How to build a supercomputer by linking common PCs on a network?

Fellows,  I have several computers, some new, some old ( I collect them, since my first one, which has 2Kbytes of RAM, from 1979 ). The collection is getting huge, but the purpose of this question is related to the fact that I always loved the power of supercomputers, or at least, the power of the big machines ).   I ever thought about the idea of joinning machines in order to get a more powerful one. I run a LAN ( local area network ) 1Gbit apeed, where there are 4 machines intel i7 2600k running at 4.8Ghz watercooler, each one with 16Mb RAM, SSD and common hard drives, for a total of 30Tb of space ( total on the LAN ). Having read articles and watched many videos about virtualization, I question for the possibility of installing bare metal ( Type 1 ) hypervisors on each machine, then, creating a virtual machine which spread across the physical machines, so I could install an operational system like windows on top, to run softwares that need much resources, like CPU, RAM, Hard disk, etc.   I imagine that there must be a way that a virtual machine "thinks" that it´s installed on a single machine, but indeed, it´s spread along several nodes ( like a cluster ). For the virtual machine, it sees the system as only one big machine, but indeed, there´s shared CPU, shared RAM and shared hard drives.   Using this way, we could install an OP and run for instance, Adobe After Effects, or Adobe Premiere, which needs an outstanding parallel processing ( or cpu power ) in order to make previews in real time, or to run complex software which could benefit from multiple processors. I know many people would suggest purchasing a big multi-cpu, multi-core xeon machine for parallel processing, but it´s not the case...I like to think that with the current technology, there must be a way to join PCs and get more computational power.   I see people joinning Raspberry pi and making "supercomputers" at youtube, with kind of 1 teraflop, so why can´t we do it with our own machines, which has LAN, ram, disks...isn´t it the same thing, we only need the software and how to do it, no ? Is it possible ? How to do it ?  Thanks


What happens to the energy when I push my hand against a wall but there is no displacement? How to calculate it?

If I push my hand against a wall, the wall doesn't move, so there is no displacement and so no work done. But energy is being used to generate the force, so what is happening to the energy? Does that mean the total energy is being lost as heat? If so how would you calculate this energy? I though of a way to do it, but I'm not sure if its correct, and would like to know that. Work done i.e. W = F x s can be converted to a function of time and so it  becomes W =  F^2 * s^2 / 2m. And then if I knew the force I applied, the duration for which I applied it, and the mass of my hand, I can calculate the total energy lost as heat, based on the potential distance my hand would have gone if there was no wall. Will this give an accurate result for the energy being transferred to heat?


I have a CSV file that I'm uploading via an HTML form to a Python API  The API looks like this:  @app.route('/add_candidates_to_db', methods=['GET','POST']) def add_candidates():     file = request.files['csv_file']     x = io.StringIO(file.read().decode('UTF8'), newline=None)     csv_input = csv.reader(x)     for row in csv_input:         print(row)   I found the part of the file that causes the issue. In my file it has Í character.   I get this error: UnicodeDecodeError: 'utf8' codec can't decode byte 0xea in position 1317: invalid continuation byte  I thought I was decoding it with .decode('UTF8') or is the error happening before that with file.read()?   How do I fix this?  ** **  Edit: I have control of the file. I am creating the CSV file myself by pulling data (sometimes this data has strange characters).   One the server side, I'm reading each row in the file and inserting into a database.


What are the do and do nots with regards to sexual relations between a professor and graduate student? As long as they aren't your advisor or on your committee is it considered OK? How does this work?


How many genes are needed for a living organism?

I am interested in this question as I'm doing research into early life on earth which is believed to have been single-celled. Therefore, by extension, it seems only logical that the first life would be as genetically simple as is possible, therefore I present the above question.  How many genes / pairs of AA would be the bare minimum for something to be considered alive and function as an organism.


Why was Episode 1 named "The Phantom Menace"?

This is the only title name that didn't make to me; all the other titles make sense to me, but this the only one that stumped me. "The Phantom Menace" never made sense because all the other movies have self-explanatory names.


18.04 downgrade from bionic-proposed to main

My Ubuntu 18.04 installation sometimes randomly freezes. I saw in one question that maybe this is a Gnome problem, and the solution proposed was to downgrade from bionic-proposed to main. What does that mean, and how can I do that?


For the longest time my ignored tags have been working but today they are not. They work on the home page but not the /questions page. However, if you choose the "Gray out questions" option then that fails. Arqade is the only site I've ever had a long-standing ignore list so I don't think I can blame cache. The same behavior seems to be exhibited on Stack Overflow but I added those ignore tags just moment ago so cache could be an issue. If it matters, I am using Chrome x64 v91.0.4472.77 on Windows 10 Via comments, this issue has been confirmed for Watched Tags as well.


Does viewing your own question add to its view count?


After a UK visitor visa is refused, does it mean you can never go to the UK?

If someone was refused a UK visitor visa, does that mean they cannot visit the UK at all? If so, for how long?


UV mapping a straight image around a ring shaped flat mesh

Is it possible to mapping a image around a ring shaped mesh? I would imagine there should be a way to curve/distort the image around the mesh. If not, how can I straighten out the mesh easily instead to fit the image?


Run a command which returns a string when reading a file

I have this idea and maybe it is not feasible, but I think it worth asking.  Let's say a user is running this command:  cat ~/file.txt   Whenever something tries to read from this file, I would like to run a script or command in the background instead and return the response of that script as content.  Somehow like doing:  ln -s /folder /symlink   But for scripts (idea of what I have in mind):  symlinkcommand /filepath/file.txt "command to run"   Hope I made myself clear. Please reply with your ideas and suggestions if any.  Thanks.


I have a problem with my bitnami wordpress hosted on Google cloud. I have both the www and the non-www version running in parallel. I want to have all the non-www traffic 301 to the www version.  I added these lines into the conf file:      RewriteEngine On     RewriteCond %{HTTPS} !=on     RewriteRule ^/(.*) https://example.com/$1 [L,R=301]   But it does not fix the issue. Anyone has a solution?


Who or Whom? Which is the right one here?

I read this sentence:     "One of the women whom dislikes me made it"   I was wondering whether 'whom' is the right word in the sentence above or it should have been "who". I think "who" is the right one. Am I wrong?


If $X$ is independent of $Y$ and $Y$ is independent of $Z$, is $X$ independent of $Z$? In other words, is independence transitive?


Mapping value from dictionary to dataframe


What is the meaning of this sentence:     He met a girl who was to become a queen.   Does it show the plan of the girl?   Does it mean: He met a girl who 'was going to' become a queen?  How and in which sense is 'was to'  used in this sentence?


Time Dependant Workflows and transactions

The environment setup is as follows: 1) there is a workflow triggered by some criteria which has a time dependent action which will update a field on the object. 2) With apex-code I update a List of 10 of such objects so that the criteria will fire for all of them  When the time countdown expires, will there be 10 different transactions or will there be 1 transaction with the 10 objects?


Do elevator upgrades increase your passive credit earnings, too?

When you upgrade your Death Star elevator the speed increases, and the tips go up by a predetermined factor.  But, does this also increase the passive traffic to your levels?  In other words, does it increase the number of bitizens you do not ferry in the elevator that make sales on your levels?  I noticed that the descriptions include a PPM rating, but it's not clear what this means.  I assume it's People Per Minute, but I don't know.


How can I change the position of alerts pop up?

With Yosemite we got handy, growl-like, alert popups from the notification center. It's great but it often hides handy utils which also take the top right position of the screen.  Is there any way change the position of those alerts (via system preferences, plist, or an app)?


Correctness of "of my sending the picture"

Is this sentence correct?     I don’t think Linda would have approved of my  sending the picture; but I did it anyway.   Specifically, is of my sending the picture correct?


Opps usage in javascript using prototype keyword

i saw a code where people used prototype keyword in javascript but i do not understand what is the importance of this keyword and when to use it.  here is some code related to javascript prototype  1st example  function Person(fn,ln) {     this.FirstName = fn;     this.LastName = ln; }  Person.prototype.GetFullName = function() {     return this.FirstName + ' ' + this.LastName; }  var p = new Person('jon','smith'); alert(p.GetFullName());    2nd example  function Person(fn,ln) {      this.FirstName = fn;     this.LastName = ln;     Person.prototype.GetFullName = function()     {         return this.FirstName + ' ' + this.LastName;     } }  var p = new Person('jon','smith'); alert(p.GetFullName());   1) just see the code what prototype keyword will do here?  2) also see two same code in 1st example prototype used outside of Person function and in second example prototype is wrapped in person function. looking for good explanation with more sample example to understand it properly . thanks


Having Trouble using Dash and managing windows

I recently switched to the Dell XPS 13 DE from a Mac.  I'm trying to replicated the super + spacebar motions to open up a dialog to run applications on the computer but I can't seem to get it going.  Also, is there a quick guide on the best way to use key combos to snap windows?


Can I mount a 60" TV and mount weighing a combined 95 pounds to a drywall or plaster?

I cannot find studs on my firewall but, when I drilled a hole on the wall, it seems to me that either the plaster or drywall was thick enough (like 1/2"). Can I Mount a 60" TV and Mount Weighing a Combined 95 pounds to that Drywall or Plaster?


\nameref breaks for star versions of section/paragraph when titlesec is loaded

\nameref breaks for the star versions of section, paragraph when titlesec is loaded. I have a document that numbers paragraphs by default, but I have a few I do not want to number but would like to refer to. These are marked with \paragraph*, however, if the titlesec package is loaded at the same time, it causes nameref to display an empty string (the link box of hyperref is still visible).  MWE:  \documentclass[12pt]{article} \usepackage[sf]{titlesec} %comment this out and it works fine. \usepackage{hyperref} \begin{document} \section{Sections} \label{sec} This is \nameref{sec} \paragraph{A named Paragraph} \label{par} This is \nameref{par} \paragraph*{A starred named Paragraph} \label{par:star} This is \nameref{par:star} \end{document}   I suspect titlesec causes this defect for ALL star variants of sectioning commands but have not tested this. For me only paragraph* is relevant however a fix for all variants would be the best.  I have a hunch it might be related to this:  however this happens to go way beyond my latex knowledge and is just "magic" for me.


The reCAPTCHA has become too difficult for humans to solve

The reCAPTCHAs have suddenly become almost illegible. I regularly have to change it four or five times before I find one I can read. I am tempted to just enter the known word (an easy guess), and leave the other. Can something be done?


Can somebody explain me or give me a link with a intuitive point of view of Bernoulli numbers? I mean, somebody just saw a typical sequence of numbers that appears in some Taylor expansions, and them called them "Bernoulli numbers"? How do they become with a method for finding these numbers? What's the intuition behind this?  I'm asking it because I can only find non-intuitive PDFs that only accept strange formulas and don't even explain them. And I wanted to know how to calculate a Bernoulli number.


