Steps to reproduce:   Find a deleted question (or answer) with a suggested edit.  I used  (10k only) on Stack Overflow. Click the edit button, observe the "This post has been deleted; no edit suggestions are available" message. Open the edit in the Suggested Edits review window (right click on the edit button -> open in new tab/window or copy link).  . Observe that the suggested edit can be reviewed though the answer has been deleted.

In some cases, questions and answers that have been deleted are still showing up on /review pages. They do not have "Improve" buttons, but they can still be approved or rejected. I'm not sure what causes a post to end up in this limbo state instead of being removed from the queue entirely, which I think is what's supposed to happen.  The suggested edit I noticed this on was , but it just leads to a "Page Not Found" message now.  Tim Stone provided the following screenshot of another instance :


I am having problems to prove the following:     Let V be a K-Vectorspace and $dim(V)=\infty$. Prove that the canonical linear transformation $e: V \rightarrow V^{**}$ is not surjective.     I think I get the idea of the proof, since if $(v_{i})_{i \in I}$ is a basis of $V$ and $(v_{i}^{*})_{i \in I}$ is the dual family in $V^{*}$ then it might - or even can't - span the whole space $V^{*}$. But I am neither sure how I can show this, nor the actual proof. Help would be much appreciated. Thanks in advance!

For the finite-dimensional case, we have a canonical isomorphism between $\mathbf{V}$, a vector space with the usual addition and scalar multiplication, and $(\mathbf{V}^*)^*$, the "dual of the dual of $\mathbf{V}$." This canonical isomorphism means that the isomorphism is always the same, independent of additional choices.   We can define a map $I : \mathbf{V} \to (\mathbf{V}^*)^*$ by $$x \mapsto I(x) \in (\mathbf{V}^*)^* \ \text{ where } \ I(x)(f) = f(x) \ \text{for any } \  f \in \mathbf{V}^*$$  My Question: what can go wrong in the infinite-dimensional case? The notes I am studying remark that if $\mathbf{V}$ is finite-dimensional, then $I$ is an isomorphism, but in the infinite-dimensional case we can go wrong? How?


I've just installed xubuntu-desktop on my trusty Lenovo X61 on top of Lubuntu 13.10. However, when the machine boots up it always logs straight into a Lubuntu session without asking. To resolve this I tried uninstalling lubuntu with sudo apt-get remove lubuntu-desktop but this turned out to be a bad idea as it booted to a black screen.  In tty1 I re-installed lubuntu and now I'm back to square 1. But I want Xubuntu!  I've heard taskel can be used to manage startup but wondered what the community would recommend. Many thanks.  Robin

I wanted to switch to Xfce (I had KDE and GNOME installed), and I did this :    sudo apt-get install xubuntu-desktop sudo apt-get remove kubuntu-desktop sudo apt-get remove ubuntu-desktop sudo apt-get autoremove   but to my surprise, I could still pick gnome, kde plasma, etc during the log in.  So, how do I completely remove KDE and GNOME desktops?


I want to show that $f(a) = \int _ 0 ^\infty \frac {\sin ( x^2 + ax )}{ x } dx$ converges for all $a \ge 0$ and $f$ is continuous on $[0, \infty ) $.

I want to show that the following converges for $a\ge 0$ $$\int_0^\infty \frac{\sin(x^2+ax)}{x}\,dx$$  We can show that $\lim_{x\to 0} \frac{\sin(x^2+ax)}{x} = a$, and with that fact it's straightforward to prove that $$\left|\int_0^\delta\frac{\sin(x^2+ax)}{x}\,dx \right|< \infty$$ where $\delta >0$ is a constant.  However I'm having trouble showing that the function decays quickly enough as $x$ goes to infinity. I know how to prove this when taking the integral of $\sin(ax)/x$, but that $x^2$ is causing me problems.  Any ideas? Thanks.


Our UTM (Firewall) logs showed Spyrix(Key Logger) has been downloaded on a particular IP in our network. While, on that system, we couldn't see Spyrix. what are the ways to detect traces of syprix in a system after it has been uninstalled? This is the link of the keylogger

This is a  about Server Security - Responding to Breach Events (Hacking)   See Also:                  Canonical Version I suspect that one or more of my servers is compromised by a hacker, virus, or other mechanism:   What are my first steps? When I arrive on site should I disconnect the server, preserve "evidence", are there other initial considerations? How do I go about getting services back online? How do I prevent the same thing from happening immediately again? Are there best practices or methodologies for learning from this incident? If I wanted to put a Incident Response Plan together, where would I start? Should this be part of my Disaster Recovery or Business Continuity Planning?   Original Version       2011.01.02 - I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a    attack on our provider. The servers access to the Internet   has been shut down which means over 5-600 of our clients sites are now   down. Now this could be an FTP hack, or some weakness in code   somewhere. I'm not sure till I get there.      How can I track this down quickly? We're in for a whole lot of   litigation if I don't get the server back up ASAP. Any help is   appreciated. We are running Open SUSE 11.0.            2011.01.03 - Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed   to resolve this problem, although it may not apply to many others in a   different situation. I'll detail what we did.      We unplugged the server from the net. It was performing (attempting to   perform) a Denial Of Service attack on another server in Indonesia,   and the guilty party was also based there.      We firstly tried to identify where on the server this was coming from,   considering we have over 500 sites on the server, we expected to be   moonlighting for some time. However, with SSH access still, we ran a   command to find all files edited or created in the time the attacks   started. Luckily, the offending file was created over the winter   holidays which meant that not many other files were created on the   server at that time.      We were then able to identify the offending file which was inside the   uploaded images folder within a  website.      After a short cigarette break we concluded that, due to the files   location, it must have been uploaded via a file upload facility that   was inadequetly secured. After some googling, we found that there was   a security vulnerability that allowed files to be uploaded, within the   ZenCart admin panel, for a picture for a record company. (The section   that it never really even used), posting this form just uploaded any   file, it did not check the extension of the file, and didn't even   check to see if the user was logged in.      This meant that any files could be uploaded, including a PHP file for   the attack. We secured the vulnerability with ZenCart on the infected   site, and removed the offending files.      The job was done, and I was home for 2 a.m.            The Moral   - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole   world is made aware of the vulnerability.   - Always do backups, and backup your backups.   - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server   Fault.


When installing HPLIP latest version it keeps writing this message, when trying to install manually the python "missing" packages it says they are already installed.   Tried so many solutions here - none worked :((   screen shows :   Distro set to Ubuntu 16.04  Initializing. Please wait...   ENTER ROOT/SUPERUSER PASSWORD ----------------------------- Please enter the root/superuser password:    SECURITY PACKAGES ----------------- AppArmor is installed.  AppArmor protects the application from external intrusion attempts making the application secure  Would you like to have this installer install the hplip specific policy/profile (y=yes*, n=no, q=quit) ? y   RUNNING PRE-INSTALL COMMANDS ---------------------------- OK   MISSING DEPENDENCIES -------------------- Following dependencies are not installed. HPLIP will not work if all REQUIRED dependencies are not installed and some of the HPLIP features will not work if OPTIONAL dependencies are not installed. Package-Name         Component            Required/Optional    python3-notify2      gui_qt5              OPTIONAL             python3-pyqt4-dbus   gui_qt4              OPTIONAL             python3-pyqt4        gui_qt4              REQUIRED             python3-pyqt5-dbus   gui_qt5              OPTIONAL             python3-pyqt5        gui_qt5              REQUIRED             python3-dbus         fax                  REQUIRED             python3-reportlab    fax                  OPTIONAL             Do you want to install these missing dependencies (y=yes*, n=no, q=quit) ? n error: Installation can not continue because all REQUIRED dependencies are not installed.

Let's assume that one has some modern HP printer and/or scanner which is not supported by HPLIP package from official repository. Currently Ubuntu versions have :  trusty (14.04LTS): 3.14.3-0ubuntu3.4 xenial (16.04LTS): 3.16.3+repack0-1 bionic (18.04LTS): 3.17.10+repack0-5 focal (20.04LTS): 3.20.3+dfsg0-2 groovy (20.10): 3.20.5+dfsg0-3build1 hirsute (21.04): 3.21.2+dfsg1-2   What can one do if printer is supported in newer version of HPLIP (checked this in )?


On my RT-N56U router I'm trying to create a ext3 partition on an attached usb drive to store my media center data. The problem is I am unable to create to a mount point after creating the partition. When I run this command: mkdir /media/AiDisk_a1, it says it can't do it because file system is read only. This is probably because it's the in memory router OS. How can I mount my ext3 partition to /media/AiDisk_a1?  Also, is there a way in Linux to create a mount point without having write access to the main OS volume?


I am stuck trying to prove the following: let $\mathbf R$ be a nontrivial commutative ring, $\mathcal M$ be the class of proper maximal ideals of $\mathbf R$ and $J=\bigcap \mathcal M$. Prove that $1+a$ is invertible for all $a\in J$.  My attempt so far: every $M\in\mathcal M$ is maximal, so that $R|M$ is a field. Thus for all $a\in J$ and all $M\in\mathcal M$  there is $b_M$ such that $[1+a]_M [b_M]_M=[1]_M$. From this I deduce that $b_M+ab_M-1\in M$ for all $M$, that $b_M(1+a)\notin M$, that $b_M\notin M$, and so that $[b_M]_M\cap M=\emptyset$ for all $M$, but I really don't know how to use these informations or how to try for a different proof

I have in my notes that the Jacobson radical of a ring $R$ is:  $J(R) = \cap${$I$ | $I$ primitive ideal of $R$} $= \cap$ {$Ann_R M$ | $M$ simple $R$-module}.  I have now seen elsewhere that $J(R) = \{x ∈ R: xy-1 ∈ R^\times \text{ for all } y ∈R\}$  I was just wondering would anyone be able to provide an explanation as to how to get from one definition to the other? Thanks.


Hey  I've problem with blurred stars when I shoot stars with my Canon 700D with EF 50mm f/1.8 STM lens I've set up with 10-20 second shutter speeds and  ISO settings from 400-1600. I try on f/1.8 and in all pictures, the stars are blurry. How do I focus them?

Last night, when I was attempting to do some astrophotography, I found it rather difficult to focus on the stars/tress/buildings in nearly pitch darkness. The Live View feature doesn't show much as it is so dark, and you can't see through the viewfinder either (when it's dark)  The one single lens I have, an 18-55mm IS Canon lens doesn't have an infinity marker on the focus ring. It's just a standard lens. Also my first lens (I'm an amateur)


Is it: Less than/Fewer than 20 percent of the doctors replied.  Thank you.

I've just received a memo which says (effectively)      As more people leave, there will be less people available.   I want that word to be fewer. Are there guidelines for which word ought to be used when?


I installed ap-hotspot in kubuntu 13.10 and it was working but then I upgraded my os to 14.04 and then it stopped working. I tried everything I removed the ap-hotspot completely and then again started it but it is not working it gets stuck in "Starting Wireless Hotspot..."  Is there any other way of creating a hotspot in kubuntu.

