Find the residue  : \begin{equation} 1^{965}+2^{965}+...+2018^{965}  \equiv x\ (\textrm{mod}\ 2021), x=? \end{equation} My attempt so far: \begin{equation} \varphi(965)=\varphi(5)\varphi(193)=768. \end{equation} But from Euler theorem applied for all numbers coprime with both 5 and 193 we have:\begin{equation} \Rightarrow\ 2^{768}\equiv 1\ (\textrm{mod}\ 2021) \Rightarrow\ 2^{965}\equiv 2^{197}\ (\textrm{mod}\ 2021). \end{equation} In the same fashion we get that \begin{equation} 3^{965}\equiv 3^{197}\ (\textrm{mod}\ 2021). \end{equation} Unfortunatelly this does not seem to work. Any ideas how to start?

Prove that for any odd natural number $n$, the number $1^{2007}+2^{2007}+\cdots+n^{2007}$ is not divisible by $n+2$.


Before I ask the question, I know for sure this following question makes sense:  Prove that a necessary condition for $ f(z) $ to be analytic is that the Cauchy-Riemann equations are satisfied.  This question makes sense because if the Cauchy-Riemann equations are satisfied, $f(z)$ need not be analytic. Hence, why it's called a necessary condition.  But in order for $ f(z) $ to be analytic , there are 2 sufficient conditions, the Cauchy-Riemann equations must be satisfied and the partial derivatives must be continuous.  Now for the main question I want to ask:  Prove that a sufficient condition for $ f(z) $ to be analytic is that the Cauchy-Riemann equations are satisfied.  I'm asking this because I had it on my exam yesterday, now how could this make sense, the Cauchy-Riemann equations being satisfied should not be enough, the question did not mention the continuity of the partial derivatives, thus I treated this question as if it was asking "Prove that a sufficient condition for the Cauchy-Riemann equations to be satisfied is that $f(z)$ must be analytic".  So am I right and should I argue with my professor about that?  My question is not about when a function is holomorphic, my question is if the following makes sense as a proof question or not:  Prove that a sufficient condition for f(z) to be analytic is that the Cauchy-Riemann equations are satisfied.

It is, of course, one of the first results in basic complex analysis that a holomorphic function satisfies the Cauchy-Riemann equations when considered as a differentiable two-variable real function. I have always seen the converse as: if $f$ is continuously differentiable as a function from $U \subset \mathbb{R}^2$ to $\mathbb{R}^2$ and satisfies the Cauchy-Riemann equations, then it is holomorphic (see e.g. Stein and Shakarchi, or ). Why is the $C^1$ condition necessary? I don't see where this comes in to the proof below.   Assume that $u(x,y)$ and $v(x,y)$ are continuously differentiable and satisfy the Cauchy-Riemann equations. Let $h=h_1 + h_2i$. Then \begin{equation*} u(x+h_1, y+h_2) - u(x,y) = \frac{\partial u}{\partial x} h_1 + \frac{\partial u}{\partial y}h_2 + o(|h|) \end{equation*} and  \begin{equation*} v(x+h_1, y+h_2) - v(x,y) = \frac{\partial v}{\partial x} h_1 + \frac{\partial v}{\partial y} h_2 + o(|h|). \end{equation*} Multiplying the second equation by $i$ and adding the two together gives  \begin{align*} (u+iv)(z+h)-(u+iv)(z) &= \frac{\partial u}{\partial x} h_1 + i \frac{\partial v}{\partial x} h_1 + \frac{\partial u}{\partial y} h_2 + i \frac{\partial v}{\partial y} h_2 + o(|h|)\\\  &= \left( \frac{\partial u}{\partial x} + i \frac{\partial v}{\partial x} \right) (h_1+i h_2) + o(|h|). \end{align*}  Now dividing by $h$ gives us the desired result.   Does there exist a differentiable but not $C^1$ function $f: U \rightarrow \mathbb{R}^2$ which satisfies the Cauchy-Riemann equations and does NOT correspond to a complex-differentiable function?


Because a picture is worth a thousand words:    Should that not be You've earned the "Strunk & White" badge rather than the "Strunk &amp; White" badge?

Here’s a screenshot from my achievements inbox:    The rep gain on the Meta question has the &ldquo; and &rdquo; rendered correctly, but I see plain HTML entities on the badge notification.  I found a couple of similar questions about rendering in badges being different to rep changes, but I couldn’t find one that specifically mentioned special characters.  I can see the problem in Safari 8.0 (10600.1.25) and Chrome 38.0.2125.101, both on OS X 10.10 (14A388a), but the quotes are displayed correctly in the latest public version of the iOS app.


I was writing some code in aura and came across this scenario which I feel is more like a bug.  and function with more than 2 parameters gives incorrect values.  <aura:application >     <aura:attribute name="first" type="Boolean" default="true"></aura:attribute>     <aura:attribute name="second" type="Boolean" default="true"></aura:attribute>      <aura:attribute name="third" type="Boolean" default="false"></aura:attribute>      Print Answer: {!and(v.first,v.second,v.third)} </aura:application>   And to my surprise output was      Print Answer: true   I tried it in W18 and Spring 18, Still same output. The  for logical expression doesnt provide an answer, I belive the behavior should be consistent. The same formula works fine with database formula fields.

As I use the client side to enforce various pieces of business logic with aura:if statements, I'm finding that a given formula operator cannot handle more than two parameters.  For example, this works:  <aura:if isTrue="and(v.myAttributeString == 'Open', v.myAttributeBoolean == true)">     //do some stuff </aura:if>   But the following does not work (or at least the third "v.myAttributeSecondString" is not evaluated):  <aura:if isTrue="and(v.myAttributeString == 'Open', v.myAttributeBoolean == true, v.myAttributeSecondString == 'Yes')">     //do some stuff </aura:if>   Has anyone seen the same effect occur? Any documentation on this? Am I crazy and this actually does work, just not for me?  Thanks!


A lot of us have waited a very long time for the SE team to respond to a contact request via the contact form. Some of us just get impatient waiting, especially if we believe that the issue is (quote) "important". Also, the SE team gets a rather large volume of contact requests within each category.  The automatic response message to contact requests says that a response will be sent within 24 hours. However, the majority of contact requests I've sent overall aren't responded to within 24 hours, some get a response weeks later.  Based on this, it would be nice to have a more accurate "estimated response wait time" that loads live based on the current backlog of contact requests made and that have yet to be handled. This way, we reasonably know how much time to expect to wait before we get a response. For example, if this didn't exist, I might start to get anxious if I don't get a response a week later (since I was told I'd get one "within 24 hours"), but not so if the page clearly notes that the expected response time is two weeks. (To avoid confrontation if the team doesn't respond within the "expected" time frame or just a little bit too late, we can pad the number, e.g. say "within 2 weeks" if it's estimated at 10 days.)

So I had a dispute with the moderators at a specific SE site. As a result, I got suspended there. As per SE guidelines, I pressed the "Contact us" button and wrote to the higher powers to appeal.  That was 5-6 weeks ago. There was zero feedback, neither positive, nor negative, not even "it's in progress, please wait".  So what is this "contact us" thing supposed to do? Is it a placebo to make me feel better while being routed to dev/null?  What is the normal time it takes to process a "contact us" message?  Notes:   As far as I remember, I did not contact the team before. I'm a longtime user of multiple SE sites and never had any problems except for that one site. I'm pretty sure my form was submitted. I didn't make screenshots or anything, because I did not think I would need them in a post like this. I didn't expect a super-fast reply either, so I wasn't wondering after a week or two.


I would like to create a new image texture and define its name and size entirely via Python. The closest I can get is to generate the popup window where I change these parameters. I can't seem to find the answer anywhere. Is this possible?  I'm trying to create a script that auto-bakes a color ID map, tied into a single fat "Bake" button. I want the image texture's name and size to be predefined when generated.

I'm currently trying to extract textures from a binary file, and ideally I'd like to save each texture to a file or embed in the .blend file. However, before saving an image, I need to be able to create an image in memory from an array of pixel data.  The PIL library contains the kinds of functions I need to use, but it is not included with Blender. Is there anything similar to PIL in Blender? bpy.ops.image seems to be close to what I need, but lacks necessary pixel set/manipulation functions.


I am trying to match IP addresses found in the output of traceroute by means of a regex. I'm not trying to validate them because it's safe enough to assume traceroute is valid (i.e. is not outputting something like 999.999.999.999. I'm trying the following regex:  ([0-9]{1,3}.?){4}   I'm testing it in  and it does validate an IP address. However, when I try   echo '192.168.1.1 foobar' | grep '([0-9]{1,3}.?){4}'    I get nothing. What am I missing?

How to extract a text part by regexp in linux shell? Lets say, I have a file where in every line is an IP address, but on a different position. What is the simplest way to extract those IP addresses using common unix command-line tools?


Im trying to prove that every natural number is divisble by three if and only if the sum of its digits are divisible by three.  First i proved by induction that $10^n-1$ is divisible by 9 (and therefore 3) so i could use this in the next step, would this be valid...  ANy natural number can be given a decimal representation  Let $s\in N$  Let $k_0,k_1...k_n\in ${${0,...10}$}  $S=k_0 +10k_1+100k_2+...k_n10^n$  $= 9k_1 + 99k_2 + ... + k_n(10^n-1) + (k_0+k_1+...k_n)$  All terms are divisible by 3 but the sum of the digits in S. Therefore Dividing S by 3 will leave the same remainder as dividing the digits bys 3.  Is this a valid proof of the claim? Thank you for your time

I don't know if this is a well-known fact, but I have observed that every number, no matter how large, that is equally divided by $9$, will equal $9$ if you add all the numbers it is made from until there is $1$ digit. A quick example of what I mean:  $9*99 = 891$ $8+9+1 = 18$ $1+8 = 9$  This works even with really long numbers like $4376331$ Why is that? This doesn't work with any other number. Similarly for $11$ and alternating digits sums.


the following question has me stumped: Show that for a linear operator $T$ defined on a finite-dimensional space, the eigenvalues of $T^*T$ and $TT^*$ are the same. Its given in a tutorial chapter on finite-frame theory without proof.

First of all, am I being crazy in thinking that if $\lambda$ is an eigenvalue of $AB$, where $A$ and $B$ are both $N \times N$ matrices (not necessarily invertible), then $\lambda$ is also an eigenvalue of $BA$?  If it's not true, then under what conditions is it true or not true?  If it is true, can anyone point me to a citation?  I couldn't find it in a quick perusal of Horn & Johnson.  I have seen a couple proofs that the characteristic polynomial of $AB$ is equal to the characteristic polynomial of $BA$, but none with any citations.  A trivial proof would be OK, but a citation is better.


I am trying to access the GRUB menu by pressing shift, esc, space, etc, but I just can't get into it. I can't change the /etc/default/grub file unless I login. But I lost my password, so I can't do that!

