I have a $n\times n$ matrix $A$. I know that every element in the matrix belongs to the range $(0, 1)$. I want to prove that $A^k\rightarrow 0$ when $k \rightarrow \infty$. Here $ 0 $ means $n\times n$ zero matrix. I am working on a larger problem and wanted to use this property, which intuitively looks that is correct, but I do not have idea how to prove it.   Thank you.

Let $n$ be a positive integer. Let $A$ be a square matrix. Let $I$ be the identity matrix with the same size as $A$.  I want to simplify $f_n(A) = I + A + A^2 + A^3 + A^4 + \cdots + A^n$  Now I know that for a complex number $z$ we have $1 + z + z^2 + z^3 + z^4 + \cdots + z^n= \dfrac{z^{n+1}-1}{z-1}$ when $z$ is not equal to $1$ ... and even if $z=1$ then by computing the limit we get the right answer : $n+1$. This is well known as the geometric series and leads to the so-called q-analogue ideas.  But for matrices $A$ this does not work if the determinant of $A-I$ is $0$ , because then $\dfrac{A^{n+1} - I}{A - I}$ is not well defined.  This frustrates me a lot. Now I have heard about pseudoinverses but I do not know much about them and I even wonder if they can be of any help here.  I tried some things from calculus and continued fractions too, but nothing worked for me.  I also considered this problem for infinite (square) matrices but I assume that is analogue to this problem and so is its solution.


Juan Dela Cruz is a former member of this District formerly assigned at ABCD. Said employee was transferred to ZXC.  Does capital Said infront of the sentence correct? it seems to me it' wrong

In our electron pump, when you turn the crank, one side gets a surplus of electrons, or a negative charge, and on the other side the atoms are missing said electrons, resulting in a positive charge.   The part in a bold font is confusing to me. I can't make grammatical sense of it. One side gets a surplus of electrons and the other side gets the atoms. How does are missing said electrons fit into the rest of the sentence?


, the user details of the user who made the last activity used to float nicely to the right:  However, now they don't:  Can this please be fixed?

In the  (homepage), the asked/modified X mins ago text was left-aligned next to the tags. Previously the text was right-aligned. Seems some alignment issue introduced on that page recently. Screenshot for reference:      Configuration Version     Operating System Windows 10 Pro   Mozilla Firefox 89.0 (64-bit)   Google Chrome 91.0.4472.101 (Official Build) (64-bit)     Update: I see the same alignment issue in all other Stack Exchange site's "Top Questions" page too.


Suppose I work/learn on/about a specific subject, let's say JPA, after making searches and asking questions on SO, I've noticed that some person is very good at JPA and it would be very interesting to be notified about his posts. Is it possible to be told about their new activities on SO?  I think that it would be interesting to have this feature in this situation.

I think it would be nice to have a "friends list" on Stack Overflow. This would allow us to be able to follow the questions and answers that are posted by users that we want to watch/monitor.  I suggest it be implemented in the same fashion as DotNetKicks.com; where you can add someone to your "friends list" without them needing to approve you the way that other social networks do it. It should be completely open for us to add anyone to our "friends list" that we like.


I am looking for command line which tells me what is the model of my wireless card? For example if that is Atheors. The result should be atheros.

Is there any built-in software or terminal method allowing me to view the hardware profiles on my system? Windows equivalent of such a feature would be Device Manager.


<?php  class MyClass {     public $prop1 = "I'm a class property!";      public function __construct()     {         echo 'The class "', __CLASS__, '" was initiated!
';     }      public function __destruct()     {         echo 'The class "', __CLASS__, '" was destroyed.
';     }      public function __toString()     {         echo "Using the toString method: ";         return $this->getProperty();     }      public function setProperty($newval)     {         $this->prop1 = $newval;     }      public function getProperty()     {         return $this->prop1 . "
";     } }  class MyOtherClass extends MyClass {     public function __construct()     {         parent::__construct(); // Call the parent class's constructor         $this->newSubClass();     }      public function newSubClass()     {         echo "From a new subClass " . __CLASS__ . ".
";     } }  // Create a new object $newobj = new MyOtherClass;   ?>   Question:  If change $this->newSubClass(); to self::newSubClass();, it also works, so when I need to use $this->newSubClass();, and when need to use self::newSubClass();?

In PHP 5, what is the difference between using self and $this?  When is each appropriate?


I studied BSc chemistry and because I didn't like it, my BSc GPA is 2.46. Alongside with BSc duration, I studied mathematics at home as a self-learner. Since my BSc-GPA was too low, so I got admission to a very low ranking university in MSc-Maths. However, in my first year of MSc I got GPA 3.78 p. I am discouraged to apply for a PhD for a nice university because:  1- My current university's world ranking is >>4000 and I doubt that it would be a 'university' from the viewpoint of universities that I am trying to get my PhD admission.   2- I don't have BSc in math and very low BSc-GPA in completely different field.   My questions are:  1- Is it possible to get admission for PhD (with full scholarship) to a high-ranking universities in mathematics with such a conditions that I have?  2- If I have to study my PhD in the same university or a little better one, do my university reputation and and low GPA-in-BSc threat my future career after PhD (even if I show strong research ability and good recommendation letters)?  My target for PhD admission is countries: Canada (first priority), Europe and Australia. And I am not targeting USA.   Thank you for your helps. And, sorry for my terrible English.      Please feel free to edit the question to improve it.

When applying to a PhD program in the US, how does the admissions process work? If an applicant is weak in a particular area, is it possible to offset that by being strong in a different area?  Note that this question originated from this . Please feel free to edit the question to improve it.


I'm a non-EU country citizen and going to start my study at end of this month in Italy. I'm a valid D-type national Italy visa holder, it's multiple, valid for 5 months (>150 days long-stay) from now on and it says "VALID FOR: ITALIA". I don't have anything else but that visa.  I've changed my travel plan yesterday, I want to stay for couple days in Sweden before entering to Italy. After my trip I will turn back my non-EU country and later I'll go to Italy.  Authorities I asked in my country said, It's valid for Italy and the situation belongs to the officers in the airport. They can let you go or decline.  Can I enter to Sweden with my visa? Do I need anything else? Like supporting documents or anything else? I have all my travel docs, for Italy and will have for Sweden if this thing can be.

In case, if I get a multiple-entry Schengen visa in one of the embassies in Ukraine, Kyiv - should my first trip be to the country which issued the visa?  Any there any requirements of this sort? Does this condition vary depending on embassy which issued the visa?  What are the possible consequences on not visiting that country first? Does it somehow depend on country where the embassy is (i.e. non-Schengen and not EU members)?


can you help me with my homework:  If $A^3 = 0$ , is $A$ not invertible? and please justify why.

How can I show that if the cube power of a matrix is the null matrix, then the matrix itself is singular?


Worldwide 1024x768 is still the most common screen resolution. Why they had chosen the width as 1024 and not a user remembrance number like 1020 or 1030?

I need to justify my choice of screen resolution for a website that has to run on old PCs. When did 1024x768 first become popular? Are there stats somewhere about how far back you'd have to go to find a desktop with resolution smaller than 1024x768? Failing that, anyone want to take a guess?


I am fitting a logistic regression model using lassoglm in matlab. I issued the following command  [B,FitInfo] = lassoglm(ec50,Y,'binomial','Lambda',0.0001,'CV',10);   Now once I get the coefficients B, how am I supposed to use it. I mean do I have to do  $P(y=1) = \frac{e^{(\theta^tx)}}{1 + e^{(\theta^tx)}}$ where $\theta$s are obtained from B. Is it the case?

We're working with some logistic regressions and we have realized that the average estimated probability always equals the proportion of ones in the sample; that is, the average of fitted values equals the average of the sample.  Can anybody explain me the reason or give me a reference where I can find this demonstration?


I used my usbdrive to install software in many computer of lab  but when i plugged it in a computer then due to virus now it is became unreadable or can not be detected now in any other computer . what to do

I have a USB flash drive which is no longer recognized by my computer. Windows Disk Management and DiskPart report No Media with no storage space (0 bytes) on the drive and I cannot partition or format the drive:     If the drive appears in Windows Explorer, trying to access it returns an error message indicating that there is no disk inserted, such as the following:     Please insert a disk into drive X:.   Various disk partitioning and data recovery utilities don't recognize the drive or only give a generic name for the drive and cannot access the contents of the drive.  What can I do? How do I recover data from the drive?     This question comes up often and the answers are usually the same. This post is meant to provide a definitive, canonical answer for this problem. Feel free to edit the answer to add additional details.


There is a scene where Bullock's foot was tangled in the parachute's strings and she was holding onto the tether which Clooney is also holding onto. Clooney was still floating away, almost like he was getting blown away by wind.  How does that work? I don't understand why Clooney was still floating away after Bullock aught the tether. Eventually Clooney had to detach himself so she would be saved.

In the scene where Dr. Ryan Stone's (Sandra Bullock) leg is entangled in Soyuz's parachute cords and she is tethered with Matt Kowalski (George Clooney) through a strap, there is tension in the strap, suggesting act of some external force. Where is this force coming form that is causing tension in the strap and pushing both Dr. Ryan and Matt outwards?  I'm guessing that the tension might be coming from centrifugal force, but immediate events before this scene, as well as other parts of ISS in same scene do not suggest presence of such force (or presence of any kind of rotation).


Two days ago, I asked a question  but was answered just once. However, I am finding it hard to understand the proof provided.  Please, I'll need thorough explanation or another proof. As to the proof, I don't understand   why triple sum was used and not double. If we differentiate $g(x)=f(b)-f(x)-f'(x)(b-x)$, what do we get?   I am asking because I find it hard to comprehend the proof. Please, can anyone explain these to me? Alternative proofs are welcome.  Thanks.

Let $\Omega$ be an open set in $\Bbb{R}^n$ and $f:\Omega\to \Bbb{R}^m $ be of class $\Bbb{C}^2.$ Let $a,b$ be in $\Omega$ such that $[a,b]\subset \Omega.$ Prove that  \begin{align}\Vert f(b)-f(a)-f'(a)(b-a) \Vert\leq \sup_{x\in [a,b]} \Vert f''(x)\Vert\Vert b-a\Vert^2.\end{align} where $$f'(a)(b-a)=\big<\nabla f(x),(b-a)\big>=\sum^{n}_{k=1}\frac{\partial f_i}{\partial x_k}(a)(b_k-a_k).$$  I  think the idea of Mean Value Theorem for $C'$ functions in $\Bbb{R}^n$ () will help me in showing it but I don't know how to! Please, can anyone show me a proof or reference?