I was trying to create an WiFi hotspot for my android device. I used ap-hotspot to do so.    I configured the ap-hotspot using    sudo ap-hotspot configure   Then I started ap-hotspot using   sudo ap-hotspot start   Then it shows this   Starting Wireless Hotspot...   And then nothing happens, no further message is displayed, hotspot is not created.  What is Wrong? How to fix it?


I'm trying to install the 'listings' package through MiKTeX package manager and I get the following error:  MiKTeX Problem Report Message: parse error - unexpected end of input; expected '}' MiKTeX: 2.9 OS: Windows 7 Enterprise, 64-bit, Service Pack 1, build 7601

Every once in a while after updating MiKTeX, the installation gets into an inconsistent state. This might be a problem with the packages (an example is described in ), but sometimes packages are split or renamed. The cases I remember are when  and when miktex-etex-base-2,9 was renamed to miktex-etex-base-2.9 (if I recall correctly; I am sure it was either that or something very similar). In each case the MiKTeX Update process suggested to remove the "old" packages but it didn't give the user any hints about him having to manually add the respective replacement packages back in the package manager to get one's MiKTeX installation back into a usable state.  What are best practices for keeping MiKTeX up to date? Note that I'm not asking about installing new packages or fonts in general; there are other questions covering this area.   In which order should one execute the Update process and the Synchronization of the repository? , it is recommended to check the MiKTeX homepage before updating. What else should one do? When and in which order (and why) should one execute the "Refresh FNDB" and "Update Formats" processes within the MiKTeX Options menu? What else can happen? Other advice?


As I could not find any question dealing with this problem: Is there some kind of method that holds the current scope (such as a function for instance), aiming at printing where an exception was thrown (and caught)? I know that, for instance, some real time OSses offer such functionality. Working environment is Windows 7/8, but an OS independent call is preferred. (C++1x is ok!)  Thanks for help!

I want to have a way to report the stack trace to the user if an exception is thrown. What is the best way to do this? Does it take huge amounts of extra code?  To answer questions:  I'd like it to be portable if possible. I want information to pop up, so the user can copy the stack trace and email it to me if an error comes up.


I made a login and register form in windows form using C#. Could somebody modify my code in a way to prevent a mysql injection attack?  What else do I need to add in the code?   //MySql Connection         try         {             string myConnection = "datasource=localhost;port=3306;username=root;password=ally123;";             MySqlConnection myConn = new MySqlConnection(myConnection);              MySqlCommand selectCommand = new MySqlCommand("select * from justinsdatabase.login where username='" + this.txtBoxUser.Text + "' and password='" + this.txtBoxPw.Text + "';", myConn);               MySqlDataReader myReader;             myConn.Open();             myReader = selectCommand.ExecuteReader();             int count = 0;             while (myReader.Read())             {                 count = count + 1;             }             if (count == 1)             {                 MessageBox.Show("Login sucessful.");                 Close();                 MainMenu menu = new MainMenu();                 Hide();                 menu.Show();             }             else if (count > 1)             {                 MessageBox.Show("Duplicate username/password.");             }             else             {                 MessageBox.Show("Username or password is incorrect.");                 myConn.Close();             }         }         catch (Exception ex)         {             MessageBox.Show(ex.Message);         }         //End MySQL Connection

I need to avoid being vulnerable to SQL injection in my ASP.NET application. How might I accomplish this?


I always understood that the concept of absolute temperature stems from the third law of thermodynamics and that the lowest theoretical possible temperature is zero degrees Kelvin.    However, recently I came across . Given at the end of this question is the abstract of the said article. This article was also covered  in a somewhat more pop-science style, however I'm still unable to understand what the article is trying to cover.  What does negative absolute temperature mean in the given context?     Article's abstract:      Absolute temperature is usually bound to be positive. Under special   conditions, however, negative temperatures—in which high-energy states   are more occupied than low-energy states—are also possible. Such   states have been demonstrated in localized systems with finite,   discrete spectra. Here, we prepared a negative temperature state for   motional degrees of freedom. By tailoring the Bose-Hubbard   Hamiltonian, we created an attractively interacting ensemble of   ultracold bosons at negative temperature that is stable against   collapse for arbitrary atom numbers. The quasimomentum distribution   develops sharp peaks at the upper band edge, revealing thermal   equilibrium and bosonic coherence over several lattice sites. Negative   temperatures imply negative pressures and open up new parameter   regimes for cold atoms, enabling fundamentally new many-body states.

I saw  Nature article today, which cites e.g. . And it makes no sense to me. The temperature of a collection of particles is the average kinetic energy of those particles.  Kinetic energy cannot be less than zero (as far as I'm aware), so I don't understand what this article is trying to say, unless they're playing around with the conventional definition of "temperature". The only thing I can think of is if you have something like this: $$\frac{1}{kT} ~=~ \left(\frac{\partial S}{\partial E}\right)_{N,V}$$ And they've created a situation where entropy decreases with increasing energy.


I was shooting with a Nikon 16-35 f/4 while suddenly it started drizzling. Before even I could rush back under a shade, there were a few droplets of water all over my camera and lens, especially on the front element of the lens, too. Back home, I cleaned the front glass with a piece of flannel cloth, yet I can see a few stain of the dried water. How can I safely clean the front element of my $1000+ worth lens?

After removing dust with an air pomp and a brush, what are you using to remove stains from the lens and filters?  So far I'm using the liquid from a Giotto's CL 1002 cleaning kit for the lens, but I'm not sure what should I use for the filters, and if there is some better alternative.  Also, what kind of brushes are recommended?


When the action of curvature of spacetime happen, does that mean that spacetime is moving? But if it is, How can space be curved in space? That means that space needs space to be curved, which I can't understand.

I've seen many science popularisation documentaries and read few books (obviously not being scientist myself). I am able to process and understand basic ideas behind most of these. However for general relativity there is this one illustration, which is being used over and over (image from Wikipedia):    I always thought that general relativity gives another way how you can describe gravity. However for this illustration to work, there needs to be another force, pulling the object down (referring to a direction in the attached image). If I put two non-moving objects in the image, what force will pull them together?  So where is my understanding incorrect? Or is general relativity not about explaining gravity and just describes how heavy objects bends spacetime (in that case the analogy is being used not correctly in my opinion)?    UPDATE Thank you for the answers and comments. Namely the XKCD comics is a spot on. I understand that the analogy with bent sheet of fabric pretty bad, but it seems that it can be fixed if you don't bent the fabric, but just distort the drawn grid.   Would you be so kind and answer the second part of the question as well - whether general relativity is explaining gravitational force. To me it seems that it is not (bending of spacetime simply can not affect two non-moving objects). However most of the time it is being presented that it does.


I've already searched Physics StackExchange for some similar question but I didn't find anything about this.  Assumptions:   Earth is a perfect sphere with it's core (X,Y,Z) -> (0,0,0) as a reference-frame center Air resistance can be ignored Earth rotation can be ignored Moon gravity-effect can be ignored   And if I know (projectile starting properties):   Current Earth GPS-coordinates Starting angle Starting direction (relative to (0,0,0)) Starting velocity (can be larger than Earth-escaping speed) (mass of the projectile is irrelevant (I guess) when we know starting velocity of the projectile)   How could I calculate aprox. coordinates of a projectile landing somewhere around the Earth globe (OR detect that projectile will "leave" the Earth)?  EDIT: I've found tons of links on the net about projectile trajectories when starting velocities are quite small (& Earth can be considered like a flat plane), but non about upper situation.

I'm trying to calculate the initial launch angles and velocity of a projectile (atmosphere's effects can be neglected), assuming that I know the lat/lon coordinates of both the launch and the destination points. Can you recommend any software libraries or reading materials that could help? Thank you.


After upgrading from Ubuntu 19.10 to 20.04, software looks working fine, but the main GNOME desktop screen is showing these green lines. Also Gedit text icon in the Dock has some buggy look and some characters are missing in upper clock as seen in the below screenshot. In Ubuntu 19.10 everything worked fine. When the screen image changes the green lines disappear, but after rebooting they come back again.  If I don't find out how to fix it, I'll have to downgrade back to Ubuntu 19.10. I am disappointed, because this is the first problem I've had with Ubuntu after four years of using it.

I have recently upgraded Ubuntu 19.10 to latest LTS Ubuntu 20.04. After updating, I get serious artifacts on my screen. Every time I reboot (or log-in), my screen is fuzzy or scrambled (picture attached):     This is temporary. The fuzzy screen goes away when I change the background. But it reappears the moment I reboot or log back in.   I have Intel HD Graphics 520 (Skylake GT2).  The output of lspci -nn |grep -E 'VGA|Display' is:  00:02.0 VGA compatible controller [0300]: Intel Corporation Skylake GT2 [HD Graphics 520] [8086:1916] (rev 07)   Update:   On enabling Wayland in Ubuntu 20.04 and logging in to, these artifacts are however cured.   This is okay for now, but I am not sure about Wayland as I have not yet used it before.   Is there a way to correct the graphic issue with normal Ubuntu startup?


In 2000, I traveled to the US via a J-1 Work And Travel program and lived there, illegally, for 11 years. I was never arrested, or had any trouble with the law, I was never deported. I paid my taxes (had a SSN), had numerous jobs, bank account, etc. About 6 years ago, I decided to leave as I was tired of living like that, not able to be legal, in fear of deportation and losing everything. I just bought a ticket and left to Europe.   I would like to visit my friends back in the US. Is there any chance I won't be let in because they know I've overstayed? I'm living in a European country now, and I no longer need a visa to enter the US (the visa laws have been changed for my country). Would Immigration admit me into the country were I to arrive at the border?

I have a particular situation here, In March of 1997 I travelled to the US as a tourist and lived there illegally for almost 9 years. I was never arrested, or had any trouble with the law, I was never deported. I paid my taxed (had a TFN) had a job, bank account bought a house, etc. About 9 years ago I decided to leave as I was tired of living like that, not able to be legal, in fear of deportation and loosing everything. I also got married (to a person in the exact situation as me) we were able to legally migrate to Australia and now we are Australian citizens. We never returned our I-94s and in 2005 left through Mexico (walked through the border) so there are no records of us ever leaving. We have lived here in Australia for over 9 years.  OK so my question is... We have been thinking we would like to visit our friends and family back in the US now that we have a little girl. Is there any chance they won't let us in because they know we overstayed? We would be travelling with our Australian passports.


I have a project for my regression course. I'm curious how one chooses the dependent/independent variables. From my understanding, we want a model that has as little variance as possible, so would I choose the model that has the fewest outliers?

I'm new to this, and am struggling with the concept of how to determine what is the independent variable and what is the dependent variable.   Here's an example that I think would go a long way for me: I'm studying baseball, specifically the home run rate for all players over the course of the season. Is the player the independent variable, and the home run rate dependent on the player?


