My question is about the current accepted theory of Gravity.  First of all, let me start by saying that I am not a physicist, and that my mathematical understanding of Special/General Relativity (SR and GR) is extremely limited at best (so please try not to make fun of my thoughts/views).  I do agree that the presence of Mass (matter) in the universe does warp (curve) space, but I have a very hard time accepting that it also does the same to “Time”.    Let me try to explain to the best of my abilities:  I see time as just a necessary tool, a reference scale, like the ticking of a clock or the swinging of a pendulum, etc.  There really is no “time” per se, there is only movement and space, so when time appears to be affected, it is really just a change (warp, curve) in distances of the space of the measuring/reference tool.  I do feel the passing of time (due to memories, sunrise, sunsets, getting old, etc.) but it is really an illusion.  Because of this view, I can see how the path of an object that already has movement (momentum and energy) through space can be curved from its straight trajectory by the influence of a large mass encountered in the vicinity of the travel (ex: small asteroid passing by close to earth).    However, if there is no motion whatsoever (let us pretend that both objects appear instantaneously and are absolutely motionless with respect to each other in space), I just can’t see how they would start moving towards each other (ex: the asteroid begins moving towards earth).  From what I have read, SR/GR state that the static objects are always moving in time when stationary, and that is what causes the objects to begin to move, and to “accelerate” towards each other (the asteroid obviously accelerating towards the earth due to its much smaller size).  And then, once the asteroid lands on earth’s soil, and remains there on top of the surface, motionless, that it is “time” again (time passing by) what keeps it under the earth’s gravity force, per say.    So, since I do not think that time exists as described in the beginning of my question, it makes it very hard for me to even begin to understand this.  It feels that there has to be something else at play, involving only space and its characteristics, plus motion.  Sometimes I would like to think that it is the constant expansion of space which would cause the initial movement of the objects, and the subsequent acceleration.  Has anyone ever tried to find some kind of relationship between the rate of expansion of the Universe and the acceleration of gravity on earth?

It seems to me that there is no such thing as time. There  is only movement in the universe and we compare our own movement to a different object to have a sense of time. It can be a clock or a atomic vibration.  Does this view of time work within the current framework of phsics?  Do physicists have an explanation/proof about time's existence?


I have created a batch file and in inside the file i'm executing the below 2 commands in db2 command line. db2cmd -i -w db2clpsetcp db2 -tvmf D:\Db2_old.sql > D:\Vikas.log  I need to Pass a parameter to the batch file which will be used in the sql file for the extraction. Is there any way that we can achieve this?

I need to pass an ID and a password to a batch file at the time of running rather than hardcoding them into the file.  Here's what the command line looks like:  test.cmd admin P@55w0rd > test-log.txt


Let $n \geq 2$. Show that every element of $S_n$ can be written as a product of transpositions of the form $(1 i )$, for various $i$.  I have proved by induction that if $n \geq 2$, then every permutation in $S_n$ is a product of transpositions. Using the following, if $\sigma=(123\cdots k ) $ then $(123\cdots k )= (1k)(1(k-1))\cdots(12)$. But I don't know how to relate what I have to this exercise.  How could I finish the proof?

Prove that $S_n$ is generated by elements of the form $(1k)$.   I know that all elements in $S_n$ can be expressed as a multiplication of transpositions. I tried to take the direction of proving that every transposition can be written in the form of a product of elements of the form $(1k)$.  I started with a simple example of $(23)\in S_3$, but no matter what I tried I could not write it in the form of a multiplication of elements of the form $(1k)$. Am I in the right direction?


When I check the flagged post, flagged by me   I found there are several post in recent first order but there is are filters.  As if I want to filter as per the status of the flag    and also as per type of flag

Here is my flagging summary on SU:   Your flagging history   32 posts flagged as requiring moderator attention    2 are waiting for review   3 were marked valid   1 were marked invalid   (older flags were not recorded valid/invalid)    2 posts marked as spam    It is too complicated to look for invalid flags. Would it be possible to make filters on the top of the page (like on favorites for example) with:  By date, By type (off-topic, spam, dupes), By status (accepted, pending, rejected)  It would make it easier for reviewers to check their flagging and eventually know what to improve on.  Or is there another easy way to audit this?


I've badly damaged my package system. So I found another solution,  sudo apt-get build-dep <package>  But when I typed sudo apt-get build-dep update-manager, I got,  E: You must put some 'source' URIs in your sources.list     Then I accessed it using the sudo nano /etc/apt/sources.list. The list was blank. Now I'm unsure on how to add more source URIs. I cannot access the software updater to change it. I've tried Synaptic Package Manager.   sudo apt-get -f install    Reading package lists...  Done   Building dependency tree                                                                              Reading state information... Done   E: The package python3 needs to be reinstalled, but I can't find an archive for it.   Update:  I have edited sources.list using  on  and replacing bionic with cosmic.  Now when I try to launch software-properties-gtk, I'm getting:  bash: /usr/bin/software-properties-gtk: /usr/bin/python3: bad interpreter: Too many levels of symbolic links   Outputs for symbolic links of python3:  $ ls -l /usr/bin/python3                                                      lrwxrwxrwx 1 root root 18 May 27 20:30 /usr/bin/python3 -> /usr/bin/python3.6  $ ls -l /usr/bin/python3.6   lrwxrwxrwx 1 root root 25 May 27 16:31 /usr/bin/python3.6 -> /etc/alternatives/python3  $ ls -l /etc/alternatives/python3 lrwxrwxrwx 1 root root 18 May 27 16:31 /etc/alternatives/python3 -> /usr/bin/python3.6     Output of ls -l /usr/bin/python*:     lrwxrwxrwx 1 root root      18 May 27 23:10 /usr/bin/python -> /usr/bin/python3.2    lrwxrwxrwx 1 root root       9 Jun  7  2018 /usr/bin/python2 -> python2.7    -rwxr-xr-x 1 root root 3691008 Apr  9 05:50 /usr/bin/python2.7 lrwxrwxrwx 1 root root      18 May 27 20:30 /usr/bin/python3 -> /usr/bin/python3.6   lrwxrwxrwx 1 root root      25 May 27 16:31 /usr/bin/python3.6 -> /etc/alternatives/python3       lrwxrwxrwx 1 root root      33 Apr  9 05:59 /usr/bin/python3.6-config -> x86_64-linux-gnu-python3.6-config      -rwxr-xr-x 1 root root 4530552 Apr  9 05:59 /usr/bin/python3.6m lrwxrwxrwx 1 root root      34 Apr  9 05:59 /usr/bin/python3.6m-config -> x86_64-linux-gnu-python3.6m-config     -rwxr-xr-x 2 root root 4804160 Apr  9 05:56 /usr/bin/python3.7    -rwxr-xr-x 2 root root 4804160 Apr  9 05:56 /usr/bin/python3.7m    lrwxrwxrwx 1 root root      16 Oct 25  2018 /usr/bin/python3-config -> python3.6-config        lrwxrwxrwx 1 root root      10 Oct 25  2018 /usr/bin/python3m -> python3.6m lrwxrwxrwx 1 root root      17 Oct 25  2018 /usr/bin/python3m-config -> python3.6m-config

I am looking for the best method to restore /etc/apt/sources.list to default from the command line.  Is there no way to reference the source code of the package which generates this file or something like that? I want a trusted and version-independent way of restoring this file.  Solutions Ruled Out  Before you mark this as a duplicate, note that I have reviewed  already. It is only applicable if you have the Ubuntu GUI available. This question is specific to the command line.  I have also reviewed  where the accepted solution is someone pasted the contents of their sources.list file. This is not an appropriate way to restore the file as the intentions of the person providing the file contents cannot be verified and the file is subject to change with new releases.  I checked out the , but this is also not from Ubuntu so I do not plan to use it.


Whenever I tried to do, it failed. Is there anyone to help? $$\int_0^\infty \frac{dx}{1+x^6}$$

$$I=\int_0^\infty\frac{1}{1+x^6}dx$$  How do I evaluate this?


I'm having a bit of trouble imagining the time evolution of non-gaussian wavepackets. For a free particle, I usually imagine a diffusing gaussian (in both $x$ and $p$ where $<p>(t)=p_0$) with it's peak having a velocity $p_0/m$. I want to see some more variety of initial wavefunctions and their time evolutions such as a finite sum of these Gaussians with different $<p>$ or infinite superposition of these wavepackets. We can talk similarly for the hydrogen atom. Time evolution for the CoM frame as Gaussian(s) along with non-CoM states. I can only imagine if the overall wavefunction is like (diffusing Gaussian in $R$)$\times$(Superposition of bound states) i.e. separable wavefunction. I haven't seen many books talk about proper time evolution of hydrogen atom as whole (including CoM). Does anyone of you know of any resources such as animations/applets which show time evolution of probability distribution assuming some normalizable initial states? I think this is important to get an intuition for quantum mechanical treatment of particles.

I'm having a hard time finding animations for 1D or 2D square well, SHO, free particle with barriers, etc, that I'm sure are "trustworthy". It's the sort of thing I would do in python in my spare time if I had any, and I know plenty of people have done it, but I don't like trusting someone's random github repo or youtube channel. Is there a recommended Youtube channel or PC/Mac program that is maintained, trustworthy, and somewhat user-friendly? I'm aware of some of the pedagogy outfits like QuiLT and Phet that make flash programs for teaching, but I find those a bit clunky/old/low-level; I'm looking basically for a more general Schrodinger equation solver for a user-specified potential, or just a repository of animations.


