I've got 'Webform 7.x.3.20" installed on my Drupal 7 and it works perfectly, apart from it seems to have 'broken' the MySQL database. I first noticed this when I tried to use the 'Backup and Migrate' module - I got the following error: Additional uncaught exception thrown while handling exception.  Additional uncaught exception thrown while handling exception. Original PDOException: SQLSTATE[HY000]: General error: 2013 Lost connection to MySQL server during query: show table status; Array ( ) in backup_migrate_source_db_mysql->query() (line 435 of /home/example.com/public_html/sites/all/modules/backup_migrate/includes/sources.db.mysql.inc). Additional PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: INSERT INTO {watchdog} (uid, type, message, variables, severity, link, location, referer, hostname, timestamp) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5, :db_insert_placeholder_6, :db_insert_placeholder_7, :db_insert_placeholder_8, :db_insert_placeholder_9); Array ( [:db_insert_placeholder_0] => 1 [:db_insert_placeholder_1] => php [:db_insert_placeholder_2] => %type: !message in %function (line %line of %file). [:db_insert_placeholder_3] => a:6:{s:5:"%type";s:12:"PDOException";s:8:"!message";s:112:"SQLSTATE[HY000]: General error: 2013 Lost connection to MySQL server during query: show table status; Array ( ) ";s:9:"%function";s:39:"backup_migrate_source_db_mysql->query()";s:5:"%file";s:96:"/home/example.com/public_html/sites/all/modules/backup_migrate/includes/sources.db.mysql.inc";s:5:"%line";i:435;s:14:"severity_level";i:3;} [:db_insert_placeholder_4] => 3 [:db_insert_placeholder_5] => [:db_insert_placeholder_6] =>  [:db_insert_placeholder_7] =>  [:db_insert_placeholder_8] => 82.29.92.127 [:db_insert_placeholder_9] => 1409596675 ) in dblog_watchdog() (line 160 of /home/example.com/public_html/modules/dblog/dblog.module). Uncaught exception thrown in session handler. PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT 1 AS expression FROM {sessions} sessions WHERE ( (sid = :db_condition_placeholder_0) AND (ssid = :db_condition_placeholder_1) ); Array ( [:db_condition_placeholder_0] => Zy8B5O3kHHKb5uIZnFFODRyXl9C_a82Ek-o9why5wNU [:db_condition_placeholder_1] => ) in _drupal_session_write() (line 209 of /home/example.com/public_html/includes/session.inc).  I then went to look on phpMyAdmin to find that if I clicked on the database itself, it showed that there were no tables and has started logging me out of phpMyAdmin almost immediately. However, if I click on the '+' to the left of database name on the left hand side, I can view all of the tables in the database and even browse them individually. Finally, I have used mysqlcheck over SSH and found that all the tables are OK until it reaches any belonging to webforms, and then I get "Got error: 2013..." again. I know for definite it is the module because I tried removing the tables for the database, and everything goes back to normal. Any ideas why this is happening and how this can be fixed? The webform module is excelllent and I do make good usage of it, however I'm going to have to find an alternative if this continues as I can't even update Drupal core or backup the database at the minute!

Recently I started getting an error every time I try and add a content no matter what type.  This is the error that shows up in the browser:     Additional uncaught exception thrown while handling exception.        Original   PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT COUNT(cid) FROM {comment} WHERE status = :status; Array ( [:status] => 0 ) in comment_count_unpublished() (line 313 of /Applications/MAMP/htdocs/modules/comment/comment.module).        Additional      PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: INSERT INTO {watchdog} (uid, type, message, variables, severity, link, location, referer, hostname, timestamp) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5, :db_insert_placeholder_6, :db_insert_placeholder_7, :db_insert_placeholder_8, :db_insert_placeholder_9); Array ( [:db_insert_placeholder_0] => 1 [:db_insert_placeholder_1] => php [:db_insert_placeholder_2] => %type: !message in %function (line %line of %file). [:db_insert_placeholder_3] => a:6:{s:5:"%type";s:12:"PDOException";s:8:"!message";s:154:"SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT COUNT(cid) FROM {comment} WHERE status = :status; Array ( [:status] =&gt; 0 ) ";s:9:"%function";s:27:"comment_count_unpublished()";s:5:"%file";s:56:"/Applications/MAMP/htdocs/modules/comment/comment.module";s:5:"%line";i:313;s:14:"severity_level";i:3;} [:db_insert_placeholder_4] => 3 [:db_insert_placeholder_5] => [:db_insert_placeholder_6] => ; [:db_insert_placeholder_7] =>  [:db_insert_placeholder_8] => 127.0.0.1 [:db_insert_placeholder_9] => 1338336955 ) in dblog_watchdog() (line 154 of /Applications/MAMP/htdocs/modules/dblog/dblog.module).   I also get the following error in my php error file:     PHP Fatal error:  Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General error: 2006 MySQL server has gone away' in /Applications/MAMP/htdocs/includes/database/database.inc:2136        Stack trace:   0 /Applications/MAMP/htdocs/includes/database/database.inc(2136): PDOStatement->execute(Array)   1 /Applications/MAMP/htdocs/includes/database/database.inc(664): DatabaseStatementBase->execute(Array, Array)   2 /Applications/MAMP/htdocs/includes/database/database.inc(2315): DatabaseConnection->query('SELECT expire, ...', Array, Array)   3 /Applications/MAMP/htdocs/includes/lock.inc(167): db_query('SELECT expire, ...', Array)   4 /Applications/MAMP/htdocs/includes/lock.inc(146): lock_may_be_available('theme_registry:...')   5 /Applications/MAMP/htdocs/includes/theme.inc(447): lock_acquire('theme_registry:...')   6 /Applications/MAMP/htdocs/includes/bootstrap.inc(427): ThemeRegistry->set(Array)   7 [internal function]: DrupalCacheArray->__destruct()   8 {main}         thrown in /Applications/MAMP/htdocs/includes/database/database.inc on line 2136   I am having a little trouble deciphering these error messages. Could anyone help me understand what's going on here?


I tried the Euler substitution: $t=x+\sqrt{x^{2}+a}$ and I got $\int \frac{4ta}{(t^{2}+a)^{2}}dt$ and I don't know wnat now or if it is the right way.   Thank you in advance.

Integrate: $\int (x^2+a^2)^{-3/2} \cdot dx$        My Approach:       $\int (x^2+a^2)^{-3/2} \cdot dx$ $\int (x^2+a^2)^{-3/2} \cdot d(a^2+x^2)\cdot \frac{dx}{d(x^2+a^2)}$       But this doesn't give the right answer. I showed this to my friend and he said $d(x^2+a^2)$ is not possible which makes sense since you can't take a small element of the  form $(x^2+a^2)$. How can I then solve this integration without using trigonometry?


There's a similar post here. but I haven't got the answer:    I just started learning calculus for physics, so I don't understand well yet. I was watching an MIT OpencourseWare Lecture (link below), and I just couldn't understand the last section of the video where the proof of a theorem was being explained. I did search online for answers but didn't understand their explanations, and it feels like I'm missing something really obvious.  The theorem states: If $f$ is differentiable at $x_0$, then $f$ is continuous. The proof goes like this:  1) $$ \lim_{x\to x_0} f(x)-f(x_0) = 0 $$ 2) $$ \lim_{x\to x_0} \dfrac{f(x)-f(x_0)}{x-x_0}\cdot(x-x_0)=f'(x_0)\cdot0=0 $$  What did I understand is that the first equation is just the definition of continuity: $\lim\limits_{x\to x_0} f(x) = f(x_0)$ rearranged. But I do not understand the second part at all.    Can someone please explain what is happening in the second equation? Also:  1) Where does the $f'(x_0)$ suddenly come from?  2) Why is it being multiplied with $\dfrac{x-x_0}{x-x_0}$?  It does look vaguely familar to the difference quotient: $\lim\limits_{\Delta x\to 0} f'(x_0) = \dfrac{f(x_0+\Delta x) - f(x_0)}{\Delta x}$  I am suspecting that it has something to do with $\Delta x$ being implied somewhere.  Here are the links:  (starts at 46:10)

Claim: if $f$ is differentiable at $x = x_0$ then $f$ is continuous at $x = x_0$.   Please, see if I made some mistake in the proof below. I mention some theorems in the proof:   The condition to $f(x)$ be continuous at $x=x_0$ is $\lim\limits_{x\to x_0} f(x)=f(x_0)$.  (1) If $f(x)$ is differentiable at $x-x_0$, then $f'(x)=\lim\limits_{x\to x_0} \dfrac{f(x)-f(x_0)}{x-x_0}$ exists and the function is defined at $x=x_0$.   (2) Therefore, by the Limit Linearity Theorem, $\lim\limits_{x\to x_0} f(x)$ exists and we'll show it is equals $f(x_0)$.   (3) We'll do this by the Precise Limit Definion: given $ \epsilon>0, \exists\delta|0<|x-x_0|<\delta$, then $0<|f(x)-f(x_0)|<\epsilon$. As this limit exists by (2), we can make $f(x)$ as close to  $f(x_0)$ as one wishes, therefore $\lim\limits_{x\to x_0} f(x)=f(x_0)$, what satisfies the condition for $f(x)$ be differentiable at  $x=x_0$. The end.


My target is compare date plus time for start and end date time.   The following code which only handles date did not work  var startDate = "22-Apr-2016"; var endDate = "22-Apr-2016"; var stdate = new Date(startDate); var endate = new Date(endDate); var startTime = "10:14 AM"; var endTime = "11:14 PM"; var stTime = startTime.substring(0, 5); var enTime = endTime.substring(0, 5); var stAMorPM = startTime.substring(6, 8); var enAMorPM = endTime.substring(6, 8);  if( (stdate > endate)) {     console.log("first date is greater"); }  if((stdate == endate)) {     console.log("Equal dates"); }   UPDATE:  Comparing dates and time for start and end datetime by concatenation get them, is supposedly not the correct way to do it.  var start = "22-Apr-2016"+ " "+startTime; var end   = "22-Apr-2016"+ " "+endTime; start     = new Date(start); end       = new Date(end); if(start.getTime() > end.getTime()){   console.log("start greater ") } else if(start.getTime() < end.getTime()) {   console.log("start lesser ") } else if(start.getTime() == end.getTime()) {   console.log("start equals ") }

Can someone suggest a way to compare the values of two dates greater than, less than, and not in the past using JavaScript? The values will be coming from text boxes.


I want to compare two numbers:    -3.123 -3.123456   I will use double to store them and I just want to consider the first 3 decimals, so:   import java.math.RoundingMode; import java.text.DecimalFormat;  public class DecimalComparator {     public static void main(String[] args) {         areEqualByThreeDecimalPlaces(-3.123, -3.123456);     }      public static boolean areEqualByThreeDecimalPlaces (double one, double two) {         boolean same = true;          DecimalFormat df = new DecimalFormat("#.###");         df.setRoundingMode(RoundingMode.FLOOR);         System.out.println(df.format(one));         System.out.println(df.format(two));          if (df.format(one).equals(df.format(two))) {             same = true;             System.out.println("true");         } else {             same = false;             System.out.println("false");         }         return same;     } }   The code is returning me:   -3.123 -3.124 false   why the second number is rounding to -3.124?

