Prove $p (\bigcup A_i) \leq \sum p (A_i) $  Now i doubt that this has not been proven already as it is a common question, but i am typing latex on my tablet because i spilled water on my computer so i am having trouble finding the question in the archives. if somebody could post a link. Thanks.  In case it has not been proven, i am thinking of using induction, but it just doesnt feel like the right thing to do to prove this question.

I am trying to prove Boole’s inequality  $$P\left(\ \bigcup_{i=1}^\infty A_i\right) \leq \sum_{i=1}^\infty P(A_i).$$  I can show it of any finite $n$ using induction. What to do for $\infty$ ?


Have a look at the MWE example below. I want the text to appear at the bottom of the page rather than on top. I tried the \vfill option, but this does not seem to do the job. Any ideas?  \documentclass{report} \begin{document} \vfill © Copyright by KU Leuven\\  Without written permission of the promotors and the authors it is forbidden  to reproduce or adapt in any form or by any means any part of this  publication.    Requests for obtaining the right to reproduce or utilize parts of this publication  should be addressed to KU Leuven, Faculteit Wetenschappen, Geel Huis,  Kasteelpark Arenberg 11 bus 2100, 3001 Leuven (Heverlee), Telephone +32 16 32 14 01.\\ \end{document}

Using \vfill between two texts works:  \newpage bla \vfill blabla   but it doesn't work if there is no text before it:  \newpage \vfill blabla   How can this be achieved?


I could really use some advice on my current employment situation (web developer) and whether it is helpful or harmful for me at this point. I'm not sure where I should ask such a question.

The  specifically says not to ask  for career advice but people do it anyway.  Should I consider the Help Center outdated or only loosely enforced?    And what about a career advice site on the network?  There are 70+ sites, and most of them are for relatively narrow interests (which is not a criticism, I enjoy looking through the many sections).  A career section seems like it would be very popular.  Also, a careers section would help keep career questions off the other sites.


I can easily catch click event of a checkbox as shown below:  <input type="checkbox" id="checkbox1" />  $('#checkbox1').change(function () {     if (this.checked) {         //Do stuff     } });   On the other hand, I create a checkbox on callback of AJAX (in jQuery DataTable) as HTML and click event of the same element cannot be catched:   //... "ajaxSource": "/Student/GetStudents", "fnServerData": function (sSource, aoData, fnCallback) {     aoData.push({ "name": "all", "value": all });     $.getJSON(sSource, aoData, function (json) {         fnCallback(json);         $("div.toolbar").html('<input type="checkbox" id="checkbox1" /> Get all records');     }); },   What is the most suitable method to get the checkbox value in the HTML string?

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


I had a western digital bookworld nas.  It has died.  How can I get the contents off of it?  Thanks.

My Western Digital 500GB NAS drive (which is my main backup device) has recently broken. Windows can no longer use it as a network drive (using Map Network Drive), and the web-based control panel is INCREDIBLY sluggish, taking as much as 5 minutes to load a single page.  However, when it does load, it reports the Drive Status as OK, and has the correct disk usage values, which leads me to think the actual drive is OK, and it's the networking components that have failed.  I have checked the wires and router, and so it their isn't another point in the network causing the problem.  Is there any way to get the data back? It's a backup, so I still have about 80% of the data spread out across 3 computers (the only major loss being my music library, and I have the discs for a fair proportion of that).  However, it'd be much more convenient if I can get the data from the drive itself, as it is organised properly on the drive.


What are the rules for reporting posts that belong on other sites (forked of Stack Overflow)?  I tried to go through the LaTeX questions and reported those that were absolutely clearly only about LaTeX (no programming, etc...). But 50% of these reports were ignored/refused (can't see the resolution).  So what are the rules for reporting?  Specifically:   old posts posts with positive rating posts with multiple answers posts with accepted answer

How do I report that a question should be moved to a different site (from stackoverflow.com to superuser.com, in example)?


As we know , we have two kinds of presentation in binary classification , one is 0/1 and the other is -1/1 .   For 0/1 case , we often use "negative logarithmic likelihood" loss function for it , also known as cross entropy function , certainly other options such as "hinge" loss also can also be in consideration . Here , we just consider the former one . And the formula should be like : $$L(w) = -\frac{1}{N}\sum_{i =    1}^{N}log(p_{i}^{y_{i}}*(1 - p_{i})^{1 - y_{i}}) + regPart$$ while both p(i) and regPart should be function of w . As in -1/1 case , we often use "exponential" loss function for it , and its formula should be like : $$L(w) = log(1 + \exp^{-y_{i} *    s_{i}}) + regPart$$ while both s(i) and regPart should be function of w .   My model behaved in a strange way while training in an experimental environment few days ago .   I used logistic regression to solve binary classification problem , and tried these two types of loss function showed above . The metrics on validate data while training are listed below :   In the case of logarithmic loss for 0/1 , the accuracy values on validate data were       0.48 0.57 0.68 0.74 0.76 0.78 0.78 0.78 0.79 0.79 0.80 0.80 0.81   It seemed normal same as what I expected earlier .   While in the case of exponential loss for -1/1 , the accuracy values on validate data were       0.48 0.34 0.32 0.30 0.28 0.26 0.25 0.24 0.23 0.23 0.23 0.23 0.23   Strangely , the ratio of positives in validate data is 0.23 .  It seemed to go in the wrong direction against with what I expected . I checked the parameters in each iteration , and found out that each dimensional parameter went up while iteration went .   Do I have to choose the logarithmic loss function for logistic regression ? And why ?  Much appreciated if you can give me some constructive tips or detailed explanations for that -)

I've been thinking about this problem.  The usual logistic function for modeling binary data is: $$ \log\left(\frac{p}{1-p}\right)=\beta_0+\beta_1X_1+\beta_2X_2+\ldots $$ However is the logit function, which is an S-shaped curve, always the best for modeling the data?  Maybe you have reason to believe your data does not follow the normal S-shaped curve but a different type of curve with domain $(0,1)$.  Is there any research into this?  Maybe you can model it as a probit function or something similar, but what if it is something else entirely?  Could this lead to better estimation of the effects?  Just a thought I had, and I wonder if there is any research into this.


Firstly, I should note that this is a cross-post from Reddit r/AskAcademia, and the link to the question is:  I really hope to improve my situation, thus, I would love to get more perspectives on this problem!  Hi there! I'm a first-year undergrad student looking for my first ever research position. I have a hard time understanding the big picture/question/goal the professor is trying to solve/work towards when reading about their projects. I am often overwhelmed with the technical details that are way beyond my current scope of knowledge, and this has made their research appear a lot more tedious to me I'm seeking ways to improve this situation, particularly things I could do to aid me in understanding the broader goal of the project. Thanks in advance for any help!

When needing to ask a professor about something important and potentially delicate, what is an appropriate way to phrase the question or write the email?  Examples include:   Requesting a recommendation letter Asking for exceptions to policy (e.g., ignoring a course prerequisite, rescheduling an exam) Asking if you can do research with them, join a group, get into a program Scheduling a meeting, exam, or defense Letting them know about a change of plans Letting them know about a life event affecting your work or studies (e.g., wedding, funeral, sickness, vacation)


I am seeking to divide this 200 acre polygon into 5 polygons of 40 acres.  I have yet to find a concrete solution to this task by searching this forum.  Is there a pragmatic tool in existence that can help accomplish this task?  I am using ArcGIS 10.5.  I have attempted the fishnet tool but all that accomplished was create a grid.  Another suggestion I found (The Parcel Editor toolbar) is unavailable with my current license.

I've a set of regions within a city. I'd like to split each region into five subregions and then get the centroid of each one of them.  I know how to make a vector grid, but the problem I have is that the generated points are not taking into account the regions, they're only related to the general map.  I have this:    And I want to split each region in five equal size areas. Something like this:    I'd like to build a visualization similar to this one: . In order to accomplish that, I need to split each region, because the original ones are pretty big.


I have no idea what I'm doing. I needed to back up my iPhone, but the storage on my computer was too low, so I followed a guideline on how to back it up directly to an external hard drive. It required moving the backup folder to the external hard drive, deleting the original file location on my PC, and then running a command: MkLink /J "C:\Users\UserName\AppData\Roaming\Apple Computer\MobileSync\Backup" "M:\MobileSync\Backup" This was successful, but I didn't realize this hard drive was also low on memory. Now I would like to have my iPhone backed up directly to my other hard drive, but I have no idea what to do next or what script to write. What I've done so far is cut/paste the backup folder from hard drive 1 to hard drive 2, and try to create a junction from 1 to 2: MkLink /J "M:\MobileSync\Backup" "H:\MobileSync\Backup"  the system cannot find the path specified.  Have I mentioned I really have no idea what I'm doing? How do I go about solving this problem? I would really appreciate any help!

I believe in Windows Vista, we could use linkd command. However, I cannot find this command in Windows 7. I know I can use Windows Explorer and delete the junction, but I wonder if this can be done in Command Prompt.  I can use mklink command to create a junction from a Command Prompt, so, what is the opposite of it (something like linkd)?


Definition. A subset of $\mathbb{R}$ is called open if it is a union of open intervals.  Example.  $\mathbb{R} \backslash \mathbb{Z}$ is open.  Proof (is from my lecture notes).$\mathbb{R} \backslash \mathbb{Z}=\cup\left\{ \left( n,n+1\right) :n\in \mathbb{Z}\right\}$.  My question is: why $n$ in $\mathbb{Z}$? I think, $n$ cannot be in $\mathbb{Z}$ because  we say $\mathbb{R} \backslash \mathbb{Z}$.

So I've been trying to prove that a set $\mathbb{R}$ \ $\mathbb{Z}$ is an open set but I don't quite know where to start since the relative complement is still infinite. So theoretically in $\mathbb{R}$ \ $\mathbb{Z}$ one could pick a real number as close to an integer as needed but you could of course never pick the integer itself. So my idea was that $a-\epsilon<a$ for any $\epsilon>0$ with $a\in \mathbb{Z}$ but I have a feeling I'm doing it wrong. Any ideas or hints on how to solve this properly?


I have a field that I need a value assigned to, I want this field to be populated with a particular value when the node is being saved. Where should the code be placed? And how would I go about accomplishing this?

Basically, I want to put first name & surname together into $node->field_par_contact_name  But it gives me warning. (See below)   function partnership_node_presave($node) {   if($node->type == 'partnership') {     $first_name = $node->field_par_contact_first_name['und'][0]['name'];     $surname = $node->field_par_contact_surname['und'][0]['name'];      // https://drupal.org/project/field_hidden     // Hidden variable     $node->field_par_contact_name['und'][0]['value'] = $first_name. ' '. $surname;      // Warning after save: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 173 of .../drupal-7.23/includes/entity.inc   } }   Updated, please see image:


I wonder what these shortcuts mean and since I already can figure out that "shortcut" is not the right word for it, I don't even know what to google so I'll just strike a question here.  Here's the screenshot:   So, what does M, A, ? and all other shortcuts mean exactly ?