I have looked every pages, links, forums etc. It is a standalone application.  I add all paths that I can find to the PATHS and PYTHONPATH is here:  C:\OSGeo4W64\apps\qgis-dev\python C:\OSGeo4W64\apps\qgis-dev\python\plugins C:\OSGeo4W64\apps\qgis-dev\python\qgis   However it doesn't work and gives the same error for 12 days...  from qgis.core import * from qgis.gui import * from qgis.utils import * from PyQt5.QtCore import * from PyQt5.QtGui import *  app = QgsApplication([], True) path = "C:/OSGeo4W64/apps/qgis-dev" app.setPrefixPath(path, True) app.initQgis()  canvas = QgsMapCanvas() title = "PyQGIS Standalone Application Example" canvas.setWindowTitle(title) canvas.setCanvasColor(Qt.white)  layer_info = 'LineString?crs=epsg:4326' layer = QgsVectorLayer(layer_info, 'MyLine', "memory") pr = layer.dataProvider() linstr = QgsFeature() wkt = "LINESTRING (1 1, 10 15, 40 35)" geom = QgsGeometry.fromWkt(wkt) linstr.setGeometry(geom) pr.addFeatures([linstr]) layer.updateExtents() QgsProject.instance().addMapLayer(layer) canvas.setExtent(layer.extent()) canvas.setLayers([layer]) canvas.zoomToFullExtent() canvas.show() exitcode = app.exec_() # QgsApplication.exitQgis() sys.exit(exitcode)   Here is the error:  Traceback (most recent call last):   File "C:/Users/Mustafa Uçar/Desktop/sil.py", line 1, in <module>     from qgis import _core   File "C:\OSGeo4W64\apps\qgis-dev\python\qgis\__init__.py", line 72, in <module>     from qgis.core import QgsFeature, QgsGeometry   File "C:\OSGeo4W64\apps\qgis-dev\python\qgis\core\__init__.py", line 34, in <module>     from qgis._core import * ImportError: DLL load failed: Specified module could not found.   System information:  QGIS 2.99 - Python 3.6 - Win10*64

I am trying to run a standalone application. However, it does not run the program because of mentioned error in title. Here is my code:  from qgis.core import * from qgis.gui import * from qgis.utils import * from PyQt5.QtCore import * from PyQt5.QtGui import *  app = QgsApplication([], True) path = "C:/OSGeo4W64/apps/qgis-dev" app.setPrefixPath(path, True) app.initQgis()  canvas = QgsMapCanvas() title = "PyQGIS Standalone Application Example" canvas.setWindowTitle(title) canvas.setCanvasColor(Qt.white)  layer_info = 'LineString?crs=epsg:4326' layer = QgsVectorLayer(layer_info, 'MyLine', "memory") pr = layer.dataProvider() linstr = QgsFeature() wkt = "LINESTRING (1 1, 10 15, 40 35)" geom = QgsGeometry.fromWkt(wkt) linstr.setGeometry(geom) pr.addFeatures([linstr]) layer.updateExtents() QgsProject.instance().addMapLayer(layer)  canvas.setExtent(layer.extent()) canvas.setLayers([layer]) canvas.zoomToFullExtent() exitcode = app.exec_() QgsApplication.exitQgis() sys.exit(exitcode)   When I run it, I get this error:  Traceback (most recent call last):   File "C:/Users/DELL/Desktop/MyMap/myMap.py", line 1, in <module>     from qgis.core import *   File "C:\OSGeo4W64\apps\qgis-dev\python\qgis\__init__.py", line 72, in <module>     from qgis.core import QgsFeature, QgsGeometry   File "C:\OSGeo4W64\apps\qgis-dev\python\qgis\core\__init__.py", line 34, in <module>     from qgis._core import *   ImportError: DLL load failed: The specified module could not be found.  Python version is: 3.6 PyQt   version is: PyQt5.9 Windows 10 - 64bit  I also add many path:  %SystemRoot%\system32 %SystemRoot% %SystemRoot%\System32\Wbem %SYSTEMROOT%\System32\WindowsPowerShell\v1.0\ C:\OSGeo4W64 C:\OSGeo4W64\apps C:\OSGeo4W64\apps\gdal-dev C:\OSGeo4W64\apps\gdal-dev\bin C:\OSGeo4W64\apps\gdal-dev\pymod3\Lib\site-packages C:\OSGeo4W64\apps\grass\grass-7.2.2\bin C:\OSGeo4W64\apps\Python36 C:\OSGeo4W64\apps\Python36\Scripts C:\OSGeo4W64\apps\Python36\DLLs C:\OSGeo4W64\apps\Python36\lib\site-packages C:\OSGeo4W64\apps\qgis-dev C:\OSGeo4W64\apps\qgis-dev\bin C:\OSGeo4W64\apps\qgis-dev\lib C:\OSGeo4W64\apps\qgis-dev\python C:\OSGeo4W64\apps\qgis-dev\python\qgis C:\OSGeo4W64\apps\Qt5 C:\OSGeo4W64\apps\Qt5\lib C:\OSGeo4W64\bin C:\OSGeo4W64\apps\qgis-dev\python C:\OSGeo4W64\apps\Python36\lib C:\OSGeo4W64\include C:\Users\Mustafa Uçar\AppData\Roaming\QGIS\QGIS3\profiles\default C:\Users\Mustafa Uçar\AppData\Roaming\QGIS\QGIS3\profiles\default\QGIS   How can I fix this error?


I'm replacing a mailbox post that rusted at the ground level

I have a steel pole holding up part of my house. It is bolted to concrete footings. I am about to build a deck around but would like to rust-proof the bottom before I do this to prevent any future issues.   Given that the bottom 30cm will not be visible, what is the best way I can ensure it will not rust? I was thinking some Kill-Rust primer and possibly some bitumen paint to keep the water away.


I want to do a build that is Paladin and Oracle, but I can't seem to find any concrete information on going about this. If I start at Paladin, get to level 2, then level Oracle to 4, can I then continue getting levels in Paladin at total level 7, or can I not go back to previous classes?  One friend has told me you cannot do that, but I can't find anything online about it. We are playing Pathfinder and this is a new half-elf character starting at level 4, so I'm not invested in it yet.

In 3.5 D&D,  have severe restrictions on multiclassing:     Like a member of any other class, a paladin may be a multiclass character, but multiclass paladins face a special restriction. A paladin who gains a level in any class other than paladin may never again raise her paladin level, though she retains all her paladin abilities.   Because Pathfinder is based on 3.5 D&D, do Pathfinder paladins face the same restriction? That is, if a Paladin multiclasses to say, a fighter, can she take another level of Paladin later on?


I just started learning Blender from YouTube. I got a problem here:   I am on a GNU/Linux system with XFCE DE (XFWM4 WM). My problem is when I want to select vertices of an object (also, described in the video) with Alt + Primary Mouse button, it starts dragging the windows of Blender. Alt + Primary mouse button is also what I use all the time to drag windows. What is the alternative way to select all the edges of an object?

I am trying to use the Alt+Right Click to select edge loops in Linux Mint but this shortcut doesn't work it is already used for Linux to reduce a window. I have checked the keyboard shortcut but it doesn't appear.


How am I supposed to install nvidia drivers from X-Swat? I try  sudo add-apt-repository ppa:ubuntu-x-swat/x-updates -y sudo apt-get update sudo apt-get install nvidia-graphics-drivers-304   and I get  E: Unable to locate package nvidia-graphics-drivers-304   The  says there is nvidia-graphics-drivers-304 for trusty, why wouldn't it install?

How am I supposed to install nvidia drivers from xorg-edgers? I try  sudo add-apt-repository ppa:xorg-edgers/ppa -y sudo apt-get update sudo apt-get install nvidia-graphics-drivers-331   and I get  E: Unable to locate package nvidia-graphics-drivers-331   The   nvidia-graphics-drivers-331 for trusty, why wouldn't it install?


I and my friend are both members of Stack Overflow.  I told my friend to vote me up.  He upvoted almost all of my questions and answers.  I got almost 150 upvotes.  On the next day, when I visited Stack Overflow, I found my reputation as it had been before the upvotes.  How does Stack Overflow identify, differentiate, and track dummy/unnecessary upvotes?

How many users have created more than one profile on SO to vote themselves on their other original profile? There are some benefits when you have more reputation and sometimes you don't want a single -1 vote on your question or answer. In this case you may have an extra account to convert that -1 vote into 0 vote and  upvote for each of your questions and answers to gain reputation. I think it is not a good thing to do as a good developer.  Is there any way to recognize this situation? I think there should be some stats in each user's profile about how many votes are posted by each user on him/her or something like that.  So how many users have more than one profile? How to handle this situation? I have not created one yet but............ I don't think so :)


Find $\text{Aut}\left(\Bbb{Z}_{15}\right)$. Use the Fundamental Theorem of Abelian Groups to express this group as an external direct product of cyclic groups of prime power order.  For this would it just be as simple as $U(5) \oplus U(3)$ due to $3$ and $5$ being the only factors of $15$ in $\Bbb{Z}_{15}$? I feel as though I am definitely missing a key piece since this seems to be easy.

I am writing another exam in Algebra this week and this time the main topic is automorphism. I was again going through the example exercises and exams from previous years and this problem is giving me a hard time to understand:  Prove that for group of automorphisms $\def\Aut{\operatorname{Aut}}\Aut(\mathbf{Z_{n}})$ holds  $\Aut(\mathbf{Z_{n}})\simeq \mathbf{Z_{n}^{*}}$ where $\mathbf{Z_{n}^{*}}=\{1 \leq k \leq q | \gcd(k,n)=1\} $.  My main issue with this problem is that it seems very "general" and I don't really know how to address it with any of the techniques we have used.  Could you please show me some ways this could be approached? I appreciate your help.


I search online for the solution, but nothing :(.  I write this simple rule  RewriteRule ^(.*)$ http://www.mysite.com/$1 [P,NE,QSA,L]   In mysite.it i have an .htaccess with this rule and it's ok, but if i have a link  " name.html"  the server point to ""  I try many solution but i can't solve.  I try this and many shades of...  RewriteRule ^(.*)(%20)(.*)$ "http://www.mysite.com/$1$3" [P,NE,QSA,L]   Thanks!

This is a  about Apache's mod_rewrite.   Changing a request URL or redirecting users to a different URL than the one they originally requested is done using mod_rewrite. This includes such things as:   Changing HTTP to HTTPS (or the other way around) Changing a request to a page which no longer exist to a new replacement. Modifying a URL format (such as ?id=3433 to /id/3433 ) Presenting a different page based on the browser, based on the referrer, based on anything possible under the moon and sun. Anything you want to mess around with URL   Everything You Ever Wanted to Know about Mod_Rewrite Rules but Were Afraid to Ask!  How can I become an expert at writing mod_rewrite rules?   What is the fundamental format and structure of mod_rewrite rules? What form/flavor of regular expressions do I need to have a solid grasp of? What are the most common mistakes/pitfalls when writing rewrite rules? What is a good method for testing and verifying mod_rewrite rules? Are there SEO or performance implications of mod_rewrite rules I should be aware of? Are there common situations where mod_rewrite might seem like the right tool for the job but isn't? What are some common examples?   A place to test your rules  The  web site is a great place to play around with your rules and test them. It even shows the debug output so you can see what matched and what did not.


I have a table where I save authors and songs, with other columns. The same song can appear multiple times, and it obviously always comes from the same author. I would like to select the author that has the least songs, including the repeated ones, aka the one that is listened to the least. The final table should show only one author name.

Table:   UserId, Value, Date.   I want to get the UserId, Value for the max(Date) for each UserId. That is, the Value for each UserId that has the latest date. Is there a way to do this simply in SQL? (Preferably Oracle)  Update: Apologies for any ambiguity: I need to get ALL the UserIds. But for each UserId, only that row where that user has the latest date.


I would like to be able to globally showing and hiding proofs on a document, and be able to use macros to open and close the proof environments. Here is my current MWE:  \documentclass{article} \usepackage{amsmath} \usepackage{amsthm} \newif\ifshowproof \newcommand{\bp}{\ifshowproof\begin{proof}} \newcommand{\ep}{\end{proof}} \showprooffalse  \begin{document} Goodbye. \bp Hello. \ep\fi Test. \end{document}   As explored here: , I cannot simply add \fi to the definition of \ep, however, I would like to have a "catch-all" macro so to say, that is, ideally something that would execute as \end{proof}\fi. Is there an easy way to do this?

