I tried this question by multiplying explicitly the matrices but I think I'm not getting anything, so I think, well let's suppose false so $C(AB-BA)=C$ and find a contradiction but also I'm not getting anything.

The following question is from Artin's Algebra.      If $A$ and $B$ are two square matrices with real entries, show that $AB-BA=I$ has no solutions.    I have no idea on how to tackle this question. I tried block multiplication, but it didn't appear to work.


I was testing something out with suggested edits so I went into the review queue and picked the first edit. After reading it, I planned on rejecting it because it seemed to drastically change the post. But in my experiment I wanted to click on "Improve"...so I did. Of course it turned out to be an audit! So I failed for clicking "Improve" instead of "Reject", which I ultimately planned on doing after cancelling out of it because I really didn't plan on improving it.  This isn't a huge deal because I don't think I fail too many audits. So my question is, should you not actually fail when clicking "Improve" until you click to save the edit. That way, there is still the chance to cancel out of it and skip or reject? This might be minor and not worth the trouble but I thought it was interesting that I came across it. I don't expect this happens too often but it seems like an easy change.  Edit  Now I just experienced an audit where I rejected the edit but still had to say why before it said I passed. This still seems minor but inconsistent with my last audit experience. If it is going to fail for clicking "Improve" but not allowing the action to be finished (by cancelling which should result in a pass or by submitting the improvement) then shouldn't it also pass as soon as the reject button is clicked?

For the first time I failed an audit in review, but I sure don't think I should have.  I saw the edit wasn't that good, so I hit the improve button to clean things up and got this message:     This was an audit, designed to see if you were paying attention. You didn't pass. This edit vandalizes the post. Don't improve it – Reject it   Sure, I could have rejected it, but some of those can just be improved, especially if the original post needed editing.  Maybe SO could keep track of my successful improves and see that I know what I'm doing, and let me hit the improve button and not fail me for the audit.  EDIT:  I realized after it happened to me again today, that my workflow is to see that there is an error, and instead of checking the whole post, I go into edit mode, and then completely go over the post editing it as needed.  Since SO doesn't seem to want to adapt to that kind of workflow, I'll unfortunately have to change mine, or just do less.  It really slows things down to have to completely go over a post twice (kind of like the inbox zero concept, try to deal with things immediately).


When I was looking at the badges I started reading the Legendary Badge and noticed that it says:     Hit the daily reputation cap on 150 days    Now, I interpreted this as: "On the 150th day you have been here, if you get the daily reputation cap, you will earn this badge". Now, my first reaction was like "Wth?" because the Epic badge says "Hit the daily reputation cap on 50 days" and if you interpret it the way I did for the Legendary badge, you would probably think "Why is Epic only Silver and why is Legendary Gold?" Maybe it's just me, but, if I understand what you guys really mean wouldn't:      Hit the daily reputation cap for 150 days in a row   be better. Or am I completely misunderstanding this?

Formerly List of all badges with full descriptions.  What are badge name's requirements? Why didn't I get badge name ? Which badges can I earn multiple times?    Jump to:                    Note: Some badges are awarded based on score. The term score means the total number of upvotes minus the total number of downvotes.  Any badge with a *** next to it is one of 20 badges that count towards the  displayed on a moderator candidate in an election. The candidate score is a total of 40 points: the first 20 are awarded based on the user's rep divided by 1000 and rounded down; the second 20 represents the total number of unique badges earned of the 20 that count. Note that if the same badge is earned multiple times, it will only count once towards the candidate score.  Any badge with a "(retired)" next to it is no longer awarded, but is retained by users who previously earned them. See  for more info on what it means for a badge to be retired.       Visit the  of the  on any site to see a complete list of badges that you can filter by earned, unearned, or type.


I am working on a VR project with a 360 video in it. I am trying to set the start rotation of the video to the same rotation as my phones.   How can I convert Input.gyro.attitude to a float? That way I can use it in this line of code: videoSphere.transform.Rotate(initialX - Input.gyro.rotationRateUnbiased.x, initialY - Input.gyro.rotationRateUnbiased.y, float);  Help is really appreciated!

I am making a mobile VR project in Unity, and I have a 360-degree video that starts playing where I can look around using a VR headset.  I am trying to set the start rotation of the video to the same rotation as my phone. So no matter where I look when I start the video, that should be my start rotation. I used Input.gyro.attitude in the start but that did not fix my problem. I think I am using it wrong.  This is my code (on the camera inside the sphere):  using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.UI;  public class Gyroscope : MonoBehaviour {     private bool gyroEnabled;     private Gyroscope gyro;     private GameObject cameraContainer; //A camera container for my main camera     private GameObject videoSphere; //The sphere my video is in     private Quaternion rot;      private void Start()     {         videoSphere = GameObject.FindGameObjectWithTag("Video");         cameraContainer = new GameObject("Camera Container");          gyroEnabled = EnableGyro();          cameraContainer.transform.position = transform.position; // put the cameracontainer into the sphere         cameraContainer.transform.rotation = Input.gyro.attitude; // here I want to set the cameracontainer to the rotation of my phones gyroscope          transform.SetParent(cameraContainer.transform); // make my main camera a child of the camera Container          videoSphere.transform.localRotation = cameraContainer.transform.rotation; // Here I wanted to set my sphere rotation to the camera rotation         Debug.Log(videoSphere.transform.localRotation);     }      private bool EnableGyro()     {         if (SystemInfo.supportsGyroscope)         {             Input.gyro.enabled = true; // turn on my gyroscope              cameraContainer.transform.rotation = new Quaternion(0, 90, -90, 0); // rotate my camera container so the video shows good             rot = new Quaternion(0, 0, 1, 0); // set the variable rot so that you can turn your device             return true;         }         return false;     }      private void Update()     {         if (gyroEnabled)         {             transform.localRotation = Input.gyro.attitude * rot; //this makes you turn the device and it recognizes the input of the phones gyroscope                 }     } }


How to find the most popular word in a text file through the linux terminal? Need to write a script

I want to find, say, 10 most common word in a text file. Firstly, solution should be optimized for keystrokes (in other words - my time). Secondly, for the performance. Here is what I have so far to get top 10:  cat test.txt | tr -c '[:alnum:]' '[\n*]' | uniq -c | sort -nr | head  -10   6 k   2 g   2 e   2 a   1 r   1 k22   1 k   1 f   1 eeeeeeeeeeeeeeeeeeeee   1 d   I could make a java, python etc. program where I store (word, numberOfOccurences) in a dictionary and sort the value or I could use MapReduce, but I optimize for keystrokes.   Are there any false positives? Is there a better way?


Which app should I install to download videos from YouTube?

What are instructions on how to download videos from YouTube?    Notice: Terms of Service Violation  Please be aware that by following any of the answers below, you will be violating YouTube's . In particular, from Section 5.B.:     Content is provided to you AS IS. You may access Content for your information and personal use solely as intended through the provided functionality of the Service and as permitted under these Terms of Service. You shall not download any Content unless you see a “download” or similar link displayed by YouTube on the Service for that Content. You shall not copy, reproduce, distribute, transmit, broadcast, display, sell, license, or otherwise exploit any Content for any other purposes without the prior written consent of YouTube or the respective licensors of the Content. YouTube and its licensors reserve all rights not expressly granted in and to the Service and the Content.


The Olympus PEN-F has a "Black and White" dial setting. Is this just a gimmick, or will it give images that are not possible using color settings?  In other words, obviously a color image can be converted to black and white in Photoshop or other image-processing software. Does the B&W setting on the PEN-F offer some special benefit that is not (easily) reproducible using software?

For black and white photography, will there be any quality difference between using the built-in black and white mode, or shooting in color initially and then removing the color later using Photoshop (or similar application)?  I have a high-end compact camera, the .


It can be observed that $$\sin^2 \left( x + \frac{\pi}{2} \right) = \cos^2 (x)$$ Being the squared cosine an even function, the squared sine will be symmetrical as well, but with respect to $x = \pi / 2$.  Are there any other approaches for this proof? Is there anything else that can be observed, hopefully about the $\sin^2 x$ function itself, without considering the space-shift $x + \pi / 2$ and the cosine?

Any tips on how to show that $$\int_0^\pi f(\sin x) \, \mathrm{d}x = 2\int_0^{\pi/2} f(\sin x) \, \mathrm{d}x \text{ ?}$$


There is a way to see that $\lim \frac{k}{\sqrt[k]{k!}}=e$ from these definitions?  $$e=\lim\left(1+\frac1k\right)^{\frac1k};\quad e=\sum\frac1{k!}$$  If it is not possible, how to deal with the limit of the title to get it limit? Thank you.

I'm trying to find  $$\lim_{n\to\infty}\frac{n}{\sqrt[n]{n!}} .$$   I tried couple of methods: Stolz, Squeeze, D'Alambert  Thanks!  Edit: I can't use Stirling.


