Where's the head on an Atlantean jumper?

On several Stargate Atlantis and late Stargate SG-1 episodes they spend a very long time on a jumper.   For example, in Atlantis 4x17 "Midway", at the end, Bill Lee, Kavanagh, McKay and Shepard are on a gateship for more than a day      after Midway is destroyed until the Daedalus picks them up in intergalactic space   But there's no apparently place for a head (toilet).  I'm familiar with Nobody Poops (not putting TVTropes link as a public service), but this is a little different because usually you can imagine it is somewhere but not seen.   In a jumper, there is literally no place for it.    Because of this unique case, and Stargate's propensity to break the fourth wall, I'm wondering if there's anything out there.   Any discussion by show personnel or any canon information?   And I'll even just take a tongue-in-cheek "Man's I gotta take a leak real bad" when someone returns to Atlantis.


Let $a$ and $b$ be positive integers. Prove that $(a,b)|[a,b]$.

Hi everyone here is my question;  So, let $a$ and $b$ be positive integers. Prove that $(a,b)|[a,b]$. Here what I have so far;  $(a,b)=d$  $[a,b]=m$ so I need an equation of the form $m=d()$. I just need some hints on how to proceed.  Thank you so much in advance.


What is the right term for a person who has the ability to put himself in other's shoes and understand their part?

I'm a person who understand things from multiple perceptive. Say you do something which seems wrong to other person. I kinda have the ability to imagine myself in your shoes and see if I would have done the same thing. I generally don't see people around me who understand things like this, they only think from their own perspective and don't usually have the ability to think from the other side. At times, this really helps me to stay neutral/unbiased.  I wanted to know about the term which can be used to refer this quality of mine. Is there any term?  Thanks.


Merging multiple tex files into one standalone tex file

Suppose I have two tex files, document.tex and content.tex document.tex: \documentclass{article}  \begin{document}  This is some content.  \input{content.tex}  \end{document}  content.tex: This is some more content.  Compiling with pdflatex document.tex produces the expected document as pdf. However, I'd like to create a new standalone tex file, that would look like this: \documentclass{article}  \begin{document}  This is some content.  This is some more content.  \end{document}  I'm almost sure there must be a standard tool to do this, but I wasn't able to find anything.


I had created a bootcamp partition. I have now removed it using the Bootcamp Assistant. I thought I could then recreate it at a larger size. Bootcamp assistant does not allow me to choose a larger size.  I have now tried to see if I can shrink the APFS partition, but disk utility insists the minimum size is 1.74TB. Only 500Gb is actually used.  Why is the minimum size 1.74TB? Is there any way to shrink it?


I can't add an UTF-8 string into MySQL DB. Here's the code:  <html>     <head>         <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />     </head>     <body>     <?php         $temp='papà';         mysql_query("SET NAMES utf8");         mysql_query("SET character_set_results = 'utf8', character_set_client = 'utf8', character_set_connection = 'utf8', character_set_database = 'utf8', character_set_server = 'utf8'");         mysql_query("INSERT INTO comment VALUE ('$temp')") or die(mysql_error());      ?>     </body>  </html>   the variable in DB is a CHAR(120) and with a non-utf8 string it works properly. The error is the generic "You have an error in your SQL Syntax ecc."  Thanks in advance for your help.


PHP equivalent of a Ruby assignment idiom

what's the PHP equivalent of Ruby's "||=" assignment idiom?  The scenario is I want to instantiate an object or array "on demand," and not necessarily when a class is initialized.  I've tried to find this in the PHP docs, but I'm having difficulty finding things I need in there (miss the Ruby).  Thank you!


I need to change baseoa to quake3. How would I go about doing that?


The text in file looks like this:   [homes]             comment = Home Directories             path =              browseable =              writable = yes             valid users = %S             valid users = MYDOMAIN\%S  [printers]         comment = All Printers         path = /var/spool/samba         browseable = no         guest ok = no         writable = no         printable = yes   I want output as:  [homes]         comment = Home Directories         path = /data         browseable = yes         writable = yes         valid users = %S         valid users = MYDOMAIN\%S  [printers]         comment = All Printers         path = /var/spool/samba         browseable = no         guest ok = no         writable = no         printable = yes   I am using this command:  sed -i "\#path# s#.*#& /data#" file   It makes changes to everywhere in file where path is located.  Can anyone help me with this?


I was trying to write a "MAXIFS" formula on my excel 2019, but when I opened the file on a computer with excel 2016 it didnt work. And i read that for 2016's version, i should use the "MAX" instead of "MAXIFS" So what should i write if originally the formula was : =MAXIFS(Reference!C:C;Reference!B:B;Sale!B8;Reference!E:E;"<="&Sale!A8;Reference!F:F;">="&Sale!A8)*F8


Why is upvoting icon enabled on deleted question comments?

As discussed , if you try to upvote a comment on a deleted answer, you get an error message:     Comments on deleted answers cannot be upvoted   Wouldn't it be better, though, if the upvote icon were simply not available in this case?


How to measure field-of-view of a camera with fisheye Lens?

For a camera with a rectilinear lens a simple measurement would consist of taking images from known distance of an object of known size. For example using a sheet of paper as an object set on a wall perpendicular  to optical axis of the camera and taking images from several distances to have  an average value (or do linear fit).  Then say horizontal fov can be calculated from images as  hfov = 2 * arctan(Img_w/(2*d))  where    Img_w = Img_wp * (Obj_w/Obj_wp) Img_w - image width       [mm] Img_wp    - Image width in pixels Obj_w - object width      [mm] Obj_wp    - object width in pixels d - distance to object    [mm]   As I understand, for rectilinear lenses and fixed distance to the object the ratio Obj_w/Obj_wp would not change  regardless of where the object is located in the image. But for lenses with distortion like fisheye, this ratio would depend on the object location on the image and  the method would not work.  Is there a simple similar method to measure fov for fisheye lenses ?  What method is used in the industry to measure fov of camera systems ?  Since I have a camera a with small S-Mount lenses and working distances are about ~1 meter, one possible way could be  to have a ruler or tape measure set on a wall spanning the whole image horizontally. Then calculating the fov from the distance d and scene width seen on the tape measure in the image. But I'm not sure if that would work.


What's wrong with my code to read and replace python text file line by line?

I have a text file. I would like to use python v3.6 to read the text file line by line, append each line with a sub-string and replace the existing line with the appended string line by line.  To be clearer, here is the original text file;  1,2,3 4,5,6   The desired output text file should look like this;  appended_text,1,2,3 appended_text,4,5,6   This is how my code looks like;  with open(filename, 'r+') as myfile:     for line in myfile:         newline = "appended_text" + "," + line                     myfile.write(newline)   I did not get what I want. What I got instead was a huge line of text appended at the end of the file. How should the code be modified? Is there a better way to implement what I want?


What is the formula for $\frac{1}{1\cdot 2}+\frac{1}{2\cdot 3}+\frac{1}{3\cdot 4}+\cdots +\frac{1}{n(n+1)}$

How can I find the formula for the following equation?  $$\frac{1}{1\cdot 2}+\frac{1}{2\cdot 3}+\frac{1}{3\cdot 4}+\cdots +\frac{1}{n(n+1)}$$  More importantly, how would you approach finding the formula? I have found that every time, the denominator number seems to go up by $n+2$, but that's about as far as I have been able to get:  $\frac12 + \frac16 + \frac1{12} + \frac1{20} + \frac1{30}...$ the denominator increases by $4,6,8,10,12,\ldots$ etc.  So how should I approach finding the formula? Thanks!


When I used to create the record in Event object it is showing error like:     Error: Invalid Data.   Apex trigger General_Event_Trigger caused an unexpected exception, contact your administrator: General_Event_Trigger: execution of BeforeINsert caused by: System.NullPointerException: Attempt to de-reference a null object: Class.EventClass.updateNewCustomFieldsEvent: line 369, column 1   Trigger code:  trigger General_Event_Trigger on Event (...) {     if (trigger.isBefore)     {         if (trigger.isInsert)         {             EventClass.updateNewCustomFieldsEvent(trigger.new);         }         else if (trigger.isUpdate)         {             EventClass.updateNewCustomFieldsEvent(trigger.new);         }     } }   Apex class:  public static void updateNewCustomFieldsEvent(List<Event> eventList) {     for (Event eve : eventList)     {         if (Administrators__c.getInstance().Update_field_Last_Modified_End_User__c)         {             String userIdString = eve.LastModifiedById;             eve.Last_Modified_By_End_User__c = userIdString.subString(0, 15);             eve.Last_Modified_Date_End_User__c = eve.LastModifiedDate;         }     } }


The conversation often continues in the Comments and important information is held in the comments. I'd like to have threaded comments there.


How to restrict mouse to current display?

In multiple monitor setup mouse often unintentionally leaves the screen e.g. when trying to click close, trying to click the scroll bar.   Is there any way (on Windows OS) to snap the mouse to the edge of the screen like snapping windows so that it only leaves the current screen when really required to?


I seem to have lost over 2500 rep today. Could this be on purpose?

I seem to have an anomalous drop in rep.  2656 points gone in the past hour.  I know that the ways of SO are fleet and mysterious, but I would really like to know what triggers this, if not a bug.    Since I also see that my username was changed (from NewAlexandria), I presume this is probably a bug.   Any insight is appreciated.  I've left my contact info in the shot in case anyone needs to contact me directly about the tech details.  I also seem to have lost all my badges - so I'm thinking bug, or I garnered some kind of extreme ban-punishment.  This is the only SO profile affected.  Note: I've received some upvotes, and my rep didn't correct.


Are there specific numbers for which the Collatz Conjecture is proven?

Obviously it is proven that all powers of 2 fall to one after applying the rules an arbitrarily large number of times. But are there some other subsets of natural numbers, for which the Collatz Conjecture has been proven? As some comments have pointed out there are some proofs by brute force for at least the natural numbers to 2^64. Are there other known subsets, not proved by brute forcing but because of a rigorous mathematical proof?


I want to change the date format from what I chose in the Ubuntu installation, and it works by going to Region & Language and selecting the format that I want, but when I log out of the user, the date that is shown in the top of the screen is still the same and hasn't changed. is there anyway to change the date format for there?


Prove that $\binom {n}{k} = \frac {n!} {(n-k)!k!}$, viewed as a function of $k$, has maximum at $k=\lfloor n/2 \rfloor, \lceil n/2 \rceil$.

Prove that the binomial coefficient $\binom {n}{k} = \frac {n!} {(n-k)!k!}$, viewed as a function of $k$, has maximum at $k=\lfloor n/2 \rfloor, \lceil n/2 \rceil$ if $n$ is odd and maximum at $k=n/2$ if $n$ is even.  Also how do I see that $\binom {n}{k} = \frac {n!} {(n-k)!k!}$ is increasing on $[0;n/2]$ and decreasing on $[n/2;n]$ ?  I see that $\binom {n}{k} = \frac {n!} {(n-k)!k!} = \frac {n!} {(n-(n-k))!(n-k)!} = \binom {n}{n-k}$, so clearly the function is symmetric around $n/2$.  If it is possible, I would like an answer not depending on the derivative, but more on algebra.


