I am a computer engineering major so I do not understand a lot of quantum science but from what I hear about quantum computers, it sounds like they are just massively parallel computers.  In quantum computers there are Qubits which are in a superposition state of 0 and 1. Two qubits are in the states 00, 01, 10 and 11 states simultaneously.   Now let us take a look at a NP-complete problem, . If it is a three variable satisfiability problem, classical computer would have to try every single combination, one after another. (000,001,010...)   But say if my computer has 8 cores I can ask each core to solve for just one of these combinations. So I will get the solution in polynomial time. For a N variable satisfiability problem I need 2^N cores and I will still be able to solve in polynomial time.  My question is, does the quantum computer do just that or is there more to it?  I am learning OpenCL and it utilizes the GPU which has a massively parallel architecture having thousands of cores(kind of). Then can it emulate a quantum computer to a certain extent?

If you have an infinite memory infinite processor number classical computer, and you can fork arbitrarily many threads to solve a problem, you have what is called a "nondeterministic" machine. This name is misleading, since it isn't probabilistic or quantum, but rather parallel, but it is unfortunately standard in complexity theory circles. I prefer to call it "parallel", which is more standard usage.  Anyway, can a parallel computer simulate a quantum computer? I thought the answer is yes, since you can fork out as many processes as you need to simulate the different branches, but this is not a proof, because you might recohere the branches to solve a PSPACE problem that is not parallel solvable.  Is there a problem strictly in PSPACE, not in NP, which is in BQP? Can a quantum computer solve a problem which cannot be solved by a parallel machine?  Jargon gloss   BQP: (Bounded error Quantum Polynomial-time) the class of problems solvable by a quantum computer in a number of steps polynomial in the input length. NP: (Nondeterministic Polynomial-time) the class of problems solvable by a potentially infinitely parallel ("nondeterministic") machine in polynomial time P: (Polynomial-time) the class of problems solvable by a single processor computer in polynomial time PSPACE: The class of problems which can be solved using a polynomial amount of memory, but unlimited running time.


I have submitted my mathematical paper to a journal in November 2018. After that, it has the status "Awaiting Referee Selection" during 4 months. I contacted the Editor-in-Chief for his support, luckily, he is very nice. The result is that the status of the paper has been "under review" in March 2019 and he said that:     I hope to receive the reports of the referees by mid-April.   However, today (April 24, 2019) I still has not received the first decision.  Should I contact the Editor-in-Chief again or not? Thank you for your comments.

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.


Question: Carefully prove the Principle of Cauchy Induction: Suppose $P(n)$ is a property that a natural number $n$ may or may not have. Suppose that   $P(2)$ holds, For every $n ≥ 2$, if $P(n)$ holds, then $P(2n)$ holds, and For every $n ≥ 3$, if $P(n)$ holds, then $P(n − 1)$ holds.   Then $P(n)$ holds for every natural number $n ≥ 2$.

I was reading a blogpost here:  () One thing that threw me off was that after the first four large displayed equations, there is the statement "it is sufficient to prove that if the theorem holds for $n=m+1$, then it holds for $n=m$." How is this type of induction valid? I browsed around for things like backward induction, reverse induction, and Cauchy induction, but couldn't find a justification for how this is valid. With the usual forward induction of verifying a base case and proving $P(n)\implies P(n+1)$, it's easy to intuitively understand how induction will show a property holds for all natural numbers (or at least starting at the base case). But with this reverse induction, it seems to me that if you prove $P(m+1)\implies P(m)$, then if you were able to verify a specific case like $P(15)$, then you would only know it's true for numbers up to $15$. How does it actually prove the property for all naturals?


This is a problem for a graduate level discrete math class that I'm hoping to take next year (as a senior undergrad). The problem is as stated in the title:     Given that $\gcd(k, l) = d$, prove that $\gcd(2^k - 1, 2^l - 1) = 2^d  - 1$.   The problem also says "hint: use Euclid's lemma," although I'm not sure what part of the problem should be applied to. I've been thinking about it for a few days and I'm completely stumped.   I'm not really even sure how to show that it divides either $2^k - 1$ or $2^l - 1$. From the given, we know that $\exists c: dc = k$. We need to show that $\exists c': (2^d - 1)c' = 2^k - 1$. Obviously $c' = 2^c$ gives you $(2^d - 1)c' = 2^k - 2^c$, but I can't figure out how to get rid of the extra terms that the $- 1$ brings in in various places.  From Euclid's lemma on the left side, you know $\exists i: di = k - l$, and applying it on the right side, you know it suffices to show that $\gcd(2^k - 2^l, 2^l - 1) = 2^d - 1$. And by Bezout's identity, it's enough to show that $2^d - 1$ can be written as a linear combination of either of those things.  Can anyone give me a hint?


I have run an analysis on data using SPSS. I have a repeated measures design with 7 conditions. I chose to do pairwise comparisons to see where the effects lie and used the Bonferroni correction. If I've understood it correctly k(k-1)/2 would give an adjusted p value of .002. However, what I'm confused with is the output in SPSS. It says something is significant at .003. Could somebody explain this and how would I report it? I wasn't sure if I was supposed to check the significance value against the new .002 one and therefore should conclude it isn't significant.

I'm probably being a bit simplistic here, but from what I understand the Bonferroni post hoc test is simply when we adjust the alpha to account for inflated error when several post hoc tests are conducted. You divide the alpha by number of tests. So what exactly does SPSS do when we click the button for Bonferroni?   Shouldn't the dividing of alpha be done by us in interpreting the result, e.g. if we do 10 post hoc tests our alpha criterion should be .005 so if the p value is .012 then it is not significant, but SPSS hasn't done anything there, we have just changed our interpretation. So what exactly is it adjusting?


In a between-subjects experiment, we have 2x2 conditions and several 7-point Likert dependent variables. What would be the best way to visualize this data? I am a statistics newbie, so please forgive my simple questions. I have, of course, searched the web and this forum. But most posts I found seem to be dealing with binary dependent variables. In contrast, we have, I think, binary independent variables. Is it OK to treat the Likert answers as a continuous variable? I seem to recall some discussion (I forget where - maybe a textbook, maybe a paper) whether or not this is OK. It does not seem to be a categorial variable to me. Maybe it's an ordered categorial variable? But, more importantly, what would you suggest to plot the data? Simple box-plots (with whiskers) don't seem to work really well, because in almost all dependent variables we had a few participants answering with the lowest, and some with the highest scores. Also, it would be nice if one could show the answers for one dependent variable for all 4 conditions in one single plot in an intuitive way.

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 <- rep(1:5, times = c(30, 42, 75, 93, 60)) often <- 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 <- 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:


We used to capitalize references to  "the President" (of the US) even when his name wasn't included. And we used to capitalize "state" even when a particular state (State of California) was not mentioned. Is it now considered proper usage not to capitalize either of those?

I was taught at an early age in the USA that when we write about our President, we are supposed to capitalize the title in order to signify that it's on the federal level. Is it correct to always do this? And what about saying "the presidency" -- should that be "the Presidency"?


How would it be possible to copy all new contents from one directory to another so that only new files are copied from the source directory (both directories have the same naming tree). For example, here is the layout of directory A:  /dirA      a.php      b.txt      subdirA1/               readme.txt               config               source_file1.c  /dirB      c.php      subdirA1/               readme.txt   at the end dirB should have all the new files in dirA. Assume that there are only new files in dirA and its sub directories. The result should be the union of the two directories:  /dirB      a.php      b.txt      c.php      subdirA1/               readme.txt               config                                 source_file1.c   I have tried using cp -ra:  cp -ra dirA/* dirB/   but dirB is completely overwritten by dirA.

How do I copy an entire directory into a directory of the same name without replacing the content in the destination directory? (instead, I would like to add to the contents of the destination folder)


I have multiple buttons which are Order 1  and a contact form below it with a  field with multiple options (Order 1, Order2, etc...)  When I click on the "Order 1" button , I want the  field to select Order 1. And if I click on the "Order 2" button, I want the  field to select Order 2 for example. Is there a way to do that with javascript?  I've seen this done in some websites but can't remember exactly where.

I have a select control, and in a javascript variable I have a text string.  Using jQuery I want to set the selected element of the select control to be the item with the text description I have (as opposed to the value, which I don't have).  I know setting it by value is pretty trivial. e.g.  $("#my-select").val(myVal);   But I'm a bit stumped on doing it via the text description. I guess there must be a way of getting the value out from the text description, but my brain is too Friday afternoon-ed to be able to work it out.


Question: Bernardo chooses a three-digit positive integer $N$ and writes both its base-5 and base-6 representations on a blackboard. Later LeRoy sees the two numbers Bernardo has written. Treating the two numbers as base-10 integers, he adds them to obtain an integer $S$. For example, if $N = 749$, Bernardo writes the numbers $10,\!444$ and $3,\!245$, and LeRoy obtains the sum $S = 13,\!689$. For how many choices of $N$ are the two rightmost digits of $S$, in order, the same as those of $2N$? $\textbf{(A)}\ 5 \qquad\textbf{(B)}\ 10 \qquad\textbf{(C)}\ 15 \qquad\textbf{(D)}\ 20 \qquad\textbf{(E)}\ 25$  I am not sure where to start with this question (the only thing that I can think of is an equation). Also, I read the aops solutions and didn't understand them.   My equation: $$(625a+125b+25c+5d+e)+(216f+36g+6h+I)=N$$ (I am not sure if this is correct).

