Why do some AC adapters and power supplies generate a whining noise, and what can I do about it?

I have many different AC adapters and power supplies for a variety of devices, ranging from small 5V/1A USB chargers to laptop power adapters and desktop PSUs. However, I often hear a whining noise from  some of these power supplies. This happens most often when they are not connected to a device or otherwise in use, and stop making noise when I connect a load to it such as by plugging in a device that is not fully charged.  Why do some AC adapters and power supplies make this whining noise? Why do some not make this noise? Is there anything I can do to suppress it?


How to install Ubuntu OS on a Windows 7 OS PC and use both of them?

How can I install the Ubuntu OS on a PC running Windows 7?  Is it possible to use both Ubuntu and Windows 7 at the same time?  Can I return back to Windows 7 later on?


I have a trip next month to Moscow. I am flying to LGA and have 2.5 hours to switch to JFK before my departure on Aeroflot to Moscow. Is that enough time to switch airports?


Is there a keyboard shortcut to enable/disable hidden files in Finder?

Is there an easy way to show and then hide and then show and then hide (as in toggle) “hidden” files in macOS High Sierra?  I’ve found I can use the following terminal commands to show them:   defaults write com.apple.finder AppleShowAllFiles TRUE   killall Finder  and then use these terminal commands to hide them:  defaults write com.apple.finder AppleShowAllFiles FALSE   killall Finder  but this is clumsy!  I then came across  which allows me to do this at will, but unless I want to keep it open, it’s not a good option because it takes forever to launch!  I did check the list of keyboard shortcuts at  in the hope it may be that simple, but no go.  What is the absolute easiest way to enable/disable this option? If there's no keyboard shortcut, what's the next best option?


How to load a raster layer at the top of the QGIS ToC?

The following code inserts my new_layer just above the active layer in the QGIS ToC.  new_layer = iface.addRasterLayer(...)    Instead, I'd like my new_layer to be inserted at the top of the QGIS ToC.   Do you know how can I do it?


Prove or find a counter example to the claim that for all sets A,B,C if A ∩ B = B ∩ C = A ∩ C = Ø then A∩B∩C ≠ Ø

This is a homework question of mine that Ive answered and I'd really like some feedback on my solution.       Prove or find a counter example to the claim that for all sets $A,B,C$, $$\text{if  }A\cap B=B\cap C=A\cap C=\emptyset \text{ then } A\cap B\cap C\neq \emptyset$$.   Since I can only either prove it is true, OR find a counter example I have gone with the latter because I think this statement is not true. My counter example is as follows:  Let $A = \{1,2,3 \}$ , $B = \{4,5,6 \}$ and $C = \{7,8,9 \}$. It is then clear that $A ∩ B =  B ∩ C =  A ∩ C = \emptyset$ .  If we let $x ∈ A\cap B\cap C$ then $x$ must be in $A$ and $B$ and $C$. Since this cannot be possible because there are no common elements then this implies that $A∩B∩C$ has to be equal to a null set i.e $A∩B∩C = \emptyset$ and thereby showing that (at least for this scenario) if $A \cap  B =  B \cap  C =  A \cap  C = \emptyset$ then $A\cap B\cap C = \emptyset$.  Is this okay? Any feedback will be greatly appreciated thank you!


I delete C:\Windows\SystemApps\Microsoft.MicrosoftEdge_8wekyb3d8bbwe but it remain on the all apps list. It didn't work but I want to remove it too.


Trying to attach a file from SD Card to email

I am trying to launch an Intent to send an email. All of that works, but when I try to actually send the email a couple 'weird' things happen.  here is code   Intent sendIntent = new Intent(Intent.ACTION_SEND); sendIntent.setType("image/jpeg"); sendIntent.putExtra(Intent.EXTRA_SUBJECT, "Photo"); sendIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("file://sdcard/dcim/Camera/filename.jpg")); sendIntent.putExtra(Intent.EXTRA_TEXT, "Enjoy the photo"); startActivity(Intent.createChooser(sendIntent, "Email:"));   So if I launch using the Gmail menu context It shows the attachment, lets me type who the email is to, and edit the body & subject. No big deal. I hit send, and it sends. The only thing is the attachment does NOT get sent.  So. I figured, why not try it w/ the Email menu context (for my backup email account on my phone). It shows the attachment, but no text at all in the body or subject. When I send it, the attachment sends correctly. That would lead me to believe something is quite wrong. Do I need a new permission in the Manifest launch an intent to send email w/ attachment? What am I doing wrong?


Is there any evidence of black holes existing?

Yes, I am aware of observations of "massive objects", for example near the center of the galaxy. But is there any evidence that the object in question is a black hole, with all its commonly attributed properties? Or are black holes just an unconfirmed artifact of general relativity, i.e. something that is an abstract mathematical concept and not a real object?  I am not asking about means of detecting them, I am aware of those means. I'm interested if there's anything suggesting that the properties commonly attributed to black holes, considered a "fact", other than large mass, have anything to do with reality, or are completely abstract and deduced from math.


Is it more acceptable to list interview talks on CV if they're also part of a seminar series?

Consider someone invited on a job interview (in the sciences) at a university or a national lab or something of that sort with a regular seminar series. As part of the interview, the person is asked to give a talk as part of the seminar series.  Is that appropriate for inclusion on the CV as an invited talk?  I saw one related question to this but it was different enough that it didn't really answer my question:   However, the thread really just has a couple answers with equal support for opposite positions. The difference here is the distinction that the talk is given as part of an interview but also is part of a regular seminar series. I was wondering if this changed people's feelings on the matter at all.  It seems to me that any other person would list that as an invited talk. It also just seems to get grayed a bit by the fact that it is technically being used as part of a job interview.


I want to solve the following exercise from Durrett:  "Let $X_n, n\geq0$ be a submartingale with $\sup X_n<\infty$. Let $\xi_n = X_n - X_{n-1}$ and suppose $\mathbb{E}\left(\sup\xi^+\right)<\infty$.  Show that $X_n$ converge a.s. "  I am not sure to understand the hypothesis on the increments because I have the feeling that I can solve the exercise without it : $\sup X_n<\infty$ implies that we can find $K$ such that for all integer n $X_n<K$ thus we can consider the submartingale $Y_n = X_n - K$ and since $\sup\mathbb{E}(Y_n^+)=0 < \infty$ by the Martingale convergence theorem $Y_n$ converge a.s and thus $X_n$ too.  Is this correct ?


How can I change the shell to english? (I especially need this for git.)

I'd like to know how I can change my shell language (not the OS) to english. The language I have in my OS windows is German (Switzerland).  Answer: I've put export LC_ALL=C into the hidden ~/.bashrc file as some suggested. This solved my problem.


Block certain script in the Chrome / Chrome DevTools

Is there a way to block, let's say some_script.js from domain.com, but not all of them?


I searched this forum but didn't quite find an answer for my questions. Here is the situation and I really appreciate everyone's help in advance.  I have two passports, calling it A and B. And I booked a flight from home country to Y, with a transit in X. I will stay one night in X so I will need a visa for X.  On my passport A, I have a visa for country X. I could get a visa on passport B as well but it's super time-consuming and it's hard to squeeze in another application between now and travel.  My passport A does not get me into country Y but my passport B allows me to get into Y without a visa.  So here is what I thought I could do:   Check in at home country with passport A to fly to country X. Enter country X with passport A and visa. Check-in at country X for flight to country Y with passport B. Use passport A to clear immigration when exiting X because Immigration will check my visa and chop it. Use passport B to enter country Y. Direct flight from Y to home country so no more issue.   Does it make sense? A few things I'm not sure:   When I check-in at country X for flight to Y using passport B, will the check-in desk ask questions, since I don't have a visa on B to stay in X. When I exit X with passport A, will immigration ask me for a visa to Country Y since I don't have country Y's visa on passport A? Can I show my passport B to immigration as well?   Thank you!


Is it possible to take a desktop PC as carry-on luggage?

I am moving from Egypt to the Netherlands and I need to take my PC with me. I won't be taking the monitor, just the case, but I'm wondering what the best way would be.  Am considering taking it as carry-on because I'm allowed 8kg and at least then I can handle it myself. Has anyone done this before and can give me tips or warn me that this doesn't work? Would putting it in my normal suitcase as checked baggage be a better idea?


How to download SSH keys in Debian on GCP?

I'm trying to download my SSH keys so that I can use Filezilla to connect to my webserver. This SHOULD be pretty straightforward - but everything I've tried has failed.  I currently have access to the etc/ssh directory through an SSH connection. I can see the files the folder - but I'm unclear which one is the correct key file.  Secondly, how do I download a file through terminal from SSH?  Thanks in advance!


How to SELECT an entire row using MAX()?

So basically I have a table with two fields, 'number' and 'title', and I need a query to select the row with the highest value in 'number', for this i used  SELECT MAX('number') FROM table   Now I need to get the value of 'title' that corresponds to the highest value of 'number'.  How can this be achieved?


How to make a pair of columns unique in mysql

+----+---------------+-------+---------------+ | id |     name      | phone |    ip_addr    | +----+---------------+-------+---------------+ |  1 | customname001 |  1234 | 192.168.100.1 | |  2 | customname002 |  2156 | 192.168.100.2 | |  3 | customname003 |  9685 | 192.168.100.3 | |  4 | customname004 |  1546 | 192.168.100.1 | |  5 | customname005 |  1234 | 192.168.100.1 | +----+---------------+-------+---------------+   In my codeigniter project I am trying to build a model which will help me insert a new row into a table which looks something like the above one. The condition I want to apply here is to check if the combination of name, phone and ip_addr is unique or not.  I know that for a single column if we set the value to be unique then the values can't be repeated but my example is a different case where I want the combination of all the columns(except the id) to be unique.  Can anyone help me here in building the model which will help me to add new pair of name, phone and ip_addr and check if the pair already exists and accordingly give a feedback.


Is it possible to display Swing components in a JSP?

