Getting a java NPE for the below code snippet. Not sure what is wrong

import java.awt.Robot; import java.awt.Toolkit; import java.awt.datatransfer.StringSelection; import java.awt.event.KeyEvent;  import org.openqa.selenium.By; import org.openqa.selenium.Keys; import org.openqa.selenium.WebDriver; import org.openqa.selenium.WebElement; import org.openqa.selenium.firefox.FirefoxDriver; import org.openqa.selenium.interactions.Actions; import org.openqa.selenium.support.FindBy; import org.openqa.selenium.support.PageFactory; import org.openqa.selenium.support.ui.ExpectedConditions; import org.openqa.selenium.support.ui.WebDriverWait;  public class EmployeeTest {  @FindBy(xpath="//input[@id='email']") public static WebElement emailIDField;  @FindBy(xpath="//input[@id='password']") public static WebElement passwordField;  @FindBy(xpath="//a[@id='submitButton']") public static WebElement loginButton;  static String subscriptionsAndBillingTabXpath="//a[contains(text(),'Silling')]"; @FindBy(xpath="//a[contains(text(),'Silling')]") public static WebElement subscriptionsAndBillingTab;  public static WebDriver driver;  public static WebDriverWait wait;  public static void main(String[] args) {     // TODO Auto-generated method stub     driver = new FirefoxDriver();      driver.get("http://url.domain.com");      wait.until(ExpectedConditions.visibilityOf(emailIDField));     emailIDField.click();     emailIDField.sendKeys("abc@abc.com");      wait.until(ExpectedConditions.visibilityOf(passwordField));     passwordField.click();     passwordField.sendKeys("xyz");      loginButton.click();      wait.until(ExpectedConditions.visibilityOf(subscriptionsAndBillingTab));     if(driver.findElements(By.xpath(subscriptionsAndBillingTabXpath)).size()!=0)         System.out.println("Login successful!");      else         System.out.println("Failed to login!");     driver.close();  }  }   exception seen is below,  Exception in thread "main" java.lang.NullPointerException     at org.openqa.selenium.support.ui.ExpectedConditions.elementIfVisible(ExpectedConditions.java:227)     at org.openqa.selenium.support.ui.ExpectedConditions.access$1(ExpectedConditions.java:226)     at org.openqa.selenium.support.ui.ExpectedConditions$7.apply(ExpectedConditions.java:213)     at org.openqa.selenium.support.ui.ExpectedConditions$7.apply(ExpectedConditions.java:1)     at org.openqa.selenium.support.ui.FluentWait.until(FluentWait.java:208)     at EmployeeTest.main(EmployeeTest.java:43)


How to check whether port 25 is open or not from ssh access to server

I have ssh access to my Linux server and I want to check whether port 25 open or not.  I discussed with hosting service provide and they said port 25 is open.  I checked using PHP script for port 25 and it says it is open.  I want to know how to check using command on linux server like in Windows I can use telnet example.com 25  Any idea?


Better way of saying "those who are curious"?

I am writing a note in which I want to ask (curious) readers to refer another paper. The phrase curious minded comes to mind, but it seems somewhat awkward.  Is there a better way to convey similar import?


I have a following problem: when I plug-in my USB flash drive, it isn't shown in Windows Explorer or recognized by system at all. In device properties, it is shown as:     USB MEMORY BAR     There's no partitions on the drive, so I can't format it:    DISKPART:     Virtual Disk Service error:   There is no media in the device.   HP USB format tool:     There is no media in the specified device.   Any help will be greatly appreciated! Thank You!


Does Python automatically unset environmental variables at the end of the script?

Suppose created an environment variable in your Python script (which is a process). Is the lifetime of the environment variable the same as the lifetime of the script while it runs? I've set my environment variable and ran my Python code until completion and if I tried to do      echo $MY_CREATED_ENV_VAR   it returns empty. I know that my script creates this environment variable because I could use it within the script itself.  Here is part of the script  import os  os.environ['MY_CREATED_ENV_VAR'] = "1"  # Returns-> MY_CREATED_ENV_VAR = 1 (and usable by other processes in the script) print("MY_CREATED_ENV_VAR = " + os.environ["MY_CREATED_ENV_VAR"])  # Script ends   does MY_CREATED_ENV_VAR automatically become unset? If not, how would I manually unset this environment variable in the script so as to clean up my code?  Thanks in advance!  Edit: I see that you can unset the variable, but then my question still stands, does python automatically unset the environmental variables? I cannot echo the env variable back in my terminal after the script has finished executing.


How can I stop my lava moat from burning down my house?

I have a house in Minecraft and since wood planks was the most abundant resource in my inventory, that is what I made it out of.  I put a lava moat around my house for defensive purposes.  My house keep catching on fire, how can I stop this from happening?


Pass parameter to Bash function which will serve as a pattern to awk

I would like to know how to pass a argument to a Bash function which would consequently serve as a pattern to awk. I have read several Q/As which tend to answer the same question, however, I am missing something.  I use the following one-liner to find a package, which in this example is vivaldi, using Arch Linux packman:   pacman -Sl | awk '$2~ /^vivaldi/{print $2, $3, $4, "[" $1 "]"}' | sort   I've written the following function but executing it outputs no result:  function pacname() {     #pattern="$1"     pacman -Sl | awk -v pattern="$1" '$2~ /^"pattern"/{print $2, $3, $4, "[" $1 "]"}' | sort }


Why does time dilation imply length contraction?

This is probably a nonsensical question, but I'm having trouble wrapping my head around it. I'm thinking of the classic scenario where a stationary observer is watching a spaceship move horizontally. It makes perfect sense to me that a beam of light bouncing up and down will appear to move more slowly vertically, since it has to also move horizontally. This produces the time dilation effect. However, I don't see why this same dilation factor has to apply to a beam of light moving horizontally. This is the way that I have seen length contraction derived. It sounds peculiar, but couldn't there be a different time dilation factor for objects moving horizontally versus vertically on the spaceship? edit: I believe this can be explained by thinking about a beam of light moving diagonally on the spaceship, but I'll leave the question up in case someone has a better explanation.


Do I really need apt-daily.service and apt-daily-upgrade.service?

The startup with 18.04 seems to take a bit longer than 17.10 so I ran systemd-analyze blame and found that apt-daily.service and apt-daily-upgrade.service are taking up over three minutes between them.  :~$ systemd-analyze time     Startup finished in 9.173s (kernel) + 3min 30.201s (userspace) = 3min 39.375s     graphical.target reached after 15.268s in userspace :~$ systemd-analyze blame     1min 52.265s apt-daily-upgrade.service     1min 27.579s apt-daily.service           6.603s NetworkManager-wait-online.service           5.105s plymouth-quit-wait.service           1.517s plymouth-start.service           1.439s dev-sda1.device.............   So, what are these services actually doing (checking apt is up to date I imagine), why do they take so long and do I really need them to run on every bootup?


tikz cd: ! I can't find file `librarycd.code.tex'

The cd package for tikz seems to be failing, or missing. I am using Kile in Ubuntu 10.4, and I installed all the tikz-related packages my package manager could find.  MWE:  \documentclass[a4paper,10pt]{article} \usepackage[utf8]{inputenc} \usepackage{tikz} \usetikzlibrary{cd}   \begin{document}  bla  \end{document}


Why can objects that are passed into a function be mutated but not reassigned in javascript?

I'm a beginner with Javascript and just need some clarification. I'm not really trying to achieve anything in particular here. Just a bit confused about this scenario. When a variable assigned to an object is passed into a function as an argument, we can mutate the object permanently. However, we can't reassign it and make the changes stick. Why is that? Here is some example code to what I mean: Example1 - Mutation. const house = {   color1: 'white',   color2: 'blue' };  let paintIt = obj => {   obj.color1 = 'gold' };  paintIt(house);  house.color1 // Returns 'gold'  Example2 - Reassignment. let house = {   color1: 'white',   color2: 'blue' };  let paintItReassignment = obj => {   obj = {     forSale : false,     includesGarden : true   }   console.log(obj) // Prints {'forSale':false, 'includesGarden':true} };  paintItReassigment(house) // The reassignment does not work house // Still returns {color1:'white', color2:'blue'}  house = {  forSale : false,  includesGarden : true }; // Regular reassignment still works  Why does it stick when you modify the objects property (example1) but not when you reassign it (example2)?


the java.net.SocketException: Connection reset error

Only at the level of studies and take out doubts and curiosity. I would like to know how to fix this error      java.net.SocketException Error: Connection reset.   How do you identify it?


$d = \gcd(c,m),\ ac≡bc\pmod{\! m}\Rightarrow a≡b\pmod {\!m/d}\ $ [Congruence Cancellation & Division Rule]

How would you show that if $ac≡bc$ $\mod m$ and $\gcd(c,m)=d$, then  $a≡b$ $\mod \frac{m}{d}$?  Any help would be much appreciated!


What is purpose of sideway transformer in PSU?

In another question someone ask about repair of laptop PSU. I cannot find it ATM - possibly because it was closed as about repair and off topic. However an attached schematic to one of the answers had a sideway transformer (XFRM1 on schematic below)) surrounded by 2 caps (C1 and C2) before transformer to (I presume) lower the voltage. As far as I can tell it doesn't 'do anything' which leads me to think it may be a safety feature. What may be a purpose of it?     – Schematic created using


If $d=(m, n)$, with $m, n>0$, do $a, b$ integers exist such that $1=(\frac{m}{a}, \frac{n}{b})$ and $d=ab$?

I've been doodling around with some numbers and I think this is true, however I have not been able to prove it yet. I'd like to know if you have a suggestion or a counterexample for this. Thanks!


Consider $$ L = \lim_{n\to \infty} \sqrt n\int_{0}^1 \frac{1}{(1+x^2)^n}dx$$ Given is that $$L < 1/2$$ What is the minimum upper bound on L. What have i tried :  Generating a recurrence relation for the involved integral : I however could not find a proper line of reasoning to calculate the minimum upper bound.  Finding the value of integral involved for n= 1, 2, 3... and guess a pattern for n. The value for n=1 , 2 , 3 however does not offer an easily observable pattern. . It finally struck me that if i change the denominator of the involved integral from $1+x^2$ to $x^2$ I can argue as follows $$\sqrt n\int_{0}^1 \frac{1}{(1+x^2)^n}dx < \sqrt n \int_{0}^1  \frac{1}{x^{2n}}dx$$ This however did not help me as the integral on the RHS could not be evaluated at the lower limit.I then replaced $(1+ x^2)$ by $(1+x)^2$ As this will also ensure the following: $$\sqrt n \int_{0}^1 \frac{1}{(1+x^2)^n}dx < \sqrt n \int_{0}^1 \frac{1}{(1+x)^{2n}}dx$$ The RHS integral had the value : $$\sqrt n\frac{1}{-2n+1}(\frac{1}{2^{2n-1}}-1)$$ Imposing the limit n goes to infinity on this gives $0$ which is certainly not what I expected. . What am i missing here ?