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


I would like to find the coefficients of a parabola passing through 2 known points. I also know the slope that the parabola should have at this 2 points. Let me show you a picture of the problem.    Known quantities: $(x_{N}, y_{N})$, $(x_{E}, y_{E})$, $\theta_{N}, \theta_{E}$.  Working with the equations I came up with: $$ \begin{align} x_{N} &= a \, y_{N}^{2} + b \, y_{N} + c \tag{1} \\ &\Rightarrow \frac{\partial x_{N}}{\partial y_{N}} = 2 a y_{N} + b = \frac{1}{\tan{\theta_{N}}} \tag{2} \\ x_{E} &= a \, y_{E}^{2} + b \, y_{E} + c \tag{3} \\ &\Rightarrow \frac{\partial x_{E}}{\partial y_{E}} = 2 a y_{E} + b = \frac{1}{\tan{\theta_{E}}} \tag{4} \\ \end{align} $$  I could write a system of three equations, for example:  $$ \left[ \begin{matrix} y_{N}^{2} & y_{N} & 1 \\ 2 y_{N} & 1 & 0 \\ y_{E}^{2} & y_{E} & 1 \end{matrix} \right] \left[ \begin{matrix} a \\ b \\ c \end{matrix} \right] = \left[ \begin{matrix} x_{N} \\ \frac{1}{\tan{\theta_{N}}} \\ x_{E} \end{matrix} \right] $$  but this will not consider the slope at point E.   If I write this system:  $$ \left[ \begin{matrix} y_{N}^{2} & y_{N} & 1 \\ 2 y_{N} & 1 & 0 \\ 2 y_{E} & 1 & 0 \end{matrix} \right] \left[ \begin{matrix} a \\ b \\ c \end{matrix} \right] = \left[ \begin{matrix} x_{N} \\ \frac{1}{\tan{\theta_{N}}} \\ \frac{1}{\tan{\theta_{E}}} \end{matrix} \right] $$  it will not consider the separation $x_{E} - x_{D}$.  How can I write a system that satisfy all my constraints?

I am trying to find the equation of a parabola with the two tangent equations to two points.  I found this post () but it did not really help me so I tried to do the math on my own.  First:   I have two points whose coordinates I know, I have two lines passing through these points whose slope I know because of their angles of inclination.   Let's say that these lines are tangents to a parabola in these two points.  How can I find the equation of this parabola given the two tangent equations and the two points ?  Here is a picture of my calculations:    According to the picture I drew I am suppose to get the following equation:  $f(x) =\dfrac{\tan(\alpha)-\tan(\beta)}{2 \cdot x_1}\cdot x^2 + \tan(\beta)\cdot x + y_2$  When I plot $f(x) =\dfrac{\tan(60)-\tan(30)}{-2 \cdot 10}\cdot x^2 + \tan(30)\cdot x + 10$ I get the following graph:    As you can see I do not get the graphic drawn in the first picture, and if I set the window to $x\in\left[x_1,0\right]$ and $y\in\left[0,y_2\right]$ I get an empty window:    What am I doing wrong ?  I hope my explanations are good enough. Please tell me if I was not clear so that I can modify my post for you and others.


Is it just for me, or has the privilege to review new posts and late answers changed for everyone?  I recently started being more active in reviewing, but the rep requirement just shot up and I can not review anymore? The rep requirement has shot up to 500. Is this just for me, as a 'process", or has it been changed site wide?

As , the retag privilege serves a lot more confusion and a lot less of its benefit due to the suggested edit system. It must be done away with. It will be done away with. ♪  In light of this decided course of action, we're going to need a new snack for the road between "Create Tags" at 300 reputation and "Established User" at 1000 reputation. We'd like your help in thinking about some ideas on what would be a nice privilege to sit at this level. Since we're... a bit dry on our end.  The primary guideline in deciding what kind of privilege to put here is acknowledging its position in the overall hierarchy of privileges. 500 reputation is an early-intermediate user, one who has started to really get the hang of the site and its function. It can be something that provides convenience in how they currently can act on the site, or it could be some new functionality that fits as an early ability (especially considering there's no new abilities until 2000 reputation's "Edit Everywhat" ability).  I look forward to hearing what creative ideas y'all can provide.


My problem is simple and I couldn't find the proper answer in this forum. My bad... I want to do that :     const dataReceived = foo;     foo(state);  How can I do that? I read it is better to avoid eval, and I couldn't get success with new Function. Thanks for your help! EDIT Thanks for your answers. I work with React. In my reducer, I have a create_item case. I can reach action.category, that can be the word 'currency' or 'country'. What I want to do is to launch either the method createCurrency or createCountry according what is inside action.category. That's why I tried to join 'create' and 'action.category' to create a dynamic function name. But it seems to be a poor idea...

I have the name of a function in JavaScript as a string. How do I convert that into a function pointer so I can call it later?  Depending on the circumstances, I may need to pass various arguments into the method too.  Some of the functions may take the form of namespace.namespace.function(args[...]).


I've set up my own server and I'm really struggling to stop any outgoing email go to spam.  I've used allaboutspam and mail-tester.com to test it and they both come back with perfect results. No issues with reverse lookup, dkim or spf records. As far as I'm aware, I'm not on any black lists.  Below is the SPF record I'm using. The record name is cornhillfarm.co.uk  v=spf1 ip4:95.138.166.68 +a +mx ~all   Here's a brief clip of the header sent to gmail from the account  Delivered-To: me@email.co.uk Received: by 10.70.38.39 with SMTP id d7csp343605pdk;         Mon, 1 Dec 2014 08:46:42 -0800 (PST) X-Received: by 10.194.121.129 with SMTP id lk1mr30339186wjb.99.1417452401636;         Mon, 01 Dec 2014 08:46:41 -0800 (PST) Return-Path: <info@cornhillfarm.co.uk> Received: from grid3.woodbridgemedia.co.uk (grid3.woodbridgemedia.co.uk. [95.138.166.68])         by mx.google.com with ESMTP id xv5si30948234wjc.162.2014.12.01.08.46.40         for <me@email.co.uk>;         Mon, 01 Dec 2014 08:46:40 -0800 (PST) Received-SPF: pass (google.com: domain of info@cornhillfarm.co.uk designates 95.138.166.68 as     permitted sender) client-ip=95.138.166.68; Authentication-Results: mx.google.com;        spf=pass (google.com: domain of info@cornhillfarm.co.uk designates 95.138.166.68 as permitted sender) smtp.mail=info@cornhillfarm.co.uk;    dkim=pass header.i=@cornhillfarm.co.uk Received: from grid.woodbridgemedia.co.uk (grid3.woodbridgemedia.co.uk [127.0.0.1]) by grid3.woodbridgemedia.co.uk (Postfix) with ESMTPA id 32C32B4490 for <me@email.co.uk>; Mon,  1 Dec 2014 16:46:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cornhillfarm.co.uk; s=default; t=1417452404; bh=ARgAG5dpW0g4y11fXdXMWe/ZrWwUJlaCkCKhW45skOU=; h=Date:From:To:Subject; b=jMEbxoDGBpx5U9MGmvoQ11Xzf3SFy5EZbtS1j5uIysR9g/uc02vP/9anss7tUpKhn  QAML+qYjGGo7CU9lfdQqtyxhYukWHoZysQsy2nIVm/uYzmQDbWFiiiOJopMqQdgnkm  xArDQ7FucQgChsGF9g1iX1qyzpkMRGCbEJ1JFpOs=   Any ideas on what I've done wrong here to try and get it out of the spam folder?  If you need any other information about my setup that I've missed, let me know and I'll send the relevant information.  Thanks in advance!

This is a  about how to handle email sent from your server being misclassified as spam.  For additional information you may find these similar questions helpful:                    Sometimes I want to send newsletters to my customers. The problem is, that some of the emails get caught as spam messages. Mostly by Outlook at the client (even in my own Outlook 2007).  Now I want to know what should be done to create "good" emails. I know about reverse lookup etc., but (for example), what about a unsubscribe link with an unique ID?  Does that increase a spam rating?


Let $R$ be a ring with the property that whenever $a, b, c ∈ R$ with $a \neq 0$ and $ab = ca$, it follows that $b = c$. Prove that $R$ is commutative.  Does the cancellation statement imply it's also an integral domain?

Show that a ring is commutative if it has the property that ab = ca implies b = c when $a\neq 0$.   This is my proof to show that a ring is commutative if it has the property that ab = ca implies b = c.  We need to show that if x, y ∈ R then xy = yx. Let a = x, b = yx and c = xy. Then ab = x(yx) = (xy)x = ca. Thus, by the hypothesis, b = c, or xy = yx. Thus, for x, y ∈ R we have xy = yx.   How would I show when $a\neq 0$?


I currently have a visa on my lost passport to Dubai. I want to get a new one but the numbers will not be the same though I was told that the new one will have a reflection of the old one in it. Would this be a sort of problem for me? It's actually an employment visa.

I need a visa to travel to UAE. My passport will expire soon (June), so today I applied for a new passport and it will be delivered to me on March 17. I need to travel to Dubai on March 18. clearly not enough time to get a visa for the new passport.  Can I send a scan of my old passport to the agency who's getting the visa for me, get a visa with the old passport number on it and then travel with both passports to Dubai? My new passport to satisfy their 6 months validity requirement and the old passport to match the passport number?


In the climactic battle of ROTS, where Anakin and Obi-Wan fought, Obi said, "Only a Sith deals in absolutes." But isn't that very statement an absolute? Plo Koon, another famed Jedi Master and general, was also known to see things in black and white, which is absolute.  When Obi-Wan said that statement, was that a way of showing that the Jedi weren't very different from the Sith? Or was that unintentional on George Lucas' part?

Obi-Wan tells Anakin that "Only the Sith deal in absolutes", and uses that as his identification that Anakin had actually turned to the Dark Side.  But it would seem the statement itself "Only the Sith deal in absolutes" would be an absolute statement itself, and that his rash actions based on this single statement is just as 'Sith-like' as Anakin's statement of "Either you're with me or against me" (paraphrased, I forget the exact statement.)  Is this not a very clear indicator that the Dark Side is present in all who use the force, and reinforces Palpatine's assertion that the Jedi are simply blind to the powers of the dark Side instead embracing their full potential?


I'd like some help. My first idea was to use induction, but then I get stuck. The base case works just fine, as you'd imagine, and then...   If  $ \sum_{i=0} ^n j {n \choose j} = n 2^{n-1} \rightarrow  \sum_{i=0} ^{n+1} j {n+1 \choose j} = (n+1) 2^{n}  $ $$ \sum_{i=0} ^{n+1} j {n+1 \choose j} =  \sum_{i=0} ^{n} j {n+1 \choose j}  + n+1 = \sum_{i=0} ^{n} j (n! / ((n-j)!j!))*(n+1)/(n+1-j)  + n+1$$ And well I can't seem to do anything else.   Another way, also using induction.  $$ \sum_{i=0} ^{n+1} j {n+1 \choose j} = \sum_{i=0} ^{n} j ({n \choose j} - {m \choose j-1}) + m + 1$$  And then I also get stuck.  I know there's another way of proving this without using induction and only with some properties and a couple of tricks I do not see to see.  Any help? Thanks.

