I have installed Ubuntu 14.04 myself. After reboot  the network (wifi) doesn't work anymore, I do not have cable, so haven't tried  ifconfig  the eth0 doesn't have inet or inet6 item   and  lspci -knn! grep Net -A2  03:00.0 Network controller (0280): Broadcom Corporation BCM43142 802.11b/g/n (14e4:4365) (rev 01) Subsystem: Lenovo Device (17aa:0611) Kernel driver in use: bcma-pci-bridge   quite emergency. How could I deal with it ?

I have installed Ubuntu alongside Windows 8.1. But the wifi is not working in Ubuntu (perhaps the drivers are not present), which worked fine in windows. Also I cant connect with Ethernet since my laptop does not have an Ethernet port. So is there any way for me to connect to the internet in ubuntu? Edit: Output of the terminal command  lspci -knn | grep Net -A2:  vikram@vikram-Inspiron-11-3148:~$ lspci -knn | grep Net -A2 01:00.0 Network controller [0280]: Broadcom Corporation BCM43142 802.11b/g/n [14e4:4365] (rev 01)     Subsystem: Dell Device [1028:0018]     Kernel driver in use: bcma-pci-bridge vikram@vikram-Inspiron-11-3148:~$    I did what Pilot6 suggested. Here is the output:    vikram@vikram-Inspiron-11-3148:~$ sudo dpkg -i *.deb [sudo] password for vikram:  Selecting previously unselected package bcmwl-kernel-source. (Reading database ... 163804 files and directories currently installed.) Preparing to unpack bcmwl-kernel-source_6.30.223.141+bdcom-0ubuntu2_amd64.deb ... Unpacking bcmwl-kernel-source (6.30.223.141+bdcom-0ubuntu2) ... Selecting previously unselected package dkms. Preparing to unpack dkms_2.2.0.3-1.1ubuntu5.14.04_all.deb ... Unpacking dkms (2.2.0.3-1.1ubuntu5.14.04) ... Setting up dkms (2.2.0.3-1.1ubuntu5.14.04) ... Setting up bcmwl-kernel-source (6.30.223.141+bdcom-0ubuntu2) ... Loading new bcmwl-6.30.223.141+bdcom DKMS files... First Installation: checking all kernels... Building only for 3.16.0-30-generic Building for architecture x86_64 Building initial module for 3.16.0-30-generic ERROR (dkms apport): kernel package linux-headers-3.16.0-30-generic is not supported Error! Bad return status for module build on kernel: 3.16.0-30-generic (x86_64) Consult /var/lib/dkms/bcmwl/6.30.223.141+bdcom/build/make.log for more information. modprobe: FATAL: Module wl not found. update-initramfs: deferring update (trigger activated) Processing triggers for man-db (2.6.7.1-1ubuntu1) ... Processing triggers for initramfs-tools (0.103ubuntu4.2) ... update-initramfs: Generating /boot/initrd.img-3.16.0-30-generic vikram@vikram-Inspiron-11-3148:~$


I installed TeXLive 2016 via PPA and used following set of commands-  sudo add-apt-repository ppa:jonathonf/texlive sudo apt update sudo apt install texlive-full   Due to some reasons, I tried to remove it but I couldn't. Later, I installed TeXLive from the official website by following this link  I used the following command-  ravi@home:~/Downloads/install-tl-20180527$ sudo ./install-tl   Now, I am able to use TeXLive 2018 on Ubuntu 14.04 LTS using Texmaker 4.1 (compiled with Qt 4.8.4 and Poppler 0.24.3). However, my Ubuntu shows the following error-    It seems that TeXLive2016 is the culprit. I used sudo apt-get purge texlive* but it didn't work. Please see below-  The following packages have unmet dependencies:  asymptote : Depends: texlive-latex-base but it is not going to be installed              Depends: texlive-base-bin              Depends: texlive-pstricks but it is not going to be installed  dvipng : Depends: texlive-base-bin  feynmf : Depends: texlive-latex-base but it is not going to be installed           Depends: texlive-font-utils but it is not going to be installed           Depends: texlive-extra-utils but it is not going to be installed  fragmaster : Depends: texlive-base-bin               Depends: texlive-latex-base but it is not going to be installed               Depends: texlive-latex-recommended but it is not going to be installed               Depends: texlive-extra-utils but it is not going to be installed               Depends: texlive-font-utils but it is not going to be installed  latex-beamer : Depends: texlive-latex-base but it is not going to be installed  latex-xcolor : Depends: texlive-latex-recommended but it is not going to be installed  latexmk : Depends: texlive-latex-base but it is not going to be installed  pgf : Depends: texlive-latex-recommended but it is not going to be installed  prosper : Depends: texlive-latex-base but it is not going to be installed            Depends: texlive-pstricks but it is not going to be installed            Depends: texlive-latex-recommended but it is not going to be installed  purifyeps : Depends: texlive-metapost but it is not going to be installed  tex4ht-common : Depends: texlive-base-bin                  Recommends: tex4ht but it is not going to be installed  tipa : Depends: texlive-latex-base but it is not going to be installed         Depends: texlive-base-bin E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).   Also tried sudo apt-get autoremove and sudo apt-get -f install. Plese, see below-  ravi@home:~$ sudo apt-get -f install Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... Done The following extra packages will be installed:   luatex texlive-binaries texlive-extra-utils texlive-font-utils   texlive-fonts-recommended texlive-fonts-recommended-doc   texlive-generic-recommended texlive-latex-base The following packages will be REMOVED:   context The following NEW packages will be installed:   luatex texlive-binaries texlive-extra-utils texlive-font-utils   texlive-fonts-recommended texlive-fonts-recommended-doc   texlive-generic-recommended texlive-latex-base 0 upgraded, 8 newly installed, 1 to remove and 264 not upgraded. 1 not fully installed or removed. Need to get 0 B/30.2 MB of archives. After this operation, 9,608 kB of additional disk space will be used. Do you want to continue? [Y/n] y (Reading database ... 295461 files and directories currently installed.) Removing context (2016.05.17.20160523-1~ubuntu14.04.1york0) ... unknown option: format dpkg: error processing package context (--remove):  subprocess installed post-removal script returned error exit status 1 Errors were encountered while processing:  context E: Sub-process /usr/bin/dpkg returned an error code (1)   Any workaround to fix it, please?

How can I remove everything that is related to TeX Live from my Ubuntu 12.04? I first used the backport packages from ppa:texlive-backports/ppa and later the manual install via . Somehow, everything screwed up, so I want to remove everything to start from scratch.  I want to get a recent TeX Live with Biber support and extended font support, i.e. support for Source Sans Pro.  What to do?


Is there a way to prove  $$1+\frac{1}{2}+\frac {1}{3}+...+\frac{1}{n-1} = \ln(n)+c+o(n)$$ where c is a constant? Any idea will be appreciated, thanks!

How to find the sum of the following series? $$1 + \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \dots + \frac{1}{n}$$ This is a harmonic progression. So, is the following formula correct? $\frac{(number ~of ~terms)^2}{sum~ of~ all ~the~ denominators}$ $\Rightarrow $ if $\frac{1}{A} + \frac{1}{B} +\frac{1}{C}$ are in H.P. Therefore the sum of the series can be written as : $\Rightarrow \frac{(3)^3}{(A+B+C)}$ Is this correct? Please suggest.


I have three Google accounts configured in my phone. I want to remove my master Google account without losing other important data of my phone.   When I am trying to delete it, it is not allowing me to remove it, as some of the dependent application are installed with that Google account. I tried with removing those application also but still not able to remove it.   Please suggest any solution other than factory reset?

While setting up my HTC Hero phone, I have entered my gmail account in the setup. But now I want to remove it (I don;t want to change with another account). How do I do it ?  I have searched a lot on Google and everywhere I found that I have to do factory reset but this is not my favoured option.  If there is another way, please let me know.


Problem : Let $S$ be the relation G~H iff G is isomorphic to H.   Show reflexive, transitivity and symmetric.  First show G is automorphism, which will imply G~G. So the identity mapping gives us this automorphism.  So G~G. My question is, is this the right process for showing reflexiveness?  Now we show symmetry. Assume G is isomorphic to H. Thus there exists a mapping $\phi:G ->H$.  We must show H is isomorphic to G. Since $\phi$ is this mapping, consider $\phi^{-1}.$ This is a bijection since $\phi$ is a bijection. How do I show it is homomorphic?  Finally show its transitive. This I have done in a previous problem.  This is different than the duplicate as suggested because previously I had done it incorrectly. I know now I must do it this way.

Let $S$ be the collection of all groups. Deﬁne a relation on $S$ by $G \sim H$ iﬀ $G ≈ H$. Prove that this is an equivalence relation. So $S$ is partitioned into isomorphism classes.   Proof: Let $S$ be a relation on S defined by $G \sim H$ iﬀ $G ≈ H$. Show reflexive, symmetric, transitive. It is obvious that $G≈G$ so $G\sim G$.  Assume $G\sim H$, thus $G≈H$, which implies that $H≈G$, so $H\sim G$, thus symmetric.  Assume $G\sim H$ and $H\sim K$, for $K$ a group in $S$. Thus $G≈H$ and $H≈K$. (I have already shown that if $G≈H$ and $H≈K$, then $G≈K$). From earlier this implies that $G≈K$, so $\sim$ is an equivalence relation.  Thus $S$ is partitioned into isomorphism classes. QED.


I have a list of object which contain all user information.  List<UsrProfile> listUsr = GetAllUser();   In dashboard I have to show only 10 user profile randomly from list on each page refresh.

I need a quick algorithm to select 5 random elements from a generic list. For example, I'd like to get 5 random elements from a List<string>.


So, this is a question from an econometric tutorial and I am simply confused (and nervous) about this question. Is an assumption the same as a condition? What kind of example can I give that best explains this?

First, don't panic. Yes, there are many similar question on this site. But I believe none gives a conclusive answer to the question below. Please bear with me.  Consider a data generation process $\text{D}_X(x_1, ... , x_n|\theta)$, where $\text{D}_X(\cdot)$ is a joint density function, with $n$ variables and parameter set $\theta$. It is well known that a regression of the form $x_n = f(x_1, ... , x_{n-1}|\theta)$ is estimating a conditional mean of the joint distribution, namely, $\text{E}(x_n|x_1,...,x_{n-1})$. In the specific case of a linear regression, we have something like $$ x_n = \theta_0 + \theta_1 x_1 + ... + \theta_{n-1}x_{n-1} + \epsilon $$ The question is: under which assumptions of the DGP $\text{D}_X(\cdot)$ can we infer the regression (linear or not) represents a causal relationship? It is well known that experimental data does allow for such interpretation. For what I can read elsewhere, it seems the condition required on the DGP is exogeneity: $$ \text{E}(x_1, ... x_{n-1}|\epsilon) = 0$$ The nature of randomisation involved in experimental data ensures the above is the case. The story goes then to argue why observational data normally fails in achieving such condition, reasons including omitted variable bias, reverse causality, self-selection, measurement errors, and so on. I am however uncertain about this condition. It seems too weak to encompass all potential arguments against regression implying causality. Hence my question above. UPDATE: I am not assuming any causal structure within my DGP. I am assuming that the DGP is complete, in the sense that there must be some causality (an ontological position it could well be debated), and all relevant variables are included. The key is to identify the set of assumptions which ensure me causality goes from certain variables to the other, without assuming from the outset such direction of causality.  Many similar posts on the site spend time mentioning why correlation does not imply causation, without providing hard arguments about when it does. That is the case, for instance, of  very popular post. Additionally, in the  on the site about the topic, the accepted answer gives the very vague answer:  Expose all hidden variables and you have causation.  I do not know how to translate that to my question above. Neither is the second most upvoted answer. And so on. That is why I believe this post does not have an answer elsewhere.


