The title says it all. What makes Ubuntu so special that it deserves a particular treatment that is not received by any other distribution? Shouldn't it be merged with Unix & Linux SE? For users of other distributions it would be VERY beneficial to have their own sites in Stack Exchange. I know  is not a proof. But do we have a proof that Ubuntu is used WAY more than the other distros? Edit: So my question is challenged to ask practically the same as  one. That's false. My question is about what the merit for Ubuntu is to have it's own SE, not for knowing what the differences are. Of course there are differences, I have no doubt what there are. I understand what their differences are, perfectly, and this question didn't ask for them. As a metaphor, the fact that I understand the differences between a democracy and a dictatorship doesn't mean I have to agree with both existing in the world.

What's the difference between , , and ? In general, what's a rule for deciding where to post a question when I have one (which might apply to any of those 3)?  If I'm having a problem with Linux Mint, which seems likely to be the same in Ubuntu, is it appropriate to post it on Ask Ubuntu?


I am using a lamp with shader glossy, without the lamp the scene is good, but when I bring the lamp with the shader increases the amount of noise. what do I do?

I know that this question is a bit old or maybe overdone, but I'm running the latest edition of Blender and when I use the Cycles engine I get really fuzzy results and I can't find a simple, non-compromising solution to the quality.  I don't know exactly what I'm doing wrong here, but I'm sure others share my frustration.  Leaving everything in default settings, I started a new project and switched to the Cycles render.  I duplicated the cube and set colors for two Diffuse BSDF shaders, then went ahead and made walls and a floor all sharing the same diffuse shader.  I made two windows to emit blue light.  The screenshot has gaps between the walls because of the setup:  I'm aware that it's considered very incomplete and many have come to terms with some amount of noise, but is this normal?  Furthermore, with default settings or not, I can't change the amount of noise produced.  Supposedly, using "progressively refine" in the rendering tab should make it refine itself indefinitely, however Cycles only counts to 10 refines and then stops, creating a render which is a pixel-perfect match of the ordinary rendering method when it's completed.  I understand that there are tricks that can be used to reduce noise, but at the cost of extra processing time and usually small quality conflicts, like blurring.  My question essentially boils down to is this Cycles' current limit?


Just curious, is it possible to search all stack exchange sites via one form?   Thanks!  Christian

I was just wondering if there were any posts already about which tablet would be the best buy for this holiday season.  I wasn't sure which site I should look on.   maybe?  maybe?   I would prefer an Android tablet, so maybe even ?  Then I thought, if only there were a way to search all Stack Exchange sites for a topic.  Maybe there is, and I don't know about it. If not, there should be.


Could someone help with this, please? I don't know how to solve this problem. Maybe it helps that $(a-b)$ is a multiple of $(a^n-b^n)$, but I'm not really sure about it

Prove $a \equiv b \pmod{c} \implies a^n \equiv b^n \pmod{c}$.   Here is my proof, which I'm slightly doubtful I've done correctly:  Suppose  $a \equiv b \pmod{c}$ and $d \equiv e \pmod{c}$  We have:  $a-b=ck$ and $d-e=cs$  $a=ck+b$ and $d=cs+e$  And hence:  $$ad=(cs+e)(ck+b)=c^2sk+cab+eck+eb$$  $$=c(csk+ab+eck)+eb$$  Therefore,   $$ad-eb=cn$$  $$ad \equiv eb \pmod{c}$$  The special case $d=a^{n-1}$ and $e=b^{n-1}$ through induction is reduced to:  $$a^n \equiv b^n \pmod{c}$$  For $n \geq 1$  Induction:  If $n=1$, then by the proof above  $a=b \pmod{c}$  implies $a^2=b^2 \pmod{c}$. Assume that $a^{n-1}=b^{n-1} \pmod {c}$ is true, then we have  by the proof above: $a^{n}=b^{n} \pmod{c}$. Hence because we proved $a^{2}=b^{2} \pmod{c}$,  $a^{3}=b^{3} \pmod{c}$. And because of this $a^{4}=b^{4} \pmod{c}$. And because of this $a^{5}=b^{5} \pmod{c}$. Etc..  Is my proof valid? Because this question is more of a yes or no one, a different proof would also a nice supplement to the answer (or just  a nice answer) if you wish to provide one.


I am attempting to show that Gaussian Integers are countable.  Is it valid to map $a + bi$ to an ordered pair $(a, b)$ and then map this to the set of rationals $a/b$ ?  I am unsure if this works since  $a/b$ is not defined at $b = 0$ and am unsure of a different way to go about this. Any hints welcome, thanks!

I know that Gaussian Integers are a subset of complex numbers. They are numbers in the form   $G = \{a + ib \,\vert\, a,b \in \mathbb{Z}\}$  So to prove that a set is countable, I need to find a function $G \rightarrow \mathbb{N}$ such that every $n$ has finitely many preimages (from ).  How should I go about proving that it is countable? I don't really understand what preimages mean.


On Windows, x64 versions of the OS can run both x86 and x64 binaries.  However, x86 Windows can only run x86 binaries. Even if the underlying CPU is 64-bit capable, it cannot run x64 binaries.  Is the situation with x86 / x64 binary compatibility on Linux the same? Or is there more (or less) compatibility?

The output from uname:  root@debian:~ # uname -a Linux 5asnb 2.6.32-5-amd64 #1 SMP Mon Jun 13 05:49:32 UTC 2011 x86_64 GNU/Linux   However the /sbin/init executable shows up as 32-bit:  root@debian:~ # file /sbin/init /sbin/init: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, stripped   Other aspects of the system seem to contradict things as well:  root@debian:~ # echo $HOSTTYPE i486  root@debian:~ # getconf LONG_BIT 32


I know it's much better to use \[ \] over $$ $$ when typesetting math equations on their own line (I believe this is called display math?) But is it also inappropriate to use $ $ for in-line math over \( \)? If so, what are the reasons? I find the latter much more cumbersome to type, so I'd only like to use it if there's a good reason.

Along the lines of , what reasons are there (if any) to favor \( ... \) over $ ... $?


I tried to install ubuntu-restricted-extras using the terminal, but a "Microsoft Eula" screen poped up and I closed the terminal (now I know I should not have done it). After failing to "click" on the "ok" option of such screen. The result is that I broke apt-get... I tried apt-get install -f and also apt-get remove -f but it did not work.  jan@jan-Satellite-C855:~$ apt-get install -f E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root? jan@jan-Satellite-C855:~$ apt-get remove -f E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?   I read the article  but nothing worked...  So, what should I do now?

I get this error when trying to use apt-get:  E: Could not get lock /var/lib/dpkg/lock - open (11 Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?     How can I fix this?


The fixed point method $g(x)= x - \frac{f(x)}{2f ^\prime (x)}$  (can also be written as $x_{k+1} = x_k - \frac{f(x_k)}{2f ^\prime (x_k)}$) is similar to Newton's method except for the 1/2 coefficient. My question is how do I show the order of convergence for this method using Taylor series?  EDIT  I believe the goal is to get it into the form $|x_{k+1} - a| = C|x_{k} - a|^n$ and that $n$ is the order of convergence.   I tried getting it into the form $g(y) = g(x) + g^\prime(x)(y-x) + \frac{g ^{\prime\prime}(x)}{2!}(y-x)^2 + ...$  Since $g^\prime (x) = \frac{1}{2} + \frac{1}{2} \cdot  \frac{f ^{\prime \prime} (x) f(x)}{[f^\prime (x)]^2}$   Substituting in I get $g(x_k) = g(a) + \frac{1}{2}(x_k -a) + \frac{g^{\prime \prime}(a)}{2}(x_k-a) $  But I'm not sure what to do from here

Let $f(x)$ be a polynomial in one variable $x$ and let $\alpha$ be its $\delta$-multiple root  ($\delta\ge2$).   Show that in the Newton's $x_{k+1}=x_k-f(x_k)/f'(x_k)$, the rate of convergence to $\alpha$ is not quadratic.  My solution: Suppose that $\alpha$ is one regular root of equation.Then  $$x_{k+1}=x_k-\frac{f(x_k)}{f'(x_k)}=\phi(x_k)$$ convergence rate to $\alpha$:  $$x_k-\alpha=\phi(x_k)-\phi(\alpha)=(x_k-\frac{f(x_k)}{f'(x_k)})-(x-\frac{f(x)}{f'(x)})$$ $$(x_k-\alpha)=(f'(x_k))^{-1}(f(x_k)-f(x))=(x_k-\alpha)+(f'(x_k))^{-1}\{ f'(x_k)(x_k-\alpha)+O((x_k-\alpha)^2)\}=f'(x_k)^{-1}O((x_k-\alpha)^2))  \tag{1}$$  so the convergence rate to $\alpha$ is quadratic.  But if $\alpha$ is not regular root, then $(f'(x))^{-1}$ has no meaning. We need do slightly change in $(1)$, $$(x_k-f'(x_k)^{-1}f(x_k))-(x-f^{(\delta)}(x)\delta!f(x))=(x_k-x)-f'(x_k)(f(x_k)-f(x))$$ $$=(x_k-x)-f'(x_k)^{-1}(\frac{f^{(\delta)}(x_k) (x_k-x)^{\delta}}{\delta!}+O((x_k-x)^{\delta+1}))$$  convergence rate to non regular root $\alpha$ is one.  Is my solution correct?  Then I do same thing to next nonlinear equation:  $$f(x)=x^2(x-1) $$, m is integer.  so the newton's formula is above, and how about convergence rate to $0,1$?  I think convergence to 1 is one, absolutely convergence to 0 is quadratic. when convergence rate is 1, the how about the convergence rate?


Currently I have Ubuntu 18.04 LTS Bionic set up but no internet. So I can't install/download applications. What would be the easiest way to install applications de a USB drive onto Ubuntu?

I have a friend who has got a computer that is not connected to the Internet. Is there any way to install software offline easily?


I have google chrome and terminal always write: you cannot translate the name of the machine. Command not found...  What I must to do?

I know, it's been asked before but I couldn't really get a satisfying answer for some details/backgrounds and I guess it's an important question for many.    Some application seem only to be running with Adobe Flash 15 (or at least I know it does, because I have that version on my Windows Partition).  The official Adobe website says:     NOTE: Adobe Flash Player 11.2 will be the last version to target Linux as a supported platform. Adobe will continue to provide security backports to Flash Player 11.2 for Linux.   Some search on the web like "Ubuntu Adobe Flash 15" or similar does not return any good websites.  I found something that says   (using a "pepper-based version"), and  .   Is it impossible to use this for Firefox too? Would it be a privacy risk?  Are there no alternative projects (I know it's closed source but there are so many so very bright people out there using something similar to wine but just for the plugin....)?  How about the Mac-Version? Shouldn't someone be able to port that one to Linux?