I was wondering if I could pop up JOptionPanes or other Swing components from within a browser using JSP.


checking group of dynamically created checkbox

I am creating group of check boxes dynamically and one extra check box also for selecting all group at once that one too is generated dynamically  this is html output  <input type="checkbox" id="all">all
 <input type="checkbox" name="question">a
 <input type="checkbox" name="question">b
 <input type="checkbox" name="question">c
 <input type="checkbox" name="question">d   this is jquery  $("document").ready(function() {     $("#all").on('change', function() {         if ($(this).is(":checked")) {             $("input[type=checkbox][name=question]").prop('checked', true);         } else {             $("input[type=checkbox][name=question]").prop('checked', false);         }     });       });   this is implementation.   It works fine when checkboxes are not generated dynamically  But when they are generated dynamically code has bug  I am able to check whole group but I am not able to check single checkbox  This is dynamically generated code  $('#demo3').on('change', function() {     if ($('input[type=checkbox]:checked')) {         var value = $('input[type=checkbox]:checked').val();         alert(value);         $("#demo3").hide();          $.getJSON("json/question.json", function(jd) {              var size = jd.length;               var table = "

<input id=\"" + "selectall" + "\" type=\"" + "checkbox" + "\"/>" +                     "	Question	Option A	" + "Option B	Option C	" +                             "Option D	Answer
";               for (var n = 0; n < size; n++) {                   table += "
" + "<input name=\"" + "question" + "\" type=\"" + "checkbox" + "\" value=\"" + jd[n].questionid + "\"/>" +                  "	" + jd[n].question + "	" + "" + jd[n].a + "	" + jd[n].b + "	" + "" + jd[n].c + "	" +                         "" + jd[n].d + "	" + "" + jd[n].ans + "
";               }             table += "
";             $('#demo4').html(table);          });      } });  $('#demo4').on('change', function() {     if ($("input[type=checkbox][id=selectall]").is(":checked")) {         $("input[type=checkbox][name=question]").prop('checked', true);     } else {         $("input[type=checkbox][name=question]").prop('checked',false);     }  });


i am having trouble to get my biblatex to recognize any references. here is the output of a minimal examples i found on the web (others behave similar). can you help me? I am using full Miktex installation (all packages pre-installed), and the results below are same for both TexWorks and TexStudio.   Minimal example taken from    \begin{filecontents}{\jobname.bib} @book{Labov1972,     Address = {Philadelphia},     Author = {William Labov},     Publisher = {University of Pennsylvania Press},     Title = {Sociolinguistic Patterns},     Year = {1972}}  @book{Chomsky1957,     Address = {The Hague},     Author = {Noam Chomsky},     Publisher = {Mouton},     Title = {Syntactic Structures},     Year = {1957}} } \end{filecontents}  \documentclass{article} \usepackage[style=authoryear]{biblatex} \addbibresource{\jobname.bib} \begin{document} Some famous linguists wrote a couple of books \autocite{Labov1972,Chomsky1957}. \printbibliography \end{document}   gives me    instead of     the log says   Citation 'Labov1972' on page 1 undefined Citation 'Chomsky1957' on page 1 undefined Empty bibliography There were undefined references. Please (re)run Biber on the file:(biblatex) spielwiese3(biblatex) and rerun LaTeX afterwards.   The .bib file generated by the second minimal example reads (dunno if this is relevant)  %% LaTeX2e file `spielwiese3.bib' %% generated by the `filecontents' environment %% from source `spielwiese3' on 2018/07/31. %%  @book{Labov1972,   Address = {Philadelphia},   Author = {William Labov},   Publisher = {University of Pennsylvania Press},   Title = {Sociolinguistic Patterns},   Year = {1972}}   @book{Chomsky1957,   Address = {The Hague},   Author = {Noam Chomsky},   Publisher = {Mouton},   Title = {Syntactic Structures},   Year = {1957}} }   Running Bibtex results in  Prozess gestartet: bibtex.exe "spielwiese3"  This is BibTeX, Version 0.99d (MiKTeX 2.9.6500 64-bit) The top-level auxiliary file: spielwiese3.aux I found no \citation commands---while reading file spielwiese3.aux I found no \bibdata command---while reading file spielwiese3.aux I found no \bibstyle command---while reading file spielwiese3.aux (There were 3 error messages)  Prozess endete mit Fehler(n)   as of writing this cry for help i discover that manually running Biber (not Bibtex!) => PDFLatex returns the desired result:    could someone explain me what happens?


round double with N significant decimal digits in an overflow-safe manner

I want a overflow-safe function that round a double like std::round in addition it can handle the number of significant decimal digts.  f.e.  round(-17.747, 2) -> -17.75 round(-9.97729, 2) -> -9.98 round(-5.62448, 2) -> -5.62 round(std::numeric_limits<double>::max(), 10) ...   My first attempt was  double round(double value, int precision) {     double factor=pow(10.0, precision);     return floor(value*factor+0.5)/factor; }   but this can easily overflow.  Assuming IEEE, it is possible to decrease the possibility of overflows, like this.  double round(double value, int precision) {     // assuming IEEE 754 with 64 bit representation     // the number of significant digits varies between 15 and 17      precision=std::min(17, precision);     double factor=pow(10.0, precision);     return floor(value*factor+0.5)/factor; }   But this still can overflow.  Even this performance disaster does not work.  double round(double value, int precision) {     std::stringstream ss;     ss << std::setprecision(precision) << value;     std::string::size_type sz;     return std::stod(ss.str(), &sz); } round(std::numeric_limits<double>::max(), 2.0) // throws std::out_of_range   Note:    I'm aware of setprecision, but i need rounding not only for displaying purpose. So that is not a solution. Unlike this post here  , my question is especially on overflow safety and in C++ (the anwser in the topic above are Java-specific or do not handle overflows)


serious errors were found while checking the disk for /

Ubuntu 14.04 after installation:  serious errors while checking for drive /.


How to align objects side by side with a specified distance between them in Illustrator?

I am creating an animated sprite list in Adobe Illustrator. I finished creating the sprites and used the Horizontal/Vertical Distribute Center commands to distribute the objects equally in some area.  But, if the objects are spread too far apart, the Distribute Center tool leaves, albeit equal, much distance between the objects. The opposite is true: if the objects are too close then distributing them will just overlap them.  My question is, is there any tool that just puts objects side by side?  I imagine that this tool would work if the objects aren't even equal in size.   I have viewed  and answer but it is not what I need.


How to get 3D points of a Mesh in world space coordinates?

I have a blender file with this scene (below) seen from the camera. Now I need to get the 3D points of the mesh (the doughnut) in world space according to the camera perspective, pragmatically. Meaning I need a python script I can run to save a text file with the list of 3D points I need. I also need to know the camera direction vector. I'm using Blender 2.83 and I have python 3.7 installed. Thanks in advance.


A couple of weeks ago I was travelling in a car (120 km/h approximately) and I saw a  flying in front of me (inside the car, near my nose, windows closed). I wonder how was that possible.   Does it mean is really flying at 120 km/h or the fly is being affected by some kind of gravity/force?


What is the ID at the end of the Enterprise SOAP service end point URL?

Is that the Organization Id at the end of SOAP service end point URL? I have checked the organization Id in my salesforce account and this Id did not match with it. Please suggest.  0DF90000000DHQR


Prove that an analytic function with a constant imaginary part is constant itself

I want to prove that if $f$ is an analytic function for which $\Im f$ is constant, this implies that $f$ itself is constant.  So to start off, it's not given that the function is entire or anything, ruling out Liouville. Rather, I'm guessing the maximum modulus theorem will prove useful here (?).  If I were to show using that the real part of $f$ was constant, proving the statement would be easy (just take the absolute value and investigate $e^f$), but in this case I'm none the wiser from that. Should I use the same parametrization $e^f$ and apply the Cauchy-Riemann equations somewhere? Any suggestions welcome.


why the first code gives output as "true" and second code gives output as "false"?  code 1 ...............  String str1="abc";       String str2="abc";    if (str1==str2)       System.out.println("true");   else        System.out.println("false");    code 2   NOTE : Input to both string will be same value  ....................   Scanner sc=new Scanner(System.in);  System.out.println("enter string 1");  String String1=sc.next();  System.out.println("enter string 2");  String String2=sc.next();   if(String1==String2)      System.out.println("true");  else      System.out.println("false");


Name of short story about earthlings trapped on foreign planet

There was a short story I read in 2004 about people from earth trapped on a foreign planet.  General ideas were as follows: people only lived for one week.. They grew quickly over the span of 7 days, people could only go out for 2 hours a day due to extreme temperatures, enemies and friendships were formed quickly...  The narrator is a man and ventures off to find the crashed spaceship (running the whole time to avoid the coming temperature drop). He is accompanied by a woman.. She is his love interest.  He successful saves the stranded civilization and everyone returns to earth. My question is WHAT IS THE NAME OF THE STORY??


Why isn't temperature definable for a single, classical particle?

I read that the relation between temperature and kinetic energy of an ideal gas is only applicable to a large number of particles so that the mean value for kinetic energy has to be considered, so the temperature concept makes sense only as a statistical quantity. But why is that?  Using the aforementioned relation for a single, classical, non-rotating particle, it should always be possible to apply some work on it such that its velocity with respect to the ideal box that contains the particle is zero, hence making the kinetic energy of the particle zero too. But doing so, the temperature obtained is zero kelvin.  This leads to the fact that the temperature to kinetic energy relation only applies to a large number of particles. However, it sounds odd to me. Albeit being highly improbable, such a zero kinetic energy configuration should be possible for a large collection of particles too. This means that temperature is somehow related to entropy, but again, if I'm not wrong, the entropy of such a system is zero.  In conclusion, why is that the temperature for a single classical particle can't be defined? Does it exist a different temperature definition that makes it possible?


Converting from shapefile or raster formats to LAS?

I am looking for a solution to convert either from ESRI shapefile format to LAS or from a common raster format to LAS. I have access to following software:   ArcGIS 10.2 for Desktop (arcinfo with spatial analyst and 3d analyst extensions), Global Mapper, LASTools (unlicensed), QGIS 2.8, Whitebox GAT.   I have the functionality in the LASTools shp2las.exe tool, but as I do not have a licence it can only handle 2 million points before it adds XYZ noise.  Due to the large volume of data I am working with, it is impractical to cut it into thousands of smaller pieces in order to process with tiles under 2 million points.  There was the potential of a workaround using the text2las tool, but outputs from this tool are also unacceptable due to a stepping/contouring effect. Despite efforts to ensure no rounding or truncation of input data occurs during transformation.  Is there a way through open source or free software to successfully convert between these formats?   Or am I looking at buying a licence for FME or LASTools or some other software?


I'm studying cavity QED and I'm confused about Vacuum Rabi Splitting.  Mostly, Vacuum Rabi Splitting has been described when the two-level atom are in the excited state at the beginning with no photon in the cavity, and then it emits the photon with the atom in the ground state.   With interaction hamiltonians, I could see the normal mode splitting, but I wonder why it is called "vacuum" splitting.  I guess it's because there's no photon at the beginning in the cavity so that's why it is called "vacuum" splitting.  What if the atom is in the ground state at the beginning? I guess it is impossible to see normal mode splitting in the cavity without at least a single photon.  So, my question is why this procedure is called "vacuum" splitting even though there is a single photon in the cavity?  Please help me out.


If every ideal is principal show the same is true for the image of a homomorphism.

I was working on a worksheet for class and came across this problem:      Let $\varphi:R\to S$ be an onto ring homomorphism with the property that every ideal of $R$ is principal. Show that the same must be true for $S$.    I honestly do not know how to do this one!


Viber notification is not in the right position

This question is basically the same question as , but the guy there didn't get any answer.   So I am also posting it as I couldn't find any answer anywhere.    As you can see there is a very annoying icon of viber on the top left, that is on top of the exit symbol "x" of the other applications. Is it possible to remove that thing completely, or to move it at the place where the skype or the dropbox is?  I have Ubuntu 14.04 Desktop edition installed.