[NOTE: Not a duplicate post]  I posted in the Graphic Design stack exchange and my post got automatically deleted by "Community". I read  but it doesn't have the answer to my question, and I couldn't find any other SE questions that offer an effective answer, so I'm creating "this" new post.  My question is two-fold:  How can I undelete one of my questions that was deleted by "System" or "Community" user?  AND  If that's not possible, would I be better off just reposting?  Here is the post that got deleted:    Thanks

On Dec 23, 2013 I edited two of my questions on Physics.SE:         Then I flagged them because one was marked duplicate and other as closed. The flags remained active for nearly four days. I left a comment on  asking the moderator to take some action on my flags, for I was worried that mods had forgotten my flags. Then eventually both of the questions got deleted by the "community moderator".   I suspect the posts deleted by the "community moderator" are indeed deleted by the human moderators. Because my questions were deleted before 9-days I had edited them. That very moderator wanted to show me an action which I requested from him.    Still no action was taken by moderatorss on my flags. After my questions were deleted by the "community moderator" one more surprise came to me: Question 1 was completely removed by moderator. when I tried to enter its URL, I was denied access to it. After this removal the moderator took action on my flags explaining that I need to edit them more.    After some time another weird thing happened: Question 2 was undeleted by the community and Question 1 was unremoved but it is still deleted by the community.    Consequently, I have two questions:     How can a question deleted by community be undeleted? It seems impossible because a question is automatically deleted when it becomes outdated  as explained here:()   How is a removed question unremoved?         Through the constructive comments of some nice users i got another question:    Does Community♦ represents a bot or the present working moderators of Stack Exchange websites?         Addendum: Question 1 has been deleted by the "community moderator" by Dec 28 '13 at 13:15


I am a recent graduate from India and currently working in an analytics company as interaction designer.   Few days back I was filling the job application form for interaction designer post in yahoo (Job located in Paris) and I have encounter a section where I have to mention that if I am legally authorized to work in the country where the job is located. I am really confused what to fill in the box.   First of all, I don't have any visa for any country and secondly I don't have any criminal record (as I presumed by the question) so what should I do.   I have heard that after getting the acceptance from the company it provides you an offer letter which can be used as a leverage to get the visa. Is that true or do I need to apply for the visa first?    So I am rephrasing my question again: Question: If the job is open for international applicants then can I apply for the job if currently I don't have any legal right to work in job location?  And If I can apply for the job then is it possible to get the legal rights to work in the job location?

I mostly ask this because I'm from Spain and I wouldn't mind working on the United States.  I have the legal right to work there ... provided a did get a Green Pass for which usually helps a lot having a job offer in the first place so... Does it refer just to something like I'm of age and I'm not crazy nor do I intent to kill the USA president?   Or should I uncheck the "legal right" checkbox? And if I do, would that mean that I won't be appearing on US employers searches?


I have a question regarding which it should be:     He acted as if he were owner of the place   or     He acted as if he was owner of the place.   Which is correct?

You can place the script in the head or body as you like. The   script will behave as if it was located exactly where you put the   script tag in the document.   The sentences above are taken from  (at the very bottom). I think they made a grammatical mistake here: it should be behave as if it were rather than it was. I'm not 100% sure, so want to confirm it.


If a company has several products, is that a products line or a product line?

Is it correct to say user accounts or users account when referring to the accounts any user has on a site like this one?  In general, in the case of a noun that is used as adjective for the noun that follows, is it better to use <plural-noun> <singular-noun> or <singular-noun> <plural-noun>?


I seem to be unable to install gitk.   Can anyone help me decipher the below:  $ git --version git version 1.8.3.2 $ sudo apt-get install gitk Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  gitk : Depends: git (< 1:1.7.9.5-.) but 1:1.8.3.2-0ppa1~precise1 is to be installed  E: Unable to correct problems, you have held broken packages.

Occasionally, when I'm installing stuff, I get an error like the following:  Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  package1 : Depends: package2 (>= 1.8) but 1.7.5-1ubuntu1 is to be installed E: Unable to correct problems, you have held broken packages.   How can I resolve this?


How do I achieve a physically accurate laser beam within Blender? This is what I want to achieve:

I am modeling a laser pointer in Blender, but I am not sure how to make the laser's light beam.   The Spot light comes the closest to what I am looking for, but its starting diameter is 0, and you cannot set the spread amount to less than 1 degree.  I would like to be able to do this in the Cycles rendering engine if possible.      Edit: I am not trying to see the actual beam of light, like when you shine a laser beam through fog. Rather, I simply want to have the light beam go straight from the laser. So that if you were to shine it at an object up close, the dot would be the same size as if you were to shine it at a object farther away.  Not this:                              But this:        *Laser images from images.google.com


I have a question in mind. Let say I travel from country A to country B and in these countries, the time difference is about 10 hours. So when I reach to country B from country A, does that affect my age. I mean, can I say that if the country B is 10 hours behind the country A, so my real age doesn't get affected?

If I turn, say, 18 at home, and immediately travel westwards into a different time zone where it's still the previous day, will I be legally 17 or 18 there?  And if 17, how would that affect e.g. any rules that would require me to be of age for that specific journey (can't think of any specifics, and yes this is getting rather academical now).  This question is about the legal aspects, not the practical side of how to actually do it.


I have found this question answered before but I am stuck going from  $$m^{\phi(n)}+n^{\phi(m)}\equiv1 \pmod{n}\\ n^{\phi(m)}+m^{\phi(n)}\equiv1 \pmod{m}$$ to $$m^{\phi(n)}+n^{\phi(m)}\equiv1 \pmod{mn}$$  Why can we combine $\pmod{m}$ and $(\pmod{n}$ into $\pmod{mn}$? I know it's overall because $\gcd(m,n)=1$, but I don't understand why it is so. Is there a theorem for this specifically? I found this, but  seems to not multiply what is in the modulus together.   Here is the beginning of my proof:  $\gcd(m,n)=1\implies m^{\phi(n)}\equiv1 \pmod{n}$ and $n^{\phi(m)}\equiv1 \pmod{m}$ by Euler's theorem.  $ m^{\phi(n)}\equiv1 \pmod{n} \equiv  m^{\phi(n)}+n^{\phi(m)}\equiv1+n^{\phi(m)}\pmod{n}$ and $n^{\phi(m)}\equiv1 \pmod{m}\equiv n^{\phi(m)}+m^{\phi(n)}\equiv1+m^{\phi(n)} \pmod{m}$.  But $m^{\phi(n)} \equiv 0\pmod{m}$ and $n^{\phi(m)}\equiv 0\pmod{n}$.  So we have $m^{\phi(n)}+n^{\phi(m)}\equiv1\pmod{n}$ and $n^{\phi(m)}+m^{\phi(n)}\equiv1 \pmod{m}$...  ... which implies $m^{\phi(n)}+n^{\phi(m)}\equiv1\pmod{mn}$.

I would like to prove the following equality: $$k^{\phi(l)} + l^{\phi(k)} \equiv1\pmod{lk}$$if $\gcd(l,k)=1$. What methods can I use? Thank you for your help.


I have a Playfair cipher text and I know a portion of the text (one world). How can I decode the cipher from here? Thanks.

I have a ciphertext generated by a  I do not know what was cipher used to generate it. I do however have the beginning of the plaintext.    What are the cryptanalysis approaches for classical ciphers?  How do you suggest trying to recover the plaintext in this instance? How can I leverage the known plaintext to attack the cipher?   I have this ciphertext:     NUVRRIEZWBRVRFFAPUUKFVRYNQBCINHZKNETUVDVUMRTEANPAFIELBPOANIXLCMEZQETKDKVWBMNCTRVUMRFNTFDGWRUMCSCTHSGKDULRFCNABNCGSNMMGRFNTLOWQRBETZRMUBQYURFRFASANGPEQRFFAFCZACAZCTUBTHKUNEZHPPWSGPNABHZKZQNREANLCHUCZDLMLPUNTMNETDAUINQADUNSUMGETETHFBNMNNONTFBBPOQEMZPETEQUIDTHKNABKDZWBDBRZUSRASUMNIRARETETHFBZKRHPNQFAKRICMGETMULCTCULSLGBIVWBDBIEMUFCUVNUGPINFBQTMPNUMSRNNANTNANCMNNTFUMUKRILRFFAPUUKFVRYNTCMETNUVFWDABBRFNRIEFRFNTHGPUHPNKCILEGBUTWUSCPQSLMNIBWQINFBQTFAVRLCKRHKLZNFAZLSNTBDBEASTD   It begins with the partial plaintext:      it turns out that


Can we argue that the square of every odd integer is of the form $8k+1$ using non inductive proof?

How can we prove that every odd perfect square is congruent to $1$ modulo $8$?


Suppose that there are 3 players and 1 fair coin.  Devise a strategy such that we can have a clear winner. The coin can be tossed any number of times and the probability of winning for each candidate must be same.

Me and my wife are often not knowing which DVD to watch. If we have two options we have a simple solution, I put one DVD in one hand behind my back and the other DVD in the other hand. She will randomly choose a hand and the DVD I have in that hand will be the one to watch.  This procedure is easy to expand to any power of 2. If we have 4 DVD's I hold 2 in one hand, 2 in the other. When a pair of DVD's is chosen, I split them out to two hands and she choses again.  The question is, what can we do when we have  3 DVD's. The assumptions we make are:   I am not impartial. If I can influence the result somehow I will try to do that My wife really choses randomly a side every-time, independent of what she chose earlier. I don't have any other place to hide the DVD's, so every DVD is either visible or in one of the two hands.   As requirement we have that it must be a procedure with a predetermined number of steps. Not more, not less. If this is not possible, a solution that guarantees to finish with an upperbound, this is a good second choice. Off course the DVD we choose must be really random!


Do I capitalize the c and s in Cognitive science when referring to the career? What about the n in Neuroscience, or Neurobiolgy. And the P in Psychology?

Do I say "I study computer science," or "I study Computer Science"? Similarly, "I really liked that computer science course," vs. "I really liked that Computer Science course."


I am currently trying to check whether 2 values, saved in my Firebase database, are equal to or greater than the other. Although I'm having no problems getting the value's and creating a Toast which displays the correct values, when I put them in an 'if' statement, both value's come up 'null'. Is there any solution to this?  Here some code.   public void onDataChange(DataSnapshot dataSnapshot) {                                                if (dataSnapshot.child("endTime").exists()) {                                                        Long timeOpened = dataSnapshot.child("timeOpened").child("time").getValue(Long.class);           Long serviceEnd = dataSnapshot.child("endTime").child("time").getValue(Long.class);              Toast.makeText(StoryPreset.this, timeOpened + " " + serviceEnd, Toast.LENGTH_LONG).show();       if (timeOpened >= serviceEnd) {                                                                      Toast.makeText(StoryPreset.this, "Values are not null.", Toast.LENGTH_LONG).show();      } else {                                                                                Toast.makeText(StoryPreset.this, " they are null.", Toast.LENGTH_LONG).show();      }      As I mentioned, the 'Toast' present in the above code displays both values fine. It is only when they are put into an if statement that they become null. Any help is greatly appreciated!   EDIT: just to be more clear, inside the 'if' statement, bith 'timeOpened' and 'serviceEnd' are highlighted in yellow & when hovered over, a popup states that they may produce NullPointerExceptions. When testing, I also made sure I tested when I knrw 'timeOpened' was greater than 'serviceEnd' of which I got the result 'they are null'  EDIT: This question has been marked as a duplicate of the question "What is a NullPointerException". Just to be clear, I understand what a NullPointerException is and why it occurs, however I cannot understand as to why I cannot reference and compare values within the Firebase Database without them becoming NullPointerExceptions, and how I can compare them without having the NullPointerException result.

