Discrete Math On Induction proof: $\sum_{i=1}^n n2^n = (n-1)2^{n+1} + 2$

Show by induction that the following formulas hold.   $\sum_{i=1}^n n2ⁿ = (n-1)2^{n+1} + 2$   What did a similar problem to this but this one is a little different. I think is because this one has a power n and I'm not sure how to start with this one?


Can the Lorentz force expression be derived from Maxwell's equations?

The electromagnetic force on a charge $ e $ is   $$ \vec F = e(\vec E + \vec v\times \vec B),$$   the Lorentz force. But, is this a separate assumption added to the full Maxwell's equations? (the result of some empirical evidence?) Or is it somewhere hidden in Maxwell's equations?


Failed to download repository information on Ubuntu Unity 16.04 LTS

When I ran Software Updater I was given an error message saying     Failed to download repository information, check your internet connection.   This is what it says:  W:The repository 'http://ppa.launchpad.net/upubuntu-com/icons/ubuntu xenial Release' does not have a Release file. W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use. W:See apt-secure(8) manpage for repository creation and user configuration details. E:Failed to fetch http://ppa.launchpad.net/upubuntu-com/icons/ubuntu/dists/xenial/main/source/Sources  404  Not Found,  E:Some index files failed to download. They have been ignored, or old ones used instead.


I am a highschooler who eventually wants to deeply understand the properties of elements and compounds etc. I have been dabbling in some Chemistry books lately  but I find them  a bit superficial, and thus I have come to realize that I need a good understanding of Physics. What  branches of Physics are the  most related  to these  questions? I think  they are Quantum and Solid  State  Physics  but I am not sure.  And what are the prerequisites  for  these  branches of Physics? Books definitely  do not look beginner-friendly.   I am  aware  that  achieving  a real  understanding  of these  subjects  is  very hard but you have  to start somewhere, right?  I was actually  thinking  to major  in something  related  to Chemistry, but  as I said I have been disillusioned and now I think I will major in something related  to Physics (And I enjoy  Physics as well).


Pre-70s science-fiction short story: "Cracker for my Megatherium?"

Looking for a science-fiction short story written before the 1970s, which involves starship travel in the 1950's style. Written from the point of view of a male researcher, who encounters a planet of humans who have stalled at a technologically primitive level despite high intelligence.  I remember a line from a kid:     Hey Mister, could I have a cracker for my Megatherium?   The humans see the Earthlings using wheeled carts, and think, ~"odd round legged little tables."    Over the course of their stay, the primitives go from using unwheeled sledges to inventing roller bearings, and the male researcher thinks they could advance quickly, but not so quickly as to be a threat to his galaxy spanning civilization.        Twenty years later, it didn't seem so funny.


Suppose that $a$, $b$ and $c$ are positive real numbers and that $a \leq b + c$. By cross multiplying or otherwise, show that  $$\frac{a}{1 + a} \leq \frac{b}{1 + b} + \frac{c}{1 + c}$$  Anyone able to get this to work out? I cross multiplied them but am unable to manipulate it into an expression that verifies the statement.


Is it possible to dynamically set Views' pager settings?

Say for instance, you have a view that displays when viewing a certain node type, but you want the pager settings to be different for each individual node. I was thinking of making a CCK field like "pager setting" and then give it an integer option of x-y. But I don't know if it's possible to somehow dynamically plug that field into the Views' settings. Or is there another way to do this maybe?


Hosting SSL tunneled OpenVPN and HTTPS on the same server at the same 443 port

Is there a way to host a SSL-tunneled (using stunnel) OpenVPN server and a regular Apache HTTPS server on the same server using HAProxy? It seems that by using stunnel, the format of the packets should all the way be the same. Is there any ways to make a difference between the two kinds of packets (which is not detectable by DPI) for the HAProxy to sort them out? I tried to use different domain names for the HTTPS server and the OpenVPN Server (though they point to the same IP address) but seems it doesn't work because OpenVPN does not use SNI.  Thanks a lot!


Combine two normal maps and control the strength of each

I use this node setup to combine my two normal maps.   I adapted this method from here.    It works perfectly to just combine the maps. But now i need individual contol over the strength each of them.   Is there a way to do this ?


Is it possible to not create keyframes automatically when drawing with Grease Pencil?

Is it possible to use the grease pencil without creating keyframes when you draw: I just want a single drawing so I don't need keyframes, but I need to be able to scrub through the timeline when drawing.  I know I can move the keyframes or delete them, but it would be easier not to have any.  I have already tried turning the "automatic keyframe" button from the timeline off.


Non-unitarity of finite dimensional Lorentz group and its implications

In Peskin and Schroeder, section 3.2, it is stated that Lorentz group being non-compact it does not have any finite dimensional, faithful unitary representation. But it has also been said that one shouldn't worry because $\psi$ is not a wavefunction but a field.  Now my question is, (editing as per recommendation by Qmechanic to ask the subquestions in separate posts)  Why do we not have to worry about non-unitarity in the case of a field?


Still showing up as "new contributor" more than 3 weeks after joining

I've been here on meta SE for almost a month now, but on all my posts I still show up as a "new contributor". I've seen plenty of people who have been a member for barely over a week, but they don't show up as a "new contributor". Why is this happening?


I have seen both sentences below:  I will get married. I will marry.  So what is the difference? Which one is recommended? Is there any difference in meaning or just grammar?


How to Protect Uploads, if User is not Logged In?

I use WordPress for a private site where users upload files. I use the "Private WordPress" to prevent access in to the site if the user is not logged in.  I would like to do the same to the files uploaded in the uploads folder.  So if a user its not logged in they wont be able to access to :  if they try to access but they are not logged then they should be redirected to login page for example.  I found a plugin called private files but last time updated was  in 2009 and it does not seems to work on my WordPress.  Anyone know any method?  Hotlinking method will be enough to protect this?  I also found this method :  # BEGIN WordPress <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteCond %{REQUEST_URI} ^.*uploads/private/.* RewriteCond %{HTTP_COOKIE} !^.*wordpress_logged_in.*$ [NC] RewriteRule . /index.php [R,L] RewriteRule ^index\.php$ - [L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule> # END WordPress   But then any user that replicate the cookie could pass this right? Regards


How to typeset an inner product in Latex?

I want to write an inner product in Latex. Using the normal characters < and >, the inner product brackets end up looking more like less-than and greater-than signs. How do I typeset  more narrow brackets, like this?


I'm trying to concatenate some creditcards data I have on my customers.   For example I'm having the next table (call it Table A):   custNum  totAmount  creditCardType   10        100        Visa   10        250        Mastercard   27        350        Visa   10        500        AmericanExpress    27        100        AmericanExpress   etc...  and I'm trying to concatenate this data in the next format:       custNum   totAmount    creditCardType       10        850        Visa,Mastercard,AmericanExpress        27        450        Visa,AmericanExpress    is there a smart and simple way of doing it?   Thank you in advance!


As per google meaning I understood like,  Anyone - any person or any people  Anybody - anyone  It seems both are relevant. I am trying to understand the proper place for using these words. Please help me.  Thanks in Advance.


Wi-Fi process using up to 16GB of memory

Sometimes when I switch Wi-Fi network or connect to a VPN via Global Protect the memory usage of /System/Library/CoreServices/WiFiAgent.app shoots up and my fans go mental. Why?    This screenshot is one of the worst times it has happened, the usage is not alway consistent sometimes its 2GB, sometimes 6GB etc etc  Basic macbook pro 13" 2017


Put the § symbol before each section number

I'm writing a document (article class). I'm using the clever reference package to crossreference sections, and I have modified the references so the \cref{label} produces, for example if it's section 2, the symbol §2. I have also modified the (sub)section and part title formats via titlesec, all with the following code:  \crefname{section}{§}{§§} \Crefname{section}{§}{§§} \crefname{part}{§}{§§} \titleformat*{\section}{\Large §\scshape\centering} \titleformat*{\subsection}{\large §\scshape} \titleformat{\part}[display]    {\LARGE §\scshape\centering}    {\thepart}    {0em}    {}   The last thing I would like to do is to make it print the symbol § before the number of the section in each section. I have tried doing like above, just putting it in the second {} of the titleformat command for each of them, but that obviously writes it before the title of the section, leaving something like this:  3.1 §This is a section.   Plus Auctex returns an error when compiling with Latex (Error ocurred after las TeX file closed) although it produces the correct dvi file.  How could I correctly achieve that?  Thanks in advance.


GRASS Toolbar for QGIS missing the tools I expect to see

I am trying to learn GRASS and QGIS using the instructions here: . I am running on Windows and open the version of QGIS with GRASS. When I enable the GRASS plugin, however, I see only two buttons on the toolbar. The panel is telling me to open a GRASS mapset but the button to create a new mapset is not visible in the toolbar. What am I missing here?  I'm using QGIS 2.14.3 with GRASS 7.0.4


cd - can move to the last visited directory. Can we visit more history other than the last one?


"no such file or directory" message when deleting a file that exists on NTFS

I have a directory with images. Suddenly I found out that there's a new image with a new name. The image content is similar to another image in another directory but with a different name. I didn't copy this image to this directory.  Also a directory with the same name as the image suddenly appeared there. I didn't create any of them. When I tried to delete them I got this message "No such file or directory" even though it already existed there. I used the command sudo rm -rf imagename.jpg to delete it but it didn't work.   Can anyone explain why this is happening and how to solve it?  The output of ls -l "large (2).jpg":  -rw------- 1 alaa alaa 2859942 Jun  8 04:01 large (2).jpg   The output of rm "large (2).jpg":  rm: cannot remove ‘large (2).jpg’: No such file or directory   The output of printf %s\\0\\n ./large* | sed -n l  ./large (20).jpg\000$ ./large (26).jpg\000$ ./large (2).jpg\000$ ./large (5).jpg\000$   The filesystem is NTFS.


Find all natural roots of the equation : $1!+2!+...+n!=m^2$    Is there any relation between perfect squares and factorial?? I have really no idea for this one!


