I want to know one thing about a fused disconnect. If it's fused for a certain amount of current, would you be ok with not adding additional fuses to protect your loads?   If you have a 30 A fused disconnect and you have 2-5 hp motors and 1-3 hp motor it sounds to me like you might need to add fuses to protect each motor?   I know that for my application since my hp total is less then the 20 hp max that you can have for that disconnect at 480 V. I'm not in any trouble of tripping that breaker.   But would the motors need fusing still?
so i have a 30A disconnect available for use at a customer site for running 2 5HP motors ( at 480V)  the only question i have though is if the line is sized for a 10HP motor would both the 5HP motors need additional fuse protection?   Or could i get away without having addtional fuses protecting the motors ?
Column vs Field: have I been using these terms incorrectly? I feel kind of embarrassed here, I've always used the terms "column" and "field" completely interchangeably, which recently caused some confusion in a technical discussion.   I was told, though, that this wasn't correct, that it should be (translating each term into spreadsheet terminology, ignoring data types and all the other stuff that make databases useful):   Database Column: like a spreadsheet column  Database Record: like a spreadsheet row Database Field: like a spreadsheet "cell" (a specific column of a specific row)   Is this right? I could have sworn that column and field are used more interchangeably than that. I certainly have been.  So we don't add fields to a table, we add columns to a table, and fields are only relevant when talking about data within a record?  Other thoughts on column vs field?  Edit: to clarify, the current context is MS SQL Server. My background before SQL server was MS Access, which might influence my use of these terms. How to list all functions in a Python module? I have a Python module installed on my system and I'd like to be able to see what functions/classes/methods are available in it. I want to call the help function on each one. In Ruby I can do something like ClassName.methods to get a list of all the methods available on that class. Is there something similar in Python? eg. something like: from somemodule import foo print(foo.methods)  # or whatever is the correct method to call A problem of missing energy when charging a second capacitor A capacitor is charged. It is then connected to an identical uncharged capacitor using superconducting wires. Each capacitor has 1/2 the charge as the original, so 1/4 the energy - so we only have 1/2 the energy we started with. What happened? my first thoughts were that the difference in energy is due to heat produced in the wire. It may be heat, or it may be that this is needed to keep equilibrium. Looking for title of a fantasy fiction with huge war, invader on airship with warlock, island fortress with sorcerer, mnemonic storyteller and dragon This was a thick book that I read over fifteen years ago that I never finished reading because someone borrowed it and didn't return it to the school library. I want to find its title.  The story takes place in a kingdom that is preparing for the a cycle of war, where every time the winds changes (50 or 100 years), invaders will try to cross the sea from another continent using airships with air balloons, filled with soldiers and warlocks. The kingdom has made several man-made island fortress along their coastline, filled with soldiers with war machines, sorcerers, and enchanters who act as the main guard/defence for the kingdom, calling lightning and fireballs, and using machines to stop and destroy and bring down as many of the invader airships as possible while countering the warlocks on board.  The book involved a man and a girl whose journey brought them apart in preparing for the imminent war.   The women found herself adept in magic and went to the academy in the capital to learn to be a sorceress.   The man found a different calling. With a good memory, he was sent to learn to become a mnemonic storyteller (to train with battle staff and fighting skill and mnēmonikos skill) who carried the history, literature of the entire culture in their heads. They used their knowledge to convey the kingdom's literature, poetry, history and stories to the people from generation to generation.  