Why is it that a listener on a cell phone cannot hear music on the other end?  For example, the source phone is located either in a car with music being played, or is at a concert.  The listener hears some notes, but for the most part the music is garbled and rarely is distinguishable what is being played.  I figured it has something to do with distortion, the size of the pickup mic, or the range of the pickup mic, but don't know.

Why can't you hear music well well over a telephone line?  I was asked this question in an interview for a university study placement and I unfortunately had no idea.  I was given the hint that the telephone sampling rate is 8000 samples per second.


I am ussing the PHPMailer with SMTP authentication. The mail is sending only if the completed mail from form it is from Gmail.  I am taking the postst from a contact page, $nume = firstName, $prenume = last-name, $telefon = phone, $email = email, $mesaj = message (translated). If completed mail (from form submission) is a Yahoo mail, everything goes to spam. If a Gmail, the first mail goes to imbox, the response goes to spam.  This is the code:  $nume = $_POST['nume']; $prenume = $_POST['prenume']; $telefon =  $_POST['telefon']; $emailT = $_POST['email']; $mesaj = $_POST['mesaj'];  $mail = new PHPMailer;  $mail->isSMTP();                                       $mail->Host = 'mail.iulianbesliu.ro';   $mail->SMTPAuth = true;                              $mail->Username = 'contact@iulianbesliu.ro';                  $mail->Password = 'password';                                           $mail->Port = 25;   $mail->From = $emailT; $mail->FromName = $nume; $mail->addAddress('contact@iulianbesliu.ro'); $mail->AddCustomHeader('Reply-to:info@xpal.com');   $mail->Subject = 'Utilizator Site'; $mail->Body    = 'Nume: ' . $nume . ' ' . ' Data Eveniment: ' . $prenume . ' ' . 'telefon: ' . $telefon . "\r\n" . $mesaj;  if(!$mail->send()) {     ?>     <script>         alertify.error("Message could not be sent.");     </script>     <?php     //echo 'Mailer Error: ' . $mail->ErrorInfo; } else {     ?>    <script>        alertify.success("Message has been sent");    </script>     <?php }  $responseMail = new PHPMailer; $responseMail->isSMTP();                                       $responseMail->Host = 'mail.iulianbesliu.ro';   $responseMail->SMTPAuth = true;                              $responseMail->Username = 'contact@iulianbesliu.ro';                  $responseMail->Password = 'password';                                               $responseMail->Port = 25;   $responseMail->From =  'contact@iulianbesliu.ro'; $responseMail->FromName = 'Iulian Besliu'; $responseMail->addAddress($emailT); $responseMail->AddCustomHeader('Reply-to:info@xpal.com');   $responseMail->Subject = 'Utilizator Site'; $responseMail->Body    = 'Buna ziua dl/dna ' . $nume . "\r\n" . 'Va multumim pentru interesul acordat in vizualizarea paginii noastre, mesajul dumneavoastra a fost inregistrat si vom revenii cu un raspuns in cel mai scurt timp posibil !' . "\r\n" . 'Toate cele bune,' . "\r\n" . 'Iulian B`enter code here`esliu'; $responseMail->send();

This is a tricky one and I've always relied on techniques, such as permission-based emails (i.e. only sending to people you have permission to send to) and not using blatantly spamish terminology.  Of late, some of the emails I send out programmatically have started being shuffled into people's spam folder automatically and I'm wondering what I can do about it.  This is despite the fact that these particular emails are not ones that humans would mark as spam, specifically, they are emails that contain license keys that people have paid good money for, so I don't think they're going to consider them spam  I figure this is a big topic in which I am essentially an ignorant simpleton.


I'm taking in an input from the user and storing it in a variable called videoType.  My question is, how do I take the string the user gives to videoType and convert that into a function name that I already have defined along with many others in python?  Ex. user input: "get_MPEG()" which is stored in videoType  And I would use that input as a function name.

What is the best way to go about calling a function given a string with the function's name in a Python program.  For example, let's say that I have a module foo, and I have a string whose content is "bar". What is the best way to call foo.bar()?  I need to get the return value of the function, which is why I don't just use eval. I figured out how to do it by using eval to define a temp function that returns the result of that function call, but I'm hoping that there is a more elegant way to do this.


I have a custom user profile edit twig file.How can i check current language code in user twig file in drupal8?

In Drupal 7 the current language is a global variable we can access with   global $language; $langcode = $language->language;    I want to know how can we access the current language in a Twig file in Drupal 8 (in page--front.html.twig for example)?


I'm trying to find a solution to my problem : . So I decided to take a look to the package source code and I found this :   \def\@tempa{none}%     \edef\@tempb{\ganttvalueof{today}}%     \ifx\@tempa\@tempb\else%       \draw [/pgfgantt/today rule]         (\ganttvalueof{today} * \ganttvalueof{x unit}, \y@upper pt) --         (\ganttvalueof{today} * \ganttvalueof{x unit}, \y@lower pt);%       \node at (\ganttvalueof{today} * \ganttvalueof{x unit}, \y@lower pt)         [anchor=north] {\ganttvalueof{today label}};%     \fi%   I understood what the code does so I decided to do like that :   \draw [/pgfgantt/today rule]         (\ganttvalueof{2014-05-19} * \ganttvalueof{x unit}, \y@upper pt) --         (\ganttvalueof{2014-05-19} * \ganttvalueof{x unit}, \y@lower pt);%       \node at (\ganttvalueof{2014-05-19} * \ganttvalueof{x unit}, \y@lower pt)         [anchor=north] {Validation date};%   The problem of solution is that \ganttvalueof take a key name not the key value. How to do get the coordinate of date? Someone could show me how to do to make this code work.  Edit  I changed my code :  \draw [/pgfgantt/today rule]         (\pgfcalendardatetojulian{2014-05-19}{} * \ganttvalueof{x unit}, \y@upper pt) --         (\pgfcalendardatetojulian{2014-05-19}{} * \ganttvalueof{x unit}, \y@lower pt);%       \node at (\pgfcalendardatetojulian{2014-05-19}{} * \ganttvalueof{x unit}, \y@lower pt)         [anchor=north] {Validation date};%   It's still not working. What's the second argument of \pgfcalendardatetojulian?  MWE  \documentclass{article} \usepackage[frenchb]{babel}   \usepackage{pgfgantt} \usetikzlibrary{shadows}  \begin{document} \begin{tikzpicture} % optional    \begin{ganttchart}[x unit=1.8mm,                    y unit chart=0.87cm,                    time slot format=isodate,                    vgrid=*{5}{dotted},                  ]                   {2014-04-14}{2014-07-11}        \gantttitlecalendar{month=name} \\          \ganttbar[progress=100]{title1}{2014-04-14}{2014-04-15} \\         \ganttbar[progress=100]{title2}{2014-04-15}{2014-04-17}    \end{ganttchart} \end{tikzpicture} \end{document}   What I want to do is to have a command \verticalline[style=style, label=some label]{date} that will draw a vertical line like the vertical line for today but at a specified date.

I want to add a command to pgfgantt package that draw vertical line at a specified date (like the one for the today line). Here's what' I want to get (green line) :    So I looked to pgfgantt.sty to see how the today line was drawn and I came with this code that I added into pgfgantt.sty file :  \newcommand\drawverticalline[1]{%  \begingroup%   \begin{pgfinterruptboundingbox}%    \begin{scope}     \gtt@tsstojulian{#2}{\gtt@today@slot}     \gtt@juliantotimeslot{\gtt@today@slot}{\gtt@today@slot}%      \pgfmathsetmacro\x@mid{%        (\gtt@today@slot - 1 + \ganttvalueof{today offset})%                   * \ganttvalueof{x unit}%      }%      \draw [/pgfgantt/today rule]                 (\x@mid pt, \y@upper pt) -- (\x@mid pt, \y@lower pt)                 node [/pgfgantt/today label node] {\ganttvalueof{today label}};%      \end{scope}     \end{pgfinterruptboundingbox}%     \endgroup% }     Now normally I could use the command like this : \drawverticalline{2014-05-07} but when I do this I got this error :  ! Package PGF Math Error: Unknown function `pt' (in 'pt').   The error came from this code :  \pgfmathsetmacro\x@mid{%        (\gtt@today@slot - 1 + \ganttvalueof{today offset})%                   * \ganttvalueof{x unit}%      }%   that doesn't have pt on it. So I decided to comment it and replace \x@mid by a constant (5) but now I get this error :  ! Undefined control sequence.   Why I get this error? the command is defined!  Here's the code from pgfgantt that draw the today line :  \def\@tempa{none}% \edef\@tempb{\ganttvalueof{today}}% \ifx\@tempa\@tempb\else%   \pgfmathsetmacro\x@mid{%     (\gtt@today@slot - 1 + \ganttvalueof{today offset})%     * \ganttvalueof{x unit}%   }%   \draw [/pgfgantt/today rule]     (\x@mid pt, \y@upper pt) -- (\x@mid pt, \y@lower pt)     node [/pgfgantt/today label node] {\ganttvalueof{today label}};% \fi%     MWE  \documentclass{article} \usepackage[frenchb]{babel}   \usepackage{pgfgantt} \usetikzlibrary{shadows}  \begin{document} \begin{tikzpicture} % optional    \begin{ganttchart}[x unit=1.8mm,                    y unit chart=0.87cm,                    time slot format=isodate,                    vgrid=*{5}{dotted},                  ]                   {2014-04-14}{2014-07-11}        \gantttitlecalendar{month=name} \\          \ganttbar[progress=100]{title1}{2014-04-14}{2014-04-15} \\         \ganttbar[progress=100]{title2}{2014-04-15}{2014-04-17} \\         \drawverticalline{2014-05-07}    \end{ganttchart} \end{tikzpicture} \end{document}


I have recently encountered a problem whereby if I multiply a nested list of strings by an integer value, then attempt to add strings from another nested list, the positions at which I expect these string values to appear are not consistent with the index I am providing (apologies, finding this quite hard to explain).  Essentially, this is what I have done.  a = 0 b = 2 c = 2  lst = [['a','b','c'],['d','e','f']] lst = lst*c  lst_2 = [['w','x'],['y','z']]  for item in lst_2:     for i in range(a,(a+b)):         lst[i]+=item      a+=b  print(lst)   My output is:  [['a', 'b', 'c', 'w', 'x', 'y', 'z'], ['d', 'e', 'f', 'w', 'x', 'y', 'z'], ['a', 'b', 'c', 'w', 'x', 'y', 'z'], ['d', 'e', 'f', 'w', 'x', 'y', 'z']]   What I want/expected is this:  [['a', 'b', 'c', 'w', 'x'], ['d', 'e', 'f', 'w', 'x'], ['a', 'b', 'c', 'y', 'z'], ['d', 'e', 'f', 'y', 'z']]   I can achieve my desired output if I define lst to be [['a', 'b', 'c'], ['d', 'e', 'f'], ['a', 'b', 'c'], ['d', 'e', 'f']] explicitly, however I need to be able to do this dynamically.  I hope this is clear enough, thanks in advance for the help.