Is there a way to change the height of the titlebar in gnome-shell?  As it's currently too big for my taste, I'd like to make it a bit smaller.  Some themes get it right, but I don't know exactly where to look. I can only assume it may be css/js related.  My current GNOME Shell version is 3.16.4 and I am running Ubuntu.   This doesn't help: . Wouldn't expect it either, but might have given me a direction...

I'm running GNOME 3.18 and I would like to reduce the title bar height. How could I do it?


When voice typing, I know that you can say comma or period or question mark to get a , . or ?. Those were all in the android instructional video. But I just saw that you can say new paragraph and it will skip a line. I want to know if there's a list of these punctuation commands somewhere?

I'm on a Sprint Samsung Galaxy S3 with Android 4.3.  I would love to become a power user of the dictation feature to dictate text messages and emails. More often than not, however, I have to hand-edit the dictated text not because of text comprehension issues but because of punctuation, capitalization and spacing problems.  These are the "commands" I've found to work. What is the full list?  "period"     --> .   (works fairly reliably) "comma"      --> ,   (works fairly reliably) "new line"   --> \n  (works about 50% of the time)   I've not gotten capital or anything like that to work, or acronyms. If you know how it works, please share.


Spuriously high R-squared is one of the pitfalls of regression through the origin (i.e. zero-intercept models). If the predictors do not contain zeroes, then is it an extrapolation? What are the uses and other pitfalls of regression through the origin? Are there any peer-reviewed articles?

I am running linear regression models and wondering what the conditions are for removing the intercept term.   In comparing results from two different regressions where one has the intercept and the other does not, I notice that the $R^2$ of the function without the intercept is much higher. Are there certain conditions or assumptions I should be following to make sure the removal of the intercept term is valid?


I want to fill a table with in 1st row the index and in 2nd row an element generated on a uniform law. To follow the steps of my work I did a non-executable file: import java.util.Random;  public class CSignal {     private int N, V;     private double[][] tabSig;     public double k;      public CSignal() {         V = 4;         N = 10;          Remplit();     }      public void Remplit() {         for (int i = 0; i < N; i++) {             tabSig[0][i] = i;             Random e = new Random();             k = e.nextDouble();             tabSig = new double[2][2];             this.tabSig[1][i] = k * V;         }     }      public int get_N() {         return N;     }      public int get_V() {         return V;     }      public double[][] get_tab() {         return tabSig;     }      public void Affiche() {         System.out.println(tabSig);     }  }   and then the executable: public class TP {      public static void main(String[] args) {         // TODO Auto-generated method stub         CSignal signal;         signal = new CSignal();         signal.Affiche();     } }    When i try this prog I got the following error: Exception in thread "main" java.lang.NullPointerException: Cannot load from object array because "this.tabSig" is null

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?


This (gawky) question is concerning command dd:     dd if=/dev/DVD of=whatever.iso   seems not to work ... and then output follows like:     could not open /dev/DVD - file or directory not found   Is here usage of dd incomplete or not exactly enough - or path simply not correct ?  I wonder about that (this usb-dvd-burner) is not written in /etc/fstab - but     wodim -v -eject whatever.iso   has no trouble to burn iso-images contrary to command dd ?

Problem:  I created 3 DVD's filled with Windows system recovery disks in case I ever have a hardware problem and need to re-install Windows in order to run diagnostic tests.  However, I don't want to worry about losing them, so I would like to make backups of the recovery disks as ISO images which I can store on an external hard drive.  A Google search revealed that I can do this using the dd (or "disk dump") unix command.  dd if=/dev/who-knows-where? of=/home/wdkrnls/x201-recovery-2011-09-30.iso   But the snag is that Ubuntu doesn't use the old convention of associating /dev/cdrom with the cd-rom drive.  Instead Nautilus automagically creates /media/CD_ROM which is a directory, and not the drive itself.  I tried to run dd anyways and got:     /bin/dd: reading '/media/CD_ROM/': is a directory   0+0 records in   0+0 records out   0 bytes (0 B) copied, 0.0158501 s, 0.0 kB/s   I tried running dmesg | tail and saw a reference to:     [215135.134164] sr 9:0:0:0: Attached scsi generic sg1 type 5   So I tried ls /dev/sg1, but there wasn't any file called that.  Only my partitions show up with sudo fdisk -l, leaving me stumped as to what to try next.  Solution:  I figured out I could solve my problem with brasero or k3b and so abandoned my exploration of Ubuntu's internals.  Nevertheless, I still wouldn't mind knowing how I would use dd to accomplish the same task.  How would I solve my problem with dd?


How much more damage is caused after hitting a wall at 100mph over 50mph? It is clear that there is just twice as much force generated after hitting a wall at 100mph, since the deacceleration is twice as large. But is the energy produced four times as much? This is unclear to me.

If a car hits a wall at a speed of $v$, and an identical car hits a wall at a speed of $2\,v$, with the kinetic energy equation $E_K = \frac{1}{2}mv^2$ (the speed goes from $v$ to $0$) the second car will lose 4 times the energy, and therefore cause 4 times the damage, but with the force equation $F = ma$ (the car hits the wall and decelerates), it will hit with 2 times the force, and cause 2 times the damage.  How can this be explained?


Why is a compressed air tank cold to the touch when it’s in a compressed state before use?

When you spray gas from a compressed spray, the gas gets very cold, even though, the compressed spray is in the room temperature.  I think, when it goes from high pressure to lower one, it gets cold, right? but what is the reason behind that literally?


class A{ public:    A() { cout << "constructing A." << endl; }    virtual ~A() { cout << "destructing A." << endl; } }; class B : public A{ public:     B() { cout << "constructing B." << endl; }    ~B() { cout << "destructing B." << endl; } }; int main() {     B b;     A *a = &b;     delete a; }  Above example is test code for virtual destructor. It works fine with A* a = new B(); delete a; but fails at runtime when A *a = &b; delete a; Why?

Ignoring programming style and design, is it "safe" to call delete on a variable allocated on the stack?  For example:     int nAmount;    delete &nAmount;   or  class sample { public:     sample();     ~sample() { delete &nAmount;}     int nAmount; }


When we install ubuntu as a separate partition along windows, we create mount point for root. /home also resides inside /.Then why do we need to create separate mount point for /home.What is the significance of this? And also what is the difference between selecting primary and logical for the mount points?

This is not a question about how to create a home partition, just as a caveat. :)  What are the pros and cons to having a separate home partition? How do I know if having one is right for me? Will it increase or decrease speed of file retrieval? Are there any risks?


I have seen a few references of instantiating a new object as follows, especially when using Inheritance.  Cat cat = new Animal();   However, I do not know what this concept is called. and so, I'm unable to read up on it.  I have two questions.   What is this concept called? How is this possible, that, you can     hold/refer to an object using a type that is different from it's     original class?

I have seen this mentioned a few times and I am not clear on what it means. When and why would you do this?   I know what interfaces do, but the fact I am not clear on this makes me think I am missing out on using them correctly.   Is it just so if you were to do:  IInterface classRef = new ObjectWhatever()   You could use any class that implements IInterface? When would you need to do that? The only thing I can think of is if you have a method and you are unsure of what object will be passed except for it implementing IInterface. I cannot think how often you would need to do that.   Also, how could you write a method that takes in an object that implements an interface? Is that possible?


If we know that $\sum_{n=1}^{\infty}(a_n)^2$ and $\sum_{n=1}^{\infty}(b_n)^2$ both converge can we say that $\sum_{n=1}^{\infty}(a_nb_n)$ converges?

Let $\sum_{n=1}^{\infty}a^2_n$ and $\sum_{n=1}^{\infty}b^2_n$ prove that: $\sum_{n=1}^{\infty}a_nb_n$ converges.  I thought about this answer: In order for a sum to converge i has to be bounded, Means Let $M_1\epsilon R$, So that $ \sum_{n=1}^{\infty}a_n<M_1 $. Same goes for $b_n$. [And lets say $M_2$].  So is it just: $\sum_{n=1}^{\infty}a_nb_n\le \max(M_1*M_2, \sqrt{M_1*M_2}$)?  And one more question: Let $\sum_{n=1}^{\infty}a^2_n$ prove that  $\sum_{n=1}^{\infty}\frac{a_n}{n}$ converges.  If i go the same as before, I have hard time cause i get something like:  $\sum_{n=1}^{\infty}\frac{M_1 }{n}$ which doesn't converge [I think].  Any guidelines please?


Can I set IP address manually on one Wi-Fi network and "Using DHCP" for another? So when I connect to the first one my mac uses static IP, when I connect to 2nd one - use DHCP.    Edit 1.    What I do all the time is. When I come at work I set DHCP for Wi-Fi. When I come home I set "manually" and specify IP, subnet mask, and router. I don't have problems with Proxies. I need to setup my Mac's IPs correctly.    Edit 2. Location works just fine.  Thanks to people in comments.

Sometimes I need to send my traffic to a proxy, sometimes I don't.  Currently, I have to go to the settings every time to click it.  Is there any simple way for me to switch this? For instance, use a shell command to do this.


Yesterday I posted , about 5 minutes after I clicked on the "Post Your Answer" button I got some comments from a mod.  In one of them he said I had edited my answer in the first 5 minutes after posted and so that edit won't show up on the edit history. The thing is that I didn't make any edits to the answer (before or after the first 5 minutes).  He was pretty convinced that I had done those edits, so now the only theory that I have is that he was able to see the draft of the answer while I was writing it, that would explain why he saw different versions of the answer (the parts he said I added were at the end of the answer, so that would make sense).  So the question is, can moderators see answer drafts from other users?  Note: some of the comments are now deleted, so only mods/staff would be able to see the full thread, but this question still can be answered without seeing the complete thread.

I just would like to know if a question or an answer saved draft is visible to someone else, apart from the OP.  Will a copy of a saved draft remain visible even after it has been deleted? Who has access to it?


Let $X$ be an inner product space, and let $M$ be a non-empty subset of $X$. Then we have the following:   (a) If the space of $M$ is dense in $X$, then $M^\perp = \{0 \}$, that is, $x \in X$, $x \perp M$ imply $x =0$.   (b) If $X$ is complete and $M^\perp = \{0 \}$, then the span of $M$ is dense in $X$.   In (b), what if the space $X$ is not complete? In such a case, can we have a set $M$ such that $M^\perp = \{0\}$, but the span of $M$ is not dense in $X$?

I am looking for an example such that in a pre-Hilbert space $H$ we have for a subspace $U$ that  (i) $\bar{U} \oplus U^\perp \neq H$  (ii) $ \bar{U} \neq U^{\perp \perp}$  Since finite and closed subspaces will probably not do it, I am not good at inventing nice examples. Does anybody here have a few at hand?


