If I have this:  for (auto iSong = 1; iSong <= iMaxSongNumber; iSong++)   Can I use the new for range approach?  I understand that for containers they need a begin and end method for them to work. But if we have literal max values?

I'm aware of the range iterators in boost, and as for , it seems there should be an easy way of doing what I want, but it's not obvious to me.  Say I want to represent a numerical range, 0 to 100 (inclusive or not), say range(0,100). I would like to do something like:  for_each(range<int>(0,100).begin(), range<int>(0,100).end(), do_something);   where do_something is a functor. This iterators shouldn't have the overhead of having an underneath vector or something like this, but to just offer a sequence of integers. Is this possible with the range implementation in boost? Possible at all with normal, standard STL iterators?


The main idea is that if you have some well defined function $f$, is there a function $f^{\frac{1}{2}}$ such that $f^{\frac{1}{2}}\left(f^{\frac{1}{2}}\left(x\right)\right) = f\left(x\right)$. For lack of a better name, I will call the process of finding $f^{\frac{1}{2}}$ anti-composition. My question is, are there any known techniques to anti-composing function? Is this even a problem that conventional mathematics has looked at?   For example, the problem I am working on finding the anti-composition of $f\left(x\right) = x^2+C$. I know that when $C=0$, $f^{\frac{1}{2}}\left(x\right)=x^\sqrt{2}$, because $\left(x^\sqrt{2}\right)^\sqrt{2}=x^2$. Due to this rather simple form, I assume that $f^{\frac{1}{2}}\left(x\right)=\left(x-h\right)^n+k$ for some $h$,$k$, and $n$, which may depend on $C$. However, the composition of this is $f\left(x\right)=\left(\left(x-h\right)^n+k-h\right)^n+k$. I assume that $n=\sqrt{2}$, so $x^{n^2} = x^2$. Also, I know that $h=0$, because any change in $h$ will translate the whole function, whereas $x^2+C$ definitely has no x-translation. This means $f\left(x\right)=\left(x^\sqrt{2}+k\right)^\sqrt{2}+k$. However, in order for this to equal $x^2+C$, $k$ must equal $0$ and $C$ simultaneously, which is not possible unless $C=0$.  That's all I've worked on it so far, but I really have no idea what to try next.  I have an idea to use the above properties and use a point to get other points of the function and then manipulate the inputs until it looks like a function, but I have no idea how to generalize it or fill in the intervals between the points produced. My attempt at can be found at , but I didn't find anything useful, except for the general shape of the function.  Any help is appreciated!

This is a problem I was casually discussing with friends:     Given any function $g(x): \mathbb{R} \rightarrow \mathbb{R}$, find a   function $f(x): \mathbb{R} \rightarrow \mathbb{R}$ such that $f(f(x)) = g(x)$.   Is it possible to find a solution for $f(x)$ or prove that there isn't a solution for $f(x)$ such that $f(f(x)) = g(x)$ for any given $g(x)$?   For example, if $g(x) = x + 2$, then $f(x)$ could easily be $f(x) = x + 1$. But if $g(x) = x^2 - 1$, then it's not clear to see what $f$ can satisfy such solution.   What approach might be promising? My first gut reaction would be some analytical method but can't think of a way still...Discussions are welcomed!


The passport which has my u.s visa expired recently (I got a new passport). However, the old passport bio page is now partially damaged (bottom part with the signature and Expiry & issuse date tore out). The visa is intact with absolutely no damage. Do I need to apply for a new visa in my new passport???

I have a valid B1/B2 US visa expiring about a year from now. The passport it's in expired a few years ago, and I recently got a new one.   The passport number does not match, but the national ID number, mentioned in both, does (it used to be the same as your national ID, but not anymore)  Can I travel to the US carrying both passports? Or is it asking for trouble? (I read a few years ago that it was possible, but that might have changed)  Should I just get a new visa to avoid potential complications?


Let $C \subset \mathbb{R}^n$ be a convex set.  Is it true, that there exists a convex function $f$ such that   $C = \{x | f(x) \leq a\}$ for some $a \in \mathbb{R}$

Let $A \subset \mathbb{R}^n$ be closed and $d_A(x) = \inf_{a \in A} \|x-a\|$. I need to show that $d_A$ is convex if and only if $A$ is convex.  I have no good ideas in either direction. Can somebody please give me a hint?  For the direction ($\Longleftarrow$), my attempt was:  Let $a_1 := \operatorname*{argmin}_{a \in A} \|x-a\|, a_2 := \operatorname*{argmin}_{a\in A} \|y-a\|$, then:  \begin{align*} d_A(x) &= \inf_{a \in A} \|\lambda x + (1 - \lambda)y - a\| = \inf \|\lambda(x-a) + (1-\lambda) (y-a)\|\\ &\leq \lambda \|x-a_1\| + (1-\lambda)\|y-a_2\| = \lambda d_A(x) + (1-\lambda)d_A(y) \end{align*}  However, I'm not sure whether the inequality in the third step is actually correct.


16.4 ubuntu   apt-get update W: chmod 0700 of directory /var/lib/apt/lists/partial failed - SetupAPTPartialDirectory (1: Operation not permitted) E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied) E: Unable to lock directory /var/lib/apt/lists/ W: Problem unlinking the file /var/cache/apt/pkgcache.bin - RemoveCaches (13: Permission denied) W: Problem unlinking the file /var/cache/apt/srcpkgcache.bin - RemoveCaches (13: Permission denied) E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?

I get this error whenever I try to install programs using the terminal:  home@ubuntu:~$ apt-get install myunity E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied) E: Unable to lock the administration directory (/var/lib/dpkg/), are you root?   Also I'm unable to install updates using the terminal.


Problem  I'm trying to locate a node using EntityFieldQuery. Using fieldCondition removes all of my search results. What am I doing wrong?  So Far  I've built my function using . It's running in a custom form submit.  function mymodule_form() {     $query = new EntityFieldQuery();     $query      ->entityCondition('entity_type', 'node')      ->entityCondition('bundle', 'contact_details')      ->fieldCondition('field_user_reference_manual', 'value', '154');     $result = $query->execute();  }   If I remove the fieldCondition query line it returns both contact_details nodes that I've created. One has field_user_reference_manual = 154 the other 140   The important values in my MySQL table are:  Field: field_data_field_user_reference_manual  Column: field_user_reference_manual_value

With the following code, if the current user does not have 'bypass node access' (see  for exact verifications), then the query checks for node_access, even though I do not use the "node_access" tag.  How can I avoid the node_access check with the following query for a non-admin user?   I'm using this code from a module, so I can verify permissions myself, no need for node_access checks.    $query = new EntityFieldQuery;   $result = $query     ->entityCondition('entity_type', 'node')     ->entityCondition('bundle', 'foo')     ->fieldCondition('custom_id', 'value', $custom_id)     ->execute();


We tried to rename a project in Xcode 7 using the  but it didn't work.   After the rename the build option was greyed out.  Seems there are additional steps required but I haven't found a list which is up to date as of v7.  How can you do the rename in v7?

I began an iPhone project the other day with a silly development code name, and now I want to change the name of the project since it's nearly finished.   But I'm not sure how to do this with Xcode, trying the obvious of changing the application's name in the info.plist file, causes the signing process to go wrong (I think...) and my app won't launch giving me a Launcher error.  I guess I could make a new project and copy paste everything over, but it seems so primitive that I'm hoping for a more civilized solution.


I have an old CentOS based, shared hosting environment with Bash 3.2.52; The hosting service team created a symlink from the directory www to the directory public_html, appearing in CLI as:  www -> public_html/  I don't want to delete it but if I wanted to how could I do that (I think unlink SOMETHING)?

I have the following situation:  [ORACLE]/u01/app/grid/12.1.0.2/network> ll total 20 lrwxrwxrwx. 1 root root 36 May 11  2016 admin -> /u01/app/grid/12.1.0.2/network/admin [ORACLE]/u01/app/grid/12.1.0.2/network> cd  /u01/app/grid/12.1.0.2/network/admin -bash: cd: /u01/app/grid/12.1.0.2/network/admin: Too many levels of symbolic links   I am not sure who or why the symbolic link was created, but I would like to remove it without removing the contents of the admin folder.  Is it just rm admin or is there a different command?


Could any one please suggest me on which boot level or /etc/rc.x folder should I include my shell script so that it runs automatically immediately after login or just before the system prompts for login in LTS 12.04  Thanks

How can I run scripts automatically when Ubuntu starts up so I don't have to run them manually after startup?


I have a basic debug message in my code that prints a message as to what function is called.   #ifdef _DEBUG      std::clog << "message etc" << std::endl; #endif   How do I redirect the output to send the message to a textfile?

I've been wondering, what is the point of clog? As near as I can tell, clog is the same as cerr but with buffering so it is more efficient. Usually stderr is the same as stdout, so clog is the same as cout. This seems pretty lame to me, so I figure I must be misunderstanding it. If I have log messages going out to the same place I have error messages going out to (perhaps something in /var/log/messages), then I probably am not writing too much out (so there isn't much lost by using non-buffered cerr). In my experience, I want my log messages up to date (not buffered) so I can help find a crash (so I don't want to be using the buffered clog). Apparently I should always be using cerr.  I'd like to be able to redirect clog inside my program. It would be useful to redirect cerr so that when I call a library routine I can control where cerr and clog go to. Can some compilers support this? I just checked DJGPP and stdout is defined as the address of a FILE struct, so it is illegal to do something like "stdout = freopen(...)".   Is it possible to redirect clog, cerr, cout, stdin, stdout, and/or stderr? Is the only difference between clog and cerr the buffering? How should I implement (or find) a more robust logging facility (links please)?


I have an employees table with an employeeNumber 1313 which I would like to change in the table by finding the maximum of all employee numbers and adding 1 to it. Which means 1313 will be changed to max(employeeNumber) + 1  I have a MySQL statement which returns the error 1093:  update employees set employeeNumber = (select max(employeeNumber) from employees) + 1  where employeeNumber = 1313;   I have looked everywhere but I haven't found any question close to this one. I have seen solutions of inner join but don't know how to make it work in this situation.  A simple MySQL statement would be much appreciated.

I have a table story_category in my database with corrupt entries. The next query returns the corrupt entries:  SELECT *  FROM  story_category  WHERE category_id NOT IN (     SELECT DISTINCT category.id      FROM category INNER JOIN         story_category ON category_id=category.id);   I tried to delete them executing:  DELETE FROM story_category  WHERE category_id NOT IN (     SELECT DISTINCT category.id      FROM category        INNER JOIN story_category ON category_id=category.id);   But I get the next error:      #1093 - You can't specify target table 'story_category' for update in FROM clause    How can I overcome this?