I'm working on a Ubuntu system, and my client has completely forgotten his administrative password. He doesn't even remember entering one; however it is there.  I've tried the suggestions on the website, and I have been unsuccessful in deleting the password so that I can download applets required for running some files. Is there a solution?


I am missing the last word of string. this is code I used to store word into array. string arr[10]; int Add_Count = 0; string sentence = "I am unable to store last word" string Words = ""; for (int i = 0; i < sentence.length(); i++) {     if (Sentence[i] == ' ')     {         arr[Add_Count] = Words;         Words = "";         Add_Count++;     }     else if (isalpha(Sentence[i]))     {         Words = Words + sentence[i];     } }  Let's print the arr: for(int i =0; i<10; i++) {   cout << arr[i] << endl; }

I'm trying to iterate over the words of a string.  The string can be assumed to be composed of words separated by whitespace.  Note that I'm not interested in C string functions or that kind of character manipulation/access. Also, please give precedence to elegance over efficiency in your answer.  The best solution I have right now is:  #include <iostream> #include <sstream> #include <string>  using namespace std;  int main() {     string s = "Somewhere down the road";     istringstream iss(s);      do     {         string subs;         iss >> subs;         cout << "Substring: " << subs << endl;     } while (iss); }   Is there a more elegant way to do this?


Update  As was pointed out by Jiri Tousek, the error that was being thrown in my code has misled many amateur (and experienced) Java developers. Contrary to what the name seems to imply, ConcurrentModificationException does not have anything to do with multi-threading. Consider the following code:  import java.util.List; import java.util.ArrayList;  class Main {   public static void main(String[] args) {     List<String> originalArray = new ArrayList<>();     originalArray.add("foo");     originalArray.add("bar");     List<String> arraySlice = originalArray.subList(0, 1);     originalArray.remove(0);     System.out.println(Integer.toString(arraySlice.size()));   } }   This will throw a ConcurrentModificationException despite there being no threading involved.  The misleading exception name led me to think my problem was the result of how I was handling multi-threading. I've updated the title of my post with the actual issue.  Original (title: How to inform Java that you are finished modifying an ArrayList in a thread?)  I have code that looks roughly like the following:  class MessageQueue {     private List<String> messages = new ArrayList<>();     private List<String> messagesInFlight = new ArrayList<>();      public void add(String message) {         messages.add(message);     }      public void send() {         if (messagesInFlight.size() > 0) {             // Wait for previous request to finish             return;         }          messagesInFlight = messages.subList(0, Math.min(messages.size, 10));         for( int i = 0; i < messagesInFlight.size(); i++ )         {             messages.remove(0);         }          sendViaHTTP(messagesInFlight, new Callback() {             @Override             public void run() {                 messagesInFlight.clear();             }         });     } }   This is utilized in my code for analytics purposes. Every 10 seconds I call messageQueue.send() from a timer, and whenever an event of interest occurs I call messageQueue.add(). This class works *for the most part* -- I can add messages and they get sent via HTTP, and when the HTTP request completes the callback is run  The issue lies on the second tick of the timer. When I hit the line if (messagesInFlight.size() > 0) {, I get the following error:  java.util.ConcurrentModificationException         at java.util.ArrayList$SubList.size(ArrayList.java:1057)   It seems like I can't read the .size() of the array in one thread (the second timer's callback) because it thinks the array is still being modified by the other thread (the first timer's callback). However I would expect the first timer's thread was destroyed and cleaned up after my call to sendViaHTTP, since there was no additional code for it to execute. Furthermore, the HTTP request is completing within 500 milliseconds, so a full 9.5 seconds passes without anything touching the empty messagesInFlight array  Is there a way to say say "hey, I'm done modifying this array, people can safely read it now"? Or perhaps a better way to organize my code?

We all know you can't do the following because of ConcurrentModificationException:  for (Object i : l) {     if (condition(i)) {         l.remove(i);     } }   But this apparently works sometimes, but not always. Here's some specific code:  public static void main(String[] args) {     Collection<Integer> l = new ArrayList<>();      for (int i = 0; i < 10; ++i) {         l.add(4);         l.add(5);         l.add(6);     }      for (int i : l) {         if (i == 5) {             l.remove(i);         }     }      System.out.println(l); }   This, of course, results in:  Exception in thread "main" java.util.ConcurrentModificationException   Even though multiple threads aren't doing it. Anyway.  What's the best solution to this problem? How can I remove an item from the collection in a loop without throwing this exception?  I'm also using an arbitrary Collection here, not necessarily an ArrayList, so you can't rely on get.


This a tricky math question I encountered. I know a little bit about the answer. But I want somebody who is very good at math to help me find the real reason behind this.  OK  Lets start  $1^2 = 1$  $2^2 = 2+2$  $3^2 = 3+3+3$  ...........................  ................................  $x^2 = x+x+x+x+.....(x times)$  Differentiating with respect to $x$  We get  $2x = 1+1+1+1...... (x times)$  which is equal to  $2x = 1*x$  $2x = x$  Which is incorrect.  Where did I go wrong?? :O :O

Consider the following:   $1 = 1^2$ $2 + 2 = 2^2$ $3 + 3 + 3 = 3^2$   Therefore,   $\underbrace{x + x + x + \ldots + x}_{x \textrm{ times}}= x^2$   Take the derivative of lhs and rhs and we get:   $\underbrace{1 + 1 + 1 + \ldots + 1}_{x \textrm{ times}} = 2x$   Which simplifies to:   $x = 2x$   and hence    $1 = 2$.     Clearly something is wrong but I am unable pinpoint my mistake.


I don't understand why the work represent the change in energy of a system. I understand the work energy theorem but where did we get the formula of the work from in the first place. Also when I search for a derivation of the kinetic energy the only thing I find is a derivation using the work formula. Isn't there any other way to derive it?  I know that work and kinetic energy can be derived from one another but which formula came first and how??  Sorry for my bad English.

In all the places I've looked kinetic energy is derived from the definition of work, but I don't understand how the definition of work was developed with out the concept of kinetic energy. My question really is:  What is the logic behind the definition of  without referring to kinetic energy?  OR  What is the logic behind the definition of  without referring to work?


The dd command is one method to copy files from one device to other device. Other method is using Clonezilla. What are other ways to do it. What are the differences? In what conditions it's preferable to use this and not that?

This question exists because it has historical significance, but it is not considered a good, on-topic question for this site, so please do not use it as evidence that you can ask similar questions here.  While you are encouraged to help maintain its answers, please understand that "big list" questions are not generally allowed on Ask Ubuntu and will be closed per the .   Backup is incredibly important. Obviously there's no best backup tool, but a comparison of the options would be very interesting.   Graphical Interface? Command line? Incremental backups? Automatic backups? Install method: In standard repositories? PPA?


I have a list of tuples like [(module_name, module_abs_path)(mod2, path2), ...]  The modules are located in the 'modules' subdir where my script lives. I am trying to write a script which reads a conf file and makes some variables from the conf file available to the modules from the modules dir. My intention is to load and run all the modules from this script, so they get access to these variables.   Things I have tried so far but failed:   Tried using  __import__() but it says running by file name is not allowed Tried importlib.import_module() but gives the same error.   How should I go about doing this?

How can I load a Python module given its full path? Note that the file can be anywhere in the filesystem, as it is a configuration option.


My Asus Vivobook S200E has a problem with its touchscreen: it keeps pressing the right side of the screen, even when untouched.   I managed to disable the touchscreen in the Windows 8.1, and the configuration is saved every time I restart the PC. But if I boot into Ubuntu, the touchscreen is active again (of course). I have to run this in the terminal to turn off the touch:  xinput disable 'device name'    The touch would be off, but if I reboot Ubuntu, the touch is on again, so I have to type the script again at the start of my work with Ubuntu. I find this annoying, and is there any way that I can run the script at every startup?

How can I make an application automatically start when I have logged in?


If 7 accidents (all are indistinguishable i.e we care only about whether accident happen or not, not the details of it) happen in a week.  What is the probability of exactly two accidents on at least one day of a week.  My solution is given below  $$ \frac{1}{13 \choose 6} \Bigg[{7 \choose 1}{10 \choose 5} - {7 \choose 2} {7 \choose 4} + {7\choose 3} 4 \Bigg] = 0.681 $$  I used the equation that number of ways $r$ balls can be arranged in $n $ cells in ${n+r-1 \choose n-1}$ distinguishable ways.  Is it correct ?

If 7 accidents happen in a week, what is the probability that exactly 2 accidents happen in any day of the week.  I tried to work it this way.  2 accidents out of 7 can be taken in ${7}\choose{2}$$= 21$.  Now this can happen in any of the 7 days, so we have $7 \times 21$.  Now, the remaining 5 can happen in $6^5$ ways.  So the probability is  $\frac{7\times 21 \times 6^5}{7^7} = \frac{3 \times 6^5}{7^5}$   But this gives me a value greater than 1.   I know I am doing something wrong.  Can anyone help me ?


Let $n$ be an integer, $4|n$ if and only if the last two digit of $n$ are divisible by $4$.  I tried to use $4|n$ implies that $n\equiv 0 \pmod4$

Claim: A number is divisible by $4$ if and only if the number formed by the last two digits is divisible by $4$.   Here's where I've gotten so far.  Let $x$ be an $(n+1)$-digit number. So $x= a_na_{n-1} \dots a_2a_1a_0$. If $a_1 = 0$ and $a_0 =0$, then $x$ is a multiple of $100$ and therefore clearly divisible by $4$. So we must deal with the case when $(a_1 \neq 0 \lor a_0 \neq 0)$.  Then if $10a_1 + a_0 \equiv 0 \mod 4$ is true, then $x$ is divisible by $4$.  Do I need to do anything else or is this done? I feel like it's not quite complete, but I'm not sure how to proceed.


Some amount of bacteria are placed in a glass. One second later each  bacterium divides in two, the next second each of the resulting bacteria divides  in two again and again. After one minute the glass is full. When was the glass  half-full?

Suppose one bacterium is in a jar at 12AM, and then suppose there are two bacteria at 12:30AM,  and then there are four bacteria at 1AM, etc.  (a)  How many bacteria will be in the jar at 12PM that day?  (b)  Use trial and error to estimate at what time there will be 1 billion (1,000,000,000) bacteria in the jar.  for a) is it going to be 44 bacterias ? or am i wrong? Please help with b), i have no idea how to figure it out in short term Thanks


in the example at      // map::begin/end #include <iostream> #include <map>  int main () {   std::map<char,int> mymap;   std::map<char,int>::iterator it;    mymap['b'] = 100;   mymap['a'] = 200;   mymap['c'] = 300;    // show content:   for (std::map<char,int>::iterator it=mymap.begin(); it!=mymap.end(); ++it)     std::cout << it->first << " => " << it->second << '\n';    return 0; }   why is the iterator it preincremented in the for loop?

