Consider the following sentence:     I am developing an application to be installed on Android.   And this:     This has been a major flaw in Android...   To be clear I am unsure of the usage of "in" vs. "on". When should I use "in" and when to use "on"?


Lately, I've been seeing some pretty liberal definitions of "exact duplicate" in some people closing SO questions.  If I recall correctly, Jeff had intended to make it so that there were loose rules on closing duplicate questions.  So I had always assumed that an exact duplicate was meant to be... well... an exact duplicate.  So that if someone were to accidentally double-post a question, the second one would be closed.  Extremely similar topics should be posted in the thread itself.  If I wanted to be berated for not utilizing search better, I'd go post on usenet.  Now I realize that people who close threads don't mean to berate people.  But it's difficult not to take offense at having a thread closed as a duplicate, and I feel that this may chase newbies away.  What is your interpretation of "exact duplicate?"


Postgresql PDO, can't run a SELECT using HTML5's datalist

I am new to PDO, really new, I'm trying to read documentation from several site (, for example) but I just don't fully understand it.  Still, I wish to update an internal website I'm using in my company because this project is becoming bigger and important and I want to rewrite it to shape it better.  I was able to "convert":  <?php $sql = "SELECT name FROM table order by name ASC"; $result1 = pg_query($conn, $sql); while ($row = pg_fetch_row($result1)) {   echo "<option value='$row[0]'>$row[0]</option>"; } ?>   to:  <?php $sql = "SELECT name FROM table order by name ASC"; $stmt_menu = $pdo->prepare($sql); $stmt_menu -> execute(); foreach ($stmt_menu as $row){   echo "<option value=".$row['name'].">".$row['name']."</option>"; } ?>   Even though I would have preferred to continue using the row[0] for simplicity, but Apache's logs complained about PHP Notice:  Undefined offset: 0 in /var/www/pdo-test-website/left-menu.php on line 20  Following other tutorials (like  one), I am trying to replace the current datalist SQLs into a PDO based statements.  Before I had:  <input type="text" list="test_list" class="form-control input-sm" name="test_name" id="test_name_id" />  <?php echo '<datalist id="test_list">'; $test_name = pg_query("SELECT DISTINCT ON (FOO) FOO FROM table;"); while ($row = pg_fetch_row($test_name)) {   echo "<option value='$row[0]'>$row[0]</option>"; } echo '</datalist>'; ?>   Now:  <?php $datalist_foo = "SELECT DISTINCT ON (:value) :value FROM table;"; $stmt_datalist = $pdo->prepare($datalist_foo);   echo '<datalist id="test_list">'; $stmt_datalist->execute(['value' => "FOO"]); foreach ( $stmt_datalist as $row ) {     echo "<option value=".$row['FOO'].">".$row['FOO']."</option>"; } echo '</datalist>'; ?>   I am trying my best to have it working but I keep reading errors in the Apache's error log file. I tried rewriting this statement in many different versions, it would be not so useful if I would paste the log file for your reviewing because I should also write, for each error row, its full php code.  The last error, the one that I get after trying the code I posted above, is:  PHP Notice:  Undefined index: FOO in /var/www/pdo-test-website/datalist.php   I just want to note, that the non-pdo version works, the (test) database have data inside and I am able to fetch them using the "old" pg_query method.  I hope you can give me some advice, I also tried the solution at this link:  but I can't get it working.


I have a standard account salesforce page, where i have a custom visualforce page included as a section. Now i want to reload a whole standard page if the button at the custom vf-page  was clicked. Is it possible?


Let $f: X \rightarrow Y$ and $g: Y \rightarrow X$  If $f \circ g$ is surjective, then f is surjective, too.  I think that is true.   Question: How can I proove that? I have so far:   $\forall y \in Y: \exists x \in X : f(x)=y$  $\forall x \in Y : \exists y \in Y : f \circ g(y)= x$


I'm about to connect our network to the IPv6 Internet and need to control the kernel ipv6 settings found under /proc. I know there are configurations for each interface, for all interfaces, and the default config. My question is: which settings win if the individual values contradict each other? While I was able to find good documentation on the individual settings, I don't know about setting precedence ...  There is a , but it mainly talks about the differences of all, default and the individual interfaces.  From that I gather the concrete settings are always somehow logically combined. However, the fields most important to me (see the following examples) are not covered, and IPv6 seems to be implemented differently so that the referenced kernel source file in the referenced answer does not help my IPv6 issue and the following examples.  A few examples:  cat /proc/sys/net/ipv6/conf/all/accept_ra 0 cat /proc/sys/net/ipv6/conf/eth1/accept_ra 1   Will eth1 accept router advertisements?  cat /proc/sys/net/ipv6/conf/all/forwarding 1 cat /proc/sys/net/ipv6/conf/eth1/forwarding 0 cat /proc/sys/net/ipv6/conf/eth1/accept_ra 1   Will eth1 accept router advertisements?  cat /proc/sys/net/ipv6/conf/all/disable_ipv6 1 cat /proc/sys/net/ipv6/conf/all/accept_ra 1 cat /proc/sys/net/ipv6/conf/eth1/disable_ipv6 0 cat /proc/sys/net/ipv6/conf/all/accept_ra 0   Will eth1 accept router advertisements?  cat /proc/sys/net/ipv6/conf/all/disable_ipv6 1 cat /proc/sys/net/ipv6/conf/all/fowarding 1 cat /proc/sys/net/ipv6/conf/eth1/disable_ipv6 0 cat /proc/sys/net/ipv6/conf/all/accept_ra 1   Will eth1 accept router advertisements?


Windows 8.1 apps Calculator, Alarms, Weather (just a few) crash immediately when opened

When I open some apps from the Start Screen in Windows 8.1, it just closes right away and brings me back to Start.  It won't show me why it closed at all, but I looked in Event Viewer and it says in the description of the event: Activation of app Microsoft.WindowsCalculator_8wekyb3d8bbwe!App failed with error: The remote procedure call failed. See the Microsoft-Windows-TWinUI/Operational log for additional information.  This only started happening recently. It was not right after my Windows 8.1 upgrade, it happened about a week after. I don't remember anything I did differently that could've caused this.  Update: There is a more detailed error about what happened in the Event Viewer. It looks like a message from the original process. It's not a wwahost.exe process, so there must be a native executable for the Calculator app.  Faulting application name: Numbers.exe, version: 6.3.9600.16422, time stamp: 0x5252aa2a Faulting module name: Windows.UI.Xaml.dll, version: 6.3.9600.16408, time stamp: 0x523d4b78 Exception code: 0xc000027b Fault offset: 0x0000000000a4f30a Faulting process id: 0x510 Faulting application start time: 0x01ced4f4c2172eb3 Faulting application path: C:\Program Files\WindowsApps\Microsoft.WindowsCalculator_6.3.9600.20278_x64__8wekyb3d8bbwe\Numbers.exe Faulting module path: C:\Windows\System32\Windows.UI.Xaml.dll Report Id: 003d791e-40e8-11e3-825f-e89a8fb9d4bb Faulting package full name: Microsoft.WindowsCalculator_6.3.9600.20278_x64__8wekyb3d8bbwe Faulting package-relative application ID: App   Update 2: The Weather app also crashes, and this one runs under wwahost.exe. I don't know if this helps anything.  Faulting application name: wwahost.exe, version: 6.3.9600.16384, time stamp: 0x5215d0bb Faulting module name: KERNELBASE.dll, version: 6.3.9600.16408, time stamp: 0x523d557d Exception code: 0x00000004 Fault offset: 0x000000000000ab78 Faulting process id: 0x5d8 Faulting application start time: 0x01ced4f76d555461 Faulting application path: C:\Windows\system32\wwahost.exe Faulting module path: C:\Windows\system32\KERNELBASE.dll Report Id: ab102e6a-40ea-11e3-825f-e89a8fb9d4bb Faulting package full name: Microsoft.BingWeather_3.0.1.203_x64__8wekyb3d8bbwe Faulting package-relative application ID: App


I want to remove desktop from my Ubuntu server (I installed gnome desktop to be able to run Firefox and other programs with GUI). But I don't want to use desktop itself. I want to see command prompt most of the time. How can I solve this problem?


Private Java Hosting with 512 or more heap size

I would like to know service provider for private java hosting with 521 or more heap size with unlimited mysql databases with apache tomcat.  Edit:max $400


How to call a C++ class Constructor from another Constructor

I'm trying to create an object in C++ that requires multiple object constructors. Say Foo() and Foo(int) where Foo(int) then calls Foo(). The simplified code is written below:  #include <iostream> class Foo{  private:         int iX;   public:         void printX(string sLabel){             cout << sLabel << " : " << " Foo::iX = " << Foo::iX << endl;         };           void setX(int iX){             Foo::iX = iX;              Foo::printX("setX(void) Method");         };           Foo(){             Foo::iX = 1;             Foo::printX("Foo(void) Constructor");         };         Foo(int iX){             Foo::setX(iX);             Foo::printX("Foo(int) Constructor");             Foo::Foo();             Foo::printX("Foo(int) Constructor");          };   };  int main( int argc, char** argv ){      Foo bar(2);      return 0; }   The output of which is  setX(void) Method :  Foo::iX = 2 Foo(int) Constructor :  Foo::iX = 2 Foo(void) Constructor :  Foo::iX = 1 Foo(int) Constructor :  Foo::iX = 2   As the results indicate setX method works as expected. Foo::iX is equal to 2 inside and outside of scope of that function.  However when calling the Foo(void) constructor from within the Foo(int) constructor, Foo::iX stays equal to 1 only within that constructor. As soon as it exits out that method, it reverts back to 2.  So my question is 2-fold:   Why does C++ behave this (a constructor cannot be called from within another constructor without values that were assigned)? How can you create multiple constructor signatures, but without redundant duplicate code doing the same thing?


An apparent paradox while computing limits

On trying to compute the following limit, $$\lim_{n\to \infty}\bigg({\frac{1}{n^2+n+1}+\frac{2}{n^2+n+2}+\dots+\frac{n}{n^2+n+n}\bigg)}$$ I used the well-known addition property of limits to conclude that the above expression is equal to $$\lim_{n\to \infty}{\bigg(\frac{1}{n^2+n+1}\bigg)}+\lim_{n\to \infty}{\bigg(\frac{2}{n^2+n+2}\bigg)}+\dots+\lim_{n\to \infty}{\bigg(\frac{n}{n^2+n+n}\bigg)}$$ Now, since reach of the individual limits tends to $0$ as $n$ tends to infinity, I concluded that the final answer is $0$.  But the solution given to this problem uses the Squeeze theorem and states that the limit is $\frac{1}{2}$, and so does WolframAlpha. I found the problem and its solution here:   Where am I wrong????!!!!  Thanks for any answers!


Does This System Of Electric Charges Violate Conservation Of Energy?