First of all, I'm not looking for an answer on how to remove the files. I am looking for a reason why this doesn't work - and a suggestion on how to remove the files without sudo.  I have a directory in my Desktop that has a few inner directories (don't judge the naming - I just extract what I need from files I'm given) and after getting the files I try and remove the files with rm -rf Bengal\ Tiger\ Creative/, I am surprised to see the following warning for each image.     rm: cannot remove ‘Bengal Tiger Creative/Bengal Tiger Creative/images/customer-services-landscape.jpg’: Permission denied   Below is some code outputs.  tree  nathan@nathan-pc:~/Desktop$ tree . ├── Bengal Tiger Creative │   └── Bengal Tiger Creative │       └── images │           ├── awards.jpg │           ├── blank.gif │           ├── bullet1-light-green.gif │           ├── bullet2-light-green.gif │           ├── bullet3-light-green.gif │           ├── bullet4-light-green.gif │           ├── customer-services-landscape.jpg │           ├── desktop.ini │           ├── header-img1.jpg │           ├── header-img2.jpg │           ├── header-img4.jpg │           ├── header-img5.jpg │           ├── softhr.gif │           ├── Thumbs.db │           ├── tiger_main-img1.jpg │           ├── tiger_main-img2.jpg │           ├── tiger_main-img3.jpg │           ├── tiger_main-img4.jpg │           ├── Vanquis-benefits-icons_iphone-green.gif │           └── white-arrow-green.gif   ls -laR  nathan@nathan-pc:~/Desktop$ ls -laR Bengal* Bengal Tiger Creative: total 12 drwxrwxr-x 3 nathan nathan 4096 Aug 10 11:30 . drwxr-xr-x 6 nathan nathan 4096 Aug 10 11:34 .. drwxrwxr-x 3 nathan nathan 4096 Aug 10 11:34 Bengal Tiger Creative  Bengal Tiger Creative/Bengal Tiger Creative: total 12 drwxrwxr-x 3 nathan nathan 4096 Aug 10 11:34 . drwxrwxr-x 3 nathan nathan 4096 Aug 10 11:30 .. dr-xr-xr-x 2 nathan nathan 4096 Aug 10 11:36 images  Bengal Tiger Creative/Bengal Tiger Creative/images: total 356 dr-xr-xr-x 2 nathan nathan   4096 Aug 10 11:36 . drwxrwxr-x 3 nathan nathan   4096 Aug 10 11:34 .. -rwxrwxrwx 1 nathan nathan  14910 Mar 18 12:29 awards.jpg -rw-rw-r-- 1 nathan nathan   1093 Mar 21  2014 blank.gif -rw-rw-r-- 1 nathan nathan   1978 May  8  2014 bullet1-light-green.gif -rw-rw-r-- 1 nathan nathan   1969 May  8  2014 bullet2-light-green.gif -rw-rw-r-- 1 nathan nathan   2416 May  8  2014 bullet3-light-green.gif -rw-rw-r-- 1 nathan nathan   2449 May  8  2014 bullet4-light-green.gif -rw-rw-r-- 1 nathan nathan 113138 Apr 14  2014 customer-services-landscape.jpg -r--r--r-- 1 nathan nathan    142 Mar 25 11:58 desktop.ini -rw-rw-r-- 1 nathan nathan  14312 Mar 23 11:39 header-img1.jpg -rw-rw-r-- 1 nathan nathan   1480 Mar 23 11:41 header-img2.jpg -rw-rw-r-- 1 nathan nathan   1278 Mar 23 11:41 header-img4.jpg -rw-rw-r-- 1 nathan nathan   1168 Mar 23 11:41 header-img5.jpg -rw-rw-r-- 1 nathan nathan   1703 Mar 21  2014 softhr.gif -rw-rw-r-- 1 nathan nathan  88064 Aug  4 10:39 Thumbs.db -rw-rw-r-- 1 nathan nathan  23607 Mar 23 11:56 tiger_main-img1.jpg -rw-rw-r-- 1 nathan nathan  23400 Mar 23 11:56 tiger_main-img2.jpg -rw-rw-r-- 1 nathan nathan   6970 Mar 23 11:56 tiger_main-img3.jpg -rw-rw-r-- 1 nathan nathan   8996 Mar 23 11:57 tiger_main-img4.jpg -rw-rw-r-- 1 nathan nathan    275 Jul 31  2014 Vanquis-benefits-icons_iphone-green.gif -rw-rw-r-- 1 nathan nathan   1821 Jul  9  2014 white-arrow-green.gif   Doing chmod 777 and then delete does not work.  Doing rm -rf * inside the directory does not work.  Doing sudo rm file does work.   I can easily remove these files using sudo, however, I cannot see why they cannot be removed without sudo. As a relatively new Ubuntu user, I would like to learn why.  Thanks in advance, Nathan


X fails to start after update with reboot on Ubuntu 14.04

After an update that included the kernel and a reboot, X no longer started for my Ubuntu 14.04 machine.  An attempt to startx manually failed as well with this message:    Note: the underlying issue has been addressed by a more general question and answer and is linked in my answer below.


How can I manually delete old backups to free space for Time Machine?

I use a Time Capsule for backup and now I want the drive to back up data from an extra Mac. But the drive is filled up with old backups from Mac 1. There simply is not enough space available for the backup for Mac 2.  I get this error message when running Time Machine backup:     Time Machine could not complete the backup.   This backup is too large for the backup disk. The backup requires   28.68 GB but only 626.2 MB are available.      Time Machine needs work space on the backup disk, in addition to the   space required to store backups. Open Time Machine preferences to   select a larger backup disk or make the backup smaller by excluding   files.   I know Time Machine itself is able to remove old backups when it needs more space. But in this case it does not remove any Mac 1 backups to make space for Mac 2.  Question is, how do I do it manually?


Hanging captions with first line also indented

I'm trying to match the formatting between a word document and latex document. In the word doc, captions have the caption label at the left margin, the label separator is effectively a tab character with a tab stop at 2cm, and then the caption text is formatted with a hanging indent at 2cm from the left margin.  This results in all of the blocks of caption text lining up down the page.   I can't work out how to replicate this in LaTeX.   The hang caption format gets close, but it sets the hanging indent relative to the caption label. Is there anyway to set an absolute value?


What software can I use to view epub documents?

What software can I use to view .epub documents?


Is there a simpler expression for $f(f(f(...f(x)...)))$ (total n '$f$')?

Is there a simpler expression for $f(f(f(...f(x)...)))$ (total n '$f$') ?   Thank you.


$\frac{-y}{x^2+y^2}dx+\frac{x}{x^2+y^2}dy$ is non exact differential equation.    Here above equation satisfies $\partial M/\partial y=\partial N/\partial x$.  I know that above equation doesnot exist for $(0,0)$ but. How to prove that above given is not exact?  I don't know to how to show above?  Any Help will be appreciated.


Can't install a package due to "Something wicked happened resolving" error

I'm following  to install git on my laptop. When I do:  $ sudo apt-get install git-core  This is what my terinal shows:  Reading package lists... Done Building dependency tree         Reading state information... Done The following packages were automatically installed and are no longer required:      libasprintf0c2:i386   libcroco3:i386   libgettextpo0:i386   libgomp1:i386   libunistring0:i386 Use 'apt-get autoremove' to remove them. The following extra packages will be installed:   git git-man liberror-perl Suggested packages:   git-daemon-run   git-daemon-sysvinit   git-doc git-el   git-arch git-cvs   git-svn   git-email   git-gui   gitk gitweb The following NEW packages will be installed:   git git-core git-man liberror-perl   0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.  Need to get 6,825 kB of archives. After this operation, 15.3 MB of additional disk space will be used. Do you want to continue [Y/n]? y  WARNING: The following packages cannot be authenticated!    liberror-perl git-man git git-core Install these packages without verification [y/N]?       E: Some packages could not be authenticated lucas@lucas-Inspiron-N5050:~$ sudo apt-get install git-core Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required:   libasprintf0c2:i386   libcroco3:i386   libgettextpo0:i386   libgomp1:i386   libunistring0:i386 Use 'apt-get autoremove' to remove them. The following extra packages will be installed:   git git-man liberror-perl Suggested packages:   git-daemon-run git-daemon-sysvinit   git-doc git-el git-arch git-cvs git-svn   git-email git-gui gitk gitweb The following NEW packages will be installed:   git git-core   git-man liberror-perl  0 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.  Need to get 6,825 kB of archives. After this operation, 15.3 MB of additional disk space will be used. Do you want to continue [Y/n]? y WARNING: The following packages cannot be authenticated!   liberror-perl git-man git git-core Install these packages without verification [y/N]? y Err httpq://py.archive.ubuntu.com/ubuntu/quantal/main liberror-perl all 0.17-1    Something wicked happened resolving 'py.archive.ubuntu.com:http' (-5 - No address associated with hostname) Err httpq://py.archive.ubuntu.com/ubuntu/ quantal/main git-man all 1:1.7.10.4-1ubuntu1    Something wicked happened resolving 'py.archive.ubuntu.com:http' (-5 - No address associated with hostname) Err httpq://py.archive.ubuntu.com/ubuntu/ quantal/main git amd64 1:1.7.10.4-1ubuntu1    Something wicked happened resolving 'py.archive.ubuntu.com:http' (-5 - No address associated with hostname) Err httpq://py.archive.ubuntu.com/ubuntu/ quantal/main git-core all 1:1.7.10.4-1ubuntu1    Something wicked happened resolving 'py.archive.ubuntu.com:http' (-5 - No address associated with hostname)  Failed to fetch httpq://py.archive.ubuntu.com/ubuntu/pool/main/libe/liberror-perl/liberrorperl_0.17-1_all.deb    Something wicked happened resolving 'py.archive.ubuntu.com:http' (-5 - No address associated with hostname)  Failed to fetch httpq://py.archive.ubuntu.com/ubuntu/pool/main/g/gi/git-man_1.7.10.4-1ubuntu1_all.deb    Something wicked happened resolving 'py.archive.ubuntu.com:http' (-5 - No address associated with hostname)  Failed to fetch httpq://py.archive.ubuntu.com/ubuntu/pool/main/g/git/git_1.7.10.4-1ubuntu1_amd64.deb    Something wicked happened resolving 'py.archive.ubuntu.com:http' (-5 - No address associated with hostname)  Failed to fetch http://py.archive.ubuntu.com/ubuntu/pool/main/g/git/git-core_1.7.10.4-1ubuntu1_all.deb   Something wicked happened resolving 'py.archive.ubuntu.com:http' (-5 - No address associated with hostname) E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?   How could I install git on Ubuntu 12.10? I can't even do it from the Ubuntu Software Center.  Thanks in advance!


How can we show that $ \sum_{n=1}^{\infty} \frac{n}{2^n} = 2 $?

How can we prove the following?  $$ \sum_{n=1}^{\infty} \frac{n}{2^n} = 2 $$  It would be great to see multiple ways, or hints, about how this can be proven.   I know this is a power series $\sum_{n=0}^\infty c_n \, (x-a)^n$ where $c_n = n$ and $x = \frac{1}{2}$ and $a = 0$, but otherwise I am stuck.


The following code works:  \def \robble {robble} \def \robbles {\robble\robble}   But the following but doesn't:  \def \robbles {robble} \def \robbles {\robbles robble}   The overall goal is to get robbles to be robblerobble. I need something like the second example, where I am appending on to the current value of a variable. The way it is written right now causes a stack overflow. Is there a way to append to variables in LaTeX?


I am using Ubuntu 12.04 (dual os windows 7)  Now I have total 2 hard drives. 1st is a system hard drive and having two partitions another is 1tb my work hard drive with no partition.  My system hardrive partitions named with it's size like 157 GB Filesystem, 293 GB Filesystem` etc. I want to change this name.    I have tried using GParted but it doesn't shows that drive but only Works drive and DVD`    How to change these label? and if can't than how to access on terminal? because if use this  cd /157 GB Filesystem   It doesn't work.