Prove that   $$\sum^{n}_{i=1}\binom{n}{i}i=n2^{n-1}$$   I can't find counting interpretations for either of the sides. A hint of "if $S$ is a subset of $\{1, . . . , n\}$ and $S^\prime$ is its complement then $|S| + |S^\prime| = n$" was also given, but I still don't know how to begin.


Show that      $$\int_{0}^{1}\log(\sin(\pi x)) dx=-\log(2).$$   I've tried using a toy contour consisting of a rectangle, but I don't know what to do with the singularities at $0$ and $1$.   Every solution is welcomed, but I prefer to use complex analysis.

I need help with a textbook exercise (Stein's Complex Analysis, Chapter 3, Exercises 9). This exercise requires me to show that $$\int_0^1 \log(\sin \pi x)dx=-\log2$$ A hint is given as "Use the contour shown in Figure 9."    Since this is an exercise from Chapter 3, I think I should use the residue formula or something like that. But the function $f(x)=\log(\sin \pi x)$ becomes singular on $x=0$ and $x=1$, which makes the contour illegal for the residue theorem. Can anyone give me a further hint on this problem? Many thanks in advance!  P.S. This is my first time on Math Stack Exchange. If you find my post ambiguous, let me know.


This one I saw when I was very young on Cinemax (when they would show B-flicks like nobody else's business), so I will write the stuff I remember:   Story happened on a ship (colony or something), enroute to another planet. Captain died in cryo-sleep at the beginning, crew gets message that they are all that remains of mankind. Or Earth was already destroyed and they were coming out of cryo-don't recall. Crew turns on each other, start killing each other. One of crew members (a woman) is android, is last to be killed. Two crew members remaining (man and woman) try to arm escape pod to run away from ship self-destruct that android triggered, but are unable to. They open eyes after bracing to be blown up to discover that they are in a simulation in a bunker. They get message from unknown man in hologram that tells them about status of simulation (namely, that they "won"). Man ends his message by saying that "Darwin was right" or something. Both crew members leave bunker to find out that they are still on Earth… which has been destroyed.   Need help with, at the very least, the title.  I'll appreciate any help.

I searched wide and far and couldn't come up with a title for a movie I watched somewhere around the mid-90ies up to early 00's as a rerun in late-night television (in Germany, specifically on Vox; but I'm sure it was an American movie to begin with).  Basically, what I remember from the story revolves around a crew in a space station or maybe space ship of some sort. Some crew members murder other crew members and there is some kind of door they are not supposed/unable to go through. Late in the movie they do go through the door and I'm pretty sure one of the first views is a skeleton of a dead security guard. It turns out the whole thing was some kind of simulation gone wrong and they find themselves to be in a (nuclear?) wasteland. And that's pretty much the revelation/wrap-up of the movie, as I recall it.  I would be delighted if somebody had any idea what movie this could be :) Thanks!  EDIT: The whole movie was in color and I think it was feature-length, not just 45 mins.


following , they said:  The game has become a staple of party-favor bags since it was introduced in the 1870s.     You’ve probably played a 15 puzzle. It’s that frustrating yet addictive game with 15 tiles and a single empty space in a 4-by-4 grid. The goal is to slide the tiles around and put them in numerical order or, in some versions, arrange them to form an image.      The game has become a staple of party-favor bags since it was introduced in the 1870s. It has also caught the attention of mathematicians, who’ve spent more than a century studying solutions to puzzles of different sizes and startling configurations.   What does “staple of party-favor bags” mean? I don't understand the sentence, can you explain it?

Source:      The airport has become a symbol of Ukraine's fight against separatists, and the "cyborgs" are Ukrainians who have held on to it despite persistent rebel attack.   The nickname was first used online and has since become a media staple in Ukraine. It stuck, because to some the Donetsk airport defenders' exploits have appeared superhuman.   What does that actually mean?


We currently have a 3-year-old daughter and twin 2-year-old boys.  We are both 32 years old and have decent jobs.  I have many reservations on having another child, but my wife does not seem to want to listen to the reasons I have these reservations, she only says she doesn't feel like she is done yet.  Some of my concerns are as follows:   Cost of Daycare (already pay $23,000/year) New house we built last year would not be big enough. Need different vehicles to fit 4 kids When they are older we will have to choose who's events we can go to and who to disappoint Cost of school when they are older Not having enough time with each of the kids to make them feel special Not having any adult time  Very hard to find baby sitter for 3 under three, it would be worse for 4. My personal sanity (I have 2 jobs and no time to myself already) Strain on our relationship (feel like roommates sometime instead of husband/wife)   I could add quite a few more but I think you get the idea.  Please any advise will be appreciated.

My wife wants a 4th baby, but I don't.  We have been talking about it for the last few days (talking strongly).   I have raised points such as:   We will get less time to spend with our current kids. The age gap between the first and the last will be too wide. It will cost more money. She will be out of work longer. We will need a bigger house. And we don't even have our own house yet (we are still renting). We will have to start again. Sleepless nights, nappies, feeding, new cot, car seat, etc etc.   She says:   She feels like she is missing something. She has always wanted a large family. Things will be the same regardless of having 3, or 4 kids. She agrees that money will be tighter, but wants to push through it.   Our current kids are 9 months, 2 years, and 4 years. We are young married couple (25), and I have a fairly decent job.  What would be the pros and cons of having another child?   How can we rationally talk to the other about having/or not having another child?  And what should we do if we cannot agree?


When there is no space in comparison, it outputs wrong. I'd like to know why. #!/bin/bash  VAR2=2  if [[ $VAR2 = 1 ]]; then     echo "10a: \$VAR2 is 1." else     echo "10b: It's not 1." fi  if [[ $VAR2=1 ]]; then     echo "11a: \$VAR2 is 1." else     echo "11b: It's not 1." fi  This outputs: 10b: It's not 1. 11a: $VAR2 is 1.

The following script does not behave as I would have expected.  Adding spaces around the '=' in the conditional made it perform how I wanted, but it got me thinking, what is it actually doing inside the conditional?  #!/bin/bash S1='foo' S2='bar' if [ $S1=$S2 ]; then     echo "S1('$S1') is equal to S2('$S2') fi echo $S1 echo $S2   The output is:  S1('foo') is equal to S2('bar') foo bar   The contents of S1 and S2 don't change from what they are assigned, so the = doesn't perform an assignment.


I download curl deb file from curl official site : . I want to install curl deb file but meet this trouble:     Please tell e how to fix this trouble. I'm not edit anything on /etc/apt/sources.list. Why this trouble happend to me?

Say, I have foo-1.2.3.deb which depends on perl and python, however, running command:  dpkg -i ./foo-1.2.3.deb   won't install these dependencies. So I must apt-get install perl python by hand.  How to make dpkg -i install these dependencies for me automatically?


I know that theoretically, neutronium cannot exist. However, no work was done until now even looking for neutronim around us. So my question is that, if neutronium actually existed with some minimum mass number (above 2, excluding the observed unbound dineutron in 2012), can we observe them? They don't interact with optical light, as the minimum photon energy to excite surface neutrons should be very high, and they are not charged! So how we can proof our theoretical look for neutronium? My question is about how can we roof our theoretical look for neutronium?

Neutron matter is matter comprised entirely of neutrons, as it exists in .  Most optical phenomena encountered in everyday life, such as light reflection and spectral absorption (i.e. color appearance) are the result of mechanisms involving electrons.  My simple question: How would a macroscopic sample of matter consisting entirely of neutrons (without electrons) appear to the naked eye?  Assume the matter is  and stable.  Let me add here that I'm not specifically asking about the appearance of a neutron star, as Wikipedia states that it would radiate so much that it appears white.


Not a COM32R image boot   is a message that the console infinitely keeps spitting out when I try to install Ubuntu 10.04 from a USB. I created the USB using the StartupDiskCreator in 11.04.  What is the reason for this behavior? What do I do to set it right?   I have followed the steps perfectly, as enlisted in the .

I downloaded Ubuntu 14.04 (64 bit) lts. I made a bootable usb stick. But I keep receiving this error message upon booting:  SYSLINUX 4.04 EDD 20110518 Copyright (C) 1994-2011 H. Peter Anvin et al Unknown keyword in configuration file: gfxboot.c32: not a COM32R image


We have a piece of artwork (~21 x 30 cm) originally scanned at 300 dpi  Should we rescan it at another resolution if it is going to be printed on a poster of 1 x 2,5 m ?  Thanks in advance

(This question is meant to be a resource to direct others to given that this is a common question.)  Given the task of creating an image that will be printed at a certain size, what pixel dimensions and resolution should I be setting my file at?


I have multiple tables with data on some clients. What I want to achieve is to output the amount that a certain client was billed for, in the first month he was billed.   So I run the code similar to the one bellow:  SELECT company,clientid,COALESCE (signed.value,reactivated.value) as 'Activation' , Amount FROM `tblclients` LEFT JOIN tblcustomfieldsvalues  as signed  ON tblclients.clientid = signed.relid and signed.fieldid = 5 LEFT JOIN tblcustomfieldsvalues  as reactivated ON tblclients.userid = reactivated.relid and reactivated.fieldid = 27 LEFT JOIN (     SELECT clientid,sum(total) as Amount FROM tblinvoices       WHERE month(invoicedate)=month(Activation) Group by clientid) as f on tblclients.clientid = f.clientid    My problem is that when I do the last join it gives an error : Unknown column 'Activation' in 'where clause'.  If I switch that to current_date the rest of the query works.  Any idea on how to make this work ?  Later edit: I might have oversimplified the query, I also have a COALESCE

I need to use an alias in the WHERE clause, but It keeps telling me that its an unknown column. Is there any way to get around this issue? I need to select records that have a rating higher than x. Rating is calculated as the following alias:  sum(reviews.rev_rating)/count(reviews.rev_id) as avg_rating


says every point of wavefront emit wavelet in all directions. Then why does a back ward wave not exist? Can any expert tell real answer? On different sites I get different and contradictory answer.  I am asking question from my class 12 book. It says " Huygens argued that the amplitude of the secondary wavelets is maximum in forward direction and zero in the backward direction; by making this adhoc assumption, Huygens could explain the absence of backwave. However, this adhoc assumption is not satisfactory and the absence of the backwave is really justified from more rigorous wave theory."  What justification is given by wave theory?  answer explained by Marty green on   is different from answer given by Acuriousmind on     Which is correct?

