I was trying to understand an aspect of rotational dynamics and thought of a problem to help me learn. I'm sure this problem has been considered by countless people in the past, but I'm having some trouble arriving at a solution.     Consider a disk of uniform mass distribution $\rho$ (measured in $kg / m^2$) and radius $R$ centered at the origin of an xy coordinate system at time $t=0$.   Apply a constant force $F$ in the positive $y$ direction to the disk at distance $r$ to the right of the center of the disk, where $0 \le r \le R$.   What will be the rotational speed and translational velocity of the disk at time $t_1 \gt 0?$   (Note that after some time has elapsed, the disk may have rotated from its original position.  If this happens, continue to apply the force at the same distance to the right of the center of the disk.  Also, assume that there is no friction anywhere in the system.)   My work so far:  I've figured out that if the force is applied to the center of the disk so that $r = 0$, then it's rotational speed will remain $0$ $radians/s$, and it's translational velocity can be obtained from Newton's second law $(F = ma)$.  In other words,  $$ F = ma, $$ $$ F = \rho \pi R^2 \frac{dv}{dt}, $$ $$ \int_0^{t_1} F dt = \int_0^{t_1} \rho \pi R^2 \frac{dv}{dt} dt, $$ $$ F t_1 = \rho \pi R^2 \int_0^{t_1} \frac{dv}{dt} dt, $$ $$ F t_1 = \rho \pi R^2 v_1, $$ $$ v_1 = \frac{F t_1}{\rho \pi R^2}. $$  It seems to me that the same should hold true in the case where $r \gt 0,$ although intuitively, it also seems like some of the impulse from the force should cause the disk to rotate.  If the above calculation is used to obtain the translational velocity of the disk, then the same impulse applied off-center for the disk will result in the disk reaching the same amount of translational kinetic energy as in the above case along with some additional rotational kinetic energy from the applied torque, which can't be right (this is like getting something for nothing). So I'm pretty stuck at this point.   I tried considering simpler systems, like a ring with uniform mass distribution $\lambda$ $(kg/m)$, but I think I would run into the same problems.  Another related system that can be considered is when an equal and opposite force is also applied left of the center of the disk at the same distance from the center of the disk as the first force.  In this case, all of the impulse from the two forces combined would go into the rotational kinetic energy of the disk, leaving its translational speed at $0$ $m/s$.  We can set the total impulse imparted to the disk equal to its change in rotational momentum.  So,  $$ \int_0^{t_1}2F dt = \int_0^{t_1} \int_0^R \int_0^{2\pi} \rho\;d\theta\;r^2\;dr\;\frac{d\omega}{dt}\;dt $$ $$ 2Ft_1 = \frac{2\pi\rho R^3\omega_1}{3} $$ $$ \omega_1 = \frac{3Ft_1}{\pi\rho R^3}. $$  However, I'm not sure if this helps me find how much impulse is used towards the translational versus rotational momentum of the disk in the general case of the original problem.  Is there a basic law of mechanics that I'm missing and need to apply in order to understand this system?  I feel like I'm missing something conceptually...


How can I see the fingerprint of my adbkey?

You should know that Android 4.2.2 (or just before) introduced RSA key checking for adb access. – The device asks now if you want to allow access.  To avoid asking every time, the computer presents an RSA key, which can be permanently accepted.  The dialog on the phone shows the RSA key fingerprint. – On Linux, the public/secret key pair is here: ~/.android/adbkey(.pub).  How can I show the fingerprint of that key file? (I’m looking for a command line to do that on the Linux system.)


How can I burn a 706MB image onto a 703MB CD?

The Ubuntu image ubuntu-12.04.3-alternate-i386.iso is 706MB large.  I thought that little 3MB extra at the end is just the MB/MiB error - so the image should fit on the disk. But I was wrong.   My disk has 703MB. Is there a trick to burn the image regardless?


Generating a high-dimensional dataset where nearest neighbor becomes meaningless

In the paper "" we read that,      We show that under certain broad conditions (in terms of data and query distributions, or workload), as dimensionality increases, the distance to the nearest neighbor approaches the distance to the farthest neighbor. In other words, the contrast in distances to different data points becomes nonexistent. The conditions we have identied in which this happens are much broader than the independent and identically distributed (IID) dimensions assumption that other work assumes.   My question is, how I should generate a dataset that produces this effect?   I have created three points each with 1000 dimensions with random numbers ranging from 0-255 for each dimension but points create different distances and do not reproduce what is mentioned above. It seems changing dimensions (e.g. 10 or 100 or 1000 dimensions) and ranges (e.g. [0,1]) do not change anything. I still get different distances which should not be any problem for e.g. clustering algorithms!   Edit: I have tried more samples, based on my experiments distances between points do not converge to any number, on the contrary the max and min distances between points get more apparent. This is also in contrary to what is written in the first post of  and also many other places which claim the same thing like . I would still appreciate it if someone can show me with a piece of code or real dataset that such effect exist in practical scenarios.


How can I remove the left panel at Stack Exchange sites?

This left panel narrows the width. I don't use it, and is a great waste of space:    How can I remove it, and left the same (and more practical) structure that StackExchange sites had a few moths ago?


Apply the intermediate value theorem to the intersection of two functions

Prove the following using the intermediate value theorem:  $f$, $g$ are continuous on $[a,b]$, $f(a)< g(a)$ but $f(b) >g(b)$  Prove: $f(c)=g(c)$ for some $c \in (a,b)$   I am not sure if i am correct:   $g$ is continuous: using IVT $g(c)=j$,   $g(a)< j <g(b)$  , c belongs to (a,b)  $f$ is continuous: using IVT $f(c)=k$,   $f(a)< k < f(b)$ , therefore by the given inequality: $f(a)< j <f(b)$ Hence, by IVT $j= f(c)= g(c)$


Does Fiumicino Airport allow for airside transit on separate reservations?

I have a connection in Italy coming from outside Schengen area flying to outside Schengen area, and I'm wondering if I need to go through immigration and customs in Italy or not. The flights are separate reservations but it's the same airline (Alitalia) and same airport (FCO) and the waiting time between the flights is about 3.5 hours.


Cardinality of cartesian product of an infinite set with N

Here the problem 1.4.26 from Sohrab, Basic Real Analysis  Duplicate  This are not duplicate of this question:    the answer gives no proof  despite the title is not really connected  only finite set   Problem  Show that, if $A$ is an infinite set, then $|A\times\mathbb{N}|=|A|$. Hint: Let $\mathcal{F}$ denote the set of all bijective maps $f:S\times\mathbb{N}\to S$, where $S\subset A$. Since $|\mathbb{N}\times\mathbb{N}|=|\mathbb{N}|$, we have $\mathcal{F}\neq \varnothing$ (Why?) Show that Zorn's Lemma can be applied in $\mathcal{F}$ to produce a maximal bijection $h:B\times\mathbb{N}\to B$, with $B\subset A$, and that we must have $B=A$, by examining the cases where $S\setminus B$ is finite or infinite.  Proof  Let $\mathcal{F}$ denote the set of all bijective maps $f:S\times\mathbb{N}\to S$, where $S\subset A$. Since $|\mathbb{N}\times\mathbb{N}|=|\mathbb{N}|$ (see exercise 1.4.10(i)), we have $\mathcal{F}\neq \varnothing$ (From Exercise 1.4.22(d) we know that for a infinite set $A$, we have $|A|\geq\aleph_0$, and $|\mathbb{N}|=\aleph_0$, thus there is an injection from $g:\mathbb{N}\to A$, and, by defining $S:=g(\mathbb{N})\subset A$, we get a bijective map (composition of two bijective maps) $S\times\mathbb{N}\to\mathbb{N}\times\mathbb{N}\to\mathbb{N}\in\mathcal{F}$).  If we consider the inclusion as partial order, then every chain $S_i\subset A$, $i\in I$, has $A$ as upper bound and applying Zorn's Lemma, we get the existence of a maximal $\bar{S}$ and hence a bijection $h:\bar{S}\times\mathbb{N}\to\bar{S}$, with $\bar{S}\subset A$.  Now we prove that $\bar{S}=A$. $R:=A\setminus \bar{S}$. $\bar{S}$ is infinite, since the example of element of $\mathcal{F}$, that we gave above is bijective to $\mathbb{N}$. We have to do this. The second is trying to follow the hint and is incomplete:   Consider that $A\neq\bar{S}$, then there is $r\in R:=A\setminus\bar{S}$. We chose an element $s\in\bar{S}$ and define the bijection $h':\bar{S}\cup\{r\}\times\mathbb{N}\to \bar{S}\cup\{r\}$ as follow  $h'(a,n)=\begin{cases}h(s,2n-1)&\text{for }a=s\\ r&\text{for }a=r,n=1\\ h(s,2n-2)&\text{for }a=r,n\neq 1\\ h(a,n)&\text{otherwise}\end{cases} $  Since $\bar{S}\subsetneq \bar{S}\cup\{r\}$ we get a contradiction to the maximality of $\bar{S}$. Now either $R$ is finite or infinite. 1) $R$ finite, let say $R=\{r_1,\cdots,r_n\}$. Then chose $n$ elements $s_1,\cdots,s_n\in\bar{S}$ and we define the bijection $h':A\times\mathbb{N}\to A$ as follow $h'(a,n)=\begin{cases}h(a,2n-1)&\text{for }a\in\{s_1,\cdots,s_n\}\\ a&\text{for }n=1,a\in\{r_1,\cdots,r_n\}\\ h(s_i,2n-2)&\text{for }a=r_i\\ h(a,n)&\text{otherwise}\end{cases}$  In case $n>0$ we get a contradiction with $\bar{S}$ being the maximal element.   Thus we have only to exclude the case 2) $R$ infinite. HOW TO DO THAT?   Question  Above I tried two proofs. The first part is the same. The two second parts are given by the two bullets.  The second proof tries to follow the hint.  My questions are:   - Is my proof correct?   - In which direction should go the proof from the hint?


Passing object into classes, will they just be references to original?

This is the class which contains all characters and objects within a level.  CollisionListener is an interface, and CollisionListener.beginContact() is called whenever a character collides with another object.  I'm wondering, since I'm passing level into CollisionListener, does this mean 2 objects are stored in memory?   Or is private Level level inside CollisionListener just a reference to original level? How is this handled internally by JVM?  Since when I modify level inside CollisionListener, the original level is updated too.  public class Level extends World {      private Player player;     private Enemy enemy;      public Level(){          this.setContactListener(             new CollisionListener(this));          player = new Player();         enemy = new Enemy();     }      /**      * Move characters      */     public update(){          player.update();         enemy.update();     } }   This is an interface, thats added to my Level object. It needs a reference to a Level object so level.doSomething() can be invoked.  public class CollisionListener implements ContactListener{      private Level level;      public CollisionListener(Level level){          this.level = level;     }      public void beginContact(Contact contact) {          this.level.doSomething();     }      /* other interface methods .. */ }


Why is ScreenToWorldPoint always giving same coordinates with mouse position?