Update  Sorry for the delay! I’ve been thinking about this feedback in between my other projects, and I’ve landed where I’ve started 😕  I’ve made sure to continue highlighting spoilers in gray. The differentiation from normal blockquotes is super important since their behavior is so different. I explored keeping spoilers yellow, but that still has the same theming issues throughout the network. Red seemed too powerful, with its error connotations.  I understand completely that folks are using blockquotes to highlight images. However, I don’t think that’s a  we want to formally pave. I’m ok with being opinionated here—blockquotes should be used for quoting, not as a way to highlight images. I understand that this will be frustrating to Machavity who made excellent points about differentiation in his answer, but I don’t think image highlighting ought to dictate how blockquotes are styled.  I’m also cautious of adding borders to images as explored by user1306322 for the same reasons and for the additional fear of being too prescriptive in how we display images there.  It’s a tough one! I went back and forth with the design team and I still think this is the best path forward.  Original post  We’re making a few changes to blockquotes soon. Historically, we had a bit of feedback that the yellow backgrounds were overpowering, reducing the contrast of the quote itself. The yellow border also lacks contrast with the background. Others have indicated that there should be  and between .  These yellows also compete with theming in our communities, especially those with backgrounds that aren’t perfectly white like English Language & Usage and Role-Playing Games.   We’re proposing we switch to a single gray bar in our blockquotes. This should fix those theming issues and make it easier to distinguish between quotes, spoilers and code.  This will also improve blockquote nesting, since our current nesting is a mess because the darker yellow bar is barely noticeable on the paler yellow background.  Spoilers should pretty much behave exactly the same way. More room for later improvements there.  Here’s how our current blockquotes look. You can click to expand:    Here’s what we propose:    There is a lot of prior art out there for this approach. GitHub has styled theirs this way for a long time. So has Slack.     Let me know what y’all think. I think these changes will be an improvement, and I hope you do too.  Huge thanks to Catija for gathering some meta posts on blockquotes and creating an awesome blockquote playground post for testing.


Splitting a semicolon-separated string to a dictionary, in Python

I have a string that looks like this:  "Name1=Value1;Name2=Value2;Name3=Value3"   Is there a built-in class/function in Python that will take that string and construct a dictionary, as though I had done this:  dict = {     "Name1": "Value1",     "Name2": "Value2",     "Name3": "Value3" }   I have looked through the modules available but can't seem to find anything that matches.    Thanks, I do know how to make the relevant code myself, but since such smallish solutions are usually mine-fields waiting to happen (ie. someone writes: Name1='Value1=2';) etc. then I usually prefer some pre-tested function.  I'll do it myself then.


Proof that $\sum_{i=1}^{n}e_i X_i = 0$ in simple linear regression

I'm tasked with proving that $\sum_{i=1}^{n}e_i X_i = 0$ in the context of simple linear regression. We have that $e_i X_i = (Y_i - \hat{Y}_i)X_i = (Y_i - \hat{\beta}_0 - \hat{\beta}_1X_i)X_i.$ It follows that $$ \sum e_i X_i = \sum X_iY_i - \hat{\beta}_0 \sum X_i - \hat{\beta}_1 \sum X_i^2. $$ Now use the fact that $\hat{\beta}_0 = \bar{Y} - \hat{\beta}_1 \bar{X}$. It follows that \begin{align} \sum e_i X_i & = \sum X_iY_i - (\bar{Y} - \hat{\beta}_1 \bar{X}) \sum X_i - \hat{\beta}_1 \sum X_i^2 \\ &= \sum X_iY_i - \bar{Y}\sum X_i - \hat{\beta}_1 \bar{X} \sum X_i - \hat{\beta}_1 \sum X_i^2 \\ &= \sum X_iY_i - \frac{\sum Y_i \sum X_i}{n} - \frac{\Bigl(\sum X_i\Bigr)^2}{n} - \hat{\beta}_1 \sum X_i^2. \tag{*} \end{align} Now I've noticed that equation $(*)$ looks a lot like the expression for $\hat{\beta}_1$ (a solution to the normal equations), which makes me think I'm on the right path, because in proving that $\sum e_i = 0$ we use one solution to the normal equation, but I can't seem to manipulate the expression into the answer. Thanks for any help.


Was prejudice against droids common in the “Star Wars” universe? Or was it just the bartender at the Cantina?

When —the bartender at the Cantina at Mos Eisley spaceport in the first Star Wars—says:     “We don’t serve their kind here.”   In reference to C-3PO and R2-D2 entering the bar, it’s certainly a bit prejudicial, but are these commonly held views in this universe? We don’t see it happen anywhere else in the films but is it implied elsewhere?


Common observables and associated operators: operator momentum

Starting from my previous question  and considering that the commutator  $$\left[i\hbar\frac{\partial}{\partial x},x\right]=i\hbar, \tag{1}$$ the associated linear operator momentum (for example the momentum $p_x$ of the $x$-axis) is:  $$p_x\longrightarrow -i\hbar\frac{\partial}{\partial x}=\frac{\hbar}{i}\frac{\partial}{\partial x} \tag{2}$$ The association of $p_x$ with $-i\hbar\partial/\partial x$ is it a postulate or exist a proof that $$\left[i\hbar\frac{\partial}{\partial x},x\right]=i\hbar\color{red}{\boldsymbol{\equiv}[p_x,x]\,\,?} \tag{3}$$


Trying to install Ubuntu and got message about Kernels

We have a lot of computers that have been donated to our school, but they are all running very slow. I am trying to find a way to make the computers run better without costing us an arm and a leg.  Someone suggested I try Ubuntu and I just tried installing it on one of our old computers. I got the following message:     This kernel requires an x86-64 CPU, but only detected an i686 CPU. Unable to boot.   Is there an older version that I would be able to install so we can use the computers. I have about 20 computers throughout the school and we have not been able to use very many of them for a few years. We are trying to make them run faster, so we can run some new math and reading software we will be getting in the fall.


What faction quests are the point of no return?

I am aware that I seem to be approaching the end of the game, if you can't tell you are yet then do not read this as it may include some spoilers of future quests, if this doesn't affect you then continue.  I am trying to get the Brotherhood of Steel ending of the game, currently up to the quest "Blind Betrayal", however trying to clear up as many other faction quests as possible before going too far into the Brotherhood of Steel quest line.  I'm currently at the Institute quest "The Battle of Bunker Hill", it has optional objectives such as inform the Railroad/Brotherhood of Steel or simply continue on behalf of the institute.  I have read somewhere that if I were to simply following the Institute here then it will result in being sided with them.  I'd ultimately like to free the synths from the bunker (Railroad) but side with the Brotherhood of Steel overall, however when I return to the Railroad I am given the quest "Underground undercover", will proceeding with this quest make the Brotherhood of Steel dislike me/prevent me getting the Brotherhood of Steel ending?  If the above is true, it seems I am going to have to kill the synths in the bunker which I was trying to avoid as I have been trying to give synths better lives.


What are the benefits of PGFPlots/TikZ compared to importing PDF?

What are the benefits of using tools like pgfplots or tikz directly in LaTeX compared to importing PDF/PGF generated by say matplotlib?   believed that the main reason is to match the plots with the rest of the document. It also mentioned that no other plotting packages from R or python can generate graphs that have the same high image quality as those generated by pgfplots in LaTeX directly, but no examples or reasons were given. Is there evidence to back up this claim?    Another related question is that, is there any reason for exporting a plot to PGF instead of PDF?  said that the reason is PGF will generate the whole graph in LaTeX while importing to PDF even with  will only use LaTeX for the text part of the graph. But if the main reason for plotting in LaTeX is that we can match the plots with the rest of the text document, usetex exactly does that.  My current adopted approach to producing PDF documents with graphs is (i) generate graphs using tools like matplotlib or other plotting packages in a scientific programming language so that I can do computations before plotting or plot repetitive graphs; (ii) export to PDF files and use usetex if I want to match the font with my document; (iii) import the PDF files using \includegraphics and make final adjustments.  This seems to work out just fine and I didn't notice any image quality issues or graph not matching with the rest of the document.   So are there any other reasons to use native plotting utilities like pgfplots in LaTeX that I overlooked?


Can a file appear to be modified before it was created?

Is it possible to have a file which has a modified date that is before its created date? What actions would cause this event to occur?


"The car is high quality" VS. "The car is of high quality"

What's the difference here? The word, of, is among the most difficult English word to learn, I guess...


IsAssignableFrom() returns false when it should return true

I am working on a plugin system that loads .dll's contained in a specified folder. I am then using reflection to load the assemblies, iterate through the types they contain and identify any that implement my IPlugin interface.   I am checking this with code similar to the following:   foreach(Type t in myTypes ) {     if( typeof(IPlugin).IsAssignableFrom(t) )     {        ...     } }   For some reason IsAssignableFrom() keeps returning false when it should be returning true. I have tried replacing the t by explicitly giving it a type that should pass, and it works fine, but for some reason it isn't working with the types that are returned from the loaded assembly. To make things stranger, the code works fine on my co-worker's machine but not on mine.  Does anyone know of anything that might cause this sort of behavior?  Thanks


I came up with a question: What is the distribution of $(X−Y)^2+(Z−Y)^2$, where $X$,$Y$ and $Z$ are independent normal distributions with their own means and variance? The common part is $Y$ in both of the summands that introduces correlations, otherwise it is χ2. Thanks for the help!


I just installed Blender for the first time, never used this software before and when I tried using it, it had a big delay between when I click something and the response, everything is lagging, moving the cube in the scenery takes 5 seconds before showing on screen. I get this error :   Failed to set 44100hz, got 48000hz instead   I don't think this is the cause of my problem, but I hope it helps.  Thanks for helping.


Which is correct? "Christmas came three days early to felons" or "Christmas came three days earlier to felons"?  The wave of corrupt presidential pardons began Wednesday. Christmas came three days early to felons George Papadopoulos, former Congressmen Duncan Hunter and Chris Collins, and 17 others. Hunter and Collins lined their family's pockets by misusing campaign funds or inside information. Papadopoulos lied to the FBI in the Mueller investigation. Source:


My teacher once said, for any positive number $\ n, $ $\ n^k - 1 $ would always have $\ n-1 $ as a factor for all positive odd values of $\ k $. Could anyone tell me the proof? I have written my approach below.  Assuming $n-1$ to be a factor.  $n^k - 1 = (n-1)x $  $n^k = (n-1)x + 1 $  $k = \lg( (n-1)x + 1 ) / \lg (n) $   If my approach is right could you tell me where should I go from here?  Edit :  clears my doubt.  Edit 2 : My question is "why for any positive number $\ n, $ $\ n^k + 1 $ would always have $\ n+1 $ as a factor for all positive odd values of $\ k $ ".


How to show operations on two random variables (each Bernoulli) are dependent but not correlated?

I was looking at the following question from "One Thousand Exercises in Probability" by Grimmett, page 25, question 16 (not homework just self-study):     Let $X$ and $Y$ be independent Bernoulli random variables with $p = 1/2$.   Show that $X + Y$ and $|X − Y|$ are dependent though uncorrelated.   Now, the solution given on page 176 goes as follows:  $\mathrm{cov}(X+Y, |X-Y|) = E[(X+Y)\cdot(|X-Y|)] - E[X+Y]\cdot E[|X-Y|]$  I can work out that   $E[X+Y] = (0)(1/4) + (1)(1/2) + (2)(1/4) = 1$  and  $E[|X-Y|] = (0)(1/2) + (1)(1/2) = 1/2$  But I can't work out how to do  $E[(X+Y)\cdot(|X-Y|)]= ?$  The solution in the book for the covariance is:  $1/4 + 1/4 - 1(1/2) = 0$  To show dependence, the book provides the following solution:   $P(X+Y=0, |X-Y|=0) = 1/4$ is not the same as $P(X+Y=0)\cdot P(|X-Y|=0) = 1/8$


How to swap order of extensions of matching files?