I was reading French's Vibrations & Waves where he discusses Huygens-Frensel Principle.   The principle talks about how secondary sources give rise to secondary wavelets to form the displaced wavefront. However, any secondary source can form two wavelets one moving forward & other towards the original source as pointed by French:     [...] The Huygen's construction would define two subsequent wavefronts , not one. In addition to a new wavefront farther away from the source, there would be another one corresponding to a wavefront back toward the surface, But we know this does not happen.    Then he writes:     If the Huygens way of visualizing wave propagation is to be acceptable, it must introduce the unidirectional property of a traveling wave. This can be achieved by requiring that the disturbance  starting out from a given point in the medium at a given instant is not equal in all directions. Specifically, if $O$ is the true original source ,& $S$ is the origin of Huygens wavelet, & $P$ is the point at which the disturbance is being recorded, then the effect at $P$ due to the region near $S$is a function of $f(\theta)$ of the angle $\theta$ between $OS$ & $SP$.     I am not understanding how his reasoning actually averts the possiblity of formation of back-waves. Can anyone help me visualise what he is talking? How does his reasoning maintain the unidirectional propagation of waves? Can anyone explain his argument?


Consider the following steps than I've taken:   I created a new java project, named 'A' in my eclipse work space.   I created a new class named 'Class1' and mentioned no package name for it. So it was created in the default package.   I created a new package named 'somepackage' and created a new class named 'class2' in this package.     Now I need to import class1 in class2, and use its features and services. But whatever I do I can't do this. What is the way to overcome this problem?

I'm working now together with others in a grails project. I have to write some Java-classes. But I need access to an searchable object created with groovy. It seems, that this object has to be placed in the default-package.   My question is: Is there a way to access this object in the default-package from a Java-class in a named package?


They are not a form of electromagnetic radiation, are they? So, why do gravitational waves move at the speed of light?

In electromagnetism, Maxwell's equations predict that electromagnetic disturbances travel at the speed $$c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}.$$ Does general relativity predict that gravitational waves travel at the same speed or is this "put in by hand", that is, is there a wave equation with constants that presumably include the gravitational constant $G$ and other constants?


The following is part of the conversation between a detective and Nick in the movie "Gone Girl":       Detective: “What do you do now for work?”      Nick: “My sister and I own The Bar downtown.”      Detective: “Oh, The Bar? Love the name. Very meta.”       Nick: “Thanks.”     What does "very meta" mean?

I asked about  a few days ago, quoting Maureen Dowd’s review of the movie, “J. Edgar” in New York Times.   I received six answers. But I still don’t get a clear idea of what “It’s meta” means because I don't understand (or have a total inability to comprehend) the concept of “self-referential.”   An answerer : “Meta in this fairly recent, casual context is supposed to mean self-referential, or recursive in some way. This is the sense in which my teenagers would use this term.”  So let me resubmit the question on “meta” in simpler format. When your teenager boy says “It’s (or this is) meta,” what does it mean? In what situation and of what sort of object they use this phrase?  I’m sorry for many users who lent me kind answers to my previous question. But I would like to get it fully on the meaning and usage of “it’s meta,” as a colloquial expression, not the meaning of meta as a prefix.


Can anyone help me move this table to the middle in overleaf? I've tried to look every where online but I can't seem to find the answer.   Here is the code to my table if it help:  \begin{table}[h!]  \caption{Variables and Parameters in SIR}  \centering  \begin{tabular}{c c c}  \hline\hline  S & Susceptibility stage for humans and mosquitoes \\  I & Infection stage for humans and mosquitoes\\  R & Recovered stage for humans\\  \alpha & Transmission rate of human becoming infected\\  \beta & Removal rate parasites from human  \\  \gamma & The rate which recovered individuals return to the susceptible statue due to loss of immunity\\  \epsilon & Probability of transmission of infection from a infected human to a susceptible mosquito, given that a contact between the two occurs \\  \delta & Probability of transmission of infection from a recovered human to a susceptible mosquito, given that a contact between the two occurs. \\  \zeta & Transmission rate of mosquito becoming infected\\  \eta & Probability of transmission of infection from an infectious mosquito to a susceptible human, given that a contact between the two occurs.\\  \hline   \end{tabular}  \end{table}   Here is how my table looks:

I have a document containing a table which is slightly too wide for the page. But instead of growing to the right side only, I would like to have it centered on the page.  I have tried to use the center environment but this doesn't seem to help.


How to find which folder in home directory is largest by the number of files? (excluding directories)

I'm looking for a program to show me which files/directories occupy the most space, something like:  74% music  \- 60% music1  \- 14% music2 12% code 13% other   I know that it's possible in KDE3, but I'd rather not do that - KDE4 or command line are preferred.


I want to create a table as shown below. Can someone provide me an MWE?

I've found question , but the link to the documentation isn't helping me at all.  I'd like to know how to color a table column given my column code, but the documentation only gives the syntax of the command. It doesn't give any code example of where to use it.  \usepackage{colortbl}  \begin{table}[h]     \centering     \begin{tabular}{|c|c|c|c|c|c|c|c|}         \hline         \cellcolor[gray]{0.8}128&64&32&16&8&4&2&1\\\hline         1&0&1&1&0&1&0&1\\\hline     \end{tabular} \end{table}   As you can see, I got \cellcolor to work, but I don't want to color individual cells. I want to color a whole column of the table. Does anybody know how I can go about to do this?


I have following if statement:  if (node.left.left == null && node.left.right != null)   Related to a binary tree. Before this if statement I have a other if statement that checks if node.left is null.  Why am I getting null pointer exception on this statement?  Full code in the method up until the exception:   BinaryTreeNode node= root;   if (root==null)     return true; else     {         while(node!=null)         {         if (node.key>key && node.left !=null)         {             if (node.left.key==key)                 {                     if(node.left.left==null && node.left.right==null)                         node.left=null;                     if(node.left.left==null && node.left.right!=null)                         node.left=node.left.right;

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?


What happens when a site makes it to beta, but isn't good enough to become a real site by your requirements? Will it be removed from SE altogether? Or will it be in beta forever? I'm just wondering..

I am answering questions on  - some of those answers are quite lengthy, including images and code (as are answers by others) and it would be a pity if they were just lost one day.   If the Beta site closed, I could envisage one or more of:   Moving some of the questions and answers to my own forum Moving them to the StackOverflow site (which already has a lot of questions/answers about Arduino) Move them to the , at which I am a moderator   Of course, in the case of my own answers there would be no issue of getting permission, and in the case of answers by other people this could follow discussion with the authors.  I would prefer to be able to access the markdown (question source) rather than having to redo the markdown when reposting.    So, my question is:   If a Beta site is closed down, is this after a warning period, so we have the ability to grab the markdown for answers we want to save (and any images)? Do we have the option to migrate them to other sites? (I currently don't have enough rep for that, perhaps I might have when and if the site closed). Even after the closing date, is there still a time period in which authors can migrate their questions/answers? Are some questions/answers migrated automatically (eg. if they have a good score)?   (My searches haven't revealed an exact answer to this).


How can I rename all these folders at once to remove "-v4"?  My directories look like this:  drawable-hdpi-v4/ drawable-ldrtl-v4/ mipmap-mdpi-v4/

I have a directory full of images:  image0001.png image0002.png image0003.png ...   And I would like a one-liner to rename them to (say).  0001.png 0002.png 0003.png ...   How do I do this?


If I take a really big magnet and use it to pull a large metal object then clearly there will be a force pulling this metal object toward the magnet.  But is Newtons third law obeyed here? Will the magnet also have the same force applied to it, pulling it toward the metal object? Or will the magnet experience no force at all, and have the metal object just come toward it?  I'm comfortable with vector calculus and electromagnetism (engineering) but as far as I know there is nothing in any of my textbooks which would explain this interaction, because the magnet isn't really causing a force on the metal object... its just creating the magnetic field which attracts the object because of the magnetic field created by the metal object... which should also attract the magnet.  But is Newton's third law going to hold here?

Consider a system of the two identical positive point charges situated in free space (isolated from the influence of any other external fields) as shown in the attached diagram. Particle $1$ is at $(a,a,0)$ and particle $2$ is at $(0,a,0)$. Their velocities, at the considered instant of time, are as shown in the diagram ($\mathbf{v}_1$ along the $+x$ axis, $\mathbf{v}_2$ along the $+z$ axis).    Now, by applying the Biot-Savart law, we find that the magnetic field due to particle $2$ at the position of particle $1$ is along $+y$ axis, which means that the force acting on particle $1$ is along $+z$ axis according to Fleming’s left-hand rule. A similar analysis shows that there is no magnetic force on particle $2$ as the magnetic field of particle $1$ should vanish at positions (relative to particle $1$) located along its velocity vector.  Now, if we observe the net torque on the system of two particles about the $y$ axis then it is non-zero and is directed along the $-y$ axis. Here, there are no external forces or torques acting on the isolated two-particle system, and yet the net torque, as well as the net force on the particles, are nonzero. Why? Also, Newton's third law of motion seems to be broken in this scenario. Why?    Edit $1$  I have come to know from the responses that the electromagnetic field itself takes away some momentum and angular momentum about the considered axis. However, I think that if I consider only two charged particles as my system then the Abraham-Lorentz force can be assumed to be acting upon the system, and that is sufficient to make sure that we have considered the momentum being carried away by the electromagnetic field itself.   Even after considering the action of the Abraham-Lorentz force for the two-particle system, the scenario breaks both Newton's third law and the conservation of linear and angular momentum. This is because the Abraham Lorentz forces do not exactly counterbalance the force and the torques, on the two-particle system under consideration, due to the magnetic field.    Edit $2$  The previous edit was a result of confusion and misunderstanding on my part. The force associated with the momentum carried away by the electromagnetic field as a result of the electromagnetic interaction described in the question is the Lorentz force itself which simply doesn't obey the third law of motion. The Abraham-Lorentz force is a different story. It is associated with the momentum carried away by the radiation emitted by the accelerated charged particles. This is an additional force apart from the Lorentz force and corresponds to an additional carriage of momentum by the electromagnetic field. The momentum carried away by the electromagnetic field in correspondence with the Lorentz force doesn't correspond to radiation.


TL;DR Is there a way under Linux to know which file access caused an hard disk to   spin up?   Full story My laptop has a NVME disk, which contains the operating system and my home dir, and a spinning hard disk, which contains a second home dir which I use to store bulk data that do not fit on the NVME. I believe it is a common arrangement.  One of the nice things is this layout is that when I am not working on the projects that require files on the spinning disk, the disk itself can spin down, saving on energy, battery time, noise, etc. And this happens quite frequently.  However, every now and then the hard disk spins up even if what I am doing in that moment has no clear link with data that are stored there. It is still a consequence of an action done by me, not of a cron script or something else, because it still happens as a consequence of my doing something, like opening an application. However I cannot see what opening that application should produce an access to the spinning disk, knowing which file are supposed to be there. So I would like to understand more of what happens, and this justifies the question above.

