I have noticed that comments are expanded in a different way when I click "see more comments". For example, if an answer has 10 comments, on loading the page it shows only limited comments with a bottom view "View 4 more comments". But the comments are getting expanded in a non-linear manner as the hidden comments are being shown between the existing comments when I click "View 4 more comments". Is there any specific reason for that or is it designed in that manner?

I'm curious how it is decided how many comments to display before the "Show more comments" link. Sometimes I see a dozen comments on a question and no "Show more comments" link, in other occasions no comments are visible at all, only the link.


java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.OutputStream java.net.Socket.getOutputStream()' on a null object reference   Before you mark down this, I am very new to this, I have tried to search on ways to solve this before posting but I can't seem to find a solution. I hope you understand.  I get this error when i run the on change listener.   seekbarbrightness.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {       @Override       public void onProgressChanged(SeekBar seekbarbrightness, int progress, boolean b) {            if(b==true) {                 tblumens.setText(String.valueOf(progress) + " Lumens");                 try {                      socket.getOutputStream().write(String.valueOf(progress).getBytes());                      } catch (IOException e) {                       }            }      } });   I run the below code in the onCreate method.  class ClientThread implements Runnable {      @Override     public void run() {         try {             InetAddress serverAddr = InetAddress.getByName(SERVER_IP);             check = "fail";             socket = new Socket(serverAddr, SERVERPORT);             check = "success";          } catch (UnknownHostException e1) {             e1.printStackTrace();         } catch (IOException e1) {             e1.printStackTrace();         }     } }   What is the problem? Is it because my socket connection is not initialized properly? (Also, i have not got my server running yet, however, the catch would show an error won't it?)  I've tried to use a if socket.isConnected() function then do the try and catch, but it makes no difference..  Please help! I've searched for many tutorials and arrived at these codes for the socket client connection.

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?


To start off I am not really sure if this is hardware (headphones or the phone) or android specific issue/feature. Maybe there is an android workaround for the hardware feature hence this kind of fits here the best.  Google is full of similar topics, but all I've seen are related to windows and not really this kind of delay.  Up until recently I've been using wired headphones, but I started using bluetooth ones and I hit this weird delay when using an app like Duolingo. When there is no sound for a few seconds playing there is a slight delay when the sound is actually played. Let's say I do 5 exercises in a row and I do it very quick- no issue. Then I come to a more complex one that I need more time to do, the sound that plays after submitting an answer is slightly delayed.  When listening to music there are no issues, which would point me to believe that the headset is actually going to some sort of sleep mode when there is no audio played from the source device.  Sony Xperia M2 android 5.1.1  Headphones are Marshall Major II wireless  Do you know of a way to fix/counter-act this annoying bug/feature?

Recent android phone.  I initially observed this issue just with Boom and Megaboom bluetooth speakers, but I now have Jabra buds, and see the same issue:  The first 100-500 milliseconds of audio do not play.  This is an issue if it is a language app (that says a word), or a workout app (that says "start" and then 30 seconds later says "stop") because all or most of the sound does not play at all.  What is the resolution?  I have been forced to use wired buds for language learning (which is NO fun!)  When I used apple airpods I did NOT have this issue. (I no longer use airpods because they  or battery-replaced)


I am probably unnecessarily concerned, but if you use the bobblehead stand or magazine rack instead of keeping them in your inventory, do you still receive the benefits of the items? It would be counterproductive if that were not the case. I have not seen any thing that states they work the same on the stand/racks as on your character so just  wanted to ask. Thanks!

In Fallout 4 the Bobbleheads are back.  Once you pick them up they stay in your inventory with a weight of 0 and a value of 300. Will I need them later ? Do I lose the bonus if I sell them or drop them somewhere ? Same with the magazines.  Is there any disadvantage to selling them ?


I have some questions about the AND-gate which is made by two transistors in this picture below.   When input A or B or both are open (z) the output is '0' by default; is it right? When input A and B are '1', two transistors drive '1' to output so it is conflict because '0' and '1' are driven to output. But according to the truth table, the output is 1 when A & B are '1'. This is ambiguous for me. Please explain about it.

My problem is about AND-gate when its inputs are open. I want to know: What is the output when inputs are open? The output is Z (open) or 0?   What is your idea about this AND-gate transistor structure?     ()  My answer to the above structure is that the output is 0 when the two inputs are open, or at least one of them is 0.


I learned my c++ from , which is an excellent website and I would recommend, but it never teaches delegates and events (among other subjects). When I try to learn those subjects I run a lot to the unary postfix ^ operator, for example "String^ str".   This operator is used much like the * for pointers and & for references, so I assume it does something in the same vain. This operator is never really explained anywhere.   Can someone explain to me what is this operator?  Thanks.  Edit: The question has been answered well in the comments. Thanks you!

I just came across this code and a few Google searches turn up no explanation of this mysterious (to me) syntax.  Hashtable^ tempHash = gcnew Hashtable(iterators_);  IDictionaryEnumerator^ enumerator = tempHash->GetEnumerator();   What the heck does the caret mean? (The gcnew is also new to me, and I asked about that .)


I recall reading a short story, novella, or novel of a crash-landed (?) redheaded scout who educates a backwater isolated planet of humans on how to use paperwork to avoid exploitation by an expanding human empire.  When empire finally came, his redheaded descendants use fees, fines, documentation, paperwork, and procedural methodology to protect the planet and its people from those who would exploit the "ignorant savages."  What is the name of this story/novel?

A spaceship technician landed (crashed?) on a pristine planet (strong Polynesian resemblance) where a tribe of humans lives in harmony with nature, isolated from predatory capitalist humanity, colonising more and more space.  He decides to train them how to resist against expected land grab and corporate invasion. Dies before first space mission arrives, leaving detailed handwritten plan.  The whole plot is about the -- eventually successful --  resistance, run non-violent and legally-supported way.  Possible title "X's Planet" or "X's Plan" -- X being the name of the said spaceman.


My data is in the form: [{'value': 2, 'year': u'2015'}, {'value': 4, 'year': u'2016'}, {'value': 3, 'year': u'2018'}, {'value': 0, 'year': u'2014'}, {'value': 0, 'year': u'2017'}]  I want to sort it by year. Can you please help?

I have a list of dictionaries and want each item to be sorted by a specific value. Take into consideration the list: [{'name':'Homer', 'age':39}, {'name':'Bart', 'age':10}]  When sorted by name, it should become: [{'name':'Bart', 'age':10}, {'name':'Homer', 'age':39}]


I would like to replace a value in a specific index with specific value retrieved from excel. I'm getting my whole array being replace with the last value retrieved.  details= [[""] * 2 ] * 2 details_index=3 for count1 in range(len(details)-1):     details[count1][0] = sheet.cell(row=count1+2, column=details_index).value   the output always return  [['0009', ''], ['0009', ''], ['0009', ''], ['0009', ''], ['0009', ''], ['0009', ''], ['0009', ''], ['0009', ''], ['0009', ''], ['0009', '']]   any idea what did the loop did wrong?

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


If $f:\mathbb{R}\to\mathbb{R}$ satisfies $f(x^2+y+f(y))=2y+f(x)^2,$ prove that $f(x)=x$ for all $x.$  Here's my work so far: $x=0$ gives that $f$ is surjective. Let $f(c)=0.$ Then $x=y=c$ gives $f(c^2+c)=2c,$ so $f(f(c^2+c)/2)=0.$ From $y=0,$ we have $f(x^2+f(0))=f(x)^2,$ so $f$ is non-negative for $x≥f(0).$ Let $y=-x^2$ to obtain $f(f(-x^2))=f(x)^2-2x^2;$ not sure what to do with this observation just yet.  Let $f(y)=-x^2$ to obtain $2y+f(x)^2=-x^2,$ which becomes $f(-0.5(x^2+f(x)^2))=-x^2.$ From $x=y=0,$ we have $f(f(0))=f(0)^2.$ Now we get $f(-0.5f(f(0))=0.$ Put $y=0$ to get $f(x^2+f(0))=f(x)^2.$ Now the FE becomes $f(x^2+y+f(y))=2y+f(x^2+f(0))$ and we have rid ourselves of that pesky "square of a function" term.  Some plans of attack:    Prove that $f(0)=0.$ Prove that $f$ is injective. Prove that $f$ is increasing.   Any ideas on how to accomplish any of these? Any ideas on alternative approaches? What's next? Am I close to solving the problem?

I want to find all functions $f:\mathbb{R}\rightarrow \mathbb{R}$ such that for all $x,y\in\mathbb{R}$: $$f(x^2+y+f(y))=2y+f(x)^2.$$  Suppose we have given a solution $f$. Then $f$ is surjective (set $x=0$). Moreover, I have shown that $f(-x)^2=f(x)^2$ for all $x\in\mathbb{R}$ as well as $f(x)=0\Rightarrow x=0$. But I could not make any progress.  I tried for example $y:=-f(x)^2/2$. Then we get $x^2-f(x)^2/2+f(-f(x)^2/2))=0$. Can someone tell me how to proceed?  Best wishes


I moved my website from SquareSpace to wordpress, I exported the content and posts, the post url's are most important in terms of SEO but I have an issue here.     In wordpress %monthnum% tag is 2 digits so it is adding 0 before   single months lets say January to September in wordpress it is 01-09   but the same in Squarespace is just 1-9.   This small differnce will impact my SEO because my currently indexed posts are all like this in squarespace    but the same post is this way in Wordpress    Is there a way in wordpress to make 01-09 to just 1-9, if yes please let me know.  Thanks much   Remove Duplicate on my question the provided answer in linked question doesn't work. I need more inputs from other forum users.  I added this code in my function.php but it didn't work  add_filter( 'the_permalink', 't5_strip_leading_zeros_in_url' );     add_filter( 'month_link', 't5_strip_leading_zeros_in_url' ); add_filter( 'day_link',   't5_strip_leading_zeros_in_url' );  function t5_strip_leading_zeros_in_url( $url ) {     // no pretty permalinks     if ( ! $GLOBALS['wp_rewrite']->get_month_permastruct() )     {         return $url;     }      return str_replace( '/0', '/', $url );  }   also tried this code  function remove_leading_zeroes_in_permalink($permalink, $post) {     if ($post->post_type == 'post') // change to your post     {                    if ('' != $permalink && !in_array($post->post_status, array('draft', 'pending', 'auto-draft')))         {                            $permalink = str_replace(array('%monthnum%', '%day%'), array(date('n', strtotime($post->post_date)), date('j', strtotime($post->post_date))), $permalink);         }     }     return $permalink; } add_action('post_type_link', 'remove_leading_zeroes_in_permalink', 10, 2); // for custom post types add_action('post_link', 'remove_leading_zeroes_in_permalink', 10, 2); //for post    Both didn't work

My WordPress website currently uses this custom permalink structure: %author%/%year%/%monthnum%/%day%/%postname%  In this case, %monthnum% instantiates numbered dates with a leading zero -- e.g., "09" for September. So, a sample URL might look like this: mywebsite.com/username/2012/09/12/post-name  Is there a function I can add or .htaccess change that I can make which will remove the leading zeros from my permalink stucture? So, using the example above, my URLs would ideally look like this: mywebsite.com/username/2012/9/12/post-name  Thank you! I've read up on WordPress' structure tags documentation (http://codex.wordpress.org/Using_Permalinks), but I can't find any solutions or plugins for the above-mentioned problem.