I am merging two folders with the following command:  rsync -a --checksum --backup --suffix=.merge-bkup src/ dst/   The idea is that if a file exists in both folders, both versions are preserved.  However, I am doing this on an operating system with a UI that uses extensions to associate files with applications. So while it may technically preserve both "My File.txt" and "My File.txt.merge-bkup" the latter file will not be useful to many users since it can no longer be opened automatically in the right application.  Can I use find to somehow take every file named "My File.txt.merge-bkup" and rename it to "My File (Backup).txt"? Even better would be to end up with "My File (Backup N).txt" if "My File (Backup).txt" already exists but I suspect that might be a stretch.


Story about boy raised by two necromancers/warlock/dark wizards

I can't find the story I read which is about a boy raised by two male dark wizards in a kingdom where dark wizards are hunted.       He meets a princess that escaped and I think one of his foster parents die in the end.


I made a non-refundable booking on booking.com earlier today and was told that I would be paying on the day in the hotel. However I just received an email telling me that my credit card was invalid and if I did not update my credit card in 24 hours I would lose my booking.   I have no way to get money onto this card within 24 hours as I was not anticipating having to pay anything until the day, can they still charge me the full amount if THEY cancel my booking if I don't update my details? This has quite frankly annoyed me and I am considering booking elsewhere now so I wouldn't be upset about losing the booking if I knew I wouldn't be charged.


How to check if Node connected to another node input in Python

I am doing a process to some switch links in materials. I need to know if something is ever linked or not before to process. I can't find out how to :/ The script works well if something is linked only.  import bpy for m in bpy.context.object.material_slots:     mat = m.material     nodes = mat.node_tree.nodes      # get node input (socket)     alphasocket = mat.node_tree.nodes.get("Principled BSDF").inputs[18]     # get node link that connects into the socket     lnk = (link.from_socket for link in mat.node_tree.links if link.to_socket == alphasocket)      #add emission node     emi= nodes.new('ShaderNodeEmission')     emi.name= "emibak"     outepute= mat.node_tree.nodes.get("Material Output").inputs[0]      #make new link destination     #here 's where I cant find out how to check     if lnk != None:         print(mat.name + " alphanod found")        # mat.node_tree.links.new(lnk, emi.inputs[0])     else :         print(mat.name + " alphanod missing")      mat.node_tree.links.new(emi.outputs[0], outepute)     here is another way I am searching...  import bpy  for m in bpy.context.object.material_slots:      mat = m.material     nodes = mat.node_tree.nodes          print("**** Material " + mat.name+ " ****")      for mat_node in mat.node_tree.nodes:         if mat_node.type == 'BSDF_PRINCIPLED':             print("From " + mat_node.name )                         alphasocket = mat_node.inputs[18]             #print(alphasocket)             node_in = mat_node.inputs             #print(node_in)                    for n in alphasocket.links:                                print("Alpha connected to " + n.from_node.name)   This show me what is connected to the alpha channel but if nothing is connected I want to connect a new node.


Area 51 Site is quite different from other SE sites and needs an SE footer

Honestly, navigation through Area 51 is a bit confusing and seems to be much different from the other SE sites.    The feature that is very lacking is the footer with all the sites you are subscribed to so that a user can easily return to a different SE site. This one really bugs me.  Can this be easily fixed?  Also, unlike all the other sites there is no "meta" site to add comments specifically about that site.    Again Area 51 seems out of sync with the other SE sites.


Find the interval over which this function is greater than 1

Consider the product $\left|w\sigma'(wa+b)\right|$, where $\sigma(x) = \frac{1}{1+e^{-x}}$. Suppose that $|w| \geq 4$, and $|w\sigma'(wa+b)|\geq 1$. Show that the set of $a$ satisfying that constraint can range over an interval no greater in width than  $$\frac{2}{|w|}\ln\Bigg( \frac{|w|(1+\sqrt{1−4/|w|}}{2}−1\Bigg).$$  Not quite sure where to start, I tried to work with the original equation:  $$e^{wa+b}/\left(e^{wa+b}+1\right)^2 \geq 1/|w| \implies wa+b - 2\ln\left(e^{wa+b}+1\right) \geq -\ln(w).$$  However, this doesn't seem to be going anywhere, and I'm just not sure how to go about finding the width of an $\textit{interval}$. Appreciate any suggestions/solutions, thanks!


Cross merge list elements to get a list of tuples in Python

I have already checked this post  but it doesn't seem to fit to my issue.  I want to merge multiple lists together to get a tuple for each multiplication. So let's say:  listA = ['a', 'b', 'c', 'd'] listB = [ 1 ,  2 ,  3 ,  4 , 5 ] listC = ['!', '?', '=']   The lists do not have the same length. My desired result would be:  result = [('a', 1, '!'), ('a', 1, '?'),  ('a', 1, '='),  ('a', 2, '!')...   As far as I got it, the zip() functions only joins two elements to a list together with the same index which is not what I want.


What is the meaning, usage and formality of the greeting "What's up"?

"What does it really mean when one asks - what’s up?"  What should be my reply? What I am busy with or upto? I am assuming its informal usage.  Also I doubt if one should use it in formal meetings. Any guidance/suggestions ?  Thanks


How to find the last $4$ digits of $2^{2020}$ with Euler

I tried to find the $4$ digits of $2^{2020}$ with Euler. i find without Euler the last digits (6) , but i dont know how to find it using Euler . its look very simple but im getting trouble on it...


How can I have a second alias for a node to be displayed in a different view mode?

I have nodes whose content type is X that I would like to render differently based on the node path.  I'd like to use the default view mode for a path alias and a custom view mode for the other path alias.  These aliases were created using the Pathauto module; both of them point to the same node.   /url/alias1/path => /node/123 (default view mode)  /url/alias2/path => /node/123 (custom view mode)   I tried using mymodule.routing.yml to do this, but it does not appear to be picked up by the route system.  mymodule.program:   path: '/url/alias2/path'   defaults:     _controller: '\Drupal\mymodule\Controller\RoutesController::setViewMode'   requirements:     _access: 'TRUE'   When I click on the alias with the custom view mode, I get the default view mode.  I put a logger statement in the routes controller setViewMode function and it is not reached. This suggests that the routing is not being 'tripped'.   Am I missing something or trying to do something Drupal 8 cannot handle?  I looked at  but that doesn't quite address my question.


Find a number 111...1 which is divisible by 2019

Find a number in the form of 111...1 (e.g. 111111) that is divisible by 2019.  What I thought so far...  I know of Fermat's little theorem, which states following: $a^{p-1}\equiv 1$ for  $p \in \mathbb{P} \land a\in \mathbb{Z}$  111...1 (with n 1's) can be written as $\frac{10^n-1}{10-1}$. Unfortunately, 2019 is not a prime.  $\frac{10^n-1}{10-1} = 2019*k$ is also no solution to the problem since there are two variables.   Can anyone give me a hint how to find the solution or at least how to proof that the solution exists? Thanks.


Compare the following ideals: $(I+J)/I$ and $J/(I\cap J)$

As the question says I have to compare the following ideals. I am not quite sure what "comparison" in this case would mean and I really have no idea how to do that. I have defined $(I+J)/I=\{(i+j)+I| i \in I, j\in J\}$ and as far as I have read this is the smallest ideal containing I and J. I have absolutely no clue how to define $J/(I\cap J)$ since I don't know how to define the intersection. I would be very thanful for some insight regarding comparing them with each other. EDIT: The ideals are in a commutative unitary ring.


Why doesn't the Young's modulus change when an alloy is strengthened?

There is one thing about Young's modulus that I find unexpected and confusing.  When certain solid materials, pure metal, steel or an alloy of a certain composition, gets strengthened by cold working or by heat treating, the Young's modulus stays exactly the same as before even though the yield strength of that material gets doubled, and the elongation gets reduced by an order of magnitude.  Take maraging steel 350 for example. Annealed yield strength = 830 MPa ... Annealed elongation = 18% ... Annealed Young's modulus = 190 GPa  Aged yield strength = 2300 MPa ... Aged elongation = 4% ... Aged Young modulus = 190 GPa  This seems crazy to me. Strength triples and elongation is reduced to less than a quarter, yet the Young's modulus doesn't change one bit? I don't understand.  If the definition of Young's modulus is the ratio between stress and strain, when steel after aging gets 300% stronger, and that strength is achieved at 20% elongation, how could the Young's modulus possibly not get massively changed too?


"Every day" and present continuous vs simple present

Every day I'm eating vegetables. I eat vegetables every day.   Can someone explain if there's a nuance in meaning of the two? If there's a better situation to use one than the other? (doesn't have to be the sample sentences)


How to remove all files and subdirectories in a directory WITHOUT deleting the directory in bash?

Is there a command to remove all files and subdirectories in a directory without deleting the directory?  For example if I have directory dontDeleteMe with subdirectories 1, 2, 3 and each subdirectory has a few pictures in it, how can I remove the subdirectories 1, 2, and 3 and all the files in the them, without removing the parent directory dontDeleteMe?


I was trying to install ubuntu 13.04 on a mini notebook acer, but an error occurred while almost completing the installation...Now it doesn't charge, only if I enter the Windows 7 partition.How do I start the process?Or can I uninstall the ubuntu to start again to install it? Thank you in advance for your answers.


Why are apt-get repositories hardcoded to a specific release?

From the usability point of view, I do not understand why on each release upgrade you have to manually patch all the URLs of apt in order to make them point to the newer distribution.  Why is not possible for apt to auto-detect the current and use it, so when you upgrade there is no need to upgrade the urls anymore?


How change locale language setting to english in ubuntu 14.04

My laptop have default setting to my local language. Thus all system configuration like time and date and others showing as this language. Also, it shows language specific number in different system application. But i want to back it as english. How i do this in ubuntu 14.04


I want to both read from and write to a file. This doesn't work.   static void Main(string[] args) {     StreamReader sr = new StreamReader(@"C:\words.txt");     StreamWriter sw = new StreamWriter(@"C:\words.txt"); }   How can I both read from and write to a file in C#?


Windows 10 calculator app does not respect region format decimal symbol

I recently installed Windows 10 (upgrade from 7). It is an English version Windows, which I configured to the German locale(*), which uses a comma (",") instead of a dot (".") as the decimal separator, i.e. the number Pi is 3,14 not 3.14.   This works fine in Excel. However, it does NOT in the standard Windows calculator, which simply IGNORES a comma key press COMPLETELY. If I use a dot, it produces a dot which works as a decimal separator (which is wrong).  Note that I'm talking about the actual comma key here, not the numpad comma, which works fine but produces a dot in the Calculator (it produces a comma in Excel!).  My question: Does anyone have any ideas how to get Calculator to respect the German locale and recognize the comma key and display a comma?  (*) Control Panel > Change date, time, or number formats > Format: German (Germany). Under additional settings, the decimal separator is correctly set to ",".


Script to write all filenames inside a folder and its subfolders to a csv file

I would like to write a shell script in order to write all files ending with .tif in  a given directory and all its subdirectories to a csv file.  The directory contains various sub-directories and those can also contain .zip folders so the script should be able to extract the names from zip folders too.  I first thought about separating these steps though (unzipping and getting the filenames) but I'm not sure if this is really necessary.   Since I'm really new to working with the Shell, any help would be appreciated.


Difficulty in creating macro '\newcommand' for the beginning and end of frames in Beamer

I would like to create a Latex macro for my beamer presentations. I use beamer frequently, and want to make macros for the \begin{frame} and \end{frame} to require fewer keystrokes. At the beginning of the document I have:  \newcommand{\bfrm}{\begin{frame}}%start new frame \newcommand{\efrm}{\end{frame}}%end new frame   Which compiles fine. I then test the first of the two macros for the beginning of the frame:  \bfrm{New frame testing}     blah blah \end{frame}   Which produces the result I am looking for. I then test the second of the macros:  \bfrm{New frame testing}     blah blah \efrm   Fails to compile, saying that there is a runaway argument. What is the reason for the failure?