Matrix multiplications is in general non-commutative. But in the special case that $$AB=I_n$$ where $A$, $B$ are $n\times n$ square matrices.  How to prove that $$BA=I_n?$$


Why, in Trig is Tan, the slope of the triangle called the "Tangent" when it is perpendicular to the actual tangent?

In trigonometry, the functions $\sin$, $\cos$, $\tan$ all make sense to me.  However, in reality, $\tan(\theta)$ is the slope of the hypotenuse, not the slope of the tangent.  Can anyone tell me why this is backwards?


Does a complex number multiplication have a geometric representation and why?

When dealing with complex numbers they can be presented as vectors, at least that is stated in my textbook. And the addition operation defined for complex numbers:  $$z_1 + z_2 = x_1 + x_2 + i(y_1 + y_2)$$  fully corresponds with the rules for vector addition.    But why the multiplication operation does not have a geometric (vector) representation? I wonder, because my textbook states that $\sqrt{i} = e^{\frac{i\pi}{4}}, e^{\frac{i5\pi}{4}}$, that is:    But if I try to multiply $W_1 \times W_2$ I will get a zero vector. And even if $W_1$ and $W_2$ were not collinear I would have get a vector which lies in another plane.  So, could anyone give me an answer about whether I'm correct at all and if I am whether any explanation of this situation exists, or may be I just have to live with it?  Thank you.


Why $E(X|Y)=E(E(X|Z,Y)|Y)$?   I know that $E(U)=E(E(U|V))$. So, $E(U|W)$ should be $E(E(U|V,W))$. But the latter expression is free from $W$ so it is not possible.   I can get a intuitive idea that right hand side of the above expression should be a function of $Y$, so we are conditioning two times. But how to prove it rigorously?


is a typical example for , though it is said that long time no see has been accepted by the mainstream English speakers.  Recently, there is a  movement in the , and a few new Chinglish words have been invented to demonstrate the characteristics of the Mainland.  The most outstanding examples (in my opinion) are:   shitizen - a citizen without citizen rights freedamn - the freedom for shitizens (no freedom) democrazy - the democracy for shitizens (no democracy) smilence - the speeches under the freedamn of speech () z-turn - to make effort in vain ( (Pinyin))   Here are my questions. Has there ever been any neologism movement in the history of English? What are the criteria to adopt new words into English?


What animal is depicted in this image labelled “weefil”?


Any way of not to render the pane in panel using custom module?

I dont want to use PHP visibility rule  to add a custom condition but I want to hide a pane based on some condition. How can I do that?


How do i play 1 audio file and playback them to 2 different speakers?

I want to play a chill music beat, one for my default speaker and one for my mic input ( the devices are in the same computer ). How do I playback audio to 2 speakers on the same computer with VLC? I'm using Windows 10, Thanks for helping!


Matrices commute if and only if they share a common basis of eigenvectors?

I've come across a paper that mentions the fact that matrices commute if and only if they share a common basis of eigenvectors. Where can I find a proof of this statement?


Does the item level in Team Fortress 2 affect the particular item?

I notice that most weapons other than the original weapons have a level above 1.  Can this number be different from player to player (or even item to item in the backpack of one player) for the same item?  If so, does it have any effect in game?


Have been using blender for months now and recently upgraded to the newest version 2.75a. It worked for about 2 days fine but now when i launch it the console flashes and immediately closes and blender doesn't open...  This is incredibly annoying, i have even uninstalled and reinstalled but the same thing happens.  Does anyone have a solution?  Edit: i saw those answers.... none of them work. i dont have a config file at C:\Users\USER_NAME\AppData\Roaming\Blender Foundation\Blender\2.xx\config  so i cant delete startup.blend or userpref.blend


How can I conclude that f(z) is constant?

I'm struggling a bit to arrive at the conclusion that $f(z)$ is a constant.  Suppose $f(z)$ is holomorphic on and inside the unit disk, and that it has no zeroes on the interior.  Also, assume that $|f(e^{i\theta}|$ = 1, for $0<\theta< 2\pi$.  Then by the maximum principle, the maximum of $f(z)$ is attained on the boundary -- that is, the unit circle.  But since $g:=\large \frac {1}{f(z)}$ is holomorphic on and inside the unit disk, too, then it also attains its maximum on the boundary, and so this forces $f(z)$ to be minimal on the circle as well.  Knowing now that $f(z)$ attains both its max and min on the circle, how can I conclude that it is constant?  This is tricky of course since $f(z)$ could assume infinitely many different values that have modulus = 1.  So, I hope to make use of the open mapping theorem.  Is this too ambitious?  If I can say that the open set, namely the interior of the unit disk, maps onto the unit circle in the w-plane, then we know that the image is compact, and by Heine-Borel's theorem, the image is closed and bounded.  In particular, the image is closed.  By the open mapping theorem, the holomorphic function $f(z)$ must be constant.  ...unfortunately I don't see why $f(z)$ has to be an onto mapping carrying the interior of the unit disk onto the unit circle in the w-plane.  Any hints or comments are welcome.  Thanks,


I have a series of PNGs that have transparent backgrounds.  When I place them on the strip in Video Editing and render, the background on the video is black.    I've made certain that the Transparent box is checked, and that any file formats, container or codec selections allow for RGBA, before rendering animation.  Still, the background of the video turns out black!  The file is here, and I'm desperate (and appreciative) for direction:   I would like to render the PNG files, within the Sequencer, as an mp4, WITH A TRANSPARENT BACKGROUND.  Hope this is descriptive enough to gather a response?


Can we prove that every entire one-to-one function is linear?


VirtualBox :: USB 2 devices - No devices available

I've got an Ubuntu 14.04 PC with VirtualBox 4.3.10 installed and running OK. In there I have a Windows 7 guest OS running OK.  However, the issue is that USB devices cannot be seen by VirtualBox. I have successfully installed the necessary extension pack and even enabled USB 2 for the Win 7 guest OS, but USB just says "No devices available". The same USB devices like flash disks work perfectly OK in the Ubuntu host OS. I also have guest additions installed OK.  Would really appreiate some help on this, pls.


US International without dead keys layout Windows 10

I have a problem with my keyboard layout. When I bought my new keyboard, I set the Windows layout to US International cause it has US layout but I still need to type international characters.   Everything worked just fine as I wanted it to, that is. For example, I had to press AltGr+E to type é and pressing '+E resulted in 'e and not é.   The problem is, I don't know how but this just changed 10 minutes ago, and now if I press '+E, it types é and not 'e, as I want. I did some research and found out this is what "dead keys" do, and unfortunately it is not how I want my keyboard to work.   I read a lot of people suggesting to use the Microsoft keyboard layout creator or just switching to the US layout to disable the dead keys, but, unless I just got crazy, I can assure you all I was using the international layout WITHOUT dead keys just till 10 minutes ago.  I am not confusing ' Apostrophe and ` Grave Accent (backtick).  I am 100% sure, because my language has a lot of apostrophes followed by vowels, so if this was happening before I would have recognized – typing, for example, límbuto instead of l'imbuto. It is annoying.  Please, does someone know if there is some way to disable this dead keys feature in the US International layout?


Non-abelian group $G$ satisfying $(a \cdot b)^i=a^i \cdot b^i,$ for two consecutive integers.

Given an example of a non-abelian group $G$ satisfying $(a \cdot b)^i=a^i \cdot b^i, \forall a, b \in G$ for two consecutive integers.   This is question 5 from Herstein Page 35. I have proved that conclusion holds for three positive integers.Thanks.


Which flag for off-topic, but specified questions?

Related to this specific question:   Which clearly does not belong on Stack Overflow – I mean, he's asking where to buy a tool. But I wasn't sure how to flag it – it's off-topic, but none of the flag options I get when I choose 'off-topic' really apply – it doesn't belong on Super User or Server Fault either, it's not really opinion based, etc.  It's not really unclear what he's asking either – it just isn't on topic for this site. And although I am not 100% sure, it doesn't really look like spam either.  I could just use 'other' and flag for a mod's attention, but just wondering if there is something in the existing options more appropriate.


Disable Google Chrome session restore functionality

Chrome offers to restore the last session when it did not shutdown properly (power outage, Chrome crashed, ...).  How do I disable that? (Setting or command line switch)  I'm using a batch file that starts (among other things) chrome in kiosk mode for a single page on windows startup. Even after power outage etc. it should only launch that page without the ruckus.


I know that exist several packages, like fp that allow to make all kinds of computations.  But I do not understand the correct way to use them.  I need some simple examples of multiplication and division.  I would like compute some data and output them with a custom .sty file.  An Example is:     Italy = 800 000 km of roads (by wikipedia)      SRS = 14 839.9 km (the paths of the project)      SRSpercent = SRS / Italy * 100   And I would like that Italy and SRS as the input variables, SRSpercent as one of the output variables.  I need this so that I do not have to rewrite the numbers in the papers every day.


Definition of Likelihood in Bayesian Statistics

Can the likelihood be defined as the probability of the rate parameter given a range of data. Or as the probability of the data, given a range of rate parameters?


The expected area of a triangle formed by three points randomly chosen from the unit square

"Three points are chosen uniformly and at random from a unit square. What is the expected value of the area of the resulting triangle?"  I need to do a research about that problem and i found this suggested solution: .  Now, I understand almost everything except anecdote (2) when he computes the expected value of $b$ and $v$.  I can't understand how he reaches those calculations.  If someone can explain to me this that would be great.  Thanks.


Debugging code to export .shp that gives invalid SQL statement was used?

I have a shapefile composed of a number of polygons. The shapefile has table column entitled as name (field: NAME).  How can I export with ArcPy each polygon so I get a shapefile for each one and it's name (ex: name.shp) corresponds with the ones in the table column?  I've attempted to use the following code:  import arcpy shp = "c:/temp/folder/shapefile.shp" TargetFolder = "c:/temp/folder" query = """"NAME" > 2""" with arcpy.da.SearchCursor(shp, ["NAME","SHAPE@"], query) as cursor:     for row in cursor:         arcpy.FeatureClassToFeatureClass_conversion(row[0], TargetFolder, row[1])   I get the error code: An invalid SQL statement was used.   I used code from  as the basis for mine.


Alright, so I made this really nice house in Terraria, I'll provide pictures to help. So the left side of the house says the housing is valid and the left side is symmetrical to the right side exactly. But the right side says the housing is invalid! I'm super confused of what might be happening...    I'm currently standing in the right side where it says invalid housing, but directly on the left side it's valid housing and someone is living in it too.


Inputting user input automatically through bash script?

I am creating a bash script which creates a user and sets a password. When the command "passwd user" is run it requires the user to enter a password and stops my script.  Is there any way to fulfill user input without having the user intervene?  #!/bin/bash  yum -y update adduser test-user passwd test-user "Password here?"


Is it possible to undo the changes caused by the following command? If so, how?  git reset --hard HEAD~1


Change of boarding point on Indian Railways train

I booked a train ticket on the Yeswantpur (Yeshvantapur, YPR) to Pondicherry (Puducherry, ODY) . I gave my boarding point as Hosur. My reservation is from Yeswantpur. Am I entitled to board at Banaswadi (BAND) or Krishnarajapuram (KR Puram, KJR)?