Table A (users)  id     | name   | ip 52433    Yashas   1.1.1.1 512      Admin    5.6.7.8   Table B (admin_record)  id    | admin | time    | date    | reason | action  52433   512     2312352   1213213   Test     WARN   id is FOREIGN key  Table B keeps a log of all actions an administrator takes on his users. And the table A stores the account information of the users & administrators.  I am trying to display a list of actions taken by a administrators on a user.   I want to write a query which gets me all the rows of table B where id = fixed number.  Here is what I want to display:  "Administrator1 [Name]" took action on "User Name" for "[Note]" on XX/XX/XXXX. "Administrator2 [Name]" took action on "User Name" for "[Note]" on XX/XX/XXXX. "Administrator3 [Name]" took action on "User Name" for "[Note]" on XX/XX/XXXX.   All I have is the user's id using which I need to obtain all the entries in the log along with the administrator names. I need to obtain the admin's name, users name and all the contents of table B related to a particular user in one single query. If possible, I want the to change the field name(not literally change, but want the SQL server to send the data with new field names to separate admin name & user name) of the admin's name to admin_name and user's name as . I mean something like this  SELECT users.name AS admin_name WHERE users.id = %i  AND SELECT users.name AS user_name WHERE users.id = %i   (the query isn't correct,it us just an example to show what I am trying)  Progress so far:   SELECT player.name, player.ip, admin.name, record.date, record.time, record.action, record.reason FROM admin_record AS record JOIN users AS player ON player.id = record.id JOIN users AS admin ON admin.id = record.admin WHERE player.id=%i   where admin_record is table B & users is table A.

I have two tables A & B. Table A id | name | num  Table B id | date | roll  id in table B is a foreign key which relates to the id in table A. I want to get the contents of table B where id is given and also along with that data, I need the name whose id is given from table A. NOTE: cannot use multiple queries separated by commas; need to do both the SELECTs in one query.


$f(x) \in F[x]$ is irreducible over $F$ if $f(x) = g(x)h(x)$ implies that $g(x) \in F$ or $h(x) \in F$ where $F$ is a field.  If $g(x) \in F$ or $h(x) \in F$, then doesn't that make $f(x)$ reducible since it has factors in $F$?

Let $D$ be an integral domain. A polynomial $f(x)$ from $D[x]$ that is neither the zero polynomial nor a unit in $D[x]$ is said to be irreducible over $D$ if, whenever $f(x)$ is expressed as a product $f(x)= g(x)h(x)$, with $g(x)$ and $h(x)$ from $D[x]$, then $g(x)$ or $h(x)$ is a unit in $D[x]$.  This is the definition of the irreducible polynomial in Gallian's book. What I don't understand is how this definition translate to the fact that the polynomial cannot be factored into a product of polynomials of lower degree when $D$ happens to be a field.  There is also this examples that the polynomial $f(x)=2 x^2+ 4$ is irreducible over $\mathbb R$, but reducible over $\mathbb{C}$.  To me it seems that it is also irreducible over $\mathbb{C}$ since in its factorization $2(x^2+2)$, $2$ is unit over $\mathbb{C}$.


Okay. This is similar to a question I asked a few days ago. I am trying to show that $Aut~ Z_p$ is isomorphic to $Z_{p-1}$, where $Z_p$ denotes the congruence class of integers $\mod p$ and $p$ a prime. I have shown $Aut~ Z_p$ consists of $p-1$ elements, using the fact that a homomorphism is uniquely determined by how it maps $[1]_p$, the generator of $Z_p$; the only element it cannot be mapped to is $[0]_p$, otherwise $[1]_p \rightarrow [k]_p \neq [0]_p$ extends to an automorphism.  Now I am trying to show that $Aut~ Z_p$ is a cyclic, and show that mapping the generator of $Aut~ Z_p$ to $Z_{p-1}$ defines an isomorphism. However, I am having trouble showing this. I could use some hints.  Note: At this point, I don't know anything about fields (let alone rings), the order of an element, and related concepts.   Edit: I noticed that the question was asked , but from my cursory reading I didn't see any ideas I could use yet.

I'm trying to prove that Aut $\mathbb Z_p\simeq \mathbb Z_{p-1}$ (p prime).  I know that Aut $\mathbb Z_p$ has $p-1$ elements because $\mathbb Z_p$ has $p-1$ possiblities of generators, so intuitively I see Aut $\mathbb Z_p\simeq \mathbb Z_{p-1}$, but I couldn't prove it formally.  I'm trying to build an isomorphic function, but I don't how to do it.  Am I in the right way? Maybe I'm forgetting some trick or something.  Thanks


Two circles touch each other internally at point A as shown in the figure: () O is the centre of bigger circle. If CB = 9 cm and  DE = 5 cm. Find the area of the crescent shaped part of the figure. Take the value of pi as 22/7

I found this problem on a thread on Stack overflow where it was posted as "job interview question". Unfortunately I cannot find the question. But I saved the picture and just cannot figure it out.  The problem is to calculate the area of the crescent.


I'm aware of English's unpredictable nature in wording, but this phrase got me thinking.  What is the origination of the phrase word up... a lot of times shortened to just word!  I understand the meaning of the phrase to be:   Great! Alright! Ok! I agree! That's awesome!   , but how did word end up being a synonym for these?

Several times, I have had conversations, all over instant messenger, finish with "word" or "Word up G".  As it ends a conversation, I am guessing it is like "goodbye".  My question is what is the meaning of "word" and "word up g"? Also, what is the origin?  I am more interested in the meaning as that will help with understanding its usage.


I am using a custom-built PC with an AMD FX 8350 CPU and an ASUS M5A78LM USB 3 motherboard and a AMD Radeon R9 280X graphics Card.  I am currently using Windows 10 and i want to install Ubuntu alongside it with dual boot.  I just wanted to know if my hardware is completely supported and safely runs Ubuntu and it wont damage my hardware. Also i would like to know if anyone with my hardware has successfully run Ubuntu without any issues.

I am a bit financially strapped and received a Gateway GT5056 tower. The tower has an AMD dual core 64-bit processor in it. Will Ubuntu 12.04 run on this machine? I will not have any other application other than LibreOffice installed.


For mean value theorems like Lagrange's and Rolle's, we have the following conditions:  For applying mean value theorem to any function $f(x)$ for the domain $[a,b]$ , it should be (1) continuous in $[a,b]$ (2) differentiable in $(a,b)$  So why is it that for the criteria of differentiablity, we have the open interval ?? Is it possible for a function differentiable in $(a,b)$ and continuous in $[a,b]$ to be non- differentiable at the end points? Also why is the first statement needed ?? Doesn't the second statement of differentiablity also mean that the function is continuous ?? I'm not very experienced in calculus and still in high-school,  so it might be something too obvious I'm missing , please help :)

Why does the Mean Value Theorem assume a closed interval for continuity and an open interval for differentiability?  The MVT says: Let $f$ be a continuous function on $[a,b]$  that is differentiable on $(a,b)$, then....  Is there any example where one of them isn't true so that the MVT is not true?


Oops! Something Bad Happened!  Just me, or global issue?  I'm thoroughly enjoying the lolcatz apologies... ;).

I hope the staff can see this question, not sure if I will once I post.    Update: This does not happen on meta, this happens in programmers, and in StackOverflow. Happens in meta-programmers too.   If this helps you, here are the response headers.  HTTP/1.1 500 Internal Server Error Cache-Control: private Content-Type: text/html; charset=utf-8 X-Frame-Options: SAMEORIGIN Date: Tue, 02 Jul 2013 21:09:39 GMT Content-Length: 18814


My doubt is: Which of these two sentences is correct?     We are always looking for ways to reach all the learners in our classroom as effectively as we are able.      OR:     We are always looking for ways to reach all the learners in our classroom as effectively as we are able to.   Note that the second one ends with to.

Which of these is grammatically correct?   As educators, we are always looking for ways to reach all the learners in our classroom as effectively as we are able.   As educators, we are always looking for ways to reach all the learners in our classroom as effectively as we are able to.


Well, robots.txt prevent crawling and meta robots tag in HTML (or) X-Robots-Tag HTTP header prevents indexing (and other functionalities available too).  So, even when a URL is disallowed in robots.txt, it can be indexed in Google if it is referenced somewhere using an anchor tag.  So, my question is, how can I prevent public CDN URL being indexed by Google?  For example, I upload an image on Facebook which is private. But, the CDN URL holding the data is actually public, so anyone with the complete link can access the content. How does Facebook prevent these URLs being indexed?  Example textual URL:   Now, I posted the above URL here. Will google index this URL? Update:  How about this anchor URL: .  Will this be indexed if this is referenced this way?  Update:  When I say "link indexing", I'm not talking about  but .   Example:  in the site's  but you can see that it is actually indexed.  My question is, how does Facebook prevent the FBCDN URL above being indexed while you search like this in Google: site:fbcdn.net inurl:21616414_867163746798211_8462429064810946636_n.jpg  This didn't work, and my question is how does Facebook do this.  Reference 1:   Reference 2:   Reference 3:  (Check the table at bottom)

From what I learned, there's one way I could cause all URLs on a domain strictly serving images not to be indexed and that is with the x-robots-tag HTTP header. Now I check my logs and find out that google and even baidu are downloading the entire contents of the image URLs. I was hoping they'd stop downloading when they came across this line:  X-Robots-Tag: noindex, noimageindex   Either I formatted that line wrong (used wrong casing or wrong order of values or something), or search engines are just plain dumb and they just decide to download everything just to waste customer's money.  I looked into robots.txt and thought of using the noindex line but when I did, google complained about having no access to what they call an "important url" when it isn't important.  I don't want to block their IP's because I have text-based content on another domain running on the same server that I want them to index.  I'm tempted to offer search engines the equivalent of what users get if they requested the URL via the HEAD method (full headers but no actual content), but I might get penalized for content cloaking.   Is there something I can do to rectify this?


I have a 500gb external hdd that I'm using to boot Ubuntu. I don't need 500gb it was just so I didn't mess up my internal drive running OS x. I just bought a 64gb usb that I would like to make bootable with all the stuff from my external drive(only using lk 18 gb). Everything website I've found says I need 500gb(same size) or bigger to clone the drive and settings. Is there any way to make the 64gb drive bootable by cloning from my external drive?

My current situation is:   One hard disk Dual boot Ubuntu 11.04 and Windows 7. Partitions:  100MB Windows System thingy 144GB Main Windows 160GB Ubuntu 4GB Swap 12GB System Restore stuff    Now I want to install an 80GB SSD and move Ubuntu to it. AFAIK I need to:   Shrink the 160GB Ubuntu partition to 80GB Copy it over to the SSD Change fstab to mount the SSD as /   How do I do the second? And what do I need to do about Grub?