I have a 24/7 always-on Debian Jessie based headless home server that has a large 1TB SSD for the OS and all of my frequently accessed files. This same system has 4 larger hard disk drives in a SnapRAID array. These are mainly for archiving infrequently accessed Blu-rays and want those drives to remain spun down in standby unless I actually read or write to them. They are all formatted as ext4 and mounted with noatime and nodiratime enabled.  So even though no process or program should be regularly accessing those drives in any direct way, the hard drives constantly get spun up from standby. It seems to be related to graphical programs that provide a gui file browser, even something like Chromium. If I don't even browse into those drives, I'm thinking that these processes by simply getting a list of available drives spins up the hard disks. Much like blkid does. The problem is, it's hard to determine the root cause of this since none of these processes are actually reading or writing the filesystem on those drives, so no files are actually changing or being touched. Is there some sort of cache that I can populate or a buffer to prevent these programs from spinning up the hard drive simply by getting a list of available disks? This is honestly driving me insane, since I can't find a reliably way to keep these disks spun-down even though there is no direct access of the filesystem.  UPDATE: Thanks to Stephen's answer, I was able to trace the disk activity to gvfs and udisks. It's a real shame that these processes insist on waking up disks in standby when they aren't actually being accessed to do any real I/O with the filesystem. So far I just uninstalled them, knowing that it will remove some functionality from PCManFM and the like.


Is it possible to change the email address associated with all my stack exchange accounts, and can I do this from the Android app?   The Android app logs me in automatically but not my web browser at the moment and I even forgot the actual email address associated with my account.

I registered my Stack Overflow account using the Stack Exchange OpenID provider. I later changed my e-mail, but I cannot change the e-mail address associated with my OpenID for some reason. Why is that, and how do I change it? I logged in to Stack Exchange and it lets me change my password, but never my e-mail.


I am doing a Ph.D. in a university in New Zealand. I started 3 months ago and am about two years away from finishing. Since they do not issue visas (due to the pandemic), I had to start online and paid one year of tuition. For the next year, it looks like I will have to do the same thing. Now I got admission to a different PhD program in a slightly different subject in Europe with funding. Can I study for two PhDs at the same time? I am confident I can handle the workload (already finished much of the work for the NZ program). I am not asking whether this is a good idea, just whether it is allowed / legal.

I am studying a combined bachelor of engineering (electrical) and bachelor of mathematics; I just started this year and will graduate in 2018. The reason why I am doing double degrees and not a single degree is because I love both electrical engineering and mathematics and I could not ignore any of them. So with this in mind, I am thinking of doing two PhDs when I graduate (one in electrical engineering and one in mathematics). Is this a good path or I should concentrate on only one of them?


I manage a list of contact names, phone, fax, location/address, job title and department in a simple text file. That text file is then turned into a JSON file. I want to have drupal pages with departments of course, and under each department I want drupal to use that very JSON file to show only those in that department. How using very standard drupal methods can I do this. I am a new to drupal.      The data is used for other purposes so I need it to stay outside drupal but when it is updated I want drupal to show those changes.

I have Data in JSON format, and I want to insert and update that data into Drupal. I have to update all the records which I got from an external link.  How can I achieve this?


When trying to install/update Adobe Flash on Ubuntu, I get the following error.  Reading package lists... Error! E: Encountered a section with no   Package: header E: Problem with MergeList   /var/lib/apt/lists/www.geekconnection.org_remastersys_repository_karmic_en   E: The package lists or status file could not be parsed or opened.   mcalab2@mcalab-Veriton-Series:~$      How can I solve this?

The computer gave me this output in a window:  E: Encountered a section with no Package: header E: Problem with MergeList /var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_natty_main_binary-i386_Packages E: The package lists or status file could not be parsed or opened.   How can I fix this?


I am travelling from Chile to Hong Kong, with a short lay over in USA. I do not have USA visa but hold a Spanish Passport, that I can use to enter the US. However, my visa for entering China, where I will go to after Hong Kong, is on my Chilean passport. Will I have trouble when entering and exiting USA using my Spanish passport?

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


Let $S$ := {$(x, y) ∈ \mathbb R^2: x^2 + y^2 = 1$} be the unit circle. Let $p = (0, -1)$ ∈ $S$. Define a map $F$ from $\mathbb R$ × {$0$} to $S$ as follows: Given $(t, 0)$, let $F((t, 0)) = (x, y)$ ∈ $S$ be the intersection of $S$ with the line through $p$ and $(t, 0)$. Derive a formula for $F$. Show that $t$ → $F((t, 0))$ is a bijective map from $\mathbb R$ to $S$ \ {$p$}, and also derive a formula for its inverse.  Please I need help solving this If we express $S$ in polar coordinates: $$S:=\{(r,\varphi):r=1,\varphi∈(-\frac\pi{2},\frac{3\pi}{2})\}$$ then, from simple trigonometric relations, the inverse function $\Phi$ is: $$\Phi(\varphi)=\tan\frac{\frac\pi2-\varphi}2$$ and its inverse $F$ is: $$F(t)=\frac\pi{2}-2\arctan t$$ After changing coordinates back to cartesian, $F$ will look like: $$F(t)=(\cos(\frac\pi{2}-2\arctan t),\sin(\frac\pi{2}-2\arctan t))$$ which can be further simplified to: $$F(t)=(\frac{2 t}{t^2 + 1},\frac{1 - t^2}{t^2 + 1})$$ Is this the formula of $F$? And I know that to show that $\phi$ : $\mathbb R$ →  $S$ \ {$p$} is a bijective map, I have to show that $\phi$ is injective and surjective. But how do I do that? Can someone please help me in showing that $\phi$ is bijective? and how can I derive a formula for its inverse?

Let $S$ := {$(x, y) ∈ \mathbb R^2: x^2 + y^2 = 1$} be the unit circle. Let $p = (0, -1)$ ∈ $S$. Define a map $F$ from $\mathbb R$ × {$0$} to $S$ as follows: Given $(t, 0)$, let $F((t, 0)) = (x, y)$ ∈ $S$ be the intersection of $S$ with the line through $p$ and $(t, 0)$. Derive a formula for $F$. Show that $t$ → $F((t, 0))$ is a bijective map from $\mathbb R$ to $S$ \ {$p$}, and also derive a formula for its inverse.  If we express $S$ in polar coordinates: $$S:=\{(r,\varphi):r=1,\varphi∈(-\frac\pi{2},\frac{3\pi}{2})\}$$ then, from simple trigonometric relations, the inverse function $\Phi$ is: $$\Phi(\varphi)=\tan\frac{\frac\pi2-\varphi}2$$ and its inverse $F$ is: $$F(t)=\frac\pi{2}-2\arctan t$$ After changing coordinates back to cartesian, $F$ will look like: $$F(t)=(\cos(\frac\pi{2}-2\arctan t),\sin(\frac\pi{2}-2\arctan t))$$ which can be further simplified to: $$F(t)=(\frac{2 t}{t^2 + 1},\frac{1 - t^2}{t^2 + 1})$$ Is this the formula of $F$? Is it correct? And I know that to show that $\phi$ : $\mathbb R$ →  $S$ \ {$p$} is a bijective map, I have to show that $\phi$ is injective and surjective. But how do I do that? Can someone please help me show that $\phi$ is bijective? and how can I derive a formula for its inverse?


I am wondering if there is a way to orient an object to my viewing rotation? I have a slope that I want to place things on, this slope was made by hand so I don't know the exact X and Z rotation. I can make my view look at it from the top down with shift + 7, is there a way to make my selected object take this same rotation? the rotation on the sloped object isn't applied yet, does that make a difference?

I usually face this problem when I cut objects to make them printable in my 3D printer. As you may know, you need your object to have a nice base to be printed.  So I usually use bisect to cut an object to different pieces. As in this example:    and I need to rotate the top part to have a face as bottom:    I'll share my workflow in an answer, but I'm asking for a simpler solution, if there were any.


Below is my formula if condition, which is working fine. I just want to add formula like is property__c!= null, Only then below formula will run.  how can i do that?  Ex. If property__c!= null  Only then   IF(   NOT(     OR(     CASE( REOHQ__REOHQ_Basement__c, "N/A",1,  "Crawl",1, "Slab",1, "None",1, 0)=1,     CASE( Top_Property__r.REOHQ__REOHQ_Basement__c, "N/A",1,  "Crawl",1, "Slab",1, "None",1, 0)=1    )),   True,   false )

In my object record type i have created formula field. Now i want my formula field to work as below.  If Basement__c = NA and Property__r.Basement__c = NA OR  Basement__c = Crawl and Property__r.Basement__c = Crawl OR  Basement__c = Slab and Property__r.Basement__c = Slab Then it will return Type__c(formula field) = "MAtch"  And (Another rule) Basement__c DOES NOT contain any of the following "N/A,Crawl,Slab,None and Property__r.Basement__c Does not contain any of this then formula field will return "HAs basement"  How can i achieve this? Please help.


I updated my Windows 10 system to the 1607 "Anniversary Update" version and I can't find the Ubuntu Bash console.  So... Where is it?

I'd like to install the  on my Windows 10 machine.  How do I do that?


I saw this sentence in a book, and the verb "happen" has no "s":     I have seen it happen to friends.   May the sentence be wrong? and if it is correct in what cases we can not give "s" to a verb?

I have been reading Men With Brooms for a few days. I read a sentence which did not make any sense to me, so I landed here to get some help on it. I have pasted the sentence from the novel. Please go through it and let me know your valuable feedback on it.  An excerpt from the novel (Men With Brooms: A Sweeping Epic, paperback 2002, a novelization by Diane Baker Mason):     Gordon was about to walk away from the Impala when he saw it stop and his son get out. So it was real the boy had come.   As per my opinion it should have been:     Gordon was about to walk away from the Impala when he saw it stopped and his son got out. So it was real the boy had come.   I have two questions here:   Why did the writer use stop and get instead of stopped and got? As she is telling us a story which happened in the past. Let's say the writer is telling us her mind's situation and she used the present tense for it but why did she use stop and get instead of stops and gets?


Let $a$, $b$ and $c$ be non-negative numbers such that $a^3+b^3+c^3=3$. Prove that:   $$a^4b+b^4c+c^4a\leq3$$   This inequality similar to the following.     Let $a$, $b$ and $c$ be non-negative numbers such that $a^2+b^2+c^2=3$. Prove that:   $$a^3b+b^3c+c^3a\leq3,$$   which follows from the following identity.   $$(a^2+b^2+c^2)^2-3(a^3b+b^3c+c^3a)=\frac{1}{2}\sum_{cyc}(a^2-b^2-ab-ac+2bc)^2.$$   I tried Rearrangement.  Let $\{a,b,c\}=\{x,y,z\}$, where $x\geq y\geq z$.  Hence, $$a^4b+b^4c+c^4a=a^3\cdot ab+b^3\cdot bc+c^3\cdot ca\leq x^3\cdot xy+y^3\cdot xz+z^3\cdot yz=$$ $$=y(x^4+y^2xz+z^4)$$ and I don't see what is the rest.  Thank you!


