but I don't know what flavor is the best for my system. What are the minimum and recommended hardware requirements? What kind of CPU? How much memory? Should I have Hardware Acceleration? What flavor should I use?  This is an attempt of a canonical answer. My answers have the "official  requirements", the recommended are a mix of official sources and opinion based (along with the answer it's told the source). You can comment or edit if you feel that the information is obsolete or incomplete. It is a good rule of thumb that any system capable of running Windows Vista, 7, 8, x86 (Intel) OS X will almost always be a lot faster with any Ubuntu flavor even if they are lower-spec than described below.


So, this is my first time DMing a continuous campaign. I'm finally (after five or so sessions) getting good grips on a lot of the stuff, but I'm very much still struggling with the role-playing element of it all.   I'm a female, and I find it very hard to do any sort of male voice, as well as accents that differ from my own. The module I'm running is Curse of Strahd, and with next session being their first proper encounter with the big guy himself, I'm terrified I will mess everything up by just failing to deliver anything but my own (arguably dull) voice. I am pretty shy about doing this sort of stuff, so any tips to help me git gud at accents, or even just to get out of my shell & do something would be so greatly appreciated.   :)

As a GM should I use a different voice for a NPC who is, for instance, a sick old man, or if it's a kid, or even a member of the opposite sex? What advice can you give me to enrich NPC acting?


I have installed apache2 , php7.2.5 and mysql-server and also install phpmyadmin. Apache2 , php and mysql are running well. But when i try to run phpmyadmin , it displays a bunch of code in the browser.  Looks like this:  <?php /* vim: set expandtab sw=4 ts=4 sts=4: */ /**  * Main loader script  *  * @package PhpMyAdmin  */  /**  * Gets some core libraries and displays a top message if required  */ require_once 'libraries/common.inc.php';  /**  * display Git revision if requested  */ require_once 'libraries/display_git_revision.lib.php'; require_once 'libraries/Template.class.php';  /**  * pass variables to child pages  */ $drops = array(     'lang',     'server',     'collation_connection',     'db',     'table' ); foreach ($drops as $each_drop) {     if (array_key_exists($each_drop, $_GET)) {         unset($_GET[$each_drop]);     } } unset($drops, $each_drop);   Help me to fix this problem. Thanks

I am totally new to Linux, servers and websites. I recently set up Apache2, Python, PHP, and MySQL for setting up a LAMP server. I am using Xubuntu 16.04 and PHP 7.0.11. I followed a guide and placed a PHP file named testing.php in it with:  <?php phpinfo(); ?>    It doesn't show anything on localhost/testing.php All it shows is the code itself.


Ideally, I would like something like  for WhatsApp.  But I'm just looking for a way to receive and send messages from my Ubuntu Desktop.  Is there some client or any other way to achieve that?

How can I install WhatsApp in Ubuntu? Related:


This is the letter I'm trying to reproduce: ǘ  There's an umlaut and, on top, an acute accent. I can do one or the other but not both.  Any suggestion?

As linguistics student, I have to put more than one thing on a character every now and then. For example, I need to type ā̆. I thought I could simply do that by typing \={\u{a}}, but then the macron is placed above an empty space in front of the character.  How can I solve this? Thanks  P.S. I'm using MiKTeX 2.9, running on Windows 8; in case it might be of use.


So i have tried some other solutions from here but none have worked. My current method is trying to use the TimeSpan method:  unixtime is an int, contains '1502557200'  var test_date = TimeSpan.FromSeconds(unixtime);   test_date became '{17390.17:00:00}'  What am I doing wrong? I was trying to avoid creating a method to handle the conversion, and just trying to do it inline,  Thankyou

There is this example code, but then it starts talking about millisecond / nanosecond problems.  The same question is on MSDN, .  This is what I've got so far:  public Double CreatedEpoch {   get   {     DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, 0).ToLocalTime();     TimeSpan span = (this.Created.ToLocalTime() - epoch);     return span.TotalSeconds;   }   set   {     DateTime epoch = new DateTime(1970, 1, 1, 0, 0, 0, 0).ToLocalTime();     this.Created = epoch.AddSeconds(value);   } }


I know that this question was already answered, but I would like to know if the second step of induction its okay the way I did it.  This question is different from  and  since it is just about to check a part from a proof that I did (if the way I thought is correct or not).  Suppose that   $9 \mathrel| (4^k+6k-1)$ is true for $k\in \mathbb{N},  k\geq1$. I want to prove $P(k+1)$: $ 9 \mathrel| 4^{(k+1)} +6(k+1) - 1$  Since $9 \mathrel| (4^k+6k-1)$, I can rewrite as:  $4^k+6k-1 = 9q$,  where $q \in \mathbb{Z} $. By the definion of Divisibility.   Multiplying the equation on both sides by 4, I'll get:   $4^{(k+1)} +24k-4 = 36q$   Adding 3 on both sides   $4^{(k+1)} +24k - 1 = 36q + 3$   Subtracting $18k$ on both sides   $4^{(k+1)} +6k - 1 = 36q + 3 -18k$   Adding 6 in order to have $6(k+1)$ as a factor   $4^{(k+1)} +6k + 6 - 1 = 36q + 3 -18k + 6$  $4^{(k+1)} +6(k+1) - 1 = 36q + 9 -18k $  Note that $36q + 9 -18k$ can be written like this: $9(4q + 1 - 2k)$. Thus $9Q$, $Q=(4q + 1 - 2k), Q \in \mathbb{Z}$.  Therefore:   $4^{(k+1)} +6(k+1) - 1 = 9Q$. Which means that $4^{(k+1)} +6(k+1) - 1$ is also divided by 9.   Does my proof look fine? If there is a problem, please tell me. All help is appreciated.

Prove that for all $n\in\mathbb N$, $9 \mathrel| (4^n+6n-1)$.  I have shown the base case if $n=0$ (which is a natural number for my course).  I'm now trying to prove that $9k=4^n+6n-1$.  I substituted $n+1$ for $n$, and have $4^{(n+1)}+6(n+1)-1$, which equals $4*4^n+6n+5$.  I'm stuck. Is that not the right way to go? I don't know how to get from the “$+5$” to “$-1$” so I can substitute $9k$ to the right side of the equation. Any help would be greatly appreciated.


Accidentally formatted lost data my SanDisk SSD PLUS 480GB Internal SSD - SATA III 6 Gb/s, 2.5"/7mm - SDSSDA-480G-G26  so I need to recover los data my SanDisk SSD PLUS 480GB. any suggesion?

What steps can I take to try to recover lost or inaccessible data from any storage device?  Answers:   This applies to any computer storage device, e.g. internal/external hard drives, USB sticks, flash memory. The most important thing is to STOP using it, any type of I/O can ruin your chances of a recovery.     We have separate questions covering common problems with USB flash drives in greater detail:


I would like to know how to capture the output of this command into a variable   ssh -q $ssh_host  'ps -eo comm,lastcpu'  Once the information is captured, I want to check the variable if it returned more then one result and label it  Example  rpciod/0          0    rpciod/1          1    rpciod/2          2    rpciod/3          3  After processing I want the output to be  it adds the hostname and puts the output on separate line, removing /1 /2 if it find it  Hostname1 being the value of $ssh_host  hostname1  rpciod          0  hostname1  rpciod         1  hostname1  rpciod          2  hostname1  rpciod         3

I want to assign the result of an expression (i.e., the output from a command) to a variable and then manipulate it – for example, concatenate it with a string, then echo it.  Here's what I've got: #!/bin/bash cd ~/Desktop; thefile= ls -t -U | grep -m 1 "Screen Shot"; echo "Most recent screenshot is: "$thefile;  But that outputs: Screen Shot 2011-07-03 at 1.55.43 PM.png Most recent screenshot is:   So, it looks like that isn't getting assigned to $thefile, and is being printed as it's executed. What am I missing?


I plugged in the summations, tried to square both sides but couldn't reach the desired conclusion. I'm not sure what the second vector would be for the Cauchy inequality. Even when I use the vector itself as the second vector, I still don't see how I could do this.

I am trying to prove that for $x \in \mathbb{R}^n$ $$\frac{1}{\sqrt{n}}||x||_1 \le ||x||_2 \le ||x||_1$$  So far I have successfully proven that $||x||_2 \le ||x||_1$, which was fairly easy.  I took the square of both norms and used that to show that $||x||_2^2 \le ||x||_1^2$.  The needed result then follows easily.  Where I am getting stuck is in proving that $\frac{1}{\sqrt{n}}||x||_1 \le ||x||_2$.  I took the square of both norms again, which results in $$(\frac{1}{\sqrt{n}}||x||_1)^2 = \frac{1}{n} \sum_{i=1}^n|x_i|^2+\frac{2}{n}\sum_{i \neq j}|x_i||x_j|$$ and $$(||x||_2)^2 = \sum_{i=1}^n|x_i|^2$$  My next step was to prove that $\frac{2}{n}\sum_{i \neq j}|x_i||x_j|$ must be less than the difference between $\frac{1}{n} \sum_{i=1}^n|x_i|$ and $\sum_{i=1}^n|x_i|$, meaning that $$\frac{2}{n}\sum_{i \neq j}|x_i||x_j| \le \frac{n-1}{n}\sum_{i=1}^n|x_i|$$ Which is where I am now stuck.  Is there some identity that I am missing here that will make this easier?