I am looking over , and I came across a solution containing this:  Problem Bernardo chooses a three-digit positive integer $N$ and writes both its base-5 and base-6 representations on a blackboard. Later LeRoy sees the two numbers Bernardo has written. Treating the two numbers as base-10 integers, he adds them to obtain an integer $S$. For example, if $N = 749$, Bernardo writes the numbers $10,\!444$ and $3,\!245$, and LeRoy obtains the sum $S = 13,\!689$. For how many choices of $N$ are the two rightmost digits of $S$, in order, the same as those of $2N$? $\textbf{(A)}\ 5 \qquad\textbf{(B)}\ 10 \qquad\textbf{(C)}\ 15 \qquad\textbf{(D)}\ 20 \qquad\textbf{(E)}\ 25$ Solution 1 First, we can examine the units digits of the number base 5 and base 6 and eliminate some possibilities. Say that $N \equiv a \pmod{6}$ also that $N \equiv b \pmod{5}$ Substituting these equations into the question and setting the units digits of $2N$ and $S$ equal to each other, it can be seen that $b < 5$ (because otherwise $a$ and $b$ will have different parities), and thus $a=b$. $N \equiv a \pmod{6}$, $N \equiv  a \pmod{5}$, $\implies N=a \pmod{30}$, $0 \le a \le 4$ Therefore, $N$ can be written as $30x+y$ and $2N$ can be written as $60x+2y$ Just keep in mind that $y$ can be one of five choices: $0, 1, 2, 3,$ or $4$, ; Also, we have already found which digits of $y$ will add up into the units digits of $2N$. Now, examine the tens digit, $x$ by using $\mod{25}$ and $\mod{36}$ to find the tens digit (units digits can be disregarded because $y=0,1,2,3,4$ will always work) Then we take $N=30x+y$ $\mod{25}$ and $\mod{36}$ to find the last two digits in the base $5$ and $6$ representation.[N \equiv 30x \pmod{36}][N \equiv 30x \equiv 5x \pmod{25}]Both of those must add up to[2N\equiv60x \pmod{100}] $N\equiv{30x\mod{36}}\\N\equiv{30x}\equiv{5x\mod{25}}$ Both of these must add up to $2N\equiv{60x\mod{100}}$ [...]  I'm not really sure which modular arithmetic rule to apply in the final three congruences, or where to start. How would I go about understand this?


I'm kinda new in this and I was wondering if I could get some help.  I am trying to build a AC-DC converter, through a full wave rectifier. Ideally a 220V AC source, freq: 50hz stepped down to 22V AC and rectified to a DC voltage but I'm struggling to get a definite formula to calculate the smoothing capacitance. I was planning to channel the output of the rectified DC to a 7812 voltage regulator. Thanks in advance.

I have a 9V AC source which will have a max load of 100mA.  I'm trying to figure the value of a smoothing capacitor with less than a 10% ripple.  I don't have a scope or else I'd just try a bunch out.  I'm just a hobbyist, but I'm trying to understand this.  Since I'm not sure if I'm doing this right, I'll just step through what I've done so far.  First I found this formula: $$V_{ripple}={V_p \over R_LC} \times \Delta T$$  I'm using 60Hz 9VAC that is full wave rectified and I want a 10% ripple so:  $$(9V \times .1)={9V \over R_LC} \times {1 \over 60Hz}$$  I'm calculating my resistive load with Ohm's law. $$R = {9V \over .1A} \quad R = 90 \Omega$$  So plugging that in I get: $$.9V={9V \over 90\Omega \; C} \times {1 \over 60Hz}$$  If I solve for C (admittedly using wolfram alpha), I get: $$C={1\over 540}F \quad C=1851 \mu f$$  1850µf seems pretty high to me...  And if I lower the ripple percent it get crazy high.  Is this the right way to find this?  Or did I screw up somewhere?  Also, my circuit has the capacitor between the full bridge rectifier's positive and negative outputs.  I've only seen this type of smoothing circuit, but maybe my circuit needs to change?


$\sum_{n=1}^{\infty}\frac{1}{n(n+1)(n+2)}$  I know it converges via comparison test, but how to actually find the series value?

I got this question in my maths paper     Test the condition for convergence of $$\sum_{n=1}^\infty \frac{1}{n(n+1)(n+2)}$$   and find the sum if it exists.   I managed to show that the series converges but I was unable to find the sum. Any help/hint will go a long way. Thank you.


I was wondering if it is possible to remove the portion of a soul inside a Horcrux without the person whose soul is actually in the Horcrux. I’m writing a Harry Potter fan fiction, and would really appreciate it if anyone could tell me.

As anyone who is familiar with Harry Potter knows, a horcrux is made when someone commits murder and stores a piece of their soul in something. Would it be possible for this someone to later recover and reintegrate their soul piece(s), should they want to?


We have  $$ 1^3 + \dotsb + n^3 = (1 + \dotsb + n)^2 $$ as we can establish by induction. But why does this hold? Can we connect it to something else?

I recently proved that  $$\sum_{k=1}^n k^3 = \left(\sum_{k=1}^n k \right)^2$$  using mathematical induction.  I'm interested if there's an intuitive explanation, or even a combinatorial interpretation of this property. I would also like to see any other proofs.


Does there exist a continuous function     $f\colon \Bbb R\rightarrow \Bbb R$ such that $f(f(x))=-x$ for all $x\in\Bbb R$?

I've been perusing the internet looking for interesting problems to solve. I found the following problem and have been going at it for the past 30 minutes with no success:     Find a function $f: \mathbb{R} \to \mathbb{R}$ satisfying $f(f(x)) = -x$ for all $x \in \mathbb{R}$.   I am also wondering, can we find $f$ so that is continuous?  I was thinking of letting $f$ be a periodic function, and adding half the period to x each time. I had no success with this, and am now thinking that such a function does not exist.  Source:


How can I force the equation of text line to fit \textwidth? Here is the demo code:  \documentclass{article}  \begin{document} \section{Width of equation in text line} text text text text text text text text text text text text text text text text text text text text\,\,\, This model $\sum\limits_{i=1}^N a_i^2$ looks not good. \,\,text text text text text text text text text texttext text text text text text text \begin{enumerate}   \item text text text text text text text text text text text text    \item It's not good in enumerate environment like $\sum\limits_{i=1}^N a_i^2$. text text   \item text text text text text text text text text text text text  \end{enumerate} \end{document}

I'm very familiar with how symbols display differently in inline mode (with $ ... $) vs. how display math shows them (with \[ ... \] or $$ ... $$).  Two examples would be with limits  $\lim_{n\rightarrow \infty}f(x)$   vs.  \[ \lim_{n\rightarrow \infty}f(x) \]   and with sums  $\sum_{n=1}^{x} n^2$   vs.  \[ \sum_{n=1}^{x} n^2 \]   My Question is:     How do you display these things in inline mode (with all the nice inline formatting) as if they were in display mode ?   The inverse -- how to display things in display mode as if they were in inline mode -- is also of interest.


Ok, so this is a follow up to my last post. So Pilot6 told me to connect my phone to my computer and turn on personal hotspot. Then I booted up to Ubuntu 20.04 to install the drivers by doing: sudo apt install bcmwl-kernel-source But it didn't work, because it didn't have dkms, libc6-dev and linux-libc-dev. So I tried to install those three packages and it still didn't work and it outputted an error saying: E: Package (every package i mentioned) has no installation candidate. So what should I do now? Edit: Alright so I did a little bit of researching and found that the error means that I need to install a ppa.

I'm having serious problems installing the Broadcom drivers for Ubuntu. It worked perfectly on my previous version, but now, it is impossible.   What are the steps to install Broadcom wireless drivers for a BCM43xx card?  I'm a user with no advance knowledge in Linux, so I would need clear explanations on how to make, compile, etc.    lspci -vnn | grep Network showed:   Broadcom Corporation BCM4322 802.11a/b/g/n Wireless LAN Controller [14e4:432b]      iwconfig showed:  lo        no wireless extensions. eth0      no wireless extensions.   NOTE: Answer below is updated every time new information is added and confirmed working.


This seems to be a recent change... When I put the mouse over the new contributor indicator, the little pop up is created but seems to be confined within the question container -- creating an off-putting scrollbar:  This is on Chrome in Windows.

Not sure when this started happening, but the new contributor hover information now makes a scrollbar appear, and keeps all of the hover card information constrained to a small area surrounding the post. Here's a gif representation, from :  This appears to happen on every site I visit, so I assume it's network-wide. I'm using Chrome version 88.0.4324.182 (Official Build) (64-bit) on Windows 10, if that matters. Could this be looked into and fixed?


It is often stated that because the energy in an em wave is $E=hf$, the energy comes only as multiples of $h$, ie quantized. But we know that $f$ is a real number, and you could have fractions of one Hertz. The difference in energy of two such waves can be a fraction of $h$ in this case. Is this a correct thinking. I can accept that absorption and emission of energy is quantized, but this is not the same thing- as in this case the quantization is a property of the material not the wave.

I'm just starting to learn physics and I have a question (that is probably stupid.)  I learned that energy levels that the bound electron can have are discrete. I also learned that when an electron transitions from one level to another, a photon with a specific wavelength (energy) is created and released into the wild.  My question is this: are there holes in the electromagnetic spectrum, values of frequency that the created photon can't possibly have?


I have a bike with 27 1 1/4 rims. I plan to buy  a pair of Kenda K161 (27 1 3/8) because the roads get really slippery during the winter. Will these tires fit on my rims? I aldo don't want to buy a new 200c wheelset because it's expensive. Another option is DIY studded tires but buying these tires seems the cheapest option. There is a similar question  but the answer isn't really conclusive.

Will the kenda K161 cyclocross tires (27x1 3/8s) fit on a 27x1 1/4 rim?  I havent been successful at finding this question on here or on google, apologies if it has been asked a million times.  Thanks!


Could any one explain me, why does a click event is not triggered, when an element is inserted in the dom from a variable    Consider  HTML

 <input type="button" value="clickme" id="cme"/>   jQuery  $("#cme").click(function(){     var inside = '<input type="button" value="clickme again" id="sme"/>';     $("#disp").html(inside); });  $("#sme").click(function(){     alert("clicked me");   });   When you click clickme button, new button clickme again is added inside the disp and when clickme again button is clicked, it does not fire the click event attached to it. it does not alert clicked me ? why ?  But when I have tried this way, it works   $("#cme").click(function(){     var inside = '<input type="button" value="clickme again" id="sme"/>';     $("#disp").html(inside);     // when i put here , it works     $("#sme").click(function(){         alert("clicked me");       }); });   I want to put the $("#sme").click outside. Any help is greatly appreciated. Thanks

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off.  This happens on page ready and works just fine.  The problem I have is that any select boxes I add via Ajax or DOM after the initial loop won't have the event bound.  I have found this plugin (), but before I add another 5k to my pages with a plugin, I want to see if anyone knows a way to do this, either with jQuery directly or by another option.


Some writings in Computer Science papers/conferences usually include the "Preliminaries" section, where we write the general notations and basic knowledge necessary for understanding the contents of the papers.   Can I use the same thing that I wrote in Preliminaries section for (conference or journal) paper A, in Preliminaries section for other papers B, C etc. also? Because basically I will need to say the same thing over and over again..

I am currently a referee for a paper. One of the authors of the paper had written an earlier paper, which I will refer to as the "original paper," and the paper which I am now refereeing is an extension of the original paper, which I will refer to as the "extension paper."  I have found that large portions of the extension paper are copied from his original paper. In particular, a whole section of definitions is copied from his original paper; and some paragraphs in the introduction and literature review are copied wholesale or with slight modifications from the original paper.  Is it acceptable for an academic paper to copy paragraphs and even a section from an earlier paper by the same author?  My intuition suggests that it is acceptable to copy the definition section, with an acknowledgement that it came from the original paper, since definitions are standard. But it seems strange to me for the introduction and literature review to be too similar to the original paper.


