I need both PHP 5.4.7 and 5.3.17 running on Windows 7 x64 with Apache 2.2.23. This is my virtual host configuration:    <VirtualHost *:80>     DocumentRoot  "C:/WAMP/Apache/htdocs/php54"     ServerName php54.local     PHPIniDir "C:/WAMP/PHP54"     LoadModule php5_module "C:/WAMP/PHP54/php5apache2_2.dll"     php_value extension_dir "C:/WAMP/PHP54/ext"      <Directory "C:/WAMP/Apache/htdocs/php54">         Order allow,deny         Allow from all     </Directory> </VirtualHost>   The PHPIniDir and LoadModule directives work fine and using phpinfo() inside my script prints the right PHP version.  But I need to load extensions, and this is where it fails. php_value extension_dir should be C:/WAMP/PHP54/ext but it's (default one) C:/php.  What I'm missing here?  EDIT: Of course I can set this value directly in C:/WAMP/PHP54/php.ini, but I prefer passing it using vhost configuration:  ; Directory in which the loadable extensions (modules) reside. ; http://php.net/extension-dir ; extension_dir = "./" ; On windows: extension_dir = "C:/WAMP/PHP54/ext"

This is a  about  the use of a *AMPP's stack.    I recently had a talk with some experienced people and they suggested to me not to use a WAMP stack, and instead install apache, mysql and php separately.  I don't understand why they have suggested this, though, so can anyone tell me?  Is there a particular disadvantage of WAMP, or a particular advantage to installing all of them separately?  Since a WAMP stack itself is composed of apache, mysql and php, then what's the difference between using the WAMP stack and installing them all separately?


I am trying to shoot some garments such as hoodie tshirts.  I am using 2 softboxes with white lights of 350W each on a white background. The lighting looks good.  As per camera, I am using my 18-105mm Nikon lens shooting on Aperture mode with 200 ISO and some extra exposure, not zooming too much. I had the aperture at f3.4 or so and did not use a tripod.  However, when checking my photos, the background does not come white at all, it is still very yellow. The garment looks ok. It could be better but my concern is the background. It definitely has to do with the camera settings as the lighting set up is good.  How can I get a good white background so I can avoid too much Photoshop post retouching? What settings in my camera can help me with this?

I'm looking for suggestions to blow out the background when shooting down for clothing on the ground.  I've tried putting the clothing on a plain white background that I typically use when shooting clothing on a mannequin, but I can't light the background more than the clothing when it's on the ground.  I'd like to be able to completely blow out the background and simplify any post-processing work.  Some ideas that I've thought of are:   Raising the clothing (difficult since it's irregular) and trying to light the background. Put the clothing on a translucent material and light from the back.  (But what material that I can afford?) Buy a light box, but I'm not sure if that will help.  Will a light box somehow let me illuminate the background more than the product?   What has worked for you (and not cost too much)?


My impression is that, if one wishes to be able to delete a certain file completely, without wiping an entire drive, one should never store it on an SSD.  Is that right?  Even with whole-disk-encryption, if the key is obtained, there seems to be no way to be sure forensic methods couldn't recover the file, short of issuing a firmware wipe command to the drive AND filling all of it with non-data (since the firmware command can't generally be relied on).  So, if one wants the ability to delete something completely securely, and not the entire drive it's stored on, one should only store it on HDDs and USB sticks.  Right?

I know that most files, when deleted, aren't actually removed from the disk, and can be recovered later.  How can I ensure that a directory I had deleted will actually be removed from the disk? Are there utilities for that?  I'm using Debian Linux.


What is a reasonable amount of RAM needed to run a Minecraft server?  I've already tried running a server with 256MB. However, within an hour, the server was crashing due to being out of memory.

What is the minimum RAM needed for a Minecraft server (without using custom servers)? There will be at the most 5 players, the VPS will be OpenVZ.


There have been one or two past questions on different variations of "blowhard," but no answer quite gets at an emblematic recent incident.  A famous senator attributed the quote "all sound and fury, signifying nothing" to Shakespeare and a famous journalist "corrected" him and told him, "no, that's Faulker." So, eager to one-up someone based on ignorance and laziness (i.e., couldn't be bothered to google the quote).  "Ignorant blowhard" doesn't quite capture the implied feverish desire to put one over on someone without really knowing what you're talking about.  Other words?

Many a times, we tend to meet someone who is ignorant yet arrogant; to the extent that they can go a long way blabbing about something they don't really know with so much vigour. What can you refer to such a person as?


So I have taken a first course in Special Relativity and the Relativistic Mass is defined as: $$m = \frac{m_o}{\sqrt{1 - v^2/c^2}}.$$  Now, when this was introduced in the course, it was introduced as something profound and very important. Not only did it show why no particle can be accelerated to a speed equal or larger than c but it also was required for momentum to be conserved in SR.  So why is it then that I keep reading here on SE that this term is deprecated, obsolete, etc. ?  This also eventually led to the famous $E = mc^2$ so I gotta ask, does mass increase in a moving frame or does it not?   This is quite confusing!

Some people say that mass increases with speed, some people say that the mass of an object is independent of its speed.  I understand how some (though not many) things in physics are a matter of interpretation based on one's definitions. But I can't get my head around how both can be 'true' is any sense of the word.  Either mass increases or it doesn't, right?  Can't we just measure it, and find out which 'interpretation' is right? e.g.: (in some sophisticated way) heat up some particles in a box and measure their weight?  ------------------------------  UPDATE  Right, so I've got two identical containers, each with identical amounts of water, each on identical weighing scales, and each in the same g field. If one container has hotter water, will the reading on its scale be larger than the other? If the answer is yes, and g is constant, does this mean that the m in w=mg has got bigger?


My question is not a duplicate of . The latter talks only about linked questions; my request is about both questions and answers.   I would appreciate to receive a notification when my own post (question or answer) is linked to in another post. That way, I could see how my question or answer is relevant to other questions, possibly leave a comment in case the reference needs clarification/correction, or notice when a post I am the author of is discussed on meta.    It has actually happend to me several times that I accidentally encountered a post referencing something I wrote elsewhere and thought "I should have seen that earlier, then I could have added a comment to clarify what I actually meant" or "I should have seen this earlier, then I might have been able to write an aswer to or read about this interesting related question."  You already get notified whenever a comment is left under your post, so I think it would make sense to also get notified when a comment to your own post is left in another post.      If notifications are too pushy (but I don't think links to your posts happen so often it gets annyoing), a small section somehwere in the "activity" tab on my profile that I could check from time to time would do too.

Sometimes a question I ask will get answers that don't help me, or maybe it doesn't receive any answers at all.  How about making a notification when somebody links to my question?   It could be something like this:     New information regarding your question might be available at {link}   It might help me getting an answer from related questions that weren't there when I first asked the question.


I've heard of factorials such as $5!$ and $3!$, which work like this: $5!=5\times4\times3\times2\times1=120$ and $3!=3\times2\times1=6$.  At least this is what we get.  Also, surprisingly, $0!=1$, but how can we figure out values for factorials in decimal form such as $(2.5)!$ and $(3.34)!$?  Maybe we should use gamma for part of it?  What else?  I also know that we can draw graphs for factorials.  I just want to know how to find values for factorials in decimal form?

I did not know that you could find an answer for that. However, I can only use Excel so far to do it.  How to calculate 3.6! by hand?


Supposing I have data which I know is normally distributed, but because the recording process is right censored, how do I estimate the parameters of the distribution?

My dependent variable shown below doesn't fit any stock distribution that I know of.  Linear regression produces somewhat non-normal, right-skewed residuals that relate to predicted Y in an odd way (2nd plot).  Any suggestions for transformations or other ways to obtain most valid results and best predictive accuracy?  If possible I'd like to avoid clumsy categorizing into, say, 5 values (e.g., 0, lo%, med%, hi%, 1).


So in $\mathbb{R}$ and $\mathbb{C}$ you have both associative and commutative property, but as you extend to $\mathbb{H}$ you lose the commutative property, and $\mathbb{O}$ loses the associativity. What more can you lose once you extend beyond $\mathbb{O}$? Are there some lesser known or weaker properties which holds for all extensions, or are do all such rules eventually disappear as you extend?  Thanks in advance.  [Also if someone could correctly tag this question, that would be nice]

Quaternions remove the commutative property and octonions eliminate the associative property can we go any higher and eliminate more properties?


Can anyone please explain these hats? What if someone has all the hats? Is there an improvement in someone's profile or something else?

Winter Bash 2020 has started and the hats (and masks) are listed below. As always, there are only two answers: one for the secret hats, and one for the regular hats. The secret hat list will be updated as we learn them. Please, only edit the secret hat answer with definitive and correct triggers. This is not the place to post guesses. Winter Bash is a fun event, so secret hat triggers should be put behind spoilers (use the >! markup) in order to not to spoil the fun for those users who want to discover the triggers themselves. If you'd like to discuss Winter Bash, hats or just have a question about it please come over to the . Please keep the comments here clean. As always, comments are not meant for discussion, conversation, "I just got hat X", etc. use the  for that (comments may be cleaned up without further notice). Here are the hats from previous years:


I using the pyqt5 line edit box as my input boxes. I want to take the input from the input boxes and convert it from string to hex to send to serial capture. For example I did this but I didn't succeed: a = hex(self.slave1.text()) b = hex(self.function1.text()) c = hex(self.address_msb1.text()) d = hex(self.address_lsb1.text()) e = hex(self.register_msb1.text()) f = hex(self.register_lsb1.text()) g = hex(self.crc_lsb1.text()) h = hex(self.crc_msb1.text()) hexConvert = [a,b,c,d,e,f,g,h]  Imagine: a = "01" b = "03" c = "00" d = "0A" e = "00" f = "04" g = "64" h = "0B"  And my expected output is [0x01, 0x03, 0x00, 0x0A, 0x04, 0x64, 0x0B]

How do I convert a hex string to an int in Python?   I may have it as "0xffff" or just "ffff".


A pseudoterminal has a pair of master and slave.   How can we find out the master device file from a slave device file (e.g. /etc/pts/3)? I only find /dev/ptmx and /dev/pts/ptmx, but they can't be shared by multiple slaves.  Given one of the processes working on the master and slave, how can we find out the other?  For example, ps provides information about the controlling tty of each process.  Can it be helpful?  Thanks.

In bash in lxterminal  $ tty /dev/pts/2 $ ls /dev/ptmx -l crw-rw-rw- 1 root tty 5, 2 May 26 09:38 /dev/ptmx   On Ubuntu, is there only one master for all the processes, and all the slaves are paired with the same master?  If different slaves are paired with different masters,    why is only one master   shown above? how can I find out the master for a given slave, and find out the slave for a given master?   Thanks.


Photoshop is very popular for retouch pictures taken by photographers. But how did photographers touch up photographs before the invention of Adobe Photoshop?