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?


I while ago, I saw 1 legitimate question, that did not have an answer yet, and another question (not by the same user), which looks something like:     I have the same problem as link.   followed by a brief explanation of the question that was linked.  Naturally, I would flag such question, but that duplicate question does not have any answer.  Should I flag the post, or is this tolerated?

I got  question in review. First sentence is:     I know there is a  question, but no answers.   And indeed the two questions are virtually identical. I started to flag as duplicate - but the original question had no answer at the time, so it wouldn't be correct and apparently . (I didn't go so far as to try to submit the flag).  What is the proper action here? How do we want such a question to be handled? Should both (or more) questions stay open indefinitely until either is answered and somebody gets the good idea to do the duplicate linking?   As the new question is essentially a bump to the front page (perhaps with re-tagging), especially in the case where the OP knows that a previous question exist, perhaps something should be done to enable bumping re-emphasizing without writing the new question.  As I wrote this,  actually got an answer. So the old one should now be closed as a duplicate of the new - but my question remains for the case where all known/found duplicate questions have no answer?  Ironically, just before asking this, the "Questions that may already have your answer" gave me ... (Although the suggestion has no answer). So it has been asked before - the comment there even suggest the ability to re-emphasize.


I met with a gentleman from church today with a rather unique situation that I wasn't sure how to deal with. Two years ago he impulse bought a new car in IL @ 19% interest (poor credit) so he'd have reliable transportation for his kids. Within days he tried to take it back but the dealer wouldn't budge. Anyway, within weeks he lost his job and has not made a single payment! He recently got another job but only brings in about $800/month, and custody arrangements and school are keeping him from taking more hours or a different job. Ideally, he needs to get rid of this $25,000 vehicle and into something much cheaper but still reliable, but I'm not sure what he needs to do to get out of this. He's told the lender in the past to just take it, but nothing has happened. He said he's not even received any collection notifications.

I purchased a car a little over 1 year ago a 2012 Dodge Avenger and recently went to get it refinanced and found out that because I'm so upside down that I can't get it refinanced I still owe over 15,000 and the car is only worth about 8000. I'm so bothered by this a few days ago I received a pre-approval letter from capital one bank for 35,000 so how can I go about doing this if I trade the car in I will have to put down a substantial amount of money in order to get out of this car. Can I just get the other car and turn the other one in. What should I do


Suppose I ask a question on Stack Exchange. Now someone comments on the question asking for some additional details or makes some points to which I need to reply.  Typically to respond to it, I add another comment to that post. However, the comments have a word limit, so if my response is exceeding that, what is the correct way to reply -   Split the response and post more that 1 comment Edit the original question I posted Add an answer to the question where I reply to the comment

Across the Stack Exchange network you may leave comments on a question or answer.  How do comments work? What are comments for, and when shouldn't I comment? Who can post comments? Who can edit comments? How can I format and link in comments? My comment doesn't contain some of the text I typed in it; why? My comment appears to be long enough, but I can't post it because it's too short; why? Who can delete comments? When should comments be deleted? Why can't I comment on specific posts even if I have enough reputation to comment? When can comments be undeleted? What are automatic comments? How can I link to comments? Anything else I should know about comments?  Also see the FAQ articles on  and .


I want to deploy sensors to the door to a private room in order to track people's presence in the room. These are the requirements:   sensors must be outside of the door; it should detect both entrance and exit or whatever it takes to know there are someone in the room; due to the nature of the room, it can be assured that at most one person will be in the room at one time; the sensor should be able to communicate with a computer using either wifi or other wireless medium.   It has been pointed out by this post () that PIR sensors can be the solution. However, I know very little of electrical engineering. I'd really appreciate it if you could explain this in details, e.g. what components to buy, where I can buy them, how do I collect the sensor data from a laptop using wireless media, etc.  I have a background in computer science, so the actual coding should be less of a problem.

This is a hobby project about home automation. The idea is that of distributed system of cheap microcontrollers that take measurements, communicate, output data and control appliances.  One important task that this system should perform is detect at every room if there are humans inside (awake or asleep distinction would be a over-the-top bonus :) ). I am still at a loss if this is feasible. PIR-s? Webcameras? Microphones? Optical counters at the doors? Ultrasound?  Available processing power per sensor output: 5MIPS of avr instructions (8-bit RISC) for 3 seconds = 15 million instructions.  Typical usage scenario would be:     The apartment is empty (the system should know that).   The door opens and a group of 4 people enters the hallway. (the system should know that someone is in the hallway).   Two go to a room (the system should track their path by room, with a lag of no more than several seconds, plus know that there is still someone in the hallway). , one of them returns, the other sits on a chair, (the first one is to be tracked. the system should also know in which room is the sitting person).  In the meantime the rest two wander randomly in a 2 x 2 meter area in the hallway (taking shoes off, hanging coats) (the system should know they are still in that area). One goes to another room, turns the radio on and goes to sleep (the system should know that there is a sleeping person there). Someone leaves the apartment and returns 10 minutes later (here the only requirement is that the system know that there are still persons inside). The three leave (the system should know that there is still someone inside). Much later, the sleeper gets up, wanders around for half an hour and then leaves the apartment (the system should track his position by room with a lag no more than several seconds, and know when he leaves that there is now no one inside).     I have no pets.


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

I recently looked at some  relating to this topic but as far as I can tell there is currently not a working plugin or script for QGIS 2.0 to achieve a four color theorem for styling polygon vector data (it doesn't necessarily have to be 4 colors, just so that each neighboring polygon is a different color, though keeping it at a minimum number of 4-6 colors would be elegant).


From  I arrived to  and found out that December 22nd, 21:11 is 2 days away from December 23rd, 13:25. The time now is 2013-12-23 13:30:17Z.    (I'm hovering over 2 days, not 12 hours, confirmed the title attribute on the 2 days element)  I also checked this on my tablet yesterday evening (in UTC time) and it listed 2 days back then as well. I couldn't check the tooltip, though, as it's hard to hover with touch controls.  Could it be changed so that only full days count as a day? It's very confusing to see "2 days ago" less than a day later (even few minutes later if you registered right before 00:00 UTC), and most importantly, it's wrong.

Looking at , I see "asked yesterday" (which I really hate; I'd like to see an exact time specification rather than this vague one, especially in the list of questions). But it was not asked yesterday! When I hover over it to show the exact time, it shows it was actually the day before yesterday!  This snapshot was taken at 2012-03-31 15:00 UTC (plus or minus a few minutes):    Whatever different opinions you may have on the implementation, yesterday is a word with a certain meaning. Redefining it is not a good idea. At least rephrase this as "1 day ago" or something.


I created a cube and scaled it to dimension 1m x 1m. I can't see the entire cube and only see part of cube. Can anybody help me how to fix it?

I'm having an odd issue - When I try to zoom in on a detail using my MMB, the "camera" in the 3D view seems to be cutting off the exterior surface of my object and showing me the inside instead. I'd expect this behavior, but only when I was much more zoomed in.  If I zoom out a bit (one click on the scroll wheel) then I can see the exterior as I intend.  Is there any way to adjust this behavior?  Thanks!


Here are my examples.  Edit// Here is a video showing what I want exactly, how "shaders" and "renderer" should work.   notice how easy it is to set the shadows on the character in the video here?      Somehow they have controls over the shading, and normals. And the shader draws smooth lines around the edges. Here are more examples.    Animation:     This here is actually created in blender.   I actually think it's better than most of the other ones, I don't know what tricks he used, or if it holds up in full 3D animation though.  The others are all pretty much 3DS MAX Pencil+ plugin.  here's some more examples even.  I would like to know, what kind of settings, what kind of stuff I should be looking for, to copy this style with blender, or if anybody pro enough to create a short tutorial it would be amazing!  Here are a few more. Supposedly, this style is "easy" if you have the 500$ 3DS Max plugin...   Anybody know here?

Is there a way to make a true toon shader material in Cycles?  Here's, in order of importance, what would be ideal to find in such a shader:   Must use Cycles Must be an actual shader Must not rely on lighting Must be independent of camera position Must react directly to lighting rather than manually having to change it to emulate it Should be easily made into a node-group Should have the following configurability:   Main color Darkness color Shadow depth (how far the shadow goes from the unlit side)    Below, I'll be listing some already-found methods and their flaws:    Cycles's Toon BDSF:  Source: Blender  Result:    Node setup:    Cons:   Not a clear-cut two-color shading Reacts to diffusion of surrounding objects      Mask & Ramp:  Source:   Result:    Node setup (Compositor):    Cons:   Very grainy Does not support colour textures Not easy to change shadow depth in a nodegroup Not a material, requires compositor Requires use of object indexes     Shadeless Fresnel:  Source:   Result:    Node setup:    Cons:   Uses camera's direction Ignores lighting Not easy to change shadow depth in a nodegroup     Shadeless Normal:  Source:   Result:    Node setup:    Cons:   Ignores lighting Direction of shadow is manually changed Not easy to change shadow depth in a nodegroup   However, this one is easily the best one. It's pretty great, and would work still images very well.    That's all I've got. Does anyone else have any methods that fall under most of the criteria I listed above? Also note that OSL is totally fine, if it works.


