I want to see developers' opinions on the use of a certain language feature, where is the right place to ask that question?

I understand and agree that opinion based questions are a bad thing on Stack Overflow, but shouldn't we have a place to ask this kind of question? There are so many times where I look at different frameworks and have to make decisions that will affect the next 3 years of my life without actually having all the pros and cons of both sides.  So my question is: Is there a place to ask these questions?  And if the answer is no, could that be a new Stack Exchange sub-website?


I am getting java.lang.NullPointerException at FileUploadBean.uploadFile, not sure why as I have data in my list of string fileData.  Java code:  private List<String> fileData;  public void uploadFile(FileEntryEvent event) {     System.out.println("Event: " + event.getSource());     System.out.println("Test");     FileEntry fileEntry = (FileEntry) event.getSource();     FileEntryResults results = fileEntry.getResults();     for (FileEntryResults.FileInfo fileInfo : results.getFiles()) {         if (fileInfo.isSaved()) {             System.out.println("File is saved sucessfully");             fileData.add("FileName: " + fileInfo.getFileName());             fileData.add("FileSize: " + fileInfo.getSize());             fileData.add("FileStatus: " + fileInfo.getStatus());         }     } }  public List<String> getFileData() {     System.out.println("inside getFileData");     List<String> data = fileData;     return fileData; }  public void setFileData(List<String> fileData) {     this.fileData = fileData; }   Exception:      Caused by: java.lang.NullPointerException         at FileUploadBean.uploadFile(FileUploadBean.java:54)         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)         at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)         at java.lang.reflect.Method.invoke(Method.java:597)         at org.apache.el.parser.AstValue.invoke(AstValue.java:264)         at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278)         at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)         at org.icefaces.ace.component.fileentry.FileEntry.broadcast(FileEntry.java:306)         ... 28 more

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


My question reads:   If A is finite and B is infinite, then B-A is infinite.

Prove: If $A$ is a finite set and $B$ is an infinite set, then $B \setminus A$ is an infinite set.   I've tried proving the contrapositive, that if $B \setminus A$ is a finite set then $A$ is infinite or $B$ is finite, but I don't think this is the way to go.


I know that energy stored in electric field / unit volume = $\frac{1}{2} \epsilon\,E^2$.  so can I say that for any configuration calculating $\int \frac{1}{2} \epsilon\, E^2 \,d^3r$ over whole space - gives me the potential energy stored stored in the system  for instance for $Q_1$ and $Q_2$ ....separated by distance $d$,  $\int \frac{1}{2} \epsilon\, E^2 \,d^3r$ over whole space $= \frac{KQ_1Q_2}{d} $?

The electric energy stored in a system of two point charges $Q_1$ and $Q_2$ is simply $$W = \frac{1}{4\pi\epsilon_0}\frac{Q_1Q_2}{a}$$ where $a$ is the distance between them.  However, the total energy can also be calculated through the volume integral of magnitude squared of the electric over all space: $$W = \frac{\epsilon_0}{2}\int_{\mathbb{R}^3} E^2\,dV$$  Suppose that $Q_1$ sits on the origin and $Q_2$ a distance $a$ away on the $z$-axis.  Then the electric field is $$\vec{E}(x,y,z) = \frac{1}{4\pi\epsilon_0}\left[\left(\frac{Q_1}{r^3} + \frac{Q_2}{d^3}\right)x\hat{x} +\left(\frac{Q_1}{r^3} + \frac{Q_2}{d^3}\right)y\hat{y} + \left(\frac{Q_1z}{r^3} + \frac{Q_2\left(z-a\right)}{d^3}\right)\hat{z}\right]$$ where \begin{align} r &= \sqrt{x^2+y^2+z^2} \\ d&= \sqrt{x^2+y^2+\left(z-a\right)^2}  \end{align}  Calculating $W$ through $\int_{\mathbb{R}^3} E^2\,dV$ seems extremely difficult; Mathematica, for example, appears stumped.  Yet its result should simply be $\frac{1}{4\pi\epsilon_0}\frac{Q_1Q_2}{a}$, correct?  The integral formula still applies to point charges, correct?


$$\int \frac{\sin x}{\sin 4x}\mathrm dx$$ I have tried to do this by expanding $\sin 4x$ but it was worthless.

Integrate the following  :   $$\int \frac{\sin x}{\sin4x}dx$$  My approach :   $$=\int \frac{\sin x}{2\sin2x \cos2x}dx$$  $$= \int \frac{\sin x}{4\sin x \cos x \cos2x}dx$$ $$= \int \frac{1}{4\cos x \cos2x}dx $$ [ didn't get the hint here ] then I did the following way.  $$= \int \frac{\sin x}{4\sin x \cos x (\cos2x) }dx$$  Now putting $\cos x =t$ $\Rightarrow -\sin x \, dx = dt $   $$= \int \frac{-dt}{4\sqrt{1-t^2} t(2t^2-1)}$$  [Using : $ \cos2x = 2\cos^2x-1]$


I have a date stored as a string:-   16/07/2014 13:00:00  I want to convert this into timestamp.  Also from timestamp to this format again.  Please suggest the best possible way to do this in python.

I've got a huge list of date-times like this as strings:  Jun 1 2005  1:33PM Aug 28 1999 12:00AM   I'm going to be shoving these back into proper datetime fields in a database so I need to magic them into real datetime objects.   This is going through Django's ORM so I can't use SQL to do the conversion on insert.


I'm new to QGIS and used to ArcMap.  I'm trying to project to Winkel III and it's not included in  my version 2.18.2  I came across a thread outlining how to define a North American Conic, which included a link to  where the user apparently got the proj4 line that they plugged into the custom CRS in QGIS with success.  However, there is no proj4 line on spatialreference.org for Winkel III.  Does anybody have it/willing to share it?  Then again, another thread mentions how Winkel cannot be custom defined in this manner:

I have QGIS with proj 4.8.0 installed. I'd like to add Winkel Tripel projection which seems to be defined as  +proj=wintri   But that definition string does not work. Is this a bug in my proj version, or what's the correct definition string?


I've created a document whose margins have different odd and even pages. I want to write a paragraph with no margin in two pages runs. If I use the command \newgeometry new paragraph starts at the top of new page, that I want to start at the same place. And the command \begin{adjustwidth}{}{} such marginalized different odd and even pages are not useful. Please guide me in this regard. I use this command for create margin:  \documentclass[11pt,fleqn]{book}  \usepackage[total={215mm,285mm},top=3cm,bottom=3cm,headsep=10pt,     vmargin=2cm,     outermargin=7cm,     innermargin=2.5cm,     marginparwidth=5cm,     marginparsep=10pt]{geometry}     \reversemarginpar       \usepackage{changepage}       \usepackage{lipsum}           \begin{document}                \lipsum[5]\lipsum[5]\lipsum[5]\lipsum[5]  \begin{adjustwidth}{}{-5cm}   \lipsum[6]\lipsum[6]   \end{adjustwidth}            \newgeometry{left=2.5cm, right=2.5cm}  \lipsum[6]\lipsum[6] \end{document}


Can Eldritch Knights Use Spell Foci and if so what things do they use as them?

My PC is an Eldritch Knight. I was wondering what is an Arcane Focus? Do I need to have it in my hand? If I get the War Caster Feat does my arcane focus become obsolete?


Okay, so the formula for Gravitational Potential Energy (GPE) of satellites is: $$ U=-GmM/d$$ Mass and distance can't be negative, and $G$ is constant that is not negative.  Why is a satellite's GPE negative?  For other objects, like a ball, the GPE is calculated as: U=mgh  Correct me if I am wrong, but this is what I think:   Satellite's GPE is measured relative to earth's center, while a ball's GPE is measured relative to earth's surface. The satellite was sent to its orbit with energy from the fuel, and it was launched from the earth's surface. While for the ball, it was sent to its height with energy (say, from a human body) and it was carried from the earth's surface.   So is a satellite's GPE negative because: Energy needed to bring the satellite to earth's center is greater than the energy expended when it was sent to orbit?

I had to do a problem, and part of it was to find the mechanical energy of satellite orbiting around mars, and I had all of the information I needed. I thought the total mechanical energy would be the kinetic energy+ the potential energy, or $KE+PE$. However, I had the answer sheet and it said that I had to do $KE-PE$, because when you integrate $Gm_1m_2/r^2$ you get a negative sign. I can see why it works out mathematically, but I don't understand why you are actually losing energy when orbiting in a gravitational field.


Using awk, how we can remove extra spaces, where it finds more than one space? We just need to keep one space between words, as usual. The file size is 3kb.

If I am having a line as:  Thhiisss iisss mmyyy nameeee   I want to print this as:  This is my name   What is the unix command for this?


So I've been trying to find a solution for this all afternoon, but haven't found a good place to start:     Prove that if $f:[a,b]\to\mathbf{R}^+$ is a continuous function with maximum value $M$, then    $$ \ \lim_{n\to\infty}\left(\int_a^b f(x)^n\,dx\right)^{1/n} = M $$   Here are some of the paths I've considered, though none have been very successful:  (1) Considering the sequence of functions for all increasing integer $n$ and trying to show that the sequence converges. We've had plenty of work on converging sequences, but with the integral expression, I am not sure how to simplify.  (2) Showing that that sequence is increasing (again, how?) and then showing there to be a supremum at $M$. I'm not sure how the maximum of the function arrives in this problem.  (3) Mean value theorems for integrals  If anyone could give me a solid place to start or perhaps point me to a place where this question has been asked before (I can't seem to find it), I would be very grateful.

Find $$\lim_{n \rightarrow \infty}\left(\int_0^1(f(x))^n\,\mathrm dx\right)^\frac{1}{n}$$if $f:[0,1]\rightarrow(0,\infty)$ is a continuous function.   My attempt:  Say $f(x)$ has a max. value $M$. Then $$\left(\int_0^1(f(x))^ndx\right)^\frac{1}{n}\leq\left(\int_0^1M^ndx\right)^\frac{1}{n} =M$$  I cannot figure out what to do next.


I ran the following command, hoping to be able to paste a file's contents into it.  sudo cat > /usr/bin/sasquatch   And keep getting the following error, even after changing the file permissions with sudo.  bash: /usr/bin/sasquatch: Permission denied   Why is this happening, and how can I fix it?

I've been given sudo access on one of our development RedHat linux boxes, and I seem to find myself quite often needing to redirect output to a location I don't normally have write access to.  The trouble is, this contrived example doesn't work:  sudo ls -hal /root/ > /root/test.out   I just receive the response:  -bash: /root/test.out: Permission denied   How can I get this to work?


I never became a vampire lord, killed Harkon I think his name was, and cured Serana. Is there anyway I can become a vampire lord?  I'm playing on the Xbox 360.