Protection of shell command with string variable

Within a programming language, i execute a simple shell command  cd var; echo > create_a_file_here   with var being a variable that contains a string of (hopefully) a directory to the place where i want to create the file "create_a_file_here". Now if someone sees this line of code, it is possible to exploit it by assigning for instance:  var = "; rm -rf /"   Things can get pretty ugly. One way to avoid the above case would be maybe to search the string in var for some special characters like ';' before executing the shell command, but i doubt this covers all possibly exploits.  Does anyone know a good way to ensure that "cd var" only changes a directory and nothing else?


How to find suitable manual exposure settings based on the light and subject?

I'm using Canon 700d with 18-55mm and 55-250mm Kit lenses. Somedays my camera manual settings suits the environment and I'm able get some great shots.(Sea shore,Road,Terrace). But sometime I'm getting blurred, dark very poor shots, I tried with shooting many different setting but nothing helps.low-light(Indoor, using flash, evening). While I try to focus a subject it produces a brighter preview image but the resultant image is darker that it shown in preview. How to calculate the suitable aperture, shutter speed, ISO and white balance for the lighting condition and the subject. I do use tripod wherever necessary. Please advise.


How can I more aptly describe acceptable laziness?

A lot of words for laziness (thesaurus: apathy, lethargy, negligence, indolence, sloth) carry some serious negative connotations. However, some forms of laziness are not necessarily that bad: for example if you have the money for it, eating out for dinner when you don't feel like cooking is not some mortal sin; it's relatively neutral. In fact in my chosen profession of programming, some forms of laziness are downright meritorious; "I quickly pasted a couple of things together that will let a computer solve this problem over the next week, rather than spending two days slaving over getting it Done Right" shows an excellent frugality-of-time. What is a good  for the adjective "lazy" so that I can better deal with the "I" and "you" cases (positive, neutral) when we all know how to deal with the "he/she" case (negative)? More examples:  "I'm going to buy a new shirt from the clothing store across the way because I spilled some tea on this one; it's [neutrally-lazy] and ideally I'd go home and change, but I have an important meeting in a few hours and I don't want to spend time stressing about being in too many different places at once." "Yeah, those search phrases you put in the system overnight generated lots of garbage." "Can you run it again by hand with these phrases?" "Well, I'm trying to be [positively-lazy], so why don't I just set that client to run on Wednesdays rather than Tuesdays, and it will just run like usual tonight? It's not urgent, right?"  Ideally I would like an answer to take the form of an emotive conjugation, so that it's clear that the denotation is remaining the same (some answers like smart seem to be straying a bit from laziness per se), such as the examples "I am well-traveled; you are a sightseer; he is a tourist" or "I'm intelligent; you're intellectual; she is a smarty-pants." So I'm looking for something like "I am [positively-lazy]; you are [neutrally-lazy]; she is downright lazy."


Preventing user from accessing parent folders

I have a user who I only want to be able to access /var/www/ucp/ (his home directory). I have executed the following command on the / directory, the /var/ directory and the /var/www/ directory: chmod o-rwx ~  However, when I connect to this user via SSH, they can still navigate out of the /var/www/ucp/ directory. I do not want them to be able to access any other directory at all, but I do want them to have full access to everything inside /var/www/ucp/.  How can I do this?


Explain the season one climax (technical) of Silicon Valley

I accidentally came across Silicon Valley (2014) TV series and I liked it a lot, but I am unable to understand the climax of season one of this series. I am not a hardcore programmer but I know some basics of programming.   During the TechCrunch event what kind of modifications the protagonist made to his compressing software Pied Piper which helped his team to win the event?   Why the protagonist initially become gloomy while compressing a 3D data file which size was greater than 100 GB (from judges) to mere 20 GB?  Why he became happy when the software showed no error?


Is it Possible or impossible to do a 100% testing?   We had tested an application and solved all critical or major bugs, but after some time we found some functionality bugs in it.   So my question is, is it possible to deliver bug free applications?


Proof that $n^3-n$ is a multiple of $3$.

I'm struggling with this problem of proof by induction:  For any natural number $n$, prove that $n^3-n$ is a multiple of $3$.   I assumed that $k^3-k=3r$  I want to show that $(k+1)^3-(K+1)=3r$  The final statement is $K^3 +3K^2+2K$  Am I missing something ?


How do I depower overpowered magic items without breaking immersion?

At one point my party cleric found a magic item that allowed him to pull anything smaller than the item out of it, like a Star Trek replicator. Now nothing is a challenge for him anymore. How would I make the item less powerful without just saying "your item is now less powerful" and breaking the immersion of the game by violating continuity?


How do I move SharePoint Lists and Libraries to another Site Collection?

I'm in the process of upgrading/cleaning up a large Web Application with a lot of Site Collections. On a SharePoint Foundation 2013 env.  I have found some questions about moving document libraries and lists but nothing really covers it good. At least not what from what I have found.  Is there a way to move Libraries and/or Lists from one site collection to another on the same web application without effecting any metadata on the files and keeping all versions of document/ListItems.  I would preferably like to do this using PowerShell.  Have any tips/links?    that this question might be a duplicate of, but i don't believe the answer covers if there is a way to to this with PowerShell.  UPDATE  I have now investigated this more and tested some different ways to move Lists and Libraries.   Granular Backup and Restore ()   This worked but some metadata was lost. I found that user fields like custom user fields, Created By, Modified by and Create Date and so on, was not kept. Sadly, other ways this was easy to do.  How to: In Central Admin go to Back Up and Restore -> Granular Back up -> Export a site or list. Use PowerShell to Import it. (Import-SPWeb http://site -Path export.cmp -UpdateVersions Overwrite)  Save List as Template, Include Content.   Sometimes Include Content is "greyed-out".  Using code.   Looses Metadata if I move SPFolder. (Time consuming if I recreate the list on a different site collection and move all items and tag the metadata per document.)


Why is it that after 8,000 years, technology in Westeros has not evolved in the world of the Game of Thrones?

In Game of Thrones, their society dates back 8,000 years.  Why have there been no advances in technology?


Transfering styles from QGIS to ArcGIS Desktop?

We have a QGIS project that has symbols for a lot of different lines. Data comes from a geodatabase that is accessible to both QGIS and ArcGIS.  We now want to use the symbology of the QGIS project to style the features in the ArcGIS map document.  My first approach was to use SLDs. The QGIS style can be exported to SLD easily, but how can you style your features according to a SLD using ArcGIS Desktop?  Setting up a simple WMS does not suffice, both QGIS and ArcGIS Desktop need editing capabilities on the features.  If one could provide a SLD with a WFS (in a Esri-readable way) that would also be a possibility. Have found nothing for that, either.


Here is some code that I got from another website, but I am not able to understand what the <> sign does.  Can someone please explain it?     Dim FldrPicker As FileDialog     Application.ScreenUpdating = False    Application.EnableEvents = False    Application.Calculation = xlCalculationManual     Set FldrPicker = Application.FileDialog(msoFileDialogOpen)     With FldrPicker        .Title = "Select folder:"        .AllowMultiSelect = False        If .Show <> -1 Then GoTo NextCode        myPath = .SelectedItems(1) & "\"    End With


How do you create an arc for text without distorting in Illustrator?

Good day, I am currently creating a circular logo in Adobe Illustrator CC, what I did in the upper part is making a circle and inserting text using a type on a path tool. My concern is in the lower part of the design. How do you arc it so that it is aligned in the bottom without distorting the text? Any help would be wonderful, thank you for reading this.


Which episodes are required to watch before jumping directly into Star Trek: Voyager?

I want to introduce Star Trek to a girl (who doesn't know anything about Star Trek) and I am thinking about Star Trek: Voyager because it features a female captain.  What episodes should I present to her before that? Probably, the episode from Star Trek: The Next Generation in which USS Voyager lost from alpha quadrant (episode name not in my mind). Any more episode?  I am too much into the feeling of Star Trek, so I am unable to emulate condition of a Star Trek virgin. Please, help.  Species intro isn't that necessary (except Borg of course), but I'd like your help in this matter. And, if some episodes can be skipped using small mouth-telling story from small portion of that episode, tell me that too.


Splitting Line.shp at Point.shp with Python/ogr

I'm trying to modify some ESRI Shapefiles using Python with gdal/ogr module. What I want to do is quite simple, but I didn't find any solution by now.  I have two shapefiles: (1) Lines.shp and (2) Points.shp The features of the Points.shp mark intersections of the lines in the Lines.shp  Is there any way to split the line-features at the given points?    edit: It should work like the "Split Line at Point"-tool from ArcMap (Data Manangement Tools --> Features --> Split Line at Point)  edit2: I already knew about the , but I don't want to use shapely. Also I don't want to save my Points into a list. I just wanted to know, if tehre is any function/method like ESRIs "Split Line at Point"


I have read a lot of code examples in this subject but it doesnt work. It should be no problem but it failed in my project where in other people project it work. I have text box in C# that should be contains only numbers. In my project if i have a text box with text :   ----------------------- |         32          | |                     | ----------------------|   and i add a char " T" my resualt is :  ----------------------- |         T3          | |                     | ----------------------|   It remove the first char instead the last char My code :  private void txt_NumOfIkun_KeyPress(object sender, KeyPressEventArgs e)     {         char charAdded = e.KeyChar;          if (txt_NumOfIkun.TextLength > 1)                 txt_NumOfIkun.Text = txt_NumOfIkun.Text.Substring(0, txt_NumOfIkun.TextLength - 1);             else                 txt_NumOfIkun.Text= "";     }


While a window of the File manager is opened, on clicking the files icon, in Unity, should open the minimised screen. But Files application opens another new Window. This is reaally annoying as I end up 2 or 3 Windows while I was trying to open a minimised Window.  I checked Preferences but I got no clue.  I am using Ubuntu 14.04 Files Version : 3.10.1


Add space between headings and body in the home of the iPad app

It's a pain in the ass for me to quit the app, draw a red circle in another app and return to the app, so...    If you notice the three questions in the bottom, you will notice that the emboldened headings (New Answer, Comment) are stick to the next character. Imperfect.    App Version: 1.4.0.249 Device: iPad 2 (GSM) OS Version: Version 9.1 (Build 13B143)


What method is there to denest square roots?

$$\sqrt{4+2\sqrt3}=1+\sqrt{3}$$   What steps would one take to get $1+\sqrt{3}$? Squaring the right side obviously gets to the expression under the square root on the left side, but I don't know how to go the other way.


Broken screen/glass, turned off, pc-controll? HELP?

I was wondering if there is any ways for me to controll my phone (Sony Xperia V) with my computer? Half of the glass/screen is broken, so i cant write anything on the lower part of the screen! The phone is not rooted, and has also been turned off, so im kinda stuck.  So, my question is: Is there any ways for me to controll my non-rooted, turned off, screenbroken phone with my computer?  Cheers!


Why does the question filter always return 96 questions?

After the , I can now see question counts.  I noticed that my preferred settings (new questions, recommended tags, sort by active) returns a set of 96 questions.    What (if any) is the significance of 96 questions?


