Does rolling without slipping imply pure rolling? Also please explain what is slipping, skidding, rolling involving and not involving slipping and when to take max or min friction?

Fundamentally, what does a friction force do for a rolling object? I am very confused by the way my textbook explains it. In my textbook , it says:  A wheel rolling on a horizontal flat surface at a constant velocity experiences no friction force. Why?   On the same surface, there is an acceleration of the wheel pointing to the right (probably caused by a force), so the ball is angularly accelerating in the clockwise direction. In this case, a friction force appears, and it is also pointing to the right. How come? What does the friction do for this wheel?  On an inclined plane, a ball freely rolls down the surface. The direction of friction is up the ramp, which confuses me because in the previous example the friction force was in the direction of the wheel's acceleration.   And there is a difference if a wheel is freely rolling and if there is a torque acting on the ball's center of mass. WHY???  What does friction do in these cases? How does it cause an object to roll?


My counterexample I wanted to try is $D_{8}$ and its center $Z(D_{8})$. However, is $Z(D_{8})$ abelian? I am guessing it is because it is cyclic? I am not very knowledgeable with dihedral groups.

it seems like it... should be? In that I can't think of any counterexamples off the top of my head. I was looking up these  and saw the quaternion group, but the subgroups of the quaternion group aren't abelian...


if each user is storing a profile-picture size image (max 9 pictures per user) what is better to use store it ? I can't find related to my question and I can't comment yet.

My question is fairly generic and I know there might not be an 100% answer to it. I'm building an ASP .NET web solution that will include a lot of pictures and hopefully a fair amount of traffic. I do really want to achieve performance.  Should I save the pictures in the Database or on the File system? And regardless the answer I'm more interested in why choosing a specific way.  Many thanks, Stefan   DUPLICATE: , ,  and probably some others.    COMMENT: Thanks for many good answers. I will go for a file based solution even if I like the idea of having a 100% database driven solution. It seems that there are today good solutions to do what I want with databases etc but I have a few reasons for not doing it.   I will be on a hosted solution, I have huge amount of storage(10gb) but only 300mb for the database. It will cost a lot for extra storage in the DB. I'm not an DB expert and as well not in control of settings of the DB. A DB based solution might need custom configuration as it looks like.   If we will move to run the site on our own server I might consider a DB based solution. thanks, Stefan


Ctrl+M creates a math box. I type something like \cdot and it is converted to natural symbols. How can I edit the Latex-code without copying+inserting it to somewhere out of the math box. Deleting and retyping is very annoying. There must be a shortcut to switch between this two views? Or is it possible to turn this automatically converting inside a math box off and do it manually or the other way round?  Note: The Option instant preview under tools/preferences/view & handle/view is already turned off (standard). This has nothing to do with the automatic math box converting.

Is there a way to toggle the display of math expressions in LyX between the default, which makes an attempt at replacing TeX code with easy to read symbols (but is short of actual rendering), and the underlying TeX code?  For example, I'd like the be able to toggle between this    and this


How can I prove that the interval $[0,1]$ is compact in real line topology?  I know how to prove it using concept of boundedness and closedness, but I wish to understand it by using the "open cover" definition of compactness: a set is compact if its every open cover has a finite subcover.  Kindly help me to see the compactness topologically.

Let $[a,b]\subseteq \mathbb R$. As we know, it is compact. This is a very important result. However, the proof for the result may be not familar to us. Here I want to collect the ways to prove $[a,b]$ is compact.   Thanks for your help and any link.


The following question came to my mind:     Let $I$ be the unit interval. Suppose that $X$ and $Y$ are topological spaces such that $X \times I$ is homeomorphic to $Y \times I$. Does it follow that $X$ is homeomorphic to $Y$?   It doesn't look so hard, but somehow I couldn't find a proof or counterexample.  If the answer turns out to be negative, I would be interested in what one should assume about $X$ and $Y$ to make the implication true.  Now reposted at .

I'm trying to find two compact, nonhomeomorphic subsets of the plane, say $X$ and $Y$, such that $X \times [0,1]$ is homeomorphic to $Y \times [0,1]$. I can not think of how a homeomorphism arises when you product with the interval.


I am following a tutorial on wxPython and the tutorial shows the following code:  class Example(wx.Frame):      def __init__(self, parent, title):         super(Example, self).__init__(parent, title=title,             size=(350, 250))   def main():      app = wx.App()     ex = Example(None, title='Sizing')     ex.Show()     app.MainLoop()   if __name__ == '__main__':     main()   I am assuming   if __name__ == '__main__':         main()   is how the main() method is called but I am not really sure. Can someone explain what this bit of code does?

Given the following code, what does the if __name__ == "__main__": do?  # Threading example import time, thread  def myfunction(string, sleeptime, lock, *args):     while True:         lock.acquire()         time.sleep(sleeptime)         lock.release()         time.sleep(sleeptime)  if __name__ == "__main__":     lock = thread.allocate_lock()     thread.start_new_thread(myfunction, ("Thread #: 1", 2, lock))     thread.start_new_thread(myfunction, ("Thread #: 2", 2, lock))


Consider the following hybrid encryption scheme (B3||4 is for concatenated IV and AES-CBC encrypted message):   ------------------------------------------------------------------- |     Encrypted with RSA     | HMAC  |    |                       | |     HMAC_KEY || AES_KEY    |  of   | IV | AES-CBC Encrypted MSG | |   (using PK of recipient)  | B3||4 |    |                       | -------------------------------------------------------------------   Let's say some message was encrypted with AES-128-CBC with a randomly generated secret key and IV. Then the HMAC was calculated for blocks 3-4 concatenated together. And then the HMAC key and AES encryption key was encrypted with RSA using a public key of a recipient (B).  My question is do I need to include HMAC or even any other digest in such a packet that would be transmitted over reliable connection (let's say TCP) from sender (A) to receiver (B)?  Is the following simplified scheme is worse in terms of security?   ----------------------------------------------------------- |     Encrypted with RSA     |    |                       | |           AES_KEY          | IV | AES-CBC Encrypted MSG | |   (using PK of recipient)  |    |                       | -----------------------------------------------------------   My thoughts:   As message will be 100% delivered to a receiver there is not way it can be damaged during the transmission With MITM attack there is no way to alter the encrypted message in a meaningful way so it would be still decryptable with the key from a block 1. There is no better way to manipulate transmitted data then to substitute the whole packet to other one which would hold other message and AES encryption key. In order to prevent altering in the way described above it's enough to sign the AES key in the block 1 with secret key of a sender (and add the signature to the first block). In such a way the receiver can verify that the key was indeed send by the original sender. If with the above tweak MITM would alter 3rd or 2nd block of a packet the decryption would not be possible at all - so there is no way to spoof the message leaving the signed key in the first block as is.   The only thing I can think about is some way to alter the block 3 so it would be still decryptable. Is it possible to accomplish for an attacker?

Suppose there is a message that is encrypted with AES-128-CBC.  The message is as follows, new lines are used to delimit the 16 byte boundary for each block:  Wire funds from: Alice to Bob in   the amount of $ 1   Because this message is encrypted using CBC mode,  any modification of the first block of cipher text would propagate throughout the message.   However, the amount of the fund transfer falls in the last block.  I am under the assumption that an attacker can use the property of  to alter the last block and produce a valid amount that is greater than \$1 in far fewer than $2^{128}$ operations.   Is this a correct assumption?  Is there a name for this attack or do you know of a real world example?    My instinct is that if you just need one byte of the 16 byte block to be of a specific value then it would only require $2^8$ operations because the other 120 bits of the plain text could be any value. For example lets say we wanted the last block of cipher text to decrypt to 9\0 (where \0 denotes a single null byte, and the message would be interpreted as \$9), then it would take only $2^{16}$ operations to find this cipher text block.  Is there something I am missing?


After casting my votes in an election on the network, I had notice popup saying I cast my 3rd vote and thanking me for doing so. However, in the middle of the popup was a visible <br/> tag. See below.

Over on Lifehacks (a beta site with the standard beta template) we're having an election. I just cast my votes and was presented this tooltip:    Please fix the escaped line break tag so it either displays an actual new line or is simply replaced with a space.


Quoting from :     Everything submitted is initially treated like a string, so forcing known-numeric data into being an integer or float makes sanitization fast and painless.   This was the sanitization method I had independently come up with for a quick and dirty query (looking up a name in a table from a numeric ID); the only variable being plugged into the query is the ID, and I know the ID should be greater than zero and less than 255, so my sanitization is as follows (with a little bit of validation thrown in too):  $id = (int)$_REQUEST['id']; if ($id < 1 || $id > 255) errmsg("Invalid ID specified!"); $name = $DB->query("SELECT name FROM items WHERE id=${id}")->fetch_all()[0][0];   Is this sufficient to prevent SQL injection attacks or any other malicious attacks based on the user-specified value of $id, or can it still be exploited?  NOTE: the ID/name are not "sensitive", so if some input inadvertently casts to "1" or another valid ID value, I don't care. I just want to avoid antics along the lines of .

If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example:  $unsafe_variable = $_POST['user_input'];   mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')");   That's because the user can input something like value'); DROP TABLE table;--, and the query becomes:  INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--')   What can be done to prevent this from happening?


We have just created a new website and have submitted a sitemap via google search console. When we run site://example.co.uk the search results have appeared but for some unknown reason they have "Kyle insurance brokers" tagged on the end of the title but there is no reference to that within our site. Why does this happen?

I'm just wondering how it is possible that IGN.com has this in its title tag:      Video Games, Cheats, Walkthroughs, Game Trailers, Reviews, News, Previews & Videos at IGN   while on Google its title is simply "IGN".   How can one achieve such a thing? Does it use some special meta tag I can't see?


The idea is to use a static member function to update the value of a static data member in the same class  template<typename K,typename U> class Map{ private:     static pair<K,U> default_value; public:     static void set_default(K& k,U& u){default_value=make_pair(k,u);} };  int main(){     int a{8};     int b{9};     Map<int,int>::set_default(a,b);     return 0; }   Here I get an error: undefined reference to Map<int,int>::default_value

Can anyone explain why following code won't compile? At least on g++ 4.2.4.  And more interesting, why it will compile when I cast MEMBER to int?  #include <vector>  class Foo {   public:       static const int MEMBER = 1;   };  int main(){       vector<int> v;       v.push_back( Foo::MEMBER );       // undefined reference to `Foo::MEMBER'     v.push_back( (int) Foo::MEMBER ); // OK       return 0; }


So,I am playing a multiclass character with level 14 in fighter and level 1 in Warlock. Now Hexblade's curse damage depends on player's proficiency bonus.My level 15 character's proficiency bonus is +5 but a level1 warlock's proficiency bonus is +2. So, which proficiency bonus should I add as hexblade's curse damage?