Whenever I use ScreenToWorldPoint(Input.mousePosition) and display the output in console this always gives me the same coordinates. MyCode: Vector3 screenToWorld;  void Update() {     screenToWorld = Camera.main.ScreenToWorldPoint(Input.mousePosition);     Debug.Log(screenToWorld); }


I currently have an ec2 "t2.nano" instance up and running. I would like to switch to a "t2.micro". In order to do that, I need to stop the instance. But I would lose my IPv4 address in the process. And I do not want that (because I have several ssh tunnels up and running from rasps in the wild that are currently hard coded to connect to this IPv4 address). I decided to create an Elastic IP address. But I understand that by creating an Elastic IP address and assigning it to my current ec2 instance, I would lose my current IPv4 address too. Is it possible to create an Elastic IP address from the current IPv4 address of my ec2 instance? If so, how can I do this operation?


Symbol with overline and subscript leads to wrong kerning

I stumbled over a problem, which I assume should be quite common, but I couldn't find a satisfying answer (e.g.  and  are not what I am looking for).    I'd like to get an overline over a symbol, but not over its subscript. Though this is no problem, the grouping destroys the kerning of the subscript. Consider the example:    How can I get the overline just over f like in the second line, but the kerning of the subscript of the first line?  Of course I could adjust it manually with negative spacing, but I wonder if there is a more generic solution.  MWE  \documentclass{article}  \usepackage{amsmath} \usepackage{helvet} \usepackage{sansmathfonts}  \begin{document}  without overline: \[f_t\] with overline and subscript outside: \[\overline{f}_t\] with overline and subscript inside: \[\overline{f_t}\]  \end{document}


how to unlock bluetooth service in Ubuntu 15.10

After installing ubuntu 15.10 i have some problems with bluetooth file sharing:my PC has established BT connection to Samsung phone and I can send files from my PC to phone, but can't do it otherwise. When my phone sends file my PC shows lock beside bluetooth simbol.Thank you in advance


I am using HtmlAgilityPack.  I create an HtmlDocument and LoadHtml with the following string:  <select id="foo_Bar" name="foo.Bar"><option selected="selected" value="1">One</option><option value="2">Two</option></select>   This does some unexpected things.  First, it gives two parser errors, EndTagNotRequired.  Second, the select node has 4 children - two for the option tags and two more for the inner text of the option tags.  Last, the OuterHtml is like this:  <select id="foo_Bar" name="foo.Bar"><option selected="selected" value="1">One<option value="2">Two</select>   So basically it is deciding for me to drop the closing tags on the options.  Let's leave aside for a moment whether it is proper and desirable to do that.  I am using HtmlAgilityPack to test HTML generation code, so I don't want it to make any decision for me or give any errors unless the HTML is truly malformed.  Is there some way to make it behave how I want?  I tried setting some of the options for HtmlDocument, specifically:   doc.OptionAutoCloseOnEnd = false;  doc.OptionCheckSyntax = false;  doc.OptionFixNestedTags = false;   This is not working.  If HtmlAgilityPack cannot do what I want, can you recommend something that can?


How to show that $R^3$ is the direct sum of $W_1=$Span$(1,1,1)$ and $W_2=$Span$(\{1,0,0\}, \{1,1,0\})$?  So we write it as $R^3=W_1+W_2$ because every $(x_1, x_2, x_3)\in R^3$ can be written as $a((1,1,1)-(1,1,0))+b((1,1,0)-(1,0,0))+c(1,0,0)$   Do I have the correct direction?


I am trying to generate the triple integral in the following equation (The preamble is large, due to other requirements)  \documentclass[11pt,headings=small,fleqn]{scrreprt} % highest level is chapter %\documentclass[12pt,journal,compsoc]{report} \usepackage[Glenn]{fncychap} %To add a rectangle at the beginning of each chapter \usepackage[greek,english]{babel} % for English text only %\usepackage[ngerman]{babel} % for German text only %\usepackage{ngerman}        % for German text only \usepackage{mathtools}    %To split equations \usepackage{amsmath} \usepackage{esint} \usepackage{mathdesign} \usepackage[ansinew]{inputenc} \usepackage[T1]{fontenc} \usepackage{rotating} \usepackage{multirow} \usepackage{microtype} % improves font spacing, needs pdfTEX >= 1.20 \usepackage{hyperref}  % hyperlinks  \usepackage{graphicx} \usepackage{subfigure}  \usepackage{makeidx}     \begin{flalign}     \frac{\partial}{\partial t}\oiiint \rho dv + \oiint \rho \stackrel{\rightarrow}{V}\cdot \stackrel{\rightarrow}{ss}=0     \end{flalign}   But I keep getting the error undefined control sequence \oiiint  Can any one help please?


Effects of a constant magnetic field on the human body (especially blood circulation and ion channels)?

Recently, while searching for the safety of MRI, I read in several places that hemoglobin and iron in the blood are not significantly affected by magnetic fields, so MRI is safe.  However, since the human body contains many kinds of metal ions, I'm wondering what effect would the long-term exposure to magnetic fields have on the human body, unlike in the case of MRI.


Why am I under-counting when calculating the probability of a full house?

I was trying to answer      Find the probability of getting a full house from a $52$ card deck. That is, find the probability of picking a pair of cards with the same rank (face value), and a triple with equal rank (different from the rank of the pair of course).   My idea was this:  Take one rank. The number of ways you can get a pair from a rank is $C(4, 2)$.   Take another rank. The number of ways you can get a triple from that rank is $C(4, 3)$.   Therefore, the number of ways you can get a full house from just $2$ ranks is $C(4, 2) \cdot C(4, 3)$. But there are $13$ different ranks, and the number of ways you can select $2$ ranks out of $13$ is $C(13, 2)$. For each of these pairs of ranks, you can have $C(4, 2) \cdot C(4, 3)$ full houses. Therefore the number of possible full houses is $C(4, 2) \cdot C(4, 3) \cdot C(13, 2)$, and the probability of selecting a full house is  $\dfrac {C(4, 2) \cdot C(4, 3) \cdot C(13, 2)}{C(52, 5)} \approx 0.000720288$  However, this is way lower than the actual answer of $.00144$. Where did I go wrong here?


Showing that $1^k+2^k + \dots + n^k$ is divisible by $n(n+1)\over 2$

For any odd positive integer $k\geq1$, the sum $1^k+2^k + \dots + n^k$ is divisible by $n(n+1)\over 2$.   I used induction principle for the solution but cannot prove it.  I took $P(k) = 1^k+2^k+\dots+n^k$.  For $P(1)$ it is true.  For $P(n)$ let it be true.  But for $P(n+1)$ I cannot solve it.


Where can I find a structured presentation of the equations of physics?

I recently realized how odd it is that studying physics has never been able to hold my interest despite how interesting I find physics. I came to the conclusion that it is because I've always felt lost while studying physics. There are so many theories and it is hard to figure out how they all relate to each other. For example, it is rarely clear to me which theories describe high-level phenomena (e.g., thermodynamics) and which are currently considered fundamental (I don't know an example). Also, I am rarely sure of the context in which a theory holds.  I would love a resource that gives the important equations in physics in some logical order with a focus on the model in which the equation operates. It should describe the aspects of the real world that the model is capable of representing and those that it cannot. It should describe the mapping between the model and the real world. It should describe which models subsume other models and which equations derive from more fundamental equations. In the end, I would like to understand (or at least have some insight into):   which models and equations are currently accepted as the most fundamental, the current state of the problem of finding a unifying theory, and which real-world phenomena have yet to be captured by any model/equation.    So, I'm basically looking for a mathematical road map of physics so that I can orient myself before learning more in depth about specific topics. Does such a resource exist?


I have to find a $F_t$ such that $B_T^3=E[B_T^3]+\int_0^T F_t dB_t$. I have shown by ito formula that $B_T^3=\int_0^T 3 B_s^2 dB_s+\int_0^T 3 B_s ds$. Could you please help me?


Does a Cleric with high Wisdom get all their bonus spells?

How do bonus spells work?  Bob is a Level 2 Cleric with a 16 Wisdom.  The class table grants him the following spells per day  [O:4] [L1:2+1]  But his high casting stat grants him the following Bonus spells per day  [O:0] [L1:1] [L2:1] [L3:1]  What is the earliest level that Bob can cast a level 2 spell?  Is there a citation for this in the actual rules?


How to resolve server certificate not trusted in postfix on Debian?

I've configured my postfix which is installed in debian 10 to send email, it was working previously but it all of a sudden just stopped working, I don't know why it stopped sending email, I checked the log file, and saw this in the postfix log file:  May  8 07:44:20 mail postfix/smtp[32042]: 48D557896B: Server certificate not trusted May  8 07:44:21 mail postfix/smtp[32042]: certificate verification failed for alt2.gmail-smtp-in.l.google.com[**.***.***.**]:25: untrusted issuer /OU=GlobalSign Root CA - R2/O=GlobalSign/CN=GlobalSign May  8 07:44:21 mail postfix/smtp[32042]: 48D557896B: to=<*****@gmail.com>, relay=alt2.gmail-smtp-in.l.google.com[**.***.***.**]:25, delay=1.4, delays=0/0/1.4/0, dsn=4.7.5, status=deferred (Server certificate not trusted)   Here is my etc/postfix/main.cf file  #myorigin = /etc/mailname  smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU) biff = no  append_dot_mydomain = no  readme_directory = no  compatibility_level = 2  smtpd_tls_cert_file = /etc/letsencrypt/live/mail.example.com/fullchain.pem smtpd_tls_key_file = /etc/letsencrypt/live/mail.example.com/privkey.pem smtp_use_tls=yes smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache  smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination myhostname = mail.example.com mydomain = example.com alias_maps = hash:/etc/aliases alias_database = hash:/etc/aliases #myorigin = /etc/mailname mydestination = $myhostname, example.com, localhost.com, , localhost relayhost = mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128 mailbox_size_limit = 0 recipient_delimiter = + inet_interfaces = all inet_protocols = all smtpd_tls_security_level=encrypt smtp_enforce_tls=yes   Please, why is my email not sending messages and how can I resolve this issue?


Let $E$ be a measurable subset of $R$ of positive lebesgue measure. Define the set $K$ by $K = {s + t: s \in E, t \in E}$  Prove that $K$ has nonempty interior.  I tried to prove it by contradiction. By measurability we can assume that $E$ is contained in an open set and with difference of measure at most $ε$. But I only can find countably many points not in this open set and can't conclude a contradiction.


What commands are there for horizontal spacing?

I know that \: in LaTeX produces a space when rendered.  Are there any alternatives, because my LaTeX renderer doesn't support \: (it renders it as text), and there is no help / FAQ that I can find.


Ubuntu Server 12.0.4 LTS cannot Load after fresh install but gives a Blinking Cursor Screen

After installing Ubuntu server 12.0.4 LTS from a booteble USB created using Universal-USB-Installer-1.9.5.1.exe I removed the USB to allow it to boot from the disk. But it only booted to a Black Screen with a blinking cursor. Several reboots have not  helped. What should I do? I am new to Linux commands so give me clear step by step guidance. I do have another bootable Slax USB. How can I use this to get to the Hard disk?