So, yes, I'm intrigued as to how they post process pictures before Photoshop (or computers, for that matter) came about. Or is post processing a by-product of the computer revolution?  My understanding of film photography (all from the film equivalent of a point-and-shoot we had when I was a kid) is that light burns into film then film gets developed. And, well, unlike bits, your end-product is tangible and "permanent", for lack of better term.  I'm woefully ignorant about film processing but I guess this is where the post-processing takes place? How do they tweak color temperatures? Remove red eyes? Retouch skin blemishes? Do they use special dyes/inks to achieve better colors/contrast?


I was hit with fridge logic, and I am curious:  Is it possible that the gravitational influence of photons inside of galaxies (And all throughout the universe) could account for dark matter?  Photons would be most concentrated close to the core and inner galaxy... And have a lessening concentration as they expanded away from galaxies due to the inverse square law..  I am struggling to understand the math involved, because I've not yet reached that level in my education.... But I'm really curious how the total photons stack up vs the measured dark matter in the universe?

EM radiation has a relativistic mass (see for instance, ), and therefore exerts a gravitational pull.   Intuitively it makes sense to include EM radiation itself in the galactic mass used to calculate rotation curves, but I've never actually seen that done before...  So: if we were to sum up all the electromagnetic radiation present in a galaxy, what fraction of the dark matter would it account for?


I've always installed Debian/Ubuntu without problems with Windows but this time I cannot.  I had a w10/debian9 build but I wanted to start from 0 so I formatted my partitions and reinstalled my os. There wasn't problems for w10 but I couldn't install any Linux distro, I tried with Mint 19, Ubuntu, Kubuntu 18.04 and 16.04 and it always says that I have no space when installing even though my disk has 930 GB empty space. I tried to restart even my partition tablet.  I don't know what to do, any idea?  Edit: I post pictures since pc gets mad and doesnt allow me to copypaste. I added syslog where my PC starts to iterate this error. Any idea?  Edit2: I finally got the solution that was to add  pci=nomsi after quiet splash as grub boot parameters

I'd like to see the full How-To on how to use manual partitioning during Ubuntu installation. The existing guides (at least those I found here) cover only automatic part and leave untouched the manual part (or extremely short and contain no pictures).  I'd like to cover such situations:     If your disk contains other systems:


I'm using Ubuntu 16.04 with Chrome 53.0.2785.101, and am experiencing the problem,that whenever I boot my laptop and open up Chrome, I'm logged out. I see a yellow triangle next to my name and have to reenter my password. This happens every time, and I don't know why. I don't delete my cookies etc. after I close chrome, but have to log into every website again (Facebook is pretty annoying because of 2FA).  Things I considered why this could happen:   I recently changed my password.  I'm using a WiFi connection (Can't use wired atm)   How do I find out what's the problem here and why this is happening? On my desktop pc I don't have the problem.   Update This is not a duplicate of  because the accepted answer didn't work. Maybe I should try one of the others in that thread?  Update 2 After the weekend, I had the same problem again. :( Online account is still connected though, but I was still logged out from every site and my Google account.

If I reboot Ubuntu, then I need to log on each site and into Google Chrome account. What is the reason?  My system is Ubuntu 16.04 and Google Chrome 53.0.2785.101 (64-bit).


What words does English have more? Romance or Germanic ?

It's often said that , with Germanic words an additional 26%. Wikipedia has , however, a random spot check of many words shows that they have often come via French (I can't check 29% of all English words myself). Also, many of the words on that list are quite obscure, compared to the many French derived words that are in everyday use.  I like looking up the etymologies of words, and in my experience, it's very rare to find a word that's come directly from Latin. Some words like ad hoc don't seem fully naturalised into English. I know scientific language is very highly influenced by Latin, but I consider that to be specialised terminology, as is legal terminology which quite often uses Latin phrases.  If Latin and French really each contributed 29% of our modern lexicon, with French words not counting towards Latin words, why are Latin-only derived words so difficult to find?


Problem: Let polynomial $Q_n (x) = \frac{x(x-1) \dots (x-n+1)}{n!} \in R[x]$ for some ring $R$. Show that $\forall t \in \mathbb{Z}, Q_n (t) \in \mathbb{Z}$.   My solution: For each $t \in \mathbb{Z}$, we have $t-1, t-2, \dots, t-n+1 \in \mathbb{Z}$, so $\frac{t(t-1) \dots (t-n+1)}{n!} \in \mathbb{Z}$ and $Q_n (t) \in \mathbb{Z}$.  Please check my solution. Thank all!

How can we prove that the product of $n$ consecutive integers is divisible by $n$ factorial?     Note: In this  and the comments here the OP has clarified that he seeks a proof that "does not use the properties of binomial coefficients". Please post answers in said newer thread so that this incorrectly-posed question may be closed as a duplicate.


I am trying to compile a program which uses  library. Actually I am using an example program given in the  of the library. But while compiling, it gives error. The errors I get are:   example.c:(.text+0x7): undefined reference to 'ud_init' example.c:(.text+0x7): undefined reference to 'ud_set_input_file' . . example.c:(.text+0x7): undefined reference to 'ud_insn_asm'   The command I am using is:  $ gcc -ludis86 example.c -o example    as instructed in the user-manual.  Clearly, linker is not able to link libudis library. But if I change my command to:  $ gcc example.c -ludis86 -o example    It starts working. So can please someone explain what is the problem with the first command?

Why does the order in which libraries are linked sometimes cause errors in GCC?


From what I've been reading, all that Wolverine needs in order to regenerate is a single cell. No matter how badly he's been damaged, blown-up or incinerated, he's survived because, supposedly, a single cell survived and that was enough for him to regenerate. With that in mind, can he be reproduced at will simply by slicing a piece off and regenerating that into a whole new second, third, fourth, etc., Wolverine? His healing factor can obviously be stolen and transferred to another. Why not an engineered body?

Wolverine has . He can .  Cut off Wolverine's finger. A new finger will be grown from his body, but the dismembered finger will not be grown back into a full body.  I want to know which types of cells are capable of regeneration to a full Wolverine and what decides it.  Something more: Blow up the body of Wolverine so that only his Adamantium skeleton is left.  Now, cut this skeleton into two equal parts using Antarctic Vibranium. Which part of the skeleton would regenerate to the full Wolverine?


I am wondering if the masslessness of photons is due to the local gauge invariance of $u(1)$-gauge fields. The reason why I consider about this question is that I remember that the  is not locally $u(1)$-invariant. How do I prove this explicitly in field theory?

Why can't photons have a mass? Could you explain this to me in a short and mathematical way?


Pretty simple, but I'm sure there's some subtlety to it I'm missing.  $$(-i)^2=1 \Rightarrow \sqrt{1}=-i \Rightarrow 1=-i$$  Looking at an Argand diagram however, gives some reason to doubt this.  Edit: as is pointed out in the comments/answers this is all kinds of wrong:  primarily, $(-i)^2=(-1)(-1)(i)(i)=i^2=-1$.  also, $a^2=b \Rightarrow \pm a=\sqrt{b}$

I know there must be something unmathematical in the following but I don't know where it is: \begin{align} \sqrt{-1} &= i \\\\\ \frac1{\sqrt{-1}} &= \frac1i \\\\  \frac{\sqrt1}{\sqrt{-1}} &= \frac1i \\\\  \sqrt{\frac1{-1}} &= \frac1i \\\\  \sqrt{\frac{-1}1} &= \frac1i \\\\  \sqrt{-1} &= \frac1i \\\\  i &= \frac1i \\\\  i^2 &= 1 \\\\  -1 &= 1 \quad !!? \end{align}


From what I know, changing your username will change it everywhere but looking at , Robert Harvey ♦'s name is still showing as The Grinch as the name of the question OP.    It is also still showing as The Grinch on the question in .    Is there a reason for this or this a bug?

On a whim the other day, I changed my meta name from Lord Torgamus to Popular Demand.  I just noticed that the old name has "stuck" to the author tag of ; everywhere else on meta, my new name displays as expected.  Is this a feature?  Is it a bug?  Mostly I'm just curious, as I can't think of a strong reason in favor of keeping this behavior or a strong reason for changing it.  A question somewhat like this has been raised before as , but the previous poster implied that the issue had something to do with migration, which my situation shows is not the case.


So I have a slight ethical issue.  A few years ago, I answered  question with what I believed at the time to be a good answer. I had just started out in my field (iOS Development) at the time and was chuffed that I was able to assist another developer so early into my own career.  As my career progressed and my knowledge grew, I became more aware of the pitfalls of using an approach such as the one I suggested in my answer. This was also pointed out by a couple of other users who suggested better approaches in alternative answers.  Unfortunately, most people who visit an SO question usually grab the answer with the most upvotes (generally new users/programmers), which is mine, given that it's been there the longest, meaning that they are potentially setting themselves up for said pitfalls they could avoid by simply taking another answer.  This seemed like madness to me, so I edited my original answer to explain the pitfalls of the approach and suggest my new favourite alternative approach. I made sure to suggest that the reader scrolls down in the thread and browse the host of suggestions from different users, as most of them are valid.  Now it should be noted that this isn't about reputation at this stage; it's a case of 'my answer is what 80% of people will take and I want their code to be solid'. That said, others in the thread suggested the same thing I edited into my answer, first. Does that mean I'm capitalising on their efforts unfairly?  This is where my problem lies. I'm torn between the dilemma of potentially absolving others of well deserved reputation, and knowingly allowing users to use potentially unpredictable code. I considered straight up deleting my answer, but I think it serves as a valuable lesson, particularly for new developers, as to why approaches such as that are not best.  Would love to hear the community's thoughts on this one.

I was thinking about this issue from time to time but I didn't know whether it really exists or just an speculation on my side until today when I woke up [!], I saw  downvoted (in the meantime I'll leave that answer unedited for the sake of discussion; note that this is just a sample. I'm not asking "how to deal with this specific answer." The question is completely general as it's nearly impossible to keep track of all of your answers to see whether they require updating or not). While the downvoter didn't explain a thing, I suspect the reason is that the answer is no longer applicable (It's one of the new features in iPhone OS 3.0). As we go to celebrate a long sequence of birthdays for Stack Overflow (hopefully!), we're going to see lots of answers become obsolete. How we're going to deal with this issue?


I have a user (interface) on Ubuntu MATE 18.04 I need it to log in automatically and without requiring a password to do so.  The built-it screen on the case of my Raspberry Pi is too small for this to be done via the GUI, since not all of it fits on the ridiculous resolution of the screen. So I need to do this using the terminal.  screen resolution is 420x360

how do i set the password settings of a user (named: interface) to not asked on login via the command line on ubuntuMATE?  i need to do this via the command line because the screen resolution on the raspberry pi is a very low 420x360 making doing it via the GUI impossible since it doesn't display fully.


I am working on a dataset that has a dependent variable that is binary, but it contains 98% of 0's and 2% of 1's. I am trying to use Logistic regression to predict purchase of a product. But because of the huge number of 0's, the model is not predicting well and getting a large number of false positive result.  Kindly suggest how can I approach this.