Imagine a system of 3 point charges and some kind of circular "rail".  All charges have the same magnitude - 2 are positive and one negative.  One positive charge is placed at some distance from the center of the circular rail.  The two other, are "glued" together so they must move together, and they are placed on the rail which   force them to move only on the rail path.  Now imagine i give them a slight push.  Calling the glued charges the "system", We can say that the force between the system and the positive charge outside the rail is both attractive and repulsive (depending on what part of the rail the system is) but we can identify that the Parallel component of the force (with respect to the velocity vector) will always be in the direction of motion.  Thinking it through, i think you will agree that the charges on the rail will accelerate every 1 period -   therefore "generating" energy !  Can you spot what's "wrong" here ?     In this figure i used rectangular charges just to make it more clear, The "Paradox" is of course about point charges.


How do you make a command block say something in chat?

I want to make a command block output a message in chat every half hour on my server. The purpose of this is to remind players to read the rules of the server.  Would plugins be necessary to do something like this?


I have defined a function to loop over the range of 10^-9 to 10^3 for every 10^3 steps.     import math     a = 2     b = 2     def f(L):        f = ab/L     for i in range(10**-9, 10**3, 10**3):         print (f(i))    I get following error with this code:   TypeError: range() integer step argument expected, got float.


How to write a LaTeX package that bundles not only .sty and .cls files but also some logos in .pdf or .eps formats?

I would like to make a LaTeX package with the following subdirs:   tex/latex/common (a common .tex file shared among beamer and letter) tex/latex/resources (lots of pdf and eps files with graphical resources) tex/latex/mybeamer (a custom beamer theme with 5 .sty files) tex/latex/myletter (a .cls file for a letter template)   I would like to package these files into a single LaTeX package that users could install in an easy way. I read about the .ins and .dtx files and I can see how to pack the .sty and .cls files but what about the extra graphics - the resources folder which contains several PDF and .eps files?


90's YA novel: Youth leaves village against village taboos

I'm trying to find the name of a book I read in the early-to-mid '90's, from my school's library (in Canada, should that help). I'm pretty sure it was a young adult novel.  From what I can remember, it involved a youth (I think a boy) becoming disillusioned with his primitive village and its superstitious people, and setting out on a journey, beyond the boundaries of his village (which were marked by metal stakes with coloured stripes or ribbons) into the wilderness beyond. He eventually discovers a cave, which turns out to be a man-made structure.  Here is a list of points I remember:   Rural village, superstitious/fearful elders imposing many taboos on the people, including one against leaving. Our protagonist, a young man (or woman) leaves village against elders' wishes, and it is implied that he wouldn't be welcome to return again. The village boundary is marked with a metal pole (which is unusual as the villagers don't have metal of it's quality) with a coloured ribbon or stripe on it. I have vague memory of the character fighting his way upstream along a cliffside during his journey.


What is the difference between test, [, and [[ in terms of binary vs. builtin?

It is often written:   /usr/bin/test is a synonym for /usr/bin/[ [[ is a bash improvement for [ test and [ are also builtins   I understand the difference between [ and [[ but I am confused with the binary vs. builtin relationship here. What is really used in my scripts when I use [ or [[ if /usr/bin/test and /usr/bin/[ are also present in my system?  In the manpage for test, there is missing the often-used option -a, which is listed in help test. I would guess [ is used as a builtin, if this option works.


Can a D&D 3.5e character be used without changes in 5e?

Can a player character created with the build rules of D&D 3.5e be played in 5e without conversion? Or is the difference between the editions too much?


Let $a_1 = 1$ and $a_{n+1} = \frac{a_n}2 + \frac2{a_n}$, $n ≥ 1$. Find the limit of the sequence $\left \{a_n \right \}$ if it exists.

Should monotonic sequence theorem be used? Thanks in advance.


I searched SE.Meta and was unable to find such question.  Someone just swore at us in a  as an  (warning: profanity, may be NSFW), sure, Arqade (profanity in phrases in games) or some SE (ELU, ELL or Anime.SE maybe?) can sometimes contain profanity as a small parts of question.  I think that a part should be added to the review system that will automatically hide questions/answers with profanity, just like the close vote system, the question/answer will be on hold and will be voted to be shown or be deleted.  Tip, if this gets implemented, u can be typed as \/ or v, and most other can be written as leet (l = 1 etc). Maybe it can be called "suspicious activity", and can be triggered when there is too many number or Unicode characters. (I can write hi as |-| |, |-|I, |-|l, l-li, hî, 1-1i, H1 and many more)


I am trying to redirect to url in jquery but it redirects on same page like when i try to redirect to this url- any.com it redirects to            setTimeout(function(){                window.open(redirect_url);               },2000);  any thoughts ?


I am having trouble implementing a red black tree which uses a template. I have read and understand the purpose but do not know exactly how to implement it into the header file and .cpp file. I was reading in some forums that they must in the same file as the template and others say that they can be separate but in a .hpp file.  header file  enum nodeColor { RED, BLACK };  template <class myType> struct nodeType {      myType  keyValue;     nodeColor color;     nodeType<myType> *left;     nodeType<myType> *right;     nodeType<myType> *parent;  };  template<class myType>  class redBlackTree {  public:     redBlackTree() {}     ~redBlackTree() {}     void destroyTree();     unsigned int countNodes() const;     unsigned int height() const;     void printTree() const;     void insert(myType);     bool search(myType);  private:     bool search(myType, nodeType<myType> *);     void destroyTree(nodeType<myType> *);     unsigned int countNodes(nodeType<myType> *) const;     unsigned int height(nodeType<myType> *) const;     void printTree(nodeType<myType> *) const;     void rightRotate(nodeType<myType> *);     void leftRotate(nodeType<myType> *);  };   .cpp file  #include "redBlackTree.h" using namespace std;  redBlackTree::redBlackTree() { }    redBlackTree::~redBlackTree() { } void redBlackTree::destroyTree() { } unsigned int redBlackTree::countNodes() const { } unsigned int redBlackTree::height() const { } void redBlackTree::printTree() const { } void redBlackTree::insert(myType) { } bool redBlackTree<myType>::search(myType) { }  bool redBlackTree::search(myType, nodeType<myType> *) { } void redBlackTree::destroyTree(nodeType<myType> *) { } unsigned int redBlackTree::countNodes(nodeType<myType> *) const { } unsigned int redBlackTree::height(nodeType<myType> *) const { } void redBlackTree::printTree(nodeType<myType> *) const { } void redBlackTree::rightRotate(nodeType<myType> *) { } void redBlackTree::leftRotate(nodeType<myType> *) { }   I also know that I did not include parameters. I am mostly asking for how to approach this so that I can get to coding away.


I am a novice to arcgis 10 so please forgive my ignorance.I have this 2000 survey points shapefile and I was told to , I guess is dislocate, generate new survey points, each new should be 500m west and 500m south from the original point. How can I do that in arcgis 10? I remember there use to be in a move button, but I canot find it now. Can you help me?


Full-page ads randomly pop up in Chrome ("Sponsored by")

Sometimes I get this odd behavior while using Google Chrome:    It appears only sometimes; I can usually get rid of it by refreshing. Is this from some extension? Should I suspect malware? What should I do to figure out what's injecting this stuff?  Also, subjectively speaking, Chrome's felt much slower lately.  edit: there is a rogue extension (). I will debug.  update: it was JQuery Injector, which has now been removed from the Chrome store.


Well I didn't find previous similar questions in the search and I'm stuck at this question. Given $0<k<1$ and sequence $|a_{n+1}-a_n|\le k*|a_n-a_{n-1}|$ for each $n \in \mathbb{N}$ ,Prove the sequence Convergent I tried playing with the absolute values and show somehow its converges but no luck.


"The University of X", "University of X", or "X University"? Is there any rule?

I cannot understand that why the name of some universities starts with "The University of....", in some cases we see "University of...", and finally we see ".... University"!!!! Some examples are as follows:   University of Oxford McGill University The University of Manchester   QUESTION: Is there any general rule on using the above three options? Or it has been chosen by chance? At first, it seems to me that when we are talking about a university bearing the name of a city or province, we should use "The". But this is not the case in general. For example we have "University of Alberta", without "The". What is going on here?


How to prove $A \subset B \iff A \cup B = B$

Let A, B be two sets. Prove that $A \subset B \iff A \cup B = B$  I'm thinking of using disjunctive syllogism by showing that $\neg \forall Y(Y \in A).$ However, I'm not sure how the proving steps should proceed such that it leads me to that premise. Edit: Thanks for the input. FYI, I need to prove this using predicate logic.


Font in "Geometric Invariant Theory" by Mumford

Does anyone know what is the font used in Mumford's Geometric Invariant Theory? If yes is it available as package in LaTeX?  PS: Look up the book in Google books. Note that the final chapters which were added later are typeset with CM fonts.


Do forced shutdowns cause a laptop's HDD to fail?

I recently bought a new laptop (Acer Aspire E14 (E5-475G-380U)) this last Dec. 2017, it had problems on booting up and i had some numerous "hard resets" on boot time because it was always stuck on the manufacturer logo. And hard resets usually fix it, but sometimes, it does not, and i end up on startup repair. One time, when the startup repair finished, my user profile got corrupted (temporary user login only), and i'm not sure if it is related to the hard drive. I ended up resetting and everything was fine again. I also did a hard reset once on a BSOD error, but it didnt show any "noticeable errors". Not until a few weeks ago. My laptop suddenly displayed a "No Bootable Drive" error while the laptop is running. I checked the BIOS and it does not detect my HDD. i tried these:   Shaked the laptop to check if something's loose Applied pressure Few taps on the laptop Checked BIOS   But so far, they did not help. I sent the laptop to the service center and im still waiting for it up until now. My question is, do my hard resets at boot caused my HDD to fail? or is it a problem with the HDD itself? Or is it overuse?  Tasks i'm doing with the laptop that probably damaged the laptop(?):   Gaming (usually GTA 5 with mods, running at a bottleneck. CS:GO, and Flight Simulators) Programming (C# and Android Studio) Daily tasks


Find $f$ and $g$ by trial and error and a rigorous proof for showing that $\mathbb{Q}[\sqrt{2} + \sqrt{3}] = \mathbb{Q}[\sqrt{2},\sqrt{3}]$

Here is the question I am trying to solve: Find polynomials $f(x), g(x) \in \mathbb{Q}[x]$ such that $\sqrt{2} = f(\sqrt{2} + \sqrt{3})$ and $\sqrt{3} = g(\sqrt{2} + \sqrt{3}).$ Deduce the equality of fields: $\mathbb{Q}[\sqrt{2} + \sqrt{3}] = \mathbb{Q}[\sqrt{2},\sqrt{3}].$ And I found the following solution online:       My questions are: 1- How did we know that $f$ and $g$ look like that? what are the trials that lead to this? 2- Is there a more rigorous way of proving that  $\mathbb{Q}[\sqrt{2} + \sqrt{3}] \subseteq \mathbb{Q}[\sqrt{2},\sqrt{3}]$? or what is written is enough? 3- the stated reason for showing that  $ \mathbb{Q}[\sqrt{2},\sqrt{3}] \subseteq \mathbb{Q}[\sqrt{2} + \sqrt{3}]$ is not that much clear for me ......could anyone explain it in details for me please? Note: $F[\alpha]$ is a symbol for subring while $F(\alpha)$ is a symbol for a subfield for any $\alpha$


Delete and cast. Will delete free the right amount of bytes?

