I have two Laptops, Samsung Notebook (32bit System) and Dell (64bit system) both running Ubuntu 14.04. I have connected a Dlink USB 3G modem to Samsung Notebook and set up a WiFi Hotspot on it. So I am currently using the internet on all other devices in my home using this WiFi Network.   Can I share the files on one laptop with other one over this WiFi network? If yes, how should I configure both computers?  Also if it is not possible how can I share files over internet, so that I can access those from my other laptop and also from any other computer(outside my network, say from computer in my college) over internet? (I don't want to setup a FTP server).  I tried Bit-torrent Sync but for different locations I have to set different passwords.  Also how can set my Mobile Broadband connection (3G using USB Dlink Modem) to redial automatically? because sometimes it gets disconneted automatically.. The inbuilt option in Ubuntu's Default connection manager works sometimes and sometimes it doesn't work especially when modem gets disconnected due to removal of USB cable or due to spike in electrical wires when speed of an electrical fan is changed from the Regulator. The connection will dial itself automatically when the option "Enable Mobile Broadband" is selected, but when the connection gets disconnected due to reasons stated above, the "Enable Mobile Broadband" option get unchecked and hence the connection will not be able to dial itself automatically.    Please give in detail instructions.
I have a desktop (Ubuntu 13.04 &amp; Win 7 Home Premium) and a Laptop (Ubuntu 12.04), both having WiFi adapters. I also have a WiFi router connected to internet which both my computers can access.  I want to share files between my desktop and my laptop using WiFi (similar to Homegroup on Windows 7 but without using Ethernet cables).  How do I set-up that?  I want to share files using both OSs, if anyone have have information about sharing files with any of the OS please answer!
Let $R$ be a UFD. Then for any two elements $a,b \in R \setminus \{0\}$ $ab \sim \gcd (a,b){\operatorname{lcm} (a,b)}$.   My attempt :  Let $d = \gcd (a,b)$.Then $d|a$ and $d|b$.Then $\exists x,y \in R$ such that $a = dx$ and $b = dy$.Now it is to be shown that $c = dxy$ is the lcm of $a,b$.Which I find difficulty to show.It is clear that $a|c$ and $b|c$. Now if $u$ is any common multiple of $a$ and $b$.Then $dx|u$ and also since $y|b$ we have $y|u$ i.e. $dxy|u^2$ $\implies c|u^2$.But I have to show $c|u$ to complete the proof which I fail to prove.Please help me to complete the proof.  Thank you in advance. How do I ignore ampersands in a SQL script running from SQL Plus? I have a SQL script that creates a package with a comment containing an ampersand (&amp;). When I run the script from SQL Plus, I am prompted to enter a substitute value for the string starting with &amp;. How do I disable this feature so that SQL Plus ignores the ampersand? How do I enter a file or directory with special characters in its name? I want to enter the following folder in the terminal:  Milano, Torino (Jan)-Compressed   How should I write the command cd to enter this directory?  Spaces and several other special characters like \, *, ), ( and ? cause problems when I try to use them in the command line or scripts, e.g.:    $ cd space dir bash: cd: space: No such file or directory  $ cat space file cat: space: No such file or directory cat: file: No such file or directory  $ cat ( bash: syntax error near unexpected token `newline'  $ echo content &gt;\ &gt; ^C  $ ls ? (  )  *  ?  \   How do I enter file or directory names that contain special characters in the terminal in general? I came to think about some situations where it would be almost impossible to miss a melee spell attack (target is grappling you or vice versa, target is holding you or is close to you, your character already has it's hand on the target, etc.). How do you manage those situations?    Do you give an advantage to the caster? Does the spell automatically succeed? Or you just don't ask yourself the question and just play along with the base rules? What exactly is a kilogram-meter? This question isn't just about kilogram-meters, it's about multiplied units in general.  I have a good mental conception of divided units, e.g. meters per second or grams per cubic meter.  Meters per second just (usually) means how many meters are traversed by an object each second.  Simple.  But I don't really have a mental conception of what it means when units are multiplied, e.g. a kilogram-meter.  