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


Preface  I'll preface this by saying two things:   I'm new(er) to python/pandas, and trying not to reinvent the wheel I've read the documentation for  I've read  and . I understand the concepts we're working with here, and am trying to figure out a "good" solution to getting a modicum of precision I know it would be easier to ensure users only enter numbers, but I don't have control over the source data; the program is a large-scale data validation tool which has to accept everything from the user no matter what was provided   Background  I'm working on porting a project from R to python, and am struggling to find a good way to translate a text-to-float conversion process. Specifically, I'm:   Reading a pandas dataframe in from a SQL database (pandas.read_sql) Casting a column which is stored as text back into a number using pd_to_numeric   Using the error='coerce' option to force the coercion from text to floats  Checking the before/after to see if/where input was coerced to NaN    Question  How to I get pandas to neatly coerce a text representation of a float value to the corresponding float cleanly?  The issue I'm running into is with the numerical precision. For example:  In[1]: pd.to_numeric('3.785', errors='coerce') Out[2]: 3.7850000000000001   I understand why that's happening (i.e. 3.785 is represented in a way that's not easily presentable in the underlying binary representation). What I'm trying to figure out is if there's a way to work around why it's happening efficiently.  For example, in R, there's a lot that goes on under the hood, but in the as.numeric API, you get the number that's ostensibly represented by the text value:  > as.numeric('3.785') [1] 3.785   which is my desired behavior. Is that possible using pandas/python?  I'm open to incorporating other packages, or being told "that's impossible."

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


How can I prove that a Gaussian integer is prime? For instance, how can I prove that $7+0i$ is a prime number?    On wikipedia, I found that a Gaussian integer is prime either if its norm is a prime in the real numbers, or if either the real or imaginary part of the number is zero, while the other part is of the form 4+3n, but this doesn't seem like a sufficient proof.

Prove: If a prime number $p\in \mathbb N$ is from the form $p=4k+3,k\in \mathbb N$, then its also a prime number in $\mathbb Z[i]$,i.e. if $p|(z_1\cdot z_2)$ then $p|z_1$ or $p|z_2$.  I dont have any idea how to solve it, so I am looking for some hints.  Thanks in advance :)


I am about to reach the end of my patience with both my desktop computer, which has Ubuntu 18.04.4 LTS, and on a new Pinebook Pro that has Manjaro.  On the desktop, I am able to get to the desktop and do some tasks, but I am not able to add or remove any file that requires the password.  It almost seems that the password has been changed from what I had entered.  On the PBP there is a similar problem.  When I try to turn the laptop on, it will work fine up to an initial log-in page.  At that page /I have not been able to enter any acceptable password since this past Saturday.  And, on the PBP I can not find any way to reset the password.  If possible, I could use some help with both computers preferably through the email address on file. Thank you, Jim

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


I'm using the BOOK class, where \tableofcontents command seems that include always the subsubsection and paragraph titles too  How can I exclude the latter?   thanks in advance Dom

So we have something like:  \documentclass{article} \setcounter{secnumdepth}{2} \setcounter{tocdepth}{2} \usepackage{amsmath}  \begin{document}  \tableofcontents  \section{Brushless Motor Fundamentals} \subsection{Brushless Motor Operation} \subsubsection{DC Motor Operation} Torque is generated in DC motors from the magnetic force, also known as the Lorentz force, which is produced when an electric current is passed through a coil in a magnetic field. This force is given by $F=q[E+(v\times B)]$, where $F$ is the force perpendicular to the coil, $E$ is the electric field in the coil, $B$ is the magnetic field, and $v$ is the velocity of the charged particles in the coil. From mechanics, torque is $\tau=F\times r$.  \section{Brushless Motor Fundamentals 2} \subsection{Brushless Motor Operation} \subsubsection{DC Motor Operation 2} If the electrical force is ignored and the remaining magnetic force is used, with the assumption that $v$ is perpendicular to $B$, we find that $\tau=qvBrsin\theta$.  \end{document}   How to show subsubsections and paragraphs in TOC?


Please give me full proof. I am expected to prove by induction. I tried all sort of things but I got stuck at $$ \frac{s_1..s_{n-1}+\tan A_n+\tan A_n(-s_2+s_4....s_{n-1})}{1-s_2+s_4...s_{n-2} - \tan A_n(s_1-s_3...s_{n-1}} $$  Where $s_r$ is sum of products of tangents of angles $A_1,A_2,...A_n$ taken $r$ at a time

$$\tan(\theta_1+\theta_2+\cdots+\theta_n)=\frac{S_1-S_3+S_5+\cdots}{1-S_2+S_4+\cdots}$$  where  $S_i$ denotes the sum of product of tangent of angles taken $i$ at a time.     For example,$$\tan(\theta_1+\theta_2)=\frac{S_1}{1-S_2}=\frac{\tan\theta_1+\tan\theta_2} {1-\tan\theta_1\tan\theta_2}$$   (This formula is given  in my textbook with no derivation or background)  How to derive this?


Not really a big problem I’m just wondering

I have a big music library that I assembled through years of purchasing music from iTunes and CDs.  I would like to give Apple Music a try but what happens to the music that I own? Particularly worried about the music that I bought from iTunes as I paid a lot for that.


When I visit my personal website on my phone (chrome app), the page language is detected as 'Portuguese' and asks me if I want to translate it. However the page is in English and I have set the language to English using the tag: <html lang="en">  Why is my page being registered as Portuguese and how can I prevent the translate button from triggering?

Several of my site's pages are appearing in search results with [Translate this page] next to it. When I click that it takes me to Google Translate and translates my page "from Catalan to English".  The pages are in English but have a couple of foreign words (actually Japanese romanisations, not Catalan) that appear to be tripping Google up.  A few weeks ago I set the html tag to <html lang="en"> which from research appears to be the best method to specify the language of a document. Google has cached the pages with this attribute but it is still offering to translate.  More research led me to a "notranslate" attribute which prevents translation entirely: <html lang="en" class="notranslate">. The problem now is users cannot translate from English to their desired language!  Are there any other solutions that force Google to parse my site as English only?


I want to predict a value Y (numeric) using numerical features $X_1, ... X_n$.  I have a neural network (MLPRegressor in sklearn) that does a pretty good job at it (Adjusted R squared = 0.70), but I need an extra property: my prediction function should be increasing in the first variable if $ x_1'< x_1, prediction(x_1',x_2,...,x_n) \leq prediction(x_1,x_2,...,x_n) $. And that is often not the case with my neural network (in 30% of the cases that I have tested the prediction is superior)  In my case, $n=59$, my training dataset contains approximately 240 000 rows.  I know that to do that I would probably have to decrease the quality of my model (R2), and that is okay as long as it stays with a correct level. The only kind of model I see that is ensuring me that is a linear model but it does not fit my data very well (R2=0.31), though I admit I could do better feature engineering for the linear model.  As $X_1$ is independant from the other variables, I thought of doing a first prediction with a neural network (or RandomForest...) only using $(X_2,...X_n)$ as features to sum up all the info contained in the other features,  and then do a linear model with two features : $X_1$ and the prediction from my first model without $X_1$  Does it seem logical to you ? Thank you very much

Is there a way or theorem that allows me to constrain a function $N(x)$, where $N(x)$ is a feedforward mlp such that it will always be a monotonic function. The simplest way is of course to use a penalty method, but this does not 100% guarantee, I am looking to see if there is a function or transformation that can be applied to $N(x)$ that constrains its form to being monotonic.  The only way I can currently think of is by making all weights $w_{i,j,k} >0$ and that the activation function $f(a)$ are monotonic and non-negative (using $f(a) = \frac{tanh(a)+1}{2}$) and having a zero bias.


I have that $G=S_4$ and $N = \{1, (12)(34), (13)(24), (14)(23)\}$, and thus far I have shown that N is a normal subgroup of G. I'm trying to figure out what group $G/N$ will be isomorphic to, but I can't figure it out. Any ideas on what the group is, and how I'd proceed proving that is the case?  I think the subgroup will be of order 2, but past that I'm not sure.

If $G:=S_4$ and $H:=\{id,(12)(34),(13)(24),(14)(23)\}$ Show that $G/H$ has order $6$ and all of its elements have order less than or equal to $3$ (so by the classification of the groups of order 6 up to isomorphism, $G/H\cong S_3$)   $H$ is normal, since left- and right cosets are equal, There are $6$ cosets:  $\{id,(12)(34),(13)(24),(14)(23)\},\ \{(12),(34),(1423),(1324)\},\ \{(13),(24),(1234),(1423)\}$  $\{(123),(134),(243),(142)\},\ \{(14),(23),(1243),(1342)\},\ \{(132),(143),(234),(124)\}$  What does it mean: All elements of $G/H$ have order less than or equal to $3$?  Each element is a set of 4 permutations, what is the order here ?  $G/H\cong S_3$: How can I construct an isomorphism, since the cosets are disjoint, can I just pick an element from each group and compare them with $S_3$ ?  Thanks in advance.


Let $k$ be a field, and $A$ and $B$ be both $k$-algebras. Suppose $B$ is integral over $A$, and also that $B$ and $A$ are integral domains.   Let us denote $F(B)$ and $F(A)$ as the field of fractions of $B$ and $A$ respectively. Does it then follow that $F(B)$ is an algebraic extension of $F(A)$?

Let $A\subset B$ be an integral extension. If $F$ and $E$ are the fields of fractions of $A$ and $B$, respectively, I want to show that $E$ is an algebraic extension of $F$.  I know that since $A \subset E$, it follows that $F \subset E$. Now I consider an arbitrary element $b_1/b_2\in E$. I would like to show that $b_1/b_2$ is algebraic over $F$. Since $B$ is algebraic over $A$, there exist monic polynomial $f_1(x), f_2(x)\in A[x]$ such that $f_1(b_1) = f_2(b_2) = 0$. But how do I obtain a polynomial $f(x) \in F[x]$ such that $f(b_1/b_2) = 0$?