This is in my garage. I am trying to add a second circuit in order to be able to run the dust collector and the table saw at the same time. I did run them on the existing circuit with no load and the breaker did not trip but I want o be on the safe side.  There is one circuit that enters the garage right where you see the GFI power outlet. I extended that to a workbench that I have to the left of the door on the left side (conduit not shown) and to the right to feed the garage door lift and to add one more power outlet also connected with a wire run through plastic conduit. This circuit is grounded.  Now I have wiring coming into the garage from the porch then it is run as seen down to the bottom level of the first garage front light. The cable goes into the wall outside to feed that light bulb and then it comes back it goes above the garage door opening and it lands on the other side of the garage door (not pictured) to feed the other garage door light (extreme right of the picture) The above are on a 15A circuit that has a on/off switch in the house.   Can I run a ground wire from the power outlet that is next to the new power outlet that I want to add (highlighted in blue)?  ..all my regular circuits are 15A ..

I have an older home where some of the house has updated electrical and some doesn't.  In a few rooms I still have several of the 2 prong outlets with no ground wire in the box and I want to replace them with 3 prong tamper proof outlets with proper grounding.  If I had an easy way to run a new line from the panel I would not be wasting your time, but I live in a split level home and several of these rooms have their lines fed from below, in-between floors, so I don't have any way to run a new line easily.   I know I can add GFCI outlets for some human protection but I want to do better.   I need to know if it is safe and/or legal to run a ground wire from a junction box in my attic (there are several) down the wall to use as ground when I replace the 2 prong with a 3 prong.  The junction box likely leads back to a different circuit but it is all originating from the same panel (I only have 1)


I think I generally understand what half-life means. What I wonder is, in a large collection of atoms of a radioactive element, are some atoms more likely to decay than others due to internal state or is it completely random? If the former, can an atom be examined to determine if it is more likely to decay than some other atom?

So, as I understand it, in a substance that is made of radioactive elements, the half-life tells us how long until the half of those atoms decay into their next atom [is there a name for that: the element or isotope that is the result of a prior radioactive decay?]. My question is, is there some sort of pattern to which atoms decay at which time, or is it some miraculous property of quantum mechanics that somehow each atom knows when to decay? or do I just understand radioactive decay incorrectly?   Are the particles entangled or in some otherway attached (aside from their molecular bonds)? If there is no known answers, I would prefer any serious, leading theories.


I have to automate the logic with Trigger. If the Comment__c field is updated in 1 Tool__c record, it should be updated in all another Tool__c records. It's about 700-1000 actual records.  When I'm trying to update it with my Trigger, I'm getting the error: Update failed. First exception on row 163 with id a0G1w000001d91sEAA; first error: SELF_REFERENCE_FROM_TRIGGER, Object (id = a0G1w000001d91s) is currently in trigger ToolTrigger, therefore it cannot recursively update itself: []. And I'm trying to update the field exactly in the Tool__c with Id from the Error: a0G1w000001d91sEAA.  My code:      trigger ToolTrigger on Tool__c (before update) {     List<Tool__c> tools = [SELECT Id, Comment__c FROM Tool__c WHERE EndDate__c >=: DateTime.NOW()];      for(Tool__c t : Trigger.new){         if(Trigger.oldMap.get(t.Id).Comment__c != t.Comment__c){             for(Tool__c  tool : tools){                 tool.Comment__c = tool.Comment__c;             }          }     }     update tools; }   How can I avoid this error and realize my logic?

Can any one out here give me a scenario for recursive trigger. Why don't we able to control the trigger in the same place. Why do we go for a class under every trigger Context. Please provide me a scenario where recursive trigger occur.


I am trying to compute the following integral using the Residue Theorem but am quite stuck: $$\int_0^\infty \frac{\sin^2x}{x^2}dx$$ I have tried applying Jordan's lemma, having written $\sin(x)$ as $\dfrac{\mathrm{e}^{ix}-\mathrm{e}^{-ix}}{2i}$, to not much avail. I have also tried using a rectangular integration path but it didn't get me far. I'd be grateful for an insightful advice.

I am looking for a short proof that $$\int_0^\infty \left(\frac{\sin x}{x}\right)^2 \mathrm dx=\frac{\pi}{2}.$$ What do you think?  It is kind of amazing that $$\int_0^\infty \frac{\sin x}{x} \mathrm dx$$ is also $\frac{\pi}{2}.$ Many proofs of this latter one are already in this .


Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at com.example.converter.MainActivity.onCreate(MainActivity.java:30)   that's where it shows error         btnMiles.setOnClickListener(new View.OnClickListener()

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?


In compass we use a magnet or magnetized metals to interact with the earth magnetic fields, Can't we just use iron or any unmagnetized metal?

We know that the needle that is used in a compass is a permanently magnetized ferromagnetic material and commonly steel is used.  If we used an unmagnetized iron needle instead, would it still align with Earth's magnetic field lines? If yes, how?


Network Manager reports:  device not managed   Output of sudo lshw -C Network:  *-network DISABLED            description: Ethernet interface    product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller    vendor: Realtek Semiconductor Co., Ltd.    physical id: 0    bus info: pci@0000:02:00.0    logical name: enp2s0    version: 15    serial: 2c:60:0c:f6:97:a6    size: 10Mbit/s    capacity: 1Gbit/s    width: 64 bits    clock: 33MHz    capabilities: pm msi pciexpress msix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation    configuration: autonegotiation=on broadcast=yes driver=r8168 driverversion=8.042.00-NAPI duplex=full latency=0 link=no multicast=yes port=twisted pair speed=10Mbit/s    resources: irq:47 ioport:4000(size=256) memory:c4404000-c4404fff memory:c4400000-c4403fff *-network    description: Wireless interface    product: QCA9377 802.11ac Wireless Network Adapter    vendor: Qualcomm Atheros    physical id: 0    bus info: pci@0000:03:00.0    logical name: wlp3s0    version: 30    serial: 48:e2:44:46:07:ab    width: 64 bits    clock: 33MHz    capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless    configuration: broadcast=yes driver=ath10k_pci driverversion=4.8.0-34-generic firmware=WLAN.TF.1.0-00267-1 ip=192.168.1.101 latency=0 link=yes multicast=yes wireless=IEEE 802.11    resources: irq:53 memory:c4200000-c43fffff   Output of nmcli d:  DEVICE  TYPE      STATE      CONNECTION              wlp3s0  wifi      connected  FASTWEB***************  enp2s0  ethernet  unmanaged  --                      lo      loopback  unmanaged  --      Output of ifconfig:  lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536         inet 127.0.0.1  netmask 255.0.0.0         inet6 ::1  prefixlen 128  scopeid 0x10<host>         loop  txqueuelen 1  (Local Loopback)         RX packets 2487  bytes 383935 (383.9 KB)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 2487  bytes 383935 (383.9 KB)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0  wlp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500         inet 192.168.1.101  netmask 255.255.255.0  broadcast 192.168.1.255         inet6 2001:b07:6452:4630:d631:dc14:aa32:46e7  prefixlen 64  scopeid 0x0<global>         inet6 fe80::7932:6d1f:e49b:9b8d  prefixlen 64  scopeid 0x20<link>         ether 48:e2:44:46:07:ab  txqueuelen 1000  (Ethernet)         RX packets 29742  bytes 30300740 (30.3 MB)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 22589  bytes 4019841 (4.0 MB)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0   Output of ip a:  1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00     inet 127.0.0.1/8 scope host lo        valid_lft forever preferred_lft forever     inet6 ::1/128 scope host         valid_lft forever preferred_lft forever 2: enp2s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000     link/ether 2c:60:0c:f6:97:a6 brd ff:ff:ff:ff:ff:ff 3: wlp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000     link/ether 48:e2:44:46:07:ab brd ff:ff:ff:ff:ff:ff     inet 192.168.1.101/24 brd 192.168.1.255 scope global dynamic wlp3s0        valid_lft 42392sec preferred_lft 42392sec     inet6 2001:b07:6452:4630:d631:dc14:aa32:46e7/64 scope global noprefixroute         valid_lft forever preferred_lft forever     inet6 fe80::7932:6d1f:e49b:9b8d/64 scope link         valid_lft forever preferred_lft forever   How do I fix this?

I am using Ubuntu 16.10 and recently I have not been able to connect to internet using Ethernet. The network manager shows device not managed. The WiFi network is working fine.      I've tried the solution from this questionn  with no use.  My /etc/network/interfaces file:  # interfaces(5) file used by ifup(8) and ifdown(8) auto lo iface lo inet loopback   My /etc/NetworkManager/NetworkManager.conf file:  [main] plugins=ifupdown,keyfile,ofono dns=dnsmasq  [ifupdown] managed=true   Output of nmcli d:  DEVICE  TYPE      STATE      CONNECTION  wlp2s0  wifi      connected  eduroam     enp8s0  ethernet  unmanaged  --          lo      loopback  unmanaged  --


Assuming the Druid's level is high enough to stay in Wild Shape, can the Druid's beast form regain lost Hit Points resting this way? If so, does he use the beast's hit dice or the Druid's?

Do the druid's uses of the Wild Shape feature recharge while still in Wild Shape?  Say a 10th-level Circle of the Moon Druid spends two uses of Wild Shape to transform into an Air Elemental, whose form she can stay in for the next 5 hours. After 2 hours, she takes a short rest, but does not drop the Wild Shape. She has another couple of hours to keep the Air Elemental form.  My main concern: Does she get her two uses of Wild Shape back with that short rest? Or, does she have to drop the Air Elemental form first before taking the short rest to recharge Wild Shape?


The following packages have unmet dependencies:  winehq-stable:i386 : Depends: wine-stable:i386 (= 5.0.2~focal) E: Unable to correct problems, you have held broken packages.  I am getting this error message Could anyone let me know how to rectify the problem? Also I am getting errors while running sudo apt update command, does that have something to do with this?

After upgrading from 10.04 to 12.04 I am trying to install different packages.  For instance ia32-libs and skype (4.0).  When trying to install these, I am getting the 'Unable to correct problems, you have held broken packages' error message.   Output of commands:  sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   After running this:  sudo dpkg --configure -a foo@foo:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree        Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.


