When working with objects that implement IDisposable, the common pattern is;  using(ManagementObject mObj = new ManagementObject()) {     //Work with mObj }   However, in the instance of System.Management.ManagementObject, IDisposable has been declared on the ultimate parent class, in this instance, System.ComponentModel.Component  Dispose has been implemented as follows (extracted using ILSpy):  public void Dispose() {     this.Dispose(true);     GC.SuppressFinalize(this); }   Dispose on the ManagementObject however, has been implemented as follows:  // System.Management.ManagementObject /// <summary>Releases all resources used by the Component.</summary> public new void Dispose() {     if (this.wmiClass != null)     {         this.wmiClass.Dispose();         this.wmiClass = null;     }     base.Dispose();     GC.SuppressFinalize(this); }   It appears that on completion of the using block, Dispose is called from the class which directly implements the interface; that is System.Component, and so the wmiClass field is not cleaned up at this point as this implementation is not executed.  If I recreate this with a simple hierarchy:  public class Parent, IDisposable {      public void Dispose(){         System.WriteLine("Parent Disposing");     } }   public class Child : Parent {     public new void Dispose()     {         System.WriteLine("Child Disposing");         base.Dispose();     } }   and write a small test program;  using (Child child = new Child()) {     System.WriteLine("Do Stuff"); }   I get the output: Do Stuff, Parent Disposing  Generally, if we wanted the inheritance to work as expected wouldn't it have been safer to declare Dispose as virtual on Parent and override on Child? If I do that I get exactly the order of events expected vs what happens in the original example (which makes sense if Dispose is being called on the class that directly implemented the interface).  Is there a reason why you'd implement Dispose in this way rather than as a virtual call on the base class? This forces the use of a try {} finally {} pattern where you explicitly call the Dispose implementation to get the expected result.

I know from reading  that the "primary" use of the IDisposable interface is to clean up unmanaged resources.  To me, "unmanaged" means things like database connections, sockets, window handles, etc.  But, I've seen code where the Dispose() method is implemented to free managed resources, which seems redundant to me, since the garbage collector should take care of that for you.  For example:  public class MyCollection : IDisposable {     private List<String> _theList = new List<String>();     private Dictionary<String, Point> _theDict = new Dictionary<String, Point>();      // Die, clear it up! (free unmanaged resources)     public void Dispose()     {         _theList.clear();         _theDict.clear();         _theList = null;         _theDict = null;     }   My question is, does this make the garbage collector free memory used by MyCollection any faster than it normally would?  edit:  So far people have posted some good examples of using IDisposable to clean up unmanaged resources such as database connections and bitmaps.  But suppose that _theList in the above code contained a million strings, and you wanted to free that memory now, rather than waiting for the garbage collector.  Would the above code accomplish that?


Let $R$ be a UFD. Let $r,a,b \in R$. Then how can I show that $\operatorname{gcd} (ra,rb) \sim r \operatorname{gcd} (a,b)$?   If $\operatorname{gcd} (a,b) = d$ and $\operatorname{gcd} (ra,rb) = d'$.Then $d|a$ and $d|b$ $\implies$ $rd|ra$ and $rd|rb$ i.e. $rd$ becomes a common divisor of $ra$ and $rb$. Hence we must have $rd|d'$. But I fail to show the converse part i.e. $d'|rd$.  How can I show this? Please help me.  Thank you in advance.

I need to prove that $z\gcd(a,b)=\gcd(za,zb)$.    I tried a lot, for example, looking at set of common divisors of the two sides, but I can't conclude anything from that. Can you please give me some advice how I can handle this problem? And $a,b,z \in \mathbb{Z}$.


How did bird able to call the method fly if it's private  public class Bird {     private static void fly() {          System.out.println("Bird is flying");      }     public static void main(String[] args) {         fly(); // make sense         Bird bird = new Bird();         bird.fly();     } }

In Java, are there clear rules on when to use each of access modifiers, namely the default (package private), public, protected and private, while making class and interface and dealing with inheritance?


I'm quite interested in the following algorithmic problem, on which I can't find any information. Phrased as a decision problem:  Given a set of vectors $V$ in $\text{GF}(2)^n$, a vector $\mathbf u$ in $\text{GF}(2)^n$, and an integer $k$, decide whether there exists a subset $S \subseteq V$ such that $|S|\leq k$ and  $\sum_{\mathbf v\in S} \mathbf v = \mathbf u$.  Note that despite sounding similar to the subset sum problem, it's actually quite different – in particular without the $|S|\leq k$ restriction it's basic linear algebra. My attempts to google the problem have failed so far. Is this a problem already explored in some papers? Is it equivalent to another well-known problem? Is it solvable by a practical algorithm? Is it NP-complete? I would be surprised if there was no literature about this problem at all given the short formulation. What I figured out by myself is that this problem could be polynomially reduced to the problem of  Given a set of vectors $V$ in $\text{GF}(2)^n$, a vector $\mathbf u$ in $\text{GF}(2)^n$, and an integer $k$, decide whether there exists a subset $S \subseteq V$ such that the vector $\mathbf u+\sum_{\mathbf v\in S} \mathbf v$ consists of at most $k$ ones.  Maybe this one is better-known?

In  vzn asked about the following problem, which I'll call Vector-Subset-Sum.     Given a set of vectors $v_i$ over GF(2) and a target vector $y$, is there a subset of the $v_i$ summing to $y$?   In the answers, comments, and referenced papers I noted   The decision problem is in P. The natural minimization problem (finding the smallest subset) is NP-hard. It's related to the problem of finding sparse codewords in a linear code.   My question is: are there any known polynomial-time approximation algorithms for the minimization problem in (2)? I know very little about coding theory, so there may be some obvious or well-known approximation-preserving reductions to (3) that I have not seen.


I just lost my laptop charger and I found another one on my house, I was wondering if it is compatible with my laptop and if you would recommend it using, the specs are the following:  ORIGINAL CHARGER (HP) Input: 100-240 V ~ 1.4A  50-60 Hz Output: 19.5V  2.31A 45W  REPLACEMENT CHARGER (Lenovo) Input: 100-240 V ~ 2.5A. 50-60 Hz Output: 20V  2A 46.08W  Thank you very much for your help.

I have a Toshiba Satellite laptop. My charger has stopped working.  I have access to a Lenovo charger. Can I use this charger on my laptop?


I apologize, as this is a somewhat off-the-beaten-trail question.  I'm looking for textbooks (or other educational materials) on TeX and LaTeX that fulfill one or more of the following:   Reads/renders well with a screen reader (namely ); is typeset (or can be re-typeset) with a LD-friendly font such as ; comes with online materials in the vein of  or MyCommunicationLab (viz. flashcards and quizzes); has an audiobook version (MP3 or ); and/or is available via .   I hope this question isn't too off-topic, because I have been having a genuinely hard time finding a textbook or primer that meets my needs.    P.S: Are there any TeX/LaTeX tutors in the Washington, D.C. area? 1:1 instruction is how I learn best, to be frank.  P.P.S: Are there any good flashcard sets for memorizing LaTeX snippets, macros, and commands?

Which book (free or otherwise) was the most useful to you when you started learning LaTeX?  I am frequently asked this question by friends who want to learn LaTeX, and I recommend the book which got me started, , but I feel that there might be better options around.  Also see .


How can I check if a weirdo character I'd like to use is included in the used font?

I'm working on a project that generates PDFs that can contain fairly complex math and science formulas.  The text is rendered in Times New Roman, which has pretty good Unicode coverage, but not complete. We have a system in place to swap in a more Unicode complete font for code points that don't have a glyph in TNR (like most of the "stranger" math symbols,) but I can't seem to find a way to query the *.ttf file to see if a given glyph is present.  So far, I've just hard-coded a lookup table of which code points are present, but I'd much prefer an automatic solution.  I'm using VB.Net in a web system under ASP.net, but solutions in any programming language/environment would be appreciated.  Edit: The win32 solution looks excellent, but the specific case I'm trying to solve is in an ASP.Net web system.  Is there a way to do this without including the windows API DLLs into my web site?


I've been trying to understand the Lightning component event model, to see what would be the best way to do what I need to do.  I have a component that contains a component, like this:  <!-- parent component --> <aura:component>     <c:childComponent/> </aura:component>   The child component contains a data table that is populated via an init().  When I do something in the parent component that changes the data displayed in the child component, what is the best way to tell the child component to refresh the data displayed by the data table?

I have this below code where i am trying to first search an account name and on hit button it displays the result set.  On the button click i am also loading an child component which is displaying the id of the record.  I need the child component should get displayed once i click on the record.  How can i achieve this -   Parent Component -   <aura:component controller="SimpleAccountController">     <aura:attribute name="account" type="account[]"/>     <ui:outputText aura:id="outName" value="" class="text"/>     <ui:inputText aura:id="name" label="Enter Name:" placeholder="Your Name" />     <ui:button aura:id="button" buttonTitle="Click to see what you put into the field" class="button" label="Click me" press="{!c.getInput}"/>     <aura:iteration var="acc" items="{!v.account}">
{!acc.Name} : {!acc.Type} : {!acc.Industry} : {!acc.Rating}
                      <c:HelloWorkdChildCmp selectedaccount="{!acc.Id}" />     </aura:iteration> </aura:component>   COntroller -   ({     getInput : function(cmp, evt) {         var myName = cmp.find("name").get("v.value");         var myText = cmp.find("outName");         var greet = "Hi, " + myName;         myText.set("v.value", greet);         var action = cmp.get("c.seaAcc");         action.setParams({ "s" : myName });         action.setCallback(this, function(response) {             var state = response.getState();             if (state === "SUCCESS") {                 cmp.set("v.account", response.getReturnValue());                 //alert("From server: " + response.getReturnValue());             }         });         $A.enqueueAction(action);     },      accountselected : function(cmp, evt) {        console.log(evt.currentTarget.getAttribute("data-recId")) ;     }  })   Child component -   <aura:component >     <aura:attribute name="selectedaccount" type="String"/>
Id: {!v.selectedaccount}
 </aura:component>


Is there a good example of an equivalence of categories $F:\mathcal{A}\to\mathcal{B}$ such that $F$ is neither left nor right adjoint to its inverse $G:\mathcal{B}\to\mathcal{A}$?

Let $C$ and $D$ be categories and $F:C\to D$, $G:D\to C$ two functors.  $F$ is left-adjoint to $G$, if there are natural transformations $\eta:id_C\to GF$ and $\epsilon:FG\to id_D$ such that \begin{eqnarray} F&\xrightarrow{F\eta}&FGF&\xrightarrow{\epsilon F}F\\ G&\xrightarrow{\eta G}&GFG&\xrightarrow{G\epsilon}G \end{eqnarray} are the identity (!) transformations.  $F$ is an equivalence of categories (with inverse $G$) if there are natural isomorphisms $\eta:id_C\to GF$ and $\epsilon:FG\to id_D$ without any further properties.     Is $F$ left-adjoint to $G$, if $F$ is an equivalence of categories (with inverse $G$)?If not, suppose that $F$ is an equivalence of categories with inverse $G':D\to C$ and suppose further that $F$ is left-adjoint to $G$. Does it follow that there is a natural isomorphism $G\to G'$ or is there even an identity $G=G'$?