We have the question   What's the answer for C++?


I currently use mysql_real_escape_string to escape variable in mysql query. I know how to use bindValue, but I have a question about protection when I'm trying to insert table name from variable. For example  $tablename = mysql_real_escape_string($name_from_form); $get = mysql_query("SELECT * FROM ".$tablename." WHERE keyword='something'");   Can anybody help me with an example of how to do PDO prepared statements which will do the same as above?

Why can't I pass the table name to a prepared PDO statement?  $stmt = $dbh->prepare('SELECT * FROM :table WHERE 1'); if ($stmt->execute(array(':table' => 'users'))) {     var_dump($stmt->fetchAll()); }   Is there another safe way to insert a table name into a SQL query? With safe, I mean that I don't want to do  $sql = "SELECT * FROM $table WHERE 1"


My newborn's umbilical cord stump just fell off, we are wondering if it is necessary or even good to clean the newly exposed belly button with alcohol or hydrogen peroxide or anything else. The Doctor didn't really give much instruction other than "keep the stump dry".

Our pediatrician said that some doctors say to leave the umbilical cord stump alone but he likes to suggest using a cotton swab with alcohol to wipe the perimeter.  I am fine with just leaving it be so long as it stays clean and dry. Do you think he suggested that solely for cleanliness or does the drying effect of alcohol help it move along to fall off? What did you do for your newborn?


I can't manage to train the MLPRegressor with 'lbfgs' algorithm to better R2 score than around -14. How comes? First I tried randomly guess the hidden layers shape, then I even tried to use Grid Search CV, but doesn't help much. How can I train it better? How can I know the model is trained to best accuracy? How comes that a simple linear regression would have at least 40% score R2 while the above has -14%? from sklearn.neural_network import MLPRegressor from sklearn.model_selection import train_test_split from sklearn.preprocessing import StandardScaler, MinMaxScaler from sklearn.metrics import r2_score from sklearn.model_selection import GridSearchCV from sklearn.metrics import mean_squared_error import math import numpy as np from scipy.stats import uniform   X = [     [390973, 262345, 324807],     [188322, 120766, 174883],     [185967, 173290, 175605],     [179309, 117915, 169950],     [166298, 40042, 153851], ]  X_test = [     [164077, 73041, 147249],     [152734, 52099, 77967], ]  y = [     8080000,     1940000,     3300000,     1970000,     624000, ]  y_test = [     1580000,     118000, ]  scaler = StandardScaler() X_scaled = scaler.fit_transform(X) X_test_scaled = scaler.fit_transform(X_test)  # https://stackoverflow.com/questions/52032019/sklearn-mlp-classifier-hidden-layers-optimization-randomizedsearchcv class RandIntMatrix(object):     def __init__(self, low, high, shape=(1)):         self.low = low         self.high = high         self.shape = shape      def rvs(self, random_state=None):         np.random.seed(random_state)         return np.random.randint(self.low, self.high, self.shape)   parameters = {     'hidden_layer_sizes': RandIntMatrix(1, 50, (500, 2)).rvs().tolist(),     'solver': ['lbfgs'], }  grid = GridSearchCV(MLPRegressor(random_state=1, max_iter=500), parameters, cv=2) grid.fit(X_scaled, y) print(grid.score(X_test_scaled, y_test)) print(grid.best_params_)  R2 score and Best params output: (for shape 2) -14.423559240364366 {'hidden_layer_sizes': [11, 24], 'solver': 'lbfgs'}  R2 score and Best params output: (for shape 3) -14.024830648388866 {'hidden_layer_sizes': [7, 19, 49], 'solver': 'lbfgs'}

I'm training a neural network but the training loss doesn't decrease. How can I fix this?  I'm not asking about overfitting or regularization. I'm asking about how to solve the problem where my network's performance doesn't improve on the training set.    This question is intentionally general so that other questions about how to train a neural network can be closed as a duplicate of this one, with the attitude that "if you give a man a fish you feed him for a day, but if you teach a man to fish, you can feed him for the rest of his life." See this Meta thread for a discussion:   If your neural network does not generalize well, see:


You can get sample trees from random forest (e.g., see: )  However, rather than getting a single tree from random forest, is there any way to get an "optimum" or "recommended" tree which is generated considering the many trees?  Basically, I would like to replace decision tree models with random forest but would like to know what would be the best splits.

I've read through the following posts that answered the question I was going to ask:      Here's what I've done so far: I compared Logistic Regression to Random Forests and RF outperformed Logistic. Now the medical researchers I work with want to turn my RF results into a medical diagnostic tool. For example:  If you are an Asian Male between 25 and 35, have Vitamin D below xx and Blood Pressure above xx, you have a 76% chance of developing disease xxx.   However, RF doesn't lend itself to simple mathematical equations (see above links). So here's my question: what ideas do you all have for using RF to develop a diagnostic tool (without having to export hundreds of trees).   Here's a few of my ideas:   Use RF for variable selection, then use Logistic (using all possible interactions) to make the diagnostic equation. Somehow aggregate the RF forest into one "mega-tree," that somehow averages the node splits across trees.  Similar to #2 and #1, use RF to select variables (say m variables total), then build hundreds of classification trees, all of which uses every m variable, then pick the best single tree.    Any other ideas? Also, doing #1 is easy, but any ideas on how to implement #2 and #3?


Just upgraded from 13.04 to 13.10.  Everything went fine but I don't see the time in the top right corner of the 'top bar' anymore. I tried to right click on it so I could get some options but nothings shows.  I'm sure it's obvious but I don't see it.

I like Unity very much. Recently, I installed Compiz manager and Nautilus Elementary also then tried to Play. During some of my playing around, Unity's clock applet has vanished.  I want to make it show the time again. How can I do this?


Assume in a certain year the number of credit obligors of a bank who are at risk of default is Poisson distributed with intensity $\lambda = 10$. Each individual obligor may actually default in that year with probability $p = 0.2$. Assume mutual independence  of the obligors. Let $X$ be the number of obligors that default in that year. Show that $X$ is Poisson distributed and determine its intensity.   I denote $N$ the number of obligors at risk.  And by using the identity  $$P(X = k) = \sum_E P(X = k\mid N = n)P(N = n)$$ to find the pmf I think I am supposed to arrive at the Poisson distribution.  $P(N=n)$ is already Poisson. I am having trouble figuring out the $P(X = k\mid N = n)$ and coming up with the probabilities of the pmf which need to be summed up to yield the final Poisson.

I thought I figured out this problem, but my answer is different than the solutions manual. Hoping someone here can stear me in the correct direction:     Assume the number of automobile collisions that occur on a given stretch of highway per year is a Poisson random variable $X$ with $\mu = 20$. The probability is $p=0.05$ that there will be one or more fatalities in each accident; occurrences of fatalities are independent from one collision to the next. If $Y$ is the number of collisions with one or more fatalities on this stretch of road in one year, find the probability law for $Y$.   So as said, X is poisson, so:  $$p_X(x) = \frac{20^x}{x!}e^{-20}$$  The conditional probability of $Y$ given $X=x$ is a Binomial random variable:  $$p_{Y\mid X}(y\mid x) = \binom{x}{y}p^yq^{x-y}$$  where $Y =$ number of fatal traffic accidents and $x =$ given number of accidents (from poisson distribution)  Therefore the joint probability for $X$ and $Y$ is:  $$p_{X,Y}(x,y)= p_{Y\mid X}\cdot p_X(x) = \binom{x}{y}p^yq^{x-y}\frac{20^x}{x!} e^{-20}$$  to find the marginal probability of $Y$, I sum over $P_{X,Y}$ for all $x$:  \begin{align} p_Y(y) & = \sum_{x=y}^\infty{\binom{x}{y}p^yq^{x-y}\frac{20^x}{x!}e^{-20}} = \frac{(20p)^ye^{-20}}{y!} \sum_{x=y}^\infty {20^{x-y}\frac{q^{x-y}}{(x-y)!}} \\[10pt] & = \frac{(20p)^ye^{-20}}{y!} \sum_{x-y=0}^\infty {20^{x-y}\frac{q^{x-y}}{(x-y)!}} = \frac{(20p)^ye^{-20}}{y!}e^{20q} \end{align}  So:   $$p_Y(y) = \frac{(20p)^ye^{-20p}}{y!}$$  however, the correct answer is apparently $p_Y(y)=\dfrac{e^{-1}}{y!}$


How to write $\text{codim}(Y)$ without \text{codim}?  Is there command like \dim that I can use to write codimension?

I'm unsure of when it is preferable to use \text versus \mathrm, is there some unwritten rule about the use of these?  For example, I saw the following code in a math post:  \frac{\mathrm{lcm}(m,n)}{\mathrm{gcd}(m,n)}\quad\text{divides}\quad  \frac{\mathrm{lcm}(m,n)}{|\langle x\rangle\cap\langle y\rangle|}\quad \text{divides}\quad \mathrm{ord}(ab)\quad\text{divides}\quad \mathrm{lcm}(m,n).   and there is a mix of both. Is there a general reason why the author would choose to do so?


The error message I get suggests  "sudo apt-get clean"  I try running it but nothing happens.  Just get back to the prompt.  Is there any other terminal commands I should try to clean temporary files out of my boot partition?

I'm getting an error in software updater when I try and do my daily updates. it says:  The upgrade needs a total of 25.3 M free space on disk `/boot`. Please free at least an additional 25.3 M of disk space on `/boot`. Empty your trash and remove temporary packages of former installations  using `sudo apt-get clean`.   I tried typing in sudo apt-get clean into the Terminal but I still get the message. All of the pages I read seem to be for experienced Ubuntuers. I'm running Ubuntu 12.10. I want to upgrade to 13.04 but understand I have to finish these first.  This is the output from typing in cat /etc/fstab into the Terminal:  # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point>   <type>  <options>       <dump>  <pass> /dev/mapper/ubuntu-root /               ext4    errors=remount-ro 0       1 # /boot was on /dev/sda1 during installation UUID=fa55c082-112d-4b10-bcf3-e7ffec6cebbc /boot           ext2    defaults        0       2 /dev/mapper/ubuntu-swap_1 none            swap    sw              0       0 /dev/fd0        /media/floppy0  auto    rw,user,noauto,exec,utf8 0       0 matty@matty-G41M-ES2L:~$    Output of df -h:  Filesystem               Size  Used Avail Use% Mounted on /dev/mapper/ubuntu-root  915G   27G  842G   4% / udev                     984M  4.0K  984M   1% /dev tmpfs                    397M  1.1M  396M   1% /run none                     5.0M     0  5.0M   0% /run/lock none                     992M  1.8M  990M   1% /run/shm none                     100M   52K  100M   1% /run/user /dev/sda1                228M  222M     0 100% /boot matty@matty-G41M-ES2L:~$    And dpkg -l | grep linux-image gives:  ii linux-image-3.5.0-17-generic 3.5.0-17.28 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP ii linux-image-3.5.0-18-generic 3.5.0-18.29 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP ii linux-image-3.5.0-19-generic 3.5.0-19.30 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP ii linux-image-3.5.0-21-generic 3.5.0-21.32 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP ii linux-image-3.5.0-22-generic 3.5.0-22.34 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP ii linux-image-3.5.0-23-generic 3.5.0-23.35 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP ii linux-image-3.5.0-24-generic 3.5.0-24.37 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP ii linux-image-3.5.0-25-generic 3.5.0-25.39 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP ii linux-image-3.5.0-26-generic 3.5.0-26.42 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP iF linux-image-3.5.0-28-generic 3.5.0-28.48 i386 Linux kernel image for version 3.5.0 on 32 bit x86 SMP


I have done free groups. I studied it from Rotman two semesters back. But this semester I am doing combinatorial group theory and obviously it starts with free groups. I have to revise Free groups but I have never got a  good intution about free groups and always have been on backfoot with them whenever have studied them. This time in one month break Ii have before semester starts I want to Free groups and all related concepts used for combinatorial group theory so that I can do well with combinatorial group theory and can get into the subject deep. Any good conceptual/elaborate references? Please suggest some books. Thanks

I would please like some recommendations for an introductory level book on combinatorial group theory, by which I mean a group theory book which places emphasis on generators and relations and free groups, and then discusses common concepts such as quotient groups in terms of these. Thank you.