Prove that if $n^x$ is an integer for every natural number $n$, then $x$ is also an integer.

Question above is self-explanatory.  Update  $n$ is every natural number!


At the end of Prisoners Keller Dover was forced to jump into the dark pit hole below the junked car on gunpoint by Mrs Jones. He was seen finding a red whistle that fell from his daughter using a mobile torch. Was he able to make a phonecall to his wife or Detective Loki or did the last scene mean to give us all hope?  I think it was at least 2 days since Keller had been confined to the hole. It'd be difficult to find him alive. Was Keller rescued?


Good and Thorough Quantum Mechanics Textbook Recommendations

I've decided to pursue introductory quantum mechanics as an independent study next year at my high school, and I am looking for a good textbook. Specifically, I would like a book that does not limit the math it uses to describe concepts. I'm familiar with multivariable calculus, differential equations, and linear algebra, as well as some basic concepts of abstract algebra. With that in mind, I'm looking for a book that rarely, if ever, sacrifices the formality and mathematical rigor of the topics covered for the kind of intuitive, conceptual presentation that glosses over important subtleties. The ideal book would also not require extensive prior understanding of physics; I have only learned as much as is taught in AP Physics C, and I plan to study pertinent material, like waves, that was not part of the curriculum but is essential to quantum mechanics. So let's suppose my experience by the time I start quantum will be at most all of the material covered in a sizable first-year physics textbook with calculus (specifically, University Physics by Young and Freedman).  In short, I am looking for a book that will cut me some slack with prior physics knowledge but not with prior math knowledge. Any ideas?


How do fix this NullPointerException in my .txt word-counter

I am trying to make a Java program that counts the words and the lines in an '*.txt' - file. So far so good. The code works only if the '.txt' has only 2 lines. If put more lines into it I get a NullPointerException at the .split(" "); part in my code. I have read somewhere that could be something with .readLine()-function. But I have really no clue what really causes it.  import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException;  public class txt_counter { static String FilePath = "C:\\Users\\diasc\\Desktop\\test.txt";  public static void main(String[] args) throws IOException{     FileReader finput = null;     BufferedReader binput = null;      try {         finput = new FileReader(FilePath);          System.out.println("Orignal txt output:");         int a;         while ((a = finput.read()) != -1) {             System.out.print((char) a);             }           binput = new BufferedReader(new FileReader(FilePath));          int Zcount = 1;          int Wcount = 1;          while ( binput.readLine() != null ) {             String[] woerter = binput.readLine().replaceAll("\\s+", " ").split(" ");             System.out.println("\n\nsplitted String: ");             for(int i =0; i<woerter.length; i++)             {                 System.out.println(woerter[i]);             }             Wcount = Wcount + woerter.length;             Zcount++;          }          System.out.println("\nLines: " + Zcount);          System.out.println("Words: " + Wcount);      }finally {          if (finput != null) {              finput.close();          }          if(binput != null) {              binput.close();          }     } }   Console Output:     Orignal txt output: lol   I   am pretty stupid. haha idk     send halp        splitted String:   I   am   pretty   stupid.   haha   idk   Exception in thread   "main" java.lang.NullPointerException    at txt_counter.main(txt_counter.java:32)


How can i set a cookie for a standardController?

I'm doing a test class and i need to set a cookie for my page (ApexPages.StandardController).  I have to use something like: apexPages.currentPage().setCookies();  But, since i am simulating a page and not using a actual one, how can i do it?


Proving $9^n - 8n - 1$ is divisible by $8^2$ for $n\ge 0$?

My textbook provided the following proof:        Base case: When $n=0, 9^n-8n-1=0=64\cdot0$, so $64\mid\left(9^n-8n-1\right)$.      Induction step: Suppose that $n\in\mathbb N$ and $64\mid\left(9^n-8n-1\right)$. Then there is some integer $k$ such that $9^n-8n-1=0=64k$. Therefore:      $$\begin{align} 9^{n+1}-8(n+1)-1&=9^{n+1}-8n-9\\ &=9^{n+1}-72n-9+64n\\ &=9\left(9^n-8n-1\right)+64n\\ &=9(64k)+64n\\ &=64(9k+n) \end{align}$$      so $64\mid\left(9^{n+1}-8(n+1)-1\right)$.      What I don't understand is how the equation goes from   $$= 9^{n+1} - 8n - 9$$  to   $$= 9^{n+1} - 72n - 9 + 64n$$


"Many of our employees hold a master's degree."  "Many of our employees hold master's degrees."  "Many of our employees hold masters' degrees."  Which of the above is the correct expression, assuming none of the employees have more than one master's degree? (You can either have 1 or none).  For me, I feel #1 sounds the most natural, but I'm not sure it is correct.  Thanks in advance!  Edit: This isn't a duplicate as the question isn't about whether or not you need an apostrophe at all (all three of my examples given have apostrophes in them)!


I have a hybrid Dawes, about 25 years old. I think it's currently got 700x35mm. I would like to fit thinner tires but how do I know if the rims will accept them. Is there a way to know?


A connected k-regular bipartite graph is 2-connected.

I've been struggling with this exercise; all ideas have been unfruitful, leading to dead ends. It is from Balakrishnan's A Textbook of Graph Theory, in the connectivity chapter:     Prove that a connected k-regular bipartite graph is 2-connected.   (That is, deletion of one vertex alone is not enough to disconnect the graph).  I think the objective is to make use of Whitney's theorem according to which a graph (with at least 3 vertices) is 2-connected iff any two of its vertices are connected by at least two internally disjoint paths. But I'll welcome any ideas or solutions.  Thank you!


I installed wordpress latest version in Ubuntu 16.04 with nginx. But after some days of installation I see some unknown file in root directory.  like alias99.php. How to prevent/block this. I already add   location ~ /\. {     deny all; }  location ~ ^/wp-content/uploads/.*\.php$ {     deny all; }  location ~* /(?:uploads|files)/.*\.php$ {     deny all; }   in conf file. How can ensure security level. Thank you.


Here's I'm trying to slice a nested list but i'm getting the following output. Explain?

I've tried the following code but this is giving me a output that i'm unable to predict. Please help me in scanning this code. l=[['d','e','f'],['a','b','c'],2,3,4,5] l[:2][1:2]  Output: [['a', 'b', 'c']]


Copy text from quick look in El Capitan or Sierra?

I used to be able to just quicklook files and copy the text directly from there, removing the need to launch applications to open it which is just awesome, however, it doesn't seem to work since El Capitan. I have tried running the terminal command (defaults write com.apple.finder QLEnableTextSelection -bool TRUE) that enables it but it didn't work.  What options exist to customize quick look or replace the default plug in with one that allows text selection?


Questions regarding proof of probability integral transform

I'm attempting to understand the proof of the probability integral transform in [1].  First they define $Y = F_X ( X )$. Yet, the cumulative distribution function is defined in [2] as $$F_X ( x ) = P(X\leq x).$$  Q1. Can you define $F_X ( X )$ (preferred answer would provide a measure-theoretic definition [4], but any definitions are welcome)?   Continuing to read from [1], there is a step such that  $$P(F_X ( X ) \leq y)  = P(  X   \leq F^{-1}_X ( y )).$$  Q.2. Can you explain how come this equality holds?  I imagine its related to the properties shown in [3]. Namely that $$F^{-1}(F(x)) \leq x$$ and $$F(F^{-1}(p)) \geq p.$$ Even so, such seems to me to be insufficient to understand why the equality holds.  [1]   [2]   [3]   [4]


How to allow Desktop Sharing to work after reboot?

Ubuntu 16.04  I can enable Desktop Sharing and it works great.  If the system is rebooted, I cannot VNC to the login prompt, I have to have someone log in first.  I could enable auto login, but I have heard this may not work if you need CUDA loaded.  Is there a good way to just have a VNC server running all the time where I can use a basic VNC client and connect, login and use the computer?


Getting error code -128 on a late-2015 iMac

Late 2015 iMac is rebooting on its own. Only Finder running, OSX 10.11.6. (2) 8GB RAM sticks. Got to catch it in the act today.  After reboot I find kernel: Previous shutdown cause: -128  That doesn't appear to correspond to anything useful in the old MacOS error codes documentation from 1998:  -128  userCanceledErr         User canceled an operation    The is a refurb unit, hoping it doesn't need to go back for another refurbishment.   thanks


What is the difference between a shallow copy and a deep copy with JavaScript arrays?

According the MDN documentation calling array.slice() will create a shallow copy of the array.  See this .  However, if I run a simple test as such in the console:  var test = [[1,2,3],7,8,9]; var shallow_copy = test.slice();   and inspect shallow_copy, I can see that the entire 2 dimensional array appears to be copied over.  What is the difference between a shallow copy and a deep copy?  If I were to guess, I would have called this a deep copy.


I saw somewhere a new TV series. Here's what I remember:  Sometime in the future, when the Earth could no longer support life (or something similar), a group of people goes to the past of the Earth.  They found themselves in pre-historic times. They try to build a colony etc.  Does anyone know something about this series?


I was working my way through some number theoretic proofs and being a newbie am stuck on this problem :     If $(x, 4) = 2$ and $(y, 4) =2$, then $(x + y, 4) = 4$,     where $(a,b)$ denotes the greatest common divisor of $a$ and $b$.   My Solution  (Incorrect)   $x-4 = 2t$ $y-4 = 2p$ $x + y - 8 = 2(t+p) \Rightarrow x + y - 4 = 2f + 4 = 2(f+2)\Rightarrow 2$ divides $(x+y , 4)$   My Question:  My solution is definitely inadequate. Can someone help me out?


How to rotate blocks while giving a set command?

I have two wooden blocks, one facing up and one facing the side as you can see in the image, I do not want the block to be vertical, I want it to be horizontal when I give the command //set <block>  Does the //set <block> command have more than one argument to do this? Or is there another command to rotate an already placed block?  The command I am using is this: //set 17:1   The server version is 1.5.2, so the WorldEdit plugin version is 5.5.6


Consider a continuous system of cogs which extend from the sun to the earth. Light takes eight minutes to reach the earth. However, if one was to rotate the initial cog(near the sun) then the all the cogs would rotate simultaneously(I don't know is this will actually happen!) there by working as a signalling mechanism which can be used to transmit information from the sun to earth(or the other way) instantaneously. Therefore information(I don't know what information exactly means.) could be transmitted faster than the speed of light. Isn't this counter intuitive? If not where am I making a mistake? I request anyone to shed some light on this matter.