I have a data set where I need to detect fraud. 99% are not fraud and 1% are.  What methods can be used to solve problems where classes are imbalanced?


I have this file:  mmD_154Lbb_e_dxk_83233.orc 154L_bbe_Bddxk_3259.txt 14Lbe_3233.orc m2_154Lbbe_dxk_67233.op mZZ_1A4Lbbe_dxk_32823.op mmD_154Lbbe_dxk_99333.orc mmD_oS154be_dxk_12338.txt   I'm trying to use sed or awk to split the numbers and I don't have solution:  I need out put:  83233 2597 3233 67233 32823 99333 12338   How can I get it to split on each delimiter?  Thanks

I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?


I'll be straightforward. What do you call a test for someone who missed the actual test date/schedule? For example, one should have taken the test last Monday, but he missed it. Then he got another chance to take the test on Wednesday. Let's pray he doesn't miss that one. What do you call that test on Wednesday? I tried googling and the closest I can find was "late test". Any ideas would be helpful. Thanks.

I'm looking for one word which describes what a student who missed classes needs to do in order to complete his missing.   For example if he missed biology class he needs to seat with the teacher and study this missed class together with her and then he get the mark for this missed class. Someone -who isn't native English speaker- told me that it's called "rework". But I looked for it in some dictionaries (such as ) and I didn't find such definition.   : "SCHEDULE of reworks of missed classes"


What time did Monarch flight ZB7014 from Gatwick land in Rhodes on 2nd September 2015. It was due at 12 noon and we calculated our arrival as 3hrs 15 minutes late. Monarch airlines say it was only 2 hrs 45 minutes. The original plane had a technical problem and was withdrawn, the replacement aircraft from Prestige, a Spanish company blew a tyre on arrival which had to be replaced before we could finally take off.

The question  only deals with flights in the US sourced from the  . Is there some similar source for EU, Asia etc?


Perhaps this amount should instead be 250 (because the email confirmation gives 50 rep). I ran into a  who has >2k rep on A51 and he didn't give the association bonus to his other two accounts (which are at 1 rep).

My Area51 account crossed 200 rep today, but still other accounts don't reflect the change in reputation. When will the changes be applied? or is there no association bonus for Area51 account?


I want to check if specific id element is exist or not. For ex. id="tbvAccountProc:frmFinancingDocumentProcess:btnSave" here i want to check btnSave exist or not.  if ($('#btnSave').length) {     }   and  if ($('#btnSave').length > 0) { }   and   if ($('#frmFinancingDocumentProcess').length) { }   and   if (document.getElementById('btnSave')) { }   tried these but btnSave exist in the view but these are not working as I expected.  if i check btnSave exist it must be return alert('true') else false.  Html:

How can I check the existence of an element in jQuery?  The current code that I have is this:  if ($(selector).length > 0) {     // Do something }   Is there a more elegant way to approach this? Perhaps a plugin or a function?


This happened when I reviewed the question as "leave closed".  It's rather confusing.  I clicked cancel, and my review was registered and it moved to the next item. Le bug!

This is rather difficult to describe with fancy pictures with red circles but it's easily reproducible.  Whenever I click Leave Closed in the re-open queue on MSO the "nominate this question for re-opening" pop-up appears. I normally press escape out of shock and a leave closed vote is recorded.  This is the latest review it's happened to me on:   You can also test it on , I clicked reopen this time and a leave closed vote was recorded but I also got a red popup stating that an error had occurred.  This is also occurring when the Edit & Reopen button is clicked, the edit box opens for a second before being overridden by the popup.


I would love a list of Shell commands for Windows. Not to be confused with commands that you would run in Windows DOS. Over time I have come across these commands here and there. Like for example if you need to access the users startup folder in Windows 8, you go to run (Windows Key + R) and then type shell:startup then you would get your startup folder so you could load programs on startup upon Windows logon. This commands also works in Windows 7 as well. Can some please tell me were I can find a list all of the shell: that you can run?

to open send to folder in windows 7, we type  shell:sendto  and to open apps folder in windows 8, we type  shell:appsfolder  first of all, i would like to know what is this syntax known as (shell: something)  secondly, if anybody can tell me, please give the complete list of commands similar to this  thanks Gagan


The code below shows the use of List interface in existing code.        LinkedList<Song> playList = new LinkedList<Song>();    List was applied:    List<Song> playList = new LinkedList<Song>();  Then LinkedList was changed to ArrayList:    List<Song> playList = new ArrayList<Song>();    And after these two edits, the codes worked exactly as before. It was actually for a media player with features (methods)like play, skip forward, skip backwards and replay. Hence the prior need to use LinkedList for the songs.  I have a limited understanding of both LinkedList and ArrayList. I know they are implementations of List interface (hence they are both bound by the methods dictated by the List interface).   However, does that mean that once I use a List interface it matters not whether I initialise the code with ArrayList or LinkedList? Do the LinkedList and ArrayList become indistinguishable placeholders?  Or are there specific differences in the instances by LinkedList and ArrayList when both are referenced by List interface?

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


I about to tear out and rebuild a portion of an exterior wall in which I will be installing a door, is it possible since it's new construction to purchase and inswing door and convert it to an outswing door?   Thanks

I like my current wooden front door a great deal, but it's hinged to swing inward to the right, and traffic flow (getting a bike into the mud room, for example) would be a lot easier if it swung in to the left.  Problem is, the latch edge of the door is beveled the standard 15 degrees to permit closing with a smaller gap, whereas the hinge edge is square. And I can't flip the door top-to-bottom/left-to-right to move that bevel; its design has a clear "up"... if I rotate it only on the other axis the latch edge will be bevelled the wrong way, definitely not an improvement.  Best solutions I've come up with so far involve keeping the door in its current orientation, swapping hardware (requires disguising the old lock borings; I have an idea for that), bevelling what used to be the hinge side... and maybe, if I can't get away with just letting the hinge absorb the angle difference, applying a wedge or wedges to re-square it.  How insane am I? Should I try without changing the bevels first? Or should I not try at all, get a new front door, and try to find a good home for this one?


Can one travel for tourism to Norway with Schengen business visa- single entry  (given for Sweden)?

My friends and I planned to visit Germany, so I got a single entry tourist Schengen visa to Germany. However, my travel plans have changed since then, because my friends are going to Italy instead. I don't have time to apply for a visa to Italy, but I have been told that I can use my Schengen visa to enter Italy. Is that true?


Let $f:(a,b) \mapsto \mathbb{R}$ be continuous function such that $f(\frac{x+y}{2})\leq \frac{1}{2}f(x) + \frac{1}{2}f(y) \;\; \forall x,y \in (a,b)$    Show that $f$ is convex function.   Please give me hints to prove it.

Given that $$f\left(\frac{x+y}{2}\right)\leqslant \frac{f(x)+f(y)}{2}~,$$ how can I show that $f$ is convex. Thanks.      Edit: I'm sorry for all the confusion. $f$ is assumed to be continuous on an interval $(a,b)$.


Ok, so I got this laptop from a friend, wen I turn it on it asks for a password, for an account with username: Nobuntu , or the guest account. Well I cannot log in to this Nobuntu account because I do not have the password and I need it in-order to make any updates, installs, anything. Please help me! Ive tried holding down the shift at boot up iv we tried fn. F8 I cannot figure it out , i am no computer wiz

I'm working on a Ubuntu system, and my client has completely forgotten his administrative password. He doesn't even remember entering one; however it is there.  I've tried the suggestions on the website, and I have been unsuccessful in deleting the password so that I can download applets required for running some files. Is there a solution?


Been at this for a pretty long time, been trying all types of alternatives, so I've come here for help. I need 16 squares to fill an 800x800 pixel area. I have completed that task. However, now that I want each square to have a circle centered ontop of it, I thought of making an array of StackPanes. Each stackPane in the array will hold the square, then the circle (so that circle is on top of this square). This is what I've got.   import javafx.application.Application; import javafx.stage.Stage; import javafx.scene.Group; import javafx.scene.Scene; import javafx.scene.layout.BorderPane; import javafx.scene.layout.Pane; import javafx.scene.layout.StackPane; import javafx.scene.control.RadioButton; import javafx.scene.layout.VBox; import javafx.scene.shape.Rectangle; import javafx.scene.shape.Circle;  /**  * @author Dominic Barbuto  * @date 03/28/2020  *  */ public class DAB_ShapeGrid extends Application {     //Scene dimensions     final int SCENE_WIDTH = 1000, SCENE_HEIGHT = 800;     //Square Dimensions     double width = 200, height = 200;      public static void main(String[] args)      {         launch(args);     }      public void start(Stage primaryStage)     {         StackPane[] stackPane = new StackPane[16];         DAB_Square[] squareArray= new DAB_Square[16];          int index = 0;         for(int posX = 0; posX < SCENE_WIDTH-200; posX += 200)         {             for(int posY = 0; posY < SCENE_HEIGHT; posY += 200)             {                 squareArray[index] = new DAB_Square(posX, posY, width, height);                 stackPane[index].getChildren().addAll(squareArray[index], new DAB_Circle(posX+100, posY +100, 100.0));                 index++;             }         }          Pane pane = new Pane(stackPane[0], stackPane[1], stackPane[2], stackPane[3],                                         stackPane[4], stackPane[5], stackPane[6], stackPane[7],                                         stackPane[8], stackPane[9], stackPane[10], stackPane[11],                                         stackPane[12], stackPane[13], stackPane[14], stackPane[15]);          RadioButton radioButton = new RadioButton("Test");         VBox rightVBox = new VBox(radioButton);          BorderPane borderPane = new BorderPane();         borderPane.setLeft(pane);         borderPane.setRight(rightVBox);          Scene scene = new Scene(borderPane, SCENE_WIDTH, SCENE_HEIGHT);          primaryStage.setScene(scene);         primaryStage.setTitle("Filling the Grid With Shapes Program");         primaryStage.show();     } }   I am getting a NullPointerException pointing to this line: stackPane[index].getChildren().addAll(squareArray[index], new DAB_Circle(posX+100, posY +100, 100.0)); and I can't for the life of me find out why.

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?


I have a question that asks:  "Describe bijections $f$ : $(A\times B) \times C \rightarrow (A\times B)\times C, A\times B \rightarrow B\times A$  I have no idea how to start, or precisely what the question wants: do I find some function explicitly, or state something else?

The question I have states:   "Describe a bijection $f:A\times B\rightarrow B\times A$"  The simplicity and lack of a domain or codomain that I can look at has caused this question to throw me off.   Is describing $f(a,b)=(b,a)$ where $a\in A, b\in B$ enough to do this? To what extent do I have to prove that this is a bijection?   I can say that $(x,y)=(x',y')$ if and only if $(x=x')\ \cap \ (y=y')$ and prove injectivity and surjectivity and so on, but I am a bit confused..


So I've been highly interested in D&D through watching streams of it but unfortunately no one plays D&D anywhere close to me. I don't have a clue on how to make characters etc. So if anyone could help me then that'd be greatly appreciated.