What do the result codes in SVN mean? I need a quick reference.


Let $X$, $Y$ be normed space and $$T:D(T)\subseteq X\to Y$$ be linear operator.  Prove $T$ continuous if and only if $T$ bounded.  $(\Leftarrow)$  Given $T$ bounded, so there exist $c\in \mathbb{R}$ such that $\Vert T(x)\Vert\leq c\Vert x\Vert$.  Let $\varepsilon>0$, we choose $\delta=\dfrac{\varepsilon}{c} >0$ such that $\forall x\in D(T)$ with $$\Vert x-a\Vert<\delta.$$   We can see that  $$\Vert T(x)-T(a)\Vert=\Vert T(x-a)\Vert\leq c\Vert x-a\Vert<c\delta= \varepsilon.$$  So, we can conclude that $T$ continuous function.   Is it correct proof? Please correct if I made mistake.  $(\Rightarrow)$  Given T continuous, so for all $\varepsilon>0$ there exist $\delta>0$ such that for all $x\in D(T)$ with $\Vert x-a\Vert<\delta$ imply $\Vert T(x)-T(a)\Vert<\varepsilon$.  $$\Vert T(x)-T(a)\Vert=\Vert T(x-a)\Vert<\varepsilon.$$   Now I confuse how to prove $\Vert T(x)\Vert\leq c\Vert x\Vert$, for some $c\in \mathbb{R}$  Anyone can give me hint how to proof this part?

Let $(V,||\cdot||_V),(W,||\cdot||_W)$ be normed spaces over $\mathbb{C}$.  Let $T:V\rightarrow W$ be a linear transformation.  Assume $T$ is continuous.  Then, how do i prove that $\exists c>0$ such that $\forall v\in V, ||Tv||_W<c||v||_V$?


I have an array which has a single element which I delete with the following code:  delete array[0]   At this point the array is empty. I'm therefore confused why array.length has an output of 1.   When I use console.log it displays the following:    Am I doing something fundamentally wrong or how do I check that the array is empty? Maybe an explanation of typescript array memory management would be useful.

What is the difference between using  on the array element as opposed to using ?   For example:  myArray = ['a', 'b', 'c', 'd'];  delete myArray[1]; //  or myArray.splice (1, 1);   Why even have the splice method if I can delete array elements like I can with objects?


I'm on Ubuntu 17.10. , says that Flash is available in the software center, but it is not for me at least. I tried downloading from their ; first I tried APT which failed with the message "unknown channel: artful-partner." I also tried downloading the tar.gz - first I followed the instructions on their website and the I tried just extracting everything to ~/.mozilla/extensions. Nothing worked.

I know, it's been asked before but I couldn't really get a satisfying answer for some details/backgrounds and I guess it's an important question for many.    Some application seem only to be running with Adobe Flash 15 (or at least I know it does, because I have that version on my Windows Partition).  The official Adobe website says:     NOTE: Adobe Flash Player 11.2 will be the last version to target Linux as a supported platform. Adobe will continue to provide security backports to Flash Player 11.2 for Linux.   Some search on the web like "Ubuntu Adobe Flash 15" or similar does not return any good websites.  I found something that says   (using a "pepper-based version"), and  .   Is it impossible to use this for Firefox too? Would it be a privacy risk?  Are there no alternative projects (I know it's closed source but there are so many so very bright people out there using something similar to wine but just for the plugin....)?  How about the Mac-Version? Shouldn't someone be able to port that one to Linux?


I'm planning to visit Iran in a couple of months. I'm German and when skimming through some stuff on the embassy website I couldn't find any helpful information.  What is the usual visa processing time?

Most Westerners do not only need a visa to visit Iran, they first need a "Letter of Invitation" to be able to apply for the visa.  Most people get this through travel or special visa agencies, some of them are online only.  What are any trustworthy agencies that do this? Experiences in quality and duration?


The background is that I was doing C1 tests and got wrong the following:     It's time you ____ up your mind.   As it seems right to me, I wrote "make". However, the answer shows "made" as the correct answer.   Why is the past tense used?   I could understand the ussage of made if the word "already" was in the sentence. But it is not.  Thank you in advance!

What does It's time I went to bed mean?  and can we say It's time I go to bed ?  and what's the difference between the two sentences?


Let $f\in\mathbb{F}[x]$ be a monic, irreducible polynomial of degree $d$.   We define $\mathbb{K}=\{g\in\mathbb{F}[x] \ | \ deg(g)<deg(f)\}$.  Let $g\in\mathbb{K}$, assume that $g\neq 0_\mathbb{F}$, prove that there exist a polynomial $q\in\mathbb{K}$ such that $g\cdot q=s\cdot f+1_\mathbb{F}$ for some polynomial $s\in\mathbb{F}[x]$.

Let $K$ be a field and $f(x)\in K[x]$. Prove that $K[x]/(f(x))$ is a field if and only if $f(x)$ is irreducible in $K[x]$.   How to prove? I really have no idea... Thank you a lot.


Basically, I am asking for two words-   What do we call a person who spreads rumor?    And on the flip side, there will always be some people who easily believe rumors.    What do we call people who believe in rumours?   Is there a word, or phrase for both types of people?

What is the single word that describes a person who always gossips? (For example, telling things about others which are not true.)


I have a question, which I have been thinking about the last 50 years. I know, that the word "blood" is prononcued "blaad" and I know. that "roof" is prononcued "ruuf", boot like "buut" , tool like "tuul". They all have 2 oo, which gives "UU", but why is blood then "blaad" and not "bluud".? Do you understand me. :)  Best regards  Kurt Denmark

My German colleagues were laughing at the way I pronounce google, and it led to a discussion.   With words like google, yahoo, poodle and loose, the oo has a sound similar to the German ü sound. With words like good and book, it is more similar to how Germans pronounce a oo sound. For words like door we are not sure if that is the same or different.   The Germans want to know what the pronunciation rules are so they can improve their English. I am guessing that there are no rules, and the pronunciation possibly comes from the original language that the word comes from.  Are there any rules? Is there any reason why there are two different pronunciations? Can non-native speakers work out the correct pronunciation by looking at the other letters in the word or the etymology?


Map<String, Map<Long, String>> regions = Service.getWhseByRegions(); for(String region:regions.keySet()){ warehouseList=getAuthorizedWarehouse(dashboardWarhs,regions.get(region)); if(warehouseList!=null && warehouseList.size()>0){       regions.put(region, warehouseList); }else{       regions.remove(region); } }   Hi , I am getting ConcurrentModificationException, please help

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


I bought an external hard drive from a computer repairman when he could not fix the computer I brought in for repair. I have not been able to access it since bringing it home to use because access is denied to me and I do not have permission to access the files. I did not do this and he wants to charge me to undo what he did. How can I remove these permissions myself  or is this money wasted? Computer needing repair was an ace notebook eMachines

I'm running Windows Vista, which is installed on my primary drive.  I have a second hard drive installed, which used to host my Windows XP install, and I'm trying to delete the Documents folder, but I don't have permissions to do so.  Is there a way I can reset the permissions on all subfolders of my second drive?


Prove that if A has rank r > 0, then A has an r x r invertible matrix. I have tried looking at the properties of invertible matrices, but I can't prove those qualities using just the rank of matrix A.

Let $A$ be a $m \times n$ matrix with entries from some field $F$. Define the determinant rank of $A$ to be the largest possible size of a nonzero minor, i.e. the size of the largest invertible square submatrix of $A$. It is true that the determinant rank is equal to the rank of a matrix, which we define to be the dimension of the row/column space.  It's not difficult to see that $\text{rank} \geq \text{determinant rank}$. If some submatrix of $A$ is invertible, then its columns/rows are linearly indepedent, which implies that the corresponding rows/columns of $A$ are also linearly indepedent.  Is there a nice proof for the converse?


Hi I am trying to find the verb that describes a correspondent meaning as following:     While reading text on something, add/write in some addtional/referential information to it.   Like,   While reading a book if I want to leave some 3M memos on it with some explanatory figures, which verb will describe it properly?  Any recommendations would be appreciated.

I research Latin texts which discuss a peculiar medieval practice: the addition of minute graphic symbols into the margins of the page, for example in order to indicate passages of interest, flaws in argumentation or for some other technical purpose. The Latin-users had a very clear technical terminology for such signs: they called them notae (sg. nota) and the verb that they used to talk about this addition was adnotare (plus there was a whole range of words that could be formed from these two). Modern English does not seem to have a term that would have the same technical meaning and I have a constant problem with both native and non-native English speakers when I am trying to write or speak about these notae.  I have tried the English word markup (and its derivates), but this did not find favour with my audience. Translation as signs or marks is too vague and broad to be helpful. I cannot use the Latin word nota indefinitely, especially since I cannot make a verb out of it that would make sense in English.  What would you call this 'thing'?  An example of the technical signs in question:  (PX- and PO-shaped symbols in the right margin)


I have a dict like: example = {'a':2, 'b':2, 'c':1, 'd':1}  I want to keep only the maximum values and keys. The output should be: {'a':2, 'b':2}  This is different from just getting the maximum value, as has been asked in other places. What is the best way to do this?

I have a dictionary: keys are strings, values are integers.  Example:   stats = {'a':1000, 'b':3000, 'c': 100}   I'd like to get 'b' as an answer, since it's the key with a higher value.  I did the following, using an intermediate list with reversed key-value tuples:  inverse = [(value, key) for key, value in stats.items()] print max(inverse)[1]   Is that one the better (or even more elegant) approach?


I was reviewing questions with close votes in StackOverflow and for some of the questions, the question was voted to be closed because the user had not updated the question with enough details on the problem they are facing, or proper code examples.  For new users, I feel it to be discouraging for the user when the question gets closed soon before the user can update more information on the question. Right after the question is posted, some user or the other immediately posts a link for rules to be followed when posting a question. So shouldn't we wait for some time before we allow that question to be voted for closure?  Can we consider something about this behaviour?

Since it's currently impossible to delete a "vote to close",* when I see a poorly asked question, should I immediately vote to close, or should I comment, and give the OP a chance to improve his question?  Waiting increases the chance that I'll forget, and never vote to close, potentially leading to a cluttered site.  Voting to close immediately increases the chance that the question will be closed, and the author will be forced to re-post his (hopefully improved) question, which leads to a cluttered site. :)  *It is now possible to , but that doesn't change the fundamental nature of this question.


In previous version there was a button REMOVE to uninstall or remove the addon. Im using 2.82 how can i uninstall or remove the addon. I do not want to disable the addon by uncheck. I want to remove completely. No option seen. Any suggestion. Thanks

I asked a question yesterday about how to bring filled polylines in from AutoCAD without them coming in as joined filled shapes.  I was directed to a download site to get a new dxf importer.  I installed it as directed but now I have two dxf converters installed in Blender and they conflict so that I can't bring dxf files in at all.  How can I uninstall the old one?  I suppose I could uninstall Blender and then reinstall it, but then I would have the same question.  Can I bring in polylines from AutoCAD without them linking to each other and creating a maze of linked filled shapes?