I would like to understand if there is any alternative to force:refreshView in lightning-web-components. I have a small component embedded in Account Detail page which creates a new Contact. My requirement is to refresh only the component, and not the entire page, once one Contact is created. Please note : I do not want to use, window.reload(), as it will refresh the entire page, and that is not a good user experience. No data is getting updated once the record, is updated. Just the form needs to get refreshe, so I am not sure if I can use getRecordNotifyChange() I would like to undertand if there is something which does the exact same thing as force:refreshView, does in aura.

In Aura, we can do      $A.get('e.force:refreshView').fire();   to cause standard components to update.  How can we do an equivalent in LWC because sfdx refuses to publish .js code with $A in it saying the usage is disallowed in LWC?  For now i tricked it with   eval("$A.get('e.force:refreshView').fire();");   but that is obviously less than ideal....


I am working with texshop on Mac and because of an upgrade to El Capitan, I had to reinstall tex live. Now I have a problem with older files where figures are inserted. I get the message  LaTeX Error: Unknown float option `,'.  I do not even know what this is, let alone how to fix it. The figure does appear, but is there something else in another place in the file that went wrong? I am typesetting a whole book and this problems appears with some, but not all of the figures.

I have two tables in an article written by somebody else which compiles fine with TeXLive 2013, but after an upgrade to the 2015 version xelatex hangs at them. Pressing enter the file still compiles and looks fine on first view, just I'm wondering what the d option is/was, if I can just delete it, or if I would be missing something. The table environment starts \begin{table}[htdp]. If I get it right, h means to place it where it has been defined, t means the top of the page, p means that it should have a page of its own (which the second table, 15 rows long, doesn't have), but so far I didn't find a d option of floats.


I am in the process of a large rebuild and redesign of my real estate website. Through this process, I am expanding my content and number of internal pages which are structured as Wordpress custom post types with category archives. I am at a decision point with permalink structure for my site and can choose two different directions to go, not sure which is best or if there is any impact on SEO for the two options. Most of it comes down to location of keyword search terms being placed in the permalink structures.   Is there any difference in SEO power for the following keywords whether they are placed all at the end of the permalink, versus being distributed more throughout the entire link address depth when there is a hierarchy and some keywords are in the domain name, partly in the category name, sub category name, and partly in the post slug of the link?    Since I have one of the keywords in my main domain, is it redundant and not necessary to have it in the post slug ending as well?  Either way in terms of number of clicks or depth to get to the targeted page, it would be the same regardless of how the permalink is structured.  Which of these would be better for SEO? Keywords: grayhawk, scottsdale, arizona   Option 1 (category-subcategory-post slug):  dwellarizona.com/luxury/scottsdale/grayhawk Option 2 : dwellarizona.com/luxury/grayhawk-scottsdale-arizona

Let’s take an example of a movie site. So a well structured set of URLs for this site can be:     Movie page - example.com/movies/the-matrix Review for movie - example.com/movies/the-matrix/reviews Trailers for movie - example.com/movies/the-matrix/trailers Specific trailer for movie - example.com/movies/the-matrix/trailers/trailer1   where it’s possible to navigate the resource even by directly deleting/appending resource name seamlessly.  For SEO purpose I read somewhere that for two given pages, Google will prefer the page which have search query up in the URL hierarchy among other things. So for the given 2 URLs and the query "the matrix trailer"    example.com/movies/the-matrix/trailers example.org/trailers/the-matrix/    `     Google might prefer the second URL as it has the keyword "trailer" at first level comparing to first URL which has "trailer" at 3rd level (a resource deeper in URL hierarchy may be less important).    If it is correct, one may be tempted to create URL hierarchy somewhat like      Movie page - example.com/movies/the-matrix Review for movie - example.com/reviews/the-matrix/ Trailers for movie - example.com/trailers/the-matrix/ Specific trailer for movie - example.com/trailers/the-matrix/trailer1     which will break the seamless hierarchy.    My questions are:   Is it true that resource deeper in URL hierarchy is tend to be less important when comparing to URLs of other site?   Is sacrificing meaningful, seamless hierarchy worth for this SEO optimization?


The site reasonably has a limit to the number of questions per time period, e.g. .  Is there a comparable limit to the number of answers per time period? If not, why not?  Is there a theory that writing good answers is easier/harder than writing good questions? For instance, if the theory is that it is twice as hard to write good questions as good answers, the limit for answers might be 12 answers with a 24-hour period.

I noticed that I can only perform certain actions such as commenting a finite number of times in a given period of time. Obviously, rate limiting is in place to prevent accidental misuse or intentional abuse of certain features.  Where else is rate limiting applied on Stack Exchange sites, and what are the limits?


I have been encountering the word "formal" in several math books, and I don't understand what it means in context.  For example, Hatcher describes n-chains as "finite formal sums" on p. 105 and p. 108. What is a "formal sum?"  Are there "informal sums?"  Similarly, Steve Awodey on p.15 of "Category Theory" says opposite (or dual) categories are derived from other categories "with all the arrows formally turned around."  What does "formally" mean here?  This may be more of a language question than a math question, but I'd appreciate any clarification.

I know the definition of formal power series, power series and polynomials. But what does the adjective "formal" mean? In , does it mean "9. Of or relating to linguistic or logical form as opposed to function or meaning" or maybe another one in the link?   Or does "formal" have some mathematical meaning which is other than usual dictionary meaning?


We want to be able to change the text/image on our JLabel array but we can´t understand why it does not work.   import java.awt.*;  class layoutWindow extends JFrame implements ActionListener {`        String[] classStrings = { "EN1A", "EN2A", "EN3A", "EN1B", "EN2B", "EN3B",             "ES1A", "ES2A", "ES3A", "ES1B", "ES2B", "ES3B", "H1", "H2", "H3",             "N1A", "N1B", "N1C", "N1D", "N1E", "N2A", "N2B", "N2C", "N2D",             "N2E","N3A","N3B","N3C","N3D","S1A","S1B","S2A","S2B","S3A","S3B" };     String[] FormationStrings = { "3-3-3", "3-3-2", "2-4-2", "4-4", "2-2-2-2","3-4-3" };     // Create the combo box, select item at index 4.       JLabel[] deskLabels = new JLabel[96];        JComboBox classList = new JComboBox(classStrings);     JComboBox formationList = new JComboBox(FormationStrings);       JButton seatbButton = new JButton(" randomize");     JButton backButton = new JButton("back");     JButton groupButton = new JButton("Make groups");      JLabel classLabel = new JLabel("choose class");     JLabel formationLabel = new JLabel("choose formation");      JPanel layoutPanel = new JPanel(new GridLayout(8, 12, 1,15));     JPanel top = new JPanel(new GridLayout(1, 2, 15,1));        public layoutWindow() {         super("layout Example");         setExtendedState(JFrame.MAXIMIZED_BOTH);         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);          setVisible(true);         Container contentArea = getContentPane();          top.setVisible(true);         layoutPanel.setVisible(true);              int i = 1;             for (JLabel label : deskLabels) {                 label = new JLabel();                 if ((i % 12) != 100) {                     label.setText("" + i);                     layoutPanel.add(label);}                 else {                     label.setText("  ");                     layoutPanel.add(label);                 }                 i++;      }          top.add(backButton);         top.add(classLabel);         top.add(classList);         top.add(formationLabel);         top.add(formationList);         top.add(seatbButton);          contentArea.add("North", top);         contentArea.add("Center", layoutPanel);          setContentPane(contentArea);         formationList.addActionListener(this);         classList.addActionListener(this);         backButton.addActionListener(this);      }      @Override     public void actionPerformed(ActionEvent event) {           String string = (String) formationList.getSelectedItem();           if(string == "4-4"){             deskLabels[5].setText("aasdggnmh");           }         }         }   layouttaskwindow  public class layouttaskwindow {      public static void main(String[] args) {          layoutWindow win = new layoutWindow();     }  }   We don't understand why this does not work. We create all labels from the array using a for loop but when we try to change them it does not work.we have tried to change it in the ActionEvent but we get no response, could someone please explain how this could be solved?

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


If you are dealing with strings as nvarchar and varchar in SQL Server what is the correct way to drop leading zeros without casting to an INT type?  Say '000123' for example. I would like to convert this into '123'

I am working on a SQL query that reads from a SQLServer database to produce an extract file. One of the  requirements to remove the leading zeroes from a particular field, which is a simple VARCHAR(10) field. So, for example, if the field contains '00001A', the SELECT statement needs to return the data as '1A'.  Is there a way in SQL to easily remove the leading zeroes in this way? I know there is an RTRIM function, but this seems only to remove spaces.


My question is that can i go to uk without any visa for a holiday with my husband and children under 18.all of them are european national.only i have an indian  passport but having a 10 year permanent card in spain as a  family member of eea natinal mentioned in my card.

I am citizen of Uzbekistan, and I am living in Czech Republik 7 years, I do hold a permanent Resident card - Family member of EU Citizen.  Me, my boyfriend (he is Czech citizen) and our son (Czech citizen) would like to travel together for 5 days to United Kingdom (London).  Do I need a visa before travel?   I did find information on Internet that:  The UK cannot block family members who are originally from outside Europe but now live in the EU entering the country without a visa, European judges say.  Non-EU family members do not need visa to enter UK, says European court Judges’ decision in McCarthy case is another setback in campaign by British government to control immigration from EU.


I know multiple object having same hashcode in java objects.It doesn't make any problem at all.So, What is the purpose of overriding hashcode in java...  In which situation it is advisable to do override the hashcode in java?

What issues / pitfalls must be considered when overriding equals and hashCode?


Consider the ordered square $I^2,$ then the set $[0,1]\times [0,1]$ with the dictionary order. Let the general element of $I^2$ be denoted by $x\times y,$ where $x,y\in[0,1].$ The closure of the subset $$S=\{x\times\frac{3}{4}:0<a<x<b<1\}$$ in $I^2$ is  $(A)S\bigcup ((a,b]\times \{0\})\bigcup ([a,b)\times \{1\})$  $(B)S\bigcup ([a,b)\times \{0\})\bigcup ((a,b]\times \{1\})$  $(C)S\bigcup ((a,b)\times \{0\})\bigcup ((a,b)\times \{1\})$  $(D)S\bigcup ((a,b]\times \{0\})$  **My attempt:-  Case 1:-  $a\times b \notin S$. There is an open set containing $a \times b$ which does not intersect $S$(shown in the figure).   Case 2:-   $a\times b \in S$. There is an open set containing $a \times b$ which does not intersect $S\setminus \{a\times b\}$  So, none of the points is a limit point in $I^2$. But Options are different. Can you help me to visualize?