Is the mean of n independent Bernoulli random variables normal?

I'm trying to figure out the difference between an A/B split test and an ANOVA test and I came across this . It suggests that the mean of $n$ independent Bernoulli random variables is normally distributed. Is this true?  If I have a random variable $y$ that follows a Bernoulli distribution:  $F(\theta) = \theta^{y}(1-\theta)^{1-y}$  And it takes values of 1 or 0, will the mean of $n$ of these variables be normally distributed?  $\frac{1}{n}\sum y_{i}$


So I did a fresh install of Ubuntu 20.04 on a computer with the new RTL8125B Realtek network card and I cannot get the network to work. I was very suprised since this is supposed to be the new feature of the 5.4 kernel (I have 5.4.0-26-generic installed). Does anyone have any idea on how to get it working? Thank you. $ lspci -knn | grep Eth -A3 06:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 04) Subsystem: ASUSTeK Computer Inc. RTL8125 2.5GbE Controller [1043:87d7] Kernel modules: r8169 07:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 470/480/570/570X/580/580X/590] [1002:67df] (rev e7)  $ dmesg | grep -i r8169 [    0.911236] r8169 0000:06:00.0: unknown chip XID 641


Do  exist from our point of reference? From our point of reference nothing actually goes inside the event horizon right? So is there anything inside the event horizon from our reference? If not then no black holes actually exist  but hollow spheres that have the center of mass inside them? So no information paradox :)


Is there some easy way to pad Strings in Java?  Seems like something that should be in some StringUtil-like API, but I can't find anything that does this.


How to retrieve values from json object using awk or sed


Will I be able to play my Destiny Characters if I buy Legendary Edition (PS3)

So I have Destiny on PS3. If I were to buy the Legendary Edition (Containing House of Wolves and Dark Below Expansion) will I be able to play with my characters from my original Destiny disc? May sound silly, but I need confirmation.


Reference for combinatorial game theory.

What is a good reference material for elementary combinatorial game theory?  By combinatorial game theory I mean chiefly the study of zero-sum, deterministic two-player games (perhaps even more adjectives could be added), with a view to determining which of the players has the winning strategy, and perhaps determining the strategy where possible. Example games that fall under this heading are Nim, Hex, and nearly everything that might appear as a "game" at a mathematics contest.  By elementary I mean not going deep into a general theory, but rather exposing some elegant and accessible examples and ideas. For instance, the discussion of winning strategy for Nim, and the idea of strategy-stealing are topics that I would find welcome.  The request arises from the need to clear up some terminology and find additional examples for a talk that I am to give. Many thanks for all your help.


How do I change directory to home directory in Script? (bash)

Hi this is my first time writing bash and I'm trying to practice creating a bash script and am attempting to do the following:    Using absolute path the script changes directory to your home directory. Next it verifies whether a subdirectory called project exists. If it does not exist it creates that directory. Next it changes directory moving into the project subdirectory using relative path.   I'm already stuck on the first step:  #!/bin/bash cd if [ -d ./project ]     then          echo hi it exists!     else         echo it doesn't exist! cd project/   I would appreciate if someone could help! thank you so much!


Grep command to find files containing text string and move them

I am able to locate files in a folder containing a specific text string using this command:  grep -lir 'string' ~/directory/*   How do I move the files that appear in the above result to another location?


What is the right way to encode a string with backslashes?

In the given example: "\info\more info\nName" how would I turn this into bytes  I tried using unicode-escape but that didn't seem to work :(  data = "\info\more info\nName" dataV2 = str.encode(data) FinalData = dataV2.decode('unicode-escape').encode('utf_8') print(FinalData)   This is were I should get b'\info\more info\nName' but something unexpected happens and I get DeprecationWarnings in my terminal I'm assuming that its because of the backslashes causing a invalid sequence but I need them for this project


How do you call "expanding" *args and **kwargs in Python?

In Python you can write something like this:  a = (1, 2, 3) b = {'foo': 'bar'} my_function(*a, **b)   Is there a specific term for what happens in the last line with a and b and, if yes, what is it? It's not "destructuring" I suppose. And "variable expansion" sounds wrong too.


ubuntu-gnome-16.04.3-desktop-amd64 USB installation problem

I'm trying to install ubuntu-gnome-16.04.3-desktop-amd64 on Windows 64 via USB stick.  When i try to "install Ubuntu", i get a screen like this:  (same when i select "try ubuntu") and nothing happens afterwards. I already updated my BIOS (asus b150m-k)  I'd be glad to hear your comments. Thanks in Advance    System Information    Time of this report: 8/19/2017, 12:42:07          Machine name: DESKTOP-09H2588            Machine Id: {6B6C5EC4-9E66-437E-9FB7-B4EBE5A85B4C}      Operating System: Windows 10 Pro 64-bit (10.0, Build 15063) (15063.rs2_release.170317-1834)              Language: Turkish (Regional Setting: Turkish)   System Manufacturer: System manufacturer          System Model: System Product Name                  BIOS: 3016             Processor: Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz (4 CPUs), ~3.2GHz                Memory: 16384MB RAM   Available OS Memory: 16312MB RAM             Page File: 2649MB used, 16093MB available           Windows Dir: C:\WINDOWS       DirectX Version: DirectX 12   DX Setup Parameters: Not found      User DPI Setting: Using System DPI    System DPI Setting: 96 DPI (100 percent)       DWM DPI Scaling: Disabled              Miracast: Available, with HDCP


How can I tell linux kernel to completely ignore a disk as if it was not even connected?

Notice  Please  (it has few points but it is the correct one). The problem is solved by a patch that will be in kernel 3.12.7 and up; I hope it will back-ported to earlier ones, too.  My laptop is a Samsung Chronos serie s 7. Ubuntu Gnome Remix 13.04, with Intel updated drivers.   I have a problem with the internal SSD drive (8G capacity). It fails with COMRESET and  input/output errors. I am quite convinced that the problem is hardware; unfortunately I do not have Windows installed in the laptop to check if it's a matter of SSD configuration or whatever.   The problem is that the disk is recognized by udev:   KERNEL[9.515930] add      /devices/pci0000:00/0000:00:1f.2/ata2/host1/target1:0:0/1:0:0:0/block/sdb (block) ACTION=add DEVNAME=sdb DEVPATH=/devices/pci0000:00/0000:00:1f.2/ata2/host1/target1:0:0/1:0:0:0/block/sdb DEVTYPE=disk MAJOR=8 MINOR=16 SEQNUM=1785 SUBSYSTEM=block UDEV_LOG=3   and after that it fails in a lot of checks, delaying boot, delaying shutdown, and making (I think) suspend impossible.   Is it possible to tell Linux to completely ignore anything on the ata2 link? I tried adding this line to /etc/udev/rules.d/10-local.rules   SUBSYSTEMS=="pci"  DRIVERS=="ahci" KERNELS=="ata2" OPTIONS=="ignore_device"   but it doesn't work.   On the other hand, if anyone knows how to reset the SSD if it was left in "cache" mode without using Windows... or to boot a "live" windows to do the same...   Thanks!  Data added:  Full udevadm info -a -n /dev/sdb pasted to   smartctl -i /dev/sdb -T permissive gives:  root@samsung-romano:/home/romano# smartctl -i /dev/sdb -T permissive smartctl 5.43 2012-06-30 r3573 [x86_64-linux-3.8.0-31-generic] (local build) Copyright (C) 2002-12 by Bruce Allen, http://smartmontools.sourceforge.net  Vendor:               /1:0:0:0 Product:               User Capacity:        600,332,565,813,390,450 bytes [600 PB] Logical block size:   774843950 bytes >> Terminate command early due to bad response to IEC mode page   which is clearly wrong. Nevertheless:   root@samsung-romano:/home/romano# fdisk -b 512 -C 970 -H 256 -S 63 /dev/sdb fdisk: unable to read /dev/sdb: Input/output error   (SSD data from  ).   ADDITIONAL THOUGHT:  Could all this being a side effect of the Intel Smart Response Technology not being disabled before installing Linux? If yes, how can I check it short of reinstalling a windows on the machine? Or this is a shot in the dark? (In the bios the SSD drive doesn't show and there is nothing about Intel SRT).   ABOUT MARKING AS DUPLICATE:  I changed the title of the question; I do not think that the linked question answers my problem. I positively  know that the SSD is failing. I am asking if it's possible to tell the linux kernel to not probe for it at all.


When I put my USB in my laptop I get the following error, on the USB is some data what I must have is there a way to get this?


Adjective for someone who exaggerates emotions to get sympathy

What's the word for someone who tries to get sympathy from others by exaggerating their emotions or constantly reminding them of something tragic that happened to them?  I'm looking for an adjective - no disorders or health related definitions please.


How to handle concurrent bids in auction app?

I am studying on starting a new Django project with reverse auctions (countdown timer). Every time a user makes a bid the price increases by a specific amount (eg 0.05$) and the clock resets. If no one bids in the given time the last bidder wins. I am thinking on using AJAX calls in order to update values and avoid page reload.  But what is the best way to handle concurrent bids?  Thanks in advance


What is $1^k+2^k+\cdots+ (p-1)^k$ modulo $p$? (From Ireland and Rosen).

I've been working through a bit of Ireland and Rosen's Number Theory for fun. Problem 4.11 of Ireland and Rosen asks     Prove that $1^k+2^k+\cdots+(p-1)^k\equiv 0\pmod{p}$ if $p-1\nmid k$, and $-1\pmod{p}$ if $p-1\mid k$.    My work is leading where I didn't expect to go. Here I assume $p$ id odd. First, if $p-1\mid k$, then we can wrike $k=(p-1)j$ for some $j$. But then $$ 1^k+\cdots+(p-1)^k\equiv 1^{(p-1)j}+\cdots+(p-1)^{(p-1)j}\equiv \underbrace{1+\cdots+1}_{p-1\text{ times}}=\frac{(p-1)p}{2}\equiv 0\pmod{p} $$ since $p-1$ is even.   Secondly, I suppose $p-1\nmid k$. WLOG, I can assume $0<k<p-1$, Since if $k=(p-1)j+r$ with $0<r<p-1$, then  $$ a^k\equiv a^{(p-1)j+r}\equiv a^r\pmod{p}. $$  Then if $g$ is a primitive root, $$ 1^k+\cdots+(p-1)^k=\sum_{i=1}^{p-1}(g^k)^i=\frac{g^k(1-g^{k(p-1)})}{1-g^k}. $$ Since $g$ is primitive, $p\nmid 1-g^k$, but $p\mid 1-g^{k(p-1)}$, so the above sum is again congruent to $0\pmod{p}$.  So in all cases, I get the sum is congruent to $0$ regardless. Have I messed up, or is there a typo? Thanks.


Stacking labels in ArcMap without Maplex?

I do not see any obvious setting for stacking labels in ArcMap (ArcView license).   Am I missing something or do i have to write a complex expression to stack my labels?