My book says that according to first law force applied is proportional to mass times acceleration is $$F=kma.$$ Now it says that for convenience we take $k=1$ and it does not affect anything. But my question is if we take any other value of $k$,equations of kinetic energy, motions of equation etc would change? how can we take $k=1$ conveniently. EDIT-Previous answers say that k=1 because force is defined so that it is "easy" to remember. Therefore my new question is if we define F=2Ma and then derive new results for kinetic energy etc,will they be valid too?

It seems intuitive that $a\; \propto \frac{F}{m}$, as the greater the force that is applied on an object, the greater its acceleration will be. Inversely, the greater the mass of the object, the slower the acceleration will be.  However, when rewriting proportions as equations, you must introduce a constant of proportionality, and in this case of a direct proportion, if $a \propto \frac{F}{m}$ then when rewriting as an equation you will have $$a = k\cdot\frac{F}{m}$$  In order to get the standard formula $F = ma$ this constant must be $1$. However, how do we know that this is the case? How do we know that the constant isn't $2$ and the formula $F = \frac{1}{2}ma$, for instance?


Show that a ring $R$ with $|R|>1$ is a division ring if it satisfies the following condition : for each $a\neq 0$ in $R$ there exists a unique element $x$ such that $axa=a$  We need to show that $R^*,*$ is a group. Take $a,b\in R^*$ where $R^*=R\setminus\{0\}$ then $ab\neq 0$ if $ab=0\implies a(b+x)a=aba+axa=a\implies b+x=x\implies b=0$ How to show that for each $a\in R^* , a $  has an inverse. Please help.

Let $\left(A,+, \cdot\right)$ be a ring with $1$  that satisfies the following condition:  For any nonzero $a\in A$, there exists a unique $b\in A$ such that $aba = a$.  Show that $b$ also satisfies $bab = b$, and that all nonzero elements of $A$ are invertible.


Is there any difference between accepting date and First Online date? For example in the journal  , I see this  Received, Revised, First Online   03 April 2014, 17 February 2015, 04 October 2018  from    and there is no information about accepting date. I would like to know what is the difference between them and when papers are accepted in this journal.   the journal Applications of Mathematics only shows the  Received, First Online date and not the revised date.  thanks

What steps does a manuscript typically go through from submission to publication (or rejection) in a typical journal? How are these steps referred to, in particular by editorial systems, and how long do they each typically take?  Note that this question is about the typical situation and hence not about:   Journals with an atypical workflow, e.g. those that allow for an instantaneous reviewer–author interaction. Exceptional steps or rare occurrences such as withdrawal or .   This is a canonical question on this topic as per . Due to its nature, it is rather broad and not exemplary for a regular question on this site. Please feel free to improve this question.


Consider the wave equation $$\frac{\partial^2u}{\partial t^2}-c^2\frac{\partial^2u}{\partial x^2}=0\tag{1}$$ which can be written as $$\Big(\frac{\partial}{\partial t}-c\frac{\partial}{\partial x}\Big)\Big(\frac{\partial}{\partial t}+c\frac{\partial}{\partial x}\Big)u=0\tag{2}.$$  The question  claims that (2) implies both $\Big(\frac{\partial}{\partial t}+c\frac{\partial}{\partial x}\Big)u=0$ as well as $\Big(\frac{\partial}{\partial t}-c\frac{\partial}{\partial x}\Big)u=0$.  I do not get this. Eq. (2) can be satisfied if $\Big(\frac{\partial}{\partial t}+c\frac{\partial}{\partial x}\Big)u=v\neq 0$ and $$\Big(\frac{\partial}{\partial t}+c\frac{\partial}{\partial x}\Big)v=0.$$  Am I missing something?

The solution of the wave equation $$u_{tt}-c^2u_{xx}=0$$ is given as $$u(x,t)=f(x+ct)+g(x-ct)$$ where $f,g$ are arbitrary functions of one variable.  One way to prove this is the following:  $$(\partial_{tt}-c^2 \partial_{xx})u=0$$ $$(\partial_t-c \partial_x)(\partial_t+c \partial_x)u=0$$  So solutions must satisfy  $$ (\partial_t-c \partial_x)u=0 \;\;\cup\;\;  (\partial_t+c \partial_x)u=0 $$  $\displaystyle{(\partial_t-c \partial_x)u=0 \Rightarrow u=f(x+ct)}$  $\displaystyle{(\partial_t+c \partial_x)u=0 \Rightarrow u=g(x-ct)}$    Could you explain me why the last two equations stand??


Let $n$ be a positive integer and let $A=[a_{ij}] \in M_{n\times n} (R)$ be the matrix defined by   $a_{ij}=0$  if $i=j$     $1$ otherwise  To be honest, I've only calculated determinants of matrices with numbers, nothing like this.

How do I calculate the determinant of the following $n\times n$ matrices  $$\begin {bmatrix} 0 & 1 & \ldots & 1 \\ 1 & 0 & \ldots & 1 \\ \vdots & \vdots & \ddots & \vdots \\ 1 & 1 & ... & 0 \end {bmatrix}$$  and the same matrix but one of columns replaced only with $1$s?  In the  above matrix all off-diagonal elements are $1$ and diagonal elements are $0$.


I find the idea of string theory fascinating, but I'm not a student of physics, mathematics or science in general. Are there any books which effectively break down the concepts in a way that laymen like me can understand without being overly simple but also overly technical?

I'm not a physicist but I'm interested in , and I do not know how to start learning about it. What would be a good book to read to start learning about this topic?


Hi,  It is kind of an annoying feature that I have to wait to accept an answer after I upvote it.  Why is it done like that?

I keep on seeing a fair number of questions (such as ) which get marked as answered within 5-10 minutes of being posted. Sometimes the questions like this are insanely popular and actually see some proper discussion, however often I see questions have few views and only 1 answer. The trouble with these questions is that very few people have scrutinised the answer for correctness, or possibly a better solution. I always make a point of not accepting my answers until a day or so has passed — would it not be a good idea to put a short (1 hour or so) time limit on accepting answers on new questions with few views or votes, or perhaps just an additional confirmation dialog, something along the lines of:  Your question is new and not many people have had a chance to look at it yet.  Are you sure you don't want to wait to see if anyone else has a better suggestion?


When we design our signature in evolution mail, 2 dashes are automatically added before the signature, like this: -- regards fram  How can we remove those two hyphens?

I am using html emails with outlook style signature and with every reply in a thread, the signatures for each email gets a few additional lines above it... any ideas? (the issue is roughly like this)  # initial email Hello world,  -- # <- signature starts here from a. # next reply Hello back,  -- from b. ... Hello world    -- # <- additional lines above signature. from a.   etc.


What happens if a character's stats are lowered, reducing the number of spells they can prepare?  Say a level 1 cleric has a Wisdom score of 18. According to the  feature , they can prepare 5 spells (Wisdom modifier of 4 + 1 level of cleric). Now say the cleric obtains an  and attunes it. They now have a Wisdom modifier of 5, so they can prepare 6 spells and do so.  What happens if they then unattune to the ioun stone?  The rules say they can only prepare 5 spells again, but they don't indicate that the character automatically loses one prepared spell from what I can see.

A Wizard prepares a number of spells equal to his Wizard level + his Intelligence modifier.  But what happens if he loses Intelligence (the most obvious way I can think of is unattuning to a Headband of intellect and having a base Intelligence score of less than 18) after preparing his spells? Does he...   Lose access to the first [INT mod lost] spells he prepared? Lose access to the last [INT mod lost] spells he prepared? Randomly lose access to [INT mod lost] of the spells he prepared? Keep access to all his prepared spells (but will be able to prepare fewer spells after his next long rest, unless he regains the lost intelligence)?


So, when you throw a ball and you miss, the ball rolls around. You can click on it to get it back and not waste 20 balls on a Pidgey. Well, this works sometimes, and the ball is just laying there, behind the pokemon, but most of the time, the ball disappears almost immediately without me clicking on the screen or anything and its not back in my inventory ? SO what's going on, am I retrieving my balls wrongly or are they disappearing by design ?

Can you recover Pokeballs that miss when trying to catch Pokemon?


In Ubuntu 12.04 I used LightDM config parameter session-cleanup-script to run a script when a user logs out.  In Ubuntu 16.04 this script is also fired when a user types the wrong username or password. So the user wasn't even logged in.  How can I run a script in Ubuntu 16.04 only if a user logs out?  EDIT:  OK, I thought this is an easy one. But it seems to be more complex. I use this on public terminal PCs. At first LightDM is not loaded. The user has to choose between Windows (via VMware View), Ubuntu and a Kiosk browser. He clicks a specific button to login to Ubuntu. Now LightDM (and some other stuff) gets started. When the user logs out LightDM gets stopped from the script in session-cleanup-script.  I think the Upstart/systemd method wont work as I need some environment variables like $USER and $HOME, right?.  The DBus signal seems to fire when the user wants to logout. I need a event when the user already is logged out to clean some things.

At the risk of posting a duplicate question: How can I run a local script (as the current user) when I log out? I read (and tried) among others:   (Marton's version), which did perfectly nothing, used on a simple script creating a file, absolute paths to the script (being executable) and the file. , which must be outdated; it made me remove the file from command line to be able to use my system again. I also looked into , without succes.  I believe I must be doing something wrong here, but cannot find out what is my blind spot. Context Looking for an elegant solution (workaround) to , presumably the result of a bug, I made a script that, depending on the argument, either takes a snapshot of the current desktop icon arrangement, or arranges the icons, according to the last snapshot. The script works fine, but is really no candidate to run as a background script. The script therefore should run on logout to get the arrangement, obviously run by the current user.


I want to use boost converter to to supply higher voltage to LED .I have confusion about which smps power supply to use on input side. From specs. I am unable to understand why input current limitation is given?? and what happens if higher input current supply used?? Some websites blogs saying that in electonics devices donts consume power more than that they requires. and What about linear voltage regulators??In datasheet of regulators they also mention input current limitations.  Below is of details of my project and spec: 1)SMPS spec.=12V 20 amps 2)led spec =35v 4 amps I am using this boost converter   boost converter spec:   Input voltage : DC8.5V-48V []Input current : 10A (MAX) exceeds 8A please enhance heat dissipation []Output voltage : 10-50V continuously adjustable 12-80V fixed output [Output current] : 10A MAX exceed 6A please enhance heat dissipation     PLZ SEE BELOW IMAGE:

Power supplies are available in a wide range of voltage and current ratings.  If I have a device that has specific voltage and current ratings, how do those relate to the power ratings I need to specify?  What if I don't know the device's specs, but am replacing a previous power supply with particular ratings?  Is it OK to go lower voltage, or should it always be higher?  What about current?  I don't want a 10 A supply to damage my 1 A device.


I have a directory containing around 24800 .mp4 files how can I split it into 4 directories containg all the files without keeping the original 24800 files in one directory ? is there any MV/move command to do this?