Using  apt-get update I am getting    Err http://ppa.launchpad.net precise/main amd64 Packages               404  Not Found  W: Failed to fetch http://ppa.launchpad.net/webupd8team/jupiter/ubuntu/dists/precise/main/binary-amd64/Packages 404  Not Found  E: Some index files failed to download. They have been ignored, or old ones used instead.   The machine is behind proxy and proxy is configures correctly and the error is not coming for  other packages fetched from the internet. It is more common with ppas. Never got a problem with other sources.  had the problem with:   deb http://_ppa.launchpad.net/rabbitvcs/ppa/ubuntu precise main deb [arch=amd64] http:__ppa.launchpad.net/webupd8team/jupiter/ubuntu precise main   also tried using Acquire::http {No-Cache=True;}; and treid cleaning the cache of list sudo rm /var/lib/apt/lists/*  Nothing worked out. The url that fails opens perfectly in browser or using wget.  This problem only happens when using proxy.

PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?


I would like to represent the ɛ-neighborhood of a convex polygon, which is the  of the polygon and a disk of radius ɛ. The polygon is given by its vertices, from which of course I could calculate a drawing, but I hope that there is a simpler solution using TikZ (though I'm equally happy with any other solution). , the ɛ-neighborhood of a triangle.

I'm trying to draw a boundary around a convex set of circular nodes in TikZ. The aim is to have it padded by 1cm, with an arc at the corners between segments, like this:    I currently have the following code:  \documentclass{article} \usepackage{tikz} \usetikzlibrary{calc}  \begin{document} \begin{tikzpicture}[every node/.style={circle,draw=blue}]    \node at (0,0) (a) {};   \node at (1,3) (b) {};   \node at (2,2) (c) {};    \draw[red]   ($(a)!1cm!-90:(c)$)   let \p1 = ($(a)!1cm!-90:(c) - (a)$),     \n1 = {atan2(\x1,\y1)},     \p2 = ($(a)!1cm!90:(b) - (a)$),     \n2 = {atan2(\x2,\y2)},     \n{delta} = {-Mod(\n1-\n2,360)}   in      arc [start angle=\n1, delta angle=\n{delta}, radius=1cm]   --   ($(b)!1cm!-90:(a)$)   let \p1 = ($(b)!1cm!-90:(a) - (b)$),     \n1 = {atan2(\x1,\y1)},     \p2 = ($(b)!1cm!90:(c) - (b)$),     \n2 = {atan2(\x2,\y2)},     \n{delta} = {-Mod(\n1-\n2,360)}   in      arc [start angle=\n1, delta angle=\n{delta}, radius=1cm]   --   ($(c)!1cm!-90:(b)$)   let \p1 = ($(c)!1cm!-90:(b) - (c)$),     \n1 = {atan2(\x1,\y1)},     \p2 = ($(c)!1cm!90:(a) - (c)$),     \n2 = {atan2(\x2,\y2)},     \n{delta} = {-Mod(\n1-\n2,360)}   in      arc [start angle=\n1, delta angle=\n{delta}, radius=1cm]   -- cycle;  \end{tikzpicture} \end{document}   I'm going to have to draw a lot of these, so it would useful if I could replace the \draw statement by something like:  \draw[red] \convexpath{(a) (b) (c)}{1cm};   where (a) (b) (c) are the nodes in the corners of the convex set in a clockwise direction. In the case of one node I would like it to draw a circle of the specified radius around the node in question.  Does anyone have any suggestions for how to go about writing such a macro?


I would like to work with 3 different workspace.  One folder (D:\stegdq\rasters) contains only rasters, this is satellite images folder, I would like to read only; one file geodatabase for the temporaly files (D:\temp.gdb); and one other gdb for the results - arcpy.env.workspace=r'D:\tes\gfrd\ujhateq\result.gdb'.  I would like to write one script containing every different steps in all, but how can I change between 3 workspaces? Now I have to run one by one, and I have to set workspace again. I'm a beginner in ArcPy.  input poligon (from results.gdb) bufferig-"25 Meters" (temp); then ListRasters (from the rasters folder); set env.snapRaster rasters[0]; input elevation_point.shp (from the result.gdb) with env.snapRasters interpolating (temp); sa.ExtractByMask rasters[0] (from satelite image with temp buffer); from these extract image RasterToPoint_conversion shp (temp) and RasterToPolygon_conversion shp (result); with temp_point ExtractMultiValuesToPoints (all satellite images from rasters folder); and extractValueToPoint (from elevation raster-temp) do some calculation in the attribute table (in the temp point table); join temp_point values to the polygon (from result.gdb)  Is it possible to handle this workspace change in one script? (ArcGIS 10.6)

I've created 1 script to perform 2 specific tasks but it not working correctly due to how the arcpy.env.workspace is set.   The first part of the script deletes and recreates the sub folders in "C:/EIS/SHP Files"  arcpy.env.workspace = "C:/EIS/SHP Files"   The second part of the script looks inside a particular sub folder in "C:/EIS/SHP Files/Master folder" and copies Pipe data back into the newly created folders  arcpy.env.workspace = "C:/EIS/SHP Files/Master Folder"   Problem: I can't reference 2 environments at once in a script. The script will give out an error message since it can't look in 2 paths at once. So how can we do this?  import sys import platform import imp print "Importing arcpy... this may take a moment\n" import arcpy from arcpy import env  # Set workspace arcpy.env.workspace = "C:/EIS/SHP Files"  # Creates the county folders out_folder_path = "C:/EIS/SHP Files/"  # Set local variables # List of folder values in load order folderList = ["1","2","3","4","5"]  # Store all the folder names in a dictionary with the folder code as the   # "key" and the folder description as the "value" (folderDict[code]) folderDict ={"1":"OH_ADAMS","2":"OH_ALLEN","3":"OH_ASHLAND","4":"OH_ASHTABULA","5":"OH_ATHENS"}  # Wayne Pipe in_data_WayneMain =  "WayneMain.shp" out_Geauga_WayneMain = "C:/EIS/SHP Files/OH_GEAUGA/WayneMain.shp"  # The Code below will utilize the [arcpy.CreateFolder_management] tool in  # order to rebuild the directory for C:\EIS\SHP Files\.. County Folders  # Process: Add valid material types to the domain # use a for loop to cycle through all the domain codes in the dictionary for code in folderList:     if arcpy.Exists(out_folder_path):         arcpy.Delete_management(folderDict[code])         arcpy.CreateFolder_management(out_folder_path, folderDict[code])  # The Code below will utilize the [arcpy.Copy_management] tool in order to    # copy files from the C:\EIS\SHP Files\Master Folder to C:\EIS\SHP Files..  # County Folders  # Wayne Pipe (Copied) To => County Folders arcpy.Copy_management(in_data_WayneMain, out_Geauga_WayneMain)


How can make an environment in which I can write my text and in output, I see it indented with a coloured vertical line?  I want the code be like the following:  \begin{textbox}[orange][1cm] % [colour of the line][distance from left margin] \lipsum[1] \end{textbox}     \documentclass{book} \usepackage{lipsum} \begin{document} \lipsum \end{document}

I'm looking for a way in Plain TeX to make a continuous vertical rule along the left side of a paragraph (or arbitrary block of text), such that it observes normal page-break rules. I started with the following, which looks exactly how I want, except of course it has the undesirable side-effect of preventing page breaks for large runs of text, since it uses \vbox:  % Definition \def\codeblock#1{%   \hbox{%     {\vrule width .6pt}%     \hskip 1em%     \vbox{\tt #1}%   }% }  % Example \codeblock{% \hbox{void main(int argc, char *argv[]) \char123}% \hbox{{\ }{\ }printf("Hello, world!{\char92}n");}% \hbox{\char125}% }   As a workaround, I'm currently resorting to breaking things into separate lines and a series of kludged non-continous-but-overlapping vertical rule segments:  % Definition \def\codeline#1{%   \hbox{%     \vrule width .6pt height .85em depth .46em%     \hskip 1em%     \tt #1%   }%   \vskip -.11em% }  % Example \codeline{void main(int argc, char *argv[]) \char123} \codeline{{\ }{\ }printf("Hello, world!{\char92}n");} \codeline{\char125}   In a perfect world, I'd like to simply pass an arbitrary block of text to a macro and have it apply normal pagination rules to the block of text, while at the same time making a vertical rule down the left. I don't have much experience with TeX but I suspect the answer is that it's not trivial?  While typing this question,  appeared in the margin. I will definitely give that a try — and it looks really powerful and well thought out — but it also seems quite heavyweight for something that I would think ought to be reasonably straightforward. Also, not that I have anything against LaTeX, but I'd prefer to use a solution as close to Plain TeX as possible, so that I can have some hope of understanding it.


I have a double 2D array:  a[0,0]=1.1      a[0,1]=0.1      a[0,2]=2.9      a[0,3]=1.6  a[1,0]=-2.2     a[1,1]=-1.7     a[1,2]=0.3      a[1,3]=-0.4  a[2,0]=2.0      a[2,1]=-0.1     a[2,2]=-1.8     a[2,3]=-3.1   1) I want to sort it in descending order AND save the 2 indexes (in order to know which array indexes has the absolute higher/lower values):  a[2,3]=-3.1 a[0,2]=2.9 a[1,0]=-2.2 a[2,0]=2.0 a[2,2]=-1.8 a[1,1]=-1.7 a[0,3]=1.6 a[0,0]=1.1 a[1,3]=-0.4 a[1,2]=0.3 a[0,1]=0.1 a[2,1]=-0.1   2) I also need a different sort: on the first index and save the 2nd index:  a[0,2]=2.9 a[0,3]=1.6 a[0,0]=1.1 a[0,1]=0.1  a[1,0]=-2.2 a[1,1]=-1.7 a[1,3]=-0.4 a[1,2]=0.3  a[2,3]=-3.1 a[2,0]=2.0 a[2,2]=-1.8 a[2,1]=-0.1   I don't know if I'm a moron of not :-) but I've unsuccessfully tried to understand the Microsoft "Array.Sort()" function variations to solve these problems.  Is it possible with "Array.Sort()" ?  I'm a beginner, some help will be greatly appreciated!  Thank you very much!

I have a two-dimensional array (of Strings) which make up my data table (of rows and columns).  I want to sort this array by any column.  I tried to find an algorithm for doing this in C#, but have not been successful.  Any help is appreciated.


I have a matlab script that loads values by reading non-standard length bits.  For example:  [file, errmsg] = fopen(FileName,'r');  year = fread(file,1,'ubit12','ieee-le');  month = fread(file,1,'ubit4','ieee-le');  day = fread(file,1,'ubit5','ieee-le');  version = fread(file,1,'ubit11','ieee-le');   The values loaded are:  year =2016 month =7 day =21 version =0   While the binary version of the file is:   11100000 01110111 00010101 00000000   (as retrieved by doing '{0:08b}'.format(ord(byte)) in python)  In other words,  year -> 4 lsb of byte 2 + byte 1 (011111100000) month -> 4 msb of byte 2 (0111) day -> 5 lsb of byte 3 (10101) version -> 3 msb of byte 3 + byte 4 (00000000000)   Is there a pythonic way to achieve the same functionality?

I need a compact representation of an array of booleans, does Python have a builtin bitfield type or will I need to find an alternate solution?