I have manually edited /etc/resolvconf/base to add openDNS name servers, and then run sudo resolvconf -u to update the /etc/resolv.conffile.  However changes are discarded on each reboot.  How do I preserve those changes?  $ cat /etc/os-release  NAME="Ubuntu" VERSION="16.04.3 LTS (Xenial Xerus)" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 16.04.3 LTS" VERSION_ID="16.04" HOME_URL="http://www.ubuntu.com/" SUPPORT_URL="http://help.ubuntu.com/" BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/" VERSION_CODENAME=xenial UBUNTU_CODENAME=xenial   edit:  /home/pkaramol $ cat /etc/resolvconf/resolv.conf.d/base nameserver 208.67.222.222 nameserver 208.67.220.220 /home/pkaramol $ sudo resolvconf -u /home/pkaramol $ cat /etc/resolv.conf  # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN  nameserver 127.0.1.1

Let me narrate you my small story:  So right now, I am using an Ubuntu 16.04 LTS distribution in my lab. After installing Ubuntu, I tried just check my Internet access by googling. However that was impossible. So firstly I try to ping Google's server:  ping 8.8.8.8   This first ping was successful. So secondly I try to ping yahoo site:  ping yahoo.com   The answer was that the name was unknown so I decide to check the resolv.conf file in /etc:  # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN nameserver 127.0.0.1 search <www.some-sites>   The problem is the nameserver. My collaborators told me that the have copied some lines in /etc/resolvconf/resolv.config.d/base:  domain bla.bla search <www.some-sites> nameserver 111.222.3333.4444 nameserver 555.666.7777.8888   They proposed me to reboot or just run the following commands  resolvconf --enable-updates resolvconf -u   When I checked /etc/resolv.conf it was again the same as that beginning   Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) #     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN nameserver 127.0.1.1 search <www.some-sites>   So how I can input the domain and my two new specific nameservers??? I don't really know hot to configure interfaces and if it is possible. I cannot also understand why this happened since base is a file that should be copied into resolv.conf file. Could you explain me why that error happened?  Thank you


As relating to  I am now running into a different error. I have 2 pieces of diamond gear that each provide 3 bars of armor, but when both worn they will only provide 3. If EITHER ONE is worn by itself it will provide it's respective 3 bars but together only 3 bars show up. Is there another tag that I am missing?  Commands:  /replaceitem entity @p slot.armor.head diamond_helmet 1 0 {display:{Name:"Tank Helmet",Lore:["You feel slower, but protected"]},AttributeModifiers:[{AttributeName:"generic.armor",Name:"armor",Slot:"head",Amount:3.0,Operation:0,UUIDMost:1,UUIDLeast:1},{AttributeName:"generic.movementSpeed",Name:"generic.movementSpeed",Amount:-0.05,Operation:0,UUIDMost:66122,UUIDLeast:55689}],ench:[{id:0,lvl:1}],Unbreakable:1}  /replaceitem entity @p slot.armor.feet diamond_boots 1 0 {display:{Name:"Tank Boots",Lore:["You feel stronger, and protected"]},AttributeModifiers:[{AttributeName:"generic.armor",Name:"armor",Slot:"feet",Amount:3.0,Operation:0,UUIDMost:1,UUIDLeast:1},{AttributeName:"generic.attackDamage",Name:"generic.attackDamage",Amount:1,Operation:0,UUIDMost:101245,UUIDLeast:5744789}],ench:[{id:0,lvl:1}],Unbreakable:1}

I am trying to make a new set of armor called the Fullerite armor. It has its own custom resource but it is made of gold. I'm trying to modify the gold to have more protection than diamond. It also is going to give you more health. This is the command I am using:   Helmet:  /give @p golden_helmet 1 1 {display:{Name:"Fullerite Helmet"},AttributeModifiers:[{AttributeName:"generic.maxHealth",Name:"generic.maxHealth",Amount:2,Operation:0,UUIDMost:61127,UUIDLeast:23056},{AttributeName:"generic.armor",Name:"generic.armor",Amount:3,Operation:1,UUIDMost:88181,UUIDLeast:199509},{AttributeName:"generic.armorToughness",Name:"generic.armorToughness",Amount:2,Operation:1,UUIDMost:17664,UUIDLeast:119384}],Unbreakable:1,ench:[{id:0,lvl:4}],HideFlags:2}   Chestplate:  /give @p golden_chestplate 1 1 {display:{Name:"Fullerite Chestplate"},AttributeModifiers:[{AttributeName:"generic.maxHealth",Name:"generic.maxHealth",Amount:2,Operation:0,UUIDMost:61127,UUIDLeast:23056},{AttributeName:"generic.armor",Name:"generic.armor",Amount:8,Operation:1,UUIDMost:88181,UUIDLeast:199509},{AttributeName:"generic.armorToughness",Name:"generic.armorToughness",Amount:2,Operation:1,UUIDMost:17664,UUIDLeast:119384}],Unbreakable:1,ench:[{id:0,lvl:4}],HideFlags:2}   Leggings:  /give @p golden_leggings 1 1 {display:{Name:"Fullerite Leggings"},AttributeModifiers:[{AttributeName:"generic.maxHealth",Name:"generic.maxHealth",Amount:2,Operation:0,UUIDMost:61127,UUIDLeast:23056},{AttributeName:"generic.armor",Name:"generic.armor",Amount:6,Operation:0,UUIDMost:88181,UUIDLeast:199509},{AttributeName:"generic.armorToughness",Name:"generic.armorToughness",Amount:2,Operation:0,UUIDMost:17664,UUIDLeast:119384}],Unbreakable:1,ench:[{id:0,lvl:4}],HideFlags:2}   Boots:  /give @p golden_boots 1 1 {display:{Name:"Fullerite Boots"},AttributeModifiers:[{AttributeName:"generic.maxHealth",Name:"generic.maxHealth",Amount:2,Operation:0,UUIDMost:61127,UUIDLeast:23056},{AttributeName:"generic.armor",Name:"generic.armor",Amount:3,Operation:0,UUIDMost:88181,UUIDLeast:199509},{AttributeName:"generic.armorToughness",Name:"generic.armorToughness",Amount:2,Operation:0,UUIDMost:17664,UUIDLeast:119384}],Unbreakable:1,ench:[{id:0,lvl:4}],HideFlags:2}   When I put this on, it works just fine, but when I put another piece of armor on it doesn't add any armor points or it replaces the armor points it already had. Same for the extra health. I am playing in 1.9.2. Anyone know why they won't add up and they only work when worn separately?


How do you evaluate this integral?   $$\int_0^{\sqrt{R^2-1}}g(x)-f(x)\,\mathrm dx$$   where $f(x)=1$ and $g(x)=\sqrt{R^2-x^2}$.   Wolfram tells me I exceeded my computational limit. Mathematica gives me a long answer which is very difficult to read (for me).  EDIT: I was  to  consider instead $x=f(y)$, so: $$\int_0^{1}\sqrt{R^2-y^2}\,\mathrm dy$$

Suppose, for the sake of illustration, that $AF=2$, where $F\mathbb{'s}$ coordinates are $(2,0)$ and $A$ is the point of origin; $E=(0,1)$ and circle $A$ has $R=1.5$  How do I solve the area of the intersection of the circle and rectangle by integration?  If we let $f(x)=1$, then the area of the rectangle is defined by: $$\int_0^Ff(x)dx$$   If we let $g(x)=\sqrt{R^2-x^2}$, then the area of the circle is defined by: $$4\int_0^Rg(x)dx$$ Now my best attempt to find the area is through: $$\int_0^Rg(x)dx-\int_0^{\sqrt{R^2-1}}(g(x)-1)dx$$  The first integral gives me a quarter of the area circle $R$, the second gives me the area of the circle that is outside the rectangle, because the circle and the top line intersects at $x=\sqrt{R^2-1}$  Is my solution correct?


I have a script which gives output in a file and doing few awk operations on that output file and mixing the output of two files using paste -d and then sending the email of newly created file to email. If i run same script from command line, its giving output and sending email as well, but if i use same command for cron job. Its not sending email and /var/log/cron gives this message. "CROND[6235]: (root) MAIL (mailed 125 bytes of output but got status 0x0043#012)". No info for message code (0x0043#012). Please suggest.

This is a  about using cron & crontab.   You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is not answered below then the answers will help you gather information that will help the community help you. This information should be edited into your original question.  The answer for 'Why is my crontab not working, and how can I troubleshoot it?' can be seen below.  This addresses the cron system with the crontab highlighted.


Obviously we don't have precedent for mRNA vaccines like the now available SARS-CoV-2 vaccine from German-American Joint Venture Biontech/Pfizer. But how about the other, more conventional vaccine technologies? Was there at some point ever a trial which needed to be suspended because e.g. after 3 years people, which initially (first few months after being administered a vaccine) seemed totally fine, got health issues? This seems to be the crucial question, as we already vaccinated a large group of people, but were not able to observe them for very long.

The current prognosis for a COVID-19 vaccine to become available is "12-18 months" and a big part of the reason for such a long timeline is the fact that scientists want to ensure that the vaccine is safe enough. But did this ever happen in practice? An article on CNN mentions the :      In 1976, President Gerald Ford's administration reacted at speed to a novel swine flu outbreak, ignoring the World Health Organization's words of caution and vowing to vaccinate "every man, woman and child in the United States." After 45 million people were vaccinated, the flu turned out to be mild. Worse, researchers discovered that a disproportionately high number of the vaccinated -- roughly 450 in all -- had developed Guillain-Barré syndrome, a rare disorder in which the body's immune system attacks the nerves, leading to paralysis. At least 30 people died. Upon discovery of the risk, the program was terminated in late 1976. A crush of lawsuits against the federal government followed.   However this looks like a very rare complication, only causing problems for 1 in 100,000 patients. And even that complication could've been detected :     About a week after getting the swine flu shot, she recalled, “I was so weak I couldn’t push down the toaster button.” She spent a month in the hospital, paralyzed from the neck down, before gradually recovering.   So has there ever been a vaccine trial satisfying the following conditions?   Significant side effects were detected Those side effects appeared in otherwise healthy candidates after more than 3 months since they were injected with the vaccine These side effects were something other than birth defects (those obviously take up to 9 months to show up)   If not, what causes scientists to be so cautious about testing a new vaccine quickly?


I need to prove that $X=Z(xy-1)\subset \mathbb{A}_k^2$ is not isomorphic to $\mathbb{A}^1_k$.  I solved an exercise where I proved that, for instance, some $X\subset \mathbb{A}_k^3$ is isomorphic to $\mathbb{A}^2_k$, by constructing a morphism and showing that it is bijection (is the idea correct?).  However, I am stucked to show that is not isomorphic.  Well, I thought that $\mathbb{A}^1_k$ being a field and $X$ not (because $(0,0)\not\in X$), so they are not isomorphic.   However, this is as I've done with homomorphisms (rings, etc.), not morphisms between algebraic sets. I do not know if I can consider such thing as be or not a field.  Many thanks in advance!

Why is $K[X,Y]/(XY-1)$ not isomorphic to $K[T]?$  As a hint I should think about units. But I don't get a helpful idea.