When you multiclass, do you only use the highest proficiency bonus of any of the classes you have, do you add together all the proficiency bonuses from any classes you might have levels in or do you use the proficiency bonus that corresponds to your character level from your original class? (For example, a level 13 character starts as a fighter so they use the fighter 13 proficiency bonus.)


I need some help and would love to find a developer to help me figure out how much power can be drawn from the Lightning port for a powered device ... similar to a fan or a camera connected to the Lightning port and how to do it.

How much power can be drawn from the iPhone/iPad lightning connector by a external device?  Update: The use case is a audio-related device for iPhone/iPads. It would require around ~100 mA at 3,3 volts, so I'm trying to find out if we could draw this from the iPhone/iPad. (That would allow us to skip an external battery –> smaller size...)  (This question has been asked for the old 30-pin connector , but a new connector might imply new power constraints.)


I need to prove that $f(x)=1/[|x|(log|x|)^2]$, $0<|x|<1/2$ is Lebesgue integrable. How can I do this? I tried to find inequalities or some good function to majorate this, but I didn't get. Any types?

I'm wondering if it's possible for a function to be an $L^p$ space for only one value of $p \in [1,\infty)$ (on either a bounded domain or an unbounded domain).  One can use interpolation to show that if a function is in two $L^p$ spaces, (e.g. $p_1$ and $p_2$,with $p_1 \leq p_2$ then it is in all $p_1\leq p \leq p_2$).   Moreover, if we're on a bounded domain, we also have the relatively standard result that if $f \in L^{p_1}$ for some $p_1 \in [1,\infty)$, then it is in $L^p$ for every $p\leq p_1$ (which can be shown using Hölder's inequality).  Thus, I think that the question can be reduced to unbounded domains if we consider the question for any $p>1$.   Intuitively, a function on an unbounded domain is inside an $L^p$ space if it decrease quickly enough toward infinity. This makes it seem like we might be able to multiply the function by a slightly larger exponent. At the same time, doing this might cause the function to blow up near zero. That's not precise/rigorous at all though.     So I'm wondering if it is possible to either construct an example or prove that this can't be true.


so today I tried to make an animation got it finished, then started rendering it and it would load a image that had nothing to do with my animation, so there I waiting for like 3 hours to find a 10 second video of that image. Ok so it might be corrupted file but then I rendered it as an image and the images were that odd image... here is the video of what keeps happening:

I have a problem with rendering in cycles. In blender render my object is rendering fine, but in cycles when I pushed F12 I got only this:    One more thing: when I click 0 on keyboard I'm not in camera persp, but in object as camera, it looks like invisible layer, I don't know how to undo this, and be in camera persp again.  Does anybody have any idea how to fix this?


I want to show given that $f:\mathbb{C} \to \mathbb{C}$ is holomorphic then  $g(z)=\overline{f(\overline{z})}$ is also holomorphic. I used the definition of the derivative to write $$g'(z_0)=\lim_{z\to z_0} \frac{\overline{f(\overline{z})}-\overline{f(\overline{z}_0)}}{z-z_0}=\lim_{z\to z_0}\frac{f(\overline{z})-f(\overline{z}_0)}{\overline{z}-\overline{z}_0}.$$ Now I argue that conjugation is continuous so if $z\to z_0$ then $\overline{z}\to \overline{z}_0$, does this mean $g'(z_0)=f'(\overline{z}_0)$?   Since $f$ is differentiable on an open set $U$ then $g$ would be differentiable for $\overline{z}_0\in U$ and also holomorphic.

Prove that the functions $f(z)$ and $\overline{f(\overline{z})}$ are simultaneously holomorphic.   I take this to mean that $f(z)$ is holomorphic if and only if $\overline{f(\overline{z})}$ is holomorphic.  Let $g(z)=\overline{f(\overline{z})}$. Note that $\overline{g(\overline{z})}=f(z)$. So it suffices to prove that if $f(z)$ is holomorphic, then $g(z)$ is holomorphic.  Write $f(z)=u(z)+iv(z)$. Since $f(z)$ is holomorphic, the real and imaginary parts satisfy the Cauchy-Riemann equations:  $$\frac{\partial{u(z)}}{\partial{x}} = \frac{\partial{v(z)}}{\partial{y}}, \frac{\partial{u(z)}}{\partial{y}} = -\frac{\partial{v(z)}}{\partial{x}}.$$  We have $g(z) = u(\overline{z})+i(-v(\overline{z}))$. To prove that $g(z)$ is holomorphic, we must prove that its real and imaginary parts satisfy the Cauchy-Riemann equations:  $$\frac{\partial{u(\overline{z})}}{\partial{x}} = \frac{\partial{(-v(\overline{z}))}}{\partial{y}}, \frac{\partial{u(\overline{z})}}{\partial{y}} = -\frac{\partial{(-v(\overline{z}))}}{\partial{x}}.$$  How can we obtain this from the above relations?


I have this TXT file that is created by a bash script and at the end I want to remove the last line of that file that is an empty one.  head --lines=-1 r3.txt > r4.txt  sed '$d' r3.txt > r4.txt  cat r3.txt | head -n -1  > r4.txt   r4.txt continues to have the last empty line...  I am on a linux CentOS 6.x server.  Does this have anything to do with line endings (unix x windows)?  Any clues?

Some compilers (especially C or C++ ones) give you warnings about:  No new line at end of file   I thought this would be a C-programmers-only problem, but github displays a message in the commit view:  \ No newline at end of file   for a PHP file.  I understand the preprocessor thing explained in , but what has this to do with PHP? Is it the same include() thing or is it related to the \r\n vs \n topic?   What is the point in having a new line at the end of a file?


I installed Ubuntu 12.04 a few days ago but strangely I seem to have skipped the part about choosing to encrypt home folder. Now if it is encrypted I do not know what is the encryption key. How do I check if it is really encrypted? (and also the swap partition).

How do I check if a partition is encrypted? In particular I would like to know how I check if /home and swap is encrypted.


How can I go about drawing a colored box around a column in a matrix with an arrow and text like this:    Here is the code that I have thus far:  \documentclass[11pt]{book}  \usepackage{amsmath,amsfonts,amssymb,amsthm}  \makeatletter \renewcommand*\env@matrix[1][*\c@MaxMatrixCols c]{%   \hskip -\arraycolsep   \let\@ifnextchar\new@ifnextchar   \array{#1}} \makeatother  \usepackage{tikz}   \begin{document}  \begin{equation} \begin{bmatrix}[cccc|c]   1 & 0 & -1 & 0 & 0 \\   0 & 1 & 2 & 0 & 0 \\   0 & 0 & 0 & 1 & 0 \end{bmatrix}\\ \end{equation}  \end{document}

I have a matrix and need to highlight some elements in the matrix. I have found how to highlight a single element (I want to put the cell in the square):  $$ A = \begin{bmatrix} \fbox{0} & \fbox{0} & 0 \\  \fbox{0} & \fbox{0} & 0 \\ 1 & 1 & 1 \\  \end{bmatrix}$$   But how can I outline elements of the submatrix like in the picture below? I need just a frame where some elements are located.


Imagine a very long continuous stick with one end being pushed into the event horizon, all outside observers must agree that this end of the ruler come to a complete halt while I'm still pushing at the opposite end? Question is do I feel any opposite force from the stick while I push the entire stick into this event horizon? The stick is nigh indestructible just for this thought experiment.

The classical explanation of a black hole says that if you get to close, you reach a point - the event horizon radius - from which you cannot escape even travelling at the speed of light. Then they normally talk about spaghetti.  But here's a thought experiment. What if I have a BH with event horizon radius R such that the gravitational gradient at the event horizon is far too weak for creating pasta. I build a Ring with radius R+x around the BH. Then I lower a pole of length x+d from my ring towards the BH, so that the tip passes beyond the event horizon.  Now what happens when I try to pull the pole back?


I have a little problem with my first JOptionPane program. I don't get my if-statements to output anything. What did I do wrong?  package test1;  import javax.swing.JOptionPane;  public class Lol1 {   public void test() {     String res;     res = JOptionPane.showInputDialog("Does this work?");     if (res == "Yes") {         JOptionPane.showMessageDialog(null, "Good.");      }     if (res == "No") {         JOptionPane.showMessageDialog(null, "You're lying.");          } }    public static void main(String[] args) {     Lol1 l1 = new Lol1();     l1.test();     } }

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


I am a newbie in the world of storage and I am having a hard time digesting the physical architecture of some of the RAID levels. I am particularly interested in RAID 10, and 50. I asked the question specifically about RAID 10, because I feel if I understand that, I'll understand the other.  So, I get the definition of RAID 10 - "minimum 4 disks, a striped array whose segments are mirrored". If I've got 4 disks and Disks 1 and 2 are a mirrored pair, and Disks 3 and 4 are a mirrored pair - where does the data get striped?  Thanks.

This is a  about RAID levels.    What are:   the RAID levels typically used (including the RAID-Z family)?  deployments are they commonly found in? benefits and pitfalls of each?


In a battery are electrons generated at the negative electrode due to chemical reactions and do they flow to the positive electrode due to a difference in electronegativity of the electrodes? Is an electric field generated as a result?  I always thought it was due to a difference in charge between terminals which created an electric field from positive to negative, is this wrong?  Thanks

I'm having an hard time understanding primary cells. There are plenty of videos and explanations about the reactions that happen inside the battery, but you must have a strong background in chemistry to really understand them. Instead, I would love to have a description that abstracts from the chemicals details, and still manages to explain its basic working princeples! I would like it to address the following questions/doubts:     Electrons flow form higher potential to lower potential so, when you buy a  battery, is an electric field already there, before connecting it to a wire? (I presume yes) So,How is this field created? Are the electrons at the top and the protons at  the bottom, or just electrons at the top and the bottom is neutral? How are electrons kept together in the same place before connecting the battery  to the wire? What does prevent them to flow inside the battery? How does the battery pump up the electrons? and at which rate? What makes it burn out? and after many cycles does it burn out?       I know there are a lot of questions but my mind is exploding. I don't expect everything to be abstracted from the chemicals but as long as you can through analogies, or intuitive principles, i'd love that. Anyway the main intent of the answer must be addressing the doubts listed.


$$\int\cos^n x \ dx = \frac{1}n \cos^{n-1}x \sin x + \frac{n-1}{n}\int\cos^{n-2} x \ dx$$   is valid for n>1  The derivation of the reduction formula is well-discussed on the forum , but I can't find anywhere explaining why it is only valid for n>1. Can someone explain?