We have an Ubuntu 12.04 server running on a VMware ESXi host, with multiple partitions, running Zimbra 8 (mta/ldap only). One of partitions is a 30GB partition mounted as /opt/zimbra/data. I had a rude wake up call this morning from my manager claiming the mail server was down.   I logged in and took a look and sure enough, all commands were reporting that there wasn't enough free space on the /opt/zimbra/data partition. I was trying to figure out which file it was that was using up all the space, but both df and du failed me. Here are the outputs from the various commands after I had tracked down the file by doing an ls one directory at a time:  zimbra@mail:/opt/zimbra/data/ldap/mdb/db$ du -sh . 20M .  zimbra@mail:/opt/zimbra/data/ldap/mdb/db$ du --apparent-size data.mdb 31409532    data.mdb   zimbra@mail:/opt/zimbra/data/ldap/mdb/db$ df -h . Filesystem      Size  Used Avail Use% Mounted on /dev/sde1        30G  1.3G   28G   5% /opt/zimbra/data   zimbra@mail:/opt/zimbra/data/ldap/mdb/db$ ls -allh total 20M drwxr-xr-x 2 zimbra zimbra 4.0K Nov 26 13:50 . drwxr-xr-x 3 zimbra zimbra 4.0K Jul 16 05:47 .. -rw------- 1 zimbra zimbra  30G Nov 26 14:04 data.mdb -rw------- 1 zimbra zimbra 8.0K Nov 26 14:07 lock.mdb   Note that the file data.mdb is using up all 30Gigs, but is not being taken into account when reporting the total space.   We have since created a new partition, copied the files over, and have things up and running, but I am still curious what would have caused the incorrect reporting of used space on the partition. We still have the old partition lying around, so if there are other commands I don't know of that would yeild more accurate results, I would like to try them out.  Update:  Output from ls -alsh  root@mail:/opt/zimbra/data/ldap/mdb/db# ls -alsh total 20M 4.0K drwxr-xr-x 2 zimbra zimbra 4.0K Nov 26 13:50 . 4.0K drwxr-xr-x 3 zimbra zimbra 4.0K Jul 16 05:47 ..  20M -rw------- 1 zimbra zimbra  30G Nov 26 14:04 data.mdb 4.0K -rw------- 1 zimbra zimbra 8.0K Nov 26 14:07 lock.mdb   So it looks like the file is indeed a sparse file, and was very close to the partition size. I still have no idea why commands like touch or cp started returning no space left on disk, as this file only seems to have actually been using around 20 MB.  Wrapping up, here is what I have come up with to list all files, including sparse files, recursively and order the results by file size desc:  ls -aldSh $(find .) | grep -v '^d'  For any Zimbra users who might end up here with a similar issue, the following links will help:      Update 2:  Another thing to check is if the partition has run out of inodes. Of particular interest are the logger and zmstat subdirectories. These contain a number of small files, and can quickly run out of inodes before running out of space, if mounted on their own partitions. Most commands will still return a "no space left on device" error, which can be misleading.  df -i can be used to show information on the number of free inodes. For example, I have a partition that has about 80% free space according to df -h, but still returns a "no space left on device" error because it is out of inodes:  root@mail:/opt/zimbra/logger# df -h Filesystem       Size  Used Avail  Use%  Mounted on /dev/sdh1        20G   3.9G   16G  21%   /opt/zimbra/logger  root@mail:/opt/zimbra/logger# df -i Filesystem       Inodes   IUsed     IFree IUse% Mounted on /dev/sdh1        5120     5120         0  100%  /opt/zimbra/logger

I'm running an Ubuntu 12.04.1 server in a VMware virtualized environment that has a strange issue. Twice now, at seemingly random times, the machine has suddenly been unable to write to the root partition despite plenty of space seemingly available. I'm at a loss trying to figure out what's wrong.  "df -h" shows all mounted volumes with 40% or more free space. Both times this has happened, rebooting resolved it for a few minutes, and then it was back to saying "no space left on device." Restoring it from a snapshot seems to fix it for longer, but since this has now happened again, I'm not sure what to do with it.  If it helps, the machine is a network print server running CUPS 1.5.3 and Samba 3.6.3.


Let $a_1, a_2, \ldots, a_n \in \mathbb{R}$. Prove that the following inequality holds: $$\sqrt[3]{a_1^3+ a_2^3 +\cdots+a_n^3} \le \sqrt{a_1^2 + a_2^2 +\cdots+a_n^2}$$    I first tried to restrict the inequality to $\mathbb{R}^{+}$ and that's fairly easy to do since:  $$\sqrt[3]{a_1^3+ a_2^3 +\cdots+a_n^3} \le \sqrt[3]{|a_1^3| + |a_2^3| +\cdots+ |a_n^3|}$$  and  $$\sqrt{a_1^2 + a_2^2 +\cdots+a_n^2} = \sqrt{|a_1^2| + |a_2^2| +\cdots+ |a_n^2|}$$  I tried using the Jensen's Inequality on $x^{\frac 32}$ and $x^{\frac 23}$, but the inequality goes in the opposite direction. Also I tried to divide with $n^{\frac12}$ and $n^{\frac13}$ and use the power mean inequality, but again the inequality goes in the opposite direction.  Anyway, I managed to solve it by raising the inequality to sixth power and we get:  $$\sum a_1^6 + 3\sum a_1^4a_2^2 + 6\sum a_1^2a_2^2a_3^2 \ge \sum a_1^6 + 2\sum a_1^3a_2^3$$  Which is true since:  $$a_1^4 a_2^2 + a_1^2 a_2^4 \ge 2a_1^3 a_2^3$$  and all terms on the LHS are positive. But this prove looks kind of messy. Is there any better proof?  Also it's seems that we can extend this inequality to:  $$k_1 \ge k_2 \implies \sqrt[k_1]{a_1^{k_1}+ a_2^{k_1} +\cdots+a_n^{k_1}} \ge \sqrt[k_2]{a_1^{k_2} + a_2^{k_2} +\cdots+a_n^{k_2}}$$ But can we actually do that?

I can't seem to work out the inequality $(\sum |x_n|^q)^{1/q} \leq (\sum |x_n|^p)^{1/p}$ for $p \leq q$ (which I'm assuming is the way to go about it).


public class Node {    int value;   List<Node> childNodes;    Node(int x) {     value = x;   } }   Above is the definition of the tree node and we have a tree.  Node root = new Node(0); Node n1 = new Node(1); root.childNodes.add(n1);  Line 1   This is how I construct the initial tree structure in main, however, I got a nunllpointerexception in line 1. Anybody knows the reason?

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?


How long is beef suet good in fridge?   Does it make any difference if I store it as a whole or chopped into pieces?  EDIT: This is suet, not tallow, which can even be left outside the fridge for 1 year. This not a duplicate question.  EDIT: Suet is raw fat not raw protein.

I kept all of the bacon grease from making bacon this weekend, and now I have a jar of solidified grease in the fridge. How long can I use this to impart bacony goodness to my fried vegetables before it goes bad?  What is the shelf life of the fat drippings from bacon, roast and other meats?


Musical styles, for instance.  Specifically I am dealing with choosing "blues" or "Blues"? I assume it would be the same for visual art styles.

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


I want to make a bootable USB of Windows 8.1 from Ubuntu 14.10 so that I can install it on my laptop.   I tried using winusb and UNetbootin, but both of them failed.   What else can I try?  I have Windows 8.1 Pro 64-bit iso, and I am using Ubuntu 14.10 64-bit.

I'd like to create a Windows bootable USB stick, but I don't have a Windows machine with me at the moment to do so. How could I achieve the same using Ubuntu?


Which of the following is the correct usage of the plural possessive word "user"?     We would like to store a cookie in every user's browser.   or     We would like to store a cookie in every users' browser.

Is it correct to use: Not every student is as rude as you mentioned   Or  Not every student are as rude as you mentioned.  Thanks


I am from Nigeria, and I have UK visa to visit for 6 months. I didn't use it to travel because I am pregnant and due for delivery. My doctor says I can't travel. Will I be able to get another visa when next I want to travel again? I don't know if this will affect my chance of getting another visa.

Last year, my wife and I were issused 6-month visieor visas for the UK. She did not travel with me and, therefore, didn't use her visa. I am currently applying for a visitor visa for my daughter and myself.  Will the fact that my didn't use her visa have any negative affect on our new application?


Why does Stack Exchange choose to track reputation in separate categories? Like you could have 100,000 rep in the Arqade one, but only have 100 over in Role-Playing? And that’s because they reward you with a hundred for ‘trusting you’. Can someone explain the sites' potential reasoning for doing this?

Possible Duplicate:        I am talking about surepuser, serverfault and stackoverflow altogether.  There are two reason for this opinion, one is philosophical and the other is practical. Let me start with the philosophical first.   mail.google.com, reader.google.com and www.google.com provides three different functionalities, yet, same person, log in once, and he's logged in to all of them.  In practice, many developers are ending up installing their software on server machines, many of them are required to maintain these bytes regularly or even build some other tools that will do this for automatically (serverfault.com) - That's why I see no reason having two separate accounts for the same  senior developers usually can be considered as power users, so why would it be a different for the very same developer when posting a question or answering one on suerpuser.com.  and most of all, having meta.stackoverflow on a separate account is totally mistaken - imagine a guy scoring 27k on stackoverflow. One day, this fellow has an idea how to improve the site so to make it even easier to answer questions.  If this fellow answered 12k questions a year, his suggestion must be considered differently that one who answered 3 question a year, right? Since he's a proven heavy user of the site and a major contributor. Yet, when he will first login to the meta.so and create the account one will not notice their stackoverflow activity and might ignore their feature request altogether.


If 'quantum foam'-generated particles are made of matter and antimatter in equal amounts, why don't the matter particles that fall into the black hole add to the black hole's mass just as much as the antimatter particles subtract from it? How, then, can the black hole evaporate due to Hawking radiation? P.S.: Someone else asked a very similar question, but it was never answered....

I was reading Brian Greene's "Hidden Reality" and came to the part about Hawking Radiation. Quantum jitters that occur near the event horizon of a black hole, which create both positive-energy particles and negative-energy particles, produce the so-called Hawking radiation. However, I do not understand why only the negative-energy particles are being absorbed into the black hole, while the positive-energy particles shoot outward. Shouldn't there be 50/50 chance that each type of particle is being absorbed by the black hole? Also, the book mentions that a negative-energy particle would appear to an observer inside the black hole as positive. Why?


Jane's mother will come to pick her up soon.    Jane's mother will come pick her up soon.       The kid Jane is being looked after at her grandparents' home. In a hour, her mother will arrive at the house to pick her up. What's the most appropriate way to express this?

Reading the book on which I'm learning English, I've come across a weird (for me) omitting the "to" in sentence: "I'd better go meet with him then."  Say, if it were "I'd better go to meet with him then.", would there be any difference between the two sentences? When I should prefer using one instead the other?  P.S. Sorry for my bad English. If I made a mistake somewhere, please correct me.


In the field of computer science, what should users who are  not experts and scientists be called?  I've come up with ordinary users or regular users. Any formal alternative or widely-accepted term/word?

For example, you're a fashion designer who wants to get the opinion of both a professional and someone who doesn't know much about fashion. What's a term for the latter person?


A. function foo( ){ }  B. var foo = function foo( ){ }  I write all my JavaScript functions in the A fashion because I think B is redundant. My coworker likes to go in and do mass find/replace to rewrite my functions like B because he says it's best practice according to airbnb.   What is the fundamental/practical difference between the two? Is there danger of him breaking my code by doing this? Is one better practice than the other (can you cite any sources)?