I revised my previous hand drawing schematic to a clear one.   As discuss, Block A seem to be a non-inverting amplifier. But not same with classic non-inverting OPA, the input is at inveting-input at OP, is this works? Or it's a schmitt trigger? Block D seems to be a current source, How to calculate the current Id? How to analyze block B & C?  What is C1 function?   The image from circuit lab looks a litter small. I attached a bigger on pic.  Sorry for many questions, I'm really new to analog circuit.  Thanks a lot for your patience.            – Schematic created using

Could anyone help to analyze the circuit? I think block A should be a OP comparator. How about the other blocks function? Thanks a lot! The V1 is a adjust voltage source from a DAC between 4V to -4V


The problem is as follows:  let: $$ 0<a<\frac{\pi}{2} , 0<b<1 $$  show that: $$ \int_{0}^{a}\sin(x)dx+\int_{0}^{b}\arcsin(x)dx\geq ab $$  I've tried to calculate the second integral over y and not over x (over $\sin(y)$, didn't got very far.  The solution should be simple, and may involve using double integrals or using the graphs of the sine function and it's inverse in the rectangle that $a$ and $b$ form in $\mathbb{R}^2$.  even an hint would be appreciated.  Thanks

The following problem is from Spivak's Calculus.  Suppose that $f$ is a continuous increasing function with $f(0)=0$. Prove that for $a,b \gt 0$ we have Young's inequality   $$ ab \le \int_0^af(x)dx+\int_0^bf^{-1}(x)dx$$, and that equality holds if and only if $b=f(a)$.  It is enough to consider the case $f(a) \gt b$, and show that the strict inequality occurs in this case.  I've tried proving this using the theorem  $$ \int_a^bf^{-1}=bf^{-1}(b)-af^{-1}(a)-\int_{f^{-1}(a)}^{f^{-1}(b)}f$$  but I got stuck along the way.   How may I show this rigorously using the definition or properties of integrals? Any hint, suggestions or solutions would be appreciated.


For statements like the one below, I need a large left bracket to precede the array.  \Biggr\{ is not big enough.  Ideally I could use \left\{ and make the right bracket white, but there doesn't seem to be any way to do that.  \( P(Y = y) = \Biggr\{  \begin{array}{l l}  0.064&amp; \mbox{ for }y = -3 \\  0.360 &amp; \mbox{ for }y = 0 \\  0.360 &amp; \mbox{ for } y=3 \\  0.216 &amp; \mbox{ for } y=6 \\  0 &amp; \mbox{ otherwise.}  \end{array} \)

How do I produce a conditional expression with large brackets? For example: X = 0 if a=1, 1 otherwise, with a large left bracket and specifying each condition in a line?


So I am looking over some topology, and am stuck on this problem.   I have that $(K_n)_{n\in \Bbb{N}}$ is a nested sequence of non-empty compact sets in a metric sets. I have managed to prove the first part of the problem, that $\bigcap K_n \ne \varnothing $. From here I want to prove that if an open set $U$ contains $\bigcap _{n \in \Bbb{N}}K_n$ then there exists an $n_0$ such that $K_n \subseteq U$ for all $n \geq n_0$.   Hoever, I am stuck on this. I was thinking that I might want to reason along the lines that as $K_{n+1} \subseteq K_n$ for every $n$, as $n \rightarrow \infty$ there must only be a small ball, say of radius $ \epsilon \gt 0$, about a point, say $z_0$ which is in $\bigcap K_n$: $B(z_0, \epsilon)$  in $K_{n+1}$. Thus, as U is open, it is a neighbourhood of all of its points, so we can see that for $K_{n+1}$ such that it can be expressed as a ball about the point in  the intersection, $K_{n+1} \in U$. I don't know if this is correct, and I don't know if, to assert this I need to prove somehow that there is only one point on the intersection, or is it sufficient to just see that the the $K_n$s must constantly be decreasing in diameter as they are nested, meaning there can only be one point in the intersection?   Thanks

I have the following proposition:  "If $(S_n)$ is a sequence of compact subsets of a metric space such that  $S_1 \supseteq S_2 \supseteq ... \supseteq S_n$  Then $\bigcap^\infty_{i=1} S_i$ $\neq$ $\emptyset$"  My lecture notes provide the following proof, whose last step I don't understand:    Proof: Assume by way of contradiction that $\bigcap^\infty_{i=1} S_i$ = $\emptyset$. Let $V_n := (S_n)^c$ for each $n$. The class $\mathbb{C} :=\{V_n: n \in \mathbb{N} \}$ is an open covering of $S_1$. Since $S_1$ is compact, $\exists I$ finite, $I \subset \mathbb{N}$, s.t $\{V_i: i \in I \}$ covers $S_1$. Let $n:=max(I)$. The class $\{V_1, ..., V_n \}$ also covers $S_1$ and we get the following contradiction   $\emptyset = \bigcap^n_{i=1} S_i = S_n$    So, I don't get the part from "Let $n:=max(I)$..." onwards, especially the contradiction. I have tried applying DeMorgan's Law and the only way the last equalities makes sense is if the union of $\{V_1, ..., V_n \}$ equals the whole metric space, a property I haven't been able to understand from the steps of the proof. This is a corollary to the finite intersection property, so it must have a connection but again I can't quite get it.  Thanks in advance


I am searching for the ungenerate command in argis10 desktop. I get to know that is available only for workstation. But i don't have workstation. Is there any way to use this command or any other way to get the same result as that of ungenerate command.

How can I convert a shapefile (GIS) to text, or, how can I extract the information in a shapefile?


In my equation I have a unit measured in MET      $1MET=58.2 W/m^2 $. But my other parameter which is metabolic heat generation is measured in  $W/m^3$ .    I want to convert  $W/m^2$ units to  $W/m^3$. Can someone suggest me a method to do this please?  My original equation is .    For this I am trying to include the effect from exercise intensity as well. The unit that measures exercise intensity is $W/m^2$.  In my equation the term that actually exists is $Q_e \over \omega_bp_bc_b$. Units of $Q_m \over \omega_bp_bc_b$ is $m^0C$. But what I want is to actually have in celcius. $^0C$. So to get in $^0C$ what sort of adjustment can be done to $Q_e$. Should I use $Q_e $per length or something?

I have the following equation  where $ T_0(x) $ measures the temperature in Celsius at point x.    The parameter values are as follows.   My question is how to handle the second term $Q_m \over \omega_bp_bc_b$, which should give a unit of Celsius right?    What conversions in these terms do i have to make in order to measure the temperature in Celsius     I am trying to include the effect from exercises as well to this equation and modify the equation by adding a extra $Q_e\over \omega_bp_bc_b$ term. The exercise intensity $Q_e$ is measured by the unit MET. 1 MET is also defined as $58.2W/m^2$ . Can someone please tell me how to handle the units of $Q_e\over \omega_bp_bc_b$ to come up with Celsius temperature


As far as i know that read in bash contains many argument such as -a -d -e -r. The webpage list all arguments of read.  In my console, man read contains no argument on it. I upload man read > read.txt into dropbox,please download it and verify.

I keep seeing parentheses and a number after a command in Unix or Linux or C function.   For example: man(8), ftok(2), mount(8), etc.  What do these mean? I see them in man too.


I am re-posting this question, because it was marked as duplicate. However, the other ask-and-answers did not address my key question: Where/when during the Thalys ride does the ticket get stamped? This is important to anyone in my situation -- i.e., needing to return to Amsterdam after boarding the Thalys, but needing their ticket stamped to ensure their return itinerary is not cancelled.  Original question   Supposed duplicate   I purchased a ticket to Brussels via Amsterdam on KLM, with the Schiphol to Brussels-Midi portion on the Thalys. The return portion of my itinerary is on Air France several days later. This was done in good faith (i.e., not as a fare dodge) since I really do need to go to Brussels.  However, it now turns out that I have a meeting in Amsterdam the day I arrive.  I realise I am required to board the train to Brussels to fulfil the terms of my KLM ticket, and that I will need to get my ticket stamped on the Thalys in order to board my return flight. What I want to know is where and when this takes place, since I need to return to Amsterdam. Will I need to ride the train all the way to Brussels, or can I get my ticket stamped and then disembark in Rotterdam or Antwerp?  Alternatively, is there any possibility of getting my KLM Thalys ticket issued for a later train, so that I can attend my meeting in Amsterdam before heading to Brussels?

I purchased a ticket to Brussels via Amsterdam on KLM, with the Schiphol to Brussels-Midi portion on the Thalys.  The return portion of my itinerary is on Air France several days later.  This was done in good faith (i.e., not as a fare dodge) since I really do need to go to Brussels.  However, it now turns out that I have a meeting in Amsterdam the day I arrive.  I realise I am required to board the train to Brussels to fulfill the terms of my KLM ticket, and that I will need to get my ticket stamped on the Thalys in order to board my return flight.  What I want to know is where and when this takes place, since I need to return to Amsterdam. Will I need to ride the train all the way to Brussels, or can I get my ticket stamped and then disembark in Rotterdam or Antwerp?  Alternatively, is there any possibility of getting my KLM Thalys ticket issued for a later train, so that I can attend my meeting in Amsterdam before heading to Brussels?  NOTE: Some users have marked this question as duplicate.  Be assured that I read other Thalys/KLM questions others carefully prior to posting, but none of them address my key question: Where/when during the Thalys ride does the ticket get stamped?  This is important to anyone in my situation -- i.e., needing to return to Amsterdam after boarding the Thalys, but needing their ticket stamped to ensure their return itinerary is not cancelled.


Following on from a previous question of mine, where I was given coords in degree-mins, I have successfully converted them to decimal degrees, thanks for the help.    I have created a CSV file from the stated coordinates, and then created a shapefile. The CRS was EPSG:4326 (WGS84).  The remainder of my mapping is displayed in TM65/Irish Grid (EPSG:29902). With the on the fly projections activated, everything is displayed properly. I need to provide this to a 3rd party.    How do I use QGIS to add a geometry colunm using the Current CRS? Using either QGIS 1.8 or 2.0.

I need to extract the Lat/long coordinates of the centroids of districts. My QGIS project SCR and the different layers have all been set on "WGS 84 / UTM zone 18N".   I've created the centroids using the usual tool. I could then extracted the coordinates using the "Vector > Geometry Tools > Export/Add Geometry Columns", or saving the layer in CSV typing "GEOMETRY=AS_XY" in the "Layers" part of the "OGR creation options".  Nevertheless, both methods output Cartesian coordinates, whereas I need Lat/long coordinates.


I know how to prove the following exercise ( from Folland) :      If $X$, $Y$ are Banach spaces. $T:X\rightarrow Y$ is a linear map such that $f\circ T\in\operatorname{dual}(X)$ whenever $f\in \operatorname{dual}(Y)$, then $T$ is bounded.    Now I want to know whether the result is still true if $X$ and $Y$ are just normed vector spaces instead of Banach spaces.   Thank you so much.

Let $X$ and $Y$ be normed spaces, $T:X \rightarrow Y$ a linear operator. Show that $T$ is continuous if $y' \circ T$ is continuous for every $y' \in Y'$. My idea is the following: Suppose $T$ is not continuous, then there exists a sequence $x_n$ with $\|x_n\|=1$ such that $\|Tx_n\|>n$. If I could assure there is a subsequence $x_{n_k}$ such that $Tx_{n_k}$ are linearly independent I think I could construct an element $z'$ of $Y'$ such that $|(z' \circ T)x_{n_k}|>n_k$.  The first thing is, can I assure the existence of that subsequence? And if I can, how do I conclude applying H-B?  I'd like a solution with this same approach, but if there is a simpler proof i'd like to see it too.