Storing two kinds of point geometry in shapefile or creating multipoint shapefiles?

Following , can I have a mixture of two kinds of geometry in a shapefile of type point. Just like I have about shapefiles of type polygon or I should always create a shapefile of type multipoint in order to support multipoints in my layer?    My problem is as you see at , I can't use ogrinfo in order to understand that the geometry type of a multipoint shapefile will be known as wkbMultipoint or wkbPointwhen I use this line of code:    OGRwkbGeometryType GeometryType = poLayer ->GetGeomType();     for a layer of type multipoint before programming.     Will OGR know a layer of type multipoint as wkbpoint or wkbmultipoint?   When we create a shapefile in ArcCatalog, we have point and multipoint, but not multipolyline or multipolygon for polyline and polygon.Why?


My jQuery is a little rusty, hence this noob question:  I have this unordered list,

   which I populate from a JSON-object:  function updateChecklists(){     requestAllForms = $.get("/list-all-forms");      requestAllForms.promise().done(function(data){         $.each(data,function(key, val){             $("
" + val.name +"
").appendTo("#list-all-forms");         });         $('ul').listview('refresh');     }); };   However, when I try to get the click event from a link with the class checklistObject in the list, nothing happens...  $(".checklistObject").on("click", function(){     console.log("click on list object!");  });   How can I get that function to fire?


How do I kill a process in the "Uninterruptible Sleep" state?

OS is Debian 10. Using thunar as my file manager. I'm assuming some sort of error occurred trying to read a cheap SD card, and now thunar is not responding. I tried kill -9, no such luck. ps shows the process is in the "Uninterruptible Sleep" state. I would like to be able to:  Launch a new instance of thunar so I can continue to use my system, and Clean up the 30 old thunar windows that will not redraw.  I absolutely do not want to restart my system, the whole point for me of switching from Windows and to Linux is high uptime (which it mostly succeeds at). Perhaps there is some kernel feature that must be enabled, that covers a user like myself. I understand that the kernel is designed to work for most users, but perhaps there is some sort of flag that can be enabled "tolerate cheap io devices" or something similar, that will allow me to use SD cards without having to reboot constantly.


Looking for suggestions on how much to serve on meat.  They would like pulled pork, ribs, and brisket


Is it possible to program an OS X screen lock?

I want the ability to lock my Macbook at my command. I don't want a screensaver or sleep lock. Don't you get tired of repeatedly typing in your password in all day? I don't want to wait for my computer to lock itself in 10 minutes or 1 minute when the screensaver or sleep begins. I don't want to save and close all my apps and documents and logout.  So just let me lock my computer, simple request. Hit a hotkey? Close the lid?    I walk out my door, I lock my door. I get out of my car, I lock my car. Why can't I just lock my computer?    I've been told you can't reconfigure this type of setting in OS X, is this true?


Sorry I have an similar question asked before. But I'm a newbie with mysql and I don`t get it.. I don't know how it works.. hope someone can help me again. Thank you!  I have an SQL select, that gives one row back. The SQL update gives the error message 1093 back;     mysqli error: [1093: Table 'ASSET_ASSOCIATION' is specified twice,   both as a target for 'UPDATE' and as a separate source for data]   UPDATE ORG1.ASSET_ASSOCIATION SET ASSOCIATED_ASSET_ID =  ( SELECT ASSET_ID FROM ORG1.HD_TICKET WHERE ID = (<TICKET_IDS>) ) WHERE ASSOCIATED_ASSET_ID =  ( SELECT ASSOCIATED_ASSET_ID FROM ORG1.ASSET_ASSOCIATION WHERE ASSET_FIELD_ID = 11 AND ASSET_ID = (SELECT ID FROM ORG1.ASSET WHERE ASSET.NAME = (SELECT CUSTOM_FIELD_VALUE0 FROM ORG1.HD_TICKET WHERE ID = (<TICKET_IDS>))) OR ASSET_FIELD_ID = 111 AND ASSET_ID = (SELECT ID FROM ORG1.ASSET WHERE ASSET.NAME = (SELECT CUSTOM_FIELD_VALUE0 FROM ORG1.HD_TICKET WHERE ID = (<TICKET_IDS>))) OR ASSET_FIELD_ID = 1111 AND ASSET_ID = (SELECT ID FROM ORG1.ASSET WHERE ASSET.NAME = (SELECT CUSTOM_FIELD_VALUE0 FROM ORG1.HD_TICKET WHERE ID = (<TICKET_IDS>))) )


How can a command in a pipe read from a keyboard?

I randomly tried to execute the following command in bash1  cat /some/file | ssh user@machine 'cat >/destination/file   There are no keys installed on the remote machine, so the only way to authenticate is with the password mechanism. I thought this wouldn't work, since the pipe will disconnect SSH's stdin from the terminal. I was surprised when I was prompted for a password, and the file was successfully sent.  Any thoughts on how SSH is able to read the keyboard to prompt for a password, despite not being connected to it?    1I am aware there are better alternatives to copying a file between two machines.


Is there any difference between using pretty, and quite, in the following sentences?     I am pretty good at playing soccer.        I am quite good at playing soccer.        How are you?   I am quite well.         How are you?   I am pretty well.   The reason I am asking is that, in Italian, the translation of pretty, and quite, are respectively piuttosto, and abbastanza, which have very similar meanings.


Is the rank of $AB$ always equal to the rank of $BA$?

I know that matrix multiplication is not commutative: $ AB \neq BA$.  Still, it may be possible that $\operatorname {rank} (AB) = \operatorname {rank}  (BA)$. But it seems to be not true.  How can it be proved that $ \operatorname {rank} (AB) \neq \operatorname {rank} (BA)$?   (Usually it's not a big deal to prove a negative statement since it only take to find one example when the equality is not satisfied.)


Plane booking - owner changed her name after getting married

In many countries, the wife takes the husband name after getting married.  Let's say that a woman changes her last name, but she had a booking using her previous last name. She also has a marriage certificate and a document that shows that she had another last name before marriage.  Questions:   Is the booking valid? Does she need to change the name in the booking system before check-in? Is this paid or is it for free? If the check-in was already performed and the boarding pass was generated, can she use the boarding pass in the airport together with her new ID + the marriage certificate + the document that attests her surname change?   Details:   the companies are from Europe (low-cost) the flights are inside Europe


Where in the world do Stack Overflow users say they are from?

I wanted to know more about . Is there any way I could get more data for this? Are there any more maps or charts to further identify where users are coming from across the world? How could I go about generating my own maps or charts?  Note: The original statistics and images provided with this question in 2009 are available in the .


git: find a filename of a specified object file

I found a big object file from .git/objects/ , I am wondering that what the file is(when added, from which file in working directory).  I tried cat-file but it shows only contents, not file names.  Is there a git command find file name(path) from object hash, It is like:  % git find-path? <object-hash> -> List of filename(path) of this object


How do we calculate Statement coverage, Branch coverage , Path coverage and Condition coverage in White box testing?

I am preparing for a testing certification. These types of questions are asked frequently.  Example 1: Read P Read Q IF P+Q > 100 THEN Print “Large” ENDIF If P > 50 THEN Print “P Large” ENDIF   Example 2:  READ X  READ Y  I F X>Y THEN Z = 0  ENDIF   Example 3: 1 READ X  2 READ Y  3 Z =X + 2*Y  4 IF Z> 50 THEN  5 PRINT large Z  6 ENDIF     What are Nodes and Edges in the flowchart?  Statement Coverage: 1A-2C-3D-E-4G-5H = 1 Branch Coverage: 1A-2C-3D-E-4G-5H , 1A-2B-E-4F = 2 Path Coverage: 4 1A-2B-E-4F 1A-2B-E-4G-5H 1A-2C-3D-E-4G-5H 1A-2C-3D-E-4F   Please explain , how the answers came by?  In these example, how do we identify that which is a statement, branch and condition? How do we measure coverage? Please give detailed explanations of ALL 3 examples.


Global sections of $\mathcal{O}(-1)$ and $\mathcal{O}(1)$, understanding structure sheaves and twisting.

In chapter 2 section 7 (pg 151) of Hartshorne's algebraic geometry there is an example given that talks about automorphisms of $\mathbb{P}_k^n$. In that example Hartshorne states that $\mathcal{O}(-1)$ has no global sections. However, we know that $\mathcal{O}(1)$ is generated by global sections. This is stated at the first of the section that if $\mathbb{P}_k^n = Proj k[x_0,...,x_n]$ then the $x_0,...,x_n$ give rise to global sections $x_0,...,x_n\in\Gamma(\mathbb{P}_k^n,\mathcal{O}(1))$.  I guess I don't understand this twisted structure sheaf very well, or to be honest I don't think I understand structure sheaves in general as well as I would like. The twisting part seems simple at first- you shift the grading of Proj over and then take the structure sheaf.  Admittedly I don't feel comfortable using the structure sheaf other than using the basic facts about it that Hartshorne gives when it is introduced. If anyone could give some insight as to what's going on here or how I might be able to understand this better it would be much appreciated. Thanks.


How do I quickly rename a MySQL database (change schema name)?

The MySQL manual at  covers this.  Usually I just dump the database and reimport it with a new name. This is not an option for very big databases. Apparently RENAME {DATABASE | SCHEMA} db_name TO new_db_name; .  This needs to work with , which stores things very differently than .


Encoding error PHP and MySQL for languages of Europe

I want to insert some word which is languages of Europe to MySQL. e.g á, ó, Ö,ü.(Sorry, I don't know what language it is. Maybe somebody can help me fix title.)  But it become something can't read.  I try this solution   I find out my PHP version is 5.1.6. So I can't use mysql_set_charset   Mysql charset is utf8_general_ci and version is 5.0.45.  How can I fix this problem?


Windows keep changing position when disconnect and reconnect monitors

I'm  on a windows 8 laptop and I have two external monitors I hook up to it. Whenever I take the laptop somewhere (and have to disconnect my monitors), the windows all go to my small laptop screen, naturally.  Its super annoying to reposition every single window every time i reconnect. When I reconnect my monitors, I'd like the windows to appear back where they were before I disconnected. How can I do this?


Subordinate conjunctions - Semicolon before acceptable?

What would be correct?   The word "sacred" means "regarded with great respect and reverence", and the word is most commonly used in religious meaning; however,...   Or   The word "sacred" means "regarded with great respect and reverence", and the word is most commonly used in religious meaning. However,...   Or   The word "sacred" means "regarded with great respect and reverence", and the word is most commonly used in religious meaning, however,...


Textbook recommendation for computational physics

Can anyone recommend some good textbooks for undergraduate level computational physics course? I am using numerical recipe but find it not a very good textbook.


Keyboard shortcuts are now integrated into the site

we had implemented keyboard shortcuts as a user script. We have now finally made the change to have them integrated into the site.  When you go to the Edit Profile & Settings page on your profile, and then select the Preferences submenu, you’ll find a new checkbox labeled Enable keyboard shortcuts (which is located about half the way down on that page). Click it, and from there on, everything works as with the user script. Press ? to get started.  .  If you already have the user script installed you don’t need to do anything. We detect the user script, disable its functionality, and run the built-in version instead. That means you don't have to manually enable anything, while still running the correct version of the keyboard shortcuts (currently the two are identical, but in the future, fixes and improvements will be made to the built-in version).