I read the following :  Technically, online searches would stop looking for URLs  (the Uniform Resource Locator) and start looking for URIs (Uniform Resource Identifiers).   and I am wondering, what does that mean ? I understand the difference between URL and URI but I don't get this. How can I reach a server by just using URI ?


Is there a word and/or term that describes the intention of converting words into an acronym?

I wanted to say this to somebody today, but couldn't find the word for it (neither in my head nor via Google). I have a task that acronyms would be better-suited to.  Instead of saying "I want to create acronyms from these location names", I wanted to say, "let's just acronym them" to my colleague, but it sounded all kinds of wrong in my head so I kept quiet. For example, I have a list of entries in a field that I need to refer to within a data processing script that I have built, and I decided that rather than the system I have built looking for "Site One, Location 2", it would be better to have the system look for "SOL2". Is there a word and/or term that describes the intention (not the process) of creating an acronym from a given set of words?


Floating point comparisons don't yield the expected output in pandas


After installing Ubuntu 16.04 with the "erase disk" option three partitions show

As the tile says, I did a fresh install from a USB (LiveRecoveryCD). Now my system boots up with three mounted volumes (499 Mb, 10Gb, 10 Gb). Is this an issue? I did not create them when installing. Whenever booting up I get a "System error prompt" but everything seems to work alright. However I can't open the Ubuntu Software center. Any command I could use to diagnose/fix this issues? Thanks.    Very odd: seems as if everything from my system is scattered through the different partitions!          After running lsblk .


Use of definite article before phrases like Heathrow Airport, Hyde Park, Waterloo Station, Edgware Road and Parliament Square

In  related question (), the OP asks if it is grammatical to use the definite article before phrases like Advanced programming in Java whitepaper and Microsoft Office 2010 product. The accepted answer by @Kosmonaut was:     Yes, it is. This is because the "Advanced programming in Java"   whitepaper phrase forms a syntactic unit, with whitepaper as the head   of the unit. The definite article for a phrase always corresponds to   the head of the phrase, so using the definite (or indefinite) article   for these phrases makes perfect sense and is correct English.   My question is whether the same answer applies to phrases like Heathrow Airport, Hyde Park,  Waterloo Station, Edgware Road and Parliament Square. I ask becase it seems to me that airport, park and station, etc. sound like they are part of the proper noun itself, and not simply a common noun. Moreover, I think the head of the unit in these cases would be the place name (first noun) and not the place type (second noun). If that's true, then I assume that no definite article should precede these phrases. Is that correct?


I'm using Canvas to create polygons like this:    I want each of those polygons to represent a clickable province. How do I know which province is clicked when the user clicks on something? I have a list of vertices (thousands) but I feel like each time looking for the closest vertex is too slow (I think I might be wrong). What's a fast way to do it? Thanks.


How can my husband travel to Europe while on a business visa to the UK?

My husband is on a business trip to London. His trip is getting extended for a couple of months, and he holds a visa until April 2018.  I tried to apply for a UK tourist visa, since it's our anniversary in January, so that I can visit him. I had my uncle sponsoring my trip and showed a bank balance of 150,000 INR from my end as well. My visa got rejected twice: the first time saying insufficient funds and the second time saying that I will not return back to India.   I am considering applying for a Schengen visa, but how can my husband come to Europe to visit me? He doesn't have a Schengen visa and I think he has to return back to India to apply for one. Is there any other possibility for us to meet?


Proving that an element of a ring annihilates a module

Let $R$ be a commutative ring with $1$, $M$ be a finitely generated $R$-module, $\mathfrak{i}$ an ideal of $R$, and $\phi$ an $R$-homomorphism such that: $$1.\;\phi(M)\subseteq \mathfrak{i}M=M$$ i. Prove that for some $n$ and $a_i\in\mathfrak{i}:\;\phi^n+a_{n-1}\phi^{n-1}+\cdots+a_0=0$  As was suggested by the author, I proved this by adapting the proof of Cayley-Hamilton I know, using $\mathbf{A}\,\text{adj}\,\mathbf{A}=I\det \mathbf{A}$. My set-up was that since $\phi$ is an $R$-homomorphsim its action can be represented by a matrix $\mathbf{P}$ with entries in $R$, and since $\phi(M)\subseteq\mathfrak{i}M$ these entries must lie in $\mathfrak{i}$. Moreover $M\cong R^n/N$ for some $n$ since finitely generated, so this matrix does indeed have finite dimension.     is this enough justification to then carry on with the usual Cayley-Hamilton proof?   ii. deduce that there exists $r\in R$ such that $rM=0$ and $r-1\in \mathfrak{i}$.   plugging in $M$ (I interpret $a_0$ as the map $a_0\,\text{id}$), I get $Q+a_0M=0$ where $Q$ is a submodule of $M$. If we had $Q=M$ then $r=1+a_0$ gives me what I want, but I can't see why $Q$ should be the whole of $M$ (if it indeed should), so a little stuck here.   Thank you for any help.


Notify me when someone forgets a chat ping

TL;DR: Chat should ping like comments do. If someone forgets to @mention me and we're the only two people with access to the room, I'd like to receive a notification. As a moderator, I increasingly find myself communicating with users for ad-hoc requests using the  feature in chat. A common use-case (one that recently happened, even) is where a user flags their post asking for it to be deleted, so I ping them in chat and ask if a disassociation would suffice. This is great and all, but I find it really difficult to keep on top of all these chatrooms floating out in space, especially for less frequent users, who may take a week to respond to me. The trouble is that these often-less-experienced users (who typically don't even have chat accounts in the first place) either don't know they can, or forget to @mention me. I try to check back every few days, but sometimes I forget, and sometimes a few days is just too long. This leads to conversations that go something like:  Matthew: Hey, I saw your flag. Would disassociation work? Other user: Yes, please do that. Other user: Yes Other user: Hello?  Which is, frankly, embarrassing. I don't want people feeling like their moderator team is ignoring them. I know I could theoretically keep on top of these, and I generally do, but I really don't like the fact that some could also slip through the cracks. I think this has happened twice for me, which seems like two times too many.  As a solution, I'd like to see chat notifications behave more like comment ones. In the process of a super ping like this, I always use private rooms. If the room is set up as private with only two users explicitly granted access (me, the owner and room creator, and the user as a writer), I want to be notified whether or not they include an @mention. I recognize that this may not be a one-size-fits-all solution, and there are lots of requests out there for subscribing to chatrooms and receiving notifications for every message posted, but I understand that's not a priority, and it would be overkill for this anyway.


Add multiple commands to a single command block, and alternate with +/- redstone power

I am playing around with command blocks, and I just wanted to know if you could have multiple commands in one command block. If you can, is it possible to have one of the commands active when the command block is powered, and the other activate when the block is not powered?  Example:     CMD 1) is powered would be   {setblock ~ ~1 ~ 152}   CMD 2) is not powered would be  {setblock ~ ~1 ~ 0}   Is it possible?


How can I undo the changes after compiling a package?

Let's say that I have build a package using the typical method  ./configure make make install   and then I would like to uninstall this package. There is no any uninstall script. How can I revert my system back to the state it was before do the building/compiling ?


How to prevent cells from printing in Excel

How can I prevent the contents of specific cells (or entire row or column) from printing in Excel, while keeping them visible on the screen when I'm editing the file? Ideally I should be able to do this to cells in the interior of the spreadsheet (i.e., not just the rightmost column(s) or the bottom row(s)). Hiding row(s) or column(s) is not acceptable because I need to maintain the cell size, to maintain the overall appearance of the sheet.  I've looked for a way to define a conditional format that's conditional on whether Excel is currently printing, but there doesn't seem to be any such thing. I've been manually setting the text color to white before printing (and manually reverting it afterwards), but it seems there should be an automagic way of doing this.


Allow the search of content and/or users based on your preferences and quality?

Voting is a rough measure of quality * quantity or more specifically for questions/answers: quality * views/popularity.  This leads to poor search results if you are looking specifically for hidden gems in fields that are either too niche or the subject is relatively advanced and demands a high level of expertise to fathom.  Sometimes I come to the site with a desire to learn/teach new things (read and/or answer questions) that suit my preferences. I don't specifically have an issue I want to solve, I just wish to interact with the knowledge base that is relevant to my domain/hobbies/interests.  Currently, you can only search by tags - which are highly generic and lack some specificity. You can't discern between beginner/advanced/expert questions and can't look specifically for low popularity questions with a good score.  After you gain some reputation, the system should have enough data to predict which questions are of interest to you or alternatively, let you have the tools to search for them (so you can answer them). It should probably also take note of which users may have similar interests. This data could then be used to recommend questions/answers that are more valuable to a specific user.


$$\sum_{j=0}^n j\cdot j!$$  I got $(n+1)!-1$ as the answer but I'm not sure if that's right or how I even got to that answer exactly. (my paper is a mess of random work and I can't make it out). Can somebody tell me if that's correct and explain the best and condensed way to get to the answer?


Cannot install Oracle Virtual Box 6.1 in Ubuntu 20.04.1 LTS (Focal)

I installed some weeks ago  Oracle Virtual Box 6.1 to Ubuntu 20.04.1 without any problems. Since 10 January 2021 I have tried to install it to to my backup  computer with the same configuration but it does not work. I have followed many instructions I have found with Google, but without success. My conclusion is that something has been updated in Virtual Box or Ubuntu since my last installation which makes the VB broken. Has anybody else this problem with installing  Oracle Virtual Box 6.1 to Ubuntu 20.04.1  and know how to solve it? As my last trial I tried the official VB page instructions on  and I followed "Debian-based Linux distributions" by using "focal" in "mydist" But when I try to open a new box I get error:  Kernel driver not installed (rc=-1908) The VirtualBox Linux kernel driver is either not loaded or not set up correctly. Please try setting it up again by executing '/sbin/vboxconfig' as root. If your system has EFI Secure Boot enabled you may also need to sign the kernel modules (vboxdrv, vboxnetflt, vboxnetadp, vboxpci) before you can load them. Please see your Linux system's documentation for more information. where: suplibOsInit what: 3 VERR_VM_DRIVER_NOT_INSTALLED (-1908) - The support driver is not installed. On linux, open returned ENOENT.  I tried : sudo /sbin/vboxconfig But I got a serie of other and errors and tried to solve with Google, but they are too long to describe.


I have the Intel Atom® Processor N450 (supports x64 but its not amd processor) on my netbook but here  says:  If you have a non-64-bit processor made by AMD, or if you need full support for 32-bit code, use the i386 images instead. Choose this if you are at all unsure.


Given the marginal distributions of $X$ and $Y$, how do I find the joint distribution?

Let $X$ and $Y$ be some random variables. How do I find their joint distribution?  If I would have the joint distribution, I would find $X$ and $Y$ by integrating over the other variable. Also, if $X$ and $Y$ were independent, the joint distribution would be the product of the distributions of $X$ and $Y$. However, do I find the joint distribution in the general case, when $X$ and $Y$ are not necessarily independent?