So, I am working on a new playthrough of Skyrim with the two new DLCs and I would like to work in being a vampire lord early into the game. Doing a bit of reading however it seems I have to select to be a dawnguard if I want to be able to craft crossbows and bolts... which I do want..  Can I choose to join the dawnguard up front and then become a vampire lord later down the road or is this the only time this option will come up?


(precise)thecreeperdestryer@localhost:~$ unzip VoidLauncher Linux.zip unzip:  cannot find or open VoidLauncher, VoidLauncher.zip or VoidLauncher.ZIP.

Suppose my file name is äbc def  When I type in the terminal like cat ¨abc def¨ it shows error. Can anybody tell me how to print this file that has spaces in between the name.


Is is possible to check if an analog voltage is zero (or very close)? If it helps, the input to this circuit will be the output this differential amplifier:  (source: )

Im a beginnerish will electronic and im looking for a switch that is only ON if the reference voltage is matched -+ 0.25 volts. So if i have a reference of 2.7v to match and i feed the switch a 2.75v the switch would be ON. But if i feed it  2.5v or 2.85v the switch would is OFF.   This might be a simple google search, but i am lacking the correct terminology.


I was just at a W3C meeting last night and realized that a Stack Exchange community might just be the type of community that this standards body needs.    How do the other community sites (English Language and Usage, Drupal, Wordpress) get started?

I have an idea or subject that should have a Q&A, and want to propose a new site. How can I do this?  Related:


$$\lim_{x\to 1}\left(\frac{p}{1-x^p}-\frac{q}{1-x^q}\right)  , p,q\in N$$   I tried fitting the formula $\lim_{x\to a}\frac{x^n - a^n}{x-a} = na^{n-1}$ but could not proceed further. Also I don't think that we should directly apply L'Hôpital's rule as it will be too lengthy.

How does one evaluate the following limit? $$\lim_{x \to 1} \left(\frac{23}{1-x^{23}}-\frac{11}{1-x^{11}} \right)$$ The answer is $6$.  How does one justify this answer?  Edit: So it really was just combine the fraction and use L'hopital's rule twice (because function and its first derivative are of indeterminate form at $x=1$). This problem is more straightforward than it seems at first.


I have the following author field in a bibtex file:  author = "Lastname, Theo and Surname, Sam"   In the reference list, when using a style that applies initials, I want it to print:  Th. Lastname and S. Surname   instead of  T. Lastname and S. Surname   Is there any way to do this?

BibTeX can abbreviate first names, e.g. change Smith, John to J. Smith.  In some languages, certain (not all) first names must be abbreviated  (it's not optional as in the case of Ch. for Charles).  How can I force BibTeX to do this for particular first names?  EDIT:  I encounter this all the time, including for my own name which should be abbreviated Sz rather than S.  I used to work around the problem by hand editing the reference list in the final version of the paper, but I'd prefer using BibTeX for everything if possible.  Requested example:  .tex file:  \documentclass{article} \begin{document} Text \cite{kovacs, smith}.  \bibliographystyle{abbrv} \bibliography{references} \end{document}    .bib file:  @Book{smith,   author  = "Peter Smith",   title   = "Title 1",   year    = 1980,   publisher = "Addison-Wesley" }  @Book{kovacs,   author  = "Csaba Kov\'{a}cs",   title   = "Title 2",   year    = 1986,   publisher = "Addison-Wesley" }   The output I get:     Text [1, 2].      References       [1] C. Kovács. Title 2. Addison-Wesley, 1986.      [2] P. Smith. Title 1. Addison-Wesley, 1980.   I need to tell bibtex that for Csaba Kovács I need to get Cs. Kovács in the output, and not C. Kovács, as this is incorrect.  The document is in English, so this is not a babel-issue.  This applies only to certain author names, and it's because in Hungarian C and Cs are considered to be distinct units of the alphabet.


After searching, finally, I find out that I should use an interface to pass a list of objects from an activity to a fragment. before that, I made my object class Perceilable to send in as an argument to fragment, but it seems that it's not a good approach because I have to initiate my fragment for the first time without setting any argument and after my list of the object is ready I can pass it. So now I want to send my list via Interface but I get this error :  java.lang.NullPointerException: Attempt to invoke interface method 'void com.x.x.Interfaces.CurrenciesSync.syncCurrencies(java.util.List)' on a null object reference     at com.x.x.DashboardActivity$1.onResponse(DashboardActivity.java:124)   here is my interface file codes:  public interface CurrenciesSync {   public void syncCurrencies(List<CurrencyModel> currencies);  }   here is the way I set currencies List in DashboardActivity to syncCurrencies method:  public class DashboardActivity extends AppCompatActivity {         CurrenciesSync currenciesSync;   currenciesSync.syncCurrencies(currencies);     } And how I implement it's method :  public void syncCurrencies(List<CurrencyModel> currencies) {  // using currencies here }

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


After studying  it seems like there is a "consensus like" understanding that the "official" goal of the "question weight change" is about encouraging users to ask questions, and that adapting the "downvote effect" accordingly would undermine that goal.  I can see that line of thought. Now I am wondering if there would be another way to reduce the negative side effect of increasing the upvote weight, without adapting the downvote weight.   For me, the biggest problem is that new users required 3 upvotes to get to upvote privileges before. Now it is just "half". So establishing "malicious upvote networks" is even simpler now.  A simple solution to that problem: the privilege system could be adapted. "Upvote privileges" could be increased from 15 to 30, or maybe 50.  Would that be a meaningful alternative?  Edit: I agree that the other question addressed part of this one, but the key part that I don't see there: that specific discussion "is getting to upvote privilege faster" a significant problem for the community?!

(or at least those of use who have asked positive questions), is there going to be any change to the rep required for, as an example, ? I can see myself suddenly getting a significant chunk of rep, and that may push me past the 25k boundary required for "Access to site analytics". I'm not any more knowledgeable than I was prior to the calculation though, so does this make sense?  Are rep boundaries like those for the association bonus, privileges, commenting etc. going to be adjusted? Or is this adjustment meant to more accurately reflect the site knowledge associated with asking a good question, so no change will happen?


I'm using SSH host with Ubuntu 16.04. When I use it i can't use in command line arrow keys for moving cursor (^[[D ^[[C) and using previously used commands (^[[A ^[[B), but when I use nano i can do it. How can I fix it?

I have installed ubuntu minimal(mini.iso) on my vm. I then used recovery mode to login as root and create an account with useradd -m admin and then set a password with passwd admin.  When I login on the new account, instead of the normal prompt I only see a $ sign. If I try to tab-complete a command or file name it prints a normal tab. If I try to use the arrow keys it prints ^[[A, ^[[B, ^[[C or ^[[D. Also, ls no longer adds colors.  None of these problems were in recovery mode. How can I fix this?


I am trying to create service from JAR file and after some research I was able to create window service using SC   sc create "ServiceName" binPath= "PathToJava.exe -jar PathToJarFile"   but when I tried to start the service it displayed the bellow error  [SC] StartService FAILED 1053: The service did not respond to the start or control request in a timely fashion.   Can anyone help me out regarding this, any help is valuable

I've just inherited a java application that needs to be installed as a service on XP and vista. It's been about 8 years since I've used windows in any form and I've never had to create a service, let alone from something like a java app (I've got a jar for the app and a single dependency jar - log4j).  What is the magic necessary to make this run as a service?  I've got the source, so code modifications, though preferably avoided, are possible.


.main-heading {   display: block;   font-family: "Josefin-Sans", sans-serif;   font-size: 70.6px;   font-weight: bold;   text-align: center;   color: #ba9a45; }  .subheading {   font-family: "Cardo", sans-serif;   font-size: 23.5px;   text-align: center;   color: #fff;   padding-top: 30px; }

ATLANTIC

CASINO

FEED YOUR DESIRES

    I seem to not be able to make my h1 and h3 background only as wide as the text and not span the whole width of the line. How can I reduce the background of the h1 and h3 so it only spans to the end of the text? -- I've managed to resolve my issue by taking into consideration all the advice given by users below. Have a look at my revised code which works:

ATLANTIC

CASINO

FEED YOUR DESIRES

   .main-heading{   display: block;   margin-left: auto;   margin-right: auto;   width: max-content;   font-family: "Josefin-Sans", sans-serif;   font-size: 70.6px;   font-weight: bold;   color: #ba9a45; }  .subheading{   display: block;   margin-left: auto;   margin-right: auto;   width: max-content;   font-family: "Cardo", sans-serif;   font-size: 23.5px;   color: #fff;   padding-top: 30px; }

I have a layout similar to:  <div>     <table>     </table> </div>   I would like for the div to only expand to as wide as my table becomes.


I'm using Dell Inspiron N4030 laptop. I'm using Ubuntu 13.04 64 bit.   Bluetooth adapter is not found. How to active that?  rfkill list 1: phy1: Wireless LAN     Soft blocked: no     Hard blocked: no 2: brcmwl-0: Wireless LAN     Soft blocked: no     Hard blocked: no

Bluetooth is on but can't find or be found by any other devices.  Output of sudo service bluetooth status:  ● bluetooth.service - Bluetooth service    Loaded: loaded (/lib/systemd/system/bluetooth.service; enabled; vendor preset: enabled)    Active: active (running) since ხუთ 2015-06-04 22:33:18 GET; 13min ago  Main PID: 26678 (bluetoothd)    CGroup: /system.slice/bluetooth.service            └─26678 /usr/sbin/bluetoothd -n  ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/HFPAG ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/HFPHS ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/A2DPSource ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/A2DPSink ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/HFPAG ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/HFPHS ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/A2DPSource ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Endpoint registered: sender=:1.63 path=/MediaEndpoint/BlueZ4/A2DPSink ივნ 04 22:39:14 Rangoo bluetoothd[26678]: Adapter /org/bluez/26678/hci0 has been enabled ივნ 04 22:39:14 Rangoo bluetoothd[26678]: bluetoothd[26678]: Adapter /org/bluez/26678/hci0 has been enabled   Output of lsusb:  Bus 003 Device 005: ID 0a5c:21d7 Broadcom Corp. BCM43142 Bluetooth 4.0   How can I fix it?