I have my app on play store. When I check the listing from the desktop my app size is shown as 8 MB, while if I check the same on the device's play store app, it is shown as 6.75 MB. I checked this on multiple devices and on each it is showing the same. I googled about the same but couldn't found anything relevant. Can someone please provide some information about this?   Update: This question has been marked as duplicate. Just to clarify, I am not talking about difference in sizes of installed app and the actual apk size. I am saying when I check google playstore on desktop, there my app size is displayed as 8 MB, while, when I check the same listing on playstore app in devices phone there it shows as 6.75 MB. I am not getting why google play store is showing two different size on desktop and in google play app.

The Play Store lists the size of all apps available in their store.  When a user downloads and installs apps, the actual sizes reported by Android are often larger than the sizes listed by the Play Store.  Of importance, this discrepancy occurs before applications are even run for the first time.  What is the reason for the discrepancy?


I've been reading about the difference between a python constructor (__new__) vs. an initializer (__init__) on .  Given that __new__ is used to create class instances, and __init__ is used to customise those instances.   Why do most examples & working code of python classes built only with __init__?  Examples  and  (search "5. Classes")

I'm just trying to streamline one of my classes and have introduced some functionality in the same style as the .  However, I'm a bit confused as to why __init__ is always called after __new__. I wasn't expecting this. Can anyone tell me why this is happening and how I can implement this functionality otherwise? (Apart from putting the implementation into the __new__ which feels quite hacky.)  Here's an example:  class A(object):     _dict = dict()      def __new__(cls):         if 'key' in A._dict:             print "EXISTS"             return A._dict['key']         else:             print "NEW"             return super(A, cls).__new__(cls)      def __init__(self):         print "INIT"         A._dict['key'] = self         print ""  a1 = A() a2 = A() a3 = A()   Outputs:  NEW INIT  EXISTS INIT  EXISTS INIT   Why?


I'm very new to learning Python and as part of trying to get more familiar with what it, I've been messing around with writing little bits of code that do things not explicitly taught in source I'm learning from but use the same concepts.   One thing that I was trying to do was have two lists, for example list=["apple", "banana", "orange", "grape"] and otherlist=["ok", "good", "better", "best"] and using them to create a dictionary where the end result was dict={"ok":"apple","good":"banana","better":"orange","best":"grape"}.  But I couldn't figure out how to do it. To my best understanding, I'd have to iterate through both lists sort of...in parallel so as to assign the first string in 'otherlist' as the key for the first string in 'list', and so on.   I tried doing some kind of for loop, as in  for word in otherlist:     dict[word]=???   Where the "???" is where I get stuck, a since I can't figure out how to iterate through 'list' at the same time. Any help for this curious noob is appreciated! :)

Imagine that you have the following list. keys = ['name', 'age', 'food'] values = ['Monty', 42, 'spam']  What is the simplest way to produce the following dictionary? a_dict = {'name': 'Monty', 'age': 42, 'food': 'spam'}


I am trying to figure my needs regarding web service hosting.  After trying Azure I have realized that the default MySql they provide (through a third party) limits the account to 4 connections. You can then upgrade the account to 15, 30 or 40 connections (which is quite expensive). Their 15 connections plan is descirbed as:      "Excellent choice for light test and staging apps that need a reliable   MySQL database".   I have 2 questions:   if my application is a web service which needs to preform ~120k Queries a day (Normal/BELL distribution) and each query is ~150ms(duration)/~400ms(fetch), how many connection do I need? If instead of using cloud computing, I will choose a VPS, how many connections will I be able to handle on a 1GB 2 cores VPS?   Thank you!

This is a  about capacity planning for databases. Related:      I'm looking to create a canonical question of tools and methods of capacity planning for databases. This is intended to be a canonical question. Obviously, the general workflow is:  Put your scenario in place Add monitoring Add traffic Evaluate results Remediate based on results Rinse, repeat until reasonably happy  Please feel free to describe different tools and techniques for different web-servers, frameworks, etc., as well as best-practices.


I am currently working on this  and it is working the way I wanted it to. However, I needed to have one of the contents have a content change upon clicking a certain selection . I added it on the main responsive gallery content after checking that it works ok on a separate file.  Is it due to my placing of the content changing script? I tried placing it inside the main script below but it didn't work. I tried creating its own script tag and placed it at the end but same result. Right now, I tried adding it inside the head tag and it still won't work. Can somebody please help me T^T  Kindly click the atkinsons menu since that is where I inserted the content change  Here is the script tag i'm referring to who is responsible for selecting the appropriate pages to change the content.  <!--Content Change Script-->   <script type="text/javascript">     $(document).ready(function() {       $("a").click(function() {         var id = $(this).attr("data-id"); // Using a custom attribute.         $("#pages div").hide(); // gather all the div tags under the element with the id pages and hide them.         $(".div" + id).show(); // Show the div with the class of .divX where X is the number stored in the data-id of the object that was clicked.       });     });   </script>   PROBLEM Under the Atkinsons page, the content is not changing whenever i click the selection. under the first link, the outcome should look like  The title and Page should change whenever I click on the selection.   THE CHANGES I already applied the code advise from the 1st answer below. it is now changing the title upon clicking the selection, but not all section is clickable. I applied the same changes in both codepen and localhost but it produces different clickable links that doesn't work. The random letter not working depends on the size of the window. Also the paragraph is not showing

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


I made this table (see attached picture) by mixing two tables but how could I create like this table

I'm going crazy in trying to draw the following table in LaTeX:    Can you help me please? Thank you in advance  Here's what I've done:  \begin{tabular}{c c c}     A & \multicolumn{2}{c}{B}\\ E & F \\ C\\    D & G\\   \end{tabular}   Thank you all, guys, but I have to draw a table just using the following packages: array, multirow, tabularx, and the supertabular.


This code is working fine but mails are going to spam folder instead of inbox.   public function get_in_touch_always(){  $this->_Creating_get_in_touch_always();     if ($this->form_validation->run() === TRUE){         $data = array();         $data['name'] = $_POST['name'];         $data['email'] = $_POST['email'];         $data['phone'] = $_POST['mobile'];         $data['message'] = $_POST['message'];         //$data['charges'] = $_POST['charges'];         $data['upload_date'] = date("d M Y");         $data['upload_time'] =  date("h:i a");         if ($this->b->insert_in_touch_always($data)) {     $this->load->library('email');     $config['protocol']='smtp';     $config['smtp_host']='xxx.com';     $config['smtp_port']='465';     $config['smtp_timeout']='60';     $config['smtp_user']='xxx@yy.com';     $config['smtp_pass']='xxx';     $config['charset']='utf-8';     $config['newline']="\r\n";     $config['crlf']="\r\n";     $config['wordwrap'] = TRUE;     $config['mailtype'] = 'html';     $this->email->initialize('email',$config);     $this->email->from('xxx@yy.com', 'xxx');     $this->email->to('yyyy');     $this->email->bcc('zzz@gmail.com');            $this->email->subject('Notification Mail');     $this->email->message('Hie world');     if($this->email->send()){         echo "Sent";     }else{         echo "fail";     }     die();     echo "ok sent";     show_error($this->email->print_debugger());                                $this->outputData['error'] = 'Successfully Your Query is Created';         } else {             $this->outputData['error'] = 'Failed To Insert';         }     } else {         $this->outputData['error'] = validation_errors();     }     $this->load->view('thanku', $this->outputData); } }   Please let me know the solution for this. I am getting the mails but it is still going to spam folder. Is there anything to be added for this?

This is a tricky one and I've always relied on techniques, such as permission-based emails (i.e. only sending to people you have permission to send to) and not using blatantly spamish terminology.  Of late, some of the emails I send out programmatically have started being shuffled into people's spam folder automatically and I'm wondering what I can do about it.  This is despite the fact that these particular emails are not ones that humans would mark as spam, specifically, they are emails that contain license keys that people have paid good money for, so I don't think they're going to consider them spam  I figure this is a big topic in which I am essentially an ignorant simpleton.


I have a python script and I use it through my toolbox but I use it many times in a day.  Is it possible to assign a keyboard shortcut to my tool ?

How can I change or add keyboard shortcuts in ArcMap?   I have tried Customize --> Customize mode --> Commands --> Keyboard. However, this does not seem to actually work. I can add shortcuts and link them, but nothing happens when I use them even though they seems to be saved (my created shortcut still shows up after restarting Arcmap).  I'm not using English keyboard layout so, for example, I can't use the [Ctrl] + [Shift] + [=] for Zoom to selected features, since I need Shift to even get a =. It would be really useful to be able to change or add alternative shortcuts for the tools I use regularly.   Does anyone know how? Preferably something within Arcmap, but if it comes down to writing an AutoHotkey script that'll work too if you can give me some hints.  There are a few questions relating to  already, but none that I found is giving me a useful answer. I have also looked at all the lists of shortcuts that's been implemented, both on ArcGIS Resources Online and . No hints on how to change the shortcuts though.  COMMENT: If the shortcut includes [ALT GR] it doesn't seem to work properly.


I have a question about the installation on Ubuntu. I'm actually running Centos 7 on my laptop, but i need some things only available on Ubuntu. So i've created a bootable USB with my Ubuntu on it, i start my PC over Boot Device but when I choose the USB Key, i came back to grub to choose Centos ... Do I miss somethings ? I hope my English is not to bad and comprehensible ^^"" Thanks a lot for your help and Time  Pixi

I would like to see a full how-to guide on how to install Ubuntu.


In diagrams in classical kinematics, the time coordinate $t$ is drawn horizontally and the spatial coordinate $x$ is drawn vertically.  Why are Minkowski diagrams drawn the other way round?  In classical kinematics, we like to picture position as a function of time, so having time on the horizontal axis in a diagram simply corresponds to the usual way we draw the graph of a function.  I get that in relativity, position and time are on equal footing, so that the functional aspect may be deemphasized. But since it is a pretty big hurdle to compare relativistic kinematics to classical kinematics if we always have to flip the diagrams in our heads, I would expect that this would be only done if there are some striking advantages. However, I couldn't think of any.  What's even more strange is that we still write vectors as $(ct,x)$ instead of $(x, ct)$. So we are also making it harder to apply visual intuitions based on the usual conventions in linear algebra (like picturing the action of a familiar matrix on a vector). Maybe the conventions in linear algebra are actually more recent than the conventions of special relativity.  edit: Although the other question has an accepted answer, it does not answer the question of why the convention from classical kinematics was discontinued. It simply reiterates that it is a convention (and a comment expands that this convention can be traced at least to a 1909 paper by Minkowski himself).