For the last few days one of my websites has been receiving hundreds of requests per minute with non-existent random domains as HTTP_REFERER and from different IPs (therefore using deny from IP is not an option):  REMOTE_ADDR     | HTTP_REFERER    | HTTP_USER_AGENT 95.133.126.178  | 1dljlc2jm2.info | Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; QihooBot 1.0 qihoobot@qihoo.net) 188.232.31.38   | 3r28169e6v4.net | Mozilla/5.0 (compatible; ShunixBot/1.x; http://www.7vlc8pngqk7zmx.com/bot.htm) 177.184.135.114 | 3p10jjujbn.ru   | Mozilla/5.0 (compatible; Bot; +http://w4n2e2mte8.ws/spamfilter 188.235.184.231 | 06d94hx.biz     | Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; iRider 2.21.1108; FDM) 42.119.240.12   | ho0gg8r7.net    | Mozilla/3.0 (WorldGate Gazelle 3.5.1 build 11; FreeBSD2.2.8-STABLE) ...   Any ideas how to fight this, please?  UPDATE (after problem was successfully solved)  My question is not a duplicate for  because I knew "what is happening" (small DDoS attack) and therefore I have asked for the exact rules to be added to .htaccess to block attackers.  BTW, here  is suggested to contact hosting provider. I did, but my hosting provider (one of the most popular ones) proposed to buy a more expensive package with more resources included. :)  Froggiz's  was exactly what I was looking for.

This is a  about DoS and DDoS mitigation.   I found a massive traffic spike on a website that I host today; I am getting thousands of connections a second and I see I'm using all 100Mbps of my available bandwidth.  Nobody can access my site because all the requests time out, and I can't even log into the server because SSH times out too!  This has happened a couple times before, and each time it's lasted a couple hours and gone away on its own.  Occasionally, my website has another distinct but related problem: my server's load average (which is usually around .25) rockets up to 20 or more and nobody can access my site just the same as the other case.  It also goes away after a few hours.  Restarting my server doesn't help; what can I do to make my site accessible again, and what is happening?  Relatedly, I found once that for a day or two, every time I started my service, it got a connection from a particular IP address and then crashed.  As soon as I started it up again, this happened again and it crashed again.  How is that similar, and what can I do about it?


In attack on titan, if someone were swallowed by a titan (it doesn't matter if the person if dead or alive) what happens to the body if a titan dies before it pukes them up?

In Attack on Titan, it is said that titans do not have any digestive organs and the only way they get stuff out of their stomach is by puking it out.  Now, if a human is swallowed whole by the titan, will the human survive inside the titan? Yet no one is said to have survived this way.


So, I am following the Hibernate documentation to configure interceptors (). Then, I am registering my interceptor in the AnnotationSessionFactoryBean as follows:  <bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean"> <property name="entityInterceptor"> <bean class="domain.interceptor.AddressInterceptor"/> </property> </bean>   What I want to achieve is to insert a row in my log table when something is caught in my Interceptor. Though, this introduces a cyclical configuration dependency: the Interceptor needs the SessionFactory and the SessionFactory needs the Interceptor. How could I wire in the SessionFactory in my Interceptor?

I want to declare two beans and instantiate them using Spring dependency injection?  <bean id="sessionFactory" class="SessionFactoryImpl">  <property name="entityInterceptor" ref="entityInterceptor"/> </bean>  <bean id="entityInterceptor" class="EntityInterceptorImpl">  <property name="sessionFactory" ref="sessionFactory"/> </bean>   But Spring throws an exception saying "FactoryBean which is currently in creation returned null from getObject"  Why is inter-dependent bean wiring not working here? Should i specify defferred property binding anywhere?


first question here. Hope I'm doing it right.  English is my native language, and the first option sounds correct to me. "Bitcoin is great, it's products like this which are driving innovation, etc." (just to give you an idea of the type of sentence I have at hand.  It's this seemingly contrasting singular / plural aspect that is making it extremely hard to explain why it is that I believe the first is correct.  The subject of my sentence is singular (in the example above it's Bitcoin), which is why I'm using the third person "it", and then "this".  I think it boils down to "products" throwing people off here. Long story short, am I right in using "it's products like this", or should I be saying "these", and presume that along with Bitcoin there are other - unspoken things that are part of this sentence?  Thanks!

On a  to one of my other questions on this site, a user said:     It’s much easier to answer questions like this when you specify where   you've come across the word.   Is the use of the word this correct in such case?  I would be inclined to say “questions like these”, or if I wanted to use the singular form I would rephrase it as “a question like this”.


I am trying to teach myself data science by solving some of the problems available on the internet. Currently I am trying to predict a fraud event with the aid of 4 categorical variables. Each of the categorical variables have 100 of levels. Some of the levels occur frequently, some none at all.  Currently I have tried the following    Throwing the categorical variable directly into linear regression. I get memory related errors Dummy encoding each categorical variable. Throw all of them into a linear regression. This also fails due to memory error Throwing the categorical variable into a Random ForestTM. This fails as Random Forest can only handle 52 distinct levels   None of the approaches I tried above have worked. What else can I try?  Any help is appreciated.   Update #1: The categorical variables are groupings like zip code, county, etc. In addition to these the customers are grouped into different buckets based on presence or absence of certain factors.  Update #2: I was able to use memory.limit() and increase the maximum memory size available to R. This has solved my memory issues.  Update #3: The current approach I was to use linear regression with regularization to find average fraud rate per factor level (for example average fraud rate per zip code). Now the categorical variable with hundreds of factors has been reduced to a numeric variable. I follow the same approach to convert all the 4 categorical variables into numeric. I throw these 4 numeric variables into a random forest. My results with the approach are okay with lots of room for improvement.    Update #4: I am using the R ecosystem

I have a dataset that consists of only categorical variables and a target variable. I want to predict the (binary) target variable with the categorical variables.  I am trying to do this in Python and sklearn.  The categorical variables have many different values. I was thinking to create dummy variables for each value in all the categorical variables. However, in the end this results in a sparse data set with thousands of variables.  How would you go about to reduce the number of dummy variables? Would you use Chi2 to select useful features?  Or would you not make dummy variables at all?


Can the Ubuntu 16.04 Operating System be removed / emptied from my computer? Help me to solve this, I want to restore my computer like a new situation, which is without an operating system.

I have installed bootable ubuntu on hard disks but now I can not format them with Disk Utility program. When I try to format it says "One or more partitions are busy on /dev/sdb" for both hard disks. Is there any way to format these drives?  EDIT: With "Disk Utility" program when I select one of the hard drives It shows 3 volumes;  99 MB FAT 111 GB EXT4 9 GB UNKNOWN   I can not format this unknown volume.  With Gparted program, It doesn't shows Unknown volume only shows 111GB EXT4.


Found this script on one of the questions answered in the forum but I don't know enough to make it work. I would like it to time-stamp date and time in column B when they check in and then a separate script when they clock out to time-stamp date and time in column D.  Not sure how to do this in Google Spreadsheets.  Here is the script below that I found but it will only time-stamp column N when changes are made in column M:  function onEdit() {  var s = SpreadsheetApp.getActiveSheet();  if( s.getName() == "Sheet1" ) { //checks that we're on the correct sheet    var r = s.getActiveCell();    if( r.getColumn() == 13 ) { //checks the column      var nextCell = r.offset(0, 1);      if( nextCell.getValue() === '' ) //is empty?        var time = new Date();        time = Utilities.formatDate(time, "GMT", "HH:mm:ss");        nextCell.setValue(time);    };  }; }   Let me know how to change this.

Need help in adding another function using the below script. I would like to have a timestamp "start" and "end" on two different columns, whenever the other two separate columns are edited. Based on the below script, I could only have one time stamp, from one column which is the column 2 and time stamp on column 10.  function onEdit()  {  var s = SpreadsheetApp.getActiveSheet();  if( s.getName() == "Sheet1" ) { //checks that we're on the correct sheet    var x = s.getActiveCell();    if( x.getColumn() == 2 ) { //checks the column      var nextCell = x.offset(0, +8);      if( nextCell.getValue() === '' ) //is empty?        var time = new Date();      time = Utilities.formatDate(time, "GMT", "hh:mm");        nextCell.setValue(time);    };  }; }


According to walkthrough steps for ECDSA topic from wikipedia as shown below, What if the impact if we don't apply the hashing function (highlighted in blue in the image) to the raw messages? Although this sounds a bit silly, but let's say we have both with or without SHA256 engine test cases like below. Hex Message (256 bits): "0123456789012345678901234567890123456789012345678901234567890123" Hex Message after SHA256 (256 bits): "9674d9e078535b7cec43284387a6ee39956188e735a85452b0050b55341cda56" Can anyone explain what is the problems with the first Hex Message if I proceed with this to the subsequent ECDSA signing flow? Just assume Alice signed the raw message in this case?

In (EC)DSA as per , the message to sign is first hashed. Imagine that we skip this hashing stage, instead put the message where the hash was, and constrain the size of message $h$ to the original hash's output width $N$ bits. The resulting scheme is vulnerable to (at least) these existential forgeries ($q$ is the multiplicative group order):   any signature for message $0\le h<2^N-q$ is also valid for message $h+q$; a valid signature for messages $h=0$ and $h=q$ is easy to obtain: in DSA, $(r,s)$ with $r=s=y\bmod q$ does the trick, where $y$ is the public key; there's an analog with , which $r=s=x_A\bmod q$, where $x_A$ is the $x$ coordinate of the public key, and $q=n$.   Are other attacks possible? In particular, does temporary access to a signing oracle allow a total break (key extraction or other mean to sign any message)?    The question is of direct interest when one wants to lower the communication overhead between a signing device and a host using it to (EC)DSA-sign large messages: can we fully offload the hash computation to the host? I believe that holds (and as noted in comments, that seems to be practice), but can we demonstrate that? If not, how can we safely offload most of that computation, without breaking standard conformance?


The difference between alerts and banners is that alerts require user input to disappear, whereas banners go away on their own. Is there a way to close all notification alerts at once?   In the example below, there are 6 alerts from one application. I'd like to be able to OPTION-click "Close" or hit a keyboard shortcut to dismiss all of them. Ideally, I'd be able to dismiss all alerts on a per application basis. But I'd settle for the ability to dismiss alerts universally.

Every time I turn on my mac, a set of like 10 recurring reminder popups clog up my OSX Desktop screen.  I may be a procrastinator and all, but Reminders.app's interface on OSX feels downright buggy without a button to close all reminders at once, or at least all recurring reminders.  Is there a keyboard shortcut or something to make them all "close" at once? A "Saturday shortcut", lets call it.