I have been told that roleplaying is great fun. I've looked and looked and it all seems so complicated. Could anyone tell me a good place to start, and what sort of things you end up doing in roleplaying?


I'm trying to prove whether $\cos(11^\circ)\over \sqrt{1+\sin(15^\circ)}$ is constructible. I suspect it is not, and would like to use the triple angle identity to use RRT and prove there is no constructible root, but to do this I'd need $\cos(33^\circ)$, of which I don't know the exact value. Is there a better way to go about this?

Over the numerous math tests I've taken, I have yet to understand what angle can be constructed and what cannot. From my understanding, 30, 45, 60, and 90 degree angles can be constructed. You can then use these angles and subtract or add them to create other angles like 15 or 75. Also, any angle can be bisected. Are there any other basic angle measures that can be constructed like 30, 45, etc.? So 82.5° is an angle measure  that can be constructed because you can add 60+60+45 to get 165 and then bisect it.


Usually, I use many macros in my documents to save time. I am searching for clever "ideas, methods, tools" which can replace macros by its definition.  For example, if we have a the following document    \documentclass[a4paper,10pt,english]{article} \usepackage{amsfonts} \newcommand{\bN}{\mathbb{N}} \newcommand{\bZ}{\mathbb{Z}} \begin{document} $\bN$ and $\bZ$ are closed under the operation of addition   \end{document}   I want the content to be converted to      $\mathbb{N}$ and $\mathbb{Z}$ are closed under the operation of addition     Remark: I know that I can do this using find/replace in the editor. Here, I am asking about other possibilities.  Best regards

Is it possible to have LaTeX (or another program) to expand a the macros in a .tex file, and output the expanded LaTeX source?   If no such program exists: are LaTeX macros processed simply as string substitutions, before the document is interpreted? If so, it might be easy enough to write my own such converter.  Edit: The reason I ask is journals which don't accept LaTeX submissions with macros. It would be useful to be able to develop with my usual macros, and convert automatically to the 'macro-expanded' format for submission.


Disclaimer: I have never used a Filter or Lens Hood, so this might be weird question.  I plan to do some landscape photography using my Lumix G F1,7/20 mm MFT Lens. Unfortunately I just realized that this lens does not have any thread to screw something on:    Is there still a way to mount filters, maybe using some accessory?

I was looking to get a circular polarizing filter and an UV filter for my Canon 550D, 18-135mm lens. When I checked online I found these filters came in different sizes, like 62mm, 67mm, 72mm, 77mm. How do I know which is right?  Also, will there be any degradation of photo quality if I put both these filters on the lens?


This is a 32 GB memory machine and the following top/free command says 30.5 GB memory is used, but the total RES is actually much less than 30.5 GB. Why?  top - 21:54:46 up 20 days,  1:46,  4 users,  load average: 0.59, 0.43, 0.34 Tasks: 238 total,   2 running, 233 sleeping,   0 stopped,   3 zombie %Cpu(s):  3.8 us,  0.7 sy,  0.1 ni, 94.0 id,  1.5 wa,  0.0 hi,  0.0 si,  0.0 st GiB Mem:    31.523 total,   30.609 used,    0.913 free,    0.456 buffers GiB Swap:    4.000 total,    0.134 used,    3.866 free.   22.733 cached Mem     PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND  2600 xxxxxxx   20   0 12.048g 2.002g 0.034g S   0.3  6.4  14:24.92 xxxxxx  1443 xxxxx     20   0  1.302g 0.837g 0.019g S   0.3  2.7 102:19.93 xxxxxx  9782 xxxxxxx   20   0  1.942g 0.573g 0.043g S  17.0  1.8 164:53.02 cinnamon 20730 xxxxx     20   0  0.619g 0.289g 0.055g S   0.3  0.9 102:19.50 xxxxxx 29920 xxx       20   0  0.787g 0.189g 0.020g S   0.3  0.6  60:42.72 xxxxxx 31377 xxxxxxx   20   0  3.390g 0.169g 0.006g S   0.0  0.5  38:45.66 xxxxxx  9497 xxxxxxx   20   0  0.367g 0.168g 0.036g S   1.3  0.5  16:00.60 xxxxxx  1402 root      20   0  1.010g 0.154g 0.024g S   0.3  0.5  54:30.61 xxxxxx 14176 root      39  19  0.306g 0.118g 0.011g S   0.0  0.4   4:32.76 xxxxxx   903 xxxxxxx   20   0  0.383g 0.101g 0.034g S   0.3  0.3   0:43.40 xxxxxx               total       used       free     shared    buffers     cached Mem:            32         31          1          0          0         23 -/+ buffers/cache:          8         24 Swap:            3          0          3   The following ps command calculates total RSS, which is 7 GB, but top/free command returns 30.5 GB used. Why?  ps -e --format rss  | awk 'BEGIN{c=0} {c+=$1} END{print c/1024}'   My big mistake is this machine is actually 32 GB memory, not 64 GB.

I'm a bit confused on some of the results I am seeing from ps and free.  On my server, this is the result of free -m  [root@server ~]# free -m              total       used       free     shared    buffers     cached Mem:          2048       2033         14          0         73       1398 -/+ buffers/cache:        561       1486 Swap:         2047         11       2036   My understanding of how Linux manages memory, is that it will store disk usage in RAM, so that each subsequent access is quicker. I believe this is indicated by the "cached" columns. Additionally, various buffers are stored in RAM, indicated in the "buffers" column.  So if I understand correctly, the "actual" usage is supposed to be the "used" value of "-/+ buffers/cache", or 561 in this case.  So assuming all of that is correct, the part that throws me is the results of ps aux.  My understanding of the ps results, is that the 6th column (RSS), represents the size in kilobytes the process uses for memory.  So when I run this command:  [root@server ~]# ps aux | awk '{sum+=$6} END {print sum / 1024}' 1475.52   Shouldn't the result be the "used" column of "-/+ buffers/cache" from free -m?  So, how can I properly determine the memory usage of a process in Linux? Apparently my logic is flawed.


I am building a Linked list here.   public ListNode addNode(ListNode head, ListNode temp){     if(head == null){         head = temp;     } else{         ListNode curr = head;         while(curr.next != null){         curr = curr.next;         }      curr.next = temp;     }     return head; }   I have to merge two Linkedlist here. For e.g. we assume head as 1->2->3->null, temp as 4->5->null, I need the output as 1->2->3->4->5->null  On the head list, we have to move to last node so that we can merge the temp list. To move the pointer to the last node of the head list, I am iterating till I get next element as null which means the curr list will have 3->null alone when the while loop exists. Then, I am adding the temp list as the next element of curr. So, I assume I get 3->4->5->null.  But, when I return head element, I am getting 1->2->3->4->5->null.  How this works> Both curr and head are pointing to same objects right? When we change curr, head should point to the same. How is this working?

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 this code where it does not work:  if (desctiption == "net :: ERR_INVALID_ARGUMENT" ")    instead if I write   if (desctiption! =" Net :: ERR_INVALID_ARGUMENT "")    I create the Toast object and the text is equal to   net: : ERR_INVALID_ARGUMENT   The code:  webView.setWebViewClient(new WebViewClient() {           @Override         public void onReceivedError(WebView view, int errorCode,                                     String description, String failingUrl) {             super.onReceivedError(view, errorCode, description, failingUrl);               Toast toast = Toast.makeText(getBaseContext(),description, Toast.LENGTH_LONG);              if (description == "net::ERR_INVALID_ARGUMENT"){             toast.show();}            }       }); }

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


I currently have an array in my program, and each entry in the array is structured like this:  {'ts': '0', 'ph': '308.8', 'am': '-40.408'}   I want to change the numbers, which are currently stored as strings, to floats, but I'm clueless as to how to do it.  Any help would be greatly appreciated!

In Python, how can I parse a numeric string like "545.2222" to its corresponding float value, 545.2222? Or parse the string "31" to an integer, 31?  I just want to know how to parse a float str to a float, and (separately) an int str to an int.


There is a new official policy on reporting underage users by moderators: . This is posted with the  tag, so it is officially part of the moderator agreement. This is one of the new things in the changed moderator agreement, and I'm not entirely sure how this will be interpreted in practice. The linked policy does use the imperative asking mods to report underage users, but it doesn't use stronger language like "must report" or similar. I'm not sure if this is still SE asking politely or SE requiring moderators to report underage users at a similar level as other clauses in the main moderator agreement. The main moderator agreement is quite clear to me, it does use straightforward language and clearly spells out the obligations of a moderator. The linked policies are referenced with the following sentence there:  I will abide by all other officially announced moderator and user policies made available to me.  So they are supposed to carry the same weight as other obligations in the main moderator agreement. But those linked policies are written in a very different way, they are much less explicit and contain much more context. So my main question in the end is, are moderators required to report any underage user they notice, and is avoiding to report underage users you know of a violation of the moderator agreement, with all the potential consequences?

Just today (December 2, 2020), a  was enacted, which requires moderators to report users that they find to be underage:  If you find a user claiming to be under 16 escalate it to us through the "Contact Community Team" button and select the "underage user" template - this will flag the on-duty CM for action so we can investigate and, if deemed necessary, delete that account and all personal data associated with it. [...] This policy only applies to sites where you are a moderator. If you see things on a site where you’re not, there is no obligation to escalate.  Being part of the , moderators are required to follow the instructions there, and not following them is considered a violation of the moderator agreement. However, this contradicts a , which states (bold added):  Users and moderators are not legally responsible for underage users and are under no obligation to report them to us. If out of concern you would like to report it, [...]  As part of the re-enaction of the policy on December 2, the text "and moderators" in the above quote was edited out of that statement. Why are moderators now required as per policy to report underage users that they come across? Is there a legal explanation as to why SE's stance on this changed? I'm aware of  from a then-employee, which stated that moderators are expected, but not required as a condition of remaining a moderator, to report underage users. However, the new policy requires reporting them. Why? An example of a case where a moderator may not want to report an underage user is if the user claims to be from an EU country that has reduced the required age from 16. While SE's Terms of Use specify a blanket limit of 16 to comply with regulations in all EU countries, individual member states do have the ability to reduce the limit, so long as it's not below 13. There is no law violation if, say, a 15-year-old user from an EU country that has reduced the age limit to 14 registers, so a moderator may not feel like reporting them (since in that case they're merely enforcing the Terms of Use, which they're not otherwise expected to do).  The policy was recanted a few days after it was originally enacted on October 15, 2020, but was enacted again on December 2 after minor revisions following a review among moderators. The same question still applies to the revised policy, however.


As everyone knows, the conditional probability of A given B is $P(A|B) = \frac{P(A\cap B)}{P(B)}$, and Bayes' theorem is derived from that equation to $P(A|B) = \frac{P(B|A)P(A)}{P(B)}$.  I'm pretty new to probability, so I'm more than likely missing something, but why has Bayes' theorem become the "popular" equation? It seems to be just a complicated rewriting, and requires more information than the original definition of conditional probability (which Bayes' rule "decomposes" to anyways).