My colleagues are in the design department of a given product, and when asked to add that information to the e-mail signature, they have written:     ProductName's Design   I'm objecting that the usage of the Saxon genitive there is incorrect, because the product is neither a person or animal owning anything, and Design in this context is not even a property of the product (Maybe I would admit the Saxon genitive in a context like "I think ProductName's design is not fail-safe"), but an activity.  Am I right? ^_^  update:  After reading the answers and the comments, I think the issue has been clarified a little bit. In this case ProductName is acting as an adjective qualifying Design [Department], so that's the actual reason for not using the genitive case (rather than the product being a "weak entity" unable to possess things, that is merely an stylistic rule of thumb).


Prove that a commutative ring without proper ideals is a field

Let $R$ is a commutative ring which has no proper ideals. Prove that $R$ is a field.


I have this Json  var data = "{"2144":{"quantity":"350"},"2095":{"quantity":"100"}}"   how can i get each value like this order using jquery?  2144 - quantity:350 2095 - quantity:100


I'm not an engineer professionally but I'm interested in. So my question is, how to recognise the wattage of a resister? And how to measure it using multimeter?


I am using a MacBook Pro Retina with US international keyboard layout, latest OS. Is there a way to change ˜ to produce ~ without pressing the space after it? And is there a way to configure ' to work the same way? Like I don't need accents so If I type 'a I want to get 'a and not á without the extra space key press.


How to remove a frame from the total number of frames?

I'm using Warsaw as outer theme. I use some images in different slides to create an effect of 'image in evolution' but the problem is that I don't want that the number of slides increase with every frame used to create the effect. How can I do to remove a frame from the total number of frames. I've been reading about 'overlay' and tikspicture but I just receive errors in compilation. I use Winedt v5.4. Thanks in advance to everybody.   P.S. The images stay always in the same position.  Here is the link to the pdf showing the effect I want:   I'd like to have all the images from slide number 3 until slide number 20 in the same frame to avoid count them and increase the total number of frames. It looks that I've got the effect wanted using \setbeamercovered{invisible} but I can't use \caption and have a 'footprint' for the images. And while the images are being uncovered the footline where are found the total number of frames disappears. The error for the \caption says: \caption outside float.  Here is my code:  \documentclass{beamer} \usepackage[spanish]{babel} \usepackage[latin1]{inputenc} \usepackage{listings} \usepackage{algorithm} \usepackage{algorithmic} \usepackage{tikz} \usepackage{ragged2e} \justifying \usefonttheme{professionalfonts} \usetheme{Warsaw} \usecolortheme{albatross}  \setbeamercovered{transparent}  \title[This is the title      \hspace{18mm}                  \insertframenumber/\inserttotalframenumber]{\small{\texttt{Name a little bit long}}} \author{This is author} \institute[Name]{SCHOOL}  \date{\today}  \begin{document}  \begin{frame} \titlepage \end{frame}  \section{Section 1} \begin{frame} \frametitle{Content}     \scriptsize{ \tableofcontents[]} \end{frame}  \begin{frame}  \setbeamercovered{invisible}  \begin{tikzpicture} \node(first image){ \includegraphics[width=9cm]{./IMAGENES/1.png}\caption{We are young}  }; \pause   \node(2 image){ \includegraphics[width=9cm]{./IMAGENES/2.png}\caption{We are young} }; \pause  \node(3 image){ \includegraphics[width=9cm]{./IMAGENES/3.png}\caption{We are young} };\pause  \node(4 image){ \includegraphics[width=9cm]{./IMAGENES/4.png}\caption{We are young} };\pause  \node(5 image){ \includegraphics[width=9cm]{./IMAGENES/5.png}\caption{We are young} };\pause  \node(6 image){ \includegraphics[width=9cm]{./IMAGENES/6.png} };\pause  \node(7 image){ \includegraphics[width=9cm]{./IMAGENES/7.png} };\pause  \node(8 image){ \includegraphics[width=9cm]{./IMAGENES/8.png} };\pause  \node(9 image){ \includegraphics[width=9cm]{./IMAGENES/9.png} };\pause  \node(10 image){ \includegraphics[width=9cm]{./IMAGENES/10.png} };\pause  \node(11image){ \includegraphics[width=9cm]{./IMAGENES/11.png} };\pause  \node(12image){ \includegraphics[width=9cm]{./IMAGENES/12.png} };\pause  \node(13image){ \includegraphics[width=9cm]{./IMAGENES/13.png}     };\pause  \node(14image){ \includegraphics[width=9cm]{./IMAGENES/14.png} };\pause  \node(15image){ \includegraphics[width=9cm]{./IMAGENES/15.png} };\pause  \node(16image){ \includegraphics[width=9cm]{./IMAGENES/16.png} };\pause  \node(17image){ \includegraphics[width=9cm]{./IMAGENES/18.png} };\pause  \node(18image){ \includegraphics[width=9cm]{./IMAGENES/19.png} };\pause \end{tikzpicture} \end{frame}  \end{document}      So, how can I add the number of frames using \setbeamercovered{invisible} and write a footline for the images?  Thanks in advance.


My laptop is hp pavilion g4 1303au and Processor- AMD A4-3330MX APU (Dual Core Processor with 2200 Mhz). I have a problem with Ubuntu 20.04 latest version. When I installed Ubuntu 20.04 it goes ok and I spent some time on it. But when I tried to reinstall windows 7 then on the partition section it said that windows cannot be installed on this drive. It has no option to delete the ubuntu drive. So I cancelled the process and removed my pendrive from laptop and restarted it. But it won't restart and stuck with black screen with blinking horizontal cursor on it. I pressed alt+f2 alt+f1 enter But nothing is working. Please help sir.


StreamTokenizer input number and parsed number are different

I have a StreamTokenizer that accepts numbers. However, the parsed number is not the same as the input.  Sample code:  String str = "1000000000000.0000000000000"; double initial = 1000000000000.0000000000000; InputStream in = new ByteArrayInputStream(str.getBytes()); StreamTokenizer input = new StreamTokenizer(new BufferedReader(new InputStreamReader(in))); input.parseNumbers(); int n = input.nextToken(); if (n == StreamTokenizer.TT_NUMBER) {     System.out.println("Original: " + str);     System.out.println("Parsed: " + input.nval);     System.out.println(initial + " == " + input.nval + " -> " + (initial == input.nval)); }   Output:  Original: 1000000000000.0000000000000 Parsed: 9.999999999999999E11 1.0E12 == 9.999999999999999E11 -> false   How can this be prevented so the two double values are equal?  EDIT: Linked question discusses why this issue appears. I am asking what are the possible ways to avoid this issue.


modify an element of struct object defined in other struct (linked list)

struct triangle { triangle( vertice * p0,  vertice * p1,  vertice * p2)     :tv1(0)     ,tv2(0)     ,tv3(0) {     m_Vertices[0] = p0;     m_Vertices[1] = p1;     m_Vertices[2] = p2;     //SetCircumCircle();  };  triangle *tv1,*tv2,*tv3;}   struct vertice  {         vertice (  int init_val=0) :id (init_val) {};     vertice (double xx, double yy=0):x(xx),y(yy) { };     int id;     double x,y; };  std:: vector <triangle> triangles;  void cre_triangle() {     triangle r(0,1,2);     triangle r2(3,4,6);     r.tv1= &r2;     r.tv2=0;     r.tv3=0;     cout << r.tv1->m_Vertices[0]->id << r.tv1->m_Vertices[1]->id << r.tv1->m_Vertices[2]->id;           //the result is  3 4 6      triangles.pushback(r); }  int main () {     cre_triangle();     cout << triangles[0].tv1->m_Vertices[0]->id <<triangles[0].tv1->m_Vertices[1]->id       <<triangles[0].tv1->m_Vertices[2]->id << endl ;        // problem here  (....exe has stopped working)       return 0; }     i went to access to the ids and the coordinates of vertices of triangle r2 by r (tv1 is the neighbor 1) and modify its but i have a problem ( appilcation.exe has stopped working) please can you help me ..


In light of the discovery of the Higgs boson. The Higgs Boson is a force particle which interacts with matter particles. My question is what does the Higgs Boson interact with to give itself mass.


Is there a way to display text on the 3d viewport. (not text objects) After running a script I would like to display instructions on what to do next.  I have tried this scrip and it works well.. is there a way to use a script to get rid of it?  import bpy import blf  class DrawingClass:     def __init__(self, context, prop):         self.prop = prop         self.handle = bpy.types.SpaceView3D.draw_handler_add(                    self.draw_text_callback,(context,),                    'WINDOW', 'POST_PIXEL')      def draw_text_callback(self, context):         font_id = 0  # XXX, need to find out how best to get this.          # draw some text         blf.position(font_id, 15, 50, 0)         blf.size(font_id, 20, 72)         blf.draw(font_id, "%s %s" % (context.scene.name, self.prop))      def remove_handle(self):          bpy.types.SpaceView3D.draw_handler_remove(self.handle, 'WINDOW')  context = bpy.context              dns = bpy.app.driver_namespace dns["dc"] = DrawingClass(context, "Draw This On Screen")


Reason why MFT are less bright than FF cameras?

My understanding is that low-light performance is a function of the amount of light received on the sensor per unit area (correct if wrong). If this is the case, wouldn't an MFT system have the same light sensitivity of a comparably proportioned FF system? For example, if using a 50mm/1.4 lens on a FF and a 25mm/1.4 lens on the MFT, the FF will gather four times as much light, but it will spread that light over a sensor that is four times as big, so won't the amount of light per unit area on the sensor remain the same?


How to revert from LVM installation to normal plain partition without data lose?

We have done a installation of Ubuntu server 16.10 with LVM disk cofiguration on a customer server and we need to revert our installation to ext4 old disk configuration without losing data.  here is disk configuration exported by parted:  Model: VMware Virtual disk (scsi) Disk /dev/sda: 1100GB Sector size (logical/physical): 512B/512B Partition Table: msdos Disk Flags:  Number  Start   End    Size   Type      File system  Flags  1      1049kB  512MB  511MB  primary   ext2         boot  2      513MB   322GB  322GB  extended  5      513MB   322GB  322GB  logical                lvm  3      322GB   429GB  107GB  primary  4      429GB   644GB  215GB  primary                lvm   and here is the lsblk out put:  NAME                             MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT sda                                8:0    0     1T  0 disk ├─sda1                             8:1    0   487M  0 part /boot ├─sda2                             8:2    0     1K  0 part ├─sda3                             8:3    0   100G  0 part │ └─server--shahrsazi--vg-root   252:0    0 587.5G  0 lvm  / ├─sda4                             8:4    0   200G  0 part │ └─server--shahrsazi--vg-root   252:0    0 587.5G  0 lvm  / └─sda5                             8:5    0 299.5G  0 part   ├─server--shahrsazi--vg-root   252:0    0 587.5G  0 lvm  /   └─server--shahrsazi--vg-swap_1 252:1    0    12G  0 lvm  [SWAP] sdb                                8:16   0   650G  0 disk sdc                                8:32   0    16G  0 disk sr0                             11:0    1  1024M  0 rom   we want to move all data to sdb and detach sda.