Will delete free the right amount of bytes ? unique_ptr<sockaddr_in> up = make_unique<sockaddr_in>();         // or unique_ptr<sockaddr_in> up( new sockaddr_in ); ???  /*      Some stuff      sockaddr and sockaddr_in are two different types of struct and are not relateted  */  sockaddr *p = reinterpret_cast<sockaddr *>( up.release() );  delete p;


Limit of S_n, where $S_n = \int_{0}^{1}\frac{nx^{n-1}}{1+x} dx$ for $n\ge 1$

$$S_n = \int_{0}^{1}\frac{n x^{n-1}}{1+x} dx \quad n \ge 1$$  My attempt:  $$|S_n| \le \int_{0}^{1}\left|\frac{n x^{n-1}}{1+x} dx\right| = \int_{0}^{1}\frac{n x^{n-1}}{1+x} dx \le \int_{0}^{1}n x^{n-1} dx$$  $0 \le x \le 1$, and $n \ge 1$.  So, $|S_n|=[x^n]_{0}^{1}$ and thus $|Sn| = 1$.  So, $\lim_{n \to \infty} S_n = 1$.  But the answer mentioned is $0$. I don't know what I am doing wrong. Please help.


Battery overheating and drain while suspended!

I have a new ASUS ZenBook UX533F with Ubuntu 19.04. Initially, battery life was excellent, heat was low and suspend worked properly.  I was trying to find a way to limit the battery charge to 80% to extend the life of the battery, so:   I installed tlp and tlp-rdw.   However, sudo tlp-stat --battery reported that I could not set thresholds for charging:  natacpi    = inactive (no kernel support) tpacpi-bat = inactive (laptop not supported) tp-smapi   = inactive (laptop not supported)   Foolishly, I thought that if I could get kernel support for natacpi, I would be able to use this feature, so I did:   sudo apt install acpi-call-dkms - had read somewhere that this would make the feature work.   When I did that, it told me that it needed to "register" something on the BIOS or UEFI (I did not understand what it meant - I saw the word "MOK" somewhere).   It was too late!  Now, my battery life is much lower, my laptop is constantly overheating and it even produces a high level of heat when it is suspended.  I have already verified that the laptop enters suspend:  Oct 03 11:21:15 myuser kernel: PM: suspend entry (s2idle)  Did I ruin my new laptop? Somebody help!!!


The following codes return errors   \documentclass{article} \begin{document} cd\\ [asd] \end{document}   But this one will work  \documentclass{article} \begin{document} cd  [asd] \end{document}


What are the official resources available for guild recruitment?

What are the official (provided by Blizzard) resources (forums, websites, in-game mechanics) for guild recruitment or for finding a guild that fits your criteria?


Illustrators standard colour swatches has vanished in "rogue" pdf document

Apologies for the term "rogue" document, by that I mean a pdf file that has been downloaded (not created by myself first), then opened in Illustrator.  The problem I'm getting is that when I try to open up the colour swatches from the top left, I get nothing but none or registration black as fill choices:    Is there a way to load my standard pallet back in this document or have certain setting disabled this?


Can the latest version of Lubuntu be installed on my Lenovo IdeaPad A1_07? Thanks.


Find a closed form for the power series $f_p(x)=\sum\limits_{n=0}^\infty\frac{n^p}{n!}x^n$

I have come across a power series as follows, \begin{equation} f(x)=\sum_{n=0}^\infty\frac{n^p}{n!}x^n. \end{equation} It shows that for some small $p$ values, we can derive simple closed forms:  $p=1: f(x)=e^xx$;  $p=2: f(x)=e^x(x+x^2)$;  $p=3: f(x)=e^x(x+3x^2+x^3)$;  $p=4: f(x)=e^x(x+7x^2+6x^3+x^4)$;  ...  Is it possible to derive a closed-form for this power series for general $p$?


How do I create a user-defined aggregate function?

I need an aggregate function that MySQL doesn't provide.  I would like it to be in MySQL's flavor of SQL (that is, not in C).  How do I do this?  What I'm stuck on is creating an aggregate function -- the  don't seem to mention how this is done.  Examples of desired usage of a product function:  mysql> select product(col) as a from `table`; +------+ | a    | +------+ |  144 | +------+ 1 row in set (0.00 sec)  mysql> select col, product(col) as a from `table` group by col; +-----+------+ | col | a    | +-----+------+ |   6 |   36 | |   4 |    4 | +-----+------+ 2 rows in set (0.01 sec)


Can I get a Continue Discussion In Chat button earlier?

If a commenter says some fact that I don't entirely agree with, I tend to reply. Sometimes we do not immediately come to a consensus and I can tell it has a good chance of creating a long back-and-forth dialogue.  Could I request a way to quickly create a chat room to continue the discussion? (similar to the button that appears after the dialogue gets rather long)  I tried creating it manually once, but it is so tedious to go over there, enter a description, and then post a link back to the new chat room, on the original comment discussion.  Perhaps this Move To Chat button appears earlier only when I reach a certain level of reputation? IDK, but it would be nice to pre-emtively prevent cluttering of the comments trail.


Msfconsole-metasploit framework bad ruby interpreter

When I type msfconsole in my terminal i got something like this:  bash: /usr/bin/msfconsole: /usr/share/metasploit-framework/ruby: bad interpreter:   Please help me.  After ls -l /usr/share/metasploit-framework/ruby I got:  total 276  drwxr-xr-x  9 root root  4096 Aug 24 13:10 2.2.0 drwxr-xr-x 12 root root  4096 Aug 26 03:55 2.3.0 drwxr-xr-x  2 root root  4096 Aug 24 14:19 backward -rw-r--r--  1 root root  6252 Apr 14 08:16 changelog.gz -rw-r--r--  1 root root  3036 Apr 14 08:16 copyright -rw-r--r--  1 root root  4232 Apr 25 19:06 debug.h -rw-r--r--  1 root root  5785 Apr 25 19:06 defines.h -rw-r--r--  1 root root  1316 Jun 18 01:28 digest.h -rw-r--r--  1 root root 17849 Apr 25 19:06 encoding.h -rw-r--r--  1 root root 36172 Apr 25 19:06 intern.h -rw-r--r--  1 root root  5200 Apr 25 19:06 io.h -rw-r--r--  1 root root  4953 Apr 25 19:06 missing.h -rw-r--r--  1 root root   318 Apr 14 08:16 NEWS.Debian.gz -rw-r--r--  1 root root 37881 Apr 25 19:06 oniguruma.h -rw-r--r--  1 root root  1191 Apr 14 08:16 README.Debian -rw-r--r--  1 root root   777 Apr 25 19:06 regex.h -rw-r--r--  1 root root  1465 Apr 25 19:06 re.h -rw-r--r--  1 root root 69536 Apr 25 19:06 ruby.h -rw-r--r--  1 root root  5339 Apr 25 19:06 st.h -rw-r--r--  1 root root   374 Apr 25 19:06 subst.h -rw-r--r--  1 root root   996 Apr 25 19:06 thread.h -rw-r--r--  1 root root  1333 Apr 25 19:06 thread_native.h -rw-r--r--  1 root root  2050 Apr 25 19:06 util.h drwxr-xr-x  4 root root  4096 Aug 24 14:18 vendor_ruby -rw-r--r--  1 root root  1854 Apr 25 19:06 version.h -rw-r--r--  1 root root  1677 Apr 25 19:06 vm.h


I would like to know if there are any other tenses or grammatical structures to use for speaking about the future apart from will (perfect tense included), going to, simple and continuous present.  I mean not the obvious ones. For example, simple present (I could never have imagined it could be used for the future).     My mom arrives tomorrow.   I go to the doctor at 4 o'clock this afternoon.


Short story involving pieces of orange glass that seek out each other and defend themselves with heat

I was reminded of this by . I think it was an older story, one I read in an anthology somewhere in the early 90s (decent chance of it being one of the Alfred Hitchcock collections). At the beginning of the story, an itinerant is found dead on a beach, horribly burned on one side. The assumption is that he died from a lightning strike, supported by that there's an orange ball of glass (about marble-sized) underneath him, posited to be caused by the lightning fusing the sand into glass.  Over the course of the story, the protagonists (I want to say there's at least two, one who's sort of the "viewpoint" protagonist and one who actively researches the bits of glass, maybe a doctor or scientist) learn that the bit of glass can move slowly on its own, and generate a fair amount of heat if trapped, the itinerant likely burned when he collapsed on top of it. I have a vague memory that they found a way to demonstrate the balls effect on-command by striking it with a hammer and seeing it glow with heat. Tracking the ball, they find it's seeking out other bits of glass with the same properties. They set a trap with some dynamite and blow up a much larger sphere (I don't remember the size, at least beach-ball sized if not  sized), thinking they have solved the problem. The story ends with two orange grains of sand beginning to move towards each other, restarting the process...


There is a tiny icon on macOS dock that is not clickable!

After Visual Studio Code update, its icon on Dock has changed to a very tiny one which is literally inaccessible!  There is no way you can click on it or view options.  Does anyone know how to remove it from the Dock?  macOS: Mojave (10.14)


How to add right-click (on desktop) to create text file functionality 16.04.2 Ubuntu GNOME

How can I add a right-click desktop menu entry to create a text file to Gnome 3 in Ubuntu 16.04.02?


If a matrix is triangular, is there a quicker way to tell if it is can be diagonalized?

I hope it is alright to ask something like this here, I am having trouble keeping up with all the special cases and my book is being kind of vague.  I know how to do the standard method of finding diagonal matrices, but I know that triangular matrices are special and my book makes a connection, but it is hard to tell what it is.  Thanks.


`--no-install-recommends` only specified packages

I want to install xfce4-goodies but I don't want Midori Browser. With --no-install-recommends I don't know how to specify only Midori. I want the rest of packages. How to do that? Thanks!


What determines which character gets to use a summon?

During long/hard fights you get a chance to use a summon after the gauge is full, but despite having summons equipped on all characters only one character can call their summon.  How does the game determine which character will be able to use the summon once the gauge is full?  Update: So it doesn't seem to happen all the time. I have had a couple times now where I can select which summon I want to use, but sometimes I haven't had the choice so want to know why it isn't always a choice.


How do I add 'www' before a subdomain, like www.subdomain.domain.com?

I want to add www in front of a subdomain e.g. www.subdomain.domain.com.  My blogs are hosted on Blogger and am using GoDaddy for having custom domains.  I have HOST @ entries for 'domain' pointing specified by blogger. The following subsdomains are configured by adding CNAME alias as follows:  subdomain -> ghs.google.com www -> ghs.google.com      For domain (including www.domain) I have one blog.  For subdomain, I am pointing it to seperate blog using above entries and subdomain.domain.com works fine.   I read articles on this issue and tried adding following CNAME entry but no luck:  www.subdomain  ->  subdomain.domain.com   How do I make www.subdomain.domain.com work ?


How can I implement fast, accurate 2D collision detection?

I'm well aware of how to detect if two or more 2D objects collide but I'm interested in how to decide whether to check for a collision. In previous projects, I just had every object check against every other object (I know, O(n^2) level of stupidity) and it created a less than fluid gameplay.  Various forums hail the greatness of Quadtrees, B-Trees, and any other kind of tree or structure you can think of.  What is the most efficient structure for determining whether a collision should be checked?