In my .bib archive I have other references, but when compiling only shows those that I have reference them in my .tex document.  How could I make that those that I dont reference in my .tex document shows at the end of my document in my bibliography? –

Is there any way to have BibTeX or biblatex insert a bibliography without having citations in the body of the document itself? Maybe a way to hide the in-text citations, so that BibTeX still sees them and includes them in the bibliography, but does not print them in the body?


be warned: I'm a complete newbie to everything Linux, so please ELIF and I'll try to keep up :)  I'm trying to set up Lubuntu on a cheapo laptop that currently has Windows 10. I have my live USB and successfully booted Lubuntu, but while checking to ensure that everything works, I see that I can't connect to wifi. My wifi adapter (Realtek RTL8723DE 802.11b/g/n PCIe Adapter) doesn't appear on Lubuntu's Additional Drivers page, and when I run lshw -C network, this adapter is listed as "network UNCLAIMED" and doesn't list a driver. This is similar to the problem described by this user: .  So apparently this problem arises from a device with no drivers attached. The solution given in that thread seems to apply specifically to Ubuntu JauntyJackalope; so my questions are as follows:   How do I determine which driver/backport/etc to install based on my distro and my network adapter, and can I just install them with sudo apt-get install? (Ideally I'd like a general way to figure it out in case I want to, say, install Linux Mint instead.) Although I can access the Internet to install things with apt, it's a pain; is there a way to load the driver onto a flash drive and install it from there?   EDIT: As requested, some more terminal output:  $ lspci -nnk | grep 0280 -A3 03:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8723DE 802.11b/g/n PCIe Adapter [10ec:d723]     DeviceName: WLAN     Subsystem: Hewlett-Packard Company RTL8723DE 802.11b/g/n PCIe Adapter [10ec:d723]  $ uname -r 5.3.0-18-generic

How do I install Wi-Fi drivers for Realtek RTL8723DE device in Ubuntu 16.04?  lspci -v | grep -i network 02:00.0 Network controller: Realtek Semiconductor Co., Ltd. Device d723


I right click on a server in the Registered Servers pane and select New Query.  Sometimes (like 1 out of 3), it will just hang for 5-15 seconds with the Connect dialog (below).  Other times, it connects immediately. I thought this may have been a network issue, so I have ping running indefinitely just for comparison and the ping times are steady.  So it's not a network issue.  The servers themselves are not CPU pegged by any stretch of imagination. This problem occurs with all the SQL corporate boxes that I connect to during the day. All the SQL Server boxes are v2017, Enterprise edition, running on Windows 2016, which is running in a VMWare VM.  I am using SSMS 17.9.1. I am also running the Redgate SQL Prompt add-on v8.0.7.1917 in SSMS, but (from my testing) it seem to have any bearing on the connection times. How do I troubleshoot this issue?

I'm getting extremely long delays (10~30 seconds) in SQL Server Management Studio 2014 when attempting to connect to a SQL Server 2012 instance over TCP using Windows Authentication. This happens when connecting Object Explorer or a new blank query window. Once connected, running queries is fast. The problem does not happen when I connect using SQL Server authentication.  Environment:   Windows 7, logged in as a domain user TCP connection via IP address (not hostname) The server is at a remote location connected via VPN No encryption   When I logged into a co-worker's Windows 7 computer with my domain account, and connected to the same SQL Server through the same VPN, there was no delay. When the same co-worker logged into my PC with his own domain account, he experienced the delay. These tests show that the problem is unique to my PC. Also, the problem only appears when connecting to this specific SQL Server and VPN; I can connect to other SQL Servers on the local network via Windows Authentication without any delay.  Things I've tried with no success:   Disabled anti-virus and firewall Renamed the "12.0" folder under "%userprofile%\AppData\Roaming\Microsoft\SQL Server Management Studio" to "_12.0" to force SSMS to recreate my user settings. Force Network protocol to TCP rather than <default>. I also tried Named Pipes but my server isn't setup for that. Installed SSMS 2012 and tried that instead of 2014. Disabled IPv6 Blackholed crl.microsoft.com to 127.0.0.1 in my etc\hosts file. Disabled the Customer Experience Improvement Program in SSMS, Visual Studio, and Windows. Uninstalled all SQL Server related apps from my PC and reinstalled just 2012.   TCPView clues:   Using TCPView, I noticed that when I make a new connection, its state becomes ESTABLISHED right away, but then one or two more connections with the SQL Server are continually attempted and closed with TIME_WAIT. On my co-worker's computer, these connections are ESTABLISHED and solid. So I'm pretty sure this is the source of the timeouts, but what are the connections for, and why do they fail? (I don't have any addons in my SSMS.)   Any ideas?  Update: Intellisense/Autocomplete clue(?):  I noticed that once I finally do connect, Intellisense/Autocomplete doesn't work. Do those require separate connections from SSMS? I tried disabling them, and it didn't seem to resolve the long connection delay.


I've figured out two ways of assigning global variables.   The first method assigns an attribute to a function.   The second method changes a global variable name.  I will be implementing this into a text-based adventure game.   What is the difference between these methods. When is each method commonly used. What method is suitable for my task?   Here is the code.   # Method 1. Assigning attributes to function.  def coin():     print "You see a coin. Pick it up?"      choice = raw_input("> ")      if choice == "yes":         coin.amount = coin.amount + 1         print coin.amount     elif choice == "no":         print "No monies for you."   # Method 2. Assigning global name within function.   def coin2():     global purse     print "You see a coin. Pick it up?"      choice = raw_input("> ")      if choice == "yes":         purse = purse + 1         print purse     elif choice == "no":         print "No monies for you."  coin.amount = 0 coin()  purse = 0 coin2()    Note:  Previous answers I've discovered have seem to broad, so I will ask a new question specific to my problem of deciding which is most suitable for a text-based adventure game.

Not many are aware of this feature, but Python's functions (and methods) can have . Behold:  >>> def foo(x): ...     pass ...      >>> foo.score = 10 >>> dir(foo) ['__call__', '__class__', '__delattr__', '__dict__', '__doc__', '__get__', '__getattribute__', '__hash__', '__init__', '__module__', '__name__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__str__', 'func_closure', 'func_code', 'func_defaults', 'func_dict', 'func_doc', 'func_globals', 'func_name', 'score'] >>> foo.score 10 >>> foo.score += 1 >>> foo.score 11   What are the possible uses and abuses of this feature in Python ? One good use I'm aware of is 's usage of the docstring to associate a syntax rule with a method. But what about custom attributes ? Are there good reasons to use them ?


I encountered the following three distributions of a continuous random variable, with the corresponding pdf's;  the normal(Gaussian) distribution $$f_{\mu,\sigma}(x)=\frac1{\sigma\sqrt{2\pi}}e^{-\frac12\left(\frac{x-\mu}{\sigma}\right)^2}$$ the Cauchy distribution  $$f_{x_0,\gamma}(x)=\frac1{\pi\gamma\left[1+\left(\frac{x-x_0}\gamma\right)^2\right]} =\frac1{\pi\gamma}\left[\frac{\gamma^2}{(x-x_0)^2+\gamma}\right]$$  the student t-distribution $$f_\nu(t)=\frac{\Gamma(\frac{\nu+1}2)}{\sqrt{\nu\pi}\; \Gamma(\frac\nu2)}\left(1+\frac{t^2}\nu\right)^{-\frac{\nu+1}2}$$  The formulas are all from wikipedia. And it says the first two distributions are special cases of the third one. Setting $\nu=1$ to the third pdf, we get the second pdf with $x_0=0$ and $\gamma=1$ very easily. The only nontrivial part of which is to evaluate $\Gamma\left(\frac12\right)=\sqrt{\pi}$, but  anyway. But how come are the first and the third related? Wikipedia says that the third 'approaches' to the first($\mu=0$, $\sigma=1$) as $\nu\to\infty$. But how? Can anyone give me a possible answer?

Prove that t-distribution is close to normal distribution when degree of freedom is large.   $$f(x)=\frac{\Gamma[(n+1)/2]}{\sqrt{n\pi}\Gamma(n/2)}\left(1+\frac{x^2}{n}\right)^{-(n+1)/2}$$  using limit of density and Law of large number.  Anyone can help me with this question please? Thank you and appreciate your help!


In offline mode, I can't even look at my acheivements. But say I make a lot of progress in a game in offline mode anyway. Do I still obtain them?

I know of  where it is asked if you can get Steam achievements offline. The accepted answer to that was no.   But I do earn achievements for some Steam games while playing in offline mode!  For example, right now I am earning achievements for Cave Story+ as I play in offline mode. In other games I also earn achievements while playing in offline mode. Not just when I am disconnected but still in "online" mode as might be suggested in the linked question.  But what is really bugging me is that this does not happen with all games that have Steam achievements.  So, is allowing offline achievements something that Steam allows, the game devs allow, or is it something decided by a magical elf in the steam servers rolling some d20 dice around?  Edit:  As per request, I was able to attain visual evidence:    You should be able to see the achievement-get in action while in offline mode.  What is worth noting, (and something that I forgot to mention before) is that I only started earning achievements after I had went into online mode with the game installed. This is why I was able to earn this achievement with the ones after unlocked. I had started the game for the first time in offline mode, and did not notice that I was not earning achievements. When I had connected once, I did not have to start the game while online. I was able to earn achievements offline.  I also must state publicly: I do not play on easy. This was for testing purposes only people. It was for Science!


Why this funcion add class only when you click on li elements that are originaly from html file. If i create new li element with add button, then add class doesnt work on it. How can i solve this?  <input type="text" id="new"><button id="add">Add</button>

one

two

three

   javascript  $(document).ready(function(){ $("li").click(function(){     $(this).addClass("current"); });  $("#add").click(function(){     var a=$("#new").val(); $("#list").append("
"+a+"
"); }); });

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


When you read some quotes, it gives a feeling. You realise that it is profoundly true and it brings a smile on your face as you admire the brilliance in it. Is there a word to describe this feeling? For example I got that feeling when I read this quote:  the depth of your attention determines the depth of your experience. If your attention is profoundly, your experience of life is profoundly.

I'm trying to express being shocked in a good way, but all I can find are negative phrases such as:   "It hit me like a ton of bricks." "It hit me like a bucket of ice cold water."   I would like to know if there are some ways to say it in a positive way, as in being shocked in a good way. Thank you so much!  Edit: Pardon me, I should've added context before! I'm translating a sentence in Spanish, in which someone is saying they were shocked (they describe it as being hit suddenly) and very touched (therefore, it's in a positive light).   The answers supplied by Dan and J O S H are exactly what I needed, both "It took my breath away" and "It blew me away" work perfectly.  I'd still like to thank you kindly, all of you! I appreciate your help immensely, having found this forum feels like a blessing. However, I'm not certain as to how to proceed now, do I delete the question? Once more, thank you for all your help!


