How to set a particular glyph to be of a particular typeface in XeLaTeX

Suppose that I have the following XeLaTeX document:  \documentclass{article} \usepackage{fontspec} \setmainfont{Arial} \begin{document} Proin quis (tortor) orci. Etiam at risus et $(a + b)x$. \end{document}   Is there a way to globally set, for example, the font Georgia for just the parentheses?  A similar thing could be done in the math mode with unicode-math. For example,  \documentclass{article} \usepackage{fontspec} \usepackage{unicode-math} \setmathfont[range="0028]{Georgia} \setmainfont{Arial} \begin{document} Proin quis (tortor) orci. Etiam at risus et $(a + b)x$. \end{document}     Possibly related:


I'm working on a debian:9 image pulled from . When I ran apt update or apt-get update, I got the following error messages:  Ign:1 http://security.debian.org/debian-security stretch/updates InRelease Ign:2 http://deb.debian.org/debian stretch InRelease           Err:3 http://security.debian.org/debian-security stretch/updates Release        400  Bad request: request method denied Ign:4 http://deb.debian.org/debian stretch-updates InRelease                   Err:5 http://deb.debian.org/debian stretch Release  400  Bad request: request method denied Err:6 http://deb.debian.org/debian stretch-updates Release      400  Bad request: request method denied Reading package lists... Done                                   E: The repository 'http://security.debian.org/debian-security stretch/updates Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://deb.debian.org/debian stretch Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://deb.debian.org/debian stretch-updates Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.   My sources.list file looks like this (official example from ):  deb http://deb.debian.org/debian stretch main deb-src http://deb.debian.org/debian stretch main  deb http://deb.debian.org/debian stretch-updates main deb-src http://deb.debian.org/debian stretch-updates main  deb http://security.debian.org stretch/updates main     deb-src http://security.debian.org stretch/updates main   I also tried other releases, but got the same error. Does anyone have a clue what might cause the problem? Many thanks!  EDIT:  Thanks to , I finally solved it by manually setting the network proxy for the Debian image in Dockerfile before I do apt update.  Although the question is marked as duplicate, it has nothing to do with , because it was 400 error and the sources.list file was actually correct.


How do you solve the Initial value probelm $dp/dt = 10p(1-p),    p(0)=0.1$?

The problem is...  $$ \frac{dp}{dt} = 10p(1-p),$$   $p(0)=0.1$.  Solve and show that $p(t) \to 1$ as $t\to \infty.$  I know this is probably really simple, I was trying to go down the line of finding a general solution and then imposing the boundary condition.  But I can't even see how to find the general solution... Then for the second bit taking the limit of the general solution $p(t)$?


Why is this isomorphism $M \otimes_K L \stackrel{\simeq}{\longrightarrow} M^{[L:K]}$ an isomorphism of $M$ - algebras?

Suppose that $L/K$ is a finite separable extension of fields and let $M$ denote the Galois closure of $L$. Let $\textrm{Hom}_K(L,M)$ denote the set of all $K$ - algebra homomorphisms from $L$ to $M$. Since $L/K$ is separable we know that the number of elements in $\textrm{Hom}_K(L,M)$ is equal to $[L:K]$. Now I want to prove that we have an isomorphism of $M$ - algebras   $$\varphi : M \otimes_K L \stackrel{\simeq}{\longrightarrow} M^{[L:K]}$$  Proof that they are isomorphic as $K$ - modules : Write $L = K(a)$ for some $ a\in L$ (we can do this via the primitive element theorem). Then  $$\begin{eqnarray*} M \otimes_K L &=& M \otimes_K K[a] \\ &\cong& M\otimes_K K[x]/(f) \hspace{3mm} \text{where $f$ is the minimal polynomial of $a$ over $K$} \\ &\cong& M[x]/(f)\\ &\cong& M[x]/(f_1\ldots f_{[L:K]}) \hspace{3mm} \text{where the $f_i$ are the distinct}\\ && \hspace{1.5in} \text{irreducible factors of $f$ since $M/L$ is Galois} \\ &\cong& M^{[L:K]}\end{eqnarray*}$$  where  the last step was using the Chinese remainder theorem. For the third last step, we consider the ses   $$ 0 \to (f) \to K[x] \to K[x]/(f) \to 0$$  and tensor with the exact functor $-\otimes_K M$ to get $$0 \to (f) \otimes_K M \to K[x] \otimes_K M \to K[x]/(f) \otimes_K M \to 0$$  and so $$\begin{eqnarray*} M \otimes_K K[x]/(f) &\cong& K[x]/(f) \otimes_{K} M \\ &\cong& \frac{K[x] \otimes_{K} M}{f \otimes_K M}\\ & \cong& M[x]/(f) \end{eqnarray*}$$ where $(f)$ is now viewed as an ideal of $M[x]$.          My question is: The tensor product $M \otimes_K L$ is a left $M$ - module, but why is it also an $M$ - algebra? Also why are the isomorphisms above isomorphisms of $M$ - algebras and not just $K$ - modules?


This is a two part question, and it might have to do with biology a bit.  Part 1: I grab a heavy dumbbell and curl it. Halfway up I stop the curl and just hold it there with my elbow at 90 degrees. There is no net acceleration, so there is no net force on the object, so no work is being done. But clearly I am using energy to do this, as my muscles are tensed. Since my chemical energy is not going into any sort of mechanical energy, is it simply going into heat?  Part 2: If we assume that all of the chemical energy of my muscles turns to heat, what if I now lift the weight? If I accelerate this weight up, now I'm converting some of this chemical energy into mechanical energy, so less can go to heat. Doesn't that mean your arms get hotter if you don’t do any work onto the object than if you do? This just seems counterintuitive to me.


Proof by induction that $n!\gt 2^{n}$ for $n \geq 4$

$n!\gt 2^{n}$ for $n \geq 4$.  Then there is an inductive proof:  We assume that $n! \gt 2^{n}$ for every random $n \in \mathbb{N}$ with $n\geq4$, and we need to proof that $(n+1)!\gt 2^{n+1}$. Because $(n+1)\gt0$ and $n!\gt2^{n}$, it follows that $(n+1)n!\gt(n+1)2^{n}$. In the left part of the equation we have $(n+1)!$, but in the right part we don't have $2^{n+1}$.  And here comes the part I don't understand:  We want to replace$(n+1)2^{n}$ with $2^{n+1}$, or $n+1$ by $2$. We can do this without any problems, because it is sure that for $n\geq4$ that $n+1\gt2$, and thus that $(n+1)\cdot2^{n}\gt2\cdot2^{n}$  How much I try, I just don't see the connection. So you multiply $n+1\gt2$ by $2^{n+1}$ on both sides, and that makes $(n+1)n!\gt(n+1)2^{n}$ into $(n+1)!\gt2^{n+1}$? I don't see how you can get from $(n+1)2^{n}$ to $2^{n+1}$ with what they're saying. To me, it seems like they're just saying "Hey, because $n+1\gt2$ is greater than $2$, we can just replace it with $2^{n+1}$".


Single word for "going along with the crowd"

What is a word to describe the behaviour where you do something because everyone is also doing this, to the point where you do it without any clear reason?


How can I mount SMB drive as folder with chmod 777?

I am trying to use Freefilesync to sync my local HDD with a Samba shared NAS. When connecting directly in Konqueror like smb:// etc. I am able to read and write without problem but I need to mount is as folder to make Freefilesync to see it.  I am able to mount it this way (I replaced the IP with nines to not publish it here)::  juhele@Latitude:~/Dokumenty$ sudo mount -t cifs //999.999.99.99/Public /media/jan_helebrant/QNAP_NAS -o user=juhele Password for juhele@//999.999.99.99/Public: juhele@Latitude:~/Dokumenty$    But this does not Tried chmod 777 before mounting but after mounting it changes to chmod 755. I assume this is because I have to mount as root but I have no idea how to give my user account privileges to moun this particular drive as it is not listed in /etc/fstab and I do not see it in Gparted of course so I cannot use the tutorials I found.  any idea?  thanks


Any better way to make a object into another object in javascript

Oldobject = {'name':'Joe','age':12}; newObject = {'address':'XXX'};   I want to get result like :  {'name':'Joe','age':12,'address':'XXX' }   I use   Oldobject.address = newObject   Is there any graceful way to do this ?


Does the wielder of the Gauntlet actually need to snap, or is the snap action simply dramatic?

In Avengers: Endgame, is the snap simply dramatic, or does the wielder of the Gauntlet needs to follow this ritual to actually activate it?


It's pretty normal when people use inversion in a sentence like this one (with the aux verb at the front): "In no way do I agree with what you're saying." But I'm not sure if these belong to a type of inversion: "To the west of Ethiopia near the Sudanese border lies a place called the Asosa zone." "In the middle of the room stands a sculpture by Penny Byrne" If so, where are the aux verbs? I'm so confused, please help!


How to free up "Other" in Storage Management

Storage management show me "Other" is 127.51 GB but I can't do anything even see any information.  What is inside? And how to get rid of it?


What's the "Bad magic number" ImportError in python, and how do I fix it?  The only thing I can find online suggests this is caused by compiling a .py -> .pyc file and then trying to use it with the wrong version of python. In my case, however, the file seems to import fine some times but not others, and I'm not sure why.  The information python's providing in the traceback isn't particularly helpful (which is why I was asking here...), but here it is in case it helps:  Traceback (most recent call last):   File "run.py", line 7, in <module>     from Normalization import Normalizer


I understand what an ordered pair is, but I'm having trouble the formal Kuratowski definition which says that $\langle a,b \rangle = \{\{a\},\{a,b\}\}$. What about this definition imposes order on the pair?