In my 2nd and 3rd reference, there is a large space after URL, why and how can I remove it? \usepackage{natbib}  \begin{document}  \bibliographystyle{agsm} % Harvard style \bibliography{ref.bib}  \end{document}  And the ref.bib entries with the problem. @article{Tabish2007,    author = {Syed Amin Tabish},    issn = {1658-3639},    issue = {2},    journal = {International journal of health sciences},    month = {7},    pages = {V-VIII},    pmid = {21475425},    publisher = {Qassim University, Kingdom of Saudi Arabia},    title = {Is Diabetes Becoming the Biggest Epidemic of the Twenty-first Century?},    volume = {1},    url = {https://pubmed.ncbi.nlm.nih.gov/21475425 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3068646/},    year = {2007}, }  @article{Ramachandran2014,    author = {A Ramachandran},    issn = {0971-5916},    issue = {5},    journal = {The Indian journal of medical research},    keywords = {*Physical Examination,Diabetes Mellitus/diagnosis/*epidemiology/physiopathology,Humans,Prediabetic State/*diagnosis/epidemiology/physiopathology,Risk Factors},    month = {11},    pages = {579-581},    pmid = {25579136},    publisher = {Medknow Publications & Media Pvt Ltd},    title = {Know the signs and symptoms of diabetes},    volume = {140},    url = {https://pubmed.ncbi.nlm.nih.gov/25579136 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4311308/},    year = {2014}, }

How do I remove this space please? I'm using the natbib package    Code from ref.bib  @article{stats2017,   title={Digest of Education Statistics 2017},   author={\text{Statistics Mauritius}},   year={2017},   url={\url{http://statsmauritius.govmu.org/English/Publications/Pages/Edu_Stats_Yr2017.aspx}} }   bibliography style  %\printbibliography \setcitestyle{numbers} % set the citation style to ``numbers''. \bibliographystyle{agsm} \bibliography{ref.bib}


If a transistor works as a 'switch' and I turn it on using a controller (Arduino), how can I burn the controller?  I pass a 5v, 0.02A charge from my Arduino controller to transistor's base. The transistor opens and lets the electricity flow from the collector to the emitter powering on my other larger 40v device.   Can the current get in from the collector into the base? What's the reason for adding a resistor between the controller and the base? so that I don't add 'extra' current from Arduino into the other devices chain? Thanks!

I know that this is a very basic question but I really do not know the answer.  I was making simple logic gates using transistors and I used PNP transistor as NOT gate.   I made the following circuit: (A) AND (B) AND (NOT C)   This circuit does not work without the resistors R1,R2 and R3. Why are these resistors important ?         – Schematic created using   The Following NOT gate does not need a base resistor. I connect Vcc or ground directly to base and it works.  How can it work without resistors although it is very similar to the previous circuit ?


I am studying for my finals, and I came across a question I don't really understand. We have a finite group $G$ with two generators: $a$ ($a^3=E$) and $b$ ($b^2=E$), where $E$ is the identity. We are also given the relation $(ab)^2=E$. Now the question asks to show that $G$ has $6$ elements that can be represented as $$E, a, a^2, ab, a^2b, b$$ I am not sure how I can deduce the number of elements in my group from my generators? Thanks!

I'm going through Dummit and Footes Abstract Algebra book, and have a question on their characterization of group presentations.  They state that:      In general, if some group $G$ is generated by a subset $S$ and there is some collection of relations, say $R_1, R_2, \ldots , R_m$ (here each  $R_i$ is an equation in the elements rom S $\bigcup$ {1} ) such that any relation among the elements of S can be deduced from these, we shall call these generators and relations a presentation of G and write $G = \langle S | R_1, R_2, R_3, ... , R_m \rangle$.     He goes on to give the dihedral group presentation as:      $$  D_{2n} = \langle r,s | r^n = s^2 = 1, rs = sr^{-1} \rangle \space\space (1)   $$   The authors had shown geometrically that $D_{2n}$ has order $2n$ but they went on to say that as a result any group with only the relations in (1) must have order at least $2n$.  They also claim that any any group with the (1) presentation must also have order at most 2n ( the author states that using the relation $rs = sr^{-1}$ accomplishes this). Hence the order must equal $2n$.  Edit: To quote the others directly from page 27, chapter 1.2:       " This kind of collapsing does not occur for the presentation of D$_{2n}$ because we have showed by independent (geometric) means that there is a group of order 2n with generators r and s satisfying the relations in (1). As a result, a group with only these relations must have order at least 2n. On the other hand, it is easy to see (using the same sort of arguments for X$_{2n}$ above and the commutation relations rs = sr$^{-1}$) that any group defined by the generators and relations in (1) has order at most 2n. It follows that the group with presentation (1) has order exactly 2n and also that this group is indeed the group of symmetries of the regular n-gon."    Can someone please provide the details behind this argument for why the presentation guarantees the order to be equal to $2n$? Why do we have that if a group $G$ ONLY has the relations in (1) then we must have $|G| \ge 2n$? If such an argument works to show $|G| \ge 2n$, why doesn't that same argument work for showing $|G| \le 2n$?


I need to change the hosting server for a website referenced in France. If i take a hosting server in Belgium (google gce eu-west-1) would this affect my site natural SEO ?

I have been hosting in a server from last 2 years. I am planning to change the hosting server. Before I change the hosting server I would like to know whether it affects my site's rankings or not?


I want to accelerate an object from resting state to a velocity $v_1$ then from a linear movement at speed $v_1$ to linear movement at speed $v_2$.  By conservation of energy law, the energy spent will be the difference between kinetic energy at the end and kinetic energy ar the beginning state. So for the first experiment I spend $\frac{1}{2}mv_1^2$ and for the second experiment $\frac{1}{2}m(v_2^2-v_1^2)$.  Now If I accelerate a resting object of mass 1Kg to a speed of $10ms^{-1}$ and then accelerate it to a speed of  $20ms^{-1}$, the energy spent will be respectively 50J and 150J. Why does it take more energy to add $10ms^{-1}$ of velocity to a resting object than to an already moving object?

As  says:     [...] the kinetic energy of a non-rotating object of mass $m$ traveling at a speed $v$ is $\frac{1}{2}mv^2$.   Why does this not increase linearly with speed? Why does it take so much more energy to go from $1\ \mathrm{m/s}$ to $2\ \mathrm{m/s}$ than it does to go from $0\ \mathrm{m/s}$ to $1\ \mathrm{m/s}$?  My intuition is wrong here, please help it out!


I'm studying the Axiom of Choice. But it is so hard for me to apply the exercise.  The question is:  Let $A$ be any set with more than one element. Prove that there exists a bijective function  $f : A\to A$ such that $f(x)\neq x\text{ }\forall x \in A$.  I don't feel sure that the question is only for applying axiom of choice. I learned the Zorn's lemma but I dont feel certain to apply the Zorn's lemma.  Please help me.

I cannot prove this statement so need help. This problem is one of exercises right after the chapter about Hausdorff's maximal principle and Zorn's Lemma. Thus, you cannot use the concept of cardinal number. I found the exact same question on this website, but the proof is done by using the concept of cardinal number. Please make sure that this question is at right after introducing the axiom of choice and Zorn's lemma.  Let $A$ be any set with more than one element. Prove that there exists a bijective function $f:A \to A$ such that $f(x)\neq x$ for every element $x$ in $A$.


I have been using wine for a while now but it started showing some problems a few days ago so I used this command to remove it  sudo apt-get purge wine\*   Now my system has none of the in built programs such as the terminal or the software center. What can I do to get them back apart from re installing Ubuntu?

I accidentally lost some of the system files by executing the following command in the terminal:   sudo apt-get purge wine\*   Most of the installed software (terminal, software center, libreoffice etc.) are now lost.  Does anybody have a solution for this issue?


Here is my program          String thisSchool=buffer.readLine();         String thisLine;          while((thisLine = buffer.readLine()) != null){             if(thisLine=="*")             {                 thisSchool=buffer.readLine();             }             else             {                 School school = new School(thisSchool);                 Student student = new Student(thisLine, school);                 StudentList.add(student);             }        }   My text file reads like this:  School1 A B C * School2 D E * School3 F   The output of my driver class is:  A School1 B School1 C School1 * School1 School2 School1 D School1 E School1 * School1 School3 School1 F School1   This is what I WANT it to look like  A School1 B School1 C School1 D School2 E School2 F School3   Here's what the problem looks to be The "currentSchool" variable is never changing, and I don't know why! The " * " is treated as a student (I want to use it as a delimiter, i.e., the program will ignore it when it is encountered). Instead, the "if line= * " command is being ignored completely, and consequently, the school never changes, and the students are being written incorrectly

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


I'm studying for a probability exam and came across this question. I watched the video solution to it but I don't really understand it. I was hoping someone could explain this problem to me. Are there different ways to go about this?

I am told that a fair coin is flipped $2n$ times and I have to find the probability that it comes up heads more often that it comes up tails.     Please, how do I find the required probability?


I understand that we calculate a posterior belief by updating our prior belief with the information from given data, like  $$ p(\theta|y_1,...,y_n)\propto p(y_1,...,y_n|\theta)p(\theta)$$  But I dont fully understand the concept of a predictive distribution (the distribution of $\tilde{Y}$ having observed $\{Y_1=y_1,...,Y_n=y_n\}$ from the population.  What is the difference between a posterior distribution and a predictive distribution?

I'm taking an Intro to Bayes course and I'm having some difficulty understanding predictive distributions. I understand why they are useful and I'm familiar with the definition, but there are some things I don't quite understand.   1) How to get the right predictive distribution for a vector of new observations  Suppose that we have built a sampling model $p(y_i | \theta)$ for the data and a prior $p(\theta)$. Assume that the observations $y_i$ are conditionally independent given $\theta$.   We have observed some data $\mathcal{D} = \{y_1, y_2, \, ... \, , y_k\}$, and we update our prior $p(\theta)$ to the posterior $p(\theta | \mathcal{D})$.   If we wanted to predict a vector of new observations $\mathcal{N} = \{\tilde{y}_1, \tilde{y}_2, \, ... \, , \tilde{y}_n\}$, I think we should try to get the posterior predictive using this formula $$ p(\mathcal{N} | \mathcal{D}) = \int p(\theta | \mathcal{D}) p ( \mathcal{N} | \theta) \, \mathrm{d} \theta = \int p(\theta | \mathcal{D}) \prod_{i=1}^n p(\tilde{y}_i | \theta) \, \mathrm{d} \theta, $$ which is not equal to $$ \prod_{i=1}^n  \int p(\theta | \mathcal{D}) p(\tilde{y}_i | \theta) \, \mathrm{d} \theta, $$ so the predicted observations are not independent, right?  Say that $\theta | \mathcal{D} \sim$ Beta($a,b$) and $p(y_i | \theta) \sim$ Binomial($n, \theta$) for a fixed $n$. In this case, if I wanted to simulate 6 new $\tilde{y}$, if I understand this correctly, it would be wrong to simulate 6 draws independently from the Beta-Binomial distribution that corresponds to the posterior predictive for a single observation. Is this correct? I don't know how to interpret that the observations are not independent marginally, and I'm not sure I understand this correctly.  Simulating from posterior predictives  Many times when we simulate data from the posterior predictive we follow this scheme:  For $b$ from 1 to $B$:  1) Sample $\theta^{(b)}$ from $p(\theta | \mathcal{D})$.  2) Then simulate new data $\mathcal{N}^{(b)}$ from $p(\mathcal{N} | \theta^{(b)})$.   I don't quite know how to prove this scheme works, although it looks intuitive. Also, does this have a name? I tried to look up a justification and I tried different names, but I had no luck.  Thanks!