I may be biased, and will delete if I'm wrong, but why are there so many more insects when compared to quad bugs?

Apparently, there is an advantage to having 6 legs in the insect world. What is that advantage, if anything? Why would such an advantage exist for insects, but not for other, larger land animals?  What do those middle legs do that the front and hind legs cannot, if anything? Are they really essential, or do they just generate more muscle power?


When I opened Mac OS X overview panel to check out how much storage I have left, I saw this strange thing. It doesn't affect the performance by any means, but it is not aesthetically pleasing. How can I get rid of it?

Suddenly all the system windows have this weird font. I can't read nor understand what the system is asking me. How can I change it to normal fonts?    I'm using OS X Yosemite 10.10.3


I’ve been trying to kill a bunch of bosses for a while now but most of the time, I’ve looked up the best weapons for the jobs and they say to use things that I can only obtain after fighting another boss. Is there a good way to go abour defeating these guys, or should I just choose one and go for it with a normal weapon?

I am attempting to defeat all of the bosses, to beat Terraria. This includes hard mode.   Who are the main bosses, throughout both regular and hard mode? Is there a particular preference I should take in defeating them?  It would definitely be worth considering multiple platforms, and the optional bosses, to make the answer more useful to other users.


Sorry that the question title is unclear, I didn't know how to ask it.  Take set $A \subseteq [0,1]$, measurable. Does there exist a sequence $x_1,x_2,\dots$ such that $\forall x_i$,   \begin{align*} \displaystyle\frac{\mu\left([x_i,x_{i+1}]\cap A \right)}{\mu\left([x_i,x_{i+1}]\right)} \in \{0,1\} \end{align*}  where $\mu$ is the Lebesgue measure?

I was wondering how one can construct a Borel set that doesn't have full measure on any interval of the real line but does have positive measure everywhere.   To be precise, if $\mu$ denotes Lebesgue measure, how would one construct a Borel set $A \subset \mathbb{R}$ such that $$0 < \mu(A \cap I) < \mu(I)$$ for every interval $I$ in $\mathbb{R}$?   Moreover, would such a set necessarily have to contain infinite measure?


The task is to find a pair of numbers whose digits are 1-9, no digit repeated such that their product is maximum possible.  eg. 123 and 456789 is one such pair.  Question: Please suggest a way to do it.  I tried writing a code in Python but failed. Any logical approach is appreciated.

Given $A = B \times C$  Using any $9$ digits form two numbers $B$ and $C$.All digits must be used exactly once.   What is the maximum possible value of $A$?


So, I have a laptop, and a desktop, both Windows 8.1. The laptop follows me wherever I go, and the desktop doesn't. The desktop has 5 external drives, and I am using Storage Spaces to pool the drives together. I have shared the resultant drive (REFS format) on my network, and have mapped to a drive letter on my laptop. So far, so good.  However, when I take the laptop off my home network to, say, the office, whenever I try to open a program that enumerates drives, the system hangs while it tries to connect to the drives. When I open Explorer at the office, it shows the network drive as available, but hangs for a long time, then discovers the network drive is not present.  I have confirmed that this hang is being caused by the mapped drive, because after disconnecting it, the hanging stops and everything goes back to normal.  I have experienced the hanging with the following software:   Explorer FileZilla (takes about 2 minutes to open) Skype (when saving a file) Sublime Text 2 (first time a file dialog box is opened) Oxygen XML Editor (any file dialog operation)   Is there anything I can do to either change the timeout when testing a network drives existence, or telling the system to ignore mapped drives unless specifically called?  I have tried working with just shortcuts to the network shares, but with some of the software I use, they don't support explicit network shares (Oxygen XML), and manual intervention would completely undermine the file version history tracker I have set up (would only index bulk commits made during a manual copy, rather than each and every change as I go along).    Additional  I found this issue originally in FileZilla last year at some point, and after raising a case with FileZilla, they came back saying that the hang was being caused by a lower level system component. The only difference between then and now is, then, I was on Windows 8, and the network drive was a single drive instead of storage spaces drive. Sadly, I can't find the case, but there are many others like it.  At that point, I gave up and resigned myself to slow FileZilla startup times, however, the hanging at that time was around 30 seconds, and now it has jumped to 2 minutes, so I really want this problem solved.

When a network drive () is physically disconnected, Windows Explorer (and other programs) keeps trying to enumerate and/or use it for maybe 60 seconds.  Is there some way to reduce this timeout to maybe 5 seconds?  Just to clarify, I'm not asking about network drives that are automatically disconnected by Windows after a certain period of time, or about automatic reconnections during login.  The question is about this:  Connect a network drive to another computer. Then turn that other computer off. Then try to reconnect the network drive, e.g. by double-clicking in Windows Explorer → very long timeout. How do I reduce this timeout?


In figure 12 of  EMI Design Guidelines for USB Components, I can see that VBUS and Gnd signals from the USB receptacle are bypassed with ferrite beads and then connected to their respective power and ground planes, while the USB receptable itself is tied to the ground plane at its connection points. Following this guide, my design should look like the one below:  However, after reverse engineering the PCB layout of a simple wired Razer mouse, I saw that they implemented the filtering of the ground signal slightly differently. Specifically, the ground signal from the USB cable is tied to the ground plane (no f.bead) while the USB shield* connects to the ground plane through a ferrite bead. *Noted that in this case the USB cable is not connected to the PCB via a standard micro-B USB receptable like in the first case, but instead through a permanently attatched vertical 2mm pitch 5-pin header. So when I say shield for this second case I mean the 4th pin of the Razer USB cable which is the extension of a  bundle of thin copper wires (acting as a shield) that are wrapped around the other 4 wire signals (V, D-, D+, GND). In the first case, where a USB receptable is used, the 4th pin is the ID pin meant for  , unrelated to this question. My question: Are those two methods of connecting the gnd signal to the respective ground plane similar in terms of EMC performance, or should I expect to see my board fail at the test house after following one design over the other? I would be inclined to follow the design guide had I not seen an actual product designed in a different way.

This is about the seemingly controversial shield to ground connection. The system is basically a body-worn intel-based computer, powered by a battery. Two USB 3.0 (or 3.1 Gen1) cables come out to a PCB that contains two USB 3.0 hub chips (). Two external cameras plug in to this usb hub PCB (one camera for each hub). So the usb hub PCB has 4 usb connectors (2 upstream and 2 downstream).  The question is, what to do with each of the usb connector shields? The main directive is USB connection robustness.  I have seen many recommendations. For example:  Recommendation 1  TI's TUSB8020B hub reference design  ties all shells directly to ground.    Intel's  also recommends to tie to ground (although this was written for USB 2.0).    Recommendation 2  TI's TUSB8020B EVM (and datasheet) connect shields together, and to ground using RC filter:    Microchip's  also ties shields together and uses an RC filter, but a 3 orders of magnitude smaller R:    Recommendation 3  Cypess  ties each shield independently to ground using either LC or L filter (chokes really):    The cameras themselves (off the shelf) use Cypress recommendation (LC to ground). The embedded computer seems to tie to ground from visual inspection and checking continuity to ground, but I'm not 100% sure (schematics are not available).  Now we face the shield dilemma with the hub PCB (which by the way currently does not have a metallic enclosure, it is a 3d printed plastic enclosure).   What is your say?


I installed the new version of QGIS 2.16 and I want to import an image (SVG file) as symbol for my point, but the setting style supports only xml format in import. Before, with an older version of QGIS, importing SVG files was possible.  How can I do this in the new version?      if i check svg symbol, I don't have the windows svg groups and images, my screen shot it's different

I've downloaded the SVG icon pack from   Using the Import from URL has never worked for me, so how do I import these symbols into QGIS?   As far as I can tell I need an .XML defining each symbol.


Currently, if a question gets put 'on hold' or is 'closed', the user is asked to edit the question so that it conforms to the website's guidelines.   The problem with this system is that it assumes that moderators are always right. Maybe in the box that says whether a question is 'closed' or 'on hold', there could also be an option to challenge the decision?  If a user wanted to challenge the decision, they would be required to write why they think the decision was wrong and submit it. After it's submitted, the challenge would be sent to a random group of moderators from around the Stack Exchange network.   If they vote that it isn't against the rules, then that would override the original decision.

As a newcomer to StackOverflow, I recently asked my first . I wanted to start with a fairly safe general question, to get the feel for how the site worked. My question was intended to be programming-related, but my original wording was not clear enough, so another user decided to close it.  I've re-phrased my question, and had received one useful answer before the question was closed, but I'm not sure what the procedure is after your question is closed to allow people to post answers again...  I've checked the FAQ and About pages, searched the SO questions, but have had no luck. Could someone point me in the right direction as to how I get my question re-opened, or if it is possible to do at all?


in a bash script i'm using an associative array to create tables, tablespaces, indexes and partitions in my database. this is the script (the main script is too long with complicated queries so i summarize it into something smaller):    #!/bin/bash ##**** definition of variables **** DB2PATH=/bin/db2 DBNAME=mydb SchemaName=customer declare -A tables tables=( [REQUEST]=REQ [RESPONS]=RES [METHOD]=MTH )  for t in "${!tables[@]}" do key=${tables[$t]}  $DB2PATH -x "SELECT HIGHVALUE as LastHighValue FROM SYSCAT.DATAPARTITIONS  WHERE TABSCHEMA='$SchemaName' AND TABNAME='$t' AND  DATAPARTITIONNAME=$key "   done   i changed all of $DB2PATH -x with echo to check the generated commands before execution and i got this output:    SELECT HIGHVALUE as LastHighValue FROM SYSCAT.DATAPARTITIONS WHERE TABSCHEMA='customer' AND TABNAME='METHOD' AND DATAPARTITIONNAME=MTH SELECT HIGHVALUE as LastHighValue FROM SYSCAT.DATAPARTITIONS WHERE TABSCHEMA='customer' AND TABNAME='RESPONS' AND DATAPARTITIONNAME=RES SELECT HIGHVALUE as LastHighValue FROM SYSCAT.DATAPARTITIONS WHERE TABSCHEMA='customer' AND TABNAME='REQUEST' AND DATAPARTITIONNAME=REQ   i defined my associative array with this order REQUEST,RESPONS,MTH but the out put is in reverse order and in my main script the order is REQUEST,RESPONS,MTH but i get this order REQUEST,MTH,RESPONS. in main script there are so much relational commands that connect tables together so it's really important that the commands be executed as the order that is defined in array. why this happens and how i can fix this?