I am working to make a large array of structs in C. I need the array to hold over 1 million struct instances. However when the array size gets above a couple hundred thousand the program crashes. It runs fine for the first bit then it crashes. I am running Windows 7 with 6 gb of RAM.  What is the root cause of this problem? Below is the code  struct Job {    unsigned long id;    unsigned int num_preds;    unsigned int resources;    unsigned int* pred_array; };  int main() {     //Counter and loop variables (Do not use for any other purpose)     unsigned int i,j,k,count;     unsigned long height,num_jobs;     // This is our input section     height = 1000;     //Calculate the number of jobs     num_jobs = (height+1)*height*0.5;     printf("%d \n",num_jobs);      struct Job jobs[num_jobs];     return 0; }

I'm using MinGW with GCC 3.4.5 (mingw-special vista r3).  My C application uses a lot of stack so I was wondering is there any way I can tell programatically how much stack is remaining so I can cleanly handle the situation if I find that I'm about to run out.  If not what other ways would you work around the problem of potentially running out of stack space?  I've no idea what size of stack I'll start with so would need to identify that programatically also.


I want to get the text of the input text field on click of the go button. I have read a few tutorials on this, followed them step by step, but still failed to do so. Here is my code :    function go() {   content.html($("#textfield").value); } <!DOCTYPE html>
     <input type="text" id="textfield">     <button type="button" id="btn" onclick="go()">Go</button>
           May I ask what is wrong with it?

I can get the element like this $("#txtEmail") but I'm not sure how to get the actual value.


Yesterday after running my ubuntu HDD in VMware on win7 I found that I had somehow lost unity. Even after actually booting into Ubuntu, unity was GONE. Every answer on the web couldn't bring it back. Finally, I reformatted and reinstalled ubuntu.  Now, while trying to figure out how in god's name to run a .run file, I ended up punching in a command that somehow disabled unity. I cannot get it back. "unity --reset" doesn't work. (ERROR: the reset option is now deprecated)  I can log out and log in as a guest, and bam, unity is there. But if I log into my account it is just a desktop wallpaper and nothing more.  I'm about to give up on converting to linux, and I'm a computer savvy person. I thought I could handle this, but this is just ridiculous. I've spent HOURS researching ways to restart unity. I can't just reformat every time Unity doesn't restart.  In summation: I cannot restart Unity. Someone...please...I'm begging you help me. I don't want to go back to windows.

When I login, nothing happens.   I am presented with my desktop wallpaper.    No Dash, no Launcher, nothing.


Is this question correct? What is the chronological order of John as the president of our country?

I want to make a question having an answer as follows:     5 is the third prime number.   The bold part is the answer. How to phrase the question?


Let us consider two plane waves of same amplitude and frequency but having 180 degrees phase difference.Both the waves are having energy E in them which is directly proportional to the square of the amplitude.So the total energy is two times E.Now if both waves interfere,the amplitude of resulting wave is zero and the energy in the resulting wave is zero.What happend to the energy in both plane waves

What happens to the energy when waves perfectly cancel each other (destructive interference)? It appears that the energy "disappear" but the law of conservation of energy states that it can't be destructed. My guess is that the kinetic energy is transformed into potential energy. Or maybe it depends on the context of the waves where do the energy goes? Can someone elaborate on that or correct me if I'm wrong?


I'm using Ubuntu 18.04.3 LTS with kernel version 4.15.0-55-generic.  How can I upgrade the kernel to 5.0? I have run the update-manager -d command already.

I'm going to install Xenial Xerus, but I'm not sure which variant I should use. I get to choose between the normal kernel and HWE kernel.  Now I understand that HWE kernel means that support for new HW will be available faster. On the other hand the HWE kernel may be less well tested than the GA kernel which means that one perhaps shouldn't use the HWE kernel if one don't actually need it.  As I'm currently using old hardware, I'm currently running Vivid Vervet without problems so any kernel would support my current hardware. On the other hand I cannot rule out that I might upgrade with newer hardware in the future which means that I might need the HWE kernel then.  So the question is if I can install using the normal kernel and then in the future just switch to the HWE kernel if I should need it.


We have recently launched our web page but cannot find it on Google.if we type in our name nothing comes through but if we include.com then the site comes up on google. We used many key words thinking this would help customers locate our site, but type these key words in and still we are not listed. Can you advise if we are doing something wrong Thank you

This is a general, community wiki  question and answer pair intended to address any questions   concerning the reasons a site or specific site contents do not appear   in search engine results.      If your question was closed as a duplicate of this question and you   feel that the information provided here does not provide a sufficient   answer, please open a discussion on .   My site (or specific pages on my site) is not appearing in search engine results.  Why isn't my content indexed and what can I do about it?


I have this entry in my crontab (Proxmox 6 on Debian 10) : * 3 * * * scp -i /home/myuser/.ssh/proxmox_user.id_rsa /nas-zfs/backup/dump/vzdump-lxc-*-$(/bin/date +"%Y_%m_%d")* proxmox_user@proxmox2:/mnt/ftp-backup/proxmox1/dump  When I run scp... from the shell, it works and does not prompt me for a password. proxmox1 : server from which the files are copied proxmox2 : server to which the files are copied proxmox_user : a user on proxmox2 that can authenticate with a ssh key I cannot find the cron logs yet in Proxmox (it differs from a standard debian) but the job obviously fails to run.  Any help is of course welcome ;-)

I want to create a log file for a cron script that has the current hour in the log file name. This is the command I tried to use:  0 * * * * echo hello >> ~/cron-logs/hourly/test`date "+%d"`.log   Unfortunately I get this message when that runs:  /bin/sh: -c: line 0: unexpected EOF while looking for matching ``' /bin/sh: -c: line 1: syntax error: unexpected end of file   I have tried escaping the date part in various ways, but without much luck. Is it possible to make this happen in-line in a crontab file or do I need to create a shell script to do this?


I have tried installing PHPMyAdmin via terminal by using the next command: sudo apt-get install phpmyadmin, the results of the terminal are as shown:  > root@ns382469:~# apt-get install phpmyadmin Leyendo lista de > paquetes... Hecho Creando árbol de dependencias Leyendo la información > de estado... Hecho Se instalarán los siguientes paquetes extras:   > dbconfig-common libltdl7 libmcrypt4 php5-mcrypt Paquetes sugeridos:   > libmcrypt-dev mcrypt www-browser Se instalarán los siguientes paquetes > NUEVOS:   dbconfig-common libltdl7 libmcrypt4 php5-mcrypt phpmyadmin 0 > actualizados, 5 se instalarán, 0 para eliminar y 0 no actualizados. > Necesito descargar 6.441 kB de archivos. Se utilizarán 17,5 MB de > espacio de disco adicional después de esta operación. ¿Desea continuar > [S/n]? S Des:1 http://debian.mirrors.ovh.net/debian/ wheezy/main > libltdl7 amd64 2.4.2-1.1 [352 kB] Des:2 > http://debian.mirrors.ovh.net/debian/ wheezy/main libmcrypt4 amd64 > 2.5.8-3.1 [83,2 kB] Des:3 http://debian.mirrors.ovh.net/debian/ wheezy/main dbconfig-common all 1.8.47+nmu1 [487 kB] Des:4 > http://security.debian.org/ wheezy/updates/main php5-mcrypt amd64 > 5.4.39-0+deb7u2 [16,1 kB] Des:5 http://debian.mirrors.ovh.net/debian/ wheezy/main phpmyadmin all 4:3.4.11.1-2+deb7u1 [5.503 kB] Descargados > 6.441 kB en 0seg. (8.520 kB/s) Preconfigurando paquetes ... Could not exec dpkg!  E: Sub-process /usr/bin/dpkg returned an error code (100)   Note: My system is set to Spanish Language.  When I try to install somethink I have this same error when running the sudo apt-get install command.  Edit  After following Geppettvs D'Constanzo advice on permissions on dpkg I receive this in the terminal:  Root@ns382469: ~ * chmod 755/usr/bin/dpkg chmod: it is not possible to accede to "/usr/bin/dpkg": the file or the directory does not exist   Any help is appreciated.

OS: Ubuntu 12.04  Accidentally deleted dpkg. Now, packages can't be installed. So, needs an dpkg installer which installs packages.


Can I take fudge that has been produced in Guernsey (Channel Islands) into Australia together with my personal luggage?

Australia is well known for having very strict rules on what food and plant-based materials can be brought into the country, to try to keep the country free of diseases. Some food/animal/plant things can never be brought into the country, some may be if suitably declared, and a very small number are always fine.  What's the situation with chocolates though? I'd quite like to take a nice box of chocolates with me as a gift for someone when I go to Australia, but only if I'll be allowed to take them in. Does anyone know what the rules are for chocolates? Are they a never / usually ok if declared / normally fine thing?


So, assuming, for some reason, floats are absolutely required in the programme one is creating despite the inaccuracy regarding decimal points, is there any method one can use to round them to 2 decimal places without converting them into doubles?

What I would like is a method to convert a double to a string which rounds using the half-up method - i.e. if the decimal to be rounded is 5, it always rounds up to the next number. This is the standard method of rounding most people expect in most situations.  I also would like only significant digits to be displayed - i.e. there should not be any trailing zeroes.  I know one method of doing this is to use the String.format method:  String.format("%.5g%n", 0.912385);   returns:  0.91239   which is great, however it always displays numbers with 5 decimal places even if they are not significant:   String.format("%.5g%n", 0.912300);   returns:  0.91230   Another method is to use the DecimalFormatter:  DecimalFormat df = new DecimalFormat("#.#####"); df.format(0.912385);   returns:  0.91238   However as you can see this uses half-even rounding. That is it will round down if the previous digit is even. What I'd like is this:  0.912385 -> 0.91239 0.912300 -> 0.9123   What is the best way to achieve this in Java?