Can anyone explain in simple physical terms what a kilogram-meter is? The title says it all. I'd like to know how I can install software - an example is the Chromium web browser. Example where $f\circ g$ is bijective, but neither $f$ nor $g$ is bijective Can anyone come up with an explicit example of two functions $f$ and $g$ such that: $f\circ g$ is bijective, but neither $f$ nor $g$ is bijective?  I tried the following: $$f:\mathbb{R}\rightarrow \mathbb{R^{+}} $$ $$f(x)=x^{2}$$  and  $$g:\mathbb{R^{+}}\rightarrow \mathbb{R}$$ $$g(x)=\sqrt{x}$$  $f$ is not injective, and $g$ is not surjective, but $f\circ g$ is bijective  Any other examples? On mu Ubuntu 12.04 setups my tmux clipboard copy and paste commands are setup as follows:  set -g prefix M-a unbind C-b bind C-c run "tmux save-buffer - | xclip -i -sel clipboard" bind C-v run "tmux set-buffer \"$(xclip -o -sel clipboard)\"; tmux paste-buffer"   This worked great for the longest time up until a month or so ago, when I suspect some configuration change or package change was made that broke the above. In GNOME terminal, pasting still works fine with both prefix+ctrl-v and ctrl-shift-v.   However the xclip copy command no longer works no matter what I do, and I have tried removing the custom prefix binding above, using -select instead of -sel, not using clipboard etc. This is pretty much a show stopper for a GVim user like me, since I don't even have the GNOME terminal workaround of ctrl-shift-c with tmux taking over the shell. I go into copy mode, select text with space+movement, and when I execute prefix+ctrl-c absolutely nothing happens. Before this broke, tmux would display a confirmation message in the notification section at the bottom.  Does anybody have suggestions as far as how one might debug this? This is a pretty big productivity hit. I can probably use the , but it'd be great to know just what happened to xclip. I'd like to be able to search for questions by multiple tags; for example "questions tagged 'nhibernate' and 'web-services'".  I can get close by searching for "nhibernate web-services" but the results tend to be a few questions that relate to both terms--but much more largely just questions that relate to one or the other. When defining a method on a class in Python, it looks something like this:  class MyClass(object):     def __init__(self, x, y):         self.x = x         self.y = y   But in some other languages, such as C#, you have a reference to the object that the method is bound to with the "this" keyword without declaring it as an argument in the method prototype.    Was this an intentional language design decision in Python or are there some implementation details that require the passing of "self" as an argument? Linux Equivalent of Windows Ctrl to show Mouse Pointer In Windows, it is possible to set pressing Ctrl to display the current location of the mouse pointer, as per .  Is there a way of setting a key or key combination to perform the same action in Ubuntu? Note, this is the opposite of turning this function off, as detailed at . I have opened Disks program today and noticed that there is FAILING in the Assessment column for the SMART status.     What does this error mean? Is it serious problem?  I have Lenovo G50-45 laptop, disk is SEAGATE ST1000LM014-SSHD-8GB(LVD3) 1TB SSHD with 8GB NAND Flash (original disk in this latop).  Update 2017-09-24:  The disk has died yesterday. 1 year and 3 months have passed since 1st hint of problem. About 4 months ago I had few issues with it not booting, but I was able to make another clean install. Since yesterday the disk is non-responsive. As this was long expected I had backup of all important data.(!) The disk was about 2 years old, so that was quite premature death. Moving SQL Server to different domain There is a 2d rotation matrix around point $(0, 0)$ with angle $\theta$.  $$ \left[ \begin{array}{ccc} \cos(\theta) &amp; -\sin(\theta) \\ \sin(\theta) &amp; \cos(\theta) \end{array} \right] $$  Next, there is a 3d rotation matrix around point $(0, 0, 0)$ and unit axis $(u_x, u_y, u_z)$ with angle $\theta$ ().  \begin{bmatrix} \cos \theta +u_x^2 \left(1-\cos \theta\right) &amp; u_x u_y \left(1-\cos \theta\right) - u_z \sin \theta &amp; u_x u_z \left(1-\cos \theta\right) + u_y \sin \theta \\ u_y u_x \left(1-\cos \theta\right) + u_z \sin \theta &amp; \cos \theta + u_y^2\left(1-\cos \theta\right) &amp; u_y u_z \left(1-\cos \theta\right) - u_x \sin \theta \\ u_z u_x \left(1-\cos \theta\right) - u_y \sin \theta &amp; u_z u_y \left(1-\cos \theta\right) + u_x \sin \theta &amp; \cos \theta + u_z^2\left(1-\cos \theta\right)  \end{bmatrix}  How it is possible to generalize rotation matrix on $N$ dimension around zero point and $N-2$ dimensional unit axis with angle $\theta$? Fibonacci addition law $F_{n+m} = F_{n-1}F_m + F_n F_{m+1}$ Graph for relationship between two ordinal variables What is an appropriate graph to illustrate the relationship between two ordinal variables?  