Let $A$ and $B$ be sets. If there exists a surjection $f : A \to B$ then there exists an injection $g : B \to A$.   Proof: given $b \in B$ select an element $a \in f^{-1}(b)$. Denote this element by $g(b)$. Then $g(b) \in f^{-1}(b)$ so that $f(g(b)) = b$. Consequently $g(b_1) = g(b_2)$ implies $f(g(b_1)) = f(g(b_2))$ so that $b_1 = b_2$. We conclude $g$ is an injection. QED  Is the axiom of choice required to make this argument rigorous?

Theorem. Let $X$ and $Y$ be sets with $X$ nonempty. Then (P) there exists an injection $f:X\rightarrow Y$ if and only if (Q) there exists a surjection $g:Y\rightarrow X$.  For the P $\implies$ Q part, I know you can get a surjection $Y\to X$ by mapping $y$ to $x$ if $y=f(x)$ for some $x\in X$ and mapping $y$ to some arbitrary $\alpha\in X$ if $y\in Y\setminus f(X)$. But I don't know about the Q $\implies$ P part.  Could someone give an elementary proof of the theorem?


I am a high school student writing a report about Newton’s law of cooling. Due to environnemental effect, the temperature of the environment might vary therefore I am planning on exploring how such problem could be applied and what math should be used. Would it be possible to use Taylor series as we would expect a sine graph for the variation in temperature. Please let me know what you think and thanks a lot. Website used for the idea:

I have been researching for a while looking for what to include more than just deriving the equation of Newton’s law of cooling and a website gave me inspiration by stating what if the temperature of the environment is changing (± C). In conclusion, I wasn’t sure if that person carried out the mathematical process in the right way and the only place I could ask for accurate information is here so please let me know what you think about the mathematical process he went for and if it is right or wrong. Thanks a lot. Website:


When showing the job-search results, it would be incredibly useful if there was an indication for which of those jobs I've already applied for.  As it stands, I risk thinking I already applied for a position that I didn't, or re-applying for a position, potentially irritating the company.  I know , but some companies have more than one similarly titled positions, and it isn't always clear if a position is one I've applied for, or just another position within the same company.

I am not able to find on my Careers profile the positions I applied to in the past. Is there a way to see positions I have previously applied to?  I've sent in applications to around 8-10 positions in the last month or so and would like to be able to check or track which companies and/or positions I've already applied for.


I installed android studio using ubuntu-make like  umake android   after starting android studio, it asks some questions and then starts downloading SDK components, but it never finishes that successfully. I tried that using ubuntu 14.10 already and had the same problems there. Now, with ubuntu 15.04 things haven't changed, I got my homedirectory completly new on the install, so I doubt there is anything from an old installation.  The install of SDK compoments fails with the following output:   Refresh Sources:   Failed to fetch URL http://dl.google.com/android/repository/addons_list-2.xml, reason: File not found   Fetched Add-ons List successfully   Refresh Sources   Failed to fetch URL http://dl.google.com/android/repository/repository-10.xml, reason: File not found Refresh Sources:   Failed to fetch URL http://dl.google.com/android/repository/repository-10.xml, reason: File not found There is nothing to install or update. The following SDK components were not installed: platform-tools, extra-android-m2repository and extra-google-m2repository   So, how can I get android studio to work?

Please tell me the full process of installing Android Studio and its necessary dependencies.


I'm using rhel7 and trying to print my output from shadow for example to be like this : test1 !! test2 !! test3 *  I am running this command: i=`cat /home/mydir/shadow1 |awk -F ':' '{print $1,$2}' `  When I do echo $i, it will print the output in 1 line: test !! test2 !! test3 *  Can anyone advice how should I modify my '{print $1,$2}' so that it will print a new line?

Or, an introductory guide to robust filename handling and other string passing in shell scripts.  I wrote a shell script which works well most of the time. But it chokes on some inputs (e.g. on some file names).  I encountered a problem such as the following:   I have a file name containing a space hello world, and it was treated as two separate files hello and world. I have an input line with two consecutive spaces and they shrank to one in the input. Leading and trailing whitespace disappears from input lines. Sometimes, when the input contains one of the characters \[*?, they are replaced by some text which is is actually the name of files. There is an apostrophe ' (or a double quote ") in the input and things got weird after that point. There is a backslash in the input (or: I am using Cygwin and some of my file names have Windows-style \ separators).   What is going on and how do I fix it?


I am trying to count the number of $(0,1)$ $m \times n$ matrices that contain exactly $k$ ones distributed such that no row and no column contains only zeros (clearly, $k \ge m$ and $k \ge n$ yield interesting cases). I looked at similar questions (e.g., ), but they usually do not contain global constraints such as the total number of ones. Similarly, unlike , this question does not have any constraints on column/row sums.  Thanks in advance for your help!

So I want to find the number of ways to fill an $m\times n$ matrix with only 0s and 1s such that each row and column has an even number of 1s.  I'm pretty stumped here.  I've set up m+n equations summing the respective rows and columns yielding 0 mod2, but other than that I'm not too sure of a clean way to approach this.  The subsequent part asks for the same thing except that there's an odd number of 1s.  Any hints and/or tips very much welcome.


I'm looking for a command line to update my already installed software.I want to update all of them.

When I log into my web server via SSH I see the information:  88 packages can be updated. 80 updates are security updates   I tried apt-get update then apt-get upgrade but each time I log in I still see the message about updates. How do I install them?


I need to find the reduction formula for the integral of $\cos^n(x)$.  Ive split it into $\cos(x)\cos^{(n-1)}x$ in the hope of integrating by parts, but I'm unsure how to differentiate $\cos^{(n-1)}$, how should I proceed?

I am trying to prove  $$\int\cos^n x \ dx = \frac{1}n \cos^{n-1}x \sin x + \frac{n-1}{n}\int\cos^{n-2} x \ dx$$  This problem is a classic, but I seem to be missing one step or the understanding of two steps which I will outline below.   $$I_n := \int\cos^n x \ dx = \int\cos^{n-1} x \cos x \ dx \tag{1}$$  First question: why rewrite the original instead of immediately integrating by parts of $\int \cos^n x \ dx$?  Integrate by parts with $$u = \cos^{n-1} x, dv = \cos x \ dx \implies du = (n-1)\cos^{n-2} x \cdot -\sin x, v = \sin x$$  which leads to  $$I_n = \sin x \ \cos^{n-1} x +\int\sin^2 x (n-1) \ \cos^{n-2} x \ dx \tag{2}$$  Since $(n-1)$ is a constant, we can throw it out front of the integral:  $$I_n = \sin x \ \cos^{n-1} x +(n-1)\int\sin^2 x \ \cos^{n-2} x \ dx\tag{3}$$  I can transform the integral a bit because $\sin^2 x + cos^2 x = 1 \implies \sin^2 x = 1-\cos^2 x$  $$I_n = \sin x \ \cos^{n-1} x + (n-1)\int(1-\cos^2 x) \ \cos^{n-2} x \ dx \tag{4}$$  According to Wikipedia as noted , this simplifies to:  $$I_n = \sin x \ \cos^{n-1} x + (n-1) \int \cos^{n-2} x \ dx - (n-1)\int(\cos^n x) \ dx \tag{5}$$  Question 2: How did they simplify the integral of $\int(1-\cos^2 x) \ dx$ to $\int(\cos^n x) \ dx$?  Assuming knowledge of equation 5, I see how to rewrite it as  $$I_n = \sin x \ \cos^{n-1} x + (n-1) I_{n-2} x  - (n-1) I_{n} \tag{6}$$  and solve for $I_n$. I had tried exploiting the fact that  $$\cos^2 x = \frac{1}{2} \cos(2x) + \frac{1}{2} $$  and trying to deal with $\int 1 \ dx - \int \frac{1}{2} \cos (2x) + \frac{1}{2} \ dx$  which left me with $\frac{x}{2} - \frac{1}{4} \sin(2x)$ after integrating those pieces. Putting it all together I have:  $$I_n = \sin x \ \cos^{n-1} x + (n-1) I_{n-2} x \left(-(n-1) (\frac{x}{2} - \frac{1}{4} \sin 2x) \right) \tag{7}$$  but I'm unsure how to write the last few terms as an expression of $I_{something}$ to get it to match the usual reduction formula of   $$\int\cos^n x \ dx = \frac{1}n \cos^{n-1}x \sin x + \frac{n-1}{n}\int\cos^{n-2} x \ dx$$


I know that in the case of the Kepler problem there is a quantity (other than energy, momentum,...) conserved which is the Runge-Lenz vector.  Is there also an "exotic" quantity conserved for a 2-Body system with a potential: $V(r)=\alpha r^2$? I'm asking this because the radial harmonic oscillator and the inverse square force are the only ones that have a bounded orbit.  If the answer is positive; is there a symmetry associated to the conservation of this quantity?

The Runge-Lenz vector is an "extra" conserved quantity for Keplerian $\frac{1}{r}$ potentials, which is in addition to the usual energy and angular momentum conservation present in all central force potentials.    I suppose it is not a coincidence that $\frac{1}{r}$ potentials have this extra conserved quantity and are also one of the two central force potentials that have closed orbits.  Indeed, one may think of the RL vector as an expression for the orientation and eccentricity of the elliptical orbit, which is conserved iff the orbit closes on itself.    This then leads me to think that there must be an analog to the RL vector in an $r^2$ potential, which is the other central force potnetial that has closed orbits.  Surely, we can define a vector pointing along the direction of the orbit's major axis, that has magnitude proprtional to the eccentricity, and this will be conserved.  Is there any way to write down such a vector in terms of dynamical variables, and thus obtain an $r^2$ analog for the RL vector?


I removed nautilus from my laptop and I had lost everything. When iam trying to install nautilus it requires some dependencies. How can I get it now?? I used sudo apt-get remove --purge nautilus to remove nautilus

Trying to run a Ubuntu server for the first time... But everything is in a terminal. Is there a way to switch to a GUI?


Let $\mathscr{B}$ be the set of Borel sets on $R$, how to prove that $\overline{\overline{\mathscr{B}}}=\aleph$? That is ,  the cardinality of it is continuum?

It seems it's well known that if a sigma algebra is generated by countably many sets, then the cardinality of it is either finite or $c$ (the cardinality of continuum). But it seems hard to prove it, and actually hard to find a proof of it. Can anyone help me out?