I am trying to prove the following proposition rigorously given at Michael Atiyah commutative algebra book. There is one step which I am currently stuck in.  Suppose that $N,N^{\prime}, \ and \ N^{\prime \prime}$ are A-modules.   The following exact sequence $$0 \xrightarrow \ N^{\prime} \xrightarrow{u} N \xrightarrow{v} N^{\prime \prime}$$ is exact iff for all A-modules M we have that the following sequence is exact  $$0 \xrightarrow \ Hom(M,N^{\prime}) \xrightarrow{\bar{u}} Hom(M,N) \xrightarrow{\bar{v}} Hom(M,N^{\prime \prime}).$$  I proved the reverse direction, however in the forward direction I have one step I am currently stuck in. Here is what I have so far.  So we want to show that $ker(\bar{v}) = im(\bar{u})$. I showed the inclusion $im(\bar{u}) \subset ker(\bar{v})$. Suppose that $\psi \in ker(\bar{v})$. Then, we have $\bar{v}(\psi) = v \circ \psi = 0$.  Then $im(\psi) \subset ker(v) = im(u) \cong N^{\prime}$. Then, we can reinterpret $\psi : M \rightarrow N$ as a morphism $\phi : M \rightarrow N^{\prime}$. Denote this new map by $\phi$. Now I am having troubles showing that $\bar{u}(\phi) = \psi$.  Please maybe provide a hint as I would like to discover this by myself.   In my question I am not asking for a proof. I am asking to check certain aspect of my argument and improving on that. Thus, this post isn't a duplicate.

If    $$ 0 \to A \to B\to C,$$    is a left exact sequence of $R$-module, then for any $R$-module $M$,    $$ 0 \to \operatorname{Hom}_R(M,A)\to \operatorname{Hom}_R(M,B)\to \operatorname{Hom}_R(M,C), $$    is left exact.   I proved the above, and highlighted what I'm a little unfamiliar with: Let $$ 0 \to A\ \xrightarrow{i}\ B\ \xrightarrow{f}\ C, $$  and  $$ 0 \to \operatorname{Hom}(M,A)\ \xrightarrow{\operatorname{Hom}(M,i)}\ \operatorname{Hom}(M,B)\ \xrightarrow{\operatorname{Hom}(M,f)}\ \operatorname{Hom}(M,C). $$  We need to show that  $$ \ker\left(\operatorname{Hom}(M,f)\right)=\operatorname{Hom}(M,i)(\operatorname{Hom}(M,A)). $$   Let $i \circ \varphi \in \operatorname{RHS}$. Then $f \circ i \circ \varphi : M \to C$ is $0$ since $f \circ i \circ \varphi(M) \subseteq f( i(A)) = f(\ker(f))=0$.  Conversely, let $\psi \in \operatorname{LHS}$. Then $f \circ \psi = 0$ so that $ f(\psi(M))=0$. Hence $\psi(M) \subseteq \ker(f)=i(A)$. Since the image of $\psi$ is contained in the image of $i$, we may factor $\psi$ as $\psi=i \varphi$ with $\varphi : M \to A$. (Here is my trial, but I'm not fully understanding this: Since $i$ is injective, $i(A)$ is isomorphic with $A$. So $i^{-1}(\psi (M)) \subseteq A$ and if we let $\varphi=i^{-1} \psi$, then $\psi = i \varphi$.)  And I have one more question: The above looks very messy, especially the notation. Is there a better proof/understanding about it?


I'm providing the following sentences as representatives of other similar instances.     The survival of a TV channel depends on it attracting as many viewers   as possible.      The survival of a TV channel depends on its attracting as many viewers   as possible.    Which one would be preferable?   I've seen both of the forms before. What is the related grammar/usage called so I can study further?

I assume that the following sentences are grammatically correct:   He resents your being more popular than he is. Most of the members paid their dues without my asking them. They objected to the youngest girl's being given the command position. What do you think about his buying such an expensive car? We were all sorry about Jane's losing her parents like that.   I'm still getting used to this possessive gerund structure. It sounded so weird to me at first. Is the structure used in both formal and informal contexts? Are there any alternative structures that result in the same meaning and are more frequently used? (Examples taken from )


case 7 :             scan.nextLine();             System.out.println("Ievadiet reisa sākuma staciju");             k = scan.nextLine();             System.out.println("Ievadiet reisa gala staciju");             v = scan.nextLine();                 for(i=0; i<50; i++){                  for(j=0; j<5; j++){             if(A[i][0].equals(k) && A[i][1].equals(v) && A[i][j]!=null)                         System.out.println("Biļetes cena:"+A[i][4]);                 }                 if(A[i][j-1]!=null)                     System.out.println();             }             break;   I can't find a solution for my problem. I need to print on screen the lines with asked text content. Everything works but in the end it shows this error. Can anybody help?

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?


If 2 Lasers collide in the air, could they interfere with one another? Given 2 lasers with a max reach of 10 meters (beyond 10 meters they´re not visible with human eyes) If those two lasers meet at the exact same point at 11 meters of reach, would it be possible that those lasers create a point visible for human eyes? So this "point of interference" appears to be hovering? A smokey or foggy environment could help. Would it be possible? If yes, what laser should I use, (what wave length)?

It seems that if the coherence length of a laser is big enough, it is possible to observe a (moving) interference picture by combining them. Is it true? How fast should photo-detectors be for observing of the interference of beams from two of the "best available" lasers? What is the coherence length of the best-available laser? More specifically, does there exist any (optical single-wavelength) laser with coherence length exceeding 500 meters?


In the movie Indiana Jones and the Last Crusade (1989)  there is a scene with a dreathtrap:                                  The joke is, naturally, that in the classical latin alphabet there was no 'j' letter. Which brings the question why was there a 'j' letter on the plate at all? Or perhaps it was a different one distorted by time, or a cracked plate?

Were the traps in Indiana Jones and the Last Crusade made by the three knights?  In the  question there is a comment that the "J" shouldn't even exist on the trap, because there isn't a J in the Latin alphabet. Since the answer is spelled out in Latin, that means the trap wasn't written in a language written or spoken at the time of Christ (ie Aramaic or Hebrew).


We know that universe is expanding and galaxies are moving away from each other. Does this mean the galaxies are also expanding in itself and therefore I guess growing larger in volume? Depending on the answer of that, does the solar system also expands?

I have looked at other questions on this site (e.g. "why does space expansion affect matter") but can't find the answer I am looking for.  So here is my question: One often hears talk of space expanding when we talk about the speed of galaxies relative to ours. Why, if space is expanding, does matter not also expand? If a circle is drawn on balloon (2d plane), and the balloon expands, then the circle also expands. If matter is an object with 3 spatial dimensions, then when those 3 dimensions expand, so should the object.  If that was the case, we wouldn't see the universe as expanding at all, because we would be expanding (spatially) with it.  I have a few potential answers for this, which raise their own problems:   Fundamental particles are 'point sized' objects. They cannot expand because they do not have spatial dimension to begin with. The problem with this is that while the particles would not expand, the space between them would, leading to a point where the 3 non-gravity forces would no longer hold matter together due to distance Fundamental particles are curled up in additional dimensions a la string theory. These dimensions are not expanding. Same problems as 1, with the added problem of being a bit unsatisfying. The answer seems to be (from Marek in the previous question) that the gravitational force is so much weaker than the other forces that large (macro) objects move apart, but small (micro) objects stay together. However, this simple explanation seems to imply that expansion of space is a 'force' that can be overcome by a greater one. That doesn't sound right to me.


I was wondering what the python script to type in the Text Editor would look like if I wanted to key every other 5th frame of my timeline?? I've got a picture of my problem below if that helps! ALSO, what would the code look like if I wanted to delete every other 5th frame instead? Thank you for your time!

I've got the following dope sheet keyframes setup. I want to automate the process to select every 2nd keyframe of an object. It's sort of an edge loop selection on keyframes, but slightly different.


Can I say:     I understand your wanting to wait a while longer.   I have heard it being said, but how correct is it?


This is a short story I read more than 20 years ago, but I don't recall at all where.  It opens with a pair of sorcerers (with innate, mental-based powers like telekinesis) competing.  One pulls down some rocks from space at the other, and the target just barely manages to deflect them.  It is revealed that their mental powers are stronger the farther away they are exerted.  Thus it's easier to yank rocks out of space hundreds of kilometres away than it is to deflect them just a few kilometres away.  The two aren't really friends, but there's a certain amount of respect and camaraderie between them; they may be the two most powerful in the world, and it's basically by competing that they stave off boredom.  Somehow the idea comes up that if they are so powerful at short range, they would be vastly more powerful at huge range.  Each of them wraps the other in a shell of protection and then starts pushing the other away.  If I'm remembering correctly, by the time each had reached the opposite end of the field they were in they were able to levitate the other.  And they kept pushing.  Fast forward years (I'm probably missing bits of the story here) and they are (literally) light years apart; each is able to accelerate the other with immense power and still keep the other protected from the effects.  Their  is huge, and time is flitting by on the world they left behind.  (This question was inspired by  about two connected people moving apart.)

I am trying to remember a short story I read back in the mid 1980s.  It's about two wizards whose magic kept humanity from developing technology and science many centuries ago. The two wizards cast spells to protect each other. They also cast spells to repel each other. The spells caused the wizards to repel each other faster and faster until they left Earth in opposite directions. As the wizards gained speed over the decades and centuries, their experience of time slowed down due to Special Relativity. Because of time dilation, their hold on preventing normal humans from learning technology lessened. Many centuries later, humans began to develop science and technology at ever increasing rates.  Can anyone tell me the name of this story, the author, and when it was published?


Lately, I see more and more code pieces that use the template of:  do {     ... some code ... } while (false);   Why to do this? If I'm not mistaken, the code will run only one time so the loop is seem not to be needed.  My main encounters with this style were in Windows drivers, and low-level operations in some APIs.

In many C/C++ macros I'm seeing the code of the macro wrapped in what seems like a meaningless do while loop.  Here are examples.  #define FOO(X) do { f(X); g(X); } while (0) #define FOO(X) if (1) { f(X); g(X); } else   I can't see what the do while is doing.  Why not just write this without it?  #define FOO(X) f(X); g(X)


I have this electronics that uses 3V rechargeable coin cell battery (ML2032) to power the RTC when the system is off. When the system is powered on it'll trickle charge the battery instead.  I'm looking for ways to allow the usage of regular non-rechargeable CR2032 battery instead. One way I see people doing on Amiga, which also uses 3V rechargeable battery, is to simply add a Schottky diode in series. However, I wonder if there is something even better. To me a voltage drop of at least 0.15V is a lot for a 3V battery.

To power my microcontroller (ATmega8), I am using a ~5.4V voltage source. I want to ensure that I don't accidentally connect the voltage source in reverse, and figured a diode would be a nice way to accomplish this as from what I have learned so far, a diode allows current to flow in one direction, and blocks it in the other.  But what I also learned is that diodes create drops in voltage. I have a few of the typical diodes (1N4001, 1N4148, etc.), and would like to use them to achieve the aforementioned result without dropping the voltage as it would be too low to power the IC.  My question is, is there any way to do this with a diode? Or do I need some other component (if so, what would you recommend)?