Given 2 events $E, F$, I know that $P(E | F) = \frac{P(E \cap F)}{P(F)}$. However sometimes the Bayes' theorem is used instead: $P(E | F) = \frac{P(F | E) P(E)}{P(F|E)P(E)+P(F|E^{c})P(E^{c})}$. However, when do I know to use the former, simpler definition and when do I use the Bayes' theorem? When I get a problem, how can I recognize which definition to use?


Getting this on keyword reports: 100% bounce rate, 1 pageview and average session duration 24 minutes. I've gone through all of my other analytics properties and this is the first time I see this situation, in my opinion makes a bit of no sense.  Thinking about a couple of posibilities: - A user hits the site through that keyword, then exits, then comes back: session still valid but Analytics does not atribute the session to that particular keyword anymore. - Maybe a non-interaction event is set on the page affecting only the session duration (not sure this is a plausible scenario)  Anyone knows what's up?

Google Analytics reports 100% bounce rate for a page which has lots of page views and an Avg Time on Page of 32 seconds. Shouldn't one of the following be true?  Either the bounce rate is less than 100% when the Avg Time on Page is greater than 0 or the Avg Time on Page is 0 when the bounce rate is 100%.  I fail to see how or why the report does not conform the above two conditions.


Let $A,B,U,O$ four matrix of real entries. $A$ is a square matrix of size $m$, $B$ is a square matrix of size $n$, while $U$ is a $n\times m$ matrix of all entries $=-1$ and $O$ is a $m\times n$ matrix of all entries $=0$. Let us consider the square (block) matrix of size $n+m$: $$M=\left(   \begin{array}{cc}     A & U \\     O & B \\   \end{array} \right) $$ Prove that the set of eigenvalues of $M$ is the union of eigenvalues of $A$ and $B$. This property of determinants should follow immediately if we can show $\det M=\det A \det B$ but I do not know to prove this statement. Any suggestions please?

Let $A$ be a block upper triangular matrix: $$A = \begin{pmatrix} A_{1,1}&A_{1,2}\\ 0&A_{2,2} \end{pmatrix}$$ where $A_{1,1} ∈ C^{p \times p}$, $A_{2,2} ∈ C^{(n-p) \times (n-p)}$. Show that the eigenvalues of $A$ are the combined eigenvalues of $A_{1,1}$ and $A_{2,2}$  I've been pretty much stuck looking at this for a good hour and a half, so any help would be much appreciated. Thanks.


I am not professional physicist; but I am curious about Stephen Hawking's "imaginary time". It would be better to elaborate exactly what it is. I am not confused because of the word "imaginary" but I find it confusing to imagine a two dimensional "plane time". If we express time in a plane instead of a one dimensional axis, then what does the movement of an observer along the imaginary axis signify physically?

What is imaginary (or complex) time? I was reading about Hawking's wave function of the universe and this topic came up. If imaginary mass and similar imaginary quantities do not make sense in physics, why should imaginary (or complex) time make sense?    By imaginary I mean a multiple of $i$, and by complex I mean having a real and an imaginary part, i.e., $\alpha + i\beta$, where $\alpha, \beta \in {\mathbb R}$.


let $x_1....x_n$ be positive integers. Prove by induction the following for natural numbers n:  $(\sum_{k=1}^n x_k)\cdot(\sum_{k=1}^n \frac{1}{x_k})\ge{n^2}$  Hint: for all positive integers a,b: $\frac{a}{b}+\frac{b}{a}\ge2$

If $x_1,...,x_n$ are positive real numbers and if $y_k=1/x_k$, prove that $$\left(\sum^n_{k=1}x_k\right)\left(\sum^n_{k=1}y_k\right)\geq n^2.$$   I've been learning induction, and I've come across this problem that I really can't even break down and begin to think about. I've been told it has something to do with Cauchy-Schwarz, but I cannot figure out how to apply it. I would appreciate help figuring out how to go about and formulate this proof. Thanks!


With this product:  $$(a,b)\cdot (x,y):=(ax-by,ay+bx)$$  $\,\Bbb R^2$ becomes a field, actually isomorphic to $\,\Bbb C$.  Are there other interesting products that turn $\,\Bbb R^2$ into a field?

Let $\mathbb{C}=\{a+bi | a,b \in \mathbb{R}\}$, denote the set of complex numbers, where $i$ has the property that it's square is $-1$.   We define the two binary operation, $+, *$ on this set $\mathbb{C}$, namely addition and multiplication of complex numbers as follows $$(a+bi)+(c+di)=(a+c)+(b+d)i$$ and  $$(a+bi)*(c+di)=(ac-bd)+(ad+bc)i$$  We observe that $(\mathbb{C},+,*)$ forms a mathematical object called field.  Note that $*$ has "usual" properties like distributivity, associativity and commutativity.  I have the following Question, Are there many ways of defining binary operation $*$ (or call it multiplication of complex number ), such that these above mentioned properties are satisfied.


This is a lock screen wallpaper from Windows 8 Developer/Consumer/Release Preview, where was this taken?

Windows 10 has an extensive collection of lock screen photos, many of which have  here on Travel.SE.  Is there a website which lists the location of all of these photos? I imagine Microsoft has purchased an official license, so they should have a record about the photographer and the place where the photo was taken.


Suppose that there are two (instantaneous) events $E_{1}$ and $E_{2}$, of which (special relativistic) spacetime interval is $S$. Is it possible that $E_{1}$ and $E_{2}$ are not simultaneous with respect to any possible observer? If so, what's the condition under which this happens in terms of S? In other words, what is the condition for S to make it the case that $E_{1}$ and $E_{2}$ are not simultaneous to any observer? (Assuming that spacetime is flat.)

In relativity, if two events are simultaneous in a specified frame, they cannot be simultaneous in any other frame.   My question is this: given any two events, is there always a frame in which these two events are simultaneous? For example, if I drop a blue ball on one side of a tennis court, and my friend drops a red ball on the opposite side of the court one day later -- from my frame one day later -- is there a frame in which the blue and red balls hit the ground simultaneously?


Here's my screenshot: How can I rewrite this query to display a single record but have all four "ColumnName" data fields in a single field?  So basically, I'm after a single row that looks like:  TableName: 20180301_Vitality  ColumnData: _CustomObjectKey | Email address | Subscriber key | opCoCode 2

Consider a database table holding names, with three rows:  Peter Paul Mary   Is there an easy way to turn this into a single string of Peter, Paul, Mary?


I'm new in win 2008 server so i have a question.  I have 2 Child domain under a single Forest.every thing is fine but when client in each domain want to  log in to windows in login on to list user can see 2 child domain names and the forest domain name. how can i show just its child domain name in the login list?

I need to create a bidirectional trust between two Active Directory domains. But management is worried that users will be puzzled out when seeing  another domain name in the drop-down list in the Windows logon screen (many of them use Windows XP), and that help desk calls for failed logins due to having selected the wrong domain will skyrocket. Also, the two domain names are quite similar, adding to the possible user confusion.  Is there any way to hide a trusted domain from the drop-down list in the Windows logon screen?


OK, so you can run something like   start iexplore   in cmd and have it run internet explorer.  Is there a way to allow the same sort of behavior with something like, javac.exe (or some other utility exe)?  I don't want to have to type   "C:\Program Files\Java\jdk1.8.0_31\bin\javac.exe"   to run javac every time I need to via CL.

Questions about    setting environment variables the PATH   are very common here, and in most cases the answers are very similar to each other. In the future it would be nice to have a good Q/A for this.  So the question is: What are environment variables, like the executable PATH, and how can I change and use them on major operating systems?  A good answer would include a simple explanation of what environment variables and especially PATH mean to the OS, as well as simple guidelines on how to set and read them accordingly.


I tried to follow this method () with no luck. When I put my modem, it always show Mass Storage Mode, here's my lsusb result:  denny@GIGABYTE-PC ~ $ lsusb Bus 001 Device 009: ID 12d1:15ca Huawei Technologies Co., Ltd. E3131 3G/UMTS/HSPA+ Modem (Mass Storage Mode)   Note here that vid:pid value should be 12d1:1506 then I try modprobe -v option and followed by   sudo echo "12d1 1506" >/sys/bus/usb-serial/drivers/option1/new_id bash: /sys/bus/usb-serial/drivers/option1/new_id: Permission denied   No matter what vid:pid that I supplied, system always spouts permission denied. So what's wrong ? and is there easier way to use my USB modem with Ubuntu ?

When using sudo to allow edits to files, I regularly get 'permission denied'.  For example, my mouse is jittery and sluggish, so I want to disable polling:  sudo echo "options drm_kms_helper poll=N">/etc/modprobe.d/local.conf   I'm prompted for a password, and then get:  bash: /etc/modprobe.d/local.conf: Permission denied   So I tried to do a temporary change to disable polling by using:  sudo echo N> /sys/module/drm_kms_helper/parameters/poll   Yet again the system responded with:  bash: /sys/module/drm_kms_helper/parameters/poll: Permission denied   Any ideas?


I need to split a number of 27 digits into groups of 5 digits. I already had a look at siunitx, telprint and numprint. But these just allow me to generate groups of two or three digits. Is there any known way to do split the number into groups of 5?