I'm trying to compute the symmetry plane of a 3D mesh representing an animal footprint in R.  I've ran a PCA on the 5755 points that are making up the 3D mesh (see below):  The output of the PCA is the following matrix of variable loadings (i.e., a matrix whose columns contain the eigenvectors):  The question is how can I now link these Principal Components to the symmetry plan (𝑎𝑥+𝑏𝑦+𝑐𝑧=𝑑) that passes thought the centre of mass of the 3D mesh (i.e. mean x, mean y and mean z)? I've read many times the following post but unfortunately I couldn't find a solution to my problem:  Here is my script (so far): library(Rvcg) library(rgl)  path_ply <- "/Volumes/eTrack/eTrack - Segmented 3D models"  filelist_ply1 <- list.files(path_ply, pattern = ".ply",full.names = TRUE)  i=1  filelist_ply1[i]  #Read 3D mesh (.ply) Specimen <- vcgPlyRead(filelist_ply1[i], updateNormals = TRUE,  clean = TRUE)  #Remove unwanted components Specimen <- vcgIsolated( Specimen, facenum = NULL, diameter = NULL, split = FALSE, keep = 1, silent = FALSE)  X <- t(Specimen$vb[1:3,])  #Demeaning the variables mean_vec <- colMeans(X)  X_demeaned <- matrix(NA, ncol = 3, nrow = length(X[,1])) X_demeaned[, 1] <- X[, 1]-mean_vec[1] X_demeaned[, 2] <- X[, 2]-mean_vec[2] X_demeaned[, 3] <- X[, 3]-mean_vec[3]  cov.X=cov(X_demeaned) eigen_vectors <- eigen((cov.X))$vectors eigen_values  <- eigen((cov.X))$values eigen_vectors eigen_values  a <- eigen_vectors[1, 3] b <- eigen_vectors[2, 3] c <- eigen_vectors[3, 3] d <- a * mean_vec[1] + b * mean_vec[2] + c * mean_vec[3]  open3d() plot3d(X[, 1], X[, 2], X[, 3], type = "p", col = "red", size = 1) rgl.planes(a, b, c, d, alpha=0.2, color = "#D95F02")

I am trying to estimate a midplane of a 3D model using the midpoints of paired landmarks, in order to reconstruct missing data (midplane refers here to the middle/saggital plane of the cranium which cuts the skull into two symmetrical halves, left and right).  I therefore need to estimate a plane from 27 points in 3D. I need to get the equation of the plane as $$ax+by+cz=d.$$  I have looked into orthogonal regression and principal component analysis (PCA) as methods, however I didn't take maths past A-levels and am struggling. I know I can supposedly use the eigenvectors to get the equation of the plane of best fit, but need someone to explain exactly how. I am using R for the PCA but am not great at R either.  Alternatively, if there's a better way to estimate the plane I would be glad to hear it!


This tag is about discussion on creating new StackExchange sites. Why is this tag named area51. Does it have anything to do with the US Air Force Facility in Nevada? How did the tag name originate for its use in StackExchange?

According to : "We like the little aliens."  This seems well targeted to appeal to the Stack Overflow / Server Fault / Super User audience, but way off the mark if the goal is to "make the Internet a better place to get expert answers to your questions."    There are experts who aren't interested in or focused on technology oriented topics.  Little aliens are unlikely to be something that someone interested in organizing a site on gardening would gravitate too.  No, I'm not suggesting that no one interested in gardening would be bother to look at a site with little aliens, but won't it be likely that the sort of mass appeal to to a very broad cross section of the internet will be lacking?


This is my code:    This is my first value. That is 8.    This is my next value. That is 11.    This is my integer value. That is 107.    My expect return value is 271.78 but it return back me 271.78(0)3. That make me wonder why? I tried to casting foot and inch to double but it not work.     show me how to compare but i need to return a right number. It can't help me.

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


When I toggle a push button switch on and off, instead of getting a pure on/off continuity levels I sometimes get "transitional" values. I need it to be purely on/off with nothing in between. What components do I need to add to the switch to make that happen?  There is +5v being applied at what is labeled "TIP".  Here is am drawing of the original circuit I am trying to replace:  Hopefully that helps explain what I am trying to do.

I recently read an  about button debouncing and was wondering if I should keep this in mind when working with, for example, an Arduino (ATMega mC)? I assume it is an issue, especially when working with interrupts.  So is it better to detect bounce in code, or should this be taken care of with hardware? Please elaborate.


How can I install libavcodec-extra-53 on ubuntu 14.04?  When I use the following command:  root@sana:/home/sana/topology# sudo apt-get install libavcodec-extra-53   I receive the following message:  Reading package lists... Done Building dependency tree        Reading state information... Done Package libavcodec-extra-53 is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source However the following packages replace it:   libav-tools:i386 libav-tools  E: Package 'libavcodec-extra-53' has no installation candidate

On Ubuntu 14.04.5 I just upgraded firefox to version 50.0; now there is a message on some pages which reads:   libavcodec may be vulnerable or is not supported, and should be updated to play videos   So how can I update libavcodec?  A simple   sudo apt-get install libavcodec   gives the following output:  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package libavcodec   So maybe I don't have libavcodec installed in the first place? So why do I get this message...?


I have not broken this down very far. I have come to the conclusion that there are infinitely many values for n where there exists  12 coprimes to n. Since there are infinitely many primes, and primes are coprimes to any number smaller than that prime, I reach that conclusion. Can anyone stop me and tell me where I'm going wrong or how to approach this.   I've used the theorem:  $ \varphi (n) = ((1-\frac{1}{p_{1}})...(1-\frac{1}{p_{k}})) $  But to compute these values would one not need to write a program to run which slots in all these primes?

How do I generalize the equation to be able to plug in any result for $\phi(n)=12$ and find any possible integer that works?


Trvially, the empty set $\emptyset$ is a subset of every set $V$(say). Does it mean that $\emptyset$ is also a subset of every subset of $V$? i.e , if $A$ is an arbitrary subset of $V$, then will it be right to say that $\emptyset$ $\subseteq A$?

This problem is from Discrete Mathematics and its Applications  My question is on 9b. I know that the sign represents an element is a member of. (from book)  I know that the O with a slash across it is the empty set which "is a special set that has no elements". From , I got that the empty set is a subset of all sets, meaning that every member of the empty set(nothing) is also a member of any other set. Based on all of this, for 9b, would {0} contain the empty set because it fundamentally has the elements that consist of the empty set(nothing) or does it physically have to have the empty set?


I need to show that $$\frac{1}{\sqrt {2\pi}} \int_{-\infty}^{+\infty} x^{2n} e^{\frac{-x^2}{2}}dx = (2n-1)!!$$  Integration by parts seems to be the best apporach but I cannot seem to figure my way through it.

I need help proving the following:  Let $X$ be normally distributed with parameters $\sigma=0$ and $\mu=1$. Let $n$ be a positive integer. Show that:  $$E(X^{2n})=\frac{(2n)!}{2^nn!}=:(2n-1)!!$$  I've tried the change of variables $Y=X^2$ and then calculating the integral, but got nowhere. Any hints?  Thanks in advance!


Since today my software-center won' start properly. I tried starting it with software-center from bash but the command cannot be found. I also tried reinstalling the software-center with the terminal sudo apt-get install --reinstall software-center but there is no installation canditate. Also I followed all of the instructions here:  Now the really weird thing is, that I can start it from the sidebar but only if I right-click it and then click on 'Show Details'... then it finally shows up. Any help is appreciated, thanks! Question reframed here since a partial solution was given without solving the core issue:

I have had trouble with sound (now fixed) since upgrading to 19.10, and in the middle of trying the common solutions, the Software Center "disappeared". I got aware of quite late, so I don't know what caused it.  Anyway, would you know how to reinstall it ? Trying sudo apt-get install software-center doesn't work.


EDIT: Thank you for all the links you provided answering the first part of the post, regarding the stacking of Polearm Master (PAM), War Caster (WC) work and Spell Sniper (SS) feats. [if someone didn't know, the consensus is that combining the three will allow you to cast booming blade in place of an opportunity attack when an enemy enters or exits your reach of 10 ft]  I would be grateful if someone could help with the second part regarding the damage output. From a damage point of view, using the cantrips as the main source of damage, I will not allow me to use the PAM bonus attack. That is until level 7 when I use the cantrips until Level 7 where EK gets War Magic     Beginning at 7th level, when you use your action to cast a cantrip, you can make one weapon attack as a bonus action.   However, I will also be losing the Extra Attack feature since I will not be able to attack twice when using a cantrip. Then scaling past level 10, I will lose even more Extra Attacks.  My questions are:  a) Is that how Extra Attack and War Magic interact? In that regard, is it worth becoming an Eldritch Knight?  b) Other than thematically, does it make sense in terms of damage to use 3 feats for what appears to be a less than synergistic character, between normal attacks, cantrip attacks and extra attacks?   c) Should the natural progression be level 1 PAM, level 4 SS and then level 6 WC?  Again, thank you for taking the time to read this and reply!