Both eventually "graduate". Sadly, and with great emotion, both have to part ways. She was sent to a fortress island and began her role as a sorcerer who will stand guard there. He, as a storyteller, began his own journey without her, going from town to town, village and soldier barrack, across the kingdom, telling stories of great men and their deeds, and courageous heroes who fought the war, to uplift the spirit of the people and bring valor to the soldiers stationed at the border and people in the coming war.   In brief, he meets a dragon (who used to be involved in the war in ages past), long thought to be extinct. He finds himself able to communicate with it and has a "born" friendship with it. The dragon teaches him to become a "dragon rider", a long-lost ability of his people (due to the "extinction" of dragons.)   The wind changes with the dread of war hanging on the kingdom.  Airships start to blacken the sky again with soldiers and war machines battling each other. Concatenate several columns into one in Google Sheets Is there a simple way to flatten a list of iterables with a list comprehension, or failing that, what would you all consider to be the best way to flatten a shallow list like this, balancing performance and readability?  I tried to flatten such a list with a nested list comprehension, like this:  [image for image in menuitem for menuitem in list_of_menuitems]   But I get in trouble of the NameError variety there, because the name 'menuitem' is not defined.  After googling and looking around on Stack Overflow, I got the desired results with a reduce statement:  reduce(list.__add__, map(lambda x: list(x), list_of_menuitems))   But this method is fairly unreadable because I need that list(x) call there because x is a Django QuerySet object.  Conclusion:   Thanks to everyone who contributed to this question.  Here is a summary of what I learned.  I'm also making this a community wiki in case others want to add to or correct these observations.  My original reduce statement is redundant and is better written this way:  &gt;&gt;&gt; reduce(list.__add__, (list(mi) for mi in list_of_menuitems))   This is the correct syntax for a nested list comprehension (Brilliant summary !):  &gt;&gt;&gt; [image for mi in list_of_menuitems for image in mi]   But neither of these methods are as efficient as using itertools.chain:  &gt;&gt;&gt; from itertools import chain &gt;&gt;&gt; list(chain(*list_of_menuitems))   And as @cdleary notes, it's probably better style to avoid * operator magic by using chain.from_iterable like so:  &gt;&gt;&gt; chain = itertools.chain.from_iterable([[1,2],[3],[5,89],[],[6]]) &gt;&gt;&gt; print(list(chain)) &gt;&gt;&gt; [1, 2, 3, 5, 89, 6] If the Standard Normal PDF is $$f(x) = \frac{1}{\sqrt{2\pi}} e^{-x^2/2}$$  and the CDF is  $$F(x) = \frac{1}{\sqrt{2\pi}} \int_{-\infty}^x e^{-x^2/2}\mathrm{d}x\,,$$  how does this turn into an error function of $z$? Dirac Delta function inverse Fourier transform We know that the Fourier transform of the Dirac Delta function is defined as $$\int_{-\infty}^{\infty} \delta(t) e^{-i\omega t} dt = 1,$$  and if I were to reconstruct the function back in time domain, the inverse Fourier transform is defined as  $$\delta(t) = \frac{1}{2\pi}\int_{-\infty}^{\infty} e^{i\omega t} d\omega.$$  How do I compute this integral analytically? hotel occupancy counting problem The multiple-choice question:  A hotel has four vacant rooms. Each room can accommodate a maximum of four people. In how many different ways can six people be accommodated in the four rooms? (A) 4020 (B) 4068 (C) 4080 (D) 4096.  My attempt:  If there were no 'four person' constraint, the six people could be accommodated in $4^6=4096$ ways. however, this number includes combinations with 5 or 6 people in one room, which should be excluded.  If one room has 5 occupants, one other room has 1 occupant. The number of '1,5' combinations is ${{4} \choose {2}}$=12. If one room has 6 occupants, the other three rooms have no occupants, and there are four such combinations.  I believe the answer should be $4096-12-4=4080$, but am not confident. I'd be grateful for any comments on my attempt. This is a  about IPv4 Subnets.      Related:               How does Subnetting Work, and How do you do it by hand or in your head?  Can someone explain both conceptually and with several examples? Server Fault gets lots of subnetting homework questions, so we could use an answer to point them to on Server Fault itself.   