I am trying to get nice smooth contours using ArcGIS. I have already smoothed out the DEM using focal statistics, simplified and smoothed the contours. The current result looks like this, which is way too pixel-y whenever the line is not straight:  And zoomed in on my peeve:  What I am going for is something less raster-y and more vector-looking like this:  I don't know if something like that is even possible within ArcGIS or whether I need a different application. Nevertheless I hope someone can guide me onto the right path towards perfect contours.

How can I export 2d vector graphic from ArcScene so I can edit it with Adobe Illustrator? I've tried changing the options when I export 2D scene as AI file or PDF file, but they always remain as a unique image that does not allow me to edit the lines and polygons.


Can someone direct me to an Android emulator outside of Android Studio, that's open source and for Ubuntu, not Wine. I used to use Android SDK but don't like the Studio update and am now using a paid for application that I'm not thrilled with.

I will like to know some of the android emulators that work really well with Ubuntu 11.10 and above. I want to try 'whatsapp' on Ubuntu through an android emulator. Thanks in advance


I could not find this feature in the alpha version of Blender 2.8, nor could I find any information on whether the feature will still be available with the release. I only found a hint in  where a responder said the interface for the layers is not yet fully implemented. Does anyone know if this feature will still be available with the new release? Thank you.

I have a collection that contains linked assets. I would like to override their materials and give them a unique material. Is it possible to assign a material to a whole collection, and how ?  Thanks !


In a local xampp server which I set up for development, I have a table like so:  CREATE TABLE `entries` (  `id` int(10) UNSIGNED NOT NULL,  `title` varchar(100) NOT NULL,  `entry` text NOT NULL,  `date_entered` datetime NOT NULL  )   In order to learn how to secure my queries against SQL injections, I want to induce one (I am intentionally not using prepared statements). I have a query to insert an entry in this table like so:  $sql = 'insert into entries ( title , entry , date_entered ) '     . 'values("'     . $postTitle     . '","'     . $postEntry     . '","'     . $dateEntered     . '")';   It works (it does insert entries in the table), but I failed to induce SQL injection attack against it. Here is what I tried to insert in the $postEntry field:  ;drop table entries; ;drop table entries;' ';drop table entries;' `;drop table entries;' q';drop table entries; q","e");drop table entries; --' q","e");drop table entries;--   For the last value the SQL query became:  insert into entries ( title , entry , date_entered ) values("r","q","e");drop table entries;--","2016-08-18 10:35:36")   Still the entries table intact!  I modified the SQL string to use single quotes like so:  $sql = 'insert into entries ( title , entry , date_entered ) '     . ' values(\''     . $postTitle     . '\',\''     . $postEntry     . '\',\''     . $dateEntered     . '\')';   Then tried:  q','2016-5-5');drop table entries; --'   But still no luck! How should I produce SQL injection attack then? note : the proposed duplicate is not duplicate and not even an answer . the whole point of this question is to demo the expoite so that i make sure the security measures are working.

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


I am a UK citizen living in the UK and tax based in the UK. I have created a small Windows Store App which will be sold at about $4. I will be very lucky to get about 250 sales in a year (ie $1,000 per year). In my Windows Store account it is asking me about 'Effectively Connected Income'. I have not got a clue what they are on about.  It says the following:  "Certificate of Foreign Status Numbers in parentheses refer to line numbers on the official IRS W8 forms. Is the income you receive from Microsoft effectively connected with the conduct of a trade or business in the United States? Persons/entities must file an annual U.S. income tax return to report income claimed to be effectively connected with a U.S. trade or business (See Effectively Connected Income)"  It then has two radio buttons with 'Yes' and 'No'.   What do I click? Do I really have to submit tax forms to the US every year? How on earth do I go about doing that?

I  own a website and I sell digital content. I'm a nonresident alien with the US. Most of my customers are US based so I was wondering will I have to pay any taxes to the US?  I have read that      For nonresidents, taxable income is separated into two categories:         Income that is effectively connected with a U.S. trade or business, after the deductions that are allowed, is subject to U.S. income tax   at graduated rates - the same rates that apply to U.S. citizens and   residents - or lower rates if the provisions of a tax treaty apply.   Income that is subject to U.S. income tax, for being U.S. source income, but that is not effectively connected with a U.S. trade or   business, is subject to a flat 30% tax      Is this true and do I belong to any of these categories?  If I form an LLC or C corp am I liable for this withholding tax?  My customers are based in the US and I believe all income is considered FDAP income according to the IRS:     Fixed, Determinable, Annual, or Periodical (FDAP) income is all   income, except:         Gains derived from the sale of real or personal property (including market discount and option premiums, but not including original issue   discount)   Items of income excluded from gross income, without regard to the U.S. or foreign status of the owner of the income, such as tax-exempt   municipal bond interest and qualified scholarship income      The thing is the IRS also says:     Effectively Connected Income, after allowable deductions, is taxed at   graduated rates. These are the same rates that apply to U.S. citizens   and residents. FDAP income generally consists of passive investment   income; however, in theory, it could consist of almost any sort of   income. FDAP income is taxed at a flat 30 percent (or lower treaty   rate) and no deductions are allowed against such income. Effectively   Connected Income should be reported on page one of Form 1040NR. FDAP   income should be reported on page four of Form 1040NR.   In the last quote, it’s like they say it only applies to passive income but if they feel like it, they can apply this to all income??


Hello I am wondering how to prove that a function that takes 2 numbers from the Natural number and produces one is bijective. I have the following function $$\operatorname{f}(x,y) = \frac{1}{2}(x+y)(x+y+1)+y$$ For injectivity I tried to start with assuming that $$\operatorname{f}(x,y) = \operatorname{f}(x_1,y_1) \rightarrow x = x_1 \land y=y_1$$ but I couldn't proove it. For showing that it is surjective, I have no idea. Thank You :)

How would you prove the  bijective? I only know how to prove a bijection by showing (1) If $f(x) = f(y)$, then $x=y$ and (2) There exists an $x$ such that $f(x) = y$  How would you show that for a function like the Cantor pairing function?


I must use after a period an abbreviation which is "mtDNA" (mitochondrial DNA). It is always abbreviated with the two first letters in lowercase. I'm struggling to find a rule to know whether the "m" has to be capitalised or not after a period. For example would you write :  lorem ipsum. MtDNA is very important for cells. lorem ipsum. mtDNA is very important for cells.  It appears to me more natural to have it lowercase also because I'm used to read it almost everyday.  Is there a rule that can be applied?  Best ,

In the beginning of a sentence, should I capitalize abbreviations such as the following:   hPSC (human pluripotent stem cell) mESC (mouse embryonic stem cell) rDNA (recombinant deoxyribonucleic acid)   I have seen both lower and upper case for the two first, while rDNA always seems to be in lower case. I'm curious which is the linguistically correct form.


Trying to install ubuntu 13.04 64 bit with windows 8 64bit .. but its not show win 8 .. just laptop harddisk without any window's options  update .. I have installed windows 8 64bit but when i try to install  ubuntu 13.04 64bit using USB .. it dont detect windows 8 and just show me to erase disk to install ubuntu instead  of this screen

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


I'm just read  from Atmel corporation in comparing RSA with ECC cryptography algorithms.  First of all please read these two paragraphs quoted from the article:  P1: Strength of an algorithm     The level of security in systems is becoming a primary concern as you   would expect. Most cryptographic experts recommend that current   systems offer at least 128 bits of security, but what does that really   mean? Note that this is not the same thing as key length as many may   think. Security comes from the combination of the specific algorithm   and its key length. For example, it is generally thought that 128 bits   of security can be achieved with 128-bit AES keys, 256-bit Elliptic   Curve keys, and 3072-bit RSA keys. If implementation issues are   ignored, then these algorithms with those specified key lengths will   generally have the same level of security.   P2: Performance of an algorithm     When it comes to performance at 128-bit security levels, RSA is   generally reported to be 10-times slower than ECC for private key   operations such as signature generation or key management. The   performance disparity expands dramatically at 256-bit security levels,   where RSA is 50- to 100-times slower. RSA’s key generation is also   very slow compared to ECC key generation, with the RSA’s being 100- to   1000-times slower. However, this may or may not be a significant   consideration in systems that generate keys infrequently. It does   matter for certain protocols or policies that require more frequent   key generation. Public key signature validation is generally faster   with RSA compared to ECC, which can provide a benefi   Well, I feel conflicts between these paragraphs. As far as I know, Required time to break an algorithm (An empty of bug one!) is the only thing that determine strength of that algorithm.   And what is this Required-Time depends on?   NK -->  Number of forms of key that is 2^(key-length). NI --> Number of instruction required to check a single key.   In the other words, algorithm A is stronger than algorithm B, only if NK*NI for algorithm A was greater than NK*NI for algorithm B. Am I right?  If so, why ECC-160 is stronger than RSA-1024? I mean, okay, based on the performance paragraph, RSA is only 10 times slower than ECC in this security level, but in return the attacker must check 2^1024 different keys in RSA instead of 2^160 keys of ECC!

I understand how ECC is based on the discrete log problem and RSA on integer factorization. I've read several references that show how a solution to either of these problems can typically be adapted to solve the other - for example,  claims:      The asymptotic running time of the best discrete logarithm algorithm   is approximately the same as that of the best general-purpose   factoring algorithm. Therefore, it requires about as much effort to   solve the discrete logarithm problem modulo a 512-bit prime as it does   to factor a 512-bit RSA modulus.   Now, I suspect that this isn't true, but I'd like to get a feel for why it isn't true.  For instance, as I understand it, the generalized number field sieve can be applied both to solve integer factorization and to solve discrete log. Why is it that it gives such an extreme speed up in integer factorization compared to brute-force, and less so in improving discrete log?  If the asymptotic running times for both applications are approximately the same, then I'm completely confused. I suspect that I'm comparing the wrong parameters, but how is it that ECC key-sizes can be so much smaller that in RSA?


How to evaluate the following limit $$\displaystyle\lim_{x\to 0} \dfrac{e-\left(1 + x\right)^{1/x}}{\tan x}$$ I have tried to solve it using L-Hospital's Rule, but it creates utter mess. Thanks for your generous help in advance.

find value of the $$\lim_{x\to0}\frac{e-(1+x)^{\frac{1}{x}}}{x}$$I use hospital law and can't find answer


I have a file called C:\skor\test.xlsx And I need create a copy of it in C:\skor2\ pd.read_excel and df.to_excel - cannot be used Basically I need to copy the file without opening it.

How do I copy a file in Python?  I couldn't find anything under .


Would the observation from a camera have the same effect on wave function as the observation from a living being?

My question is not about (pseudo) philosophical debate; it concerns mathematical operations and experimental facts.  What is an observer? What are the conditions required to be qualified of observer, both mathematically and experimentally?