Consider the ordered square $I_0^2$, the set $[0,1]\times [0,1]$  with the dictionary order topology. Let the general element of $I_0^2$ be denoted by $x\times y$, where $x, y\in [0,1]$. Then the closure of the subset $$S = \big\{x\times \frac{3}{4}: 0<a<x<b<1\big\}$$ in $I_0^2$ is   $S\cup \big((a, b]\times\{0\}\big) \cup \big([a, b)\times \{1\}\big)$ $S\cup \big((a, b]\times\{0\}\big) \cup \big((a, b]\times \{1\}\big)$ $S\cup \big((a, b)\times\{0\}\big) \cup \big((a, b)\times \{1\}\big)$ $S\cup \big((a, b]\times\{0\}\big)$   please explain it properly. I have no idea how to start with?


Imagine there is a huge black hole with  so that one doesn't get killed by spaghettification after even nearing the event horizon.   Now imagine a very curious creature wanting to know how the universe would evolve. Even though it isn't sure it will be able to return, it decided to travel just close enough to the event horizon to survive, and stay there until for as long as it can make.  For how far would the creature see the future? Is this even possible? What should one expect?     This question was inspired by Miller's planet from the movie Interstellar.

Let's do this thought experiment. You have an insanely powerful rocket and it can accelerate to 0.999999c. Now you fly to a supermassive black hole and hover just above its event horizon, where the inner gravitational pull towards the singularity matches the outward thrust of your rocket.  Consider: 1. The black hole is non spinning, and doesn't distort space-time into swirling around it.   The black hole is so massive that above the event horizon, you are not sphagettified. The rocket can shield the energy of extreme blueshifted photons that bombard you.    At this point over the event horizon, you would see like 1 million or even 1 billion years of the universe in 1 second of your life, right? Can you witness the end of the universe if you hung around for long enough?  And what if the black hole evaporates by Hawking Radiation before that? Will you immediately return to real time?  PS: This is quite different from falling into a black hole. In this thought experiment, we are not crossing the Event Horizon of the black hole in a split second, but we are physically hanging in there for a long time by Counter Force.  Edit: I'm not sure why this question has been marked as a duplicate, but this differs vastly from an observer falling into a black hole, and nowhere else has it been answered so perfectly and succinctly, as done by Mr. Bob. Many thanks to him.


When typing a question and "similar questions" appears, it travels over the bottom footer (from Software Engineering):    On MSE a similar problem exists with the "How to Format" toolbar, though it appears the transparency is different for the background:    It seems this should not do this at all as it's pretty ugly appearance wise. And rather Clippy like, to be honest.  Using Chrome, with a resolution of 1080x960.

I have noticed that while asking questions and scrolling to the bottom of the page, the right sidebar containing recent questions covers the footer partially. Also, a part of it goes beyond the browser's boundary. It may not be a big problem but it still doesn't look good.    This also happens on the  page


To typeset a collection of equations with alignment, I am using align* from amsmath.  Some of these equations have right-hand sides that have multiple lines that should be indented.  So far I am using a nested aligned environment and \MoveEqLeft from the mathtools package:  \documentclass{article} \usepackage{amsmath} \usepackage{mathtools}  \begin{document} \begin{align*}   x+y &= z+w \\     a &= \begin{aligned}[t]            \MoveEqLeft[0.5]            b+c+d \\            &+e+f \\            &+g+h+i+j          \end{aligned} \end{align*} \end{document}   The problem is that the aligned environment seems to introduce extra horizontal space to the left (and possibly on the right as well).   How can I eliminate the extra space from aligned?   I am open to other solutions that might avoid aligned, but I do not want to need to manually insert spaces to indent the lines.

Near the beginning of the definition of the amsmath environments aligned and gathered (and also mathtools' multlined) there's an explicit thin space \,. This often  has to be cancelled  with  \!, as has been observed  various  times:         I'd like to know why this explicit \, is there – what would go wrong without it?    From amsmath.dtx:  \newcommand{\start@aligned}[2]{%     \RIfM@\else         \nonmatherr@{\begin{\@currenvir}}%     \fi     \savecolumn@ % Assumption: called inside a group %    \end{macrocode} %    The \cs{null} here is to keep the \cs{,} glue from causing the %    invocation of the clause in \tex/'s built-in tag placement %    algorithm that can cause an equation to be shifted all the way over %    to the margin. %    \begin{macrocode}     \null\,%


Is there any bijection between $\mathbb{R}$ and $\mathbb{R}^2$ ? If have then what is the mapping ? Please define the mapping. They have same cardinality then it is possible to have a bijection between them.

Could any one give an example of a bijective map from $\mathbb{R}^3\rightarrow \mathbb{R}$?  Thank you.


Part of my thesis tries to investigate the extent to which students "test Score" on the topic of electrical circuits in physic can be predicted from how they find the topic to be "interesting" ,Their "enjoyment" of the topic, and  their perception of how "difficult"  the topic is. I intend to use linear multiple regression analysis to do this, where "test Score" will be my independent variable and the predictors will be the "Student's enjoyment", "Students perception of difficulty" and how "interesting" student find the topic. I think student's test score is a continues variable. However the suspected predictors were obtained thus:   1.  Working with electric circuits in physics  is not  interesting  Strongly Agree[       ]     Agree[     ] Undecided[      ]  Disagree[   ]            Strongly Disagree[      ]  2.  Working with electric circuits in physics  is not  difficult  Strongly Agree[       ]     Agree[     ] Undecided[      ]  Disagree[   ]            Strongly Disagree[      ]  3.  I do not enjoy practical work involving electrical circuits in physics  Strongly Agree[       ]     Agree[     ] Undecided[      ]  Disagree[   ]            Strongly Disagree[      ]  the options are given these values:  Strongly Agree ---- 1 Agree ------------- 2 Undecided --------- 3 Disagree ---------- 4 Strongly Disagree - 5   Now since this is an ordinal scale, is it proper to use linear multiple regression  analysis ?

I am performing ordinal regression, I have 5 response categories and several predictors both continuous and categorical. I would like to add a predictor which is categorical but ordered (1, 2, 3, 4). I don't think it would be appropriate to apply the usual dummy coding for unordered categorical predictors, but when I searched for how to code this I did not find much information.  In  "linear coding" or "assuming linearity of the predictor effect" is mentioned, but without further details.  Does it mean I just use my ordered values as they are, i.e. use them as a continuous variable?


I'm new to LaTeX and I wanna know how to make exactly this with LaTeX code.    I tried to use eqnarray to get the numbers but I get errors. Also, I tried to align the last 3 matrices but they all get centered and get appeared in a row one after another.   My code:  \[ \textbf{I=}\begin{pmatrix} 1&0&0&0 \\ 0&1&0&0 \\ 0&0&1&0 \\ 0&0&0&1 \end{pmatrix} \]  \[ \textbf{I=}\begin{bmatrix} 1&0&0&0 \\ 0&1&0&0 \\ 0&0&1&0 \\ 0&0&0&1 \end{bmatrix} \]  \[ \textbf{I=}\begin{Bmatrix} 1&0&0&0 \\ 0&1&0&0 \\ 0&0&1&0 \\ 0&0&0&1 \end{Bmatrix} \]  \[ \textbf{I=}\begin{vmatrix} 1&0&0&0 \\ 0&1&0&0 \\ 0&0&1&0 \\ 0&0&0&1 \end{vmatrix} \]  \[ \textbf{I=}\begin{Vmatrix} 1&0&0&0 \\ 0&1&0&0 \\ 0&0&1&0 \\ 0&0&0&1 \end{Vmatrix} \]

I would like to draw a matrix with top left, top right, bottom left and bottom right blocks. The top left should be a 3x3 matrix with numerical entries, the top right is 0, the bottom left is 0 and the bottom right is just a "single" entry uJ. Here is my attempt.    $ \left[ \begin{array}{c|c} [\begin{array{c|c|c} 0 & 0 & 2\mathrm tr(MM^{*}) \\ 0 & 0 & -ua \\ u & -ua & 0 \end{array}]     &  0\\ \hline 0 & uJ  \end{array}\right]. $    I would like to emphasize that the non-top-left entries are not just single entries, but blocks, so I do not want to just make a 4 by 4 matrix with vlines and hlines and additional 0's.


I have the company name SOME COMPANY and my main keyword some keyword. What is more clever to do, to buy  somecompany.com   or  some-keyword.com   What is the best approach?  In the old days i would use some-keyword.com but now days i heard that the CONTENT is more important and the domain doesn't count that much, what do you guys think?  Thank you for every answer.

Most people advice to buy a domain name that exactly matches your main business field. For example if you sell computers the best one will probably be computers.com but with millions(maybe billions) of website all over the web the chance the perfect domain for you to be free is (lets be hones) less than zero. So you have to satisfy yourself with something else like company-name-computers.com or just company-name.com. So the question is how much does this counts when the search engines calculate your website position in SERPs cause I have always thought that having high quality and related content, pretty URLs and back-links from valuable sources is more important then the domain name itself.


I wrote this simple script, and it's seems to work fine, but only once. I click div-container - the radio within gets checked. I click another div - another radio gets checked. But now, when I click the previous div again, the radio won't get checked.  Here's the code:  $('div').click(function () {    $(this).find('input:radio').attr('checked', true); });   And example:   Thanks for suggestions!

I'd like to do something like this to tick a checkbox using jQuery:  $(".myCheckBox").checked(true);   or  $(".myCheckBox").selected(true);   Does such a thing exist?


MBPro 10.14.6 Mojave. Ubuntu on 32G USB key.   Boots and works fine but all modifications and downloads go unsaved. On next boot, it's like new again.  I hear of "persistence"?

I would like to see a full how-to guide on how to install Ubuntu.


I see many threads here about how can a software be programmed to ask for administrator privileges on Windows, but in my case I have a software installer that runs with administrator privileges and, in the end of installation, it must execute another process with limited privileges (as the logged user). Both installer and installed softwares was created by me using Delphi.  I am researching about this subject for all day long and it seems to be a very difficult task to achieve by programm language only. My question is if there is some Windows command that I can use to "call" the executable with lower privileges or maybe a manifest configuration that I can incorporate to the installed software to avoid it runs with admin privileges. Well, any ideas are welcome!  Thank you!

Is there any way that I can force a program that normally requires administrator privileges (via UAC) to run without them? (ie: no UAC prompt and no system-wide access.)  Added: Without modifying the executable itself.    In spite of James's answer, I have found a few ways that it can almost be done:   By modifying the executable I can remove the trustInfo entry from the manifest (or the manifest entirely, so I can use an external one), allowing the program to start without UAC. Unfortunately this modifies the executable, so it exits shortly after due to an internal checksum test. By using Process Explorer I can launch it as a Limited User. However this seems to limit it significantly more than I would like (it runs like Protected Mode IE and so can access significantly less than what my standard un-elevated user can).