How to simplify expression $\int_a^b f(x)dx+\int_{f(a)}^{f(b)} f^{-1}(x)dx \ ?$

How to simplify expression  $$\int_a^b f(x)dx+\int_{f(a)}^{f(b)} f^{-1}(x)dx \ ?$$  The answer is $bf(b)-af(a)$  but I am wondering how to get the answer.


Contraction of quotient ideal is quotient of contractions?

Let $\mathfrak a,\mathfrak b$ be ideals in a ring $A.$ The quotient of $\mathfrak a$ and $\mathfrak b$ is $(\mathfrak a:\mathfrak b)=\{x\in A:x\mathfrak b\subseteq \mathfrak a\}$ and if $f:B\to A$ is a ring homomorphism, then the contraction of $\mathfrak b$ is $\mathfrak b^c=f^{-1}(\mathfrak b).$     In one of the exercises in the first chapter of Atiyah-Macdonald (commutative algebra), one is asked to show that $(\mathfrak a:\mathfrak b)^c\subseteq(\mathfrak a^c:\mathfrak b^c).$ I did this perfectly fine, but one of the remarks after the exercises implies to me that this should be an equality, which doesn't seem right.   Explicitly, they remark "Thus extension is closed under the operations of ideal addition and multiplication, while contraction is closed under [intersections, radicals, and quotients]." Indeed, part of the exercise was to show that the extension of the sum is the sum of the extensions, etc. This is the only one (of those mentioned in the remark) in which equality was not shown.  Is the remark a mistake, or is there a typo in the exercise and I'm wrong?


Is there a way in C# where I can use reflection to set an object property?  Ex:  MyObject obj = new MyObject(); obj.Name = "Value";   I want to set obj.Name with reflection. Something like:  Reflection.SetProperty(obj, "Name") = "Value";   Is there a way of doing this?


I've a just bought a iPad from eBay. The iPad came today and I found it to be locked to somebody else's iCloud account. Is there any way I can sort this situation out or not? Thanks in advance.


Timeline vote summary shows votes for the 24 hours following the timestamp, which is confusing

The new timeline is pretty snazzy. But there's one thing I've noticed that's a bit jarring; the timestamp for vote summaries is always 0:00:00 on a particular day, and the summary covers the rest of that day. So you end up with a summary that always shows up earlier than the events that presumably triggered the votes that show up in it.  A simple solution is to have it display 23:59:59 instead, and sort accordingly. This way the summary comes in after the events it summarizes.


't Hooft showed that Yang Mills theory with spontaneous gauge symmetry breaking Higgs potential is still renormalizable.  Is the Standard Model fully renormalizable?   The potential issues to addressed in your answer are:   Includng the electroweak and strong interaction sectors The issue of chiral gauge theories.   (previous answer  does not address the last issue on chiral gauge theories.)


Test the series $\sum_{n=1}^\infty \frac{1}{n^{1+\frac{1}{n}}}$ for convergence or divergence.

I am trying to test $\sum_{n=1}^\infty \frac{1}{n^{1+\frac{1}{n}}}$ for convergence or divergence.   I thought to compare $\sum_{n=1}^\infty \frac{1}{n^{1+\frac{1}{n}}}$ to $\sum_{n=1}^\infty \frac{1}{n^{2}}$ as i reasoned that for the first series the term $\frac{1}{n}$ in the exponent can be at most $1$ and for all $n\gt1$ that term will be a fraction, hence the exponent of $n^{1+\frac{1}{n}}$ will be at most $n^2$. The second series is a convergent p-series as $p=2 \gt1$. However, this does not really help me as i see now that ${n^{1+\frac{1}{n}}} \lt n^2$ and a smaller denominator means that $\frac{1}{n^{1+\frac{1}{n}}}$ will actually be bigger than $\frac{1}{n^2}$  Any advice appreciated.


Read Command : How to verify user has typed something

I'm trying to create an if else statement to verify that the user has entered something. If they have it should run through the commands, and if not i want to echo a help statement.


What's the process to change a site logo?

Who is responsible for defining a site logo? I mean, there are moderators of the site that define it, or stackexchange defines it?


Positive correlation coefficient, but negative Beta weights in multiple regression

I have a situation where IVs positively correlate with the DV, and the IVs also correlate with eachother.  I do not explain how the beta weights are negative. No multicollinearity is detected, and the model is justified, and has an r-squared value of 5. Note for example, issue with Lev and Size; both correlate do DV CSRDI, both correlate to eachother, but negative beta for LEV and low significance?  This question specifically is asking about sign reversal. I am confused with this due to the lack of a multicollinarity issue. Lev and Size are correlated but not excessively, so why do IVs such as lev have a sign reversal in the regression model? Also is this classified as suppression? I am in no way a statistics expert and am only interested in understanding this for an assignment for my undergrad degree. So if possible, could you please explain in laymans terms. Thanks you    I was wondering if you anyone can explain this, and perhaps help with interpretation


How to prove existence of an element of order $\text{lcm} (m,n)$ in an abelian group having elements of order $m$ and $n$?

This particular question was asked in my algebra quiz and I was unable to think of what result I should use to prove this statement.  Let $G$ be a finite abelian group and $a,b \in  G$ with $|a|=m$ and $|b|=n$. Then prove that there always exists an element of $G$ whose order $= \text{lcm}(m,n)$  I proved that there always exists an element whose order divides $\text{lcm} (m,n)$. If $\gcd (m,n) = 1$ then $|ab|=\text{lcm}(m,n)$ .But how to prove it in case when $\gcd(m,n)>1$? Which result should I use?


How to prevent accidental modification of an array from the method? Without making the array immutable

In the following method, how can I prevent the contents of my array from being modified accidentally or otherwise?  Can it be done without changing the array to another type, such as a list?      public static int LinearSearch(int[] myArray, int target)     {         int idx = -1;         for (int i = 0; i < myArray.Length; i++)         {             if (myArray[i] == target) { idx = i; break; }         }         return idx;     }


Why won't this virus be removed by Microsoft Security?

I don't know how but Windows Security still detects such virus unlike other anti-virus softwares.


Why did nobody ever use the Room Of Requirement to it's full potential?

In all the time The Golden Trio spent fighting Lord Voldemort, why did nobody ever go to the Room of Requirement (once they had discovered it), and say "I need a way to defeat Lord Voldemort permanently"?  Am I the only one to find it suspiciously convenient that Hermione, who was the much-vaunted "Brightest Witch Of Her Age", never once suggested they make use of the Room Of Requirement to learn everything they possibly could about either defeating Lord Voldemort for good, or at the very least learning everything there was to know about Horcruxes and how to destroy them?  If you read the series, you find out that the specific books pertaining to Horcruxes which initially resided within the school library's Restricted Section were removed by Dumbledore around the time Tom Riddle started asking pointed questions about the Horcrux process. Those books remained in Dumbledore's office until Hermione summoned them in Book 6 after his death (which raises another question about warding which I won't get into here).  If the Room had so much potential, and was capable of providing a fully-functional DADA training facility, why not a library to research either a way to defeat the Dark Lord, a way to destroy Horcruxes, or both?  For that matter, if Tom Riddle knew about the Room of Requirement, why not side-step Dumbledore's attempts at blocking him by asking the Room for everything he needed to know about Horcruxes?  And after the all the Time Turners were destroyed during the Big Fight in the Ministry of Magic, why didn't anybody go to the Room of Requirement later on and ask for a room full of them?  It seems to me that this Magic Room probably has infinite (or very nearly) potential powered by the very magic of the Castle itself, and is at least semi-sentient in order to understand, and process requests then produce the expected results, and yet, was probably the most under-used asset available to Harry.  Let's be honest here! If you were in Harry's place, and you knew (as he did before he left the school at the end of Book 6) what you needed to do, wouldn't you go to the Room of Requirement and ask for a room full of Time Turners and books with everything there is to know about finding and destroying Horcruxes?  Bottom Line (or TLDR): Is there a clear reason given for why the Room of Requirement (which doesn't appear to have any limitations) was so under-used?


How to switch from Natbib to Biblatex in pre-made document class/template?

I am using  to write my thesis. The template uses Natlib for references, whereas I really need Biblatex.   When I simply try to change \usepackage[natbib] for biblatex I get the error message  This is BibTeX, Version 0.99d (TeX Live 2016/Debian) Capacity: max_strings=100000, hash_size=100000, hash_prime=85009 The top-level auxiliary file: aagot-1-report.aux The style file: acm.bst Illegal, another \bibstyle command---line 80 of file aagot-1-report.aux  : \bibstyle  :          {acm}  I'm skipping whatever remains of this command Database file #1: Mendeleytry.bib.bib Warning--I didn't find a database entry for "" You've used 14 entries,code here   The solution  \usepackage[backend=bibtex, natbib=true, style=numeric]{biblatex}   didn't work.  Another possible solution was said to be to recompile from scratch to delete the .aux file, but that resulted in  /usr/share/texlive/texmf-dist/tex/latex/biblatex/biblatex.sty:462: LaTeX Error:  Command \bibhang already defined.            Or name \end... illegal, see p.192 of the manual.  See the LaTeX manual or LaTeX Companion for explanation. Type  H <return>  for immediate help.  ...                                                l.462 \newlength{\bibhang}   I have tried to use this "marco" to override the \requirePackage settings, but that also didn't work and resulted into  LaTeX Error: Two \documentclass or \documentstyle comm ands.  See the LaTeX manual or LaTeX Companion for explanation. Type  H <return>  for immediate help.  ...                                                l.45 \documentclass[whitelogo]{                            tudelft-report}    Where I can't seem to delete any of the document classes without getting the functionality of the tudelft-package and the biblatex citing (or in fact getting it to work at all!)  (no line number): [0] Config.pm:343> INFO - This is Biber 2.5 [0] Config.pm:346> INFO - Logfile is 'aagot-1-report.blg' [62] biber:290> INFO - === Tue Apr 24, 2018, 22:24:06 [246] Utils.pm:165> ERROR - aagot-1-report.bcf is malformed, last biblatex  run probably failed. Deleted aagot-1-report.bbl [246] Biber.pm:113> INFO - ERRORS: 1   Is there any way I can still make this template work with Biblatex? Natlib seems to deeply rooted in the file and I don't know how to change it/access the settings/the ".sty"-file. Can I use the example documentclass combined with biblatex (instead of the standard natbib) without losing the great parts of the rest of the document class?  Thanks very much :)


\empheqlbrace autoscaling problem with dukedissertation document class

I am using the empheq package to group equations organized using the align command.  If used in an article document class the left brace automatically scales wonderfully to group equations organized in an align environment.  If used in the duke dissertation document class the left brace does not scale appropriately: it is too small, which leads to the complete omission of the first line in larger groups of equations.  Why is the behavior of the auto-scaling feature inconsistent across these different document classes?  What can I do to make it behave as intended in the dukedissertation document class?  I have linked to .cls files for both document classes involved as well as provided below minimal working examples for each of the two document classes.   article class is good:  \documentclass{article}  \usepackage{amsmath} \usepackage{empheq}  \begin{document}  \section{Section Something}  Words for reference of where text would be. \begin{subequations} \begin{empheq}[left=(1.1)\empheqlbrace]{align} v &= \dot{x}\\ a &= \dot{v}\\ j &= \dot{a} \end{empheq} \end{subequations} More words for more reference of text location.  \end{document}       dukedissertation class is bad:  \documentclass[]{dukedissertation}  \usepackage{amsmath} \usepackage{empheq}  \begin{document}  \chapter{Chapter Something}  A new chapter.  \section{Section Something}  Words for reference of where text would be. \begin{subequations} \begin{empheq}[left=(1.1)\empheqlbrace]{align} v &= \dot{x}\\ a &= \dot{v}\\ j &= \dot{a} \end{empheq} \end{subequations} More words for more reference of text location.  \end{document}      Link to Duke webpage where LaTeX zip file containing dukedissertation.cls file can be found:   Direct link to article.cls file:


Prevent the Feature Attributes dialog box in QGIS

Any time I am inserting new point feature in QGIS, the Feature Attribute dialog box is popping up. Is there a way to prevent it? (I am willing to insert many points at once and this pop up box slows down the process).