In the recent post , Werner helped me to redefine a proof environment which can be hidden by an optional boolean argument (showProof). Without an argument, somehow the line/paragraph breaking is not correct. How can one fix this?  \documentclass{scrartcl}  \usepackage{ifthen} \usepackage{environ} \usepackage{amsthm}  \newboolean{showProof}% for showing proofs \setboolean{showProof}{true}% setting the switch \newif\ifstarttheorem  % proof environment (with hide feature) \makeatletter \providecommand{\env@proof@save@env}{} \providecommand{\env@proof@process}{} \RenewEnviron{proof}[2][showProof]{   \gdef\@tmp{#1}%   \ifthenelse{\boolean{#1}}{\par\pushQED{\qed}%     \normalfont\topsep2\p@\@plus2\p@\relax     \trivlist\item[\hskip\labelsep\sffamily\bfseries Proof~#2]\gdef\mycurrenvir{proof}\global\starttheoremtrue\mbox{}\hfill\\*\ignorespaces     \BODY}{\ignorespaces} }[\ifthenelse{\boolean{\@tmp}}{%   \gdef\mycurrenvir{\relax}   \popQED\endtrivlist\@endpefalse }{\ignorespacesafterend}] \makeatother  \begin{document} Just some text \begin{proof}   Just some text in a standard proof. As we can see, there is a problem. \end{proof} \begin{proof}[false]   Proof with optional argument set to \texttt{false}. This proof correctly does   not appear. \end{proof} \begin{proof}[showProof]{(Heading)}   Proof with optional argument (\texttt{true}) and second argument ``(Heading)'' \end{proof} \end{document}


I have instlled windows 7 in my pc. I need a linux os, hence i chose Ubuntu. Can i install Ubuntu in my c drive ?

I need my pre-installed version of Windows 7 (or any other version of Windows), how could I install Ubuntu without erasing it?


I'm trying to pin down a word or phrase that concisely describes a person who intentionally gets other people to do things for them that they could easily do themselves, as a form of either conscious or subconscious power-play. A mix somewhere between being lazy, manipulative, exploitative, discourteous, and so on. An example of how it would be used is, "Look at Stella being ... again, lying on the couch and getting her father to get pass her the remote while he was sitting even further away from it than her!"

In a way like a slave master. More though like say someone who had robots do all their work and they were never themselves productive and had no drive. If you've read R.U.R. you'll understand the question better. I'm looking for a word with more definition than just lazy.  Update 1: It think I may actually go with drone if anything. I think that definition fits what I'm looking for the best. I also liked the definition of the British term layabout that one person mentioned, but I will probably use drone. Thanks for all the help and sorry if I was confusing or unclear.  Update 2: I needed this word for use in an essay I was writing which I have now handed in. Thanks for the help guys. No more suggestions needed.


I am looking for the title of a book / series i read many years ago, i have tried google but i just cant seem to get the search right so any help would be great.  The basis of the story is about a young guy who ends up winning the lotto which allows him to get the best health care and in the end transfer his mind to a computer and travel around on a star ship.  I cannot remember the characters name.  If i remember correctly it was a 2 or 3 book series.  If there are any other details that may help let me know what could be useful.  Again thank you.

I am looking for a novel that I'd love to re-read it with my wife (my 13-year old self must be proud of me I guess). Key Plot points The plot was about humanity finding an alien station on an orbit of Earth. (I'm not sure if it wasn't Moon itself). On this station there were thousands of ships ready to travel so there rose a company that paid people to get on those ships and explore the galaxy. The problem was humans didn't understand how to steer those ships so they had to rely on preset targets. Of course there was no telling where particular ship was to go and fair amount of them never returned. Chronology and other relevant information I read it as an early teenager back in early 2000s. It was Polish translation of a foreign (possibly English) story. I think (not sure) that the book wasn't new at the time. It was just one of those books you dig out in a library and take to see if it's good. I don't recall cover either and even if I did it'd be of the Polish version. Additional information could be that the narration was led along the psychoanalytics of the main protagonists where he relives his memories from inside the station and his journeys.


I'm working through a pair of power series questions.  Find the radius of convergence for the following series: (1) $\sum_{n=0}^{\infty} 2^{n/2}x^n$ (2) $\sum_{n=0}^{\infty} 2^{n/2}x^{2^n}$ The unusual series is the second one.  It has the term $x^{2^n}$.  In particular its exponent is $2^n$ and I'm not sure how to proceed for figuring out its radius of convergence. How would you figure out the radius of convergence?  What would you use to do this?

So i got this  power series $$\sum_{k=0}^\infty 3^k \cdot z^{2^k}$$  Can i do the convergence test like this:  $$\text{ratio test} \Longrightarrow \frac{3^{k+1}\cdot z^{2^{k+1}}}{3^k \cdot z^{2^k}} = \frac{3 \cdot z^{2^{k+1}}}{z^{2^k}} = 3 \cdot z^2 \lt 1 \Longleftrightarrow |z| < \frac{1}{\sqrt3}$$


I have a directory in which I have lot of files in this format only. Below are just examples for two of my files.  file_948_of_2000_push_data_12345.log file_950_of_2000_push_data_12345.log   As you can see only difference is this file number 948 and 950. Now I want to rename all these files in this particular format as shown below:  files_948.log files_950.log   What is the best way I can do this?

I have a directory full of images:  image0001.png image0002.png image0003.png ...   And I would like a one-liner to rename them to (say).  0001.png 0002.png 0003.png ...   How do I do this?


Why do we define the convolution?  Why is convolution useful?  What is the purpose of the geometry of convolution of two functions in plane? Can we draw the convolution of two functions without compute the integration?  What is idea of definition of convolution?  What is relation between convolution and probibility?  I have already read

I am currently learning about the concept of convolution  between two functions in my university course. The course notes are vague about what convolution is, so I was wondering if anyone could give me a good explanation. I can't seem to grasp other than the fact that it is just a particular integral of two functions. What is the physical meaning of convolution and why is it useful? Thanks a lot.


I want to know why, in kinematics, is velocity described as $v = \frac{\Delta x}{\Delta t}$, and why it is not described as any other expression (like a multiplication), why does a division is the one that fits for velocity.

I have a rather basic, maybe even dumb, question. I was wondering why speed is defined as it is:  $s = d/t$  Of course, what the equation means is not too difficult to understand. However, there are many ways that d and t could be related, for instance:  $s = d + t$  I am not sure who the first person to define speed was, but I was wondering how they made the decision to define speed as distance divided by time.


I am trying to prove the following (Please let me know if it isn't actually true): Consider the range $[1,n]$ where $n \in \mathbb{Z}^+$. Consider $a,b \in \mathbb{Z}^+$.Prove that, in this range, there are $\left\lfloor\frac{n}{\text{lcm}(a,b)}\right\rfloor$ numbers that are divisible by both $a$ and $b$. I have the intuition for this. E,g, let a=2, b=5 and n=200. Being divisible by 2 and 5 implies being divisible by 10, and 201 = 20*10 + 1 thus there are 20 numbers divisible by both 2 and 5. However, I am not able to formulate a proof. One of the first issues was when I was attempting to prove $a|x \cap b|x \implies \text{lcm}(a,b)|x$. I'd start with $a|x \iff x = ac$ and $b|x \iff x = bd$ thus we have $x = ac = bd$ but not be sure where to continute. I know that $\text{lcm}(a,b) = \frac{ab}{\text{hcf}(a,b)}$ and think I need to apply this at some point but not sure how. Would this be easier to prove with the restriction that a,b are coprime? Any help would be appreciated.

Is $$d_1\mid n,d_2\mid n\iff [d_1,d_2]\mid n$$ true ? And if yes, how can I prove it ? I recall that $[d_1,d_2]$ is the least common multiple.  My tries  For the implication : Let $d_1\mid n$ and $d_2\mid n$. Then, $d_1d_2\mid n^2$. By the way, since $d_1,d_2\mid n$, we have that $(d_1,d_2)\mid n$ where $(d_1,d_2)=:\gcd(d_1,d_2)$  and thus $$[d_1,d_2](d_1,d_2)\mid n^2.$$  Question: How can I get $[d_1,d_2]\mid n$ from this?  For the converse, since $d_1,d_2\mid [d_1,d_2]\mid n$, the claim follow.


I've been looking around the forums for some answers to the question I have. I've found some answer that seem to help but nothing that answers my specific question. That question being how to rotate an object in world space around a non origin point.  I have a grappling hook that I am trying to implement inside of a game I am making for a final college project. This grappling hook collides with another object in world space and I then want the player to rotate around this point as if a rope were present.  I have the point at which the grapple collides the point at which the player is located and the origin. I tried the standard translate to the origin rotate and translate back and that did not work.  This is being done in DirectX 9 and it is a C++ game. Any  help you could offer would be greatly appreciated. If you need anymore info please ask.  Edit: I should also add that we are doing a vector based storage for this setup. So I store the matrices in vectors(i.e Forward,Direction,Right,Position) and build the matrices on the fly  void CSpatialFrame::RotateAbout(D3DXVECTOR3 _Point, float _fDegPitch, float _fDegYaw, float _fDegRoll) {     D3DXMATRIX RotationMatrix;     D3DXMatrixRotationYawPitchRoll(&RotationMatrix, D3DXToRadian( _fDegYaw ), D3DXToRadian( _fDegPitch ), D3DXToRadian( _fDegRoll ));     D3DXVECTOR3 playerPos = m_Position;     m_Position = _Point;      D3DXMATRIX PlayerMatrix;      PlayerMatrix._11 = m_RightVector.x;     PlayerMatrix._21 = m_RightVector.y;     PlayerMatrix._31 = m_RightVector.z;      PlayerMatrix._12 = m_UpVector.x;     PlayerMatrix._22 = m_UpVector.y;     PlayerMatrix._32 = m_UpVector.z;      PlayerMatrix._13 = m_DirectionVector.x;     PlayerMatrix._23 = m_DirectionVector.y;     PlayerMatrix._33 = m_DirectionVector.z;      PlayerMatrix._14 = m_Position.x;     PlayerMatrix._24 = m_Position.y;     PlayerMatrix._34 = m_Position.z;      D3DXMatrixTranslation(&PlayerMatrix, _Point.x, _Point.y, _Point.z);      //D3DXMatrixTranslation(&PlayerMatrix, m_Position.x, m_Position.y, m_Position.z);      D3DXMatrixMultiply(&PlayerMatrix, &RotationMatrix, &PlayerMatrix);      //D3DXMatrixTranslation(&PlayerMatrix, _Point.x, _Point.y, _Point.z);      m_RightVector.x = PlayerMatrix._11;     m_RightVector.y = PlayerMatrix._21;     m_RightVector.z = PlayerMatrix._31;      m_UpVector.x = PlayerMatrix._12;     m_UpVector.y = PlayerMatrix._22;     m_UpVector.z = PlayerMatrix._32;      m_DirectionVector.x = PlayerMatrix._13;     m_DirectionVector.y = PlayerMatrix._23;     m_DirectionVector.z = PlayerMatrix._33;      m_Position.x = PlayerMatrix._14;     m_Position.x = PlayerMatrix._24;     m_Position.x = PlayerMatrix._34; }

I have some models that I want to rotate using quaternions in the normal manner, except instead of rotation about the origin, I want it to be offset slightly. I know that you don't say, in 3d space, that you rotate about a point; you say you rotate about an axis. So I'm visualizing it as rotating about a vector whose tail is positioned not at the local origin.  All affine transformations in my rendering / physics engine are stored using SQT (scale, quaternion, translation; an idea borrowed from the book Game Engine Architecture.) So I build a matrix each frame from these components and pass it to the vertex shader. In this system, translation is applied, then scale, then rotation.  In one specific case, I need to translate an object in world space, scale it, and rotate it about a vertex not centered at the object's local origin.  Question: Given the constraints of my current system described above, how can I achieve a local rotation centered about a point other than the origin? Automatic upvote to anyone who can describe how to do this using only matrices as well :)


scenerio: runners on second and third, two outs.  Ball hit to shortstop who immediately tags out the runner going from second to third.  This happens before runner gets to first and before runner from third scores. Would the run count since the last out was not a force but a tag out?