Triple integration, Spherical coordinates

How do we get limit such as $0\le\theta\le\pi$, $0\le\phi\le2\pi$ in spherical coordinate system where $$x=r \sin\theta\cos\phi, y=r \sin\theta\sin\phi, z=r \cos\theta$$  Why is the $\theta$-limit $[0,\pi]$ and not $2 \pi$?  I think that the angle of the foot of perpendicular from the point taken in spherical coordinate can lie within $[0,2 \pi]$


Prove that $ n^3 + 5n$ is divisible by 6 for all $n\in \textbf{N}$

Prove that $ n^3 + 5n  $ is divisible by 6 for all $ n \in \textbf{N} $.  I provide my proof below.


How does one choose a random isotropic direction and then have the vector have norm 1?

I want to choose a random vector in high dimensions such that it all directions have the same uniform chance (i.e. isotropic in all directions). My current idea is the following algorithm:   sample v from a high dim multivariate Gaussian then normalize that vector by dividing by its norm   I believe this is sufficient but don't know how to prove it. I know that high dimension stats can have weird behaviours (like most of the volume of a Gaussian is at the "edge") so I wanted to make sure I didn't miss anything trivial but important. Anyone know if this is correct? If it is how do I prove it?    What I have in mind in pytorch looks as follows:  v = MultivariateNormal(torch.zeros(10000), torch.eye(10000)) v = v/v.norm(10000)


Connecting Headphone Jack to Amplifier Help

I have this image that is for the amp I am using which allows you to add a headphone jack to it:   I have already hooked up the regular speakers and power to the amp, now I just want to add a headphone jack. It says to wire the grounds from both speakers together, then to the jack, and to wire the left and right audio points to it directly. Can someone explain what the "wire to internal speaker" points mean? I know it sounds simple, but for instance what are the arrows for? They look like diode symbols to me (I thought this because they could have easily done without the arrows).


Showing that in a given set of 7 distinct integers that there must be at least one pair in the set whose sum or difference is a multiple of 10.

Show that, given any set of seven distinct integers, there must be at least one pair in the set whose sum or difference is a multiple of 10. I've been thinking a lot on how to show that this is true, but I've not managed to come up with anything yet. If anyone could offer their viewpoint I'd appreciate it.


"Active bounties" section on user profiles page is borked

The "Active Bounties" section on the user profile page is currently in a font totally different from all the other ones. The awesome-style selection menu has also been converted into an ugly, unstyled combo box.  This looks pretty ugly and should be fixed.


How much of Gandalf's power is tied to his staff?

Before Gandalf freed Théoden from Saruman/Gríma's hold, he refused to give away his staff.      Háma: I cannot allow you before Théoden King so armed, Gandalf Greyhame... by order of Gríma Wormtongue.   [Gandalf nods, and they hand over their weapons]   Háma: Your staff.   Gandalf: Oh... you would not part an old man from his walking stick?     After that, while he was breaking theirs hold on him, Gríma shouted to the guards      His staff! I told you to take the wizard's staff!   But what if he was denied the use of his staff? How much of his power is tied to his staff? Is he harmless/defenseless without his staff? If his staff is taken by an other magically capable being, how much of Gandalf's power would it have?


On which Stack Exchange Q&A sites can I ask about business side of cloud computing?

I would like to ask about business side of cloud computing - trends, business models etc. Which Stack Exchange Q&A site should I go to?


A fantasy novel about protagonist who absorbs gems to fight demons

I'm looking for a fantasy novel that has the back story of having two great elemental magic users (not sure what they are called in the novel).  One can use fire and earth, the other water and air.  They join forces to defeat demons.  The novel starts long after that has ended, and only one remains.  The demons are posing a threat again so the master seeks an apprentice, fusing him with a gem to grant him power.  The gem tries to gain control of the boy, but the boy emerges with the power instead.  It is then learned that the gems are actually technology from a long-lost race, and the demons are actually aliens.


I accidently ran 'sudo chmod -R 775 /' and it completely broke my OS/Shell

So I accidentally did sudo chmod -R 775 / when I meant to do sudo chmod -R 775 ./. I quickly realized and hit Ctrl^C, but not in time to save everything. I realize this is a really stupid mistake and all that but I'm aware of that and I would just like to fix my OS now.  Anyway, this completely broke my OS (Ubuntu 12.04). Currently, several functions of the shell, including tab completion prints the error      bash: cannot create temp file for here   And running any bash command that I have tried on any file in my home (/home/$USER) folder crashes the terminal. Several other random things don't work around the OS now.


How does SSH used for dynamic port forwarding know where a request wants to go?

Dynamic port forwarding using SSH uses SOCKS protocol. How does SSH know where a request wants to go? For example if the request is a HTTP request, SSH doesn't understand HTTP, so where  does it find out where the HTTP request wants to go? Thanks.


What is the dual category of topological spaces?

What is the dual category of topological spaces $Top$?  I know that the order theoretic dual of a topological space is a closed set system rather than an open set system. However, this doesn't answer my question (I think) since it is just a transformation of the objects, and not of the morphisms.  I thought that maybe it would be the same as $Top$ but have morphisms involving closed sets instead of open sets somehow -- however the definition of a continuous function as one for which preimages of closed sets are closed is equivalent to the definition for which preimages of open sets are open, so this doesn't seem to lead anywhere unless $Top$ is self-dual, which seems unlikely.    EDIT: let's see if we can start with a simple example and generalize.  Consider two copies of the real line, one with the discrete topology (call it $A$), and one with the regular Euclidean/metric topology (call it $B$).  The space of continuous functions from $A$ to $B$ is simply the space of all real-valued functions on the real line, i.e. $Hom(A,B)=\{\text{real valued functions on the real line}\}$.  So now for $Top^{opp}$, the dual category to topological spaces, $$Hom^{opp}(B,A)=\{\text{relations whose "inverses" are real valued functions on the real line}\}?$$  (since the range of a function doesn't have to be its codomain).  This is a simple/special case of two objects and their morphisms in $Top^{opp}$, but already the morphisms seem likely to be pretty useless in general since they aren't even functions in general.  Still, now what confuses me is that it seems like this problem wouldn't be unique to defining the dual category of $Top$; any category whose morphisms aren't all invertible would seem to have the same problem. Thus it seems more likely that I am misinterpreting the definitions.     EDIT: I am looking for a more precise definition than given in the answer to this question:    However, it seems that looking at that question (which I couldn't find before asking this one) that there is no simple answer to what the dual category of topological spaces $Top$ is, which perhaps is unsurprising considering how pathological the simple example given above seems to be.  Therefore I am going to vote to close this question as a duplicate.


Prove that all cyclic groups of the same order are isomorphic

I want to prove that 2 cyclic groups of the same order are always isomorph. So, let $G,H$ be cyclic groups with $|G| = |H|$. Then: I suspect the isomorphism would be the one that maps a generator g to a generator h. Thus, consider this function:  $f: G \rightarrow H$ defined by $f(g^k) = h^k$. I already showed that this mapping is surjective and a homomorphism, but I get stuck at the injectivity part. Can someone give a hint (my attempts: I tried to deduce whether the kernel is $e_G$ and I also used the definition of injectivity but I got stuck in both approaches)?


Lenovo Thinkpad E480 - No Wifi Adaptor Found in Ubuntu 18.04

I have recently a purchased Lenovo Thinkpad E480 laptop, I have installed Ubuntu 18.04 on it, everything is working fine except am not able to connect to network via WiFi. Please help.  I followed this , but am unable to solve the issue.  Below are the outputs of some commands.  lsb_release -a  No LSB modules are available. Distributor ID: Ubuntu Description:    Ubuntu 18.04.1 LTS Release:    18.04 Codename:   bionic   uname -r  4.15.0-33-generic   rfkill list all  0: tpacpi_bluetooth_sw: Bluetooth     Soft blocked: no     Hard blocked: no 1: hci0: Bluetooth     Soft blocked: no     Hard blocked: no   lspci -nnk | grep 0280 -A3  05:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8821CE 802.11ac PCIe Wireless Network Adapter [10ec:c821]     Subsystem: Lenovo RTL8821CE 802.11ac PCIe Wireless Network Adapter [17aa:c024] 06:00.0 SD Host controller [0805]: O2 Micro, Inc. SD/MMC Card Reader Controller [1217:8621] (rev 01)     Subsystem: Lenovo SD/MMC Card Reader Controller [17aa:5068]   sudo lshw -C network   *-network                         description: Ethernet interface        product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller        vendor: Realtek Semiconductor Co., Ltd.        physical id: 0        bus info: pci@0000:03:00.0        logical name: enp3s0        version: 10        serial: 8c:16:45:a3:d9:f1        size: 100Mbit/s        capacity: 1Gbit/s        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation        configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168g-3_0.0.1 04/23/13 ip=192.168.2.2 latency=0 link=yes multicast=yes port=MII speed=100Mbit/s        resources: irq:16 ioport:d000(size=256) memory:f1204000-f1204fff memory:f1200000-f1203fff   *-network UNCLAIMED        description: Network controller        product: Realtek Semiconductor Co., Ltd.        vendor: Realtek Semiconductor Co., Ltd.        physical id: 0        bus info: pci@0000:05:00.0        version: 00        width: 64 bits        clock: 33MHz        capabilities: pm msi pciexpress cap_list        configuration: latency=0        resources: ioport:c000(size=256) memory:f1100000-f110ffff   It seems I have to clone, compile and install the required WiFi driver, please guide me which WiFi driver to use and how to install (with steps if possible).  P.S.: Let me know if any further information is needed to solve this issue, I will add the required info (if any) in the question as per the guidance given.


Casting a Somatic, non-Material spell while holding a focus

In  a side issue came up of whether you can cast a spell with Somatic components but no Material components while holding a focus in the hand used for Somatic components.  My reading of the rules sees "A spellcaster must have a hand free to access a spell's material components--or to hold a spellcasting focus--but it can be the same hand that he or she uses to perform somatic components." - it doesn't say you have to be holding the focus for the purpose of avoiding materials.  However, @Adeptus and @enkryptor argue that - since that rule is in the section on Material components - you don't consult it in for spells without Material, and fall back to the Somatic rule "the caster must have free use of at least one hand".  (I also appeal to the logic of fluff - why should it be harder to cast a spell with fewer components?)  Is there an official RAW or Word Of God on this matter? Can you cast a material-less, somatic spell while holding a focus in your only free hand?


How to add a URL to a LaTeX bibtex file?

I'm using bibtex for my bibliography in LaTeX. I have some URL's I need to cite in the paper. How do I add URLs into the .bib file?  A typical section in my .bib file looks like this:  @conference{eigenfacepaper,   title={{Face recognition using eigenfaces}},   author={Turk, M. and Pentland, A.},   booktitle={Proc. IEEE Conf. on Computer Vision and Pattern Recognition},   volume={591},   year={1991} }   I tried some misc sections in bibtex but they don't show up in my document.