Create single TELNET object for multiple functions in Python

I want to create single Telnet object which will be used in multiple functions.  tn = (Telnet object declaration only)  def Function1(): #for connection only     tn = telnetlib.Telnet(ip)     #code  def Function2(): #to run command 1     tn.write()  def Function3(): #to run command 2     tn.write()  Function1() #Call for telnet connection Function2() #Call to execute command 1 Function3() #call to execute command 2   What could be the solution for this?


complex number $\sum_{k=1}^{n-1} (n-k) cos\frac{2πk}{n}=\frac{-n}{2}$

Prove that $\sum_{k=1}^{n-1} (n-k) cos\frac{2πk}{n}=\frac{-n}{2}$ where  n $\ge$3  is an integer .  My approach, we need to find real part of the equation. Where k is increasing, i am getting confused. Is there any other method of approaching this question.


java.lang.NullPointerException:ava.io.File android.content.Context.getCacheDir()' on a null

I'm trying to use Retrofit & OKHttp to cache HTTP responses. But I'm Getting java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.File android.content.Context.getCacheDir() on a null object reference. Here I will put my API Java Class.Please help me,your Help will be Appreciated.  Here is my ApiManager class which contains the interceptor , the getAPI() which has the retrofit building part:   public class ApiManager {       private static Context context;      public static final String API_URL = "https://www.alot.com/webservice/"; //Production      private static ProductionAPIService service;      public ProductionAPIService getService() {         return service;     }       private static OkHttpClient okClient;     private static ApiManager apiManager = null;      private ApiManager() {     }      public static ApiManager getApi() {         if (apiManager == null) {             apiManager = new ApiManager();                  File httpCacheDirectory = new File(context.getCacheDir(), "responses");             int cacheSize = 10 * 1024 * 1024; // 10 MiB             Cache cache = new Cache(httpCacheDirectory, cacheSize);               OkHttpClient client = new OkHttpClient.Builder()                     .addNetworkInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)                     .cache(cache)                     .build();              Retrofit retrofit = new Retrofit.Builder()                     .baseUrl(API_URL)                     .addConverterFactory(GsonConverterFactory.create())                     //    .client(SelfSigningClientBuilder.createClient(MyApplication.context))                     .client(client)                     .build();               service = retrofit.create(ProductionAPIService.class);         }         return apiManager;     }      private static final Interceptor REWRITE_CACHE_CONTROL_INTERCEPTOR = new Interceptor() {         @Override         public Response intercept(Chain chain) throws IOException {             Response originalResponse = chain.proceed(chain.request());             if (AppUtils.isConnectedToInternet(context,true)) {                 int maxAge = 60; // read from cache for 1 minute                 return originalResponse.newBuilder()                         .header("Cache-Control", "public, max-age=" + maxAge)                         .build();             } else {                 int maxStale = 60 * 60 * 24 * 28; // tolerate 4-weeks stale                 return originalResponse.newBuilder()                         .header("Cache-Control", "public, only-if-cached, max-stale=" + maxStale)                         .build();             }         }       }; }


After reading a bunch of past stack exchange posts like  and RFCs , , and  I felt comfortable that a 32-byte key was sufficient for HMAC-SHA256.  However, I am implementing my code in C# and someone pointed out to me that the  recommends a 64-byte key:     The key can be any length. However, the recommended size is 64 bytes.   Is there any good reason to use a 64-byte key instead of a 32-byte key?


Is the function $\mbox{tr}(XAX')$ convex?

Is the function $\mbox{tr}(XAX')$ convex, where $A$ is a positive semidefinite (PSD) matrix? I know that for a general $A$, the above trace function is not convex. But for a PSD $A$, is the function convex?


Ubuntu 19.10 has white calendar in top bar even when using yaru dark theme

I've upgraded my Ubuntu 19.04 to 19.10 and all work good but I have a little problem. Some elements in top bar have white color instead dark.


How can I defrag an NTFS hard drive from Ubuntu?

I state I am asking if it is possible and HOW. I note many forum answers are 'you can't' or 'you don't need to on Linux cause it is perfect and wonderful' - none of these answers will help.  Firstly, the HDD in question is SATA 163 GB and contains ONLY backup data like music, video and NO windows programs or installations. I have had a HDD failure in second HDD that is completely FUBAR so have lost my windows installation, this HDD had linux and windows dual boot, HDD is undetectable in BIOS.  The working HDD is 130GB full with capacity of 163GB (it is badly fragmented due to excessive use...). I intend to defrag this drive using USB linux OS (bootable USB with installation files and 'trial') and any other programs that will enable this task. Once this is done I intend to locate which data areas are free (the end of HDD data storage area), create a new partition on this free space, install linux full version and get things working.  +++  I understand fully the following:  I can buy a new HDD for install.  I can get an external hard drive, back up the data.  I also understand that copying off backup hdd and then copying back will do the same as defrag.  I ask this question to find out how to complete this action I have requested and NOT to complete it using the methods unavailable to me at this time.  Thanks


How do I pause one of the NSTimer thats running then resume it?

I have one timer firing to go to a void statement. Which has another timer in it. I want to pause the one thats firing or going off then resume it.  movement3 = [NSTimer scheduledTimerWithTimeInterval:0.2 target:self selector:@selector(jone) userInfo:nil repeats:NO];   - (void)jone{  [jumperguy setImage:[UIImage imageNamed:@"jumperguy_a_a3.png"]];  movement4 = [NSTimer scheduledTimerWithTimeInterval:0.2 target:self selector:@selector(jtwo) userInfo:nil repeats:NO]; }


Can I use double negative in the following structure: "not that..."?

We are taught in schools that in English, double negatives are not so welcome, which is hard to understand because of my own language in which it is quite common.   Nevertheless, I come across some sentences which use double negatives from time to time and it's starting to cloud my mind... (e.g. : I ain't need no sleep)  And here's a new example I've just read : "I think you should set this pic as your profile picture. Not that the current one isn't nice, but this one is better."   So, is this okay to say this in this example?   Thank you very much in advance!


Does setting one pointer to an object to nil affect the object or other pointers to it?

Although I know the main difference between Deep Copy and Shallow Copy but what I want to ask here is something practical.  I have  NSArray *firstArray = [NSArray arrayWithObjects:@"first", @"second",@"third",  nil]; NSArray *secondArray    = firstArray; secondArray             = nil;  NSLog(@"First Array : %@",firstArray); NSLog(@"Secon Array : %@",secondArray);   Both the firstArray and secondArray has the same reference as seen by putting break point.  Now my question is this, if both have same REFERENCE then why the firstArray does not change if the secondArray is changed.  I am really confused here... Can any one please make me clear.   Thanks in anticipation.


How do we know that superposition exists?

If I was a god that could see the state of a particle in superposition without touching it, wouldn't I know what the particle is at that moment? Wouldn't that make the superposition concept just switching between states very fast and being fragile to being observed? Do we call that a particle is in superposition, just because if we measure it, the measured value is not relevant anymore to calculate the next state? So basically we cannot measure it, but in the background the particle is still changing it's state right? So, the particle is not actually in superposition. All the sites just talk about this concept as, "the particle being in the two states at the same time, because we cannot predict it" but that's like very vague for me.


What is the purpose of dimension reduction in classification?

We use Principal Component Analysis for dimension reduction, why is it important?


Number of equivalence classes of matrices under switching rows and columns

I have been thinking about this problem:  Suppose we have all $R$ by $C$ matrices, where the values are integers in $[1,n]$. Two matrices are equivalent under interchanging rows and columns. For example,   1 5     0 0       would be equal to itself and to  0 0 1 5   and would be equal to  0 0  5 1   and would be equal to   5 1 0 0   How many unique such matrices are there?  Any ideas how to go about it? Any help much appreciated!


Hi can you help me solve this exercise? Thanks. Let $f: [0;+\infty) \to \mathbb{R}$ be nonnegative and continuous function. Suppose $\forall a > 0$  $\sum_{n=1}^{\infty} f(na)$ is convergent. Prove that $\int_{0}^{\infty}f(x) dx$ is convergent. I tried to solve it by using the Riemann sum, but for fixed a it doesn't work. I have no other ideas.


Using (leaky) ReLU as an activation function

I am building a convolutional neural network to classify certain types of greyscale images (chess puzzles).  I can see obvious advantages for using ReLU as my activation function e.g. I can treat the input layer feed to the first hidden layer in the same way as the input into any other hidden layer in terms of the domain of the input.  But I have a question about how to use ReLU activations at the other end - i.e. as the output of the fully connected output layer.  I am looking to classify images of chess boards and so it seemed to me obvious that I could classify a part of the board as being a white square or a black square and then with some other (optional, as it were) classifications e.g. with pawn which itself could be black or white.  I cannot really see how to do this with ReLU - and so that suggests that what I really have to do is implement every possible outcome as a separate output neuron e.g., empty black square, empty white square, white square with white pawn, white square with black pawn, black square with white pawn ... etc.  Is that correct?  (I originally asked this on Stack Overflow and got no answers, but a recommendation to ask here. So I have deleted the original and posted this. Since I originally asked I have built a network and, using random weights - learning is about to begin, see that the overall results, after several layers of leaky ReLU activated filters and a leaky ReLU fully connected layer,  don't stray too far from the 0 - 1 range, though this may be luck more than anything else: but I am still intrigued by this problem so would welcome answers.)


Badge notifications do not open on Android app

I click either of the "electorate" or "java" badges and just end up where I started if I click the "Open with Stack Exchange" option.


Use tracking point to move a plane with an image on it,

I'm looking to track an object within a strip of frames in the video editor.  To clarify, I'm not trying to track an object and solve the camera motion. I'm looking to use a single tracking point to track the head of a character from a video and i would like to make a plane with an image on it follow that point.


How do I connect multiple devices to an ISP that gives web-based portal for logging in?

I have an ISP (Beam telecom, if it's relevant) that provides only a LAN cable connection. Using this, whichever site you initially open, you are redirected to its portal page where you are required to log in. After this you can access internet as normal.  The problem that I am facing is when I am trying to setup my ADSL router to use it as a WiFi router so that multiple devices can connect to the internet.  I have connected the ISP's RJ-45 cable into one of my ADSL router's LAN ports and I am able to connect to the internet through the WiFi network using the same process.  The problem is that, when one of the devices has successfully authenticated with the portal (and has been assigned an IP), if I try to use that WiFi from any other device, I am again greeted with the portal page. After authenticating I get access to the Internet in this device, but the previous device loses Internet access and that device is greeted with the portal login page.  So in effect only one device is able to connect to the Internet at a given time.   I have seen few forum posts saying if I use a normal WiFi router which has a WAN port and not the ADSL that I currently have. Would resolve the issue. But I am in doubt if this would really fetch me anything, and I don't want to spend money on another router if it is still in vain.  So any ideas if a non-ADSL router would resolve this issue or if I can change my existing router's settings so that I can connect more than one device?  My ADSL router is a Linksys Wireless-G ADSL Home Gateway, model WAG200G.  Would a flash of DD-WRT custom firmware on my device provide new options that would allow me to make use of my ADSL to work as a normal WiFi router?


Was Dumbledore related to any characters mentioned in Harry Potter?

There were a lot of family connections between everyone and everyone in HP... Harry and Ignotus, Voldemort and Slytherin, the Blacks and everyone else (Tonks, Weasleys, etc...)  Was there any info (canon or JKR) that Dumbledore was related to anyone? He lived in Godric's Hollow, but that is not necessarily a basis for any leaps of logic.


i need to validate differents input value lengths.   Inputs value can have a max length of 6 / 15 / 25 characters. Now i was asking to my self if it's a good practice use only one dynamic regex to validate differents max lengths, instead of copy paste the same regex.   During my research i found that i've to use the the const regex = new RegExp()  the problem is that i tried     const lengthValidation = () => {   const maxLength = 4;   const inputValue = 'ciao';   const regex = new RegExp(`/^.{6,${maxLength}}$/`);   const isValid = regex.test(inputValue);   return console.log('regexTest', isValid); };  lengthValidation();     but it's invalid.   where is my mistake ?


Can anyone give me an example of one? I know it's equivalent to finding a noetherian that isn't PID, but I'm not sure!


Unable to install, update, or upgrade any packages on ubuntu 20.04 aws ec2 instance

I am trying to install net-tools using sudo apt install net-tools  but I get Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package net-tools  So I tried the following commands sudo apt update  sudo apt upgrade  sudo apt dist-upgrade sudo apt -f install sudo apt autoremove  each of them respond with Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.  any suggestions to fix this issue without breaking the server would be appreciated!


Why my reputation for upvote is missing?

In few of my answer to a question, my reputation is missing for upvote. See the screenshots below for that.     In first one im missing 20 reputation and in second one 10.  Please tell me why this??


Is there a dictionary api or something similar where I can find the definition of words in PHP?