This story I am sure was in Analog. A confederation of aliens come to earth and are able to break through a force field enclosing earth. The field was put there by aliens since they were not able to break earth's defenses in an older war. Earthlings appear completely non-technological, and the good aliens think they may at least be able to dress them up to be scary. One alien falls in shaft through hundreds of stories of tech before being saved. They bring down the force field and earth celebrates. Even the horses and dogs have conversations about it. Earth has not been idle during their imprisonment. They take on challenging the evil alien empire by moving the earth into space, and they take the moon along. I remember a cute seen where the human says he is making ice cream, but he is not sure he has enough for a large alien. The alien tries to hunch up, but it not sure if "ice cream" is something good or if it is used to remove reluctant teeth. A really great story.

First we are told that the Galactic Empire/Federation/Powers-that-be have kept the Earth locked up for being too warlike, but now their help is needed against invaders from another galaxy.  When the aliens land the first thing they meet is a talking bunny.      at the end when humans have accepted to join the fight the alien offers to send ships to transport them. The human leader tells that there is no need...  and the Earth accelerates away.   I must have read this sometime in the mid eighties, so no later than 84 or 85, but the story may be from the sixties or before.


Given:  $eG=P$, $kG=(r,y)$  ECDSA signature transmits (r,s) and does this calculation:  $u = \frac{z}{s}$, $v = \frac{r}{s}$  $uG+vP=(r,y)$ means the signature is valid  Why do we transmit $s$ and not $s^{-1}$?  Currently, $s=\frac{z+re}{k}$, why not $s=\frac{k}{z+re}$? The equations would all go through:  $u=zs$, $v=rs$  $uG+vP=zsG+rsP=zsG+rseG=(zs+rse)G=s(z+re)G=\frac{k(z+re)}{z+re}G=kG=(r,y)$  Given that finding the inverse is very expensive computationally, what are we gaining by transmitting $s$ instead of $s^{-1}$?

A DSA signature consists of two scalars $(r,s)$.  When signing $s$ is generated as:   $s=k^{-1}(H(m)+xr) \mod q$ The signature is $(r,s)$   When verifying $s$ is only used to compute $w = s^{-1}$. So why does DSA store $s$ in the signature instead of $w$?  Using $w$ has no performance effect on signing since computing either $s$ or $w$ requires one modular inversion. $w = s^{-1} \mod q = k (H(m)+xr)^{-1} \mod q$. It would speed up verification since the modular inversion to compute $w$ isn't necessary anymore.  The only advantage of $s$ I see is that the modular inversion can be computed before the hash is known. Did the DSA designers consider that pre-computation more important than the verification slowdown, or is there some other advantage of using $s$ that I don't see?


My Panasonic Lumix DMC-ZS15 P&S (about 2yrs. old, records in JPEG) takes fine pictures for my purposes (at most 5x7 prints). It has 12.1MP, 16x zoom, and a 1/2.3 MOS sensor. I always use the "high quality" setting and auto settings for aperture and shutter. I have always wondered which MP setting would give me the best resolution vs. noise in the final image. I asked a similar question 2days ago, but now I am looking for a more specific answer. I realize this new question may be more specific, elementary,and possibly neurotic than you guys care to deal with, so please feel free to ignore me if that is the case. I have experimented and learned that I probably do not need all 12MP but still cannot make up my mind between 5 & 8MP. Thank you for your consideration.

Suppose you want to store your photos at some lower resolution, let's say about ~1 MB large.  You own a camera able to make photos at 5 MPix and more.  And, you want to have the maximum quality at the smaller size.  Would it be better to make a photo at highest resolution and then resize it with PC software (with a good filter of course), or to directly set the camera to make photos at 2 MPix only?


This has been happening for a while, I've noticed that whenever I'm playing Minecraft with my brothers, (On LAN, I'm not sure if it works on public servers.) I can see my skin, but they can't. It's really annoying because I just finished my custom skin of myself, AND NOBODY CAN SEE IT! If you need more details just ask.  What do I need to do to make my skin visible ?

I made a skin by using Skincraft and I exported it to minecraft.net. I chose my skin and uploaded it. At the top it says,      "Your skin has been changed! Please wait a few seconds for it to   update."   I went to Minecraft, clicked singleplayer and chose a random world at the top. I looked at my character, but it's still default. Multiplayer won't load for some reason. I don't know what I've done wrong!


Wondering if anyone has ever attempted this? Basically looking for the same functionality as PHPs DOTNET() function.

I am interested in using/learning RoR in a project where I have to use a .NET dll. Is Ruby capable of importing a .NET dll?


I was told that the motion of a simple pendulum is harmonic only when its amplitude is much less than the length of the pendulum (let's take this as first statement). Why it is so?  Also my teacher told me that a simple pendulum is SHM for small angular displacement and that's the reason for the above statement. But I felt that both the statements are implying the same idea. What could be the reason for the first statement?

Considering an ideal case(neglecting drag of air, damping etc.), a pendulum follows SHM if the angular displacement is small (upto 10 degrees). But, for large angular displacement(more than 10 degree), it does not follow SHM. Why? What force cause the pendulum not to follow SHM?


My Sysconfig file looks like below   <?xml version="1.0" encoding="utf-8"?>   <configuration>     <appSettings>     <MESCustomMenuID value="" />   </appSettings>   </configuration>  I want to change tag value <MESCustomMenuID value="" /> to <MESCustomMenuID value="SOLUMTE" />  I tried below coding to change tag value @echo off set CWD=%~dp0  set _FilePath=C:\Epicor\ERPDT\Client-Pilot\config\ set _FileName=Default - Copy.sysconfig  set _WrkFile=Default - Copy_bak.xml set OldStr="<MESCustomMenuID value="" />" set NewStr="<MESCustomMenuID value="SOLUTMES" />"   set _Found=Not found  SETLOCAL SETLOCAL ENABLEDELAYEDEXPANSION  for /f "usebackq tokens=*" %%a in ("%_FilePath%%_WrkFile%") do (     set _LineChk=%%a     if "!_LineChk!"==%OldStr% (         SET _Found=Found          SET NewStr=!NewStr:^"=!          echo !NewStr!         ::echo ^<MESCustomMenuID value="SOLUTMES"^>         ) else (echo %%a)         )>>"%_FilePath%%_FileName%" 2>&1  The code above is collapsed sysconfig file XML tags

I am writing a batch file script using Windows command-line environment and want to change each occurrence of some text in a file (ex. "FOO") with another (ex. "BAR"). What is the simplest way to do that? Any built in functions?


I am training a feed-forward network on a regression problem (MSE error) to predict a scalar value 1x1 given an input of size Nx1. My batch size is 400 (though this problem is robust to multiple batch sizes).   My problem is that the optimizer always converges to a solution where it predicts the same value for every element of the batch. For example, my real labels (for a batch of 400) might be:  [34, 50, 12, ... , 23, 45, 22] (size = 1x400)  And what it predicts will be something like this:  [29, 29, 29, .... , 29, 29, 29] (size = 1x400)   I think I get why it is doing this and it has to do with using MSE. Basically, MSE is computed over a whole batch and so that is the signal the optimizer receives to update the weights. The signal is not informative of the fact that predicting the same value for every element of the batch is a sub-optimal solution.   I have tried a couple solutions to this but all of them run into the same problem above. For example, I have tried adding a penalty for the variance prediction not matching the variance of the labels. Basically matching second moments. i.e. instead of,  $$ loss = (\hat y-y )^2$$ I do, $$ loss =  (\hat y-y )^2+ (var(\hat y) -var(y) )^2 $$  And it still does the same thing.   Reading some other questions it seems that this is to be expected with MSE and I am just wondering if anyone has tried something different or a different variation of MSE or batching that solves this problem. I get that this is a difficult problem but given the limitations of softmax classification on a regression type problem I think it is a very worthwhile one to solve.   Anyone else encountered this or have a solution for it?  (I am using tensorflow and a setup with 4 GPUs if it makes a difference.)

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


Let $A$ and $B$ be $n$ x $n$ matrices over reals. Show that $I - BA$ is invertible if $I - AB$ is invertible. Deduce that $AB$ and $BA$ have the same eigenvalues.  I know how to prove that $AB$ and $BA$ have same eigen values, when either $A$ or $B$ is non-singular.   But here, that condition is not mentioned.   Please help me.

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


Everyone says I'm crazy, but I love playing Drow. The only tiny, little, gigantic problem is the disadvantage on EVERYTHING in direct sunlight. So, is there any way to negate the disadvantage on a roll in sunlight, or should I just play lots of Underdark campaigns?

My friends and I are trying to come up with ways to get around the drow's sunlight limitations. We thought of using spells, but Darkness makes it impossible to see, which would defeat the purpose.  The best I've been able to come up with is lashing a large patio umbrella to a mule and making it follow the drow everywhere. Would this work, at least for a low level melee character?  What other options does our drow have?  This question is about what I can do as a player to take advantage of RAW; the players in my group don't mind being munchkin-y. Telling the GM to make the campaign take place at night isn't an option.


I am trying to disable several application from auto starting after restarting computer.   However - can not see Startup folder in Task Manager:    Where to find it / how to enable it?

I'm trying to delay the startup of a specific program that loads at login. As per an answer in , I should be able to do it using Task Scheduler. The problem is, I can't find the program listed anywhere. Is there a particular pane I should be looking in? The program is Razer Synapse so I don't think it would be in the Microsoft or Western Digital folders.    If it's not in Task Scheduler, is there another way I can delay it at startup?  Out of curiosity how many ways are there for a program to be run at Startup in Windows?


This is a phenomenon that occurs mostly among non-native English speakers. The other day, 4 non-native speakers were discussing the USSR flag. All of them described it as red-colored flag with a hammer and a cutting knife (example: That hook-like knife used for reaping or simply a knife). Now this kind of description would surely bring up the image of the actual USSR flag but would not be treated as a qualified description. When the topic digressed, I purposely mentioned the sickle in the ongoing conversation and everyone knew what a sickle was and all of them then said the reaping knife that they had described earlier was a sickle. Now the question is: They could not associate a sickle (which they knew already) with the image of a sickle on the USSR flag while describing the flag but once the sickle itself was the topic they knew that the knife on the flag was in fact a sickle. What does this communication-association-memory problem or issue called that occur mostly among Non-native English speaker. I don't know if it occurs among native English speaker at all. Addition after the question being flagged as duplicate + already answered: They wouldn't necessarily say that it was on the tip of their tongue as "tip of one's tongue" suggest that they has inkling of the word but they just didn't come up with it during the original flag conversation. I want to make distinction 1.) During the flag conversation, they would not bring up sickle in any case as there is not association, although they know sickle in isolation. But they just can't associate it with the sickle that they know on the flag during the flag conversation. 2.) The other is tip of the tongue which i understand is they know that the image on the is sickle but could not utter as they were not able to recall the word. They just don't experience any recall phenomenon. Would you still call it Tip-of-the-tongue (TOT) phenomenon (since the very phrase suggest that the association is made but it lacks utterance due to some sort of mental block (probably temporary) at the moment.