If you have the spell sniper feat (doubles range of spells), and you use a weapon with reach, can you cast booming blade and hit a creature at 10ft? Can you also combine this with the feats Polearm Master and War Caster to make a booming blade opportunity attack when a creature enters your reach (of 10ft)?


I have two pgfplots plots that have exactly the same width as far as their displayed data goes, but have different x-label widths and y-label widths. How can I get them to align such that the part where the data is displayed is on the same x-position on the document? first plot:    ^ 200| 150| 100| some data  50|  --|----------->    | 50 100 150  second plot:       ^ 200000| 150000| 100000| some data  50000|     --|----------->       | 50 100 150  Here's how they align in my document (using \centering):      ^   200|   150|   100| some data    50|    --|----------->      | 50 100 150        ^ 200000| 150000| 100000| some data  50000|     --|----------->       | 50 100 150  Here is how I want them to align (but they still have to kind of be in the center of the document):       ^    200|    150|    100| some data     50|     --|----------->       | 50 100 150        ^ 200000| 150000| 100000| some data  50000|     --|----------->       | 50 100 150  I have an idea on how this could work: Is there some option (I searched online but didn't find anything) that tells pgfplot to kind of have "floating" labels? (I am rendering these pgfplots as seperate pdf files and then I include them in my main tex-file, because somehow I can't get them to externalize, but that is a different story)

Hello I have a Problem with the alignment of the y-axis in TikZ! The y-axis of the last plot isn't aligned to the other two plots! trim axis left doesn't work! Can somebody help me? Thanks!  \documentclass[svgnames,a4paper,ngerman,fontsize=12pt]{scrreprt} \usepackage{tikz} \usetikzlibrary{arrows} \usepackage{pgfplots}  \begin{document} \begin{figure}[!h]\centering  \begin{tikzpicture}[xscale=8,yscale=5] \draw [->, thick] (0,0) -- (0,0.5)node[left]{$U,I$}; \draw [->, thick] (0,0) -- (1.1,0)node[below]{$t$};  \draw [blue, ultra thick, rounded corners] (0,0.3)--(0.1,0.3)--(0.15,0.22)--(0.2,0.22)--(0.22,0.02)--(0.8,0.02)--(0.85,0.4)--(0.88,0.3)--(1,0.3)node[above,blue]{$u(t)$}; \draw [red, ultra thick, rounded corners] (0,0)--(0.1,0)--(0.18,0.4)--(0.2,0.3)--(0.83,0.3)--(0.85,0.0)--(1,0.0)node[above,red]{$i(t)$}; \end{tikzpicture}  \begin{tikzpicture}[xscale=8,yscale=5] \draw [->, thick] (0,0) -- (0,0.5)node[left]{$P$}; \draw [->, thick] (0,0) -- (1.1,0)node[below]{$t$};  \draw [orange, ultra thick, rounded corners] (0,0)--(0.1,0)--(0.15,0.4)--(0.22,0.05)--(0.8,0.05)--(0.85,0.3)--(0.9,0.0)--(1.0,0.0);  \end{tikzpicture} \begin{tikzpicture}[xscale=8,yscale=5] \draw [->, thick] (0,0) -- (0,0.5)node[left]{$E$}; \draw [->, thick] (0,0) -- (1.1,0)node[below]{$t$};  \draw[purple, ultra thick, rounded corners] (0,0)--(0.1,0)--(0.2,0.2)--(0.8,0.3)--(0.9,0.4)--(1,0.4); \draw[thick](0.1,-0.01)--(0.1,0.01); \draw[thick](0.2,-0.01)--(0.2,0.01); \draw (0.15,0)node[below]{$E_{on}$}; \draw[thick](0.8,-0.01)--(0.8,0.01); \draw[thick](0.9,-0.01)--(0.9,0.01); \draw (0.85,0)node[below]{$E_{off}$}; \draw[decorate,thick,decoration={brace, mirror}] (0.2,-0.01)--node[below]{xxx}(0.8,-0.01) ;  \end{tikzpicture} \caption{Plot}\label{fig:PvIGBT} \end{figure} \end{document}


How does a manual tester become expert in automation testing in Selenium? Please also explain where to start and how to start. I am also not good in Java but I have  basic knowledge. I want to do selenium using Java

So I've been testing web based analytical software now for the past 4 years or so with mostly manual techniques. But for 2015, I've set myself the goal of getting setup and start writing automated tests and to introduce automated testing into my company.  I've done a little research and it seems that Selenium is quite big when it comes to writing automated tests, but most of the tutorials I've come across reference the Java language.  Some questions:   Is Java the primary language used for Selenium tests?  Do you recommend it over C# ?  Wat is the process of writing test scripts?  Are there Frameworks that I should use that can make the process even easier?


I'm trying to use the unirest library to make some requests, but when I try to use it I get the following error:     Exception in thread "main" java.lang.NoClassDefFoundError:   org/apache/http/HttpRequest   at   java.base/java.lang.ClassLoader.defineClass1(Native Method)   at   java.base/java.lang.ClassLoader.defineClass(Unknown Source)   at   java.base/java.security.SecureClassLoader.defineClass(Unknown Source)     at   java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(Unknown   Source)   at   java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(Unknown   Source)   at   java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(Unknown   Source)   at   java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown   Source)   at   java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown   Source)   at java.base/java.lang.ClassLoader.loadClass(Unknown Source)     at java.base/java.lang.ClassLoader.defineClass1(Native Method)  at   java.base/java.lang.ClassLoader.defineClass(Unknown Source)   at   java.base/java.security.SecureClassLoader.defineClass(Unknown Source)     at   java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(Unknown   Source)   at   java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(Unknown   Source)   at   java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(Unknown   Source)   at   java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown   Source)   at   java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown   Source)   at java.base/java.lang.ClassLoader.loadClass(Unknown Source)     at java.base/java.lang.ClassLoader.defineClass1(Native Method)  at   java.base/java.lang.ClassLoader.defineClass(Unknown Source)   at   java.base/java.security.SecureClassLoader.defineClass(Unknown Source)     at   java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(Unknown   Source)   at   java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(Unknown   Source)   at   java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(Unknown   Source)   at   java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown   Source)   at   java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown   Source)   at java.base/java.lang.ClassLoader.loadClass(Unknown Source)     at   com.mashape.unirest.request.BaseRequest.asJson(BaseRequest.java:68)     at incandescent.Interface.main(Interface.java:14) Caused by:   java.lang.ClassNotFoundException: org.apache.http.HttpRequest     at   java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(Unknown   Source)   at   java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(Unknown   Source)   at java.base/java.lang.ClassLoader.loadClass(Unknown Source)     ... 29 more   I did imported the required libraries to my path in Eclipse as the following printscreen shows:    Thanks everyone!

I am getting a NoClassDefFoundError when I run my Java application.  What is typically the cause of this?


I've been using  for a while now and sometimes it suggests that I invert the if. I guess an example would be a better explanation of my situation:  public void myfunction(int exampleParam){     if(exampleParam > 0){         //Do something with form controls for example.     } }   Now ReSharper suggests that I invert the if to this:  public void myfunction(int exampleParam){     if(exampleParam <= 0)         return;     //Do something with form controls for example }   Does this "improve" performance somehow? Or is it just aesthetic?

When I ran  on my code, for example:      if (some condition)     {         Some code...                 }   ReSharper gave me the above warning (Invert "if" statement to reduce nesting), and suggested the following correction:     if (!some condition) return;    Some code...   I would like to understand why that's better. I always thought that using "return" in the middle of a method problematic, somewhat like "goto".


So the question would be fairly short.  I would like to add options and arguments to alias created by us in .bashrc file it so how can I do it(cause almost everything is possible in computers) if it is possible

I want to know if I can pass an argument with an alias command.  for example:  alias d="dmesg|grep -iw usb|tail -5"    Now d will print the last 5 lines. If I want to use d to print a different number of lines, I have to make change in the alias command declaration of d again.  Is there any way I can modify the declaration of an alias so that I don't have to retype the declaration to change the number of lines. Like incorporating passing the number of lines as an argument while declaring alias for d? Or is there some other method to solve this?


It is mathematically proven that the solid angle of any closed surface which does not contain the origin, is zero.  Following the definition of solid angle, the total projection of the surface upon a sphere with radius one is zero. Does it not mean if someone was standing on the sphere, they wouldn't see the surface? Is my intuition right? How does it apply to real life then? I'm sure it is way more complicated than that. I will be glad for some physical intuition of how is it possible.