How to change transparency color in material options? 2.8+

I have two images. One on black background and the other on white. How to pick a color to act like transparency mask? How to separate it and put in alpha?


when I execute the command sudo apt upgrade, the terminal showed the following message Reading package lists... Done Building dependency tree        Reading state information... Done You might want to run 'apt --fix-broken install' to correct these. The following packages have unmet dependencies:  libc6-dbg : Depends: libc6 (= 2.27-3ubuntu1.4) but 2.27-3ubuntu1.3 is installed  libc6-dev : Depends: libc6 (= 2.27-3ubuntu1.4) but 2.27-3ubuntu1.3 is installed  linux-image-4.15.0-126-generic : Depends: linux-modules-4.15.0-126-generic but it is not installable E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).  and when i try sudo apt --fix-broken install I received the following answer Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following packages were automatically installed and are no longer required:   linux-headers-4.15.0-126 linux-headers-4.15.0-126-generic linux-headers-4.15.0-129 linux-headers-4.15.0-129-generic   linux-image-4.15.0-129-generic linux-modules-4.15.0-129-generic linux-modules-extra-4.15.0-129-generic Use 'sudo apt autoremove' to remove them. The following additional packages will be installed:   libc6 Suggested packages:   glibc-doc The following packages will be REMOVED:   linux-image-4.15.0-126-generic The following packages will be upgraded:   libc6 1 upgraded, 0 newly installed, 1 to remove and 1 not upgraded. 6 not fully installed or removed. Need to get 0 B/2 832 kB of archives. After this operation, 8 419 kB disk space will be freed. Do you want to continue? [Y/n] y debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable (Reading database ... 259024 files and directories currently installed.) Preparing to unpack .../libc6_2.27-3ubuntu1.4_amd64.deb ... debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable dpkg: error processing archive /var/cache/apt/archives/libc6_2.27-3ubuntu1.4_amd64.deb (--unpack):  new libc6:amd64 package pre-installation script subprocess returned error exit status 1 Errors were encountered while processing:  /var/cache/apt/archives/libc6_2.27-3ubuntu1.4_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1)


Which ubuntu should I download for my asus x542u?

I am new in Linux. I do not have much knowledge about Linux. So I would like to learn Linux. I have chosen Linux Ubuntu as I have been heard it is good for learning Linux. But now I can not understand which Ubuntu I should download. There are many versions as well as LTS and other term. So, please Help me.  My laptop has 8 gb ram, i5-8250u, up to 3.4 ghz, hdd 1tb


Keep service running after ssh session ends

i have an ubuntu-server box to which i connect via ssh.  now when i start a service (in this case teamcity) i would like to keep it running after the ssh session ends.  right now the service stops as soon as i disconnect.  i am starting the service using:  sudo service teamcity start   and the service script looks like this:  #! /bin/sh # /etc/init.d/teamcity #  # Carry out specific functions when asked to by the system case "$1" in   start)     echo "Starting script teamcity "     /home/m/TeamCity/bin/runAll.sh start     ;;   stop)     echo "Stopping script teamcity"     /home/m/TeamCity/bin/runAll.sh stop     ;;   *)     echo "Usage: /etc/init.d/teamcity {start|stop}"     exit 1     ;; esac  exit 0


Superposition of distinct vevs in spontaneous symmetry breaking

The simplest account of spontaneous symmetry breaking goes like this.   Take a potential $V(\phi)$ with symmetric minima that are not at $\phi = 0$, like the Mexican hat potential shown in this site's logo. Since variations in the field cost energy due to the $(\partial_\mu \phi)^2$ term, minimum energy configurations have constant $\phi$. Therefore, the lowest energy states have $\phi$ equal to one of the minima of $V(\phi)$. Thus we have symmetry breaking, because the vacuum state (whichever one we choose) does not have the symmetry that $V$ had. In the quantum case, everything works the same, except the classical solution $\phi = c$ becomes $\langle \phi \rangle = c$. Then we have multiple vacuum states, each of which break the symmetry.   I'm suspicious about the last assertion. Suppose $V$ has two mimima, giving two degenerate vacuum states, $|+\rangle$ and $|-\rangle$.  Quantum mechanics allows superposition, so can we not take $(|+\rangle + |-\rangle)/\sqrt{2}$ as our vacuum? This state does not break the symmetry at all.


What does the symbol := mean in mathematics? for example, C(continuum) := |R|


Let $n$ be an integer such that if $d | n$ then $d + 1 | n + 1.$ Show that $n$ is a prime number

Let $n$ be an integer such that for any integer $d$, if $d | n$ then $d + 1 | n + 1$.   Show that $n$ is a prime number or equal to $1$  My workout...  Suppose $n = xy$ for some postive integers $x$ and $y. x|n$, and hence we assume without loss of generality $x + 1|n + 1.$   Then $x|xy + 1$. However, $xy + x$ is divisible by $x$.  This implies $x − 1$ is divisible by $x$, which is an impossibility if $x$ is not equal to $1$.  Therefore whenever $n$ is decomposed into two factors, one must turn out to be $1$. Hence $n$ must be a prime.  I am looking for any other method which solves this quickly and more quickly...


How reliable is a system backup created with the dd command?

I'm using a raspberry pi running 24/7 and created a crontask that backups the complete sd card to my NAS on a regular basis. I checked such a backup by copying it back to an SD card and it worked perfectly. So far so good. Nevertheless I'm worried. Since such a backup takes hours over my network it seems obvious to me that it isn't a snapshot of one particular moment, but a mix of files from different moments since certain data on the card get modified while it's copying. For example, if there is a database installed or other running software changing regularly the contents of certain files. Or even changing system files. I can imagine that this might create inconsistencies in the backup copy, which in worst case, according to my perception, might create a corrupt backup that can't be used for a recovery. In worst case it might even not boot after recovery... Is this a real risk or do I misunderstand the way this dd command works?


Given $(x+y+z)^{15}$ find the coefficient of $x^2y^{10}z^{3}$

Given $(x+y+z)^{15}$ find the coefficient of $x^2y^{10}z^3$   Weak in this chapter. Don't know how to proceed. Please help  Sorry for the typo made before


When does the limit $\lim_{(x,y)\to(0,0)} \frac{x^ky^l}{x^{2p}+y^{2q}}$ exist?

In this case, $k,l,p,q\geq0$ and are integers. I have attempted the substitution $u=x^p$ and $v=y^q$ $$\lim_{(x,y)\to(0,0)} \frac{x^ky^l}{x^{2p}+y^{2q}}=\lim_{(u,v)\to(0,0)} \frac{u^{k/p}v^{l/q}}{u^2+v^2}$$  Then, note that $|u|<\sqrt{|u|^2+|v|^2}$ and $|v|<\sqrt{|u|^2+|v|^2}$. So we have  $$\bigg|\frac{u^{k/p}v^{l/q}}{u^2+v^2}\bigg|=\frac{|u|^{k/p}|v|^{l/q}}{|u|^2+|v|^2}<\frac{(|u|^2+|v|^2)^{k/(2p)+l/(2q)}}{|u|^2+|v|^2}$$ Thus, the limit equals $0$ when $\frac{k}{p}+\frac{l}{q}>2$. We need to show that otherwise, the limit does not exist.   If $\frac{k}{p}+\frac{l}{q}=2$, taking the limit along the axes yields $0$ but letting $x^p=y^q$ gives  $$\frac{|u|^{k/p}|v|^{l/q}}{|u|^2+|v|^2}=\frac{|u|^{k/p+l/q}}{2|u|^2}\to\frac{1}{2}$$ so the limit does not exist.   Similarly, if $\frac{k}{p}+\frac{l}{q}<2$, taking the limit along the axes still yields $0$, but letting $x^p=y^q$ instead gives  $$\frac{|u|^{k/p}|v|^{l/q}}{|u|^2+|v|^2}>\frac{|u|^{2}}{2|u|^2}\to\frac{1}{2}$$ showing that the limit does not exist.  I'm not sure if all of the steps I've taken are correct - especially some of the inequalities as $(u,v)\to(0,0)$. Also, for the last two cases, I'm not exactly sure if the absolute values around $u$ and $v$ should be there or whether I should have let $|x|^p=|y|^q$.


How to repair cupboard hing that tore off particle board

The top hinges of the cupboard have been torn out of the particle board taking a big chunk with it and leaving quite a deep crater with just a couple of dents for where the holes used to be as illustrated below.  The picture doesn't really show the depth of the ripped hole, but it's fairly deep and those screw holes are really just dents now.  Is there a fairly quick and easy way to fix this?


How does Linux know where its swap partition is?

I've read that you need to put the swap partition on HDD rather than SSD.   My questions are the following:    When and how is the "checking" done by the distribution (or something else) to find its Swap partition?  Does it happen during boot?  It just checks all available disks and searches for a partition with 'swap' flag?  What happens if there are several partitions like that?  Also, how many swap partitions do I need to have if I run, for example, two different distributions on the same disk, let's say Fedora and Ubuntu?


When cutting a 1-1/8" to 1-1/2" carbon steer tube, what is the maximum length you can leave outside the head tube and the stem clamp? Is there a maximum? How would you determine what the maximum steer tube length for you frame could be? Does it make a difference if the steerer is 1.5" on the bottom?


Help finding an anime whose protagonist's biggest dream was that he was never born

I'm trying to find an anime I watched in 2005/2006. It was a short one (probably around 12-13 episodes) and I remember only one character - a dark haired guy (his name started with Y, but I'm not sure) whose biggest dream was to have never been born. The point was that he didn't want to commit suicide, but simply never have existed in the first place.  All I remember from the storyline is that there was another guy who fought to make the dark haired guy's dream come true. In the end, he succeeds and the other one disappears/vanishes - as if he was never been born. It wasn't a yaoi or shounen-ai, but it did have a certain atmosphere of a shounen-ai.  Truth be told it was a really sad story, but I can't stop thinking about it and as it wasn't popular I can't find its title. Unfortunately, that's all I remember.  Does anyone of you maybe recognise this anime? Thank you in advance!


Adding USB Dual Port Charger Receptacle Blows Mains

I purchased a Hubbell "USB Dual Port Charger with 15A Duplex Receptacle" from Lowes to replace the duplex receptacle on my kitchen island.  I first opened the circuit labelled for the island.  The breaker takes two slots.  I removed the existing receptacle and noticed that the brass screws had a black and red wire.  The bridge between the screws was not broken.  I connected the new USB charging receptacle as: white wire to silver screw, bare to green screw, and the black and red wires to the brass screw.  I put everything back together.  When I closed the circuit the fuse blew as well as tripping the mains to the house.  I took the receptacle out of the metal gang box to ensure that it wasn't touching.  I verified the connections as stated above.  With the receptacle hanging outside of the gang box I closed the breaker only to have it and the mains trip.  I reconnected the old simple receptacle and closed the breaker with no problems.  I tried with just the black wire in the new receptacle and it worked!  But now I can't connect the new receptacle with this new red wire.  I researched the uses of the red wire however none of them seem to apply to my kitchen.  The fuse box lists the island as the only part to control and nothing else in the kitchen turned off when I opened the circuit.  There is only one receptacle on the island and no other electrical items including lights.  Why would the kitchen island of only one receptacle require both black and red? why would this USB charger receptacle be so sensitive to two hot wires? why would this single outlet require such a large breaker switch?  And finally... is there anything I can do so that I can install this receptacle?  Thanks!