What is a word to represent a situation in which we feel short of word to be able to express what we want to or what we are feeling .


I am dual booting Windows 10 and Ubuntu, using the GRUB boot loader. I also have a Bluetooth keyboard that works fine when booted into either OS, but it doesn’t work in the boot loader (I have to get out my cable and plug it in). From what I’ve read to use Bluetooth in the boot loader I would have to enable Bluetooth in BIOS. The problem is I don’t see any setting in BIOS that remotely resembles enabling Bluetooth.  I have an MSI Tomahawk B350 Motherboard, which doesn’t have WiFi or Bluetooth, so I bought a wireless network card to add the functionality. Since my motherboard doesn’t have wireless capabilities natively, does that mean it’s not possible to enable Bluetooth in BIOS? Or am I just missing some setting?

Can I use a bluetooth keyboard to enter BIOS and edit the values there? I'm thinking of two scenarios:   A new machine - no OS (yet). So to me seems no possibility to pair the keyboard. Hence no access to BIOS? I have booted to an OS (Windows/Mac) once and paired the keyboard with the computer. Will the keyboard work before OS drivers are loaded?


I used a C400 64GB USB2 Flash Drive EMTEC green to record digital MP4 using a converter of VHS tapes and transferred them to a PC. This has worked very well. But a moment after I deleted one by one all the processed files, I found that by viewing the properties, approximately 2GB of the space remained occupied when no files were reported.   That had already been the case with key 8 or 32GB, because recording ended badly, and in this case I proceeded to reformat to recover all available space.   So I reformatted the default key with exFAT 64B and 32 kilobytes. But since then I can no longer use the key on the converter. As I do not know what the characteristics of this key were before reformatting, I sent a request for information to EMTEC to be able to reproduce the initial format that worked correctly.   But I received no response. I tried to format in FAT32 but can not do it because I have such options as exFAT or NTFS for reformatting the key. Who can help me find my intitial formatting Flash Drive

In windows 10, when you want to format a partition specifically as FAT32 (for example an SDcard that is going to be used in your phone) when you right-click the disk and choose format, only NTFS and exFAT are shown as possible format options.  Is there another way, preferably without installing an additional tool or booting into a different mode to format as FAT32?


From what I understand, standard deviation is a way to quantify how individual results differ from their mean. Since $E[X - E[X]] = 0$, we square that difference and take the square root of the expectation to get a value that represents the "expected" deviation of a value from its mean.  But is there some specific reason we use $E[(X-E[X])^2]^{1/2}$, and not $E[(X-E[X])^3]^{1/3}$ or $E[(X-E[X])^n]^{1/n}$ for any other $n$ (e. g. a more analytical way to derive standard deviation). Does the case when $n=2$ represent something particularly useful, and what would other cases represent?  I also wonder what's the relationship between standard deviation and Euclidean distance / $L^2$-norm.  $\left(\int_{\mathbb{R}} (x-E[X])^pf(x)\ dx\right)^{1/p}$ also looks similar to $\left(\int_{\mathbb{R}} |f|^p \ d\mu\right)^{1/p}$

Equivalently, about variance?  I realize it measures the spread of a distribution, but many other metrics could do the same (e.g., the average absolute deviation). What is its deeper significance? Does it have    a particular geometric interpretation (in the sense, e.g., that the mean is the balancing point of a distribution)?  any other intuitive interpretation that differentiates it from other possible measures of spread?   What's so special about it that makes it act as a normalizing factor in all sorts of situations (for example, convert covariance to correlation)?


What physical properties does direction exhibit when applied on a physical on an object.    This maybe leaning into mathematics/philosophy but my question is what is direction? It is defined by wikipedia as: Direction is the information vested in the relative position of a destination (or target) point with respect to a starting point, absent the distance information. I have to some degree known that all my life. But lately I thought what IS direction if you know what I mean. What does direction measure fundamentally? I don't have advanced knowledge of physics but you get base units, why is direction not one or rather what kind of unit is direction? (I don't mean it basically, I just can't think how to put it into advanced terms) I might be overthinking it.. lol and I might look stupid but do you know what I mean?? Maybe I should head to the philosophy section. I put a large emphasis on (WHAT IS DIRECTION) in a deep intellectual and mathematical/physical way (do you get my drift?). Are there any important equations that define direction in mathematics and physics?. Are there any notable facts about direction (is there anything notable relating to direction when it comes to black holes, (for example at the centre))? You get direction in space and you also get direction in time, in what ways do these types of direction vary and are they or have been given different units of measurement. Do particles exhibit physical properties that define their direction (please try to understand I mean in a complex way not in ways like (particle A that has direction exhibit properties such as it moves from 0,1 to 7,0)). I would appreciate it a lot if you could expand on what I have asked and show some flare (what effects that are exhibited in quantum mechanics that relate to direction and the changes of what direction is in each nth direction with theory such as string theory). Maybe this is a simple concept and I will get embarrassed and get a very short answer but it just one of those questions that popped up in my head and seemed intriguing. Are there any cases that a physical particle or object does not exhibit direction (maybe it's in the 0 dimension... I don't have advanced knowledge).   I posted this question and I feel very nervous that I look very stupid please can someone confirm? I've been doing alot of programming so I can see where them mixup of concepts might come in.

Is there an actual definition of "direction" (that is, spatial direction) in physics, or is it just one of those terms that's left undefined? In physics textbooks it's always just taken for granted that the reader knows what it means (and it is true that just about everyone does indeed have an "intuitive" idea of what it is). But it would be more satisfying to have an concrete definition, if possible.


I was reading this article (Faster R-CNN: Towards Real-Time Object Detection with Regional Proposal Network) and in yellow line:  What is the meaning of fine-tuned end-to-end?

I want to know what it is, and how it is any different from ensembling?  Suppose, I want to achieve high accuracy in classification and segmentation, for a specific task, if I use different networks, such as CNN, RNN, etc to achieve this, is this called an end to end model? (architecture?) or not?


Is it possible for example to sell a property you own to another player for 1$? I was playing with some friends and one of them had to pay me 1200$ and since he didnt have enough he sold all his houses reached 1200 gave me the money and then sold all his stuff for 1$ to another player.

I play with some serious board gamers, but we have neglected Monopoly for a number of years, so our knowledge is mostly based on high school & house rules.  We played last week and enjoyed it, but there was a piece of contention. There are times where we decide that we don't like one of our friends for some reason and don't want them to win (i.e. we landed on their property a bunch, or they refused to make a deal, etc.).  So when player 1 has some property and player 2 lands on it and cannot pay the rent their assets (houses/hotels get liquidated), their property gets transferred to the other player. (Please correct me if I'm wrong.) In this case, though, player 3 "traded" the amount of money owing for a piece of property (way overpaid). In this case they did it so that player 1 would not get the properties. Player 2 had no chance of winning the game (all properties mortgaged, no cash to speak of and many of the other properties with 3+ houses/hotels on them).  To summarize: Is it OK for a third player to purchase/trade property or cash to/from a player who is about to lose?


Given $a,b\in \mathbb{N}$ where $1<a<b$, when is it so that $a^b > b^a$?  I feel like this should be a known result but I cannot for the life of me find it.

I was trying to find a simple relationship between mutual exponentiation of two positive real values, if one of them is greater/smaller to another.


If object made of atoms and atoms are invisible then when we look at an object or touch an object what we see or feel?

If you've ever been annoyingly poked by a geek, you might be familiar with the semi-nerdy obnoxious response of      "I'm not actually touching you! The electrons in the atoms of my   skin are just getting really close to yours!"   Expanding on this a little bit, it seems the obnoxious geek is right. After all, consider Zeno's paradox. Every time you try to touch two objects together, you have to get them halfway there, then quarter-way, etc. In other words, there's always a infinitesimal distance in between the two objects.   Atoms don't "touch" each other; even the protons and neutrons in the nucleus of an atom aren't "touching" each other.  So what does it mean for two objects to touch each other?   Are atoms that join to form a molecule "touching"? I suppose the atoms are touching, because their is some overlap, but the subatomic particles are just whizzing around avoiding each other. If this is the case, should "touching" just be defined relative to some context? I.e, if I touch your hand, our hands are touching, but unless you pick up some of my DNA, the molecules in our hands aren't touching? And since the molecules aren't changing, the atoms aren't touching either?  Is there really no such thing as "touching"?


Just had a memory issue on a 64GB of RAM machine with SQL Server 2012 SP2. 3 running db engine instances, each limited to 16GB (16384). But noticed in Task manager that sqlservr.exe was at over 30GB memory for one of them.  What is the cause ? And is there any way to see what's eating up the RAM, next time it happens ?  Can anyone explain if there's any way to limit the memory used by one instance, besides the "Maximum server memory" setting ?

I would like your input on this. I have a sql server 2008r2 Ent. Ed. 64bit with 16 cores and 64GB RAM. There is one instance of SQL server patched fully as of 20111014.  The max ram is set to 60000MB. Amount of free ram is 0 according to task manager after a few days online.  If I change the max ram to below 53GB it will after a few days to stabilize and have some free ram.   It is the sql process that does allocate the ram according to task manager. How do i come to terms with what the problem really is? It goes without saying that i did alot of testing already but havn't solved this to my liking yet. and ohh we do not get the typical memory starvation lagging when the available ram is down to 0 free.  Update 1:  Inspired by another Q/A related to RAM on this page  . I used these two to see what the RAM is being used for.  SELECT TOP ( 10 )         [type] AS [Memory Clerk Type] ,         SUM(single_pages_kb) AS [SPA Mem, Kb] FROM    sys.dm_os_memory_clerks GROUP BY [type] ORDER BY SUM(single_pages_kb) DESC OPTION  ( RECOMPILE ) ;  SELECT  DB_NAME(database_id) AS [Database Name] ,         COUNT(*) * 8 / 1024.0 AS [Cached Size (MB)] FROM    sys.dm_os_buffer_descriptors --WHERE   database_id > 4 -- system databases --        AND database_id <> 32767 -- ResourceDB GROUP BY DB_NAME(database_id) ORDER BY [Cached Size (MB)] DESC OPTION  ( RECOMPILE ) ;   The amount used shown by these are  first select 7948432    Kb second one 44030,57812  MB that is a total of about 52GB used by sql server... so where did the rest of my RAM go? :-) Task manager show right now cached 363, available 401, free 40 and sqlservr.exe has Memory private set 64 459 656. Max Ram set to 60000MB as before.