Let $V$ a Euclidean $\mathbb{R}$-vector space with a general scalar product $\langle \cdot,   \cdot \rangle$. Let $v,w$ with $v\neq 0$ and $w\neq 0$. Show: If $v$ and $w$ are orthogonal to each other with respect to the scalar product $\langle \cdot,   \cdot \rangle$, they are also linearly independent. (It should be a general scalar product)  Not really sure how to start. I would assume, that they are linear dependent, but that didn't lead to any good solution.   Let $v=\lambda w, \lambda \in \mathbb{R}$ and $\langle v,w\rangle=0\dots$

[Theorem] Let $V$ be an inner product space, and let $S$ be an orthogonal subset of $V$ consisting of nonzero vectors. Then $S$ is linearly independent.     Also, orthogonal set and linearly independent set both generate the same subspace.  (Is that right?)    Then orthogonal $\rightarrow$ linearly independent but orthogonal $\nleftarrow$ linearly independent is that right?    One more question. For T/F, Every orthogonal set is linearly independent (F) Every orthonormal set is linearly independent (T) Why?


I have Ubuntu 20.10. For some days, I have to work my PC without any backup-battery-stuff for blackout. Please advise me about backup tools, if any. For, regretfully, blackouts are commonplace in our district. However, if Ubuntu 20.10 is strong enough to withstand blackout (a wrong shut down) without any special backup installed, kindly let me know. Thanks.

This question exists because it has historical significance, but it is not considered a good, on-topic question for this site, so please do not use it as evidence that you can ask similar questions here.  While you are encouraged to help maintain its answers, please understand that "big list" questions are not generally allowed on Ask Ubuntu and will be closed per the .   Backup is incredibly important. Obviously there's no best backup tool, but a comparison of the options would be very interesting.   Graphical Interface? Command line? Incremental backups? Automatic backups? Install method: In standard repositories? PPA?


My MacBook Pro's display has the anti-reflective coating damaged. What can I do about it?

A couple months ago, I started to see some very small stain spots on the bottom of my MacBook Pro early 2015 screen. It's very annoying to see while I'm using it. When the screen is turned off, I see it as in the picture below. But when it's turned on, I see it as very small water-ish drops. I tried to clean it using water, screen cleaner, and even alcohol, but it didn't go away.  Also that area doesn't feel as smooth as the unaffected area. So, I think it's on the outside of my screen not inside.  Have you ever seen this before? Any suggestions on how to remove it without the need of replacing the whole screen?


$A = \{ 2, 4, 6, 8, 10 \}$  I'm unsure how to 'show' that $R$ is an equivalence relation. My conclusion is it is not as $x-x$ reflexive as given any number in the set will equal $0$ therefore $4$ divides $0$ Am I Wrong?

I have been able to figure out the the distinct equivalence classes. Now I am having difficulties proving the relation IS an equivalence relation.   $F$ is the relation defined on $\Bbb Z$ as follows:      For all $(m, n) \in \Bbb Z^2,\ m F n \iff  4 | (m-n)$   equivalence classes: $\{-8,-4,0,4,8\}, \{-7,-3,1,5,9\} \{-6,-2,2,6,10\}$ and $\{-5, -1, 3, 7, 11\}$


I found  script on GitHub that checks whether you susceptible to spectre and meltdown. Due to this script I am still susceptible. But I read that Ubuntu 16.04 got all patches on 9-th January. I use  Linux 4.13.0-26-generic #29~16.04.2-Ubuntu SMP Tue Jan 9 22:00:44 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux   UPD: I've done all apt update/upgrade magic but my kernel version is 4.13.0-26-generic. I've tested it on 2 machines. The update server is set to main server. Does anybody know why I do not see the latest kernel version?  UPD (about duplicate): It's not about official status of fixing this vulnerabilities on Ubuntu. It's about why I cannot install patches

Any questions relating to status updates, or asking if anything is going to be patched for these vulnerabilities should be closed as duplicates of this question.    are in the news right now and sound pretty severe. I don't see any security updates from Ubuntu that cover these vulnerabilities.  What is Ubuntu doing about these vulnerabilities, and what should Ubuntu users be doing?  These are CVE-2017-5753, CVE-2017-5715 and CVE-2017-5754.


when I try running a program file downloaded in terminal ubuntu 18.04 by ./filename.exec Input.data as per the program user manual, it says no such file or directory, but when I do ls, ls -l , it shows the file in executable state, but still does not run...why? can anyone help me, being a newbie in bioinformatics. The program file contains executable file and input files. $ pwd /home/ubuntu/Downloads/program_directory $ file ./filename.exec Input.data ./filename.exec: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked, interpreter /lib/ld-, for GNU/Linux 2.6.15, BuildID[sha1]=41506b3ff2b0a8a1a10c2d856fc68be667a93df3, not stripped`  Input.data:                  ASCII text $ ./filename.exec Input.data bash:No such file or directory $ ldd sRNAscanner_Ubuntu10.exec | grep not     not a dynamic executable   I even tried running as root, but same response

I've downloaded a game (Shank) but the bin file doesn't run. The error that is shown when I try to launch the executable is:  bash: ./shank-linux-120720110-1-bin: No such file or directory


I've seen that arrays work when you declare them like this:  int[] myarray = {2,4,6,8,10}; //Notice the brackets are with the type   And when you declare them like this:  int myarray[] = {2,4,6,8,10}; //Here the brackets are with the array name   So which one is the correct way of declaring an array and what are the differences (if any) between the 1st and the 2nd.  Thanks.

I have recently been thinking about the difference between the two ways of defining an array:   int[] array int array[]   Is there a difference?


I am a bachelor student and I have a question going round my mind about the universe. Every one says that the universe is ever expanding and it is also said that the vast possible space is also the universe. So my point is some empty space is required for the universe to expand. Then what do we call that space? Hope someone will kill my curiosity!

If the universe is expanding, what is it expanding into? When the big bang happened where did it occur?  When the big bang happened how did it occur?  Where did the energy come from? Energy can not be created or destroyed does that mean, energy has existed before the universe was here?


In logic, what is the difference between a predicate and a function?   To be specific, I am just interested in First Order Logic.  Thanks!

I need to to understand the difference between predicates and functions in the context of Clasual Form Logic in order to define the Herbrand universe.  If I have p(x) :- q(f(x)) would I be right in saying that p and q are predicates while f is a function because it is "nested"?  By this thinking then if I have p(x) :- q(x) both p and q are predicates and I have no functions?  If this is incorrect then how can I tell the difference between a predicate and function?


Let $G$ be a group and $H$ a subgroup with finite index $n$.  Prove that $G$ has a normal subgroup $N$ such that $N\subseteq H$and $|G: N| \le n!$.

I would be very thankful if someone could give me a hint with proving this. It's a very common exercise in abstract algebra textbooks.     If $G$ is a group with a subgroup $H$ of finite index $n$, then $G$ has a normal subgroup $K$ contained in $H$ whose index in $G$ is finite and divides $n!$.   I found the proof on  at some point (although the proof appears to be no longer there), but I got lost in one of the details.


When I searched libmicrohttpd package using apt search, I got this  libmicrohttpd-dbg/xenial 0.9.44+dfsg-1ubuntu2 amd64   library embedding HTTP server functionality (debug)  libmicrohttpd-dev/xenial 0.9.44+dfsg-1ubuntu2 amd64   library embedding HTTP server functionality (development)  libmicrohttpd10/xenial,now 0.9.44+dfsg-1ubuntu2 amd64   library embedding HTTP server functionality   I don't know what's the difference between the package ending with -dev/-dbg and the ordinary one. What's the  between them? Thanks in advance!

sometimes, apt-cache give "-dev" package, for example:  libdianewcanvas2     - a gtk+2 vectorial canvas with extra features libdianewcanvas2-dev - a gtk+2 vectorial canvas with extra features   I am wondering when should I install the "*-dev" package? what is the different between libdianewcanvas2 and libdianewcanvas2-dev?


I understand that there are 2 devices so that the signal cannot have a local stimulation as a source. But why couldn't it be seismic activity for instance?  Given the accuracy of the devices couldn't it even be someone jumping on the ground between the two measurement stations?

Recent reports claim that the gravitational waves detected by LIGO match up with the signal expected from two black holes merging as predicted by general relativity.  Additionally, the masses of both black holes were estimated. Questions:  How certain are we that the detected of gravitational waves are necessarily from two black holes merging?  Since supermassive black holes are typically at the center of a host galaxy, what happened to the galaxies that contained the two merging black holes?  For example, did their host galaxies merge?    Edit After reading the answers, I understand that the signals detected by LIGO are proof of the validity of gravitational wave generational artifacts as predicted by general relativity.  When additionally gravitational waves, caused by the merger of the supermassive black holes (those which ARE indeed located in the centers of the merging galaxies) will be detected, since mergers of galaxies could be observed by the methods independent of gravitational waves such as registering the fact of the quasar appearance (). Additional questions:  Could someone offer me the historical ASTRONOMY precedent when the second degree of inference (from the mathematical model, being associated with the theory of Physics) was accepted as the discovery of the astronomical object?  Could someone give a reference to trustable scientific publication, with the subject of study being discussion of requirements satisfying claim of astronomical discovery of an astronomical object?  Have independent scientific sources (outside of members of the LIGO team) analyzed methodology and results of the LIGO signal detection, and published their conclusions with regards of what was actually discovered?


I have to prove the following is a density function $p(t)=\lambda e^{-\lambda t}$ when $t>=0$.  $p(t) = 0$  for $t<0$  If I understand correctly, if solve the integral, I should get $1$, because this the definition of a density function.  I tried the following...  $$\int_{0}^{\infty}\int_{-\infty}^{\infty}\lambda e^{-\lambda t}$$ ...which resulted in... $$\int_{0}^{\infty}[(-\lambda e^{-\lambda t})/\lambda]^{\infty}_{-\infty}$$  I do not know how to proceed. If I just plug in the infinities then I $0$ I think. How do I check if the function is a density function?

If I have   $$f(x)=\sin(x\pi/10)\qquad\text{for}\;0\leq x\leq10.$$  How do I tell if it is a probability density function? And if it isn't how do I normalize it?


Is it she had survived, she has survived or she survived? Thanks. Edit: In one scenario, she's dead, and in another one, she is still alive. Is "There is no way she could have had survived the attack." - even though she has survived back then, she's now dead from old age. "There is no way she could have survived the attack." She is still alive. Can we use just survived in the past simple? Wouldn't that be incorrect because if she had survived, well then there still would be effects in the present (the effects are that she's alive), shouldn't we go with the present perfect?

Non-native speakers often get confused about what the various tenses  and aspects mean in English. With input from some of the folk here I've put together a diagram that I hope will provide some clarity on the matter.  I offer it as the first answer to this question. Consider it a living document. Input is welcome, and good suggestions will be  incorporated into the diagram.    Nota bene: What this is not is a discussion of whether there are  more than two tenses in English. , to which this question is not intended to supply arguments one way or the other.  Here, the aim is to provide an overview of what constructions English-speaking people use for conveying information about actions referring to past, present, and future, and to provide it first and foremost to precisely the people who are likely to use "tense" as a catch-all term in their search, rather than to linguists who know better.  Breaking News There is now an excellent ELU blog article titled  . It is highly recommended reading.