Is there an ordered (by insertion) map in bash?  I know there's an  data structure in bash, but when iterating over it, the order of the elements is not by insertion. Example below.  I'd like to keep the map ordered by insertion.  Associative array not preserving insertion order:  declare -A REPLACE_MAP REPLACE_MAP['b']='2' REPLACE_MAP['a']='1' for key in "${!REPLACE_MAP[@]}"; do     echo "$key - ${REPLACE_MAP["$key"]}"     value=${REPLACE_MAP["$key"]} done   Result:  a - 1 b - 2   I'd like a data structure that will yield the following result:  b - 2 a - 1


$ n,m \in \mathbb{N} $. proof with induction to $m$:  $$\binom{n}{n} + \binom{n+1}{n} + \binom{n+2}{n} + ... + \binom{n+m}{n} = \binom{n+m+1}{n+1}$$  Try to use: for $k < n$ its $$\binom{n+1}{k+1} = \binom{n+1}{k} + \binom{n}{k}$$  Now i have to do the Start of Induction and set for $m$ = 1 because i have to do it to $m$ if im not wrong.  $$\binom{n}{n} + \binom{n+1}{n} = \binom{n+1+1}{n+1}$$  so now in short its:(i think)  $$\binom{n}{n} + \binom{n+1}{n} = \binom{n+2}{n+1}$$  and if i use the rules down i get:  $$1 + \binom{n+1}{n} = \binom{n+2}{n+1}$$  the 1 is because $$\binom{n}{n} = 1$$  but now i dont know how can i go on i hope someone can help.  down below some more Rules:  $ \binom{n}{0}=1 \quad \binom{0}{0}=1 \quad \binom{n}{1}=n \quad \binom{n}{n-1}=n \quad \binom{n}{n-1}=n$  $ \binom{n}{k}= \frac{n!}{k!(n-k)!} \quad \binom{n}{k}= \binom{n}{n-k} \quad \binom{n}{2}=\frac{n(n-1)}{2} \quad \binom{n}{3}=\frac{n(n-1)(n-2)}{6} $  Sorry for my bad english. i try to formulate all understandable.

After reading , the most popular answer use the identity $$\sum_{t=0}^n \binom{t}{k} = \binom{n+1}{k+1}.$$  What's the name of this identity? Is it the identity of the  modified.  How can we prove it? I tried by induction, but without success. Can we also prove it algebraically?  Thanks for your help.    EDIT 01 : This identity is known as the  because, on Pascal's triangle, when the addends represented in the summation and the sum itself are highlighted, a hockey-stick shape is revealed.


How can I calculate polygon area if I have only boundaries lengths? Let check this simple example:  I have all boundaries length from this picture in the following format:  K6-K5: 24.15m K5-K10: 10.54m K10-K7: 23.63m K7-K6: 12.29m  What is suitable approach for calculating polygon area? I think we have only 2 ways:  Calculate current area of above plot, then scaling up Draw a "real polygon" by boundaries lengths, then calculate area on "real polygon"  Is there another approach for getting more suitable and accurate way?

I have only lengths for the sides of an irregular polygon, can anyone tell me how I can measure the area of the polygon? Remember only lengths of all the sides, no angles or coordinates. Few forums mention about trangulation of the polygon etc. But I only have side lengths. Does anybody have any feedback?


A Fermat polynomial is a polynomial which can be written as the sum of squares of two polynomials with integer coefficients. Let $f(x)$ be a Fermat polynomial such that $f(0)=1000$. Prove that $f(x)+2x$ is not a Fermat polynomial.

A polynomial is called a Fermat polynomial if it can be written as the sum of the squares of two polynomials with integer coefficients. Suppose that $f(x)$ is a Fermat polynomial such that $f(0) = 1000$. Prove that $f(x) + 2x$ is not a Fermat polynomial.  What I have done:  Let $p(x)$ be a Fermat polynomial such that $p(0)$ is divisible by $4$. Suppose that $p(x) = g(x)^2+h(x)^2$ where $g(x)$ and $h(x)$ are polynomials with integer coefficients. Therefore $g(0)^2 + h(0)^2$ is divisible by $4$. Since $g(0)$ and $h(0)$ are integers, their squares are either $1 (mod 4)$ or $0 (mod 4)$. It therefore follows that $g(0)$ and $h(0)$ are even. From here, I can not proceed any further. Please help


I'm a beginner at circuits (I'm a high school student interested in electronics), and I'm currently working on a school project about a Magnetostriction Oscillator. The circuit construction is as follows, and I need some help understanding certain aspects of the same.  So from my understanding, the circuit working is as follows:  When the battery is attached a voltage V is supplied to the LC oscillator. Which induces an oscillating flux in the rod: A question I had is that since its a DC supply, won't the capacitor saturate after the time constant is completed, making the induced magnetic field constant (all current directed through L1) The apparently oscillating magnetic field in the rod induces an EMF in L2 - which gets amplified through the BJT and gets fed back into the parallel LC oscillator (is this why it acts as an AC voltage allowing the parallel LC to oscillate??): I get the induced EMF (provided magnetic field is oscillating) - but don't get the amplification. Won't the induced emf/current get amplified and move towards the reference ground node instead of the LC oscillator?? If it does could you please explain why? Any additional help on understanding how the LC circuit oscillates and how the transistor plays a role in the same would be much appreciated!  Thanks a lot!!

Could someone please explain the role of the transistor in this circuit? I have a feeling it has to do with the LC circuit but I'm not sure and don't understand completely. The following is an image of the circuit (the transistor is n-type. It is used in lots of sensors to detect and generate ultrasonic waves.


Is it possible to number tex files? I'm avoiding it now but, I would like to order a list of files (chapters in a book) so that each chapter is easy to find. Will this cause a problem? I have in mind:  aaa_introduction 001_chapter_one.tex 002_chapter_two.tex bbb_backmatter.tex etc.   Mike

What's the best practice for naming LaTeX files?  I know R, Matlab, and Java all differ in their use of ., _, -, camel case, capitalization, etc. What do people generally use for naming LaTeX files? Is this easily portable across systems?  I remember having a HUGE problem interpreting a Matlab program of mine. Turned out that I had named the file in a way that Matlab couldn't handle. To avoid such issues in the future, I'd just like to start naming my LaTeX files using best practices.


Prove the following inequality for $a,b,c,d \in (0,1)$:   $$(1-a)(1-b)(1-c)(1-d) > 1-a-b-c-d$$   I have a problem. I don't know if my idea is good  $a=b=c=d $  $(1-a)^4 > 1- 4a $  So, this is true..

Prove $(1-a)(1-b)(1-c)(1-d)>1-a-b-c-d$ and $ a,b,c,d$ are real and between 0 and 1.    I can do this with $$(1-a)(1-b)>1-a-b  \\ 1-a-b+ab>1-a-b  \\ ab>0  $$  But with $c$ and $d$, this becomes much more difficult. Can someone nudge me in the right direction?


I'm looking for a way to find out what kind of RAM a system has (clocking speed, DDR-X etc.). Is there a specific command for that? I'm only aware of free or lspci which don't offer those things.

How shall I find out the frequency and type of my current RAM? My OS is Ubuntu 12.04.


i am Vietnamese citizens travelling to caribbean islands thru korea to  usa to Caribbean do i need usa transit visa in order to connect to flight in NY to Caribbean

In Europe usually you don't need to go through immigration to change planes (unless you are entering/exiting Schengen). Is it the case in the US as well? May I catch a connecting flight on one of the US airports if I don't have US visa?


I have an ArrayList of words with duplicate entries.  I want to count and save occurrences for each word in a data structure.   How can I do it?

I have an ArrayList, a Collection class of Java, as follows:  ArrayList<String> animals = new ArrayList<String>(); animals.add("bat"); animals.add("owl"); animals.add("bat"); animals.add("bat");   As you can see, the animals ArrayList consists of 3 bat elements and one owl element. I was wondering if there is any API in the Collection framework that returns the number of bat occurrences or if there is another way to determine the number of occurrences.  I found that Google's Collection Multiset does have an API that returns the total number of occurrences of an element. But that is compatible only with JDK 1.5. Our product is currently in JDK 1.6, so I cannot use it.


I came to the UK as a US citizen, got indefinite leave to remain, and have just become a naturalised UK citizen. However, I am scheduled to travel abroad in a few days, and do not have time to apply for a UK passport. If I travel as scheduled, will I be able to re-enter the UK on my US passport (now without the biometric residence permit, which I had to destroy and send in when I became a UK citizen), provided that I travel again within 6 months? Or would I be turned away because I am not really a tourist?

I'm a British National (Overseas), which basically means that while I don't have the right of abode in the UK, I am permitted to visit the UK without a visa. However, my passport has expired, and while it's being renewed, the schedule is a bit tight.  At the same time, I'm an US Citizen, and since I'm only planning to visit the UK, I don't need a visa if I enter on my US passport.  I'm not familiar with UK immigration law, and given that this probably isn't too common a situation, the UK Border Agency website doesn't have an answer that I can can find, nor do they seem to have a contact form that fits my situation, so here's hoping someone knows—given that I'm a British National (Overseas), am I required to enter the UK on my UK passport, or can I just use my (valid) US passport?


I have 2 text files:  $ cat /tmp/test1 "AAP" bar "AEM" bar "AA" bar "AEO" bar "A" bar  $ cat /tmp/test2 "AEM" foo "AAP" foo "A" foo "AEO" foo "AA" foo   I want to sort them  $ sort /tmp/test1 "AA" bar "AAP" bar "A" bar              <-- "A" is in position 3 "AEM" bar "AEO" bar  $ sort /tmp/test2 "AA" foo "AAP" foo "AEM" foo "AEO" foo "A" foo              <-- "A" is in position 5   Why does "A" end up in position 3 in /tmp/test1 and in position 5 in /tmp/test2?  My expectation is that each character per column will be compared.   As such, when comparing column 3, 'A', 'E' and '"' will be compared against each other, and this would be the ultimate determinant in the final sort order of this test data.  Clearly my expectation is wrong, so how does sort work, if not in the way I expected?  Is there command line option to sort or some other utility I can use to get the sort order I desire?