How to obtain real observation from simulated pseudo observation? (from the copula)

I have fitted a normal copula to my data in R using the copula package and generated pseudo observations in the unit square [0,1]^2. I am having trouble retrieving the simulated values: how can I get x and y from u1?  from my understanding of the process, assuming x and y are normally distributed (for the sake of simplicity), I should do the following  x <- qnorm(u1[,1],mean(mat[,1]),sd(mat[,2])) y <- qnorm(u1[,1],mean(mat[,1]),sd(mat[,2]))   and these x and y should be my simulated real observations right? For some reason they do not fit that well my data as you can see below (simulated data are in RED and skewed upwards, and actual data are in BLUE).    What I need to know is: is the process correct or am I missing something? Is the use of qnorm correct as it is above or should I've used it differently?  By trying to use qnorm with the default mean=0 and sd=1 the simulated x and y seem to fit better, which I find odd since I thought actual mean and sd of x and y should be used. Am I correct?    Here is my code (except for the last part which is above)  library(copula)  x <- read.table("x.txt") y <- read.table("y.txt")  mat <- matrix(nrow=100,ncol=2)  for(i in 1:100) {     mat[i,1] <- x[,1][i]     mat[i,2] <- y[,1][i] }  #Actual observations plot(mat[,1],mat[,2],main="Returns",xlab="x",ylab="y",col="blue")  #Copula fitting normal.cop <- normalCopula(dim=2) fit.cop<- fitCopula(normal.cop,pobs(mat),method="ml")  #Coefficients rho <- coef(fit.cop) print(rho)  #Simulate data u1 = rCopula(500,normalCopula(coef(fit.cop),dim=2)) points(u1[,1],u1[,2],col="red")   Here you can find the data for x and y should you need it to run the code.   x and y are returns from two stocks


How was it exactly that Nagato came upon his Rinnegan?  Madara states that it was his, and that he gave it to him: how did he do that? Did he transplant it into Nagato, or did he transfer it otherwise?  Note: I do not recall whether this was explained in the manga or not.


C# serial port does not show output in textbox

Hi all I am pretty new to C# and Arduino. When i send to text to my Arduino it does not send it back to the textbox in the app. I can send it to my Arduino but I get the error when the message I send has to be in the textbox in the application.  Here is the part I am getting a error:  private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e) {        Output.Text = serialPort1.ReadExisting(); }   Here is my code:  public partial class ArduinoSerial : Form {     public ArduinoSerial()     {         InitializeComponent();         string[] serialPorts = System.IO.Ports.SerialPort.GetPortNames();         cboPorts.Items.AddRange(serialPorts);         cboBaud.Items.Add(2400);         cboBaud.Items.Add(4800);         cboBaud.Items.Add(9600);         cboBaud.Items.Add(14400);         cboBaud.Items.Add(19200);         cboBaud.Items.Add(28800);         cboBaud.Items.Add(38400);         cboBaud.Items.Add(57600);         cboBaud.Items.Add(115200);         cboPorts.SelectedIndex = 0;         cboBaud.SelectedIndex = 2;     }      private void cboPorts_SelectedIndexChanged(object sender, EventArgs e)     {         string[] serialPorts = System.IO.Ports.SerialPort.GetPortNames();         cboPorts.Items.AddRange(serialPorts);     }      private void cboBaud_SelectedIndexChanged(object sender, EventArgs e)     {         cboBaud.Items.Add(2400);         cboBaud.Items.Add(4800);         cboBaud.Items.Add(9600);         cboBaud.Items.Add(14400);         cboBaud.Items.Add(19200);         cboBaud.Items.Add(28800);         cboBaud.Items.Add(38400);         cboBaud.Items.Add(57600);         cboBaud.Items.Add(115200);     }      private void btnStart_Click(object sender, EventArgs e)     {         serialPort1.PortName = cboPorts.SelectedItem.ToString();         serialPort1.BaudRate = Convert.ToInt32(cboBaud.SelectedItem.ToString());          if (!serialPort1.IsOpen)         {             btnStart.Enabled = false;             btnStop.Enabled = true;             serialPort1.Open();         }     }      private void btnStop_Click(object sender, EventArgs e)     {         if (serialPort1.IsOpen)         {             btnStart.Enabled = true;             btnStop.Enabled = false;             serialPort1.Close();         }     }      private void btnSend_Click(object sender, EventArgs e)     {         if (!serialPort1.IsOpen) return;          serialPort1.Write(txtInput.Text + "\n");     }      private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)     {            Output.Text = serialPort1.ReadExisting();     } }   My ino file  /*  Name:      LOOP_C.ino  Created:   9/8/2017 10:51:31 AM  Author:    Jari */  // the setup function runs once when you press reset or power the board void setup() {     Serial.begin(9600); }  // the loop function runs over and over again until power down or reset void loop() {     while (Serial.available()) {         Serial.write(Serial.read());     } }   I am already trying for over 2 hours, I can't find the answer anywhere.


Why is the spirit of Anakin's young while Obi-Wan and Yoda's spirits are old?

In the end of Star Wars Episode VI: Return of the Jedi, Anakin, Yoda and Obi-wan's spirits appear in a vision on Endor.  Obi-wan and Yoda look old (as they are when die), but Anakin is young.   Why is Anakin the only one to appear young if, when he died, he was old and deformed?


Right-hand-side assignment - how is this possible?

I have some basic angular code grabbing navigation menus for logged in and logged out users and storing the menus in $localStorage then toggling them to the $rootScope when the user logs in/out etc.   Below is a simplified version of that code for the purposes of this question.   It seems like one of the lines of code actually results the left-hand-side to be assigned to the right.  $localStorage.navigation = {}; $rootScope.nav = {};  // save the nav menus in local storage $localStorage.navigation.loggedIn = "nav menu json";      // use local storage to set the rootscope $rootScope.nav = $localStorage.navigation;    /*  should be..     $rootScope.nav = {loggedIn:'nav menu json'};     $localStorage.navigation = {loggedIn:'nav menu json'}; */  // set the nav menu - Right-hand-assignment??? $rootScope.nav.current = $localStorage.navigation.loggedIn;  /*  should be..     $rootScope.nav = { loggedIn:'nav menu json', current: 'nav menu json' };     $localStorage.navigation = { loggedIn:'nav menu json' }; */  console.log($rootScope.nav.current);    // 'nav menu json' as expected console.log($localStorage.navigation.current);    // 'nav menu json', WHAT??!!  /*  actually..     $rootScope.nav = { loggedIn:'nav menu json', current: 'nav menu json' };     $localStorage.navigation = { loggedIn:'nav menu json', current: 'nav menu json' }; */   What in the hell is happening here??


How to fix incompatibilities between etex package and new filecontents?

Since filecontents is usable into document (LaTeX2e <2019-10-01> patch level 3), the etex package breaks the filecontents new \write...  With TeXLive 2018, the following code is ok:  \documentclass{article} \usepackage{etex} \usepackage{filecontents} \begin{filecontents*}{\jobname-0.vrb} content \end{filecontents*} \begin{document} A \end{document}   With TeXLive 2019 and LaTeX2e <2019-10-01>, the following (equivalent) code is broken:  \documentclass{article} \usepackage{etex} %\usepackage{filecontents} \begin{filecontents*}[force]{\jobname-0.vrb} content \end{filecontents*} \begin{document} A \end{document}   The error message is:   ! No room for a new \write . \ch@ck ...\else \errmessage {No room for a new #3}                                                   \fi  l.4 \begin{filecontents*}[force]{\jobname-0.vrb}


I'm stuck on a problem where I have the following,  $A \subset \mathbb R$. Then there exists sequence ${a_{n}}$ and ${b_{n}}$ of  $A$ such that $$\lim_{n \to \infty}{a_{n}}=\sup(A),\ \ \ \ \lim_{n \to \infty}{b_{n}}=\inf(A).$$  I have a small outline of the proof that I have done however I'm not exactly sure if this is the right way to go, I want to find a sequence $x_n$ in $\mathbb R$ such that $x_n<\sup(A)$ for each $n$ and $x_n\to a$ and if $\alpha=\sup(A)<\infty$ I let $x_n=\alpha-\frac{1}{n}$ and if $\sup(A)=\infty$ then I'll let $x_n=n$. I also would follow this same pattern for the $\inf(A)$ since $\sup(A)=-\inf(-A)$. Or would it be better to show that $a_n$ is increasing in $A$ and $b_n$ is increasing in $A$ and since both sequences are part of $A$ we know they are bounded both above and below so $sup(A)$ and $inf(A)$ exists so I can use that to prove the initial proof. Any help is welcomed.


How to switch between tty and xorg session

My xorg session is on tty1 and if I want to issue a command from tty (because I cannot do it from xorg session for some reasons), I press Ctrl+Alt+F2, for example, and type a command. But I cannot start graphical applications from any tty except first since there is no xorg session in it. Then I am curious how can I switch to tty1 where xorg session is running and back to the session?


We are facing the problems when running the batch apex getting below error      First error: Update failed. First exception on row 0 with id   0061A000012kKuBQAU; first error: UNABLE_TO_LOCK_ROW, unable to obtain   exclusive access to this record or 156 records   Can any one please suggest how to avoid these error?


Proving existence of a root in second derivative

Let $f:[0, 1] \to \mathbb{R} $ be double differentiable function such that line segment between points $(0,f(0))$ and  $(1,f(1))$ pierces function at point $(a,f(a)) $  where $0<a<1$.  So now i have to prove that there exists such $x_0$ that  $f''(x_0)=0$  So i know that the function has a second derivative, but what can i say about it, since i only have the function, not second derivative.  My first idea to somehow to use that line for describing first derivative. And i know that if i do that i will just have to show that f'(0)=f'(1) and will use Rolle's theorem  to prove the statement. Any help or tips are welcome. Thank you in advance.


I have two dependent variables y1 and y2 with highly skewed distributions. In order to do ANOVA, I was trying to transform the data to normality.      y1 is a proportion expressed as percentage.  For y1 I tried log of reflected data. log10(k - y1), where k = max(y1) + 1.   y1 being a proportion, I also tried a logit transformation. log(y1/(100 - y1)). However, there were many Inf values.  For y2 I tried log10 of the data.   The residuals of the ANOVA model in both the cases are heavy tailed distributions.      Should I transform the data for ANOVA? If so, what is the most appropriate strategy?


In how many ways can $m$ employees be assigned to $n$ projects if every project is assigned to at least one employee?

In how many ways can we assign $m$ employees to $n$ projects so that every employee is assigned to exactly one project and every project is assigned to at least one employee? Also, $m>n$.  My answer:  Let's choose $n$ employees from $m$ and assign them projects such that each project has exactly one employee working under it. Thus, $mPn$.  For the remaining $m-n$ employees, each employee can work under $n$ project options. Thus, $n^{m-n}$.  Thus, total answer $= mPn \cdot n^{m-n}$.  For $m = 5$ and $n = 4$, my answer $= 480$ and expected answer $= 240$.  For $m = 6$ and $n = 3$, my answer $= 3240$ and expected answer $= 540$.