How to change the time server in ubuntu 12.04 LTS without installing the `ntp` package

I am on Ubuntu 12.04 LTS, in the dialog "Time and Date settings" there is a set of radio buttons labeled as "Set the time", the two options are "Manually" and "Automatically from the Internet":    My current selection is "Automatically from the Internet" and I am fine with that apart from the fact that I would like to change the synchronization server (I would like to set it to ntp1.inrim.it). Is it possible without installing the ntp package? I did not find any way to change the server from the dialog.


What do the symbols in service --status-all mean?

I really miss the graphical "Services" tool from older versions of Ubuntu, but I understand why it had to go. I always have terminals open anyway, so I use (because I have to now, I guess) service --status-all to see what services are running. This would be ok except that the command produces output like the following:   [ + ]  winbind  [ ? ]  wpa-ifupdown  [ - ]  x11-common   I'm guessing that those symbols mean something like listening, blocked, or stopped, but which is which? More importantly, why doesn't the man page say?


Caption labelfont in uppercase, what am I doing wrong?

I'm trying to get the subcaptions and captions in sanserif font and Uppercased. According the manual of the caption package this should be possible in the following way.However, this doesnt seem to work. Am I defining something in the wrong way here?  \documentclass{article} \usepackage{floatrow} \usepackage[demo]{graphicx} \usepackage{subfig} \usepackage{caption} \floatsetup[figure]{subcapbesideposition = top}  \captionsetup{labelfont={sf,up}, labelsep=period, format = plain, singlelinecheck = false, textfont=rm, skip = 2pt} \captionsetup[subfloat]{labelfont = {up,sf},format = plain,textfont = rm,labelformat = simple, labelsep = period}  \begin{document}   \begin{figure}[h!]   \ffigbox[\textwidth]     {\begin{subfloatrow}         \sidesubfloat[]{\includegraphics[width = 0.4\textwidth]{A.pdf}}%         \sidesubfloat[]{\includegraphics[width = 0.4\textwidth]{B.pdf}}%       \end{subfloatrow}       \begin{subfloatrow}         \sidesubfloat[]{\includegraphics[width = 0.4\textwidth]{C.pdf}}%         \sidesubfloat[]{\includegraphics[width = 0.4\textwidth]{D.pdf}}%       \end{subfloatrow}}     {\caption{this is a caption}} \end{figure}  \end{document}


Doing something only if there is little room left on the current line

Say we wish to set attributions flush right and on the same line if there is ample room (at least 2em extra).  If there is not, they should be set on the next line, also flush right.  How would one write a macro \whence that took care of that?  My attempt below is not able to figure out whether or not there is room and requires a manual \\.     \documentclass{article}     \usepackage{showframe}      \textwidth=1.5in      \newcommand\whence[1]{\unskip\mbox{}\hskip2em\hfill#1}      \begin{document}      % attribution to the right, same line     all is water     \whence{thales}      % no room!     sum res cogitans     \whence{descartes}      % take new line     sum res cogitans\\     \whence{descartes}      \end{document}


Is it possible to achieve the "Unachievable" achievement in "The Stanley Parable"?

I know that according to the text it should be impossible, but global achievement statistics suggest otherwise. Is there a legitimate way to get this achievement?


I am trying to write a batch. And I have a problem that none of the batch operations callback functions are getting called.  I wrote drupal_set_message at the start of each callback and none of the messages are displayed.  I can get the batch page, but the callback ops aren't called at all.  Here's the code I used:  function mymdoule_node_batch() {     $batch = array(         'title'         => t("Migrating"),         'operations'    => array(             array('mycallback_001'),             array('mycallback_002'),         ),         'finished'      => 'mycallback_finished',         'init_message'  => t('Initializing...'),         'error_message' => t('An error occurred.'),     );      batch_set($batch);     drupal_set_message("step: 0"); // this is the only message the system returns }   function mycallback_001(&$context) {     drupal_set_message("step: 1");     $nids = db_select("node", "n")             ->fields("n", array("nid"))             ->orderBy("nid", "ASC")             ->execute()             ->fetchCol(); }  function mycallback_002(&$context) {     drupal_set_message("step: 2");     $nids = db_select("node", "n")             ->fields("n", array("nid"))             ->orderBy("nid", "ASC")             ->execute()             ->fetchCol(); }   P.s. The batch is getting called in form submission.  What's wrong in that?


Why does not putting this code into a function cause a null pointer exception?

I'm doing Google's android courses on Udacity to learn Android and Java. Currently, the project I'm working on is building an app which represents ordering coffee. There's a quantity TextView, along with a + and - button which on click either increment or decrement the quantity, as well as a submit order button which calls a method that prints out an order summary.  Unfortunately, I lost the original source code for the app, so I tried rebuilding it myself. I got it to work, but not in the way I originally designed it. The issue I'm having is that if I reference the TextView which stores the quantity of coffees ordered outside of its own method, the app immediately crashes due to a NullPointerException. However, if I reference that TextView by creating a method called display(int number), the app runs fine. What is causing this NullPointerException? I've provided links below to the two source codes, one of which works fine and the other of which crashes immediately.  NullPointerException:  The part that is crashing the app in this code is at line 18 in the MainActivity.java file  Works fine:  In this one, on lines 37-39, I create a method that holds the same code to reference the TextView as in the example above, which is later called by the methods for the + and - buttons.  Thank you!


mds and mds_stores constantly consuming cpu

mds and mds_stores are constant CPU consumers even when I think nothing should have changed on the hard drive. Activity Monitor:  I have a circa 2009 Macbook Pro with lots of software installed over the years. Dropbox and Crashplan are active background processes among many others. I have included many locations in the privacy settings of Spotlight to exclude from its index:  USB drive Crashplan folder /Library/Caches /Users/me/Library/Caches  Still, mds and mds_stores are constant consumers of CPU hovering around 10-12% each. My fan keeps running due to the heat. Any ideas as to what it could be due and how I can troubleshoot?


If $\forall x \in G$ where G is a group $x=x^{-1}$ then how is this group abelian?

If $\forall x \in G$ where G is a group $x=x^{-1}$ then how is this group abelian .   This question is from Gallian's book where question provides information that G is a group and $\forall x \in G$ , $x=x^{-1}$ then we have to prove that G is abelian , how is it possible ??


How to design a new board comprised of multiple already designed sub-boards separated by breakable tabs?

I want to take advantage of the entire 5cmx5cm given to me by places like DirtyPCBs and Elecrow so i want to design multiple separate PCBs on kicad and then combine them onto one board (like shown in the "panelizing" section of page) with this type of breakable tab (slots or mouse bites) as shown in . I just started to learn how to design boards with kicad and so far all i have designed is a 777 timer LED blinker and a bluetooh module breakout. I ordered these designs already from OSHPark for one and Elecrow for the other but I want to try and combine the completely separate PCBs onto a single one and add the breakable slots.  Is there an easy way to do this with KiCAD? Or on another program? Can i design all the circuits schematics separately and make all their board layouts separate and then import the board layouts into another board layout project to combine and add the slots?  Note that these aren't V-Grooves. These are just parts of the PCB that are meant to be broken away.  EDIT: by "or another program" i mean a third party program that takes the output of kicad pcb modules or even just gerbers and does it. That way i dont have to rework my entire design flow


Theoretical: Minimum Number of Support Vectors

I wanted to check if I am understanding the concept of the support vectors correctly. Let's say I am not using any kind of kernel, and it is a hard-margin SVM.  In this case, whatever the number of the dimensions is for our features, the minimum possible number of support vectors equals to 2 (1 for +, 1 for -). Am I correct? Do we still need more support vectors even in such an ideal case in $R^{d}$?


QM: Why does the creation operator not have eigenstates?

I know that coherent states are the eigenstates of the annihilation operator and i assumed that  $a^{+} |n \rangle =\sqrt{n+1}|n+1\rangle$ was the creation operators eigenstate, why is this not an eigenstate?


Tool for contradiction proof that $S^2 \not\approx \mathbb{R}^2$

Assume by contraposition, there was a homeomorphism $f:S^2 \to \mathbb{R}^2$ (hint: there isn't). Let $x_0 \in S^2$. How does one show that under this hypothesis, $f$ implies the existence of a homeomorphism $f_0:S^2 \setminus \{x_0\} \to \mathbb{R}^2 \setminus \{f(x_0)\}$ ? $S^2 \setminus \{x_0\}$ is still path-connected...


Reduce image collection to get daily sum from hourly precipitation

I'm using GSMaP image collection in Google Earth Engine, which has hourly precipitation data from 2000 to present. I have a script which helps getting data (as a table) from points from each available image in given period. Could anyone please assist me on how to make the function that it will sum the values of hourly data to daily. Please, find the script which should be improved below:   //Points var p1 = /* color: #d63000 */ee.Geometry.Point([69.15, 54.8331]),     p2 = /* color: #98ff00 */ee.Geometry.Point([70.917, 54.433]),     p3 = /* color: #0b4a8b */ee.Geometry.Point([66.967, 54.367]);      // Collection of point     var pts = ee.FeatureCollection(ee.List([ee.Feature(p1),ee.Feature(p2), ee.Feature(p3)]))      // Import GSMaP data     var gsmap = ee.ImageCollection('JAXA/GPM_L3/GSMaP/v6/reanalysis')     .filterDate(ee.Date.fromYMD(2014,1,1), ee.Date.fromYMD(2015,1,1))     .select('hourlyPrecipRateGC');      // Empty Collection to fill     var ft = ee.FeatureCollection(ee.List([]))      var fill = function(img, ini) {       // type cast       var inift = ee.FeatureCollection(ini)        // gets the values for the points in the current img       var ft2 = img.reduceRegions(pts, ee.Reducer.first(),30)        // gets the date of the img       var date = img.date().format()        // writes the date in each feature       var ft3 = ft2.map(function(f){return f.set("date", date)})        // merges the FeatureCollections       return inift.merge(ft3)     }      // Iterates over the ImageCollection     var newft = ee.FeatureCollection(gsmap.iterate(fill, ft))      // Export     Export.table.toDrive(newft,     "KZ_GSMaP_14-15",     "KZ_GSMaP_point data",     "KZ_GSMaP_14-15")


Most documents I'm opening in notepad.exe under windows 7 lately, there are no linebreaks... everything just runs together.  The same documents in any other program, even previewed directly in Explorer, will show the linebreaks correctly.  this is happening with many .info files, .css, .js.. but not all of them.   I am guessing it's some kind of character encoding unix line endings something or other, but wondering if there's anything I can do or if anyone else has experienced similar and if I can make notepad work correctly. I prefer it to notepad++/other text editors for certain uses.


Can I leave O'Hare airport during my layover?

I am flying into Chicago tomorrow and have a 5.5 hour layover. I am arriving from Holland and flying to Canada afterwards. Is this possible?