Please clarify the use of => in MVC Razor. For example, in the context of a statement such as:  @Html.LabelFor(m => m.AnswerText)

I just came over this syntax in some of the questions in this forum, but Google and any other searchengine tends to block out anything but letters and number in the search so it is impossible to search out "=>".  So can anyone tell me what it is and how it is used?


I'm working on an eCommerce site where we're implementing a feature that allows the user to cancel an order (of physical goods) that's in transit.   On the line item (parcel level) the user can 'cancel this parcel'.  On Click, I want to display a warning along the lines of: Are you sure you want to cancel this parcel? This cannot be undone.   Here's the bit I'm struggling with.  There should be a positive Yes, I want to cancel, and a negative, No I do not want to cancel.   It feels like I've got to be cognisant of the word 'cancel' in this solution.   The cancel of the cancel order action might cause confusion unless I get it crystal clear.  Any ideas on the button text for the two options?  I want to keep the button actions super clear, easy to understand and not too long.

Designing an interface for a CMS (Content Management System), I stumbled upon a paradox and I'm a bit confused about what to do and why to do it..  Context  Before deleting an album, the user is asked to confirm the action.  Green "Yes"    Red "Yes"    Which option is more intuitive for the user?


As we all know about the Microsoft Certified Professional Programs. I need to ask is there any institute offering online certification for iOS Professional Developer. I have visited , as it is offering a course but I could not get it that is it like MCP or not?

Are there any official certification programs by Apple for iOS App Development?


I'm new to Linux and wondered where I can get useful info so started here. 1st off can I use the same PICTURES, VIDEOS, MUSIC & DOCS already on hard drive. I remember a window appearing during Linux installation saying it would require about 300gb for this, I clicked on OK but don't know how to get to them to appear.  Since this my hard drive has gone down by 300 odd gb?


I have read this question:       Entangled states can produce nonclassical correlations, but this is not necessarily the case.   So far so good.     For instance, for a two-particle system of spinful particles with the constraint that the total spin is zero, you always have the correlation that if you measure the spin of one particle to be up (in one direction), the spin of the other particle will be down (in that direction). This is true regardless of whether the system is in an entangled state."    This is exactly what I am asking. What more does in this case entanglement add? Will entanglement change the measurement other then what correlation of the total spin=0 gives?  These do not answer my question.   I have read this question:      where Luboš Motl says in a comment:     Entanglement is nothing else than correlation between two objects ("subsystems") and this correlation is always a consequence of their mutual contact or common origin in the past.    These answers state that QM entangelement is always based on a spatial mutual contact or common origin in the past.       If we both choose to open our envelopes from the bottom, we always (or nearly always) find papers of identical colors.   Now try telling a story like yours --- where the envelopes carry true information about what's "really" in the other envelope --- that fits these facts. Good luck.   Now this summarizes my question basically. What is the reasoning behind this difference between the two statements? One says QM entanglement is just correlation. The other one says it is not, because QM entanglement gives you examples in the envelopes that classical correlation cannot explain. Which one is right?  Question:   Will an entangled system give different measurement then just correlation?

Some authors exclusively use "Correlation" to classify composite quantum states, whereas most only speak of "Entanglement".  Correlation basically means that measurements on the subsystems are stochastically dependent and entanglement means non-separability of the composite state.  I am wondering, are those classifications equivalent, or is there any hierarchy (e.g. if a composite state is non entangled, it is always uncorrelated). Does the entropy of entanglement (in some cases) predict whether a state is (un)correlated?  References to a proof would be much appreciated!  Feel free to criticize me on the casual definitions given above as well.


I tried factoring the denominator and performing partial fraction decomposition, but the algebra becomes too cumbersome for me...  Is there a cleaner approach for this integral?

Evaluate the indefinite integral   $$\int \frac{x^2 \,dx}{a x^5 + b},$$   for real parameters $a, b \neq 0$.   No apparent substitutions simplify the expression (if the exponent of $x$ were an integral multiple of $3$, this would suggest the substitution $u = x^3$, $du = 3 x^2 \,dx$, but the exponent is not). Applying integration by parts with $u = a x^5 + b$, $dv = x^2 dx$ is straightforward, but it produces an integrand with a much larger degree in the denominator and so appears only to make the situation worse. Applying integration by parts instead with $dw = \frac{x^k dx}{a x^5 + b}$ results in integrating $\frac{x^k dx}{a x^5 + b}$, which except when $k \equiv 4 \pmod 5$ (which doesn't appear immediately fruitful), doesn't appear much easier than the given integral.


Let $\theta$ be an unknown population characteristic (say average height).  A confidence interval written as $P(\hat \theta - \delta < \theta < \hat \theta + \delta) = 1 - \alpha$ makes perfect sense as $\hat \theta$ and $\delta$ are random variables.  If we do, however, write the result, say for estimated $\hat \theta = 180$, $\delta = 13$, does the following syntax (which is the standard in the books I'm studying) make sense, since the numbers are constant and $\theta$ is an unkown characteristic (and therefore a constant in frequentist probability)?  $P(167 < \theta < 193) = 0.95$

It seems that through various related questions here, there is consensus that the "95%" part of what we call a "95% confidence interval" refers to the fact that if we were to exactly replicate our sampling and CI-computation procedures  many times, 95% of thusly computed CIs would contain the population mean. It also seems to be the consensus that this definition does not permit one to conclude from a single 95%CI that there is a 95% chance that the mean falls somewhere within the CI. However, I don't understand how the former doesn't imply the latter insofar as, having imagined many CIs 95% of which contain the population mean, shouldn't our uncertainty (with regards to whether our actually-computed CI contains the population mean or not) force us to use the base-rate of the imagined cases (95%) as our estimate of the probability that our actual case contains the CI?   I've seen posts argue along the lines of "the actually-computed CI either contains the population mean or it doesn't, so its probability is either 1 or 0", but this seems to imply a strange definition of probability that is dependent on unknown states (i.e. a friend flips fair coin, hides the result, and I am disallowed from saying there is a 50% chance that it's heads).  Surely I'm wrong, but I don't see where my logic has gone awry...


I am adding sort option to column in my table view controller based on touching the header. Do you think the best solution is adding images to my project and using them for upside/downside arrows?

I have to maintain a large number of classic ASP pages, many of which have tabular data with no sort capabilities at all. Whatever order the original developer used in the database query is what you're stuck with.  I want to to tack on some basic sorting to a bunch of these pages, and I'm doing it all client side with javascript. I already have the basic script done to sort a given table on a given column in a given direction, and it works well as long as the table is limited by certain conventions we follow here.    What I want to do for the UI is just indicate sort direction with the caret character ( ^ ) and ... what?  Is there a special character that is the direct opposite of a caret?  The letter v won't quite cut it.  Alternatively, is there another character pairing I can use?


I recently edited an answer from another StackOverflow user in order to clarify some parts it by adding some quotes from the  - the user however rolled back my edit immediately and told me to "not add copyrighted text" to the answer.  Am I infringing the copyright (and committing a crime) when citing the Standard Working Draft? I've seen many answers containing quotes from the Standard Working Draft on StackOveflow before, and I also think it would be really unfortunate to be unable to cite it.  Does citing the Standard Working Draft fall under "Fair Use" for nonprofit educational uses? Or should I avoid doing it and edit out answers that cite the Standard Working Draft?

On Stack Overflow, I'm a pretty frequent contributor with over 3K in reputation. Almost all of which earned by answering real user questions about Windows programming and other topics.  Last night, somone posted a .  I knew the easiest thing to do would be to direct him to an appropriate documentation page on MSDN that I thought would help. And I literally did this:   Copied the URL directly into the post. Below the URL, copied two lines of content from that page that was relevant. Small code snippit below that.   Literally, this is what the answer looked like:           This warning is automatically promoted to an error. If you wish to   modify this behavior, use #pragma warning. For example, to make C4235   into a level 2 warning, use the following line of code  #pragma warning(2:4235)    I felt that by cutting and pasting a quote from the website, and attributing it with the URL was proper form. Such that it's not ambiguous where the answer originated from - both from a copyright perspective as well as a courteous to the content owner.  About an hour later, I observed two things:   One moderator downvoting the answer and flagging it because "Copy/pasting. Nice. Did you see "© 2011 Microsoft. All rights reserved" at the bottom of that page" Another moderator deleted it with just a link to the FAQ - which says nothing about cut and paste or copyright rules.   Well that was disappoining. It wasn't like I was pasting a writeup without giving credit to the original author. Just a small quote from a well known reference site.  So here's my questions:   What is the policy around answers coming from other online reference sources? Is pasting a URL to a page with an answer OK? Is pasting content from the URL OK?  Even if it's attributed? Is there a proper way to attribute content when it originates from another site? Is there a proper way to attribute an answer if it originates elsewhere? Was I wrong to paste a snippet of content from MSDN, or was I wronged by aggressive moderators?   Now here's the real kicker - my day job is a software engineer at Microsoft. I am certain that my employer would not take issue at all with me helping the Windows development community by referencing pages they publish. So in some sense, the Stack Overflow communinity is just making it harder for the Windows experts to help the Windows community. It seems odd.