Does anybody know of any? (I'd be using a php page to call the terms)  THANKS!


Show that if a function is not negative and its integral is $0$ than the function is $0$

Suppose $f$ is continuous, $f(x) \ge 0$ on $[a,b]$ and $\int_a^b f(x) dx=0$. Show that $f(x)=0$ on $[a,b]$.   I know that if $f$ in continuous at $x_0$ and $f(x_0) > 0$, then there exists $\delta > 0$ s.t. $f(x) \ge \frac{1}{2} f(x_0)$ for $|x-x_0| < \delta$ and I think it should help me but I'm stuck at this point.


how to select the most frequently appearing values?

I've seen examples where the query orders by count and takes the top row, but in this case there can be multiple "most frequent" values, so I might want to return more than just a single result.  In this case I want to find the most frequently appearing last names in a users table, here's what I have so far:  select last_name from users group by last_name having max(count(*));   Unfortunately with this query I get an error that my max function is nested too deeply.


I have been thinking about one problem, which is not understandable to me. Consider the following: I have a deck of cards (52 cards). I pick card after card (no replacement), but I stop when the current card belongs to the same family (Aces, Kings, etc.) as the card picked before. The number of observations is an event, so we can say in our sample space there are 50 events (2-52), BUT we should add another, which is that nothing happens at all. This last part gives me a huge headache and I don't know how to consider even start thinking about a problem and create a formula for this problem, such as find probability for the formula for an event. I would really really appreciate it if someone could help me understand this problem. Thank you. edit: the current card must match the card picked before, not any card picked before.


Maximum wavelength of a photon/electromagnetic radiation?

This asked:   And also this:     The second question is contradictory; maximum frequency -> minimum wavelength.   I am asking the very opposite;    What is the minimum frequency and maximum wavelenght of electromagnetic radiation?   The lowest measured/defined seems to be 3 Hz;  Which means a wavelenght 1/3 of the speed of light; ~100 000 000 m.   But this can't be the physical limit for the wavelenght. Does such a physical limit for the wavelength exist? (Similar limit like the speed of light is for velocity).


Photoelectric effect, low frequency light

Let's say we have a emitter, emitting light that has frequency f, less than the threshold frequency of a metal.  If you leave light shining onto that metal, for long enough, does the energy of the individual photons accumulate, on the electrons, so eventually they will ionize, or does this not happen? What am I missing?


Did I break my system with apt-get autoremove?

I'm running Ubuntu 16.04 LTS. I used sudo apt-get autoremove  Reading package lists... Done Building dependency tree        Reading state information... Done The following packages will be REMOVED:   apt-clone archdetect-deb canonical-poke dmeventd dmraid   gir1.2-timezonemap-1.0 kde-config-screenlocker kinit kio kpackagelauncherqml   kpackagetool5 kpartx kpartx-boot kwayland-data kwayland-integration kwin   kwin-common kwin-data kwin-x11 libbonobo2-0 libbonobo2-common libdb5.3++   libdebian-installer4 libdevmapper-event1.02.1 libdmraid1.0.0.rc16 libfam0   libgnome-2-0 libgnome2-common libgnomevfs2-0 libgnomevfs2-common   libkdecorations2-5v5 libkdecorations2private5v5 libkf5activities5   libkf5archive5 libkf5attica5 libkf5auth-data libkf5auth5   libkf5bookmarks-data libkf5bookmarks5 libkf5calendarevents5   libkf5codecs-data libkf5codecs5 libkf5completion-data libkf5completion5   libkf5config-bin libkf5config-data libkf5configcore5 libkf5configgui5   libkf5configwidgets-data libkf5configwidgets5 libkf5coreaddons-data   libkf5coreaddons5 libkf5crash5 libkf5dbusaddons-bin libkf5dbusaddons-data   libkf5dbusaddons5 libkf5declarative-data libkf5declarative5   libkf5globalaccel-bin libkf5globalaccel-data libkf5globalaccel5   libkf5globalaccelprivate5 libkf5gpgmepp5 libkf5guiaddons5 libkf5i18n-data   libkf5i18n5 libkf5iconthemes-bin libkf5iconthemes-data libkf5iconthemes5   libkf5idletime5 libkf5itemviews-data libkf5itemviews5 libkf5jobwidgets-data   libkf5jobwidgets5 libkf5kcmutils-data libkf5kcmutils5   libkf5kdelibs4support-data libkf5kdelibs4support5 libkf5kdelibs4support5-bin   libkf5kiocore5 libkf5kiofilewidgets5 libkf5kiontlm5 libkf5kiowidgets5   libkf5newstuff-data libkf5newstuff5 libkf5notifications-data   libkf5notifications5 libkf5package-data libkf5package5 libkf5parts-data   libkf5parts-plugins libkf5parts5 libkf5plasma5 libkf5plasmaquick5   libkf5quickaddons5 libkf5service-bin libkf5service-data libkf5service5   libkf5solid5 libkf5solid5-data libkf5sonnet5-data libkf5sonnetcore5   libkf5sonnetui5 libkf5textwidgets-data libkf5textwidgets5 libkf5wallet-bin   libkf5wallet-data libkf5wallet5 libkf5waylandclient5 libkf5waylandserver5   libkf5widgetsaddons-data libkf5widgetsaddons5 libkf5windowsystem-data   libkf5windowsystem5 libkf5xmlgui-bin libkf5xmlgui-data libkf5xmlgui5   libkscreenlocker5 libkwalletbackend5-5 libkwin4-effect-builtins1   libkwineffects7 libkwinglutils7 libkwinxrenderutils7 liblvm2app2.2   liblvm2cmd2.02 liborbit-2-0 libparted-fs-resize0 libphonon4qt5-4   libpolkit-qt5-1-1 libqt4-designer libqt4-help libqt4-opengl   libqt4-scripttools libqt4-test libqt5script5 libqtassistantclient4   libqtwebkit4 libreadline5 libvoikko1 libxcb-composite0 libxcb-cursor0   libxcb-damage0 linux-headers-4.4.0-23 linux-headers-4.4.0-23-generic   linux-headers-4.4.0-40 linux-headers-4.4.0-40-generic   linux-image-4.4.0-23-generic linux-image-4.4.0-40-generic   linux-image-extra-4.4.0-23-generic linux-image-extra-4.4.0-40-generic   linux-signed-image-4.4.0-23-generic linux-signed-image-4.4.0-40-generic   linux-tools-4.4.0-23 linux-tools-4.4.0-23-generic lvm2 plasma-framework   python3-icu python3-pam python3-pyqt4 python3-sip   qml-module-org-kde-kquickcontrols qml-module-org-kde-kquickcontrolsaddons   rdate sonnet-plugins 0 upgraded, 0 newly installed, 164 to remove and 0 not upgraded. After this operation, 803 MB disk space will be freed. Do you want to continue? [Y/n] y   Did it remove some stuff that was not to be removed?


Slashbox with tables: Adjusting the diagonal separator for multiple rows

I am using the slashbox package in a table as shown next. However as you can see, the diagonal line in the first cell is not the real diagonal of that cell. This is because of the existence of more than a row in that cell. So how to make the diagonal line reach from the top left corner to the bottom right corner of the first cell to the left?     Here is my code:  \documentclass[12pt]{article} \usepackage{slashbox}  \begin{document}  \begin{table}[htbp] \begin{center} \begin{tabular}[htp]{||l|c|c|c|c||} \hline \backslashbox{Adult}{Motion types} & can definitely & \multicolumn{2}{c|}{can definitely } & can definitely\\ person & walk & \multicolumn{2}{c|}{jump} & run\\ \cline {3-4} & & more than & more than & \\ & & 10 cm & 20 cm & \\[4mm] \hline \hline Joe & Yes & No & No & No \\[4mm] \hline \end{tabular} \end{center} \end{table}  \end{document}   Thank you.


Why does multiplying by some numbers sometimes return a slightly larger number?

When I do, for example, 14 * 0.2, I get 2.8000000000000003 instead of 2.8. Why does it do this, and how can I fix it?    According to  page, Strings automatically cut trailing 0s off, so I tried    var foo = 14 * 0.2; console.log(foo.toFixed(3).toString());   but it still comes back with trailing 0s (2.800).


Inequality involving rearrangement: $ \sum_{i=1}^n |x_i - y_{\sigma(i)}| \ge \sum_{i=1}^n |x_i - y_i|. $

If $x_1 \ge x_2 \ge \cdots \ge x_n$ and $y_1 \ge y_2 \ge \cdots \ge y_n$ are real numbers, and $\sigma$ is any permutation, then $$ \sum_{i=1}^n |x_i - y_{\sigma(i)}| \ge \sum_{i=1}^n |x_i - y_i|. $$ This must be a known inequality. What is it called, and how is it proven? (Just a reference is OK.)    The conditions are similar to . The inequality is a simple statement about minimizing the $\ell^1$ distance between a finite sequence and any rearrangement of another finite sequence.  I searched around and clicked through various pages but couldn't find something relevant. If it is true, perhaps a proof could be constructed by decomposing the permutation into a sequence of transpositions.


How to make efficient PhD research in absence of the supervisor?

I am a PhD student, in my situation I work totally alone and freely , the good thing here is that I have learned to be autonomic and I can guide my research by my own, however, In comparison with the other Phd student , I don’t have a guide or even a corrector that I can discuss my work with; so that; as a solution I feel more comfortable when I write,  still less experienced, but when I write I read and I learn more and more, for the moment, writing replaces the absence of my supervisor!!! Working alone is not so dramatic; I try to extract the maximum of positivity facing the challenge of doing a PhD almost alone, I shared my experience because I’m curious; what can we learn from that? are there student in the same situation? If not; what would you do in such a case?