Learning special relativity and working with Minkowski diagrams for a while now i am still trying to get my head around some oddity.   From my understanding time can often be seen as the dependent variable in those diagrams, so why put it to the vertical axis? What confuses me even more is the apparent convention to denote a point in space time $(t,x)$ even though $x$ is on the horizontal and $t$ is on the vertical axis, so the usual notation would be to refer to that vector as $(x, t)$.  Are there mostly historical reasons or why is it beneficial to use this notation and to violate usual conventions?


I have defined a homorphism $\phi: Z/100Z * Z/10Z  \rightarrow Z/1000Z$ defined as $\phi ((a,b)) \rightarrow a*10 + b$ and from what I can tell this is a valid isomorphism. Can someone explain to me why my function is not an isomorphism?  edit: reworded to show uniqueness of question

How does one prove $\Bbb{Z}_{100} \times \Bbb{Z}_{10}$ is not isomorphic to $\Bbb{Z}_{1000}$  Do you have to show one is cyclic and the one isn't? (why does this work?)


Hi in the below where click on this fragment my list view getting null pointer.  If it is normal activity it is working fine.it is crashing my app  can any one please help me where i did the mistake.  public class HomeFragement extends Fragment {      EditText et_building;     TextView Add;     ListView lv;     ArrayList<String> arrayList;     ArrayAdapter<String> adapter;        public HomeFragement() {     }      @Override     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {          ((NavigationViewActivity) getActivity()).setActionBarTitle("ADD BUILDING");          View rootView = inflater.inflate(R.layout.activity_building, container, false);          init();          return rootView;     }      private void clickListener() {         Add.setOnClickListener (new View.OnClickListener ( ) {             @Override             public void onClick(View v) {                 String result=et_building.getText ().toString ();                 arrayList.add (result);                 adapter.notifyDataSetChanged ();              }         });     }      private void init() {         et_building=(EditText)getActivity ().findViewById (R.id.build_name);         Add=(TextView)getActivity ().findViewById (R.id.addbuild);         lv=(ListView)getActivity ().findViewById (R.id.list_building);         arrayList=new ArrayList<String> ();         adapter=new ArrayAdapter<String> (getActivity (),android.R.layout.simple_list_item_1,arrayList);         lv.setAdapter(adapter);         clickListener();     }

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


I want to know how to prove the following formula 1)$\gcd(k^{2^i}+1,k^{2^j}+1)=1$ when $i \ne j$ and $k$ is even. 2)$\gcd(k^{2^i}+1,k^{2^j}+1)=2$ when $i \ne j$ and k is odd. Thanks!

I'm trying to understand the following proof of why      No two Fermat numbers have a common divisor greater than $1$.   Hardy and Wright show the following proofs:   If $x = 2^{2^n}$, we have  $$\frac{F_{n+k} - 2}{F_n}(\circ) = \frac{2^{2^{n+k}}-1}{2^{2^n}+1} = \frac{x^{2^k}-1}{x+1} = x^{2^k-1} - x^{2^k-2} + \ldots -1$$  The main issue I'm having is the $\circ$ part. I don't understand how they get that. The rest of the proof makes sense but the first part is really confusing me. Can someone please explain where they get that fraction?  Thanks a bunch!


When I use curl -s to access a text file, it will display the entire content. Is there any way to ignore the first line of content?  Test text file link:  curl -s https://raw.githubusercontent.com/Automattic/_s/master/languages/readme.txt

Is there a simple way I can echo a file, skipping the first and last lines? I was looking at piping from head into tail, but for those it seems like I would have to know the total lines from the outset. I was also looking at split, but I don't see a way to do it with that either.


If $B_{1},B_{2}$ are two bases for a vector space $V$, prove that there exists a bijection $f:B_{1}\rightarrow B_{2}$. It is known to all that the statement is true for finite-dimensional vector spaces, with quite a lot of elegant proofs. I suppose there at least should be one or two similarly elegant proofs for the infinite-dimensional version, assuming that the Axiom of Choice is correct.

I am having a difficulty setting up the proof of the fact that two basis of a vector space have the same cardinality for the infinite-dimentional case. In particular, let $V$ be a vector space over a field $K$ and let $\left\{v_i\right\}_{i \in I}$ be a basis where $I$ is infinite countable. Let $\left\{u_j\right\}_{j \in J}$ be another basis. Then $J$ must be infinite countable as well. Any ideas on how to approach the proof?


my character that i have models is one object, i want to subdivide the head and other body parts, however i dont know how to keep the one i want with sharp edges to stay  i want to keep the mouth the way it is, sharp, i dont know how to, can anyone help me

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


Why is "letter" not plural in "two letter words"?  For me it's very strange as the equivalent in French would be plural but my English friend finds it totally normal.

Which is correct, a "two-year" program or "two-years" program?  The difference between two expressions is the absence/presence of "s", i.e., singular or plural.


Given a group of $p_1$ ladies and $p_2$ gents and a round table with exactly $p_1+p_2$ places. For reasons which I do not dare to mention, I want to find a seating arrangement such that nobody is sitting in-between two ladies.  1) Say that $p_1$=$p_2$=$p \geq 10$. For which values of $p$ it is possible to make a seating arrangement?   2) Give an expression for the number of possible seating arrangements  for those values of $p$ for which a seating arrangement is possible. In this case, a host and hostess have fixed places abreast each other and all the ladies and gents are distinguishable.   Results so far:  I know that there a no possibilities if $p_1$>$p_2$. It seems to me that a seating arrangement is possible if $p$ is odd. But I don't know if this is true.

Say there are $p_{1}$ red balls and $p_{2}$ green balls. We put all the balls in a circle with $p_{1}+p_{2}$ places in total. It is forbidden that a ball (red or green) is placed between two red balls.    Show that this is impossible if $p_{1}>p_{2}$.   Further on, say $p_{1}=p_{2}=p\geq10$. For which values of $p$ the ordination is possible?  Can somebody help me? Thanx in advance!


'document.cookie' in JavaScript does not work without a web server. Using the protocol for local file-access 'document.cookie' will always contain an empty string.  Please see the accepted answer in this !  As far as I know are cookies text-files stored in some sub-directory of the particular used browser. Containing key-value pairs.  So, after setting a cookie it should be there on the client-side.  Why has a web server to be involved?  I have made myself this demo:    writeMessage(); // Call the function when page is loaded. => No cookie there.  function writeMessage() {   var message;    document.cookie.indexOf('foo') === -1 ?     message = 'Cookie does not exist.' :     message = 'Cookie is there!';    document.querySelector('div').innerHTML = message }  document.querySelector('button').addEventListener('click', () => {   document.cookie = "foo=bar";   writeMessage(); // Call the function again when the cookie has been set. });

 <button>Set Cookie</button>     When the button is clicked then the cookie is set.  Then the function checks if a cookie exists. It finds that this is true and shows the according message.  !! There haven't been a second request to the web server !!  So why doesn't work cookies when using  for accessing the page?

I am using the jQuery Cookie plugin ( and  and ) to set and read a cookie. I'm developing the page on my local machine.  The following code will successfully set a cookie in FireFox 3, IE 7, and Safari (PC). But if the browser is Google Chrome AND the page is a local file, it does not work.  $.cookie("nameofcookie", cookievalue, {path: "/", expires: 30});   What I know:   The plugin's  works with Chrome. If I put my code on a web server (address starting with http://), it works with Chrome.   So the cookie fails only for Google Chrome on local files.  Possible causes:   Google Chrome doesn't accept cookies from web pages on the hard drive (paths like file:///C:/websites/foo.html) Something in the plugin implentation causes Chrome to reject such cookies   Can anyone confirm this and identify the root cause?


I've tried solving this, but I'm stuck at one point.  Here's what I did:  Let $ z = x + yi $, where $x, y \in \mathbf R$  Then , $ (x + yi)^2 + \sqrt{x^2 + y^2} = 0 $  Or, $x^2 + {(yi)}^2 + 2xyi + \sqrt{x^2 + y^2} = 0 $  Or, $ x^2 - y^2 + 2xyi + \sqrt{x^2 + y^2} = 0 + 0i$  Thus, $ x^2 - y^2 + \sqrt{x^2 + y^2} = 0\qquad\qquad\qquad\qquad\qquad\qquad\ (i)$ and $2xy = 0 \qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad(ii)$  If $2xy = 0$, then either $x = 0 $ or $y = 0$  Now, if I take $ x = 0$, and subsitute in $(i)$, I get either $y = 0$ or $y  = 1$.  So far, so good, but if I take $y = 0$, and substitute in $(ii)$:  We have $x^2 + \sqrt{x^2} = 0$  so $x^2 = -\sqrt{x^2} $  or $x^2 = -x$  or $\frac{x^2}{x} = -1 $  or $x = -1$  However, this solution doesn't satistfy the equation $x^2 + \sqrt{x^2}$ or the original equation.   What am I doing wrong here ?

Solve for $z$: $$z^2+|z|=0$$ I found this question on my textbook but I unable to derive an answer to it as a modulus of $z$ is present. I am unable to take an approach please guide me ..thanks


I started a bounty just now on . The "Reward existing answer" reason was visible so I chose that option and the system let me use it even though there are no existing answers (AnswerCount=0).

It strikes me that the most popular reason for starting a bounty on a question is because the question hasn't received any answers thus far. However, when starting a bounty, whether there are any answers or not, it still presents you with the full array of reasons for starting the bounty.  Three of the reasons should surely be removed in this instance:     Current answers are outdated   Improve details   Reward existing answer     If the screen is still shown I'd advocate that they were greyed out rather than removed for the sake of consistency.  However, in truth, I think I'd go one step further and suggest this entire screen is skipped in the case where there are no answers. Surely in that case, it's pretty obvious that the reason you're starting a bounty is just "there's no damn answers and I need an answer!" (Or, out of the current options, perhaps that should be "draw attention".)


In a book1 I have encountered the following:     To check your understanding of [the importance of quantifier order], consider the following two statements. One is true, and the other is false. Which is which?   $$ \exists y > 0\ \text{such that}\ \forall x > 0, y < x $$   $$ \forall x > 0\ \exists y > 0\ \text{such that}\ y < x $$   (The type of $x$ and $y$ aren't specified, but I've assumed they are real numbers)  I think I understand how the two statements are different. However, to me, both statements appear to be false:  Start by assuming either statement is true. Since $y < x$, we can state that $y = x - d$, where $d > 0$. Let us consider the case that $x = d$. Substituting $x$ for $d$ gives us: $y = d - d \implies y = 0$. This contradicts the requirement in both statements that $y > 0$. Both statements must be false.  Alternatively stated: Whatever the value of $y$, there is a value of $x$ where $x = y$, contradicting the requirement that $y < x$.  Has the author made a mistake or am I making one? If so, please explain my mistake and help me understand which one is true, and why (with emphasis on the order of the quantifiers if possible).    1How to Study for a Mathematics Degree by Lara Alcock, p73

I am reading nested quantifiers. I am confused in between two cases,   1. Existential Quantifier before Universal Quantifier  2. Universal Quantifier before Existential Quantifier   I would be very thankful if someone highlights the difference between them and also give an example.   Thanks in advance.