I am trying to make, with tikz package, curved arrows like this:   Can somebody help me? Thank you in advance

After reading Gonzalo's answer to , I thought  I would be able to modify it so that I could have the corresponding coefficients circled and an arrow going from one circle to the next. For example, I would like the coefficient of x^2 on the left, a, circled and the coefficient of x^2 on the right, 5 circled, then a curved arrow drawn between the two circles. How might I achieve this? Also, how would I add some text along the path of the arrow? I reproduce his code here.  \documentclass{article} \usepackage{amsmath} \usepackage{tikz} \usetikzlibrary{calc}  \newcommand{\tikzmark}[1]{\tikz[overlay,remember picture] \node (#1) {};}  \begin{document}  \begin{equation}   a\tikzmark{a}x^2 + bx + c = 5\tikzmark{b}x^2 + bx + c.   \begin{tikzpicture}[overlay,remember picture,out=315,in=225,distance=0.4cm]     \draw[->,red,shorten >=3pt,shorten <=3pt] (a.center) to (b.center);   \end{tikzpicture} \end{equation}  \end{document}


In Batman V Superman it's shown that Batman brands criminals with a 'bat brand'.    This brand on someone means they will definitely be killed. Why does he choose this instead of killing them himself or not doing it at all?

Why do the prisoners attack the guy with the bat brand in Batman V Superman: Dawn of Justice?  I'd think many of them are in there because of Batman.  Why would a person branded by Batman be especially in danger?


We know that $$e^{\pi i}+1=0$$and $$e^{\pi i}=-1$$  So$$(e^{\pi i})^2=(-1)^2$$$$e^{2\pi i}=1$$  Because $1$ is the multiplicative identity,$$(e^{2\pi i})^x=1^x$$$$e^{2\pi xi} =1$$should also hold true.  But we also know that $$e^{xi}=\cos(x)+i\sin(x)$$and so$$e^{2\pi xi}=\cos(2\pi x)+i\sin(2\pi x)$$which does not equal 1 for all values of $x$.  Now I realize I probably didn't break math, so I must be making an invalid assumption. What is wrong with my reasoning?

Could someone please tell me why this exponentiation rule does not work when the exponent is imaginary?  The following seems to be true but is only true if $x$ is an integer.  $$e^{2\pi ix} = \left( e^{2\pi i} \right)^x = 1^x = 1$$


The three clocks $A, B, C$ at the same position in spacetime at the beginning of the measurement. $A$ starts moving to the right with the velocity $v$ with respect to $B$ and $B$ starts tracing $A$ with the velocity $u$ with respect to $C$, $v>u$. By time dilation relations can be written $$t_A=t_B\sqrt{1-\frac{v^2}{c^2}}, t_B=t_C\sqrt{1-\frac{u^2}{c^2}}$$. Then one can find $$t_A=t_C\sqrt{1-\frac{v^2}{c^2}}\sqrt{1-\frac{u^2}{c^2}}$$. Using the rule of the addition of velocities, the velocity of $A$ with respect to $C$ is defined as $$w=\frac{u+v}{1+\frac{uv}{c^2}}$$ Then $$t_A=t_C\sqrt{1-\frac{w^2}{c^2}}=\frac{t_C\sqrt{1-\frac{v^2}{c^2}}\sqrt{1-\frac{u^2}{c^2}}}{1+\frac{uv}{c^2}}$$ which is different from the one obtained by chaining up the relations.  What is wrong here?  I tried to understand this in the following way. But there the question is still unanswered.  We can describe the motion of $A$ in $C$(stationary) and $B$(moving) frames using the Lorentz transformations. $$t_C=\frac{t_B+\frac{ux_B}{c^2}}{\sqrt{1-\frac{u^2}{c^2}}}$$ (1). $t_B$ is dilated time seemed to a stationary observer on $C$. $x_B=vt_B$ the position of $A$ in $B$ frame. Standing on $B$ one can write $$t_B=\frac{t_A}{\sqrt{1-\frac{v^2}{c^2}}}$$ (2) and replacing $t_B$ in (1) relation is derived the expected relation between $t_C$ and $t_A$  $$t_C=\frac{t_A(1+\frac{uv}{c^2})}{\sqrt{1-\frac{u^2}{c^2}}\sqrt{1-\frac{v^2}{c^2}}}$$  The question is if $t_B$ in equations (1) and (2) are equivalent? In relation (1) it is dilated time seemed to a stationary observer on $C$ frame. In equation (2) it is the proper time of $B$  frame?

I'm trying to derive the relativistic velocity addition equation using the time dilation equations but I get a wrong result. Assume the widely used scenario in which there are 3 clocks: O, A and B. A is moving relative to O at velocity $v$. B is moving relative to A at velocity $w$. Find the velocity of B relative to O (in O's frame of reference). The time dilation equations says:  $$t_A = t_O \sqrt{1-v^2/c^2}$$  $$t_B = t_A \sqrt{1-w^2/c^2}$$  $$t_B = t_O \sqrt{1-u^2/c^2}$$  From these 3 equations we want to derive $u$. Then we get:  $$t_O \sqrt{1-u^2/c^2} = t_O \sqrt{1-v^2/c^2} \sqrt{1-w^2/c^2}$$  $$1-u^2/c^2 = (1-v^2/c^2) (1-w^2/c^2)$$  $$1-u^2/c^2 = 1-v^2/c^2-w^2/c^2+v^2 w^2/c^4$$  $$u^2 = v^2 + w^2 - v^2 w^2/c^2$$  This is different from the equation  $$u = \frac{v + w}{1+v w/c^2}$$  Why doesn't the derivation of velocity using the time dilation equations alone work?


Suppose that $\theta$ is a real number with $- \pi \leq \theta \leq \pi$, then I am trying to see why the identity $|1 - e^{i\theta}| \geq 2 |\theta|/\pi$ holds. In this answer , we see that $|e^{i\theta} - 1| \leq |\theta|$ using the fundamental theorem of calculus (among other proofs, some using geometry).  I realize this seems easy but I'm not sure how to show this. If $\theta = \pm \pi$, then  $|e^{i\theta} - 1| = 2 = 2 \frac {|\theta|}{\pi} $, but more generally I am not sure.

I would like to show that show $|t|\leq \pi$ implies $ |e^{it}-1|\geq 2|t|/ \pi$. I tried to proof it geometrically but without success.


I am using a Qualcom Broadband (EVDO) dongle on Ubuntu 13.04. I have used this dongle well for a number of days on Ubuntu 13.04 but recently I had to do a fresh install of Ubuntu 13.04 but when I try to use the dongle the option for Enable Mobile Broadband keeps unchecking itself and I get a "not enabled" as the name of my connection. After a few tries of checking the Enable Mobile Broadband option I get this  error :  "Creating Object path /org/freedesktop/NetworkManager/ActiveConnection/6 failed in libnm-glib"

Recently I have installed an older version of Ubuntu on my old machine. Whenever I try to install any software, I get an error saying it couldn't be found:  $ sudo apt-get install vlc Reading package lists... Done                Building dependency tree        Reading state information... Done     E: Couldn't find package vlc


I'm looking for a way to block Facebook newsfeed browsing (in any browser, so browser proxy settings are not an option here), but still give user ability to use social login buttons/API. I've tried modifying hosts file, but this blocks the entire domain and I cannot specify any specify URL path that must continue working.  Would appreciate ideas for both: Windows and OSx machines.

I want to block Facebook (the Facebook site) for concentrating purposes, but I don't want to break the share or like buttons on other pages (like a good article or a nice clip on YouTube I want to like or share). How can I do that? I use both Windows and Linux.


I want to to shift  a signal which is varying from 1.2 to 3.3 volts ( a shifted square wave) to some other ground. I don't how to do this. Frequency of this signal is 10 kHz with duty cycle around 10-60%. And signals should be galvanic isolated.

I want to implement a simple circuit which can map -10V  +10V voltage range to 0V 5V voltage range. Thus I'm planning to use two op-Amps, one for the slope and the other for the offset. So basically I'm planning to use an inverting amplifier and a summing amplifier consecutively.  But Inverting amplifiers multiplies the input voltage with a minus sign. I need a positive slope. How can I overcome this?  Also Could you gibe me any ideas for a cheap op-Amp models for this purpose?


def Answer():      A = var1.get()      if "." not in A and A.isdigit():          Right1.insert(END,str(A)+"est un entier")       elif "." in A  and A.isdigit():            B,C = A.split(".")           Right1.insert(END,str(B)+"est decimal" + str(C)+"est entier")     else :          Right1.insert(END,"ERROR")   That is my function Answer for my thinker. When I enter an Interger(12), I see the "Integer(12) est un entier". But when I enter a decimal number (12.7), it prints: ERROR instead of splitting the number to two part. I should have on my screen: "12 est decimal"   "7 est entier". Any ideas where I am doing wrong?

What is the best possible way to check if a string can be represented as a number in Python?   The function I currently have right now is:  def is_number(s):     try:         float(s)         return True     except ValueError:         return False   Which, not only is ugly and slow, seems clunky. However I haven't found a better method because calling float in the main function is even worse.


I am trying to install httpie:  » sudo apt update Hit:1 http://archive.ubuntu.com/ubuntu bionic InRelease Hit:2 http://archive.ubuntu.com/ubuntu bionic-security InRelease Hit:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease Reading package lists... Done                      Building dependency tree        Reading state information... Done All packages are up to date.  » sudo apt install httpie Reading package lists... Done Building dependency tree        Reading state information... Done Package httpie is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'httpie' has no installation candidate   But the package is   This happens for other packages also:  E: Unable to locate package git-annex E: Package 'httpie' has no installation candidate E: Unable to locate package jshon E: Unable to locate package python-pip E: Unable to locate package tree   But they exist too:          What is going on?  This is my sources.list:  » cat /etc/apt/sources.list deb http://archive.ubuntu.com/ubuntu bionic main deb http://archive.ubuntu.com/ubuntu bionic-security main deb http://archive.ubuntu.com/ubuntu bionic-updates main   And this is my system:  » lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description:    Ubuntu 18.04.1 LTS Release:        18.04 Codename:       bionic   EDIT  This is an ubuntu server system, no gui.

How do I get to the Universe Repository in supported versions of Ubuntu?


I am Pakistani passport holder and I have a Schengen Visa and studying in Sweden going back to my country and the flight I booked has a 21-hour layover at Manchester do I need to apply for a transit visa.

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


say you have sphere and plane meshes and you want to take the plane and slide it to the sphere without it clipping through but you also need it to deform around the sphere. is there a way to do this?  im asking because im trying to put windows on a boeing 777 and i need the windows to take the shape of the plane's body and i dont want to go editing them to fit each area one by one. i tried the snap function but i need something that can deform it too

I couldn't find this anywhere, which is really strange, but I'm trying to wrap a curve, imported from a .svg made with a vector image program around a sphere to create the Earth.  Basically, this is what it currently looks like:    I'd like to wrap the curve of the outlines for the land around the sphere in the middle of the scene.  I don't mind converting the curve to mesh at some point in the process, but it will be beveled or extruded first.  I tried Lattice (which didn't work because I couldn't get a result that matched the sphere's shape), I tried Curve modifier with a circle curve but that only made the map cylinder-shaped, I tried Simple Deform, Shrinkwrap and Warp but couldn't get these to make what I wanted either.  When using Shift+W here's what happens:


I have an SSD and therefore no swap. However, when I open a lot of tabs in the browser, the system tends to grind to a halt. If I'm lucky, I can close one or two tabs before the system is completely unresponsive. Is it possible to use the OOM in this case to kill a few browser processes (chromium) to avoid the unresponsiveness? There is still a bit of memory available, but apparently there's still a resource conflict.