I am given this expression and I have to prove it using mathematical induction  ${\displaystyle \forall }n\ge 1 $ , $$ \sum _{k=1}^n\left(\frac{1}{\sqrt{k}}\right)\ge 2\left(\sqrt{n+1}-1\right)$$  I have proved it is true for $n=1$, then suposed it was true until $n$ and wanted to prove it was also true until $n+1$.   I have operated a bit and arrived to this expression I want to prove: $${\frac{1}{2\sqrt{n+1}}}\ge (\sqrt{n+2}-\sqrt{n+1})$$ , and I don't know how to continue to clear that inequality to prove it. Can you help me please?? (I have just started studying this method so I'm a bit lost :/ )

The exact question:  Prove:  $\displaystyle\sum_{k=1}^n \frac{1}{\sqrt{k}}\gt2(\sqrt{n+1}-1)$  I have looked at similar problems but still don't understand how to prove this inequality by induction. So far I have this:  Induction basis:  Let n=1  $\displaystyle\sum_{k=1}^n \frac{1}{\sqrt{k}} = \frac{1}{\sqrt{1}} = 1 > 2(\sqrt{1+1}-1) = ~.828$  $1>.828$  So it proves the inequality true when n=1.   Now i really don't know how to continue even with all the examples i have browsed through. One of them i came across showed that the induction hypothesis should let P(n) equal the equation above and do something with P(n+1). I am not looking for the answer I just need help on how to continue with the problem. What other steps are necessary for me to complete this proof by induction.


Is there any quantifiable evidence to support power cycling routers for 10 seconds or any arbitrary amount of time, instead of just unplugging and plugging back in?  This is related to troubleshooting a misbehaving router. The theory is based on 'things' needing to be cleared from memory, and that this could take a few seconds.  This is also a theory related to electronics from over a decade ago, and I'm sure it was equally as anecdotal then.  As a person allergic to anecdotes, I became curious when I recognized that I never investigated this issue.  Is there any quantifiable reason to support power cycling routers for 10 seconds or any arbitrary amount of time, instead of just unplugging and plugging back in? Sources welcome

When calling support the other day he told me to reset my DSL modem by pulling out the power, leave it out for 10 seconds, and then plug it back in. This is something I have heard many times with different kinds of equipment. I have also heard it in relation to computers. That when you turn it off, you should wait at least 10 seconds before you turn it on again.    Why not just plug it in again right away? Why 10 seconds, instead of, say... 3 or 30? Should you really, always do this; just with certain types of equipment; just in certain circumstances; or is it just a "myth" thing that people have said so often that they believe it to be fact?


I am using Ubuntu 16.04 which comes with python 2.7 and python 3.5 pre-installed. I am currently working on a project where it requires to install python 3.6 and some additional packages. I have searched the Internet but i couldn't manage to get the comprehensive tutorial steps where I could follow. Please help me. Thanks in advance...

I've tried the normal way, sudo apt-get install python3.6, but... well... that didn't work.   So, how would I go about it? (I'd preferably not build it on my own)  I'm using Ubuntu 16.04.


In the word mentality, how should the letter i be pronounced?  In , it's a shwa.  In , it's a shwa.  In , its American dictionary(at the middle of this page) says it's a short I.  In , it's a short I.  I'm confused by these dictionaries.   Is there a distinction between AmE and BrE? One say short I while the other say shwa?  Or they are both okay in the USA and the UK?

I've seen that some words in English are pronounced with the /ɪ/ sound when the vowel is not stressed.  Some examples include: pocket /ˈpɒkɪt/, comet /ˈkɒmɪt/. But hundred /ˈhʌndrəd/.  Is there any pronunciation rule here when the words end in /t/?


I asked  two month back. It got answer which does not quite  work for me. A while after I came back to the problem at hand and decided to flag my post to have it moved to  or . Yet, I have been denied that due to question being asked more than 60 days ago:  What shall I do to ask this question again and avoid duplicates across the sites? Would closing work, or is there something else that should be done? Besides, why do we want to deny old posts being moved in the first place?

This has come up    : migrating old questions causes problems.   The most popular solution to this to date has been to . This is do-able, but frankly it feels like treating a symptom, and doing so in a way that penalizes folks who answer what are by all appearances valid, on-topic questions.   Migration works best as a way to salvage good but off-topic questions and give them new life on a site where they can thrive. But shuffling old, answered, on-topic questions around for the hell of it is a waste of everyone's time.   Therefore, I think the real solution is much simpler: just disable the migration of old questions. They're rarely welcomed or heavily improved post-migration, often overtly disliked by folks on the destination site, and can end up causing a rather bad experience for folks who were participating in good faith on the original.   I suggest that questions older than 601 days should not be eligible for migration, either by normal user close-votes or by moderators. In extreme cases, we can perhaps provide an alternate means of moving old questions, but under normal circumstances these should be done quickly or not at all.   1 60 days is actually based on a  introduced this past spring: migrated and then rejected questions older than 60 days cause the authors to suddenly gain (permanent) reputation on the destination.


In the following code, I check the menuitem for android.R.id.home to handle up button clicks to finish the activity, but on a Gionee device running Android 4.2.2, this causes a NullPointerException.  @Override public boolean onOptionsItemSelected(MenuItem item) {     switch (item.getItemId()) {         case android.R.id.home:             finish();             return true;     }     return super.onOptionsItemSelected(item); }   The crash happens on the finish() line. And I'm not overriding the onFinish() function.  The stacktrace is:  java.lang.NullPointerException        at android.os.Parcel.readException(Parcel.java:1434)        at android.os.Parcel.readException(Parcel.java:1379)        at android.app.ActivityManagerProxy.finishActivity(ActivityManagerNative.java:2114)        at android.app.Activity.finish(Activity.java:4165)        at com.Valmeeki.Valmeeki.activities.ReadingRoomActivity.onOptionsItemSelected(ReadingRoomActivity.java:115)        at android.app.Activity.onMenuItemSelected(Activity.java:2566)        at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:325)        at android.support.v7.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:147)        at android.support.v7.internal.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:100)        at android.support.v7.internal.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:100)        at android.support.v7.internal.widget.ToolbarWidgetWrapper$1.onClick(ToolbarWidgetWrapper.java:196)        at android.view.View.performClick(View.java:4248)        at android.view.View$PerformClick.run(View.java:17723)        at android.os.Handler.handleCallback(Handler.java:800)        at android.os.Handler.dispatchMessage(Handler.java:100)        at android.os.Looper.loop(Looper.java:194)        at android.app.ActivityThread.main(ActivityThread.java:5421)        at java.lang.reflect.Method.invokeNative(Method.java)        at java.lang.reflect.Method.invoke(Method.java:525)        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:844)        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:611)        at dalvik.system.NativeStart.main(NativeStart.java)   Any idea what I'm doing wrong here? Is it some Android bug? Or am I safe in forgetting about this and just calling finish() within a try-catch?  As a final note, this is not a duplicate of . I know very well what a NPE is and I've had my fair share during my life as a programmer. This question was asked only because it is thrown only on a certain device and at a seemingly improbable place for a NPE. I request the user who flagged this as a duplicate to read the question atleast once.

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?


After updating my system as usual from the terminal it goes on fetching updates but at last it shows the following messages. What does it mean and how do I fix the red icon. Actually to fix the red icon I updated but it isn't fixed.  The message:  W: GPG error: http://ppa.launchpad.net trusty  Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 1DB8ADC1CFCA9579 W: Failed to fetch http://in.archive.ubuntu.com/ubuntu/dists/trusty-updates/main/i18n/Translation-en  Hash Sum mismatch E: Some index files failed to download. They have been ignored, or old ones used instead.   And also I could not update recommended Updates, every time I hit Install off course after authentication a message pops up. How do I fix this annoying message. I want to run my system with anomaly(s). Who wouldn't?

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


If $G$ is a finite group s.t. $|G|=4$, is it abelian ? To me it's isomorphic to $\mathbb Z/2\mathbb Z\times \mathbb Z/2\mathbb Z$ or $\mathbb Z/4\mathbb Z$, but a friend of me said that they are not the only group of order 4, and there exist some non-abelian. Do you have such example ?

How can I show that every group of order $4$ is abelian?  Let's denote $e,a,b,c$ as the four elements of the group.  Since $e$ is identity, we have $e*x=x*e$ for every $x$:  $$\begin{array}{|c|cccc|} \hline     & e & a & b & c \\\hline   e & e & a & b & c \\   a & a &   &   &   \\   b & b &   &   &   \\   c & c &   &   &   \\\hline \end{array}$$  Now $a*a=$? We have several possibilities.  If I choose $a*a=b$ I can show $a*b=a*(a*a)=(a*a)*a=b*a$.   But so far I have shown only that $a$ and $b$ commute, there are also other pairs. And I have only discussed the choice $a*a=b$, there are also other possibilities. Is there a simpler way to do this?


I'm wondering if there exists a way to identify the same user across different stack exchange sites. Like Id are unique for user across this sites? If not, is there some data like information that user logged in using Stack Exchange account and which account? I really want to identify which users are using which sites to check:  a) common part of different sites by knowing how many users they share,   b) examine flow of people between different fields of science and technology by examining mix of sites data, tags and activity  c) and much more...

to  implies that you can write cross-site Data Explorer queries, but the sample query doesn't appear to do what I think it should.  SELECT TOP 1 *     FROM [StackOverflow.Exported]..[Users] u1     INNER JOIN [ServerFault.Exported]..[Users] u2 ON u1.Id = u2.Id   I had assumed that this would find a linked account between Stack Overflow and Server Fault, but as far as I can tell user IDs are not preserved across the Stack Exchange network. Is it possible to write a query that joins linked accounts across Stack Exchange sites?


I would appreciate if someone could help me write the mathematical equation for the seasonal ARIMA (0,0,5) x (1,0,1) period 12. I'm a little confused with how to go about this.

I would appreciate if someone could help me write the mathematical equation for the seasonal ARIMA (2,1,0) x (0,2,2) period 12. I'm a little confused with how to go about this. I would prefer an equation involving $Y_t , e_t, θ$ and $Θ$.