I am trying to prove  $$\int\cos^n x \ dx = \frac{1}n \cos^{n-1}x \sin x + \frac{n-1}{n}\int\cos^{n-2} x \ dx$$  This problem is a classic, but I seem to be missing one step or the understanding of two steps which I will outline below.   $$I_n := \int\cos^n x \ dx = \int\cos^{n-1} x \cos x \ dx \tag{1}$$  First question: why rewrite the original instead of immediately integrating by parts of $\int \cos^n x \ dx$?  Integrate by parts with $$u = \cos^{n-1} x, dv = \cos x \ dx \implies du = (n-1)\cos^{n-2} x \cdot -\sin x, v = \sin x$$  which leads to  $$I_n = \sin x \ \cos^{n-1} x +\int\sin^2 x (n-1) \ \cos^{n-2} x \ dx \tag{2}$$  Since $(n-1)$ is a constant, we can throw it out front of the integral:  $$I_n = \sin x \ \cos^{n-1} x +(n-1)\int\sin^2 x \ \cos^{n-2} x \ dx\tag{3}$$  I can transform the integral a bit because $\sin^2 x + cos^2 x = 1 \implies \sin^2 x = 1-\cos^2 x$  $$I_n = \sin x \ \cos^{n-1} x + (n-1)\int(1-\cos^2 x) \ \cos^{n-2} x \ dx \tag{4}$$  According to Wikipedia as noted , this simplifies to:  $$I_n = \sin x \ \cos^{n-1} x + (n-1) \int \cos^{n-2} x \ dx - (n-1)\int(\cos^n x) \ dx \tag{5}$$  Question 2: How did they simplify the integral of $\int(1-\cos^2 x) \ dx$ to $\int(\cos^n x) \ dx$?  Assuming knowledge of equation 5, I see how to rewrite it as  $$I_n = \sin x \ \cos^{n-1} x + (n-1) I_{n-2} x  - (n-1) I_{n} \tag{6}$$  and solve for $I_n$. I had tried exploiting the fact that  $$\cos^2 x = \frac{1}{2} \cos(2x) + \frac{1}{2} $$  and trying to deal with $\int 1 \ dx - \int \frac{1}{2} \cos (2x) + \frac{1}{2} \ dx$  which left me with $\frac{x}{2} - \frac{1}{4} \sin(2x)$ after integrating those pieces. Putting it all together I have:  $$I_n = \sin x \ \cos^{n-1} x + (n-1) I_{n-2} x \left(-(n-1) (\frac{x}{2} - \frac{1}{4} \sin 2x) \right) \tag{7}$$  but I'm unsure how to write the last few terms as an expression of $I_{something}$ to get it to match the usual reduction formula of   $$\int\cos^n x \ dx = \frac{1}n \cos^{n-1}x \sin x + \frac{n-1}{n}\int\cos^{n-2} x \ dx$$


I am new to Java programming and have a question that I have been curious about. Any help will be appreciated :)  How are private, package-private, protected, and public variables differentiated behind the scenes, so as to keep variables safe?  By safe I mean for example, how does it make sure that private variables are accessible only to methods inside the class?  I want to know what actually happens inside the computer/JVM. Does Java have a different memory space for each of these types? And if so what makes the different memory spaces inaccessible? After all it is still in the memory right?  Thank you in advance :-)

In Java, are there clear rules on when to use each of access modifiers, namely the default (package private), public, protected and private, while making class and interface and dealing with inheritance?


I built an uploader where users can upload their own files. The way I name the saved files is: const fileName = generateRandomString(10) + "_" + file.name; I want to add the file.name so the user can "double-check" that the right file was uploaded when I return the link to them. However, I now ran into some issues that people named their files with spaces or special characters such as ö, ä, or ß which shouldn't be in a URL name. Do you have any advice on how to transform file.name in an URL safe way?

How do you safely encode a URL using JavaScript such that it can be put into a GET string?  var myUrl = "http://example.com/index.html?param=1&anotherParam=2"; var myOtherUrl = "http://example.com/index.html?url=" + myUrl;   I assume that you need to encode the myUrl variable on that second line?


Text mode boot screen shows when the PC is started. (it shows when for some reason, restart was not done safely, but in remote location I must need to boot the PC on power on)    How can I on power ignore this screen and take the default to boot urgent to Ubuntu?

I have Ubuntu Server 11.04, but it is headless (no monitor). The only way I want to be able to access it is remotely via SSH. But, sometimes, say after a power loss, when the server restarts, it will get stuck on the Grub boot menu, and it won't count down. It will just hang there waiting for me to choose the first boot entry. This means I have to go there and plug in a monitor and keyboard.  But I can't do that remotely. How can I force it to continue booting to boot entry 1 (default) regardless of power loss or whatever?


i've got lock screen, I do not know how I got into the phone, and I do not even know how to fix it, is it a virus? please answer, phone isn't rooted

I think my device got a malware. A lock screen with ads sometimes appear, and I must swipe an area at the bottom of the screen to open the phone. I am in Eastern Europe, some ads are in Slavic languages, and they are seemingly related to travel.    Image resized. Click to view the full image  I have seen ads for Lot Air (Polish carrier). I recently went to their site.  Considering my recent surfing activity and the nature of the ads, I guess the malware is connected to airlines active in Eastern Europe.  The lock screen also promotes the app "DU Quick Charger" by claiming it has recharged the phone extra fast during screen off. (!?) It also shows battery level. I have never installed DU Quick Charger. I doubt DU Quick Charger is installed on the phone.  The problem started after installing Ryanair app. The problem is maybe, but not surely, related to this. Uninstalling Ryanair and restarting the phone doesn't remove the occasional appearance of this lock screen. After a while the situation has changed for the worse, now this lock screen appears after EVERY screen off.  I have always used Avast. I am not rooted and only install via Google Play.  What is this? And how do I remove it?


Some accepted answers do not have a valid accept-vote in Votes table, even though the question owner still exists. Stack Overflow alone has over  such answers. A recent example is :  The  says that the answer was unaccepted on July 3, 2014. However, it still has the green checkmark However, the checkmark does not show acceptance time on hover.  Is the answer accepted or not? Is it some kind of ?

My reputation listing is showing that on Mar 4 and 5, some of my answers got unaccepted, but when I go to those answers, they are still showing as accepted -- they still have the green check mark. Can somebody please explain what is happening with my profile?     Here are three of the answers that are listed above:


Let $\{a_n\}n \in \mathbb{N}$ a sequence of non-negative numbers such that  $ \sum_{n=1}^{\infty} a_n <\infty$. Prove that exists a sequence $ \{c_n\}n \in \mathbb{N} $  of non-negative numbers such that $\lim_{n \rightarrow \infty}c_n= \infty$ and  $ \sum_{n=1}^{\infty}c_n a_n < \infty $

Given a real positive sequence $\{a_n\}$ such that $\sum_{i=1}^n a_i$ converges.  Prove that there exists a real sequence $\{c_n\}$ monotonically increasing to $\infty$ such that $\sum_{i=1}^\infty a_nc_n$ converges.  What I have done:  I have written $$\sum_{i=1}^{N+1}a_ic_i=c_{N+1}\sum_{i=1}^{N+1}a_i-\sum_{i=1}^N(c_{n+1}-c_n)S_n$$  and then try to prove the convergence by the Cauchy criterion. However my evaluation is still not good enough. I'm really stuck.


I getting an error when I passing values between two activities using intent. "Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference" first activity intent code  private void add() {     String name = nameAdd.getText().toString();     String date = dateAdd.getText().toString();     Intent intent = new Intent(this,Anniversary.class);     intent .putExtra(NAME,name);     intent .putExtra(DATE,date);     startActivity(intent); }  the second activity where I get the error in .setText private void add() {     Intent intent = getIntent();     String name = intent.getStringExtra(Add.NAME);     String date = intent.getStringExtra(Add.DATE);      Datetxt.setText(date);   // error here     Nametxt.setText(name);   // and here }

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?


I have something like this in my models.py:  class Section(models.Model):     title = models.CharField(max_length=50)  class Lesson1(models.Model):     section = models.ForeignKey(Section)     title = models.CharField(max_length=50)     ...     sort_index = models.IntegerField()  class Lesson2(models.Model):     section = models.ForeignKey(Section)     title = models.CharField(max_length=50)     ....     sort_index = models.IntegerField()   And I need to display them mixed, like this:  section title: -lesson1 title -lesson2 title -lesson1 title  next section title: -lesson2 title -lesson2 title -lesson1 title   Is there a nice way to do this?

I am trying to build the search for a Django site I am building, and in that search, I am searching in three different models. And to get pagination on the search result list, I would like to use a generic object_list view to display the results. But to do that, I have to merge three querysets into one. How can I do that? I've tried this: result_list = [] page_list = Page.objects.filter(     Q(title__icontains=cleaned_search_term) |     Q(body__icontains=cleaned_search_term)) article_list = Article.objects.filter(     Q(title__icontains=cleaned_search_term) |     Q(body__icontains=cleaned_search_term) |     Q(tags__icontains=cleaned_search_term)) post_list = Post.objects.filter(     Q(title__icontains=cleaned_search_term) |     Q(body__icontains=cleaned_search_term) |     Q(tags__icontains=cleaned_search_term))  for x in page_list:     result_list.append(x) for x in article_list:     result_list.append(x) for x in post_list:     result_list.append(x)  return object_list(     request,     queryset=result_list,     template_object_name='result',     paginate_by=10,     extra_context={         'search_term': search_term},     template_name="search/result_list.html")  But this doesn't work. I get an error when I try to use that list in the generic view. The list is missing the clone attribute. How can I merge the three lists, page_list, article_list and post_list?


I am trying to replicate with biblatex a very simple specification that works with bibtex (but I want to migrate to biblatex because it's better). This works fine (which proves as well that my .bib file has no errors): \documentclass[11pt,a4paper]{article}  \usepackage{setspace} \usepackage[a4paper,includeheadfoot,margin=2.54cm]{geometry}  \begin{document}  \title{\vspace{-2.54cm}Simple Test of \texttt{bibtex}} \author{} \date{} \maketitle  Three items are cited: \begin{itemize} \item \textit{The \LaTeX\ Companion} book \cite{latexcompanion} \item The Einstein journal paper \cite{einstein} \item The Donald Knuth website \cite{knuthwebsite} \end{itemize}  The \LaTeX\ related items are \cite{latexcompanion,knuthwebsite}.   \bibliographystyle{plain} \bibliography{sample}  \end{document}  But this won't work: \documentclass[11pt,a4paper]{article}  \usepackage{setspace} \usepackage[a4paper,includeheadfoot,margin=2.54cm]{geometry} \usepackage{biblatex}  \addbibresource{sample.bib}  \begin{document}  \title{\vspace{-2.54cm}Simple Test of \texttt{biblatex}} \author{} \date{} \maketitle  Three items are cited: \begin{itemize} \item \textit{The \LaTeX\ Companion} book \cite{latexcompanion} \item The Einstein journal paper \cite{einstein} \item The Donald Knuth's website \cite{knuthwebsite} \end{itemize}  The \LaTeX\ related items are \cite{latexcompanion,knuthwebsite}.   \printbibliography[title={References}]  \end{document}  The references are undefined. Anyone that can point out to me what I am doing wrong would be doing me a very great favour. My sample.bib file, for what it's worth, is as follows: @article{einstein,     author =       "Albert Einstein",     title =        "{Zur Elektrodynamik bewegter K{\"o}rper}. ({German})         [{On} the electrodynamics of moving bodies]",     journal =      "Annalen der Physik",     volume =       "322",     number =       "10",     pages =        "891--921",     year =         "1905",     DOI =          "http://dx.doi.org/10.1002/andp.19053221004" }  @book{latexcompanion,     author    = "Michel Goossens and Frank Mittelbach and Alexander Samarin",     title     = "The \LaTeX\ Companion",     year      = "1993",     publisher = "Addison-Wesley",     address   = "Reading, Massachusetts" }  @misc{knuthwebsite,     author    = "Donald Knuth",     title     = "Knuth: Computers and Typesetting",     url       = "http://www-cs-faculty.stanford.edu/\~{}uno/abcde.html" }  Thanks!