"1.5 hours" are "One hour and half" or "One and half hour"?

1.5 hours are "One hour and half" or "One and half hours"?  Examples:      He will be there in 1.5 hours.      I spend there 1.5 hours.


Are double-slit patterns really due to wave-like interference?

According to various sources on the web, it seems like the general concensus is that there isn't actually any wave-particle duality with quantum particles. For example,  implies that diffraction patterns in  were interpreted as wave interference due to apparatus limitation at the time they were first performed.  Does this mean that all those sources and animations showing two waves interfering are simply incorrect, classical conclusions which don't have anything to do with (quantum) reality?  What's actually the most confusing is that most sites which state that it is now possible to pass individual photons through these slits, also claim that these individual photons somehow interfere with themselves resulting in the observed patterns. That seems like a rather thin explanation, doesn't it?  So, is there actually any need to use wave interference to explain the phenomena, or can we simply state that the pattern is probabilistic in a certain way, without involving the "spooky" explanations?


Can I create a bootable Linux live USB flash drive using a Windows computer?

I have a rescued 2013 MacBook Air with a broken screen backlight due to a beverage spill and missing its internal SSD. I don't yet have any OS installed on it. I have access only to (32 bit) Windows PCs otherwise.  I believe there are bootable live USBs these days like we used to use live CDs back in the day. For a Mac live USB stick I'm not sure what partitioning / formatting / filesystem is needed for it to be bootable by Mac firmware. Thus I'm not sure if or how I can create one using a Windows box.  Existing questions that I originally thought were identical are about creating a USB key from an Intel machine running Linux. I currently don't have Linux on any of my Intel machines, all are running only Windows. Thus it appears mine is a novel question here.


murphy@murphy-Compaq-Presario-C700-Notebook-PC:~$ sudo apt-get install clipgrab [sudo] password for murphy:  E: dpkg was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem.  murphy@murphy-Compaq-Presario-C700-Notebook-PC:~$ sudo dpkg dpkg: error: need an action option  Type dpkg --help for help about installing and deinstalling packages [*]; Use `dselect' or `aptitude' for user-friendly package management; Type dpkg -Dhelp for a list of dpkg debug flag values; Type dpkg --force-help for a list of forcing options; Type dpkg-deb --help for help about manipulating *.deb files;  Options marked [*] produce a lot of output - pipe it through `less' or `more' ! murphy@murphy-Compaq-Presario-C700-Notebook-PC:~$    am getting this error when i try to install clipgrab. please help


How do I pin a file shortcut to Ubuntu dock?

I would like to pin a file's shortcut to the dock in the Ubuntu 18.04 GNOME desktop so that the file opens directly when I click it, for example a spreadsheet file that opens with LibreOffice Calc. Is this possible?


How to run scripts without typing the full path?

I'd like to know if there is a way to run  program/shell script without typing full path:  /opt/idea/bin/idea.sh


I want to calculate new value upon keypress in a textbox inside a datatable. However, the textbox inside the datatable is not triggering upon keypress.  $(document).on('mouseover', '#table1 tr', function() {   rndex = this;   jindex = this.rowIndex; });  var dtable = $('#table1').DataTable(); var origval = $('#table1 tr:eq(' + parseInt(rndex) + ') >td:eq(' + 1 + ')').html(); var $textvalue = $(jindex).find(".txtBox"); var newval;   $textvalue.on('keypress', function(e) {   if (e.which != 8 && e.which != 0 && (e.which < 48 || e.which > 57)) {     e.stopImmediatePropagation();     return false;   } }).on('keyup change', function(e) {   newval = parseFloat(origval) + this.value;   alert(origval); });     Thank you in advance!


applying two different textures to a plane

when we apply a texture to a plane it shows on both side. i know this is a single face. but i want to model a movie poster which is normally white on backside. i want to make it some part rolled up and loosly hanging from wall, so that some portion of its white blank backside shows. anyway to do that with a plane ?? or i have to make a very thin cube to do that?? cube doesn't look convincing as a movie poster.


Drop in XML Sitemap Index Numbers in Google Search Console?

what is going on .. my sitemaps aren't index anymore... I have a really sudden decreasing in sitemap index


Displaying features at map scale corresponding to attribute?

Suppose one had a large dataset of features of vastly different sizes - perhaps political boundaries ranging from country to county.  It would be useful to be able to display only the large countries at a distant scale while increasingly displaying smaller boundaries as the map is zoomed.  In ArcMap, the only way I know how to accomplish this is by creating multiple copies of the layer in the Table of Contents and choose the maximum and minimum display scales.  However, can I set an attribute, say display_scale_min and display_scale_max where it specifies at which scales the individual feature should be displayed?  This wouldn't add too much complexity because the database could quickly narrow the results given the current map scale.  It would be handy because the display scale could be programmatically assigned.  It would also be handy when one feature class had several scale-dependent classes (such as having eight or so ways to simplify the display of roads).


Can an animal cast spells via a Ring of Spell Storing?

Based on , (answered ), I have a follow up question: Can a normal animal cast spells via a Ring of Spell Storing? It seems that any animal, if properly trained, can attune to the Ring. But do they have the ability to cast spells stored within? This is strictly about trained, wild animals; not familiars where there is a telepathic link, not Beast Master beasts where there is a deeper connection. This is referring to the pig I grew up with, the owl I nursed back to health, or the rat I bought from the local store. The best I could find so far is the  spell which states:  ...  the creature's Intelligence and Charisma scores become 1. The creature can't cast spells, activate magic items, understand language, or communicate in any intelligible way. The creature can, however, identify its friends, follow them, and even protect them.  But is the ability score or 1 what prevents the spell casting, or an effect from the spell? But if we take an owl, it has an Int of 2. Is that enough to cast a spell? Consider that a PC can still become a Wizard even with the lowest die roll of 3. They just can't multiclass. Also, from the Ring's :  While wearing this ring, you can cast any spell stored in it. The spell uses the slot level, spell save DC, spell attack bonus, and spellcasting ability of the original caster, but is otherwise treated as if you cast the spell. The spell cast from the ring is no longer stored in it, freeing up space.  There is no mention of whether components are required or not. If they are, could a beast form the words/sounds needed for Verbal components?


QGIS 2.x - 4 colors theorem - TopoColour and Map Coloring plugins

I try to use  to color :  Both of them doesn't work or I do something wrong. Maybe somebody knows any other plugins which color shapes according to 4 color theorem?


I read , but I wonder what  a "systemd login session" is? Is it  called more frequently as a "systemd logind session"?  Is it some process? (like a lxsession process?) What is its process name or command name?   Is it itself a process session or process group? Is it related to the process session lead by thelogin  process?   Thanks.


why are qubits such a game changer in quantum computing?

Qubits are in a superposition which means that they can currently be both digits of 1 and 0 at the same time BUT this is my question:  If Qubits have to be filtered to be used then what makes them better than normal bits after they are filtered? they are going to become 1 OR 0 because they can't be used in their superposition (If I'm correct), so the way I see it they are just normal bits we just have to take the extra time to filter first. It would be much more efficient (the way I see it) to simply re-arrange bits (like 1001 to 1100 or 1010 they use the same bits but get multiple results) to get faster results ya-know?  So if someone could tell me why quantum computing is so much better I would appreciate it a lot! If I said anything wrong than please correct me!


systemctl throwing errors on start/enable after package instal

In the effort to lock down a new Centos box I am building I am installing  iptables. I would like to be able to put this in a script so I can do this to other boxes but I am getting some odd errors and the roll back requires a reboot? Installing with  yum install iptables   which works fine, but before reboot:  [root@ip-10-0-0-132 ~]# systemctl start iptables Failed to issue method call: Unit iptables.service failed to load: No such file or directory. [root@ip-10-0-0-132 ~]# systemctl enable iptables Failed to issue method call: Access denied [root@ip-10-0-0-132 ~]#   and after  [root@ip-10-0-0-132 ~]# systemctl enable iptables ln -s '/usr/lib/systemd/system/iptables.service' '/etc/systemd/system/basic.target.wants/iptables.service' [root@ip-10-0-0-132 ~]# systemctl start iptables [root@ip-10-0-0-132 ~]#   I am new to systemd and if this is completely trivial please point me to a man page/guide/wiki so I can research this. I just haven't found anything obvious as yet.


Renew a German visa without having used the previous visa

I have a valid German visa, which I could not use in the time period allowed. So I will not enter Germany with the current visa. But I need to travel to Germany two weeks after the visa expiry.  Can I get a new visa or extend the current visa? Is there any policy for visa stamping if the previous visa hasn't been used?


Does gravity exist in higher dimensions?

I’m very curious to know whether gravity exists in higher dimensions. Because it follows the inverse square law it seems to me that it should be 3D only (just intuition). Is there any mathematical evidence of your answer or any experiment that can test it?


Levi-Civita connection between conformal metrics

I am doing this problem:  Let $g$ be a Riemannian metric on  manifold $M$ and $\tilde{g}=e^{2f}g$ another metric conformal to $g$, where $f$ is a smooth function on $M$. Give the relation between the Levi-Civita connection $\nabla$ of $g$ and the Levi-Civita connection $\tilde{\nabla}$ of $\tilde{g}$.  I am currently at this step, but don't know how to continue next:  $2\tilde{g}(\tilde{\nabla}_{X}Y,Z)-2e^{2f}g(\nabla_{X}Y,Z)=X(e^{2f}g(Y,Z))+Y(e^{2f}g(Z,X))-Z(e^{2f}g(X,Y))-e^{2f}Xg(Y,Z)-e^{2f}Yg(Z,X)+e^{2f}Zg(X,Y)$  Any help is appreciated!


express tan(x) as a power series using maclauran's theorem.

the theorem states that if f(x) can be expanded as a power series for a given range of values of x then:  $$f(x)=f(0)+xf'(0)+\frac{x^2}{2!}f''(0)+\frac{x^3}{3!}f'''(0)+\cdots$$  ($'$ means derivative) if $f(x)=\tan(x)$, what is the power series?


Change the size of the footnote counter IN the footnote

The footmisc package is quite useful for changing the layout/style of a footnote text itself. Eg:  \renewcommand\footnotelayout{\scriptsize}   However, how do you change the size of the footnote number/counter (not in the body of your document, but in the footnote itself). I don't see any reference to this in the footmisc package.  Thanks!


How many ways can the average of n dice be a?


Review queue for questions should show comments on question

I recently reviewed a suggested edit on  which simply added a tag to a question.  The comment was "added derby tag based on comment", which surely made sense to the editor, but to check whether the edit was appropriate I had to visit the question in a new window to see the comments.  Would it be reasonable to show the comments on questions and answers in the reviews for suggested edits?  A possible problem with this is that the comments justifying the edit may not make sense if the comments on which they were based are later deleted.


I don't know how I locked "view offset", but how do I unlock it?