Under what conditions can a run be scored on a play that results in a 3rd out for the team?  I was under the impression that if a 3rd out happens, all runs that might have scored before time during that at-bat are invalid, but apparently there is more to it than that.


So I am taking a logic course and I supposed to write down a couple of math statements using only mathematical logic symbols (the most basic ones but I can use disjunction and there exists). There are statements that require "such that" symbol in my opinion but I am pretty sure that is implied and I am not sure how to proceed . For example, Any two real numbers can divide some one number. I don't have the symbol for divide so I would have to work around that. What I would do is write for all $a,b$, there exists $x$ "such that" there exists $v_1,v_2$ "such that" $x=av_1$ and $x=bv_2$. Is this correct? Do I just ignore the such that and not write it when I use symbols?

If $A$ is a set, we can use the set notation  $$A=  \{ b \mid\text{property $p_1$ of $b$}\}$$  But say $A$ is an element like $b$,  $$A = b \mid \text{property $p_1$ of $b$}$$  is this a usual notation?  I am trying to say that $A$ is a $b$ that such that( $\mid$ ) it satisfies property $p_1$ of $b$, and assume that exactly one $b$ satisfies property $p_1$.  Otherwise, is there a more usual convention to express this?


Until a few weeks ago, the style worked perfectly and this was the result:    But recently it has stopped working without any modification and I have no idea why, now it produces:   How can I recover that style? Or how can I make one equal.  the code is  \documentclass{report}  \usepackage{color,lmodern,titlesec}  \newcommand\chptitle[1]{\parbox[b]{\dimexpr\textwidth-87pt}{\raggedright#1}}  \newcommand{\hsp}{\hspace{12pt}}  \titleformat{\chapter}[hang]{\huge\bfseries}{{     \fontsize{4.1em}{4.1em}\selectfont\color{black}%      \thechapter}\hsp\textcolor{blue}{\vrule height 2.7em width 1pt}\hsp}{0pt}{\Huge\bfseries\chptitle}   \begin{document}    \chapter{Aaaa bbbb}     aa     \chapter{Aaaa bbbb Aaaa bbbb Aaaa bbbb}     bb     \end{document}   The list of files generated by \listfiles in the log file is   *File List*   report.cls    2014/09/29 v1.4h Standard LaTeX document class   size10.clo    2014/09/29 v1.4h Standard LaTeX file (size option)    color.sty    2016/01/03 v1.1b Standard LaTeX Color (DPC)    color.cfg    2007/01/18 v1.5 color configuration of teTeX/TeXLive   pdftex.def    2011/05/27 v0.06d Graphics/color for pdfTeX infwarerr.sty    2010/04/08 v1.3 Providing info/warning/error messages (HO)  ltxcmds.sty    2011/11/09 v1.22 LaTeX kernel commands for general use (HO)  lmodern.sty    2009/10/30 v1.6 Latin Modern Fonts titlesec.sty    2016/03/15 v2.10.1 Sectioning titles   ot1lmr.fd    2009/10/30 v1.6 Font defs for Latin Modern supp-pdf.mkii  ***********

After reinstalling TeXLive distribution (install-tl-20160318, Ubuntu 14.04), a issue occurs with the updated version of the titlesec package: the section numbering is lost.  What could it be missing? Is there a modification I have not seen?  Below is a MWE comparison of the two versions. The prevtitlesec package is a reinstall of the previous version (2011/12/15).  \documentclass{book} \usepackage[margin=2cm,a4paper]{geometry} %\usepackage{prevtitlesec}% 2011/12/15 version \usepackage{titlesec}% 2016/03/15 version \usepackage{lipsum}  \begin{document}  \chapter{Title of the first chapter} \lipsum[1] \section{A test section} \lipsum[4] \subsection{A test subsection} \lipsum[4] \subsection{A test subsection} \lipsum[4]  \end{document}   titlesec package 2011/12/15:    titlesec package 2016/03/15:


I need to do an IN clause in my ID (INT)  But when I do this:        strQuery = "SELECT something FROM some table \n";   strQuery += "WHERE ID IN ({0})";    var idParameterList = new List<string>();    foreach (var id in lstLigID)   {       idParameterList.Add(id.ToString());   }    dbContext.Database.ExecuteSqlCommand(strQuery, string.Join(",", idParameterList));   I get this error:

How do I parameterize a query containing an IN clause with a variable number of arguments, like this one?  SELECT * FROM Tags  WHERE Name IN ('ruby','rails','scruffy','rubyonrails') ORDER BY Count DESC   In this query, the number of arguments could be anywhere from 1 to 5.  I would prefer not to use a dedicated stored procedure for this (or XML), but if there is some elegant way specific to , I am open to that.


Is every complete ring $R$ with respect to some ideal $I$ integral domain? I heard somewhere completion of a ring is motivated to eliminate torsion elements. I'd like to know,Is every complete ring $R$ an integral domain? If there are some counterexamples,I'd like to know that. Thank you for your help.

Complete valuation ring is obviously complete local, because valuation ring is always local ring. I would like to know the example of  Complete local ring which is not complete valuation ring  Any examples? I could find example of local ring which is not valuation ring, but the example ring is not complete. Thank you for your help.


I don't have much knowledge about cryptography beyond using libraries for it. So just wanted to understand if the following two cases differ sufficiently in security or is it just psychological:  Say I have a plain text T and I use the following scheme to encrypt:   Take SHA512(T) = H(T) Use any good symmetric encryption scheme to encrypt T with H(T).  Result cipher text = C Keep H(T) safely secret.   How secure is cipher text C in the wild now ? (I can do (1) a few times if it adds anything - so instead of H(T) use H(H(H(T))) etc. - you get the idea).  How would this compare with using an encryption key unrelated to T ? Since H(T) shouldn't be reversible how much more does an unrelated key  add to the security ?

Recently a company called  demonstrated a product of cloud storage. they indicated that they would use "Convergent Encryption" to secure your data and de-duplicate, essentially one copy of the same file between users.  From what I can read on a  about Secure Data Duplication which makes mention of "" and assuming this is what this is referring too.  My question is, what security implications of using this technology and is it truly secure that you cannot get the key based on chunk data being used to generate different keys between users.  Reference interview on


How to find the sum of Beatty sequence of $\lfloor e \rfloor+\lfloor 2e\rfloor+\lfloor 3e \rfloor\dots$ and so on?  Can it be reduced to recursion?

How to solve $$\sum_{i=1}^n \lfloor e\cdot i \rfloor $$    For a given $n$.    For example, if $n=3$, then the answer is $15$, and it's doable by hand. But for larger $n$ (Such as $10^{1000}$) it gets complicated . Is there a way to calculate this summation?


Unable to edit ~/.bash_profile file on my mac. I did some changes in this file and rebooted. From then nothing is working on my command line:    Any help would be appreciated.

in .bash_profile I accidentally set the path to:  PATH="~/Tools/apache-maven-3.3.3/bin"   and now the default path is gone. Nothing in Terminal works anymore:  Korays-MacBook-Pro:~ koraytugay$ ls -bash: ls: command not found Korays-MacBook-Pro:~ koraytugay$ mkdir test -bash: mkdir: command not found   I can not see hidden files in Finder so I can not modify .bash_profile from Finder as well.  How can I fix this situation?


Is it idiomatic to say "take off - of"? For example:  Don't take your headband off of your head.

I have read a sentence from “Diary of a Wimpy Kid 4”:     The teachers have really been cracking down on kids copying off of each other this year.   How to understand "off of"? Please parse it.


Mjolnir is one of the constantly talked about icons of the Marvel universe. The main question is generally who is/has been capable of wielding it, and, as it turns out, quite a few over the years. (Good on ya guys).  But my question is more about the qualities that allow a person to be granted worthiness by Mjolnir, or, to put it another way, what qualities in a person does Mjolnir deem as "being worthy"?  The most surprising characters (I believe) are:        While the others used themselves as a distraction for the serpent it allowed Widow to go on a retrieval mission to find Thor's hammer, Mjolnir. While she saw the Quinjet purposely torpedo itself in a kamikaze attack on Jormungand, Natasha was found worthy to pick up Mjolnir which allowed her to become the new Goddess of Thunder.   As an assassin and a spy for most of her life, her track record doesn't exactly show qualities that most would really consider as "good".      Hulk being the strongest one there is, he's attempted to lift Mjolnir with varying degrees of success in their many battles. Perhaps the closest Hulk has come to truly lifting Mjolnir was in Avengers Assemble #4. Thor attempted to wallop Thanos with Mjolnir, only for Thanos to mind-control Hulk and force the Jade Giant to catch the hammer. Hulk was able to both deflect Mjolnir and whack Thor in the face with it. Granted, Thor was still holding onto Mjolnir throughout the brief skirmish, but we'll give Hulk the accomplishment all the same.    Ok, so maybe not the last one so much, as other characters have been able to lift it unassisted (such as Vision and "The Destroyer", who have also been able to lift it unassisted, without being bestowed the powers of Thor).  So, my question is, what are the qualities that make a person worthy of wielding Mjolnir?

Consistently across the Marvel version of Thor's various incarnations only the 'worthy' may lift Mjolnir, his enchanted hammer.  The inscription reads, "Whosoever holds this hammer, be he worthy, shall posses the power of Thor."  In the movie, of course, a large part of the story is centered upon Thor       becoming worthy.   In the comics and crossovers, many people have been able to wield Mjolnir, including Storm, Captain America, Beta-Ray Bill, Conan, a random paramedic (who hands it to an astonished Thor, laying on a stretcher), and Wonder Woman.  However, Superman wields it briefly in one crossover, but then can't lift it.  Thor says Odin had briefly lifted the enchantment to allow Big Blue to use it.  So what determines one's 'worth' to the hammer?  I know  and all, but that  is hardly canon.