Derive both MAC and AES keys from same PBKDF2?

When doing password-based encryption, is it OK to create one instance of PBKDF2 from the password, and then use it to create both the AES key and the MAC key? (Or should a new instance of PBKDF2 be created using a different salt or iteration count, for each?)      seems to say this isn't a good idea. While    seems to say it is. Am I misunderstanding one of them? (Or both.)  (And by the way, the first is marked as a duplicate of a question which deals with an initially strong key, while it itself deals with a simple passphrase.)


"Nobody but him was present." or "Nobody but he was present."

Nobody but him was present.   Nobody but he was present.      Which is the correct usage and why?


$f:\mathbb{R} \to  \mathbb{R}$ be defined as  $f(x)$= $x^2 , x \in \mathbb{Q} \\ 0 \ \ , x \in \mathbb{Q^c}\\ $  How to show that $f$ is differentiable at $x=0.$  I want to try this approach.  here  $f'(x)=$ $2x  \in \mathbb{Q}  \\  0  \in \mathbb{Q^c} $  since $lt \\ x \to 0+$$f(x)$ = $lt \\ x \to 0-$$f(x)= 0$   so $f$ is differentiable at $x=0$


Setting rendering order of line layers in QGIS

I have a dataset where different road types are in separate layers, i.e. motorways, primary roads and secondary roads. In turn, each layer is subdivided by embedded codes into different sub-types - 4 lane roads, 2 lane roads etc.  I currently have the layer style set so that each road is outlined in black. Thanks to another answer to a question here on GIS SE, I already know how to make different road segments 'blend together' so the black outline remains 'underneath' the colour using symbol levels, and that works fine.  However, because for example, the primary roads are in an entirely separate layer to the secondary roads, and are obviously above them in the rendering order, the black outline of the primary roads cuts over the colour line of the secondary roads. This has the effect of making any secondary road that meets a primary road look like a dead end.  The drawing order is essentially:  Primary road colour Primary road outline Secondary road colour Secondary road outline   When it needs to be:  Primary road colour Secondary road colour Primary road outline Secondary road outline   So that the colour line of the Secondary road blends seamlessly with that of the Primary road. Within a layer this is obviously handled by Symbol Levels, but this is overridden by the layer order. Drawing Layer 0 in the Primary road layer is still higher than Drawing Layer 1 in the Secondary road layer.  How can I fix this?


Is there a way to get notifications whenever something in my server crashes? (like apache2, mysql, ect' that cause the website not to work)

I have a website on a server I created on Amazon AWS (Ubuntu).   A few days ago my "mysql" stopped working due to insufficient RAM. I got a call from my boss reguarding this problem and tried to fix it (by expanding the RAM on my.cnf file).   Then a few days later I got the same issue, and we decided to get a server with more RAM.   A few days later apache2 stopped working for some reason, and I don't remember what was the problem there, but it was solved.   The bottom line is:   I want to find a way to get notifications in situations like this via email/SMS text messages or in any other way, that will give me instant updates about "errors" on the server, so I won't get surprise calls from my boss and know immediately about issues on the website so there won't be situations that the website is down for too long (that cause us to loose sales ect').


Displaying folders ordered by size shows the following:  So about 235GB in all. However when I inspect the "Get Info" for the same drive, it shows the following:  So some 395GB in all. Where could the mysterious missing 160GB be hidden?! Thanks!


Why is ciphertext from low entropy plaintext not compressible?

This comes following a discussion with a colleague.   My plaintext file plain consists of a about 100,000 lines of "all work and no play...". It's size is: 2.2 MB. Compressed it is: 5.4kB I encrypt the original:  openssl aes-128-cbc -in plain -out plain.ENC   plain.ENC is marginally bigger than the original, which I would expect. I compress the encrypted copy: gzip plain.ENC. But I observe that the compressed copy is now marginally larger than plain.ENC.   Assuming the entropy of the original file is on the order of ~1000-10000 bits, why is the corresponding ciphertext incompressable? My intuitive notion of the entropy of a string is the minimal number of bits required to produce that string. If the string is the 3 MB long cipher text, it was generated with a 1000-bit entropy string encrypted with an AES implementation (probably no more than a few thousand bits), as well as a few-hundred bit key. Intuitively, to me, the entropy of the cipher text should be no more than the sum of the entropies of the strings and procedures that generate it.  So, my question is: Is my intuitive notion completely wrong? If we extended the low-entropy file to be orders of magnitude larger, would we begin to observe compressibility in the ciphertext?


Absolute value and max/min function: why $a + b + |a - b|=2\max(a,b)$?

I am being told that $a + b + |a - b|$ is equal to $2\max(a,b)$.  What is the reasoning behind this?


For which values of $x$, will $f (x) . f '(x) < 0$?

Give $f (x) = x^3 - 4x^2 - 3x + 18$  For which values of $x$, will $f (x) . f'(x) < 0$?  And also, how can I understand these type of questions? I always get stuck on them. Other examples are:  $$\frac{f(x)}{f'(x)} > 0$$ $$xf (x) > 0$$


Does it follow that $(n!)^n$ divide $(n^2)!$

It is well known that $(n!)^2$ divides $(2n)!$.  Does it follow that $(n!)^3$ divides $(3n)!$ and so on up to $(n!)^n$ dividing $(n^2)!$?  If yes or no, could you provide the details behind the argument?  As a quick test, I tried $n=3$ and $n=4$ which worked.  Thanks,  -Larry


How to interpret the curl and div geometrically?  My book said the vector derivative operator '$\nabla $' is considered as vector as follows :  $$\left(\frac{\partial}{\partial x}, \frac{\partial}{\partial y}, \frac{\partial}{\partial z}\right)$$  Let $\mathbf F$ be  a vector field.  First,  I know the fact that the $\operatorname{curl}$ is the tendency of rotation and the pivot is $\operatorname{curl} \mathbf F$  However, why the curl is the tendency of rotation geometrically?  Easily, when calculating the outer product between two vector, we can interpret the result. The value is $\mathbf a\mathbf b\sin\theta$ and the direction is perpendicular to the two vectors.  I want to know to draw $\nabla$ as vector.  Second, the $\operatorname{div}$ is tendency of divergence or convergence.  But which direction? If the result of $\operatorname{div} \mathbf F$ is plus, then the tendency is same direction to $\mathbf F$? (If minus, then opposite direction?)


When I try to use command blocks in Minecraft is there a way to make them not show feedback in chat?

So when I want to use a command block without other people seeing the feedback in chat I don’t know how to do it.


how do i log into my computer using ubuntu

I set up external flash drive to run ubuntu. How do I get it to work and not load windows XP?


I have finished rendering my animation into PNG files, how do I edit?

I don't know how to make all the PNGs into one seamless short, via iMovie/Filmora


Deriving decimal numbers in float input sometimes minus the value by 1

I am trying to separate the numbers in a floating input (xx.yy) and extract them out. Not so sure if this is the online compiler fault but for some reasons, there are times when I run my following code, the decimal places that I extract seemingly -1 in value.  I am using this online compiler ().  #include <stdio.h>  int main() {     int whole_num = 0;     int dec_num = 0;      float u_input = 0.0;     printf("Input in a float: ");     scanf("%f", &u_input);      whole_num = (int) u_input;     printf("1. Whole number is %d\n", whole_num);      dec_num = (u_input - whole_num)*100;     printf("2. Decimal number is %d\n", dec_num);      return 0;  }   For example, there are times when I input in 99.95, instead of expecting 95 for my dec_num, it gave me 94. Then again, if I used another input such as 123.95 it returns me 95 instead. And as a result, if my code is giving me the -1 result, it will fails in other parts of my code.Decimal  I can't find out if it is an error with the way I have written my code and/ or if it is an issue with the compiler (also tried it with other online compilers which seemingly giving me similar results)  Can anyone share any insights to me on this? Or if there is a proper method that I will get the decimal number I expected without the -1?


Using UFW to completely block internet provider

I am facing a DDOS attack from a few hundred IP addresses, all of them coming from various cities in India and have the same organization: "................ for GPRS Service". (I'm not mentioning the whole name).  The attack started around 5 hours ago and it consists on hundreds of IP addresses that open 1 to 5 connections (as opposed to one or a few IPs making thousands of connections). The IP addresses are coming from a wide range of subnets.  Is there a way to tell the firewall to block the internet provider of the remote IPs, at least until the problem is solved?


Is it possible to obtain AES-128 key from a known ciphertext-plaintext pair?

I have a file, which was encrypted with AES-128 in ECB mode. I know the format of the original file and know that all files in this format have the same headers. So, I have an encrypted block and the original block.  Can I get the encryption key, using this information?


Is “Am I needing to. . . ?” grammatical?

In the course of answering  (which is now deleted and may be viewed only by 10K+ community members), we have evoked some dispute over whether the phrase      Am I needing to read this book?   is grammatical.  I think it is correct, although not common, but others think differently. Is this a correct grammatical structure, albeit perhaps a bit odd?    EDIT: I think I should clarify further.  I don’t disagree that this phrasing is unusual; in fact, that’s what I said in the other answer.  What I am interested in is whether it is correct or not. I think it is because of its uncommonness that I am not certain. It might be more straightforward to ask it this way:     Is the sentence “I am needing to read this book” grammatical?  If not, why not?


"Set time zone automatically using current location" is not working. Why?

Although I keep my system time & date in check using time.asia.apple.com, I can't "Set time zone automatically using current location". I get the error message, "Unable to determine current location at this time" every time I try this.    Does anyone know why this is happening?  Thanks.