All of my images are in a single folder which are in excess of 1.6K. I want to make a batch of 30 images from the folder, and copy that batch over to its respective separate folder. The names of these folders can be anything, like folder1, folder2, fodler3, and so on. I have no idea how to approach the problem. I thought about writing a Python script to copy the files one by one and, as soon as the count reaches 30, change the folder. But I thought that maybe you guys have a better idea on how to do it with Bash.


I'm new to Blender and the way it works with Python, so I still don't understand quite well the way the different commands work.  But I wanna create a small tool where i can assign a modifier to a list of selected objects and play with the properties. So far I achieved adding the modifier to the selected objects, but if I happen to create new elements and select all objects in the scene I need to find a way to query which objects already have the modifier and which do not. So if I run the script again, only the ones without the modifier get it, otherwise it gets duplicated.    So far I haven't been able to find a way to do this using  bpy.context.selected_objects , I don't know if there is another way or if i'm using it wrong.  Here's the script i have to apply the modifier:  import bpy  objSel = bpy.context.selected_objects   for i in objSel:    if i.type == "MESH":                   subD = i.modifiers.new(name = "Subdivisions",type = 'SUBSURF')        subD.show_only_control_edges = True   Any help is appreciate it!

How can I check if the Active Object has a specific modifier so that when I run my code, it doesn't add the modifier again to the object? It should add the modifier only to the object which does not use that modifier.


Ubuntu now has by default a night light mode, so you don't have to use redshift or flux. What is the name of it ? I mean, technical name, like the corresponding package. Could I install and use it on another distro ?

f.lux is software which adjusts temperature of your display according to time of the day. Is it possible to make f.lux work in Ubuntu 14.04? If so, maybe you can share your knowledge or point me to a guide.


When I run installation of Ubuntu 12.04 LTS on my notebook Toshiba Intel core i5, 6mb RAM, 500 Gb.   I receive a message of "no root file system is defined"  What can I do?

I'm very new with Ubuntu and generally with linux. I saw ubuntu and it seems like this OS is really good and stable, and so I decided to install it alongside my windows 7 OS.  I have a few problems with the installation. Here is what I did:   I downloaded the 64bit version from Ubuntu official website, and burned it on a dvd. I set the boot sequence to first load from my CD-Rom. Ubuntu installation started, and I chose "Install Ubuntu" in the menu. (where there is also a "Try Ubuntu" option) I clicked forward until I got into the installation type screen    As you can see, the installation wont show my actual details about my hard drive! I have 1 hard drive with 750 GB - 80 GB - My main drive with windows 7 OS 600GB - All of my stuff 20GB Free space that I saved for Ubuntu But the installation wont show that!


There is gc() method both in System & Runtime classes, and System class's gc() method calls that of Runtime.  public static void gc() {         Runtime.getRuntime().gc();     }   As per Java code documentation for gc() in Runtime class      Calling this method suggests that the Java virtual machine expend effort toward recycling unused objects in order to make the memory they currently occupy available for quick reuse. When control returns from the method call, the virtual machine has made its best effort to recycle all discarded objects.   Is there anything special that happens when Runtime.getRuntime().gc() is called? What will happen if I call it and do not call it?   What I already know?  Calling gc() do not invoke Garbage Collector instantly and its upto jvm when Garbage Collection should happen.  EDIT  I want to understand why gc() is still there in Java8. Discussions on other thread do not have accepted answer and are very old.

I know that garbage collection is automated in Java. But I understood that if you call System.gc() in your code that the JVM may or may not decide to perform garbage collection at that point. How does this work precisely? On what basis/parameters exactly does the JVM decide to do (or not do) a GC when it sees System.gc()?  Are there any examples in which case it's a good idea to put this in your code?


I'm starting to work with unit tests in android  I have trying to test a method that uses:  android.util.Patterns.EMAIL_ADDRESS.matcher(validEmail).matches()   it should return true as I added this in my build.gradle  testOptions {      unitTests {         returnDefaultValues = true     } }    Still the test throws a NullPointerException.   I have two questions:  1- How do I fix this?  2- Should I reconsider my design and remove the android dependency to a mock object.   // @ LoginPresenterTest @Test public void clickOnLogin_loginSuccess(){     loginPresenter.login(validEmail, validPassword);     verify(loginView).setLoginButton(false); } // LoginPresenter public void login(String email, String password) {      loginView.setLoginButton(false);     if(!isValid(email, password)){         loginView.setLoginButton(true);         return;     } } // Validation public static boolean isEmailValid(String email){     return !(email.isEmpty() || !android.util.Patterns.EMAIL_ADDRESS.matcher(email).matches()); }   When android.utills is commented their will be no exception.

What are Null Pointer Exceptions (java.lang.NullPointerException) and what causes them?  What methods/tools can be used to determine the cause so that you stop the exception from causing the program to terminate prematurely?


As you may know, Google came out with the new Android 6.0 but it is not available in my country right now. I was wondering if I bought an Android 5.0 device from the store, would I be able to upgrade to Android 6.0 manually in the future?

Android "M" was officially announced on at the Google I/O conference on May 28, 2015 and revealed to be 6.0 Marshmallow on August 17, 2015.  You can review the high-level changes at the  and the announcement on the official .  Of course, not all devices will get this update right away and others won't get it at all. Each manufacturer and carrier often choose to add their custom modifications which tend to delay the official release.  When will each device get Android 6.0, either officially or unofficially, if ever?  See also:


This was posted on another website, but there are no responses so far:  Let $a,b$ and $c$ be complex numbers such that $|az^2+bz+c| \le 1$ for $z$ in the closed unit disk. Show that $|bc| \le \frac{3\sqrt{3}}{16}$.

Question:     Given complex numbers $a,b,c$, we have that $|az^2 + bz +c| \leq 1$ holds true for any complex number $z, |z| \leq 1$. Find the maximum value of $|bc|$   It is said this is answer is $$|bc|\le \dfrac{3\sqrt{3}}{16}$$  My idea: let $z=1$,then $$|a+b+c|\le 1$$ let $z=-1$,then $$|a-b+c|\le 1$$ let $z=0$, then $$|c|\le 1$$  let $|\theta|=1$,then we have $$|a(z/\theta)^2+b(z/\theta)+c|\le 1\Longrightarrow |az^2+b\theta z+c\theta^2|\le 1$$ and only this can't solve this problem,Thank you


$z$ is a complex number. I have to write its solution(s) in the form $z= a +bi$ given that :  $$ z^2 + 1 - i = 0 $$  I put $1 -i$ on the other side and took the root. That would give $z= \sqrt{-1+i}.$ I tried to manipulate $ -1+ i,$ obtaining $ z=i \sqrt{1+i^3} $ but that doesn't help me further.   Thanks for your help.

If I'm given a complex number (say $9 + 4i$), how do I calculate its square root?


I would like to transform a string like this  "¿Cómo puede hacerse esto?"   Into something that can be used within an XML resx file like this:  "&#191;C&#243;mo puede hacerse esto?"   I have tried HttpUtility.UrlEncode and WebUtility.HtmlEncode without any success.  I have searched online and can't seem to find the right solution.  I think I may need to put the string into a character array and iterate through each character and work out which one needs to be transformed.  Can anyone help me please?

I was looking for a generic method in .Net to encode a string for use in an Xml element or attribute, and was surprised when I didn't immediately find one.  So, before I go too much further, could I just be missing the built-in function?    Assuming for a moment that it really doesn't exist, I'm putting together my own generic EncodeForXml(string data) method, and I'm thinking about the best way to do this.    The data I'm using that prompted this whole thing could contain bad characters like &, <, ", etc.  It could also contains on occasion the properly escaped entities: &amp;, &lt;, and &quot;, which means just using a CDATA section may not be the best idea.  That seems kinda klunky anyay; I'd much rather end up with a nice string value that can be used directly in the xml.  I've used a regular expression in the past to just catch bad ampersands, and I'm thinking of using it to catch them in this case as well as the first step, and then doing a simple replace for other characters.    So, could this be optimized further without making it too complex, and is there anything I'm missing? :  Function EncodeForXml(ByVal data As String) As String     Static badAmpersand As new Regex("&(?![a-zA-Z]{2,6};|#[0-9]{2,4};)")      data = badAmpersand.Replace(data, "&amp;")      return data.Replace("<", "&lt;").Replace("""", "&quot;").Replace(">", "gt;") End Function   Sorry for all you C# -only folks-- I don't really care which language I use, but I wanted to make the Regex static and you can't do that in C# without declaring it outside the method, so this will be VB.Net  Finally, we're still on .Net 2.0 where I work, but if someone could take the final product and turn it into an extension method for the string class, that'd be pretty cool too.  Update The first few responses indicate that .Net does indeed have built-in ways of doing this.  But now that I've started, I kind of want to finish my EncodeForXml() method just for the fun of it, so I'm still looking for ideas for improvement.  Notably: a more complete list of characters that should be encoded as entities (perhaps stored in a list/map), and something that gets better performance than doing a .Replace() on immutable strings in serial.


I have a Linux Debian machine that I own (root access).   I would like to create a new user called "testuser" and give him the right to view, edit and delete files from only one specific folder located in  /var/www/html/specificfile   I do not mind if the user can see which other files exist in /var/www/html/ (or anywhere else). But the user definitely can only view, edit and delete the files contained in the folder /var/www/html/specificfile.  The user ("testuser") isn't created yet.   How do I  perform this action?  The user will access the machine only over FTP.

I am running vsftpd as ftp server on my linux (rasbian), I log in to the machine as a root user.  I would like to be still locked to using only /var/www, how can I configure vsftpd conf to accomplish it?


Can someone please explain the origin of complex numbers in physical values. For instance, denoting a plane wave with Euler's identity and also the complex relative permittivity?  Thank you.

It is commonly known that waves can be express in terms of sine or cosine function. But when I study further, I seen that for analyising the waves, it is common to use complex functions in the form $$y=y_{_0}e^{i(kx-\omega{t})}$$ where $y_{_0}$ is the amplitude, $k$ is the wave number, $\omega$ is the angular velocity and $x$ & $t$ are position an time respectively. Ofcourse, I know that the function $e^{ix}$ can be written in the form $\cos{x}+i\sin{x}$ and so it is a periodic function with period $2\pi$ but my question is for what purpose we define it in terms of complex numbers? It seem to be more convenient to use real functions for real variables such as amplitude, electric and magnetic field of an electro magnetic wave, and also in quantum mechanics. What actually this interpretation means or what is the advantage of such functions?


Please let us know how can I find out unused and duplicate indexes from SQL servers, I searched in Google but there is no good information.

I am working on a Data warehouse. I have tables with up to 200M records. Some of these tables have around 20+ indexes (I can't provide a reason why they have been created in the first place). This is making the job of maintaining these indexes too painful and has a direct impact on the DWH import job in both performance and run time.  How can I find the least used indexes on each table? (in order to get rid of them)


Many have argued that the test of IQ is simply a test of language. The application of the test consists of asking a number of questions. The person should understand the question presented to them and should be able to answer the questions properly. If a person does not understand the question or do not know to answer or give a wrong answer it results in a negative point.   is there a genetic component in this equation?