I'm tryng to stress a web server with requests, I used vmstat to get the memory usage of the server, but I don't understand few things.   When the requests start, the free memory decreases and the swpd increases, but after a while, even if the requests continue at the same rate, the free memory goes up. I think it's because the system goes out of free memory, or at least to avoid that before it's to late, allocates new memory with swap memory, am I right? Is there a way to limit the swap memory allocation?


How can I run a Minecraft Server on multiple CPU cores? Mac

How can I set my bukkit server on my mac to use more than 1 core? I set my server to use 12 gigs of RAM for now, considering that I will be adding more servers soon.  My iMac has these configurations:   3.5GHz Quad-core Intel Core i7, Turbo Boost up to 3.9GHz 32GB 1600MHz DDR3 SDRAM - 4X8GB 1TB of PCIe-Based Flash Storage NVIDIA GeForce GTX 780M 4GB GDDR5   It uses mavericks.  Also, is it possible to use the graphics card for the server (considering that the RAM on it is MUCH faster than the standard 1600MHz RAM) when the card is not in use?  Thanks so much guys!


Term for the use of "you" to refer to "the hypothetical person in question"

My wife was discussing pudding consistency this morning and used a sentence along the lines of, "I only like the pudding you make". I blinked and asked if she really liked the pudding I make and she replied, "No, I mean the pudding you make, you know, like if I were to make some pudding". She was using the "you" in a sense of a hypothetical person, I guess, like saying, "That's what you do in a crisis" when commenting on a riot scene in the news. You're not using "you" to refer to the person you're speaking to, but rather a form of general humanity.  Anyhow, is there a term for such a usage such that you might be able to answer, "Oh, sorry, I was using 'you' in the [term] context, not referring to you specifically"?


First Order Language for vector spaces over fields

I'm attempting to come up with a first order language $L$ that is able to describe vector spaces over fields. I came up with a few sets of nonlogical symbols.  $Rs_L=\{Scal,Vec\}$ where $Scal,Vec$ are unary relation symbols which I interpret to be true or false depending on whether $x$ is a scalar or vector.  Also, $Fs_L=\{+,\cdot,\}$ which are the usual addition and multiplication for both vectors and scalars.  For constant symbols, $Cs_L=\{0,1,0_V\}$, where $0$ and $1$ are regular field scalars for the additive and multiplicative identities, respectively, and $0_V$ is the additive identity for vectors.   Using these, I was able to formulate axioms for scalar multiplication on a given structure, and I define addition between a scalar and a vector to simply always give the 0 vector and define multiplication between two vectors to always be the 0 vector. This gives a theory such that a structure models it if and only if it is a vector space in the regular algebraic sense. It is easy to see that all linear transformations in the algebraic sense are included in the class of homomorphisms (in the logical sense), but I am having difficulty proving they are the only ones in this class.   I suppose I want to show that for any $L$-homomorphism $T$, $T(av+w)=aTv+Tw$ for $a$ a scalar and $v,w$ vectors. Since $T$ is a homomorphism, I see that $T(av+w)=Tav+Tw=TaTv+Tw$, so it would be enough to show that all homomorphisms act as the identity on all scalars? Is there a way to show this, or an extra axiom to include?


jquery animate body background color not working

I want to change the color of the body whenever I scroll, if I use the jquery css() method, everything works but the thing is I want to put some delay on this effect so I need to animate instead but when I use the following code, the color is not animating, what am I missing?  $("body").animate({     backgroundColor: "white !important" });  // works well with $("body").css("background-color", "white");   I don't want to use css transitions.


Background  Recently  was implemented. With this feature the amount of questions with new activity is shown in parenthesis at the beginning of the page title, e.g.     (2) Meta Stack Overflow   means that MSO has two questions with new activity since the user last viewed it.   this feature is unrelated to inbox updates. Here is an example to illustrate this:    Even though there are two inbox messages in this screenshot this is not reflected by the page title. The page title is currently only sensitive to questions with new activity.  Suggestion  I suggest that the page title also reflects inbox updates. For the screenshot above this would mean that the page title shows that there are two inbox updates and two questions with new activity.  I am not sure what format is best for showing this. For chat * in the page title is used to show that there are messages directed at you which is similar in meaning to inbox updates. However, * if is placed after the number in parenthesis to denote inbox updates there might be confusion as there is no connection between the number in parenthesis and * like in chat. Thus, one might prefer another format such as one of the following (all are meant to reflect the status of the screenshot above):      * (2) Meta Stack Overflow     2* (2) Meta Stack Overflow     [2] (2) Meta Stack Overflow     2i 2q  Meta Stack Overflow     (2/2)  Meta Stack Overflow     (2|2)  Meta Stack Overflow    For the alternatives without an explicit hint of which number refers to what it might be best to place the number for questions with new activity first as it will in most cases be greater. This will to a greater degree avoid combinations such as "(0/2)" which may be confused zero of two.  An advantage of the suggested feature is that if the user has a browser tab with a Stack Exchange site then they will be instantly notified of inbox updates. They do not need to focus a tab with a Stack Exchange site to know if there are inbox updates, they merely have to check the relevant page titles among their tabs.  A disadvantage of the suggested feature is that it might be experienced as verbose. I suggest that it is implemented such that it is as unobtrusive as possible while still being informative. Think of a situation where a user has   one Meta Stack Overflow tab with two inbox updates relating to Meta Stack Overflow and two questions with new activity, and one Super User tab with one inbox updates relating to Super User and three questions with new activity.   Then the sum of the inbox notification in the page titles should be local to sites and not global. The page titles for the tabs above should be something like the following pair:      2i 2q  Meta Stack Overflow     1i 3q  Super User


Word for someone who loves to create and organise noisy, lively, chaotic events

Some people love creating or fostering the creation of events that are noisy, chaotic and fun, such as parties, arguments, reunions, etc. Sometimes there's a negative connotation to this (like in provoking an argument), but sometimes there is not (like in organising a big, noisy party).  The word I'm looking for would be the English equivalent to the Spanish armadanzas, just in case this is helpful.  Any ideas?


Remove Google Play Services from no-root Android 8.1 phone

How does user remove the stubborn 'Google Play Services' from the Android phone? Android 8.1 'Google Play Services' does not allow remove updates option. Why does 'Google Play Services' behave similarly like the Microsoft Edge web browser that is stubborn and can't be removed.   User buy the Android phone should not be denied from uninstall stock apps such as the notorious 'Google Play Services' that use data usage without user permission!  Please do not provide answers such as root the android phone because this question is about no-root phone (meaning the phone is not rooted). Also,  PoGO has new TOS that does not care about user privacy!


What are the most popular references for mixed models?

What are the most popular references (especially texts) you think in the area of mixed models? Or what are those you think were helpful to you when you learnt this topic?


Null Pointer Exception to a RecyclerView that was defined

I defined my recycler view and I'm still getting a null pointer exception when I try invoking methods on it, but it was working before  My layout is activity_main.xml      <android.support.v7.widget.RecyclerView         android:layout_width="match_parent"         android:layout_height="0dp"         android:layout_weight="1"         android:id="@+id/recyclerView"         android:layout_marginTop="8dp"         android:visibility="gone"/>   My java MainActivity.java(on create)   @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);     recyclerView = findViewById(R.id.recyclerView);      LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);     recyclerView.setLayoutManager(linearLayoutManager);     recyclerView.setHasFixedSize(true);  }   FULL LOGCAT: FATAL EXCEPTION: main     Process: com.example.atry, PID: 31310     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.atry/com.example.atry.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3115)         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3258)         at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)         at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)         at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1955)         at android.os.Handler.dispatchMessage(Handler.java:106)         at android.os.Looper.loop(Looper.java:214)         at android.app.ActivityThread.main(ActivityThread.java:7058)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference         at com.example.atry.MainActivity.onCreate(MainActivity.java:84)         at android.app.Activity.performCreate(Activity.java:7327)         at android.app.Activity.performCreate(Activity.java:7318)         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1275)         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3095)         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3258)          at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)          at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)          at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1955)          at android.os.Handler.dispatchMessage(Handler.java:106)          at android.os.Looper.loop(Looper.java:214)          at android.app.ActivityThread.main(ActivityThread.java:7058)          at java.lang.reflect.Method.invoke(Native Method)          at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)


$E$ measurable set and $m(E\cap I)\le \frac{1}{2}m(I)$ for any open interval, prove $m(E) =0$

Ran across this problem and need some help.   Let $E$ be a measurable subset of the real numbers and suppose that for any open interval $I$ one has $m(E\cap I)\le \frac{1}{2}m(I)$, where $m$ is the Lebesgue measure. Prove that $m(E)=0$.


How to configure my linux machine to send emails from terminal.  I tried the following  apt-get install postfix mailutils sudo systemctl start postfix echo "Email Text" | mail -s "Subject" "user@address.com"   But the mail isn't sent.  I also checked postfix status and there is some error with guidelines.  sudo systemctl status postfix  ... Our system has detected that 550-5.7.1 this message does not meet IPv6  sending guidelines regarding PTR 550-5.7.1 records and authentication. ...   Is there an easy way to configure my linux machine to send emails?  I'm using debian.


What's the difference between the prefix "re-" and the adverb "again"

For example, "I will reread this article" and "I will read this article again". Are they equivalent? When should I use a hyphen after the prefix "re"?


Rewriting of functional equation $f(xy)=f(x)+f(y)$

Given the following equation:  $f(xy)=f(x)+f(y)$  and the fact that $y=x^{-1}$,  I've to find how this could became:  $f'(x) = f'(1)/x$,  where it is said that $f'(x)$ is the total derivative of $f$  I really miss some steps..someone could help?


With the geometry package, we can set margins for the whole document (with options like left, right, etc.). Now, how do we set margins for an individual page so that it doesn't affect the whole document. The reason for this question is that, when using book class, the left and right margins are equal in the left page and the right page respectively and the spline is a bit larger. How do I set left and right margins to be equal in the titlepage. Here is the MWE:  \documentclass[12pt]{book} \usepackage{kantlipsum} \begin{document} \begin{titlepage} \noindent \rule{\textwidth}{4pt} \rule{\textwidth}{4pt} \kant[1-3] \end{titlepage} \end{document}


How to detect two different mice at the same time, and record their separate movements?

I would like to use two computer mice simultaneously, and to record data their separate movements on windows. I have successfully used TeamPlayer to create two cursors, but the software that I am using to record the movement data records only one output - the sum of the two cursors. How am I to use both computer mice at once, and record their separate outputs? I have looked at the thread , but this is quite old now and most of the solutions offered are now unavailable.


Is there a way to edit unassigned materials in the shader editor?

I have a material, that is not assigned to any object. I use it as a material override in a pass (View Layer) only.  Do someone knows a way to edit (see) materials in the shader editor, that are not assigned to any object?  Thank you


Can I still use unity low graphics mode in place of unity 3d?