Running the minimal example  \documentclass{article} \usepackage{filecontents} \begin{filecontents*}{\jobname.bib} @ARTICLE{example,   author  = {Other, Anthony Norman},   title   = {Some things I did},   year    = {2014},   journal = {J.~Irrep. Res.},   volume  = {1},   number  = {1},   pages   = {1-10} } \end{filecontents*} \usepackage[backend=biber]{biblatex} \addbibresource{\jobname.bib} \begin{document} Hello\cite{example}. \printbibliography \end{document}   I get the warning There were undefined references.  I have read  and know that I need to run:   LaTeX Biber LaTeX   However, my editor is only set up to run BibTeX. How do I go about setting up my editor/IDE to be able to run Biber, and how do I run the LaTeX/Biber/LaTeX cycle?  Answers (sorted alphabetically by editor name)                    Answer guidelines   Each answer should be for one editor. If the editor is cross-platform, if possible give a single answer with notes covering the minor platform variations. Please edit the question to include new answers in the 'link list' Each answer should be 'stand alone', i.e. don't say 'It's almost the same as editor Y but ...' for the editor part Instructions for 'build tools' such as arara or latexmk are welcome but should explain how to set up the editor in question as not all editors allow simple addition of arbitrary tools


I am trying to find all of the files that are named, in the directory that I have chosen. The code that I have works when I do something like C:\Program Files, or C:\Users. But when I do c:/ I get stuck in the recycle bin and get a java.lang.NullPointerException and stops at c:\$Recycle.Bin\S-1-5-21-1478355014-127360780-1969717230-1002144.  public void DirectorySerch(String target, String dirName){     File f = new File(dirName); System.out.println("H");     if(!f.isDirectory()){         throw new IllegalArgumentException("that is not a valid directory");     }     for(File folderItem : f.listFiles()){         if(folderItem.isDirectory()){             System.out.println(folderItem.getAbsolutePath());             if(!folderItem.equals("")){                 DirectorySerch(target,folderItem.getPath());             }             // Return the result if it is not empty             /*  if (!result.equals(folderItem.getName())){             files[filesFounfd] = folderItem.getAbsolutePath();             filesFounfd++;             }*/         }else{             if(folderItem.getName().equals(target)){                 files[filesFounfd] = folderItem.getAbsolutePath();                 System.out.println(folderItem.getAbsolutePath());                 filesFounfd++;             }         }             } }   What can I do to not get this issue as it works in cases when it does not have to deal with the recycle bin?


I am communicating to a REST server which is expecting something like http://example.com/1.0/editor/5/bla/26 along with body parameters of x, y, and z.  Or maybe instead of /1.0/editor/5/bla/26, it should be 1.0/editor/5/bla/what about item #26, but of course with what about item #26 escaped.  There are many post describing how to use  to encode parameters, however, that is not my question.  How chould the actual url be created using jQuery of JavaScript?  $.ajax({     type:'PUT',     url:'/1.0/editor/'+$('#id').val()+'/bla/'+$('#wha').data('id'),     data:{x:x,y:y,z:z},     success: function (error){} });


I have read    that there are differences between the multitude of dots commands that TeX and amsmath offer. However, I am not sure up to this day when to use which, and how critical it really is whether I use the correct one or not.  The document  by Herbert Voss points out:     It is not easy to see the differences between some of them.   That obviously does not help me any further.  Could you provide some explanation for each of the commands, and in which context to use them for the rest of us? Further, some example explaining how big the difference between the commands really is would be great.

Is there a difference between \dots and \ldots, the ellipsis?  If yes: Which? When to use \dots and when to use \ldots?  If no: Why are there both at all?


Let $a_0=1$, $a_1=1$ and $a_{n+2}=\frac1{a_{n+1}}+\frac1{a_n}$ for every natural number $n$. How can I prove that this sequence is convergent?    I know that if it's convergent, it converges to $\sqrt2$ since if $\lim\limits_{n\to\infty}a_n=a$ then: $$\lim_{n\to\infty}\left(a_{n+2}-\frac1{a_{n+1}}-\frac1{a_n}\right)=a-\frac2a=0$$ $$\therefore\quad a^2=2$$ Now it's easy to see that every $a_n$ is positive, so $a\ge0$ and thus $a=\sqrt2$.  Assuming the sequence is convergent, I can calculate an estimation of the rate of convergence too. Let $\epsilon_n:=a_n-\sqrt2$. We have: $$\epsilon_{n+2}=\frac1{a_{n+1}}-\frac1{\sqrt2}+\frac1{a_n}-\frac1{\sqrt2}=-\frac{a_{n+1}-\sqrt2}{\sqrt2a_{n+1}}-\frac{a_n-\sqrt2}{\sqrt2a_n}=-\frac{\epsilon_{n+1}}{\sqrt2a_{n+1}}-\frac{\epsilon_n}{\sqrt2a_n}$$ Now because $a_n\sim\sqrt2+\epsilon_n$ and $\lim\limits_{n\to\infty}\epsilon_n=0$, therefore from the above equation: $$\epsilon_{n+2}\lesssim-\frac{\epsilon_{n+1}+\epsilon_n}2$$ which yields $\epsilon_n\lesssim\alpha\left(\frac{-1-\sqrt7i}4\right)^n+\beta\left(\frac{-1+\sqrt7i}4\right)^n$ for some constants $\alpha$ and $\beta$, using induction on $n$. Hence $\frac1{\sqrt2}$ is a good estimation for the rate of convergence since $\left|\frac{-1\pm\sqrt7i}4\right|=\frac1{\sqrt2}$. (Edit: Thanks to @AlexRavsky for his confirming graphs.)  Edit (some more of my thoughts):  Let $b_n:=\min\left\{a_n,a_{n+1},\frac2{a_n},\frac2{a_{n+1}}\right\}$. It's easy to see that $b_n\le a_n\le\frac2{b_n}$ and $b_n\le a_{n+1}\le\frac2{b_n}$. Now using induction we can prove that $b_n\le a_{n+m}\le\frac2{b_n}$. Especially, $a_{n+2}\ge b_n$ and $\frac2{a_{n+2}}\ge b_n$ which yields $b_{n+1}\ge b_n$. The problem can be solved if I show that the sequence $\left(b_n\right)_{n=0}^\infty$ increases to $\sqrt2$.

I have a sequence defined by $$ a_1=1,\quad a_2=1,\quad a_n=\frac{1}{a_{n-1}}+\frac{1}{a_{n-2}}\text{ for } n\ge2. $$ Now, if $\lim_{n\to \infty}a_n=g$ then $\lim_{n\to \infty}a_n=\lim_{n\to \infty}\Bigl(\frac{1}{a_{n-1}}+\frac{1}{a_{n-2}}\Bigr)=\frac{2}{g}$ so $g=\sqrt{2}$ or $g=-\sqrt{2}$ but $a_n>0$ so $g=\sqrt{2}$.  Now, how do I prove that it has an actual  limit? Also, it can be proven that $1\le a_n\le2$, and it's not monotonic because $a_4 \gt a_5 \lt a_6$. Also, it's not monotonic after some $N\in\mathbb N$


I'm using Ubuntu GNOME 16.10 and was trying to install WPS Office. I tried to install using software centre But it wasn't installing without giving any error logs. Then I opened it with Gdebi installer. Here is what I saw.    I have already trying enabling multiverse repositories.  Edit: I have downloaded the amd64 package from the WPS official site, but even now installing through terminal I still get the missing dependencies error.

I tried to install WPS Office on my laptop (ubuntu 16.10 Gnome, 64 bit) with  Gdebi installer but it said   Dependency is not satisfiable: libpng12-0   Then I tried to open this library as follows  sudo apt-get install libpng12-0   But I encountered an error:  Reading package lists... Done Building dependency tree        Reading state information... Done Package libpng12-0 is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source  E: Package 'libpng12-0' has no installation candidate   Can anyone help? Thanks a lot


I am attempting to give a player a named diamond sword using this command: /give @p diamond_sword 1 0 {display{name:"Burn"}}  But I'm getting the following error: Syntax error: Unexpected "{": at "0 {display>>{<<name:"Burn"  This happens on both Minecraft Pocket Edition and Minecraft PC. Can someone help me fix this? I really want to know how to use these and I haven't used command blocks untill now.