Assuming that intelligence has a genetic component,   • do we know which genes contribute to it?   and, if so,  • can we predict intelligence from genomic analysis?


Let $X$ be a topological space containing two closed points $x,y$ and let $i : \{x,y\} \to X$ denote the inclusion map. Notice that $\{x,y\}$ carries the discrete topology. Let $F$ be a sheaf on $X$. Then $i^{-1} F$ is a presheaf on $\{x,y\}$ which is given by $(i^{-1} F)(\emptyset)=1$ (the terminal set), $(i^{-1} F)(\{x\}) = F_x$ (the stalk at $x$), $(i^{-1} F)(\{y\})=F_y$ (the stalk at $y$) and $$(i^{-1} F)(\{x,y\}) = \varinjlim_{ U \subseteq X \text{ open}, ~ x,y \in U } F(U).$$ Why is, $i^{-1} F$ a sheaf if and only if the canonical map $$\varinjlim_{ U \subseteq X \text{ open}, ~ x,y \in U } F(U) \to F_x \times F_y.$$ is an isomorphism ?.   Thanks a lot to all of you.


I went to a relatively unknown state college for my Bachelor's degree.  I've been working in the field for about 5 years now, but I'm interested in going back for a PhD.   Would it be nearly impossible to get into say, MIT or Carnegie Mellon given where my Bachelor's degree is from?  Also, how much does work experience account for in the selection process? For example work related patents or product development work.  Edit  Some of this question is duplicated see   I would like to focus more on how relevant work experience can aid in the selection process.

Due to a combination of factors, I ended up going for my undergraduate studies to a relatively unknown university that was close to me geographically.  Let's say that I have a relatively standard background for someone trying to apply to top tier schools for graduate studies (some research experience, some low to medium quality publications, very strong grades, good recommendation letters). Then how much does the alma mater have an impact for someone like me? I obviously know that it is still possible to be accepted, but how much of a disadvantage am I looking at exactly?


I just created a USB bootable for ubuntu (but also tried other distributions) but it did not succeed as GRUB displays this error:  error: unknown filesystem Entering rescue mode... grub rescue> ls (hd0)(hd1)   I have a XPS 13 (9360) and I don't know how to fix this problem. I tried some solutions proposed over the web, but it did not work for me.  PS: I switch the SATA mode from RAID to AHCI but I don't think it's related

I have a multiboot system set up. The system has three drives. Multiboot is configured with Windows XP, Windows 7, and Ubuntu - all on the first drive. I had a lot of unpartitioned space left on the drive and was reserving it for adding other OSes and for storing files there in the future.  One day I went ahead and downloaded Partition Wizard and created a logical NTFS partition from within Windows 7, still some unpartitioned space left over. Everything worked fine, until I rebooted the computer a few days later.  Now I'm getting:    error: unknown filesystem.   grub rescue>   First of all I was surprised not to find any kind of help command, by trying:    help, ?, man, --help, -h, bash, cmd, etc.  Now I'm stuck with non-bootable system. I have started researching the issue and finding that people usually recommend to boot to a Live CD and fix the issue from there. Is there a way to fix this issue from within grub rescue without the need for Live CD?  UPDATE  By following the steps from , I was able to boot to initramfs prompt. But not anywhere further than that.  So far from reading the manual on , I was able to see my drives and partitions using ls command. For the first hard drive I see the following: (hd0) (hd0,msdos6) (hd0,msdos5) (hd0,msdos2) (hd0,msdos1)  I now know that (hd0,msdos6) contains Linux on it, since ls (hd0,msdos6)/ lists directories. Others will give "error: unknown filesystem."  UPDATE 2  After the following commands I am now getting to the boot menu and can boot into Windows 7 and Ubuntu, but upon reboot I have to repeat these steps.    ls ls (hd0,msdos6)/ set root=(hd0,msdos6) ls / set prefix=(hd0,msdos6)/boot/grub insmod /boot/grub/linux.mod normal   UPDATE 3  Thanks Shashank Singh, with your instructions I have simplified my steps to the following. I have learned from you that I can replace msdos6 with just a 6 and that I can just do insmod normal instead of insmod /boot/grub/linux.mod. Now I just need to figure out how to save this settings from within grub itself, without booting into any OS.  set root=(hd0,6) set prefix=(hd0,6)/boot/grub insmod normal normal   UPDATE 4  Well, it seems like it is a requirement to boot into Linux. After booting into Ubuntu I have performed the following steps described in the :  sudo update-grub sudo grub-install /dev/sda   This did not resolve the issue. I still get the grub rescue prompt. What do I need to do to permanently fix it?  I have also learned that drive numbers as in hd0 need to be translated to drive letters as in /dev/sda for some commands. hd1 would be sdb, hd2 would be sdc, and so on. Partitions listed in grub as (hd0,msdos6) would be translated to /dev/sda6.  UPDATE 5  I could not figure out why the following did not fix grub:  sudo update-grub sudo grub-install /dev/sda   So I downloaded  based on an answer from  post. That seemed to do the trick after I picked the "Recommended Repair (repairs most frequent problems)" option.


I am not an Android developer, but one of the apps I use is now saying "Unfortunately ... has stopped." I would like to look at the system logs to help figure out why, but all I can find is references to  and it would be a lot more convenient if I didn't have to download Android Studio just to do this one thing. Is there a way to get the logs without using Android Studio?

There is a lot of interesting stuff in the Android system log, that is helpful in many ways   find root causes of problems identify misbehaving apps   How can I view and examine the Android log?


I have read a lot about this stuff.    Is the vacuum empty? How is it not-empty?    But nobody can it explain serious and simple that I can fully understand it.  Some physicists tell may that virtual particles were a big lie.    There don't arises in the vacuum?  What is the truth about the vacuum?   I found this:      Is the Universe a Vacuum Fluctuation?      EDWARD P. TRYON      1.Department of Physics and Astronomy, Hunter College of the City University of New York, New York, New York 10021      Top of page   Abstract      The author proposes a big bang model in which our Universe is a fluctuation of the vacuum, in the sense of quantum field theory. The model predicts a Universe which is homogeneous, isotropic and closed, and consists equally of matter and anti-matter. All these predictions are supported by, or consistent with, present observations.      Nature 246, 396-397 (14 December 1973) | doi:10.1038/246396a0    What does this paper tells us?  Is the vacuum empty or not?  Are virtual particles in the vacuum?  Can a universe arise from nothing?

I am reading the book of Lawrence Krauss "A universe out of nothing", where he explained that the vacuum is not empty. It is a boiling brew of virtual particles that come out of their existence. And they can create a universe, even space.  But virtual particles are inner lines in a feynman-diagram. They converge in a vertex and so on. They are off-Shell.  I am a layman and I cannot grasp clearly about this stuff.  My question are:    Is the vacuum empty or is it not?  Are there particles in the vacuum and can they create a universe? But when virtual particles are just a mathemacical "trick" to calculate something, what does Lawrence Krauss mean? What is the matter about the vacuum?


I want to add a block that contains a link to a specific page. this is can be created using the l() function but it must be declared in a module,So i created a module with two files .info and .module. I know that .module file must contain the l() function but have no idea about hooks that i should use . thanks for any help .

Learning Drupal. I know now that I can create block through the backend, but I would rather precreate them programmatically, if it's possible. In fact I'm pretty sure that it's possible. But what's the easiest way?


Is it correct to say I am happy for you are improving! or does it necessarily have to be with that, as in here: I am happy that you are improving! ?

He will understand that I was not joking.   He will understand I was not joking.  Which of the sentences is correct? Are there any specific rules about the use of "that" in the sentences I reported as example?


I am running the latest Ubuntu on my server VPS on linode and I get this error when installing cronkeep     Oh Snap!      at is not available on this system. CronKeep uses this slick command   internally to run jobs independently from your web server, whenever   you hit "Run". This means you could restart your web server and still   have the process running in the background.      Here's the raw output from the command that may help you debug this   further: sh: 1: at: not found   Is there a tool called at or is this something available on the C compiler?.

Simple enough question: is there some shell command (or GUI method) I can use that, given the path to a file on my system, tells me what package put it there? Assuming the file did in fact come from a package, that is.  Bonus question: what if it's a file that isn't installed on my system? Is there, say, a website that will let me look up a file and see what packages, if any, provide it?


I have bought some olive oils glass bottles. My question is - can I buy olive oil from the shop and add it to the bottle and add in some decoration like chillies, herbs etc? Or is there a process for decoration? Thanks

I have some basil from my garden that I would like to infuse with olive oil to flavor it. I was going to pack the jar with the herbs and then pour the oil over it, keep it in a jar for about a week and then strain and store the oil for cooking.  Are there any issues I should be aware of?


I want to schedule a shell script to run everyday excluding sunday at 7:30 pm using crontab can you please help

I want to schedule a task to run on a regular basis and have heard that Cron is the way to do this.  How do I add Cron jobs in Ubuntu?


Using Fermat's little theorem I proved that     $$121^{199} = 121^{39} \mod 300$$   (as $\phi(300)$ is $80$) but I don't think I can leave it like this.  My question being how can I solve $121^{39}\hspace{-3mm}\mod 300$. Any ideas, suggestions?

How do I efficiently compute $a^b\bmod c$:  When $b$ is huge, for instance $5^{844325}\bmod 21$? When $b$ is less than $c$ but it would still be a lot of work to multiply $a$ by itself $b$ times, for instance $5^{69}\bmod 101$? When $(a,c)\ne1$, for instance $6^{103}\bmod 14$?  Are there any other tricks for evaluating exponents in modular arithmetic?  This is being asked in an effort to cut down on duplicates, see  and .


I am refloating  and will give a good bounty if somebody can solve it, cause it has been bothering me for the longest time, and cannot find a solution to it...  I have some problems when trying to make my Beamer presentations in handout format with notes, for printing and study them before the presentation day.  While the PDF seems to be generated with no problem, when trying to print it IT SHRINKS, and this happens with ALL THE PDF VIEWERS I HAVE TRIED, including Okular and Acrobat... This tells me that there is an inherent problem with the PDF itself...  This is the MWE I currently use:  \documentclass[handout]{beamer} \usepackage{pgfpages} \pgfpagesuselayout{2 on 1}[a4paper,border shrink=5mm] \setbeameroption{show notes on second screen=bottom}  \setbeamercolor{background canvas}{bg=pink}  \mode<presentation> {     \usetheme{Singapore} } \begin{document}   \begin{frame}[plain]     \titlepage   \note{     Notes for the title page } \end{frame}   \section*{Outline} \begin{frame}[plain] \frametitle{Outline}     \tableofcontents  \note{     Notes for the table of contents } \end{frame}   \section{Frame 1} \begin{frame} \frametitle{Frame with notes 1}     FIRST FRAME CONTENTS  \note{     Notes for the first frame } \end{frame}   \section{Frame 2} \begin{frame} \frametitle{Frame with notes 2}     SECOND FRAME CONTENTS \note{     Notes for the second frame } \end{frame}   \section{Frame 3} \begin{frame}     \frametitle{Frame with notes 3}     SECOND FRAME CONTENTS     \note{         Notes for the third frame     } \end{frame}   \end{document}   When I open the PDF with Okular, for example, it seems to open correctly (though the navigation links do not work):    But just going to the PRINT PREVIEW (same when actually printing), look what happens:    It shrinks to like half the size, and it has nothing to do with my printing properties, or with the printer...  Please help!!