I want to split a character string n by n. I know how to do that 1 by 1 :  \documentclass{article} \makeatletter  \def\s@plit<#1#2>{%   \ifx\empty#2%     #1%   \else     #1,\s@plit<#2>%   \fi}  \def\Split#1#2{\s@plit<#2\empty>} \makeatother  \begin{document} \Split{1}{123456789} \end{document}   It gives : 1,2,3,4,5,6,7,8,9  But I also want 1,23,45,67,89 or 123,456,789 ... depending from the first parameter.  EDIT  Work straight and reverse, even with foreach.        \documentclass{article}     \usepackage{tikz,xparse,xstring}  \DeclareDocumentCommand{\split}{smmo}{%     \xdef\Entree{#3}%     \let\Sortie\empty%     \IfBooleanTF #1     {% sans étoile         \loop         \StrRight{\Entree}{#2}[\tmp]%         \edef\Sortie{\Sortie,\tmp}%         \StrGobbleRight{\Entree}{#2}[\Entree]%         \unless\ifx\Entree\empty         \repeat         \StrGobbleLeft{\Sortie}{1}[\Sortie]%     }     {% avec étoile dans l'ordre inverse         \loop         \StrRight{\Entree}{#2}[\tmp]%         \edef\Sortie{\tmp,\Sortie}%         \StrGobbleRight{\Entree}{#2}[\Entree]%         \unless\ifx\Entree\empty         \repeat         \StrGobbleRight{\Sortie}{1}[\Sortie]%     }     \IfNoValueTF{#4}{\Sortie}{\edef#4{\Sortie}}     }  \begin{document} \split{2}{6513782}  \split*{2}{6513782}  \split*{2}{6513782}[\bob]  \foreach \x in \bob {[\x] }  \end{document}


If I have two stones A and B with estimated weights (and associated uncertainties) of   A=100 +/- 5kg B=102 +/- 2kg     Is there any formula (or good approximation) to compute the expected value of max(A,B)?  That is, the best guess at how much the heavier of the two stones will weigh?  It's obvious to me that this expected value should be slightly higher than 102 ("the expected value of the stone that's most likely to be the heaviest"). Also helpful to me would be     Is there a way to compute the uncertainty of the expected value of max(A,B)?   Is there a way to extend the formula to apply to "N-stone" situation?     The best I've been able to do is run a 1-billion-sample simulation pulling values for A and B from their respective 95% confidence intervals, then computing the average of max(A,B) over all simulations to get close approximation of what the expected value should be:      Max(A,B) = 102.375 +/- 2.340  (stddev = 1.194)  Admittedly, this tells me nothing about how to solve the problem, but it does allow me to check the validity of proposed solutions.  EDIT: Duplicate verified.  Formula at link was able to replicate my simulated results  Simulated E(max(A,B)) = 102.3751.  The formula on the "duplicate" link indicates expected value of this max function should be: E(X) = u1*CDF((u1-u2)/θ) + u2*CDF((u2-u1)/θ) + θ*PDF((u2-u1)/θ) where θ = sqrt((2.55*2.55)+(1.0209*1.0209)) θ = 2.747  Substituting θ, u1, and u2: E(X) = 100*CDF((100-102)/θ) + 102*CDF((102-100)/θ) + θ*PDF((100-102)/θ) E(X) = 100*CDF(-0.728) + 102*CFD(0.728) + 2.747*PDF(-0.728) E(X) = 100*0.233+102*0.767+2.747*0.306 E(X) = 102.3746    The same paper linked in duplicate also has direct formula for variance/stddev of E(X).  Thus, I am only missing a direct "N-stone" formula.  I'll search using recommended search strings - but if that comes up empty, could I just apply the 2-stone solution to N-stone problem iteratively?  So for 4 stones, A, B, C, D; I just compute 2-stone(A,B) to get A', then compute 2-stone(A',C) to get A'', and then compute 2-stone(A'',D) to get 4-stone(A,B,C,D) max-val stats.

I have been reading this  about the maximum and minimum of two normal distributed variables.   Inside the paper there is the formula for the expectation of this the maximum of the two variables. It is given below:  $$ \DeclareMathOperator{\E}{\mathbb{E}}    \E(X) = \mu_1 \Phi\left( \frac{\mu_1-\mu_2}{\theta} \right) + \mu_2 \Phi\left( \frac{\mu_2-\mu_1}{\theta} \right) + \theta \phi\left( \frac{\mu_1-\mu_2}{\theta} \right) $$  Where:   $\mu_1$ is the mean of the first normally distributed random variable. $\mu_2$ is the mean of the second normally distributed random variable. $\Phi$ is the CDF of the standard normal. $\phi$ is the PDF of the standard normal. $\rho$ is the correlation co-efficient between the variables.  $\theta$ is $\sqrt{\sigma_{1}^2 + \sigma_{2}^2 + 2\rho\sigma_{1}\sigma_{2}}$     I am trying to use this to get the mean of the new distribution but I run in to what feels like an obvious problem.  If $\mu_{1} \neq \mu_2$ then the argument to the $\Phi$ function in either the first or second term of the sum will be negative. The standard CDF does not allow negative values‽   I feel like I have fundamentally misunderstood something here. Where have I gone wrong?


I was wondering if SO could have a mailing feature. Yes it is not a social site, but then there are times, when a piece of code is just too large, or when a portion of code alone may not be shared, because its interlinked with other classes. It really becomes easy sharing a file to a single user or may b multiple through mails instead of dumping code on pastebin. I don't know if thats a valid reason really to have a mail feature, but it's  worth it. What say ?

There has been quite a few times that I wished I could send a message to another user on SO - not ask a question for everyone to see, but just a short message informing them of something or requesting them to do something.  Are there any plans to allow this to happen in the future?  Related:


This thing ran out of the wall of my dorm hallway. It had a lot of what look like antennae, and it's very fast.    (click to enlarge)

I found this animal, which I suspect it's an insect, on the floor of a kitchen in Spain some days ago. It's about 8-10 mm long. I don't think I've ever seen it before. What is it?


I have an Ubuntu source on a flash stick and I want to know any way that let's me to know the following with out need to run it. The test computer is Windows 7:  1- the version of Ubuntu. 2- 64 bit or 32 bit.

How can I determine which architecture (x86 or x64) my Ubuntu installation medium is for?  I don't have it installed, I just need to know which files on the installation media I can use to determine the architecture.


How can I prove the following statements are equivalent using laws of set theory?  $\neg((A\cap B)\cup (\neg A \cap C)) = (A\cap\neg B)\cup (\neg A\cap \neg C)$  Using De Morgans laws to simplify the first statement:  $(\neg A\cup\neg B)\cap (A \cup \neg C)$ but I have no idea where to go from here.

How can I prove the following statements are equivalent using laws of set theory?  $\neg((A\cap B)\cup (\neg A \cap C)) = (A\cap\neg B)\cup (\neg A\cap \neg C)$  I managed to use De Morgans laws to simplify the first statement down to:  $(\neg A\cup\neg B)\cap (A \cup \neg C)$ but I have no idea where to go from here.


Let$\{x_n\}$ be a sequence such that there exists a $0<C<1$ such that    $$|x_{n+1} - x_n | \le C|x_n - x_{n-1}|.$$   Prove that $\{x_n\}$ is Cauchy. Hint: You can freely use the formula (for $C \not=1$)    $$1+C+C^2+...+ C^n = \frac{1-C^{n+1}}{1-C}.$$   Let $x_n - x_{n-1} = y_n$. Then, $\frac{|y_{n+1}|}{|y_n|}\le C < 1$. This implies that $y_n$ converges to $0$ by ratio test. I also have the theorem that $y_n$ converges iff $y_n$ is Cauchy. But, I think that this does not mean $x_n$ is Cauchy. Could you give me some help? How can I use the hint given?

Let $\{x_n\}$ be a sequence such that there exists a $0 < C < 1$ such that $$|x_{n+1} - x_n| \le C |x_n - x_{n-1}|.$$  Prove that $\{x_n\}$ is Cauchy. Hint: You can freely use the formula (for $C \not = 0$) $$1+C+C^2+...+C^n = \frac {1-C^{n+1}}{1-C}.$$  My attempt : $\frac {|x_{n+1} -x _n|}{|x_n - x_{n-1}|}<C$. Then, $\frac {|x_{n+1} -x _n|}{|x_n - x_{n-1}|}<1$. So, I thought that it goes to zero as $n \to \infty$ because the difference between $x_n$ and $x_{n+1}$ is getting smaller as $n \to \infty.$ But, I don't know how to use the hint in the question, and how to write the answer properly.  Could you give some hint?


While coding, i faced a problem in resolving variables in a code similar to the code below:   function foo(callback) {      callback();  }  foo( function(parameter) {       // how variables are resolved here? what is the outer scope?        console.log('helloWorld');  });    The questions are:  how variables are resolved inside the anonymous function defined in foo parameters spot?  I know that javascript resolve variables using the lexical scope, but in that function, what is the outer scope ?

What is the scope of variables in javascript? Do they have the same scope inside as opposed to outside a function? Or does it even matter? Also, where are the variables stored if they are defined globally?


In all the examples of SSB in our course/the books (even in our SUSY course) we have just looked at minima of the scalar potential.  Why do we restrict ourselves to the scalars, why not also minimise the fermions and vector bosons?

In quantum field theory, scalar can take non-zero vacuum expectation value (vev). And this way they break symmetry of the Lagrangian. Now my question is what will happen if the fermions in the theory take non-zero vacuum expectation value? What forbids fermions to take vevs?


I have been playing a survival world with my friend for a while. The only thing we haven't done, is find the Mineshaft. So, what is the best way to find a Mineshaft, while avoiding the anoyying Cave Spider Spawners.

, and one place I'm fairly sure I can find them is a mineshaft.  Which leaves me back at square one, how do I find a mine shaft?  It seems they were made substantially harder to find between 1.8 and 1.0.  What's the fastest way to find a mineshaft?


Here I have this shape with 2 concave angles and I want to sharpen them without affecting the surrounding loops. I dont want to use crease or edge split because it create a 100% sharp edge which I dont want.

How can I use the subdivision surface modifier to create more high poly meshes without ruining sharp edges? For example this mesh  The sphere should be subdivided but the rim of the cylinder should stay the same because it is a sharp edge. This is the result of the subdevision  How can I get sharp edges to not be affected by the sub surf mod?


One of my friend had just given me an inequality to solve which is stated below.   Consider the three positive reals $a, b, c$ then prove that      $$a+b+c\le \frac {a^3}{bc} + \frac {b^3}{ac} + \frac {c^3}{ab}$$   I have solved this inequality very easily using Muirhead. But my friend has no idea what Muirhead inequality is. So I want to know whether there is any other method to solve this problem except for Muirhead's inequality.

How to prove this for positive real numbers? $$a+b+c\leq\frac{a^3}{bc}+\frac{b^3}{ca}+\frac{c^3}{ab}$$  I tried AM-GM, CS inequality but all failed.


I want to change the email address that I am using to sign in using the Stack Exchange. I tried editing and updating my email address on my profile and saving the changes to all my accounts. Then, I removed the Stack Exchange account from my logins and added it again. But, still it's using my old email address to sign in! Is there any direct way to change the email address for Stack Exchange Account?

How can I change my login email address for Stack Overflow?   I tried editing from my account, but that didn't work if I used that email during login.


I need to show that if all row-sums of a square matrix $A$ are equal to $0$, then the matrix is singular.  My idea was that to represent the situation, I can do as follows:  $$A\vec{x} = \vec{0}$$  and let $\vec{x} = \vec{u} = \begin{pmatrix} 1_1 \\ 1_2 \\ \vdots \\ 1_n\end{pmatrix}$, since   $$\begin{pmatrix} a_{11} & a_{12} & \cdots & a_{1n} \\ a_{21} & a_{22} & \cdots & a_{2n} \\ \vdots & \ddots \\ a_{n1} & a_{n2} & \cdots & a_{nn} \end{pmatrix} \begin{pmatrix} 1_1 \\ 1_2 \\ \vdots \\ 1_n\end{pmatrix}  = \begin{pmatrix} 0_1 \\ 0_2 \\ \vdots \\ 0_n\end{pmatrix}$$ which would mean that the null-space of $A$ is non trivial (i.e. it contains other objects rather than just the $\vec{0}$), in fact it contains also $\vec{u}$.  Does this fact alone proves what I wanted to prove?