I am a Canadian permanent resident planning to transit via Munich airport. I read the transit visa exceptions at  It says      Still, there are some categories of people, who may be nationals of the above-mentioned countries, but if they belong to one of the following they do not need to obtain a visa of this kind:   - holders of a valid visa for a Schengen Member State, Bulgaria, Canada, Croatia, Cyprus, Ireland, Japan, Romania or UK   I am a citizen of one of the countries listed above that statement that that would usually need a visa but are exempt under that condition. However, do they differentiate between a PR card (permanent residency proof) vs. just a visa? I.e. is PR card a stronger document than a visa (I would assume so but wanna be sure).   For e.g. one of my other stops on the way back is Zurich. I also read their requirements:   I am again, a citizen of the countries who would usually need a visa but am exempt under the condition:     Holders of a valid residence permit, issued by one of the following states:    - Canada   here they make a clear distinction between a visa and a residence permit. Is there anything to be worried about? I have transited many times through Europe but at that time I had a valid US visa. Anyone with experience in these matters please give your opinion.  EDIT: Did additional research and found the link of German embassy/mission in Canada:   which states:     If one of the following conditions applies to you, you WILL NOT require an airport transit visa when transiting through one German or Austrian airport:         you hold a valid Canadian Permanent Resident Card   you hold a valid Canadian visa   you leave Canada after having used a Canadian visa

I found many related questions on this site but I am still not sure about the rules. How can I decide if I need a visa to transit? Schengen members as of May 2021 are as follows:  Austria Belgium Czech Republic Denmark (excluding Greenland and the Faroe Islands - but an open border with the Schengen Area is maintained) Estonia Finland France (excluding overseas departments and collectivities) Germany Greece Hungary Iceland Italy Latvia Liechtenstein Lithuania Luxembourg Malta Netherlands (excluding Aruba, Curaçao, Sint Maarten and the Caribbean Netherlands) Norway (excluding Svalbard) Poland Portugal Slovakia Slovenia Spain (except Ceuta and Melilla) Sweden Switzerland


I want to calculate precision and recall for word sense disambiguation. Naturally, for that I need to calculate TP, TN, FP and FN. I know TP is the number of documents that the tag of the test sentences equals to the tag of the classifier and FN is the number of documents that the tag of test sentences is not equal to the tags that the classifier found. But what is TN and FP? I can't see any other case more than the two cases I described above. For example my test sentence is as like as below:  fist sentence:         word1 word2 word3 word4 tag1 second sentence:  word1 word2 word3 word4 tag2  If my classifier finds the correct tag which is equal to the tag in sentences, it's TP unless it's FN. So what is TN and FP? My classifier finds whether the right tag or the wrong. There is no other case. Is there any TN and FP in this condition?

I wonder how to compute precision and recall using a confusion matrix for a multi-class classification problem. Specifically, an observation can only be assigned to its most probable class / label. I would like to compute:    Precision = TP / (TP+FP)   Recall = TP / (TP+FN)   for each class, and then compute the micro-averaged F-measure.


Baby hit something and now whenever I roll over something with my mouse or type this voice says the letter or the name of the webpage or if I adjust the volume it tells me what volume (i.e. "volume setting 29") It's driving me nuts!!! It's like the baby enabled a hearing impaired setting or something. I have Ubuntu 14.04 and Firefox. Help?

I accidentally opened Orca Screen Reader from the Dash when I was trying to open Screenshot. Now everything I type or click on is spoken out loud.  How do I make it stop?  For reference, here is a screenshot of Orca Screen Reader running:


My command is   give @p stone_pickaxe 1 0 {     display:{         Name:"Level 1 Pickaxe",         Lore:["A basic pickaxe."]     },     ench:[{         id:32,lvl:1     }],     Unbreakable:1 } {     CanDestroy:["minecraft:stone","minecraft:stonebrick"] }   How would i add the next part? (only allowed to break stone blocks)

I'm trying to create an item that can break certain blocks, but also has a colored name in 1.13.2   Here's the command I'm using.  /give iAugust minecraft:shears{display:{Name:"[{\"text\":\"Arcane Shears\",\"color\":\"aqua\",\"italic\":false,\"bold\":false}]CanDestroy:[minecraft:iron_bars]"}}   But it only has a colored name, and it can't break specific blocks.


please tell me the necessary packages that I must use to get blue colored cross-referring to Fig.1 and Eq.(1). I want to change the color of Fig.1 from black to blue. Thank you very much in advance.  \documentclass[5p]{elsarticle}   \usepackage{lineno} \modulolinenumbers[5]  \journal{Journal of \LaTeX\ Templates}  \usepackage{times}   \begin{document}   %\linenumbers  \section{Introduction} Piezoelectric Fig.1 and Eq.(1) effect has been employed to a very great extent in many applications since its discovery by the Curie brothers.   \end{document}

If I use  \usepackage[colorlinks]{hyperref}   I get colored links for \cite (not good for printing or even viewing) but table of content looks fine.  If I use  \usepackage[colorlinks=false]{hyperref}   I get \cite  links in black with a colored frame (this looks very good) but the table of content looks strange with extra long boxes.  What are my other options? Can you have two styles in different parts of a document?   How do you make the page numbers in TOC to be the links instead of the section headers?


For a complete graph with vertices $2n+1$ and its edges colored with $n$ colors, how to prove that there exists a cycle with all edges of the same color.  I have proceeded by calculating the number of edges in a complete graph of $2n+1$ vertices which gives $ \binom{2n+1}{2} = n(2n+1) $ edges.  Now using the pigeonhole principle there must be at least $2n+1$ edges of the same color. Now how do I show that this forms a cycle in the graph?

We have a connected graph $G(V,E)$ that has $|E|= n$ edges and $n$ vertices.    Prove that the graph has one cycle in it.   I'm little bit confused here. I tried some ways but failed. Can you direct me?


I want to know if the page is being accessed via http or https using JavaScript.  Is there some sort of isSecure() method, or should I just parse it out of the URL somehow?

Is it possible to detect, on the client side, whether the user is using an encrypted page or not?  Put another way -- I want to know if the URL of the current page starts with http or https.


Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies...Starting pkgProblemResolver with broken count: 0 Starting 2 pkgProblemResolver with broken count: 0 Done  Done Starting pkgProblemResolver with broken count: 0 Starting 2 pkgProblemResolver with broken count: 0 Done The following additional packages will be installed:   libefl-bin The following NEW packages will be installed:   libefl-bin 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. 2 not fully installed or removed. Need to get 0 B/864 kB of archives. After this operation, 3,081 kB of additional disk space will be used. Do you want to continue? [Y/n]  (Reading database ... 176074 files and directories currently installed.) Preparing to unpack .../libefl-bin_1.20.7-0bionic0_amd64.deb ... Unpacking libefl-bin (1.20.7-0bionic0) ... dpkg: error processing archive /var/cache/apt/archives/libefl-bin_1.20.7-0bionic0_amd64.deb (--unpack):  trying to overwrite '/usr/bin/edje_cc', which is also in package libedje-bin 1.8.6-2.5build1 dpkg-deb: error: paste subprocess was killed by signal (Broken pipe) Errors were encountered while processing:  /var/cache/apt/archives/libefl-bin_1.20.7-0bionic0_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)   I tried all solutions which could help but I couldn't achieve what I wanted to do.

For example:  $ sudo apt-get install curl Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: bsh : Depends: libjline-java but it is not going to be installed groovy : Depends: libjline-java but it is not going to be installed rhino : Depends: libjline-java but it is not going to be installed E: Unmet dependencies.   Try 'apt-get -f install' with no packages (or specify a solution).   I get the same or similar errors when I attempt to install clojure1.3, leiningen, and several other packages.   When I try the suggestion made in the error message, this is what happens:  $ sudo apt-get -f install  Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following packages were automatically installed and are no longer required:   diffstat linux-headers-3.2.0-26-generic linux-headers-3.2.0-26 dh-apparmor dkms html2text libmail-sendmail-perl libsys-hostname-long-perl Use 'apt-get autoremove' to remove them. The following extra packages will be installed:   libjline-java Suggested packages:   libjline-java-doc The following NEW packages will be installed:   libjline-java 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. 23 not fully installed or removed. Need to get 0 B/72.0 kB of archives. After this operation, 129 kB of additional disk space will be used. Do you want to continue [Y/n]? Y (Reading database ... 226243 files and directories currently installed.) Unpacking libjline-java (from .../libjline-java_1.0-1_all.deb) ... dpkg: error processing /var/cache/apt/archives/libjline-java_1.0-1_all.deb (--unpack):  trying to overwrite '/usr/share/java/jline.jar', which is also in package scala 2.9.2-400 Errors were encountered while processing:  /var/cache/apt/archives/libjline-java_1.0-1_all.deb E: Sub-process /usr/bin/dpkg returned an error code (1)  $ sudo apt-get upgrade Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies:  bsh : Depends: libjline-java but it is not installed  groovy : Depends: libjline-java but it is not installed  rhino : Depends: libjline-java but it is not installed E: Unmet dependencies. Try using -f.


In hot questions tab , I can't determine which sorts of order was invoke. By hoverring on hot tab , below message was appeared.     Questions with the most views,answers and votes over the last few days   But in case , that's similar randomly.   not order by view counts not by answer counts not by vote points ( up or down or up + down ) and not by date-time   I thought , "ah ! first top of question was hottest and followed by others with orderly." As hover message that I described (brief information of tab ) , I assume these are ordered by   view counts > answer counts > vote counts ....  Can anyone explain to me ?

I know questions on the "hot" tab of a site homepage are based on some sort of views/velocity criteria, but does anyone know the actual algorithm used?  Background: I was considering a feature-request about the "hot" tab, but I don't have enough information to speak about it intelligently.


Given $x,y\neq 0$ such that $x^2+xy+y^2=0$. Evaluate the following, $$\left(\frac{x}{x+y}\right)^{2013}+\left(\frac{y}{x+y}\right)^{2013}$$   I have tried to merge the fraction, factorize the numerator and simplify the fraction, but I don't know when to use the initial equation. Any ideas or solution would be helpful.

Given two non-zero numbers $x$ and $y$ such that $x^{2} + xy + y^{2} = 0$. Find the value of $$\left(\frac{x}{x + y}\right)^{2013} + \left(\frac{y}{x + y}\right)^{2013}$$.  I found out that $(x + y)^2 = xy$ and I'm stuck at $\frac{x^{2013} + y^{2013}}{(x + y)^{2013}}$ Does anyone know how to solve this?