After compiling, I receive several warnings of the following form:  Author undefined for citation`Lin1995' (natbib) on page 25   Here are some examples:   The relevant LaTeX code:  For instance,~\citeauthor{Lin1995} observed...   The corresponding text in the compiled document appears as:  For instance, (author?) observed...   The .bib entry:  @article{Lin1995, annote = {less than half the corrision rate for any boundary fraction.}, author = {Lin, P and Palumbo, G and Erb, U. and Aust, K.T.}, doi = {10.1016/0956-716X(95)00420-Z}, file = {:C$\backslash$:/Users/Oliver/Documents/Research/MIT/Papers/Influence of grain boundary character distribution on sensitization and intergranular corrosion of alloy 600 - Lin.pdf:pdf}, issn = {0956716X}, journal = {Scripta Metallurgica et Materialia}, month = nov, number = {9}, pages = {1387--1392}, title = {{Influence of grain boundary character distribution on sensitization and intergranular corrosion of alloy 600}}, url = {http://linkinghub.elsevier.com/retrieve/pii/0956716X9500420Z}, volume = {33}, year = {1995} }  But sometimes it gets the citation, just not the author, as in:  ...the spectral framework of~\citet{Johnson2013}...   which appears as:  ...the spectral framework of (author?) [40]...   and here is the .bib entry:  @article{Johnson2013, author = {Johnson, Oliver K and Schuh, Christopher A}, doi = {10.1016/j.actamat.2013.01.025}, file = {:C$\backslash$:/Users/Oliver/Documents/Research/MIT/Papers/The uncorrelated triple junction distribution function - Johnson.pdf:pdf}, issn = {13596454}, journal = {Acta Materialia}, keywords = {grain boundary engineering,microstructure design,triple junction,triple junction distribution function}, month = may, number = {8}, pages = {2863--2873}, title = {{The uncorrelated triple junction distribution function: Towards grain boundary network design}}, url = {http://linkinghub.elsevier.com/retrieve/pii/S1359645413000529}, volume = {61}, year = {2013} }    Here is my preamble, in case it is helpful:  \documentclass[12pt,twoside,singlespace]{mitthesis} \usepackage{lgrind} \usepackage{cmap} \usepackage[T1]{fontenc} \pagestyle{plain}  %---packages---% \usepackage{amsmath} \usepackage{amsfonts} \usepackage{amssymb}  \usepackage{graphicx} \usepackage{mathtools} \usepackage{cases} \usepackage[font=footnotesize]{caption} \usepackage[section]{placeins}  \usepackage{leftidx} \usepackage{mathrsfs} \usepackage{bm} \usepackage[numbers,sort&compress]{natbib}  %---macros---% \newcommand{\threej}[6] {\begin{pmatrix} #1 & #2 & #3 \\ #4 & #5 & #6 \end{pmatrix}} \newcommand{\sixj}[6] {\begin{Bmatrix} #1 & #2 & #3 \\ #4 & #5 & #6 \end{Bmatrix}} \newcommand{\ninej}[9] {\begin{Bmatrix} #1 & #2 & #3 \\ #4 & #5 & #6 \\ #7 & #8 & #9 \end{Bmatrix}} \newcommand{\so}[1]{\ensuremath{SO\left( #1 \right)}} \renewcommand{\(}{\left(} \renewcommand{\)}{\right)} \renewcommand{\d}{\mathrm{d}} \renewcommand{\figurename}{Fig.}  \DeclareMathOperator{\real}{Re\!} \DeclareMathOperator{\imag}{Im\!} \newcommand{\suchthat}{\;\ifnum\currentgrouptype=16 \middle\fi|\;} \newcommand{\conj}{\,^{\scalebox{1}{$*$}}} \newcommand{\CG}[6]{C_{#1,#2,#3,#4}^{#5,#6}} \renewcommand{\(}{\left(} \renewcommand{\)}{\right)} \renewcommand{\d}{\mathrm{d}}


Does it make sense to pay tuition fees for a PhD degree?

Some Ph.D. programs . Others are . Does a  have the same gravity as a Ph.D. done on stipend when it comes to an academic career? When does it really make any sense to pursue a Ph.D. by paying tuition fees?


I'm finishing professional school and over the years have acquired a pile of notes and articles that I'd like to hang onto.  I'd like to add to them and create sort of an archive of article and files that may be useful down the road.  I'd also like to organize this collection of files not only by simple grouping but also with tags.  I feel like that will make searching through them years later much easier.  Suggestions on software that would be good for this?  Just a general file manager, something that uses tags that can be attached to each file?


I created a dynamic  button in html table using java script. Code is in this way                                           $('#dataTables-data').empty();                                          jQuery.each(searchTO, function(i, item) {                                              historyrowid += '
' + Math.round(item.SNo * 100) / 100+                                                              '	' +Math.round( item.DistributorId* 100) / 100 +                                                              '	' +item.DistributorName+                                                                  '	' +item.Bonuspercent +                                                                '	' +Math.round( item.PrevCumPV * 100) / 100+                                                               '	' + Math.round(item.exclpv* 100) / 100 +                                                                  '	' + Math.round(item.SelfBV * 100) / 100+                                                                  '	' + Math.round(item.grouppv * 100) / 100+                                                              '	' + Math.round(item.Totalpv * 100) / 100+                                                                                '	' + Math.round(item.totalBv * 100) / 100+                                                                 '	<button type="button" class="Downline_button"   id="'+item.DistributorId+'" >Downline</button>
';                                         });                                       $('#dataTables-example').append(historyrowid);   and created table is this     But when i create an event on this button nothing is happen.. My event code on button is like this      $(".Downline_button").click(function(){             debugger;             var id = this.id;             });   so please tell me how can i create an event on dynamic button and how can i read button ID  ??


Resuming rendering image sequence after blender crash

I usually render my animation into image sequence format, It usually takes a lot of time, so I turn off my monitor and come back later to check the rendered result then find that blender crashed before rendering all the frames.  Since rendering can be done from the command prompt I thought about writing a script (running in my OS) to automatically restart rendering from the last successful rendered frame until all frames are finished*.  But I believe this problem is facing a lot of people out there, is there a way to deal with it? instead of reinventing the wheel?     for example if the total render time is 8 hours I don't want come back to check my computer every 20 minutes (some times this is not available I'm asleep or away from my PC)


Is there any difference in meaning between seem and look? For example, “He seems to be popular.” v. “He looks popular.”


Does marijuana inhibit cognitive functioning?

There's a lot of conflicting information regarding this question and people have different agendas. I'm not a doctor, but from what I've read marijuana has been shown to inhibit healthy brain development in adolescents and lead to lower IQ scores. And although it's not nearly as addictive as opiates, like all other psychoactive drugs that work on the dopamine system there is the potential for psychological dependence.   However, my question relates to adults that use it responsibly. If one is over 25 (brain stops developing), active, and only uses marijuana occasionally without smoking is it unhealthy? Does it cause cognitive decline in that population? I think smoking all day, every day is a horrible way to live. Those people have long forgotten what it means to "feel their emotions." However, I'm still not sure whether it is considered unhealthy when used sensibly like the occasional glass of wine.


What are these white dots around my wheel?

I just started blender and wonder what are these white circles around my wheel.


A (probably trivial) induction problem: $\sum_2^nk^{-2}\lt1$

So I'm a bit stuck on the following problem I'm attempting to solve. Essentially, I'm required to prove that $\frac{1}{2^2}+\frac{1}{3^2}+\cdots+\frac{1}{n^2} < 1$ for all $n$. I've been toiling with some algebraic gymnastics for a while now, but I can't seem to get the proof right. Proving it using calculus isn't a problem, but I'm struggling hither.


Polynomial is irreducible (gcd/field extension)

Let $K \subset L$ be a finite field extension and $f(x) \in K[x]$ a monic and irreducible polynomial. Also, $\gcd(\deg f(x),[L:K])=1$. How to prove that $f(x)$ is irreducible in $L[x]$?  My idea was to show that $L \subset \overline{K}$. Then I want to consider $K \subset L \subset L(a)$ and $K \subset K(a) \subset L(a)$ to find a root $a \in \overline{K}$ of $f(x)$ to show that $f(x)$ is the minimal polynomial of $a$ over $L$. But I have some trouble to show it. I tried this: Since $K \subset L$ is finite, it implies that $[L:K] < \infty$. So $L \subset \overline{K}=\lbrace a \in L | a$ is algebraic over $K \rbrace$, as all polynomials of $L$ have roots in $K$. I'm not sure if this is right. And how to continue?


What is difference between Server.Transfer and Response.Redirect?   What are advantages and disadvantages of each? When is one appropriate over the other? When is one not appropriate?


Were Muggle-born wizards free to talk about their experiences?

Obviously, in the Harry Potter universe, some Muggles know all about wizards.  The Dursleys, for example, and the British government, as well as Hermione's family.  But at the same time, the Wizarding World has a vested interest in keeping themselves hidden, often going to extreme lengths to preserve the Muggles' ignorance about what's really going on.  Some things (like ) seem to take care of themselves, but word-of-mouth still seems like it would be an issue.  Are there any details provided about how they navigated this issue?  Did Hermione ever mention (before the events of the final book where she straight-up mind-wiped them) an inability to tell her parents about anything she was doing?  Was there a legal reason why the Dursleys could know about Hogwarts but Marge Dursley couldn't (aside from the Dursley's self-imposed shame)?  Did we ever hear about family members' memories being altered after graduation, or any loose-lipped gossips needing to be told to hush up?


Does a tire need to slip to generate force?

Recently, I have been doing some research on racing and tire modelling.  While I was doing this, I encountered many curves like those shown below.  (source: ) While I understand the need of slip angles to generate lateral forces (those perpendicular to the direction of motion), the need to have slip in the direction of motion in order to produce longitudinal force has me confused. After all, wouldn't a tire with no slipping (i.e. perfect traction), be able to produce forward forces far more efficiently than one that didn't use all of that potential? So, does anyone have an explanation for this phenomenon?