Actually my question comes from Gauss law which says charges outside a closed surface, doesn't effect on the whole electric flux of the surface.  The reason of that is that the solid angle of a closed surface while measuring it from outside of the surface, is zero. ( on the other hand, the solid angle of a closed surface from inside the closed surface is $4\pi$)  My question is why solid angle of a closed surface from exterior  is zero? Please don't use Stokes' theorem!


I want to find two connected graphs, with the same score. One of them having hamiltonian cycle and the other not.   Do such graphs even exist?

I'm trying to find out if it is possible to construct a connected Hamiltonian and a connected non-Hamiltonian graph using the same degree sequence. For disconnected graphs it would be easier, I could choose a degree sequence of $(2,2,2,2,2,2)$ and have $C_6$, which has a Hamiltonian path, and two disjoint 3-cycles, which are non-Hamiltonian.  How to do it with two connected graphs?


I was watching Star Trek: First Contact again, and one thing I noticed was the scene where Picard mows down a couple of Borg drones with a Tommy gun.  It got me wondering if the Borg could adapt to projectile weaponry. If they can't then why hasn't Starfleet started using them again specifically for anti-Borg operations?

In "First Contact" Picard kills a couple of Borg drones in the Holodeck with a holographic Tommy gun.  It would appear that while the Borg are able to adapt to become impervious to energy weapons, they are vulnerable to bullets.  This looks like a gaping logical hole: why couldn't Star Fleet replicate "primitive" assault rifles to fight the Borg, if they knew that phasers were useless against them?  Has this ever been addressed?


What is reliable way to get the node id from the path alias in Drupal 8?

I want to be able to get the nid but the only information I have is .  Is there a way to get either the internal path of /node/*  for that alias if I am not on the page?  Or is there a way to just get the nid from that alias right away?


I need a Iterator<Character> from a String object. Is there any available function in Java that provides me this or do I have to code my own?

StringTokenizer? Convert the String to a char[] and iterate over that? Something else?


In Breaking Bad Saul has been shown at Andrea's new house, where he delivers Jesse's money directly to Andrea. Both her and Brock are familiar with him, we even see him conversing with Brock.  Also later in the 5th season, Walt randomly shows up on their door-step, I don't recall Jesse ever telling him where they live...it connects the dots a little, it would also explain how Brock was poisoned. Saul gave him Lily of the Valley     The doctors and Jesse believed that Brock came across the flower growing naturally and ate some poisonous berries.   And how often would a kid question someone they knew? All Saul would have to do was hold out his hand and watch him eat the poison. It parallels nicely too, with Jesse's all too foreboding words "you're just feeding them hamburgers, just like every time.  Also note that Saul is distant with Walt throughout the 5th season, and uncomfortable whenever asked to perform a task for him.  So did Saul poison Brock?

I've seen Breaking Bad complete series 2-3 times, but I never found out how Walter White was able to poison Brock.  I mean did he himself directly feed the Valley of the Lilly berries to Brock or did he let Saul do the work? I can't figure it out.


Just as title, could we edit bookmark sidebar? I mean there has two layers I guess. First one is default area, and the others, Editable area, for the second area.    In the sidebar, do I edit(add, delete, and sort) default area on some config files?

I want to remove Videos and Music from the left side panel. But, I can't seem to find the option to do so. How do you do that?


Someone said to me today:     You can solve any derivative using your standard derivative techniques like the product rule or chain rule, but you cannot solve every integral   Of course referring to derivatives that exist.  Is it true that I can do any derivative using my standard techniques? Why can't I do any integral with my standard techniques for integration? What's stopping me?

If a function is a combination of other functions whose derivatives are known via composition, addition, etc., the derivative can be calculated using the chain rule and the like. But even the product of integrals can't be expressed in general in terms of the integral of the products, and forget about composition! Why is this?


I thought I understood python's pass-by-reference and pass-by-value processing... can anyone explain what is the difference between pass-by-reference and pass-by-value in python

When you pass a collection like list, array to another function in python, does it make a copy of it, or is it just a pointer?


I am trying to make a program that can save data as "data.ser" and retrieve it and output it. However, although it does the task, the program shows that there is an issue with the NullPointerException. public void loadData(){                  ArrayList<Object> deserialized = new ArrayList<Object>();          try {             FileInputStream fileIn = new FileInputStream("data.ser");             ObjectInputStream in = new ObjectInputStream(fileIn);             deserialized = (ArrayList<Object>)in.readObject();             in.close();             fileIn.close();         } catch(IOException i  ){             i.printStackTrace();                      } catch(ClassNotFoundException c){             c.printStackTrace();                      } catch(NullPointerException e) {             e.printStackTrace();                  }  The message that always pops up when I run the whole program is Exception in thread "main" java.lang.NullPointerException at student_Copy.Main.loadData(Main.java:94) at student_Copy.loadData.main(loadData.java:9)  There is also a class that retrieves the file public class loadData {  public static void main(String[] args) {     Main main = new Main();     main.loadData();      }

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


Currently I'm using RecyclerView from Android to show some data that I get from Firebase. I'm using MVC design pattern so I had to pass some data from the view (actViewDB), to the controller(Controller) and then to the Model class (DataModel). Unfortunately I always get the Java NullPointerException error like this  E/AndroidRuntime: FATAL EXCEPTION: main     Process: com.example.ryzen.pajakcerdas, PID: 3138     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ryzen.pajakcerdas/com.example.ryzen.pajakcerdas.actViewDB}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.ryzen.pajakcerdas.dataAdapter.setNotes(java.util.List)' on a null object reference         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)         at android.app.ActivityThread.-wrap11(Unknown Source:0)         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)         at android.os.Handler.dispatchMessage(Handler.java:105)         at android.os.Looper.loop(Looper.java:164)         at android.app.ActivityThread.main(ActivityThread.java:6541)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.ryzen.pajakcerdas.dataAdapter.setNotes(java.util.List)' on a null object reference         at com.example.ryzen.pajakcerdas.actViewDB.showModelList(actViewDB.java:22)   Here is the code  actViewDB.java  public class actViewDB extends AppCompatActivity {      private List<DataModel> modelList;     private RecyclerView rc;     private dataAdapter adapter;      @Override     protected void onCreate(@Nullable Bundle savedInstanceState) {         super.onCreate(savedInstanceState);          setContentView(R.layout.recycle_viewdatabase);          rc = findViewById(R.id.recycler_view);         rc.setLayoutManager(new LinearLayoutManager(this));         rc.setHasFixedSize(true);          modelList = new ArrayList<>();     }      private void showModelList() {         modelList.add(new DataModel("a", 2, 1, 3));         adapter.setNotes(modelList);         rc.setAdapter(adapter);     } }   Why is this happening? I'm sorry if this question is already asked, I already search for the answer multiple times from the last week but still can't fix this. The closest problem I found is this  but still doesn't fix my problem.


I installed a package on my linux machine. When I run the installed binary, it hangs:  $installedBinary --help   is supposed to return a list of command line options. Instead, the program hangs and doesn't respond. It closes when I run control+c.  How can I investigate this problem?

A colleague once told me that the last option when everything has failed to debug on Linux was to use .  I tried to learn the science behind this strange tool, but I am not a system admin guru and I didn’t really get results.  So,   What is it exactly and what does it do? How and in which cases should it be used? How should the output be understood and processed?   In brief, in simple words, how does this stuff work?


What is the difference between Luminance and Brigthness? If there is any...

The more I read about this, the more confused I become. Illuminance, as I understand it,  measured in lux, is the perceived brightness of light on a surface. It's what you'd measure with an incident light sensor. Luminance, then, is how much reflected light you'd perceive looking at that surface. This is what the light meter in a camera measures. Am I correct so far?  In both cases, the word "perceived" is important, because the scales are weighted using a  to map wavelengths to . However, in the case of illuminance, there's only actual perception if your eye happens to be the surface in question.  I can basically grasp this, but then I come across charts saying things like "family living room: 50 lux". Wait, hold on! Does that really mean that the typical lights in a house are that bright, or is it just confused and wrong, or am I confused and wrong?  If you're not taking pictures of light sources directly, why would an incident light meter reading ever be useful in photography? Reflected light recorded on film or by a sensor is usually what makes a photograph. So, if I have an incident light meter, how does that reading relate meaningfully to my camera settings?  Since incident light meters are sold and used, this implies that there must be some useful conversion. But this is where my brain explodes. Google tells me that 1 lumen equals 1 candela, so therefore 1 lumen/m² (i.e. 1 lux) must equal 1 candela/m2 (i.e. 1 nit). But clearly something is missing from this. There's something called a "steradian". Cones are involved. I'd never heard of this before; how does it fit in? I can see how it might be determined when calculating the usefulness of LED home lighting, but for a photo, I'm at a loss.  Some part of my (exploded, from the last paragraph) brain is trying to relate this to the difference between flash metering with TTL and with an incident meter. But how can the incident meter work without knowing the reflectance properties of the objects in the scene? Is this what the "C" in the  is all about? Is it just an average-this-probably-will-work value, or is there more to it than that? And if it is just an average, what knowledge is necessary for compensating for off-averages scenes? (As with the , where the photographer simply judges if the scene should be rendered brighter or darker than the average given by the meter.)  So yeah, so much confusion. In short:   What's the difference? Can one meaningfully convert between the two? When and how are illuminance / incident light measurements useful for photography?     Update: I appreciate Stan's answer, which covers the third point of when and how pretty well. And I think I've basically got the first point figured out, as described above. But I'd appreciate some answers covering the issue of conversion as well, both in the mathematical abstract and as the practical for photography. And I wouldn't mind more why and how, either.