Is it possible to have the system preemptively swap out inactive pages (vm.swappiness), but invoke the oom-killer when the system runs out of RAM (as opposed to running out of memory) and is forced to swap?  The ultimate goal is to keep the system from grinding to a halt when it starts thrashing the disk because of major page faults, but still let inactive pages get swapped out.  Another desire would be to configure how much swap memory the system is forced to use before oom-killer triggers. This way the system can dip into swap just a little bit, as long as it doesn't go too far.  Or I could set such a threshold to trigger oom-killer before using all the RAM so there will always be room for the file system cache (and thus avoid more disk thrashing).  It doesn't seem like this would be that hard to do. It seems like you could just tell the oom-killer to trigger when the system has X ram used/free. But this is why I'm asking; I don't know.  For clarification, I am not looking to turn off swap, or adjust the vm.swappiness parameter


Can someone explain to me whether an efficient estimator can be biased? What I've read so far seems to be always about efficiency being a property being alluded to unbiased estimators but I was thinking that a biased estimator with smaller variance can thus be efficient. I am unsure if my main question has a single definitive answer.

Is unbiasedness a necessary condition for an estimator to be efficient?  For example, if $\hat {\theta}= \frac{\sum_i^n X_i}{3}$, I assume $\hat {\theta}$ can't be efficient in a Cramer-Rao lower bound context because $E[\hat {\theta}]= \frac {\theta}{3}$.


I need to take a 2-minute exposure shot of a landscape scene on a regular sunny day at, let's say, f/4.5. I suppose I'll need to use ND filters for this purpose, but how do I figure out how many filters will I need to buy?

I've seen a few related posts on the site but nothing specifically on this point:  I'd like to be able to take long exposure photos during daylight (like the examples in ). I'm told that you can do this by using a neutral density filter. So my question is: what is a neutral density filter exactly, and how is it used to achieve that smooth long exposure effect?


Let $V$ be the set of real numbers. Regard $V$ as a vector space over the field of rational numbers, with the usual operations. Prove that this vector space is not finite-dimensional.  MY ATTEMPT  Suppose $V$ is finite dimensional. Thus it is spanned by some set $S = \{r_{1},r_{2},\ldots,r_{n}\}$ of linearly independent real numbers. Therefore any real number $R$ can be written as \begin{align*} R = q_{1}r_{1} + q_{2}r_{2} + \ldots q_{n}r_{n} \end{align*}  where $q_{i}$ are rationals. From there, we conclude that $V$ is countable, once $|V| = |\textbf{Q}^{n}| = |\textbf{Q}|$, which is a contradiction.  Am I on the right track? If so, is there another approach to this problem? Thanks in advance!

It would seem that one way of proving this would be to show the existence of non-algebraic numbers. Is there a simpler way to show this?


Let $X=\text{Spec}(A)$ where $A$ is noetherian. Suppose $M$ is a finitelly generated $A$-module and that $M_x$ is a free $A_x$-module with finite rank for some $x\in X$. Show that there exists an open neighbourhood $U\subset X$ of $x$ such that $\widetilde{M}\big|_U$ is free. [here $\widetilde{M}$ is the sheaf on $X$ defined by $\widetilde{M}(X_f)=M_f$ when $f\in A$]  Suppose $M_x$ is generated by $\frac{m_1}{f_1},...,\frac{m_r}{f_r}\in M_x$ with $m_i\in M$ and $f_i\notin x$. In that case $\frac{m_i}{f_i}\in M_{f_i}=\widetilde{M}(X_{f_i})$. Defining $f:=f_1\cdots f_n$, we have $X_f\subset X_{f_i}$ for all $i$, so we may assume the generators are of the form $\frac{m_i}{f^{k_i}}\in M_f$. I'm trying to prove that $\widetilde{M}\big|_{X_f}$ is free. The fact that $M$ is finitely generated means that there is an exact sequence $A^n\stackrel{\phi}{\to} M\to 0$ where $\phi(a_1,...,a_n)=\sum_{i=1}^na_iu_i$ for some $u_i\in M$. Localizing at $f$, we have a new exact sequence $A_f^n\stackrel{\phi_f}{\to}M_f\to 0$ and an isomorphism $A^n_f/\ker(\phi_f)\simeq M_f$. I really can't see how to prove that $A_f^n/\ker(\phi_f)$ is free, and also why is the noetherian condition necessary. Is there maybe a better way to approach this?

I am looking for a stronger notion of generic flatness. Let $A$ be a Noetherian ring, $M$ a finitely generated module over $A$. Suppose there exists a maximal ideal $m$ of $A$ such that $M_m$ (the localization of $M$ at $m$) is $A_m$-flat (here $A_m$ is the localization of $A$ at $m$). Does there exist an open neighbourhood $U$ of $\mathrm{Spec}(A)$ containing the point corresponding to $m$ such that for all point (not necessarily closed) $u \in U$, the localization of $\tilde{M}$ (the coherent sheaf corresponding to the module $M$) at $u$ is $\mathcal{O}_{U,u}$-flat i.e., $\tilde{M}|_U$ is $\mathcal{O}_U$-flat?


I'm getting a stack overflow error message when running the below code, but ONLY when more than 6 digits are entered. I think the code is fairly simple and all I've been able to find in the way of help so far are answers about "memory allocation" which I don't yet have any concept of.  int main(void) {        printf("Please enter card number for check: \n");     long long credit_card = GetLongLong();     int card_length = log10(credit_card)+1;     int cred_array[card_length];     long long dec = 1;     int i;      printf("credit_card: %lli\n",credit_card);     printf("card_length: %i\n",card_length);     for (i = (card_length-1); i>-1; i--)     {         cred_array[i]=(credit_card/dec)%10;         dec *=10;     }     int luhn_array[(credit_card-(credit_card % 2)) / 2][2];     int j;     int n = 0;     for(j = card_length-2; j >= 0; j-=2)     {         luhn_array[n][0]=cred_array[j]*2%10;         luhn_array[n][1]=cred_array[j]*2/10;         n++;     } }

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


So, I would like to start investing for the long-haul (10 - 15 years, expecting 4% ROI). When I looked up the top Broad European Stock Funds, I get an index that includes these holdings:   Nestle SA British American Tobacco PLC Royal Dutch Shell PLC Class A BP PLC   These are not the sort of companies I want to support because I personally dislike their business. How would I go about getting a similar index that covers solar/renewable energy companies, companies that are performing R&D on improving quality of life etc.

I am a young man who has recently reached a point of financial stability. I'm starting to think about long-term plans which may one day buy a home, or provide for myself in old age.  This raises the question of savings and investments, which causes me some ethical concerns.  I don't have an issue with investment in its basic form. Providing people money to help them do business, allowing it to grow and gaining interest in gratitude is not an issue for me.  The problem comes when we realise that a lot of the most financially successful businesses succeed due to addiction in their customers. Alcohol, tobacco, gambling, pornography, high interest financial services, and a number of others all rely on customers becoming dependent, unable to keep from buying their services. Because of this dependency, a lot of money is made in ethically questionable businesses, and professional investors (whose job is only to make as much money as possible) will choose to put money into these businesses.  The alternative would be to look in to investing myself. Although without some good practical knowledge, this would resemble gambling, throwing my money at whatever business takes my fancy, hoping for the best.  Being concerned about ethics, how can I go about investments and/or savings? Are there businesses which professionally invest ethically?


The Paladin spell Wrathful Smite imposes the frightened condition on its target if they fail a Wisdom saving throw.  Since the frightened condition states "within line of sight," does this mean if the target of the spell is able to get the caster out of their line of sight, they make their Wisdom check without disadvantage imposed by frightened condition?  For example:   Can the target close their eyes, make their check, and then reopen them without disadvantage? Can the target run behind an object, make their check, and then reopen and continue moving without disadvantage on their check?

As the title says, if you cause a creature to be Frightened of you, as in the Frightened condition, but they can somehow manage to not see you, do they stop rolling with disadvantage to attacks/ability checks?  Below are scenarios to illustrate my question.  Scenarios:   If a creature is frightened of you, and they turn their back against you to hit someone else, would they no longer have disadvantage to attack rolls/ability checks? If a creature is frightened of you and they have Blindsight, can they close their eyes to stop seeing you, and hence stop rolling with disadvantage? If a creature has 60 ft of movement and is frightened of you, and there is a corner they can reach in 15 ft that will block you from sight, can they run to that corner to stop being frightened, then run back to attack without disadvantage? Assume they would not provoke OA to do this, although the OA is immaterial to the question.


How can I run a job every 2 minutes through crontab in Linux?

I have a cron job on CentOS that I want to execute every 3 minutes but I have many other cronjobs that run at every 3 minutes starting from 0, 3, 6, 9...  So, to avoid my server getting too overloaded, I wanted some of my crons to run at every 3 minutes but starting at 1 minute and so on: 1, 4, 7...  My crons are usually like this:  */3 * * * *    How can I do this?


This exercise wants me to prove that for each $m \in \mathbb{Z}$ there are infinitely many primes $p \equiv 1 \pmod{m}$. It seems that this can be based on the fact that $f$ has a root mod $p$ for infinitely many primes $p$ whenever $f$ is a nonconstant polynomial over $\mathbb{Z}$. This is from the exercise 30 on chapter 3 of Marcus' Number Fields. Please help me.