I want to get days between two dates. I got a code, but this is little bit different. Here is my code. End date is fixed by 2021/5/4. yearStart = int(input()) monthStart = int(input()) dayStart = int(input())  yearEnd = 2021 monthEnd = 5 dayEnd = 4  months = [31,28,31,30,31,30,31,31,30,31,30,31]  def isLeapYear(year):     return (year%4==0 and year%100!=0) or year%400==0  def totalDays(year,month,day):     total = year*365+day     for i in range(0,month+1):         total+=months[i]     if isLeapYear:         total+=1     return total  days = totalDays(yearEnd,monthEnd,dayEnd) - totalDays(yearStart,monthStart,dayStart) print(days)

If I have two dates (ex. '8/18/2008' and '9/26/2008'), what is the best way to get the number of days between these two dates?


I am confused between logical implication and local and. When to use what. Logically i can make sense on which to use but intuitively i am not able to. For ex., Not All that glitters is gold Diagrametric representation: Glitters set is disjoint with gold set It can be expressed as $\neg \forall x \{ glitters(x) \implies gold(x)\} \equiv \exists x \{ glitters(x) \land  \neg gold(x)\}$ But if i think 2 disjoint sets. I think i can write it as $\forall x \{ glitters(x) \land \neg gold(x) \}$ or $\exists x \{ glitters(x) \land \neg gold(x) \}$  or $\forall x \{ \neg glitters(x) \land  gold(x) \}$ or $\exists x \{ \neg glitters(x) \land  gold(x) \}$ . But if i use logical implication formulae , these seem to be wrong. But the above representations look like 2 disjoint sets right? I am not able to grasp the differences between the above.

I am trying to determine which of the following expressions are a valid formalisation of the phrase "Not all that glitters is gold". I have the following options:  (1) ∃x. (𝖦𝗅𝗂𝗍𝗍𝖾𝗋(x)→𝖦𝗈𝗅𝖽(x))  (2) ∀x. (¬(𝖦𝗅𝗂𝗍𝗍𝖾𝗋(x))→𝖦𝗈𝗅𝖽(x))  (3) ¬∀x.(𝖦𝗅𝗂𝗍𝗍𝖾𝗋(x)→𝖦𝗈𝗅𝖽(x))  (4) ∀x. (¬(𝖦𝗅𝗂𝗍𝗍𝖾𝗋(x)→𝖦𝗈𝗅𝖽(x)))  I know that option 3 is valid since it can be rewritten as ∃x ¬(𝖦𝗅𝗂𝗍𝗍𝖾𝗋(x)→𝖦𝗈𝗅𝖽(x)). However, I am not sure whether any of the other options are correct. I don't think option 1 is correct since it states that there exists some x such that if x glitters it is gold, but this doesn't show that "not all that glitters is gold".   I don't believe option 2 is correct either, since it is saying that for all x if x does not glitter then it is gold, which doesn't show that that "not all that glitters is gold" either.  Option 4 is not correct either, since it is saying that for all x the statement "if x glitters then it is gold" is false. But for the phrase "not all that glitters is gold" there could be still be some x which glitters and is gold, it's just that not all x that glitters is gold.  However, I am not sure whether my reasoning about options (1), (2) and (4) being wrong are correct. Any insights are appreciated.


Can we use a computer fan with magnets attached to its blades, and another magnet, to generate electricity, as shown in this video?

There are many videos on youtube in which people arranged magnets in circle and rotated one placing in middle of that circle on a shaft, and the magnet (magnet motor) starts madly and continues its movement. Do they really rotate infinitely? If so, do they from where they get that extra energy to move so fast and infinitely?    EDIT: This question is about real world scenario  UPDATE: I am unable to find that particular video about which i talked about -- I added them to my favourites, but they are all now deleted :( -- there are hundreds of that that kind of videos. Some example videos links


Can I install Ubuntu 13.04 on a windows 8 HP computer with the UEFI? If so are there any special things I must do to insure the UEFI doesn't block the installation.

I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu?


I can't find any information on whether or not it is ok to have multiple lines of info in a javadoc param. I'm making a chess engine and I want to be able to parse a string to generate a board. Is it ok to do it as I've done below?  /**  * Creates a board based on a string.  * @param boardString The string to be parsed. Must be of the format:  *      "8x8\n" +  *      "br,bn,bb,bq,bk,bb,bn,br\n" +  *      "bp,bp,bp,bp,bp,bp,bp,bp\n" +  *      "  ,  ,  ,  ,  ,  ,  ,  \n" +  *      "  ,  ,  ,  ,  ,  ,  ,  \n" +  *      "  ,  ,  ,  ,  ,  ,  ,  \n" +  *      "  ,  ,  ,  ,  ,  ,  ,  \n" +  *      "wp,wp,wp,wp,wp,wp,wp,wp\n" +  *      "wr,wn,wb,wq,wk,wb,wn,wr"  */   Edit: This has been marked as a duplicate. The reason I believe it is not a duplicate is because the other question is simply about creating a multiline javadoc comment, while this one is about having multiple lines as part of the param argument.

I have a small code example I want to include in the Javadoc comment for a method.    /**  * -- ex: looping through List of Map objects --  * <code>  * for (int i = 0; i < list.size(); i++) {  *      Map map = (Map)list.get(i);  *      System.out.println(map.get("wordID"));  *      System.out.println(map.get("word"));  * }  * </code>  *   * @param query - select statement  * @return List of Map objects  */   The problem is the code example shows up in the Javadoc with no line breaks making it hard to read.    -- ex: looping through List of Map objects -- for (int i = 0; i list.size(); i++) { Map map = (Map)list.get(i); System.out.println(map.get("wordID")); System.out.println(map.get("word")); }  Parameters query - - select statement  Returns: List of Map objects    I guess I am wrong in assuming the code tag would handle line breaks.  What is the best way to format code examples in Javadoc comments ?


I'm going to drop a database. I want to monitor if any user is still using the database for a couple of months. Besides profiler, is there a better way to monitoring activities on a database?

We're looking to decommission a SQL Server instance which has a couple databases still remaining on it.  How can I tell if they are still being used by users or a web application?  I found a  which had a T-SQL query you could run to retrieve the last query date. It seems to work but I want to know if this information is valid enough to drop databases. Is it?  If you have alternative methods that would help as well.


In the notes I'm studying from ( again =) ) I read:   If $(\mathbf B, \cdot)$ is a finite order group with prime order then $(\mathbf B, \cdot)$ is cyclic  Could someone give me a justification for this?

Show that every group of prime order is cyclic.   I was given this problem for homework and I am not sure where to start. I know a solution using Lagrange's theorem, but we have not proven Lagrange's theorem yet, actually our teacher hasn't even mentioned it, so I am guessing there must be another solution. The only thing I could think of was showing that a group of prime order $p$ is isomorphic to $\mathbb{Z}/p\mathbb{Z}$. Would this work?    Any guidance would be appreciated.


using the memoir document class, and including graphics using \begin{figure}[!h].  For some reason, if the graphic shows up near the end of the chapter, something weird happens.   If there isn't enough space on the last page to include all text and the figure as well, then it'll put the graphic on a page all to itself, and put it in the middle of the page.   Now. I have no problem with it being all alone on a page. I just don't want it in the middle.

I have multiple figures placed in my document (all of which are using [htbp], [ht] etc. and are placed correctly). The last figure receives a separate page (which is alright) but it's centered on this page, which looks weird as the figure is quite small.  Is there any way to get this figure on top of this page? As written above, its a separate page and the last one in this chapter.  I can't really provide a minimal example (since I guess that the position depends on my previous figures), but here's the code I use for the figure (I've tried [ht], [ht!], [htbp] etc but none of them work - I've also deleted the .aux files before compiling):  \begin{figure}[t!] \centering \begin{tabularx}{\columnwidth}{cc} \subfloat[Results 1] { \centering    \includegraphics[width=0.47\textwidth,height=0.47\textheight,keepaspectratio]{images/plot1} } & \subfloat[Results 2] { \centering    \includegraphics[width=0.47\textwidth,height=0.47\textheight,keepaspectratio]{images/plot2} } \end{tabularx} \caption{Blabla} \end{figure}   Thanks in advance!


I have some pdf support and how tos that I would like to end up on every install, is there a way of doing this from my usb startup disk? Or would I need to make a customer iso

I would like to customize Ubuntu live CD by installing some additional packages. I have followed   but it doesn't seems to work. Can anyone provide clear instructions?   Note: I do not prefer Remastersys, manual way will be appreciated.  Customization  Packages that I want to install:   Thunderbird    Samba    SSH       Changes that I need:   Remove Games menu from the Application menu Firefox shortcut on Desktop Radiance as the default Theme Different default Ubuntu Wallpaper   Configuration file changes   I want the panel to be placed at the bottom I want to paste my Samba configuration file instead of default Samba configuration I have few Firefox shortcuts and folders I would like to show that in Desktop Also it will be nice if you say me how to change the icon sets   Recent Updates   I have customized Ubuntu 10.10 with Firefox shortcuts and few folders on desktops. Everything went smooth. But the installer gets crashes after choosing the timezone. How do i fix this issue? Also setting wallpaper affects the login screen. The wallpaper which i set is displayed on the login screen also. I just want the default one for the login screen.


Prove that group of order 203 is abelian.

I just constructed the semidirect product in Lang, and I'm trying to tie some facts together. From Ash's Algebra, I know that if $p\lt q$ are distinct primes, if $q\not\equiv 1\pmod{p}$, then any group $G$ of order $pq$ is abelian.  Is the converse true, that for any primes $p\lt q$, if $q\equiv 1\pmod{p}$ then there exists a nonabelian group of order $pq$?  One example I found online is that $\mathbb{Z}_3\ltimes \mathbb{Z}_7$ is nonabelian, and here $7\equiv 1\pmod{3}$. I was considering then semidirect products $\mathbb{Z}_p\ltimes\mathbb{Z}_q$ where $q\equiv 1\pmod{p}$ and some homomorphism $\phi\colon \mathbb{Z}_p\to\operatorname{Aut}(\mathbb{Z}_q)$ I calculate that  $$ (1,0)(0,1)=(1+0,\phi_0(0)+1)=(1,1) $$ and $$ (0,1)(1,0)=(0+1,\phi_{-1}(1)+0)=(1,\phi_{p-1}(1)). $$ Is it true somehow that $\phi_{p-1}(1)\neq 1$ in each case to show the group is nonabelian? I guess if it did this would imply $\phi_{p-1}$ is the trivial automorphism, so maybe there's something there? If not, is there a way to show $\mathbb{Z}_p\ltimes\mathbb{Z}_q$ is nonabelian in these cases in general? Thanks.


how can I put a legend outside on a single line under the x axis  \documentclass[a4paper,12pt]{book} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc} \usepackage[english,italian]{babel} \usepackage{url,amsfonts,epsfig} \usepackage{amsmath} \usepackage{caption} \usepackage{subcaption} \usepackage[backend=biber]{biblatex}  \usepackage{matlab-prettifier} %pacchetto per scrivere come Matlab  \usepackage{tikz} \usetikzlibrary{calc,quotes,angles} \usepgflibrary{arrows.meta} \usepackage{pgfplots} \usetikzlibrary{calc}  \begin{document}    \begin{figure}[h]     \centering     \begin{tikzpicture}     \begin{axis}[name=plot,     %xmin=49.9,      %xmax=50,      xlabel={$[s]$},      ylabel={$amplitude$},     %ymin=0.651,     %ymax=0.6535,     width=1\textwidth,     %yticklabel style={/pgf/number format/.cd,fixed zerofill,precision=5},     xticklabel style={rotate=-90,/pgf/number format/.cd,fixed zerofill,precision=2},     legend style={at={(0.5,-0.17)},anchor=north,legend cell align=left},     ]               \addplot{x}; \label{x}     \addplot{-x + 10}; \label{x10}     \addplot{x*x}; \label{x2}          \end{axis}          \end{tikzpicture}     \caption{\textit{legend outside on a line}}   \label{fig:legend} \end{figure}   \end{document}

I am having a plot with legend entries. The entries are not really long, it would be nice to have them in a single row. The default behavior adds a line break after each entry. Furthermore, the are all centered, I would prefer left flushed.  I did not find the correct parameter for changing that. Anyone any suggestions or pointers fore me?