Every closed subset of a Banach separable space is separable

Could you give me some hint to prove this assertion? I've found a proof when the closed subset doesn't have isolated points:  If $X$ is a separable space, then it admits a numerable dense basis. Now consider the internal points of a closed subset $C$, since it is open, it is a numerable union of elements of the numerable basis. Now, let we consider $C$ a closed subset of $X$; $C$ doesn't have isolated points, so the closure of the interior of $C$ is the closure of $C$, since we can write the interior of $C$ like a numerable union of elements in the numerable basis, there exists a subset of $C$ with cardinality $\leq \aleph_0$ such that its closure is all $C$, so $C$ is separable.  Another approach to prove the assertion is make the projection of $N$ (the numerable dense subset of $X$ whose closure is all $X$), in the closed subset $C$, but I doubt this thing will works in Hilbert spaces only, because in a Banach space I don't know if $\forall m\in N$ $\arg\inf_{c\in C}{d(m,c)}$ is unique.  -The problem is that I can't visualize how $\mathbb{R}\setminus\mathbb{Q} $ is a separable space... who is its numerable dense subset whose closure is all $\mathbb{R}\setminus\mathbb{Q} $?-


I am trying to make a JK flip-flop in ActiveHDL environment. I want to make it with logic gates.  It should look like this:     This is my code:  --nand3.vhd library ieee; use ieee.std_logic_1164.all;  entity nand3 is      port(     A,B,C: in std_logic;     D: out std_logic     ); end entity;  architecture nand3 of nand3 is  begin     D <= not(A and B and C); end architecture;     --nand2.vhd library ieee; use ieee.std_logic_1164.all;  entity nand2 is      port(     A,B: in std_logic;     C: out std_logic     ); end entity;  architecture nand2 of nand2 is  begin     C <= not (A and B); end architecture;     --JK.vhd library ieee; use ieee.std_logic_1164.all;  entity JK is      port(     J,K: in std_logic;     Q, NQ: out std_logic;     CLK: in std_logic     ); end entity;  architecture JK of JK is component nand3      port(     A,B,C: in std_logic;     D: out std_logic     ); end component;  component nand2     port(     A,B: in std_logic;     C: out std_logic     ); end component;    signal s1, s2: std_logic;  begin     C11: nand3 port map(NQ,J,CLK,S1);     C12: nand3 port map(Q,K,CLK,S2);     C21: nand2 port map(S1,NQ,Q);     C22: nand2 port map(S2,Q,NQ); end architecture;   The problem is that i am getting this error when I compile JK.vhd file:  # Error: COMP96_0411: JK.vhd : (31, 22): Actual of mode "out" can not be assigned to formal "A" of mode "in" # Error: COMP96_0411: JK.vhd : (32, 22): Actual of mode "out" can not be assigned to formal "A" of mode "in" # Error: COMP96_0411: JK.vhd : (33, 25): Actual of mode "out" can not be assigned to formal "B" of mode "in" # Error: COMP96_0411: JK.vhd : (34, 25): Actual of mode "out" can not be assigned to formal "B" of mode "in"   I think the problem is the backward signals.    Edit1 Improved JK.vhd file. It compiles, but it still does not work:  --JK.vhd library ieee; use ieee.std_logic_1164.all;  entity JK is      port(     J,K: in std_logic;     Q, NQ: out std_logic;     CLK: in std_logic     ); end entity;  architecture JK of JK is      component nand3 port(         A,B,C: in std_logic;         D: out std_logic     );     end component;      component nand2 port(         A,B: in std_logic;         C: out std_logic     );     end component;  signal s1, s2: std_logic;  -- internal copies of output signals -- initialize signal Q_int: std_logic := '1'; signal NQ_int: std_logic := '0';  begin     C11: nand3 port map(NQ_int,J,CLK,S1);     C12: nand3 port map(Q_int,K,CLK,S2);     C21: nand2 port map(S1,NQ_int,Q_int);     C22: nand2 port map(S2,Q_int,NQ_int);      -- Assign values to output ports     Q <= Q_int;     NQ <= NQ_int; end architecture;


My GitHub Pages site doesn't appear in google search index

Yesterday, I created my  and I tried to add in the google search index. Here's what I did:    I went to  google search console and added new "property" with "URL prefix".  Then I added the meta tag on my github-pages site (html-head) as described, it looked like   Then I pasted my page URL (kirusha05.github.io) to the "search bar" on the top of the search console  I was redirected to URL adress verification page, where I saw "URL adress is not on Google". I clicked "request indexing". A live test started , then a message like "The live test failed" showed up.    I saw again "URL adress is not on Google" . This page is not included in index , but not because of an error. And under that a Coverage section, near it I saw "Google doesn't know the URL adress" . What is wrong ? How can I get my site indexed ? Thanks in advance!


24v Power supplies - input and output power

I have been reading your articles on power supply in readiness for starting to build a home automation system using Loxone equipment.  I feel confident in the project but the power supply situation leaves me a bit perplexed.  I am intending to use 8 TDK Lambda (DRF240-24-1) power packs to drive the 24V DC LED lighting in my new house.  Each power pack has a rated input of 100 – 240 VAC 2.7A. The output is 24 – 28 V DC 10 – 8.6A.  So that is a power requirement of 648W for an output of 240W.  My first question is where is the missing 408W?  I realise that the pack itself will require some energy to work, but I would have thought that would be around 20% of the input.  Secondly; if the input is rated at 2.7A x 8 power packs then I will need an RCB in the consumer unit rated at over 21.6A, - or more likely several lower rated RCBs to split the load into zones.  Am I missing something here?    From the 8 Power packs there is a total power available at 24V DC x 80 A  =  almost 2,000W whereas to provide this I have to supply 21.6A x 240VAC = over 5,000W.  Am I going wrong somewhere?  Any observations would be appreciated especially if I am completely failing to understand this issue.  Thanks in anticipation.


Basic GR question: For two arbitrary observers measuring same two events, is $ds^2$ numerically the same for both?

In special relativity, the spacetime interval between the same two events measured by two different inertial observers are numerically the same: $$c^2dt^2-|d\vec{x}|^2=c^2dt^{'2}-|\vec{dx'}|^{2}.$$ In general relativity, does the same thing remain true i.e. if two arbitrary observers measure the same two events, does their spacetime intervals $g_{ab}(t,|\vec{x}|)dx^a dx^b$ and $g_{ab}(t',|\vec{x}'|)dx^{'a} dx^{'b}$ are also numerically equal?


How does cover interact with the Arcane Archer's Curving Shot?

One of the features of the Arcane Archer fighter subclass is Curving Shot:  At 7th level, you learn how to direct an errant arrow toward a new target. When you make an attack roll with a magic arrow and miss, you can use a bonus action to reroll the attack roll against a different target within 60 feet of the original target. [XGtE, pg. 28]  How does this interact with cover? The PHB description of cover says, among other things:  A target can benefit from cover only when an attack or other effect originates on the opposite side of the cover. [PHB, pg. 196]  So what's the origin of a Curving Shot attack?  I see two possibilities:  The origin of the redirected attack is the original, missed target.  The origin remains at the archer.    Related:


What's the best way to generate a tag cloud from an array using h1 through h6 for sizing?

I have the following arrays:  $artist = array("the roots", "michael jackson", "billy idol", "more", "and more", "and_YET_MORE"); $count = array(5, 3, 9, 1, 1, 3);   I want to generate a tag cloud that will have artists with a higher number in $count enclosed in h6 tags and the lowest enclosed h1 tags.


Low-RAM Linux Distro Specifically for serving static sites

I'm looking for a near-zero-configuration linux distro that is designed specifically for serving static web sites and nothing else on a low-RAM machine (I'm planning on 128MB, but the option of less would be nice).  Any ideas of a linux distro specifically tuned for serving static sites in a small footprint?


I have followed the instructions  and in the  that is provided there. However nowhere does it appear to say how I can change the colours of the different parts, because currently I set it to:  PS1='${debian_chroot:+($debian_chroot)}[\t] \u@\h:\w\$ '   But the text is still all white, how could I perhaps make the numbers for the time green, and my username and computer name light blue? I am running Ubuntu GNOME 15.04.


Assume $0 < a_i\leq 1$ for $i = 1,2,...,n,$ and $$\sum_{i=1}^{n} {a_i} = a.$$ Show that $$\sum_{i=1}^{n} \frac {a_i}{1+a-a_i} + \prod_{i=1}^{n} {(1-a_i)} \leq 1.$$   I first substituted $b_i = 1-a_i, 0 < b_i\leq 1$ to simply the problem to $$\sum_{i=1}^{n} \frac {1-b_i}{a+b_i} + \prod_{i=1}^{n} {b_i} \leq 1.$$ Rearranging: $$\sum_{i=1}^{n} \frac {1-b_i}{a+b_i}  \leq 1 - \prod_{i=1}^{n} {b_i}.$$  From here I thought about trying to telescope the sum and but didn't really get far, and I'm not sure how to deal with the product and sum in the same inequality.


I've had a recent discussion regarding the possibility of using a bonus action, while casting a spell with a casting time of 10 min. I haven't been able to find anything, so I'm curious to what you guys think?


I would like to print a backslash character:  \   But whne I try to use escape characters  print(\"\"\)   I get a syntax error. I have looked into ecape characters, however is their a specific one for backslash ()?


Is there a name for the red circle and slash in a No Smoking sign?

When my daughter asked me and my husband about a No Smoking sign, we explained that it means no cigarettes are allowed.  (We had to explain cigarettes to her too.)    Unfortunately, she now thinks that the red circle and diagonal line are called a "cigarette", so she'll talk about the cigarette in the No Parking sign:    Is there a name we can teach her for the red circle and slash?


How to recover SSD formated and repartitioned

I have accidentally format, repartitioned and installed the MacOS on SSD installed on my Macbook Pro months ago, and now I just realized i loss my very important data during that, So i need the recommendation for the best recovery software which will be Compatible/Trustable by Apple which help me to recover that data.


Log Sum Exponential Trick On Weibull Mixture

I am trying to evaluate the log-likelihood of a mixture of weibull distributions and am running into problems with the numerical aspect. In short, I have $M$ mixtures and want to evaluate: $$   \log \left[ \sum_{m=1}^M \pi_m \frac{\beta_m}{\alpha_m} \left( \frac{x}{\alpha_m}\right)^{\beta_m -1} e^{-\left( \frac{x}{\alpha_m}\right)^{\beta_m}} \right] $$ with $\pi_m$ being the mixing probability, $\alpha_m$ and $\beta_m$ being parameters for distribution $m$ and $x$ being some data-point we've collected. My problem comes from evaluating the exponential term here, where I often just get 0 on my computer due to the power being very negative. I have been reading and found the 'log-sum-exponential trick' at various sources, but it is unclear to me if this is valid when we have coefficients in-front of the exponential. Is there a known numerically stable way to evaluate this, and if the log-sum-exponential trick is indeed valid, can someone show how this works with the coefficients?


How can I check if share certificates I found have value?

I have been clearing my parents flat and found share certificates from    P and O  European Ferries   Can I find out if they are still valid? If not, is there a market for them as collectibles or the like?


I purchased an AZIO backlit L70 today, volume control is not working.


My site is on localhost and I have access to database too. This is the structure of "users" table:    The password field is of type "varchar(32)" having collection "utf8_general_ci". I tried to decrypt the password online but it displays that password can't decrypted.  I manually updated the table and changed the password using md5 but whenever I try to login to the site as admin, it displays "Access Denied".  How to change the password for site?


Finding the last modifided file with certain names?

I am trying to find the last modified version of a file, I have this working but when i try to find a certain file I get a NULLPointerException. My code :  public static File getFile(String dir, String chat) {      File fl = new File(dir);     File[] files = fl.listFiles(new FileFilter() {                   public boolean accept(File file) {             return file.isFile();         }     });     long lastMod = Long.MIN_VALUE;     File choice = null;     for (File file : files) {         if (file.lastModified() > lastMod && file.getName().contains(chat)) {             choice = file;             lastMod = file.lastModified();         }     }     return choice; }   The code works when you take the "&& file.getName().contains(chat)" out. Otherwise, it has been given me NullPointerException error.  I know that something like this works because I had it working but needed to start from scratch with my code :(