I’m currently analyzing a data set from a customer satisfaction survey. Customers have indicated their satisfaction with certain attributes on a five-point Likert scale. Additionally, they have also given a score for overall satisfaction on a ten-point Likert scale. I now want to estimate a model which tells me how the average customer has (knowingly or unknowingly) weighted the single attributes into the score for the overall satisfaction. My first thought was to regress overall satisfaction on the single attributes, where the betas would have given me the weights. However, this is obviously not a very good idea for a model with only discrete data. Additionally, most variables (including the dependent variable) are negatively skewed. Does anyone have an idea on how I could solve my problem?

My data is almost only ordinal data. My dependent variable is a 4 point scale:    1 = completely agree 2 = agree to some extent 3 = disagree to some extent 4 = completely disagree     I want to use regular OLS using SPSS. Should I use ordinal regression? What is the difference between ordinal regression and linear regression? When I try to use linear and my dependent variable, SPSS refuses to run the analysis. What should I do?


Recently, when clicking on the field for new incoming reputation points (in the top right corner), nothing happens.   I have the feeling that when clicking in between the notification icon and the points icon, the points menu is opening while it does not when clicking right in the middle of the points icon. I only experience clicking problems in the SE app.    App Version: 1.6.2.5 Device: iPhone SE OS Version: Version 10.2 (Build 14C92)

The navbar button for the rep/activity log can't be tapped when displaying a rating change (+5).     Persists between app runs.    App Version: 1.6.2.5 Device: iPhone 5 (Global) OS Version: Version 10.2 (Build 14C92)


I've played through GTA V offline a couple times, but I can't seem to get enough money to buy the Los Santos Golf Club, which is $150,000,000 according to the .  The question I want to ask is; does anybody know how I can get more money? I've swam past the crashed plane and gotten the briefcase (see below), but collecting that briefcase is around $25,000, if I remember correctly. I feel like the briefcase is more for a little spending money, something you can carry around and not have to worry about losing, if you get killed.    I want to make as much money as possible, and buying the second most expensive property, The Tivoli Cinema, which costs $30,000,000, is the most efficient, I think. That will still take me a lot of time, though.  Anybody know a way which I can get $150,000,000 in less than 24 hours?

What are some of the most efficient ways to make money?   Based on:    time initial investment required progress (in the game) special equipment/gear


I am checking for string inside of a div element using jquery but it allways returns the if never the else even when the dom doesn't contain then $ what stupid mistake am i making?   $('.bw-switcher').on('click', function() {     $(this).toggleClass('toggledrate', 1000);     $('.toggledrate > .bwswitch-button:before').toggle('fast');     $('.toggle_rates').toggle('fast');     if ($(".deatils.dailyPrice:contains($)")) {         $('.deatils.dailyPrice').toggle('fast');         console.log('I am the if');     } else {         console.log('I am the else');         $('.deatils.dailyPrice').toggle('fast').prepend('$');     }     $('.toggledrate > .bwswitch-button:after').toggle('fast'); });

How can I check the existence of an element in jQuery?  The current code that I have is this:  if ($(selector).length > 0) {     // Do something }   Is there a more elegant way to approach this? Perhaps a plugin or a function?


I'm playing Pro Evolution Soccer 2018 with Logitech K200 (with default keyboard settings) on Windows 8.1 Pro, and to sprint in north-west direction I'm pressing left_arrow + top_arrow + E and it is not working also to shoot in south-west direction left_arrow + down_arrow + A are not working together, but I'm able to sprint in north-east, south-east and south-west using the arrows keys and the E key.  So, some 3 key combinations are working some aren't working.  Please help me fix this so that I can play well :)

Whenever I play a PC game with the directional keys, I can only press two buttons at a time.  For instance if I am playing a shooter like R-Type, I cannot hold down the fire button while moving diagonally at the same time.  The computer simply ignores the extra button press.  How do I remove this limit so I can shoot while moving diagonally?  This limitation seems to apply for every game.  I am running Windows 7 if it makes any difference.  I noticed the same problem back when I used Windows XP.


I am somewhat new to git any advice would be appreciated. Even a link to learn a more in depth free video/course practice could be useful to me here.

What are the differences between git pull and git fetch?


When I go through the flagging dialog it jumps to a different position. Steps to reproduce:   Click "flag" on my post. Click "Should be closed."  Dialog Jumps to another position. Click "Flagging" (in the top left corner)  Notice that the flag dialog jumps again.   This happens on all stack sites (tested here, ,  and )   As mentioned in the comments, this doesn't seem to happen with the close vote dialog.

When flagging a question or answer on stackoverflow.com or even meta.stackexchange.com and some other sites (didn't test more of them), each time the Flagging modal has to be re-rendered completely, it appears 59 pixels lower than the past one, causing it to slowly go away to the bottom of the page while navigating through its links.  Here's an image that explains it :   The easier way to reproduce it is by simply clicking successively between "Should be closed" and the "Flagging" breadcrumb link.


I'd like to get a more compact case, such as as a .  However, that case is for mini-ITX mobos while I'm currently using a , and I don't have the courage to reinstall Windows and all my apps.  So I was wondering if I could just plug my current Windows 7 system disk onto the new mobo and expect Windows to resume working after downloading new drivers?  Thank you.

I recently upgraded my motherboard from a Gigabyte 78LMT-S2p to a Gigabyte 990FXA-UD3. When I tried booting up Windows it blue-screened, and after some research I learned that it has something to do with the drivers and that the easiest solution would be to reinstall Windows 7. I also read that it is possible to get Windows running without reinstalling it, but I was unable to find any sort of guidance on how to go about that. I'm currently running Windows 7 off of a spare HDD I had, so I'm wondering if there is some way to fix the old installation from this new installation on a different drive.


I am trying to fit a SVM to my data. My dataset contains 3 classes and I am performing 10 fold cross validation (in LibSVM):   ./svm-train -g 0.5 -c 10 -e 0.1 -v 10 training_data   The help thereby states:  -c cost : set the parameter C of C-SVC, epsilon-SVR, and nu-SVR (default 1)   For me, providing higher cost (C) values gives me higher accuracy. What does C in SVM actually mean? Why and when should I use higher/lower values (or the LibSVM given default value) of C?

In a SVM with linear kernel, could you explain to me what exactly the C parameter is/represents?  An example why it's important to select a good value for C would also be appreciated.  Thank you.


– Schematic created using   In the above diagram what is the current through 10ohms resistor. Can we apply superposition principle.

– Schematic created using   The diagram above, the voltage sources are equal and wired parallel, they would increase the current(2x) flow to the load(R), but what about this case:          Are the two voltage sources in series now?


I'm now in the UK with a Standard Tourist Visa (valid for six months until August) for my graduation ceremony and a holiday. I arrived here on the 10th of Feb and planned on leaving on the 10th of March (so I'd stay here for a month). I've written the date of my intended departure date on the immigration (arrival card) and the officer took the card when she interviewed me at the airport and then let me enter. Unfortunately three days after my graduation I caught a cold and it triggered my asthma. I was sick for over a week. Considering this, I'm thinking of extending my stay until end of this month. But I'm worried if this is allowed. Considering that I've already put my departure date in the immigration/arrival card.   If I did extend, should I inform the immigration? And if so, would this be a problem the next time I visit the country?

I would like to enquire about the maximum length of stay possible for an individual with a 6-month UK visit visa.  Although it's mentioned in the Home Office webpage that granting a 6-month visitor visa allows the person to stay for a maximum of 6 months , I've seen friends of mine who were refused a second visa as they previously stayed for 2 or 3 months during their first visit to the UK.


I'm a PhD student in social science. Recently, I have been invited to present my work at a conference and a lab meeting. I'm glad about the opportunities to present my work in front of colleagues. But at the same time, I'm afraid that I won't be able to answer questions from audience and they will think that I'm dumb. To be clear, I don't have anxiety about giving a talk per se, or at least know how to deal with it. I have a script for my talk, rehearse it so many times to the point I almost memorize it. I even practice my facial expressions and voice tone during the talk. I just learn and practice how to present my "ideal" academic self to colleagues. However, when it comes to Q & A after my talk, I sometimes couldn't answer questions professionally. I think there are two reasons for why sometimes I couldn't answer questions.  I'm not a native English speaker. When someone asks me a question that I couldn't understand, I ask the person to repeat the question or ask a follow-up question for clarification. But this strategy doesn't always work. One time, at a conference, I couldn't understand the question after asking the person to repeat the question twice. It was so embarrassing.  When I'm under pressure, my brain stops functioning and I couldn't really think! When people suggest a new idea that I'm not familiar with, I feel like my brain stops working, my mind goes blank and I cannot really provide "sophisticated" answer, which is possible only when I fully understand what their question actually meant and when I know how to connect their idea with my work. Also, it is so hard for me to come up with a good answer in a minute. I cannot really think when everyone is looking at my face waiting for my answer.   Given that how judging academia is, I feel like people will eventually find out that I'm not that smart. My frustration is that I cannot prepare for questions in advance. They are often unpredictable and random. I'm wondering if you have any tips or advice about how to deal with questions after talk or how to overcome anxiety about questions.

In a few days, I will be giving my first conference talk. I have only spent less than a year in the field, and the talk will be attended by several well-known researches, who are familiar with all of my advisor's work and all of the other literature in the area as well. Of the people in the room, it is probably them who will be listening most intently -- but it is also them who I feel the least well-equipped to answer questions from.  The questions I am most worried about will be about related work. Take it as a given that:   I clearly should know the answer to the question, because the related work is very relevant at a surface-level. Indeed, my advisor is familiar with the work and has told me to try to be prepared for any questions about it. But I don't know the answer, because I failed to sufficiently prepare. Or, to make some excuses, maybe I am relatively new to the field and have not had a chance to read every paper in full detail. Of course I have tried some to read through this work, and I have gotten from my advisor some idea of how it compares, but I am not nearly so familiar as I should be.   It seems likely that a poor response to such a question will make me come across as incompetent, unfamiliar with related work in the field, and even unfamiliar with the context of our own work. Similarly, this may damage the reputation of our research itself. How can I best respond to such a question, so as to minimize the damage?