Total subsets in incomplete inner product spaces

I'm reading Induced Representations of locally compact groups by Kaniuth and Taylor and I don't understand how total subsets work (in particular in Lemma 2.24).  I know that a total subset of an inner product space is a set such that the closure of its linear span coincide with the entire space.  Shortly, in this lemma the authors want to prove that a particular subset $D$ of an Hilbert space $H$ is total. To prove this, they are showing that its linear span is dense in $V$, an inner product space which is dense in $H$ (actually $H$ was constructed as the completion of $V$).  Letting $v \in V$, it happens that $\langle d,v \rangle = 0$ for every $d\in D$ implies $v = 0$. By this last fact, the authors say that the span of $D$ is a linear dense subspace of $V$: this is what I can't understand. I looked for some informations on other books and it seems that in Hilbert spaces this can be viewed as an equivalent fact to being a total subset, but here we're considering $D$ a total subset of $V$ and not of $H$.  Is completeness necessary to prove this equivalence? I tried to prove it by myself, but I didn't manage to do it, nor I found books about this topic, since many of them (like Rudin's Real and complex analysis) introduce inner product spaces and switch to Hilbert spaces after a few pages. How does the fact that the orthogonal space of $D$ is trivial imply that $D$ is total?


Questions on Multi-stage transistor Op-Amp

I would like to know how to understand/analyse the circuit below. And sorry but my level in electronics is not that high and I could only tell that the opposing transistors on the left are meant to cancel any current from the input , yet I don't really understand the B stage which I think the C stage is well related to , and if I wanted to analyse the nodes around the circuit apart from (A,B,C) How can I do it ?  Is it by measuring the current on resistors/nodes?  and note that the output voltage of the circuit in node C is zero this is what it meant to be.I would appreciate any help.  Regards


In Prisoner of Azkaban, Hermione took 12 subjects, and needed a Time-Turner to do so. However, it is mentioned in the series that both Bill and Percy Weasley got 12 OWLs, so would have taken 12 subjects as well, so both would have needed Time-Turners for three years to do this. Doesn't this seem a little unusual, given how strict the Ministry is over the use of Time-Turners,  that they would give them to several Hogwarts students?


kotilin: Attempt to invoke virtual method 'java.lang.String android.content.Intent.getStringExtra(java.lang.String)' on a null object reference

I want to reveive value that i passed throught Intent from activity to another and access it, but it's showing:     Attempt to invoke virtual method 'java.lang.String android.content.Intent.getStringExtra(java.lang.String)' on a null object reference   So here what i did... in the Login Activity I passed username thourgh Intent:  val intent = Intent(this@LoginActivity,MainActivity::class.java) intent.putExtra("username", "johnDoe") startActivity(intent)   Main Activity  class MainActivity : AppCompatActivity() {      val username = intent.getStringExtra("username")      private val firebaseHelper = FirebaseHelper(username)      override fun onCreate(savedInstanceState: Bundle?) {         super.onCreate(savedInstanceState)         setContentView(R.layout.activity_main)          Toast.makeText(applicationContext, username.toString(), Toast.LENGTH_LONG).show()     }      override fun onStop() {         super.onStop()         firebaseHelper.deleteDriver()     } }   Fore example: if i use val username = intent.getStringExtra("username") it will work, but then i will get problem with firebaseHelper.deleteDriver().  i don't know where i missed it, but hope there's solution you can make guys


Automate a command line when I power on my computer?

With Ubuntu 18.04, I need the command line xrandr --output DP-1 --scale 0.5x0.5. How can I automate that command when I power on my computer?  EDIT  I created the /etc/rc.local file, and in that file I have written  #!/bin/bash  xrandr --output DP-1 --scale 0.5x0.5  exit 0   The problem is if I restart the computer, the screen is identical and wrong. It seems to work if I run the command bash /etc/rc.local, but not if I restart the computer. How can I fix that?


I have found some ID3 tag editor in the web but unfortunately they are no longer available in 13.04 repository. Can anyone give me some recommendation for an ID3 Tag editor program? I need features like being able to tag lots of files at once and to read/write embedded (not linked) album art cover to/from Mp3 files.


"Downloads" folder shortcut on the left pane of nautilus disappeared; how do I get it back?

The Downloads folder shortcut on the left pane of nautilus has disappeared. How do I get it back?  Today, I opened the terminator and removed the "Downloads" folder. Then I linked it to a folder on another disk.   rm -r Downloads ln -s '/media/my_name/my_disk/dl' Downloads   I did the same to the Pictures folder and it looks fine. But I lost my Downloads folder shortcut on the left pane of nautilus (file browser).  I tried to revert this change. So I removed the link and recreated the Downloads folder, but the shortcut didn't come back. What should I do?  I use Ubuntu 20.04, Unity Desktop, Nautilus (3.36.2-0ubuntu1).


Why can a regex correctly identify bracketing such as ((a)) but not (((a)? I don't have any specific regex in mind but I am curious on why it is the case.


`/usr/bin/cd` is not working in mac terminal

I was checking the path of cd command in macOS terminal using which cd, I got /usr/bin/cd, so whenever I use this full path to execute cd it doesn't work as expected.  So here are some examples.   Any valid path here root(/) as arg.  /usr/bin/cd / -> doesn't change dir as specified Any invalid path here (kjfd) as arg.  /usr/bin/cd kjfd -> /usr/bin/cd: line 4: cd: kjfd: No such file or directory   So, I really don't understand why cd with complete path address(/usr/bin/cd /) is not working while other commands like bin/echo do work.


I noticed in the man pages for find, that the {} always have single quotes around them.   find -exec '{}' \;  The description states:     Notice          that the braces are enclosed in single quote marks to protect them from          interpretation  as  shell  script punctuation.   The semicolon is simi-          larly protected by the use of a backslash   I have never had an issue using just find -exec {} \; What is an example where the single quotes are required.


If A is countable subset of $\mathbb{R}^2$ , then $\mathbb{R}^2 - A$ is pathwise connected.

This is a question from Section 3.2 of Wayne Patty's topology.  Question :Prove that if A is countable subset of $\mathbb{R}^2$ , then $\mathbb{R}^2 - A$ is pathwise connected.  The intution is very easy to get but I am not getting ideas on how should I define a continuous function f such that f(0)= a and f(1)=b for any a , b in $\mathbb{R}^2$. Kindly guide me with that.


Hash Sum mismatch error when trying to upgrade

I am getting this error when trying to upgrade:  E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/l/linux-firmware/linux-firmware_1.157.15_all.deb  Hash Sum mismatch   To check what is wrong I downloaded the package from  and checked the md5 which is showing something different in my machine from the one given on the website.


Why is current the same everywhere in a circuit? (DC)

In a series circuit, the voltage is the same everywhere on that circuit. However, thinking about Voltage as a steady force or potential, I imagine that at parts of the circuit without resistance, the current would be greater as the force would be able to move them faster, without any obstruction. Why is this not the case?


Is all of eigenvalues of $A^n$ in a form $\lambda^n$, where $\lambda$ is an eigenvalue of $A$?

This is related to this question:  Let $A$ be a complex square matrix. In one of the answers, they used eigenvalues of $A^2$ to calculate eigenvalues of $A$. I have a question in terms of this. We can easily show that if $\lambda$ is an eigenvalue of $A$, then $\lambda^n$ is an eigenvalue of $A^n$. So, in set notation, If $\{\lambda_1,\cdots \lambda_k\}$ is a set of eigenvalues of $A$, $\{\lambda_1^n,\cdots,\lambda^n_k\}\subset \{\textrm{Set of eigenvalues of }A^n\}$ holds. My question is, does $\{\lambda_1^n,\cdots,\lambda^n_k\}=\{\textrm{Set of eigenvalues of }A^n\}$ hold? If so, how can we prove it?


Implement a "tennis rule" for approving suggested edits

The winner of a tennis game must win with a two point advantage.  Similarly, a suggested edit should not be approved unless it can get two more approvals than rejections.  This should greatly reduce incidents like  from happening.


Change storage Disk for Windows Subsystem for Linux

I had recently installed the Windows Subsystem for Linux in my Notebook, where I have two disk for storage:  - C:/ an SSD of 128GB  - D:/ an HDD of 1TB By default the Windows Subsystem for Linux its installed on my C disk, but that's got me without space. Does it exist any way to change the Subsystem Installation to the other disk (D)?  Thanks for the help!


How can I solve this logic question using propositional logic (Natural deduction)?

$$\big((P\rightarrow Q)\rightarrow P\big) \rightarrow P$$  I need to solve this using simple natural deduction rules  these can be hypothesis, $\rightarrow$ intro, $\rightarrow$ elim, conj and disjunct intro and elim, and negation intro (Reductio ad absurdum) and negation elimination (Double)


Python print one by one list and add count

I'm trying to print a list of objects 1 by one and at the same time print count next to them. Add something to the code so for i in items:     print(i)  returns:  wool  honey etc.


Does $A^2$ similar to $B^2$ imply that $A$ is similar to $B$?

So we have square matrices $A$ and $B$. Now suppose $A^2$ and $B^2$ are similar, does it follow that $A$ and $B$ are similar? I don't think so, but I'm having trouble showing is not.  My attempt: If $A$ is similar to $B$, and $A$ is similar to $C$, then $B$ is also similar to C. More importantly, $A$ is similar to the diagonal matrix of its eigenvalues, then $B$ must also be. So $A$ and $B$ have the same eigen values. But then I realised that this question doesn't even make the assumption that $A$ and $B$ are invertible, so they may or may not have those eigen values.  Can someone give me some hints to this question? If this is a proof by counterexample, is there at least some way to narrow the possible contradictions down by some theorem?


Run a script on shutdown and not on reboot

I'm executing a script on Ubuntu 14.04.1 LTS when the server is stopping But I would like to execute it only on shutdown behavior, not whendoing a reboot.  I tried to get the value with $1but for reboot or shutdown, but it always sending a stop message  The script I'm currently running:  #! /bin/sh ### BEGIN INIT INFO # Provides:          shutdown # Required-Start:     # Required-Stop:     sendsigs # Default-Start: # Default-Stop:      0 6 # Short-Description: shutdown # Description:  ### END INIT INFO  shutdown_script.sh  exit 0   And run by sudo update-rc.d shutdown_job start 19 0 6 .


How to Install Skype for Linux in Ubuntu 16.04 Via Console only?

I use Ubuntu 16.04  I want to install Skype for Linux through the console.   Is it possible?  If I try to install via Software Installer, it closes automatically.


Why is my lenght in Array Mod not matching up with Transform Menu in 3d veiw?