Recently after upgrading to ubuntu 17.10 the top application menu is missing most of its links:    This is happening for all applications, a few may have more links in the dropdown like terminal, most just show Quit.  For Firefox, I can choose "Menu Bar" to be shown like this:    but that is not what I want.  I want it to be shown like it used to be:

I installed the latest version of Ubuntu (17.10) , but the problem is, I can't find the menu bars of applications in the GNOME panel. For instance, the Chrome menu bar doesn't appear on the panel like in Ubuntu 17.04 and earlier versions.


My Chrome recently updated and now there's a new profile switcher thingie and I don't think I like it.     Can I remove it?

Since Chrome version 38, there's a pretty ugly button in the title bar of the Chrome window that allows you to switch profiles quickly.  Since I'm the only one that uses my computer, this is not really useful to me, and I'd rather reclaim the space for more open tabs.  I've looked in the settings but don't see a way to disable it.  How can I get rid of the button?


I am trying to launch a cron job every hour (an interactive system upgrade).  The code that does the actual update ( a no-password sudo yum update) is in my .zshrc (I use zsh as my shell). To launch zsh, I am invoking a new terminal process, so I have /usr/bin/gnome-terminal as the process. I have an email from cron saying that the command errorred out with "Failed to parse arguments: Cannot open display:" This is strange, since the command works fine from a terminal.  How do I fix this problem?

How do I get a gnome-terminal window to open from a crontab?  I have tried this:      * * * * * /usr/bin/gnome-terminal       * * * * * source /home/user_name/.bashrc ; /usr/bin/gnome-terminal      * * * * * source /home/user_name/.profile ; /usr/bin/gnome-terminal      * * * * * source /home/user_name/.bashrc ; /home/user_name/bin/opengnometerminal.sh   None of these seem to work.


I have been given a problem and need to find the best statistical method that would help. The problem is as follows: A business has approx. 100,000 active customers who spend between £500 per annum and £200,000 per annum.  The smaller ones transact irregularly, once per year, the larger ones maybe once per week.  They are distributed across 15 different market sectors. The business has started to decline, and whilst we have implemented a process for making offers to customers once they have closed their account, it is thought this would be much more effective if we could predict which customers are likely to close, and make offers to keep them before they close.  How would you go about determining which customers to make offers to?


Let $a, b\geq 0$, then prove or disprove $$(a+b)^{r}\leq a^r+b^r$$ where $r \in [0, 1]$.

If $p,q$ are positive quantities and $0 \leq m\leq 1$ then Prove that $$(p+q)^m \leq p^m+q^m$$    Trial: For $m=0$, $(p+q)^0=1 < 2= p^0+q^0$  and for $m=1$, $(p+q)^1=p+q =p^1+q^1$.   So, For $m=0,1$ the inequality is true.How I show that the inequality is also true for $0 < m < 1$.   Please help.


I'd prefer to use root user as my default user instead of writing sudo command to get temporary root access. is the root user disabled by default ? how can i start using root user? what are the costs/benefits of this?  ps: I'm using Ubuntu 14.04 LTS and I'm completely new in Linux world.  Thanks,

I would like to enable the root account on my Ubuntu installation.  I realize the security implications of this.


Basically i tried to output a double variable with but only PrintDigit(char ). Here is my code  void    printDigit(const char c) { cout << c ; }  void    PrintDigits(double target) {     if (target < 0)     {         printDigit('-');         target = -target ;         PrintDigits((int)target / 10);     }     else if ((int)target / 10 == 0)     {         printDigit('0' + (int)target % 10);         if (target - (int)target % 10 != 0)         {             target -= (int)target % 10;          do {             target *= 10 ;             //for debugging             cout << endl << target << endl;             cout << floor(target)<<" "<<ceil(target)<<endl;         } while (floor(target) != ceil(target));          printDigit('.');         PrintDigits(target);     } }   }  And there are some strange problems ,here is the output when i tried to input 3.53:   My question is why floor(target)==52 while target==53 ? And is there any better way to do this ?(with only PrintDigit(char) function and don't transfer the double variable to string)

Consider the following code:   0.1 + 0.2 == 0.3  ->  false   0.1 + 0.2         ->  0.30000000000000004   Why do these inaccuracies happen?


I'm trying to use an integer to count loop iterations, but after the loop is finished, the variable is blank. I've googled for clues, but no luck.  I have this code:  #!/bin/bash  declare -i count  echo entering loop  while read var do   (( count++ ))   echo $count done  echo exited loop echo count is $count   When I run it interactively, pressing Ctrl+D after entering "c", I get output like this:  $ ./example entering loop a 1 b 2 c 3 exited loop count is 3   But when I pipe input into the loop:  #!/bin/bash  declare -i count  echo entering loop  ls -la | while read var do   (( count++ ))   # do something interesting here   echo $count done  echo exited loop echo count is $count   ... I get output like this:  $ ./example entering loop 1 2 3 4 5 exited loop count is $   Why doesn't it say "count is 5" here after exiting the loop?

Why do I get different values for $x from the snippets below?  #!/bin/bash  x=1 echo fred > junk ; while read var ; do x=55 ; done < junk echo x=$x  #    x=55 .. I'd expect this result  x=1 cat junk | while read var ; do x=55 ; done echo x=$x  #    x=1 .. but why?  x=1 echo fred | while read var ; do x=55 ; done echo x=$x  #    x=1  .. but why?


I want to align a div horizontally center and vertically middle of the body of a page.  The css:  .loginBody {     width: 100%;     height: 100%;     margin: 0;     padding: 0;     background: #999; /* for non-css3 browsers */     filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#cccccc', endColorstr='#000000'); /* for IE */     background: -webkit-gradient(linear, left top, left bottom, from(#ccc), to(#000)); /* for webkit browsers */     background: -moz-linear-gradient(top,  #ccc,  #000); /* for firefox 3.6+ */ } .loginDiv {     position: absolute;     left: 35%;     top: 35%;     text-align: center;             background-image: url('Images/loginBox.png');     width:546px;     height:265px; }   And I have this html:  <body class="loginBody">     <form id="form1">     <div class="loginDiv">      </div>     </form> </body>   Now it is behaving as I want it to, but if I resize the browser, it became completely distorted, perhaps this is because the absolute positioning. I am showing some of the screenshots: in resized firefox:   in resized chrome:   in resized ie:   in maximized window it is:   Is there any way to solve this problem and achieve this centered alignment using relative positioning?   Thanks.    Edit:  In firefox no scrollbar appears while resizing but it appears in other browsers.

Best way to center a <div> element on a page both vertically and horizontally?  I know that margin-left: auto; margin-right: auto; will center on the horizontal, but what is the best way to do it vertically, too?


So I have recently downloaded Okami HD, and I have noticed that the directional input seems to be a bit clunkier than in the original. I.e. I can only travel in 45 degree directions.  I have come up with an alternative in the meantime, (rotating the camera to allow for smoother cornering). The only problem is that if I turn too sharply too suddenly, it ruins my sprint. (This is not new, I have tested the original and the same thing happens).   I should also note I am not using a standard PS3 controller, but I have not had this issue with other games (Tested with Gran Turismo 5, Infamous 2, Crash Bandicoot series, Spyro series).

Okami is now reborn in High Definition for PS3. The graphics are obviously better, sharper and yet preserves the gist of the original game, however I can swear some of the texts have changed as well.  My PS2 console is no longer available to me so I can't test it myself, but does anyone know whether there are any changes to the game (aside from graphics) or not?


i need to be able to completely clear the network credentials that i use to open a shared folder on my NAS. I want to be able to do it without a reboot, i've tried the following solutions so far:  1) start -> Control Panel -> User Accounts and Family Safety -> Credential Manager. I found the stored credentials and deleted them.  2) by using an elevated prompt: net use Z: /d  In both cases, something was deleted, but as soon as i try to connect again to the network folder, it connects directly without asking me for any login credential  Any suggestion?  thanks in advance.

I have a small script that runs on each workstation which runs defrag and chkdsk and connect each workstation temporarily to a network share that they, normally, do not have access to. The command I use to connect to them is:  net use \\server\sharename [password] /USER:domain\username P:No   Is there a command to log that user out of the drive share without restarting the computer?  Workstations run on Windows XP SP3  EDIT: I've used:  net use \\server\sharename /delete   but the command returns "The network connection cannot be found". However, I can still navigate to \\server\sharename in MyComputer address line and have full access to it still.  EDIT2: Assume I've read through the help files for net use   ;D  EDIT3: Would a reboot suffice? Yes... however it is more convenient to log the user out of the share instead =D. I know I'm difficult.


How can I insert an ID into an identity column in SQL Server? I'll make a special item into my table and I will quickly detect that item by the ID. So because all other ID's are bigger or equal to one, I will give that special item the ID zero.  The problem is now, when I've created that table I've place the identity of the column ID on true. If I insert now the special item with code below, I've got next error:  INSERT INTO MyTable(ID, Name, Description)  VALUES (0, 'Special title', 'special item');   Error:     Cannot insert explicit value for identity column in table MyTable when IDENTITY_INSERT is set to OFF.   How can I change this table, column or property so I can create a record with ID zero?

I get the command set identity_insert table_name on;, but for some reason it is not actually changing the attribute. I've done it with the account that I created the table with, and I've also created an 'admin' account and gave it permissions to do anything (to the best of my knowledge).    Whenever I run the command under either account I get the result of '0 rows affected', then I am unable to run the query to insert the rows I wish to insert with the following error:     Cannot insert explicit value for identity column in table 'table_name' when IDENTITY_INSERT is set to OFF.     Additionally I've tried to include the schema name in the query like:  set identity_insert mySchema.table_name on;    but I get the following error:     Cannot find the object "mySchema.table_name" because it does not exist or you do not have permissions.   Also of note, my project looks like:  localhost\SQLEXPRESS -Databases --System Databases --mySchema   Does anyone know a solution to this problem?


I would like to remove a small portion (around 10 seconds) of a long video (2 hours). How can I do it using FFMPEG?

If just need to crop Audio/Video from a longer track, what can I use? I tried OpenShot, but I find the export video slow, perhaps its compling all the "layers" into a new movie? Perhaps I just need a simple "crop" tool for audio/video will surfice?