Suppose that each of the row sums of an $n\times n$ matrix $A$ is equal to zero. Show that $A$ must be singular.  I can show this for $2\times2$ by using the fact that $det(A)=0$, whenever $A$ is singular. But do not know how to make it valid of for all square matrices.  Thanks!


If there is a string initialized in python:  s="SLICE"   When trying to run this code:  print(s[4::-1])    #Line-1 print(s[4:-1:-1])   #Line2   I thought both are the same thing and give the same output. Instead, Line 1 outputs as expected but Line 2 does not.

I need a good explanation (references are a plus) on Python's slice notation.   To me, this notation needs a bit of picking up.   It looks extremely powerful, but I haven't quite got my head around it.


In i3blocks, I have defined a block like this: ~/.config/i3blocks/config: [test] interval=persist format=json  The corresponding executable script: ~/.config/i3blocks/config.scripts/test: #!/usr/bin/python  from time import sleep  while True:      print("test")      sleep(5)  I intend to replace "test" with an actual JSON-String later, I just stripped it down to this version for debugging purposes. When I execute this on the command line, test gets printed to stdout every 5 seconds, as expected. I can get the PID with ps aux and check strace: $ sudo strace -p82267 -s9999 -e write strace: Process 82267 attached write(1, "test\n", 5)                   = 5 write(1, "test\n", 5)                   = 5 [...]  ps aux also shows me the other process that i3blocks has started. strace with that process gives me no output, and I don't understand why. The loop seems to be running, but there is no stdout. To verify this, I removed the loop and restarted i3blocks, and the process is not listed anymore. Why is there no stdout when i3blocks starts the process, and what can I do about that? Edit: I let it run for a long while and just noticed: strace shows me that a whole bunch of text was dumped to stdout all at once: $ sudo strace -p79878 -s9999 -e write strace: Process 79878 attached --- SIGSTOP {si_signo=SIGSTOP, si_code=SI_USER, si_pid=79873, si_uid=1000} --- --- stopped by SIGSTOP --- --- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=79873, si_uid=1000}  write(1, "test\ntest\n[...a big big block of output here...]test\ntest", 8194) = 8194  The SIGSTOP and SIGCONT also happened several times. So it seems like the output is stored in some buffer for very long, and then dumped to stdout all at once at some point. What can I do about that?

When trying to write the stdout from a Python script to a text file (python script.py > log), the text file is created when the command is started, but the actual content isn't written until the Python script finishes. For example:  script.py:  import time for i in range(10):     print('bla')     time.sleep(5)   prints to stdout every 5 seconds when called with python script.py, but when I call python script.py > log, the size of the log file stays zero until the script finishes. Is it possible to directly write to the log file, such that you can follow the progress of the script (e.g. using tail)?   EDIT It turns out that python -u script.py does the trick, I didn't know about the buffering of stdout.


Why is it that the dot product of two vectors $u_1=(a, b, c)$ and $u_2=(x, y, z)$ plays out like this: $u_1 \cdot u_2 = ax+by+cz$. I have seen and understand why this is the case for 2D but why is it the case for 3D? I though the dot product is $|u||v|\cos \theta$? This would result in $\sqrt{a^2+b^2+c^2} \sqrt{x^2+y^2+z^2} \cos \theta$. Are they the same? Edit: Again, I have seen the proof for the second dimension but I have not seen any proof for the equation $u_1 \cdot u_2 = ax+by+cz$. Can anybody guide me? Also, does this apply in all dimensions?

Geometrically the dot product of two vectors gives the angle between them (or the cosine of the angle to be precise). Algebraically, the dot product is a sum of products of the vector components between the two vectors.  However, both formulae look quite different but compute the same result. What is an easy/intuitive proof showing the equivalence between the two definitions?  I.e., demonstrate that $a_x b_x + a_y b_y + a_z b_z = \lvert a \rvert \lvert b \rvert \cos{\theta}$


Let X = (X1, X2) be normally distributed random variables with mean m = (m1, m2) and covariance matrix S. Y = max(X1, X2) = X1 + max(0, X2 - X1) = X1 + D (X2 - X1), where D = 1 if X2 > X1 and 0 otherwise (bivariate). What are E(Y) and Var(Y)? What if X1 and X2 are independent and what if X2 = c, a constant? Thank you for sharing your brilliant insights into these matters!

Say I have two standard normal random variables $X_1$ and $X_2$ that are jointly normal with correlation coefficient $r$.   What is the distribution function of $\max(X_1, X_2)$?


Whenever I remove my headphone, my MacBook pro mid 2012 (macOS Mojave, 10.14.5) defaults to "Digital Out — Optical digital-out port" (and the port is usually "red" -digital out light), but sometimes it doesn't show it [usually when sound is not playing]) which is not OK since it should be "Internal Speakers — Built-in".     I've tried these terminal commands and they don't work.   sudo pkill coreaudiod sudo killall coreaudiod   Are there similar commands to redirect the automatic "Digital Out" setting?   The only fix I found so far for that bug, is to blow air inside the jack for ~5-10 seconds and then I have access to my speakers again... weird.

My Macbook (the unibody aluminum version) has lost its internal speakers. When I open System Preferences -> Sound -> Output, all I see is "Digital Out". If I plug in a pair of headphones, this switches to "Headphones". I don't see "Internal Speakers" at all any more. Headphones seem to work fine.  In System Profiler -> Audio -> Available Devices, I do see "Speaker: Connection: Internal".   I just clean-installed Snow Leopard, so it appears to be a hardware problem.  Is there anything I can do to fix this, short of taking it back to Apple? It's out of warranty.


Currently I'm having this code:       <div id="groups">         <select multiple="multiple" id="availableGroups" name="availableGroups">           <option >Opt 1</option>           <option >Opt 2</option>         </select>     </div>   The "select" element has a click event listener which attach to it.   What I'm to do is to change the $('div#groups') content with <p> element when the user click next button, so I do like this:  var $groupContent=$('div#groups').children(); //save the content $('div#groups').html($("<p>").append("Opt 1"))   And if the user click the prev button,I will restore the "select" element like this:   $('div#groups').append($groupContent);   The problem is the click event listener also has been remove when I'm using .html() as stated on this   So the question is,is there a workaround I can implement same action like .html() without removing the event listener?

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.


In D&D 4e (4e PHB pg.288) you can Delay, which allows you to save all your actions for a later time, coming back into the Initiative Order "After any other combatant has completed a turn."  Is there a similar mechanic in D&D 5e? I know about being able to "Ready" (5e PHB pg.193), which is similar to 4e's "Ready An Action" option. My players want a similar Delay ability in 5e, but there doesn't appear to be anything specific in the rules. Is there something I've missed?

In D&D 4e there was an option to Delay your initiative:     Perform your actions as desired and adjust your initiative to your new   position in the order.   Does this rule to change initiative order still exist in 5th edition? I cannot find it in the PHB.


To reiterate: Why does array_name[index] == index[array_name] in C++?  I am struggling to find anything online that explains why you can reference an element like this in C++. I have a java background and do not understand the nuances of C++ that well.  Here is an example illustrating the question:  #include <iostream>  using namespace std;  int main() {     int data[3] = {1, 2, 3};     if (data[2] == 2[data])     {         cout << "equal" << endl;         cout << data[2] << ", " << 2[data] << endl;     }     else     {         cout << "not equal" << endl;     } }   Output:  equal 3, 3

As Joel points out in , in  (aka: K & R), there is mention of this property of arrays in C: a[5] == 5[a]  Joel says that it's because of pointer arithmetic but I still don't understand. Why does a[5] == 5[a]?


I've had two Android phone up til now (HTC Wildfire and SGS2). Sometimes they crashed and the only way to get them restart was to remove the battery. Now I'm thinking about buying a Sony Z1 Compact. Removing the battery is no longer something you can do without tools, and looking at youtube videos I think I will never do this.  Now I'm wondering - in those cases where a phone does not react anymore, how can you reboot the phone if you cannot remove the battery? Waiting until the batter is dead is one option, but that could take a day or longer, and is no option either. Or was I too impatient and is it just a matter of waiting?   In short: Is it always possible to reboot the phone without removing the battery?  There are many phones out there with a fixed battery, so I'm not the first with this problem. What are your experiences?

I'm planning to buy my first android phone which has non-removable battery. But in case the phone hangs what to do ? As in general case we remove the battery from the device and plug it in after a few seconds. But what can be done with non-removable device in cases where the phone just stops to responds and even refuses to restart ?


Consider the integral  $$I(m,n):=\int_0^{\infty} \frac{x^m}{x^n+1}\,\mathrm dx$$  For $m=0$, a general formula is $$I(0,n)=\frac{\frac{\pi}{n}}{\sin\left(\frac{\pi}{n}\right)}$$  Some other values are $$I(1,3)=\frac{2\pi}{3\sqrt{3}}$$ $$I(1,4)=\frac{\pi}{4}$$ $$I(2,4)=\frac{\pi}{2\sqrt{2}}$$  For natural $m,n$ the integral exists if and only if $n\ge m+2$.      Is there a general formula for $I(m,n)$ with integers $m,n$ and $0\le m\le n-2$ ?

I've been looking at  $$\int\limits_0^\infty  {\frac{{{x^n}}}{{1 + {x^m}}}dx }$$  It seems that it always evaluates in terms of $\sin X$ and $\pi$, where $X$ is to be determined. For example:  $$\displaystyle \int\limits_0^\infty  {\frac{{{x^1}}}{{1 + {x^3}}}dx = } \frac{\pi }{3}\frac{1}{{\sin \frac{\pi }{3}}} = \frac{{2\pi }}{{3\sqrt 3 }}$$  $$\int\limits_0^\infty  {\frac{{{x^1}}}{{1 + {x^4}}}dx = } \frac{\pi }{4}$$  $$\int\limits_0^\infty  {\frac{{{x^2}}}{{1 + {x^5}}}dx = } \frac{\pi }{5}\frac{1}{{\sin \frac{{2\pi }}{5}}}$$  So I guess there must be a closed form - the use of $\Gamma(x)\Gamma(1-x)$ first comess to my mind because of the $\dfrac{{\pi x}}{{\sin \pi x}}$ appearing. Note that the arguments are always the ratio of the exponents, like $\dfrac{1}{4}$, $\dfrac{1}{3}$ and $\dfrac{2}{5}$. Is there any way of finding it? I'll work on it and update with any ideas.    UPDATE:  The integral reduces to finding   $$\int\limits_{ - \infty }^\infty  {\frac{{{e^{a t}}}}{{{e^t} + 1}}dt} $$  With $a =\dfrac{n+1}{m}$ which converges only if   $$0 < a < 1$$  Using series I find the solution is     $$\sum\limits_{k =  - \infty }^\infty  {\frac{{{{\left( { - 1} \right)}^k}}}{{a + k}}} $$


What is the reasoning by which people decided not to use ’s to indicate the possession of pronouns?  For example, one might write   It is Jack's dog. The dog is Jack's.   But not   It is their dog. The dog is their's.   Why does using a pronoun not follow the same apostrophe-s pattern as used for the noun it replaces?