I was just watching some footage from last year's EVO... and something is bothering me.  Why do some players affiliate with gaming 'teams' such as Complexity or Evil Geniuses?  I understand that in the Counter Strike or League of Legends scene, where there is a teamwork aspect to the game itself - those are the people that you play with, you work as a team, know each other's strengths and weaknesses etc.   However, in the hand-to-hand fighting games such as Marvel vs Capcom, the actual fighting is always 1v1, you don't have 'teammates' per se. In fact you probably spend more time fighting your teammates then you do rooting for them!  So what are the advantages of being part of a competitive team for fighting games?

Many professional gamers are on a team for whatever game they play.  This makes sense for games like League of Legends where you play with your team mates, but what about games like Hearthstone where the games are always played 1v1?   Why not just compete/play independently?


My problems in Aptitude: I keep getting this error  E: The method driver /usr/lib/apt/methods/http could not be found. W: Is the package apt-transport-http installed? And I can't update anything, if I'm installing I get this:  E: The method driver /usr/lib/apt/methods/http could not be found. E: The method driver /usr/lib/apt/methods/http could not be found.   or sometimes this with the log above:   E: Internal error: couldn't generate list of packages to download   And when I installed Aptitude just earlier, it uninstalled apt.  My problems with apt:  Sometimes, I can't use sudo apt-get update and sudo apt-get upgrade.  I forgot the rest because I can't do it again because Aptitude uninstalled it. PLEASE HELP ME!

The apt-get command and the sudo command does not work for me. which apt-get returns nothing. I checked by bin folder to make sure, and there is no aptget. I however have wget. Can I install apt-get with wget? If not, how can I install it?


Example: Three days ago I was serial downvoted        After these weren't automatically reversed, 24 hours later, I flagged one of the posts. It was eventually marked as helpful, but the downvotes are still there.  It could be that it was 2 users, but it looks like too much of a coincidence.  What should you do in these circumstances?

I just noticed that I lost a bunch of points from my reputation score, and I used the "reputation" tab on my user profile page to try and track down the cause.  During my investigation, I noticed there was an unusual event of type "reversal". In the normal place of a question title, it says "voting corrected".     What does this mean, and what caused it?  Did I do something wrong? Why did I lose all of that reputation? Is the system punishing me for leaving too many good answers?  Is there any way to earn it back?


<!DOCTYPE html>       <title>My first website</title>     <meta charset="utf-8">

My First Website

 Welcome to my webiste! Here are some things I enjoy.

Web Development

Chess

Reading

Learning

Favorite Quotes

Here is a favorite quote of mine...

 ...and another"

      why isnt this working? I want to have everything in the div to be at the center of the page, currently it is aligned to the left. Thanks in advance.

How can I horizontally center a
 within another
 using CSS?

Foo foo


How do I show that every family of open nonempty disjoint sets (in $\mathbb{R}$) is countable?  I think I should use the fact that every nonempty open set is the disjoint union of a countable collection of open intervals, but I'm not sure. The question here is pretty simple but I can't even start to think of a way to solve it.

Let $U$ be a collection of pairwise disjoint open intervals. That is, members of $U$ are open intervals in $\mathbb{R}$ and any two distinct members of $U$ are disjoint. Show that $U$ is countable.  My attempted proof:  Let $U \subseteq \mathbb{R}$ be a collection of pairwise disjoint opern intervals. Let $(a,b) \subseteq U$ be one such interval. Since $\mathbb{Q}$ is dense in $\mathbb{R}$, there exists a rational number $q_{a,b} \in (a,b)$. Define $f: U \to \mathbb{Q}$ by $f((a,b))=q_{a,b}$. As $f(a_1,b_1)=f(a_2,b_2)$, or $q_{a_1,b_1}=q_{a_2,b_2}$, implies $(a_1,b_1)=(a_2,b_2)$, we deduce that $f$ is injective. It was proved already in my lecture class that $\mathbb{Q}$ is countable, and that union of countable sets is countable. Thus, we deduce that $U$ is countable. (End of attempted proof)  I feel confident about my proof except the injectivity part. I was looking for help there, assuming the rest of my proof is cogent. If not, please let me know how I can improve on it.


$$Rad(I)=\{a \in R | \exists n \in \mathbb{N} \text{ such that } a^n \in I\}$$   R is a commutative ring, I is an ideal.   To show that $Rad(I)$ is an ideal of $I$, we have to show that for $a,b \in Rad(I)$ it stands that $a-b \in Rad(I)$ and for $r\in R$ it stands that $a\cdot r\in Rad(I)$, right??   When $a,b \in Rad(I)$ we have that $a,b \in R$ and $a^n, b^m \in I$.   $a-b \in R$.   But how can we show that $(a-b)^x \in I, x \in \mathbb{N}$ ??

Given that R is commutative ring with unity, I want show that set of all nilpotent elements is an ideal of R.    I know how to show ideal if set is given but here set is not given to me. Can anyone help me?


I was trying to speed up my tiny laptop by switching off OpenGL using Compiz.  I guess there were also whole bunch of related plugins got disabled in the process.  Then I lost the entire GUI desktop interface.  Could someone please tell me how to get everything back through command line?  Thanks.

My Ubuntu is stuck in a login loop when trying to enter my desktop. When I login, the screen gets black and soon after that the login screen comes back.   I've read that the problem might be caused by an error depending on the graphics, here's my graphics card: ATI Radeon 7670M


I have installed first public beta yesterday. Now App Store says there is a second update to public beta. There is no problem with network or internet at all but somehow update stucks at 0 bytes and no progress. Any suggestions to fix this problem?

I opened GarageBand for the first time, to find that most of the loops required me to download the Apple Loops from Software Update. I agreed to this.  The App Store opened and gave me the option to install the update from Updates - I clicked Install and waited for the download to complete. It did, and then the installation began.  About half an hour later, the update is stuck on (Installing - Calculating...) This doesn't seem normal - the last time I installed the Loops, they were done in about ten minutes.  Force quitting and re-opening the App Store doesn't help, nor does a reboot. When I open the App Store, the update is still at the same process.  Is there anything that I could do to get the update to finish installing?  Here is a screenshot of the App Store in this state:


From "O Captain! My Captain!" by Walt Whitman:  O Captain! my Captain! rise up and hear the bells; Rise up—for you the flag is flung—for you the bugle trills, For you bouquets and ribbon’d wreaths—for you the shores a-crowding, For you they call, the swaying mass, their eager faces turning;  While I cannot recall any concrete examples at the moment, I do remember encountering the prefix "a-" in poetry a couple of times before. Can anyone explain what it is all about?

I have always found the a- prefix to words (as in anew, ajar, aside, awake, afoot, a-hunting, etc.) fascinating. The NOAD says on this topic:     a- 2.  prefix      •to; toward : aside | ashore.      • in a specified state or   manner : asleep | aloud.      • in the   process of (an activity) : a-hunting.      • on : afoot.      • in : nowadays.      ORIGIN   Old English , unstressed form of on.      a- 4. prefix      1 of: anew.      [ORIGIN: unstressed form of of ]      2 utterly: abash. [ORIGIN: from Anglo-Norman   French (corresponding to Old French   e-, es-), from Latin ex.]   While this gives quite a few examples, it leaves some areas of doubt to me:   At what time did this phenomenon happen? It seem quite restricted to words of Saxon origin, as I don't see it used with words of Romance languages. Is that a consequence of point 1, or is it because usage wouldn't aggregate an Old English prefix with, e.g., a word of French origin? Were there others words formed which haven't endured?  Arguably subjective: I wonder how it came to pass that the same prefix is used with so many different meanings.


I have been logging into SE using my Google account and SE have always asked to "View your email address".  Today it also asked for "basic profile info":    This is a NEW development (I was not asked for "basic profile info 3 days ago).  What has happened?  I do not want to divulge my "basic profile info".  What are my options?  Can I create an SE account and move my old account history over?

I just created a SE account using my Google account. It said that it needs to "Know who you are on Google" (I guess my connections). As far as I know, SE is not a social network. I can't even follow other people (seeing when they post questions and answers).  What is the reason you need to know my Google connections?  This was on code review. Actually I have an account there, but for some reason it asked me to reconnect. This is the same on MSO; one sees this explained as "This app is requesting permission to associate you with your public Google profile":


I've got a button on my page that allows a user to add a form. When a button within the new form is clicked, a jquery function should run. Unfortunately, the jquery function doesn't seem to run on the newly appended divs (it does run divs  that existed on initial page load).

         Remove

     Add Another Form
        When the user clicks the deletebox within the newly appended form, nothing happens. I.e. jquery doesn't register that it was clicked and no message is printed to the console. Do you know how this issue can be addressed?  Thanks!

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


I am totally new to Linux so I don't know how to do anything :S I was trying to open Software Center ( to install spotify) but I always get this error message:   Please run this software with administrative rights. To do so, run this program with kdesudo.   Hope that somebody can help me with this

When downloading an application from the terminal it said I couldn't download it because I wasn't root, and when I got to search for the specific software in the Ubuntu software center it doesn't even come up as a search result. I need to get/download ttf-mscorefonts and preload please.


These are the strings I have:  "test123.00" "yes50.00"   I want to add the 123.00 with 50.00.  How can I do this?  I used the command parseInt() but it displays NaN error in alert box.  This is the code:   str1 = "test123.00";  str2 = "yes50.00";  total = parseInt(str1)+parseInt(str2);  alert(total);

In javascript, what is the best way to parse an INT from a string which starts with a letter (such as "test[123]")?  I need something that will work for the example below.  My JS:  $(document).ready(function() {      $(':input').change( function() {         id = parseInt($(this).attr("id"));  //fails for the data below         alert(id);     }); }   My generated HTML:  <select id="attribute[123]"> <!-- various options --> </select> <select id="attribute[456]"> <!-- various options --> </select>   Thank you!


Is there an alive Ubuntu wish list?  The main reason why I use Unity desktop is the top bar which is able to take away the menu bars of the application window.  It was published, that in the future Unity will be dropped and Gnome desktop will be the default instead.  My wish if this desktop could have a Unity like top bar.  Can I configure a gnome desktop this way right now, or it needs an amount of programming, and a better knowledge of the gnome system?  There is no kind of bugs mentioned in this question.

I found a problem with an application on Ubuntu.   Questions :   How do I best report the issue?  What sort of information should I provide?


I'm trying to split a string in java based on brackets with the possibility that there are nested brackets, example: "{one two {three}}{one {two} {{three}}}"  what I would like to get is an array with array [0] = {one two {three}}  array [1] = {one {two} {{three}}}  I tried using the \ {(. *?) \} Regex but I get substrings like {one two {Three}  which do not take into account which is the correct closing parenthesis How can I do it?

I need a regular expression to select all the text between two outer brackets.  Example: some text(text here(possible text)text(possible text(more text)))end text  Result: (text here(possible text)text(possible text(more text)))


I have not used my HP Photosmart C4795 printer in some time and now ink does not come through.  Could the ink cartridges be clogged?  Can this be corrected? Ink level is still showing within normal limits.