I have some trouble to understand what is happening here:  [guido@localhost 9]$ ls -1 Star\ Wars\ Episode\ * Star Wars Episode II Attack of the Clones.avi Star Wars Episode III Revenge of the Sith.avi Star Wars Episode I The Phantom Menace.avi Star Wars Episode IV A New Hope.avi Star Wars Episode VI Return of the Jedi.avi Star Wars Episode V The Empire Strikes Back.avi   III\b before I\b, but II\b before III\b? Whatever is causing this, it is not behaving consistently. This is also the same sorting result I get in the GUI. I checked all the blanks are actually blanks, and there are no case difference among the filenames. How can it be? Is it skipping the roman numeral, and trying to sort after it?  Other tests:  [guido@localhost 9]$ find -name "Star Wars *" -print ./Star Wars Episode I The Phantom Menace.avi ./Star Wars Episode II Attack of the Clones.avi ./Star Wars Episode III Revenge of the Sith.avi ./Star Wars Episode IV A New Hope.avi ./Star Wars Episode V The Empire Strikes Back.avi ./Star Wars Episode VI Return of the Jedi.avi   But:  [guido@localhost 9]$ find -name "Star Wars *" -print | sort ./Star Wars Episode II Attack of the Clones.avi ./Star Wars Episode III Revenge of the Sith.avi ./Star Wars Episode I The Phantom Menace.avi ./Star Wars Episode IV A New Hope.avi ./Star Wars Episode VI Return of the Jedi.avi ./Star Wars Episode V The Empire Strikes Back.avi   While:  [guido@localhost 9]$ find -name "Star Wars *" -print | sort -f ./Star Wars Episode I The Phantom Menace.avi ./Star Wars Episode II Attack of the Clones.avi ./Star Wars Episode III Revenge of the Sith.avi ./Star Wars Episode IV A New Hope.avi ./Star Wars Episode V The Empire Strikes Back.avi ./Star Wars Episode VI Return of the Jedi.avi   I don't think my locale may be affecting this (I also set it to en_US.utf8 anyway) as the doc suggests. What am I missing?  [guido@localhost 9]$ sort --version sort (GNU coreutils) 8.22


I'm very new to ACL, and at the moment I've been trying to set up a shared folder such that any user belonging to a certain group (lets call it "thegroup") can have full access to the folder (which includes read, write, execute, and "creation" of files). When a user belonging to a group creates a file, the ownership should be automatically set to the user as well as "thegroup", and the file should be accessible in every single way by other members of the "thegroup". I'm not sure what the user ownership of the folder should be called so I just decided to set it to root.   I've been following the instructions here but so far I can only list the files located in the directory as a normal user. I do not have read, write, or creation capabilities after doing the following commands:  mkdir folder setfacl -m u:root:7 folder setfacl -m -d u:root:7 folder setfacl -m g:thegroup:7 folder setfacl -m -d g:thegroup:7 folder   From what I understood, by setting the default ownership all the files that are created inside the folder should inherit the parent folder's permission, right? However, this doesn't seem to be the case.  Is there something I'm missing?  Note: the debian manual mentions that for each user that I want to add access to I have to explicitly add him to the ACL. I'm trying to avoid this by simply adding the user to a group, and then giving the group full access to the folder. Is this possible with ACL, or do I have no choice but to manually specify every user that's going to access the folder?

I want to set a folder such that anything created within it (directories, files) inherit default permissions and group.    Lets call the group "media".  And also, the folders/files created within the directory should have g+rw automatically.


I just upgraded to Windows 8.1, and immediately I notice that unless I deliberately wind up and "slam" my mouse cursor against the edges of my screens, it gets stuck on the last pixel before crossing. I'm guessing this was in response to people who had a hard time using the charms with a mouse in Windows 8.0. Dealing with Windows 8.0's single-pixel traps in the corners was annoying enough! I don't want to have a chug a five-hour energy every day just to use a multimonitor workstation.     Things like this seem to commonly have a setting somewhere, be it in the control panel, the registry, some group policy thing, or elsewhere. I'm at a loss so far. How can I stop windows from grabbing my cursor?

In windows 8.1 and below, the mouse would seamlessly move through all my monitors.  However, in windows 8.1 update 1 the mouse needs to be going at a certain speed before it goes to a different monitor. How do I disable this?  A google search has turned up nothing, so I'm not sure what exactly is going on


I have some filenames as such.  a2.txt.gz d12.txt.gz k5.txt.gz m4.txt.gz ...   one character followed by 1 or 2 numbers followed by .txt.gz. I would like to add single numbers with a zero before the number like below.  a02.txt.gz d12.txt.gz k05.txt.gz m04.txt.gz ...   I tried something like this but it doesn't seem to work.  find . | grep -E "[a-z][0-9]{1}\.+" | sed -er s/\([a-z]\)\([0-9]{1}\)\(.txt.gz\)/\10\2\3/   My logic was to first grep single digit filenames, then split into 3 parts character, number and .txt.gz and then add add 0 before number. But I can't get it to work. And I am not sure about the rename part.

I have a directory of files such as:  file.1.png file.2.png … file.10.png … file.1000.png file.1001.png …   How can I pad the number to 4 digits? It should end up like this:  file.0001.png file.0002.png … file.0010.png … file.1000.png file.1001.png …


My wall plate won't come off - I've removed the screw on it, I can force the bottom part away from the wall as shown in the picture, but it seems there is some attachment behind the the top part. Has anyone run into this kind of wall plate? How should I remove the wall plate from the wall? (I need it come off so that I could check the wiring - Originally it was used as a phone jack, now I would like to ).

I'm amazed how complicated this wall plate is to remove. It is made of plastic and accommodates a phone jack and a coaxial cable. Please see the images that accompany this question. I've searched it thoroughly and there are no tabs anywhere on the face or edges to press in. There are no screws. I've pulled on it pretty hard, hoping that it would pop off, but if I pulled any harder it surely would break. Of course, I had the coaxial off while I tried to remove the plate. The brand name on the phone jack part is "KRONE". Has anyone seen a wall plate like this? If so, how do you remove it? I have to say, I'm absolutely blown away by how ridiculously difficult this is. Any help would be appreciated.


I have been looking at certain Taylor expansions of the exponential function $$ e^{iy} = 1 + iy + \dfrac{\theta_1 y^2}{2},$$ $$ e^{iy} = 1 + iy - \dfrac{y^2}{2} + \dfrac{\theta_2|y|^3}{3!},$$ which hold for any real number $y$ with some $\theta_1=\theta_1(y)$, $\theta_2=\theta_2(y)$ such that $|\theta_1|\leq 1$ and $|\theta_2|\leq 1$. Could anyone explain how one gets to both? and if their is a general rule one should consider. Thanks!

How to show the expansions \begin{gather*} e^{iy} = 1 + iy + \frac{\mu_1 y^2}{2}\\ e^{iy} = 1 + iy - \frac{1}{2}y^2 + \frac{\mu_2 |y|^3}{3!} \end{gather*} where $y \in \mathbb{R}$ and $|\mu_1| \leq 1$ and $|\mu_2| \leq 1$ for all $y$?  I attempts to consider the remainder of Taylor expansion of one real-variable function: $e^{iy} = \cos y + i\sin y$, and their Taylor expansions with Lagrange remainders are \begin{gather*} \cos y = 1 - \frac{y^2}{2}\cos (\theta_1 y) y^2\\ \sin y = y - \frac{1}{2}\sin (\theta_2 y) y^2 \end{gather*} So we may put $\mu_1 = -[\cos (\theta_1 y) + i \sin (\theta_2 y)]$. But here we only have $|\mu_1| \leq 2$, which does not satisfy the requirement...  Any help will be appreciated!


I am using ubuntu 14.04, kindly assist how to install drivers for my ATI Radeon graphics card [Mobility Radeon HD 5650/5750 / 6530M/6550M].  I read some documentation on the given site but I am not sure if I really need to do all this.

I am planning on doing a fresh install of Ubuntu and want to know what is the correct way to install ATI Catalyst Video Driver?      There are multiple valid answers for this question spanning over several versions of Ubuntu. For your convenience an index of each below:


I stumbled upon  problem and thought I would try to finish it (it did not get answered in the previous post), but the part with $n$ a power of two seems rather tricky. The problem is as follows:     Let $a$ and $n$ be positive integers with $a > 1$. Prove that, if   $a^n+1$ is a prime number, then $a$ is even and $n$ is a power of $2$.   Suppose $a$ is odd. Then $a=2k+1$ and therefore $a^n+1$ is even, hence not a prime. So $a$ must be even.  Now, by way of contradiction, suppose that $n$ is a power of $2$ but $a^n+1$ is composite, i.e. $$a^n+1=mk$$ for some integers $m,k$. Then $a^n=mk-1$, and since $a \mid a^n$, we must have $a \mid mk-1$. Hence $ak'=mk-1$, or $ak'+1 =mk$. I was hoping this would land a contradiction, but I can't seem to find it.  I also tried proving by contrapositive, i.e. assuming that $n$ is not a power of two and then showing that it wasn't a prime, but this did not seem to bring about much.  Any ideas?

A little bird told me that if $2^n+1$ is prime, then $n$ is a power of $2$. I tend not to trust talking birds, so I'm trying to verify that statement independently.  Suppose $n$ is not a power of $2$. Then $n = a \cdot 2^m$ for some $a$ not a power of $2$ and some integer $m$. This gives $2^n+1 = 2^{a \cdot 2^m}+1$. Now I suspect there's a way to factor that, but I don't see how. Can someone give me a hint?


jovan@jovan-HP-ProBook-4540s:~$ sudo apt-get install skype 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: skype : Depends: skype-bin  E: Unable to correct problems, you have held broken packages.

I want to install Skype, but I can't locate it in Software Center or by using Synaptic Package Manager. Can anyone help me?


This has always baffled me.  There is no absolute speed as I understand(or is there)?  Speed is a relationship between two objects.  So how can you calculate how much time slows down for an object based on its speed without specifying which other object you are relating it to?  Also, since the selection of the object you are relating it to is totally arbitrary how can the answer have any meaning at all?

I can't get something strait... Lets use the usual example: A man is flying away from earth on a very fast spaceship. So, His time is now not moving in the same "speed" like earth time but slower. But why do we say that the man is moving faster than earth? why is it not that earth is moving faster than the man? I mean, it's not like there is a direction that if you move that way then you are faster and the other way means you moves slower.  So, how can we assume that's time is moving slower for the man and not on earth?  Maybe the man is flying the "other" way and now he is slower than earth...  If the man is not accelerating than it could appear to him that earth is moving fast and he is stationary... isn't it?  So, I can sum it as: In relation to what do we say that something is faster than some other thing?  Thanks!


I have a question about how long it might take to program a piece of software that creates electronic circuit schematics and stuff. In order to answer the question, one needs to know how logic gates are built and how multiple levels of algorithmisation can save a lot of time and effort. Should I ask on , , or ?