I'm porting an application to Windows and I need to decide where to store user settings and session information on the filesystem. Under linux I put everything under ~/.myapp. I could do the same on Windows, but I'm wondering what the canonical approach is for this.  Things that will be stored in this directory:   user settings that need to persist across app lifetimes user authentication information logs

I am used to using   cd ~   to get right into my home directory. In Windows command prompt I have to do  cd Users\username   to get there. Is there a shortcut like the Linux one? It would be nice if I could get there by doing  cd username   Is something like this possible in Windows Vista?


It says I have to get a Link Device but I'm not getting it I don't know why. I'm connected to Gmail and when I connect to supercell ID, it's a new village.

I have installed the latest version of Clash Royale on both my devices (the old device and the new one which is iOS device).  Also both my devices are connected to a stable WiFi and my android is connected to Google Play & Google Play Games. My iOS device is connected to Game Center too.  I want to move my Clash Royale from my old Android device to my new iPhone I tried to follow the steps mentioned in the link below:    But unfortunately both of my devices do not show the Link device button.  My Settings section looks like below:    But the link says that it should look like this:    How can I fix this issue?


Does domain extension affect SEO rank? For example, I know that the extension .com means commercial, or .org means something non-commercial but how about SEO ranking stand-point?  .com vs .website vs .me vs .us vs .co

If I am thinking about using one of the 'fancy' top level domains such as .me or .tv should I be worried about how Google treats such domains?  Or to put it another way, if all other things are equal (good content, links etc.), will Google regard a .tv or .me as equal to a traditional .com or co.uk site?


So this is a question about the polymorph and true polymorph spells. Both spells include in their description an explanation as to what happens to the gear of the target of the polymorph spells ...     The target’s gear melds into the new form. The creature can’t activate, use, wield, or otherwise benefit from any of its equipment.   ... but nothing about what happens if you take away a part of the creature, like a feather, does it disappear once the spell is over, do you keep it ?  This is probably a subjective matter who's gonna gather subjective answers, but I don't mind. I have found nothing in the SAC or the erratas about that and even tho my current GM has ruled that I could keep the feather of the hummingbird I had polymorphed into, but I also do feel like it's a debate I could have with every future DM ... might as well see what RPG Stack Exchange thinks ?

So I'm playing a wild magic sorcerer and rolled a 78 on my Wild Magic Surge, polymorphing me into a sheep after my unsuccessful wisdom save.  My friendly companion now wants to shear me, but I will turn into my previous form in an hour.  If they shear me and polymorph ends, what will happen with my wool? Will I loose hair on my real body? Will the wool disappear?    Our DM made the following ruling, considering []:     You can shear the sheep.           A successful Animal Handling check is needed vs the sheeps Insight     check. If the sheep is charmed or tamed (by whatever action) you get     advantage on the Animal Handling throw.


Please solve this doubt : we know that  $\sqrt{a}\sqrt{b}=\sqrt{ab}$ and $i^2 = -1$. But $i= \sqrt{-1}$ which implies that $i^2 = i \cdot i = \sqrt{-1}\sqrt{-1} = \sqrt{1} = 1$ that is $i^2 = 1$. So what is the correct value of $i^2$? Is it $1$ or is it $-1$? Please explain.

We know $$i^2=-1 $$then why does this happen? $$ i^2 = \sqrt{-1}\times\sqrt{-1} $$ $$ =\sqrt{-1\times-1} $$ $$ =\sqrt{1} $$ $$ = 1 $$  EDIT: I see this has been dealt with before but at least with  I'm not making the fundamental mistake of assuming an incorrect definition of $i^2$.


Let $n,m\in\mathbb{N}_0$ and $\sqrt{n}\not\in\mathbb{Q}$. Conclude that $\sqrt{n}+\sqrt{m}\not\in\mathbb{Q}$   What would you recommend me to read to be able to solve this?  Because apart from the case that if $\sqrt{m}\in\mathbb{Q}$ I am kinda stuck.  If $\sqrt{m}\in\mathbb{Q}$ then by "rational+irrational=irrational" the statement holds. (still left to prove tho..)

Can the expression $\sqrt{n} + \sqrt{m}$ be rational if neither $n,m \in \mathbb{N}$ are perfect squares? It doesn't seem likely, the only way that could happen is if for example $\sqrt{m} = a-\sqrt{n}, \ \ a \in \mathbb{Q}$, which I don't think is possible, but how to show it?


I need to insert complete bibliographic entries in a couple of points in the middle of a text (i.e. not just a reference, but actually the entire formatted entry, as it would appear in the bibliography listing).  Is there anyway to do this while still pulling the reference from an existing .bib file and having the text be automatically formatted like the rest of the bibliography?  It is not important whether the inserted citation actually appears in the printed bibliography.

I have a reference which has a bib entry and appears in the bibliography. I want to be able to include the entire entry, exactly as it appears in the bibliography, somewhere else in the document.   Is there any way to do that other than to manually write it and format it to look similar?


$$ \text{Let }f(x)=x ,x\in \mathbb{Q}\\ \text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ } \text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }=2-x , x \in \mathbb{R}-\mathbb{Q}$$ show that (i) $\lim_{x\to1}f(x) =1$  , (ii)$\lim_{x\to c}f(x) \text {does not exist, if }c\neq 1$

So, I'm stuck with this proof for a homework assignment, and don't know where to start - my first instinct is to go with a proof by squeeze theorem. Would that work here though? I'm just not sure right now. Here's the question:  Suppose $g$ and $h$ are both defined as being in the neighborhood of $c$ and   $$\lim_{x\to c}g(x)=L=\lim_{x\to c}h(x)\;.$$  Define $f$ by   $$f(x) =\begin{cases} h(x),&\text{if }x\in\Bbb Q\\ g(x),&\text{if }x\in\Bbb R - \Bbb Q\;. \end{cases}$$  Show that $\lim\limits_{x\to c} f(x) = L$.


I am trying to solve this question, but have no idea how one can prove it:  Let $m$ be the median of the array $A$ with $n$ real numbers. Show that $$\sum_{i=1}^{n}\bigg|A[i]-x\bigg|$$ is minimal for $x = m$.  Thank you for your help!

Suppose we have a set $S$ of real numbers. Show that   $$\sum_{s\in S}|s-x| $$   is minimal if $x$ is equal to the median.    This is a sample exam question of one of the exams that I need to take and I don't know how to proceed.


One mole of a certain ideal gas is contained under a weightless piston of a vertical cylinder at a temperature $T$. The face of the piston opens into the atmosphere. What is the heat supplied in the process to expand the gas from volume $V_1$ to $V_2$ isothermally ? Friction of the piston against the cylindrical wall is negligibly small.   Now thermodynamics is a common topic to both physics and chemistry and as per my understanding of thermodynamics,I am getting different results for the heat that will need to be supplied.  According to physics :$$∆Q =∆U+∆W$$  And here the Work done is the Work done by the gas. That is :  $$W = \int PdV=\int \frac{RT}{V}dV = RT( \ln V_2)-RT( \ln V_1)$$ and as for Isothermal process: $$∆U =0 , ∆Q =RT( \ln V_2)-RT( \ln V_1)$$   Chemistry on the other hand  says: $$∆U =∆Q +∆W $$ and defines it as the Work done on the gas and this will give: $$W = -P_{atm}(V_2-V_1) $$ and as for isothermal process:$$ ∆U =0 , ∆Q =P_{atm}(V_2-V_1)$$  I am also uncertain that maybe neither of these is the correct expression and the network is actually in that work from both these forces and we have to take the sum of these to yield :$$∆Q =RT( \ln V_2)-RT( \ln V_1)-P_{atm}(V_2-V_1)$$  Now the value of $Q$ should be unique because in the real world when we perform an experiment, only one value of $Q$ would be supplied.  So which one of these is correct and where am I lacking in my understanding of thermodynamics from a physics standpoint ??  Now as this question links both physics and chemistry, I want to post it on both sites (I hope it's fine) and the link to it is

I use the sign convention:   Heat absorbed by the system = $q+$ (positive) Heat evolved by the system = $q-$ (negative) Work done on the system = $w +$ (positive) Work done by the system = $w -$ (negative)   Could anyone please tell me, that volume increased in system does positive or negative work?