When I attempted to navigate within the 3D viewport by using the CTRL-numpad options, it didn't seem to work, and I noticed a message in the communication part of the main header that gave the usual warning sign (an exclamation point within a red edged yellow triangle), followed by the text "View offset is locked". The warning appeared and closed so quickly I was not able to obtain a screenshot.  I don't know what I did to cause this, and cannot find any information in the manual or other Blender documentation about this warning message. How do I unlock the "viewport offset"?


Let $\alpha$ be algebraic over $F$. Suppose the degree of $\alpha$ over $F$ is odd. Show that $F(\alpha)=F(\alpha^2)$?

I am trying to solve the following exercise:  Let $\alpha$ be algebraic over $F$. Suppose the degree of $\alpha$ over $F$ is odd. Show that $F(\alpha)=F(\alpha^2)$  It's not clear to me how to solve this. I've been thinking and I guess that $F(\alpha^2)\subset F(\alpha)$ but I don't know about the other direction. Can you help me?


Set dropdown to default value using javascript

I have a dropdown on my html page, when it is first loaded, it is set to a default value. But when a user changes the value, I'm checking the selected value against another text field. If the condition does not satisfy, I want to show an alert to the user and reset the dropdown.   I'm able to show the alert with my condition, but how do I reset the dropdown after showing an alert to the user.


Windows 10 "Service Host: Local Service (No Network)" drains CPU constantly

I've had this problem for at least several months.  I noticed a lot of threads without a happy ending:         And I did try all the suggestions made in these threads including:   Updating the windows to the latest version Troubleshoot network, update, etc killing all other software, changing MSISUPPORTED of my SSD disk in regedit etc.   One thing I noticed is that the problem disappears in safemode.


How can I remove my user name from a friends Google login page?

I checked my Gmail on a friend work computer, whose company also has a work Gmail account. Now when either of us login to email, part of the other person's name appears. This is frustrating for me since my Google photos are linked to Gmail. Doubly frustrating for him because it's a work computer. Any advice would be greatly appreciated.


Will a DDR3 532 MHz CL7 work with DDR3 1333 MHz CL9?

I want to upgrade my laptop's RAM but I doubt wether the combination will work. Are there any risks of damage?  Here are the specifications of my laptop:   Processor         : Core i3 M380 @ 2.53 GHz Ram Installed     : 2 GB DDR3 532.1 MHz, CL7. Operating System  : Windows-7 Ultimate (64-bit)   The RAM I want to install: 4 GB DDR3 1333 MHz CL9.  If it works will I get 6 gigabytes of RAM?


When I run a .command by double click, can I pass it its directory?

I have a bash script that I want to run when I double click it, so I've renamed my script.sh file to script.command. The script now gets executed when I double click it, but its working directory is my user's home, so I have to ad a cd to my script's path before I can get things working. Since I want to commit this script to my git repo and share it with my team, I'm looking for a way to automate this "cd to the .command file's directory before doing anything else". Is there a way to achieve this? For now each person on the team has to edit the script and add their path at the top of the script.


There are five boxes consisting of several identical coins. The first box contains 4 coins, the second box contains 9 coins, the third box contains 7 coins, the fourth box contains 10 coins, and the fifth box contains 3 coins. Some coins are taken from the boxes such that at least a coin taken from each box. In how many ways in taking the coins, such that the numbers of the coins taken are 12?  My attempt was solving it using repetition combination of which, there are only seven coins remaining considering that at least a coin taken from each box. By using the repetition combination, i.e. taking 7 from 9 (five boxes and four borders), resulting in 36 ways. However, there is no 36 ways in the choices.


Is the closure of the unit ball of $C^1[0,1]$ in $C[0,1]$ compact?  For this let us take a sequence $x_n$ in $C^1[0,1]$ to show it has a convergent subseqence  How to proceed with this.I am not so sure whether  it is the way to ask a question here


Is it possible to pass string of ids in Where IN dynamic Soql the dynamic part should accept Set id's and Lis id's

I have a dynamic soql in where I pass a string of ids in the WHERE IN clause this thtrows me a error:      expecting a colon, found '{'   My where clause is as follows:   WHERE Id IN {x0x0o000000000xXXX}   I also tried  WHERE Id IN :{x0x0o000000000xXXX}   I also tried adding {x0x0o000000000xXXX} to a string and do  WHERE IN :String    this gives the error:     IN operator must be used with an iterable expression   So is it not possible to use a string in the SOQL itself and does it has to be :Set or :List?  I get the use of :Set my question is: is it in any way possible to use a string directly in de dynamic soql so use   testString = String.valueOf(Set<id>);  WHERE IN testString


Sorting a date key in an array of objects in Python


I have an app. When i run it for hours i notice it starts getting big. It gets 4x bigger later then t does in the first hour. Since its running on a server with limited ram space i cant have that. I tried doing memory sampling in .NET but all it told me was my json serialization allocates the most memory. Thats inside a loop so i know its gone every iteration.  How do i find what objects is holding my memory? Forcing the GC to collect does not help. So something appears to be holding memory.


I appreciate anyone who answer this question and I anyone who design appropriate graph.


Let A denote the set of those 6-digit positive integers in which each of the digits $1, 2, 3, 4, 5, 6$ appears exactly once. An integer in A, having standard decimal representation $d_1d_2 \cdots d_6$, is called nice if for each $k = 1, 2, 3, 4, 5$ the set {$d_1,.., d_k$} contains at least one digit strictly greater than $k$ (for example, 234561 is nice, whereas 321645 is not nice). From $A$, an integer $n$ is randomly picked. What is the probability that $n$ is nice?   My try:  Run the last digit from 1 through 6 and find the combinations by scanning the digits greater than the last digit across the first five positions in each of these scenarios.  It is pretty cumbersome and I am wondering if there could be anything simpler by means of symmetry or something like that as it does not give us any pattern. :  $234561 - 5!=120$  $345612 - 4*4! =96$  $456123 - 3*4!+3*3! = 90$  $561234 - 2*4!+4*3!+6*2! = 84$  $612345 - 1*4!+3*3!+8*2!+13*1! = 71$  $123456 - =0$  Total number of ways = $6! = 720$  Required probability = $$\frac{120+96+90+84+71}{720} = \frac{461}{720}$$  A simpler solution would be very much appreciated after verifying the answer.


I have programmed all night long and I can't find a mistake anymore :/ :/ If intro == 1 or 2 then do this and that.. and if intro != 1 or 2 then ask number again, till the number is 1 or 2... I can't find the mistake :/     do{         System.out.println("Enter number: ");         Scanner scanintro = new Scanner(System.in);         intro = scanintro.next();     }while (intro == ("1")|| intro == ("2"));


With the new Imgur upload how do I upload from a URL?

I want to take an image address from online and put the picture into my Stack Exchange answer.  I used to be able to paste the image URL and it would be uploaded to Imgur and inserted into my post.  Now I don't see how to do this any more.


I'm looking for a tale that features an outcast colony on the moon

The points I recall:   colony on the moon populated by people that naturally just cause technological malfunction colony is self-sufficient: they charge earth-bound corps a testing fee on new tech one of the items under test is an airlock made up of a mesh of nanobots: you can just walk through and the nanobots seal around you   I read it once, enjoyed, want to reread and can't for the life of me google up the title or author.  Thanks in advance.  ...Stu


So I have no clue what the name of this movie is, I saw it when I was a little kid and can't remember for the life of me the name.  But the tidbits I do remember are as follows: A movie is being made about a dragon and they have this huge impressive dragon animatronic thing they plan to use. This guy wants to help make the movie, this other guy who made the dragon animatronic is like, world famous or something (I think?). Anyway they find the guy who wants in on the movie is able to make the little baby dragons move realistically and they hire him in. So he goes to work for them and works late into the night at which he finds the giant animatronic comes to life and talks with him.  Can anyone name that movie for me? I would love to see it again.


"We're no longer accepting" message should not be hosted on meta

When users receive a question ban they  in the  tag.  I would like to put forward the hypothesis that this is the way most of the users who post blatantly off-topic questions on meta find meta in the first place.   If this is true then hosting that link anywhere other than on meta would go a long way towards cutting the volume of "I got banned so I asked it here instead" questions that meta sees.  Proposal: the link question banned users see should be hosted on the site the ban relates to itself, not on meta. The text of that message could link to meta still, it's a layer of additional indirection.  Rationale: The people who post these questions clearly don't read the contents of the message, it seems like the thought process runs approximately as "I'm banned, but what a stroke of luck - another Q&A site, I'll just ask there, someone is bound to solve this for me". This would remove the "another Q&A site" aspect and make reading the text the only option.  It's hard to say for certain that this is indeed the cause, questions of this nature get deleted quickly and it's not possible to do more than guess if a user is indeed question banned. (I would give example of these questions, but I can't see them once they're deleted on meta and I think it's fairly obvious what the sort of questions I'm referring to are)  I think this hypothesis could be tested (by a developer) with something like  on the number of closed+deleted off-topic questions after making the change.  I can't quite believe I'm the first one to suggest this, but searching for this mostly just turns up thousands of duplicates of the "Help I'm banned" questions.


Does deferring admissions to PhD affect future (post-PhD) career path?

I'm currently in my final year of undergraduate study, and will be applying to physics PhD programs (for condensed matter theory) soon. Without going into details, I am convinced that deferring my admission for a year, i.e. taking a "gap year", would be beneficial for me personally, and it is my understanding that most schools permit a one-year deferral. I would most likely work in the tech industry for this time.   I am not worried about my physics/math abilities atrophying; I plan on actively keeping up with my studies independently during this time.   Assuming I am permitted to defer for a year, are there any negative perceptions related to time off before graduate school that might affect my future academic career, after the PhD?  Will some people in the community look down on me for taking time away from academia, or is this considered a fine thing to do? Could this hinder me in the future when applying for postdocs (both the year away from academia and the fact that I am probably finishing my PhD a year later than I otherwise would)?  I am asking about the general perception of a gap year as it pertains to and affects a career path, not about how a gap year impacts a PhD application (which is addressed in ).


Is it true that $\int_{a}^b h^2=0\implies h=0$?

I am working on a few examples where my author said this is true if $h$ is continuous. Can someone explain why? Just because the integral is $0$ doesn't mean the integrand is zero as well.   $\int_{a}^b h^2=0\implies h=0$?


I put in a texture diffuse and normal texture image for my floor but it doesn't work. It has the texture correct in the preview but it doesn't show in the render?I would appreciate some help.


How to add face to parallel edges of two hemispheres?