I have been stuck on this problem for almost an hour and couldn't find a solution or a work around.  Here is my problem:  I have a subprocess that starts a subscriber S  that listens to some real time data publisher P. P randomly publish data at a random time, and I want to get all the data within a timespan (say 30 seconds).    subscriber = subprocess.Popen('/start/process', stdout = PIPE, stderr = PIPE)  max_time = 30  inital_time = time.time()  while time.time()-initial_time < max_time:      try:          print(subscriber.stdout.readline())      except:          pass   After compiling, I find the while loop blocked by the readline() when P doesn't publish data. The loop stops at the print until P publish some data, and then the loop prints the data and go to the condition check. So if P never publish data, the program never ends.  I'm assuming that this is because readline require some sort of input in order for it to return, so my questions is how to I work around this? I have read  and I don't see anything related.

I'm using the  to start a subprocess and connect to its output stream (standard output). I want to be able to execute non-blocking reads on its standard output. Is there a way to make .readline non-blocking or to check if there is data on the stream before I invoke .readline? I'd like this to be portable or at least work under Windows and Linux. Here is how I do it for now (it's blocking on the .readline if no data is available): p = subprocess.Popen('myprogram.exe', stdout = subprocess.PIPE) output_str = p.stdout.readline()


I am a student of physics at graduation level.I want to Masters and PHD in CSE in USA.  can it possible?

When applying to a PhD program in the US, how does the admissions process work? If an applicant is weak in a particular area, is it possible to offset that by being strong in a different area?  Note that this question originated from this . Please feel free to edit the question to improve it.


I got some output for my python script on the console. I would like to save the output in a separate file. can anyone have any idea?

Is it possible to launch Blender in a mode where everything that appears in the Blender Console is sent to a file?


After upgrading to Ubuntu 13.10 I have problems with Aptana and Titanium IDE. The menu bar doesn't work normally. Only one menu works, in Aptana the "Window" menu, in Titanium the "Run" menu. Other menus look empty.  Aptana:    Titanium:    Also HUD doesn't search in those menus.   What is the problem and how can I fix it?

I'm using Ubuntu 13.10 (with JDK 1.7.0_45).  I've downloaded and uncompressed Eclipse Kepler for Java EE Developers.  The software menus are messed up. I didn't notice similar problems in other software.  When I click any menu in Eclipse, the drop-down seems to be "cut". Sometimes the drop-down shows, but the options are invisible.  I tried Eclipse Indigo, but the same problem occurs.


Fix a field extension $k\subseteq K$ and consider a  linear system $Ax=b$ where $A$ is a matrix (not necessarily square) with coefficients in $k$. I don't understand why if the above linear system has a solution in $K$, then there exists also a solution in $k$.   Thanks in advance.

I saw this question     Let $A ∈ M_{m\times n}(\mathbb{Q})$ and $b ∈ \mathbb{Q}^m$. Suppose   that the system of linear equations $Ax = b$ has a solution in   $\mathbb{R}^n$. Does it necessarily have a solution in $\mathbb{Q}^n$?   and I thought I'd give an interesting, possibly wrong, approach to solving it. I'm not sure if such things can be done, if not maybe you can help me refine.    I considered the form of the equality as  $$ A^{(1)}x_1+\cdots+A^{(n)}x_n=b, $$  where $A^{(i)}$ is a column vector of $A$. I then noticed that for $x_i\in\mathbb{R\setminus Q}=\mathbb{T}$ then, and this is where I think I'm doing something forbidden, each $x$ has the represenation  $$ x_1  =  k_{11}\tau_1+\cdots+k_{1p}\tau_p \\  x_2= k_{21}\tau_1+\cdots+k_{2p}\tau_p \\ \vdots \hspace{4cm} \vdots \\ x_n=k_{n1}\tau_1+\cdots+k_{np}\tau_p,$$  where $\tau_i$ is a distinct irrational number, $k_{ij}\in\mathbb{R}$, and $p$ is the number of such distinct irrational numbers. I wound this out, but there may be a discrepancy with $p$ and $m$. I feel this method can lead me to the answer, but I'm not sure where to go from here.  EDIT$^1$:  I end up getting something like this, I believe, after substitution:  $$ A(k^{(1)}\tau_1+\cdots+k^{(p)}\tau_p)=b$$  Here, $k^{(i)}$ is the vector  $$\begin{pmatrix} k_{1i} \\ \vdots \\ k_{ni} \end{pmatrix}.$$  EDIT$^2$:  I think there is no discrepancy with $p$ and $m$ because $A\in M_{m\times n}(\mathbb{Q})$, $K\in M_{n\times p}(\mathbb{R})$, and $\tau\in M_{p\times 1}(\mathbb{T})$, so  $$ (m\times n)\cdot (n\times p)\cdot (p\times 1) = m\times 1. $$


Is there a word to describe a person who habitually expresses strong opinions on a subject without having any facts or background knowledge to base their opinion on. Examples include many politicians, the media when they don’t do research, and many loud opinionated people who “Like the sound of their own voice”. With so many words in our language with very specific meanings it seems a single word to describe this [commonly occurring] situation would useful?

Many a times, we tend to meet someone who is ignorant yet arrogant; to the extent that they can go a long way blabbing about something they don't really know with so much vigour. What can you refer to such a person as?


I'm using LyX version 2.3.5.2 on Windows 10. When I click on the "Update" icon, I would prefer for the PDF output to go to the same directory as the LyX file instead of a temporary directory.  Is this possible? Note: This is not a duplicate of the similar question at .  That question applies to Mac OS.

I use LyX 2.0.4 (on Mac OS 10.7) and would like it to do the following:   whenever I hit "View" it should automatically save the pdf output of the lyx file in the same folder the lyx file resides. Whenever I hit "View" again it should overwrite the older version of the pdf. Is that possible?  This is similar to the behavior I know from TeXShop.


I got the following error while installing Wine from the Terminal.   Err http://za.archive.ubuntu.com/ubuntu/ precise/multiverse wine-gecko1.4 amd64     1.4.0-0ubuntu2                                                                            Connection failed [IP: 41.73.43.3 80] Err http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu/ precise/main wine1.4-amd64 amd64 1.4.1-0ubuntu1~precise1~ppa4                                                        Connection failed Err http://za.archive.ubuntu.com/ubuntu/ precise/multiverse wine-gecko1.4 i386 1.4.0-0ubuntu2                                                                             Connection failed [IP: 41.73.43.3 80] Err http://ppa.launchpad.net/ubuntu-wine/ppa/ubuntu/ precise/main wine1.4-i386 i386 1.4.1-0ubuntu1~precise1~ppa4   Connection failed   It is installing everything else fine, it just seems to be a select few files that it is not able to download for some reason. Why is this? And what should I do from here to fix the install? Rerun the command in the Terminal?  I apologise if this seems simple or common knowledge but I honestly have no idea what to do from here, as a completely new Ubuntu user.  If there is a way to 'clean up' this action and reverse what I have done that may also be great. I could then just use the Ubuntu Software Center to download and install Wine.   I am running Ubuntu Studio 12.04  Much Appreciated!

Since installing Ubuntu I have been unable to install new packages, it has even failed to update. Below is a dump of connection error I see when I tried to install Wine:  E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/u/unixodbc/odbcinst1debian2_2.3.1-4.1_amd64.deb  Connection failed [IP: 91.189.88.152 80]  E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/universe/f/fonts-wqy-microhei/ttf-wqy-microhei_0.2.0-beta-2_all.deb  Connection failed [IP: 91.189.88.162 80]  E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?


I always read "rule #1: never use less than 14GA wire on a 15A breaker, and never use less than 12GA wire on a 20A breaker". The idea being that if the circuit gets to the max current allowed by the breaker, too small of wire can get too hot.  So recently I installed a direct-wire light fixture, and attached to the light and switch on the fixture where they wanted me to connect power were 18GA wires. So, excited about my new fixture, I connected my 14GA from the wall to the 18GA wires in the fixture, buttoned it all up, enjoyed my new light, but now am wondering "what was I supposed to do to not violate rule #1?".  It is "ok" for the wire to potentially get hot as long as it's in a metal fixture or something (vs in the drywall)? Or is it "ok" for the wire to get hot because it is onl 10" (presumably not?)? What gives??

why do cables joining the wall sockets in a house need to be thicker than the cables joining the light fittings? I don't understand and I need to know before I buy it.


Find a bijection between $[0,1)\sim(0,1)$.   Well I know that $$[0,1)\sim(0,1)=[0,\frac{1}{2})\cup [\frac{1}{2},1)\sim(0,\frac{1}{2}]\cup [\frac{1}{2},1).$$  So I found this function: \begin{align} f(x)&=-x+\frac{1}{2} &\text{ if } x\in [0,\frac{1}{2})\\ f(x)&=x &\text{ if } x\in [\frac{1}{2},1)\\ \end{align} Which is surjective but not injective because $f^{-1}(\frac{1}{2})=0,\frac{1}{2}$. Is this the correct conclution to make about $f(x)$? What is a function that works/is bijective?  This question is different than the other questions on bijections between simple real intervals because I want feedback on this specific function, $f(x)$, and I find mapping from a half closed set to an open set more confusing than mapping an open set onto a closed set.

How to define a bijection between $(0,1)$ and $(0,1]$?   Or any other open and closed intervals?   If the intervals are both open like $(-1,2)\text{ and }(-5,4)$ I do a cheap trick (don't know if that's how you're supposed to do it): I make a function $f : (-1, 2)\rightarrow (-5, 4)$ of the form $f(x)=mx+b$ by \begin{align*} -5 = f(-1) &= m(-1)+b \\ 4 = f(2) &= m(2) + b \end{align*} Solving for $m$ and $b$ I find $m=3\text{ and }b=-2$ so then $f(x)=3x-2.$  Then I show that $f$ is a bijection by showing that it is injective and surjective.


I have this file inside DCIM on internal memory. It takes up a lot of space and I'm getting short of it. So I checked what is taking that much space and found out this file alone takes space upto a GB. So can I remove it and will my mobile malfunction if it is removed?

I have recently noticed a huge (>3.5GB) file in the DCIM/.thumbnails folder. I have tried deleting it, but the next time I open the Camera app it rebuilds the file (and locks up the phone, sometimes displaying a "media scanning in progress" message, in the process.)  The total file size of all the (approximately 2,000) photos displayed in the Gallery is around 500MB. There are in addition around 35,000 images in folders which contain .nomedia files to instruct Android to ignore the media therein. The total file size of these is around 1.5GB. The Gallery app is correctly ignoring these images, but I wonder whether the Camera app is misbehaving and actually processing them.  I think this problem has emerged since the ICS upgrade ... either when the phone (Samsung Galaxy Note) was first updated from Gingerbread or at some later date.  Any ideas, please?


I saw a sentence like:     Maximum number of minutes are 60   but I feel like it must be "is 60" not "are" as we are describing about the word number here which is singular.  and after search I came across two different questions with two different answers ( , ) and I don't know what exactly is the correct behavior here and if I'm able to use both of them or not.