The title really says it all. I am looking for a (preferably friendly and compact) modern introductory text on supersymmetry (SUSY) and beyond-the-standard-model (BSM) particle physics.  As a little bit of background, I am a first-year graduate student working on experimental particle physics (ATLAS). I have some exposure to quantum field theory (Mandl & Shaw, a little bit of Schwartz) and am reasonably comfortable with standard-model particle physics (Halzen & Martin, Thomson).  Most of the materials that come up when I search for such books in SUSY and/or BSM seem too mathematical and/or outdated (some written by some of the first developers of the concept). Despite not finding definitive SUSY signatures yet, particle physics has achieved a lot since the first theoretical development of SUSY, and I am somewhat surprised that it is so difficult to find a nice modern summary of the theory and it status.  So, to sum up: I am looking for study material for introduction to SUSY and BSM. In particular, if I were to be picky, I would prefer it is was (a) relatively modern, (b) not too mathematical/theoretical, but more emphasis on phenomenology and searches for them in experiments, and (c) gives some perspectives on the current status of SUSY.  Any recommendation?

I have an idea of supersymmetry in quantum mechanics, can you suggest a book on "supersymmetry in quantum field theory", which has sufficient mathematical rigour like "Peskin and Schroeder"


In my visa application I stated that I planned to arrive in the UK on 1st September, but me and my family now want to enter the UK on 13th September. Will that be a problem?

I just finished applying for my visa and had originally planned to travel on the 30th of September, so I put that as my intended date of travel. But now I will not be leaving until close to the second week of October.  How does this work, will I still be able to travel with this visa even though it says I intended to arrive on September 30th?


I want to create an integer array that can hold 8 bytes of data, I have used this code   int n =50;  long long *buffer = new long  long [n];   the size of long long is 8 bytes but    sizeof(buffer)    only gives 4 bytes is it that the heap doesn't allow more than 4 bytes allocation? there is something that I have missed here but don't know what it is.

This question was inspired by a similar question:   My question is a little different:  Is there any way to determine the size of a C++ array programmatically?  And if not, why?  Every function I've seen that takes an array also requires an integer parameter to give it the size.  But as the linked question pointed out, delete[] must know the size of the memory to be deallocated.  Consider this C++ code:  int* arr = new int[256]; printf("Size of arr: %d\n", sizeof(arr));   This prints "Size of arr: 4", which is just the size of the pointer.  It would be nice to have some function which prints 256, but I don't think one exists in C++.  (Again, part of the question is why it doesn't exist.)  Clarification: I know that if I declared the array on the stack instead of the heap (i.e. "int arr[256];") that the sizeof operator would return 1024 (array length * sizeof(int)).


I want to switch a spare laptop I have from Windows 10 to Linux. I don't wish to keep windows on there at all and have nothing on there to back up. Can anyone point me towards a guide that shows me how to do this please? Thanks

My laptop is filled with viruses and Windows XP is just becoming impossible to work with.   I've been interested in Ubuntu for a while, so, would I be able to use something like Debian to clear my HDD and OS and then install Ubuntu and start fresh?


I have a View, and when a certain field in the result has a specific value, I want to add a CSS class to that row.  How I can add css class to the matching row in views result in table result mode directly in views pages, without template files?

I've actually reached the bottom of Google trying to figure out how to add a css class to each row of a view.  The trick is that I need the class for each row to be dynamically determined based on some of the data from the node that the view pulls from.  The function that pulls this off neatly for the node is -   function pgc_preprocess(&$variables) {   $node = $variables['node'];   if ($node->type == "event") {     $variables['event_class'] = '';     $num_trainers = $node->field_number_of_trainers[0]['value'];     $count = count($node->field_trainer);     if($count < $num_trainers) {         $variables['event_class'] = 'red';     } else {         $variables['event_class'] = 'green';     }     return $variables;   } }   The point of this is to color code an event that hasn't had enough folks sign up.  There will be a list of events on the front page, and I need  them to be color coded also.  I really hope there some simple solution along the lines of -  function pgc_preprocess_views_view_unformatted(&$variables) {   // Magic here, preferably having something to    // do with the function I already wrote. }   Just dropping <?php print $event_class ?> in the view .tpl doesn't do it.


I have decided to switch from Powerpoint to Beamer, and for my first presentation I'd like to use the , and the same colors as in this goggle slide template:  .  I tried to do some research about it, the closest answers I found are the question  and the . I tried this code:  \documentclass{beamer} \usepackage[frenchb]{babel} \usepackage[T1]{fontenc} \usepackage[utf8]{inputenc}  \usetheme{metropolis}  \definecolor{bluegreen}{rgb}{3, 166, 155} \definecolor{pitchblack}{rgb}{0, 0, 0} \definecolor{lightbeige}{rgb}{255, 251, 241} \definecolor{mediumgray}{rgb}{183, 183, 183}  \setbeamercolor{background canvas}{bg=pitchblack} \setbeamercolor{normal text}{fg=lightbeige} \setbeamercolor{headline}{bg=bluegreen, fg=mediumgray}  \begin{document} \begin{frame}     \frametitle{The title}     Lorem ipsum... \end{frame} \end{document}   I does everything I want, except that the title bar's background color is lightbeige:    What did I do wrong? Or what argument should I pass to \setbeamercolor to get it right? Thanks in advance :-).

How could I change the color of color of infolines and frame title in beamer. I am using this now   \documentclass[xcolor=dvipsnames]{beamer} \usetheme{CambridgeUS} \useinnertheme{rectangles} \useoutertheme{infolines} \usecolortheme[named=Brown]{structure}    I need to change the color from red to brown. [named=Brown] doesn't work for \useoutertheme{infolines}. This is my current output. I also need to change the background of frame title (mouse pointer)


I have a feature class called Ref_Point I need a field that creates a sequential number as points are added. Im using the feature class as a numbering tool for different jobs, so when I finish a job and clear the data I want the field to start back at number 1

So I'm relatively new to ArcGIS and ArcCatalog.  I have created a field name of PROJECTID in a feature class in a Personal Geodatabase.  The data type is TEXT.  This will be a ten digit ID.  The first five characters will be a acronym.  The sixth character will be a digit that represents the type of feature.  It will be a number.  The last four characters will be numbers that should be incremented starting at 0001.    Example:     WATER-1-0001  Screen shot of the field:   So my question is how can I do this in ArcCatalog.  I've seen some Python code that will autoincrement like the following:  rec=[OBJECTID] def autoIncrement(a):   global rec   return "water" + str(a) + "-" +  format(rec, '04d')   Again I'm a newbie when it comes to ArcGIS . Now I am getting an error NameError name 'OBJECTID' is not defined.


I have purchased a HP laptop with Windows 10 home single language OEM pre-installed on it,However I've formatted my system without making recovery disks.I've downloaded Windows 10 ISO from Microsoft's site and burn it on a dvd and did a fresh install on my system.It gets activated digitally on my system.Is it legal to use this type of fresh installation or do I have to face problems in updates from HP and Microsoft.I went through superuser post  I've not changed the hard disk.It's all about a fresh install.

I've been using Windows 10 for a couple of month now (joined the Insider Preview).  Now my hard drive started ticking so I've bought a new SSD and I want to move the windows installation to the new hard drive, which has been connected to the computer (unpartitioned). I don't mind and I even prefer reinstalling it over again.   Since I have the free version of Windows 10 pro, can I still reinstall it anew? Does the windows 10 installation offer disk management and partition like the older Windows installations used to? How should I reinstall Winodws 10 x64 the easiest but still remain on free mode?


I have an iPhone 4S running iOS 8.0.2. For the past few days, my phone has been shutting off when the battery reaches around 20%. It will not turn back on until I plug it into a power source. When I plug it in, it automatically powers itself on, and the battery shows about 20%.  This is my battery info:   CycleCount: 298 DesignCapacity: 1430 FullChargeCapacity: 1000 Status: Success BatteryCurrentCapacity: 72 BatteryIsCharging: true ExternalChargeCapable: false ExternalConnected: true FullyCharged: false GasGaugeCapability: true   Questions: does anyone knows why this is happening, and how can I make the battery function until 2-4% like it used to before?

Today I was walking using my iPhone 6S running iOS 9.3 as a pedometer and it shutdown.   When I got home and plugged it in, it said 30% capacity.   That seems strange. I would expect it for 2% or 5% to preserve RAM, but 30%? Maybe there is a setting I don't know about.   My question is: Why does my iPhone power off when the battery is down to 30%?   Edit: this is not a duplicate of the low battery crash as I witnessed the low power shutdown and it was not a crash.


What are the differences between:   I did this for the first time in Tibet.  I did this in Tibet for the first time.    Which one should I use if I have done 'this' before, but it is my first time doing 'this' in Tibet? Which one should I use if I have never done 'this' before, and it is my very first time doing it and I am doing it in Tibet?

tells us that the order should be place–manner–time. However,  tells that it should be manner–Place–Time. Which one is correct?   I have one sentence in two different orders:   No child should grow up in poverty in America in the 21st century. No child should grow up in America in poverty in the 21st century.


In one of my first reviews in Stack Overflow, I've found this clearly SPAM answer:     American eagle limo give you the Party Bus with Stripper Pole in DC of the extended limos for the substantially more individuals, as just constrained individuals can conform in the normal limos .The extended limo will be bigger than the customary limos with the same offices so no compelling reason to stress that whether what number of companions you do welcome for your u......Washington USA    I've flagged it as spam, but I cant delete the answer itself, so... in order to mantain forum order, should I delete the content or i must wait to a moderator to delete it?

I noticed that the posts of the recent spam surge on Ask Ubuntu were all edited by community members into something like     EDITED - REMOVED SPAM ANSWER   or similar.  While I understand why the users have done this and I too don't want to leave the spam content visible for longer than absolutely necessary, it made flagging more time consuming for me.  I had to check the revision for every of those possible spam posts to check if it is actually spam, instead of being able to flag directly from the review site. Spam flags carry a serious penalty, I'm not willing to add my spam flag without checking that it's really spam.  I see the benefit of editing spam, but it also causes some more effort for the later flaggers. Should we as a general policy edit out the content of spam posts, or should we deal with them solely by flagging?