If I have a network, how do I figure out how to split it up? If I am given a netmask, how do I know what the network Range is for it? Sometimes there is a slash followed by a number, what is that number? Sometimes there is a subnet mask, but also a wildcard mask, they seem like the same thing but they are different? Someone mentioned something about knowing binary for this? virtual methods I know that \: in LaTeX produces a space when rendered.  Are there any alternatives, because my LaTeX renderer doesn't support \: (it renders it as text), and there is no help / FAQ that I can find. How to enable root login again after changing password? I had enabled root login before and tried to change its password using this . But after successfully changing the password and locking it via sudo passwd -dl root. I cannot login back to SSH, it says Access is denied.  I have two users on my machine. root and admin, admin does not have su permission. When I try to use sudo on admin user, it says that admin is not in the sudoers file. That is why i need my su user back. How to log out of a Stack Exchange site? Per the title, where is the logout button?  All the existing questions I can find refer to the previous design of the site, where hovering over your name in the top bar brought up a menu. Prove Borel Measurable Set A with the following property has measure 0. This question is exercise 4.10 of Richard F. Bass's Real Analysis for Graduate Students, 2nd edition.  Let $\epsilon \in (0,1)$, let $m$ be Lebesgue measure, and suppose $A$ is Borel Measurable subset of $\mathbb R$. Prove that if $$ m(A\cap I)\leq (1-\epsilon)m(I)$$  for every interval $I$, then $m(A)=0$.  Collection of my thoughts  1. Try to prove by contradiction, suppose $m(A)=a&gt;0$ Borel Measurable Set satisfies the condition given. A property of any Borel Measurable Set on $\mathbb R$ is $A$ contains a closed set $F$ and is contained in open set $O$, and the measure of $F$ and $O$ can be arbitrarily close to $a$. 2. Obviously $A$ contains no interval, but it does not lead to contradiction, because we can find an example of $m(A)&gt;0$ that contains no interval(fat Cantor Set(remove middle 1/4 each time) has measure $1/2$ and contains no interval).  2'. For fat Cantor Set $C$ and given $\epsilon&gt;0$ how could we construct an interval I satisfies $m(C \cap I)&gt;(1-\epsilon)m(I) ?$   Maybe try to write Borel measurable set as countable union/intersection of intervals.   I'm stucked here and will appreciate any help, some examples/special case will be great too. Suppose I know that I can find the $\gcd$ of two integers with the Euclidean algorithm. What is the 'extension' so I can use this method also for polynomials?  Edit: I found an easy answer with less rigor which is approachable without knowledge of matrices:    also the first 3 subchapters of Will be glad for a little hint: let x and n be positive integer such that $1+x+x^2+\dots+x^{n-1}$ is a prime number then show that n is prime What is the best way to share/distribute Excel macro? How to remove `t=canonical` from Firefox browser searches made on DuckDuckGo? In Ubuntu 14.04, when I do a search in Firefox using either the address bar or the search bar, the system always adds t=canonical to my searches. So the full string becomes: https://duckduckgo.com/?q=cat+cooking+salmon&amp;t=canonical.  However, if I perform the same search by going directly to the search engine, i.e. typing the search engine name and doing the search from the presented search box, this does not happen. In this case the string is: https://duckduckgo.com/?q=cat+cooking+salmon.    How do I stop Ubuntu/Firefox from adding t=canonical to my search queries? And, why is this behavior there in the first place? Lets say I have a function defined as $f(x) = \sqrt {x^2}$. Common knowledge of square roots tells you to simplify to $f(x) = x$ (we'll call that $g(x)$) which may be the same problem, but it isn't the same equation. For example, say I put $-1$ into them:  $\begin{align} f(x) &amp;= \sqrt {x^2} \\ f(-1) &amp;= \sqrt {(-1)^2} \\ f(-1) &amp;= \sqrt {1} \\ f(-1) &amp;= 1 \end{align}$  $\begin{align} g(x) &amp;= x \\ g(-1) &amp;= -1 \end{align}$  thereby, we conclude that $f(x)$ and $g(x)$ do not produce the same results even though they are mathematically the same. This is also shown when we try to graph the functions:  :    :    :    From this, we can see that given $f(x) = \sqrt {x^2}$, when simplified is not the same as $f(x) = x$. So, is there any way to prove that $y = \sqrt {x^2}$ is not the same as $y = x$ for negative values, but is infact the same as $y = \mid x \mid$?