I've recently started maintaining someone else's JavaScript code. I'm fixing bugs, adding features and also trying to tidy up the code and make it more consistent.  The previous developer used two ways of declaring functions and I can't work out if there is a reason behind it or not.  The two ways are:  var functionOne = function() {     // Some code };     function functionTwo() {     // Some code }   What are the reasons for using these two different methods and what are the pros and cons of each? Is there anything that can be done with one method that can't be done with the other?


I am trying to implement the functionality to confirm whether "Leaving the page" whenever the user tries to close the browser. As of now i have implemented,  function closeIt(e) {     // For IE and Firefox prior to version 4 if (e) {     e.returnValue = 'Sure?'; }   } window.onbeforeunload = closeIt;  This works fine for closing the browser, but instead works for all the links in the page aswell, as there is condition to identify what is causing the onbeforeunload event. Can anyone help me identify them.  Thanks in advance.

I tried the following code to get an alert upon closing a browser window:  window.onbeforeunload = confirmExit; function confirmExit() {   return "You have attempted to leave this page.  If you have made any changes to the fields without clicking the Save button, your changes will be lost.  Are you sure you want to exit this page?"; }   It works, but if the page contains one hyperlink, clicking on that hyperlink raises the same alert. I need to show the alert only when I close the browser window and not upon clicking hyperlinks.


suppose $n$ , $k$ are positive integers both. if for any set $ \{ a_1,a_2,....,a_k \}$ with sum of $n$ we write down multiplication of $a_1,a_2,....,a_k$. now I want to prove that the sum of written numbers is $\binom{n+k-1}{2k-1}$ .

I am trying to solve a problem from Stanley's book, it says:  Fix $k,n \in \mathbb{P}$. Show that: \begin{align} \sum a_1 a_2 \cdots a_k = \binom{n+k-1}{2k-1} \end{align} where the sum ranges over all compositions $(a_1 , a_2 , \ldots , a_k)$ of $n$ into $k$ parts.  I am trying to reason like this:  we need to find the coefficient $c_n = \sum a_1 a_2 \cdots a_k$ from this generating function --  \begin{align} \sum_n c_n x^n &= \sum_n \sum a_1 a_2 \cdots a_k x^n \\  &= \sum_n \sum a_1 a_2 \cdots a_k x^{a_1 + a_2 + \cdots + a_k}\\ &= \sum_n \sum a_1x^{a_1} a_2x^{a_2} \cdots a_kx^{a_k} \end{align}  after that, I have no clue, how do I solve this ?   moreover, what is the range in the inner sum ?    If we consider Mark Riedel's answer, and assume $n=4$, $k=2$; then the sum will be  \begin{align} \sum (z + 2z^2)^2 = z^2 + 4z^3 + 4z^4 \end{align}  On the other hand the compositions will be $(1,3), (2,2), (3,1)$, therefore the above sum will be counted as:  \begin{align} (1.3)z^{1+3} + (2.2)z^{2+2} + (3.1)z^{3+1} &= 1z^1.3z^3 + 2z^2.2z^2 + 3z^3.1z^1\\  &= 3z^4 + 4z^4 + 3z^4 = 10z^4 \end{align}   what's going on? what am I missing?


Why can visible light, which lies in the middle between X-ray and radio waves in terms of frequency/energy, not penetrate walls?

I did search the question on Physics S.E considering it would be previously asked. I found this  But in this question , the answers are w.r.t to or in comparison with microwaves , their absorption and certain other things. I didn't find a sort of general answer that could be the answer to the question. So the question is - wifi or radio waves  reach us through concrete walls . They also reach us through the ceiling (if some one is using it in the flat above ours ). Even through the air they travel such a lot , bending around corners or doors . Now I would not compare them to microwaves (because I don't want the answer in terms of properties of the material but physics). Visible light which is so much powerful than them can't penetrate black opaque paper leave alone the walls. Same is true for gamma rays (penetration through a very thick wall). So why then radio waves being so very less powerful than light  waves are able to travel through walls? There should be a general concept as to why the radio waves are able to pass through walls but microwaves or light waves cannot ! A linked question is also that sound travels much faster in solids(walls) but is not audible in it though it is in air. After reading @BillN's answer, it would be really helpful if any one could explain it in terms molecular resonance or crystalline structure or electrical conductivity or how does molecular resonance or crystalline structure or electrical conductivity cause this.


I would like to display information of a line feature in parallel. For example, a river line feature with its different qualities. I want to avoid a parallel copy of line features. Is it possible to achieve this with display symbology options in ArcMap? For clearance:   from:

My data of polylines has lots of attributes to be rendered with a symbology, I made it such that each attribute of interest would be a layer. I would like to display each of these layers at the same time so that the attributes could be seen at the same time. Since the top layers cover the lower ones, I set the symbology so that the layers would have increasing different thickness, with the most bottom layer having the thickest line.  Is there a better way to do this, like offsetting a layer's symbology a little bit to the left or right so that each layer can be displayed side by side? Visually, something like .  I'm using ArcGIS 10.


I got the following code:      html {   height: 100%; } html, body {     min-height: 100% !important;     /* prevent horizontal scrolling */     max-width: 100% !important;     overflow-x: hidden !important;     -webkit-box-sizing: border-box;        -moz-box-sizing: border-box;             box-sizing: border-box; }   #menuButton {     float:left;     background-image: url("../images/hamburger_menu.png");     width: 50px;     height: 40px;     margin-right: 5px; }  #powerButtonBox {     float: right; }  #outerBox {     min-height: 100%;      height: auto !important;     height: 100%; }  #title {     background: #E95353;     padding: 10px;     color: white;     font-size: x-large; }   #outerBox {     width: 100%;     height: 100%; }   .nav a small {     display:block; } .nav {     background: #E95353; } .nav a {     border-radius:0px;     color: white; }  .nav-pills>li {     text-align: center;     padding: 10px;     font-size: large; }  .nav-pills>li.active {      background-color: #E95353; /*EF8686*/     border-bottom: 5px solid white;     color: white; }  .nav-pills>li.active>a, .nav-pills>li.active>a:hover,   .nav-pills>li.active>a:focus {      color: #fff;  }

         This is the Title
It is powered on

New Stuff

Done

     My Problem is, that the div with the button is spilling out of the title-div when the display width is too small. You can simply recreate the error when sliding the width smaller in the jsfiddle.  It is okay for me, that there is a line break. That is perfect. But it should still have the red background and be in the title-div. How can I accomplish that?

I have a page structure similar to this:

       /*Content*/

       /*Content*/

    I would like for the parent div to expand in height when the inner div's height increases.  Edit: One problem is that if the width of the child content expands past the width of the browser window, my current CSS puts a horizontal scrollbar on the parent div.  I would like the scrollbar to be at the page level. Currently my parent div is set to overflow: auto;  Can you please help me with the CSS for this?


I can't figure out how to change the margin guides in Print Composer to inches rather than metric.   In the "Composition" tab, under "Page size" I have ANSI A (8.5 x 11 in) selected.   However, the "Units" box below that is greyed out. The "Guides and Grid" section below that only gives options in terms of "mm".   This was indicated as fixed at    However, as was noted there,  "I am having the same issue as above, and have not been able to reproduce your answer. In my installation, choosing a paper size in inches only changes the presets box. The width, height and units are all still in 'mm', and the units are locked and grayed out. – Get Spatial Oct 28 '15 at 23:13"  I am having the same experience as "Get Spatial". Does anyone have any idea why we continue to have this problem, although it seems to have been fixed for some?

I open a new composer and select ANSI A for my paper. The notation after the name is "Letter; 8.5inx11in", but the width and height are displayed in mm, and the units selection is grayed out, so I can't change it. The rulers at the top and left of the layout are in mm, and the parameters for "Snap to grid" are also in mm. If I then select "Custom", I can select inches for units, and the Width and Height display as 8.5 and 11. However the rulers in the layout are still in mm, as are the units for the grid.   Can the entire composer project be converted to inches?    qgis 2.01 64 bit windows 7, 64 bit


I'm still really new to coding, and was just wondering if the following was possible.  I created a program just for fun using java, and want to put the program on a USB stick for my friends to see. But after I finished the program I found out I can only make '.jar' files, which will need to have JDK installed to run.   Is there anyway to have my program converted to a exe file, so that my friends/family can see the program I created without having to install all the java files(jdk etc)?

If I have a Java source file (*.java) or a class file (*.class), how can I convert it to a .exe file?  I also need an installer for my program.


Must the prime finite field, Fp, an elliptic curve is defined over always have a greater number of elements than the cardinality of an elliptic curve.   For example, If I have Elliptic Curve defined by y^2 = x^3 + x + 1 and I can calculate that the  E.cardinality() = 14. Must the prime field I chose be >14? Would there be any loss in security if I chose 11 as the prime field?   Would this be different if I chose the prime field beforehand?

I am reading up on ECC and having trouble understanding how these are related.   In a finite field, all point operations are taken modulo $p$.  $n$ is the order of the generator $G$ — which apparently is the number of different points on the curve which can be generated by multiplying a scalar with $G$. This is clear. But —   How is this $n$ chosen? Is $G$ chosen so that $n$ is a certain number? Does $n$ effect the security of the curve? Do all the points of the crypto operations with a given $G$ fall in the set of $n$ points for that $G$?    $h$ is the cofactor which is the $\#E(\mathbb F_p)/n$.    What is the significance of this?  $\#E(\mathbb F_p)$ is the number of points of the curve apparently. Why is dividing that with $n$ interesting?


I  am aware of $$ 2^{2n} = (1 + 1)^{2n} = \sum_{k = 0}^{2n} \binom{2n}{k} $$ I then tried grouping the terms and using that $\binom{n}{k} = \binom{n}{n-k}$, to obtain $$ \begin{align} \sum_{k = 0}^{2n} \binom{2n}{k} &= \binom{2n}{0} + \binom{2n}{1} + \ldots + \binom{2n}{n - 1} + \binom{2n}{n} + \binom{2n}{n + 1} + \ldots + \binom{2n}{2n} \\ &=  2 \left[ \binom{2n}{0} + \binom{2n}{1} + \ldots + \binom{2n}{n - 1}\right] + \binom{2n}{n} = \left( 2 \sum_{k = 0}^{n-1} \binom{2n}{k} \right) + \binom{2n}{n} \end{align} $$ But I don't know if I'm on the right track or how to progress from here.

I'm repeating material for test and I came across the example that I can not do. How to calculate this sum: $\displaystyle\sum_{k=0}^{n}{2n\choose 2k}$?


I am asking this as there does not seem a clear way to diagnose the problem. I have searched several sites including this one.  After a few minutes Xubuntu freezes and I can't use the mouse or keyboard. I need to hard reboot but the cycle starts again. I have a desktop PC running Xubuntu 14.04 LTS on kernel 3.13.0-48-generic. It is an older PC.

All operating systems freeze sometimes, and Ubuntu is no exception. What should I do to regain control when...   just one program stops responding? nothing at all responds to mouse clicks or key presses? the mouse stops moving entirely? I have an    In what order should I try various solutions before deciding to pull the power plug?  What should I do when starting up Ubuntu fails?  Is there a diagnostic procedure I can follow?


I apologize in advance to experts for the naivety of the question. It should be a duplicate but I didn't find any satifying question or answer about that.    The proton is composed by two up quarks and one down quark.    mass(proton) $\sim 940 \  MeV/c^2 $ mass(up) $\sim 2.3 \ MeV/c^2 $ mass(down) $\sim 4.8 \  MeV/c^2 $    It follows that: $2$mass(up) $+$ mass(down) $\sim  9.4 \sim \frac{1}{100}$ mass(proton).  Question:  Where does $99\%$ of the remaining mass of the proton come from?