I want to see if I can charge my netbook with solar panels. With 16 smalls solar panels(they are from Westinghouse Turbo Rocket Solar Path Light with a 1.2v 150mAh a piece) the voltage and amps come out to be 19.2V and 2.4A. The power strip that came with the netbook has an output of 19V and 2.1A. Will charging it with a slightly higher volt and amp mess it up or anything? Thanks

I have a Toshiba Satellite laptop. My charger has stopped working.  I have access to a Lenovo charger. Can I use this charger on my laptop?


I am using Ubuntu 16.04, and have added the below config:  $ cat  /etc/dconf/db/local.d/locks/00_default-interface  /org/gnome/desktop/interface/cursor-size   I have changed cursor-size from 24 to 60, and run sudo dconf update. It works fine for the session, but after a reboot, the setting is not saved.

I have recently created an Ubuntu 12.04 partition on my Windows 7 laptop. When installing it, I switched to "high contrast" mode, which has rather large cursors (by large I mean about twice as large and thick as they should normally are).  Now I have successfully installed the partition, the large cursors have stuck around even after exiting this high contrast mode, but only when I am hovering over stuff e.g. hovering over text inputs, links, and when resizing windows. All of these cursors are too large. They cursor is only normally sized when the computer should be displaying the normal mouse pointer.  Does anyone know how I might go about fixing this?


My question is simple. I'm using a rarely used operation which requires a rarely used Greek symbol to represent it. My current way of writing it when written out in basic LaTex looks like   $$\Omega_{j=0}^\infty \phi_j$$   Which attaches the \{j = 0\} part to the lower right and the {\infty} to the upper right of the Greek symbol \Omega.   My trouble is simple. I want it to look like how it looks when we type  $$\sum_{j=0}^\infty \phi_j$$   Except with the capital Sigma replaced with a capital Omega.   That is, I want the {j=0} to appear directly below the \Omega and the {\infty} to appear directly above the \Omega. I also want the \Omega to appear as largely as the \Sigma appears in $$\sum$$.  Is this possible?  Disclaimer: I've never posted here before so I'm wary of the format of my question; I'm not sure if this matches the guidelines. I'm happy to edit if necessary.

How can i write my own math operator with limits? I want it to look like:  \sum\limits_{e=1}^{m} but with a capital A (if possible bigger than the normal text) instead of the sum.  Thanks for the help!


Prove that $ n^3 + 5n  $ is divisible by 6 for all $ n \in \textbf{N} $.  I provide my proof below.

At our college, a professor told us to prove by a semi-formal demonstration (without complete induction):   For every odd natural: $24\mid(u^3-u)$   He said that that example was taken from a high school book - maybe I din't get something, but I really have no idea to prove that without using complete induction.  Any idea of smart demonstration?  Thanks for your help. (Excuse my bad English.)


So I was working on something today, needed to use online banking, and the bank asked me to install a security module, refusing to let me bank without it. The annoying thing is that the standard Ubuntu install did not work my 14.04 LTS due to dependency versions, so I tried the other distros install. Here's the link of instructions I followed (not too good of any idea of what's inside warsaw.run):   I can't say for sure this caused my problem, but my shell terminal quits abruptly when I run dmesg, history, ls -la, sudo apt-get update, ls /usr/bin and probably others.   I have no idea how to even diagnose this! I can run these commands just fine from a tty1, and my PATH seems to be intact. How can I discover more about the problem to fix it? I'd rather not reinstall, as I've got tons of work I need to finish.  stat /tmp  controlfreak ~ $ stat /tmp   File: ‘/tmp’   Size: 4096            Blocks: 8          IO Block: 4096   directory Device: 807h/2055d      Inode: 14811137    Links: 6 Access: (0775/drwxrwxr-x)  Uid: (    0/    root)   Gid: (    0/    root) Access: 2017-03-08 21:58:28.233840725 -0300 Modify: 2017-03-08 22:17:01.273853887 -0300 Change: 2017-03-08 22:17:01.273853887 -0300  Birth: -   error messages upon crashing gnome-terminal that was opened from xterm:  controlfreak ~ $ gnome-terminal  (gnome-terminal:7062): GLib-GIO-CRITICAL **: g_settings_get: the format string may not contain '&' (key 'monospace-font-name' from schema 'org.gnome.desktop.interface'). This call will probably stop working with a future version of glib.  **Vte-2.90:ERROR:/build/vte3-dpQaUV/vte3-0.34.9/./src/vtestream-file.h:319:_file_write: assertion failed: (_file_isopen (f) || !len) Aborted (core dumped)

I just move my /home and /tmp to another partition and after that I cannot call the commands ll or ls -l without crashing the console. anything wrong? thank you


I'm converting csv data to shapefiles using the pyshp python library. What I want to do is very similar to , except that I don't know how to handle polygons.  My data is in a csv file. Each row corresponds to a named rectangle, i.e. a string and the latitude or longitude coordinates of each side of the rectangle:  left side (xl), right side (xr), top (yt) and bottom (yb).  So my data looks like this:   name,xl,xr,yt,yb some Name,-25.3125,22.5,47.517193,31.353634 another Name,-103.359375,-0.703125,80.87282,74.40216 ...   And my python code is pretty simple. It is only slightly modified from the points example. But when I try to import this data into google maps, it has some errors parsing it. So I think I'm doing something wrong, but I'm not sure what?  #Set up blank lists for data name, polyPart = [],[]  #read data from csv file and store in lists with open(in_file, 'rb') as csvfile:   r = csv.reader(csvfile, delimiter=',')   for i,row in enumerate(r):     if i > 0: #skip header        # parse data into a point array representing the bounding box       xl = float(row[1])       xr = float(row[2])       yt = float(row[3])       yb = float(row[4])       tl = [xl, yt]       tr = [xr, yt]       br = [xr, yb]         bl = [xl, yb]       parr = [tl, tr, br, bl, tl]        # array of one "part", the part is an array of points       polyPart.append([parr])       name.append(row[0])  #Set up shapefile writer and create empty fields maxStringLength = 50 w = shp.Writer(shp.POLYGON) w.field('name','C',maxStringLength)  #loop through the data and write the shapefile for j, name in enumerate(name):   w.poly(parts=polyPart[j])   w.record(name)  #Save shapefile w.save(out_file)


I am trying to make a script to log in with my username directly without entering the password. The password should be entered automatically in the background, like the normal user you create in Ubuntu when you first install the OS when you sudo nano  vlad@Vlad:~$ sudo nano [sudo] password for vlad:   I want the password to be entered automatically so I should have direct access to the editor where we make aliases.  I don't want to remove the password by any means. I want to write it in the script so it should connect automatically.

I want to run a command that requires the sudo password say:  sudo apt-get update   Isn't this supposed to work (I have stored the password in a normal text file passwd.txt):  sudo apt-get update <~/passwd.txt   This is my logic for for why it SHOULD work: when the password is required, the user is asked to input the password from the keyboard. But redirecting the stdin to read from the passwd.txt file should work.  Shouldn't it?


I am very new to irssi (and IRC in general), and I have the need to log only the last N number of lines from irssi to a text file, but I can't find any information on how to do something like that - be it with built in features or a script.  What I want to do is overlay the last 10 or so lines of chat on a video in real time. To do this I can use and ffmpeg filter which updates when a text file is changed on disk. Therefore what I want to do is continuously write the most recent 10 lines from an active irssi session to a text file.  How could I do that?

I have a growing log file for which I want to display only the last 15 lines. Here is what I know I can do:  tail -n 15 -F mylogfile.txt   As the log file is filled, tail appends the last lines to the display.  I am looking for a solution that only displays the last 15 lines and get rid of the lines before the last 15 after it has been updated. Would you have an idea?


Prove that if random variables $X_n$ are dominated by an integrable random variable then $E[X_n] \to E[X]$ follows if $X_n$ converges to $X$ in probability.  Hint: Use the following theorem :   A necessary and sufficient condition for $X_n \to _p X$ is that each subsequence $\{X_{n_k}\}$ contain a further subsequence $\{X_{n_k}\}$ such that $\{X_{n_k}\}\to X$ with probability 1 as $n \to \infty$  The problem is that I have a.s. convergence for a subsequence one level lower for which I have to prove convergence in mean. So, stuck.

If random variables $X_n$ are dominated by an integrable random variable then $E[X_n]\to E[X]$ follows if $X_n$ converges to $X$ in probability.  Proof: Take any subsequence $\{E[X_{n_k}]\}$. I need to show that it converges to $E[X]$. Now I know that $X_{n_k}$ contains a further subsequence $X_{n_k(i)} $where almost sure convergence is guranteed. and so, $E[X_{n_k(i)}]\to E[X]$. We can say upto this much. But, I have to prove $\{E[X_{n_k}]\} \to E[X]$ . How to proceed from here.


I'm trying to make a USD <-> JPY converter. If the numbers seem off to you, trust me - I did the math. Also, I know the spacing's off, but it doesn't matter. Morph it in N++ if you need to.  import java.util.Scanner; import java.lang.Math;  public class jpy_usd { public static void main(String[] args) {     //Initializing variables and the scanner     boolean isSourceUSD;     double usd;     double usdMult = 0.00803568;     int jpy;     double jpyMult = 124.449;     Scanner scanner = new Scanner(System.in);      //Selecting an input currency and checking for valid input arguments     System.out.println("Choose your input currency. Type \'USD\' for U.S. Dollars or \'JPY\' for Japanese Yen.");     while(isSourceUSD != true && isSourceUSD != false) {         if(scanner.nextLine == "USD") {             isSourceUSD = true;         } else if(scanner.nextLine == "JPY") {             isSourceUSD = false;         } else {             System.out.println("Invalid argument. Please use \'USD\' for U.S. Dollars or \'JPY\' for Japanese Yen.");         }     }      //Asking for the input in the chosen currency and converting     if(isSourceUSD) {         System.out.println("Please enter the value to convert");         usd = scanner.nextDouble;         System.out.println(usd " in JPY is " (Math.round(usd * jpyMult)));     } else if(!isSourceUSD) {         System.out.println("Please enter the value to convert");         jpy = scanner.nextInt;         System.out.println(jpy " in USD is " (Math.round(jpy * usdMult)));         }     } }   If you want me to add the error messages, I suppose I could. Without much explanation, there's 6 errors split evenly across these two lines:  System.out.println(usd " in JPY is " (Math.round(usd * jpyMult))); System.out.println(jpy " in USD is " (Math.round(jpy * usdMult)));   There's two of each error - one per line - so the similarities in the lines have to be the same issues (duh). So, anybody got any clues?  P.S.: If there's anyhing wrong with the code other than that, please do mention it.  P.S. 2: I know I'm basically making this code public by putting every single character into this block of text, but please don't steal. I know someone's about to do it, but please don't. ~wundr

I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.  Is == bad? When should it and should it not be used? What's the difference?