A few options I can think of:   Scatter plot with added random jitter to stop points hiding each other. Apparently a standard graphic - Minitab calls this an "individual values plot". In my opinion it may be misleading as it visually encourages a kind of linear interpolation between ordinal levels, as if the data were from an interval scale. Scatter plot adapted so that size (area) of point represents frequency of that combination of levels, rather than drawing one point for each sampling unit. I have occasionally seen such plots in practice. They can be hard to read, but the points lie on a regularly-spaced lattice which somewhat overcomes the criticism of the jittered scatter plot that it visually "intervalises" the data. Particularly if one of the variables is treated as dependent, a box plot grouped by the levels of the independent variable. Likely to look terrible if the number of levels of the dependent variable is not sufficiently high (very "flat" with missing whiskers or even worse collapsed quartiles which makes visual identification of median impossible), but at least draws attention to median and quartiles which are relevant descriptive statistics for an ordinal variable. Table of values or blank grid of cells with heat map to indicate frequency. Visually different but conceptually similar to the scatter plot with point area showing frequency.   Are there other ideas, or thoughts on which plots are preferable? Are there any fields of research in which certain ordinal-vs-ordinal plots are regarded as standard? (I seem to recall frequency heatmap being widespread in genomics but suspect that is more often for nominal-vs-nominal.) Suggestions for a good standard reference would also be very welcome, I am guessing something from Agresti.  If anyone wants to illustrate with a plot, R code for bogus sample data follows.  "How important is exercise to you?" 1 = not at all important, 2 = somewhat unimportant, 3 = neither important nor unimportant, 4 = somewhat important, 5 = very important.  "How regularly do you take a run of 10 minutes or longer?" 1 = never, 2 = less than once per fortnight, 3 = once every one or two weeks, 4 = two or three times per week, 5 = four or more times per week.  If it  would be natural to treat "often" as a dependent variable and "importance" as an independent variable, if a plot distinguishes between the two.  importance &lt;- rep(1:5, times = c(30, 42, 75, 93, 60)) often &lt;- c(rep(1:5, times = c(15, 07, 04, 03, 01)), #n=30, importance 1            rep(1:5, times = c(10, 14, 12, 03, 03)), #n=42, importance 2            rep(1:5, times = c(12, 23, 20, 13, 07)), #n=75, importance 3            rep(1:5, times = c(16, 14, 20, 30, 13)), #n=93, importance 4            rep(1:5, times = c(12, 06, 11, 17, 14))) #n=60, importance 5 running.df &lt;- data.frame(importance, often) cor.test(often, importance, method = "kendall") #positive concordance plot(running.df) #currently useless   A related question for continuous variables I found helpful, maybe a useful starting point: Write a well designed async / non-async API I have upgraded from Ubuntu 16.04 LTS to Ubuntu 18.04 LTS. I was surprised to see that the context menu entry "Make Link" (keyboard shortcut Ctrl+M) in Nautilus doesn't seem to exist anymore. It used to appear upon right mouse click on a file or folder and allowed the user to create a symbolic link. Why are votes anonymous? Let's make with the transparency and have them publicly attributed G is the product of its Sylow subgroups I want to prove the following:     If every Sylow subgroup of $G$ is a normal subgroup, then $G$ is isomorphic to the product of its Sylow subgroups.   So far, I have gotten to realize that for every prime factor $p_i$ of $|G|$, there is exactly one Sylow subgroup and that these form a partition of $G$. However, I am having trouble finding the isomorphism between $G$ and the product which I will call $G_1 \times \ldots \times G_r$. My idea was just to use the mapping $(g_1, \ldots, g_r) \mapsto g_1\ldots g_r$, which is a bijection, but I don't see whether it is a homomorphism. In general, not all elements of $G_i$ commute with elements of $G_j$, so one cannot simply change the order of the elements in the product.