I'm trying to add a custom condition in a query:   $today = new DrupalDateTime();  $today = $today->format("m-d");  $ids = Drupal::entityQuery('user')   ->condition('status', 1)   ->condition("date_format('field_birthday','%m - %d')", $today, '=')   ->execute();   Error:     PHP message: Uncaught PHP Exception   Drupal\Core\Entity\Query\QueryException:   "'date_format('field_birthday','%m-%d')   Version Drupal 8.8.4  What is the best way to solve this?

I need to select entities with specific dates.   How should the following be formatted. Do I need to parse 15-May-2010  Also how I get the error page.   function events2() {  $query = new EntityFieldQuery(); $query   ->entityCondition('entity_type', 'node', '=')   ->propertyCondition('status', 1, '=')   ->propertyCondition('type', 'event')     ->propertyCondition('field_event_date', '15-May-2010', '=');  $result = $query->execute();   return $result;  }


When using an unfamiliar Linux/BSD/Unix computer (e.g. by SSH) from the command line, how can you tell what distribution (and what version of that distribution) you're using?  Some options I've tried:   lsb_release --all: doesn't exist on OpenSuSE 11.3; works on Debian squeeze and Ubuntu 10.10. uname --all: doesn't give distro information on SuSE and Debian; works in Ubuntu. cat /etc/apt/sources.list in you can see which distribution's servers the machine connects to for updates. Obviously, only works for Debian-based distributions. Won't work if the computer has been configured to use a custom repository server.   Unfortunately none of these seem to work across many distributions. Is there a simple command to check?

Is there a way to determine what version (distribution & kernel version, I suppose) of Linux is running (from the command-line), that works on any Linux system?


Let $A=\mathbb{Z}[x]$ and $I=(2,x)\lhd A.$ Show that $x\otimes x+2\otimes2$ is not an elementary tensor in $I\otimes_{A}I$.   I have $$I\otimes_A I = \frac{L_A(I\times I)}{T}$$  where $T$ is the submodule generated by the elementary tensors $$\{(am,n)-a(m,n);(m,an)-a(m,n);(m,n)+(m,n')-(m,n+n');(m,n)+(m',n)-(m+m',n)\}$$  I haven't been able to to much work here. I have a couple of ideas: showing that $x\otimes x+2\otimes2$ can't be written in one of the form above to prove is not elementary. A possible alternative would show that the tensor given is can be written as a linaer combination of elementary tensors (and is this always true? question arise because not every tensor consists only of elementary tensors).

This question is related to .  Another exercise of Dummit-Foote is to show that     Let $I = (2, x)$ be the ideal generated by $2$ and $x$ in the ring $R = \mathbb{Z}[x]$ . Show that the element $2 \otimes_R 2 + x \otimes_R x$ in $I \otimes_R I$ is not a simple tensor, i.e., cannot be written as $a \otimes_R b$ for some $a, b \in I $.    I know how to show that a tensor is not simple in tensor products like $M \otimes_R N$ where $M$ and $N$ are free $R$-modules, but here we can't use this fact; so how to do it ?


I have the following code:  dp = [[False]*n]*n for i in range(n):     dp[i][i] = True   But it will set all elements to true. For example, for n=2, I will get [[True, True], [True, True]] where I am expecting [[True, False], [False, True]]  Can anyone explain this?

I needed to create a list of lists in Python, so I typed the following: my_list = [[1] * 4] * 3  The list looked like this: [[1, 1, 1, 1], [1, 1, 1, 1], [1, 1, 1, 1]]    Then I changed one of the innermost values: my_list[0][0] = 5  Now my list looks like this: [[5, 1, 1, 1], [5, 1, 1, 1], [5, 1, 1, 1]]    which is not what I wanted or expected. Can someone please explain what's going on, and how to get around it?


How can I protect midori from poodle? I have found fixes for Firefox and Chrome but not for midori.

After the  and , now I've heard about a new vulnerability in SSL/TLS called . How do I protect myself against being exploited?   Are only servers or also clients affected? Is this OpenSSL/GnuTLS specific? What kind of services are affected? Only HTTPS or also IMAPS, SMTPS, OpenVPN, etc.?   Please show me examples on how to avoid this vulnerability.


I believe this is an old movie, since I watched it 10+ years ago. The story is about a robot (female robot) who is pregnant with—I'm not sure, a robot or human baby. The opening sequence is pretty similar to Future World (2018), where there are motorcycles cruising the desert. However, after near the compound, those motorcycles suddenly stopped and threw their drivers in the air because of an anti-electronic measure of some sort.

I watched it maybe more than 8 to 12 years ago, but as far as I remember there was this place where androids (or maybe they were cyborgs) lived. (I think it was more like a hidden town). This guy finds them by accident (or at least I remember it that way) and tries to help them. I don't remember seeing any aliens or spaceships or anything like that. It was live-action, and I think US-based.  So, what I remember:   The bad guy is a human who has one red flashy robotic eye (not like terminators, it looks like a square eye patch above one of his eyes that functions like a second eye), he is collecting eyes from these androids/cyborgs. He also kills some of these androids/cyborgs but not all of them, some of them he just collects their eyes and doesn't kill (or get to kill). There was this woman who was a sexbot or something, she tried to give pleasure to the bad guy at some point, yet the bad guy added one of her eyes to his collection instead, but didn't/wasn't able to kill her. Towards the end she says something like "I used to give pleasure, now I only want to give pain" The human guy who found them tried to help them defend themselves from the bad guys, but they were in bad shape, many of them needed repair. To repair some of them, they needed spare parts they didn't seem to have, but one of the android/cyborg dudes said something like "we don't really bury our dead" and he brought a box of spare parts (or maybe android/cyborg body parts), they used these parts to repair some of the androids/cyborgs. There was this android/cyborg guy who was an assassin or something, but lost his fingers or hands, they couldn't find any hands compatible to his, but he said something like "I can still feel my trigger finger, just attach the weapons to my hands".   I remember it as a great movie/tv show, but I can't find anything about it. Can someone help me?  Please and thank you in advance...


I got this question in my topology exam and I had no idea how to make it, topology can be so weird sometimes it's hard to imagine some spaces.  My heart told me that it is not possible, but I do not know how to proceed on this. The easiest way seems to be using some topological invariant, line connectedness.   Please note that the factors on the product are the same.

I wonder if it is possible to consider $\mathbb R$ as a Cartesian product $X\times X$ for some set $X$. From the point of view of the dimensionality, there are spaces with a Hausdorff dimension $1/2$ (sort of Cantor sets), but I guess there are other problems in this construction  unrelated to the dimension.  Edited: replying on the comment by Asaf. I want that for all $r\in\mathbb R$ there exists a unique representation $r=\langle x,y\rangle$ where $x\in X$ and $y\in X$. Also, what if we want to have $X$ to be a topological space and $h:X\times X\to\mathbb R$ to be a homeomorphism?


Background  We know that the integral $\int f(x)~dx$ represents the area under the curve, where the area is represented by the sum of individual areas of elemental strips of the width $dx$ and height $f(x)$. As $dx$ is infinitesimal, we can ignore the error due to the curvature of the curve, and treat the elemental strips as almost 1-dimensional. As the curvature disappears at infinitesimal scale, the area becomes that of a perfect rectangle, $dx \times f(x)$.    Similarly, this can be extended to working out the volume of revolution, which consists of elemental "disks" of the face area $\pi f^2(x)$ and length $dx$. The name "disk" used in textbooks is really a cylinder with a large face area relative to a small (really, infinitesimal) length. The volume of a cyliner is equal to a face area $\times$ length, so the volume of revolution is $\int \pi f^2(x)~dx$. Again, this ignores the curvature of the original curve $f(x)$ and assumes that at each $dx$ the elemental unit is perfectly cylindrical.  The above are uncontroversial established textbook results.  Question  Why can't we extend the same principles in deriving the surface of revolution? If we take the cylinder as the elemental shape, the surface of revolution of the whole curve could be represented by the sum of lateral surfaces of the elemental cylinders, each equal to $2\pi f(x)\times dx$. So the whole surface would be equal to $\int 2\pi f(x)~dx$. But apparently this is wrong.  Instead, here, the textbook derivations () do take account of the curvature in $f(x)$, and use the elemental surface area equal to $2\pi f(x) \times ds$, where $ds$ is the curved length of the curve in each interval of $dx$. Hence, the elemental shape assumed is that of a tube, instead of a cylinder.  Why is it not acceptable to ignore the curvature here, but is acceptable in the calculations of area under the curve and volume of revolution?

For me, intuitively, integral $2\pi y~dx$ make more sense. I know intuition can not be proof, but by far, most part of math I've learned does match with my intuition. So, I think this one should 'make sense' as well. Probably I didn't understand the way surface area is measured. It will be great if any one could tell me how 'integral $2\pi y~dx$' is wrong. (By the way, how to use mathematical symbols in texts?)