I know that this Problem was addressed before but my SQL knowledge is not that good to figure it out. Maybe you can help me.  select      ProductionLine,     Product,      POId,      BatchNumber,      Sum(Prime) as Prime,      Sum(Offspec) as OffSpec,      Sum(InQ) as InQ,      Sum(Prime) + Sum(Offspec) + Sum(InQ) as Total   from @t2   group by      ProductionLine,      BatchNumber,      POId,      Product;   I now need a Column PercentagePrime where the column Prime is defined by the alias Total


alternatives to adding entry in /etc/hosts

I would like to access a remote host using a short name. On a system where I have admin rights, I would achieve this by adding an entry in /etc/hosts file, something like this  121.121.122.1  shortname  Is it possible to achieve this using some other method which does not require modifying /etc/hosts or other admin level or system wide changes?


Children naming system in Naruto universe

Naruto's naming system always confuses me. Naruto is named Uzumaki, after his mother. But Boruto is named Uzumaki, after his father. So whose surname is taken while naming a child in Narutoverse? Are there some governing factors?


How does "dragon branch ads" get installed on a PC?

This annoying app called "dragon branch ads" was installed on my PC and I have no idea how or what installed it on my PC. My question is.. Does anyone know how "dragon branch ads" may have been installed on my PC?   I also read through the question  but could not find any mention of "dragon branch adds" or what third party app "installs" "dragon branch adds"  Steven's answer has instructions on how to remove "dragon branch adds" from a PC. It doesn't directly answer my question but did point me in the direction of a YouTube downloader program.  After looking further into this, I think, don't know with certainty, but I think this “Free YouTube Downloader” program published by HOW Inc is the application that also installed "dragon branch adds" on my PC.  I think this Free YouTube Downloader is the culprit, two days ago I manually removed "dragon branch adds', last night I uninstalled the “Free YouTube Downloader” and I have not seen “dragon branch adds" since so..  I do not know for sure that this "Free YouTube Downloader" also installed "dragon branch adds" but it sure seems like thats where it came from


When I discover that an answer has been blatantly stolen from another user's answer I never know whether to comment and ask the user to delete the post or whether to flag it for moderator attention.  What is the best course of action?


When you speak of someone being on the ward, is on the only acceptable preposition? Is there a difference between American and British English on this? Would complements change the preposition required? (On the ward, but in the maternity ward?)  The COCA tells me "in" is slightly more prevalent than "on", but I'm not sure about the difference in usage in American English.  Thanks in advance for enlightening me.


Can question have multiple interpretations?

In Simple Terms  Annie and Ben are both doing the question...  A 100m cliff erodes by 2/7 of its height each year. (a) What will the height of the cliff be after 10 years?  Annie believes the answer is 100*(5/7)^9 because using the geometric progression formula exactly is common sense. Ben believes the answer is 100*(5/7)^10 because it's 10 years later. In your answer, determine whether Annie is right or wrong, giving reasons. Also determine whether Ben is right or wrong, also giving reasons. The Actual Question  An extension to . Can the question...  A 100m cliff erodes by 2/7 of its height each year. (a) What will the height of the cliff be after 10 years?  ...Be interpreted in different ways so that you could answer like this:  100*(5/7)^10 =976562500/282475249 =3.46m to 2d.p.  Or this:  100*(5/7)^9 =195312500/40353607 =4.84m to 2d.p.  I tried to convince my teacher that his answer wasn't correct but he said that his answer was an interpretation. The answer made in  supported my answer, but my teacher still thinks he is right. Can you really interpret this question in the 2 ways above or is there only just one right and the rest wrong? (Excluding the simplification of answers. Also some other questions are designed to have more than one answer.)


How can I determine which process owns a hotkey in Ubuntu?

One of my highly used hotkey got hijacked by another program in Ubuntu. But I don't know which program it is. By some researching, I found there is a discussion for Windows. (). But I could not find related solution for Ubuntu.   So, Is there some way in Ubuntu to determine that: when I press a key combination, which program consumes this key combination?    The  does solved my situation. But I think this question here should be kept as a separate thread, because finding a generic solution here will help solve other hotkey related problems in Ubuntu.


In a trailer for Kinect Star Wars, I saw Yoda driving a Jungle Speeder and that got me wondering. Can and has Yoda ever piloted a starfighter?  During the Clone Wars, it seems plausible that they could commission a small-sized green Jedi starfighter. Is their any indication that he has piloting experience?


Can't do smart scan on my new WD My Passport HDDs 2Tb on Ubuntu 16 LTS

(1) So it basically my problem: I tried most of what I know I installed smart and did this command to check if smart is available it seems it is available but when I do a smart test it says need -T permission, or that it's not on. It's external hdd. I don't know what to do. (2) As well, I want to ask I just bought it yesterday. But when I mounted it for the third time it said I don't haver permission to write on it when I wanted to make a new folder but it allowed me to create a new text file. Strange, the fourth time it didn't happen, I ask how to prevent it from happening again? (3) Do you advise me to format it ext4? Since I will be using it mainly for Linux and how to encrypt it for Linux? Sorry for my noob question. Hope some one help. Thanks.


Printing all elements of an array in one println statement in Java

public class Test {      public static void main(String[] args) {          int[] a= new int[]{1,2,3};          System.out.println(a);       } }   I expected to take a compile or run-time error.I took an output.It's "[I@1ba4806".What's the reason of it in Java?


Let $d_1 = 1 < d_2 < . . . < d_k = n$ be all the positive divisors of the positive integer n, and let $d = \sum_{i=1}^{k-1} d_id_{i+1}$.  Show that $d < n^2$.


How to describe a scenario where there is a mutually exclusive unintended negative affect after a positive intention

Disney World has a promotion offering tickets for half price on all rides for the day. John buys tickets for him and his girlfriend and imagines having a wonderful day. Although when he arrives as Disney world they have to spend an additional half and hour in queue at every ride because of the additional number of people in the park.   This wanted/unwanted expectation where the wanted has a direct relationship with the unwanted that follows it is called [...]     Sally spends 2 hours in the morning to make herself look beautiful as she want to impress the jocks at school. However she finds herself attracting the attention of not just the jocks but the geeks and when the geeks stare at her it makes her uncomfortable.   This postive/negative outcome where the negative the follows it has a mutual relationship with the preceding positive ...  The negative effect might also not be obvious to the original user who benefits as it could be another person who suffers the causal effect.  I can think of causal effect or symbiotic relationship but both sound to scientific for the above examples and the context of what I want to say.


I am writing a script to kill a job which runs more than 30 minutes. My epoch time format is like 1503935475067 and I am using current_time_stamp=`date +%s%3N`  How to find difference between two epoch time stamps?


How many ways to split n elements in k groups?

The order of the groups does not matter The size of group must be at least 1   For example, in a more specific question , we got the answer 15 from Jared, which is the sum of 5 ways to split in group size 1 and 4, and 10 ways to to split in group size 2 and 3.  For more general cases, what is the formula to calculate this?


While thinking on Pacific Rim, it occurred to me that several factors suggested the Kaiju were actually a creature that goes through metamorphic changes (like how caterpillars become butterflies).  Those factors are:   They had identical DNA (I forget who mentions that), yet.. Each had a different appearance. They became progressively larger. There were gaps in sending them. Towards the end, they started to arrive in groups. They had a psychic connection.   I thought that those points would all make sense if:   The Kaiju were all born of the same parent (identical DNA). They were a metamorphic creature (different appearance). Creatures typically become larger as they grow (true of both metamorphic and non-metamophic creatures, but supporting the 'same batch/age' part) The gaps could be explained by a period in which the creatures were undergoing metamorphosis (like the caterpillar in the cocoon). The alien intelligence felt the younger ones had less chance of surviving long/doing much damage, so only sent one at a time.  Later they progressed to more at once. The psychic connection again (vaguely) supporting 'relatedness'.   I realize there was no direct suggestion in the film that they were metamorphic.  What I was wondering was:  Is there any commentary or 'background information' (interviews etc.) that suggests that was a concept the movie makers were considering putting forward, but (for whatever reason) it got dropped during the process of making the movie?


Any good resources for Lagrangian and Hamiltonian Dynamics?

I'm taking a course on  and  Dynamics, and I would like to find a good book/resource with lots of practice questions and answers on either or both topics.  So far at my university library, I have found many books on both subjects, but not ones with good practice questions and answers. I have Schuam's outline of Lagrangian Dynamics, but didn't really find a lot of practice questions.  Any suggestions would be greatly appreciated!


GRUB Doesn't detect windows: Disk is MBR but booting via UEFI

I dun goofed. I thought my Windows was booting using UEFI, and I installed Ubuntu using UEFI. But now I think my Windows was booting using MBR, and GRUB can't detect it.  I'm confident the disk is MBR:  > sudo gdisk -l /dev/sdb GPT fdisk (gdisk) version 1.0.3  Partition table scan:   MBR: MBR only   BSD: not present   APM: not present   GPT: not present   and that I'm booting via UEFI:  > ls /sys/firmware/efi/ config_table  fw_platform_size  runtime      systab efivars       fw_vendor         runtime-map  vars   How can I fix my GRUB so that it boots using MBR instead of UEFI?  I've tried:   Running os-prober and update-grub Running boot-repair    Neither gave me a GRUB menu with Windows listed.


`rm` prompt when given more than one file

For some reason, my finger memory has converted mv to rm. Until I manage to retrain those fingers, how might I have rm prompt when provided multiple locations (one of which likely does not exist)?  I know that the -I option will prompt on more than three files, and the -i will prompt on every file, but I need something similar that will prompt on more than one file.


jQuery Syntax error, unrecognized expression - Using {

I'm using jQuery with SharePoint 2013, and have to get the table Id to add an attribute. The table Id is   {44C80A95-F3E4-40DA-9A97-50CADFFFED61}-{DD02CEA7-CC2B-4E4A-A725-86E82C6D11FC}   When I use:  jQuery("#{44C80A95-F3E4-40DA-9A97-50CADFFFED61}-{DD02CEA7-CC2B-4E4A-A725-86E82C6D11FC}").attr("width","100%");   It gives me this erro:  Uncaught Error: Syntax error, unrecognized expression: #{44C80A95-F3E4-40DA-9A97-50CADFFFED61}-{DD02CEA7-CC2B-4E4A-A725-86E82C6D11FC}    The problem is with the "{".  How to solve this problem?