I can not run unity 3d on my Chromebook but unity 2d in Ubuntu 12.04 works fine so is it possible to run unity low graphics mode on Ubuntu 14.04 as an alternative? If I can run low graphics mode as an alternative then how would I go about that? If I can not then what would be a good unity like alternative for Ubuntu 14.04?  I have tested these DE's on Ubuntu 14.04 on my Chromebook:   LXDE: works fine XFCE: works fine Gnome: does not work at all Unity: does not work at all KDE: Have not yet tested this DE   I am using crouton to install unity and according to the maker(s) of this script say that unity 3d will not work for me as it requires hardware acceleration that my Chromebook does not offer.  What happens when I run unity 3d is a black/gray screen followed by a complete lockup of Ubuntu that I must terminate from crosh (the Chromebooks developer console that Ubuntu is running in).  This is the modified target script that I am using with  to install unity 3d on samsung arm chromebook (Please note that it is not yet fully functional).  #!/bin/sh -e # Copyright (c) 2014 The crouton Authors. All rights reserved. # Use of this source code is governed by a BSD-style license that can be # found in the LICENSE file. REQUIRES='gtk-extra' DESCRIPTION='Installs the Unity desktop environment. (Approx. 700MB)' HOSTBIN='startunity' CHROOTBIN='startunity gnome-session-wrapper crouton-unity-autostart' CHROOTETC='unity-autostart.desktop unity-profiled' . "${TARGETSDIR:="$PWD"}/common"  ### Append to prepare.sh: install ubuntu-desktop ubuntu-artwork gnome-session nautilus \         ubuntu-settings,ubuntu~precise= \         ubuntu-session,ubuntu~precise+ubuntu~quantal+ubuntu~raring+ubuntu~saucy+ubuntu~trusty= \         -- network-manager  # XDG autostart/profile.d additions only needed in saucy and later if release -ge saucy; then     autostartdir='/etc/xdg/autostart'     # Remove previous indicator-only desktop file     rm -f "$autostartdir"/crouton-unity-indicator.desktop      # Set up global autostart script     mkdir -p "$autostartdir"     ln -sfT /etc/crouton/unity-autostart.desktop \         "$autostartdir"/crouton-unity-autostart.desktop      # Set up profile.d     chmod 755 /etc/crouton/unity-profiled     ln -sfT /etc/crouton/unity-profiled /etc/profile.d/crouton-unity-profiled.sh fi  if release -ge trusty; then     autostartdir='/etc/xdg/autostart'     # Remove previous indicator-only desktop file     rm -f "$autostartdir"/crouton-unity-indicator.desktop      # Set up global autostart script     mkdir -p "$autostartdir"     ln -sfT /etc/crouton/unity-autostart.desktop \         "$autostartdir"/crouton-unity-autostart.desktop      # Set up profile.d     chmod 755 /etc/crouton/unity-profiled     ln -sfT /etc/crouton/unity-profiled /etc/profile.d/crouton-unity-profiled.sh fi  TIPS="$TIPS You can start Unity via the startunity host command: sudo startunity "   The current problem with this script is that I need to implement unity low graphics mode right into it on install and I can not figure out how to do that.  If you would like to test the script with crouton then follow these steps:  Fist save the script as an extensionless file under the name "unitylowg" in the Downloads directory of chrome os.  Then meet its dependencies by running these scripts one by one:  sudo sh -e ~/Downloads/crouton -t core -r trusty sudo sh -e ~/Downloads/crouton -t audio -r trusty -u sudo sh -e ~/Downloads/crouton -t xephyr -r trusty -u sudo sh -e ~/Downloads/crouton -t x11 -r trusty -u sudo sh -e ~/Downloads/crouton -t gtk-extra -r trusty -u   Then finally run the script with the following:  sudo sh -e ~/Downloads/crouton -T ~/Downloads/unitylowg -r trusty -u


Why are there upvotes without reputation in a user's profile?

I have noticed graphs like this in few Stack Overflow top user profiles.   Why are some posts not getting reputation? Why are users not getting it, even if they're worth it? Is there any daily limit for reputation? Or any rules?     Then on an another day


I need to use unsigned double in C structure, but i can't compile. An error says: short, signed or unsigned invalid for `myvar'  this is my code:  #include <stdlib.h> #include <stdio.h>  struct eReg{    int key;    unsigned char a;    unsigned short int b;    unsigned double myvar;    }MyReg;   Does anyone know what is wrong?  EDIT I did not know "unsigned double" equals "unsigned float", then I didn't knew I had to find the answer to my question as "unsigned floats in C?" Anyway after reading the post, I've accepted my question as "duplicate". I suggest deleting this question.


"I shall" vs. "I will" in an e-mail to a superior

In an e-mail to a superior, should I write "I shall create a page", or "I will create a page"?


What intuitive explanation is there for the central limit theorem?

In several different contexts we invoke the  to justify whatever statistical method we want to adopt (e.g., approximate the binomial distribution by a normal distribution). I understand the technical details as to why the theorem is true but it just now occurred to me that I do not really understand the intuition behind the central limit theorem.  So, what is the intuition behind the central limit theorem?   Layman explanations would be ideal. If some technical detail is needed please assume that I understand the concepts of a pdf, cdf, random variable etc but have no knowledge of convergence concepts, characteristic functions or anything to do with measure theory.


Show this linear map over a finite field is not the zero map

Let $q=p^k$ be a prime power, let $m\in\mathbb{N}$ and consider the map   $$ \tau:\mathbb{F}_{q^m}\longrightarrow\mathbb{F}_{q^m},\quad a\longmapsto\sum_{i=0}^{m-1} a^{q^i}. $$   Show that $\tau$ is not the zero map.   I was able to show that this map is $\mathbb{F}_{q}$-linear, and that $\text{im }\tau\subset\mathbb{F}_q$. However, I am stuck on showing this map is not the zero map. I suppose I could look at $\tau(1)$ but if $m=p$, then $\tau(1)=0$ since the characteristic of $\mathbb{F}_{q^m}$ is $p$. Do I have to handle this as a special case, or should I do something else? Thanks.


how to generate data from a distribution whose cdf is not in closed form?

I am working on a distribution whose pdf and cdf is $$f(x,\alpha,\beta)=\frac{(\frac{\beta}{\alpha})(\frac{x}{\alpha})^{\beta}}{(1+(\frac{x}{\alpha})^{\beta})^{2}}\frac{\sin(\frac{\pi}{\beta})}{(\frac{\pi}{\beta})}$$ $x>0$, $\alpha>0$, $\beta>0$ $$F(x)= \frac{\sin(\frac{\pi}{\beta})}{(\frac{\pi}{\beta})}\frac{1}{\beta}(\frac{x}{\alpha})^{1-\beta}\log{\left(1+\left(\frac{x}{\alpha}\right)^{\beta}\right)}-\frac{\frac{x}{\alpha}}{1+\left(\frac{x}{\alpha}\right)^{\beta}}-\frac{1-\beta}{\beta}\left[\frac{x}{\alpha}+\sum_{r=1}^{\infty}\frac{(-1)^{r}\left(\frac{x}{\alpha}\right)^{1+r\beta}}{r(1+r\beta)}\right]$$ clearly, cdf is not in neat form. So how do I generate data from this cdf in r as inverse cdf method can't be applied here? I am using following R program to generate sample from this dist but I am not able to justify every steps. Here is my code: alpha=1.5;beta=3.2; pdf=function(x)((beta/alpha)*((x/alpha)^beta)*sin(pi/beta))/(((1+(x/alpha)^beta)^2)*(pi/beta)) rand_smplfunc <- function(func, lower, upper){ x_values <- seq(lower,upper,by = 10^-3) sample(x = x_values, size = 1, replace = TRUE,prob = func(x_values)) } replicate(10,rand_smplfunc(pdf,0,10))


Avatars aren't loading, with a status 301 (permanently moved) response

Some avatars (including my own) aren't loading anymore, and instead I get a transparent box. This occurs particularly after I refresh a page.  In my developer tools network tab, every request for an i.stack.imgur.com avatar seems to get a response of 301 (permanently moved) without content, which might explain why those avatars don't load up.  Related:


ClearType Text Tuner: what exactly do all steps do?

In Windows, when adjusting ClearType text, following the option to turn on/off ClearType & ensuring the monitor is set to native resolution, one is supposed to follow 5 steps. I've already tried various combinations but none of them yielded the satisfying result. While the 3rd step makes the user choose between subpixel or grey-scale rendering (I think), I'm wondering what exactly other steps do?


Computer booting to a black screen with white text

NOOB WARNING I was using my computer as normal when I got a notification that I was almost out of space in my computer. I checked in files and it said I had 420 gb or something left. I thought that was weird. I had recently plugged in a Harddrive in my computer to install Windows on because I had some troubles before while installing Windows before on my ssd. I unplugged the hdd and I tried booting my pc without the hdd plugged in (btw I had nothing installed on this drive) but when I booted it came in to this weird black screen with a lot of text on. I cant do anything, I have tried to press ctrl alt f1 or f2 but they dont work and neither does ctrl alt t. I dont know what to do because im a noob with ubuntu. I have plugged the drive back in again but I keep booting in to the same black screen with text on. I run version 18.04 (I think) right now,


"He didn't dare [verb]" vs. "He didn't dare *to* [verb]"

Which one is correct? If both are correct, is there any difference in the meaning?  He didn't dare to contradict his parents. He didn't dare contradict his parents.


Add days to date format MM/dd/yyyy in selenium webdriver

The question is simple, how to add days to this date format:  MM/dd/yyyy like 11/06/2015


Effect of the tail of the cat in the falling cat problem

To explain why a falling cat can turn by 180 degree without external torque and without violation of the conservation of angular momentum, one usually models the cat as two cylinders as in     This may explain the turn. However I often heard contrary to this that she can rotate her body simply because she rotates her tail very fast into the opposite direction (and essentially keeps the rest of the body rigid).  So, what effect does the tail have in reality? Is there any detailed model, which takes the tail rotation into account and calculates how large its effect is?


Quickly place a window to another screen using only the keyboard

I know that using Alt+F7, I can use the keyboard to move the window around. I can also use the "Grid" plugin of Compiz to position quickly the window around my current monitor. The grid plugin doesn't seem work across monitor however.  What I need is a quicker way to move the current window to the other screen. In my current dual-monitor setup, I find myself needing to move the focus window to the other monitor as I focus on working on something else (and move it back afterward).  If I use XMonad (or other tiling managers), this would be rather easy. However, many applications that I use (Gnome Do, MATLAB, image viewers, custom apps that I write, ...) do not work well with a tiling manager.   So my question is: is there a shortcut key combination that moves the currently focused window to the other monitor (and back)?


How to remove all event handlers from an event

To create a new event handler on a control you can do this  c.Click += new EventHandler(mainFormButton_Click);   or this  c.Click += mainFormButton_Click;   and to remove an event handler you can do this  c.Click -= mainFormButton_Click;   But how do you remove all event handlers from an event?


Interpreting what this means in a paper - significantly different at the .05 level?