I am trying to compile a ODBC software with the unix-odbc library which I installed with the following command on Ubuntu 16.04.   apt-get install unixodbc-dev unixodbc-bin unixodbc   The library worked fine until I tried to call SQLCancelHandle in my software. And I started to get:  error: undefined reference to 'SQLCancelHandle'   After investigation, I realized that in sql.h the function was defined in the package. (call with the wrong parameters issue into an error of compilation complaining about the parameters)  My conclusion is the shared library associated with doesn't implement the function.   Question: Where am I supposed to put issue about Ubuntu packages? Is it possible to suggest a fix?

I found a problem with an application on Ubuntu.   Questions :   How do I best report the issue?  What sort of information should I provide?


I shall travel to Mexico and then to the USA with a Lesotho passport. I have a 6 hour layover in London at Heathrow airport out of South Africa. I have a US visa in an old passport which is still valid until 2019.    DO I need a transit airside visa for London - I will not require to pass through customs/passport control while waiting at Heathrow.  DO I need to have my US visa transferred into my new passport before I leave home?  - Nothing has changed, such as my names in the new passport.

I have a valid B1/B2 US visa expiring about a year from now. The passport it's in expired a few years ago, and I recently got a new one.   The passport number does not match, but the national ID number, mentioned in both, does (it used to be the same as your national ID, but not anymore)  Can I travel to the US carrying both passports? Or is it asking for trouble? (I read a few years ago that it was possible, but that might have changed)  Should I just get a new visa to avoid potential complications?


Why do we need to have a reference temperature to define thermal coefficient of resistance (TCR)?   TCR is the change in resistance per change in temperature divided by the resistance at a specified, fixed reference temperature:

In my textbook, a relationship is plotted between the resistance of the material and the temperature, and the temperature coefficient is defined as the slope of that graph divided by an arbitrary resistance $R_1$ on the graph. Does that mean that the coefficient varies depending on the temperature I choose to divide the slope by?  If so, how does it stand as a valid reference to the material’s resistance growth rate with temperature?  If not, then where did I go wrong with this train of thought?


I read through the question  which is quite similar to my questions. But I still have some doubts in the answers -   "The particle will complete the circle when at the highest point if the string doesn't slack at the highest point when θ=π." - Is it because if the rope slacks, then the mg component will pull it inwards and so the particle will not move as a circle? When we talk about conditions for the bob to oscillate (u <= sqrt(2gR)), why do we say that velocity must be equal to zero before tension is equal to zero? And likewise for conditions for leaving the circle, why should tension be zero and velocity not 0? What really is meant by leaving the circle? Is it like following a different parabolic path for some time? Please illustrate.

If a bob attached to a string is swinging in vertical circular motion, we say that the bob leaves the circular path when the tension in the string becomes zero, but even when tension becomes zero, there's always a component of the bob's weight towards the center of the circle. Why then does the bob leave the circular trajectory?


I need to prove that $x_n = \frac{3^n}{n!}$ converges and to find the limit. I am wondering if I can use the squeeze theorem for this problem. If so, how would I structure my proof?

I have the proof but i don't understand one part. The proof (for $a>1$) goes as follows:  there exists $k \in N$ such that$a<k, \frac{a}{k}<1$ and since $\frac{a}{k+i}<\frac{a}{k}, i \in N$ $$\frac{a^n}{n!}=\frac{a}{1} \cdot \frac{a}{2} \cdot...\cdot\frac{a}{k}\cdot\frac{a}{k+1}\cdot...\cdot\frac{a}{n}<\frac{a^k}{k!}(\frac{a}{k})^{n-k}=\frac{a^k}{k!}\cdot \frac{a^na^{-k}}{k^nk^{-k}}$$  $$0<\frac{a^n}{n!}<\frac{k^k}{k!}(\frac{a}{k})^n$$  then $$0 \leq \lim_{n\to\infty}{\frac{a^n}{n!}}\le\frac{k^k}{k!}\lim_{n\to\infty}{(\frac{a}{k})^n}$$  Now, the part I don't understand is in the expansion of $\frac{a^n}{n!}$. How does one come with $<\frac{a^k}{k!}(\frac{a}{k})^{n-k}$ part, to be more precise, how does one come up with $(\frac{a}{k})^{n-k}$ part of the inequality?


I was wondering how to find all the files under a directory whose contents contain any of several strings  word1, word2, word3, ...? Thanks.

A real example is: I have a Python file util.py, and I changed one of the function name from foo to bar. There might be other files using foo as function name and they are irrelevant.  I want to update all the Python files in the project from foo to bar. So I would like to do a search on files for imports such as:  import project.path.util   or   from project.path.util import foo   and any calls to foo such as one starting with:  foo(   The solution has to be whitespace tolerant. I can search each of them using grep but I am uncertain about the combined search. Any suggestions will be appreciated.


Running Ubuntu 18.04.3 Desktop, Virtual Machine Manager (virt-manager) seems to be stuck at v1.5.1.  I've added the universe repo and tried the cli 'apt-get install virt-manager'  The current version is 2.2.1 (July 03 2019)

Why are packages in the official Ubuntu repositories older than the latest (upstream) versions from Debian Sid, PPAs, the authors, etc.?


There’s a folder with a file named “Physio_Invoice_June21_img001.jpg” and typing "Physio" into the search bar at the top turns up nothing. Why is this? I tried using regular expressions (including *) but it didn't help. How do I search when I only know part of the file name, and want to search all of my Google Drive?

Is there any way I can search based on the last three digits of a file name?  I have a file with many invoices that are easy to reference with the last three numbers. Is there any way I can search something like *765 to search for ends with 765  Another example.. sometimes files are prefixed with a 0, sometimes not.. 093241251 vs 93241251 and if I just search 93241251 it will not find the 0 prefix version


When the computer starts, GRUB shows a long list of previous kernels in addition to the usual stuff, e.g.  Ubuntu 10.10, kernel 2.6.35-23-generic Ubuntu 10.10, kernel 2.6.35-23-generic (recovery mode) Ubuntu 10.10, kernel 2.6.35-22-generic Ubuntu 10.10, kernel 2.6.35-22-generic (recovery mode) [6 more similar] Ubuntu 10.10, memtest86+ Other operating systems: Dell Utility Partition Windows Vista (loader)   Is it safe to delete those extra "Ubuntu 10.10, kernel" lines from /etc/grub/menu.lst? Currently I have commented-out from the third one up to (not including) memtest86. But I wonder if they are ever needed for a particular reason?

Every time I install a new Linux kernel, it gets left in the grub_config, making the boot menu longer each time.    I know I can manually search through the installed packages and remove them.  Does Ubuntu provide any easier way to clean them up or keep them from showing in the boot list?


I need to install network tools on a computer which has no network connection. It has working USB ports. Can I do this with apt? If so, how do I get network packages onto a USB stick?

I have a friend who has got a computer that is not connected to the Internet. Is there any way to install software offline easily?


I have a Asus C300 and I was wondering if it is possible to uninstall chrome OS and replace it with Ubuntu. If it is possible can I also have some instructions on how to do it.

I have installed Ubuntu 13.04 on my desktop (runs like a charm). Then I used Crouton to install Ubuntu 12. 04 on my chromebook samsung (ARM). It also works quite well.  Here comes my question. Can we have a true Ubuntu (preferably 13.04) on my ARM chromebook?  It seems that the Crouton/Ubuntu is not 100% the real thing.  The best option would be to have the full Ubuntu 13.04 and remove the Chrome OS.


I was reading about torque and pseudo forces and my book says that the torque about centre of mass for a  Pseudo/Fictious force is zero.  I cant really get that as it is non-intuitive for me .  Can someone explain it in a simple manner.  Any help is appreciated

Is inertial force always attached to the centre of mass of the object? Why? What rules cause this to happen?  See the  below of the leaned bike in a corner.    The force $m\frac{v^2}{r}$ pointing to the right is the centrifugal force (inertial force - because it's a rotating reference frame, therefore a non-inertial reference frame). It is attached to the centre of gravity of the bike.  I'm thinking that inertial force is attached to the centre of mass because of the fact that it should simply avoid creating a torque on the object. That's intuitive, but there must be a general rule that allows us to conclude that.


I am trying to use my proof of the Division Algorithm and evaluation map to prove the Remainder Theorem which states:   Let F be a field, a in F, f in F[x]. Then the remainder when f is divided by the polynomial x - a is equal to f(a).  I would like some guidance as to where to start. Thanks in advance.

Remainder theorem:  If the polynomial $P(x)$ is divided by $(x-a)$, then the remainder is $P(a)$.  Factor theorem: If $P(a)=0$, then $(x-a)$ is a factor of $P(x)$  I am wondering if they are equivalent - if both imply the other, or one is a consequence of the other.  My intuition is that they are equivalent, but I am not sure how to prove. It seems clear that the remainder theorem implies the factor theorem (by definition of factor). I am not sure about the other direction.  Am I on the right track? Thank you.


At my latest exam was the following problem:     Prove that $\sqrt{2}+\sqrt[3]{2}$ is irrational.   The solution is to find a polynomial with integer coefficients, a root of which is $\sqrt{2}+\sqrt[3]{2}$ and to prove it is not a rational root of it. How do you find polynomials for similar expressions (like the general case of $\sqrt[k]{m}+\sqrt[l]{n}$, given $\sqrt[k]m, \sqrt[l]n \not\in \mathbb{Q}$)?