I have Stamp 4 on my IRP card in Ireland(formerly GNIB) and working full-time here. I am traveling from Dublin to Delhi via Heathrow Airport in London and would be changing terminals at the airport.  So, my question is, do I need to apply for a UK transit visa. My colleagues have gone via the same route and they said to me that a UK transit visa isn't necessary if you have an IRP card but just wanted to make sure.

Is there a website or some other way to find out if I need a transit visa for a short stop in the UK on my way somewhere else? Ideally this should give me the answer for all nationalities, and take into account any other visas I may have.


I have a model rocket I'm planning to launch. I heard from someone that you can calculate the altitude by timing the rocket from the time it takes off to the time it lands. Does anyone know how to do this?

Assignment Basic data I was launching a rocket model and I tried to calculate the reached altitude.  The engine (C6-0) impulse is 10 Ns Total weight is 65,7 g (includes the engine)  I calculated speed = 152 m/s $$\vec F \cdot t = \Delta m \vec v$$ Then I calculated the altitude 1007 m which seems too much to me. I guess something about 200 m (you may see the video) $$y_{\max} = \frac{v_0^2 \ }{2 g}$$ Drag I guess, I have to consider drag  Diameter of rocket 2,5 cm Drag coefficient 0,05 (I guess)  $$F_D\, =\, \tfrac12\, \rho\, v^2\, C_D\, A$$ But what about now, what is really achieved altitude? Engine description  (source: )  (source: ) Rocket Altitude Calculation


I am a newbie into the photography world and would like to buy a DSLR. I am currently shooting with my phone and usually take photos with auto mode. While choosing for a camera I have narrowed my search Canon 700D. However, i am still trying to decide onto the lens to buy.  In India, there are 2 options available. 18-55 + 55-250 IS II and 18-55 IS STM lens. Both cost almost the same.  Can anyone guide me as to which option I should go for? Can 18-55 STM suffice my needs of general photography? If so, I can go for STM, or else I would rather like to go with IS II since I get 2 lenses. May be once I grow from novice to expert, I can surely look for other options as well like 18-135 or so.

I'm trying to figure out the difference between the IS MKII lens and the IS STM lens.  Specifically, I am looking at the . On that Amazon page, there are three options; of the EF-S, one is listed as IS MK II; the other is IS STM.  I'm still not sure which is best to purchase - given the comparable price - I have heard pros and cons of each.  I understand that STM is a newer lens technology w/ a stepper motor for focusing, if I understand correctly, on manual focus, rather than adjusting the focus directly, you adjust the focus ring, and the stepper motor brings the lens to that focus point.  I have read that STM can be slower to focus than USM - however, I don't think the MK II has USM. The STM is supposed to be quieter, and thus better for AF while filming video.  Since the STM lens is newer (I think), is there any reason to buy the MK II? (The MK II is actually more expensive on the page listed.) Are there benefits to it, or pitfalls to the STM that I should consider?  Side note; my camera is an older Rebel XS; I'm not sure if the STM will work fully with it.


I have a partial proof of the following problem but I am struggling with a final case. Hints would be appreciated to solve this final case I am left with and please don't post a full solution. Thanks in advance!   Problem:   Show that if |G| = pq for some primes p and q (not necessarily distinct) then either G is abelian or Z(G) = 1.   notes:   Z(G) is the center of a group G.   Proof  Let G be a group with |G| = pq, where p and q are prime.   Let Z(G) $\ne$ {1}.   Then let z $\in$ Z(G) such that z $\ne$ 1.   Then if we can find an element of order pq, we are done since its cyclic group would have order pq and hence G is cyclic and hence abelian.   So assume |z| = p (it can be either q, p or pq by Lagrange's theorem, but pq would yield us our desired result that G is abelian).   case 1:   Let |x| = q where p $\ne$ q.   Then we have that (zx)$^p$ = z$^p$x$^p$ = x$^p$ $\ne$ 1 since p cannot divide q since q is prime.   Then (zx)$^j$ = 1 for some j where j must divide pq. j cannot be p as shown above and similarly cannot be q. Then j can only be 1 or pq.   If j = 1 then we have that zx = 1 and that z = x$^{-1}$. But then we have that z$^p$ = 1 which implies x$^{-p}$ = 1. But this cannot be the case since q = |x| = |x$^{-1}$| = p. Hence j must equal pq and so zx generates all of G and G is thus abelian.   case 2:  Let p = q.   Then |G| = p$^2$. Also we know that every element of G must be of order 1 or order p by Lagrange's theorem. If there is an element of order p$^2$ then we are done in showing G is abelian.   I'm not sure how to proceed though, I noted that the normalizer of Z(G) = G and tried to construct the product of the two subgroups Z(G) and a cyclic subgroup but that didn't get me very far.   Hints would be appreciated on how to proceed! Thanks.

The center of a group $G$ is defined as $Z(G):=\{ z\in G : gz = zg, \; \forall g \in G\}$.  The goal is to show that if $\vert G\vert = pq$, where $p$ and $q$ are not necessarily distinct primes then either $G$ is abelian or $Z(G) = \{ e\}$.  I want to suppose that $Z(G) \neq \{ e\}$ and then use the fact that $G/Z(G)$ is cyclic to imply that $G$ is abelian, which is something I have already proven. But how do I show that $G/Z(G)$ is cyclic when I am not certain what exactly $Z(G)$ looks like. I only know that it has at least one non-identity element in it, which will be of order $p$ WLOG, (the case where it is of order $pq$ is trivial).  Any help is appreciated. Thank you.


I am trying to create points inside a console window based on a 80x49 grid. But I am getting stuck on the basic idea. My thought was to first of all print out spaces on the entire page so that later, when my method Draw() is called, it replaces a space with a character of choosing. Keep in mind that the application should be able to print out new points on the same "canvas" again and again. Say that we first print a * at 4,5 and then a * at 4,7 . I am guessing SetCursorPos wouldn't work?

What is the best way to write data to the text console at arbitrary locations on the screen and with custom fore/background colors?


I got a first posts audit (, on ), and not knowing it was an audit, I wanted to leave a comment indicating a case where the answer would not have helped.  For some reason this is an audit fail, because apparently good answers are immune to comment.  Can it not be one?  I realize that this means someone could bypass the review by clicking "add comment" all the time, but that is still more effort than roboreviewing, and it's more important that the audit not harass well-intending reviewers.

I just failed these   in First Post, I read the question and thought it seemed reasonable but the user was deleted so to be on the safe side I clicked add comment and I failed the audit.  I'm not sure why adding a comment would be considered a negative action, is the correct option to click No Action Needed or edit?  What was I supposed to do in this situation?  Adding a comment should not be a review audit fail.


I have already created a class named "Category"  In some online examples I have seen - they have implemented #import "Category.h"  In some examples - class in pre declared like @category before @interface new class  So I am confused  => When to use #import & => When to use @class?

It is to my understanding that one should use a forward-class declaration in the event ClassA needs to include a ClassB header, and ClassB needs to include a ClassA header to avoid any circular inclusions. I also understand that an #import is a simple ifndef so that an include only happens once.  My inquiry is this: When does one use #import and when does one use @class? Sometimes if I use a @class declaration, I see a common compiler warning such as the following:     warning: receiver 'FooController' is a forward class and corresponding @interface may not exist.   Would really love to understand this, versus just removing the @class forward-declaration and throwing an #import in to silence the warnings the compiler is giving me.


I'm a sophomore and I'm taking my introductory real analysis course this summer.  What I'm not sure about is the proper textbook to use in order to learn it properly, at MIT they jump to Rudin at once, they don't bother studying any lowered down books before it so I know that I do not have to study mathematical analysis from lowered down books before I jump to the real deal.  Courses I have taken so far:    Calculus (although I'm bad at the multivariable calculus I still can revise anything I need whenever needed). Elementary Set Theory Abstract Algebra (Group Theory)   and I'm taking topology this semester as well. I know nothing of linear algebra though but I do not think its really necessary. So what do you think is the proper textbook to use?   Is it Rudin/Pugh/Apostol or Do I have to learn from books like Abbott/Kenneth Ross/Bartle first? I have already studied few sections from Bartle regarding Continuity and Differentiation and I find the exposure to the material quite weak, doesn't matter if I do all the problems I still do not taste the beauty of analysis from this *hit textbook because all I can find in it is just a bunch of definitions with no explanation on why are they there or what is the point of having them and the problems are just direct random applications so if I do them I still feel like I learned absolutely purely nothing new just calculus written in a different way really.

I am a sophomore in US with double majors in mathematics and microbiology. I am interested in self-studying the real analysis starting now since it will help me on my current research on computational microbiology, prepare for upcoming math research (starting on this Fall) on the analytic number theory, and prepare for the real analysis course I will take on Fall and Putnam competition. I just finished "Calculus with Analytic Geometry" by G. Simmons, "How to Prove It" by Daniel Velleman, and "How to Solve It" by G. Polya. I also read some portions of Apostol's Calculu Vol.I to get a deeper view on the calculus theories. I was originally planned to read Apostol's Calculus Vol.I and Spivak's Calculus first, but I think it would be a better idea to start with real analysis since it covers all ideas in those "advanced calculus" textbooks and much more. My current plan is to start with one "dumbed-down" real analysis textbook and one "comprehensive, detailed, and intermediate" textbook, and advance into Rudin's PMA (required textbook for my real analysis course) starting on Summer and use it in accordance with other real analysis textbooks. Could you help me on selecting one book from each category?   Elementary Real Analysis textbooks:  **Elementary Analysis: The Theory of Calculus (Kenneth Ross)  **Understanding Analysis (Steven Abbott)  **The Way of Analysis (Robert Strichartz)  **Real Mathematical Analysis (Charles Pugh)   Intermediate, detailed Real Analysis textbooks:  **Mathematical Analysis (Tom Apostol)  **Undergraduate Analysis (Serge Lang)  **Introduction to Real Analysis (Bartle, Sherbert) **Elements of Real Analysis (Bartle, Sherbert)  **Mathematical Analysis I (Vladimir Zorich)   Thank you very much for your time, and I look forward to your advice!   Sincerely, PK


I have two independent variables to predict my independent variable. For both theoretical and practical reasons, it made sense to log all of the three variables.  In R formula: log(y) ~ log(x1) + log(x2) The model works great and meets all assumptions of linear regression with flying colors. Now, I'd like to transform the fitted model including the fitted parameters to its 'unlogged' state, i.e., without the logs. I think this should be: $$y = exp(\hat{\alpha}) \cdot exp(\hat{\beta_1})^{x_1}  \cdot exp(\hat{\beta_2})^{x_2}$$ where each of the three parameters are the estimates from the regression, transformed exponential. Is this correct?