Where did the practice of using apostrophes for possessive nouns but not pronouns originate?  For example, possessive nouns (both proper and common) are written with a apostrophe before the final s:        Bill’s, not Bills   Sarah’s, not Sarahs   the bear’s, not the bears   the lizard’s, not the lizards      On the other hand, several possessive pronouns do not have apostrophes before the s:        his, not hi’s   hers, not her’s   its, not it’s   theirs, not their’s   ours, not our’s   yours, not your’s      When and where did this usage originate? Was there any technical advantage of this usage?


i want to use good and stable and fast and updated version of ubuntu also able to install new versions of python library and all required program in my master study like new version of tensorflow and so on

What are the differences between an Ubuntu Long Term Support release (LTS) and a normal release?


So the question is how can I prove that for any 2 Sets, A and B, the symmetric difference between the power set of A and the power set of B IS NOT equal to the powr set of A symmetric difference B. 𝑃(𝐴) Δ 𝑃(𝐵) ≠ 𝑃(𝐴 Δ 𝐵) I have been stuck on this question for a while and I can't find a way to prove it.


Should kenward-roger degrees of freedom correction be used with generalized linear mixed models fitted with penalized quasilikelihood/"PQL"? There's no reason it isn't implementable but the question is whether this provides any advantage for making inferences.

Is it beneficial/possible regarding inferences to use kenward-roger standard errors in generalized estimating equations? I know kenward-roger is used with mixed-effects model when we have n<<p and can't estimate the degrees of freedom correctly as a competitor to REML. Does kenward-roger apply to generalized estimating equations or only gls and lme?


I've seen , but there seem to be no proper solution.  I suggest an ability to insert a "Let us continue this discussion in chat" comment before the thread gets messy enough to fit the requirement. The point is to prevent the problem before it occurs.  Perhaps this should become a privilege for users of X reputation or more?  Your opinions on the subject?

Question: For an answer on a stack exchange site with say 8 comments, how can I / is it possible to import the comments into a chat room? Background: I was helping with a  and made several comments before I saw the link to auto-import comments into a chat room.  This was awesome by the way!! Note that the person who asked the question left a link to the chat room in a comment. I wanted to make a similar chat room  because I edited an answer which wasn't mine and added a paragraph.  I wanted to chat with the answer's author @JonHopkins to say, 'hey feel free to remove my edit -- just wanted to add my $0.02' -- especially as the stack exchange engines said not to add an additional answer.  HOWEVER, there was no link to auto-import the comments -- probably because I hadn't previously left one, but I'm not sure. So I ask here, Stack Exchange Gurus, could a static link be added to auto-import a series of comments into a chat session?


I have been trying lately but I just can't find where is the null object, help me understanding this error: 2021-01-24 01:10:47.244 24211-24211/com.salmanibrahim.firebasechat E/AndroidRuntime: FATAL EXCEPTION: main     Process: com.salmanibrahim.firebasechat, PID: 24211     java.lang.NullPointerException: Attempt to read from field 'java.lang.String com.salmanibrahim.firebasechat.model.User.name' on a null object reference         at com.salmanibrahim.firebasechat.ui.UserProfileFragment.setupArrayListInfo(UserProfileFragment.java:243)         at com.salmanibrahim.firebasechat.ui.UserProfileFragment$1.onDataChange(UserProfileFragment.java:93)         at com.google.firebase.database.Query$1.onDataChange(Query.java:189)         at com.google.firebase.database.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:75)         at com.google.firebase.database.core.view.DataEvent.fire(DataEvent.java:63)         at com.google.firebase.database.core.view.EventRaiser$1.run(EventRaiser.java:55)         at android.os.Handler.handleCallback(Handler.java:808)         at android.os.Handler.dispatchMessage(Handler.java:101)         at android.os.Looper.loop(Looper.java:166)         at android.app.ActivityThread.main(ActivityThread.java:7529)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:245)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:921)  (UserProfileFragment.java:243) Configuration userNameConfig = new Configuration(USERNAME_LABEL, myAccount.name, R.mipmap.ic_account_box);  (UserProfileFragment.java:93) setupArrayListInfo(myAccount);   The app runs correctly, login is succesfull but as soon as code reaches this point: if (listFriendID == null) {             listFriendID = new ArrayList<>();             dialogFindAllFriend.setCancelable(false)                     .setIcon(R.drawable.ic_add_friend)                     .setTitle("Fetching Friends Data...")                     .setTopColorRes(R.color.colorPrimary)                     .show();             getListFriendUId();         }  Dialog Appears correctly but when it ends loading the app crashes then and there. Implementation for getListFriendUId();: private void getListFriendUId() {         FirebaseDatabase.getInstance().getReference().child("friend/" + StaticConfig.UID).addListenerForSingleValueEvent(new ValueEventListener() {             @Override             public void onDataChange(DataSnapshot dataSnapshot) {                 if (dataSnapshot.getValue() != null) {                     HashMap mapRecord = (HashMap) dataSnapshot.getValue();                     Iterator listKey = mapRecord.keySet().iterator();                     while (listKey.hasNext()) {                         String key = listKey.next().toString();                         listFriendID.add(mapRecord.get(key).toString());                     }                     getAllFriendInfo(0);                 } else {                     dialogFindAllFriend.dismiss();                 }             }              @Override             public void onCancelled(DatabaseError databaseError) {             }         });     }  I just can't figure out, where to look for error.

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?


I just grabbed this picture from Site Analytics/Traffic Sources of :    What strikes me as peculiar is that visits from all sites except Google are either 274 or a multiple of it (274 \times 3 =822).   Is this a default value when traffic is too low or non-existent? Or...?

The analytics for the beta site I moderate (Lego Answers) provides unreliable search keywords.  The first ten or so results are unique, but every search keyword after has 41 views, and there are hundreds of results with supposedly '41' views. Some of the referring sites also have 41 views.  Something doesn't seem right. I can understand each search keyword having one or two visits each.  See Also:


I've been setting up my environment on a fedora 20 64bit, the last week. After a restart tonight I am unable to boot into my system. It boots into this terminal/prompt and it says:   [ Minimal bash-like editing is supported. For the first word, TAB lists possible completions of a device/filename. ]  grub>   I've tried to rescue the system, with the dvd, but no luck. I have installed a lot of software and I would rather not have to do it for the third time this week, last crash was because I installed grub2 and made some configurations, to include xen hypervisor support in the bootup  forgetting to turn "Secure boot" off in the bios.  Can anyone tell me what to do? What I can do.

So I started out with a 250GB HDD, the stock drive from an EeePC 1015pem that I am trying to turn into a MintBook. The drive is physically operable, but all data has been nuked, including the old OS. Given this, I attached the HDD to my desktop and installed Linux Mint 16 Xfce from a live USB created through Unetbootin-585. Set aside 10GB for swap and 240GB for ext4 and /.  The drive now refuses to boot for either the desktop or netbook. Both motherboards are sounding the correct sequence of beeps, so they seem healthy, and I can successfully access the BIOS on both systems. However, the only thing that comes up after starting the computer is a nonresponsive command-line. There is no error message, no grub or grub-rescue, nothing.  Is there anything I can try besides reformatting and starting over? How would I go about installing a boot loader that can boot my OS?


Lets say I'm using atan2 to get the angle between two vectors.  atan2 gives a value in radians. I convert it to degrees using a built in function in Java. This gives me a value between 0 and 180 degrees or between 0 and -180 (the nature of atan2).  Is there a way to convert the value received with this function (after it's been converted to degrees), to the standard 360-degree-system, without changing the angle - only the way it's written? It would make it easier for me to work with.  Thanks

I know that atan2 gives me the absolute angle of any vector. But it doesn't give a value from 0 to 360 degrees. Instead, it gives a value (if I'm not mistaken), between 0 and 180, or between 0 and -180. For example, instead of giving angle 270, it will say -90.  This is a little confusing for me. Let me try to describe how I think this works, and please tell me if I'm correct. Actually, I'll draw it.    Is this correct? I'm having a little trouble understanding this. Thanks


Though it is a really simple question, I am stuck in explaining myself where I break the rules. $$\sqrt{-3}\sqrt{-3} = i^2\sqrt{9}=-3=(-3)^{\frac{1}{2}}(-3)^{\frac{1}{2}} = (-3)^{\frac{1}{2}+\frac{1}{2}}=-3$$ but in the next one, there's something wrong and I do not understand what it is: $$(-3)^\frac{1}{2}(-3)^\frac{1}{2}=((-3)(-3))^\frac{1}{2}=\sqrt{9}=3$$ That is, why cannot I get the product of the bases since I have the same exponent?

I know there must be something unmathematical in the following but I don't know where it is: \begin{align} \sqrt{-1} &= i \\\\\ \frac1{\sqrt{-1}} &= \frac1i \\\\  \frac{\sqrt1}{\sqrt{-1}} &= \frac1i \\\\  \sqrt{\frac1{-1}} &= \frac1i \\\\  \sqrt{\frac{-1}1} &= \frac1i \\\\  \sqrt{-1} &= \frac1i \\\\  i &= \frac1i \\\\  i^2 &= 1 \\\\  -1 &= 1 \quad !!? \end{align}


I am new in concurrency in Java, but I have problems in understanding the work of the executor service.   My problem: I'm executing below code separately and I wonder that array of threads faster then executor service (3s vs 30s, by System.currentTimeMillis()).  public class SimpleExample { private static final int THREAD_COUNT = 10; private final AtomicInteger cnt;  private SimpleExample() {     cnt = new AtomicInteger();     cnt.set(0); }  public static void main(String[] args) throws IOException, InterruptedException {     // threads();     // service(); }  private static void threads() throws InterruptedException {     SimpleExample example = new SimpleExample();     ParallelTask task = new ParallelTask(example);     Thread[] threads = new Thread[THREAD_COUNT];     for (int i = 0; i < threads.length; i++) {         threads[i] = new Thread(task);     }      long a = System.currentTimeMillis();     for (Thread thread : threads) {         thread.start();     }      for (Thread thread : threads) {         thread.join();     }     System.out.println("time: " + (System.currentTimeMillis() - a)); }  private static void service() {     SimpleExample example = new SimpleExample();     ParallelTask task = new ParallelTask(example);     ExecutorService service = Executors.newFixedThreadPool(THREAD_COUNT);      long a = System.currentTimeMillis();     Future future = service.submit(task);     while (!future.isDone()) {         // do nothing     }     service.shutdown();     System.out.println("time: " + (System.currentTimeMillis() - a)); }  void run() {     while (cnt.get() < 300) {         try {             Thread.sleep(100);             System.out.println(cnt.get());             cnt.incrementAndGet();         } catch (InterruptedException ignore) {}     } }  static class ParallelTask implements Runnable {     private final SimpleExample example;      ParallelTask(SimpleExample example) {         this.example = example;     }      @Override     public void run() {         example.run();     } }   }  How it's possible? Thanks.

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