Kindly, what are your thoughts on the following sentences:        The maximum number of wordbooks (%d) have been saved.   The maximum number of wordbooks (%d) has been saved.      My opinion is that (1) is more appropriate as "save" relates to wordbooks (a plural noun) and "The ... number" is some kind of determiner.  The dissenting opinion is that "The number" is obviously singular, and the "wordbooks" are subsidiary.  I agree that (2) is grammatically correct but I maintain it implies merely a single number was saved, not the wordbooks themselves.


How is R used with ArcGIS for Desktop?   I have seen posts talking about combining rasters while using R.   I have not had much experience with R so not 100% certain of its capabilities.   I had thought that R was a scripting language for data analysis with tabulated data and data bases, but its seems much more than that.   Are there particular R libraries to incorporate it with ArcGIS for Desktop?

I've used the integration of  with QGIS, and found it a very uesful tool. Having taken a look at the R toolbox  and the  it appears they both offer only point clustering to demonstrate the proof of concept.   Can other analysis methods available in R be implemented in ArcGIS Desktop through a python script (for example, implementing specific parts of the  package)?


For my bachelor thesis I would like to create the following arrows, or more precise orientated subgraphs, so far I was not able to create them. Can anyone help?

I would like to show, in my latex document, some in-text arrows similar to the ones in the attached figure. I know about the \leftrightarrow and \updownarrow commands, but I don't know how to combine them, nor how to rotate them. Is tikz necessary to achieve this?    Any help will be much appreciated.  EDIT: I clarify better, I'm sorry if my question was unclear. I would like to avoid math mode (but it's not important) and tikz as well (to avoid loading too many packages), but having a look around it seems that tikz is necessary to do it. In the end, I'd like to have something like A \to B but with the symbols I described.  For future reference, my question would be similar to .


When I crafted a golden pickaxe to mine some Crimtane ore down in a dungeon right under my house. I went on a mining trip to get gold. (Also, I haven't found the merchant yet.. I've searched a lot..) Anyway, I crafted my pickaxe and I get Broken Gold Pickaxe.. And I dont know why its broken or not.. I'm confused.  How Do I fix the broken part of my golden pickaxe?

I crafted my first silver pickaxe in Terraria 1.1. I did not examine its stats until some time later. The name color is grey with -14% damage.  I have no problem mining with it but killing monsters especially cave bats (which I have been doing a lot) got weaker.  Can anyone give an insight into why this happened? I am split between weapon degradation and crafting fluke.


Will inactive accounts be deleted? If so, what happens to questions and answers made by those accounts? What are the criteria for deletion?

Prior to May 2017, accounts used to be automatically deleted if they met . However, in May 2017, we stopped culling inactive users (see ).  Today, in the , it says:     As part of our new data-retention policy, we will now delete accounts that have been inactive for more than two years and where the user has never engaged in any meaningful activity.   What is the definition of "meaningful activity" here?


In LaTeX , can we remove equation number that we did not use in a paper automatically?

I have a paper where all equations are numbered, but I want to number equations only if they are actually referred to in the .tex file using \ref{}. How can I make that happen? Alternatively, how can I make all equations that have no \label next to them (because then I know I don't refer to them) not have a number? Do I have to use \nonumber separately for each such equation?


I have a simple Java method here Below , which passes a string , but inside the method another string variable is to be assigned a value. But its not assigning new value- based on the String Input. Instead returning "NA". Kindly have a Look and help me find the fault in the code. Suppose if h is "NRM" even then aId = "NA", not "01"  private static String getAID(String h) {      System.out.print("AId : 01 to 25 for "+h);           String aId = "NA";      if(h == "NRM") {         aId= "01";         System.out.print("inside Nrm of fn"+aId);      }       Scanner scanner = new Scanner(System.in);      if(h=="EPB") {             System.out.print("Emergency ON/OFF press 1 or 0  - ");              String in= scanner.next();              if(in == "0") aId="11";              else if(in=="1") aId="10";              else { aId="10";}                    }      if (h=="CRT") {             aId="16";             System.out.print("Critical Alert Enter 16/03/17/22/23/20/21 - ");             String in= scanner.next();             String[]  arr = {"16","03","17","22","23","20","21","13","14","15","06","04","05","09","18","19"};             for(String i : arr) {                 if( i.equals(in) ) aId=in;             }   //aId="04";        }     if(h=="BTH" || h=="ALT") {             aId="13";             System.out.print("AId Enter :/13/14/15/06/04/05/09/18/19 - ");             String in= scanner.next();             String[] arr = {"16","03","17","22","23","20","21","13","14","15","06","04","05","09","18","19"};             for(String i : arr) {                 if( i.equals(in) ) aId=in;             }                         }     switch(aId) {     case "01":System.out.println("Normal 2");          break;     case "02":System.out.println("l History");     // remaining cases      // remaing cases //      case "23":System.out.println("IMPACT");           default: System.out.println(" Wrong Entry -is"+aId );      }          return aId;      }  Here when I checked , It s never Entering the If Statements at all... But instead entering default part of the Switch case and return aId = "NA" ;

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


So, I have a class with some vectors and I'm trying to add elements to those vectors. But, when I try to push elements with add method, it throws NullPointerException. I'm using eclipse as editor. package com.vogella.eclipse.ide.first;  import java.util.Vector;  public class Qr {       // The class   int x,y;   Vector<String> at = new Vector<String>(); }   public class cls {   public static void main(String[] args) {     Qr[] var = new Qr[5];     String q = new String("ggg");      var[1].at.add(q);     System.out.print("gg");   } }  It throws an error  Exception in thread "main" java.lang.NullPointerException  at sf.eclipse.ide.first.nfd.main(nfd.java:89)  Is this correct or am I doing something wrong?

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


I'm trying to make a program that takes input from the user for how many students they have in their class and their names/grades and calculate average and letter grades. I'm trying to get better with For Loops and Arrays and this is what I chose to do. The only problem is when the init() method is called to make the window. The class is extending JFrame  import java.util.Scanner;  import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTextField;  @SuppressWarnings("serial") public class GradesGUI_2 extends JFrame {  static Scanner s = new Scanner(System.in); static int num;  public static void main(String[] args) {      System.out.println("How many students are in your class?");     num = s.nextInt();      GradesGUI_2 window = new GradesGUI_2("Title");     window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  }  //-------------------------------------------------  static JPanel p; JTextField[] name = new JTextField[num], grade = new JTextField[num]; JLabel[] nlabel = new JLabel[num], glabel = new JLabel[num]; int height = 50;  //-------------------------------------------------  GradesGUI_2(String title) {     super(title);     this.init();     this.setVisible(true);     this.setLocationRelativeTo(null); }  //-------------------------------------------------  void init() {     //Create JLabel/JTextField     for(int i = 0; i < num; i++) {         nlabel[i] = new JLabel("Name " + i);         glabel[i] = new JLabel("Grade " + i);         name[i] = new JTextField(10);         grade[i] = new JTextField(1);          height += 25;     }      for(int i = 0; i < num; i++) {         p.add(nlabel[i]);         p.add(glabel[i]);         p.add(name[i]);         p.add(grade[i]);     }        this.setSize(350, height);     this.add(p); }   }  What the console displays:  How many students are in your class? 7 Exception in thread "main" java.lang.NullPointerException     at GradesGUI_2.init(GradesGUI_2.java:59)     at GradesGUI_2.<init>(GradesGUI_2.java:40)     at GradesGUI_2.main(GradesGUI_2.java:20)   The error happens when the components are added to the panel. Please answer. Thank you!


Alternative tokens are  c++ , yet in Visual Studio 2013 the following emits a compilation error (undeclared identifier):   int main(int argc, const char* argv[]) {     int k(1), l(2);     if (k and l) cout << "both non zero\n";      return 0; }   Since and or not have been around for quite some time, is there a reason for not implementing them?

I've just read this  from Reddit.  They mention and and or being "Alternative Tokens" to && and ||  I was really unaware of these until now. Of course, everybody knows about the , but and and or? Since when? Is this a recent addition to the standard?  I've just checked it with Visual C++ 2008 and it doesn't seem to recognize these as anything other than a syntax error. What's going on?


i am following the complete beginners guide 2.8 on youtube but when he changes the color of the guys legs and hands, on mine it is all linked to the same color and i dont know how to fix it. top picture is the video and bottom is what i did. first time ever on blender

How do you add more than one material to a mesh?   I have tried adding two materials to the object, and then assigning one of the materials to a vertex-group, but I could not find a place to assign it.  I am making a striped bouncy ball that I want to deform, so adding a different material by separating the mesh into different objects would not be ideal.


I am trying to tail a log file. At some point the program writing to the log file will say "your foo is ready". I expect my tail -f to conclude gracefully. So I came up with the following lines of code: tail -f out.log | grep ready | while read ln; do   echo "ln: $ln" done  I stopped my coding prematurely since I cannot understand why I don't see any output.

In Bash, piping tail -f to a read loop blocks indefinitely.   while read LINE0  do      echo "${LINE0}";  done < <( tail -n 3 -f /tmp/file0.txt | grep '.*' )  # hangs   Remove the -f or | grep '.*', then the loop will iterate.   The following does not hang.  tail -n 3 -f /tmp/file0.txt | grep '.*'    What causes this behavior?    Is there anyway in Bash to follow a file and read in a pipe expression?


The other houses’ mascots make sense. Lions represent bravery, snakes represent cunning, and eagles have a refined quality about them. But what exactly does a badger symbolize? Hufflepuffs are known for their patience, hard work, and loyalty.

In Harry Potter each Hogwarts house has its own animal that represents it; is it ever explained how these animals came to represent a specific house? I never read a canon explanation to who chose the animals, is that known?


I invested in the stock NYSE:CC but it has been dropping for no reason. I am thinking it may be because of Trump's ban on foreign investment but doesn't that only apply to tech companies? This is a chemical company. The price dropped by 4% yesterday and hasn't rebounded. Should I be concerned?

Why does a stock price suddenly drop for no reason? There is no bad news coming out, the S and P 500 is going up. My stock dropped by 4% today. Should I be concerned there is some bad news that I don't know coming out soon?  Edit: The company is Chemours Company ticker code:CC.  Thanks for your help!