I'm fitting a regression on the $\log(y)$.  Is it valid to back transform point estimates (and confidence/prediction intervals) by exponentiation?  I don't believe so, since $E[f(X)] \ne f(E[X])$ but wanted other's opinions.  My example below shows conflicts with back transforming (.239 vs .219).  set.seed(123)  a=-5 b=2  x=runif(100,0,1) y=exp(a*x+b+rnorm(100,0,.2)) # plot(x,y)  ### NLS Fit f <- function(x,a,b) {exp(a*x+b)}  fit <- nls(y ~ exp(a*x+b),  start = c(a=-10, b=15))  co=coef(fit) # curve(f(x=x, a=co[1], b=co[2]), add = TRUE,col=2,lwd=1.2)  predict(fit,newdata=data.frame(x=.7)) [1] 0.2393773  ### LM Fit # plot(x,log(y)) # abline(lm(log(y)~x),col=2) fit=lm(log(y)~x) temp=predict(fit,newdata=data.frame(x=.7),interval='prediction') exp(temp)         fit       lwr       upr 1 0.2199471 0.1492762 0.3240752


I've a question that many of yours could consider stupid: if i sum a matrix with its transpose, I obtain a particular result? E.g. $A + A^T = B$, $B$ has some particular properties?

Prove that if $A$ is a square matrix, then:  a) $A+ A^T$ is symmetric.  b) $A-A^T$ is skew-symmetric.  c) Use part (a) and (b) to show $A$ can be written as the sum of a symmetric matrix $B$ and a skew-symmetric matrix $C$, with $A = B + C$.


I was wondering about this idea. That if we lets say have a metal cube in a vacuum sealed container and use a magnetic field to keep the metal cube afloat so that it doesnt have contact with anything. Before any of that we heat the metal cube. What I know is that heat transfer due to molecules colliding in this case there is no contact. Does this mean that the thermal energy of the cube will never be lost therefore we can store thermal energy. Is this possible?

Supposing someone says they have a sample of insulanium with the following properties:   If you make a thermos out of insulanium, it will keep a drink hot or cold forever. If you put your hand on a sheet of insulanium, it won't feel hot or cold, because no heat is exchanged with your hand. A sheet of insulanium looks like a mirror at all frequencies, because it neither absorbs nor emits radiation.   Is such a material possible? Could you use the above properties of insulanium to design an experiment that would break the laws of physics?


In Python, I can use list.index to find the index of an element, e.g. [1,2,3,4].index(1) returns 0, since the element 1 occurs at position 0. I'd like to do this with multi-dimensional arrays. That is, I'd like to be able to write something like x = np.array([[0, 1, 2],               [3, 4, 5]]) y = np.array([0, 1, 2]) print(x.index(y))  The output should be 0, because again the target element is in the first position. Using the built-in list.index method doesn't work because the == operator for numpy arrays returns an array rather than a boolean. And np.argwhere doesn't do any broadcasting. I know I could always do idx = 0 while idx < x.shape[0] and (x[idx] != y).any():   idx += 1 print(idx)  but that feels so clumsy!

I know there is a method for a Python list to return the first index of something:  >>> l = [1, 2, 3] >>> l.index(2) 1   Is there something like that for NumPy arrays?


It is known that the closure $\overline{S}$ of a set $S$ is the union of $S$ and its boundary $\partial S$ : $\overline{S} = \partial S$ $\cup$ $S$ . I know that $\overline{S} = \partial S$ $\cup$ $\mathring{S}$ but I was wondering if we can write it with a disjoint union : $\overline{S} = \partial S$ $\sqcup$ $\mathring{S}$ since I remember that $\partial S$ $\cap$ $\mathring{S}= \emptyset$.

I'll denote closure of A with $\overline{A}$, $A^\circ$ as the interior of A, $\partial A$ as the boundary of $A$ and $A'$ as the accumulation points. I'm trying to prove the following:   $$\overline{A}=A^\circ \cup\partial A$$  Is this a valid proof?  Take $x \in A^\circ \cup \partial A$ then $x \in A^\circ$ or $x \in \partial A$   if $x \in A^\circ$ then $x \in \overline{A}$  if $x \in \partial A$ then $x \in \overline{A} \cap\overline{(X\setminus A)}$ thus $x \in\overline{A} $ so $A^\circ\cup\partial A\subset\overline{A}$  Take $x \in \overline{A}$ then $x \in A' \cup A$ thus $x \in A'\setminus A$ or $x \in A^\circ$  if $x \in A'\setminus A$ then $x \in \overline{(X\setminus A)}$ so $x \in \overline{A}\cap\overline{(X\setminus A)}$ and $x \in\partial A$ so $x\in A^\circ\cup\partial A$  if $x \in A^\circ$ then $x \in A^\circ\cup \partial A$ so $\overline{A}\subset A^\circ\cup\partial A$


I use JetAudio basic on Windows and I'd love to have the same modularity that it has on Ubuntu. Specifically, the ability to customize displays and the ability to separate playlist from the main window. I've tried a few but they all looked like iTunes clones, which is really cluttered and has too much information on screen.  It'd also be great if it could play FLAC files but that's not a necessity.  This is the look I'm looking for (just the playlist and nothing else that will clutter the screen when I restore it from minimized status):

I've been thinking about switching to Ubuntu full time, but there are still some programs left behind that I haven't found any equivalent to yet. Does anyone know of a music player similar to Foobar2000 (I've read it doesn't handle well in WINE)?


Considering the Method Declaration Like this :  public void MethodName(string param){        // method body }   And then Calling it like this :  obj.@MethodName("some string");   What is the effect of @ before the method name ? Does it behave like putting it before a string which contains escaped characters?

Possible Duplicate:          I understand that the @ symbol can be used before a string literal to change how the compiler parses the string.  But what does it mean when a variable name is prefixed with the @ symbol?


I am trying to generate Correlated Uniform Random Variables with given mean, standard and correlation structure. I have looked through various posts in this topic including this() and seems to can't get through.   Here is how I am proceeding.  set.seed(12) corr_raw=matrix(0.7, nrow = 4,ncol=4) # Correlations diag(corr_raw)=c(1,1,1,1) colnames(corr_raw)<-c("A","B","C","D") rownames(corr_raw)<-colnames(corr_raw)  Cov=(std_dev%*%t(std_dev))*corr_raw # covariance matrix  #mean and standard deviation  mu<-c(1,3,2,4) std_dev<-0.4*mu #assumed std_dev = 0.4*mean  #Cholesky Decomposition matrix L L<-chol(Cov, pivot =T) Z<-matrix(nrow = 0,ncol=10000)  for (i in colnames(Cov))   {   #stddev(Unif)=(B-A)/sqrt(12)=1; and mean(Unif)=(B+A)/2=0; A=-sqrt(3) and B=+sqrt(3)   Z<- rbind(Z,runif(10000,-1.732,1.732))   } x=mu+L%*%Z  #transform to get the desired mean and variance corr<-cor(t(x)) #find correlation of the generated random variable x   However, the corr(x) and corr_raw does not match. What am I doing wrong ?

I'm interested in finding out a method for generating correlated, non-normal data. So ideally some sort of distribution that takes in a covariance (or correlation) matrix as a parameter and generates data that approximates it. But here's the catch: the method I'm trying to find should have the flexibility to also control its multivariate skewness and / or kurtosis.   I'm familiar Fleishman's method and the use of the power method of normal variates, but I believe most of those extensions only allow the user for certain combinations of marginal skewness and kurtosis, leaving the multivariate skewness / kurtosis just out there. What I was wondering is if there is a method that helps specify the multivariate skewness and / or kurtosis, alongside with some correlation / covariance structure.   About a year ago I took a seminar on copula distributions and I remember the professor casually mentioning that through the use of vine copulas, one could generate data which is, say, symmetric in each one of its 1-D marginals but jointly skewed and vice-versa. Or, even further, that any lower-dimensional margins could have some skewness or kurtosis while keeping the highest dimensions symmetric (or not). I was marveled by the idea that such flexibility could exist I've been trying to find some sort of article or conference paper that describes said method but I have been unsuccessful :(. It doesn't have to be through the use of copulas, I'm open to anything that works.  Edit: I have added some R code to try to show what I mean. So far I am only well-acquainted with Mardia's definition of multivariate skewness and kurtosis. When I first approached my problem I naively thought that if I used a symmetric copula (Gaussian in this case) with skewed marginals (beta, in this example), univariate tests on the marginals would yield significance but Mardia's test for multivarite skewness/kurtosis would be non-significant. I tried that and it didn't come out as I had expected:  library(copula) library(psych) set.seed(101)  cop1 <- {mvdc(normalCopula(c(0.5), dim=2, dispstr="un"),              c("beta", "beta"),list(list(shape1=0.5, shape2=5),              list(shape1=0.5, shape2=5)))}              Q1 <- rmvdc(cop1, 1000)             x1 <- Q1[,1]             y1 <- Q1[,2]   cop2 <- {mvdc(normalCopula(c(0.5), dim=2, dispstr="un"),              c("norm", "norm"),list(list(mean=0, sd=1),              list(mean = 0, sd=1)))}              Q2 <- rmvdc(cop2, 1000)             x2 <- Q2[,1]             y2 <- Q2[,2]  mardia(Q1)    Call: mardia(x = Q1)  Mardia tests of multivariate skew and kurtosis Use describe(x) the to get univariate tests n.obs = 1000   num.vars =  2  b1p =  10.33   skew =  1720.98  with probability =  0 small sample skew =  1729.6  with probability =  0 b2p =  22.59   kurtosis =  57.68  with probability =  0  mardia(Q2) Call: mardia(x = Q2)  Mardia tests of multivariate skew and kurtosis Use describe(x) the to get univariate tests n.obs = 1000   num.vars =  2  b1p =  0.01   skew =  0.92  with probability =  0.92  small sample skew =  0.92  with probability =  0.92 b2p =  7.8   kurtosis =  -0.79  with probability =  0.43   Upon inspecting the contours for 'cop1' VS 'cop2' as well as the empirical bivariate density plots, I can also see that none of them look symmetric at all. That's when I realized this is probably a little more complicated than I thought.  I know that Mardia's is not the only definition of multivariate skewness/kurtosis, so I'm not limiting myself to finding a method that only satisfies Mardia's definitions.  thank you!


What would be the difference of stacking objects into each other and extruding by starting with one single primitive. How does it influence performance and what are the advantages and disadvantages using either of them? For reference. Between this  and this

Is there any benefit of creating model in one piece or I can create separate pieces and just overlap them to create a visually joint part.  For example, the below image were made from two parts 1. Blade 2. Spinner  Is there any benefit to model them (e.g. extrude from the spinner) or it is actually ok to have them separated since visually I can achieve the same effect (See picture 2)


A friend of mine did a P2V of his Acer physical Windows 7 Home Premium to run on his Mac using VMware Fusion.  Now the VM complains it is not properly licensed. Microsoft is directing him to Acer, and Acer to Microsoft.  In the mean time, he bought a new retail Windows 7 Home Premium License and Media, but doesn't want to reinstall his machine. However that license does not work; he gets a Dutch message (that has an error code 0xC004C008 when going to "Details") which I've tried to translate.   Dutch   Geef een andere productcode voor activeren op. De opgegeven productcode kan niet worden gebruikt om Windows op deze computer te activeren.  English   Enter a different product code to activate. The entered product code cannot be used to activate Windows on this computer.    What ways are there to get this machine properly licensed?