It is well known that the most of the proton (or any other hadron with light quarks) mass is not made up from quark masses, but it is dynamically generated by QCD mess inside. I've also heard that, even if quarks would be massless, protons (and other hadrons) would still have a nonzero mass.  However, if proton mass does not (in most part) arise from the quark masses, from which dimensionful constants does it arise?  I've heard that proton mass arises from spontaneous symmetry breaking of scale invariance. However, this is a troublesome explanation, or non-explanation at best, because it opens more questions:  If a theory is scale invariant, how can it pick a scale when breaking this symmetry? The proton mass is a constant, so how can the scale invariance be broken across entire universe the same way? Is there a field, very resistant to change, that permeates entire space to ensure the constancy of proton mass?


Consider tossing a fair coin 100n times, where n is geometrically distributed with mean 6. Due to a counting error, it is reported that the fraction of heads is in [0.5, 0.51]. What is the most likely value for n?    My professor calculated the value of n=3, but I have no idea how to get that. Can anyone explain ?

Problem 3: Central Limit      Consider tossing a fair coin $100n$ times, where n is geometrically distributed with mean 6. Due to a counting error, it is reported that the fraction of heads is in $[0.5,0.51]$. What is the most likely value for $n$?   We've been using the de Moivre Laplace approximation using a standardized sum.     $$ P\left(.50\times100n\leq \frac{S_n -\frac{1}{p}}{\frac{\sqrt{1-p}}{p}}\leq .51\times100n\right) = S_n \Phi(b) - \Phi(a) $$  and we start with $\frac{S_n}{n}$ and manipulate the bounds so we have $S_n^*$.  Which $\approx \Phi(285.34n) - \Phi(279.86n)$  I can't imagine this is correct. How does the Bernoulli trial enter the calculation?


Many people copies/pastes text/data from msword, actually into web forms.  The standart upper coma character is " ' " this but msword's upper coma is " ‘ " so that lead some problems like turning into "?" character after posting the data.  Is there any way to prevent this rather than using functions like string replacement or regular expressions ?

I'm setting up a new server and want to support UTF-8 fully in my web application. I have tried this in the past on existing servers and always seem to end up having to fall back to ISO-8859-1.  Where exactly do I need to set the encoding/charsets? I'm aware that I need to configure Apache, MySQL, and PHP to do this — is there some standard checklist I can follow, or perhaps troubleshoot where the mismatches occur?  This is for a new Linux server, running MySQL 5, PHP, 5 and Apache 2.


Firstly,  I have already looked into  feature request. But its still not implemented.  Problem:  We, as a room owner, are responsible to cancel a few stars which are not quite meaningful. See the below screenshot. There are some messages which were not worth starring. (I have highlighted those stars with a red mark.)    Now I am not able to cancel the stars as these stars don't come up in the right side starred section of room due to new messages got starred.   Feature request:  Either  Room owner and moderator should be able to cancel stars from message itself  Or  Room owner and moderator should be able to cancel stars from starred section in room info.  I think second option is good to be considered.  Edit: I am nominating the question to be reopened, as the old question does not contain any answer. And the feature is must.

Currently, the only way to cancel stars in a chat transcript is when the chat-message is visible in the chatroom's sidebar.    However, in a fast-moving, multi-star chatroom, the window of opportunity to cancel can be short, and rapid changes in starring can quickly make this impossible to do in a timely way.  We use stars as markers in moderator chat events (where the Community managers disseminate important information to the moderator teams) as well as for town halls during elections.  Feature request: Allow mods/room owners to cancel stars from the chat message menu box, including in the transcript.


I have a directory named - AB02530618-20191217-163059.bin_decomprypted (1) created using window. How can I delete this in Linux using command?

I made a text file called hello world in my home directory. Via the shell I am trying to remove it with the rm command. However, when I execute rm hello world the shell thinks that I am trying to delete two separate files, one called "hello" and the other called "world." How do I go about doing this correctly?


I can't get my head around the collation as compared to the character set.  What is collation actually used for ?

I can read the MySQL documentation and it's pretty clear. But, how does one decide which character set to use? On what data does collation have an effect?  I'm asking for an explanation of the two and how to choose them.


I just chose a Pokemon at the start  of the game, but then I realised I could walk away 4 times and get Pikachu.  Is there a way to restart the game?

I accidentally have choosen Bulbasaur for my starter where I wanted Squirtle. Is there anyway to reset it? I have looked in the options menu and there does not appear to be a way to reset it. I guess that I could make a new Google Play account for it, but that seems like a mess.


Stationary states are separable solutions with $\Psi(x, t)=\psi(x)e^{-iEt/\hbar}$. But why is that there? Griffiths (Section 2.1 Stationary states, equation 2.8) says that observables for these states are constant in time, so the time-dependent factor can be left out. So why do we include that factor?  Unlike the duplicate, I want to ask "Can we safely assume $\Psi(x,t)=\psi(x)$ and simply abandon that whole $\exp$ altogether?"

In the particle in a box, harmonic oscillator and in Hydrogen Atom, we can safely assume $$\Psi(x,t) = \psi(x)e^{-i\omega t}.$$ So why not make it a postulate to consider the wave function to be always in the form $$\psi(x)e^{-i\omega t}$$ We can still explain all the foundational experiments, so my question is why not make this amendment to the theory so that we can avoid a lot of nightmares and some peace of mind. Why unnecessarily consider so general thing when we can do away with simple things most of the time?  Oh my actual question is where do we run into problems (practical physical situations/experiments) if we consider such a thing? If we run into problem anywhere, I hope to make any other simple changes to fix them but without going back on this one.


I have a regular windows-based keyboard, what button do I press to have it register the "super" key? I don't see anything that says super on it. what do I do?

In System -> Preferences -> Keyboard -> Layout -> Options ->Alt/Win key behavior  What do meta, super, hyper mean?


If $f: \mathbb R \to \mathbb R$  and $f$ is continuous and for every real value of $x : f(f(x))=x$ , prove that there is a $c$ where $f(c)=c$.  I know how to prove that a continuous function like $f: [a,b] \to [a,b]$ has a fixed point, but I don't know how to distinguish intervals in this question.

If $f:\mathbb{R} \to \mathbb{R}$ is a continuous function such that $f(x)=x$ has no real solution, then show that $f(f(x))=x$ has no real solution either.   Is the proof trivial as it seems or does it need an analytical approach?


if(ApexPages.currentPage().getParameters().get('ScheduleFlag') == 'True'){             schId = ApexPages.currentPage().getParameters().get('schId');             schReport = [Select Id,Report_Name__c,Selected_Fields__c,Labels__c  from Schedule_Report__c where Id = :schId];             allFields = schReport.Selected_Fields__c;             allLabels = New List<string>();             for(string lab :schReport.Labels__c.split(',')){               allLabels.add(lab.trim());               }             ScheduleFlag = true;             directSchedule = true;             WeeklyFlag = true;             userList = new list<SelectOption>();             for(user usr : [SELECT Id,IsActive,Name,Email FROM User where IsActive = true]){                 userList.add(new SelectOption(usr.Email,usr.Name));             }              //Next4();         }     }

I created a test Opportunity -       Opportunity Opp = new Opportunity();     Opp.Name = 'Test Opportiunity ';     Opp.AccountId = acct.id;     Opp.Business_Line__c = 'Capital Markets';     Opp.Result_Reason__c = 'Amenities';     Opp.CloseDate = System.today();     Opp.StageName = 'Qualified';     Opp.LeadSource = 'Web';     Opp.Type = 'New Customer - New Business';     Opp.Product_Type_Interests__c = 'ActiveDisclosure';     insert Opp;   and then created the controller and passed onto my class:  ApexPages.StandardController sc = new ApexPages.StandardController(Opp); AssociateECPController   ac = new AssociateECPController(sc);  PageReference myVfPage = Page.AssociateECP; Test.setCurrentPage(myVfPage);  // Put Id into the current page Parameters ApexPages.currentPage().getParameters().put('id',Opp.Id); String id = ApexPages.currentPage().getParameters().get('id'); System.assert('true',id==null);   and Put Id into the current page Parameters:  ApexPages.currentPage().getParameters().put('id',Opp.Id);   However when I run the test class the id is coming as null in the actual class and I'm not able to cover the if part.  Any ideas?


I am designing a portfolio page which is showcasing the list photographs. Below are the blue print and doubts.  Doubts:  How the user will know the portfolio items have a description on the hover states?. Do I need to put any hint for the same?. In mobile devices don't have the mouse over concept. So how can I represent the same idea (To replace the hover state) in the mobile design.  Thanks in Advanced

Take  as an example (possibly in Firefox only):    As you hover over each search result, an "+ Add to Firefox" button appears.  However, that idea of the button appearing upon hovering doesn't apply to touchscreen users. How might this functionality be re-worked for the touchscreen?  The button could be always displayed, regardless of hover. However, then you would have a long line of identical "+ Add to Firefox" buttons down along the page.


I use many applications every day, so it's important for me to get the complete desktop state (all windows, shells, etc. in the same state they were in, etc.) back instantly when I turn on the computer. Can I use sleep mode all the time (not just during the day, but every night, and anytime I don't use the laptop)? That practically means the computer is never turned off completely, it's always under some power.  Can it hurt some circuitry if the computer is never fully switched off? Or is it OK with today's computers?

For the last 1.5 years I've tended to put my laptop in sleep mode rather than turn it off. Recently I started to feel it's not as fast as it was when I bought it, even if I restore a fresh Windows 7 image (I made it 1 week after installing the system for the first time).  Maybe it's just an impression, I'm not sure...   Can it be a result of putting my laptop in sleep mode? What computer parts get worn down over time? Is there software to test if these parts are worn?


How can I get Google Chrome's bookmarks other than starting the browser and exporting?  I'm running Ubuntu.

Where can I find my Favorites in Google Chrome ?  Where to find the folder that contains them ?


public static ArrayList<Character> removeDuplicates (ArrayList<Character> data) {     ArrayList<Character> newList = new ArrayList<Character>();      for (int i = 0; i < data.size() - 1; i++) {       if (!newList.contains(data.get(i)))           newList.add(0,(data.get(i)));     }     return newList;   }   Here is my code so far. I'm not understanding how this is not working

I have an ArrayList<String>, and I want to remove repeated strings from it. How can I do this?


what is the reason people die naturally even though they have no known disease?  I see people become physically weak at times they get old and die eventually in case they are not attacked by any known disease.   My question is what reasons leads human to death?

Why does evolution not make life longer for humans or any other species?  Wouldn't evolution favour a long life?


I have the following string "*&abc=123&**&defg=hh&*" and so on the pattern start and end is && and I would like to have the following when I do regex.matches or regex.split  first match  = &abc=123& 2 match = &defg=hh&  appreciate any help

I don't really understand regular expressions.  Can you explain them to me in an easy-to-follow manner?  If there are any online tools or books, could you also link to them?


Could someone please tell me what the symbol ringed in red represents?     I know it has ON Switch pointing to it, but the symbol has other lables in different parts of the document.

The below image is from a service manual for a mobile radio. Note the small symbols that appear to be four triangles, point to point. I've searched far and wide and cannot identify that symbol. I have a nagging feeling that I've seen something like it in hydraulics, but never in an electronics diagram. I know that my radio doesn't have a bunch of stars of David printed inside it, so what could this symbol be?  Some of them have a line through the middle, others don't. Compare for example the ones near the labels "mic int" and "mic ext". Does this represent something, or is it a typo?