How do I mount a partition with UFS filesystem (FreeNAS) in Ubuntu 11.10?  I'm a total Ubuntu newbie and just switched from FreeNAS.  There should be ll the info I need I guess, but if anyone would help me get going i'll by glad =)


Adjusting space between array rows and columns

\documentclass[english]{article} \usepackage[T1]{fontenc} \usepackage[latin9]{inputenc} \usepackage{babel} \begin{document} % ... \[ \begin{array}{ccccc} x(1) & = & \frac{x(0)}{1} & = & x(0)\\ x(2) & = & \frac{x(1)}{2} & = & \frac{x(0)}{2}\\ x(3) & = & \frac{x(2)}{3} & = & \frac{x(0)}{2.3}\\ x(4) & = & \frac{x(3)}{4} & = & \frac{x(0)}{4!}\\  &  &  &  & \vdots\\ x(n) & = & \frac{x(n-1)}{n} & = & \frac{x(0)}{n!} \end{array} \] % ... \end{document}   Because of the fractions in the array cells, array elements are vertically too close to each other, they are literally touching to each other. Also the horizontal spacing is too much as you see in the image (screen shot from the output PDF file).  How do I make these cell-spacings look better?


Disconnect Microsoft account from my local account

I was happily using local account on my Windows 8/8.1 machine. Was. Today I wanted to install some app from Windows Store. I wanted to assess some UX scenario in it. To do so I had to sign in using my Microsoft account. So I did. Not only I signed into Windows Store, but Windows also quickly connected my local account with Microsoft's one and somehow changing it for an online one. I've realised that when I restarted my machine and I had to logon using my Microsoft account credentials rather than my previous local ones. What I tried I found on the net, that I can disconnect my Microsoft account from my user account. I followed these simple steps:  Open Charms > Settings > Change PC Settings > Accounts > Your account > Disconnect Windows asked me for my current Microsoft account password (for obvious reasons) and I clicked Next It then asked me to provide local account credentials that I want to use from now on  My username was already pre-filled with my previous name (I'm not sure whether this has to do with previous local account username as it's the same as Display name on my Windows account). So I entered my local account password twice and my password hint as required and clicked Next. Error Windows is already using that name. Please enter a different user name.  I've read on the net that if I did provide a different user name I'd end up with a new local account which is not what I want here as I don't want to loose all my account related data. How should I revert to my local account without risking my profile data? Should I try providing a new username and verify whether my old account's data is persisted or is that too much risk and I should take some other steps?


Which is more grammatically correct:  "I like to speak Japanese."   or   "I like speaking Japanese."   Also, do they mean the same thing? Why is one better than the other, if they differ?


How to determine with certainty that a function has no elementary antiderivative?

Given an expression such as $f(x) = x^x$, is it possible to provide a thorough and rigorous proof that there is no function $F(x)$ (expressible in terms of known algebraic and transcendental functions) such that $ \frac{d}{dx}F(x) = f(x)$? In other words, how can you rigorously prove that $f(x)$ does not have an elementary antiderivative?


What is the difference between id and class in CSS, and when should I use them?

#main {     background: #000;     border: 1px solid #AAAAAA;     padding: 10px;     color: #fff;     width: 100px; }
     Welcome
   Here I gave an id to the div element and it's applying the relevant CSS for it.  OR  .main {     background: #000;     border: 1px solid #AAAAAA;     padding: 10px;     color: #fff;     width: 100px; }
     Welcome
   Now here I gave a class to the div and it's also doing the same job for me.  Then what is the exact difference between Id and class and when should I use id and when should I use class.? I am a newbie in CSS and Web-design and a little bit confused while dealing with this.


Kit weights don't seem to match contents. Am I missing something?

I was looking though a kit I wanted for a character and I calculated out the weight of the items and it came out as heavier that the kit itself.  The kit is the Fighter's Kit containing:     backpack, a bedroll, a belt pouch, a flint and steel, an iron pot, a mess kit, rope, soap, torches (10), trail rations (5 days), and a waterskin.   Assuming the rope is hemp, the total weight is 42 lbs. whereas the kit is 29 lbs. The items are as follows:                      Weight Cost Backpack             2     2 Bedroll              5     0.1 Belt Pouch           0.5   1 Flint and Steel      0     1 Iron Pot             4     0.8 Mess Kit             1     0.2 Rope, hemp (50ft)   10     1 Soap                 0.5   0.01 Torches (10)        10     0.1 Trail Rations (5)    5     2.5 Waterskin            4     1                     42     9.71   Am I missing something? Without multiplying out the quantities, it works out to 29 lbs.


How to make a bootable ISO from a bootable DVD using the command line?

I need to create an image to be able to mount the install DVD inside virtualbox in order to boot and install Windows.  Important: I need to do it using the command line.  I tried with genisoimage  and created an image using the command below but it turned out not bootable...  genisoimage -r -J -o cd_image.iso /cdrom   What I need is to RIP my original bootable DVD into a bootable IMAGE that I can mount in virtualbox.  So I thought I would ask how to A) convert that ISO file into a bootable one or B) re-create the ISO making it bootable with genisoimage or other command.


Why does the water keep escaping in my fluid simulation?

I am trying to do a water simulation. I have a small cup that I have created in blender (as an obstacle) and my water source (just an oval). My domain box is large enough to encompass both the glass and the water source:    Here are my settings for my domain:    I am using the default blender renderer. I have the cup setup as a collision for a water simulation and I have the sphere inside of the cup set as a fluid in a fluid simulation. When I bake the scene, here is what I get:    As you can see, the water is going through the cup, but the cup is having an effect on the water. Here is the rendered view:    How can I keep the water in the cup??


Example of normal random variable $X,Y$ s.t. $(X,Y)$ is not a Gaussian vector.

Does someone has an example of r.v. $X,Y$ that are normal, $(X,Y)$ has a density, but $(X,Y)$ is not Gaussian ? I can't find such an example.    I saw as an example, $X$ is $N(0,1)$ distributed, $\mathbb P(S=1)=\mathbb P(S=-1)=\frac{1}{2}$ and $Y=SX$. Then $X$ and $Y$ are normally distributed, but $(X,Y)$ is not Gaussian. But since $\mathbb P(X^2-Y^2=0)=1$, $(X,Y)$ has no density. So, this "counter-example" doesn't work. Any idea of a counter-example ?


If moderators can view , can we see comments we've deleted? We can see our deleted answers, but why not our deleted comments?


newcommand for index inserts unwanted spaces when using {}

I'm creating a technical document with lots of index entries. To reduce typing I defined an index command that typesets the word to be indexed using \emph{}:  \newcommand{\ind}[1]{\index{#1@\emph{#1}}}   I turns out the .ind file gets different entries when I use this command, compared to typing the \index{} command myself: the entries created with the \ind{} command get two spaces inserted before the { of the \emph command. Consequently, the index will contain two entries for the same word if I use both the \ind{} command and the \index{} command (e.g. when defining a region using   \index{someword@\emph{someword}\(}   to start a region for that word.   Here is an MWE:  \documentclass[a4paper]{article}  \usepackage{makeidx} \makeindex  \newcommand{\ind}[1]{\index{#1@\emph{#1}}}  \begin{document} Testing our self-defined command\ind{italictext}. This is the normal way\index{italictext@\emph{italictext}}.  \printindex \end{document}   The contents of the .ind corresponding file is:  \begin{theindex}    \item \emph  {italictext}, 1   \item \emph{italictext}, 1  \end{theindex}   Note 1: my actual use case is not with \emph{}, but with \lstinline{} from the listings package, but this simplified example already shows the problem. I observed the same behaviour when using the imakeidx package.  Note 2: using \DeclareRobustCommand instead of \newcommand doesn't change anything.  Note 3: I am actually using a KOMA class documentclass, so the scrindex package would be an option since the spacing problem doesn't appear there (in fact, both entries end up as one index entry with a single space between the \emph and opening { in the .ind file. However, with that package I haven't managed to get the page numbers for the index entries hyperlinked when using the hyperref package.


Researching ways to keep my system slim I came across this post:   Following the suggestion I did:  sudo sh -c "echo 'DSELECT::Clean "always";' >> /etc/apt/apt.conf.d/99AutomaticClean"   I'm not 100% sure about the timeline, but about at that time chromium kept asking me to sign into all my accounts and didn't remember my choices anymore, e. g. acknowledging a website using cookies. So that command above might erase chromiums cache, is that it?  Now I removed chromium and am using google-chrome, but that didn't help.   So A) Do you think the action above is the reason for my problems? and more importantly B) How do I undo this?  *I initially forgot to mention I already went gksudo nautilus and deleted /etc/apt/apt.conf.d/99AutomaticClean, but it didn't show up in gksudo nautilus' trash, so I suppose it is still available to be called on.


How to force any program to run with no admin privileges in Windows 7?

I'm looking for a way to force any program on Windows 7 to run with no admin privileges. If the program actually needs admin privileges, it may throw errors or crash. This is acceptable.  What I'm specifically looking to prevent is programs that ask for admin privileges to run but actually would run fine in normal privilege mode.  I scoured the Internet with over 20 searches and all I found was inconclusive garbage about program manifests (and absolutely no help or instructions on how to change the manifest to remove admin privilege requests).  So here are the rules for answers in this question:   Solution must remove the UAC "shield" marker from the program icon. The program must not attempt to gain elevated privileges for any reason. No disabling or attempting to circumvent UAC. If a program with the admin privilege requests removed needs to do anything that requires admin privileges, it is allowed to crash or throw an error. I would rather have a program crash or throw errors than to give the program elevated privileges that it doesn't need.   As a side note I would like to say that Windows Vista/7 UAC is defective by design and doesn't promote safer computer use, because it is too restrictive for a normal user account and programs are allowed to request admin privileges even if those aren't needed.  This only encourages average/non-advanced users to do stupid stuff like running everything as administrator or disabling UAC which puts their computers at even more risk.   The proper solution would be a complete rework of UAC "admin privileges" definition defining "admin privileged" as being only stuff that can actually damage your computer, such as boot sector changes, BIOS changes, operating system/Windows folder changes, startup program changes, etc. There is no valid reason for demanding admin privileges just so something can be added to Program Files.  I much prefer the Linux approach where you run a program, and if it crashes or breaks, then run it with sudo.    NOTE: I already found this   and none of the solutions were useful. That question just turned into unconclusive chatter and inaccurate/incorrect "solutions".


How to force a node group input field to display a slider?

I have created a couple of node groups with some "group-inputs-sliders" (The one called "Roughness" in the bottom picture). I would like it to have the blue-bar slider like the blender native ones. Thanks (:


How to produce such a matrix with braces in LaTeX?

Currently I am working on an assignment that needs me to typeset the following Sylvester matrix in LaTeX.     I have no idea how to typeset the two braces on the right side so I would like to ask for it. I am using the document class of amsart and I can implement any package if needed.  Thanks in advance..  ps. The enclosed is what I have so far  \begin{align*} Syl_i(A,B)= \underbrace{ \begin{bmatrix} a_m & \cdots & a_0 & & \\ &\ddots & \cdots & \ddots & \\ & & a_m & \cdots & a_0 \\ b_n & \cdots & b_0 & & \\ &\ddots & \cdots & \ddots & \\ & &b_n & \cdots &b_0 \\ \end{bmatrix} }_{m+n-i} \end{align*}   The problem is that I don't know how to add the two braces right to the matrix..


Generating DEM from contour Shapefile using QGIS?