I use the code below to produce handouts of my presentations.  When I open the resulting pdf with any pdf viewer, it is viewed correctly, but when I print it, it is always printed very small, no matter the program I use (Okular, Evince, Acrobat...). Bonus to anyone that can make the pdf be printed correctly by Okular under Ubuntu! Thanks!  MWE here:  \documentclass[handout]{beamer} \usepackage{pgfpages} \pgfpagesuselayout{2 on 1}[a4paper,border shrink=5mm] \setbeameroption{show notes on second screen=bottom}  \setbeamercolor{background canvas}{bg=pink}  \mode<presentation> {     \usetheme{Singapore} } \begin{document}   \begin{frame}[plain]     \titlepage   \note{     Notes for the title page } \end{frame}   \section*{Outline} \begin{frame}[plain] \frametitle{Outline}     \tableofcontents  \note{     Notes for the table of contents } \end{frame}   EDIT:   If I place the line "\pgfpagesuselayout{2 on 1}" after the line "\setbeameroption{show notes}" I do not experience the printing problem anymore!! However, the slide preview and notes that appear at the bottom belong to the NEXT SLIDE, instead of to the CURRENT SLIDE!! What is going on with that?


Let $G$ be the rotation group of a cube $Q.$ How many ways (up to symmetry under the action of $G$) can we colour the $8$ vertices of $Q$ using $2$ colours?  I know the Burnside or Cauchy-Frobenius Lemma, which says that for a finite group $G$ that acts on a set $S, |G| |S/G| = \sum_{a\in G}|Fix(a)|,$ where $Fix(a) := \{x \in S : ax = x\}.$ I know there are $24$ elements in $G$. Let $S$ be the number of colourings without considering symmetry. Then $|S| = 2^8.$ The rotation group induces a natural action on the set $S$, but I'm not really sure how to formally describe this action. However, once I can formally describe the $24$ elements of $G$ and then determine their corresponding $Fix$ cardinalities (the corresponding $Fix$ cardinality of element $A\in G$ is $|Fix(A)|$) it should be fine. For instance, $|Fix(I)| = 2^8,$ where $I$ is the identity rotation.  Could someone help me uncover the cardinalities of $Fix(A)$ for $A\in G$?

How many distinct ways are there to $2$-color the $8$ vertices of a cube, with colorings only considered distinct up to rotation?


As you know there are times when using a nationality (without any modification) is a correct way to refer to a person of that nationality and there are times when it is incorrect. For example "He is a German" vs. *"He is a French".  Are there any rules for deciding if a nationality can be used as a noun?

Which one is correct? I am quite sure about "I'm Spanish", but is it wrong if I add an "a" before "Spanish"?


I've looked at all previous posts and tried many suggestions/things, but I still can't mount my new hard drive to enable network access (via smb and for windows 10). Basically this is for my windows computers to use as backup location. I've tried a ton of different fstab stuff and all I ever get is this error: mount error(2): No such file or directory here is my fstab entries for this drive (the drive mounts locally no problem I can transfer files). UUID=BEE3-E4B0 /media/abemd/Ububak01   auto nosuid,nodev,nofail,x-gvfs-show 0 0  //192.168.0.107/share /media/abemd/Ububak01 cifs credentials=/home/abemd/.smbcredentials,iocharset=utf8,gid=1000,uid=1000,file_mode=0777,dir_mode=0777 0 0  I have made a proper .smbcredentials file and chmod 600 as others suggested. Of course I have latest cifs and samba installed. Ubuntu version 20.04 lts. I've been trying to figure this out for a week now and sheesh!! I've done this before no problem, I feel like I'm missing something obvious and stupid. It's driving me crazy. Thanks for any help. p.s. here is the result of 'mount' for this drive: /dev/sdc on /media/abemd/Ububak01 type fuseblk (rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096,x-gvfs-show)

right now   I have setup /etc/fstab like this:  //192.168.5.167/H /mnt/ssd cifs credentials=/root/.smbreds,noauto,x- systemd.automount 0 0   I want to set it up like first network should be connected and then fstab mount should get mounted.


When converting my code from php to js, I can't get this bit to work:  searchEntity.translations[0].translation ?? searchEntity.name ?? searchEntity.name_en   I tried using two ||  searchEntity.translations[0].translation || searchEntity.name || searchEntity.name_en   but vue compiler only sees the first one and does't display whole component when second should be rendered, hovever if I display just second everything works:  searchEntity.name || searchEntity.name_en   however entity is polymorphic and it can be either of those 3.  I don't want to use v-if, it will need a repetitive code  (code is in the template, not computed)  EDIT  checking if translations exists in computed function solves issue  translatedName: function () {                 if(this.searchEntity.translations) {                     return this.searchEntity.translations[0].translation                 } else {                     return this.searchEntity.name || this.searchEntity.name_en || this.searchEntity.translation_fallback;                 }             }

Is there a null coalescing operator in Javascript?  For example, in C#, I can do this:  String someString = null; var whatIWant = someString ?? "Cookies!";   The best approximation I can figure out for Javascript is using the conditional operator:  var someString = null; var whatIWant = someString ? someString : 'Cookies!';   Which is sorta icky IMHO. Can I do better?


I noticed that applications distributed as 'appimage' when run, they did not present the "add to favorites" in the command bar, when you right click on the icon. Why? Is there an alternative? Ubuntu 18.04.

To Clarify:   install  how to add to launcher? how to pin app to dock?    The last two things do not work. The app does not apear any where, you need to launch manually from the appimage file.


Edit: there's another post asking the same thing, but it is not satisfactorily answered. At least not in what I believe is close to the simplest way.    Trying to prove property 3 below, in a "clean" way. That is using elementary definitions of linear algebra.    Attempt:   $$\nabla_A \text{tr}\left(ABA^TC\right) = \nabla_A \text{tr}\left(\left(A\right)BA^TC\right) \stackrel{(1)}{=} C^TAB^T$$  I think I'm missing some product rule stuff, but I don't see that defined anywhere in my text.    Edit2: Ahh, the second try is way wrong. Deleted it.

How is the derivative of $\mbox{Trace}\left\{ X^T A X B\right\}$ with respect to matrix $X$ equal to $AXB + A^TXB^T$?  \begin{align}   \nabla_X \ \textrm{Trace}\left\{ X^T A X B\right\} = AXB + A^TXB^T \end{align}  where $A$ and $B$ matrices are given.


My mom's passport will be expired on 28 however she has ticket to back to Iran on 27 from Toronto via Frankfurt. She has permanent residence card but she is not Canadian citizen, therefore the only passport she has is the Iranian one. When she changes the flight in Frankfurt, her passport will be expired. Can she travel in this situation?

I am a Canadian citizen and I am traveling to Iran (back home) this December. My Iranian passport expired on 17/05/2015. I was wondering if I can use it. I want to renew my passport in Iran because it is much cheaper there.


If $a, b, c$ are positive and $a+b+c=1$, prove that $$8abc\le\ (1-a)(1-b)(1-c)\le\dfrac{8}{27}$$  I have solved $8abc\le\ (1-a)(1-b)(1-c)$ (by expanding $(1-a)(1-b)(1-c)$)  but do not get how to show that $(1-a)(1-b)(1-c)\le\frac{8}{27}$

The entire exercise was like $$8xyz≤(x+y)(y+z)(x+z)≤\frac8{27}(x+y+z)^3\quad x,y,z>0$$  and I managed to solve (demonstrate) the first inequality (from the left) using $$\frac{x+y}2≥\sqrt{xy}$$ but I can't solve the second one. I tried several ideas but I haven't succeeded. Thanks a lot.


i recently have installed Ubuntu 12.04 LTS, then I notice that Ubuntu will release newer LTS version very soon. I have dual boot between Ubuntu 12.04 LTS and Windows 7, but what if I upgrading my Ubuntu to new version  does it:   erase my Windows 7 os? make me to download new update like I'm installing fresh Ubuntu OS? does it erase my data (Music, picture, etc etc) inside my Ubuntu or Windows 7?   Sorry for a very 'unacknowledged' question about it, I am very new to Ubuntu, I just want to know. Some information will help me a lot!

What are the different ways I can use to upgrade Ubuntu from one release to another?


I am trying to reduce the size of rich text area field in Visualforce page. Here is the code have written-  <apex:column headerValue="Extra Curricular Activities"  >     <apex:inputField value="{!c.Extra_Curricular_Activities__c}" style="width:50px" /> </apex:column>   Where i need to make the changes,can anybody help me with this? Thanks in Advance!!

I know this question has been asked earlier. but did not see proper responses so asking again.  <apex:pageBlockSection title="Preview Pane" columns="1">     <apex:inputTextarea richtext="true" id="EmailBody" label="EmailBody"            cols="1" ondblclick="false" disabled="false"           value="{!emailTemplateSelected.htmlValue}"/> </apex:pageBlockSection>   I have tried to set the column value for the pageblock section. As well as for the inputtextarea. Still the column width dose not span the entire page.    <apex:inputTextarea richtext="true" id="EmailBody" label="EmailBody" cols="1"     ondblclick="false" disabled="false" value="{!emailTemplateSelected.htmlValue}"     style="height:200px;width:200px;"/>


I am creating a shared library that is utilizing Spring Framework, without Spring Boot.  I am trying to use the @Value("${foo.bar}") to retrieve properties set in application.properties, but I am unable to do so.  Part of the reason is because Spring (without Boot) doesn't know anything about application.properties, so I am hoping you know how I can configure that in my code to utilize that as a properties file.   Sorry if I confused you.    I have tried adding @PropertySource("classpath:application.properties"), but doesn't seem to be working.