I am having a hard time interpreting what something means in a paper I'm trying to get through. If you care, this is the paper: Gender Differences in the Effect of Education on the Slope of Experience-EarningsProfiles: National Longitudinal Surveyof Youth,1979-1988. By KEVINC. DUNCAN*  In one of the tables of the regressions, it explains that a little "a" (next to the coefficient) means the coefficient is significantly different at the .05 level from the comparable coefficient for white males.  What exactly does this mean?  Here is my understanding: If there are 2 correlations with sample sizes n’s, they are each changed into z values. Under the null hypothesis that the population correlations are equal, the following has a standard normal distribution (one equation using both z’s). If the z is great than or equal to 1.96 or less than or equal to -1.96, the two correlations are significantly different at the .05 level of significance. If the z is not significant at the .05 level, sampling error is a possible explanation for the difference. If the two are significantly different, the null hypothesis is rejected! There must be fairy large sample sizes used. Coefficients with p value of .05 or less would be judged to be statistically different.  Is this correct? Can you explain it a little more if I'm wrong.  Here is a link to the paper?   Also which coefficients would you consider significant in Table 2?


Do in-universe characters look down on Hufflepuff?

Out of universe, some people think that Hufflepuff is "bad", in a condescending sort of way.  Is there anything that parallels this in the books?  Do the other wizards frown down upon Hufflepuffs and think that "getting sorted into Hufflepuff is a pat on the head and a kindly expectation that you'll never accomplish much"?    This question was based on , which seemed somewhat disdainful towards the Hufflepuffs.


How secure is an encrypted LUKS filesystem?

I recently installed 11.10 on a fresh disk using entire disk encryption.  Can someone tell me how secure the encryption algorithm is?  Has there been any recent breaches with said algorithm?  I use a 36 character random passphrase so I know thats not a weak link.  What are the chances my client's data could be compromised if the hard drive was stolen?


sed append path to end of specific line pattern search

Would like to append path variables to end of line on a specific row with search pattern and append, "Defaults    secure_path" string I want to append: :/etc/bla/foo/  the file,      filename   # asdf # lkaj # asdah  Defaults    secure_path = /sbin:/bin:/usr/sbin:/usr/bin  ## safdafdhdahdabfdabf ## Aedhadhfdahdahadhda   Tried pattern search for "Defaults    secure_path" and append to end of line:  sed '/^Defaults    secure_path = / s/$/ :/etc/bla/foo/' filename   But, got error:   sed -e expression #1, char 38: unknown option to `s'


Suppose $R$ is a relation on $N_4=\{1,2,3,4\}$ such that $R\circ R = R$. How would I prove that $R$ is reflexive? Could you give me some tips about how to start off?


MySQL has a lot of different highly available solutions, I would like to know what are the differences between all the current implementations, here are the implementations that look currently up to date :   MySQL Group Replication (by Oracle) MySQL NDB Cluster (by Oracle) Galera Cluster (by Galera) XtraDB Cluster (by Percona) MySQL Fabric Cluster (by Oracle) MySQL Orchestrator (by Github)   What would be the recommended options (or any others) for a high available setup with automatic failover ? (For something equivalent of the SQL Server DB Mirroring with synchronous replication)


Bottom Status Bar Doesn't Show Verts, Faces, Tris Information In v2.9a

I don't see the statistics information that's supposed to be on the status bar running along the bottom of the main window towards the right in version 2.9.


An elementary question about cardinal arithmetic without AC

Suppose $|X|=2^{2^{\aleph_0}}$, $A \subset X$ and $|A|=2^{\aleph_0}$. Is it possible to prove that $|X \setminus A|=2^{2^{\aleph_0}}$ without using the axiom of choice and its consequences?


New largest prime number discovery - what's all the fuss

So I've read about the latest largest prime number discovery (M74207281), but I find it hand to understand what's the big deal because using Euclid's proof of the infinitude of primes we can generate primes as large as we want.  I'll be happy to know what I'm missing


What criteria is used to select an Ubuntu release codename, and who is ultimately responsible for the decision?


I'm trying to substitute include guards in headers with same include guards, prepended with #pragma once:  #ifndef _HELLO_H #define _HELLO_H   Becomes:  #pragma once #ifndef _HELLO_H #define _HELLO_H   Also, i want to leave line endings as-is. If it was LF then use LF, if it was CRLF then use CRLF.  I came up with following command:  find . -type f -name "*.h" -print0 | xargs -0 sed -i -E -e 's/#ifndef ([a-zA-Z_][a-zA-Z_0-9]+)(\r?\n)#define \1/#pragma once\2#ifndef \1\2#define \1/g'   But i got just line endings replaced in all headers, and no #pragma once added.  Command executed within MSYS2 terminal under windows.


I would like to number my table so that I have, e.g.  Theorem 1.3  Table 1.4  Lemma 1.5   How can I achieve this result? I am also using cleveref, so ideally \cref{ThatTable} would produce a linked ``Table 1.4'' when I am done as well.


I've planned to buy the new basic 2019 Mac Pro, essentially for use with blender. Is that a good idea? I own a mid2010 Mac Pro for now but it's a little bit slow as soon as there are a few textures in my projects. ...or should I switch on a Windows solution? Thanks


In Empire Strikes Back and Return of the Jedi we see Yoda, Obi Wan and Anakin reappear as a Force Ghost/Spirit.  The overall objective of the Sith was the achieve immortality, this was one of the reasons why they detached themselves from the Jedi Order.  Immortality seems achievable on the light side of the Force, yet not on the dark side, or at least in canon. Have there been any Sith who achieved this?


How to get the menu with Add Gear options back?

I'm new to Blender and I've figured out how to make a gear but I have a question!   Shift+A > Mesh > Gears > Gear will add a new default gear to the build area and will bring up an Add Gear menu in the Toolshelf on the left where you can change all aspects of the gear.    But once the gear's object was moved / the interaction mode was changed / any other action was done, the Add Gear menu on the left disappears. How do I get this menu back?


Follow and Share Button is missing from SharePoint online

follow and share Button is missing from SharePoint online site. have activated the following content even though the options are not displaying.  is there any option?


Is there a way to prevent questions with a specific tag form showing up?

I wanted to see questions that were tagged Java. But I keep seeing questions with the Android tag. The problem is that I don't know how to help with questions that are to do with Android applications. I want to remove those tagged questions from my view so that I don't see them. That way I can focus on the questions that are relevant to me and that I can actually help answer.  Just how there is a "Favorite Tags", there should be "Unwanted Tags".  Is this possible?


Is it possible to make this tip box using the tcolorbox package?

Is it possible to make the ‘tip box’ in the photograph below using the tcolorbox package (or any other way for that matter)? My abilities in tcolorbox are severely lacking, so any help is greatly appreciated.  Thank you in advance for any assistance.


I have that $2^{947} (\bmod 1373)$ how does one solve this without a calculator? Can you separate it into nice $2^x2^y$ or $(2^x)^y$? I'm really not sure how to go about this problem. Thanks for any help!


What are the available $A JavaScript functions in Lightning?

The  lists a few common $A functions and the  references some others that are useful for certain situations.  I can view the $A object in the JavaScript console and get a list of a whole lot more, including some nested such as the $A.util functions.    Is there documentation on the $A functions that are part of the published API (i.e., safe to use)?


How do I find out which Game Center account a game is tied to?

I played Clash of Clans one year ago and I have many game center accounts.  My problem is that I forgot which game center account has my game progress. How do I know which registered account is linked with Clash of Clans?


Trigonometric fraction Inequality question

Let     $$ 1< \alpha_1<\alpha_2<......<\alpha_n< \pi/2$$ then prove that $$ tan(\alpha_1)< \frac{sin(\alpha_1)+sin(\alpha_2)+.....+sin(\alpha_n)}{cos(\alpha_1)+cos(\alpha_2)+......+cos(\alpha_n)} < tan(\alpha_n)$$   I tried to solve the problem but I am not actually able to get a well established answer or you can say I am not even able to advance ahead to solve this one. It tried to use AM-GM inequality, but its didn't work as I couldn't establish any direct relation.


My repos became corrupted: Unable to parse package file

Suddenly ubuntu 14.04 started to print this:  Reading package lists... Error! E: Unable to parse package file /var/lib/apt/lists/ru.archive.ubuntu.com_ubuntu_dists_trusty_restricted_i18n_Translation-en%5fUS (1) E: The package lists or status file could not be parsed or opened.   I did use only "Software updater". What is the right way to fix it?  Here is an ls -la output     ls -la /var/lib/apt/lists/ | grep restricted_i18n_Translation   -rw-r--r-- 1 root root        0 окт.  18  2013 ru.archive.ubuntu.com_ubuntu_dists_trusty-backports_restricted_i18n_Translation-en   -rw-r--r-- 1 root root  5062829 мая    8  2014 ru.archive.ubuntu.com_ubuntu_dists_trusty_restricted_i18n_Translation-en%5fUS   Confused with the date of the file: the 8th of May, 2014. I've met the problem few days ago.


Understanding cost-complexity pruning in regression trees

I am trying to understand how an optimal tree length is determined using cost-complexity pruning.  Visit this lecture note screenshot:   In the highlighted equation, I don't understand how C(T) or alpha is calculated. My thought process is that a large tree is grown and then a subtree is created and then they are compared but I don't understand how.  Thanks in advance.


In the Force Awakens, Han says that Luke disappeared to find the first temple. I assume that's what he and Leia were told, or assumed themselves. However in the Last Jedi, Luke says he went there to die.


Issues trying to download and install ubuntu

I tried to download the iso file for Ubuntu 14.04 desktop. But when I tried to install I got invalid parameter error. So a friend loaned me his Ubuntu 8.0 disk and I got the following error on that:  /bin/sh: can't access tty; job control turned off.    I am running an HP h8-1214 computer with an AMDfx 6160 six core 3300mhz processor and windows 7 home. Can anyone tell me how I can get Ubuntu onto my computer please?


Accepting the speed of light in vacuum and infinite mass and all that, I wonder why light does not have infinite speed?  I know light does not have rest mass, but people use the term infinite mass when taking about the speed of light in vacuum so I am assuming that is kind of correct in this case.  Some background to my question:  I am sure there have been lots of experiments that slow light down. I even believe there was one that used a gas that managed to slow light down to almost 0 for a small fraction of time.  That's all easy to understand (I think) but once the light is free from restriction, i.e. after it makes it though the gas (or whatever is slowing it down) its speed increases back to light speed. So firstly, how is its speed increasing back to light speed? What force is involved in getting it back up to speed? Then, why is it stopping at that speed?  Aside from all the business of slowing light down or speeding it up, why is it so slow in the first place? what is keeping it from going faster?  Is it possibly going faster but we are only able to observe and measure the sub-light part?  Is there something in the universe that makes it difficult for the light to move, some sort of friction if you will?