I want to create a DEM from depth contours (shapefile) in QGIS. I've been trying to work out how to do this based on , notably from  from that page, however I'm stuck, and was hoping someone could help.  My progress/process so far:   open new map in  QGIS, import the contour shapefile set GRASS extent, set new GRASS mapfile, etc try to 'import' the shapefile into grass by converting it into a grass file, based on a hunch from the wording in  (search in page: 'use of qgis and grass'): file management, import into grass, import vector into grass, import loaded vector (v.in.ogr.qgis), then view output. This creates an identical looking layer. try to use r.surf.contour on this - doesn't allow layer to be selected. try to use r.surf.contour2 on this - either crashes QGIS or produces a full block of colour.   Any thoughts/tips on what I should be doing differently?    Interpolation failing, tried everything in GRASS & in GRASS plugin, failed, could problem be due to source shapefile?  Something I learnt from elsewhere was 'geometry tools > check geometry validity' which I ran on the contour shapefile and it found loads of errors.   I'm wondering if this could be the reason that all my efforts to create a DEM are failing?   Would anyone do me the huge favour of having a look at my shapefile to see if I'm just being useless, or if it's a problem that a relative novice would be excused for not anticipating?


How to see object from multiple perspectives in real time

I'm trying to model a helmet, I have a reference image of the head from frontal view and side view, I would like to see the helmet overlapping both views of the head, and I want to be able to modify one view of the object and see the changes in the other view as well, something like a link between the two objects, the same way you would create a texture pattern.


VS Code Setup - Create project with manifest error

When I try to create project with manifest it is giving me this error:    Starting SFDX: Create Project  12:39:56.757 sfdx force:project:create --projectname Dev --outputdir c:\ --template standard --manifest { AssertionError [ERR_ASSERTION]: Trying to copy from a source that does not exist: C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\lib\templates\project\standard\ScratchDef.json     at EditionInterface.exports.copy (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\node_modules\mem-fs-editor\lib\actions\copy.js:49:3)     at EditionInterface.module.exports [as copyTpl] (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\node_modules\mem-fs-editor\lib\actions\copy-tpl.js:29:8)     at ProjectGenerator.writing (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\lib\generators\projectGenerator.js:57:17)     at Object.<anonymous> (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\node_modules\yeoman-generator\lib\index.js:427:27)     at C:\Program Files (x86)\Salesforce CLI\client\node_modules\run-async\index.js:25:25     at new Promise (<anonymous>)     at C:\Program Files (x86)\Salesforce CLI\client\node_modules\run-async\index.js:24:19     at self.env.runLoop.add.completed (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\node_modules\yeoman-generator\lib\index.js:428:13)     at runCallback (timers.js:705:18)     at tryOnImmediate (timers.js:676:5)   generatedMessage: false,   name: 'AssertionError [ERR_ASSERTION]',   code: 'ERR_ASSERTION',   actual: false,   expected: true,   operator: '==' } { AssertionError [ERR_ASSERTION]: Trying to copy from a source that does not exist: C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\lib\templates\project\standard\ScratchDef.json     at EditionInterface.exports.copy (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\node_modules\mem-fs-editor\lib\actions\copy.js:49:3)     at EditionInterface.module.exports [as copyTpl] (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\node_modules\mem-fs-editor\lib\actions\copy-tpl.js:29:8)     at ProjectGenerator.writing (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\lib\generators\projectGenerator.js:57:17)     at Object.<anonymous> (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\node_modules\yeoman-generator\lib\index.js:427:27)     at C:\Program Files (x86)\Salesforce CLI\client\node_modules\run-async\index.js:25:25     at new Promise (<anonymous>)     at C:\Program Files (x86)\Salesforce CLI\client\node_modules\run-async\index.js:24:19     at self.env.runLoop.add.completed (C:\Program Files (x86)\Salesforce CLI\client\node_modules\salesforcedx-templates\node_modules\yeoman-generator\lib\index.js:428:13)     at runCallback (timers.js:705:18)     at tryOnImmediate (timers.js:676:5)   generatedMessage: false,   name: 'AssertionError [ERR_ASSERTION]',   code: 'ERR_ASSERTION',   actual: false,   expected: true,   operator: '==' } 12:40:03.206 sfdx force:project:create --projectname Dev --outputdir c:\ --template standard --manifest  ended with exit code 0   Can you please let me know what I am missing:   I have:   installed vs code, salesforce extension pack, salesforce cli, set the environment variable for my user, there is jdk installed (I have not set the path for it, not sure if it is required?)    What I am missing?   Thanks in Advance!!


Question: how to delete all unmet dependencies? I'm just rage now and hate apt. >.< UPD: output of sudo apt install -f Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following additional packages will be installed:   libvdpau1:i386 The following NEW packages will be installed:   libvdpau1:i386 0 upgraded, 1 newly installed, 0 to remove and 13 not upgraded. 218 not fully installed or removed. Need to get 0 B/24,4 kB of archives. After this operation, 116 kB of additional disk space will be used. Do you want to continue? [Y/n]  (Reading database ... 203285 files and directories currently installed.) Preparing to unpack .../libvdpau1_1.3-1ubuntu2_i386.deb ... Unpacking libvdpau1:i386 (1.3-1ubuntu2) ... dpkg: error processing archive /var/cache/apt/archives/libvdpau1_1.3-1ubuntu2_i386.deb (--unpack):  trying to overwrite shared '/etc/vdpau_wrapper.cfg', which is different from other instances of package libvdpau1:i386 Errors were encountered while processing:  /var/cache/apt/archives/libvdpau1_1.3-1ubuntu2_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1)


I have 16 meters of  LED Strips . The strips have 60 LED/s per meter and run on 5 volts. They come in 4 meter reels.  I know how i want to control them but i am unsure about how to hook them up safely and so that they draw enough power. I know that i cannot just hook up a power supply to one end and expect the entire 16 meters to be powered. I read online that for the non-addressable ones that run on 12volts you need to hook up the power supply in multiple places, is this the same case with the 5Volts?   Also how do i know what kind of power supply i need and how do i hook it up so that all the LEDs are fully powered? Will i need more than one power supply or should one be enough?


Can we search posts by number of comments?

Based on the existing advanced search options, I expected a comments:# to exist so I can search posts depending on the number of comments they have applied to them; at worst, I expected a hascomments.  Either I missed them, or neither exists.  Is there a reason search posts by number of comments doesn't exist beyond it simply not having been implemented yet?  If no, then please consider this a request to implement the functionality.  This is different from the   requests, which request solutions for searching within comments themselves.  This question asks for the ability to search by number of comments.


I've read all the postings here including the one that said it was already answered and elsewhere for this apparently common problem but so far I have not been able to resolve it. The other answers did not help. Typically I keep my systems up to date but this PC has been in storage for a year and a half during a remodel and now that it is back online, it needs to be updated/upgraded from the EOL 19.10 to 20.10 but it fails, then immediately wants to update again. $ sudo apt update Ign:1 http://us.archive.ubuntu.com/ubuntu eoan InRelease Err:2 http://us.archive.ubuntu.com/ubuntu eoan Release                           404  Not Found [IP: 91.189.91.38 80] Hit:3 http://archive.ubuntu.com/ubuntu xenial-updates InRelease                Hit:4 http://archive.canonical.com/ubuntu xenial InRelease Hit:5 http://archive.ubuntu.com/ubuntu xenial-backports InRelease Hit:6 http://archive.ubuntu.com/ubuntu xenial-security InRelease Reading package lists... Done E: The repository 'http://us.archive.ubuntu.com/ubuntu eoan Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.


Why are not all microtyping features enabled by default?

According to the microtype manual, Kerning, Spacing and Tracking are not enabled by default in pdftex (>= 1.4). What are the reasons for this?


How to remove failed file with backspace in its name?

Sorry if I am not using the right terms for naming these "backspace chars".  I would like to clean up a directory that contains two files which looks like they contain backspace in their name. If I list the directory:  ls -la   I get this:  -rwxrwxrwx    1 guy guy        729 Jun 26 2007  z_regular.mk -rwxrwxrwx    1 guy guy          1 Sep  7 2016 -rwxrwxrwx    1 guy guy       3220 Sep 27 2   I am thinking I mistakenly imputed the file names with "backspace chars", so we do not see the names any more.   How do I rename these last two files?  I don't know how to call them. Is there an ls option allowing me to display the file names in hexa or something, and how could I use the latest in an mv command? I'm with AIX Unix TLS v6.  edit:  the files are respectively 2 and 4 del chars:  ls -lb   gives   -rwxrwxrwx    1 guy guy          1 Sep  7 2016   \177\177 -rwxrwxrwx    1 guy guy       3220 Sep 27 2      \177\177\177\177\177   But solutions found at  doesn't work for my case in AIX.  I tried the below without success so far:  l>ls -l $'\0177\0177' $\0177\0177 not found l>ls -l '\0177\0177' \0177\0177 not found l>ls -l '\177\177' \177\177 not found


Often times I am not interested in the question so much as I am the answer. Unfortunately, the only site option for bookmarking an optimal answer is to bookmark the question. This leaves you having to remember that no the question wasn't that great, but there's an answer in here worth a million. It'd be nice to be able to favorite an answer allowing you to jump immediately to the answer that was much more valuable than the question. I understand that I can bookmark the answers link using my browser but it seems being able to favorite the answer within the site's ecosystem is useful.


Must the angle bisectors of a triangle all intersect at a common point- proof?

How could you informally write a proof, proving that all the angle bisectors intersect at one common point in a triangle?


Using wildcards with GQL -- Google App Engine

Is it possible to use a wildcard with GQL?  I would like to be able to pull all records that contain a particular word somewhere in their values.  I don't believe there is a "LIKE" filter.   Here is basically what I am trying to do: Any advice you can give is greatly appreciated-  mentors_with_topic = db.GqlQuery("SELECT * FROM MentorServices WHERE Services LIKE 'Reading'").get()


Concatenate multiple result rows of one column into differents rows (horizontal)

I have the following query (SQL SERVER):  select id,id_nivel_estructura from estructuras_empleado where id in (1,2)   The result is the following:    but I want to display in columns in the following way:   1 | 4 | 67 | 146 | 345 | 2158   2 | 3 | 34 | 267 | 345 | 2152   Could you help me?


Nigerian citizen (university student) was refused a UK visit visa due to lack of funds and connection to school - how to resolve?

I am a Nigerian citizen. I was refused a visitor visa to the UK. Here is my rejection letter:     How can I apply again so as to not be refused? How soon can I apply? My university undergraduate course will be finished in a few weeks.