I have a bunch of Spring beans which are picked up from the classpath via annotations, e.g.  @Repository("personDao") public class PersonDaoImpl extends AbstractDaoImpl implements PersonDao {     // Implementation omitted }   In the Spring XML file, there's a  defined:  <bean id="propertyConfigurer"    class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">     <property name="location" value="/WEB-INF/app.properties" /> </bean>    I want to inject one of the properties from app.properites into the bean shown above. I can't simply do something like   <bean class="com.example.PersonDaoImpl">     <property name="maxResults" value="${results.max}"/> </bean>   Because PersonDaoImpl does not feature in the Spring XML file (it is picked up from the classpath via annotations). I've got as far as the following:  @Repository("personDao") public class PersonDaoImpl extends AbstractDaoImpl implements PersonDao {      @Resource(name = "propertyConfigurer")     protected void setProperties(PropertyPlaceholderConfigurer ppc) {     // Now how do I access results.max?      } }   But it's not clear to me how I access the property I'm interested in from ppc?


I made a serial MergeSort and a parallel MergeSort. Both divide the input list in a left and right half and call sort on those. The source code is almost identical; the difference between them is that parallel MergeSort has an if-statement that checks if it needs to make threads or just calls sort like the serial version. Codesnippet:      if (threadDepth < maxThreadDepth) {         // make threads that call sort     } else {         sort(left, threadDepth + 1, maxThreadDepth);         sort(right, threadDepth + 1, maxThreadDepth);     }   When I use maxThreadDepth = 0 the if-statement is always false and the parallel works the same as the serial version.  I calculate the time both algorithms take and see something very strange. When maxThreadDepth = 0 the parallel version is faster than the serial version! I expected it to be slower, since it has an extra if-statement to process. Even when the JVM optimises this if-statement (it knows it is always false), it should never be faster!  I ran both algorithms 1000 times and kept track of the time they took like this:  List<Long> times = new ArrayList<>(); for(int i = 0, i < 1000, i++){     long start = System.nanoTime();     serial.MergeSort.sort(...); // or parallel.MergeSort.sort(...)     long end = System.nanoTime();     times.add(end - start); }   I discarded the first 900 times and calculated the average time it took both algorithms to run. Does someone have any idea why the no-extra-threaded parallel version is faster than the serial? As input, I used a list of integers with various sizes (1000, 10000, 100000) and all of them had this suprising behaviour.

How do you write (and run) a correct micro-benchmark in Java?  I'm looking for some code samples and comments illustrating various things to think about.  Example: Should the benchmark measure time/iteration or iterations/time, and why?  Related:


Every time I try to open Eclipse in Ubuntu 18.04.2 I get an Unsatisfied Link Error and it will not open. I tried uninstalling but that did not help.  The error message:  An error has occurred.  See the log file /home/NAME/.eclipse/org.eclipse.platform_3.8_155965261/configuration/1549828758313.log   log file:  !SESSION Sun Feb 10 20:52:07 CET 2019 ------------------------------------------ !ENTRY org.eclipse.equinox.launcher 4 0 2019-02-10 20:52:07.624 !MESSAGE Exception launching the Eclipse Platform: !STACK java.lang.ClassNotFoundException: org.eclipse.core.runtime.adaptor.EclipseStarter     at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:466)     at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:566)     at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)     at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:626)     at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)     at org.eclipse.equinox.launcher.Main.run(Main.java:1438)     at org.eclipse.equinox.launcher.Main.main(Main.java:1414)   In terminal error message:  OpenJDK 64-Bit Server VM warning: Ignoring option MaxPermSize; support was removed in 8.0 Gtk-Message: 21:05:17.924: Failed to load module "canberra-gtk-module"

I installed eclipse via Ubuntu Software. When I start it, it take some seconds and then comes an error window showing the path of the error.  The following is the .log file:  !SESSION Wed May 02 12:53:28 BRT 2018 ------------------------------------------ !ENTRY org.eclipse.equinox.launcher 4 0 2018-05-02 12:53:28.587 !MESSAGE Exception launching the Eclipse Platform: !STACK java.lang.ClassNotFoundException: org.eclipse.core.runtime.adaptor.EclipseStarter     at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:466)     at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:566)     at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)     at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:626)     at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)     at org.eclipse.equinox.launcher.Main.run(Main.java:1438)     at org.eclipse.equinox.launcher.Main.main(Main.java:1414)   What is the problem and how can I fix it?


In the fill up, "it is difficult ____ affection on her.", I chose "showering" out of the given options. But the answer is given as "to shower".  Now I look up on net and get that we mostly use "it is difficult to do something" rather than "it is difficult doing something"  But I wonder how can we increase accuracy on such questions. Of course, one way is wide reading but that's a long term goal, but I doubt even after that one could be sure on such things. And perhaps the other way is to cram all things. But that is hardly possible given how extensive English is.  So, I wonder if there is third way where we can learn the underlying concept or rule which would hold in most cases.  After all, it is not that we always use infinitive. At times we use gerund, like "I am looking forward to seeing you" rather than "I am looking forward to see you."  So, how do we choose infinitive over gerund or vice versa?

English isn't my mother tongue. I'm familiar with the notions of infinitive and gerund but I sometimes just don't know which of the two should be used in combination with which verb.  Thomson and Martinet [1986] provide some verbs that may take either infinitive or gerund without changing the meaning (advise, allow, ...).  I am looking for a list of verbs and the allowed construction (gerund/infinitive/both). Ideally this should be a text-based list so I can search it on my computer without having to use the internet.  [Thomson and Martinet, 1986] A. J. Thomson and A. V. Martinet, A Practical English Grammar, Oxford University Press, isbn: 0-19-431342-5, 1986.


each time i go to the root and try to change my passwd an error occurs and it says authencation manipulation error or some thing like that.and btw the passwd s match. whoever knows whats happening please help.HOw DO I CHANGE MY PASSWD .

I am logging in to my Ubuntu Server using my username. Once I am logged in I am typing passwd command. Entering a new password but a second after getting following error messages:  passwd: Authentication token manipulation error passwd: password unchanged   What is wrong here? How can I change my password otherwise if I don't have access to that server physically, i.e. I am connecting remotely with ssh using terminal.


I'm currently using mysqli_real_escape_string. It is working fine but I want to know whether there is a function more broader, which will escape more characters than the predefined ones like ',",\r etc.

Is there a catchall function somewhere that works well for sanitizing user input for SQL injection and XSS attacks, while still allowing certain types of HTML tags?


My visa was refused and all the necessary documentations were provided but the decisions don't add. So better clarifications are needed. Thanks

The UK Visas and Immigration Directorate publishes  that provides helpful tips that can result in successful visa applications. Section 2 of this guidance opens is entitled "other documents you may want to provide" (emphasis mine).  Section 2: other documents you may want to provide – all visitors This section provides guidance on the types of documents that you may want to provide to help us consider your application against the Immigration Rules. Previous travel documents/passports, which show previous travel. Financial documents showing that you have sufficient funds available.  These must clearly show that you have access to the funds, such as:  bank statements building society book proof of earnings such as a letter from employer confirming employment details (start date of employment, salary, role, company contact details) where a third party (who is either in the UK or will be legally in the UK at the time of your visit) is providing financial support to you e.g. a business, a friend or a relative, documents to show that they have sufficient resources to support you in addition to themselves and any dependant family should be provided   The first item is "bank statements" and this ties in with the , which says...  evidence that you can support yourself during your trip, eg bank statements or payslips from the last 6 months  (Note 'eg' is a Latin abbreviation meaning "for example"; this appears to be optional rather than a fixed requirement.) Question: How should someone interpret this such that the chances of success are maximized? How many statements should I submit? What are they looking for and what do my bank statements tell about me?


My MacBook Pro MacOS High Sierra 10.13.5 Beta (17F66a)  shuts down very time I close my lap top

Every time I close the lid of my Macbook Air, it turns off and I have to manually start it later when I open the lid again.  It also doesn't persist some of my settings such as volume level, desktop layouts (order of screens and which applications are full screened), and command line PATH changes such nvm's currently used node version.  Kind of a "you don't know what you don't know" situation. I'm not sure what to terms to use to search for this kind of behavior.  Edit: Adding some extra information as requested. I am on the following:   13-inch Macbook Air from Early 2014 Mac OS X El Capitan (10.11.6)   In System Preferences > Energy Saver > Battery, I have "Put hard disks to sleep when possible" checked and "Enable Power Nap while on battery power" unchecked.  I've looked through other potentially relevant areas of System Preferences and haven't found anything that works. I've done some Googling, but haven't found anything that is related and I'm unsure of what other terms I could use to search.  Edit 2: The issue seems to have been resolved. There's nothing in particular that I tried that worked, but it's resolved now. Thanks for reading and responding!


Let $a,b,c$ be the sides of a triangle and $a+b+c=3$  Prove that:  $\frac{a}{b}+\frac{b}{c}+\frac{c}{a} \geq \frac{1}{a}+\frac{1}{b}+\frac{1}{c}$  My Attempt   I think this inequality could be proved using the A.M. - G.M. however, I am not sure if I am correct or not. I request someone to please post the solution for the problem as soon as possible.

Give $a, b. c$ be the lengths of a triangle and $a+ b+ c= 3$. Prove that: $$\frac{a}{b}+ \frac{b}{c}+ \frac{c}{a}\geq  \frac{1}{a}+ \frac{1}{b}+ \frac{1}{c}$$ My try  We have England MO inequality: $$\left ( \frac{a}{b}+ \frac{b}{c}+ \frac{c}{a} \right )^{2}\geq  \left ( a+ b+ c \right )\left ( \frac{1}{a}+ \frac{1}{b}+ \frac{1}{c} \right )$$  and $$\frac{a}{b}+ \frac{b}{c}+ \frac{c}{a} \geq  3=  a+ b+ c$$  But it cannot be used to prove the above inequality and how to use triangle inequality in this inequality. I need the help. Thanks!


On what appears to be every other boot of my computer, I find that three service host tasks consume a significant amount of CPU cycles.    If I let the computer sit, untouched, for 10-15 minutes, these three tasks remain the greatest consumers of cpu time.  If I reboot, however, they stop being cpu hogs:    What surprises me is that I can reproduce this behavior by simply rebooting my computer, at which point the three service host tasks will resume their place as top CPU users.  I am looking for suggestions on how to troubleshoot this issue.

I am having a problem with Windows 7. When I boot up, the CPU jumps to 100% execution for about 10-15 minutes. During this time, it is really slow, and if I play any music, the songs play slowly and sound distorted.  I tried to scan my computer with different antivirus programs, I used Spybot, HijackThis, and CCleaner, but I didn’t find anything of note.  I watched the process list in Task Manager and saw that there are two processes that are to blame. There are two copies of svchost.exe, one using ~48% CPU, the second (under the Network Service account) using ~37%. For the first 15 minutes, the CPU runs at about 70-80%, then eventually drops to 30-40%.  I don’t know what to do. I could not find a way to stop the services, and if I try to kill them, sometimes the system crashes.