This is problem from I.N Herstein Page 35 Q3 .How should i start doing this ?Hints ? Thanks

Prove that if in a group $(ab)^2= a^2 b^2$ then the group is commutative.  I am having a hard time doing this. Here is what I have so far: Proof:  $a^2 b^2= a^1 a^1 b^1 b^1$ =$aa^{-1}bb$ =ebb Hence,$aa^{-1}=e$  I am stuck, I do not know if this is the right process in proving this


I have a broken phone which doesn't even switch on. I would like to get all the data from the phone, is there a way to remove flash memory from motherboard and read all the data? My phone was an Asus ZenFone Max M1 Pro, no root privileges, Android 8.0 I think.

Phone worked perfectly. Then one day completely dead, nothing at all. It may have been that "one day" was after some time of laying around, cannot recall.  Model: Android AT&T Samsung Galaxy S3 (SGH-i747 SKU S9255)  Already tried;   Charging phone: no visual output at all, no leds Removing battery while charging: no visual output at all, no leds Removing SIM and SD card: no visual output at all, no leds Attempt to turn on: no visual output at all, no leds   I need to get our family photo's off this phone (stored on internal memory). I care less about the hardware/phone itself.  Thank you for any help you can offer!


For two sequences $\{a_n\}$ and $\{b_n\}$ with $a_n\le b_n,\forall n \in\mathbb{N}$, it is true that $\lim a_n \le \lim b_n$, right? I need this result to prove something but I can not find it  anywhere.

I'm stuck with the proof of the following:  Suppose that $(s_n)$ converges to $s$, $(t_n)$ converges to $t$, and $s_n \leq t_n \: \forall \: n$. Prove that $s \leq t$.   I've tried starting with $s_n \leq t_n \: \forall : n$ and the definitions of each limit (i.e. $|s_n - s| \leq \epsilon \: \forall \: n > N_1$), but I'm not really getting very far. Any help is appreciated!


This is my demo.sh file  #!/bin/bash if [[ $(ls -A) ]]; then echo "there are files" else echo "no files found" fi   but when i run this i get output as       demo.sh: 3: demo.sh: [[: not found     no files found   but there is some file on this directory

I'm writing a script to copy some files around, and trying to use shopt -s dotglob  like .jshint and whatnot.    I can run shopt -s dotglob directly at a bash prompt with no error.  However, running the script throws the error:  script.sh: 81: script.sh: shopt: not found   I'm running this script in bash shell, with the shebang header #!/usr/bin/env bash.  Error line:  shopt -s dotglob cp -r $TEMP/img/* $TARGET/img/ cp -r $TEMP/js/* $TARGET/js/ cp -r $TEMP/less/* $TARGET/less/   Not finding anything helpful on google, any idea what the problem is here?


I am just worried about the performance issues of running Ejabberd(XMPP) chat server on 1GB RAM and 1CPU core AWS t2.micro instance.  Ejabberd documentation says it can easily accept concurrent connections of 100K to 300k if the machine has 16GB of RAM and 4 CPU cores.  But I have only 1GB RAM and 1CPU. If I run Ejabberd chat server on this machine can it withstand at least 10000 connections? And how efficient is it to run a chat server on this machine(1GB,1CPU) for 10000 connections?

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


What is the $\sqrt{x^2}$? Is it just $x$ or $\pm x$? When is it $\pm x$? So if I had $\sqrt {\sin^2(x)}$ is it then $\sin(x)$?  I feel like its just $x$ as $x^2$ is always positive. Thoughts?  Thanks

It is perhaps a bit embarrassing that while doing higher-level math, I have forgot some more fundamental concepts. I would like to ask whether the square root of a number includes both the positive and the negative square roots.  I know that for an equation $x^2 = 9$, the solution is $x = \pm 3$. But if simply given $\sqrt{9}$, does one assume that to mean only the positive root? And when simply talking about the square root of a number in general, would one be referring to both roots or just the positive one, when neither is specified?


$+(+x) = +x$ but why is $-(-x) = +x$??? What's the reason behind the rule, it's really basic and "obvious" because a no turns a no to a yes But I don't want to reason like that, lol. So how would you explain it? Do I just say on a real number line $-x$ makes a turnaround and $-(-x)$ would turn it positive again? Also if I say for example: $-x = 5$ then I do have $-(-x) = -5$ Is it correct? It wouldn't matter, right? (Btw: I don't know if the tag "elementary-number-theory" is correct) **The question is different to $(-x)*(-x)=x$

Context: Rings.     Are $x \cdot 0 = 0$ and $x \cdot 1 = x$ and $-(-x) = x$ axioms?   Arguably three questions in one, but since they all are properties of the multiplication, I'll try my luck...


I am working on one project where I want to send mail using smtp.  I have tried below code but it is giving me error as Failed in Sending Mail  try     {         MailMessage message = new MailMessage("From@gmail.com", "to@gmail.com", "Testing Mail", "Testing mail recv");  SmtpClient client = new SmtpClient(); client.Host = "smtp.googlemail.com"; client.Port = 587; client.UseDefaultCredentials = false; client.DeliveryMethod = SmtpDeliveryMethod.Network; client.EnableSsl = true; client.Credentials = new System.Net.NetworkCredential("myPage@gmail.com", "123@123"); client.Send(message);  } catch (Exception exception) {   MessageBox.Show(exception.Message); }   In place of client.Host = "smtp.googlemail.com";  I have Tried some other code as client.Host = "smtp.google.com"; and client.Host = "smtp.gmail.com";. also have tried with different Port No as 25 and 587.  Can anyone tell me what's wrong with this code?  Thank you in Advance.

Instead of relying on my host to send an email, I was thinking of sending the email messages using my Gmail account. The emails are personalized emails to the bands I play on my show.   Is it possible to do it?


I've been creating a regex to catch a person's name from a larger chunk of tex twith this following format:      Last Name, First Name and Additional Names (2 Additional Names Maximum)    No Additional special characters except for comma (,)    Only Names that can be derived from English alphabet [A-Z]|[a-z]   Example of Format Name:  Johnson, Carl  Scott, Michael Mark  Smith, Robert Angelo John    The first Example contains only Last Name and First Name The second Example contains Last Name, First Name and Additional Name The third Example contains Last Name, First Name and two Additional Names   So far, I've been on trial and error in Regex and this is my current regex:   ^([A-z]|[a-z])*[,][\s]*([A-z]|[a-z]|[\s])*

Just starting to explore the 'wonders' of regex.  Being someone who learns from trial and error, I'm really struggling because my trials are throwing up a disproportionate amount of errors...  My experiments are in PHP using ereg().  Anyway.  I work with first and last names separately but for now using the same regex.  So far I have:  ^[A-Z][a-zA-Z]+$     Any length string that starts with a capital and has only letters (capital or not) for the rest.  But where I fall apart is dealing with the special situations that can pretty much occur anywhere.   Hyphenated Names (Worthington-Smythe)   Names with Apostophies (D'Angelo)   Names with Spaces (Van der Humpton) - capitals in the middle which may or may not be required is way beyond my interest at this stage. Joint Names (Ben & Jerry)   Maybe there's some other way a name can be that I'm no thinking of, but I suspect if I can get my head around this, I can add to it.  I'm pretty sure there will be instances where more than one of these situations comes up in one name.  So, I think the bottom line is to have my regex also accept a space, hyphens, ampersands and apostrophes - but not at the start or end of the name to be technically correct.


I am new to Salesforce and I was playing around. So I have a vf page in which I am displaying a modal and closing it once its done. The functionality is working well. I'm just stuck at how to write a test class for it. Can anybody help me out here?  public class TrialClass {     public boolean displayPopup {get; set;}     public void closePopup() {            displayPopup = false;     }      public void showPopup() {              displayPopup = true;         } }

This is a canonical question and answer developed by the community to help address common questions. If you've been directed here, or your question has been closed as a duplicate, please look through the resources here and use them to shape more specific questions. To browse all canonical questions and answers, including more unit test resources, navigate to the  tag.  This canonical question is intended to address several classes of common questions by providing a quick summary and links to comprehensive resources:   How do I start writing my first unit test?  How do I unit test this code?  I need help writing this unit test.   Salesforce Stack Exchange looks for detailed, specific questions that the community can help you with, and can't write tests on your behalf. We feel that working with the resources below can help you get started, and we encourage you to make an attempt to write your test and return to SFSE with your specific questions when you encounter challenges you can't resolve.


Prove using the basic properties of a sequence that $\lim \frac{n}{2^n} = 0$  I tried to prove this using the standard epsilon-definition of a limit but the math got really hard, so I stopped. Then, I tried to represent the sequence as a quotient or a product of two sequences, but those sequences were not convergent. Thus, I've got no more ideas on how to tackle this problem. Any suggestions would be most appreciated.

In other words, how to prove:  For all real constants $a$ and $b$ such that $a > 1$, $$\lim_{n\to\infty}\frac{n^b}{a^n} = 0$$  I know the definition of limit but I feel that it's not enough to prove this theorem.


I want to update component from JSF bean . but receive NullPointerException :    java.lang.NullPointerException     at org.primefaces.PrimeFaces$Ajax.update(PrimeFaces.java:335)     at org.primefaces.PrimeFaces$Ajax.update(PrimeFaces.java:359)     at ir.moke.logmag.view.LogView.start(LogView.java:21)     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)     at java.lang.reflect.Method.invoke(Method.java:498)     at org.jboss.weld.injection.StaticMethodInjectionPoint.invoke(StaticMethodInjectionPoint.java:95)     at [internal classes]     at ir.moke.logmag.api.TestLog.addLog(TestLog.java:20)     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)     at java.lang.reflect.Method.invoke(Method.java:498)     at com.ibm.ws.jaxrs20.cdi.component.JaxRsFactoryImplicitBeanCDICustomizer.serviceInvoke(JaxRsFactoryImplicitBeanCDICustomizer.java:302)     at [internal classes]       this is my example code :   LogView.java  @SessionScoped @Named public class LogView implements Serializable {     private String name;      public void start(@Observes String name) {         this.name = name;         System.out.println("Receive : " + name);         PrimeFaces.current().ajax().update("form:log");     }      public String getName() {         return name;     } }    TestLog.java  @Path("/log") public class TestLog {      @Inject     private Event<String> event;      @POST     @Path("/add")     public Response addLog(String name) {         System.out.println("API " + name);         event.fire(name);         return Response.accepted().build();     } }   HTML  <h:body>     <h:form id="form">         <p:outputLabel value="Output : "/><br/>         <p:outputLabel id="log" value="#{logView.name}"/>     </h:form> </h:body>       I want to send message from rest api and update component on JSF page . How can fix this problem ?      My environment : Liberty 19.0.0.4 JavaEE 8 JSF 2.3

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?