A complex number $z=\cos(\alpha)+i\sin(\alpha)=e^{i\alpha}$ is called an $n$th root of unity if $z^n-1=0$, and is a primitive $n$th root of unity if in addition $z^k-1\neq0$ for $1\leq k<n$. The $n$th cyclotomic polynomial, $\Phi_n(x)$, is the monic polynomial of which the zeros are the distinct primitive $n$th roots of unity. Take $n>1$.      (a) Show that $\zeta=e^{2\pi i/n}$ is a primitive $n$th root of unity.      (b) Show that   $$\Phi_n(x)=\prod_{\substack{1\leq j\leq n\\ (j,n)=1}}(x-\zeta^j),$$   and that $x^n-1=\prod_{d\mid n}\Phi_d(x)$.      (c) By applying the inversion formula to $\log \Phi_n(x)$, or otherwise, show that   $$\Phi_n(x)=\prod_{d\mid n}(x^{n/d}-1)^{\mu(d)}.$$   In particular, conclude that $\Phi_n\in\mathbb{Z}[x]$.      (d) Suppose that $p$ is prime, $p\nmid n$, and $\Phi_n(a)\equiv 0\pmod p$. Show that   $\qquad$ (i) $\hskip0.11in p\nmid a$;   $\qquad$ (ii) $\hskip0.07in t\mid n$, where $t=\operatorname{ord}_p a$;   $\qquad$ (iii) $\hskip0.03in$if $a^{n/d}\equiv 1\pmod p$, then $d\mid\frac{n}{t}$;   $\qquad$ (iv) $\hskip0.03in$if $p^s\| (a^t-1)$, then $p^s\|(a^{mt}-1)$ when $p\nmid m$;   $\qquad$ (v) $\hskip0.07in$if $n/t>1$, then $p\nmid \Phi_n(a)$ [use (c)];   $\qquad$ (vi) $\hskip0.03in$the congruence $\Phi_n(x)\equiv0\pmod p$ is solvable if and only if $p\equiv 1\pmod n$.      (e) Show that there are infinitely many primes $p\equiv 1\pmod n$. [Hint: Consider $\Phi_n(np_1\cdots p_ry)$, where the $p_i$ are $\equiv1\bmod n$.]   These are a bunch of exercises on cyclotomic polynomial from Fundamentals of Number theory, p. 131, William J. Leveque. I have thought really hard, but still cannot prove most of them. Could anyone talk something about them or give me some reference books on that? I am really curious about their proofs. Thanks in advance.


I sometimes need to ask code questions on which is the best way to do something or code something.  On Stack Overflow I get downvoted, not sure if there is a community on Stack Exchange where to ask.  To give an example, the question I need to ask is:  "In a PHP / MySQL application which is the best way to save some code snippets? Should I save them in database or would it be better to let the user upload some files with the snippet?"  I'm pretty sure that if I ask this question on Stack Overflow I will get downvoted because it doesn't have any code example or code puzzle to solve, but is a generic question instead.  EDIT: I'm not sure is a best practice question, it may be. I can technically solve it both ways but one may could be the wrong one. Is more like asking if i an store my images in database, technically you can but i would say is the wrong way to do it.

Stuff like polls, recommendations based on subjective constraints, puzzles, webcomics etc. do not belong on the serious main SE sites, where professionals should be considered at work and having just a few spare minutes ("code's compiling") to answer questions, so they should not be distracted by such things. However, I'd also like to have a home for these things still using the SE engine. For the reason I mentioned before, this needs to be a separate place though. Let's call it four.[sitename-here].com.


I am attempting to embed a YouTube video into my app, as described here:   However, I seem to be encountering a NullPointerException error when I access the fragment and I cannot seem to find the causation.  java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.VideoView.setVideoURI(android.net.Uri)' on a null object reference   The code for the fragment is as follows.  import android.widget.MediaController; import android.net.Uri; import android.os.Bundle; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.VideoView;   public class VideosFragment extends Fragment {   public VideosFragment() {     // Required empty public constructor }   @Override public View onCreateView(LayoutInflater inflater, ViewGroup container,                          Bundle savedInstanceState) {     View view = inflater.inflate(R.layout.fragment_compare, container, false);     VideoView videoView;     videoView = (VideoView)view.findViewById(R.id.videoView);     MediaController mediaController;     mediaController = new MediaController(view.getContext());     mediaController.setAnchorView(videoView);     Uri uri= Uri.parse("rtsp://r7---sn-4g57kue6.googlevideo.com/Ck0LENy73wIaRAmk3cJBg-iaXhMYDSANFC3u0pRWMOCoAUIJbXYtZ29vZ2xlSARSBXdhdGNoYIaluaTkzciOVooBCzVxRjNraG5XcXdnDA==/D693A8E7577C3A29E60C292B42C9C87D7C25A565.762A63DC4CA0A028DA83256C6A79E5F160CBEDA3/yt6/1/video.3gp");     videoView.setMediaController(mediaController);     videoView.setVideoURI(uri);     videoView.requestFocus();     videoView.start();        return inflater.inflate(R.layout.fragment_videos, container, false); }   }  Here is the layout file:  <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.[left out for security].VideosFragment" android:background="?android:attr/colorBackground">  <!-- TODO: Update blank fragment layout -->  <VideoView     android:id="@+id/videoView"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_centerVertical="true"     android:layout_centerHorizontal="true" />     Thanks for any help!

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


I have a rooted Samsung s3 mini, android version 4.1.2  How to show the saved wifi password of the router I am connected to?

I have an Android phone which is connected to a secured Wi-Fi hotspot.  How can I find out the password of the hotspot from the phone?


I would like to ask for clarification regarding changing my name from Maria Elena to Melita. The name printed on my US visa is Maria Elena, while in my new passport it is Melita. In my amended birth certificate, on the lower portion it shows an annotation for the name change, which states the change from Maria Elena to Melita. Is there a discrepancy here?

I am considering a name change, which seems to be a relatively straightforward action, when one remains in the same country: certain documents are replaced with new ones bearing the new name, and others are presented together with the name change document.  However, I travel internationally multiple times per year, and I often change temporary residence from one country to another. So I often deal with immigration and similar things. Furthermore, I have a lot of things going on like work and studies.  Quite obviously, if I change my name, I would often have to produce a proper translation of the name change document, which may include notarized translation thereof with apostille or, for example, traduction assermentée in France.  However, it would be great to hear about experiences of people, who have dealt with this issue first-hand, so I can weight the disadvantages against advantages of this correctly. In particular, I would like to know if anyone has encountered unforeseen difficulties with this, and how people rate the overall difficulty of such experiences.


I reinstalled Ubuntu few months ago. By accident I chose to install Ubuntu without Windows (I had dual boot operating systems before that).   This is a disaster! I lost all my data in Windows and lost the operating system as well.   Do you know if I can recover my operating system? Bring Windows back to the laptop, or at least recover those data files in Windows?

Are there any tools, methods, incantations to recover recently deleted files on Ubuntu?  If it makes any difference, I want to recover a  2.x database file. But would be better to have a method/tool that works on any kind of file.


Recently, I found out  that Winter Bash 2012 used quite an interesting domain, .  Just curious, why isn't it being reused, since it's a fitting domain name and that it's redirected to stackpromos.com?

Visiting  redirects to . This domain should be reused, and should redirect to . Why did I think this would happen? The use of this domain was announced in the original email to moderators, which read in relevant part:  This event will run from 16 December 2013 to 3 January 2014. Users will be able to see their entire hat collection on . That site will also have a landing page, explaining the rules and other details of the event.


If electric field inside a conductor is zero then why is there an electric current in a resistor when an emf is applied across it for a long time?

I came across this statement while studying electric currents and I am confused:  "There is no electric field inside a conductor. Hence no current can flow through it".  Is there a fallacy in this statement?  Any help would be appreciated.  The conductor being discussed is ideal. What is the driving force for the current in this case?


It would be very nice if Ctrl+W while writing a comment would trigger the same confirmation dialog as it does for questions & answers:     This page is asking you to confirm that you want to leave - data you have entered may not be saved.     Very often, in the middle of writing a long comment I press CtrlW, thinking I'm in vim or the shell or somewhere and attempting to delete the last word; but in Firefox, this closes the current tab instead, and everything I've written so far is lost without any prompt which would have been shown if I were writing a post.  Using "Undo close tab" is also ineffective, since the comment box does not exist in page's HTML and is only added after clicking the "Add comment" link; meaning, Firefox doesn't have anywhere to restore my text to.

If I add a comment but navigate (by mistake) to another page, I lose my unfinished comment (ok, depends on browser etc). On the other hand, when formulating a question, and I click on a link by mistake, I'm asked if I really want to leave.  It would be nice to have this warning for comments as well.


During tonight's game, the party's wizard became confused because of a failed save against Yeenoghu's flail, which had the effect of:  The target must succeed on a DC17 Wisdom saving throw or be affected by the confusion spell until the start of Yeenoghu's next turn.  Dispel Magic says:  Choose one creature, object, or magical effect within range. Any spell of 3rd level or lower on the target ends. For each spell of 4th level or higher on the target, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a successful check, the spell ends.  With this in mind, I had the following question: Is the confusion caused by Yeenoghu's flail a targetable magical effect for the purposes of Dispel Magic? Or does the wizard have to wait for this effect to expire in the normal fashion? To clarify, I'm trying to determine if the magical effect on the Wizard can be removed without hitting the wizard as a creature with Dispel Magic. The latter has some pretty negative consequences for the wizard.

The description of the  spell states (emphasis mine):  Choose one creature, object, or magical effect within range. Any spell of 3rd level or lower on the target ends. For each spell of 4th level or higher on the target, make an ability check using your spellcasting ability. The DC equals 10 + the spell’s level. On a successful check, the spell ends.  There has been a lot of debate in my D&D group about the specific wording of Dispel Magic, and it has not  been not resolved by the D&D . Can Dispel Magic remove multiple magical effects on a single target? The primary issue revolves around the interpretation of the word "any" here. In English, the word "any" could mean "any one" or "any of your choice". I have seen a couple of forum posts suggesting that if three mages each cast Haste on a single target, and you use Dispel Magic on that target, then it will only remove one instance of Haste. This seems to run counter to the next sentence:  For each spell of 4th level or higher on the target, [...]  The word "each" is not ambiguous in English; however, there is an alternate interpretation of this sentence which I included in another question:


I have some trouble to centre text over an image in flexbox. I am trying to make 3 images that are next to each other and in the middle of each image there is some text which also has a semitransparent background. I've created a short  to demonstrate my problem.  .hello li {     margin: 24px 0px;     display: flex; }  .hello img {     height: 180px;     width: 300px;     justify-content: space-between; }  .hello li p {     text-transform: uppercase;     background: rgba(36, 36, 36, 0.5);     color: white;     width: 180px;     height: 60px;     position: absolute;     left: 50%;     top: 50%;     transform: translate(-50%, -50%);     justify-content: center;     align-items: center;     text-align: center;     display: inline-flex; }

I want to overlay one image with another using CSS. An example of this is the first image (the background if you like) will be a thumbnail link of a product, with the link opening a lightbox / popup showing a larger version of the image.   On top of this linked image I would like an image of a magnifying glass, to show people that the image can be clicked to enlarge it (apparently this isn't obvious without the magnifying glass).


Why the M1 chip memory limit is set to 16GB,it is mentioned  that it is based on 64 bit ARM architecture, shouldn't it share the same memory limit which is 16 Exabytes? According to the linked answer, it should have 34 address lines, has that number been made official?

My specific question is with the ASUS M3N78-VM motherboard that my home server uses. I currently have 4x2GB installed for a total of 8GB but I was hoping to upgrade to say 16GB (4x4GB). The official specifications of that motherboard says it only supports up to 8GB but it was released back when only 2GB sticks were available. What, if any, would prevent it from working with 4GB sticks now that 4GB sticks are available?  My general question is with motherboards in general... what would prevent a motherboard from working with bigger sticks if its all just the same type (DDR2 for example and same speeds) of memory?