There are many questions out there already that answer how to add horizontal spacing in  and also how to deal with a .  So my question, with all these different spacings one can add in mathematical equations. Is there any convention in using spacing between variables?  For example, if all my variables were 1 character only (with an optional descriptive subscript) then I could write something like equation 1 and be able to move variables around without there being any confusion as to what the variables are if the reader would know beforehand that all variables are one character only. But if I have variables with multiple characters as well than there might be confusion as in equation 2, where one might think that Re is suddenly a variable of its own like in equation 4 instead of two separate variables. So then how do we deal with this? What's the general way to deal with this? (The general way I deal with it is to add spacing between the variables as in equation 7, but the right hand side looks a bit weird to me with all the spacing, or is equation 6 better?)    Sample code:  \documentclass{article}  \begin{document}      \begin{equation}         R = \frac{x}{e}     \end{equation}      \begin{equation}         Re = x     \end{equation}      \begin{equation}         R \, e = x     \end{equation}      \begin{equation}         Re = \frac{\rho v d}{\mu}     \end{equation}      \begin{equation}         Re\mu = \rho v d     \end{equation}      \begin{equation}         Re \, \mu = \rho v d     \end{equation}      \begin{equation}         Re \, \mu = \rho \, v \, d     \end{equation}  \end{document}

Is there a canonical way to typeset such quantities in equations and inline math?  \documentclass{article} \begin{document} $Re$, $Nu$ are clearly not an option. $\mathit{Re}$, $\mathit{Nu}$ appear ok to me. \end{document}


I am trying to render a scene where I run a script with given parameters and then render the animation by passing parameters to the blender executable through the command line.  Given the following example for the command passed:  blender <file_path> -P <python_script> -- <input_parameters> --frame-start <num> --frame-end <num> -a   When executed it does not render and I presume it treats what ever is after the '--' as parameters for the python script. I am aware that I can pass these parameters and use the Blender API in the python script to render the scene with these parameters but for my case this does not suit.

I have a very very slow computer, but would like to animate 3D. I'm aware we can render via the command line. but I don't know how. I want to render the entire animation of my Tutorial.blend file in the background.


Im using this script in order to detect Metamask: if (typeof window.ethereum !== 'undefined') {     console.log('MetaMask is installed!');      const ethereumButton = document.querySelector('.enableEthereumButton');     const showAccount = document.querySelector('.showAccount');          ethereumButton.addEventListener('click', () => {       getAccount();   });      async function getAccount() {     const accounts = await ethereum.request({ method: 'eth_requestAccounts' });     const account = accounts[0];     showAccount.innerHTML = account;   }   }else{     const ethereumButton = document.querySelector('.enableEthereumButton').innerText = "InstallMetamask";   }  If metamask is not enabled, the user sees the else statement which shows a button on the UI saying "Install metamask" How can i add a link to this? What i want to achieve is when the users sees the button saying "install Metamask" i want the user to redirect to google chrome where he can install metamask. I tried to do ... .innerText = Install Metamask"  but of course i cant add html inside my script file like that. So how can i do this? and this is in my html file <button class="enableEthereumButton">Enable Ethereum</button>
Account:

I am trying to insert a chunk of HTML into a div. I want to see if plain JavaScript way is faster than using jQuery. Unfortunately, I forgot how to do it the 'old' way. :P  var test2 = function(){     var cb = function(html){         var t1 = document.getElementById("test2");         var d = document.createElement("div");         d.id ="oiio";         d.innerHtml = html;         t1.appendChild(d);         console.timeEnd("load data with javascript");     };     console.time("load data with javascript");     $.get("test1.html", cb); }   what am i doing wrong here guys?  edit:  Someone asked which is faster, jquery or plain js so i wrote up a test:   plain js is 10% faster


Currently, the script works if the .py files are on the desktop but I can't get it to work in the 'code' folder. Every time I try and run it with no .py files on the desktop it gives me the error "python3: can't open file '/home/antonf/Desktop/1.py': [Errno 2] No such file or directory" import os  for files in os.listdir(r'/home/antonf/Desktop/code/'):     os.system('python3 {}'.format(files))  I tried to add a line that would open to the 'code' folder but it also didn't work. Like this. import os  for files in os.listdir(r'/home/antonf/Desktop/code/'):     os.system('cd /home/antonf/Desktop/code/')     os.system('python3 {}'.format(files))

cd is the shell command to change the working directory. How do I change the current working directory in Python?


I have a big dataset of sensor data (body temperature) acquired on a lot of people and each person is assessed for several days.   person1 = [temp_day1, temp_day2, .... , temp_dayn]   During each day the temperature is assessed 24 times (1 every hour).  temp_day1 = [temp_01h, temp_02h, ....,temp_24h]   Sensors could have some problems...for example they could be not calibrated and they could be influenced by enviromental temperature etc..  In order to process the data (compare temperature across the people) I had in mind to standardize the data of each subject according to the mean and standard deviation of his temperature during all his assessed days.  Is that correct? Do dividing for the standard deviation have any meaning? Are there other ways to make the data comparable?  Thanks

In some literature, I have read that a regression with multiple explanatory variables, if in different units, needed to be standardized.  (Standardizing consists in subtracting the mean and dividing by the standard deviation.)  In which other cases do I need to standardize my data?  Are there cases in which I should only center my data (i.e., without dividing by standard deviation)?


How can I write a loop in Python that behaves exactly like this JavaScript loop:  for (i = 0; i < cars.length; i++)   That is, I want the variable i to hold the value of the index of the character as I iterate over a string.

How do I access the index in a for loop like the following?  ints = [8, 23, 45, 12, 78] for i in ints:     print('item #{} = {}'.format(???, i))   I want to get this output:  item #1 = 8 item #2 = 23 item #3 = 45 item #4 = 12 item #5 = 78   When I loop through it using a for loop, how do I access the loop index, from 1 to 5 in this case?


I have two feature classes, one that contains all counties for 5 states and the other contains 90 polygons I need clipped only to their pertaining county boundary, but they overlap/ cross the county boundary (See image below).  Both feature classes have a field with a unique 5 digit ID for each county as well. Being that I am relatively new to Python, is there a way I can use a loop or searchcursor to clip each of the 90 polygons to their respective county boundary using their 5 digit ID?   *The red rose colored polygons show the overlapping polygons I need to clip and the tan colored polygons show what I need the final product to look like.

I have a feature class with over 2,000 features, and I need to make them all individual feature classes based on a field.   Is there a way to do this?


We say big bang was the explosion not in the space but of the space itself that took place in a fraction of seconds. Speaking practically, we say the universe has no edge and is infinite. If the universe expanded to infinite in a fraction of seconds, can we say the rate of expansion during big bang (predicted) exceeded the speed of light?

just after the Big Bang and before inflation the currently observable universe was the size of a coin. One millionth of a second later the universe was the size of the Solar System, which is an expansion much much faster than speed of light. Can space expand with unlimited speed?


I have a script that I want to run at startup and on shutdown.  I have placed the file in /etc/init.d and named it testscript.sh  Then I changed permissions sudo chmod 755 testscript.sh  Then I made link ln -s /etc/init.d/testscript.sh /etc/rc2.d/S99testscript.sh  So far so good, now the script runs at startup. I tried doing the same but making the links in rc0.d and rc6.d but that didn't work, the script still won't run at reboot/shutdown.   What am I doing wrong?  I'm running Ubuntu on putty client.

My script is not running on boot in a vagrant box under Ubuntu.  My script looks like this -  #!/bin/bash # /etc/init.d/mailcatcher ### BEGIN INIT INFO # Provides: scriptname # Required-Start: $remote_fs $syslog # Required-Stop: $remote_fs $syslog # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6 # Short-Description: Start daemon at boot time # Description: Enable service provided by daemon. ### END INIT INFO mailcatcher --http-ip 192.168.50.10   My permissions on the file look like this -  -rwxr-xr-x 1 root root 352 Apr 30 09:59 mailcatcher.sh   I run the command -  sudo update-rc.d "mailcatcher.sh" defaults   If I run the script manually, it works and starts mailcatcher. If I reboot the computer, the mailcatcher daemon does not start. Am I missing something?


Proof via induction for $n,m \geq 0$ that if $\gcd(a,b) = 1$ then $\gcd(a^n, b^m) = 1$ for any $n,m$ that are positive integers.

I'm solving some problems in Apostol's Intro to Analytic Number Theory. He asks to prove  $$(a,b)=1 \wedge c|a \wedge d|b\Rightarrow (c,d)=1$$  My take is  $$\tag 1(a,b)=1 \Rightarrow 1=ax+by$$  $$ \tag 2 c|a \Rightarrow a=kc$$  $$\tag 3d|b \Rightarrow b=jd$$  $$(1),(2),(3) \Rightarrow 1=ckx+djy=cx'+dy'\Rightarrow (c,d)=1$$  Is this correct or is something missing?  I intend to use something similar to prove   $$\eqalign{   & \left( {a,b} \right) = 1 \wedge \left( {a,c} \right) = 1 \Rightarrow \left( {a,bc} \right) = 1  \cr    & \left( {a,b} \right) = 1 \Rightarrow \left( {{a^n},{b^k}} \right) = 1;n \geqslant 1,k \geqslant 1 \cr} $$  so I'd like to know.


I have a file that has some lines like:  account_1 account_2  account_3   I have to add a path like /home/info/ before each line and save the same file with those updates like this:  /home/info/account_1 /home/info/account_2  /home/info/account_3   How can I handle this on AIX?

I am looking for a way to add some string to the beginning of every line (same string for every line). Not something customizable but rather something that will be easy to remember and available on every POSIX-compliant platform (and every shell as well).


I have the proxy address, a user name and a password for the proxy server I need to connect through, but when I set the proxy details under System Setting => Network => Network Proxy, only Firefox seems to be able to connected to the Internet.   The Ubuntu Software Centre and apt-get does not seem to be able to connect to the internet, I have already tried  and a bunch of other things but nothing seems to work.

For the command   sudo apt-get update   I get following error:  W: Failed to fetch http://ch.archive.ubuntu.com/ubuntu/dists/maverick-updates/multiverse/binary-i386/Packages.gz   407  Proxy Authentication Required (The ISA Server requires authorization to fulfill the request. Access to the Web Proxy filter is denied. )   I am running Ubuntu 10.10 installed on Windows XP using VirtualBox. For Internet connections I am using proxy server with an authentication. I tried to use gnome-network-proxy tool to set proxy settings system-wide.   After that /etc/environment has been updated by http_proxy variable with the format http://my_proxy:port/, there were no authentication data.  I checked this with Firefox. Browser asked my for login and password and everything was working fine. It was unfortunately not the case for apt-get. I have also tried to do as described . Unfortunately it does not work.  May it be somehow related to the fact that a proxy is in a Windows domain, any ideas?  My proxy name is http-proxy. Is '-' a special character here?


I use Ubuntu 16.04 (xenial) via WSL.  I copy this code  #!/bin/bash read -p "Have you created db credentials already?" yn case $yn in     [Yy]* ) break;;     [Nn]* ) exit;; esac   When I paste it in Ubuntu I get only part of it:  read -p "Have you created db credentials already?" yn Have you created db credentials already?   Why when it is pasted, it is pasted partially?  Update  I copy the code from GitHub, when the case conditions are indented with tabs and when the code is without a line break in the last line (no extra empty note after the last line).

Right, this is a slightly annoying feature because something this happens, and other times it doesn't, very odd.  I paste a command into the terminal with a view to tweaking its arguments, and sometimes it executes the second I paste it. Sometimes it doesn't.  This ranges from embarrassing ( posting nonsensical comments on an IRC ) to dangerous.   How can I shut this feature off for good? I never, never, never want the terminal to auto execute when I paste to it.