I got this question in interview, it seems simple one but I want to confirm my understanding about its functioning.  f (char *p, char *q, int n) {     int i1 = n >> 2;     int i2 = n & 3;      switch (i2)      {         do {             *q++ = *p++;             case 3:  *q++ = *p++;             case 2:  *q++ = *p++;             case 1:  *q++ = *p++;             case 0:  ;         } while (i1--);     } }   I was asked below questions in interview:    What this function does? Why would somebody write such convoluted code? Is there any way to write it differently (simpler, faster)?   Answers given:   This function copies the number of elements from the memory where *P is pointing to the memory where *q is pointing. if you will write it with for loop as below (writing only loop)  for(i=0;i<n;i++)    *q++ = *p++;   then the compiler taking more MIPS/time in condition checking. In this it will first subtract i from n and then checks is I non zero ? In the given code while loop maintain condition only 1 condition if i1 is non-zero ? So in while loop there is less condition checking. We can write as:  f (char *p, char *q, int n) {   for(i=n;i--;)     *q++ = *p++; }   It seems simple and faster to me.   Please give me your opinion.

I've read the , and I don't get it. I am really interested, but I've read the explanation there a couple of times and I still don't get it how the Duff's device works.  What would a more detailed explanation be?


How can I find out what my wifi password is for my iphone?  I entered what I thought was password but it will not connect.  I can't find it written down anywhere to be sure.

I've previously connected to a wifi network on my iPhone but I've no way of finding out the password. So is there any way to view saved wifi passwords on the iPhone?


Somehow I do not have sudo on my PC anymore, perhaps I may have uninstalled it somehow? I pasted this into my terminal earlier:   sudo rm osbuddy sudo nano osbuddy   And now it seems sudo is not there anymore.  When I write sudo, the terminal outputs  Command 'sudo' not found, but can be installed with: sudo apt install sudo   Obviously this does not work since when I write sudo apt install sudo  The sudo command is not found of course.  If I just write apt install sudo   It says that I need to be root. What do I do?

I accidentally deleted the /usr/bin/sudo file. How can I restore it?  I have found , but it seems to be not solved.


This is really interesting. In any editor or formatting language I ever used images and text would appear in the order in which you have entered them. Not so much in LaTeX. I have a following figure:  Blah blah blah:  \begin{figure}[htb]   \centering   \includegraphics[scale=0.8]{image.eps}   \caption{this is image} \end{figure} blah blag. Blah.   These are in the document headers:  \usepackage{graphicx} \usepackage{grffile}  \usepackage[outdir=./]{epstopdf}   And the image jumps to the end of the end of my PDF, leaving the text like this:     Blah blah blah:    blah blag. Blah.   Which looks stupid. The image looks stupid too, so alone at the end:     Why does LaTeX do this and in which cases it's a good thing? How to prevent it when it's not a good thing?

Is there any package or a method to force LaTeX to keep floating environments like table and figure closer to where they are declared?


We mean here $L_2$, and $L_1$ the usual Lebesgue spaces on the unit-interval. It is excercise 2.4 from Rudin. There's several ways to show that $L_2$ is nowhere dense in $L_1$.  But in (b) they ask to show that  $$\Lambda_n(f)=\int fg_n \to 0 $$   where $g_n = n$ on $[0,n^{-3}]$ and 0 otherwise, holds for $L_2$ but not for all $L_1$. Apparantly this implies that $L_2$ is of the first Category, but I dont know how.  Second, I can show this holds for $L_2$ but I cant find a counterexample in $L_1$.  Theorem 2.7 in Rudin says:  Let $\Lambda_n:X\to Y$ a sequence of continuous linear mappings ($X,Y$ topological vector spaces) If $C$ is the set of all $x\in X$ for which $\{\Lambda_n x\}$ is Cauchy in $Y$, and if $C$ is of the second Category, then $C=X$.  So if we find a $f\in L_1$ such that $\Lambda_n(f)$ is not Cauchy, then we proved that $L_2\subset C \subset L_1$ is of the first category. However I dont see why showing that $\Lambda_n(f)$ does not converge to 0 for some $f\in L_1$ is enough here.  Am I missing something?

I want to prove that $L^2$ is of the first category in $L^1$, thus I have to prove that $L^2$ is the countable union of nowhere dense subsets. The hint I get is: Take $g_n(x)=n$ for $0\leq x\leq\frac{1}{n^3}$ and show $\int{fg_n}\rightarrow 0$ for all $f\in L^2$ but not for every $f\in L^1$.   My question: What does this hint help for proving that $L^2$ is of the first category? I don't know how to use this hint. Can someone help me? :)  Thanks


I am using Ubuntu 12.04 on my Samsung Chromebook and I have found that Ubuntu 14.04 does not work with unity on my Chromebook. So do I have to update Ubuntu to 14.04 now or can I continue to use 12.04 for as long as I want? If I don't have to update then will I be subject to many problems? or will I be just fine?

I'm using Ubuntu 12.04 LTS, and although I would like to upgrade to 14.04 LTS, I don't want to have any troubles after upgrading. For example, I don't know if I can no longer use some of my software and have to reinstall it.  I'm also worry if my computer have the system requirements necessary to 14.04 LTS version.  That's why I'm asking if it is necessary to upgrade, I mean, will be any problem if I skip the upgrade? Can I stand in 12.04 LTS forever?


Enhancing this , I got:  def pretty(d, steps = -1, indent = 0):     for key, value in d.iteritems():         c = 0         print '\t' * indent + str(key)         if isinstance(value, dict):             pretty(value, indent+1)         else:             print c             if(c == steps):                 return             c += 1             print '\t' * (indent+1) + str(value)   which dreams of printing until a certain number of values of the original key are printed. For example, without a limit:  1 5299     1 1229     1 2068     1 7223     1   but when steps = 2, then it would print:  1 5299     1 1229     1   The reason its dreams are not coming true is that c is not a static variable (like one would do in C, I tried static c = 0 and got a syntax error), thus at every call of the recursion, c is created again, it doesn't remember its former value.  How would one do this in Python?

What is the idiomatic Python equivalent of this C/C++ code?  void foo() {     static int counter = 0;     counter++;     printf("counter is %d\n", counter); }   specifically, how does one implement the static member at the function level, as opposed to the class level? And does placing the function into a class change anything?


I have been trying to login into the Stack Exchange app from the Play Store on my , but it shows: "Error while attempting to login: 'key' is not valid for passed 'access_token', token not found.  I am on Stack Exchange daily with the computer, so my login credentials are right.  I even did a copy paste of the password to ensure there were no mistakes.  Did anybody have the same issue? Any advice?

I am unable to log on to . I receive the following error as soon as I try "Log in using Google". (This is the same Gmail account I use for Stack Exchange.)     'key' is not valid for passed 'access_token', token not found.     On my Android Device (Galaxy S4 4.4.2), I have two Google accounts – will this have an effect, or am I missing a step in order to log on with a Google account using the Stack Exchange Android app?


The      "The Code of Conduct change has been pushed through and . – Tonepoet "   (as a few others)  refers to deleted  page. (The reason of deletion of the page is discussed on ).  I've noticed that     “This question was voluntarily removed by its author.”   But according to      You can't delete your own question if it has an answer with upvotes   I understand that  is relatively new, and may not know rule details, but I also read somewhere (unfortunately, could not find a quote) that shog9 consulted Cesar M and advises to delete the question.  Cesar M in his role of moderator can delete any post, but, according to the system, he deleted the question being in a role of author, which is not allowed.  As it was a genuine mistake, I suggest to Cesar to undelete the question ASAP.  There are multiple options of further steps, e.g.   Make the question locked, as suggested in many highly-upvoted answers here:  Ask some other moderator to delete the question, if they find, that there is no better way to do it. Change the system to not allow the question with upvoted answers to be deleted by the author, even the author is a moderator. Also update  to clarify that “You can't delete your own question (even you are a moderator)” Change the system to show that the question was removed by moderator, if the author and moderator is the same person. Also update  to clarify that “You can't delete your own question (unless you are a moderator)” Automatically redirect links to  or    I hope that Cesar will undelete the question to comply with existing rules. If not, will he potentially be suspended as not comply to the rules or suspension rules are applicable to elected moderators only?  I also have doubts, that “the question was voluntarily removed by its author.” Quite likely, that the decision about the deletion of the question was made by management, such as the Director of Public Q&A.

When regular users delete their questions, users with less than 10,000 reputation that stumble across the link are shown the following message:  Page not found This question was voluntarily removed by its author.   When other users vote to delete someone's question (or delete it unilaterally with moderator abilities) a different message is shown:  Page not found This question was removed from Meta Stack Exchange for reasons of moderation. Please refer to the help center for .   Generally speaking, regular users do not have the ability to delete their own questions if there are already upvoted answers posted thereto. Now what happens when users with moderation powers delete their own posts that already have upvoted answers? While the question was still technically voluntarily removed by its author, I would expect the 404 page to display the other message. This is because the question was not deleted by the moderator in their mere capacity as the author of the post, but in their official capacity as a moderator. The real reason such a post was deleted would indeed be for reasons of moderation, as it was only possible to delete it because of special moderator powers. However, the opposite is apparently true.  was posted by a Community Manager (i.e. someone with full moderation powers), and deleted by the same Community Manager. Had he not been a Community Manager (or moderator) he would not have been able to delete his question. Thus, the question was indeed deleted for reasons of moderation (), and it is apparently merely a coincidence that the one who actually clicked the delete button also happened to be the one who had posted it. When I (as a less-than-10,000-reputation-user) view that question, it tells me that it was voluntarily removed by its author:  Can this be fixed so that the other explanation, which seems to be more accurate, will be displayed instead?


Billy wants to send a message to Bob. He generates secure primes p and q for each time he sends a message. However, he accidentally sends the same message multiple times. Is Billy's message still safe? More formally, I know that e=3 and that the plaintext remains the same for more than 1 message, but the value of n (and subsequently the ciphertext, c) changes. e=3 n=pq c=123 plaintext=my-cool-mesage  e=3 n=p'q' c=456 plaintext=my-cool-mesage  If an attacker has access to the e, n, and c for each message, can they recover the plaintext with the fact that the plaintext is shared, even when n changes?

I have three different 1024-bit public keys with common exponent $e$ but different moduli. A message $m$ is encrypted (without padding) using the three keys, which results in three different encrypted messages.  Given the three pairs of public keys $(N_i,e)$ and the encrypted messages $c_i=m^e\bmod N_i$ , how do I decipher the original message $m$ ?


I am deriving logistic regression's likelihood. I have seen two different versions:   $$\begin{equation}  f(y|\beta)={\displaystyle \prod_{i=1}^{N} \frac{n_i} {y_i!(n_i-y_i)!}} \pi_{i}^{y_i}(1-\pi_i)^{n_i - y_i}  \tag 1 \end{equation}$$  Or this    $$\begin{equation}  L(\beta_0,\beta_1)= \displaystyle \prod_{i=1}^{N}p(x_i)^{y_i}(1-p(x_i))^{1-y_i}  \tag 2 \end{equation}$$  Why is there $\frac{n_i} {y_i!(n_i-y_i)!}$ in equation 1?  Sources:     First:  (page 3 equ. 2)    Second:  (page 5 equ. 12.6)   Note: This question is not a duplicate of  One can trace the answer back to binomial distribution, after seeing how it is done. But nobody would have known the question in that post is the answer to this question.