This question was recently split into different questions for each workaround. See   meta posts for more information.   Can you use NBT tags in commands? I’ve tried commands that normally work in Java Edition like: give @s minecraft:planks 30 1 {display:{Lore:["Wooden planks"]}} give @s stone_pickaxe{Unbreakable:1b} give @s item_frame{EntityTag:{Invisible:1b}} summon villager ~ ~ ~ {Offers:{Recipes:[{buy:{id:"emerald",Count:5b},sell:{id:"diamond_sword"}}]}} summon tnt ~ ~ ~ {Fuse:20s}


I want to split the text from the following to given format. My string format is id,quantity|id,quantity|id,quantity  Example:1,3|2,4|3,6|4,0  I want it in the below format:  Id     |       Quantity 1      |       3 2      |       4 3      |       6 4      |       0    I need exactly query to get the above result:  ANSWER IS AS BELOW  IF EXISTS ( SELECT * from dbo.sysobjects WHERE id = object_id(N'[dbo].[doubleSplit]')          AND OBJECTPROPERTY(id, N'IsTableFunction') = 1 ) DROP FUNCTION [dbo].[doubleSplit] GO CREATE FUNCTION dbo.doubleSplit (      @sourceString varchar(MAX),     @primaryDelimiter varchar(100),     @secondaryDelimiter varchar(100) ) RETURNS @tblArray TABLE    ( Id smallint IDENTITY(1,1), InventoryId varchar(MAX), Quantity varchar(MAX)   ) AS BEGIN  DECLARE @primaryIndex smallint DECLARE @secondaryIndex smallint DECLARE @primaryStart smallint DECLARE @secondaryStart smallint DECLARE @primaryDelimiterSize smallint DECLARE @seondaryDelimiterSize smallint DECLARE @primaryElement varchar(MAX); DECLARE @seondaryElement varchar(MAX); SET @primaryDelimiterSize = LEN(@primaryDelimiter) SET @seondaryDelimiterSize = LEN(@secondaryDelimiter) --loop through source string and add elements to destination table array WHILE LEN(@sourceString) > 0 BEGIN     SET @primaryIndex = CHARINDEX(@primaryDelimiter, @sourceString)     IF @primaryIndex = 0     BEGIN         SET @secondaryIndex = CHARINDEX(@secondaryDelimiter, @sourceString)         IF @secondaryIndex = 0         BEGIN             INSERT INTO @tblArray (InventoryId, Quantity) VALUES(@sourceString, '')         END         ELSE         BEGIN             SET @secondaryStart = @secondaryIndex + @seondaryDelimiterSize;             INSERT INTO @tblArray (InventoryId, Quantity)              VALUES(SUBSTRING(@sourceString, 1, @secondaryIndex - 1),                     SUBSTRING(@sourceString, @secondaryIndex + @seondaryDelimiterSize, LEN(@sourceString) - @secondaryStart + 1))         END         BREAK     END     ELSE     BEGIN         SELECT @primaryElement = SUBSTRING(@sourceString, 1, @primaryIndex - 1);         SET @secondaryIndex = CHARINDEX(@secondaryDelimiter, @primaryElement)         SET @secondaryStart = @secondaryIndex + @seondaryDelimiterSize;         INSERT INTO @tblArray (InventoryId, Quantity)          VALUES(SUBSTRING(@primaryElement, 1, @secondaryIndex - 1),                 SUBSTRING(@primaryElement, @secondaryIndex + @seondaryDelimiterSize, LEN(@primaryElement) - @secondaryStart + 1))         SET @primaryStart = @primaryIndex + @primaryDelimiterSize         SET @sourceString = SUBSTRING(@sourceString, @primaryStart , LEN(@sourceString) - @primaryStart + 1)     END END RETURN END GO  SELECT Id,Quantity FROM dbo.doubleSplit('1,3|2,4|3,6|4,0|','|',',')

Using SQL Server, how do I split a string so I can access item x?  Take a string "Hello John Smith". How can I split the string by space and access the item at index 1 which should return "John"?


Why was the Ministry just questioning Harry in part 5 about the Dementors instead of trying Legilimens, as the Dementors were also shown in the movie when Snape performed the same on Harry?

It seems to me that Harry could have saved himself a lot of grief if he had allowed people to see his memories (either through extraction or Occlumency). For instance:   He could have proved Lucius Malfoy placed the diary in Ginny's basket. He could have proved Sirius's innocent (with the memory of Wormtail's confession). Most importantly, he could have proven Voldemort was back.    Maybe it would have made for a less exciting story, but it sure would have made his life easier.


Let $S$ be bounded in $\mathbb{R}^n$, let $f:S\rightarrow \mathbb{R}$ be bounded continuous function. Give an example where $\int_{\mathrm{Int} S} f$ exists and $\int_S f$ does not.   Notice this is not the same as given $\int_\bar{S} f$ exists and $\int_S f$ not.  I think the key is the following theorem:  Let S be bounded on $\mathbb R^n$, $f:S\to \mathbb R$ be bounded continuous. Let $E$ be the set of points $x_0$ of $\partial S$ (the boundary of $S$) for which $$\lim_{x\to x_0} f(x) \ne 0$$ fails to hold. Then $f$ is integrable over S if $E$ has measure zero.

In the book of Analysis on Manifolds by Munkress, at page 121, it is asked that     Let $A$ be a bounded open set in $\mathbb{R}^n $; let $f: \mathbb{R}^n > \to \mathbb{R} $ be a bounded continuous function. Give an example   where $\int_{\bar A} f$ exists but $\int_A f$ does not.   I couldn't find any such example. I mean I do noticed that $A$ should not be rectifiable, and the only way I can think of that $f$ is not integrable on $A$ is that the set $E$ where the limit  $$\lim_{x \to x_0} f(x) = 0$$ fails for $x_0 \in \partial A$ has a non-zero measure, but then this set $E$ also contained in $\bar A$, so in such a case $\int_{\bar A} f$ also wouldn't exists.  In short, I'm looking for such an example.  Note: I have read  answer, but I have no idea what the answerer is talking about, so I wanted to ask a new question including my own thoughts.


On 11.1.21. I'm going to start working with a Jamaican learner of English to support her with her spoken and written English. I understand that θ and ð may be difficult for her to say, but please can anyone identify any other sounds that may be challenging for her? I want to be well-prepared for our meeting so I can be as helpful to her as possible. I believe she was brought up speaking Jamaican Patois. Is she likely to find any particular aspects of English grammar difficult? If anyone's able to throw any light on these questions, I'd be very grateful!

I'll soon be supporting a speaker of Jamaican Patois with her spoken and written English. (I'm in the UK) I understand that the sounds /θ/ and /ð/ are not used in Jamaican Patois, but would like to know if there are any other sounds that may be difficult? Also, what aspects of English grammar are likely to be tricky for her?  Can you recommend any useful resources to support her learning? If anyone can throw any light on these questions, I'd be very grateful, as I'd like to be as helpful to her as possible.  Many thanks!


I know that $\langle \{(123…n),(12) \}\rangle  \subset S_n$. I was thinking that if I could show that $\langle \{(123…n),(12)\} \rangle $ contains all the transpositions of $S_n$ then it would contain $S_n$. How would I go about showing this?

How can you prove that $S_n$ is generated by $(1\space 2)$ and $(1\space 2\space 3\space ... \space n))$ for $n\geq 2$?


Why is it not possible to cover the chess board with 3X1 dominoes if one of the corner squares is missing (e.g. the top right square)?

If we remove the square in the upper right corner of a $8\times 8$ chessboard.  The question is: Is it possible to cover the entire remaining area, with $1\times 3$ chocolate bars? (they can be laid on the chessboard vertically and horizontally aswell)  For the answer: We know that there will be $63$ squares left on the chessboard, of which $32$ are white and $31$ are black, since the one in the upper right corner was black. $63$ is divisible by $3$, so it could be possible to cover the area, but that doesn't prove that an arrangement exists to do it. I'm not sure how to continue and am seeking help. Thanks.


I'm having this dilemma regarding the result for Database.Upsert(List, boolean).   Database.Upsert returns Database.UpsertResult and it provides as the Id of the record that was successfully inserted/updated.  However, if an ERROR happens during Insert, when you try to get the Id in UpsertResult via getId() function, you will see that the Id is NULL.  Now I understand this part because the record does not yet exist in DB but I need to return the UpsertResult to another method that needs to know which record failed.  Ex:  List<Asset> finalAssetList = new List<Asset>();     //Loop exists here that fills up finalAssetList      List<Database.UpsertResult> upsertAssetResult = Database.upsert(finalAssetList, false);     List<ResultMessage> rmList = new List<ResultMessage>();     for(Database.UpsertResult ur : upsertAssetResult) {         ResultMessage rm = new ResultMessage();         rm.error_message = ur.getErrors();         rm.recordId = ur.getId();         rmList.add(rm);     }      return rmList;   Please take note that ResultMessage is an inner class whose variables are recordId and error_message.  If an Error happens during Insert, my rmList will contain a record with NULL in its recordId.   Is there any way that I can circumvent this?  Thanks.

I am upserting list of records based on externalId as follows:  List<Database.upsertResult> results = Database.upsert(lstRecords, CustomObject__c.External_Id__c,true);   The results returns as follows:  (Database.UpsertResult[getErrors=();                         getId=a1k0j000000P6CmAAK;                         isCreated=true;                         isSuccess=true;],   Database.UpsertResult[getErrors=();                         getId=a1k0j000000P6CNAA0;                         isCreated=false;                         isSuccess=true;])   The first record is inserted and 2nd record is updated.  Since I am upserting based on externalId, I need to know for which ExternalId the records have been successfully inserted or updated.   doesn't expose any methods. It returns SalesforceId and NOT externalId  I need a results structure like this:  (Database.UpsertResult[getErrors=();                         getExternalId = '1234';                         getId=a1k0j000000P6CmAAK;                         isCreated=true;                         isSuccess=true;],   Database.UpsertResult[getErrors=();                         getExternalId = '1235';                         getId=a1k0j000000P6CNAA0;                         isCreated=false;                         isSuccess=true;])   What would be the best way to achieve this.


As per title, how can I forward all the emails I’m receiving? I have tried the rules option, but I can’t select all the incoming mails and I cannot find an appropriate action to forward to another email.

How do I make the out-of-office option visible in Lotus Notes?   It was usually available under the Tools drop down but now only Preferences is visible under this drop-down.  I am using Lotus Notes 8.5.


ORIGINAL QUESTION:  When I try to mount an ISO file using:   Right click the file and select [Open With] > [Archive Mounter] Right click the file and select [Open With] > [Disk Image Mounter] [gnome-disk-utility] > [Disks] > [Attach Disk Image] sudo mount -o loop '/media/oshirowanen/250GB.iso' /media/iso   I get the following error message for attempts 1, 2, 3, and 4:  Unable to access “New Volume” Error mounting /dev/loop10p1 at /media/oshirowanen/New Volume: Command-line `mount -t "ntfs" -o "uhelper=udisks2,nodev,nosuid,uid=1000,gid=1000" "/dev/loop10p1" "/media/oshirowanen/New Volume"' exited with non-zero exit status 21: ntfs-3g-mount: mount failed: Permission denied Failed to sync device /dev/loop10p1: Input/output error Failed to close volume /dev/loop10p1: Input/output error   Anyone know how to resolve this?    UPDATE 1:   sudo mount -o ro,loop /media/oshirowanen/250GB.iso /media/iso   The following error is given for attempt 5:  mount: wrong fs type, bad option, bad superblock on /dev/loop12,        missing codepage or helper program, or other error         In some cases useful info is found in syslog - try        dmesg | tail or so.     Possible useful info  The iso was created from an ntfs drive using the command  sudo dd if=/dev/sde | pv | sudo dd if=/media/oshirowanen/250GB.iso

I made an image of my entire disk with  dd if=/dev/sda of=/media/external_media/sda.img   Now the problem is I'd like to mount an ext4 filesystem that was on that disk but  mount -t ext4 -o loop /media/external_media/sda.img /media/sda_image   obviously gives a superblock error since the image contains the whole disk (MBR, other partitions) not just the partition I need. So I guess I should find a way to make the disk image show up in the /dev/ folder...  Does anyone know how to do that?  PS: I can always dd back the image to the original disk, but that would be very inconvenient (I updated the OS and I'd like to keep it as it is)