How can we get "Developer" bugs logged with Technical Support?

I recently found a bug, which I mentioned on , as well as submitting a case, and after a few days fumbling around with the case, they closed it by saying that they only provide this type of support for Premier Support customers.  Is there a better channel for reporting bugs than by submitting a case, or is there something "special" we have to do? I realize this question is similar to , except that I've already gone the route of , as suggested by the answer there (i.e. submitting a case), to no avail.  How can I make sure that a bug like this can find its way to someone capable of at least confirming that the behavior was expected? This behavior isn't documented anywhere, and so I assume that it's a bug that needs to be addressed.


How to derive the close form of a power series with a ${2n\choose n}$ binomial coefficient?

In a step in a proof that the probability to return to origin in a symmetric random walk is $1$ the following combinatorics result seems important:  $$\displaystyle \sum_{n=0}^\infty{2n\choose n}\,x^n = \frac{1}{\sqrt{1-4x}}$$  I understand that the proof involves the generalized binomial theorem, but I don't know how to get about solving the interplay between the $x^n$ in the power series and the binomial coefficients.


Can't delete files in trash because they don't exist on OS X 10.6?

Something funky happened on one of my external drives and now whenever I plug it in 2 files show up in my Trash.  If I empty the Trash via Finder, nothing happens.  Ditto for the Option+Empty Trash method.  Listing them via Terminal shows them as there  $ sudo ls .Trashes/501 ¶_|íìê<-.b?†            æâù©ìë—‡.*?§   But attempting to rm them or get any information about them shows them as not there  $ sudo ls -F .Trashes/501/ ls: ¶_|íìê<-.b\032†: No such file or directory ls: æâù©ìë—‡.*\026§: No such file or directory  $ sudo rm .Trashes/501/* rm: .Trashes/501/¶_|íìê<-.b\032†: No such file or directory rm: .Trashes/501/æâù©ìë—‡.*\026§: No such file or directory   Any thoughts?  I've never seen anything like this.  Thanks in advance!


awk: detect content separated by arbitrary character instead of spaces?

Is there a way to make awk detect content separated by commas (or any other character) instead of spaces?   e.g. a file (.csv) contains a list of contacts in the format "title","first-name","last-name","e-mail". How would you use awk to print all the first names?


"Taste" is to "flavor" as "touch" and "sight" are to what?

For the senses, we have:    flavor for taste aroma/odor/scent for smell sound for hearing ____? for touch/feel ____? for sight/see   So one tastes a flavor, smells an aroma, hears a sound, feels a(n) _____, and sees a(n) _____. For the former, part of me wants to say texture, but I feel that is too specific; for the latter, I want to use visual or sight, but but does that make sense, seeing a visual or a sight?


How to play VOB files that were inside a DVD disc?

I just downloaded a DVD which is for a movie. After uncompressing the DVD file I see .VOB, .IFO and .BUP files. If I open the first .VOB file it shows me the DVD menu but I can't interact with it. So, my question is... is Totem able to play those kind of files? If so, how can I achieve that? What other app could I use in order to reproduce those files?  Edit  Using VLC didn't work neither. I forgot to mention I have already tried that. Let me rephrase: if I open the first video file it shows the DVD menu, BUT I can't interact with it.


How do I model a scene by using objects from other blend files?

So I am trying to get how to use Blender. But I don't get its 'file system'. For example, My approach used to be if I was modeling a bedroom, I would create the walls and I would place boxes instead of furniture. I would save those files. As I modeled each piece of furniture I would overwrite each box file and it would start populating the room. Blender seems to save everything inside a single file, or am I doing it wrong? How do you guys do your library of models? Are they all 'scenes' just with the model/object? is there a preferred way of doing it? I could not find information about this... help...


How to get AHCI support on an IDE Windows 7 installation?

I installed Windows 7 onto a SSD with the motherboard in IDE mode. Now when I try to change the motherboard to AHCI mode, Windows 7 will not successfully boot (blue screens mid-boot).  How can I add AHCI support to the Windows 7 installation? If I can not add AHCI support I plan on doing a reinstall of Windows 7 with the motherboard in AHCI mode.  As a note, I just did the Windows 7 install yesterday, so I don't need to worry about losing any data on the hard drive due to reinstall.


How to install ubuntu touch for smartphone?

I am using samsung galaxy trend smarttphone. Can I install ubuntu touch in my smartphone? If yes how?


Are eggs predetermined before you hatch them?

In Pokémon Go are eggs predetermined before you hatch them? What I mean is, has it already been decided what you are going to get from that egg before it's been hatched? Or is it a random selection during the hatching?


Can't boot to windows after removing ubuntu

If this is not the right place, please tell me where to ask this.  I tried to remove ubuntu from windows, and I deleted the partitions. after starting up windows, I executed in command line: bootrec /fixmbr and bootrec /fixboot, and expected to start windows normally, I didn't. When I restarted, It showed me something like "bad configuration booting", I don't really remember, and I don't have access to the error anymore, because I installed xubuntu. In the installation, xubuntu didn't recognized any OS on the computer, but I have access to data in windows. currently, I'm trapped in xubuntu, which is a horrible thing, because I need windows really bad. I beg you to help me


Burnside's lemma for counting orbits in M x N matrix

This is a similar question to , where I'm trying to understand how Burnside's Lemma is used to compute orbits of of a matrix. I've been working through the example of how this applies to a cube rotation or the bead arrangements, but what I don't really get is how this applies to a matrix.  Given this specific example where I have a 2x2 matrix where each cell can have 2 values (black/white), I know there are 7 orbits from manually drawing them out.  In reading Burnside's Lemma, I think I have to get to the form:  1/n(...) = 7  but I'm not sure how to create the terms inside the parenthesis. I'm not really looking for heavy mathematical notation here for the general case (if possible), but I'm looking for more of an explanation of how the equations translate to actual numbers in this particular case.  More generally, when the matrix is MxN and not NxN, how do I compute the number of orbits?


Submitting a form by pressing enter without a submit button

Well I am trying to submit a form by pressing enter but not displaying a submit button. I don't want to get into JavaScript if possible since I want everything to work on all browsers (the only JS way I know is with events).  Right now the form looks like this:  <form name="loginBox" target="#here" method="post">     <input name="username" type="text" /><br />     <input name="password" type="password" />     <input type="submit" style="height: 0px; width: 0px; border: none; padding: 0px;" hidefocus="true" /> </form>   Which works pretty well. The submit button works when the user presses enter, and the button doesn't show in Firefox, IE, Safari, Opera and Chrome. However, I still don't like the solution since it is hard to know whether it will work on all platforms with all browsers.  Can anyone suggest a better method? Or is this about as good as it gets?


Proof of paracompactness of CW-complexes (J. Lee, Introduction to Topological Manifolds)

I have a question about a proof in John Lee's Introduction to Topological Manifolds (5.22).  Given CW-complex $X$ with skeletons $X_n$ and open cover $\left(U_\alpha\right)_{\alpha\in A}$, we inductively define partitions of unity $\left\{\psi_\alpha^n\right\}$ on $X_n$ subordinate to cover $\left(U_\alpha^n=U_\alpha \cap X_n\right)_{\alpha\in A}$, such that   $\psi_\alpha^k\mid_{X_{k-1}}=\psi_\alpha^{k-1}$ If $\psi_\alpha^{k-1}\equiv 0$ on an open subset $V \subset X_{k-1}$, then there is an open subset $V'\subset X_k$, containing $V$ on which $\psi_\alpha^k\equiv 0$   At the end of the induction step, prof. Lee proceeds to argue that supports of $\left\{\psi_\alpha^{n+1}\right\}$ form locally finite family.     If $x$ is in the interior of an $(n+1)$-cell, then that cell is a neighborhood of $x$ on which only finitely many of the functions $\psi_\alpha^{n+1}$ are nonzero by construction. On the other hand, if $x\in X_n$, because $\left\{\psi_\alpha^n\right\}$ is a partition of unity there is some neighborhood $V$ of $x$ in $X_n$ on which $\psi_\alpha^n\equiv 0$ except when $\alpha$ is one of finitely many indices, and then (2) shows that $\psi_\alpha^{n+1}\equiv 0$ on $V'$ except when $\alpha$ is one of the same indices.   I don't understand why does this imply local finiteness. Because of (2), there is a $V'$ for each such $\alpha$, but unless I'm missing something obvious, there can be infinitely many such alphas. How can we conclude there is a single neighborhood of $x$ in $X_n$ on which all these functions vanish?


How to put a subscript in the center of two letters

I have the following code \sum_{i<j}^{}\sum Cov(X_i, X_j) which renders     How can I move the i<j subscript to the center underneath the two sigmas (which will result in a "shift")? Preference will be given to the simplest solution.


Deep NNs, backpropagation and error calculation

I was following the backpropagation tutorial by Michael Nielsen on , one of the very few places where the backprop algorithm is nicely explained both in theory and practice with an actual implementation in python.  Now, something is not clear when he explains how to calculate the error on a specific layer in terms of error in the next layer (I will provide a screenshot because I don't want to mess with notation):    Here, $\delta^l$ is the error in layer l, $\odot$ is the elementwise product betweeen vectors, $w$ is a weight matrix, and $\sigma'$ indicates the derivative of an activation function.  Now, observe he points out that by applying the transpose of $w$ to the next-layer-error vector (which is the previous layer during backprop), one is "sending back" the error across the network, and then, multiplying by the derivative of sigma, one applies (I presume) the chain rule which completes the backprop step.  I have troubles understanding what does he really mean by saying that the traspose "sends back" the error. Why should it? Perhaps he wants to apply the inverse trasformation? But unless the matrix happens to be orthogonal, which is not the case AFAIK, the transpose does NOT equal the inverse.. What is the algebraic significance of the transpose operator in this specific context?  In any case, I would have thought, reasoning about the chain rule, of applying some kind of differential operator to matrix $w$, instead of transposing it.  Before asking that question, I researched the topic for a long time, but I was unable to find whatever information about that particular point.  Opinions?


I pressed something and now many edges do not appear in edit mode

in blender 2.8 I pressed a button unintentionally, and as a consequence the mesh specifically only for this object had this change in which many edges do not appear even when I select the face that is still there for some reason does not appear


can you tell me how can I put questions and get more answers ! what I should do to get more interaction with my posts ! waiting for hours and days maybe months to get an answer or comment is not good ... Really I  want some advices , thanks in advance


H2G2 — Teleportation Also Results in Time Travel?