Does anyone know how to get glass to be transparent. I'm using GPU render to render a bowl and cloth but the GPU and CPU final render have different results on the glass bowl   The top image is using the CPU to render      the bottom one is the GPU.  Does anyone know why this happens and how i can fix it or work around it?  thanks for any help :)

I downloaded Blender v2.77 and try to render Suzanne with HDRI Lighting.   First I've used a glossy shader, then a glass shader and it surprises me that the glass shader totally looks like glossy, it's not glass. When I switch back to Blender v2.76b and render the same file again, everything goes fine, glass is glass and glossy is glossy. See the images and the test file below.          Any ideas?


I'm making 51 XMLHttpRequest calls to receive 161.3 MB of data for a mapping project. Every time I reload the page, these calls go out again, and it seems like they are all being cached, because the memory of the web browser (Firefox) continues to rise on every page reload until the tab crashes. I'm trying to prevent these results from being cached.  The original code returns the result fine:  var xhr = new XMLHttpRequest(); var url = 'http://briennakh.me/accessibility-maps/data/census tracts/geojsons/Alabama.json'; xhr.addEventListener('load', function() {     console.log(this.response); }); xhr.open('GET', url); xhr.responseType = 'json'; xhr.send();   When I add the request header xhr.setRequestHeader('cache-control', 'no-cache'); below xhr.open('GET', url); to specify no caching, it throws the following error  Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote  resource at http://briennakh.me/accessibility-maps/data/census%20tracts/geojsons /Alabama.json. (Reason: CORS request did not succeed).   How can I stop these results from being cached?  Note: My site is served on Github pages. I do not have access to the backend code.

It looks like if I load dynamic content using $.get(), the result is cached in browser.  Adding some random string in QueryString seems to solve this issue (I use new Date().toString()), but this feels like a hack.   Is there any other way to achieve this? Or, if unique string is the only way to achieve this, any suggestions other than new Date()?


I have the next sentence in past simple tense.  Yesterday, I went to visit my friends.  So, I make past simple with verb go in past simple form (went), but why do I need to use the verb visit in infinitive form? Why not use visited? I know that I could use on this way.  Yesterday, I went and visited my friends.  But question is, why in first case is possible just to put first verb in past simple and all other verbs in infitive after word to?

Here are two sentences:        Once he got the passport, he went to the Chinese consulate in Toronto and applied for a visa.   Once he got the passport, he went to the Chinese consulate in Toronto to apply for a visa.      Are the two sentences grammatical, and do they sound natural?  If they are both fine, what's the difference?


I'm planning to travel to Philadelphia on january and I would like to rent a car (to avoid walking around or having problems with flight timing), but searching on the net, I haven't been able to find any manual transmission car, be it sedan, sport, deluxe, a transport van, everything is automatic.  Does anybody here know where i could find a manual one?  Edit : this question will stay here as a "how to get a manual car in PHL Intl, and will open new ones for the existing questions if required.

Neither specific websites of Hertz, Budget, Alamo, Enterprise, Thirftly or FOX allow you to specify that you want to rent a manual car. Neither do Kayak, Hotwire and Priceline.   Is there a way to book a manual car in the US?


One of my answers to a question was "edited" by another user.  The "editing" consisted in inserting a hyphen in one of the words I had used, and "replacing" some other words with the identical spellings.  What should I do in such circumstances?

has been edited by .   , see revisions 3 to 4.   Now what he did is totally inexplicable to me, as a matter of fact he destroyed the answer. The new version is neither syntactically valid nor does it make any sense.  Still, the edit got "peer-reviewed" and nodded off.  Is there any way to deal with these kinds of things, other than sighing heavily and rolling back the edit?  Rhetorical side question: Could this be a side-effect of people grinding for reviewer badges?


As I know, when photons hit the surface of a mirror, atoms on the surface of the mirror are excited and when they back to some lower states, they emit photons. I have two questions about this process.  First, why atoms back to a lower state while photons are hitting with the surface of the mirror continuously? The second question is that why emitted photons are emitted in a way that their angles with the mirror are the same as the angle of the photons before hitting the mirror? In another word, why the image in the mirror is not disordered?

The "equal angles" law of refection on a flat mirror is a macroscopic phenomenon. To put it in anthropomorphic terms, how do individual photons know the orientation of the mirror so as to bounce off in the correct direction?


There are many archive formats: tar, tar.gz, tar.bz2, zip, rar, tar.xz and more. I would like to have a single command that would determine the type of archive I give to it as input and extract the files from it using the respective algorithm. It's tedious to remember so much extract command variants. Is there an utility to do this?

With an  of archive/compression file formats, is there a single free/open-source command line tool to rule them all? Perhaps something with a consistent / unified set of flags? (note my  friendly )  I once run into a set of aliases meant to largely simplify the task of compressing/de-compressing files with bindings to tar and other utils, but I can't find this anymore.  Update: How can I configure something like atool to not use unzip to extract zip files (which apparently can't handle files larger than 4GB) and to use gunzip instead?  $ aunpack large_file.zip error:  Zip file too big (greater than 4294959102 bytes) Archive:  large_file.zip warning [large_file.zip]:  1491344848 extra bytes at beginning or within zipfile   (attempting to process anyway) error [large_file.zip]:  start of central directory not found;   zipfile corrupt.   (please check that you have transferred or created the zipfile in the   appropriate BINARY mode and that you have compiled UnZip properly) aunpack: unzip ...: non-zero return-code


I used a truth table and it showed that this is a tautology, although I am unsure how to prove this through logical equivalence laws.  Your help would be greatly appreciated.  Below is the logical statement.  ((p ∨ q) ∧ (p → r) ∧ (¬r)) → q

Verify is tautology by using logical equivalence:  $$((p ∨ q) ∧ (p → r) ∧ (∼ r)) → q$$  by showing what laws are using, step by step explanation needed.  Logical equivalence: de morgan's laws, commutativity, associativity, double negative, distribution, idempotent, absorption, identity, universal bound, negation  Rules of inference: modus ponens, modus tollens, generalisation, specialisation, conjunction, ellimination, transivity, proof by division into cases, contradiction  What I got so far:  I need to prove   $$((p ∨ q) ∧ (p → r) ∧ (∼ r)) → q ≡ \text{tautology}$$ Since $p → r$ same as $∼ p ∨ r$: $$((p ∨ q) ∧ (p → r) ∧ (∼ r)) → q ≡ ((p ∨ q) ∧ (∼ p ∨ r ) ∧ (∼ r)) → q$$  I am stuck here


I know that there exists a duplicate of this question somewhere on Stack Overflow. I have seen it, but I couldn't find it despite pages and pages of googling. It asks for a way to extract only the article text out of Wikipedia, ignoring all the menus and overhead. It turns out that there is a parameter which, if added to the URL, produces human-readable articles that look as if you cropped the Wikipedia page, removing the menus and leaving the article itself looking identical. What is this parameter?

I try to fetch a Wikipedia article with Python's urllib:  f = urllib.urlopen("http://en.wikipedia.org/w/index.php?title=Albert_Einstein&printable=yes")            s = f.read() f.close()   However instead of the html page I get the following response: Error - Wikimedia Foundation:  Request: GET http://en.wikipedia.org/w/index.php?title=Albert_Einstein&printable=yes, from 192.35.17.11 via knsq1.knams.wikimedia.org (squid/2.6.STABLE21) to () Error: ERR_ACCESS_DENIED, errno [No Error] at Tue, 23 Sep 2008 09:09:08 GMT    Wikipedia seems to block request which are not from a standard browser.  Anybody know how to work around this?


How do I test something like this in multithreaded environment. I know it's gonna fail, cause this code is not thread-safe. I just wanna know how can i prove it? Creating bunch of threads and trying to add with those different threads? This code is intentionally not written properly cause of testing purposes !!!   public class Response_Unit_Manager {  private static HashMap<String, Response_Unit> Response_Unit_DB =         new HashMap<> ();  /**  *   * This subprogram adds a new Response_Unit to the data store.  The  * new response unit must be valid Response_Unit object and it's ID must be   * unique (i.e., must not already exist in the data store.  *   * Exceptions Thrown:  Null_Object_Exception  */ public static void Add_Response_Unit (Response_Unit New_Unit)          throws Null_Object_Exception, Duplicate_Item_Exception {     String Unit_ID = New_Unit.Unit_ID ();      if (New_Unit == null)         throw new Null_Object_Exception ();      else if (Response_Unit_Exists (Unit_ID))         throw new Duplicate_Item_Exception (Unit_ID);      else         Response_Unit_DB.put (Unit_ID, New_Unit); } //end Add_Response_Unit

I have thus far avoided the nightmare that is testing multi-threaded code since it just seems like too much of a minefield.  I'd like to ask how people have gone about testing code that relies on threads for successful execution, or just how people have gone about testing those kinds of issues that only show up when two threads interact in a given manner?  This seems like a really key problem for programmers today, it would be useful to pool our knowledge on this one imho.


In $C[a,b]$, define the product   $\langle f,g\rangle= \int f(t)g(t) \, dt $.   Show that this product satisfies the property, $\langle f,f\rangle$ is greater than zero for all non zero $f$ using a non graphical proof and no  δs to explain your answer.   Although this question was claimed to be a duplicate of , I would like an explanation without  δs.

There is a proof in my textbook where I am a little bit unsure about a small detail.  It would be great if someone could clarify it for me.  We are supposed to prove positivity of the $L^2$ inner product on the space of continuous functions on $[a,b]$.  The book does this as follows:   We wish to show that the $L^2$ inner product on the interval $[a,b]$ satisfies the positivity axiom; this means we must show that if $0 = \langle f,f \rangle = \int_{a}^{b} |f(t)|^2 dt$, then $f(t) = 0$ is zero for all $a < t < b$.  Suppose by contradiction that there is a $t_0$ with $f(t_0) \neq 0$.  Let $\displaystyle\epsilon = \frac{|f(t_0)|}{2} > 0$ in the definition of continuity; which states that there is a $\delta > 0$ such that it $|t - t_0| < \delta$, then $\displaystyle|f(t) - f(t_0)| < \epsilon = \frac{|f(t_0)|}{2} > 0$.  This implies $\displaystyle|f(t)| > \frac{|f(t_0)|}{2}$ for $|t - t_0| < \delta$.  Assuming $\delta$ is chosen small enough so that the interval $[t_0 - \delta, t_0 + \delta]$ is contained in $[a,b]$, then  $$\int_{a}^{b}|f(t)|^2 dt \geq \int_{t_0 - \delta}^{t_0 + \delta} |f(t)|^2 dt \geq \frac{|f(t_0)|^2}{4} [2 \delta] > 0$$  This shows that if $f(t_0) \neq 0$, then $\langle f,f \rangle > 0$.  Therefore, we conclude that if $\langle f,f \rangle = 0$, then $f(t_0) = 0$ for all $a < t_0 < b$.  OK, so the only thing I don't fully understand here is that if we have shown that $|f(t)|$ is greater than $\displaystyle\frac{|f(t_0)|}{2}$ for $|t - t_0| < \delta$, then why, when we look at the integrals later do we write: $\displaystyle\int_{t_0 - \delta}^{t_0 + \delta} |f(t)|^2 dt$ is greater or equal to $\displaystyle\frac{|f(t_0)|^2}{4} [2 \delta]$.  If someone could explain to me why we use "greater or equal to" in this last step, then I would be extremely grateful!