I would call this a curiosity more than a problem or anything else:  When using diff on two specific PDF files that are similar but not the same, I get some garbage dumped on the next command line.  For comparison, if I use two completely different files, I would get something like this  $ diff file1.pdf file2.pdf Binary files file1.pdf and file2.pdf differ   However, when used on the files in question:  $ diff version1.pdf version2.pdf | head 13,15c13,15 <          <xmp:CreateDate>2017-07-17T09:04:45-07:00</xmp:CreateDate> <          <xmp:MetadataDate>2017-07-17T09:06:06-07:00</xmp:MetadataDate> <          <xmp:ModifyDate>2017-07-17T09:06:06-07:00</xmp:ModifyDate> --- >          <xmp:CreateDate>2017-07-17T09:05:14-07:00</xmp:CreateDate> >          <xmp:MetadataDate>2017-07-17T09:06:04-07:00</xmp:MetadataDate> >          <xmp:ModifyDate>2017-07-17T09:06:04-07:00</xmp:ModifyDate>   [long output of differences removed]  > 0018068809 00000 n > 0018069141 00000 n > 0018073003 00000 n %%EOF189f22/Root 1 0 R/Info 321 0 R/ID[<1D82D53AF59549CBACDAEB25B1EED3D4><4527C00DC1904519AEFEA4304FBA532E>]>> \ No newline at end of file $ 1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;1;112;112;1;0x1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c1;2c   The files are obviously different, but why should anything come out on the next command line? Should this be considered a bug with diff?  I couldn't find anything relevant except  (I thought it was relevant because (a) it's also related to PDF files and (b) the garbage output looks similar).  If you're curious about the actual files in question, they came from  ( and ).  UPDATE: As suggested in the comments by @cas and @thecarpy, this is related to , because if I do $ cat file1.pdf, I get a very similar situation as when using diff.  However, there seems to be a difference (if I understand correctly) in what the OP of that question considers to be "messed-up terminal": I also tried $ cat img.png, and I got , because, no doubt, of content in the binary file that matched control codes; but in my question, characters are entered into the command line after the diff (or cat) process is terminated. This also seems to me to be contradicting @x-tian's accepted answer to that question (that you need to pipe for commands to be interpreted).  To make the question more specific and more explicit: why is this happening exactly (i.e., what causes this)? If there's a pattern in the PDF file of the form  ******** X 1;2c1;2c1;2c1;2c1......  where X is a control sequence that causes process to exit back to command line, what is X?

If I understand the cat manual correctly:       concatenate files and print on the standard output   cat will take files as argument and print them on standard output. What I don't get is if I use the command:    cat img.png > copy.png   I will obtain 2 png files identical while if I just    cat img.png     I have all chance that my terminal get messed up and misinterpret what I type.     How's that possible?   Binary values are still binary data. Why it does not simply shows a series of 0 and 1 or the interpretation of those binary data in ASCII or whatever the encoding in terminal is?   Is this behavior also possible by cating a text file containing strange characters?   Should a mechanism to prevent this behavior  like try{}catch{} statement should be implemented?


I am new to Linux. I am getting warning message every time saying my boot partition is having low memory. Following are the contents of my /boot.   ls /boot/ abi-4.10.0-28-generic         initrd.img-4.13.0-37-generic abi-4.10.0-40-generic         lost+found abi-4.10.0-42-generic         memtest86+.bin abi-4.13.0-26-generic         memtest86+.elf abi-4.13.0-32-generic         memtest86+_multiboot.bin abi-4.13.0-36-generic         retpoline-4.13.0-36-generic abi-4.13.0-37-generic         retpoline-4.13.0-37-generic config-4.10.0-28-generic      System.map-4.10.0-28-generic config-4.10.0-40-generic      System.map-4.10.0-40-generic config-4.10.0-42-generic      System.map-4.10.0-42-generic config-4.13.0-26-generic      System.map-4.13.0-26-generic config-4.13.0-32-generic      System.map-4.13.0-32-generic config-4.13.0-36-generic      System.map-4.13.0-36-generic config-4.13.0-37-generic      System.map-4.13.0-37-generic efi                           vmlinuz-4.10.0-28-generic grub                          vmlinuz-4.10.0-40-generic initrd.img-4.10.0-28-generic  vmlinuz-4.10.0-42-generic initrd.img-4.10.0-40-generic  vmlinuz-4.13.0-26-generic initrd.img-4.10.0-42-generic  vmlinuz-4.13.0-32-generic initrd.img-4.13.0-26-generic  vmlinuz-4.13.0-36-generic initrd.img-4.13.0-32-generic  vmlinuz-4.13.0-37-generic initrd.img-4.13.0-36-generic   Please advise how can I clean my /boot partition as I have no idea what these files do.  OS: Ubuntu 16.04

Every time I install a new Linux kernel, it gets left in the grub_config, making the boot menu longer each time.    I know I can manually search through the installed packages and remove them.  Does Ubuntu provide any easier way to clean them up or keep them from showing in the boot list?


I have a unique 6 digit number that I am generating a IV from. I am trying to make it as unique as possible. From my programming, I am able to get it down to only have 100 duplicate IVs per unique 6 digit number. Now I have read that reusing IV's is a big no no because it leaks information. My question now, assuming I am only using 1 key and if someone has gained access to my database of 1 billion records and has the encrypted string as well as the IVs. If each IV is only reused 100 times, would they be able decrypt the encrypted string based off only that information? If so, how would they be able to?

I'm doing a code review for a crypto solution that reuses the same key with a constant IV.  I want to demonstrate that this is not the right way to do things by figuring out the key and decrypting all of their test data.   I have access to lots of ciphertext. I know the same key is used. I know the same IV is used. Cipher is AES/CBC/PKCS5 Plaintext is 16 bytes. Ciphertext is 32 bytes (PKCS5 padding?) I can put whatever plaintext I want through the system and then get that ciphertext.   What's the high-level pseudo code or process to break this system?


It's nice that SO offers this cute little feature called Winter Bash as you all might have notice.   I am only a new user so my question here is to the old timers:   Did you guys use to have something similar in this past Winters? Or is this the first time ever?  My another question here is: is it possible to submit a request for this feature, a feature that allows the user to at least drag and move around the Hat Image over one's profile picture a little bit as to adjust the hat position?  It would be nice, because some of the users I have seen with hats have their hats positioned in a way it covers the eyes or partially of them, which reminds me of Audrey Hepburn's Image in "Breakfast' at Tiffany's".  Happy Holidays to everyone.

The hats seem to be designed for passport-photo-like avatars. Perhaps it would be better if you could choose where exactly it fits?


I have seen Inception many times. Every time I come with a new conclusion. What I feel is that he is in dream right from the beginning, when he comes to meet syto. But, this is also confusing that he see's his children's face at the end but still at the end Totem is still spinning. Any one with the answer.?

Sorry for the vague title--I don't want the title to be a spoiler.  I've seen the movie three times, and the last two times I looked specifically for clues to this question, but found none.  The final scene in  shows       Cobb's top spinning, as he goes off to be reunited with his children.  The top continues to spin, then the movie ends, without telling us if the top topples--and therefore revealing whether he's in the "real world" or still in a dream. Do we know if he was in a dream at the end of the movie?   I'm assuming the answer is that we simply cannot know.  But did I miss anything?  Were there clues that I missed?


If I run the following command on Ubuntu 14.10:  sudo dd if=/dev/zero of=/dev/sdb bs=1M count=100   It effectively erases my SD card.  If I run the exact same command on Ubuntu 16.10 (or 16.04), nothing happens. I've tried it on two different Ubuntu 16 machines. Literally nothing happens. I see the same dd output, but when I unplug and plug the SD card back in all the folders are still there, the partition is still there, everything.  Does anyone have insights as to how this could happen?  Edit:  As per request:  user@cobalt:~/Desktop$ sudo parted /dev/sdb print Model: Generic- SD Card (scsi) Disk /dev/sdb: 7948MB Sector size (logical/physical): 512B/512B Partition Table: msdos Disk Flags:   Number  Start   End     Size    Type     File system  Flags  1      1049kB  7948MB  7947MB  primary  ext4

I have a MicroSD card reader in my notebook. When I insert a MicroSD memory card into it, I can't write any data on it - it's read-only. The same thing happens when I try to do it under root. And I can't change the permission policy for it. This problem happens for all microSD cards (I've tested 2 cards). I've encountered it on Ubuntu 12.04 LTS, now I'm on Ubuntu 12.10, the problem is still on it's place. When I try to insert such a "read-only" card in my mobile phone, everything's OK and I can write data on it. So, can anybody tell me, how can I write a data onto the card?  UPD: here's fdisk -l output:  Disk /dev/sdc1: 2013 MB, 2013135360 bytes 62 heads, 62 sectors/track, 1022 cylinders, total 3931905 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000   Device Boot      Start         End      Blocks   Id  System   The file system of the card is msdos. As to me it's weird.   UPD2: I've found a small "lock" switch on my card adapter, and it turns out, that when I insert it in my notebook, it switches on. Perhaps, I have to find some glue or something to get that switch stuck...  UPD3: There was no glue near me, so I've decided to buy another card-reader.


Here is my problem and I have never seen this before in Blender:  I'm making a Minecraft Animation and on multiple frames there are unrendered transparent pixels scattered across the image (resulting in black spots). I have googled around and only found answers related to Cycles render which doesn't apply to my situation as I use Blender Internal.  I made a video explanation to show in detail what is happening:    UPDATE: Thank's all those who helped me out. It turned out to be a problem with "Auto Ray Bias." This thread answered my problem.