My sister and I are trying to play Minecraft together, but no matter what we try, we can't get it to work. We've had this problem numerous times in the past, and it's always stopped us from playing together, unless on servers like Hypixel. We've spent the last two hours trying to fix this and reading/watching tutorials, but nothing has helped. When I try to connect, I have to do direct connect because it will not show the world automatically, despite us playing on the same IP and same version. It gives me the error message io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: no further information. I've tried turning off the firewall, but that doesn't do anything. What should I do?

I am getting the following error when I try to connect to a Minecraft server:  This is all servers, not just one. The error says:  io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection refused: no further information: Version 1.12  I've tried:  Restarting Minecraft Restarting Computer Uninstalling and Reinstalling Mincraft Uninstalling and Reinstalling Java Altering Firewall Restarting Internet I've messed with my port, made a second windows account, reset netsh winsock Checked hosts Made a new WINDOWS account  The overlay in the bottom right is Geforce's Overlay for game capturing. I don't have any mods installed. A Mojang support ticket wouldn't help. Im desperate.


I inserted foreign lang into mysql db through html form and the result is as below.   à°¯à±‡à°¸à± à°•à±à°°à±€à°¸à±à°¤à± à°œà°¨à°¨à°®à±    When i insert data by the below statement it works very fine.  $conn->set_charset('utf8');     $sql = INSERT INTO table_name (column1, column2) VALUES (value1,value2);   Im facing problem when i use a html form to insert data.  Here is the code i use.  <?php  $db_database = 'xxxxx'; $db_hostname = 'xxxx'; $db_username = 'xxxxx'; $db_password = 'xxxxx';  $db_server = mysql_connect($db_hostname, $db_username, $db_password);  mysql_select_db($db_database)     or die("Unable to connect to database: " . mysql_error());  $title =$_POST['title']; $lang =$_POST['lang'];  mysql_query ("set character_set_results='utf8'");   $sql="INSERT INTO lyrics_a (title, lang)VALUES('$title', '$lang')"; $result=mysql_query($sql);  if($result){ echo "Successful"; echo "
"; echo "Back to main page"; }  else { echo "ERROR"; } ?>   Html form:  <form method="post" action="/insertdata.php"> TITLE <input name="title" type="text" id="title" class="form-control">  LANGUAGE <input name="lang" type="text" id="lang" class="form-control">  <button type="submit" name="submit" id="submit" value="Update">Submit</button>  </form>   Worked for me. Hope this help others.     I made changes to my code as below:   Include below lines in mysql statements. mysql_connect(); mysql_query("SET NAMES 'utf8'");  Change <form> as below. <form method="post" action="/insertmysql.php"  enctype="multipart/form-data" accept-charset="UTF-8">  Add the below line at the top of the forms PHP page. header("Content-Type: text/html;charset=UTF-8");

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


I implemented a filter in angular to sort an array of objects. I used  to implement that and was able to complete the task sucessfully.  Now i'm trying to optimize the filter that i have implemented and need to know how the Array.prototype.sort() is implemented and what is the algorithm it uses for sorting.

Which algorithm does the JavaScript Array#sort() function use?  I understand that it can take all manner of arguments and functions to perform different kinds of sorts, I'm simply interested in which algorithm the vanilla sort uses.


Can someone tell me which is grammatically sound in this context -- would or will? I've looked through some of the responses to similar questions, but the explanations weren't too clear for a non-native speaker like myself.  I'm not sure if this would make things more convenient for you, but I can meet you directly at the airport...  Or...  I'm not sure if this will make things more convenient for you, but I can meet you directly at the airport...  Many thanks.

What would be the correct use of will & would in these sentences?  1) What will happen if I say to my boss that I will not come tomorrow?  2) What will happen if I would say to my boss that I will not come tomorrow?  3) What will happen if I will say to my boss that I will not come tomorrow?  4) What would happen if I would say to my boss that I will not come tomorrow?  There are four sentences which one should I use and in which situation?


I have a simple script that terminates some processes and closes ports as below. I am running metasploitable.    However, whenever I run this, it gives the below error. (note that on this file everyone has permissions)

Why do we use ./filename to execute a file in linux?  Why not just enter it like other commands gcc, ls etc...


I've read a couple of paper on Fisher's Fundamental Theory of Natural selection that states: $W(t+1) = W(t) + Var_{W}(t)$  Given a population with some degree of genetic variability, and assuming that no new mutations can appear, eventually the most fit strain will be fixed (discarding the effect of drift). The FFTNS allows to predict, given the mean fitness at any point and the fitness variance, the mean fitness of the population in the next generation. However, can we predict the variance on fitness for the new population?  Given the possible complexity of the problem, the situation I'm focus have specific conditions, but I would also like to know the general answer. But in my case:   Individuals reproduce asexually Random mating Diploids Expanding population with recurrent bottlenecks (we can approximate to Wrigth-Fisher population with certain effective population size)   More generally, given only the initial mean fitness and variance of the fitness can we predict the trajectory of the mean fitness during adaptation? If not, what do we need more? Number of strains present? Or only the full composition of the population allow for such prediction?  Thanks in advance

Background  Importance of the additive genetic variance  As stated , the fundamental theorem of Natural Selection (NS) by Fisher says:     The rate of increase in the mean fitness of any organism at any time ascribable to NS acting through changes in gene frequencies is exactly equal to its genetic variance in fitness at that time.   NS reduces the additive genetic variance  On the other hand, NS reduces additive genetic variance (discussion about the origin of this knowledge can be found ). The genetic variance of a population for multiple traits is best described by the G-matrix ( is a post on the subject).  What is a G-matrix  A G-matrix is a matrix where additive genetic variance of trait $i$ can be found at position $m_{ii}$. In other words, the diagonal contains the additive genetic variance for all traits. The other positions $m_{ij}$, where $i≠j$ contains the additive genetic covariance between the traits $i$ and $j$.  Question  How can one model how the G-matrix changes over time because of selection (assuming no mutation)?


Money does not exist in the Star Trek world. Therefore, you cannot reward Starfleet staff with bonuses and money.   I cannot imagine how this will work today on any company staffed by humans. Suppose you promote your favourite staff. Give them a big pat on the shoulder, load them with lots of responsibities and stress, then tell them they will be paid the same as the bottom person. Your company will lose the best people in no time. Today, CEO salaries have gone up and up so that companies can keep their CEOs. It is just human nature.  With Holodeck technologies, most humans will simply indulge themselves with their wildest fantasies all day long, coming out only to eat free and delicious food from the replicators. It sounds like a tempting lifestyle to many humans. Why join Starfleet? So much responsibilities and stress.  I do not see how Starfleet can attract humans without using money to take on risky assignments to boldly go where no one has gone before.   Lots of things change with time. However, human nature never changes. Kirk and Riker still have soft spots for women. Why should humans in the Star Trek world lose their greed for money? How do you keep humans motivated without using money?

Watching Star Trek made me think of a few "deeper" questions about Starfleet, which are all related to the Star Trek TV series.  So, let's take for example the Dominion War: people are dying every second, ships get destroyed and cadets are still joining although they know they are probably going to die unless they are with Picard or Sisko.  As I read and got to understand, money has no value anymore, latinum is the general trading currency in the universe. But people on Earth don't trade and don't earn their paychecks. Earth is a much better place than today and yet young boys and girls from every culture/civilization are joining Starfleet as they are willingly signing their death note.  Why are they joining, what motivates them? They might know that they're probably going to die.  They don’t earn paychecks. They could be doing any other job, yet they choose this. And what's more interesting how many died on battlefields must be lined up in front of StarFleet every day?  What do they receive after service? Why are they doing it other than preserving their homes?


I have seen that the maximum number of equidistant point on $\mathbb{R^2}$ is 3 and that makes a equilateral triangle and that can be inscribed in a circle where vertex are on the circumference and centroid is at the centre of circle. now my question is that for: does it hold for $\mathbb{R^3}$ the maximum number of equidistant point is 4 and does it form a regular tetrahedron?and like $\mathbb{R^3}$ can it be inscribed in a sphere  where vertex is on the sphere and centroid is at origin?? And can this be generalized to any n dimension with n dimensional regular polyhedra?

The question is quite straight forward, on $\mathbb{R}^2$ the maximum number of equidistant distinct points that can be layed (using the euclidean distance) is 3, forming thus an equilateral triangle. On $\mathbb{R}^3$ the maximum number of points is 4, forming thus a tetrahedon. My question is quite simple, is the maximum number of points that can be layed in $\mathbb{R}^n$ equal to $n+1$?