I'm reading  where the authors are leading from a discussion of maximum likelihood estimation to Bayes' Theorem, ostensibly as an introduction for beginners.  As a likelihood example, they start with a binomial distribution:  $$p(x|n,\theta) = \binom{n}{x}\theta^x(1-\theta)^{n-x}$$  and then log both sides  $$\ell(\theta|x, n) = x \ln (\theta) + (n-x)\ln (1-\theta)$$  with the rationale that:     "Because the likelihood is only defined up to a multiplicative constant of proportionality (or an additive constant for the log-likelihood), we can rescale ... by dropping the binomial coefficient and writing the log-likelihood in place of the likelihood"   The math makes sense, but I can't understand what is meant by "the likelihood is only defined up to a multiplicative constant of proportionality" and how this allows dropping the binomial coefficient and going from $p(x|n,\theta)$ to $\ell(\theta|x,n)$.  Similar terminology has come up in other questions ( and ), but it still not clear what, practically, likelihood being defined or bringing information up to a multiplicative constant means. Is it possible to explain this in layman's terms?


We notice that $1=1^2$   ,$1+3=4=2^2$,$1+3+5=9=3^2$,$1+3+5+7=16=4^2$ How we can generalize this and give a proof?Any ideas?

I stumbled across this relationship while I was messing around. What's the proof, and how do I understand it intuitively? It doesn't really make sense to me that the sum of odd numbers up to $2x + 1$ should equal $x^2$.


I think not, but I may be mistaken. I've seen Ned's wife, Catelin being called Catelyn Tully several times.  What is the custom in Westeros, of married noblewomen surnames? Do they change, or not?  Example: when Sansa was forced to marry (twice), did she became Sansa Lannister or Sansa Bolton? Or did she remain Sansa Stark?

I've watched the first two seasons of the TV series, and I'm in the middle of the first book. While reading, I noticed that Catelyn is usually referred to by her married name:     Scarlet-tinged spittle flew from the fat innkeep's mouth as she begged of Catelyn Stark, "Don't kill him here!"   Her maiden name is only used in the past tense:     "I was still Catelyn Tully the last time I bedded here," she told the innkeep.   The same seems to be true for Lysa Arryn (can't find an example right now) and other married ladies. Yet, the book calls the queen by her maiden name:     Cersei Lannister entered behind him, a jeweled tiara in her hair.   Is there an in-world explanation for that? Are the "naming rules" different for the royal couple?


I have a small problem. The f12 wont render correctly. This is my viewport:    and this is the f12 image:    Blender File here:   Could someone please help me :)?

This is meant to solve this problem once and for all. What is every reason an object isn't showing up in a render or viewport in when using the cycles render engine?


I came across this sample sentence in Oxford Dictionary，under the entry "spook":     They spooked a couple of grizzly bears.   I consulted an Oxford dictionary of English-Chinese edition, and it translates the sentence into  "They frightened two grizzly bears".   Maybe OK but I am still not fully convinced it means only two bears in the sentence. Does "a couple of bears" necessarily mean two, or have a meaning of more than two in most cases? As to in this sample sentence, I would prefer to interpret it as "they frightened some grizzly bears"(maybe they weren't quite sure of or didn't notice the exact number).  Help me.

Today I said some event was a couple of weeks away. A native speaker from Australia corrected me and said, no it's at least three weeks away. What followed was a discussion as to whether a couple always means two, or if it can mean more than two.  What does a couple, in particular a couple of weeks, mean to a native speaker?  According to :        Two partners in a romantic or sexual relationship.   Two of the same kind connected or considered together.   (informal) A small number.      According to :        two people or things of the same sort considered together:   'a couple of girls were playing marbles'   [treated as singular or plural] two people who are married or otherwise closely associated romantically or sexually:   'in three weeks the couple fell in love and became engaged'   'a honeymoon couple'   [informal] An indefinite small number      Yet my colleague — a native speaker — insists that a couple never means three, although there can be a small error bar on the two. We asked one other native speaker who agrees with him, yet three non-native speakers point at the above-mentioned sources to claim they're wrong. But it's a bit tricky for non-native speakers to claim native speakers are wrong. Note that both native-speakers are from Australia/New Zealand.


I am solving the following question  $$\int\frac{\sin x}{\sin^{3}x + \cos^{3}x}dx.$$  I have been able to reduce it to the following form by diving numerator and denominator by $\cos^{3}x$ and then substituting $\tan x$ for $t$ and am getting the following equation. Should Iis there any other way use partial fraction to integrate it further or   $$\int\frac{t}{t^3 + 1}dt.$$

I'm new here!  The problem: integrate from zero to infinity x over the quantity x cubed plus one dx. I checked on wolfram alpha and the answer is that the indefinite integral is this:  $$\int \frac{x}{1+x^3} dx = \frac{1}{6}\left(\log(x^2-x+1)-2 \log(x+1)+2 \sqrt{3} \arctan((2 x-1)/\sqrt{3})\right)+\text{constant}$$  and the definite integral is this:  $$\int_0^\infty \frac{x}{1+x^3} dx = \frac{2 \pi}{3 \sqrt{3}}\approx 1.2092$$  I am trying to figure out all the steps in between. I see that there are logs, which are equivalent to the ln variant that i am more familiar with, which means it was integrating $1/x$ at some point; I also see an inverse tangent in there.  I started with long division to simplify and I got (which could be wrong because I am very tired right now) $x/(x^3+1) = x^2+ 1/(x^3+1)$ which seems to be a step in the right direction. Wolfram Alpha thinks I definitely did that step wrong. The two equations do not evaluate as equal.  Then I cheated and took the wolfram alpha factorization of $(x^3+1) = (x+1)(x^2-x+1)$...I probably should have known that but didn't offhand. Now it is looking like $x^2$ plus the partial fraction decomposition $1/(x^3+1) = A/(x+1)+(Bx+C)/(x^2-x+1)$. Am I heading in the right direction with this? At this point do I just plug in and crunch?


I have a List of colors that I would like to be shuffled and mixed up at least a little.  I create a list using   List<Color> colors = new List<Color> ();  colors.Add(Color.Black);  colors.Add(Color.White);  colors.Add(Color.Red);   But there is no .Shuffle I noticed a .Sort but I don't think that's what I need. I searched for a while but all methods and other questions I found seem to be way over complicated for such a simple task, if there is a simpler way.  I tried using  List<Color> colorList = new List<Color>(); public void SetupColors()     {         List<Color> colors = new List<Color> ();         colors.Add(Color.BLACK);         colors.Add(Color.WHITE);         colors.Add(Color.RED);         Random random = new Random();         int n = colors.Count;          for (int i = colors.Count; i > 1; i--)         {             int rnd = random.Next(i + 1);              var value = colors[rnd];             colors[rnd] = colors[i];             colors[i] = value;         }         colorList = colors;     }      public List<Message> getMessages()     {         List<Message> items = new List<Message>         {             new Message             {                 . . .                  Background = colorList[0]             },             new Message             {                 . . .                  Background = colorList[1]             }         };          return items;     }   but I keep getting IndexBound errors at colorList[0] and colorList[1]

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


I'm confused between these two phrasal verbs. I'm going to quote here two examples but since I'm learning so I might be wrong, do correct me here. "It turns out that it was a conspiracy against him" and "it turns out to be a conspiracy against him".

E.g:        Turns out that it was a conspiracy against him.   It turned out to be a conspiracy against him.       I'm confused here in the usage of these phrasal verbs.


Just like the other operation on sets is addition of sets using + symbol defined? I encountered a question on my exam which towards the end required the addition of 2 identical sets (0,1) and the answer given is (0,2). Is there any defined convention of this sort.

Given two sets $A$ and $B$, what is the difference between $A + B$ and $A \cup B$? For example, if $A = \left\{ a, b, c \right\}$ and $B = \left\{ d, e, f \right\}$, what are $A + B$ and $A \cup B$, respectively?


When I go to a Stack Exchange page (especially Stack Overflow), sometimes it will display a notification bar on top saying: 'click on "xxxxx" user id, and refresh the page'. Once the user clicks that link, we have then logged in again.    I am a little bit confused. Since the page had already shown my user id on the notification bar, I assume the Stack Exchange server has probably found my session. Why does it require me to refresh it again?   My little guess is the Stack Exchange server did find my session, but my session is almost expired, so it gives me a notification to prolong the session again.

After logging into one Stack Exchange site, when I visit another SE site, it says to me, welcome back - user - click here to refresh - web page.   Isn't it possible to refresh the page using code & without the user's interaction?


I'm making a circle with a radius of 400 pixels, the edge of it looks like this:    But the look I'm trying to achieve is a circle with hard edges, meaning no transparency, the edge of it would then look like this:    So how do I do it?

Whenever I create a square shape at 100% zoom, I get perfectly sharp edges. However, once I zoom in at any amount, drawing a perfect square (without anti-aliasing) is very difficult. Is there a way I can turn this off?


Consider the following subsets of the complex plane:  $$ \Omega_1=\left\{ C\in \mathbb{C} :  \begin{bmatrix}         1  & C\\         \overline C &1         \end{bmatrix}\text{ is positive semi-definite} \right\} $$  $$ \Omega_2=\left\{ C\in \mathbb{C} :  \begin{bmatrix}         1  & C &C\\         \overline C &1 &C\\         \overline C & \overline C & 1         \end{bmatrix}\text{ is positive semi-definite} \right\} $$  Let $\overline {\mathbb{D}}= \{z \in \mathbb{C} :\vert z \vert \le 1\}$.Then   $\Omega_1=\overline {\mathbb{D}},\Omega_2=\overline {\mathbb{D}}$. $\Omega_1\neq\overline {\mathbb{D}},\Omega_2=\overline {\mathbb{D}}$. $\Omega_1=\overline {\mathbb{D}},\Omega_2\neq\overline {\mathbb{D}}$. $\Omega_1\neq\overline {\mathbb{D}},\Omega_2\neq\overline {\mathbb{D}}$.   $\Omega_1$ is positive semidefinite implies that its determinant $1-\vert z \vert^2 \ge 0$ impliying that $\vert z \vert \le 1$.Thus $\Omega_1=\overline {\mathbb{D}}$.  As far as $\Omega_2$  is concerned it being positive semi definite would suggest that the determinant of every principal submatrix of $\Omega_2$ is non-negative. The two diagonal ones which are basically same as $\Omega_1$ give  $z \in \mathbb{C} :\vert z \vert \le 1$.But the other submatrices result in the relation that $z^2-z$  is real and non-negative.This definitely means:  $\Omega_2\neq \overline {\mathbb{D}}$. Right?  That would mean 3 is the right answer? Am I correct?

$$\Omega_1=\left\{c\in\Bbb C:\begin{bmatrix}1&c\\\bar c&1\\ \end{bmatrix}\text{ is non-negative definite } \right\} $$  $$\Omega_2= \left\{c\in\Bbb C:         \begin{bmatrix}         1 & c & c \\         \bar c & 1 & c \\         \bar c & \bar c & 1 \\         \end{bmatrix} \text{ is non-negative definite } \right\}$$  Let $$\bar D=\{z\in\Bbb C:|z|\le1\}$$ Then 1) $\Omega_1=\bar D,\Omega_2=\bar D$  2). $\Omega_1\neq\bar D, \Omega_2=\bar D$  3). $\Omega_1=\bar D, \Omega_2\neq\bar D$  4). $\Omega_1\neq\bar D, \Omega_2\neq\bar D$  How to proceed? Thank you.