This is my Minecraft Animation. It is made in Blender Internal and is intended to be rendered in Blender Internal. The animation consists of me running infront of Minecraft trees. These trees are mapped with UV textures of Minecraft Leaves with alpha turned on so that the leaves are transparent in places. The Animation starts at frame 8 and ends at 40. This is not a case Z fighting.  However when I render the animation I get square alpha (sometimes black pixel) artefacts in the render. Every frame has diffrent result but still has the artefacts. This is what it looks like. The white is the alpha. Open in a new tab for closer inspection.    As I said some frames have this problem and some don't    This one has AA disabled. This makes the alpha only one pixel each. (Open in new tab to see individual pixels)   This problem does not occur in the rendered mode viewport.   Leaves' Material Settings     Leaves' Texture Settings     Edit: I decided to restrict the leaves from render and this is the result I have. Pretty ugly. Also added, glare and vector nodes just fyi.    I then decided to remove the wood as well and now this happened.    And now there's black and alpha.    Here is a link to a  showing the problem.  What is going on here! Is this blend file corrupted? Please if you know the answer or what causes this please mention this down below.  And because you asked here a stripped down version of the file:


Class1.java  public List<UMRDTO> getDocumentationList(Session session) {     List<UMRDTO> documentationList = null;      try     {         Query query = null;         query        = session.createQuery(UMRSQLInt.DOCUMENTATION_LIST);         documentationList = query.list();     }      return documentationList; }   I need to use the documentationList that is returned to a static method in this like but getting error like non static method cannot be refrenced from static context  class2.java  static { UMRMetadataSupportDAOImpl d=new UMRMetadataSupportDAOImpl();     listDocuments= d.getDocumentationList(); //error here     for (UMRDocumentationDTO listDoc: listDocuments)     {         if(listDoc.equals(MMTConstantsInt.DOMAIN_NAME))             domainDocumentationMap.put(listDoc.getId().getObjectName(), listDoc.getDocumentationLink());         else             domainComboDocumentationMap.put(listDoc.getId().getObjectName(), listDoc.getDocumentationLink());     }

The very common beginner mistake is when you try to use a class property "statically" without making an instance of that class. It leaves you with the mentioned error message:     You can either make the non static method static or make an instance of that class to use its properties.   Why? I am not asking for solutions. I would be grateful to know what is the reason behind it. The very core reason!  private java.util.List<String> someMethod(){     /* Some Code */     return someList;             }  public static void main(String[] strArgs){                // The following statement causes the error. You know why..     java.util.List<String> someList = someMethod();          }


It said cannot find mismatch id.  Now I am logged using a Facebook account.   App Version: 1.0.95 Device Manufacturer: Xiaomi Device Model: Redmi Note 3 OS Version: 7.1.2 (f31aab0341)

I tried logging in with a Google account, but I got the following error:


I understand that hard drive companies do it to market a 900GB HD as an 1TB one, but what is the reason that Nautilus uses base 10 as well?  Shouldn't we try to be right rather than handy?

I read on  that Ubuntu will no longer use the familiar file size units we all know by now (kB, MB, GB, TB) and switch to a different IEC standard (KiB, MiB, GiB, TiB). If this is true, I would like to know what's the reasoning behind this change, and the impact (if any) this change has, especially with multiplatform applications or applications run with Wine.


I am reading the following, which seems true but cannot prove myself :     Let $p$ be a prime, and $n>p$ with the condition that $n$ has all its primes factors greater than $p$. Then $2^n-1$ divides $2^{pn}-1$.   I can see that $2^n-1=\sum_{j=0}^{n-1}2^j$ and $2^{pn}-1=\sum_{j=0}^{pn-1}2^j$ but cannot go further.  On an example we have $p=3$, $n=5$ so $2^5-1=31$ and indeed $2^{15}-1=32767=31\times 1057$.  Thank you for a precise explanation (this is not part of any homework, I actually am an older person and forgot lots).

I did some mathematical induction problems on divisibility   $9^n$ $-$ $2^n$ is divisible by 7. $4^n$ $-$ $1$ is divisible by 3. $9^n$ $-$ $4^n$ is divisible by 5.   Can these be generalized as $a^n$ $-$ $b^n$$ = (a-b)N$, where N is an integer? But why is $a^n$ $-$ $b^n$$ = (a-b)N$ ?  I also see that $6^n$ $- 5n + 4$ is divisible by $5$ which is $6-5+4$ and $7^n$$+3n + 8$ is divisible by $9$ which is $7+3+8=18=9\cdot2$.  Are they just a coincidence or is there a theory behind?  Is it about modular arithmetic?


I have used latex for preparation of my thesis. My references look like following. How to avoid white space in the references?

A picture is worth a thousand macros:    I don't blame LaTeX for having difficulty in formatting this entry.   What can I do, however, to alleviate the effects and avoid the Word-like indentation?   A related question suggested by the site is  which indeed produces a better aligned entry:   While I like the sane alignment, I'm not not very happy with the switch to a monospaced font (while it works in the regular text, in bibliographical entries it attracts too much attention and takes too much space).  Any other suggestions?  The entry for the above test bibitem is:  \begin{thebibliography}  \bibitem{anything-here} "Lorem Ipsum Society, \emph{dolor sit amet, consectetur}, May 2010 retrieved on Oct 16, 2010 from http://www.lorem-ipsum.com/whatever-here/about\%20something/here\%20takes/space\%20in\%20a\%20long/url\%20foobar.aspx   \end{thebibliography}


I have a small problem with a program that when running, sends me a segmentation violation apparently occurs in the function "ejer6" when trying to access the position [0] of char * mensaje to assign 9 my code :  #include <pthread.h> #include <stdlib.h> #include <stdio.h>  struct structure {      char * message;     int integer; };  void * ejer6(void * arg) {      printf("Enters within");      struct structure * turas;     turas=((struct structure *)arg;      turas->integer=turas->integer+1;     turas->message[0]='9';      printf("%d\n", turas->integer);     printf("%s\n", turas->message);       pthread_exit(NULL); }  int main(int argc, char ** argv) {     if(argc!=2) {         printf("Enter the appropriate number of parameters\n");     }     else {          pthread_t h[argc];         struct structure turas[argc];         int i;          for(i=0; i<argc; i++) {             turas[i].integer=13;             turas[i].message="hello world";         }          for(i=0; i<argc; i++) {              printf("\nThis is the value of the structure before the strand: \n");             printf("Integer: %d \n", turas[i].integer);             printf("Message: %s \n", turas[i].message);               pthread_create(&h[i], NULL, ejer6, (void *)&turas[i]);             pthread_join(h[i], NULL);              printf("\nThis is the value of the structure after the strand: \n");             printf("Integer: %d \n", turas[i].integer);             printf("Message: %s \n", turas[i].message);          }     }      return 0; }

The following code receives seg fault on line 2:  char *str = "string"; str[0] = 'z';  // could be also written as *str = 'z' printf("%s\n", str);   While this works perfectly well:  char str[] = "string"; str[0] = 'z'; printf("%s\n", str);   Tested with MSVC and GCC.


I am taking a course in statistics. It covers:  Parameter estimations: point and interval estimations, etc.  Hypothesis testing: comparison of means, comparison of probabilities, Chi square tests, etc.  Analysis of variance..  And the like.  What are some books that you would recommend for such a course?   Thanks.

To give you some background, I have a grasp on the basics of statistics and probability theory and even remember touching Bayes theorem at the university data mining course. But being a few years away from the university made my math got extremely rusty (so much for last-minute pre-exam cramming). While I remember various random basic concepts, there are a lot of gaps in my understanding of them.  What would be a good material (a book, a site, or otherwise equally accessible medium) to revise the fundamentals and go beyond basics? I'd like a book that can be actually read as a book (most statistics books are really dry and are close to being reference material, rather than a book).


I want to know a way to download or export or view all the records for each custom settings without querying them individually. I have tried a chrome extension called Custom settings exporter for Salesforce. But, if we have many custom settings, it only downloads some of them, it did not work for me

I have retrieved the metadata from sandbox to deploy it to the higher org using ANT. ANT have created folders for all the components like objects, classes, etc. But, it did not retrieved many records which are useful for configuration purposes like custom settings records(it have retrieved metadata for custom settings but not the records), remote site settings, etc. So, I want to know what are other components like custom settings records which are not retrieved using ANT but are necessary? Also, in my sandbox org, there are many custom settings and each have multiple records. So, I came to know that you need some post deployment steps which include exporting custom settings records from sandbox org and deploying it to higher org. So, is there any way to export or download or view each records from every custom settings without querying them individually. I have tried a chrome extension called Custom settings exporter for Salesforce. But, if we have many custom settings, it only downloads some of them, it did not work for me. Any custom sfdx plugins or any other reliable tool will be helpful. Thanks!


I know rank AB is not same as rank BA.    I take here particular case.  Is this particular case true?

How do we prove that  $\operatorname{rank}(A) = \operatorname{rank}(AA^T) = \operatorname{rank}(A^TA)$ ?  Is it always true?


and   These above are not the same as this question and I am struggling to find a definitive answer.  I am trying to ascertain whether or not there is an equivalent program to the windows explorer.exe for Ubuntu. I have worked for years on windows and just cannot get used to the mac/linux file explorer.  In windows explorer the current position of where you are is represented in a nice expandable tree on the left with the contents of the current folder in the main window on the right.  Eg:   In Ubuntu's "file" and Mac's "Finder" there is no such thing (as far as i can tell), merely a single representation of your current position in the file structure.  EG:   In the windows explorer screen shot (please ignore the somewhat garish aesthetics) you can clearly see all the folders in c:/ on the left hand side and the contents (folders and files) on the right.  In the ubuntu screen shot, i am in "/home/john/Documents/test folder" yet the "Documents" folder on the left is still closed. Meaning if you are alien (for whatever reason, a new project or what ever) to the fileset you are working on it becomes extremely time consuming as you have to head somewhat blindly into different folders... but if you are generally a busy person with far too much work to do the very last thing i want to do is waste any time on what should be the simplest IT task... navigating a file system.  Is there any way I can achieve a windows explorer style file navigation?  NB  I am not looking to replicate anything else of windows file explorer.

As a happy Linux user for almost a year now, this is the bane of my existence. Does the Linux community hate tree views for some obscure reason?  I don't mean a tree view in the side panel. That's useless. I mean a proper tree view, such that, when I click the triangle, all files and subdirectories contained within the directory show beneath, and I can drag and drop files, open and close trees.   It is extremely frustrating to navigate and move files around deeply nested directories without this feature.  I've tried: Nautilus, PCManFM, emelFM2, Krusader. I find it hard to believe that even crazilly-full-featured file managers like Krusader would be missing this most obvious of features... and yet, here I am.  For all the effort put into those file managers, is this so far-fetched to ask for?    I just need a simple, single-pane file manager with a tree view option. Help!   And -- please -- HOW IS THIS FUNCTION INVOKED ??  (Do I left/right click while pressing control/alt/shift? Is some setting required?)


