I'm installing a small baseboard heater in a back bedroom, adding it to a 240V circuit with two heaters already installed in other rooms. I mainly use the two heaters on low when I am away to prevent pipes from freezing. I heat with wood when there. I would like to be able to totally cut off power to the newly added third heater. This bedroom gets closed off when I am away and since the heater has a built in thermostat with lowest setting of 32degrees it will likely come on when the room is closed off. I don't need or want that...waste of electricity! No pipes back there. I would like to install a switch to the line before it reaches the heater to simply cut the power to that back bedroom heater when I'm away.   Would there be any issues with this type set up?  Do I need any special kind of switch or will a basic 20amp 120/240V light switch do the trick?  Thanks.
I posted this question but for some reason I can't get back into my account:    Most things I see with 220V have both hot legs going through the switch or relay, current "returns" through the switch.  Is it against code to wire one leg directly to the equipment and the other leg is switched as opposed to having both legs switched.  It seems useless and a waste of wire to switch both legs.  Basically  vs  (minus the GFCI as I'm not allowed to have that)  As a bonus question.  I assume I need a "motor rated switch" as standard switches can weld due to the high startup current.  Is  one legal\safe?
How to find and delete files older than specific days in unix? Why do we notate the greatest common divisor of $a$ and $b$ as $(a,b)$? In my textbook on elementary number theory from a class last year, as well as elsewhere through my academic experience and even posts here, I often see the greatest common divisor notated as $(a,b)$ (where this represents the greatest common divisor of $a,b$).  My question is, why is such an unusual notation used? I say it's unusual (if not a bit absurd), for a couple of reasons:   It is unintuitive. It does not grant the reader an immediate knowledge of what it means. In particular, I can easily see it being misinterpreted as an ordered pair of points, and not as a function (which it basically is and I touch on in a second) or representing a single value. Good notation would be immediately understood, no? One should not struggle with parsing through the context or meaning. A clearer notation is often used, and just three letters away. You could certainly think of $(a,b)$ as an ordered pair, if we consider it a function. I often see the alternate $gcd(a,b)$: a function, which takes in two inputs ($a$ and $b$), and outputs their greatest common divisor (or factor, if you prefer). Merely adding the three letters makes the notation clearer by clarifying it is  a function, and using a relatively well-accepted acronym. (Or, at least, I often hear it abbreviated "g.c.d." in school.)   I've mulled this over for a while and I can't think of much without borrowing inspiration from other "unusual" notations. For example:   Common understanding in context: consider the $\log(x)$ function. Depending on context, without a base stated as seen here, it can be presumed to mean whatever is most "appropriate." It could be base $e$ (common in mathematics), base $10$ (common in engineering), or base $2$ (common in computer science). The ambiguity is essentially resolved by context in other words - personally, not a fan of that (I like the explicit stating of bases for full clarity), but if such a motivation holds elsewhere, it might stand to reason that $(a,b)$ could just be taken as a shorthand and "understood" in the context of number theory to simply be the greatest common divisor. That it is in fact used despite $gcd(a,b)$ being clearer and somewhat common also does seem to suggest this playing a role. Perhaps it just started that way and it kept being used. For example,  (based on a ) regarding how logarithms, roots, and exponentiation can be unintuitive from a notation perspective, and proposes an alternative, easier to understand notation. I haven't been in middle school in nearly a decade, but guessing from discussions online, that obviously hasn't really picked up too much. In that sense, perhaps it's like that for $(a,b)$: like we still notate exponentiation, etc., the same way today despite how counterintuitive it is (at least for students), perhaps it just "stuck" and proliferated?   I wasn't able to easily find any reason why online, and it bugs me a bit, so I ask:     Why do we so unintuitively notate the greatest common divisor of two numbers $a,b$ as $(a,b)$?   I of course recognize that this is somewhat moot in light of how easily it's made clear - as established above, all I have to do is append the front of the parenthetical by $gcd$ or $gcf$ to make it way better. And of course, people do that. But I'm more curious in where this ambiguous former notation arose and, in light of a better notation, why it is still used today. I forgot the passcode for my iPad restrictions. How can I disable them? OK guys I have this problem:  For $x,y,p,q&gt;0$ and $ \frac {1} {p} + \frac {1}{q}=1 $ prove that $ xy \leq\frac{x^p}{p} + \frac{y^q}{q}$  It says I should use Jensen's inequality, but I can't figure out how to apply it in this case. Any ideas about the solution? Force alt + tab to switch only on current workspace in GNOME shell Compress a directory using tar/gz over SSH to local computer? I'd like to essentially tar/gz a directory on a remote machine and save the file to my local computer without having to connect back into my local machine from the remote one. Is there a way to do this over SSH? The tar file doesn't need to be stored on the remote machine, only on the local machine. Is this possible? Derivation of survival copula $$ \begin{align}F(x,y) &amp;= P(X\leq x, Y\leq y) \\  &amp;= C(F(x), F(y)) \end{align}$$ The copula of a bivariate distribution is equal to its CDF, $C(u,v) = F(x,y)$. The density of the data's CDF therefore can be expressed as $$f(x,y) = c(u,v) \times f_X(x) f_Y(y)$$ where $c(u,v)$ is the copula density and $f_X(x)$ is a marginal. If $\hat{C}(u,v)$ is the survival copula for determining $$ \begin{align}\bar{F}(x,y) &amp;= P(X&gt; x, Y &gt; y) \\  &amp;= \hat{C}(1-F(x), 1-F(y)) \end{align}$$ how is the first equation of the ordinary copula, $C(u,v)$, linked to the survival copula as $$\hat{C}(u,v) = u + v - 1 + C(1-u,1-v)$$ are $u$ and $v$ merely vectors containing the (ranked) observations of the uniform marginals? A derivation in integrals and probabilities (rather than $F$s) would be good. How to activate the Gedit terminal plugin? I have the following packages installed:   gedit gedit-common gedit-plugins   In Ubuntu 12.04 with these packages installed all that was needed was to activate the terminal plugin and the press Ctrl+F9 to show the bottom panel. This isn't the case with Ubuntu 13.10 (Gedit 3.8.3) and I can't figure out how to do it. How to create animated GIFs of prototype mockups, like the ones on Dribbble? I'm sure you've seen Dribbblers upload animated mockups of their designs.   