Has this statement any relation with continuum hypothesis ?

Is it consistent with ZF for there to exist a set $S$ such that the power set $P(S)$ is countable? If so, what is the weakest form of the axiom of choice needed to prove that no such set exists?


Assume $X_1$ .. $X_n$ ~ iid beta($\theta$,1)   I'm supposed to construct a Maximum likelihood ratio test for:  $H_0$: $\theta$ = $\theta_0$  $H_1$: $\theta$ != $\theta_0$   But I'm stuck at the last step of simplifying the rejection region.  My steps are as follows:  1) Obtain the MLE (skipping derivation)  $$\theta_{mle} =  \frac{-n}{\sum_{i=1}^n log(x_i)}$$  2) Likelihood ratio:  $$ \frac{\prod_{i=1}^n  \frac{\Gamma(\theta_0+1)}{\Gamma(\theta_0)\Gamma(1)} x_i^{\theta_0-1} (1-x_i)^{1-1}}{\prod_{i=1}^n\frac{\Gamma(\theta_{mle}+1)}{\Gamma(\theta_{mle})\Gamma(1)}x_i^{\theta_{mle}-1} (1-x_i)^{1-1}}$$  Simplify the gamma terms and Cancel the last term:  $$ \frac{\theta_0\prod_{i=1}^n  x_i^{\theta_0-1}}{\theta_{mle}\prod_{i=1}^nx_i^{\theta_{mle}-1}}$$  Combine the product terms:  $$ \frac{\theta_0}{\theta_{mle}}\prod_{i=1}^n{x_i^{\theta_0 - \theta_{mle}}} $$  Rejection Region:  $$ P (\frac{\theta_0}{\theta_{mle}}\prod_{i=1}^n{x_i^{\theta_0 - \theta_{mle}}} < K) $$  And now I'm stuck. I know i must get to something like   $$ P (\bar{x} < c) $$  But I'm unsure how to proceed. Any help will really be appreciated!!

Suppose I have a sequence of iid random variables $X_1, \ldots, X_n$ following the pdf:  $$ f_\theta (x) = \theta x^{\theta-1} $$  for $\theta >0$ and $0 <x<1$.  I would like to obtain a level-$\alpha$ likelihood ratio test for the null hypothesis $H_0: \theta = \theta_0$ versus the two-sided alternative $H_1: \theta \neq \theta_0$ where $\theta_0$ is a known constant.  MY ATTEMPT:  I first construct the ratio:  \begin{align} \lambda(x) &= \dfrac{sup_{\theta=\theta_0}L(\theta|X)}{sup_{\theta\neq\theta_0}L(\theta|X)} \\ &= \dfrac{\theta_0^n \left(e^{\sum log x_i}\right)^{\theta_0-1}}{\left(\frac{n}{-\sum logx_i}\right)^n \left(e^{\sum logx_i}\right)^{\left(\frac{n}{-\sum log x_i} - 1\right)}} \\ &= \left(\dfrac{-\theta_0 \sum log x_i}{n}\right)^n e^{n+\theta_0 \sum log x_i} \end{align}  The denominator is calculated using the MLE of $\theta$ which is $\theta^{MLE} = \frac{n}{-\sum log x_i}$. Now, I'd like to find the likelihood ratio test, in that I would like to choose a constant $c$ such that:  $$ \alpha = sup_{\theta = \theta_0}P_\theta\left(\lambda(x) \leq c\right) $$  Now, $-\sum logx_i \sim Gamma(n, \theta)$ but I CANNOT isolate the above equation due to the $log$ form. What is the right answer here? Thanks!


Prove that for all $n \in \mathbb{Z}^+$, $\sum_{i=1}^n i^3 = \left(\sum_{i=1}^n i\right)^2$.  I understand how to do the base case using the proof of induction, but I don't know how you would show the inductive step given that there is a summation on either side of the equal sign.

How can I prove that     $$1^3+ 2^3 + \cdots + n^3 = \left(\frac{n(n+1)}{2}\right)^2$$    for all $n \in \mathbb{N}$? I am looking for a proof using mathematical induction.  Thanks


I am traveling from USA to India via Vienna, Austria in June 1st week of 2015. I am having a valid I-797 valid until Dec 2016 and also EAD documents. However I don't have valid USA visa now because I did not go out of USA for last 8 years.   I have a layover of around 4.5 hrs in Vienna on my way to India. Do I need any kind of transit visa in Vienna. I am not planning to go anywhere outside the waiting area of international travel lounge. Please advise.  I hold Indian Passport and valid USA EAD documents.

I found many related questions on this site but I am still not sure about the rules. How can I decide if I need a visa to transit? Schengen members as of May 2021 are as follows:  Austria Belgium Czech Republic Denmark (excluding Greenland and the Faroe Islands - but an open border with the Schengen Area is maintained) Estonia Finland France (excluding overseas departments and collectivities) Germany Greece Hungary Iceland Italy Latvia Liechtenstein Lithuania Luxembourg Malta Netherlands (excluding Aruba, Curaçao, Sint Maarten and the Caribbean Netherlands) Norway (excluding Svalbard) Poland Portugal Slovakia Slovenia Spain (except Ceuta and Melilla) Sweden Switzerland


How to become an Editorial board member?Is it appropriate to contact journal's Editor in Chief to show interest for joining editorial board?

Being an editor of a journal can be , but has obvious  (especially if one enjoys reading and reviewing manuscripts). So I expect many academics have a desire to become an editor.  I have never seen an advertisement for a position on an editorial board, which leads me to believe that most positions are not filled this way.  How do most people become editors, and how might a person wishing to become an editor achieve this (without )?


The null hypothesis for the t-test is the means between two groups are the same (i.e. the difference between the means of two groups equals 0). However, my null hypothesis is the difference between the means of two groups is less than 5 (alternate hypothesis is > 5). What's the appropriate test/approach in this situation?

In t-tests (paired or independent) we test if the difference in means if 0 (or another value).  I'm wondering if it's possible to instead test if the difference is less than x?


First of all tell me whats this, this is input type val or div or what? then how can I create One of them?

Would anyone recommend a particular JavaScript charting library - specifically one that doesn't use flash at all?


For example, it would take me 3 min to email a supplier about an update on a recent purchase, or I could start a new task board, set up an account for my PA, and assign him this task, which would take 15 minutes (so 5 times the amount of time) - what's the word for that type of pen pushing overkill?

For an example, I'll quote C.S. Lewis' The Voyage of the Dawn Treader:     One day the cat got into the dairy and twenty of them were at work moving all the milk out; no one thought of moving the cat.   Is there an idiom for this type of situation?


I'd like to perform some methods before my app closes due to user inactivity (i.e., the screen going black and the phone locking when you haven't touched it for a while). What method(s) is/are called when this happens?  I'm guessing:   This method / these methods would be part of my AppDelegate class. This method / these methods would be analogous to -[UIAppDelegate applicationWillResignActive:], -[UIAppDelegate applicationDidEnterBackground:], -[UIAppDelegate willTerminate:].   I didn't see anything in the documentation for UIApplicationDelegate and I had difficulty Googling the right terms (e.g., "method inactivity app objective c"). I also didn't see anything on Stack Overflow.    EDIT / CLARIFICATION: Multiple people have directed me towards the following Stack Overflow post as a possible duplicate:   However, I do believe my question is very different. Please let me know what I am misunderstanding if my understanding is off.   My question: Is there a built-in method in Objective-C akin to -[UIAppDelegate applicationWillResignActive:] et al. that is called or property that is changed when the screen turns black after a period of inactivity while an app is still open? Other question: How can I trigger a method after a predetermined period of user inactivity, regardless of screen state?   I could see how the other question could answer my question if there is a method for obtaining the length of time the user has set for "Auto-Lock" under Settings (either 1 min, 2 min, 3 min, 4 min, 5 min, or Never), but I don't see such a method or property in the documentation for UIApplication. I suppose a compromise would be to assume that the screen is "off" after 1 minute of inactivity, but this to me would be a less-than-desireable assumption.

Has anybody implemented a feature where if the user has not touched the screen for a certain time period, you take a certain action? I'm trying to figure out the best way to do that.  There's this somewhat-related method in UIApplication:  [UIApplication sharedApplication].idleTimerDisabled;   It'd be nice if you instead had something like this:  NSTimeInterval timeElapsed = [UIApplication sharedApplication].idleTimeElapsed;   Then I could set up a timer and periodically check this value, and take some action when it exceeds a threshold.  Hopefully that explains what I'm looking for. Has anyone tackled this issue already, or have any thoughts on how you would do it? Thanks.


My question is, how is software not listed in Ubuntu Software Center uninstalled?

Seeing there are various ways to install on Ubuntu. What are the various ways to uninstall items?  Which ways always work? How can I be sure something was uninstalled?


I have been tasked with determining if my observed data follow a normal distribution.  With 119 observations (continuous data from -4 to 4), I was able to create a histogram with 25 bins, and upon observation it looks bell-shaped.  I was recommended to do a chi-squared for goodness of fit test to determine if the data is normally distributed, but in the examples I've seen the data is categorical. So, I'm stuck.

From , there are three interpretations of the degrees of freedom of a statistic:     In statistics, the number of degrees of freedom is the number of   values in the final calculation of a statistic that are free to vary.      Estimates of statistical parameters can be based upon different   amounts of information or data. The number of independent pieces of   information that go into the estimate of a parameter is called the   degrees of freedom (df). In general, the degrees of freedom of an   estimate of a parameter is equal to the number of independent scores   that go into the estimate minus the number of parameters used as   intermediate steps in the estimation of the parameter itself (which,   in sample variance, is one, since the sample mean is the only   intermediate step).      Mathematically, degrees of freedom is the dimension of the domain of a   random vector, or essentially the number of 'free' components: how   many components need to be known before the vector is fully   determined.   The bold words are what I don't quite understand. If possible, some mathematical formulations will help clarify the concept.  Also do the three interpretations agree with each other?