There seems to be more than a few computer science/programming Stack Exchange networks (is that the correct term?). Stack Overflow, being the first, has by far the most users, questions, and answers.  What is the reasoning for creating the others, and are there clear guidelines for which kinds of questions should be posted? I can see a large amount of potential overflow, many cases of people not getting a good answer to their question, because the person who has the answer isn't browsing that particular network at the moment.  I understand that they were probably created for organizational purposes, but wouldn't it almost make more sense to just have them as categories under Stack Overflow, keep them separated but still connected, instead of making people have to create multiple 'account's, one for each network?  I am sure there was a very good reason to break them up, but as someone that is new to SE, it can be somewhat intimidating to decide which one to post in to ensure you get a good answer. For example, if I am a computer science student, my first instinct might to be to post in the computer science network, until I see that it literally has 1% of the users as the Stack Overflow network, which still seems to be for programming/computer science related questions.  So my second instinct would then to be to post it into the Stack Overflow site on the basis that I have a significantly higher chance of my question being seen and getting a good answer. Then I notice that there is also a 'programmers' network, and I don't even begin to know where that fits in. I, and I am assuming most people, will probably just post on Stack Overflow to be safe.  My question is, other than the short little description blurb of each one, is there a clear cut set of guidelines which what each network is intended for, what kinds of questions should go to each one, and is anything being done to encourage people to post in these newer, smaller (more specialized?) networks as opposed to just posting in big daddy Stack Overflow?  Now again, this is for computer science/programming/"why isn't this code doing what I want?" related questions, I am not saying that if I had a question about Linux or WordPress or something I would have the same confusion.


I am trying to install Windows 10 (64 bit) OS in Virtualbox in Ubuntu 16.04. When I run the setup from virtual box to install Windows 10, it hangs at the Windows logo screen and never proceeds further and shows NO error messages. Check the screenshot  What's the problem here?

I've installed VirtualBox using the Software Centre and I'm running a system on Ubuntu 14.04 with 8gb RAM, 64-bit dual core processor.  I want to run Windows 10, I've tried both 64 and 32 bit versions, in virtualbox. However, every time I start up windows 10 it gets to the point where the dots go round in a circle, then it freezes up and crashes back to the virtualbox manager. The only information it gives me is that the virtual machine was aborted.  I've changed the settings around a lot and nothing is working.  Any help would be appreciated.  Oh, and I've run Windows 10 technical preview on this machine before, a while ago  Thanks for any help in advance.


I saw a question yesterday asking about civilian starships and shields, and that reminded me of another question I had. Is every starship supposed to have blasters, or some kind of weapon on them? Or do only certain ships have weapons?

First things first, let's just pretend the hyperspace ramming in the Last Jedi didn't happen, because hyperspace ramming means every FTL-capable vessel in the galaxy is a deadly weapon capable of destroying star destroyers, making this thread irrelevant.  Okay, so according to Wookieepedia, Han Solo won the Millennium Falcon . This explains how he was able to afford the ship. The Falcon is a . Wookieepedia defines freighters as such:      A freighter, cargo ship, or barge was a kind of spacecraft used for   hauling cargo from one place to another. Although light freighters   could usually hold their own in combat against other fighter craft,   larger vessels tended to be less capable. These large freighters could   be easy targets considering their large size, slow speed, and weak   armament. For this reason most heavy freighters required escorts when   navigating more dangerous regions of the galaxy.   This is troubling; does this mean civilians are allowed to pilot spacecraft mounted with weapons capable of destroying other vessels? Spaceships can't be cheap, and I'm assuming Han has some sort of title and registration for the falcon, but in the real world most vehicles much bigger than an RV are owned by organizations, and in the case of naval vessels owned by shipping companies, merchant marines, or part of a country's fleet. With that comes all sorts of regulations, licensing fees, ID numbers, permits...   So what is Han Solo's official job title? We all know he's a smuggler, but that implies that his "official" job is something like cargo shipper or merchant. Or does he fly under the radar at all times, running from every authority he sees? What about other private vessels? Wookieepedia makes it clear that other freighters are allowed to have weapons mounted on their ships.   In the past during wartime private vessels were temporarily allowed to be mounted with weapons (), but that was an exceptional time (although granted the original trilogy does take many cues from WWII). Yes, armed guards with small arms are allowed, though expensive (, )... but ship-mounted weapons are a different story (, ). but what is the rationalization for a private spaceship like the Millennium Falcon being outfitted with weaponry capable of shooting down a pursuing fleet of Imperial Tie Fighters (the equivalent of fighter jets attacking a merchant freighter)? This "freighter" took out a Death Star for crying out loud.   My guess is it's allowed because of space pirates or the difficulty of maintaining law in the vast reaches of space, but then again, you'd think the Empire wouldn't allow much leeway considering their greatest threat is a massive covert rebellion and all. It seems like it would make more sense for freighters to be escorted or dangerous areas patrolled by the Empire.   I'm writing a sci-fi story of my own so it would be nice to know if there is a decent explanation other than "because it's cool." Example from sci-fi works other than Star Wars are welcome as well.


Hi i get a weird segmentation fault from this code:  int main(void){    int array1[10000000];    int n = sizeof(array1);    printf("%d \n", n );      return 0; }   However if i change   int array1[10000000];   to  int array1[1000000];  ( one less zero)   The program works and prints 4000000  I'm running it on Fedora 21(64bits)  Is this because there is a maximum size for array in C?  Thank you in advance

The following code is generating a stack overflow error for me  int main(int argc, char* argv[]) {     int sieve[2000000];     return 0; }   How do I get around this? I am using Turbo C++ but would like to keep my code in C  EDIT:  Thanks for the advice.  The code above was only for example, I actually declare the array in a function and not in sub main.  Also, I needed the array to be initialized to zeros, so when I googled malloc, I discovered that calloc was perfect for my purposes.  Malloc/calloc also has the advantage over allocating on the stack of allowing me to declare the size using a variable.


I have a DLL file that contains a class that I want to use inside of my c# script in a unity project. I recently searched about dlls and learned to create dlls and use them inside c# this is the way i use the dll import attribute to import a method from a dll and use it inside of c# private const string dll= "MyDllFile";  DllImport(Dll, CallingConvention = CallingConvention.Cdecl)] static extern float percent(float percent, float of);  The main dll file that i want to work on has a custom class called Factory and i want to make an instance of that class which is inside of a dll file in my c# script. since i don't have the factory class in my c# project, i can not write something like DllImport(Dll, CallingConvention = CallingConvention.Cdecl)] private static extern factory(string name);  Factory factory = Factory("myFactory");  This won't work because Factory class is a custom class. the factory() in the dll file, returns an instance of Factory class. Any help would be appreciated.

I have a dll that was written in c++, I need to use this dll in my c# code. After searching I found that using P/Invoke would give me access to the function I need, but these functions are defined with in a class and use non-static private member variables. So I need to be able to create an instance of this class to properly use the functions. How can I gain access to this class so that I can create an instance? I have been unable to find a way to do this.   I guess I should note that the c++ dll is not my code.


This is a problem in my graph theory class and I'm unsure about how to solve it..  Let $X$ be the set $\{1,2,\dots,mn\}$. Suppose we partition $X$ into $m$ sets $P_1,\dots,P_m$, each of size $n$. Suppose we choose another partition $Q_1,\dots,Q_m$, each of size $n$. Show that the sets $P_i$ can be renumbered so that $P_i \cap Q_i$ is non-empty for every $i$.  Thanks in advance! Edit: I'm attempting to use Hall's Marriage theorem to solve this but I'm struggling with formulating the solution in a way that would get me to my answer.

I have been wrestling with an exercise concerning latin squares from the textbook A First Course in Discrete Mathematics by Ian Anderson. The exercise is formulated thus:     A set $S$ of $mn$ elements is partitioned into $m$ sets of size $n$ in     two different ways: $S = A_1 \cup ... \cup A_m = B_1 \cup ... \cup   B_m$. Show that the sets $B_i$ can be relabelled so that $A_i \cap B_i   \neq \emptyset$ for each $i = 1, ..., m$. [Hint: consider the sets   $S_i = \{ j : A_i \cap B_j \neq \emptyset\}$.]   I am not sure how to prove this. Here is an example I have completed:  Let $S = \{1,...,25\}, m = 5, n = 5$ and let $$(s_{mn}) =  \begin{pmatrix} 1 & 2 & 3 & 4 & 5 \\ 6 & 7 & 8 & 9 & 10 \\ 11 & 12 & 13 & 14 & 15 \\ 16 & 17 & 18 & 19 & 20 \\ 21 & 22 & 23 & 24 & 25 \end{pmatrix}$$.  Furthermore, let $$A_1 = \{1,6,11,16,21\}, A_2 = \{2,7,12,17,22\}, A_3 = \{3,8,13,18,23\}, A_4 = \{4,9,14,19,24\}, A_5 = \{5,10,15,20,25\}. $$  $$B_1 = \{1,2,3,4,5\}, B_2 = \{6,7,8,9,10\}, B_3 = \{11,12,13,14,15\}, B_4 = \{16,17,18,19,20\}, B_5 = \{21,22,23,24,25\}.$$  Furthermore, $S_1 = S_2 = S_3 = S_4 = S_5 = \{1,2,3,4,5\}$.  I can e.g. relabel the $B_i$s so that $B_1$ becomes $B_2$ etc. and $B_5$ becomes $B_1$ and thus get:  $$(s_{mn}) =  \begin{pmatrix} 21 & 22 & 23 & 24 & 25 \\ 1 & 2 & 3 & 4 & 5 \\ 6 & 7 & 8 & 9 & 10 \\ 11 & 12 & 13 & 14 & 15 \\ 16 & 17 & 18 & 19 & 20 \\ \end{pmatrix}$$.  Then the condition $A_i \cap B_i \neq \emptyset$ still holds for each $i = 1,...,m$.  I guess I in some kind of way have to use Hall's theorem:     The sets $A_1,...,A_m$ possess an SDR if and only if they satisfy the Hall condition.


i got this error when i tried to implement Circular Reveal Effect. Does anyone have an idea?  private void ChooseFile() {      int cx = (mRevealView.getLeft() + mRevealView.getRight());         int cy = (mRevealView.getTop() + mRevealView.getBottom())/2;    // int cy = mRevealView.getTop();      int radius = Math.max(mRevealView.getWidth(), mRevealView.getHeight());

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


This screenshot says it all:  I am on ELL.SE, opening a recent notification in top frame.  The notification is about a Badge received on Linguistics.SE site.  The icon apparently belongs to the theme of ELL.SE, while it must be from the theme of Linguistics.SE.

It's so cool that the notification reminds you of the colour of badge you've earned. But I am a little puzzled by the symbols:      Is it feasible to use the symbol from the earned site? At the moment it uses the symbol from the site I happen to be on (as you can see by looking to the left of the dropdown in each case.)


And is Waterloo the right station for a train to Corbridge?  (They need to come into London first to do some on-arrival shopping and to store a bag they won't need until they get back to London, so I think that does mean finding a "central" station...)

My wife and I will be arriving in London via Heathrow Airport (LHR) and are staying at a hotel near King's Cross station. So, we were wondering what the best (which means fastest but also easiest when carrying two large pieces of luggage and two carry-ons) way to get from LHR to King's Cross?  I gather that, with only one changeover, we can take the Tube. However, in the interest of other passengers, we thought it would be best to take a taxi, or maybe a bus?  Thoughts?