I am new on Linux based operation systems.It will be my first time so I need your help. I just bought HP Pavilion 14-CE3005NT and it has great hardwares but the processor. The hardware list of this computer is: Graphics Card:Nvidia GeForce MX250 RAM:16GB(DDR4) 512 GB SSD Processor:Intel i7 1065G7 (1.3 GHz) And when I read Ubuntu 20.04 system requirements,it says 2 GHz dual core processor required.And my processor speed is 1.3 GHz. Would it cause a problem to run latest version of Ubuntu perfectly? Note:I will be computer science student from this year. I will just use my laptop for coding and I wanna start using Ubuntu to improve myself quickly.So,please let me know if I can run compilers and other software for game development etc. too. Thank you.

I have a device on which I would like to install Ubuntu. How do I find out if Ubuntu will work on it?


I'm trying to solve a problem from set theory. The problem is simple: is the set of automorphisms of natural numbers $Aut(\mathbb{N})$ countable?   It seems to me the answer is "not" and my attempt for a proof is following. Let us find any injective map $F:Aut(\mathbb{N})\rightarrow (0,1)$. I think it is possible to construct such a map explicitly. Let $Aut^{+}(\mathbb{N})$ be a subset of $Aut(\mathbb{N})$ which consist of automorphisms of $\mathbb{N}$ which map any element $n\in\mathbb{N}$ to $n+1,n+2,...$.   Comment: for any $m\in\mathbb{N}$ consider a map $p_{m}$ which sends any $n\in\mathbb{N}$ to $n+m\in\mathbb{N}$. The constructed map $p_{m}:\mathbb{N}\rightarrow \mathbb{N}$ is bijective which implies that it is an element of $Aut(\mathbb{N})$ and I think we can say that $Aut^{+}(\mathbb{N}) = \cup _{m\in \mathbb{N}} \:p_{m}$.   For any $n,m\in\mathbb{N}$ let $p_{m}(n)$ be an image of $n$ under the action of $p_{m}$ - map. Let us try to define $F$ as follows:  $F_{n}:p_{m}(n)\rightarrow \frac{n}{p_{m}(n)}$  For fixed $n\in\mathbb{N}$ defined above $F_{n}$ is a map from $Aut^{+}(\mathbb{N})$ to $(0,1)$ which sends a tuple $\{p_{1}(n),p_{2}(n),...\}$ to $\{\frac{n}{n+1},\frac{n}{n+2},...\}$. It is not surjective. We can consider   $F:p_{m}\rightarrow \cup_{n\in\mathbb{N}} F_{n}(p_{m})$   and it seems to be a good map but it is not injective and I have a trouble. Is it possible  to continue this attempt for a proof or should I turn to another ideas?

I guess it is too difficult a question to ask about the cardinality of $S_{\mathbb{N}}$ so I would like to ask whether it is countable or not.  I tried to prove it is uncountable somewhat mimicking the Cantor's diagonal argument but failed.


I am currently studying Circuits and it is written in my book that the Potential Drop across a wire with zero resistance is 0. If there is no potential drop then why do electrons flow through the wire since potential difference is required to generate a force on electron. The electric field inside the wire is constant (correct me if I am wrong), then the potential drop should be V = EL (here L is length travelled along the wire). Then why potential drop across a wire with no resistance is 0.

I'm having trouble conceptualizing why the voltage drop between two points of an ideal wire (i.e. no resistance) is $0~V$. Using Ohm's Law, the equation is such:  $$ V = IR \\ V = I(0~\Omega) \\ V = 0$$  However, conceptually I can't see how there is no change in energy between these two points.  It is my understanding that the electrical field of this circuit produces a force running counterclockwise and parallel to the wire which acts continuously on the electrons as they move through the wire. As such, I expect there to be a change in energy equal to the work.  Voltage drop is the difference in electric potential energy per coulomb, so it should be greater than $0~V$:  $$ \Delta V = \frac{\Delta J}C \\ \Delta J > 0 \\ \therefore \Delta V > 0 $$  For example, suppose I have a simple circuit consisting of a $9~V$ battery in series with a $3~k\Omega$ resistor:    If the length from point 4 to point 3 is $5~m$, I would expect the following:  $$ W = F \cdot d \\ W = \Delta E \\ F > 0 \\ d = 5 > 0 \\ \therefore W > 0 \\ \therefore \Delta E > 0$$  Since work is positive for any given charge, the change in energy for any given charge is positive -- therefore the voltage drop must be positive. Yet, according to Ohm's Law it is $0~V$ since the wire has negligible resistance.  Where is the fault in my logic?


Not sure how to get started on this question. Do I have to form the summation? If yes, how do I go about doing it? Any help will be really appreciated!

How do I evaluate this?  $$\lim_{n\to \infty }\sum_{k=1}^{n}\frac{k}{k^2+n^2}$$  I got concerned for that, I've tried make it integral for Riemann but it still undone.


So, in Harry Potter and the Philosopher’s Stone (or Sorcerer’s Stone). We see Draco Malfoy attempt to befriend Harry. Even as he does so, he declares that some families are 'better than others', and offers to help Harry identify the better ones.  So, there's a few reasons this is out of character:   Draco's talking about 'better' families refers to magical heritage (we see this lined out more explicitly later in the series). Harry's mother is a Muggle-born witch, so technically Harry wouldn't be Muggle-born, but his completely magic lineage only goes back one generation. Harry's parents fought against Voldemort alongside Dumbledore and the Order of the Phoenix. Part of the reason to do this was to protect Muggles, Squibs and Muggle-born wizards. So his family would definitely be described as blood traitors. Draco's parents are Death Eaters, they support Voldemort and apparently don't feel the need to hide this fact from Draco. Harry was responsible for the downfall of Voldemort, making him Malfoy enemy number one.    So, that's lots of reasons for instant enmity and yet Draco makes an attempt to befriend Harry, along with a lot of pure-blood ideology. This seems really out of character. Imagine the older Malfoys learning of this friendship.  Is there anything which explains this unusual action?  (Note: I did wonder about Harry's house being a reason against this, but the attempted befriending takes place before their sorting.)

When they just meet, Draco Malfoy seemingly was trying to cozy up/befriend Harry Potter (before realizing Harry would rather hang with Ron/Hermione).  Given that he was a son of a Death Eater, wouldn't Lucius have warned him to NOT associate with such riffraff as Harry?


I am from Pakistan. My husband and I have applied for UK visit visas. I filled both applications. After submitting and paying, when I took the prints, I realized that I had made 3 minor (in my opinion) mistakes:   My husband visited France in September 2014. I checked 02 instead of 09 for month  I wrote my husband's personal cell number instead of his employer no. I wrote the wrong postal code of our sponsor in my application. I also write the wrong house no. of our sponsor in my application.   Now I have an appointment at Gerry's on 4th March for the application submission. I am really worried. Will these mistakes matter?  It's worth mentioning that I visited the UK in 2016 with my kids, and this time only me and my husband.

I'm from the Philippines, and I plan on travelling to the UK with my sister to visit a relative.  I have just submitted my visa application and have already paid online, when I noticed that I've made a clerical error. In the 'visit or stay' portion of section "Do you have any friends or relatives in the UK?", I clicked the 'no' box, instead of 'yes'.  My sister's application is correct. She selected 'yes'. Our appointment is due next month. I am planning to email them about this, and also inform them on the day of application submission.  Is this the right path to take?


As we lift object above planet, it's gravitational potential energy increases so according to E=mc^2 will it's mass increase?

Related to this question:   $E=mc^2$ - energy equals mass. So, if an object has gravitational potential energy relative to another object, it should have additional mass to represent that extra energy.  So, if I have an apple in my hand, it should have quite a large amount of gravitational potential energy relative to a black hole at the edge of the observable universe. I did a quick calculation of how much this gravitational potential energy would be (using Newton's Law of Gravitation) and it came out to be the equivalent of around 500 tons (and that's just for one black hole!).  So, why does my apple not weigh a lot more than it appears to?  EDIT: Here's my calculation of the GPE:  Assumptions:   The apple has mass $m_a=0.3 kg$ The black hole has a mass equal to 1000 solar masses, $m_b=2\times10^{33} kg$ Distance between the apple and black hole is 60 billion light years   Obviously $GPE=mgh$ can't be used, because the gravitational acceleration is not constant and varies with distance, so it has to be integrated.  I used Newton's Law of Gravitation to provide the acceleration:  $$ F=\frac{G{m_1}{m_2}}{h^2} $$  A small change in height produces a small change in energy, which can be used to integrate:  $$ \begin{eqnarray*} \delta E&=&F \delta h\\ \int_0^EdE&=&G{m_a}{m_b}\int_1^R\frac{1}{h^2}dh \end{eqnarray*} $$  I'm integrating the force starting at 1m from the center of the black hole, as the force goes to infinity at $h=0$. It's a little crude, but it should provide a conservative estimate.  $$ \begin{eqnarray*} E&=&G{m_a}{m_b}(1-\frac{1}{R})\\ E&\approx& G{m_a}{m_b}\;\;\;\;\;\;(R>>1)\\ G&=&6.673\times 10^{-11}\;\;N(\frac{m}{kg})^2\\ G{m_a}{m_b}&=&4\times 10^{22}\;\;Nm\\ E&=&mc^2\\ \Delta m&=&\frac{4\times 10^{22}}{(3\times 10^8)^2}\\ &\approx&444,000\;\;kg \end{eqnarray*} $$  So, a little short of 500 tons, but still pretty big!


I would like to have a higher resolution, but my dell monitor (P2210) only supports up to 1680x1050 60Hz, but I would like to have a resolution that is higher than fullHD, aka. 1920x1200 60Hz. When ever I do change it (I set it to the max resolution in my AMD settings) to 1920x1200, it triggers the "max resolution is 1680x1050" message (see in the picture), and I need to wait 10 seconds before it changes back to my native resolution. I also tried changing it with this CRU thing, and I got the same results.

I have a 17 inch LCD, with a maximum resolution of 1280x720. It works fine, but there are some apps that require 1024x768. I know that the maximum resolution is called like that for a reason, but is there no way of increasing the resolution, other than getting a bigger monitor?


I'm doing principal component analysis on my dataset and my professor told me that I should normalize the data before doing the analysis. Why?   What would happen If I did PCA without normalization?  Why do we normalize data in general?  Could someone give clear and intuitive example which would demonstrate the consequences of not normalizing the data before analysis?

What are the main differences between performing principal component analysis (PCA) on the correlation matrix and on the covariance matrix? Do they give the same results?


Find the last four digits of $2^{ 27653} - 1. This is one of the questions in a mathematics contest. I have tried to find the sequence but I found it impossible. (I have used excel to do this and the sequence repeat after 2 ^ 15XX - 1)

How do I efficiently compute $a^b\bmod c$:  When $b$ is huge, for instance $5^{844325}\bmod 21$? When $b$ is less than $c$ but it would still be a lot of work to multiply $a$ by itself $b$ times, for instance $5^{69}\bmod 101$? When $(a,c)\ne1$, for instance $6^{103}\bmod 14$?  Are there any other tricks for evaluating exponents in modular arithmetic?  This is being asked in an effort to cut down on duplicates, see  and .


I recently renewed my passport in February 2020. I have a valid Canadian visitor visa in my old passport (with expiry date 30/09/2020, the visa also expires 30/09/2020).  I had planned to travel to Canada from Mumbai airport with Ethiopian Airlines on 11/03/2020, but since I don't have visa in my new passport, they didn't allow me to travel. So what is the next step to do?