In Stack Overflow question closing dialog, link texts like SSCCE.org, Super User were misaligned.  The issue is happening, only if there is at-least one vote for that particular category.  Issue 1:   Issue 2:

"Should" word in italics is shifted down in the vote-to-close popup when there is at least one pending close vote.  Just have a look at this:        Now without close votes:        So the issue occurs when there is a close vote on it. It doesn't look good.    Tested on Chrome 27.0.1453.116 m, Windows XP. And it looks fine on Firefox 21.0 and Opera 12.02 (Windows XP)  Here is an example of a slightly different but obviously related problem in Windows 7 SP1 and Firefox 21.0:    This seems to have something to do with how line-height and/or margin attributes are being interpreted.  Can this be fixed?


I know that usually when you set up a connection between a data source and a data receiver that you need to port forward to gain access to the data source computer  so I was wondering why you don't need to port forward in bit torrent because all of the computers are sources and how they avoid the firewall of the modem?

Could anyone please explain me how the deluge torrent client can get incoming requests to my local machine from the Internet, while I'm behind router's firewall and do not have any port forwarding etc.?  Initially I was going to ask about a strange network activity in my LAN, namely continuous incoming requests to 6881 port from different ip addresses, whereas I'd already stopped my torrent client deluge. But while I was composing the question I spotted that these requests ceased, so I concluded that the reason was in the deluge torrent client and the requests continue to come for a while after program's quit. Then I changed ports in the program's settings and the destination port of these requests changed too. So the reason of these requests is deluge.  So here is the situation. I was trying to setup the deluge torrent client, and opened ufw.log file. And what it showed to me surprised me a lot. It was showing constant incoming requests from different ip addresses to 6881 port. Here is an output of tail -f /var/log/ufw.log (I've cut sensible data):  Dec 28 18:13:32 foo-host kernel: [44034.890870] [UFW BLOCK] IN=eth0 OUT= MAC=xx:xx SRC=46.182.x.x DST=192.168.xxx.xxx LEN=131 TOS=0x00 PREC=0x00 TTL=50 ID=13882 PROTO=UDP SPT=59696 DPT=6881 LEN=111  Dec 28 18:13:32 foo-host kernel: [44035.682998] [UFW BLOCK] IN=eth0 OUT= MAC=xx:xx SRC=111.240.x.x DST=192.168.xxx.xxx LEN=294 TOS=0x00 PREC=0x00 TTL=113 ID=4012 PROTO=UDP SPT=17621 DPT=6881 LEN=274  Dec 28 18:13:34 foo-host kernel: [44037.400502] [UFW BLOCK] IN=eth0 OUT= MAC=xx:xx SRC=210.187.x.x DST=192.168.xxx.xxx LEN=131 TOS=0x00 PREC=0x00 TTL=55 ID=25753 PROTO=UDP SPT=57274 DPT=6881 LEN=111  Dec 28 18:13:47 foo-host kernel: [44050.142172] [UFW BLOCK] IN=eth0 OUT= MAC=xx:xx SRC=118.81.x.x DST=192.168.xxx.xxx LEN=129 TOS=0x00 PREC=0x00 TTL=46 ID=29946 PROTO=UDP SPT=59765 DPT=6881 LEN=109  Dec 28 18:13:54 foo-host kernel: [44056.727176] [UFW BLOCK] IN=eth0 OUT= MAC=xx:xx SRC=128.127.x.x DST=192.168.xxx.xxx LEN=131 TOS=0x00 PREC=0x00 TTL=113 ID=37504 PROTO=UDP SPT=13835 DPT=6881 LEN=111   So could anyone please give me an answer to this: how do torrent clients (may be only deluge) circumvent router's firewall?  Here is my router's configuration screen shot, so I suppose that the firewall is running. Also I cannot access a local webserver from the outside without port forwarding, so this convinces me more in this conclusion.


I've noticed that users who were not previously ranked on the  have total reputation less than their year reputation.  Here is an example:    I imagine this should be at least their year reputation. This appears to be the case for quarter as well, but not for week and month.

When I went to the  to see my ranking in the reputation league, I saw this. Is this an error? My total reputation is less than my monthly reputation.


I am trying to tweak colors for Termite, but instead of the expected I'm getting a total mess (colors differs from my ~/.config/termite/config. In screenshot numbers should be gray, text yellow and etc.)  Also, can I set Vim's colorscheme different from terminal?    PS. I don't think this is a duplicate, because the issue seems to be due to the terminal.  Vim is just an unrelated point.   It really seems like it's a Termite internal problem, because one can get it only through compiling sources. It seems like no one really tested it on Ubuntu.

For most vim colorschemes, they appear different than advertised when I open vim in xterm.   I've been using xterm-256color and set t_Co=256.  A similar thing happens when I use xfce-terminal, but the colors in the colorschemes will vary depending on which colors I set in the terminal's preferences menu. I've read that some colorschemes will rely on terminal colors, and that appears to be what's happening here.  Is there a way to prevent the vim colorscheme from conflicting with the terminal one?


Why surface of water behaves as a denser medium inspite of the fact speed of sound is greater in water than in air as seen in case of Resonance tube.  To achieve resonance again we lower the level of water  so that node again forms at the surface of water.  As far my knowledge concerns reflection from denser medium brings a phase difference of π but not in case of rarer medium.  It resembles with the one end closed organ pipe.

We know that speed of sound is higher in a denser medium. So when a sound wave strikes a wall, why does it echo instead of passing through it with a speed faster than the speed of sound in air?


Recently my question got labeled as - 'Post is related to a rapidly changing event.'  who does decide such tags and labels ?

The recently introduced "Current event"  feels incomplete:  At the very least, it needs a period at the end to complete the sentence. Aside from that, what is a future visitor of a question supposed to take away from this notice? The "citation needed" text explains what expectations are placed on the question bearing the notice and invites action. Is the "current event" notice purely informational? What's the desired effect of adding it to a question? The current on-question notice is:  This post relates to a rapidly changing event.  In addition to answering those questions, I'm hoping we can work out a proposal for a wording change to make it more clear. I can't come up with anything to start with, since I don't quite get what the notice is supposed to achieve in the first place.


The following works to give the title all in black:  \title{The Title}   But this does not work to make the first word in the title red:  \title{{\color{red}The} Title}   How does one make just one word in the title a different color?

I'm looking for a way to change the color of the main title of a document without redefining the \maketitle.  A Google search only yields how to systematically change the section titles that does not include the main title.


I have created an azimuth orthographic projection map (basically a globe, I've used this custom CRS: +proj=ortho +lat_0=51.470129 +lon_0=-0.452751 +x_0=0 +y_0=0 +a=6371000 +b=6371000 +units=m +no_defs with QGIS 3.4.4. The labels are flat, as you would expect for readability purpose. Does anybody know if it's possible to have the labels following the earth surface curvature instead, like if it was an actual picture of a physical globe?  If it's not possible with QGIS, how about other software programs?

I've been experimenting with orthographic projections and I've run into a problem with the labels.    I would like to label the countries but I want the labels to run west-east along the country which isn't (currently) an option in the QGis labeling options.  So, I know I can place them along a line but I lack the patience to draw a line in each country. So I'm looking for an automatic way to draw a line through the centroid of a polygon and to the edges so that I can use it as a label placement line.   By 'label placement line' I mean I need a line that crosses the country that I can use as the basis of my labels so that I can use follow line (parallel I think) in the labeling panel. (see for example this ). So they will be a straight horizontal line in EPSG:4326 but nicely curved in my orthographic projection (+proj=ortho +lat_0=51.470129 +lon_0=-0.452751 +x_0=0 +y_0=0 +a=6371000 +b=6371000 +units=m +no_defs).  Ideally it would be a dense line so it curves when reprojected but I can always run a densify process on the output.


How do you prove that $n^5 \equiv n\pmod {10}$ Hint given was- Fermat little theorem. Kindly help me out. This is applicable to all positive integers $n$

I was trying to prove this, and I realized that this is essentially a statement that $n^5$ has the same last digit as $n$, and to prove this it is sufficient to calculate $n^5$ for $0-9$ and see that the respective last digits match. Another approach I tried is this: I factored $n^5-n$ to $n(n^2+1)(n+1)(n-1)$. If $n$ is even, a factor of $2$ is guaranteed by the factor $n$. If $n$ is odd, the factor of $2$ is guaranteed by $(n^2+1)$. The factor of $5$ is guaranteed if the last digit of $n$ is $1, 4, 5, 6,$ $or$ $9$ by the factors $n(n+1)(n-1)$, so I only have to check for $n$ ending in digits $0, 2, 3, 7,$ $and$ $8$.  However, I'm sure that there has to be a much better proof (and without modular arithmetic). Do you guys know one? Thanks!


consider the following class:  package org.cloudbus.cloudsim.ACO;  /** * * @author Dinesh Gupta */ public class VMLOADFITNESSTABLE { public int vmid; public double memoryused; public double cpuused; public double fitnessvalue; public int loadstatus;  };   i have created a list of objenter code hereects for this class using the following state:  List<VMLOADFITNESSTABLE> vlft = new ArrayList<VMLOADFITNESSTABLE>();   then i have added multiple elements to the same list. when i try to display all elements in the list, i observe that the last element is displayed multiple times. it feels like that the elements have been overwritten by the last element.  please suggest some answer,

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


I have conducted a 2x3 mixed factorial ANOVA, my interaction effect has come out as significant but when I go on to do an independent t-test to determine where the differences are my t-tests all come out as non-significant. My question is how would I interpret this? what does it mean?

I'm analyzing reaction time data from a repeated measures ANOVA with the following design: Factor 1 (between-group): GROUP (controls, clinical) Factor 2 (within-group): TASK TYPE (social, non-social) Factor 3 (within-group): DECISION DIFFICULTY (easy, hard)  ANOVA results indicate a significant 2-way interaction (GROUP×DIFFICULTY). No other main effects, 2-way interactions, nor the 3-way interaction are significant (all $p > .4)$.  Since there was no effect of task, I pooled data across the 2 task types. I'm not sure what is the right way to go from here in terms of reporting and interpreting the results. My specific questions are:   Should I always perform follow-up tests with a significant 2-way interaction, or should I just stop there and interpret based on the figures (and without further stats)? Between- or within-group post-hoc: Should post-hoc tests be restricted to an independent t-test between groups (i.e. comparing "pooled easy" data between groups, and "pooled hard" data between groups)? Can I also perform and report a within-group paired t-test comparing "pooled easy" to "pooled hard" within each group? Interpretation: If neither independent t-test from (2) is significant, can I still interpret the 2-way interaction based on a significant paired t-test from (2)? (The clinical group's reaction times appear to increase with task difficulty, whereas reaction times don't change with task difficulty in controls.)   In the absence of significant between-group t-tests, can I still report these results based on the 2-way interaction and a within-group t-test as "task difficulty affects reaction times in the clinical group and not the control group"?  Thank you. I appreciate any help you can give!