These email newsletter services probably send millions of emails per day.  How do they successfully do this without having their system black listed?  Don't services like otmail/gmail block emails if they reach a certain threshold from a single domain?  I'm interested in running a service that will be sending a lot of emails on behalf of other companies, so just want some tips/ideas on how they do it at such a large scale. (I might not be admining the box, but want an idea of what is involved technically)

This is a  about how to handle email sent from your server being misclassified as spam.  For additional information you may find these similar questions helpful:                    Sometimes I want to send newsletters to my customers. The problem is, that some of the emails get caught as spam messages. Mostly by Outlook at the client (even in my own Outlook 2007).  Now I want to know what should be done to create "good" emails. I know about reverse lookup etc., but (for example), what about a unsubscribe link with an unique ID?  Does that increase a spam rating?


I've noticed that I do far more damage with the Huntsman than I do with the standard sniper rifle, and,  not only do my arrows hit enemies more often than sniper bullets, but they also head-shot far more often as well.  However, according to the TF2 , both the sniper rifle and the Huntsman have the same accuracy, but the Huntsman is actually weaker (having a damage output of 44-137, as opposed to the stock sniper's 43-172). Why is it, then, that the Huntsman hits enemies (and head-shots them) more often than the stock rifle, and why does it seem to be more accurate than the stock?

As arrows are projectiles, they must use the (large unrotating unintuitive) physics hitbox instead of the bullet hitboxes. So how does the game know where the head is? Is it the same for all classes? How large is the headshot area?


I have two variables $x$, and $y$. That are related by $Bx=y$. There is also a linear inequality constraint on $x$: $Ax \leq b$. Is it possible to write down the feasible set of $y$ as a linear inequality constraint? How would I do this? I also know that the columns of $A$ are linearly independent, but I don't have any such condition on $B$.

Suppose $P$ is a polyhedron whose representation as a system of linear inequalities is given to us: $$ P = \{ x ~|~ Ax \leq b\}$$ Define $P'$ be the image of $P$ under the linear transformation which maps $x$ to $Cx$: $$ P' = \{ Cx ~|~ x \in P \}.$$ Given $A,b,C$, our goal is to compute a representation of $P'$ as a system of linear inequalities, i.e., to compute $D,e$ satisfying $$ P' = \{ x ~|~ D x \leq e \}.$$ What is the complexity of this problem (i.e., how many arithmetic operations or bit operations are required)?   Let us adopt the convention that $A \in R^{m \times n}$ while $C \in R^{k \times n}$ so the answer should be in terms of $m,n,k$. Further, one may suppose that entries of $P$ are rational numbers whose numerators and denominators take $B$ bits to specify, so that in the bit-model answers should be in terms of $B$ as well.


I have a little confusion over the following problem:       Find the $20$ consecutive composite numbers.     HINTS:  $$\color {green} {\text{Numbers}\,\, 20!+2,20!+3,\cdots ,20!+21 \,\,\text{will do the trick. The following result by Euclid has been known for more than 2000 years.}}$$   But the solution is not very clear to me specially I do not understand why $k$  has been added to $20!$ where the numbers are of the form $20!+k,k=2....,21$.   Can someone explain it? Thanks and regards to all.

Hello and I'm quite new to Math SE.  I am trying to find the largest consecutive sequence of composite numbers. The largest I know is:  $$90, 91, 92, 93, 94, 95, 96$$  I can't make this series any longer because $97$ is prime unfortunately.  I can however, see a certain relation, if suppose we take the numbers like (let $a_1, a_2, a_3,...,a_n$denote digits and not multiplication):  $$a_1a_2a_3...a_n1,\ a_1a_2a_3...a_n2,\ a_1a_2a_3...a_n3,\ a_1a_2a_3...a_n4,\ a_1a_2a_3...a_n5,\ a_1a_2a_3...a_n6,\ a_1a_2a_3...a_n7,\ a_1a_2a_3...a_n8,\ a_1a_2a_3...a_n9,\ a_1a_2a_3...(a_n+1)0$$  The entire list of consecutive natural numbers I showed above can be made composite if:   The number formed by digits $a_1a_2a_3...a_n$ should be a multiple of 3 The numbers $a_1a_2a_3...a_n1$ and $a_1a_2a_3...a_n7$ should be composite numbers   If I didn't clearly convey what I'm trying to say, I mean like, say I want the two numbers (eg: ($121$, $127$) or ($151$, $157$) or ($181$, $187$)) to be both composite.  I'm still quite not equipped with enough knowledge to identify if a random large number is prime or not, so I believe you guys at Math SE can help me out.


I have a question about one example in Linear Algebra.  Let $\mathbb R^∞$ be the vector space of infinite sequences $(\alpha_1, \alpha_2, \alpha_3, \ldots )$ of real numbers.  Scalar multiplication are defined in the natural way: the sum of $(\alpha_1 , \alpha_2 , \alpha_3 , \ldots )$ and $(\beta_1,\beta_2,\beta_3,\ldots)$ is $(\alpha_1 +\beta_1, \alpha_2 + \beta_2, \alpha_3 + \beta_3,\ldots)$ the product of $(\alpha_1,\alpha_2,\alpha_3,\ldots)$ by a scalar $\lambda$ is the sequence $(\lambda \alpha_1, \lambda\alpha_2, \lambda\alpha_3, \ldots )$.  There exists infinite linear independent set of vectors $(e_1, e_2, e_3, \ldots)$ \begin{align} e_1 &= (1, 0, 0, \ldots)\\ e_2 &= (0, 1, 0, \ldots)\\ & \,\,\,\vdots \end{align}  The problem is that this set (lets call it $X$) is not a basis of this vector space. Because for example $v = (1, 1, 1, \ldots)$ cannot be written as a linear combination of set $X$ (Linear combination must be a finite sum).  My task is to add "some vectors" to the set $X$ to create a basis of that vector space. If I add $v$ its not basis ($\langle X, v\rangle \ne\mathbb R^∞$)  Is there any proof that the process of adding vectors to set $X$ is not finite? Or is it possible to create a basis with adding vectors to $X$?  Thanks for answers

Assuming the Axiom of Choice, every vector space has a basis, though it can be troublesome to show one explicitly. Is there any constructive way to exhibit a basis for $\mathbb{R}^\mathbb{N}$, the vector space of real sequences?


$\sum_\limits{k=0}^n \binom {k+m} {k} = \binom {m+n+1} {n}$, where $n, m \in \Bbb N$.  I missed two lectures due to illness and now have this for homework. I am completely out of my depth, mostly due to there being  a second variable to deal with.

After reading , the most popular answer use the identity $$\sum_{t=0}^n \binom{t}{k} = \binom{n+1}{k+1}.$$  What's the name of this identity? Is it the identity of the  modified.  How can we prove it? I tried by induction, but without success. Can we also prove it algebraically?  Thanks for your help.    EDIT 01 : This identity is known as the  because, on Pascal's triangle, when the addends represented in the summation and the sum itself are highlighted, a hockey-stick shape is revealed.


Does any aspect of a Hero Mode game affect the street pass battle feature of Link Between Worlds?

I've completed the game, and have been given the option to start a new playthrough in "Hero Mode." I know that in Hero Mode, the damage dealt by all enemies is multiplied by four, but are there any differences other than that? For example, have any of the puzzles or boss fights been changed, or are there any exclusive secrets?


Does LuaTeX have an equivalent of \XeTeXglyph? Or better yet, is there a command to select a glyph by number that works both with xelatex and lualatex? I did find a , but isn’t there a better way?  I am aware of the \symbol command, but as far as I can tell it takes a unicode code point, and the font that I am using has several different glyphs that map to the same code point, so I need to select the glyph by glyph ID.

I'm trying to access a glyph, but it's only mentioned in the "Basic Latin and Latin 1" set for a font. The glyph has no name or unicode ID, but it does have a glyph ID or GID. fontspec doesn't mention possibilities for using this glyph. Neither does Adobe in the adobe feature file syntax:   I'd still like to be able to access a glyph through its ID, since it's the only way I can access it (I think).  My specific case requires to access the glyph ID 554 from Stevens Titling Pro Sable Brush. I will only post this font if it's strictly necessary, since I don't like to distribute these fonts to the wide world.  I posted an MWE containing another (free) font. This is not the font I intend to use, but perhaps a starting point to try and access glyphs manually.   \documentclass{article}  \usepackage{fontspec} \setmainfont{EB Garamond}  \parindent=0pt \begin{document}  Some text int EB Garamond. How can I access glyph 123 now?  \end{document}


I am using Ubuntu 16.04 LTS. I was updating the software on my PC through the Software Updater. It downloaded all the packages but unfortunately during the installation process it stopped responding from the last 3 hours. Please suggest the safest possible way to get out of this situation.

I have the exact question as this but there's no solution. I tried but it doesn't work    $ locale locale: Cannot set LC_CTYPE to default locale: No such file or directory locale: Cannot set LC_ALL to default locale: No such file or directory LANG=en_US.UTF-8 LANGUAGE= LC_CTYPE=UTF-8 LC_NUMERIC="en_US.UTF-8" LC_TIME="en_US.UTF-8" LC_COLLATE="en_US.UTF-8" LC_MONETARY="en_US.UTF-8" LC_MESSAGES="en_US.UTF-8" LC_PAPER="en_US.UTF-8" LC_NAME="en_US.UTF-8" LC_ADDRESS="en_US.UTF-8" LC_TELEPHONE="en_US.UTF-8" LC_MEASUREMENT="en_US.UTF-8" LC_IDENTIFICATION="en_US.UTF-8" LC_ALL=  $ locale -a locale: Cannot set LC_CTYPE to default locale: No such file or directory C C.UTF-8 en_US.utf8 POSIX   Is this because of en_US.UTF-8 and en_US.utf8 mismatch?  How to fix?