I am a beginner in Latex and I have a problem such as: I was able to make the first and third pages of the bibliographer empty, but I cannot make the second page empty. An idea please. This is the tex code \documentclass[a4paper,12pt,openany]{book} \usepackage{etex} \usepackage[utf8]{inputenc} \usepackage{chngcntr}    \usepackage{fontenc} \usepackage[french]{babel}   \usepackage{amsthm} \usepackage{amsmath} \usepackage{amssymb} \usepackage{amsfonts} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \usepackage{titletoc} \usepackage{tikz} \usepackage{titletoc} \usepackage{lipsum} \usepackage{calc} \usetikzlibrary{shadows.blur} \newcommand{\printmyminitoc}{ \noindent\hspace{0cm}\begin{tikzpicture} \node[rounded corners,align=left,fill=white,blur shadow={shadow blur steps=5},inner sep=5mm]{% \color{black}% \begin{minipage}{15cm}%minipage trick \textbf{\Large Contents}\\ \rule{\textwidth}{1.5pt} \printcontents[chapters]{}{1}{} \end{minipage} }; \end{tikzpicture} \ \vspace{1cm} \\} \usepackage[colorlinks=true,urlcolor=green, citecolor=red, linkcolor=blue]{hyperref} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \usepackage{titleps} \newpagestyle{mine}{ \headrule \sethead{\itshape\chaptername\thechapter}{}{\itshape\chaptertitle} \footrule \setfoot{}{\thepage}{} } \renewpagestyle{plain}{ \setfoot{}{}{\thepage}} \pagestyle{mine} %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \usepackage{footnote} \usepackage{etoolbox} \usepackage{mathrsfs} \usepackage{graphicx}            \usepackage{hyperref} \usepackage{indentfirst}             \usepackage{xcolor} \usepackage[final]{pdfpages}  \usepackage{fancybox} %\usepackage{biblatex} \usepackage[   backend=biber, % bibtex  % bibtex or biber (prefered)   natbib=true,   style=numeric,   sorting=nty  % none, nty % no sorting or standard sorting ]{biblatex} \addbibresource{bibliogra.bib} \usepackage{color} \usepackage{dsfont}  \usepackage{lastpage}  \usepackage{sectsty} \usepackage[left=2cm,right=2cm,top=2.75cm,bottom=3cm]{geometry} \usepackage[Bjornstrup]{fncychap} \usepackage{hyperref}   \definecolor{9ahwi}{rgb}{0.5, 0.1, 0.005} \definecolor{khdar}{rgb}{0.0, 0.5, 0.8} \definecolor{ocre}{RGB}{243,102,25} \usepackage{newunicodechar}  \begin{document} \tableofcontents \thispagestyle{plain} \chapter{Bib} \cite{Bal89}\cite{DeB86}\cite{Dil93}\cite{Gue97}\cite{Kru00}\cite{Bal90}\cite{Kom67}\cite{Bal96}\cite{Amr92}\\\cite{Ord66}\cite{Hes90}\cite{Hes02}\cite{Hes00}\cite{Hes91}\cite{Lev76}\cite{Mol05}\cite{Ion69}\cite{Val07}\\\cite{Rud91}\cite{Les16}\cite{Bre10}\cite{Sho97}\cite{Die77}\cite{Gio13}\cite{Ric75}\cite{Cha77}\cite{Dan13}\\\cite{Mau75}\cite{Pap02}\cite{Cha99}\cite{Sch70}\cite{Sch86}\cite{Ben15}\cite{Gar79}\cite{Bae72}\cite{Kak39}\cite{Nis63} \newpage \addcontentsline{toc}{chapter}{Bibliographie} \newpage \printbibliography \thispagestyle{plain}\thispagestyle{plain} \end{document}


How to sed and put back the part of the match?

So these are the original texts:   $ printf 'bbb\nb2b\n' bbb b2b   This is what I'm doing  $ printf 'bbb\nb2b\n' | sed 's/^b[0-9]/XXX/g' bbb XXXb   And this is the output that I want :D  $ printf 'bbb\nb2b\n' | SOME_SED_MAGIC bbb XXX2b   My question: How can I swap the "b2b" to "XXX2b", so I put back the "2" from the sed match? "2" could vary.


I'm trying to randomly select 6 numbers for a lottery application. Then add the numbers to an array. When I try to display the information contained within the array, it returns [I@63376afa. If I display randomInt outside of an array it displays correctly, but that isn't added to an array. If I try to add randomInt to an array after the for loop has been processed I get an error Type mismatch can't convert int to int[] which makes sense.  import java.util.Random; public class PracRandom1  {     public static void main(String[] args)      {         int randomInt=0;         int[] numArray = new int[randomInt];         int[] array = new int[5];         Random randomNum = new Random();{             for (int i = 0; i <= array.length; ++i){             randomInt = 1+randomNum.nextInt(6);                          System.out.println("Array Random numbers: " + numArray);             } }}}


A limit formula for the Schwarzian derivative involvng cross-ratios


Is it possible to list everything a specific process is trying to do?

I have a web app in a jboss application server that gives a not understandable error.  I’m 100% sure it is because it is trying to access a forbidden file system location. Is it possible to profile the program, in particular what is doing step by step (ex. Spawning processes, opening files, writing files, etc)


How can I use command expansion on `\{\}` in `find -exec`?

I would like to find some directories via  find /path/to/a/dir -type d  -links 2    and then for each pathname found by find,  assumed to be stored in variable pathname, I would like to   stow -d "$(dirname "$pathname")" -t /home/t/bin "$(basename "$pathname")"    How can I combine the above with find -exec, something similar to:  find /path/to/a/dir -type d  -links 2 -exec stow -d "$(dirname \{\})" -t /home/t/bin "$(basename \{\})" \;   I think it doesn't work because the shell performs the command substitutions before running find, and no pathname is found yet to replace \{\} in the command substitutions.  Thanks.


What to do with statistically insignificant dummy/categorical variables?

From the research I've done the common answer is that you can not remove insignificant dummy variables from a regression. I'm having a hard time finding academic papers or books that back up this thought. If anyone knows of any papers dealing with this issue or a good place to search through statistics papers that would be great!


Why can't I assign List to ICollection where T implements interface I?

Why can't I assign List<T> to ICollection<I> where T implements interface I?  For instance:  public interface IObject {} public class MyObject : IObject {}  public class Stuff {     ICollection<IObject> Objects {get;set;}     public Stuff()     {         Objects = new List<MyObject>(); //<--  Cannot implicitly convert type 'ICollection<IObject>' to 'List<MyObject>'. An explicit cast exists.     } }   I realize the solutions to this error are as follows:  Objects = (ICollection<IObject>)new List<MyObject>();   or   Objects = new List<IObject>();   but I am just curious as to why.


I am interested in retracting my old journal articles. Would it have any negative effects on my academic career?

I managed to successfully publish my old bachelor thesis in a good quality national journal in my country. However, I am thinking of retracting the article due to certain circumstances. First, I felt really embarrassed by the low quality research methodology used in my bachelor thesis. I only used simple correlation in my research. After it was published, I realized that the journal editor team forgot to include a reference in that article because they were rushing me throughout the editing process. I informed them about their mistake and it seems that they have done nothing to fix the problem. I became a bit annoyed because the editor team has never made this problem in the past.  I felt that it would be better for me to simply ask for retraction to solve this issue, but I am a bit afraid of negative consequences in the future. Is it okay to do this? I am really interested of entering the academic world in the future.


3x3 real matrices with same minimal polynomial but different jordan normal form

This is to show that the minimal polynomial does not determine the jordan normal form. I've tried a few but haven't got anywhere.  Why is this marked as duplicate? The other post does not give me an answer.


How to remove the \homepage symbol in awesome-cv

I'm writing up my resume right now. My code looks like this:  \name{}{John Doe}   \email{John_Doe@gmail.com} \mobile{839-839-8399}   and the output currently looks like this:    But when I add \homepage, the symbol pops up, as following:    Is there a way to remove the home symbol?


When tapping preview on editing an existing answer, the app crashes

Post a question, tap edit, tap preview. Boom.   Version 0.1.25


Textures turn black in material and render mode

I downloaded a free shader setup from a site and after unwrapping it, the texture comes fine in the texture shading viewport. But when I shift to Material, or render shading, the object is just plain black. I cannot seem to understand where the mistake is. I am using cycles render.  When I tried using an another random image texture, there was no problem. I could see the texture in all modes. So idk where I am going wrong with this shader.  Edit: Sorry for being so vague. So I am using Blender Cycles v2.78. I downloaded a wood shader from a site called Chocofur, with the node setup as attached. This is how it looks in Texture Shading.    The node setup:    However, when I go to material, or rendered shading, this is how it turns out.     Now just to check whether I was doing something wrong, I used a plain image as a texture in one of them, and it seemed to appear fine both in material and render shading.    So I am guessing there is something within the shaders settings.The thing in red in the node setup is probably the problem since it says something isn't defined. I am not very thorough with using nodes and maybe that's why I can't figure it out. I hope I've been clearer this time. Let me know if I need to attach the blend file for reference.


Is it possible to use more than 20 layers?

Is it possible to use more than 20 Scene layers or Render layers in Blender?


Getting the Hostname or IP in Ruby on Rails

I'm in the process of maintaining a Ruby on Rails app and am looking for an easy way to find the hostname or IP address of the box I'm on (since it's a VM and new instances may have different hostnames or IP addresses). Is there a quick and easy way to do this in Ruby on Rails?  Edit: The answer below is correct but the clarification Craig provided is useful (see also provided link in answer):     The [below] code does NOT make a   connection or send any packets (to   64.233.187.99 which is google). Since UDP is a stateless protocol connect()   merely makes a system call which   figures out how to route the packets   based on the address and what   interface (and therefore IP address)   it should bind to. addr() returns an   array containing the family (AF_INET),   local port, and local address (which   is what we want) of the socket.


I am currently running Ubuntu Server 10.10 through a virtual machine to use as a stack for web development and a chance to get to grips with the Ubuntu command line, however I'd really like to set up a clean, minimal install with only the bare minimum of core utilities so I can get only what I need as I go along.  The Ubuntu Server iso seems to install a lot of extras already and I'd prefer just the bare minimum so I can spend more time aquainting myself with the installation and set up of the packages I need. Can I obtain an image that does this?


Is there a way to give a "name" to the arguments of a command and use them in its definition? What I'd like to do is to be able to get the value of an argument with a "label" like #myargname instead of #<number>. For example, I'd like to define a \foocommand like \newcommand{\foocommand}[#normal,#bold,#italics,#smallcaps,#emphasis]%            {#normal \textbf{#bold} \textit{#italics} \textsc{#smallcaps} \emph{#emphasis}}  instead of \newcommand{\foocommand}[5]%            {#1 \textbf{#2} \textit{#3} \textsc{#4} \emph{#5}}


I plan to display my Python script run result to share with others. thus, I plan to do a android apps and also a websites. I have use Pythonanywhere to run my python script and send my result to MYSQL. Unfortunately free account has its limitation. I plan to host in free web hosting in long term. I found heliohost but I am unsure if it is suitable for my requirements. I need a python script taht can run everyday at a certain time and save the output to MySQL so that people can access from android apps or webs. Besides, hekiohost, any web hosting that I can run python script fro free and allow higher bandwidth and storage? There are some free web hosting with large storage but does not disclosed if I can run my Python script.  Thanks in advance


How do I cd into a directory called "."?

I'm doing OverTheWire and looking for a password hidden somewhere on the server. I did ls -a to view the hidden contents inside the current directory and received this as the output:  .    ..    .bash_logout    .bashrc    .profile   I checked the file type of . and it says it's a directory:  bandit6@bandit: file ./. ./.: directory   I then tried to cd into this directory but I didn't have any success, it accepted the command but I just stayed in the same directory.  I'm not sure if the syntax is wrong or if the . and .. directories refer to the current and parent directory respectively.   Sorry if this is painfully obvious, but I am new to the command line.


"Didn't use to get" or "Didn't used to get"?

I just made a minor , and  the grammar correction was unnecessary.  The original text was     Another factor--sometimes life happens and you can't fly. In the old days you could simply sell your ticket to someone else, now you either have to eat a hefty change fee or lose it outright. That's money in their pockets that they didn't used to get.   It was corrected to:     Another factor--sometimes life happens and you can't fly. In the old days you could simply sell your ticket to someone else, now you either have to eat a hefty change fee or lose it outright. That's money in their pockets that they didn't use to get.    Was this grammatical correction an improvement? Was the original text grammatically correct? Is the edited text grammatically correct?