I have to find the minimal polynomial of $\sqrt 2 + \sqrt[3] 2$ over $\mathbb Q$. The suggested way of doing it is to prove that $\mathbb Q[\sqrt 2 + \sqrt[3] 2]=\mathbb Q[\sqrt 2,\sqrt[3] 2]$ first.  I can prove that. It's enough to prove that $\sqrt 2,\sqrt[3] 2\in \mathbb Q[\sqrt 2 + \sqrt[3] 2]$ and that $\sqrt 2 + \sqrt[3] 2\in \mathbb Q[\sqrt 2,\sqrt[3] 2]$. The latter is obvious and $\sqrt[3] 2\in \mathbb Q[\sqrt 2 + \sqrt[3] 2]$ will follow from $\sqrt 2\in \mathbb Q[\sqrt 2 + \sqrt[3] 2].$ It remains to prove $\sqrt 2\in \mathbb Q[\sqrt 2 + \sqrt[3] 2].$  For $\alpha=\sqrt 2 + \sqrt[3] 2,$ we have   $$ \begin{eqnarray} &\alpha^0&=1,\\ &\alpha^1&=\sqrt 2 + \sqrt[3] 2,\\ &\alpha^2&=2+\sqrt[3]4+\sqrt 2\sqrt[3]2\\ &\alpha^3&=2+2\sqrt 2+6\sqrt[3]2+3\sqrt 2\sqrt[3]4\\ &\alpha^4&=4+4\sqrt 2+12\sqrt[3]4+8\sqrt 2\sqrt[3]2\\ &\alpha^5&=32+4\sqrt 2+20\sqrt[3]2+4\sqrt 2\sqrt[3]2 \end{eqnarray} $$  If I can express $\sqrt 2$ as a linear combination of $\{\alpha^0,\alpha^1,\cdots,\alpha^5\}$, I'm done. I don't know how to find out whether $$\{1,\sqrt 2,\sqrt[3]2,\sqrt[3]4,\sqrt 2\sqrt[3]2,\sqrt 2\sqrt[3]4\}$$ are linearly independent over $\mathbb Q$ but I think I don't have to care. I can use Gaussian elimination anyway. I write the matrix  $$\left[ \begin{array}{rrrrrr|r} 1 & 0 & 2 & 2 & 1 & 8 & 0\\ 0 & 1 & 0 & 2 & 1 & 1 & 1\\ 0 & 1 & 0 & 6 & 0 & 5 & 0\\ 0 & 0 & 1 & 0 & 3 & 0 & 0\\ 0 & 0 & 1 & 0 & 2 & 1 & 0\\ 0 & 0 & 0 & 3 & 0 & 5 & 0 \end{array}\right]$$  and by performing row operations I obtain a row echelon form, which proves that I'll obtain the reduced row echelon form if I want, which will give me the desired coefficients $a_0,\cdots,a_5$ such that   $$\sqrt 2=\sum_{i=0}^5a_i\alpha^i.$$  I don't have to find the coefficients -- I'm just satisfied with their existence.  If this is correct, I have proven that   $$\mathbb Q[\sqrt 2 + \sqrt[3] 2]=\mathbb Q[\sqrt 2,\sqrt[3] 2].$$  But I don't know how to proceed further. Of course, I can find the minimal polynomials of $\sqrt 2$ and $\sqrt[3] 2$ over $\mathbb Q$ but I don't know how to find the minimal polynomial of $\sqrt 2$ over $\mathbb Q[\sqrt[3]2]$ or the minimal polynomial of $\sqrt [3]2$ over $\mathbb Q[\sqrt 2].$  What I did is this. I wrote the equation  $$x=\sqrt 2+\sqrt [3]2$$  and by squaring and cubing obtained  $$W(x):=x^6-6x^4-4x^3+12x^2-24x-4=0.$$  I belive this is the required polynomial but I would need to prove that it's irreducible over $\mathbb Q.$ Eisenstein's criterion doesn't work, which means I'm lost.  Could you please help me with this? I would like to know three things.  1) Is my proof of $\mathbb Q[\sqrt 2 + \sqrt[3] 2]=\mathbb Q[\sqrt 2,\sqrt[3] 2]$ correct?  2) How can I use this fact? I believe it's supposed to make the solution easier to find.  3) How can I tell whether $W(x)$ is reducible over $\mathbb Q$ or not?  EDIT: 1) has been answered by André Nicolas in a comment. All of this answers 3) but I would like to ask whether we could know that the polynomial is irreducible without knowing that $\sqrt 2+\sqrt[3]2$ is its zero. Also, it would be to know whether  4) there is a theorem that would give me $\mathbb Q[\sqrt 2 + \sqrt[3] 2]=\mathbb Q[\sqrt 2,\sqrt[3] 2]$ without the need of performing the Gaussian elimination?  For these numbers it was possible to do, but a bit higher dimension and it would turn out impossible without a computer.


Since this question was already ask , I hope that it isn't a duplicate because it isn't answered. In my question I'll use another graph to make it more clear:      The left plot is describing the lasso-problem. My question is regarding to the cases when it is more likely to intersect the corner (in this case $\beta_j=0$) or the side of the constrained area.   I more or less figured out two dependencies:   As in the picture, if we increase the budget of the constrained area or decrease the tuning parameter $\lambda$, the diamond will be getting bigger. It will be more likely to intersect with a side as with a Corner. The intersection depends on the "graphical position" of the OLS solution. But I can't explain to myself how the dependence works. Can some of you give me some graphical intuition in the case of $p=2$, when the LASSO will not set coefficients to zero?

I've a question regarding to the graphical intuition of the LASSO. I'm understanding why the lasso produce zero coefficient in case of intersecting a corner of the diamond. But I don't understand the case when the lasso Regression just shrink the paramters and don't set them to Zero. So if the RSS lines intersect with the "side" of the diamond. Assume in the case of the figure, that $\beta_1$ bigger and $\beta_2$ smaller. So the RSS-line would likely intersect a side.   Could you give me some intuition when the RSS-Line tangents with the side of the diamond instead of the corner?


maybe this is a silly question but I am stuck. When I was trying to change the \subpart enumeration in the exam class from i,ii,iii to (i), (ii), (iii) it worked with the MWE that I am including  %https://tex.stackexchange.com/questions/241670/how-to-change-the-  enumeration-of-subpart-in-exam-document-class \documentclass[11pt, spanish]{exam} %\documentclass{exam} %caracteres en español \usepackage[spanish]{babel} %\usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage[latin1]{inputenc} %%%%%%%%%%%%%%% \renewcommand{\thesubpart}{(\roman{subpart})} \renewcommand{\subpartlabel}{\thesubpart}   %% to remove the dot \begin{document} \begin{questions}   \question ¿Hola cómo estás?    \begin{parts}    \part ...     \begin{subparts}      \subpart ... Hola ¿qué haces?      \subpart ...      \subpart ...    \end{subparts}   \part ... \end{parts} \end{questions} \end{document}   but when I am trying to change the language to spanish the \subparts change again to Uppercase (I), (II), etc. Only works in english. I have been trying with UTF and ANSI and does not work. Please help, I do not know what I am doing wrong, thanks in advance.

I want to use lower-case roman numerals in a list, and I used:  %Redefine the first level \renewcommand{\theenumi}{\Roman{enumi})} \renewcommand{\labelenumi}{\theenumi}  %Redefine the second level \renewcommand{\theenumii}{\roman{enumii})} \renewcommand{\labelenumii}{\theenumii}   But I get upper-case roman numerals for both the first and the second level (I actually get smaller roman numerals for the second level).  Is there a way to use lower-case roman numerals?  Here is an example of the code I used:  \documentclass[letterpaper]{article}  \usepackage[utf8x]{inputenc} \usepackage[T1]{fontenc} \usepackage[spanish]{babel} \usepackage{parskip} \usepackage{amsmath} \usepackage{amsthm} \usepackage{mathtools} \usepackage{amssymb} \usepackage{fullpage} \usepackage{graphicx} \DeclareMathOperator{\lcm}{lcm}  \newtheorem{mydef}{Definición} \newtheorem{theorem}{Teorema} \newtheorem{lemma}{Lema} \newtheorem{proposition}[theorem]{Proposición} \newtheorem{corollary}[theorem]{Corolario} \newtheorem{remark}{Nota}  %opening \title{Tarea I} \author{Pedro     \and Mateo} \date{11 de Diciembre de 2013}  \begin{document}  \maketitle  %Redefine the first level \renewcommand{\theenumi}{\Roman{enumi})} \renewcommand{\labelenumi}{\theenumi}  %Redefine the second level \renewcommand{\theenumii}{\roman{enumii})} \renewcommand{\labelenumii}{\theenumii}  \begin{enumerate}     \item \     \begin{enumerate}         \item Muestre que $\mathbb{Q}(\sqrt[3]{2})$ no tiene automorfismos no triviales.         \begin{proof}             Dada la extensión de campos $\mathbb{Q} \subset \mathbb{Q}(\sqrt[3]{2}$         \end{proof}      \end{enumerate} \end{enumerate}   \end{document}


I has the files shortcut in my sidebar forever, as i opened it it's background always went red, one day as I opened it it's Bg went yellow/orange.  Nothing else seems to have changed except by the bg color.  I`m very curious as i have never seen this happen before and no one I asked so far gave me an answer. Why did this happen? (14.04)

Example:      My question is simple.  What are the different colors representing in the unity launcher background for each icon.  I mean, it seems consistent (firefox is always orange), but it's not jumping out at me what the pattern is.  On my screen, it's:   Firefox: Orange Chrome: Yellow Terminal: Grey RDP App: Blue KeyPassX: Green NetBeans: Blue   I'd like to turn it off if possible, but first I'd like to understand more about it.  Any launcher experts?


I have a thread Class that implements Thread. I want to have 3 instances of this class and each of these instances has different implementation of the run method of the thread class. Can i do that? I tried passing parameters to the run method, but no luck. This is what ive tried so far.   class thread extends Thread{     int reelValue;     JButton name;     boolean stop;     Reel r;     int k;      thread(int reelValue, JButton name, boolean stop, Reel r, int k){         this.name = name;         this.reelValue = reelValue;         this.stop = stop;         this.r = r;         this.k = k;     }     public void run(){         r = new Reel();         while (!stop){              k = ThreadLocalRandom.current().nextInt(0, 5 + 1);             name.setIcon(r.symbols.get(k).getImage());             reelValue = r.symbols.get(k).getValue();             try {                 sleep(100);             } catch (InterruptedException e) {                 e.printStackTrace();             }         }      }  }  public static void main(String[]args) {     thread t1 = new thread(reelOneValue, reel1,stopT1, r1, a);     thread t2 = new thread(reelTwoValue, reel2, stopT2, r2, b);     thread t3 = new thread(reelThreeValue, reel3, stopT3, r3, c);      t1.start();     t2.start();     t3.start(); }

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


So this is an argument I'm actually having, silly as it may seem. Can atheism be said to be a property of an individual? His argument is that it the lack of a property is not a property at all. This seems to make little sense to me. The notorious odorlessness and colorlessness of carbon monoxide certainly seem like properties of sorts and from what I've seen on SEP "atheism" certainly seems to meet many of the criteria mentioned, such as that it can be predicated on individuals. What is your stance on this issue?

For a proposition, such as:     P: Socrates is a man   Then not P is also a proposition:     Not P: Socrates is not a man   But do the same goes for properties? One can argue in the following way:    red is a property of red flags, or of red apples; but not red is not a property; for no thing instantiates not redness; that is not redness does not cohere in some substrate - here a flag, or apple; even though whiteness, which is an example of not redness, coheres in a white wall.  Q. Is this right?  All this, I think, takes it for granted that properties cohere in some substrate or substance - this is a commitment to a specific ontology; we may choose something else; the obvious choice being a world where all that there is are bundles of properties, and no substrate or substance to which to hang them on; there, existence is also a property - a property which all existing entities have.   Q. Given this ontological commitment; then is not P also a property?