Are there any particular conditions for a wave equation to represent a travelling wave? If yes, are they more than one? As an example could you please explain if $y=\dfrac{1}{x+vt}$ represents or does not represent a travelling wave?

A function which represents a wave must satisfy the following differential equation: $$\frac{\partial^2 y}{\partial t^2} = k\frac{\partial^2 y}{\partial x^2}$$ Any function that satisfies the wave differential equation represents a wave provided that it is finite everywhere at all times.  What does "it is finite everywhere at all times" mean?  Question:Which of the following functions represent a wave? a) $(x - vt)^2$ b) $\ln(x + vt)$ c) $e^{-(x - vt)^2}$ d) $(x + vt)^{-1}$  Only option (c) is given as the answer though all 4 satisfy the differential equation. I believe I did not understand the significance "function should be finite everywhere at all times" which is why I am unable to answer the aforementioned question.


I was reading  introduction to quantum computing that says that when one photon in a pair of entangled photon is measured, the other one will have the opposite result when measured in the same way. But how do we know that all the responses for all the possible measures are not decided for each qubit when the pair is created?   The first photon of the entangled pair would have a surface of half a sphere for which measurements give a positive result, and the other photon would have the other half of the sphere. If you measure both photons on the same axis, then they will never give the same result, as it's impossible for a single point to be in the two halves of the sphere at once, but as you increase the distance between the axes of measurment, the probability for one point to be in the top half of the sphere and the second in the bottom half of the sphere increases.

Consider that we have two balls, one white and one black, and two distant observers A and B with closed eyes. We give the first ball to the observer A and the second ball to the observer B. The observers don't know the exact color (state) of their balls, they know only the probability of having one or another color, until they look at them (measure). If the observer A looks at his ball he will see its color, which is white, so he immediately knows the color of the second ball. Lets call this “classical entanglement”.  My question is: What is the difference between this “classical entanglement” and the quantum entanglement, for example, of two entangled electrons with opposite spins states? Can this analogy be used to explain the quantum entanglement?


If $a\equiv b\pmod m$ and $c+d\equiv 0\pmod m$ then $ac+bd\equiv 0\pmod m$.   The response, posted below is correct??

If $a+b\equiv0\pmod m$ and $c+d\equiv 0\pmod m$ then $ac\equiv bd\pmod m$ How to show?$$$$ I tried $$a+b\equiv0\pmod m\Longrightarrow m\mid a+b\\c+d\equiv0\pmod m\Longrightarrow m\mid c+d\\a+b=mk\;\;\text{and}\;\;c+d=mj\\(a+b)(c+d)=m(mjk)\\m\mid ab+ad+bc+bd$$ But from here could solve anything.


I am using Ubuntu 18.04 64-bit as my main OS on my HP laptop. I recently installed Phoenix-OS in dual-boot, but when I boot up my laptop the GRUB screen for OS selection is not showing. It boots into a purple screen which I believe is the GRUB menu, but there is nothing written on it or any options shown. This screen keeps showing for the exact amount of time I selected in GRUB customizer.  What can I do to get the proper GRUB menu?   Edited: So apparently, the grub decided to show up randomly when I click esc, but I can't do anything, the only key is esc, and I click it, "Minimal BASH-like editing is ......." show up with a kind of a terminal "grub>". Now how can I resolve my issue ?

This keep happening when I install the Ubuntu as a dual boot for my laptop. I get a black that appears when booting with the following messages.  Minimal BASH-like line editing is supported.    For the first word, TAB lists possible command completions.  Anywhere else TAB lists possible device or file completions.     grub>   grub>   grub>   grub>   grub>   grub>   grub>   grub>   grub>    I have to enter these commands like this:  grub> set prefix=(hd0,msdos6)/boot/grub/  grub> insmod normal  grub> normal   And the GRUB menu appears. How to make my GRUB menu appear without having to type those command at my GRUB prompts?  I tried sudo grub-install and it give me this error message.    I tried to check if i have chosen the right disk, which come two possibilities, /dev/sda1 and /dev/sda6, but neither of these two works, and they gave the same error message.  /dev/sda1/    /dev/sda6


I am working with an interceptor (extended from RealProxy) which interacts with our caching service. I supply the key and am returned a JSON payload. The return type is reflected from the calling function (MethodInfo.ReturnType) and is used to cast the returned object as needed.  public object Get(string key, Type type) {     string value = cache[key];     return JsonConvert.DeserializeObject(value, type); }   Out of curiosity I wanted to make use of generics to accomplish this. I know you cannot specify a generic type from a Type variable. Is there any way to accomplish the following?  public T Get<T>(string key) {     string value = cache[key];     return JsonConvert.DeserializeObject<T>(value); }   The calling code is (simplified):  Type returnType = methodInfo.ReturnType; object cachedValue = cacheService.Get(key, returnType);  if (cachedValue != null) {     // return cached value } else {     // continue running }   The reason I am interested in doing this is I would like to use a different caching provider (redis, in particular StackExchange.Redis.Extensions.Newtonsoft) and our current method of caching/retrieving won't plug in quite so simply with calls like this:  User cachedUser = cacheClient.Get<User>("my cache key");

What's the best way to call a generic method when the type parameter isn't known at compile time, but instead is obtained dynamically at runtime?  Consider the following sample code - inside the Example() method, what's the most concise way to invoke GenericMethod<T>() using the Type stored in the myType variable?  public class Sample {     public void Example(string typeName)     {         Type myType = FindType(typeName);          // What goes here to call GenericMethod<T>()?         GenericMethod<myType>(); // This doesn't work          // What changes to call StaticMethod<T>()?         Sample.StaticMethod<myType>(); // This also doesn't work     }      public void GenericMethod<T>()     {         // ...     }      public static void StaticMethod<T>()     {         //...     } }


How do I enable Parallel Data Warehouse on my Microsoft SQL Server. I am trying to run this SQL statement below and received this error.  ERROR:  Msg 11305, Level 15, State 10, Line 2 The Parallel Data Warehouse (PDW) features are not enabled.   CODE:  select A.gender, A.firstname, A.weight,        SUM(a.weight) over (partition by a.gender                            order by a.weight) as 'New Column'  from ChildStat A  order by a.gender, a.weight;

I have the following virtual column generated from an aggregate over a sorted partition,  MIN(picture_id) OVER ( PARTITION BY [360_set] ORDER BY picture_id ASC )   However, when I execute that, I get the following.  Msg 11305, Level 15, State 10, Line 12 The Parallel Data Warehouse (PDW) features are not enabled.   This is where it gets interesting though, without a sort order on the partition, it works:  MIN(picture_id) OVER ( PARTITION BY [360_set] )   And, further, ROW_NUMBER() a window function (not an aggregate function) works with an explicit order on the partition.  ROW_NUMBER() OVER ( PARTITION BY [360_set] ORDER BY picture_id ASC )   How come the desired statement doesn't work? Where is this documented? The version information was requested, this is what I in Help → About.  Microsoft SQL Server Management Studio          10.0.5512.0 Microsoft Analysis Services Client Tools        10.0.5500.0 Microsoft Data Access Components (MDAC)         6.1.7601.17514 Microsoft MSXML                                 3.0 6.0  Microsoft Internet Explorer                     9.10.9200.16635 Microsoft .NET Framework                        2.0.50727.5472 Operating System                                6.1.7601   The result from SELECT @@VERSION is Microsoft SQL Server 2008 (SP3) - 10.0.5512.0 (X64)   Aug 22 2012 19:25:47   Copyright (c) 1988-2008 Microsoft Corporation  Standard Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1) (VM)


Let $ f(x) = \begin{cases} f:[a,b] \rightarrow\mathbb R  \\ \int_{a}^{b}f = 0 \end{cases}$. Prove: if $f$ is continuous, then $f\equiv 0$.  I'm still trying to get the intuition on the situation. For instance, if $f(x) = sin(x), x \in {[0, 2\pi]}$, it's true that $\int_{0}^{2\pi}sin(x) = 0$, but it does not imply $sin(x) \equiv0$. What did I misinterpret here? After the understanding of the situation, I'd like to know how would a formal proof follow.   I'm a freshman Pure Math student who barely started the course and has very few practice in writing proofs, although slightly less worse at reading them. I'd like a level of rigor in  line of thought.  EDIT: as it is noticeable from the comments below, there is a condition missing in the statement: $f \geq0$.

Let $f$ be a continues function in $[a,b]$  $\forall x \in [a,b] \ \ \ f(x)\geq 0$  $ \int_{a}^{b}f(x)dx \ = 0$  Proof that $ \forall x \in [a,b] \ \  f(x) = 0 $  So how do I do that ?  What I know is:  because $f$ is continues function in $[a,b]$ I know it bounded and because  $\forall x \in [a,b] \ \ \ f(x)\geq 0$ I know that $ \exists M \in \mathbb{N} \ \forall x \in [a,b] \ \ \ M \geq f(x)\geq 0$.  I also know that because $f$ is continues function in $[a,b]$ that $f \in R[a,b]$ meaning that there exists $F$ so that $F(a) = F(b)$, but how can I show that $ \forall x \in [a,b] \ \ F(b) = F(a) = F(x)$ ?  So how do I continue from here ?


I am from India and learning blender from few weeks.  When I render demo file bmw27 it takes 22 minutes with CPU and 11 minutes with GPU (gtx 750ti). Default settings.  I see some video on YouTube same GPU and same file within 2 minutes.  I want to know that this time is ok or there is problem.  My pc is  I5 3330 H77m-d3h (gigabyte) 8gb ddr3 ram Gtx MSI 750ti 2 GB ddr5  Windows 7 64 bit

I am currently using Sheep It! to render my blend (built on v2.68c) on multiple computers, and I noticed something rather strange. According to the log on-site, the frames rendered from other people's blends were completing in 3 to 4 minutes. This was on an 4 core i5. My main rig (with an 8 core i7) was completing frames in no less than half an hour. How is this possible?  To clarify, these people's frames are very complex, often with very detailed textures. I have 2 objects in my blend. Below are the options I changed for my blend:   Aspect Ratio: 1000px x 1000px Output: PNG Clamp Indirect: 0.98 Render Sampling: 128 Min Light Bounces: 0 Max Light Bounces: 4 Cycles Render   Is there something in there that I should change to make it go faster? I can't really comprehend how it's going to quickly.  EDIT: To answer what @Duarte asked...   System Specs: i7-920, 3GB DDR3, GT 630, Windows 10 I have two circles, extended to form a sort of coin with a star on it. It is not complex at all. I have Firefox and Steam running in the background, but not actively. I've been away from the computer for 8 hours and noticed this behavior. (I am running Blender from Steam.) I made sure when I began rendering that the blend was set for CPU rendering.          And to answer what @pycoder asked, yes, I am using Cycles Render.