Made array of boards..wanted a Spec length of 24" in Array with a 1/2 gap. Array did not work(?) Entered 24" in my Transform Menu but my array length box = 60" x = 48" y = 24" z = 1.6"


Terence Tao, Analysis I, Ex. 5.5.2: Entry point needed

Terence Tao, Analysis I, 3e, Exercise 5.5.2:     Let $E$ be a non-empty subset of $\mathbb{R}$, let $n \ge 1$ be an   integer, and let $L < K$ be integers. Suppose that $K/n$ is an upper   bound for $E$, but that $L/n$ is not an upper bound for $E$. Without   using Theorem 5.5.9, show that there exists an integer $L < m \le K$   such that $m/n$ is an upper bound for $E$, but that $(m-1)/n$ is not   an upper bound for $E$. (Hint: prove by contradiction, and use   induction. It may also help to draw a picture of the situation.)    does not do the trick for me, since I'm looking for the proof by contradiction, equipped only with the set of propositions and theorems covered so far.  What I'm actually looking for is an entry point to the proof, since I find it quite hard to negate the assumption.  My attempt is to induct over $n$. Assume I have been able to prove the statement for $n = 1$, is the following a valid negation of the assumption?  For all integers in the range $(L, K]$, at least one of the following statements holds:   $(m-1)/(n+1)$ is not an upper bound and $m/(n+1)$ is not an upper bound. $(m-1)/(n+1)$ is an upper bound and $m/(n+1)$ is not an upper bound. $(m-1)/(n+1)$ is an upper bound and $m/(n+1)$ is an upper bound.   If I were able to prove that there is an integer in the given range such that none of the above holds, am I done?       Theorem 5.5.9 (Existence of least upper bound). Let $E$ be a non-empty subset of $\mathbb{R}$. If $E$ has an upper bound, (i.e.,   $E$ has some upper bound $M$), then it must have exactly one least   upper bound.     I went through another loop considering  of Steve Kass, but I ended up wondering why the proof needs induction at all:  Assume for all integers $m$ where $L < m \le K$ we have that $m/n$ and $(m-1)/n$ are upper bounds of $E$. Then $(m-1)/n = L/n$ is also an upper bound. But $L/n$ is no upper bound, by assumption. Assume $m/n$ and $(m-1)/n$ are no upper bounds. Then $m/n = K/n$ is also no upper bound. But $K/n$ is an upper bound, by assumption.   Hence, there is an integer in the range $(L, K]$ s.t. $m/n$ is an upper bound for $E$, and $(m-1)/n$ is not.


What is the difference between those 2 logic gates symbols

I was wondering the difference between two symbols (we can found the diagram page 2 at  )  Between the logic gate NOT (a triangle then a circle) and the other symbol (a circle then a triangle) which is located in the right of the CLOCK10  I searched on the internet but I only find information about the NOT gate (and nothing about the other one)  Thank you very much,


got a problem when changing my appendix. The problem is that tex is producing two extra blank pages which I want to be removed.   Before the problem:  Main.tex  [...]  \begin{appendix}     \include{anhang/Apple1}     \include{anhang/Apple2}     \include{anhang/Apple3}     \include{anhang/Banana1}     \include{anhang/Banana2} \end{appendix}  [...]   Content of anhang/Apple1:  \includepdf[pages=1,scale=.8, offset= 0 -75,pagecommand={\chapter{blabla}\label{somelabel}}]{pdf/anything.pdf}   Content of anhang/Apple2:  \includepdf[pages=1,scale=.8, offset= 0 -75,pagecommand={\chapter{blabla2}\label{anotherlabel}}]{pdf/another.pdf}   and so on...  This worked fine. No extra pages were included. But when extending my work there was a few more appendix and I didn't want to get a new entry for every single page. So I decided to change the appendix to:  [...]  \begin{appendix}     \include{anhang/Apple}     \include{anhang/Banana} \end{appendix}  [...]   Content of anhang/Apple:  \chapter{Apple}  \includegraphics[width=15cm]{pdf/apple1.pdf} \includegraphics[width=15cm]{pdf/apple2.pdf} \includegraphics[width=15cm]{pdf/apple3.pdf}   same for banana. So hopefully you get my point. Tried to merge contents and not to have an extra appendix for every single pdf file. It looks okay this way but my problem is: TeX adds two extra blank pages BEFORE appendix A. If more information is needed please ask.  Anyone have some advice please? Thanks.


When/if sensitive people fall in love, they become totally mad

When sensitive people fall in love, they become totally mad.        Or        If sensitive people fall in love, they become totally mad.       I think both are correct but mean different things.


I need help solving the recurrent relation:  a(n) = 5a(n-1) – 6a(n-2) + 3 for n > 2 (n represents what # of a, it isn't another variable)  with initial conditions a(1) = 3/2, a(2) = 3  I started by solving the next few values: a(3) = 9, a(4) = 30, a(5) = 99, a(6) = 318  But I'm having difficulty trying to think of an equation that is equivalent to the original but can only use the value n oppose to a(n).


Do you write "here is some stuff" or "here are some stuff"?

I am new here so sorry if this question has been asked before.  Which one is correct "here is some stuff" or "here are some stuff" ?


When coding with Collections:  Why use:   List<String> mList= new ArrayList<String>();   Why not:   ArrayList<String> mList=new ArrayList<String>();   When I ask the answer is : "It is JAVA convention".  I need a comprehensive, logical and expressive answer on this.


Problems importing reference.bib database to Latex file

I am currently having problems importing my .bib file to my latex file.  the bib file's name is reference.bib, it was compiled using JabRef and it contains the following  @Book{alexander2009market,   Title                    = {Market Risk Analysis, Value at Risk Models},   Author                   = {Alexander, Carol},   Publisher                = {John Wiley \& Sons},   Year                     = {2009},   Volume                   = {4} }   I made sure that the reference.bib was in the same directory as the tex file.  When inputing   \bibliographystyle{plain} \bibliography{reference}   nothing happens. Additionally, the font changes when I input the \bibliography command to bold blue unlike the \bibliographystyle that remains with the standard command font.


Up until now, I implemented all-against-all collision detection in my games. It worked fine.  But I reached a point where implementing this kind of collision detection, makes the game run poorly, because there are two many objects to iterate through and check for collision.  I have searched this site and found something about 'uniform grids'. But I didn't completely understand what it is and how to implement it. Tried to Google it but nothing easy enough to understand came up.  I am a beginner to 2D-game programming. Do you mind trying to explain to uniform-grids, or link me to some good tutorial?  Thanks a lot


turn level-based input to edge-triggered input

I'm trying to figure out with the most minimal part count how to convert an input of a digital IC to an edge-triggered input.  I am using the 82C55 IC and the input on it I want to make negative edge-triggered is the WR input. This is because I want to control both WR and the clock of an external latch (74HC574) with only one GPIO pin of a microcontroller.  I am able to pull this off by using a multivibrator (CD4538) and connecting the output of it to WR but the thing with that is I have to add a capacitor and resistor to create my own timing.  Is there a simpler way to convert a level-based input (where an output happens based on what level the input is at) to an edge-triggered input without introducing unnecessary long timings (which could happen with my multivibrator approach) and without using too many extra parts?


How to change the size of monitor in "Customize your display" (NOT RESOLUTION)

I have a multi-monitor setup which looks like this:    The resolutions are correct (all are 1080p), but the sizes are incorrect and I can't seem to find where to change the size (so the cursor will jump to the correct position). In reality the size difference between monitor 1 and 2 are this:    This is bad because the mouse pointer then jumps, example: if you move from left edge of screen one(1) to screen two(2) (vertically up), the cursor jumps 15 cm to the left, this is unwanted behaviour.   How can I change the screen size in Windows to reflect the real size of my screens (NOT THE SCREEN RESOLUTION!) ?  I'm using Windows 10 but would need to know this for Windows 7 too if possible.


Why was Loki affected by the bullets in this scene?

As mentioned in the answer , within the scope of MCU and as well as in the comic books, Asgardians are quite resistant to bullets.  However, I was recently re-watching The Avengers (2012) movie and something caught my eye.  At the beginning, when the Tesseract opens the portal and Loki appears, the S.H.I.E.L.D agents start shooting him and he was completely unaffected by it. As a matter of fact, he seemed completely immune and the bullets simply bounced off of him. This, may well be plausible as Asgardian physiology is different from humans.   But when Loki and Hawkeye are leaving the premises, Loki, for a moment, is seen to be straining himself and show pain as if those bullets hurt him (I can't put this into better words so I've added a video and a photo below to show it).                                    In the video, pay attention at around the 3:30 ~ 3:40 minute mark.   So, how can Loki be hurt by the bullets if bullets don't affect him?


How to prove the Fibonacci sum $\sum \limits_{n=0}^{\infty}\frac{F_n}{p^n} = \frac{p}{p^2-p-1}$

We are familiar with the nifty fact that given the Fibonacci series $F_n = 0, 1, 1, 2, 3, 5, 8,\dots$ then $0.0112358\dots\approx 1/89$. In fact,  $$\sum_{n=0}^{\infty}\frac{F_n}{10^n} = \frac{10}{89}$$  How do we prove that, more generally, for $p > 1$ then,  $$\sum_{n=0}^{\infty}\frac{F_n}{p^n} = \frac{p}{p^2-p-1}$$  (The above simply was the case $p = 10$.)


why member function inherit from base is undefined?

I am going to write some class for test like following files. I get some errors when I compile those files: I call inherited function via derived class. but the compiler says that undefined reference to 'Base<someStruct>::func()'.    I get this error where I try to call inherited member function actually.  the base class and derived class are in the same file. why I get this error?    //tool.h template <class Addr> struct Base { ... public:     bool func(); ... }  class Tool : public Base<struct someStruct> { ... public:     int func1(); ... }   and the following is implementation file.  //tool.cpp #include "tool.h"  template <class Addr> bool Base<Addr>::func() {     ... }  int Tool::func1() { }   the main is here:    //test.c #include "tool.h"  int main() {     Tool tool;      tool.func();  //error is here; }


How do we see that the axion is a pseudoscalar?

The axion is the pseudo-Goldstone boson associated to the breaking of the conjectured Peccei-Quinn Abelian symmetry. The axion couples to the SM gauge fields in a CP-invariant manner (e.g. $aF\tilde F \sim a\ \vec E\cdot \vec B$), which means that the axion has to be a pseudoscalar.  Do we assume that the axion is a pseudoscalar? Or is there a means to realise that it is indeed so?    EDIT: Note that I am NOT asking for a proof of why claiming that the axion $a$ is a pseudoscalar ensures that $aF\tilde F$ is CP-invariant (which is the content of ). I understand that very well. The fact is when I ask why $aF\tilde F$ is CP-invariant, the usual answer given is that because $a$ is a pseudoscalar. Therefore, either one has to first establish that $a$ is a pseudoscalar without making an appeal to consequences (namely that it makes $aF\tilde F$ CP-invariant), or establish that $aF\tilde F$ is indeed CP-invariant which should prove that $a$ is a pseudoscalar.  The only other safe alternative is to claim it is so by definition.    To make it absolutely clear that this question is not a duplicate, define proposition $A$ as "the axion $a$ is a pseudoscalar" and proposition $B$ as "$aF\tilde F$ is CP-invariant".   The linked question asks for a proof of $A\Leftrightarrow B$. I accept the truth of this proposition. However, I ask for a proof of $A$ alone (or a clarification that it is indeed so by defintion of $a$). Note that if you can prove $B$, then $A$ follows from $A\Leftrightarrow B$.