One can switch between running applications with Super+Tab or Alt + Tab. This requires visual feedback - you have to look at the screen and press Tab or Shift + Tab a certain number of times to cyclically select the needed application. This could be annoying if a lot of applications are running and you need to switch between them frequently.   So my question - is it ever possible (maybe some utilities exist) to 'bind' a specific keyboard shortcut to a specific application to instantly switch on its window without visual feedback?   For example in modern web browsers you can press Alt + 1 to instantly switch on the first tab, Alt + 2 to instantly switch on the second, etc. It would be wonderful to have similar functionality for application windows. Press Alt + Tab + 1 and go to browser, Alt + Tab + 2 and go to source code editor, Alt + Tab + 3 to mail client, Alt + Tab + 4 to messenger, etc  EDIT: The solution is Super + N, where N is 1, 2, 3, ...9. It may be required to set this config in dconf utility: org.gnome.shell.extensions.dash-to-dock click-action 'minimize'

I am using Unity desktop environment. I find it difficult to switch between multiple open applications frequently. I currently use the ALT+TAB to get list of open applications and then switch to the required one. I want to know whether we can switch directly to the required application by somehow ordering the applications and then switching to required application by some shortcut like ALT+3 for third application. Thanks.


This may seem like a far fetched idea, but consider this system.  Imagine a simple system of just the Moon orbiting around the Earth, creating low tides and high tides with its gravity.  Now imagine we add a paddle wheel that produces work based on the flow of water when it is changing tides.   If the tidal cycle repeats itself many times we could expect a lot of work, but where does this energy come from?  The gravitational potential energy of the moon would be converted into what I believe is internal energy of the water and work of the paddle.   It seems to me that as long the moon orbits the Earth, then "free energy is created".   This leads me to think that if mass would be destroyed by gravity, then conservation of energy still applies. However, I have never heard about such a thing being done by gravity. Is there anything that I did not consider in my analysis of this situation? How is energy conserved?

Kind of an odd, random question that popped into my head. Tidal energy - earth's ocean movement, volcanism on some of Jupiter's moons, etc. - obviously comes from the gravitational interaction between large bodies. On earth the interactions with the moon are pulling water around the surface, creating some amount of heat due to friction, etc.   My question is, where does that energy come from exactly? More specifically, what potential energy source is getting depleted to do that work? Is the earth minutely slowing down in its spin - or are the orbits of earth and the moon subtly altered over time by the counteractive movement and friction of liquids and gasses?


Let $\gcd(m,n)=1$, prove that $m\mathbb Z/mn\mathbb Z$ is isomorphic to $\mathbb Z/n\mathbb Z$

If $\gcd(m,n) =1, $ then $m\mathbb{Z}/ mn\mathbb{Z} \cong \mathbb{Z}/(n)$.   Here is my proof to the a/m problem. But I did not make use of $\gcd(m,n) =1.$ Could anyone hence point out and explain the mistakes in my proof? Thank you.   $\text{Define}\ \phi: m\mathbb{Z}/ mn\mathbb{Z} \to \mathbb{Z}/(n)$ by $\phi(ms + mn\mathbb{Z})= [s']_n, \text{where}  \ s \in [s']_n \ \text{and} \ s' \in \{0,...,n-1\}$  $\phi$ is well-defined:  $mx + mn\mathbb{Z} = my + mn\mathbb{Z}$  $\implies mx = my + mr,$ for some $r\in \mathbb{Z}$  $\implies n | x-y$  $\implies [x]_n = [x']_n= \phi(mx + mn\mathbb{Z}) = [y]_n = [y']_n= \phi(my+ mn\mathbb{Z})$  $\phi$ is injective:  It suffices to prove that $\ker(\phi) =\{mn\mathbb{Z}\}.$  Since $\phi(0+mn\mathbb{Z}) = [0]_n, \ker(\phi) \neq \emptyset.$ Given $x = ms+mn\mathbb{Z} \in \ker(\phi),\ $ $ \phi(x)= [s]_n = [0]_n$ $\text{hence}\  s = nk,  \text{for some}\  k \in \mathbb{Z}.$  Clearly, $mnk + mn\mathbb{Z}\subseteq mn\mathbb{Z}.$ Given $y \in mn\mathbb{Z},$ let $y = mnk + (mnc -mnk),$ for some $c \in \mathbb{Z}.$ Then $y \in mnk + mn\mathbb{Z},$ i.e. $mnk + mn\mathbb{Z} = mn\mathbb{Z} $ and hence $\ker(\phi) =\{mn\mathbb{Z}\}.$  $\phi$ is homomorphism:  Let $a = ms + mn\mathbb{Z}, a' = ms'+ mn\mathbb{Z} \in m\mathbb{Z}/mn\mathbb{Z}. $ Then, $\phi(a+a')= \phi(m(s+s') + mn\mathbb{Z}) $  $\exists r \in \{1,...,n-1\}$ such that $[r]_n = [s+s']_n$ and so $\phi(m(s+s') + mn\mathbb{Z}) = \phi(mr + mn\mathbb{Z}) = [r]_n = \phi(a) +_n \phi(a').$   $\phi$ is surjective:  $\text{Given} \ [r]_n \in \mathbb{Z}/(n),\  \text{let}  \ x= mr + mn\mathbb{Z}. \ \text{Then}   \ \phi(x) =[r]_n$


Editing my post I found that in the "How to edit" and "How to format" sections there isn't a background.    This happens too in any other post on stackexchange.com

When I can scroll down far enough to have the hot network questions overlap the footer (because my question is short) there is no background under the text:    Could they either be given a white background: (just disable the transparency option)    Or stop at the footer:      This also happens with the help text on some sites, as per this bug report:     Ubuntu 14.04.1 (Latest LTS Version), . Same problem with  and .  Windows 10 Pro,  and .  (Images linked to screenshot of browser)  My question is different from  because my issue is the lack of background on the footer.   I think there was a site redesign?


I am trying to create a quite long table that will also contain citations inside, but the \breakcites macro apparently does not work inside tabular environment. Placing \citep inside \makecell does not work, either.  Here is MWE: (I am using XeLaTeX)  \documentclass[fontsize=12pt]{scrbook} \usepackage[paperwidth=8.5in, paperheight=11in, top=1.88in, bottom=1.25in, left=1.25in, right=1.13in]{geometry} \usepackage{newlfont} \usepackage{epstopdf} \usepackage[utf8]{inputenc} \allowdisplaybreaks  \usepackage{breakcites} \usepackage{longtable} \usepackage{setspace} \usepackage{fontspec} \setmainfont{Times New Roman} \pagestyle{plain} %\usepackage[style=authoryear,backend=biber]{biblatex}   \usepackage[natbibapa]{apacite} \bibliographystyle{apacite}  \doublespacing \usepackage{times}  \begin{document}  \begin{longtable}{ll} \caption{Summary of relevant computational parameters from various computational studies. This table is modified from \cite{Rojas}.} \hline Computational parameter            & Utilized parameter \\  \hline Program                            & \begin{tabular}[c]{@{}l@{}}\makecell{Spanish Initiative for Electronic Simulation with \\ Thousands of Atoms (SIESTA) \citep{lopezcorral,Sigal}} \\  \\ Vienna Ab-Inito Simulation Package (VASP) \\ \citep{Gurel,Rojas,ZhouMiao,Li2015,ChiChen} \\ Gaussian 09 \\ \citep{Gholami2016,Rad} \\ Quantum Espresso \\ \citep{Khodadadi,Wong} \\ DMol3 \citep{Jungsuttiwong} \end{tabular}                     \\ \hline \end{longtable}  \bibliography{biblio}  \end{document}   I used a separate bib file for the references. Here is screenshot of what happens when I compile the code above:    Is there a way to force line breaks at the \citep?   Note: I know the tabular inside tabular is not the optimal way to do stuff but I did not change it to another form since the output looks nice, and I don't think it has something to do with the problem. I have tried a cleaner code but the same problem arises.

I would like to create a table with some columns' width specified, while the text in those columns should be centered both horizontally and vertically. I found out that  \usepackage{array} \begin{tabular}{| c | c | m{5cm} |}   vertically centers the text in the last column, but justifies it horizontally (like text in normal paragraphs).  Update: With Jake's method, it seems both \\ and \hline cause an error. How to fix it?


I'm sorry if this question has come up before, but numerous searches proved fruitless.  How do I include a block of HTML markup in a code snippet within a post here, without the post editor trying to render it? I have a PHP/HTML/CSS question and can't for the life of me figure out how to include the relevant code.

How do I post text so that it is formatted as code?  What do I need to do so that my code shows up properly — not escaped or removed — when posted? And how to get the correct syntax highlighting?     For more information, see "" in the .


I would like to rename an external drive (USB).   How can I rename an external drive?

I'm new at Ubuntu; I installed Ubuntu 12.10 and the partitions appear like 30 GB volume and like 78EF-2C5E in task bar. I tried to rename it but rename and remove buttons are deactivated so I tried by using disks but it gives me error:  (Error setting label: Command-line `mlabel -i "/dev/sdb8" ::"windows"' exited with non-zero exit status 1: Total number of sectors (18550784) not a multiple of sectors per track (63)! Add mtools_skip_check=1 to your .mtoolsrc file to skip this test  (udisks-error-quark, 0))   and this happen also to any attached usb to my laptop.


I have been presented with an option to make a virtual tour for my school. Kind of like a Google's Street View but for a school building. It should be made so that everyone on the school's webpage can click on it and take a virtual tour of the school.   I am looking for a software that can do that and that is compatible with websites after exporting the tour if it's managed that way. The best would be a free software, if not, what are the best ones?   Any suggestions and precautions I should take before making such a virtual tour?   Thank you!

I am currently working to design a flash virtual tour, but I know little about how the photographs are taken.  Ideally I'd like to be able to take a set of 6 shots from a single focal point, and be able to align them seamlessly into a cube form. The other solution is to take a special fisheye image, and stretch it dynamically in flash.  I've seen examples of both as virtual tours, and ones formatted as a rotating cube are more responsive and have a higher image quality. The airbus and Cruden Homes are definitely in the cube format, I'm not entirely certain which format the New York VT uses:        I have a set of questions, the first is the most important, the others may become separate questions if I don't get an answer here:   How are those photos taken? Is there a specific mount that can be used? How long does it take to set up? How much post-processing is necessary on the images?


I have read in available sources that  is just a term that is defined because it is useful in calculating the minimum and maximum moments of inertia of a body and also in finding the moments of inertia about a rotated system of axes with respect to the original system of axes. But does not there stand any physical significance of ?

In classical mechanics about rotation of rigid object, the general problem is to study the rotation on a given axis so we need to figure out the moment of inertia around some axes. In 3-dimensional case, we have a matrix (i.e. moment of inertia tensor)  $$   I =  \left( \begin{matrix} I_{xx} & I_{xy} & I_{xz}\\ I_{xy} & I_{yy} & I_{yz}\\ I_{zx} & I_{zy} & I_{zz} \end{matrix} \right) $$  I am curious what's the physical significance of the matrix element. I guess the moment of inertia in element $ij$ is the moment of inertia when the object is rotating about the axis $ij$. For example, $I_{xy}$ is the moment of inertia when the object is rotating about $xy$ axis and $I_{yy}$ is the moment of inertia when the object is rotating about $y$ axis, is that correct?  When I read further into the text, it then introduce the a method to diagonalize the moment of inertia tensor such that the non-vanishing elements only appears on diagonal. In that case, the text call the diagonal elements as the principal moment of inertia, my question is what's the physical significance of the principal moment of inertia?