My friend just told me, That i could have more than one desktops in Ubuntu and then choose which one to use when the Ubuntu starts up and goes to login screen. I have Ubuntu 12.10 and i think my default desktop is unity, so can i have gnome desktop and more desktops? And if so, How and where to install them and how to use them?

I am using Ubuntu 12.04. I want to try out KDE and other desktop environments.   But I'm not sure if I'll like them enough to switch permanently. I want to be safe and make a transition in a piecemeal fashion.  Is it possible to install KDE on Ubuntu and yet not do away with the default Unity shell?  Could I install multiple desktop environments and switch between them by tweaking some startup configuration and then rebooting?


It is one of the most odd behaviors I've stumbled in my JavaScript learning,   this is example:  function multiplier(factor) {   return function(number) {     return number * factor;   }; }  var twice = multiplier(2); console.log(twice(5)); // → 10   this is an example taken from the book , the author explained it in a confusing way, that makes it more odd:     In the example, multiplier returns a frozen chunk of code that gets   stored in the twice variable. The last line then calls the value in   this variable, causing the frozen code (return number * factor;) to be   activated. It still has access to the factor variable from the   multiplier call that created it, and in addition it gets access to the   argument passed when unfreezing it, 5, through its number   parameter.   Could anyone explain how the second call of multiplier function in twice()  assigned the parameter to the nested function, and what if there were more nested function, what is the concept and the rule for this?

How would you explain JavaScript closures to someone with a knowledge of the concepts they consist of (for example functions, variables and the like), but does not understand closures themselves?  I have seen  given on Wikipedia, but unfortunately it did not help.


Here is my header file:  class MapObject: public ScreenObject {     static float xoffset, yoffset; public:     static float Getxoffset() {         return xoffset;     }  };  #endif // MAPOBJECT_H   However on the line return xoffset; I get the following error: undefined reference to `MapObject::xoffset' why?

Can anyone explain why following code won't compile? At least on g++ 4.2.4.  And more interesting, why it will compile when I cast MEMBER to int?  #include <vector>  class Foo {   public:       static const int MEMBER = 1;   };  int main(){       vector<int> v;       v.push_back( Foo::MEMBER );       // undefined reference to `Foo::MEMBER'     v.push_back( (int) Foo::MEMBER ); // OK       return 0; }


I have an object like these  var itemlist= {"50271":2,"50025":1,"90012":3}1   It indicates the reagent to include in a mixture. The property name is the ID of the reagent and the property value the quantity. I would like to generate HTML to display the reagents of a mixture as follows   x 2  x 1  x 3   How can I loop the object to get my expected output?

How do I enumerate the properties of a JavaScript object?  I actually want to list all the defined variables and their values, but I've learned that defining a variable actually creates a property of the window object.


I have two Red Hat 7 Linux servers that I want to keep user accounts synced. I have a bash script that copies these files between servers: /etc/passwd /etc/shadow /etc/group /etc/gshadow /etc/subuid /etc/subgid The script is run from a cron job every 5 minutes on each server, the problem is, how do I make sure only one server runs the script? I was thinking of adding a test into the script running stat on /etc/shadow and if the file modify time is not within the last 5 minutes exit the script. Since the modify time is copied over with the file the second server would also then run the copy script, which I don't want. Is there a better method of doing this?

Dealing with hundreds of RHEL servers, how can we maintain local root accounts and network user accounts? Is there an active directory type solution that manages these from a central location?


Is there any general formula to sum following series:  $$S = 1^1 + 2^2 + 3^3 + \dotsb+(n - 1)^{n - 1} + n^n, n \in N$$  I mean for $S = f(n)$, is there a formula to compute $f(n)$?

Is there a way of finding a formula for $\sum\limits_{k=1}^n k^k$? Maybe I'm missing something really obvious, but I've looked around a bit on the Internet and I haven't been able to find anything.  So, what I'm looking for is a formula in closed form to generate the sequence $1,5,32,288,3413,\dots$


What is the best practice of keeping past data in the database? For example lets say we have transaction tables like AttendanceTrans, SalaryTrans in a payroll solution. So every month we have to insert hundreds or thousands of new records to these tables. So all the past and current data in same table.  Another approach would be to keep  AttendanceHistory and SalaryHistory tables. So that end of every period (month) we empty the Trans tables after coping the data to respective History tables.  When considering factors like performance, ease of report generation, ease of coding and maintenance,  what would be the optimum solution?   Note : RDBMS is SQL Server 2008 and programming environment is .NET (C#)

I'm trying to determine how I should store historical transactional data.  Should I store it in a single table where the record just gets reinserted with a new timestamp each time?  Should I break out the historical data into a separate 'history' table and only keep current data in the 'active' table.  If so, how do I best do that?  With a trigger that automatically copies the data to the history table?  Or with logic in my application?  Update per Welbog's comment:  There will be large amounts of historical data (hundreds of thousands of rows - eventually potentially millions)   Primarily searches and reporting operations will be run on the historical data.  Performance is a concern.  The searches shouldn't have to run all night to produce results.


I ran a logistic glm using the following code: model10<-glm(Info_Choice~A*Group+C*Group+D*Group,data=database,family=binomial(link="logit")) summary(model10)  Info Choice is binary (0 or 1) and Group is binary (C or S). Reference group for Info Choice was 0. Reference group for Group was C.  A, B, and D are continuous variables. My output was: Coefficients:                  Estimate Std. Error z value Pr(>|z|)     (Intercept)      -0.33179    0.05155  -6.437 1.22e-10 *** A                 0.22279    0.05434   4.100 4.13e-05 *** GroupS            0.33019    0.06961   4.744 2.10e-06 *** C                 0.12254    0.05716   2.144    0.032 *   D                 0.28853    0.05645   5.111 3.21e-07 *** A:GroupS         -0.07168    0.07308  -0.981    0.327     GroupS:C         -0.04923    0.07588  -0.649    0.517     GroupS:D          0.03666    0.07606   0.482    0.630     How do I interpret the interaction results? I am confused by the negative coefficients.

I am conducting a correlation study and have developed a logit model. I would like some help interpreting the interaction variable's coefficient.  The coefficient of the interaction term smoking*female, where female =1, is 0.16   How can I interpret this?


I created a div container which contains a div for image and a div for text. The parent div's height is set to text div's height automatically. I don't want to set a actual height to the container. What I want is to center the image div vertically in the container, and when I changing the window size horizontally, the image will also change its size, but still at the middle of the container. How should I do?  I've tried 'table-cell', 'inline-block', 'vertical-align: middle', 'position: absolute' methods, but they didn't work.  <!DOCTYPE html>       <title>test</title>

Heading

                 Bacon ipsum dolor amet leberkas pancetta porchetta tenderloin ground round, shoulder doner. Ribeye corned beef ground round tri-tip chicken kevin. Shankle burgdoggen ham hock t-bone brisket jowl pork chop tongue pork belly jerky ham tail venison. Filet mignon porchetta short loin swine fatback, turducken meatball ham hock tongue corned beef pancetta hamburger boudin tenderloin burgdoggen.

                 Strip steak landjaeger ham hock, pig picanha cow beef ribs drumstick prosciutto ball tip chicken cupim tongue salami. Cupim flank kielbasa, strip steak pork buffalo boudin. Turducken meatball sausage short ribs bacon pig venison t-bone hamburger. Strip steak alcatra boudin burgdoggen cupim. Leberkas frankfurter swine prosciutto hamburger ball tip.

                 Cupim buffalo pork loin, pork chop picanha corned beef turkey sausage cow chuck ham hock flank. Pork belly frankfurter meatloaf andouille spare ribs jowl leberkas venison salami capicola sausage kevin chuck. Flank beef ribs fatback, strip steak bresaola turducken biltong salami boudin tongue spare ribs pastrami shoulder frankfurter cupim.

    *{     box-sizing: border-box; }  .container{     padding: 0 5vw;     overflow: auto; }  .img{     width: 25%;     float: left; }  .img>img{     width: 100%; }  .text{     width: 75%;     float: left;     padding: 0 0 0 2em; }

I want to center a div vertically with CSS. I don't want tables or JavaScript, but only pure CSS. I found some solutions, but all of them are missing Internet Explorer 6 support.
Div to be aligned vertically
   How can I center a div vertically in all major browsers, including Internet Explorer 6?


I happened upon  question, where the questioner commented on every answer with "I'd love an up vote!"    Is it correct to flag such clutter, perhaps as not constructive / off-topic, or is there a better way to correct users that beg for up votes (and similar behavior) via comments.

Is begging for upvotes looked down upon in the SO/SE community?


I need to know if this two sentences have different meaning a) The client has been telling us that the site is likely to be around the Krakow area. B) The client has told us that the site is likely to be around the Krakow area

I have studied "present perfect" and "present perfect continuous" for a week. I know forms, verb and helping verb I should use when I write them.  For me, they have nearly same definition because I can use them interchangeably in Thai language. (My native language)  For example, the sentences        I have learned English language in the past few weeks.    I have been learning English language in the past few weeks.       have no difference in meaning to me. They both mean "I began learning the English language in the past and I am still learning it"  Can I use them interchangeably in English? Or is there any difference between them? For example, when should I use present perfect but not present perfect continuous?


My current layout looks like this:  \documentclass[12pt, onecolumn]{revtex4}    \tableofcontents  \section*{Acknowledgements} \section{Chapter 1} \section{Chapter 2} \section{Chapter 3} \section{Chapter 4} \section{Chapter 5} \section*{Appendix}   How do I remove the * sections (Acknowledgements and Appendix) from the contents page?  Although this question has been asked, I can't find a reasonable answer.

I'm having a problem with REVTeX adding unnumbered sections to my TOC. Here's a small example:  \documentclass[]{revtex4-1} \usepackage{lipsum}  \begin{document}  \tableofcontents \newpage  \section{Numbered section} \lipsum \section*{Unnumbered section} \lipsum  \end{document}   Outputs the following:   Contents page:  Body:   Is this a bug? Is there a problem with my installation?   The unnumbered sections are not there if I use a different document class (e.g. article).


There are many instructions on how to enable autologin on various Ubuntu-based distros. However, I couldn't find a solution explicitly for Lubuntu 16.04 LTS with LightDM.