Twin Paradox, calculating spacetime intervals from both perspectives

I've very recently started to try to understand special relativity. I'm want to get a decent understanding of the twin paradox. I'll post what I've done so far and highlight what's gone wrong for me.  The situation is that Alice and Bob both begin at point $x_1$ in Alice's coordinate system $(x,t)$ (we have orientated the axis so that y and z will not matter). Bob then instantaneously moves off with velocity $v$ in the positive $x$ direction. Bob's coordinate system is now $(x',t')=(\gamma (x-vt), \gamma (t-v\frac{x}{c^2}))$. In Alice's coordinates, Bob reaches point $x_2$ after having moved distance $d$, then instantly turns around and travels back to Alice at $-v$. I want to show that Alice's space time interval $\Delta s_A^2$ is greater than Bob's $\Delta s_B^2$, as each path's space time interval is proportional to the proper time passed along that path.    According to Alice: $\Delta s_A^2=-c^2\Delta t^2 + \Delta x_A^2$ where $\Delta t=\dfrac{2d}{v}$ and $\Delta x_A=0$ as she didn't move, but the time elapsed is the time it took bob to travel the distance and then come back. Thus $\Delta s_A^2=-\dfrac{4c^2d^2}{v^2}$  Still according to Alice, Bob's $\Delta s_B^2=-c^2\Delta t^2+\Delta x_B^2$, where the change in time is the same, but now bob has moved distance $d$ twice, thus $\Delta x_B=2d$ ($\Delta x$ refers to total distance traveled rather than displacement which is 0 in this case). Now we have $\Delta s_B^2=-\dfrac{4c^2d^2}{v^2}+4d^2$.     The |size| of Bob's spacetime interval now definitely smaller than Alice's, and this would be all OK, except that when I do the calculations in Bob's frame, they don't agree. This is contradictory to the fact that $\Delta s^2$ is conserved under Lorentz transformations.    According to Bob: $\Delta {s'}_A^2=-c^2\Delta t'^2 + \Delta {x'}_A^2$ where $\Delta t'=\dfrac{2d'}{v}$. I'm not sure if I'm right in saying that $v$, the relative velocity of the two frames, is the only velocity upon which both Alice and Bob will agree on, other than the speed of light. Anyway, $d=\gamma d'$ as lengths contract by $\gamma$ i.e. $d'$ is smaller than $d$ by factor $\gamma$. Also, $\Delta {x'}_A=2d'$, so we have $\Delta {s'}_A^2=-\dfrac{4c^2d'^2}{v^2}+4d'^2=-\dfrac{4c^2d^2}{\gamma ^2 v^2}+\dfrac{4d^2}{\gamma ^2}=4d^2\dfrac{v^2-c^2}{\gamma^2 v^2}\neq \Delta s_A^2$  Although I haven't included them here, my calculations for $\Delta {s'}_B^2$ and $\Delta s_B^2$ agree. Sorry for the ultra-long post, but any help would we well appreciated!


Why can users down-vote without an explnanation or if they don't understand the issue?

Sometimes users down-vote if they don't understand the issue, but others did, also vote to close. There are many different minds over the world. What I said, maybe you don't realize it but maybe and maybe not others know what I meant.   If the programmers had the same minds, there'd be no Google, no Yahoo!, no Microsoft, no Facebook, even Stack Overflow would never exist. The people are not on the same mind. Up-vote means I have the same issue, I agree with you. But down-vote seems like I don't like your question, I don't realize your mind. If you don't agree, just leave. Maybe someone else knows what the question means.   I think Stack Overflow needs to help programmers, but down-vote the helpless. Tt is help for the others, but not for the one who has the question.       Why is Stack Overflow still using down-votes? Is it help to the one who has questions? Even on meta, which was supposedly founded to discuss Stack Overflow issues. I think I will receive an answer saying "For person like you".


Why doesn't L'Hospital's rule work in this case?

I have a very simple question. Suppose I want to evaluate this limit:  $$\lim_{x\to \infty} \frac{x}{x-\sin x}$$  It is easy to evaluate this limit using the Squeeze theorem (the answer is $1$). But here both the numerator and the denominator are going to infinity as $x\to \infty$ so I tried using L'Hospital's rule: $$\lim_{x\to \infty} \frac{x}{x-\sin x}=\lim_{x\to \infty} \frac{1}{1-\cos x}$$  However there's no finite $L$ such that $$\lim_{x\to \infty} \frac{1}{1-\cos x}=L$$ which is a contradiction. I don't understand why in this case L'Hopital's rule doesn't work. Both the numerator and the denominator are differentiable everywhere and both are tending to infinity - which is all we need to use this rule.


How to get content from an url by client ip address NOT server address

What I'm actually trying to do is getting content of an URL from another site there I want get the content by client ip address NOT server. Is there any way to do this?  Here I tried some how but, not succeed :/  <?php $homepage = $_SERVER['REMOTE_ADDR']file_get_contents('http://www.example.com/'); echo $homepage; ?>   I'll accept if there is a way in javascript also.


Is there anyone here can explain for me, which is better to use, and why?. In my opinion Sandbox solution is using for site collection and farm solution using for the all web application. Is that true???


When I render or when I use the verge3D app manager and open the model, the world background is gray and not white, even after setting the world color to white. I cant figure out what is doing this. This is what the background looks like:  The background should be completely white. here is the blender file:


I see that there are a few ways to prove this, but I don't know why my method isn't working.  I set ${^{n - 1}C_r} = \dfrac{(n - 1)\cdot(n-2)\cdot\cdots\cdot(n - 1 - r + 1)}{r!}$ so the last term in the numerator is $n-r$. Call the numerator $N_1$.  Then ${^{n - 1}C_{r - 1}} = \dfrac{(n - 1)\cdot(n - 2)\cdot\cdots\cdot(n - 1 - (r - 1) + 1)}{(r - 1)!}$ so the last term in the numerator is $n-r+1$. Call this numerator $N_2$.  Then the sum is $\dfrac{N_1 + r\cdot N_2}{r!}$.  I don't know if I made a mistake or I'm failing to see how this equals $^nC_r$.


I'm currently working with drivers in Blender 2.81 and want to use self but it doesn't work.   For example drive the rotation by the location, I'm adding a driver to the rotation, check the Use Self box and write self.location.x  Blender return the message: ERROR Invalid Python expression.  Have I missed something, is it a bug?  edit:


Consider only finite-dimensional spaces; I know that infinite-dimensional spaces are different.  Let V be a finite-dimensional vector space, V* its dual, and V** its double-dual.  I do not understand how V** is "naturally isomorphic" to V?  As nearly as I can tell, V** is no better than V*.  The answers on this forum are too confusing.  Is there anyone kind enough to give me a very detailed answer?  I need all the nuts and bolts.  I haven't seen an answer on the internet that I have liked.


Windows server 2012/6 Limit copying size

we need to add a limit for pasting to SMB Folder from Windows Server 2012. Is any way, users within MS Server to have quota/limiter once pasting files to SMB share? The share is mounted at Windows Server.  Thank you


Does the Draconic Bloodline sorcerer's Elemental Affinity feature apply to the spell Dragon's Breath?

The  feature Elemental Affinity states:     [When] you cast a spell that deals damage of the type associated with your draconic ancestry, you can add your Charisma modifier to one damage roll of that spell.   The  spell (XGtE, p. 154) incorporates a damage roll, but it is not a direct consequence of the spell:     Until the spell ends, the creature can use an action to exhale energy of the chosen type in a 15-foot cone. Each creature in that area must make a Dexterity saving throw, taking 3d6 damage of the chosen type on a failed save, or half as much damage on a successful one.   Would one of these exhalations qualify for the application of the Elemental Affinity feature? If so, is only one eligible or every one throughout the duration of dragon's breath


If there monomorphisms $f : A \rightarrow B$ and $g : B \rightarrow A$ then there is an isomorphism $h : A \rightarrow B$

Consider the following set theoretical result of Schröder-Bernstein-Cantor:  Let $A$, $B$ be sets. Assume we have injections $f : A \rightarrow B$ and $g : B \rightarrow A$. Then there exists a bijection $h : A \rightarrow B$.  Although this fact seems obvious, its proof is not completely trivial (see  ) But what about the following statements?   Let $A$ and $B$ be finite-dimensional vector spaces. Assume we have monomorphisms $f : A \rightarrow B$ and $g : B \rightarrow A$. Then there exists an isomorphism $h : A \rightarrow B$. (true) Let $A$ and $B$ be vector spaces. Assume we have monomorphisms $f : A \rightarrow B$ and $g : B \rightarrow A$. Then there exists an isomorphism $h : A \rightarrow B$. (true?) Let $A$ and $B$ be Hilbert spaces. Assume we have monomorphisms $f : A \rightarrow B$ and $g : B \rightarrow A$. Then there exists an isomorphism $h : A \rightarrow B$. (true) Let $A$ and $B$ be groups. Assume we have monomorphisms $f : A \rightarrow B$ and $g : B \rightarrow A$. Then there exists an isomorphism $h : A \rightarrow B$. (true?)   How far can you generalize the original result of Schröder-Bernstein-Cantor, at least in categories where monomorphisms are injective and isomorphisms are bijective?


Clicking the top bar sometimes loads the SE homepage, sometimes shows the site switcher

When I click the "hamburger menu" in the right part of the top bar:    I usually get the site switcher drop-down:    But sometimes, I'm taken to  instead:    It isn't very consistent.  I tend to get the drop-down if the page has been loaded for more than a few seconds.  I most often get the SE homepage if I click in the first couple seconds after the page loads, although sometimes I get the drop-down even if I click very quickly. But it doesn't always seem to happen.  When I started writing this question I had no trouble getting it to occur, five minutes later I couldn't reproduce it, and ten minutes later I could again.  At the moment my guess is that it's related to how quickly some page element loads. Being unable to predict the results of clicking the top-bar is somewhat confusing, although it does work most of the time, so it's not terribly frustrating. It took me a while to figure out that it wasn't my own fault—at first I thought that the "StackExchange" text linked to SE and the down arrow showed the drop down, and that the inconsistency was a result of my inaccurate clicks.  Doing some experimentation, it seems that this is not the case, and the entire rectangle (circled above in red) has the same behavior. I've observed this behavior in SeaMonkey 2.26 and Firefox 28, and Nick Stauner has reproduced the problem in Chrome 34 ().


It seems that iOS 10 Public Beta 3 fixed all of this. All is good.    I've found this bug on mobile where some icons have white squares on them. Is this already reported? Or is this supposed to happen? I am on iOS 10 public beta #1…     App Version: 1.5.3.5 Device: iPhone 6 OS Version: Version 10.0 (Build 14A5297c)   Also it happened on mobile site...


Python - Randomly select words to display in a quiz

I'm in need of some help. Here we have my two lists:  wordlists1 = ["hot","summer", "hard", "dry", "heavy", "light", "weak", "male",              "sad", "win",  "small","ignore", "buy", "succeed", "reject", "prevent", "exclude"]  wordlists2 = ["cold", "winter", "soft", "wet", "light", "darkness", "strong", "female", "happy", "lose", "big",          "pay attention", "sell", "fail", "accept", "allow", "include"]   Okay, so many people are misunderstanding me, so I have these two lists, I use the random.choice to pick a word from each lists, once we have those words, I needed them to be printed out as a question such as, if hot and weak are selected, then it would be displayed as, "Hot is to cold as weak is to___?" I really need help on this, and detailed steps would be appreciated.