I recently renewed my passport. I also have an expired passport which has my Canada visa (visitor's) valid for another three years. I have already used my Canadian visa which is multiple entry. I am planning to visit Canada this summer.  Since my valid Canadian visa is in my old/expired passport, do I need to renew/transfer my Canada visa or can I simply travel with valid visa in old passport?


This equation: $$\int_0^\infty \frac{x^{s-1}}{e^x-1} dx=\Pi(s-1)\zeta(s) $$ was used by Riemann in his famous paper from 1859. Seemingly it follows from: $$ \int_0^\infty e^{-nx}x^{s-1}dx= \frac{\Pi(s-1)}{n^s}$$  a result achieved by repeated integration by parts. How does the first equation follows from the second?

How does one get from this $$\zeta(s)=\sum_{k=1}^{\infty}\frac1{k^s}$$ to the integral representation $$\zeta(s)=\frac1{\Gamma(s)}\int_{0}^\infty \frac{x^{s-1}}{e^x-1}dx$$ of the Riemann Zeta function?  I can see that it can be rewritten as  $$\Gamma(s)\zeta(s)=\int_{0}^\infty \frac{x^{s-1}}{e^x-1}dx$$ and the Gamma function as an integral yields  $$\zeta(s)\int_{0}^\infty \frac{x^{s-1}}{e^x}dx=\int_{0}^\infty \frac{x^{s-1}}{e^x-1}dx$$  But this approach does not work as the right integral does not converge.  So how does one go from the summation to the integral representation?


Goodmorning everyone. In my thesis I need to cite authors with the following rules,but with the citation style authoryear it doesn't work (I'm using biblatex):  Author et al. year - if there is more than two authors Author and coauthor year - if there are two authors Author et al. year a - if there is more than a pubblication with the same author  An example: This is my database: @article{sism,     author = {Mantovani, E.  and Tamburelli, C. and Babbucci, D. and Viti, M. and Cenni, N.},     date = {2020}, } @article{geodin,     author = {Mantovani, E. and Viti, M. and Babbucci, D. and Tamburelli, C. and Cenni, N.},     date = {2020}, } @article{mant14,     author = {Mantovani, E.  and Viti, M. and Babbucci, D. and Tamburelli, C. and Cenni, N. and Baglione, M. and D'Intinosante, V.},     date = {2014}, }  @article{savage70,     author = {Savage, J. C. and Burford, R. O.},     date = {1970}, }  If I cite \cite{sism} it shows Mantovani, Tamburelli et al. 2020 instead of Mantovani et al. 2020a If I cite \cite{geodin} it shows Mantovani, Viti, Babbucci, Tamburelli and Cenni 2020 instead of Mantovani et al. 2020b If I cite \cite{mant14} it shows Mantovani, Viti, Babbucci, Tamburelli, Cenni, Baglione and D'Intinosante 2014 instead of Mantovani et al. 2014 If I cite \cite{savage70} it shows Savage and Burford 1970 and it's ok. I tried to set maxcitenames=1 but doing so if I \cite{savage70} it shows Savage et. al 1970 instead of Savage and Burford 1970. Thanks for the help! EDIT: with maxcitename the three first long citations don't change, don't know why.

In the header of my document I set the maximal author names to 2:  \usepackage[style=authoryear-icomp, maxbibnames=9, maxcitenames=2, backend=biber]{biblatex}   Now, when I cite texts with two authors, LaTeX gives me the following:     (Author_A/ Author_B 2012: 232)   When I have three authors or more, LaTeX makes it:     (Author_A/ Author_B et al. 2012: 232)   But I want LaTeX to just name the first author if there are more than two authors ... like this:     (Author_A et al. 2012: 232)   Any tips on how to achieve this ?


Gengar is my #1 favorite, but I haven't been finding Gastly's =(. Where has everyone else been finding theirs? I thought Graveyards would be the place to look, but I just find Pidgeys.

I know you can find water Pokémon near water, and grass Pokémon near... well grass. But what about Ghost/Poison/Psychic (let's just say "GPP" for short) type Pokémon?  I heard a rumor that you can find GPP Pokémon at night, but the only GPP Pokémon I've caught have just been in random suburb areas during the daytime, along with grass type Pokémon. Is there a specific location where you can find GPP type Pokémon? Or are they just rare and randomly placed?


In the prior top bar, the rep dropdown would show you the votes you got after you hit the rep cap, just with no rep showing.  The new dropdown for the new top bar no longer shows you that you received those votes.  I end up having to go to my profile and hit the reputation tab to see if I got any upvotes after I hit the rep cap.    Please put this functionality back into the rep dropdown.  Note, that this also applies to up and down CW votes.

When you cap, you don't see any upvotes you get on your profile, therefore, you don't have any update on how your questions / answers are doing unless you look at them manually.   Capping the 200 daily rep is not a reason to stop posting here so could I get notified somehow that my posts are being voted on ? Maybe put a little +X in a different color letting me know that I got these votes but I won't get the reputation for it.   I can go and see in my reputation feed inside my profile and see it :    So I don't see why it wouldn't show up in the feed above.  Maybe putting the feed button green without any +X just like when you aquire a badge.


I have Ubuntu 20.04 installed on my laptop. I want to go back to Windows 8.1, but it doesn't work. When I put in my install USB it doesn't work. It says "Insert proper boot device". I checked the Windows installation USB on an another PC and it worked there.

I'd like to create a Windows bootable USB stick, but I don't have a Windows machine with me at the moment to do so. How could I achieve the same using Ubuntu?


Using biblatex with the chicago-authordate style, I want to typeset a citation with multiple sources and page specifications as "(Hacking 1975, p. 49; Hald 1990, p. 31)".  Ideally, it would something like the MWE below:  \documentclass{article} \usepackage[style=chicago-authordate,natbib=true,backend=biber]{biblatex} \bibliography{references}  \begin{filecontents}{references.bib}     @book{hald,     title={Reference},     author={Hald},     year={1990}, } @book{hacking,     title={Reference},     author={Hacking},     year={1975},     } \end{filecontents}  \begin{document}     \citep[p. 49; p.31]{hacking,hald} \end{document}   The MWE however produces the citation typeset as     (Hacking 1975; Hald 1990, p. 49; p.31)   rather than     (Hacking 1975, p. 49; Hald 1990, p. 31)   Can I have the wanted typesetting using either the biblatex or the biblatex-chicago package?

How can I do multiple citations with page numbers using bibLaTeX/biber?  I have tried \cite[2,3,4]{ref1,ref2,ref3,ref4} but it doesn't work.


I implemented a recommender using tensorflow, based on e-commerce data. This recommender is predicting the next item a user will buy. I will judge the performance of my fitted model, by getting the next estimate of the model and comparing, if the user did actually buy this item (compare  with k == 1).  My precision is around 20% (meaning in 20% of the cases the user did actually buy the product the system recommended). Our shop has about 150 Products and my evaluation is based only on properties of the user, not his/her purchase history.   In this case, is 20% good? Are there other, similar systems I can compare to? What would be a good precision for, e.g. 100.000 products?

I've fitted my model and am trying to understand whether it's any good. I've calculated the recommended metrics to assess it ($R^2$/ AUC / accuracy / prediction error / etc) but do not know how to interpret them. In short, how do I tell if my model is any good based on the metric? Is an $R^2$ of 0.6 (for example) sufficient to let me proceed to draw inferences or base scientific/business decisions?     This question is intentionally broad, to cover a wide variety of situations that members frequently encounter; such questions could be closed as duplicates of this one. Edits to broaden the scope beyond the metrics mentioned here are welcome, as are additional answers - particularly those that offer insight about other classes of metrics.


The Lagrangian of the two-body problem in terms of polar coordinate $r$ and $\phi$ is $$\mathcal{L}=\frac{1}{2} \mu (\dot{r}^2+r^2\dot{\phi}^2)-U(r)$$ And the Lagrange equation corresponding to $\phi$ is a statement of conservation of angular momentum $$\frac{\partial \mathcal{L}}{\partial \dot{\phi}}=\mu r^2 \dot{\phi}=const=l$$ If I use this equation to eliminate the $\dot{\phi}$ in the first equation, I'll have $$\mathcal{L}=\frac{1}{2} \mu \dot{r}^2+\frac{l^2}{2\mu r^2}-U(r)$$ We can define $U_{eff}(r)=U(r)-\frac{l^2}{2\mu r^2}$ so that $\mathcal{L}=\frac{1}{2} \mu \dot{r}^2-U_{eff}(r)$  However, in Taylor's book Classical Mechanics, he first looks at the Lagrange equation corresponding to $r$ (or radial equation) $$\mu r \dot{\phi^2}-\frac{dU}{dr}=\mu \ddot{r}$$ Then define centrifugal force as the first term in LHS $$F_{cf}=\mu r \dot{\phi}^2= \frac{l^2}{\mu r^3}=-\frac{d}{dr}(\frac{l^2}{2 \mu r^2})= -\frac{d U_{cf}}{dr}$$ Return to the radial equation, we have $$\mu \ddot{r}=-\frac{d}{dr}[U(r)+ \frac{l^2}{2 \mu r^2}]=-\frac{d}{dr} U_{eff}(r)$$ It seems that $U_{eff}(r)=U(r)+\frac{l^2}{2 \mu r^2}$ in Taylor's book, instead of $U_{eff}(r)=U(r)-\frac{l^2}{2\mu r^2}$ as we got previously.  I'm quite confused that why I get a minus sign in the definition of $U_{eff}(r)$ if I look directly at the Lagrangian, using the statement of conservation of angular momentum. I wonder I have this minus sign because I change the form of Lagrangian too early but I can't figure out why I can't do it.

If there is a system, described by an Lagrangian $\mathcal{L}$ of the form   $$\mathcal{L} = T-V = \frac{m}{2}\left(\dot{r}^2+r^2\dot{\phi}^2\right) + \frac{k}{r},\tag{1}$$   where $T$ is the kinetic energy and $V$ the potential energy, it is also possible to define the total energy $E$ of the system   $$ E = T + V =\frac{m}{2}\left(\dot{r}^2+r^2\dot{\phi}^2\right) - \frac{k}{r}.\tag{2}$$  If the angular momentum $M$ is defined by $$ M = m r^{2} \dot{\phi},\tag{3}$$ then $E$ can be written as  $$ E = \frac{m}{2}\dot{r}^2 + \underbrace{\frac{M^2}{2mr^2}-\frac{k}{r}}_{V_\textrm{eff}\left(r\right)},\tag{4}$$  where the last two terms are written as new, "effective" potential $V_\textrm{eff}\left(r\right)$.    In addition, using the definition of $M$, the Lagrangian $\mathcal{L}$ can be written as  $$ \mathcal{L} = \frac{m}{2}\dot{r}^2 + \underbrace{\frac{M^2}{2mr^2}+\frac{k}{r}}_{-V_\textrm{eff}\left(r\right)},\tag{5}$$  where the sign of $V_\textrm{eff}\left(r\right)$ has been changed, since $\mathcal{L} = T-V$. But from this argument, it appears that there are two different possible ways to construct the same effective potential. This seems to me contradictory. Where is my mistake?


I submitted my paper to a engineering journal. It underwent a major revision and then a minor revision. The minor revision was some grammatical stuff. Now it is in the "Awaiting Editors Decision" mode for the past one week. I am sort of tensed about it. What does this mode mean for a journal review process in general?