So in this example I want to find the extension produced in the spring. The two methods are given in the image.( First one is by force method and the other one is energy method). The two yield different results. Where did I commit the mistake?  In the second method I have assumed that kinetic energy of the block is zero as it is slowly released, not suddenly.

Why do I have to use law of conservation of energy to solve problems regarding calculation of extension in spring length when a box attached to the lower end of the spring is released from rest (such that the spring was in it's natural length initially) and allowed to fall under gravity? I mean why can't I just simply use $x = mg/k $?


Noether's theorem implies that if there is a continuous symmetry in the Lagrangian of a system, this necessarily implies a corresponding conservation law. But does the theorem also imply the reverse? Is it possible for a system that obeys a conservation law to not have a corresponding symmetry in its Lagrangian?

states that any differentiable symmetry of the action of a physical system has a corresponding conservation law.  Is the converse true: Any conservation law of a physical system has a differentiable symmetry of its action?


When my co-founder and I were creating our project (with a scientific background), we always listed our universities as our affiliation, or we listed ourselves as the Co-Founders of the project with an e-mail. For the last two years or so, my co-founder has worked at a technology company in the UK, while I am still on my PhD in the US.  Now, if we author a paper, is it okay to list my university and his work affiliation (the company)? Formally, this would be correct. However, he does not work on our stuff during work hours but only in his freetime and at home.  If we do list the two affiliations (university me, company him), does it imply that the paper has a commercial touch? His employer is okay with it.   Would this setup complicate creating a startup from now on?

I am preparing to submit a paper with a friend who is working at a tech company.  The company that he is working with is in no way associated with our research work.  Is it appropriate to list his employer as his affiliated institution?  Otherwise, I would leave his affiliated institution field blank.  Or, should I list the institution where he graduated from 2 years ago?  Update: Thank you very much for all of your feedback, answers, comments, and suggestions.  We really appreciate it.  I discussed with my collaborator and we will likely be listing him as an "Independent Researcher".  Although, we concluded that it wouldn't be unreasonable to list his employer purely as a personal affiliation (or point of contact) as long as he got approval from their HR department.


While delving deep in Java concurrency I found an example of Reenterant locking mechanism in Java Concurrency in practice   public class Widget {      public synchronized void doSomething() { ... } } public class LoggingWidget extends Widget {    public synchronized void doSomething() {        System.out.println(toString() + ": calling doSomething");        super.doSomething(); // which object is locked this or super    } }   while calling method LoggingWidget.doSomething() LoggingWidget object's lock is acquired by thread . This method also call super.doSomething() in method its body. Which object is locked while calling super.doSomething() , Widget or LoggingWidget?

I was wondering if in Java I would get any odd behaviour if I synchronise twice on the same object?  The scenario is as follows  pulbic class SillyClassName {      object moo;     ...     public void method1(){         synchronized(moo)         {             ....             method2();             ....         }     }      public void method2(){         synchronized(moo)         {             doStuff();         }     } }   Both methods use the object and are synchronised on it. Will the second method when called by the first method stop because it's locked?  I don't think so because it's the same thread but I'm unsure of any other odd results that might occur.


I need a short formula to calculate the original price. e.g A fridge cost £ 200 after 50% reduction. Calculate the original price

I have a database of prices that already have a 10% discount.  For example a product could be $100 after a 10% discount.  Is there a reusable formula I can use to determine what the original price was of all the 10% discounted prices in the database?  Edit: Thank you for the fast responses.  Is there any way to account for rounding errors?  A real example is a product with a discounted price of \$129.00  Using the X/.9 formula, I get \$143.33 as the original price, which does not actually work out.  To have had \$129.00 as the discount price, the original price would have needed to have been \$143.34.


I am trying to install the software-centre package on Terminal..  I have entered these commands:  sudo apt-get install software-center*  I get this:  The following package was automatically installed and is no longer required   thuderbird-global menu use 'apt-get autoremove' to remove them.   another  'software-center' has no installation candidate   any ideas?

What does the above Error mean? What is an installation candidate?  I was trying to do  sudo apt-get install munin-memcached     and I get this message:  Reading package lists... Done Building dependency tree        Reading state information... Done Package munin-memcached is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package munin-memcached has no installation candidate   I googled for the problem and someone said to do a apt-get upgrade but it still did not solve my problem.


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

I just ran across the following error (and found the solution online, but it's not present in Stack Overflow):     (.gnu.linkonce.[stuff]): undefined   reference to [method] [object   file]:(.gnu.linkonce.[stuff]):   undefined reference to `typeinfo for   [classname]'   Why might one get one of these "undefined reference to typeinfo" linker errors?  (Bonus points if you can explain what's going on behind the scenes.)


How do I extract such pattern using sed?  This is my path: /sample/xyz/logs/test.logs  Output should be : xyz  How is that possible if the path keeps changing for example like   /example/xyz/log/test.logs?   using sed or awk?

I need to get the directory in the second column after depot. For example given the below file(s) list, I need "Directory2" as the output.  //depot/Directory2/Dir3/Dir4/Dir5/Dir6/Filename1  //depot/Directory2/Dir3/Dir4/Dir5/Dir6/Filename2


I want to plot 2 images. When I plot first image, I can see that in figure1. But as I plot another image it is again displayed in the same window figure1.  What I want is to plot 2 different images in two different window. Please don't suggest me to use subplot or hold on, becuase my requirement are different than those.

Usually when I plot in , it always draws on the same figure. How do I make it draw in a new figure?   I know it is pretty elementary, but I'm not finding it using Google Search.


I am new to blender and I'm trying to move the cube using XYZ csv file. How can I merge the file with the object and make it moving using that file. Can someone help me. Thank you

I would like to do 3D animations.  M spheres appear moving around and rotating along N frames (all spheres will appear in every frame).   For each sphere at every frame, these values are saved in a text file, which I'd like Blender to read:   position   angle rotation   Is it possible to read this file from blender, (so that Blender will create N frames and move and rotate at each frame the M spheres with the data read)?  I can write the file with the positions and angles in the most easily format to perform this. Eg. csv file:  time step | sphere number | x | y | z | mx | my | mz   (where m is refered to the rotation components)


I have a couple of domains (abc.com, def.com, ... , xyz.com) and I have a dns server (ns1.example.com, ns2.example.com). All my domains use ns1 and ns2 dot example dot com as their name servers. example.com uses Godaddy as its name servers. So far so good. Now I'm thinking whether I can use example.com as its own ns servers? Could it cause any problem if I use a dns server to resolve itself? Can there be any chicken-or-egg paradox?  Thanks for pointing me to the glue record, but the answer to glue record still does not make much sense to me.  I found this article about Glue record that seems to make more sense to me:   I recalled that when I started to setup my own dns server. I put in 3 records as Host Names in Godaddy, which is a 3 record map like this:  NS1: 12.34.56.78 NS2: 23.45.67.89 NS3: 34.56.78.90   Are these records considered glue records?

This is a  about DNS glue records.   What exactly (but briefly) is a DNS glue record?  Why are they needed and how do they work?


$\mathbb{F}_p(X)=\Big \{\frac {f}{g} \:\Big|\: f,g \in \mathbb{F}_p[X], g\neq 0 \Big \}$  Where $p$ is prime, it is an infinite field with finite characteristic.  I need an example of an infinite integral domain which is not a field with finite characteristic.

For curiosity: can a ring of positive characteristic ever have infinite number of distinct elements? (For example, in $\mathbb{Z}/7\mathbb{Z}$, there are really only seven elements.) We know that any field/ring of characterisitc zero must have infinite elements, but I am not sure what happens above.


Is there an option to keep the reputation blurred out when you're on stackoverflow? I mean, it stays blurred or hidden with an overlay until you hover on it or click it. Because I often have to pair-program or show some stackoverflow answers to my peers and since the header is sticky on top, I have often heard remarks about my reputation. Would be nice to have a feature to have the reputation revealed only when you interact with it.

Is there a way to view the site without having to look at reputation information? I do not want to track my rep information or see anyone else's.  I think that'll let me focus more on the questions themselves.  Is anyone else interested in this feature? I don't see anything on Stack Overflow itself, but are there any add-ins or  scripts that do this?


I have the following tables  Item   ID Name   Item taxes   ID percent item_id   An item can have more than one tax  I want to write a query that will give me all items with no tax. This query needs to be as fast as possible.  I was thinking   select id from Item where Id NOT in (select item_id from Item_taxes)   Is this the best way?