In , Arthur, Ford, Zaphod, Trillian, and Marvin have just stolen Hotblack Desiato's stunt ship after leaving Milliways and traveled into the past 2 million years before their own time.      ”Trouble is,” said Ford, ”that the one instrument in this whole ship that   is giving any reading is worrying me. If it is what I think it is, and if it’s   saying what I think it’s saying, then we’ve already gone too far back into   the past. Maybe as much as two million years before our own time.”   As they realize that this ship is about to crash into the sun, they discover a teleportion device (their only means of escape) and leave Marvin behind to control it so they can escape despite the fact they have no idea where they might end up. Arthur and Ford end up on the Golgafrincham ship which shortly thereafter crash landed on pre-historic Earth (i.e. roughly 2 million B.C.), and Zaphod and Trillian end up back on The Heart of Gold.      ”I trust you had a pleasant meal?” said Zarniwoop to Zaphod and Trillian   as they rematerialized on the bridge of the starship Heart of Gold and lay   panting on the floor.   As I understand from the beginning of the book, at this point the Heart of Gold had been left with Zarniwoop alone on the ship in Arthur's "own time" (in the 1980's). There doesn't really seem to be any explanation as to why the teleportion device sent Zaphod and Trillian 2 millions years into the future as far as I can tell.   So, am I misinterpreting something to the story and the gang really left The Heart of Gold 2 million years before their own time, or did the teleportion device also act as a time machine when Zaphod and Trillian stepped into it? Or perhaps did Zarniwoop have The Heart of Gold travel back in time?


Is the discoloration on my bed frame rails mold?

So the wood panels lay on top of the metal beams, it's a bed frame but I noticed these spots on the metal and rubbed them off and smelt like rotten eggs please let me know 😑


$S=\{x\in\mathbb{R}: 2x^2\cos{1\over x}=1\}$  $T=\{x\in\mathbb{R}:2x^2\cos{1\over x}\le 1\}\cup\{0\}$  I need to tell whether they are complete metric space under usual metric. As they  are closed subsets of complete metric space $\mathbb{R}$, so they are complete. Am I right?  Edit: $S=f^{-1}\{1\},T=\{0\}\cup f^{-1}(-\infty,1]$  $f$ is continuous.


Editing Sudoers to avoid typing a password for iwconfig command

I wanted to follow this guide to avoid typing a password every time I want to use "sudo iwconfig" command    I tried the steps with "apt-get" command and it worked  sudo select-editor sudo visudo add %admin ALL=(ALL)NOPASSWD:/usr/bin/apt-get to the bottom line   but they didn't work with "iwconfig"  I believe the reason behind that is "iwconfig" source files are not stored in "/usr/bin/" directory because ls /usr/bin/ | less doesn't show anything named iwconfig  So, what is the directory I should enter before iwconfig?  Thanks in advance


Default keyboard layout of a Gnome Terminal

In Ubuntu 16.04 I have 2 input methods (keyboard layouts) configured, CZ (default) and US. Also I have enabled different input methods for different windows. This configuration works as expected and so far I like it, but I would like to modify its behavior in one special case.  I would like to set the initial layout of a terminal window (GNOME Terminal) to US. The problem is that now, when I open the terminal window, a default language or the language of the previous window (according to the configuration) is used, which is not US every time.  I tried to add setxkbmap -layout us to ~/.bashrc, it changed the layout, but the layout indicator (in the top right corner) did not change and when the terminal window lost and regained focus, the modification done by setxkbmap was no longer applied. It seems to me that the daemon which takes care of managing per-window layouts didn't register the modificatin by setxkbmap. A command which tells the daemon to use a given layout for the actual window would probably solve my problem.


Add "open as administrator" option to folders?

Is there a way to add "open as administrator", when I right-click on a folder, because there are some folders you cannot access graphically because that would need administrator privileges?


After installing tightvncserver, I can't log in locally anymore

I'm new to linux world, and I'm trying to set up a computer for a small office on a quite old computer.  I setup Lubuntu with some office apps (LibreOffice, ...) and it's working.  I'm now trying to setup a remote access for administrative support and/or user assistance.  SSH is setup and is working. I'd like also a remote GUI access. My bet is that VNC is the answer. But it's not as easy as windows to allow remote access (a single checkbox!). So my question are:   I installed tightvncserver, but there are plenty of vnc server software. Which one is suited? now I've setup tightvncserver, I also created an /etc/init.d/vncserver script to always run tightvncserver. This is working, I can remotely access the computer. However, I can no more login to the computer locally :(. Each time I try to log, the screen blink, some text scroll and the login prompt reappears. when accessing remotely, I only have the vnc password to type. I don't have the user's prompt.   Basically, I'd like to mimic the behavior of teamviewer. I'd like to replicate the screen, whether or not a user is loggued in. And it's where I'm stuck.  Thx for any help


How can I tell if I have static or dynamic IP Address?

Maybe a stupid question but how can I tell if I have a static IP address or a dynamic IP address? Running Fedora-13


$a,b,c$ are positive real numbers such that, $a+b+c\ge abc$. Prove that $a^2+b^2+c^2\ge \sqrt{3}abc$    My work: I tried using Cauchy-Schwarz inequality to find that, $(a^2+b^2+c^2)(1^2+1^2+1^2)\ge (a+b+c)^2$ $(a^2+b^2+c^2)\ge \dfrac13(a+b+c)^2$ $\sqrt{(a^2+b^2+c^2)}\ge \dfrac{1}{\sqrt{3}}(a+b+c)\ge \dfrac{1}{\sqrt{3}}abc$ which is not what I need and neither I can use it to prove the required inequality. Please help.


System of linear and nonlinear diff equations

I am looking for a help with solving this chemical-engineering problem. Is there anybody, who can help?   The task is about this: Concentration profiles $cA,dA$ during extraction of A-component from solvent C into solvent B in countercurrent colony with axial mixing of continual phase of solvent B are described with following diff equations which I have to solve: \begin{align} dA'' &= -(uB/E)\, dA'-kL \,(cA-dA/psi)\\ cA' &= -(kL/uC)\, (cA-dA/psi), \end{align}  where $cA,dA$ represent concentrations of A-component in original and new solvent, $kL$,$uB$,$uC$,$E$ are constants, "psi" is partition coefficient. Then we have following initial and boundary conditions - z=0 m is inlet of feedstock, z=2 m is inlet of extraction agent.   $cA(0) = 100$  $uB* \,dA(2)+E\,* dA'(2) = 0$  $dA'(0) = 0$    Firstly, I have to solve it for $psi = 100$ (at this moment system of diff equations is linear) and find value for $cA(2)$ in raffinate then. Then I have to calculate using shooting method and then use proper Runge-Kutta approximation (using $psi = 10*sqrt(dA)$, for non-physical option $dA$ $=<0$ I have to use $dA/psi = 0$).   Firstly I want understand the problem in general - the final numbers are not important. I want to try it using your advices (or some similar problems which I can use in my solution) and how to use the substition for the diff equation with rate 2, then how to calculate three diff equations with rate 1 with these written conditions for both cases - linear and nonlinear.  Thank you, J.


Unable to update Ubuntu due to error with update manager

This is the error message: Could not initialize the package information  An unresolvable problem occurred while initializing the package information.  Please report this bug against the 'update-manager' package and include the following error message:  E:Problem parsing dependency  Breaks,  E:Error occurred while processing zekr (NewVersion2),  E:Problem with MergeList /var/lib/apt/lists/ca.archive.ubuntu.com_ubuntu_dists_precise_multiverse_binary-i386_Packages,  E:The package lists or status file could not be parsed or opened.'  Any ideas how this could be fixed?


I've recently seen latest mac os is having invisible scroll bars which will be visible only once your mouse comes onto it. I think it is a bit tough for the user to know if there is a page overflow or not. Is it not a bad User experience.


If I wanted opinion-based answers to a naming question, where would I go?

It seems like Stack Exchange is geared solely towards fact-based answers. This makes some sense, in that it allows answers to stay relevant, whereas opinions can't be viewed as "right" and can change over time.  I want to be able to ask the same people who help me with programming problems questions for which answers would be considered opinions.  Mainly, sometimes I'll name something, and the name feels wrong, but I can't think of what would be a better name, or why. Where can I have these discussions?


I am learning blender and can't understand why edge loops "get broken" (May be a specific name for it).  Taking the picture below as example:   When I try to create an edge loops it stops on the top of the front face (marked edges).  I don't understand what make edge loops not being possible to be continued. I mean I expect the edgle loop to go all the way like the line I draw in red.  I could understand if there are n-gons or double vertices, but what's wrong in the mes below?   Just for info, the left object is just the "preview" of an array modifier used on the right object.


I work for a magazine and every so often we get ads (PDF format) that run through the pre-flight process with no errors. I will export a PDF with the ads out of InDesign and these boxes appear. This does not show up when we go to print, but we have an online edition which has the boxes. Does anyone know what causes this? Thanks!


Prove $(n!) ^2 > n^n$ for all $n > 3$ using Induction

Prove $(n!) ^2 > n^n$ for all $n > 3$ by induction. I know that we will have to use Binomial theorem somehow but I can't figure out how? Please provide some hint.


Extend the clickable area to author name in authoryear style

With the authoryear style the when using hyperref only the year is "clickable" but not the author. What should I change so to have a sigle clickable area author+year?  \documentclass{article} \usepackage{hyperref} \usepackage[style=authoryear]{biblatex} \bibliography{dummybib} \begin{document} \cite{dummyentry} \end{document}


PHP / MySQLi: How to prevent SQL injection on INSERT (code partially working)

II would like to store two values (an email and a password) in a MySQL db using PHP. The input is passed to the PHP page via Ajax in jQuery (through an onclick event on a website). Now I want to protect this PHP query against SQL injection - I am talking about a standard website so I don't want to overdo it but I think some standard protection can't be bad. Below is what I had before just to ensure that the general procedure is working which it is. I then tried to increase security by using password encryption and statements but I am not sure if I did this the right way + I don't know if and how this needs to be applied to the Select part as well (where I am checking if the email already exists). I've seen plenty of pages on this topic but as a beginner that's exactly my problem here. Can someone tell with this as an example what should be changed or added here and maybe provide some short explanations ? I would like to keep using MySQLi if possible. Old PHP: $conn = new mysqli($servername, $username, $password, $dbname); $conn->set_charset("utf8"); if($conn->connect_error){     die("Connection failed: " . $conn->connect_error); } $email = $_POST["email"]; $pw = $_POST["pw"];   $sql = "SELECT email FROM Users WHERE email = '" . $email . "'"; $query = $conn->query($sql); if(mysqli_num_rows($query) > 0){     echo "Record already exists"; }else{     $sql = "INSERT INTO Users (email, pw) VALUES ('" . $email . "', '" . $pw . "')";     if($conn->query($sql)){         echo "Update successful";     }else{         echo "Update failed";     }; } $conn->close();  New PHP: $conn = new mysqli($servername, $username, $password, $dbname); $conn->set_charset("utf8"); if($conn->connect_error){     die("Connection failed: " . $conn->connect_error); } $email = $_POST["email"]; $pw = password_hash($_POST["pw"], PASSWORD_BCRYPT);   $sql = "SELECT email FROM Users WHERE email = '" . $email . "'"; $query = $conn->query($sql); if(mysqli_num_rows($query) > 0){     echo "Record already exists"; }else{     $sql = $conn->prepare("INSERT INTO Users (email, pw) VALUES ('" . $email . "', '" . $pw . "')");     $sql->bind_param('s', $name);     $sql->execute();     $result = $sql->get_result();     if($result){         echo "Update successful";     }else{         echo "Update failed";     }; } $conn->close();


I was just thinking, Is there some mathematical rule that is a formula for all the palindromes? And if there is a rule what is it?