How to allow an account to login at the greeter without typing the password in Lubuntu 16.10?  I think I remember that worked in Ubuntu but I have not found a way to make that work in Lubuntu  GUI Try 1  I tried the gui way: "user & groups" -> change password -> [check] "don't ask password on login". And then reboot computer.  That doesn't work. The lightdm gtk greeter surely doesn't ask for a password for the user (let's say it is called user2), but then after I click ok, then the hard disk run for a while and then I go back to the login in screen again.  Original Config  /etc/lightdm/lightdm.conf:  [SeatDefaults] # Check https://bugs.launchpad.net/lightdm/+bug/854261 before setting a timeout user-session=Lubuntu greeter-session=lightdm-gtk-greeter allow-guest=false   Config File Try 1  I undo the gui try. Added the following lines to /etc/lightdm/lightdm.conf.d/20-lubuntu.conf, which was empty before I added these lines.  [SeatDefaults] user-session=Lubuntu autologin-user=user2 autologin-user-timeout=delay   I reboot the computer, and find that I still need to password to login at lightgreeter.  Config File Try 2  I undo other changes to the configuration files. Undo the gui try. I followed   Add the following lines to /etc/lightdm/lightdm.conf  [Seat:*] pam-service=lightdm pam-autologin-service=lightdm-autologin autologin-user=user2 autologin-user-timeout=0   After that I reboot the computer. Still need password to login.  Config File Try 3  I undo other changes to the configuration files. Undo the gui try. I followed   add the following lines under the existing section [SeatDefaults] to  /etc/lightdm/lightdm.conf,  autologin-user=user2 autologin-user-timeout=0 user-session=Lubuntu greeter-session=lightdm-gtk-greeter   After that , I reboot the computer. Still need password for login.  Config File Try 4  I undo config file try 3, and didn't use the gui try. I back up /etc/lightdm/lightdm.conf to /etc/lightdm/lightdm.conf.orig and then replace /etc/lightdm/lightdm.conf with 's config file:  [Seat:*] autologin-guest = false autologin-user = user2 autologin-user-timeout = 0  [SeatDefaults] allow-guest = false   After that, I reboot the computer. Still need password to log in as user2 at the greeter.  New Account (Workaround 1)  I create a new account called user3. When I create it I choose not to encrypt homefolder, I also choose to login automatically before I actually log into the account. After that, automatic login on the account seems to work, so far.  I can try to replicate everything I did for user2 at the user3 account. But ideally, I should just click the checkbox for user2, and make autologin work for the existing account...  Summary  I don't know why only the gui way changes the behavior of the greeter (it makes the greeter doesn't ask for a password, but it also doesn't let me login. I certain hear some hard-disk noise for a few seconds though.).


What I feel confused is that:  For example, if $\{x^n|x\in F \}$ is normal, then the reduced word $yx^ny^{-1}\in \{x^n|x\in F \}$, How could it be possible?  This is also the exercise 3 on page 68 of Hungerford's textbook Algebra.

How can I prove that, if we have a group G, then subgroup of G generated by all n-th powers of elements from G is normal subgroup of G?


Assume we have a non empty, open convex set $ K \subseteq \mathbb{R}^d $. Then $\overline{K}$ is also convex. How can we prove that statement? I thought that breaking it into cases would help. If $x,y \in int(K)=K^o$ then from hypothesis the statement holds. If $x \in K^o $ and $y \in \partial K$ then from a theorem of my notes :P means $[x,y) \in K $. I have stacked how to show it with details that for each $x,y \in \overline{K}$ then $[x,y] \in \overline{K}$

Today I was going through my text book exercise and got hold of the following question.     Let $X$ be a normed linear space with norm $\lVert\cdot\rVert$ and $A$ is a non empty convex subset of $X$ then prove that $\operatorname{Closure}(A)$ is also a convex subset of $X$.   I gave it a try but could not succeed.


global class Batch_Class implements Database.Batchable<sObject>{      public String Field;     public String Query;     public String Value;      public Batch_Class (String f, String q, String v){          Field = f;         Query = q;         Value = v;      }     global Database.QueryLocator start(Database.BatchableContext bc){             return Database.getQueryLocator(Query);         }              global void excute(Database.BatchableContext bc,List<Account>scope){          for(Account a: scope){             a.put(Field,Value);          }         update scope;     }     global void finish(Database.BatchableContext bc){}  }

Here is my complete code sample   global class b1 implements Database.Batchable<sObject> {   global final string query;  global final string s_object;  global final string field;  global final string field_value;   global b1 (string q, string s, string f, string v){        Query =q;        s_object=s;        field = f;       field_value =v;    }    global Database.QueryLocator start (Database.BatchableContext BC){   return Database.getQueryLocator (query);   }    global void excute(Database.BatchableContext BC, List<sObject> batch) {   for(s_object o= batch){   o.put(field,field_valu);    }   update batch;   }     global void finish(Database.BatchableContext BC){    } }


Sometimes, when I try to edit a question that I encounter in the Low Quality Posts review queue, I am unable to. Specifically, the standard edit page opens, but I am unable to actually edit the text in the box, though I can still select it. As far as I can tell, this only happens when I click the edit button in the low quality posts queue, and even then only happens about 10% of the time.

Basically when reviewing a low quality post, if I choose to edit the item, I cannot move the cursor by clicking in the textarea. The keyboard is working fine, but any mouse interaction appears to be disabled.  The issue only appears if you review one item first, then the next item is loaded in. Editing this item will have disabled mouse input.  I haven't tested other review queues yet but will do so as soon as possible. This seems to only affect low-quality posts.  Browsers I've tested:  Broken   Chrome 33, Win 7 Chrome 34, Win 7 | OSX Mavericks Chrome 36, Win 7 Firefox 28, Win 7 Safari 8, Yosemite   Working   Safari 7 OSX Mavericks (Intermittent)


I have some texts in a mysql database, that are in several languages, including portuguese and russian, and have a lot of special characters, like á, à, ç, ã. Is there a way for me to create a search function, that is able to search using the following wildcards:  smil? - finds: smile, but not smiling - the '?' represents one character. It can be used in the begining or in the end of the search term; smil* - finds: simle, smiling, etc - the '*' represents any number of characters. It can be used in the begining or in the end of the search term; real |AND| madrid - returns the records that contain both words; real |OR| madrid - returns the records that contain at least one of the words; real |NOT| madrid - returns the records that contain only real, but not madrid; "real madrid" - returns the records that contain the exact expression;  I would also like to use multiple situations, like:  rea? |AND| madr* |AND| "manchester united"   One other problem is with the special characters. re* should also return reál, real, reãl...  And another situation is, if I search for test, it should find: tést, têst, etc...  Is this possible to accomplish? Can someone point me on the right direction?  Thank you so much!

I'm creating a site that allows users to submit quotes.  How would I go about creating a (relatively simple?) search that returns the most relevant quotes?  For example, if the search term was "turkey" then I'd return quotes where the word "turkey" appears twice before quotes where it only appears once.  (I would add a few other rules to help filter out irrelevant results, but my main concern is that.)


Yesterday I was finally able to install ubuntu 12.04.3 (64 bits) on my pre-installed Windows 8 (64 bits) Lenovo Ideapad Z500 (if that is of any help). I'll just explain the problem that I have now and if you need more info just ask me (such as the steps I followed to install Ubuntu, etc.) So I boot the computer (UEFI Bios, SecureBoot Disabled, Fast startup on Windows 8 disabled) and GRUB appears correctly (I already ran BootRepair to achieve this), then if I choose Ubuntu, it loads correctly. The problem is when I choose Windows 8 I receive this error:  unknow command `drivemap' invalid EFI file path   Furthermore, in GRUB I see 2 Ubuntu Boot options alongside many windows options and I just discovered that clicking one: "Windows Boot UEFI Recovery" actually boots my Windows 8 as usual. So, I actually have a working dual boot, but instead of choosing "Windows 8 (loader)" which doesn't boot Windows 8 (and just shows the drivemap error) I have to select the mentioned "Windows Boot UEFI Recovery" option to correctly boot windows 8. Is there any way to solve this issue?? Thanks in advance!!  Cheers, Alejandro.  P.S.: The BootInfo generated by BootRepair can be found here

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


My son has built a computer. It has no operating system. We want to install ubuntu via a usb. His computer has no internet access, so I want to download ubuntu to a usb through my laptop, then use the usb to install it on his. The usb is Fat/32. It looks like the instructions I find on this site are for installing on machines with existing Microsoft or Apple operating systems.

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


I'm trying to solve this question from my textbook:     Let $f:X\rightarrow Y$ be a continuous map and let $Z \subset X$.   Prove the inclusion $f(\bar Z)\subset\overline {f(Z)}$.   Thanks in advance for any help!

As a part of self study, I am trying to prove the following statement:  Suppose $X$ and $Y$ are topological spaces and $f: X \rightarrow Y$ is a map. Then $f$ is continuous if and only if $f(\overline{A})\subseteq \overline{f(A)}$, where $\overline{A}$ denotes the closure of an arbitrary set $A$.   Assuming $f$ is continuous, the result is almost immediate. Perhaps I am missing something obvious, but I have not been able to make progress on the other direction. Could anyone give me a hint which might illuminate the problem for me?


So I can use Twitter. It is okay when I use WiFi. But in 3G I cannot change DNS.

I live in Canada and use an unblocking service to access US Netflix content, Pandora and Hulu. I would like to be able to use this service while not on my WiFi is there a way to set the DNS server to the ones i need for my unblocker to work for the mobile network


Sometimes I answer questions that are kind of OK, neither bad enough to downvote, nor good enough to upvote (although they probably could become good ones with edits).  Per answers to  seems that I'm doing the right thing. But on the other hand comments to my recent question here  suggest, that I shouldn't expect answers to be accepted or upvoted if I "don't participate" by upvoting the question.   Should I really upvote the question just because I think it's worth my time to answer it?

Whenever I submit an answer (a real answer, not some @someone comment) I upvote the question.  I generally do this because if the question is good enough to take time to answer it, it's good enough to be brought to someone else's attention.  Do you do this?  What are your guidelines for upvoting a question that you answer?


My bachelors lists my maiden name. I took a 4 year break - during which I got married and took my husband's last name - and will soon be starting my masters and eventually PhD in a STEM field. I would like to use my maiden name on my degrees and professionally. I have not published and am not yet established in my field. My married name is extremely ordinary in the US and shared with a well known celebrity. My maiden name is very unique. It may seem arbitrary, but when I do eventually publish and become established in the field, I would like to do so with distinction. I'd like to use my maiden name consistently throughout my professional life, not just in publications but on resumes, staff, in person, etc. Is this legally possible since I didn't retain my maiden name at all? Hyphenating would be way too long and sound weird. I like my middle name, but I would consider adding my maiden name as a second middle name if that is my only option. Thoughts? Comments?

I have a question about my choice of name for publication.  I recently got married and legally changed my name to my husband's surname (for example's sake: from Hunter to Jones). So, despite legally being Ms Jones now, I would quite like to use the hyphenated name Hunter-Jones in the professional context and in publications. This is so that people realise that it is still me and so that I can somewhat keep my maiden name.  Is this possible or do I have to use my legal name professionally and when publishing? Thank you for any help


From book to book I always find the same sentence. For example:  8 bits is an even power of 2, which makes it somewhat easier to design computer hardware with 8-bit bytes than with 9-bit bytes.  The Computer Book (Sterling Milestones) by Simson L Garfinkel & Rachel H. Grunspan I cannot find any circuit or detailed explanation why that statement is true. The perfect answer will be a circuit that shows why it is easier to implement. I know about all other reasons i.e., BCDIC, ASCII, IBM System / 360 and etc. But it's just words, I need a proof with circuit. If one say that it is easier to implement, it means nothing without proof. It's like to say 1 + 2 + 3 + ... = -1/12. This statement is true, but it is complete nonsense without proof. Same thing with byte. Show circuit and I will believe.