We get a lot of questions on Super User about Windows activation and licensing. This question is an attempt to answer the most common questions in one place with a .   When reinstalling Windows, the following questions often come up:   Can I transfer the copy of Windows from my old computer to a new one? Does the license key on the sticker on my computer work on any computer? If I have a 32-bit version, can I install a 64-bit version? I have an OEM version of Windows, but only a retail disk. Can I still use it? I want to install Windows with a different language. Do I need a new license in that language? I changed some hardware. Will I be able to reactivate my computer? Can I back up my activation before doing a reinstall? How many computers can I install my license on? Do I have to deactivate my old installation before transferring a license? If so, how? How does licensing work in Windows ? What are the restrictions on transferring, reinstalling, and changing versions of Windows?


Why is  not in the featured section?  It currently has a bounty open.

I have put a bounty on , however I don't see it appear in the  (also not when I'm not logged in).  Why is this. Aren't all bounty questions supposed to be visible there?


I am trying to change ssh port from 22 to 1111. I have taken following steps, but not able to.   sudo nano /etc/ssh/ssh_config Removed # where it says Port 22 Changed Port 22 to Port 1111 Ctrl + W -> Y -> Ctrl + O -> Enter -> Ctrl + X sudo ufw allow 1111 sudo systemctl restart ssh sudo systemctl status ssh   Output:   Server listening on 0.0.0.0 port 22 Server listening on :: port 22.

I want to change the ssh port from 22 to 2800. I tried to change the /etc/ssh/ssh_config and removed the # from Port line and changed the number to 2800. after trigger the command: service ssh restart The connection continued. When I tried to connect from the port 2800, It refused. The Content of /etc/ssh/ssh_config is: Removed commented lines  Host * Port 2800     SendEnv LANG LC_*     HashKnownHosts yes     GSSAPIAuthentication yes     GSSAPIDelegateCredentials no   The command service ssh status gives the following output:  ● ssh.service - OpenBSD Secure Shell server    Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)    Active: active (running) since Fri 2017-09-22 20:31:45 IRST; 1s ago  Main PID: 1825 (sshd)     Tasks: 1    Memory: 724.0K       CPU: 5ms    CGroup: /system.slice/ssh.service            └─1825 /usr/sbin/sshd -D  Sep 22 20:31:45 GoodMind systemd[1]: Starting OpenBSD Secure Shell server... Sep 22 20:31:45 GoodMind sshd[1825]: Server listening on 0.0.0.0 port 22. Sep 22 20:31:45 GoodMind sshd[1825]: Server listening on :: port 22. Sep 22 20:31:45 GoodMind systemd[1]: Started OpenBSD Secure Shell server.   I tried other ports too. But still it has the same status. What do I do wrong?


I want to do is put a default image file in the img tag if it is empty or the user havent uploaded his picture yet.  current output:   html:  <form id="form1" runat="server">
     <input type='file' id="imgInp" /> </form>   script:  $(function () {     var loader = 'http://i38.photobucket.com/albums/e149/eloginko/profile_male_large_zpseedb2954.jpg';     $('img[data-src]:not([src])').each(function () {         console.log(this);         var $img = $(this).attr('src', loader),             src  = $img.data('src'),             $clone = $img.clone().attr('src', src);         $clone.on('load', function () {             $img.attr('src', src);         });     }); });  function readURL(input) {     if (input.files && input.files[0]) {         var reader = new FileReader();          reader.onload = function (e) {             $('#Picture').attr('src', e.target.result);         }          reader.readAsDataURL(input.files[0]);     } }  $("#imgInp").change(function(){     readURL(this); });

I have a web page that includes a bunch of images. Sometimes the image isn't available, so a broken image is displayed in the client's browser.  How do I use jQuery to get the set of images, filter it to broken images then replace the src?    --I thought it would be easier to do this with jQuery, but it turned out much easier to just use a pure JavaScript solution, that is, the one provided by Prestaul.


I see the following statement: "BELLINGHAM, Wash. — Jan. 19, 2021 — eXp World Holdings, Inc. (Nasdaq: EXPI), today announced that its Board of Directors has approved a 2-for-1 stock split in the form of a stock dividend to make stock ownership more accessible to employees and investors. Each stockholder of record on Jan. 29, 2021 will receive one additional share of common stock for each then-held share, which will be distributed after the close of trading on Feb. 12, 2021. eXp World Holdings common stock will begin trading on a stock split-adjusted basis on Feb. 16, 2021." If I buy the stock today, what will happen? Will I get another share after Feb. 12th? Or, the value of my share will be slashed to half after Feb. 12th?

Stock split announcements usually mention a few dates — record date ("date of record"), split date ("distribution date", "pay date", or "payment date"), ex date ("ex-split date"). Examples:  :  Each Apple shareholder of record at the close of business on August 24, 2020 will receive three additional shares for every share held on the record date, and trading will begin on a split-adjusted basis on August 31, 2020.   :  Each stockholder of record on August 21, 2020 will receive a dividend of four additional shares of common stock for each then-held share, to be distributed after close of trading on August 28, 2020. Trading will begin on a stock split-adjusted basis on August 31, 2020.    In the case of the Tesla split, the record date is August 21, the split date is August 28 (Friday), and the ex date is August 31 (Monday). Apple's  provides definitions of these dates:  What is the effective date of the split? There are several key dates. The Record Date – August 24, 2020 - determines which shareholders are entitled to receive additional shares due to the split. The Split Date – August 28, 2020 - shareholders are due split shares after the close of business on this date. The Ex Date – August 31, 2020 - the date determined by Nasdaq when Apple common shares will trade at the new split-adjusted price.  However, further down in the FAQ, there is an explanation that seems to contradict the definition of the record date given above:  What happens if I buy or sell shares on or after the Record Date and before the Ex Date? [...] If you buy shares on or after the Record Date but before the Ex Date, you will purchase the shares at the pre-split price and will receive (or your brokerage account will be credited with) the shares purchased. Following the split, you will receive (or your brokerage account will be credited with) the additional shares resulting from the stock split.  Judging by the Apple FAQ, the way the record date works for stock splits is completely different from the way the record date works for cash dividends. With cash dividends, people who become shareholders of record after the record date are not entitled to the dividends. With stock splits, however, people who purchase shares after the record date (but before the ex date) are entitled to the stock split. Furthermore, for stock splits, the record date comes before the ex date, whereas for cash dividends, the record date comes after the ex date. It appears that I am not the only one confused about this. A quick internet search reveals years and years of confusion regarding the record date for stock splits. An extremely common point of confusion is the apparently incorrect assumption that the record date for stock splits works in the same way as the record date for cash dividends. A few questions:  Am I right that the record date for stock splits works differently from the record date of cash dividends? The only relevant dates for a stock split seem to be the split date (on which I will receive new shares after the market closes), and the ex date (on which I can sell the new shares on stock exchanges at a post-split price). It seems that the record date is completely irrelevant. What is the record date for? From my understanding, the price of the stock will be reduced at the instant the new shares are distributed (on the split date). Is this correct?


How to create a itterative number 10digit long by taking a base number

I have a dictionary of values read from two fields in a database: a string field and a numeric field. The string field is unique, so that is the key of the dictionary.  I can sort on the keys, but how can I sort based on the values?  Note: I have read Stack Overflow question here  and probably could change my code to have a list of dictionaries, but since I do not really need a list of dictionaries I wanted to know if there is a simpler solution to sort either in ascending or descending order.


I saved the default cube and exported it as an obj file. I imported it in python no issue.  bpy.ops.import_scene.obj(filepath=obj_path) bpy.context.scene.objects.active = bpy.context.selected_objects[0] data_in=bpy.context.scene.objects.active   I then opened a new blender file and made a different geometry with a few modifications. I attempted to load the obj file again. An error occurs:  An error ocurred while starting the kernel  AL lib: (EE) UpdateDeviceParams: Failed to set 44100hz, got 48000hz instead Error: Not freed memory blocks: 8, total unfreed memory 0.008392 MB   This error only seems to happen when loading the new object into python, but sometimes it happens on the old object. How can I fix or ignore this?

I have Win 10 and when I open Blender I have the error:     AL lib: UpdateDeviceParams: Failed to set 44100hz, got 48000hz instead


I vaguely remember a video clip from a decade or so.. I need help from community to identify it (the band and the song).  Where should I ask for help ?

Is there a Stack Exchange where questions can be asked regarding musical artists, music videos, etc?  For example, if someone was wondering about how a band formed, which artists hail from a certain country, the meaning of lyrics, mentions of a town in songs, etc.  This question comes from the fact that I have a music video where it seems like the artist's voice is cut out at certain times and I was wondering what the missing words were.


Having wifi crash issues on rebooting after 16 march 2019 dell lattitude 3490 ubuntu 16.04 LTS 4.4.0.139 generic kernel System.  Plz suggest... Prabashis, India

I found a problem with an application on Ubuntu.   Questions :   How do I best report the issue?  What sort of information should I provide?


It's not a question (however see bottom of the post). Just for fun - just I trained with new C# features.  Haskell vs C# 8.0 :)  static class CS8_Tests {     public static void Deconstruct<T>(this IEnumerable<T> items, out T head, out IEnumerable<T> tail)         => (head, tail) = (items.FirstOrDefault(), items.Skip(1));      /// <summary>     /// Famous Haskell implementation:     /// quicksort :: (Ord a) => [a] –> [a]     /// quicksort[] = []     /// quicksort(x:xs) =     /// let smallerSorted = quicksort[a | a <– xs, a <= x]     ///     biggerSorted  = quicksort[a | a <– xs, a >  x]     /// in smallerSorted ++ [x] ++ biggerSorted     /// </summary>     static IEnumerable<T> quickSort<T>(IEnumerable<T> items) where T : IComparable<T>         => items switch         {             _ when items.Count() == 0 => items,             (var x, var xs) => quickSort(xs.Where(a => a.CompareTo(x) <= 0))                               .Append(x)                               .Concat(quickSort(xs.Where(a => a.CompareTo(x) > 0)))         };      static int indexOf<T>(IEnumerable<T> items, T target, int index = 0) where T : IEquatable<T>         => items switch         {             (var h, _) when h.Equals(target) => index,             (_, var tail) when tail.Count() == 0 => -1,             (_, var tail) => indexOf(tail, target, index + 1),         };      public static void RunTests()     {         var items = new List<int> { 2, 5, 7, 5, 1, 4, 3, 1 };         var sorted_items = quickSort(items).ToList();         var index = indexOf(items, 1);     }      //public static IEnumerable<T> operator +(IEnumerable<T> elms1, IEnumerable<T> elms2)     //    => elms1.Concat(elms2);    }   Unfortunately, we cannot define "+" operator for IEnumerable - then this code would be more compact (see commented lines at the bottom of the code). It is interesting - why? - this may be my question.