Why didn't Harry, Hermione, and Ron discover the Bubble-Head Charm in advance of the second task?

In Harry Potter and the Goblet of Fire, Harry finds out several weeks before the second task of the Triwizard Tournament that he would be required to survive underwater for an hour. Harry, Hermione, and Ron all proceed to spend hours and hours researching a solution to this problem, even engaging the librarian's help:  So Harry, thinking that he would soon have had enough of the library to last him a lifetime, buried himself once more among the dusty volumes, looking for any spell that might enable a human to survive without oxygen. However, though he, Ron and Hermione searched through their lunchtimes, evening and whole weekends -- though Harry asked Professor McGonagall for a note of permission to use the Restricted Section, and even asked the irritable, vulture-like librarian, Madam Pince, for help -- they found nothing whatsoever that would enable Harry to spend an hour underwater and live to tell the tale. Goblet of Fire -- Bloomsbury -- chapter 26, The Second Task  Hermione, in particular, has a charm in mind as the most probable solution:  "I think your best chance is some sort of charm." Hermione -- Goblet of Fire -- Bloomsbury -- chapter 26, The Second Task  Despite many hours spent searching, and despite Hermione's formidable researching skills, they are unable to find any solution. However, in the second task itself, both Cedric Diggory and Fleur Delacour use a Bubble-Head Charm to survive underwater:  Miss Fleur Delacour, though she demonstrated excellent use of the Bubble-Head Charm, was attacked by Grindylows as she approach her goal, and failed to retrieve her hostage. ... Mr Cedric Diggory, who also used the Bubble-Head Charm, was first to return with his hostage, though he returned one minute outside the time limit of an hour. Goblet of Fire -- Bloomsbury -- chapter 26, The Second Task  The Bubble-Head Charm doesn't appear to be particularly difficult to perform, as it is in widespread usage among students by Harry's fifth year:  Dungbombs and Stink Pellets were dropped so frequently in the corridors that it became the new fashion for students to perform Bubble-Head Charms on themselves before leaving lessons, which ensured them a supply of fresh air, even though it gave them all the peculiar appearance of wearing upside-down goldfish bowls on their heads. Order of the Phoenix -- Bloomsbury -- chapter 30, Grawp  Why did Harry, Hermione, and Ron all fail to discover the Bubble-Head Charm in advance of the second task, despite spending weeks specifically researching a charm to survive underwater, and despite both Cedric and Fleur learning that charm?


Pair of 2-tuple composite FKs pointing to same table (closure table pattern)

I don't have much experience with DB design, and having a hard time figuring out what's wrong with the following:   Table father has a composite PK (col1, col2) Table closure has ancestor(a-col1, a-col2), descendant(d-col1, d-col2) and length. Ancestor and Descendant are composite FKs, each pointing to the PK of father. The 4 columns (a-col1, a-col2,d-col1, d-col2) are a composite PK.   Look at the following fiddle:   I am working with MySQL.  I have constraints in CASCADE, but when I try to update the father table, the constraints give me errors. I can't do the following update to father table row:  UPDATE father  SET `col1` = "UPDATE_MY_ID_PLEASE"  WHERE `col1` = 'A' AND `col2` = 1;   Is the design wrong? How should this be done?


Differentiating Propagator, Green's function, Correlation function, etc

For the following quantities respectively, could someone write down the common definitions, their meaning, the field of study in which one would typically find these under their actual name, and most foremost the associated abuse of language as well as difference and correlation (no pun intended):    Two-point function Wightman function         Maybe including side notes regarding the distinction between Covariance, Covariance function and Cross-Covariance, the pair correlation function for different observables, relations to the autocorrelation function, the $n$-point function, the , the relation to transition amplitudes, retardation and related adjectives for Greens functions and/or propagators, the  and its seemingly privileged position, the spectral density, spectra and the resolvent.    Edit: I'd still like to hear about the " interpretation" of the quantum field theoretical framework. Can transition amplitudes be seen as a sort of auto-correlation? Like... such that the QFT dynamics at hand just determine the structure of the temporal and spatial overlaps?


How to redirect STDOUT and STDERR in a file for every command?

I'm trying to store both STDOUT and STDERR from the terminal (and if possible STDIN given by user) in a file for every command.  So i started creating a trap function to execute every command in a edited manner like:  shopt -s extdebug  preexec_invoke_exec () {     [ -n "$COMP_LINE" ] && return  # do nothing if completing     [ "$BASH_COMMAND" = "$PROMPT_COMMAND" ] && return # don't cause a preexec for $PROMPT_COMMAND      eval `history 1 | sed -e "s/^[ ]*[0-9]*[ ]*//"` |& tee ~/recent_output.txt     return 1 # This prevent executing of original command } trap 'preexec_invoke_exec' DEBUG     and saving the above file and executing   source file.sh   This did the work what i wanted but stopped some commands from executing like   cd ..   The reason for this was piping creates a sub-shell and then executes every command in it. So the main shell remains unaffected.  Even the script functionality of bash i.e  script ~/recent_output.txt   worked but only gives output after you do exit in in terminal  So, basically i want to store/get the output of previous command executed in the bash terminal. You can help me with any language (golang,python...).


Existence of group $G$ with $|G|>2$ and automorphism group of odd order

In Rotman's introduction to the theory of groups, there is an exercise (7.9) where one has to prove that the following facts for a finite group $G$.    If $G$ is abelian and $|G|>2$ then $\text{Aut}(G)$ has even order $\text{Aut}(G)$ is not cyclic when $G$ is not abelian $\text{Aut}(G)$ is never cyclic of odd order >1.    This is all fairly easy, but I was wondering if there even exists a group $G$ with $|G|>2$ which has automorphism group of odd order. Anyone has an example or reference (couldn't find it by simple internet search)?  Clearly $G$ can't be abelian, symmetric, alternating, dihedral, ... so the most obvious counterexamples don't work.  Thanks in advance!


Do we get -1 Reputation when we downvote a post? If so why?

I was under review where I found some posts of low quality and downvoted them. When I saw my reputation sometime later, it was down and in details it was because I downvoted few posts. Can anyone explain the logic behind this?


I am about to travel to St Petersburg for one day and I am concerned about mobile internet. I own both a German and a Romanian SIM card, but none of the providers seem to offer a plan for Russia (only EU, USA, Canada, Turkey, etc). Please correct me if I'm wrong, but there is no logical reason why the EU plans should include Russia.  Is my only option buying a prepaid SIM as soon as I get there? It seems quite odd that there are no plans available for Russia. How did other other people who traveled there solve this problem?  Thank you.


What is the way to give bitter medicine to a 2 year old child?

Child is 2 years and 1 month old.  No, I will not close her nose to make her open her mouth.  What are the other non torturous ways to give bitter medicine to the child?


Directing to custom error page on 404 triggered by a URL with '.' at the end

In my web.config I have the following:   <customErrors mode="Off" defaultRedirect="~/error" redirectMode="ResponseRewrite">   <error redirect="~/error" statusCode="404" />   <error redirect="~/error" statusCode="500" /> </customErrors> ... <httpErrors errorMode="Custom">   <clear />   <remove statusCode="404" />   <remove statusCode="403" />   <remove statusCode="401" />   <error statusCode="404" path="~/Error" responseMode="ExecuteURL" prefixLanguageFilePath="" />   <remove statusCode="500" />   <error statusCode="500" path="~/Error" responseMode="ExecuteURL" prefixLanguageFilePath="" /> </httpErrors>   In my global.asax I have the following:   protected void Application_Error(object sender, EventArgs e)     {         // Do whatever you want to do with the error          //Show the custom error page...         //Server.ClearError();         RouteData routeData = new RouteData();         routeData.Values["controller"] = "Error";          Exception exception = Context.Server.GetLastError();         if (exception != null && !ExceptionUtilities.IsExceptionIgnored(exception))             ErrorSignal.FromCurrentContext().Raise(exception);          Server.ClearError();          HttpException httpException = Context.Server.GetLastError() as HttpException;         if (httpException != null && ((Context.Server.GetLastError() is HttpException) && (httpException.GetHttpCode() != 404)))         {             routeData.Values["action"] = "Index";         }         else         {             // Handle 404 error and response code             Response.StatusCode = 404;             routeData.Values["action"] = "NotFound";         }         Response.TrySkipIisCustomErrors = true; // If you are using IIS7, have this line         IController errorsController = new ErrorController();         HttpContextWrapper wrapper = new HttpContextWrapper(Context);         RequestContext rc = new System.Web.Routing.RequestContext(wrapper, routeData);         errorsController.Execute(rc);     }   }   When I navigate to http://localhost:56469/sss I get the custom error page I created for this. However when I navigate to http://localhost:56469/sss. (note the period) I get the ugly yellow IIS screen stating The resource cannot be found.  What do I need to do to cover this "flavor" of 404?


Why does the light at the bottom of the pool form this awesome pattern?

Take a look at the following picture:   Why does the light at the bottom of the water form this pattern? I have also seen the same phenomenon in all the swimming pools I've ever visited, of whatever depth they may be. How does this happen?


Find all sub-fields of $\mathbb{Q}(\sqrt[4]{5},i)$

Find all sub-fields of $K:=\mathbb{Q}(\sqrt[4]{5},i)$ by giving generators.    I have shown that $K/\mathbb{Q}$ is a Galois extension and that its Galois group $G:=\text{Gal}(K/\mathbb{Q})$ is generated by $\tau$ and $\sigma$, where $\tau(i)=-i, \tau\left(\sqrt[4]{5}\right)=\sqrt[4]{5}$ and $\sigma(i)=i, \sigma\left(\sqrt[4]{5}\right)=-i\sqrt[4]{5}$. Hence, $G\cong D_4$, where $D_4$ denotes the dihedral-group of $8$ elements.  Thus, there are $9$ sub-fields of $K$ (as $D_4$ has $9$ sub-groups), two of which are obviously $K$ and $\mathbb{Q}$. Now I don't know how to find the others. For example, what is the sub-field $K_1$ respectively $K_2$ generated by the subgroups $H_1:={\langle \sigma\rangle}$ respectively $H_2:={\langle \sigma^2\rangle}$?  I know that $[K_1:\mathbb{Q}]=2$ and $[K_2:\mathbb{Q}]=4$, but don't know how to find elements that generate $K_1, K_2$.


What are these birds eye view stock photos called and where can I find them?    I am trying to find pictures of the birds eye view images above, such as the book, stapler, pencil, and hand.


Book about a teenager programmed to be an assassin and trying to get back at the people responsible

I read this book a few years back (around 5?). It was part of a multibook series but I have only read one book.  It's about this teenager who I think had been programmed to be an assassin but then somehow retained his conscience and was out to get the people responsible for that.  I briefly remember a girl, and this one part where he realizes he can ride a horse and then there's a chase too. I think the guy's name was Jim or Jimmy, but not quite. I'm also quite sure he was either part computer, or had a chip or something in his brain which had been programmed to give him a host of mental and physical abilities which he retained and used as well as the series progressed.


What really is voltage, what effect does a higher voltage have on an unit of charge and what makes electrons flow?