I working on an app that has different select box that are cloned. I used the first selectbox to clone the second one I want to get the id of the generated select box. it is one the first selectbox that works second one does not triger event when selected.   var selectid = "select-test"  $("#addbtn").on("click", function(e) {   e.preventDefault();    selectid = "select-" + Date.now();    var testdone = $('#testdone')     .clone().val('') // CLEAR VALUE.     .attr("id", testdoneid)     .appendTo("#appendcontainer");    $("#" + testdoneid + " .select-test").attr('id', selectid); });  $("form select").on("change", function() {   var strChosen = $(this).attr('id');   alert(strChosen); }) <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <div id="testdone">   <select name="tests[]" class="form-control select-test" id="select-test">     <option value="">Select Patient Test</option>     <option value="1">HIV</option>   </select>    <select id="select-3339" class="select-id">     <option value="">Select Patient Test</option>     <option value="1">HIV</option>   </select> </div>

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.


So let's assume that the relatively ambiguous Tower of Joy scene in season 6 confirms that Jon is indeed       Lyanna Stark's child, sired by Rhaegar Targaryan.    In that case, considering the current situation in Westeros as of season 7 (or as of book 5 + released chapters of book 6), how does this get proven in the eyes of the lords, ladies, and commoners of Westeros?  It feels like an impossible claim to prove given that Eddard Stark is dead, Howland Reed seems to have vanished off the face of Planetos, and anyone else who was alive at the time with that knowledge appears to be dead and gone. EVEN IF Howland Reed manages to crawl out of the woodwork to corroborate Bran/3-eyed Raven's claim (assuming he even makes that claim) about Jon's true heritage, we're still just talking about the word of two relatively unknown (outside of the North) Westerosi noblemen.  The only way I can see of "proving" anything is if Jon ends up riding a dragon. But even then, would that, in addition to the theoretical claims of Howland Reed and Bran Stark be enough to prove that Jon Snow is actually Jon Targaryan (assuming R and L actually got married, and assuming that marriage is even recognized in the eyes of Westeros since polygamy is very much looked down upon...) ?  I am looking for theories or speculation based on the books, the TV show or historical events that end up with the people of Westeros generally accepting that Jon Snow is either:   Still a bastard of different heritage, or A legitimate Targaryan, and trueborn heir of Rhaegar Targaryan.     Edit to explain first dupe:  I am not asking who knows, I am asking: how do you prove it in the eyes of everyone in the 7 kingdoms?    Edit based on S7E05:  In the scene where Sam decides he's had it with the silly Citadel, Gilly reads an old record of Rhaegar Targaryan receiving an annulment of his marriage to Elia Martell, and of his remarriage to... Lyanna Stark?  Assuming this is true, and assuming Jon Snow is indeed their offspring, then he is indeed a true-born Targaryan. Now as to how to prove it, obviously this record would come in handy when attempting to do so...    Edit to explain second dupe:  This is very similar to . However, I am asking how it would be proved, either with tangible evidence or by proclamation or by some other strategy I hadn't thought of, in the eyes of Westeros. In other words, with proof, or no proof, how are the people (nobles+commoners) of Westeros to be convinced of this truth? I accept that this question is related, and should certainly be linked, but I don't think it is a duplicate.

Spoilers Alert!!!      Bran sees that Jon is the son of Lyanna at Tower of Joy.   However, People of the north won't just believe words.  Howland Reed was with Eddard at the tower, Eddard is dead, but Howland could be alive. Even if Howland Reed comes forth and tells Jon's true lineage. It will still be just words.   Why would the people believe the words of a child and an old man?


I'm trying to edit a user guide in which the word such is used frequently  to describe the way things have to be done. For example:     Step 1: Position the frame on the cone using the sliding bar, such that/so that/in a way that the cursor of the meter is on the crosshairs.   Or     Step 4: Position the lens such that/so that/in a way that the lower segment marking is on the measuring dial.   Which usage correct? Should I use a different phrase?

Are these the same?  The image will be sheared such that the x-axis goes through (1,1). The image will be sheared so that the x-axis goes through (1,1).  I think I have usually seen the former, I didn't even know that “so that” is allowed in English until I once saw it in a text from a (as I assume) native English speaker. Simon


I have a 12v, 0.9A dc motor. Currently I have two 12v dc supplies which I borrowed from my friend. The current of the 2 dc supplies is 1.0A and 0.5A respectively. Is it safe for me to use the higher current  supply from 12v dc supply (1A) or a 0.5A 12 dc supply to my dc motor?

Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.


Sometimes, a question is perfectly solved by suggestion or actual resolution given in "comments" under it. In such case, how to mark that answer (comment) as "Accepted Answer"? Due to this, the question remains unanswered even if solution is provided in comment.

I have a question and have seen others to which the best and most relevant answer (at least the one that solved my particular problem) is placed in the comments to the question as opposed to the answers:   I would like to recognize the commenter as the person who correctly answered the question, but there doesn't seem to be any way to do that. The only thing I could think of was to ask the commenter to repost his comment as an answer, but I cannot figure out a way to contact him. In the meantime the question is sitting unanswered and I am getting other "answers" (leading me to believe that people are not reading the comments and answers already posted before trying to answer it themselves).  How are we supposed to do this?  Note: I don't want to accept the comment as an answer (I agree completely with the answers to this question that comments are comments and answers are answers and they should stay that way). I do wonder if there should be some way to contact people in a reasonable manner (comments on their profile that they must opt in to receiving in email?).


need to find sum of $$\sum_{k=1}^n \frac{(k-1)2^k}{k(k+1)}$$ this is much harder as I see. Or maybe it's my eyes, because I'm new in studying sums. I tried this one using differences , factorial  powers, didn't help.

I am trying to find a general summation for $$\sum_{k=1}^{n} \frac{(k-1)2^k}{k(k+1)}$$ I tried to expand it and look for some pattern. $$\frac{(1-1)2^1}{1(1+1)} + \frac{(2-1)2^2}{2(2+1)}+...+\frac{((k-1)-1)2^{k-1}}{(k-1)((k-1)+1} + \frac{(k-1)2^k}{k(k+1)}$$ If it can be solved through telescoping, I couldn't see how.


For a presentation in physics I am going to talk about black body radiation since our book just mentions , Wien's displacement law and Stefan-Boltzmann's law. I want to derive Wien's law and Stefan-Boltzmann's law from Planck's law. I have managed to derive Stefan-Boltzmann's law from: $$u(\nu)=\frac{2\pi h \nu^3}{c^2}\frac{1}{e^\frac{h\nu}{kT}-1}$$ by integrating over all $\nu$ from $0$ to $\infty$. However, my textbook says: $$u(\lambda,T)=\frac{2\pi hc^2 }{\lambda^5}\frac{1}{e^\frac{hc}{\lambda kT}-1}$$ If I can get from the second formula to the first, I will be happy alltough, a simple and informal derivation of Plack's law would be very satisfying.   I also managed to derive Wien's law by derivation and setting equal to zero by using: $$u_\lambda=\frac{8\pi hc }{\lambda^5}\frac{1}{e^\frac{hc}{\lambda kT}-1}$$ What are the differences? And please, since I am Norwegian and do not know very advanced physics, do not use any advanced expression without explaining them. Thanks!

I am drawing a blank when it comes to equation transformation. Wikipedia  for the spectral radiance of black body:   First as a function of frequency $\nu$: $$I(\nu, T) = \frac{2 h \nu^3}{c^2}\cdot\frac{1}{e^\frac{h \nu}{k T} - 1}$$ Then as a function of wavelength $\lambda$ : $$I'(\lambda, T) = \frac{2hc^2}{\lambda^5}\cdot\frac{1}{e^\frac{h c}{\lambda k T}-1}$$   And I don't see how they get $\lambda^5$ term. I'm assuming that the transformation is just $\nu \rightarrow c/\lambda$, but that gives $$ \frac{2 h \nu^3}{c^2} \Rightarrow \frac{2 hc}{\lambda^3} \neq \frac{2hc^2}{\lambda^5} $$  Similar transformation happens at other parts in the article also. I'm obviously missing something, likely completely trivial.


(retrying my phrasing)  What are the odds of having 4 (and only 4) naturally conceived, naturally birthed, singleton children (with the same and only mate) on a given day of the week (ie, Wednesday)?  Equations with explanations appreciated. Thanks

I have been teaching statistics for many years at the university level - but this question is beyond my understanding - due to the variables involved.  Several years ago, I was entertaining a relocation to a different area and a different way of life. I was very unsure and skeptical - as the change would have followed my heart - but not the rational practicality of my head.  Then a sequence of events took place - none of which were of my own choosing. I want to know what the statistical probability is of these events occurring by chance alone. They are as follows:  1) The property I had wanted to buy was already under contract, yet came back on the market on the anniversary of my father's death.  2) My immediate offer to purchase was accepted by the sellers (two days later) on the anniversary of my grandmother's death.  3) My loan was approved by my bank on the anniversary of my late grandmother's birthday (7 days later)  4) Our closing date was set by the title company on the anniversary of my late, great-aunt's birthday.  5) The permit for our business (for which we brought the property) was approved and issued on my parent's anniversary.  Can the probability of these dates be statistically determined?


Which one is more acceptable?     1. Each boy and each girl has done his duty.      2. Each boy and each girl has done his or her duty.      3. Each boy and each girl has done their duty.   Edit: Here is what I think.  I think (1) isn't acceptable because 'his' is in masculine gender, which doesn't fit the noun 'girl'. (3) isn't acceptable because the verb 'has' is singular but the pronoun 'their' is plural. (2) is ok but the expression "his or her" looks awkward.

When I start a sentence with words like "someone" or "somebody", I don't know how to choose the right pronoun at the end of the sentence.  Examples:      If anybody asks you about the money, tell (Him - Her - It - Them) that it is in my bank account.     I felt that somebody was in the garden but I did not see (Him - Her - It - Them).     Speaker 1: A friend of mine helped me a lot.      Speaker 2: You should thank (Him - Her - It - Them).     Congratulations on your new baby! What's (His - Her - Its - Their) name?    Those are the cases or situations that I can think of. If you have any other different situations, please let me know.


Eärendil's setting foot upon the shores of Aman - the first Man to do so - eventually led to the raising of Númenor from the seas and the simultaneous imposition of the Ban of the Valar. After Ar-Pharazôn and his army landed on the shores of the Undying Lands, violating the Ban, the Valar called upon Eru for divine intervention, triggering the events of the Akallabêth.  Why are the Valar so strongly opposed to the entry into Aman by any Man ever again? To those unfamiliar with the LotR universe, there may appear to be two possible reasons:   Any Man who enters and dwells in Aman - the Undying Lands - will attain immortality and not die, hence the need to restrict entry to ensure all Man will die and thus receive Eru's Gift of Man as intended. The arrival of mortal Man will corrupt Aman, causing it to lose its "Undying" status or enchantment.   Anyone familiar with the story will know these reasons are untrue. Exceptions were made for the mortals Bilbo, Frodo, Sam and Gimli to live out the remainder of their lives in the Undying Lands, and they too will die in time. And throughout all of these there is no indication that Aman loses its Undying properties either.  So why this prohibition? Everything that has transpired were to prevent Man from visiting Arda ever again after Eärendil did so, with increasingly stronger measures being taken. It's not like the Valar made exception for the aforementioned on their own initiative: Gandalf had to argue for the Ring-Bearers to be let into the Undying Lands, and Galadriel for Gimli. Their entry did not affect anything as far as we know.