I have a xubuntu pc at work, so I wanted to remove all users and create just one sudoer user with the name of the new person using the pc, so that he would be able to install programs etc. without having to disclose my admin password.  The steps I made were:   Created a new user: Jonathan, as administrator Deleted all desktop users and its files Logon as Jonathan Deleted the only sudoer user   Basically, my mistake was that I created an administrator user which is not a root user.   So now when I am going to install a program, xubuntu asks me for a root password, which of course I don't have, I believe that root user is a kind of root default user for Xubuntu.  So before I format the pc, I wondering if there is any other way to fix this?  One option could be to reboot the machine, then open the console as root from the recovery mode on GRUB, create a new user, etc.. This could be great but unfortunately the screen says out of range when I try to start recovery mode, and in order to change the resolution for that screen I need to modify a file that requires root permissions. So basically I am stuck on a endless-loop. I could use another monitor with higher resolution and that might allow me to boot as recovery mode.   So how would you fix this issue, without swapping monitor, and formatting the pc? Is there a default password for that Xubuntu Root user?  This is not duplicated, as I cannot log into recovery mode or GRUB because of the resolution.


Expanding a dataset based on a weight field

I have a table that contains records in an un-expanded form. Each record has an associated integer weight that essentially informs us how many times the record should be replicated in order to get the true population.   Say, I have 3 records in my table. sampn ids a unique record and weight is the frequency weight. The un-expanded dataset looks like this:  sampn   weight  attrib1 attrib2 attrib3     1       2       23      32      65     2       1       32      56      75     3       3       54      25      87   Once expanded, the dataset will be like this (note - I removed the weight field - but this is not essential):  sampn   attrib1 attrib2 attrib3     1       23      32      65     1       23      32      65     2       32      56      75     3       54      25      87     3       54      25      87     3       54      25      87   I have tried to do this using cursors but it is taking a really long time to execute. Is there a clever way to do this really fast? Any predefined T-SQL stored procedure that achieves this?  Update All, Thanks for the answers! Really great learning experience! Performed the expansion operation on my dataset. Paul's auxiliary table of numbers had the best execution time.


How to find out the co-ordinate system using .prj file

I'm very new to GIS concepts. Is there a way or procedure of finding out whether the co-ordinate system is in UTM, latitude/longitude or in stateplane using .prj file?   My .prj file contains the following text:      GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS   84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]]


Adequate hyphenation of words already containing a hyphen

Unlike in English, in German there are quite a few words that contain a hyphen, e.g., "Arbeiter-Unfallversicherung" (workers' accident insurance). By default, (La)TeX will only break such words after the existing hyphen and disregard all other breakpoints. This behaviour will often result in overfull hboxes for German texts.  There are at least three ways to achieve proper hyphenation, two of which use shorthands of the babel package and none of which I consider to be really satisfactory:   The "= shorthand: Arbeiter"=Unfallversicherung. This allows every (otherwise legal) breakpoint and therefore may produce correct but unfavourable hyphenation (e.g. Arbeiter-Un-fallversicherung). This seems to be a method of last resort, suited for documents to be created with (almost) no manual intervention. The \- command: Ar\-beiter-Unfall\-ver\-si\-che\-rung. By manually setting allowed breakpoints, one can avoid unfavourable ones shortly before or after a present hyphen (I use a minimum of four characters as a rule of thumb). As a downside, one has to look up the correct breakpoints of the respective words. Also, the body of a LaTeX document may become quite cluttered. The "- shorthand: Ar"-beiter-Unfall"-versicherung. This method (the one I'm currently using) also avoids unfavourable breakpoints and allows for a tidier document body. But one still has to look up the correct breakpoints.   To cut a long story short: Is there a way to automatically allow hyphenation of words already containing a hyphen, while disregarding breakpoints less than, say, four characters before or after the existing hyphen?


Getting used to projective coordinates, need help describing (2) objects geometrically

I'm trying to get an intuition for what things look like in projective coordinates. There are two curves that I have to work a problem with, but I'm not sure how to visualize them. They are  $V(u^2 X + v^2 Y + uvZ) \subset \mathbb{P}^2 \times \mathbb{P}^1 $  $V(u^2 X^2 + v^2 Y^2 + uvZ^2) \subset \mathbb{P}^2 \times \mathbb{P}^1$  where $[u : v]$ are the projective coordinates of $\mathbb{P}^1$ and $[X : Y : Z]$ are the projective coordinates of $\mathbb{P}^2$. Is there any way to describe these objects geometrically?


I just tried a new pair of ear pods connected via Bluetooth to my MacBook Pro (early 2011), where I run Ubuntu 19.10 . The WiFi connection stopped working properly, with about 42% packet loss.   I've tried @Pilot6's suggestion:  sudo tee /etc/modprobe.d/iwlwifi-opt.conf <<< "options iwlwifi bt_coex_active=N"   ...and @Buried Alive (Here's the link tot he post: ) (what a nickname), but none of theirs worked.  Anybody else who may know if there is a solution to this?  Here's the output of lspci -knn | grep Net -A3; lsusb:  antonio@mclinux:~$ lspci -knn | grep Net -A3; lsusb 02:00.0 Ethernet controller [0200]: Broadcom Inc. and subsidiaries NetXtreme BCM57765 Gigabit Ethernet PCIe [14e4:16b4] (rev 10) Subsystem: Broadcom Inc. and subsidiaries NetXtreme BCM57765 Gigabit Ethernet PCIe [14e4:16b4] Kernel driver in use: tg3 Kernel modules: tg3 02:00.1 SD Host controller [0805]: Broadcom Inc. and subsidiaries BCM57765/57785 SDXC/MMC Card Reader [14e4:16bc] (rev 10) -- 03:00.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM4331 802.11a/b/g/n [14e4:4331] (rev 02) Subsystem: Apple Inc. AirPort Extreme [106b:00d6] Kernel driver in use: wl Kernel modules: bcma, wl Bus 002 Device 003: ID 05ac:8242 Apple, Inc. Built-in IR Receiver Bus 002 Device 002: ID 0424:2513 Standard Microsystems Corp. 2.0 Hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 003: ID 05ac:8509 Apple, Inc. FaceTime HD Camera Bus 001 Device 006: ID 045e:07fd Microsoft Corp. Nano Transceiver 1.1 Bus 001 Device 005: ID 05ac:0252 Apple, Inc. Internal Keyboard/Trackpad (ANSI) Bus 001 Device 009: ID 05ac:821a Apple, Inc. Bluetooth Host Controller Bus 001 Device 004: ID 0a5c:4500 Broadcom Corp. BCM2046B1 USB 2.0 Hub (part of BCM2046 Bluetooth) Bus 001 Device 002: ID 0424:2513 Standard Microsystems Corp. 2.0 Hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub   PS: I cant get it connected to another Bluetooth device and have both connection working simultaneously, what might suggest that the problem is with the ear pods, but it works just fine with a Sony Vaio computer, also running Ubuntu 19.10.  Any attempt to help is appreciated.  Cheers, A


iPhone no message alert sound when near MacBook

I've noticed that when my phone is near my MacBook, I only receive notifications for Messages on my MacBook. My iPhone remains silent, and the screen does not light up.   Is this an expected behavior (feature not a bug?), and is there a way to ensure that the phone always dings and lights up for message notifications?  Thanks!


Supercooled water immedaitely freezes to ice when a tiny ice is touched to it.How is it possible?


"Removed" question, is it possible to see the history of changes?

A bit disappointed to see     ... since I have put quite a lot of effort and time answering the question also received 55 rep points from it so I can't understand the reason it was removed.   After some discussion in the comments section and some tips from @Molot and @Gnat, I'd like to ask a favor from our moderators; please see the revision history as I believe the question may have got poorer through the editing. I honestly can't remember the question in the original form. All it takes is a simple verification to conclude one of the below two points:   If there were no significant changes made to the question I will accept the fact that I shouldn't have answered that question in first place and try to improve my judgement skills in future.  If the question got poorer through editing I'd like to ask for the removal to be reversed.     Was the user removed? Please, explain to me why was this deleted?  Some have said that the question was really poor. In the format  yes I do agree it was quite poor, but was it poor enough that it needed to be deleted?


How to find all ring homomorphisms from $\mathbb Z_{12} \to \mathbb Z_{30}$?    I know that it is enough to determine $f([1]_{12})$ ; moreover $f([1]_{12})$ should be an idempotent element of $\mathbb Z_{30}$ and $\text{ord}(f([1]_{12})\mid 12$ and $30$, so we must find the idempotents in $\mathbb Z_{30}$ whose additive orders divide $\gcd(12,30)=6$. But this still leaves a lot to check. Is there any further restrictions on homomorphisms of such type?


We have an application which we need to integrate with salesforce.   Unfortunately this legacy application supports RPC SOAP calls only, we cannot use out of the box wsdl2apex to build the integration on it. Doing so gives the error:     Unsupported WSDL style 'rpc'. Only supports Document/literal/wrapped services.   We are considering an inbetween Heroku layer where we can build a custom java app to build the integration between salesforce and other application. Is there a better way to do this or how do you guys currently do an SOAP RPC call using apex? Is there any tool which can do SOAP RPC integration?


At work we are being asked to create XML files to pass data to another offline application that will then create a second XML file to pass back in order to update some of our data. During the process we have been discussing with the team of the other application about the structure of the XML file.   The sample I came up with is essentially something like:  <INVENTORY>    <ITEM serialNumber="something" location="something" barcode="something">       <TYPE modelNumber="something" vendor="something"/>     </ITEM> </INVENTORY>   The other team said that this was not industry standard and that attributes should only be used for meta data. They suggested:  <INVENTORY>    <ITEM>       <SERIALNUMBER>something</SERIALNUMBER>       <LOCATION>something</LOCATION>       <BARCODE>something</BARCODE>       <TYPE>          <MODELNUMBER>something</MODELNUMBER>          <VENDOR>something</VENDOR>       </TYPE>    </ITEM> </INVENTORY>   The reason I suggested the first is that the size of the file created is much smaller. There will be roughly 80000 items that will be in the file during transfer. Their suggestion in reality turns out to be three times larger than the one I suggested. I searched for the mysterious "Industry Standard" that was mentioned, but the closest I could find was that XML attributes should only be used for meta data, but said the debate was about what was actually meta data.  After the long winded explanation (sorry) how do you determine what is meta data, and when designing the structure of an XML document how should you decide when to use an attribute or an element?


Is the "Journal of Advances in Mathematics" a real journal?

While looking for a journal to publish my paper I noticed that one of the people I follow on ResearchGate has published his paper in      Journal of Advances in Mathematics   I never heard of this journal before yet it has impact factor of 1.244 or at least that is what it says on the journal .  Is this a real mathematics journal or fraud? Thanks.