System: Ubuntu 18.04 LTS  If you run the following command   $ apt-cache pkgnames python    . . . python3-case python3-rpy2 python3-pycurl-dbg python3-structlog python-natsort python-protobuf python-rpm python-starpy python3-rpyc python-nbxmpp-doc python-rpy python-jpylyzer-doc python-bottle-doc python-logbook python-pyside.qthelp python-agate-doc   The result list skip packages names like python3.7 python3.7-venv python3.6 python3.6-venv, I mean all packages names containing dot.  We have to run explicitly the below command to list all python packages containing dot in their names.  $ apt-cache pkgnames python3.    python3.7-venv python3.6-venv python3.6-examples python3.6 python3.7 python3.7-dbg python3.7-dev python3.7-doc python3.7-minimal python3.6-minimal python3.7-examples python3.6-dbg python3.6-dev python3.6-doc

I recently tried to install GIMP (photo-editor) using the terminal and I think it required me to install flatpak, which I don't really understand and shouldn't have installed it I guess, because now I can't do what I could before. I have since uninstalled flatpak, but still have same problem. Earlier, when I was using dpkg --list to get the name of a program I wanted to uninstall, I could see a full list of all installed programs. Now I just get this weird list that doesn't look like programs, and it starts in alphabetical order but only starting at the letter "L", e.g.: libgphoto2-6:a 2.5.16-2     amd64        gphoto2 digital camera library  is the first entry. And then: zlib1g:amd64   1:1.2.11.dfs amd64        compression library - runtime  is the last entry. It doesn't seem to be listing programs. Like, I have clementine installed and its no longer listed with that command. I am so confused. To give another example, I installed and uninstalled a media player successfully earlier today using the terminal, using dpkg --list to determine said program's name. I can no longer see any real programs using this or similar commands I have found here. EDIT: apt list --installed gives the same stupid incorrect list. Maybe it's showing libraries instead of programs now??


What powers does a Department Chair have in a University setting? For instance, is a Dept. Chair the "boss" of a tenured full professor within the department?

In the past few years, I've become very interested in staying in academia for as long as possible. I really wanted to be a professor, and I still do. Using the internet and meeting with a few professors, I've researched various aspects of life as a professor, including daily schedules, salaries, etc. While trying to get an idea of what a typical professor's salary might look like, I always stumbled upon "Head of Department" salaries, which were considerably greater than other professor salaries. I liked the idea of being paid more, but I always dismissed the idea of becoming a "Head of Department" because I thought that their work was more related to administration than teaching or talking about the field of their department. (One of the main reasons I want to be a professor is the opportunity to be directly involved in the fields I'm passionate about every single day.) However, I recently traveled to a university in my state with the company I am interning at, and I met the head of the department of mechanical engineering. Though that is not my field of interest, I was very glad to have the chance to meet with her. I learned all about her day-to-day life as head of department: I learned that she is quite actively involved in many PhD students' projects, and oversees many research projects. There is also an administrative aspect in her job, but it isn't nearly as overwhelming or burdensome as I thought. Since the visit, I've become very interested in a job like hers.  Is my perception of "Head of Department" skewed? What can I do to be involved in my field like she is in hers?  I would love to learn about and teach my passions for a living.  Side question: How involved are deans of __ in their respective fields?


I've seen a proposition like that Proposition: If $f:X\longrightarrow Y$ is an open and continuous function and $D$ is dense in $Y$, then $f^{-1}(D)$ is dense in $X$. Is that proposition correct? if so, here is my approach : if $D$ is dense in $Y$, then for all nonempty open $G$ in $X$, $f(G)\cap D\neq\emptyset$ then $f^{-1}(f(G)\cap D)\neq\emptyset$ so $f^{-1}(f(G))\cap f^{-1}(D)\neq\emptyset$, then $G\cap f^{-1}(D)\subseteq f^{-1}(f(G))\cap f^{-1}(D)$. So how can I guarantee that $G\cap f^{-1}(D)\neq\emptyset$ or any solution for that?

Let $X,Y$ be topological and $f:X \to Y$ be open and continuos.  I am studying Baire space and I would like to try the following facts :      $(i)$ The inverse image of dense set is dense.       $(ii)$ The inverse image of comeager set is comeager.   I am studying Baire space and I would like to try the following facts  Can we collaborate to verify the above claims?    Thanks.


How could I ban a incoming number?  What is the sequence of menu actions I should follow to get an appropriate menu if any and where to find help documentation on Android user interfaces? I have searched in the net but I'd unable to find any.  I have android 2.3 operating system on my ARM qualcomm 7225a application processor.

Last night I got a telemarketing call on my Verizon Droid X. I was horrified, to say the least. I absolutely do NOT want telemarketers wasting my time and minutes with their B.S.  I looked into screening blocking calls through Verizon, but it seems Verizon only lets you block a total of FIVE numbers. I think this is unacceptable.  I went to the app store and there are a number of such applications available. From reviews and comments it's really hard to choose.   Is there a way to solve this problem? An app? A procedure? Something within the phone itself?  I'm using the soak release of Gingerbread, 2.3.3. I don't care about price. I just want something that is fast and effective.


Solve in $\mathbb{C}$ the following equatios: $$z^2=\frac{1}{2}-i\frac{\sqrt{2}}{2}$$ I was solving the exercise from the book A to Z complex numbers, I tried this in two ways one by taking $z=x+iy$ but then I am getting another quadratic equation in $y$ where the constant term is a complex number. I also tried to get it in the form $re^{i\theta}$ but there $\theta=\arctan{\sqrt{2}}$. Any help will be truly appreciated.

If I'm given a complex number (say $9 + 4i$), how do I calculate its square root?


I have visited the USA and I have VWP to my passport now it is out of date, but my ESTA is still valid. Am I able to enter the USA again if my VWP is out of date but my ESTA is valid?  I am little bit curious because I was told by officer that the VWP needs to be taken out of my passport when leaving the USA for the very last time and the customs officer didn't do that, so I am little bit worried now. Sorry for my English though. I am from the EU.

I wish to travel to the US and think I am eligible to do so under the Visa Waiver Program. I found a lot of information out there but am still having some trouble understanding how this works.  What is the US Visa Waiver Program? What is an ESTA?


What is a ctools plugin? Why would one want to use a ctools plugin ? What advantages does it have over the current hook system?   Is there currently documentation regarding usage of ctools plugin?  I often see contrib modules require ctools and depend on it. You see it in various different modules like commerce, feeds, etc.

What are Ctools plugins, and how does one create them?


I'm looking for the title or author of a sci-fi short story about two spacecrafts somehow meeting and exchanging plants for gold or other items. Both crews think that they have gotten the better of the deal and speed off in opposite directions.   I read this in the 60's.

I am looking for information on a short story that was written probably in the late 60's early 70's. This was part of a short story collection; I can't be certain but it was possibly edited by Groff Conklin.  The story is told from the point of view of the aliens who meet human explorers on a planet they have both landed on. We can tell because of the description that the narrators provide of the humans. I remember specifically they thought the humans skin was ugly - too thin, they could see parts of the circulatory system through the skin.  The aliens are entranced with the human's hydroponic system, have never seen anything like it. The don't explicitly use the term 'hydroponics' since they've never see one before, but evidently food is in short supply and they really need something like this. The aliens, though, have this really cool pop-up survival tent that incorporates life support, power, etc. The humans and aliens swap hydroponics for the tent. Each think they've taken advantage of the other.  At the end, both high-tail it off the planet fearing the others will realize they've been ripped off and change their minds. The final line, said by the alien, is something like "The way they're behaving would make you believe that they - not we - have committed the perfect crime."


In a set endowed with an associative operation with a left identity and where every element has a left inverse, I was wondering, is every element bound to have a right inverse too? Or is there at least one set with a respective operation and such properties that at least one element doesn't have a right inverse? Clearly, an easy proof shows that if there is a right and a left inverse and the aforementioned properties hold, they have to be equal.  Note: This is merely a question of mine and not somehow part of homework.

Let $G$ be a nonempty set closed under an associative product, which in addition satisfies :      A. There exists an $e$ in $G$ such that $a \cdot e=a$ for all $a \in G$.      B. Given $a \in G$, there exists an element $y(a) \in G$ such that $a \cdot y(a) =e$.      Prove that $G$ must be a group under this product.   Attempt -Since Associativity is given and Closure also, also the right identity and right inverse is given .So i just have to prove left identity and left inverse.  Now as $ae=a$ post multiplying by a, $aea=aa$. Now pre multiply by a^{-1} I get hence $ea=a$. And doing same process for inverse Is this Right?


I have a 20 amp breaker for my dedicated man cave home theater. It's a rental unit. Recently I had a few loose-fitting plugs on some of the receptacles so I just went downstairs and found the breaker and saw it was 20 amps.   So I went and bought 20 amp receptacles. Only a few fit loosely so I chose to only replace the loose ones. After the install I noticed that the other 2 receptacles were in fact 15 amp receptacles. Is it ok to leave it like it is with both 15 and 20 amp receptacles in that room on the 20 amp breaker and if so what's the max amps i can pull through that circuit?   I think the 15 amp receptacles are on each end of the rooms circuit and the 20's are in the middle. Will that matter in any way? Right now i am pulling around 11-12 amps from that room but most is on a better quality power strip rated at 15 amps. Thanks in advance for the help.

I have noticed in a few different houses in Oklahoma that 20 amp breakers are used, but all of the outlets and switches only seem to be rated for 15 amps. This goes against everything I know to be proper and safe. The wire used is 12 gauge, so at least that is fine.  I have started to replace all of the switches and outlets with the decorative switches (the rectangular ones) and have found it very difficult to find switches that are rated for 20 amps. As for the outlets, I have can find them rated for 20 amps, but not in the 10 packs that I see for the 15 amp versions. To be clear I am not speaking about the shape of the plug, rather I am talking about the rating of the internal components of the outlet.  Is there something about electrical code that I am missing?


I'm struggling with this problem  Compute the following sum: $$ \frac{1}{1 \times 2} + \frac{1}{2 \times 3}  + \frac{1}{3 \times4} + \cdots +\frac{1}{99 \times 100} $$ Hint: Consider telescoping series,  Please help me.

Please help me calculate the following sum     $$\frac{1}{2\cdot 3}+\frac{1}{3\cdot 4}+\dots+\frac{1}{99\cdot 100}$$


Prove that complex numbers $z_1$, $z_2$ ,$z_3$ on complex plane are collinear iff $\displaystyle\frac{z_3-z_1}{z_2-z_1}\in\mathbb R$  I think if $\displaystyle\frac{z_3-z_1}{z_2-z_1}\in\mathbb R$ then $\displaystyle\frac{z_3-z_1}{z_2-z_1}$ lies on the real axis.   So, $\displaystyle\arg\left(\frac{z_3-z_1}{z_2-z_1}\right)=\arg(z_3-z_1)-\arg(z_2-z_1)=0$ or $\pm\pi$.  Can I conclude $z_1, z_2, z_3$ are collinear? and if $z_1, z_2 ,z_3$ on complex plane are collinear. How to prove $\displaystyle\frac{z_3-z_1}{z_2-z_1}\in\mathbb R$ Please help!