What does the '@' mean in an SQL stored procedure?

Some of the fields in a stored procedure have an '@' symbol before it. What does this mean?  Ignore the fields and data themselves.  , cast(hi.date_closed as date) hiclose , @helloclose:=cast(ifnull(audit.date_created,hello.date_entered) , cast(@hi-INTERVAL WEEKDAY(@hiclose)DAY as datetime) himonclose , @oppentered:=cast(opp.date_entered - interval 5 hour as datetime) hicreate , cast(@oppentered - INTERVAL WEEKDAY(@oppentered)DAY as datetime) himoncreate


How do I recover from the Heartbleed bug in OpenSSL?

a.k.a.  is a vulnerability in OpenSSL. It looks scary.  How do I determine whether I am affected?  If I'm affected, what do I need to do? Apparently upgrading isn't enough.


If $p, q$ are primes and $p$ does not divide $n-1$ and $p$ divides $n^q-1$. How to prove that $q|p-1$.  What we can see is that $p|(n^{q-1}-n^{q-2}+\cdots -1)$. Now how do I prove that $p|q-1$


Using \hyperref within prenote of \citep

I want to add a link to the appendix in a prenote of a citep reference. However, using \hyperref[label_name]{Text with link} () instead of \ref{label_name} fails.   Here is a MWE illustrating the issue:  \begin{filecontents}{ref.bib} @article{paper1, title = {{Title here}}, journal = {Journal of Articles}, year = {2019}, author = {Author, A.}, pages = {1-2}, number = {1}, } \end{filecontents}  \documentclass[a4paper,12pt]{book} \usepackage[english]{babel} \usepackage[utf8]{inputenc} \usepackage{hyperref} \usepackage{cleveref} \usepackage[noibid,authordate-trad,backend=biber,natbib,maxcitenames=2,maxbibnames=99,uniquelist=false]{biblatex-chicago} \bibliography{ref} \hypersetup{colorlinks=true, linkcolor=blue, urlcolor=blue, citecolor=red}  \begin{document}      \chapter{Chapter Title}     Combine: (see \hyperref[app1]{appendix \ref*{app1}}) \citep{paper1}\\     Not working: \citep[see \hyperref[app1]{appendix \ref*{app1}},][]{paper1}\\     Working but \textit{appendix} not included in link: \citep[see appendix \ref{app1},][]{paper1}     \appendix     \chapter{Appendix Title}\label{app1}  \end{document}   Which results in   Is there a simple way to add custom text to a hyperlink within a prenote of citep?


Return a tuple of arguments to be fed to string.format()

Currently, I'm trying to get a method in Python to return a list of zero, one, or two strings to plug into a string formatter, and then pass them to the string method. My code looks something like this:  class PairEvaluator(HandEvaluator):   def returnArbitrary(self):     return ('ace', 'king')  pe = PairEvaluator() cards = pe.returnArbitrary() print('Two pair, {0}s and {1}s'.format(cards))   When I try to run this code, the compiler gives an IndexError: tuple index out of range. How should I structure my return value to pass it as an argument to .format()?


Why is the speed of light constant in all inertial frames?

I know this is a physical principle and cannot be derived at from other physical laws. But how can it be arrived at? What observations or what train of thoughts leads to this conclusion?  e.g. the Newton's second law of motion is also a physical principle and cannot be derived. But from observations like 'a body moving at constant velocity on a frictionless surface doesn't tend to stop' and many others, it is understandable to arrive  at the Newton's laws. What observations or thought process lead Einstein to this postulate?


Fourier package causes equation to not show up properly

In the MWE below, I do not get the equation to show up properly.  This is how it shows up:   when this is the equation:  E(T) = C_{1} + C_{2}f_{1}[p(t)] + C_{3}f_{2}[T(t)] + C_{4}f_{3}[p(t),T(t)] + v(t)   I did the updmap.exe and also ran  the "REFRESH FNDB" in MiKTeX for Windows but still did not get the equation to show up properly.  I am using the Fourier package because it is being used in the chapter title headings.  Can the Fourier package work here in conjunction with the equations showing up correctely?  Here is my MWE:  \documentclass{book} \usepackage{etoolbox,fancyhdr} \usepackage[top=3cm,bottom=3cm,left=3.2cm,right=3.2cm,headsep=10pt,a4paper]{geometry} \usepackage{graphicx, rotating, ltablex, dcolumn, booktabs} \usepackage{siunitx}  \usepackage{booktabs} \usepackage{xcolor} \definecolor{ocre}{RGB}{52,177,201} \usepackage{amsmath,amsfonts,amssymb,amsthm} \usepackage{microtype} \usepackage[utf8]{inputenc}  \usepackage[T1]{fontenc} \usepackage{tikz} \usepackage{calc}  \usepackage{fourier} \usepackage{mathptmx}  \begin{document}  \chapter{Chapter 1}  \section{Problem 2.4}\index{Problem 2.4}  (Mendel, 1973, Exercise 1-17, pp. 46-47).  The efficiency of a jet engine may be viewed as a linear combination of functions of inlet pressure $p(t)$ and the operating temperature $T(t)$; i.e., \begin{equation*} E(T) = C_{1} + C_{2}f_{1}[p(t)] + C_{3}f_{2}[T(t)] + C_{4}f_{3}[p(t),T(t)] + v(t) \end{equation*} where the structures of $f_{1}$, $f_{2}$, and $f_{3}$ are known a priori and $v(t)$ represents modeling error of known mean and variance.  From tests on the engine a table of values of $E(t)$, $p(t)$, and $T(t)$ is given at discrete values of $t$.  Explain how $C_{1}$, $C_{2}$, $C_{3}$, and $C_{4}$ are estimated from these data.  \end{document}


I have two layers, one of points (locations of fruit trees) and one of Atlanta zip codes, in ArcMap 10, but the layers are not aligning. The fruit trees are in a corner and the map is in the middle top.   The fruit points were successfully converted to a shp file from a csv file.   The two layers have the same projected coordinate system NAD_1983_StatePlane_Georgia_West_FIPS_1002_Feet  and the same geographic coordinate system GCS_North_American_1983  I thought the error would be that the systems didn't match up, but that's not the case.


How to install Ubuntu Software Center on Parrot OS?

I m using the latest Parrot OS. I would like to install the Ubuntu Software Center, so that I can install/uninstall my packages easily.  Is it possible to install the Ubuntu Software Center on Parrot OS?


"live far from each others" has 30000 Google results.  "live far from each other" has 60000 Google results.  So which one is right? "Each others" or "Each other"?


What's exactly the point of the sudo command, in terms of security?

This question is actually non Ubuntu-specific. My understanding is that sudo is to prevent non-authorized users from doing administrative and other potentially harmful operations. The premise is that someone is here in front of my PC using it... or maybe remotely (but in that case they should know my login password to connect to the computer, and this is usually the same as my sudo password...) So someone is in front of my PC and she cannot delete certain important files or dirs or install harmful software without knowing my sudo password, but she can do a lot of other harmful and privacy-violating things without sudo. So, wouldn't it be better instead asking for admin privileges each time before opening the file manager or the terminal? I know this may be time-consuming and exhausting...


How is the "normalisation" of non-normalizable states chosen?

This question is about non-normalisable states in quantum mechanics, e.g. the eigenstates of the position operator $|x\rangle$ which are defined by the eigenvalue equation  $$\tag{1} \hat{X}|x\rangle = x|x\rangle.$$  Since the spectrum of the operator is continuous, the states are not square normalisable. Instead one has an equation such as  $$\tag{2} \langle x'|x\rangle = \delta(x-x')$$  which gives the overlap meaning as a . However it is clear that there is still at least an ambiguity in choosing a constant, i.e. why no have  $$\langle x'|x\rangle = a \times \delta(x-x')$$  where $a$ is $a \in \mathbb{R} $.    So I went to see how Equation (2) is derived. In Schleich's textbook on quantum optics in phase space I found the following, very short and in my opinion not clear/complete derivation.  From Equation (1) which can be taken to be the definition of the position operator and the assumption that the operator is hermitian which is a fundamental postulate of quantum mechanics one obtains:  $$\tag{3} \left( x - x' \right) \langle x'|x\rangle = 0.$$  That was easy so far, but then Schleich jumps immediately to equation (2). But the solutions for $\langle x'|x\rangle$ of (3) are all functions/generalised functions that are non-zero everywhere except at $x=x'$. So my question is: Why is (2) the unique solution? Where does the additional information come from?  My suspicion is that we impose another requirement, which is probably the completeness of the states, which would make (2) clear since it is the identity element in the position representation.


Doubts regarding Einstein's 1905 derivation of mass-energy equivalence

This is a follow up on this .   In his [paper][2] under the title:Does the inertia of a body depend upon its energy-content, Einstein drives the famous $E=mc^2$ equation.   His argument can be summed up as follows:  Consider an object(like lantern,so it's not a point particle) that is at rest in a given inertial frame. It has energy that is given by $E_0$. Let it emit two beams of light carrying the same amount of energy in two opposite directions, So that the body will stay at rest(since the light will carry equal momenta in opposite directions). Let it's energy after emission be called $E_1$. Consider this same exact situation from an inertial frame that is in relative motion with respect the the frame at rest. And denote the energies of the body before and after the emission by $H_0$ and $H_1$.   He then considers the quantity: $H_0 − E_0 − (H_1 − E_1)$:  $H-E$ according to Einstein, is simply the difference in the Kinetic energy of the body up to an arbitrary additive constant $C$. So that:  $H_0 − E_0=K_0+C$,  $H_1 − E_1=K_1+C$,  $K$ is the kinetic energy of the body in the moving system.  He then states since $C$ does not change during the emission therefore:  $H_0 − E_0 − (H_1 − E_1)=K_0 -K_1$. In other words, the change in the energy of the body after the emission of light is given by the difference between the kinetic energy of the body before and after the emission. Now since the body does not change it's velocity, therefore He infers its mass has changed.   There's one part about this argument that us unsettling for me. Namely the constancy of $C$ during the emission.   If we have a macroscopic object, it's energy is given by(at least) the sum of its kinetic, internal(thermal) and potential energy.  That is: $H_0 − E_0=K_0+\Delta E_{T_0}+\Delta U_0$,          $H_1 − E_1=K_1+\Delta E_{T_1}+\Delta U_1$.  In other words the constant $C$ denotes $\Delta E_{T}+\Delta U$. Assuming the $C$ is the same before and after the emission is tantamount to assuming that both internal and potential energy of the emitting body is constant during the emission process. It's not self-evident to me at all why this should be the case. Why say, the internal energy(temperature) of the body won't change after emitting light? Einstein did not justify this assumption at all in his 1905 paper.  So Is it a justified assumption? If so, then what is the justification?


Is there any alternative theory that gets rid of gravitational waves, yet fits all data?

Is there any theory that gets rid of gravitational wave and still matches with all correct predictions made by standard physics theories? (e.g. General Relativity)