I have a string that comes in the format name = "1/2/2021", how can I convert this string to the format newName = "2021-2-1" original =  name day = original[0] month = original[2] year = original[4:8] combination = year + "-" + month + "-" + day  I have tried using this but brings wrong values when date or month changes to more than 2 characters


Getting exception while executing sql syntax

describe syntax is not working in PLSql :  I am using below syntax :  DESCRIBE tblcustomer;   I am getting below exception after executing above query :  ERROR:  syntax error at or near "DESCRIBE" LINE 1: DESCRIBE tblcustomer;         ^  ********** Error **********  ERROR: syntax error at or near "DESCRIBE" SQL state: 42601 Character: 1


delete millions of files within a directory

The other day I ran bleachbit on my system. I had enabled wipe disk space option in it. It took several hours and my disk space filled up completely (100GB or so). After waiting forever, I decided to terminate the program and delete the files manually.   Now the problem: I'm not able to delete the files or the directory. I cannot do an ls within the directory. I tried rsync -a --delete, wipe, rm, different combos of find & rm, etc  I followed the instructions here and noticed the "Directory Index Full!" error in my logs as well.   I noticed that the stat command returned an unusually large directory size of more than a GB. Usually it's just 4096 or something around tens of thousands.  nameh@labs ~ % stat kGcdTIJ1H1                                                                               File: ‘kGcdTIJ1H1’   Size: 1065287680  Blocks: 2080744    IO Block: 4096   directory Device: 24h/36d Inode: 9969665     Links: 2 Access: (0777/drwxrwxrwx)  Uid: ( 1000/  nameh)   Gid: ( 1000/  nameh) Access: 2014-10-31 07:43:08.848104623 +0530 Modify: 2014-10-31 07:43:19.727719839 +0530 Change: 2014-10-31 07:43:19.727719839 +0530  Birth: -   The "ONLY" command that so far seems to be able to delete files within this dir is the srm command (secure deletion toolkit by THC). All other commands do not work. srm has been running for 20 hours now and has freed up around 1.1 GB so far. It's running with the least secure mode.  sudo srm -v -rfll kGcdTIJ1H1   Ideas?  edit: My question is "how do I delete the directory quickly?". Like in a few hours or so without having to spend several days to delete the files. rm -rf does nothing.


Proof: There are infinite prime numbers of the form 4k+3

I have to proof if true or wrong: There are infinite prime numbers of the form 4k+3.  I want to proof: Yes, this is true. My ideas:  1) Assume - as a contradiction - that there are only infinite prime numbers. Let $p_k$ be the highest of them of the form 4k+3. Let $p_1 = 3, p_2 = 5, ...$ the sequence of prime numbers.  So define $N := 4*(3*5*...*p_k) - 1$. Then we have  a) N divided by 4 has remainder 3 and 3 divided by 4 has remainder 3, because: $ N \equiv -1 \equiv 3 (mod 4)$.  b) Then I'd like to show that N does have a prime-factor of the form 4k+3 which is higher than $p_k$  << here I don't know how to show this.  I'd appreciate any comments on whether my ideas are correct or not.


Unwanted vertical shift when using overlay on itemize/enumerate

The following code generate a vertical shift on the item 1. on the next slides. I don't know why and after few try, it's still moving when I go to next slides. Do you know why and how should I do to correct this ? I have the same problem for an other slide when the enumerate content appear on it.  \documentclass[hyperref={pdfpagemode=FullScreen},xcolor=table,t]{beamer}  \begin{document} \begin{frame} \frametitle{Frame Title} \begin{itemize}     \item<+-> first item     \begin{enumerate}         \item<+-> item 1.         \only<+>{         \begin{enumerate}[a.]             \item item a.             \item item b.             \item item c.         \end{enumerate}         }         \item<+-> item 2.     \end{enumerate} \end{itemize} \end{frame} \end{document}     Addition by @samcarter  The problem can be simplified a bit: a nested itemization influences the top alignment of the top-level itemization.  MWE:  \documentclass[t]{beamer}  \begin{document}  \begin{frame} \begin{itemize}     \item item 1. \end{itemize} \end{frame}  \begin{frame} \begin{itemize}     \item item 1.     \begin{itemize}         \item item a.     \end{itemize} \end{itemize} \end{frame}  \end{document}


$1 + \frac{1}{\sqrt{2}} + \frac{1}{\sqrt{3}} + \ldots + \frac{1}{\sqrt{n}} \leq 2\sqrt{n}$ by mathematical induction

I need the following by the principle of Mathematical induction:  \begin{align*} 1 + \frac{1}{\sqrt{2}} + \frac{1}{\sqrt{3}} + \ldots + \frac{1}{\sqrt{n}} \leq 2\sqrt{n} \end{align*} I can easily find out the base case for n=1 is true.  However, I can't find the proof in the induction step.   I assume: \begin{align*} 1 + \frac{1}{\sqrt{2}} + \frac{1}{\sqrt{3}} + \cdots + \frac{1}{\sqrt{n}} \leq 2\sqrt{n} \end{align*}  To proof: \begin{align*} 1 + \frac{1}{\sqrt{2}} + \frac{1}{\sqrt{3}} + \ldots + \frac{1}{\sqrt{n}} + \frac{1}{\sqrt{n+1}} \leq 2\sqrt{n+1} \end{align*} Can someone help me find a way to proof the inductive step too?  Thank you!


I ran this command : sudo apt-get install mysql-server and I got this as the output:      Reading package lists... Done     Building dependency tree            Reading state information... Done     The following additional packages will be installed:       libevent-core-2.1-6 mysql-server-5.7 mysql-server-core-5.7     Suggested packages:       mailx tinyca     The following NEW packages will be installed:       libevent-core-2.1-6 mysql-server mysql-server-5.7 mysql-server-core-5.7     0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.     Need to get 0 B/10.5 MB of archives.     After this operation, 92.9 MB of additional disk space will be used.     Do you want to continue? [Y/n] Y     Preconfiguring packages ...     Selecting previously unselected package mysql-server-core-5.7.     (Reading database ... 193811 files and directories currently installed.)     Preparing to unpack .../mysql-server-core-5.7_5.7.29-0ubuntu0.18.04.1_amd64.deb ...     Unpacking mysql-server-core-5.7 (5.7.29-0ubuntu0.18.04.1) ...     Selecting previously unselected package libevent-core-2.1-6:amd64.     Preparing to unpack .../libevent-core-2.1-6_2.1.8-stable-4build1_amd64.deb ...     Unpacking libevent-core-2.1-6:amd64 (2.1.8-stable-4build1) ...     Selecting previously unselected package mysql-server-5.7.     Preparing to unpack .../mysql-server-5.7_5.7.29-0ubuntu0.18.04.1_amd64.deb ...     Unpacking mysql-server-5.7 (5.7.29-0ubuntu0.18.04.1) ...     Selecting previously unselected package mysql-server.     Preparing to unpack .../mysql-server_5.7.29-0ubuntu0.18.04.1_all.deb      Unpacking mysql-server (5.7.29-0ubuntu0.18.04.1) ...     Setting up libevent-core-2.1-6:amd64 (2.1.8-stable-4build1) ...     Setting up mysql-server-core-5.7 (5.7.29-0ubuntu0.18.04.1) ...     Setting up mysql-server-5.7 (5.7.29-0ubuntu0.18.04.1) ...     /var/lib/dpkg/info/mysql-server-5.7.postinst: line 191: /usr/share/mysql-common/configure-symlinks: No such file or directory     dpkg: error processing package mysql-server-5.7 (--configure):      installed mysql-server-5.7 package post-installation script subprocess returned error exit status 127     dpkg: dependency problems prevent configuration of mysql-server:      mysql-server depends on mysql-server-5.7; however:       Package mysql-server-5.7 is not configured yet.  dpkg: error processing package mysql-server (--configure):  dependency problems - leaving unconfigured No apport report written because the error message indicates its a followup error from a previous failure.                           Processing triggers for libc-bin (2.27-3ubuntu1) ... Processing triggers for systemd (237-3ubuntu10.39) ... Processing triggers for man-db (2.8.3-2ubuntu0.1) ... Processing triggers for ureadahead (0.100.0-21) ... Errors were encountered while processing:  mysql-server-5.7  mysql-server E: Sub-process /usr/bin/dpkg returned an error code (1)   I tried removing and installing again but it showed the same error I followed the these steps too but was of no use sudo dpkg --configure mysql-server-5.7 and also tried sudo apt-get upgrade.


How is the curl of the electric field possible?

Taking the curl of the electric field must be possible, because Faraday's law involves it: $$\nabla \times \mathbf{E} = - \partial \mathbf{B} / \partial t$$ But I've just , where it says  The curl of the gradient of any twice-differentiable scalar field $\phi$ is always the zero vector: $$\nabla \times (\nabla \phi)=\mathbf{0}$$  Seeing as $\mathbf{E} = - \nabla V$, where $V$ is the electric potential, this would suggest $\nabla \times \mathbf{E} = \mathbf{0}$. What presumably monumentally obvious thing am I missing?


How do I lock my Mac without changing the display (keeps showing output)?

I'd like to lock my Mac, that is, require a password before any input.   This is normal.   What's different, though, is that I'd like to be able to show the exact same output as if the screen was not locked.   Let's say, for a trivial example, that I was watching a the output of a long-running process.   If I could do this, I could then lock the mac, but still be able to see the output. If I wanted to do anything other than watch the output, though, I'd need to unlock the Mac.   Note: I have done some cursory research on this.   But it's pretty hard to find this in a search engine.   Even on the StackExchange, most of the questions are about how to lock the screen without putting the Mac to sleep or activating a screen saver:         For those sorts of things, control+⌘+Q works just fine. I'm asking about something different.   Update: Looks like this guy asked something similar:    And the best Invisible Screen Saver for multiple monitors is Transparent by Monkey Bread Software.     Now I just need to find out how to lock the screen and go to that screensaver in one stroke.


mysql php selecting fields from 2 tables, with the same field names

So I have a bespoke CMS that allows dynamic creation of forms and lists etc. I have noticed an issue where it grabs the data for the list, which is conflicting with an approval table in the database.  The problem is, if the table with the data has fields names the same as field names in the approvals table, then when i mysql_fetch_array and it returns the values in an array, it will only return one field name  So an example of what is being returned  Array (     [id] => 1 )   And ideally I would want it returned as  Array (     [approvals.id] => 1     [affiliates.id] => 2 )   So how can I make it prefix the table name to the results array to counteract field names called the same thing? I dont want to go through changing the field names as its pretty  embedded.


Welcome , you have been logged in, click here to refresh

I logged in to stackoverflow from my ericsson mobile through OperaMini-6.1 browser. And, then I wanted to visit my GreatOutdoors profile. I clicked the link, and saw the pop-up stated as the title of this question. And, then I kept on refreshing, the page didn't appear. Tried it with UCBrowser-8.3, it worked. Any issue here with OperaMini-6.1?


Why only highest degree of polynomial for Big Oh?

Why do we just take the highest degree of polynomial for Big Oh notation. I understand that we can drop the constants as they won't matter for a very high value of 'n'.    But, say an algorithm takes (nlogn + n) time, then why do we ignore 'n' in this case. And the big Oh comes out to be O(nlogn). Big Oh has to be the upper bound of time taken by the algorithm. So, shouldn't it be (nlogn + n), even for very high values of n?


How should an educational institute woo good faculty?

What steps must an educational institution wanting to recruit good faculty take? There is a cycle in the academia:    Good doctorates from top universities invariably join other top universities as faculty members.  Good students aspire to study in top universities under excellent faculty members.   Suppose a new educational institution or department springs up and desires to set up a top-quality group, how does it break into this cycle? I suppose this could take some years, but is money-power the only thing that could be wielded by the institute to achieve its end?


how can the current flow if the potential difference is 0 volts?