What steps does a manuscript typically go through from submission to publication (or rejection) in a typical journal? How are these steps referred to, in particular by editorial systems, and how long do they each typically take?  Note that this question is about the typical situation and hence not about:   Journals with an atypical workflow, e.g. those that allow for an instantaneous reviewer–author interaction. Exceptional steps or rare occurrences such as withdrawal or .   This is a canonical question on this topic as per . Due to its nature, it is rather broad and not exemplary for a regular question on this site. Please feel free to improve this question.


Let $-\infty\lt a\lt b \lt \infty$. Let $C[a,b]$ is space of continuous functions and a function $\|.\|:C[a,b]\to R$ is given by $\|f\|:=\int_a^b |f(x)|d(x)$  a). Show that $\|\cdot\|$ is a norm in $C[a,b]$  b). Show that $C[a,b]$ with this norm is not a Banach space.  Well the 1st question is Kind of easy. Non-negativity, Homogenity, and Triangle inequality is easily proven. At the 2nd question I have a Problem.   I know the $$C[0,1]$$ space with Norm $$\|f\| = \int_0^1|f(x)|d(x)$$ is not complete that means Not Banach-Space. But how do I prove the generality?   Does anyone has a suggestion?  Thanks

Let $-\infty\lt a\lt b \lt \infty$. Let $C[a,b]$ is space of continuous functions and a function $\|.\|:C[a,b]\to R$ is given by $\|f\|:=\int_a^b |f(x)|d(x)$  a). Show that $\|\cdot\|$ is a norm in $C[a,b]$  b). Show that $C[a,b]$ with this norm is not a Banach space.  Well the 1st question is kind of easy. Non-negativity, Homogenity, and Triangle inequality is easily proven. At the 2nd question I have a problem.   I know the $$C[0,1]$$ space with Norm $$\|f\| = \int_0^1|f(x)|d(x)$$ is not complete that means not Banach-Space. But how do I prove the generality?   Does anyone has a suggestion?  Thanks


i am working with 72PPI  for both android and iphone ..but some has been reffered 326 has to be set for iphone can i know what difference will occur? i am getting same result in 72 itself

I have been designing web banners for more than a year but never considered the DPI. I was using the default 72 dpi, but now I want to know is it necessary to create web designs in 72 dpi? What if we use more than that, for example 200 dpi? I know that more DPI means more quality image and that's why I want to use high DPI, but recently I read somewhere that for web banners we should use 72 dpi. I just want to know if it is mandatory and if it affects negatively in any aspect?


The original question  Is it possible to override tmux's default behaviour of executing .[z|bash_]profile files on every new session, window and pane?   In other words, I'd like it to only execute only the relevant .[zsh|bash]rc script, i.e. for the new session/window/pane to behave like an xterm or urxvt, not like a tty.  More specifically (edit)  I'd like to avoid changing anything to my .*profile and .*rc scripts. I'm looking for a way to ask tmux to open non-login shells in its new sessions, windows and panes by properly configuring it in .tmux.conf, in order to keep the prior philosophy of putting only actual 'login' instructions on .*profile scripts, as recommended for instance here:   I am aware on how to circumvent the issue by hacking e.g. .zprofile as was answered to  , but the question is of how to do it from .tmux.conf  Secondary question   Why does tmux load the .*profile scripts by default, on every session, window and pane, whereas subshells on any context and all (or at least most) variants of X terminals don't?  Some background information (not necessarily relevant)  I barely started using tmux (only occasionally, for now), but I do have an ever-evolving setup, using zsh as my shell of choice, in which .zprofile expects to be called from a tty and do relevant stuff (like deciding to run startx or not based on whether it's on a laptop and the tty number), the .zshrc script expects to be called from any interactive environment and the .zshenv script expects to be loaded whether on an interactive environment or not.  EDIT: Solution (based on comments below)  Adding the following line to .tmux.conf overrides tmux's behaviour and defaults to starting non-login interactive shells (zsh in this case) on new  sessions, windows and panes:  set-option -g default-command zsh

I have a script in my .bash_profile that prompts for X sessions to boot.  When I launch tmux, I get this prompt that I had only intended for the TTY login.  Is there something I can put in .bash_profile that will simply run bash if it is part of tmux?  That is, can I check with bash if .bash_profile is being read within tmux?


The sequence of $$ a_x  ={\cos (x)\over x} $$ does converge to zero. As a result, intuitively $$ \sum_{x=1}^\infty {\cos (x)\over x} $$ should also converge right? But I've been told that the series diverges. This shouldn't be true... right?

I just came across the problem of what happens in the boundary cases of .  More concisely, for what $\theta$ will the following sum converge? $$\sum_{n=1}^{\infty} \frac{e^{ni\theta}}{n}$$ It is well known that this sum will diverge for $\theta=0$ and will converge for $\theta=\pi$. In fact, for any odd multiple of an even root of unity, since we have symmetry, for each line through the origin of the complex plane, we can use the alternating series theorem to show that they converge.  Another idea I had was to split  the sum into imaginary and real parts, and if we can prove each of these converges, then we are all set. So now we must prove that both of the following converge $$\sum_{n=1}^{\infty}\frac{\cos(n\theta)}{n}\space, \space \sum_{n=1}^{\infty}\frac{\sin(n\theta)}{n}$$ Now these can be shown to converge easily by Dirichlet's test for any rational multiple of pi, but what about irrational multiples of pi? I know it has been shown to converge with $\theta=1$, but I don't see how to generalize this.


I came across this sentence on stack exchange and it confused me.     'If you had called me 10 minutes ago, I would have been sleeping.' on    What is the structure of the above sentence called?   Why 'If you had called me? Can it be replaced with 'If you called me?'  I thought 'had called' is past perfect which means it happened before another event in the past. But in this case, it sounds like 'sleeping' came before.

If I had learnt that, I would have been doing much better right now.   Is that correct? If not, how do you say it correctly?


I read a code to convert a number to its binary equivalent, where the following statement was used:  1<<j   What is the use of such a statement?

I've been attempting to learn C in my spare time, and other languages (C#, Java, etc.) have the same concept (and often the same operators) ...   What I'm wondering is, at a core level, what does bit-shifting (<<, >>, >>>) do, what problems can it help solve, and what gotchas lurk around the bend? In other words, an absolute beginner's guide to bit shifting in all its goodness.


I am trying to understand the numerical method of finding a minimum, the steepest descent method. \begin{equation} x_1 = x_0 - \alpha \frac{df}{dx} \end{equation} I understand the idea behind it and how to set up the equation, but I do not get:   How to find the "right" weighting factor $\alpha$. Why the next search has to occur orthogonal to the previous search direction.   Thanks in advance for the answers.

Suppose a differentiable, convex function $F(x)$ exists. Then $b = a - \gamma\nabla F(a)$ implies that $F(b) \leq F(a)$ given $\gamma$ is chosen properly. The goal is to find the optimal $\gamma$ at each step. In my book, in order to do this, one should minimize  $G(\gamma)=$ $F(x-\gamma\nabla F(x))$ for $\gamma$. It also says that it should be minimized via a line search. Why can't this function be minimized by simple calculus?  I am unsure what it means to perform a line search on this function. I am also unsure why we want to minimize this function to find the optimal step size.


Find the cardinality of the set $\{ X \subset \mathbb{N} : |X| = \aleph_0\} $. First off all I could easily prove that the set given above, say $S$, is uncountable. Because $P(\mathbb{N})$ is uncountable and $|P(\mathbb{N})|=c$, and $P(\mathbb{N}) = S \cup F$, where $F$ = $ \{$family of all finite subsets of $\mathbb{N}$ $\}$. So, $S$ is countable $\implies$ $P(\mathbb{N})$ is countable as $F$ is clearly countable. Which is a contradiction. But I can't find the cardinality of $S$. Now, $$S \subset P(\mathbb{N})$$ $$\implies |S| \le |P(\mathbb{N})|=c$$ And, $$|S| \gt \aleph_0$$ Again, $$\aleph_0 \lt c$$ But in order to say, $$|S|=c$$ I have to use Continuum Hypothesis. But can I do that because I know it's a hypothesis and also with current mathematical tools it cannot be proved that this is false(I got to know this from internet)?

How many subsets of $\mathbb{N}$ have the same cardinality as $\mathbb{N}$?   I realize that any of the class of functions $f:x\to (n\cdot x)$ gives a bijection between $\mathbb{N}$ and the subset of $\mathbb{N}$ whose members equal multiples of n.  So, we have at least a countable infinity of sets which have the same cardinality of $\mathbb{N}$.  But, we could remove a single element from any countably infinity subset of the natural numbers and we still will end up with a countably infinite subset of $\mathbb{N}$.  So (the reasoning here doesn't seem quite right to me), do there exist uncountably many infinite subsets of $\mathbb{N}$ with the same cardinality of $\mathbb{N}$?    Also, is the class of all bijections $f: \mathbb{N} \to \mathbb{N}$ and a given countably infinite subset uncountably infinite or countably infinite?


I've been sick and I've missed a couple of lectures Analysis. But I didn't want to be too behind in lecture, so I was trying to catch up by reading my textbook and solving some problems.  Here's a question I was having some trouble with:  Prove $\sqrt{2} \in \mathbb{R}$ because $x^2=2$ where $x=A\mid B$ is a cut in $\mathbb{Q}$ with $$A=\{r\in \mathbb{Q}: r\le 0 \text{ or } r^2<2\}.$$  Any help would be appreciated!  Thank you! :)

So I've been sick and I've missed a couple of lectures of my Analysis class. But I didn't want to be too behind in lecture tomorrow, so I was trying to catch up by reading my textbook and solving some problems.  Here's one I was having some trouble with:     Prove $\sqrt2\in\mathbb R$ by showing $x^2 = 2$ where $x = A|B$ is a cut w/ $A = \{r \in \mathbb Q : r \leqslant 0 \text{ or } r^2 < 2\}$.   Any help would be appreciated!  Thank you! :)


I have two numeric data vectors: NA_Sales and EU_Sales, which are really similar. When I plot their ECDFs like this:  plot(ecdf(dataset$NA_Sales)) lines(ecdf(dataset$EU_Sales), col="red")   Then I get this diagram:     Which shows they are really similar. But when I run the Kolmogorov-Smirnov test like this:   ks.test(dataset$NA_Sales,dataset$EU_Sales)   or  ks.test(dataset$NA_Sales,dataset$EU_Sales)$p   Then I get a p-value equal to zero. Why? The diagram shows they are similar distributions. Isn't ks.test() supposed to tell this by their CDF? I should get a p-value higher than 0.05.

In a  of Amstat News, the authors (Mark van der Laan and Sherri Rose) stated that "We know that for large enough sample sizes, every study—including ones in which the null hypothesis of no effect is true — will declare a statistically significant effect.".  Well, I for one didn't know that. Is this true? Does it mean that hypothesis testing is worthless for large data sets?


I use Ubuntu 14.04 on my desktop. I am considering upgrading to 16.04 so I looked at . I downloaded a 16.04 iso file and then used Startup Disk Creator to create a bootable 16.04 USB stick.  Part way through the process I received a message: "A volume with software packages has been detected. Would you like to open it with the package manager?"  This worried me as I thought it may install 16.04 on my hard disk and not on the USB so I aborted the process.  Will answering "yes" install 16.04 on my hard disk?

This comes up every time I login, how do I remove this or fix it.  Thanks.


Id' like to know if exists a way to speed up the production in Photoshop in the following case: I have several images and I have to apply for each one of them the same adjustment. Doing it manually is very time consuming. So, is there a way to automatize this process?

How can I create my own Action using Photoshop? Can anyone guide me with a simple example?