I have been looking for this in the internet for a while now.  I recently read another article about    Please see the [sic] in this quote below     Could Hurricane Carla have been broken up, or greatly modified, or its   course turned back to sea, by nuclear bombs?,” asked an editorial in   the Longview Daily News. “The suggestion that man-made explosions may   effect [sic] hurricanes cannot be dismissed with the same degree of   certainty on the basis of energy comparisons as was possible with   earlier atomic weapons.

I have seen many articles that use quotes from players like:     We gonna [sic] be working hard over the summer cause we gotta [sic] get better.   What is sic? Where does it come from?


The edit buttons are disabled on the meta and not main site. Is this status by design or a bug?

I love the  that was recently added onto Stack Exchange. However, this feature seems to be missing in per-site metas.  For instance:  Server Fault Meta:    DBA Meta    The parent websites, do have the edit/improve this post link however.


I am trying to find the result of 692.79-692.45 using Excel, but find the following issue:        692.79 and 692.45 are exact numbers with only two digits, but the result is not 0.34. Is there any solution to this problem? Thanks for any help.

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


I want to print duplicate and non duplicate values separately.   String[] values= { "Java","C", "JavaScript", "JavaScript", "Java" ,"Java", "Java" , "JavaScript", "Java", "Ruby"};   My output should be below.  String[] duplicate = {"Java", "Java", "Java", "Java", "Java", "JavaScript", "JavaScript", "Java"}  String[] unique = {"C", "Ruby"}    I have tried several ways but I couldn't able to make it.  public static void main(String[] args) {          String[] a = { "Java","C", "JavaScript", "JavaScript", "Java" ,"Java", "Java" , "JavaScript", "Java", "Ruby"};           List<String> uniq = new ArrayList<String>();          List<String> dupe = new ArrayList<String>();          int count = 0;         for (int j = 0; j < a.length; j++) {             for (int k = j + 1; k < a.length; k++) {                 if (a[j] == a[k]) {                     count++;                 }             }             if (count == 1){                 System.out.println("Dupe: "+a[j]);                 dupe.add(a[j]);             }              count = 0;          }     }   Output   String[] Duplicate = {"Java", "Java", "Java", "Java", "Java", "JavaScript", "JavaScript"}  String[] Unique = {"C", "Ruby"}

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


Let $S = \sum_{n\ge 0} S_n$ be a graded commutative ring. Let $f$ be a homogeneous element of $S$ of degree $> 0$. Let $D_+(f) = \{\mathfrak{p} \in\operatorname{Proj} S\mid f \notin \mathfrak{p}\}$. Let $S_{(f)}$ be the degree $0$ part of the graded ring $S_f$, where $S_f$ is the localization with respect to the multiplicative set $\{1, f, f^2,\dots\}$. The proposition states that      $D_+(f)$ is isomorphic to Spec $S_{(f)}$ as locally ringed spaces.   Part of his proof is as follows. For $\mathfrak{p} \in D_+(f)$, let $\psi(\mathfrak{p})=\mathfrak{p}S_f\cap S_{(f)}$. Then $\psi(\mathfrak{p}) \in$ Spec $S_{(f)}$. He wrote that the properties of localization show that $\psi\colon D_+(f) \rightarrow$ Spec $S_{(f)}$ is bijective. I wonder why $\psi$ is surjective.

It is well-known that if $S$ is a graded ring, and $f$ is a homogeneous element of positive degree, then there is a bijection between the homogeneous prime ideals of the localization $S_f$ and the prime ideals of $S_{(f)}$, the subring of $S_f$ comprising the homogeneous elements of degree $0$.    This is proposition II.2.5b in Hartshorne, exercise 5.5B in Ravi Vakil's notes $[1]$ (p. $130$ of the February $24$, $2012$ version), and proposition 8.1.21 of Akhil Mathew's notes $[2]$ (p. $136$). Unfortunately I cannot follow any of those proofs to my own satisfaction, perhaps because I'm not well-versed in commutative algebra.  The crux of the proof appears to be to show that, given a homogeneous prime ideal $\mathfrak{p}$ of $S$ not containing $f$, the construction used to obtain a prime ideal $\Psi (\mathfrak{q})$ of $S$ from a prime ideal $\mathfrak{q}$ of $S_{(f)}$ will recover $\mathfrak{p}$ when $\mathfrak{q} = S_f  \mathfrak{p} \cap S_{(f)}$. To be precise, let $\Psi (\mathfrak{q})$ be the homogeneous ideal of $S$ generated by $$\bigcup_{d \in \mathbb{N}} \{ s \in S_d : s / f^d \in \mathfrak{q} \}$$ and let $\Phi (\mathfrak{p}) = S_f \mathfrak{p} \cap S_{(f)}$. It's easy to see that $\Phi \circ \Psi$ acts as the identity on $\operatorname{Spec} A$ (or, for that matter, the set of all ideals of $A$), but I cannot see any obvious reason why $\Psi \circ \Phi$ should act as the identity on the set of prime ideals of $S$ not containing $f$. A detailed proof of this point would be much appreciated.  References  $[1]$ .  $[2]$ Algebraic geometry notes (covers material at the level of the first and second volume of EGA): , and .


Is there any ide for develop iphone app on windows computer ?  I want to start to develop a i phone app on windows xp. But i do not have mac book. I want to develop it on my windows computer, is there any application which will help me to do this ?

Is there any way to tinker with the iPhone SDK on a Windows machine? Are there plans for an iPhone SDK version for Windows?  The only other way I can think of doing this is to run a Mac VM image on a VMWare server running on Windows, although I'm not too sure how legal this is.


I am planning to use Halifax clarity credit card abroad when I travel to Europe. The credit card offers good rates while using abroad with no transaction charge or non sterling transaction charge (only interest charges apply). If I use my debit card abroad there are host of charges which come into the picture.  My question is can I make payments into my credit card from my debit card bank account without even using it and then use that money for credit card transactions? This means if my credit card balance is nil (not used even once for any transaction) and I pay suppose £500 from by bank account into credit card - can I use the paid amount through my credit card transactions in the future?  My assumption here is that I won't pay interest charges unless I start using my actual credit card limit. Am I right in understanding this or am I missing something?

I want to make a large purchase at a retail store to the sum of $10,000 but the credit limit on my card is set at $2000.  If I send $10K to my credit card will the purchase be allowed to go through?  Not sure if the credit limit is a hard limit or not?  I don't want to be left embarrassed if my card is declined in the store lol.  I called my bank but the answer they gave wasn't too convincing. It was kind of "Errr yes i think its OK!"  Does any one know first hand?


I am unable to flag any question or answer on Stackoverflow mobile website. In flag pop-up, when i click '  it doesn't belong here, or it is a duplicate' radio button, it throughs error 404 instead of displaying sub-menu options to flag. This is happening from last two days, someone pls help! Any help would be appreciated.

I attempted to flag ...        ...as "off topic". Although the initial flag dialog loads correctly, every time I selected the "it doesn't belong here, or is a duplicate" option, the next pane would fail to load:        Request URL:https://christianity.stackexchange.com/flags/questions/18136/close/popup?_=1375739403107 Request Method:GET Status Code:404 Not Found   The account had 46 reputation. I tested this on other sites, but found that it only occurred on Christianity.SE. This was my only account that has the for the  but not enough for the .     I have now earned the commenting privilege on Christianity and am no longer able to reproduce this error, confirming its cause.


Where can I find the official APKs to download them, in order to install them later on my phone without using my Samsung phone data?  Regards.

How many competing Android markets (other than the Play Store itself) are there and are they any good?  Which ones do you use and why?


my ubuntu machine has pagers for taking screenshots, it is working when I run manually  root@bobby:~# pageres https://example.com 480x320 --format=jpg --filename 'page' --overwrite   But, when I enable cron entry it is not working and throwing MTA error, probably due to the output enabled.  * * * * * su bobby "/usr/bin/pageres https://example.com 480x320 --format=jpg --filename 'page' --overwrite" >> log.log  * * * * * su bobby "pageres https://example.com" >> log.log   both commands are not working.

This is a  about using cron & crontab.   You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is not answered below then the answers will help you gather information that will help the community help you. This information should be edited into your original question.  The answer for 'Why is my crontab not working, and how can I troubleshoot it?' can be seen below.  This addresses the cron system with the crontab highlighted.


Which of the following is right? "Good morning John"? or "Good morning, John"?

Example:   (1) Hello John. (2) Hello, John?   (3) How are you today John? (4) How are you today, John?   (5) I wish I could John. (6) I wish I could, John.   Must there always be a comma before someone's name?


Solve $660x\equiv 1$ mod $43$   I found $660\equiv 15$ mod $43$  So I want to solve $15x\equiv 1$ mod $43$  I tried some low numbers but none of them worked. I'm not sure what to do now.

When I am faced with a simple linear congruence such as  $$9x \equiv 7 \pmod{13}$$ and I am working without any calculating aid handy, I tend to do something like the following:  "Notice" that adding $13$ on the right and subtracting $13x$ on the left gives: $$-4x \equiv 20 \pmod{13}$$  so that $$x \equiv -5 \equiv 8 \pmod{13}.$$  Clearly this process works and is easy to justify (apart from not having an algorithm for "noticing"), but my question is this: I have a vague recollection of reading somewhere this sort of process was the preferred method of C. F. Gauss, but I cannot find any evidence for this now, so does anyone know anything about this, or could provide a reference? (Or have I just imagined it all?)  I would also be interested to hear if anyone else does anything similar.


A block of ice as big as a room will have more thermal energy than a cup of hot tea. But the tea feels hotter because the average kinetic energy (temperature) is higher in case of tea. I conclude from this that total energy doesn't matter when it comes to what feels hotter. But it is said that steam at 100 °C feels hotter than water at 100 °C because steam has more energy, which is contradictory to my conclusion. Please explain where have I gone wrong. To resolve the confusions: When we heat water, its temperature keep on increasing. Boiling starts when it reaches 100 degree Celsius and bulk vaporization takes place. These vaporised molecules, possessing same energy of water (is at same temperature as it) plus latent heat of vaporisation, is what I am referring to as steam. So, it has more energy but same temperature. I expected no confusion regarding such steam causing more severe effects. But now that it has, let me mention that this is a common secondary textbook fact, that is taught and studied in India. Here is a link to a related school material: .

Imagine that you had two boxes with of steam and water of equal mass, both at $100~^\circ\rm C$, and you decide to expose your left land to the steam and your right to the water for a short period of time. Which hand would 'feel hotter' (i.e if you were to take your hand out and measure its temperature, which would be higher?  The common answer is that the steam but that answer assumes the steam condenses, which would result in a large heat transfer during the phase change. If your hand and the steam or the water are allowed to reach thermal equilibrium then it would make sense for the steam to transfer more heat since it would transfer extra heat equal to its heat of vaporization. But in a scenario where you are not in contact with the water or the steam for very long, the steam would not condense(thermal equilibrium is not reached).  The heat of vaporization of water is quite large, so it should take a decent amount time for all that heat transfer to take place (time that is not available in this scenario). Taking the rate of heat transfer between the steam and your hand and the water and your hand into account, will the heat transferred by the steam and the water be any different?