I have been reading a lot about the subject, I've seen lots of videos (youtube, udemy) and even read some scholar papers about it and everyone explains the above in so many different ways. We all know what the scientific definition of what voltage is but I still don't know what effect it has on the electrons.  The water analogy which is used so much, seems to fail when we compare higher voltage vs lower voltage, because the higher the pressure of water in a tank is, the faster the water current will be once the tap is open, but the same does not apply to electrons. In fact, from what I've read, the velocity at which electrons move (drift velocity) is quite slow - small drift changes which propagate across the wire is what allow the fast delivery of electricity.  The other thing I have a problem is is how the voltage is represented in a circuit. I keep reading over and over again and seeing in the water analogy too, that voltage is what pushes the electrons, but if that's the case why is voltage lower at the negative terminal?   If I put a few springs in a box and apply pressure to close the box, some springs will contract and will probably fly away once I open the box, so using this analogy, is voltage the force necessary to keep the springs tight in the box?  The electrons don't really need a push to move across the hire, they have that desire, they are attracted to the positive side, how what is really the voltage role here?  Using another analogy, it seems that voltage is to electrons what fuel is to my car. At the end of a working day all I want to do is to drive home. I will always have the desire to reach home, but if I don't have enough fuel in the tank, I will never be able to, in the same manner, if there's no enough voltage the electrons will never reach the other end of the hire, even if that's all they want.  To me, it seems that voltage is simply the force that pushes electrons apart from each other. I also see in so many videos, electrons flowing from the beginning of the circuit to the end, when in fact the electrons barely more.  The more I read the more confused I become.   UPDATE 1  This is the best explanation I have read so far:  "A voltage appears whenever there is an imbalance of electrical charge (i.e. electrons). Since like charges repel and opposite charges attract, any collection of electrically charged particles creates some kind of force on each other. If there is an imbalance of negative to positive, a kind of "pressure" or "push" is formed. In conducting materials, electrons are free to flow through the material, as opposed to being fixed in atoms, and will therefore flow to the point of least "pressure"."


I am using manjaro and when i try command man -k . or apropos . or man -k . -s 2 to see all man pages it's giving me error like .: nothing appropriate. is it man different because i gnu coreutils ? what should i do for print all man pages then ? is there is alternative way to do this then let me know.


How to refer to "all" the equations when using subequations?

I've just found out  I can use the subequations environment to have equations share a number but with a letter (1a, 1b). So now, I have  \begin{subequations}   \begin{align}      a & = b\\      b & = c   \end{align} \end{subequations}   I can use labels to easily refer to eq (1a) or (1b), but how do I refer to equation (1) in its globality ?


Safe to delete "C:\WINDOWS\SoftwareDistribution\Download"

One of our Windows 2003 servers has a fairly small C-partition, which is approaching full. I've had a quick look round using  as to where the space has gone, and a fair bit of it seems to be taken up with C:\WINDOWS\SoftwareDistribution\Download  I think this folder is used as a temporary storage for Windows Update, but as all the pending Windows updates have now been installed, is it OK to delete the contents of this folder?


In D&D 5e, does the Rogue's Cunning Action allow for Two-Weapon Fighting?

For example, does the Cunning Action allow a 5th level Rogue to have a bonus action, thus letting him fight with two shortswords? I don't think he would have any other bonus action unless wielding two light weapons allowed him to attack with both. Thanks for the help.


TO BE PROVED: $$ \frac{1}{1^2}+\frac{1}{2^2}+\frac{1}{3^2}+\dots \frac{1}{n^2}<2 $$ Please prove this by mathematical induction only. My approach: I already proved it through graphs but i have to prove it through mathematical induction. Prove this equation by mathematical induction that   $\frac{1}{1} + \frac{1}{2^2} + \frac{1}{3^2} + .... + \frac{1}{n^2} < 2 $  ?


Just bought a house, 70 years old, want to upgrade 2 prong outlets

I've done some searching on this already and I think I know the answer. But I'd like to ask just to double check.  If i am not sure if the outlets are properly grounded, my best bet would be to replace the 2 prong outlets with GFCI outlets, correct? Actually, i suppose someone is going to say my best bet would be to first find out for sure if they are properly grounded or not :) Could someone suggest a relatively inexpensive tool for doing that?  If the boxes are correctly grounded, then I should be able to just replace the 2 prong outlets with regular 3 prong outlets, correct?  For right now, I mainly want to swap out a 2 prong outlet in the living room that the TV and the rest of the media/gaming stuff will be plugged in to. But there are 2 prong outlets scattered around the house that I'll probably also want to eventually replace.  I would be somewhat surprised if everything is correctly grounded since the wiring in the house is pretty old, it's all knob and tube wiring. Although the home inspector said it all looks like it's in pretty good shape. Eventually we'll have an electrician come in and replace all the wiring, but for now it's staying as is.


Power Series of a Holomorphic Function determined by its Real Part and $f(0)$?

While looking at exercise sheets from last year, I encountered the following statement but wasn't able to prove it myself.  Let $f: D_R(0) \rightarrow \mathbb{C}$ be holomorphic and $ f(z)= \sum_{n=0}^{\infty} c_n z^n $ its power series.  Then for every $0 < r < R$ and $n \geq 1$:   $$ c_n = \frac{1}{\pi r^n} \int_0^{2\pi} Re(f(re^{it}))e^{-int}dt $$  I know that we can write $c_n=\frac{1}{2\pi r^n} \int_0^{2\pi} f(re^{it})e^{-int}dt$.  Does this mean that a holomorphic function is uniquely determined by its real part and the value at zero? This looks like another "WTF?"-statement from complex-analysis to me...


Is there a spell managing program/app for D&D 3.5e?

I'm playing a necromancer wizard in a D&D 3.5e game via Roll20.  I've found that it's very tedious to manage and choose my spells because I have to look in the list of the wizard/sorcerer spells that is sorted by level and for every spell, go and find it in the alphabetical list of every spell in the entire game to see if I want it or not and then write it down in a text document or something.  Is there a more streamlined way to manage my spellbook?


Cardinality of Real numbers in arbitrary small interval.

I have been learning about the cardinality of Real numbers and it got me thinking. Since the cardinality of real numbers is uncountable and is the same as the cardinality of real numbers in the interval $(0,1)$ or for that matter any given interval. So my question is how small this interval can get and still retain the same cardinality. Does $[0, \epsilon)$ have some cardinality as real numbers as epsilon gets smaller and smaller. It is trivial to see that in the limiting case, the set contains only one element. So the question is how small can epsilon get before the cardinality of the set $[0, \epsilon)$ gets smaller than that of Real numbers.


I have an integrated webcam in my laptop. I know that it works and that ubuntu recognized it because at installation it asked if I wanted a photo taken for some kind of image associated with my account. When I look in system settings, I do not see any webcam in the hardware section. I would like to disable the webcam like you can do in Windows, but as I can't find it in my hardware section, how can I disable it? I cannot even unplug it as it is integrated into the monitor. Am I looking in the wrong place?? I am using 12.04


Use the Chinese remainder theorem to solve the system of linear congruence:

Chinese remainder theorem Z ≡ 3(mod 7) Z ≡ 7(mod 12) Z ≡ 4(mod 17)


How can I draw the Minkowski sum of two sets?

I would like to represent the ɛ-neighborhood of a convex polygon, which is the  of the polygon and a disk of radius ɛ. The polygon is given by its vertices, from which of course I could calculate a drawing, but I hope that there is a simpler solution using TikZ (though I'm equally happy with any other solution). , the ɛ-neighborhood of a triangle.


Delete an element from a linked list in java

Trying to delete a particular element from a linked list  void delete(int num) {         Node node = head;         Node prev = null;         if(head.data == num) {             head = head.next;         }         while(node.next!=null) {             prev= node;             if(node.next.data==num) {                 node.next=node.next.next;                 node=prev;             }             node= node.next;         }         if(node.data == num) {             prev.next = null;         }     }   error      java.lang.NullPointerException at hackerEarth.linkedList.delete(linkedList.java:44) at hackerEarth.linkedList.main(linkedList.java:67)   line 44 is - while(node.next!=null) line 67 is - delete(sc.nextInt());


Consider the code...  double first = 19.99; double second = 19; double firstPlusSecond = first + second; Console.WriteLine("Result: " + firstPlusSecond);   The output of this is "Result: 38.99" - which is what I expect  However...inspecting firstPlusSecond in debug, the number is actually 38.989999999999995  Which is messing with calculations elsewhere in the program.  What...?  What have I missed?


We will call a matrix positive matrix if all elements in the matrix are positive, and we will denote the largest eigenvalue with $\lambda_{\max}$, what is exist because of the .  Theorem. Let $A$ be a positive square matrix. If any element increases in the matrix then $\lambda_{\max}$ increases.  My questions.    Is there a name for this theorem and can anybody say books or papers what refer to it? How to prove it?


Find a parabola touches the line $y=x$ and $y=-x$ at $A(3,3)$ and $B(1,-1)$

If a parabola touches the line $y=x$ and $y=-x$ at $A(3,3)$ and $B(1,-1)$, then find the focus, axis of the parabola and its directrix.   What I thought: Since the 2 tangents are perpendicular,the origin must lie on the directrix and the line joining A and B is a focal chord. Don't know how to proceed from here..


Difference between “is to do” and “is doing”

I saw below sentence:     Her job is to clean the hall.   So can I also say like:     Her job is cleaning the hall.   It's present participle or gerund?  What's the different meaning between these two sentences?


How to create a service in ubuntu then access to it by url?

I am reading about how to create a sevice like:  The first link I read is.   But when I type following line in prompt  $ sudo service nameservice start Failed to start nameservice.service: Unit nameservice.service not found   I create this script  /var/www/myproject/myscript.php   I checked all the permissions  -rwxrwxrwx 1 root root 1069 feb 2 15:49 nameservice  -rwxrwxrwx 1 root root 24 feb 2 15:56 myscript.php   /var/www/myproject/myscript.php has this content  <?php     echo "OK"; ?>   Could you help me? This is the first manual script I wrote.  My intention is to add this service and then call the url http://localhost/getanswer to show it to me in the browser.


Why don't neutron stars transform into proton stars as a result of neutron beta decay?

Free neutrons, as we know them, are unstable and hence undergo a three-body decay into proton, electron and antineutrino with a mean lifetime of just under 15 minutes.   But there are astrophysical objects called neutron stars which are produced at the end of the lives of moderately massive stars. These objects are made entirely of neutrons in order to support the strong gravitational pulls. These are pretty stable objects in cosmological time scales lasting at least for billions of years.  So, why they are simply not decaying into proton stars due to unstable nature of neutrons? How to explain this apparent contradiction?


How to answer a negative question without ambiguity?

I faced a problem to answer a negative question, for example, when someone asks you:      Don't you have any money?   It's a yes/no question but how should one answer the question without ambiguity?  When you answer "yes", does it mean "yes, I don't have any money"? or the other way "Yes, I do have money"? the questioner may think you are agreeing to the negative, that yes, you do not have any money.  I know it's better to answer with "on the contrary" but is it possible to answer yes or no?


"They're going gorilla watching" - is there a verb at the end of the sentence?

In this sentence:     They're going gorilla watching.   what's the function of the verb watching?   Is it a verb? a noun? ... maybe gorilla watching means "mirador de gorilas", in spanish?  In English, I have not seen a verb at the end of a sentece.