Have "Tab" key insert spaces when writing a question or answer

Possible Duplicates:           Is it at all possible to have the Tab key insert 4 spaces in the question/answer edit area, instead of moving focus to the next control?  When writing code in questions or answers I could really use such functionality, especially for hierarchically indented code, like this:  codecode codecode      codecode         codecode         codecode     codecode   What I usually do is copy 4 spaces and then paste them over and over again, but using Tab is more natural (I actually do it by mistake quite often).  I think the usage of Tab for moving focus while editing a question/answer is minimal, and its benefits are insignificant versus the benefits of allowing Tabbed code.  A "neater" feature will be to push not 4 spaces but the differences between the next multiple of 4 and the current amount of spaces in the line (e.g. if I pressed once on space and then Tab, the Tab will insert 3 spaces, like "real" tabulation)


Whatsapp Notification does not display contact name

The problem I’m experiencing is that contact names do not appear on whatsapp notifications (locked and unlocked). For example, if I get a message from Dad, whatsapp only displays the whatsapp logo and “message”, without displaying the sender. When I turn on message previews, I can see both the contact name and the message preview, but I used to be able to see just the contact name (“Dad has sent you a message”) instead of having to see the preview. This just happened as I updated to ios 11.3.1. I reached out to whatsapp and they mentioned below:  To turn on previews that display the contact name but not message: Go to WhatsApp > Settings > Notifications > turn Show Preview on. Go to iPhone Settings > Notifications > WhatsApp > Show Previews > Never  I made the above changes and now when i get notification it reads (Dad-Notification and NOT “Dad has sent you a message”) Anyone having a similar problem? Thank you so much.


ifdown interface not configured (Debian 6)

My server is dedicated (non-virtual). I want to have 3+1 static IPs. I used aliases (eth0:0, eth0:1) previously, but read that this method is deprecated. So I added another IP and reconfigured my interface with ifup/ifdown while I'm at i;, but ifdown tells me that the interface is not configured.  /etc/network/interfaces looks like this:  auto lo eth0 iface lo inet loopback  # Main IPs (IPv4 + IPv6) allow-hotplug eth0 iface eth0 inet static         address 81.x.x.x         netmask 255.255.255.0         broadcast 81.x.x.255         gateway 81.x.x.1  iface eth0 inet6 static         address 2a02:x:x:x::x:x         netmask 64         gateway 2a02:x:x:x::1  # 2nd IP up ip addr add 81.x.x.x/32 dev eth0  # 3rd IP up ip addr add 81.x.x.x/32 dev eth0   Note that the 2nd and 3rd IP adresses are from different net ranges (don't know if it matters)  I reload the network configuration with  nohup sh -c "ifdown eth0 && ifup eth0"   The exact output (nohup) is  ifdown: interface eth0 not configured SIOCADDRT: File exists Failed to bring up eth0.   What am I doing wrong?  Edit: This questuion has been asked before. But the old question uses deprecated methods. Also the solution does not work for me. Since people here at serverfault seem not to be able to help me but rather just close this as duplicate (I doubt you have actually read what I wrote...) I have asked people at official forums. They are stuck with this problem and cannot find a solution at all - but at least try. I am getting more and more problems, so I will reinstall the server. You can leave this question closed and unanswered.


Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference...in Fragment

How to pass data from RecyclerView of fragment  to another fragment.i getting error. when I start the app, the app crash within 5 seconds with the message My RecyclerView of fragment..   @Override public void onBindViewHolder(final MyViewHolder holder, final int position) {     final Categories categories = categoriesList.get(position);     holder.name.setText((categories.getName()));     Glide.with(context).load(categories.getThumbnail()).into(holder.thumbnail);     holder.name.setOnClickListener(new View.OnClickListener() {         @Override         public void onClick(View view) {            String catId= String.valueOf(categories.getId());             Toast.makeText(context,catId,Toast.LENGTH_SHORT).show();             AppCompatActivity activity = (AppCompatActivity) view.getContext();             AudioFragment myFragment = new AudioFragment();             Bundle bundle=new Bundle();             bundle.putString("name", catId); //key and value             myFragment.setArguments(bundle);             activity.getSupportFragmentManager().beginTransaction().replace(R.id.frag_container, myFragment).addToBackStack(null).commit();          }     }); }   New Fragment  public class AudioFragment extends Fragment {  @Override public View onCreateView(LayoutInflater inflater, ViewGroup container,                          Bundle savedInstanceState) {     // Inflate the layout for this fragment     String CAT_ID = getArguments().getString("name");     Toast.makeText(getContext(),CAT_ID,Toast.LENGTH_SHORT).show();      return inflater.inflate(R.layout.fragment_audio, container, false); }   }


Compatible derailleurs with Shimano RD TY22 with dropout claw hanger

I have an older bike I love with a Shimano RD TY22 WD rear derailleur with a dropout claw hanger that needs to be replaced. I cannot find one listed anywhere. Are there any derailleurs available to replace this one? Thanks!


I need a quick proof of the following combination  $$\binom{n+1}1+\binom{n+1}2+\binom{n+1}3+\dots++\binom{n+1}{n+1}=2^{n+1}-1$$


Why isn't temperature measured in joules per mole (J/mol)?

Temperature is the average kinetic energy of  all the molecules in a system.  Thus \begin{align} T &= \frac{1}{N}\sum \frac{1}{2} m v^2 \\[6pt] &= \sum \frac{E_\text{single particle}}{n} \cdot 6.022 \times 10^{23} \, . \end{align} where $N$ is the number of particles and $n$ is the amount of substance.  The unit here is J/mol. Why isn't this used in place of temperature? (Instead of K, °C or °F)?


I have Motorola Moto G XT1033, rooted. I installed CM12 Nightly. I am not able to download apps sized more than 200 MB from Play Store. No option to uninstall updates of Play Store.  How to fix it?


How can I change inscription "RU" in Ubuntu 18.04 panel to Russian flag?  I tried to change it through the dconf-editor, used indicator-keyboard-Ru.svg file coping into /usr/share/icons/ubuntu-mono-dark/status/22. No flags.  Has anybody done it already?


I'm trying to modify [vpn-secrets], as mentioned here:    However, nmcli complains about it,  %> sudo nmcli con modify myvpn vpn-secrets.data 'password = xxx' Error: invalid or not allowed setting 'vpn-secrets': 'vpn-secrets' not among [connection, vpn, ipv4, ipv6].   Is it impossible to change the password with nmcli?


Is the impact factor the sole criteria for selecting journals?

I am planning on submitting a paper to a mechanical or materials science journal. I am looking at these two journals  (IF 4.6) and  (IF 6.2). First one is published by Elsevier and is an old journal, while second one by The Journal of the Chinese Society for Metals and is a recent one. Considering, my paper fits the scope of both the journals, should a decision of submitting a paper be made solely on the basis of the impact factor? Is the second journal better than the first one?


What is a construct like "data found" (vs "found data") called?

I learned some time ago that in some cases the "characteristic" of an object, like "found" with respect to "data" is put after the object, i.e. if we found some data we should refer to them as "data found" not "found data". Example sentence:     The findData() function returns the data it finds. To use the data found, one must call useData().   I'd like to read more about this construct, but I'm having a hard time trying to formulate a Google query.  Thus my question, what is this construct called?


SEO: best way to deal with short lifetime URLs?

I am currently in the process of redesigning a job advert site and am trying to put a lot more effort into my SEO.  My question is how should I deal with the URLs that point to job adverts when the advert expires. The options I have thought of so far are:   Return a 404 error and redirect to a 404 page. Will it have an effect on ranking if there are a lot of URLs that return 404s after only being up for a few weeks? Redirect to job listing page - When the user requests a URL for an advert that has expired just redirect to the main job listing page. Show the advert but tell the user to has closed - Show the advert page but with a notification that the advert has closed. The issue I see with this is that the user will visit the page, see its closed and then leave the site again which would not be good for rankings


I have three classes  class A {     // pure virtual funcs and member vars     virtual ~A(); }  class B : public A {     // some more pure virtual funcs     virtual ~B(); }  class C : public B {      // concrete implementations      ~C() {} }   Presently this doesn't compile with an 'undefined reference to `typeinfo' error (~B() is not defined, easily fixable) however I'm wondering if just defining 'virtual ~B {}' is the correct thing to do or whether ~C should be virtual and defined so calls to ~B are dispatched to ~C?


Is powered delivered to an Incandescent light bulb changing with time?

Initially, when the current starts flowing the temperature of the filament is less and thus resistance is less. So, more current flows through the bulb and the power delivered to the bulb is more. As, time passes and the filament starts glowing at a steady rate its temperature has increased which in turn has increased its resistance. So, less current flows through it and thus less power is delivered.  Is this the case? Please help me understand the situation.


Parameter assignment not working as expected

I am working with binary search tree for class assignment. I'm trying to replace a node with a different node by assigning the new node to the recursive method parameter.  The line node = minNode(node.right); is not working as expected. It does modify the parameter SearchTreeNode<E> node but this change doesn't propagate to this.overallRoot. For example, if the root of the tree is 5, and we remove 5, and the substitute would be 7, this.overallRoot remains 5 even though the parameter node has been changed to 7. See screenshots below.  Any idea what I'm doing wrong?  public void remove(E data) {     if (this.overallRoot != null) {         this.removeData(this.overallRoot, data);     } }  private void removeData(SearchTreeNode<E> node, E data) {     if (node.data == data) {         if (node.left == null && node.right == null) {             node = null;         } else if (node.left != null && node.right != null) {             node = minNode(node.right);         } else if (node.right == null) {             node = node.left;         } else if (node.left == null) {             node = node.right;         }     } else if (data.compareTo(node.data) < 0) {         this.removeData(node.left, data);     } else if (data.compareTo(node.data) > 0) {         this.removeData(node.right, data);     } }  private SearchTreeNode<E> minNode(SearchTreeNode<E> node) {     if (node.left == null) {         return node;     }     return minNode(node.left); }


As I was adjusting my settings I realized that my GPU is not recognized for CUDA at Cycles tab. I tried everything afterward to make it appear- went to Nvidia developers website to download CUDA toolkit(10 version as 11 is not supported on MacOs), reinstall blender, etc.. but it still does not work... Could anyone please help me here? Thanks for your help!


Can the Ubuntu logo be used for a commercial website?

Is there an Ubuntu logo that can be used on a commercial website to indicate that Ubuntu can be installed for customers?


Is there a reason why my wordpress PHP page isn't loading into my PHP template

Please bear with me because I am new to utilizing Wordpress PHP this way. I have the following script:
 <?php     // check if the repeater field has rows of data     if( have_rows('repeat_field') ):         $i = 0;          // loop through the rows of data         while ( have_rows('repeat_field') ) : the_row();             $i++;              // display a sub field value             if (!empty(get_sub_field('feature_image_post'))) {                  echo '';             }              if( $i >= 78 ) {                 break;             }                     endwhile;     else :         // no rows found     endif;     ?>

        The the Php page that I am trying to load pretty much contains the same code . It just stops after loading 200 fields.   <?php     // check if the repeater field has rows of data     if( have_rows('repeat_field') ):         $i = 0;         // loop through the rows of data         while ( have_rows('repeat_field') ) : the_row();             $i++;             // display a sub field value             if (!empty(get_sub_field('feature_image_post'))) {                 echo '';             }              if( $i >= 200 ){               break;             }                      endwhile;     else :         // no rows found     endif; ?>   I don't know why the php page (post-2.php) is not loading. The strange thing is that when I replace <?php echo get_stylesheet_directory_uri();?>/post-2.php with a test html page <?php echo get_stylesheet_directory_uri();?>/test.html The test page (test.html) loads.  I have to say that I looked on in my console using the console tab of my browser added console.log(); to view any errors and I'm not getting any errors. I also looked in my networked tag to ensure that post-2.php loaded properly and I'm not getting errors. My goal is to find out why my PHP page isn't loading  ***** Update ***** I'm being told to use $post_id but I've never used it. Does anyone have a working example of this? Would it be similar to if( have_rows('repeat_field', $post_id) ): or if( have_rows('repeat_field', 55612) ): ?


Understanding $\sum_{x = 0}^y x = \frac{y(y + 1)}{2}$ in a step of a proof

I have the following problem:  Suppose that $Y \sim \text{Poi}(1)$. Let $y \ge 0$ be an integer. Given that $Y = y$, suppose that $X$ has the discrete uniform law on $\{ 0, 1, \dots, y \}$. (a) Show that $E[X \vert Y] = \dfrac{1}{2}Y$, and use this to find $E[X]$.  The provided solution is as follows:  We are given that $P(X = x \vert Y = y) = (y + 1)^{-1}$ for $x \in \{ 0, 1, \dots, y \}$, and $P(X = x \vert Y = y) = 0$ otherwise. (a) From the conditional PMF, we can compute the conditional expectation of $X$ given $Y = y$: $$\begin{align} E[X \vert Y = y] &= \sum_{x = 0}^y xP(X = x \vert Y = y) \\ &= (y + 1)^{-1} \sum_{x = 0}^y x \\ &= (y + 1)^{-1} \left[ \dfrac{y(y + 1)}{2} \right] \\ &= \dfrac{y}{2}. \end{align}$$ Therefore, $E[X \vert Y] = \dfrac{Y}{2}$. Now, since $Y \sim \text{Poi}(1)$, we know that $E[Y] = 1$. We now compute $E[X]$ using the law of total expectation: $$\begin{align} E[X] &= E[E[X \vert Y]] \\ &= E \left[ \dfrac{Y}{2} \right] \\ &= \dfrac{1}{2} E[Y] \\ &= \left( \dfrac{1}{2} \right) (1) \\ &= \dfrac{1}{2}. \end{align}$$  How is it that $\sum\limits_{x = 0}^y x = \dfrac{y(y + 1)}{2}$? I would appreciate it if someone would please take the time to explain this.


Libreoffice PPA 4.1.x for latest Ubuntu version

I am looking for a PPA that has LibreOffice 4.1. Even though it is in Beta I wish to test it out via a PPA. So is there a PPA that has the LibreOffice 4.1.x branch?


Ring of trigonometric functions with real coefficients

Let $R$ be the ring of functions that are polynomials in $\cos t$ and $\sin t$ with real coefficients.    Prove that $R$ is isomorphic to $\mathbb R[x,y]/(x^2+y^2-1)$.  Prove that $R$ is not a unique factorization domain. Prove that $S=\mathbb C[x,y]/(x^2+y^2-1)$ is a principal ideal domain and hence a unique factorization domain.  Determine the units of the rings $S$ and $R$. (Hint: Show that $S$ is isomorphic to the Laurent polynomial ring $\mathbb C[u,u^{-1}]$.)


Output to be saved in file named same as the input file

I have one input file and run some command but want the output to be saved with the same name as the input file has.  I tried below command but it makes the output file blank:  cat file1 | grep "YISHA" > file1


The question is:     Are there square matrices $A,B$ over $\mathbb{C}$ s.t. $A^2+B^2=AB$ and $BA-AB$ is non-singular?   From $A^2+B^2=AB$ one could obtain $A^3+B^3=0$. Can we get something from this?  Edit:  $$A^2+B^2=AB\implies\\ A(A^2+B^2)=A^2B \implies\\ A^3+AB^2=A^2B \implies \\ A^3+(A^2+B^2)B=A^2B \implies \\  A^3+A^2B+B^3=A^2B \implies \\ A^3+B^3=0 $$


I have conducted PCA that has reduced the dimensions of my data from more than 20 to 7 (7 PCAs explain about 85% of the total variation). As a second step, I have to cluster my data based on these new 7 PCAs. My question is: how I should reconstruct/transform my data (cbind/rbind)? As I understand, each PCA is a weighted mix of the original variables. So should I just replace the old variables with the PCAs? Also, how should I interpret the final results? If there was no PCA, each cluster would incorporate all variables in some proportion. But after PCA, how would I describe each cluster? For instance, cluster 1 contains 40% of PCA 1 and PCA 1, in turn, has xxx loading scores? Something like this? Would greatly appreciate any help on interpreting this. Thanks!


Manga where the main character dies because of an evil god who messes up his reincarnation

So in this manga, it turns out the MC died because of an evil god having messed with his fate? So they were going to reincarnate him as an apology but the evil god messed with his life again so his abilities showed up late. He was disowned by his noble family and started working as an adventure, apparently he is strong with magic abilities and cannot be appraised by some others, meets the royal family, teachers the princess I think, and eventually gets adopted by a receptionist ex adventure guy who is the savior of the town.


A real palace of a house That idiot of a doctor  Would you show me the phrases above in some other ways that mean the same thing? Any comment would be appreciated


Selectively coloring text in RichTextBox

How can I paint in red every time I meet the letter "A" in RichTextBox?


Deselect messages easier in the new mobile chat

If you select a message in the new mobile chat the only way to deselect it is to tap the x in the upper left corner.  I think it would make more sense if you could also deselect it by tapping on the message again or tapping on the white space that appears where the text box used to be.


Is it possible to have Unity and Gnome3 installed at the same time, and then be able to switch between them?  I currently running Ubuntu 13.04 with Unity, and really want to try the Gnome3 desktop, but I still wan't to be able to use unity if I don't like it.


Eigenspace of the companion matrix of a monic polynomial

How do I prove that the eigenspace of an $n\times n$ companion matrix  $$ C_p=\begin{bmatrix} 0 & 1 & 0 &\cdots & 0\\ 0 & 0 & 1 &\cdots & 0 \\ \vdots&\vdots &\vdots&\ddots&\vdots\\ 0 & 0 & 0 &\cdots &1 \\ -\alpha_0 &-\alpha_1 &-\alpha_2 &\cdots&-\alpha_{n-1} \end{bmatrix} $$ equals $\operatorname{Span}\{v_{\lambda} \} $ where $v_{\lambda}$ is an eigenvector of the companion matrix w.r.t. the eigenvalue $\lambda$: $$ v_{\lambda} =  \begin{bmatrix} 1 \\ \lambda\\ \lambda^{2} \\ \vdots\\ \lambda^{n-1} \end{bmatrix}. $$


Why have solutions to the obstacles for the Philospher's Stone?

While I'm not debating the difficulty of the obstacles presented in the Philospher's Stone, it would seem to me that it would make more sense to just guard it.  In the cases of the potions, the keys, and the chess, why present solutions to the user?  Why not simply present a wall of fire, an enchanted door that's nigh on impossible to unlock, and some stone guardians one has to fight?


I would like to have a command \simrightarrow, that is, a \rightarrow with a \sim over it. Stealing  from @egreg, I got:  \documentclass{article}  \usepackage{unicode-math}    \newcommand{\simrightarrow}{\mathrel{\ooalign{      $\to$\cr      \hidewidth\raise.3em\hbox{$\sim\mkern3mu$}\cr     }   } }   \begin{document} \( M \simrightarrow N \) \end{document}   However, the tilde is still too big. How can I scale it down?


Installing Ubuntu 17.04 (in dual boot with Windows 10): Bootloader failed to install

After deciding elementary OS is too temperamental for my laptop, I decided to replace it with Ubuntu 17.04. I have Windows 10 installed in a separate partition and have successfully dual booted Linux in the past. This time, however, towards the very end of the installation process, I get a warning telling me that the installer was unable to install the Grub2 bootloader.  I am using a USB installation media created using Rufus 2.15. Following the advice of answers to various similar questions, I have so far ensured that the installation media is created on a freshly FAT32-formatted USB stick, and have attempted installation both directly from the boot menu and from a Live session. I also ran the boot-info utility that generated a .


Can you help me find the inverse function for $y = x^3 + x$?  This question was posed at the beginning of AP Calculus, so we can't use any math beyond precalc.  Thanks!


How can you account for COVID-19 in your models?

How are you dealing with the  in your machine learning models? Let's say you used to predict the number of sales each month. The virus affected your results last year and it will affect for at least a couple of months. So your model, I guess, is missing a lot. What are some approaches we can use to fix our models?


Can someone please tell the Usage of "its" in the following is correct?

Here is a quote from "Ever Wonder Why / the color red angers a bull? " (page 20).     It has been suggested that this reaction to red (my note: of bull which is color-blind to a shaking cape in red) may be due to its being the color of blood.   My question : the above "its" should be "it"?


Do any of the characters from GTA: San Andreas make an appearance in GTA 5?

I just bought Grand Theft Auto 5, and I am looking forward to playing it. But I'd like to know whether any of the old characters make an appearance in the new game.  I know the new game is based around new protagonists, but do any of the old characters (such as Carl Johnson, The Truth, Sweet etc) make an appearance? If so, is it simply a cameo, or are they interwoven into the storyline?


different wallpaper for each workspace ubuntu 14.04

so how to select different wallpaper for each workspace in Ubuntu 14.04?  I've tried to install unity-tweak but didn't found anything about having different background image for each workspace...


What's the proper way to install NVidia drivers now?

BACKGROUND:  Once upon a time, when I installed Ubuntu 10.x on an older machine, and kept upgrading it until 13.04 or 13.10, there was an easy-to-find option in Settings that allowed to install NVidia's proprietary drivers and keep them up to date (or not, because sometimes they released a new version with a bunch of awful regressions).  Now, when I installed 13.10 on my new laptop, which I then upgraded to 14.04, I haven't ever been able to find that option anywhere.  An attempt to install nvidia drivers with apt-get dont-remember-what resulted in a screwed up system that wouldn't properly start Unity (or even xorg, not sure), roughly equivalent to an unbootable system. But I managed to revert that.  I seem to understand that there are some sort of opensource drivers called "nouveau" that come by default in Ubuntu which kind of provide an alternative to NVidia's proprietary drivers. Is that so?   THE PRACTICAL QUESTIONS:   Is it ok to not install NVidia's drivers, or am I underutilizing the potential of the GPU (i.e. not using all the available hardware acceleration)? Or in other words: is there a test I can run to check whether hardware acceleration of my GPU is being properly used with my current setup (nouveau or whatever it is)? What's the proper recommended way to install NVidia proprietary drivers now on Ubuntu 14.04, without bricking the system?


basic linear algebra question, proving it is a diagonal matrix and scalar matrix.

Let A = $(a_{ij})_{n\times n}$ such that $AB = BA$ for every square matrix $B$ of order $n$.  $(I)$ Prove that $A$ is a diagonal matrix.  [Hint: Let $B_i$ denote the matrix whose $(i,i)$ entry is $1$, and $0$ elsewhere. Show that $a_{ij} = 0$ whenever $i ≠ j$.]  $(II)$ Prove that $A$ is a scalar matrix.  [Hint: For $i ≠ j$, let $B_{ij}$ denote the matrix whose $(i,j)$-entry is $1$ and $0$ elsewhere.Show that, $a_{ii} = a_{jj}$ for all $i ≠ j$.]  Can someone help me with this question using basic linear algebra concepts? Thanks.


Do I have to worry about copyright issues for code posted on Stack Overflow?

I was wondering about the copyright of code snippets from answers. Let's say you ask a question and the solution consists of ten lines of code, which are given in an answer. Are there any restrictions about the use of that code?   It seems that the content of this page is under the . So does one have to attribute the author if code is used in an open source project? Can it be legally used in closed source projects at all?  I guess ten lines of code are not really problematic, but is there a critical number of lines?


When I go into Setting / Wifi and try to turn Wifi on, it does not let me. The switch is grayed out.  How can I solve this issue?


Why are these techniques not feasible to crack RSA?

For $d = e^{-1} \mod \phi(n)$  $$d\cdot e \operatorname{mod} \phi(n)=1$$ $$d = (e^{-1} \operatorname{mod} \phi(n))$$  With having $e$ and $n$, we can calculate the value of $d$ , the private key for cracking. Why do people worry about factoring $d$ when this technique is available? I would like to know some real insight into this.


I have a large frozen haggis that I'd like to use for dinner Saturday night.  when do i start to thaw it, and whats the safest method of thawing to prevent both food borne illness and to preserve quality of the product?  I already read the question about cooking haggis from frozen, and decided I don't want to do that.


How do I give players already enchanted Tools/Armour/Weapons

I'm making a map where I want players to be able to choose there kits/classes. The problem I'm having with it though is giving players already enchanted Tools/Armour/Weapons.  I'm not sure if you can use the /give [player] [item] [amount] because you'll have to use the whole {} thing and I'm not sure how to make enchanted Tools/Armour/Weapons using that.  Can anyone help?


How can I make ascii-banners from the command line?

I've seen people using the terminal command: banner. This creates big ascii-art-style text.  When I try to run it, however, the terminal says it doesn't exist. Why?  How do I install it? Are there any alternatives?


QGIS 3.2.2 OpenLayers plugin isn't listed to install

I've just installed QGIS 3.2.2 and after installation, tried to use the Plug in Manager to install the OpenLayers plugin.  But it's not in the list to install.    Any ideas?


Evaluate $\lim\limits_{x \to a} \frac{x^m-a^m} {x-a}$

How to evaluate this:  $$\lim\limits_{x \to a} \frac{x^m-a^m} {x-a} ; m\in  \mathbb{N}$$   if i take:  $ m = 1  $   $$\lim\limits_{x \to a} \frac{x^1-a^1} {x-a} =1 $$  Is this correct?  but how evaluate limit where $ m = 2 $   $$\lim\limits_{x \to a} \frac{x^2-a^2} {x-a} =  ???$$


Problem to install or remove any software"lvm2-lvmetad.service"

I am trying to install or remove any software but I am facing the error below:  Failed to restart lvm2-lvmetad.service: Unit lvm2-lvmetad.socket is masked. invoke-rc.d: initscript lvm2-lvmetad, action "restart" failed. ● lvm2-lvmetad.service - LVM2 metadata daemon    Loaded: loaded (/lib/systemd/system/lvm2-lvmetad.service; static; vendor preset: enabled)    Active: active (exited) since Wed 2018-05-16 06:40:37 WAT; 1h 54min ago      Docs: man:lvmetad(8)     Tasks: 0 (limit: 4915)    CGroup: /system.slice/lvm2-lvmetad.service  May 16 06:40:37 raikone-X555UB systemd[1]: Starting LSB: LVM2 metadata daemon... May 16 06:40:37 raikone-X555UB systemd[1]: Started LSB: LVM2 metadata daemon. dpkg: error processing package lvm2 (--configure):  installed lvm2 package post-installation script subprocess returned error exit status 1 Processing triggers for shared-mime-info (1.9-2) ... Processing triggers for gnome-menus (3.13.3-11ubuntu1) ... Processing triggers for hicolor-icon-theme (0.17-2) ... Processing triggers for initramfs-tools (0.130ubuntu3) ... update-initramfs: Generating /boot/initrd.img-4.15.0-20-generic Errors were encountered while processing:  lvm2 E: Sub-process /usr/bin/dpkg returned an error code (1)   I tried to follow some tutorials here but didn't work for me.


This came up when reviewing a written English exercise, and I realized that I don't entirely trust my intuition on the answer.  Which of the following is correct?  Or are both valid?  (Or is it strongly advisable to rewrite the sentence in some other way?)   "I see what appears to be a man and his son." "I see what appear to be a man and his son."


I have attended an interview for java programmer ,After a few personal questions ,the interviewer have asked me the question "What is encapsalution and abstraction" I was really happy with question ,and i have answered it as hiding the implementation details that are not necessary for the user to know. And Abstraction is showing of only the important details to user. only seconds after my answering ,the interviewer had another question for me. showing of only the important details to user ,that means hiding irrelevant data like implementation details to user. is it?  I have replied it as yes!!!  There comes another question from .So what is the difference between abstraction and encapsolution .I think there is no difference according to your answer.  I was like i dont know ,My hands were frozen ,was a really bad day for me  Can any one explain how would you answer if someone asks such a question to you


Are there other explanations for slow tyre pressure loss?

I rode my road bike on Friday and the tyres were at the correct pressure then, around 100psi.  On Tuesday, I jumped on without checking them and quickly realised something was wrong with the rear tyre.  It wasn't completely flat but was fairly soft.  I hadn't gone far so went home and took the car to work instead.  When I got home later, I was surprised to find the tyre, while still soft, hadn't lost all pressure by any means.  It was around 40psi and felt the same as when I left it in the morning.  I decided there must be a slow leak somewhere, but I couldn't find one anywhere, putting the inner under water and going around it methodically looking for bubbles.  I've never failed to find a leak before that way.  I've switched it out anyway because I don't want to mess around with my commute, but I'm curious ... is there another explanation for that amount of pressure loss?  Or must there have been a puncture somewhere that I missed somehow?  The tyres (whole bike) are pretty new and in excellent condition.


I am getting Null pointer Exception input taking array buffereread

import java.util.Scanner; import java.io.*; class AraOfDigit{ public static void main(String[] args) throws IOException{   Scanner sc =new Scanner(System.in);  BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); PrintWriter wr = new PrintWriter(System.out); int iteration = sc.nextInt(); int count = 0; while(count<iteration){      int n = sc.nextInt();      int mod = sc.nextInt();      String arr [] = new String[n];       ****String[] arr_A =br.readLine().split(" ");****//Nullpointer Exception How to slove?        for(int i=0;i<n;i++) {         arr[i]=arr_A[i];         }            StringBuilder total = new StringBuilder();     for(int j=0;j<n;j++){       total.append(arr[j]);     }      int num = Integer.parseInt(total.toString());     num = num/10;      int op = num%mod;    System.out.println(op);    count++;    }  } }


Idempotent elements in $(\mathbb{Z}_n,+,\cdot)$

Can we find the idempotents in $(\mathbb{Z}_n,+,\cdot)$ for any $n$?  Is there a general rule?  Note: Trying to consider the prime factors!


'This is a not uncommon mistake.' 'This is not an uncommon mistake.' Are those sentences above both means 'This is somewhat common mistake.' ? or could they have different meanings?


How did this user post an answer *after* the question was put on hold?

was put on hold at 16:31.  However,  was then post afterwards 3 minutes later at 16:34.  How did the user do this? I thought answers were not allowed to be accepted after a post has been closed...?  I guess that this was possible because the user had started writing before the question was closed so it got through, but if this is the case, then this is a  because the 'Post answer' button should check to see whether the question is closed or not before allowing it, just like it checks to see whether the question has been deleted.


the diffrence between 2 method to initialize an array in Python 3

can you please someone explain to me the diffrence between the 2 statements:  l = [[None] * 3] * 4 for i in range(4):     for j in range(3):         if i == 0:             l[i][j] = 0 print(l)   M = [[None] * 3 for _ in range(4)] for i in range(4):     for j in range(3):         if i == 0:             M[i][j] = 0 print(M)   the output:  [[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]] # first statement [[0, 0, 0], [None, None, None], [None, None, None], [None, None, None]] # second statement


Can I copy Stack Overflow design, layout and color combination to create a new website?


Is there a way to  specify using regex to show results not containing specific text.Something similar to      Select * from table where id not in {3,4,6};


What's the difference between declaring a variable "id" and "NSObject *"?

In Objective-C, what's the difference between declaring a variable id versus declaring it NSObject *?


The auxiliary verb "will" for the pronoun "we" and "I" isn't correct?

I was told in the past by my teacher that the auxiliary verb "will" for the pronoun "we" and "I" isn't correct and it dhould be "shall" in the cases (i.g. "we shall be there" rather than "we will be there". But since normally I don't notice that people use "shall" I thought it is anarchonistic and it reflects the past. But yesterday I found this article () of Oxford dictionary which still claims that the correct one is shall.   Maybe some native speakers from different English speaking countries can tell us the reality about this issue.


$f(x)=\left(x-a_1\right)^2\left(x-a_2\right)^2\text{...}\left(x-a_n\right)^2+1$, where $a_1,a_2,\text{...},a_n$ are different integers.  Prove that $f(x)$ is irreducible in $\mathbb{Q}$ (rational fileld).  One thought:  $f(x)$ is a polynomial with integer coefficients, and assume $p$ is an root of $f(x)$, then $f(p)\geq 1$, there is no possible to make $f(p)=0$, so $f(x)$ is irreducible,   I think my thought is too easy, and is wrong...


Callouts in triggers not currently supported?

I'm getting an error when I am call non void method from REST API class. Trying to add the Rest Response id in contract object.  trigger RestAPIcalloutTrigger on Contract (after insert , after Update) {      Integer CaseID;      CreateCasesByContract cc = New CreateCasesByContract();     List<Contract> CList = New List<Contract>();     for(Contract c : Trigger.New)     {          if(c.Broker_Involved__c ==  'yes' )         {              c.BCR_Case_Id__c = cc.CreateCase();             c.BCR_Case_URL__c = 'http://cases.boxerproperty.com/ViewCase.aspx?CaseID='+ c.BCR_Case_Id__c;         }          CList.add(c);     }        Update CList;  }   The error is "Callout from triggers are currently not supported".


How to retrieve the first n characters of a variable in Bash?

How to retrieve the first 10 characters of a variable with Bash?  FOO="qwertzuiopasdfghjklyxcvbnm"   I need to get qwertzuiop.


How do threads work in Python, and what are common Python-threading specific pitfalls?

I've been trying to wrap my head around how threads work in Python, and it's hard to find good information on how they operate. I may just be missing a link or something, but it seems like the official documentation isn't very thorough on the subject, and I haven't been able to find a good write-up.  From what I can tell, only one thread can be running at once, and the active thread switches every 10 instructions or so?  Where is there a good explanation, or can you provide one? It would also be very nice to be aware of common problems that you run into while using threads with Python.