A follow up question of the cited question bellow.  Consider a function $f(x, y):\mathbb{R}\times\mathbb{R}\rightarrow\mathbb{R}$ is continuous in each argument. If we have continuous function $y(x):\mathbb{R}\rightarrow\mathbb{R}$, is $g(x)\equiv f(x,y(x))$ continuous?  In the former question, the joint continuity fails with a counter example. In the example the basic idea is to construct a path along which the function is not continuous, yet if we set $y(x)$ fixed, there is only one path to be verified. So is there maybe some conditions under which $f(x,y(x)$ is continuous?  @MISC {98831,     TITLE = {Continuity and Joint Continuity},     AUTHOR = {user12586 ()},     HOWPUBLISHED = {Mathematics Stack Exchange},     NOTE = {URL: (version: 2012-01-13)},     EPRINT = {},     URL = {} }

Consider a function $f(x,y):[0,1] \times [0,1] \rightarrow R.$ What is the difference between $f$ continuous in each argument and jointly continuous?


I need to analyze the output of some script  So, I know their header and their tail of some part of the output script, but not the content.  I found an approach [1] But I need something like:  $ myscript Line A Line B Line C Line D Line E Line F  $ myscript | tee /dev/stderr | <some option from C to E> > out.file  $ cat out.file Line C Line D Line E   [1] -

I want to start grepping from the lines that has CK at the end of line and stop grepping when the line has D at the end. I tried grep "$CK" "$D" file..txt, but it didn't work.  Input:  kkkkkkkkkkk    jjjjjjjjjjjjjjjjjj   gggggggggggg/CK   JHGHHHHHHHH    HJKHKKLKLLL    JNBHBHJKJJLKKL   JLKKKLLKJLKJ/D   GGGGGGGGGGGGGG   GGGGGGGGGGGGGG   The desired output:  gggggggggggg/CK   JHGHHHHHHHH    HJKHKKLKLLL    JNBHBHJKJJLKKL   JLKKKLLKJLKJ/D


I'm attempting to graph the function y=[(x-2)(x+2)]/[(x-3)(x+3)].  However, I get bizarre output, which consists of straight lines.  Any idea what's wrong?  Thanks!  \documentclass{article}  \usepackage{tikz}  \begin{document}  \begin{tikzpicture}  \draw[gray,very thin] (-5,-5) grid (5,5);  \draw[black, very thick,<->](-5,0) -- (5,0);  \draw[black,very thick,<->](0,-5) -- (0,5);  \draw[very thick,domain=-5:-3.20156] plot ({\x},{((\x-2)(\x+2))/((\x-3)(\x+3))});  \draw[very thick,domain=-2.8577:2.8577] plot ({\x},{((\x-2)(\x+2))/((\x-3)(\x+3))});  \draw[very thick,domain=3.20156:5] plot ({\x},{((\x-2)(\x+2))/((\x-3)(\x+3))});  \end{tikzpicture}  \end{document}

I am trying to plot a function but something is incorrectly written... Could anyone please help me?  \documentclass[12pt,a4paper]{article} \usepackage{amsmath, tikz} \usepackage[margin=3cm]{geometry} \usepackage{pgfplots}      \begin{document}  \begin{tikzpicture}[scale=0.45] \draw[->] (-1,0) -- (10,0) node[below] {$x$}; \draw[->] (0,-1) -- (0,10) node[above] {$y$}; \draw[dotted] (1.4,3.33) -- (1.4,0); \draw[dotted] (0,3.33) -- (1.4,3.33)  node[left = 0.65cm] {$\frac{10}{3}$}; \draw [domain=0.1:10] plot (\x,{2/(\x-0.8)}) node[right] {$f(x)=\frac{10}{5x-4}$}; \end{tikzpicture} \end{document}


I wanted to know that can we install ubuntu on the following System Requirements:--     Processor: Intel(R) Core(TM)2 Duo CPU     E4700  @ 2.60GHz (2 CPUs), ~2.6GHz                Memory: 2048MB RAM      DirectX Version: DirectX 11   Display Devices        Card name: Intel(R) G33/G31 Express Chipset Family    Manufacturer: Intel Corporation       Chip type: Intel(R) GMA 3100        DAC type: Internal      Device Key: Enum\PCI\VEN_8086&DEV_29C2&SUBSYS_75291462&REV_10  Display Memory: 256 MB

I'm thinking about installing Ubuntu Desktop, but I don't know what flavor is the best for my system. What are the minimum and recommended hardware requirements? What kind of CPU? How much memory? Should I have Hardware Acceleration? What flavor should I use?  This is an attempt of a canonical answer. My answers have the "official  requirements", the recommended are a mix of official sources and opinion based (along with the answer it's told the source). You can comment or edit if you feel that the information is obsolete or incomplete. It is a good rule of thumb that any system capable of running Windows Vista, 7, 8, x86 (Intel) OS X will almost always be a lot faster with any Ubuntu flavor even if they are lower-spec than described below.


Calculate $\frac{\sum_{n=1}^{99} \sqrt{10+\sqrt{n}}}{\sum_{n=1}^{99} \sqrt{10-\sqrt{n}}}$  I have to solve this question for a math class I'm taking, but I'm not making much headway. I tried to let $\sqrt{10+\sqrt{n}}=\sqrt{a}+\sqrt{b}$ in an attempt to make things cancel out, and got that:  $a+b=10$  $4ab=n$  But I don't think it helps me much.

Here is the question:     $$\frac{\sqrt{10+\sqrt{1}}+\sqrt{10+\sqrt{2}}+\cdots+\sqrt{10+\sqrt{99}} }{\sqrt{10-\sqrt{1}}+\sqrt{10-\sqrt{2}}+\cdots+\sqrt{10-\sqrt{99}}} = \;?$$   ()  I think we need to simplify it writing it in summation sign as you can see here:  $$\frac{\sum\limits_{n=1}^{99} \sqrt{10 + \sqrt{n}}}{\sum\limits_{n=1}^{99} \sqrt{10 - \sqrt{n}}}$$  or in Wolfram Alpha input in comments.  I can compute it too! It's easy to write a script for this kind of question. I need a way to solve it. How would you solve it on a piece of paper?


I'm a Kurdish Iraqi national, I have a UK Business Visa valid until 24th Sep 2015. I visited London on 11th May 2015 for some business meetings, and went back to Erbil on 24th May 2015.  I'm planing to travel to Manchester in the next 2 weeks (1st of Sep) to spend 10 days in Manchester as a tourist. Will I be admitted with the the business visa?

I already have a 6 month valid UK business visa received prior to April 24 2015. I was supposed to travel to the UK in April, but my trip was cancelled on medical grounds.  I am now planning to visit the UK in July for tourism. Would it be fine for me to do so? Will I be allowed to enter the UK? Should I carry the original invite letter and medical certificate to prove why I didn't go the first time?


I have an input field in HTML which is   <input type="text" id="lname" name="lname">  When i add disabled <input type="text" id="lname" name="lname" disabled>  the input is disabled in browser BUT users can input data and submit by removing the 'disabled' word in Inspect Element which kinda security problem for us. What is the alternative for this or some javascript codes to prevent?

Which is better to do client side or server side validation?  In our situation we are using    jQuery and MVC.   JSON data to pass between our View and Controller.     A lot of the validation I do is validating data as users enter it. For example I use the the keypress event to prevent letters in a text box, set a max number of characters and that a number is with in a range.   I guess the better question would be, Are there any benefits to doing server side validation over client side?    Awesome answers everyone. The website that we have is password protected and for a small user base(<50). If they are not running JavaScript we will send ninjas. But if we were designing a site for everyone one I'd agree to do validation on both sides.


Having the following inequality  $$\frac{1}{1^2}+\frac{1}{2^2}+\frac{1}{3^2}+\ldots+\frac{1}{n^2}<2$$ To prove it for all natural numbers is it enough to show that:  $\frac{1}{(n+1)^2}-\frac{1}{n^2} <2$  or  $\frac{1}{(n+1)^2}<2-\frac{1}{n^2} $

So I'm a bit stuck on the following problem I'm attempting to solve. Essentially, I'm required to prove that $\frac{1}{2^2}+\frac{1}{3^2}+\cdots+\frac{1}{n^2} < 1$ for all $n$. I've been toiling with some algebraic gymnastics for a while now, but I can't seem to get the proof right. Proving it using calculus isn't a problem, but I'm struggling hither.


I have a very tricky question....all the veg and fruit   cells contain cell wall and it is made of cellulose when we eat how our body digest though we   don't have the enzymes to breakdown 1-4 beta glucose sugar?

As we know, cellulose is the most abundant polysaccharide in nature. Why don't we have an enzyme to digest cellulose?


I want to learn ios development . I have read a few blogs and the first step seems to be learning Objective-C. Since I don't have a Mac, I want to find out if there is any way I can run objective-C on Windows& pc?

What would be the best way to write Objective-C on the Windows platform?  Cygwin and gcc? Is there a way I can somehow integrate this into Visual Studio?  Along those lines - are there any suggestions as to how to link in and use the Windows SDK for something like this. Its a different beast but I know I can write assembly and link in the Windows DLLs giving me accessibility to those calls but I don't know how to do this without googling and getting piecemeal directions.  Is anyone aware of a good online or book resource to do or explain these kinds of things?