I'm making a shallow hemisphere for a 3d printing project. I have to add some "depth" to the hemisphere for the printer to be happy so I made a copy of the current object and shrunk it down a bit. In order to close the shape up I need to add faces to hold these two objects together.  I selected the edges of both hemispheres but when I type "F" it fills each hemisphere independently to itself. I've bool > union these two hemispheres together thinking that would help but it hasn't.  How can I get these two circular shapes to close together making one shape rather than having them close independently making two overlapping shapes?  This is my first 3d project from blender so if there is a better way to be doing this please let me know. Cheers.


I am using Centos as my server OS and in my desktop I have a directory called "john", I need delete it via a command. How can I do this?


"An edit has been made to this post" hides migrated banner

I don't have idea if it has been already reported, if a post in a question is edited the banner      an edit has been made to this post; click to load   shows but if i click on it and the question have a      migrated from x    banner too this will be hidden too.  Before        After


Is this correct:  "It's parents who choose kid's future".  "Parents" is plural, but as for me "it's" seems fine here. I don't even know which other verb to use with plural noun here.  This case is completely different from, say, "it's raining" case. Because there it's pretty clear what "is" is refer to, some subject, weather etc. Here we have plural noun, and I wonder is it correct to use "is" with it.


I'v code  to override DefWndProc in winform      protected override void DefWndProc(ref Message m)     {         switch (m.Msg)         {             //Display image             case MESSAGE_CAPTURED_OK:                 MemoryStream ms = new MemoryStream();                 BitmapFormat.WriteBitmap(m_pImageBuffer, m_nWidth, m_nHeight);                 BitmapFormat.GetBitmap(m_pImageBuffer, m_nWidth, m_nHeight, ref ms);                 Bitmap bmp = new Bitmap(ms);                 this.pictureBox_FingerImg.Image = bmp;                 break;              default:                 base.DefWndProc(ref m);                 break;         }     }   'BitmapFormat' is my model class    However, I can't paste this code in WPF project  how to resolve it?


Simulating urban land use change using a Cellular Automata - Markov Model in ArcGIS

I am trying to simulate urban land use change using a Cellular Automata - Markov Model.   Is it possible to do this in ArcGIS (or any ArcGIS extension)?   I do not have access to IDRISI. I am fine with using any ArcGIS extension or other free software. My urban data has 5-7 land use classes that I need to simulate for. The output should be in map form.


Current mathematics theory used in cryptography/coding theory

What are the mainstream techniques borrowed from algebraic geometry (or some other branch of mathematics) which are currently used in cryptography/coding theory? I've only heard about a small subset of elliptic curves and hermitian curves. I've also heard about research of hyperelliptic curves but I don't know if some software has already implemented it.  Could you mention some other branches of mathematics being strongly used in cryptography/coding theory and its state? (mainstream/in research)


Prove that two qualtities are equal (possibly using binomial expansion)

How do you prove that $$\sum_{i=0}^{\frac{n}{2}} {n \choose 2i}p^{2i}(1-p)^{n-2i} = \frac{1+(1-2p)^n}{2}$$  I tried using binomial expansion but I can't because the upper limit is isn't n.   note: n cannot be odd


SQL Server 2016 memory optimised table: Precreated files constantly growing

I have a memory optimised table in SQL Server 2016, with file durability enabled. The table is only 100MB. SQL Server is constantly creating new files on disk, which start off at a few hundred MB, but then grow constantly until the drive runs out of space then they clear down and the process starts again. The files are growing at about 900MB an hour. Running the SQL below shows that all the space is in Precreated Data - so it's not even actually storing large amounts of data, just allocating space to use later.  SELECT state_desc, file_type_desc, COUNT(*) AS [count],    SUM(file_size_in_bytes) / 1024 / 1024 AS [on-disk size MB]    FROM sys.dm_db_xtp_checkpoint_files   GROUP BY state, state_desc, file_type, file_type_desc   ORDER BY state, file_type     File growth on the file group is set to unlimited, so I'm assuming I can set a value on this and stop it growing, but I can't find anything to say why it's allocating so much space in the first place. The data in the table does change very rapidly (a lot of inserts and deletes as the data is constantly processed, but it the data that isn't Precreated never gets over 4GB.  Is there a setting in SQL Server that controls this file precreation? Is it safe to set a limit on the autogrowth for the file group?


I recently upgraded to Ubuntu 20.04 from 19.10, everything is fine. but when I try some of the apps the text is shown in a boxed unicode code points:  The List of apps showing the behavior is:   File manager  Settings  GNOME Shell GNOME Tweaks Software manager Rhythmbox Calendar All the utilities applications Calculators   I have tried changing the font from the "Fonts" but it crashes every time.


What is the value of the following series

$\sum_{n\geq1}\frac{2^{n-1}}{1+a^{2n-1}}, a > 0$  I was considering the use of some power series, but to no end as the denominator of the fraction does no simply after derivation.


Let $n$ be a prime number. How can I show that the polynomial $f(x) = x^{n-1} + x^{n-2} + x^{n-3}+ \cdots + x+ 1$ is irreducible over any finite field?


I'm not finding Georeferencer on QGIS3. In version QGIS2 it was found under Raster > Georeferencer > Georeferencer (the only option available).  Forgot to say I'm on a Mac using the  version. This led to @sys49152 showing that Georeferencer is present on at least one other system.  I've, of course, looked at all the options under the Raster menu and nothing reads like Georeferencer not looks like the light hash icon shown in the plugins.  I don't know how to contact the great person creating the macOS installer.      This is close enough to being a duplicate, that I'll plan on marking it so. This post was macOS, but turns out the issue is probably on other platforms. There seems to be a bug the Plugin Manager for displaying and checking/unchecking.  It's a bit confusing that you can't "uninstall" Georeferencer which I think I took to mean that it was installed and operational. I think there is a semantic/logic issue here. Does install mean that you've downloaded the plugin in or that it's installed, that is, ready for use? That on top of the display bug.


I want to know where the Metro applications (Mail, People, Messages, ...) executable file path is.  Also, how can I run Mail application when my PC starts?


What changes occur if I do (or don't) save Cid?

At the start of the World of Ruin phase of the game, Celes can feed fish to Cid.  Based on the quality of the fish, Cid will either either live or die.  How does the rest of the game change based on whether Cid lives or dies?


What happens to a tailed beast if it's Jinkiurichi is killed?

What happens to a tailed beast if it's Jinkiurichi is killed while he still has the tailed beast inside of him/her?


Try catch block outside the main() scope

I am able to compile and run this. How it is possible to write a try-catch block outside the main scope, seems to defy my logic? Any term to describe this behavior?  int main() try {  }  catch(...){}


I posted a question which was closed as off-topic and it seems like it could fit on another site in the network. How can I go about moving it there?   What is migration? When can a question be migrated, and who can migrate it? When should I consider migration, and when is it inappropriate? What causes a migration to be blocked and what happens after? What causes a migration to be rejected and what happens after? Anything else I should know about migration?


Modal upon modal best practices - Web App

The product I am working on at the moment is a standalone product but we are creating a web app to replace it.  It currently opens modal windows on top of modal windows for the same function  i.e Create new report (modal) > add person to report (modal)  Is there a known best practice for making this nicer to use without using a wizard?


Java KeyEvent - why "Unknown" != "Unknown"?

Why does  KeyEvent.getKeyText(0).substring(0, 7) == "Unknown"   return false when  System.out.print(KeyEvent.getKeyText(0).substring(0, 7));   prints exactly "Unknown"?


Let $B_a$ be the open ball{$x: |x|^2<a$} in $\mathbb{R}^k, |x|^2 = \sum x_i^2$.   What is the inverse of the function $x \mapsto \frac{ax}{\sqrt{a^2 - |x|^2}}$?   Here I want some justification to equate $|x|^2$ with $x^2$, I don't know to justify; but otherwise I don't know how to solve it.


Regex for special characters inside brackets

I've the below string, Now I want to match the string if it contains Continue? [Y/N]. I tried couple of ways but it didn't worked as expected. Any suggestions to match the complete string if contains Continue? [Y/N]  Input String:   Warning: do you want to proceed, some-more,text. Continue? [Y/N]


I'm using a script to store the content of a txt file in a variable. Now I have a lot of these files, and I want to go over every single one of them in a for loop.  Pseudo code: for (i = 1, i < 100, i += 1) ( set var=file+i.txt [do stuff with file] )   How can I make something like this?


I've found numerous installation instructions for Node.js but they all seem so complicated -- I'm not a super sys admin but I can get around. I have yum on the system, but I didn't find any node.js packages, and I'm not sure how to compile code on the server or where to put it.


Is it possible to install WordPress within WordPress installation?

I have a website that is powered by WordPress, e.g. example.com. I would like to install a separate WordPress installation with a separate database, themes, etc in a subdirectory on my website though, for example on example.com/blog.   Will this cause problems with displaying both installations properly? For example if I try to go to example.com/blog or example.com/blog/post will this cause installation A to throw up a 401 error since it didn't find a page within the original example.com WP installation?


Date System Used Before ABY in Star Wars

Much like we use B.C.E and A.D, in the Star Wars universe they use B.B.Y and A.B.Y, standing for Before Battle of Yavin and After Battle of Yavin respectively.  But what date system had the galaxy used before the events of Episode 4?


I am new to php and stuff like that. But i decided to create my very simple insert page with PDO , so is PDO secure enough against SQL Injection attacks?  Here is my code:   <?php //Database settings  $host = 'localhost'; $dbname= 'akar'; $user = 'akar'; $pass = 'raparen';  //Setting up the PDO $dsn = "mysql:host=$host;dbname=$dbname"; $pdo = new PDO($dsn,$user,$pass);   //Check if user entered something, otherwise set the username variable string to nothing. $username = isset($_POST['username']) ? $_POST['username'] : ''; $password = isset($_POST['password']) ? $_POST['password'] : '';  //Inserting the values to the database using named placeholders  $query = "INSERT INTO users (username,password)  VALUES(:username,:password)"; $statement = $pdo->prepare($query); $statement->execute(array(     ':username'=> $username,     ':password'=> $password ));  ?>   My form:       <input type='text' placeholder='Enter Username here!' name='username' /> <input type='password' placeholder='Enter Password here!' name='password' /> <input type='submit' value='Submit' />  </form>


I want to chat with a specific user to ask them a question, how can I do that?

I want to ask a question to a specific user on Islam.SE, but I don't have the reputation to create or participate in chat.  How can I ask my question to this user?