How can I fix an inkjet printer where one of the colors isn't printing well anymore?  My  has served me well for a few years, and I print color and B&W material on a regular basis. A few days ago, the cyan has developed a defect -- the printout is striped, so some lines aren't getting printed. This affects all colors that have a cyan component, so color printing (and greyscales!) are ugly, striped, and miscolored.  I'm guessing that the print head itself has become clogged. Is there any way I can fix this?   I've tried the clean and deep clean functions in the printer's software many times  (not just twice but maybe 15 times),  and replacing the cyan ink cartridge, and printing several all-cyan pages,  but the cyan is still striped.   I am considering taking it apart, cleaning the nozzles, and putting it back together again. I'm handy with tools so there's a fair chance it would work, and if it doesn't work afterwards then not much is lost because it doesn't work well now either.


I want to recursively delete all files not accessed in a while in folder a, except all files in the subfolder b.  find a \( -name b -prune \) -o -type f -delete   However, I get an error message:     find: The -delete action automatically turns on -depth, but -prune does   nothing when -depth is in effect.  If you want to carry on anyway,   just explicitly use the -depth option.   Adding -depth causes all files in b to be included, which must not happen.  Anyone know a safe way to make this work?

So, you can use the * as a wild card for all files when using cp within context of a directory.  Is there a way to copy all files except x file?


I've been trying to understand the complex function derivatives, but there are some issues that I'm encountering. I'm following the Ahlfors Complex Analysis. When he is demonstrating the derivative via the limit, he does it both with a pure infinitesimal Real and a pure Imaginary value, but I don't get why should it be concluded that they must have the same value since you are going in different directions of the complex plane (with the real value you are going in the real axis and with the imaginary value you are going with the imaginary axis). Also, I see some similarities with the multivariate calculus, without being the same, and that might be something that is causing me to some misconception.

From Churchill - Complex Variables and Application it's shown that in order to get Cauchy-Riemman equations, we just asume a derivable function $w(z)$ and go for the limit definition. $$    w'(z_0) = \lim_{z \to z_0}\frac{w(z) - w(z_0)}{z - z_0} = L $$ Because a complex function can be seen as a $\Re^2 \to \Re^2 $ vector field, (from the z-plane to the w-plane) as $w(z) = w(x + iy) = u + iv$, with $u$ and $v$ scalar fields. Thus, we can extend the limit, into the real and the imaginary part. So, here is my problem. For C-R Equations we say that, as $L$ exists, we say that is valid, for any arbitrary choice of trajectory that is continous at $z_0$. We choose the real and imaginary axis, simplify the limit and get the C-R. This means that for any complex function $f(z)$, we can indeed have a derivative $f'(z)$ which is not so intuitive from multivariable calculus. If we have an scalar field, and derive it by limit definition and apply the exact same trick, the limit would depend on the choosed trajectory, givin birth to the partial derivatives of $f$. So Why do we assume, in the complex case, that this does not hold. And that if $f$ is derivable, at a point $ z = z_0$, it's "partial derivatives" should be the same. I know in complex analysis everithing is kind of weird, but I don't see the rationale behind that.  Is just by definition? The gradient in the Real case, would be "analogous" to the complex derivative? Is valid due to the division between complex numbers?


My surface tablet is shared with a friend. She uses a separate account, with admin rights.  Being an admin, she is able to gain access to all my files. Even my OneDrive files.   I guess I could follow  to prevent this (it basically states that you'll need to disable access for the targeted administrator), but the same scenario would be present if I were to create another administrator account.  You could say "don't make her administrator", but I don't want to mess with her personal files as well.  Somehow this feels as a security flaw... or am I mistaken?  Is there any way to protect private files from "administrator eyes" by default?

We in our club have a computer with Windows 7 Professional that every club member may use. And everyone has their own separate account.   Those accounts have to have administrator priveleges since I want everyone to be able to install any software and use any feature they want. However, there is a single thing that they shouldn't be allowed to do - that is, look into another users' profiles. Now when anyone goes to 'c:\Users(Any User Name)' a little prompt appears that this folder is secured and whether you really want to look inside. Simply clickinh 'ok' give you access to any profile.  I tried disabling taking ownership for Administrators group in Group Policies but that had no effect. How can I effectively prohibit administrators looking into each others' profiles and documents?


I have this following script which works fine on ubuntu for starting and creating a new table for MySQL database:   echo "CREATE DATABASE database_name" | mysql -u root -p   After this command is executed MySQL asks for password.  The only problem is that I want to do this on vagrant provision bash script, so I have to automate the process of entering the password. I basically have to give a single line of input to the MySQL program like this:  Enter password: password_goes_here   How do I combine the process of entering the database creation command and the password as text to the program?

I have MySQL password saved on a file foo.php, for example P455w0rd, when I try to use it:  $ cat foo.php | grep '$dbpwd=' | cut -d '"' -f 2 | mysql -U root -p mydb -h friendserver Enter password: (holds)  $ echo P455w0rd | mysql -u root -p mydb -h friendserver Enter password: (holds)   Both option still ask for password, what's the correct way to send password from stdin?


I'm in the field of Psychology. One of my manuscripts is now under review after the 1st round of revision. However, I found one of the variables was calculated in a wrong way, the results are better with the corrected variable because the significance levels were higher (i.e., p values were lower), but it didn't change the conclusions of my study, all the significant results still remain significant and non-significant results are still non-significant. I would like to know what would be the best option to deal with it.   option 1: ignore it.  option 2: correct it when I receive reviewers' feedbacks WITHOUT letting the reviewers and editor know.  option 3: correct it when I receive reviewers' feedbacks AND let the reviewers and editor know.  I'm worried that letting the editor and reviewers know would leave a bad impression on me and the quality of my work.   Thank you in advance!

Recently my paper was accepted pending major revisions (i.e., not yet accepted), and while following the reviewers' comments and revising my paper, I realized that both reviewers missed a mistake that I made in a function block diagram. What should I do?   Correct it and let them know in the joined point-by-point response? Wait until they tell me about it?  Ask them to double check that diagram?   I'm afraid it may send the wrong message and I'd look disrespectful by showing them that they missed the mistake.


I'm having trouble understanding what exactly an empty set is. Does $\varnothing$ mean $\{\}$ ? and what is the difference between $\varnothing$ and $\{\varnothing\}$ ? If someone could shed some light on this, and provide a couple of more examples to help me learn what this weird concept is, I'd greatly appreciate it.  Thanks!

Herbert in his book "Elements of set theory" on page no 3 says that      we can form the set $ \{ \emptyset \} $ whose only member is $\emptyset $. Note that $ \{ \emptyset \} \neq  \emptyset $, because $ \emptyset \in \{ \emptyset \} $ but $\underline{ \emptyset \notin \emptyset} $·   By the last argument $\emptyset \notin \emptyset$, is he saying that empty set is not a member of or does not belong to empty set  OR  it is a typo and he wanted it to be $ \{\emptyset \} \notin \emptyset $, that set containing empty set is not a member of empty set


I updated android studio and it seems that something went wrong  Internal Error. Please report to https://code.google.com/p/android/issues  com.intellij.ide.plugins.PluginManager$StartupAbortedException: java.lang.reflect.InvocationTargetException     at com.intellij.ide.plugins.PluginManager$2.run(PluginManager.java:96)     at java.lang.Thread.run(Thread.java:745) Caused by: java.lang.reflect.InvocationTargetException     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)     at java.lang.reflect.Method.invoke(Method.java:498)     at com.intellij.ide.plugins.PluginManager$2.run(PluginManager.java:93)     ... 1 more Caused by: java.lang.NoClassDefFoundError: io/netty/channel/ChannelHandler     at com.intellij.idea.SocketLock$2.call(SocketLock.java:154)     at com.intellij.idea.SocketLock$2.call(SocketLock.java:128)     at com.intellij.idea.SocketLock.underLocks(SocketLock.java:191)     at com.intellij.idea.SocketLock.lock(SocketLock.java:128)     at com.intellij.idea.StartupUtil.lockSystemFolders(StartupUtil.java:318)     at com.intellij.idea.StartupUtil.prepareAndStart(StartupUtil.java:140)     at com.intellij.idea.MainImpl.start(MainImpl.java:34)     ... 6 more Caused by: java.lang.ClassNotFoundException: io.netty.channel.ChannelHandler     at com.intellij.util.lang.UrlClassLoader.findClass(UrlClassLoader.java:207)     at java.lang.ClassLoader.loadClass(ClassLoader.java:424)     at java.lang.ClassLoader.loadClass(ClassLoader.java:357)     ... 13 more   I want to remove it completely from my laptop

I installed Android studio some time ago using the following suggested method:     To set up Android Studio on Linux:      Unpack the downloaded Tar file,   android-studio-ide--linux.zip, into an appropriate location   for your applications. To launch Android Studio, navigate to the   android-studio/bin/ directory in a terminal and execute studio.sh. You   may want to add android-studio/bin/ to your PATH environmental   variable so that you can start Android Studio from any directory.   Follow the links to install the SDK outside of the Android Studio   directories.   For whatever reason it has become corrupt and insists I must un-install and re-install. I can't for the life of me find how to un-install it however.  I didn't use apt-get so I can't do apt-get remove.  Does anyone have any suggestions?


I am trying to learn Java and am using Eclipse. For some reason the constructor I am using is not providing my Main class with the necessary information. Any help would be appreciated.  package com.wes.classes;  public class Main {      public static void main(String[] args) {         // TODO Auto-generated method stub          Ball ball = new Ball(mColor: "Blue", mName: "just ball", mCapacity: "12", mElasticity: "45");         ball.Bounce();       }  }   package com.wes.classes;  public class Ball {       //Properties of instance variables     private String color;     private String name;     private int elasticity;     private int capacity;      public Ball(String mColor, String mName, int mElasticity, int mCapacity) {         // TODO Auto-generated constructor stub         color = mColor;         name = mName;         elasticity = mElasticity;         capacity = mCapacity;     }      //Behaviors        public void Bounce() {System.out.println("Bouncing");   }     public void Deflate() {System.out.println("Deflate");   }     public void Inflate() { System.out.println("Inflate");  } }

Is it possible to call a constructor from another (within the same class, not from a subclass)? If yes how? And what could be the best way to call another constructor (if there are several ways to do it)?


I am searching a free tool to create Landing Page Buttons, cool designs, social media call-to-action tools, graphics like below - for beginners. I have it difficult finding free tools. Could you recommend me a few and if you believe that one particular paid tool is really great, which one would be worth it?  Would like to create those things for my clients as an additional service!    OR

Are there any free/ open source image designing programs that you can recommend?