(very bad things can result from Men spending too much time in Valinor)   (src: )   Given the answer's poster prior history in , my assumption is that the quoted claim is correct.  But what are those "bad things" which can result?


I have below data    I want to find distinct duplicate values of one column and add unique values to another column with a comma.

I'm trying to migrate a MySQL-based app over to Microsoft SQL Server 2005 (not by choice, but that's life).  In the original app, we used almost entirely ANSI-SQL compliant statements, with one significant exception -- we used MySQL's group_concat function fairly frequently.  group_concat, by the way, does this: given a table of, say, employee names and projects...  SELECT empName, projID FROM project_members;   returns:  ANDY   |  A100 ANDY   |  B391 ANDY   |  X010 TOM    |  A100 TOM    |  A510   ... and here's what you get with group_concat:  SELECT      empName, group_concat(projID SEPARATOR ' / ')  FROM      project_members  GROUP BY      empName;   returns:  ANDY   |  A100 / B391 / X010 TOM    |  A100 / A510   So what I'd like to know is: Is it possible to write, say, a user-defined function in SQL Server which emulates the functionality of group_concat?   I have almost no experience using UDFs, stored procedures, or anything like that, just straight-up SQL, so please err on the side of too much explanation :)


I know that it is possible to define a lot of different norms on continuous function spaces like $l_p$ norms. However, I was wondering if it is possible to define a norm on the function space consisting of all functions from $\Bbb R$ to $\Bbb R$. I have tried a few examples and none of them managed to fulfill all the requirements of being a norm, so maybe it is actually impossible to define such a norm. Edit: I know such a norm exists but I wondered if it has a “simple” representation, meaning given a function I can actually calculate its norm and not just know “it exists”.

Is there a canonical way to define on any vector space over $\mathbb{K}=\mathbb{R},\mathbb{C}$ a norm ? (Or, if there isn't, can someone give me an example of a vector space over $\mathbb{K}$ that is not normable ?)  I have now looked through several books on the subject but nowhere is something like this mentioned and I also wasn't able to find a way to construct such norm (or to find a counterexample).


I'm looking for an online tool that will let me draw lines and circles etc on a plane and then tell me the positions of any intersections, the size of any angles formed and potentially lengths of formed arcs.  Does anyone know of one?

What software do you use to accurately draw geometry diagrams?


Last year I bought a nice osprey backpack and I stupidly (after removing loose straps) put the bag through check in without wrapping it up in cling film or whatever. and it got a bit damaged by way of a cut into the fabric.   what is the best way to protect an expensive backpack in airplane luggage? I have to use it as my main way of carrying luggage as its too big to warrante taking 2 large bags.   Any tips? E.g. on the flight back I put this backpack inside a cheap quechua dry bag with rucksack straps which protected it but it was a tight squeeze and a pain to get everything in.   Cling film wrapping seems to be an obvious option but looks like a pain in the ass.

When travelling on airlines based in the US with a large backpack, I prefer to carry the bag onto the plane as part of my hand baggage allowance.  Most foreign flag carriers, however, have a significantly more restrictive hand baggage allowance.  I was caught off guard by this one time on New Zealand airlines and received my backpack with multiple broken straps and clips.  I managed to repair it, and I'm still using the same pack, but I would like to avoid so many broken parts in the future.    Once, when flying Alitalia (flight was actually booked through Delta) I carried plastic wrap to the airport, and wrapped the entire bag in it before handing it over to the airline.  @jpatokal recommends putting it into a giant, heavy-duty garbage bag in his answer to .     What are the pros and cons of using plastic wrap or a garbage bag?   Can anyone recommend any other, more effective techniques?


When should I use "amount" as opposed to "number"?  When media are referring to number rather than volume, they often use the word "amount" rather than number, as in "a large amount of people" Is this correct? Is this Preferred? Is this acceptable?

For what values of x does one write the number of x, the amount of x, or the quantity of x?


Let $\mathfrak{g}$ and $\mathfrak{h}$ be two-dimensional non abelian Lie-algebras. Show that they are isomorphic.   Suppose that $\{E_1,E_2\}$ and $\{F_1,F_2\}$ be basis for $\mathfrak{g}$ and $\mathfrak{h}$ respectively. Since both $\mathfrak{g}$ and $\mathfrak{h}$ are nonabelian, $[E_1,E_2] \ne 0$ and $[F_1,F_2] \ne 0$. Suppose that $[E_1,E_2]=aE_1+bE_2$. If $a=0$, then dividing by nonzero $b$ we have $[E_1,\frac{1}{b}E_2]=E_2$. If $a \ne 0$, then dividing by $a$ throughout we have $[E_1,\frac{1}{a}E_2]=E_1+\frac{b}{a}E_2$. Then $[E_1+\frac{b}{a}E_2-\frac{b}{a}E_2,\frac{1}{a}E_2]=[E_1+\frac{b}{a}E_2,\frac{1}{a}E_2]=E_1+\frac{b}{a}E_2$. So to start with, we can choose $\{E_1,E_2\}$ and $\{F_1,F_2\}$ such that $[E_1,E_2]=E_1$ and $[F_1,F_2]=F_1$.   Now define $\phi: \mathfrak{g} \to \mathfrak{h}$ by $\phi(aE_1+bE_2)=aF_1+bF_2$. Then $\phi$ is linear, one-to-one and onto. Moreover, we have $\phi([E_1,E_2])=\phi(E_1)=F_1=[\phi(E_1),\phi(E_2)]$. Thus, $\phi$ is an isomorphism.   I was wondering if I could do this more directy, without any assumption on the Lie brackets of both sides. If I do that and define $\phi$ as above, then I just have to show the nice behavior of $\phi$ with the Lie brackets. Now $\phi([E_1,E_2])=aF_1+bF_2$ but I don't know how to show that $[F_1,F_2]=aF_1+bF_2$.  Thanks for the help!!

I am trying to find all 1- or 2- dimensional Lie Algebras "a" up to isomorphism. This is what I have so far:  If a is 1-dimensional, then every vector (and therefore every tangent vector field) is of the form $cX$. Then , by anti-symmetry, and bilinearity:  $$[X,cX]=c[X,X]= -c[X,X]==0$$  I think this forces a unique Lie algebra because Lie algebra isomorphisms preserve the bracket.  I also know Reals $\mathbb{R}$ are the only 1-dimensional Lie group, so its Lie algebra ($\mathbb{R}$ also) is also 1-dimensional. How can I show that every other 1-dimensional algebra is isomorphic to this one? Do I use preservation of bracket?  For 2 dimensions, I am trying to use the fact that the dimension of the Lie algebra g of a group $G$ is the same as the dimension of the ambient group/manifold $G$. I know that all surfaces (i.e., groups of dimension 2) can be classified as products of spheres and Tori, and I think the only 2-dimensional Lie group is $S^1\times S^1$, but I am not sure every Lie algebra can be realized as the Lie algebra of a Lie group ( I think this is true in the finite-dimensional case, but I am not sure).  I know there is a result out there that I cannot yet prove that all 1- and  2-dimensional Lie algebras are isomorphic to Lie subalgebras of $GL(2,\mathbb{R})$ (using matrix multiplication, of course); would someone suggest how to show this last? Thanks.


Which is the difference between a server and a desktop CPU ? Why should I buy a Xeon processor for a server why don't use instead a simple Intel quad 4-core CPU for a desktop PC ?

To my knowledge a server PC and a desktop PC can have the same processor, but someone told me that servers are equipped with more powerful processors (that is these processor are designed for servers only). Is this true? Are there processors that are designed for servers?


I could understand it at a theoretical standpoint but how can one represent the dynamic stability of the bicycle mathematically using a vector diagram ?

Why does a bike/bicycle fall when its speed is very low or close to zero and is balanced when going with a high speed?


In BTTF 2, in the second timeline where Biff went back to 1955 to give the sports almanac to younger Biff, it doesn't make sense that there would be an original Marty running around.  This is my reasoning: Since in the original timeline, Doc Brown was just a local inventor in 1985, Marty was able to go back in time because Doc Brown showed him the time machine at night, which led to the terrorists killing the Doc and forcing Marty to go to 1955. In the altered timeline, however, the Doc was committed before 1985, which means that it's possible that he never managed to build a time machine at all, or even if he did, Marty wouldn't have gotten it. In this case, alternate-Marty wouldn't have been able to go back in time in the second timeline.  This is also a fact that Doc fails to reference when he's explaining the timelines. He forgets to talk about the original timeline - The 'lame parents' timeline which started the thing. Instead, everything should be fine exactly until November 5th, where the two timelines diverged. And so from November 5th-12th, there is the 'cool parents' timeline happening where Marty is back.  But the existence of the rich-Biff timeline negates the 'cool parents' timeline from existing at all.  This would imply that when normal-Marty went back to 1955 for the second time, he wouldn't have seen his own self because alternate-Marty never time travelled at all. Instead, the events would have played out exactly as they did in 1955 before Marty ever intervened, that is, George got hit by the van and the normal timeline would have been conserved. The only difference that should have been was that Old-Biff was giving Young-Biff the almanac.   Marty shouldn't have been able to see himself. Instead, he would have seen events play out exactly as they did in the 'lame-parents' timeline - George never learnt to be brave, there would be no drama about the enchantment under the sea dance.  Is this a plot hole, or is there some in-universe/retcon explanation for this?

I was doing some thinking about the paradoxes that arise during Back to the Future 2 when Marty, Doc and Jennifer travel to 2015 to see their future selves and help Marty's kid.  It was shown that BTTF (Back to the Future) uses the Multiverse theorem to solve any paradoxes of changing the past and creating a new future timeline.  I've created an info graphic to show all the jumps made in the BTTF series and the timelines they all created.    Since Marty and gang went to the future at the start of Back To the Future 2, why would Marty, Doc, and Jennifer have a life and presence there if going into the future is going into a version of the future where the time travel had existed? If Marty were to travel, the timeline he visits in the future would be a timeline where the gap from his travels would be him not existing the whole time, as if he left the universe, ceased to exist in that timeline, then started re-existing again when he arrives in the future.  It was proven that that's how the timeline works in the first BTTF when they sent Einstein 1 minute into the future. The timeline where he travelled was as if the dog hadn't existed any more for 1 minute, then existed again when he arrived at the future date.  And since any travel back into the past creates a new timeline differing from any travelled future timeline, travelling back from the future to the present would not fix the paradox, it would just make a new timeline where both the time travels would exist.  So why was Marty able to see himself at all in the future that he visited at the start of Back to the Future 2?