I have made some changes to i2c-ocores kernel code and I would like to build i2c-ocores module without building the whole kernel again.  could you please tell me how to do it ?  I am using the following commands to build the linux kernel:  #download sources in current directory sudo apt-get source linux-image-$(uname -r)  #Change into the downloaded directory and run following commands in order sudo chmod a+x debian/scripts/* sudo chmod a+x debian/scripts/misc/* sudo fakeroot debian/rules clean sudo fakeroot debian/rules editconfigs sudo fakeroot debian/rules binary-headers binary-generic skipabi=true skipmodule=true

The linux-source-... has a module which is disabled in the config /boot/config-3.4-trunk-686-pae so that it is not part of linux-image-... (This is on Debian, but the solution should be the same for Ubuntu, or?), e.g.  # CONFIG_CAN_PEAK_USB is not set   How would one compile just that kernel module, so that it can be used with the distributed kernel?  The respective linux-source-... package is already installed, uncompressed and linked to /usr/src/linux. /boot/config-3.4-trunk-686-pae is copied to /usr/src/linux/.config and modified with  CONFIG_CAN_PEAK_USB=m   With  make make modules   it is possible to compile the kernel and all modules. But how would one compile only that specific single module?  (Note: also the kernel needs to be compiled before, otherwise you get the following error: no symbol version for module_layout)


I am very impatient, when I unfortunately mistype my login-password on my laptop (Ubuntu 20.04), I don't want to wait three seconds to retry. (A delay of 0.3 seconds would be enough to prevent potential brute force and there is a longer time after 3 failed attempts anyway.) I found a lot of answers explaining how to change this delay for the console login and for sudo. I managed to set that delay to 0.3 seconds by editing the value in /etc/pam.d/login (for the tty console) to: auth       optional     pam_faildelay.so  delay=300000  and adding the same line to /etc/pam.d/common-auth (for sudo and the graphical login screen) as first line before (!) this line: auth    [success=1 default=ignore]      pam_unix.so nullok_secure nodelay  See:   on stackoverflow  on askubuntu  This kind of changes the delay that occurs on the graphical gdm3 login-screen in Ubuntu 20.04 but only until the login input field reappears (and shakes). If you set a long delay in /etc/pam.d/common-auth, it counts only for the time before the input field reappears. It has no effect on the delay after the shaking. I already activated logging in gdm and  when I pressed SUPER+L to Lock screen and tried about 6 times a false password; you see the 3s delay in the attempt. At the end of each false password attempt, there is a log: reauthentication service 'gdm-password' stopped  after this there starts the 3s delay until I get a new cursor. Maybe this is the main problem?  Update: For info: I use GNOME Shell 3.36.1. An Idea of mine was maybe disable the shaking animation will help? Because I found out, that you can use the mouse to click into the field and you can type immmediately while the box is shaking.

I am horribly impatient and can't stand the (for me subjectively long) delay of around 2 seconds after entering an incorrect password in the login screen or also as sudo password, before I can retry typing it correctly.  Is there a way to modify the delay and reduce it to around half a second or turn it completely off, both for sudo and the login screen?   The optimal solution would include a longer delay after maybe 3 or 5 incorrect passwords, to still prevent brute-forcing.  PS: I am currently using vanilla Ubuntu 16.04 with Unity Desktop and lightdm.


I have a road network and have added points indicating fire hall locations.   How would i go about creating buffers on those points following the road line.  The result am i looking for would create a buffer from the fire hall to 5km away on all possible roads/paths.   I do have the full OSGeo suite. Currently using QGIS 2.0.1  Thanks

Is there any way in QGIS to apply service area buffers e.g if I have a point on a map I wish to show the service coverage of 1 mile, 2 mile, 3 mile, breaks using  the road network?


Is this the best way to write this sentence below?  Moving forward, I hope to apply my experience to a cause that I am passionate about:  education.

Colons are usually used to introduce a list of some kind after an independent clause; however, would it work for a single item? For example, can you write     For 3 years, I ate hamburgers: my friend's favorite food.   If you do not use a colon here, what should be used?


I'm stuck thinking of how I can avoid SQL injection attacks on my code.   This is what I have now.  <?php session_start(); $email = $_POST['e-mail']; $fn = $_POST['firstname']; $ln = $_POST['lastname']; $cp = $_POST['cellphone']; $phn = $_POST['phone_number']; $comp = $_POST['company']; $prov = $_POST['province']; $brgy = $_POST['barangay']; $fadd = $_POST['address']; $sadd = $_POST['address2'];  $conn = mysqli_connect('localhost','root','','newcartdb')or die('Could not connect');  foreach($_POST['product'] as $product) {     $date = date('Y-m-d H:i:s');     $order_name = $product['item_name'];     $order_code = $product['item_code'];     $order_qty = $product['item_qty'];     $sub_total = $product['price'];      $query = "INSERT INTO `newcartdb`.`orders`(`Email`,`Firstname`,`Lastname`,`ContactNum`,`PhoneNum`,`Company`,`Province`,`Barangay`,`FAddress`,`SAddress`,`ProductName`,`ProductCode`,`Qty`,`SubTotal`,`datetime`) VALUES('$email','$fn','$ln','$cp','$phn','$comp','$prov','$brgy','$fadd','$sadd','$order_name','$order_code','$order_qty','$sub_total','$date')";     mysqli_query($conn,$query); }    mysqli_close($conn);  header('Location: order_confirmation.php'); ?>   How do I improve on this?

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


So I tried to make a table using this code:   \begin {tabular}{|l||c|p{8cm}|} \hline test & test2\\ \hline\hline test3 & test4\\ \hline\hline \end {tabular}   Between the 2 rows of thext I want to add a double line, but it splits the table in 2. How do I change this? Sorry for my bad english, I hope you guys understand it.

I need to draw a double line after the first row in a table, but when using \hline twice, this interrupts the vertical lines:  \documentclass{article} \begin{document}  \begin{tabular}{|c|c|c|} \hline  1 & 2 & 3 \\ \hline \hline 4 & 5 & 6 \\ \hline 7 & 8 & 9 \\ \hline \end{tabular}  \end{document}   produces:    This is without using any additional packages. How can I change this is such a ways that the vertical lines are not interrupted?


So my question is more general. I've the following simple code:  for(int i=0;i<10;i++){     long starttime=System.nanoTime();     System.out.println("test");     long runtime=System.nanoTime()-starttime;     System.out.println(i + ":" +"runtime="+runtime); }   i receive the following output:  test 0:runtime=153956 test 1:runtime=15396 test 2:runtime=22860 test 3:runtime=11197 test 4:runtime=11197 test 5:runtime=12129 test 6:runtime=11663 test 7:runtime=11664 test 8:runtime=53185 test 9:runtime=12130   What is the reason for the difference between the first and the second runtime?Thanks in advance =)

How do you write (and run) a correct micro-benchmark in Java?  I'm looking for some code samples and comments illustrating various things to think about.  Example: Should the benchmark measure time/iteration or iterations/time, and why?  Related:


This isn't to change to the current rejection process or review queue in any way.      There was recently a  on one of my answers.  It was correct to reject from the reviewer's point of view, because variable names in code were changed, however, the edit would have been beneficial to the post in this case, and I would have liked the suggested edit to have been accepted.  I edited my answer and manually added the rejected suggested changes myself. On this occasion it was a small edit, but this would be quite time consuming if it was a more substantial edit.    It would be useful if we had a feature where a user can approve/improve an edit on their own question or answer which was previously rejected by community review.  Ideally, there would also be the option to Edit & Approve so we can change any bits if necessary.    Perhaps (for example) an option in the Suggested Edits history where only the OP, and maybe moderators, can select to approve or improve a rejected edit.   OPs can currently approve suggested edits, overruling the review queue, so this would just be an extension of that - being able to approve after 3 users have rejected.

Today,  to one of . Before I got to see the notification, the edit already was rejected by other people (three rejections, one approval).  But the edit was actually a good one (like most edit proposals to my post I get to see) – a correction of syntax errors, so I would have definitively approved it.  (The suggested edit didn't change the main point of the answer, which was about the API to use, but it made the code example of my answer actually usable. I didn't compile it when writing my answer, it was late at the evening.)  So I did edit my post to include the proposed change, so the proposal is not fully lost. But the proposer only got the negative feedback from the rejection, and none of the reputation bonus an accepted edit gives.  My suggestion: Could there be added a way a post author can accept edits which were already rejected by other users?  Also, is there some way I can contact the rejectors and teach them not to reject good edits?


When I do prototyping I solder my PCBs by hand. That works fine most of the time, but I run into a problem when I have to solder chips with fine pitch (Google for VQ100 to get an idea of what I'm working with). The problem is not the soldering by itself but keeping the parts in place once the pins are aligned to the pads.   Now I'm looking for an adhesive that lets me temporarily stick a large SMD component onto the board so it does not slip away as soon as I touch the pins with my soldering tip.  During a Google search I found a log of SMD adhesives, but all of them are resistant to PCB cleaning substances. I need the exact opposite. Something that lets me temporarily stick a part onto the PCB and dissolves fast in PCB cleaning chemicals (I use isopropyl alcohol if that matters).  Something with the sticky properties like thick honey would work except that I'm looking for a more professional solution.  I'm certainly not the first one to look into this, so there must be a ready made product out there, right?

I go through this every time I have PCBs I need to populate with SMD parts, and this has become more an issue as pin spacings have gotten tighter, and my hands have become less steady with age.   So far I've modified some curved tweezers with a rubber band for grip tension, to help hold a component in place until 1 or 2 pins can be soldered. It works but it can be cumbersome. The clamping force needs to be very light, and it seems one slight tap with a sharp iron tip will still move it. I've also tried various glues, placing a pin drop of glue in the center of where a component would go.   That sometimes works, but all the glues I've tried either waste my time waiting for it to dry, or dry (skin over) too quickly when grabbing some more. Worse, too often even a pin drop of glue will spread onto the pads, and then I have to waste more time cleaning things up.   If I had my druthers, all SMD pars would come with peel off self stick backing. But anyway, suggestions would be welcome. It will be a long time and many test markets before anything I'm doing will be populated for me with pro pick and place machines.


When I follow a direct link to an answer (a share link, or I click an "answered 1h ago" or "modified 1h ago" link in the active questions list), the sticky top bar will cover up the top of the answer, including the upvote button.  for you to test it yourself.  Here's what I see after following a direct link on one of my sites:        ... then I scroll up by the height of the sticky top bar to see the actual top of the answer:        This isn't even a site-specific thing, since it will happen right here on meta:

With the introduction of the network-wide sticky top bar , I noticed a bug that's happening on every site (except for Stack Overflow). When you click on an answer link (of the form https://site.stackexchange.com/a/####), the very top of the answer and the upvote button are covered by the top bar:    Stack Overflow shows the correct behavior: