Iterating over 2D list using asterisk (*) operator

I saw this piece of code being used to iterate over a 2D list column-wise:  """ grid: List[List(int)] """ for col in zip(*grid):     ...   Could someone explain exactly how this works?  EDIT:  Duplicate of  question, but not  one.  I still don't understand exactly how zip(*_) converts rows into columns.


I'm trying to disable IPv6 on all of the adapters on an Ubuntu 17.10 machine. I used to be able to do so (prior Ubuntu versions) by editing /etc/sysctl.d/99-sysctl.conf to add disable parameters as follows:  echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.d/99-sysctl.conf echo "net.ipv6.conf.default.disable_ipv6 = 1" >> /etc/sysctl.d/99-sysctl.conf echo "net.ipv6.conf.lo.disable_ipv6 = 1" >> /etc/sysctl.d/99-sysctl.conf   then reloading the parameters with:  sysctl -p   With Ubuntu 17.10, this works for the current session (i.e., ifconfig or ip address will show only IPv4 addresses), but IPv6 addresses come back after a reboot. (FWIW, I also have dhcp6: no set for each adapter in the netplan 01-netcfg.yaml file, so the IPv6 address associated with each adapter is a default one.)  How do I disable IPv6 permanently on an Ubuntu 17.10 (netplan) machine?  Update  Since this was marked as an "exact duplicate" of , I'll defend my question by noting that   That answer, which I had seen, appears to be a last resort ("If your PC doesn't load /etc/sysctl.conf at boot time"). I think Ubuntu 17.10 does load /etc/sysctl.d/99-sysctl.conf at startup (though I'll do some research to confirm this if no one who knows responds to this), and There has to be a more elegant (or "correct") way to disable IPv6 within Ubuntu. I can think of lots of kludgy ways to disable IPv6 (cron script run at boot, this grub fix, etc.), but I'm worried about portability across, for example, kernel updates (will my grub edits persist across updates, or will I need to make the same edits each time?).   Since this problem appears to have started only with the move to netplan instead of /etc/network/interfaces, I'm hoping someone familiar with netplan network configuration will weigh in.  Sorry if I sound defensive, but I try very hard to do my homework first and not to post duplicate questions.


Quantum Mechanics - How do we know that the observed locations of electrons are random?

How do we know that the observed location of a electron (or any quantum object) is purely random (there is no way to predict it) within the probability-function instead of normal randomness (we don't know how to predict it)?  As an analogy if someone would only be able to measure the amount of people (amount of electrons) and their individual IQ (location) he would see a perfect distribution (obviously only if he has enough samples) within a specific range (probability) and each individual measurement seems purely random (QM-randomness). He would then assume that their IQ is purely random as he has just not enough knowledge to prove otherwise (he hasn't spoken to any of them, hasn't analysed any in respect to education nor has he analysed their DNA).  Could the same be happening when we observe electrons or have we proven that their location is purely random?


Is the word and equivalent to the && operator?  if (inner > 10 and !id) {     std::cout << "idle" << std::endl; }   This code was originally translated from Python.  I was sure that the 'if' line would result in a compilation error. But it does pass.  Visual studio (2015) marks it as an error, but it does compile with g++ (and also on this site ) and seems to run as expected.   Is this correct syntax or did I miss something?


Not able to register for Sales Cloud Consultant certification?

I have a Platform Developer 1 certification and a DEV401 certification . Currently i have applied for Platform App Builder Transition Certification .  I am unable to register for Sales Cloud exam ? do you please what might be the reason ?  So i again do Administration certification also in order to take Sales Cloud certification ?


Is there a way to create Barcodes (128 standard) on a Mac, preferably via an add-in?  I need it to create barcodes in Excel sheets (or moreso a friend of mine needs it).   I have tried all VBA macros and fonts I found on Google, but none give me a scannable result (usually there are weird characters like ó's mixed in). Does anybody have a working solution?


Find the height of a square "pyramid" *General Form*

This is the general shape of a pyramid stacked using squares. For example, the first layer would have 1 sphere, the second layer would have 4, and each layer would have $n^2$ spheres. I want to know a general formula of the height with $n$ layers expressed with $r$ as a function of $h_n(r)$. I've made to $n=2$ so far, but I can't figure out the height beyond $2$ or even the general form. My progress: Obviously, we know that the height if it's 1 layer would be $2r$, or $h_1(r)=2r$. It is also relatively easy if we have $2$ layers. We can construct a pyramid by connecting the $5$ centers. Using Pythagorean theorem, we can know that the middle portion is $\sqrt{2}r$. Therefore, the total height would be $h_2(r)=r(2+\sqrt{2})$ I start to struggle with $3$ layers. Please help me solving for that as well as a general form. Hopefully this version is more detailed and well-written question.


Minecraft command to clear all but one item entity (tile) type

I've got a capture the flag arena. One issue we keep running into during play, is that of clutter.  We have /gamerule keepInventory false, so the pitch gets rather cluttered with armor, weapons and building materials, such that it becomes difficult to pick the flag up, due to full inventories.  I've discovered the following command to remove all drops from the arena:  /kill @e[type=Item]   However, this removes all the floating items from the ground. I'd like, if possible, to preserve the flag from being destroyed.  I have this command for detecting the flag:  /testfor @e[type=Item,x=40,y=1,z=40,dx=40,dy=27,dz=80] {Item:{id:"minecraft:banner",Damage:4s}}   But I'm not sure how to combine the two in a way that it will destroy everything except for the flag.  Any ideas?


sudo apt-get -f install error, how to remove or reinstall corrupted packages

I need to install libgl1-mesa-dev lib on Ubuntu 14.0.4, because  QT 5.5 depends on this lib. I run following command and gets error, How can i fix this error:  $ sudo apt-get install build-essential libgl1-mesa-dev Reading package lists... Done Building dependency tree        Reading state information... Done build-essential is already the newest version. You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies:  libcheese-dev : Depends: libcheese3 (= 3.4.1-0ubuntu2.1) but it is not installable                  Depends: gir1.2-cheese-3.0 (= 3.4.1-0ubuntu2.1) but it is not going to be installed                  Depends: libglib2.0-dev (>= 2.28.0) but it is not going to be installed                  Depends: libclutter-1.0-dev (>= 1.6.1) but it is not going to be installed                  Depends: libgstreamer0.10-dev (>= 0.10.32) but it is not going to be installed                  Depends: libgstreamer-plugins-base0.10-dev (>= 0.10.32) but it is not going to be installed                  Depends: libgdk-pixbuf2.0-dev but it is not going to be installed  libcheese-gtk-dev : Depends: libcheese-gtk21 (= 3.4.0-0ubuntu1) but 3.4.1-0ubuntu2 is to be installed                      Depends: libcheese-dev (= 3.4.0-0ubuntu1) but 3.4.1-0ubuntu2.1 is to be installed                      Depends: libglib2.0-dev (>= 2.28.0) but it is not going to be installed                      Depends: libgtk-3-dev (>= 2.99.4) but it is not going to be installed                      Depends: libgstreamer0.10-dev (>= 0.10.32) but it is not going to be installed                      Depends: libgstreamer-plugins-base0.10-dev (>= 0.10.32) but it is not going to be installed                      Depends: libclutter-gtk-1.0-dev (>= 0.91.8) but it is not going to be installed                      Depends: libcanberra-gtk3-dev (>= 0.26) but it is not going to be installed  libcheese-gtk21 : Depends: libcheese3 (>= 3.3.5) but it is not installable                    Depends: libcogl9 (>= 1.7.4) but it is not installable                    Depends: libmx-1.0-2 (>= 1.2.0) but it is not going to be installed                    Depends: cheese-common (= 3.4.1-0ubuntu2) but 3.10.2-0ubuntu2 is to be installed  libgl1-mesa-dev : Depends: mesa-common-dev (= 10.1.0-4ubuntu5) but 8.0.4-0ubuntu0.6 is to be installed                    Depends: libgl1-mesa-glx (= 10.1.0-4ubuntu5)                    Depends: libx11-xcb-dev but it is not going to be installed                    Depends: libxcb-dri3-dev but it is not going to be installed                    Depends: libxcb-present-dev but it is not going to be installed                    Depends: libxcb-sync-dev but it is not going to be installed                    Depends: libxshmfence-dev but it is not going to be installed                    Depends: libxcb-dri2-0-dev but it is not going to be installed                    Depends: libxcb-glx0-dev but it is not going to be installed                    Depends: libxdamage-dev but it is not going to be installed                    Depends: libxxf86vm-dev but it is not going to be installed                    Depends: x11proto-dri2-dev (>= 2.6) but it is not going to be installed                    Depends: x11proto-gl-dev (>= 1.4.14) but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   Regards, Davit


Prove that sequence $ x_{(n+1)}= \frac {a}{1+x_n}$ is convergent to positive root of $x^2+x-a=0,$where $a >0$ and $x_1 >0$

Prove that sequence $$ x_{(n+1)}= \frac {a}{1+x_n}$$ is convergent to positive root of $x^2+x-a=0,$where $a >0$ and $x_1 >0$  we have $$x_{(n+2)}-x_n=\frac{-a(x_{(n+1)}-x_{(n-1)})}{(1+x_{(n-1)})(1+x_{(n+1)})}$$  Hence from this we see behaviour of even terms subsequence and odd terms subsequence  is opposite. how to proceed from there. any hint please


Does it matter that people "Game" Badges?

Lets be honest with ourselves does it really matter that people are gaming badges/rep?  Surely if someone is so obsessed with rep that they are willing to go to any length to get it, that's their problem?  I use SO to get questions I can't find the answer to answered, I don't care if the person who answers it has 1 rep or 100,000 rep. If the answer is correct thats all that matters.  If it's wrong I'll vote it down, if it's correct or kind of correct I'll vote it up and maybe comment on it.  Most of the badges could be gamed, but some person some where having "all teh badgezors" is no skin off my backnose. I don't care so long as when I have a question someone is willing to answer it.  I'm all for the community, I answer questions when I can and when it's not already been answered, I up/down vote things as I think is appropriate. Usually I'm motivated by making the community a better place, sometimes I'm motivated by making my rep a round number (I was so chuffed when my rep hit 1337) but I really don't care about who has what badges, sure I feel a little fuzzy inside when I (legitimately) get a badge, because I can see that I have benefited the community in some way, I'm not worried about the penis measuring that seems to make so many people go off the rocker. Who cares if people have more rep than you or don't legitimately have badges?  Fair enough more rep leads to higher levels of privilege but badges don't mean squat, if someone has low enough self esteem that the only way they can get their kicks is by getting virtual badges to put on their virtual sash well they have bigger problems that badge gaming. And why should we care?


When is energy converted to mass? What are the required conditions to do so?

I want to know whether every kind of energy is converted to mass like kinetic and potential energy? Is it only possible for particles like electrons and protons or even either for big objects like a car or bus. Please consider the minutest / smallest change in mass even 0.000000000000000000000001 kg of gain in mass? I mean "relativistic mass" in case when the object is moving and "rest mass" in case when the object is at rest. Can Rest mass too can increase when the gravitational potential energy of an object increases


Is it OK to ask and answer a general question?

I was getting a certain error for a while. It took long reads and days to fix it. This error could have several causes, and I learned a few of them fixing mine.  So, I was thinking about asking and answering a question to group some causes and fixes in a single thread. However, doing that will cause me to ask a general question, "What are some causes and fixes for this error?", which could be downvoted/closed for being too broad.  Is it fine if I do that? I think that would be helpful for other people.  (Note that my meta question is somewhat similar to , except that that one is about changing a question, not asking a new one.)


matrix transpose function not working properly

I have a matrix which i want to transpose and I've done this before and it's worked, but it's only today while I've been going through my code and updating it that it has suddenly stopped working. I really don't know why, as it has worked fine before. Here's the main bit of code  class Matrix:     def __init__(self, cols, rows):         self.cols = cols         self.rows = rows         self.matrix = [[0]*self.rows]]*self.cols      def transpose(self):         transposed_matrix = Matrix(self.rows, self.cols)          for i in range(self.cols):             for j in range(self.rows):                 transposed_matrix.matrix[j][i] = self.matrix[i][j]          return transposed_matrix   So say I have a matrix like this  [      [0, 1, 1, 0, 0, 0]      [1, -1, 0, 0, 0, -1]      [-1, -1, 0, -1, 1, 0]      [-1, 1, -1, -1, -1, 0] ]   I'm expecting   [     [0, 1, -1, -1]     [1, -1, -1, 1]     [1, 0, 0, -1, -1]     [0, 0, -1, -1]     [0, 0, 1, -1]     [0, -1, 0, 0] ]   But instead I'm getting  [     [0, -1, 0, 0]     [0, -1, 0, 0]     [0, -1, 0, 0]     [0, -1, 0, 0]     [0, -1, 0, 0]     [0, -1, 0, 0] ]   If you can help shed some light on this then that would be really appreciated


The 'microsoft.ace.oledb.12.0' provider is not registered error

I know that this must have been asked but I think I have tried all the suggestions written.  I am using:   Win 7 x64 Office 2010(32 bit). MSFT Access Database 2010(32 bit) MSFT Office Access Database engine 2007.   My project is ANY CPU but still getting this error. Here is my connection string   "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + fileLocation + ";   Extended Properties=\"Excel 12.0;HDR=Yes;IMEX=1\";"   I have also checked my App Pool is currently set to False for 32 bit applications.  Any ideas guys?


What website is appropriate for asking questions related to legitimacy, details of online websites?

I wanted to buy a few parts so after searching I came upon this website. I want to know if this website is fake so which website is appropriate for asking this question?


What item should I use to keep track of my creature’s Power and Toughness?

I’m a new player to MTG and I was wondering what item I should use to keep track of the Power and Toughness in my creatures. Like if I would enchant one of my creatures with a +1/+1 I would need to be able to show it right? I thought I could use dice but I saw many people online discourage it because it can get knocked down easily and other problems. I don’t know if I should use dice or use something more convenient and better.


Geolocation distance SQL from a cities table

So I have this function to calculate nearest cities based on latitude, longitude and radius parameters.  DELIMITER $$ DROP PROCEDURE IF EXISTS `world_db`.`geolocate_close_cities`$$ CREATE PROCEDURE `geolocate_close_cities`(IN p_latitude DECIMAL(8,2), p_longitude DECIMAL(8,2), IN p_radius INTEGER(5)) BEGIN         SELECT id, country_id, longitude, latitude, city,         truncate((degrees(acos( sin(radians(latitude))          * sin(radians(p_latitude))          + cos(radians(latitude))          * cos(radians(p_latitude))          * cos(radians(p_longitude - longitude) ) ) )          * 69.09*1.6),1) as distance          FROM cities         HAVING distance < p_radius         ORDER BY distance desc;     END$$  DELIMITER ;   Here's the structure of my cities table:  > +------------+-------------+------+-----+---------+----------------+ | > Field      | Type        | Null | Key | Default | Extra          | > +------------+-------------+------+-----+---------+----------------+ | > id         | int(11)     | NO   | PRI | NULL    | auto_increment | | > country_id | smallint(6) | NO   |     | NULL    |                | | > region_id  | smallint(6) | NO   |     | NULL    |                | | > city       | varchar(45) | NO   |     | NULL    |                | | > latitude   | float       | NO   |     | NULL    |                | | > longitude  | float       | NO   |     | NULL    |                | | > timezone   | varchar(10) | NO   |     | NULL    |                | | > dma_id     | smallint(6) | YES  |     | NULL    |                | | > code       | varchar(4)  | YES  |     | NULL    |                | > +------------+-------------+------+-----+---------+----------------+   It works very well.  What i'd lke to do (pseudcode) is something like:  SELECT * FROM cities WHERE DISTANCE(SELECT id FROM cities WHERE id={cityId}, {km))    and it'll return me the closest cities.  Any ideas of how I can do this?  At the moment, I just call the function, and then iterate through the ids into an array and then perform a WHEREIN in the city table which obviously isn't very efficient.  Any help is MUCH appreciated. Thanks.


We have the sum:  $\sum\nolimits_{n=0}^\infty \frac{n}{n!}$  Why is this sum a representation of $e$ when the sum:  $\sum\nolimits_{n=0}^\infty \frac{1}{n!}$  is already a representation of $e$?  For me it seams that the first row is greater then the second.


Black screen and cursor only when I log in in 13.10

When I log in to my user account, or guest or any other, I get a black screen and I can see a cursor icon and move it.  But nothing else is on screen, can't run commands with ALT-F2, meta keys don't do anything it seems. I can switch to another console, but the graphical interface does not work.  Even if I create another user account or guest account, it's still the same.  I've installed gnome from terminal (with lightdm though) and it is the same.   What could be the problem here, how can I reset stuff?  I have tried installing gnome, switching to gdm etc.  I have Ubuntu 13.10 installed (about 10 days ago). Didn't do anything funky recently or install new software before the incident, it just got b0rked suddenly.  Update: When I startX from 'nother console, the log says that the stuff is initializing. The last thing done is I see:  Loading extension GLX (II) [KMS] Kernel modesetting enabled. The XKEYBOARD keymap compiler (xkbcomp) reports: > Warning:           Type "ONE_LEVEL" has 1 levels, but <RALT> has 2 symbols >                    Ignoring extra symbols  Errors from xkbcomp are not fatal to the X server


Is the splitting field equal to the quotient $k[x]/(f(x))$ for finite fields?

maybe that's an idiot question. Given a finite field $k$ and some irreducible polynomial $f(x) \in k[x]$, then $k_f \cong k[x]/(f(x))$? I know that it's true if $k$ is the prime field and I think that the statement is not true for general finite fields, however I could not find any counter example.  Thanks in advance.


I have noticed that BBC will frequently not use closing quotes when quoting long paragraphs of text, as an example it occurs twice in this article:   Here:     "One application we are working on is indoor navigation which means we   have sensors within the shoe that measure the acceleration of the   foot, the angular velocity - whether you're turning the foot or not -   and the magnetic field.   and here:     "Generated power scales with size, but if you want to be able to   reasonably integrate such a device within a shoe sole, you have to   work with strict constraints, like a small height and limited length   of the device.   Is this correct? This is not just an editor's oversight, they do it frequently.  Why do they omit the closing quote, is it because the end of the paragraph implies the end of the quote?


Professionals: Would you choose GIMP over Photoshop and/or Inkscape over Illustrator?

I know Adobe's solutions are more advanced, but, as professionals, do you think you would survive (against competition) using GIMP and/or Inkscape instead of Photoshop and/or Illustrator for your actual work?  Would it be worth it or would it actually complicate your work?  I am specially interested to see if there is anyone that actually made the switch to the open source solutions and know why you did it.  My question is with regards to the possibility of fully divorcing from Adobe's solutions and still being able to function as a graphic design studio.


Does anyone here know how to print elements from the array one by one? I have this code here:   import java.util.ArrayList; import java.util.Iterator;  public class SimpleCollection {      private String name;     private ArrayList<String> elements;      public SimpleCollection(String name) {         this.name = name;         this.elements = new ArrayList<>();     }      public void add(String element) {         this.elements.add(element);     }      public ArrayList<String> getElements() {         return this.elements;     }      public String toString(){         String printOutput = "The collection "+ this.name+ " has "+ elements.size()+ " elements: ";         String e = "";         if(elements.isEmpty()){             return(printOutput+ " is empty.");         }if(elements.size()==1){             return "The collection "+ this.name+ " has "+ elements.size()+" element:"+ "\n"+ elements.get(0)+ "\n";          }             e = printOutput + "\n"+ getElements() + "\n";          return e;     }  }   The toString method of mine prints elements as an array: how can i print them one by one? Something like:  The collection characters has 3 elements: magneto mystique  phoenix


Ubuntu 20.04 Software Installation Issue

On Ubuntu 20.04 I installed Bluemail.  Then I tried to use the Software app to install an app called "Info Center" and got "Error while installing package: installed bluemail package post-installation script subprocess returned error exit status 1".    When I ran "sudo apt-get install -f", I got:  sudo apt-get install -f  Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded. 1 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Setting up bluemail (1.1.14-536) ... Installing curl... E: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 18429 (apt-get) E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it? Unable to install curl! dpkg: error processing package bluemail (--configure):  installed bluemail package post-installation script subprocess returned error exit status 1 Errors were encountered while processing:  bluemail E: Sub-process /usr/bin/dpkg returned an error code (1).   Bluemail is installed and working properly and I have rebooted, so I am not sure why this error is lingering around.  Can someone clue me in on how to clear it?


Tensor product of a sheaf of module and a residue field

Let $S$ be a scheme over a finite field $\mathbb{F}_q$ and $\mathcal{L}$ an invertible sheaf on $S$.   In Pink's article (, see section 1.4 on page 13), he states that:  For any section $\ell\in \mathcal{L}(S)$ and any point $s\in S$ we let $\ell(s)\in \mathcal{L}\otimes_{\mathcal{O}_S}k(s)$ denote the value of $\ell$ over the residue field $k(s)$ of $s$.  My question is: what is the definition of $\mathcal{L}\otimes_{\mathcal{O}_S}k(s)$?  We know we can define the tensor product of two $A$-modules or of two $\mathcal{O}_X$-modules, but what is the tensor product of an $\mathcal{O}_X$-module and a field?


The Prime Minister said: "I have indicated in opening remarks that I do not intend to be Prime Ministerial candidate if the UPA were to come to power after the general elections. BJP leader Narendra Modi will prove to be "disastrous" for India if he were to become the Prime Minister, Prime Minister Manmohan Singh said.  What does the use of were to in above sentences indicate? If I don't use were to, does it then mean something different? Or can I use only were instead?


Retagging questions in terms of possible answer technologies

When entering the title of this query I was pointed to , which has tentatively endorsed this concept, especially once an answer has been accepted.  Can I get a confirmation that it is actually good practice before an answer has been accepted? (IMHO it is not.)  Two examples:   : I didn't need a WCF answer, which I would have assumed if I had seen the question tagged with WCF even if I didn't mention it in the question or title.   : It looks probable that the answer (if there is one) is related to AOP, but the questioner does not require it.


Spinning wheel has pauses after each rotation?

there is a part of my model that I want to be spinning at the same velocity forever. However, every time the wheel turns its full 360 degrees it seems to slow down and stop toward the beginning of each rotation. I assume this is because my first and last keyframes are exactly the same. Outside of calculating the angle that the wheel should be on the last keyframe, is there any way to keep my spinning velocity consistent? Please help, thank you.


Installation error from terminal and ubuntu software center

I am trying to install sublime using terminal but it pop out error:  Reading package lists... Done Building dependency tree        Reading state information... Done E: Unable to locate package sublime   And when I try to install vlc from Ubuntu Software Center then also I can't install since there is no install icon.  Upon execution of sudo apt-get update terminal pops out following output  E: Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable)  E: Unable to lock directory /var/lib/apt/lists/


if bounded linear operator $T$ is positive definite,then $T$ has a bounded inverse $T^{-1}$

Let X be a complex Hilbert space with the inner product $\langle⋅,⋅\rangle$ and norm $||⋅||$. Suppose T is a bounded linear operator on $X$ and $T$ is positive definite, means there is a constant $K>0$, such that $K\langle x,x\rangle \leq \langle T(x),x\rangle$, prove $T$ has a bounded inverse $T^{-1}$ and the norm of $T^{-1}$ is less than or equal to $K$.  I simply put $K$ into the inner product, then $K\langle x,x\rangle \leq \langle T(x),x\rangle$, is that means  $Kx \leq T(x)$? hope get prove of this question


Is it ok to eliminate the "I" in informal English (e.g. "Am sorry" vs "I am sorry")?

I have seen writing where "I" is being dropped in sentences. For instance, "Am on my way" vs. "I am on my way". Is this acceptable usage?


How to see process created by specific user in Unix/linux

I want to see list  of  process created by specific user or group of user in Linux Can I do it using ps command or is there any other command to achieve this?


Is it possible to trade Pokemon from the 1st generation games to the most recent ones?

I know that you can trade Pokemon between games of the same generation (Gold/Silver, Ruby/Sapphire) and even trade between 1st gen and 2nd gen. However, I haven't been able to find a way to trade Pokemon so that I can play with my 1st generation Pokemon in HeartGold, for instance. If it is possible, how many steps would it take and what equipment would I need?


If one fails, then he must simply try harder. If one fails, then one must simply try harder.   I have been trying to find the answer to this one for some time now. Some books and websites say second is correct while others say they both are same. Can someone explain which one is grammatically correct?


Can you please explain. How to answer these type of questions with permutation/combination? Is there a way I should approach probability questions?


I have a MacBook which OS was upgraded from Snow Leopard 10.6.3 to 10.6.8 and then to El Capitan 10.11.  I want to completely reinstall  El Capitan, to "factory state", in order to really "clean" the Mac. (However, I don't need to prevent data recovery.)  I started the MacBook holding down the "Alt" key and selected the partition for reinstalling, logged to Apple and the download of El Capitan was progressing.  Then, I moved away from the Mac for about two hours.  When I came back, the user account is unchanged, with previously installed apps. Seems like the installer decided in my absence to keep the user files.  Can I resintall El Capitan to "factory state" without wiping the whole drive? Or should I create a new user and then delete existing one?


Starting scheduled task by detecting connection of USB device

I know it has been discussed that it is not possible to start an application from an usb drive upon connection due to limitations of autorun (or autoplay??) in Win 7. But it is possible to create a scheduled task having an event type trigger. Surely there must be an event occurring when the drive -- or any USB device, for that matter -- is connected.    Does anybody have the slightest idea which Event ID should I use? Or at least what type of event? Where can I find the event in event viewer?


How to reset validation errors in ajax callback?

I would like to not validate fields if I submit button with ajax callback. Currently, on every button click it displays validation errors of another fields. The button doesn't submit the form, it does some another action (add more fields).


I've created a wood floor material using an image texture node, I'm happy with how it is displayed in the material preview.  However when I apply the material to any object, in this case the 'wood_floor', the shader seems to only apply a single color to the object rather than the textured material I've created.  Here is the .    What is causing this effect and how can I get the material to apply to the entire floor object?


If $A \subseteq B$, does $\mbox{dist}(x,\partial A) \le \mbox{dist}(x, \partial B)$ hold for all $x \in A$

Let $A,B \subseteq \mathbb{R}^n$ with euclidean metric. Furthermore let $$ \mbox{dist}(X, Y) := \inf\{|x - y| : x \in X, y \in Y\}. $$ Does the following implication hold?     $A \subseteq B \implies \forall x \in A: \mbox{dist}(x,\partial A) \le \mbox{dist}(x, \partial B)$    Problems could arrise if one of the boundaries $\partial A$, $\partial B$ is empty. But in this case $A$ or $B$ would be clopen, and hence equal to $\mathbb{R}^n$ or $\emptyset$. I think I am better off assuming $A \neq \emptyset$ and $B \neq \mathbb{R}^n$ to avoid problems.    Thanks to a suggestion by GEdgar I came up with the following proof:  Let $s \colon [0,1] \to \mathbb{R}^n$ be the straight line with $s(0) = x \in A$ and $s(1) = y \in \partial B$. I want to show, there exists $t' \in [0,1]$ with $s(t') \in \partial A$.   It is safe to assume $x \not \in \partial A$, since then $\mbox{dist}(x,\partial A) = 0$ and the inequality holds trivially. Same goes for the assumption $y \not \in \partial A$.  Consider now the function $$ f(x) := (1-2 \chi_A(x)) \cdot \mbox{dist}(x,\partial A). $$ One can check that this function is continuous on $\mathbb{R}^n$:   No problems on $\mathbb{R}^n \setminus \partial A$, since as a property of metric spaces $\mbox{dist}(\cdot,\partial A)$ is continuous and furthermore $(1-2 \chi_A(x))$ is constant. Let $\lim_{n \to \infty} x_n = x \in \partial A$. Then  $$ |(1-2 \chi_A(x_n)) \cdot \mbox{dist}(x_n,\partial A)| \leq \mbox{dist}(x_n,\partial A) \to 0 = \mbox{dist}(x,\partial A), $$ since the closedness of $\partial A$ implies $\mbox{dist}(x,\partial A) = 0$ iff $x \in \partial A$.   Now the claim follows by application of the intermediate value theorem.  Is this proof correct?  Does the claim also hold for more general metric spaces $(X,d)$ which are only connected/path connected? Of course the definition of $\mbox{dist}$ would be modified accordingly $(| x - y | \to d(x,y))$


Prove a given distance function is in fact a metric: $ d(f,g) = \sup\limits_{x\in X}|f(x)-g(x)| $

Let $X$ be a metric space and $C(X)$ be the set of all continuous and bounded functions with domain $X$. If $f,g\in C(X)$ define the distance between these functions by: $$ d(f,g) = \sup\limits_{x\in X}|f(x)-g(x)| $$ To prove $d$ is a metric, we have to show it satisfies $4$ properties: $$ d(f,g)\geq0 $$ $$ d(f,g)=0 \quad\text{iFF}\quad f(x)=g(x) $$ $$ d(f,g) = d(g,f) $$ $$ d(f,g) \leq d(f,h)+d(h,g) $$ I showed the first three without much difficulty, so my question is related to proving the last property. To do this, I let $f,g,h \in C(X)$ and fixed $x_0\in X$. Then by the triangle inequality for real numbers we know that: $$ |f(x_o)-g(x_o)|\leq|f(x_0)-h(x_0)|+|h(x_0)-g(x_0)| \quad \ \forall \  x_0\in X $$ If the above statement is true for all $x_o \in X$ that it must be true that we can simply take the supremums of both sides of the inequality and it still holds true. I'm not quite convinced of this logic, however, because couldn't the given distances be dependent on different points (i.e. maybe $d(f,g)=k$ occurs at $x_o$ while $d(g,h)=l$ occurs at $x_1$. If this were the case, I don't believe my argument holds up. However, I'm also not sure what else to try. Any hints would be much appreciated!


I was wondering if it was possible to change the font of one letter in my Latex document ?  I have an equation where I want one of the letters in that to be Arial instead of Times New Roman, which is my main font.  So, is it possible ?


Count number of lines that starts with & character in CSV file

I am trying to make a function that will count how many lines starts with & in given file. So far i came up with following function    public int CountNumberOfTexts(String filename)  {          try{              File file = new File(filename);              if(file.exists()){                  FileReader fr = new FileReader(file);                 LineNumberReader lnr = new LineNumberReader(fr);                  int linenumber = 0;                  while (lnr.readLine() != null){                     if (lnr.readLine().substring(0,1) == "&") {                         linenumber++;                     }                 }                  Log.d("Count", "NUMBER OF LINES: " + linenumber);                  lnr.close();                  return linenumber;              }else{                 System.out.println("File does not exists: " + filename);             }          }catch(IOException e){             e.printStackTrace();         }          return 0;     }   Current Function error is: Not recognizing lines starting with & character.


I do really need your help.  following this post :   I read this .  I think this package have everything I need, but I don't know how to write it exactly :/  I searched how to do the following things :  I need to define a few boxes that will be the shell of the theorems, the examples and the exercices of my document. I want to define a structure at the beginning of the document to use it in the rest of it.  I would like to have my theorems in a red box, the exemples with just a line on the left and that they are a little shifted on the right (not on the same vertical axis as the rest) , the exercice in an orange box with the solution following the same typography as the examples (meaning shifted on the right and with a line on the left).  To do so, I find this in the document :  first, i need to create some boxes like this:    the thing that is the most similar i ve done is this :  \usepackage{tcolorbox} \tcbuselibrary{theorems} \newtcolorbox{mybox}{colback=red!5!white,colframe=red!45!white, title = Myboxy}  \begin{document}  \begin{mybox} This is my own box. \end{mybox}   but it doesn't suit me because I want the title to be in another box like on the image...they explain the options on page 155 but I don't understand what the heck is going on... ^^'    Moreover, I heard that usually they are problems with counting the theorems. How do you manage this ? It is not crucial but it would be great if I have a counter for every chapter for the theorems and the exercices.  p46, they are talking about toggling, "Toggle Left and Right", I think that is the option to shift a box in a direction ? I don't understand how they implement this option in the options of the box :/ and moreover, I need also a line on the left, that is what i found :  p178 they are talking about border line... about border lines I found the perfect example in an other package and it looks like this :   The S one suits perfectly...  I want the line to take the color violet and green. How can I do this using tcolorbox?  thank you very much, i would be great if someone have the answer to this question. I'm struggling with this since a few days and I really don't how to do this.


Next-Button cannot be clicked after cancellation of suggested edit

I encountered a bug regarding the Next button in the review section.     Steps to reproduce:         Review a "first post".   Complete the first review regularly and review another "first post".   Start editing the post.   Wait for some time, so that someone else likely completes the review.   Click the browser's back button.   Try clicking the Next-button.         Expected behavior:      The next review is being displayed, or a message appears stating that there are no posts to review.      Current behavior:      Nothing happens. The button looks "clickable", but cannot be clicked.   After reloading the page the button gets clickable.   Edit: After several "edit" -> "cancel" -> "edit" -> "back" cycles I managed to get this result (Note the two "cancel"-links at the top):


Is .asc supported raster data source for QGIS?

I am new using QGIS and struggling with this error "...... .asc is not a supported raster data source" when trying to add a ."asc" file as a raster.   I downloaded the files from   I tried Layer: Add Raster Layer, and also Raster: Conversion: Translate (convert format) but neither recognized the .asc


Is "exposure fusion" different from HDR?

Is "exposure fusion" distinct from HDR compositing techniques, or is it essentially a marketing term for a specific HDR process.  Or is it just a synonym for HDR?  Or, to put this in "meta" terms, should exposure fusion be treated as a distinct tag from HDR, or should it get lumped in with ?


System calls supported in running Kernel

Is there a way to get the number of or list of system calls supported by currently running Linux Kernel? So I want to find a way to 'read' the syscall table of a running kernel.


I know this sounds like a silly question and it may be closed before it may get a single answer but there is something strange in my house which beeps infrequently. I tried to troubleshoot the sound but no luck. I thought may be its coming from the living room but there is nothing special in the living room which may make a beep sound.  Can someone point me what should i look for to figure out what is making this sound?


How can I bootstrap Drupal 8 from an external script?  This an example script from the .  require_once __DIR__ . '/vendor/autoload.php'; use PhpAmqpLib\Connection\AMQPStreamConnection;  $connection = new AMQPStreamConnection('localhost', 5672, 'guest', 'guest'); $channel = $connection->channel(); $channel->queue_declare('task_queue', false, true, false, false); echo " [*] Waiting for messages. To exit press CTRL+C\n"; $callback = function ($msg) {   echo ' [x] Received ', $msg->body, "\n";   sleep(substr_count($msg->body, '.'));   echo " [x] Done\n";   $msg->delivery_info['channel']->basic_ack($msg->delivery_info['delivery_tag']); };  $channel->basic_qos(null, 1, null); $channel->basic_consume('task_queue', '', false, false, false, false, $callback);  while (count($channel->callbacks)) {   $channel->wait(); }  $channel->close(); $connection->close();   Within a worker script like this, I need to be able to create nodes.  How can I bootstrap Drupal 8 in this script?  ? and  bootstraps passing a fake request to the kernel, which to me looks like a work-around.  In Drupal 7 you could do something like this, apparently.  // Bootstrap Drupal. include_once './includes/bootstrap.inc'; drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);


I am trying to use the "navigateToSObject" to redirect to the detail page. But the method $A.get("e.force:navigateToSObject") is always returning null. I dont have a namespace. SO this isn't namespace related issue I assume.  Here is the code of my component  <aura:component > <aura:attribute name="contactName" type="String"></aura:attribute> <aura:attribute name="lastName" type="String"></aura:attribute> <aura:attribute name="cid" type="String"></aura:attribute>

{!v.lastName}

{!v.contactName}

{!v.cid}

 </aura:component>   Here is the code of my java-script controller      ({     navigateToRecord : function(component, event, helper){         var cid=component.get("v.cid")        console.log('inside navigateToRecord '+cid);       var navEvent = $A.get("e.force:navigateToSObject");        navEvent.setParams({         "recordId": cid,            "slideDevName": "detail"     });      navEvent.fire();  } })   I am getting null in navEvent hence am not able to set parameters into it. The error is "Uncaught error in $A.run() : Cannot read property 'setParams' of null"


Increasing speed and reducing effort on steel MTB on the road

I have a low end steel MTB, which is heavy by itself, and I also a heavy man weighting in at 100kg, and on my MTB I have knobby dirt tires.  As you can imagine, riding on the road any faster than 20km/h is a pain. I would be satisfied if I could cruise at 30km/h easily, which I can't now. I'm finding comfort in 20km/h.  What do I need? Road tires? Loose weight? Get more fit?  I was thinking on purchasing a set of Schwalbe Marathon tires, in 26x1.75 size for my MTB to potentially lower the rolling resistance and go faster.  Currently I have Kenda tires, made for the dirt in the 26x2.10 size. These tires also sound horrible, making a lot of noise on the pavement.   How could I increase the speed of my bike?   Also, at what pressure should I inflate my current Kenda tires to potentially go faster? I currently have them at around 60PSI.


In SQL, what’s the difference between count(*) and count('x')?

I have the following code:  SELECT <column>, count(*) FROM <table> GROUP BY <column> HAVING COUNT(*) > 1;   Is there any difference to the results or performance if I replace the COUNT(*) with COUNT('x')?  (This question is related to a )


I am using Ubuntu GNOME 16.04 LTS. Today I tried to install conky with the commands:  sudo-apt get conky sudo-apt get conky-manager   But when I open the manager and select something, it always has the problem shown in the picture    I also tried:  sudo apt-get install conky-all   I've tried this , but it does not work for me.


Using files that have spaces in their name in pipes

I have folder named play which contains a file damn file (with space). When I use find and pipe the output to tar:  find play/ -name 'damn*' | tar cf archive.tar -T -   It works perfectly. Why does this works The output of find contains space that should cause problem for tar. When I use this command:  tar cf archive.tar $(find play/ -name 'damn*')   bash shows these errors:  tar: play/damn: Cannot stat: No such file or directory tar: file: Cannot stat: No such file or directory tar: Exiting with failure status due to previous errors   I'm confused. Why does the first example work?


Problem with bkcrack from a terminal - remove password

First, I will describe how I use bkcrack: I am using LINUX in the live version (Ubuntu 20.04.2.0 LTS). I downloaded the LINUX version of bkcrack from GITHUB and put the password file in this folder (bkcrack). Then I right clicked on the main bkcrack folder and chose the "open in terminal" option and typed the commands. I would like to crack a password in a .zip file I created a few years ago and forgot my password. The compression algorithm is ZipCrypto Deflate. There is only one file in MYFILE.zip - ABCD.pdf. I have an older copy of this PDF that is identical to the one that has a password of about 90%. I tried to use BKCRACK. I opened the MYFILE.zip file in the HxD program and saw the header of the zip file in HEX format (50 4B 03 04) and the name ABCD.pdf in HEX format (41 42 43 44 2E 70 64 66) - offset 30. Thanks to this I have 12 bytes known text. Then I used the command: ubuntu@ubuntu:~/Desktop/sam-zip$ echo -n "ABCD.pdf" > plain.txt ubuntu@ubuntu:~/Desktop/sam-zip$ time ./bkcrack -C MYFILE.zip -c ABCD.pdf -p plain.txt -o 30 -x 0 504B0304 > 1.log & tail -f 1.log [1] 6505 bash: line 2: ./bkcrack: Permission denied  real    0m0.003s user    0m0.002s sys 0m0.001s  So I used additionally: sudo -s but that didn't help either: ubuntu@ubuntu:~/Desktop/sam-zip$ sudo -s root@ubuntu:/home/ubuntu/Desktop/sam-zip# echo -n "ABCD.pdf" > plain.txt root@ubuntu:/home/ubuntu/Desktop/sam-zip# time ./bkcrack -C MYFILE.zip -c ABCD.pdf -p plain.txt -o 30 -x 0 504B0304 > 1.log & tail -f 1.log [1] 6704 /bin/bash: line 2: ./bkcrack: Permission denied  real    0m0.002s user    0m0.002s sys 0m0.000s  Please help.


Is there a way to evaluate the derivative of $x$! without using Gamma function?

Taking the factorial function $x!$  I wonder if there is a method to find the first derivative of this function without making any use of the Gamma function (or related integral representations of the factorial). Maybe something like that  $$ \begin{align} \frac{\text{d}}{\text{d} x}\ x! & = \frac{\text{d}}{\text{d} x}\ (x\cdot (x-1)\cdot (x-2)\cdot \cdots) \\\\ & = ((x-1)\cdot (x-2)\cdots) + x\cdot ((x-3)\cdot (x-4)\cdots) + x\cdot ((x-2)\cdot (x-4)\cdots) + \cdots  \\\\ & = (x-1)! + x\cdot N(x) \end{align} $$  What I'm missing is a suitable $N(x)$ to express the remaining terms.  Does such a function exist?  I thought about this, observing term by term:  $$N(x) = \left(\prod_{k = 3}^{n} (x-k)\right) + \left((x-2)\prod_{k = 4}^n (x-k)\right) + \left((x-2)\cdot(x-3)\prod_{k = 5}^n (x-k)\right) + \cdots$$  But still it seems quite messy, isn't it?


Unexpected issue with List initialization

I found something a bit weird when playing with lists. I usually use print() to debug or understand how things work but in this case the print() outputs are not helping me at all.  Here is a simple code, you will quickly see what I'm talking about:  a = [[]] * 5  b = [[]] * 5 b[0] = [] b[1] = [] b[2] = [] b[3] = [] b[4] = []  # It prints the same thing: print(a)  # [[], [], [], [], []] print(b)  # [[], [], [], [], []]  a[0] += ["test"] b[0] += ["test"]  # Different results: print(a)  # [['test'], ['test'], ['test'], ['test'], ['test']] print(b)  # [['test'], [], [], [], []]   I was expecting a to behave like b, but it doesn't. Can someone explain this?


According to  the resistance drops liniar along the path.  In scenario 1 at the start of R1 the resistance the current encounters is 100\$\Omega\$ and at the end of R1 it encounters 0\$\Omega\$.  In scenario 2 at the start of R1 the resistance the current encounters is 200\$\Omega\$ and at the end of R1 it still encounters 100\$\Omega\$ because of R2.  If this is true, why does point A in scenario 2 have more volt left if it has encountered the higher resistance of 200\$\Omega\$ at the beginning opposed to scenario 1 where it encountered 100\$\Omega\$ at the beginning?  I know about Ohm's law and how to use it, but that doesn't explain how this occurres.         – Schematic created using   Edit  I have written an answer , thanks to answer from @Neil_UK in this post.


Should I formally use static_cast in C++ projects instead of C-style casts?

As title, should I always use static_cast for C++ project; if I just want to handle the conversion from double to int and the conversion from a base-pointer to a derived-pointer. Is my thought correct?  Thanks all


What is the window of time I have to buy a month subscription for the sender to get its reward?

My friend sent me yesterday a Scroll of Resurrection for World of Warcraft and I activated it.  I was wondering how much time I have to subscribe for a month if I want to be sure he gets his reward.  Is it before the end of 7 free days?  As pointed in the comments, what I'm really looking for is the window of time I have to buy a month to ensure my friend will have its reward for sending a scroll of resurrection.  Thank you.


Why does randomForest has higher test AUC than train AUC? Is this possible?

I am having some question with the randomForest. I use the "creatFolds" in "caret" package to partition the data into training set and test set. After building the model, I found that the test data has higher AUC than the training data. Is this possible? The following is code. Could anyone help me with this? Thanks a lot!  library(randomForest) library(pROC) library(ROCR) library(caret) # prep training to binary outcome train0 <- iris[iris$Species %in% c('virginica', 'versicolor'),] train0$Species <- droplevels(train0$Species) set.seed(1) index <- createFolds(iris$Species, k = 2, list = TRUE, returnTrain = TRUE) train <- train0[index$Fold1,];train <- na.omit(train) test <- train0[-index$Fold1,];test <- na.omit(test) # build model rfmodel <- randomForest(Species~., data=train, importance=TRUE, ntree=2)  #the train AUC rf_p_train <- predict(rfmodel, type="prob")[,2] rf_pr_train <- prediction(rf_p_train, train$Species) r_auc_train <- performance(rf_pr_train, measure = "auc")@y.values[[1]]  r_auc_train   #0.8098  #the test AUC rf_p_test <- predict(rfmodel, type="prob",newdata = test)[,2] rf_pr_test <- prediction(rf_p_test, test$Species) r_auc_test <- performance(rf_pr_test, measure = "auc")@y.values[[1]]  r_auc_test    #0.956


Insert a "Let us continue this discussion in chat" comment before thread gets messy

I've seen , but there seem to be no proper solution.  I suggest an ability to insert a "Let us continue this discussion in chat" comment before the thread gets messy enough to fit the requirement. The point is to prevent the problem before it occurs.  Perhaps this should become a privilege for users of X reputation or more?  Your opinions on the subject?


Consider this shell redirect: telnet towel.blinkenlights.nl >> starWarz when it ends, the session will break, detach from host or something like that. I want to know how long the connection lasts. How might I determine this?


Is there a way to get functionality similar to mkdir -p on the shell from within Python.  I am looking for a solution other than a system call.  I am sure the code is less than 20 lines, and I am wondering if someone has already written it?


To test the convergence $\sum{\frac{1}{(\ln {n})^{\ln{n}}}}$

How to test the convergence of following series $$\sum{\frac{1}{(\ln {n})^{\ln{n}}}}$$  I have tried Cauchy condensation test and gives me nothing


A proposed problems from American Math Monthly from Vol 119 NO.10 Dec 2012

Let ${\rm Aut}\, G$ denotes the automorphism group of $G$. Prove that there is no finite group with $|{\rm Aut}\,G|=|G|+1$. I begin by suppose there is a finite group with the above property. First of all $G$ cannot be non-abelian, For if does then as ${\rm Inn}\,G\cong G$ so we have $\gcd(|{\rm Aut}\,G|,|G|)>1$. And this is false as $\gcd(|G|+1,|G|)=1$. So $G$ must be abelian. From now on I have no progress. Any hint? I think maybe decompose $G$ into a finite direct product of $\mathbb{Z}_n$ could help to derive some contradiction.


I am trying to model a packet data with 1 dimensional CNN but I have a very imbalanced classes in my target. I have 3 classes as class 0 has 53000 cases, class 1 has 300 cases and class 2 has 150 cases. Thanks in advance! I have tried what you have suggested but I do not think I am getting a good results(loss and accuracy), from the model.


"England (have/has) been the weaker side..."?

It is written in the online :     England have definitely been the weaker side in the first half of the game.   While Grammarly.com corrected the sentence to:     England has definitely been the weaker side in the first half of the game.   Which version is the correct one?


How can we have negative work in electrostatics, if $W=(\epsilon_0/2)\int\! E^2\ \mathrm{d}\tau$?

This question is motivated by Section 3.2.3 in Griffiths. Therein, we are considering the force of attraction between a point charge and an infinite conducting plane.  One can calculate the field using the method of images, and from that the force of attraction exerted by the induced charge to be  $$\mathbf{F}=-\frac{1}{4\pi\epsilon_0}\frac{q^2}{(2d)^2}\widehat{\mathbf{z}}.$$  One one hand, the energy associated with a field is given by $$W=\frac{\epsilon_0}{2}\int\! E^2\ \mathrm{d}\tau.$$  Since the dot product is positive definite, this implies that $W$ must be positive.  On the other hand, the work is also given by \begin{align} W&=\int_\infty^a\! (-\mathbf{F})\cdot \mathrm{d}\mathbf{l}\\ &=\frac{1}{4\pi\epsilon_0}\int_\infty^a \frac{q^2}{4z^2}\ \mathrm{d}z\\ &=-\frac{1}{4\pi\epsilon_0}\frac{q^2}{4d}<0 \end{align} Intuitively, it makes sense that the work should be negative: to bring the particle in from infinity under constant acceleration, we must oppose the attractive force of the induced charge.  But I am having trouble reconciling this with the equation $W=(\epsilon_0/2)\int\! E^2\ \mathrm{d}\tau.$  I am sure I am missing something, and would greatly appreciate a nudge in the right direction.


What is The most detailed Mathematical Methods for physics book?

I am taking a course in Mathematical Physics Junior Level (Undergraduate).  We are working from Arfken's "Mathematical Methods for physicists", but i am finding trouble with it specially in the determinants and matrices chapter, since it is not detailed enough. any suggestions for a more detailed book?


Live resize of root partition in case of "LUKS on LVM"

Having read about the pros and cons of "LUKS on LVM" vs "LVM on LUKS" I came to the conclusion that "LUKS on LVM" does not provide live resize. But why? And is this even true as of todays implementations?  For the context this is what I have in my /etc/crypttab:  decrypted_root  /dev/vg_ubuntu/LV_crypted_root none luks   This is my /etc/fstab:  /dev/mapper/decrypted_root   /   ext4    errors=remount-ro 0       1   Here is what I did:  lvextend -L +10G /dev/vg_ubuntu/LV_crypted_root cryptsetup resize decrypted_root resize2fs /dev/mapper/decrypted_root   And now my overall question: What could possibly go wrong with this?


Create a shower hose with correct physics

I'm making a shower hose that follows the handle when it moves.  I've created it successfully following  tutorial, but the hose is too "elasticy". I'm wondering which settings I should change (from the tutorial) to make it more rigid.  I also want it to have less "bending points" when it's moved, it should really only have one major curve like shower hoses do when you move them around.  Cheers.


On the dimensionality of the Hilbert space for a central potential

So, we have that for particles in a central potential, the wavefunction can be expressed as: $$\psi(\mathbf{x})=R(r)Y^m_l(\theta,\phi)$$  Explanation (not crucial in the question):      $Y^m_l(\theta,\phi)$ are spherical harmonics (functions associated to the eigenvalues of the orbital angular momentum $\mathbf{L}^2$ and one of the components of $\mathbf{L}$). And $u(r)=rR(r)$ satisfy the following form Schrödinger equation: $$Eu(r)=-\frac{\hbar^2}{2\mu}\frac{d^2u(r)}{dr^2}+\left[V(r)+\frac{l(l+1)\hbar^2}{2\mu r^2}\right]u(r)$$ Source: Weinberg, S. (2015). Lectures on Quantum Mechanics. Cambridge: Cambridge University Press. doi:10.1017/CBO9781316276105   My question is:     In this case what is the dimensionality of the space $\mathcal{H}$ of the solutions?   On the one hand, the solutions in the particular case of the Hydrogen atom are products of Laguerre polynomials and Spherical Harmonics, which can be identified using the quantum numbers $n, l, m$, thus the states are linear combinations of $\varphi^m_{n,l}$, a countable set:$$\psi=\sum_{n,l,m}C_{n,l,m}\varphi^m_{n,l}$$  On the other hand, as functions, the $\psi(\mathbf{x})$ can be thought of as linear combinations of the position basis $\delta(\mathbf{x})$, since there are as many $\delta(\mathbf{x})$ as there are $\mathbf{x}\in \mathbb{R}^3$, this set is uncountable: $$\psi=\int_{\mathbb{R}^3}d\mathbf{x}\:C(\mathbf{x})\delta(\mathbf{x})$$  This baffles me since on the one hand we have that the basis is countable ($\aleph_0$-dimensional) and on the other the basis appears to be uncountable ($\aleph_1$-dimensional*). Clearly they can't both be right.  *assuming that the continuum hypothesis holds.


Problem regarding the speed of two points $A$ and $B$ moving with constant speed in the plane

Consider a Point A that moves linearly on the positive x-axis with the speed 1 m/s and another Point B at a distance L from A with position (L,0). With each forward motion of point A the Point B moves in an arc consistently maintaining the distance L from point A. As soon as Point A reaches x=L, the Point B is perpendicular to Point A and its position is (L,L). Both the points move at a constant speed.  How then do you determine the speed of B?  Note that in this problem I considered the Center of Mass of the objects as points.   Is it possible to determine the equation of the curve that point B traces and its arc length? If yes, then how?


How to respond to "fix my code" questions?

I often see questions such as this:     Hey my code isn't working. It's supposed to do XY but I can't figure   out why it doesn't work. Here is my code:      { insert 300 lines of code here }   I'd like to help these kind of people with their problems, but it just isn't economical for answerers to sift through 300 lines of code to try to deduce the problem, and it doesn't teach the asker how to debug their code.  Thus, usually these questions go unanswered.  Is downvoting such a question appropriate? What about moderator flags to place the question "On Hold"?  What kind of comment is helpful in this situation to encourage the user to improve their question? I don't even know where to start in explaining to them why this is a terrible question.


Is the center of the fundamental group of the double torus trivial?

I know that the fundamental group of the double torus is $\pi_1(M)=\langle a,b,c,d;a^{-1}b^{-1}abc^{-1}d^{-1}cd\rangle$.  How can I calculate its center subgroup $C$? Is $C$ trivial?  Let $p$ be the quotient map from $\pi_1(M)$ to $H_1(M)$, maybe it's easy to prove that $p(C)$ is $0$ in $H_1(M).$ That will also solve my problem.  Thanks, Yan


how to unzip .zip file and its sub directories

I have a zip file and in that I have multiple folders zipped. How do I unzip all the files in one shot.  I tried unzip -r  but it didn't work  Regards, Vikas


I installed Ubuntu 13.10 on an HP Compaq D530 cmt and I can only see the desktop pic and I have found out that I don't have the unity plugin enabled. I went  to see what this person did. I got ccsm and I have no way of applying changes to the unity plugin, so I can enable it, but that does no good because the changes don't take effect. If I leave ccsm and come back the unity plugin is uncheckmarked. I really do not know what to do, some people have mentioned there are missing drivers for my PC also, but when I go to the update manager and go to drivers it says there are no drivers available for this computer. I don't know what is stopping me from enabling the unity plugin, can anyone tell me a command I can use in terminal to fix my problems. Thanks


Why, oh why, don't the Weasleys "conjure" up some diamonds/gold/etc, sell 'em to Muggles, and get rich? They could buy a mansion (like the Malfoys), and live there happily ever after.  I know there's  that prohibits one from conjuring food (which doesn't make much sense to me, either). Even if it applied to gold, what about all the other elements/compounds/materials? Could the law really be 'don't let a wizard conjure something if it'll make them richer'? That's totally nonsensical.  Why does Wizard society still have poor people, especially if they're talented?


Is it better to use the UK or USA server?

I live in the UK, so it should be better to use the UK ones. But, the USA one is more likely to be well maintained and have the better connection speed.  Which should I use - is there a testing tool, either built in or installable?  I, personally, would prefer a GUI method over command line.


What is a script and how do I write one?

There are a couple of times I have been presented with some codes as solutions to problems. My question is how do write these type of scripts myself for some fairly routine tasks?


how to create EFI partition from scratch

I have an internal SSD containing a single partition with Ubuntu on it.  I am currently booting from this partition.    However, to actually boot a second (HDD) drive is required which has an EFI partition on it.  I want to remove the HDD and continue to boot Ubuntu from its location on the SSD, without having to reinstall anything.  I am thinking what I need to do is to resize the partition on the SSD to allow space for an EFI partition, move it (the start of the existing partition ahead/up), create an EFI partition before it, and then install something on the new EFI partition so it will boot from the existing Ubuntu install on what would now be the second partition.   I have bits and pieces of what I think I need to do (for instance, I think GParted can do the moving and resizing) but I don't have a clear enough picture of exactly what I need to do in order to avoid risking data loss.  Also, it seems like this is an uncommon procedure, as I see these various activities mentioned as parts of other processes, but never creating an EFI partition from scratch.  Exactly what steps do I need to do to safely modify my single partition SSD to boot by itself?


sharing network using adb port forwarding

A bit of background I have an Android phone, which unfortunately cannot usb-tether while it is connected to the internet (using wifi or mobile data, but it works when the device is not connected to the internet. Wifi and Bluetooth tethering have this problem too). Now I want to connect my PC to the internet using my android phone (using only wired connection). The unideal solution I came up with a rather hacky solution which has a minor problem: I compiled  - a proxy server - for my device (FYI, I used GOOS=linux GOARCH=arm environmental variables to build the binary) and ran the binary on my Android phone on port 8080 (I placed the binary in /data/local/tmp. I ran it the obvious way using adb shell without superuser privileges). Then I used adb forward tcp:8080 tcp:8080 to forward device's port 8080 to my PC's port 8080. After that I used localhost:8080 as a socks5 proxy on my PC and could access the internet. The problem is that I cannot use certain applications as they don't support connecting through proxy (some of them run on a lower network layer than a socks5 proxy, so there is no way for them to work). My question Is there any way to run a VPN server on my Android phone (which conveniently has root access too) and use it like the way I currently do? If so, I'm only interested in solutions using well-maintained opensource software.


Use all 5.1 speakers with 2 channel audio sources

I would like to upmix 2 channel audio sources such that they use all of my 5.1 speakers. I have a realtek sound card (with updated drivers) and Windows 7.   Here's what i've tried:    Using the "Speaker Fill" option under the speaker properties "Enhancements" tab. This tries to guess what the audio should sound like in a 5.1 environment which results in only parts of the audio being played out of the additional speakers. I could deal with that if it were only the rear speakers but it also impacts the sub too. The 2 channel audio sources have significantly less low-end than true 5.1 sources when using "Speaker Fill".       Using the "Room" environment. This seems to help a bit but it also introduces a slight echo effect/distortion that can be annoying with certain music/sources.      I'm MusicBee for playing music as it has it's own upmix option that works perfectly. The rear speakers are exact clones of the front speakers and the subwoofer sounds great too. I'd love to be able to have that same quality upmix with other sources such as YouTube.   Are there any other options out there?  Related:


What is the Fastest way of looping over an array on javascript?


$R$ is a commutative ring. We need to prove that $R[x]$ has a subring isomorphic to $R$.   Let $S$ be that subring of $R[x]$ which has polynomials of even degree. Now I consider a mapping from $S$ to $R$ as : $f(x) \to f(0)$ where $f(x)$ is a polynomial of even degree and $f(0)$ is clearly in $R$.  The mapping defined as above "seems" one-one and onto. But I couldn't prove it.  I took the kernel of the mapping as $\ker \phi = ( f(x) \in S | \phi ( f(x)) = 0 )$ ,  Which only gives $a_0 = 0$ ,  $ f(x) = a_0 + a_1 x + a_2 x^{2} $ . . . ... $ a_n x^{n} $   We know if kernel only contains the " 0 " element then the mapping is one-one . But I'm unable to prove that here. Can anyone help me out here ?


What do the words 'RELATED' and 'ESTABLISHED' individually signify in RELATED,ESTABLISHED state in iptables?


How can changing magnetic field produce instantaneously the electric field and vice versa?

Maxwell's curl equation for electric field says that time varying magnetic field produces electric field instantaneously but nothing can happen instantaneously according to special relativity. What is the mistake in my understanding since Maxwell's equations are accepted?  Since nothing can happen instantaneously so how is changing magnetic field producing the electric field instantaneously in EM wave according to   $$E(x,t) = E_\text{max} \cos(kx - \omega t+\phi)$$  $$B(x,t) = B_\text{max}cos(kx - ωt + \phi)$$ which shows that they are in phase(means no delay)? I feel there should be some delay in wave of electric field as nothing is instantaneous( vice versa if changing electric field).   Please give an intuitive understanding. Thanks in advance.   Edit: the argument I am giving here is different from the question mentioned in possible duplicate. I am asking about instantaneous production of field and not about how they have same expressions.


I'm looking for some good tools in the Ubuntu platform which does convert the PDF to CHM files. I googled a lot. But I almost finding the tools for other way around (i.e CHM to PDF).


How to find what causes Windows 10 to boot slowly

My Windows 10 boots very slowly. At startup it remains stuck on the boot image with no hard disk working for 1-2 minutes; after that it starts normally.   I've already checked if I have "fast boot up" option active, but I don't have that option.   So my question is: how to find what program/service causes this lag?


The irrationality of the square root of 2

Is there a proof to the irrationality of the square root of 2 besides using the argument that a rational number is expressed to be p/q?


Variance of the product of correlated normal variables

Suppose that $X$ and $Y$ are scalar random variables that are jointly normally distributed:  $$ \begin{pmatrix} X \\ Y \end{pmatrix} \sim N \left( \begin{pmatrix} \mu_x \\ \mu_y \end{pmatrix}, \begin{pmatrix} \sigma_x^2 & \sigma_{xy} \\ \sigma_{xy} & \sigma_y^2 \end{pmatrix} \right) $$  I would like a formula for $\operatorname{Var}(XY)$ in terms of $\mu_x, \mu_y, \sigma_x^2, \sigma_{xy}, \sigma_y^2$. The answers at  are too general and don't help much with this particular problem. The second answer at  starts but doesn't finish the derivation.  I can reduce to the problem of finding $E[X^2Y^2]$, using the definition of the covariance $\sigma_{xy}$: \begin{align*} \operatorname{Var}(XY) &= E[ (XY)^2 ] - E[XY]^2 \\ &= E[(XY)^2] - (\sigma_{xy}+\mu_x\mu_y)^2 \end{align*}  I have an idea about how to do that, but I'm not sure if it's correct. Write $Y = E[Y \mid X] + \varepsilon$ where $\varepsilon \sim N(0, \sigma_\varepsilon^2)$ and is independent of $X$. In fact, $$ E[Y \mid X] = \mu_y + \frac{\sigma_{xy}}{\sigma_x^2} (X - \mu_x) $$ so $\sigma_\varepsilon^2 = \sigma_y^2 - (\sigma_{xy})^2/\sigma_x^2$. Then \begin{align*} Y^2 &= E[Y \mid X]^2 + 2 E[Y \mid X] \,\varepsilon + \varepsilon^2 \\ E[X^2Y^2] &= E[ X^2 \, E[Y \mid X]^2 ] + E[ 2 X^2 E[Y \mid X] \, \varepsilon] + E[X^2 \varepsilon^2 ]. \end{align*}  The third term is just $$ E[X^2] E[\varepsilon^2] = (\sigma_x^2 + \mu_x^2)\sigma_\varepsilon^2. $$ The second term is zero. For the first term, rewrite $E[Y \mid X] = \alpha + \beta X$, where $\beta = \sigma_{xy}/\sigma_x^2$ and $\alpha = \mu_y - \beta \mu_x$, to get $$ \alpha^2 \, E[X^2] + 2 \alpha \beta \, E[X^3] + \beta^2 \, E[X^4] $$ or $$ \alpha^2 (\mu_x^2 + \sigma_x^2) + 2 \alpha \beta (\mu_x^3 + 3 \mu_x \sigma_x^2) + \beta^2 (\mu_x^4 + 6 \mu_x^2 \sigma_x^2 + 3 \sigma_x^4). $$ Putting these all together and simplifying: $$ E[(XY)^2] = 2 (\sigma_{xy})^2 + 4 \sigma_{xy} \mu_x \mu_y + (\mu_x^2 + \sigma_x^2)(\mu_y^2 + \sigma_y^2). $$ Two questions:   Is the derivation here correct? Is there a simpler way to derive this result?


when my son sleeps VERSUS while my son sleeps

Do you agree that  1) I often read when my son sleeps.  2) I often read while my son sleeps.  mean different things?  Do you find 1) wrong?


SEO semi-mirrored sites that don't anger google

I'm working with a client who manages real-estate agents. All of these agents have their own individual sites, and they all want the same layout and functionality. So, I have a "master" site designed which is dynamically changed to fit the agent/area/whatever through a MySQL database. We have relatively static content in the DB about the agent and the area, then the rest is very dynamic content from a listing service, which is updated daily.  My question is how to set this up so that we can keep on using all the different domains and identical programming (i.e. all the files are identical, except pictures) and have decent SEO as well.  They had some trouble in the past with Google blacklisting their sites because they were considered "mirrored sites". Which...they pretty much are, but the difference between mirrored sites is that we're searching very different areas of the listings DB.  Ideally, all the listings are relatively unique to each site, but sometimes there aren't any listings for the area, or the listings for two sites overlap...that's when they get busted for the mirrorring.  Does anyone have any suggestions on how to both have decent SEO for the individual sites, and keep it easy to manage? There are currently over 100 sites (20 agents, about 5 sites each--one agent site, and a few "area" sites), so not mirroring things is just a ton of work.


If I have Computer-A, and share a folder to be accessed by Computer-B, can I take that same shared folder and share it with Computer-C?   Computer-B has two itnerface cards, eth0, and eth1. eth0 is connected on the same network as Computer-A, and eth1 is connected on an alternate network that Computer C.  Computer-B is on both networks.   Computer-A <--> Computer B <--> Computer C  Platform: Ubuntu 10.04   Thanks  -Manny


Reheating potentially unsafe canned goods unsafe?

I am into home brewing and one of the popular practices is for people to can wort - this is basically a sugary barley like tea- for growing yeast. A lot of people simply can wort in a pressure cooker or via normal steam canning methods, but after reading about the time variations necessary to can certain foods, and after failing to find a specific time recipe for wort even after emailing a government body asking for recommendations, I reached the conclusion that I did not need edible wort out of a can.  Instead I could just boil the wort once out of the can to kill any potential botulism toxin and still have the ability to portion large batches of wort into cans. The question is this: is there anything that won't be killed off in the boil that I need to worry about? After all, even though this is for yeast growth, I will end up drinking a small amount as it will end up in my beer.


I want to prove that $\forall \tau \in S_n$ and for pairwise different $x_1,...,x_k \in [n]$ it holds true that:  $\tau (x_1 x_2 ... x_k) \tau^{-1} = (\tau(x_1) \tau(x_2) ... \tau (x_k))$  I don't quite understand the notation. I assume that $S_n$ is the symmetric group and $\tau$ is any permutation in $S_n$ and $(x_1 x_2 ... x_k)$ is a cycle of length $k$. However I don't understand what the second part of the equation: $(\tau(x_1) \tau(x_2) ... \tau (x_k))$ means.


What's up with Bob Taylor in Prisoners (2013)?

I never really understood the character of Bob Taylor in Prisoners - his motives and why he is important to the story at all.   Firstly, for some reason, he is attracted to children's toys and clothing. At the candlelight vigil, we can see him gently stroking a teddy bear, almost like a child. He buys children's clothing at the mall. Secondly, he breaks into people's houses to steal the children's clothes. Not to mention, he soaks them in pig's blood. Thirdly, he is a maze fanatic who has snakes in his house. He even confesses the abductions/ murders of the girls.   I didn't really get this man's motif. He is not even responsible or has anything to do with the abductions, so how does he lead our protagonists to Mrs. Holly's house? I understand that he was abducted by Mrs. Holly, but that still doesn't explain how he contributed to solving the mystery? And what's with the clothing fetish and the mazes and the snakes? Mrs. Holly does mention Alex's "snake accident", but how is that related to Bob Taylor's snakes at all? And why does he confess to the abductions?   Now, I understand I'm asking way too many questions in one post and am technically breaking the SE rules. So answer this one question:  What's up with Bob Taylor in this movie?


How to make use of custom external Python modules in Blender or an add-on on Linux

The path for the Python executable used in Blender (up to 2.79) is not configurable.  I looked around and did not find a consistent way to be able to use custom  3rd party Python modules without installing then directly in the O.S. Python.  This would work, although not the ideal solution, but then I had issues with that in Linux, as running pip install system wide adds the modules to /usr/local/lib, but /usr/local is not the in the PYTHONPATH when Blender is started.   An active Python virtualenv - Python's own way of isolating 3rd party modules is ignored by Blender - as the way to activate a virtualenv is simply using it's Python binary (in a different Path than the one used by Blender).


wonderlands.com annoying pop-up redirects

Dear moderators  This question is not a duplicate, as it is about a special case, not a general question. please open this up and let the problem be solved, as this relates to so many people. you may find the view count intresting  Problem  As for  or  or even , my computer has been infected to this sh-t and my browsers open an annoying pop-up (  ) on every single click to whatever web page I am visiting and this is repeated really unlimited times, getting me more and more nervous.  It was just Google Chrome ( 47.0.2526.106 m ), but now I have it on Opera ( 34.0.2036.25 ) too, and I think it will go through the Firefox, IE, ... soon.  Environment   Windows 10 x64 Enterprise (1151) Build 10586.29   My efforts   I found  which would be useful. Used Chrome's Help > Report and issue menu to report it to the Google.  Used the  to remove any problems at the very first moment (just before my opera get infected too). Using the tool, I noticed that the exe file ( Chrome Cleanup Tool ) gets deleted automatically right after usage and so I added an audit on the file for deletion to suspect what process deletes the chrome_cleanup_tool.exe file using Security section under Windows Logs in Windows Even Viewr. The answer was:  Object:     Object Server:          Security     Object Type:            File     Object Name:            C:\Users\{my-user-name}\Downloads\chrome_cleanup_tool.exe     Handle ID:              0x2c     Resource Attributes:    S:AI  Process Information:     Process ID:             0x179c     Process Name:           C:\Windows\SysWOW64\rundll32.exe  Access Request Information:     Accesses:               DELETE     Access Mask:            0x10000   So I am almost sure that my windows has been infected with virus and there is nothing to do with Chrome, Opera, ...   My question   How can I remove the infection from my computer? Any suggestions or similar efforts would be appreciated.


(Minecraft Java 1.14.4) How do I continuously test if there is air below an entity?

I am trying to make an explosive snowball, but I need to test if there is air or a block under the snowball. I tried tags so when it is in the air the snowball gets a tag "air":  /execute as @e[type=minecraft:snowball] at @e[type=minecraft:snowball] if block ~ ~-1 ~ minecraft:air run tag @s add air  But I realized it would not remove the tag if the condition was false.   Is there a block name or something I can put in, like /execute as @e[type=minecraft:snowball] at @e[type=minecraft:snowball] if block ~ ~-1 ~ !minecraft:air run summon tnt ~ ~ ~ {Fuse:0} ?


intersection of the empty set and vacuous truth

Let $\mathbb S = \varnothing$.      Then from the definition: $ \bigcap \mathbb S = \left\{{x: \forall X \in \mathbb S: x \in X}\right\}$      Consider any $x \in \mathbb U$.      Then as $\mathbb S = \varnothing$, it follows that: $\forall X \in \mathbb S: x \in X$ from the definition of vacuous truth.      It follows directly that: $\bigcap \mathbb S = \left\{{x: x \in \mathbb U}\right\}$      That is: $\bigcap \mathbb S = \mathbb U$. ()   Proofwiki uses the above "proof" to "prove" that intersection of the empty set is the whole universe.   My question is, is the use of vacuous truth really allowed in axiomatic set theory, like ZFC? I don't see how the use of vacuous truth is justified.   The next problem I can think of is that we cannot really "define" the elements of empty set (to my knowledge, there is no element in empty set) so how can we then prove as the above proof did? This seems to contradict the use of vacuous truth.  And of course, there is issue of using the whole universe as a set, and I don't think this is allowed.... (Maybe proof above is using a different axiomatic set theory, as I am using ZF-minded thoughts...)


How do I record the sound output from my mac?

I am trying to record the sound output on my mac. Like if there was a meeting going on and I want to record what other people are speaking. Is there a way I can do this without having to record my screen for it. I am using macOS Big Sur 11.3.


I would like to know if there is any man page documenting the construction of the most basic script commands like if/then/else, while, for each, and all the relative switches, like -eq, -e, -ge, and so on.


On per-site metas, users are given a rank based on meta participation, and this ranking is seen on the default tab of the users page on each per-site meta. How is this participation numerically calculated to give a ranking? Is it by votes? Something else? Are community wiki posts included in this?


What is the best word for "kitchen products" on an e-commerce website?

I am wondering what the best word is for all things used in the kitchen, including:   kitchen gadgets dishes pans forks, knives.. kitchen towels kitchen decorations   What is the best word to sum it all up?   kitchen products? kitchen things?


Combining varying vertex variable and vertex variable in OpenGL. How to?

Let's say I have 2 triangles sharing an edge defined by 4 vertices. Though the normals for these 2 triangles are unique for each triangle and are defined per vertex. So say I have 4 vertices, 6 normals (as shown in the figure below).    I would like to know how this can be dealt with in OpenGL? I have been using glDrawElement so far, but I understand that this would only work if I had 4 normals (1 normal per vertex) and this it wouldn't allow me to define 3 normals per triangle.  What's the best/common/most efficient of dealing with this case? Do I need to also duplicate the vertices (3 unique vertices per triangle or is there a more clever solution to this?) so that I have as many vertices than I have normals?


Didn't Imperial officers (or the general public) know that the Emperor was a Sith?

In Episode IV, everyone seems to believe that Vader is the only one left who can use the Force.     Tarkin: The Jedi are extinct. Their fire has gone out of the universe. You, my friend, are all that's left of their religion.   Of course, they thought the Jedi were all killed, but what about the Emperor?  I realize that he is not even mentioned in Episode IV, so did nobody know that he was a Sith? Or is it just the fact that he was not intended to be brought up in the movie at that point?


Part of LaTeX exam class document does not work

The code below works by printing "page x of y" on each page on the left, and go to next page on the right (or end of Exam for the last page). What I cannot get it to do is to write question xx continues as a central footer. Since I was not able to paste this code as a reply to comments/suggestions on my earlier post here , This is a repeat of that post.  \documentclass[addpoints,10pt,fleqn]{exam} \RequirePackage{amssymb, amsfonts, amsmath, latexsym, verbatim, xspace, setspace} \usepackage{setspace}% http://ctan.org/pkg/setspace \RequirePackage{tikz, pgflibraryplotmarks} \usepackage{lipsum}% http://ctan.org/pkg/lipsum \usepackage[margin=1in]{geometry} \usepackage{enumerate,mdwlist} \usepackage{mathtools}  % for 'bmatrix*' environment \usepackage{paralist}   % for 'inparaenum' environment\newcommand{\dist}{\displaystyle} \usepackage{enumitem} \usepackage[normalem]{ulem} \usepackage{geometry} \geometry{ a4paper, total={210mm,297mm}, left=20mm, right=15mm, top=20mm, bottom=15mm,} \singlespacing \pagestyle{headandfoot} \runningheadrule \runningheader{Linear Algebra-MAT 2200} {Tutorial shhet 7, Page \thepage\ of \numpages} {June, 2015}  \begin{document} \raggedright \begin{center} \bf{Linear Algebra} \end{center} Handout 2 \hfill{May, 2015}\\ \flushright Tutorial Sheet 7 \noindent\makebox[\linewidth]{\rule{\textwidth}{1pt}} \pagestyle{headandfoot} \footrule \lfoot{\footnotesize Page \thepage\ of \numpages} \cfoot{\newcommand{\continues}{\ifincomplete {\footnotesize Question \IncompleteQuestion\ continues \hfill Please go to next page\ldots}{}}} \rfoot{\iflastpage{End of Tutorial Sheet 7.}{\footnotesize Please go to next page\ldots}} \begin{questions} \begingroup\onehalfspacing \question Given the vectors \\ \begin{inparaenum}[a)] \item (2, -1, 1) and (1, 2, 1) \\ \item (2, 1, -3) and (1, 1, 1) \\ \item (2, -1, 2) and (1, -1, 2) \\ \end{inparaenum} \break  Find \\ \begin{inparaenum}[i)] \item Which of the pairs of vectors are perpendicular \\ \item A vector perpendicular to both of the given vectors \\ \end{inparaenum} \endgroup \end{questions} \end{document}


How to display only third match of Find statement?

None of answers that I've seen works for me, I have code like this  OLDVER=`readlink current` OLDDATA=`find ! -newer $OLDVER   And I want to get only third match from FIND statement, because I need this name file to my script.


I just flagged a comment on a deleted post - bug?

I was looking at  (10k only), and noticed some comments on it. Not one to let an opportunity for experimentation slip by, I hovered over it:    I tried to upvote it, but that didn't work. Got a big red nasty box.  Looky there! A flag link!  I bet it doesn't work... Wait, the dialog box came up... Hmm, might as well try it, I bet I get a red box when I hit flag...    Sorry, mods :).  So apparently I can flag comments on a deleted posts - is it ? Or is it a ?


Pass Batch variable as parameter to Java class using command line

How can we pass a batch variable as parameter to a Java class main method using command line? I want to pass the contents of a text file as an argument to a Java class using command line. for eg : Java -jar TestJar.jar %BATCH_VAR%  I have tried the below code and it doesnt seem to work :  echo "starting"  echo off  set keyvalue=^&Type TestDoc.txt  echo %keyvalue%  /// This is printing the right value.  pause  java -jar ErrorUpdate.jar "%keyvalue%" //// This does not pass anything to the Java class :(  pause


Combinatorics That Looks Similar to Vandermonde's Identity

How do I simplify: $$\sum_{r = 0}^{\lfloor \frac{k}{2} \rfloor} \dbinom{k}{2r} \cdot \dbinom{n-k}{k-2r}?$$ Basically, the sum is: $\dbinom{k}{0} \cdot \dbinom{n-k}{k} + \dbinom{k}{2} \cdot \dbinom{n-k}{k-2} + \dbinom{k}{4} \cdot \dbinom{n-k}{k-4} \cdots.$ This seems very similar to Vandermonde's Identity but because we skip two everytime instead of one, I don't see how I can apply it to this problem.


Is there a direct, elementary proof of $n = \sum_{k|n} \phi(k)$?

If $k$ is a positive natural number then $\phi(k)$ denotes the number of natural numbers less than $k$ which are prime to $k$. I have seen proofs that $n = \sum_{k|n} \phi(k)$ which basically partitions $\mathbb{Z}/n\mathbb{Z}$ into subsets of elements of order $k$ (of which there are $\phi(k)$-many) as $k$ ranges over divisors of $n$.  But everything we know about $\mathbb{Z}/n\mathbb{Z}$ comes from elementary number theory (division with remainder, bezout relations, divisibility), so the above relation should be provable without invoking the structure of the group $\mathbb{Z}/n\mathbb{Z}$. Does anyone have a nice, clear, proof which avoids $\mathbb{Z}/n\mathbb{Z}$?


What are some of your favourite integration techniques that are rare or unusual

Hello could any one tell me some unusual or advanced integration techniques, I am already familiar with the standard ones like u-substitution, integration by parts, trig substitution, partial fractions, Feynman technique (differentiation under the integral), integrating the inverse, Laplace transforms In the integral and matrix inversion so I was wondering if anyone knew some rare ones (definite or indefinite)  Please do not answer with any already listed Otherwise Any help is appreciated  Thanks in advance


I've recently fallen upon a problem with biblatex formatting of headers/footers: by default it prints on the even page the word ‘bibliography’ in the left part of the even page header, followed by the page number, and also ‘bibliography’ in the left part of the even page footer. So far so good, even if I don't how to change it.  What is more troublesome is that the same word appears in the rest of my text (index, index of notations, &c.). If I want to get rid of it, I have to use the emptyor plain styles – but not any customised page style (I do that with titleps).  I couldn't find in biblatex where the pagestyle for bibliographies is coded. Any help is very welcome!


Should a "thank you" comment be flagged?

Should a "thank you" comment, for instance Thanks for your answer, be flagged as non-constructive?  If a "thank you" comment is flagged as non-constructive what would the moderator reaction to this flag be? Would it be marked as helpful, or not?


I had ripe bananas so I peeled them, put them in Rubbermaid cont and in the fridge. Are they still ok to use?

They are darkish in color but not black. Still ok for bread?


Metric tensor multiplied by its inverse. I always see this with different indices.


Check if option is selected with jQuery, if not select a default

Using jQuery, how do you check if there is an option selected in a select menu, and if not, assign one of the options as selected.  (The select is generated with a maze of PHP functions in an app I just inherited, so this is a quick fix while I get my head around those :)


How did Harry's blood being inside Voldemort save him?

There are, of course, an incredible amount of theories on how Harry Potter survived. Problem is that the most important one, the one that is canon, is the one I don't get: how Harry's blood inside Voldemort saves him?  Because all that I have read so far, leaves me with questions. I understand why Voldemort wanted Harry's blood, but why does it save Harry? Why is that necessary to keep the sacrifice alive, while it's still inside Harry? And if Harry lost it at 17 (I have seen some different ideas on this as well), why does Voldemort still have it at 69 (give or take a few)?  To clafiry, the parts I'm talking about:     "For a fleeting instant, Harry thought he saw a gleam of something like triumph in Dumbledore's eyes"    (GoF, right after Harry tells Dumbledore that his blood now goes through Voldemort.)  And:     "He took your blood believing it would strengthen him. He took into his body a tiny part of the enchantment your mother laid upon you when she died for you. His body keeps her sacrifice alive, and while that enchantment survives, so do you"   (Albus Dumbledore in DH)  I just don't get why the blood transfusion thing suddenly gave Harry the chance to survive the whole thing, and it's never really been satisfyingly answered, not to my knowledge at least, as every answer I've read raises more questions.


Determine source of ⌘⌥\ being an alias of ⌘C

TL;DR, somehow ⌘⌥\ has become aliased to ⌘C on High Sierra (possibly earlier). I cannot for the life of me determine the source of this.  I first noticed this when invoking 1Password Mini began producing a system bell tone. I finally started to dig into the problem today. In the Keyboard preference pane, there are no conflicts with the ⌘⌥\ shortcut. So I disabled the shortcut in 1Password Mini. Tested, and system bell still sounds. When I attempted to re-add the shortcut, I get the following:    To be clear, this dialog displays when I carefully type ⌘⌥\ — I am not typing ⌘C.  So something has apparently aliased ⌘⌥\ as ⌘C. I have tested this further. If I highlight text, click on the Edit menu, and type ⌘⌥\, I briefly see the Copy item flash, and text is copied to the clipboard.  Any ideas? This is driving me nuts. I've quit all other applications, including menu items. I've checked the Keyboard Shortcuts preference pane for conflicts. And everything has come up short.  Update: I've installed Key Codes from the App Store, and even this application indicates I'm pressing ⌘C! However there's some slight differences that might provide useful information for debugging:  ⌘⌥\:    ⌘C:    Update 2:  As additional information, this happens with both an external Apple Wireless Keyboard as well as the internal keyboard on the MacBook Pro.  Update 3:  This is the full log from Key Codes, including modifier keys being pressed, up to and including pressing the \ key. It indicates immediately after the \ key is pressed (which it identifies as the c key), the c key is released and a modifier change is made as well (despite no keys actually having been released).


Installing php5 gives "Package has no installation candidate"

I tried to install php5.  However, I got an error saying   Package has no installation candidate   What should I do?


Server 2012 deduplication: run on Hyper-V host or guest VM?

I have a Windows Server 2012 Hyper-V host with VMs on a dedicated RAID-5 volume. One VM is also running Server 2012 and is being used to serve files. The other VMs are smaller and mostly used for temporary testing scenarios.   The main file server VM has two dynamically expanding VHDX files - one for the OS and one for storage. The VHDX being used for storage has quite a few duplicated files on it.  Should I run Server 2012 deduplication on the volume containing the storage VHDX file on the host, or within the file server VM itself? I understand that running it within the VM will not decrease the size of the VHDX file on the host, but my goal is to enable as much storage capacity within the VHDX file itself. I also understand that if I run it on the host, I will have to take the VM offline to do it. Downtime isn't a concern in this instance, just the best way to do this.


Why can the mass of a multi-particle system be greater than or less than the sum of the masses of individual particles in that multi-particle system?

My question explains it all. I don't know how else to explain my question.


Where is Gnome 12 in the Stranger Things game?

Its the only thing I'm missing, and I'm going crazy


The website is facing a Japanese keyword hack issue. What to do?

We are currently facing a Japanese keyword hack issue on our website (). The issue is faced on 25-11-2019 when we got the mail that shows someone is the new google search console property owner. After, Our almost all URLs converted into the Japanese language. We had resolve website recovery from the developer, submit a new sitemap and manually fetched pages from the Google search console.  Our traffic went down for 2 days and after recovery, traffic comes back. Even when we type the name of our company then it does not show on the listing but after recover, it has displayed and the traffic is back.  The problem is that there is 70-80 URLs are present on the google search index now which is not available on our website database. Some of that is below.       We had removed that URLs from the search console and resubmit the sitemap. Also used URL parameter tools and exclude parameter "?/", "nost" on 29-11-2019, 5-12-2019 but the issue remains there.  The main issue is website traffic is back but the spam URLs are still shown on the google index and also new spam pages are generated and indexed on google. Most of the traffic from that spam URLs are from japan.  What we can do? Please give the solution so that we can remove that URLs from the search index and maintain the visibility of our site. We think that this issue is also faced by other sites and this solution may helpful for them.


I'm trying to round up numbers using C# in a way that it always rounds to the next number. For instance:  0.409 -> 0.41 0.401 -> 0.41 0.414 -> 0.42 0.499 -> 0.50 0.433 -> 0.44   Is there a way to do this using .NET built-in functions?


I'm solving a probability problem and the expected value of a random variable is this series I need some hint to find the sum of it.  $\displaystyle \sum_{n=1}^{\infty}\frac{n}{2^n}$


I'm trying to update from 13.10 to 14.04, but whenever I try to update from terminal by using sudo apt-get update I get the error:  W: Failed to fetch cdrom://Ubuntu 13.10 _Saucy Salamander_ - Release amd64 (20131016.1)/dists/saucy/main/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs  W: Failed to fetch cdrom://Ubuntu 13.10 _Saucy Salamander_ - Release amd64 (20131016.1)/dists/saucy/restricted/binary-amd64/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs  W: Failed to fetch cdrom://Ubuntu 13.10 _Saucy Salamander_ - Release amd64 (20131016.1)/dists/saucy/main/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs  W: Failed to fetch cdrom://Ubuntu 13.10 _Saucy Salamander_ - Release amd64 (20131016.1)/dists/saucy/restricted/binary-i386/Packages  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs  E: Some index files failed to download. They have been ignored, or old ones used instead.


Unable to Display Text in Hindi Language in PHP Website

I want to display text in Hindi Language in my website but it is giving me error. In return the value is showing as "????"  How do I display the text in Hindi or other language.  I have the META tags as well in place.


I've installed xubuntu-desktop and I want to get rid of all the ubuntu-desktop and Unity-related packages. But all the guides I've found are either outdated (psychocatz) or simply don't work (aptitude). What can I do to remove all the ubuntu-desktop packages?


Is it possible to make git to track empty folders?

I read from this  which explains that to make git to track a folder there must atleast an empty file:  Currently the design of the Git index (staging area) only permits files  to be listed and nobody competent enough to make the change to allow  empty directories has cared enough about this situation to remedy it.  Directories are added automatically when adding files inside them.  That is, directories never have to be added to the repository,  and are not tracked on their own. You can say "git add <dir>" and it  will add the files in there.  If you really need a directory to exist in checkouts you should create a file in it.   I have faced some problems because git not tracking empty folders, i am list a few:  Problem1:  I have a apache/log directory in one of my git repository.  when I pushed it to server and run the website it didn't worked. Where it worked fine in my localsystem. after a lot of research i found out that git push did n't pushed the empty folder /log. the serve checked folder log to create logfiles. since folder log did not exist, it is not possible to automatically create a folder and put these files. That is why the error.  Problem2:   I have lots of branch. Only one of my particular branch say frontend have folder caps.  Sometime one of a folder in the directory my_git_repo/caps/html/home/ will be empty.  branch master doesn't have folder caps  if i make git checkout master it will have empty folder ie caps/html/home/tmp so i want to manually delete the folder caps sometimes it will create confusion.  usually i solve these problems by putting an empty file(README) in the folder.  So I would like to make git to track all empty folders. is it possible by editing .git/config or something?  Any help will be appriciated.:))