Make script to create subdirectories based on file name and move matching files into it

A folder has a huge number of files; each pair of files has the same name but  different extensions (.obj and .mtl). I want to make a folder for each pair of files with the same name, then move each pair of files into its matching folder. File names always have letters; some also have underscores and numbers.  What I need to do is: A) Read a file name B) Make a subdirectory with the same name as the preceding file C) Move the pair of files matching the filename into the matching subdirectory D) Repeat for the next file    Example: Files: Big_Column1.obj , Big_Column1.mtl To be moved into subdirectory: Big_Column1


I am using the Atom editor with the  package (a port of the similar one for Sublime) and I can write for example  % !TEX option = -shell-escape   in the begining of my document to make it escape the shell (and use the Minted package).  My question is, where does this command come from? Is it from the latextools package or is it some standard syntax? Is it portable to other IDE?  When building I see this:  latexmk -cd -e -f -pdf -interaction=nonstopmode -synctex=1 -latexoption="-shell-escape" "main.tex"


How to create a sub-window in a terminal?

I would like to print to a clean terminal, but not issue a clear or reset command such that the user will not lose data. After the printing is done, I would like to put the user in their old (root) window. I see this done in programs like htop, tmux, less and the like. My understanding is that they create a new window on top of the root, use that, and return the user to the root window when done. How can I emulate the same behaviour in a shell script? I (think I) cannot just pipe what I want to print to less as I need to capture the user's input. Here's a template for what I need: begin-window # a top-layer window is created echo data read input echo processed input read _ # press enter to exit end-window # user is returned to the original window


Calculate the coordinates of one of the vertices of a rectangular triangle with data on the length of one side

I am using a cartesian coordinate system, and I have the coordinates of two points (red dots in the figure). By Pythagoras I can calculated the distance between those two points. However I want to know the coordinates of the green dot, which is perpendicular the side $b$, given that I know the distance $a= 80.$ I cannot find a way to calculate the coordinates of the green point. Any suggestions will be most welcomed.


Is it possible to change the path of latex output files (e.g .aux, .log, .etc) to a different directory. The main directory is becoming a mess. Thank you


Windows 7 takes 15 min before even downloading WIndows Updates

Every time I go to install updates--regardless of whether it's a single 2KB update or a dozen 300MB updates, the screen sticks at the "Please wait while windows..." for a good 15 minutes before it even starts the "1% downloaded..." etc.  The network is very fast on this machine--it appears to be something with Windows Update itself. I have a couple other Win7 machines at home the others begin downloading and installing updates immediately.  Related, likely, I very often get updates on this machine that simply fail.  After reboot I get the "Failure configuring windows updates...Reverting changes...".  I've done some research and have installed the October 2014 "Windows Update Readiness tool", and have cleared out various logfiles which seemed to be recommended be a large number of sites I generally trust (including here).  Yet the problem remains.  Does anyone have a suggestion, aside from a complete re-install of Windows, that I might try? Thanks


Can you help identify this common style of photo editing, it's like a faded style?

These 2 photos below have a similar editing style, which I'm trying to identify. They're all like faded out and slightly bland/muted in colour, which I really like.   Any ideas?


Prove that $\sqrt{ab+c}+\sqrt{bc+a}+\sqrt{ac+b} \ge 1+\sqrt{ab}+\sqrt{bc}+\sqrt{ac}$  It is given that $a+b+c=1$ and $a,b,c$ are positive real numbers  Then I reduced the inequality to  $\sqrt{(1-a)(1-b)}+\sqrt{(1-b)(1-c)}+\sqrt{(1-c)(1-a)} \ge 1+\sqrt{ab}+\sqrt{bc}+\sqrt{ac}$.    I know that   $\sqrt{(1-a)(1-b)} \ge \sqrt{ab}$. Similarly we can deduce other too.By this we get  $\sqrt{(1-a)(1-b)}+\sqrt{(1-b)(1-c)}+\sqrt{(1-c)(1-a)} \ge \sqrt{ab}+\sqrt{bc}+\sqrt{ac}$  I don't know how they got 1 on rhs.Any help??


Why is the laptop charger thing (transformer) making a noise?

The laptop power cable consists of two cables with a transformer in the middle. The transformer is making a tiny noise while plugged in. I think it's normal... is it normal? What is it exactly?


Enable WiFi not showing up on a fresh install of Ubuntu 15.10

I recently switched from Elementary OS to Ubuntu 15.10 for Virtualbox, but when I completed the installation and tried to connect to my local WiFi network, there was no Enable WiFi button. Only an Enable Networks button.  The Network Connections window also only shows a wired Ethernet Connection, which I've never even used on this laptop.  EDIT:  When I use ifconfig -a it only shows the     enp5s0   And     lo   No wlan0.  Can someone please help?  The output of     lspci | grep -i intel   Is  00:00.0 Host bridge: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub (rev 07) 00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) 00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) 00:1a.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 03) 00:1a.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 03) 00:1a.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 03) 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03) 00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 03) 00:1c.1 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 2 (rev 03) 00:1c.2 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 3 (rev 03) 00:1d.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 03) 00:1d.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 03) 00:1d.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 03) 00:1d.3 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 03) 00:1d.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 03) 00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev 93) 00:1f.0 ISA bridge: Intel Corporation ICH9M LPC Interface Controller (rev 03) 00:1f.2 SATA controller: Intel Corporation 82801IBM/IEM (ICH9M/ICH9M-E) 4 port SATA Controller [AHCI mode] (rev 03) 00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 03) 00:1f.6 Signal processing controller: Intel Corporation 82801I (ICH9 Family) Thermal Subsystem (rev 03)   lspci | grep -i wireless    gives no output


How to calculate a wheel's linear velocity if there is slipping

I am working on a car simulation game and I need to know how to calculate a vehicle's velocity if the gas pedal was floored and the car started accelerating from rest with some slippage in the wheels. So, is the traction force completely gone, or it decreases? And how long will the wheels keep slipping till it rotates again? Given the angular velocity of wheels, mass of car, and both the static and kinetic friction coefficients.


Prove that the nonhomogeneous Neumann problem has a solution only if $\int_Ωf = 0$.

Let $Ω ⊂ \mathbb{R}^n$ be a bounded domain with smooth boundary $∂Ω$, and denote by $\vec{n}$ the outer unit normal to $∂Ω$. Prove that the nonhomogeneous Neumann problem  $$ \begin{cases}       ∆u = f & \text{ in }Ω \\       \langle∇u ,\vec{n}\rangle = 0 & \text{ on }∂Ω \\ \end{cases} $$  has a solution only if $\int_Ωf = 0$.  How would I go about doing this? Can anyone help to me understand where to start better?


How to find the General expression of $\sum_{k=0}^ {\lfloor n/3\rfloor} {n \choose 3k}$

Well as the title says I'm having problems trying to derive a general expression for this sum which involves cubic roots of unity   $$\sum_{k=0}^ {\lfloor \frac n 3\rfloor} {n \choose 3k}$$  Need help guys!


I left unopened pack of lamb burgers to thaw on the counter for 2-3 hours, if I cook them thoroughly should they still be safe to eat? Please advise, haste is appreciated.


What is the sum of this infinite series of roots: $$\sqrt{1+\sqrt{2+\sqrt{3+\sqrt{4 + \cdots+\sqrt{\infty}}}}}$$  This is an interesting expression because the increase created by the addition of the next term is offset by the square root introduced with the next term. the key is determining what the relationship between these two is exactly  I know it converges on an irrational number around 1.75 as I have tried computing it for a few small iterations. But I was wondering how to algebraically simplify this expression.  I have tried many things and ways to manipulate the expression but to no avail.


Are there other less famous yet accepted formalisms of Classical Mechanics?

I was lately studying about the Lagrange and Hamiltonian Mechanics. This gave me a perspective of looking at classical mechanics different from that of Newton's. I would like to know if there are other accepted formalism of the same which are not quite useful compared to others (because otherwise if would have been famous and taught in colleges)?


I want to print out handout for my beamer presentation. I am trying to get pgfpages package from MiKTeX package Manager without success? Can you please help?


To solve the non linear IVP $y'(t)=1-y^2(t)$

Let $y: \mathbb{R} \rightarrow \mathbb{R}$ satisfy the initial value problem $$y'(t)=1-y^2(t), \ t \in \mathbb{R},$$ $$y(0)=0$$   Then which of the following is true      $(A)$ $y(t_1)=1$ for some $t_1 \in \mathbb{R}$      $(B)$ $y(t)>-1$ for all $t \in \mathbb{R}$      $(C)$ $y$ is strictly increasing in $\mathbb{R}$      $(D)$ $y$ is increasing in $(0,1)$ and decreasing in $(1,\infty)$   I am a biology researcher learning differential equations for related work. I did  an undergraduate course in differential equations but have forgotten most of it. Any help would be appreciated.


What does small R squared mean in linear regression

I'm applying linear regression on. problem and getting very small R squared, e.g. 0.087 and adjusted R squared 0.057. This is very small for R squared. What does this mean for my regression? Does it mean the variables do not have enough predictive power?


Proving that the series 1 + ... + $1 / \sqrt{x}$ < $2 \sqrt{x}$  I am doing it by simple induction adding $1/\sqrt{x+1}$ to both sides, but I can't find a way to manipulate this expression and find that the new series is $< 2 \sqrt{x+1}$.  Can someone show me the correct process?  I failed many times and the furthest I've gotten has been to prove that it's $< 2 \sqrt{x+1} + 1$ which is close, but not enough.


Group commutator relations and the neutral element.

In Serge Lang: Algebra it is stated on page 69 that for a group $G$ that, if for $x,y,z\in G$ $y=[x,y]:=xyx^{-1}y^{-1}, z=[y,z], x=[z,x]$ is satisfied, we have $x=y=z=e$. I see that $y=[x,y]$ directly implies $y=x^{-n}y^{2^n}x^n$ for $n>0$, but I need a hint why it is true for $n=0$.  Edit: As pointed out in the comments: the relation should be $y^n=x^{-1}y^{2^n}x$.


Approximating a three-times differentiable function by a linear combination of derivatives

Let $\,f$ be three times differentiable on the interval $[a, b]$. Show that there is a $c$ such that: $$f(b) - f(a) = \frac{b-a}{2}(f'(a)+f'(b)) - \frac{(b-a)^3}{12}f'''(c).$$ Answered in the comments.


Do I need a transit visa for waiting 23 hours in Dubai airport?

I am an Indian citizen living in Ukraine. I will be traveling to India but I need to wait in Dubai airport 23 hours for my next flight to India. I will not be leaving Dubai airport.  So in this case do I need a transit visa?


MVC DateFormat show days - hours - minutes until now

I have one app in MVC for editing Users in Database. I also have CreatedDate(when the user was created) but ofcourse it shows me Date and Time when it was Created, but I need it to show me how many days, hours, minutes it was ago.   So when I created user 2 hours ago, it will show me like 0 days 2 hours 0 minutes instead of 8.9.2015 13:48. I know I have to customize this in Model, but I dont really know how. Thanks for help, there is the model.   public DateTime? CreatedDate { get; set; }


For which ideals $I$ is $k[x_1,\ldots,x_n]/I$ finite degree extension of $k$?

While reading about the Hilbert's Nullstellensatz, the following question naturally posed itself:     Question. Let $k$ denote a field, not necessarily algebraically closed.      For which ideals $I$ is the quotient ring $k[x_1,\ldots,x_n]/I$ a finite dimensional vector space over $k$?