So I have this code:   @Override public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.favourites);     assert getSupportActionBar() != null;     getSupportActionBar().setDisplayHomeAsUpEnabled(true);      SharedPreferences prefs = getSharedPreferences("myFavs", 0);     Map<String, String> m = (Map<String, String>) prefs.getAll();     List<String> list = new ArrayList<>(m.values());      ListView listView = (ListView) findViewById(R.id.favsList);     ArrayAdapter<String> adapter = new ArrayAdapter<>(this,R.layout.listlayout, android.R.id.text1, list );     listView.setAdapter(adapter);   And it outputs this error in logcat:  10-08 08:48:44.114  19390-19390/com.example.me1jmo.insult_generator E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.me1jmo.insult_generator, PID: 19390 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference         at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:399)         at android.widget.ArrayAdapter.getView(ArrayAdapter.java:369)         at android.widget.AbsListView.obtainView(AbsListView.java:2346)         at android.widget.ListView.measureHeightOfChildren(ListView.java:1280)         at android.widget.ListView.onMeasure(ListView.java:1188)         at android.view.View.measure(View.java:18788)         ...   I have read the articles on why this happens but I can't figure out what bit of my code I need to change to get it working.


Question about the ways a child class can call superclass's methos

Consider the inheritance in the code below: class Person:     def __init__(self, fname, lname):         self.firstname = fname         self.lastname = lname      def printname(self):         print(self.firstname, self.lastname)   class Student(Person):     def m1(self):         super().printname()      def m2(self):         Person.printname(self)  s1 = Student("John", "Doe") s1.m1() s1.m2()   Why in Python there are two ways for a child class call a superclass's method like super().printname() and Person.printname(self) in above example ? What are the differences between the two ways? Is there another way of calling  a superclass's method ?


Help with Trailhead - Lightning Component Basics - Attributes & Expressions

Has anyone had any success completing the s module?   I attempted the challenge using the Trailhead playground. And think what I did is correct. Yet I get the following error...   "Challenge Not yet complete... here's what's wrong:  The Packed field is either not using the lightning input component, the checked value of the item's Packed__c attribute or the correct type of input"  Following is the component I have written:  Component Bundle Name : "campingListItem"  <aura:component >     <aura:attribute name="item" type="Camping_Item__c" required="True"/>   <ui:outputText value="{!v.item.Name}"/>   <lightning:formattedNumber value="{!v.item.Price__c}" style="currency"/>   <lightning:formattedNumber value="{!v.item.Quantity__c}" style="decimal"/>   <lightning:input type="checkbox" label="Packed?" name="packed" checked="{!v.item.Packed__c}"/>       </aura:component>   Object schema is :   Name - Text (80),  Packed__c - Checkbox,  Price__c - Currency (16,2), Quantity__c - Number (18,0).  What could I be doing wrong. Any advice?


What is the benefit of using get and set properties in this example?

What is the benefit of using get and set properties in the following example?:  class Program {     public class MyClass     {         private int age;          public int persons_age         {             get             {                 return age;             }              set             {                 age = value;             }         }      }      static void Main(string[] args)     {         MyClass homer = new MyClass();         homer.persons_age = 45; //uses the set property         homer.persons_age = 56; //overwrites the value set by the line above to 56         int homersage=homer.persons_age; //uses the get property         Console.WriteLine(homersage);      } }   what is the difference between doing that and the following?:  public class MyClass     {         public int age;     }   static void Main(string[] args)      {         MyClass homer = new MyClass();         homer.age = 45;         homer.age = 56; //overwrites the value set by the line above to 56         int homersage=homer.age;         Console.WriteLine(homersage);      }   What is the benefit of using the get and set property when there is no difference at all in what the above two programs do? Unlike the scenario where the client has limited ability to assign vales to the field via the set method through some logic checking, in this situation I don't see any functional difference between the two programs show here.  Also, some programming books use the phrase "...breaks the client code" if such properties are not used for class fields.  Can someone explain this?   Thanks.


How to change real screen timeout settings for the Lock Screen?

I have my PC connected to a TV, because it's significantly cheaper than the same screen with "computer display" label.  To make us regret for the money saved, manufacturers of both types of devices ensured, that TVs should not turn off when no input signal. They use to display very bright, ugly and annoying screen "no signal" and eventually, they would turn off after minimum of 15 or 30 minutes.  However, Windows 10 lock screen turns the screen off like in a minute. Then it requires one click to "wake up", another click to activate pin or password input. It looks bad, it's annoying. BTW, what's the point in choosing lock screen background picture if it's hardly shown?  So I'm looking for the way to change power management settings for the lock screen. It's different form user settings.  It is NOT in Lock Screen Settings (where I would expect it). There is even an option "Screen timeout settings", but it is set to 1 hour. The screen is turned off after like 1 minute, not 1 hour, so it doesn't work. 1 hour is my user setting, it's works when I'm signed in to my desktop.


If gcd (a,b)=1 and gcd (c,d)=1 and a/b=c/d, prove a=c and b=d

I proceeded this way:  gcd(a,b) = 1 leads to ax + by = 1  gcd(b,c) = 1 leads to cl + dm = 1  a/b = c/d = k and ax+by = cl+dm   Then I trying to operate the equation so that I end up finding k=1 but Im stuck at:   lets a = ck and b = dk  ckx + dky = cl + dm  k(cx+dy) = cl + dm   k = 1/(cx+dy)  and nothing tells me that cx+dy=1 since we have to prove that a=c and b=d  Help please?


Err:6 https://repo.skype.com/deb stable InRelease             The following signatures were invalid: EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository <se-um@microsoft.com> Reading package lists... Done W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://repo.skype.com/deb stable InRelease: The following signatures were invalid: EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository <se-um@microsoft.com> W: Failed to fetch https://repo.skype.com/deb/dists/stable/InRelease  The following signatures were invalid: EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository <se-um@microsoft.com> W: Some index files failed to download. They have been ignored, or old ones used instead.  This is coming when I am going to update my Ubuntu via terminal. Could you please suggest to me how can I update my Ubuntu? Thanks in advance.


WesternDigital My Passport Ultra creates strange folders

I have bought WD MY PASSPORT ULTRA one year ago and didn't have any problems till now. Strangely named folders create automatic like:   21f6f6c95cd7485f8f1b fde4dbe0ee62bce74f96a9a6dde8   What to do ? I have important information for me on this drive.


Why do laptop screens flicker during video mode changes?

Changing the display mode (resolution and/or refresh rate) causes the screen to flicker or go dark for a few seconds before the image stabilizes. At least this happens on all laptops and desktops I've used. Why ?  As , when using a complex operating system, part of the delay is due to the display software. However I'm not interested in the "software" delay due to heavy user-interfaces and window management, but only in the "hardware" delay which causes flickering, backlight blinks, etc.  This flickering and delay happens between the firmware greet (bios/efi) and the first installed software (OS splash or bootloader), and the same happens when changing resolution from within all the windows and linux versions I've tried, so it obviously has nothing to do with higher level software such as graphical shells or windows managers.  I see multiple (hypothetical!) causes:   Physical delay ?, like for old CRT display there was a low noise probably indicating the power electronics driving the electron beam was reset. Maybe on LCD the backlight power is reset, which causes flickering and delay, but why does it have to be reset? Very slow protocol ? Brian suggested that the resolution change protocol between the GPU and the display panel is slow. Experience shows that the flickering is not as long on newer laptop, which points in this direction. What I don't get is this : listing available resolutions and sending the desired one should take a few (kilo) bytes and video signals transit @Gbps speeds and a few ms latencies, so how come it takes around a second to negotiate a resolution change ? Display embedded electronics reconfiguration : kreemoweet states on  question that there is no protocol involved but each frame caries its resolution. When a frame has a different resolution than the last, the on-board electronics driving the display needs to be reconfigured: registers and buffers are reallocated, etc. The details are blurry but the electronics can efficiently process the video frames once configured, but takes a (relatively) long time to get configured. Maybe some other reason ?


I often get confused when trying to use who vs that.  Some examples that often confuse me:  That     The person that went to the store.      The people that went shopping.      The persons that went shopping.      The group that went shopping.   Who     The person who went to the store.      The people who go shopping.   Please explain when to use either for plural subjects and singular subjects.  Animate and inanimate objects as well.


Dynamic select list in the form (dependent dropdown)

I'm using Drupal seven. I want to make the options in a select list be dependent on the value chosen in another select list in a form.  I'm sure this has been asked many times before, but I am having difficulty finding a clear answer for how to do this.  The form is for users to enter a work history.  They need to select a squadron which is a node reference to the squadron field type, and this is in a drop-down list.  However, the squadron, is dependent upon a city drop-down list.  Users first need to select a city which will then filter the options for the squadron.  In the squadron content type, I created a taxonomy for city which gets tagged to the squadron.  I would be very grateful for any pointers as to the best way (simplest?) to go about this, or for any useful resources online which would help.


Why do English people pronounce 'sixth' as 'sicth'?

It's common practice in Ireland (and the US as far as I know) to pronounce the x in the middle of sixth: six-th [sɪksθ]. However, I've noticed from visits to England as well as watching British television, that a lot of English people pronounce it as 'sicth' [sɪkθ]. Why is this, and is it an accepted usage?


I have a server that returns a String of this format: {"success":true,  "visible":false,  "data":      {"ref":"asfdasfsadfaeweatsagsdfsad",       "userRef":"asdfsadfsa","accountType":"REAL",balance":43}, "code":"2200", "msg":null, "msgRef":null, "successAndNotNull":true, "failedOrNull":false, "failed":false, "failedAndNull":false}`  Then I extract the data by doing this: val jsonObj : Any! = JSONObject(serverResponse.toString()).get("data").toString()  and I end up with this String: "{"ref":"safdasfdwaer",  "userRef":"fdgsgdsgdsfg",  "accountType":"REAL",  "balance":43}"  Is there an efficient way to extract the the values into a HashMap with key what is on the left of ":" and value what is on the right of ":"? I have already seen the answer here () but I am not allowed to to use regex


I'm studying engineering and I'm very interested in knowing more about topology. I've studied Calculus, so I'm not new to the subject. I was looking for a book that's not too difficult, and gives an overview of topology. That way I can know if I'd like to read more about it. What should I read? Edit: do you think that I should study abstract algebra before topology?


Can the dungeon master have a player character?

I’m starting a campaign with some friends with me as the DM even though I’d rather be a player, I am the only person in my group who has had experience being a DM. I asked my friends if a DM is allowed to have a PC and not an NPC but they did not know either. Can I have a PC?


The Fibonacci numbers are recursively defined by $f_1 = f_2 = 1$, and $f_n = f_{n-1} + f_{n-2}$

This is the question: The Fibonacci numbers are recursively dened by $f_1 = f_2 = 1$, and $f_n = f_{n-1} + f_{n-2}$ for $n > 1$. Prove that every fourth Fibonacci number is a multiple of $3$.  I've been stuck on this question for a while. If someone could help me out or at least help me start it, that would be great


If $f\colon\mathbb R\to\mathbb R$ is continuous and satisfies $f(x+y) = f(x) + f(y)$ and $f(1)=1$, then $f(x)=x$ for all $x$.