I do a fair bit of macro photography, indoors with good lighting, using either a focus rail or manual focus pull to image-stack.  I've always considered that using extension tubes for this gives me the most flexibility. With one set of tubes I can vary the tube length in seconds; I can swap lenses at will; the electronics line up to the lenses so I can still vary the aperture. I can't use auto-focus, but at these magnifications I don't think that would be any benefit.  So, having read a few posts on here about reversal & that it might give me a sharper image, among them  as an overview &  for a comprehensive setup & equipment guide, & even  which really seems more concerned with why I should give up on both & get a dedicated macro lens.  I'm left wondering why I would go to all that effort to flip the lens round, investing in different mount adaptors for each lens I want to use, against simply continuing to do it the way I do, which I've become reasonably adept at.  Is the quality gain all that noticeable, even after stacking?  This is an example of about as small as I'm going, 2mm bud from an allium flower head, done with a nifty fifty f/1.4 at f/16 on 68mm extension, D5500, 4-layer stack [I've gone over 20 for larger objects] I'm pretty happy with it.    This will click through to a ⅓ size image

As far as I understand all three options help you do macro photography but are their other reasons for having the three different items? I figured reversal rings and extension tubes were just for the low cost but with additional more expensive features being added to the two options it seems there may be certain situations for each type? What are their biggest differences and advantages over each other?   Are there situations where you would have one over the other? Do all three options have the same "wafer thin" depth of field?  Do they all suffer from the same light loss? Do any of them affect your photos more negatively than the others? Can I achieve the same magnification with rings and tubes that I can with proper lenses? Would you ever combine these options together or would there be no need for that?   I ask because I recently bought a cheap extension tube and reversal ring and I'm trying to get a better overall understanding of each. I tend to use the extension tube a lot more, because I can put it on my 70-200 and have a workable distance between subject and lens.  This photo was taken with 49mm of extension tube on the 70-200 I believe which may be greater than 1:1. Would it be sharper with a macro lens?       on 500px


Sometimes, I am not satisfied with the answers that I get, though some are very good.  Do I have to accept an answer or can I just leave the question open?

I have posted questions on SO for which I have received answers that do not answer the question. No correct answers were offered (I guess I have really good questions ;) )  People tell me my accept rate is low, making my questions less attractive for answering.  Should I accept the wrong ones to boost my accept rate? Is there another option? Can I mark an answer as wrong?


I have the following code      double temp3 = 61.01;      //This can actually be various other types, but float is the one that causes problems     dynamic temp = 61.01f;     double temp2 = (double)Convert.ChangeType(temp, typeof(double));      double newValue = temp2 - temp3;      //newValue should == 0 but it does not      Console.WriteLine(String.Format("  {0:F20}", temp));     Console.WriteLine(String.Format("  {0:F20}", temp2));     Console.WriteLine(String.Format("  {0:F20}", temp3));     Console.WriteLine(String.Format("  {0:F20}", newValue));   Which produces   61.01000000000000000000  61.00999832153320000000  61.01000000000000000000    -0.00000167846679488548  Why is Convert.ChangeType losing precision?  We are using Convert.ChangeType because of the use of a dynamic variable which can be byte/uint/float/double etc

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


I have hundreds of variables each has more than 100000 observations. My aim is to determine which variables ara normally distributed. Usual tests like Shapiro-Wilk tests are likely to reject normality of distribution even the distribution is really normal. Since I have hundreds of variables, I can't use graphs to decide normality. How can I do such a mulpitle test using R? I will be very glad for any help. Thanks a lot.

I'm examining a part of my dataset containing 46840 double values ranging from 1 to 1690 grouped in two groups. In order to analyze the differences between these groups I started by examining the distribution of the values in order to pick the right test.  Following a guide on testing for normality, I did a qqplot, histogram & boxplot.       This doesn't seem to be a normal distribution. Since the guide states somewhat correctly that a purely graphical examination isn't sufficient I also want to test the distribution for normality.   Considering the size of the dataset and the limitation of the shapiro-wilks test in R , how should the given distribution be tested for normality and considering the size of the dataset, is this even reliable? ()  Edit:  The limitation of the Shapiro-Wilk test I'm referring to is that the dataset to be tested is limited to 5000 points.  To cite  concerning this topic:     An additional issue with the Shapiro-Wilk's test is that when you feed   it more data, the chances of the null hypothesis being rejected   becomes larger. So what happens is that for large amounts of data even   very small deviations from normality can be detected, leading to   rejection of the null hypothesis event hough for practical purposes   the data is more than normal enough.      [...] Luckily shapiro.test protects the user from the above described   effect by limiting the data size to 5000.   As to why I am testing for normal distribution in the first place:  Some hypothesis tests assume normal distribution of the data. I want to know whether or not I can use these tests.


Google Drive occasionally pops up this error, randomly with no obvious cause:     --------------------------- Windows Script Host ---------------------------   There is no script engine for file extension ".vbs".   --------------------------- OK    ---------------------------   Is something misconfigured on my computer?

A few days ago when I resume my computer from sleep mode in the mornings I would see an error dialog from "Windows Script Host" that read: "There is no script engine for file extension ".vbs". I am having hard time tracking down the source of this. I've looked through the event log, registry, and the scheduled tasks. But the lists are so long and I don't know where exactly to look for.   Details: It looks like it happens once a day and I only see it in the mornings. I'm on 64-bit Windows 7 Home Premium.  Any pointers are appreciated.  also, i think this started after one of those automatic windows updates.


Given two ciphertexts $c_1=Ek_1(p_1)$ and $c_2=Ek_2(p_2)$ encrpted by two different users with two different keys, i.e. $Ek_1$ and $Ek_2$ using a homomorphic crypto such as Paillier. Can a third party perform an equality test on $c_1$ and $c_2$ without knowing the keys?    As for my research efforts…  I read few papers on equality tests, and homomorphic encryption. However, in those papers almost all the scenarios are like when a client upload its encrypted data on the cloud and then search an encrypted keyword on it. In my case, I have a shared table of cipher texts and i have to find common attributes among the cipher texts encrypted by different clients stored in shared database. whereas normally comparison is made on cipher texts encrypted by a single client and done by the owner of the data.

Given two ciphertexts $c_1 = enc(p_1)$ and $c_2= enc(p_2)$ using any additive homomorphic encryption scheme (or specifically Paillier).   Can we find out whether the underlying plaintexts $p_1,p_2$ are equal without decrypting $c_1,c_2$ i.e. homomorphically?


I'm Syrian, I have an EU Student Residence Permit and soon I'll have an EU Working Residence Permit. I'm planning to visit London.   I need to have a . In applying, there are  criteria I need to prove, which are:   You’ll leave the UK at the end of your visit You’re able to support yourself and any dependents for the duration of your trip You’re able to pay for your return or onward journey and any other costs relating to your visit You have proof of any business or other activities you want to do in the UK, as allowed by the Visitor Rules   For the first point, I think it's enough to have the return ticket.  I don't think I need to do anything regarding the fourth point.  My questions are about the second and third points.   Regarding the second point: how can I show that I'm able to support myself and any dependents for the duration of your trip? Regarding the third point: it has two things, first pay for your return or onward journey, which I can handle by showing the returning ticket, but what about any other costs relating to your visit?    I see that they're focusing mainly on being able to handle myself financially, how can I prove that?  I have a job from an EU country, would that be enough?  Update  I understand now that even for the first point, having the return ticket is not enough.

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?


I have a dev board which came without power supply. As per the spec, it works on 5V 3A. I have a spare power supply 5V 5A, can it be used here?  Will there be any issue?

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 tried many things on here but all failed. I want to do this:  Don't put Einstein, Albert (1990) "Relativity" into footnote. Put in into bibliography section. Make blue-colored hyperlink within the document from Einstein (1990) to Einstein, Albert (1990) "Relativity"  Choosing Document Settings -> Bibliography -> Citation Style -> Biblatex resulted in the hyperlink created only on 1990, rather than on entire Einstein (1990). And maybe this isn't necessary. But to add what I tried and failed: Choosing Document Settings -> Bibliography -> Citation Style -> Natbib (BibTeX) resulted in an error when converting it to pdf (Though I am not sure if this is correct thing to choose)

I'm new here so I'm not sure if this is the right way to express my question:  I'm using the excellent biblatex package with the author-year style and want the links in my citations to include the name of the author as well as the parentheses. The answer presented at  did exactly what I wanted but it seems the solution is broken with the newest biblatex version 1.4b. Can anyone help me by adapting the code to the newest biblatex version?


Has anyone got this to work? Snippets appearing in search results?  Reason I ask is because I've added the script but it's not showing up in Google search results. I added the script last week and Google search console tells me three pages have been processed.

** EDIT Feb 2016 - Finally JSON-LD seems to be working now in SERPS, with extremely fast changes-to-index time, assuming you have everything with Google merchant center feeds syncd and linked. Make sure the price, stock, and identifier are the same on your JSON-LD as it is on the Google shopping feed. New organization->localbusiness types are live, organization reviews are live... however JSON-LD feed alt= endpoints still do not exist, the homepage schema defining custom site name is not active, and G support for schema itemList/dateModified is still questionable. You can still get pagination results and date modified snippets by using literal text strings in your view/template Showing 1-28 of 8977 Results (321 Pages)and Last updated on February 3rd 2016. To proceed to a deeper exploration of JSON-LD support, see these:       Original Post Below: Google seems to be flip flopping JSON-LD -> Schema.org product [or other types of] snippets. The snippets verify without error in both the testing tool and long term (10+ months) across 5 properties in GWT search console. The snippets have been applied to index, removed, applied, and removed again, seemingly not being applied again in regards to various facets. Since they worked in the past via microdata, and were applied long term, I assume it's due to the switch to JSON-LD. I have not found any official docs nor examples that say "Google will support and render products snippets that use JSON-LD". Same thing with breadcrumb snippets and review looping. All I see is a handful of Google examples for events, movies, recipes, very basic [incomplete] organization etc. This seems strange to me considering the sheer amount of ecom pages using product snippets trumps the amount of movies, recipes, and events combined. So the question is, does Google officially support, index, and render product markup using JSON-LD? If so, can anyone point me to a live example to verify this? ** This question is not intended to be "opinion/recommendation based"....im looking for a specific link and subsequent SERP result [evidence] showing that JSON-LD products/etc are indeed rendered within Google.com realm as of late August 2015. ** EDIT Nov 16 2015 - Another annoying caveat has been found. Google merchant center validates certain shopping feed fields such as condition, stock, and price against live microdata. However, it seems to not recognize JSON-LD.... although, as stated above, it's recommended to use in all the G examples, and it validates the snippet test. So due to this, your merchant center account could be suspended because of "differences in presentation data"


My current desktop setup is  [2][3][1]   where 3 is the main display and 1 is disabled.  I would like to be able to toggle between that setup and  [3][2][1]   where 3 is still the main display and 1 is still disabled. Essentially, I just want to switch monitors 2 and 3.  Ideally I would like to assign this to a shortcut, but to do so (I think...) I need to be able to do this via command line.  If possible, I'd also like to do this without third party software. [edit: although, if Windows does not support this natively, I would accept a third party solution.]  Thanks!

I have 3 monitors attached to my 8800GTS, which can only use 2 at a time. I use 3 different setups:   single screen (1) dual screen (1+2) single screen + TV out (1+3)   having to click screen resolution and select different screens etc is a bit of a pain, and to get round this I used to have an autohotkey script that opened up the NVIDIA control panel and select a different profile. However in W7, for some reason everytime I select a new profile it seems to mess up all the settings/not work at all.  I was wondering - does windows7 have any built in commands for selecting monitor 1+2, or 1+3 and just 1?   I'd love to have 3 shortcuts on my start menu like I used to!