How Can There Be Magnetic Force Without Velocity

Suppose there is a space with constant magnetic field, and a charged particle is moving in that space with a constant velocity, ofcourse it experiences a magnetic force and gets deflected.  But the particle it not necessarily moving wrt all frames. There may be some frame for which the particle doesn't move at all but still gets deflected. How is this possible, there must be some velocity for the particle to experience any deflection under influence of a magnetic field? Also a still particle in the same space doesn't experience any deflection. True, but the same particle may be moving wrt to some other frame without experiencing a magnetic force, so here we have a velocity but no magnetic force case.  I remember I have used the relation $|F| = qv|B|$ a lot before, but I am afraid to use it any more, these things are really confusing.


I want my footer to look like this   Currently, it looks like this :    My image is not fixed and I want "Thanks our friends at" to be near the image middle, like in the example above.  Another problem is when I resize the page, all the text from the footer exits from the div.  Code:     #footer {     background-color: #3f4951;     display:block;     margin:0 auto;     width:100%; }  section {     display:block; }  .row {     margin:0 auto;     width:100%; }   .footer-top {     padding: 37px 0 38px; }  .column {     padding-left: 20px;     padding-right: 20px; }  .footer-top nav {     float: left;     margin: 0;     max-width: 60%;     text-align: left; }   .footer-top nav a {    color:#a9abad; }  .footer-top .thanks {            margin-left:200px;    float:left;    max-width: 35%;    width: 250px; }  .thankstext {      color:#a9abad;      font-size: 16px; }   .footer-top * {     color:#a9abad;         }  .footimage {  }

                                        New or Existing Home Installation |                      Flushing |                      Serivicing |                      Service3 |                      Service4 |                      All Services will be listed here.

Thanks our friends at


Is "laic" an alternative word to the word "layperson"?

Can laic be used interchangeably with layperson as a gender-neutral alternative to layman and laywoman?  Example 1     The site is more suitable for the laics.   vs     The site is more suitable for laypersons.   Example 2     Laics are not allowed here.   vs     Laypersons are not allowed here.   Example 3     I am a laic to this subject.   vs     I am a layperson to this subject.


Is there an easy way to replace all symbolic links with the file they link to?


I tried to configure a NFS server with my Red Pitaya board, with a custom Ubuntu image, exactly as this page tells me to .  However when I try to mount my directories on my Client I got this error:  sudo mount 10.30.xx.xxx:/var/nfs/general /nfs/general mount.nfs: Protocol not supported   Where 10.30.xx.xxx is my Host's IP. I googled this error and found that executing this command  in my Host should tell me the allowed Protocols of my NFS service, so I got his:   rpcinfo 10.30.xx.xxx |egrep "service|nfs"    program version netid     address                service    owner     100003    2    tcp       0.0.0.0.8.1            nfs        superuser     100003    3    tcp       0.0.0.0.8.1            nfs        superuser     100003    4    tcp       0.0.0.0.8.1            nfs        superuser     100003    2    udp       0.0.0.0.8.1            nfs        superuser     100003    3    udp       0.0.0.0.8.1            nfs        superuser     100003    4    udp       0.0.0.0.8.1            nfs        superuser     100003    2    tcp6      ::.8.1                 nfs        superuser     100003    3    tcp6      ::.8.1                 nfs        superuser     100003    4    tcp6      ::.8.1                 nfs        superuser     100003    2    udp6      ::.8.1                 nfs        superuser     100003    3    udp6      ::.8.1                 nfs        superuser     100003    4    udp6      ::.8.1                 nfs        superuser   I proceed to use the option vers (and nolock because the console tells me to) but still got the same error with all 3 versions (vers=2,vers=3,vers=4)  mount -o rw,nolock,vers=2 10.30.xx.xxx:/var/nfs/general /nfs/general mount.nfs: Protocol not supported   How come all 3 versions are not supported? Am I using the options wrong?


As a monk, can I use Deflect Missiles to intentionally catch a projectile?

The description of the monk's Deflect Missiles feature says:     [...] you can use your reaction to deflect or catch the missile when you are hit by a ranged weapon attack.   If the attacker misses with the attack roll, am I able to use Deflect Missiles (hence, catch the projectile)? Or does the description imply otherwise? What if I want to catch the projectile intentionally?


How to archive files older than 7 days with 7-ZIP - command prompt line

Can someone help how to archive files using 7z commands to archive files  older than 7 days? For example in RAR we we are using  set ARCHIVE_FILE_OLDER_THEN=-to5d and how about in 7Z? Do we have any command which i can use to archives file older than 7 days? Below is the code. Thank you in advance  REM Exclude file types for archiving EXCLUDE_FILES_TYPES=-x!*.rar -x!*.zip -x!*.7z  REM Delete files after archiving set DELETE_AFTER_ARCHIVE=-sdel set EDI832_US_FILE=EDI832_US_ARCHIVE  REM Archive files only older then days **set ARCHIVE_FILE_OLDER_THEN=-to5d** - This part is not working  Set TODAY=%date:~4,2%-%date:~7,2%-%date:~10,4%-%hr%%time:~3,2%%time:~6,2%%time:~9,2%  set EXTRA_PARAM=%EXCLUDE_FILES_TYPES% %DELETE_AFTER_ARCHIVE% %ARCHIVE_FILE_OLDER_THEN%   7z a "%EDI832_US_FILE%_%TODAY%" %EXTRA_PARAM% -- This is the command where im archiving using 7 command (im giving the file name , date today )   As you can see im archiving files in this format(EDI832_US_ARCHIVE_04-13-2020-12145120.7z) but my command cannot read files older than 7 days ?  If anyone could help me optimize this code or improve it I would be greatly appreciated.


how're you doing? I am somewhat new to ubuntu and finding problem changing the root user name. My terminal displays priyank@Alex right now. I changed the second name to Alex using hostname and hosts. What I want is to make it Alex@Alex. Can anyone temme how can I do it?


I'm pretty new to the Spring Framework, I've been playing around with it and putting a few samples apps together for the purposes of evaluating Spring MVC for use in an upcoming company project. So far I really like what I see in Spring MVC, seems very easy to use and encourages you to write classes that are very unit test-friendly.  Just as an exercise, I'm writing a main method for one of my sample/test projects. One thing I'm unclear about is the exact differences between BeanFactory and ApplicationContext - which is appropriate to use in which conditions?  I understand that ApplicationContext extends BeanFactory, but if I'm just writing a simple main method, do I need the extra functionality that ApplicationContext provides? And just exactly what kind of extra functionality does ApplicationContext provide?  In addition to answering "which should I use in a main() method", are there any standards or guidelines as far as which implementation I should use in such a scenario? Should my main() method be written to depend on the bean/application configuration to be in XML format - is that a safe assumption, or am I locking the user into something specific?  And does this answer change in a web environment - if any of my classes needed to be aware of Spring, are they more likely to need ApplicationContext?  Thanks for any help. I know a lot of these questions are probably answered in the reference manual, but I'm having a hard time finding a clear breakdown of these two interfaces and the pros/cons of each without reading thru the manual with a fine-tooth comb.


Hey I know why they are there but is there anyway around having edges visible for cutting holes in ngons? I need it gone because the edges for my flashlight cut is visible on the model.


What am I missing to center this div/images?

I have 3 images here each with text underneath each image. They're all supposed to be hugging each other (so no spaces between them) and so far that's as far as I can get. The problem is that they're all going to the left side when I want the whole div to be centered.  HTML:

Text Here

Text Here

Text Here


Local webserver not accessible from local network using external IP / domain

I have a VM running a simple webhost.  But whenever I try to connect to it using my external IP (148.123.29.35) or domain (test.mydomain.com (A-record to 148.123.29.35)), my browser just tries to connect, then ends with "This webpage is unavailable".  This only happens from my local network, I have tested over VPN to my work place and it works fine from there, and a friend also tested for me.  I am using Asus RT-AC66U router with portforwarding port 80 to 192.168.1.200  Following is the result of a tracert request in cmd:    C:\Users\Username>tracert test.mydomain.com  Tracing route to test.mydomain.com [148.123.29.35] over a maximum of 30 hops:   1     1 ms    <1 ms    <1 ms  x.x.x.x.customer.cdi.cc [148.123.29.35]   Trace complete.    Following is the result of a tracert request in cmd to google.com    C:\Users\Username>tracert google.com  Tracing route to google.com [148.123.29.35] over a maximum of 30 hops:   1     1 ms    <1 ms    <1 ms  router.asus.com [192.168.1.1] 2 - 8                        << Hidden >> 9     8 ms     8 ms     8 ms  148.123.29.35   Trace complete.    I also want to point out that I am currently running a Space Engineers server which is working perfectly, both from internal and external computers (obviously port-forwarded..)  NOTE:   My actual domain has been replaced by test.mydomain.com My actual external IP has been replaced by 148.123.29.35 (google.com) My actual username has been replaced by Username My actual cdi. address has been replaced by cdi.cc Other IPs have been replaced by x.x.x.x


Where and how do I request for a new category/Q&A site?  What are the qualifications/requirements (if any have been set)?


what is the correct format of regex given to the serach method of the re module?

I'm trying to read the output of the  ~$ ifconfig command with a python script and grab the private IP-address. this is for example the output of the command: ~$ ifconfig   vmnet1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500         inet 172.16.216.1  netmask 255.255.255.0  broadcast 172.16.216.255         inet6 fe80::250:56ff:fec0:1  prefixlen 64  scopeid 0x20<link>         ether 00:50:56:c0:00:01  txqueuelen 1000  (Ethernet)         RX packets 0  bytes 0 (0.0 B)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 213  bytes 0 (0.0 B)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0  vmnet8: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500         inet 172.16.37.1  netmask 255.255.255.0  broadcast 172.16.37.255         inet6 fe80::250:56ff:fec0:8  prefixlen 64  scopeid 0x20<link>         ether 00:50:56:c0:00:08  txqueuelen 1000  (Ethernet)         RX packets 0  bytes 0 (0.0 B)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 213  bytes 0 (0.0 B)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0  so then if we go ahead and direct the output of the command to this python script... import sys import re  data = sys.stdin.read() x = re.search(r"^vmnet[2-9]:\s?.*(\n.*){7}", data) print(x)  ~$ ifconfig | ./script.py  the output should be: vmnet8: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500         inet 172.16.37.1  netmask 255.255.255.0  broadcast 172.16.37.255         inet6 fe80::250:56ff:fec0:8  prefixlen 64  scopeid 0x20<link>         ether 00:50:56:c0:00:08  txqueuelen 1000  (Ethernet)         RX packets 0  bytes 0 (0.0 B)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 213  bytes 0 (0.0 B)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0  but instead i simply get: None


When does a readied action trigger on "when the enemy moves"?

Follow up from   When my trigger is "when the enemy moves", when does the readied action trigger, after they move 5 ft, or after finished moving to their intended location?  I'm asking because I might want to use a pike to deliver the spell. If it triggers after the target move 5 ft, then I can still attack them and complete the spell. If it waits until the target completes their movement, then they might have leave the 10 ft reach of pike, and thus waste my spell.