If     $$ \sum  x_n$$  is divergent where $x_n$'s  are non negative. For $p \geq 1$, is it true that $$ \sum \frac{x_n}{(x_1 + \cdots +x_n)^p} $$  is convergent?

Let $a_n$ be a sequence of positive reals, such that the partial sums $S_n = \sum_{i = 1} ^ n a_i$ diverge to $\infty$. For given $\epsilon > 0$ do we have $$\sum_{n = 1} ^ \infty \frac{a_n}{S_n^{1 + \epsilon}} < \infty?$$  For $\epsilon \ge 1$ we can resolve this quickly by noting $$\frac{a_n}{S_n ^ 2} \le \frac 1 {S_{n - 1}} - \frac 1 {S_n}$$ so for sufficiently large $n$ we can bound $\frac{a_n}{S_n^{1 + \epsilon}}$ by $\frac 1 {S_{n - 1}} - \frac 1 {S_n}$ as well. I'm wondering if this is true for arbitrary $\epsilon > 0$. I know that the series in question diverges for $ \epsilon = 0$, so all that is missing is what happens in $(0, 1)$.


I am a 16 year old US citizen who is planning to go to Canada next week. I found out today that my passport has expired.  Can I cross the border with my birth certificate instead? The rules on this seem to have changed several times. I found  from July 2015 asserting that only children under the age of 15 can cross with a birth certificate.  However, , whose answer points to  states that any US citizen should be able to get into Canada with proof of citizenship.  So it seems like I will be able to get in, but I need to make sure there hasn't been an update to the laws since the second page was written.

I have a daughter five months old has no US passport can she go to Canada with her birth certificate?


I see the macro duo:   \@bsphack ... code ... \@esphack   appearing in different places. I noted that it suppresses spaces around the macro in which these commands are used, but when do you need to use them in your own macros / are there other use cases?

I have a command like  \newcommand{\todo}[1]{#1}   which I sometimes replace by:  \newcommand{\todo}[1]{}   In terms of spacing/whitespace, the behavior of the "empty" command is as follows:  Test.  \todo{foo} % does not generate (vertical) whitespace => good  Test\todo{foo}. Test. % does not generate (horizontal) whitespace => good  Test\todo{foo}. \todo{foo} Test. % _does_ generate (horizontal) whitespace => bad   Is there any way to avoid this, i.e., to (temporarily) replace a command in a way so that it is fully equivalent to removing all occurrences of the command?  (I know that there are packages like todonotes or verbatim, which provide similar functionality. But I always wanted to know how to solve this manually, and never had an idea how to approach this / what to search for. Using \xspace or \empty in the command did not work at least.)


I am using visual c++ on windows and i want to break the code (like wait for a key to be pressed (and I've worked this out already)) BUT detect which key WAS pressed.A bit like c#'s .ReadKey()

I can never remember how I do this because it comes up so infrequently for me. But in C or C++, what is the best way to read a character from standard input without waiting for a newline (press enter).  Also ideally it wouldn't echo the input character to the screen. I just want to capture keystrokes with out effecting the console screen.


If $d_1 =1, d_2, \cdots, d_k = n$ are the positive divisors of the   natural number $n$, show that $(d_ld_2 \cdots d_k)^2 = n^k$.   Seems a confusing question with no place to start with, please help. I see no approach except induction to work. Apart from induction, if some way to bring up a proof, then would be quite fine.

The function $d(n)$ gives the number of positive divisors of $n$, including n itself. So for example, $d(25) = 3$, because $25$ has three divisors: $1$, $5$, and $25$.  So how do I prove that the product of all of the positive divisors of $n$ (including $n$ itself) is $n^{\frac{d(n)}{2}}$.  For example, the divisors of $12$ are $1$, $2$, $3$, $4$, $6$, and $12$. $d(12)$ is $6$, and $1 · 2 · 3 · 4 · 6 · 12 = 1728 = 12^3 = 12^{\frac{6}{2}} = 12^{\frac{d(n)}{2}}$


Let $f(z)$ analytic. Prove that $\overline{ f(\bar{z})}$ is also analytic.  How do I use the concept of analytic of $f(z)$ here? any help

I'm doing a bit of self study, but I'm uncomfortable with a certain idea. I want to show that $f(z)$ is analytic if and only if $\overline{f(\bar{z})}$ is analytic, and by analytic I mean differentiable at each point. Here $f$ is a complex valued function.  What I do is write $f(z)=u(x,y)+iv(x,y)$, where $u$ and $v$ are real functions of two variables. Then $\overline{f(\bar{z})}=u(x,-y)-iv(x,-y)$.  These two forms look very similar, in the sense the one function being differentiable should immediately imply the other is differentiable, since the only thing really changing might be a $-$ sign popping out due to the chain rule.   How can I more rigorously express that $f(z)$ is analytic iff $\overline{f(\bar{z})}$ using this? Many thanks.


I am trying to install git-all using the following commands:  sudo apt update sudo apt install git-all   and I get the following results:  jonathan@Aristotle:~$ sudo apt install git-all Reading package lists... Done Building dependency tree        Reading state information... Done git-all is already the newest version (1:2.7.4-0ubuntu1). 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 2 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Do you want to continue? [Y/n] y Setting up runit (2.1.2-3ubuntu1) ... start: Unable to connect to Upstart: Failed to connect to socket /com/ubuntu/upstart: Connection refused dpkg: error processing package runit (--configure):  subprocess installed post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of git-daemon-run:  git-daemon-run depends on runit; however:   Package runit is not configured yet.  dpkg: error processing package git-daemon-run (--configure):  dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure.                                                                                Errors were encountered while processing:  runit  git-daemon-run E: Sub-process /usr/bin/dpkg returned an error code (1)   I found this response to a similar question:  but none of the solutions mentioned in it worked for me. Any ideas on how I can proceed from here?

I am trying to install php curl like so:  sudo apt-get update sudo apt-get install php5-curl   But I keep getting an error.  Reading package lists... Done Building dependency tree        Reading state information... Done php5-curl is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded. 2 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Do you want to continue? [Y/n] Y Setting up runit (2.1.2-3ubuntu1) ... start: Unable to connect to Upstart: Failed to connect to socket /com/ubuntu/upstart: Connection refused dpkg: error processing package runit (--configure):  subprocess installed post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of git-daemon-run:  git-daemon-run depends on runit; however:   Package runit is not configured yet.  dpkg: error processing package git-daemon-run (--configure):  dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure.                           Errors were encountered while processing:  runit  git-daemon-run E: Sub-process /usr/bin/dpkg returned an error code (1)   when I try sudo dpkg --configure -a I get:  dpkg: dependency problems prevent configuration of git-daemon-run:  git-daemon-run depends on runit; however:   Package runit is not configured yet.  dpkg: error processing package git-daemon-run (--configure):  dependency problems - leaving unconfigured Errors were encountered while processing:  git-daemon-run   when I try sudo apt-get install --reinstall runit I get:  Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 8 not upgraded. 2 not fully installed or removed. After this operation, 0 B of additional disk space will be used. E: Internal Error, No file name for runit:amd64   when I try sudo apt-get install runit I get:  Reading package lists... Done Building dependency tree        Reading state information... Done runit is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 8 not upgraded. 2 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Do you want to continue? [Y/n] Y Setting up runit (2.1.2-3ubuntu1) ... start: Job is already running: runsvdir dpkg: error processing package runit (--configure):  subprocess installed post-installation script returned error exit status 1 dpkg: dependency problems prevent configuration of git-daemon-run:  git-daemon-run depends on runit; however:   Package runit is not configured yet.  dpkg: error processing package git-daemon-run (--configure):  dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure.                                                                                Errors were encountered while processing:  runit  git-daemon-run E: Sub-process /usr/bin/dpkg returned an error code (1)   when I try sudo apt-get install --reinstall git-daemon-run I get:  Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 8 not upgraded. 2 not fully installed or removed. After this operation, 0 B of additional disk space will be used. E: Internal Error, No file name for git-daemon-run:amd64   How can I fix this?  System Specs:  Processor: Intel® Core™ i7-3630QM CPU @ 2.40GHz × 8 Graphics: Gallium 0.4 on AMD TURKS (DRM 2.43.0, LLVM 3.6.2) OS Type: Ubuntu 15.10 64-bit


I'd like a hint to show that:  $$\lim \frac{1}{n} \sqrt[n]{(n+1)(n+2) \cdots 2n} = \frac{4}{e} .$$  Thanks.


Let $\Omega$ be a domain in $\mathbb{C}$ and $v$ be a function on $\Omega.$ Suppose that $v(z)$ depends only on $|z|$ and not on arg$z.$ Show that $v$ is harmonic if and only if  $v(z)=A\log |z|+B$ for some constants $A$ and $B$.  Any hint. Thanks in advance!

Sources: this is an old advanced calculus exam question, which I think is asking for harmonic functions.  The problem statement is:     Suppose $F(r)$ is a smooth function of $r$ for $r>0$ . Define $\Phi(x) = F(|x|)$ with $x = (x_1, ...,x_d) \in \mathbb{R}^d$ and $|x| = (\large \sum_i^dx_i^2)^{\frac{1}{2}}$.For $d=2$ and $d=3$, find all possible functions $F(r)$ so that   $$\sum_{i=1}^d (\frac {\partial}{\partial x_i})^2\Phi(x) = 0.$$   Any hints or comments are welcome.  So, it appears that this problem statement is just a tricky way  of asking to find all functions $\Phi$ such that   $$\Phi_{x_1x_1} + \Phi_{x_2x_2} = 0 $$  and   $$\Phi_{x_1x_1} + \Phi_{x_2x_2} + \Phi_{x_3x_3} = 0$$  I.e., we are looking for all functions that are harmonic.  But what is weird about this question is that it doesn't really specify a domain in which we are to find these harmonic functions.  Unless the domain is simply understood to be for all $| x| \ne 0$.  Thanks,


I know that Principal Component Analysis (PCA) is the eigenvector of the covariance matrix. It is used as a tool for dimensional reduction. What I am confused about is whether the PCA give weights to original features in order to find out which features explain the data the most or does it come up with new set of abstract features that explain the greatest variance in the data set.

In today's pattern recognition class my professor talked about PCA, eigenvectors and eigenvalues.   I understood the mathematics of it. If I'm asked to find eigenvalues etc. I'll do it correctly like a machine. But I didn't understand it. I didn't get the purpose of it. I didn't get the feel of it.        I strongly believe in the following quote:     You do not really understand something unless you can explain it to your grandmother. -- Albert Einstein   Well, I can't explain these concepts to a layman or grandma.   Why PCA, eigenvectors & eigenvalues? What was the need for these concepts? How would you explain these to a layman?