I have read so many articles on so many websites about transistors and everywhere it says that when transistor is acting as a closed switch and conducting the voltage across collector-emitter is 0 volts, so how can the current flow if the applied voltage across two points is 0 volts?


I've been working on some problems related to multivariate distributions in my independent studies, and I came across one that I am feeling mixed about. Consider $X \sim Poisson(\lambda_x) \wedge Y \sim Poisson(\lambda_y),$ and consider $W = X + Y.$ I want to figure out the conditional distribution of $X$ given $W = w.$ I have a feeling that I should go about proving the $W \sim Poisson(\lambda_x + \lambda_y)$, but for now I will assume this (if anyone has any suggestions on how to prove that one, I'd like some help on that too).  We see that $$P(X = c | W = w) = \frac{P(X = c \wedge W = w)}{P(W = w)} = \frac{P(Y = w - c)}{P(W = w)}$$ $$=\frac{(\lambda_y)^{w-c} e^{-\lambda_y}\frac{1}{(w-c)!}}{         (\lambda_x + \lambda_y)^{w} e^{-(\lambda_x+\lambda_y)} \frac{1}{w!}}.$$  I thought this would be enough, but my professor told me that I should find some way to manipulate this into a binomial distribution. Any recommendations on where to simplify this? I am having some difficulties figuring this out.


What is different between x.shape[0] and x.shape in numpy? I code without [0] then have a bug: "TypeError: arange: scalar arguments expected instead of a tuple.", but when I add [0] in, my code runs completely.  And why i can't type x.shape[1] or x.shape[1000]?   Looking forward to receiving answers from everyone, many thanks!!


Subsurf on a crown. How can I smooth some edges and keep others sharp?

How can I smooth all crown but don't smooth the top of the crown? I did a subdivision surface, but this didn't work. All crown became smooth and changed form.


I'm a PhD student involved in  based on StackOverflow data. In doing so I am of course very interested in related work about SO. However, there seems to be no centralised place where academic papers about SE/SO are listed, although . In addition to the afore-linked blog post (that mentions some papers from 2010), I found two other questions on meta ( and ) that also list a few papers. However, this is IMO both hard to maintain as well as counter-intuitive. What I typically see for other data sources / tools is a separate section on their website where they list all publications that use their data. For example:   - a curated collection of software systems intended to be used for empirical studies of code artefacts;  - an automated program verification environment;  - a software development effort dataset.  What do you think about such a feature? PS. I already have a list of new papers about SO (compiled using Google Scholar) waiting for the right place to be added. Update: I have compiled a list of academic papers .


Likelihood Function for exponential Distribution

I am trying to do an excerise on likelihood functions and score vectors and I am having some trouble extending it to parameter vectors. The question is stated below. Suppose we have two independent samples: $X_{1}, ..., X_{n}$ are iid Exponential random variables with mean $θ_{1}$ and $Y_{1}, . . . , Y_{n}$ are iid Exponential random variables with mean $θ_{2}$. Find the likelihood and log likelihood functions for the parameter vector $θ = (θ_{1}, θ_{2})^{T}. $ In this case would the likelihood function be $$\prod{θ e^{-θ x_{i}} = θ ^ne^{-θ\sum x_{i}}}$$ (same as one with one parameter)? Or would it be the product of the two functions as shown below: $$\prod{θ_{1} e^{-θ_{1} x_{i}} θ_{2}e^{-θ_{2}y_{i}} = θ_{1} ^ne^{-θ_{1}\sum x_{i}}} θ_{2}^{n}e^{-θ_{2}\sum y_{i}}$$ Or would it be something different? Thanks!


Finding a closed form for $\cos{x}+\cos{3x}+\cos{5x}+\cdots+\cos{(2n-1)x}$

We have to find      $$g(x)=\cos{x}+\cos{3x}+\cos{5x}+\cdots+\cos{(2n-1)x}$$   I could not get any good idea .  Intialy I thought of using   $$\cos a+\cos b=2\cos(a+b)/2\cos (a-b)/2$$


It seems that, given she has given her life for Harry, why not have become a ghost and helped Harry, or even 'mothered' him as much as a ghost could, too. If I were Harry, I think I would have preferred this to never knowing his mother. And I think that Lily herself should have preferred this to see her son grow up, even help protect him especially in a time of peril in the Wizarding World.


(How) can I determine the characteristics of an unidentified SMPS transformer?

I have torn down a crappy Antec Neo HE power supply that would turn on randomly only. It's rated 430W, amongst these 3.3V/22A, 5V/14A, 3 x 12V/16A.  I'm planning to use it for parts in a home made power supply project. There is an unidentified transformer (marked VRL35W015 on its top, SBI 4.2 E150436 C on its side) which I'd like to know how I can check its features, e.g. frequency range, max current, voltage and whatnot. The SBI 4.2 marker lead me to a  that does unfortunately not publish the specification for that transformer type.  Apparently the transformer has two primary and two secondary windings. How can I check the characteristics of this transformer? Is there a typical circuitry I can build to check it out?    EDIT: Actually the only code that is specific to this transformer is VRL35W015. SBI 4.2 and E150436 seem to be reference model or something similar. There is a small transformer next to this one, both share the same SBI 4.2 and E150436 but the smaller one has a different identifier: VEE19FRC9.  This transformer also has 6 pins on the secondary, wired together in adjacent pairs on the PCB, the primary four pins, independently connected. The document pointed to by  seems to confirm, like the hinted thread, the fact that this transformer has been specifically designed for this Antec Neo HE. Not any reason to ditch this transformer, to me of course.  I will observe (frequency, voltages and apparent ratios) with my oscilloscope how the transformer behaves. This will hopefully give me basic information, which I'll further use in my "quest". Lot of fun ahead.


If I have three items that all have the Ink-Saver (Main) ability, do I have significantly reduced ink usage or is it the same as if I only had one of those?  I suppose this question may not apply to all abilities (multiple Recon abilities likely provide no additional benefit), but it would be interesting to know if certain abilities like Strength Up stack, and if they do, do they stack linearly (increases each hit's damage by a certain amount) or multiplicatively (increases damage by a certain %).  Gear Abilities in question:   Ink Saver (Main/Sub) Special Charge Up Special Duration Up Ink Recovery Up Quick Respawn Special Saver Bomb Range Up Tenacity Run/Swim Speed Up Defense/Damage Up


Got the "one-of-the-top-posters" e-mail but half was the Association Bonus (+100)

I don't think this was the intended response.  I joined and posted only one answer and managed to snag the #4 slot for that week. But had it not been for that initial 100 points I would have been only #18.


Commutation relations $[\phi(x), \phi^\dagger (y)]=-i \Delta(x,y)$ for spacelike separations $(x-y)^2<0$

In my QFT course, we studied the Klein Gordon equation, and we found that the field operators verifies : $[\phi(x), \phi^\dagger (y)]=-i \Delta(x,y)$  With $$\Delta(x,y)=i \int d\widetilde{k} (e^{-ik(x-y)}-e^{+ik(x-y)})$$  Where $d\widetilde{k}=\frac{d^3k}{2k^0(2\pi)^3}$.  And we said that : if $(x-y)^2<0$ then $\Delta(x,y)=0$  But I don't know how to prove this ? I tried to manipulate the integral to show this but nothing very useful...  How to prove this ?  And as I understand the property, it means that if we have $x$ and $y$ that have space-like separation, then they commutes.   So in more physical way, it means that if I measure $\phi$ in $x$ and then in $y$ or in $y$ and then in $x$ in a faster way than light could reach the distance between $x$ and $y$, I will have the same result. Which is logic because in thoose configurations, the field "can't be aware" of a previous measurement as $(x-y)$ lives outside of the light cone.  So my two questions :   How to prove that $\Delta(x,y)=0$ for $(x-y)^2<0$. Is my physical interpretation of this entirely correct?


Weighted random selection with and without replacement

Recently I needed to do weighted random selection of elements from a list, both with and without replacement. While there are well known and good algorithms for unweighted selection, and some for weighted selection without replacement (such as modifications of the resevoir algorithm), I couldn't find any good algorithms for weighted selection with replacement. I also wanted to avoid the resevoir method, as I was selecting a significant fraction of the list, which is small enough to hold in memory.  Does anyone have any suggestions on the best approach in this situation? I have my own solutions, but I'm hoping to find something more efficient, simpler, or both.


How can I install this programmable switch where a neutral is not present?

I'm trying install  but the instructions do not match reality. The instructions refer to the existence of a black (load) cable and a white (neutral) cable supposedly coming out of the wall, but instead I have two black cables and a naked wire. Is the naked wire the equivalent of the white in the diagram?


As we know moving objects have a shorter length as seen from a rest frame. $$L=L_0 \sqrt{1-  \frac{v^2}{c^2}   }$$ The first question that arises, is length contraction real or just imaginary for an observer in the rest frame? Secondly what about atomic distances, do they also get shorter as the object moves faster and faster? Atomic distances also effect the intermolecular forces, how do they get balanced? Many quantum problems have length as a parameter, how do you justify that the results will be the same? And finally, does length contraction mean space contraction? As in muon half life problems, one explains in the muon frame the distance travelled by the muon will be shorter.


What's the best files and directories permission for shared hosting

i'm using a shared hosting for my Drupal Website and I'm having some security troubles especially with folders and files permissions. So after some researches in the  and some  and even in  , I made my configuration like this:     Any Drupal php file: 444  Drupal folders: 555 SITES folder: 755 SITES/DEFAULT folder: 505 SITES/ALL folder: 705 SITES/ALL files:604 settings.php : 404 SITES/DEFAULT/FILES folder: 775   Is there anything to correct or to adjsut for more security?


Quoting :     The girls' and boys' teams are both in the playoffs. (Both girls and   boys have their own team--both have their own apostrophe.)       The girls   and boys' team is excited about being in the playoffs. (One team of   girls and boys--one apostrophe.)   Is there a sentence that could be formed using      girls' and boys' team — i.e. plural boys with apostrophe; plural girls  with apostrophe but a singular team?


Execute a terminal command from a Cocoa app

How can I execute a terminal command (like grep) from my Objective-C Cocoa application?


How is it possible that in scenario 1 resistor R1 converts 5V of energy to heat and in scenario 2 the same resistor R1 converts 2.5V of energy to heat?  The resistor R1 in both scenarios are exacly the same, I don't seem to grasp what happens on the physical level to the electrons how they "know" when to dump all their energy at once in resistor R1 in scenario 1 or to divide the energy they have proportionally over the resistors R1 and R2 in scenario 2.  I have read an explenation , but it's still not clear. How is it possible that the voltage is different at point A going through the same amount of resistance? I would expect a linear relation between voltage and resistance.  Could someone explain what physically happens that causes this?         – Schematic created using   Edit  Is my understanding right? According to   The resistance drops liniar along the path.  In scenario 1 at the start of R1 the resistance the current encounters is 100\$\Omega\$ and at the end of R1 it encounters 0\$\Omega\$.  In scenario 2 at the start of R1 the resistance the current encounters is 200\$\Omega\$ and at the end of R1 it encounters 100\$\Omega\$.  If this is true, why does point A in scenario 2 have more volt left if it has encountered a higher resistance of 200\$\Omega\$ at the beginning opposed to scenario 1 where it encountered 100\$\Omega\$ at the beginning?