My QGIS 2.8.2 standalone app provides several decorating layers (e.g. cartographic grid, background layers, reference points) which should be not changed by the user (neither editing nor hiding), as well as layers, the user can modify and query.  The app has a legend widget which shows all layers, since all layers are registered with map registry. The widget is populated with the layer tree as described in .  Instead of exposing all layers in the tree view, I want to restrict the tree view to the layer group, whose children represent the user mutable layers. Thus the user can change visibility and ordering of only these layers, and must keep the decoration as it is.  What I tried so far is to initiate QgsLayerTreeMapCanvasBridge with this group node (instead of layerTreeRoot), pass the group node to QgsLayerTreeModel(), or  changed the root group of the model with QgsLayerTreeModel.setRootGroup(). In each case Python crashes, with an error message like this:  QObject::connect: Cannot connect (null)::willAddChildren( QgsLayerTreeNode*, int, int ) to QgsLayerTreeModel::nodeWillAddChildren( QgsLayerTreeNode*, int, int )   Is it possible to expose only some group oder layer nodes in the treeview, and how can I implement this?

I have a number of layers in the Layers Panel inside a group but I don't want them shown (there's quite a lot so it looks untidy). These layers are also joined to several others. Is it possible to make these layers invisible to the user (i.e. not shown in the Layers Panel, it is not about setting the visibility of the layer) but can still be joined to other layers, or perhaps to make the group invisible? Closest I found was this post but hoping there's a more direct approach:


I did a do_release_upgrade on my Ubuntu 16.04 (there were errors, in particular some were related to X11 or Xorg) and now I have this at boot:  Help ! EDIT I reinstalled grub from a live Ubuntu and now I have this at boot, still need help!  BOOT INFO is here  BOOT REPAIR report is here  lsb_release -a gives 18.04 Bionic . $ lspci -k | grep -A 2 -i "VGA" gives VGA compatible controller: Intel Corporation HD Graphics 5500 (rev 09) Subsystem: Lenovi HD Graphics 5500 kernel driver in use i915  then: sudo apt-add-repository ppa:ubuntu-x-swat/updates sudo apt-get update && sudo apt-get upgrade  EDIT 2 I have access to command line via tty1, I tried to reinstall xserver sudo apt-get install --reinstall xserver-xorg but it still boots on the black screen with [ OK ] lines as in the screeshot above. EDIT 3 I tried reinstalling GDM sudo apt purge gdm gdm3 sudo apt install gdm3 ubuntu-desktop sudo dpkg-reconfigure gdm3 #to choose GDM systemctl restart gdm  I also tried startx and I get: X.Org X Server 1.19.6 ... using system config directory "/usr/share/X11/xorg.conf.d" xf86EnableIOPorts: failed to set OIPL for I/O (Operation not permitted) xinit: connection to server lost waiting for X server to shut down. (II) server terminated sucessfully (0). Closing log file.

Just ran the latest batch of updates on 20.04 (Xubuntu), and now I'm getting a GRUB error: symbol 'grub_calloc' not found  I'm dropped into the 'grub rescue' shell, but have no idea what to do there that might be useful. To me, 'symbol not found' implies some sort of build error with the grub package, but I don't really know how grub works. I noticed that this update also included 'firmware', not sure if that could be related. Is my best bet just to boot from a live CD and see if I can roll back the update to grub somehow? Edited to add: OK, thanks to lots of people ! Here's what I think I now understand.  On 'non-UEFI' systems, grub is installed in two separate parts. The first, most basic, part is the part that is started on bootup. But for most of it's functionality, it needs the second part. These parts must be aligned - neither part must require any functionality from the other part which is not actually there. The visible, run-time problem occurs when these parts are not aligned, and the function grub_calloc is not supplied. It's not 100% clear to me if grub_calloc belongs in the second, larger part or the first. I would have expected the second, but the grub build system is a work of considerable art, so I don't know :).  The root cause of the problem is that the grub update has not ensured that both parts have been updated. Ideally, failure to do this should cause grub installation to fail, and the system should be reverted to a safe state. This does not happen. This is actually still a bit of a mystery to me. All that the update needs to do by default is put each part where the current parts are, because obviously that worked. If the install locations/drives are configuration - driven, and one of these locations can't be reached, then somehow a mismatch has arisen between that configuration data and reality. This might not show up as a problem as long as no new dependency was introduced between the parts.   All flavours of solution involve reinstalling grub to ensure that the two parts are aligned. It's not actually necessary to go back to the previous version ( although that will work ), because it's not the grub runtime per se that is broken. There are numerous ways to achieve this, depending on your environment, but running the Boot-repair live disk worked for me. It may be useful, for the purpose of avoiding such a misalignment in future, to ensure that the grub installer on your system is configured to install to the correct devices. This update resolves some important bugs (). If you have reverted grub to resolve this problem, be aware that you are exposed to these issues.


In my algebraic geometry course, somewhere in a proof we've used the fact that, for $f_1, \ldots, f_r \in K[x_1, \ldots, x_n]$ and $X = V(f_1, \ldots, f_r) \subset \mathbb A^n$, every irreducible component of $X$ has dimension at least $n - r$ but I really don't understand why this is true. We have see the following result that may help.  Let $X$ be an irreducible affine variety. If $f \in A(X)$ is non-zero, every irreducible component of $V(f)$ has  dimension $\dim X - 1$.  I have the intuition that we have to use the above property, but I am not able to write the details. Could one of you help me ?

My question is about  about solving Hartshorne's Exercise I-1.9 by using exercise I-1.8:  Hartshorne's Chapter 1, exercise 1.9: Irreducible components of $Z(\mathfrak a)$ have dimension $\geq n-r$ if $\mathfrak a$ is an ideal generated by $r$ elements. Hartshorne's Chapter 1, exercise 1.8: Let $Y$ be an affine variety of dimension $r$ in $\mathbf A^n$. Let $H$ be a hypersurface in $\mathbf A^n$, and assume that $Y \nsubseteq H$. Then every irreducible component of $Y \cap H$ has dimension $r-1$.  Suppose $\mathfrak{a}$ can be generated by $f_1, \dots, f_r$ and no one is in the ideal generated by the rest of them (note they are not necessarily irreducible. But it seems to me that I don't need to assue $H$ in Ex. 1.8 is the zero set of an irreducible polynomial. Let me know if I am wrong). We'll induct on $r$. I can prove that any irreducible component $Y$ of $Z(\mathfrak{a})$ is contained in an irreducible component $Y'$ of $Z(f_1, \dots, f_{r-1})$. But, to use 1.8, I have to show that $Y'$ is not contained in $Z(f_r)$ and that $Y$ is an irreducible component of $Y' \cap Z(f_r)$ Question 1: does the assumption that $f_r\notin (f_1,\dots, f_{r-1})$ imply that $Y'$ is not contained in $Z(f_r)$? If not, how do we remedy this? Question 2: how to prove that $Y$ is an irreducible component of $Y' \cap Z(f_r)$ (something might be missing here and I can't prove it at least)? It is irreducible but why it appears in the irreducible decomposition of $Y' \cap Z(f_r)$?


Why is Severus Snape's Patronus the same as Lily Potter's? Are Snape and Lily related somehow? Are Snape and Harry related?

If Snape didn't fall in love with Lily, or "got over" it, would he still be able to summon a Patronus or would he then become a run of the mill Death Eater? According to J. K. Rowling, Snape is the only Death Eater with a Patronus.  Samantha: Was snape the only death eater who could produce a full patronus J.K. Rowling: Yes, because a Patronus is used against things that the Death Eaters generally generate, or fight alongside. They would not need Patronuses.   Snape's Patronus is a doe, explained as being because of his love for Lily, which may very well be his happy memory to generate the Patronus.  If this was no longer the case, would the consistent presence of the Dementors on his supposed side mean he's no longer able to summon a corporeal Patronus?


it's Trumpy again!  Here is the code:  public static void main(String[] ar){     int[] a={1,2,3};     int x=3;     foo1(a);     foo2(x);     System.out.println(a[0]);     System.out.println(x); } public static void foo1(int[] a){     a[0]=55; } public static void foo2(int x){     x=77; }   The output:             55 3   Trumpy's question: when I call to foo2 function it doesn't change the x variable, the change remained in the scope of the function. but when I call foo1 it changes the array itslef, am I right?

I always thought Java uses pass-by-reference. However, I've seen a couple of blog posts (for example, ) that claim that it isn't (the blog post says that Java uses pass-by-value). I don't think I understand the distinction they're making. What is the explanation?


I have been doing D.J. Griffiths's book on electrodynamics. The new level of mathematical formalism does make things a bit less farmiliar...  So, I'm asking if there is any fundamental difference (advantage, disadvantage) in writing equations in their integral form vs the vector derivative form...  For example, does writing down Maxwell's equations using the curl or divergence make it any easier to solve certain configurations, or are the operators simply there to make things look less tedious... ?  Another example would be Poisson's equation. How would one go about setting up and solving Poisson's equation for some configuration (say, a charged ring)?

I am not sure which form of  is fundamental, integral form or differential form. Imagine an ideal infinitely long solenoid. When a current is changing in time, can we detect classical effects outside a solenoid, for example generating a circular current around solenoid by Faraday's law. If the differential form is fundamental, we won't get any current, but the integral form is fundamental we will get a current.


Does the consecutive days on the profile page reflect that I'm actively using the iOS app ?    Is this count added to the consecutive days ?   OR does only visiting the website count ?      P.S. I know that an answer for the android app is already  ; but I sure will be grateful if someone can tell me whether the same happens for the iOS App

The title says it all, just wondered if accessing the iOS will count towards your consecutive visited days.


I get a null pointer exception for this statement.  accountList.getTrxnList().getTrxns().size() > 0  accountList is a list of accounts I get from an external API call. And I am sure that a non-null accountList value is returned.But I am not confident about getTrxns() has any values. So before processing I check whether there are any Trxns but this also results in a null pointer exception.  This is my model class   public class AccountList{      private TrxnList trxnList;      public static class TrxnList {          private List<Trxn> trxns;          public List<Trxn> getTrxns() {             return trxns;         }     } }   Can someone please point out why this is raising nullpointer exception? I did some research on this so I cannot understand this raising nullpointer exception even if there are no items in trxns List.  Thank you.

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


What is the remainder when $32^{32}$ is divided by 3 ?  MY ATTEMPT  $$32^{32}=(2)^{160}$$  $$32^{32}=(3-1)^{160}$$  $$32^{32}=3M+(-1)^{160}$$  According to binomial expansion $$32^{32}=3M+1$$  Thus the remainder is 1.  Am I correct ?

I've read about Fermat's little theorem and generally how congruence works. But I can't figure out how to work out these two:   $13^{100} \bmod 7$ $7^{100} \bmod 13$   I've also heard of this formula:  $$a \equiv b\pmod n \Rightarrow a^k \equiv b^k \pmod n $$  But I don't see how exactly to use that here, because from $13^1 \bmod 7$ I get 6, and $13^2 \bmod 7$ is 1. I'm unclear as to which one to raise to the kth power here (I'm assuming k = 100?)  Any hints or pointers in the right direction would be great.