Here's an example:     I can create mockups on Photoshop and even apply simple Tween Animations to them but I can never get my GIFs to look like the example here.   What are Dribbblers using to create these animations?   Notice that the animations also include touch points and perfect motion. I would like to convert my Photoshop mockups to do the same.  How can I create an animated example of my mockups, similar to the ones created by Dribbblers? Evaluating $\lim\limits_{n\to\infty} e^{-n} \sum\limits_{k=0}^{n} \frac{n^k}{k!}$ I'm supposed to calculate: $$\lim_{n\to\infty} e^{-n} \sum_{k=0}^{n} \frac{n^k}{k!}$$ By using WolframAlpha, I might guess that the limit is $\frac{1}{2}$, which is a pretty interesting and nice result. I wonder in which ways we may approach it. How do I set an environment variable on the command line and have it appear in commands? Tools to get a pictorial function call graph of code What is the expected value of the maximum of 500 IID random variables   with uniform distribution between 0 and 1?   I'm not quite sure of the technique to go about solving something like this. Could anyone point me the right direction?  Thanks Search using symbols is broken We used to be able to , but that now appears to be broken.  I'd expect a  to return a result, but instead the search engine appears to put quotes around the whole request; the search box shows the search has been replaced with "[python] += list" and the  I was looking for doesn't appear among the returned questions.  Using quotes around the symbols do not seem to help here;  returns an empty result. I need to be able to compare some month names I have in an array.  It would be nice if there were some direct way like:  Month.toInt("January") &gt; Month.toInt("May")   My Google searching seems to suggest the only way is to write your own method, but this seems like a common enough problem that I would think it would have been already implemented in .Net, anyone done this before? After using gdalwarp to project and align-to-grid (via -tap) a number of rasters I noticed that the output rasters were significantly larger than the original rasters. A fairly thorough web search turned up :  Frank Warmerdam explained the reason: &quot;On careful review, the difference in the file in question is because gdal_translate uses the TIFFWriteScanline() interface to write the output file from within GTiffDataset::CreateCopy?(), and this only writes as much of the final 'strip' of the file as is required to complete image area. But gdalwarp goes through the blockio interface which writes the complete final strip, even the portion that falls off the end of the file.&quot;  This Trac issue is ~7 years old, however, and I know some changes to the GDAL utilities, including gdalwarp have been made since. I'd like to know if the above reasoning still holds and if the file size inflation I'm seeing is &quot;normal.&quot; The word &quot;normal&quot; here might be taken to mean unsurprising or expected but, more importantly: is there anything that can be done to mitigate the effects i.e. reduce the output raster file size? Below is a table of the file size inflation I'm experiencing. Input File Size (bytes)     Output File Size (bytes)    Inflation 1437380431                  1698334217                   18% 1428001178                  1698334433                   19%   41683165                   137036637                  228%  The input TIFF files were created in ArcGIS and thus have external Worldfiles, XML and DBF files but these do not make up the difference in file size. Here is a sample gdalwarp call as I've used it in all of these cases; the actual execution was handled by a Python subprocess (subprocess.Popen): $ gdalwarp -tap -tr 30 30 -t_srs &quot;+proj=aea +lat_1=20 +lat_2=60 +lat_0=40 +lon_0=-96 +x_0=0 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs&quot; -co &quot;COMPRESS=LZW&quot; input_file.tif output_file.tif  I understand that in rare cases compression makes a larger file, but the effect is the same without the LZW compression. The ratios in the table are with LZW compression. How to position the paper's authors' addresses on the front page (maketitle)? When I use the following code for the title page of a paper (please see below), the authors' addresses and emails appear on the last page of the paper. However I need them to appear on the first-title page (after the authors' names before the abstract). How can I do this?  \documentclass [reqno, 12pt ]{amsart} ... \begin{document}  \title[paper]{Nice paper}  \author{Me} \address{University} \email{mmm@lala.com} \thanks{.} \author{my friend} \address{Institute} \email{kkk@lala.edu} \thanks{.}  \date{\today} \keywords{XXX }  \begin{abstract} Lalala \end{abstract}  \maketitle Find $x,y$ given $\gcd(x,y)$ and ${\rm lcm}(x,y)$ "All our X" vs. "all of our X" Is the word "of" optional in this instance? Is either of these considered preferable to the other?        Taste all our delicious treats.   Taste all of our delicious treats. According to Ohm's Law, if the resistance is zero, the power dissipated by a resistor is unmeaning.  $$P_d = R \times I^2$$  $$I = \sqrt{ \frac {P_d}{R} }$$  Can one calculate the resistance given that power is defined? Only by knowing power, how can one calculate the maximum current of a zero-Ohm resistor?   I'm a bit confused as I've seen there is zero-Ohm resistors with specified power in the market.