An 8 bit value can range anything from 0 to 255 in decimal, or 00 to FF in hexadecimal. But why did they choose 8 bits for the byte, out of all of the powers of 2 they could have chosen? Even still, a nybble seems like a more suitable value for the smallest addressable memory unit, because it takes only one hexadecimal digit to write down. The main downside with nybbles though, is that they will require double the fetch cycles to execute properly. But in that case, why not just make the byte length equal to the word length, requiring only one fetch cycle per instruction? And if its so useful for a byte to be 8 bits, what is its use in microprocessors that aren't 8-bit? This could really help me out in designing my first Logisim CPU, so why are bytes 8 bits, and what is the use of an 8-bit value in non-8-bit computers?


Suppose $A$ and $B$ are $n\times n$ matrices and they are both invertible. Can we say that $AB$ and $BA$ have the same eigenvalues?

Let $ A, B $ be two square matrices of order $n$. Do $ AB $ and $ BA $ have same minimal and characteristic polynomials?   I have a proof only if $ A$ or $ B $ is invertible. Is it true for all cases?


Which is the correct form?    Try to read a book this holiday, you might find it interesting. Try reading a book this holiday, you might find it interesting.    So try reading or try to read?   Next question same verb:    I tried reading a book this weekend, but it was too long. I tried to read a book this weekend, but it was too long.

Some verbs are followed by ing, e.g. I enjoy swimming. We can't say I enjoy to swim. Likewise, some verbs are followed by to, e.g. I decided to make a plan.   Which particular verbs are followed by ing and to? Can you please provide a list for that?  Moreover, which verbs can be followed by both without having the meaning changed?


Assuming we have a Poisson process of density $\lambda$ I'm trying to find a distribution of a random variable $\tau_k$ - the time when k-th event has happened. E.g. in case of $\tau_1$ it is an exponential distribution. My approach is the following: $$ F(t) = P(\tau_k \le t) = 1 - P(\tau_k > t) = 1 - \sum_{i=1}^{k}P(\xi_t = i-1), where \\ P(\xi_t = k) = \frac{(\lambda t)^k}{k!}e^{-\lambda t} $$ I'd further need to calculate an expectation and a dispersion which is complicated in case of this sum. Any help appreciated.

I have a process which consists of a number of events and what is known is the timings between the events. What I'm trying to determine is a distribution that allows me to determine a likelyhood that a new sample fits the distibution.  The issue is mainly that if you have lots of samples you can approximate the result using a standard gaussian and use the mean and standard deviation. But if you only have a handful of samples, the gaussian does not accurately represent the situation.  From what I've read it is common to model waiting times using the gamma distribution. Looking at how the process evolves it looks like it matches well. The unknown is the scale parameter, since the shape parameter I think should be the number of samples. What I've worked out so far is that given the timings $X_1 ... X_N$ you can say:  $$ \sum_{n=1}^N X_n \sim \Gamma(N,\theta) $$  ($N$ is known and fixed)  However, $\theta$ is unknown, but the maximum likelihood parameter is the average of the $X_i$ (according to wikipedia anyway).   My question is, can I use this to estimate a distribution for $X_i$, that is, since the $X_i$ are independent:  $$ N X_i | \sum_n X_n \sim \Gamma(N, \tfrac{1}{N}\sum_n X_n) $$  Something else I've wondered about. Suppose I do have information about $\theta$, say a distribution. How can I incorporate this into the model?  Edit: Clarified that N is fixed.


n+ contact of p type Ge is ~700µm thick compared to p+ contact of n type Ge only ~0.3µm. The process of adding the contact is different. n+ contact Li is added by diffusion process but p+ contact B is added by ion implantation technique. In diffusion we can get only thick contact but in ion implantation we can achieve thin contact, Fine. With a thin (~0.3µm) Li ion implantation, low energy efficiency of p type HPGe detector can be on par with n type HPGe detector (as per the attached fig).    Why Li is also not added as contact by ion implantation method? Is it a mandatory requirement of having thick (~700µm) n+ contact or only due to technology used for doping, we are getting thick (~700µm) contact?

Whether the reason is as follows? Predominantly HPGe is p type. So compensation of large p type impurity requires more n+ contact. (700um) But n type Ge is made by doping of excess addition of n type impurity in p type HPGe. So n type impurity addition always slightly excess of p type impurity. Hence, slight excess n type impurity in n type HPGe requires, p+ contact with very less thickness. (0.3um)


Can we have any equipment as such? If light can emit form a hand held device, why not darkness

Can we ever have a black colored (the color of the light and not the body's color) torch that darken (or dis-illuminates) everything? While compared to a normal torch it would function in an opposite manner. If not now, will it be possible to create this in the near future?


Previously I'm using Lubuntu because the installer can be burnt in CD.  Now the 16.04 x64 installer image size more than 700MB. Plus, it feel too heavy on my computer.  I'm now using Bodhi Linux but looking for several more choice.

I want to burn Ubuntu Minimal CD ISO to an old, 1 GB USB thumbdrive. Regular ISO doesn't fit. I already tried Startup Disk Creator and Unetbootin but both failed. I tried installing GRUB and pointing it to boot like this:  insmod part_msdos linux /linux initrd /initrd.gz   but it doesn't work. I also tried dd but I ended up with not bootable drive.  Rufus worked on Windows with the same thumbdrive but I no longer use Windows.  What else can I do?


I'm trying to create a program which takes user input of two words and determines whether or not these words are the same.   import java.util.Scanner; public class L7E3 {     public static void main(String[] args) {         Scanner keyboard = new Scanner(System. in );         String word1, word2;          System.out.println("Please enter a word: ");         word1 = keyboard.nextLine();         System.out.println("Please enter a word: ");         word2 = keyboard.nextLine();          if (word1 == word2) {             System.out.println("The words are " + word1 + " and " + word2 + ". These words are the same.");         } else {             System.out.println("The words are " + word1 + " and " + word2 + ". These words are not the same.");         }     } }   I figured that word1==word2 would have worked to determine whether the two strings were equal, I'm using JGrasp and it goes directly to my else option regardless of input. Am I doing something wrong with strings?

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


I have recently imported a mysql 5.7 database to mysql8 a table which was myisam in mysql 5.7 is now Innodb in mysql8 any content which contains a £ either doesn't display at all and I mean not just the symbol itself the entire row doesn't show or it is appended with a funny A symbol. is there a way to fix this?

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


I am just wondering if there is any information on what will be available for later versions of blender, as 2.81 no longer has rock generator as standard which is very annoying.  Because many things are not updated for add-ons, how do I know what blender will include and not include?  In 2.81 the Eevee renderer works fine for me but not in 2.8, but 2.8 has more add-ons.  So is 2.82, 2.83, 2.84 going to become even more less useful unless I pay for everything? If even someone has the add-ons for the newer release that is?

I want to install the rock generator for v2.81.16 and I found this answer,   I have downloaded the zip and installed it as described but I still do not have the rock generator. I have lots of other addons so I think I placed the contents in the correct directory. Has something changed since this linked question was answered?


I am using the packages xcolor and tikz.  I have defined my own color in rgb which name is MyColor1. I am using multiple times in TikZ MyColor1!50!white and I want to define it as Mycolor2 so that if I want to modify the percentage of white I don't have to do it manually each time I am using MyColor1!50!white. I don't know if I can do it in xcolor or in TikZ.  Thank you in advance for your help!

I am new in TeX, so question may be little silly.  Is any chance to use already defined color to define new color which will be darkner or lighter? I want to use only TeX. So i have defined color like this:  \def\mainColor{\pdfliteral{0.1 0.5 1 rg}}   How i define new color (lighter) from this color?


If the current flows from the left side of the circuit namely positive side Why doesnt the led burn as the resistor is placed after the LED or if flows from the negative side.Where does the base of thw transistor get current?

Please be kind, I am an electronics nub.  This is in reference to getting an LED to emit photons.  From what I read (Getting Started in Electronics - Forrest Mims III and Make: Electronics) electrons flow from the more negative side to the more positive side.  In an example experiment (involving a primary dry cell, a SPDT switch, a resistor and an LED) it states that the resistor MUST be connected to the anode of the LED.  In my mind, if the electrons flow from negative to positive, wouldn't the electron flow run through the LED before the resistor; thereby making the resistor pointless?


In computing environments a lot of software and processes are moving to VMs or virtual machines.  I am always at a loss as to how to refer to a real, physical computer in comparison to a virtual environment.  For example,      Our amazing software can be installed on a VM (virtual machine) or on a real computer.      Our amazing software can be installed on a VM (virtual machine) or on a physical machine.   Is there a better word choice to refer to a real, physical computer particularly in contrast to a VMWare or XenServer virtual computer?

What is the antonym of 'virtual machine'?  A  (VM) is a piece of software pretending to be a piece of hardware. There can be virtual servers, virtual desktops...  I googled around a bit and did not find anything.    I am creating a list that has Servers, Desktops and Virtual Machines; where Servers & Desktops are understood to only include non-VMs, I need to add two more items to the list    Severs VM & (virtual machine antonym) Desktop VM & (virtual machine antonym)   I need a word to replace "(virtual machine antonym)" I was thinking "Hard" but not sure that is appropriate.    The Audience is IT Professionals.


Here is my Model. I want to display all users except "peter". Here is my code:          //iterating through all the values in database             for (DataSnapshot postSnapshot : snapshot.getChildren()) {                 User user= postSnapshot.getValue(User.class);                 if (user.getUsername()!="peter"){                 users.add(user);}             }             //creating adapter             adapter = new MyAdapter(getApplicationContext(), users);              //adding adapter to recyclerview             recyclerView.setAdapter(adapter);   problem: my list still displays the user Peter!!


I need to check difference between two dates - from db and actual, but in minutes in JS/jQuery (I need to run function to check by ajax). This is format of my date:    19-01-2016 22:18   I need something like this:    if ( (date_actual - date_db) < 1 minute ) {    //do something }   How can I do this?    EDIT: I created something like this, but I always getting same log, it's not change -     EDIT 2: Here it's working code, BUT now it's checking in the same hour/minute, ex. 12:50:50 and 12:50:58 show log only for this 2 seconds, but I need to 'stay' log on 1 minute

Can someone suggest a way to compare the values of two dates greater than, less than, and not in the past using JavaScript? The values will be coming from text boxes.