Select a block of text from a file using powershell

Disclaimer:    I know to read in text files with the -raw switch I know about the (?sm) and -AllMatches qualifiers I've read the other similar solutions ( and ) but can't successfully modify their solutions for my use case   I have a log file ~1200 lines long, so not overly huge. The log file is a mixture of 'plain text' and then that 'plain text' is repeated as XML. I want to select (and ultimately remove) the blocks of 'plain text' so the blocks of XML remain.  The plain text blocks start with Log Name: then some more text on that line, then multiple lines with text, finishing with Event Xml: (nothing else on this line).  Example plain text block:  Log Name:      AD FS Tracing/Debug (multiple lines of text) Event Xml:   My attempts either select nothing, or everything, or eveything from the first Log Name: to the last Event Xml:  Example regex pattern:  '(?smi)Log Name:.*Event Xml:'   Have tried this in powershell and notepad++. The log files are from Event Viewer on Windows 2012R2, so alternative solution to solve my overall issue: How to you export just the XML from Event Viewer?  Edit: (@ )  '(?si)Log Name:.*?Event Xml:' selects the entire log file. I had tried modifying the similar questions, but it doesn't select what I want. Hence why I asked my specific question - it's not a duplicate.


Is there a size limit on external USB hard drives?

The internal SATA hard drives have a limit on a lot of motherboards of 2TB and if I want to get a 3TB HDD then I need to connect it using a PCI card (or get a new motherboard).  But I wanted to ask: If I connect a 3TB harddrive to a external USB enclosure, will it work? The  I want to buy says it supports up to 3TB HDD but I want to make sure.


How can I make a process I start during an SSH session run after the session has ended?

Possible Duplicate:          I have a process which is basically a web-server, I start it during an SSH session. However, when I leave the session (by closing the PuTTY windows), it stops running and responding to requests. This is true even if I end the command with a &. With Apache, I don't have this problem, it comes with a stop, a start, and a restart script. I'd like to create something like that for this program.  How can I start a process, so that it will continue running even after I end the SSH session I started it in? Also how can I set it to restart itself if it stops for some reason?  Thanks!


How can you sync Blender configs between multiple machines?

I run Blender on several machines, it is a hassle to copy configs around, in order that you don't have to configure everything from scratch every time. Is there a sync functionality that does this?


How to get all parents associated to a child, one row for each association

I have a table with two columns, Parent and Child.  i need to get an output list showing a child and all associated parents, one parent per row.  The youngest child will show as a child in rows equal to the total number of parents, as shown in the output table.  Input table  +-------+--------+ | Child  | Parent| +-------+--------+ | b | a  |       | c | b  | | d | c  | | e | d  | | f | e  | | x | f  | +----------------+   Output table  +------------------------------+ | Child | Parent  | level  | +------------------------------+ | a | NULL    | 0      | | b | a   | | c | a   | | c | b   | | d | a   | | d | b       |  | d | c   | | e | a   | | e | b   | | e | c       | | e | d       | | f | a       | | f | b       | | f | c       | | f | d       | | f | e       | | x | a       | | x | b       | | x | c       | | x | d       | | x | e       | | x | f       | +--------------------------+   Here is my syntax from SSMS 2017  create table tx  ( parent varchar(10), child varchar(10) )  insert into tx values ('a','b'), ('a','c'), ('b','e'), ('b','f'), ('a','d'), ('b','g'), ('c','h'), ('c','i'), ('d','j'), ('f','k'), ('x','y'), ('y','z'), ('m','n');   WITH REC AS ( SELECT child, parent FROM tx  UNION ALL SELECT a.child, a.parent  FROM tx A INNER JOIN REC B ON B.parent = A.child) SELECT Child, Parent FROM REC order by child   It is not giving me the results i expect as shown in the output table.  Any idea on how to modify my recursive query to get the output table?


Universal property of free abelian group implies $\phi(S)$ generates F

I saw some definition of free abelian group of an arbitrary set $S$:     An free abelian group on $S$ is a abelian group $F$ and a map $\phi:S\to F$, s.t. for any ableian group $G$ and any map $\rho:S\to G$, there exists an unique homomorphism $f:F\to G$ s.t. $f\circ \phi=\rho$.   A problem ask me to prove that $\phi(S)$ generates $F$. The hint is consider $\phi(S)$ as a subgroup of $F$. This implies that there exists an unique homomorphism $f:F\to \phi(S)$ s.t. $f|_{\phi(S)}$ is identity function. But I don't know what to do next. Could you give me some hints?


Why does the address-of operator create a reference?

Consider the following code:  #include <iostream> using namespace std; void test0(const int &a){   cout << "const int &a passed *ptra "<< a << endl; } void test1(const int &a){   cout << "const int &a passed ptra "<< a << endl; } void test2(const int &a){   cout << "const int &a passed *a "<< a << endl; } void test3(const int &a){   cout << "const int &a passed a "<< a << endl; } void test4(int *a){     cout << "int *a passed &a "<< *a << endl; } void test5(int *a){     cout << "int *a passed a "<< a << endl; } void test6(int *a){     cout << "int *a passed *a "<< a << endl; } int main(){   int a = 3;   int *ptra;   *ptra = 3;   test0(*ptra);   //test1(ptra);   //test2(*a);   test3(a);   test4(&a);   //test5(a);   //test6(*a);   //int &b = a; }   How come (int &a) when passed a becomes a reference? Is it essentially creating an int a and setting its address to the passed a? Wouldn't it make more sense for the resulting reference to point the address of the value of a (if a = 3 points to address 3), where if you passed like so:  void stuff(int &a); int *ptr; stuff(ptr);   a would set its address to the value passed (the address pointed to by ptr); What's the difference between a pointer and a reference?  What's more, if you uncomment //int &b = a the program ceases to output anything. Why?


In Latex typesetting system, I want to write the symbol 'P'. What is the command to write it?

Could you tell me how to write the following P in Latex?    It is not equal to \mathcal{P} in Latex.


Directory structure for a large CTAN package upload

I'm going to upload my first package to CTAN.  But after reading all the upload guides from CTAN and TeXLive I'm still feeling daunted by the directory structure. My package is rather complex and by now consists of >160 files which will become a lot more when the package matures (for example there are a bunch of small pdf files used by the package, along with the sources to recreate them).  So I'm far from being able to produce a package with four or five files in one single directory.  Do such large numbers of files and changing package contents present special problems for CTAN (and the distros consecutively)?  Has best practice for uploading and maintaining such large packages been documented?    Details: the package is in good shape, and a few testers fetched it from Github and got it to run without problems.  If you want to have a look: the package resides at   Edit  Right now I'm trying to understand the TDS and how I can prepare a lilyglyphs.tds.zip file.  Am I right that I a) provide the directory as I would use it myself, and when someone downloads from CTAN she will put the complete directory under texmf/tex/latex/lilyglyphs b) provide a tds.zip that will allow the distributions to put my files in the right locations in their distribution (that is, the files are stored at different locations) ?  If that's true I still have a few questions about where some of my files should go, but I will come back to this after having tried to tackle the tds documentation.


how to add figure numbers in listoffigures continously

I have used \listoffigures in my report and the list contains indexing like 2.1 if it belongs to chapter 2 first image and 5.4 for chapter 5 ,fourth image, how can I change this to continuous arabic numeral indexing like 1,2,3,... without taking consideration for the chapter and figure number in that chapter.


Javascript: Addition of Floating numbers gives incorrect precision

I add this floating numbers in javascript, 1403.07+1000.00 result is 2403.0699999999997  It should be 2403.07  I got a work around (1403.07+1000.00).toFixed(2), but this will fail if precision changes meaning; it will fail for addition of 1403.072+1000.01.  Is there any way I can achieve by jQuery/Javascipt, i dont need external library.


How to describe the quotient group $\mathbb{Z} \times \mathbb{Z} / \langle (1, 2) \rangle$

How do you describe the quotient group $\mathbb{Z} \times \mathbb{Z} / \langle (1, 2) \rangle$? It is easy to get it when it is $\mathbb{Z}_n$, but it is difficult when it is $\mathbb{Z}$.  How should I start and solve the problem?


I have been trying to breed pigs, sheep, cows, and chickens, but I can only feed the cows, meaning I can only breed them and not the other animals. This is very annoying and I was wondering if anyone knew why this is happening


What's so special about standard deviation?

Equivalently, about variance?  I realize it measures the spread of a distribution, but many other metrics could do the same (e.g., the average absolute deviation). What is its deeper significance? Does it have    a particular geometric interpretation (in the sense, e.g., that the mean is the balancing point of a distribution)?  any other intuitive interpretation that differentiates it from other possible measures of spread?   What's so special about it that makes it act as a normalizing factor in all sorts of situations (for example, convert covariance to correlation)?


How do I switch back into third person after being in first person in Mad Max

I accidentally switched into first person and don't know how to return to the third person again.


I saw this diagram on an exam paper and noticed that it was too clean to have been made in the usual MS Word program. So I figured that it may have been made in either TikZ or PSTricks.   What stood out for me was the method of shading the region, which was to use a 'dotted background' as opposed to the usual grey paint. Is this something possible in either TikZ or PSTricks? I have never seen it before in either of the two, but perhaps you may have. I can't imagine somebody manually assigning dots coordinate by coordinate.


Prove that the only integer solution of the equation $a^2 + b^2 + c^2 = a^2 b^2$ is $a = b = c = 0$.

Any tips are welcome! I have tried various methods, but to no avail. I could use a pointer as to the right direction. Thank you.


Hi guys could you help me with this:  proof if $\sum a_{n}^{2}$ convergs then $\sum \frac{a_{n}}{n}$ convergs absolutely.  i tried:  if $\sum a_{n}^{2}$ convergs then exists m $\geq n\geq n_{0}$ ; given $\varepsilon > 0$   so.  $| a_{n+1}^2 + a_{n+2}^2 + ... + a_{n+m}^2| < \varepsilon $  i was goona use triangular inequality but it doesn't helps.  and i can't keep continue. Maybe i've taken the wrong way to solve this problem.


Moving a washer and dryer when relocating across the country

I have been contemplating accepting a job offer on the opposite side of USA. If everything works out, I was thinking about putting all my belongings to a couple of u-haul u-boxes and have them shipped.  So for this reason I wanted to ask if I needed to somehow secure the drums on my washer and dryer?  Both are electric (not gas) and of the front-loading variety.


I am playing with  since all state of the art results in machine learning seem to be using it (for example, see ). I am familiar with all the guidelines (train longer, increase capacity of the model, use higher learning rates), but still cannot see it working. I've tried several different examples: , , MLP for MNIST, , and turning off dropout makes all my results better even though the default configurations have dropout (taken from the ). For example, I am attaching my results for one of the models trained on the IRIS dataset. The configuration without dropout has clearly the best performance.   What am I missing?  The code for the IRIS example is .


I was trying to solve the problem asked in . The answer that had been accepted didn't work for me, but I eventually an answer that worked for me. I would like to add my answer to the original question to help other people like me who come across this question. However, I can't find the answer question button. Is there something I'm missing?