Let      $f: \mathbb{R} \rightarrow \mathbb{R}$ be a continuous function such that: $$f(x+y) = f(x) + f(y)$$ $$f(1) = 1$$ Show that $$f(x) = x$$ I have been having trouble approaching this problem. I have shown, through a system of equations, that $f(x+y) = x + y$, but that's about as far as I can get. Appreciate any help anyone has to offer!


Why does a stationary object start moving if there is no force acting on it in general relativity?

I understand that gravity is not a force, but the function of curved space time.  But what gets an object in motion if no force acts on it?  For example, if I roll a ball, its path will curve towards a massive object due to the curvature of space time.  But, if a ball is suspended by a string, and I cut the string, why does it drop if there is no force pushing or pulling it?


Proving Two Limits Are Equal to Each Other

Let $P_{ij}$, where $P_{ij}$ is a real number and $i, j$ natural number, allow the three statements to hold:   $P_{ij}\ge 0$ for all $i, j$ $\lim_{i\to\infty}P_{ij}=0$ for all $j$ $\sum_{j=1}^i P_{ij}$ =1 for all $i$   Let $(x_i)$ be a convergent sequence and let a sequence $(y_i)$ be defined by  $$y_i=\sum_{j=1}^i P_{ij}x_j$$  Prove $(y_i)$ is a convergent sequence, and prove $\lim y_i=\lim x_i$  Ok so here's what I have:  Fix arbitrary $\epsilon>0$, there exists $N$ such that $|x_i-x|<\epsilon $ for all $i>N$, so $\lim x_n = x$, which exists since ($x_n$) is a convergent sequence.  We may assume that $|x_i-x|<M$ holds always, for a constant M.  Then  $y_i=\sum_{j=1}^i P_{ij}x_j $, so by triangle inequality and since $\sum_{j=1}^i P_{ij} =1$ for all $i$, the following occurs:  \begin{align*} |y_i-x|\leq {}&\sum_{j=1}^i P_{ij}|x_j- x|\\ ={}&\sum_{j\leq N} P_{ij}|x_j- x| +\sum_{j> N} P_{ij}|x_j- x|\\ <{}&\sum_{j\leq N} P_{ij}M +\sum_{j> N} P_{ij}\epsilon\\ \leq{}&\sum_{j\leq N} P_{ij}M +\epsilon \end{align*}  Now I don't know what to do with the sum that remains, if I factor out the $M$ and make the sum that remains equal to $1$, then I don't really get anywhere.  Thanks in advance.


What is the difference between "Look who has decided to show up" and "Look who decided to show up"?

I always get confused between deciding whether to use present perfect or past simple with expressions like these. So how can I use them correctly?


How to discover workstation or server is installed

Is there a way to discover if an installed OS is workstation or server? Is it just a matter of the packages that are installed or is there some difference that can be detected?


Which is grammatically correct: He and I was or he and i were?

which is correct between following two sentences: 1. He and I was going to temple. or 2. He and I were going to temple.


We have all heard the old problem about forming a triangle from breaking a stick into three pieces, with the breaks randomly distributed. Some variations make the second break contingent on the first in some way. I present a new variation (not original to me).   Problem: Take a stick and break it at a location selected with uniform density along its length. Throw away the left-hand piece and break the right-hand one at a location selected with uniform density along its length. Continue forever. What is the probability that one of the discarded left-hand pieces is more than half as long as the original stick?  I do not have a particularly elegant to solution to this one, and was wondering if one exists. Of course, any answers that solve the problem are welcome.


Evaluating $\int_1^\infty \frac{1}{x(x^2+1)}\ dx$

$$I=\int_1^\infty \frac{1}{x(x^2+1)}\ dx$$    I tried to use partial fractions, but am unsure why I cann't evaluate it using partial fractions. Would appreciate any explanation about which step is incorrect.    $$\frac{1}{x(x^2+1)} = \frac{1}{2} \left(\frac{1}{x}-\frac{1}{x+i} -\frac{1}{x-i}\right)$$ So   $$I = \frac{1}{2}\int_1^\infty\frac{1}{x}-\frac{1}{x+i} -\frac{1}{x-i} \ dx \\ = \frac{1}{2}\left[\log |x| - \log(|x+i|) - \log(|x-i|)\right]_1^\infty   $$ which evaluates to be $\infty$.


I am trying to build model of apollo/apolloauto which throws this error.  I have already followed   and also sudo apt-get install oracle-java8-installer which gives   $ sudo apt-get install oracle-java8-installer Reading package lists... Done Building dependency tree        Reading state information... Done oracle-java8-installer is already the newest version (8u131-1~webupd8~2). 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   oracle-java8-installer is already installed then also it throws error 'oracle-java8-installer' has no installation candidate  Package oracle-java8-installer 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 'oracle-java8-installer' has no installation candidate The command '/bin/sh -c bash /tmp/installers/install_bazel.sh' returned a non-zero code: 100


When will Trusty be available in old-releases?

I have a bunch of legacy servers still running on 14.04 that are in the process of being migrated. Do we know when will the updates be available in old-releases so I can plan to update the sources beforehand ?


I'm trying to correctly use a forward declaration for enums. Therefore I searched the Internet, but I can't find something that works. I'm using this in a header: // Forward declaration enum myEnumProcessState;  I'm then using this enum in a struct: struct myStruct {     [...]     myEnumProcessState osState;     [...] };  And in another header: enum myEnumProcessState {     eNotRunning,     eRunning };  I found out that the type should be put in the enum forward declaration to be accepted. However, I don't know which "type" I should put for a Process State. These don't work: enum myEnumProcessState : unsigned int; enum myEnumProcessState : String;  I wanted to skip the forward declaration, but my struct is crying since it can't find it any more... So I'm a bit confused. Is there a solution?


Went through, Been through and Gone through usage

What are the differences between went through, been through and gone through. For instance:  I have BEEN THROUGH a lot this year.  I WENT THROUGH a lot this year.  I have GONE THROUGH a lot this year.


Hi just started in Ubuntu and can't install any program from Ubuntu Software I read some solutions and need to install gdebi , I download the package installer.deb but still can't install gdebi , please help me how to install gdebi   Note : i dont have internet access , need to install gdebi before access to the internet


Ws on transcript affecting admission to engineering masters?

I have a 3.67 GPA at Rutgers in Materials Engineering and I plan on going to UConn for a masters in Mechanical Engineering since my job after graduation is more aerospace and mechanical engineering ( I am working for Pratt & Whitney) and I am more interested in the crossovers between MechE and MSE. However I have some W's on my transcript. One was a Matlab course my freshmen year I took that I hated and dropped a week after the withdrawal deadline (wasn't needed for my major). Another was during my junior year when I did a full time internship and this was an elective in industrial engineering for systems and reliability engineering. The course was in the evening but at a horrible time after work and I disliked it by the middle of the semester and I didn't have an interest in the material anyway. I also withdrew from 2 major classes because of courseload problems one semester my senior year but I took them the next semester and got an A in both. I dropped a graduate level MSE class in thermo recently because the course subject matter was dry (I don't like phase diagrams and chemical thermo too much) so I dropped it; I took the class originally to see if I would like MSE at the graduate level despite my career path moving towards mechanical engineering just to get a feel for things. I anticipate doing well on the GRE and I can have many letters of recommendation. Will these W's hurt my chances of being accepted into the UConn engineering masters program?


This question arose while I was answering this question, (). First the original question:  $ABCD$ is a quadrilateral. A line through $D$ parallel to $AC$ meets $BC$ produced at $P$ we need to show $$Area(\Delta APD)=Area(ABCD)$$    Its easy to see that the OP must have meant to prove, $Area(\Delta ABP)=Area(ABCD)$, the proof of which is given in my answer. However, it set me thinking when actually $Area(\Delta ADP)=Area(ABCD)$ is true? I have not been able to derive any good conclusion (I mean, in terms of the elements (diagonals, angles or sides) of $ABCD$). Can anyone help?


How to remove an element from an array in C#

so I here is my code: I have 2 forms, - abutton in form1 takes you to form2 . -form2 has Datagridview in it - you enter the informations(name, age) in form 1 and then you load them in a datagridview in form2  -when I chose a row to delete fom datagrid view I want that row to be deleted too from the array.(how can I do it)  thankyou in advance  class Class1 {    public struct client     {         public string nom;         public string prenom;         public int age;     }     public static client[] TC = new client[100];    public static int i = 0; }  public partial class Form1 : Form {     public Form1()     {         InitializeComponent();     }      private void button3_Click(object sender, EventArgs e)     {         this.Close();     }      private void button2_Click(object sender, EventArgs e)     {         Form2 f2 = new Form2();         f2.Show();     }      private void btn_ajouter_Click(object sender, EventArgs e)     {          Class1.TC[Class1.i].nom = textBox_nom.Text;         Class1.TC[Class1.i].prenom = textBox_prenom.Text;         Class1.TC[Class1.i].age = int.Parse(textBox_age.Text);          textBox_age.Clear();         textBox_nom.Clear();         textBox_prenom.Clear();          Class1.i = Class1.i + 1;     } }   public partial class Form2 : Form {     public Form2()     {         InitializeComponent();     }      private void btn_afficher_Click(object sender, EventArgs e)     {         dataGridView1.Rows.Clear();         for (int j = 0; j <= Class1.i-1; j++)         {             dataGridView1.Rows.Add(Class1.TC[j].nom,Class1.TC[j].prenom,Class1.TC[j].age);         }     }      private void btn_supprimer_Click(object sender, EventArgs e)     {         dataGridView1.Rows.Remove(dataGridView1.CurrentRow);     } }


Which fundamental force acts while pushing a book on the table?

I know that this is a total novice question. When I push a book from point A to point B, a force is applied by me. The book has mass and some acceleration was also achieved in this example. I recently read about the fundamental forces of nature. They included Gravitation, Electromagnetism, Strong interaction, and weak interaction.  I have no deep knowledge regarding any of the 4 forces. A simple explanation would be appreciated. My question is :     In the act of pushing a book, which of the 4 fundamental forces of nature come in the picture? Which one force could I relate to this event?


excel 2016 autoupdates from one workbook to other (emailed) workbooks

I have this same question. I want to send a workbook to my collogues (each worksheet will be locked/protected) and I will keep the master (unprotected). When I make a change(s) how can all the other workbooks be automatically updated to show that change(s)? A pivot table will not work for me. I need all books to be updated as I make changes (prefer w/o sending new books every time a change is made)?


When using \usepackage[T1]{fontenc}, the text output produced by tikz-timing is rastered; the following MWE  \documentclass{article} \usepackage{tikz-timing} \usepackage[T1]{fontenc}                  \begin{document}  \begin{tikztimingtable} & 2D{a} \\ \end{tikztimingtable}  \end{document}   results in this output:    This is independent of the document class, and only happens if I specify \usepackage[T1]{fontenc}. Even with just \usepackage{fontenc}, the output is ok. Unfortunately, I have no idea on how to even approach debugging this...