Built in .Net algorithm to round value to the nearest 10 interval

How to, in C# round any value to 10 interval? For example, if I have 11, I want it to return 10, if I have 136, then I want it to return 140.   I can easily do it by hand  return ((int)(number / 10)) * 10;   But I am looking for an builtin algorithm to do this job, something like Math.Round(). The reason why I won't want to do by hand is that I don't want to write same or similar piece of code all over my projects, even for something as simple as the above.


This a screenshot of . As you can see I am missing the icons for: "Appearance","Online Accounts", "Security & Privacy", and "Time & Date". How can I restore them?  For comparison this is a screenshot of .


Why is my regex not matching the string input?

I have the following code below: def convertint(prices):     output_list = []          for alist in prices:         print (alist)         price_int = re.match(r'([0-9]{2,3})', alist)         print (price_int)          #         print (price_int.group()) #         output_list.append(price_int.group())              return output_list     ###  convertint(['$27' , '$149' , '$59' , '$60' , '$75'])  It's output is below: $27 None $149 None $59 None $60 None $75 None  I want my regex match in my code to return 27, 149, 59, etc. without the $ but it's returning None when I try to match it. What am I doing wrong?


If $n>3$ is not prime, show that we can find positive integers $a,b,c$ such that $n=ab+bc+ca+1$.   When $n=4$, pick $a=b=c=1$. When $n=6,$ pick $a=2$ and $b=c=1$. When $n=8$, pick $a=b=c=2$. I don't get the pattern here. I know that if $n>3$ is not prime, then $n=xy,$ where $1<x<n$ and $1<y<n$. But how do I proceed from here?


They says that Stack Overflow is a community-driven web-site. But, as a matter of fact, it is not.  There is no community at all. It's more like an imageboard, as a number of participants makes them pretty much like anonymous to each other despite of registration.   Stack Overflow is a site of passers-by.  Passers-by who want to solve their silly typo problem and passers-by who eager to share their vast knowledge in spotting silly typos. And - oh - sometimes to perform a civic duty and vote to close a question they have no idea what to answer to and thus calling it "not a real question".  So, as a funny consequence, whatever question can get   answered upvoted downvoted closed deleted   depends not on its quality but only on the fluctuation happened to "community" at the given moment, at a pretty random rate.  It is not only quite discouraging. It makes the very idea of collecting and improving knowledge quite impossible.


How to expire a php session after certain time?

I have the following code:  The page Login.php    <?PHP       session_start();       include("conexion.php");       $conn = conexion();       extract($_POST);        $password = md5($pass);       echo $password;       $sql1="Select * from miembro where user='".$user."'and pass ='".$password."'";       $re= mysqli_query($conn,$sql1);      $numrows1 = mysqli_num_rows($re);       echo $sql1;       echo $numrows1;      if ($numrows1==0 or $numrows1>=2){         $_SESSION['session'] = "no";       header('Location:' . getenv('HTTP_REFERER'));      }else{         $row = mysqli_fetch_array($re);         $_SESSION['nombre'] = $row["nombre"];         echo $_SESSION['nombre'];         $_SESSION['codigo'] = $row["codigo"];         $_SESSION['pass'] = $row["pass"];         $_SESSION['apellido'] = $row["apellido"];         $_SESSION['telefono'] = $row["telefono"];         $_SESSION['user'] = $row["user"];         $_SESSION['cargo'] = $row["cargo"];         $_SESSION['correo'] = $row["correo"];         $_SESSION['session'] = "si";         $_SESSION['last_time'] = time();         header("Location: ./actions/perfil.php");       }     ?>     And perfil.php (where the user is taken once logged in)    <?php  include("./menu_actions.php");  include("../conexion.php");  if($_SESSION['session'] != "si"){   header("location: ../home.php");  }   $us = $_SESSION['user'];     $sql="select * from miembro where user = '$us';";    echo $sql;    $query = mysqli_query(conexion(),$sql);    $row = mysqli_fetch_array($query);    session_start();   if(isset($_SESSION["user"])){     if((time() - $_SESSION['last_time']) > 10){ //After 10 sec     header("location:logout.php");     }   }   else{     header('Location:login.php');   }   ?>    //HTML     It's not working and I don't understand why. The time of the start of the session is kept in a variable and analyzed later with an if loop, so if the time exceeds 10 seconds, the user should be forced out and taken to the login page again, but I can't make it work. Could somebody help me, please?


Let $A$ be an algebra. For $a, b \in  A $ we define maps $L_{a}, R_{b} : A \longrightarrow A$, called the left multiplication map and right multiplication map, by  $L_{a} (x) := ax, R_{b} (x) := xb$.  Note that for all $a, b \in  A, \lambda , \mu \in F ( field)  $ we have  $L_{a}b = L_{a}Lb, R_{ab} = R_{b}R_{a} $,  $L_{a}R_{b} = R_{b}L_{a}$,  $L_{\lambda a+\mu b} = \lambda L_{a} + \mu L_{b}, \quad  R_{\lambda a+\mu b} = \lambda R_{a} + \mu R_{b}$  so , is there an element in $M ( \mathbb{H} ) $  (  $ \mathbb{H}$ is  division algebra of quaternions )  that cannot be written as $ L_{a} R_{b}$,  $  a, b \in  \mathbb{H} $?


How to make the text color changing within a label in QGIS?

I would like to keep in black a part of my label (title) and make the other one varying according to a value.  In this (simplified) example, as required, the value color is varying according to a concentration, but also the title.     I would like to keep the first line in black and make the second one varying.  Text formula:  'Drill ' ||  "id"    ||  '\n'  ||  CASE     WHEN "Conc" >100          THEN               "Polutant"  || ': ' ||  "Conc"          else         '' END   Color formula:  if  ("Conc"> 220, color_rgb( 255,0,0) , color_rgb( 0,0,0))   Can QGis handle such a situation and how, or have I to program a function? In this last case, do you have an example to put me on the right way?


If $f'$ is differentiable at $a$ then $f'$ is continuous at $(a-\delta,a+\delta)$

Is there a counterexample?  Proposition: Let $f:\mathbb{R} \longrightarrow \mathbb{R}$ be a differentiable function  such that $f':\mathbb{R} \longrightarrow \mathbb{R}$ is differentiable at $a\in\mathbb{R}$ (possibly differentiable at a single point). Then $f':\mathbb{R} \longrightarrow \mathbb{R}$ is continuous at an interval $(a-\delta,a+\delta)$ for some $\delta>0$.  Any hints would be appreciated.


Manga where a guy, his childhood best friend and (I think) three other guys get transferred to another world. And the MC has 10 skill slots

A manga where a guy, his childhood best friend and (I think) three other guys get transferred to another world. And the MC has 10 skill slots. The three other guys bullied him back on Earth. When he got transferred over, him and his childhood friend (it's a girl) both got 10 skill slots that they can fill up by people or monsters dying and them dropping their skill cards. His girl best friend betrayed him to survive by siding with one of the bullies. The MC got pushed into a dungeon where time goes like 500 times slower.


Given a matrix $A$ of rank $n$, show that $\det(\operatorname{adj}(A))=\det(A)^{n-1}$ and $\operatorname{adj}(\operatorname{adj}(A))=(\det A)^{n-2}A$

$\newcommand{\adj}{\operatorname{adj}}\newcommand{\rank}{\operatorname{rank}}$If $\adj(A)$ denotes the classical adjoint and we are given that, for an $n \times n$ matrix $A$ over $\mathbb{R}$,  $$\rank(\adj(A)) = \begin{cases} n& \rank(A)=n\\1& \rank(A)=n-1\\0& \rank(A)<n-1\end{cases}$$  show that for $n \geq 2$   $\det(\adj(A)) = \det(A)^{n-1};$ $\adj(\adj(A)) = \det(A)^{n-2}A.$     The first is easy, actually. If $\rank(A) = n$, $\adj(A)A = \det(A)I$; taking determinants of both sides easily yields the result; if $\rank(A) < n$, $\det(A) = 0 = \det(\adj(A))$.


Let $Tor(G) = \{ g \in G | \exists n >0 , g^n = e \}$ of a group $G$ , give an example to $G$ such that $Tor(G)$ is not sub group ?  Easy to prove that $G$ must be non-Abelian and infinite in size, so i thought of matrix but i don't have concrete example


How to identify and remove unnecessary files from Windows Driverstore?

My Windows\System32\DriverStore\FileRepository is 48 Gigabytes in size.  That is way bigger than I have ever seen anywhere else, and is way out of proportion for a 128GB SSD.  I know how to list the files in it, and I know how to delete them individually.  What I do not know is Which drivers are unnecessary, and which can I delete?  I use Windows 7, Home Premium, with Service pack 1, and fully up to date.  Windows Disk Cleanup and PrivaZer have not reduced the file size.  The question  is not a duplicate of this one because it does not ask How do I know a driver in the driver store CAN be safely deleted?


Is there a way to define a new command so that existing  \includegraphics[scale=x]{fig_name}   becomes  \includegraphics[scale=x]{fig_name.eps}   for any x and fig_name? This is for automatic conversion of eps to pdf because eps may cause out of memeory issues with xdvipdfmx: .


I'm a graduate physics student from Italy, and I'll be graduating in one year or so. I would like to pursue a PhD in theoretical physics, and I don't really want to close any possible path, so I'm considering both Europe and USA (should I also consider somewhere else?) since my English is pretty fluent and I have an high school diploma from my exchange year in the US. I think I have a good idea about the application process in Europe: deadlines to start in the fall 2022 are around February-May 2022, and one just needs some documents and forms to be filled out and sent. I'll be working on that from the end of the year, and send a lot of applications to a lot of universities and institutes. Does it work the same way in the US? I think I read somewhere that the deadlines are much earlier, and I need some tests, but I couldn't find consistent information online. What's the standard application process for US PhD?


I am using a regular expressionvalidator in my application to validate emails. It's using ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"  This has worked great for a long time but recently there was a report from a customer that could not create a client with the email adress marie-@domain.com, its a little bit weird address but never the less it works in gmail.  I dont quite understand the expression, so could anybody help me adjust the expression so it also accepts emails in that format?


I've two step motors with 12V-0.4A each, A4988 as stepper motor driver and CNC shield on Arduino. As I know I should use at least 2x voltage for stepper motors and I would like to know, if I use 24V-4.5A power supply, can it lead to any problem with these devices?  Or should I use something equal to needed current? (2*0.4A + cnc shield etc. let's say 1A for example...)


How faster is the effect of force exerted by gravity?

We all know that Earth revolves around the Sun due to Gravitational force of the Sun. Also we know that it takes just over 8 minutes for the Sun's light to reach Earth.  Now let us say, hypothetically if the sun were to suddenly extinguish (or disappear), would the Earth still not experience any effect of it until just over 8 minutes later (equivalent to time taken by light to reach from Sun to Earth) ?  That is, Would the earth still continue to revolve (due to the centripetal force) for next 8 minutes after Sun disappearance and then thrown out of its revolving orbit (due to centrifugal) OR will it be immediately thrown out on the moment the Sun disappeared (i.e., not after 8 minutes) ?