How to prove that a semilocal ring such that all of its localizations at any maximal ideal are Noetherian is a Noetherian ring?   For example, for the easier example, $\operatorname{Max}(R)=\{m_1,m_2\}$, and $R_{m_1}$ and $R_{m_2}$ are noetherian rings. I believe that the ring $R$ is Noetherian, but I don't know how to prove it.  Thanks in advance.

Let $R$ be a ring with finitely many maximal ideals such that $R_{\mathfrak m}$ ($\mathfrak m$ maximal ideal) is noetherian ring for all $\mathfrak m$. Is $R$ noetherian?   I think $R$ has to be noetherian. Let $p_1 \subset p_2 \subset \cdots \subset p_n \subset \cdots$ be an infinite ascending chain of prime ideals in $R$, then I claim that there exist a maximal ideal $m$ which will contain all the prime ideals in this chain (from finiteness of the maximal ideals), this will give a chain of prime ideals in $R$ localised at $m$, but since that has to be finite (the local ring $R_m$ is noetherian) so the chain pulled back will terminate in $R$.


What does it mean when we say signal is 20% modulated or 40% modulated? Need detailed explanation. Also i want to know what happens when signal is overmodulated?

The  is very short and doesn't explain the concept very well, and there aren't any other sites that I can find that give a simple explanation. What does it mean by 100% modulation? I understand the basic concepts behind amplitude modulation, frequency modulation, and pulse width modulation, but I have never really understood what is meant by the "amount" of modulation or modulation depth.   Can somebody please shed some light on the subject?  Thanks!


I'm from the UK and will be visiting Florida for the second time this year to spend the summer under an ESTA. I have enough money to cover accommodation for two months and expenses without having to work. I will genuinely not be looking for work, I'm just over visiting and maybe going to see some other states.  I visited Florida in March for 11 days for the music week and it two months will have passed from then and when I return again.  I will be staying for 61 days total this time.  I am a student in the middle of a degree so there is no way I would be staying in the US even if it was possible to.  Is the two month gap too short?

I am currently visiting the USA from the UK (I am a UK citizen) and am intending on staying here for the full 90 days under the Visa Waiver Program.     How long would I have to stay out of the US at the end of this period before returning again?    Would I have to return to the UK, or could I stay with friends in another country (such as Canada) for a while?


There are a number of occasions in the mathematics where the word "form" is used:      ...   It seems that form is a special kind of function.  But I cannot readily see what properties a function should satisfy to be eligible to be called a form?

As in differential form, modular form, quadratic form?   I'm sorry if this is a really silly question.


A four-divergence term $\partial_\mu K^\mu$ when added to a Lagrangian, the action changes as $$S\to S^\prime=S+\int_R d^4x \partial_\mu K^\mu\tag{1}$$ where $R$ is a region of spacetime. Using Gauss' theorem, the term $\int_R d^4x \partial_\mu K^\mu$ can be converted to a surface integral $$\int_{\partial R} d\sigma_\mu K^\mu$$  where $\partial R$ represents the boundary of $R$. Now consider a pure Yang-Mills action $$S=-\int d^4x~ \frac{1}{4}G_{\mu\nu}^a G^{\mu\nu a}.$$ We add to it a term $\int_R d^4x \partial_\mu K^\mu$ where $K^\mu$ has the form $$K^\mu=\frac{1}{16\pi^2}\epsilon^{\mu\nu\lambda\rho}A_\nu^a\Big(G^a_{\lambda\rho}+\frac{g}{3}f^{bca}A_\lambda^b A_\rho^c\Big).$$ Here, $G_{\mu\nu}^a=\partial_\mu A_\nu^a-\partial_\nu A_\mu^a+gf^{abc}A_\mu^b A_\nu^c$ denotes the gluon field strength tensor, $A_\mu^a$ are the gluon gauge fields and $a,b,c$ denote the color index. Therefore, the action changes to \begin{eqnarray}S\to S^\prime &=& S+\int_R d^4x \partial_\mu K^\mu\\ &=& S+\int_{\partial R} d\sigma_\mu K^\mu\\ &=& S+\frac{1}{16\pi^2}\epsilon^{\mu\nu\lambda\rho}\int_{\partial T}d\sigma_\mu A_\nu^a\Big(G^a_{\lambda\rho}+\frac{g}{3}f^{bca}A_\lambda^b A_\rho^c\Big).\end{eqnarray} Now, if we consider pure gauge i.e., a boundary condition of the form $A_\mu^a\neq 0$ but $G_{\mu\nu}^a=0$ at $\partial R$, we see that the action changes by a nonzero amount $$S^\prime-S=\frac{g}{48\pi^2}\epsilon^{\mu\nu\lambda\rho}f^{bca}\int_{\partial R}d\sigma_\mu A_\nu^a A_\lambda^b A_\rho^c\neq 0.$$ Question Does this mean that the action can change even if a four-divergence is added to the Lagrangian?

Assume a certain action $S$ with certain symmetries, from which according to the Lagrangian formalism, the equations of motion (EOM) of the system are the corresponding Euler-Lagrange equations.  Can it happen that the equations of motion derived by this procedure have different kinds and/or numbers of symmetries than the action one has started with? And if yes, are there underlying principles that state why which kind of symmetries the action does not have can emerge in corresponding EOMs or which kind of symmetries of the action can potentially disappear in the EOMs derived from the Euler-Lagrange equations?


In my program, I have a score multiplier variable of type 'Number' When I try to add 0.1 to it, I have a problem. Here is the code:  scoreMultiplier += 0.1; trace(scoreMultiplier);   scoreMultiplier is originally set to 1, and after the first run through, I correctly get a value of 1.1. However, the second time, the trace shows 1.2000000000000002, and the next time 1.3000000000000003.  There is no other code which modifies scoreMultiplier. This is a problem, first because it is shown on my game screen and goes off the screen, and second because if conditionals where    scoreMultiplier==2    for example do not work due to the bizarre fault in the addition.  If anyone knows what's causing this, or at the very least how to truncate the value to 1 decimal place, that would be great.

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


Is there a way of arranging Mission Control's workspaces in a two dimensional layout (like 5x5)? So far I've only been able to arrange them in a one dimensional straight line (like 1x9) across the top.  I'm finding that even though there are fewer workspaces, I get "lost" more often with 1x9 than 5x5. Thanks.

Mac has horizontal workspace switching, which is great. However, I find it very useful to have a 2D workspace grid (which I am used to from Linux) and I can switch both horizontally and vertically. Is there a way to do the same in Mac?


I'm solving a combinatorics problem using generating function and reached the following expression: $$\frac{x^4}{(1-x^2)(1-x)^2}$$   How can I expand it to find a general expression for the coefficient of $x^n$?  Any help would be appreciated.

I want to find a general expression for $x^{n}$ in $\frac{1}{(1-x)^3(1+x)^2}$.   I have tried to use partial fraction but that got complicated and I got stuck.   Any help would be appreciated.  Note: I would need a closed form expression


I'm trying to check to see if the address accessed is using a secure connection when accessing a certain page, or not.  If not, I want to redirect the traffic to the proper https:// address.    I have tried doing this in several ways in the .htaccess file.    I was able to rewrite http://foosite.com/contact.shtml and http://www.foosite.com/contact.shtml addresses as https://www.foosite.com/contact.shtml with:  RewriteEngine on RewriteCond %{HTTPS} off RewriteCond %{REQUEST_URI} (contact.*) RewriteRule (.*) https ://www.foosite.com%{REQUEST_URI}   ...but this only rewrites the URL, it does not reload the page, therefore there is no encryption and there is a warning/caution sign next to the HTTPS in the address bar (as there should be).  I need to reload that page so that the encryption is enforced.  Based on what I am looking at I was thinking something like:  RedirectCond %{HTTPS} off RedirectCond %{REQUEST_URI} (contact.*) Redirect 301 https ://www.foosite.com/contact.shtml   ...but this is based purely on conjecture after looking at some posts in here and imagining what might work.  Conjecture is not a good thing to count on, anyway.  I don't even know if there is a RedirectCond tag.  So, as I am not familiar with .htaccess at all, just looking to secure a single form, what would work to redirect a page to the HTTPS address of it when it isn't loaded securely?

This is a  about Apache's mod_rewrite.   Changing a request URL or redirecting users to a different URL than the one they originally requested is done using mod_rewrite. This includes such things as:   Changing HTTP to HTTPS (or the other way around) Changing a request to a page which no longer exist to a new replacement. Modifying a URL format (such as ?id=3433 to /id/3433 ) Presenting a different page based on the browser, based on the referrer, based on anything possible under the moon and sun. Anything you want to mess around with URL   Everything You Ever Wanted to Know about Mod_Rewrite Rules but Were Afraid to Ask!  How can I become an expert at writing mod_rewrite rules?   What is the fundamental format and structure of mod_rewrite rules? What form/flavor of regular expressions do I need to have a solid grasp of? What are the most common mistakes/pitfalls when writing rewrite rules? What is a good method for testing and verifying mod_rewrite rules? Are there SEO or performance implications of mod_rewrite rules I should be aware of? Are there common situations where mod_rewrite might seem like the right tool for the job but isn't? What are some common examples?   A place to test your rules  The  web site is a great place to play around with your rules and test them. It even shows the debug output so you can see what matched and what did not.


Now, I know that there is that remarkable result which finds that $$\sum_{n=1}^{\infty}n=-\frac{1}{12}$$ for $n\in\mathbb{N}$, under some kind of Cauchy limit.   Are there any such convergences for the following series summations?   $\sum_{n=0}^{\infty} n$; $\sum_{n=0}^{\infty} n^2$.

$\displaystyle\sum_{n=1}^\infty \frac{1}{n^s}$ only converges to $\zeta(s)$ if $\text{Re}(s) > 1$.  Why should analytically continuing to $\zeta(-1)$ give the right answer?


I called "ls" command using the execvp system call from inside a c file. But there seems to be a slight difference.    The exe files in the default ls call are highlighted green But not in my own execvp ls call. Am I missing something?  This is the piece of code that is calling ls.  else if (rc == 0)  {      // child (new process)     printf("hello, I am child (pid:%d)\n", (int) getpid());     char *myargs[2];     myargs[0] = strdup("ls");     // program: "wc" (word count)     myargs[1] = NULL;//strdup("p3.c"); // argument: file to count     //myargs[2] = NULL;     // marks end of array     execvp(myargs[0], myargs); // runs word count     printf("this shouldn’t print out"); }

I've just been fooling around with some code in C, an example of a really basic program is as follows which just, obviously, lists the directories using the ls system command.  #include <stdio.h>  int main (void) {     system("ls -l -d */");     printf("I've just listed the directories :-)\n");     return 0; }   This runs fine, but it shows the ls output in monochrome, whereas Bash would output the list using colors for the directories (or files if I included files). How can I make my C code use the bash colors? Thanks