I have two tables that represent a list of urls and their related word indexes. Here are the table definitions for reference.  desc urllist; +-------+---------------------+------+-----+---------+----------------+ | Field | Type                | Null | Key | Default | Extra          | +-------+---------------------+------+-----+---------+----------------+ | id    | bigint(20) unsigned | NO   | PRI | NULL    | auto_increment | | url   | text                | NO   |     | NULL    |                | +-------+---------------------+------+-----+---------+----------------+   and  desc wordlocation; +----------+---------------------+------+-----+---------+-------+ | Field    | Type                | Null | Key | Default | Extra | +----------+---------------------+------+-----+---------+-------+ | urlid    | bigint(20) unsigned | NO   |     | NULL    |       | | wordid   | bigint(20) unsigned | NO   |     | NULL    |       | | location | int(10) unsigned    | NO   |     | NULL    |       | +----------+---------------------+------+-----+---------+-------+   The software app is a web spider. It crawls a list of urls, extracts those urls, and inserts these into the urllist table. Then, an indexer checks to see what urls have not yet been indexed, and then proceeds to index said urls.  Here is the query I am using to find items in the left table (urllist) that have not yet been indexed in the right table (wordlocation). This query is as suggested on the :  select * from urllist ul  left join wordlocation wl on ul.id = wl.urlid  where wl.urlid IS NULL;   As of this writing my test database has only 600 indexed urls, and the wordlocation table has 1.3 million rows.  However, my CPU is at 100%, and the longest I've waited to see if the query would complete is a half hour (which, it never did by the way).  To be thorough, here is the explanation of the query:  explain select * from urllist ul left join wordlocation wl on ul.id = wl.urlid where wl.urlid IS NULL; +----+-------------+-------+------+---------------+------+---------+------+---------+-------------------------+ | id | select_type | table | type | possible_keys | key  | key_len | ref  | rows    | Extra                   | +----+-------------+-------+------+---------------+------+---------+------+---------+-------------------------+ |  1 | SIMPLE      | ul    | ALL  | NULL          | NULL | NULL    | NULL |   50364 |                         | |  1 | SIMPLE      | wl    | ALL  | NULL          | NULL | NULL    | NULL | 1351371 | Using where; Not exists | +----+-------------+-------+------+---------------+------+---------+------+---------+-------------------------+   I need this query to finish in seconds, not minutes. Also, I'm worried about scalability. I have 40,000 unique urls that are waiting to be added to the index, so how do I take that into consideration with my table and query design? 400,000 urls?  Just a couple notes about my decisions on the current table structure.  I have no intention of stopping at 400,000 urls, but perhaps bigint(20) is a bit overzealous?   Url as text is for more practical reasons. I index a lot of Asian and other foreign language domains which do not appear as their equivalent Kanji or other characters in the database and frequently take more than 255 characters.  I'm using MySQL. I'm definitely open to suggestions as to better table and query design. Please let me know if I can provide more information.


While some of my friends argue that cycling causes erectile dysfunction and sterility (because the testicles are held tightly  close to the body by the padded shorts and because of the constant rubbing of the testicles against the saddle) others contend that it improves sexual performance and enhanced control over premature ejaculation  through strengthening of the pelvic floor muscles.   I'm confused by the diametrically opposite views.   What is the scientific position?   Thank you for your help in advance.

Is there any evidence to suggest that cycling adversely affects male fertility?


Killer B is able to transform into the 8 tails at will and be in control as he befriended the 8 tails.  .   Naruto has befriended the 9 tails too, but we never saw him transform into the Nine Tails like he did when he was fighting Pain and lost control of the Nine Tails (made of bones and muscles).     Now all we get to see him transform into is a kind of Susanoo like Nine Tails cloak.     Why doesn't he transform into the actual Nine Tails(made of flesh and bones like in picture below)?

Why is Naruto's Jinchuriki transformation so different from the true form of Kuarama??       In the first image, Kurama is in its true form and in the second one naruto is in biju transformed mode. Why is it so different? I mean all the lines and stuff drawn on it and it even looks different that the transformations undergone by other Jinchuriki's!! Is there an explanation for that?


I have something like:  \subsection{FooBar-$\mu$Something}   and I get a warning:  Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding): (hyperref) removing `\mu' on input line 267.   What is going on? Why I cannot use a greek letter in my subsection title? Any suggested fix?

Possible Duplicate:          The following code:  \subsection{The classes $\mathcal{L}(\gamma)$}   generates the errors:  Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding): (hyperref)                removing `math shift' on input line 1938.   Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding): (hyperref)                removing `\gamma' on input line 1938.   Package hyperref Warning: Token not allowed in a PDF string (PDFDocEncoding): (hyperref)                removing `math shift' on input line 1938.   What do I have to do to keep \gamma in the subsection, so that it is also listed in the table of contents?


Do both heavy & light objects fall at same velocity? Isn't heavier objects have greater pull, according to law of gravitation?

The common understanding is that, setting air resistance aside, all objects dropped to Earth fall at the same rate. This is often demonstrated through the thought experiment of cutting a large object in half. The halves clearly can't then fall more slowly just by being sliced in two.  However, I believe the answer is that when two objects fall together, attached or not, they do "fall" faster than an object of less mass alone does. This is because not only does the Earth accelerate the objects toward itself but the objects also accelerate the Earth toward themselves. Considering the formula: $$ F_{\text{g}} = \frac{G m_1 m_2}{d^2} $$  Given $F = ma$ thus $a = F/m$, we note that the mass of the small object doesn't seem to matter as when calculating acceleration the force is divided by the $m$ term, its mass. However, this overlooks that the force is actually applied to both objects, not just to the smaller one. The acceleration on the second, larger object is found by dividing $F$, in turn, by the larger object's mass. The two objects' acceleration vectors are exactly opposite, so closing acceleration is the sum of the two:  $$ a_{\text{closing}} = \frac{F}{m_1} + \frac{F}{m_2} $$  Since the Earth is extremely massive compared to everyday objects, the acceleration imparted on the object by the Earth will radically dominate the equation. As the Earth is $\sim 5.972 \times {10}^{24} \, \mathrm{kg} ,$ a falling object of $5.972 \, \mathrm{kg}$ (just over 13 pounds) would accelerate the Earth about $\frac{1}{{10}^{24}}$ as much, which is one part in a trillion trillion.  Of course in everyday situations, we can for all practical purposes treat objects as falling at the same rate because of this negligible difference—which our instruments probably couldn't even detect. But I'm hoping not for a discussion of practicality or what's measurable or observable, but what we think is actually happening.  Am I right or wrong?  What really clinched this for me was considering dropping a small Moon-massed object close to the Earth and a small Earth-massed object close to the Moon. This made me realize that falling isn't one object moving toward some fixed frame of reference, but that the Earth is just another object, and thus "falling" consists of multiple objects mutually attracting in space.


The following fails:  \documentclass{article} \usepackage[utf8]{inputenc} \usepackage{listings} \usepackage{sclang-prettifier}  \begin{document} \begin{lstlisting}[style=SuperCollider-IDE] current = x[0].collect(_.asArray); \end{lstlisting} \end{document}      Improper alphabetic constant.   This is with Texlive 2016 and texlive-science installed for sclang-prettifier, but I suspect it's a general problem with lstlistings.  If I prefix with backslash:  \documentclass{article} \usepackage[utf8]{inputenc} \usepackage{listings} \usepackage{sclang-prettifier}  \begin{document} \begin{lstlisting}[style=SuperCollider-IDE] current = x[0].collect(\_.asArray); \end{lstlisting} \end{document}   That backslash is printed which is not desired:

My editor requires me to have a non-white background in my code listings. In order to make my code listings look nicer, I use the literate setting of listings to change underscores (which are very wide in the T1 font encoding) into narrower rules. Since I want the reader to be able to copy code from the PDF into a text editor and get syntactically valid code out, I am currently inserting an "invisible" textual underscore in addition to the rule.  I make the underscore invisible by using \textcolor to make it the same color as the non-white code listing background. However, this doesn't work when I typeset code with \lstinline where the background is white.  Thus I want the color of the underscore to change: In the lstlisting environment it should be grey, and in \lstinline it should be white. How do I achieve this?  Minimal Working Example:  \documentclass{article} \usepackage[T1]{fontenc} \usepackage{color,listings} \lstset{backgroundcolor=\color[rgb]{0.85,0.85,0.86},         literate={_}{\niceunderscore}1} \newcommand{\niceunderscore}{%   % Invisible underscore that can be copied in the PDF:   \makebox[0pt][l]{\makebox[3pt][c]{%     \textcolor[rgb]{0.85,0.85,0.86}{\_}}}%   % Visible, noncopyable rule:   \rule[-0.4pt]{3pt}{0.4pt}} \begin{document} This is what \lstinline+foo_bar+ looks like: \begin{lstlisting} foo_bar \end{lstlisting} \end{document}     As you can see, the underscore is visible as a grey character below the black rule in the inline text, but in the lstlisting environment, it is invisible like I want it to be.


I am writing a code for a Signals Software. The summary of logic goes as: users input --> String--> split at white spaces--> ArrayPerWord --> SignalArrayPerArrayPerWord. Output is loop. Up to here my code works well. Only the remaining part left is how to join this loop-output  in a sequence. I am searching  for concatenating these arrays like String concatenation as:    str=str+str1;   something like:  SignalArrayPerArrayPerWord=SignalArrayPerArrayPerWord   + SignalArrayPerArrayPerWord1;   in other words:  array=array+array1;   I need help at this last step.

I need to concatenate two String arrays in Java.  void f(String[] first, String[] second) {     String[] both = ??? }   What is the easiest way to do this?


I'm looking for something in Gmail like '3456jdjdsnfg'. It is there as I can find it with the exact phrase. But if I search for 3456 it doesn't find anything.  Is there a way I can wildcard the search i.e. 3456*?


I came across a different symbol for the letter 'S' on Wikipedia:      What is the symbol called, replacing the letter 'S' in "Paradise" and "Lost" (and lower down in many other words, like "Bishopsgate-street")?  Further, why does it only replace some 'S' symbols? It seems that when used for pluralization, the modern 'S' is used. Examples in the image above are "Books" and the first and final 'S' in "St. Dunstons", but not the 'S' in the middle of that word.  What are the rules for when to use one vs the other?  The symbol looks rather like a lowercase 'f'...

I was at a museum in London yesterday, and one of the items on exhibit is a document from the eighteenth century. It uses the letter f a lot where s should be used—for example, in Majefty.     Did the letter f once have the same sound as s today, or were some of those words actually spoken with an f ?