Hi i am having a two picklist in salesforce  one is on account object and one is on contact object. If i am having a1,a2,a3 as picklist values in both.  if i select a value in contact is a1 and in contact's account is a2 then it must show an error

I'm trying to create a validation rule formula in Salesforce, that uses two picklist fields which have the same values : p1, p2, p3.  One of the picklists is on the account object and the other one on the contact object.  If the selected value on the contact record is p1 and on the contact's account record is p2 then I would like to throw an error.  Any help would be greatly appreciated.


I want to know are they repositories for Ubuntu like for Arch. I mean that for arch all programs you can download it(latest version) from software repositories. But for Ubuntu some aps like Eclipse, i need to download it from official site and when i download it i don't get updates from apt-get. (In official repositories is old version).

I have  about how to upgrade ghostscript to a version that is available on 15.04 but not on 14.04LTS (which I have). On this site there are numerous almost identical question regarding different packages, a few examples include:         So I thought it would be very useful in general to know: is there  a general, automated way to upgrade a package, including all its dependencies, to a version that is newer than Ubuntu's repos? Is this more easily done if the newer version exists in more recent Ubuntu releases?


So how can I prove that there exists a bijection between R (real numbers) and C (complex numbers) I think that I should prove that there exists a bijection between RxR and C which is not too hard and then find a bijection between R  and RxR, but isn't there a simple solution to find a direct bijection between C and R? P.s: I'm in terminal highschool so I'm fairly ignorant about set theory.

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


I'm running Ubuntu 13.04, 64 bit, and I can't install wine.  I've tried the solutions presented  and , but to no avail.    When I use the command sudo apt-get install wine, the terminal returns   Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming.` The following information may help to resolve the situation:  The following packages have unmet dependencies: wine : Depends: wine1.6 but it is not going to be installed E: Unable to correct problems, you have held broken packages.   How can I install wine if these solutions do not work?  EDIT:  It should be noted that I'm dual-booting Ubuntu 13.04 and Win7 EDIT:  By following theseI was able to successfully install wine.  Whether or not this is a result of all of the answers and these results, or just these results, I'm not sure.

Occasionally, when I'm installing stuff, I get an error like the following:  Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  package1 : Depends: package2 (>= 1.8) but 1.7.5-1ubuntu1 is to be installed E: Unable to correct problems, you have held broken packages.   How can I resolve this?


I am having trouble with questions like these: $$\sqrt{x-y\sqrt z}$$ Or as an example: $$\sqrt{17-12\sqrt2}$$ I cannot see how to go about this. I have tried squaring the expression, which ends up giving $\sqrt{289}-\sqrt{288}$, but I do not know where to go from here. Can anybody help?

$$\sqrt[4]{161-72 \sqrt{5}}$$  I tried to solve this as follows:  the resultant will be in the form of $a+b\sqrt{5}$ since 5 is a prime and has no other factors other than 1 and itself. Taking this expression to the 4th power gives $a^4+4 \sqrt{5} a^3 b+30 a^2 b^2+20 \sqrt{5} a b^3+25 b^4$. The integer parts of this must be equal to $161$ and the coeffecients of the roots must add to $-72$. You thus get the simultaneous system:  $$a^4+30 a^2 b^2+25 b^4=161$$ $$4 a^3 b+20 a b^3=-72$$  In an attempt to solve this, I first tried to factor stuff and rewrite it as:  $$\left(a^2+5 b^2\right)^2+10 (a b)^2=161$$ $$4 a b \left(a^2+5 b^2\right)=-72$$  Then letting $p = a^2 + 5b^2$ and $q = ab$ you get  $$4 p q=-72$$ $$p^2+10 q^2=161$$  However, solving this yields messy roots. Am I going on the right path?


If $$C_{0} + \frac{C_1}{2} + \cdots+ \frac{C_{n-1}}{n} + \frac{C_{n}}{n+1} = 0\,,$$ prove that $$C_{0} + C_{1}x + \cdots+ C_{n-1}x^{n-1} + C_{n}x^{n} = 0$$    has at least one real root between $0$ and $1$.   I know how to prove the result by using the mean value theorem, but I am not understanding how the result from the mean value theorem allows us to conclude the final result. What I am asking is how does the existence of an $x \in (0,1)$ such that $f'(x) = 0$ mean that there exists a real root between $(0,1)$? All I can conclude from that is that there is an $x \in (0,1)$  such that the slope is the same as a secant line from the endpoints.

Problem: If   $$C_0+\frac{C_1}{2}+\cdots + \frac{C_{n-1}}{n}+\frac{C_n}{n+1} =0,$$  where $C_0,...,C_n$ are real constants, prove that the equation  $$C_0+C_1x+\cdots +C_{n-1}x^{n-1}+C_nx^n=0$$  has at least one real root between $0$ and $1$.  Source: W. Rudin, Principles of Mathematical Analysis, Chapter 5, exercise 4.


Why the leverage is the diagonal elements of the Hat matrix? I know the meaning of leverage, just do not know the relation with the formula. Any proof? Or intuitive explanation?

What is Hat matrix and leverages in classical multiple regression? What are their roles? And Why do use them?   Please explain them or give satisfactory book/ article references to understand them.


trigger PaymentTrigger on Money_Received__c (after insert, after update, after delete) {      Money_Received__c moneyReceived = [SELECT Reservation__c FROM Money_Received__c];      Reservation__c reservation = [SELECT Id, Name, Total_Recieved__c FROM Reservation__c where Id =: moneyReceived.Reservation__c];     Decimal totalReceived = reservation.Total_Recieved__c;      if(Trigger.IsInsert){         for(Money_Received__c payment: Trigger.new){             totalReceived += payment.Amount_Received__c;         }         update reservation;     }      if(Trigger.IsDelete){          for(Money_Received__c payment: Trigger.old){             totalReceived -= payment.Amount_Received__c;         }         update reservation;     } }   I'm trying to write a trigger that sum up payments.  reservation__c and money_received__c are look-up relationship.  sum of Money_Received__c. Amount_Received__c  should be equal to Reservation__c. Total_Recieved__c.  I wrote this trigger, but gives me an error message saying     PaymentTrigger: execution of AfterInsert caused by: System.QueryException: List has more than 1 row for assignment to SObject Trigger.PaymentTrigger: line 3, column 1   Any suggestions on how to fix this? Also, how do I write 'trigger.updated'?  your help is appreciated.

I am trying to get this trigger to work but it is giving me an error and I am not able to figure out why. The error I am getting is "attempt to de-reference a null object)  Why trigger? We have a Destinations object which is linked to Supplier products object via a lookup relationship. There are two types of supplier products(marketplace and curated) We want to count the number of live Supplier products and put them in a separate fields(live counts for each type).  I have gotten so far to actually count the number of live products and it is giving me an error. Can any one help? I am posting the code below  Trigger code :   trigger NoOfLiveProducts on Supplier_Product__c (after insert, after Delete, after update, after undelete) {       set<string> destinationids = new set<string>();      if(trigger.isInsert) {         for(Supplier_product__c products : Trigger.new) {             destinationids.add(products.Destination__c);         }     } else if(trigger.isDelete) {         for(Supplier_product__c products : Trigger.old) {             destinationids.add(products.Destination__c);         }     }else if(trigger.isUnDelete) {         for(Supplier_product__c products : Trigger.new){             destinationids.add(products.Destination__c);         }      } else if(trigger.isUpdate) {         for(Supplier_product__c products : Trigger.new) {             destinationids.add(products.Destination__c);         }     }      if(destinationids.size() > 0){         Productcounter pc = new Productcounter();         pc.updateproductCount(destinationids);     }    }   Class code :  public class Productcounter {      public void updateproductcount(set<string> productIDs) {           if(productIDs == null){                return;         }          if(productIDs.size() == 0){             return;         }           list<Supplier_Product__c> ProductList = new list<Supplier_Product__c>();         ProductList = [Select ID,Destination__c                     From Supplier_Product__c                     Where Destination__c = :productIDs];          integer totalCount;         map<string, integer> DestinationIDToProductCountMap = new map<string, integer>();                for(Supplier_product__c ProductItem : ProductList){             if(DestinationIDToProductCountMap.containsKey(ProductItem.Destination__c)){                 totalCount = DestinationIDToProductCountMap.get(ProductItem.Destination__c);             }else{                 totalCount = 0;             }             totalCount += 1;             DestinationIDToProductCountMap.put(ProductItem.Destination__c, totalCount);         }          list<Destination__c> DestinationUpdateList = new list<Destination__c>();         Destination__c DestinationTemp;         for(string ProductID : DestinationIDToProductCountMap.keySet()){             DestinationTemp.ID = ProductID;             DestinationTemp.No_of_Live_Curated_Products__c = DestinationIDToProductCountMap.get(ProductID);             DestinationUpdateList.add(DestinationTemp);         }         if(DestinationUpdateList.size() > 0){             update DestinationUpdateList;         }           }           }


I've read about this in so many web sites but none of them explicitly states the difference between URI and URL.  what are the specific differences? and can somebody give me examples for both URI and URL ..

People talk about URLs, URIs, and URNs as if they're different things, but they look the same to the naked eye.  What are the distinguishable differences between them?


I want to put a general 'authorblockA' for every author like this:            THIS IS A TITLE   George Orwel     George Campbell orwel@mail.com   campbell@mail.com      General Georges Asotiation.  Artists and writters Asotiation.    This is what I have so far:  \title{THIS IS A TITLE} \author{     \IEEEauthorblockN{George Orwell}     \IEEEauthorblockA{orwell@mail.com}     \and     \IEEEauthorblockN{George Campbell}     \IEEEauthorblockA{campbell@mail.com} \\     \IEEEauthorblockA{General Georges Asotiation.}     \IEEEauthorblockA{Artists and writters Asotiation.} }   Which produces this (with wrong indentation of the two last fields):

I am in the process of creating a LaTeX template for a conference submission, and up until now I've been working only with the anonymous submissions. Now I need to create the "camera-ready" version, which means I need to add authors to the document.   The template is based on article.cls, with some tweaks to meet the font and formatting specifications. The following image contains the examples from the Word template for the conference:    Basically, I need to be able to bold the author's name (which could I suppose be done manually in the document rather than in the template) and more importantly: divide the authors into two columns, with an optional centered last column with an odd number of authors. The font size of the author block corresponds to my \LARGE defined in the class file.  Are there any packages that facilitate this type of conditional formatting, either in a document, or in a .cls file? How can I use those packages to achieve the formatting I require?


I'm running Ubuntu 14.04 on VirtualBox from Mac OS X and am having no problems running it. I'm just wondering how to change the screen resolution so that the virtualized Ubuntu software fits my computer screen. I used Host F to go to fullscreen mode, but there are black borders on the edges, and I'd just like to get rid of them. Thank you.

I've recently installed Ubuntu on Oracle's Virtualbox.  Now I want to install the guest additions.  I started up my Ubuntu guest OS, clicked "Devices" and chose "Install Guest Additions". Nothing happened, and I don't see the CD icon on my desktop.  How can I make this work?