$z_1, z_2, z_3 \in \mathbb{C}$ $$\frac{z_1 - z_3}{z_2 - z_3} \in \mathbb{R}$$  The only idea I'm coming up with is that either $ \operatorname{Im}(z_1) =  \operatorname{Im}(z_2) =  \operatorname{Im}(z_3)$ or $ \operatorname{Re}(z_1) =  \operatorname{Re}(z_2) =  \operatorname{Re}(z_3)$. If I were to do the division properly, i.e. express all complex numbers in the $( x+iy )$ format and multiply both the numerator and denominator by the conjugate of $z_2 - z_3$, I'd end up with 6 variables, which seems very complicated. Do you have any ideas as to how to solve this? thanks!


At my English lesson I said "They had good relations" (about two neighbors), but my teacher corrected me "They had good realtionship". Why?

What is the difference between relation and relationship? Some say that relationship often refers to social connections. For instance,  She has a close relationship with her daughter.  How about the following?  the relationship between poor housing and health problems (Longman Dictionary) the special relationship between Britain and the US (Longman Dictionary)


Let $(s_n)$ and $(t_n)$ be two sequences of real numbers. Suppose there exists $N_0$ such that for all $n>N_0$, $s_n \leq t_n$.  Two Questions:    Suppose that $\lim s_n$ and $\lim t_n$ both exist. Show that lim $ s_n \leq $lim $ t_n$.    Is this a reasonable answer:  Proof: By assumption since there exists $N_0$ such that for all $n>N_0$ then $s_n \leq t_n$ then  sup{$t_n: n>N_o$} $\geq$  sup{$s_n: n>N_o$} and thus lim sup{$t_n: n>N_o$} $\geq$  lim sup{$s_n: n>N_o$} and since both of these limits exist and are equal to lim $t_n$ and lim $s_n$ respectively then the desired result follows.   Second question where I am stumped. show that lim inf $s_n$ $\leq$ lim inf $t_n$ and that lim sup $s_n$ $\leq$ lim sup $t_n$

This is half of Theorem 3.19 from Baby Rudin. Rudin claims the proof is trivial. What I've come up with so far doesn't seem trivial, however, and is probably also wrong (my problem with it is pointed out below). This makes me wonder whether I'm overlooking some useful fact and/or using an unprofitable approach.  Theorem. If $s_n \leq t_n$ for $n \geq N$, where $N$ is fixed, then  $$ \liminf_{n \rightarrow \infty} s_n \leq \liminf_{n \rightarrow \infty} t_n. $$  Proof. Suppose that $s_n \leq t_n$ if $n \geq N$, but that  $$ \liminf_{n \rightarrow \infty} s_n > \liminf_{n \rightarrow \infty} t_n. $$  Let $E_s$ denote the set of all subsequential limits of $\{s_n\}$, and let $E_t$ denote the set of all subsequential limits of $\{t_n\}$. Then  $$ \inf E_s > \inf E_t. $$  This implies that there exists some $x \in E_t$ such that $\inf E_s > x > \inf E_t$, since otherwise $\inf E_t$ would not be the greatest lower bound of $E_t$. Hence some subsequence of $\{t_n\}$, say $\{t_{n_i}\}$, converges to $x < \inf E_s$.  Lemma. (from Rudin) If $x < \liminf_{n \rightarrow \infty} s_n$, then there exists an integer $N$ such that if $n \geq N$, then $s_n > x$.   By the lemma, there exists an integer $N_0$ such that if $n \geq N_0$, then $s_n > x$.   Now, let $\epsilon = \inf_{n \geq N_0} \{s_n - x\}$. This is where I think my proof breaks down. Can't $\epsilon$ be zero? Then, since $\{t_{n_i}\}$ converges to $x$, there exists an integer $N_1$ such that if $n_i \geq N_1$, then $|t_{n_i} - x| < \epsilon$. But this means that, if $n_i \geq \max\{N, N_0, N_1\}$, we have both  $$ s_{n_i} > t_{n_i}, $$  as well as $s_{n_i} \geq t_{n_i}$, a contradiction.


In looking over the , I noticed  (bronze level) and  (also bronze level) are very similar. Shouldn't they be grouped in to the same badge-family?  Suffrage: Used 30 votes in a day Vox Populi: Used the maximum 40 votes in a day  In a related note, if the max votes/day is 40, shouldn't Vox Populi be a gold level badge? This is of course, just from a logical data standpoint - if a badge levels (bronze/silver/gold) have additional requirements beyond just being various stages of a type of interaction, perhaps the entire above argument is irrelevant.

The Suffrage badge is awarded for using 30 votes in the day, and the Vox Populi for using 40.  I understand from  that the idea of Vox Populi is to incentivise voting on questions, but is there any evidence that having two badges does so better than just having Vox Populi?


I want to create a temporary folder in  my local system and upload file into that particular folder as ZIP.  Note: the file path is getting from SharePoint document library  Thanks in advance

What's the best way to get a temp directory name in Windows?  I see that I can use GetTempPath and GetTempFileName to create a temporary file, but is there any equivalent to the Linux / BSD  function for creating a temporary directory?


I understand that it is generally recommended to always upgrade Debian sequentially. For example upgrade Debian Jessie (8) to Stretch (9) and then to Buster (10). But I couldn't find any clear instructions on how to do this exactly. Is it sufficient to edit APT's source-list files (/etc/apt/sources.list and files under /etc/apt/sources.list.d/) to refer to my target release version while following the upgrade instructions in the release notes? E.g. to upgrade from Jessie to Stretch I'd replace every reference to jessie (or stable, ...) with stretch and perform the upgrade? And afterwards again replace stretch with buster and perform the next upgrade? Answers to other questions here like  only explain that it is recommended to upgrade sequentially but don't explain how. Maybe this is really obvious and I just lack the experience. I'm a little worried that apt-get dist-upgrade might directly upgrade from Jessie to Buster leaving out Stretch. Kind regards :)

Just started working with a Debian Jessie (8) in a production environnent. While presently deployed it is not seeing any heavy use yet. I was looking at the OS , and I was thinking about how convenient it would be to just upgrade it before is start seeing some more steady use in our environment and possibly making things more complicated with a later upgrade.  I was looking for a procedure to upgrade from Debian v.8 to v.10 but most documented  are sequential in order (e.g. 8 -> 9, or 9 -> 10).  My question: should I upgrade sequentially, or there is some proper documented way to skip a main version while upgrading?


I looked everywhere for my bin folder (even in the trash) but I can't seem to find it anywhere. I looked at some other answer people said to do but that didn't work either please help me. I am using a mac so maybe someone who might know where my bin folder is at please help. thanks

The other day I was trying to download something for Minecraft and it involved my bin folder. So I was looking for it and couldn't find it. I then thought that I might have accidentally deleted it, but didn't find it in the trash. I have no idea how to get the bin folder back with all the Minecraft binary files in them.


In my DNS settings, I want to point this website domain - www.websiteA.example to the following IP address which has a path http://xxx.xxx.xxx.xxx/pathA (this is a VPS, if it makes any difference) Is this possible? If so can you please provide more information on how I can achieve this?

This is a  about DNS/Hostnames resolution to IPs/Ports   Example 1  I'm running a web server on port 80 and another on port 87. I would like to use DNS so that www.example.com goes to port 87. How can I accomplish this using DNS only?  Example 2  I'm running a service on my server on a non-standard port. How can I get clients to connect to this non-standard port automatically? Can I use DNS? Is there some application specific support where DNS could indicate the IP and Port?   Example 3  Do some application protocols specifically support hostname awareness, and allow special actions to be taken based on this information? Are there other questions on Server Fault that cover some of these?  Commandeering: This question was originally asking about running IIS and Apache on the same server, but the same concepts can be applied to any server software receiving connections from clients. The Answers below describe the technical problems and solutions of using DNS and application protocol support to assign a port number for a client to connect.


I break it down into two parts the numerator one into $\dfrac{n(n+1)(2n+1)}{ 6}$ but what should be summation of $n!$ ?

I was exploring the fact that $$ \sum_{n=0}^\infty \frac{n^p}{n!} = B_pe,$$ where $B_n$ is the $n$th Bell number.   I found this result by exploring the series on wolframalpha and looking up the sequence of numbers generated. I have no experience with Bell numbers other than knowing that they represent the number of ways of partitioning a set.   What I tried  Looking at the base case we can verify $$\sum_{n=0}^\infty \frac{n}{n!} = \sum_{n=1}^\infty \frac{1}{(n-1)!} = e. $$  But then I realize that $n^2$ is going to be difficult.  Specifically what I want  I am doing this for fun, so I just want to glean some sort of lesson out of this. Resources that let me learn for myself are just as good!   An accepted answer will have any one of the following:   A proof that $\sum_{n = 0}^{\infty} \frac{n^2}{n!} = 2e$ (this interests me a lot) A description of why this series is related to Bell numbers and the number of partitions of a set A link to some resource that introduces Bell numbers and/or their connection to this series.


I'm running Windows 7 as a VM in Virtualbox.  I have created the group vboxusers and have set my main account as part of the group.  Whenever I enter the Win7 machine it can not detected my USB flash drive.  I go in Device Manager and try to find the driver online but it doesn't find it.  What am I doing wrong?

The the following to add my user to the group:  sudo usermod -aG vboxusers karl   Got the error message:  usermod: group 'vboxusers' does not exist   My groups are as following:  karl adm cdrom sudo dip plugdev lpadmin sambashare vboxsf   I'm using VirtualBox 5.0.14, Ubuntu 14.04, Guest Additions 5.0.14 and Extension Pack 5.0.14. I can see my USB device in my host OS.


When I try starting VirtualBox 6.1, it gives me the error "Failed to acquire the VirtualBox COM object":  I am running Ubuntu 16.04.7 dual booted alongside Chrome OS using crouton.

here is ubuntu 12.10  virtual-box is somehow not working:  I was trying to install win7 on to an usb-hard-disk.  boinc is switched off and RAM-size is set to 4096 MB (too big ? of possible 8 Gibi )  report of virtual-box is:  the com-object for virtualbox could not be created.  the application is now ended.  Start tag expected, '&lt;' not found.  Location: '/home/$user/.VirtualBox/VirtualBox.xml', line 1 (0), column 1.  /build/buildd/virtualbox-4.1.18-dfsg/src/VBox/Main/src-server/VirtualBoxImpl.cpp[484] (nsresult VirtualBox::init()).  Fehlercode:NS_ERROR_FAILURE (0x80004005) Komponente:VirtualBox Interface:IVirtualBox {c28be65f-1a8f-43b4-81f1-eb60cb516e66}   comment of me: why is virtualbox installing xml into folder of $user in .VirtualBox ? should it not be on usb-harddisk ? (with 500 Gibi )  first installation attempt was breaking off (with win7 in 64Bit) should I try virtual-box (ubuntu 64Bit) with win7 in 32Bit ? should I leave RAM-size of virtual-box to default 512 MB ?  thanks for reply