Is there any Q&A site under the Stack Exchange network where we can discuss about supernatural incidents? If not, then whom should I petition to create it?


Sed command won't run if inside a string

When trying to extend a script, for some reason, if a sed expression is inside a variable it won't run. Minimal example: echo lorem >> /tmp/testsed CMD="sed --debug -i.bak -e 's/lorem/ipsum/' /tmp/testsed" $CMD  results in: sed: -e expression #1, char 1: unknown command: `''  I've looked at a few (, ,  and  ) similar posts, but none solved the issue. For now I'm using eval (like 4 initially suggests), but it's not an ideal solution; also creating a function is not an option. I feel like it's related to having to escape some characters on the expression, but from my tests I could not find which. This sed expression is set as a action that another script executes after some specific action.


Why my computer is not able to use Full Ram?

I have Windows 7 Pro 32 bit. having 4 GB Ram and only 932 Mb is usable. Why is that ?  My system configuration -


Question is to Evaluate :  $$\frac{1}{3}+\frac{1}{4}\frac{1}{2!}+\frac{1}{5}\frac{1}{3!}+\dots$$  what all i could do is :  $$\frac{1}{3}+\frac{1}{4}\frac{1}{2!}+\frac{1}{5}\frac{1}{3!}+\dots=\sum_{n=1}^{\infty} \frac{1}{(n+2)n!}=\sum_{n=1}^{\infty} \frac{n+1}{(n+2)!}=\sum_{n=1}^{\infty} \frac{n}{(n+2)!}+\sum_{n=1}^{\infty} \frac{1}{(n+2)!}$$  I have $$\sum_{n=1}^{\infty} \frac{1}{(n+2)!}=\sum_{n=0}^{\infty} \frac{1}{n!}-1-\frac{1}{2}=e-\frac{3}{2}$$  Now, I am not able to see what $$\sum_{n=1}^{\infty} \frac{n}{(n+2)!}$$ would be.  I would be thankful if some one can help me to clear this.  Thank you.


Android Studio CardView element returns Null

I have a file called row_list.xml which holds the style of a CardView. This CardView is the root object of this xml file. I'm using this CardView in a RecyclerView in my activity_main. row_list.xml <?xml version="1.0" encoding="utf-8"?> <androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:app="http://schemas.android.com/apk/res-auto"     android:id="@+id/card_view"     android:layout_width="wrap_content"     android:layout_height="wrap_content">      <LinearLayout         //codes>          <TextView             //codes />      </LinearLayout>  </androidx.cardview.widget.CardView>  In my MainActivity.java I want to get the current height of this CardView, and then use this height for something. But when I call the code below, I got Attempt to invoke virtual method 'int androidx.cardview.widget.CardView.getHeight()' on a null object reference. MainActivity.java public class MainActivity extends AppCompatActivity {      CardView cardView;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);      cardView = findViewById(R.id.card_view);      System.out.println(cardView); //prints null      int height = cardView.getHeight(); //I get "null" object error  Why does cardView = findViewById(R.id.card_view) returns null? How can I get the attributes of a CardView? Couldn't find a related question/solution on the web. Edit after comment     @NonNull     @Override     public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {layoutInflater = LayoutInflater.from(context);          View v = layoutInflater.inflate(R.layout.row_list,parent,false);         ViewHolder vh = new ViewHolder(v);         return vh;     }


External quality factor of an inductor capacitively coupled to a waveguide

I have an inductor coupled via coupling capacitance $C_c$ to a transmission line (waveguide, feedline?) with impedance $Z_L$. Given that the inductor has some internal losses and a capacitance, I imagine that for all intents and purposes it can be modeled as an RLC circuit. This gives a simple circuit shown below:    Here I have to admit that putting the resistance in series might actually make sense instead, I'm a bit stuck on that mentally; the losses originate from losses in the superconducting that makes up the inductor. However, what I am interested in here is an analytic expression for the external quality factor $Q_E$ of the circuit in terms of $C_c$, $C$, $L$, $Z_L$, and perhaps $R$ but I imagine that only goes into the internal quality factor regardless of how we put it in.  Now, from the definition of the quality factor, we can write that  $$Q_E = \omega \frac{E}{P}$$  where $\omega$ is the frequency, $E$ is the energy stored in the RLC circuit, and P is the power lost in the transmission line, essentially due to the coupling. But I have to admit, at this point I'm already starting to get stuck in relating it to the circuit parameters; my circuit analysis is definitely somewhat rusty beyond $E = 1/2 CV^2$, $E =  1/2 LI^2$ and $P = V^2/R$.   does look at a circuit along these lines, but this is not an identical system. They transform their circuit using Norton equivalences (I have to admit I can't follow this step all that well, not familiar with the equivalence in this context). If one were to take their figure 5c and make some adjustments, perhaps that helps?    Taking the above with $R* = R_L$, $C* = 0$, and replacing $C \rightarrow \frac{C_c C}{C_c + C}$, would that not be identical? In that case the external quality factor is given in the paper to be  \begin{equation} Q_E = \frac{Z_L}{2} \frac{C_c C}{C_c + C}\omega_0 \end{equation} where $\omega_0$ is then the resonant frequency of the circuit taking into account the coupling capacitance. I am not 100% sure this is correct; could someone help me out there?


What is the difference between Salesforce and Salesforce1?

Can any one help me out? What is the difference between Salesforce1 and Salesforce? Can we create an app based on the requirement in Salesforce1 as we do in Salesforce? Salesforce1 is used in Mobile. Can any one brief me about Salesforce1? Any help is very much appreciated.  One of client is using the app exchange application which is a unmanaged package and would like to change the look and feel app with related to the Android device. Also would like to connect with the third party e-commerce site. Can it be done on Salesforce1 app with the SDK devices?


I'm from the northeast US. When describing the phenomenon of going to bed at night, or falling asleep, I always formulate the verb like that, as in "I went to bed at 10" or "I didn't fall asleep until midnight."  However I frequently hear the formulation "Last night, I slept at 10" or "I usually sleep at midnight". I'm interested in whether there's any interesting known dialect or historical distinction between the formulations. I now live on the west coast US and know many people who use these latter forms, and it still sounds wrong to my ear, like it's missing the helper verb (fall, go).   (The one case where I might crossover is in the sentence "I couldn't sleep until midnight", which sounds right to me, although "I didn't sleep until midnight" sounds wrong.)    It feels to me (though I don't have the professional vocabulary for this) that for me, "sleep" is an indefinite-duration, continuous action ("I'm sleeping"). So when I want to mark the time that it starts, I need to help it with "go to sleep". When I hear people say "I slept at 10", it sounds to me like they were asleep for only a moment, at 10 o clock, but not after, if that makes sense.


If $f:\mathbb R \to \mathbb R$ satisfies $f'(x) <L$ for some $L<1$, then $f$ has a unique fixed point

Assume that $f: \mathbb{R} \rightarrow \mathbb{R}$  is differentiable.  If there exists an $L<1$ such that for each $x \in \mathbb{R}$, $f'(x)<L$, prove that there exists a unique point $x$ such that $f(x)=x$.  So far I have that where I fixed $a$ to be zero and came up with three cases to show existence for  $f(0) = 0$, $f(0) < 0$, and $f(0) > 0$  $f(0)=0$ was fairly trivial following from the mean value theorem but the other two cases I was only able to eliminate half of the possible fixed points by contradiction and I need help showing it explicitly.  Edit as to avoid confusion here is the work I have garnished so far:  From the mean value theorem it follows for some arbitrary $a,b \in \mathbb{R}$ and $a\neq b$ that there exists a point $c$ such that $a<c<b$ or $b<c<a$ then implies that $\frac{f(b)-f(a)}{b-a}=f'(c)$ and this is because it is differentiable on $\mathbb{R}$ and, by convention, is also continuous on $\mathbb{R}$ as well.  Then the result of $\dfrac{f(b)-f(a)}{b-a}=f'(c)$ then follows for $L<1$ such that $\forall x \in \mathbb{R}$ means $f'(x)<1$ from our hypothesis. Which then follows  (*) $\dfrac{f(b)-f(a)}{b-a}=f'(c)<L<1 \Rightarrow f(b)-f(a)<L(b-a)<b-a$  Now without loss of generality choose $a=0$ and let $b$ be some arbitrary value in $\mathbb{R}$ then there are three cases that need to be considered for the value of $f(a)$:  (i) $f(0) = 0$, (ii) $f(0) < 0$, (iii) $f(0) > 0$  (i) For $f(0)=0$   Then $0$ is a fixed point of point of $f(x)$ and it follows from (*) that if $f(0)=a=0$ then $f(b)-f(0)=f(b)<Lb<b$ which shows that $f(b)<b$ thus shows that for any arbitrary value $b\in \mathbb{R}$ that no $f(b)=b$ thus shows that $0$ is the only fixed point if $f(0)=0$  (ii) For $f(0)<0$  Suppose there exists a fixed point $d>0$ then:  $\frac{f(d)-f(0)}{d}<L<1 \Rightarrow d-f(0)< dL<d \Rightarrow -f(0)<d(L-1)<0\Rightarrow 0<-d(L-1)<f(0)$ but this contradicts that $f(0)<0$  thus no other fixed point exists if $d>0$ when $f(0)<0$  (iii) For $f(0)>0$


Why is this an eigenvector of this matrix?

The matrix is  $$ \begin{bmatrix} 1 & 1 & -3 \\ 2 & 0 & 6 \\ 1 & -1 & 5 \end{bmatrix} $$  I understand where the eigenvector $[-3, 0, 1]$ comes from because the eigenvalue is $\lambda = 2$ and when you substitute it into the matrix and then row reduce you get $$ \begin{bmatrix} 1 & 0 & 3 \\ 0 & 1 & 0 \\ 0 & 0 & 0 \end{bmatrix} $$ But the answer also puts $[1, 1, 0]$ as an eigenvector. Any idea where this comes from?


Jack is trying to prove:     Let $G$ be an abelian group, and $n\in\Bbb Z$. Denote $nG = \{ng \mid g\in G\}$.      (1) Show that $nG$ is a subgroup in $G$.      (2) Show that if $G$ is a finitely generated abelian group, and $p$ is prime,    then $G/pG$ is a $p$-group (a group whose order is a power of $p$).   I think $G/pG$ is a $p$-group because it is a direct sum of cyclic groups of order $p$. But I cannot give a detailed proof.


Many of the latex packages used the term macro what does it mean and what is the definition of macro according to LaTeX and what is the use of this macro? Kindly let me know with examples. Thanking you in advance.


How to recover from a chmod -R 000 /bin?

And now I am unable to chmod it back.. or use any of my other system programs. Luckily this is on a VM I've been toying with, but is there any way to resolve this? The system is Ubuntu Server 12.10.   I have attempted to restart into recovery mode, unfortunately now I am unable to boot into the system at all due to permissions not granting some programs after init-bottom availability to run- the system just hangs. This is what I see:  Begin: Running /scripts/init-bottom ... done [   37.062059] init: Failed to spawn friendly-recovery pre-start process: unable to execute: Permission denied [   37.084744]  init: Failed to spawn friendly-recovery post-stop process: unable to execute: Permission denied [   37.101333] init: plymouth main process (220) killed by ABRT signal   After this the computer hangs.


An unresolvable problem occurred while initialising the package information.  Please report this bug for the 'update-manager' package and try to include the following error message:  'E:Malformed line 57 in source list /etc/apt/sources.list (dist parse)'