Boot Menu Screwed up, computer won't boot

I've been using Ubuntu to for years now, I'm an EE and love the system. This week I was having trouble with Ubuntu so I decided to do a fresh install parallel with Win XP.  The install crashed midstream and now I can not boot at all. I believe all I need to do is repair the grub.cfg file, or maybe another file?  So, I booted from my liveCD and went into the file structure and everything seems intact, However, the grub.cfg file looks like it's a mess. I don't remember how to gain access to GRUB via permissions. I did it once before a year ago.  Any one with any ideas?


I am currently unable to find any wifi connections in Ubuntu. It works fine on Windows 10, however. Ive scoured the internet, but all of the posts are extremely old and i appear to be the only user with this problem. Im on the newest released version, 6.30.223.248 . Also, assume i have very little experience, because i have no idea what im doing.  I entered      sudo lshw -C network  *-network                   description: Ethernet interface    product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller    vendor: Realtek Semiconductor Co., Ltd.    physical id: 0    bus info: pci@0000:02:00.0    logical name: enp2s0    version: 15    serial: 2c:60:0c:81:c0:dd    size: 100Mbit/s    capacity: 1Gbit/s    width: 64 bits    clock: 33MHz    capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation    configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168h-2_0.0.2 02/26/15 ip=192.168.1.252 latency=0 link=yes multicast=yes port=MII speed=100Mbit/s    resources: irq:48 ioport:4000(size=256) memory:c4204000-c4204fff memory:c4200000-c4203fff *-network    description: Network controller    product: Qualcomm Atheros    vendor: Qualcomm Atheros    physical id: 0    bus info: pci@0000:03:00.0    version: 30    width: 64 bits    clock: 33MHz    capabilities: pm msi pciexpress bus_master cap_list    configuration: driver=ath10k_pci latency=0    resources: irq:53 memory:c4000000-c41fffff   entering lspci -nnk | grep -iA2 net comes back with   02:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 15) Subsystem: Acer Incorporated [ALI] RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller [1025:098a] Kernel driver in use: r8169 Kernel modules: r8169  03:00.0 Network controller [0280]: Qualcomm Atheros Device [168c:0042] (rev 30) Subsystem: Lite-On Communications Inc Device [11ad:1806] Kernel driver in use: ath10k_pci   entering dmesg | grep ath returns   [    9.909508] ath10k_pci 0000:03:00.0: pci irq msi-x interrupts 8 irq_mode 0 reset_mode 0  [   10.152414] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/cal-pci-0000:03:00.0.bin failed with error -2  [   10.152427] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware-5.bin failed with error -2  [   10.152430] ath10k_pci 0000:03:00.0: could not fetch firmware file 'ath10k/QCA9377/hw1.0/firmware-5.bin': -2  [   10.152437] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware-4.bin failed with error -2  [   10.152440] ath10k_pci 0000:03:00.0: could not fetch firmware file 'ath10k/QCA9377/hw1.0/firmware-4.bin': -2  [   10.152447] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware-3.bin failed with error -2  [   10.152449] ath10k_pci 0000:03:00.0: could not fetch firmware file 'ath10k/QCA9377/hw1.0/firmware-3.bin': -2  [   10.152456] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware-2.bin failed with error -2  [   10.152458] ath10k_pci 0000:03:00.0: could not fetch firmware file 'ath10k/QCA9377/hw1.0/firmware-2.bin': -2  [   10.152465] ath10k_pci 0000:03:00.0: Direct firmware load for ath10k/QCA9377/hw1.0/firmware.bin failed with error -2  [   10.152467] ath10k_pci 0000:03:00.0: could not fetch firmware (-2)  [   10.152470] ath10k_pci 0000:03:00.0: could not fetch firmware files (-2)  [   10.152472] ath10k_pci 0000:03:00.0: could not probe fw (-2)


I plan on receiving a $200,000 personal loan via wire transfer. Do I have to report this to the IRS?

After researching online, I found many websites that said wire transfers are not reported to the IRS, but others said that they were reported. I just want to make sure that I do not have to pay taxes on a loan. I am planning on depositing this loan in a traditional brokerage account for investment purposes and I hope that the only time I need to pay taxes is when I sell the securities that I end up buying.   Are there any pitfalls that I should watch out for as far as taxes go by receiving a loan as a wire transfer? Also, how would I report capital gains on trades that I have made? Do I actually have to send every single trade I make to the government and show profits and losses on each trade?


Can I rotate an object around it's own axis if it's parented to another object?

These wheels are both parented to the leg of a robot u see in the picture below. I want to make the wheels spin while they move with the legs but they rotate around the wrong axis. I already searched for solutions but they all talk about an empty, the thing is, I can't parent them to an empty because they're already parented to the leg.  When I put the transformation of the wheel on local, it uses the same axis as the parent object (I think? correct me if wrong), but this object (the leg) has a different angle so that's why it spins weird. Is there another way to fix the axis? Without parenting to an empty because I can't parent to 2 objects.


Prove that if $3|(a^2+b^2)$, then $3|a$ and $3|b$, where $a, b$ are integers

I would like to know how to prove the above statement by contradition. Somebody said that one should prove it by this method but I have no idea what it is.


How to get posts from two categories with WP_Query?

I'm using WP_Query to create 'latest posts' & 'popular posts' sections on my home page. I'm trying to just pull 5 posts from 2 categories (9 & 11) but it will only show posts from cat 9.  Here's the php I'm using for 'latest posts'-
         <?php           $cat = array(9,11);         $showposts = 5;         $paged = (get_query_var('paged')) ? get_query_var('paged') : 1;         $args=array(             'category__in' => $cat,              'showposts' => $showposts,             'paged' => $paged,             'orderby' => 'post_date',             'order' => 'DESC',             'post_status' => 'publish',            );          $the_query = new WP_Query ( $args ); //the query           $i = 0;while ($the_query->have_posts() ) : $the_query->the_post(); //start the loop         ?>          <?php         if($i==0){ //Sets the output for the top post         ?>

<a href="<?php the_permalink(); ?>"><?php the_post_thumbnail(350,187); ?>

<a href="<?php the_permalink(); ?>"><?php the_title(); ?>

<?php the_time('F jS, Y') ?>

<?php the_excerpt(); ?>

<a class="more-link" href="<?php the_permalink(); ?>">Read More »

           <?php             $i++;              } else { ?>

<a href="<?php the_permalink(); ?>"><?php the_post_thumbnail(145,93); ?>

<a href="<?php the_permalink(); ?>"><?php the_title(); ?>

<?php the_time('F jS, Y') ?>

          <?php } endwhile; //end of the loop ?>         <?php wp_reset_postdata(); // reset the query ?>
    Any suggestions?


$\epsilon - \delta$ proof that $\lim_{x \to a} \sqrt x = \sqrt a$

I am trying to prove,  $\lim_{x \to a} \sqrt x = \sqrt a$  As per the definition of limit for every $\epsilon > 0$ there is some $\delta > 0$ such that   $ 0 < |x-a| < \delta$ implies $|f(x) - \sqrt a| < \epsilon$  $|\sqrt x - \sqrt a|  = \frac {|x -a|}{\sqrt x + \sqrt a} $  since  $ 0 < |x-a| < \delta$  $\frac {|x -a|}{\sqrt x + \sqrt a} < \delta$  Can I stop my proof at this point since I found $\epsilon$ ( which is $\delta$ in this case)


I need to do an IN clause in my ID (INT)  But when I do this:        strQuery = "SELECT something FROM some table \n";   strQuery += "WHERE ID IN ({0})";    var idParameterList = new List<string>();    foreach (var id in lstLigID)   {       idParameterList.Add(id.ToString());   }    dbContext.Database.ExecuteSqlCommand(strQuery, string.Join(",", idParameterList));   I get this error:


For $n\geq 3$ there exist $x,y\in S_n$ such that $x$ and $y$ have order $2$ and $xy$ has order $n$.

Assume that $n\geq 3$. Let $S_n$ be the symmetric group with $n!$ elements. Prove that there exists $x$ and $y$ in $S_n$ such that $x$ and $y$ have order $2$ and $xy$ has order $n$.  For $n=3$, it is easy to see that $x=(1, 2)$ and $y=(1, 3)$ works. How to prove it for the general case?


I committed to Lifehacks, but now it has vanished from my profile page

For those who don't believe it:      Though it is good for me that now I don't have to fulfill my commitment, but I'd like to do it so can you bring it back?


How to write zeros in one pass to free space on FAT32 drive?

Most people will think either using dd or sfill to usually wipe free space with zeros... however, the limit with FAT32 drives are that the largest file size can only be 4 GB.   How can I create multiple, smaller, files, to wipe free space of a FAT32 drive, to overcome this limit?


If $P(z)=z^n+a_{n-1}z^{n-1}+a_{n-2}z^{n-2}+...+a_1z+a_o$ a polynomial whose coefficients are all real.

If $P(z)=z^n+a_{n-1}z^{n-1}+a_{n-2}z^{n-2}+...+a_1z+a_o$ a polynomial who's coefficients are all real.   Explain why if $z_1$ is a root of $P$, then $\bar{z_1}$ is also a root.  And give an example as to why the contrary is false if the coefficients of $P$ are not all real.


Why to use 50/60 Hz Frequency and Not other Higher/Lower Values?

At our homes and utilities, the frequency is 50/60 Hz. Why not use any other value such as 500 Hz, 200 Hz or a small value 40 Hz, 30 Hz. Previously I searched it over the StackExchange but I want to know the technical and logical reason.


Change css of static class with javascript

I'm trying to change the css rules on a class called active which have static css already but i would like to alter a rule in it to make an div animate slide. i don´t know how to target a class instead of an element with the name of the class.  Javascript  var active = document.getElementsByClassName('active'); active.style.color = 'red';   I´ve tried both these methods but none seems to work.  var i = 0;     while(i < divs.length) {         if(divs[i].className == "active") {             var b = 0;             for (var a = 0; a < 10; a++){                 divs[i].style.left = b+'em';                 b += 6;              }         }         i++;     }   I´t wont add left to the css rule nor color.  CSS  .active{ position:absolute; left:-60em;   Jquery is not an option in this case.


Logic Levels between 5(V) and 3.3(V) devices

I am using a 5V microcontroller to communicate with a Bluetooth module operating at 3.3V.  I have regulated the output from the 5V microcontroller rail to 3.3V rail for the Bluetooth module.   Since I am using a UART, I need to use a TX pin to go to the RX. The issue here I found is that the pins to the Bluetooth module aren't tolerable to 5V. So I decided to use a voltage divider to get 3.3V on the output.   Now, I got the UART TX working on the microcontroller side. Connecting to the RX of the Bluetooth, I see a logic 1 at the output.  After some debugging I found that infact the logic level is shifting between 2.3V for logic 1 and 1.79V for logic 0 (but this doesn't register as a 0). I presume 1.79V. Looking at the schematics of the Bluetooth Module, I found that the RX pin seems to be in tri-state between 2 resistors to VCC and GND. I need a 0V or lower than a certain tolerance for logic 0.  What can I use to get the proper logic level on the output for proper serial communication?