I'm attempting to use extension methods to add an operater overload to the C# StringBuilder class.  Specifically, given StringBuilder sb, I'd like sb += "text" to become equivalent to sb.Append("text").  Here's the syntax for creating an extension method for StringBuilder:  public static class sbExtensions {     public static StringBuilder blah(this StringBuilder sb)     {         return sb;     } }    It successfully adds the blah extension method to the StringBuilder.  Unfortunately, operator overloading does not seem to work:  public static class sbExtensions {     public static StringBuilder operator +(this StringBuilder sb, string s)     {         return sb.Append(s);     } }    Among other issues, the keyword this is not allowed in this context.  Are adding operator overloads via extension methods possible?  If so, what's the proper way to go about it?


Given a phone with a password, the screen turns off and the phone locks by single pressing the power button, or if the sleep time-out is reached.  The user then must enter the password to get access.  In order to conserve battery power, is is possible to have the screen dim but NOT lock the phone?  The user could increase the sleep setting so the screen would take longer to auto-dim, but that would not preserve the battery.  There are references to a "screen mode widget" that would dim the screen without locking, it does not appear to be available any longer.  Is there a trustworthy app that does this? By trustworthy I mean one that has an Internet presence other than their own page.

I just updated to Jelly Bean on my GS3 and am mostly impressed.   I am having trouble with the screen timeout setting, however.  When I go into Display>Screen Timeout and select a time, say 30 seconds, I get a message that says "Screen will turned off when screen is locked.  Secured lock time is currently set to 5 seconds." My question is where? I cannot find this Secured Lock time setting in Display settings, Lock Screen settings or Security settings, which would seem to be the intuitive places to look for it. Further, even though I get this message, my screen now does not turn off at after 5 seconds, or ever as far as I can tell.  After walking away from the phone for 20 minutes, I returned to the screen  blazing in all its AMOLED glory.


I'm learning math.  I've recently thought more about the proof by contradiction technique, and I have a question that I would like cleared up. Let me set the stage.  Suppose I am trying to prove a theorem.  Theorem: If A and $\neg$B, then $\neg$C.  Proof (contradiction): Let us suppose that A is true and $\neg$B is true. Let us assume that C is true ($\neg$C is false).  [blah blah blah]  From this, we arrive at a contradiction because we see that B is true ($\neg$B is false), but we know that $\neg$B is true (because we assumed it to be true). Thus, since assuming that C is true lead us to a contradiction, it must be the case that C is false ($\neg$C is true). QED.  My issue with this: why is it that C leading to a contradiction must mean that $\neg$C is true? What if $\neg$C also leads to a contradiction? In that case, doesn't a proof by contradiction not prove anything? Why can we be sure that C leading to a contradiction must mean that $\neg$C doesn't lead to a contradiction?  I'm sorry if this question has already been asked. I searched for a bit before asking to see if anyone had this same specific question, but most results just asked why a proof by contradiction works in general without any clear question.

Let's say that I prove statement $A$ by showing that the negation of $A$ leads to a contradiction.   My question is this: How does one go from "so there's a contradiction if we don't have $A$" to concluding that "we have $A$"?  That, to me, seems the exact opposite of logical. It sounds like we say "so, I'll have a really big problem if this thing isn't true, so out of convenience, I am just going to act like it's true".


I have a network wired connected heatpump with a static IP address on my LAN, my son's Nintendo Switch has an identical MAC address. Even though it connects via Wi-Fi from an access point, it refuses to connect to the internet. I can get it to see the local network and it appears briefly in the access point log but will not connect out to the internet. It would seem impossible to alter either bit of kit's MAC address.  Any ideas how I can get them working?  I have turned off MAC filtering but all that achieved was enabling the Switch to connect to the network, it could not make the next step to the internet.  Update: The MAC in question is 98:e8:fa:53:c1:01 and is the same on both the Nintendo Switch and the Nibe Heat pump. I keep all my permanent devices locked on static IP addresses (From a reserved list) and hardwired back to the router, there is a uplink to my wireless Access point (Ubiquiti) which then serves both main and guest wifi networks with its own DHCP server function using a specified range not used anywhere else on my networks. I had thought that giving the Switch its own static IP address might work but although it appears in the wifi log it refuses to connect and it looks like the MAC id takes precedence over the static IP address I assigned it.   @Tonny, the Vlan option might work as the Ubiquiti has this capability , although I have never explored it before - so will give that a try, wish me luck. Otherwise I agree with you about changing the NSwitch although it is over three months since we got it (this Christmas was the first time we tried the internet connected aspect of it) so Currys may not play ball : (Sorry for the duplication of the question but the original was not showing up on my account and was very hard to search for every time).

I have a network wired connected heatpump with a static IP address on my LAN, my son's Nintendo Switch has an identical MAC address. Even though it connects via Wi-Fi from an access point, it refuses to connect to the internet. I can get it to see the local network and it appears briefly in the access point log but will not connect out to the internet. It would seem impossible to alter either bit of kit's MAC address.   Any ideas how I can get them working?    I have turned off MAC filtering but all that achieved was enabling the Switch to connect to the network, it could not make the next step to the internet.  Update: The MAC in question is 98:e8:fa:53:c1:01 and is the same on both the Nintendo Switch and the Nibe Heat pump. I keep all my permanent devices locked on static IP addresses (from a reserved list) and hardwired back to the router, there is a uplink to my wireless Access point (Ubiquiti) which then serves both main and guest WiFi networks with its own DHCP server function using a specified range not used anywhere else on my networks. I had thought that giving the switch its own static IP address might work but although it appears in the WiFi log it refuses to connect and it looks like the MAC id takes precedence over the static IP address I assigned it.   @Tonny, the VLAN option might work as the Ubiquiti has this capability, although I have never explored it before - so will give that a try, wish me luck. Otherwise I agree with you about changing the NSwitch although it is over three months since we got it (this Christmas was the first time we tried the internet connected aspect of it) so Currys may not play ball. (Sorry for the duplication of the question but the original was not showing up on my account and was very hard to search for every time.)


I want to join the Hypixel server, but I can’t figure out how to add it.  Is it possible? If so, how do I do it?

Can players on a PC and an Xbox play together in any way? I.e. can Xbox users connect to a (modfied?) PC server, or vice versa?


I spend hours trying to solve this, but I can't.  Well, I simply have a table call invoices  I have data like this    I want to know each customer rank by their total sum  How can I archive this?

I have a very simple MySQL table where I save highscores. It looks like that:  Id     Name     Score   So far so good. The question is: How do I get what's a users rank? For example, I have a users Name or Id and want to get his rank, where all rows are ordinal ordered descending for the Score.  An Example  Id  Name    Score 1   Ida     100 2   Boo     58 3   Lala    88 4   Bash    102 5   Assem   99   In this very case, Assem's rank would be 3, because he got the 3rd highest score.  The query should return one row, which contains (only) the required Rank.


I have been reading all over the internet trying to solve this problem but I have not found a solution to my situation. I am running out of space on my ubuntu partition (dual-boot with windows 10) and I am trying to increase the size of it:    I have been trying from both ubuntu and windows. Now that I have created an unallocated partition (well, two) I thought I would just be able to increase the size by dragging it. But I am unable to change the size of the ubuntu partition, even decreasing it.   What can I do?

Previously, I have installed Windows 7 on my 320 GB laptop with three partitions 173, 84 and 63 GB each. The 63 GB partition was where the Windows was installed. The rest were for file containers.  Now I changed my OS to Ubuntu 12.04 LTS. I installed Ubuntu by replacing the entire Windows 7 on the 63 GB partition. The rest of the partitions remain as an NTFS Windows partition and I can still access them both (the 173 and 84 GB partitions).  Now I want to change the two partitions of Windows into an Ubuntu format partitions plus most importantly, I want to extend the 63 GB partition to more than a 100 GB because at the moment I am running out of disk space. Whenever I try to install any application, especially using wine, it always complains for a shortage of disk space.  How do I do the extending activity before I entirely format my laptop again and lose all the important files on my partitions?


It is well known that the ring of formal power series over a field $K[[x_1,x_2,\ldots,x_n]]$ is an UFD. My question is the following: the ring $K[[x_1,\ldots,x_n]][x_1^{-1},\ldots,x_n^{-1}]$ is also UFD? I was not able to find any reference on such a result.

I was wondering, is the localization of a UFD also a UFD?    How would one go about proving this? It seems like it would be kind of messy to prove if it is true.  If it is not true, what about localizing at a prime? Or what if the UFD is Noetherian?


I'm trying to install the latest updates from my software manager and it wants me to install untrusted packages? Should I install the packages, if so, how? It just says it requires the untrusted packages and when I click OK it goes back to the Software Updater.

I tried installing VLC Player yesterday, and I got the Requires installation of untrusted packages error.  I searched for hours for a solution to this problem, and finally came upon a suggestion that said to change servers for downloading updates from.  I did this, and it gave me a 404 error when I clicked on "Check" in the Update Manager.  I tried switching my server back to the main one (and after that, several other ones), but I am now still getting a 404 error:   And the other error I get when downloading or updating:   Edit: Output of cat /etc/apt/sources.list:  deb-src http://us.archive.ubuntu.com/ubuntu/ precise main restricted #Added by software-properties  # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to # newer versions of the distribution. deb http://us.archive.ubuntu.com/ubuntu/ precise main restricted multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ precise multiverse universe #Added by software-properties  ## Major bug fix updates produced after the final release of the ## distribution. deb http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ precise-updates restricted main multiverse universe #Added by software-properties  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu ## team. Also, please note that software in universe WILL NOT receive any ## review or updates from the Ubuntu security team. deb http://us.archive.ubuntu.com/ubuntu/ precise universe deb http://us.archive.ubuntu.com/ubuntu/ precise-updates universe  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu  ## team, and may not be under a free licence. Please satisfy yourself as to  ## your rights to use the software. Also, please note that software in  ## multiverse WILL NOT receive any review or updates from the Ubuntu ## security team.  ## N.B. software from this repository may not have been tested as ## extensively as that contained in the main release, although it includes ## newer versions of some applications which may provide useful features. ## Also, please note that software in backports WILL NOT receive any review ## or updates from the Ubuntu security team. deb http://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse #Added by software-properties  deb http://us.archive.ubuntu.com/ubuntu/ precise-security main restricted multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ precise-security restricted main multiverse universe #Added by software-properties deb http://us.archive.ubuntu.com/ubuntu/ precise-security universe  ## Uncomment the following two lines to add software from Canonical's ## 'partner' repository. ## This software is not part of Ubuntu, but is offered by Canonical and the ## respective vendors as a service to Ubuntu users. deb http://archive.canonical.com/ubuntu precise partner deb-src http://archive.canonical.com/ubuntu precise partner  ## This software is not part of Ubuntu, but is offered by third-party ## developers who want to ship their latest software.


I want to install ubuntu on my windows7 PC (64 bit intel corei3) For Dual-Booting. How can I do it? Which version of ubuntu is suitable for my PC?.

I currently have Windows 7 on my computer and I want to install Ubuntu alongside Windows safely.  Could someone please provide clear instructions?